JP2918450B2 - Filter structure in diesel particulate filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel particulate filter incorporated in an exhaust system for purifying exhaust gas discharged from a diesel engine.

[0002]

2. Description of the Related Art Diesel engine combustion is based on so-called heterogeneous mixing in which fuel is injected into high-temperature, high-pressure air. Heterogeneous mixing differs from a homogeneous mixture in that air and fuel are not mixed uniformly, so the carbon component in the fuel changes to soot, HC, etc. due to the high-temperature heat of combustion, which aggregates into particulates. Release to the outside, polluting the surrounding environment.

Conventionally, as an exhaust gas treatment apparatus for treating exhaust gas of an engine, a filter has a large area, and carbon is deposited and collected on a front surface of the filter. In order to incinerate the deposited carbon, a heater is attached to a part of the particulate filter, and the filter is regenerated by burning the particulate containing the deposited carbon.

Conventionally, Japanese Patent Application Laid-Open No. 2-256812 discloses an electrically reproducible particulate trap. The electrically reproducible particulate trap comprises a gas permeable support, a fiber layer comprising a plurality of ceramic fibers, and a heater, and the fiber layer is disposed together with the heater in a space extending radially from the gas permeable support. The exhaust gas flows through the gap between the fiber layers to collect particulates in the exhaust gas in the vicinity of the heater, and energize the heater to incinerate the collected particulates. The fiber layer is 1.5 L / M / cm
Woven fabric having a uniform air permeability of less than ² , wherein the woven fabric is stable at a temperature of about 1150 ° C for a long time, and the distance between yarns is not more than 7.5 times the yarn diameter. It is. The ceramic fibers are selected from continuous fused silica, glass, alumina silica, zirconia silica, alumina chromia, titania, graphite, silicon carbide, and alumina boria silica. Furthermore, the ceramic fibers are braided or wound directly on the gas permeable support or heater.

[0005]

The diesel particulate filter is mounted on a vehicle or the like.
Construct as compact as possible and use carbon, soot, HC
It is necessary to manufacture such that particulates are efficiently collected. Generally, particulates are mainly composed of carbon and hydrocarbons contained in diesel engines, and their size is from several μm to several tens μm.
Are dispersed. The particulates react with oxygen and burn easily, but combustion requires high temperatures,
Complete combustion cannot be achieved only with the exhaust gas temperature.
Conventional renewable diesel particulate filters have two filters of the same size arranged in parallel in the exhaust gas stream. If one filter becomes clogged due to particulate collection, the other filter will be flushed with the exhaust gas. The air required for incineration of the particulates is sent to the other filter to heat the filter, and the collected particulates are incinerated to regenerate the filter. Many conventional renewable diesel particulate filters have been developed to remove particulates and smoke. However, all of them have drawbacks such as complicated structure and complicated functions. At present, it cannot be provided. For example, in a renewable diesel particulate filter, the particulates are collected by the filter, and when the particulates accumulate on the filter, the particulates are incinerated by heating with an ignition glow plug or a heater.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a filter for collecting particulates such as carbon, soot and HC contained in combustion gas of a diesel engine. A wire mesh heater is provided adjacent to the filter to heat and burn the particulates collected by the filter. The filter is made of a material that is resistant to heat and oxidation, and the collection efficiency of the particulates in the exhaust gas is increased. An object of the present invention is to provide a filter structure in a diesel particulate filter, in which a filter is formed into a three-dimensional structure by combining a nonwoven fabric and a woven fabric, and furthermore, scattering of the nonwoven fabric can be prevented to prevent environmental pollution.

Another object of the present invention is to provide a filter having the above-mentioned characteristics, comprising a main filter and a sub-filter through which exhaust gas flows during heating and regeneration of the main filter. The balance is set in advance so that an open / close valve is provided in the sub-filter, and a wire mesh heater is provided in the main filter for regeneration, so that the collection of particulates and the regeneration of the filter are simplified. An object of the present invention is to provide a filter structure to be incorporated into a diesel particulate filter.

