VARIABLE DISPLACEMENT VANE PUMP

摘要

A variable displacement vane pump is provided. This pump includes a pump housing including, a driving shaft, a rotor, a plurality of vanes, a cam support surface, a cam ring, an intake port formed at the pump housing, a discharge port formed at the pump housing, and a cam ring control mechanism disposed at the pump housing and configured to control an eccentric amount of the cam ring with respect to the rotor. The cam support surface is formed in such a manner that a shortest distance between the cam support surface and a reference line decreases from a second confining region side toward a first confining region side, and the cam ring is formed in such a manner that a cam profile radius change rate decreases first and then increases again on the second confining region side when eccentric amount of the cam ring is maximized.

主权项

1. A variable displacement vane pump comprising:
a pump housing including a pump element containing portion; a driving shaft rotatably supported by the pump housing; a rotor disposed in the pump housing and configured to be rotatably driven by the driving shaft, the rotor including a plurality of slits in a circumferential direction; a plurality of vanes disposed so as to be configured to be projected from and inserted into the slits; a cam support surface formed on an inner circumferential side of the pump element containing portion; a cam ring disposed movably as if it rolls on the cam support surface in the pump element containing portion, the cam ring being annularly formed and defining a plurality of pump chambers on an inner circumferential side thereof together with the rotor and the vanes; an intake port formed at the pump housing so as to be opened in an intake region of the plurality of pump chambers, the intake region being a region where volume thereof increases as the rotor rotates, the intake port being disposed opposite of the driving shaft from the cam support surface; a discharge port formed at the pump housing so as to be opened in a discharge region of the plurality of pump chambers, the discharge region being a region where volume thereof decreases as the rotor rotates, the discharge port being disposed closer to the cam support surface with respect to the driving shaft; and a cam ring control mechanism (a control valve, first and second fluid pressure chambers, and the like) disposed at the pump housing and configured to control an eccentric amount of the cam ring with respect to the rotor, wherein the cam support surface is formed in such a manner that a shortest distance between the cam support surface and a reference line decreases from a second confining region side toward a first confining region side, and the cam ring is formed in such a manner that a cam profile radius change rate decreases first and then increases again on the second confining region side when eccentric amount of the cam ring is maximized, assuming that a start end of the intake port is a point where one of the plurality of vanes is placed into alignment with the intake port for the first time after moving away from the discharge region as the rotor rotates, a terminal end of the intake port is a point where one of the plurality of vanes is in alignment with the intake port for the last time in the intake region as the rotor rotates, a start end of the discharge port is a point where the vanes are placed into alignment with the discharge port for the first time after moving away from the intake region as the rotor rotates, a terminal end of the discharge port is a point where the vanes are in alignment with the discharge port for the last time in the discharge region as the rotor rotates, the first confining region is a region between the terminal end of the discharge port and the start end of the intake port, the second confining region is a space between the terminal end of the intake port and the start end of the discharge port, when the circumferential direction is a rotational direction of the driving shaft, a reference point is a middle point between the start end of the intake port and the terminal end of the discharge port in the circumferential direction, the reference line is a line perpendicularly intersecting with a rotational axis of a driving shaft and passing through the reference point, a cam profile radius is a distance between a center of an inner circumferential surface of the cam ring and the inner circumferential surface of the cam ring, the cam profile radius change rate is a change rate of the cam profile radius in the rotational direction of the driving shaft, and a cam ring profile defining angle is defined in such a manner that, when the cam ring is placed in such a manner that the center of the inner circumferential surface of the cam ring coincides with the rotational axis of the driving shaft, an angle of 0 degree as the cam ring profile defining angle is set to one of a pair of points intersecting with the reference line that is located on the first confining region side among points on the inner circumferential surface of the cam ring, and the respective points on the inner circumferential surface of the cam ring have angles increasing along the inner circumferential surface of the cam ring in the rotational direction of the driving shaft so that an angle defined by one rotation throughout the inner circumferential surface of the cam ring becomes 360 degrees.