| 摘要 |
PURPOSE:To make rich the air-fuel ratio quickly thus to prevent degradation of operationability by quickly closing an air control valve arranged in secondary intake air supply path when transferring to the operation for stopping air-fuel ratio feedback control. CONSTITUTION:Two air control paths 11a, 11b are juxtaposed in the way of secondary intake air supply path 11 opening to the downstream of the throttle valve 5 of carburetor 3 while an air control valve 12 and a solenoid valve 15 are arranged sequentially in the first path 11a. Negative pressure controlled through negative pressure control section 32 is led into the negative pressure chamber 12a of air control valve 12. Another air control valve 16 is arranged in the second path 11b to communicate the negative pressure chamber 16a with the downstream of throttle valve 5 through negative pressure feed path 17 while a surge tank 20, a solenoid valve 18, a constant negative pressure control valve 21, a storage tank 22 and a check valve 23 are arranged sequentially in the negative pressure supply path 17. The negative pressure chamber 16a of negative pressure supply path 17 and the surge tank 20 are communicated with the atmosphere through atmospheric pressure supply path 49 arranged with a solenoid valve 50.
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