JPH0544438A - Exhaust gas purifying device for diesel engine - Google Patents

Abstract

PURPOSE:To properly grasp a period during which a filter is regenerated through combustion of exhaust particulate collected by a filter. CONSTITUTION:Two operation conditions forming a reference are set by a reference operation condition setting circuit 13. An exhaust gas pressure difference on the upper stream side of a filter 3 between the two operation conditions detected by a pressure sensor 5 is stored in an exhaust gas pressure memory value comparing circuit 19. When, the stored pressure difference is decreased by a given value or more after it is increased by a given value or more, it is decided by a blow deciding circuit 21 that exhaust gas particulate stuck to the filter 3 is removed from the sticking part thereof. It is decided by a regeneration period deciding circuit 25 that a period during which the blow occurs the given number of times or more is a regeneration period of the filter 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device for a diesel engine in which a filter for collecting exhaust particulates in exhaust gas is provided in an exhaust passage.

[0002]

2. Description of the Related Art A diesel engine contains exhaust particulates such as carbon in its exhaust due to combustion of fuel in a combustion chamber, and if it is directly discharged into the atmosphere, it is not preferable because it causes environmental pollution. In order to prevent this, a method of providing a filter made of porous ceramic or the like in the exhaust passage and collecting exhaust fine particles by allowing the exhaust gas to pass through the filter is well known in the related art. In this case, the exhaust particles adhere to the surface of the filter and gradually accumulate.However, if the amount of exhaust particles deposited increases, the exhaust pressure increases and the engine performance is adversely affected. It is necessary to remove it to regenerate the filter.

[0003] Examples of the regeneration work of the filter include burning the exhaust particulates by an electric heater provided immediately before the filter, or burning the exhaust particulates by igniting the fuel injected from the fuel injection valve. To determine when to burn the exhaust particulates, that is, to determine when to regenerate the filter, the differential pressure between the exhaust pressure on the upstream side of the filter and the exhaust pressure on the downstream side of the filter was measured, and this differential pressure exceeded a prescribed value. There is a method of utilizing exhaust pressure, such as time (see Japanese Patent Laid-Open No. 60-67713).

[0004]

By the way, when the amount of exhaust particulates deposited on the surface of the filter increases, the deposited particulates may be separated from the adhering part and diffused inside the filter (blow) depending on operating conditions. A blow-off phenomenon occurs, which is discharged to the outside. When a blow or blow-off phenomenon occurs, the exhaust pressure on the upstream side of the filter drops,
As a result, the exhaust pressure difference between the upstream side and the downstream side of the filter decreases, but the exhaust particulates adhering at this time do not blow uniformly from the exhaust inflow side surface of the filter,
There is a portion where exhaust particles remain on the filter surface without being blown locally. The blow or blow-off phenomenon here means that when exhaust particulates adhering to the filter surface diffuse inside, the soluble organic substance (SOF) such as hydrocarbon contained in the exhaust gas is oxidized to the SOF. It also includes the removal of adsorbed exhaust particulates.

Further, blow and blow-off are hereinafter referred to as blow.

FIG. 13 shows fluctuations in the exhaust pressure difference ΔP between the upstream side and the downstream side of the filter and the corresponding accumulated weight of exhaust particulates (PCT). According to this, when the blow occurs, the exhaust pressure on the upstream side of the filter sharply decreases, so that the exhaust pressure difference ΔP sharply decreases, and the accumulated weight of the exhaust particulate matter is increased every time the blow occurs. It can be seen that it is gradually accumulating. Figure 1
4 and FIG. 15 show the exhaust particulate PC attached to the filter F.
T is a cross-sectional view showing a change inside the filter when exhaust gas blows from the left side to the right side in the drawing. 14
Changes from the state on the left side (increase in differential pressure across the filter) to the right side (increase in differential pressure across the filter) (decrease in differential pressure across the filter) from the state on the left side (increase in differential pressure across the filter) where exhaust particulate PCT has accumulated on the exhaust inflow surface of the filter F. Fig. 1 shows the situation
No. 5 blows in the left side state (increase in differential pressure across the filter) where the partial diffusion amount of the exhaust particulates into the filter F increases due to repetition of the above-mentioned blowing, and a partial clogging portion G is generated. It shows a state in which G further diffuses inside and changes to the state on the right side where the deposition amount gradually increases (decrease in differential pressure across the filter).

