JP2001241448A - Ball bearing cage and ball bearing - Google Patents

Abstract

(57) [Problem] To reduce dynamic torque while preventing generation of cage sound. A plurality of projections are formed on the inner surface of each pocket. These pockets 10, 10
The above problem is solved by narrowing the range in which a thin oil film is formed between the inner surface of the ball and the rolling surface of the ball to reduce the shear resistance of the oil film acting between these two surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The ball bearing retainer and ball bearing of the present invention include a hard disk drive (HDD), a video tape recorder (VTR), a digital video disk (DVD), a mini disk (MD) spindle motor and the like. The present invention relates to a ball bearing incorporated as a rotation support portion of various devices, such as a ball bearing incorporated as a rotation support portion of various electric devices, and an improvement of a retainer incorporated in the ball bearing to guide a plurality of balls in a freely rolling manner.

[0002]

2. Description of the Related Art A ball bearing 1 as shown in FIG. 5 is widely used to rotatably support a rotating portion such as a rotating shaft constituting various devices with respect to a fixed portion such as a housing. In this ball bearing 1, an inner race 3 having an inner raceway 2 formed on the outer peripheral surface and an outer race 5 having an outer raceway 4 formed on the inner peripheral surface are arranged concentrically, and between the inner raceway 2 and the outer raceway 4 is provided. A plurality of balls 6, 6 are provided so as to roll freely. The plurality of balls 6, 6 are rotatably held by a holder 8.
The outer peripheral edges of the annular shield plates 7 and 7 are engaged with the inner peripheral surfaces of both ends of the outer ring 5, respectively, and the grease existing in the portion where the balls 6 and 6 are installed is secured by the shield plates 7 and 7. Is prevented from leaking to the outside, or dust floating outside is prevented from entering the installation portion.
In addition, as the sealing device, the non-contact type shield plates 7 and 7 are used.
Instead, a contact-type sealing plate may be used.
In the case of a ball bearing for an HDD, a shield plate or a seal plate may be provided only on one side in the axial direction.

[0003] In the case of the illustrated example, the retainer 8 is a so-called crown type retainer, and is configured as shown in detail in Figs. The retainer 8 includes an annular main portion 9 and a plurality of pockets 10 and 10 provided at equal intervals on one axial surface of the main portion 9. These pockets 10, 10
Is a pair of elastic pieces 1 spaced from each other.
1 and 11 and a concave portion 12 provided on one surface (the upper surface in FIGS. 7 and 8) of the main portion 9 and between the pair of elastic pieces 11 and 11 respectively. 8 are open on the inner diameter side and the outer diameter side. Each of the balls 6, 6 is held in each of the pockets 10, 10 so as to be able to roll freely. Each pocket 1 configured in this way
The inner surfaces of 0 and 10 are entirely spherical concave surfaces, and the radius of curvature of the spherical concave surface is slightly larger than the radius of curvature of the rolling surfaces of the balls 6 and 6. Such a cage 8
Are integrally formed by injection molding a synthetic resin.

[0004] Each of the balls 6, 6 is connected to each of the pockets 10,
The pair of elastic pieces 11, 11 forming the pair 10 are pushed into the space between the pair of elastic pieces 11, 11 while elastically expanding the interval between the distal ends thereof. Then, in the pushed-in state, as shown in FIG. 9, the balls 6, 6 are rollably held in the pockets 10, 10, respectively. In this state, there is a small gap between the rolling surface of each of the balls 6, 6 and the inner surface of each of the pockets 10, 10. Therefore, in a state where the balls 6, 6 are held in the pockets 10, 10, the retainer 8 holds the balls 6, 6 at equal intervals in the circumferential direction, and the balls 6, 6, 6 restricts the position of the retainer 8 in the diameter direction.

