JPH04347317A - Exhaust gas treatment system for diesel engine - Google Patents

Abstract

PURPOSE:To promote the practical use of a self-heating filter type exhaust gas treatmen system by preventing the extent of required electric power from generating while keeping off any over-rise in filter temperature at the time of regeneration. 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 driver 6 energize this self-heating filter 3 itself, heating this filter 3 up to an ignition temperature of the diesel particulate for incineration. Especially in this invention, a filter resistance value detecting means (low resistor 7 and ECU 5) detects or estimates the filter resistance value, and on the basis of the obtained filter resistance value, the extent of supply power for the filter 3 is controlled, through which any secular change in the resistance value is prevented from being affected to a variation in filter temperature.

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. 122216/1983 discloses a filter for collecting diesel particulates discharged from a diesel engine, etc., and a filter for collecting diesel particulates discharged from a diesel engine.
In an ignition and spread type exhaust gas treatment device equipped with a heater (igniting means) for burning particulates, a pair of heaters simultaneously generate heat when the battery voltage is high, and when the battery voltage is low, This disclosure discloses an energization control method that sequentially causes each heater to generate heat.

0003

[Problems to be Solved by the Invention] The above-mentioned ignition and spread type exhaust gas treatment device basically 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. The disadvantages are that if there is too much, the trap will become too hot and its durability will deteriorate, and the temperature distribution of each part of the trap may vary due to the positional relationship with the ignition means, which may cause the trap to crack. Ta.

[0004] In view of these problems, the applicant first constructed a filter using a porous conductive material (for example, porous metal), and during regeneration, the filter itself was heated to the ignition temperature by passing electricity through it. Diesel particulates deposited on the filter surface as a source of ignition energy.
He invented a self-heating filter that incinerates waste gas, and filed an application for an exhaust gas treatment device for a diesel engine equipped with this self-heating filter. According to this method, the entire filter reaches almost the ignition temperature at the time of ignition, so even if there is a small amount of diesel particulates, it will burn reliably, and the filter can be made of a material such as high-strength metal, which increases its durability against heat stress. It was confirmed that the filter was significantly better than conventional ceramic filters.

However, in this type of self-heating filter made of a material such as sintered metal, it has been impossible to avoid changes in its resistance value due to changes over time, particularly due to oxidation in a high temperature oxidizing environment during energization. As a result, if the resistance value increases over time, there is a possibility that diesel particulates may remain unburned even if a predetermined voltage is applied for a predetermined period of time. Of course, even in this case, it is possible to set the applied voltage and energization time with a margin from the beginning, but in that case, power consumption will be wasted before the resistance value increases, and the filter temperature will rise too much. There is a possibility that

On the other hand, when the resistance value decreases over time, when a predetermined voltage is applied for a predetermined period of time, the applied power increases in inverse proportion to the decrease in the resistance value, which may cause the filter temperature to rise excessively. . Furthermore, a porous metal filter is usually used for the above-mentioned self-heating filter, but this type of metal filter is more resistant to cracking than ceramic filters, but has lower heat resistance, so diesel particulate If the temperature becomes too high during combustion, various problems such as plastic deformation may occur even if the filter does not melt, so it is desirable to avoid the above-mentioned excessive rise in filter temperature.

[0007] Furthermore, 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, and it is desirable to avoid wasteful expenditure of power consumption. . The present invention has been made in view of the above-mentioned problems, and aims to promote the practical application of self-heating filter type exhaust gas treatment devices by reducing the required power and preventing excessive rise in filter temperature during regeneration. , that purpose.

[0008]

[Means for Solving the Problems] An exhaust gas treatment device for a diesel engine according to the present invention has a large number of small holes for collecting diesel particulates in the exhaust gas. an electrically conductive self-heating filter disposed in an exhaust path; an energization control means for controlling current to the self-heating filter for incinerating the diesel particulates; and a resistance value of the self-heating filter. filter resistance value detection means for detecting the energization control means;
In order to suppress fluctuations in the filter temperature due to changes in the resistance value over time, the energizing current is controlled based on a parameter related to the resistance value of the self-heating filter.

[0009] The self-heating filter can be constructed from a metal material or a conductive ceramic material.

0010

[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.

In the present invention, the filter resistance value detecting means detects or estimates the filter resistance value, controls the supplied power based on the obtained filter resistance value, and prevents changes in the resistance value over time from affecting fluctuations in the filter temperature. is prevented. That is, according to the present invention, it is possible to eliminate the waste of applying current more than necessary, thereby reducing power consumption and preventing excessive rise in filter temperature.

