JPH11344036A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lengthen durability life when a bearing is used at a high temperature and in vacuum by forming a cage by a material in which polytetrafluoroethylene and polyoxybenzoyl are blended so as to be content of specified polyoxybenzoyl. SOLUTION: A cage 4 is formed by a material in which polytetrafluoroethylene(PTFE) and polyoxybenzoyl are blended by content 10 to 70 wt.% of polyoxybenzoyl. PTFE is high in melt viscosity even beyond a melting point of 327 deg.C, although it is crystalline resin, and is fluorine-contained resin of property which is difficult to deform and is molded by compression and extrusion. As polyoxybenzoyl, there are homopolymer and copolymer, and homopolymer is extremely high in crystalline property and hardly flows at a temperature of 400 deg.C or below, injection molding is difficult to be performed for simple substance and the melting point is estimated to be 450 deg.C or more. When content is less than 10 wt.%, self lubricity becomes insufficient and when content exceeds 70 wt.%, heat resistance becomes insufficient. Therefore, durability life under environments such as at a high temperature of 300 deg.C or more and in vacuum can be lengthened in a bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing suitable for a device used in a high-temperature environment of 300.degree.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices and magnetic recording devices, a film forming process is performed in a high-temperature environment in a vacuum. A transfer device that moves a wafer or the like to a film forming apparatus repeatedly moves between a vacuum and the atmosphere. As a method of lubricating the rolling bearing used for the rotating unit in such a transfer device or a film forming device, a method using a fluorine-based grease or a method using a self-lubricating cage and not performing lubrication with grease is used. Has been adopted.

[0003] In particular, in an environment where the temperature is higher than 250 ° C in a vacuum, if fluorine-based grease is used, there is a problem that gasification of the grease occurs in large quantities and the product is contaminated in the manufacturing process. It is preferable to use a self-lubricating cage without performing lubrication with grease.

[0004] As a conventional example of a self-lubricating cage, Japanese Patent Laid-Open Publication No. HEI 9 (1999) discloses that a cage is made of a material obtained by mixing a carbon powder as a lubricant and a glass fiber as a reinforcing fiber in a polyetheretherketone resin. It is disclosed in Japanese Patent Application Laid-Open No. 4-351319. It is described that the rolling bearing having this cage can be used without lubrication at a high temperature of 300 ° C. or higher.

JP-A-7-197936 discloses a material in which a solid lubricant such as graphite or molybdenum disulfide and a reinforcing fiber such as carbon fiber or glass fiber are added to a polybenzimidazole resin having a self-lubricating ability. It is disclosed to form a retainer with.

As a resin composition capable of forming a self-lubricating cage, Japanese Patent Publication No. 3-59938 discloses a resin composition based on 100 parts by weight of a fluororesin (polytetrafluoroethylene is not applicable) which can be injection-molded. , Oxybenzoyl polyester and natural flaky graphite in a weight ratio (90: 1)
0) to (40:60), the mixture of
There is disclosed a composition formulated with 00 parts by weight.

As a similar resin composition, Japanese Patent Publication No.
No. 00 discloses polyarylene esters of 95 to 30.
A composition containing 2.5 to 60% by weight of polytetrafluoroethylene (PTFE) and 2.5 to 60% by weight of oxybenzoyl polyester (polyoxybenzoyl) is disclosed. In addition, 7-1089
No. 51 discloses a linear polyphenylene sulfide resin having a melt viscosity measured under a predetermined condition of not less than a predetermined value.
0 to 85% by weight of oxybenzoyl polyester
A composition containing 30% by weight and 10 to 60% by weight of a fluororesin is disclosed.

Japanese Patent Application Laid-Open Nos. Hei 2-24554, Hei 3-117721, Hei 4-102718, and Japanese Laid-Open Patent Publication No. Hei 4-102718 disclose a bearing retainer to which a uniform radial load and axial load are applied. 5-23
No. 105, respectively.

