JP2564543Y2 - Turbo molecular pump - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo-molecular pump, and more particularly to a turbo-molecular pump having an improved bearing mechanism for supporting a rotor.

[0002]

2. Description of the Related Art Conventionally, turbo molecular pumps have been used as vacuum devices for electron microscopes, analytical instruments, and the like.

[0003] In this turbo-molecular pump, a plurality of stator blades are arranged on the inner wall surface of a substantially cylindrical casing in the axial direction of the cylinder, and are arranged on the outer wall surface of a rotor arranged in the casing. A plurality of rotor blades are arranged alternately with the stator blades, and the rotor is constituted by a motor mechanism acting as a rotor of the motor.

Then, the rotor rotates at high speed by this motor mechanism, and induces a molecular flow between the stator blades and the rotor blades, thereby discharging the gas on the intake side to the exhaust side, and raising the gas on the intake side. A vacuum is formed.

[0005] Since the rotor rotates at a so-called ultra-high speed, a magnetic bearing is generally used recently.

That is, the rotor is levitated and held by a magnetic bearing mechanism, and the rotor is rotated at a high speed without contact with the stator column in the casing. A radial and axial electromagnet for maintaining the direction is provided, and a position sensor for detecting the position in both directions is provided, and a detection signal of the position sensor is fed back to control the exciting current of the electromagnet so that the rotor is at a target floating position. This is a general configuration.

[0007] Further, when any abnormality occurs in the magnetic bearing, for example, when the rotor can no longer be controlled by the magnetic bearing due to a power failure (usually called touchdown), a gap is provided between the magnetic bearing and the stator column that supports the rotor for rotation. Protective bearings using ball bearings are usually installed to smoothly support the rotor at the time of touchdown and to ensure high reliability of the turbo-molecular pump.

[0008]

As described above, the conventional magnetic bearing type turbo-molecular pump has a structure in which the rotor is supported via the protective bearing at the time of touchdown. Therefore, solid lubrication is used. Therefore, when a load is applied to the protective bearing due to touchdown or the like, the inner ring, the outer ring, and the ball of the protective bearing are severely abraded, and the inner and outer rings of the bearing are backlashed. Becomes

In the case where the insertion groove of the full ball type protection bearing with the insertion groove is aligned with the direction of gravity, if the protection bearing is worn by touchdown, the ball is likely to come off. If the ball falls off, the ball gets caught between the inner and outer rings of the protective bearing.
It has been pointed out that the bearing stops suddenly, does not function as a protective bearing, and causes problems such as seizure of the rotor.

Further, since there is a problem in the durability of the protective bearing, the mounting position of the turbo-molecular pump is restricted in anticipation of the ball falling off. If used in a state, there is a possibility that a big trouble may be caused, and the fact is that the mounting posture of the turbo molecular pump is greatly restricted.

The present invention has been made in view of such circumstances, and an object of the present invention is to improve the durability of a protective bearing used in a magnetic bearing type turbo-molecular pump to improve the touch. An object of the present invention is to provide a turbo-molecular pump that ensures protection of a rotor at the time of downtime, ensures high reliability of the turbo-molecular pump, and enables free mounting even in the mounting posture of the turbo-molecular pump.

[0012]

In order to achieve the above object, the present invention provides a stator blade mounted on an inner wall surface of a casing and a rotatable bearing via a magnetic bearing on a stator column inside the casing. And rotor blades attached to the outer wall surface of the rotor to be alternately arranged in the axial direction of the rotor, and a turbo molecular pump that rotates the rotor and takes in air from one direction of the rotor shaft and exhausts the other direction. It is installed between the rotor and the stator column, and is a full-ball type protective bearing with a groove, and faces the groove of the protective bearing, and regulates the ball from falling off the protective bearing. And a projection.

[0013]

As is evident from the above configuration, the protection groove using the full ball type ball bearing with a groove has a projection for restricting the ball from falling off. Even if the bearing is worn many times and the wear of the bearing progresses, the protrusion can reliably prevent the ball from falling off, so that the function of the protective bearing does not decrease.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a turbo-molecular pump according to the present invention will be described below in detail with reference to the drawings.

Referring to FIG. 1, a turbo molecular pump 1 according to the present invention has a plurality of stator blades 3 disposed on an inner wall surface of a substantially cylindrical casing 2 along an axial direction thereof. A rotor 5 is rotatably supported via a magnetic bearing on a stator column 4 installed inside the rotor, and rotor blades 6 are arranged on the rotor 5 so as to be located on the outer periphery of the stator column 4. The stator blades 3 and the rotor blades 6 are arranged alternately along the axial direction of the casing 2.

Further, the rotor 5 is driven by the high frequency motor 7.
Is rotationally driven. As a bearing structure accompanying the rotational drive of the rotor 5, the radial position adjustment of the rotor 5 is performed by exciting the radial electromagnets 9 by the radial direction sensor 8,
In addition, the axial direction sensor 10 excites the rotor 5 in the axial direction by exciting the axial electromagnet 11.

Further, during an emergency (touch down) of the magnetic bearing mechanism such as a power failure, the rotor 5 and the stator column 4
Between them, the protective bearings 12 and 13 formed of ball bearings function so that the rotor 5 is smoothly supported for rotation.

The feature of the present invention is that the reliability of the turbo-molecular pump 1 is enhanced by increasing the durability of the protective bearing 12 installed on the upper part of the rotor 5.

That is, as shown in FIG. 2, the protective bearing 12 includes an outer ring 14 attached to the stator column 4 side, an inner ring 15 contacting the rotor 5 for rotationally supporting the rotor 5 at the time of touchdown, and an outer ring 14. It is composed of a plurality of balls 16 between the inner ring 15 and a ball bearing with a groove provided with a groove 17 for inserting the ball 16 between the outer ring 14 and the inner ring 15. . Normally, since the rotor 5 is magnetically levitated, the rotor 5 and the inner ring 15 are not in contact with each other.
5 make contact.

A support member 20 for supporting the protective bearing 12 is screwed to the upper end of the stator column 4. A protrusion 21 provided at the tip of the support member 20 is provided.
Are set so as to face the inside groove 17 of the protective bearing 12.

Therefore, when the magnetic bearing of the rotor 5 cannot be controlled by the magnetic bearing mechanism at the time of touchdown of the turbo molecular pump 1, a high load is applied to the protective bearing 12, and the outer ring 14, the inner ring 15 and the ball 16 are worn. Also, since the projection 21 for restricting the ball 16 from falling off faces in the receiving groove 17, the ball 16 can be reliably prevented from falling off.

Accordingly, the present invention effectively solves the conventional problem that, when the touchdown occurs many times, the function of the protective bearing is impaired due to the ball falling off and the reliability of the turbo-molecular pump is reduced. be able to.

As described above, according to the present invention, the projections 21 for restricting the balls 16 from falling off are provided on the protective bearings 12 so that the high reliability of the turbo molecular pump 1 is ensured and the conventional turbo molecular pumps It is also possible to solve the problem that the mounting position is restricted, and it is possible to mount the device in any position, so that the degree of freedom in setting the turbo-molecular pump 1 can be greatly increased.

FIGS. 3 and 4 show a modified embodiment of the present invention. As shown in FIG.
The upper end of the stator column 4 corresponding to the groove 17 is extended upward, and a ball drop prevention piece 22 is screwed and fixed to the extension 4a. A projection 23 provided at the tip of the ball drop prevention piece 22 is provided. Into the groove 17
The falling off of the ball 16 may be restricted.

Further, as shown in FIG. 4, the protective bearing 12 is provided between the stator column 4 and the rotor 5 so that the groove 17 of the protective bearing 12 faces downward, and is provided integrally with the stator column 4. The projection 24 may be set so as to face the groove 17 of the bearing 12 for protection.

In this case, there is an advantage that the function of the protective bearing can be maintained at a low cost since the number of steps for mounting the separate member can be eliminated, so that no extra steps are required.

[0027]

As described above, the turbo-molecular pump according to the present invention has a projection for restricting the ball from falling off in the configuration of the protective bearing for rotatingly supporting the rotor in the emergency of the turbo-molecular pump (during touchdown). By setting, there is an effect that the function of the protective bearing can be maintained satisfactorily for a long time with a simple and inexpensive configuration, and high reliability of the turbo molecular pump can be secured.

Further, by improving the durability of the protective molecular pump, even when the turbo molecular pump is installed in an inverted posture, the balls of the protective molecular bearing can be reliably prevented from falling off. The reliability of the degree of freedom is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of a turbo-molecular pump according to the present invention.

FIG. 2 is a sectional view showing a configuration of a main part of the turbo-molecular pump shown in FIG. 1;

FIG. 3 is a sectional view of a main part showing a configuration of another embodiment of the turbo-molecular pump according to the present invention.

FIG. 4 is a sectional view of a main part showing a configuration of still another embodiment of the turbo-molecular pump according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turbo molecular pump 2 Casing 3 Stator blade 4 Stator column 5 Rotor 6 Rotor blade 7 High frequency motor 8 Radial sensor 9 Radial electromagnet 10 Axial sensor 11 Axial electromagnet 12, 13 Protective bearing 14 Outer ring 15 Inner ring 16 Ball 17 Put Groove 20 Support member 21, 23, 24 Projection 22 Ball drop prevention piece

Claims (1)

(57) [Scope of request for utility model registration] A stator blade mounted on an inner wall surface of a casing, and a rotor blade mounted on an outer wall surface of a rotor rotatably supported via a magnetic bearing on a stator column inside the casing. In a turbo-molecular pump, which is alternately arranged in the axial direction of the rotor, and rotates the rotor to take in air from one direction of the rotor shaft and exhaust it in the other direction, the turbo-molecular pump is provided between the rotor and the stator column and has a groove. A turbo-molecular pump comprising a full-ball type protective bearing and a projection which faces a groove of the protective bearing and regulates a ball from falling off the protective bearing.