JPH05288037A - Exhaust gas purifying device for diesel engine - Google Patents

Abstract

PURPOSE:To accurately judge a regeneration timing of a filter by providing pressure sensors to detect gas flow condition after regeneration of the filter and a control circuit to judge the regeneration timing of the filter. CONSTITUTION:Pressure introducing pipes 14 and 15 are respectively connected to the exhaust pipe 2 on the upper stream and that on the lower stream of a filter 1 as means to detect gas flow condition after regeneration of the filter 1. A first pressure sensor 16 and a second pressure sensor 17 are provided for detecting the exhaust pressure in this exhaust pipe territory. Analog signals from the first pressure sensor 16 and the second pressure sensor 17, besides an analog signal from an exhaust temperature sensor 22 provided on the upper stream side of the filter 1 and detecting exhaust temperature Th, and the like are input to the input side of a control circuit 6a. In the control circuit 6, pressure difference across the filter in the standard operating condition is computed, and the filter regeneration timing is judged by whether the pressure difference reaches a prescribed value or not. In this way, the regeneration timing of the filter 1 can be accurately judged.

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 equipped with a particulate filter for collecting diesel particulates discharged from a diesel engine.

[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. As the amount of particulates accumulated inside the filter increases as it is used, the air permeability will gradually deteriorate, and the engine performance will also deteriorate.Therefore, it is regularly regenerated according to the amount of particulates trapped. It must be.

In determining the filter regeneration timing, the differential pressure across the filter (pressure loss value) ΔP 'is detected as a parameter for detecting the degree of filter clogging which increases with the collection of particulates, and this is determined. After converting into the differential pressure value ΔP before and after the filter in the reference state of the intake air amount and the predetermined exhaust temperature, the predetermined differential pressure value a as the regeneration reference
There is already known an exhaust gas purifying apparatus that determines the clogging degree of the current filter by comparing with the above to determine the filter regeneration time.

By the way, as substances that change the degree of filter clogging in such an exhaust gas purification device, there are ash contained in engine oil, that is, inorganic substances such as Ca and Fe, in addition to the above-mentioned particulates. It cannot be removed from the filter by such filter regeneration processing. When the amount of ash collected in the filter increases as the filter is used, even if the filter is regenerated, the air permeability of the filter cannot be restored to the aeration state of the new filter before use. The differential pressure across the filter rises, and the particulate collection period is shortened. As a result, the amount of particulates to be burned at the time of filter regeneration is small and regeneration may be defective.

With respect to such a problem, Japanese Patent Application Laid-Open No. 62-3
In Japanese Patent Publication No. 5009, the relationship between the amount of increase in the differential pressure due to the ash collected by the filter and the travel distance is experimentally obtained in advance, and the ash content corresponding to the vehicle travel distance is calculated from the detected differential pressure across the filter. A regeneration device is disclosed in which correction is performed so as to reduce the increase in the differential pressure due to deposition, and the regeneration time is delayed as the traveling distance increases so that the filter regeneration is performed at an optimal regeneration time.

[0006]

However, in the above-described regeneration device, since the differential pressure increase due to the ash accumulation is centrally estimated only by the traveling distance of the vehicle, the traveling distance can be reduced. The amount of ash accumulated is different each time depending on the operation history until reaching, and the corrected regeneration time is not always appropriate.

As a result, the amount of particulates burned at the time of filter regeneration does not always become a constant value, and depending on the case, there is a possibility that the amount of particulates will be burnt out due to an excessive amount of particulates, or conversely regeneration failure. .. The present invention has been made in view of the above-mentioned problems of the conventional device, and an object of the present invention is to provide an exhaust gas purification device capable of accurately determining the filter regeneration timing.

[0008]

To achieve the above object, according to the present invention, a diesel engine exhaust system is provided with a filter for collecting particulates and a regenerating means for regenerating the filter, In the exhaust gas purification device of the diesel engine that ignites and burns the particulates collected in the filter by operating the regeneration means, the clogging degree detection means for detecting the filter clogging degree average value after the plurality of times of filter regeneration, An exhaust emission control device for a diesel engine, comprising: a regeneration timing correction unit that corrects the filter regeneration timing according to the detected clogging degree average value after a plurality of times of filter regeneration.

Further, according to the present invention, in the above-mentioned exhaust gas purification device, a device having an alarm means for issuing an alarm to the outside when the detected average clogging degree after a plurality of times of filter regeneration is a predetermined value or more. Is also provided.

[0010]

[Function] If the average value of the degree of filter clogging after a plurality of times of filter regeneration is different from the degree of clogging of a new filter or the clogging degree at the beginning of use of the filter, the change is due to the ash content captured by the filter. It can be seen as doing. The present invention does not infer the clogging degree change in which ash content contributes from the traveling distance, but detects the filter clogging degree average value after a plurality of times of filter regeneration, thereby directly measuring the clogging degree change caused by ash content. Detect and correct the filter regeneration time.

Further, since the engine performance may be deteriorated depending on the degree of increase in the clogging degree after the regeneration, the warning means issues a warning to the outside when the clogging degree average value of a plurality of times is a predetermined value or more.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust gas purifying apparatus according to the present invention will be described below with reference to the drawings based on an embodiment in which a differential pressure across a filter is used as a parameter representing a degree of filter clogging. 1 shows a schematic configuration of an exhaust emission control device according to the present invention, 1 is a filter for collecting particulates, 2 is an exhaust pipe for guiding exhaust gas from a diesel engine main body (not shown) to the filter 1 at the time of collecting particulates , And 3 is exhaust gas from the filter 1 when the filter 1 is regenerated.
It is a bypass pipe that makes more detours.

Inside the exhaust pipe 2 and the bypass pipe 3, respectively, a first exhaust control valve 4 and a second exhaust control valve 5 that achieve the exhaust gas flow during particulate collection and filter regeneration as described above. Is provided, and the operation is controlled by the control circuit (ECU) 6 so as to occupy the valve position as shown in the figure at the time of particulate collection and the position as shown by the dotted line around the valve at the time of filter regeneration. ..

Between the first exhaust control valve 4 arranged inside the exhaust pipe 2 and the filter 1, a regeneration gas (for example, secondary air) for particulate combustion during filter regeneration is exhausted from the filter 1. An electric air pump 7 is provided for supplying to the upstream side (hereinafter referred to as the upstream side), and this is supplied with electric power from a battery 9 together with a filter regeneration electric heater 8 arranged at the front end of the filter 1. Incidentally, regarding the elements for reproducing these filters, 10 and 11 are control circuits 6.
Is a semiconductor relay that is turned on and off by a filter 12, an air pump filter 12, and a stop valve 13 that prevents exhaust gas from flowing back to the air pump 7.

As means for detecting the particulate collection state in the filter 1 and for detecting the ventilation state of the filter 1 after regeneration, pressure introducing pipes are provided in the exhaust pipe 1 above and below the filter 1, respectively. 14 and 15 are connected to each other, and a first pressure sensor 16 (upstream side of the filter) and a second pressure sensor 17 for detecting exhaust pressure in the exhaust pipe region.
(Downstream side of the filter) is provided.

Further, in this embodiment, the pressure introducing pipe 1 described above is used.
In the middle of 4 and 15, rotary type pressure detection line switching valves 18 and 19 driven by the control circuit 6 are provided respectively. This pressure detection line switching valve 1
Reference numerals 8 and 19 determine the pressure introduced into each pressure sensor 16 or 17 to be either the exhaust pressure from the exhaust pipe 1 or the atmospheric pressure at the time of correcting the sensor output difference. At the time of collecting particulates other than when the sensor output value is corrected, it occupies the operating position as shown in the drawing, and guides the exhaust pressure before and after the filter to the pressure sensors 16 and 17. 2
Reference numerals 0 and 21 are pressure sensor filters.

The first pressure sensor 1 is provided on the input side of the control circuit 6.
6 and the analog signal from the second pressure sensor 17, an analog signal from the exhaust temperature sensor 22 provided on the upstream side of the filter for detecting the exhaust temperature Th, and an air flow meter 23.
Various signals indicating the current operating state of the engine, such as a signal indicating the intake air amount Ga detected by, are input. Then, the control circuit 6 controls the engine based on the operating information obtained from these various sensors, and in the case of the filter 1, the intake air amount Ga and the exhaust temperature Th are calculated from the exhaust pressures obtained from the pressure sensors 16 and 17. The differential pressure ΔP before and after the filter in the standard operating state is calculated based on the above, to determine the filter regeneration timing of whether or not this has reached a predetermined differential pressure predetermined value ΔPr, and to determine the electric air pump 7 and the electric heater 8 at the time of regeneration. Execute the process to drive.