[0005] The ball bearing 1 incorporating the retainer 8 as described above.
Is generally performed with a lubricant such as grease injected between the pair of shield plates 7. In order to smoothly rotate the ball bearing 1 based on the lubrication of a lubricant such as grease, the rolling surface of each of the balls 6, 6 and the inner surface of each of the pockets 10, 10 are required. In the interim, it is necessary to ensure that an appropriate amount of lubricant is present. In view of such circumstances, Japanese Unexamined Patent Application Publication No. 10-68421 describes a ball bearing retainer in which minute irregularities are formed on the inner surface of each pocket. In the case of the prior art described in the above publication, an oil film is formed between the rolling surface of each ball and the inner surface of each pocket based on the existence of such fine irregularities, and the rolling of each of these balls is performed. The oil film is interposed over the entire surface of the portion facing the inner surface of each pocket. The size of the fine unevenness is 2 to 10 μm Ra (R
(a: center line average roughness) is described in the above publication.

[0006]

When only the lubrication of the rolling surface of each ball and the inner surface of each pocket is considered, the prior art described in the above-mentioned publication is sufficient, but the dynamic torque of the ball bearing is sufficient. A problem arises when trying to reduce it. That is, the lubricant such as grease that has entered the pocket having the fine irregularities formed on the inner surface spreads over substantially the entire surface of the inner surface of the pocket and the rolling surface of the ball that oppose each other. In other words, the entire minute gap existing between the inner surface of the pocket and the rolling surface of the ball is almost completely filled, and a thin oil film is formed between these two surfaces. In such a thin oil film portion, a relatively large shear resistance is generated when the ball rolls, and the force required for rolling the ball increases, thereby increasing the dynamic torque.

[0007] An increase in the dynamic torque caused by the above-mentioned causes can be prevented to some extent by reducing the amount of lubricant such as grease sealed in the ball bearing. However, when such a method is employed. In this case, the amount of lubricant such as grease existing between the inner surface of the pocket and the rolling surface of the ball tends to be insufficient, instead of reducing the torque. Then, the frictional state between these two surfaces becomes unstable, and noise or vibration called retainer sound is likely to occur. The ball bearing retainer and the ball bearing of the present invention have been made in view of such circumstances.

[0008]

SUMMARY OF THE INVENTION Among the ball bearing cages and ball bearings of the present invention, the ball bearing cage described in claim 1 is different from the conventional cage shown in FIGS. Similarly, in order to hold a plurality of balls rolling freely, the whole is formed in an annular shape,
At a plurality of positions in the circumferential direction, there are provided pockets each opening on the outer diameter side and the inner diameter side. In particular, in the ball bearing retainer according to the first aspect, an uneven surface is formed on the inner surface of each pocket. In addition, in the uneven shape referred to in this specification,
It does not include fine particles that cannot be restricted in specific shape and that can only form an oil film that generates a large shear resistance, as expressed by the concept of surface roughness specified in JIS B0601. In other words, the uneven shape can regulate a specific shape, and in an oil film having a thickness corresponding to the height difference between the concave portion and the convex portion, no shear resistance is generated, or even if generated, the shear resistance is negligible. Say things. More specifically, the height difference between the concave portion and the convex portion is 0.03 mm or more, and more preferably 0.05 mm or more.

Further, among the ball bearing cage and the ball bearing of the present invention, the ball bearing according to the second aspect has an inner race having an inner raceway formed on the outer peripheral surface, similarly to the ball bearing shown in FIG. When,
An outer ring having an outer raceway formed on an inner peripheral surface thereof; a ball bearing retainer disposed between the outer peripheral surface of the inner race and the inner peripheral surface of the outer race so as to be rotatable relative to the inner race and the outer race; and the ball bearing. And a ball disposed between the inner raceway and the outer raceway while being rotatably held in a plurality of pockets provided in the cage. In particular, in the ball bearing described in claim 2, the ball bearing retainer is the ball bearing retainer described in claim 1.

[0010]

The ball bearing retainer of the present invention having the above-described structure can hold a lubricant such as grease in a concave portion of the concave / convex shape formed on the inner surface of the pocket. The lubricant held in the recesses in this way, along with the rolling of the ball in the pocket,
It enters between the rolling surface of this ball and the convex portion of the inner surface of this pocket, forming an oil film between these two surfaces,
The rolling of the ball in the pocket is performed smoothly.
Even in this case, since a relatively large gap exists between the rolling surface of the ball and the concave portion, no oil film is formed between the rolling surface and the concave portion, or even if the oil film is formed. , Does not result in a thin oil film that generates large shear resistance. Therefore, the shearing resistance acting between the rolling surface of the ball and the inner surface of the pocket is reduced, and the dynamic torque of the ball bearing incorporating the ball bearing retainer can be reduced.