The present invention relates to a diesel particulate filter for collecting and heating and incinerating particulates contained in exhaust gas with a filter arranged in a case incorporated in an exhaust system of a diesel engine. A non-woven fabric made of silicon carbide fibers for collecting the particulates, the non-woven fabric being disposed in contact with a downstream side of an exhaust gas flow of the non-woven fabric, preventing scattering of the non-woven fabric, and passing the particulates without being collected by the non-woven fabric; A woven fabric made of ceramic long fibers that collects air, a wire mesh heater disposed in contact with the upstream side of the exhaust gas flow of the nonwoven fabric, and for heating and burning the collected particulates; The nonwoven fabric and the woven fabric are brought into contact with each other so as to sandwich the nonwoven fabric and the woven fabric in a tightly held state. It consists disposed in and locking member, diesel non-conductive material such as Al ₂ O ₃ on the surface of the heat-resistant steel wire material containing Ni-Cr constituting the wire mesh heater is characterized in that it is coated The present invention relates to a filter structure in a particulate filter.

The ceramic long fibers constituting the woven fabric are selected from Si-C-based and Si-C-Ti-O-based long fibers.

A woven fabric made by laminating Si-C-based or Si-C-Ti-O-based long fibers having a coarser mesh than the woven fabric is provided on the upstream side of the exhaust gas flow of the wire mesh heater. It is arranged adjacent to.

Alternatively, the present invention provides a main filter for collecting and heating and burning in particulates contained in exhaust gas disposed in a case incorporated in an exhaust system of a diesel engine. A sub-filter, which has a coarse mesh for filtering from the main filter in the disposed bypass cylinder and is disposed in parallel with the main filter, and opens and closes an inlet of the sub-filter disposed on the exhaust gas inflow side of the sub-filter. A diesel particulate filter, comprising: a bypass valve that performs the operation, and an actuator that opens and closes the bypass valve, wherein an air passage resistance of the sub-filter is set smaller than an air passage resistance of the main filter. For the filter structure.

Further, the main filter and the sub-filter are disposed in contact with a non-woven fabric made of silicon carbide fibers for trapping the particulates, and the non-woven fabric is disposed in contact with a downstream side of an exhaust gas flow of the non-woven fabric. And a woven fabric made of ceramic long fibers that collects the particulates that have passed without being collected by the nonwoven fabric, and the collected particulates disposed in contact with an upstream side of an exhaust gas flow of the nonwoven fabric. Is constituted by a wire mesh heater for heating and incinerating.

[0013] When the bypass valve provided in the sub-filters stacked in parallel with the exhaust gas flow is opened, the main filter is energized to the wire mesh heater and the particulate matter collected by the main filter. After the main filter resumes collection, the wire mesh heater provided in the sub-filter is energized to heat and incinerate the particulates collected in the sub-filter to recover the sub-filter. Regenerate the filter.

Since the filter structure of the diesel particulate filter according to the present invention is constructed as described above, the filter material is rich in heat and oxidation resistance,
In addition, the exhaust gas flows between the laminated filter fibers in a zigzag manner, and the particulates such as carbon, soot, smoke, etc. contained in the exhaust gas are caught or collected at the intersections of the fibers or the fibers along with the flow, and this portion is collected. Becomes a nucleus and particulates accumulate, and a three-dimensional filter effect can be exhibited. Further, the fibers of the non-woven fabric are easily separated and scattered from the layer, but the fibers are held by the woven fabric and do not scatter, and are prevented from flowing out to the downstream.

In this filter structure, a sub-filter is arranged in parallel with an exhaust gas flow via a bypass cylinder at the center of a main filter having a heater arranged on a surface on an exhaust gas inflow side. A bypass valve is provided at the inlet,
The present invention can be applied to a diesel particulate filter in which the air passage resistance of the sub-filter is set smaller than the air passage resistance of the main filter. In this case, there is no need to provide a switching valve at the inlet of the main filter, and the sub-filter can There is no need to install a heater, and there is no need to provide a pump for feeding air to the main filter during regeneration of the main filter, so that the entire structure can be made compact.

However, in a diesel engine, the supplied air is set excessively with respect to the fuel.
Even at full load, the exhaust gas exhausted from the diesel engine contains about 20% of air. Therefore, when playing the main filter, it is allowed to flow a small amount of exhaust gas to the main filter, so that can supply O ₂ for burning particulates trapped in the main filter. Therefore,
If the air passage resistance of the sub-filter is set smaller than the air passage resistance of the main filter, a large amount of exhaust gas flows through the sub-filter when the bypass valve is opened, but particulates are collected. to and will also flow through a small amount of exhaust gas to the main filter can be supplied with O ₂ required for the incineration of the particulate main filter.

