| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the thrust load applied to the rotary shaft of a composite vacuum pump by arranging a thread groove pump element and a swirl pump element at both end sections of the rotary shaft, and forming a gas passage so that the pressure differences with the atmospheric pressure applied to rotors are made reverse. SOLUTION: When a rotary shaft 2 is rotated by a motor 6 in a composite vacuum pump, the gas sucked from an intake port 11 is boosted when passing through a gas passage 7a by the pumping action of thread grooves T1-T3 of a thread groove pump element A, is sucked to a swirl pump element B through an exhaust port 12 and a connecting pipe, and is discharged to the atmosphere from an exhaust port 18. An upward thrust load is applied via a rotor 3 during this operation, the gas is passed through an air passage 7b below the rotary shaft 2 by the pump element B, the pressure on the lower face side of the rotary shaft 2 is reduced, a downward thrust load is applied to the rotary shaft 2, and the thrust load is reduced as a whole.</p> |
