JP3067365B2 - Exhaust gas purification device for internal combustion engine - Google Patents

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 a diesel engine provided with a collecting member for collecting exhaust fine particles in exhaust gas by passing the exhaust gas.

[0002]

2. Description of the Related Art Diesel engines contain exhaust particulates such as carbon in the exhaust gas due to the combustion of fuel in a combustion chamber, and if discharged directly into the atmosphere undesirably causes environmental pollution. In order to prevent this, a method of providing a filter made of a porous ceramic or the like in an exhaust passage and collecting exhaust particulates by passing exhaust gas through the filter has been well known.

As a filter material, for example, Japanese Patent Application Laid-Open
As disclosed in JP-A-124417, the first passage having the exhaust inlet side open and the exhaust outlet side closed, and the second passage having the exhaust inlet side closed and the exhaust outlet side open, on the contrary, are mutually reciprocal. A so-called plugging trap having a honeycomb structure, in which exhaust gas passes through a porous partition wall provided between a plurality of first passages and a second passage to trap exhaust fine particles in the exhaust, As in JP-A-62-45309, a porous foam filter type is generally used.

When such a filter is used, an increase in the amount of trapped exhaust particulates increases the exhaust pressure and adversely affects the engine performance. Therefore, the collected exhaust particulates are periodically removed by, for example, a heater. It is necessary to perform a regeneration operation of the filter by burning and removing by a regeneration device such as the above.

[0005] However, the plugging trap is filtered and collected by the porous partition walls, so that a high trapping efficiency can be obtained. On the other hand, accumulation of oil additives and the like becomes a problem.
It is necessary to reliably burn and remove the collected exhaust particulates.
For this reason, if the detection of the regeneration time or the regeneration operation fails, the filter temperature may rise excessively, possibly leading to breakage.

On the other hand, the form filter type is
There is no problem such as sedimentation due to oil additives, etc., because exhaust particulates are collected by adhesion collection.However, since the collection concentrates on the inlet surface against the exhaust flow, the pressure loss increases significantly as the collection proceeds. In addition to the increase, the effective collecting area is smaller than that of the sealed type, so that it is necessary to devise a larger area, resulting in an increase in the size of the filter itself. Also,
This foam filter has a problem in that if the exhaust pressure rises sharply in a state where the collection has progressed, the collected exhaust fine particles suddenly separate, that is, a so-called blow-off occurs, which prevents the filter itself from becoming large. When the thickness in the exhaust gas flow direction is reduced in order to achieve this, it becomes more remarkable. For this reason, it is necessary to reliably burn and remove the exhaust particulates even before the blow-off occurs in the foam filter.

Japanese Patent Application Laid-Open No. Sho 60
Japanese Patent Application Laid-Open Nos. 59-90713 and 58-16
No. 2711, Japanese Patent Publication No. Hei 3-27732, Japanese Utility Model Application Laid-Open Publication No. 2-30111, in which a heater is arranged on the front surface of a filter, JP-A-56-130545, JP-A-61-112716, Kaisho 59-16231
Japanese Patent Application Laid-Open No. 6-153413 discloses a method in which a filter is heated by heat of oxidation of a fuel, and a method in which an additive for lowering a regeneration temperature is supplied to a fuel system or an exhaust system.

[0008]

[0009]

[0010]

Among these, the heater disclosed in Japanese Patent Publication No. Hei 3-27732 has a heater in which eight heater wires are arranged close to each other in almost the entire area on the exhaust inlet side of the filter. Therefore, these heater wires hinder the filter collecting operation, and the exhaust particulates enter the gap between the heater wire and the filter and accumulate. When the heater is energized in this state, the carbon is separated by heat, and the efficiency is reduced. There is a problem that exhaust particulates cannot be burned well and good flame propagation cannot be formed in the filter.

[0011] Further, Japanese Utility Model Application Laid-Open No. 2-30111 using a heater.
In the publication, a metal porous body having a small heat capacity is arranged in contact with a front surface of the filter between the heater and the heater provided on the exhaust inlet side of the filter. This is because when the heater is energized, the temperature of the metal porous body rises in a short time, whereby the metal porous body becomes an ignition source and ignites the exhaust fine particles deposited on the filter, and the combustion is sequentially performed. It is something that goes on.

