EXHAUST GAS PURIFYING DEVICE

摘要

PURPOSE: To provide an exhaust gas purifying device for an engine having a self-diagnosing function. CONSTITUTION: An exhaust gas purifying device comprises a catalyst device 11; an adsorption device 12 situated downstream of the catalyst device 11; a reflux means 15 through which a spot situated downstream from the adsorbing device 12 is connected to a spot situated upper stream from the catalyst device 11; and a switching means operated in such a manner that when the temperature of exhaust gas is below a given value, exhaust gas is let to flow to a second flow passage 32 in which the adsorbing device 12 is located and when the temperature of exhaust gas exceeds a given value, exhaust gas is let to flow to a first flow passage 31 in which no adsorbing device 12 is located. Exhaust gas sensors 21 and 22 are arranged upper stream side from the reflux means 15 and the adsorbing device 12. The trouble of a device is diagnosed through measurement of a time te in which the outputs of the two exhaust gas sensors are let to coincide with each other after operation of the reflux means 15 or a correlation factor C between two outputs.