Engine speed limiting control circuit

Abstract

A system for limiting the speed of a gasoline engine includes a circuit responsive to the engine speed which provides control signals to a solenoid valve which in turn controls a vacuum actuator. The vacuum actuator then overrides a manual throttle control to move the throttle towards closed position when a governed engine speed is approached. The control circuit provides a signal having three components: one proportional to engine speed, a second proportional to engine acceleration and a third which is the integrated difference between the engine speed and a preset governed speed. In addition, the third signal is high at low engine speed and gradually diminishes as engine speed increases to intermediate or high values. The control signal controls a duty cycle oscillator which actuates the solenoid valve. The duty cycle oscillator is inhibited at low speeds to prevent interference with manual throttle control.