JPH04347316A - 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 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 itself, heating this filter 3up to an ignition temperature of the particulate for incineration. Especially in this invention, the current-energizing control means 5, 6 abate the extent of energized power in the case where this exhaust gas temperature is high on the basis of the exhaust gas temperature out of an exhaust gas temperature detecting means 15.

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. 59-194021 discloses a particulate trap for collecting diesel particulates discharged from a diesel engine, etc., and a particulate trap for combusting the collected diesel particulates. A burner that supplies oxygen-containing high-temperature gas to the trap.
(ignition means), further detecting the temperature downstream of the trap, and controlling the supply amount of the oxygen-containing high temperature gas based on this temperature signal.

[0003] JP-A-63-57811 discloses a particulate trap that collects diesel particulates discharged from a diesel engine, etc., and a particulate trap that reduces the temperature of the exhaust gas by restricting the flow rate of the exhaust gas passing through this trap. A valve device that raises the collected diesel particulates and thereby ignites and spreads the fire, and a control section that detects various operating conditions and opens and closes the valve device during regeneration to maintain the temperature of the exhaust gas flowing into the trap at a desired level. An exhaust gas treatment device is disclosed.

JP-A-63-212713 discloses a particulate trap for collecting diesel particulates discharged from a diesel engine, etc., and a catalyst for combusting the collected diesel particulates. A particulate ignition means for dispersing liquid into the exhaust gas, an exhaust gas temperature detection means for detecting the exhaust gas temperature, and an auxiliary fuel supplied into the exhaust gas to assist ignition when the detected exhaust gas temperature is low. Disclosed is an exhaust gas treatment device including an ignition assisting means.

[0005] Japanese Patent Laid-Open No. 2-256813 discloses a particulate trap for collecting diesel particulates discharged from a diesel engine, etc., and a heat source for burning the collected diesel particulates. an ignition means such as a burner, an air supply means for introducing air into the trap during regeneration, a temperature detection means for detecting the trap inlet temperature, and a control for controlling the amount of introduced air based on the trap inlet temperature. Disclosed is an ignition spread type exhaust gas treatment device comprising means.

[0006]

[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 problem is 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.

[0007] Furthermore, according to the above-mentioned prior art, in which the exhaust gas inflow into the trap is restricted by a valve device to raise the exhaust gas temperature, thereby igniting the collected diesel particulates, the exhaust gas itself serves as the ignition energy source. However,
To do this, the exhaust gas itself must be heated to a fairly high temperature. In addition, there was a drawback that the control configuration was also complicated. In addition, the catalyst liquid is dispersed in the exhaust gas to create diesel particulates.
According to the above-mentioned prior art technique for starting the oxidation (ignition) reaction of catalyst, there is a problem that requires complicated catalyst liquid processing control.

In view of these problems, the applicant first constructed a filter from a porous conductive material (for example, porous metal), heated the filter to the ignition temperature by applying electricity to the filter itself during regeneration, and the filter itself 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 has almost reached the ignition temperature at the time of ignition, so there is no unburned residue or
It has been confirmed that it burns reliably even with a small amount of accumulated diesel particulates, and because the filter can be constructed from materials such as high-strength metal, its durability against heat stress is much better than that of conventional ceramic filters. Ta.

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. Furthermore,
A porous metal filter is usually used as the above self-heating filter, but although this type of metal filter is more resistant to cracking than ceramic filters, it has lower heat resistance, so it cannot be heated excessively during diesel particulate combustion. At high temperatures, various problems such as plastic deformation could occur even if the material did not melt.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the required power and promote the practical use of a self-heating filter type exhaust gas treatment device.

[0011]

[Means for Solving the Problems] An exhaust gas treatment device for a diesel engine according to the first invention has a large number of small holes for collecting diesel particulates in the exhaust gas.
a conductive self-heating filter disposed in an exhaust path of a diesel engine; an energization control means for controlling current flowing to the self-heating filter for incinerating the diesel particulates; and the self-heating filter. exhaust gas temperature detection means for detecting an exhaust gas temperature on the upstream side, and the energization control means controls the energization current according to the exhaust gas temperature on the upstream side of the self-heating filter. There is.

The exhaust gas treatment device for a diesel engine according to the second invention has a large number of small holes for collecting diesel particulates in the exhaust gas, and is arranged in the exhaust path of the diesel engine. an electrically conductive self-heating filter provided therein, an energization control means for controlling current flowing to the self-heating filter for incinerating the diesel particulates, and detecting the exhaust gas temperature downstream of the self-heating filter. The exhaust gas temperature detection means is characterized in that the energization control means controls the energization current according to the exhaust gas temperature downstream of the self-heating filter.

The exhaust gas treatment device for a diesel engine according to the third aspect of the invention has a large number of small holes for collecting diesel particulates in the exhaust gas, and is arranged in the exhaust path of the diesel engine. a conductive self-heating filter provided therein, an energization control means for controlling current flowing to the self-heating filter for incinerating the diesel particulates, and a flow rate of gas flowing into the self-heating filter; gas flow rate detection means, and the energization control means controls energization to the self-heating filter in accordance with the detected gas flow rate.

The exhaust gas treatment device for a diesel engine according to the fourth aspect of the invention has a large number of small holes for collecting diesel particulates in the exhaust gas, and is arranged in the exhaust path of the diesel engine. a conductive self-heating filter provided therein; an energization control means for controlling the current flowing to the self-heating filter in order to incinerate the diesel particulates; It is characterized by comprising a gas flow rate adjustment means for adjusting the flow rate of gas flowing in.

[0015] The self-heating filter can be made of a metal material or a conductive ceramic material.

[0016]

[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, these currents or gas flow rates are adjusted depending on the exhaust gas temperature and the gas flow rate flowing into the self-heating filter. Therefore, when the exhaust gas temperature is high or the gas flow rate is low, the applied current can be reduced to reduce power consumption and prevent the filter temperature from rising excessively. Furthermore, when the gas flow rate is large, the gas flow rate is reduced to prevent the filter temperature from rising excessively.

[0018] As a result, it is possible to reduce power consumption and improve filter durability in a self-heating filter type exhaust gas treatment device, and as a result, it is possible to reduce power consumption and improve filter durability.
It has excellent properties such as being able to consistently achieve good incineration depending on the amount of particulate deposits, and being much stronger than ceramic filters, making it less likely to break due to temperature changes or variations in temperature distribution during the combustion cycle. It is possible to promote the practical use of self-heating filters having a self-heating filter.

Further, the effects of each invention will be explained. In particular, in the first aspect of the present invention, during filter regeneration, the applied current is controlled according to the exhaust gas temperature on the upstream side of the self-heating filter. In this way, when the exhaust gas temperature is high and the filter temperature increase due to self-heating is small and ignition is possible, the current applied can be reduced, reducing the burden on the vehicle power supply unit, engine, etc. be able to.

In particular, in the second aspect of the present invention, during filter regeneration, the applied current is controlled in accordance with the exhaust gas temperature on the downstream side of the self-heating filter. In this way, before ignition, the same effect as the first invention can be achieved, and after ignition, when the exhaust gas temperature during diesel particulate combustion is high, power saving and excessive rise in filter temperature can be achieved. It can be prevented.

In particular, in the third aspect of the invention, the applied current is controlled in accordance with the gas flow rate passing through the filter. In this way, when the gas flow rate is low and less heat is removed from the filter, the current applied can be reduced, and the burden on the vehicle power supply device, engine, etc. can be reduced.

In particular, in the fourth invention, the flow rate of gas passing through the filter is adjusted to prevent undesired fluctuations in filter temperature due to fluctuations in the flow rate of combustion gas. In this way, when the gas flow rate is high, it can be throttled down to save filter heating power, while when the gas flow rate is low and there is a concern that the filter temperature will rise excessively, the gas flow rate can be increased. You can prevent it.

[0023]

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 engine control. It receives the rotational speed signal, accelerator opening signal, and water temperature signal, and also receives the exhaust gas temperature signal from the exhaust gas temperature sensor 15, determines the regeneration timing of the filter 3 based on these signals, and also controls the control module (described later) during regeneration. - The driver 6 is controlled intermittently in the - mode. The driver 6 supplies power supplied from the battery 14 to the filter member 31, and the filter unit 34
heat up.

Here, the ECU 5 and the driver 6 constitute energization control means according to the present invention. An exhaust gas temperature sensor (exhaust gas temperature detection means in the present invention) 15 is disposed in the outer cylindrical portion 30 on the upstream side of the filter member 31, and detects the exhaust gas temperature and outputs it to the ECU 5. A vertical 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.
Two electrically insulating fixing members 40 and 41 are disposed inside the outer cylinder 30 at a predetermined interval in a direction perpendicular to the axis of the outer cylinder 30. A total of 40 filter members 31 are supported at both ends by these fixing members 40 and 41, arranged in 4 horizontal rows and 10 vertical rows.
arranged in tiers. 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).

Furthermore, the outer end of the electrode member 13a is connected to the battery 1.
It is connected to the high-level electrode terminal H of No. 4, and the electrode member 13b
Its outer end is connected to the collector of a driver 6 consisting of a power transistor, and its emitter is connected to the lower electrode terminal L of the battery 14. FIG. 3 shows a perspective view of two vertically adjacent filter members 31, 31 in FIG.
A cross-sectional view taken along line AA is shown in FIG.

Each of the filter members 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.

[0030] 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 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 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.

[0037] 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 arranged in 10 columns and one row in the horizontal direction 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 method of controlling the energization will be explained with reference to the flowchart of FIG. First, an engine rotation speed signal, an accelerator opening signal, and a water temperature signal are read from an engine rotation speed sensor, an accelerator opening sensor, and a water temperature sensor (not shown) (10
0), it is determined whether the filter 3 should be regenerated based on these signals (102). This step 102
To explain in more detail, the amount of diesel particulates deposited is the integral value of the amount emitted from the engine, and the amount of diesel particulates emitted per engine revolution is correlated with the accelerator opening degree and water temperature (engine temperature). have a relationship. Therefore, by storing the correlation between the accelerator opening degree and water temperature (engine temperature) in the memory in advance as a map, diesel particulate emissions can be calculated based on the input accelerator opening degree and water temperature. The amount of diesel particulates discharged can be estimated, and by multiplying this amount of diesel particulates by a predetermined coefficient, the amount .DELTA.P of accumulated diesel particulates per engine revolution can be estimated. Furthermore, by integrating this ΔP for each input engine revolution, it is possible to estimate the cumulative amount of accumulated diesel particulates ΣP. On the other hand, the accumulated diesel particulate cumulative amount value (threshold) Pth for starting filter regeneration is stored in advance in the memory, and in step 102, if the calculated ΣP is equal to or greater than Pth, the current The engine speed is higher than the idle speed (e.g. 700r)
pm or higher), and if ΣP is higher than Pth and the current engine speed is higher than the idle speed,
It is assumed that the regeneration condition is satisfied and the process proceeds to 104, and if the regeneration condition is not satisfied, the process returns to the main routine of the ECU 5.

At 104, the exhaust gas temperature is input from the exhaust gas temperature sensor 15, and the energizing voltage value is determined in accordance with the exhaust gas temperature (106). Here, the temperature of the exhaust gas flowing into the filter member 31 is the power required to ignite after a predetermined time from the start of energization (referred to as required ignition power).
Therefore, if this correlation is stored in advance as a map in memory and the required power is determined based on the input exhaust gas temperature, ignition can be ignited a predetermined time after the start of energization. Note that since the filter member 31 is a resistive load and the battery voltage is approximately constant, the required power is proportional to the square of the applied voltage. Therefore, in this embodiment, the relationship between the exhaust gas temperature and the applied voltage is used as a map. The required applied voltage value is searched from this map.

Next, energization of the filter member 31 is started using the searched applied voltage value (108). The applied voltage value is controlled by adjusting the duty ratio of the pulse current supplied to the base of the driver 6. Next, the exhaust gas temperature is detected again (110), the applied voltage value is controlled according to the detected exhaust gas temperature (112), and it is checked whether the energization time has reached a predetermined time (114). If not, the process returns to 110, and if it has been reached, the power supply is cut off (116) and the routine ends.

As explained above, according to this embodiment,
Since the applied voltage value during regeneration is controlled based on the exhaust gas temperature detected upstream of the filter member 31, when the exhaust gas temperature is high, the supplied power can be reduced to save power and prevent the filter temperature from rising too high. Can be done. FIG. 6 shows an example of a map of exhaust gas temperature and applied voltage values. (Modification) In the above embodiment, the supplied power was adjusted by controlling the pulse duty ratio of the applied voltage value, but the applied voltage value may be kept constant and the energization time may be controlled, or both may be controlled to provide the supplied power. may be controlled.

(Embodiment 2) 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 (FIG. 2) differs in that the exhaust gas temperature sensor 15 is disposed downstream of the filter member 31 and in the method of controlling energization.

FIG. 8 shows the method of energization control in this embodiment.
This will be explained with reference to the flowchart. First, an engine rotation speed signal, an accelerator opening signal, and a water temperature signal are read from an engine rotation speed sensor, an accelerator opening sensor, and a water temperature sensor (not shown) (200), and based on these signals, it is determined whether or not the filter 3 should be regenerated. It is determined (202).

Step 202 is step 10 of the first embodiment.
Same as 2. If the regeneration conditions are satisfied, the current is applied at a predetermined initial applied voltage value (here, the duty ratio is 1), and the exhaust gas temperature t is input from the exhaust gas temperature sensor 15 (20
8), it is detected whether the exhaust gas temperature t has become equal to or higher than a predetermined threshold temperature t1 (210). Here, the temperature of the exhaust gas flowing out from the filter member 31 (filter downstream gas temperature) t increases as shown in FIG. 9 when constant current is applied.

This threshold temperature t1 is the diesel particulate ignition temperature, and is set to a constant value in this embodiment. Of course, it is also possible to detect various operating parameters and change the threshold temperature t1 based on the data. At 210, if the exhaust gas temperature t is lower than a predetermined threshold temperature t1, the process returns to 208, and if it is above, the average applied voltage value is controlled according to the exhaust gas temperature t (212
). Control is performed by controlling the pulse duty ratio of the driver transistor 6 in the same manner as in the first embodiment. To explain further, after ignition, the exhaust gas temperature increases due to the heat generated by combustion, so even if the supplied power is reduced by that amount, combustion can be maintained at an appropriate level. In this embodiment, after this ignition, enough power to maintain combustion at a predetermined combustion speed (combustion maintenance power) is supplied to the filter member 31, and the exhaust gas temperature at that time (filter downstream gas temperature) t2
is controlled to be constant at a desired level (see FIG. 9). Note that the applied voltage value may be reduced from the time when the exhaust gas temperature t reaches the desired temperature t2, but in this embodiment, the exhaust gas As the temperature t increases,
That is, the rate of temperature rise after ignition is suppressed to reduce thermal stress in each part of the filter.

Thereafter, it is checked whether a predetermined time has elapsed since the start of energization (214), and if it has not elapsed, the process returns to step 208.
When the time has elapsed, the current supply is stopped (216), and the routine ends. As explained above, according to this embodiment, since the applied voltage value during regeneration is controlled based on the exhaust gas temperature detected downstream of the filter member 31, power consumption after the start of ignition is reduced, and Excessive rise in filter temperature can be prevented.

(Embodiment 3) Another embodiment of the present invention is shown in FIG.
Explain with reference to. This exhaust gas treatment device differs from the device of Example 1 (FIG. 2) in that the exhaust gas temperature sensor 15 is omitted and in the method of controlling energization. The method of energization control 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 met, the engine speed and accelerator opening are read (304), and the exhaust gas flow rate is detected based on the read engine speed and accelerator opening (306). Here, since the exhaust gas flow rate has a correlation with the engine speed and the accelerator opening,
The relationship between the exhaust gas flow rate, the engine rotation speed, and the accelerator opening degree may be stored as a map or a function in a memory, and the exhaust gas flow rate may be searched or calculated from the read engine rotation speed and accelerator opening degree.

