Axial piston pump

Abstract

An axial piston pump for supplying two separate oil circuits including two pistons units (6, 8) of which one is situated upon an external circle and the other upon an internal circle. The external piston unit (6) must be regulatable so that it can feed a hydromotor of a radiator fan. The internal piston unit (8) must supply a level regulation with a constant flow of oil. Accordingly, both piston units (6 and 8) suck oil via separate suction bores (11 and 26). In the suction bore (11) of the external piston unit (6) leading to the swash-plate chamber (4) is inserted an electromagnetically actuable controlling valve (12). In order that the pistons (5) of the external piston unit (6) cannot run dry when the controlling valve (12) is regulated, there branches off from the suction bore (11), upstream of the controlling valve (12), a constant-flow bore (23) which via an annular groove (24) and radial bores (25) supplies a relatively small amount of oil to each piston (5) in the dead-center position thereof. The pistons (7) of the internal piston unit (8) receive the oil via an annular groove (27) branching off from the suction bore (26) and discharging in the cylinder chambers (7A) via radial bores (28). The radial bores (28) are open in the lower dead-center position. In this manner pressurized oil can be fed separately to each piston unit without mutual interference. Pressure channels (13A and 30A) of both piston units (6 and 8) discharge in a common sealing surface (35) of a piston carrier (10). In the annual grooves (14 and 31) of a rear housing part (40) exhaust valves (13 and 30), respectively, are located consisting of a ring plate (33, 34) and a rubber elastic ring (36 or 37) and tightly fitting against the sealing surface (35).