JP2004324502A - Reducing-agent injector for exhaust-emission control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reducing-agent injector for exhaust-emission control in which a thermal trouble is not caused even being exposed to a reducing agent at high temperature, a driving force for a solenoid controlled valve for control of an injection-quantity is minimized, and an ensured vaporization of the reducing agent in an exhaust-gas path is effected. <P>SOLUTION: The injector comprises an injection part 20A in which an injection hole 21 and a valve element 19 are provided for introducing a high-pressure/high-temperature reducing agent, and a driving part 30A in which a pressure chamber 38a for driving the value element 19 and a solenoid-controlled valve 41A for controlling the drive of the pressure chamber. The driving part 30A is cooled by the reducing-agent for cooling and the injection hole 21 is opened /closed by opening/closing the outlet of the pressure chamber 38a by the valve 41A to utilize the pressure of the cooling reducing-agent. Thus, a precise control of reducing-agent injection can be performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a reducing agent injector used in an exhaust gas purifying apparatus for decomposing NOx (nitrogen oxide) contained in exhaust gas with a reducing agent and a reducing catalyst to make the NOx harmless.
[0002]
[Prior art]
2. Description of the Related Art In order to prevent air pollution caused by exhaust gas discharged from machinery and equipment such as a diesel engine, a boiler, a gas turbine, and a coke oven, removing and reducing NOX in the exhaust gas has been widely practiced. As a denitration means, it is common to use a method in which an aqueous solution of ammonia or urea is used as a reducing agent, and this is sprayed and added to exhaust gas and then brought into contact with a reduction catalyst.
[0003]
When the reducing agent is sprayed into the exhaust gas, especially if the urea aqueous solution remains liquid, it generates a solid compound derived from the reducing agent and adheres and accumulates on the reduction catalyst and the exhaust pipe to prevent functional problems such as clogging. There is a problem of causing. In order to evaporate the reducing agent, Japanese Patent Application Laid-Open No. 5-31327 proposes a method in which the reducing agent is directly sprayed into the exhaust gas and vaporized by the heat of the exhaust gas. Is sprayed into compressed air, mixed with exhaust gas, and vaporized by the heat of the exhaust gas. Japanese Patent Application Laid-Open No. 5-57146 proposes means for spraying a reducing agent into superheated steam of an exhaust gas boiler and vaporizing the same to discharge the exhaust gas. Means have been proposed in which a reducing agent is sprayed and vaporized into air heated by a heater and injected into exhaust gas.
[0004]
The means for vaporizing the reducing agent by using the heat of the exhaust gas described above does not require a special heat generating means for vaporizing, but when the exhaust gas temperature is lower than the vaporizing temperature of the reducing agent, the solid compound Inconveniences such as generation and NOx emission into the atmosphere are produced. Means for vaporizing a reducing agent by using heat of superheated steam of an exhaust gas boiler is a means in a very limited specific field, and is not widely and generally available.
[0005]
Further, the means using the heat generated by the electric heater, although similar to the technology using the heat of the superheated steam, can easily achieve the purpose of removing and reducing NOX even when the exhaust gas temperature is low, but consumes a large amount of electric power, In particular, when electric power obtained from a generator attached to an automobile diesel engine is used, problems such as a reduction in fuel consumption and an increase in the capacity of the generator are unavoidable. In addition, this means does not consider adjusting the amount of the reducing agent in accordance with the NOX concentration in the exhaust gas as in the other means described above. In addition to this, there is a risk that not only will excess waste be released into the atmosphere, but also further pollution of the atmosphere will occur. In particular, it is almost impossible to always spray an appropriate amount of reducing agent in response to a drastically fluctuating NOX concentration, such as in an automotive diesel engine whose operating conditions change drastically and frequently.
[0006]
On the other hand, the inventor of the present application and the applicant of the present application have disclosed in Japanese Patent Application No. 2002-298498 that, in addition to increasing the pressure of the reducing agent by a pump and heating it to a temperature slightly lower than the boiling point by a heater, We have proposed an exhaust gas purifier that removes NOx efficiently by injecting it into the exhaust gas passage with an injector while controlling the pressurizing / heating state with an electronic controller.
[0007]
This prior art uses an electronic control device to control the reducing agent injection amount according to the NOx concentration, and to control the reducing agent heating temperature according to the temperature of the reducing agent or exhaust gas. It is highly useful in that it can be reliably vaporized when sprayed into the exhaust gas passage without causing excess or deficiency.