[0009]

However, among the above prior arts, the retainer described in Japanese Patent Application Laid-Open No. 4-351319 and Japanese Patent Application Laid-Open No.
Self-lubricating properties are not sufficient when used in a high-temperature environment of ℃ or more and in a vacuum, and wear progresses on the contact between the cage and the rolling element and on the guide surface of the cage, generating wear powder. The product may be contaminated, and the bearing life is short. Also,
Since these cages have high rigidity, there is also a problem that it is difficult to incorporate them into a bearing at room temperature.

[0010] Japanese Patent Publication No. 3-59938, Japanese Patent Publication No. 61700, and Japanese Patent Publication No. 7-108951
The retainer formed of the resin composition described in
When used in a high-temperature environment of 0 ° C. or higher, there is a problem that it becomes difficult to hold the rolling elements due to softening of the resin.
In addition, the self-lubricating property when used in a high-temperature environment of 300 ° C. or more and in a vacuum is not sufficient, and the product may be contaminated by wear powder generated by wear of the retainer.

The present invention has been made in view of such problems of the prior art, and provides a rolling bearing having a long durability when used in a high-temperature environment of 300 ° C. or more and in a vacuum environment. The task is to

[0012]

In order to solve the above-mentioned problems, the present invention provides a rolling bearing having an inner ring, an outer ring, a rolling element, and a retainer, wherein the retainer is made of polytetrafluoroethylene (PTFE) and polytetrafluoroethylene (PTFE). Provided is a rolling bearing characterized in that oxybenzoyl is formed from a material blended with a polyoxybenzoyl content of 10 to 70% by weight.

[0013] PTFE is a fluororesin which is a crystalline resin and has a high melt viscosity even at a melting point of more than 327 ° C and is hardly deformed, and is an injection-moldable fluororesin such as ethylene tetrafluoroethylene copolymer. Unlike molding, it is formed by compression molding or extrusion molding. Examples of commercially available PTFE include “Polyflon TFE” manufactured by Daikin Industries, “Teflon TFE” manufactured by DuPont Mitsui Fluorochemicals, and “Fluon TF” manufactured by Asahi Fluoropolymer.
E ", DuPont" Teflon TFE ", Ho
"Hostaflon" manufactured by echst, "Fluon" manufactured by ICI, and the like.

The polyoxybenzoyl includes a polyoxybenzoyl homopolymer having a structural unit represented by the following formula (1) and a polyoxybenzoyl copolymer having a structural unit represented by the following formula (2). The polyoxybenzoyl homopolymer is sold under the trade name "Econol E101", and the polyoxybenzoyl copolymer is sold under the trade name "Econol E1000", both of which are sold by Sumitomo Chemical. Among them, “Econol E101” has extremely high crystallinity, hardly flows at a temperature of 400 ° C. or less, and it is difficult to mold it alone by injection molding. The melting point is estimated to be 450 ° C. or higher.

[0015]

Embedded image

[0016]

Embedded image

In the rolling bearing of the present invention, since the cage is formed of a material in which PTFE and polyoxybenzoyl are mixed at a polyoxybenzoyl content of 10 to 70% by weight, In addition, sufficient self-lubricating properties and heat resistance can be obtained in a vacuum environment. When the content of polyoxybenzoyl is less than 10% by weight, the self-lubricating property when used in the environment (particularly,
Wear resistance) becomes insufficient. When the content of polyoxybenzoyl exceeds 70% by weight, heat resistance when used in the above environment becomes insufficient. The preferred range of the polyoxybenzoyl content is 20 to 50% by weight.

Regarding the shape of the retainer, in order to easily incorporate the rolling element into the retainer and to prevent the rolling element from dropping out of the retainer, the opening dimension of the rolling element insertion portion should be equal to the diameter of the rolling element. It is preferably 75% or more and less than 97%.

The gap between the rolling element diameter and the pocket diameter is preferably 2 to 17% of the rolling element diameter. If it is less than 2%, the abrasion of the retainer becomes large, and if it exceeds 17%, the play of the rolling element in the pocket is large, so that abrasion powder due to this play is easily generated.

