Patent ID: 7886521

Claim:
An exhaust purification catalyst diagnosis device for diagnosing a degree of performance degradation of a catalyst provided in an exhaust system of an engine for exhaust purification, the diagnosis device comprising: a catalyst temperature determination device that determines whether temperature of the catalyst is in a predetermined diagnosis permission range before the diagnosis processing of the catalyst; and a catalyst temperature control device that controls the temperature of the catalyst into the diagnosis permission range before the diagnosis processing of the catalyst when the catalyst temperature determination device determines that the temperature of the catalyst is outside the diagnosis permission range, wherein, when the catalyst temperature determination device determines that the temperature of the catalyst is outside the diagnosis permission range, the catalyst temperature control device controls the temperature of the catalyst into the diagnosis permission range before termination of the diagnosis routine, wherein said temperature control by the catalyst temperature control device terminates when it is determined that the temperature of the catalyst has entered the diagnosis permission range, wherein said temperature control by the catalyst temperature control device is not the normal operation of the engine, but a forced change to the temperature of the catalyst, and wherein, when the catalyst temperature determination device determines that the temperature of the catalyst is inside the diagnosis permission range, the catalyst temperature control device does not control the temperature of the catalyst.