Secondary air supply system and secondary air supply method

A secondary air supply system comprising:

• an exhaust gas control catalyst which is provided in an exhaust system in an internal combustion engine, and which purifies a harmful component in exhaust gas;
• secondary air supply means for supplying secondary air into the exhaust gas upstream of the exhaust gas control catalyst;
• secondary air supply stop means for stopping the secondary air supply performed by the secondary air supply means;
• fuel supply means for supplying fuel to the internal combustion engine;
• fuel amount increasing means for increasing a fuel amount supplied to the internal combustion engine when the secondary air supply means supplies the secondary air;
• and
• fuel amount increase stop time delaying means for delaying, by a predetermined delay period, a stop time at which the increase in the fuel amount caused by the fuel amount increasing means is stopped even when the secondary air supply is stopped by the secondary air supply stop means.

A secondary air supply method comprising the steps of:

• purifying a harmful component in exhaust gas using an exhaust gas control catalyst provided in an exhaust system of an internal combustion engine;
• supplying secondary air into the exhaust gas upstream of the exhaust gas control catalyst;
• stopping the secondary air supply;
• supplying fuel to the internal combustion engine;
• increasing a fuel amount supplied to the internal combustion engine when the secondary air is supplied;
• and
• delaying, by a predetermined delay period, a stop time at which the increase in the fuel amount is stopped even when the secondary air supply is stopped.