As described above, when the blow is repeated, a portion where exhaust particulate matter is accumulated, such as a clogging portion G, is locally generated. Therefore, the exhaust pressure difference before and after the filter is simply detected as in the conventional example. With this method, the amount of exhaust particulate cannot be accurately determined, and the determination of the filter regeneration timing will be erroneous. For this reason, for example, when the regeneration of the filter is delayed, the trapped amount becomes excessive and the exhaust pressure rises, which deteriorates the operability and causes problems such as poor combustion and shortened filter life. ..

[0008] Therefore, an object of the present invention is to accurately grasp the timing for regenerating the filter by burning the exhaust particulates collected by the filter.

[0009]

In order to achieve the above object, the present invention provides a filter 3 provided in an exhaust passage 1 for collecting exhaust particulates in exhaust gas, as shown in FIG. The exhaust particulate that adheres is burned to filter 3
By means of a regeneration means 4 for regenerating the exhaust gas, a pressure detection means 5 provided in the exhaust passage 1 on the upstream side of the filter 3, and the pressure detection means 5 between two preset operating conditions that serve as a reference. The storage means 20 for storing the detected exhaust pressure difference, and when the stored pressure difference rises by a predetermined value or more and then drops by a predetermined value or more, the exhaust particulates adhering to the filter are detached from the adhering portion. The blow judgment means 21 for judging that the blow blow occurs a predetermined number of times or more, and the regeneration time judgment means 25 for judging that the regeneration time of the filter 3 by the regeneration means 4 is reached.

Further, according to the present invention, as shown in FIG. 2, the filter 3 provided in the exhaust passage 1 for collecting the exhaust particulates in the exhaust gas, and the exhaust particulates adhering to the filter 3 are burned to remove the filter 3. The regeneration means 4 for regeneration, the differential pressure detection means 31 for detecting the pressure difference between the exhaust passages 1 on the upstream side and the downstream side of the filter 3, and the preset operating condition for one point are set. The differential pressure detection means 31
Differential pressure storage means 35 for storing the differential pressure detected by
Blow determination means 21 for determining that the exhaust particulates adhering to the filter 3 have separated from the adhering portion when the stored differential pressure rises by a predetermined value or more and then falls by a predetermined value or more.
And a regeneration timing determining means 25 for determining that it is the regeneration timing of the filter 3 by the regeneration means 4 when the blow occurs a predetermined number of times or more.

[0011]

According to the exhaust emission control system of the diesel engine constructed as described above, the upstream side of the filter 3 detected by the pressure detection means 5 between the two preset operating conditions serving as the reference. Is stored in the storage means 20, and when the stored pressure difference rises by a predetermined value or more and then drops by a predetermined value or more, it is determined that the exhaust particulates adhering to the filter 3 have separated from the adhering portion. When the means 21 makes a determination and the blow has occurred a predetermined number of times or more, the regeneration time determining means 25 determines that the regeneration time of the filter 3 has come.

