Patent ID: 8014931

Claim:
A secondary air supply system that supplies secondary air to an exhaust passage of an engine, comprising: a supply source of the secondary air; first and second paths through which the secondary air is supplied from the supply source to the exhaust passage; an engine state determination device arranged to determine a state of the engine; and a path switching device arranged to selectively switch the first and second paths to a communicated state in which the first and second paths communicate the secondary air between the supply source and the exhaust passage, or a shut-off state in which the first and second paths do not communicate the secondary air between the supply source and the exhaust passage, respectively, based on the state of the engine determined by the engine state determination device; wherein the state of the engine includes a first state and a second state set in advance based on an amount of nitrogen oxide exhausted from a combustion chamber of the engine, and the amount of the nitrogen oxide in the first state is smaller than the amount of the nitrogen oxide in the second state; and the path switching device brings the first and second paths into the communicated state when the state of the engine is determined to be the first state by the engine state determination device, and brings either one of the first and second paths into the communicated state when the state of the engine is determined to be the second state by the engine state determination device.