METHOD AND APPARATUS FOR CONTROLLING SUPPLY OF SECONDARY AIR TO EXHAUST GAS OF INTERNAL COMBUSTION ENGINE

PURPOSE: To control secondary air supply quantity and to obtain excellent exhaust gas characteristic and noise characteristic by performing a secondary air supply to exhaust gas by an electrically driving secondary air pump and driving the secondary air pump in at least two stages in accordance with operating parameters of an internal combustion engine. CONSTITUTION: Secondary air from a secondary air pump 10 is supplied to an exhaust pipe 4 of an internal combustion engine 1 via a conduit 9. At least intake air quantity Q, a number of rotation (n) from a sensor 7, a temperature T from a sensor 7', a position LL of a throttle valve, a fuel/air mixed composition lambda L and a measuring signal U from a function block 16 are supplied to a control device 8. The function block 16 has two switching means, an alternative operation is performed in accordance with an input signal of the control device 8, different voltage is impressed on the secondary air pump 10 and secondary air supply quantity is adjusted in two stages according to exhaust gas quantity. Thus, an exhaust gas characteristic is made excellent in accordance with an operating state and noise of the pump 10 is effectively reduced.