JPH068257Y2 - Particle collection and purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a particulate collection and purification device arranged in an exhaust gas passage of a diesel engine.

(Prior Art) Exhaust gas from a diesel engine contains fine particles (particulates) mainly composed of carbon, and these particulates need to be collected, purified, and discharged into the atmosphere. Is. In order to collect such particulates, conventionally, a particulate collection and purification device equipped with a particulate collection filter made of a porous material such as ceramics is arranged in the exhaust gas passage of the engine.

FIG. 3 shows a state in which such a fine particle collecting and purifying device is arranged in an exhaust gas passage of an engine. The fine particle collecting and purifying device 1 includes a metallic container 11 and a fine particle collecting and purifying device housed in the container 11. Collecting filter 12 and heater 13 for burning particulates arranged upstream of the filter 12 in the container 11.
Composed of and. The container 11 is usually formed in a cylindrical shape,
It is attached in the middle of the exhaust passage 4 by the flange portions 11a and 11b at both ends. The particulate collection filter 12 is made of, for example, a porous body such as ceramics and is formed in a cylindrical shape having a diameter slightly smaller than the container 11. Between the outer peripheral surface of the filter 12 and the inner peripheral surface of the container 11, for example, An elastic support member 14 such as a wire mesh is interposed to elastically support the filter 12 in the container 11. Further, the heater 13 is connected to the battery 2.

FIG. 4 shows an example of the structure of the particulate collection filter 12, FIG. 4 (a) is a longitudinal sectional view thereof, and FIG. 4 (b) is an end view thereof. Along the axial direction of the particulate collection filter 12, a large number of passages 12a closed on the upstream side and a plurality of passages 12a 'closed on the downstream side are alternately formed in, for example, a grid pattern, and the passages 12a and 12a are formed. It is separated from ′ by a porous thin wall 12b (FIG. 4 (b)). Therefore, as shown in FIG. 4 (a), the passage 1 having an upstream opening
The exhaust gas flowing in from 2a 'proceeds through the passage 12a', but the downstream side of this passage 12a 'is blocked, so
Exhaust gas passes through the porous thin wall 12b and is adjacent to the passage 1
It flows into 2a, at which time particulates in the exhaust gas are collected and particulates adhere to the porous thin wall 12b. Then, after the particulates are removed, the exhaust gas is discharged to the exhaust passage 4 from the passage 12a which is open on the downstream side.

A bypass passage 5 that bypasses the particulate collection and purification device 1 is formed in the exhaust passage 4, and a bypass valve 6 is provided at an upstream branch point of the bypass passage 5.
When the engine is running, close this bypass valve 6,
The exhaust gas is passed through the particulate collection / purification device 1 and particulates are collected by the particulate collection filter 12. When the particulate adheres to the porous thin wall 12b of the filter 12 by a predetermined amount or more, that is, when the filter 12 needs to be regenerated, the exhaust gas becomes difficult to flow in the passages 12a and 12a 'of the filter 12, The differential pressure of the exhaust gas between the upstream side and the downstream side of the filter 12 becomes large. Therefore, for example, a pressure sensor detects this differential pressure, and when the differential pressure exceeds a predetermined value, a control circuit (not shown) that operates by a signal from the pressure sensor opens the valve 7 to open the air tank 8 from the air tank 8. Air is supplied to the actuator 9,
The actuator 9 is operated to open the bypass valve 6 and energize the heater 13 to heat it. When the bypass valve 6 is opened, most of the exhaust gas flowing through the exhaust passage 4 flows through the bypass passage 5, and the remaining exhaust gas is heated by the heater 13 to become a high temperature gas. Flowing. The high-temperature gas ignites and burns the particulates to filter 1
Play back 2.

