JPH04347315A - Exhaust gas treatment system for diesel engine - Google Patents

Abstract

PURPOSE:To reduce the required electric power for an exhaust gas treatment system with a self-heating filter. CONSTITUTION:A conductive, porous self-heating filter 3 catches the particulate being exhausted out of a diesel engine, while an engine control unit 5 as a current-energizing control means and a heater relay 6 energize this self-heating filter 3 itself, heating this filter 3 up to an ignition temperature of the particulate for incineration. Especially, since each filter block is energized in order at every specified time capable of incinerating the accumulated diesel particulate at a time when the current-inergizing control means 5, 6 regenerate the filter, the accumulated diesel particulate is incinerated at every filter block in order.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment device for a diesel engine, and more particularly to an exhaust gas treatment device equipped with a filter that generates heat by itself when energized.

0002

[Prior Art] Japanese Patent Application Laid-Open No. 55-131518 discloses that diesel particulates discharged from a diesel engine, etc. are collected by a ceramic filter, and
An ignition/burning type exhaust gas treatment device is disclosed in which an ignition heater provided upstream of a ceramic filter is energized to ignite and incinerate diesel particulates.

[0003] Japanese Patent Application Laid-open No. 61-25907 discloses the above-mentioned sequential ignition type ignition spread type exhaust gas treatment device,
It is disclosed that the incineration performance of diesel particulates between adjacent ignition heaters is improved by overlapping the energization periods to adjacent ignition heaters. Japanese Unexamined Patent Publication No. 1-182519 discloses that in the above-mentioned sequential ignition type ignition spread type exhaust gas treatment device, the regeneration state of each part of the ceramic filter is improved by appropriately changing the order of energization to each ignition heater. Disclosed.

0004

Problems to be Solved by the Invention The above-mentioned ignition and fire spread type exhaust gas treatment device has the following points: If the amount of diesel particulates deposited at the time of ignition is small, the fire will not spread sufficiently and regeneration will be insufficient.
If the amount of deposition is too large, the ceramic filter will become too hot and its durability will deteriorate, and there will be large variations in temperature distribution between the area near the ignition heater and the area away from it, which may cause the ceramic filter to crack. point was the problem.

[0005] Furthermore, according to each of the above-described sequential ignition type proposals, variations in the temperature distribution in each part of the ceramic filter become more pronounced, and there is a fear that the ceramic filter may crack due to the thermal stress. In view of these problems, the applicant first constructed a filter using a porous conductive material (e.g., porous metal), heated the filter to the ignition temperature by applying electricity to the filter itself during regeneration, and deposited on the filter surface. We invented a self-heating filter that incinerates diesel particulates, and filed an application for an exhaust gas treatment device for a diesel engine equipped with this self-heating filter.

However, this self-heating filter has the disadvantage that the entire filter, which has a large heat capacity, must be heated to the ignition temperature, resulting in large power consumption. That is, there is a limit to the maximum power that a vehicle power supply device can generate, and it has been necessary to take measures such as increasing the size of the vehicle power supply device or stopping power supply to other loads. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the power required for an exhaust gas treatment device having the above-mentioned self-heating filter.

[0007]

[Means for Solving the Problems] The present invention provides a conductive particulate matter disposed in the exhaust path of a diesel engine having a large number of small holes for collecting diesel particulates in exhaust gas. a self-heating filter; and energization control means for controlling the current supplied to the self-heating filter for incineration of the diesel particulates, the self-heating filter comprising a plurality of filter blocks electrically insulated from each other. The energization control means is characterized in that during filter regeneration, the energization control means energizes each filter block in turn at predetermined time intervals during which the accumulated diesel particulates can be incinerated.

[0008] The self-heating filter can be constructed from a metal material or a conductive ceramic material.

[0009]

[Operation and Effects of the Invention] In this device, a conductive and porous self-heating filter collects diesel particulates discharged from a diesel engine, and the energization control means energizes the self-heating filter itself. The self-heating filter is heated to the ignition temperature of diesel particulates, and the diesel particulates are incinerated.

[0010] Particularly, in the present invention, the energization control means sequentially energizes each filter block at predetermined time intervals during filter regeneration to allow the accumulated diesel particulates to be incinerated. Each block is incinerated in turn. In this way, although the total incineration time will be extended, the maximum power required will be reduced approximately in proportion to the number of filter divisions, significantly reducing the burden on the vehicle power supply unit and engine. be able to.

[0011] As a result, good incineration is always possible depending on the amount of diesel particulates deposited, and because it is much stronger than ceramic filters, it does not crack due to temperature changes or variations in temperature distribution during the combustion cycle. The present invention has great effects in realizing a self-heating filter that has characteristics such as difficulty.

0012

Embodiment 1 A block diagram of a diesel particulate collection device using the self-heating filter of the first embodiment is shown in FIG. A filter (self-heating filter in the present invention) 3 is connected to an exhaust pipe 2 of a diesel engine 1, and a muffler 4 is provided at the tip of the exhaust pipe 2.

On the other hand, an engine control unit (ECU) 5 for engine control including a microcomputer is provided, and this ECU 5 receives an engine rotation speed signal output from a rotation speed sensor (not shown) mounted on the engine. The regeneration timing of the filter 3 is determined based on the cumulative value of the engine rotational speed, and furthermore, during regeneration, the heating is controlled in a control mode to be described later.
Make the tally relay 6 conductive. The heater relay 6 is constituted by four electromagnetic switches, and supplies electric power supplied from the battery 14 to the filter 3 to heat the filter 3. Here, the ECU 5 and the heater relay 6 constitute energization control means in the present invention.

A longitudinal cross-sectional view of the filter 3 is shown in FIG. The filter 3 includes a metal outer cylinder part 30 whose openings at both ends are connected to the exhaust pipe 2, and inside the outer cylinder part 30, two electrically insulating fixing members 40 and 41 are installed at a predetermined interval. It is disposed in a direction perpendicular to the axis of the section 30. A total of 40 filter members 31 are supported at both ends by these fixing members 40 and 41 and arranged in 4 rows horizontally and 10 stages vertically. The filter members 31 are provided at a predetermined distance from each other and from the outer cylinder portion 30 at a predetermined distance.

Further, the outer cylindrical portion 30 is insulated with one grounding electrode member 13a and four power supplying electrode members 13.
b1, 13b2, 13b3, 13b4 (see Figure 6, Figure 2
13b1 (only 13b1 is shown)) extends from the outside to the inside. As will be described later, the inner end of the grounding electrode member 13a is connected to the uppermost (first stage) filter member 31 in FIG.
are connected to one end of each power feeding electrode member 13b1,
13b2, 13b3, and 13b4 are individually connected to one end of the lowest (first stage) filter member 31 in each row.

On the other hand, the outer end of the grounding electrode member 13a is connected to the lower electrode terminal L of the battery 14, and the outer end of each power supplying electrode member 13b is connected to each electromagnetic switch of the heater relay 6 separately. The high electrode terminal H of the battery 14 via
It is connected to the. FIG. 3 shows a perspective view of two vertically adjacent filter members 31, 31 in FIG.
A cross-sectional view taken along the line is shown in FIG.

Each filter member 31 has two hollow plate-shaped filtration sections 34, upper and lower, which have a filter function and are arranged parallel to each other, and a connecting section 35 that connects one end of each of the two filtration sections 34. It consists of two upper and lower filter members 31.
The other end of each of the four filter sections 34 in total is fixed to one holding section 36. More specifically, the filter section 34 has a length of 130 mm, a width of 13 mm, a thickness of 2.5 mm, and a wall thickness of 0.2 to 0.3 mm. It is formed by supporting powder and sintering it. This alloy powder is made of Fe-Cr-Al-REM with an Al content of 5 wt% or more, and is made of Fe-Cr-Al-REM by sintering.
It has a dimensional network structure with many fine pores for collecting diesel particulates. Further, as shown in FIG. 4, the filtration part 34 has two filtration members 34a and 34b each having a corrugated plate shape stacked on top of each other, and a plurality of hollow parts 34c for exhaust gas flow paths between them. They are formed in parallel. As shown in FIG. 4, the gas flows into the hollow portion 34c from the outside of the filtration portion 34, and can flow out to the opening at the other end of each filtration portion 34, that is, to the holding portion 36 side.