0012

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

On the other hand, an engine control unit (ECU) 5 including a microcomputer is provided for controlling the engine, and this ECU 5 receives an engine speed sensor (not shown) attached to the engine, and applies a filter based on the engine speed. 3, and furthermore, during the reproduction, the driver 6 is intermittently controlled in a control mode to be described later. The driver 6 connects the high-level electrode terminal H of the battery 14 with a low resistance 7 for current detection.
Electric power supplied through the filter 3 is supplied to the filter 3 to heat the filter section 34.

Here, the ECU 5 and the driver 6 constitute energization control means according to the present invention, and the low resistance 7 constitutes filter resistance value detection means according to the present invention. A vertical cross-sectional view of the filter 3 is shown in FIG. The filter 3 has a metal outer cylinder part 30 whose openings at both ends are connected to the exhaust pipe 2.
Two electrically insulating fixing members 40 and 41 are disposed within the outer cylindrical portion 30 at a predetermined interval in a direction perpendicular to the axis of the outer cylindrical portion 30. And these fixing members 40,
A total of 40 filter members 31 are supported at both ends by 41.
are arranged in 4 rows horizontally and 10 columns 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, a pair of electrode members 13a and 13b are provided in the outer cylindrical portion 30 at positions facing each other and insulated with an insulator, penetrating from the outside to the inside. The inner end of the electrode member 13a is connected to one end of the filter member 31 in the uppermost stage (first stage) in FIG.
They are individually connected to one end of the filter member 31 (first stage).

Further, the outer end of the electrode member 13a is connected to a high-level electrode terminal H of the battery 14 through a low resistance 7, and the outer end of the electrode member 13b is connected to the collector of a driver 6 consisting of a power transistor. Its emitter is connected to the lower electrode terminal L of the battery 14. FIG. 3 is a perspective view of two vertically adjacent filter members 31, 31 in FIG. 2, and FIG. 4 is a cross-sectional view taken along the line AA.

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 ends of the four filter sections 34 in total are 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 further explained with reference to FIG. 2. As shown in FIG. 2, 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. This fixing member has holes formed therein at predetermined intervals vertically and horizontally when viewed from the downstream side, and one filter portion 34 of each filter member 31 is inserted into each hole. As a result, the elongated holes 36a to 36d of each holding section 36, which become openings on the downstream side of each filtration section 34 (see FIG. 3)
is open on the downstream side of the fixing member 40.

Here, only one filter member 31 (that is, each pair of filtering parts 34, 34) is fixed to the holding parts 36x and 36y on the top and bottom floors in FIG. The electrode member 13b is connected to the floor holding portion 36x. On the other hand, the ground electrode member 13a is connected to the holding portion 36y on the lowest floor. The fixing member 40 is made of Fe-Cr
-Al-REM alloy, Cr is 18-24wt%, Al
is 15wt% or more, REM is 0.2% or more, and the balance is F.
After the filter member 31 is assembled, this alloy material is oxidized in the atmosphere at a temperature of 900° C. or higher for 0.5 to 20 hours to provide sufficient electrical insulation. An aluminum oxide-based insulating layer is formed.

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 43, are connected to different holding parts 36 through the filtering part 34, and as a result, the current flows between the electrode members 13b, Holding part 36
y, the filtration part 34, the connection part 35, the spacer 43, the upper connection part 35, the filtration part 34, and the like, flowing in a zigzag shape, and finally flowing from the holding part 36x to the ground electrode member 13a,
Each filter member 31 is heated equally.

This electrically conductive spacer 43 is also made of the same material as the connecting portion 35, and a rod portion protruding 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 an electrically insulating plate made of the same material as the fixing member 40, and is fixed to the inner surface of the outer cylinder portion 30. Below, a method for manufacturing the filter section 34 will be explained.

First, a lath metal material that will become the skeleton is processed into a wave shape parallel to the longitudinal direction by pressing or the like, and two sheets 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.
Weld to. 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.

[0025] 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-mentioned 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, where the diesel particulates are collected in the filtration section 34, and the clean exhaust gas passes through the muffler 4 into the atmosphere. is discharged. When diesel particulates accumulate on the filter 3, the pressure loss in the filter section 34 increases, so electricity is passed between the electrode members 13a and 13b to heat the filter 3 and incinerate the accumulated diesel particulates. Play 3.

