| 摘要 |
PURPOSE:To enable an operative condition to be stabilized in an engine, when it is in idle operation or the like, by intermittently opening a linear type solenoid valve to perform a duty control of secondary air so that control accuracy of air-fuel ratio is prevented from worsening, when the engine is in operation with a low quantity of intake air. CONSTITUTION:When an engine is in operation with a low quantity of intake air, where a control circuit 20 discriminates an engine speed detected by a crank angle sensor 11 and in-intake pipe absolute pressure detected by an absolute pressure sensor 10 to be less than a predetermined value, a solenoid opening and closing valve 17 closes. And the engine, in which a solenoid valve 9 opens to an opening in accordance with a supplied current value fixed to a predetermined value in a predetermined period only for a predetermined time, performs a duty control of secondary air while supplies it into an intake manifold 4 only passing through a throttle valve 18. When the engine is in operation with an intermediate and high quantity of intake air, the solenoid opening and closing valve 17 opens, and the engine, in which the supply current value is determined by correcting a reference current value in accordance with an output level of an oxygen concentration sensor 14, opens the solenoid valve 9 to an opening in proportion to the supply current value.
|
