| 摘要 |
PURPOSE:To increase the torque controllability of an engine while keeping its fail-safe at a low machine temperature. CONSTITUTION:An idle control valve 4 and a control valve 5 for fail safe are interposed in their serial connection in a bypass air path 3 and the idle control valve 4 is controlled by control signals output from an engine control unit 6 and the control valve 5 for fail safe is controlled by a control circuit 10. The control circuit 10 controls the opening of the control valve 5 for fail safe in relation to the throttle valve opening, on the basis of the throttle valve opening detected signals output from a throttle sensor 9 and the detected signals output from an engine water temperature switch 12 and further, controls the control valve 5 for fail safe to its complete closure at a temperature lower than a specified engine temperature. In this way, the control valve 5 for fail safe shows a stroll-characteristic concerning the throttle valve opening. And the fail safe is secured at a low machine temperature. |
