JP2015001165A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of failure determination of a particulate sensor.SOLUTION: An internal combustion engine control device is applied to an internal combustion engine which has a particulate collection filter in an exhaust passage and a particulate sensor. The internal combustion engine control device: detects or estimates both a temperature of an element section of the particulate sensor and the temperature of exhaust gas at a downstream side of the particulate collection filter in the exhaust passage; executes regeneration control to remove particulates attached to the particulate collection filter by combusting the same; and determines whether or not failure occurs in the particulate sensor according to output thereof after finishing the regeneration control and when identifying that the temperature of the exhaust gas at the downstream side of the particulate collection filter is not less than the temperature of the element section.

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to a control device for an internal combustion engine that is installed in an exhaust passage of the internal combustion engine and has a particulate sensor for detecting the amount of particulates in the exhaust gas.

  For example, in Patent Document 1, a DPF (Diesel Particulate Filter) that collects particulate matter (hereinafter also referred to as “PM”) in exhaust gas is disposed in an exhaust passage of an internal combustion engine. A system in which a particulate sensor (hereinafter also referred to as “PM sensor”) for detecting the amount of PM that has passed without being collected is disclosed.

  In such a system, PM discharged from the internal combustion engine is collected by the DPF. Therefore, when the DPF is functioning normally, the amount of PM reaching the vicinity of the PM sensor is very limited. However, when performing failure determination control for determining the presence or absence of a PM sensor failure, it is necessary to determine whether or not the output of the PM sensor changes normally according to the amount of PM attached to the electrode. Therefore, in order to increase the accuracy of the failure determination control, it is desirable that a certain amount of PM exists near the PM sensor downstream of the DPF when the failure determination control is executed.

  In this regard, in Patent Document 1, the output of the PM sensor is acquired during a period in which the PM collection rate of the DPF decreases immediately after the DPF regeneration control for burning and removing the PM adhering to the DPF. It has been proposed to perform fault determination.

JP 2010-275977 A JP 2005-325812 A JP 2012-013058 A

  For example, when the low load operation of the internal combustion engine is executed immediately after the regeneration control of the DPF, the temperature of the exhaust gas is rapidly decreased, and the temperature of the exhaust gas is temporarily lower than the temperature of the element portion of the PM sensor. There is a case. In this way, under the situation where the exhaust gas temperature in the vicinity of the element part of the PM sensor is lower, the thermophoresis of PM occurs, and the PM hardly enters the PM sensor side. As a result, the output of the PM sensor does not show a change according to the amount of exhaust gas, but deviates from a value according to the actual amount of PM in the exhaust gas. Therefore, even immediately after the DPF regeneration control, if the PM sensor failure determination is performed at a timing when the exhaust gas temperature is lower than the element temperature, an erroneous determination may be made on the presence or absence of the PM sensor failure.

  An object of the present invention is to improve the internal combustion engine so as to determine the presence or absence of a PM sensor failure with high accuracy by optimizing the execution timing of PM sensor failure determination control. An engine control apparatus is provided.

  The control device for an internal combustion engine of the present invention is installed in the exhaust passage of the internal combustion engine for collecting particulates in the exhaust gas, and in the exhaust passage downstream of the particulate collection filter. And a PM sensor (particulate sensor) that emits an output corresponding to the amount of particulates in the exhaust gas. The control device for the internal combustion engine includes means for detecting or estimating the temperature of the element portion of the PM sensor and the temperature of the exhaust gas downstream of the particulate collection filter in the exhaust passage. Furthermore, the control device of the present invention includes a means for performing regeneration control for burning and removing particulates adhering to the particulate collection filter, and the temperature of exhaust gas after completion of regeneration control and downstream of the particulate collection filter. When it is recognized that the temperature is equal to or higher than the temperature of the part, a determination unit is provided that executes determination control for determining whether or not the PM sensor has failed according to the output of the PM sensor.

  In the present invention, the determination means may execute the determination control according to the output of the PM sensor after the lapse of the reference time from the time when the regeneration control of the particulate collection filter is completed.

  The control device for an internal combustion engine according to the present invention includes an EGR device that recirculates a part of the exhaust gas as EGR gas from the exhaust passage to the intake passage of the internal combustion engine, and until determination control is executed after completion of the regeneration control. And a means for executing an increase control for increasing the amount of EGR gas.

