JP2503966Y2 - Rolling bearing - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing most suitable for semiconductor manufacturing equipment used especially in a vacuum.

[0002]

2. Description of the Related Art Conventionally, a supporting column of an industrial robot (for example, a semiconductor manufacturing robot), a revolving arm, and revolving arms are relatively rotatably supported via rolling bearings.
(See, for example, JP-A-1-182624). For such a rolling bearing, a fluid lubricant such as lubricating oil or grease is used, and a cross roller or an angular contact ball bearing is used to prevent backlash even if moment loads with different load directions are applied. I try to use them in combination.

[0003]

However, the above-described conventional rolling bearing has a problem that it cannot be used in a vacuum atmosphere because it uses a fluid lubricant such as lubricating oil or grease. Further, as described above, two bearings must be combined in order to cope with the radial and axial loads, which causes a problem that the entire device becomes large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rolling bearing which is small in relative displacement between an inner ring and an outer ring, so-called rattling, and is small in size and can be used in a vacuum atmosphere even when subjected to a moment load. To do.

[0005]

To achieve the above object, a rolling bearing according to a first aspect of the present invention has an inner ring having a raceway portion on an outer peripheral surface, an outer race having a raceway portion on an inner peripheral surface, and the inner ring and the outer ring. In a rolling bearing having a ball fitted between races, a coating layer containing polytetrafluoroethylene is formed on at least the race of the inner ring and the outer ring, and the ball is formed on the race of the inner ring. It is characterized in that it is arranged in a state where a preload is applied between the surface of the coated layer and the surface of the coating layer formed on the raceway portion of the outer ring. A rolling bearing according to claim 2 is provided with an inner ring having a raceway portion on an outer peripheral surface, an outer ring having a raceway portion on an inner peripheral surface, and a ball fitted between the inner race and the raceway portion of the outer ring. In the bearing, the races of the inner ring and the outer ring are each formed with two radii of curvature that are larger than the radii of curvature of the balls so that the balls come into contact with the ball at two points. A coating layer containing polytetrafluoroethylene is formed, and the ball has a radial direction and an axial direction between the surface of the coating layer formed on the race portion of the inner ring and the surface of the coating layer formed on the race portion of the outer ring. It is characterized in that it is arranged so that the clearance in the direction becomes a negative clearance.

[0006]

In the rolling bearing according to the first aspect of the present invention, the balls are provided at predetermined positions in a pre-loaded form when assembled to the inner ring and the outer ring. Therefore, no matter what direction the moment load is applied, there is almost no play between the inner ring and the outer ring. Further, the coating layer containing polytetrafluoroethylene formed on the races of the inner ring and the outer ring does not peel off even if it creeps and reattaches, so that a good lubricating action is performed for a long time. Further, due to this lubricating action, even if the balls slip, the balls do not seize. Furthermore, since polytetrafluoroethylene has self-lubricating property, this bearing is used in a vacuum without lubrication. In the rolling bearing according to claim 2, the balls are brought into point contact with the raceway portions of the inner ring and the outer ring at two points, respectively, a total of four points, and the ball is provided between the surfaces of the coating layers formed on both raceway portions. By arranging so that the clearances in the radial direction and the axial direction are negative clearances, there is almost no play in the bearing in all directions. Moreover, since it is not necessary to combine two bearings, the device can be downsized. The action of the coating layer containing polytetrafluoroethylene is similar to that of the rolling bearing of claim 1.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the illustrated embodiments. First, the rolling bearing of the first embodiment will be described. As shown in FIG. 2, this rolling bearing includes an inner ring 10 made of stainless steel having a raceway portion 10a on an outer peripheral surface thereof, and an outer race 11 made of stainless steel having a raceway portion 11a on an inner peripheral surface thereof.
A stainless steel ball 12, ..., 12 fitted in a preloaded state between the races 10a, 11a of the inner ring 10 and the outer ring 11 and a copper cage 13 for holding the ball 12 are provided. Prepare Stainless steel is, for example, SUS44
0C, SUS630, etc., and stainless steel prevents corrosion without lubrication.

As shown in detail in FIG. 1, the raceways 10a, 11a of the inner ring 10 and the outer ring 11 have two curvature radii b, which are larger than the radius of curvature a of the ball 12, when viewed from the cutting plane in the axial direction. b, and two points c and d, respectively, on the ball 12 through a coating layer 14 described later.
Point contact is made between e and f. Outer peripheral surface including the raceway portion 10a of the inner ring 10, the raceway portion 11 of the outer ring 11
A coating layer 14 is formed on each of the inner peripheral surface including a and the pocket surface of the cage 13. The coating layer of the cage 13 is not specifically shown.

The coating layer 14 is used for the inner and outer races 1.
The outer peripheral surface and the inner peripheral surface of 0 and 11 have a film thickness of 3 to 5 μm, and the cage 13 has a film thickness of 8 μm ± 3 μm, and the component thereof is polytetrafluoroethylene.
(Hereinafter referred to as PTFE.) 75 to 90 wt% and polyamide imide 25 to 10 wt%. Polyamideimide acts as a binder for the PTFE powder and also improves the adhesion to the surface to be coated. The coating layer 14 can be formed by the following method. First, the inner ring 10 and the outer ring 1 that are the members to be coated
1 and the holder 13 are degreased. Next, a portion other than the coated portion of the coated member, that is, the outer peripheral surface of the inner ring 10, the inner peripheral surface of the outer ring 11, and the surface portion of the cage 13 is covered with a mask. Next, the surface roughness is Ra = 0.8, Rmax =
It is about 3S. The purpose of this treatment is to increase the adhesion of the coating layer to the surface to be coated,
The raceway surface must withstand high surface pressure. Next, the sand used in the sandblasting process is removed. The above process is a pretreatment for forming the coating layer 14. Subsequently, a fluid obtained by dissolving polytetrafluoroethylene and polyamideimide in N-methylpyrrolidone, which is a solvent, is sprayed onto the surface to be coated, which is not covered with a mask, a plurality of times to coat the fluid. Apply to the surface. This method is called a bonded film method. The component ratio of the fluid is 5% polyamideimide powder, 25% PTFE powder, and 70% N-methylpyrrolidone. The ball 12 is the inner ring 10
And the raceway portions 10a, 11a of the outer ring 11 are arranged in such a manner that the clearances in the radial direction and the axial direction are preloaded so as to have a negative clearance (for example, -20 μm) via the coating layers 14, 14 described above. .

As described above, the balls 12 are respectively brought into point contact with the raceway portions 10a, 11a of the inner ring 10 and the outer ring 11 through the coating layers 14, 14 at two points, that is, four points in total,
By arranging so that the radial and axial clearances are negative, there is almost no play even when moment loads in various directions are applied. Also, as a result of assembling the ball 12 with a negative clearance,
Although the rolling load of the balls 12 increases and slippage easily occurs, the balls 12 do not seize due to the lubricating action of the PTFE coating layer 14. In addition, by setting the clearance of the ball 12 to a negative clearance,
Even if the coating layer 14 creeps as shown in (a) and (b), sufficient lubricity can be secured even with a slight coating layer 14 between the ball 12 and the raceways 10a and 11a, and the seizure of the ball 12 Can be prevented. Also, PTF
The coating layer 14 of E does not form a lump in the raceway portion and does not cause fluctuations in the rotation torque. On the other hand, when a soft metal solid lubricant such as Ag or Pb is used, when a moment load is applied, the soft metal is lumped on the raceways of the inner and outer rings 10 and 11 due to transfer (transfer). As a result, the fluctuation of the rotating torque becomes large, and the bearing reaches the end of its service life early.

In the above embodiment, the ball 12 is replaced by the inner ring 1
0 and the races 10a, 11a of the outer ring 11 have a negative clearance, the outer ring 11 is axially divided into two with the center of the ball 12 as a boundary, and the divided outer ring 11 is separated on both sides when assembled. It is good to fit them. Also, the outer ring 11 and the inner ring 10
The bearing may be assembled by shrink fitting or cold fitting without dividing. Further, in the above embodiment, the balls 12 have a negative clearance in the radial direction and the axial direction with respect to the raceways of the inner and outer races 10 and 11. However, only the surface of the coating layer 14 of the inner and outer races has the ball. May have a negative clearance. Further, the cage 13 is
Although the holding hole for the ball 12 is formed in the center, a so-called crown type cage having a holding groove for the ball 12 on one side may be used. Further, a full-ball type having only the balls 12 without the cage 13 may be used. Furthermore, the balls 12 and the inner and outer rings 10, 11 do not have to be made of stainless steel, and may be made of ceramics.

FIG. 4 is a sectional view of an angular ball bearing according to a second embodiment of the present invention. In this embodiment, two angular ball bearings 20, 20, which are symmetrically formed, are assembled by abutting the front faces. The angular contact ball bearings 20, 20 are made of stainless steel having a raceway portion 21a on the outer peripheral surface and a stainless steel raceway portion 22a on the inner peripheral surface, similarly to the rolling bearings shown in FIGS. 1 and 2. Outer ring 22 of each of the inner race 21 and the outer race 22 of each outer race 22
, 23, which are fitted between a and 22a in a preloaded state, and a copper cage 24 that holds the balls 23. Outer peripheral surface including the track portion 21a of the inner ring 21, the track portion 21a of the outer ring 22
A coating layer 14 is formed on each of the inner peripheral surface including the above, the pocket surface of the cage 24, and the surface of the ball 23. The coating layer 14 is applied to each surface by the same material and the same method as in the first embodiment. Then, the ball 23 has the coating layer 14
Are formed between the races 21a and 22a of the inner ring 21 and the outer ring 22 in a state in which a preload is applied after the formation of the races.

A performance evaluation test was conducted on the angular ball bearing 20 (bearing A) having the above-described structure and the angular ball bearings (bearings B and C) having a coating layer having the following structure as a comparative example under the following same conditions. The apparatus used for the test has a structure capable of evaluating two test bearings, and the measurement of the frictional force has a structure capable of being detected as a rotational torque of the two bearings. (A) Coating layer structure of comparative example (i) In the case of bearing B Lubricant: MoS ₂ binder: organic (ii) In the case of bearing C Lubricant: MoS ₂ binder: inorganic (B) Test condition Pressure: 1 × 10 ^-5 Torr Temperature: Room temperature Load: Radial load: 0.5Kgf Axial load: 60Kgf Rotation speed: 200rpm Test time: Max. 50 hours The relationship between test time and torque of each test bearing A, B, C is shown in Fig. 5. Shown in. As can be seen from FIG. 5, the bearing A of this embodiment
Shows a stable rotation torque immediately after the start of the test, and almost no abnormality was recognized until the maximum test time of 50 hours. On the other hand, bearings B and C using MoS ₂ as a solid lubricant
All showed stable rotation torque immediately after the start of the test, but after 6 to 9 hours, the rotation torque sharply increased and reached the end of life. In addition, as a result of surface observation after the test, in the case of the bearing A of this example, only slight wear was observed on the inner ring surface, and the balls were not worn at all. On the other hand, adhesive wear was observed on the inner ring surface of both bearings B and C of the comparative example, and adhesive wear occurred in the case of bearing C. In this test, "life" means that the rotational torque of two test bearings is 20
It means the time when it reaches 00 gf · cm. From this test result, it was demonstrated that the bearing of this example coated with PTFE has an extremely long life as compared with the bearing coated with the solid lubricant MoS ₂ other than PTFE. In other words, even if the same soft material is used, MoS ₂ cannot be used if a preload is applied.
E proves that there is no problem even if preload is applied.

In the second embodiment, the two angular contact ball bearings 20 are combined in the front direction, but it goes without saying that they may be combined in the rear direction. In addition, in the second embodiment described above, a two-point contact type angular ball bearing with a single row non-separable type in which the shoulder portion of the inner ring is provided on only one side of the raceway portion is used.
Alternatively, a single-row angular contact ball bearing of four-point contact type may be used in which one or both of the inner ring raceway and the outer ring raceway are separated into two in a plane perpendicular to the central axis.
Further, it may be a deep groove ball bearing having shoulder portions provided on both sides of the raceway portion. Further, in the second embodiment, the coating layer 14
Although (a) was provided on all of the races of the inner and outer rings, (b) the cage, and (c) the ball surface, it may be provided only on the above (a).

[0015]

As is apparent from the above description, in the rolling bearing according to claim 1 of the present invention, the surface of the coating layer formed on the race portion of the inner ring and the surface of the coating layer formed on the race portion of the outer ring. And the ball is placed between and in the state where a preload is applied. Therefore, with this preload, it is possible to suppress the occurrence of rattling with respect to moment loads in various directions, and when it is used for a turning arm of a semiconductor manufacturing robot, the positional accuracy is improved. Also, PT
Since the FE coating layer does not peel off even when it creeps, the lubricating effect prevents the balls from sticking. Further, since it is a solid lubricant, it can be used in a vacuum atmosphere.

Further, in the rolling bearing of the second aspect, balls are provided at two points between the surface of the coating layer formed on the raceway portion of the inner ring and the surface of the coating layer formed on the raceway portion of the outer ring. It is arranged so that the radial and axial clearances are negative while making point contact. Therefore, as in the case of the rolling bearing according to claim 1, there is almost no rattling even when moment loads in various directions are applied. Therefore, when the rolling bearing is used for a semiconductor manufacturing robot, the positional accuracy is improved. To do. In addition, since the backlash does not occur even if a plurality of bearings are not combined as in the conventional case, the device becomes compact. Further, due to the fitting due to the negative clearance, the balls are likely to slip, but like the rolling bearing of the first aspect, the balls are not seized due to the lubricating action of the PTFE coating layer. Therefore, since it is not necessary to use a fluid lubricant, it can be used even in a vacuum atmosphere.

[Brief description of drawings]

FIG. 1 is an enlarged view of a main part of a rolling bearing according to a first embodiment of the present invention.

[Figure 2] Cross-sectional view of rolling bearing

FIG. 3 is an explanatory diagram of creep of the coating layer.

FIG. 4 is a sectional view of an angular contact ball bearing according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the results of a bearing performance evaluation test.

[Explanation of symbols]

10 ... Inner ring, 10a ... Raceway part, 11 ... Outer ring, 11a ... Raceway part, 12 ... Ball, 14 ... Coating layer, 21 ... Inner ring, 21a ... Raceway part, 22 ... Outer ring, 22a ... Raceway part, 23
…ball.

Claims (2)

(57) [Scope of utility model registration request] 1. A rolling bearing comprising an inner ring having a raceway portion on an outer peripheral surface, an outer race having a raceway portion on an inner peripheral surface, and a ball fitted between the raceway portions of the inner ring and the outer ring. A coating layer containing polytetrafluoroethylene is formed on at least the race portion of the outer ring, and the balls have a surface of a coating layer formed on the race portion of the inner ring and a surface of the coating layer formed on the race portion of the outer ring. A rolling bearing characterized in that it is arranged in a state in which a preload is applied between and. 2. A rolling bearing comprising an inner ring having a raceway portion on an outer peripheral surface, an outer ring having a raceway portion on an inner peripheral surface, and a ball fitted between the raceway portions of the inner ring and the outer ring. The races of the outer ring and the outer ring are each formed with two radii of curvature that are larger than the radius of curvature of the ball so as to contact the ball at two points, respectively. A coating layer containing the same is formed, and the ball has a negative radial and axial clearance between the surface of the coating layer formed on the inner ring raceway portion and the surface of the coating layer formed on the outer ring raceway portion. Rolling bearing characterized by being arranged so as to have a clearance.