Although the guide surface of the cage can be any surface of the inner ring and the outer ring, the outer circumferential surface of the bearing inner ring is preferable in terms of the sliding speed when the cage rotates. The ratio of the inner ring guide clearance of the retainer to the retainer inner diameter is preferably 16% or less. If this ratio exceeds 16%, the amount of eccentricity of the cage increases, and the life is shortened.

The thickness of the column of the cage may be smaller than the radial gap between the inner and outer rings, but the linear expansion coefficient of the material of the cage is larger than that of the metal which is the material of the inner and outer rings, and the thickness of the cage is as described above. If the gap exceeds 97%, there is a high possibility that the retainer will be restrained by the outer ring when rotated at a high temperature of 300 ° C., and the torque will increase.

The thickness of the bottom of the pocket portion is set to 0.3 mm or more in order to prevent breakage when the cage is assembled or the bearing rotates. The upper limit of the thickness of the pocket portion is not particularly limited as long as the thickness of the pocket portion can keep the balance of the retainer.

[0023]

Embodiments of the present invention will be described below. First Embodiment FIG. 1 shows an outer ring 1, an inner ring 2, a rolling element 3,
FIG. 2 is a cross-sectional view showing a structure of a rolling bearing including a retainer 4 and a seal 5, FIG. 2 is a cross-sectional view showing a structure of a crown-shaped retainer, and FIG. 3 shows a pocket portion of the retainer of FIG. It is an enlarged view. <Differences in performance due to differences in cage materials> The configurations of the inner ring, outer ring, and rolling elements and the shape of the cage are common, and rolling of No. 1-1 to 1-3 with different cage materials is performed. The bearing was assembled.

The inner diameter of this rolling bearing is 8 mm, the outer diameter is 22 mm, the width is 7 mm, and the number of rolling elements is 6
The rolling element diameter is 3.96 mm, and the material for forming the inner ring, the outer ring, and the rolling elements is SUS440C.

The retainer is crown-shaped. As shown in FIG. 2, the crown-shaped retainer has a circular pocket 41 and a rolling element insertion portion 4.
2 2 and FIG. 3, reference symbol R1 denotes an inner diameter, reference symbol R2 denotes an outer diameter, reference symbol w denotes a width, reference symbol a denotes a pocket diameter, reference symbol b denotes an opening dimension of the rolling element insertion portion 42, and reference symbol c denotes a bottom of the pocket portion 41. The thickness, symbol d, is the thickness of the column of the cage 4 (the thickness of the peripheral surface portion).

The shape of the retainer of this embodiment has an inner diameter of 1
2.5mm, outer diameter 17mm, pocket diameter 4.1mm
And the opening dimension of the rolling element insertion portion is 3.4 mm,
The thickness of the bottom of the pocket part is 0.5 mm, the thickness of the pillar of the retainer is 2.25 mm, and the width is 4.5 mm.

In this rolling bearing, the radial gap between the inner and outer rings indicated by the symbol σ in FIG. 1 is 2.9 mm, and the inner ring guide gap indicated by the symbol e is 0.3 mm. 60% by weight of PTFE "Teflon TFE7J" for compression molding manufactured by Du Pont-Mitsui Fluorochemicals and 40% by weight of polyoxybenzoyl homopolymer "E101" manufactured by Sumitomo Chemical Co., Ltd. were stirred in a Henschel mixer to give a total amount of 2 kg. A uniform resin composition was obtained.

This resin composition was placed in a die steel mold, heated to 350 ° C. at a rate of 150 ° C./hour by applying a pressure of 1000 kgf / cm ³ , and then kept at this temperature for 5 hours. . Thereafter, by cooling to room temperature at a cooling rate of 20 ° C./hour, a diameter of 28.5 mm × a thickness of 10
A 0 mm cylindrical compact was obtained. By cutting this molded body, a cage having the above-mentioned shape was produced with a processing accuracy of dimensional tolerance ± 0.1 mm. This is designated as cage No. 1-1.

