JPH1089047A - Exhaust fine particle purifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an abnormality of a pressure sensor system (a pressure introducing pipe and a pressure sensor), to be generated caused by sticking of particulates and moisture in an exhaust fine particle purifying device for estimating the trapping amount of a filter on the basis of filter differential pressure and for regenerating the filter. SOLUTION: When it is judged (step 101) that the specified time in which the exhaust gas flow is vanished passed after an engine is stopped, filter differential pressure is found (step 102), and processing for setting a threshold value for judging an abnormality of a pressure sensor system is performed (step 103 to 108). The set threshold value and the filter differential pressure found at this time are compared with each other (step 109). When the filter differential pressure is larger than the threshold value, an abnormality of the pressure sensor system is stored (step 110), and the abnormality of the pressure sensor system is informed to a driver in starting of the next operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for purifying exhaust particulates which collects exhaust particulates contained in exhaust gas of a diesel engine using a filter and burns the collected exhaust particulates to regenerate the filter. .

[0002]

2. Description of the Related Art Since the exhaust gas of a diesel engine contains a large amount of exhaust particulates (hereinafter referred to as "particulates"), a filter for trapping the particulates is provided in an exhaust passage. As the amount of particulates accumulated inside the filter increases with use, the permeability gradually deteriorates and the performance decreases, so that the amount of particulates collected by the filter exceeds a predetermined amount. Then, the filter is regenerated.

[0003] The regeneration of the filter means that the particulates are burned and removed by operating a regeneration means such as an electric heater provided on an end face of the filter or an air pump for supplying air required for burning the particulates. means. The amount of particulates collected by the filter can be estimated by using a differential pressure (filter differential pressure) generated in the filter.
In this case, the filter differential pressure can be obtained by subtracting the downstream pressure from the upstream pressure of the filter.

[0004]

The pressure on the upstream side of the filter is detected by being introduced into a pressure sensor by a pressure introducing pipe. However, since the upstream side of the filter contains a large amount of particulates and moisture from a diesel engine, the pressure on the upstream side of the filter is high. Adheres to the pressure introduction pipe and pressure sensor that compose the pressure sensor system,
The filter differential pressure cannot be accurately detected, and the amount of trapped particulate cannot be accurately estimated.

The present invention has been made in view of the above problems, and has as its object to detect an abnormality of a pressure sensor system due to adhesion of particulates, moisture, and the like.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a pressure sensor system is provided based on a filter differential pressure detected after a lapse of a predetermined time from a stop of a diesel engine. Characterized in that an abnormality determining means for determining an abnormality of the above is provided. During operation of the diesel engine, the pressure in the pressure inlet pipe on the upstream side of the filter is high, but if particulates or moisture adheres to the pressure inlet pipe or pressure sensor, the pressure will be introduced even if the diesel engine stops. The pressure in the pipe is less likely to decrease. By utilizing such a phenomenon and detecting the filter differential pressure after stopping the diesel engine, an abnormality of the pressure sensor system can be detected.

Further, since the exhaust gas flows immediately after the diesel engine stops, the abnormality of the pressure sensor system can be accurately detected by detecting the filter differential pressure after a lapse of a predetermined time when the exhaust gas stops flowing. The invention according to claim 2 is characterized in that a threshold value for determining abnormality of the pressure sensor system is set according to a change state of the filter differential pressure. Therefore, the abnormality of the pressure sensor system can be detected accurately with the threshold value according to the change state of the filter differential pressure.

In this case, a value obtained by adding a predetermined value to the past minimum value of the filter differential pressure is set as the threshold value as in the invention according to claim 3, and as in the invention according to claim 4. If the minimum value is gradually increased every time the number of stoppages of the diesel engine reaches a predetermined number, an appropriate threshold value can be set according to the change state of the filter differential pressure.

Further, if the abnormality of the vehicle is notified to the driver of the vehicle when the abnormality is determined, the parts can be replaced quickly.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an overall configuration diagram of an exhaust gas purifying apparatus for a diesel engine. Diesel engine 1
On the exhaust pipe side, a filter 2 and a filter 3 for collecting particulates to be exhausted are provided in parallel on the branch downstream side of the exhaust pipe. On the upstream side of the filters 2 and 3, electric heaters 4 and 5 for igniting the collected particulates are provided. Then, the exhaust pipes merge again and are connected to the muffler 6. An air cleaner 7 is provided on the intake side of the diesel engine 1.

