JPH05106428A - Dual filter type exhaust emission control device - Google Patents

Abstract

PURPOSE:To accomplish a leveling of regenerating conditions of the filters in a dual filter type exhaust emission control device. CONSTITUTION:In this dual filter type exhaust gas purifying device, all amount of the exhaust gas is by passed by a bypass passage 11 when a filter is regenerated. And in a filter regenerating time, while two filters 2 and 3 are regenerated continuously, the regenerating order of the filters is alternately changed at every regeneration. Or only one filter is regenerated in the filter regenerating time, and the filters to be regenerated are alternately changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device provided in an internal combustion engine, and more particularly to a so-called dual filter type exhaust gas purification device in which two filters for collecting diesel particulates discharged from a diesel engine are arranged in parallel. ..

[0002]

2. Description of the Related Art For example, exhaust gas of a diesel engine contains a large amount of exhaust particulates, that is, particulates. Therefore, the exhaust system of the engine has a particulate filter (hereinafter referred to as a filter) for collecting the particulates. Called) is installed.

Further, in this filter, if the amount of particulates accumulated inside the filter increases with use, the air permeability is gradually deteriorated and the engine performance deteriorates. Therefore, depending on the particulate collection amount. It is played back regularly.

By the way, in the exhaust gas purification apparatus having the above-mentioned filter, in order to improve the performance of collecting particulates, a so-called dual filter in which one exhaust pipe is branched and the filters are arranged in parallel inside each other. Type exhaust emission control device is known, and the applicant of the present application has previously described an electric heater as a regeneration means in order to reduce filter regeneration variation at the time of filter regeneration in connection with the dual filter type exhaust emission control device. We have applied for an exhaust gas purification device that keeps the power supplied to the electric air pump and the electric air pump (Patent application 3
-21078).

[0005]

SUMMARY OF THE INVENTION The above exhaust purification device is
A bypass passage is provided for bypassing the filter with respect to the exhaust passage, and at the time of filter regeneration, two filters are sequentially regenerated for each filter regeneration while the exhaust gas is completely bypassed. Filter regeneration processing is in progress.

However, in such a regeneration method, as shown in FIG. 6 in which the maximum temperature of each filter is plotted, the remaining temperature remains during the regeneration period of the first filter (which will be called filter A). Since exhaust gas does not flow through the filter (also referred to as filter B), the filter B cools in this regeneration standby stage, and even if the filter B is regenerated, it is difficult for particulate combustion to propagate, and a specific portion of the filter A defective regeneration portion, that is, a particulate unburned residue, tends to occur (for example, near the outer periphery of the filter end portion away from the electric heater).

Since the filter reproduction order for each reproduction between the two filters is conventionally fixed,
If regeneration and collection are repeated in a state where it is easy for residual particulate matter to remain in the same filter B at all times,
If a particulate trapped distribution is gradually biased inside the filter B, and if the particulate trapped excess portion burns at once during filter regeneration, the particulate combustion heat generation amount at this portion will be There is a possibility that it will be oversized and overheated, causing filter melting damage and cracks.

The present invention solves the above problem in such a dual filter type exhaust emission control device by reducing variations in filter regeneration between two filters and leveling the regeneration state.

[0009]

In order to achieve the above object, in the present invention, the exhaust passages of the internal combustion engine are bifurcated and rejoined, and a filter is provided in each branch passage portion, so that these two passages are provided. A dual filter type exhaust purification device that collects particulates in exhaust gas by a filter, provides a bypass passage that bypasses the above two filters in the exhaust passage, and regenerates the filter while bypassing the exhaust gas during filter regeneration Regeneration control means is provided for continuously regenerating the two filters at each filter regeneration time, and for alternating the filter regeneration order between the two filters for each regeneration.

In order to solve the same problem in the present invention, in addition to the exhaust gas purification device, in a dual filter type exhaust gas purification device, one of the two filters is alternately regenerated at each filter regeneration time. A reproduction control means is provided.

[0011]

In these exhaust emission control devices, in order to alternate the filter regeneration order for each filter regeneration, or to change the filter to be regenerated for each regeneration, the unburned particulates remain in the specific portion of the specific filter every time. Is eliminated, and the filter regeneration state can be leveled.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. With reference to FIG. 1 showing a schematic configuration of an exhaust emission control device according to the present invention, 1 is an exhaust pipe through which exhaust gas from an engine body (not shown) to be located on the left side in the drawing flows, 2
Reference numerals 3 and 3 denote two filters for collecting particulates in the exhaust gas, and reference numerals 4 and 5 branch the exhaust gas flowing in the exhaust pipe 1 to the filters 2 and 3, and after passing the filter, It is a branch pipe that joins again.

