Patent ID: 9541085
Date: 2017-01-10
CPC Classifications: F04C

Claim:
1. An internal gear pump comprising a pump rotor ( 4 ) in which a meshing point between an inner rotor ( 2 ) having n teeth and an outer rotor ( 3 ) having (n+1) teeth is located rearward, in a rotational direction of the inner rotor, relative to an eccentric axis (CL) along which a center (O I ) of the inner rotor and a center (O O ) of the outer rotor are disposed, wherein an outer rotor tooth profile at an outer side of the outer rotor relative to a changing point where positive and negative directions of the tooth-surface curve connect, is a duplicate of an inner rotor tooth profile, wherein the inner rotor tooth profile is formed by a first method, and the outer rotor tooth profile is formed by a second method, and wherein the tooth-surface shape of a corresponding position of the inner rotor ( wherein the first method includes: moving an addendum forming circle (B) and a dedendum forming circle (C) on a basis of first to third movement conditions, drawing a locus curve of a point (j) on each forming circle (B, C) that is aligned with a reference point (J) on a base circle (A) concentric with the center (O inverting the locus curve symmetrically with respect to a line (L wherein the movement conditions of each forming circle (B, C) include: the first movement condition in which each forming circle (B, C) is disposed such that the point (j) on the forming circle is in alignment with the reference point (J) on the base circle (A), a center (pa, pb) of the forming circle at that time is set as a movement start point (Spa, Spb), and the forming circle (B, C) is rotated from the movement start point (Spa, Spb) at a constant rate while the center of the forming circle is moved along a forming circle-center movement curve (AC the second movement condition in which a distance, in a radial direction, from the center (O the third movement condition in which, in the radial direction of the base circle (A), a distance between the center (O wherein the second method includes: revolving the center (O forming a principal outer rotor tooth profile by duplicating the tentative outer rotor tooth profile at an outer side of the outer rotor relative to the changing point where the positive and negative directions of the tooth-surface curve change to the inner rotor tooth profile.