JPH04301130A - Filter for cleaning exhaust gas of internal combustion engine - Google Patents

Abstract

PURPOSE:To maintain the collecting capacity and the renovation capacity of a filter successively and improve the reliability, concerning the filter which scavenges the particles contained in the exhaust gas flow of an internal combustion engine (diesel engine) and then is renovated. CONSTITUTION:This filter is of such structure that it has center face 20 vertical to the direction of a fluid passage and surrounding face 21 inclined to the direction of the fluid passage at on end of a honey comb structure or of such constitution that the through hole 16 of the honey comb structure has a spiral shape. The heat conduction from the incline of the filter to the heating chamber storing the filter is suppressed, and the renovation of the periphery, where particulates are existing, of the end face of the filter can be performed efficiently, and the heat energy of the combustion of the particulates accumulating on the bulkheads of the through holes 16 is conducted to the filter at large, and the reclamation ratio improves. Moreover, by making the above filter bear a catalyst, which decomposes the particulates at low temperature, or an electric wave absorbing material, it has high effect.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is an exhaust gas of an internal combustion engine that collects particulates (particulate matter) contained in an exhaust gas stream discharged from a diesel engine and regenerates them using heating means. This invention relates to a purification filter.

0002

BACKGROUND OF THE INVENTION In recent years, there has been a movement in countries around the world to tighten air pollutant emission regulations for stationary sources such as cogeneration and mobile sources such as automobiles.

[0003] Among automobiles, diesel cars are subject to stricter emission regulations for particulates as well as nitrogen oxides. At present, it is considered impossible to achieve exhaust gas regulation values only through reduction measures such as combustion improvement, and it is essential to install an after-treatment device to purify exhaust gas. As this after-treatment device, a method using a filter that collects particulates whose main component is black smoke contained in the exhaust gas stream is being considered.

However, if the above-mentioned filter continues to collect particulates, it becomes clogged and its collection capacity is significantly reduced, and the flow of exhaust gas becomes poor, resulting in a reduction in engine output or the engine stopping. causing problems such as

[0005]Currently, technological development is being carried out all over the world to regenerate the collection ability of filters, but this has not yet been put to practical use.

[0006] Particulates are known to burn at temperatures of about 600°C. As a heating means for raising the temperature of particulates to this temperature, a burner method, an electric heater method, a microwave method, etc. are considered.

FIG. 2 shows a filter regeneration device in which the heating means is a microwave system (for example, disclosed in Japanese Patent Laid-Open No. 59-1260).
Publication No. 22). In the figure, 1 is an engine, 2 is an exhaust manifold, 3 is an exhaust pipe, 4 is an exhaust branch pipe, 5 is a filter, 6 is a heating chamber housing the filter, 7 is a microwave generator, and 8 is a microwave generator. 9 is a microwave reflecting plate; 1 is a waveguide that guides the generated microwave to the heating chamber;
0 is an air pump, 11 is an air supply path, 12 is a driving power source for the microwave generating means, 13 is a muffler, 14 is an air switching valve, and 15 is an exhaust gas switching valve.

In the above configuration, the exhaust gas from the engine is guided to the filter 5 by the exhaust gas switching valve 15 or directly discharged to the atmosphere. In the particulate collection process, the exhaust gas is guided to the filter 5, and the particulates contained in the exhaust gas are collected by the filter 5. When the collection capacity reaches its limit, the exhaust gas switching valve 15 is controlled to cut off the exhaust gas to the exhaust pipe 3, and all of the exhaust gas is discharged to the atmosphere via the exhaust branch pipe 4. During this time, the filter 5 is regenerated.

In this filter regeneration process, energy for heating the particulates is supplied from the microwave generating means 7, and air necessary for combustion is supplied from the air pump 10. When the filter regeneration is completed after a predetermined period of time, the exhaust gas switching valve 15 is controlled again to guide the exhaust gas to the filter 5 and start collecting it. This process of collection and regeneration is repeated.

The filter 5 of the filter regeneration device has a honeycomb structure having a large number of through holes formed from partition walls of porous ceramic such as cordierite and mullite. In this honeycomb structure, airtight sealing plugs are alternately provided at both ends of the through holes so that the exhaust gas flow passes through the porous ceramic partition wall and is discharged, and the particulates are arranged in the exhaust gas flow. is collected on the porous ceramic partition wall on the inlet side of the chamber.

[0011]

[Problem to be Solved by the Invention] Particulates collected by the filter in the filter regeneration process of the above configuration are heated by a heating means such as a microwave system, and then combustion is started by blowing the air necessary for combustion. do. At this time, thermal energy is taken away from the outer periphery of the filter end face on the exhaust gas inflow side by the heating chamber housing the filter, which prevents the particulates from rising in temperature, making it difficult to regenerate the outer periphery of the filter end face.