When exhaust gas flows through the main filter by closing the bypass valve, exhaust gas leaking from the bypass valve flows through the sub-filter, and particulates collected by the sub-filter during regeneration of the main filter are the same. Is supplied to the sub-filter, and since the sub-filter is arranged inside the main filter, the particulates collected by the sub-filter are contained in the exhaust gas without being cooled by receiving heat from the main filter. It is incinerated at O _2.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a filter structure in a diesel particulate filter according to the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway perspective view showing an embodiment of a filter structure in a diesel particulate filter according to the present invention, FIG. 2 is a cross-sectional view showing an example of the filter structure of FIG. 1, and FIG. FIG. 4 is a sectional view showing an example, and FIG. 4 is a sectional view showing still another example of the filter structure.

One embodiment of the filter structure in the diesel particulate filter will be described with reference to FIGS. A filter structure according to the present invention is disposed in an exhaust system of a diesel engine, collects particulates such as carbon, soot, and smoke contained in exhaust gas, and can heat and incinerate the collected particulates. It can be applied to In this embodiment, as shown in FIGS. 1 and 2, the filter 25 includes a non-woven fabric 28 made of silicon carbide fiber and a Si-C-based filter disposed adjacent to the non-woven fabric 28 on the downstream side of the exhaust gas flow. Alternatively, it is made of a woven fabric 29 made of Si-C-Ti-O-based long fibers. Furthermore,
This filter structure includes a wire mesh heater 6 disposed adjacent to the nonwoven fabric 28 on the upstream side of the exhaust gas flow, and the nonwoven fabric 2.
8, a woven fabric 29 and a locking member 30 for holding the wire mesh heater 6 together. The locking member 30 is, for example,
U-shaped needles, staples, U-shaped clasps, basket-shaped wires and the like can be used. When exhaust gas is passed through the nonwoven fabric 28,
Although the fibers may be separated and scattered, by disposing the woven fabric 29 downstream of the nonwoven fabric 28, the fibers separated from the nonwoven fabric 28 are caught by the woven fabric 29, This prevents the fibers separated from the splatter from scattering.

The surface of the wire constituting the wire mesh heater 6 is coated with a non-conductive material such as Al ₂ O ₃ . By coating the wire mesh heater 6 with Al ₂ O ₃ , when the wire mesh heater 6 is energized, even if the wire meshes come into contact with each other, the wire mesh heater 6 will not be heated unevenly due to abnormal electricity supply. This filter 25 can be used as the main filter 1 when incorporated in a diesel particulate filter described later.

Next, another embodiment of the filter structure of the diesel particulate filter will be described with reference to FIG. In this embodiment, the filter 26 is
As shown in FIG. 7, in the filter 25 of the above embodiment, the Si-C-based or Si-C-
A woven fabric 31 made of a Ti-O-based long fiber is arranged adjacent to the upstream side of the exhaust gas flow of the wire mesh heater 6, and other configurations are the same as those of the filter 25 of the above embodiment. Since they are the same, the same members are denoted by the same reference numerals. A wire mesh heater 6 is provided upstream of the wire mesh heater 6.
The extremely coarse woven fabric 31 is laminated and locked to prevent the wire mesh 6 from contacting each other due to the deformation of the wire mesh heater 6 due to the thermal stress, and the heating of the filter 26 becomes uneven. It is prevented and will be heated uniformly. This filter 26 can be applied as the main filter 1 when incorporated in a diesel particulate filter described later.

Another embodiment of the filter structure will be described with reference to FIG. In this embodiment, as shown in FIG. 4, the filter 27 is the same as the filter 26 of the above embodiment except that the wire mesh heater 6 is provided inside the nonwoven fabric as compared with the filter 26 shown in FIG. , The same members are denoted by the same reference numerals. This filter 27
Is applicable as the sub-filter 2 when incorporated in a diesel particulate filter described later.

With reference to FIGS. 5 and 6, an embodiment of a diesel particulate filter to which this filter structure is applied will be described. In this embodiment of the diesel particulate filter, the filter 25 shown in FIG.
Or, apply the filter 26 as the main filter 1, and
The filter 27 having no wire net heater is used as the sub-filter 2.

