JP2003278749A - Bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing unit wherein optimization of rigidity and reduction of torque are simultaneously satisfied, while increasing speed and improving precision of control of an object to be borne. <P>SOLUTION: The bearing unit 1 is furnished with a sleeve 8 capable of assembling a shaft 2 and a plurality of bearings 4, 6 and integrally molding a steppe part 8a to hold the bearings with a specified interval, and each of the bearings is provided with an inner ring 10 on which an inner ring inside diameter surface S1 and an inner ring raceway surface R1 forms a round shape and an outer ring raceway surface R2 forms an oval shape. A radial clearance in the major axial direction X is set larger than a radial clearance in the minor axial direction Y on the outer ring raceway surface R2. Radial rigidity in the minor axial direction of the outer ring raceway surface is set larger than radial rigidity in the major axial direction in a state of giving a specified pre-load by assembling the bearings on the sleeve. A mark M free to visually confirm the major axial direction and the minor axial direction of the oval outer ring raceway surface is attached on each of the bearings. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing unit used in a spindle motor for information equipment such as a hard disk drive (HDD) and a spindle motor for audio / visual equipment such as a video tape recorder (VTR).

[0002]

2. Description of the Related Art Conventionally, in this type of bearing unit, when a bearing and a shaft are assembled to a metal sleeve integrally formed with a step portion functioning as a spacer, the rigidity in the radial direction (hereinafter, referred to as radial rigidity). ) Is given a predetermined preload so that all are at the same level in the circumferential direction.

[0003]

In recent years, there has been an increase in the speed and accuracy of control of a bearing application object to which a bearing unit is applied (for example, a swing arm used in a magnetic disk device or other rotary drive system). In order to meet the demand, the bearing unit is required to prevent occurrence of abrupt torque fluctuation such as torque spike and to reduce the torque. However, conventional bearing units
The preload is adjusted to increase or decrease the radial rigidity, and if the radial rigidity is increased to satisfy the high-speed controllability of the bearing application object, the problem that the torque increases occurs. In this case, a method of increasing the radial rigidity by changing the radial clearance may be considered, but this method causes a problem that the axial rigidity decreases. The present invention has been made to solve such a problem, and an object thereof is to simultaneously achieve optimization of rigidity and reduction of torque while achieving high-speed control and high-precision control of a bearing application object. It is to provide a bearing unit capable of performing the above.

[0004]

In order to achieve such an object, the bearing unit of the present invention is capable of assembling a shaft and a plurality of bearings, and holds the bearings at predetermined intervals. The stepped portion is provided with a sleeve that projects along the circumferential direction and is integrally molded.The bearing has an inner ring whose inner ring inner diameter surface and inner ring raceway surface are circular and an outer ring outer diameter surface is circular. And an outer ring whose outer ring raceway surface has an elliptical shape. In this case, on the raceway surface of the outer ring having an elliptical shape, the radial clearance along the major axis direction is set larger than the radial clearance along the minor axis direction orthogonal to the major axis direction. The radial rigidity of the bearing unit along the minor axis direction of the outer ring raceway surface when the shaft and multiple bearings are attached to the sleeve and a predetermined preload is applied is the radial rigidity along the major axis direction orthogonal to the minor axis direction. It is set larger than the rigidity. Furthermore, each bearing is provided with at least one or more marks by which the major axis direction and minor axis direction of the elliptical outer ring raceway surface can be visually confirmed. When assembling each bearing into the sleeve, visually check the marks on each bearing to make sure that the outer ring raceway surface of each bearing is aligned with the major axis direction and the minor axis direction of the bearings It is possible. Also, when applying a bearing unit to a bearing application target, by visually checking the mark on the bearing, the bearing with the major axis direction of the outer ring raceway of each bearing aligned with the longitudinal direction of the bearing application target. The unit can be positioned with respect to the bearing application object.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A bearing unit according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The technique of the present invention can be applied to rolling bearings including thrust bearings and radial bearings. In the following description, as one example, a bearing unit in which a plurality of ball bearings (two in the drawing) are incorporated in the axial direction will be described as an example, but the present invention is not limited to this. As shown in FIGS. 1A to 1C, in the bearing unit 1 of the present embodiment, the shaft 2 and a plurality of bearings 4 and 6 can be assembled, and the bearings are held at predetermined intervals. The stepped portion 8a for projecting is provided with a sleeve 8 integrally formed by projecting along the circumferential direction, and the bearings 4 and 6 have an inner ring inner surface 1 and an inner ring raceway surface R1 having a perfect circular shape, respectively.
0, and the outer ring 12 whose outer ring outer diameter surface S2 has a perfect circular shape and whose outer ring raceway surface R2 has an elliptical shape. In this embodiment, the shaft 2 is attached to the inner ring inner diameter surface S1 and the sleeve 8 is attached to the outer ring outer diameter surface S2. Bearing 4,
6 are each made of a predetermined metal material (for example, high carbon chrome steel such as stainless steel), and have a plurality of rolling elements 14 installed between the raceways R1 and R2 of the inner and outer rings, and a plurality of these rolling elements. Cage 1 that holds the rolling element 14 of the same
6 and a sealing plate (contact type or non-contact type seal or shield) 18 (the sealing plate 18 is omitted in the right side view of FIG. 1A). The shaft 2 and the sleeve 8 are also preferably made of the same metal material as the bearings 4 and 6. In addition, the outer ring raceway surface R of the bearings 4 and 6
In No. 2, the radial clearance along the major axis direction X is set to be larger than the radial clearance along the minor axis direction Y orthogonal to the major axis direction X. Hereinafter, in this specification, the minor axis direction of the ellipse is defined as the minor axis direction Y of the outer ring raceway surface R2, and the major axis direction of the ellipse is defined as the major axis direction X of the outer ring raceway surface R2. When the bearings 4 and 6 are assembled together with the shaft 2 into the sleeve 8 and given a predetermined preload, the radial rigidity of the bearing unit 1 along the minor axis direction Y of the elliptical outer ring raceway surface R2 is short. The radial rigidity is set to be larger than the radial rigidity along the major axis direction X orthogonal to the direction Y. Specifically, the radial rigidity corresponding to the major axis direction X of the elliptical outer ring raceway surface R2 is set to the smallest and the radial rigidity corresponding to the minor axis direction Y is set to the maximum, and the radial rigidity from the major axis direction X to the minor axis direction Y is set. The radial rigidity is set to continuously increase as the position goes to.