[0012] Furthermore, combustion occurs from the center of the end face of the filter where the temperature is high, and particulates in that part are removed and pressure loss is reduced, so that the combustion air is concentrated in the center. Therefore, air is difficult to be supplied to the outer periphery of the filter, making it difficult to regenerate the outer periphery of the filter.

[0013]Furthermore, the heat combusted in the center of the filter is not efficiently transferred to the outer circumference because the partition walls forming the through holes are made of a ceramic material with low thermal conductivity. Therefore, there are particulates that do not reach the combustible temperature in the outer circumference of the filter, making it difficult to regenerate the entire filter.

[0014] As a result, particulates accumulate on the end face of the filter during continuous repetition of particulate collection and regeneration, and the through holes become clogged, causing the filter to lose its ability to collect and regenerate. There was an issue of decreased ability.

The present invention solves the above-mentioned problems, and provides a highly reliable filter that can efficiently regenerate particulates on the end face and outer periphery of the filter and continuously maintain the collection and regeneration ability of the filter. It is intended to provide.

[0016]

[Means for Solving the Problems] In order to achieve the above object, the filter for purifying exhaust gas of an internal combustion engine according to the present invention includes a honeycomb structure having a plurality of through holes formed from a porous ceramic partition wall, at one end thereof. The central portion has a surface perpendicular to the fluid passage direction, and the portion other than the central portion has a surface inclined in the fluid passage direction, and one end of the honeycomb structure has a
First sealing plugs made of an airtight ceramic cement material are provided in the through-holes that are present at individual intervals, and the other end of the honeycomb structure is not provided with the first sealing plugs. A second sealing plug made of an airtight ceramic cement material is provided in the through hole.

[0017] Furthermore, in a honeycomb structure having a large number of through holes formed by a porous ceramic partition wall surrounded by an outer frame, the through holes have a spiral shape, and one end of the honeycomb structure has one at every other end. A first sealing plug made of an airtight ceramic cement material is provided in the through-holes existing at intervals of , and the through-hole is not provided with the first sealing plug at the other end of the honeycomb structure. A second sealing plug made of an airtight ceramic cement material is provided at the bottom.

The present invention also provides a filter for purifying exhaust gas of an internal combustion engine according to the above-mentioned invention, in which a catalyst for decomposing particulates at low temperature or absorption of microwaves is provided in a honeycomb structure having a large number of through holes formed by ceramic partition walls. The structure supports a material with high radio wave absorption rate.

[0019]

[Operation] When a predetermined amount of particulates is collected in an exhaust gas purifying filter for an internal combustion engine, the particulates are heated by a microwave heating means, and air necessary for combustion is blown.

However, the filter for purifying exhaust gas of an internal combustion engine of the present invention has a surface at one end of the honeycomb structure, the center part of which is perpendicular to the fluid passage direction, and the other part of the honeycomb structure having a surface that is inclined in the fluid passage direction. This structure suppresses heat transfer from the sloped part of the filter to the heating chamber that houses the filter, efficiently regenerates particulates existing on the outer periphery of the filter end face, and allows combustion air to flow through the filter. Since it is possible to create a flow that can be supplied to the through-holes on the outer periphery of the filter, the air diffuses into the through-holes on the outer periphery of the filter, improving the regeneration ability.

Furthermore, since the through-holes of the honeycomb structure have a spiral shape, thermal energy due to combustion of particulates deposited on the partition walls of the through-holes is transmitted to the entire filter, improving the regeneration rate. Furthermore, since the total length of the through holes can be made longer than in a filter with straight through holes, the amount of particulates collected can be increased.

Furthermore, in each of the exhaust gas purifying filters for internal combustion engines of the present invention, the particulates can be combusted at a low temperature by supporting a catalyst that decomposes the particulates at a low temperature on the honeycomb structure. It is possible to further improve the ability to regenerate particulates deposited on the surface.

Furthermore, when a microwave system is used as the heating means, the end face of the filter can be efficiently heated by supporting a radio wave absorbing material with a high absorption rate of microwaves instead of the above-mentioned catalyst. It is possible to further improve the regeneration ability of the particulates.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a plan view and a sectional view of an exhaust gas purifying filter for an internal combustion engine according to an embodiment of the present invention. A honeycomb structure having a large number of through holes 16 formed by porous ceramic partition walls is formed in a cylindrical space surrounded by an outer frame 17, and one end of the honeycomb structure has a central portion perpendicular to the fluid passage direction. A surface 21 inclined in the direction of the fluid passage is provided in areas other than the flat surface 20 and the center portion. Reference numeral 18 denotes first sealing plugs made of an airtight ceramic cement material and provided so as to protrude from the end surface of the through hole 16 at intervals of every other sealing plug. A second sealing plug 19 made of an airtight ceramic cement material is provided at the other end of the through-hole 16 that is not in use.