[0008]
Here, since the injector used in the prior application requires high-precision and sensitive flow control from a small flow rate to a large flow rate, an electromagnetically driven fuel injection valve used for fuel supply of an internal combustion engine for an automobile is required. Preferably, similar ones are used.
[0009]
However, since such an injector is exposed to a high-temperature reducing agent, the reliability of heat resistance is poor in the nichrome wire coating of the electromagnetic coil, the resin portion of the connector, the O-ring for airtightness, and the like, and a trouble is likely to occur. There's a problem.
Further, this injector is of a type in which a valve element (needle valve) is directly driven via a plunger by the attraction force of an electromagnetic coil. However, when the injection pressure is high, it is necessary to increase the attraction force accordingly. Therefore, it is necessary to increase the voltage of the current flowing through the electromagnetic coil, or to use an electromagnetic coil having a low resistance value through which a large current flows, and in addition, power consumption tends to be a problem.
[0010]
Furthermore, in the above-described technology in which the reducing agent is heated and then injected into the exhaust gas, a heater such as a heat exchanger or an electric heater using waste heat of the exhaust gas is used. The reducing agent is provided in the reducing agent pipe, and when the engine is started in which the reducing agent in the pipe is at a low temperature, the reducing agent downstream of the heater and in the injector remains at a low temperature. Therefore, if this is injected into the exhaust gas as it is, the exhaust gas at the time of start-up is also at a low temperature, and the reducing agent is not sufficiently vaporized, causing a problem of adhesion and deposition of a solid compound.
[0011]
[Problems to be solved by the invention]
The present invention is intended to solve the above problems, the injector of the reducing agent used in the exhaust gas purification device, so as not to cause trouble even when exposed to high-temperature reducing agent, Minimize the driving force of the solenoid valve required for injection amount control.Furthermore, when the reducing agent immediately before injection is in a low temperature state or when the operating state of the exhaust gas generating machine / equipment changes transiently Another object is to realize reliable vaporization in the exhaust gas passage.
[0012]
[Means for Solving the Problems]
Therefore, the present invention provides a method for injecting a high-pressure and high-temperature reducing agent into an exhaust gas passage extending from an exhaust gas generating machine / equipment and in which a denitration reactor is installed, thereby bringing the reducing agent into contact with the reduction catalyst of the denitration reactor in a vaporized state. A reducing agent injector used in an exhaust gas purifying device that decomposes NOX in exhaust gas by the above-described method has an injection hole, a valve body, and an injection reducing agent passage that introduces the high-pressure / high-temperature reducing agent into the injection hole. A drive unit having an injection unit, a cooling reducing agent passage through which a high-pressure and normal-temperature reducing agent passes, and a pressure chamber for driving a valve element provided in the middle thereof, and an electromagnetic valve for controlling the reducing agent pressure in the pressure chamber. The drive unit is cooled by the passage of the high-pressure / room-temperature reducing agent, and the solenoid valve is turned off the outlet of the pressure chamber by a drive signal generated by an electronic control device according to the NOx concentration in the exhaust gas. Open and close When the pressure in the pressure chamber decreases when opened, the valve element opens the injection hole to inject the high-pressure and high-temperature reducing agent, and when closed, the pressure in the pressure chamber increases, so that the valve element The first means for solving the above-mentioned problem was achieved by closing the injection hole.
[0013]
This makes it possible to use a urea aqueous solution that is harmless to the reducing agent and easy to handle, and introduces a high-pressure, normal-temperature reducing agent into the electromagnetic drive unit separately from the high-pressure, high-temperature reducing agent supplied to the injection unit. In particular, by cooling the solenoid valve portion, it is possible to easily prevent the low heat-resistant component used in the drive section from being thermally damaged by the high-temperature injection reducing agent. Further, since the valve element of the injection unit is driven by using the high pressure of the reducing agent introduced into the driving unit, the suction force of the electromagnetic coil is sufficient to open and close the outlet of the pressure chamber. Therefore, it is possible to easily cope with high-pressure injection with a small solenoid valve that consumes less power. In the present invention, the high-temperature reducing agent refers to a reducing agent that is heated to a temperature slightly lower than the vaporization temperature, and the high-pressure reducing agent is sufficiently atomized when injected from an injection unit and is in a pressure chamber. Refers to a reducing agent that is pressurized to a pressure that can provide a driving force for the valve element.
[0014]
Further, as a second means for solving the above problem, in addition to the first means, an electric heater for heating a reducing agent in the injection reducing agent passage is provided in the injection unit, and the electric heater is provided with a reducing agent. When the temperature is lower than the temperature at which the fuel can be vaporized when injected, the reducing agent is heated to a temperature at which the reducing agent can be vaporized by a command from the electronic control unit. This makes it possible to perform precise temperature control during the injection of the reducing agent, and in particular, eliminates the disadvantage that the low-temperature reducing agent is injected into the exhaust gas passage at the time of starting, etc. In this way, sufficient vaporization can always be realized.
[0015]
Further, in the first or second means, a temperature sensor is provided in the injection reducing agent passage of the injection unit, and the electronic control device controls the electric control based on the temperature of the reducing agent immediately before injection detected by the temperature sensor. The third means is to control the heater. Thus, the temperature of the reducing agent immediately before the injection can be precisely controlled, and the vaporization of the reducing agent injected into the exhaust gas passage is further ensured.
[0016]
Still further, in the first, second or third means, the high-pressure and high-temperature reducing agent is pressurized by a pump, and then heated by a heater and sent to the injection section. The fourth means is that the reducing agent pressurized by the pump is diverted in front of the heater, passed through the driving section, and returned to the suction side of the pump. Thereby, the reducing agent pressurized by the pump is heated so as to be suitable for vaporization and is sent to the injection unit, and the reducing agent is not heated so as to be suitable for cooling and is sent to the driving unit at room temperature without being heated. Since the reducing agent that has been diverted surely and fed into the drive unit passes through the drive unit while cooling, it is returned to the suction side of the pump, so that it can be reused effectively.
[0017]
In addition, in the first, second, third or fourth means, the injection unit and the drive unit may be arranged so as to sandwich a thin cylindrical body that limits heat conduction. The fifth means. As a result, a large amount of heat is prevented from being transmitted from the injection unit to the drive unit, and the temperature of the injection unit is reduced by the cooling action from the drive unit, so that the reducing agent temperature during injection is reduced. Can be prevented.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings. Note that, even in different embodiments, the same components will be described with the same reference numerals. The reducing agent used in the present embodiment is an aqueous urea solution from the viewpoint of safety and ease of handling.
[0019]
First, the configuration and operation of an exhaust gas purifying apparatus 50 in which the injector of the present invention is arranged will be described with reference to FIG. In the present embodiment, an exhaust gas generating machine / equipment is an automobile diesel engine 1, an exhaust gas passage is an exhaust pipe 2, and an injection unit having an injection unit 20A and a drive unit 30A shown in FIG. The vessel 6A is used.
[0020]
The reducing agent stored in the tank 9 is sent to the injector 6A by a pipe 12, and a low-pressure pump 8, a high-pressure pump 15, a heater 14, and an electric heater 13 are provided on the path. The reducing agent guided by the pipe 12 extending from the tank 9 is pressurized by the low-pressure pump 8 and further pressurized by the high-pressure pump 15. The pressure of the reducing agent is adjusted by the pressure regulator 7 a on the discharge side of the low-pressure pump 8, and the pressure is also adjusted by the pressure regulator 7 b on the discharge side of the high-pressure pump 15. Further, the injection of the reducing agent by the injector 6A is controlled by the electronic control device 10, and is built in the drive unit 30A of the injector 6A by an operation command (duty cycle signal) from the electronic control device 10. The solenoid valve repeats opening and closing to adjust the injection amount from the injection unit 20A.
[0021]
In general, when a liquid is heated and vaporized, the lower the pressure of the liquid, the easier it is to vaporize, and the higher the pressure, the more difficult it is to vaporize. Therefore, it is widely known that when a reducing agent in a liquid state is heated to a high pressure and then heated, the temperature in a liquid state can be increased to a high temperature. It is being done. Therefore, also in the present embodiment, the reducing agent is pressurized before heating. The high-pressure reducing agent is heated to a vaporization temperature by the heater 14 or the electric heater 13, that is, a temperature slightly lower than the boiling point, so that the high temperature is maintained in a liquid state and completely vaporized when injected. It becomes possible. In addition, in the present embodiment, the pump has two stages and the respective discharge pressures are adjusted to be constant, whereby the pressure fluctuates and the reducing agent boils in the heater 14 or the electric heater 13. It is possible to eliminate the concern that air bubbles or solid compounds are generated in the pipe. Further, by eliminating bubbles in the injected reducing agent, the amount of the reducing agent injected from the injector 6A can be made accurate and the exhaust gas purification efficiency can be increased.
[0022]
The pipe 12 is branched between the high-pressure pump 15 and the heater 14 into an injection reducing agent pipe 12a toward the injection unit 20A of the injector 6A and a cooling reducing agent pipe 12b toward the driving unit 30A of the injector 6A. You.
The high-pressure / room-temperature reducing agent that has entered the injection reducing agent pipe 12 a is heated by the heat of the wall of the exhaust pipe 2 by the heater 14 controlled by the temperature controller 16. The pipe wall of the exhaust pipe 2 is heated by the heat of conduction from the diesel engine 1 and the heat of the exhaust gas flowing through the inside thereof, thereby making it possible to heat the reducing agent to a high temperature.
[0023]
An example of the configuration of the heater 14 and the temperature control device 16 is shown in detail in the enlarged view in the dashed line at the bottom of FIG. That is, the temperature control device 16 attaches the pedestal 16c to the pipe wall of the exhaust pipe 2, fixes the heater 14 to the pedestal 16c with the heat insulating material 16d interposed therebetween, and enables the heat transfer member 16b to slide on the pedestal 16c. The heat transfer member 16b is connected to a rod 16f extending from the solenoid 16a so as to be in contact with or away from the heater 14. The pedestal 16c and the heat transfer member 16b are made of metal excellent in heat conduction. The heater 14 has a heat transfer path 14b formed inside a solid body 14a also made of a metal having high heat conductivity, and a temperature sensor 17a is provided at an exit portion of the heat transfer path 14b. I have.
[0024]
Then, the high-pressure / high-temperature reducing agent heated by the heater 14 is further heated by the electric heater 13 and then supplied to the injection unit 20A of the injector 6A in a high-pressure / high-temperature state. Here, by heating the reducing agent whose boiling point has been raised by pressurization to such an extent that it does not evaporate, it can be instantaneously vaporized when injected into the exhaust pipe 2 at substantially atmospheric pressure. Further, in addition to heating by the heater 14, heating by the electric heater 13 is different from boilers and gas turbines which generate relatively high-temperature waste heat, and generates relatively low-temperature waste heat. This is because sufficient and appropriate heating is performed in accordance with the characteristics of a diesel engine that is easy and the temperature change of waste heat is large. Since the heater 14 heats the reducing agent by using the waste heat from the exhaust pipe 2 and the electric heater 13 heats the auxiliary, it is necessary to newly heat the reducing agent. The consumption of electric power, which is assumed to be energy, is small.
[0025]
Further, in addition to the temperature sensor 17 a being disposed on the heater 14, the temperature sensor 17 b is also disposed on the outlet portion of the electric heater 13, and the temperature sensor 5 is also disposed on the exhaust pipe 2. NOX sensors 4a and 4b are arranged before and after the denitration reactor 3 in the exhaust pipe 2, respectively. Then, based on the values detected by these temperature sensors 17a, 17b, 5 and the NOx sensors 4a, 4b, the electronic control device 10 issues operation commands to the temperature control device 16, the electric heater 13, and the injector 6A. The temperature control of the reducing agent corresponding to the exhaust gas temperature and the injection amount control according to the NOx concentration in the exhaust gas can be performed. In addition, by controlling the heater 14, the injector 6A, and the electric heater 13 by the electronic controller 10 in this manner, the temperature of the reducing agent is precisely controlled to completely vaporize the exhaust gas in the exhaust pipe 2, and the exhaust gas is exhausted. It is possible to respond instantaneously to changes in the state of exhaust gas in the pipe 2.
[0026]
As described above, in the path until the reducing agent is injected by the injector 6A, the pressure and the temperature are appropriately controlled and controlled so as not to evaporate. In addition to not generating it, it is extremely significant in that it can reliably prevent the problem that the reducing agent pressure fluctuates by generating the gas phase and that the amount of reducing agent injected by the injection of the gaseous phase portion is incorrect. It is.
[0027]
Next, the injector 6A will be described in detail with reference to FIG.
This injector 6A is not limited to the case of being used in the exhaust gas purifying apparatus 50 of the diesel engine 1 described above. The configuration is common to the electromagnetically driven fuel injection valve used to supply fuel for the internal combustion engine for automobiles.
