Abstract: An exhaust gas cleaning apparatus is provided that has a main exhaust passage, a main catalytic converter disposed in the main exhaust passage, a bypass exhaust passage, a bypass catalytic converter disposed in the bypass exhaust passage, a selector valve and a controller. The controller controls 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.

Abstract: An exhaust gas passageway of an internal combustion engine is basically provided with a main exhaust passageway, a bypass exhaust passageway, a bypass catalytic converter provided in the bypass exhaust passageway, a bypass control valve, an upstream air-fuel ratio sensor and a downstream air-fuel ratio sensor. The bypass exhaust passageway bypasses a portion of the main exhaust passageway between an upstream junction and a downstream junction. The bypass control valve opens or closes a portion of the main exhaust passageway. The upstream air-fuel ratio sensor is disposed upstream of the bypass catalytic converter to sense air-fuel ratio of an exhaust gas flowing into the bypass catalytic converter. The downstream air-fuel ratio sensor is disposed downstream of the bypass catalytic converter to sense air-fuel ratio of the exhaust gas flowing out of the bypass catalytic converter.

Abstract: An exhaust gas cleaning apparatus is provided that has a main exhaust passage, a main catalytic converter disposed in the main exhaust passage, a bypass exhaust passage, a bypass catalytic converter disposed in the bypass exhaust passage, a selector valve and a controller. The controller controls 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.