JP2003269473A - Bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing unit having excellent response and vibration absorbent characteristics, wherein rigidity is optimized and torque, weight and costs are reduced at the same time with increased speed and accuracy of control of an object to be borne with the bearing. <P>SOLUTION: This bearing unit comprises a bearing assembly 10 formed by a shaft 2, a plurality of bearings 4, 6 and a spacer 8 for holding the respective bearings with a predetermined interval, and a resin bush 12 mountable to the outer periphery and having a cutout part 12a partly cut out in the shaft direction. The resin bush has a complete round inner periphery R1 and an elliptic outer periphery R2. <P>COPYRIGHT: (C)2003,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 in a metal sleeve (or a metal bush) integrally formed with a step portion functioning as a spacer, A predetermined preload is applied so that the rigidity (hereinafter, referred to as radial rigidity) becomes the same level in the circumferential direction.

[0003]

By the way, in the conventional bearing unit, the sleeve (bush) is made of the same metal material as the bearing and the shaft (for example, high carbon chrome steel such as stainless steel). This is to prevent the preload characteristic of the bearing from changing due to a temperature change during the operation of the bearing, for example. In recent years, there has been a demand for high-speed and high-precision control of a bearing application object to which a bearing unit is applied (for example, a swing arm used in a magnetic disk device, other rotary drive system, etc.). In order to meet such requirements, the bearing unit is required to prevent abrupt torque fluctuations such as torque spikes from occurring and to reduce the torque, and to have a faster response characteristic and an excellent vibration absorbing characteristic as well as a lighter weight. However, if the bearing unit is made of a metal material as in the conventional case, it is difficult to satisfy all the requirements at the same time. Further, in a bearing unit made of a metal material, a high design accuracy is required for the sleeve (bush) because it is necessary to securely assemble the bearing and the shaft to the sleeve (bush), which increases the manufacturing cost. There is also the problem of being lost. Furthermore, since the conventional bearing unit adjusts the preload to increase or decrease the radial rigidity, increasing the radial rigidity to satisfy the high-speed controllability of the bearing application object increases the torque. There is a problem that it will end up. 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 its object is to optimize rigidity, reduce torque, and reduce weight while achieving high-speed control and high-precision control of a bearing application object. Another object of the present invention is to provide a bearing unit that is excellent in response characteristics and vibration absorption characteristics and can satisfy both low cost and low cost.

[0004]

To achieve the above object, a bearing unit according to the present invention comprises a bearing assembly comprising a shaft, a plurality of bearings, and a spacer for holding the bearings at predetermined intervals, and a bearing assembly. A resin bush that is attachable to the outer periphery of the assembly and has a notched portion that is partially notched along the axial direction, and the resin bush has a perfect circular inner periphery. The outer circumference has an elliptical shape. In the present invention, the wall thickness of the resin bush in the minor axis direction is formed thinner than the wall thickness in the major axis direction orthogonal to the minor axis direction. Further, when the bearing unit is applied to the bearing application target, the bearing unit is positioned so that the minor axis direction of the resin bush is aligned with the longitudinal direction of the bearing application target. Further, when the bearing unit is installed in the bearing application object at a predetermined pressure, the radial rigidity of the bearing unit along the major axis direction of the resin bush is greater than the radial rigidity along the minor axis direction orthogonal to the major axis direction. It is set. Further, according to the present invention, there is provided a first displacement prevention mechanism for preventing displacement of the resin bush in the axial direction when the resin bush is mounted on the outer periphery of the bearing assembly. The position deviation prevention mechanism includes a first bush fitting portion formed on the inner circumference of the resin bush, and an assembly side fitting portion formed on the outer circumference of the bearing assembly and capable of fitting the first bush fitting portion. It consists of Further, a second displacement prevention mechanism is provided for preventing displacement of the bearing unit in the axial direction in a state where the bearing unit is installed in a bearing application target at a predetermined pressure. The deviation prevention mechanism includes a second bush fitting portion formed on the outer circumference of the resin bush and an object-side fitting portion formed on the inner circumference of the bearing application object and capable of fitting the second bush fitting portion. It consists of and.

