JP2020169585A - Engine control device - Google Patents

Abstract

To enable regeneration of a filter with an air-fuel ratio accurately controlled.SOLUTION: In the case where learning of a regeneration learning value that is a learning value for compensating a steady deviation of an air-fuel ratio in a regeneration execution region that is an engine operating region where temperature rise treatment and purification treatment for filter regeneration are executed has not been completed when filter regeneration is requested (NO in S130), the purification treatment is started (S160) after learning of the regeneration learning value is performed (S150).SELECTED DRAWING: Figure 3

Description

The present invention relates to an engine control device applied to an engine in which a filter for collecting fine particles in exhaust gas is provided in an exhaust passage.

In some engines such as in-vehicle engines, a filter for collecting fine particle substances in the exhaust gas is provided in the exhaust passage. As the deposition of particulate matter on the filter progresses, the filter becomes clogged. Therefore, when the accumulation of the filter progresses to some extent, the filter may be purified to burn and purify the accumulated fine particle substance.

Conventionally, in Patent Document 1, NOx storage reduction is performed by alternately performing a lean combustion operation in which the air-fuel ratio is leaner than the theoretical air-fuel ratio and a rich combustion operation in which the air-fuel ratio is richer than the theoretical air-fuel ratio. A technique for raising the temperature of the type catalyst device and recovering the catalyst device from sulfur poisoning is described. The purification treatment of the filter as described above can be performed through the same alternating execution of the lean combustion operation and the rich combustion operation.

JP-A-2003-293832

By the way, some engines for vehicles and the like perform air-fuel ratio learning control that learns the deviation of the measured value from the target value of the air-fuel ratio as the air-fuel ratio learning value based on the measurement result of the air-fuel ratio sensor installed in the exhaust passage. is there. On the other hand, the temperature raising treatment and the purification treatment of the filter as described above may be performed only in the operating region which is usually rarely used. In such a case, the air-fuel ratio learning value is exclusively learned in an operating region different from the operating region in which the temperature rise treatment or purification treatment is performed. Therefore, the learned air-fuel ratio learning value may deviate from an appropriate value in the operating region where the temperature raising treatment or the purification treatment is performed. If the purification treatment is performed under such a situation, combustion may be performed at an inappropriate air-fuel ratio, and the NOx and CO emissions of the engine may be significantly increased. In addition, the speed of combustion purification of fine particle substances during purification treatment in the filter changes depending on the oxygen excess rate of the exhaust gas, so if there is a deviation in the air-fuel ratio during purification treatment, excess or deficiency will occur during the purification treatment implementation period. There is also a risk that it will end up.

An engine control device that solves the above problems is applied to an engine in which a filter that collects fine particles in the exhaust gas is installed in an exhaust passage. Then, the engine control device performs a temperature raising process for raising the temperature of the filter in response to the regeneration request of the filter, and performs a purification process for burning and purifying the fine particle substance deposited on the filter. It will be carried out after completion. Further, the engine control device learns the air-fuel ratio learning value for regeneration, which is the air-fuel ratio learning value in the regeneration execution region when the engine is operating in the regeneration execution region, which is the operation region of the engine for which purification processing is performed. Perform the air-fuel ratio learning process for regeneration. Then, when the learning of the regenerated air-fuel ratio learning value is not completed when the filter is requested to be regenerated, the engine control device performs the purification process after learning the regenerated air-fuel ratio learning value. ..

In the engine control device configured as described above, the purification process is performed in a state where the learning of the regenerated air-fuel ratio learning value in the operating region of the engine to be purified is completed. Therefore, the air-fuel ratio of the engine during the purification treatment is less likely to deviate, and the deterioration of the exhaust properties of the engine during the purification treatment and the excess or deficiency of the purification treatment implementation period can be suppressed.

The figure which shows typically the structure of one Embodiment of an engine control device. The graph which shows the setting mode of the air-fuel ratio learning area in the engine control device. The flowchart which shows the flow of the process which concerns on the filter regeneration control in the engine control device.

Hereinafter, an embodiment of the engine control device will be described in detail with reference to FIGS. 1 to 3.
As shown in FIG. 1, the engine 10 mounted on the vehicle includes a cylinder 12 in which the piston 11 is housed so as to be reciprocating. The piston 11 is connected to the crankshaft 14 via a connecting rod 13. Then, the reciprocating motion of the piston 11 in the cylinder 12 is converted into the rotational motion of the crankshaft 14.

An intake passage 15 which is an air introduction path to the cylinder 12 is connected to the cylinder 12. The intake passage 15 is provided with an air flow meter 16 that detects the flow rate of air flowing through the intake passage 15 (intake air amount GA). A throttle valve 17 is provided in a portion of the intake passage 15 on the downstream side of the air flow meter 16. Further, a fuel injection valve 18 is installed in a portion of the intake passage 15 on the downstream side of the throttle valve 17. The fuel injection valve 18 injects fuel into the air flowing through the intake passage 15 to form an air-fuel mixture.

The cylinder 12 is provided with an intake valve 19 that opens and closes the intake passage 15 with respect to the cylinder 12. Further, the air-fuel mixture is introduced into the cylinder 12 from the intake passage 15 according to the opening of the intake valve 19. The cylinder 12 is provided with an ignition device 20 that ignites and burns the air-fuel mixture in the cylinder 12 by a spark.

An exhaust passage 21 which is an exhaust path for exhaust gas generated by combustion of the air-fuel mixture is connected to the cylinder 12. Further, the cylinder 12 is provided with an exhaust valve 22 that opens and closes the exhaust passage 21 with respect to the cylinder 12. Exhaust gas is introduced into the exhaust passage 21 from the inside of the cylinder 12 according to the opening of the exhaust valve 22. A three-way catalyst device 23 that oxidizes CO and HC in the exhaust gas and reduces NOx at the same time is installed in the exhaust passage 21. Further, a filter 24 for collecting fine particle substances is installed in a portion of the exhaust passage 21 on the downstream side of the three-way catalyst device 23. Further, an air-fuel ratio sensor 25 for detecting the oxygen concentration of the gas flowing through the exhaust passage 21, that is, the air-fuel ratio ABYF of the air-fuel mixture is installed in the portion of the exhaust passage 21 on the upstream side of the three-way catalyst device 23. ..

The electronic control unit 27 as an engine control device for controlling the engine 10 is configured as a microcomputer having an arithmetic processing circuit for executing arithmetic processing for control and a memory for storing control programs and data. ing. The detection signals of the above-mentioned air flow meter 16, air-fuel ratio sensor 25, and catalyst outflow gas temperature sensor 26 are input to the electronic control unit 27. Further, a detection signal of the crank angle sensor 28 that detects the crank angle θc, which is the rotation angle of the crankshaft 14, is input to the electronic control unit 27. Then, the electronic control unit 27 calculates the engine speed NE from the detection result of the crank angle θc. Further, the electronic control unit 27 is also input with the detection signals of the vehicle speed sensor 29 that detects the vehicle speed V, which is the traveling speed of the vehicle, and the accelerator position sensor 31 that detects the accelerator opening ACC, which is the operation amount of the accelerator pedal 30. ing. Then, the electronic control unit 27 controls the opening degree of the throttle valve 17, the amount and timing of fuel injection of the fuel injection valve 18, the execution timing (ignition timing) of the spark of the ignition device 20, and the like based on the detection results of these sensors. By doing so, the operating state of the engine 10 is controlled according to the traveling condition of the vehicle.

