JP2006226267A - Bearing structure of vacuum pump and vacuum pump using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing structure of a vacuum pump in which damage of a bearing holder is prevented while securing a heat radiating property of a bearing, and a vacuum pump using it. <P>SOLUTION: A turbo molecular pump (a vacuum pump) is provided with a rotor 2, a housing 3 for accommodating the rotor 2, a rolling bearing 4 for supporting the rotor 2 so as to be rotatable to the housing 3, a drive unit such as an electric motor for rotatively driving the rotor 2 around an axial line, wherein the rolling bearing 4 is held by the housing 3 through the medium of a bearing holder 16 made up of a thermal conductor. In the surface of the bearing holder 16, a hard anodic oxide film 19 is formed on an annular plane 17b (an abutting part) receiving the rolling bearing 4 at least. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bearing structure of a vacuum pump and a vacuum pump using the same.

Generally, as a vacuum pump, for example, a turbo molecular pump described in Patent Document 1 described below is known.
The turbo molecular pump includes a rotor having moving blades on the outer periphery, a housing that houses the rotor, a bearing that rotatably supports the rotor with respect to the housing, and a drive device that rotationally drives the rotor.

  As the bearing, for example, a rolling bearing such as a ball bearing or a needle bearing is used. Specifically, the bearing includes an inner ring that receives the rotor, an outer ring that is supported by the housing, and a ball (or needle) that is provided between the inner and outer rings and that allows the inner and outer rings to rotate relative to each other about their axes. ). Further, grease is enclosed between the inner and outer rings, and lubrication between the inner and outer rings and the ball (or needle) is performed by this grease.

In the turbo molecular pump, the bearing is held in the housing via a bearing holder such as a sleeve case or a bearing sleeve. The outer ring of the bearing has its end face in the axial direction pressed against the bearing holder by a spring or the like with a predetermined force. This prevents the inner ring and the outer ring from rotating and keeps the rotor rotating stably. It is like that.
The bearing is provided with a slight play with respect to the bearing holder in the radial direction, and the bearing can be displaced relative to the bearing holder in the radial direction. As the bearing is displaced in the radial direction in this manner, the vibration of the rotor is absorbed and abnormal vibration of the rotor is prevented.

  The turbo molecular pump configured in this way is used to make the atmosphere previously depressurized by a rotary pump or the like into a higher vacuum state, and the rotor is rotated at a high speed by a driving device. This is a vacuum pump that sweeps out gas molecules from the atmosphere by making the speed of the moving blade provided on the outer periphery faster than the movement speed of the gas molecules. For this reason, in general, the rotor of the turbo molecular pump is rotationally driven at a very high speed of 10,000 revolutions per minute or more.

For this reason, during operation of the turbo molecular pump, the inner ring that receives the rotor that rotates at high speed in the bearing rotates at high speed relative to the outer ring supported by the housing, and the ball provided between these inner and outer rings rotates at high speed. Thus, frictional heat is generated between the ball (or needle) and the inner and outer rings.
Since the grease is enclosed in the bearing as described above, if the temperature of the bearing becomes too high, the grease may evaporate or melt and flow out, and there is a possibility that sufficient lubrication cannot be performed.
For this reason, conventionally, the bearing holder is made of a material having high thermal conductivity, such as a copper alloy (for example, brass), and the heat of the bearing is released to the bearing holder to prevent an abnormal increase in the bearing temperature.

JP 2003-172288 A (paragraphs [0026] to [0031] and FIG. 1)

However, although copper alloy has a high thermal conductivity, it is a relatively soft metal. Therefore, in a bearing holder made of copper alloy, the bearing is displaced in the radial direction relative to the bearing holder due to the vibration of the rotor or the like. Therefore, the contact surface with the bearing is likely to be rough due to wear. For this reason, as the use of the turbo molecular pump continues, the frictional resistance between the bearing and the bearing holder will gradually increase, so that the smooth sliding of the bearing with respect to the bearing holder will not be difficult. Maintenance is required.
Further, when the bearing holder is made of a copper alloy as described above, the bearing holder may be scraped off due to friction with the bearing, and metal powder may be generated. If such metal powder penetrates into the bearing, the wear of the bearing proceeds and the life is shortened, which is not preferable.

  This invention is made in view of such a situation, Comprising: The bearing structure of the vacuum pump which is hard to damage a bearing holder while ensuring the heat dissipation of a bearing, and a vacuum pump using the same are provided. Objective.

In order to solve the above problems, the bearing structure of a vacuum pump of the present invention and a vacuum pump using the same employ the following means.
That is, the bearing structure of the vacuum pump according to the present invention includes a rotor, a housing that houses the rotor, a rolling bearing that rotatably supports the rotor with respect to the housing, and the rolling bearing that is held in the housing. A bearing structure of a vacuum pump having a bearing holder, wherein the bearing holder is constituted by a heat conductor, and a hard film is formed on at least a receiving surface for receiving the rolling bearing among the surfaces of the bearing holder. It is a feature.