[0011]

1 and 2 show a first embodiment of the present invention. The feature of the present invention is that by modifying the shape of the inner surface of the pocket, the ball acts between the inner surface and the ball rolling surface without reducing the amount of lubricant such as grease. Reduce the resistance to rolling of
The point is to achieve both low torque and prevention of cage noise at a high level. Since the configuration and operation of the other parts are the same as those of the above-described conventional structure, the illustration and description of the equivalent parts are omitted or simplified, and the following description will focus on the characteristic parts of the present invention.

A plurality of pockets 10 provided in a crown-shaped retainer 8a, which are integrally formed by injection molding a synthetic resin,
A large number of projections 13 are formed on the inner surface of each of the projections 13, each of which is a projection having an uneven shape. Each of these projections 1
Reference numerals 3 and 13 are formed in an arbitrary shape considering a workability and an oil film forming property, such as a partial spherical shape, a cylindrical shape, a square prism shape, a truncated cone shape, a truncated cone shape, and the like. 1 to
The height is about 0.2 mm and the height is about 0.05 to 0.1 mm.
In addition, as a synthetic resin constituting such a retainer 8a,
Although various types which have been conventionally used for manufacturing a cage can be used, preferably, a polyamide resin, an oil-containing polyamide resin, a polyacetal resin, an oil-containing polyacetal resin, or the like is used. Further, reinforcing agents such as glass fiber, potassium titanate, and whiskers can be added to these synthetic resins.

When the cage 8a constructed as described above is incorporated in a ball bearing and this ball bearing is rotated, a large number of projections 13, 13 formed on the inner surfaces of the pockets 10, 10 are formed.
A lubricant such as grease can be held in a concave portion of the uneven shape, which is a portion deviated from the shape. The lubricant held in the recesses in this manner causes the rolling surface of the ball and the respective pockets 10 and 10 to roll along with the rolling of the ball in the pockets 10 and 10.
Of the inner surface of each of the projections 13, 13 and the tip of each of the projections 13, 13 to form an oil film between the two surfaces, so that the rolling of the ball in each of the pockets 10, 10 can be smoothly performed. Let them do it. For this reason, the rolling of the ball in each of the pockets 10 and 10 can be smoothly performed, and generation of noise or vibration called retainer sound can be effectively prevented.

As described above, even when the rolling of the balls in the pockets 10 and 10 is performed smoothly, the rolling surfaces of the balls and the concave portions which are portions deviated from the projections 13 and 13 are formed. There is a relatively large gap (thickness of 0.05 mm or more) between them. Therefore, no oil film is formed between the rolling surface and the concave portion, or even if it is formed, it does not become a thin oil film that generates large shear resistance. For this reason, the rolling surface of each ball and each pocket 10,
The shearing resistance acting on the inner surface of the ball bearing 10 can be reduced to reduce the dynamic torque of the ball bearing incorporating the retainer 8a.

As a modification of the shape of this embodiment, it is conceivable to form a large number of recesses on the inner surface of each pocket. However, in order to form a large number of recesses on the inner surface of the pocket, it is necessary to form a large number of projections on a part of the mold, and this processing of the mold is troublesome and increases the cost. On the other hand, in the case of this example, in order to form each of the projections 13, 13, it is sufficient to form a concave hole in a part of the mold. , 13 can be kept low.

Next, FIGS. 3 and 4 show a second example of the embodiment of the present invention. In the case of this example, the concave grooves 14 each having a concave-convex shape are formed on the inner surfaces of the plurality of pockets 10, 10 provided in the crown-shaped retainer 8 b integrally formed by injection-molding a synthetic resin. , 14 are formed two for each of these pockets 10, 10. These concave grooves 14 and 14 are respectively provided at the portions where the inner diameters of the respective pockets 10 and 10 are the largest.
0 in the circumferential direction.

