Patent ID: 8176728
Filing Date: 2012-05-15
Classification: F01N,F02D,Y02T

Abstract:
1. An air-fuel ratio control device for controlling an air-fuel ratio of an engine, comprising: an exhaust passage for conveying exhaust flow in a downstream direction away from the engine; a bypass passage diverging from the exhaust passage at an upstream junction and rejoining the exhaust passage at a downstream junction located downstream from the upstream junction; a bypass catalytic converter disposed in the bypass passage; a main catalytic converter disposed in the exhaust passage downstream from the downstream junction; a valve mechanism disposed in the exhaust passage between the upstream junction and the downstream junction, the valve mechanism moving between a closed state and an open state; and a first air-fuel ratio sensor disposed in the bypass passage; a second air-fuel ratio sensor disposed in the exhaust passage downstream of the valve mechanism; a controller configured to control the air-fuel ratio such that: