Patent ID: 8342815

Claim:
An oil pump comprising: a fluid inlet portion for introducing a hydraulic fluid; a fluid outlet portion for discharging the hydraulic fluid, the fluid outlet portion including a plurality of outlet ports; a drive shaft that rotates about an axis thereof; a plurality of volume variable pump chambers arranged about the drive shaft and rotated by the same, the pump chambers being arranged between the fluid inlet portion and the fluid outlet portion for compressing the hydraulic fluid from the fluid inlet portion before discharging the same from the fluid outlet portion, the pump chambers being exposed to the outlet ports separately one after another when the pump chambers are rotated by the drive shaft; and a discharge rate varying mechanism that varies a fluid discharge rate of each of the outlet ports by varying the amount of the fluid led to the outlet ports; wherein the fluid outlet portion comprises first and second outlet ports, wherein the discharge rate varying mechanism is constructed so that when the fluid discharge rate of the first outlet port is reduced, a discharge pressure of the first outlet port is reduced and at the same time the discharge pressure of the second outlet port is increased, wherein each of the outlet ports comprises one side outlet port part and the other side outlet port part which are respectively provided in paired defining members that define therebetween the pump chambers, the one side outlet port part and the other side outlet port part being communicated to each other, and wherein the discharge rate varying mechanism is so constructed as to make a relative movement between the paired defining members thereby to make a relative movement between the one side outlet port part and the other side outlet port part.