[0028]
In the injector 6A, a drive unit 30A is provided on the base end side (upper side) of a substantially cylindrical metal body case 18, and an injection unit 20A is provided on the distal end side (injection nozzle side). The main body case 18 includes an upper main body case 18a forming the driving unit 30A, a lower main body case 18b forming the injection unit 20A, and a thin cylindrical body 18c sandwiching the upper main body case 18a and restricting heat transfer at a substantially central position. It consists of:
[0029]
The injection unit 20A has a nozzle 20a provided with a nozzle chamber 22 and an injection hole 21, and has an injection reducing agent inlet 25 on a side surface near the cylindrical body 18c. A needle-shaped valve element 19 having a sharp tip is inserted into the nozzle chamber 22 movably in the vertical direction in the drawing, and the tip closes or opens the injection hole 21 by vertical movement.
[0030]
The injection reducing agent inlet 25 is connected to the nozzle chamber 22 via an injection reducing agent passage 24 extending toward the injection port 21. The nozzle chamber 22 is a substantially cylindrical space in which the base end is enlarged and the injection hole 21 is open at the front end, and the front end of the valve body 19 is inserted therein. The valve element 19 is linearly connected via a piston rod 27a to a piston 27 fitted in a cylinder hole 38 forming a pressure chamber 38a described later in the driving unit 30A, and is also injected by a spring 23. It is urged in the direction of pressing (closing) the tip against the hole 21.
[0031]
On the other hand, the drive unit 30A has a cooling agent outlet 35 at the upper end, and has a built-in electromagnetic coil 41, a valve 29a, an electromagnetic valve spring 36, and an electromagnetic valve 41A having a valve seat 30a in the center, It has a support member 30d which has a cylinder hole 38 near the cylindrical body 18c and in which the piston 27 is fitted slidably up and down. The space on the side opposite to the piston of the cylinder hole 38 constitutes a pressure chamber 38 a, and an outlet orifice 38 b provided substantially at the center of the ceiling of the pressure chamber 38 a communicates with the cooling agent outlet 35.
[0032]
A cooling reductant inlet 32 is opened on the outer peripheral side surface of the upper main body case 18a near the cylinder hole 38, and the cooling reductant inlet 32 is opened to a side wall of the pressure chamber 38a through a reducing agent inflow passage 33a. It is connected to an inlet orifice 37.
[0033]
The valve seat 30a is formed at an upper opening of the outlet orifice 38b. The valve 29a has a short axis and has a flange-shaped movable iron core 29f fixed to the base end. The conical tip is urged by the electromagnetic valve spring 36 in the direction in which it comes into contact with the valve seat 30a, and is supported slidably up and down by the support member 30f. An electromagnetic coil 31 controlled by the electronic control device 10 is disposed above the valve 29a. The movable iron core 29f is attracted by a magnetic force generated at the time of energization, and the valve 29a resists the urging force of the electromagnetic valve spring 36. And pull it up.
[0034]
The outlet orifice 38b passes through the inside of the solenoid valve spring 36 through the through hole 34a provided in the support member 30f and the hole provided in the flange portion of the valve 29a, and communicates with the cooling reducing agent outlet 35. ing.
[0035]
FIG. 2 shows a reducing agent injector 6A using a two-way solenoid valve 41A as the solenoid valve. FIG. 2 (A) shows that the solenoid coil 31 is not energized and the injection hole 21 is in the valve body 19. FIG. 2B shows a state in which the electromagnetic coil 31 is energized, the valve element 19 is retracted, the injection hole 21 is opened, and the reducing agent is injected. Show.
[0036]
In the non-energized state shown in FIG. 2A, the high-pressure / room-temperature reducing agent pressurized by the high-pressure pump 15 and supplied to the cooling reducing agent inlet 32 through the cooling reducing agent pipe 12b is supplied to the reducing agent. The gas is introduced from the inlet orifice 37 into the pressure chamber 38a via the inflow passage 33a. At this time, since the electromagnetic coil 31 is not energized, the distal end of the valve 29a is pressed against the valve seat 30a by the urging force of the electromagnetic valve spring 36 to close the outlet orifice 38b of the pressure chamber 38a. Therefore, the piston 27 is pressed and moved downward by the high-pressure / normal-temperature reducing agent in the pressure chamber 38a.
[0037]
On the other hand, in the injection section 20A, the reducing agent supplied to the injection reducing agent inlet 25 through the injection reducing agent pipe 12a is in a high-pressure and high-temperature state. Will be introduced. At this time, the force acting in the valve closing direction, which is the sum of the spring load of the spring 23 and the pressure of the reducing agent in the pressure chamber 38a, is applied to the valve body 19 by the reducing agent supplied to the nozzle chamber 22. Since the force acting in the valve opening direction received by the annular valve body pressure receiving portion 19b in the side large diameter portion is larger, the injection port 21 is closed.
