Internal gear pump

Abstract

In an internal gear pump 9, a diameter of a base circle is set to A mm, a radius of a rolling circle is set to b mm, a diameter of a locus circle is set to C mm, and an amount of eccentricity is set to e mm. A trochoidal curve T is drawn by rolling the rolling circle along the base circle without slipping and by using a locus of a fixed point distant from a center of the rolling circle by e. A tooth profile of an inner rotor 2 having n teeth is formed based on an envelope of a group of the locus circles each having a center on the trochoidal curve T. A pump rotor 1 is formed by combining the inner rotor with an outer rotor having (n+1) teeth. A tooth-profile curve of the inner rotor satisfies the following expression (1). Because K<1 is satisfied, cusps s are not formed at opposite edges of each addendum of the inner rotor 2. K = C 6 · n + 2 n + 1 · n + 2 3  n   ( b 2 - e 2 ) < 1 ( 1 )

Dependencies are inferred from the claim text.