JPH08326760A - Retainer for low torque variation bearing - Google Patents

Abstract

PURPOSE: To provide a retainer for a low torque variation bearing of high performance which is mounted in a bearing, can be used in the condition of small torque variation at low torque, and the condition of low noise and low generation of dust can be maintained for a long time. CONSTITUTION: A crown-shaped bearing retainer in which spherical-surface- shaped ball holding pockets 6 are formed opening on one face in the axial direction of a ring-like retainer main body 5, is formed out of a porous resin compact adopting a polyimide resin sintered body having communicating vent holes at porosity of volume ratio 5-25%, by volume, impregnated with lubricating oil of viscosity 10-350cSt at 40 deg.C, the leaching quantity and the leaching speed of lubricating oil are stabilized, and hence this bearing retainer is constituted. The leaching quantity of lubricating oil to a friction face is limited to the degree so as to form monomolecular oil film, and generation of dust is low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a bearing cage,
In particular, the present invention relates to a low-torque bearing retainer used in a rolling bearing that requires low torque and low torque fluctuation during rotation.

[0002]

2. Description of the Related Art It is desirable to mount a bearing retainer that is most suitable for the operating condition of the bearing in terms of lubrication performance and strength. In particular, it has low torque and low torque fluctuation characteristics (Jitter) during rotation. Regarding the cage used for the rolling bearing of the required equipment, consideration of material selection is extremely important as well as its shape.

Here, as a typical example of equipment required to have a low torque and a low torque fluctuation characteristic at the time of rotation, a spindle of a hard disk drive (hereinafter abbreviated as HDD), a laser beam printer (hereinafter abbreviated as LBP). Scanner motor, a video tape recorder (hereinafter abbreviated as VTR) cylinder motor, and the like.

As a shape of the cage, which can easily obtain a low torque and a low torque fluctuation relatively stably, there is, for example, a crown type.

The crown type bearing cage shown in FIG. 2 has one reference plane 4 perpendicular to the axial direction of the annular cage body 1.
A pair of holding claws 2 facing each other at regular intervals in the circumferential direction are provided. The holding claws 2 are curved in a direction approaching each other, and a spherical ball holding pocket 3 is formed between them to reduce low torque fluctuation. Bearing retainer.

Such a bearing cage usually has an inner diameter of 6
It is an ultra-compact bearing cage of mm or less, the ball (rolling element) is stably held by a relatively large area holding claw, and the torque fluctuation is relatively small with low torque, but the cage material is that much. Since it is easily affected by the sliding characteristics due to the above, grease was used for filling the important points.

[0007]

However, when the bearing rotates at a high speed of about 10,000 revolutions / minute while the bearing is in use, the agitation resistance of grease becomes remarkable and the torque of the shaft supported by the bearing becomes large. And the torque fluctuates.

Further, since grease is usually used for lubrication, there is a problem that minute particles (mist) of grease and dust adhering thereto are generated in the atmosphere around the bearing during use of the bearing.

Such a dusting phenomenon occurs in HDDs, VTRs, DATs, Ls, which must be manufactured and assembled in a clean atmosphere.
It is a very important problem in precision machine factories such as BP and semiconductor manufacturing facilities.

The problem associated with such dust generation is shown in FIG.
In the cage shown in Fig. 4, a cylindrical protrusion is formed on the reference surface 4 to prevent the grease from moving out of the cage, or a grease scattering prevention wall is provided along the outer diameter surface or the inner diameter surface. It didn't improve enough.

As an example of improving the lubricant of the cage,
Example using a small amount of liquid lubricating oil (Japanese Patent Laid-Open No. 64-460)
No. 11, JP-A-6-249244) is also known, but with this, the amount of lubricating oil cannot be supplied sufficiently to the rolling contact surface, so durability was not sufficient.

Therefore, an object of the present invention is to solve the above-mentioned problems and to use a bearing in a stable state with a low torque and no torque fluctuation, and further, a low noise and a low dust generation state for a long time. It is an object of the present invention to provide a retainer for a high-performance low-torque variable bearing which can be maintained.

[0013]

In order to solve the above-mentioned problems, in the present invention, a porous resin molding having open pores with a porosity of 5 to 25 volume% in volume ratio has a viscosity of 10 at 40 ° C. The cage for the low torque variable bearing was constructed by impregnating with lubricating oil of up to 350 cSt.

As the above-mentioned porous resin sintered body, a polyimide resin sintered body can be adopted.

[0015]

In the cage for low torque variable bearings according to the present invention, the porous resin molding having the communicating pores with the predetermined porosity is impregnated with the lubricating oil having the predetermined viscosity, so that a large amount of the lubricating oil can be efficiently added. It becomes possible to keep the amount of lubricating oil leached and the rate of leaching stable, and to exhibit extremely stable lubricity for a long period of time.

Further, since the amount of lubricating oil leached to the friction surface is always limited to the extent that the oil film forms a monomolecular film, the amount of lubricating oil scattered or evaporated in the atmosphere is small,
Low dust emission.

When a polyimide resin sintered body is adopted as the porous resin molded body, it has excellent heat resistance, chemical resistance, mechanical properties, and electrical insulation as a retainer for a low torque variable bearing, and it is a precision electronic device. Applicable to equipment bearings.

[0018]

[Embodiment] The resin used as a molding material for the cage for low torque variable bearings of the present invention may be a known resin that can be molded into a porous body. The cage used for the bearing that supports the shaft rotating at high speed also needs to have heat resistance, and thus polyimide resin can be used as a suitable resin.

The polyimide resin (hereinafter abbreviated as PI resin) referred to herein is a resin having an imide bond in the main chain, which is obtained by polycondensing an aromatic carboxylic acid and an aromatic amine, and has heat resistance. , Having a well-known chemical structure having chemical resistance, mechanical properties, and electrical characteristics (either a thermoplastic resin or a thermosetting resin may be used). In addition, PI
The resin is a generic term that includes a resin having a imide bond and an amide bond in the main chain and called a polyamide-imide resin (hereinafter abbreviated as PAI resin).

Commercially available PI resins that can be used in the present invention include those manufactured by Ranging AG of Austria:
P84-HT, manufactured by Toray: TI-3000, manufactured by Ube Industries: UIP-SR, manufactured by DuPont: Vespel, manufactured by Mitsui Toatsu Kagaku: Aurum, and particularly, as a PAI resin, manufactured by Amoco: Torlon. 4000TF is mentioned.

In order to improve the moldability and sliding properties of PI resin, PTFE, graphite, molybdenum disulfide,
A solid lubricant such as boron nitride may be added.

As a method for producing a porous resin molded body, a powdery resin is pressure-molded at room temperature (or room temperature) and then fired in an inert gas or a pressure atmosphere, or heat compression molding or a ram. A molding method such as extrusion molding or CIP can be adopted.

The porous resin molded body is manufactured so as to have continuous air holes with a porosity of 5 to 25% by volume. Because, if it is less than 5% by volume, the retention rate of the impregnated oil becomes low, and the cage cannot exhibit lubricity for a long period of time. If the porosity exceeds 25% by volume, the exudation amount is controlled and the mechanical strength of the cage is reduced. The reason is that a preferable one cannot be obtained. The molded product having the porosity of the above volume ratio can be obtained by appropriately adjusting the particle size (average particle size) of the raw material resin powder, the molding pressure, the firing temperature, and the like.

The lubricating oil used in the present invention has a viscosity at 40 ° C. of 10 to 350 cSt. Because, in a lubricating oil having a viscosity less than a predetermined range, the lubricating oil retained in the porous resin molded body having the above-mentioned porosity oozes out early,
This is because lubrication becomes defective in a short time and torque and torque fluctuation increase, and in extreme cases, seizure occurs, resulting in poor rotation of the bearing. Also, if the viscosity of the lubricating oil exceeds the predetermined range, it is difficult for the lubricating oil to enter the pores of the resin molded body due to the high viscosity, and the amount of retained lubricating oil becomes too small, which may cause the rotation failure of the bearing. In addition, the stirring resistance of the lubricating oil becomes large, the torque for rotating the shaft supported by the bearing becomes large, and the torque easily fluctuates.

In order to impregnate the porous resin molded product having the open pores having the predetermined porosity as described above with the lubricating oil having the predetermined viscosity, it is preferable to impregnate the porous resin molded article in a reduced pressure atmosphere, preferably in a heated state. It is preferable to remove air and moisture, and after impregnation, wipe off excess lubricating oil,
A cage for a low torque variable bearing can be manufactured.

[Example 1] PI resin powder having a structural formula represented by the following chemical formula 1 (manufactured by LENZING: P84-H)
T, average particle size 25 μm) molding pressure 2000 kgf / c
m ² , firing temperature in nitrogen atmosphere 350 ° C., sintering time 2
A cage (equivalent to 684 model number: outer diameter φ) made of a porous resin sintered body that is molded and sintered under the conditions of time and has a porosity of 25%.
6.87mm, inner diameter φ5.30mm, height 1.90m
m) was obtained.

[0027]

Embedded image

That is, as shown in FIG. 1, the shape of the retainer for low torque variable bearing has a spherical shape for retaining a spherical ball which is open on one surface in the axial direction of the annular retainer body 5. It is a crown-shaped bearing cage in which pockets 6 are formed.

The porous resin sintered body was dipped in a polyol ester oil, depressurized to 1 Torr and impregnated into the continuous ventilation hole. Then, the excess oil on the surface of the sintered body is wiped off with a clean cloth, and the cage is attached to the bearing steel (S
UJ2) test bearing (corresponding to the 684 model number mentioned above)
Built in.

The torque fluctuation (jitter), torque, sound, dust generation amount, and durability time of this bearing under predetermined conditions were measured by the following test methods, and the results are shown in Table 1.

Measurement of rotational speed fluctuation rate (jitter) The rotational speed was measured with an FG jitter measuring instrument. The measurement conditions are 10 rpm and 15,000 rpm.
After aging for a minute, jitter measurement was performed 5 times for 30 seconds, and the maximum value (rotational speed fluctuation rate:%) was obtained.

Measurement of Torque The torque (gf · cm) was measured under the conditions of a rotation speed of 15000 rpm and an axial load of 1 kgf.

Acoustic measurement Rotation speed 10,000 rpm, axial load 0.5 kgf
The acoustic value (dBA) after 100 hours of operation was measured under the conditions.

Measurement of dust generation amount In a room temperature atmosphere, a test bearing (having a retainer of an example or a comparative example described later) was rotated under the conditions of an axial load of 1 kgf and a rotation speed of 10,000 rpm,
With a dust detector (a system that counts with a sensor that uses a laser beam) placed directly below it,
Dust having a size of 0.38 μm or more was detected for 150 hours, and the total number (pieces) was examined.

Durability test At room temperature, axial load 1 kgf, rotation speed 10000 rp
Under the condition of m, the durability time in which the vibration acceleration of the bearing rotates within three times the initial value was examined. In that case, the target was 5000 hours, and the test was stopped when the vibration value exceeded a predetermined condition.

[0036]

[Table 1]

[Second Embodiment] In the first embodiment, a predetermined P
Instead of the I resin, PI having the structural formula shown in the following chemical formula 2
Resin (made by Toray: TI-3000, free sinter product,
A cage and a test bearing incorporating the cage were manufactured in exactly the same manner except that the porosity of 7%) was used.

[0038]

Embedded image

With respect to this test bearing, the above-mentioned tests
The results are shown in Table 1.

Example 3 A PI resin powder having a structural formula represented by the following chemical formula 3 (UIP-San Co., Ltd .: UIP-S, average particle size 10 μm) was molded under a nitrogen atmosphere at a molding pressure of 4000 kgf / cm ² . Was molded and sintered under the conditions of a firing temperature of 400 ° C. and a sintering time of 2 hours to obtain a cage (corresponding to 684 model number) made of a porous resin sintered body having a porosity of 15%.

[0041]

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This cage was impregnated with polyol ester oil in exactly the same manner as in Example 1, and the test bearings incorporating the cage thus obtained were subjected to the above-mentioned tests 1 to 3, and the results are also shown in Table 1. .

Example 4 A PI resin powder having a structural formula represented by the following chemical formula 4 (manufactured by Mitsui Toatsu Chemicals Inc .: Aurum, average particle size 25 μm) was molded at a molding pressure of 1000 kgf / cm ² ,
A cage (corresponding to a 684 model bearing) made of a porous resin sintered body having a porosity of 20% was obtained by molding and sintering under a nitrogen atmosphere at a firing temperature of 350 ° C. and a sintering time of 2 hours. .

[0044]

[Chemical 4]

This cage was impregnated with the polyol ester oil in exactly the same manner as in Example 1, and the test bearings incorporating the cage thus obtained were subjected to the above-mentioned tests 1 to 3, and the results are also shown in Table 1. .

Example 5 A PI resin powder having a structural formula represented by the following chemical formula 5 (manufactured by Amoco, USA: Torlon 400)
0TF, average particle size 30μm), molding pressure 2000kg
A cage made of a porous resin sintered body having a porosity of 25%, molded and sintered under the conditions of f / cm ² , a firing temperature of 300 ° C. under a nitrogen atmosphere, and a sintering time of 2 hours (equivalent to a 684 model bearing). Stuff).

[0047]

Embedded image

This cage was impregnated with the polyol ester oil in exactly the same manner as in Example 1, and the test bearings incorporating the cage thus obtained were subjected to the above-mentioned tests 1 to 3, and the results are also shown in Table 1. .

Example 6 A cage was manufactured in exactly the same manner, except that the cage manufactured (sintered) in Example 1 was used and impregnated with an ester synthetic oil having a viscosity at 40 ° C. of 10 cSt. Then, the test bearings incorporating the obtained cage were subjected to the above-mentioned tests 1 to 3, and the results are also shown in Table 1.

