WO2019181151A1 - Exhaust gas purification device - Google Patents

Exhaust gas purification device Download PDF

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Publication number
WO2019181151A1
WO2019181151A1 PCT/JP2019/000805 JP2019000805W WO2019181151A1 WO 2019181151 A1 WO2019181151 A1 WO 2019181151A1 JP 2019000805 W JP2019000805 W JP 2019000805W WO 2019181151 A1 WO2019181151 A1 WO 2019181151A1
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WO
WIPO (PCT)
Prior art keywords
urea water
urea
injection valve
filter
filter case
Prior art date
Application number
PCT/JP2019/000805
Other languages
French (fr)
Japanese (ja)
Inventor
仁視 西口
俊憲 藤井
暢春 伊美
Original Assignee
日立建機株式会社
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Publication date
Application filed by 日立建機株式会社 filed Critical 日立建機株式会社
Publication of WO2019181151A1 publication Critical patent/WO2019181151A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous

Definitions

  • the present invention relates to an exhaust gas purification device that is mounted on a construction machine such as a hydraulic excavator and removes harmful substances in exhaust gas discharged from an engine.
  • a construction machine such as a hydraulic excavator is equipped with an exhaust gas purification device for removing harmful substances contained in exhaust gas discharged from an engine (internal combustion engine).
  • the urea SCR system used in this type of exhaust gas purification device includes a urea selective reduction catalyst, a urea water injection valve, a urea water tank, a urea water pipe, and a urea water supply device (urea water pump). Yes.
  • the urea selective reduction catalyst is connected to the exhaust pipe of the engine and removes nitrogen oxides in the exhaust gas.
  • the urea water injection valve injects urea water, which is a reducing agent, upstream of the urea selective reduction catalyst.
  • the urea water tank stores urea water supplied to the urea water injection valve.
  • the urea water pipe line connects between the urea water tank and the urea water injection valve.
  • the urea water supply device is provided in the middle of the urea water pipe and supplies urea water from the urea water tank toward the urea water injection valve.
  • the urea water stored in the urea water tank needs to be replenished regularly. Since the urea water replenishment operation is performed with the cap of the urea water tank removed, foreign matter (contamination) may be mixed in the urea water. Foreign matter mixed in the urea water penetrates into the urea water supply device and the urea water injection valve, thereby inhibiting the urea water supply to the urea water injection valve and the proper urea water injection from the urea water injection valve. To do. On the other hand, it is known that a urea water filter is provided in the middle of the urea water pipe connecting the urea water tank and the urea water injection valve, and foreign substances mixed in the urea water are collected by the urea water filter. (See Patent Document 1).
  • urea water freezes at -11 ° C or lower. For this reason, when a hydraulic excavator equipped with a urea SCR system is used in a cold region, the urea water freezes inside the urea water tank, urea water injection valve, urea water supply device, urea water pipe, etc. There is a problem that the urea SCR system does not function properly. On the other hand, it is known that the urea water tank and the urea water pipe line are warmed by using the cooling water pipe through which the engine cooling water flows to prevent the urea water from freezing inside the urea water tank and the urea water pipe line. (See Patent Document 2).
  • the urea water SCR system performs an operation of returning urea water into the urea water tank by the urea water pump (hereinafter referred to as after-run operation) after the engine is stopped.
  • the urea water SCR system freezes the urea water remaining in the urea water injection valve, the urea water pipe, the urea water supply device, etc., or the urea water remaining in the urea water injection valve evaporates and crystallizes. Is preventing.
  • the urea SCR system is suitable for supplying urea water in the urea water tank to the urea water injection valve and for injecting urea water from the urea water injection valve by using the discharge pressure of the urea water pump. Control to increase the pressure (hereinafter referred to as start-up operation).
  • the urea SCR system When the start-up operation is performed, the urea SCR system operates the urea water pump to the urea water supply side with the urea water injection valve opened, and the urea water is supplied to the urea water pipe line and the urea water supply device. It is discharged into the exhaust pipe through the injection valve.
  • the urea SCR system closes the urea water injection valve. In this state, when the discharge pressure of the urea water pump reaches a specified value suitable for injecting urea water from the urea water injection valve, the urea SCR system determines that the start-up operation is successful. Then, the urea SCR system shifts to an operation of injecting urea water from the urea water injection valve toward the upstream side of the urea selective reduction catalyst (hereinafter referred to as urea water supply operation).
  • urea water supply operation an operation of injecting urea water from the urea water injection valve toward the upstream side of the urea
  • the urea SCR system temporarily operates the urea water pump to the urea water return side to return the urea water to the urea water tank, and then operates the urea water pump to the urea water supply side again.
  • urea water is supplied to the urea water injection valve. If the urea water pump discharge pressure does not reach the specified value while the operation of the urea water pump is repeated a plurality of times on the urea water supply side and the urea water return side, the urea SCR system starts up. It is determined that the operation has failed, and the urea SCR system stops.
  • the urea water filter that collects foreign matters mixed in the urea water is located between the urea water tank and the urea water pump and is provided in the middle of the urea water pipe.
  • the urea water filter includes a filter case that stores urea water therein, and a filter element that is provided in the filter case.
  • the filter case is connected to an inlet of a urea water pipe through which urea water from the urea water tank flows and an outlet of a urea water pipe through which urea water flows toward the urea water supply device.
  • the inlet and outlet of these urea water pipes are normally open on the upper surface side of the filter case in consideration of workability when the filter element is replaced.
  • air may be mixed into the urea water supplied to the urea water pump.
  • the air mixed in the urea water is normally separated from the urea water when the urea water flows into the urea water filter.
  • the air in the urea water filter Prior to the urea water flowing out from the urea water filter, the air in the urea water filter is discharged into the exhaust pipe through the urea water injection valve. Therefore, urea water that does not contain air can be supplied from the urea water filter toward the urea water pump.
  • the present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to suppress a decrease in the discharge pressure of urea water discharged from the urea water supply device in a start-up operation, and It is an object of the present invention to provide an exhaust gas purifying device that can prevent the urea water from freezing.
  • the present invention provides a urea selective reduction catalyst connected to an exhaust pipe of an engine to remove nitrogen oxides in exhaust gas, and urea water as a reducing agent upstream of the urea selective reduction catalyst.
  • a urea water injection valve that injects, a urea water tank that stores urea water supplied to the urea water injection valve, a urea water pipe that connects between the urea water tank and the urea water injection valve, and the urea water pipe
  • a urea water supply device that is provided in the middle of the road and supplies urea water from the urea water tank toward the urea water injection valve; and the urea water pipe positioned between the urea water tank and the urea water supply device
  • the present invention is applied to an exhaust gas purification device provided with a urea water filter that is provided in the middle of the road and collects foreign matters mixed in urea water.
  • the urea water filter includes a filter case having a top surface and a bottom surface and a container for storing urea water therein, and the filter case for collecting foreign matter mixed in the urea water.
  • a filter element that divides the inside of the filter case into a pre-filtration chamber for storing urea water before foreign matter is filtered and a post-filtration chamber for storing urea water after foreign matter is filtered,
  • a thawing device for thawing urea water frozen in the filter case is provided in the post-filter chamber of the filter case, and one end of the urea water conduit is connected to the urea water tank, and the other end is the filter case.
  • a tank-side urea water pipe that is located in the pre-filtration chamber and opened to the bottom surface of the filter case, and one end of the tank-side urea water conduit is located in the post-filtration chamber of the filter case. Open to the surface position, the other end is in that it is constituted by a connected injector side urea water pipe to the urea water injection valve.
  • the filter case by the after-run operation, most of the urea water in the filter case can be returned from the other end of the tank side urea water pipe to the urea water tank. Therefore, the air mixed in the urea water is separated in the filter case until the filter case is filled with the urea water by the start-up operation, and only this air is discharged from the urea water filter before the urea water. Can do. As a result, it is possible to suppress a decrease in the discharge amount of the urea water supply device due to the air mixed in the urea water flowing into the urea water supply device. In addition, a thawing device is provided in the filter case. For this reason, even if the urea water remaining in the filter case is frozen, the frozen urea water can be efficiently thawed from the central portion to the outside, and the filter element can be protected.
  • FIG. 1 is a front view showing a hydraulic excavator equipped with an exhaust gas purifying apparatus according to a first embodiment of the present invention. It is a top view which shows an upper revolving body in the state which omitted a cab, a building cover, etc. It is a block diagram which shows a urea SCR system schematically. It is a longitudinal cross-sectional view which shows the urea water filter, tank side urea water pipe line, injection valve side urea water pipe line, and thawing
  • FIG. 5 is a cross-sectional view of the filter case, the filter element, the tank side urea water pipe, and the thawing device as seen from the direction of arrows VV in FIG.
  • FIG. 7 shows the urea water filter by the 3rd Embodiment of this invention, an expansion chamber formation body, a tank side urea water pipe, an injection valve side urea water pipe, and a defroster.
  • FIG. 4 shows the 1st modification of this invention.
  • FIG. 4 shows the 2nd modification of this invention.
  • FIG. 4 shows the urea SCR system similar to FIG. 3 which shows the 3rd modification of this invention.
  • the excavator 1 is a self-propelled crawler type lower traveling body 2, an upper revolving body 3 that is turnably mounted on the lower traveling body 2, and an earth and sand provided on the front side of the upper revolving body 3 so as to be able to move up and down. It is comprised with the working apparatus 4 which performs the excavation work of this.
  • the upper revolving unit 3 is provided on the left side of the front part of the revolving frame 5, the revolving frame 5 that forms the support structure, the counterweight 6 that is provided on the rear side of the revolving frame 5 and that balances the weight with the work device 4.
  • the cab 7 on which the operator is boarded and the building cover 8 provided on the front side of the counterweight 6 are configured.
  • the building cover 8 accommodates an engine 9, an exhaust gas purification device 14 and the like, which will be described later, inside.
  • the revolving frame 5 has a bottom plate 5A extending in the front and rear directions, a left vertical plate 5B and a right vertical plate 5C standing on the bottom plate 5A and extending in the front and rear directions, and on the left side of the left vertical plate 5B. It is provided with a left side frame 5D that is disposed in the front and rear directions and a right side frame 5E that is disposed on the right side of the right vertical plate 5C and extends in the front and rear directions.
  • the revolving frame 5 includes a bottom plate 5A, a plurality of extended beams 5F extending left and right from the vertical plates 5B and 5C, and a connection erected on the bottom plate 5A located on the front side of the engine 9.
  • the connecting plate 5G connects the left and right vertical plates 5B and 5C.
  • a urea water supply device 30 and a urea water filter 34, which will be described later, are attached to the rear surface side of the connecting plate 5G.
  • the engine 9 is located in front of the counterweight 6 and is provided in a horizontally placed state on the turning frame 5 extending left and right.
  • a cooling fan 9 ⁇ / b> A for supplying cooling air to a heat exchanger 11 described later is provided on the left side of the engine 9.
  • a hydraulic pump (not shown) is provided on the right side of the engine 9. The hydraulic pump is driven by the engine 9 to discharge hydraulic oil supplied from a hydraulic oil tank 12 described later as hydraulic oil to a hydraulic actuator mounted on the hydraulic excavator 1.
  • an exhaust pipe 10 for discharging exhaust gas to the outside is connected to the engine 9.
  • the exhaust pipe 10 is formed as a metal pipe line extending in the left and right directions on the front side of the engine 9, and the high-temperature exhaust gas discharged from the engine 9 is supplied to a first exhaust gas aftertreatment device 15 described later. Lead.
  • the heat exchanger 11 is disposed on the left side of the engine 9.
  • the heat exchanger 11 is provided so as to face the cooling fan 9 ⁇ / b> A of the engine 9.
  • the heat exchanger 11 includes, for example, a radiator that cools engine cooling water that circulates in the water jacket of the engine 9, an oil cooler that cools hydraulic oil, an intercooler that cools air that the engine 9 sucks, and the like.
  • the hydraulic oil tank 12 is located on the right side of the revolving frame 5 and is located on the front side of the hydraulic pump.
  • the hydraulic oil tank 12 stores hydraulic oil for driving actuators provided in the lower traveling body 2, the work device 4, and the like.
  • the fuel tank 13 is located on the front side of the hydraulic oil tank 12 and is provided on the revolving frame 5.
  • the fuel tank 13 stores fuel supplied to the engine 9.
  • the exhaust gas purification device 14 is mounted on a purification device mounting base (not shown) disposed on the right side of the engine 9.
  • the exhaust gas purification device 14 is connected to the exhaust pipe 10 of the engine 9 and removes harmful substances in the exhaust gas discharged from the engine 9. Further, the exhaust gas purification device 14 is provided with a silencer mechanism for reducing exhaust gas noise.
  • the exhaust gas purification device 14 includes a first exhaust gas aftertreatment device 15, a connecting pipe 18, and a second exhaust gas aftertreatment device 19 which will be described later.
  • the first exhaust gas aftertreatment device 15 is connected to the outlet side of the exhaust pipe 10.
  • the first exhaust gas aftertreatment device 15 includes a cylindrical tube 16 extending in the front and rear directions, and an oxidation catalyst 17 provided in the tube 16.
  • the cylindrical body 16 is formed as a sealed container with both ends closed, and the exhaust pipe 10 is connected to a front side portion that is upstream in the flow direction of the exhaust gas.
  • the oxidation catalyst 17 disposed in the cylinder 16 is made of, for example, a ceramic cell-shaped cylinder, and has a large number of through holes formed in the axial direction thereof, and the inner surface is coated with a noble metal.
  • the oxidation catalyst 17 oxidizes and removes carbon monoxide (CO), hydrocarbons (HC), and the like contained in the exhaust gas by causing the exhaust gas to flow through each through hole at a predetermined temperature. Further, the oxidation catalyst 17 burns and removes particulate matter (PM) as necessary.
  • the connecting pipe 18 connects between the first exhaust gas aftertreatment device 15 and the second exhaust gas aftertreatment device 19.
  • the connecting pipe 18 includes a cylindrical tube portion 18A extending in the front and rear directions in parallel with the tube body 16, an upstream lid portion 18B that closes an edge on the inlet side that is the upstream side of the tube portion 18A, and a tube portion. It is comprised by the downstream cover part 18C which obstruct
  • a urea water injection valve 24 described later is attached to the upstream lid portion 18B.
  • the second exhaust gas aftertreatment device 19 is arranged on the upper right side of the first exhaust gas aftertreatment device 15.
  • the second exhaust gas aftertreatment device 19 is connected to the outlet side of the connection pipe 18 and has a cylindrical cylinder 20 extending in the front and rear directions in parallel with the first exhaust gas aftertreatment device 15, and a cylinder
  • the urea selective reduction catalyst 21 provided in 20 and the oxidation catalyst 22 arranged on the downstream side of the urea selective reduction catalyst 21 are configured.
  • the urea selective reduction catalyst 21 constitutes a part of a urea SCR system 23 described later, and removes nitrogen oxides in the exhaust gas.
  • the urea selective reduction catalyst 21 is made of, for example, a ceramic tubular body made of ceramics. A large number of through holes are formed in the axial direction, and the inner surface is coated with a noble metal.
  • the urea selective reduction catalyst 21 selectively reduces the nitrogen oxide (NOx) contained in the exhaust gas discharged from the engine 9 by ammonia generated from the urea aqueous solution (urea water), and decomposes it into nitrogen and water. To do.
  • the oxidation catalyst 22 is provided downstream of the urea selective reduction catalyst 21 in the exhaust gas flow direction.
  • the oxidation catalyst 22 is formed of a ceramic tubular body, which is substantially the same as the oxidation catalyst 17 of the first exhaust gas aftertreatment device 15 described above.
  • a number of through holes are formed in the axial direction of the oxidation catalyst 22, and the inner surface is coated with a noble metal.
  • the oxidation catalyst 22 of the second exhaust gas aftertreatment device 19 oxidizes the remaining residual ammonia after the nitrogen oxide is reduced by the urea selective reduction catalyst 21 and separates it into nitrogen and water.
  • the urea selective reduction catalyst 21 provided in the second exhaust gas aftertreatment device 19 constitutes a part of the urea SCR system 23, and the urea SCR system 23 will be described below.
  • the urea SCR system 23 injects urea water toward the exhaust gas flowing through the exhaust pipe 10, and selectively reduces nitrogen oxide (NOx) contained in the exhaust gas with ammonia. Thereby, nitrogen oxides are decomposed into nitrogen and water, and the exhaust gas is purified.
  • the urea SCR system 23 includes a urea selective reduction catalyst 21, a urea water injection valve 24, a urea water tank 25, a urea water pipe 26, a urea water supply device 30, a urea water, which will be described later.
  • a filter 34 is included.
  • the urea water injection valve 24 is attached to the upstream lid portion 18B of the connection pipe 18, for example.
  • the urea water injection valve 24 injects urea water (urea aqueous solution) as a reducing agent toward the exhaust gas flowing in the connection pipe 18 on the upstream side of the urea selective reduction catalyst 21.
  • the urea water injection valve 24 is connected to a urea water tank 25 via a urea water pipe line 26.
  • the urea water tank 25 is provided in the revolving frame 5, for example.
  • the urea water tank 25 stores urea water supplied to the urea water injection valve 24.
  • the urea water tank 25 is provided with a water supply port (not shown) for supplying urea water, and urea water is supplied into the urea water tank 25 through this water supply port.
  • the urea water conduit 26 connects between the urea water tank 25 and the urea water injection valve 24.
  • a urea water supply device 30 is provided in the middle of the urea water pipe line 26.
  • the urea water stored in the urea water tank 25 is supplied to the urea water injection valve 24 through the urea water pipe line 26 by operating the urea water supply device 30.
  • the urea water pipe 26 is a tank side urea water pipe 27 that connects between the urea water tank 25 and the urea water filter 34, and an injection valve that connects between the urea water filter 34 and the urea water injection valve 24.
  • a side urea water pipe 28 is a side urea water pipe 27 that connects between the urea water tank 25 and the urea water filter 34, and an injection valve that connects between the urea water filter 34 and the urea water injection valve 24.
  • the tank side urea water pipe line 27 connects between the urea water tank 25 and the urea water filter 34. That is, the tank side urea water pipe 27 has one end 27 ⁇ / b> A connected to the urea water tank 25 and the other end 27 ⁇ / b> B connected to the urea water filter 34.
  • the other end 27 ⁇ / b> B of the tank-side urea water conduit 27 is located in a pre-filtration chamber 35 ⁇ / b> E of the filter case 35 described later and opens to the bottom surface position of the filter case 35.
  • the injection valve side urea water pipe line 28 connects between the urea water filter 34 and the urea water injection valve 24. That is, the injection valve side urea water pipe 28 has one end 28 ⁇ / b> A connected to the urea water filter 34 and the other end 28 ⁇ / b> B connected to the urea water injection valve 24. In this case, one end 28 ⁇ / b> A of the injection valve side urea water conduit 28 is located in the post-filtration chamber 35 ⁇ / b> F of the filter case 35 and is open to the upper surface position of the filter case 35.
  • one end 29 A of the urea water return pipe 29 is connected to the middle part of the injection valve side urea water pipe 28, and the other end 29 B of the urea water return pipe 29 is connected to the urea water tank 25.
  • the urea water return pipe 29 is for returning the surplus portion of the urea water supplied toward the urea water injection valve 24 to the urea water tank 25.
  • the urea water supply device 30 is provided in the middle of the injection valve side urea water pipe 28 constituting the urea water pipe 26.
  • the urea water supply device 30 supplies urea water from the urea water tank 25 toward the urea water injection valve 24.
  • the urea water supply device 30 includes a urea water pump 31, a pressure sensor 32, and a throttle 33.
  • the pressure sensor 32 is located between the urea water pump 31 and the urea water injection valve 24 and is provided in the middle of the injection valve side urea water pipe 28 to detect the pressure in the injection valve side urea water pipe 28.
