JPS5752400A - Driving circuit of electromagnetic clutch - Google Patents

Abstract

PURPOSE:To prevent a clutch from sliding, by detecting pressure or temperature for enlarging a duty ratio of an intermittent current to be flown to an electromagnetic coil of a clutch when a load of a clutch is enlarged. CONSTITUTION:At a steady time the signals of an airconditioning temperature detector 8 and those of a setter 9 inside of a compartment are compared by a comparator 10 to control a transistor Q3 through a delay circuit 11 and a nonstable multivibrator 12 for driving an electromagnetic clutch for a vehicle air conditioning device 1 through a continuous current at a starting time and through an intermittent current after starting. Further when a compressor load is enlarged, the temperature thereof is detected through the detector 13 to be given to a switching circuit 15 through a comparator 14 and the transistor Q4 to change a resistance value to be inserted into the nonstable multivibrator 12 for enlarging a duty ratio. Consequently when the load is increased, the supply input to the electromagnetic clutch 1 can be increased to eliminate sliding for performing constant and good air cooling.