JPH07189657A - Exhaust particulate collection filter for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve regenerating efficiency on a filter outer circumferential part and both end parts thereof by arranging a hollow cylindrical pipe so as to cover a filter element, forming a communicating hole on the circumferential wall part which is provided in the vicinity of both end parts of the hollow cylindrical pipe, and circulating exhaust gas at the time of regeneration of a filter so as to cover the filter. CONSTITUTION:When a filter is regenerated, exhaust gas E is passed from the inner circumference of filter elements 12 (12a to 12d) toward an outer circumference, and passed in spaces 18 (18a to 18d) which are formed between an element outer circumferential wall and hollow cylindrical pipes 17 (17a to 17d), and circulated into communicating holes 20 which are provided on the circumferential wall parts provided in the vicinity of the both end parts of the hollow cylindrical pipe 17. The elements 12a to 12d are covered by exhaust gas E which is heated by combustion heat of exhaust particulates which is generated by heating of a heater 16 and combustion transmission extending from a filter center part to the both end parts. It is thus possible to improve heat insulating effect, improve a temperature difference between the central part and the both end parts, and eliminate a regeneration failure range so as to enable uniform regeneration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust particulate collection filter for an internal combustion engine for collecting particulates such as soot contained in the exhaust gas of a diesel engine and removing them by combustion.

[0002]

2. Description of the Related Art Conventionally, from the standpoint of environmental protection, a ceramic or the like is interposed in an exhaust system in order to prevent exhaust particulates such as soot contained in the exhaust of a diesel engine from being discharged into the atmosphere. Various exhaust particulate collection filters in which exhaust particulates are collected and removed by a filter element have been proposed.

In this type of collecting filter, when exhaust particulate matter is deposited, the filter is clogged and pressure loss is increased. Therefore, it is indispensable to burn the deposited exhaust particulate matter to regenerate the filter. is there. Therefore, it is proposed that a heater is provided on the inner peripheral surface of the filter element for collecting exhaust particulates, and the exhaust particulates deposited on the filter element by energizing the heater are forcibly ignited and burned to be removed. (See JP-A-58-8219).

As for the shape of the filter element, one end of a cylindrical filter element made of electrically conductive heat-generating ceramic is closed, and exhaust gas flows from the inner peripheral side to the outer peripheral side of the filter element inside the casing. Exhaust particles that are stored and accumulated on the filter element
A device has been proposed in which the filter element is forcibly ignited and burned by energization (Japanese Patent Laid-Open No. 2-4).
2112).

There is also one in which a cylindrical filter element is formed by alternately winding a ceramic fiber and a heater on a supporting member having air permeability (see Japanese Patent Laid-Open No. 256256/1990).

[0006]

However, in such a conventional exhaust particulate collection filter for an internal combustion engine that uses a cylindrical filter element, if a heater for regeneration is evenly arranged inside the filter element, regeneration will occur. When the heater is energized and heated, the heat escapes from both ends of the cylindrical filter element to the casing.
As indicated by A, the temperature of the central portion of the filter element is high and the temperatures of both end portions are lowered. As a result, when the temperature is set to a temperature suitable for re-combustion of exhaust particulates in the central region, as shown in FIG. 8, defective regeneration occurs at both ends and uniform regeneration cannot be performed. On the contrary, if the temperature is set to be suitable for exhaust particulate re-combustion at both ends, the temperature of the central part rises too much, and the voltage applied to the heater is wasted.
There is a problem that the durability of the filter element may be impaired.

If the heaters are arranged inside the filter element so that both ends are denser than the center,
When the heater is energized and heated during regeneration, the temperature difference between the central portion and both end portions is improved as shown in FIG. 7B, but the central portion is more easily regenerated than both end portions, and as shown in FIG. When the regeneration of the central part is completed, there will still be defective regeneration areas at both ends, and if the regeneration of both ends is attempted completely, the central part will be heated unnecessarily, resulting in power consumption. Wasted.

The present invention has been made in view of the above-mentioned conventional problems, and provides an exhaust particulate collection filter for an internal combustion engine capable of performing uniform regeneration while preventing wasteful consumption of electric power. With the goal.

[0009]

Therefore, according to the present invention, exhaust gas is introduced from the upstream end of the engine exhaust passage through the open end of a hollow cylindrical porous filter element having one end closed, and the exhaust gas is introduced into the inner circumference of the filter. In the exhaust particulate collection filter of an internal combustion engine, which is provided with a heater for collecting exhaust particulates in exhaust gas while passing through the exhaust gas to the outer periphery and incinerating and removing the collected exhaust particulates, the filter element is covered. To
A hollow cylindrical tube is arranged in a state where a gap is maintained between the outer peripheral wall of the filter element, and communication holes are formed through the peripheral wall portions near both ends of the hollow cylindrical tube.