  The control device for an internal combustion engine according to the present invention includes an EGR device that recirculates a part of exhaust gas as EGR gas from an exhaust passage to the intake passage of the internal combustion engine, and downstream of the particulate collection filter after regeneration control is completed. Means for stopping the recirculation of the EGR gas until the temperature of the exhaust gas becomes lower than the reference temperature.

  According to the present invention, after completion of regeneration of the particulate collection filter, and when it is recognized that the exhaust gas temperature is equal to or higher than the temperature of the element portion, the determination control for the presence or absence of the PM sensor failure is performed. The Therefore, it is possible to execute PM sensor failure determination control in an environment where there is a large amount of PM inflow into the vicinity of the PM sensor while avoiding erroneous determination due to PM thermophoresis. The accuracy of determining whether or not a PM sensor has failed can be improved.

It is a schematic diagram for demonstrating the whole structure of the system in Embodiment 1 of this invention. It is a figure for demonstrating the content of the control in Embodiment 1 of this invention. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 1 of this invention. It is a figure for demonstrating the content of the control in Embodiment 2 of this invention. It is a figure for demonstrating the content of the control in Embodiment 3 of this invention. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
[System configuration of this embodiment]
FIG. 1 is a diagram for explaining the overall configuration of a system according to an embodiment of the present invention. In the system shown in FIG. 1, an oxidation catalyst 6 and a DPF (Diesel Particulate Filter) 8 are installed in the exhaust passage 4 of the internal combustion engine 2. The DPF 8 is a particulate collection filter that collects particulate matter (PM) contained in the exhaust gas. A PM sensor 10 (particulate sensor) and a temperature sensor 12 are installed downstream of the DPF 8 in the exhaust passage 4. The PM sensor 10 is a sensor that emits an output corresponding to the amount of PM in the gas to be detected. Here, the PM sensor 10 is used to detect the amount of PM in the exhaust gas that has passed through the DPF 8. The temperature sensor 12 is a sensor that emits an output corresponding to the temperature of the gas to be examined. Here, the temperature sensor 12 is used to detect the temperature of the exhaust gas downstream of the DPF 8.

  In the present embodiment, the PM sensor 10 has a pair of electrodes arranged to face each other. When a voltage for collecting fine particles is applied between the pair of electrodes, PM in the exhaust gas is collected and deposited between the electrodes. As the PM deposited between the electrodes increases, the electrical characteristics between the electrodes change according to the amount of deposited PM, for example, the number of conductive points between the electrodes increases and the resistance value between the electrodes decreases. The PM sensor 10 emits a sensor output related to this change in electrical characteristics. The amount of PM deposited on the electrode of the PM sensor 10 is considered to be proportional to the amount of PM in the exhaust gas. Therefore, the amount of PM in the exhaust gas can be detected based on the sensor output of the PM sensor 10. Note that the PM sensor 10 is not limited to outputting the PM amount, and may output an electrical characteristic (voltage value, current value, resistance value, etc.) correlated with the PM amount. However, in order to simplify the description, in the following embodiment, the PM sensor 10 outputs a value that increases as the PM deposition amount between the electrodes increases.

  This system includes a control device 20. Various sensors are connected to the input side of the control device 20 in addition to the PM sensor 10 and the temperature sensor 12, and output signals of the various sensors are taken into the control device 20. Various actuators of the internal combustion engine 2 are connected to the output side of the control device 20. The control device 20 processes the signals of the various sensors taken in, and operates the various actuators according to a predetermined control program. There are many actuators and sensors connected to the control device 20 other than those shown in the figure, but such description is omitted in this specification.

[Outline of control in this embodiment]
In the present embodiment, the control performed by the control device 20 includes regeneration of the DPF 8 and failure determination control of the PM sensor 10.

(1) Regeneration of DPF 8 (filter regeneration control)
The DPF 8 is a filter that collects PM in the exhaust gas. However, if the DPF 8 continues to collect PM, the amount of PM deposited on the DPF 8 eventually reaches a limit, and the PM cannot be collected any more. In order to avoid such a state, when the amount of accumulated PM in the DPF 8 reaches a certain level, the PM is burned and removed to regenerate the DPF 8.

  Specifically, in the regeneration control of the DPF 8, the control device 20 executes control for increasing the exhaust gas temperature, for example, control for injecting fuel again after fuel injection or control for delaying the injection timing, according to a predetermined control program. . Thereby, the PM deposited on the DPF 8 is burned and removed. By executing such PM combustion removal for a certain period of time, most of the PM deposited on the DPF 8 is removed, and the regeneration of the DPF 8 is completed.