Further, according to the present invention, the exhaust pressure difference between the upstream side and the downstream side of the filter 3 detected by the differential pressure detecting means 31 under a preset operating condition of one point is a differential pressure. When the pressure difference stored in the storage means 35 rises by a predetermined value or more and then falls by a predetermined value or more, the blow determination means 21 determines that the exhaust particulates adhering to the filter have separated from the adhering portion, When this blow has occurred a predetermined number of times or more, the regeneration time determination means 25 determines that it is the regeneration time of the filter 3.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is an overall configuration diagram showing an exhaust emission control device for a diesel engine according to an embodiment of the present invention. The exhaust passage 1 of the diesel engine is provided with a filter 3 made of porous ceramic or the like. This filter 3
As the exhaust gas passes through the exhaust gas, exhaust gas particles such as carbon particles in the exhaust gas are attached to the filter 3 and collected. When the amount of exhaust particulates collected by the filter 3 increases and the filter 3 reaches the regeneration time, an electric heater 4 as a regeneration means provided immediately before the filter 3 is energized to generate exhaust particulates. To burn. In the exhaust passage 1 on the upstream side of the filter 3, a pressure sensor 5 as pressure detecting means for detecting the exhaust pressure for judging the regeneration timing of the filter 3.
Is provided.

The operating condition judging circuit 7 for judging the operating condition of the diesel engine receives the detection signals of the rotation sensor 9 for detecting the engine speed and the load sensor 11 for detecting the engine load. The reference operating condition setting circuit 13 sets two operating conditions, which are the reference operating frequencies of the engine, such as the low load operating region A and the high load operating region B, which are frequently used. The standard operating condition exhaust pressure selection circuit 15 includes the pressure sensor 5, the operating condition determination circuit 7, and the standard operating condition setting circuit 13.
When the operating conditions (low-load operating region A or high-load operating region B) set by the reference operating condition setting circuit 13 are received by the respective output signals of 1, the exhaust gas detected by the pressure sensor 5 under these operating conditions Select each pressure. The output signal of the standard operating condition exhaust pressure selection circuit 15 is sequentially input to the exhaust pressure storage circuit 17 as a storage unit and stored therein.

The exhaust pressure storage value comparison circuit 19 sequentially compares the stored values of the exhaust pressure under the above-mentioned two operating conditions, which are sequentially stored in the exhaust pressure storage circuit 17. The exhaust pressure difference storage circuit 20 as a storage unit sequentially stores the pressure difference calculated by the exhaust pressure storage value comparison circuit 19. When the blow determination circuit 21 determines that the stored value of the exhaust pressure difference sequentially stored in the exhaust pressure difference storage circuit 20 has increased by a predetermined value or more and then decreased by a predetermined value or more, the exhaust particulates adhering to the filter 3 are blown. It is judged that it did. An increase of the stored value above a predetermined value means that the amount of exhaust particles adhering to the filter 3 has increased, and a decrease of the stored value above the predetermined value means that the accumulated exhaust particles have blown.

This change in the accumulation amount can be explained by the change in the exhaust pressure P on the upstream side of the filter 3 with respect to the exhaust flow rate shown in FIG. The exhaust flow rate increases as the engine speed increases and as the engine load increases, as shown in the exhaust flow rate map of the engine speed N and the engine load Q shown in FIG. The exhaust flow rate side is the low load side operating condition A, the high exhaust flow rate side is the high load side operating condition B, and these two operating conditions are the standard operating conditions. In FIG. 4, the broken line indicates the exhaust pressure after fresh or regeneration, where the exhaust particles hardly adhere to the filter 3, the solid line indicates the exhaust pressure when the accumulated amount of exhaust particles is large, and the dashed-dotted line indicates the exhaust pressure. The exhaust pressure is shown when the exhaust particulates are released and blown.

The exhaust pressure difference between the operating conditions A and B indicated by the broken line is almost the same as the operating conditions A and B, and the exhaust pressure difference between the operating conditions A and B where the exhaust particulate amount is large is indicated by the solid line. f, operating conditions A and B after blow indicated by the alternate long and short dash line
If the exhaust pressure difference between the two is g, these pressure differences e,
f and g are stored in the exhaust pressure difference storage circuit 20. Then, the blow determination circuit 21 as blow determination means determines that the blow has occurred when the stored value rises from e to f and then drops to g.

