| 摘要 |
PURPOSE:To prevent the engine from over-running by a method wherein the operation of a computer is monitored and, when abnormality is decided, valve timing is held at one of two timings or, for example, at the low speed timing in the program-controlled titled device. CONSTITUTION:A timing control member 28, which is coupled to a suction camshaft 18, is pivoted rightward or leftward through cranks 31 and 30 driven by a motor 32 so that the valve timing is controlled in two stages or high speed and low speed timings. Said motor 32 is controlled by a control circuit 36 which receives output signals from a throttle positioner 38 and a rotational frequency sensor 40. When the control circuit 36 detects the abnormality of the microcomputer contained within the circuit 36, the control circuit 36 invalidates the operation of the motor 32 by said computer and simultaneously drives the motor 32 to the side to select the low speed valve timing. |
