JPH0681629A - Exhaust emission control device for diesel engine - Google Patents

Abstract

PURPOSE:To provide an exhaust emission control device lightening a burden on a battery at the time of regenerating a filter. CONSTITUTION:An exhaust emission control device has numerous heating wires 5 disposed at a filter 1. One ends of the respective heating wires 5 are connected being divided into plural groups, and the other ends are connected being divided into plural groups each of which is formed of the heating wires 5 selected one by one from each previously formed group. At the time of regenerating the filter 1, one out of the one-end groups and one out of the other-end groups are selected by relay-type first and second switches 9, 10 and connected to a power supply 8. This power supply connection is performed on every combination of two groups, and a current is applied in turn to all heating wires 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device provided in a diesel engine, and more particularly to a diesel particulate filter which is a main component of the device and has a large number of cells.

[0002]

2. Description of the Related Art Since the exhaust gas of a diesel engine contains a large amount of exhaust particulates, that is, particulates,
An exhaust system of the engine is equipped with a diesel particulate filter (hereinafter referred to as a filter) for collecting the particulates.

This filter is composed of a large number of elongated cells defined by, for example, partition walls made of a porous ceramic material, and one end of each cell is closed by a plug (plug member). Therefore, at the time of collecting particulates, the exhaust gas that has flowed in from the cell that is open on the upstream side of the exhaust gas passes through the partition wall to the cell that is open on the downstream side of the exhaust gas, and passes through the filter. When passing through the partition walls, particulates in the exhaust gas are trapped by the partition walls.

By the way, when the amount of particulates accumulated inside the filter increases as the filter is used, the air permeability is gradually impaired and the engine performance deteriorates. It is necessary to perform a filter regeneration process in which the filter is heated to ignite and burn the particulates in the filter. In this filter regeneration process, a plurality of electrodes are inserted in the filter cell in the filter axial direction, and an arc is generated by applying a discharge voltage to each electrode during filter regeneration, thereby burning the particulates. The above filters are already known (Japanese Patent Laid-Open No. 27107/1990).

[0005]

In the above electrode insertion type filter, since the electrodes are arranged along the axial direction of the filter, it is possible to perform particulate combustion over the entire filter at the time of regeneration, so that an electric heater is provided on the end face of the filter. Compared with the type in which the gas is distributed and the combustion gas is propagated from one end surface side to the other end surface side together with the supply of the regeneration gas, there is an advantage that the amount of unburned particulates is small and the so-called regeneration efficiency is high.

However, since this filter energizes a plurality of electrodes at the same time during regeneration, the power consumption per hour is considerably large.
It has been confirmed that several kilowatts of electric power is required to raise the temperature to 600 ° C. or above where particulates can be combusted, and the load on the battery is extremely large, which may make it impossible to reproduce depending on the battery capacity at that time. .

In view of the problems of the conventional filter as described above, it is an object of the present invention to provide an exhaust gas purification device which can reduce the load on the battery per filter regeneration time.

[0008]

In order to achieve the above object, according to the present invention, a heater is provided in a filter, and the heater is arranged in the filter in an exhaust gas purification apparatus that burns particulates by energizing the heater to regenerate the filter. A plurality of heater wires that are connected to each other, and one end of each heater wire is divided into a plurality of groups to be connected, and the other end of each heater wire is selected one by one from each of the groups. When the filter is regenerated, a switch means for connecting one to one of the groups at one end and one of the groups at the other end to connect to the power source is provided. There is provided an exhaust gas purification device provided with a regeneration control means for controlling the operation of a switch means so as to energize each heater wire in a predetermined order.

Further, preferably, in the exhaust emission control device having the above-mentioned configuration, each of the heater wires is arranged substantially parallel to the axial direction of the diesel particulate filter and arranged in a grid shape when viewed from the axial direction, and on the front and rear end faces of the filter. Each of the above groups is connected in a straight line vertically and horizontally.