Exhaust gas flow containing particulates discharged from a diesel engine or the like flows into the through hole 16 on the first sealing plug 18 side, passes through the porous ceramic partition wall, and flows into the second sealing plug side. is discharged from the through hole 16. At this time, the porous ceramic partition wall has a pore size that allows the gas component of the exhaust gas flow to pass through, but does not allow the particulate component to pass through. Therefore, particulates accumulate on each partition wall of the through hole 16 on the first sealing plug side. Process of burning and removing particulates when a certain amount of collected particulates is reached (regeneration)
Is required.

[0027] In the filter regeneration process of the above structure, the particulates collected by the filter are heated by a heating means such as a microwave system, and air necessary for combustion is blown. However, in the exhaust gas purifying filter for an internal combustion engine of the present invention, at one end of the honeycomb structure,
Since the central portion has a surface 20 perpendicular to the fluid passage direction and surfaces 21 other than the central portion inclined in the fluid passage direction, the outer peripheral portion of the end face of the filter does not come into contact with the heating chamber in which the filter is housed. Heat transfer from the inclined portion to the heating chamber is suppressed. Therefore, the particulates present at the outer periphery of the end face of the filter are heated to a combustible temperature in a short period of time, so that they can be regenerated as efficiently as in the center of the filter. Further, the surface 21 inclined in the direction of the fluid passage can create a flow that allows air necessary for combustion of particulates to be supplied to the through holes in the outer circumference of the filter. Therefore, air can diffuse better into the particulates deposited in the through-holes on the outer periphery of the filter, so that combustion starts smoothly, stable combustion is always achieved, and the filter regeneration ability is improved.

As a result, it is possible to prevent a decrease in the filter's collection ability and regeneration ability due to particulates clogging the through holes during continuous repetition of particulate collection and regeneration, and the filter's ability to collect and regenerate can be prevented. It is possible to continuously maintain the ability to collect and regenerate.

In addition, in the filter of the present invention, a surface 20 provided at one end of the honeycomb structure, the center of which is perpendicular to the fluid passage direction, and a surface 2 whose outer peripheral part is inclined in the fluid passage direction.
The ratio of 1 is not limited and is appropriately selected depending on the heating means, the amount of air necessary for combustion, the size of the filter, etc.

Next, another embodiment of the present invention will be described. Another embodiment of the present invention is a honeycomb structure having a large number of through holes formed by a porous ceramic partition wall surrounded by an outer frame, wherein the through holes have a spiral shape and are arranged at one end of the honeycomb structure. is provided with first sealing plugs made of an airtight ceramic cement material in the through holes present at intervals of every other hole, and the first sealing plug is provided at the other end of the honeycomb structure. A second sealing plug made of a ceramic cement material having airtightness is provided in the through hole where there is no airtightness.

In the above structure, since the through holes of the honeycomb structure have a spiral shape, combustion of particulates deposited on the partition walls of the through holes progresses as if rotating inside the filter. Therefore, the heat energy due to combustion of particulates is transmitted to the entire filter, and the number of particulates that reach the combustible temperature increases, so that the particulates present in the entire filter can be efficiently combusted, improving the regeneration rate. Can be done. Furthermore, when the filter storage volume is the same, compared to a filter in which the through hole is straight, the filter in which the through hole of the present invention has a spiral shape can increase the total length of the through hole, so the amount of particulates collected can be increased. can be increased.

[0032] In the filter of the present invention, the spiral-shaped through holes can be obtained by rotating both ends of a honeycomb structure having a large number of through holes formed by partition walls of porous ceramic in opposite directions. Further, the level of rotation is not limited, and is appropriately selected depending on the heating means, the amount of air blown necessary for combustion, the size of the filter, etc.

Furthermore, in each of the exhaust gas purifying filters for internal combustion engines of the present invention, the particulates can be combusted at a low temperature by supporting a catalyst that decomposes the particulates at a low temperature on the honeycomb structure. It is possible to further improve the ability to regenerate particulates deposited on the surface. Catalysts for decomposing the above particulates at low temperatures include carbonates made of alkali metals and alkaline earth metals, vanadium, molybdenum,
Examples include oxides of tungsten, copper, manganese, and cobalt, and at least one of these is supported on the honeycomb structure.

