JP2002139050A - Ball bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drop the dynamic torque when a ball bearing is in operation and reduce the torque variation without bringing about any obstacle in the operation of the ball bearing. SOLUTION: The thickness in the radial direction in that part of a rim 7a to form a retainer 6a which is positioned in dislocation from pockets 9 is made thinner over the whole circumference than the parts where the pockets 9 are provided, and thus a thin walled portion 14 is formed. It is arranged so that grease has not easy access to the gaps between the inside and outside surfaces of the thin walled portion 14, the outside surface of the inner ring 2, and the inside surface of the outer ring 4, and thereby the purpose is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A ball bearing according to the present invention is, for example, a spindle motor of a hard disk drive (HDD) or a flexible disk drive (FDD), or a micro-processing unit (MPU) or an integrated circuit (IC). ) Is used to constitute a rotation support portion for a cooling fan drive motor or the like.

[0002]

2. Description of the Related Art Small ball bearings as shown in FIG. 5 are widely used to support rotating parts of various information devices such as HDDs as described above. In this ball bearing, an inner race 2 having an inner raceway 1 on an outer peripheral surface and an outer race 4 having an outer raceway 3 on an inner peripheral surface are arranged concentrically with each other, and the inner peripheral surface of the outer race 4 and the outer periphery of the inner race 2 are arranged. A crown-shaped retainer 6 is provided in a space 5 between the outer ring 4 and the inner ring 2 so as to be rotatable relative to the outer ring 4 and the inner ring 2. This cage 6 is made of polyamide resin,
It is formed integrally by injection molding a synthetic resin having a low friction coefficient, such as an oil-containing polyamide resin, a polyacetal resin, and an oil-containing polyacetal resin. In addition, if necessary,
A reinforcing agent such as glass fiber, potassium titanate, or whisker is added to such a synthetic resin. In any case, the retainer 6 is formed by forming a plurality of elastic pieces 8 on one surface in the axial direction (the right surface in FIG. 5) of the annular rim portion 7, and the elastic pieces 8 adjacent to each other in the circumferential direction and the rim portion. 7 and a plurality of pockets 9 are provided in a portion surrounded by. And such a retainer 6
Balls 10 and 10 held in each pocket 9 of
Roller is provided between the outer raceway 3 and the inner raceway 1. The positioning of the cage 9 in the diametrical direction is achieved by engagement between the rolling surface of each ball 10 and the inner surface of the pocket 9. In other words, the positioning structure of the retainer 6 is a rolling element guide.

The outer peripheral edges of the sealing plates 12 and 12 are engaged with engaging grooves 11 and 11 formed in the inner peripheral surfaces of both ends of the outer race 4 respectively. ,
Both ends of the inner ring 2 are closely opposed to the outer peripheral surfaces. Such sealing plates 12 and 12 prevent the grease injected into the space 5 from leaking to the outside and prevent foreign substances existing outside from entering the space 5.

[0004]

In the case of a ball bearing to be incorporated in a rotation support portion such as a spindle motor for an HDD, it is required that the dynamic torque required for relative rotation between the outer ring and the inner ring (torque fluctuation) be low. You. That is, the torque fluctuation leads to an increase in NRRO (Non Repetable Run-Out, rotation non-rotational fluctuation) at the time of high-speed rotation, and becomes an obstacle in increasing the density of the HDD. On the other hand, the conventional structure as described above may not always be able to sufficiently suppress torque fluctuations when sufficient durability is taken into consideration. The reason is as follows.

In order to lubricate the rolling contact portions, a part of the grease injected into the ball bearing adheres to the rolling surface of each ball 10 with the operation of the ball bearing. Accordingly, it is sent to the rolling contact portion. At this time, each of these balls 10
A part of the grease adhering to the rolling surface of
And grows gradually on this inner peripheral surface. That is, a part of the grease adhering to the rolling surface of each of the balls 10 is scraped off at the inner peripheral side opening peripheral portion of the pocket 9 of the retainer 6, and the grease adheres to the inner peripheral surface of the retainer 6. Adhere to.

