A/C Compressor Control Valve

A/C compressor control valve, purpose
The A/C compressor control valve regulates the stroke volume of the A/C compressor depending on the refrigeration requirement.

Component Identification, Part 1:

Function
Variable volume control in partial load range
(e.g. at low ambient temperature or low refrigeration requirement)
The refrigeration requirement is always dependent on the intake side, i.e. if the intake pressure (Ps) drops below the diaphragm pressure (Ps1) in the A/C compressor control valve and the control current is simultaneously reduced, the passage Pd to Pc in the A/C compressor control valve is opened by the control piston (2). This allows refrigerant to flow from the high pressure side (Pd) into the crankcase, increasing the pressure in the crankcase (Pc).
The total of the forces on the left side is open from the crankcase pressure (Pc), return force of the swash plate (centrifugal force) and spring return force is therefore greater than the sum of the piston forces. This causes the swash plate to move to the upright position reducing the piston stroke or displacement volume.

In addition the refrigeration control is dependent on the humidity, i.e.:
At high humidity the control valve is actuated externally (PWM signal) resulting in an increase in the refrigeration output (reduction of window fogging).

At an output rate less than 5 cubic cm the A/C compressor is switched off automatically.

Component Identification, Part 2:

Function
Control at max. stroke volume
(e.g. at high ambient temperature or refrigeration requirement)

If the intake pressure (Ps) increases above the diaphragm pressure (Ps1) in the A/C compressor control valve and the control current is increased simultaneously, passage Pd to Pc in the A/C compressor control valve is closed by the control piston (2). The crankcase pressure (Pc) decreases because refrigerant cannot flow from the high pressure side (Pd) through the A/C compressor control valve into the crankcase.
The bypass (1) allows long-term pressure compensation between the intake housing and crankcase (Ps Pc), i.e. the reaction force on the left side consisting of the crankcase pressure (Pc), return force of the swash plate (centrifugal force) and spring return force is therefore less than the sum of the piston forces. The swash plate angle increases from the "0 position", i.e. the angle increases continuously up to the mechanical limitation of the swash plate against the stop plate. The piston stroke increases linearly in relation to the angle of the swash plate up to the max. output volume.