Compressor HVAC: Description and Operation

DESCRIPTION
The Variable Displacement Compressor (VDC) provides maximum air conditioning performance in most ambient conditions. It is designed to operate continuously without any cycling of the compressor clutch. The basic compressor mechanism is a variable angle wobble plate with six axially oriented cylinders.

OPERATION
The compressor will change displacement to match the vehicle air conditioning demand. The pumping stroke is governed by the pressure differential of the suction and the crankcase pressures. when the suction pressure is higher than the crankcase pressure, the wobble plate angle in the compressor will increase. This will cause the compressor pumping stroke to increase. When the suction pressure is lower than the crankcase pressure, the wobble plate angle will decrease and so will the compressor pumping stroke. When the heat load at the evaporator decreases, or when RPM increases, the suction pressure increases which causes the main control valve to close off discharge pressure to the crankcase. As the crankcase pressure reduces, the wobble plate angle increases and lengthens the piston stroke, increasing the refrigerant flow to the evaporator during high load periods. When quick cooling is needed, the sub-control valve allows for quicker release of crankcase pressure to the suction side.