In this embodiment, the exhaust gas passage defined by the exhaust pipe 1 is the exhaust passage 6, and the branch pipes 4,
The exhaust gas passages defined by 5 will be referred to as branch passages 7 and 8.

According to this embodiment, the upstream side connecting portion between the exhaust pipe 1 and the branch pipes 4 and 5 (that is, the exhaust gas branch portion a).
The exhaust passage portion 6a on the exhaust upstream side and the exhaust passage portion 6 on the exhaust downstream side of the downstream side connecting portion (that is, the merging portion b) and on the exhaust upstream side of the muffler 9 communicate with each other via the bypass pipe 10. To be connected.

Further, in the middle of the bypass passage 11 defined by the bypass pipe 10, the bypass passage 11 is closed at the time of collecting particulates, and the exhaust gas from the engine body is guided to the filters 2 and 3 side. At the same time, an exhaust bypass valve 12 is provided which is opened during filter regeneration to divert exhaust gas from the filters 2 and 3.

The exhaust bypass valve 12 has a control circuit (E
Negative pressure switching valve (V
The SV) 14 and the VSV 14 are adapted to be opened and closed by an actuator 15 which is operated by introducing a negative pressure.

Further, a regeneration gas discharge pipe 16 for discharging particulate combustion gas (regeneration gas) at the time of filter regeneration to the outside is connected to the exhaust pipe 1 on the exhaust upstream side of the filter, and the filter is connected to this connection portion. At the time of regeneration, the first exhaust control valve 17 for guiding the regeneration gas from the filters 2 and 3 to the regeneration gas exhaust pipe 16 while blocking the exhaust passage 6a as shown by the dotted line in the figure to prevent the introduction of the exhaust gas filter Is provided. The first exhaust control valve 17 is also VSV.
It is opened and closed by the actuator 14 and the actuator 18.

As means for regenerating the filters, electric heaters 19 and 20 near the end faces on the exhaust downstream side of the filters 2 and 3 are used to heat the filters 2 and 3 to regenerate the particulates during filter regeneration. The electric power supplied from the battery 21 to the electric heaters 19 and 20 is controlled by the heater relay 22 operated by the control circuit 13.

Further, in this embodiment, a regeneration gas (secondary air) for particulate combustion with respect to the filter to be regenerated at the time of regeneration of the filter is provided downstream of the filter.
An electric air pump 23 for supplying the electric power is provided. The filter regeneration gas from the electric air pump 23 is supplied to the filters 2 and 3 from the downstream side in the exhaust flow direction. Therefore, in the present embodiment, the exhaust passage 6 is provided.
Exhaust passage 6b on the exhaust downstream side of the regeneration gas supply section to b
Shuts off the exhaust passage 6b during filter regeneration,
A second exhaust control valve 24 is provided to prevent the regeneration gas from directly flowing to the downstream side. The second exhaust control valve 24 is opened and closed by the VSV 25 and the actuator 26.

Further, in this embodiment, each filter 2, 3 is further added.
During the filter regeneration, the branch passages 7 and 8 on the more downstream side are opened by opening the branch passages 7 and 8 and introducing the regeneration gas from the downstream side to the corresponding filters 2 and 3 A control valve 27 and a second gas control valve 28 are provided. These control valves, like other control valves, also have corresponding VSV 29, 3
0 and the actuators 31, 32 are adapted to be opened and closed.

From the output side of the control circuit 13, the VSVs 14, 25, for operating the control valves described above,
The drive signals of 29 and 30 are output, and as described above, the drive signals of the heater relay 22 and the electric air pump 23 that control the energization of the electric heaters 19 and 20 are output. Also, on this input side, as shown in the figure, to determine the filter regeneration time,
An exhaust pressure signal, an exhaust temperature signal, a cooling water temperature signal, and an engine speed signal are input from the engine body in order to detect a pressure difference across the filter.

In the exhaust gas purification apparatus constructed as above, the regeneration procedure at the time of regeneration of the filter according to this embodiment is shown in FIG.
Will be described with reference to. That is, in the filter regeneration of the conventional dual filter type exhaust emission control device shown in the lower part of FIG. 2, the regeneration order of the two filters A and B at each filter regeneration time is, for example, the regeneration of the filter B after the regeneration of the filter A. So it was always constant.

On the other hand, the reproduction procedure according to this embodiment is as follows.
As shown in the upper part of FIG. 2, when the reproduction order of this time is the filter A and the filter B by the reproduction control means described later,
The filter regeneration order is alternated between the two filters for each regeneration so that the next regeneration order is the filter B and the filter A, or, as shown in the middle part of FIG. The playback interval can be changed to filter A this time and filter B next time by alternately changing the playback interval to approximately half the conventional one (the playback interval when focusing on one filter is almost the same as the conventional one). ..

3 and 5 are flow charts showing the operation of the control circuit 13 at the time of filter regeneration as the regeneration control means for achieving the two types of filter regeneration according to the present invention shown in FIG. It should be noted that these flowcharts can be executed as a premise for execution thereof when it is determined that the particulate collection amount has reached a predetermined value, for example, by detecting the exhaust pressure difference before and after the filter as described above. is there.

First, regarding the flow chart of FIG. 3 for executing the filter regeneration control shown in the upper part of FIG. 2, when it is judged that the filter regeneration time is reached and the filter regeneration routine is started,
First, at step 41, it is judged if the flag F for first reproducing the filter A is set. If F = 1 in this step (Yes), step 42
Then, a series of filter A regeneration processing is executed here.

The filter reproduction processing is, specifically,
If the filter A is the filter 2 of FIG. 1, the exhaust bypass valve 12 is opened, and the exhaust passages 6a and 6b are closed by the first exhaust control valve 17 and the second exhaust control valve 24 so that the exhaust gas is filtered by the filter 2. , 3 are bypassed, the electric heater 19 of the first filter 2 is energized for a predetermined time, the electric air pump 23 is operated, and the second gas control valve 28 is closed to supply the regeneration gas only to the filter 2. It means that.

If it is judged that the predetermined filter regeneration time has elapsed after the start of energization of the electric heater 19 and the regeneration of the filter A is completed, the routine next proceeds to step 43.
Then, it is determined whether the flag F is reset to 0 or not.

If it is assumed that the filter A is the first in the reproduction process this time, the flag F is naturally 1 so that it is determined to be No here, and the process proceeds to step 44 where the remaining filter B is reproduced. Processing will be executed. Note that the specific processing content in this step 44 is different from the regeneration of the filter A, except that if the filter B is the filter 3 in FIG. 1, the operation of the first gas control valve 27 and the second gas control valve 28 is The position is reversed and the electric heater 20 is simply energized.

As in the case of filter A, electric heater 20
If it is determined that the predetermined filter regeneration time has elapsed after the start of energization to the filter B and the regeneration of the filter B is completed, the routine proceeds to step 45, where the flag F is again detected.
Is determined to be 0 or not. In this step, No, that is, the filters A and B as described above.
When playing in the order of, proceed to step 46,
The flag F is reset to 0 for the next filter regeneration order, and this routine ends.

By the way, in the state where the flag F is reset as described above, when the next filter regeneration timing comes, it is judged No in step 41, and the routine proceeds to step 44, where the filter B Playback occurs first. Then, in the following step 45, in this case,
Since the determination is Yes, the routine proceeds to step 42, where the regeneration processing of the filter A is continuously executed, and then it proceeds to step 43 to determine whether or not the flag F is reset. Will be.

If it is judged No in step 43, the routine next proceeds to step 47, in which the flag F for determining the reproduction order for the next filter reproduction is set to 1
Then, the reproduction process as the reproduction procedure of the filters B and A is completed as described above.

As described above, according to this flow chart, the flag F is set and reset every time the filter regeneration is completed, so that the filter regeneration order can be interchanged alternately. As a result, for example, in the current filter regeneration, Even if one filter has a particulate unburned residue due to the last regeneration, this filter will be regenerated first when the filter is regenerated next time, and the unburned residue is completely regenerated here without accumulating the unburned amount. It can be incinerated and the two filter regeneration states can be leveled.

FIG. 4 is an operation time chart of each control valve, the electric heater and the electric air pump when the filters A and B (or the filters 2 and 3) are regenerated in the order, in the reverse order. In the case of the filter regeneration described above, the operation of the first gas control valve 27 and the second gas control valve 28 is naturally reversed, and the energization timing of the electric heaters 19 and 20 is also reversed. In addition, in this time chart, when the electric heaters 19 and 20 are energized, the electric air pump 23
The energization timing of is slightly delayed to ensure the ignition of particulates.