The blow number storage circuit 23 stores the number of blows determined by the blow determination circuit 21. When the number of blows stored in the blow number storage circuit 23 reaches or exceeds a predetermined number, the regeneration time determination circuit 25 as a regeneration time determination means determines that it is the regeneration time of the filter 3 and energizes the electric heater 4. The exhaust particulates adhering to the filter 3 are burnt and removed.

Next, the control operation in the exhaust emission control system of the diesel engine constructed as described above will be explained based on the flow chart shown in FIG.

First, the engine speed N detected by the rotation sensor 9 is read (step 101), and the load sensor 1 is read.
The engine load Q detected by 1 is read (step 1
03), it is judged whether or not the reference operating condition exhaust pressure selection circuit 15 is the operating condition A on the low load side which is a reference (step 105). If the operating condition is not A here, it is judged whether or not it is the operating condition B on the high load side (step 10).
7). When the operating condition is A or B in step 105 or 107, the reference operating condition exhaust pressure selecting circuit 15 determines whether or not there is the exhaust pressure data PA or PB under each operating condition. (Steps 109 and 111). Exhaust pressure data P
If there is no A or PB, exhaust pressure P
Read A and PB respectively (steps 113, 11
5) The read pressure values are stored in the exhaust pressure storage circuit 17 (steps 117 and 119).

At the next step 121, it is judged whether or not the above two exhaust pressures PA and PB are stored.
If it is stored, the exhaust pressure difference X between the two operating conditions A and B is compared and calculated (X = PB-PA) in the exhaust pressure stored value comparison circuit 19 (step 123), and the flag L is set. However, it is determined whether the set state in which the exhaust pressure difference X has increased by a predetermined value or more from the previous time or the reset state in which it is not (step 125). In the reset state of the flag L,
It is determined whether the exhaust pressure difference X is equal to or more than a predetermined value (step 127). If the exhaust pressure difference X is equal to or greater than the predetermined value, the flag L is set (step 129) and the exhaust pressures PA and PB are cleared (step 131,).
133), and the exhaust pressure difference X at this time is stored in the exhaust pressure difference storage circuit 20 as MX (step 13).
5). If the exhaust pressure difference X is less than the predetermined value in step 127, the exhaust pressure PB on the high load side is cleared (step 137).

In step 125, in the set state of the flag L in which the exhaust pressure difference X has risen by a predetermined value or more from the previous time, the difference between the exhaust pressure difference MX stored in step 135 and the exhaust pressure difference X this time is set. Is greater than or equal to a predetermined value, that is, whether or not the exhaust pressure difference X this time has decreased by a predetermined value or more with respect to the previous pressure difference MX (step 139).
Here, when the value is lower than the predetermined value, the blow determination circuit 21 determines that the exhaust particulates adhering to the filter 3 have separated and blow has occurred, and the blow number storage circuit 23 counts the number of blow occurrences. (Step 141). After that, the flag L is reset (step 143),
The stored exhaust pressures PA and PB are each cleared (steps 145 and 147), and the stored value MX in which the exhaust pressure difference is a predetermined value or more is also cleared (step 149).

Then, in the next step 151, it is judged whether or not the operating time of the engine after burning and removing the exhaust particulates adhering to the filter 3 to regenerate the filter 3 has exceeded a predetermined value, and then the regeneration timing The determination circuit 25 determines whether or not the number of blows generated is equal to or larger than a predetermined value (step 153), and even if the number of blows is equal to or larger than the predetermined value, the exhaust particulates left locally adhered are blown. When it is considered that the amount is large, it is determined that it is time to regenerate the filter 3 (step 155).

In step 151, the operating time after the regeneration of the filter 3 is determined. It is possible that the blow is erroneously determined due to a detection error of the pressure sensor 5 or the like. This is because the unnecessary regeneration operation is prevented and the filter 3 is protected by determining the regeneration time after a lapse of time or more. Further, even if a predetermined time or more has not elapsed after the regeneration, the deposition amount may continuously increase under a low load operation condition that does not result in blow, so that the pressure difference X between the exhaust pressures PA and PB is predetermined. It is determined whether or not the value is equal to or more than the value (step 157), and the amount of exhaust particulates accumulated is determined.

The reproducing operation of the filter 3 is shown in the flowchart of FIG. Here, if it is determined that it is the regeneration time (step 159), the electric heater 4 is energized to heat it (step 161), whereby the exhaust particulates adhering to the filter 3 are burned and removed, and the filter is removed. When the reproduction of No. 3 is completed (step 163), the number of blows in the blow number storage circuit 23 is cleared (step 165).

Further, in step 135, the exhaust pressure difference X
In step 157, it is further determined whether or not the exhaust pressure difference X is equal to or greater than a predetermined value, in preparation for the case where the low load operation condition in which the blow does not occur as described above continues after the value becomes equal to or greater than the predetermined value. When the exhaust pressures PA and PB are not stored in step 121, and after the exhaust pressure PB is cleared in step 137, the process also proceeds to step 157.

As described above, since the filter 3 is regenerated at the time when the blow has occurred a predetermined number of times or more, even if the locally accumulated portion of exhaust particulates caused by the repeated blow remains, the filter 3 It is possible to accurately grasp the judgment of the reproduction time of. As a result, the filter 3 is regenerated at an appropriate time, and it is possible to prevent an increase in exhaust pressure and deterioration of drivability due to, for example, an excessively large amount of trapping, and to prevent combustion failure during regeneration. It is also possible to prevent the deterioration of the life of No. 3 above.

FIG. 9 is an overall configuration diagram of an exhaust emission control device for a diesel engine showing another embodiment of the present invention. In this embodiment, blow is determined based on the change in the differential pressure between the exhaust pressure on the upstream side of the filter 3 and the exhaust pressure on the downstream side of the filter 3 under a preset operating condition with a high operating frequency, and regeneration is performed. It is intended to determine the time. The same components as those of the embodiment shown in FIG. 3 are designated by the same reference numerals. However, the standard operation condition setting circuit 13 here
Is to set one operating condition with a high operating frequency as described above.

A first pressure sensor 27 is provided in the exhaust passage 1 on the upstream side of the filter 3, and a second pressure sensor 29 is provided in the exhaust passage 1 on the downstream side of the filter 3. The detection values of these pressure sensors 27 and 29 are input to a filter front-rear differential pressure detection circuit 31 as a differential pressure detection unit that detects a differential pressure between the exhaust pressure on the upstream side and the exhaust pressure on the downstream side of the filter 3. .. Standard operating condition Differential pressure selection circuit 3
3 receives the output signals of the filter front-rear differential pressure detection circuit 31, the operating condition determination circuit 7, and the reference operating condition setting circuit 13, and indicates that the operating condition set by the reference operating condition setting circuit 13 has become the operating condition. When the determination circuit 7 determines, the filter front-back differential pressure detection circuit 31
Select the differential pressure calculated by. The output signal of the reference operating condition differential pressure selection circuit 33 is sequentially input to and stored in the differential pressure storage circuit 35 as differential pressure storage means.

The differential pressure storage value comparison circuit 37 sequentially compares the differential pressure storage values stored in the differential pressure storage circuit 35 under the above operating condition of one point, and outputs a signal to the blow determination circuit 21.

The control operation of the exhaust emission control system of the diesel engine thus constructed will be described with reference to the flow charts shown in FIGS.

First, the engine speed N is read (step 1
01), the engine load Q is read (step 103), and the operating condition determination circuit 7 determines whether or not the operating condition is a reference (step 201). Here, in the case of the standard operating condition, the filter 3 is set by the standard operating condition differential pressure selecting circuit 33.
The differential pressure ΔP before and after is read (step 203), and the flag M determines whether the set state in which the differential pressure ΔP has increased by a predetermined value or more as compared with the previous time or the reset state that is not so (step 205). Here, when the flag M is in the reset state, it is judged whether or not the differential pressure ΔP is equal to or more than a predetermined value (step 207), and when it is equal to or more than the predetermined value, the flag M is set (step 209). The pressure ΔP is stored in the differential pressure storage circuit 35 as MΔP (step 2
11).