According to the present invention, in addition to the above operation, the control circuit 6 detects the differential pressure ΔP before and after the filter regeneration, and further corrects the predetermined differential pressure value ΔPr for determining the regeneration timing. The alarm 24 is activated. The operation of the control circuit 6 relating to the correction of the predetermined differential pressure value ΔPr, which is the reference for the filter regeneration processing and the filter regeneration timing determination, will be described below with reference to FIGS. 2 and 3.

FIG. 2 is a flow chart of a program for executing the operation of the control circuit 6 described above, and FIG. 3 is a new filter of the exhaust gas purification apparatus achieved by this program, which does not collect particulates. FIG. 6 is a diagram showing a temporal change in a differential pressure across the filter after repeating particulate collection / regeneration from the state. Incidentally, the differential pressure ΔP on the vertical axis in FIG. 3 is converted into the differential pressure in the standard operating state from the intake air amount Ga detected by the air flow meter 23 and the exhaust temperature Th detected by the exhaust temperature sensor 22, as described above. It was done.

Referring to FIG. 2, first, at step S21, the pressure difference between the front and rear of the filter ΔP '(before conversion) by the pressure sensors 16 and 17, the intake air amount Ga by the air flow meter 23,
The exhaust temperature Th is detected by the exhaust temperature sensor 22,
Next, in step S22, the filter front-rear differential pressure ΔP ′ is converted into the filter front-rear differential pressure ΔP under the standard operating condition by the illustrated formula from the reference exhaust temperature Tbase and the reference intake intake air amount Gbase which are predetermined as correction conditions.

The reference exhaust gas temperature Tbase and the reference intake air intake amount Gbase are preferably determined from the exhaust gas temperature and the intake air intake amount under the most frequently used operating conditions. Next, at step S23, the differential pressure Δ obtained as described above.
An averaging process is performed so that P has reliability. In this process, for example, specifically, the differential pressure detected and converted at a constant time interval (for example, every 50 mmsec) in steps S21 and 22 is determined by a predetermined number (for example, n = 30) by the illustrated arithmetic expression.
It is also possible to obtain the arithmetic moving average value over 0).

In this way, the current differential pressure across the filter Δ
If P is determined, then the routine proceeds to step S24.
And the differential pressure predetermined value ΔPr stored in a predetermined memory in the control circuit 6 is called in, and the differential pressure ΔP is changed to the predetermined value ΔP.
It is determined whether or not r is exceeded. And this step S24
If No, that is, if the differential pressure ΔP has not risen to the extent that regeneration is required, the routine returns to step S21 to detect the differential pressure in order to continue the particulate trapping operation.

On the other hand, if it is determined that the differential pressure ΔP exceeds the predetermined value ΔPr (Yes), the routine proceeds to step S25, where the filter regeneration process is executed for the first time. This filter regeneration process is exactly the same as that of the conventional exhaust gas purification device. In the illustrated device, both the exhaust gas control valves 4 and 5 are operated to the dotted line positions, and the electric heater 8 is energized while the electric air pump 7 is energized. A signal for driving the semiconductor relays 10 and 11 is output to operate the, and the particulates collected by the filter 1 are ignited and burned.

When the regeneration process of the filter 1 is completed in this way, the routine next proceeds to step S26,
From this, the detection / conversion processing of the differential pressure ΔPaf after filter regeneration, which is a feature of this embodiment, is executed. As described above, this is for detecting the differential pressure increase due to the ash content in the engine oil by comparing the detected differential pressure ΔPaf with the filter front-back differential pressure ΔPai at the time of new product. Then, after the reproduction process of step S25 is completed,
For example, the differential pressure ΔPaf ′ at the time when one minute has elapsed is detected,
This can be obtained by converting the exhaust temperature Th and the intake air amount Ga at that time.

By the way, the pressure difference ΔPf across the filter after the filter regeneration thus obtained may change depending on the filter regeneration condition, such as when the collected particulates are not completely incinerated. Therefore, in this embodiment, in order to detect the pure differential pressure change contributed by the ash, in the subsequent step S27, as shown in FIG. 3, the differential pressure data after regeneration is averaged a plurality of times (for example, 20 times). , Purify.