(Problems to be Solved by the Invention) When the filter 12 is regenerated, the particulate collection and purification device 1
Although the exhaust gas is also supplied to this, since the high-temperature gas must be generated with the limited electric power of the heater 13, the amount of gas flowing into the particulate collection and purification device 1 is set to a very small amount as described above. . However, when the above particulates are burned, the gas heated by the heater 13 and having a high temperature is dissipated to the outside as radiant heat, or rises by natural convection to flow in the upper part of the container 11 and pass through the upper passage of the filter 12 as it is. To do. Therefore, since a small amount of high temperature gas is not effectively used, the passage of the filter 12 is not uniformly heated, and in particular, the particulate matter trapped in the lower passage is not sufficiently burned, and the filter is not
12 itself has a problem that thermal stress is generated due to the temperature gradient.

The present invention has been made in view of the above-mentioned conventional problems, in which the gas heated by the combustion means during particulate combustion has a substantially uniform temperature distribution at the filter inlet, and the amount of passage through each passage of the filter is It is an object of the present invention to provide a particulate collection and purification device which is made uniform and prevents the generation of thermal stress in the filter.

(Means for Solving the Problems) According to the present invention in order to achieve the above-mentioned object, according to the present invention, a cylindrical container disposed in an exhaust passage and a large number of exhaust gas passing through the cylindrical container are provided. A particulate collection filter having a passageway for collecting particulates in the exhaust gas, and an ignition for increasing the temperature of the exhaust gas for burning the particulates collected in the filter, which is arranged upstream of the filter. In the particulate collection and purification device provided with a combustion means, a large number of exhaust gas passages are formed in the container and on the upstream side of the ignition / combustion means, and the porosity of the lower part is larger than that of the upper part. The heat transfer conversion element thus set is arranged.

(Operation) The heat transfer conversion element arranged on the upstream side of the ignition / combustion means
The heat of the exhaust gas heated to a high temperature by the ignition / combustion means is prevented from being dissipated to the outside due to the effect of radiant heat, and the amount of exhaust gas supplied to the ignition / combustion means in the downstream is controlled at the lower part of the exhaust passage. Do more. The gas that has passed through the ignition / combustion means and has reached a high temperature gradually rises in the exhaust passage by natural convection while moving to the inlet of the filter arranged downstream, and the temperature distribution near the inlet of the filter is almost uniform. In addition, the amount of passing gas is uniform. As a result, the filter is uniformly heated, the particulates are burned substantially uniformly, and the generation of thermal stress due to the temperature gradient from the lower part to the upper part of the filter is prevented.

Embodiment An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. In the figure, the same constituents as those in FIG. 3 are designated by the same reference numerals.

FIG. 1 shows a particle collecting and purifying device of the present invention. In a particle collecting and purifying device 1 ′, a heat transfer conversion element 15 is provided further upstream of a heater 13 arranged upstream of the particle collecting filter 12. It is arranged. The heat transfer conversion element 15 is made of, for example, a ceramic porous body having a large porosity.
The ceramic is not particularly limited,
For example, cordierite is used because it is required to have excellent heat resistance, chemical resistance, and thermal shock resistance.

FIG. 2 shows the structure of the heat transfer conversion element, and the heat transfer conversion element 15
Is a structure in which two semicircular ceramic porous bodies 15a and 15b having different mesh sizes are vertically combined and integrated. In this heat transfer conversion element 15, the porosity (mesh) of the lower porous body 15b is set to be larger than the porosity (mesh) of the upper porous body 15a, and the air passage amount of the heat transfer conversion element 15 is higher than that of the upper part. Also, the lower part has more. Therefore, as shown by the arrow, the amount of exhaust gas flowing into the heat transfer conversion element 15 is larger in the lower passage amount than in the upper passage amount.

The operation will be described below.