[0010]

According to this structure, the exhaust gas that has flowed into the open end of the filter element from the upstream side of the exhaust passage of the engine passes from the inner circumference of the filter through the hollow cylindrical porous filter element whose one end is closed. While passing to the outer circumference,
Exhaust particles in the exhaust collide with the wall surfaces of a large number of holes provided in the thick portion of the filter and are collected there.

Then, the collected exhaust particulates are burned and removed by the heat generated by energizing the heater provided in the filter, and the filter is regenerated. During the regeneration of this filter, the exhaust gas passes from the inner circumference to the outer circumference of each filter, passes through the gap formed between the outer peripheral wall of the filter element and the inner wall of the hollow cylindrical tube, and is in the vicinity of both ends of the hollow cylindrical tube. It will flow to the communication hole provided in the peripheral wall portion.
Therefore, the heated exhaust gas envelops the filter due to the heating by the heater and the combustion heat of the exhaust particulates starting from the inner peripheral central region of each filter. That is, since combustion is propagated from the center of the filter to both ends, the exhaust is heated as the exhaust flows from the center to both ends, without increasing the voltage applied to the heater. It is possible to improve the regeneration efficiency at the outer peripheral portion and both end portions of the filter, which has a poorer regeneration efficiency than the above. Therefore, uniform regeneration is performed while preventing the wasted voltage applied to the heater.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, referring to FIGS. 1 to 3, the overall structure of an exhaust particulate collection filter according to the present invention will be described. The exhaust passage 11 connected to the exhaust manifold of the engine 10 includes a first branch passage 11a and a second branch passage 11b. It is branched to and merges on the downstream side.

A first casing 13a, in which filter elements 12a and 12b having a heater 16 are arranged in parallel, is interposed in the first branch passage 11a, and a first casing is provided downstream of the filter elements 12a and 12b. 13a
A first opening / closing valve 14a is provided for controlling the flow rate of exhaust gas flowing into the. A second casing 13b in which filter elements 12c and 12d similarly having a heater 16 are arranged in parallel is also provided in the second branch passage 11b, and a second casing 13b is provided downstream of the filter elements 12c and 12d. The 2nd on-off valve 14b which controls the exhaust flow volume which flows into the casing 13b is provided.

Filter elements 12a, 12b, 12
c and 12d are exhaust gas introduced from the upstream side of the engine exhaust passage through the open end of a hollow cylindrical porous filter whose one end is closed, and pass through the exhaust gas from the inner circumference to the outer circumference of the filter. It is configured to collide with the wall surface of many holes provided in the thick part and collect exhaust particulates in the exhaust there, formed by winding ceramic fiber, ceramic foam, metal foam, etc. To be done.

The heater 16 is for regenerating the filter by burning and removing the collected exhaust particulates by heat generated by energizing the heater 16, and the inner peripheral surfaces of the filter elements 12a, 12b, 12c, 12d. Is inscribed in or is embedded in the inside of the filter, and an electrode 15 for energizing the heater 16 is provided at the closed end thereof, and the electrode 15 is electrically insulated from the casings 13a and 13b and externally provided. And is connected to a power source (not shown) to be energized and heated from the power source for a predetermined time, for example, 5 minutes.

The on-off valves 14a and 14b are electromagnetic valves and the like, and by alternately opening and closing, collection and regeneration by the filter elements 12a and 12b and the filter elements 12c and 12d are alternately repeated. .
The filter elements 12a, 12b, 12c, 12
d The hollow cylindrical pipes 17a, 17b,
The hollow cylindrical tubes 17a, 17b, 17d are arranged such that 17c, 17d maintain a constant gap 18a, 18b, 18c, 18d between them and the outer peripheral wall of the filter element.
A plurality of communication holes 2 are provided in the peripheral wall portion near both ends of c and 17d.
0, 20 ... Are penetratingly formed, and exhaust gas from which exhaust particulates have been removed is exhausted into the atmosphere through the communication hole 20.

