JPH07317532A - Structure of diesel particulate filter - Google Patents

Abstract

PURPOSE:To establish a filter structure for effective purification of exhaust gas, with which the device itself is embodied compactly in a desired configuration and the particulate collecting area is set off large. CONSTITUTION:A diesel particulate filter device comprises a main filter 1 set in a case 3 provided in the exhaust system, a sub-filter 2 located in the center of the main filter 1, and a bypass cylinder 4 located in the middle between the two. An opening/closing bypass valve 7 is installed on the exhaust gas flow-in side of the sub-filter 2, and the flow-in port of the sub-filter 2 is opened and closed by the bypass valve 7. A porous sheet is prepared by straining a slurry as a mixture of SiC or Si-C-Ti-O series fibers and polycarbosilane solution and is subjected to a sintering process and the polycarbosilane is turned into SiC so that a sheet filter is fabricated, and with this the main filter 1 and sub-filter 2 are fabricated. A wire meshing heater is laminated on the exhaust gas flow-in side of the main filter 1.

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 Combustion of a diesel engine is based on so-called heterogeneous mixing, in which fuel is injected into high temperature, high pressure air. Unlike the homogeneous mixture, the heterogeneous mixture does not mix the air and the fuel uniformly, so the carbon component in the fuel changes to soot, HC, etc. due to the high temperature heat of combustion, and they aggregate to form particulates. It is released to the outside and pollutes the surrounding environment. Therefore, conventionally, as an exhaust gas treatment device for treating engine exhaust gas, the area of the filter is large and carbon is deposited and collected on the 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 particulate containing the deposited carbon is incinerated to regenerate the filter.

Conventionally, Japanese Patent Application Laid-Open No. 2-256812 discloses an electrically regenerable particulate trap. The electrically regenerable particulate trap comprises a gas permeable support, a fiber layer made of a plurality of ceramic fibers, and a heater, and the fiber layer is arranged together with the heater in a space extending in the radial direction from the gas permeable support. The exhaust gas is caused to flow in the gap between the fiber layers to collect the particulates in the exhaust gas in the vicinity of the heater, and the heater is energized to incinerate the collected particulates. Fiber layer is 1.5L / M / cm
^A woven fabric having a uniform air permeability of less than ^{2, the} woven fabric being stable at a temperature of about 1150 ° C. for a long period of time, and the distance between the threads is not more than 7.5 times the thread diameter. Is. Further, the ceramic fiber is selected from continuous fused silica, glass, alumina silica, zirconia silica, alumina chromia, titania, graphite, silicon carbide, and alumina boria silica. Further, the ceramic fibers are braided or wound directly onto the gas permeable support or heater.

[0004]

By the way, since the diesel particulate filter is mounted on a vehicle or the like,
Construct as compact as possible, carbon, soot, HC
It is necessary to manufacture so that the collection of particulates etc. becomes efficient. Generally, particulates are a compound of carbon and hydrocarbon contained in a diesel engine, and their sizes are dispersed from several μm to several tens of μm. The particulate reacts with oxygen and burns easily, but the burning requires a high temperature and cannot be burned completely only by the temperature of the exhaust gas. Conventional renewable diesel particulate filters have two filters of the same size placed in parallel in the exhaust gas flow,
When one filter becomes clogged due to the collection of particulates, the exhaust gas is made to flow through the other filter and the air required for incineration of the particulates is sent to the clogged filter to heat the filter and the collected particulates. Is incinerated and the filter is regenerated. Conventional regenerable diesel particulate filters have been developed so far with many devices for removing particulates and smoke, but they all have drawbacks such as complicated structure and complicated functions, and are practically used. The current situation is that we cannot offer it.
For example, in a renewable diesel particulate filter, particulates are collected by the filter, and when particulates are deposited on the filter, they are heated by an ignition glow plug or a heater to incinerate the particulates.

An object of the present invention is to solve the above-mentioned problems, and a wire filter heater is built in or laminated on a sheet filter produced by filtering ceramic fibers into a paper-like sheet,
It is an object of the present invention to provide a filter structure which has a lightweight and compact structure. Further, the filter structure, carbon contained in the combustion gas of a diesel engine,
In order to apply to a diesel particulate filter that collects particulates such as soot and HC, a main filter and a sub-filter are made of the above-mentioned sheet filter, and a sub-filter for flowing exhaust gas during heating regeneration of the main filter is used as the main filter. A diesel particulate that is provided in the center and is preset by balancing the air passage resistance between the main filter and the sub-filter, and the opening / closing valve is provided only in the sub-filter and the wire mesh heater is provided only in the main filter for regeneration. It is to provide a filter.

[0006]

In order to achieve the above object, the present invention is configured as follows. That is,
The present invention has a filter arranged in a case incorporated in an exhaust system of a diesel engine and a reticulated heater for heating the filter, and collects particulates contained in exhaust gas by the filter, In a diesel particulate filter that heats and incinerates the collected particulates by energizing the reticulated heater, a filter in which ceramic long fibers are laminated and the ceramic long fibers are joined with a liquid ceramic raw material, and the entire surface of the filter is closely attached. The present invention relates to a filter structure in a diesel particulate filter, characterized in that the filter structure is constituted by an installed mesh conductor. Further, the filter is made by mixing a slurry of SiC or Si-C-Ti-O-based fibers with a polycarbosilane solution, a polytitanocarbosilane solution and a solution selected from polysilane styrene, polysilane and polysilazane solution. The porous sheet prepared by
Or a sheet filter converted to Si-C-Ti-O,
And a reticulated heater made of a conductive heat-resistant metal that is laminated and tightly locked on the sheet filter.

Further, the SiC or Si-C-Ti-O-based fiber is obtained by cutting the long fiber into 2 to 10 mm or is composed of whiskers produced by a vapor phase method. In addition, the filter is prepared by filtering a slurry prepared by mixing long fibers of Si ₃ N ₄ with a polysilazane, polycarbosilane, and perihydropolysilazane solution into a sheet and sintering the sheet in NH ₃ gas to form a composite. A porous ceramic sheet was produced. Alternatively, the filter is mullite Al ₆ Si ₂ O ₁₃ or Al ₂
When O ₃ is used, a slurry is prepared by using a polyaluminoxane solution as a solution, and the slurry is strained on a sheet.

Further, the reticulated heater is laminated between the sheet filters, and the sheet filter arranged on the downstream side of the exhaust gas flow is configured such that the fibers are closer to each other than the sheet filter arranged on the upstream side. It has been done. The reticulated heater is obtained by filtering a silicon carbide fiber with a fine mesh and sintering the composite layer.

Further, the filter structure is a main filter including the sheet filter arranged in the case,
It comprises a mesh heater arranged on the exhaust gas inflow side of the main filter, and the sheet filter arranged in parallel to the exhaust gas flow with respect to the main filter in a bypass cylinder arranged in the central portion of the main filter. A sub-filter, a bypass valve that opens and closes the bypass cylinder that is arranged on the exhaust gas inflow upstream side of the sub-filter, and an actuator that opens and closes the bypass valve, and the air passage resistance of the sub-filter is the main filter. It is applicable to a diesel particulate filter that is set smaller than the air passage resistance of.

Further, the main filter is formed in a pleated shape by sequentially bending the sheet filter into a cylindrical shape, and the sub-filter is arranged inside the main filter in parallel with an exhaust gas flow and is separated from the sheet filter by a cylinder. It is formed into a shape. Alternatively, the main filter is formed in a tubular shape from the sheet filters stacked in parallel with the exhaust gas flow, and the sub-filter is arranged in parallel with the exhaust gas flow inside the main filter and is tubular from the sheet filter. It is formed in.

[0011]

The filter structure of the diesel particulate filter according to the present invention is configured as described above and operates as follows. That is, the filter structure in this diesel particulate filter is composed of a filter in which ceramic long fibers are laminated and the ceramic long fibers are joined together by a liquid ceramic raw material, and a reticulated conductor closely arranged on the entire surface of the filter. Specifically, SiC or Si—C—Ti—O type long fibers were mixed with a solution selected from a polycarbosilane solution, a polytitanocarbosilane solution, and a polysilanestyrene, a polysilane, and a polysilazane solution. A sheet-shaped filter body obtained by sintering a porous sheet produced by filtering a slurry to convert the solution into SiC or Si-C-Ti-O, and a wire mesh made of a conductive metal laminated on the filter body. Since it is composed of a heater, the filter itself can be made as a thin sheet of paper and is lightweight. It can be configured into the desired filter shape, to form a filter compact. Further, the density of the filter body is, for example,
It can be easily constructed by changing the wire diameter of the ceramic fiber used.

