Patent ID: 6779969
Filing Date: 2004-08-24
Classification: F04D

Abstract:
A vacuum pump comprising:a rotor shaft rotatably supported in a pump case having a gas suction port opened in the upper surface and a gas exhaust port opened in the lower side; a drive motor for rotating the rotor shaft; a rotor fixed to the rotor shaft and formed of a multiple cylinder having a plurality of cylinders with different diameters arranged concentrically with respect to the rotor shaft center; and a thread-groove pump mechanism portion including the plurality of cylinders of the rotor, a stator formed of a multiple cylinder having a plurality of cylinders alternately located between the cylinders and fixed in the pump case, and a thread groove cut in a wall of the stator facing the cylindrical surfaces of the rotor; wherein gaps defined by the outer walls of the cylinders of the rotor and the stator walls and a gap defined by the inner walls of the cylinders of the rotor and the stator walls are formed so as to increase with the distance from the rotor shaft center, and the gaps defined by the outer walls of the cylinders of the rotor and the stator walls are formed larger than gaps defined by the inner walls of the cylinders of the rotor and the stator walls.