Then, in step S28, the average value Δ of the differential pressure before and after the filter after the reproduction thus obtained is obtained.
The initial differential pressure Δ decreases as Pav decreases engine performance.
Whether or not it has changed from Pi is determined by a predetermined differential pressure value ΔP1.
It is judged by whether it is larger than. Therefore, when the ash collection rate in the filter 1 increases, the filter itself also reaches the end of use, it is determined as Yes in step S28, and the differential pressure average value ΔPav after filter regeneration exceeds the predetermined differential pressure value ΔP1. (Right part c in FIG. 3), the routine proceeds to step S29 to activate the above-mentioned alarm device 24 to prompt the driver to inspect the filter. Incidentally, step S28
If No, step S29 is skipped.

Next, in step S30, the previous step S
The regeneration start differential pressure set value ΔPro set at the time of new filter is corrected by the following formula by the differential pressure increase due to ash collection, which is obtained from the post-regeneration filter differential pressure average value ΔPav at 27. Processing is done. ΔPr = ΔPro + (ΔPav−ΔPai) where ΔPro: first regeneration start differential pressure setting value ΔPai: differential pressure value at the time of new product Note that the differential pressure value ΔPai at the time of new product is a plurality of times (eg, , 20 times) until the completion of playback processing,
It may be a so-called average value of post-regeneration differential pressure (for example, corresponding to the one-dot chain line of the left portion a in FIG. 3) at the initial stage of using the filter.

If the first reproduction start differential pressure setting value ΔPro is corrected as described above, the latest reproduction start differential pressure setting value ΔPr (for example, two points in the central portion b in FIG. 3) is obtained. This is a control line 6 as a chain line)
It is stored in the memory and the present routine is finished. As described above, according to the present embodiment, the differential pressure ΔPa before and after the filter regeneration is detected a plurality of times, and the regeneration is started according to the difference between the differential pressure ΔPai after the regeneration when the filter is new or at the initial stage of use. Since the set pressure difference ΔPro is corrected, it is possible to detect the amount of change in the pressure difference caused by the ash trap, regardless of the engine operating state, and therefore the filter regeneration timing to be corrected can be made appropriate.

The embodiment of the present invention has been described above.
The parameter indicating the degree of filter clogging is not limited to the above-mentioned differential pressure across the filter, and the amount of ash collected in the filter due to, for example, a change in the weight of the filter may be detected. Further, in the embodiment, the first reproduction start differential pressure set value ΔPro is corrected by the differential pressure change amount (ΔPav−ΔPai) after the reproduction, but this set value is not changed and the detection at the time of particulate collection is performed. The regeneration timing may be determined based on a value obtained by subtracting the differential pressure change amount from the differential pressure (after conversion) ΔP.

In the embodiment, the exhaust gas purification apparatus of the forward flow regeneration system is used as an example of the structure, but the backward flow regeneration system is also applicable and the number of filters is not limited.

[0031]

As described above, according to the present invention, the clogging degree average value after a plurality of times of filter regeneration is detected and the regeneration timing is corrected according to the detected value, so that the engine operating state and the filter regeneration state are Regardless of the condition, it is possible to detect the change in the clogging degree caused by the ash collection, and therefore the filter regeneration timing to be corrected can be made appropriate, and the particulate collection amount for each time can be made constant and stable regeneration can be performed. You can

In addition, if the average value of the degree of clogging after a plurality of times of regeneration exceeds a predetermined value, engine performance may be significantly deteriorated. However, in the present invention, an alarm is issued to the outside, so the driver should be careful. Can be encouraged.

[Brief description of drawings]

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

FIG. 2 is a control flowchart illustrating the operation of the exhaust emission control device of FIG.

FIG. 3 is a diagram showing a change in filter clogging degree according to the present invention as a change in differential pressure over time.

[Explanation of symbols]

 1 ... Filter 6 ... Control Circuit 7 ... Electric Air Pump 8 ... Electric Heater 9 ... Battery 16, 17 ... Pressure Sensor 22 ... Exhaust Temperature Sensor 24 ... Alarm

Claims (2)

[Claims] 1. A diesel engine exhaust system comprising a filter for collecting particulates and a regenerating unit for regenerating the filter, and the regenerating unit is operated at regular intervals to collect the particulates on the filter. In an exhaust emission control device for a diesel engine that ignites and burns, a filter clogging degree detection unit that detects the filter clogging degree after the filter regeneration, and a filter regeneration timing depending on the detected clogging degree average value after multiple times of filter regeneration. An exhaust emission control device for a diesel engine, comprising: a regeneration timing correction means for performing correction. 2. The method according to claim 1, further comprising alarm means for issuing an alarm to the outside when the detected clogging degree average value after a plurality of times of filter regeneration is not less than a predetermined value. Exhaust emission control system for diesel engines.