EXTERNAL CONTROL DEVICE FOR VARIABLE DISPLACEMENT COMPRESSOR

PURPOSE:To improve the constant speed running performance of a car as automatic control performed by a compressor on its internal capacity is utilized by forcibly controlling the capacity of a variable displacement compressor to the maximum or the minimum according to a command issued from an external constant speed running control device. CONSTITUTION:During the normal operation of a car, the bypass quantity of a refrigerant toward an inlet side in the compression stroke of a variable displacement compressor 2 forming an air conditioning device is adjusted by a variable capacity mechanism 50 to perform cooling operation effectively. On the other hand, when a command signal is output from a constant speed running control device 101 during car running, a capacity control means 110 controls a capacity setting mechanism SV. At this time, a bypass passage 39 is fully opened in an accelerating state, namely the discharge capacity of the compressor 2 is set to the minimum, and the bypass passage 39 is totally closed in a decelerating state, namely the discharge capacity of the compressor 2 is set to the maximum. The running performance of the car can therefore be improved as automatic control performed by the compressor 2 on its internal capacity is utilized.