Further, in this filter structure, a main filter and a sub-filter are made of the above-mentioned filter body, the main filter is arranged in a case arranged in the exhaust system of a diesel engine, and an exhaust gas inflow side of the main filter is provided. A wire mesh heater is arranged on the surface, a sub-filter is arranged in parallel with the main filter with a bypass cylinder interposed in the center of the main filter, and a bypass valve is arranged on the exhaust gas inflow side of the sub-filter. Since the air passage resistance of the sub filter is set smaller than the air passage resistance of the main filter, it is not necessary to provide a switching valve at the inlet of the main filter, it is not necessary to install a heater in the sub filter, and the main filter There is no need to provide a pump for feeding air to the main filter during regeneration, and the entire structure can be made compact.

That is, in the diesel engine, since the supplied air is set excessively with respect to the fuel, the exhaust gas discharged from the diesel engine contains about 20% of the air even under the full load. There is. Therefore, if a small amount of exhaust gas is caused to flow through the main filter when regenerating the main filter, it is possible to supply O ₂ that burns the particulates collected 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 generated. A small amount of exhaust gas also flows into the main filter that is trapped, and O ₂ required for incineration of particulates in the main filter can be supplied. Moreover, when the main filter is regenerated, a small amount of exhaust gas flows to the main filter, excessive exhaust gas does not flow to the main filter, and the incineration of particulates is not deteriorated by being cooled by the exhaust gas.

When the bypass valve is closed and the exhaust gas flows through the main filter, the exhaust gas leaking from the bypass valve flows through the sub filter, and the particulate matter collected by the sub filter when the main filter is regenerated is the same. Is supplied to the sub-filter, and the sub-filter is arranged inside the main filter, so that the particulates collected in the sub-filter are contained in the exhaust gas without being cooled by receiving heat from the main filter. It is incinerated with O ₂ .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the filter structure of the diesel particulate filter according to the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing a manufacturing process of a filter structure in a diesel particulate filter according to the present invention, FIG. 2 is a perspective view showing an example of the filter structure of FIG. 1, and FIG. 3 is another example of the filter structure of FIG. It is a perspective view shown.

In the filter structure of this diesel particulate filter, as a filter material, a filter in which ceramic long fibers are laminated and the ceramic long fibers are bonded with a liquid ceramic raw material, and a net-like conductive material which is closely arranged on the entire surface of the filter The filter is made of SiC or Si.
Sintering a porous sheet prepared by straining a slurry in which -C-Ti-O-based fibers are mixed with a polycarbosilane solution, a polytitanocarbosilane solution, and a solution selected from polysilane styrene, polysilane, and polysilazane solution The solution is converted into SiC or Si-C-Ti-O, and a wire mesh heater made of a conductive heat-resistant metal laminated and tightly locked on the sheet filter. In this filter structure, the sheet filter manufactured as described above is laminated with a wire mesh heater made of a heat-resistant and oxidation-resistant conductive metal to manufacture a filter.

This filter structure can be manufactured, for example, by the steps shown in FIG. First, Si
C or Si-C-Ti-O based non-woven fiber 41 and polycarbosilane or molten ceramics 42 are put into a container 40 (step 30), and both are mixed to form a slurry 43.
To make. Next, the wire mesh 44 is laid and the slurry 4 is added.
3 is poured and strained into a sheet to form a sheet solidified material 45. At this time, in the sheet-like solidified material 45, polycarbosilane or polytitanocarbosilane is attached to the intersection of the fibers 41 of the non-woven fabric and the fiber 41 of the non-woven fabric, and the fiber 41 of the non-woven fabric is fixed by the polycarbosilane 42. The state of the object 1A is obtained (step 31). The sheet-shaped solidified material 45 is dried to produce a sheet-shaped molded body 1B of the dried SiC fiber sheet 46 (step 32). Then, the sheet-shaped molded body 1B is fired at 1400 ° C. to obtain the sheet filter 47.
Are produced (step 33). At this time, the polycarbosilane 42 is converted into SiC by firing the polycarbosilane 42 in Ar or vacuum, and the fiber sheet is formed into a porous sheet-shaped sheet filter 47. Further, in the sheet filter 47, the wire netting 44 is embedded, and when the sheet filter 47 is incorporated into the diesel particulate filter, the wire netting 44 functions as the wire netting heater 6 described later. At this time, in some cases, the wire mesh heater 6 may be formed by filtering silicon carbide fibers using a wire mesh with a fine mesh. Of course, wire mesh 4
The sheet filter 47 can be formed without laying 4, and then the wire netting 44 and the sheet filter 47 can be locked and fixed.