The particulate collection and purification device 1'is arranged in the middle of the exhaust passage 4 of the engine shown by the chain double-dashed line, like the conventional particulate collection and purification device 1 shown in FIG. During regeneration of the particulate collection filter 12, the bypass valve is opened as described above, most of the exhaust gas flows through the bypass passage, and a very small amount of exhaust gas flows into the particulate collection and purification device 1 '. The exhaust gas indicated by arrow A that has flowed into the particulate collection and purification device 1 ′ first passes through the heat transfer conversion element 15. Since the heat transfer conversion element 15 is designed so that the amount of exhaust gas passing through the lower portion indicated by the arrow C is larger than the amount of exhaust gas passing through the upper portion indicated by the arrow C, the heat transfer conversion element 15 is concerned. The amount of exhaust gas heated by the heater 13 disposed on the downstream side is higher in the lower portion than in the upper portion.

After passing through the heat transfer conversion element 15, the exhaust gas is heated by the heater 13 to be a high temperature gas, and the high temperature gas rises by natural convection until it reaches the upstream end surface of the filter 12. As described above, the amount of high-temperature gas after passing through the heater 13 is larger in the lower part, so that the amount of high-temperature gas that flows into the filter 12 when part of it rises as indicated by arrow D is Is substantially uniform over the entire inlet side. Therefore, the high temperature gas having a substantially uniform temperature passes through the passages 12a, 12a '(FIG. 4) of the filter 12 in a substantially uniform passage amount, and as a result, the particulates collected in the filter 12 are collected. The burning of the curate is performed uniformly and efficiently, and the filter 1
The generation of thermal stress in 2 is prevented.

In the above embodiment, the case where the ceramic porous body which is divided into the upper and lower parts is used as the heat transfer conversion element has been described, but the present invention is not limited to such a divided body, and the gas passage amount increases toward the lower part. Any configuration may be used.

(Effect of the Invention) As described above, according to the present invention, the exhaust gas has a cylindrical container arranged in the exhaust passage and a large number of passages through which the exhaust gas passes while being housed in the container. A fine particle collection filter for collecting fine particles therein, and an ignition / combustion means arranged upstream of the filter for raising the temperature of the exhaust gas for burning the fine particles collected by the filter are provided. In the particulate collection and purification device, a large number of exhaust gas passages are formed in the container and on the upstream side of the ignition / combustion means, and the lower void ratio is set higher than the upper void ratio. As a result, the temperature distribution and the gas passage amount of the hot exhaust gas flowing into the filter become substantially uniform during the regeneration of the particulate collection filter, and the combustion of the particulates collected by the filter becomes uniform. well As well as being performed, it is possible to prevent the generation of thermal stress due to the temperature gradient in the filter.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the particulate collection and purification device of the present invention, FIG. 2 is a perspective view of the heat transfer conversion element of FIG. 1, and FIG.
FIG. 4 is a configuration diagram showing a state in which a conventional particulate collection and purification device is installed in an exhaust passage of an engine. FIG. 4 (a) is a sectional view of a particulate collection filter of the particulate collection and purification device in FIG. Figure 4
(b) is an end view of FIG. 4 (a). 1 '... Fine particle collection and purification device, 4 ... Exhaust passage, 12 ... Fine particle collection filter, 13 ... Heater, 15 ... Heat transfer conversion element, 15a, 15
b ... Ceramic porous body.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Yasuaki Kumagai 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-59-520 (JP, A) 63-130611 (JP, U) Actual public Sho 63-11293 (JP, Y2) Actual public 1-15854 (JP, Y2)

Claims (1)

[Scope of utility model registration request] 1. A particulate collection filter having a cylindrical container arranged in an exhaust passage, and a large number of passages accommodated in the container and through which exhaust gas passes, for collecting fine particles in the exhaust gas. And a ignition / combustion unit arranged upstream of the filter for raising the temperature of the exhaust gas in order to burn the particles collected by the filter, in the container, A plurality of exhaust gas passages are formed on the upstream side of the ignition / combustion means, and a heat transfer conversion element having a lower void ratio set to be higher than the upper void ratio is arranged. Collective purifier.