[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. Figure 1
As shown in (a) and (b), the bearing unit 1 of the present embodiment is a bearing assembly including a shaft 2, a plurality of bearings 4 and 6, and a spacer 8 for holding these bearings at a predetermined interval. 10 and a resin bush 12 that can be mounted on the outer periphery of the bearing assembly 10 and has a notch 12a that is partially notched along the axial direction. The resin bush 12 has an inner periphery thereof. R1 has a perfect circular shape, and its outer circumference R2 has an elliptical shape. Each of the bearings 4 and 6 is formed of a predetermined metal material (for example, high carbon chrome steel such as stainless steel), and has an outer ring 14, an inner ring 16, and a plurality of rolling elements 18 incorporated between the outer and inner rings. A retainer 20 for holding the plurality of rolling elements 18 in a rollable manner, and a sealing plate (contact type or non-contact type seal or shield) 2
2 and. The shaft 2 and spacer 8 are also bearings 4, 6
It is made of the same metal material as.

Here, when the minor axis and the major axis of the ellipse orthogonal to the elliptical outer circumference of the resin bush 12 are defined, hereinafter, the minor axis direction of the ellipse is referred to as the resin bush 12.
Of the resin bush 12 in the direction of its major axis.
In the major axis direction Y. Under this condition, the wall thickness of the resin bush 12 in the minor axis direction X is thinner than the wall thickness in the major axis direction Y orthogonal to the minor axis direction X. The wall thickness of the resin bush 12 is such that the radial rigidity anisotropy as described below has an optimum value when the bearing unit 1 is installed in a bearing application object (for example, a swing arm) at a predetermined pressure. Is set. In this case, the thickness of the resin bush 12 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 object to which the bearing unit 1 is applied. The optimum wall thickness dimension is set according to the size and the like. As a material for the resin bush 12, it is preferable to use a material having good outgas characteristics (for example, 66 nylon, GF reinforced 66 nylon) and a material having a small linear expansion coefficient.

Further, the bearing unit 1 has a first displacement prevention mechanism for preventing displacement of the resin bush 12 in the axial direction when the resin bush 12 is mounted on the outer periphery of the bearing assembly 10. It is provided. The first displacement prevention mechanism is formed on the outer periphery of the bearing assembly 10 and the first bush fitting portion 24 formed on the inner circumference of the resin bush 12, and the first bush fitting portion 24 can be fitted to the first bush fitting portion 24. It is composed of an assembly side fitting portion 26. In the present embodiment, as an example thereof, the first bush fitting portion 24
Has a convex shape integrally formed by projecting along the circumferential direction on the inner circumference of the resin bush 12.
6 has a concave shape formed by digging along the circumferential direction on the outer periphery of the spacer 8. In this case, by fitting the convex-shaped first bush fitting portion 24 and the concave-shaped assembly-side fitting portion 26 to each other, the resin bush 12 can be attached to the bearing assembly 10 without displacement in the axial direction. It can be positioned and mounted on the outer circumference.

Now, the process of assembling the bearing unit 1 will be briefly described. First, the bearing 4 is assembled to the shaft 2 by press fitting or adhesion, and then the spacer 8 is brought into contact with the bearing 4. Next, the bearing assembly 10 is assembled by assembling the remaining bearing 6 to the shaft 2 and the spacer 8 with a preload by press fitting or bonding. The preloading method is not particularly limited. Subsequently, the bearing assembly 10
A resin bush 12 is attached to the outer periphery of the. In this case, by expanding the notch 12a, the resin bush 12
The inner diameter of the bearing bush 10 can be expanded and elastically deformed, and as a result, the resin bush 1 can follow the outer diameter shape of the bearing assembly 10.
2 can be mounted easily and smoothly. At the time of this mounting, the first bush fitting portion 24 and the assembly side fitting portion 26
The resin bush 12 by fitting the two together.
Are positioned and mounted on the outer periphery of the bearing assembly 10 without any positional displacement in the axial direction. The bearing unit 1 is completed through such an assembly process. 36 in the figure
Is an insert ring that is inserted after the bearing unit 1 is incorporated into a bearing application object 28 such as a swing arm described below, and its operation will be described later.

Next, a process of applying the completed bearing unit 1 to a predetermined bearing application object and incorporating it will be described with reference to FIGS. 2 (a), 2 (b) and 3. FIG. First,
When the bearing unit 1 is applied to the bearing application object 28,
The resin bush 1 is provided in the longitudinal direction of the bearing application object 28.
The bearing unit 1 is positioned so that the minor axis directions X of 2 are aligned. As the bearing application object 28, for example, a swing arm used in a magnetic disk device or another rotary drive system is assumed, but the drawings show an example in which the bearing unit 1 is applied to the swing arm 28 as an example. Has been done. In this case, the bearing unit 1 may be positioned so that the resin bush 12 is aligned with the minor axis direction of the swing arm 28 in the longitudinal direction. Then, the process of incorporating the bearing unit 1 into the bearing application object 28 at a predetermined pressure is performed. The bearing application object, that is, the swing arm 28 is formed with a fitting hole 28a (see FIG. 3) having a perfect circular shape, and the bearing unit 1 can be fitted into the fitting hole 28a at a predetermined pressure. ing. That is,
By mounting the resin bush 12 having an elliptical outer periphery, the bearing unit 1 having an elliptical shape as a whole is fitted into the fitting hole 28a having a perfect circular shape. Through this process, the bearing unit 1 is incorporated in the swing arm 28. As a result, the swing arm 28 can be rotated about the shaft 2 by the voice coil 30. As described above, the insert ring 36 in FIG. 3 is a member not related to the illustrated assembly process, and is used after the bearing unit 1 is assembled to the swing arm 28 as described later.