[0034] Furthermore, by supporting a radio wave absorbing material with a high microwave absorption rate instead of the above-mentioned catalyst, the end face of the filter can be efficiently heated, thereby further improving the ability to regenerate particulates deposited on the end face of the filter. can be done. Examples of the radio wave absorbing material include oxides of zinc, copper, manganese, cobalt, iron, tin, and titanium, composite metal oxides having a perovskite crystal structure, and silicon carbide, and at least one of these is used in the honeycomb structure. carried.

Further, in the filter of the present invention, even greater effects can be obtained by combining the respective structures.

[0036]

As explained above, the filter for purifying exhaust gas of an internal combustion engine according to the present invention provides the following effects.

(1) The exhaust gas purifying filter for an internal combustion engine of the present invention has a honeycomb structure with a surface at one end that is perpendicular to the fluid passage direction and a surface other than the central part that is inclined in the fluid passage direction. This structure suppresses heat transfer from the sloped part of the filter to the heating chamber that houses the filter, efficiently regenerates particulates existing on the outer periphery of the filter end face, and allows combustion air to flow through the filter. Since it is possible to create a flow that can be supplied to the through-holes on the outer periphery of the filter, air can diffuse better into the through-holes on the outer periphery of the filter, and the regeneration ability is improved. As a result, it is possible to prevent the particulates from clogging the through holes during continuous repetition of particulate collection and regeneration, thereby preventing the filter from reducing its collection and regeneration capabilities. ability can be maintained continuously.

(2) Furthermore, since the through-holes of the honeycomb structure have a spiral shape, the thermal energy due to the combustion of the particulates deposited on the partition walls of the through-holes is transmitted to the entire filter and reaches the combustible temperature. Since the number of particulates present in the filter increases, the particulates present throughout the filter can be efficiently combusted, and the regeneration rate improves. Furthermore, since the total length of the through holes can be made longer than in a filter with straight through holes, the amount of particulates collected can be increased.

(3) Furthermore, in the filter for purifying exhaust gas of an internal combustion engine according to the present invention, the particulates can be combusted at a low temperature by supporting a catalyst that decomposes the particulates at a low temperature on the honeycomb structure. The ability to regenerate particulates deposited on the end face can be further improved.

(4) In addition, by supporting a radio wave absorbing material with a high microwave absorption rate instead of the above catalyst, the end face of the filter can be efficiently heated, which improves the ability to regenerate particulates deposited on the end face of the filter. can be further improved.

[Brief explanation of drawings]

FIG. 1 is a plan view and a sectional view of an exhaust gas purifying filter for an internal combustion engine according to an embodiment of the present invention.

[Figure 2] Configuration diagram of a conventional filter regeneration device for purifying exhaust gas of an internal combustion engine

[Explanation of symbols]

16 Through hole 17 Outer frame 18 First sealing plug 19 Second sealing plug 20　Plane perpendicular to the fluid passage 21　Slanted surface with respect to the fluid passage

Claims (4)

[Claims] Claims: 1. A honeycomb structure having a large number of through holes formed by a porous ceramic partition wall surrounded by an outer frame, at one end thereof, a center portion is provided with a surface perpendicular to a fluid passage direction and a surface other than the center portion. has a surface inclined in the direction of the fluid passage, and is made of a ceramic cement material that has airtightness in the through holes that are present at every other end at the one end.
A sealing plug is provided at the other end of the honeycomb structure, and a second sealing plug made of an airtight ceramic cement material is provided in the through hole where the first sealing plug is not provided. A filter for purifying exhaust gas from internal combustion engines. 2. A honeycomb structure having a large number of through holes formed by a porous ceramic partition wall surrounded by an outer frame, wherein the through holes have a spiral shape, and one end of the honeycomb structure has a plurality of through holes. First sealing plugs made of an airtight ceramic cement material are provided in the through holes that are present at regular intervals, and the through holes that are not provided with the first sealing plugs are provided at the other end of the honeycomb structure. A filter for purifying exhaust gas of an internal combustion engine, comprising a second sealing plug made of an airtight ceramic cement material provided in a hole. 3. The internal combustion engine according to claim 1, wherein the honeycomb structure having a large number of through holes formed by partition walls of porous ceramic supports a catalyst for decomposing particulates contained in the exhaust gas flow at a low temperature. Exhaust gas purification filter. 4. The exhaust gas purification of an internal combustion engine according to claim 1 or 2, wherein a radio wave absorbing material having a high absorption rate of microwaves is supported on a honeycomb structure having a large number of through holes formed by a porous ceramic partition wall. filter.