JP2000234625A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing with a small change of torque in low torque and with preventable contamination due to vaporization and scattering of a lubricant, while preventing fretting wear generated in the case of a small amount of the lubricant. SOLUTION: In this rolling bearings 27, an inner ring 29 in the internal periphery of an outer ring 31 is arranged, respective raceway surfaces are formed in an internal peripheral surface of the outer ring 31 and an external peripheral surface of the inner ring 29 to interpose a plurality of rolling units (ball 37) between these fellow raceway surfaces to assemble the inner/outer ring 29, 31 relatively rotatably through the rolling unit 37. A coating or thin film obtained by vacuum drying diluted lubricating oil is formed in the raceway surface and the surface of the rolling unit 37.

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 use as, for example, a bearing for a swing arm for a magnetic disk device which slightly swings at a high speed.

[0002]

2. Description of the Related Art A swing arm for a magnetic disk device requires a high-speed, minute swing in order to seek a target track on a magnetic disk with a magnetic head at a high speed and with high accuracy. In order to realize such high-speed and minute swing, a rolling bearing is used for a base swing portion of the swing arm. FIG. 3 is a sectional view of a base end of a swing arm supported by a conventional rolling bearing. A base plate 3 is screwed into a casing 1 of an actuator (for example, a voice coil motor) that performs high-speed, minute swinging, and the lower end of the support shaft 5 is fitted and fixed to one end of the base plate 3. The upper end of the support shaft 5 is screwed to the casing 1 by a screw 6 penetrating the casing 1.

A pair of ball bearings (rolling bearings) 7 are provided on the outer periphery of the support shaft 5 at intervals in the axial direction of the support shaft 5. The ball bearing 7 has an inner ring fixed to the support shaft 5 and an outer ring fixed to the housing 9. A base end of a swing arm 11 is fixed to the outer periphery of the housing 9, and the swing arm 11 is swingably supported by the support shaft 5 via a ball bearing 7. A magnetic head (not shown) is provided at the tip of the swing arm 11. A voice coil section 13 is provided on the outer periphery of the housing 9.
Is provided in a magnetic field formed by a permanent magnet 15 disposed in the housing 9. Therefore, by supplying a predetermined current to the voice coil unit 13 by a magnetic circuit, a turning force is applied, and the swing arm 11 is swung by a predetermined amount.

[0004] In this type of ball bearing 7, a lubricant such as lubricating oil or grease is sealed inside for lubrication. Conventionally, the inside of the bearing has been lubricated with this lubricant.

[0005]

In recent years, with the increase in the density of the magnetic disk device, a narrower space is required between the magnetic head and the magnetic disk.
For this reason, management of contamination (contaminants) becomes more and more important for the reliability of the magnetic disk drive. In particular, since the swing arm is provided close to the surface of the magnetic disk, it is required that the contamination be low. For this reason, a lubricant and a lubricating method with less evaporation and scattering are required for the ball bearing than ever before. On the other hand, the track width of a magnetic disk is becoming increasingly narrower, and a swing arm is required to have faster access to a target track and higher positioning performance. For this reason, the ball bearing supporting the swing arm is required to be free from an increase in torque and a sudden change in torque (torque spike). However, conventional ball bearings for swing arms generally lubricate the inside of the bearing with a lubricant such as grease.
Outgas due to evaporation and scattering is likely to occur,
Various measures have to be taken to prevent these from adhering to the surface of the magnetic disk. In addition, when the amount of grease or the like to be filled is increased to improve durability, there is a problem that viscosity and stirring resistance increase, causing torque fluctuation and torque increase. The present invention has been made in view of the above circumstances, while preventing fretting wear that occurs when there is little lubricant,
An object of the present invention is to provide a rolling bearing which has a low torque and a small torque fluctuation and can prevent contamination due to evaporation and scattering of a lubricant.

