ABNORMALITY DIAGNOSTIC DEVICE FOR A PARTICULATE FILTER

摘要

Diagnostic accuracy is improved when abnormality diagnosis of a particulate filter is carried out by using a PM sensor arranged in an exhaust passage downstream of the particulate filter. An abnormality diagnostic device for a particulate filter includes a PM sensor arranged in an exhaust passage at the downstream side of the particulate filter so as to output a signal corresponding to an amount of PM deposited in between electrodes which constitute a sensor element, and a filter diagnostic unit to carry out filter diagnostic processing in which abnormality of the particulate filter is diagnosed based on an output value of the PM sensor, wherein it is decided whether to carry out the filter diagnostic processing based on a degree of variation in the output value of the PM sensor before the filter diagnostic processing is carried out.

主权项

1. An abnormality diagnostic device for a particulate filter which is arranged in an exhaust passage of an internal combustion engine for trapping particulate matter (PM) in an exhaust gas, said device comprising:
a PM sensor that is arranged in the exhaust passage at a downstream side of said particulate filter, has a pair of electrodes as a sensor element, and is to output a signal corresponding to an amount of PM deposition when said electrodes are made conductive with each other due to deposition of PM between said electrodes; a sensor regeneration unit that is to carry out sensor regeneration processing in which the PM deposited between the electrodes of said PM sensor is removed; a voltage application unit that starts voltage application to the electrodes of said PM sensor at a predetermined voltage application time after the execution of said sensor regeneration processing by said sensor regeneration unit ends; a filter diagnostic unit that is to carry out filter diagnostic processing in which abnormality of said particulate filter is diagnosed based on an output value of said PM sensor the output value of said PM sensor being outputted when a predetermined determination period of time has elapsed from said voltage application time; a monitor unit that is to continuously monitor the output signal of said PM sensor on and after said voltage application time; and a decision unit that is to decide whether said filter diagnostic processing is to be carried out by said filter diagnostic unit, based on a degree of variation in the output value of said PM sensor monitored by said monitor unit on and after an output starting time at which the output value of said PM sensor begins to go up from zero, in a period of time in which said determination period of time elapses after said voltage application time.