Patent ID: 8257071

Claim:
A vane pump comprising: a casing; an annular ring arranged within the casing and provided with a cylindrical inner circumferential surface; and a rotary unit rotatably held within the casing, the rotary unit including a cylindrical columnar base portion with a plurality of radially outwardly opened slits extending radially with respect to a rotational axis of the rotary unit and vanes slidably fitted in the respective slits, an annular chamber being formed around the base portion within the casing and divided into a plurality of pump chambers by the vanes, each of the pump chambers having a volume cyclically expanded and contracted during rotation of the rotary unit to discharge the fluid drawn into each of the pump chambers, wherein the annular chamber is formed between the inner circumferential surface of the annular ring and an outer circumferential surface of the base portion, wherein a leading end of each of the vanes makes sliding contact with the inner circumferential surface of the annular ring during the rotation of the rotary unit, and wherein the casing includes an inlet port through which to draw the fluid into the annular chamber, the inlet port having a width in a direction of the rotational axis smaller than that of each of the vanes and being arranged so as to face only a portion of the annular chamber extending between a middle position and a terminating position of an expanding section in which each of the pump chambers expands.