[0006]

A rolling bearing according to the present invention for attaining the above object has a track surface formed on an inner peripheral surface of an outer ring and an outer peripheral surface of an inner ring, and a plurality of track surfaces are provided between the track surfaces. In the rolling bearing assembled with the rolling elements of
A coating or a thin film obtained by vacuum-drying the diluted lubricating oil is formed on at least the raceway surface and the surface of the rolling element.

[0007] In this rolling bearing, a coating or a thin film obtained by vacuum-drying the lubricating oil is formed on the raceway surface and the surface of the rolling element, so that it is compared with the conventional case where lubricating oil or grease is sealed. In addition, the evaporation and scattering of the lubricant are reduced, and the viscosity and the stirring resistance are greatly reduced, so that the torque is not increased or changed. Therefore, if the rolling bearing according to the present invention is used as a bearing for a swing arm for a magnetic disk drive, high-speed and high-precision operation of the swing arm can be achieved with less contamination.

In the rolling bearing according to the present invention, a seal member for closing an annular gap in the space opened at both end surfaces of the outer ring and the inner ring is fixed to one of the outer ring and the inner ring. Is also good.

In this rolling bearing, the annular gap of the space opened at both end surfaces of the outer ring and the inner ring is sealed by a seal member to prevent foreign matter from entering the inside of the bearing from the outside. The coating or the thin film formed of the lubricant formed on the surface of the rolling element is prevented from scattering to the outside.
This will extend the life of the rolling bearing,
It is possible to reduce contamination due to outgassing of the coating or the thin film.

[0010] Further, a method for forming a lubricating oil film on a rolling bearing includes:
An inner ring is disposed on the inner periphery of the outer ring, raceway surfaces are formed on the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, and a plurality of rolling elements are interposed between the raceways, and the rolling element A method of forming a lubricating oil film of a rolling bearing in which the inner ring and the outer ring are relatively rotatably assembled via a nut, and injecting a pre-diluted lubricating oil into the raceway surface and the surface of the rolling element. Applying the lubricating oil to the raceway surface and the surface of the rolling element by relatively rotating the inner ring and the outer ring, and vacuum-drying the rolling bearing coated with the lubricating oil to form the raceway surface. Forming a coating or a thin film on the surface of the rolling element.

In this method of forming a lubricating oil film for a rolling bearing,
When the diluted lubricating oil is injected and then dried, an extremely small amount of lubricating oil can be easily injected. Further, by vacuum drying the lubricating oil, it becomes possible to form a coating or a thin film at a lower production cost than in the case where the lubricating oil is heat-treated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the rolling bearing according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a swinging part of a swing arm for a magnetic disk device provided with a rolling bearing according to the present invention, and FIG. 2 is an enlarged view of a main part of the rolling bearing shown in FIG.

A lower end of a support shaft 23 is fixed in a casing 21 of an actuator (for example, a voice coil motor) which performs high-speed and minute swinging, and an upper end of the support shaft 23 is screwed to the casing 21 by a screw 25 passing through the casing 21. Be worn.

A pair of ball bearings (rolling bearings) 27 are provided on the outer periphery of the support shaft 23 in the axial direction of the support shaft 23. In the ball bearing 27, the inner ring 29 is press-fitted and fixed to the support shaft 23, and the outer ring 31 is press-fitted and fixed to the housing 33.
A base end of a swing arm (not shown) is fixed to the outer periphery of the housing 33, and the swing arm is swingably supported by the support shaft 23 via a ball bearing 27.

As shown in FIG. 2, the outer race 31 of the ball bearing 27
Of the inner race 29 and the outer peripheral surface of the inner ring 29 have raceway surfaces 35 and 36, respectively.
Are formed. A plurality of balls 37 as rolling elements are interposed between the raceway surfaces 35 and 36 in the circumferential direction. An annular retainer 39 is mounted between the outer race 31 and the inner race 29 to rotatably hold the rolling element. That is, the outer race 31 and the inner race 29 are relatively rotatably mounted via the balls 37.

