JPH06264718A - Exhaust gas filter for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to burn accumulated exhaust gas particles and regenerate a filter uniformly at every section by transmitting heat of a heater 7 in response to the acculumated condition of exhaust gas particles in a cylindric filter element. CONSTITUTION:A cylindric filter element 4 made of metal form is stored inside a casing 3 and partitions 5, 6 are provided so that exhaust gas may flow from the inner circumferential side to the outer circumferential side of the filter element 4. An intense conduction part 8, which increases heat transfer rate by making porosity small at limited sections, is formed in a specified thickness on the surface orthogonal to the axial direction of the filter element 4. A plural number of intense heat conduction parts 8 are formed, which are arranged densely on the upstream side where accumulation quantity of exhaust gas particle is few and coarsely on the downstream side where accumulation quantity of exhaust gas particle is numerous.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust filter for collecting and removing exhaust particulates such as carbon, which is a problem in internal combustion engines, especially diesel engines.

[0002]

2. Description of the Related Art Various exhaust filters have been conventionally proposed in which exhaust particulates such as carbon, which are a problem in diesel engines, are collected and removed by a filter element such as ceramics interposed in an exhaust system. In this type of filter, when exhaust particulates are deposited, they become clogged, which causes an increase in pressure loss, so it is essential to regenerate the filter by burning the exhaust particulates. Therefore, for example, in JP-A-58-8219, a heater is provided in front of a filter element for collecting exhaust particulates, and exhaust particulates deposited on the filter element are forcibly ignited and burned by energizing the heater. The configuration is shown so as to allow it.

Various shapes have been proposed for the filter element in the exhaust filter, but in order to secure a large surface area of the outer surface of the filter element which comes into contact with the exhaust flow, as shown in FIG. The filter element 21 is formed in a cylindrical shape, and one end thereof is closed by a partition wall 22 so that the exhaust flow flowing as shown by the arrow A flows from the inner peripheral side to the outer peripheral side of the filter element 21. What you have done is known.

[0004]

However, in the structure using the cylindrical filter element 21 as described above, the main exhaust flow is blocked by the partition wall 22, so that
A large amount of exhaust particulate matter is deposited on the downstream side portion near the partition wall 22. That is, as shown in FIG. 3, the distribution of the deposition state of the exhaust particulate 23 is not uniform in each part, and the deposition amount is small in the upstream side portion of the cylindrical filter element 21 and large in the downstream side. Becomes Therefore, even if the exhaust particles 23 are burned from the upstream side by a heater (not shown), the combustion cannot be smoothly propagated to the downstream side, and good regeneration cannot be performed. Moreover, ignition itself by the heater becomes difficult. Although it is possible to ignite the heater from a location on the downstream side where a large amount of deposition is present, generally, at the time of regeneration, an air flow for promoting regeneration is supplied from the exhaust pipe upstream side, so It is difficult to propagate combustion ignited on the upstream side to the upstream side, and uniform regeneration cannot be performed.

[0005]

Therefore, according to the present invention, one end of a cylindrical filter element made of a three-dimensional porous body is closed, and a casing is provided so that exhaust gas flows from the inner peripheral side to the outer peripheral side of the filter element. While accommodating inside,
In an exhaust gas filter of an internal combustion engine in which a regeneration rod-shaped heater is arranged inside the filter element along the axial direction of the filter element, a high heat conduction part having a locally small porosity is formed in the filter element in the axial direction. Form so as to cross the filter element along a plane orthogonal to
In addition, a plurality of high heat conduction parts are arranged densely on the upstream side of the cylindrical filter element and roughly arranged on the downstream side.

[0006]

In the filter element composed of the three-dimensional porous body, if the porosity is locally reduced, the thermal conductivity at that portion becomes high. In the above configuration, the high thermal conductive portion having the locally increased thermal conductivity is formed along the surface orthogonal to the axial direction of the filter element. Therefore,
When the rod-shaped heater is heated during regeneration, the heat is satisfactorily transferred to the entire cross section of the filter element through the high heat conduction portion, and the exhaust particulate matter is ignited at each portion.

On the other hand, in the cylindrical filter element, as described above, a large amount of exhaust particulate matter is deposited on the downstream side and a small amount on the upstream side. Therefore, ignition and combustion on the upstream side are likely to be difficult, but in the above configuration, since the plurality of high heat conductive parts are densely arranged on the upstream side of the filter element, the ignition and combustion are reliably performed. Further, on the downstream side where a large amount of exhaust particulates are deposited, the high heat conductive portion is roughly arranged, so that unnecessary heat diffusion of the heater does not occur.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

1 and 2 show an embodiment of an exhaust filter 1 according to the present invention.

The casing 3 is provided in the middle of the exhaust pipe 2 of a diesel engine, for example, and is composed of a substantially cylindrical main body portion 3a, a substantially conical inlet portion 3b and an outlet portion 3c. . A filter element 4 having a substantially cylindrical shape is housed inside the casing 3. The filter element 4 is formed of a suitable metal three-dimensional porous body having open cells, so-called metal foam, or the like, and a space between the end of the filter element 4 and the casing 3 is formed by the annular partition wall 5 at the inlet 3b. Is blocked. On the side of the outlet portion 3c, the opening of the inner circumference of the filter element 4 is closed by the partition wall 6. That is, the exhaust gas flowing from the upstream side of the exhaust pipe 2 flows into the exhaust passage 9 on the inner circumference of the filter element 4 and flows from there to the outer peripheral side of the filter element 4.