This diesel particulate filter is disposed in an exhaust system of a diesel engine, and is capable of collecting particulates such as carbon, soot, and smoke contained in exhaust gas, and capable of heating and burning the collected particulates. It is. This diesel particulate filter is used for the exhaust pipe of a diesel engine (not shown).
Has a case 3 which is connected via a flange 23. In the case 3, a main filter 1 and a sub-filter 2 capable of collecting particulates are separated by a bypass cylinder 4 in the exhaust gas flow direction, and are connected in parallel with the exhaust gas flow from an exhaust gas inlet 15 to an exhaust gas outlet 16. It is arranged to extend. Further, a heat shield 5 is disposed between the case 3 and the main filter 1 in order to prevent heat from radiating from the main filter 1 to the outside through the case 3.

In this embodiment, the main filter 1 is arranged in the exhaust gas passage 22 and is constituted by an inner cylinder 19 and an outer cylinder 20 which are arranged concentrically and doubly. Inside the inner cylinder 19 of the main filter 1, a shielding bypass cylinder 4 that blocks exhaust gas flow between the main filter 1 and the sub-filter 2 is arranged, and the sub-filter 2 is arranged inside the bypass cylinder 4. ing. The main filter 1 and the bypass cylinder 4 are supported and fixed to the case 3 by a plurality of columns 18, and the sub-filter 2 is attached to the bypass cylinder 4 by a plurality of columns 1.
7 for fixing. Also, the exhaust gas passage 2
A shield plate 24 is provided between the sub-filter 2 and the shielding bypass cylinder 4 on the side of the exhaust gas inlet 15 of the second 2 so as to shut off the inlet side and the outlet side of the bypass passage 21. In this embodiment, the main filter 1 is constituted by a cylinder which is double-layered in parallel with the exhaust gas flow. However, the main filter 1 may be constituted by one cylinder, or a cylinder which is laminated three or more times. It may be composed of a body. That is, the sub-filter 2 is arranged in parallel with the exhaust gas flow with respect to the main filter 1 with the bypass cylinder 4 interposed at the center of the main filter 1.

Further, in this diesel particulate filter, a heater comprising a wire mesh heater 6 is disposed on the entire surface of the main filter 1 and the sub-filter 2. The wire mesh heater 6 is configured to be energized and controlled by a command from the controller 10 in order to heat and burn the particulates collected by the main filter 1 and the sub-filter 2. The wire mesh heater 6 is connected to the main filter 1 of the exhaust gas passage 22.
And the entire surface of the bypass passage 21 on the inflow upstream side of the sub-filter 2, and is connected to the controller 10 through the electrode terminal 9. The wire mesh heater 6 is preferably made of a Ni-based metal, and is configured so that the surface of the main filter 1 can be uniformly heated.

On the exhaust gas inflow side of the sub-filter 2, a bypass valve 7 for opening and closing the inflow port of the sub-filter 2 is arranged. The bypass valve 7 is opened and closed by an actuator 8 driven by a command from the controller 10. The bypass valve 7 may have a through hole through which a small amount of exhaust gas leaks for regeneration of the sub-filter 2, or may be provided in the bypass passage 21 so that the bypass valve 7 itself leaks. Good.

An exhaust gas pressure sensor 14 for detecting an exhaust gas pressure is provided at an exhaust gas inlet 15 of the case 3, and information on the exhaust gas pressure detected by the exhaust gas pressure sensor 14 is input to the controller 10. It is configured as follows. The controller 10 further includes a rotation sensor 1 for detecting an engine operating state, that is, an engine speed.
1, a load sensor 12 for detecting an engine load and a temperature sensor 13 for detecting an exhaust gas temperature are provided. The controller 10 receives these detection signals of the engine operating state, determines the particulate collection state corresponding to the detected value of the exhaust gas pressure determined in advance in accordance with the engine operating state, and , That is, the reproduction timing of the main filter 1 is controlled.

In this diesel particulate filter, in the above configuration, the air passage resistance of the sub-filter 2 is set smaller than the air passage resistance of the main filter 1. The air passage resistance between the main filter 1 and the sub-filter 2 can be ensured by changing the material constituting the filters. For example, this can be achieved by making the fiber diameter of the sub-filter 2 larger than the fiber diameter of the main filter 1. Then, the air passage resistance values of the main filter 1 and the sub-filter 2 can be set as follows. The air flow resistance between the main filter 1 and the sub-filter 2 is determined by the total exhaust gas flow rate Q _T passing through the main filter 1 and the sub-filter 2 when the bypass valve 7 for regeneration of the main filter 1 is opened, and the main filter 1 the ratio of the exhaust gas flow rate Q _{2 1} to pass through the main filter 1 during regeneration completion of 1 is set so as to satisfy _{Q T / Q 2 1> 20} .
The numerical i.e. Q _T / Q _{2 1>} 20 is about 20% contained in consideration of the excess air ratio of the diesel engine exhaust gas
Is determined by the amount of air.

The setting of the air passage resistance value of the main filter 1 and the sub-filter 2 will be described with reference to FIG. FIG. 7 shows FIG.
5 is a graph showing the air passage resistance R of the main filter 1 and the sub-filter 2 with respect to the collection time T of the diesel particulate filter of FIG.

When the main filter 1 and the sub-filter 2 have a function of filtering the exhaust gas and collect particulates in the exhaust gas, the pressure loss between the main filter 1 and the sub-filter 2 is as follows. Become. Was deposited particulate on the main filter 1 during the collection time T ₂ and particulates are collected in the main filter 1, the main filter 1 reaches a predetermined pressure loss becomes air passage resistance value R _{2 2} The actuator 8 is driven by a command from the controller 10, the bypass valve 7 is opened, the wire mesh heater 6 is energized, the main filter 1 is heated, and the main filter 1 is regenerated.
When the main filter 1 is heated, the particulates collected in the main filter 1 are heated, and O ₂ in the exhaust gas is heated.
The particulates are converted into CO ₂ and H ₂ O gas and incinerated.

At the time of regeneration of the main filter 1, most of the exhaust gas first flows through the sub-filter 2, and a small amount of exhaust gas flows through the main filter 1. However, as the regeneration process of the main filter 1 proceeds, the main filter 1 , The particulate matter in the exhaust gas is collected by the sub-filter 2, and the air-passing resistance value of the sub-filter 2 becomes larger. Therefore, the main filter 1 and the sub-filter 2
The exhaust gas flows toward the main filter 1 due to the balance of the air passage resistance of the exhaust gas. In this case, the main filter 1
It is important to prevent excessive exhaust gas and air from flowing to the main filter 1 during regeneration of the main filter 1.

The collection of the particulates in the exhaust gas by the main filter 1 is performed for a predetermined time T ₂ , a predetermined amount of the particulates is collected by the main filter 1, and the particulates are accumulated on the main filter 1 and clogged. It becomes the state at that time, i.e., the air passage resistance of the main filter 1 when starting the regeneration of the main filter 1 and R _{2 2.} Further, since no exhaust gas is flowing through the sub-filter 2, no particulates are deposited on the sub-filter 2, and the air passing resistance value of the sub-filter 2 at that time is represented by R
_{1 and 1} . Further, the air passage resistance when the reproduced main filter 1 is finished and R _{2 1,} the air flow resistance when the sub filter 2 is clogged with particulates and R _12. When the bypass valve 7 is opened and the regeneration of the main filter 1 is completed, assuming that the air passing resistance value of the entire filter is R, 1 / R = (1 / R _{1 2} ) + (1 / R _{2 1} ) holds. since a _{R = R 1 2 · R 2} 1 / (R 1 2 + R 2 1). Therefore, the function Q _{T of the} exhaust gas flow rate with respect to the differential pressure ΔP
, When the coefficient _{K, ΔP = K · Q T} × _{[R 1 2 · R 2 1 /} (R 1 2 +
Represented by R _{2 1)].} The function Q of the exhaust gas flow rate for the main filter 1
_{2 1,} and tables in when a function Q _{1 2} of exhaust gas flow rates for the sub-filter _{2, ΔP = K · R 1} 2 · Q 1 2 = R 2 1 · Q 2 1 Q T = Q 1 2 + Q 2 1 Is done. From the formulas _{above, Q 2 1 / Q T =} R 1 2 / (R 1 2 + R
_{2 1} )

