JPH09177799A - Roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roller bearing in which the service life of a bearing due to generation of uneven wear is improved, and the rotation with low torque is performed while the irregular torque is suppressed. SOLUTION: A roller bearing is provided with an outer ring 4 having an outer ring raceway 4a on an inner circumferential surface, an inner ring 6 having an inner ring raceway 6a on an outer circumferential surface, a plurality of rollers 8 interposed between the outer ring raceway and the inner ring raceway, a cage 10 to hold a plurality of rollers in a rolling manner, a pair of seal plates 12 to form a clearance part which is locked between the outer ring and the inner ring and incorporates the roller bodies and the cage, and the grease GR filled in the clearance part. The grease GR whose consistency is in the range of 310-475 is filled in the clearance part of the roller 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, and more particularly to a rolling bearing suitable as a component of a hard disk drive device.

[0002]

2. Description of the Related Art For example, a rotating portion such as a swing arm or a stepping motor of a hard disk drive device (hereinafter referred to as HDD device) is supported by rolling bearings. This rolling bearing includes an outer ring having an outer ring raceway on an inner peripheral surface, an inner ring having an outer diameter smaller than the outer ring and having an inner ring raceway on an outer peripheral surface, and a plurality of intervening rings interposed between the outer ring raceway and the inner ring raceway. The rolling element and a retainer that holds the plurality of rolling elements in a rollable manner are provided. Further, a pair of seal plates are locked on both axial side portions between the outer ring and the inner ring, and the pair of seal plates, the outer ring and the inner ring form a void portion in which the rolling element and the cage are built. There is. Then, the gap is filled with grease in order to ensure lubrication of the contact portions of the outer ring, the inner ring and the cage with respect to the rolling elements.

[0003]

By the way, the above-mentioned rolling bearings for swing arms and stepping motors are
Rotation of a small angle (swing angle) of 360 degrees or less (one rotation or less) is frequently repeated (hereinafter, this operation is referred to as a swing operation), and the contact position of the rolling element with the outer ring raceway and the inner ring raceway is locally. The wear life of the bearing is likely to be shortened because the unevenness of the worn portion is likely to occur.

Further, the conventional rolling bearing for a stepping motor requires high torque for its rotating operation.
For HDD devices aiming at downsizing and power reduction, rolling bearings that rotate with low torque are required. Further, the conventional rolling bearing may cause torque unevenness due to the phenomenon of being caught by the filled grease, which is problematic in terms of reliability of read operation and write operation of the HDD device.

As a method for solving the above problem, a rolling bearing which can reduce the torque by reducing the grease filling amount and can suppress the torque unevenness is conceivable. However, the uneven wear due to the reduction of the grease filling amount is considered. The bearing life is likely to be shortened due to the occurrence of. On the contrary, when the amount of grease filled is increased, uneven wear can be eliminated and the bearing life can be improved, but it is difficult to reduce the torque of the bearing and suppress the torque unevenness.

Therefore, the present invention has been made in view of the above circumstances, and it is possible to improve the life of the bearing shaft due to occurrence of uneven wear and to perform rolling operation of low torque while suppressing torque unevenness. The purpose is to provide a bearing.

[0007]

In order to solve the above problems, a rolling bearing according to the present invention has an outer ring having an outer ring raceway on an inner peripheral surface, an inner ring having an inner raceway on an outer peripheral surface, the outer ring raceway and the inner ring. A plurality of rolling elements interposed between the raceways, a retainer that rotatably holds the plurality of rolling elements, and a gap that is locked between the outer ring and the inner ring and that contains the rolling elements and the retainer. In a rolling bearing including a pair of seal plates forming a portion and grease filled in the void, the grease has a consistency of 310 to 475.

Here, the consistency of the grease is a numerical value indicating the degree of softness of the grease.
When the consistency is low, the softness is low and the fluidity is low, and when the consistency is high, the softness is high and the fluidity is high. As described above, the inventors of the present invention have a phenomenon that the bearing life is apt to be shortened due to the occurrence of uneven wear when the bearing swings, a high torque is required for the rotating operation of the bearing, and torque unevenness occurs. As a result of earnest research on the phenomenon of being easy, we have found the factors that cause these phenomena. That is, there is a strong correlation between the consistency of grease used as a lubricant and the above-mentioned phenomenon. When the consistency of grease is less than 310, uneven wear occurs and high torque is required to rotate the bearing. In addition, it was confirmed that torque unevenness was likely to occur. On the other hand, it was confirmed that if the consistency of the grease is higher than 475, uneven wear is likely to occur, and grease leakage also occurs.