Exhaust switching valves 8 and 9 are provided at two locations in the branch of the exhaust pipe to select a filter to be collected. In FIG. 1, the filter 3 is in a state of collecting particulates in the exhaust gas. The discharge side of the air pump (A / P) 10 is connected to the filter 2,
The air pump 10 is connected to the upstream side of the filter 3.
Is provided with an air cleaner 13 for an air pump. The downstream side of the filters 2 and 3 is opened to the atmosphere via the air control valves 14 and 15.

The air control valves 11, 12, 14, and 15 are for forming a flow path for supplying combustion air to a filter to be regenerated, and in FIG. An air flow path from the air pump 10 to the air control valve 11, the filter 2, the air control valve 14, and opening to the atmosphere is formed. The pressure on the upstream side of the filter is detected by the front pressure sensor 16, and the pressure on the downstream side of the filter is detected by the rear pressure sensor 17. In this case, the pressure on the upstream side of the filter is introduced to the front pressure sensor 16 by the upstream pressure introduction pipe 18, and the pressure on the downstream side of the filter is introduced to the rear pressure sensor 17 by the downstream pressure introduction pipe 19. Further, an engine speed sensor 20 and an exhaust gas temperature sensor 21 for detecting an exhaust gas temperature are provided.

The ECU 22 includes the sensors 16 and 1 described above.
Based on the signals from 7, 20, and 21, the amount of collection of the filter on the collection side is calculated. In this case, the ECU 22 obtains the filter differential pressure by subtracting the post-filter pressure from the pre-filter pressure based on the signals from the front pressure sensor 16 and the rear pressure sensor 17,
Further, the volumetric flow rate of the exhaust gas determined from the engine rotational speed and the exhaust temperature is determined from the signals from the engine rotational speed sensor 20 and the exhaust temperature sensor 21, and the trapping amount of the filter is determined from the filter differential pressure and the exhaust gas volume flow rate. calculate. further,
When the ECU 22 determines that the calculated trapping amount is equal to or more than the predetermined amount, the ECU 22 regenerates the trapped filter by using the air pump 10, the electric heaters 4 and 5, and the exhaust switching valves 8 and 9. , Air control valves 11, 12, 14, 1
5 and the like are operated to perform filter regeneration control. The filter regeneration control itself based on such calculation of the trapping amount is known.

In addition to the above-described control, the ECU 22 performs a process of determining an abnormality of the pressure sensor system including the upstream pressure introducing pipe 18 and the pre-pressure sensor 16. FIG. 2 shows a graph in which the filter differential pressure when a predetermined time has elapsed after the engine is stopped is plotted in correspondence with the number of engine stops. When the signals from the front pressure sensor 16 and the rear pressure sensor 17 are taken in, the signals are converted into digital signals by an A / D converter (not shown). Therefore, the signals are calculated based on a quantization error or a non-linear error of the A / D converter. As shown in the figure, the generated filter differential pressure varies. Here, if particulates or moisture adhere to the upstream pressure introduction pipe 18 or the pre-pressure sensor 16, the filter differential pressure increases as shown in the figure. Therefore, abnormality of the pressure sensor system can be determined by comparing the filter differential pressure with a predetermined threshold value.

The ECU 22 starts the processing shown in FIG. 3 when the IG switch 23 is turned off, that is, when the engine is stopped, in order to determine the abnormality of the pressure sensor system. First, it is determined whether or not a predetermined time has elapsed since the engine was stopped. Is determined (step 101). Here, the predetermined time is a time when exhaust gas flow stops immediately after the stop of the diesel engine, and specifically, a time of 2 to 3 seconds.

When the predetermined time has elapsed, the pre-pressure sensor 1
6. The filter differential pressure is obtained by subtracting the post-filter pressure from the pre-filter pressure based on the signal from the post-pressure sensor 17 (step 102). Thereafter, a process for setting a threshold value for determining an abnormality of the pressure sensor system is performed (steps 103 to 1).
08). The ECU 3 is provided with an EEPROM (non-volatile storage unit) 22a for storing a memory value for determining the threshold value, a counter value to be described later, and presence / absence of abnormality in the pressure sensor system.

First, it is determined whether or not the filter differential pressure obtained in step 102 is smaller than a memory value (step 103). Here, the memory value indicates the minimum value of the past filter differential pressure. If the current filter differential pressure is smaller than the memory value, the current filter differential pressure is stored in the EEPROM 22a as a memory value (step 1).
04). Note that a value obtained by adding the memory value stored in the EEPROM 22a and the predetermined value A is set as a threshold value in step 108.

