Patent ID: 7722342
Filing Date: 2010-05-25
Classification: F04C

Abstract:
1. A pump apparatus comprising: a housing; a first gear rotatably housed inside the housing; a second gear rotatably housed inside the housing and engaged with the first gear; a drive shaft for driving and rotating at least one of the first gear and the second gear; a suction port formed in the housing and opened in an area where hydraulic oil is sucked by rotation of the first gear and the second gear; and a discharge port formed in the housing and opened in an area where the hydraulic oil is discharged by the rotation of the first gear and the second gear, wherein the first gear is an internal gear having internal teeth on an inner periphery side, the second gear is an external gear provided on the inner periphery side of the internal gear in a rotatable state and having external teeth on an outer periphery side, the external teeth being enraged with the internal teeth, the drive shaft is provided on the external gear to drive and rotate the external gear, at least one of the internal gear and the external gear has a running-in coating in a portion where a tooth of the internal gear and a tooth of the external gear contact with each other in a sliding state, at least in a confinement area in which the hydraulic oil is confined between the internal gear and the external gear, the confinement area being a chamber having the largest capacity among a plurality of pump chambers formed between the internal gear and the external gear, and a biasing means for moving at least one of the internal gear and the external gear, wherein at least one of the internal gear and the external gear is moved in a direction in which a contact force between tooth tips of the internal gear and the external gear is enhanced is provided in the portion where the tooth of the internal gear and the tooth of the external gear contact with each other in a sliding state in the confinement area.