Pump device

A pump device comprising:

• a pump housing having a pump element accommodation space;
• a drive shaft rotatably supported by the pump housing;
• an inlet port provided in the pump housing and introducing working fluid from a reservoir tank;
• an outlet port provided in the pump housing;
• a pump element accommodated in the pump element accommodation space, sucking the working fluid from the inlet port by being rotated by the drive shaft and discharging the working fluid from the outlet port;
• an inlet passage provided in the pump housing and communicating with the inlet port;
• an outlet passage provided in the pump housing and communicating with the outlet port;
• a relief valve accommodation bore provided in the pump housing and having a substantially circular shape in cross section;
• when an imaginary line passing through a bore center of the relief valve accommodation bore, which is a center of a cross section orthogonal to an axis that extends in an axial direction that is a longitudinal direction of the relief valve accommodation bore, and extending parallel to the axis, is a center axis,
• a valve seat provided at one end side in the axial direction of the relief valve accommodation bore and having a substantially cylindrical shape whose outer peripheral surface is shaped along a shape of an inner peripheral surface of the relief valve accommodation bore;
• a penetration hole that is an axial direction hole provided at the valve seat so as to penetrate the valve seat in the axial direction, the penetration hole formed so that one end portion, which is located at the one end side of the relief valve accommodation bore, of both end portions of the penetration hole communicates with the outlet passage and so that a forming position of the penetration hole on a cross section of the valve seat orthogonal to the axial direction of the relief valve accommodation bore is positioned substantially at a center of a substantially circular cross section of the relief valve accommodation bore;
• a seat portion provided at the other end side in the axial direction of the valve seat and formed into a ring-shape so as to encircle the penetration hole, the seat portion set so that a center of the seat portion on a cross section orthogonal to the axial direction of the relief valve accommodation bore is offset from the center axis;
• a spherical valve body performing opening and closure actions of the penetration hole by separation from and contact with the seat portion;
• a retainer provided movably in the axial direction in the relief valve accommodation bore and disposed at the other end side of the relief valve accommodation bore with respect to the valve body, the retainer having a valve body holding portion for retaining the valve body and shaft portion extending from an end surface of the valve body holding portion toward the other end side of the relief valve accommodation bore;
• a coil spring provided in the relief valve accommodation bore and forcing the retainer so that the valve body retained by retainer contacts the seat portion;
• and
• a relief vent provided at the other end side of the relief valve accommodation bore with respect to the valve seat so as to be open to the relief valve accommodation bore, the relief vent discharging the working fluid in the relief valve accommodation bore into the inlet passage, and
• when a radial direction component, with respect to the center axis, of a pressing force according to a pressure of the working fluid in the penetration hole which the valve body receives in an inner side area of the ring-shaped seat portion in a state in which the valve body contacts the seat portion is F1x, and a radial direction component, with respect to the center axis, of a force which reduces the radial direction component F1x due to lean of the retainer with respect to the center axis is F2x, and also a radial direction component, with respect to the center axis, of a force according to an urging force of the coil spring, which reduces the radial direction component F1x is F3x, the seat portion being formed so as to satisfy an expression of F1x>F2x+F3x.