When the flag M is set in step 205, the differential pressure MΔP stored in step 211 and thereafter is stored.
Then, the differential pressure stored value comparison circuit 37 determines whether the difference from the differential pressure ΔP of this time is a predetermined value or more, that is, whether the differential pressure ΔP of this time is lower than the previous differential pressure MΔP by a predetermined value or more. (Step 213). Here, when the value is lower than the predetermined value, the blow determination circuit 21 determines that the exhaust particulates adhering to the filter 3 have separated and blow has occurred, and the blow number storage circuit 23 counts the number of blow occurrences. (Step 141). After that, the flag M is set to the reset state (step 143), and the stored memory value MΔP is stored.
Is cleared (step 215).

FIG. 12 shows changes in the differential pressure ΔP across the filter 3. According to this, the front-rear differential pressure ΔP is gradually changed from the fresh state R before the exhaust particulates are deposited on the filter 3 to the state S where the exhaust particulates are gradually deposited and the deposition amount is the maximum amount at which blow can occur. It can be seen that the differential pressure ΔP across the front and rear is drastically lowered to the state T near the fresh state R when blown in this state S.

After the stored value MΔP is cleared in step 215, the engine operating time after the exhaust particulates adhering to the filter 3 are burned off and the filter 3 is regenerated as in the above-described embodiment. It is judged whether or not it becomes equal to or more than a predetermined value (step 151), and then the regeneration timing judgment circuit 2
5 is determined whether or not the number of blows generated is equal to or more than a predetermined value (step 153), and when the number of blows is equal to or more than the predetermined value, the amount of exhaust particulate left locally adhered even if blown is determined. If it is considered to be large, it is determined that it is time to regenerate the filter 3 (step 15).
5). Even if the predetermined time or more has not elapsed after the regeneration, the low load operation condition that does not result in the blow may continuously increase the deposition amount. (Step 21
7) The amount of exhaust particulates deposited is determined, and if it is equal to or greater than a predetermined value, it is determined that the regeneration time of the filter 3 is reached (step 15).
5). The reproducing operation of the filter 3 is performed in the same manner as the operation in the flowchart of FIG. 8 of the above embodiment.

Further, in step 211, the differential pressure across the front and rear side ΔP
In step 157, it is further determined whether or not the differential pressure ΔP is equal to or greater than a predetermined value, in preparation for a case where the low load operation condition in which the blow does not occur continues after the value becomes equal to or greater than the predetermined value. In step 213, when the current differential pressure ΔP has not dropped more than the predetermined value with respect to the previous differential pressure MΔP, the routine proceeds to step 217, where it is determined whether the front-rear differential pressure ΔP is the predetermined value or more,
Determine the playback time.

In the embodiment shown in FIG. 9 as well, since the regeneration time of the filter 3 is set to be when the blow has occurred a predetermined number of times or more as in the above embodiment, the same effect as that of the above embodiment can be obtained.

In each of the above embodiments, the electric heater 4 is used as the filter regenerating means, but the present invention is not limited to this.

[0040]

As described above, according to the present invention, when the exhaust pressure difference on the upstream side of the filter between the two operating conditions serving as the reference is increased by a predetermined value or more and then decreased by a predetermined value or more, the filter is It is judged that the exhaust particulates adhering to the filter have separated from the adhered part and blown, and when the blow has occurred a predetermined number of times or more, it is judged that it is the filter regeneration time, so the blow is repeated. Even if the locally accumulated portion of exhaust particulate matter generated by the above remains, it is possible to accurately grasp the judgment of the regeneration time of the filter. As a result, the regeneration of the filter is performed at an appropriate time, and it is possible to prevent the exhaust pressure from rising due to the excessive amount of trapped gas and the deterioration of the drivability. Further, the combustion failure at the time of the regeneration of the filter is prevented, and the filter life is shortened. It is possible to prevent the deterioration.