In the bearing structure of the vacuum pump configured as described above, the bearing holder is formed of a heat conductor, and a hard film is formed on at least the receiving surface for receiving the rolling bearing among the surfaces of the bearing holder. The wear of the bearing holder is prevented while allowing the heat of the rolling bearing to be released through the bearing holder.
Here, the hard coating can be obtained, for example, by forming an oxide coating on the surface of the bearing holder made of metal.
Further, the hard film may be formed by subjecting the bearing holder to a film forming process such as a CVD process or a PVD process. In this case, the bearing holder can be made of any material having a high thermal conductivity (for example, a copper alloy such as brass).

  In this bearing structure of the vacuum pump, the bearing holder may be made of aluminum or an aluminum-based alloy, and the hard coating may be an anodized coating obtained by anodizing the bearing holder.

In this case, since the bearing holder is made of aluminum or aluminum-based alloy having a high thermal conductivity, the heat dissipation effect of the rolling bearing is high. Furthermore, since the anodized film has a small friction coefficient, the rolling bearing slides more smoothly with respect to the bearing holder, and abnormal vibration of the rotor can be more effectively prevented.
Here, when an aluminum-based alloy is used as the material of the bearing holder, it is preferable to use an A5000-based aluminum-based alloy having high strength and workability.

A vacuum pump according to the present invention includes the above-described vacuum pump bearing structure.
In the vacuum pump configured as described above, the bearing holder is made of a heat conductor, and at least the receiving surface for receiving the rolling bearing is formed on the bearing holder surface. Wear of the bearing holder is prevented while allowing the heat of the rolling bearing to be released via the.

  According to the bearing structure of the vacuum pump and the vacuum pump using the same according to the present invention, the heat of the rolling bearing can be released through the bearing holder, but the bearing holder is not easily damaged. Support can be performed well.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, a turbo molecular pump (vacuum pump) 1 according to this embodiment includes a rotor 2, a housing 3 that houses the rotor 2, and a rolling bearing that rotatably supports the rotor 2 with respect to the housing 3. 4 and a driving device 5 such as an electric motor for rotating the rotor 2 around its axis.

The rotor 2 has a substantially cylindrical wing portion 2b provided with a plurality of moving blades 2a on the outer periphery, and a shaft portion 2c provided coaxially with the wing portion 2b below the wing portion 2b.
The housing 3 has a substantially bottomed cylindrical shape with an upper end opened, and a plurality of stationary blades 3a are provided on the inner surface of the housing 3 facing the outer periphery of the blade portion 2b of the rotor 2. The upper end of the housing 3 constitutes a gas inlet.

The rolling bearing 4 supports the shaft portion 2 c of the rotor 2. In the present embodiment, the turbo molecular pump 1 has a fixed-side rolling bearing 4 a that is fixedly held in the housing 3 as the rolling bearing 4, and a non-slidably held axially with respect to the housing 3. A fixed-side rolling bearing 4b is provided. In the present embodiment, an example is shown in which the upper part of the shaft 2c is supported by the fixed-side rolling bearing 4a and the lower part of the shaft 2c is supported by the non-fixed-side rolling bearing 4b (note that the fixed-side rolling bearing 4a and the non-fixed side are supported). The arrangement with the rolling bearing 4b may be changed).
The fixed side rolling bearing 4 a is held in the housing 3 via a bearing holder 16 described later, and the non-fixed side rolling bearing 4 b is an O provided on the outer peripheral surface of the outer ring 12 on the lower inner peripheral surface of the housing 3. It is held by the housing 3 via the ring S.

As these rolling bearings 4, for example, angular ball bearings that receive both a radial load and a thrust load received from the rotor 2 are used.
As shown in FIG. 2, these rolling bearings 4 are provided between an inner ring 11 that receives the shaft portion 2 c, an outer ring 12 that is supported by the housing 3, and these inner and outer rings 11, 12, and these inner and outer rings 11, 12. And a ball 13 that enables relative rotation around the axis of each other. Further, grease is sealed between the inner and outer rings 11 and 12, and lubrication between the inner and outer rings 11 and 12 and the ball 13 is performed by this grease. In addition, in FIG. 2, the fixed side rolling bearing 4a is shown as an example.

The bearing holder 16 is an annular member through which the shaft portion 2c is inserted. In the present embodiment, the bearing holder 16 is made of an A5000 series aluminum alloy.
On the inner peripheral portion of the bearing holder 16, a notch-shaped concave portion 17 that houses the outer ring 12 of the fixed-side rolling bearing 4 a is provided on the lower surface side. The recess 17 has an inner peripheral surface 17 a substantially parallel to the axis of the bearing holder 16 and a downward annular plane 17 b that is substantially orthogonal to the axis of the bearing holder 16.

