JP2004076827A - Rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling device excellent in adhesion to base metal, provided with lubricating film easy to be coated, and excellent in lifetime and acoustic characteristic. <P>SOLUTION: An angular contact ball bearing is provided with an inner race 1, an outer race 2, a plurality of balls 3 arranged to roll freely between the inner race 1 and the outer race 3. The rolling surface of balls 3 is coated with the lubricating film 3a consisting of Pb, and oxidation zone 3b of 0.1μm or less is installed between the lubricating film 3a and the base metal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rolling device suitably used under vacuum and high temperature, and particularly to a rolling device suitable for a rotating anode X-ray tube and the like.
[0002]
[Prior art]
If a lubricant such as grease is used for lubricating rolling bearings in a vacuum environment or a high temperature environment, the lubrication function may deteriorate or the operating environment may deteriorate due to evaporation of the lubricant oil or scattering of the lubricant itself. Problems such as contamination may occur.
Therefore, under the above-mentioned environment, conventionally, at least one of the raceway surface of the bearing ring, the rolling surface of the rolling element, and the pocket surface of the cage (the part in rolling contact with the rolling element) has a soft metal. Lubrication was performed by coating a lubricating film consisting of
[0003]
Silver (Ag), lead (Pb), and the like are known as the soft metal forming the lubricating film. For example, a rolling bearing used for a rotating anode X-ray tube (X-ray tube having a rotating anode). , Ag is used when the ambient temperature is 400 to 500 ° C., and Pb is used when the ambient temperature is about 300 ° C. or less.
On the other hand, in recent years, in a rolling bearing for a rotary anode X-ray tube, there is an increasing demand for longer life, improved acoustic characteristics, and a shorter running-in operation time in a process of assembling the X-ray tube.
[0004]
In order to satisfy these demands, attention has been paid to improving the wettability (adhesion) of Pb to steel materials, and an intermediate layer made of Ag, Bi, etc. and a lowermost layer made of Sn, or an intermediate layer made of Sn, A rolling bearing in which a lowermost layer made of Cu is formed between an uppermost layer made of Pb and a base material has been proposed (Japanese Patent Application Laid-Open No. H7-190067).
[0005]
[Problems to be solved by the invention]
However, the rolling bearing described in the above publication has excellent wettability of Pb with respect to the base material and has an effect on improving the life in that respect, but since Sn has a lower melting point than Pb and is easily evaporated, There was a possibility that durability and acoustic characteristics would be reduced.
[0006]
In addition, a coating process must be performed by evaporating a plurality of metals, so that there is a problem that the processing steps are complicated.
Therefore, the present invention solves the problems of the prior art as described above, and provides a rolling device that has excellent adhesion to a base material and has a lubricating film that can be easily coated, and has excellent life and acoustic characteristics. The task is to provide.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration. That is, the rolling device of the present invention comprises an inner member having a raceway surface on an outer surface, and an outer member having a raceway surface opposed to the raceway surface of the inner member and disposed outside the inner member. And a plurality of rolling elements rotatably disposed between the two raceway surfaces, wherein the raceway surface of the inner member, the raceway surface of the outer member, and the rolling member At least the rolling surface of the rolling element among the rolling surfaces is coated with a lubricating film made of Ag or Pb, and an oxide layer of 0.1 μm or less is interposed between the lubricating film and the base material. And
[0008]
When the oxide layer is interposed, the wettability (adhesion) of the lubricating film with respect to the base material is improved, so that the life and acoustic characteristics of the rolling device are extremely excellent. In addition, since the metal oxide constituting the oxide layer has a high melting point (because it does not easily evaporate at a low melting point unlike Sn), there is no possibility that durability and acoustic characteristics are reduced. The thickness of this oxide layer needs to be 0.1 μm or less, and if it exceeds 0.1 μm, the life and acoustic characteristics of the rolling device may be deteriorated.
[0009]
The method for forming the lubricating film is not particularly limited, but the ion mixing method is most preferable. That is, a method of forming a coating of Ag or Pb by injecting ions such as argon while evaporating Ag or Pb with an electron beam.
When the ion mixing method is used, a coating (lubricating film) of Ag or Pb is formed, and an oxide layer having a thickness of 0.1 μm or less is formed between the lubricating film and the base material. A lubricating film and an oxide layer having excellent acoustic characteristics can be easily formed. The Ag or Pb film formed by the ion mixing method has excellent durability as compared with the film formed by the conventional ion plating method, so that the film thickness can be reduced. When the thickness of the lubricating film is small, the acoustic characteristics of the rolling device tend to be improved. Therefore, it is preferable to use the ion mixing method also from this point. Further, when the thickness of the lubricating film is small, for example, the running-in operation time in the process of assembling the rotating anode X-ray tube can be reduced.