  • the throttle 33 is provided in the middle of the urea water return pipe 29 and adjusts the pressure in the injection valve side urea water pipe 28.
  • One end 29A of the urea water return pipe 29 is connected to the injection valve side urea water pipe 28 at a portion between the urea water pump 31 and the pressure sensor 32.
  • the urea water supply device 30 is attached to the rear surface side (engine 9 side) of the connecting plate 5G constituting the revolving frame 5 via the bracket 5H.
  • a cover 5J bent in a U shape is fixed to the bracket 5H, and the periphery of the urea water supply device 30 is covered with the cover 5J.
  • the urea water pump 31 is configured using a pump that can operate in two directions, for example, a urea water supply side that supplies urea water to the urea water injection valve 24 and a urea water return side that returns urea water to the urea water tank 25.
  • a urea water supply side that supplies urea water to the urea water injection valve 24
  • a urea water return side that returns urea water to the urea water tank 25.
  • the urea SCR system 23 performs an after-run operation.
  • the urea water pump 31 is operated to the urea water return side, whereby the urea water remaining in the urea water injection valve 24, the urea water pipe 26, the urea water supply device 30 and the like is returned into the urea water tank 25. .
  • the urea water filter 34 includes a filter case 35 formed of a cylindrical container that stores urea water therein, and a cylindrical filter element (filter medium) provided in the filter case 35. 36).
  • the filter case 35 is formed as a cylindrical body surrounded by a cylindrical peripheral wall plate 35A, an upper surface plate 35B that closes the upper end of the peripheral wall plate 35A, and a bottom surface plate 35C that closes the lower end of the peripheral wall plate 35A.
  • a heater mounting hole 35D is provided at the center of the bottom plate 35C of the filter case 35, and a heater 37 described later is mounted in the heater mounting hole 35D.
  • the upper end 36A and the lower end 36B of the filter element 36 are fixed in the filter case 35, respectively.
  • the filter element 36 has a fine mesh through which only urea water passes and foreign matter (contamination) mixed in the urea water cannot pass. Further, a serrated uneven portion is formed on the entire outer periphery of the filter element 36 so that a large amount of foreign matter can be collected by increasing the surface area (filtration area). .
  • the filter case 35 is located outside the filter element 36 and stores a pre-filtration chamber 35E for storing urea water before the foreign matter is filtered, and after the foreign matter is filtered inside the filter element 36. It is divided into a post-filtration chamber 35F for storing urea water.
  • One end 28A of the injection valve side urea water conduit 28 is inserted downward into the upper surface plate 35B of the filter case 35.
  • one end 28A of the injection valve side urea water conduit 28 is positioned in the post-filtration chamber 35F of the filter case 35, and the upper surface position of the filter case 35, for example, the upper surface plate 35B of the filter case 35 and the upper end 36A of the filter element 36. There is an opening between.
  • the other end 27B of the tank-side urea water conduit 27 is inserted upward into the bottom plate 35C of the filter case 35.
  • the other end 27B of the tank side urea water pipe 27 is disposed at a position separated from the heater mounting hole 35D, for example, between the peripheral wall plate 35A of the filter case 35 and the filter element 36.
  • the other end 27B of the tank side urea water conduit 27 is located in the pre-filtration chamber 35E of the filter case 35 and is positioned at the bottom surface of the filter case 35, for example, the bottom plate 35C of the filter case 35 and the lower end 36B of the filter element 36. There is an opening between.
  • the other end 27 ⁇ / b> B of the tank-side urea water conduit 27 is open to the bottom surface position of the filter case 35.
  • the urea SCR system 23 can return most of the urea water in the filter case 35 to the urea water tank 25 through the tank-side urea water conduit 27 by an after-run operation. Therefore, after the after-run operation is completed, the liquid level L of the urea water in the filter case 35 is lowered to the position indicated by the two-dot chain line in FIG. 4, and most of the urea water in the filter case 35 is discharged. be able to.
  • a heater 37 as a thawing device is provided in the post-filtration chamber 35F of the filter case 35 of the urea water filter 34. Specifically, the heater 37 is provided in a state where the heater 37 is positioned in the post-filtration chamber 35 ⁇ / b> F and extends upward and downward in the center portion of the filter case 35.
  • the heater 37 is inserted into the heater mounting hole 35D of the filter case 35 (bottom plate 35C) and has a cylindrical body 37A extending upward and downward along the axial center position of the cylindrical filter case 35, and the cylindrical body 37A. It is comprised by the heating wire 37B provided in the inside.
  • the heater 37 generates heat when power is supplied from the power source 38 to the heating wire 37B, and thaws the frozen urea water generated by freezing the urea water remaining in the filter case 35.
  • the heater 37 is disposed on the inner side of the filter element 36 so as to extend upward and downward at an axial center position that is a central portion of the filter case 35. Thereby, the heat generated by the heater 37 can be evenly transferred to the frozen urea water frozen in the filter case 35, and the frozen urea water can be efficiently thawed.
  • the exhaust gas purification device 14 has the above-described configuration.
  • the operator gets on the cab 7 and operates the engine 9.
  • the operator can run the excavator 1 by operating a travel operation lever (not shown) disposed in the cab 7.
  • the operator can perform excavation work of earth and sand using the work device 4 by operating an operation lever (not shown) for work.
  • the exhaust gas discharged from the engine 9 is introduced into the first exhaust gas aftertreatment device 15 of the exhaust gas purification device 14 through the exhaust pipe 10. As shown by arrows in FIG. 3, the exhaust gas passes through the connection pipe 18 and the second exhaust gas aftertreatment device 19 from the first exhaust gas aftertreatment device 15 and is then discharged into the atmosphere.
  • the first exhaust gas aftertreatment device 15 oxidizes and removes carbon monoxide (CO), hydrocarbon (HC), etc. contained in the exhaust gas by the oxidation catalyst 17, and if necessary, particulate matter (PM) is burned and removed.
  • urea water is injected from the urea water injection valve 24 toward the exhaust gas, and the second exhaust gas aftertreatment device 19 converts the nitrogen oxides into nitrogen and water by the urea selective reduction catalyst 21. Decompose.
  • the oxidation catalyst 22 oxidizes residual ammonia and separates it into nitrogen and water. In this way, the exhaust gas from the engine 9 is sufficiently purified by the exhaust gas purification device 14 and then discharged into the atmosphere.
  • the urea SCR system 23 performs after-run after the engine 9 of the excavator 1 stops in order to prevent the urea water remaining in the urea water injection valve 24, the urea water pipe 26, and the urea water supply device 30 from freezing. Perform the action. As a result, the urea water remaining in the urea water injection valve 24, the urea water pipe 26, and the urea water supply device 30 is returned to the urea water tank 25. For this reason, after the engine 9 is started, the urea SCR system 23 supplies the urea water in the urea water tank 25 to the urea water injection valve 24. In addition, the urea SCR system 23 performs a start-up operation to increase the discharge pressure of the urea water pump 31 to a pressure suitable for injecting the urea water from the urea water injection valve 24.
  • the urea SCR system 23 When performing the start-up operation, the urea SCR system 23, for example, when the temperature of the exhaust gas flowing through the cylindrical body 20 of the second exhaust gas aftertreatment device 19 reaches a temperature higher than the temperature at which the urea selective reduction catalyst 21 is activated, The urea water injection valve 24 is opened (opened). In this state, the urea SCR system 23 operates the urea water pump 31 to the urea water supply side. As a result, the air in the urea water conduit 26 and the urea water supply device 30 is discharged into the exhaust gas purification device 14 through the urea water injection valve 24 and the air in the urea water tank 25 through the urea water return conduit 29. It is discharged to the layer part.
  • the discharge pressure of the urea water pump 31 increases due to pressure loss when passing through the throttle 33. .
  • the urea SCR system 23 closes the urea water injection valve 24.
  • the discharge pressure of the urea water pump 31 further increases, and the discharge pressure of the urea water pump 31 reaches a specified value (second threshold) suitable for injecting the urea water from the urea water injection valve 24.
  • the urea SCR system 23 determines that the startup operation is successful.
  • the urea SCR system 23 starts control to keep the discharge pressure of the urea water pump 31 constant, and urea water supply for injecting urea water from the urea water injection valve 24 toward the upstream side of the urea selective reduction catalyst 21. Operation is performed.
  • the urea SCR system 23 determines whether the discharge pressure of the urea water pump 31 does not reach the specified value (second threshold) within a certain time after the discharge pressure of the urea water pump 31 reaches the predetermined threshold. If the discharge pressure of the urea water pump 31 does not reach the specified value (second threshold) within a certain time after the discharge pressure of the urea water pump 31 reaches the predetermined threshold, the urea SCR system 23 Then, the urea water pump 31 is operated to the urea water return side. After the urea water in the urea water pipe 26 and the urea water supply device 30 is discharged into the urea water tank 25 through the urea water pipe 26, the urea SCR system 23 supplies the urea water pump 31 to the urea water again. And the urea water is supplied to the urea water injection valve 24.
  • the urea water pump 31 When the urea water pump 31 does not reach the specified value (second threshold) while the urea water pump 31 repeats the urea water supply side operation and the urea water return side operation a plurality of times.
  • the urea SCR system 23 determines that the startup operation has failed, and the urea SCR system 23 is stopped.
  • the urea SCR system 23 shifts to a urea water supply operation after the start-up operation is successful, and purifies the exhaust gas discharged from the engine 9 when the hydraulic excavator 1 is operated.
  • the urea water pump 31 operates on the urea water supply side.
  • the urea water in the urea water tank 25 is supplied to the urea water injection valve 24 through the tank side urea water pipe 27, the urea water filter 34, the injection valve side urea water pipe 28, and the like. Therefore, the urea water is injected from the urea water injection valve 24 to the upstream side of the urea selective reduction catalyst 21 (in the connection pipe 18).
  • the other end 27 ⁇ / b> B of the tank-side urea water conduit 27 is open to the bottom surface position of the filter case 35. Therefore, after the urea SCR system 23 finishes the after-run operation, the liquid level L of the urea water in the filter case 35 is lowered to the position indicated by the two-dot chain line in FIG. Most of it can be discharged. For this reason, when the urea SCR system 23 performs a start-up operation, the air in the filter case 35 can be discharged until the urea water from the urea water tank 25 is filled in the filter case 35 of the urea water filter 34. .
  • the air in the filter case 35 passes through the injection valve side urea water pipe 28 to form urea.
  • the gas is discharged into the exhaust gas purification device 14 through the water injection valve 24 and discharged into the air layer portion of the urea water tank 25 through the urea water return pipe 29.
  • the start-up operation before the urea water reaches the urea water injection valve 24 or the throttle 33 of the urea water supply device 30, the air remaining in the urea water pipe 26 can be discharged. As a result, a decrease in the discharge pressure of the urea water pump 31 due to air flowing into the urea water pump 31 can be suppressed. Therefore, by increasing the discharge pressure of the urea water pump 31 to a specified value suitable for injecting the urea water from the urea water injection valve 24, the start-up operation can be rapidly completed.
  • the urea water remaining in the filter case 35 of the urea water filter 34 may freeze after the end of the after-run operation.
  • the filter element 36 provided in the filter case 35 may be damaged by the frozen urea water.
  • the power from the power source 38 is supplied to the heating wire 37B of the heater 37.
  • the heater 37 generates heat in the filter case 35 and the frozen urea water frozen in the filter case 35 is thawed.
  • the heater 37 since the heater 37 is located inside the filter element 36 and is disposed in the center of the filter case 35, the heat generated by the heater 37 is evenly transferred to the frozen urea water in the filter case 35. be able to.
  • the frozen urea water can be efficiently thawed by the heater 37 and the filter element 36 can be prevented from being damaged by the frozen urea water, so that the reliability of the urea water filter 34 can be improved.
  • the exhaust gas purification device 14 injects urea selective reduction catalyst 21 for removing nitrogen oxides in exhaust gas and urea water as a reducing agent upstream of the urea selective reduction catalyst 21.
  • a urea water supply device 30 that is provided in the middle of the water pipe 26 and supplies urea water from the urea water tank 25 toward the urea water injection valve 24, and is located between the urea water tank 25 and the urea water supply device 30.
  • a urea water filter 34 is provided in the middle of the urea water pipe 26 and collects foreign matters mixed in the urea water.
  • the urea water filter 34 includes a filter case 35 having a top plate 35B and a bottom plate 35C and a container for storing urea water therein, and a filter case 35 for collecting foreign matter mixed in the urea water.
  • the filter element 36 is divided into a pre-filtration chamber 35E for storing urea water before foreign matter is filtered and a post-filtration chamber 35F for storing urea water after foreign matter is filtered.
  • a heater 37 for thawing the urea water frozen in the filter case 35 is provided in the center portion (in the post-filtration chamber 35F) of the filter case 35.
  • One end 27A of the urea water conduit 26 has a urea water tank.
  • the other end 27B is located in the pre-filtration chamber 35E and opened to the bottom surface of the filter case 35, and the one end 28A is in the post-filtration chamber 35F. Open to the upper surface position of the filter case 35 is located, the other end 28B is composed of the injection valve side urea water pipe 28 connected to the urea water injection valve 24.
  • the urea SCR system 23 finishes the after-run operation, most of the urea water in the filter case 35 can be discharged to the urea water tank 25 through the tank side urea water pipe 27. For this reason, when the urea SCR system 23 performs a start-up operation, the air in the filter case 35 can be discharged until the urea case is filled with the urea case. Thereby, even if air is mixed in the urea water flowing into the filter case 35 through the tank-side urea water pipe line 27, the urea water and the air can be separated in the filter case 35. For this reason, only air can be discharged before the urea water through the injection valve side urea water pipe 28 and the like.
  • the start-up operation before the urea water reaches the urea water injection valve 24 or the throttle 33 of the urea water supply device 30, the air remaining in the urea water pipe 26 can be discharged. As a result, a decrease in the discharge pressure of the urea water pump 31 due to air flowing into the urea water pump 31 can be suppressed. Therefore, the start-up operation can be rapidly completed by raising the discharge pressure of the urea water pump 31 to a specified value suitable for injecting the urea water from the urea water injection valve 24.
  • the heater 37 arranged in the state of extending upward and downward at the central portion (axial center position) of the filter case 35.
  • the heat from the heater 37 can be evenly transferred to the frozen urea water in the filter case 35.
  • the frozen urea water can be efficiently thawed by the heater 37, and the filter element 36 can be prevented from being damaged by the frozen urea water.
  • FIG. 6 and FIG. 7 show a second embodiment of the present invention, and the feature of the second embodiment is that the urea water filter and the urea water supply device are provided in the injection valve side urea water pipe.
  • an expansion chamber forming body which forms an expansion chamber which is located between them and has a cross-sectional area larger than the pipe area of the injection valve side urea water pipe.
  • the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
  • the injection valve side urea water pipe 41 is used in the second embodiment in place of the injection valve side urea water pipe 28 according to the first embodiment.
  • the injection valve side urea water pipe 41 connects the urea water filter 34 and the urea water injection valve 24, and an expansion chamber forming body 42 described later is provided in the middle of the injection valve side urea water pipe 41. ing.
  • One end 41 ⁇ / b> A of the injection valve side urea water pipe 41 opens to the upper surface position of the filter case 35 (between the upper surface plate 35 ⁇ / b> B of the filter case 35 and the upper end 36 ⁇ / b> A of the filter element 36).
  • the end 41B is connected to the urea water injection valve 24.
  • the expansion chamber forming body 42 is located between the urea water pump 31 and the urea water filter 34 of the urea water supply device 30 and is provided in the middle of the injection valve side urea water pipe 41.
  • the expansion chamber forming body 42 is formed, for example, as a cylindrical body surrounded by a cylindrical peripheral wall plate 42A, an upper surface plate 42B that closes the upper end of the peripheral wall plate 42A, and a bottom surface plate 42C that closes the lower end of the peripheral wall plate 42A. ing.
  • An expansion chamber 43 is formed inside the expansion chamber forming body 42, and the cross-sectional area of the expansion chamber 43 is set larger than the pipe area of the injection valve side urea water pipe 41.
  • the pressure energy of the urea water flowing backward from the injection valve side urea water pipe 41 to the urea water filter 34 in the start-up operation is, for example, the expansion of the expansion chamber forming body 42 having a large cross-sectional area, similarly to the silencing action by the expansion silencer. Diversified in the chamber 43 and converged in the injection valve side urea water pipe 41 having a small cross-sectional area. Accordingly, the pressure energy of the urea water is attenuated by the expansion chamber 43 of the expansion chamber forming body 42 before flowing into the urea water filter 34.
  • the discharge pressure of the urea water pump 31 does not reach a specified value suitable for injecting urea water from the urea water injection valve 24 within a certain time.
  • the urea SCR system 23 operates the urea water pump 31 to the urea water return side. Thereby, the urea water in the urea water supply device 30 and the urea water pipe 26 is returned to the urea water tank 25.
  • the pressure between the urea water pump 31 and the urea water injection valve 24 in the injection valve side urea water pipe 41 is released, urea water having a large pressure energy is injected into the injection valve side urea water pipe 41. Then, it flows backward to the urea water filter 34 side. For this reason, the air in the urea water supply device 30 and the urea water excessively flow into the urea water filter 34 and the tank side urea water pipe 27.
  • an expansion chamber forming body 42 is provided in the middle of the injection valve side urea water pipe 41. For this reason, even when urea water having large pressure energy flows backward from the injection valve side urea water pipe 41 to the urea water filter 34, the pressure energy of the urea water is expanded by the expansion chamber forming body 42 having a large cross-sectional area. It is attenuated by diverging in the chamber 43 and converging in the injection valve side urea water pipe 41 having a small sectional area.
  • the air in the urea water supply device 30 and the urea water are prevented from excessively flowing into the urea water filter 34 and the tank side urea water pipe 27, and the air mixed in the urea water flows into the urea water pump 31. It is the structure which can suppress this.
  • the exhaust gas purifying apparatus has the above-described configuration.
  • One end 41A of the injection valve side urea water pipe 41 opens to the upper surface position of the filter case 35, and the tank side urea water pipe
  • the other end 27 ⁇ / b> B of the opening 27 is open at the bottom surface position of the filter case 35.
  • the air in the filter case 35 is on the injection valve side.
  • the urea water pipe 41 is discharged into the exhaust gas purification device 14 (exhaust pipe 10) through the urea water injection valve 24, and is discharged into the air layer of the urea water tank 25 through the urea water return pipe 29.
  • the urea SCR system 23 when the urea SCR system 23 performs a start-up operation, if the discharge pressure of the urea water pump 31 does not reach a specified value suitable for injecting the urea water from the urea water injection valve 24, the urea SCR The system 23 operates the urea water pump 31 to the urea water return side. Thereby, the urea water in the urea water supply device 30 and the urea water pipe 26 is returned to the urea water tank 25. At this time, the pressure between the urea water pump 31 and the urea water injection valve 24 in the injection valve side urea water pipe 41 is released, so that urea water having large pressure energy passes through the injection valve side urea water pipe 41. It flows backward to the urea water filter 34 side. As a result, the air in the urea water supply device 30 and the urea water excessively flow into the urea water filter 34 and the tank side urea water pipe 27.
  • an expansion chamber forming body 42 is provided in the middle of the injection valve side urea water pipe 41.
  • the pressure energy of the urea water is expanded into the expansion chamber of the expansion chamber forming body 42 having a large cross-sectional area. It can diverge within 43 and can be made to converge and attenuate in the injection valve side urea water pipe 41 having a small cross-sectional area. Thereby, it can suppress that the air in the urea water supply apparatus 30 and urea water flow into the urea water filter 34 and the tank side urea water pipe 27 excessively.
  • the discharge pressure of the urea water pump 31 can be quickly increased to a specified value suitable for injecting urea water from the urea water injection valve 24.
  • FIG. 8 shows a third embodiment of the present invention.