[0038]
At the time of energization shown in FIG. 2B, the movable iron core 29f is attracted by the generated magnetic force against the urging force of the solenoid valve spring 36, and the distal end of the valve 29a is separated from the valve seat 30a, and the pressure chamber 38a is released. A passage is formed from the cooling water to the cooling agent outlet 35 through the outlet orifice 38b. At this time, since the flow passage area of the inlet orifice 37 is made smaller than the flow passage area of the outlet orifice 38b, the pressure in the pressure chamber 38a rapidly decreases. For this reason, the force in the valve opening direction by the high pressure and high temperature reducing agent received by the valve body pressure receiving portion 19b becomes larger than the force in the valve closing direction by the pressure chamber 38a and the spring 23, and the valve body 19 moves upward to inject the fuel. The hole 21 is opened and the reducing agent is injected. Therefore, since the electromagnetic coil 31 only needs to have an attractive force enough to drive the valve 29a, even when a high injection pressure is required during the injection of the reducing agent, the injection amount is controlled with a small amount of power consumption. be able to.
[0039]
As described above, when the energization / demagnetization by energizing / de-energizing the electromagnetic coil 31 is repeated for a long time, the temperature of the injection unit 20A exposed to the high-temperature reducing agent gradually increases, and this heat passes through the main body case 18. As a result, the electric current is transmitted to the driving unit 30A. Therefore, in addition to being heated by the electric resistance heat by energization in the electromagnetic valve 41A, the drive unit 30 is also heated by the heat from the injection unit 20A.
[0040]
However, each time the valve 29a is opened, the reducing agent at room temperature is fed into and out of the drive unit 30A, so that the inside of the drive unit 30A and the low heat-resistant components constituting the drive unit 30A are constantly cooled. Thus, the temperature is prevented from becoming high. Therefore, even if the injection unit 20A on the distal end side is exposed to a high-temperature reducing agent, the portion of the injector 6A having a problem with the heat resistance of the drive unit 30A on the proximal end side is sufficiently cooled, so that the injector 6A is thermally damaged. There is almost no worry. In the present embodiment, since the thin cylindrical body 18b is provided at a substantially middle portion of the main body case 18 which is a heat conduction path from the injection unit 20A to the driving unit 30A, the heat conduction from the injection unit 20A is performed. Is limited. In addition, the cylindrical body 18b also has a function of suppressing a decrease in the temperature of the injection unit 20A due to the cooling of the driving unit 30A and preventing the temperature of the reducing agent to be injected from being reduced.
[0041]
FIG. 3 shows a different embodiment of the injector. In the injector 6B, the driving unit 30A is the same as the driving unit 30A of the injector 6A in FIG. 2, and the injector 20B is the injection unit in FIG. An electric heater 39 and a temperature sensor 40 are provided in the injection section 20A of the vessel 6A. The configuration and operation of the driving unit 30A are the same as those in FIG.
[0042]
For example, immediately after the diesel engine 1 is started in a cold state, the waste heat temperature is low, and the temperature required for vaporization may not be reached even when the diesel engine 1 is heated by the electric heater 13. According to the present embodiment, the temperature sensor 40 detects the temperature of the reducing agent immediately before injection, and when the electronic controller 10 determines that the temperature required for vaporization has not been reached based on the value, the electric heater 39 To heat the reducing agent to the required temperature. This can solve the problem that the insufficiently heated reducing agent is injected into the exhaust pipe 2 and the solid compound is not sufficiently vaporized and adheres to the exhaust pipe 2 and the reduction catalyst. The heating by the heater 39 can be controlled by using the temperature detected by the temperature sensors 17a and 17b provided in the heater 14 and the electric heater 13 without using the temperature sensor 40. However, by detecting the temperature of the reducing agent immediately before the injection by the temperature sensor 40, the temperature management of the reducing agent to be injected can be made more appropriate.
[0043]
FIGS. 4 and 5 show injection having a drive unit 30B in which the solenoid valve 41A having a two-way valve structure is replaced by a solenoid valve 41B having a three-way valve structure in the drive unit 30A of the injector 6A of FIG. 2 or the injector 6B of FIG. It is a partial view of container 6C. This injector 6C has the same injection unit as the above-described injection unit 20A or injection unit 20B, and thus the illustration is omitted and only the drive unit 30B will be described.
