Abstract: A gear pump rotor is provided including a combination of an inner rotor and an outer rotor whose numbers of teeth are different by one, and the discharge amount of the pump is increased by an increase of the tooth depth. At least one of an addendum curve and a dedendum curve of an inner rotor is formed by a locus of one point on formation circles that satisfy moving conditions that the formation circles move from moving start points to moving end points while changing the distances from an inner rotor center to the centers of the formation circles. The centers of the formation circles move by a distance in the radial direction of a base circle, and the formation circles rotate by an angle at a constant angular velocity in the same directions of the moving directions of the formation circles.

Abstract: Flexibility is given in setting the tooth depth and the number of teeth of a pump rotor including a combination of an inner rotor and an outer rotor whose numbers of teeth are different by one, and the discharge amount of the pump is increased by the increase of the tooth depth. At least one of an addendum curve and a dedendum curve of an inner rotor (2) is formed by a locus of one point (j) on formation circles (B, C) that satisfy moving conditions that the formation circles (B, C) move from moving start points (Spa, Spb) to moving end points (Lpa, Lpb) while changing the distances from an inner rotor center (OI) to the centers of the formation circles, the centers of the formation circles move by a distance (R) in the radial direction of a base circle (A) during this, and the formation circles (B, C) rotate by an angle ? at a constant angular velocity in the same directions of the moving directions of the formation circles.