Masuda, Naosuke; Ohe, Takeshi;

Balanced dual chamber oil pump

In an oil pump of the type comprising a cartridge having an elliptical cam ring in which a rotor having a plurality of vanes is rotated to form a pair of pump chambers symmetric with respect to an axis of rotor, and a pair of suction passages and two pairs of discharge passages are provided for the pair of pump chambers. A valve opening is formed coaxially with the rotor in a pump body secured to one side of the cartridge to contain the spool valve. A metering orifice is provided in a discharge passage to actuate the spool valve in response to a pressure differential such that when the pump speed is low all outputs of both pump chambers are supplied to a load, whereas when the pump speed is high a portion of the outputs is supplied the suction side. According to this construction it is possible to decrease power consumption and to decrease the size and weight of the oil pump.

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What is claimed is:

1. An oil pump comprising:

a pump body including a rotor, a cam ring surrounding said rotor and formed with a pair of pump chambers at positions symmetrical with respect to an axis of said rotor;

suction passages and first and second pair of discharge passages opening in said pump chambers at positions a predetermined distance apart in the direction of rotation of said rotor;

a flow control valve formed in the axial direction of said pump body and including a valve opening and a spool slidable therein;

one pair of said discharge passages opening at one end of said valve opening while the other pair opening at an axial center of said valve opening at diametrically opposed positions;

said passages opening at the axial center of said valve opening being normally closed by said spool biased to an inoperative position;

check valves located between two pair of discharge passages;

said suction passages opening in said valve opening at diametrically opposed positions between openings of the two pairs of the discharge passages;

whereby when said spool is operated, said suction passages are first communicated with said other pair of discharge passages opening at the axial center of said valve opening and then communicated with said one pair of discharge passages.

2. The oil pump according to claim 1 wherein said pump body is constituted by a pump cartridge containing said rotor having a plurality of vanes, and said cam ring having an elliptical cam surface engaging said vanes, and a front body and a rear body secured to opposite sides of said cartridge, and said valve opening is formed in said rear body coaxially with said rotor.

3. The oil pump according to claim 1 wherein said spool is formed with an annular groove about its surface and said one pair of discharge passages open into said groove.

4. The oil pump according to claim 1 wherein openings of said first pair of discharge passages open into said valve opening and are normally closed by a land of said spool.

5. The oil pump according to claim 2 wherein a metering discharge passage is provided for said rear body in parallel with said valve opening, and said metering discharge passage is communicated with one of said one discharge passages through a metering orifice which creates a pressure difference for operating said spool.

6. The oil pump according to claim 5 wherein a damper orifice is provided between downstream side of said metering orifice and low pressure side of said spool which is normally closed by a relief valve.

7. The oil pump according to claim 1 wherein said spool is provided with an annular groove at its center which interconnects said pair of suction passages when said spool is inoperative.