JPH09317440A - Exhaust particulate purifier for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regenerate a filter for scavenging particulates in exhaust gas in an exhaust particulate purifier which is operated even under a temperature to activate its catalyst by providing a fuel feed means in the upstream with respect to the filter and providing exothermic bodies of fuel absorbing structure between the fuel feed means and the filter. SOLUTION: When a filter 7 is to be regenerated, if the oxidation catalysts carried by a catalyst carrier 9 and by heating bodies 4 are not heated up to their activation temperature, heaters 42 are energized to heat the heating bodies 4 from their inside after which a fuel feed means 1 injects fuel droplets 8 into exhaust gas 2. When the resultant mixed gas passes near the heating bodies 4, the exhaust gas 2 streams while curving around the respective heating bodies 4 and thus does not hardly flow into fuel absorbing members 4, while the fuel droplets 8 travel straight against the heating bodies 4 and penetrate the fuel absorbing members 41 to be oxidized or burned therein and emitted out therefrom again into the exhaust gas. As a result, the exhaust gas flowing into the catalyst carrier 9 is heated up to heat the oxidation catalyst carried by the catalyst carrier 9 up to its activation temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to an apparatus which is effectively applied to a diesel engine and which collects and purifies fine particles contained in the exhaust gas.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 58-38311 discloses, in an exhaust gas purification apparatus for an internal combustion engine having a filter, particulates (hereinafter referred to as "particulates") in the exhaust gas collected and deposited by the filter. As one of means for regenerating the trapping ability of the filter by removing the combustion, it has a structure in which a catalyst is supported on the filter and a fuel supply means is provided upstream of the filter, and the exhaust temperature is high and the catalyst is activated. Disclosed is a method for regenerating a filter in which fuel is supplied to the filter by the fuel supply means when the fuel cell is in a state, and the particulate oxidation accumulated on the filter is heated to a temperature above its ignition temperature and burned and removed by the heat of oxidation reaction of the fuel by the catalyst. Has been done.

However, in this filter regeneration method, the fuel is not oxidized even when the fuel is supplied to the filter under the operating conditions of low engine speed and low load in which the temperature of the exhaust gas is low and the catalyst does not reach the activation temperature. Moreover, the particulates cannot be burned and removed. If such operating conditions continue, not only will particulates build up excessively and exhaust pressure will rise, which will significantly reduce engine performance, but eventually the filter will become clogged, making traveling difficult. Cause

[0004]

In view of the above problems, the present invention comprises means for raising the temperature of the catalyst above the activation temperature in any operating condition where the exhaust temperature is low and the catalyst does not reach the activation temperature. Another object of the present invention is to provide an exhaust gas purification apparatus that can regenerate a filter in all operating regions.

[0005]

The present invention employs the technical means described in claims 1 to 7 to achieve the above object. According to the structure of claim 1, even when the exhaust gas temperature is low at the time of filter regeneration, the heating element having the fuel absorption structure is caused to generate heat to raise the exhaust gas temperature, and then the appropriate amount is included in the exhaust gas by the fuel supply means. Of fuel droplets. Then, the fuel droplets in the exhaust hit the heating element having the fuel absorption structure, and the fuel droplets are absorbed and heated by the heating element having the fuel absorption structure to be oxidized and burned to further raise the exhaust temperature. Then, the exhaust gas containing HC (hydrocarbon) is oxidized and burned, and finally the exhaust gas is heated to the particulate combustion temperature or higher. as a result,
The particulates trapped in the filter reach the combustion temperature or higher and are burned to regenerate the filter.

According to the second aspect of the invention, the temperature of the exhaust gas heated by the heating element is heated to the activation temperature of the oxidation catalyst carried on the catalyst carrier or higher, and the exhaust gas containing HC does not react with the oxidation catalyst. When passing through the supported catalyst carrier, it is oxidized, burned and further heated. Therefore, the exhaust gas containing HC can be efficiently heated to the particulate combustion temperature or higher.

According to the third aspect of the invention, since the electric heater and the fuel absorbing member are separate bodies, the volume of the fuel absorbing member can be freely changed regardless of the electric heater, and the electric heater can be changed. Since the fuel absorbing member is heated by heat transfer by energizing the fuel, it is possible to easily heat and oxidize and burn the fuel droplets soaked in the heating element having the fuel absorbing structure with a small amount of electric power.

