System for controlling a compressor of an air conditioner for motor vehicles

Claim 1

In a system for controlling a compressor of an air conditioner for a vehicle powered by an engine, the system having an electromagnetic clutch for coupling the engine with the compressor, an electrically operated switch provided in a circuit for engaging the clutch, vehicle speed detecting means for detecting vehicle speed and for producing a vehicle speed signal corresponding to the vehicle speed, and engine load detecting means for detecting pressure in an intake manifold of the engine and for producing an actual pressure signal corresponding to the actual pressure in the intake manifold, the improvement comprising: reference load characteristic memorizing means memorizing a characteristic comprising a desired pressure signal representing a continuously decreasing function of decreasing of the vehicle speed signal, decision means for reading out a value of the desired pressure signal from the reference load characteristic memorizing means corresponding to and in response to the vehicle speed signal, comparator means for comparing the actual pressure signal with the read out value and for producing a clutch disengagement signal when the actual pressure signal is larger than the read out value; and control means responsive to the clutch disengagement signal for opening the electrically operated switch to stop operation of the compressor so as to reduce the load on the engine to increase the power for driving the vehicle.