The reason for this is that the consistency of grease is 310
If it is less than 1, the grease with reduced fluidity will give a load to the rotation of the bearing, so a high torque is required to rotate the bearing,
In addition, the grease with reduced fluidity prevents smooth rotation of the bearing, resulting in uneven torque. Further, since the grease with reduced fluidity cannot enter the contact surfaces of the rolling elements and the outer ring raceway and the inner ring raceway, and it is difficult to form a lubricating oil film, uneven wear is likely to occur.

When the consistency of the grease is more than 475, the grease with increased fluidity is likely to leak, the grease required for lubrication is insufficient, and uneven wear is likely to occur in durability. On the other hand, the consistency is 3
The rolling bearing of the present invention in which the gap is filled with grease in the range of 10 to 475 has a fluidity such that the grease does not exert a load on the rotation of the bearing, so that the bearing is rotated with a low torque. In addition, since the grease does not have an adverse effect such as being caught at the time of rotation operation of the bearing, torque unevenness does not occur. Further, the grease having the above-mentioned consistency surely enters the contact surfaces of the rolling elements with the outer ring raceway and the inner ring raceway to form a lubricating oil film of a required thickness, so that uneven wear occurs even if the bearing oscillates. Hard to do. Furthermore, since the fluidity of the grease has not increased so much, no grease leakage occurs.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings and tables. In FIG. 1, the rolling bearing of the present invention is applied to a radial ball bearing 2. This radial ball bearing 2 includes an outer ring 4 having an outer ring raceway 4a formed on an inner peripheral surface thereof, an inner ring 6 having an inner ring raceway 6a formed on an outer peripheral surface thereof, and a plurality of balls interposed between the outer ring raceway 4a and the inner ring raceway 6a. (Rolling bodies) 8, a cage 10 for holding the balls 8 at equal intervals along a predetermined circumference, and axially separated from each other and engaged with the inner peripheral side of the outer ring 4 and the outer peripheral side of the inner ring 6. And a pair of seal plates 12 that are formed. The grease GR is filled in the space surrounded by the outer ring 4, the inner ring 6 and the pair of seal plates 12.

The grease GR is a mixture of a base oil, a thickener and various additives in a predetermined amount. As the base oil, for example, mineral oil, ester oil, ether oil, synthetic hydrocarbon oil, fluorine oil and the like are used. As the thickener, urea, lithium complex, lithium soap, fluororesin, etc. are used. Further, as the additive, a rust preventive agent, an extreme pressure agent, an antiwear agent, an antioxidant, a viscosity index improver and the like are used to the extent that the performance of the radial ball bearing 2 is not impaired.

Here, as shown in Tables 1 and 2, a plurality of radial ball bearings 2 filled with a plurality of types of grease GR having different consistency are designated as the specimens A to J, and the respective specimens A are tested.
The rocking durability, torque performance, and grease leakage of J were verified. The consistency is a numerical value indicating the degree of softness of the grease GR. When the consistency is low, the softness is decreased and the fluidity is reduced, and the consistency is large. When it becomes a numerical value, the grease GR has increased softness and increased fluidity.

