| 摘要 |
PROBLEM TO BE SOLVED: To prevent any breakage of a tightening bolt to connect a pump to a chamber even when an abnormality of the pump occurs and the breaking torque is generated. SOLUTION: In a vacuum pump comprising a pump case 1 having an intake port 2 on an upper part and an exhaust port 3 on one side of a lower part, a rotor 9 which is rotatably supported by a stator column 5 erected in the case 1 via a rotor shaft 7, and has multi-stage rotor blades on the outer circumference, multi-stage stator blades 11 alternately fixed to the rotor blades on the inner circumferential part of the case 1, and a drive motor 8 provided between the rotor shaft 7 and the stator column 5, with a flange 1a provided on an upper circumferential edge of the case 1 connected to a circumferential edge of a lower opening of a vacuum chamber 14 via a plurality of bolts 15, bolt passing holes 20 opened in the flange 1a have a plurality of stages 20a, 20b and 20c which are expanded toward a fitting surface side of the chamber 14. |