The energization control method of this embodiment is shown in the flowchart of FIG.
This will be explained with reference to a chart. First, an engine speed signal is read from an engine speed sensor (not shown) (10
0), it is determined whether the filter 3 should be regenerated based on this signal (102). To explain this step 102 in more detail, since the amount of diesel particulate deposits is approximately proportional to the cumulative amount of engine rotation, the input engine rotation speed signal is integrated (counted) and this count value is stored in memory in advance. The predetermined cumulative rotation value (
If the engine speed reaches the idle speed (for example, 700 rpm or more), it is further determined whether the current engine speed is equal to or higher than the idle speed (for example, 700 rpm or higher), and if the count value is higher than the cumulative rotation value (threshold),
If the current engine speed is equal to or higher than the idle speed, it is assumed that the regeneration condition is satisfied, and the pulse duty ratio is set to 1.
energization is started (104), and then the filter resistance value is detected (106). This rule is used if the playback conditions are not met.
It bypasses the engine and returns to the main routine of ECU5.

[0028] Naturally, the above-mentioned counting is performed from the time when collection starts after the previous reproduction ends. Here, the filter resistance value is detected as follows. That is, battery 1
The terminal voltage of 4 is V, the resistance value of low resistance 7 is r, the filter 3
If the resistance value of is R and the voltage across low resistance 7 is Vr, then
The resistance RL of the filter 3 is RL=(V-Vr)×r/V
It becomes r. In this embodiment, the battery voltage V is not detected on the assumption that it is constant, but if the battery voltage V is actually measured, a more accurate filter resistance value RL can be obtained.

Note that it is also possible to short-circuit the low resistance 7 using a switch means at times other than when detecting the filter resistance value, and it is also possible to detect the current magnetically instead of using the above-mentioned low resistance 7. is also possible. Next, the switching of the driver transistor 6 is controlled using the duty ratio determined based on the detected filter resistance value.

It should be noted that supply power P and filter resistance value RL are inversely proportional if the battery voltage is constant;
Since the average value of is proportional to the energization time, the filter resistance value R
If electricity is applied at a duty ratio inversely proportional to L, the amount of heat generated can be made constant. Next, it waits until the energization time reaches a predetermined time (110), and when it reaches the predetermined time, the energization is cut off (
112), the routine ends.

As explained above, according to this embodiment,
Since the filter resistance value is detected and the supplied power is made constant based on it, even if the filter resistance value changes over time, its influence can be eliminated. In addition, in the filter member 31 described above, the resistance value decreases over time, that is, with use, due to the oxidation and precipitation of aluminum in the sintered metal constituting the filter part 34, so power consumption decreases with constant voltage energization. increases, causing the temperature of the filter member 31 to rise excessively. This problem is solved by this embodiment. (Embodiment 2) Another embodiment of the present invention will be described with reference to FIG.

In this exhaust gas treatment device, the low resistance 7 as the filter resistance value detection means is omitted from the device of the first embodiment (FIG. 2), and the engine speed detection means 8 and the ECU 5 are replaced by the present invention. This is the filter resistance value detection means. The energization control method in this embodiment will be explained with reference to the flowchart of FIG.

First, an engine rotation speed sensor (not shown),
Reads the engine rotation speed signal, accelerator opening signal, and water temperature signal from the accelerator opening sensor and water temperature sensor (200);
Based on these signals, it is determined whether the filter 3 should be regenerated (202). Steps 200 and 202 are the same as steps 100 and 102 in the first embodiment. If the regeneration conditions are met, then estimate the filter resistance value (
204).

Note that this determination is made in the following manner. In other words, since the filter resistance value has a certain correlation with the total cumulative value of engine revolutions (from the time when the filter started to be used), the relationship between the total cumulative value of the engine revolutions from the time when the filter started to be used and the filter resistance value can be calculated. It is sufficient to find it through experiments, load it into the memory as a map, and search for the filter resistance value from the map based on the total cumulative value ΣT of the current engine speed.

Next, based on the searched filter resistance value, a duty ratio is determined in the same manner as step 108 in FIG. 5 (206), pulse energization is started at this duty ratio (208), and the energization time ends. After that (210), the energization is ended (212) and the process returns to the main routine. In this way, the power loss due to the low resistance 7 of the first embodiment can be reduced, and the circuit configuration can be simplified.

(Embodiment 3) Another embodiment of the present invention will be described with reference to FIG. This exhaust gas treatment device is as follows: Example 1
The device shown in FIG. 2 (FIG. 2) is different in the energization circuit configuration and energization control method. The energizing circuit of FIG. 7 will be explained below.