In this filter structure, the sheet filter 4
When 7 is incorporated in a diesel particulate filter, it is preferable for regeneration that the wire mesh heater 6 is arranged upstream of the exhaust gas flow of the sheet filter 47. Further, the sheet filters 47 are laminated on both sides of the wire mesh heater 6, and the sheet filter 47 arranged on the downstream side of the exhaust gas flow can be configured such that the fibers are closer to each other than the sheet filter 47 arranged on the upstream side. It is a thing. The wire net heater 6 may be locked and fixed to the sheet filter 47 by using a fixing tool such as a metal wire, or may be sandwiched and fixed to the sheet filter 47. When the wire net heater 6 is laminated between the sheet filters 47, the sheet filter 47 arranged on the downstream side of the exhaust gas flow may be made denser than the sheet filter 47 arranged on the upstream side. The particulates such as carbon, soot, and smoke contained in the exhaust gas can be efficiently collected. In order to configure the sheet filter 47 in a coarse and fine structure, for example, by changing the wire diameter of the ceramic fiber for manufacturing the sheet filter 47, the sheet filter 47 is configured to have coarse meshes or dense meshes. can do.

This filter structure is arranged in the exhaust system of a diesel engine and contains carbon contained in exhaust gas,
The present invention can be applied to a diesel particulate filter that can collect particulates such as soot and smoke and can heat and incinerate the collected particulates. FIG. 2 shows an example of a sheet filter that can be incorporated in a diesel particulate filter. The sheet filter 47 of this embodiment is a main filter 1 described later.
A filter 26 that can be used as The filter 26 is sequentially bent in the radial direction by a predetermined length to be formed into a fold shape, and the fold shape is formed into a tubular shape. In FIG. 2, the wire mesh heater 6 has a filter 2
Although the drawing is made only on a partial region of the end portion of 6, the wire net heater 6 can be projected from the entire surface of the end part to form the wire net terminal.

Alternatively, since it is incorporated into a diesel particulate filter, it can be formed into a shape as shown in FIG. FIG. 3 shows another embodiment of the sheet filter that can be incorporated in the diesel particulate filter. Sheet filter 47 of this embodiment
Is a filter 2 formed in a cylindrical shape that is arranged in parallel with the wire mesh heater 6 in the longitudinal direction in the exhaust gas flow direction.
7 and can be used as a main filter 25 described later. Although not shown, the filter 27 can also be formed in a structure in which wire mesh heaters are not laminated, and a filter not equipped with a wire mesh heater is a sub filter 2 described later.
Can be applied as.

An embodiment of a diesel particulate filter to which this filter structure is applied will be described with reference to FIGS. 4 and 5. In this diesel particulate filter, the sheet filter 47 shown in FIG. 2 is applied as the main filter 1, and the tubular sheet filter not equipped with the wire mesh heater is applied as the sub filter 2. It has a case 3 connected to an exhaust pipe (not shown) of a diesel engine via a flange 23. In the case 3, the main filter 1 and the sub-filter 2 capable of collecting particulates are separated by the bypass cylinder 4 in the exhaust gas flow direction, and the inlet 15 is arranged in parallel with the exhaust gas flow.
It is arranged so as to extend from the outlet 16 to the outlet 16. Further, a heat shield 5 is arranged between the case 3 and the main filter 1 to prevent heat from being radiated 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, the outer peripheral end of the main filter 1 on the exhaust gas inlet 15 side is closed by a shield plate 28, and the main filter 1 on the exhaust gas outlet 16 side. The end face of No. 1 is closed by a plate-like sheet filter 24. The plate-shaped sheet filter 24 can be manufactured by the sheet filter 47. Inside the main filter 1, a shielding bypass cylinder 4 that blocks the exhaust gas flow between the main filter 1 and the sub-filter 2 is arranged, and inside the bypass cylinder 4 the sub-filter 2
Are arranged. Main filter 1 and bypass cylinder 4
Are supported and fixed to the case 3 by a plurality of columns 18, and the sub-filter 2 is supported and fixed to the bypass cylinder 4 by a plurality of columns 17. Further, a sub-filter 2 is arranged in parallel with the exhaust gas flow with respect to the main filter 1 with a bypass cylinder 4 interposed in the center of the main filter 1.

