JP2002155953A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing excellent in rotating precision, which hardly produces unequal arrangement of rolling elements, and has an extremely little NRR-fc constituent. SOLUTION: This rolling bearing 1 comprises an inner ring 2; an outer ring 3; a plurality of balls 4 rotationally arranged between the inner ring 2 and the outer ring 3; and a crown retainer 5 for holing the balls 4 between both rings 2, 3. The crown retainer 5 is guided by the inner ring 2, and a guide clearance C is set to 0.25 to 1.5% of an inner diameter R of the 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 hard disk drive (hereinafter referred to as HDD), a flexible disk drive (FDD), a video tape recorder (VTR), a digital audio tape recorder (DAT), Laser beam printer (LB
TECHNICAL FIELD The present invention relates to a rolling bearing suitably used for a rotation supporting portion requiring high rotational accuracy in information equipment such as P) and audio / video equipment.

[0002]

2. Description of the Related Art In a rolling bearing used for the above-mentioned applications, runout (NRR) of an asynchronous component of rotation is a serious problem. In particular, HDDs have a recording density improvement rate exceeding 100% per year, and the number of tracks per inch (TPI: track per inch) is increasing.
RR reduction requirements are becoming more stringent. And
Among the NRRs, the NRR-fc component, which is the NRR caused by the cage and the rolling elements, is particularly important.

The causes of the increase in the NRR-fc component are, firstly, a difference in diameter between balls which are rolling elements of a rolling bearing, and secondly, balls are not arranged evenly in a rolling bearing. (Hereinafter referred to as an unequal array). First, the difference between the diameters of the balls, which is the first factor, can be suppressed to some extent by improving the processing accuracy of the balls in recent years.

Next, the unequal arrangement of balls, which is the second factor, will be described. The unequal arrangement of the balls is caused by the cage being eccentric in the rolling bearing, and as a result, the positions of the balls are unevenly distributed. Therefore, if the cage is hardly eccentric in the rolling bearing or the amount of movement of the ball in the pocket of the cage is reduced, the degree of unequal arrangement can be reduced.

On the other hand, the diameter of the pocket of the retainer is slightly larger than the diameter of the ball so that the pocket does not strongly restrain the ball. Therefore, a pocket clearance is formed between the pocket and the ball. It will intervene. The presence of the pocket allows the ball to move within the pocket. The size of such a pocket clearance is designed in consideration of the size of the rolling bearing, the operating conditions of the rolling bearing, the material of the cage and the like.

Therefore, in the conventional rolling bearing, the pocket clearance is designed to be small in order to suppress the unequal arrangement of the balls, and the amount by which the balls can move in the pocket is reduced.

[0007]

However, if the pocket clearance is too small, the ball and the retainer are always in contact with each other due to manufacturing errors, and the space for holding the lubricant is reduced and the pocket edge is reduced. Since the lubricant can be easily scraped off at the part, there is a possibility that problems such as deterioration of acoustic characteristics and seizure may occur due to poor lubrication.
Therefore, there is a limit to reducing the pocket clearance.

Accordingly, the present invention solves such a problem of the conventional rolling bearing, and provides a rolling bearing with excellent rotation accuracy, in which unequal arrangement of rolling elements hardly occurs and an NRR-fc component is extremely small. That is the task.

[0009]

In order to solve the above problems, the present invention has the following arrangement. That is, the rolling bearing of the present invention comprises an inner ring, an outer ring, a plurality of rolling elements rotatably disposed between the inner ring and the outer ring, and a holding mechanism for holding the rolling elements between the two wheels. And wherein the cage is guided by at least one of the inner ring and the outer ring, and the guide clearance is set to 0.25 to 1.5% of the inner diameter of the bearing.

When the guide type of the retainer is the raceway guide, the eccentricity of the retainer is suppressed as compared with the case of ball guide or the like, so that the unequal arrangement of the rolling elements hardly occurs. Further, since the guide clearance is set to 0.25 to 1.5% of the inner diameter of the bearing, the eccentricity of the retainer is suppressed, and the NRR-fc component at a level that is difficult to achieve in the case of ball guide or the like is reduced. It can be easily achieved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rolling bearing according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a structure of a ball bearing 1 according to an embodiment of the present invention, and FIGS. 2 to 4 are perspective views of a crown retainer 5 provided in the ball bearing 1 of FIG. The ball bearing 1 includes an inner ring 2 and an outer ring 3
And a plurality of balls 4 rotatably arranged between the inner ring 2 and the outer ring 3, and a crown retainer 5 for holding the balls 4 between the two wheels 2, 3.

The outer peripheral portions of the ring-shaped seal plates 6 and 6 are engaged with the inner peripheral surfaces of both ends of the outer ring 3 so that the opening between the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 3 is formed. Seal plate 6, 6
The grease (not shown) existing in the space formed between the inner ring 2 and the outer ring 3 (the portion where the balls 4 are installed) leaks to the outside, or the dust floating on the outside Is prevented from entering the space.

Further, the crown-shaped retainer 5 has an annular main portion 8.
And a plurality of pockets 9 provided on one surface of the main part 8. Each pocket 9 is formed by a pair of elastic pieces 10, 10 which are arranged to face each other at intervals. . A pair of elastic pieces 10, 10 constituting each pocket 9
The surfaces facing each other are spherical or cylindrical concave surfaces. The outer edge portion of the pocket 9 may be chamfered or may not be chamfered.

Then, the ball 4 is pushed between the pair of elastic pieces 10 and 10 while elastically expanding the interval between the elastic pieces 10 and 10, so that the crown-shaped retainer 5 holds the ball in each pocket 9. 4 can be held in a freely rolling manner. Such a retainer 5 is integrally formed by molding a resin material by a method such as injection molding.

Examples of the resin material include polyamide resins such as nylon 66 and nylon 46, PTFE, E
Fluorine resin such as TFE, ether ketone resin such as polyetheretherketone resin (PEEK), polyethersulfone resin (PES), polyoxymethylene resin (POM), polybutylene terephthalate resin (PB)
T), linear polyphenylene sulfide resin (LP
PS), polyamide imide resin (PAI), polyether imide resin (PEI), thermoplastic polyimide resin (T
PI), polyether nitrile resin (PEN) and the like.

A reinforcing material such as a fiber may be added to these resin materials in order to impart strength. Examples include glass fibers, carbon fibers, aramid fibers, and various whiskers such as potassium titanate. The amount of the reinforcing material to be added may be appropriately selected in consideration of the strength, moldability, assemblability and the like of the cage. Usually, it is 5 to 40% by weight. Further, a lubricant such as a lubricating oil may be added to these resin materials in order to impart lubricity.

The retainer 5 may be made of a metal material. Further, a plurality of convex portions 7 are provided at equal intervals in the circumferential direction on the inner peripheral surface of the main portion 8 of the retainer 5, and a distal end surface 7 a of the convex portion 7 (inward of the retainer 5). ) Acts as a guide surface for the retainer 5. That is, the distal end surface 7a of the convex portion 7 and the outer peripheral surface (retainer guide surface) of the inner ring 2 face each other via the guide clearance C to guide the rotation of the retainer 5 and to prevent the retainer 5 from being eccentric. The accompanying whirling is prevented. The size of the guide clearance C is 0.25 to 1.5% of the bearing inner diameter R. In addition, the number of the protrusions 7 is not particularly limited as long as it acts as a guide surface of the retainer 5.

As described above, since the guide of the cage 5 of the ball bearing 1 is the inner ring guide, the eccentricity of the cage 5 is suppressed as compared with the case of the ball guide. It is unlikely to occur. Further, since the guide clearance C is set to be small as described above, the eccentricity of the retainer 5 is suppressed, and the pocket clearance is not particularly reduced. Can easily be achieved.

The shape of the convex portion 7 is not particularly limited as long as it has a surface acting as a guide surface of the retainer 5, and in addition to the substantially rectangular parallelepiped shape as shown in FIG. It may have a cylindrical shape or a hemispherical shape (not shown). In the case of the convex portion 7 or the hemispherical convex portion as shown in FIG. 3, a curved surface (a cylindrical surface or a spherical surface) facing the inside of the retainer 5 becomes the distal end surface 7a.

The projection 7 may be provided continuously over the entire circumference of the inner peripheral surface of the retainer 5 as shown in FIG. Further, a convex portion 7 may be provided on the outer peripheral surface of the main portion 8 of the crown-shaped cage 5, and the guide type of the cage may be outer ring guide. In that case, the front end surface 7 a of the convex portion 7 (the surface facing the outside of the cage 5) acts as a guide surface of the cage 5.

That is, the front end surface 7a of the convex portion 7 and the inner peripheral surface (retainer guide surface) of the outer ring 3 are opposed to each other via the guide clearance C, and guide the rotation of the retainer 5, and 5 is prevented from whirling. The size of the guide clearance C is 0.25 to 1.5% of the bearing inner diameter R. The operation and effect of such a ball bearing are the same as those of the above-described ball bearing 1 for inner ring guide.

It is to be noted that convex portions 7 are provided on both the inner peripheral surface and the outer peripheral surface of the main portion 8 of the crown-shaped cage 5 so that the crown-shaped cage 5 is guided by both the inner ring and the outer ring. Is also good. Next, the result of calculating the NRR-fc component of the above-described inner ring guide ball bearing will be described. When the cage 5 is maximally eccentric in the radial direction, the NRR-fc component causes the ball 4 to
In the eccentric direction of the cage 5 in the eccentric direction of the cage 5 (contact with the pocket), and assuming that the unequal arrangement of the balls 4 is maximized (see FIG. 5).

As the ball bearing, the size of the guide clearance C is set to 0.25%, 0.5%, 1.0%, 1.5% of the bearing inner diameter R.
%, 2.0% and 2.5%, and
For each of them, one in which the size of the pocket gap was changed by several kinds was prepared. As a comparative example, a ball bearing provided with a ball guide retainer was also prepared by changing the size of the pocket clearance by several types. Note that this NRR-fc
In the calculation of the components, the ratio between the pocket diameter and the ball diameter of the retainer (pocket diameter / ball diameter) was used as a scale indicating the size of the pocket clearance. The ball bearing has an inner diameter of 4m.
m, outer diameter 10 mm, width 2.6 mm, ball diameter 1/16 inch, bearing number of 8 balls.

FIG. 6 is a graph showing the result of calculating the NRR-fc component for the various ball bearings described above. Straight lines 61-
66 shows the result of the ball bearing having the inner ring guide retainer, and the straight line 67 shows the result of the ball bearing having the ball guide retainer. The straight line 61 has a guide clearance C of 0.25% of the bearing inner diameter R, and the straight line 62 has a same clearance of 0.5%.
The straight line 63 is 1.0%, the straight line 64 is 1.5%, the straight line 65 is 2.0%, and the straight line 66 is 2.5%. The horizontal axis of the graph is the ratio between the diameter of the pocket of the cage and the ball diameter indicating the size of the pocket clearance, and the vertical axis is the NRR-fc component.

In the present calculation of the NRR-fc component, the pocket diameter / ball diameter is calculated up to 1.01, but when the cage is actually manufactured, the pocket roundness and tolerance are calculated based on the roundness and tolerance of the pocket. Considering this, the design limit of pocket diameter / ball diameter is about 1.02. That is, if the pocket clearance is made smaller than this, the pocket will restrain the ball due to deviation from the perfect circle of the pocket shape, dimensional tolerance, expansion and contraction due to temperature change, etc. May scrape off the lubricant and cause poor lubrication.

The pocket diameter / ball diameter is 1.0, which is the design limit.
In the case of 2, the NRR-fc component achievable in the comparative example (a ball bearing having a ball guide retainer) is 13 nm (straight line 67).
reference). With the increasing recording density of HDDs, N
A reduction in RR is required, and in that case, it is expected that the NRR-fc component needs to be 10 nm or less. However, it is extremely difficult to achieve the above with a ball bearing having a ball guide retainer as described above. It is.

As can be seen from the graph, the ball bearing provided with the inner ring guide retainer is more effective in reducing the NRR-fc component than the ball bearing provided with the ball guide retainer. However, if the guide clearance C is large, the effect tends to be small. When the guide clearance C is set to 1.5% or less of the inner diameter R of the bearing, an NRR-fc component equal to or more than the lower limit of 13 nm of the ball bearing having the ball guide retainer can be achieved. (When the pocket diameter / ball diameter is 1.02).
When the guide clearance C is less than 0.25% of the inner diameter R of the bearing, the guide surface of the retainer (the end surface 7a of the convex portion 7) and the inner race 2
The friction torque with the outer peripheral surface of the tire increases, which may cause poor lubrication or seizure. Therefore, it is preferable that the guide clearance C be 0.25% or more and 1.5% or less of the bearing inner diameter R.

