| 摘要 |
PROBLEM TO BE SOLVED: To reduce a slip component of an external tooth and improve mechanical efficiency of an oil pump, by forming the external tooth of an inner rotor in a specific value range satisfying a relation between an addendum circle diameter of the external tooth and an eccentric amount of an inner/outer rotor. SOLUTION: In a casing 30, an inner rotor 10 having (n) teeth of external teeth and an outer rotor 20 having n+1 teeth of internal teeth, meshed with this inner rotor, are provided. An axial center O1 of the rotor 10 and an axial center O2 of the rotor 20 are eccentrically positioned (e mm). In an external tooth 11 of the rotor 10, when a diameter of an addendum circle P connecting an addendum of each external tooth 11 is assumed as Dmm, in a range satisfying 0.135<=e.n/(π.D)<=0.145, a trochoid curve is generated, a generate circle group positioning the center on the trochoid curve draws an envelope, the external tooth 11 is formed along the envelope, a meshing angle of the external tooth 11 with the internal tooth 21 is set to a suitable range. Consequently, forming of an addendum edge of the external tooth 11 is suppressed, durability is ensured, a rotational component of small slip component can be ensured.
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