In such an assembling process, when the elliptical bearing unit 1 is fitted into the perfect circular fitting hole 28a with a predetermined pressure, the reaction force from the fitting hole 28a acts on the resin bush 12 to cause the resin bush 12 to move. Transform it.
The deforming force at this time acts on the outer diameter surfaces of the bearings 4 and 6 as they are, and deforms the bearings 4 and 6 into an elliptical shape. In that state, the radial rigidity of the bearing unit 1 along the major axis direction Y of the resin bush 12 is set to be larger than the radial rigidity in the minor axis direction X orthogonal to the major axis direction Y. Specifically, the radial rigidity corresponding to the minor axis direction X of the resin bush 12 is set to the smallest and the radial rigidity corresponding to the major axis direction Y is set to the maximum, and the radial rigidity is set in the direction from the minor axis direction X to the major axis direction Y. The rigidity is set to continuously increase. That is, the same effect is obtained as the radial clearance in the major axis direction Y is reduced.
The radial rigidity of is increased. FIG. 4 shows an example in which the magnitude of the radial rigidity is visually displayed, and the magnitude of the radial rigidity is continuously increased or decreased according to the change in the length of the arrow radially extending from the bearing unit 1. You can see that Resin bush 1
2, the ratio of the wall thickness dimensions in the minor axis direction X and the major axis direction Y (in other words, the resin bush 12 having an elliptical outer periphery)
Aspect ratio) of the bearing unit 1, and by adjusting this ratio, the optimum radial rigidity corresponding to the purpose and environment of use of the bearing unit 1 and the type and size of the bearing application object 28 can be set. You can

Further, as shown in FIGS. 1 to 3, the bearing unit 1 of this embodiment has a structure in which the bearing unit 1 is incorporated into a bearing application object, that is, a swing arm 28 at a predetermined pressure (that is, a swing arm). 28 insertion holes 28
A second positional deviation prevention mechanism is provided for preventing axial displacement of the bearing unit 1 when the bearing unit 1 is fitted in a). The second misalignment prevention mechanism is a second displacement prevention mechanism formed on the outer periphery of the resin bush 12.
The bush fitting portion 32 and the object-side fitting portion 34 formed on the inner circumference of the swing arm 28 and capable of fitting the second bush fitting portion 32 are configured. In the present embodiment, as an example thereof, the second bush fitting portion 32 has a convex shape integrally formed by projecting along the circumferential direction on the outer circumference of the resin bush 12, and the object side fitting portion 34. Has a concave shape formed by digging along the circumferential direction on the inner circumference of the bearing application object, that is, the swing arm 28. In this case, by fitting the convex second bush fitting portion 32 and the concave object-side fitting portion 34 to each other, the bearing unit 1 can be mounted on the swing arm 28 without displacement in the axial direction. Can be incorporated. The convex outer shape of the second bush fitting portion 32 may be any shape such as an ellipse or a perfect circle as long as it fits with the fitting portion 34 and cannot move in the axial direction. Good. The second bush fitting portion 32 is thinly formed on one end of the resin bush 12, and in this portion, a gap is formed between the outer ring 14 of the bearing 6 and the inner surface of the second bush fitting portion 32. ing. In addition, the second bush fitting portion 32 and the resin bush 1
The second connecting portion 32a has a constricted shape, and the second bush fitting portion 32 is easily bent in the radial direction. In this case, when the bearing unit 1 is assembled into the swing arm 28, the second bush fitting portion 32 elastically contracts in the radial direction, so that the second bush fitting portion 32 and the object side fitting portion 34 are smoothly and smoothly arranged. It can be fitted easily.

Further, an insert ring 36 can be inserted into the gap between the outer ring 14 of the bearing 6 and the inner surface of the second bush fitting portion 32, and the insert ring 36 has a flange shape protruding to the outside. A handle portion 36a is formed. By operating the flange-shaped handle portion 36 a, the insert ring 36 is moved to the outer ring 14 of the bearing 6.
With this, it is possible to easily insert / remove into / from the inner surface of the second bush fitting portion 32. In this case, with the bearing unit 1 fitted in the fitting hole 28a of the swing arm 28, the outer ring 14 of the bearing 6 and the second bush fitting portion 32 are further inserted.
The second bush fitting portion 32 of the resin bush 12 can be firmly fitted to the object-side fitting portion 34 of the swing arm 28 by inserting and inserting the insert ring 36 in the gap with the inner surface of the. .

As described above, according to the present embodiment, the radial rigidity of the bearing unit 1 along the major axis direction Y of the resin bush 12 is short when the bearing unit 1 is installed in the bearing application object 28 at a predetermined pressure. By setting the radial rigidity to be larger than the radial rigidity along the radial direction X, it is possible to achieve both speed optimization and high accuracy control of the bearing application object, while at the same time satisfying both rigidity optimization and torque reduction. The unit 1 can be realized. For example, in FIG.
As shown in (a) and (b), even when the swing arm 28 is swung by the angle α about the axis 2, the radial stiffness distribution in the minor axis direction X and the major axis direction Y with respect to the swing arm 28 is not distributed. Since there is no change, the radial rigidity of the bearing unit 1 can always be maintained in a constant state. Further, according to the present embodiment, since the method of increasing the radial rigidity by changing the radial clearance is not adopted, there is no problem that the axial rigidity is lowered unlike the conventional case. Therefore, the swing arm 2
The axial rigidity of the bearing unit 1 incorporated in the shaft 8 can be always maintained in a constant state. Furthermore, according to the present embodiment, the shaft 2, the plurality of bearings 4 and 6, and the spacer 8 are made of the same metal material, and the resin bush 12 is made of a material having a small linear expansion coefficient which is excellent in outgas characteristics. By doing so, it is possible to improve the motion characteristics (in particular, the response characteristics of the movable part and the vibration absorption characteristics) without changing the characteristics such as the preload of the bearing unit 1, and at the same time, it is possible to reduce the weight. it can. Furthermore, since the inner diameter of the resin bush 12 can be expanded and elastically deformed simply by expanding the notch 12a, the resin bush 12 can be easily mounted along the outer diameter shape of the bearing assembly 10. At this time, the elastic force of the resin bush 12 covering the bearing assembly 10 causes a restoring force to return to the original diameter (original shape). It can be attached while maintaining high adhesion and holdability. As a result, the vibration generated during the operation of the bearing unit 1 is
Since it is elastically absorbed by the resin bush 12,
It is possible to maintain stable bearing operation at all times.
Further, even when the bearing unit 1 is incorporated into the bearing application target, that is, the swing arm 28 at a predetermined pressure (that is, the bearing unit 1 is fitted into the fitting hole 28a of the swing arm 28 at a predetermined pressure), the bearing unit Since the resin bush 12 is attached to the outer periphery of the device 1, the assembling work (fitting work) is facilitated and galling does not occur.
Further, by mounting the resin bush 12 on the outer periphery of the bearing unit 1, it is not necessary to increase the dimensional accuracy of the fitting hole 28a formed in the bearing application object 28, and as a result, the manufacturing cost of the device can be reduced. You can

The present invention is not limited to the above-described embodiment, but can be modified in various ways as follows. As a first modification, for example, a second displacement prevention mechanism as shown in FIG. 5 may be used. That is, the second bush fitting portions 32 are integrally formed on both ends of the resin bush 12, and the insert rings 36 are inserted into the gaps between the inner surfaces of the second bush fitting portions 32 and the outer rings 14 of the bearings 4 and 6. . At this time, each of the second bush fitting portions 32 elastically deforms around the connecting portion 32a and enters the bearing application object, that is, the object side fitting portion 34 of the swing arm 28, so that the second bush fitting portion 32 and the object side fitting part 34 can be fitted together. According to this modified example, by providing the second displacement prevention mechanism at two locations, the bearing unit 1 can be robustly incorporated in the bearing application object 28.

As a second modification, for example, as shown in FIG. 6, a sleeve 38 integrally formed with the spacer 8 may be inserted inside the resin bush 12. In this case, the assembly side fitting portion 26 may be formed on the outer circumference of the sleeve 38.

In the first displacement prevention mechanism of the above-mentioned embodiment, the convex first bush fitting portion 24 and the concave assembly side fitting portion 26 are fitted to each other. On the contrary, the first bush fitting portion 24 may have a concave shape and the assembly-side fitting portion 26 may have a convex shape so that the fitting portions 24 and 26 are fitted to each other. Further, the first bush fitting portion 24 and the assembly-side fitting portion 26 may be formed intermittently or intermittently instead of being formed continuously. If formed in this way, it is possible to simultaneously prevent axial displacement and rotational displacement. In addition, in the second displacement prevention mechanism of the above-described embodiment, the convex second bush fitting portion 32 is used.
And the concave object-side fitting portion 34 are fitted to each other, but conversely, the second bush fitting portion 3
2 is a concave shape, the object side fitting portion 34 is a convex shape,
You may comprise so that these fitting parts 32 and 34 may be fitted together. Further, the second bush fitting portion 32 and the object side fitting portion 34 may be formed intermittently or intermittently, for example, instead of being formed continuously. If formed in this way, it is possible to simultaneously prevent axial displacement and rotational displacement. Further, in the above-described embodiment, the resin bush 12 in which the inner circumference R1 has a perfect circle shape and the outer circumference R2 has an elliptical shape has been described as an example, but conversely, the inner circumference has an elliptical shape and the outer circumference has Even if the resin bush 12 having a perfect circular shape is adopted, the same effect can be obtained.

[0017]

According to the present invention, it is possible to simultaneously satisfy the optimization of rigidity, the reduction of torque, the reduction of weight and the reduction of price while achieving high speed and high precision control of the object to which the bearing is applied. It is possible to realize a bearing unit having excellent response characteristics and vibration absorption characteristics.

[Brief description of drawings]

FIG. 1 (a) is a diagram showing an internal configuration of a bearing unit according to an embodiment of the present invention, and is an L- of FIG. 1 (b).
Sectional drawing which follows the L line, (b) is sectional drawing which follows the MM line of the same figure (a).

2A is a plan view showing an example in which a bearing unit is applied to a swing arm, and FIG. 2B is a sectional view taken along the longitudinal direction of FIG. 2A.

FIG. 3 is a diagram showing an assembly process when the bearing unit is applied to a swing arm.

4A and 4B are diagrams showing a distribution state of radial rigidity when the bearing unit is in operation.

FIG. 5 is a partial cross-sectional view showing an internal configuration of a bearing unit according to a first modified example of the present invention.

FIG. 6 is a partial cross-sectional view showing an internal configuration of a bearing unit according to a second modified example of the present invention.

[Explanation of symbols]

1: Bearing unit 2: axis 4, 6: Bearing 8: Zama 10: Bearing assembly 12: Resin bush R1: Inner circumference of resin bush R2: Outer circumference of resin bush X: minor axis direction Y: major axis direction

Claims (6)

[Claims] 1. A bearing assembly comprising a shaft, a plurality of bearings, and spacers for holding the bearings at predetermined intervals, and a bearing assembly which can be mounted on the outer periphery of the bearing assembly and is partially cut out along the axial direction. A bearing unit comprising a resin bush having a cutout portion formed therein, the resin bush having a perfect circular inner circumference and an elliptical outer circumference. 2. The bearing unit according to claim 1, wherein the resin bush has a wall thickness in the minor axis direction smaller than a wall thickness in the major axis direction orthogonal to the minor axis direction. 3. When the bearing unit is applied to the bearing application target, the bearing unit is positioned so that the minor axis direction of the resin bush is aligned with the longitudinal direction of the bearing application target. The bearing unit according to either 1 or 2. 4. The radial rigidity of the bearing unit along the major axis direction of the resin bush is the radial rigidity along the minor axis direction orthogonal to the major axis direction when the bearing unit is installed in a bearing application object at a predetermined pressure. The bearing unit according to claim 3, wherein the bearing unit is set larger than the above. 5. A first displacement prevention mechanism is provided for preventing displacement of the resin bush in the axial direction when the resin bush is mounted on the outer periphery of the bearing assembly, and the first position is provided. The displacement prevention mechanism includes a first bush fitting portion formed on the inner circumference of the resin bush and an assembly-side fitting portion formed on the outer circumference of the bearing assembly and into which the first bush fitting portion can fit. The bearing unit according to any one of claims 1 to 4, wherein the bearing unit is provided. 6. A second misalignment prevention mechanism is provided for preventing misalignment of the bearing unit in the axial direction when the bearing unit is installed in a bearing application object at a predetermined pressure. The position deviation prevention mechanism is a second bush fitting portion formed on the outer periphery of the resin bush and an object side fitting portion formed on the inner circumference of the bearing application target object and capable of fitting the second bush fitting portion. The bearing unit according to any one of claims 3 to 5, wherein the bearing unit is formed of a mating portion.