[0010]
The thickness of the lubricating film is preferably from 0.1 to 0.5 μm. If it is less than 0.1 μm, there is a problem that durability is insufficient. On the other hand, if it exceeds 0.5 μm, there is a problem that the acoustic characteristics are reduced and a problem that the running-in operation time is increased and the production efficiency is reduced.
Further, the types of steel materials constituting the inner member, the outer member, and the rolling elements are not particularly limited, but SKH4, SUS440C, LNS125, ES1 (alloy component: 0.45% C-13% Cr- Stainless steel such as 0.14% N) is preferred. In particular, in the case of stainless steel, those having an alloy component satisfying C% ≦ 0.05Cr% + 1.41 such as LNS125, ES1, etc. are preferable because they do not generate a huge eutectic carbide.
[0011]
Note that the present invention can be applied to various rolling devices. For example, there are a rolling bearing, a ball screw, a linear guide device, a linear motion bearing, and the like.
In the present invention, the inner member is an inner ring when the rolling device is a rolling bearing, a screw shaft when the ball screw is the same, a guide rail when the linear guide device is the same, a linear motion bearing. In this case, each axis means. The outer member is an outer ring when the rolling device is a rolling bearing, a nut when the ball screw is the same, a slider when the linear guide device is the same, and an outer cylinder when the linear bearing is the same. Respectively.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a rolling device according to the present invention will be described with reference to the drawings. FIG. 1 is a partial longitudinal sectional view showing a configuration of a full ball angular bearing which is an embodiment of the rolling device according to the present invention.
This angular ball bearing (nominal number: 708A, inner diameter 8mm, outer diameter 22mm, width 7mm, contact angle 30 °) is arranged to be able to roll freely between the inner ring 1, the outer ring 2, and the inner ring 1 and the outer ring 2. A plurality of balls (rolling elements) 3.
[0013]
The inner ring 1, the outer ring 2, and the ball 3 are all made of SKH4 steel, and the surface of the ball 3 is coated with a lubricating film 3a (outer layer) made of Pb and an oxide layer 3b (inner layer) by an ion mixing method. ing. Lubricating film 3a has a thickness of 0.2 μm, and oxide layer 3b has a thickness of 0.1 μm. Note that the retainer may or may not be provided.
[0014]
The coating process of the lubricating film 3a and the oxide layer 3b by the ion mixing method is performed by an ion beam mixing device as shown in FIG. That is, the workpiece 23 is mounted on the rotating holder 22 (provided with a detector for ions or the like) in the vacuum chamber 21. Then, the metal M such as Pb and Ag is evaporated by an e-beam evaporator 24, and ions (activating ions I) such as argon are injected from an ion source 25 into the metal M on the surface of the rotating workpiece 23. M is coated.
[0015]
Here, the results of Auger electron spectroscopic analysis (depth profile) of the lubricating film 3a and the oxide layer 3b formed on the surface of the ball 3 by the ion mixing method are shown in FIG. As a comparison, FIG. 4 shows the results of Auger electron spectroscopy of the sample formed by the ion plating method.
First, FIG. 4 will be described. As can be seen from FIG. 4, the one formed by the ion plating method has a Pb layer, a base material mainly composed of Fe, and an intermediate layer (a mixed layer of an oxide of Pb and an oxide of Fe). ) Is observed, and oxygen is detected over the entire area from the Pb layer to the base material.
[0016]
On the other hand, FIG. 3 is the same in that a Pb layer, a base material containing Fe as a main component, and an intermediate layer (a mixed layer of an oxide of Pb and an oxide of Fe) therebetween are observed. However, oxygen is detected only in the vicinity of the intermediate layer and its interface, which is significantly different from that formed by the ion plating method of FIG. Another significant difference is that the thickness of the intermediate layer is very small.
[0017]
Next, the above-described angular contact ball bearing of the present embodiment was subjected to a rotation test using a vacuum high-temperature endurance test apparatus as shown in FIG. 5 to evaluate its durability.
This testing machine includes a rotating shaft S supported by a test bearing J, a motor M for rotating the rotating shaft S, a heater H for heating the rotating shaft S, a flange S1 and walls S2 and S3 forming a vacuum chamber. And a thermocouple T for detecting the temperature of the test bearing J. The rotating shaft S is supported by a bearing indicated by reference numeral 18 in addition to the test bearing J. In addition, the code | symbol K is a heater cable which connects the heater H and a power supply.