  • the feature of the third embodiment is that an expansion chamber forming body is integrally provided on the upper surface of the filter case. Note that in the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
  • the injection valve side urea water pipe 51 is used in the third embodiment in place of the injection valve side urea water pipe 28 according to the first embodiment.
  • the injection valve side urea water pipe 51 connects the urea water filter 34 and the urea water injection valve 24, and an expansion chamber forming body 52 described later is provided in the middle of the injection valve side urea water pipe 51. ing.
  • One end 51 ⁇ / b> A of the injection valve side urea water pipe 51 opens to the upper surface position of the filter case 35 (between the upper surface plate 35 ⁇ / b> B of the filter case 35 and the upper end 36 ⁇ / b> A of the filter element 36).
  • the other end (not shown) of the injection valve side urea water pipe 51 is connected to the urea water injection valve 24.
  • the expansion chamber forming body 52 is integrally provided on the upper surface plate 35B of the filter case 35 constituting the urea water filter 34.
  • the expansion chamber forming body 52 includes a cylindrical peripheral wall plate 52A having a smaller outer diameter than the filter case 35, an upper surface plate 52B that closes the upper end of the peripheral wall plate 52A, and a bottom surface plate 52C that closes the lower end of the peripheral wall plate 52A. It is formed as a cylindrical body surrounded by.
  • the expansion chamber forming body 52 is disposed concentrically with the filter case 35, and the bottom plate 52C of the expansion chamber forming body 52 is fixed to the upper surface plate 35B of the filter case 35 by means such as welding or bonding.
  • An expansion chamber 53 is formed inside the expansion chamber forming body 52, and the cross-sectional area of the expansion chamber 53 is set larger than the pipe area of the injection valve side urea water pipe 51. Accordingly, the pressure energy of the urea water flowing back from the injection valve side urea water pipe 51 to the urea water filter 34 in the start-up operation is diffused in the expansion chamber 53 of the expansion chamber forming body 52 having a large cross-sectional area, and the injection having a small cross-sectional area. It converges in the valve side urea water pipe 51. Thus, the pressure energy of the urea water is attenuated by the expansion chamber 53 of the expansion chamber forming body 52 before flowing into the urea water filter 34.
  • the exhaust gas purifying apparatus has the above-described configuration, and the basic action thereof is not particularly different from that according to the second embodiment described above.
  • the expansion chamber forming body 52 that forms the expansion chamber 53 is integrally provided on the upper surface plate 35 ⁇ / b> B of the filter case 35 that constitutes the urea water filter 34.
  • a large expansion chamber having a cross-sectional area comparable to that of the filter case 35 can be provided, and the pressure energy of the urea water flowing backward from the injection valve side urea water pipe 51 to the urea water filter 34 in the startup operation can be efficiently obtained. Can be attenuated.
  • the other end 27B of the tank-side urea water conduit 27 is inserted upward into the bottom plate 35C of the filter case 35 constituting the urea water filter 34, so that the bottom surface of the filter case 35 is obtained.
  • the case where it opened to the position is illustrated.
  • the present invention is not limited to this.
  • the first modification shown in FIG. 9 or the second modification shown in FIG. 10 may be configured.
  • the other end 27B ′ of the tank-side urea water pipe 27 ′ is located on the lower side (bottom plate 35C) of the peripheral wall plate 35A of the filter case 35 constituting the urea water filter 34. It is good also as a structure opened to the bottom face position of the filter case 35 by being penetrated by the horizontal direction (horizontal direction). Further, one end 28A ′ of the injection valve side urea water conduit 28 ′ is bent in an L shape, and this one end 28A ′ is inserted downward into the upper surface plate 35B of the filter case 35, whereby the upper surface of the filter case 35 is It is good also as a structure opened to a position.
  • the other end 27B ′ side of the tank side urea water pipe line 27 ′ and the one end 28A ′ side of the injection valve side urea water pipe line 28 ′ extend in the horizontal direction with respect to the urea water filter 34.
  • the other end 27B ′′ side of the tank side urea water conduit 27 ′′ is directed from the upper surface plate 35B of the filter case 35 constituting the urea water filter 34 toward the bottom surface plate 35C. It is good also as a structure opened to the bottom face position of the filter case 35 by inserting downward.
  • a urea water pump 31 operable in two directions, a urea water supply side for supplying urea water to the urea water injection valve 24 and a urea water return side for returning urea water to the urea water tank 25 is used.
  • the case where the urea water supply apparatus 30 is comprised is illustrated.
  • the present invention is not limited to this, and for example, a urea water supply device 61 as in the third modification shown in FIG. 11 may be configured.
  • the urea water supply device 61 shown in FIG. 11 includes a urea water pump 62 that is provided in the middle of the injection valve side urea water pipe 28 and discharges urea water only in one direction, a direction control valve 63, and a first check.
  • the valve 64 and the second check valve 65 are configured.
  • the direction control valve 63 is composed of, for example, a 4-port 2-position electromagnetic valve, and is switched between a valve position (a) and a valve position (b). Therefore, even when the urea water pump 62 that discharges urea water only in one direction is used, the urea water in the injection valve side urea water pipe 28 is converted to urea water by switching the direction control valve 63 to the valve position (a).
  • the filter 34 can be circulated toward the urea water injection valve 24. Further, by switching the direction control valve 63 to the valve position (b), the urea water in the injection valve side urea water conduit 28 can be circulated from the urea water injection valve 24 toward the urea water filter 34.
  • the heater 37 in which the heating wire 37B for heating is provided in the cylinder 37A is used as a thawing device is illustrated.
  • a cylinder may be disposed in the center of the filter case 35 and a part of the engine coolant may be introduced into the cylinder.
  • the heater 37 may be disposed at a position slightly deviated from the central portion (axial center position) of the filter case 35.
  • the crawler excavator 1 is illustrated as a construction machine on which the exhaust gas purifying device 14 is mounted.
  • the present invention is not limited to this, and can be widely applied to construction machines equipped with engines such as wheel-type hydraulic excavators and wheel loaders.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Component Parts Of Construction Machinery (AREA)

Abstract

An exhaust gas purification device (14) is provided with a urea selective catalytic reduction catalyst (21), a urea-water solution injection valve (24), a urea-water solution tank (25), a urea-water solution conduit (26), a urea-water solution supply device (30), and a urea-water solution filter (34). A heater (37) for thawing a urea-water solution frozen within a filter case (35) which constitutes the urea-water solution filter (34) is provided at the center (position of axis) of the inside of the filter case (35). The urea-water solution conduit (26) is constituted by: a tank-side urea-water solution conduit (27) having one end (27A) which is connected to the urea-water solution tank (25), and having the other end (27B) which is open, within an unfiltered-solution chamber (35E), to the bottom surface of the filter case (35); and an injection valve-side urea-water solution conduit (28) having one end (28A) which is open, within a filtered-solution chamber (35F), to the upper surface of the filter case (35), and having the other end (28B) connected to the urea-water solution injection valve (24).

Description

排気ガス浄化装置Exhaust gas purification device
　本発明は、例えば油圧ショベル等の建設機械に搭載され、エンジンから排出される排気ガス中の有害物質を除去する排気ガス浄化装置に関する。 The present invention relates to an exhaust gas purification device that is mounted on a construction machine such as a hydraulic excavator and removes harmful substances in exhaust gas discharged from an engine.
　一般に、油圧ショベル等の建設機械には、エンジン（内燃機関）から排出される排気ガスに含まれる有害物質を除去するための排気ガス浄化装置が搭載されている。この種の排気ガス浄化装置に用いられる尿素ＳＣＲシステムは、尿素選択還元触媒と、尿素水噴射弁と、尿素水タンクと、尿素水管路と、尿素水供給装置（尿素水ポンプ）とを備えている。尿素選択還元触媒は、エンジンの排気管に接続され排気ガス中の窒素酸化物を除去する。尿素水噴射弁は、還元剤である尿素水を尿素選択還元触媒の上流側に噴射する。尿素水タンクは、尿素水噴射弁に供給される尿素水を貯える。尿素水管路は、尿素水タンクと尿素水噴射弁との間を接続する。尿素水供給装置は、尿素水管路の途中に設けられ尿素水タンクから尿素水噴射弁に向けて尿素水を供給する。 Generally, a construction machine such as a hydraulic excavator is equipped with an exhaust gas purification device for removing harmful substances contained in exhaust gas discharged from an engine (internal combustion engine). The urea SCR system used in this type of exhaust gas purification device includes a urea selective reduction catalyst, a urea water injection valve, a urea water tank, a urea water pipe, and a urea water supply device (urea water pump). Yes. The urea selective reduction catalyst is connected to the exhaust pipe of the engine and removes nitrogen oxides in the exhaust gas. The urea water injection valve injects urea water, which is a reducing agent, upstream of the urea selective reduction catalyst. The urea water tank stores urea water supplied to the urea water injection valve. The urea water pipe line connects between the urea water tank and the urea water injection valve. The urea water supply device is provided in the middle of the urea water pipe and supplies urea water from the urea water tank toward the urea water injection valve.
　尿素水タンク内に蓄えられる尿素水は、定期的に補充する必要がある。尿素水の補充作業は、尿素水タンクのキャップを外した状態で行われるため、尿素水に異物（コンタミネーション）が混入することがある。尿素水に混入した異物は、尿素水供給装置や尿素水噴射弁の内部に侵入することにより、尿素水噴射弁に対する尿素水の供給や、尿素水噴射弁からの適正な尿素水の噴射を阻害する。これに対し、尿素水タンクと尿素水噴射弁との間を接続する尿素水管路の途中に尿素水フィルタを設け、この尿素水フィルタによって尿素水に混入した異物を捕集することが知られている（特許文献１参照）。 The urea water stored in the urea water tank needs to be replenished regularly. Since the urea water replenishment operation is performed with the cap of the urea water tank removed, foreign matter (contamination) may be mixed in the urea water. Foreign matter mixed in the urea water penetrates into the urea water supply device and the urea water injection valve, thereby inhibiting the urea water supply to the urea water injection valve and the proper urea water injection from the urea water injection valve. To do. On the other hand, it is known that a urea water filter is provided in the middle of the urea water pipe connecting the urea water tank and the urea water injection valve, and foreign substances mixed in the urea water are collected by the urea water filter. (See Patent Document 1).
　また、尿素水は－１１℃以下で凍結する。このため、尿素ＳＣＲシステムが搭載された油圧ショベルを寒冷地で使用する場合には、尿素水タンク、尿素水噴射弁、尿素水供給装置、尿素水管路等の内部で尿素水が凍結することにより、尿素ＳＣＲシステムが適正に機能しなくなる不具合がある。これに対し、エンジン冷却水が流れる冷却水配管を用いて尿素水タンクおよび尿素水管路を温めることにより、これら尿素水タンクおよび尿素水管路の内部で尿素水が凍結するのを防止することが知られている（特許文献２参照）。 Also, urea water freezes at -11 ° C or lower. For this reason, when a hydraulic excavator equipped with a urea SCR system is used in a cold region, the urea water freezes inside the urea water tank, urea water injection valve, urea water supply device, urea water pipe, etc. There is a problem that the urea SCR system does not function properly. On the other hand, it is known that the urea water tank and the urea water pipe line are warmed by using the cooling water pipe through which the engine cooling water flows to prevent the urea water from freezing inside the urea water tank and the urea water pipe line. (See Patent Document 2).
　一方、例えばエンジンからの熱によって尿素水噴射弁が高温になると、エンジンが停止した後に尿素水噴射弁に残留した尿素水中の水分が蒸発する。このため、尿素が結晶化して析出して尿素水噴射弁に付着することにより、尿素水噴射弁から尿素水を噴射することができなくなる不具合がある。 On the other hand, for example, when the urea water injection valve becomes hot due to heat from the engine, the water in the urea water remaining in the urea water injection valve evaporates after the engine is stopped. For this reason, there exists a malfunction which cannot inject urea water from a urea water injection valve by urea crystallizing and depositing and adhering to a urea water injection valve.
　このため、尿素水ＳＣＲシステムは、エンジンが停止した後に、尿素水ポンプによって尿素水タンク内に尿素水を戻す動作（以下、アフターラン動作という）を行う。これにより、尿素水ＳＣＲシステムは、尿素水噴射弁、尿素水管路、尿素水供給装置等に残留した尿素水が凍結したり、尿素水噴射弁に残留した尿素水が蒸発して結晶化するのを防止している。 For this reason, the urea water SCR system performs an operation of returning urea water into the urea water tank by the urea water pump (hereinafter referred to as after-run operation) after the engine is stopped. As a result, the urea water SCR system freezes the urea water remaining in the urea water injection valve, the urea water pipe, the urea water supply device, etc., or the urea water remaining in the urea water injection valve evaporates and crystallizes. Is preventing.
　このように、エンジンを停止した後にはアフターラン動作によって尿素水が尿素水タンク内に戻されている。従って、エンジンの始動時には、尿素ＳＣＲシステムは、尿素水タンク内の尿素水を尿素水噴射弁に供給すると共に、尿素水ポンプの吐出圧を、尿素水噴射弁から尿素水を噴射させるのに適した圧力まで上昇させる制御（以下、スタートアップ動作）を行う。 As described above, after the engine is stopped, the urea water is returned to the urea water tank by the after-run operation. Therefore, when starting the engine, the urea SCR system is suitable for supplying urea water in the urea water tank to the urea water injection valve and for injecting urea water from the urea water injection valve by using the discharge pressure of the urea water pump. Control to increase the pressure (hereinafter referred to as start-up operation).
　スタートアップ動作を行うときには、尿素ＳＣＲシステムは、尿素水噴射弁を開弁させた状態で尿素水ポンプを尿素水供給側に作動させ、尿素水管路および尿素水供給装置内に残留した空気を尿素水噴射弁を通じて排気管内に排出する。そして、尿素水が尿素水噴射弁に達し、尿素水ポンプの吐出圧が所定の閾値に達すると、尿素ＳＣＲシステムは、尿素水噴射弁を閉弁させる。この状態で、尿素水ポンプの吐出圧が、尿素水噴射弁から尿素水を噴射させるのに適した規定値に達すると、尿素ＳＣＲシステムは、スタートアップ動作が成功したと判定する。そして、尿素ＳＣＲシステムは、尿素水噴射弁から尿素選択還元触媒の上流側に向けて尿素水を噴射する動作（以下、尿素水供給動作という）に移行する。 When the start-up operation is performed, the urea SCR system operates the urea water pump to the urea water supply side with the urea water injection valve opened, and the urea water is supplied to the urea water pipe line and the urea water supply device. It is discharged into the exhaust pipe through the injection valve. When the urea water reaches the urea water injection valve and the discharge pressure of the urea water pump reaches a predetermined threshold, the urea SCR system closes the urea water injection valve. In this state, when the discharge pressure of the urea water pump reaches a specified value suitable for injecting urea water from the urea water injection valve, the urea SCR system determines that the start-up operation is successful. Then, the urea SCR system shifts to an operation of injecting urea water from the urea water injection valve toward the upstream side of the urea selective reduction catalyst (hereinafter referred to as urea water supply operation).
　一方、スタートアップ動作において、尿素水噴射弁が閉弁した後に、一定時間内に尿素水ポンプの吐出圧が上述した規定値に達しないことがある。この場合には、尿素ＳＣＲシステムは、尿素水ポンプを一時的に尿素水戻し側に作動させて尿素水を尿素水タンク内に戻した後、再び尿素水ポンプを尿素水供給側に作動させることにより、尿素水噴射弁に尿素水を供給する。そして、尿素水ポンプの作動が尿素水供給側と尿素水戻し側とに複数回にわたって繰返される間に、尿素水ポンプの吐出圧が上述の規定値に達しない場合には、尿素ＳＣＲシステムはスタートアップ動作が失敗したと判定し、尿素ＳＣＲシステムは停止する。 On the other hand, in the start-up operation, after the urea water injection valve is closed, the discharge pressure of the urea water pump may not reach the specified value within a certain time. In this case, the urea SCR system temporarily operates the urea water pump to the urea water return side to return the urea water to the urea water tank, and then operates the urea water pump to the urea water supply side again. Thus, urea water is supplied to the urea water injection valve. If the urea water pump discharge pressure does not reach the specified value while the operation of the urea water pump is repeated a plurality of times on the urea water supply side and the urea water return side, the urea SCR system starts up. It is determined that the operation has failed, and the urea SCR system stops.
　ここで、尿素水に混入した異物を捕集する尿素水フィルタは、尿素水タンクと尿素水ポンプとの間に位置して尿素水管路の途中に設けられている。尿素水フィルタは、内部に尿素水を貯留するフィルタケースと、フィルタケース内に設けられたフィルタエレメントとにより構成されている。そして、フィルタケースには、尿素水タンクからの尿素水が流入する尿素水管路の流入口と、尿素水供給装置に向けて尿素水が流出する尿素水管路の流出口とが接続されている。これら尿素水管路の流入口と流出口とは、通常、フィルタエレメントを交換するときの作業性等を考慮して、フィルタケースの上面側に開口している。 Here, the urea water filter that collects foreign matters mixed in the urea water is located between the urea water tank and the urea water pump and is provided in the middle of the urea water pipe. The urea water filter includes a filter case that stores urea water therein, and a filter element that is provided in the filter case. The filter case is connected to an inlet of a urea water pipe through which urea water from the urea water tank flows and an outlet of a urea water pipe through which urea water flows toward the urea water supply device. The inlet and outlet of these urea water pipes are normally open on the upper surface side of the filter case in consideration of workability when the filter element is replaced.
　ここで、尿素ＳＣＲシステムのスタートアップ動作時に、尿素水ポンプに供給される尿素水に空気が混入することがある。しかし、尿素水に混入した空気は、通常、尿素水が尿素水フィルタに流入したときに尿素水から分離される。尿素水フィルタ内の空気は、尿素水フィルタから尿素水が流出するのに先立って、尿素水噴射弁を通じて排気管内に排出される。従って、尿素水フィルタから尿素水ポンプに向けて空気を含まない尿素水を供給することができる。 Here, during the start-up operation of the urea SCR system, air may be mixed into the urea water supplied to the urea water pump. However, the air mixed in the urea water is normally separated from the urea water when the urea water flows into the urea water filter. Prior to the urea water flowing out from the urea water filter, the air in the urea water filter is discharged into the exhaust pipe through the urea water injection valve. Therefore, urea water that does not contain air can be supplied from the urea water filter toward the urea water pump.
特開２０１０－１９６５２２号公報JP 2010-196522 A 特開２０１１－２４１７３４号公報JP 2011-241734 A
　しかし、従来技術による尿素水フィルタのように、尿素水管路の流入口と流出口とがフィルタケースの上面側に開口している場合には、尿素ＳＣＲシステムのアフターラン動作が終了した後には、尿素水フィルタ（フィルタケース）内に多量の尿素水が残留する。従って、尿素ＳＣＲシステムがスタートアップ動作を開始すると、尿素水フィルタ内の尿素水は速やかに尿素水ポンプに向けて流出する。このため、尿素水に混入した空気を尿素水フィルタ内で分離し、尿素水噴射弁を通じて排気管内に排出することができない。 However, like the urea water filter according to the prior art, when the inlet and outlet of the urea water pipe are open on the upper surface side of the filter case, after the after-run operation of the urea SCR system is finished, A large amount of urea water remains in the urea water filter (filter case). Therefore, when the urea SCR system starts a start-up operation, the urea water in the urea water filter quickly flows out toward the urea water pump. For this reason, the air mixed in the urea water cannot be separated in the urea water filter and discharged into the exhaust pipe through the urea water injection valve.
