Fail-safe device for motor vehicle speed governor

Abstract

An improved fail-safe device for a motor vehicle speed governor of the type having a control system to switch a supply of power to an actuator ON and OFF for the control of the traveling speed of a motor vehicle to keep a constant speed. A latch is connected to power supply control circuit which controls the power supply to an actuator. The actuator actuates a throttle valve in an intake manifold of an engine for providing constant speed travel by turning the throttle valve ON and OFF in accordance with an output of the latch. The latch is set with a command signal and reset with a cancel signal or a reset signal. The resetting of the latch is executed if an absence of a watch dog signal is detected or a change of output generating status of the latch is detected under certain conditions. The state of the latch can be maintained if the conduction of a switching circuit for the actuator is detected regardless of a command signal to start up the constant speed traveling.