  In the present embodiment, the control device 20 estimates the amount of PM accumulated in the DPF 8 by estimating the PM amount of the exhaust gas discharged from the internal combustion engine 2 using a model or the like. Then, when the estimated amount reaches a predetermined amount, the above regeneration control is started.

(2) Failure determination control of PM sensor 10 FIG. 2 is a diagram for explaining the contents of control in the first embodiment of the present invention. In the example of FIG. 2, the regeneration control of the DPF 8 is completed at time T10. As shown in the PM collection rate of FIG. 2, the PM collection rate of the DPF 8 is low when the regeneration control of the DPF 8 is completed, and then gradually increases and eventually stabilizes at a substantially constant collection rate. This is because PM is not attached to the pores of the DPF 8 due to regeneration control of the DPF 8, and therefore, the PM is likely to temporarily pass downstream of the DPF 8. With the change in the PM collection rate, the PM passage amount downstream of the DPF 8 is the highest at T10 when the regeneration control of the DPF 8 is completed, and then gradually decreases, and eventually stabilizes to a very small amount of PM passage.

  In FIG. 2, the solid line a of the sensor output is an output when the PM sensor 10 is normal, and the broken line b is an output when the PM sensor 10 is abnormal. Immediately after completion of regeneration control of the DPF 8, the amount of PM passing downstream of the DPF 8 relatively increases for a certain period, so that a relatively large amount of PM accumulates between the electrodes of the PM sensor 10. Therefore, when the PM sensor 10 is normal, the output of the PM sensor 10 gradually increases according to the PM passing amount as seen by the solid line a. On the other hand, when an abnormality has occurred in the PM sensor 10, the output of the PM sensor 10 does not show a change according to the PM amount, and remains at a low output.

  Therefore, in the failure determination control of the present embodiment, after completion of regeneration control of the DPF 8, failure determination control is started to energize the electrodes of the PM sensor 10. As a result, PM is deposited on the electrode. Then, the sensor output is detected at detection time T12, which is a time point after the sensor output starts to rise in accordance with the PM passing amount. When the sensor output is equal to or greater than the reference value Ref1, it can be determined that the sensor output changes according to the PM passing amount (A in the figure). Therefore, in this case, the sensor is determined to be normal. On the other hand, when the sensor output at the time of detection T12 is smaller than the reference value Ref1, it is determined that the PM sensor 10 has an abnormality.

  As shown in FIG. 2, even if the PM sensor 10 is normal, there is a certain delay after the regeneration control is completed until the PM sensor outputs an output corresponding to the PM passing amount, and the regeneration of the sensor output is completed. After a certain period of time has elapsed, the change starts according to the amount of PM. Therefore, in the present embodiment, in the failure determination control, the detection time T12 for detecting the sensor output is the time when the reference time has elapsed after the completion of the regeneration control. The time required for the sensor output to generate an output corresponding to the PM amount can be obtained based on data such as experiments and simulations. The reference time is appropriately set according to this time and stored in the control device 20.

  Further, the reference value Ref1 in the failure determination control is set to a value near the lowest value of the sensor output range predicted when the reference time has elapsed after completion of the regeneration control when the PM sensor 10 is normal.

  Incidentally, as described above, in the regeneration control, control for increasing the exhaust gas temperature is executed. Therefore, immediately after the regeneration control is completed, the exhaust gas temperature is high, and accordingly, the element temperature of the PM sensor 10 is also high. Here, immediately after the regeneration control is completed, for example, when the low-load operation of the internal combustion engine 2 is performed, the exhaust gas temperature decreases at a faster rate. In such a case, the decrease in the element temperature of the PM sensor 10 is delayed from the decrease in the exhaust gas temperature, and after the exhaust gas temperature has decreased to a certain level to a stable temperature, the element temperature also decreases to a stable temperature after a delay. Will be.

  Thus, after completion of regeneration control, the exhaust gas temperature may temporarily become lower than the element temperature. However, when the exhaust gas temperature is lower than the element temperature, PM thermophoresis occurs due to the temperature gradient in the vicinity of the PM sensor 10, and the PM is likely to move to the exhaust gas side and difficult to move to the element part side of the PM sensor 10. Become. Therefore, in a state where the exhaust gas temperature is lower than the element temperature, a sensor output corresponding to the amount of PM in the exhaust gas cannot be obtained, and erroneous determination may occur in determination failure control. Therefore, in the present embodiment, failure determination when the exhaust gas temperature is lower than the element temperature is prohibited, and sensor output is acquired in a state where the exhaust gas temperature is equal to or higher than the element temperature to perform failure determination control.

  Note that the output of the PM sensor 10 is an output that changes in accordance with the amount of PM accumulated in the element section. Therefore, it is necessary to perform PM reset that removes the PM that has been accumulated in the PM sensor 10 until a predetermined timing. At the time of PM reset, the control device 20 supplies predetermined power to the heater of the PM sensor 10 and causes the element portion of the PM sensor 10 to overheat. Thereby, PM adhering to the element part of the PM sensor 10 is burned and removed. Various timings can be considered for the execution of the PM reset. Specifically, for example, the timing before the failure detection of the DPF 8, the failure determination of the PM sensor 10 in the present embodiment, or when the internal combustion engine 2 is stopped. The timing of this is mentioned.

  FIG. 3 is a flowchart for illustrating a control routine executed by control device 20 in the first embodiment of the present invention. The routine of FIG. 3 is a routine that is repeatedly executed at regular intervals during the operation of the internal combustion engine 2. In the routine of FIG. 3, it is first determined in step S102 whether or not regeneration control of the DPF 8 has been started. If the start of regeneration control of the DPF 8 is not permitted, the current process is temporarily terminated.

  On the other hand, if it is determined in step S102 that the regeneration control of DPF 8 has been started, it is next determined in step S104 whether the regeneration control of DPF 8 has been completed. If it is not recognized in step S104 that the regeneration control of DPF 8 has been completed, the process returns to step S104 again, and the determination process in step S104 is repeated at regular intervals until the completion of regeneration control of DPF 8 is recognized. Executed.

  On the other hand, when the completion of regeneration control of the DPF 8 is recognized in step S104, control for determining the failure of the PM sensor 10 is started in step S106. Here, a predetermined voltage is applied between the electrodes of the PM sensor 10, and monitoring of the sensor output is started.

  In subsequent step S108, it is determined whether or not an elapsed time after completion of the regeneration control in step S104 has reached a reference time. The reference time is an adaptation value stored in the control device 20 in advance. If the reference time has not elapsed in step S108, the process returns to step S108. Until the elapse of the reference time is recognized in step S108, the determination process in step S108 is repeatedly executed at regular time intervals.

  On the other hand, when the passage of the reference time is recognized in step S108, the exhaust gas temperature and the element temperature are acquired in step S110. Here, the exhaust gas temperature and the element temperature are detected according to the outputs of a temperature sensor 12 installed in the exhaust passage and a temperature sensor (not shown) built in the PM sensor 10, respectively.

  Next, in step S112, it is determined whether or not the exhaust gas temperature is equal to or higher than the element temperature. When it is not recognized that the exhaust gas temperature is equal to or higher than the element temperature, the process returns to step S110. Until it is recognized in step S112 that the exhaust gas temperature is equal to or higher than the element temperature, the processes in steps S110 to S112 are repeated at regular intervals.

  On the other hand, if it is determined in step S112 that the exhaust gas temperature is equal to or higher than the element temperature, it is next determined whether or not the current sensor output of the PM sensor 10 is greater than a reference value. The reference value is a compatible value stored in the control device 20 in advance.

  If it is determined in step S114 that the sensor output is greater than the reference value, it can be determined that the PM sensor 10 is outputting an output corresponding to the PM amount. Therefore, in this case, it is determined in step S116 that the PM sensor 10 is normal. On the other hand, if it is not recognized in step S114 that the sensor output is larger than the reference value, it is then determined in step S118 that the PM sensor 10 is abnormal. After step S116 or S118, the current process is temporarily terminated.

  As described above, in the present embodiment, failure determination is performed based on the output of the PM sensor 10 when the regeneration control of the DPF 8 is completed and the reference time has elapsed and the exhaust gas temperature is equal to or higher than the element temperature. Is called. Therefore, the failure determination of the PM sensor 10 can be performed using the state in which the PM emission amount after completion of regeneration of the DPF 8 is utilized and the PM is stably attached to the electrode of the PM sensor 10. Thereby, the accuracy of the failure determination control of the PM sensor 10 can be improved.