The connecting portion 35 has an Al content of 10 wt%.
It is a U-shaped plate made of the above Fe-Cr-Al-REM alloy, and both ends of the connecting part 35 are individually welded to each upstream end of two adjacent filter parts 34. The upstream openings of each filter section 34 are sealed, and the relative distance between the pair of filter sections 34 is kept constant.

The holding portion 36 is also made of the same material as the connecting portion 35, and as shown in FIG. 3, the holding portion 36 has elongated holes 36a to 36d extending parallel to each other. The downstream end of each filtration part 34 is welded to the back surface of the holding part 36 in FIG. . Therefore, the hollow part 34c of the filtration part 34
The clean exhaust gas that has entered the
It will be discharged from d.

Next, the holding structure of each filter member 31 will be explained. 6 is a diagram of each filter member 31 viewed from the downstream side of FIG. 2, and FIG. 5 is a diagram of one vertical row of each filter member 31 viewed from the upstream side of FIG. 2. Note that FIG. 6 is upside down from FIG. 2. As shown in FIG. 6, at the downstream end of the filter member 31, an insulating fixing member 40 is fitted into the inner surface of the outer cylinder part 30. Holes are formed through the fixing member at predetermined intervals vertically and horizontally, and one filter portion 34 of each filter member 31 is inserted into each hole. As a result, each holding section 36 becomes an opening on the downstream side of each filtration section 34.
The elongated holes 36a to 36d are open on the downstream side of the fixing member 40.

Here, each of the top and bottom floors 4 in FIG.
One filter member 31 is attached to the two holding parts 36x and 36y.
(That is, each pair of filtration parts 34, 34) is only fixed, and power supply electrode members 13b1 to 13b4 are individually connected to the four holding parts 36x on the top floor. On the other hand, a ground electrode member 13a is commonly connected to each of the four holding parts 36y on the lowest floor.

The fixing member 40 is made of Fe-Cr-Al-RE
M alloy, Cr is 18-24wt%, Al is 15wt%
The filter member 3 is made of an alloy material with REM of 0.2% or more and the balance of
After the assembly in step 1, it is oxidized in the air at a temperature of 900° C. or higher for 0.5 to 20 hours to form an aluminum oxide-based insulating layer having sufficient electrical insulation.

Furthermore, at the upstream end of the filter member 31,
As shown in FIG. 2, two vertically adjacent connecting parts 35, 3
A spacer 43 is welded between 5 and 5 to enable electrical continuity. Incidentally, it is assumed that the pair of upper and lower connecting parts 35, 35, which are electrically conductive by the spacer 45, are connected to different holding parts 36 through the filtering part 34, and as a result, the current flows through the power supply electrode member 13b1. , the holding part 36y, the connecting part 35 of the filtering part 34, the spacer 43, the upper connecting part 35, the filtering part 34, and the holding part 36y flow into the ground electrode member 13a in the order of bending, and each filter member 31 is evenly distributed. Heat.

This electrically conductive spacer 43 is also made of the same material as the connecting portion 35, and a bar projecting upstream from one end of the spacer 43 is connected to the electrically insulating fixing member 4.
It is penetrated into the through hole of No. 1 and held. Fixed member 41
is composed of four plates each having five of the above-mentioned through holes (
FIG. 5 shows one of them), and both ends thereof are fixed to the inner surface of the outer cylindrical portion 30.

A method of manufacturing the filter section 34 will be explained below. First, a lath metal material that will become a skeleton is processed into a wave shape parallel to the longitudinal direction by pressing or the like, and two pieces of the processed lath metal material are stacked to form a cylindrical shape having a hollow portion 34c. Next, one end of this cylindrical lath metal material is welded to the holding part 36, and the other end is welded to the connecting part 35.

Next, it is made of Fe-Cr-Al-REM, with an Al content of 5 wt% or more and a Cr content of 18 to 24 wt%.
%, REM is 0.2 wt% or less, the remainder is Fe, and the average particle size is about 45 μm.
A slurry consisting of ~200 parts was prepared, and this slurry
A lath metal material is immersed in the slurry, and the slurry is deposited on the mesh portion of the lath metal.