According to the structure of claim 4, by energizing the fuel absorbing member itself, the entire fuel absorbing member is uniformly heated, and the contact area between the heat generating portion and the fuel is large, and the conductive fuel absorbing is efficient. The fuel droplets soaked into the member can be easily heated to be oxidized and burned. According to the configuration of claim 5, the fuel droplets in the exhaust can be efficiently attached to the heating element, and the exhaust can be efficiently heated even when the fuel droplets supplied to the exhaust are small.

According to the structure of claim 6, since the oxidation catalyst is carried on the member constituting the heating element, the fuel droplets soaked in the heating element can be oxidized and burned at a lower temperature. There is an effect that the heating by the heating element may be small. According to the configuration of claim 7, by carrying the oxidation catalyst on the filter for collecting the particulates in the exhaust gas, oxidation is carried out on the catalyst carrier carrying the oxidation catalyst,
There is an effect that exhaust gas can be purified by oxidizing and burning unburned HC.

[0010]

1 and 2 relate to a first embodiment of the present invention, FIG. 1 (a) is a side sectional view of an exhaust gas purification apparatus of the present invention, and FIG. ) Indicates that the mixture of the exhaust gas 2 and the fuel droplets 8 injected into the exhaust gas is the heating element 4
FIG. 2 is an enlarged view showing the situation when passing through the vicinity of FIG. 2, and FIG. 2 is an explanatory view showing the temperature rise process of the exhaust gas at each position along the flow of the exhaust gas of the exhaust gas purification apparatus.

As shown in FIG. 1A, a filter 7 carrying an oxidation catalyst for collecting fine particles in exhaust gas is provided in an exhaust pipe 3 of an internal combustion engine, and an oxidation catalyst is provided upstream of the filter 7. Catalyst carrier 9, a fuel supply device 1 provided upstream of the catalyst carrier 9, for supplying fuel into the exhaust gas, provided between the fuel supply device 1 and the catalyst carrier 9, and an oxidation catalyst in whole or in part A plurality of heating elements 4 carrying C are arranged in parallel with each other in the radial direction of the exhaust pipe line 3 at an appropriate interval upstream of the catalyst carrier 9 carrying an oxidation catalyst.

As shown in FIG. 1B, in the first embodiment, the heater 42 of the heating element 4 is a sheath heater or an electric heater whose outer peripheral portion is insulated, and is formed into a rod shape. Around the member 41 for absorbing fuel
As a material, a heat-resistant member molded in a mesh shape is arranged. When the filter 7 is regenerated, if the exhaust gas temperature is low and the oxidation catalyst carried on the catalyst carrier 9 and the heating element 4 has not reached the activation temperature, the heater 42 is energized so that the inside of the heating element 4 is After being heated to the activation temperature of the oxidation catalyst carried by the fuel absorbing member 41 of the heating element 4 or the combustion temperature of the fuel or higher, the fuel supply means 1 injects fuel droplets into the exhaust gas.

When the air-fuel mixture of the exhaust gas 2 and the fuel droplets 8 injected into the exhaust gas passes near the heating element 4, FIG.
As shown in FIG. 3, the flow of the exhaust gas 2 flows around the heating element 4 in a curved manner, and the exhaust gas 2 hardly flows into the fuel supply member 41 that is molded to be appropriately dense due to ventilation resistance. On the other hand, since the fuel droplet 8 has a strong inertia, even in the vicinity of the heating element 4, the fuel droplet 8 goes straight on and collides with the heating element 4, soaks into the mesh-shaped fuel absorbing member 41, and is oxidized inside by the oxidation catalyst. Alternatively, the exhaust gas which is burned by the heat of the heater 42 and escapes again into the exhaust gas and flows into the catalyst carrier 9 is heated, and the oxidation catalyst carried on the catalyst carrier 9 reaches the activation temperature.

The fuel droplets which cannot be separated in the first row of the heating element 4 are separated by the heating elements arranged in the second row in an alternating manner. At this time, the amount of exhaust gas flowing into the heating element 4 is extremely small, and the amount of heat taken by the exhaust gas inside the heating element 4 is very small. Therefore, the power consumption is low and the internal temperature is kept high. In addition, since the heating element 4 takes a method in which the fuel droplets in the exhaust gas are once impregnated into the inside of the exhaust gas to heat the fuel droplets 8, the fuel droplets 8 are exposed to the oxidation catalyst and the high temperature region for a long time. The droplet 8 can be efficiently oxidized or burned.