Vehicle three-phase alternator (alternator) 1
00, a three-phase AC voltage is applied to the three-phase full-wave rectifier 200. The three-phase full-wave rectifier 200 is connected to the vehicle battery 30
0 and a vehicle load (not shown), and an S
It consists of a CR half bridge 202 and a lower diode half bridge 203. Here, the second power storage means 40
0 consists of a battery or a large capacity capacitor.

The positive ends of the vehicle battery 300 and the second power storage means 400 are individually connected to the filter 3 through SCRs (energization control means in the present invention) 500 and 600, respectively.
The filter 3 is connected to one end 13a of the filter 3, and the other end 13b of the filter 3 is grounded together with the anode of the lower diode half bridge 203. The energization control method in this embodiment will be explained with reference to the flowchart of FIG.

First, steps 100 and 102 of the first embodiment
Determine whether the playback conditions are met in the same way as (
300, 302), if the regeneration conditions are not satisfied, return to the main routine, and if they are satisfied, read the terminal voltage of the regeneration battery 400 (304), and check whether the read terminal voltage is above a predetermined value. (306), if the value is greater than or equal to the predetermined value, the SCR is turned on for a predetermined time (306).
08), energization is terminated.

That is, in this case, the regeneration battery 4
Assuming that the charge of 00 is sufficient, the regeneration battery 400
The filter 3 is regenerated only by the following steps. On the other hand, step 306
If the terminal voltage of the regeneration battery 400 is lower than the predetermined value, it is determined that charging is insufficient, and the SCRs 500 and 600 are energized simultaneously for a predetermined time (310), and the energization is ended (312).

In other words, in this case, the regeneration battery 4
00 is insufficiently charged, the regeneration battery 40
The filter 3 is regenerated using both the 0 and the vehicle battery 300. In this way, the normal reproduction battery 40
Since the vehicle battery 300 is not discharged when it is fully charged at zero, it is possible to eliminate the problem that the terminal voltage of the vehicle battery 300 decreases and the voltage applied to the vehicle load decreases.

[0042] Each SCR of the SCR half bridge 202 for charging the regeneration battery 400 is
It is also possible to detect when there is sufficient engine output and selectively turn on the engine only at that time. (Modification 1) A modification of the above embodiment will be explained below.

In the above embodiment, when the regeneration battery 400 is insufficiently charged, the regeneration battery 400 and the vehicle battery 300 are energized at the same time. First, the regeneration battery 400 is energized for a predetermined period of time. Then, the vehicle battery 300 may be discharged. (Modification 2) Another modification is shown in FIG. The circuit of FIG. 9 is the circuit of FIG. 7 except that the high-order side diode half bridge 201 is replaced by an SCR half bridge 200. The charging control method in this embodiment will be explained with reference to the flowchart of FIG.

First, the terminal voltage of the vehicle battery (hereinafter also referred to as conventional battery) 300 is detected (400), and if the terminal voltage of the vehicle battery 300 is lower than a predetermined level, the process proceeds to 410, and the SCR half bridge 200 is activated. Turn on and selectively charge the vehicle battery 300. on the other hand,
If the terminal voltage of the vehicle battery 300 is equal to or higher than a predetermined value in step 402, the terminal voltage of the regeneration battery 400 is detected (406), and if the terminal voltage of the regeneration battery 400 is equal to or higher than a predetermined level, the process proceeds to step 410; SC if the terminal voltage of the regeneration battery 400 is lower than a predetermined level.
The R half bridge 202 is turned on to selectively charge the regeneration battery 400.

[Brief explanation of drawings]

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

[Figure 2
]Block diagram of the exhaust gas treatment device of Example 1,

[Figure 3]
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 is a flowchart showing the control operation of the first embodiment;

FIG. 6 is a flowchart showing the control operation of Embodiment 2;

FIG. 7 is a circuit diagram showing the energizing circuit configuration of Example 3;

FIG. 8 is a flowchart showing the control operation of Embodiment 3;

FIG. 9 is a circuit diagram showing a modification of Example 3;

[
FIG. 10 is a flowchart showing a control operation in a modified form of Embodiment 4;

[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 energization current to the self-heating filter in order to incinerate the gel particulates;
filter resistance value detection means for detecting a resistance value of the self-heating filter; An exhaust gas treatment device for a diesel engine, characterized in that the energizing current is controlled based on a parameter related to the energizing current.