DuPont polyimide resin molded product "Vespel" (PMDA (pyromellitic acid) -based polyimide resin, graphite (15% by weight) and PTFE (10%)
% By weight).
mm of a cylindrical molded body), a cage having the above-mentioned shape was produced with a processing accuracy of dimensional tolerance ± 0.1 mm. This is designated as No. 1-2 cage.

A Hoechst polyetheretherketone (PEEK) molded product “TF-60F” (PEEK (70
Wt%), PTFE (20 wt%) and carbon fiber (1
0% by weight) and a diameter of 2
0mm cylindrical shaped body) by cutting
A cage having the above-described shape was manufactured with a processing accuracy of dimensional tolerance ± 0.1 mm. This is designated as cage No. 1-3.

A rolling bearing is assembled by using the cages No. 1-1 to No. 1-3 and the above-described inner ring, outer ring, and rolling element, and a shaft is fitted into the inner ring, and the housing is assembled with a heater. The outer ring was fitted. The housing in which the shaft and the bearing are integrated as described above is placed under a pressure of 1 × 10 ⁻⁴ P while the bearing is constantly maintained at 300 ° C. by heating the heater.
The shaft was rotated at a rotation number of 1000 rpm while being taken in and out of the vacuum chamber every 6 hours. Thus, the bearing is alternately placed in a high-temperature and high-vacuum (1 × 10 ⁻⁴ Pa) environment and a high-temperature and atmospheric pressure (about 101 Pa) environment for 6 hours.

Thus, the thrust load of 3 kgf
A 48-hour continuous rotation test was performed without lubrication with grease. The weight of the cage and the total weight of the inner ring and the outer ring were measured before and after the test, and the value obtained by dividing the difference between each weight before and after the test by the weight before the test was calculated as the weight loss rate due to wear. The results are shown in Table 1 below.

[0033]

[Table 1]

From the results shown in Table 1, No. 1-1 in which the composition of the material forming the cage is within the scope of the present invention is compared with No. 1-2 and No. 1-3 which are not within the scope of the present invention. As a result, it can be seen that the self-lubricating property of the cage in a high-temperature and high-vacuum environment is high, so that the weight loss rate due to wear is small.

Next, a cage was prepared in the same manner as in No. 1-1 using a number of materials having different mixing ratios of polyoxybenzoyl and PTFE, and the above-mentioned rotation test was performed. The results are shown in a graph in FIG. The cage wear rate in this graph indicates the weight loss rate of the cage calculated in the same manner as described above.

As can be seen from this graph, the content of polyoxybenzoyl is within the range of the present invention (10% by weight to 70% by weight).
(% By weight) A cage made of the material in A had no breakage and a low wear rate. When the content of polyoxybenzoyl is less than 10% by weight, the abrasion rate is high, and when it exceeds 70% by weight, the matrix strength due to PTFE is extremely reduced and the cage is broken. The preferred range B of the polyoxybenzoyl content is from 40% by weight to
90% by weight, and a more preferable range C is 50% by weight or less.
80% by weight.

A molded article formed of PTFE and polyoxybenzoyl and compression-molded with a material containing polyoxybenzoyl in the range of 10 to 70% by weight has various contents of homopolymer or copolymer of oxybenzoyl polyester. Since such a molded product is commercially available, the retainer of the present invention can be easily obtained by performing a cutting process. <Differences in performance due to differences in cage shape> Rolling bearings were assembled by changing the shape of the cage and the configuration of the inner ring, the outer ring, and the rolling elements and the material of the cage.