FIG. 2 is an explanatory view showing the temperature rising process of the exhaust gas at each position along the flow of the exhaust gas of the exhaust particulate purifying apparatus. As shown in FIG. 2, the exhaust gas flowing into the catalyst carrier 9 carrying the oxidation catalyst is heated to a temperature higher than the activation temperature of the oxidation catalyst by the heat of oxidation or combustion of the fuel oxidized or burned by the heating element 4. After that, by increasing the injection amount of the fuel droplets by the fuel supply means, sufficient unburned fuel is supplied to the catalyst carrier 9, and the exhaust gas flowing into the filter 7 by the heat of the oxidation reaction of the fuel in the catalyst carrier 9 is removed. The particulates accumulated on the filter 7 are burned and removed by heating the particulates to a temperature higher than the combustion temperature of the particulates to regenerate the filter 7. Here, the catalyst carried by the filter 7 serves to oxidize and burn the fuel that has not been oxidized in the catalyst carrier 9 to purify it by the filter 7, and prevents blow-through of the fuel.

On the other hand, when the temperature of the exhaust gas is high during regeneration of the filter and the oxidation catalyst has reached the activation temperature, it is supplied to the exhaust gas by the fuel supply means without energizing the heating element 4 to heat it. The fuel droplets are oxidized in the catalyst carrier 9, and the reaction heat generated causes the temperature of the exhaust gas to rise above the combustion temperature of the particulates to burn the particulates deposited on the filter 7.

Further, at this time, the fuel droplets permeate into the heating element 4 which is not heated, but since the oxidation catalyst carried on the heating element 4 is above the activation temperature, the fuel droplets are oxidized and become gas. Therefore, the liquid fuel does not stay inside the heating element 4. The fuel absorbing member 41 is not limited to a member formed in a mesh shape, and may be a structure such as a porous body or a foamed body into which fuel is impregnated, and is insulated from the heater 42 inside.
It may be an insulator itself. Further, even if the filter 7 does not carry an oxidation catalyst, the filter 7 can be regenerated well.

FIG. 3 is a side sectional view of an exhaust particulate purifying apparatus for an internal combustion engine according to a second embodiment of the present invention. In FIG. 3, the entire heating element 4 is made of a conductive heater member, and the heating element 4 is formed into a rod shape by winding a plurality of layers of a heater member formed into a mesh shape, for example, so that the fuel permeates inside. , A heating element 4 carrying an oxidation catalyst on all or part thereof
A plurality of columns are arranged upstream of the catalyst carrier 9 carrying the oxidation catalyst in a staggered manner in parallel to the direction of the exhaust pipe diameter.

Also in this embodiment, as in the case of the first embodiment, when the temperature of the exhaust gas is low when the filter 7 is regenerated and the oxidation catalyst is not activated, the fuel is injected into the exhaust gas by the fuel supply means 1. The fuel droplets 8 soak into the inside of the heating element 4 which has been previously energized and heated, and is oxidized or burned to heat the exhaust gas flowing into the catalyst carrier 9 to activate the catalyst carried on the catalyst carrier 9. Turn into

As the heating element 4, in addition to the above-mentioned mesh-shaped heater member, a porous metal body, a foam metal body, a sintered metal body, or the like having a structure in which fuel is impregnated, the heater is used. Any material can be used as long as it can be used as a member. Further, even when the catalyst is not loaded on the filter 7, the regeneration of the filter 7 is favorably performed.

FIG. 4 relates to a third embodiment of the present invention, in which (a) is a side sectional view and (b) is A in (a).
It is -A sectional drawing. In the third embodiment, the heating elements 4 of the first or second embodiment in which rod-shaped heating elements are arranged in parallel are arranged in a spiral shape. 5A and 5B relate to a fourth embodiment of the present invention, in which FIG. 5A is a side sectional view and FIG. 5B is a sectional view taken along line AA in FIG.

In the fourth embodiment, the heating elements 4 of the first or second embodiment, in which rod-shaped heating elements are arranged in parallel, are arranged in a shape that spreads radially from the center electrode 10. is there. FIG. 6 is a side sectional view of the fifth embodiment of the present invention. In the fifth embodiment, a rectifying member 20 is provided on the upstream side of the first row heating elements 4 of the first embodiment. Exhaust gas 2 is curved by the rectifying member 20 and flows toward the heating elements 4 in the first row. Further, the fuel droplets 8 that have collided and adhered to the rectifying member 20 due to inertial force are also washed away by the exhaust gas 2 toward the first-row heating elements 4 and flow in the vicinity of the first-row heating elements 4. Is increased, the fuel droplets are efficiently absorbed by the heating elements 4 in the first row, and are oxidized or burned.