[0006] If the amount of grease adhering to the inner peripheral surface of the cage 6 in this manner is constant, there is no particular effect on torque fluctuation. However, the amount of grease increases with the continuation of the operation of the ball bearing. Therefore, the above-described torque fluctuation occurs. That is, when the amount of grease attached to the inner peripheral surface of the retainer 6 increases, this grease adheres to both the inner peripheral surface of the retainer 6 and the outer peripheral surface of the inner ring 2 (both peripheral surfaces). State). In this state, based on the relative rotation between the cage 6 and the inner ring 2 accompanying the operation of the ball bearing,
A shear force acts on the grease, and the dynamic torque of the ball bearing increases. When the amount of grease adhering to the inner peripheral surface of the retainer 6 further increases, the grease cannot be supported on the inner peripheral surface of the retainer 6 due to the centrifugal force caused by the rotation of the retainer 6, and Is shaken off. Then, the grease is shaken off in this manner, so that the dynamic torque is rapidly reduced. Further, the grease being shaken off from the inner peripheral surface of the retainer 6 may cause grease to leak from the ball bearing.

During operation of the ball bearing, the grease adheres to the inner peripheral surface of the outer race 4 and causes an increase in dynamic torque for the same reason. That is, during operation of the ball bearing, the grease moves toward the outer ring 4 due to centrifugal force, and when the amount of grease attached to the inner peripheral surface of the outer ring 4 increases, the grease is removed from the outer peripheral surface of the cage 6. And the inner peripheral surface of the outer ring 4 is adhered to both peripheral surfaces. Based on the relative rotation between the retainer 6 and the outer ring 4, a shear force acts on the grease, and the dynamic torque of the ball bearing increases. Become.

In order to suppress the increase in the dynamic torque and the fluctuation of the torque of the ball bearing caused by such a cause, the amount of grease injected into the ball bearing may be reduced, or the cage 6 may be used.
The distance between the inner peripheral surface of the inner ring 2 and the outer peripheral surface of the inner ring 2 or the distance between the outer peripheral surface of the retainer 6 and the inner peripheral surface of the outer ring 4 is increased so that grease is not spread between these two peripheral surfaces. Can be considered. However, reducing the amount of grease is not preferable from the viewpoint of ensuring the durability of the ball bearing. It is not preferable to simply increase the distance between the inner and outer peripheral surfaces of the cage 6 and the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 4 for the following reasons.

To increase the distance between the inner peripheral surface of the retainer 6 and the outer peripheral surface of the inner ring 2, the diameter of a shoulder 13 formed on the outer peripheral surface of the inner ring 2 and sandwiching the ball 10 from both sides in the axial direction. It is conceivable to reduce the thickness in the directional direction or to increase the inner diameter of the retainer 6 to reduce the diametrical thickness of the retainer 6. However, when the thickness of the shoulder portion 13 of the inner ring 2 in the diameter direction is reduced, the ball 10 is easily detached from the inner ring track 1, and the rolling surface of the ball 10 is likely to be subjected to excessive surface pressure based on edge stress. However, this is not preferable because it causes the durability of the ball bearing to be impaired. Further, when the thickness of the cage 6 in the diameter direction is reduced, the positioning of the cage 6 by the balls 10 becomes uncertain, and the rattling of the cage 6 during operation of the ball bearings increases, which causes vibration and noise. Therefore, it is not preferable.
This is the same when the distance between the outer peripheral surface of the retainer 6 and the inner peripheral surface of the outer ring 4 is increased. In view of such circumstances, the present invention reduces the dynamic torque and torque fluctuation of a ball bearing,
The present invention was invented in such a manner as not to hinder the operation of the ball bearing.

[0010]

A ball bearing according to the present invention has an inner race having an inner raceway on an outer peripheral surface, an outer race having an outer raceway on an inner peripheral surface, and an annular rim portion, similarly to the above-mentioned conventional structure. A plurality of pockets are provided on one surface in the axial direction, and in a space between the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring, a crown-shaped retainer provided rotatably relative to the inner ring and the outer ring, The retainer includes a plurality of balls rotatably provided between the inner raceway and the outer raceway while being held in the pockets. In particular, in the ball bearing according to the present invention, the thickness of the rim portion of the cage in the diametrical direction near the other surface in the axial direction is increased over the entire circumference in the diametrical direction of the portion where the pockets are provided. It is thinner than the thickness.

