Abnormality detection apparatus for electrically heated catalyst

An abnormality detection apparatus for an electrically heated catalyst, the abnormality detection apparatus comprising:

• the electrically heated catalyst provided in an exhaust passage of an internal combustion engine provided in a hybrid vehicle, wherein
• the vehicle is configured to switch between a first mode in which the vehicle is driven only by an electric motor energized by a battery and a second mode in which the vehicle is driven by the internal combustion engine and the electric motor in cooperation, and
• the electrically heated catalyst includes an exhaust gas purification catalyst and a heating element configured to generate heat when supplied with electricity, an electrical resistance of the heating element being larger when a temperature of the heating element is low than when the temperature of the heating element is high;
• and
• a controller including at least one processor,
• wherein the controller is configured to:
• apply a voltage to the electrically heated catalyst from the battery before startup of the internal combustion engine;
• adjust the applied voltage defined as the voltage applied to the electrically heated catalyst so as to make electrical power, which is a product of the applied voltage and a catalyst current, equal to a target electrical power to be supplied to the electrically heated catalyst, wherein the catalyst current is defined as an electrical current flowing through the electrically heated catalyst per unit time;
• calculate an electrical energy parameter relating to an actually supplied electrical energy defined as an integrated value of the electrical power actually supplied to the electrically heated catalyst over a specific period from the time when the application of the applied voltage to the electrically heated catalyst by the controller is started;
• acquire a charge level decrease rate defined as a rate of decrease of a charge level of the battery in the specific period during which the applied voltage is being applied to the electrically heated catalyst by the controller;
• set a specific threshold according to the charge level decrease rate acquired by the controller, wherein the specific threshold is a criterion for abnormality detection of the electrically heated catalyst;
• and
• detect an abnormality of the electrically heated catalyst by comparing the electrical energy parameter calculated by the controller and the specific threshold set by the controller.