　このため、尿素水に混入した空気が尿素水ポンプに流入（エア噛み）し、尿素水ポンプの吐出圧が低下する。これにより、尿素水ポンプの吐出圧を、尿素水噴射弁から尿素水を噴射させるのに適した規定値まで上昇させることができなくなる。この結果、尿素ＳＣＲシステムによるスタートアップ動作が失敗してしまうという問題がある。 For this reason, air mixed in the urea water flows into the urea water pump (air engagement), and the discharge pressure of the urea water pump decreases. As a result, the discharge pressure of the urea water pump cannot be increased to a specified value suitable for injecting urea water from the urea water injection valve. As a result, there is a problem that the start-up operation by the urea SCR system fails.
　一方、従来技術では、尿素水タンクおよび尿素水管路の内部で尿素水が凍結するのを防止するため、これら尿素水タンクおよび尿素水管路を保温することが提案されている。しかし、尿素ＳＣＲシステムによるアフターラン動作が終了した後には、尿素水フィルタのフィルタケース内に尿素水が残留する。このため、寒冷地等においては尿素水フィルタ（フィルタケース）内に残留した尿素水が凍結する。これにより、フィルタケース内で凍結した凍結尿素水によって、フィルタエレメントが破損してしまうという問題がある。 On the other hand, in the prior art, in order to prevent the urea water from freezing inside the urea water tank and the urea water pipe, it has been proposed to keep the temperature of the urea water tank and the urea water pipe. However, after the after-run operation by the urea SCR system is completed, urea water remains in the filter case of the urea water filter. For this reason, the urea water remaining in the urea water filter (filter case) freezes in a cold district or the like. Thereby, there exists a problem that a filter element will be damaged with the frozen urea water frozen in the filter case.
　本発明は上述した従来技術の問題に鑑みなされたもので、本発明の目的は、スタートアップ動作において尿素水供給装置から吐出される尿素水の吐出圧が低下するのを抑え、かつ尿素水フィルタ内で尿素水が凍結するのを抑えることができる排気ガス浄化装置を提供することにある。 The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to suppress a decrease in the discharge pressure of urea water discharged from the urea water supply device in a start-up operation, and It is an object of the present invention to provide an exhaust gas purifying device that can prevent the urea water from freezing.
　上記課題を解決するために本発明は、エンジンの排気管に接続され排気ガス中の窒素酸化物を除去する尿素選択還元触媒と、還元剤である尿素水を前記尿素選択還元触媒の上流側に噴射する尿素水噴射弁と、前記尿素水噴射弁に供給される尿素水を貯える尿素水タンクと、前記尿素水タンクと前記尿素水噴射弁との間を接続する尿素水管路と、前記尿素水管路の途中に設けられ前記尿素水タンクから前記尿素水噴射弁に向けて尿素水を供給する尿素水供給装置と、前記尿素水タンクと前記尿素水供給装置との間に位置して前記尿素水管路の途中に設けられ尿素水に混入した異物を捕集する尿素水フィルタとを備えてなる排気ガス浄化装置に適用される。 In order to solve the above problems, the present invention provides a urea selective reduction catalyst connected to an exhaust pipe of an engine to remove nitrogen oxides in exhaust gas, and urea water as a reducing agent upstream of the urea selective reduction catalyst. A urea water injection valve that injects, a urea water tank that stores urea water supplied to the urea water injection valve, a urea water pipe that connects between the urea water tank and the urea water injection valve, and the urea water pipe A urea water supply device that is provided in the middle of the road and supplies urea water from the urea water tank toward the urea water injection valve; and the urea water pipe positioned between the urea water tank and the urea water supply device The present invention is applied to an exhaust gas purification device provided with a urea water filter that is provided in the middle of the road and collects foreign matters mixed in urea water.
　本発明の特徴は、前記尿素水フィルタは、上面と底面とを有し内部に尿素水を貯留する容器からなるフィルタケースと、尿素水に混入した異物を捕集するために前記フィルタケース内に設けられ、前記フィルタケース内を異物が濾過される前の尿素水を貯留する濾過前室と異物が濾過された後の尿素水を貯留する濾過後室とに分けるフィルタエレメントとを有し、前記フィルタケースの前記濾過後室内には、前記フィルタケース内で凍結した尿素水を解凍する解凍装置が設けられ、前記尿素水管路は、一端が前記尿素水タンクに接続され、他端が前記フィルタケースの前記濾過前室内に位置して前記フィルタケースの底面位置に開口したタンク側尿素水管路と、一端が前記フィルタケースの前記濾過後室内に位置して前記フィルタケースの上面位置に開口し、他端が前記尿素水噴射弁に接続された噴射弁側尿素水管路とにより構成されていることにある。 A feature of the present invention is that the urea water filter includes a filter case having a top surface and a bottom surface and a container for storing urea water therein, and the filter case for collecting foreign matter mixed in the urea water. Provided with a filter element that divides the inside of the filter case into a pre-filtration chamber for storing urea water before foreign matter is filtered and a post-filtration chamber for storing urea water after foreign matter is filtered, A thawing device for thawing urea water frozen in the filter case is provided in the post-filter chamber of the filter case, and one end of the urea water conduit is connected to the urea water tank, and the other end is the filter case. A tank-side urea water pipe that is located in the pre-filtration chamber and opened to the bottom surface of the filter case, and one end of the tank-side urea water conduit is located in the post-filtration chamber of the filter case. Open to the surface position, the other end is in that it is constituted by a connected injector side urea water pipe to the urea water injection valve.
　本発明によれば、アフターラン動作によって、フィルタケース内の大部分の尿素水を、タンク側尿素水管路の他端から尿素水タンク内に戻すことができる。従って、スタートアップ動作によってフィルタケース内に尿素水が満たされるまでの間に、尿素水に混入した空気をフィルタケース内で分離し、この空気のみを尿素水よりも先に尿素水フィルタから排出することができる。この結果、尿素水に混入した空気が尿素水供給装置に流入することによる尿素水供給装置の吐出量の低下を抑えることができる。しかも、フィルタケース内には解凍装置が設けられている。このため、フィルタケース内に残留した尿素水が凍結したとしても、この凍結尿素水を中心部から外側に向けて効率良く解凍することができ、フィルタエレメントを保護することができる。 According to the present invention, by the after-run operation, most of the urea water in the filter case can be returned from the other end of the tank side urea water pipe to the urea water tank. Therefore, the air mixed in the urea water is separated in the filter case until the filter case is filled with the urea water by the start-up operation, and only this air is discharged from the urea water filter before the urea water. Can do. As a result, it is possible to suppress a decrease in the discharge amount of the urea water supply device due to the air mixed in the urea water flowing into the urea water supply device. In addition, a thawing device is provided in the filter case. For this reason, even if the urea water remaining in the filter case is frozen, the frozen urea water can be efficiently thawed from the central portion to the outside, and the filter element can be protected.
本発明の第１の実施の形態による排気ガス浄化装置が搭載された油圧ショベルを示す正面図である。1 is a front view showing a hydraulic excavator equipped with an exhaust gas purifying apparatus according to a first embodiment of the present invention. 上部旋回体をキャブ、建屋カバー等を省略した状態で示す平面図である。It is a top view which shows an upper revolving body in the state which omitted a cab, a building cover, etc. 尿素ＳＣＲシステムを概略的に示す構成図である。It is a block diagram which shows a urea SCR system schematically. 図３中の尿素水フィルタ、タンク側尿素水管路、噴射弁側尿素水管路、解凍装置を示す縦断面図である。It is a longitudinal cross-sectional view which shows the urea water filter, tank side urea water pipe line, injection valve side urea water pipe line, and thawing | decompression apparatus in FIG. フィルタケース、フィルタエレメント、タンク側尿素水管路、解凍装置を図４中の矢示Ｖ－Ｖ方向からみた横断面図である。FIG. 5 is a cross-sectional view of the filter case, the filter element, the tank side urea water pipe, and the thawing device as seen from the direction of arrows VV in FIG. 本発明の第２の実施の形態による尿素ＳＣＲシステムを概略的に示す構成図である。It is a block diagram which shows schematically the urea SCR system by the 2nd Embodiment of this invention. 図６中の尿素水フィルタ、拡張室形成体、タンク側尿素水管路、噴射弁側尿素水管路、解凍装置を示す縦断面図である。It is a longitudinal cross-sectional view which shows the urea water filter, expansion chamber formation body, tank side urea water pipe line, injection valve side urea water pipe line, and thawing device in FIG. 本発明の第３の実施の形態による尿素水フィルタ、拡張室形成体、タンク側尿素水管路、噴射弁側尿素水管路、解凍装置を示す図７と同様な縦断面図である。It is the same longitudinal cross-sectional view as FIG. 7 which shows the urea water filter by the 3rd Embodiment of this invention, an expansion chamber formation body, a tank side urea water pipe, an injection valve side urea water pipe, and a defroster. 本発明の第１の変形例を示す図４と同様な縦断面図である。It is the same longitudinal cross-sectional view as FIG. 4 which shows the 1st modification of this invention. 本発明の第２の変形例を示す図４と同様な縦断面図である。It is the same longitudinal cross-sectional view as FIG. 4 which shows the 2nd modification of this invention. 本発明の第３の変形例を示す図３と同様な尿素ＳＣＲシステムの構成図である。It is a block diagram of the urea SCR system similar to FIG. 3 which shows the 3rd modification of this invention.
　以下、本発明の実施の形態に係る排気ガス浄化装置を、クローラ式の油圧ショベルに適用した場合を例に挙げ、添付図面に従って詳細に説明する。 Hereinafter, an exhaust gas purifying apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking as an example a case where it is applied to a crawler type hydraulic excavator.
　図１ないし図５は本発明の第１の実施の形態を示している。油圧ショベル１は、自走可能なクローラ式の下部走行体２と、下部走行体２上に旋回可能に搭載された上部旋回体３と、上部旋回体３の前側に俯仰動可能に設けられ土砂の掘削作業等を行う作業装置４とにより構成されている。 1 to 5 show a first embodiment of the present invention. The excavator 1 is a self-propelled crawler type lower traveling body 2, an upper revolving body 3 that is turnably mounted on the lower traveling body 2, and an earth and sand provided on the front side of the upper revolving body 3 so as to be able to move up and down. It is comprised with the working apparatus 4 which performs the excavation work of this.
　上部旋回体３は、支持構造体をなす旋回フレーム５と、該旋回フレーム５の後側に設けられ、作業装置４との重量バランスをとるカウンタウエイト６と、旋回フレーム５の前部左側に設けられオペレータが搭乗するキャブ７と、カウンタウエイト６の前側に設けられた建屋カバー８とを含んで構成されている。建屋カバー８は、内部に後述のエンジン９、排気ガス浄化装置１４等を収容している。ここで、旋回フレーム５は、前，後方向に延びる底板５Ａと、底板５Ａ上に立設され前，後方向に延びた左縦板５Ｂ，右縦板５Ｃと、左縦板５Ｂの左側に配置され前，後方向に延びた左サイドフレーム５Ｄと、右縦板５Ｃの右側に配置され前，後方向に延びた右サイドフレーム５Ｅとを備えている。また、旋回フレーム５は、底板５Ａ、各縦板５Ｂ，５Ｃから左，右方向に張出した複数本の張出ビーム５Ｆと、エンジン９の前側に位置して底板５Ａ上に立設された連結板５Ｇとを含んで構成されている。張出ビーム５Ｆの先端部には、左，右のサイドフレーム５Ｄ，５Ｅが支持されている。連結板５Ｇは、左，右の縦板５Ｂ，５Ｃ間を連結している。連結板５Ｇの後面側には、後述する尿素水供給装置３０と尿素水フィルタ３４が取付けられている。 The upper revolving unit 3 is provided on the left side of the front part of the revolving frame 5, the revolving frame 5 that forms the support structure, the counterweight 6 that is provided on the rear side of the revolving frame 5 and that balances the weight with the work device 4. The cab 7 on which the operator is boarded and the building cover 8 provided on the front side of the counterweight 6 are configured. The building cover 8 accommodates an engine 9, an exhaust gas purification device 14 and the like, which will be described later, inside. Here, the revolving frame 5 has a bottom plate 5A extending in the front and rear directions, a left vertical plate 5B and a right vertical plate 5C standing on the bottom plate 5A and extending in the front and rear directions, and on the left side of the left vertical plate 5B. It is provided with a left side frame 5D that is disposed in the front and rear directions and a right side frame 5E that is disposed on the right side of the right vertical plate 5C and extends in the front and rear directions. The revolving frame 5 includes a bottom plate 5A, a plurality of extended beams 5F extending left and right from the vertical plates 5B and 5C, and a connection erected on the bottom plate 5A located on the front side of the engine 9. It is comprised including the board 5G. Left and right side frames 5D and 5E are supported at the tip of the overhanging beam 5F. The connecting plate 5G connects the left and right vertical plates 5B and 5C. A urea water supply device 30 and a urea water filter 34, which will be described later, are attached to the rear surface side of the connecting plate 5G.
　エンジン９は、カウンタウエイト６の前側に位置して旋回フレーム５上に左，右方向に延びる横置き状態で設けられている。このエンジン９の左側には、後述する熱交換器１１に冷却風を供給するための冷却ファン９Ａが設けられている。一方、エンジン９の右側には油圧ポンプ（図示せず）が設けられている。この油圧ポンプは、エンジン９によって駆動されることにより、後述の作動油タンク１２から供給される作動油を圧油として、油圧ショベル１に搭載された油圧アクチュエータに吐出する。 The engine 9 is located in front of the counterweight 6 and is provided in a horizontally placed state on the turning frame 5 extending left and right. On the left side of the engine 9, a cooling fan 9 </ b> A for supplying cooling air to a heat exchanger 11 described later is provided. On the other hand, a hydraulic pump (not shown) is provided on the right side of the engine 9. The hydraulic pump is driven by the engine 9 to discharge hydraulic oil supplied from a hydraulic oil tank 12 described later as hydraulic oil to a hydraulic actuator mounted on the hydraulic excavator 1.
　ここで、エンジン９には、排気ガスを外部に排出するための排気管１０が接続されている。この排気管１０は、エンジン９の前側を左，右方向に延びる金属製の管路として形成され、エンジン９から排出された高温の排気ガスを後述する第１の排気ガス後処理装置１５へと導く。 Here, an exhaust pipe 10 for discharging exhaust gas to the outside is connected to the engine 9. The exhaust pipe 10 is formed as a metal pipe line extending in the left and right directions on the front side of the engine 9, and the high-temperature exhaust gas discharged from the engine 9 is supplied to a first exhaust gas aftertreatment device 15 described later. Lead.
　熱交換器１１は、エンジン９の左側に配設されている。この熱交換器１１は、エンジン９の冷却ファン９Ａに対面して設けられている。熱交換器１１は、例えばエンジン９のウォータジャケット内を流通するエンジン冷却水を冷却するラジエータ、作動油を冷却するオイルクーラ、エンジン９が吸込む空気を冷却するインタクーラ等により構成されている。 The heat exchanger 11 is disposed on the left side of the engine 9. The heat exchanger 11 is provided so as to face the cooling fan 9 </ b> A of the engine 9. The heat exchanger 11 includes, for example, a radiator that cools engine cooling water that circulates in the water jacket of the engine 9, an oil cooler that cools hydraulic oil, an intercooler that cools air that the engine 9 sucks, and the like.
　作動油タンク１２は、油圧ポンプの前側に位置して旋回フレーム５の右側に設けられている。この作動油タンク１２は、下部走行体２、作業装置４等に設けられたアクチュエータを駆動するための作動油を貯えている。一方、燃料タンク１３は、作動油タンク１２の前側に位置して旋回フレーム５に設けられている。燃料タンク１３は、エンジン９に供給される燃料を貯えている。 The hydraulic oil tank 12 is located on the right side of the revolving frame 5 and is located on the front side of the hydraulic pump. The hydraulic oil tank 12 stores hydraulic oil for driving actuators provided in the lower traveling body 2, the work device 4, and the like. On the other hand, the fuel tank 13 is located on the front side of the hydraulic oil tank 12 and is provided on the revolving frame 5. The fuel tank 13 stores fuel supplied to the engine 9.
　排気ガス浄化装置１４は、エンジン９の右側に配置された浄化装置取付架台（図示せず）に取付けられている。排気ガス浄化装置１４は、エンジン９の排気管１０に接続され、エンジン９から排出される排気ガス中の有害物質を除去する。また、排気ガス浄化装置１４は、排気ガスの騒音を低減するための消音機構を備えている。図３に示すように、排気ガス浄化装置１４は、後述する第１の排気ガス後処理装置１５、接続管１８、第２の排気ガス後処理装置１９を含んで構成されている。 The exhaust gas purification device 14 is mounted on a purification device mounting base (not shown) disposed on the right side of the engine 9. The exhaust gas purification device 14 is connected to the exhaust pipe 10 of the engine 9 and removes harmful substances in the exhaust gas discharged from the engine 9. Further, the exhaust gas purification device 14 is provided with a silencer mechanism for reducing exhaust gas noise. As shown in FIG. 3, the exhaust gas purification device 14 includes a first exhaust gas aftertreatment device 15, a connecting pipe 18, and a second exhaust gas aftertreatment device 19 which will be described later.
　第１の排気ガス後処理装置１５は、排気管１０の出口側に接続されている。第１の排気ガス後処理装置１５は、前，後方向に延びる円筒状の筒体１６と、筒体１６内に設けられた酸化触媒１７とを含んで構成されている。ここで、筒体１６は、両端が閉塞された密閉容器として形成され、排気ガスの流れ方向の上流側となる前側部位には、排気管１０が接続されている。 The first exhaust gas aftertreatment device 15 is connected to the outlet side of the exhaust pipe 10. The first exhaust gas aftertreatment device 15 includes a cylindrical tube 16 extending in the front and rear directions, and an oxidation catalyst 17 provided in the tube 16. Here, the cylindrical body 16 is formed as a sealed container with both ends closed, and the exhaust pipe 10 is connected to a front side portion that is upstream in the flow direction of the exhaust gas.
　筒体１６内に配置された酸化触媒１７は、例えばセラミックス製のセル状筒体からなり、その軸方向に多数の貫通孔が形成され、内面に貴金属がコーティングされている。酸化触媒１７は、所定の温度下で各貫通孔に排気ガスを流通させることにより、排気ガス中に含まれる一酸化炭素（ＣＯ）、炭化水素（ＨＣ）等を酸化して除去する。また、酸化触媒１７は、必要に応じて粒子状物質（ＰＭ）を燃焼除去する。 The oxidation catalyst 17 disposed in the cylinder 16 is made of, for example, a ceramic cell-shaped cylinder, and has a large number of through holes formed in the axial direction thereof, and the inner surface is coated with a noble metal. The oxidation catalyst 17 oxidizes and removes carbon monoxide (CO), hydrocarbons (HC), and the like contained in the exhaust gas by causing the exhaust gas to flow through each through hole at a predetermined temperature. Further, the oxidation catalyst 17 burns and removes particulate matter (PM) as necessary.
　接続管１８は、第１の排気ガス後処理装置１５と第２の排気ガス後処理装置１９との間を接続している。接続管１８は、筒体１６と平行して前，後方向に延びる円筒状の筒部１８Ａと、筒部１８Ａの上流側となる入口側の端縁を閉塞する上流蓋部１８Ｂと、筒部１８Ａの下流側となる出口側の端縁を閉塞する下流蓋部１８Ｃとにより構成されている。上流蓋部１８Ｂには、後述の尿素水噴射弁２４が取付けられている。 The connecting pipe 18 connects between the first exhaust gas aftertreatment device 15 and the second exhaust gas aftertreatment device 19. The connecting pipe 18 includes a cylindrical tube portion 18A extending in the front and rear directions in parallel with the tube body 16, an upstream lid portion 18B that closes an edge on the inlet side that is the upstream side of the tube portion 18A, and a tube portion. It is comprised by the downstream cover part 18C which obstruct | occludes the edge of the exit side used as the downstream of 18A. A urea water injection valve 24 described later is attached to the upstream lid portion 18B.
