JP2002323050A - Rolling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling device which is suitable for use in a joint of a robot arm, etc., which moves in higher speed. SOLUTION: An inner ring 2 and an outer ring 3 of the rolling bearing are formed of an aluminum alloy composite material in which a ceramic particle and/or a ceramic filter are scattered in an aluminum alloy, and a ratio between the coefficient of linear thermal expansion of the aluminum alloy composite material and that of an axis to be fitted to the inner peripheral surface of the inner ring 2 or a housing to be fitted to the outer peripheral surface of the outer ring 3 is set in a range of 0.7-1.3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling device such as a rolling bearing, and more particularly, to a method for automatically positioning a silicon wafer used in a semiconductor manufacturing process or a glass substrate used in a liquid crystal panel manufacturing process at a predetermined position. The present invention relates to a rolling device incorporated in a joint of a robot arm to be conveyed.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, for example, a joint part of a robot arm for automatically transferring a silicon wafer to a predetermined position is provided between an outer member and an inner member as means for supporting a joint axis of the robot arm. A rolling device such as a rolling bearing in which the rolling elements are rollably disposed is incorporated. Conventionally, a rolling device of this type has a structure in which an outer member and an inner member are made of a bearing steel such as SUJ2 or the like to improve durability.
Most are made of stainless steel such as US440C, but some of the outer and inner members are AC8AT6
Some are formed of an aluminum alloy such as

[0003] Among such conventional rolling devices, those in which the outer member and the inner member are formed of a steel material such as bearing steel have the advantage of being excellent in durability. Since the mass of the member and the inner member is large, the inertia force when operating the robot arm increases. For this reason, when such a rolling device is used as a bearing for supporting the joint axis of a robot arm operating at a higher speed, the positioning accuracy of the robot arm is reduced, and the wafer gripper of the robot arm is moved to a predetermined position. Positioning becomes difficult.

On the other hand, the outer member and the inner member are AC8AT6
A conventional rolling device formed of an aluminum alloy such as (linear expansion coefficient: 20 × 10 ⁻⁶ / ° C.) does not have the above-described problem. For example, the joint axis of the robot arm is SUS440C (linear). When the inner member is made of stainless steel (expansion coefficient: 10 × 10 ⁻⁶ / ° C.), the linear expansion coefficient of the inner member is about twice as high as the linear expansion coefficient of the joint shaft. For this reason, creep occurs between the inner member and the joint shaft, and a large amount of wear powder is generated along with this,
There have been problems such as the surroundings of the rolling device being contaminated with wear powder and the positioning accuracy of the robot arm being hindered by the wear powder. The same problem as described above also occurs when the housing fitted to the outer peripheral surface of the outer member is formed of a steel material such as stainless steel.

Further, the outer member and the inner member are AC8AT.
In the case of using an aluminum alloy such as 6, the wear resistance of the outer member and the inner member is reduced, abnormal wear occurs even under a light load, and the surroundings of the rolling device are contaminated with wear powder, The life of the device may be significantly reduced. Further, when the outer member and the inner member are formed of an aluminum alloy such as AC8AT6, the elastic modulus, that is, the rigidity of the outer member and the inner member becomes insufficient, and the required accuracy cannot be satisfied, or When a load is applied, permanent deformation occurs at the contact point between the rolling element and the inner member or between the rolling element and the outer member, and large vibration and noise may be generated.

[0006]

As described above, conventionally, when the outer member and the inner member are formed of bearing steel or stainless steel, the inertia force at the time of operation increases, so that the robot operates at higher speed. When used as a bearing to support the joint axis of the arm, there is a problem that the positioning accuracy of the robot arm is reduced, and when the outer member or the inner member is formed of an aluminum alloy, the inner member and the There has been a problem that creep easily occurs between the fitted shaft or outer member and the fitted housing.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a rolling device that can be suitably used for a joint portion of a robot arm operating at a higher speed. Is to do.

[0008]

According to a first aspect of the present invention, there is provided a rolling device including an inner member having an inner peripheral surface fitted on an outer peripheral surface of a shaft and an inner peripheral member of a housing. In a rolling device having a plurality of rolling elements rotatably arranged between an outer member having an outer peripheral surface fitted to a surface, at least one of the outer member and the inner member is made of an aluminum alloy. It is formed of an aluminum alloy-based composite material in which ceramic particles and / or ceramic fibers are dispersed, and has a ratio of a linear expansion coefficient of the shaft or the housing to a linear expansion coefficient of the aluminum alloy-based composite material of 0.7. ~ 1.3.

According to a second aspect of the present invention, in the rolling device according to the first aspect, the content of the ceramic particles and / or ceramic fibers (short fibers, whiskers) is in a range of 15 wt% to 80 wt%. It is characterized by being inside. A rolling device according to a third aspect of the present invention is the rolling device according to the first or second aspect, wherein the aluminum alloy-based composite material has an elastic modulus in a range of 95 GPa to 280 GPa.

A rolling device according to a fourth aspect of the present invention is the rolling device according to any one of the first to third aspects, wherein an anode is provided on the surface of the outer member and / or the surface of the inner member. An oxide film is formed. A rolling device according to a fifth aspect of the present invention is the rolling device according to any one of the first to fourth aspects, wherein the aluminum alloy-based composite material has a thermal conductivity of 54 W / m · K or more. It is characterized by.

A rolling device according to a sixth aspect of the present invention is the rolling device according to any one of the first to fifth aspects, wherein the rolling element is formed of ceramics.

[0012]

According to the first aspect of the present invention, at least one of the outer member and the inner member is formed of an aluminum alloy-based composite material in which ceramic particles are dispersed in an aluminum alloy. Since the mass of the outer member and / or the inner member is reduced as compared with a member formed of a steel material such as stainless steel, the inertial force during operation can be reduced. Further, an aluminum alloy-based composite material in which ceramic particles are dispersed in an aluminum alloy has better wear resistance than an aluminum alloy such as AC8AT6, so that the amount of wear powder generated can be suppressed. Further, by setting the ratio of the linear expansion coefficient of the shaft or the housing to the linear expansion coefficient of the ceramic particle-dispersed aluminum alloy-based composite material within the range of 0.7 to 1.3, the inner member and the shaft or the outer member can be formed. Generation of creep between the housing and the housing can be suppressed. here,
The reason for setting the lower limit of the ratio of the linear expansion coefficient of the shaft or housing to the linear expansion coefficient of the aluminum alloy-based composite material to 0.7 is that if the ratio is less than 0.7, it is mainly due to the temperature change and the outer member. This is because the fitting force between the housing and the housing is weakened, and creep is likely to occur between the outer member and the housing. The upper limit of the ratio is 1.
The reason for 3 is that the fitting force between the shaft and the inner member is weakened mainly due to the temperature change, so that creep is likely to occur between the inner member and the shaft, or due to the expansion of the inner member. This is because the internal load of the rolling device increases and seizure easily occurs.

[0013] In the invention according to claim 2, the content of the ceramic particles and / or ceramic fibers is 15 wt.
The reason for setting the content within the range of% to 80 wt% is as follows.
That is, when the content of the ceramic particles and / or ceramic fibers is less than 15 wt%, the wear resistance of the outer member and the inner member becomes insufficient, and a large amount of wear powder is generated with the operation of the rolling device. If the content of the ceramic particles and / or ceramic fiber exceeds 80 wt%, not only the wear resistance may not be improved, but also the external environment may be contaminated or the life of the rolling device may be significantly reduced.
This is because the mechanical strength of the aluminum alloy-based composite material itself is reduced, the wear of the outer member and / or the inner member made of the aluminum alloy-based composite material is increased, and the life of the rolling device is shortened.

In the invention according to claim 3, the elastic modulus of the aluminum alloy-based composite material is from 95 GPa to 280 GP.
The reason for setting it within the range of a is as follows. That is, when the elastic modulus of the aluminum alloy-based composite material is less than 95 GPa, the rigidity of the outer member and the inner member becomes insufficient, and the positioning accuracy of the robot arm cannot be satisfied or a load is applied. In some cases, permanent deformation easily occurs at the contact point between the rolling element and the outer member or the inner member, and large vibration or noise is generated, so that the life is extremely shortened. On the other hand, when the elastic modulus of the aluminum alloy-based composite material exceeds 280 GPa, the rigidity of the outer member and the inner member is improved, but the contact point between the rolling element and the outer member or the inner member is excessively large. Abrasion increases rapidly due to the occurrence of delamination at the interface between the ceramic particles and / or ceramic fibers and the aluminum alloy that is the base material.
The life of the rolling device becomes extremely short, and the surroundings of the rolling device may be contaminated by wear powder. Therefore, the elastic modulus of the aluminum alloy-based composite material is 95 GPa.
280 GPa, preferably 105 GPa-2
It is desirable to be within the range of 65 GPa.

According to the fourth aspect of the present invention, since the anodic oxide film is formed on the surface of the outer member and / or the surface of the inner member, the lubricating property with the rolling elements is improved. Can be further reduced. In the invention according to claim 5, by setting the thermal conductivity of the aluminum alloy-based composite material to 54 W / m · K or more, heat generated in the bearing portion is transmitted to the housing and released to the outside. Can be suppressed, and the occurrence of creep due to the temperature rise of the bearing portion can be prevented.

In the invention according to claim 6, since the rolling elements are formed of ceramics, adhesion of the rolling elements is less likely to occur as compared with rolling elements made of a steel material such as SUS440C. The life can be improved. The ceramic particles and / or ceramic fibers include, for example, silicon carbide (SiC), alumina (Al ₂ O ₃ ), aluminum nitride (AlN), and boron carbide (B
₄ C), titanium boride (TiC), titanium nitride (Ti
N) and the like, and these may be used alone or in combination. The method for producing an aluminum alloy-based composite material in which ceramic particles and / or ceramic fibers are dispersed in an aluminum alloy is not particularly limited. For example, casting methods such as sand casting, precision casting, and die casting may be used. It can be manufactured by a method or a non-pressurized metal infiltration method.

In the rolling device of the present invention, the material of components (for example, rolling elements, cages, etc.) made of materials other than the aluminum alloy-based composite material is not particularly limited, but it is a lightweight material having corrosion resistance. Preferably, there is. Such materials include SUS440C, S
Examples thereof include stainless steel-based metal materials represented by US304 and SUS630, and ceramic materials represented by titanium alloys, silicon nitride, zirconia, alumina, and silicon carbide. Examples of the lightweight alloy include an aluminum alloy, a magnesium alloy, and a titanium alloy. Further, the above materials can be used alone or in combination.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a partial cross-sectional view of a rolling bearing according to an embodiment of the present invention. In FIG. 1, a rolling bearing 1 includes an inner race (inner member) 2 having an inner peripheral surface that is fitted to a shaft (not shown) (for example, a joint shaft of a robot arm).
And an outer ring (outer member) 3 provided on the outer periphery of the inner ring 2.
And a housing (not shown) is fixed to the outer peripheral surface of the outer race 3. In addition, the rolling bearing 1 has rolling element rolling grooves 4 on the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 3, respectively, and a plurality of spherical rolling elements 5 are interposed between these rolling element rolling grooves 4. It is arranged to roll freely. Furthermore, the rolling bearing 1 is provided with a cage 6 for holding the rolling elements 5 at equal intervals in the circumferential direction of the inner ring 2 and the outer ring 3, and a gap between the inner ring 2 and the outer ring 3 is provided on both sides of the cage 6. Is provided with an annular seal 7 for preventing intrusion of foreign matter and leakage of grease.

Next, Examples 1 to 4 of the present invention based on such a configuration are shown in Table 1 together with Comparative Examples 1 and 2.

[0020]

[Table 1]

In Table 1, the rolling bearing of Example 1 has a silicon carbide particle-dispersed aluminum alloy composite material (silicon carbide particles (average particle size: 2 μm to 150 μm)) in which the inner ring and the outer ring are dispersed in an aluminum alloy. Selangx: CSI-30, coefficient of linear expansion: 14.4 × 10 ⁻⁶ /
K, thermal conductivity: 150 W / m · K, elastic modulus: 1256
Pa) and the rolling element is formed of SUS440C. In the rolling bearing of Example 2, the inner ring and the outer ring are made of alumina particles in an aluminum alloy (average particle diameter: 2 μm).
m-150 μm) dispersed alumina particle-dispersed aluminum alloy-based composite material (manufactured by Selanx Corporation: PAL-6)
0, coefficient of linear expansion: 11.8 × 10 ⁻⁶ / K, thermal conductivity: 5
4 W / m · K, elastic modulus: 2106 Pa) and the rolling elements are formed of SUS440C.

In the rolling bearing of the third embodiment, the inner ring and the outer ring are formed of the above-mentioned alumina particle-dispersed aluminum alloy composite material and the rolling elements are formed of silicon nitride. The rolling bearing of the fourth embodiment is formed of an inner ring. In addition, the outer ring is formed of an aluminum alloy-based composite material in which alumina particles are dispersed, the rolling elements are formed of silicon nitride, and anodized films are formed on the surfaces of the inner and outer rings which come into contact with the rolling elements.

On the other hand, the rolling bearing of Comparative Example 1 uses SUS440C (linear expansion coefficient: 10.8 ×
10 ⁻⁶ / K, thermal conductivity: 24 W / m · K), and the rolling bearing of Comparative Example 2 has an inner ring and an outer ring of 20
24 aluminum alloy (linear expansion coefficient: 20.0 × 10 ^-6
/ K, thermal conductivity: 125 W / m · K) and the rolling elements are formed of SUS440C. In addition,
In Examples 1 to 4, Comparative Examples 1 and 2,
Each of the retainers is made of a fluororesin.

Embodiments 1 to 3 of the present invention configured as described above
In order to examine the durability of the rolling bearings in Example 4, Comparative Example 1 and Comparative Example 2, the present inventors used a bearing rotation tester (manufactured by Nippon Seiko Co., Ltd.) 10 shown in FIG. Rotation test was performed in a dry environment. That is, the inner ring 2 of the bearing is connected to the spindle shaft (SUS) of the bearing rotation tester 10.
440C) 11 and the outer race 3 is fixed to the inner peripheral surface of the housing 12.
To a temperature of about 60 ° C. And
In synchronization with this, the spindle shaft 11 is intermittently rotated by the motor 14 at a rotation speed of about 1000 rpm, and the rotational vibration of the inner ring 2 at that time is measured. When the measured value becomes three times the initial value, The life of the rolling bearing was evaluated.
In this case, the bearing rotation test was performed with an inner diameter of 3 as a test bearing.
0 mm, outer diameter 47 mm, width 9 mm ball bearing (model number 690
6), atmosphere: ambient temperature, radial load: 98 N, rotation speed: 1000 rpm.

Here, the configuration of the bearing rotation tester 10 will be briefly described. In FIG. 2, the axial load on the rolling bearing 1 can be adjusted by a spring 15.
A magnetic fluid seal unit 16 is provided at one end of the spindle shaft 11, and the motor 1 is mounted on the spindle shaft 11.
4 is the pulley 17, the belt 18, the pulley 19
And the magnetic fluid seal unit 16. On the other hand, the outer ring 3 of the rolling bearing 1 is connected to a minute load converter 20 via a housing 12,
Therefore, the torque of the rolling bearing 1 can be measured using the micro load converter 20.

The rolling bearing 1 comprises a container 21 and a partition 2
The bottom of the space is connected to a laser light scattering type particle counter 23. On the other hand, above the enclosed space, the air inlet 2
5 is provided, and by supplying clean air at a predetermined flow rate to a space surrounded by the container 21 and the partition wall 22,
Since an airflow is generated from the air inlet 25 to the particle counter 23, the amount of wear powder generated from the rolling bearing 1 can be detected by the particle counter 23.

