Patent ID: 8549896

Claim:
A vane pump comprising: an upper casing in the shape of a cylinder with a bottom consisting of a cylinder section substantially in the shape of a circular cylinder and a plate section having an upper flat surface substantially in a round shape blocking an opening in an end portion of the cylinder section on a first side of the vane pump; a plate-like lower casing having a lower flat surface substantially in a round shape blocking an opening in an end potion of the upper casing on a second side of the vane pump, the lower casing defining a pump chamber inside the lower flat surface, the upper flat surface and an inner peripheral wall of the cylinder section; a rotor substantially in the shape of a circular cylinder that is rotatably accommodated in the pump chamber to be decentered with respect to the cylinder section and that has a central hole penetrating through a central portion thereof in an axial direction and a plurality of vanes capable of sliding on the inner peripheral wall of the cylinder section; and a motor having a motor case substantially in the shape of a circular cylinder provided on a side of the lower casing opposite to the plate section and a shaft that extends from the motor case in the axial direction and that is loosely fitted in the central hole, the motor driving and rotating the rotor by rotating the shaft, wherein a first point on an outer peripheral end of the lower flat surface farthest from an intersection between an axis of the shaft and the lower flat surface, a second point on the outer peripheral end of the lower flat surface at which a virtual straight line extending from a central point of the lower flat surface and passing through the first point intersects with the outer peripheral end of the lower flat surface when the virtual straight line rotates by 90 degrees in a rotation direction of the rotor around the central point, a third point on the outer peripheral end of the lower flat surface opposite from the second point across the central point, a fourth point on the outer peripheral end of the lower flat surface in a range from the third point to the first point, a suction passage passing through the third point for connecting an outside and an inside of the pump chamber and for passing a fluid suctioned to the inside of the pump chamber is formed between the upper casing and the lower casing, a discharge passage passing through the second point for connecting the inside and the outside of the pump chamber and for passing the fluid discharged to the outside of the pump chamber is formed between the upper casing and the lower casing, and the lower flat surface is configured to incline with respect to the axis of the shaft such that the fourth point is farthest from the motor case among points on the outer peripheral end of the lower flat surface.