Next, the energization time is set based on the determined exhaust gas flow rate (308), and the energization is performed for the set energization time (310). To explain in more detail, when the exhaust gas flow rate is large, the gas removes heat from the filter member 31, so if the current is constant, the time required to ignite and the time required from ignition to the end of regeneration are as follows. In the opposite case, the total required time is shortened. Therefore, when the exhaust gas flow rate is small, it is possible to reduce the applied current (duty ratio of applied voltage), reduce power consumption, and prevent excessive rise in filter temperature.

FIG. 12 shows a map showing the relationship between the exhaust gas flow rate and the energization time determined through experiments. (Embodiment 4) Another embodiment of the present invention will be described with reference to FIG. This exhaust gas treatment device is the same as the device of Example 3 (FIG. 10), except that pressure sensors 41 and 42, an exhaust gas temperature sensor 43, and an aperture 44 are provided on the upstream side of the filter member 31 (on the left side in FIG. 13). The difference is in the points and the method of energization control.

[0052] The throttle 44 narrows the cross-sectional area of the outer cylindrical portion 30, and therefore a pressure difference is generated before and after the throttle 44. Pressure sensors 4 separately provided upstream and downstream across the throttle 44
The detected pressures of 1 and 42 are P1 and P2, and the exhaust gas temperature is T.
If so, the inflow gas amount Q is approximately proportional to (P1-P2)/T. Therefore, the gas flow rate P is defined as the differential pressure P1-P2 and the gas temperature T.
The exhaust gas flow rate is calculated by interpolation calculation from the input differential pressure P1-P2 and gas temperature T. In this way, there is an advantage over the third embodiment that the same map value can be used regardless of engine specifications (displacement, etc.).

FIG. 1 shows the energization control method in this embodiment.
This will be explained with reference to the flowchart No. 4. First, it is determined whether the regeneration conditions are satisfied using the same method as steps 100 and 102 of Example 1 (400, 402), and if the regeneration conditions are satisfied, the pressures P1, P2 and exhaust gas temperature T are read (404). , the exhaust gas flow rate is searched from the map based on the read pressures P1, P2 and exhaust gas temperature T (406).

Next, the energization time is set based on the determined exhaust gas flow rate (408), and the energization is performed for the set energization time (410). In this way, the same effects as in the third embodiment can be achieved. (Example 5) Another example of the present invention will be described below.

This exhaust gas treatment device differs from the device of Example 3 (FIG. 10) in the method of energization control. The energization control method in this embodiment will be explained with reference to the flowchart of FIG. First, it is determined whether the regeneration conditions are satisfied using the same method as steps 100 and 102 of the first embodiment (500, 502), and if the regeneration conditions are satisfied, the engine speed and accelerator opening are read (500, 502).
504), the exhaust gas flow rate is detected based on the read engine speed and accelerator opening (506). The steps up to this point are the same as those up to step 306 of the third embodiment.

Next, the pulse duty ratio of the applied voltage is determined according to the detected exhaust gas flow rate (508), and the switching of the driver transistor 6 is controlled using the determined pulse duty ratio (510). When the exhaust gas flow rate is large, the required power is large, so it is necessary to set a large pulse duty ratio, and when the exhaust gas flow rate is small, the required power is small, so it is necessary to set the pulse duty ratio small. In this case as well, the relationship between the exhaust gas flow rate and the pulse duty ratio of the applied voltage may be stored in advance in the memory and then searched.

Next, it is checked whether the energization time has reached a predetermined energization time value (512), and if it has not reached the predetermined energization time value, 504
If the value has been reached, the energization is cut off and the routine ends (514). In this way, the power supply can be adjusted moment by moment according to subtle changes in the gas flow rate during regeneration, reducing power consumption even when the exhaust gas flow rate changes significantly due to sudden changes in operating conditions. Moreover, excessive rise in filter temperature can be prevented.