FIG. 3 shows an example in which the magnitude of the radial rigidity is visually displayed. The magnitude of the radial rigidity continuously changes according to the change in the length of the arrow radially extending from the bearing unit 1. You can see that it is increasing and decreasing. In this case, the inner diameter dimension of the elliptical outer ring raceway surface R2 is X in each direction.
The anisotropy of the radial clearance of Y, that is, the anisotropy of radial rigidity is set to an optimum value. That is, the inner diameter dimension of the outer ring raceway surface R2 is not uniformly set, but the purpose and environment of use of the bearing unit 1, or the type and size of the bearing application target 20 to which the bearing unit 1 is applied. The optimum inner diameter is set according to the above. Specifically, the radial clearance is calculated by fixing the one of the inner ring 10 and the outer ring 12 and moving the other in the radial direction (radial direction), and by calculating the movement amount at that time. The optimum value is determined according to the type and specifications of the bearings 4, 6), the purpose of use and the environment of use. In the present embodiment, since the outer ring raceway surface R2 has an elliptical shape, the radial clearances in the major axis direction X and the minor axis direction Y increase / decrease correspondingly. Therefore, the inner diameter of the elliptical outer ring raceway surface R2 is set to a value that ensures an optimum radial clearance for each bearing (bearings 4, 6 in the present embodiment). In other words, the inner diameter dimension of the elliptical outer ring raceway surface R2 is set within a range that does not deviate from the optimum radial clearance for the bearing.

Further, each bearing 4, 6 is provided with at least one mark M for visually confirming the major axis direction X and the minor axis direction Y of the elliptical outer ring raceway surface R2. In the present embodiment, as an example, each bearing 4, 6
A mark M is attached to the outer ring 12 side surface (the portion exposed to the outside) of the outer ring 12 and to the position corresponding to the minor axis direction Y of the outer ring raceway surface R2. Note that the shape, color, size, etc. of the mark M can be arbitrarily set according to the specifications and dimensions of the bearing unit 1, and the portion marked with the mark M is also limited to the side surface of the outer ring 12. It does not matter, and any portion may be used as long as it can be visually confirmed from the outside. For example, the mark M may be provided at a position corresponding to the major axis direction X of the outer ring raceway surface R2, or the mark M may be provided in both the major axis direction X and the minor axis direction Y. Each bearing 4,
When assembling 6 into the sleeve 8, each bearing 4, 6 can be visually confirmed by checking the mark M attached to each bearing 4, 6.
In a state where the major axis direction X and the minor axis direction Y of the outer ring raceway surface R2 of 6 are aligned with each other (that is, the phases of the elliptical outer ring raceway surfaces R2 are matched with each other), the bearings 4 and 6 are It can be assembled to the sleeve 8. That is, sleeve 8
After mounting the bearing to the bearing with clearance fit, fix it with adhesive etc. so that the elliptical shape is not broken. As shown in FIGS. 2 (a) and 2 (b), when the bearing unit 1 is applied to the bearing application target 20, each bearing 4, 4 is visually confirmed by checking the mark M attached to each bearing 4, 6. In a state in which the major axis direction X of the outer ring raceway surface R2 of 6 is aligned with the longitudinal direction of the bearing application object 20,
The bearing unit 1 can be positioned with respect to the bearing application object 20. As the bearing application object 20, for example, a swing arm used in a magnetic disk device, another rotary drive system, or the like is assumed. In the drawings, an example in which the bearing unit 1 is applied to the swing arm 20 is shown as an example. It is shown. In this case, the major axis direction X of the outer ring raceway surface R2 may be aligned along the longitudinal direction of the swing arm 20. As a result, the swing arm 20 can be rotated about the shaft 2 by the voice coil 22.