[Example 7] Using the cage manufactured (sintered) in Example 1, and impregnated with a fluorinated oil having a viscosity of 350 cSt at 40 ° C (Fomblin YR manufactured by Montefluos), The cage was manufactured in exactly the same manner, the test bearings incorporating the cage obtained were subjected to the above-mentioned tests 1 to 3, and the results are also shown in Table 1.

[Comparative Example 1] A test bearing made of a bearing steel corresponding to the above-mentioned 684 model (inner and outer rings and balls are SUJ2, and a crown type cage made of polyamide resin having a porosity of 0% is incorporated, and a common oil / fat is used. Company Grease: Multemp SRL 2
(encapsulated mg) was produced, and the above-mentioned tests 1 to 5 were performed on this bearing, and the results are also shown in Table 1.

[Comparative Example 2] A test bearing made of bearing steel corresponding to the above-mentioned 684 model number (inner and outer rings and balls are SUJ2, a crown retainer made of polyamide resin is internally provided, and a retainer made of poly ale ester oil is retained. The bearing was impregnated with 1% by weight of the cage), and the above-mentioned test was performed for this bearing.
The results are shown in Table 1.

Comparative Example 3 A cage was prepared in the same manner as in Example 1 except that the cage was made of a dense PI resin molded body (porosity 0%) and was not impregnated with polyol ester oil. The test bearings manufactured and obtained and incorporating the cage were subjected to the above-mentioned tests 1 to 3, and the results are also shown in Table 1.

[Comparative Example 4] A cage obtained by manufacturing a cage in the same manner as in Example 1 except that the cage was made of a PI resin porous molded body (porosity 30%). The above-described tests 1 to 3 were carried out on the test bearing incorporating the above, and the results are also shown in Table 1.

[Comparative Example 5] In Example 1, in place of the polyol ester oil of the impregnating lubricating oil, a fluorinated oil having a viscosity of 510 cSt at 40 ° C. (Fomblin YR-1800 manufactured by Montefluos) was used. Other than the above, a cage is manufactured in exactly the same manner, and a test bearing incorporating the obtained cage is subjected to the above-mentioned tests.
The results are also shown in Table 1.

As is clear from the results shown in Table 1, the bearing in which Comparative Example 1 which is a polyamide (PA) resin cage is used and which is filled with grease is inferior in all the test items such as torque fluctuation. Met. Further, Comparative Example 2 in which a cage made of polyamide resin is impregnated with a small amount of lubricating oil without using grease has a short service life of 500 hours of the bearing, and a comparative example of 0% porosity not impregnated with lubricating oil. Three
Had an even shorter life. Further, in Comparative Example 4 in which the porosity exceeds the predetermined range, the durability time was 3000 hours,
It wasn't durable enough. Further, in Comparative Example 5 in which the viscosity of the impregnating lubricating oil exceeded the predetermined range, the amount of dust generation and durability of the bearing could not be sufficiently improved.

In contrast to these comparative examples, the bearings using the cages of Examples 1 to 7 satisfying all the conditions were evaluated for each of the test items of torque fluctuation, torque, sound, dust generation amount, and durability time. Also gave excellent results.

Therefore, a bearing using such a retainer is a miniature bearing (an ultra-small, low torque variable bearing) for precision equipment such as a HDD spindle, an LBP scanner motor, and a VTR cylinder motor. It was clear that in some cases it had very good properties.

[0059]

As described above, the present invention provides a cage for low torque variable bearings in which a porous resin sintered body having continuous pores with a predetermined porosity is held in a state of being impregnated with lubricating oil having a predetermined viscosity. Therefore, the leaching amount and the leaching speed of the lubricating oil are stable,
In addition, it has highly efficient lubricity, can be used in a stable state with low torque when mounted on the bearing, and has little torque fluctuation, and has high performance and low torque that can maintain a low noise and low dust generation state for a long time. There is an advantage in providing a cage for variable bearings.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a crown type bearing cage according to an embodiment taken along a diametrical direction.

FIG. 2 is an enlarged perspective view showing an essential part of another embodiment of a crown type bearing cage.

[Explanation of symbols]

 1, 5 Cage main body 2 Holding claws 3, 6 Pockets 4 Reference plane

Claims (2)

[Claims] 1. A porous resin molded product having continuous pores with a porosity of 5 to 25% by volume, and having a viscosity at 40 ° C. of 10 to 10.
A cage for a low torque variable bearing which is impregnated with a lubricating oil of 350 cSt. 2. The cage for low torque variable bearing according to claim 1, wherein the porous resin molded body is a sintered body of polyimide resin.