TURBO-MOLECULAR PUMP

PROBLEM TO BE SOLVED: To attenuate and absorb the rotating energy when a rotator is broken during high-speed rotation to prevent the secondary breakage by fixing, to the circumference of a support cylinder for supporting the rotor of a turbo- molecular pump, an annular stopper ring opposed to the lower inner side of a screw groove pump stage through a minute clearance. SOLUTION: When this turbo-molecular pump is operated, a current is carried to each of magnetic bearings 9-11 to lay a rotating shaft 7 and a rotor 6 into the floated state, and a motor 12 is driven to rotate the rotor 6 at high speed. At this time, a first stage compression is performed between a rotor blade 5 and a stationary blade 4 through a gas intake port 2, and a second stage compression is performed in a screw groove pump stage 8 to exhaust air through an exhaust port 3. Even if the rotor 6 is broken due to excessive vibration or internal abnormality occurrence at this time, the scattering of broken pieces of the rotor 6 can be suppressed since the center part of the rotor 6 is firmly fixed to the rotating shaft 7 by an upper stopper 31, and the lower end of the screw groom pump stage 8 is collided to a stopper ring 33 to absorb the kinetic energy of the rotor 6.