The diameter of the inner peripheral surface 17a is set to be slightly larger than the outer diameter of the outer ring 12 so that the outer ring 12 is held with some play in the radial direction. Since the fixed-side rolling bearing 4a is displaceable in the radial direction with respect to the bearing holder 16, the vibration of the rotor 2 is absorbed and abnormal vibration of the rotor 2 is prevented.
Further, a groove 17c is formed on the inner peripheral surface 17a over the entire periphery, and an O-ring 18 that elastically supports the outer peripheral surface of the outer ring 12 is fitted in the groove 17c.
Thereby, when the outer ring 12 is displaced in a direction substantially perpendicular to the axis by the vibration of the rotor 2, the force for displacing the outer ring 12 is buffered by the elastic force of the O-ring 18, so that the vibration of the rotor 2 is attenuated. It has become.

A hard anodized film 19 is formed on the annular flat surface 17b to form a hard anodized film 19. The annular flat surface 17 b is a receiving surface that receives the upper end surface of the outer ring 12.
The fixed-side rolling bearing 4a has an upper end surface of the outer ring 12 pressed against the annular flat surface 17b with a predetermined pressure by a biasing member (not shown) such as a coil spring, whereby the inner ring 11 and the outer ring 12 are supplied. The rotation is prevented, and the stable rotation of the rotor 2 is maintained.

In the turbo molecular pump 1 configured as described above, the bearing holder 16 is made of an aluminum-based alloy that is a heat conductor having a high thermal conductivity, and the heat of the fixed-side rolling bearing 4a via the bearing holder 16 is effective. Can be released.
Further, since the anodized film 19 that is a hard film is formed on the annular flat surface 17b (receiving surface) that receives the upper end surface of the outer ring 12 of the fixed side rolling bearing 4a in the bearing holder 16, the fixed side rolling bearing 4a. Wear of the bearing holder 16 due to sliding is difficult to occur.

As described above, in the turbo molecular pump 1, the heat of the fixed-side rolling bearing 4 a can be released through the bearing holder 16, but the bearing holder 16 is not easily damaged. Therefore, the rotor 2 is supported by the rolling bearing 4. It can be done well.
Furthermore, since the anodic oxide coating 19 has a smaller coefficient of friction than an aluminum-based alloy ingot, the fixed-side rolling bearing 4a slides more smoothly with respect to the bearing holder 16, and abnormal vibration of the rotor 2 is prevented. It can prevent more effectively.

  Note that an anodic oxide coating 19 may be formed on the bearing holder 16 in a region other than the annular flat surface portion 17b. Here, it is preferable not to form the anodic oxide coating 19 in a portion having a severe dimensional tolerance such as an engaging portion with another member other than the rolling bearing 4 in order to maintain the shape accuracy. In this case, for example, by subjecting the bearing holder 16 to a hard anodizing process in a state where masking is performed on a portion having a severe dimensional tolerance, an anodized film is formed on a desired region while maintaining the shape accuracy of the portion having a severe dimensional tolerance. 19 can be formed.

Here, although the example which made the bearing holder 16 the aluminum base alloy was shown in the said embodiment, it will not be restricted to this, If the bearing holder 16 is a material with high heat conductivity, aluminum, copper, Any material such as a copper alloy can be used.
Further, the hard coating is not limited to the anodic oxide coating 19 obtained by subjecting the bearing holder 16 to the alumite treatment as described above. For example, the hard coating is formed on the surface of the bearing holder 16 made of an arbitrary heat conductor by CVD treatment or PVD. The hard film may be formed by a film forming technique such as treatment.

It is a longitudinal section showing the composition of the turbo molecular pump (vacuum pump) concerning one embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG. 1.

Explanation of symbols

1 Turbo molecular pump (vacuum pump)
2 Rotor 3 Housing 4 Rolling bearing 16 Bearing holder 17b Annular plane (receiving surface)
19 Anodized coating (hard coating)

Claims (3)

A bearing structure for a vacuum pump, comprising: a rotor; a housing that houses the rotor; a rolling bearing that rotatably supports the rotor with respect to the housing; and a bearing holder that holds the rolling bearing in the housing. ,
The bearing structure of the vacuum pump which comprised the said bearing holder with the heat conductor, and formed the hard film in the receiving surface which receives the said rolling bearing among the surfaces of this bearing holder. The bearing holder is made of aluminum or an aluminum-based alloy;
The bearing structure of the vacuum pump according to claim 1, wherein the hard film is an anodized film obtained by anodizing the bearing holder.   The vacuum pump provided with the bearing structure of the vacuum pump of Claim 1 or 2.

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