Therefore, the heating element may have only the first row. Further, the rectifying member 20 of this embodiment may be applied to the second to fourth embodiments. FIG. 7 is a side sectional view of the sixth embodiment of the present invention. In the sixth embodiment, the catalyst carrier 9 is eliminated and the filter 7 carrying the oxidation catalyst is constituted by the heating element 4 and the fuel supply means 1. In the sixth embodiment, the heating element 4
Is used when the temperature of the oxidation catalyst carried by the filter 7 is raised above the activation temperature, and the oxidation reaction that occurs when the fuel droplets 8 supplied to the filter 7 are oxidized by the oxidation catalyst carried by the filter 7. The heat burns the particulates deposited on the filter 7 to regenerate the filter 7.

FIG. 8 is a radial cross-sectional view of a heating element used in the seventh embodiment of the present invention. The seventh embodiment is the first
In the heating element 4 of this embodiment, the fuel absorbing member 41 on the outer circumference of the heating element is in contact with the internal heater 42 and is formed of a thick layer 43 made of a member having high thermal conductivity, and a heat conductive layer provided outside the thick layer 43. It is composed of two thin layers 44 of low material. When the heater 42 heats the fuel absorbing member, the thick inner layer 43 has high heat conductivity and thus is heated in a short time, but the thin outer layer 44 has low heat conductivity and thus heats the thick inner layer 43. The generated heat is hard to escape to the outside, and the fuel can be efficiently oxidized or burned in the thick layer 43 on the inside.

As described above, according to the present invention, in the exhaust particulate purifying apparatus for the internal combustion engine of the type in which the particulate matter deposited on the filter is burned by the heat of the oxidation reaction of the fuel by the oxidation catalyst, the exhaust temperature is low and the oxidation catalyst has an activation temperature. The oxidation catalyst can be heated above the activation temperature of the catalyst in any operating condition that has not reached, and the filter can be properly regenerated in the entire operating region.

[Brief description of drawings]

FIG. 1 relates to a first embodiment of the invention,
(A) is a side sectional view of the exhaust particulate purifying apparatus of the present invention, (b) is a situation when the mixture of the exhaust 2 and the fuel droplets 8 injected into the exhaust passes near the heating element 4. FIG.

FIG. 2 relates to a first embodiment of the present invention,
FIG. 6 is an explanatory diagram showing a temperature rise process of exhaust gas at each position along the flow of exhaust gas of the exhaust particulate purifying device.

FIG. 3 is a side sectional view of an exhaust particulate purifying apparatus for an internal combustion engine according to a second embodiment of the present invention.

FIG. 4 relates to a third embodiment of the present invention,
(A) is a side surface sectional view, (b) is an AA sectional view in (a).

FIG. 5 relates to a fourth embodiment of the present invention,
(A) is a side surface sectional view, (b) is an AA sectional view in (a).

FIG. 6 is a side sectional view of a fifth embodiment of the present invention.

FIG. 7 is a side sectional view of a sixth embodiment of the present invention.

FIG. 8 is a radial cross-sectional view of a heating element used in a seventh embodiment of the present invention.

[Explanation of symbols]

 1 Fuel Supply Means 3 Exhaust Pipe Line 4 Heating Element 7 Filter 9 Catalyst Carrier 41 Fuel Absorbing Member 42 Electric Heater

Claims (7)

[Claims] 1. A filter provided in an exhaust pipe of an internal combustion engine for collecting particulates in exhaust gas, and a fuel supply unit provided upstream of the filter for supplying fuel into the exhaust gas. An exhaust particulate purifying apparatus for an internal combustion engine, comprising: a heating element having a fuel absorption structure provided between the fuel supply means and the filter. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein a catalyst carrier carrying an oxidation catalyst is arranged between the filter and the heating element. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the heating element comprises an electric heater and a fuel absorbing member arranged around the electric heater. An exhaust gas purification apparatus for an internal combustion engine, wherein the electric heater and the fuel absorbing member are insulated from each other. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the heating element is made of a conductive fuel absorbing member, and the fuel absorbing member itself is energized. The exhaust particulate purifying apparatus for an internal combustion engine, wherein the entire fuel absorbing member generates heat. 5. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the heating elements are alternately arranged in a plurality of rows at intervals in the exhaust pipe line. A characteristic exhaust gas purifying apparatus for an internal combustion engine. 6. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein a member constituting the heating element carries an oxidation catalyst. Exhaust particulate purification device. 7. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein an oxidation catalyst is carried on the filter for collecting the particles in the exhaust gas. Exhaust particulate purification device for internal combustion engine.