[0044]
A cylindrical outer valve 29b having a through hole 29e extending from the base end to the tip and having a flange-shaped movable iron core 29g at the base end has a thin shaft-shaped inner valve 29c inserted therein from the base end side, and The side is fitted to the support member 30e so as to be slidable up and down, and the end thereof is urged by an electromagnetic valve spring 36 so as to be pressed against the outer valve seat 30b. The electromagnetic valve spring 36 also fixes the base end of the inner valve 29c so as not to move by pushing it upward.
[0045]
Further, an inner valve seat 30c which is closed by a tip of the inner valve 29c is provided near a tip of the outer valve 29b. Further, on the wall surface of the outer valve 29b close to the inner valve seat 30c, there is provided an introduction hole 29d communicating with the cooling agent inlet 32 via a reducing agent inflow passage 33b provided in the support member 30e. On the side of the support member 30e adjacent to the outer valve seat 30b, there is provided a reducing agent outflow passage 34b through which the reducing agent flows in the direction of the cooling reducing agent outlet 35. Below the outer valve seat 30b of the support member 30e, a pressure chamber 38c connected by an outlet orifice 38d and a piston 27 fitted vertically slidably in the cylinder hole 38 are arranged.
[0046]
As shown in FIG. 4, when the electromagnetic coil 31 is de-energized, the outer valve 29b is pressed against the outer valve seat 30b by the electromagnetic valve spring 36, so that the high-pressure / room-temperature reducing agent is discharged from the pressure chamber 38c. Possible routes are closed. At this time, the inner valve 29c is separated from the inner valve seat 30c, and the reducing agent inflow passage 33b communicates with the pressure chamber 38c. Therefore, the pressure chamber 38c is in a high pressure state, and the valve body closes the injection hole 21 by overcoming the force in the valve opening direction at the injection unit.
[0047]
As shown in FIG. 5, when the electromagnetic coil 31 is energized, the movable iron core 39g is attracted by the magnetic force against the urging force of the electromagnetic valve spring 36, and the outer valve 29b is separated from the outer valve seat 30b, so that the pressure chamber 38c And the reducing agent outflow passage 34b. At this time, the inner valve seat 30c in the outer valve 29b is in close contact with the tip of the inner valve 29c, the reducing agent inflow passage 33b is cut off from the pressure chamber 38c, and the pressure in the pressure chamber 38c becomes low. For this reason, the force in the valve opening direction in the injection unit becomes larger than the force acting in the valve closing direction, thereby opening the injection hole and injecting the reducing agent.
[0048]
In this way, by making the electromagnetic valve 41B have a three-way valve structure, when the pressure chamber 38c communicates with the outlet side reducing agent outflow passage 34b by energizing the electromagnetic coil 31, the inlet side reducing agent inflow passage 34b Since the communication between the pressure chamber 33b and the pressure chamber 38c is completely closed, the pressure difference between the pressure in the pressure chamber 38c and the pressure of the reducing agent supplied to the injection unit becomes larger, so that the valve body is easily driven. Thus, the injection of the reducing agent is reliably performed. This also allows for more precise injection amount control.
[0049]
【The invention's effect】
As described above, according to the injector of the present invention, even if the injector is exposed to the high-temperature reducing agent, it is possible to prevent the drive unit from being thermally damaged. In addition, it is possible to minimize the driving force of the solenoid valve required for controlling the injection amount, and to realize reliable vaporization in the exhaust gas passage.
[Brief description of the drawings]
FIG. 1 is a partially enlarged layout view showing an example of an exhaust gas purifying apparatus using an injector of the present invention.
FIGS. 2A and 2B are longitudinal sectional views showing different states of an embodiment of the present invention.
FIG. 3 is a longitudinal sectional view of another embodiment of the present invention.
FIG. 4 is a partial longitudinal sectional view of still another embodiment of the present invention.