(Example 6) Another example of the present invention is shown in FIG.
This will be explained below with reference to FIG. In this exhaust gas treatment device, two filters 3a and 3b are arranged in parallel in the device of Embodiment 1 (FIG. 2), and a flow control valve 8 for controlling the flow of exhaust gas is provided at the upstream connection portion thereof. , and the negative pressure control valve 7 that drives this branch control valve 8 is controlled by the ECU.
It is controlled by

That is, by controlling the pulse duty ratio of the negative pressure control valve 7, which is a proportional solenoid valve, the negative pressure value sent to the diaphragm portion 81 of the flow dividing control valve 8 is controlled, and the flow is divided depending on the state of the diaphragm portion 81. The angle of the rotary valve body 80 of the control valve 8 is adjusted. Then, only the necessary amount of the exhaust gas flowing out from the engine is supplied to the filter being regenerated, and the remainder of the exhaust gas is processed by the other filter.

Naturally, in this embodiment the filters 3a, 3b are regenerated alternately, so that the driver 60 has two power transistors. Here, the negative pressure control valve 7 and the branch control valve 8 constitute a gas flow rate adjusting means in the present invention. Figure 18 shows the method of gas flow rate control in this example.
This will be explained with reference to the flowchart.

First, it is assumed that the branch control valve 8 is operated with the filter 3a side closed and the filter 3b side open. Here, it is determined whether the reproduction conditions are satisfied using the same method as steps 100 and 102 of the first embodiment (600,
602), if the regeneration conditions are satisfied, the flow control valve 8 is controlled to open the filter 3a side and close the filter 3b side to be regenerated (604), and energizes the filter 3b for a predetermined time (606, 608). ). It is assumed that this predetermined time is the time required to ensure that the accumulated diesel particulates reach the ignition temperature or higher, and that the diesel particulates are ignited.

Next, the engine speed and accelerator opening are read (610), the exhaust gas flow rate is calculated based on the read engine speed and accelerator opening, and the flow rate of the diverting control valve 8 is calculated based on the calculated exhaust gas flow rate. Calculate the opening degree of (
612), and adjusts the branch control valve 8 to the calculated opening degree (61
4), step 61 until the predetermined scheduled combustion time has elapsed.
0, and when the scheduled combustion time has elapsed, the energization is terminated and the branch control valve 8 is fully closed.

This completes the regeneration of the filter 3b, but after the start of the regeneration of the filter 3b, the filter 3a is used to collect diesel particulates. Dee
The flow rate of oxygen in the exhaust gas of a diesel engine is usually larger than the flow rate of oxygen required for filter regeneration, so when burning diesel particulates at a predetermined combustion rate, reducing the flow rate of the exhaust gas can reduce the amount of power used. can. In this embodiment as well, a three-dimensional map of engine speed, accelerator opening and exhaust gas flow rate is stored in memory, and the exhaust gas flow rate is searched from this map.

FIG. 19 shows the relationship between the opening degree of the branch control valve 8, the exhaust gas flow rate, and the energizing voltage. In this way, the exhaust gas is shut off until ignition, and ignition is performed using the minimum amount of electricity.
After ignition, combustion is performed with a small exhaust gas flow rate, so
It is possible to save electricity. (Example 7) Another example of the present invention will be described below.

In this exhaust gas treatment apparatus, the method of controlling the gas flow rate (see FIG. 18) in Embodiment 6 is changed. Figure 2 shows the method of gas flow rate control in this example.
This will be explained with reference to the flowchart of No. 0. First, it is assumed that the flow dividing control valve 8 is set to the neutral position, and normal operation is performed with exhaust gas flowing through both the filters 3a and 3b.

[0066] Here, steps 100 and 10 of the first embodiment
It is determined whether the regeneration conditions are satisfied using the same method as in 2 (700, 702), and if the regeneration conditions are satisfied, the shunt control valve 8 is controlled to open the filter 3a side, and the filter 3b side to be regenerated first is opened. is closed (704), filter 3b
The reproduction subroutine is executed (706). Note that this reproduction subroutine includes steps 606 to 616 in FIG.
It is the same as before.

Next, the filter 3b side is opened, the filter 3a side to be regenerated is closed (708), and a regeneration subroutine for the filter 3a is executed (710). This regeneration subroutine is also the same as steps 606 to 616 in FIG. 18, but the energization is naturally switched to the filter 3a. Then, the energization is ended, and the branch control valve 8 is returned to its original neutral position (712). .

[0068] In this way, diesel particulates can be collected by both filters 3a and 3b under normal conditions, so the exhaust gas pressure loss in the filters can be halved, improving engine performance. can be done. (Embodiment 8) Another embodiment of the present invention will be described below with reference to FIGS. 16 and 17.