The inner diameter of this rolling bearing is 8 mm, the outer diameter is 22 mm, the width is 7 mm, and the number of rolling elements is 6
The rolling element diameter is 3.96 mm, and the material for forming the inner ring, the outer ring, and the rolling elements is SUS440C.
The inner diameter of the outer ring is 18 mm, and the outer diameter of the inner ring is 12 mm.
mm, and the radial gap σ, which is a difference between these dimensions, is 3 mm. Pocket porosity The material of the cage is the above-mentioned “Teflon TFE7J”
After forming a cylindrical molded body in the same manner as described above using a resin composition containing 50% by weight of each of “E101” and “E101”, cutting was performed to obtain a predetermined shape. Cage is crown-shaped, inner diameter is 12.5mm, outer diameter is 17m
m, the opening size of the rolling element insertion part is 3.4 mm, the thickness of the bottom of the pocket part is 0.5 mm, and the thickness of the pillar of the retainer is 2.25.
mm and the width were constant at 4.5 mm. By changing the pocket diameter, a number of cages having different pocket gap ratios were formed. The pocket gap ratio (%) is represented by the following equation (3).

Pocket gap ratio (%) = ((pocket diameter−rolling element diameter) / rolling element diameter) × 100 (3) Rolling is performed using these cages and the above-described inner ring, outer ring, and rolling element. The bearings were assembled and two identical rolling bearings were mounted at one longitudinal position of the shaft and housed in a housing incorporating a heater. An axial load of 3 kgf was applied between the two bearings using a coil spring.
The housing is fixed in the vacuum chamber, and the bearing can be rotated by driving an external motor.

The pressure in the vacuum chamber is set to 1 × 10 ⁻⁴ Pa, the housing is maintained at 300 ° C. by a heater, and an external motor is driven to rotate the internal shaft at a rotation speed of 1000 rpm.
m. After performing this rotation for 6 hours, the amount of dust generated inside was measured using a laser type vacuum particle counter without opening the vacuum chamber. The result is shown by a graph in FIG.

As the pocket gap ratio is smaller, abrasion powder is more likely to be generated from the start of the test until the pocket shape conforms to the rolling element diameter. In addition, as the pocket gap ratio is larger, the play of the rolling elements in the pocket is larger, so that abrasion powder due to this play is more likely to be generated. Therefore, there is a problem if the pocket gap ratio is too small or too large, and the range D of 2 to 17%, in which the number of generated dust is 250 or less, is preferable.
A more preferable range F is 3 to 8% in which the number of generated particles is 100 or less. Insert part gap ratio As the material of the retainer, the above-mentioned “Teflon TFE7J”
Was formed into a predetermined shape by forming a cylindrical molded body in the same manner as described above using a resin composition containing 80% by weight of “E101” and 20% by weight of “E101”.
The cage is crown-shaped, inner diameter is 12.5 mm, outer diameter is 17
mm, the pocket diameter was 4.1 mm, the thickness of the bottom of the pocket portion was 0.5 mm, the thickness of the column of the retainer was 2.25 mm, and the width was 4.5 mm. A number of cages having different insertion part gap ratios were formed by changing the opening size of the rolling element insertion part. The insertion portion gap ratio (%) is represented by the following equation (4).

Inserting portion gap ratio (%) = (opening size of inserting portion / rolling member diameter) × 100 ‥‥ (4) A rolling bearing is formed by using these cages and the above-described inner ring, outer ring, and rolling member. Assembling, the shaft was fitted into the inner ring, and the outer ring was fitted into the housing in which the heater was incorporated. Note that no seal was attached. The housing in which the shaft and the bearing are integrated as described above is placed sideways so that the rolling element insertion portion of the retainer faces upward, and the bearing is maintained at 200 ° C., 300 ° C., and 400 ° C. by heating the heater. so,
Put in a vacuum chamber with a pressure of 1 × 10 ⁻⁴ Pa and apply a thrust load of 2.5 kgf, and rotate at 800 rpm.
To rotate the shaft. The time from the start of rotation until the cage came off was measured as the endurance time. The results are shown in a graph in FIG.