The regeneration of the main filter 1 proceeds, and the particulates collected in the main filter 1 are heated and incinerated.
To playback the main filter 1 is completed, but the air passage resistance of the main filter 1 at that time and R _{2 1.} Also, during which the sub-filter 2 particulates accumulated sub filter 2 is flowed exhaust gas was collected over a collecting time T ₁ the particulates, the air passage resistance of the sub-filter 2 at the time R _{1 and 2} . Further, a function Q _{2 1} of the exhaust gas flow rate of the main filter 1, the sub-filter 2
When the function Q _{1 2} of the exhaust gas flow rate of about, at this time, it is sufficient that equipped with conditions that can incineration of particulates in the main filter 1. Here, considering the excess air ratio of the diesel engine, the amount of air contained in the exhaust gas is 2
When about 0% to a range of _{Q 2 1 / Q T <1/20} ,
When the air passage resistance between the main filter 1 and the sub-filter 2 is set, an air amount necessary for burning the particulates collected in the main filter 1 is supplied. That is, at the time of regeneration of the main filter 1, an amount of air sufficient for heating and burning the particulates is supplied without cooling the main filter 1 by the exhaust gas, and the regeneration of the main filter 1 is completed.

When the regeneration of the main filter 1 is completed, the sub-filter 2 collects the particulates in the exhaust gas during that time, and the sub-filter 2 is in a state where the particulates are accumulated. Then, the bypass valve 7 is closed and the regeneration of the sub-filter 2 is started. At that time, since the sub-filter 2 is disposed inside the main filter 1, heat energy of the exhaust gas is stored in the sub-filter 2, and the sub-filter 2 is heated by the heat energy. Immediately after closing, the heater 6 provided in the sub-filter 2 is energized to burn the particulates collected by the sub-filter 2, and the air contained in the exhaust gas leaking through the bypass valve 7 is used. The sub-filter 2 is regenerated by burning the particulates.

This diesel particulate filter is configured as described above, and operates as follows. The diesel engine is driven, and the exhaust gas is sent to the exhaust gas passage 22 through the exhaust pipe. At this time, the bypass valve 7 is in the closed state, and the exhaust gas is sent into the exhaust gas passage 22 from the inlet 15, passes through the main filter 1 from the exhaust gas passage 22, and is contained in the exhaust gas by the main filter 1. Particulates such as carbon and smoke are collected, and clean exhaust gas is discharged to the outlet 16. The collected particulates are the main filter 1
As shown in FIG. 7, the air passage resistance of the main filter 1 gradually increases in accordance with the collection time. On the other hand, the controller 10
1, receiving the detection signals from the load sensor 12 and the temperature sensor 13 and judging the engine operating state from the detected values, and when the detected exhaust gas pressure value becomes a predetermined value, the actuator 8 is operated to bypass. Determine whether to open valve 7.

When the exhaust gas pressure sensor 14 provided in the exhaust gas passage 22 detects the preset exhaust gas pressure, the main filter 1 is in a state of collecting sufficient particulates. In order to regenerate the main filter 1, a command to operate the actuator 8 is issued, and the operation of the actuator 8 opens the bypass valve 7. When the bypass valve 7 is opened, most of the exhaust gas passes through the sub-filter 2 through the bypass passage 21, and a small amount of the exhaust gas is sent from the exhaust gas passage 22 to the main filter 1. Further, the controller 10 issues a command to flow an electric current to the wire mesh heater 6 through the electrode terminal 9, the wire mesh heater 6 is heated, and the main filter 1 is heated. In the exhaust gas passing through the sub-filter 2, the particulates contained therein are collected by the sub-filter 2, and the collected particulates are deposited on the sub-filter 2. At this time, the air passage resistance value of the sub-filter 2 is
As shown in FIG. 7, so that gradually increases from R _{1 1} to R _{1 2.}

When the wire mesh heater 6 is heated and the main filter 1 is heated, the particulates trapped in the main filter 1 use CO contained in a small amount of exhaust gas passing through the main filter 1 to generate CO2. ₂ , H ₂ O, which is incinerated and converted into gas and discharged from the outlet 16. When the playback main filter 1 progresses, as shown in FIG. 7, the air passage resistance value of the main filter 1 is changed gradually decreases from R _{2 2} to R _{2 1,} the playback is completed the main filter 1. The completion of the regeneration of the main filter 1 is determined by the controller 10 based on the exhaust gas pressure value set in advance in consideration of the engine operating state.
Is determined. At this time, the main filter 1 and the sub-filter 2
The flow of the exhaust gas is gradually increased from the sub-filter 2 to the main filter due to the balance of the air passage resistance of the main filter 1. air passage resistance R _{2 1} 1 is set to be higher than the air passing through the resistance R _{1 2} of the sub-filters 2. Therefore, the main filter 1
When the regeneration is completed, the exhaust gas flowing through the sub-filter 2 is larger than the exhaust gas flowing through the main filter 1.

When the regeneration of the main filter 1 is completed, the controller 10 operates the actuator 8 to operate the bypass valve 7.
Issue a command to close When the bypass valve 7 closes
The exhaust gas passes through the main filter 1 from the exhaust gas passage 22, and a normal exhaust gas process, that is, a process of collecting particulates by the main filter 1 is performed. At this time,
A small amount of exhaust gas passes through a through hole or a gap formed in the bypass valve 7 and is sent into the bypass passage 21. Furthermore, since the bypass passage 21 is surrounded by the main filter 1, heat is stored therein. Therefore, the particulates collected by the sub-filter 2 are energized while the main filter 1 is collecting particulates, and the air contained in the minute amount of exhaust gas passing through the sub-filter 2 from the bypass passage 21 is removed. The sub-filter 2 is incinerated by use and is regenerated. In the diesel particulate filter, the above operation cycle is repeated, and the exhaust gas is continuously purified.

[0040]

Since the filter structure of the diesel particulate filter according to the present invention is constructed as described above, the filter itself is rich in heat resistance and oxidation resistance, and the exhaust gas has a zigzag shape between the laminated filter fibers. The flow, the particulates contained in the exhaust gas accompanying the flow are collected on the fibers or their intersections,
The part serves as a nucleus, and the particulates accumulate on the filter, thereby exhibiting a three-dimensional trapping effect. Further, the fibers of the non-woven fabric are easily separated and scattered from the layer, but the fibers are held by the woven fabric and do not scatter, and are prevented from flowing out to the downstream. In particular, in the present invention, since the wire mesh heater is coated with Al ₂ O ₃ , when the wire mesh heater is energized, even if the wire meshes come into contact with each other, the wire mesh heater is abnormally heated and the wire mesh heater is heated unevenly. Nothing. In addition, this filter structure is characterized in that a woven fabric made of a Si-C-based or Si-C-Ti-O-based long fiber having a coarser texture than that of the woven fabric is provided upstream of the exhaust gas flow of the wire mesh heater. Since they are arranged adjacent to each other, even if the wire mesh heater is deformed due to thermal stress, contact between the wire meshes is prevented,
The filter itself is uniformly heated, and no local overheating occurs, the particulates collected by the filter can be satisfactorily overheated and incinerated, and the regeneration of the filter can be performed satisfactorily to improve the durability.

Further, the filter structure has a main filter housed in a case in the middle of an exhaust system of a diesel engine, and a bypass cylinder interposed at the center of the main filter to flow exhaust gas to the main filter. It can be easily and easily incorporated into a diesel particulate filter provided with sub filters arranged in parallel. As the diesel particulate filter, a heater is arranged on the exhaust gas inflow side surface of the main filter, and a bypass valve for opening and closing the inflow port of the sub-filter by an actuator is provided. When the bypass resistance is set smaller than the air passage resistance, the exhaust gas is smoothly purified by the main filter when the bypass valve is closed, and the particulates in the exhaust gas are collected by the main filter.

Further, when reproducing the main filter,
It is only necessary to open the bypass valve and energize the wire mesh heater, and there is no need to pump in air for burning the particulates collected in the main filter using a separate pump or the like. A small amount of exhaust gas is sent to the filter due to the balance of air passage resistance between the main filter and the sub-filter. However, since the exhaust gas of the diesel engine contains a small amount of air due to the phenomenon of excess air ratio which is a characteristic of the diesel engine, the particulates collected in the main filter using the air are incinerated. Will be done.