Further, according to the present invention, when the exhaust pressure difference between the upstream side and the downstream side of the filter under the standard operating condition of one point rises by a predetermined value or more and then falls by a predetermined value or more, the filter adheres to the filter. Even if it is determined that the exhaust particulates have separated from the adhered portion and blown, and when the blow has occurred a predetermined number of times or more, it is also determined that it is the filter regeneration time, the same effect as above can be obtained. ..

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a diagram corresponding to the claims of the present invention.

FIG. 3 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 4 is a characteristic diagram of exhaust pressure upstream of the filter with respect to exhaust flow rate.

FIG. 5 is a characteristic diagram of exhaust gas flow rate according to engine speed and engine load.

FIG. 6 is a flowchart showing a control operation for determining a regeneration timing in the exhaust emission control device of FIG.

FIG. 7 is a flowchart showing a control operation for determining a regeneration timing in the exhaust emission control device of FIG.

FIG. 8 is a flowchart showing a control operation of a reproduction operation.

FIG. 9 is an overall configuration diagram showing another embodiment of the present invention.

10 is a flowchart showing a control operation for determining a regeneration timing in the exhaust emission control device of FIG.

FIG. 11 is a flowchart showing a control operation for determining the regeneration timing in the exhaust emission control device of FIG.

FIG. 12 is a change characteristic diagram of the differential pressure across the filter.

FIG. 13 is an explanatory diagram showing a variation in an exhaust pressure difference ΔP between an upstream side and a downstream side of a filter and a deposited weight of exhaust particulates in a conventional example.

FIG. 14 is a cross-sectional view showing changes in the inside of the filter when exhaust particulates adhering to the surface of the filter diffuse inside and blow.

FIG. 15 is a cross-sectional view showing a change in the inside of the filter when exhausted particulates diffuse inside, and further generated clogging portions diffuse inside.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust passage 3 Filter 4 Electric heater (regeneration means) 5 Pressure sensor (pressure detection means) 20 Exhaust pressure difference storage circuit (storage means) 21 Blow determination circuit (blow determination means) 25 Regeneration timing determination circuit (regeneration timing determination means) 31 differential pressure detection circuit before and after filter (differential pressure detection means) 37 differential pressure storage circuit (differential pressure storage means)

Claims (2)

[Claims] 1. A filter provided in an exhaust passage for collecting exhaust particulates in exhaust gas, a regeneration means for burning exhaust particulates adhering to the filter to regenerate the filter, and an exhaust passage upstream of the filter. And a storage means for storing an exhaust pressure difference detected by the pressure detection means between two preset operating conditions serving as a reference, and the stored pressure difference is predetermined. Blow determination means for determining that the exhaust particulates adhering to the filter have detached from the adhering part when the value rises by a predetermined value or more and then falls by a predetermined value or more, and the filter by the regeneration means when the blow occurs a predetermined number of times or more. An exhaust emission control device for a diesel engine, comprising: a regeneration timing determining means for determining that it is a regeneration timing. 2. A filter provided in an exhaust passage for collecting exhaust particulates in exhaust gas, a regeneration means for burning exhaust particulates adhering to the filter to regenerate the filter, and upstream and downstream sides of the filter. Differential pressure detecting means for detecting a pressure difference between the respective exhaust passages, and a differential pressure storing means for storing the differential pressure detected by the differential pressure detecting means under a preset operating condition of one point. And a blow determination means for determining that the exhaust particulates adhering to the filter have separated from the adhering portion when the stored differential pressure has risen by a predetermined value or more and then falls by a predetermined value or more, and this blow is performed a predetermined number of times. An exhaust emission control device for a diesel engine, comprising: a regeneration time determination means for determining that it is the regeneration time of the filter by the regeneration means when the above occurs.