  In the present embodiment, the case where the failure determination is performed when the exhaust gas temperature is equal to or higher than the element temperature and the reference time after completion of the regeneration control of the DPF 8 has been described. However, the present invention is not limited to this, and the amount of PM required to stably output the exhaust gas temperature equal to or higher than the element temperature and the normal sensor output to output in accordance with the PM amount is equal to PM. As long as it is deposited on the sensor 10, it may not be after the reference time has elapsed. In addition, the reference time when performing failure determination based on the sensor output after the lapse of the reference time may be set each time according to, for example, the driving state. The same applies to the following embodiments.

  In the present embodiment, the case where the failure determination control of the PM sensor 10 is executed after the completion of the DPF regeneration control in the configuration in which the DPF 8 is installed in the exhaust passage 4 of the diesel engine has been described. However, the present invention is not limited to this. The present invention applies the present embodiment to a configuration having a GPF (Gasoline Particulate Filter) in the exhaust passage of a gasoline engine, and similarly executes a failure determination control of a PM sensor after performing a regeneration control of the GPF. May be. The same applies to the following embodiments.

  In the present embodiment, the case where the exhaust gas temperature downstream of the DPF 8 is detected according to the output of the temperature sensor 12 has been described. However, the present invention is not limited to this. As the exhaust gas temperature downstream of the DPF 8 used in the present embodiment, a temperature or the like estimated according to the temperature or the like at another location may be used. The same applies to the following embodiments.

  In the present embodiment, the PM sensor 10 has a built-in temperature sensor, and the element temperature of the PM sensor 10 is detected according to the temperature sensor. However, the present invention is not limited to this, and may be calculated based on, for example, the impedance of the PM sensor 10. Moreover, you may use the estimated temperature calculated according to the temperature of another part etc. as element temperature. The same applies to the following embodiments.

  Further, in the present embodiment, a case where the regeneration control of the DPF 8 is executed when the estimated value of the PM accumulation amount on the DPF 8 reaches a predetermined amount, and then the failure determination control of the PM sensor 10 is executed subsequently. did. However, the present invention is not limited to this. The regeneration control of the DPF 8 may be performed, for example, at a certain traveling distance or every certain traveling time. Further, the failure determination control of the PM sensor 10 is not limited to being executed every time after the regeneration control. For example, it is possible to set so that the failure is determined once between the start and stop of the internal combustion engine 2. In this case, for example, after the start of the internal combustion engine 2, only after the completion of the regeneration control of the first DPF 8, A failure determination may be performed.

  In the present embodiment, the case has been described in which whether or not the exhaust gas temperature is equal to or higher than the element temperature is determined by comparing the exhaust gas temperature with the element temperature in step S112. However, the present invention is not limited to this. For example, when it is recognized that the difference between the exhaust gas temperature and the element temperature is equal to or greater than a predetermined value, the exhaust gas temperature and the element temperature are approximately the same temperature, or the exhaust gas temperature is It may be determined that the temperature is higher than the temperature, and failure determination may be performed. Further, instead of the exhaust gas temperature or the element temperature, the determination may be made using a value such as an average value or an annealing value of the temperature detected or estimated over a plurality of times.

Embodiment 2. FIG.
The system of the second embodiment has the same configuration as the system of FIG. 1 except that it has an EGR device that recirculates part of the exhaust gas to the intake passage. FIG. 4 is a diagram for explaining the control in the second embodiment of the present invention. In the control of the second embodiment, in addition to the control of the first embodiment, the control for increasing the PM discharge amount is executed before starting the failure determination control of the PM sensor 10. Specifically, in the present embodiment, after completion of regeneration control of the DPF 8, control for increasing the EGR is executed.

  In each figure of the PM collection rate, the PM passage amount, and the sensor output in FIG. 4, the value when the control for increasing the EGR is performed by the control of the present embodiment is shown by a solid line a <b> 1, and for comparison A value when the EGR control of 1 is not executed is indicated by a broken line a2.

  As shown in FIG. 4, when EGR increase control is performed as compared with the case where EGR increase control is not performed, the PM collection rate is recovered to a higher state at an earlier stage after completion of regeneration control of DPF 8. . The PM passage amount downstream of the DPF 8 is larger than the case where the EGR increase control is not performed for a while immediately after the completion of the regeneration control (a2), but converges earlier than the case where the EGR increase control is not performed, and the PM passage amount It stabilizes in a state with few.