The inner peripheral surface of the outer race 31 of the ball bearing 27 and the inner race 29
A space 41 accommodating the ball 37 and the retainer 39 is formed between the ball 41 and the outer peripheral surface. The orbital surfaces 35 and 36 disposed in the space 41 and the surface of the ball 37 are provided with a coating or a thin film (in this embodiment, a lubricating oil film) obtained by vacuum-drying a diluted lubricant (lubricating oil). A thin film 42) is formed.
When the amount of the lubricant is 0.3% or less of the volume of the space 41,
It has been confirmed by experiments by the inventor that the fretting wear at an early stage and damage to the raceway surface and the rolling elements are easily caused. Further, it has been confirmed by experiments by the inventor that when the amount of the lubricant is 3% or more of the volume of the space 41, evaporation, scattering, increase and fluctuation of the torque are likely to occur.

Therefore, the thin film 42 formed on the ball bearing 27 according to the present embodiment is formed so as to have a volume of 0.3 to 3% of this space volume. Further, it has been confirmed that the upper limit of the volume of the thin film 42 is more preferably 2% or less in order to keep outgassing low.

As the lubricating oil used for forming the thin film 42, an ester oil or a fluorine oil which oozes less is preferable. In order to keep outgas low, a fluorine-based oil having high affinity is more preferable.

To form the thin film 42, first, the raceway surface 3
The lubricating oil previously diluted (10 to 200 times) with the diluent is injected into the surfaces 5 and 36 and the surface of the ball 37. Then
The inner ring 29 and the outer ring 31 are relatively rotated to apply lubricating oil to the surfaces of the raceway surfaces 35 and 36 and the balls 37. The lubricating oil has at least one of the raceway surfaces 35 and 36, the rolling surface such as the surface of the ball 37, and the sliding surface between the ball 37 and the pocket surface of the cage 39 in advance.
Enclose in places by injection. This is because the lubricating oil is transferred to the entire surface by the subsequent rotation operation, and therefore it is sufficient that the lubricating oil is injected into at least one place. Next, the entire rolling bearing coated with lubricating oil is vacuum-dried, and
A thin film 42 is formed on 5, 36 and the surface of the ball 37.
The sealing of the lubricating oil and the formation of the thin film 42 may be performed by applying an oil plate by dipping (dipping) and then drying the film in a vacuum to form the thin film 42.

As the above-mentioned diluent, an alternative fluorocarbon having high volatility (for example, AK225 trade name) is preferable. The vacuum drying conditions are as follows: a temperature of 80 to 120 ° C.
For about 0.5 to 3 hours.

According to the method of forming the lubricating oil film (thin film 42), the diluted lubricating oil is injected and then dried.
An extremely small amount of lubricating oil can be easily injected. Further, since the lubricating oil is vacuum-dried, the thin film 42 can be formed at a lower manufacturing cost than in the case where the lubricating oil is heat-treated.

In this embodiment, the thin film 42 is formed on the rolling surface and the sliding surface. However, the rolling surface and the sliding surface are preliminarily subjected to a base treatment such as coupling, and thereafter, the coating material or the coating material is formed. When the thin film 42 is formed, the affinity is further increased, and separation or peeling can be suppressed. The term “coating” as used herein refers to any formed material other than a thin film formed by vacuum-drying a diluted lubricant (for example, the film is divided into small regions individually to form an independent island shape). Small solid fats and oils).

As the material of the ball 37, ordinary bearing steel or stainless steel is used. In the case of micro-oscillation (tracking) with random seek in a range of about 30 degrees as in the case of a swing arm bearing, even if a bearing steel or stainless steel is used as the ball material, the amount of the filled lubricant is limited. It has been confirmed that if the volume is in the range of 0.3 to 3%, there is no practical problem in the durability performance of the random seek (fretting wear does not occur over several hundred million times). In applications where the durability performance of a certain area seek is important, it is more preferable to use a ceramic ball having a high hardness as the ball material in order to reduce fretting wear.

The method of fixing the inner race 29 of the ball bearing 27 and the outer race 31 to the support shaft 23 and the housing 33 is press-fitting while vibrating the inner race 29 and measuring the resonance frequency on the outer race 31 side to perform preload control. A resonant press fit method is used. This press-fitting method is a more preferable method because it has a countermeasure against contamination of the magnetic disk surface due to outgassing of the adhesive and an advantage that resonance (rigidity) can be kept constant. The ball bearing 27
The inner ring 29 and the outer ring 31 may be fixed to the support shaft 23 and the housing 33 by bonding.

In order to reduce outgassing and bleeding of the lubricant, both sides of the ball bearing 27 are provided with sealing members 43.
Is preferably sealed. Seal member 43
Is fixed to one of the outer ring 31 and the inner ring 29,
And the annular gap 4 of the space 41 opened at both end surfaces of the inner ring 29
5 is sealed. Since there is no influence on the outgas, the seal member 43 is provided with the inner seal 43 shown in FIG.
A one-sided seal without a may be used.

In the ball bearing 27 thus configured, the thin film 42 obtained by vacuum-drying the lubricating oil forms the raceway surface 35,
By being formed on the surface of the ball 36 and the ball 37, the evaporation and scattering of the lubricant are reduced, and the viscosity and the stirring resistance are greatly reduced as compared with the case where the conventional lubricating oil or grease is sealed. There is no increase or fluctuation in torque.

The annular gap 45 of the space 41 opened at both end surfaces of the outer ring 31 and the inner ring 29 is sealed by a seal member 43 to prevent foreign matter from entering the bearing from the outside, and to prevent the space 41 from entering. Evaporation and scattering of the lubricant sealed in the outside are prevented. As a result, the life of the ball bearing 27 is extended, and contamination due to evaporation and scattering of the lubricant is reduced.

Therefore, according to the above-described ball bearing 27, it is possible to prevent fretting wear at an early stage, to eliminate evaporation and scattering of lubricant, and to increase or fluctuate torque. This has the effect of realizing high-speed and high-precision operation.

In the above embodiment, the case where the rolling bearing is the ball bearing 27 has been described as an example. However, the rolling bearing according to the present invention has the same effect as described above even when used in a roller bearing. is there.

[0030]

As described in detail above, the rolling bearing according to the present invention has a coating or a thin film obtained by vacuum-drying diluted lubricating oil on at least the raceway surface and the surface of the rolling element. , Lubricating oil as a conventional lubricant,
Compared to the case where grease is sealed, evaporation and scattering of the lubricant can be reduced, and increase and fluctuation of the torque can be eliminated. As a result, when used as a bearing of a swing arm for a magnetic disk drive, high-speed and high-precision operation of the swing arm can be realized while preventing contamination.

[Brief description of the drawings]

FIG. 1 is a sectional view of a swinging part of a swing arm for a magnetic disk drive provided with a rolling bearing according to the present invention.

FIG. 2 is an enlarged view of a main part of the rolling bearing shown in FIG.

FIG. 3 is a sectional view of a swinging part of a conventional swing arm for a magnetic disk drive provided with a rolling bearing.

[Explanation of symbols]

 27 ball bearing (rolling bearing) 29 inner ring 31 outer ring 35, 36 raceway surface 37 ball (rolling element) 42 thin film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toru Takamizawa 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3J101 AA02 AA32 AA42 AA52 AA62 BA10 BA70 DA05 EA06 EA67 EA78 FA32 FA35 FA60 GA53 5D068 AA01 BB01 CC12 EE19 GG07

Claims (1)

[Claims] 1. A rolling bearing having a raceway surface formed on an inner peripheral surface of an outer ring and an outer peripheral surface of an inner ring, and a plurality of rolling elements interposed between the raceway surfaces, wherein at least the raceway surface is provided. And a coating or a thin film obtained by vacuum-drying the diluted lubricating oil on the surface of the rolling element.