ABNORMALITY DIAGNOSIS APPARATUS FOR PARTICULATE FILTER

摘要

Embodiments of the present disclosure improve the accuracy of abnormality diagnosis of a particulate filter using the output value of a PM sensor provided downstream of the particulate filter in an exhaust passage. A configuration of the invention compares a change rate of an output value of the PM sensor prior to execution of a filter diagnosis process of diagnosing an abnormality of the filter based on the output value of the PM sensor, with a reference value and determines whether a filter abnormality process is to be performed. A higher value is set to the reference value, which is to be compared with the change rate of the output value of the PM sensor, in the case where the deposition amount of PM between electrodes of the PM sensor is expected to be large, compared with the case where the deposition amount of PM is expected to be small.

主权项

1. An abnormality diagnosis apparatus for a particulate filter that is provided in an exhaust passage of an internal combustion engine to trap PM included in exhaust gas, the abnormality diagnosis apparatus comprising:
a PM sensor that is provided downstream of the particulate filter in the exhaust passage and is configured to have a pair of electrodes as a sensor element and output a signal corresponding to a deposition amount of PM between the electrodes when electrical continuity is established between the electrodes by deposition of PM between the electrodes, the PM sensor being configured such that a larger deposition amount of PM between the electrodes provides a higher variation in output value of the PM sensor relative to an increase in deposition amount of PM between the electrodes; a controller comprising at least one processor configured to perform a sensor recovery process of removing PM depositing between the electrodes of the PM sensor, and to perform a filter diagnosis process of diagnosing an abnormality of the particulate filter based on an output value of the PM sensor at a time when a predetermined determination time period has elapsed since a predetermined PM deposition restart time, which is a time when deposition of PM between the electrodes of the PM sensor is restarted after completion of the sensor recovery process; and a monitor unit that is configured to continuously monitor an output signal of the PM sensor after the PM deposition restart time, wherein the controller determines that the filter diagnosis process is not to be performed when a sensor output change rate becomes higher than a predetermined determination change rate before elapse of the determination time period since the PM deposition restart time, wherein the sensor output change rate is a variation in output value of the PM sensor monitored by the monitor unit per unit increase in reference deposition amount of PM, wherein the reference deposition amount of PM is an estimated value of the deposition amount of PM between the electrodes of the PM sensor on the assumption that the particulate filter is in a predetermined reference state, or a variation in output value of the PM sensor monitored by the monitor unit per unit time; and the controller sets a higher value to the determination change rate, which is to be compared with the sensor output change rate, in a case where the deposition amount of PM between the electrodes of the PM sensor is expected to be large at a corresponding time to the sensor output change rate, compared with a case where the deposition amount of PM is expected to be small at the corresponding time to the sensor output change rate.