　第２の排気ガス後処理装置１９は、第１の排気ガス後処理装置１５の右上方に配置されている。第２の排気ガス後処理装置１９は、接続管１８の出口側に接続され、第１の排気ガス後処理装置１５と平行して前，後方向に延びる円筒状の筒体２０と、筒体２０内に設けられた尿素選択還元触媒２１と、尿素選択還元触媒２１の下流側に配置された酸化触媒２２とにより構成されている。 The second exhaust gas aftertreatment device 19 is arranged on the upper right side of the first exhaust gas aftertreatment device 15. The second exhaust gas aftertreatment device 19 is connected to the outlet side of the connection pipe 18 and has a cylindrical cylinder 20 extending in the front and rear directions in parallel with the first exhaust gas aftertreatment device 15, and a cylinder The urea selective reduction catalyst 21 provided in 20 and the oxidation catalyst 22 arranged on the downstream side of the urea selective reduction catalyst 21 are configured.
　尿素選択還元触媒２１は、後述する尿素ＳＣＲシステム２３の一部を構成し、排気ガス中の窒素酸化物を除去する。尿素選択還元触媒２１は、例えばセラミックス製のセル状筒体からなり、軸方向に多数の貫通孔が形成され、内面に貴金属がコーティングされている。尿素選択還元触媒２１は、エンジン９から排出された排気ガスに含まれる窒素酸化物（ＮＯｘ）を、尿素水溶液（尿素水）から生成されたアンモニアによって選択的に還元反応させ、窒素と水に分解する。 The urea selective reduction catalyst 21 constitutes a part of a urea SCR system 23 described later, and removes nitrogen oxides in the exhaust gas. The urea selective reduction catalyst 21 is made of, for example, a ceramic tubular body made of ceramics. A large number of through holes are formed in the axial direction, and the inner surface is coated with a noble metal. The urea selective reduction catalyst 21 selectively reduces the nitrogen oxide (NOx) contained in the exhaust gas discharged from the engine 9 by ammonia generated from the urea aqueous solution (urea water), and decomposes it into nitrogen and water. To do.
　酸化触媒２２は、尿素選択還元触媒２１よりも排気ガスの流れ方向の下流側に設けられている。この酸化触媒２２は、前述した第１の排気ガス後処理装置１５の酸化触媒１７とほぼ同様に、セラミックス製のセル状筒体からなっている。酸化触媒２２の軸方向には多数の貫通孔が形成され、その内面には貴金属がコーティングされている。第２の排気ガス後処理装置１９の酸化触媒２２は、尿素選択還元触媒２１で窒素酸化物を還元した後に、残った残留アンモニアを酸化し、窒素と水に分離する。 The oxidation catalyst 22 is provided downstream of the urea selective reduction catalyst 21 in the exhaust gas flow direction. The oxidation catalyst 22 is formed of a ceramic tubular body, which is substantially the same as the oxidation catalyst 17 of the first exhaust gas aftertreatment device 15 described above. A number of through holes are formed in the axial direction of the oxidation catalyst 22, and the inner surface is coated with a noble metal. The oxidation catalyst 22 of the second exhaust gas aftertreatment device 19 oxidizes the remaining residual ammonia after the nitrogen oxide is reduced by the urea selective reduction catalyst 21 and separates it into nitrogen and water.
　ここで、第２の排気ガス後処理装置１９に設けられた尿素選択還元触媒２１は、尿素ＳＣＲシステム２３の一部を構成するもので、以下、この尿素ＳＣＲシステム２３について説明する。 Here, the urea selective reduction catalyst 21 provided in the second exhaust gas aftertreatment device 19 constitutes a part of the urea SCR system 23, and the urea SCR system 23 will be described below.
　尿素ＳＣＲシステム２３は、排気管１０内を流れる排気ガスに向けて尿素水を噴射し、排気ガスに含まれる窒素酸化物（ＮＯｘ）をアンモニアによって選択的に還元反応させる。これにより、窒素酸化物は窒素と水に分解され、排気ガスが浄化される。尿素ＳＣＲシステム２３は、図３に示すように、尿素選択還元触媒２１と、後述の尿素水噴射弁２４と、尿素水タンク２５と、尿素水管路２６と、尿素水供給装置３０と、尿素水フィルタ３４とを含んで構成されている。 The urea SCR system 23 injects urea water toward the exhaust gas flowing through the exhaust pipe 10, and selectively reduces nitrogen oxide (NOx) contained in the exhaust gas with ammonia. Thereby, nitrogen oxides are decomposed into nitrogen and water, and the exhaust gas is purified. As shown in FIG. 3, the urea SCR system 23 includes a urea selective reduction catalyst 21, a urea water injection valve 24, a urea water tank 25, a urea water pipe 26, a urea water supply device 30, a urea water, which will be described later. A filter 34 is included.
　尿素水噴射弁２４は、例えば接続管１８の上流蓋部１８Ｂに取付けられている。尿素水噴射弁２４は、還元剤である尿素水（尿素水溶液）を、尿素選択還元触媒２１よりも上流側で接続管１８内を流通する排気ガスに向けて噴射する。尿素水噴射弁２４は、尿素水管路２６を介して尿素水タンク２５に接続されている。 The urea water injection valve 24 is attached to the upstream lid portion 18B of the connection pipe 18, for example. The urea water injection valve 24 injects urea water (urea aqueous solution) as a reducing agent toward the exhaust gas flowing in the connection pipe 18 on the upstream side of the urea selective reduction catalyst 21. The urea water injection valve 24 is connected to a urea water tank 25 via a urea water pipe line 26.
　尿素水タンク２５は、例えば旋回フレーム５に設けられている。尿素水タンク２５は、尿素水噴射弁２４に供給される尿素水を貯えている。尿素水タンク２５には、尿素水を給水するための給水口（図示せず）が設けられており、この給水口を通じて尿素水タンク２５内に尿素水が給水される構成となっている。 The urea water tank 25 is provided in the revolving frame 5, for example. The urea water tank 25 stores urea water supplied to the urea water injection valve 24. The urea water tank 25 is provided with a water supply port (not shown) for supplying urea water, and urea water is supplied into the urea water tank 25 through this water supply port.
　尿素水管路２６は、尿素水タンク２５と尿素水噴射弁２４との間を接続している。尿素水管路２６の途中には尿素水供給装置３０が設けられている。尿素水タンク２５内に貯えられた尿素水は、尿素水供給装置３０を作動させることにより、尿素水管路２６を通じて尿素水噴射弁２４に供給される。ここで、尿素水管路２６は、尿素水タンク２５と尿素水フィルタ３４との間を接続するタンク側尿素水管路２７と、尿素水フィルタ３４と尿素水噴射弁２４との間を接続する噴射弁側尿素水管路２８とにより構成されている。 The urea water conduit 26 connects between the urea water tank 25 and the urea water injection valve 24. A urea water supply device 30 is provided in the middle of the urea water pipe line 26. The urea water stored in the urea water tank 25 is supplied to the urea water injection valve 24 through the urea water pipe line 26 by operating the urea water supply device 30. Here, the urea water pipe 26 is a tank side urea water pipe 27 that connects between the urea water tank 25 and the urea water filter 34, and an injection valve that connects between the urea water filter 34 and the urea water injection valve 24. And a side urea water pipe 28.
　タンク側尿素水管路２７は、尿素水タンク２５と尿素水フィルタ３４との間を接続している。即ち、タンク側尿素水管路２７は、一端２７Ａが尿素水タンク２５に接続され、他端２７Ｂが尿素水フィルタ３４に接続されている。この場合、図４に示すように、タンク側尿素水管路２７の他端２７Ｂは、後述するフィルタケース３５の濾過前室３５Ｅ内に位置してフィルタケース３５の底面位置に開口している。 The tank side urea water pipe line 27 connects between the urea water tank 25 and the urea water filter 34. That is, the tank side urea water pipe 27 has one end 27 </ b> A connected to the urea water tank 25 and the other end 27 </ b> B connected to the urea water filter 34. In this case, as shown in FIG. 4, the other end 27 </ b> B of the tank-side urea water conduit 27 is located in a pre-filtration chamber 35 </ b> E of the filter case 35 described later and opens to the bottom surface position of the filter case 35.
　噴射弁側尿素水管路２８は、尿素水フィルタ３４と尿素水噴射弁２４との間を接続している。即ち、噴射弁側尿素水管路２８は、一端２８Ａが尿素水フィルタ３４に接続され、他端２８Ｂが尿素水噴射弁２４に接続されている。この場合、噴射弁側尿素水管路２８の一端２８Ａは、フィルタケース３５の濾過後室３５Ｆ内に位置してフィルタケース３５の上面位置に開口している。また、噴射弁側尿素水管路２８の途中部位には、尿素水戻り管路２９の一端２９Ａが接続され、尿素水戻り管路２９の他端２９Ｂは尿素水タンク２５に接続されている。尿素水戻り管路２９は、尿素水噴射弁２４に向けて供給される尿素水のうちの余剰分を尿素水タンク２５に戻すものである。 The injection valve side urea water pipe line 28 connects between the urea water filter 34 and the urea water injection valve 24. That is, the injection valve side urea water pipe 28 has one end 28 </ b> A connected to the urea water filter 34 and the other end 28 </ b> B connected to the urea water injection valve 24. In this case, one end 28 </ b> A of the injection valve side urea water conduit 28 is located in the post-filtration chamber 35 </ b> F of the filter case 35 and is open to the upper surface position of the filter case 35. Further, one end 29 A of the urea water return pipe 29 is connected to the middle part of the injection valve side urea water pipe 28, and the other end 29 B of the urea water return pipe 29 is connected to the urea water tank 25. The urea water return pipe 29 is for returning the surplus portion of the urea water supplied toward the urea water injection valve 24 to the urea water tank 25.
　尿素水供給装置３０は、尿素水管路２６を構成する噴射弁側尿素水管路２８の途中に設けられている。尿素水供給装置３０は、尿素水タンク２５から尿素水噴射弁２４に向けて尿素水を供給する。尿素水供給装置３０は、尿素水ポンプ３１と、圧力センサ３２と、絞り３３とを有している。圧力センサ３２は、尿素水ポンプ３１と尿素水噴射弁２４との間に位置して噴射弁側尿素水管路２８の途中に設けられ、噴射弁側尿素水管路２８内の圧力を検出する。絞り３３は、尿素水戻り管路２９の途中に設けられ、噴射弁側尿素水管路２８内の圧力を調整する。尿素水戻り管路２９の一端２９Ａは、尿素水ポンプ３１と圧力センサ３２との間の部位で噴射弁側尿素水管路２８に接続されている。ここで、尿素水供給装置３０は、旋回フレーム５を構成する連結板５Ｇの後面側（エンジン９側）に、ブラケット５Ｈを介して取付けられている。ブラケット５ＨにはＵ字状に屈曲したカバー５Ｊが固定され、尿素水供給装置３０の周囲はカバー５Ｊによって覆われている。 The urea water supply device 30 is provided in the middle of the injection valve side urea water pipe 28 constituting the urea water pipe 26. The urea water supply device 30 supplies urea water from the urea water tank 25 toward the urea water injection valve 24. The urea water supply device 30 includes a urea water pump 31, a pressure sensor 32, and a throttle 33. The pressure sensor 32 is located between the urea water pump 31 and the urea water injection valve 24 and is provided in the middle of the injection valve side urea water pipe 28 to detect the pressure in the injection valve side urea water pipe 28. The throttle 33 is provided in the middle of the urea water return pipe 29 and adjusts the pressure in the injection valve side urea water pipe 28. One end 29A of the urea water return pipe 29 is connected to the injection valve side urea water pipe 28 at a portion between the urea water pump 31 and the pressure sensor 32. Here, the urea water supply device 30 is attached to the rear surface side (engine 9 side) of the connecting plate 5G constituting the revolving frame 5 via the bracket 5H. A cover 5J bent in a U shape is fixed to the bracket 5H, and the periphery of the urea water supply device 30 is covered with the cover 5J.
　尿素水ポンプ３１は、例えば尿素水を尿素水噴射弁２４に供給する尿素水供給側と、尿素水を尿素水タンク２５に戻す尿素水戻し側との二方向に作動可能なポンプを用いて構成されている。油圧ショベル１の運転時にエンジン９から排出される排気ガスを浄化するときには、尿素ＳＣＲシステム２３が尿素水供給動作を行う。このときには、尿素水ポンプ３１が尿素水供給側に作動することにより、尿素水タンク２５内の尿素水は、尿素水管路２６を通じて尿素水噴射弁２４に供給される。一方、エンジン９が停止した後に尿素水噴射弁２４、尿素水管路２６、尿素水供給装置３０等に残留した尿素水が凍結するのを防止するときには、尿素ＳＣＲシステム２３がアフターラン動作を行う。このときには、尿素水ポンプ３１が尿素水戻し側に作動することにより、尿素水噴射弁２４、尿素水管路２６、尿素水供給装置３０等に残留した尿素水が、尿素水タンク２５内に戻される。 The urea water pump 31 is configured using a pump that can operate in two directions, for example, a urea water supply side that supplies urea water to the urea water injection valve 24 and a urea water return side that returns urea water to the urea water tank 25. Has been. When purifying exhaust gas discharged from the engine 9 during operation of the hydraulic excavator 1, the urea SCR system 23 performs urea water supply operation. At this time, the urea water pump 31 is operated to the urea water supply side, so that the urea water in the urea water tank 25 is supplied to the urea water injection valve 24 through the urea water pipe 26. On the other hand, when the urea water remaining in the urea water injection valve 24, the urea water pipe 26, the urea water supply device 30 and the like is prevented from freezing after the engine 9 is stopped, the urea SCR system 23 performs an after-run operation. At this time, the urea water pump 31 is operated to the urea water return side, whereby the urea water remaining in the urea water injection valve 24, the urea water pipe 26, the urea water supply device 30 and the like is returned into the urea water tank 25. .
　次に、第１の実施の形態に用いられる尿素水フィルタ３４、およびヒータ３７について説明する。 Next, the urea water filter 34 and the heater 37 used in the first embodiment will be described.
　尿素水フィルタ３４は、尿素水供給装置３０の尿素水ポンプ３１と尿素水タンク２５との間に位置して尿素水管路２６の途中に設けられている。即ち、尿素水フィルタ３４には、タンク側尿素水管路２７の他端２７Ｂと噴射弁側尿素水管路２８の一端２８Ａとが接続されている。尿素水フィルタ３４は、尿素水タンク２５内の尿素水が尿素水管路２６を通じて尿素水噴射弁２４に供給されるときに、尿素水に混入した異物を捕集する。ここで、尿素水フィルタ３４は、尿素水供給装置３０の周囲を覆うカバー５Ｊにボルト（図示せず）を用いて着脱可能に取付けられ、ボルトを緩めることにより迅速に交換することができるようになっている。 The urea water filter 34 is located between the urea water pump 31 of the urea water supply device 30 and the urea water tank 25 and is provided in the middle of the urea water pipe 26. That is, the other end 27 </ b> B of the tank side urea water pipe 27 and one end 28 </ b> A of the injection valve side urea water pipe 28 are connected to the urea water filter 34. The urea water filter 34 collects foreign matters mixed in the urea water when the urea water in the urea water tank 25 is supplied to the urea water injection valve 24 through the urea water pipe 26. Here, the urea water filter 34 is detachably attached to the cover 5J covering the periphery of the urea water supply device 30 using a bolt (not shown), and can be quickly replaced by loosening the bolt. It has become.
　尿素水フィルタ３４は、例えば図４および図５に示すように、内部に尿素水を貯留する円筒状の容器からなるフィルタケース３５と、フィルタケース３５内に設けられた筒状のフィルタエレメント（濾材）３６とを備えている。フィルタケース３５は、円筒状の周壁板３５Ａと、周壁板３５Ａの上端を閉塞する上面板３５Ｂと、周壁板３５Ａの下端を閉塞する底面板３５Ｃとによって囲まれた円筒体として形成されている。フィルタケース３５の底面板３５Ｃの中央部にはヒータ取付孔３５Ｄが設けられ、このヒータ取付孔３５Ｄには後述のヒータ３７が取付けられている。 For example, as shown in FIGS. 4 and 5, the urea water filter 34 includes a filter case 35 formed of a cylindrical container that stores urea water therein, and a cylindrical filter element (filter medium) provided in the filter case 35. 36). The filter case 35 is formed as a cylindrical body surrounded by a cylindrical peripheral wall plate 35A, an upper surface plate 35B that closes the upper end of the peripheral wall plate 35A, and a bottom surface plate 35C that closes the lower end of the peripheral wall plate 35A. A heater mounting hole 35D is provided at the center of the bottom plate 35C of the filter case 35, and a heater 37 described later is mounted in the heater mounting hole 35D.
　フィルタエレメント３６の上端３６Ａおよび下端３６Ｂは、それぞれフィルタケース３５内に固定されている。フィルタエレメント３６は、尿素水のみが通過し、尿素水に混入した異物（コンタミネーション）は通過することができない微細な網目を有している。さらに、フィルタエレメント３６の外周側には、鋸歯状の凹凸部が全周に亘って形成され、表面積（濾過面積）を増大させることによって多くの異物を捕集することができるようになっている。これにより、フィルタケース３５内は、フィルタエレメント３６の外側に位置し異物が濾過される前の尿素水を貯留する濾過前室３５Ｅと、フィルタエレメント３６の内側に位置し異物が濾過された後の尿素水を貯留する濾過後室３５Ｆとに分けられている。 The upper end 36A and the lower end 36B of the filter element 36 are fixed in the filter case 35, respectively. The filter element 36 has a fine mesh through which only urea water passes and foreign matter (contamination) mixed in the urea water cannot pass. Further, a serrated uneven portion is formed on the entire outer periphery of the filter element 36 so that a large amount of foreign matter can be collected by increasing the surface area (filtration area). . As a result, the filter case 35 is located outside the filter element 36 and stores a pre-filtration chamber 35E for storing urea water before the foreign matter is filtered, and after the foreign matter is filtered inside the filter element 36. It is divided into a post-filtration chamber 35F for storing urea water.
　フィルタケース３５の上面板３５Ｂには、噴射弁側尿素水管路２８の一端２８Ａが下向きに挿通されている。これにより、噴射弁側尿素水管路２８の一端２８Ａは、フィルタケース３５の濾過後室３５Ｆ内に位置してフィルタケース３５の上面位置、例えばフィルタケース３５の上面板３５Ｂとフィルタエレメント３６の上端３６Ａとの間に開口している。 One end 28A of the injection valve side urea water conduit 28 is inserted downward into the upper surface plate 35B of the filter case 35. Thus, one end 28A of the injection valve side urea water conduit 28 is positioned in the post-filtration chamber 35F of the filter case 35, and the upper surface position of the filter case 35, for example, the upper surface plate 35B of the filter case 35 and the upper end 36A of the filter element 36. There is an opening between.
　フィルタケース３５の底面板３５Ｃには、タンク側尿素水管路２７の他端２７Ｂが上向きに挿通されている。タンク側尿素水管路２７の他端２７Ｂは、ヒータ取付孔３５Ｄから離間した位置、例えばフィルタケース３５の周壁板３５Ａとフィルタエレメント３６との間に配置されている。これにより、タンク側尿素水管路２７の他端２７Ｂは、フィルタケース３５の濾過前室３５Ｅ内に位置してフィルタケース３５の底面位置、例えばフィルタケース３５の底面板３５Ｃとフィルタエレメント３６の下端３６Ｂとの間に開口している。 The other end 27B of the tank-side urea water conduit 27 is inserted upward into the bottom plate 35C of the filter case 35. The other end 27B of the tank side urea water pipe 27 is disposed at a position separated from the heater mounting hole 35D, for example, between the peripheral wall plate 35A of the filter case 35 and the filter element 36. As a result, the other end 27B of the tank side urea water conduit 27 is located in the pre-filtration chamber 35E of the filter case 35 and is positioned at the bottom surface of the filter case 35, for example, the bottom plate 35C of the filter case 35 and the lower end 36B of the filter element 36. There is an opening between.