As can be seen from this graph, the durable time becomes 20 hours or more even at 400 ° C. when the insertion portion gap ratio is 95% or less, and the durable time is extremely short when it is 97.5% or more. It was confirmed that it became. Therefore, from the viewpoint of preventing the retainer from falling off, it is preferable that the insertion portion gap ratio is less than 97%. If the insertion portion gap ratio was less than 75%, the rolling element could not be inserted. Also,
When the insertion portion gap ratio is 85% or more, the rolling element can be easily inserted. However, when the insertion portion gap ratio is less than 85%, the retainer may be deformed. Therefore, it is preferable that the insertion portion gap ratio is 85% or more and 95% or less in terms of both prevention of the retainer from falling off and ease of incorporating the rolling elements. A cage having a predetermined shape was produced by cutting "SUMIKA S300" manufactured by Sumitomo Chemical Co., Ltd., which is a compression molded product of a resin composition composed of 30% by weight of the guide gap "E101" and 70% by weight of PTFE. Cage is crown-shaped, outer diameter is 1
7 mm, pocket diameter 4.1 mm, rolling element insertion opening size 3.4 mm, pocket bottom thickness 0.5 m
m, the thickness of the cage pillar is 2.25 mm, and the width is 4.5 mm
And was fixed. By changing the inner diameter to 12.0 to 14.4 mm, a number of cages having different inner ring guide clearances were formed.
The ratio of the guide gap to the inner diameter of the retainer at room temperature (guide gap ratio,%) was calculated, and a number of samples having the values ranging from 0 to 20% were prepared.

A rolling bearing is assembled using these cages, the inner ring, the outer ring, and the rolling elements described above, and two identical rolling bearings are attached to a longitudinal direction of one shaft, and the inside of a housing in which a heater is incorporated. In. Axial load 3kg using coil spring between two bearings
f was loaded, the housing was kept at 300 ° C. by the heater, and the shaft was rotated at 3000 rpm in the atmosphere. The torque applied to this shaft was measured from the start of rotation, and the time until the measured torque value became twice the initial torque was measured as the endurance time. FIG. 7 is a graph showing the relationship between the durability time and the guide gap ratio.

Even if the guide gap is zero, the rotation (revolution about the axis) of the cage rubs the inner peripheral surface of the retainer and the outer peripheral surface of the inner ring to form a clearance, thereby affecting the torque life. Has no effect. However, if the guide gap ratio is less than 0.5%, there is a high possibility that the rotation start of the retainer will be restricted depending on the fit of the rotating shaft.
It is preferable that it is above.

Further, as the guide gap ratio with respect to the inner diameter of the retainer increases, the retainer is more likely to move in the radial direction and the amount of eccentricity increases, thereby shortening the torque life. As can be seen from the graph of FIG. 7, the guide gap ratio is preferably 16% or less for a durable time of 8 hours or more, and more preferably 6% or less for a durable time of 15 hours or more. Second Embodiment <Differences in Performance Due to Differences in Constituent Materials of Bearing Members> Rolling bearings in which the shapes of the bearing members were common and the materials were changed as shown in Table 2 below were assembled. This rolling bearing is a shielded deep groove ball bearing composed of an outer ring 1, an inner ring 2, a rolling element 3, a retainer 4, and a shield 6, as shown in FIG. 8, having an inner diameter of 8 mm, an outer diameter of 22 mm, and a width of 7 mm. . The rolling element diameter is 3.96 mm and the number of rolling elements is 7
Individual. The cage is crown-shaped, the pocket gap of the cage is 0.2 mm, and the radial gap of the bearing is 8-12 μm.

Each of the assembled rolling bearings was subjected to a durability test in which a moment load was applied in a vacuum using a test machine shown in FIG. The tester includes a weight 12, which is provided in a vacuum chamber and applies a moment load to the axis S,
It comprises a rotation torque detection mechanism, a heating member 9 of the housing 8, and a rotation mechanism of the housing 8 and a magnetic seal unit 13 provided outside (inside of) the vacuum chamber. In addition, a hole 71 having a size that allows the housing 8 to be inserted is provided in the wall 7 of the vacuum chamber.

The heating member 9 is formed by winding a sheath heater 92 on the outer peripheral surface of a cylindrical body having an outwardly facing flange portion 91 at one end, and the flange portion 91 is provided on the periphery of the hole 71 of the vacuum chamber. It is fixed via a plate 11. A shaft 81 is integrated with one end of the housing 8.
The magnetic seal unit 13 is fitted on the outside. The pulley 14 is fixed to a tip of the shaft 81 on the indoor side.

As a mechanism for detecting the rotational torque, a leaf spring 16 fixed to the tip of a bracket 15 provided on the wall 7 of the vacuum chamber and a strain gauge 17 attached to the tip are provided.
It has.

At the start of the test, the bearing J
After the housing 8 is inserted into the heating member 9 from the hole 71 of the vacuum chamber with the shaft S inside the inner ring, the hole 71 is sealed by the magnetic seal unit 13. And a weight 12 according to the moment load to be applied.
Is attached to the tip of the shaft S, the vacuum chamber is sealed, and the torque from the motor is transmitted to the pulley 14,
As the shaft 81 rotates, the housing 8 in the vacuum chamber rotates. Thereby, a durability test of the bearing J in which the predetermined moment load is applied to the shaft S is performed.

The housing 8 is heated to 200 ° C. by the heating member 9.
And the housing 8 is rotated under the conditions of a degree of vacuum of 1 × 10 ⁻⁴ Pa or less, a moment load of 20 N · cm, and a rotation speed of 500 rpm, and the torque applied to the bearing J is measured from the start of rotation. The number of revolutions (revs) until five times the initial torque was measured as the durability life. The results are shown in Table 2 below.

[0052]

[Table 2]

Also, 0.1 g ± 0.02 g of fluorine-based grease is sealed in each bearing obtained in the same manner as above.
A durability test was performed using the same testing machine. The test conditions were as follows: the degree of vacuum was 1 × 10 ⁻⁴ Pa or less, and the moment load was 50 N · c.
m, and the rotation speed was 500 rpm. The results are shown in Table 3 below.

[0054]

[Table 3]

From these results, it can be seen that the bearing retainer to which a moment load is applied in a vacuum is made of ETFE (ethylene tetrafluoroethylene copolymer), PEEK (polyether ether ketone), PPS (polyphenylene sulfide), Heat-resistant resin such as aromatic polyester and P
A resin composition containing TFE (polytetrafluoroethylene), which is formed of a material containing PTFE in the range of 10 to 60% by weight, compared with a resin composition formed of another material. It can be seen that the durability life is longer. In particular, when the content of PTFE is 20 to 60% by weight, the effect is enhanced.

Further, the bearings of Example 5 and Comparative Example 1 were subjected to a durability test in which the moment load was changed using the above-described testing machine. FIG. 10 is a graph showing the relationship between the moment load ratio and the durability life based on the obtained results. In addition,
The moment load ratio is represented by the following equation (5).

Moment load ratio = Moment load / (Rolling element diameter × Dynamic rated load) ‥‥ (5) As can be seen from the results in FIG. 10, when the moment load ratio becomes 0.18 or more, Example 5 and Comparative Example Although there is a difference in the durability life from No. 1, there is no difference between them when it is 0.10 or less. That is, the effect obtained by changing the material for forming the cage from the conventional material as in Comparative Example 1 to the resin composition as in Example 5 is obtained for a bearing having a moment load ratio of 0.18 or more. The greater the moment load ratio, the higher the effect obtained. <Differences in performance due to differences in cage shape> Pocket gap ratio When a moment load is applied, the pocket gap of the cage is preferably large in order to avoid restraining the rolling elements by the cage. In order to perform sufficient lubrication with the lubricating component (PTFE) transferred from the rolling elements to the rolling elements, the smaller the size, the better. If the pocket gap ratio is small, abrasion powder is likely to be generated from the start of rotation until the pocket shape conforms to the rolling element diameter.

Using the retainer material of Example 5 above,
A number of cages having different pocket diameters were manufactured, and a number of rolling bearings having different pocket gap ratios were assembled using the inner ring, the outer ring, and the rolling elements of Example 5. For these bearings, a durability test was performed by applying a moment load using the above-described testing machine. FIG. 11 is a graph showing the relationship between the pocket gap ratio and the durability life based on the obtained results.

