JP3785691B2 - Exhaust particulate purification equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust particulate purification device that 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]
[Prior art]
Since exhaust gas from a diesel engine contains a lot of exhaust particulates (hereinafter referred to as particulates), a filter for collecting the particulates is provided in the exhaust passage. As the amount of particulates accumulated inside the filter increases with use, the air permeability gradually deteriorates and the performance deteriorates, so the collected amount of particulates collected in the filter exceeds a predetermined amount. Then, the filter is regenerated.
[0003]
The regeneration of the filter means that the particulate is burned and removed by operating a regeneration means such as an electric heater provided on the end face of the filter or an air pump for supplying air required for burning the particulate.
Further, the amount of particulates collected by the filter can be estimated by using a differential pressure (filter differential pressure) generated by 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]
[Problems to be solved by the invention]
The upstream side pressure of the filter is detected by being introduced into the pressure sensor by the pressure introduction pipe, but the upstream side of the filter contains a large amount of particulates and moisture from the diesel engine, so that the pressure introduction that constitutes the pressure sensor system If it adheres to a tube or a pressure sensor, the filter differential pressure cannot be detected accurately, and the amount of particulates collected cannot be estimated accurately.
[0005]
The present invention has been made in view of the above problems, and an object of the present invention is to detect an abnormality in a pressure sensor system due to adhesion of particulates or moisture.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided abnormality determination means for determining abnormality of the pressure sensor system based on the filter differential pressure detected after a predetermined time has elapsed since the diesel engine stopped. It is characterized by providing.
While the diesel engine is operating, the pressure in the pressure inlet pipe upstream of the filter is high, but if particulates or moisture adheres to the pressure inlet pipe or pressure sensor, the pressure is introduced even if the diesel engine stops. The pressure in the tube is less likely to decrease. By utilizing such a phenomenon and detecting the filter differential pressure after the diesel engine is stopped, an abnormality in the pressure sensor system can be detected.
[0007]
Further, since there is exhaust flow immediately after the diesel engine is stopped, 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 flow ceases.
The invention according to claim 2 is characterized in that a threshold value for determining an 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 accurately detected with the threshold value corresponding to the change state of the filter differential pressure.
[0008]
In this case, as in the invention described in claim 3, a value obtained by adding a predetermined value to the past minimum value of the filter differential pressure is set as a threshold value, and as in the invention described in claim 4, diesel is used. If the minimum value is gradually increased every time the number of engine stops reaches a predetermined number, an appropriate threshold value can be set according to the change state of the filter differential pressure.
[0009]
Further, as in the fifth aspect of the invention, when the abnormality is determined and the vehicle driver is notified of the abnormality, the parts can be replaced quickly.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an overall configuration diagram of an exhaust emission control device for a diesel engine.
On the exhaust pipe side of the diesel engine 1, a filter 2 and a filter 3 for collecting exhausted particulates 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. The exhaust pipes join again and are connected to the muffler 6. An air cleaner 7 is provided on the intake side of the diesel engine 1.
[0011]
Exhaust gas switching valves 8 and 9 are provided at two locations of the branch portion of the exhaust pipe, and a filter to be collected is selected. In FIG. 1, the particulates in the exhaust are collected on the filter 3 side.
The discharge side of the air pump (A / P) 10 is connected to the upstream side of the filter 2 and the filter 3 via the air control valves 11 and 12, and an air pump air cleaner 13 is provided on the suction side of the air pump 10. Yes. The downstream side of the filters 2 and 3 is open to the atmosphere via air control valves 14 and 15.
[0012]
The air control valves 11, 12, 14, and 15 are for forming a flow path for supplying combustion air to the regenerating filter. In FIG. 1, the air control valve 11 regenerates from the air pump 10 for regeneration on the filter 2 side. The air control valve 11, the filter 2, the air control valve 14, and an air flow path that is open to the atmosphere are formed.
Further, the upstream pressure of the filter is detected by the front pressure sensor 16, and the downstream pressure 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 temperature sensor 21 for detecting the exhaust temperature are provided.
[0013]
The ECU 22 calculates the collection amount of the filter on the collection side based on the signals from the sensors 16, 17, 20, and 21 described above. 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 pre-pressure sensor 16 and the post-pressure sensor 17, and further uses the signals from the engine speed sensor 20 and the exhaust temperature sensor 21. The volume flow rate of the exhaust gas obtained from the engine speed and the exhaust temperature is obtained, and the amount of collected filter is calculated from the filter differential pressure and the volume flow rate of the exhaust gas. Further, when the ECU 22 determines that the calculated collection amount is equal to or greater than a predetermined amount, the above-described air pump 10, electric heaters 4, 5, and exhaust switch valve 8 are used to regenerate the collected filter. 9, the air control valves 11, 12, 14, 15 and the like are operated to perform filter regeneration control. Such filter regeneration control based on the calculation of the amount of collection is known.
[0014]
In addition to the control described above, the ECU 22 performs a process for determining an abnormality in the pressure sensor system including the upstream pressure introduction pipe 18 and the pre-pressure sensor 16.
FIG. 2 shows a plot of the filter differential pressure corresponding to the number of engine stops when a predetermined time elapses after the engine is stopped. When signals from the pre-pressure sensor 16 and the post-pressure sensor 17 are taken in, they are converted into digital signals by an A / D converter (not shown), and thus are calculated based on the quantization error or non-linear error of the A / D converter. The filter differential pressure varies as shown in the figure. Here, if particulates or moisture adheres to the upstream side pressure introducing pipe 18 or the pre-pressure sensor 16, the filter differential pressure increases as shown in the figure. Therefore, an abnormality of the pressure sensor system can be determined by comparing the filter differential pressure with a predetermined threshold value.
[0015]
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 whether or not the pressure sensor system is abnormal. (Step 101). Here, the predetermined time is a time when the exhaust flow immediately after the diesel engine is stopped, specifically, a time of 2 to 3 seconds.
[0016]
When the predetermined time has elapsed, a filter differential pressure is obtained by subtracting the post-filter pressure from the pre-filter pressure based on signals from the pre-pressure sensor 16 and the post-pressure sensor 17 (step 102).
Thereafter, processing for setting a threshold value for determining abnormality of the pressure sensor system is performed (steps 103 to 108). The ECU 3 is provided with an EEPROM (nonvolatile storage means) 22a for storing a memory value for determining the threshold value, a counter value to be described later, and the presence or absence of abnormality in the pressure sensor system.
[0017]
First, it is determined whether or not the filter differential pressure obtained in step 102 is smaller than the memory value (step 103). Here, the memory value indicates the minimum value of the past filter differential pressure. When 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 104). 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.
[0018]
Further, it is determined whether or not the counter value indicating the number of engine stops has become N (for example, a value of 20) (step 105). Counting up is performed until the counter value reaches N (step 106). When the counter value becomes N, the memory value is added by a predetermined value B and the memory value is gradually increased (step 107).
As shown in FIG. 2, 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, and the number of times the engine is stopped. The memory value is incremented by a predetermined value B (for example, 1 digit) every time the value becomes 20 times. The threshold value is larger than the memory value by a predetermined value A (for example, 20 digits). By setting such a threshold value, the set threshold value changes according to the change state of the filter differential pressure.
[0019]
Then, the set threshold value is compared with the currently obtained filter differential pressure (step 109), and when the filter differential pressure becomes larger than the threshold value, the abnormality of the pressure sensor system is stored in the EEPROM 22a (step 110).
When the abnormality of the pressure sensor system is stored in the EEPROM 22a, the ECU 22 lights the warning lamp 25 at the start of the next operation (when the IG is on) to notify the driver of the abnormality of the pressure sensor system.
[0020]
Thereafter, when the pressure sensor system is replaced and the filter differential pressure is reduced to return to the normal state, the abnormal memory of the EEPROM 22a is cleared (step 111).
In the above embodiment, when the filter differential pressure is detected, the post 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 used. In addition to the configuration including the rear pressure sensor 17, a configuration that detects the atmospheric pressure using another configuration may be used.
[0021]
Further, in the above-described embodiment, the present invention is applied to a so-called dual type exhaust particulate purification device that alternately collects particulates and regenerates a filter by two flow paths, but only in one flow path. Exhaust that provides a filter and uses the other flow path as a bypass flow path, switches both flow paths with an exhaust switching valve, and regenerates the filter by bypassing the exhaust gas to the bypass flow path with the exhaust switching valve when the filter is regenerated. The present invention can also be applied to a particulate purification apparatus.
[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 graph plotting the filter differential pressure when a predetermined time has elapsed after the engine has stopped, in correspondence with the number of engine stops.
FIG. 3 is a flowchart showing abnormality determination processing of the pressure sensor system by the ECU 22;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2, 3 ... Filter, 16 ... Pre-pressure sensor,
17 ... rear pressure sensor, 18 ... upstream pressure introduction pipe, 19 ... downstream pressure introduction pipe,
22 ... ECU, 25 ... warning lamp.

Claims (5)

A filter (2, 3) provided in the exhaust passage of the diesel engine (1) for collecting exhaust particulates, and pressure detection means (17-19) for detecting an upstream pressure and a downstream pressure of the filter. The pressure detecting means has a pressure sensor system comprising a pressure sensor (16) for detecting the upstream pressure of the filter and a pressure introducing pipe (18) for introducing the upstream pressure of the filter to the pressure sensor. In the exhaust particulate purification apparatus, the amount of exhaust particulate collection is estimated based on the filter differential pressure obtained by subtracting the downstream pressure from the detected upstream pressure of the filter, and the filter is regenerated.
Exhaust particulate purification comprising abnormality determination means (101 to 109) for determining abnormality of the pressure sensor system based on the filter differential pressure detected after a predetermined time has elapsed since the diesel engine stopped. apparatus. The abnormality determining means determines an abnormality of the pressure sensor system by comparing the filter differential pressure with a predetermined threshold, and sets the threshold according to a change state of the filter differential pressure. 2. The exhaust gas particulate purifier according to claim 1, further comprising a threshold value setting means (103 to 108) for performing the operation. 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. Exhaust particulate purification device as described in 2. The exhaust particulate purification device according to claim 3, wherein the threshold value setting means includes means (105 to 107) for gradually increasing the minimum value every time the diesel engine is stopped a predetermined number of times. . The exhaust particulate purification device according to any one of claims 1 to 4, further comprising means (25) for notifying a vehicle driver of an abnormality based on an abnormality determination of the abnormality determination means.

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