Patent ID: 7118359
Filing Date: 2006-10-10
Classification: F04C

Abstract:
1. An oil pump rotor assembly comprising: an inner rotor having “n” external teeth (“n” is a natural number); an outer rotor having (n+1) internal teeth which are engageable with the external teeth; and the distance between an apex of an outer tooth of the inner rotor and an apex of an inner tooth of the outer rotor when the apexes oppose each other defining a tip clearance therebetween, wherein the oil pump rotor assembly is used in an oil pump which further includes a casing having a suction port for drawing fluid and a discharge port for discharging fluid, and which conveys fluid by drawing and discharging fluid by volume change of cells formed between tooth surfaces of the inner rotor and the outer rotor during relative rotation between the inner rotor and the outer rotor engaging each other, wherein each of the tooth profiles of the outer rotor is formed such that the tooth space profile thereof is formed using an epicycloid curve which is generated by rolling a circumscribed-rolling circle Ao along a base circle Do without slip, and the tooth tip profile thereof is formed using a hypocycloid curve which is generated by rolling an inscribed-rolling circle Bo along the base circle Do without slip, wherein the tooth space profile of the inner rotor is formed based on a hypocycloid curve which is formed by rolling an inscribed-rolling circle Bi along a base circle Di without slip, wherein the tooth tip profile of the inner rotor is formed such that an epicycloid curve, which is generated by rolling a circumscribed-rolling circle Ai along the base circle Di without slip, is equally divided into two at a midpoint thereof to obtain two outer tooth curve segments, and the two outer tooth curve segments are separated by a predetermined distance and are smoothly connected to each other using a curve or a straight line, and wherein the predetermined distance between the two outer tooth curve segments is designated by “α”, and the tip clearance is designated by “t”, “α” is set so as to satisfy the following inequalities: