JPH03258998A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To enhance the fatigue life as a rotating shaft by supporting the upper and lower end parts of the rotating shaft by two touch-down bearings, and situating the lower touch-down bearing near a spherical spiral channel bearing. CONSTITUTION:The upper and lower end parts of a rotating shaft 10 the lower end part of which is pivotally supported by a spherical spiral channel bearing 7 are supported by two touch-down bearings 18, 21. The lower touch-down bearing 21 is situated near the spherical spiral channel bearing 7. At the time of introduction of the air or generation of disturbance, the rotating shaft 10 is normally rotated by the upper and lower touchdown bearings 18, 21. As the bending load acting on the rotating shaft can be suppressed, thus, the fatigue life as the rotating shaft can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a turbomolecular pump suitable for use in semiconductor manufacturing processes.

[Conventional technology]

For example, semiconductor manufacturing equipment and the like require a vacuum chamber whose interior is in a high vacuum state.

To create this type of high vacuum state, a turbo-molecular pump, which has poor pumping performance in the molecular region, is generally employed.

Conventionally, this type of turbomolecular pump has been developed, for example, in Japanese Patent Application Laid-open No.
It is disclosed in Japanese Patent No. 135694 and is configured as shown in FIG. To explain this based on the same figure, in the same figure, what is indicated by reference numeral 1 is an inlet port 2 and an outlet port 3.
The entire pump casing has a cylindrical shape, with stator vanes 4 and spacers 5 on the inner circumferential wall.
They are provided in multiple stages in the axial direction via. Further, flanges la and lb for fixing a vacuum chamber (not shown) and a support body 6 are provided at each of the upper and lower ends of the pump casing 1.
are integrated. Reference numeral 7 denotes a spherical spiral groove bearing that pivotally supports the lower end of the rotating shaft, which will be described later, and is filled with a spherical part 7a in which a spiral groove is formed, a saucer 7b having a spherical recess for receiving the spherical part 7a, and these members. The lubricating oil 7C is used as a lubricant, and is provided in the center of the support 6 via a retainer 8. Reference numeral 9 denotes a frame body having a mounting flange 9a at its lower end, which is provided around the spherical spiral groove bearing 7 and fixed onto the support body 6. Reference numeral 10 denotes a rotating shaft, a part of which faces inside the frame 9, which is rotatably provided inside the pump casing 1, and whose lower end is supported by the spherical spiral groove bearing 7. II is the drive mechanism for pump operation,
It consists of a motor rotor 12 fixed to the rotating shaft 9, and a motor stator 13 provided around the motor rotor 12 and fixed to the inner peripheral surface of the frame 9, and is housed in the pump casing 1. . Reference numeral 14 denotes a rotary body having a dynamic R15 facing a part of the stationary blade 4, which is provided on the same axis as the drive mechanism 11, and is provided with a bolt 16.
is fixed on the rotating shaft 10 by. Also, 1
7 is a discharge pipe fixed to the support body 6 and communicates with the discharge port 3; 18 is a touchdown bearing fixed to the frame body 9 and equipped with a mechanical protection function to prevent the rotating body 14 from falling due to external disturbances, etc. , 19 is a rotor of the rotating body 14.

In a turbomolecular pump with such a structure,
Vertical turbomolecular pumps have been gaining importance in recent years due to their structural and functional aspects. Accordingly, as a bearing for increasing speeds, the spherical spiral groove bearing 7, which has a much lower profile than a ball bearing as described above, has been adopted.

By the way, in this type of turbo molecular pump, the rotating body 14 is sufficiently balanced before operation.
Therefore, the rotating body 14 is stable during normal rotation at a constant rotation speed.

[Problem to be solved by the invention]

However, in the conventional turbo molecular pump, since the lower end of the rotating shaft 10 is directly supported by the spherical spiral groove bearing 7, oscillation occurs in the rotating shaft 10 when atmospheric air is introduced or a disturbance occurs. was. As a result,
There was a problem in that an excessive bending load was applied to the rotating shaft 10, and the fatigue life of the rotating shaft was reduced.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a turbo-molecular pump that can suppress the bending load acting on the rotating shaft, thereby increasing the fatigue life of the rotating shaft. .

[Means to solve the problem]

In the turbo molecular pump according to the present invention, the upper and lower ends of a rotating shaft whose lower end is supported by a spherical spiral groove bearing are supported by two touchdown bearings, and the lower touchdown bearing is supported by a spherical spiral groove bearing. It is located nearby.

[For production]

In the present invention, the rotating shaft can be rotated normally by the two upper and lower touchdown bearings when atmospheric air is introduced or when a disturbance occurs.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the structure etc. of this invention will be explained in detail by the Example shown in the figure.

FIG. 1 is a longitudinal cross-sectional view showing a turbomolecular pump according to the present invention. In this figure, the same members as in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. In the figure, the reference numeral 21 denotes a touchdown bearing that supports the lower end of the rotary shaft 10, and is provided within the retainer 8. This touchdown bearing 21 has a lubricating oil 7c that lubricates the spherical spiral groove bearing 7 in the vicinity of the spherical spiral groove bearing 7, that is, when the atmosphere is introduced or when a disturbance occurs.
It is located in the area where the particles are scattered. Reference numeral 22 denotes a rotating body having the rotor blades 15, which is provided on the same axis as the drive mechanism 11, and which is connected to the rotary shaft 10 by Holt 23.
is fixed to the upper end surface of. At the lower central portion of the rotating body 22, convex portions 22a and 22b are provided that protrude in the vertical direction of the axis. 24 is a balancing boss having a recess 24a that fits into the projection 22aL and a flange 24b extending around the projection 22a;
3 to the rotating body 22. In addition, 2
5 is provided on the tip end surface of the rotating shaft 10, and the convex portion 22b
It is a recess that fits into the.

In the turbo-molecular pump configured in this way, the rotating shaft 10 can be rotated normally by the two upper and lower touchdown bearings 18, 21 when atmospheric air is introduced or a disturbance occurs. Bending load can be suppressed. At this time, since the lubricating oil 7C that lubricates the spherical spiral groove bearing 7 is splashed onto the touchdown bearing 21, the touchdown bearing 21 can be lubricated by this lubricating oil 7c.

〔Effect of the invention〕

As explained above, according to the present invention, the upper and lower ends of the rotating shaft, the lower end of which is supported by the spherical spiral groove bearing, are
The lower touchdown bearing is positioned near the spherical spiral groove bearing, so that when atmospheric air is introduced or a disturbance occurs, the rotating shaft can be rotated normally by the upper and lower touchdown bearings. be able to. Therefore, since the bending load acting on the rotating shaft can be suppressed, the fatigue life of the rotating shaft can be increased.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a turbo-molecular pump according to the present invention, and FIG. 2 is a vertical cross-sectional view showing a conventional turbo-molecular pump. ■...Pump casing, 4...Stator blade, 7...
...Spherical spiral groove bearing, 7c lubricating oil, 10...
Rotating shaft, 15... Moving blade, 18. 21... Touchdown bearing, 22... Rotating body.

Claims (1)

[Claims] A casing having stator blades provided in multiple stages in the axial direction, a rotating shaft rotatably provided within the casing and having its lower end supported by a spherical spiral groove bearing, and a rotating shaft fixed on the rotating shaft. In a turbo-molecular pump comprising a rotating body having moving blades facing a part of the stator blade, the upper and lower ends of the rotating shaft are supported by two touchdown bearings, and the lower touchdown bearing is supported by the lower touchdown bearing. A turbo molecular pump characterized by being located near a spherical spiral groove bearing.