Further, in this diesel particulate filter, a wire mesh heater 6 is arranged on the surface of the main filter 1. 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.
The wire mesh heater 6 extends over the entire surface of the exhaust gas passage 22 on the inflow side of the main filter 1, and is connected to the controller 10 through electrode terminals 9. Wire mesh heater 6
It is preferably made of a Ni-based metal, and is configured so that the surface of the main filter 1 can be heated uniformly.

A bypass valve 7 for opening and closing the inlet of the sub-filter 2 is arranged on the exhaust gas inflow side of the sub-filter 2. The bypass valve 7 is opened and closed by an actuator 8 driven by a command from the controller 10. In order to regenerate the sub-filter 2, the bypass valve 7 may be formed with a through hole through which a slight amount of exhaust gas leaks, or may be arranged in the bypass passage 21 so as to leak the bypass valve 7 itself. Good.

Further, in this diesel particulate filter, an exhaust gas pressure sensor 14 for detecting the exhaust gas pressure is provided at the exhaust gas inlet 15 of the case 3, and the exhaust gas pressure detected by the exhaust gas pressure sensor 14 is provided. Is configured to be input to the controller 10. Further, the controller 10 is provided with a rotation sensor 11 for detecting an engine operating state, that is, an engine speed, a load sensor 12 for detecting an engine load, and a temperature sensor 13 for detecting an exhaust gas temperature. 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 which is predetermined corresponding to the engine operating state, and determines the bypass valve 7 Is opened, that is, the reproduction timing of the main filter 1 is controlled.

In the diesel particulate filter of the above construction, 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 secured by changing the material forming the filter. For example, this can be achieved by making the fiber diameter of the fibers forming the sub-filter 2 larger than the fiber diameter of the fibers forming 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 passage resistance between the main filter 1 and the sub filter 2 is 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. When the regeneration of No. 1 is completed, the ratio with the exhaust gas flow rate Q _{2 1} passing through the main filter 1 is Q
It is set so as to satisfy _T / Q _{2 1>} 20. This value, that is, Q _T / Q _{2 1} > 20 is determined by the air amount of about 20% contained in the exhaust gas in consideration of the excess air ratio of the diesel engine.

In this diesel particulate filter, setting of air passage resistance values of the main filter 1 and the sub filter 2 will be described with reference to FIG. FIG. 8 is a graph showing the air passage resistance value 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 the particulates in the exhaust gas, the pressure loss between the main filter 1 and the sub filter 2 is as follows. When the particulate matter is collected by the main filter 1 and the particulate matter is accumulated on the main filter 1 during the collection time T ₂ , when the main filter 1 reaches the air passage resistance value R _{2 2} and reaches a predetermined pressure loss. , The actuator 8 according to a command from the controller 10
Is driven, 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 in a regenerated state. When the main filter 1 is heated, the main filter 1
The particulates collected in the exhaust gas are heated, and the particulates are converted into CO ₂ and H ₂ by utilizing O ₂ in the exhaust gas.
It is changed to 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, but as the regeneration process of the main filter 1 progresses, the main filter 1 The air passage resistance value of the sub filter 2 gradually decreases, the particulates in the exhaust gas are collected by the sub filter 2, and the air passage resistance value of the sub filter 2 gradually increases. Therefore, as the regeneration process of the main filter 1 progresses, the exhaust gas flows toward the main filter 1 side due to the balance of the air passage resistances of the main filter 1 and the sub filter 2. In this case, during regeneration of the main filter 1, it is important to prevent excessive exhaust gas and air from flowing to the main filter 1 side.

In this diesel particulate filter, the main filter 1 collects the particulates in the exhaust gas for a predetermined time T ₂ , and a predetermined amount of the particulates is collected in the main filter 1 and is collected in the main filter 1. R _{2 2} is the air passage resistance value of the main filter 1 at that time, that is, when the regeneration of the main filter 1 is started. Also,
Since exhaust gas is not passed through the sub-filter 2, particulates are not accumulated on the sub-filter 2,
The air passage resistance value of the sub-filter 2 at that time is defined as R _{1 1} . Further, the air passage resistance when the regeneration of the main filter 1 is finished is R _{2 1,} and the air passage resistance when the sub filter 2 is clogged with particulates is R _{1 2} . When the bypass valve 7 is opened and the regeneration of the main filter 1 is completed, if the air passage resistance value of the entire filter is R, then 1 / R =
Since (1 / R _{1 2} ) + (1 / R _{2 1} ) holds, R =
_{R 1 2 · R 2 1 /} (R 1 2 + R 2 1) is. Therefore,
The function Q _T of the exhaust gas flow rate with respect to the differential pressure ΔP, where K is a coefficient, ΔP = K · Q _T × [R _{1 2} · R _{2 1} / (R _{1 2} + R _2
1 )]. The exhaust gas flow rate as a function Q _{2 1} of the main filter 1, when the 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 It is represented by _{2 1} Q _T = Q _{1 2} + Q _{2 1} . From the above equations, Q
_{2 1} / Q _T = R _{1 2} / (R _{1 2} + R _{2 1} )

As the regeneration of the main filter 1 progresses, the particulates collected in the main filter 1 are heated and incinerated,
Although the regeneration of the main filter 1 is completed, the air passage resistance value of the main filter 1 at that time is R _{2 1} . Further, during that time, the exhaust gas is caused to flow through the sub-filter 2, and the sub-filter 2 collects the particulates for the collection time T ₁ and the particulates are accumulated, and the air passage resistance value of the sub-filter 2 at that time is R. _{1 and 2} . Also, the function Q ₂ 1 of the exhaust gas flow rate for the main filter 1 is used, and the sub filter 2
Assuming that the function Q _{1 2} of the exhaust gas flow rate is as follows, it is sufficient that the main filter 1 at this time has a condition capable of incinerating particulates.

Here, considering the excess air ratio of the diesel engine and assuming that the amount of air contained in the exhaust gas is about 20%, the main filter 1 is set in the range of Q _{2 1} / Q _T <1/20.
When the air passage resistance between the sub-filter 2 and the sub-filter 2 is set, the amount of air required to incinerate the particulates collected in the main filter 1 is supplied. That is,
When the main filter 1 is regenerated, the main filter 1 is exhausted by the exhaust gas.
The air amount sufficient to heat and incinerate the particulates is supplied without being cooled, and the regeneration of the main filter 1 is completed.

Further, in this diesel particulate filter, when the regeneration of the main filter 1 is completed, the sub-filter 2 collects the particulates in the exhaust gas during that period and the particulates are accumulated on the sub-filter 2. Become. Therefore, 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 arranged inside the main filter 1, the heat energy of the exhaust gas is stored in the sub-filter 2, and the sub-filter 2 is heated by the heat energy, so the bypass valve 7 Immediately after the closing of the sub-filter 2, the heater 6 provided in the sub-filter 2 may be energized to incinerate the particulates collected in the sub-filter 2, and the air contained in the exhaust gas leaking through the bypass valve 7 may be used. It burns and the sub-filter 2 is regenerated.

The diesel particulate filter is constructed 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, the exhaust gas is sent from the inlet 15 to the exhaust gas passage 22, passes through the main filter 1 from the exhaust gas passage 22, and the soot contained in the exhaust gas at 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
Therefore, as shown in FIG. 8, the air passage resistance of the main filter 1 gradually increases with the collection time. On the other hand, the controller 10 uses the rotation sensor 1
1, receiving the detection signals from the load sensor 12 and the temperature sensor 13, determining the engine operating state from the detected values, and activating the actuator 8 to bypass when the preset exhaust gas pressure detected value becomes Determine whether to open valve 7.

Therefore, 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, so the controller 10 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 pass a current through the wire net heater 6 through the electrode terminal 9, and the wire net heater 6 is heated to heat the main filter 1. The particulate matter contained in the exhaust gas passing through the sub-filter 2 is collected by the sub-filter 2, and the collected particulates are accumulated on the sub-filter 2. At this time, the air passage resistance value of the sub-filter 2 is
As shown in FIG. 8, it will be gradually increased from R _{1 1} to R _{1 2.}