[0011]

According to the ball bearing of the present invention configured as described above,
The torque fluctuation during operation can be reduced without hindering the operation of the ball bearing. That is, the portion of the rim portion of the cage near the other surface in the axial direction is a thin portion in which the thickness in the diametric direction is smaller than the diametric thickness of the portion where each pocket is provided over the entire circumference. Accordingly, the distance between the outer peripheral surface of the portion near the other axial surface of the rim portion and the inner peripheral surface of the outer ring or the outer peripheral surface of the inner ring increases. As a result, even if the amount of injected grease is not reduced, it is difficult for the grease to be spread between these two peripheral surfaces (the space between the two peripheral surfaces is not easily blocked by grease). For this reason, it is possible to prevent the dynamic torque of the ball bearing from increasing due to the shearing resistance of the grease generated by being bridged between these two peripheral surfaces, and to suppress the torque fluctuation. In addition, grease that has grown between the inner peripheral surface of the retainer and the outer peripheral surface of the inner ring is less likely to be displaced around by the centrifugal force of the retainer. Is reduced. Furthermore, since it is not necessary to reduce the thickness in the diameter direction of the shoulder portion of the inner ring or the outer ring and the pocket portion of the cage, the balls rolling on the raceway surfaces of the inner ring and the outer ring during the operation of the ball bearing are formed on the raceway surface. There is no adverse effect due to vibration or noise caused by the disengagement or rattling of the retainer.

[0012]

1 and 2 show a first embodiment of the present invention. The feature of the present invention is that the cage 6
In the shape of a, the thickness of the rim portion 7a of the retainer 6a in the diametrical direction near the other surface in the axial direction (the left surface in FIG. 1) is set to a portion provided with the pocket 9 over the entire circumference. The point is that it is thinner. Since the configuration and operation of the other parts are the same as those of the above-described conventional structure, the same reference numerals are given to the same parts, and duplicate description is omitted or simplified. The following description focuses on the differences from the structure. As shown in FIG. 1, the inner ring 2 and the outer ring 4
The retainer 6a provided in the space 5 between the upper and lower surfaces has a plurality of elastic pieces 8, 8 formed on one surface in the axial direction (the right surface in FIG. 1) of the annular rim portion 7a, and is circumferentially adjacent to each other. A plurality of pockets 9 are provided in a portion surrounded by the elastic pieces 8 and the rim portion 7a. In this example, the inner diameter d 'of the portion of the rim portion 7a of the retainer 6a near the other surface in the axial direction is larger than the inner diameter d of the portion provided with the pockets 9 on one axial side (d'> d). The outer diameter D 'of the portion of the rim portion 7a near the other surface in the axial direction is smaller than the outer diameter D of the portion provided with the pockets 9 on one side in the axial direction (D'<D). Is a thin portion 14.

The retainer 6a is incorporated in a ball bearing similarly to the conventional structure, and retains a plurality of balls 10, 10 in the pockets 9, 9, respectively. Further, a space 5 formed between the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 4 is filled with grease, and as described above, this grease is generated by the operation of the ball bearing as described above. It grows on the inner peripheral surface of the outer race 4 and both the inner and outer peripheral surfaces of the cage 6a. However, in the case of the ball bearing according to the present invention, a thin portion 14 is provided at a portion of the rim portion 7a of the retainer 6a near the other surface in the axial direction.
Is formed, it is difficult for grease to spread between the inner and outer peripheral surfaces of the retainer 6a and the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 4. That is, even if the grease adhering to the rolling surfaces of the balls 10 and 10 is scraped off at the peripheral edge of the pockets 9 and adheres to the inner peripheral surface or the outer peripheral surface of the retainer 6a, the thin portion 14 In this case, it is difficult for this grease to grow until it reaches the outer peripheral surface of the inner ring 2 or the inner peripheral surface of the outer ring 4 (before reaching, the grease is shaken around by centrifugal force). Similarly, grease adhering to the inner peripheral surface of the outer ring 4 due to centrifugal force during the operation of the ball bearing does not easily grow until reaching the outer peripheral surface of the thin portion 14 of the retainer 6a. For this reason, the increase in the dynamic torque of the ball bearing due to the shear resistance of grease generated between the inner and outer peripheral surfaces of the thin portion 14 and the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the outer ring 4 is suppressed, and torque fluctuation is suppressed. Can be reduced. or,
Grease leakage caused by grease that has grown between the inner peripheral surface of the retainer 6a and the outer peripheral surface of the inner ring 2 is thrown around by the centrifugal force of the retainer 6a is reduced by the grease between these two peripheral surfaces. Is less likely to be passed over, so that it is reduced.

