The invention relates to pumps (1), in particular oil pumps for internal combustion engines, comprising a gear- or rotor-assembly, with one each of a pressure- and suction region (7, 5) arranged in a pump housing, which may be sealed from each other, by means of an axially displaceable piston valve (10), which defines a supply chamber (9) and a housing cover (24), closing the pump housing (8). The pressure region (7) comprises a pressure channel, connected to the waist (12) of the control piston (10), whereby the control piston (10) co-operates with a plunger (13) on the end thereof facing the supply chamber (9), which is arranged at right angles to the control piston (10). Said plunger (13) is pre-tensioned against the control piston (10), by means of a pressure spring (14) and said plunger (13) and control piston (10) are connected by means of a sliding surface (15), arranged at an angle to the control piston axis (4). |