JPH04255516A - Diesel exhaust gas purifier - Google Patents

Abstract

PURPOSE:To provide an exhaust gas purifier of a diesel engine having a particulate filter, which does not cause cracks due to thermal distortion at the time of filter recovery. CONSTITUTION:A diesel exhaust gas purifier includes the first casing 1 connected to an exhaust passage, both end portions of which are opened, the second casings 3, 4, 5 disposed in the casing 1 through a gap 6 with the casing 1, both ends of which are opened to the exhaust passage, and particulate filters 8, 9, 10 stored in the interiors of the second casings corresponding to the respective casings 3, 4, 5 and held through a gap 11 with the second casings 3, 4, 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel exhaust purification device comprising a diesel particulate filter installed in the exhaust system of a diesel engine to collect solid particulates, ie, particulates, in exhaust gas.

0002

2. Description of the Related Art In diesel engines, exhaust gas contains many particulates which are a source of black smoke due to incomplete combustion. Therefore, in vehicles with such engines, a particulate filter made of a breathable, heat-resistant material such as ceramic is installed in the engine exhaust system to remove particulates from the exhaust gas. are doing.

[0003] As this particulate filter collects particulates, its air permeability gradually decreases and eventually clogging occurs, so when using the particulate filter, it is necessary to Depending on the situation, the filter must be regenerated at an appropriate time, that is, the particulates must be incinerated. When installing this particulate filter in the exhaust passage, in order to prevent the occurrence of cracks in the filter due to thermal expansion during filter regeneration, the filter is divided into multiple pieces and a gap is provided between the divided surfaces, and the filter is inserted into the filter using this gap. A particulate trap using an expansion escape space has already been proposed (see Japanese Patent Laid-Open No. 60-65219).

0004

[Problems to be Solved by the Invention] In each filter of the above-mentioned particulate trap, thermal distortion during regeneration is absorbed due to the existence of a gap in the adjacent part to another filter. Because the structure is housed in one large casing, the outer circumferential portion is cooled more rapidly than the adjacent portions during regeneration, resulting in cracks occurring due to thermal strain in this portion. There is a fear.

SUMMARY OF THE INVENTION In view of the above-mentioned problems with the trap, an object of the present invention is to provide an exhaust gas purification device in which the outer peripheral portion of the filter is not cooled rapidly during regeneration.

[0006]

[Means for Solving the Problems] To achieve the above object, according to the present invention, an exhaust inlet passage is defined by an air-permeable partition wall and has an open end on the upstream side of the exhaust gas, and an end on the downstream side of the exhaust gas. A diesel exhaust purification device comprising a diesel particulate filter provided with an open exhaust outlet passage arranged in the exhaust system of an engine, the diesel exhaust purification device having both ends connected to the exhaust passage open. a first casing; a second casing disposed within the casing with a gap in between and having both ends open to the exhaust passage; There is provided a diesel exhaust purification device characterized by having a particulate filter held with a gap between two casings.

[0007]

[Operation] Since the structure is such that the first casing surrounds the second casing, which houses the particulate filter, with a gap, the particulate filter is doubly shielded from the outside world with a gap in between, and when the filter is regenerated. , its outer peripheral portion becomes difficult to cool down rapidly.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing only a particulate filter storage section, which is the main part of the diesel exhaust purification device of the present invention. In the figure, solid line arrows indicate the flow direction of exhaust gas during particulate collection, and dotted line arrows indicate the flow direction of regeneration gas (secondary air, part of exhaust gas, etc.) during filter regeneration. That is, this embodiment is an exhaust purification device using a so-called reverse flow regeneration method in which the gas flow direction in the filter during filter regeneration is opposite to that during particulate collection. This can be applied to a so-called forward flow regeneration type exhaust gas purification device in which the gas flow direction during collection is the same.

According to this embodiment, the exhaust gas purification device has a first casing 1 which is connected to an exhaust passage (not shown) and is open at both ends. The first casing 1 has a substantially elliptical cross section perpendicular to its longitudinal axis, and has a casing support member 2 in contact with the inner peripheral surface of the casing near its front and rear ends. will be installed. Further, inside the first casing 1, a plurality of substantially cylindrical second casings 3, 4, and 5 are arranged in parallel along the longitudinal direction of the casing. These second casings 3, 4 and 5
is supported by the above-mentioned casing support member 2 at its front part and rear part, and most of it does not touch the inner circumferential surface 1a of the first casing 1, but is attached to the first casing through a space (gap) 6. It is designed to be stored inside 1.