In the engine 10 configured as described above, the fine particles in the exhaust gas are collected by the filter 24 to suppress the release of the fine particles to the outside air. Such a filter 24 may cause clogging due to the accumulation of collected fine particle substances. On the other hand, the electronic control unit 27 estimates the amount of PM deposited, which is the amount of fine particle substances deposited on the filter 24, from the operating state of the engine 10. Then, the electronic control unit 27 performs filter regeneration control for burning and purifying the fine particle substance deposited on the filter 24 when the PM deposition amount becomes equal to or more than a predetermined regeneration request value. The filter regeneration control includes a temperature rise process, which is a control process of the engine 10 for raising the temperature of the filter 24 to the regenerative temperature T1 which is a temperature at which the fine particle substance can be burned, and a combustion process of the fine particle substance deposited on the filter 24. It is performed through a purification process, which is a control process of the engine 10 for purification.

In the temperature raising process, lean combustion operation in which the air-fuel ratio of the air-fuel mixture burned in the cylinder 12 is leaner than the stoichiometric air-fuel ratio and rich combustion in which the air-fuel ratio of the air-fuel mixture burned in the cylinder 12 is richer than the stoichiometric air-fuel ratio. Driving and operation are performed alternately. In the lean combustion operation, the exhaust gas containing a large amount of oxygen is discharged from the cylinder 12, and in the rich combustion operation, the exhaust gas containing a large amount of unburned fuel is discharged from the cylinder 12. In the temperature raising process, the inside of the three-way catalyst device 23 is made into an oxidizing atmosphere with a high oxygen concentration by the lean combustion operation. Then, the rich combustion operation is performed in that state to introduce the unburned fuel into the three-way catalyst device 23, so that the unburned fuel is burned in the three-way catalyst device 23. As a result, the temperature of the exhaust gas flowing out of the three-way catalyst device 23 and flowing into the filter 24 is raised, and the temperature of the filter 24 is raised by the heat of the exhaust gas that has become the high temperature. By the way, the fuel injection amounts and periods of the lean combustion operation and the rich combustion operation in the temperature raising process are the oxygen introduced by the lean combustion operation and the unburned fuel introduced by the rich combustion operation in the three-way catalyst device 23. And are set to react in just proportion. Therefore, the exhaust air-fuel ratio of the exhaust gas flowing into the filter 24 during the temperature raising process becomes the theoretical air-fuel ratio.

The purification treatment is carried out in a state where the filter 24 is raised to a temperature equal to or higher than the renewable temperature T1 by the temperature raising treatment. Then, in the purification process, the exhaust gas containing excess oxygen is supplied to the filter 24 by the lean combustion operation to burn and purify the fine particle substances deposited on the filter 24. If only the lean combustion operation is performed in the purification process, the temperature of the filter 24 may drop below the renewable temperature T1 and the combustion purification of the fine particle substance may not be continued. Therefore, in the present embodiment, the temperature of the filter 24 during the purification treatment is maintained at the renewable temperature T1 or higher by alternately performing the lean combustion operation and the rich combustion operation in the purification treatment. In the purification process, the fuel injection amounts and periods of the lean combustion operation and the rich combustion operation are set so that oxygen becomes surplus when the unburned fuel is burned in the three-way catalyst device 23. Therefore, during the purification process, excess oxygen due to the reaction with the unburned fuel flows out from the three-way catalyst device 23, and the exhaust air-fuel ratio of the exhaust gas flowing into the filter 24 is leaner than the stoichiometric air-fuel ratio. It becomes a value. As a result, the oxygen supplied to the filter 24 reacts with the fine particle substance, so that the fine particle substance deposited on the filter 24 is burned and purified. The lean combustion operation in such a purification treatment is performed with an air-fuel ratio on the lean side as compared with the lean combustion operation in the temperature rise treatment. As described above, the purification treatment in the present embodiment is a treatment for keeping the filter 24 warm at the same time as purifying the fine particle substances deposited on the filter 24.

Incidentally, the electronic control unit 27 estimates the combustion rate of the fine particle substance in the filter 24 during the purification process, and updates the value of the PM deposition amount from the estimation result. Then, the electronic control unit 27 ends the purification process when the PM accumulation amount drops to a predetermined regeneration completion determination value.

The operating range of the engine 10 capable of efficiently performing the above-mentioned temperature raising treatment and purification treatment is limited. Therefore, the electronic control unit 27 performs the temperature raising process and the purification process after changing the operating point of the engine 10 to the regeneration execution area, which is an operation area in which the temperature raising process and the purification process can be efficiently performed. .. In the engine 10 to which the present embodiment is applied, the reproduction execution area is an operation area of low load and high rotation speed.

On the other hand, in the engine control device of the present embodiment, the electronic control unit 27 enhances the control accuracy of the air-fuel ratio by the air-fuel ratio learning control. In the air-fuel ratio learning control, the air-fuel ratio learning value, which is a correction value of the fuel injection amount necessary for compensating for the steady deviation of the air-fuel ratio, is learned based on the detection result of the air-fuel ratio of the air-fuel ratio sensor 25. The learning of the air-fuel ratio learning value is performed by updating the value of the air-fuel ratio learning value so that the difference between the control target value of the air-fuel ratio and the detected value of the air-fuel ratio of the air-fuel ratio sensor 25 is gradually reduced. In the present embodiment, the air-fuel ratio learning value is individually learned for each of a plurality of learning regions divided according to the engine speed NE and the engine load factor KL.

FIG. 2 shows a setting mode of the learning area in the present embodiment. As shown in the figure, in the present embodiment, six learning regions of regions A to F are set. It should be noted that the figure also shows the optimum fuel consumption operation line of the engine 10 and the above-mentioned reproduction execution region. The optimum fuel consumption operation line shows a set of operating points that minimizes fuel consumption with respect to the shaft output of the engine 10. As shown in the figure, in the case of the present embodiment, the reproduction execution area is a region far away from the optimum fuel consumption operation line.

The electronic control unit 27 controls the engine so that the operation is performed at the operating point on the optimum fuel consumption operation line as much as possible. Therefore, the learning of the air-fuel ratio learning values in the regions A to F is often performed in the region near the optimum fuel consumption operation line. On the other hand, even within the same learning area, the magnitude of the steady-state deviation of the air-fuel ratio may differ depending on the engine speed NE and the engine load factor KL. Therefore, the air-fuel ratio learning values in each of the regions A to F may not be appropriate values in the regeneration execution region away from the optimum fuel consumption operation line.

In such a case, the accuracy of controlling the air-fuel ratio during the temperature raising treatment or the purification treatment may deteriorate, and the amount of CO and NOx emissions may increase. In particular, the lean combustion operation in the purification treatment is performed at the air-fuel ratio on the lean side as compared with the lean combustion operation in the temperature rise treatment, and the deviation of the air-fuel ratio tends to lead to deterioration of combustion. Therefore, when the filter 24 is regenerated with the air-fuel ratio deviated, the increase in CO and NOx emissions during the purification treatment tends to be larger than during the temperature rise treatment.

Depending on the model of the engine, the filter 24 may be regenerated in a region near the optimum fuel consumption operation line. Even with such an engine, the air-fuel ratio learning value may be learned in the operating region away from the optimum fuel consumption operation line, and in such a case, an inappropriate value is learned as the air-fuel ratio learning value in the regeneration implementation region. It may end up.

Further, the combustion rate of the fine particle substance in the filter 24 during the purification treatment depends on the excess oxygen ratio of the exhaust gas and, by extension, the air-fuel ratio of the air-fuel mixture burned in the cylinder. Therefore, if the air-fuel ratio during the purification treatment deviates, the estimated value of the PM deposition amount also deviates, and there is a possibility that excess or deficiency may occur during the purification treatment implementation period.

