The cylinder block (1) contains numerous bores (32) for bolts (5) securing a front and rear housing (2) to the cylinder block with a cylinder bore (9). In the block are formed a crank (17), a suction (11), and a delivery chamber (13), with the crank chamber retaining a drive plate (25) on a drive shaft (6). The pressure passage is partly formed in one bolt retaining bore and connects the crank and suction chambers. Thus a large demand on pressure in the crank chamber can be taken and this is compressed by the piston (10) in the cylinder bore. This then leaks from the bore into the crank chamber.