[0027] Next, after sufficiently drying this lath metal material, in a vacuum of 10-3 torr or less,
Firing was performed at a temperature range of 1300° C. for 1 to 20 hours to sinter the metal powder and fix the sintered metal to the mesh portion of the lath metal 32. r on the surface of the filtration part 34 obtained in this way.
-The filter member 31 was formed by depositing Al2O3 and a catalyst. This filter member 31 is F
Since it is composed of e-Cr-Al-REM alloy,
Surface oxidation has the advantage of ensuring surface oxidation resistance while maintaining internal conductivity.

Therefore, in the above embodiment, the filter members 31 of 10 columns and 1 row of filter members constitute the filter block referred to in the present invention, and the four filter blocks can be individually energized. Next, the regeneration operation of the filter 3 will be explained below. Exhaust gas containing diesel particulates discharged from the diesel engine 1 passes through the filter 3, the diesel particulates are collected in the filter section 34, and clean exhaust gas is discharged into the atmosphere. and,
When diesel particulates accumulate on the filter 3, the pressure loss in the filtration part 34 increases, so the power supply electrode member 13b
1, 13b2, 13b3, 13b4 and ground electrode member 13
A and heat each filter 3 by passing electricity between the
The gel particulate is incinerated and the filter 3 is regenerated.

The method of energization control is shown in the block diagram of FIG. 7 and in FIG.
The explanation will be given with reference to the energization waveform diagram of and the flowchart of FIG. As can be seen from FIG. 7, switching of energization to each filter block is performed by the power supply electrode members 13b1, 13b2,
This is done by connecting one of 13b3 and 13b4 to the high-level electrode terminal H of the battery 14, and this connection is made by connecting the ECU 5.
This is done by sending a control signal to the heater relay 6 to selectively make one electromagnetic switch in the heater relay 6 conductive.

First, input the rotation speed signal from the rotation speed sensor and count it (100), and check whether the count value has reached a threshold rotation value (for example, 100,000 rotations) built in the backup ram in advance. Further, it is checked whether the current engine speed is equal to or higher than the idle speed (for example, 700 rpm or higher) (101). If the threshold rotation value is reached and the current engine rotation speed is equal to or higher than the idle rotation speed, it is assumed that the regeneration condition is satisfied and the process proceeds to step 102; if the regeneration condition has not been reached, the process returns to the main routine of the ECU 5.

At 102, first, the power supply electrode member 13
Start energizing b1 and wait for a predetermined time T1 (1
04). During this time, the first filter block (first row of filter members 31) is heated, and the diesel particulates on this first filter block are incinerated. Next, power supply to the power supply electrode member 13b1 is cut off, power supply to the power supply electrode member 13b2 is started (106), and the process waits for a predetermined time T2 (108). During this time, the second filter block (second row of filter members 31) is heated,
Diesel particulates on this second filter block are incinerated.

Next, power supply to the power supply electrode member 13b2 is cut off, and power supply to the power supply electrode member 13b3 is started (110
) and waits for a predetermined time T3 (112). During this time,
Third filter block (third row filter member 31)
is heated, and the diesel particulates on this third filter block are incinerated. Next, power supply to the power supply electrode member 13b3 is cut off, power supply to the power supply electrode member 13b4 is started (114), and a predetermined time T4 is waited (
116). During this time, the fourth filter block (third row of filter members 31) is heated, and the diesel particulates on this fourth filter block are incinerated.

[0033]The above-mentioned energization times T1, T2, T3, T
4 is determined in advance by experimentally determining the time required for the collected particulates to be burned away. For example, when regenerating the second, third, and fourth filter blocks, they are preheated by the heat generated during the previous filter block regeneration, so setting the energization times T2, T3, and T4 short will prevent wasteful power consumption. can do.

Note that the reproduction order of each filter block is as follows:
The beginning may be 1st → 2nd → 3rd → 4th, the next time may be 2nd → 3rd → 4th → 1st, and the successive times may be 3rd → 4th → 1st → 2nd. In this case, each block Since the average energization time is equalized, reliability is improved. Furthermore, the regeneration conditions for the filter 3 may take into account the magnitude of the engine load, the exhaust gas temperature, etc., in addition to parameters such as the rotational speed of the engine 1 or the travel distance.