  Since the PM discharged earlier is increased by the EGR increase control, the sensor output when the sensor is normal increases earlier than when the EGR increase control is not performed, and the sensor output when there is an abnormality It will be in a state that can be distinguished. Accordingly, the detection time T22 for detecting the sensor output for the failure determination control is set earlier than the detection time T12 when the EGR increase control is not performed. Thereby, it is possible to determine the failure of the PM sensor at an early stage after completion of the regeneration control. Further, since the PM discharge amount is increased, the PM passing amount downstream of the DPF 8 is increased, and the sensor output of the normal PM sensor 10 is increased according to the PM amount. Therefore, the output difference between the sensor output of the normal PM sensor 10 and the output of the abnormal PM sensor can be increased, and the accuracy of failure determination can be improved.

  The timing for starting execution of EGR increase control is not particularly limited as long as it is before detection time T22 in failure determination control. For example, EGR increase control may be executed after completion of DPF regeneration control is recognized in step S104 in FIG. 3, or before failure determination control is started in step S106 or immediately after failure determination control is started.

  In the present embodiment, the case where the PM emission amount is increased by increasing the EGR amount has been described. However, the present invention is not limited to this, and the PM generation amount may be increased by other control as long as the PM discharge amount can be increased during the failure detection control of the PM sensor 10. The same applies to the following embodiments.

Embodiment 3 FIG.
The system of the third embodiment has the same configuration as the system of FIG. 1 except that it has an EGR device that recirculates part of the exhaust gas to the intake passage. In addition to the system of the first embodiment, the system of the third embodiment performs the same control as that of the first embodiment except that control for stopping EGR is performed until the exhaust gas temperature falls below a predetermined temperature.

  FIG. 5 is a diagram for explaining the control of the present embodiment. In FIG. 5, each value when EGR increase control is performed after the control for stopping the EGR according to the present embodiment is represented by a solid line a1, and for comparison, the value in the first embodiment is represented by a broken line a2. Represents.

  As shown in FIG. 5, immediately after the regeneration control of the DPF 8 is completed, the exhaust gas temperature is high, and then the exhaust gas temperature gradually decreases. While the exhaust gas temperature is higher than the reference temperature Ref2, the PM behavior becomes unstable. In such a situation where PM behavior is unstable, it is desirable to avoid PM collection by the DPF 8 and PM adhesion to the PM sensor 10. Therefore, in the present embodiment, control is performed to reduce PM emission until the exhaust gas temperature falls to a reference temperature at which PM behavior is stabilized to some extent.

  Specifically, the EGR valve is closed and EGR cut is performed from time T30 after completion of regeneration control to time T31 when the exhaust gas temperature falls to the reference temperature Ref2. Accordingly, the PM emission amount from the time T30 when the regeneration control of the DPF 8 is completed to the time T31 when the exhaust gas temperature is reduced to the reference temperature decreases. As a result, between time T30 and time T31, the PM collection rate also decreases as shown by the line a1 of the PM collection rate, but the PM passing amount is also reduced because the emission amount of PM itself is suppressed. Stays low.

  Thereafter, at time T31 when the exhaust gas temperature becomes lower than the reference temperature, the EGR cut is stopped and the EGR increase control is started. As a result, the PM collection rate increases, and the PM passage amount also increases. Thereafter, as the PM collection rate increases, the PM passage amount decreases, and the PM passage amount gradually stabilizes to a very small amount.

  In the present embodiment, based on the sensor output acquired at time T32 after the reference time has elapsed from time T31 when the exhaust gas temperature has become lower than the reference temperature and when the exhaust gas temperature is equal to or higher than the element temperature, the PM sensor 10 Perform failure determination.

  The reference temperature is set according to the exhaust gas temperature at which the PM behavior is stabilized to some extent. The exhaust gas temperature at which the PM behavior is stabilized can be obtained according to data such as experiments and simulations. The set reference temperature is stored in advance in the control device. In addition, the reference time is appropriately set according to the time required for the sensor output to generate an output corresponding to the PM amount, and stored in the control device 20, as in the first embodiment.

