TECHNICAL FIELD

This invention relates to a pump device including a pump element arranged to be driven and rotated by a drive shaft.

BACKGROUND ART

A variable displacement vane pump described in Japanese Patent Application Publication No. 2011-127538 (patent document 1) is known as a background art of this technical field.

The variable displacement vane pump includes a drive shaft having a first end side rotatably supported by a first bearing received in a bearing holding portion provided to a first housing, and a second end side rotatably supported by a second bearing received within a bearing recessed portion provided to the second housing (paragraph [0020]). The first bearing and the second bearing are lubricated by a hydraulic fluid leaked from pump chambers through axial gaps formed at both end surface portions of the rotor. A seal holding groove is provided at an end portion of the bearing holding portion receiving the first bearing. The seal holding groove has a stepped portion having diameters increased toward the outside of the first housing. A seal member is disposed in the seal holding groove so as to liquid-tightly seal (so that the fluid does not pass through) between the inner circumference surface of the first housing and the outer circumference surface of the drive shaft (paragraph [0021]).

PRIOR ART DOCUMENT

Patent Document

Patent Document 1: Japanese Patent Application Publication No. 2011-127538

SUMMARY OF THE INVENTION

Problems which the Invention is Intended to Solve

In the variable displacement vane pump of the patent document 1, the seal member is disposed on a side toward the outside of the first housing with respect to the first bearing so as to prevent the leakage of the hydraulic fluid lubricating the first bearing to the outside of the first housing. When the hydraulic fluid is the high temperature and the high pressure, the hydraulic fluid passes through a minute clearance between contact portions of the drive shaft and the seal member, so that the hydraulic fluid is easy to leak to the outside of the housing. Accordingly, it is necessary to use the seal member having a high performance or a complicated structure for preventing the leakage of the hydraulic fluid. In this case, the cost of the seal member becomes high. The size of the seal member is increased. Alternatively, in a case where the contact force between the seal member and the drive shaft is increased for preventing the leakage of the hydraulic fluid, the frictional resistance force acted to the drive shaft is increased, so that the efficiency of the pump device may be deteriorated, or the temperature of the hydraulic fluid may be increased due to the heat generation by the friction.

It is an object of the present invention to provide a pump device devised to effectively suppress the leakage of the hydraulic fluid by a simple configuration.

Means for Solving the Problem

In one aspect according to the present invention, the pump device has a following configuration.

The pump device includes a first bearing and a second bearing rotatably supporting a drive shaft arranged to drive and rotate a pump element. The first bearing includes a first lubrication groove. The second bearing includes a second lubrication groove. A sectional area of a section of the second lubrication groove which is perpendicular to the rotation axis is greater than a sectional area of a section of the first lubrication groove which is perpendicular to the rotation axis.

Benefit of the Invention

By the present invention, it is possible to effectively suppress the leakage of the hydraulic fluid by the simple configuration.