The grease GR filled in each of the test objects A to J is mixed with the base oil and the thickener shown in columns a and b of Tables 1 and 2 and set to the consistency shown in column d. Has been done. The radial ball bearings 2 of the test objects A to J are
A miniature ball bearing with an inner diameter of 5 mm, an outer diameter of 13 mm, and a width (axial length) of 4 mm was used. And
The swing durability described above is the same as that of the outer ring swing tester 16 shown in FIG.
Are used to verify each of the test objects A to J. The outer ring swing tester 16 has a rotating cylinder 18 having an inner diameter substantially the same as the outer diameter of the DUT, and an outer diameter substantially the same as the inner diameter of the DUT. The fixed shaft 22 coaxially arranged in the rotating outer cylinder 18 is provided. And
Inside the rotary cylinder 18, a plurality of DUTs having the fixed shaft 22 inserted into the inner diameter portion are mounted. Here, the plurality of DUTs are arranged between the DUTs adjacent to each other by the sleeve 24a.
By sequentially mounting 24 to 24e, they are spaced from each other. In addition, the uppermost sleeve 24a and the fixed shaft 22
A preload spring 26 that applies an axial load to each DUT via the sleeves 24a to 24b is mounted between the preload spring 26 and the tip of the. Then, the rotary cylinder 18 is connected to an AC servo motor 28, and by the drive of the AC servo motor 28, the repetitive rotary motion of a predetermined minute angle (swing angle) is transmitted to the rotary cylinder 18, and each test object A is tested. ~ J outer ring 4
However, it is designed to swing within the swing angle. The axial load described above is 117.6 N and the swing angle is 8
And the number of rocking repetitions was 10 million times.

Then, the acceptance / rejection judgment of the rocking durability shown in (1) of Tables 1 and 2 is carried out after each rocking durability test.
J is disassembled and the wear state of the outer ring 4, the inner ring 6 and the cage 10 is observed, and the outer ring raceway 4a, the inner ring raceway 6a, the cage 10 have no wear points, or the outer ring raceway 4a and the inner ring raceway 6a are run. Those with a mark were judged to be acceptable (○), and those with a worn portion were judged to be unacceptable (×).

As for the torque performance, the inner ring 6 was rotated at 3600 rpm by a rotating device with an axial load of 19.6 applied to each of the test objects A to J, and the torque and torque fluctuation required at the initial stage of rotation were measured. did. Then, the torque performance pass / fail judgment shown in (2) of Table 1 and Table 2 is performed by the inner ring 6
The torque required for the rotation of 1.2 gfcm or less and the torque fluctuation of 0.2 gfcm or less were evaluated as pass (◯), and those above were rejected (x).

Further, the grease leakage is 30% of the volume when the volume of the space surrounded by the outer ring 4, the inner ring 6 and the pair of seal plates 12 of each DUT is 100%.
A pair of seal plates 1 filled with some grease GR
Each of the test objects A to J was left standing for 7 days in a state in which 2 was oriented in the vertical direction. Then, the grease leakage pass / fail judgment shown in (3) of Tables 1 and 2 is passed when the grease GR does not leak from the engaging portion of the seal plate 12 engaged with the outer ring and the inner ring 6 (○). And the grease GR leaking was rejected (x).

[0018]

[Table 1]

[0019]

[Table 2]

From the results shown in Tables 1 and 2, the test objects A to E (the test objects shown in Table 1) filled with the grease GR whose consistency was set in the range of 310 to 475 were:
It was revealed that the rocking durability, the torque performance and the grease leakage were all passed. The reason why the torque performance is deteriorated is that, for example, when the grease GR whose consistency is set to less than 310 is filled, the grease GR whose softness is decreased is the outer ring 4, the inner ring 6 and the pair of seal plates 1.
The fluidity in the void surrounded by 2 is reduced. The grease GR having the lowered fluidity gives a load to the rotation of the inner ring 6, so that the torque required for the rotation of the inner ring 6 increases.
Further, since the fluidity of the grease GR is lowered, the inner ring 6 is not smoothly rotated, and the inner ring 6 is rotated in a caught state, resulting in torque unevenness and increased torque fluctuation. This becomes clear from the pass / fail judgment of the torque performance of the test objects F, H, and J in Table 2 in which the consistency was set to less than 310.

The cause of grease leakage is that, for example, when the consistency of the grease GR is set to a value higher than 475, the grease GR, which becomes too soft and has increased fluidity, engages with the outer ring and the inner ring 6. Leakage easily occurs from the engaging portion of the seal plate 12 that is present. This means that the test object G in Table 2 having the consistency set to a value higher than 475,
It becomes clear from the pass / fail judgment of grease leakage of I.

Further, the reason why the swing durability is deteriorated is that, for example, when the grease GR whose consistency is set to less than 310 is filled, the grease GR whose fluidity is deteriorated is a contact surface between the outer ring raceway 4a and the balls 8, It cannot easily enter the contact surface between the inner ring raceway 6a and the ball 8 and the contact surface between the cage 10 and the ball, and the lubricating oil film is less likely to be formed. As a result, wear is likely to occur in the portion where the lubricating oil film is not formed. This becomes clear from the pass / fail judgment of the swing durability of the device under test J in Table 2 in which the consistency is set to less than 310.

Further, for example, when the grease GR having the consistency set to a value higher than 475 is filled, grease leakage occurs and the amount of grease required for lubrication becomes insufficient, so that the durability is deteriorated. This becomes clear from the pass / fail judgment of the rocking durability of the test objects G and I in Table 2 in which the consistency is set to a value higher than 475. Thus, in the present embodiment,
It has been clarified that the radial ball bearing 2 filled with the grease GR having a consistency of 310 to 475 has excellent swing durability, torque performance and grease leakage.

Therefore, the consistency of grease GR should be 3
The radial ball bearing 2 in the range of 10 to 475 has a fluidity such that the grease GR does not impose a load on the rotation of the bearing, and the bearing can be rotated with a low torque. It can be used as a component of an HDD device. Moreover, when the bearing is rotating, the grease G
Since R does not have an adverse effect such as being caught and torque unevenness does not occur, it does not hinder the reading operation and the writing operation of the HDD device.

Even when the swing motion is frequently repeated by using it as a swing arm or a bearing for a stepping motor, the grease having the consistency within the above-mentioned range does not contact the contact surface between the ball 2 and the outer ring raceway 4a and the inner ring raceway 6a. Further, since the lubricating oil film having a required thickness is formed by reliably entering the contact surface with the cage 10, uneven wear does not occur, and grease leakage does not occur, so that the bearing life can be improved.

In the present embodiment, the radial ball bearing used as a component of the HDD device has been described. However, even if it is used as another component, the bearing shaft life due to uneven wear is improved and the torque unevenness is reduced. It is possible to obtain the effect of lowering the torque while suppressing. Further, it is not limited to the radial ball bearing, and the same action and effect can be obtained with other rolling bearings.

The types of the base oil and the thickener are not limited to those shown in Tables 1 and 2 or the above-mentioned ones, as long as the consistency of the grease GR can be set in the range of 310 to 475. Materials may be used.

[0028]

As described above, in the rolling bearing of the present invention, the consistency of grease is in the range of 310 to 475, and the rolling bearing frequently repeats the rotation of a minute angle of 360 degrees or less. Even if the contact points of the rolling elements with the outer ring raceway and the inner ring raceway are localized, the grease with appropriate fluidity will surely enter the contact surfaces of the rolling elements with the outer ring raceway and the inner ring raceway, and have the required thickness. Since the lubricating oil film is formed, uneven wear does not occur and grease leakage does not occur, so that the life of the bearing can be improved.

Further, since the grease has a fluidity that does not give a load to the rotation of the bearing, it is possible to rotate the bearing with a low torque, and the grease is not caught during the rotating operation of the bearing. Since there is no adverse effect, torque unevenness can be suppressed.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a radial ball bearing according to the present invention.

FIG. 2 is a view showing an outer ring rocking tester used for verifying rocking durability of the rolling bearing of the present invention.

[Explanation of symbols]

 2 Radial ball bearings (rolling bearings) 4 Outer ring 4a Outer ring raceway 6 Inner ring 6a Inner ring raceway 8 Balls (rolling elements) 10 Retainer 12 Seal plate GR Grease A to J DUT (rolling bearing)

Claims (1)

[Claims] 1. An outer ring having an outer ring raceway on an inner peripheral surface, an inner ring having an inner ring raceway on an outer peripheral surface, a plurality of rolling elements interposed between the outer ring raceway and the inner ring raceway, and a plurality of these rolling elements. A retainer that holds the roll freely, a pair of seal plates that are locked between the outer ring and the inner ring and that form a void portion that houses the rolling element and the retainer, and grease that fills the void portion. A rolling bearing comprising: the grease having a consistency of the grease in a range of 310 to 475.