The effect of reducing the torque fluctuation is improved as the axial length L of the thin portion 14 is increased and becomes closer to the center of the pocket 9.
Positioning becomes uncertain, and vibration and noise due to backlash tend to increase during ball bearing operation. Conversely, when the length L is reduced, vibration and noise due to rattling are less likely to occur, but the effect of reducing the torque fluctuation is reduced. When the length L of the thin portion 14 in the axial direction is increased such that the end of the thin portion 14 is located closer to one side in the axial direction (the right side in FIG. 1) than the center of each of the pockets 9, 9, The adverse effect on vibration and noise due to rattling becomes more remarkable than the effect of reducing the torque fluctuation of 6a. Therefore,
It is desirable that the axial length L of the thin portion 14 is controlled so that the end of the thin portion 14 does not exceed the center of each of the pockets 9.

FIG. 3 shows a second embodiment of the present invention.
An example is shown. In this example, the inner peripheral surface of the retainer 6b is a single cylindrical surface. In other words, the inner diameter of the portion of the rim portion 7b constituting the retainer 6b near the other surface in the axial direction is equal to the inner diameter of the portion provided with the pockets 9 near the one surface in the axial direction. On the other hand, the outer peripheral surface of the rim portion 7b is a stepped cylindrical surface. That is, the outer diameter of the portion of the rim portion 7b near the other surface in the axial direction is smaller than the outer diameter of the portion where the pockets 9 and 9 are provided near the one surface in the axial direction, and this portion is the thin portion 14a. When a ball bearing is formed by such a retainer 7b, only the distance between the inner peripheral surface of the outer ring 4 (see FIG. 1) and the outer peripheral surface of the thin portion 14a increases. As a result, grease is less likely to be spread between the two peripheral surfaces, and an increase in the dynamic torque of the ball bearing due to the shear resistance of the grease at this portion can be suppressed, and torque fluctuation can be reduced.

Next, FIG. 4 shows a third embodiment of the present invention.
An example is shown. In this example, the outer peripheral surface of the rim portion 7c of the retainer 6c is a single cylindrical surface, and the inner peripheral surface is a stepped cylindrical surface. That is, the outer diameter of the portion of the rim portion 7c near the other surface in the axial direction is equal to the outer diameter of the portion provided with the pockets 9 near the one surface in the axial direction. On the other hand, the rim portion 7c
The inner diameter of the portion near the other surface in the axial direction is larger than the inner diameter of the portion where each of the pockets 9 and 9 is provided in the portion near the one surface in the axial direction, and this portion is used as a thin portion 14b. When a ball bearing is constituted by such a retainer 7c, only the distance between the outer peripheral surface of the inner ring 2 and the inner peripheral surface of the thin portion 14b increases.
As a result, an increase in the dynamic torque of the ball bearing due to the shear resistance of the grease in this portion can be suppressed, and the torque fluctuation can be reduced.

[0017]

According to the ball bearing of the present invention configured as described above, the amount of grease to be injected, which may lead to a decrease in durability, is not reduced, and noise or the like due to rattling of the cage is generated. Without increasing the dynamic torque due to the shear resistance of the grease during the operation of the ball bearing, it is possible to prevent the fluctuation of the torque. Also, grease leakage can be reduced. For this reason, it is possible to contribute to the performance improvement of various precision rotation support portions.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first example of an embodiment of the present invention.

FIG. 2 is a perspective view showing only a retainer.

FIG. 3 is a perspective view similar to FIG. 2, showing a second example of the embodiment of the present invention;

FIG. 4 is a perspective view similar to FIG. 2, showing a third example;

FIG. 5 is a sectional view showing an example of a conventional structure.

[Explanation of symbols]

 Reference Signs List 1 inner ring track 2 inner ring 3 outer ring track 4 outer ring 5 space 6, 6a, 6b, 6c retainer 7, 7a, 7b, 7c rim portion 8 elastic piece 9 pocket 10 ball 11 locking groove 12 sealing plate 13 shoulder portion 14, 14a , 14b Thin part

Claims (1)

[Claims] 1. An inner race having an inner raceway on an outer peripheral surface, an outer race having an outer raceway on an inner peripheral surface, and a plurality of pockets provided on one axial side of an annular rim portion, wherein an outer peripheral surface of the inner race and the outer race are provided. In a space between the inner ring surface and the inner ring surface, a crown-shaped retainer provided rotatably relative to the inner ring and the outer ring, and the inner ring raceway and the retainer held in each pocket of the retainer. In a ball bearing provided with a plurality of balls rotatably provided between the outer raceway and the outer ring raceway, the rim portion of the cage has a rim portion having a diametrical thickness that is close to the other surface in the axial direction. A ball bearing characterized in that it is thinner than the diametrical thickness of the portion where each pocket is provided.