From these results, in the case of a rolling bearing used in a vacuum and under a state in which a moment load is applied, the pocket gap ratio is preferably in a range G of 1.0 to 5.0%, It can be seen that the range H is more preferably in the range of 1.5 to 4.0%. Insertion part gap ratio Assembling of a deep groove ball bearing using a crown type cage is performed by inserting rolling elements between the inner ring and the outer ring, arranging them at equal intervals, and then inserting the cage from the side. At this time, the rolling element insert portion (reference numeral 42 in FIG. 2) of the retainer is elastically deformed, so that the rolling element enters the pocket (reference numeral 41 in FIG. 2). If the opening size of the insertion portion (reference numeral b in FIG. 2) is too large, the retainer is likely to come off. If it is too small, the insertion portion may be greatly deformed and the cage may be damaged.

Therefore, it is necessary to optimize the ratio of the opening dimension of the rolling element insertion portion to the diameter of the rolling element (the above-described insertion portion gap ratio), but the value varies depending on the material of the retainer. Specifically, when the main component of the resin composition constituting the material for forming the cage is PPS (polyphenylene sulfide), the insertion portion gap ratio is 90 to 96%,
85 to EK (polyetheretherketone)
98% is 90 to 98% for PI (polyimide)
However, in the case of PA (polyamide), 87 to 93%
In the case of TFE (ethylene tetrafluoroethylene copolymer), 88 to 94% is preferable, and in the case of polyoxybenzoyl homopolymer, 75 to 97% is preferable.

[0061]

As described above, the rolling bearing of the present invention has a long service life under a high temperature of 300 ° C. or more and a vacuum environment due to the excellent self-lubricating property and heat resistance of the cage. . Therefore, according to the present invention, it is possible to obtain a rolling bearing suitable for a film forming apparatus used for manufacturing a semiconductor element or a magnetic recording apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a rolling bearing including an outer ring, an inner ring, a rolling element, a cage, and a seal.

FIG. 2 is a sectional view showing the structure of a crown-shaped retainer.

FIG. 3 is an enlarged view showing a pocket portion of the cage of FIG. 2;

FIG. 4 is a graph showing a relationship between a compounding ratio of a resin composition (polyoxybenzoyl and PTFE) forming a cage and a wear rate of the cage.

FIG. 5 is a graph showing a relationship between a pocket gap ratio and a dust generation number.

FIG. 6 is a graph showing a relationship between an insertion portion gap ratio and a durability time.

FIG. 7 is a graph showing a relationship between a guide gap ratio and a durability time.

FIG. 8 is a schematic sectional view showing the structure of a rolling bearing used in the second embodiment.

FIG. 9 is a schematic cross-sectional view showing the structure of a tester used in the second embodiment.

FIG. 10 is a graph showing a relationship between a moment load ratio and a durability life.

FIG. 11 is a graph showing a relationship between a pocket gap ratio and a durability life.

[Explanation of symbols]

 Reference Signs List 1 outer ring 2 inner ring 3 rolling element 4 retainer 5 seal 6 shield 7 vacuum chamber wall 8 housing 9 heating member 11 heat insulating material 12 weight 13 magnetic seal unit 14 pulley 15 bracket 16 leaf spring 17 strain gauge J bearing S shaft

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiki Takagi 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Nippon Seiko Co., Ltd. (72) Inventor Shin Shinseki 1-5-150 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Nippon Seiko Co., Ltd. (72) Inventor Sonzo Hamamoto 1-5-50 Kugenuma Shinmei, Fujisawa City, Kanagawa Prefecture Nippon Seiko Co., Ltd.

Claims (1)

[Claims] In a rolling bearing having an inner ring, an outer ring, a rolling element, and a cage, the cage has a polytetrafluoroethylene (PTFE) and polyoxybenzoyl content of 10 to 70% by weight. A rolling bearing characterized by being formed of a material blended so that