Therefore, in the present embodiment, apart from the air-fuel ratio learning values of the above-mentioned regions A to F, the air-fuel ratio learning values of the regeneration implementation region are learned when the engine 10 is operated in the regeneration implementation region. ing. In the present embodiment, in the regeneration implementation region, the fuel injection amount is corrected by the regeneration learning value in addition to the correction by the air-fuel ratio learning value. Then, while the engine 10 is operating in the regeneration execution region, the update of the air-fuel ratio learning value is stopped, and then the difference between the air-fuel ratio control target value and the air-fuel ratio detected value of the air-fuel ratio sensor 25 gradually decreases. By updating the value of the learning value for reproduction so as to go, the learning value for reproduction is learned. The learning value for regeneration learned in this way is a value corresponding to the difference between the steady deviation of the air-fuel ratio in the regeneration execution region and the normal air-fuel ratio learning value. In such an embodiment, the sum of the air-fuel ratio learning value and the regeneration learning value is a value corresponding to the air-fuel ratio learning value in the regeneration implementation region.

As described above, in the engine control device of the present embodiment, the regeneration execution region is set to a region away from the optimum fuel consumption operation line. Therefore, when the engine is controlled as a matter of course, it becomes difficult to obtain an opportunity to learn the learning value for reproduction in the reproduction execution area. Therefore, in the present embodiment, when the learning of the learning value for reproduction is not completed and the engine 10 can be operated in the reproduction execution area, the engine 10 is forcibly driven in the reproduction execution area. I try to drive and learn the learning value for reproduction. Specifically, when the learning of the reproduction learning value is not completed during the idle operation of the engine 10, the target idle speed, which is the target value of the engine speed NE during the idle operation, is higher than the normal speed. Is set to. As a result, the engine 10 is forcibly operated in the regeneration execution region to learn the regeneration learning value.

Even in such a case, the learning of the learning value for reproduction may not be completed by the time the reproduction of the filter 24 is requested. Therefore, in the present embodiment, when the learning of the reproduction learning value is not completed at the time of the reproduction request of the filter 24, the reproduction learning value is learned during the execution of the temperature raising process, and after the learning is completed. I try to carry out purification treatment.

The flowchart of FIG. 3 shows the flow of processing of the electronic control unit 27 related to the filter regeneration control during the operation of the engine 10. As described above, the electronic control unit 27 estimates the PM accumulation amount of the filter 24 during the operation of the engine 10, and determines whether or not the estimated PM accumulation amount exceeds the regeneration required value. (S100).

When the PM accumulation amount becomes equal to or greater than the regeneration request value (S100: YES), the process proceeds to step S110, and in the step S110, the process of shifting the engine operating point to the regeneration execution region is performed. The shift of the engine operating point to the reproduction execution area is performed when the default filter reproduction execution condition is satisfied. The filter regeneration execution condition is satisfied when the engine 10 can be operated in the regeneration execution region and the learning of the air-fuel ratio learning value is completed.

When the engine operating point is shifted to the regeneration execution region, the temperature raising process is started in step S120. The temperature raising process is continued until the learning of the learning value for regeneration is completed (S130: YES) and the temperature of the filter 24 becomes the renewable temperature T1 or higher (S140: YES). If the learning of the regeneration learning value is not completed during the temperature raising process (S130: NO), the regeneration learning value is updated in step S150 until the learning is completed.

After the start of the temperature raising process in step S120, when the learning of the learning value for regeneration is completed (S130: YES) and the temperature of the filter 24 becomes the renewable temperature T1 or higher (S140: YES), the process proceeds to step S160. Be done. Then, in step S160, the temperature raising process is completed and the purification process is started. As described above, in the present embodiment, the purification process is carried out in a state where the learning of the learning value for regeneration is completed. After that, when the amount of PM deposited falls below the regeneration completion determination value (S170: YES), the purification treatment is completed in step S190, and the treatment is returned to step S100.

