Idling speed control system

Abstract

In idling speed control system for an engine, for use with a refrigeration circuit for circulating refrigerant through a variable capacity type compressor driven by the engine, a condenser and an evaporator, an idling adjuster is provided to adjust a quantity of an air flow bypassing a throttle valve disposed in a suction passage of the engine and sucked into a combustion chamber of the engine. The control system is arranged to detect Numerical information required for calculating a first influence degree given to an output of the engine by the compressor during operation of the refrigeration circuit, to estimate, in accordance with the numerical information, a second influence degree which will be given to the engine output by the compressor under condition that the engine drives the compressor at a predetermined idling speed and the refrigeration circuit is maintaining cooling ability in a predetermined state. The control system is further arranged to output a control signal dependent on the estimated second influence degree to the idling adjuster prior to idling operation of the engine and for rendering the idling adjuster adjusting the bypassed air flow quantity in accordance with the estimated second influence degree.