Crank Type Compressor

By 2 August 2014

Crank type compressors (Fig 2.3) are not generally used in the automotive industry any more. They may have up to two cylinders including ‘V’ shape configuration. They are driven by the engine pulley system which rotates a crankshaft inside the pump.The crankshaft is connected to a piston via a connecting rod which travels up and down the bore. Above the piston there is a valve assembly to direct the flow of refrigerant.

Pumping operation
The crankshaft and connecting rod convert the pump’s motion from rotary (Fig. 2.4) to reciprocating. The piston travels up and down the bore inducing, compressing and discharging the refrigerant.Two valves are fitted per bore: a suction valve and a discharge valve.

On the downward stroke the refrigerant enters the compression chamber through the suction port due to a vacuum being created above the piston and the low pressure of the refrigerant.

On the upward stroke the refrigerant is compressed and an increase in pressure and temperature occurs.When the refrigerant pressure overcomes the force of the discharge valves the high temperature and high pressure (superheated vapour) refrigerant leaves the compression chamber.