In this exhaust gas treatment device, an air pump 50 is added to the device of Embodiment 6 (FIG. 17) so that air can be supplied to the part of the flow control valve 8, and the flow control valve 8 is connected to the exhaust gas It is designed to rotate so as to supply the air to the filter on the gas cutoff side. Therefore, in this embodiment, only air flows into the filter during regeneration to reduce the heat loss of the filter during regeneration.
This makes it possible to save power.

The method of controlling the gas flow rate in this embodiment will be explained with reference to the flowchart of FIG. First, it is assumed that the branch control valve 8 is operated with the filter 3a side closed and the filter 3b side open. Here, it is determined whether the regeneration conditions are satisfied using the same method as steps 100 and 102 of Example 1 (800, 802), and if the regeneration conditions are satisfied, the shunt control valve 8 is controlled to close the filter 3a side. open, and close the filter 3b side to be regenerated (804);
The filter 3b is energized for a predetermined time (806), the air pump 50 is activated (808), and the process waits until the predetermined time elapses, that is, until the regeneration ends (810). Thereafter, when the scheduled combustion time has elapsed, the energization is terminated, the air pump 50 is stopped, and the routine is completed.

[0071] This ends the regeneration of the filter 3b, but after the start of the regeneration of the filter 3b, the filter 3a is used to collect diesel particulates. In this embodiment, filter regeneration can be performed without using exhaust gas, resulting in large power savings. (Modification) Also in this Example 8, Example 7
Similarly, during non-regeneration, both filters 3a and 3b are used to collect diesel particulates, and regeneration can be performed in sequence, thereby reducing filter pressure loss.

[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 relationship diagram between applied voltage value and exhaust gas temperature in Example 1,

FIG. 7 is a block diagram of the exhaust gas treatment device of Example 2,

[
FIG. 8 is a flowchart showing the control operation of Embodiment 2;

[Fig. 9] Signal waveform diagram of applied voltage value and filter downstream gas temperature,

FIG. 10 is a block diagram of the exhaust gas treatment device of Example 3,

FIG. 11 is a flowchart showing the control operation of Embodiment 3;

FIG. 12 is a relationship diagram showing the relationship between energization time and gas flow rate,

FIG. 13 is a block diagram of the exhaust gas treatment device of Example 4,

FIG. 14 is a flowchart showing the control operation of Embodiment 4;

FIG. 15 is a flowchart showing the control operation of Example 5;

FIG. 16 is an overall view of the exhaust gas treatment device of Example 6,

FIG. 17 is a block diagram of the exhaust gas treatment device of Example 6,

FIG. 18 is a flowchart showing the control operation of Embodiment 6;

FIG. 19 is a diagram showing the relationship between the opening degree of the branch control valve, the exhaust gas flow rate, and the energizing voltage,

FIG. 20 is a flowchart showing the control operation of Example 7;

FIG. 21 is a block diagram of the exhaust gas treatment device of Example 8,

FIG. 22 is a flowchart showing the control operation of Example 8;

[Explanation of symbols]

Claims (4)

[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;
exhaust gas temperature detection means for detecting exhaust gas temperature upstream of the self-heating filter, and the energization control means:
An exhaust gas treatment device for a diesel engine, characterized in that the energizing current is controlled according to the exhaust gas temperature upstream of the self-heating filter. 2. 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;
and exhaust gas temperature detection means for detecting exhaust gas temperature on the downstream side of the self-heating filter, and the energization control means includes:
An exhaust gas treatment device for a diesel engine, characterized in that the energizing current is controlled according to the exhaust gas temperature downstream of the self-heating filter. 3. 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;
a gas flow rate detection means for detecting a gas flow rate flowing into the self-heating filter, and the energization control means controls energization to the self-heating filter according to the detected gas flow rate. Exhaust gas treatment equipment for diesel engines. 4. 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;
An exhaust gas treatment device for a diesel engine, comprising: a gas flow rate adjusting means for adjusting a gas flow rate flowing into the self-heating filter when the self-heating filter is regenerated.