[0012] However, this metal porous body is premised on the fact that the temperature is likely to rise, and it does not actively collect the exhaust fine particles. It takes a considerable amount of time because it is necessary to collect exhaust particulates at the time.At the time of the ignition source, the amount of collection of the filter itself becomes large, and during combustion, the temperature becomes excessively high and the filter life is shortened. If the amount exceeds the allowable amount, blow-off may be caused.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reliable exhaust gas purifying apparatus capable of efficiently burning captured exhaust particulates.

[0014]

[0015]

In order to achieve the above object, according to the present invention, a main collecting member for collecting exhaust fine particles in exhaust gas is provided in an exhaust passage connected to an engine, and the main collecting member is provided. The sub-collecting member made of a conductive metal, which has a higher collection efficiency of exhaust particulates and generates heat by being energized by itself and burns the collected exhaust particulates, is used as the main capture member. It is configured such that a cushion member made of a heat-resistant fiber material that absorbs deformation of the sub-collection member is interposed on the exhaust upstream side of the collection member.

Further, according to the present invention, a main collection member for collecting exhaust particulates in exhaust gas is provided in an exhaust passage connected to the engine, and the collection efficiency of the exhaust particulates is higher than the main collection member.
A sub-collecting member provided with a heating means for burning the collected exhaust fine particles is arranged adjacent to the exhaust upstream side of the main collecting member, and the sub-collecting member is made of a heat-resistant fiber material. The heating means is constituted by a heater plate, the heater plate is covered with a heat-resistant fiber material to form a heater unit, and the heater unit is formed in a spiral shape.

[0017]

[0018]

According to the exhaust gas purifying apparatus for an internal combustion engine having such a configuration, when exhaust gas discharged from the engine flows through the exhaust passage and reaches the sub-collection member, the exhaust fine particles are efficiently collected here. When the trapping amount of the exhaust gas reaches a saturated state, the exhaust fine particles reach the main catching member in the downstream stream and are collected. Here, when the sub-collection member made of a conductive metal in a state of collecting the exhaust particulates is energized, the sub-collection member itself generates heat, and the sub-collection member in the high-collection sub-collection member generates heat. Exhaust particulates serve as an ignition source and ignite and combust throughout the sub-collection member.
The heat is transferred to the downstream main collection member via the heat-resistant fiber material, and sequentially proceeds. Then, a large amount of exhaust particulates accumulates on the sub-collecting member and the exhaust pressure increases, and the increased pressure deforms the metal sub-collecting member elastically or deforms the sub-collecting member due to thermal expansion. However, the heat-resistant fiber material interposed between the main collection member and the sub-collection member serves as a cushion material to absorb the elastic deformation and the thermal expansion deformation.

Further, by forming the heater unit in which the heater plate is covered with the heat-resistant fiber material in a spiral shape, the current supplied to the heater plate flows in a spiral shape, so that the heater plate uniformly generates heat.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an exhaust gas purifying apparatus according to a first embodiment of the present invention, and FIG. 2 is an enlarged view of a main part of FIG.
This exhaust gas purification device is applied to a diesel engine, and includes a front tube 1 connected to an exhaust pipe of the engine,
It is interposed between a rear tube 3 provided with a muffler (not shown). An exhaust passage including the front tube 1 and the rear tube 3 includes a first exhaust passage 5 and a second exhaust passage 7.
And a branch configuration. In order to form a branch, an upstream branch pipe 9 is provided on the front tube 1 side,
Downstream branch pipes 11 are provided on the sides, respectively, and a cylindrical case 13 connecting the respective branch pipes 9 and 11 to each other is provided between the branch pipes 9 and 11.

The cylindrical case 13 has two cylindrical portions 15, 1
In each of the tubular portions 15 and 17, for example, an open honeycomb type ceramic filter 19 or 21 as a main trapping member is provided with a wire mesh 2 serving as a buffer material.
It is housed via 3, 25. Each filter 19, 2
1, a foam metal filter 27, 29 serving as a heating means having a heater function as a sub-collecting member having a high efficiency of collecting fine particles of exhaust gas with a gap of about 1 mm.
Are held on the inner walls of the tubular portions 15 and 17, respectively. The foamed metal filters 27 and 29 are made of a conductive metal. As shown in FIG. 2, a space 30 is formed in a gap between the metal portions 27a (29a), and exhaust particles such as carbon C are formed in the space 30. Collected. And about 1m above
In the gap of m, a cloth made of ceramic fiber which is a heat-resistant fiber material having a thickness of about 1 mm is interposed.

Electrodes 31, 33 for supplying electricity to the metal foam filters 27, 29 are provided at positions close to the exhaust gas upstream side of the metal foam filters 27, 29, respectively. The electrodes 31 and 33 are inserted from the inside into the holes 37 of the flat portion 35 formed in the cylindrical portions 15 and 17, and are inserted into the cylindrical portions 15 and 1.
7 is fixed to the cylindrical portions 15 and 17 by nuts 45 via ceramic washers 41 and 43 disposed between the flange portion 39 located inside the flat portion 7 and the flat portion 35 and outside the flat portion 35, respectively. . The tips of the electrodes 31 and 33 are located at the center of the foamed metal filters 27 and 29, and a through hole 47 is formed at the tip. On the other hand, a female screw 49 is formed at the center of the metal foam filters 27 and 29. By screwing, the distal ends of the electrodes 31, 33 are fixed to the foamed metal filters 27, 29, and the electrodes 3
1, 33 and the metal foam filters 27, 29
1 and the electric conduction state via the washers 53 and 54. The metal foam filters 27 and 29 are
Heat is generated by being energized through the, and the collected exhaust fine particles are burned.

The first exhaust passage 5 and the second exhaust passage 5 of the upstream branch pipe 9
A first part for controlling the flow of exhaust gas to the first and second exhaust paths 5 and 7 is provided at each part constituting the exhaust path 7.
A control valve 55 and a second control valve 56 are provided, respectively. Rotating members 57 and 59 provided outside the upstream branch pipe 9 are connected to the first control valve 55 and the second control valve 56. Notches 57a, 59a of rotating members 57, 59
, One end of a wire (not shown) is fixed, and the other end is connected to the actuator 61. When the first control valve 55 and the second control valve 56 are opened by the operation of the actuator 61 and the operation is stopped, the valve is closed by a return spring (not shown). The operation of the actuator 61 and the control of energization of the electrodes 31 and 33 are performed by a control unit 63 as a control means including a microcomputer or the like. Reference numerals 65 and 67 denote heater control circuits, and power is supplied to the electrodes 31 and 33 from a battery (not shown).

The control unit 63 closes the first control valve 55 (regeneration operation) when energizing one of the electrodes 31 on the first exhaust passage 5, for example, and opens the other second control valve 56 at this time. Control to guide the exhaust gas to the second exhaust passage 7 (collection operation). Conversely, the electrode 3 on the second exhaust passage 7 side
When power is supplied to 3, the second control valve 56 is closed (regeneration operation), and at this time, the other first control valve 55 is opened to guide exhaust gas to the first exhaust passage 5 (collection operation).

In the exhaust gas purifying apparatus for an internal combustion engine thus configured, when the operation of the engine is started, one of the first and second exhaust passages 5 and 7, for example, the first exhaust passage 5
Side first control valve 55 is fully opened. At this time, the second control valve 56 of the other second exhaust passage 7 is fully closed. In this state, exhaust gas discharged from the engine and flowing through the front tube 1 mostly flows into the first exhaust passage 5 having the first control valve 55 in an open state.

The exhaust gas that has flowed into the first exhaust passage 5 is first introduced into the foamed metal filter 27 having a high collection efficiency.
Exhaust fine particles such as carbon enter the space 30 and are efficiently attached and collected. When the trapped amount of the exhaust particulates in the metal foam filter 27 becomes saturated, the exhaust particulates start to adhere to the surface of the downstream filter 19, and the collection proceeds gradually toward the downstream side. Then, the control unit 63, for example, notifies the filter 19 that the trapping amount is equal to or more than the predetermined amount and the filter 19 is to be regenerated.
The control unit 63 fully closes the first control valve 55, which has been fully opened until now, based on the exhaust gas pressure difference between the exhaust inflow side and the outflow side of the engine and the operation history of the engine based on fuel injection into the engine. At the same time, the second control valve 56 that has been fully closed is fully opened, and the electrode 31 is energized.

As a result, the exhaust gas flowing through the front tube 1 flows into the second exhaust passage 7 having the second control valve 56 in an open state, and the foam metal filter 29 and the filter At 21, exhaust particulates are collected. On the other hand, when the electrode 31 is energized, the foamed metal filter 27 generates heat uniformly over the entire area, and the exhaust fine particles collected at high density are heated from the surroundings, and this becomes an ignition source and reliably burns. I do. The exhaust particulates adhering to the exhaust inflow side of the filter 19 due to the combustion of the exhaust particulates in the foamed metal filter 27 are discharged through the ceramic fiber cloth 69 by the exhaust slightly leaking from the gap of the first control valve 55. The flame is ignited, the flame gradually propagates toward the downstream side, and the regeneration of the filter 19 is efficiently performed. The reproduction end time may be a time when an appropriate time set in advance is reached.

When the regeneration of the filter 19 is completed, the second control valve 56 is fully closed, and simultaneously the first control valve 55 is fully opened to perform collection on the filter 19 side. Foam metal filter 29
And the regeneration of the filter 21 is performed.

As described above, in the above embodiment, the collecting operation and the regenerating operation are alternately repeated on the first exhaust passage 5 side and the second exhaust passage 7 side. During operation, the other filter 21
In (19), the trapping operation is always performed, so that the unpurified exhaust gas is not released to the atmosphere as it is.

Further, a large amount of exhaust fine particles accumulate on the foamed metal filter 27 (29) and the exhaust pressure increases, and the foamed metal filter 27 (29) is elastically deformed or pushed by the exhaust pressure. , The ceramic fiber cloth 69 functions as a cushion material and absorbs these deformations. As a result, the elastic deformation and the thermal expansion deformation of the foamed metal filter 27 (29) do not directly act on the ceramic filter 19 (21), which is particularly susceptible to breakage. Is improved.

FIG. 3 shows an exhaust gas purifying apparatus according to a second embodiment of the present invention. In this embodiment, stainless steel filters 71 and 73 each composed of a stainless steel corrugated plate and a flat plate are used as a sub-collecting member having high collection efficiency, instead of the foamed metal filters 27 and 29 in the first embodiment. .
The stainless steel filters 71 and 73 are formed by winding a stainless steel corrugated plate and a flat plate around pipes 75 and 77 having female threads into which the bolts 51 are screwed.
Each stainless plate has been subjected to electrical insulation and wash coat treatment for supporting an oxidation catalyst.

In the exhaust gas purifying apparatus having such a structure, in addition to having the same operation and effects as those of the first embodiment, the catalyst supported on the stainless steel filters 71 and 73 is used.
It can oxidize and remove SOF (soluble organic substances), CO, and HC. Such an oxidizing and removing action is achieved by energizing the electrodes 31 and 33 even when the exhaust gas does not reach the catalyst activation temperature (about 300 ° C.) even when the engine is under a low load.
This is made possible by causing 1,73 to generate heat.

[0034]

[0035]

FIG. 4 is an exploded perspective view of a sub-collecting member unit according to a third embodiment of the present invention. This example is
A heater plate 101 as a heating means is formed in a strip shape from nickel chrome steel or the like, and the outside of the heater plate 101 is formed at both ends 1.
The heater unit 104 is formed by covering a heat-resistant fiber material such as a ceramic fiber with a cover 103 which is a high-collection-efficiency sub-collection member except for 01a and 101b. The semicircular cut portion 10 is provided on the cylindrical base 105.
5a is formed, and two female screw holes 105b are formed in the semicircular cut portion 105a, and a female screw 105c for fixing the electrode 31 (33) is formed. On the other hand, two screw insertion holes 101c are formed in the heater plate 101, and an end portion 101a and a retainer 107 having two screw holes 107a are sequentially stacked on the semicircular cut portion 105a, and two countersunk screws 109c are formed. Then, fix these.

The heater unit 104 is connected to the base 1
05 and formed into a spiral shape, which is housed in a cylindrical case 111 as shown in FIG. FIG. 5 is a view seen from the exhaust gas inflow side opposite to the filter 19 (21), and FIG. 6 is a sectional view taken along line AA of FIG. A hole 111a is formed on the outer periphery of the cylindrical case 111.
The end 101b of the heater plate 101 exposed from a is fixed to the case 111 by welding.

By configuring the sub-collecting member unit as described above, the electric current supplied to the heater unit 104 flows in a spiral shape, so that the heater unit 104 generates heat evenly. It is possible to ignite the exhaust fine particles collected by the fiber with a small electric power. Further, when the heater plate 101 is formed in a spiral shape, the heater length can be increased and the electric resistance increases, so that the target heater heat generation can be set.

[0039]

[0040]

As described above, according to the present invention, the sub-collection member provided on the exhaust gas upstream side of the main collection member has a high efficiency of collecting the exhaust particles, so that the exhaust particles have a high density. The collected exhaust fine particles are heated, and the conductive metal sub-collecting member itself generates heat by being energized, whereby the entire sub-collecting member is securely ignited, and this is used as an ignition source. As a result, the exhaust fine particles of the main collection member are ignited and burned through the heat-resistant fiber material, and the combustion propagates sequentially toward the downstream side, so that the collection member is efficiently regenerated. In addition, by interposing a heat-resistant fiber material between the main collection member and the sub-collection member, a large amount of exhaust fine particles accumulate on the sub-collection member and the exhaust pressure increases. Even if the sub-collecting member is elastically deformed or deformed due to thermal expansion, these deformations are absorbed by the heat-resistant fiber material as a cushion material, so that the main collecting member due to the deformation of the sub-collecting member Of the main trapping member is improved.

Further, by forming a heater unit by covering the heater plate with a heat-resistant fiber material and forming the heater unit in a spiral shape, the current supplied to the heater plate flows in a spiral shape. Then, the exhaust fine particles collected by the heat resistant fiber material can be ignited with little electric power. When the heater plate is formed in a spiral shape,
Since the heater length can be increased and the electric resistance increases, it is possible to set the target heater heat value.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an exhaust gas purifying apparatus showing a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is an overall configuration diagram of an exhaust gas purifying apparatus showing a second embodiment of the present invention.

FIG. 4 is an exploded perspective view of a sub-collecting member according to a third embodiment of the present invention.

FIG. 5 is a front view of the sub-collecting member of FIG. 4 as viewed from the exhaust gas inflow side.

6 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

1 Exhaust passage 19, 21 Filter (main collection member) 27, 29 Foam metal filter (sub collection member, heating means) 69 Cloth (cushion material) 71, 73 Stainless steel filter (sub collection member, heating means) 101 Heater Plate (heating means) 103 Cover (sub-collecting member) 104 Heater unit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-104322 (JP, A) JP-A-60-1909 (JP, U) JP-A-61-152716 (JP, U) JP-A-3-152716 118214 (JP, U) Japanese Patent Publication No. 62-49453 (JP, B2) Jiko 1-15854 (JP, Y2) Jiko 3-22503 (JP, Y2) (58) Fields surveyed (Int. Cl. ⁷ , DB name) F01N 3/02 301-341

Claims (2)

(57) [Claims] An exhaust passage connected to an engine is provided with a main trapping member for trapping exhaust particulates in the exhaust gas, and the exhaust trapping efficiency is higher than the main trapping member, and the main trapping member is energized. A sub-collection member made of a conductive metal that also generates heat by itself and also serves as a heating means for burning the collected exhaust fine particles,
An exhaust gas purifying apparatus for an internal combustion engine, wherein the exhaust gas purifying apparatus is disposed on the exhaust upstream side of the main trapping member via a cushion member made of a heat-resistant fiber material that absorbs deformation of the sub trapping member. 2. An exhaust passage connected to an engine is provided with a main trapping member for trapping exhaust particulates in the exhaust, the exhaust particulates having a higher collection efficiency than the main trapping member, and the collected exhaust particulates. A sub-collecting member provided with a heating means for burning is disposed adjacent to the exhaust upstream side of the main collecting member, and the sub-collecting member is made of a heat-resistant fiber material, while the heating means is a heater plate. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a heater unit formed by covering the heater plate with a heat-resistant fiber material; and forming the heater unit in a spiral shape.