Next, the operation of the control circuit 13 for executing the filter regeneration control shown in the middle part of FIG. 2 will be described with reference to the flowchart of FIG. Since this regeneration routine is performed at intervals of approximately half the normal regeneration interval as shown in FIG. 2, it is natural that the parameter for determining the filter regeneration timing (for example, the exhaust pressure difference before and after the filter) is determined. The value will be set lower than during normal intervals.

Referring to FIG. 5, when it is determined that the filter regeneration time is reached and the filter regeneration routine is started, first, at step 51, it is determined whether or not the flag F for regenerating the filter A this time is set. If F = 1 (Yes) in this step, the process proceeds to step 52, where a series of regeneration processing of the filter A as described in step 42 of FIG. 3 is executed, and in the following step 53, the next filter regeneration is performed. Therefore, the flag F is reset to 0 and this routine is finished. And at the next filter playback,
Since it is determined No in step 51, the routine proceeds to step 54, this time performing regeneration of filter B,
Next, at step 55, the flag F is set to 1 this time, and this routine is ended.

As described above, according to this flowchart, one filter is not continuously reproduced by one reproduction but one filter is reproduced every one time, so that the other filter is reproduced during this time. Even if it is cooled, it will continue to collect the particulates, and the particulates will not cause unburned residue. Also, in this reproduction, since only one filter is reproduced for each reproduction, the reproduction processing 1
It is possible to avoid consuming a large amount of battery power at one time even if the number of filter regeneration processes of the entire device is increased due to the reduction of the regeneration interval because the regeneration processing time per time is about half that of the conventional technique.

The two regenerations, which are the features of the present invention, have been described above using the reverse flow regeneration type dual filter type exhaust gas purification device as an example. However, the present invention naturally includes an electric heater in front of the filter. It can also be applied to a forward-flow regeneration type exhaust purification device that supplies regeneration gas from the front.

[0038]

As described above, according to the present invention, the filter regeneration order is alternated every time the filter is regenerated, so that the particulates will not be concentrated and unburned. Further, according to the present invention, if one filter is regenerated every time the filter is regenerated and the filters are alternately changed, two filters are regenerated under the same condition every time, so that one regeneration time is shortened. In addition to being able to do so, it is possible to equalize the regeneration states of the two filters, reduce the particulate unburned residue, and prevent the occurrence of cracks and melting damage.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a dual filter type exhaust emission control device according to the present invention.

FIG. 2 is a diagram comparing a filter regeneration mode according to the present invention with a conventional one.

FIG. 3 is a flow chart illustrating the operation of the control circuit according to the present invention.

FIG. 4 is an operation timing chart of the filter regeneration element corresponding to FIG.

FIG. 5 is a flow chart for explaining the operation of the control circuit according to the present invention, which is different from FIG.

FIG. 6 is a diagram showing a temperature change of each filter during filter regeneration.

[Explanation of symbols]

 2, 3 ... Filter 6 ... Exhaust passage 7, 8 ... Branch passage 11 ... Bypass passage 13 ... Control circuit

Claims (2)

[Claims] 1. An exhaust passage of an internal combustion engine is branched into two branches and merged again, and a filter is provided in each branch passage portion, so that these two filters collect particulates in the exhaust gas, and In a dual filter type exhaust gas purification device that provides a bypass passage bypassing the two filters in the exhaust passage and regenerates the filter while bypassing the exhaust gas from the filter at the time of filter regeneration, the two filters are continuously connected at each filter regeneration time. An exhaust purification device of a dual filter type, characterized in that the exhaust gas purification device is provided with a regeneration control means for alternately regenerating the filter regeneration order between the two filters for each regeneration. 2. An exhaust passage of an internal combustion engine is branched into two branches and merged again, and a filter is provided in each branch passage portion, so that the particulates in the exhaust gas are collected by these two filters, In a dual filter type exhaust gas purification device in which a bypass passage bypassing the above-mentioned two filters is provided in the exhaust passage and the filter is regenerated while bypassing the exhaust gas from the filter at the time of filter regeneration, A dual filter type exhaust emission control device comprising regeneration control means for alternately regenerating one filter.