[0010]

By connecting the other end of each heater wire to a plurality of groups each composed of a heater wire selected one from each of the groups divided on the one end side, one end of the heater wire is connected. In the state where one is selected from each group divided on the side and one is selected from each group divided on the other end side and these are energized via the switch means,
Only one heater wire commonly included in these groups is energized. At the time of filter regeneration, the regeneration control means controls the operation of the switch means to energize each heater wire in a predetermined order. Further, when both ends of each heater wire are grouped and connected in a vertical / horizontal linear shape on the front / rear end faces of the filter, the wiring / connection work becomes easy and the manufacturing becomes easy.

[0011]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic vertical cross-sectional view of a main body of a cylindrical diesel particulate filter 1 (hereinafter, abbreviated as filter 1) that constitutes an exhaust emission control device according to the present invention. This filter 1 can be formed of, for example, a porous ceramic material, and the inside thereof is, as shown in its schematic cross-sectional model (which is greatly exaggerated to clarify its structure) in the drawing, It is composed of a large number of cells 3 defined by a breathable partition 2, and one end of each cell 3 is always closed by a plug 4.

In the filter 1 constructed as described above, according to this embodiment, the electric heater wire 5 is inserted into each of the plurality of cells 3 through the plug 4 in parallel with the axial direction of the filter. . In the state where the heater wire 5 is arranged in the cell 3, the position and the length are determined so that both end portions 5a and 5b of the heater wire 5 slightly project from the filter end surfaces 1a and 1b as shown in the figure, and the respective end portions 5a are , 5b,
The heater wires protruding from the same end face side are welded to, for example, the collective electrode 6 under a predetermined relationship to be described later, so-called electrical connection (wiring).

FIG. 2 schematically illustrates an example of connection of each heater wire 5 in the filter and wiring to the power source. The circle on the left side of the drawing shows the appearance of the above-mentioned filter end face 1a.
The circle on the right side shows that of the filter end face 1b, and the numbers in the figure without lead lines are the serial numbers of the respective heater wires 5 used in explaining the connection example. According to this embodiment, a total of 25 electric heater wires 5 arranged in the filter 1 are arranged at substantially equal intervals so that the end portions 5a and 5b appear in a grid pattern on the end surface as shown in FIG. Then, on the filter end face 1a side, the collective electrode 6 connecting the heater wires 5 is connected.
Are grouped into a plurality of groups so as to be vertically arranged on the filter end face 1a.

That is, in the case of the filter of the present embodiment, one end 5a of each heater wire 5 is composed of five heater wires (for example, serial numbers 1, 6, 11, 16, 21), and a total of five first groups. (AI, A-II, A-III, A-IV, A-
V) and each of them is welded to each collecting electrode 6. On the other hand, on the filter end face 1b side from which the other end 5b of the heater wire 5 projects, the wires are divided into a plurality of groups as in the case of the previous filter end face 1a side, and the connection patterns are the same as those of the first group. The other end portions 5b of the heater wires 5 of a number corresponding to the number of the first groups selected one by one from among are connected via one collective electrode 6, and the heater wires 5 are connected in this manner. A plurality of collecting electrodes 6 are set to be lined up on the filter end surface 1b.

That is, in the case of the illustrated filter, the other end 5b of each heater wire 5 is connected to one collecting electrode 6 with heater serial numbers 1 to 5, for example, and serial numbers 6 to 10;
-15; 16-20; 21-25, and a total of five second groups (B-I, B-II, B-III, B-IV,
B-V), and the collective electrodes 6 are arranged side by side on the filter end surface 1b.

One contact 7 is provided for each of the collective electrodes 6 to which the heater wire 5 is connected as described above, and between the contact 7 and the electrode 8 there is a first group. A first switch 9 that selects one group from the inside to enable connection with the positive side of the power supply 8 and a contact that can similarly be connected to the negative side of the power supply 8 by selecting each contact 7 of the second group. Two switches 10 are provided, and when the filter is regenerated, the first and second signals are output by a signal from a control circuit to be described later.
The switches 9 and 10 are operated to change the contact position with the power source 8 in a predetermined order as shown by the arrow in the figure.

That is, specifically, the contacts 7 of the five groups forming the first group and the contact points 5 forming the second group.
The contacts 7 of one group are connected to the power supply 8 in a non-overlapping combination, for example, AI * BI, A.
-I * B-II, AI * B-III, etc., a total of 25 electrical connections are made. The connection between the contacts means the energization of only one electric heater wire 5 included in both groups, and according to the present embodiment, the operation of the two switches 9 and 10 is controlled. Alone
It is possible to divide and energize all the heater wires 5 inserted in the filter 1 at the same time, and to reduce the load on the power source 8.

FIG. 3 shows an example of the construction of an exhaust gas purification device including two filters in which the heater wires are connected as described above. With reference to this figure, the structure thereof will be schematically described. Reference numeral 11 denotes an exhaust pipe (exhaust passage) through which exhaust gas from an engine body (not shown), which is located on the left side in the figure, flows
A and 1B are filters for collecting particulates in the exhaust gas, 12 and 13 are branch pipes for guiding the exhaust gas flowing in the exhaust pipe 11 to the filters 1A, 1B, and 14 is a muffler.

The connecting portion between the exhaust pipe 11 and the branch pipes 12 and 13, that is, the branch portion of the exhaust gas, operates so as to occupy the position indicated by the solid line in the figure during particulate collection, and flows through the exhaust pipe 11. An exhaust control valve 15 is provided to branch the exhaust gas that has been collected into two parts, and to rotate the filter to a dotted line position during filter regeneration to prevent the exhaust gas from being introduced into the filter to be regenerated and guide the exhaust gas to the remaining filters. The exhaust control valve 15
Is driven by a control circuit (ECU) 16 and a diaphragm actuator 17.

In order to determine the regeneration timing of the filters 1A and 1B, differential pressure sensors 18A and 18B for detecting the filter pressure loss are provided before and after both filters, and the detection signal is E
It is adapted to be input to the CU 16, and in addition to this, various operating characteristics represented by the engine speed, the intake pipe negative pressure, etc. are input to the ECU 16. For the filters 1A and 1B having the heater wiring as shown in FIG.
A relay-type first switch 9 and a second switch 10 which are driven by the ECU 16 and switch the connection state between each contact and the power supply (battery) 8 as described above are provided. In the present device, the first switch 9 is a two-filter type. 1A,
It is provided commonly to 1B.

The operation at the time of filter regeneration of the exhaust gas purification device constructed as above will be described below. The regeneration timing is determined based on the detected engine speed, intake pipe negative pressure, filter differential pressure, etc. If, for example, it is determined that regeneration is required for the filter 1A, the ECU 16 drives the actuator 17 to drive the exhaust control valve. 15 is switched from the neutral position to the filter 1A side so that the exhaust gas flows only to the filter 1B side.

While maintaining this state, the ECU 16
Then activates the first switch 9 and the second switch 10,
All the heaters 5 mounted on the filter 1A are sequentially energized for a predetermined time to burn particulates to regenerate the filter. When the regeneration of the filter 1A is completed, the switch operation is stopped, the exhaust control valve 15 is returned to the original position, and the particulate collection by the two filters is restarted, or the filter 1B is restarted.
If reproduction is required also in the above, this time, on the contrary, the filter 1B is operated to perform the same reproduction processing.

As described above, in the exhaust emission control device of this embodiment, each heater wire attached to the filter is individually energized to regenerate, so that the time required for regenerating one filter is the entire filter at once. Although it tends to be slightly longer than a combustion propagation type exhaust emission control device that heats and performs particulate combustion, it has an advantage that the peak current is small and the load on the battery 8 is reduced.