FIG. 5 is a partial longitudinal sectional view showing a state different from FIG. 4 in the embodiment of FIG. 4;
[Explanation of symbols]
Reference Signs List 1 diesel engine, 2 exhaust pipe, 3 denitration reactor, 4a, 4b NOX sensor, 5, 17a, 17b temperature sensor, 6A, 6B, 6C injector, 7a, 7b pressure regulator, 8 low pressure pump, 9 tank, 10 Electronic control device, 12 piping, 12a Reducing agent piping for injection, 12b Reducing agent piping for cooling, 13, 39 Electric heater, 14 Heater, 14a Body, 14b Heat transfer path, 15 High pressure pump, 16 Temperature control device, 16a Solenoid, 16b heat transfer member, 16c pedestal, 16d heat insulator, 16e return spring, 16f rod, 18 body case, 18a upper body case, 18b lower body case, 18c cylindrical body, 19 valve body, 19b valve body pressure receiving part, 20A, 20B injection part, 20a nozzle, 21 injection hole, 22 nozzle chamber, 23 spring, 24 injection reducing agent passage, 25 injection Reducing agent inlet, 27 piston, 27a piston rod, 29a valve, 29b outer valve, 29c inner valve, 29d introduction hole, 29e through hole, 29f, 29g movable iron core, 30A, 30B drive unit, 30a valve seat, 30b outer valve seat, 30c Inner valve seat, 30d, 30e, 30f support member, 31 electromagnetic coil, 32 cooling agent inlet, 33a, 33b reducing agent inflow passage, 34a through hole, 34b reducing agent outflow passage, 35 cooling agent outlet, 36 Solenoid valve spring, 37 inlet orifice, 38 cylinder bore, 38a, 38c pressure chamber, 38b outlet orifice, 40 temperature sensor, 41A, 41B solenoid valve, 50 exhaust gas purification device

Claims (7)

NOx in exhaust gas by injecting a high-pressure and high-temperature reducing agent into an exhaust gas passage extending from an exhaust gas generating machine / equipment and provided with a denitration reactor and bringing the reducing agent into contact with the reduction catalyst in the denitration reactor in a vaporized state. An injector for a reducing agent used in an exhaust gas purification device for decomposing
An injection portion having an injection hole and a valve element and an injection reducing agent passage for introducing the high-pressure / high-temperature reducing agent into the injection hole, a cooling-use reducing agent passage through which a high-pressure / normal-temperature reducing agent passes, and A drive unit having a pressure chamber for driving the valve body provided and an electromagnetic valve for controlling the reducing agent pressure of the pressure chamber,
The drive unit is cooled by the passage of the high-pressure / room-temperature reducing agent, and the solenoid valve opens and closes the outlet of the pressure chamber by a drive signal generated by an electronic control device according to the NOx concentration in the exhaust gas, and is opened. When the pressure in the pressure chamber decreases, the valve element opens the injection hole to inject the high-temperature and high-pressure reducing agent, and when closed, the pressure in the pressure chamber increases to cause the injection of the valve element. It is supposed to close the hole,
A reducing agent injector for purifying exhaust gas, characterized in that: The injector according to claim 1,
The injection unit has an electric heater for heating the reducing agent in the injection reducing agent passage. It is supposed that the reducing agent is heated to a temperature at which the reducing agent can be vaporized by a command of the type controller,
A reducing agent injector for purifying exhaust gas, characterized in that: A temperature sensor is provided in the injection reducing agent passage of the injection unit, and the electronic control device controls the electric heater based on the temperature of the reducing agent immediately before injection detected by the temperature sensor. The reducing agent injector for purifying exhaust gas according to claim 2. The high-pressure / high-temperature reducing agent is pressurized by a pump, and then heated by a heater and sent to the injection unit. The high-pressure / normal-temperature reducing agent is obtained by pressing the reducing agent pressurized by the pump into the heater. The reducing agent injector for purifying exhaust gas according to claim 1, 2 or 3, wherein the flow is divided before and passes through the driving unit and returns to the suction side of the pump. The reducing agent injector for purifying exhaust gas according to claim 1, 2, 3, or 4, wherein the injection unit and the drive unit are arranged with a thin cylindrical body that restricts heat conduction interposed therebetween. The said electromagnetic valve is a two-way valve which raises the pressure of the said pressure chamber at the time of a valve closing state, and reduces the pressure of the said pressure chamber at the time of a valve opening state. Reducing agent injector for purifying exhaust gas. The solenoid valve includes an outer valve that opens and closes a reducing agent discharge side of the pressure chamber, and an inner valve that is slidably inserted into the outer valve and opens and closes a reducing agent inflow side. 2. A three-way valve that opens to increase the pressure in the pressure chamber and reduces the pressure in the pressure chamber when the outer valve is open by closing the inner valve when the outer valve is open. 6. A reducing agent injector for purifying exhaust gas according to claim 1, 2, 3, 4, or 5.

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