JP2651569B2 - Turbo molecular pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a turbo-molecular pump, and more particularly to a turbo-molecular pump in which a bearing of a spiral groove bearing is used for supporting a shaft below a rotor.

<< Conventional Technology >> In a bearing using a spiral groove bearing, a bearing ball provided on a rotating shaft floats from a bearing base via an oil film, so that extremely low vibration can be supported on a shaft. Proposals have been made in the past for use in supporting a shaft below a rotor in a centrifuge or the like.

According to this proposal, the shaft support at the lower portion of the rotor can be simultaneously performed in the radial direction and the axial direction by the bearings. It becomes possible to make contact.

<< Problems to be solved by the invention >> However, in this proposal, when air enters the pump in the turbo-molecular pump, a floating force is generated on the rotor by the rotating rotor blades. The provided bearing ball retreats and moves from the bearing pedestal, and the lubricating oil film between them disappears, so that it does not function as a bearing. As a result, there is a problem that the bearing is seized and the pump cannot be restarted.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a turbo molecular pump of this kind which can ensure safety reliability against intrusion of the atmosphere.

<< Means for Solving the Problems >> A spiral groove bearing composed of a shaft, a bearing ball at the tip of the shaft, and a bearing stand facing the bearing ball via lubricating oil is used for lower support of the rotor. In addition, in a turbo-molecular pump in which magnetic bearings such as permanent magnets and electromagnets are used to support the upper part of the rotor, the bearing balls are moved upward so that the lubricating oil film between the bearing balls and the bearing stand is kept constant. Preloading means such as a coil spring for urging the bearing base toward the upper part of the rotor so that the bearing base follows the movement, and a rotor stopper for blade protection retracted and disposed above the center of rotation of the rotor include: The configuration is provided.

A spring is most suitable as a biasing means for the bearing stand as compared with other means, and a magnet or the like can be used for the rotor stopper.

<< Operation >> In the present invention, even when the bearing ball moves toward the upper part of the rotor when the air enters the interior, the bearing base follows the bearing ball by the spring, so that the oil film thickness between them is kept constant. It is.

Further, collision between the rotor blades and the stator blades arranged alternately is prevented by a rotor stopper for blade protection.

<< Embodiment >> Hereinafter, a preferred embodiment of a turbo-molecular pump according to the present invention will be described with reference to the drawings.

In FIG. 1, a plurality of stator blades 12 are disposed in an axial direction on an inner wall surface of a stator 10 formed on a substantially cylinder, and a rotor 14 is disposed inside the stator blades 12.

A plurality of rotor blades 16 are alternately arranged on the outer wall surface of the rotor 14 with the stator blades 12 in the axial direction, and the rotor 14 is rotationally driven by a motor 18 disposed below the pump.

The upper portion of the rotor is supported only in the radial direction by a magnetic bearing 20 using a permanent magnet, and a bearing 21 retracted above the center of rotation of the rotor 14 is used as the rotor stopper.

The lower portion of the rotor is supported by a spiral groove bearing 22 in the axial and radial directions.

The hemispherical bearing ball 24 of this bearing 22 is provided at the tip of a shaft 26 that hangs down from the lower surface of the rotor 14, and is inserted into a receiving recess of a bearing base 30 arranged on a base 28 at the lowermost end of the pump. I have.

Further, a spring receiver having an inverted T-shaped cross section from the lower surface side of the base 28.
A coil spring 36 is press-fitted between the tip of the spring receiver 34 and the lower surface of the bearing stand 28.

Note that lubricating oil is previously injected into the bearing chamber 40 below the pump in which the bearing 22 is disposed.

The present embodiment is configured as described above. Therefore, when the atmosphere enters the inside of the pump, a floating force is generated on the rotor 14 by the rotating rotor blades 16, so that a bearing ball 24 provided on the shaft 26 below the rotor is provided. Moves upward from the bearing base 30.

The bearing base 30 is also moved by the spring 36 following the retreat of the bearing ball 24 upward, so that the film thickness of the lubricating oil therebetween is kept constant.

Therefore, the lubricating oil film between the bearing stand 30 and the bearing ball 24 is constantly kept constant, and the bearing 22 is not seized.

Further, since the floating movement of the rotor 14 is regulated by the stopper bearing 21, collision between the alternately arranged stator blades 12 and the rotor blades 16 is avoided, and their breakage is also prevented. At this time, the stopper bearing 21 receives the high-speed rotation of the rotor 14 and the upper shaft 27 at the center of rotation of the rotor 14.
Contacts the upper surface 27a of the center. Since this contact can be realized at the center of rotation of the rotor, wear of both parts is minimized.

As described above, according to the present embodiment, seizure of the bearing 22 due to entry into the atmosphere is prevented, and wear of the stopper bearing 21 and the central upper surface 27a of the shaft 27 is also prevented. In addition, it is possible to ensure the safety and reliability of the pump against the intrusion of the atmosphere.

<< Effects >> As described above, according to the present invention, the bearing pedestal detachment of the bearing sphere due to the intrusion of the atmosphere is prevented by the upward biasing of the bearing pedestal by the spring, and the stopper prevents the blade from colliding due to the floating of the rotor. Therefore, it is possible to ensure the safety and reliability of the pump against the intrusion of the inside of the atmosphere.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view showing a preferred embodiment of a turbo-molecular pump according to the present invention. 10 ... stator 12 ... stator blade 14 ... rotor 16 ... rotor blade 20 ... magnetic bearing 21 ... stopper bearing 22 ... spiral groove bearing bearing 24 ... bearing ball 26 ... shaft 30 ... bearing stand 36 ……coil spring

Claims (1)

(57) [Claims] A bearing of a spiral groove bearing composed of a shaft, a bearing ball at the tip of the shaft, and a bearing base opposed to the bearing ball via lubricating oil is used for lower support of the rotor. In a turbo-molecular pump in which a magnetic bearing such as a permanent magnet or an electromagnet is used for upper support of the bearing ball, the bearing ball follows the upward movement of the bearing ball so as to maintain a constant lubricating oil film between the bearing ball and the bearing stand. Preload means, such as a coil spring, for urging the bearing base toward the upper part of the rotor so that the bearing base moves, and a rotor stopper for retreating and disposed above the center of rotation of the rotor. A turbo molecular pump characterized by the above-mentioned.