Inside the filter element 4,
A plurality of rod-shaped heaters 7 are embedded along the axial direction of the filter element 4.

The filter element 4 is provided with a high heat conducting portion 8 having a locally small porosity along the plane orthogonal to the axial direction of the filter element 4.
It is formed to have a predetermined thickness so as to traverse. In other words, the high heat conductive portion 8 is formed in an annular shape having a predetermined thickness, is provided over the entire cross section of the filter element 4, and the heater 7 penetrates a part thereof. The high heat conducting portion 8 and other general portions are integrally formed as a metal foam. Further, the high heat conducting parts 8 are provided at a plurality of positions, specifically, five positions in the entire filter element 4. Then, the plurality of high thermal conductive parts 8
However, they are arranged densely on the upstream side of the cylindrical filter element 4, that is, at a short interval, and coarsely on the downstream side, that is, at a relatively long interval.

Next, the operation of the above embodiment will be described.

First, the time of collecting the exhaust particulates will be described. The exhaust flowing into the exhaust filter 1 through the exhaust pipe 2 passes through the filter element 4 in the radial direction from the exhaust passage 9 on the inner circumference of the filter element 4. Here, the exhaust particulates are collected and removed. Therefore, even if the porosity of the high heat conductive portion 8 is small, the pressure loss does not extremely increase. As a result of such collection, exhaust particulate matter is deposited on the filter element 4, but as described above, since the main exhaust stream is blocked by the downstream partition wall 6, the exhaust particulate matter is collected on the downstream side of the filter element 4. A large amount is accumulated on the upstream side, and a relatively small amount is accumulated on the upstream side.

Then, when the pressure loss of the exhaust filter 1 becomes large due to long-term operation, the heater 7 is energized by the control unit (not shown), and the filter element 4 is forcibly regenerated. The heat generated by the heater 7 heats the entire filter element 4,
In particular, in the high thermal conductivity section 8, the porosity is small and the thermal conductivity is locally increased, so that the heat of the heater 7 is efficiently transferred to the entire cross section of the filter element 4 via the high thermal conductivity section 8. . Therefore, the exhaust particulates are ignited along the surface of the high thermal conductive portion 8 and the combustion thereof is started. That is, even if the heater 7 is separated from the heater 7,
Heat is given to accelerate its ignition. Then, on the upstream side of the filter element 4, the self-combustion becomes weak because there are few accumulated exhaust particulates, but the heat of the heater 7 is positive because the high heat conduction parts 8 are densely arranged. The exhaust fine particles can be reliably burned and removed. On the other hand, on the downstream side of the filter element 4,
Since the interval between the high heat conduction parts 8 is wide, the amount of heat transferred from the heater 7 is small, but since the amount of exhaust particulate deposition is large, it is possible to reliably burn once ignited. That is, the high heat conduction part 8 is formed in a shape corresponding to the distribution of the exhaust particulate deposition.
Combustion can be promoted by, and the heat of the heater 7 can be used very effectively to forcefully regenerate each part uniformly.

In the above-described embodiment, the high heat conducting portion 8 and the other general portion are integrally formed as metal foam, but they are separately formed and laminated and fixed to form the cylindrical filter element 4. You may do it.

[0017]

As is apparent from the above description, according to the exhaust gas filter of the internal combustion engine of the present invention, the high heat which is partially provided in the cylindrical filter element through which the exhaust gas flows from the inner peripheral side to the outer peripheral side. The heat of the heater can be transmitted to the entire cross section of the filter element by the conductive portion, and the ignition can be uniformly promoted at each portion of the cross section. Further, since the heating effect is provided by the high heat conduction part in correspondence with the distribution of different exhaust particulates along the axial direction of the cylindrical filter element, the heat quantity of the heater can be effectively used and the entire cylindrical filter element can be made uniform. Can be played.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an exhaust filter according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an explanatory view showing a deposition state of exhaust particulates in a conventional cylindrical filter element.

[Explanation of symbols]

 1 ... Exhaust filter 3 ... Casing 4 ... Filter element 7 ... Heater 8 ... High heat conduction part

Claims (1)

[Claims] 1. A cylindrical filter element made of a three-dimensional porous body is closed at one end, housed in a casing so that exhaust gas flows from the inner peripheral side to the outer peripheral side of the filter element, and has a rod shape for regeneration. In an exhaust gas filter of an internal combustion engine in which a heater is arranged inside the filter element along the axial direction of the filter element, a high heat conduction part having a locally small porosity is formed in the filter element on a surface orthogonal to the axial direction. An exhaust gas filter for an internal combustion engine, characterized in that a plurality of high heat conduction parts are formed along the filter element along a line, and are arranged densely on the upstream side of the cylindrical filter element and roughly arranged on the downstream side.