JPH0431692A - Bearing device for vacuum pump - Google Patents

Abstract

PURPOSE:To lengthen the life of each bearing by movably supporting load in the radial direction by herringbone dynamic pressure type pneumatic bearings, movably supporting load in the thrust direction by a spiral group dynamic pressure type pneumatic bearing, and thereby preventing gas from coming in the inside of a rotor by means of a screw groove seal. CONSTITUTION:A turbo molecular vacuum pump is equipped with a turbo molecular pump 2 composed of rotor blades 2a and of stator blades 2b, and with a screw groove pump 3 wherein a rotating body 4 composed of the rotor blades 2a and of the screw groove pump 3 is fixedly coupled in a rotating shaft 4a. In this case, herringbone dynamic pressure type pneumatic bearings 6 are to be coupled in the rotating shaft 4a, the bearing is formed with a plurality of grooves 6a... in 2 steps while being faced to the first rotor 5a projected to the inner circumference of a housing 1 with a micro gap (t) spaced. In addition, the rotating shaft is equipped with a spiral group dynamic pressure type pneumatic bearing 7 wherein discs are provided while being arranged up and down, in this case, the upper and lower surfaces of each disc is furnished with a plurality of spiral grooves 7a..., and the discs are fixedly coupled in the rotating shaft 4a while the right surfaces of the discs are faced to the first and the second stator 5a and 5b with a micro gap (t) spaced.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) The present invention relates to bearing devices for turbomolecular vacuum pumps and other vacuum pumps used in the manufacture of ICs, semiconductors, and the like.

(2) Prior Art Conventional turbo molecular vacuum pumps have been known in which magnetic bearings (a) and other types of bearings are arranged side by side to support the rotating shaft of a rotating body rotating at high speed. For example, the 10th
A pivot type groove bearing (b) is provided below as shown in the figure, a ball bearing (c) as shown in the 11th figure is provided, or a 12th
As shown in the figure, there is one in which a thrust dynamic pressure type groove bearing (d) is arranged on one side of the thrust surface and a herringbone gas bearing (e) is arranged on the radial surface.

(3) Problems to be Solved by the Invention However, in the case where the pivot type grooved bearing (b) is attached as described above, the lubricating oil of the pivot type grooved bearing is not necessary for application to a turbo molecular pump. Therefore, it cannot be used horizontally or upside down, and it cannot be used as an oil-free turbo molecular pump. Also, those equipped with a ball bearing (C) have poor durability due to mechanical wear and tear of the ball bearing (C). It is inferior and requires oiling. Furthermore, those that have a thrust hydrodynamic groove bearing (d) and a herringbone gas bearing (e) have a complex bearing structure and lack rigidity against shaft tilt, making it difficult to maintain stable high-speed rotation. Met.

The present invention solves the above-mentioned problems and eliminates the need for oiling by making the bearing part non-contact in the vertical and circumferential directions during rotational operation, and sealing the inside of the housing and the bearing part to reduce atmospheric emissions. The purpose of the present invention is to provide a bearing device for a vacuum pump that can be used as a mold, has improved stability and durability, and is maintenance-free.

(4) Means for Solving the Problems In order to achieve the above object, the present invention provides a vacuum pump in which a rotating body rotates at high speed within a housing, in which a stator is provided protruding from the inner periphery of the housing. a herringbone hydrodynamic gas bearing on the rotating shaft of the rotating body facing the stator;
and a spiral group hydrodynamic gas bearing having spiral groups formed on the upper and lower surfaces to constitute a non-contact type bearing, and a thread groove seal for preventing gas from entering the housing from the bearing is attached to the rotating shaft. It is characterized by the fact that it is provided in

・(5) Operation When a high-speed rotating device is started, dynamic pressure is generated in the radial and thrust directions by the herringbone hydrodynamic gas bearing and the spiral group hydrodynamic gas bearing on the upper and lower surfaces, and the rotating body It is in a non-contact state with the stator protruding from the inner periphery of the housing, and the thread groove seal isolates the atmosphere from the inside of the housing, allowing it to rotate at high speed.

(6) Example Hereinafter, a first example in which the present invention is applied to a turbo molecular vacuum pump will be described with reference to FIGS. 1 to 3.

(1) is the housing, (2) is the movement! (2a) and Shizuka
! ! (2b) is a turbo-molecular pump, (3) is a thread groove pump, and (4) is a rotating body consisting of the rotor blade (2a) and the thread groove pump, and is fitted and fixed to the rotating shaft (4a). (5a) is a cylindrical first stator protruding from the inner periphery of the housing (1), (5b) is a disc-shaped second stator with a through hole in the center, and (6) is a rotary shaft (4a). ), the herringbone hydrodynamic gas bearing (6) is fitted with a large number of grooves (6a) formed in a V-shape with respect to the rotational direction, for example, as shown in the second figure. )...(6a), and the first stator (5
a) and are provided in two stages facing each other with an extremely small gap (1).

