JPS63117199A - Turbo molecular pump - Google Patents

Abstract

PURPOSE:To prevent the intrusion of the atmosphere to the inside by installing a prepressurizing structure for urging a bearing board on the stator side of a spiral groove bearing towards the upper part of a rotor and installing a rotor stopper for protecting vanes which is retreat-arranged on the upper side of the rotor. CONSTITUTION:When the atmosphere intrudes into the inside of a pump, a rotor 14 is provided with a floating power by a rotor vane 16, and the bearing ball 24 of a shaft 26 retreat-shifts upwardly from a bearing board 30. Since also the bearing board 30 is shifted by a spring 36, the film thickness of lubricating oil is kept constant. Further, the floating shift of the rotor 14 is regulated by a stopper bearing 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a turbo-molecular pump, and particularly to a turbo-molecular pump in which a spiral groove bearing is used to support a shaft at a lower portion of a rotor.

(Prior art) In a bearing using a spiral groove bearing, the bearing ball provided on the rotating shaft floats up from the bearing stand via an oil film, making it possible to support the shaft with extremely low movement. Conventionally, proposals have been made for use in supporting the shaft of the lower part of the rotor in centrifugal separators and the like.

According to this proposal, the shaft of the lower part of the rotor can be supported simultaneously in the radial and axial directions by its bearings, and therefore the rotor's bearing structure can be simplified by using magnetic bearings only for the radial support of the upper part of the rotor. It becomes possible to make contact.

(Problem to be Solved by the Invention) However, in this proposal, when air enters the pump in a turbo-molecular pump, floating blades are created on the rotor by the rotating rotor blades, which causes the shaft at the bottom of the rotor to The problem was that the installed bearing balls moved away from their bearing pedestals, causing the lubricating oil film between them to disappear and no longer functioning as a bearing, resulting in the bearings seizing up and making it impossible to restart the pump. The present invention has been made in view of the above-mentioned conventional problems,
The aim is to provide a turbomolecular pump of this type that can ensure safety and reliability against atmospheric intrusion.

(Means for Solving the Problems) In order to achieve the above object, the present invention uses a spiral groove bearing to support the shaft in the lower part of the rotor, and a magnetic bearing such as a permanent magnet or an electromagnet to support the shaft in the upper part of the rotor. The rotor is characterized in that it is provided with a preload structure such as a spring that biases the rotor in the opposite direction, and a rotor stopper for protecting the blades that is retracted above the rotor.

It should be noted that a spring is most suitable as a biasing means for the bearing stand, and a magnet or the like can also be used for the rotor stopper.

(Function) In the present invention, even if the bearing ball moves toward the top of the rotor when the atmosphere enters the interior, the bearing base moves to follow the bearing ball due to the spring, so that the oil film thickness between them is kept constant. It will be done.

Further, collisions between the alternately arranged rotor blades and stator blades are prevented by rotor stoppers for blade protection.

(Embodiments) Hereinafter, preferred embodiments of the turbomolecular pump according to the present invention will be described based on the drawings.

In FIG. 1, a plurality of stator caps 12 are arranged in the axial direction on the inner wall surface of a stator 10 formed into a substantially cylindrical shape, and a rotor 14 is arranged inside them.

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

The upper part of the rotor is supported only in the radial direction by a magnetic bearing 20 using a permanent magnet, and the bearing 21 is used as the rotor stopper described above.

Further, the lower part of the rotor is supported in the axial and radial directions by a spiral groove bearing 22.

A hemispherical bearing ball 24 of this bearing 22 is provided at the tip of a shaft 26 hanging from the lower surface of the rotor 14, and a bearing stand 3 is placed on a base 28 at the lowest end of the pump.
The 0 receiver is inserted into the recess.

A spring receiver 34 having an inverted T-shaped cross section is fitted and fixed from the lower surface of the base 28, and 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 at the bottom of the pump where the bearing 22 is disposed.

The present embodiment has the above-described configuration. Therefore, when the atmosphere enters the inside of the pump, floating blades are generated on the rotor 14 by the rotating rotor blades 16, which causes the bearing ball 24 provided on the shaft 26 at the lower part of the rotor to is retracted upward from the bearing stand 30.

Following the upward retraction of the bearing ball 24, the bearing stand 30
Since both are moved by the spring 36, the film thickness of the lubricating oil between them is kept constant.

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

Also, the floating movement of the rotor 14 is prevented by the stopper bearing 21.
Since the stator blades 12 arranged alternately are regulated by
As described above, according to this embodiment, seizure of the bearing 22 due to entry into the atmosphere is prevented, and damage to the blades at that time is also prevented. Therefore, it is possible to ensure the safety and reliability of the pump against atmospheric intrusion.

(Effects) As explained above, according to the present invention, the upward biasing of the bearing base by the spring prevents the bearing ball from detaching from the bearing base due to the intrusion of the atmosphere, and the stopper prevents the blade from colliding with the rotor due to levitation. Therefore, it is possible to ensure the safety and reliability of the pump against atmospheric intrusion.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing a preferred embodiment of a turbomolecular 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 or more

Claims (1)

[Claims] (1) In a turbo molecular pump in which a spiral groove bearing is used to support the shaft in the lower part of the rotor, and a magnetic bearing such as a permanent magnet or electromagnet is used to support the shaft in the upper part of the rotor, the stator side bearing stand of the spiral groove bearing is used to support the shaft in the upper part of the rotor. A turbo molecular pump characterized by being provided with a preload structure such as a spring that biases the rotor upward, and a rotor stopper for protecting blades that is retracted above the rotor.