Next, the operation of the present invention will be described with reference to FIGS. When the filter is regenerated, the exhaust gas E passes from the inner periphery of the filter element 12 to the outer periphery thereof, and passes through the gap 18 formed between the outer peripheral wall of the filter element and the inner wall of the hollow cylindrical pipe 17 to form the hollow cylindrical pipe 17 therein. Flow into the communication holes 20 provided in the peripheral wall portions near both ends of the. Therefore, the exhaust gas E after passing through the heated filter encloses the filter element 12 due to the heat generated by the heater 16 and the heat of combustion of the exhaust particulates caused by the combustion propagation from the filter center to both ends. The exhaust gas is heated as the exhaust gas flows from both ends to. Therefore, as shown by C in FIG. 4, the heat retention effect is enhanced and the temperature difference between the central portion and both end portions is improved as compared with the conventional example (A, B), and as shown in FIG. It is lost and uniform reproduction is performed. In this way, it is possible to improve the regeneration efficiency of the filter outer peripheral portion and both end portions where the regeneration efficiency is lower than that of the central portion without increasing the voltage applied to the heater, thus wasting the voltage applied to the heater. Can be prevented.

Next, another embodiment will be described with reference to FIG. That is, this is a filter element 12a.
A hollow cylindrical tube 17a formed so as to cover the outer peripheral portion is provided with a narrowed portion 19 at a substantially central portion. Since other configurations are the same as those shown in FIG. The description is omitted.

According to this structure, the hollow cylindrical tube 17a
Is exposed to high-temperature exhaust gas when the filter is regenerated. By providing this throttle portion 19, the throttle portion 19
Since it can absorb the thermal strain and does not deform even if the hollow cylindrical tube 17a is formed of a thin plate material, the gap 18 formed between the outer peripheral wall of the filter element and the inner wall of the hollow cylindrical tube 17 is formed. Therefore, it is possible to prevent the flow of exhaust gas from being cut off, resulting in an increase in pressure loss and damage to the filter.

In the above description, the exhaust particulate collection filter for an internal combustion engine according to the present invention is divided into two exhaust passages and a filter is provided in each passage, and the two filters alternately collect and regenerate. I've explained what to do,
The present invention is not limited to this, and the present invention can be applied to a structure that is configured by one exhaust passage and has a filter in the passage, and each exhaust passage that is branched into three or more has a filter. It can also be applied to things.

[0021]

As described above, according to the present invention, the hollow cylindrical pipe is arranged so as to cover the filter element with a gap maintained between the hollow cylindrical pipe and the outer peripheral wall of the filter element. In the peripheral wall portion in the vicinity of the portion, a communication hole is formed so as to penetrate, and at the time of regeneration of the filter, exhaust gas after passing through the heated filter circulates in the gap to wrap the filter,
Since the exhaust gas is heated as it flows from the central part to both ends, the regeneration efficiency of the filter outer peripheral part and both ends can be improved, and the waste of the voltage applied to the heater can be prevented, and the evenness can be maintained. Playback is performed.

[Brief description of drawings]

FIG. 1 is a system diagram showing an exhaust gas purification device equipped with an exhaust particulate collection filter for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the exhaust emission control device of FIG.

FIG. 3 is a cross-sectional view showing a portion where the exhaust particulate collection filter of FIG. 1 is interposed.

FIG. 4 is a diagram showing a temperature distribution of a filter during reproduction.

FIG. 5 is an explanatory diagram for explaining the operation of the present invention.

FIG. 6 is a cross-sectional view showing a state in which an exhaust particulate collection filter of an internal combustion engine according to another embodiment of the present invention is interposed.

FIG. 7 is a diagram showing a temperature distribution of a conventional filter.

FIG. 8 is an explanatory diagram for explaining a defective reproduction state of a filter of a conventional example.

FIG. 9 is an explanatory diagram for explaining a defective reproduction state of a filter of a conventional example.

[Explanation of symbols]

 10 engine 11 exhaust passage 11a first branch passage 11b second branch passage 12a, b, c, d filter element 13a first casing 13b second casing 14a first opening / closing valve 14b second opening / closing valve 15 electrode 16 heater 17a, b, c, d hollow cylindrical tube 18a, b, c, d gap 20 communication hole

Claims (1)

[Claims] 1. An exhaust gas is introduced from an upstream end of an engine exhaust passage through an open end of a hollow cylindrical porous filter element having one end closed, and the exhaust gas is exhausted while passing the exhaust gas from an inner circumference of the filter to an outer circumference thereof. In an exhaust particulate collection filter for an internal combustion engine, which is provided with a heater for collecting exhaust particulates and burning and removing the collected exhaust particulates, a gap is provided between the filter element outer peripheral wall and the filter element so as to cover the filter element. An exhaust particulate collection filter for an internal combustion engine, characterized in that a hollow cylindrical pipe is arranged in a state of maintaining the above condition, and a communication hole is formed through the peripheral wall portions near both ends of the hollow cylindrical pipe.