When the wire net 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 CO. ₂ , converted to H ₂ O, incinerated, turned into gas and discharged from the outlet 16. As the regeneration of the main filter 1 progresses, as shown in FIG. 8, the air passage resistance value of the main filter 1 gradually changes from R _{2 2} to R _{2 1} , and the regeneration of the main filter 1 is completed. To do. Completion of regeneration of the main filter 1 is determined by the controller 10 based on the exhaust gas pressure value that is preset in consideration of the engine operating state. At this time, the flow of exhaust gas gradually increases from the sub-filter 2 to the main filter 1 due to the balance of the air passage resistances of the main filter 1 and the sub-filter 2. However, in this embodiment, ,
The main air passage resistance of the main filter 1 during regeneration completion of the filter 1 R _{2 1} is the air flow resistance value of the sub-filter 2 R
It is set to be higher than ₁₂ . Therefore, even after the regeneration of the main filter 1 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 the. When the bypass valve 7 is closed,
The exhaust gas passes through the main filter 1 from the exhaust gas passage 22, and the normal exhaust gas processing, that is, the particulate collection processing 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 to 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 in the sub-filter 2 are incinerated by using the air contained in the small amount of exhaust gas passing through the sub-filter 2 from the bypass passage 21 and the sub-filter 2
Will be played. In the diesel particulate filter, the above-mentioned operation cycle is repeated and the exhaust gas is continuously purified.

Next, another embodiment of the diesel particulate filter to which this filter structure is applied will be described with reference to FIGS. 6 and 7. This embodiment has the same configuration and function except that the structure of the sheet filter applied as the main filter is different from that of the above embodiment, and therefore, the same reference numerals are given to the same parts, and here, A duplicate description will be omitted. In the diesel particulate filter of this embodiment, the filter 27 shown in FIG. 3 is applied as the main filter 25. Main filter 25
Is composed of an inner cylinder 19 and an outer cylinder 20. Outer cylinder 20
3, the filter 27 shown in FIG. 3 is applied, but the inner cylinder 19 uses a filter in which the sheet filter 47 and the wire mesh heater 6 are arranged inside and outside in reverse. Also,
On the exhaust gas inlet 15 side of the exhaust gas passage 22, a shielding plate 29 is provided between the sub-filter 2 and the shielding bypass cylinder body 4 to shut off the inlet side peripheral portion of the bypass passage 21. A plate-shaped filter 24 formed flat from the sheet filter 47 is arranged on the end surface of the main filter 25 on the exhaust gas inlet 15 side. The diesel particulate filter of this embodiment has the same configuration, operation, and function as those of the above-described embodiment except for the structure of the main filter, and therefore the description thereof is omitted here.

[0038]

The filter structure of the diesel particulate filter according to the present invention is constructed as described above and has the following effects. That is, this filter structure has a filter and a wire mesh heater arranged in a case incorporated in the exhaust system of a diesel engine,
The filter can be applied to a diesel particulate filter that collects particulates contained in exhaust gas, and heats and incinerates the collected particulates by energizing a wire mesh heater.
A porous sheet produced by filtering a slurry in which iC or Si-C-Ti-O-based fibers and a solution such as a polycarbosilane solution are mixed is sintered to obtain a solution such as polycarbosilane or the like from SiC or Si- Since a sheet filter converted to C-Ti-O is used and a wire mesh heater made of a conductive metal is laminated on the sheet filter, the filter itself can be configured to be lightweight, heat resistant and oxidation resistant. Since it is in the form of a sheet, it can be easily formed into an optimum shape for a diesel particulate filter, and can be formed into a shape with a large collection area, so that particulates in exhaust gas can be collected efficiently.

In addition, this filter structure has a main filter housed in a case in the middle of the exhaust system of a diesel engine and a bypass cylinder at the center of the main filter to allow the exhaust gas flow 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 surface of the main filter on the exhaust gas inflow side, and a bypass valve that opens and closes the inlet of the sub filter with an actuator is provided, and the air passage resistance of the sub filter is the main filter. When the bypass valve is closed, the exhaust gas is smoothly purified by the main filter, and the particulates in the exhaust gas are collected by the main filter.

Furthermore, when regenerating the main filter,
Only by opening the bypass valve and energizing the wire mesh heater, there is no need to send air for incinerating the particulates collected in the main filter by using a separately installed pump or the like. A small amount of exhaust gas is sent to the filter due to the balance of the air passage resistances of the main filter and the sub filter. However, due to the phenomenon of excess air ratio, which is a characteristic of diesel engines, a small amount of air is contained in the exhaust gas of diesel engines, so the particulate matter collected by the main filter is incinerated by using that air. 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 in a compact and simple structure. Moreover, the function of treating the exhaust gas emitted from the diesel engine is extremely simple and the exhaust gas can be continuously purified. For example, it can be mounted well even in a severe place due to the space of a vehicle or the like. it can.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a manufacturing process of a filter structure in a diesel particulate filter according to the present invention.