[0018]
The end of the rotating shaft S on the motor M side is arranged in a housing 15 installed outside the flange S1 (atmosphere side). Since the inside of the housing 15 is hermetically sealed by the magnetic seal unit 16, a vacuum is created. The end of the rotation shaft S and the rotation shaft of the magnetic seal unit 16 are connected in the housing 15. The rotation shaft of the motor M installed on the atmosphere side is connected to the rotation shaft of the magnetic seal unit 16 by a coupling 17.
[0019]
A torque lever L is attached to the housing JH of the test bearing J, and the torque lever L is connected to the torque detecting device 19. The torque detector 19 includes a leaf spring B with a strain gauge, and the torque applied to the test bearing J is detected by the strain gauge.
The test conditions are an axial load of 30 N, a rotation speed of 10,000 rpm, a temperature of 300 ° C., and a degree of vacuum of 1 × 10 ⁻⁴ Pa or less. The time until the torque detection value of the test bearing J became five times the initial value was defined as the life, and the rotation test was performed five times, and the life was evaluated based on the average value. In addition, the numerical values of the life described below (including the life described in the graph of FIG. 6 described later) are based on the assumption that the life of an angular ball bearing provided with a ball in which a lubricating film and an oxide layer are formed by an ion plating method is 1. It is shown as a relative value in the case. The configuration of this angular ball bearing (hereinafter referred to as a comparative example) is the same as that of the above-described angular ball bearing of the present embodiment except that a lubricating film and an oxide layer of the ball are formed by an ion plating method.
[0020]
As a result of the durability test, the life of the angular contact ball bearing of this embodiment was 2.8, which was much better than that of the comparative example.
Further, as a result of examining the relationship between the thickness of the oxide layer and the life of the bearing, as shown in the graph of FIG. 6, the life was excellent when the thickness of the oxide layer was 0.1 μm or less. Thus, it was found that when the thickness of the oxide layer analyzed by Auger electron spectroscopy was 0.1 μm or less, the durability of the bearing was excellent.
[0021]
Note that the present embodiment is an example of the present invention, and the present invention is not limited to the present embodiment.
For example, in the present embodiment, an angular ball bearing has been described as an example, but the rolling device of the present invention can be applied to various rolling bearings. For example, radial rolling bearings such as deep groove ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, self-aligning roller bearings, and thrust ball bearings and thrust roller bearings Rolling bearing.
[0022]
Further, in the present embodiment, a rolling bearing has been described as an example of a rolling device, but the rolling device of the present invention can be applied to various other types of rolling devices. For example, the present invention can be suitably applied to other rolling devices such as a linear guide device, a ball screw, and a linear motion bearing.
[0023]
【The invention's effect】
As described above, the rolling device of the present invention has excellent adhesion to the base material and has a lubricating film that can be easily coated, and has excellent life and acoustic characteristics.
[Brief description of the drawings]
FIG. 1 is a partial longitudinal sectional view showing a configuration of an angular contact ball bearing which is an embodiment of a rolling device according to the present invention.
FIG. 2 is a conceptual diagram showing a configuration of an ion beam mixing device.
FIG. 3 is a depth profile showing Auger electron spectroscopic analysis results of a lubricating film and an oxide layer formed by an ion mixing method.
FIG. 4 is a depth profile showing Auger electron spectroscopic analysis results of a lubricating film and an oxide layer formed by an ion plating method.
FIG. 5 is a schematic diagram of a vacuum high-temperature durability test apparatus for evaluating the durability of a rolling bearing.
FIG. 6 is a graph showing a correlation between the thickness of an oxide layer and the life of a bearing.
[Explanation of symbols]
1 inner ring 2 outer ring 3 ball 3a lubrication film 3b oxide layer

Claims (2)

An inner member having a raceway surface on an outer surface, an outer member having a raceway surface facing the raceway surface of the inner member, and disposed outside the inner member, and rolling between the two raceway surfaces; A plurality of rolling elements freely arranged, and a rolling device comprising:
At least a rolling surface of the rolling element among the raceway surface of the inner member, the raceway surface of the outer member, and the rolling surface of the rolling element is covered with a lubricating film made of Ag or Pb, A rolling device characterized in that an oxide layer of 0.1 μm or less is interposed between the base material and the base material. The rolling device according to claim 1, wherein the lubricating film is formed by an ion mixing method.

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