Although the example of the heater wiring of the filter and the example of the device constituting the exhaust gas purification apparatus according to the present invention have been described above, the present invention is not limited to these embodiments. That is, the number of heater wires or groups provided in the filter is not limited to the illustrated embodiment, and may be increased or decreased as necessary, and the heater wires indicated by the serial numbers 1 in FIG. However, the number of cells including the heater wires may be increased by forming the heater wires with a plurality of heater wires connected in parallel.

In the above description, the heater energization is started from the one located on the outer peripheral side of the filter.
As shown in the energization numbers in FIG. 4, the heater energization sequence is such that electricity is energized from the center of the filter to the outer periphery, and the heat of the heater in the center of the filter and the heat of particulate combustion are conducted to the outer periphery. The power consumption required for heating the cells in the latter half may be reduced.

Further, in the embodiment, each heater wire penetrates the inside of the cell and both ends thereof protrude from the filter end surface, but the wiring form is not limited to this.
A large number of heater wires may be provided only on the outer circumference of the filter or on one end face side according to the above-mentioned connection relationship, or as shown in FIG. You may make it connect for every group.

[0027]

As described above, according to the present invention, one end of each of the plurality of heater wires is divided into a plurality of groups and connected, and the other end of each of the heater wires is connected to one of the groups. Since the wiring is divided into a plurality of groups consisting of heater wires that are selected one by one, and one of the groups at one end and the other group at the other end are selected and connected to the power supply during filter regeneration It is possible to reduce the power consumption per hour during the regeneration and to reduce the load on the power source as compared with the case where the filter is regenerated by energizing all the heaters all at once.

In addition, the device can sequentially energize the heater group by controlling two switches for one filter. When the same number of heater wires are provided in the filter and a contact is provided for each of them, the device is energized. Compared with, the number of switches and the number of contacts can be greatly reduced, the wiring can be simplified, and the manufacturing becomes easy. In addition, when both ends of each heater wire are grouped and connected in a straight line in the vertical and horizontal directions on the front and rear end faces of the filter, the wiring and connecting work becomes easier and the manufacturing becomes easier.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a filter showing an example of heater wiring of a filter constituting an exhaust emission control device of the present invention.

FIG. 2 is a schematic diagram of heater wiring of the present device including the appearance of both end faces of the filter of FIG.

FIG. 3 is a schematic configuration diagram of an exhaust emission control device according to the present invention.

FIG. 4 is an external view of a filter end face for explaining a heater energization sequence as one embodiment of the present invention.

5 is a schematic vertical sectional view of a filter as another embodiment in which a heater wiring pattern is changed from that of the filter of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Filter 5 ... Heater wire 6 ... Collective electrode 8 ... Power supply 9 ... First switch 10 ... Second switch 16 ... Control circuit

Claims (2)

[Claims] 1. An exhaust gas purification system in which a diesel particulate filter for collecting particulates in exhaust gas is provided in an exhaust system of a diesel engine, and a heater is provided in the filter to burn the particulates by energizing the heater to regenerate the filter. In the apparatus, the heater is composed of a plurality of heater wires arranged in a filter, one end of each heater wire is divided into a plurality of groups and connected, and the other end of each heater wire is connected to each of the groups. A switch that connects to a plurality of groups consisting of heater wires selected one by one from the inside and further connects one to one of the groups at one end and one to the power source during filter regeneration Regeneration control for controlling the switch means so as to energize each heater wire in a predetermined order when the filter is regenerated. Exhaust gas purification apparatus for a diesel engine, characterized in that a stage. 2. Each of the heater wires is arranged substantially parallel to the axial direction of the diesel particulate filter, and is arranged in a grid shape when viewed from the axial direction. The heater wires are arranged in the vertical and horizontal straight lines on the front and rear end faces of the filter, respectively. The exhaust purification device for a diesel engine according to claim 1, wherein the exhaust purification device is divided into groups and connected.