　このように、タンク側尿素水管路２７の他端２７Ｂは、フィルタケース３５の底面位置に開口している。これにより、尿素ＳＣＲシステム２３は、アフターラン動作によって、フィルタケース３５内の大部分の尿素水を、タンク側尿素水管路２７を通じて尿素水タンク２５に戻すことができる。従って、アフターラン動作が終了した後には、フィルタケース３５内の尿素水の液面Ｌは、図４中の二点鎖線で示す位置まで低下し、フィルタケース３５内の尿素水の殆どを排出することができる。 Thus, the other end 27 </ b> B of the tank-side urea water conduit 27 is open to the bottom surface position of the filter case 35. Thereby, the urea SCR system 23 can return most of the urea water in the filter case 35 to the urea water tank 25 through the tank-side urea water conduit 27 by an after-run operation. Therefore, after the after-run operation is completed, the liquid level L of the urea water in the filter case 35 is lowered to the position indicated by the two-dot chain line in FIG. 4, and most of the urea water in the filter case 35 is discharged. be able to.
　これにより、尿素ＳＣＲシステム２３がスタートアップ動作を行うときに、空気が混入した尿素水が尿素水フィルタ３４（フィルタケース３５）に流入したとしても、フィルタケース３５内に尿素水が満たされるまでの間に、尿素水と空気とをフィルタケース３５内で分離することができる。従って、尿素水よりも先に空気のみを尿素水フィルタ３４から排出することができる。この結果、尿素水が尿素水噴射弁２４に達する前に、尿素水管路２６を流れる尿素水に混入した空気を排出することができるので、尿素水に混入した空気が尿素水ポンプ３１に流入するのを抑えることができる構成となっている。 Thus, even when urea water mixed with air flows into the urea water filter 34 (filter case 35) when the urea SCR system 23 performs a start-up operation, the time until the urea water is filled in the filter case 35 is reached. Furthermore, urea water and air can be separated in the filter case 35. Therefore, only air can be discharged from the urea water filter 34 before the urea water. As a result, before the urea water reaches the urea water injection valve 24, the air mixed in the urea water flowing through the urea water pipe 26 can be discharged, so the air mixed in the urea water flows into the urea water pump 31. It is the structure which can suppress this.
　解凍装置としてのヒータ３７は、尿素水フィルタ３４のフィルタケース３５の濾過後室３５Ｆ内に設けられている。具体的には、ヒータ３７は、濾過後室３５Ｆ内に位置してフィルタケース３５の中央部に上，下方向に延びた状態で設けられている。ヒータ３７は、フィルタケース３５（底面板３５Ｃ）のヒータ取付孔３５Ｄに挿通され、円筒状をなすフィルタケース３５の軸中心位置に沿って上，下方向に延びた筒体３７Ａと、筒体３７Ａ内に設けられた電熱線３７Ｂとにより構成されている。ヒータ３７は、電源３８から電熱線３７Ｂに電力が供給されることに発熱し、フィルタケース３５内に残留した尿素水が凍結して生じた凍結尿素水を解凍する。この場合、ヒータ３７は、フィルタエレメント３６の内側に位置してフィルタケース３５の中央部である軸中心位置に上，下方向に延びて配置されている。これにより、ヒータ３７が発生した熱を、フィルタケース３５で凍結した凍結尿素水に均等に伝達することができ、この凍結尿素水を効率良く解凍することができる構成となっている。 A heater 37 as a thawing device is provided in the post-filtration chamber 35F of the filter case 35 of the urea water filter 34. Specifically, the heater 37 is provided in a state where the heater 37 is positioned in the post-filtration chamber 35 </ b> F and extends upward and downward in the center portion of the filter case 35. The heater 37 is inserted into the heater mounting hole 35D of the filter case 35 (bottom plate 35C) and has a cylindrical body 37A extending upward and downward along the axial center position of the cylindrical filter case 35, and the cylindrical body 37A. It is comprised by the heating wire 37B provided in the inside. The heater 37 generates heat when power is supplied from the power source 38 to the heating wire 37B, and thaws the frozen urea water generated by freezing the urea water remaining in the filter case 35. In this case, the heater 37 is disposed on the inner side of the filter element 36 so as to extend upward and downward at an axial center position that is a central portion of the filter case 35. Thereby, the heat generated by the heater 37 can be evenly transferred to the frozen urea water frozen in the filter case 35, and the frozen urea water can be efficiently thawed.
　第１の実施の形態による排気ガス浄化装置１４は上述の如き構成を有している。この排気ガス浄化装置１４を搭載した油圧ショベル１を用いて作業を行うときには、オペレータは、キャブ７に搭乗してエンジン９を作動させる。そして、オペレータは、キャブ７内に配置された走行用の操作レバー（図示せず）を操作することにより、油圧ショベル１を走行させることができる。また、オペレータは、作業用の操作レバー（図示せず）を操作することにより、作業装置４を用いて土砂の掘削作業等を行うことができる。 The exhaust gas purification device 14 according to the first embodiment has the above-described configuration. When working with the hydraulic excavator 1 equipped with the exhaust gas purification device 14, the operator gets on the cab 7 and operates the engine 9. The operator can run the excavator 1 by operating a travel operation lever (not shown) disposed in the cab 7. Moreover, the operator can perform excavation work of earth and sand using the work device 4 by operating an operation lever (not shown) for work.
　油圧ショベル１の作業時に、エンジン９から排出される排気ガスは、排気管１０を介して排気ガス浄化装置１４の第１の排気ガス後処理装置１５内に導入される。そして、図３に矢印で示すように、排気ガスは、第１の排気ガス後処理装置１５から接続管１８、第２の排気ガス後処理装置１９を通過した後、大気中に排出される。 During the operation of the hydraulic excavator 1, the exhaust gas discharged from the engine 9 is introduced into the first exhaust gas aftertreatment device 15 of the exhaust gas purification device 14 through the exhaust pipe 10. As shown by arrows in FIG. 3, the exhaust gas passes through the connection pipe 18 and the second exhaust gas aftertreatment device 19 from the first exhaust gas aftertreatment device 15 and is then discharged into the atmosphere.
　この場合、第１の排気ガス後処理装置１５は、排気ガスに含まれる一酸化炭素（ＣＯ）、炭化水素（ＨＣ）等を酸化触媒１７によって酸化して除去し、必要に応じて粒子状物質（ＰＭ）を燃焼して除去する。一方、接続管１８内では、尿素水噴射弁２４から排気ガスに向けて尿素水が噴射され、第２の排気ガス後処理装置１９は、尿素選択還元触媒２１によって窒素酸化物を窒素と水に分解する。さらに、酸化触媒２２が残留アンモニアを酸化し、窒素と水に分離する。このようにして、エンジン９からの排気ガスは、排気ガス浄化装置１４によって十分に浄化された後、大気中に排出される。 In this case, the first exhaust gas aftertreatment device 15 oxidizes and removes carbon monoxide (CO), hydrocarbon (HC), etc. contained in the exhaust gas by the oxidation catalyst 17, and if necessary, particulate matter (PM) is burned and removed. On the other hand, in the connection pipe 18, urea water is injected from the urea water injection valve 24 toward the exhaust gas, and the second exhaust gas aftertreatment device 19 converts the nitrogen oxides into nitrogen and water by the urea selective reduction catalyst 21. Decompose. Further, the oxidation catalyst 22 oxidizes residual ammonia and separates it into nitrogen and water. In this way, the exhaust gas from the engine 9 is sufficiently purified by the exhaust gas purification device 14 and then discharged into the atmosphere.
　次に、排気ガス浄化装置１４を構成する尿素ＳＣＲシステム２３の動作について説明する。 Next, the operation of the urea SCR system 23 constituting the exhaust gas purification device 14 will be described.
　まず、尿素ＳＣＲシステム２３は、尿素水噴射弁２４、尿素水管路２６、尿素水供給装置３０に残留した尿素水が凍結するのを防止するため、油圧ショベル１のエンジン９が停止した後にアフターラン動作を行う。これにより、尿素水噴射弁２４、尿素水管路２６、尿素水供給装置３０に残留した尿素水は、尿素水タンク２５内に戻されている。このため、エンジン９を始動した後には、尿素ＳＣＲシステム２３は、尿素水タンク２５内の尿素水を尿素水噴射弁２４に供給する。また、尿素ＳＣＲシステム２３はスタートアップ動作を行い、尿素水ポンプ３１の吐出圧を、尿素水噴射弁２４から尿素水を噴射させるのに適した圧力まで上昇させる。 First, the urea SCR system 23 performs after-run after the engine 9 of the excavator 1 stops in order to prevent the urea water remaining in the urea water injection valve 24, the urea water pipe 26, and the urea water supply device 30 from freezing. Perform the action. As a result, the urea water remaining in the urea water injection valve 24, the urea water pipe 26, and the urea water supply device 30 is returned to the urea water tank 25. For this reason, after the engine 9 is started, the urea SCR system 23 supplies the urea water in the urea water tank 25 to the urea water injection valve 24. In addition, the urea SCR system 23 performs a start-up operation to increase the discharge pressure of the urea water pump 31 to a pressure suitable for injecting the urea water from the urea water injection valve 24.
　スタートアップ動作を行うときには、尿素ＳＣＲシステム２３は、例えば第２の排気ガス後処理装置１９の筒体２０内を流れる排気ガスの温度が、尿素選択還元触媒２１が活性化する温度以上に達すると、尿素水噴射弁２４を開弁（開放）させる。この状態で、尿素ＳＣＲシステム２３は、尿素水ポンプ３１を尿素水供給側に作動させる。これにより、尿素水管路２６内および尿素水供給装置３０内の空気は、尿素水噴射弁２４を通じて排気ガス浄化装置１４内に排出されると共に、尿素水戻り管路２９を通じて尿素水タンク２５の気層部に排出される。 When performing the start-up operation, the urea SCR system 23, for example, when the temperature of the exhaust gas flowing through the cylindrical body 20 of the second exhaust gas aftertreatment device 19 reaches a temperature higher than the temperature at which the urea selective reduction catalyst 21 is activated, The urea water injection valve 24 is opened (opened). In this state, the urea SCR system 23 operates the urea water pump 31 to the urea water supply side. As a result, the air in the urea water conduit 26 and the urea water supply device 30 is discharged into the exhaust gas purification device 14 through the urea water injection valve 24 and the air in the urea water tank 25 through the urea water return conduit 29. It is discharged to the layer part.
　そして、尿素水タンク２５内の尿素水が、尿素水供給装置３０の絞り３３および尿素水噴射弁２４に達すると、絞り３３を通過するときの圧損等によって尿素水ポンプ３１の吐出圧が上昇する。この尿素水ポンプ３１の吐出圧が所定の閾値に達すると、尿素ＳＣＲシステム２３は尿素水噴射弁２４を閉弁させる。これにより、尿素水ポンプ３１の吐出圧がさらに上昇し、尿素水ポンプ３１の吐出圧が、尿素水噴射弁２４から尿素水を噴射させるのに適した規定値（第２の閾値）に達する。このとき、尿素ＳＣＲシステム２３は、スタートアップ動作が成功したと判定する。これにより、尿素ＳＣＲシステム２３は、尿素水ポンプ３１の吐出圧を一定に保つ制御を開始し、尿素水噴射弁２４から尿素選択還元触媒２１の上流側に向けて尿素水を噴射する尿素水供給動作が行われる。 When the urea water in the urea water tank 25 reaches the throttle 33 and the urea water injection valve 24 of the urea water supply device 30, the discharge pressure of the urea water pump 31 increases due to pressure loss when passing through the throttle 33. . When the discharge pressure of the urea water pump 31 reaches a predetermined threshold value, the urea SCR system 23 closes the urea water injection valve 24. As a result, the discharge pressure of the urea water pump 31 further increases, and the discharge pressure of the urea water pump 31 reaches a specified value (second threshold) suitable for injecting the urea water from the urea water injection valve 24. At this time, the urea SCR system 23 determines that the startup operation is successful. As a result, the urea SCR system 23 starts control to keep the discharge pressure of the urea water pump 31 constant, and urea water supply for injecting urea water from the urea water injection valve 24 toward the upstream side of the urea selective reduction catalyst 21. Operation is performed.
　一方、尿素水ポンプ３１の吐出圧が所定の閾値に達した後、一定時間内に尿素水ポンプ３１の吐出圧が規定値（第２の閾値）に達しない場合には、尿素ＳＣＲシステム２３は、尿素水ポンプ３１を尿素水戻し側に作動させる。そして、尿素水管路２６および尿素水供給装置３０内の尿素水が、尿素水管路２６を通じて尿素水タンク２５内に排出された後に、尿素ＳＣＲシステム２３は、再度、尿素水ポンプ３１を尿素水供給側に作動させて尿素水を尿素水噴射弁２４に供給する。そして、尿素水ポンプ３１が、尿素水供給側の作動と尿素水戻し側の作動を複数回繰返す間に、尿素水ポンプ３１の吐出圧が規定値（第２の閾値）に達しない場合には、尿素ＳＣＲシステム２３はスタートアップ動作が失敗したと判定し、尿素ＳＣＲシステム２３は停止される。 On the other hand, if the discharge pressure of the urea water pump 31 does not reach the specified value (second threshold) within a certain time after the discharge pressure of the urea water pump 31 reaches the predetermined threshold, the urea SCR system 23 Then, the urea water pump 31 is operated to the urea water return side. After the urea water in the urea water pipe 26 and the urea water supply device 30 is discharged into the urea water tank 25 through the urea water pipe 26, the urea SCR system 23 supplies the urea water pump 31 to the urea water again. And the urea water is supplied to the urea water injection valve 24. When the urea water pump 31 does not reach the specified value (second threshold) while the urea water pump 31 repeats the urea water supply side operation and the urea water return side operation a plurality of times. The urea SCR system 23 determines that the startup operation has failed, and the urea SCR system 23 is stopped.
　尿素ＳＣＲシステム２３は、スタートアップ動作が成功した後には、尿素水供給動作に移行し、油圧ショベル１の運転時にエンジン９から排出される排気ガスを浄化する。この尿素水供給動作においては、尿素水ポンプ３１が尿素水供給側に作動する。これにより、尿素水タンク２５内の尿素水は、タンク側尿素水管路２７、尿素水フィルタ３４、噴射弁側尿素水管路２８等を通じて尿素水噴射弁２４に供給される。従って、尿素水は、尿素水噴射弁２４から尿素選択還元触媒２１の上流側（接続管１８内）に噴射される。 The urea SCR system 23 shifts to a urea water supply operation after the start-up operation is successful, and purifies the exhaust gas discharged from the engine 9 when the hydraulic excavator 1 is operated. In this urea water supply operation, the urea water pump 31 operates on the urea water supply side. Thereby, the urea water in the urea water tank 25 is supplied to the urea water injection valve 24 through the tank side urea water pipe 27, the urea water filter 34, the injection valve side urea water pipe 28, and the like. Therefore, the urea water is injected from the urea water injection valve 24 to the upstream side of the urea selective reduction catalyst 21 (in the connection pipe 18).
　ここで、第１の実施の形態では、タンク側尿素水管路２７の他端２７Ｂが、フィルタケース３５の底面位置に開口している。従って、尿素ＳＣＲシステム２３がアフターラン動作を終了した後には、フィルタケース３５内の尿素水の液面Ｌは、図４中の二点鎖線で示す位置まで低下し、フィルタケース３５内の尿素水の殆どを排出することができる。このため、尿素ＳＣＲシステム２３がスタートアップ動作を行うときには、尿素水タンク２５からの尿素水が、尿素水フィルタ３４のフィルタケース３５内に満たされるまで、フィルタケース３５内の空気を排出することができる。即ち、フィルタケース３５内に流入した尿素水の液面が、噴射弁側尿素水管路２８の一端２８Ａに達するまでの間は、フィルタケース３５内の空気は、噴射弁側尿素水管路２８から尿素水噴射弁２４を通じて排気ガス浄化装置１４内に排出されると共に、尿素水戻り管路２９を通じて尿素水タンク２５の気層部に排出される。 Here, in the first embodiment, the other end 27 </ b> B of the tank-side urea water conduit 27 is open to the bottom surface position of the filter case 35. Therefore, after the urea SCR system 23 finishes the after-run operation, the liquid level L of the urea water in the filter case 35 is lowered to the position indicated by the two-dot chain line in FIG. Most of it can be discharged. For this reason, when the urea SCR system 23 performs a start-up operation, the air in the filter case 35 can be discharged until the urea water from the urea water tank 25 is filled in the filter case 35 of the urea water filter 34. . That is, until the level of the urea water that has flowed into the filter case 35 reaches one end 28A of the injection valve side urea water pipe 28, the air in the filter case 35 passes through the injection valve side urea water pipe 28 to form urea. The gas is discharged into the exhaust gas purification device 14 through the water injection valve 24 and discharged into the air layer portion of the urea water tank 25 through the urea water return pipe 29.
　従って、タンク側尿素水管路２７を通じてフィルタケース３５内に流入する尿素水に空気が混入していたとしても、これら尿素水と空気とをフィルタケース３５内で分離することができる。このため、噴射弁側尿素水管路２８等を通じて尿素水よりも先に空気のみを排出することができる。 Therefore, even if air is mixed in the urea water flowing into the filter case 35 through the tank side urea water pipe 27, the urea water and the air can be separated in the filter case 35. For this reason, only air can be discharged before the urea water through the injection valve side urea water pipe 28 and the like.
　これにより、スタートアップ動作において、尿素水が尿素水噴射弁２４もしくは尿素水供給装置３０の絞り３３に達する前に、尿素水管路２６内に残留した空気を排出することができる。この結果、尿素水ポンプ３１に空気が流入することによる尿素水ポンプ３１の吐出圧の低下を抑えることができる。従って、尿素水ポンプ３１の吐出圧を、尿素水噴射弁２４から尿素水を噴射させるのに適した規定値まで上昇させることにより、スタートアップ動作を迅速に成功させることができる。 Thereby, in the start-up operation, before the urea water reaches the urea water injection valve 24 or the throttle 33 of the urea water supply device 30, the air remaining in the urea water pipe 26 can be discharged. As a result, a decrease in the discharge pressure of the urea water pump 31 due to air flowing into the urea water pump 31 can be suppressed. Therefore, by increasing the discharge pressure of the urea water pump 31 to a specified value suitable for injecting the urea water from the urea water injection valve 24, the start-up operation can be rapidly completed.
　一方、油圧ショベル１を寒冷地で用いる場合には、アフターラン動作の終了後に、尿素水フィルタ３４のフィルタケース３５内に残留した尿素水が凍結することがある。この場合には、フィルタケース３５内に設けられたフィルタエレメント３６が、凍結尿素水によって損傷することがある。 On the other hand, when the hydraulic excavator 1 is used in a cold region, the urea water remaining in the filter case 35 of the urea water filter 34 may freeze after the end of the after-run operation. In this case, the filter element 36 provided in the filter case 35 may be damaged by the frozen urea water.
　これに対し、第１の実施の形態では、例えば尿素水が凍結する－１１℃以下まで外気温が低下したときに、ヒータ３７の電熱線３７Ｂに対して電源３８からの電力が供給される。これにより、フィルタケース３５内でヒータ３７が発熱し、フィルタケース３５内で凍結した凍結尿素水が解凍される。この場合、ヒータ３７は、フィルタエレメント３６の内側に位置してフィルタケース３５の中央部に配置されているので、ヒータ３７が発生した熱を、フィルタケース３５内の凍結尿素水に均等に伝達することができる。この結果、ヒータ３７によって凍結尿素水を効率良く解凍することができ、凍結尿素水によるフィルタエレメント３６の破損を防止することができるので、尿素水フィルタ３４の信頼性を高めることができる。 In contrast, in the first embodiment, for example, when the outside air temperature is lowered to −11 ° C. or lower where the urea water freezes, the power from the power source 38 is supplied to the heating wire 37B of the heater 37. Thereby, the heater 37 generates heat in the filter case 35 and the frozen urea water frozen in the filter case 35 is thawed. In this case, since the heater 37 is located inside the filter element 36 and is disposed in the center of the filter case 35, the heat generated by the heater 37 is evenly transferred to the frozen urea water in the filter case 35. be able to. As a result, the frozen urea water can be efficiently thawed by the heater 37 and the filter element 36 can be prevented from being damaged by the frozen urea water, so that the reliability of the urea water filter 34 can be improved.
