| 摘要 |
PURPOSE:To reduce an output fluctuation due to the changeover of an air-fuel ratio by constituting an air-fuel ratio control means for changing the ratio in step with two valves within a bypass passage bypassing a throttle valve and opening or closing one of the valves at the time of changing the ratio over to the lean side and the like. CONSTITUTION:When an engine 1 is running, ECU 22 is inputted with a water temperature signal 'Tw' and a throttle opening signal 'TVtheta'. If 'Tw' is lower than predetermined temperature 'T1' or 'Tw' is lower than 'T1' and 'TVtheta' exceeds predetermined opening 'theta1', a secondary valve device 18 within a bypass passage 17 formed bypassing a throttle valve 5 is made to close and air-fuel ratio control is made to go on according to a theoretical air-fuel ratio. Also, when 'Tw' is higher than 'T1' and 'TVtheta' is less than 'theta1', the secondary valve device 18 is made to open and the engine 1 is operated with a lean air-fuel ratio. And when the secondary valve device 18 opens, a primary valve device 19 fitted in series therewith is controlled for the opening and closing thereof interlocked with the throttle valve 5, for keeping constant the ratio of air passing through the bypass passage 17 and the throttle valve 5. |