(7) indicates a spiral group dynamic pressure type gas bearing, and the spiral group dynamic pressure type gas bearing (7) has, for example, a large number of spiral grooves (7a) on the upper surface as shown in the third figure.
...(7a) and a disk having a large number of similar spiral grooves (7a)...(7a) formed on the lower surface are arranged vertically in parallel, and the upper surface is formed with the first groove. ．． Stator (5
In a), the lower surface faces the second stator (5b) with a very small gap (1) (1), and is fitted and fixed to the rotating shaft (4a).

(8) is a threaded seal fitted and fixed to the rotating shaft (4a), (9) is a motor, (10) is a fixing nut, (1
1) is an inlet, (12) is an outlet, and (13) is an air supply port.

Next, the operation of the vacuum pump of the above embodiment will be explained.

When the motor (9) is energized, rotational force is generated in the rotating body (4) and it starts rotating. This rotation causes the grooves (6a)...(6a) of the herringbone hydrodynamic gas bearing (6) and the grooves (7a)...(6a) of the spiral group hydrodynamic gas bearing (7).
Atmospheric air flows into 7a) from the air supply port (13) to generate dynamic pressure, and it rotates with bearing performance in the radial and thrust directions. At this time, the spiral group hydrodynamic gas bearing (7) has spiral group grooves (7a) on the upper and lower surfaces.
...(7a), so the vertical thrust forces are balanced. In this way, the one-rotator (4) is in steady rotation. And moving blade (2a) and static j! (2b) and the thread groove pump (3), the exhaust body is sucked in through the suction port (11) and discharged through the discharge port (12).

FIG. 4 shows a second embodiment, in which the two-stage Hering-Pone hydrodynamic gas bearing (6) of the pump of the first embodiment is formed into one stage, and FIG. 5 shows a third embodiment, in which the second
This is a case where the arrangement of the upper Hering Pone hydrodynamic gas bearing (6) and the lower spiral group hydrodynamic gas bearing (7) of the pump of the embodiment are reversed, and FIG. 6 shows the fourth embodiment. In the fourth embodiment, the motor (9) is interposed between the upper spiral group hydrodynamic gas bearing (7) and the lower Hering Pone hydrodynamic gas bearing (6). FIG. 7 shows a fifth embodiment, in which a spiral group hydrodynamic gas bearing (7) is interposed between the upper and lower Hering-Pone hydrodynamic gas bearings (6) (6). FIG. 8 shows a sixth embodiment, in which an upper spiral group dynamic pressure type gas bearing is installed between the upper and lower Hering-Pone hydrodynamic type gas bearings (6) (6). Gas bearing (7) and lower motor (
FIG. 9 shows a seventh embodiment, in which a spiral group hydrodynamic gas bearing (7) is provided above the pump of the sixth embodiment.
) and the lower motor (9) are arranged oppositely, and the operation in any of these second to seventh embodiments is the same as in the first embodiment.

(7) Effects of the Invention As described above, according to the present invention, the load is supported in the radial direction by a herringbone hydrodynamic gas bearing, and the load in the thrust direction is supported by the spiral group hydrodynamic gas bearing with spiral groups formed on the upper and lower surfaces. The rotor is supported in a balanced manner, and the thread groove seal prevents gas from entering the rotating body, allowing the rotating body to rotate stably and at high speed, and while rotating, the exhaust gas is isolated from the atmosphere. A completely oil-free state with no need for a back pump is achieved, and the bearing surfaces are not in contact with each other, suppressing heat generation in the bearing portion, extending the life of the bearing, and being maintenance-free.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of the first embodiment of the present invention, Fig. 2 is an explanatory diagram of the shape of the main part of a Herringpohn hydrodynamic gas bearing, and Fig. 3 is a shape of the main part of a spiral group hydrodynamic gas bearing. An explanatory diagram, FIG. 4 is an explanatory diagram of the main part of the second embodiment, and FIG. 5 is an explanatory diagram of the main part of the second embodiment.
FIG. 6 is an explanatory diagram of the essential parts of the fourth embodiment, FIG. 7 is an explanatory diagram of the essential parts of the fifth embodiment, and FIG. 8 is an explanatory diagram of the essential parts of the sixth embodiment. FIG. 9 is an explanatory diagram of the main part of the seventh embodiment, and FIGS. 1θ to 12 are longitudinal sectional views of each side of the conventional device. (6)... Herringbone hydrodynamic gas bearing (7)...
・Spiral group dynamic pressure type gas bearing (8)...Thread groove seal

Claims (1)

[Claims] In a vacuum pump in which a rotary body rotates at high speed within a housing, a stator is provided protruding from the inner periphery of the housing, a herringbone hydrodynamic gas bearing is mounted on the rotating shaft of the rotary body facing the stator, and a herringbone hydrodynamic gas bearing is mounted on the upper and lower surfaces of the rotor. A spiral group hydrodynamic gas bearing is formed to form a spiral group to constitute a non-contact type bearing, and a thread groove seal is provided on the rotating shaft to prevent gas from entering from the bearing into the housing. A vacuum pump bearing device featuring: