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Variable displacement vane pump

Variable displacement vane pump description/claims

The present invention relates to a variable displacement vane pump which serves as a hydraulic power source of a hydraulic device such as a power steering apparatus for vehicles.

Japanese Patent Application First Publication No. 2002-168179 discloses a variable displacement vane pump which is applied to a power steering apparatus for vehicles. The variable displacement vane pump of the conventional art is so constructed as to cause change in volume of pump chambers by swinging a cam ring within a pump body and thereby control a flow rate of the working fluid discharged by the vane pump. The operation of the vane pump is controlled such that when the vane pump is operated at high speed, the flow rate of the working fluid discharged is decreased. First and second fluid pressure chambers are disposed outside the cam ring in a radially opposed relation to each other. The swing movement of the cam ring is controlled by fluid pressures which are introduced into the respective fluid pressure chambers. The cam ring is swingably moved on a support surface which is disposed within the pump body. A pin is disposed adjacent to the support surface in a circumferential direction of the cam ring and restrains a rotational movement of the cam ring within the pump body. A stop for limiting the swing movement of the cam ring is formed on a side of the first fluid pressure chamber within the pump body. With contact of the cam ring with the stop, the flow rate of the working fluid discharged becomes largest and an increased fluid pressure is applied to a discharge port of the vane pump. At this time, the increased fluid pressure is exerted on the cam ring which is supported by the stop and the support surface, from an inner circumferential side of the cam ring. An outer circumferential region of the cam ring extending between the portions at which the cam ring is contacted with the stop and the support surface is exposed to such a force as to induce a radial outward deformation thereof by the increased fluid pressure.

However, in the above-described conventional art, a recessed portion which is engaged with the pin is formed in the outer circumferential region of the cam ring extending between the portions at which the cam ring is contacted with the stop and the support surface. Therefore, the recessed portion undergoes stress concentration due to the increased fluid pressure. There might occur deterioration in durability of the cam ring and pump characteristics due to change in cam profile of the cam ring.

It is an object of the present invention to solve the above-described problem in the technologies of the conventional art and to provide a variable displacement vane pump which can suppress stress concentration in a cam ring and prevent deterioration in durability of the cam ring and pump characteristics due to change in cam profile of the cam ring.

In one aspect of the present invention, there is provided a variable displacement vane pump, comprising:

a pump body;

a driving shaft supported on the pump body;

a rotor which is disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor,

a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor;

an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring;

a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively;

a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor;

a seal cooperating with the swing support surface to divide a space on an outer circumferential side of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port;

a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring;

a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and

a detent disposed between the cam ring and the pump body on a side of the second fluid pressure chamber, the detent preventing a rotational movement of the cam ring around the driving shaft.

In a further aspect of the present invention, there is provided a variable displacement vane pump, comprising:

a pump body;

a driving shaft supported on the pump body;

a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor,

a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor;

• Provisional Patent
• Utility Patent

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