As described above, according to the present embodiment, the inner ring 10 in which the inner ring inner diameter surface S1 and the inner ring raceway surface R1 form a perfect circle,
By configuring the outer ring 12 in which the outer ring outer diameter surface S2 has a perfect circular shape and the outer ring raceway surface R2 has an elliptical shape, the rigidity is increased while achieving high speed control and high accuracy control of the bearing application object 20. It is possible to realize the bearing unit 1 capable of satisfying both optimization and low torque at the same time. For example, as shown in FIGS. 3A and 3B, the swing arm 2
Even when 0 is swung about the axis 2 by an angle α, there is no change in the radial rigidity distribution with respect to the swing arm 20 in the major axis direction X and the minor axis direction Y, so the bearing unit 1
It is possible to always maintain the radial rigidity of the constant. Further, according to the present embodiment, the inner diameter dimension of the elliptical outer ring raceway surface R2 is set within a range that does not deviate from the optimum radial clearance for the bearing, so that the axial rigidity decreases as in the conventional case. There is no such problem. Therefore, the axial rigidity of the bearing unit 1 can always be maintained in a constant state. In addition,
In the above-described embodiment, the inner ring inner diameter surface S1 and the inner ring raceway surface R1 of the inner ring 10 have a perfect circular shape, the outer race outer diameter surface S2 of the outer ring 12 has a perfect circular shape, and the outer ring raceway surface R2 has an elliptical shape. As shown, on the contrary, the inner ring inner diameter surface S1 of the inner ring 10 has a perfect circular shape and the inner ring raceway surface R1 has an elliptical shape,
The outer ring outer diameter surface S2 and the outer ring raceway surface R2 of the outer ring 12 may have a perfect circular shape.

[0009]

According to the present invention, it is possible to realize a bearing unit capable of simultaneously satisfying the optimization of rigidity and the reduction of torque while achieving high speed control and high accuracy control of a bearing application object. You can

[Brief description of drawings]

FIG. 1A is a diagram showing a configuration of a bearing unit according to an embodiment of the present invention, FIG. 1B is a sectional view showing an internal configuration of a bearing, and FIG. 1C is a diagram showing FIG. 1B. Sectional drawing which follows CC line of FIG.

2A and 2B are diagrams showing a state in which a bearing unit is applied to a swing arm, FIG. 2A is a plan view thereof, and FIG.
The longitudinal sectional view.

3A and 3B are diagrams showing a distribution state of radial rigidity when the bearing unit is in operation.

[Explanation of symbols]

1: Bearing unit 2: axis 4, 6: Bearing 8: Sleeve 8a: step 10: Inner ring 12: Outer ring S1: Inner ring inner diameter surface R1: Inner ring raceway surface S2: Outer surface of outer ring R2: Outer ring raceway surface M: Mark on the bearing X: Outer ring raceway major axis direction Y: minor axis direction of outer ring raceway surface

Claims (6)

[Claims] 1. A shaft and a plurality of bearings can be assembled together, and a step portion for holding the bearings at a predetermined interval is provided with a sleeve integrally formed by projecting along the circumferential direction. Respectively, an inner ring having an inner ring inner diameter surface and an inner ring raceway surface having a perfect circle shape, and an outer ring having an outer ring outer diameter surface having a perfect circle shape and an outer ring raceway surface having an elliptical shape. Characteristic bearing unit. 2. An outer ring raceway having an elliptical shape, wherein the radial clearance along the major axis direction is set to be larger than the radial clearance along the minor axis direction orthogonal to the major axis direction. The bearing unit according to Item 1. 3. The radial rigidity of the bearing unit along the minor axis direction of the outer ring raceway surface in the major axis direction orthogonal to the minor axis direction when the shaft and the plurality of bearings are assembled to the sleeve and a predetermined preload is applied. The bearing unit according to claim 1 or 2, wherein the radial rigidity is set to be greater than the radial rigidity. 4. Each bearing is provided with at least one mark capable of visually confirming the major axis direction and the minor axis direction of the elliptical outer ring raceway surface. 4. The bearing unit according to any one of 3 to 3. 5. When assembling each bearing into a sleeve, the marks on each bearing are visually checked so that the bearings are aligned with each other such that the major axis direction and the minor axis direction of the outer ring raceway surface of each bearing are aligned with each other. The bearing unit according to claim 4, wherein the bearing unit is attachable to the sleeve. 6. When the bearing unit is applied to a bearing application target, the major axis direction of the outer ring raceway of each bearing is aligned with the longitudinal direction of the bearing application target by visually confirming the mark attached to the bearing. The bearing unit according to claim 4, wherein the bearing unit can be positioned with respect to the bearing application object in this state.