According to experiments, the regeneration time of the filter 3 is such that 25g of particulates can be collected per total filter volume in a regeneration environment where the exhaust gas emission amount is equivalent to idling and the oxygen concentration of the exhaust gas is 10% or more. When I did, 2K
The process was completed in about 60 to 180 seconds by energizing W. (Example 2) Another example of the present invention will be described below. However, components having the same functions as those in the first embodiment are given the same reference numerals.

However, in this embodiment, as shown in FIG.
The heater relay 6 is composed of four common emitter power transistors 61 to 64, and therefore, in this case, the power supply electrode members 13b1 to 13b4 are on the low end side, and the electrode member 13a is on the high end side. First, input the rotation speed signal from the rotation speed sensor and count it (
200), check whether the count value has reached a threshold rotation value (e.g. 100,000 revolutions) built in the backup ram in advance, and further check whether the current engine revolution speed is equal to or higher than the idle revolution speed (e.g. 700 rpm or higher). Check whether it is (
202). If the threshold rotation value is reached and the current engine rotation speed is equal to or higher than the idle rotation speed, it is assumed that the regeneration condition is satisfied and the process proceeds to step 204. If the threshold rotation value has not been reached, the ECU
Return to the main routine of step 5.

At 204, first, the power supply electrode member 13
Start energizing b1 and wait for a predetermined time T1 (2
06). During this time, the first filter block (first row of filter members 31) is heated, and the diesel particulates on this first filter block are incinerated. Note that the base of the power transistor 61 is
A pulse current with a predetermined duty ratio is supplied to the power supply electrode member 13b1, and a predetermined average voltage V1 is applied to the power supply electrode member 13b1.

Next, the remaining power supply electrode members 13b2, 13b
3. Start energizing 13b4 (208), and wait for a predetermined time T.
2 (210). During this time, the second, third, and fourth filter blocks (the second, third, and fourth rows of filter members 31) are heated, and the diesel particulates on these filter blocks are incinerated. In addition, the second
In the case of regenerating the third and fourth blocks, these filter blocks are preheated by the heat generated during regeneration of the first block, so the current flowing can be reduced and the time required for regeneration can be shortened. Can be done. For this,
What is necessary is to further reduce the duty ratio of the pulse current flowing through the bases of the power transistors 62, 63, and 64 to reduce the average voltage applied to each filter block.

Further, in this case, the power transistor 62,
By preventing the conduction periods of 63 and 64 from overlapping as much as possible, the maximum current flowing can be reduced. Of course, even in this case, the filter blocks that are individually energized can be changed as appropriate. Furthermore, in step 208 described above, the power supply to the power supply electrode member 13b1 may be cut off.

[Brief explanation of the drawing]

FIG. 1: Overall diagram of the exhaust gas treatment device of Example 1,

[Figure 2
] Longitudinal cross-sectional view of the filter,

FIG. 3 is a perspective view of a pair of upper and lower filter members;

FIG. 4 is a cross-sectional view of the filtration part of the filter member;

[Fig. 5] Partially enlarged back view of the filter member assembly seen from the upstream side;

FIG. 6 is a front view of the filter member assembly seen from the downstream side;

[Figure 7] Block diagram showing the electrical system,

[Figure 8] Voltage waveform diagram showing energized voltage waveform

FIG. 9 is a flowchart showing the control operation of the first embodiment;

FIG. 10 is a block diagram showing the electrical system of Example 2,

[Fig. 11] Voltage waveform diagram showing the energizing voltage waveform of Example 2

FIG. 12 is a flowchart showing the control operation of Embodiment 2;

[Explanation of symbols]

Claims (1)

[Claims] 1. A conductive self-heating filter having a large number of small holes for collecting diesel particulates in exhaust gas and disposed in an exhaust path of a diesel engine; - energization control means for controlling the current supplied to the self-heating filter for incineration of gel particulates, the self-heating filter being divided into a plurality of filter blocks electrically insulated from each other, and 2. An exhaust gas treatment device for a diesel engine, wherein the energization control means sequentially energizes each filter block at predetermined time intervals to incinerate accumulated diesel particulates during filter regeneration.