Patent ID: 7891173

Claim:
An exhaust gas cleaning apparatus comprising: a main exhaust passage configured to receive exhaust gas from an internal combustion engine therethrough; a main catalytic converter disposed in the main exhaust passage; a bypass exhaust passage including a first end connected to the main exhaust passage at a first point that is upstream from the main catalytic converter and a second end connected to the main exhaust passage at a second point that is upstream from the main catalytic converter; a bypass catalytic converter disposed in the bypass exhaust passage between the first and second ends of the bypass exhaust passage; a selector valve arranged to selectively control a flow of the exhaust gas from the internal combustion engine between the main exhaust passage and the bypass exhaust passage; and a controller configured to control a combustion state of the internal combustion engine and to selectively open and close of the selector valve, the controller being further configured to control the internal combustion engine to a rich combustion state with a rich air fuel ratio while the controller controls the selector valve to block the flow of the exhaust gas through the main exhaust passage, and then, afterwards, controls the selector valve to direct the flow of the exhaust gas through the main exhaust passage such that residual air remaining in the main exhaust passage mixes with rich exhaust gas from the bypass exhaust passage, with the controller commencing to control the internal combustion engine to the rich combustion state in response to the main catalytic converter reaching an active state.