  FIG. 6 is a flowchart for illustrating a control routine executed by the control device in Embodiment 3 of the present invention. The routine in FIG. 6 is the same as the routine in FIG. 3 except that steps S302 to S308 are included between steps S104 and S106 in the routine in FIG. In the routine of FIG. 6, when completion of regeneration control of the DPF 8 is recognized in step S104, the exhaust gas temperature is acquired in the subsequent step S302 (S302). The exhaust gas temperature is detected according to the output of the temperature sensor 12 installed in the exhaust passage.

  Next, in step S304, it is determined whether or not the exhaust gas temperature is lower than the reference temperature. If it is not recognized in step S304 that the exhaust gas temperature has become lower than the reference temperature, then PM reduction control is executed or maintained. Here, the control for closing the EGR valve and cutting the EGR is executed as the PM reduction control. Thereafter, the process returns to S302. Until it is recognized in step S304 that the exhaust gas temperature is lower than the reference temperature, the processing is repeatedly executed at regular intervals according to steps S302 to S306.

  On the other hand, if it is recognized in step S304 that the exhaust gas temperature is lower than the reference temperature, then in step S308, PM increase control is started. Here, as the PM increase control, EGR increase control for increasing the EGR amount is executed. Next, it progresses to step S106 and the process of step S106-S118 is performed as demonstrated by the routine of FIG. Thereafter, the current process is temporarily terminated.

  As described above, in the present embodiment, PM reduction correction is executed until the exhaust gas temperature falls to the reference temperature to prevent the PM from adhering to the DPF 8. Thereby, PM adhesion to the PM sensor 10 while the PM behavior is unstable can be suppressed, and the accuracy of the failure determination of the PM sensor 10 can be improved.

  In the present embodiment, the case has been described in which whether or not the exhaust gas temperature is lower than the reference temperature is determined by comparing the exhaust gas temperature with the reference temperature in step S304. However, the present invention is not limited to this, as long as it is estimated that the exhaust gas temperature is lower than the reference temperature. Therefore, for example, when the average value of the exhaust gas temperature is lower than the reference temperature, or when the exhaust gas temperature is determined to be lower than the reference temperature a plurality of times, it is determined that the exhaust gas temperature is lower than the reference temperature. You may do it.

  Further, in the present embodiment, a case has been described in which PM increase control is performed in the same manner as in the second embodiment when it is recognized that the exhaust gas temperature is lower than the reference temperature. However, the present invention is not limited to this, and the PM increase control may not be performed as in the first embodiment.

  Further, in the above embodiment, when the number of each element, number, quantity, range, etc. is mentioned, it is mentioned unless otherwise specified or clearly specified in principle. The invention is not limited to the numbers. The structures, steps, and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 Internal combustion engine 4 Exhaust passage 6 Oxidation catalyst 10 PM sensor 12 Temperature sensor 20 Control device

Claims (4)

A particulate collection filter for collecting particulates in exhaust gas, installed in the exhaust passage of the internal combustion engine;
A particulate sensor installed downstream of the particulate collection filter in the exhaust passage and emitting an output corresponding to the amount of particulates in the exhaust gas;
Means for detecting or estimating the temperature of the element portion of the particulate sensor;
Means for detecting or estimating the temperature of the exhaust gas downstream of the particulate collection filter in the exhaust passage;
Means for performing regeneration control for burning and removing particulates adhering to the particulate collection filter;
After completion of the regeneration control, and when it is found that the temperature of the exhaust gas downstream of the particulate collection filter is equal to or higher than the temperature of the element portion, the particulate sensor according to the output of the particulate sensor Determination means for executing determination control for determining whether or not there is a failure;
A control device for an internal combustion engine, comprising:   2. The determination unit according to claim 1, wherein the determination unit executes the determination control according to an output of the particle sensor after a lapse of a reference time from the time when regeneration control of the particle collection filter is completed. Control device for internal combustion engine. An EGR device that recirculates part of the exhaust gas as EGR gas from the exhaust passage to the intake passage of the internal combustion engine;
Means for executing an increase control for increasing the amount of EGR gas between the completion of the regeneration control and the execution of the determination control;
The control apparatus for an internal combustion engine according to claim 1, further comprising: An EGR device that recirculates part of the exhaust gas as EGR gas from the exhaust passage to the intake passage of the internal combustion engine;
The apparatus further comprises means for stopping the recirculation of EGR gas after completion of the regeneration control and until the temperature of the exhaust gas downstream of the particulate collection filter becomes lower than a reference temperature. The control device for an internal combustion engine according to any one of claims 1 to 3.

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