Table 1 shows the life of Examples 1 to 4 and Comparative Examples 1 and 2 obtained by the above-described bearing rotation test.
Shown in In Table 1, the life of each rolling bearing is indicated by a relative value where the life of Comparative Example 1 is 1. As is clear from Table 1, each of the rolling bearings of Example 1 and Example 2 has a service life that is 2 to 4 times as long as that of Comparative Example 1 and has a lifespan that of Comparative Example 2. 10 to 20 times. This is because the inner and outer races of the rolling bearing of Comparative Example 2 are formed of 2024 aluminum alloy, whereas the inner and outer races of the rolling bearings of Examples 1 and 2 are more wear resistant than the 2024 aluminum alloy. This is because it is formed of a ceramic particle-dispersed aluminum alloy-based composite material having excellent properties.

In addition, when Examples 1 and 2 are compared with Examples 3 and 4, it can be seen that Examples 3 and 4 have higher values of the life of the rolling bearing. This is because the rolling elements of Examples 1 and 2 are formed of SUS440C, whereas the rolling elements of Examples 3 and 4 are formed of ceramics such as silicon nitride. Because it is.

FIG. 3 shows the relationship between the ratio of the linear expansion coefficient of the shaft fitted to the inner ring of the rolling bearing to the linear expansion coefficient of the inner ring and the torque life of the rolling bearing. As shown in FIG. 3, when the ratio between the coefficient of linear expansion of the inner ring and the coefficient of linear expansion of the shaft fitted to the inner ring is 0.7 or more and 1.3 or less, the torque life of the rolling bearing has a relatively high value. However, when the value falls outside the range of 0.7 to 1.3, the torque life of the rolling bearing is sharply reduced. This is because when the ratio between the coefficient of linear expansion of the inner ring and the coefficient of linear expansion of the shaft is out of the range of 0.7 to 1.3, creep tends to occur between the inner ring and the shaft, and creep may occur. It is considered that a large amount of abrasion powder is generated and the wear of the bearing is promoted. The same can be said for the ratio between the linear expansion coefficient of the outer ring and the linear expansion coefficient of the housing.

FIG. 4 shows the relationship between the content of silicon carbide particles contained in the silicon carbide particle-dispersed composite material constituting the inner ring and the outer ring and the life of the rolling bearing. As shown in FIG. 4, the content of the silicon carbide particles is 15 wt% to 80 wt%.
%, The life of the rolling bearing is sharply reduced. This is because if the content of silicon carbide particles is less than 15 wt%, the wear resistance of the inner ring and the outer ring becomes insufficient, and the content of silicon carbide particles becomes 80 wt%.
This is because if the ratio exceeds the above, the mechanical strength of the aluminum alloy-based composite material itself constituting the inner ring and the outer ring decreases.

From the above, the inner ring 2 and the outer ring 3 of the rolling bearing are formed of an aluminum alloy-based composite material in which ceramic particles are dispersed in an aluminum alloy.
The ratio of the linear expansion coefficient of the inner ring 2 and the outer ring 3 to the linear expansion coefficient of the shaft fitted to the inner peripheral surface of the inner ring 2 and the linear expansion coefficient fitted to the outer peripheral surface of the outer ring 3 is in the range of 0.7 to 1.3. As a result, the amount of abrasion powder generated is suppressed without increasing the inertial force during operation,
In addition, since creep hardly occurs between the inner ring and the shaft and between the outer ring and the housing, it is possible to obtain a rolling bearing that can be suitably used for a joint portion of a robot arm that operates at a higher speed.

