Patent ID: 7976297

Claim:
A gear pump for moving a fluid from a suction side toward a discharge side by rotation of helical gears meshing with each other, comprising: a casing including a body, a front cover, and a rear cover; the body accommodating the helical gears and first and second gear shafts, the front cover and the rear cover closing the body at front and rear sides thereof respectively, an inside surface of the front cover facing the forwardly oriented face of the body opposite to a shaft end side of each of the gear shafts, and an inside surface of the rear cover facing the rearwardly oriented face of the body opposite to a shaft end side of each of the gear shafts; the inside surface of the rear cover includes a first introduction path formed as a bottomed groove and a first return path formed as a bottomed groove, the first introduction path extends to a rear shaft end face of the first gear shaft to communicate with a discharge opening, and a pressure of fluid flowing into the first introduction path, as a pressure against the axial thrust of the first gear shaft, is applied with the rear shaft end face of the first gear shaft, and the first return path communicates with a suction opening and is continuous with the first introduction path; and the inside surface of the front cover includes a second introduction path formed as a bottomed groove and a second return path formed as a bottomed groove, the second introduction path extends to a front shaft end face of the second gear shaft to communicate with the discharge opening, and a pressure of fluid flowing into the second introduction path, as a pressure against the axial thrust of the second gear shaft, is applied with the front shaft end face of the second gear shaft, and the second return path communicates with the suction opening and is continuous with the second introduction path.