Patent ID: 7476093
Filing Date: 2009-01-13
Classification: F04C

Abstract:
1. An oil pump rotor assembly comprising: an inner rotor formed with n external teeth where n is a natural number; an outer rotor formed with (n+1) internal teeth which are engageable with the external teeth; and a casing having a suction port for drawing fluid and a discharge port for discharging fluid, wherein the fluid is conveyed by drawing and discharging the fluid by volume change of cells formed between tooth surfaces of the inner and outer rotors during relative rotation between the inner and outer rotors engaging each other, wherein each of the tooth profiles of the outer rotor is formed such that the profile of a tooth space thereof conforms to an epicycloid curve which is generated by rolling a circumscribed-rolling circle Ao along a base circle Do without slippage, and the profile of a tooth tip thereof conforms to a hypocycloid curve which is generated by rolling an inscribed-rolling circle Bo along the base circle Do without slippage, wherein the profile of a tooth tip of the inner rotor conforms to an epicycloid curve which is generated by rolling a circumscribed-rolling circle Ai along a base circle Di without slippage, wherein the profile of a tooth space of the inner rotor conforms to a hypocycloid curve, which is generated by rolling an inscribed-rolling circle Bi along a base circle Di without slippage, the hypocycloid curve is equally divided into two external tooth curve segments, the obtained two external tooth curve segments are separated from each other by a predetermined distance along the circumference of the base circle Di and/or along a tangential line of the hypocycloid curve drawn at the midpoint thereof, and the separated two external tooth curve segments are smoothly connected to each other using a curved line or a straight line, and wherein the inner and outer rotors are formed such that the following equations are satisfied: where φDi is the diameter of the base circle Di of the inner rotor, φAi is the diameter of the circumscribed-rolling circle Ai, φBi is the diameter of the inscribed-rolling circle Bi, φDo is the diameter of the base circle Do of the outer rotor, φAo is the diameter of the circumscribed-rolling circle Ao, φBo is the diameter of the inscribed-rolling circle Bo, and “e” is an eccentric distance between the inner and outer rotors, and such that the following equation is satisfied: where “α” is the distance between the separated external tooth curve segments in the inner rotor.