Each of the grooves 14 becomes deeper toward the distal end surface of the elastic piece 11 forming the pocket 10 and becomes gradually shallower toward the center of each pocket 10. , And smoothly continue with the inner surface of the central portion of each of the pockets 10, 10. Each such groove 1
Width W ₁₄ of the 4 and 14 0.1 to 0.2 mm, the depth D ₁₄ is directed to 0.05~0.1mm most deepened portions of the tip surface portion of each elastic piece 11, 11.

When the retainer 8b constructed as described above is incorporated in a ball bearing and the ball bearing is rotated, the concave grooves 14 formed on the inner surfaces of the pockets 10
A lubricant such as grease can be retained. Thus, each groove 1
The lubricant held in the pockets 4 and 14 is applied to each of the pockets 10 and 1
With the rolling of the ball within 0, the concave grooves 14, of the rolling surface of the ball and the inner surface of each of the pockets 10, 10.
The ball enters between the pockets 10 and 10 to form a film of oil between the two surfaces so that the balls can smoothly roll in the pockets 10 and 10. For this reason, the rolling of the ball in each of the pockets 10 and 10 can be smoothly performed, and generation of noise or vibration called retainer sound can be effectively prevented.

As described above, even when the rolling of the balls in the pockets 10 and 10 is performed smoothly, there is a gap between the rolling surface of each of the balls and the bottom of each of the concave grooves 14 and 14. There are relatively large gaps. Therefore, no oil film is formed between these rolling surfaces and the concave grooves 14, or even if formed, the oil film does not become thin enough to generate a large shear resistance. Therefore, the shearing resistance acting between the rolling surface of each ball and the inner surface of each of the pockets 10, 10 can be reduced, and the dynamic torque of the ball bearing incorporating the retainer 8b can be reduced. In order to further reduce the dynamic torque, each of the concave grooves 14, 14 should be
May be formed on both sides of each of the pockets 10, and four for each of the pockets 10, 10.

[0020]

The ball bearing retainer and ball bearing of the present invention are:
Because of the above-described configuration and operation, it is possible to reduce the dynamic torque of the ball bearing while preventing generation of harmful noise and vibration such as cage noise. For this reason, it is possible to improve the performance of various rotary devices incorporating the ball bearing and to save energy.

[Brief description of the drawings]

FIG. 1 is a perspective view of a retainer, showing a first example of an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a perspective view of a retainer showing a second example of the embodiment of the present invention.

FIG. 4 is an enlarged view of a portion B in FIG. 3;

FIG. 5 is a sectional view showing an example of a ball bearing incorporating a retainer.

FIG. 6 is a half plan view showing an example of a conventional structure of a cage.

FIG. 7 is a perspective view of the same.

FIG. 8 is a view showing a cross section taken along the line CC of FIG. 7 except for cut portions.

FIG. 9 is a diagram showing a cross section taken along line DD of FIG. 8 in a state where a ball is incorporated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ball bearing 2 Inner ring track 3 Inner ring 4 Outer ring track 5 Outer ring 6 Ball 7 Shield plate 8, 8a, 8b Cage 9 Main part 10 Pocket 11 Elastic piece 12 Concave surface 13 Protrusion 14 Concave groove

Claims (2)

[Claims] 1. A ball bearing having a plurality of balls formed so as to be able to roll freely, and formed in an annular shape as a whole, and provided with pockets which are respectively opened at a plurality of positions in a circumferential direction on an outer diameter side and an inner diameter side. A cage for a ball bearing, wherein an uneven shape is formed on an inner surface of each of the pockets. 2. An inner race having an inner raceway formed on an outer peripheral surface thereof, an outer race having an outer raceway formed on an inner peripheral surface thereof, and a relative position between the outer race surface of the inner race and the inner peripheral surface of the outer race with respect to the inner race and the outer race. A ball bearing retainer rotatably disposed, and the ball bearing retainer is disposed between the inner ring raceway and the outer ring raceway while being held in a plurality of pockets provided in the ball bearing retainer so as to freely roll. A ball bearing comprising a ball, wherein the ball bearing cage is the ball bearing cage according to claim 1.