Further, it is determined whether or not the counter value indicating the number of engine stops has reached N (for example, a value of 20) (step 105). It counts up until the counter value reaches N (step 106). When the counter value reaches N, the memory value is incremented by a predetermined value B, and the memory value is gradually increased (step 107). Step 103 described above
By the processing from to 108, the memory value stored in the EEPROM 22a is updated to the filter differential pressure at that time when the filter differential pressure is smaller than the minimum value, as shown in FIG. Each time the memory value is increased, the memory value is increased by a predetermined value B (for example, 1 digit).
The threshold value is a predetermined value A (for example, 2
The value is larger by 0 digit). With such a threshold value setting, the set threshold value changes according to the change state of the filter differential pressure.

Then, the set threshold value is compared with the filter differential pressure obtained this time (step 109). When the filter differential pressure exceeds the threshold value, the abnormality of the pressure sensor system is stored in the EEPROM 22a (step 109). 110).
When the abnormality of the pressure sensor system is stored in the EEPROM 22a, the ECU 22 turns on the warning lamp 25 at the start of the next operation (when the IG is turned on) to notify the driver of the abnormality of the pressure sensor system.

After that, when the pressure sensor system parts are replaced and the filter differential pressure is reduced to return to the normal state,
The abnormal storage in the EEPROM 22a is cleared (step 111). In the above embodiment, when the filter pressure difference is detected, the rear pressure sensor 17 detects the atmospheric pressure downstream of the filter. Therefore, the downstream pressure introduction pipe 19 as shown in the above embodiment is not necessarily required. The sensor which detects the atmospheric pressure by another configuration is not limited to the configuration including the pressure sensor 17 and the rear pressure sensor 17.

Further, in the above-described embodiment, the present invention is applied to a so-called dual type exhaust particulate purifying apparatus in which collection of particulates and regeneration of a filter are alternately performed by two flow paths. A filter is provided only in the passage, the other passage is used as a bypass passage, and both passages are switched by an exhaust switching valve, and when the filter is regenerated, the exhaust gas is bypassed to the bypass passage by the exhaust switching valve to regenerate the filter. The present invention can be applied to such an exhaust particulate purification device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust particulate purification device showing an embodiment of the present invention.

FIG. 2 is a diagram in which a filter differential pressure when a predetermined time has elapsed after the engine is stopped is plotted in correspondence with the number of engine stops.

FIG. 3 is a flowchart showing an abnormality determination process of a pressure sensor system by an ECU 22.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2, 3 ... Filter, 16 ... Front pressure sensor, 17 ... Rear pressure sensor, 18 ... Upstream pressure introduction pipe, 19 ... Downstream pressure introduction pipe, 22 ... ECU, 25 ... Warning lamp.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F01N 3/00 ZAB F01N 3/00 ZABF F02B 77/08 F02B 77/08 M G01M 15/00 ZAB G01M 15/00 ZABZ

Claims (5)

[Claims] 1. A filter (2, 3) provided in an exhaust passage of a diesel engine (1) for trapping exhaust particulates;
A pressure sensor for detecting an upstream pressure and a downstream pressure of the filter; a pressure sensor for detecting an upstream pressure of the filter; A pressure sensor system comprising a pressure introduction pipe (18) for introducing an upstream pressure to the pressure sensor, based on a filter differential pressure obtained by subtracting a downstream pressure from the detected upstream pressure of the filter. An exhaust particulate purifying apparatus configured to estimate a trapped amount of exhaust particulates and regenerate a filter, wherein the pressure sensor is provided based on the filter differential pressure detected after a lapse of a predetermined time after the diesel engine is stopped. Abnormality determining means (101 to 10) for determining a system abnormality
9) An exhaust gas purifying apparatus characterized by having 9). 2. The apparatus according to claim 1, wherein the abnormality determining unit determines the abnormality of the pressure sensor system by comparing the filter differential pressure with a predetermined threshold value. Threshold setting means (10) for setting a threshold
The exhaust particulate purification device according to claim 1, wherein the exhaust particulate purification device has the following configuration. 3. The threshold value setting means includes means (103, 104, 108) for setting a value obtained by adding a predetermined value to a past minimum value of the filter differential pressure as the threshold value. The exhaust particulate purification device according to claim 2, wherein: 4. The apparatus according to claim 3, wherein said threshold value setting means includes means (105 to 107) for gradually increasing said minimum value each time the number of stoppages of said diesel engine reaches a predetermined number. Exhaust particulate purification equipment. 5. The method according to claim 1, wherein the abnormality determination unit determines an abnormality.
The exhaust particulate purification device according to any one of claims 1 to 4, further comprising means (25) for notifying the driver of the vehicle of the abnormality.