| 摘要 |
PROBLEM TO BE SOLVED: To provide a turbo-molecular pump capable of improving performance by further increasing a gas compression ratio. SOLUTION: This turbo-molecular pump is provided with an axial flow step part 20a provided with a moving vane 25 and a stator vane 23, and a thread groove step part 20b having spiral thread grooves in rotors. As the rotors, an outer rotor 36 of a roughly cylindrical form positioned on the outer circumferential side around a rotation axial line O, and an inner rotor 37 of a roughly cylindrical form positioned on the inner circumferential side of the outer rotor 36 are provided. The thread groove step part 30b is formed as a three-step part. The outer rotor 36 and the inner rotor 37 are composed as separate members from each other, and these are connected and fixed by bolts 35.
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