Patent ID: 7942645

Claim:
An oil pump assembly comprising: a plurality of pump chambers constituting a plurality of oil pumps, respectively; a plurality of rotors fitted into the pump chambers, respectively; a single driving shaft operatively connected to the plurality of rotors to form a single body; wherein oil pumped up from an oil pan is supplied under pressure from the plurality of oil pumps to different associated destinations in a power unit, the plurality of oil pumps including a high-pressure pump and a low-pressure pump; and wherein the oil pumps are provided with respective relief valves adapted to pass oil discharged from the corresponding pump chambers therethrough; wherein each of the relief valves is a cylinder-shaped relief valve with a longitudinal axis along a centerline thereof, the longitudinal axis of each of the cylinder-shaped relief valves and a longitudinal axis of said driving shaft being parallel to each other and displaced apart from each other, wherein each of the cylinder-shaped relief valves has a pair of discharge ports formed as a pair of windows which have closed perimeters and which open through a circumferential wall of the relief valve in a direction perpendicular to the longitudinal axis of the relief valve, and wherein the relief valves are off-set from each other in an axial direction with only a portion of lengths of the relief valve overlapping each other, and with the pair of windows in one of the relief valves not overlapping the pair of windows in the other of the relief valves in the axial direction.