In this case, the content of the ceramic particles is reduced to 15
wt% to 80 wt%, preferably 20 wt% to
When the content is within the range of 70 wt%, a large amount of wear powder is not generated with the operation of the rolling device, and the mechanical strength of the aluminum alloy-based composite material itself is not reduced. Can be enhanced. Further, the elastic modulus of the aluminum alloy-based composite material is set to 95 GPa to 280.
GPa, preferably 105 GPa to 265 GP
When it is within the range of a, the life of the rolling bearing is reduced,
Alternatively, a large amount of wear powder is not generated.

Further, by setting the elastic modulus of the aluminum alloy-based composite material in the range of 95 GPa to 280 GPa, preferably in the range of 105 GPa to 265 GPa, it is possible to suppress the occurrence of peeling at the interface between the ceramic particles and the aluminum alloy. In addition, the generation amount of wear powder can be effectively suppressed. Further, since the anodic oxide film is formed on the surface of the inner and outer races in contact with the rolling elements as in Example 4, the lubricating property with the rolling elements is improved, so that the generation amount of abrasion powder can be further reduced. it can.

Further, by setting the thermal conductivity of the aluminum alloy-based composite material to 54 W / m · K or more, heat generated in the bearing portion is transmitted to the housing and released to the outside. It is possible to suppress the occurrence of creep due to a rise in the temperature of the bearing portion. In addition, since the rolling elements are formed of ceramics such as silicon nitride, the adhesion of the rolling elements is less likely to occur compared to the rolling elements made of a steel material such as SUS440C, so that the life of the rolling device is improved. Can be.

In the above-described embodiment, both the inner ring and the outer ring of the rolling bearing are formed of an aluminum alloy-based composite material containing ceramic particles. However, only one of the inner ring and the outer ring is formed of the aluminum alloy-based composite material. It may be formed. Further, in the above-described embodiment, the case where the present invention is applied to a rolling bearing such as a ball bearing is illustrated. However, the present invention is not limited to this. For example, the present invention is applied to a ball screw, a linear guide, and the like. Of course, you can.

[0036]

As described above, according to the present invention,
A robot arm that operates at a higher speed because the amount of abrasion powder generated is suppressed without increasing the inertial force during operation and creep is less likely to occur between the inner member and the shaft and between the outer member and the housing. A rolling device that can be suitably used for a joint part or the like of the present invention can be provided.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a rolling bearing according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a bearing rotation tester used for checking a bearing life.

FIG. 3 is a diagram showing torque life characteristics of a rolling bearing.

FIG. 4 is a graph showing the relationship between the content of silicon carbide particles and the bearing life when the inner and outer rings of the rolling bearing are formed of a silicon carbide particle-dispersed aluminum alloy-based composite material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element rolling groove 5 Spherical rolling element 6 Cage 7 Seal 10 Bearing rotation tester 11 Spindle shaft 12 Housing 13 Heater 14 Motor 15 Spring 16 Magnetic fluid seal unit 20 Micro load converter 23 Particle counter

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Claims (6)

[Claims] A plurality of rolling elements can be rolled between an inner member having an inner peripheral surface fitted to an outer peripheral surface of a shaft and an outer member having an outer peripheral surface fitted to an inner peripheral surface of a housing. A rolling device, wherein at least one of the outer member and the inner member is formed of an aluminum alloy-based composite material in which ceramic particles and / or ceramic fibers are dispersed in an aluminum alloy; A rolling device, wherein a ratio of a linear expansion coefficient of a shaft or the housing to a linear expansion coefficient of the aluminum alloy-based composite material is in a range of 0.7 to 1.3. 2. The rolling device according to claim 1, wherein the content of the ceramic particles and / or ceramic fibers is in a range of 15 wt% to 80 wt%. 3. The rolling device according to claim 1, wherein an elastic coefficient of the aluminum alloy-based composite material is in a range of 95 GPa to 280 GPa. 4. The rolling device according to claim 1, wherein an anodic oxide film is formed on a surface of the outer member and / or a surface of the inner member. 5. The rolling device according to claim 1, wherein the aluminum alloy composite material has a thermal conductivity of 54 W / m · K or more. 6. The rolling device according to claim 1, wherein the rolling element is formed of ceramics.