Therefore, the diesel particulate filter incorporating this filter structure does not require an air supply device for incineration of the collected particulates, and the device itself is formed into a compact and simple structure. In addition, the exhaust gas emitted from the diesel engine has a very simple function of treating exhaust gas and can continuously purify the exhaust gas. it can.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing one embodiment of a filter structure in a diesel particulate filter according to the present invention.

FIG. 2 is a sectional view showing an example of the filter structure of FIG.

FIG. 3 is a sectional view showing another example of the filter structure.

FIG. 4 is a sectional view showing still another example of the filter structure.

FIG. 5 is a cross-sectional view showing an example of a diesel particulate filter to which the filter structure according to the present invention is applied, and showing a closed state of a bypass valve.

FIG. 6 is a sectional view showing an open state of a bypass valve in the diesel particulate filter of FIG. 5;

FIG. 7 is a graph showing air passage resistance values of a main filter and a sub-filter with respect to a collection time in a diesel particulate filter incorporating the filter structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main filter 2 Sub-filter 3 Case 4 Bypass cylinder 6 Wire mesh heater 7 Bypass valve 10 Controller 14 Exhaust gas pressure sensor 21 Bypass passage 22 Exhaust gas passage 25, 26, 27 Filter 28 Nonwoven fabric 29, 31 Woven fabric 30 Locking member

Claims (6)

(57) [Claims] 1. A diesel particulate filter by collecting particulates to burn pressurized heat contained in the exhaust gas arranged filter in a case incorporated in an exhaust system of a diesel engine, the filter
Is a nonwoven fabric made of carbonization silicon fibers you collect particulate matter, without being trapped by the non-woven fabric while preventing contact with disposed and scattering of the nonwoven fabric on the downstream side of the exhaust gas stream of the non-woven fabric woven fabric made from ceramic filaments as to collect particulate matter which has passed through, is disposed in contact with the upstream side of the exhaust gas stream of the nonwoven fabric and the collected money for heating burning the particulates were < a mesh heater and the nonwoven fabric in cooperation with the wire mesh heater.
The woven fabric is sandwiched between the woven fabrics so as to be held in close contact with each other.
A locking member arranged in contact with the cloth;
Heat-resistant steel wire containing Ni-Cr constituting wire mesh heater
Filter structure in a diesel particulate filter nonconductive material such as Al ₂ O ₃ on the surface of and wherein the being coated is <br/>. 2. The diesel patty according to claim 1, wherein the ceramic long fibers constituting the woven fabric are selected from Si—C-based and Si—C—Ti—O-based long fibers. Filter structure in curated filter. 3. Si-C having a coarser texture than said woven fabric
2. A woven fabric formed by laminating long fibers of Si-C-Ti-O system or a Si-C-Ti-O-based long fiber is disposed adjacent to an upstream side of an exhaust gas flow of the wire mesh heater. 3. A filter structure in the diesel particulate filter described in 1. above. 4. Incorporation into an exhaust system of a diesel engine
Included in exhaust gas placed in a closed case
Main filter, said main sub-filter network for filtering from said main filter arranged to bypass tube inside the central portion are arranged in parallel with rough且previous SL main filter of the filter to heat incineration was collected curated A bypass valve disposed on the exhaust gas inflow side of the sub-filter for opening and closing the inlet of the sub-filter, and an actuator for opening and closing the bypass valve. filter structure in the feature and be Lud I over diesel particulate filter that has been set in comparison to the air flow resistance small. 5. The main filter and the sub-filter,
It is composed of silicon carbide fibers that trap the particulates.
Non-woven fabric, which is disposed in contact with the exhaust gas flow downstream of the non-woven fabric.
To prevent scattering of the non-woven fabric and the non-woven fabric.
Collect the particulates that have passed without being collected with a cloth
Woven fabric made from ceramic long fibers
Collecting disposed on the upstream side of the woven fabric exhaust gas flow
Wire mesh for heating and burning the above particulates
The filter structure of the diesel particulate filter according to claim 4 , comprising a heater . 6. The main filter is energized by the wire mesh heater and collected by the main filter when the bypass valve provided in the sub-filter stacked in parallel with the exhaust gas flow is opened. is played by heating incinerate particulates, after the main filter resumes collected, heated incinerate particulates by supplying an electric current to the wire mesh heater provided on the sub-filter are trapped on the sub-filter The filter structure in the diesel particulate filter according to claim 5, wherein the sub-filter is regenerated.