Patent ID: 6890164

Claim:
An internal gear pump comprising: (a) an inner rotor having an addendum formed by a smooth curve and a dedendum formed by a hypocycloid; and (b) an outer rotor having a tooth profile determined by the steps of: (b1) revolving the center of the inner rotor around the center of the outer rotor so as to form a circle having a diameter of 2e+t, where “e” is the amount of eccentricity between the center of the inner rotor and the center of the outer rotor and “t” is the maximum value of the interrotor clearance between the outer rotor and the inner rotor pressed against the outer rotor; (b2) rotating the inner rotor on its own axis 1/n times while the center of the inner rotor makes one revolution in the circular orbit, where “n” is the number of teeth of the inner rotor; (b3) drawing the envelope of the group of the tooth-profile curves of the inner rotor formed by its revolution; and (b4) using the envelope as the tooth profile of the outer rotor (hereinafter the same definition of the “e,” “t,” and “n” as above is applied).