FIG. 2 is a perspective view showing an embodiment of the filter structure of FIG.

FIG. 3 is a perspective view showing another embodiment of this filter structure of FIG. 1.

FIG. 4 is a 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 bypass valve closed state.

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

FIG. 6 is a sectional view showing another 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.

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

FIG. 8 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 this filter structure.

[Explanation of symbols]

 1, 25 Main filter 2 Sub filter 3 Case 4 Bypass cylinder 6 Wire mesh heater 7 Bypass valve 10 Controller 26, 27 Filter 41 Fiber 42 Polycarbosilane 43 Slurry 44 Wire mesh 47 Sheet filter

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display area F01N 3/02 Z B01D 39/20 D F01N 9/00 ZAB Z

Claims (10)

[Claims] 1. A diesel engine exhaust system having a filter arranged in a case and a mesh heater for heating the filter, the filter collecting particulates contained in exhaust gas, In a diesel particulate filter that heats and incinerates the collected particulates by energizing the reticulated heater, a filter in which long ceramic fibers are laminated and the long ceramic fibers are bonded with a liquid ceramic raw material, and the entire surface of the filter is adhered A filter structure in a diesel particulate filter, characterized in that the filter structure is composed of arranged mesh conductors. 2. The filter is SiC or Si-C-
The porous sheet prepared by straining a slurry prepared by mixing Ti-O-based fibers with a polycarbosilane solution, a polytitanocarbosilane solution, and a solution selected from polysilane styrene, polysilane, and polysilazane solution is sintered and It is characterized by comprising a sheet filter obtained by converting the solution into SiC or Si-C-Ti-O, and a wire mesh heater made of a conductive heat-resistant metal laminated and tightly locked on the sheet filter. The filter structure in the diesel particulate filter according to claim 1. 3. The SiC or Si—C—Ti—O fiber is characterized in that its long fiber is cut into 2 to 10 mm or is composed of whiskers prepared by a vapor phase method. The filter structure in the diesel particulate filter according to claim 2. 4. The filter according to claim 1, wherein a slurry obtained by mixing long fibers of Si ₃ N _{4 and} a solution of polysilazane, polycarbosilane, and perihydropolysilazane is passed through a sheet to sinter the sheet. The filter structure in the described diesel particulate filter. 5. The filter structure for a diesel particulate filter according to claim 1, wherein the filter is made by filtering a sheet with a slurry obtained by mixing long fibers of mullite with a polyaluminoxane solution. 6. The mesh heater is laminated between the sheet filters, and the sheet filter arranged on the downstream side of the exhaust gas flow is configured such that the fibers are closer to each other than the sheet filter arranged on the upstream side. The filter structure in the diesel particulate filter according to claim 2, wherein: 7. The filter structure in a diesel particulate filter according to claim 1, wherein the reticulated heater is made of fine mesh and filtered with silicon carbide fibers to sinter the composite layer. 8. A main filter comprising the sheet filter arranged in the case, a mesh heater arranged on an exhaust gas inflow side of the main filter, and a bypass cylinder arranged in a central portion of the main filter. A sub-filter composed of the sheet filter arranged in parallel to the exhaust gas flow with respect to the main filter, a bypass valve arranged on the upstream side of the exhaust gas inflow of the sub-filter for opening and closing the bypass cylinder, and the bypass valve 3. The diesel particulate filter according to claim 2, wherein the diesel particulate filter has an actuator that opens and closes, and the air passage resistance of the sub-filter is set smaller than the air passage resistance of the main filter. Filter structure of diesel particulate filter. 9. The main filter is formed into a fold-like tubular shape by sequentially folding the sheet filter, and the sub-filter is arranged inside the main filter in parallel with an exhaust gas flow and is tubular from the sheet filter. 9. The filter structure in a diesel particulate filter according to claim 8, wherein the filter structure is formed in. 10. The main filter is formed in a tubular shape from the sheet filters stacked in parallel with an exhaust gas flow,
The filter structure in a diesel particulate filter according to claim 8, wherein the sub-filter is arranged in parallel with the exhaust gas flow inside the main filter, and is formed into a tubular shape from the sheet filter.