　かくして、第１の実施の形態による排気ガス浄化装置１４は、排気ガス中の窒素酸化物を除去する尿素選択還元触媒２１と、還元剤である尿素水を尿素選択還元触媒２１の上流側に噴射する尿素水噴射弁２４と、尿素水噴射弁２４に供給される尿素水を貯える尿素水タンク２５と、尿素水タンク２５と尿素水噴射弁２４との間を接続する尿素水管路２６と、尿素水管路２６の途中に設けられ尿素水タンク２５から尿素水噴射弁２４に向けて尿素水を供給する尿素水供給装置３０と、尿素水タンク２５と尿素水供給装置３０との間に位置して尿素水管路２６の途中に設けられ尿素水に混入した異物を捕集する尿素水フィルタ３４とを備えている。 Thus, the exhaust gas purification device 14 according to the first embodiment injects urea selective reduction catalyst 21 for removing nitrogen oxides in exhaust gas and urea water as a reducing agent upstream of the urea selective reduction catalyst 21. A urea water injection valve 24, a urea water tank 25 for storing urea water supplied to the urea water injection valve 24, a urea water conduit 26 connecting the urea water tank 25 and the urea water injection valve 24, and urea A urea water supply device 30 that is provided in the middle of the water pipe 26 and supplies urea water from the urea water tank 25 toward the urea water injection valve 24, and is located between the urea water tank 25 and the urea water supply device 30. A urea water filter 34 is provided in the middle of the urea water pipe 26 and collects foreign matters mixed in the urea water.
　そして、尿素水フィルタ３４は、上面板３５Ｂと底面板３５Ｃとを有し内部に尿素水を貯留する容器からなるフィルタケース３５と、尿素水に混入した異物を捕集するためにフィルタケース３５内に設けられ、フィルタケース３５内を異物が濾過される前の尿素水を貯留する濾過前室３５Ｅと異物が濾過された後の尿素水を貯留する濾過後室３５Ｆとに分けるフィルタエレメント３６とを有し、フィルタケース３５内の中央部（濾過後室３５Ｆ内）には、フィルタケース３５内で凍結した尿素水を解凍するヒータ３７が設けられ、尿素水管路２６は、一端２７Ａが尿素水タンク２５に接続され、他端２７Ｂが濾過前室３５Ｅ内に位置してフィルタケース３５の底面位置に開口したタンク側尿素水管路２７と、一端２８Ａが濾過後室３５Ｆ内に位置してフィルタケース３５の上面位置に開口し、他端２８Ｂが尿素水噴射弁２４に接続された噴射弁側尿素水管路２８とにより構成されている。 The urea water filter 34 includes a filter case 35 having a top plate 35B and a bottom plate 35C and a container for storing urea water therein, and a filter case 35 for collecting foreign matter mixed in the urea water. The filter element 36 is divided into a pre-filtration chamber 35E for storing urea water before foreign matter is filtered and a post-filtration chamber 35F for storing urea water after foreign matter is filtered. And a heater 37 for thawing the urea water frozen in the filter case 35 is provided in the center portion (in the post-filtration chamber 35F) of the filter case 35. One end 27A of the urea water conduit 26 has a urea water tank. 25, the other end 27B is located in the pre-filtration chamber 35E and opened to the bottom surface of the filter case 35, and the one end 28A is in the post-filtration chamber 35F. Open to the upper surface position of the filter case 35 is located, the other end 28B is composed of the injection valve side urea water pipe 28 connected to the urea water injection valve 24.
　従って、尿素ＳＣＲシステム２３がアフターラン動作を終了した後には、フィルタケース３５内の尿素水の殆どを、タンク側尿素水管路２７を通じて尿素水タンク２５に排出することができる。このため、尿素ＳＣＲシステム２３がスタートアップ動作を行うときには、尿素水フィルタ３４のフィルタケース３５内に尿素水が満たされるまでの間は、フィルタケース３５内の空気を排出することができる。これにより、タンク側尿素水管路２７を通じてフィルタケース３５内に流入する尿素水に空気が混入していたとしても、これら尿素水と空気とをフィルタケース３５内で分離することができる。このため、噴射弁側尿素水管路２８等を通じて尿素水よりも先に空気のみを排出することができる。 Therefore, after the urea SCR system 23 finishes the after-run operation, most of the urea water in the filter case 35 can be discharged to the urea water tank 25 through the tank side urea water pipe 27. For this reason, when the urea SCR system 23 performs a start-up operation, the air in the filter case 35 can be discharged until the urea case is filled with the urea case. Thereby, even if air is mixed in the urea water flowing into the filter case 35 through the tank-side urea water pipe line 27, the urea water and the air can be separated in the filter case 35. For this reason, only air can be discharged before the urea water through the injection valve side urea water pipe 28 and the like.
　これにより、スタートアップ動作において、尿素水が尿素水噴射弁２４もしくは尿素水供給装置３０の絞り３３に達する前に、尿素水管路２６内に残留した空気を排出することができる。この結果、尿素水ポンプ３１に空気が流入することによる尿素水ポンプ３１の吐出圧の低下を抑えることができる。従って、尿素水ポンプ３１の吐出圧を、尿素水噴射弁２４から尿素水を噴射させるのに適した規定値へと上昇させることにより、スタートアップ動作を迅速に成功させることができる。 Thereby, in the start-up operation, before the urea water reaches the urea water injection valve 24 or the throttle 33 of the urea water supply device 30, the air remaining in the urea water pipe 26 can be discharged. As a result, a decrease in the discharge pressure of the urea water pump 31 due to air flowing into the urea water pump 31 can be suppressed. Therefore, the start-up operation can be rapidly completed by raising the discharge pressure of the urea water pump 31 to a specified value suitable for injecting the urea water from the urea water injection valve 24.
　一方、アフターラン動作の終了後に、フィルタケース３５内に残留した尿素水が凍結したとしても、フィルタケース３５の中央部（軸中心位置）に上，下方向に延びた状態で配置されたヒータ３７を発熱させることにより、このヒータ３７からの熱を、フィルタケース３５内の凍結尿素水に均等に伝達することができる。この結果、ヒータ３７によって凍結尿素水を効率良く解凍することができ、凍結尿素水によるフィルタエレメント３６の破損を防止することができる。 On the other hand, even if the urea water remaining in the filter case 35 is frozen after the end of the after-run operation, the heater 37 arranged in the state of extending upward and downward at the central portion (axial center position) of the filter case 35. , The heat from the heater 37 can be evenly transferred to the frozen urea water in the filter case 35. As a result, the frozen urea water can be efficiently thawed by the heater 37, and the filter element 36 can be prevented from being damaged by the frozen urea water.
　次に、図６および図７は本発明の第２の実施の形態を示し、第２の実施の形態の特徴は、噴射弁側尿素水管路には、尿素水フィルタと尿素水供給装置との間に位置して噴射弁側尿素水管路の管路面積よりも大きな断面積をもった拡張室を形成する拡張室形成体が設けられていることにある。なお、第２の実施の形態では、第１の実施の形態と同一の構成要素に同一符号を付し、その説明を省略するものとする。 Next, FIG. 6 and FIG. 7 show a second embodiment of the present invention, and the feature of the second embodiment is that the urea water filter and the urea water supply device are provided in the injection valve side urea water pipe. There exists an expansion chamber forming body which forms an expansion chamber which is located between them and has a cross-sectional area larger than the pipe area of the injection valve side urea water pipe. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
　図中、噴射弁側尿素水管路４１は、第１の実施の形態による噴射弁側尿素水管路２８に代えて第２の実施の形態に用いられるものである。噴射弁側尿素水管路４１は、尿素水フィルタ３４と尿素水噴射弁２４との間を接続するもので、噴射弁側尿素水管路４１の途中には、後述の拡張室形成体４２が設けられている。噴射弁側尿素水管路４１の一端４１Ａは、フィルタケース３５の上面位置（フィルタケース３５の上面板３５Ｂとフィルタエレメント３６の上端３６Ａとの間）に開口し、噴射弁側尿素水管路４１の他端４１Ｂは、尿素水噴射弁２４に接続されている。 In the figure, the injection valve side urea water pipe 41 is used in the second embodiment in place of the injection valve side urea water pipe 28 according to the first embodiment. The injection valve side urea water pipe 41 connects the urea water filter 34 and the urea water injection valve 24, and an expansion chamber forming body 42 described later is provided in the middle of the injection valve side urea water pipe 41. ing. One end 41 </ b> A of the injection valve side urea water pipe 41 opens to the upper surface position of the filter case 35 (between the upper surface plate 35 </ b> B of the filter case 35 and the upper end 36 </ b> A of the filter element 36). The end 41B is connected to the urea water injection valve 24.
　拡張室形成体４２は、尿素水供給装置３０の尿素水ポンプ３１と尿素水フィルタ３４との間に位置して噴射弁側尿素水管路４１の途中に設けられている。拡張室形成体４２は、例えば円筒状の周壁板４２Ａと、周壁板４２Ａの上端を閉塞する上面板４２Ｂと、周壁板４２Ａの下端を閉塞する底面板４２Ｃとによって囲まれた円筒体として形成されている。拡張室形成体４２の内部には拡張室４３が形成され、この拡張室４３の断面積は、噴射弁側尿素水管路４１の管路面積よりも大きく設定されている。従って、スタートアップ動作において噴射弁側尿素水管路４１から尿素水フィルタ３４に逆流する尿素水の圧力エネルギは、例えば拡張型消音器による消音作用と同様に、断面積が大きい拡張室形成体４２の拡張室４３内で発散され、断面積が小さい噴射弁側尿素水管路４１内で収束される。これにより、尿素水の圧力エネルギは、尿素水フィルタ３４に流入する前に拡張室形成体４２の拡張室４３によって減衰される構成となっている。 The expansion chamber forming body 42 is located between the urea water pump 31 and the urea water filter 34 of the urea water supply device 30 and is provided in the middle of the injection valve side urea water pipe 41. The expansion chamber forming body 42 is formed, for example, as a cylindrical body surrounded by a cylindrical peripheral wall plate 42A, an upper surface plate 42B that closes the upper end of the peripheral wall plate 42A, and a bottom surface plate 42C that closes the lower end of the peripheral wall plate 42A. ing. An expansion chamber 43 is formed inside the expansion chamber forming body 42, and the cross-sectional area of the expansion chamber 43 is set larger than the pipe area of the injection valve side urea water pipe 41. Therefore, the pressure energy of the urea water flowing backward from the injection valve side urea water pipe 41 to the urea water filter 34 in the start-up operation is, for example, the expansion of the expansion chamber forming body 42 having a large cross-sectional area, similarly to the silencing action by the expansion silencer. Diversified in the chamber 43 and converged in the injection valve side urea water pipe 41 having a small cross-sectional area. Accordingly, the pressure energy of the urea water is attenuated by the expansion chamber 43 of the expansion chamber forming body 42 before flowing into the urea water filter 34.
　ここで、尿素ＳＣＲシステム２３がスタートアップ動作を行うときに、尿素水ポンプ３１の吐出圧が、一定時間内に尿素水噴射弁２４から尿素水を噴射させるのに適した規定値に達しない場合には、尿素ＳＣＲシステム２３は、尿素水ポンプ３１を尿素水戻し側に作動させる。これにより、尿素水供給装置３０および尿素水管路２６内の尿素水は、尿素水タンク２５に戻される。このとき、噴射弁側尿素水管路４１のうち尿素水ポンプ３１と尿素水噴射弁２４との間の圧力が開放されることにより、大きな圧力エネルギを有する尿素水が、噴射弁側尿素水管路４１を通じて尿素水フィルタ３４側へと逆流する。このため、尿素水供給装置３０内の空気と尿素水とが、過剰に尿素水フィルタ３４およびタンク側尿素水管路２７に流れ込むようになる。 Here, when the urea SCR system 23 performs a start-up operation, the discharge pressure of the urea water pump 31 does not reach a specified value suitable for injecting urea water from the urea water injection valve 24 within a certain time. The urea SCR system 23 operates the urea water pump 31 to the urea water return side. Thereby, the urea water in the urea water supply device 30 and the urea water pipe 26 is returned to the urea water tank 25. At this time, when the pressure between the urea water pump 31 and the urea water injection valve 24 in the injection valve side urea water pipe 41 is released, urea water having a large pressure energy is injected into the injection valve side urea water pipe 41. Then, it flows backward to the urea water filter 34 side. For this reason, the air in the urea water supply device 30 and the urea water excessively flow into the urea water filter 34 and the tank side urea water pipe 27.
　これに対し、第２の実施の形態では、噴射弁側尿素水管路４１の途中に拡張室形成体４２が設けられている。このため、大きな圧力エネルギを有する尿素水が、噴射弁側尿素水管路４１から尿素水フィルタ３４へと逆流した場合でも、この尿素水の圧力エネルギは、断面積が大きい拡張室形成体４２の拡張室４３内で発散されると共に断面積が小さい噴射弁側尿素水管路４１内で収束されることにより減衰される。これにより、尿素水供給装置３０内の空気と尿素水とが、過剰に尿素水フィルタ３４およびタンク側尿素水管路２７に流れ込むのを抑え、尿素水に混入した空気が尿素水ポンプ３１に流入するのを抑えることができる構成となっている。 In contrast, in the second embodiment, an expansion chamber forming body 42 is provided in the middle of the injection valve side urea water pipe 41. For this reason, even when urea water having large pressure energy flows backward from the injection valve side urea water pipe 41 to the urea water filter 34, the pressure energy of the urea water is expanded by the expansion chamber forming body 42 having a large cross-sectional area. It is attenuated by diverging in the chamber 43 and converging in the injection valve side urea water pipe 41 having a small sectional area. Thereby, the air in the urea water supply device 30 and the urea water are prevented from excessively flowing into the urea water filter 34 and the tank side urea water pipe 27, and the air mixed in the urea water flows into the urea water pump 31. It is the structure which can suppress this.
　第２の実施の形態による排気ガス浄化装置は、上述の如き構成を有するもので、噴射弁側尿素水管路４１の一端４１Ａが、フィルタケース３５の上面位置に開口すると共に、タンク側尿素水管路２７の他端２７Ｂが、フィルタケース３５の底面位置に開口している。これにより、尿素ＳＣＲシステム２３がアフターラン動作を終了した後には、フィルタケース３５内の尿素水の液面Ｌは、図７中の二点鎖線で示す位置まで低下し、フィルタケース３５内の尿素水の殆どを排出することができる。このため、尿素ＳＣＲシステム２３のスタートアップ動作において、尿素水タンク２５からの尿素水が、尿素水フィルタ３４のフィルタケース３５内に満たされるまでの間は、フィルタケース３５内の空気は、噴射弁側尿素水管路４１から尿素水噴射弁２４を通じて排気ガス浄化装置１４（排気管１０）内に排出されると共に、尿素水戻り管路２９を通じて尿素水タンク２５の気層部に排出される。 The exhaust gas purifying apparatus according to the second embodiment has the above-described configuration. One end 41A of the injection valve side urea water pipe 41 opens to the upper surface position of the filter case 35, and the tank side urea water pipe The other end 27 </ b> B of the opening 27 is open at the bottom surface position of the filter case 35. Thus, after the urea SCR system 23 finishes the after-run operation, the liquid level L of the urea water in the filter case 35 is lowered to the position indicated by the two-dot chain line in FIG. Most of the water can be discharged. For this reason, in the start-up operation of the urea SCR system 23, until the urea water from the urea water tank 25 is filled in the filter case 35 of the urea water filter 34, the air in the filter case 35 is on the injection valve side. The urea water pipe 41 is discharged into the exhaust gas purification device 14 (exhaust pipe 10) through the urea water injection valve 24, and is discharged into the air layer of the urea water tank 25 through the urea water return pipe 29.
　従って、タンク側尿素水管路２７を通じてフィルタケース３５内に流入する尿素水に空気が混入していたとしても、これら尿素水と空気とをフィルタケース３５内で分離することができる。このため、噴射弁側尿素水管路４１等を通じて尿素水よりも先に空気のみを排出することができる。これにより、スタートアップ動作において、尿素水が尿素水噴射弁２４もしくは尿素水供給装置３０の絞り３３に達する前に、尿素水管路２６内に残留した空気を排出することができる。この結果、尿素水ポンプ３１に空気が流入することによる尿素水ポンプ３１の吐出圧の低下を抑えることができる。従って、尿素水ポンプ３１の吐出圧を、尿素水噴射弁２４から尿素水を噴射させるのに適した規定値に上昇させることにより、スタートアップ動作を迅速に成功させることができる。 Therefore, even if air is mixed in the urea water flowing into the filter case 35 through the tank side urea water pipe 27, the urea water and the air can be separated in the filter case 35. For this reason, only air can be discharged before the urea water through the injection valve side urea water pipe 41 and the like. Thereby, in the start-up operation, before the urea water reaches the urea water injection valve 24 or the throttle 33 of the urea water supply device 30, the air remaining in the urea water conduit 26 can be discharged. As a result, a decrease in the discharge pressure of the urea water pump 31 due to air flowing into the urea water pump 31 can be suppressed. Therefore, by raising the discharge pressure of the urea water pump 31 to a specified value suitable for injecting the urea water from the urea water injection valve 24, the start-up operation can be rapidly completed.
　ここで、尿素ＳＣＲシステム２３がスタートアップ動作を行うときに、尿素水ポンプ３１の吐出圧が、尿素水噴射弁２４から尿素水を噴射させるのに適した規定値に達しない場合には、尿素ＳＣＲシステム２３は、尿素水ポンプ３１を尿素水戻し側に作動させる。これにより、尿素水供給装置３０および尿素水管路２６内の尿素水が尿素水タンク２５に戻される。このとき、噴射弁側尿素水管路４１のうち尿素水ポンプ３１と尿素水噴射弁２４との間の圧力が開放されることにより、大きな圧力エネルギを有する尿素水が噴射弁側尿素水管路４１を通じて尿素水フィルタ３４側へと逆流する。これにより、尿素水供給装置３０内の空気と尿素水とが、過剰に尿素水フィルタ３４およびタンク側尿素水管路２７に流れ込むようになる。 Here, when the urea SCR system 23 performs a start-up operation, if the discharge pressure of the urea water pump 31 does not reach a specified value suitable for injecting the urea water from the urea water injection valve 24, the urea SCR The system 23 operates the urea water pump 31 to the urea water return side. Thereby, the urea water in the urea water supply device 30 and the urea water pipe 26 is returned to the urea water tank 25. At this time, the pressure between the urea water pump 31 and the urea water injection valve 24 in the injection valve side urea water pipe 41 is released, so that urea water having large pressure energy passes through the injection valve side urea water pipe 41. It flows backward to the urea water filter 34 side. As a result, the air in the urea water supply device 30 and the urea water excessively flow into the urea water filter 34 and the tank side urea water pipe 27.
　これに対し、第２の実施の形態では、噴射弁側尿素水管路４１の途中に拡張室形成体４２が設けられている。これにより、大きな圧力エネルギを有する尿素水が噴射弁側尿素水管路４１から尿素水フィルタ３４へと逆流した場合でも、この尿素水の圧力エネルギを、断面積が大きい拡張室形成体４２の拡張室４３内で発散させると共に断面積が小さい噴射弁側尿素水管路４１内で収束させて減衰させることができる。これにより、尿素水供給装置３０内の空気と尿素水とが、過剰に尿素水フィルタ３４およびタンク側尿素水管路２７に流れ込むのを抑えることができる。この結果、尿素水に混入した空気が尿素水ポンプ３１に流入（エア噛み）することにより、尿素水ポンプ３１の吐出圧が低下するのを防止できる。従って、尿素水ポンプ３１の吐出圧を、尿素水噴射弁２４から尿素水を噴射するのに適した規定値まで速やかに上昇させることができる。 In contrast, in the second embodiment, an expansion chamber forming body 42 is provided in the middle of the injection valve side urea water pipe 41. Thereby, even when urea water having large pressure energy flows backward from the injection valve side urea water pipe 41 to the urea water filter 34, the pressure energy of the urea water is expanded into the expansion chamber of the expansion chamber forming body 42 having a large cross-sectional area. It can diverge within 43 and can be made to converge and attenuate in the injection valve side urea water pipe 41 having a small cross-sectional area. Thereby, it can suppress that the air in the urea water supply apparatus 30 and urea water flow into the urea water filter 34 and the tank side urea water pipe 27 excessively. As a result, it is possible to prevent the discharge pressure of the urea water pump 31 from being lowered by the air mixed in the urea water flowing into the urea water pump 31 (air engagement). Therefore, the discharge pressure of the urea water pump 31 can be quickly increased to a specified value suitable for injecting urea water from the urea water injection valve 24.
　次に、図８は本発明の第３の実施の形態を示し、第３の実施の形態の特徴は、拡張室形成体が、フィルタケースの上面に一体に設けられていることにある。なお、第３の実施の形態では、第１の実施の形態と同一の構成要素に同一符号を付し、その説明を省略するものとする。 Next, FIG. 8 shows a third embodiment of the present invention. The feature of the third embodiment is that an expansion chamber forming body is integrally provided on the upper surface of the filter case. Note that in the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
　図中、噴射弁側尿素水管路５１は、第１の実施の形態による噴射弁側尿素水管路２８に代えて第３の実施の形態に用いられるものである。噴射弁側尿素水管路５１は、尿素水フィルタ３４と尿素水噴射弁２４との間を接続するもので、噴射弁側尿素水管路５１の途中には、後述の拡張室形成体５２が設けられている。噴射弁側尿素水管路５１の一端５１Ａは、フィルタケース３５の上面位置（フィルタケース３５の上面板３５Ｂとフィルタエレメント３６の上端３６Ａとの間）に開口している。噴射弁側尿素水管路５１の他端（図示せず）は尿素水噴射弁２４に接続されている。 In the figure, the injection valve side urea water pipe 51 is used in the third embodiment in place of the injection valve side urea water pipe 28 according to the first embodiment. The injection valve side urea water pipe 51 connects the urea water filter 34 and the urea water injection valve 24, and an expansion chamber forming body 52 described later is provided in the middle of the injection valve side urea water pipe 51. ing. One end 51 </ b> A of the injection valve side urea water pipe 51 opens to the upper surface position of the filter case 35 (between the upper surface plate 35 </ b> B of the filter case 35 and the upper end 36 </ b> A of the filter element 36). The other end (not shown) of the injection valve side urea water pipe 51 is connected to the urea water injection valve 24.
　拡張室形成体５２は、尿素水フィルタ３４を構成するフィルタケース３５の上面板３５Ｂに一体に設けられている。拡張室形成体５２は、フィルタケース３５よりも外径寸法が小さい円筒状の周壁板５２Ａと、周壁板５２Ａの上端を閉塞する上面板５２Ｂと、周壁板５２Ａの下端を閉塞する底面板５２Ｃとによって囲まれた円筒体として形成されている。拡張室形成体５２はフィルタケース３５と同心上に配置され、拡張室形成体５２の底面板５２Ｃは、フィルタケース３５の上面板３５Ｂに溶接、接着等の手段を用いて固定されている。 The expansion chamber forming body 52 is integrally provided on the upper surface plate 35B of the filter case 35 constituting the urea water filter 34. The expansion chamber forming body 52 includes a cylindrical peripheral wall plate 52A having a smaller outer diameter than the filter case 35, an upper surface plate 52B that closes the upper end of the peripheral wall plate 52A, and a bottom surface plate 52C that closes the lower end of the peripheral wall plate 52A. It is formed as a cylindrical body surrounded by. The expansion chamber forming body 52 is disposed concentrically with the filter case 35, and the bottom plate 52C of the expansion chamber forming body 52 is fixed to the upper surface plate 35B of the filter case 35 by means such as welding or bonding.
　拡張室形成体５２の内部には拡張室５３が形成され、この拡張室５３の断面積は、噴射弁側尿素水管路５１の管路面積よりも大きく設定されている。従って、スタートアップ動作において噴射弁側尿素水管路５１から尿素水フィルタ３４に逆流する尿素水の圧力エネルギは、断面積が大きい拡張室形成体５２の拡張室５３内で発散され、断面積が小さい噴射弁側尿素水管路５１内で収束される。これにより、尿素水の圧力エネルギは、尿素水フィルタ３４に流入する前に拡張室形成体５２の拡張室５３によって減衰される構成となっている。 An expansion chamber 53 is formed inside the expansion chamber forming body 52, and the cross-sectional area of the expansion chamber 53 is set larger than the pipe area of the injection valve side urea water pipe 51. Accordingly, the pressure energy of the urea water flowing back from the injection valve side urea water pipe 51 to the urea water filter 34 in the start-up operation is diffused in the expansion chamber 53 of the expansion chamber forming body 52 having a large cross-sectional area, and the injection having a small cross-sectional area. It converges in the valve side urea water pipe 51. Thus, the pressure energy of the urea water is attenuated by the expansion chamber 53 of the expansion chamber forming body 52 before flowing into the urea water filter 34.
　第３の実施の形態による排気ガス浄化装置は、上述の如き構成を有するもので、その基本的作用については、上述した第２の実施の形態によるものと格別差異はない。 The exhaust gas purifying apparatus according to the third embodiment has the above-described configuration, and the basic action thereof is not particularly different from that according to the second embodiment described above.
　然るに、第３の実施の形態によれば、拡張室５３を形成する拡張室形成体５２が、尿素水フィルタ３４を構成するフィルタケース３５の上面板３５Ｂに一体に設けられている。これにより、例えばフィルタケース３５と同程度の断面積を有する大きな拡張室を設けることができ、スタートアップ動作において噴射弁側尿素水管路５１から尿素水フィルタ３４に逆流する尿素水の圧力エネルギを効率良く減衰することができる。 However, according to the third embodiment, the expansion chamber forming body 52 that forms the expansion chamber 53 is integrally provided on the upper surface plate 35 </ b> B of the filter case 35 that constitutes the urea water filter 34. Thereby, for example, a large expansion chamber having a cross-sectional area comparable to that of the filter case 35 can be provided, and the pressure energy of the urea water flowing backward from the injection valve side urea water pipe 51 to the urea water filter 34 in the startup operation can be efficiently obtained. Can be attenuated.
　なお、第１の実施の形態では、タンク側尿素水管路２７の他端２７Ｂが、尿素水フィルタ３４を構成するフィルタケース３５の底面板３５Ｃに上向きに挿通されることにより、フィルタケース３５の底面位置に開口した場合を例示している。しかし、本発明はこれに限るものではなく、例えば図９に示す第１の変形例、あるいは図１０に示す第２の変形例のように構成してもよい。 In the first embodiment, the other end 27B of the tank-side urea water conduit 27 is inserted upward into the bottom plate 35C of the filter case 35 constituting the urea water filter 34, so that the bottom surface of the filter case 35 is obtained. The case where it opened to the position is illustrated. However, the present invention is not limited to this. For example, the first modification shown in FIG. 9 or the second modification shown in FIG. 10 may be configured.
　即ち、図９に示す第１の変形例のように、タンク側尿素水管路２７′の他端２７Ｂ′が、尿素水フィルタ３４を構成するフィルタケース３５の周壁板３５Ａの下側（底面板３５Ｃの近く）に横向き（水平方向）に挿通されることにより、フィルタケース３５の底面位置に開口する構成としてもよい。また、噴射弁側尿素水管路２８′の一端２８Ａ′がＬ字型に折曲げられ、この一端２８Ａ′が、フィルタケース３５の上面板３５Ｂに下向きに挿通されることにより、フィルタケース３５の上面位置に開口する構成としてもよい。このように構成することにより、タンク側尿素水管路２７′の他端２７Ｂ′側と、噴射弁側尿素水管路２８′の一端２８Ａ′側とを、尿素水フィルタ３４に対して水平方向に延びるように配置することができる。 That is, as in the first modification shown in FIG. 9, the other end 27B ′ of the tank-side urea water pipe 27 ′ is located on the lower side (bottom plate 35C) of the peripheral wall plate 35A of the filter case 35 constituting the urea water filter 34. It is good also as a structure opened to the bottom face position of the filter case 35 by being penetrated by the horizontal direction (horizontal direction). Further, one end 28A ′ of the injection valve side urea water conduit 28 ′ is bent in an L shape, and this one end 28A ′ is inserted downward into the upper surface plate 35B of the filter case 35, whereby the upper surface of the filter case 35 is It is good also as a structure opened to a position. With this configuration, the other end 27B ′ side of the tank side urea water pipe line 27 ′ and the one end 28A ′ side of the injection valve side urea water pipe line 28 ′ extend in the horizontal direction with respect to the urea water filter 34. Can be arranged as follows.
　一方、図１０に示す第２の変形例のように、タンク側尿素水管路２７″の他端２７Ｂ″側が、尿素水フィルタ３４を構成するフィルタケース３５の上面板３５Ｂから底面板３５Ｃに向けて下向きに挿通されることにより、フィルタケース３５の底面位置に開口する構成としてもよい。 On the other hand, as in the second modified example shown in FIG. 10, the other end 27B ″ side of the tank side urea water conduit 27 ″ is directed from the upper surface plate 35B of the filter case 35 constituting the urea water filter 34 toward the bottom surface plate 35C. It is good also as a structure opened to the bottom face position of the filter case 35 by inserting downward.
　実施の形態では、尿素水を尿素水噴射弁２４に供給する尿素水供給側と、尿素水を尿素水タンク２５に戻す尿素水戻し側との二方向に作動可能な尿素水ポンプ３１を用いて尿素水供給装置３０を構成した場合を例示している。しかし、本発明はこれに限るものではなく、例えば図１１に示す第３の変形例のような尿素水供給装置６１を構成してもよい。 In the embodiment, a urea water pump 31 operable in two directions, a urea water supply side for supplying urea water to the urea water injection valve 24 and a urea water return side for returning urea water to the urea water tank 25 is used. The case where the urea water supply apparatus 30 is comprised is illustrated. However, the present invention is not limited to this, and for example, a urea water supply device 61 as in the third modification shown in FIG. 11 may be configured.
　即ち、図１１に示す尿素水供給装置６１は、噴射弁側尿素水管路２８の途中に設けられ尿素水を一方向にのみ吐出させる尿素水ポンプ６２と、方向制御弁６３と、第１のチェック弁６４と、第２のチェック弁６５とにより構成されている。方向制御弁６３は、例えば４ポート２位置の電磁弁からなり、弁位置（ａ）と弁位置（ｂ）とに切換えられる。従って、尿素水を一方向にのみ吐出させる尿素水ポンプ６２を用いた場合でも、方向制御弁６３を弁位置（ａ）に切換えることにより、噴射弁側尿素水管路２８内の尿素水を尿素水フィルタ３４から尿素水噴射弁２４に向けて流通させることができる。また、方向制御弁６３を弁位置（ｂ）に切換えることにより、噴射弁側尿素水管路２８内の尿素水を尿素水噴射弁２４から尿素水フィルタ３４に向けて流通させることができる。 That is, the urea water supply device 61 shown in FIG. 11 includes a urea water pump 62 that is provided in the middle of the injection valve side urea water pipe 28 and discharges urea water only in one direction, a direction control valve 63, and a first check. The valve 64 and the second check valve 65 are configured. The direction control valve 63 is composed of, for example, a 4-port 2-position electromagnetic valve, and is switched between a valve position (a) and a valve position (b). Therefore, even when the urea water pump 62 that discharges urea water only in one direction is used, the urea water in the injection valve side urea water pipe 28 is converted to urea water by switching the direction control valve 63 to the valve position (a). The filter 34 can be circulated toward the urea water injection valve 24. Further, by switching the direction control valve 63 to the valve position (b), the urea water in the injection valve side urea water conduit 28 can be circulated from the urea water injection valve 24 toward the urea water filter 34.
　実施の形態では、筒体３７Ａ内に発熱用の電熱線３７Ｂが設けられたヒータ３７を、解凍装置として用いた場合を例示している。しかし、本発明はこれに限らず、例えばフィルタケース３５の中央部に筒体を配置し、この筒体内にエンジン冷却水の一部を導入する構成としてもよい。また、ヒータ３７は、フィルタケース３５の中央部（軸中心位置）から僅かにずれた位置に配置されてもよいものである。 In the embodiment, the case where the heater 37 in which the heating wire 37B for heating is provided in the cylinder 37A is used as a thawing device is illustrated. However, the present invention is not limited to this, and for example, a cylinder may be disposed in the center of the filter case 35 and a part of the engine coolant may be introduced into the cylinder. Further, the heater 37 may be disposed at a position slightly deviated from the central portion (axial center position) of the filter case 35.
　実施の形態では、排気ガス浄化装置１４が搭載される建設機械としてクローラ式の油圧ショベル１を例示している。しかし、本発明はこれに限るものではなく、例えばホイール式の油圧ショベル、ホイールローダ等のエンジンを搭載した建設機械に広く適用することができる。 In the embodiment, the crawler excavator 1 is illustrated as a construction machine on which the exhaust gas purifying device 14 is mounted. However, the present invention is not limited to this, and can be widely applied to construction machines equipped with engines such as wheel-type hydraulic excavators and wheel loaders.
　９　エンジン
　１０　排気管
　１４　排気ガス浄化装置
　２１　尿素選択還元触媒
　２４　尿素水噴射弁
　２５　尿素水タンク
　２６　尿素水管路
　２７，２７′，２７″　タンク側尿素水管路
　２７Ａ，２８Ａ，４１Ａ，５１Ａ，２８Ａ′　一端
　２７Ｂ，２８Ｂ，４１Ｂ，２７Ｂ′，２７Ｂ″　他端
　２８，４１，５１　噴射弁側尿素水管路
　３０，６１　尿素水供給装置
　３４　尿素水フィルタ
　３５　フィルタケース
　３５Ｂ　上面板
　３５Ｃ　底面板
　３５Ｅ　濾過前室
　３５Ｆ　濾過後室
　３６　フィルタエレメント
　３７　ヒータ（解凍装置）
　４２，５２　拡張室形成体
　４３，５３　拡張室 9 Engine 10 Exhaust pipe 14 Exhaust gas purification device 21 Urea selective reduction catalyst 24 Urea water injection valve 25 Urea water tank 26 Urea water pipe 27, 27 ', 27 "Tank side urea water pipe 27A, 28A, 41A, 51A, 28A' One end 27B, 28B, 41B, 27B ', 27B "The other end 28, 41, 51 Injection valve side urea water conduit 30, 61 Urea water supply device 34 Urea water filter 35 Filter case 35B Top plate 35C Bottom plate 35E Pre-filtration chamber 35F Post-filtration chamber 36 Filter element 37 Heater (thawing device)
42,52 Expansion chamber forming body 43,53 Expansion chamber

Claims (4)

  1. 　エンジンの排気管に接続され排気ガス中の窒素酸化物を除去する尿素選択還元触媒と、
    　還元剤である尿素水を前記尿素選択還元触媒の上流側に噴射する尿素水噴射弁と、
    　前記尿素水噴射弁に供給される尿素水を貯える尿素水タンクと、
    　前記尿素水タンクと前記尿素水噴射弁との間を接続する尿素水管路と、
    　前記尿素水管路の途中に設けられ前記尿素水タンクから前記尿素水噴射弁に向けて尿素水を供給する尿素水供給装置と、
    　前記尿素水タンクと前記尿素水供給装置との間に位置して前記尿素水管路の途中に設けられ尿素水に混入した異物を捕集する尿素水フィルタとを備えてなる排気ガス浄化装置において、
    　前記尿素水フィルタは、上面と底面とを有し内部に尿素水を貯留する容器からなるフィルタケースと、尿素水に混入した異物を捕集するために前記フィルタケース内に設けられ、前記フィルタケース内を異物が濾過される前の尿素水を貯留する濾過前室と異物が濾過された後の尿素水を貯留する濾過後室とに分けるフィルタエレメントとを有し、
    　前記フィルタケースの前記濾過後室内には、前記フィルタケース内で凍結した尿素水を解凍する解凍装置が設けられ、
    　前記尿素水管路は、一端が前記尿素水タンクに接続され、他端が前記フィルタケースの前記濾過前室内に位置して前記フィルタケースの底面位置に開口したタンク側尿素水管路と、一端が前記フィルタケースの前記濾過後室内に位置して前記フィルタケースの上面位置に開口し、他端が前記尿素水噴射弁に接続された噴射弁側尿素水管路とにより構成されていることを特徴とする排気ガス浄化装置。     A urea selective reduction catalyst connected to the exhaust pipe of the engine and removing nitrogen oxides in the exhaust gas;
    A urea water injection valve for injecting urea water as a reducing agent to the upstream side of the urea selective reduction catalyst;
    A urea water tank for storing urea water supplied to the urea water injection valve;
    A urea water pipe connecting the urea water tank and the urea water injection valve;
    A urea water supply device that is provided in the middle of the urea water pipe and supplies urea water from the urea water tank toward the urea water injection valve;
    In the exhaust gas purification apparatus comprising a urea water filter that is located between the urea water tank and the urea water supply device and is provided in the middle of the urea water pipe and collects foreign matter mixed in the urea water,
    The urea water filter is provided in the filter case for collecting foreign matter mixed in urea water, a filter case comprising a container having an upper surface and a bottom surface and storing urea water therein, and the filter case A filter element that divides the inside of a pre-filtration chamber for storing urea water before foreign matter is filtered and a post-filtration chamber for storing urea water after foreign matter is filtered;
    A thawing device for thawing urea water frozen in the filter case is provided in the filtered room of the filter case,
    The urea water pipe has one end connected to the urea water tank, the other end located in the pre-filtration chamber of the filter case and opened to the bottom surface of the filter case, and one end of the urea water pipe The filter case is located in the post-filtration chamber and opens to the upper surface position of the filter case, and the other end is constituted by an injection valve side urea water pipe connected to the urea water injection valve. Exhaust gas purification device.
  2. 　前記解凍装置は、前記フィルタケースの中央部に上，下方向に延びた状態で設けられていることを特徴とする請求項１に記載の排気ガス浄化装置。 The exhaust gas purification device according to claim 1, wherein the thawing device is provided in a state of extending upward and downward in a central portion of the filter case.
  3. 　前記噴射弁側尿素水管路には、前記尿素水フィルタと前記尿素水供給装置との間に位置して前記噴射弁側尿素水管路の管路面積よりも大きな断面積をもった拡張室を形成する拡張室形成体が設けられていることを特徴とする請求項１に記載の排気ガス浄化装置。 An extension chamber having a cross-sectional area larger than the pipe area of the injection valve side urea water pipe is formed in the injection valve side urea water pipe between the urea water filter and the urea water supply device. The exhaust gas purification device according to claim 1, wherein an expansion chamber forming body is provided.
  4. 　前記拡張室形成体は、前記フィルタケースの上面に一体に設けられていることを特徴とする請求項３に記載の排気ガス浄化装置。 The exhaust gas purification device according to claim 3, wherein the expansion chamber forming body is integrally provided on an upper surface of the filter case.
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