| 摘要 |
PURPOSE:To well meet the change of an exhaust component in accordance with an operational condition, by freely deviating air fuel ratio of exhaust to a rich or lean side from theoretical air fuel ratio in accordance with the operational condition of an engine. CONSTITUTION:When an exhaust gas sensor 10 detects a rich state of air fuel ratio of exhaust in an exhaust pipe 6, that is, a decrease of O2 concentration, a solenoid valve 15 opens a negative pressure passage 17 by a rich signal of the sensor, and this causes the negative pressure to operate to open a control valve 14 and guide secondary air. Then if the sensor 10 detects a lean state of the air fuel ratio, that is, an increase of the O2 concentration, the valve 15 opens an atmospheric pressure passage 16 by a lean signal of the sensor, in this way, the valve 14 is pressed by a spring 14g and closed to cut off introduction of secondary air. |