The operation and effect of this embodiment will be described.
In the present embodiment, the learning value for regeneration is learned when the engine 10 is operating in the regeneration execution region, which is the operating region of the engine 10 that performs the temperature raising process and the purification process. Then, the sum of the air-fuel ratio learning value and the regeneration learning value is obtained as the regeneration air-fuel ratio learning value, which is the air-fuel ratio learning value in the regeneration implementation region. In such an embodiment, the fuel injection amount is corrected by the air-fuel ratio learning value learned in the regeneration implementation region during the temperature raising treatment and the purification treatment. Therefore, it is possible to accurately control the air-fuel ratio even during the execution of the temperature rise control and the purification control in the regeneration execution region away from the optimum fuel consumption operation line. As a result, deterioration of the exhaust properties such as an increase in NOx and CO emissions is less likely to occur due to the deviation of the air-fuel ratio during the temperature raising treatment and the purification treatment. In addition, due to the deviation of the air-fuel ratio, the estimation result of the PM accumulation amount during the purification treatment is deviated, and it is less likely that an excess or deficiency will occur during the purification treatment.

Further, in the present embodiment, when the learning of the reproduction learning value is not completed at the time of requesting the reproduction of the filter 24, the learning of the reproduction learning value is performed in parallel with the temperature raising process. Then, after completing the learning, the purification process is carried out. During the purification treatment, the deviation of the air-fuel ratio is more likely to lead to deterioration of the exhaust properties than during the temperature rise treatment. Therefore, if the control accuracy of the air-fuel ratio can be ensured even during the purification treatment, the deterioration of the exhaust property can be kept at an acceptable level.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-In the above embodiment, when the learning of the reproduction learning value is not completed at the time of the reproduction request of the filter 24, the reproduction learning value is learned in parallel with the temperature raising process, but the reproduction learning value The temperature rise control may be performed after the learning of the above is completed.

-In the above embodiment, while the engine 10 is operating in the regeneration implementation region, the difference between the regeneration air-fuel ratio learning value, which is the air-fuel ratio learning value in the regeneration implementation region, and the normal air-fuel ratio learning value is used as the regeneration learning value. Was learning as. Then, the sum of the normal air-fuel ratio learning value and the regenerative learning value is used as the regenerative air-fuel ratio learning value. Instead of the regeneration learning value which is the difference from the normal air-fuel ratio learning value, the learning of the regeneration air-fuel ratio learning value itself may be performed during the operation of the engine 10 in the regeneration execution region.

-In the above embodiment, the lean combustion operation and the rich combustion operation are alternately performed in the purification process. As a result, the filter 24 is kept warm while the fine particle substances deposited on the filter 24 are burned and purified. Such purification treatment may be performed by continuing the lean combustion operation without performing the rich combustion operation. Even in such a case, it is possible to burn and purify the fine particle substance deposited on the filter 24 by the purification treatment.

10 ... engine, 11 ... piston, 12 ... cylinder, 13 ... connecting rod, 14 ... crank shaft, 15 ... intake passage, 16 ... air flow meter, 17 ... throttle valve, 18 ... fuel injection valve, 19 ... intake valve, 20 ... Ignition device, 21 ... exhaust passage, 22 ... exhaust valve, 23 ... three-way catalyst device, 24 ... filter, 25 ... air-fuel ratio sensor, 26 ... catalyst outflow gas temperature sensor, 27 ... electronic control unit, 28 ... crank angle sensor, 29 ... Vehicle speed sensor, 30 ... Accelerator pedal, 31 ... Accelerator pedal sensor.

Claims (1)

A filter that collects fine particles in the exhaust is applied to an engine installed in the exhaust passage, and the temperature rise process, which is a control process of the engine for raising the temperature of the filter to a temperature at which the fine particles can be burned, is performed. In an engine control device, which is carried out in response to a regeneration request of the filter and is carried out after the completion of the temperature raising process, which is a control process of the engine for burning and purifying fine particles deposited on the filter.
Recycling sky that learns the regenerated air-fuel ratio learning value, which is the air-fuel ratio learning value of the regenerating region when the engine is operating in the regenerating region, which is the operating region of the engine that performs the purification process. Along with carrying out the fuel ratio learning process
An engine control device that performs the purification process after learning the air-fuel ratio learning value for regeneration when the learning of the air-fuel ratio learning value for regeneration is not completed at the time of requesting regeneration of the filter.