Casing support member 2 and first casing 1
and between the casing support member 2 and each of the second casings 3, 4, and 5 are airtight so that exhaust gas or regeneration gas that has flowed into the first casing 1 does not flow into the space 6. It is sealed in a shape. In addition, the front and rear casing support members 2, the inner circumferential surface 1a of the first casing 1,
The space 6 defined by the outer peripheral surface of each of the second casings 3, 4, and 5 may be filled with a heat insulating material 7 to improve its heat retention.

Inside each of the second casings 3, 4, and 5 arranged in the first casing 1 as described above,
Particulate filters (hereinafter referred to as filters) 8, 9, and 10 that collect particulates in diesel exhaust are housed. According to this embodiment, the individual volumes of the filters are smaller than that of the filters in a conventional exhaust gas purification device with a single filter, and the volumes of the individual filters add up to the usual filter volume. are set to be approximately equal. Note that the number of filters is not limited to the three illustrated.

As shown in FIG. 2, filters 8, 9 and 10 are held within the respective second casings 3, 4 and 5 with gaps 11 interposed therebetween. Specifically, according to this embodiment, the end of the filter on the exhaust upstream side in the exhaust flow direction when collecting particulates is connected to the annular sealing member 1.
2, and the end of the filter that is on the gas upstream side in the flow direction of the regeneration gas during filter regeneration is
The second casings 3, 4 are connected to each other via a breathable support 13.
and supported within 5.

As shown in a partial cross section, the filters 8, 9, and 10 are defined by a permeable partition wall 14 as in the conventional case, and have a large number of exhaust inlet passages 15 that are open at the end on the upstream side of the exhaust gas. , a plurality of exhaust outlet passages 16 whose ends on the downstream side of the exhaust gas are open, and an electric heater 17 as particulate ignition means is arranged near the end on the downstream side of the exhaust gas.

As explained above, the exhaust purification device according to the present invention includes filters 8 and 9 for collecting particulates.
and 10 are held by the second casings 3, 4 and 5 through gaps 11, and the second casings 3, 4 and 5 are further held by the first casing 1 through a further space 6. Therefore, cooling after filter regeneration is relatively slow due to improved heat insulation, and the temperature difference between the outer circumference and the inside of the filter is also reduced, reducing thermal strain. As a result, compared to a conventional device in which the filter is surrounded by a single trap container, the stress distribution inside the filter becomes uniform, the durability is improved, and cracks are less likely to occur.

In this embodiment, due to the above-described filter support configuration, the sealing member 12 prevents the exhaust gas from entering the gap 11 when collecting particulates, and particulates are not accumulated in this area. Conversely, during filter regeneration, regeneration gas (secondary air,
Part of the exhaust gas) also enters the gap 11 through the support material 13, making it difficult for the outer circumference of the filter to cool down due to particulate combustion. As a result, the phenomenon of poor regeneration (unburned particulates) on the outer periphery of the filter, which was previously observed, is reduced, and the thermal strain caused by the temperature difference between the inside of the filter and the outer periphery is further reduced, and cracks do not occur. It becomes difficult.

[0016]

[Effects of the Invention] As explained above, according to the present invention, the second casing housing the particulate filter is
Since the structure is such that the first casing surrounds the first casing with a gap,
The particulate filter is doubly shielded from the outside world with a gap in between, so the outer periphery will not cool down rapidly during filter regeneration.
Therefore, thermal strain caused by the temperature difference between the inside of the filter and the outer circumference is reduced, and cracks are less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of a filter storage section illustrating an embodiment of the exhaust gas purification device of the present invention.

FIG. 2 is a sectional view of the device taken along line II-II in FIG. 1;

[Explanation of symbols]

1...First casing 3, 4, 5...Second casing 6, 11...Gap 8, 9, 10...Particulate filter 14...Partition wall 15...Exhaust inlet passage 16...Exhaust outlet passage

Claims (1)

[Claims] 1. Defined by a breathable partition,
A diesel particulate filter is disposed in the exhaust system of the engine, and includes an exhaust inlet passage that is open at the upstream end of the exhaust, and an exhaust outlet passage that is open at the downstream end of the exhaust.
The diesel exhaust purification device includes a first casing that is connected to an exhaust passage and has both ends opened, and a first casing that is disposed within the casing with a gap between the first casing and both ends that are open. A diesel engine characterized in that it has a second casing that opens into an exhaust passage, and a particulate filter that is housed inside the second casing and is held with a gap between the second casing and the second casing. Exhaust purification device.