| 主权项 |
1. A failure diagnosis device for an emission control system, wherein the emission control system includes a particulate filter that is placed in an exhaust conduit of an internal combustion engine and that is configured to trap PM in exhaust gas; an exhaust gas purification device that is placed upstream of the particulate filter in the exhaust conduit and that is configured to purify the exhaust gas by utilizing a non-combusted fuel component included in the exhaust gas; and a supplier that is configured to perform in-cylinder rich control of changing an air-fuel ratio of an air-fuel mixture subjected to combustion in the internal combustion engine to a rich air-fuel ratio which is lower than a stoichiometric air-fuel ratio, so as to supply the non-combusted fuel component to the exhaust gas purification device,
the failure diagnosis device comprising: a PM sensor that is provided to detect an amount of PM flowing out of the particulate filter, the PM sensor including electrodes opposed to each other across an insulating layer and being configured to output an electric signal relating to a value of electric current flowing between the electrodes under application of a predetermined voltage to the electrodes; and a controller comprising at least one processor configured to perform a process of diagnosing a failure of the particulate filter, based on an output value of the PM sensor, wherein the controller is programmed to:
perform a measurement process, the measurement process including a sensor recovery process of removing PM depositing between the electrodes of the PM sensor, a process of starting application of the predetermined voltage to the electrodes of the PM sensor after completion of the sensor recovery process, and a process of obtaining an output value of the PM sensor after elapse of a predetermined time period since the start of application of the predetermined voltage;diagnose a failure of the particulate filter by comparing the obtained output value of the PM sensor with a predefined reference value;predict whether the in-cylinder rich control is performed in the predetermined time period, before the measurement process, or during the measurement process, or both before and during the measurement process; andperform the measurement process or continue the measurement process when it is predicted that the in-cylinder rich control is not performed in the predetermined time period, and either do not perform the measurement process or stop the measurement process when it is predicted that the in-cylinder rich control is performed in the predetermined time period. |