Next, the NRR-fc component was calculated in the same manner as described above using another ball bearing having dimensions different from those of the above-described ball bearing. This ball bearing has an inner diameter of 5 mm, an outer diameter of 13 mm,
The bearing has a width of 4 mm, a ball diameter of 2 mm, and eight balls. Also,
The size of the guide clearance C is 0.5% of the inner diameter R of the bearing.
Those having 0%, 1.5%, 2.0% and 2.5% were prepared.

The calculation results are shown in the graph of FIG. Straight line 71
Numerals 75 indicate results of the ball bearing having the inner ring guide retainer, and straight lines 76 indicate the results of the ball bearing having the ball guide retainer. The straight line 71 has the guide clearance C of 0.5% of the bearing inner diameter R, the straight line 72 has the same 1.0%, the straight line 73 has the same 1.5%, and the straight line 74 has the same value as 2.
In the case of 0%, the straight line 75 is also the case of 2.5%.

As can be seen from the graph of FIG. 7, in the case of this ball bearing, similarly, the guide clearance C is set to 1.5 times the inner diameter R of the bearing.
%, The NRR-fc component can be suppressed to a very small value. As described above, in the ball bearing of this embodiment, the guide type of the cage is the inner ring guide, and the guide clearance C is 0.25 to 1.5% of the bearing inner diameter R.
The NRR-fc component is extremely small, and the rotation accuracy is very excellent.

Therefore, such a ball bearing can be suitably used for a rotation supporting portion of an HDD. Note that the ball bearing of the present embodiment can be applied not only to the HDD but also to the rotation supporting portions of various devices. Note that this embodiment shows an example of the present invention,
The present invention is not limited to this embodiment.

For example, in the present embodiment, a ball bearing has been described as an example of a rolling bearing. However, the rolling bearing of the present invention can be applied to various other types of rolling bearings. For example, there are radial rolling bearings such as cylindrical roller bearings, tapered roller bearings, and angular ball bearings. Also, the shape and type of the cage, the type of resin material, etc.
The invention is not limited to the embodiment as long as the object of the invention can be achieved.

[0033]

As described above, the rolling bearing of the present invention has the following features.
Since the guide type of the retainer is the raceway guide, the eccentricity of the retainer is suppressed as compared with the case of the ball guide or the like, and uneven arrangement of the rolling elements hardly occurs. In addition, since the guide clearance is set to 0.25 to 1.5% of the inner diameter of the bearing, the eccentricity of the cage is suppressed, and the level of the NRR-fc component which is difficult to achieve in the case of ball guide or the like is easily reduced. Can be achieved.

Therefore, the rolling bearing of the present invention has a very high rotational accuracy.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of a ball bearing which is one embodiment of a rolling bearing of the present invention.

FIG. 2 is a perspective view of a crown cage provided in the ball bearing of FIG. 1;

FIG. 3 is a perspective view showing a modified example of the retainer of FIG.

FIG. 4 is a perspective view showing another modified example of the retainer of FIG.

FIG. 5 is a conceptual diagram showing a state of balls in which a cage is eccentric and is unequally arranged.

FIG. 6 is a graph showing a correlation between a pocket clearance and an NRR-fc component.

FIG. 7 shows the pocket clearance and NRR in another ball bearing.
It is a graph which shows the correlation with -fc component.

[Description of Signs] 1 Ball bearing 2 Inner ring 3 Outer ring 4 Ball 5 Crowned cage 7 Convex part 7a Tip surface C Guide clearance R Bearing inner diameter

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroya Anami 5-5-150 Kumeinuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3J101 AA01 AA32 AA42 AA52 AA62 AA72 BA53 BA54 FA41 GA53

Claims (1)

[Claims] 1. An inner ring, an outer ring, a plurality of rolling elements rotatably disposed between the inner ring and the outer ring, and a retainer for holding the rolling elements between the two wheels. A rolling bearing, wherein the cage is guided by at least one of the inner ring and the outer ring, and a guide clearance is set to 0.25 to 1.5% of a bearing inner diameter.