The compressor for the air conditioning is driven by a belt-drive via an electrically operated clutch. We're talking about an axial piston compressor. This tries to help the piston pump to a more continuous delivery, whereby the individual pistons, one after the other, reach TDC. The individual control valves and the inlet- or pressure pipe are housed in the cover itself.
In the above illustrated compressor, the drive-belt wheel has an electrically switchable clutch (connection on the right). Here, the delivery rate or the pressure can be adjusted. the drive-belt wheel then drives the swashplate in the center, which is responsible for the stroke movement of the individual pistons during one rotation. 10/09