JP2596088B2 - Spindle assembly - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle assembly, and more particularly to a spindle assembly suitable for a rotating mechanism requiring high precision, such as a magnetic disk drive.

[Conventional technology]

Conventional devices of this kind remove the gap between the outer ring of the ball bearing holding the spindle and the bearing housing,
A cylindrical part is fixed to the bearing outer ring, integrated with the bearing outer ring, and a part of the outer surface of the cylindrical part is cut into a plane to form two projections. By applying a pressing force from a direction opposite to the bonded portion of the housing, the gap between the outer ring of the ball bearing and the bearing housing is removed.

However, in this device, there is a problem that stress concentration is large at the bonding portion between the two projections and the bearing housing, and the projections are easily deformed or worn, so that a long life cannot be obtained.

For this purpose, for example, an apparatus disclosed in Japanese Patent Publication No. 62-11204 has been proposed. In this apparatus, the two protrusions are formed by cutting the outer surface of a cylindrical part into a curved surface so as to distribute stress concentration at the bonding portion between the protrusion and the bearing housing. Things.

[Problems to be solved by the invention]

FIG. 6 shows an outline of the above prior art. With this technology,
When the projections 12b, 12c of the outer ring 12a of the bearing 12 are formed by machining, a part 12d of the bearing outer ring 12 is cut and formed. There is a problem in that wear occurs during the use of the spindle and the spindle accuracy deteriorates.

In order to prevent this, the sharp edges after machining were conventionally sharpened slightly with sandpaper, etc. to give them a rounded shape. Did not lead to a fundamental solution.

The present invention has been made in view of the above circumstances, and an object thereof is to solve the above-described problems in the prior art, to extremely reduce the contact stress between the bearing outer ring and the bearing housing, An object of the present invention is to provide a high-precision spindle assembly free from wear.

[Means for solving the problem]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spindle assembly having a rotating shaft, a plurality of bearings for rotatably supporting the rotating shaft, and a housing for supporting the bearing, wherein at least one of the housings has two positions. Forming a plane part,
The bearing outer ring is configured to be pressed against the flat portion by pressing means, and a length of a contact portion between the flat portion and the bearing outer ring is substantially equal to a length of the bearing outer ring in a rotation axis direction. This is achieved by a spindle assembly characterized by:

[Action]

In the spindle assembly according to the present invention, the bearing outer ring has a perfect circular shape without protrusions, two flat portions are formed in the bearing housing, and the flat portions are brought into contact with the bearing outer ring. A pressing force is applied from the opposite side of the contact portion to remove a gap between the bearing outer ring and the bearing housing.

Since the bearing outer ring has a perfect circular shape and is in flat contact with the bearing housing, and the length of the contact portion is almost equal to the length of the bearing outer ring in the rotation axis direction, so-called so-called Hertz contact stress is extremely reduced. Therefore, wear (small motion wear) between the bearing outer ring and the housing due to the spindle rotation for a long time can be reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a longitudinal sectional view of a spindle unit of a magnetic disk drive including a spindle assembly according to one embodiment of the present invention. The spindle mechanism shown in this embodiment includes a rotating shaft 2 for holding a magnetic disk 1, an upper base 5 and a lower base 6 for rotatably supporting the rotating shaft 2 via two upper and lower ball bearings 3, 4. A thrust spring 11 for pressing the lower ball bearing 4 in the axial direction to apply a thrust preload, and a housing portion provided on the upper base 5 and the lower base 6 by connecting the upper and lower ball bearings 3 and 4 respectively.
U-shaped springs 7, 8 are provided which press against 5a and 6a.

More specifically, a hub 2a is fixed to the outer peripheral portion of the above-mentioned rotating shaft 2, and a plurality of magnetic disks 1 are held around the hub 2a at appropriate intervals in the axial direction, and the rotating body is Has formed. Two ball bearings 3, 4 are mounted above and below the rotating shaft 2, and rotatably support the rotating shaft 2. The ball bearings 3 and 4 are accommodated in bearing housing portions 5a and 6a provided on the upper base 5 and the lower base 6, respectively.

A motor magnet 9 is fixed to the lower end of the rotating shaft 2, and the rotating shaft 2 is rotationally driven by a drive motor constituted by this and a motor winding 10. In order to improve the rotational accuracy of the spindle, it is necessary to remove the radial gap between the inner ring and the outer ring of the above-described ball bearings (hereinafter simply referred to as “bearings”) 3 and 4. For this,
As described above, the thrust spring 11 for pressing the outer ring of the lower bearing 4 downward is provided. Further, since the fitting between the outer ring of the bearing 4 and the housing portion 6a is a so-called "clearance fit", the outer ring of the bearing 4 slides downward by the force of the thrust spring 11, and the thrust force acts on the bearing 4. Thus, the radial gap of the bearing 4 is removed.

Further, the force of the thrust spring 11 acts in a direction of pushing down the rotating shaft 2 because the inner ring of the bearing 4 is fixed to the rotating shaft 2. For this reason, a thrust force also acts on the upper bearing 3, and the radial gap of the upper bearing 3 is also removed. The outer ring of the upper bearing 3 and the housing portion 5a are fitted together with the above-mentioned "gap fit" to facilitate assembly. The inner ring of the upper bearing 3 is screwed to the rotating shaft 2. In order to prevent the rotation accuracy of the spindle from deteriorating due to the gap between the outer rings of the upper and lower bearings 3, 4 and the housing parts 5a, 6a, the outer rings of the bearings 3, 4 are respectively connected to the housing parts 5a, 6a by U-shaped springs 7, 8. By pressing, the gap between the outer ring and the housing is removed.

As described above, the fitting between the bearing outer ring and the housing is “gap fit”, and since the bearing outer ring is pressed against the housing only by the spring, there is a possibility that the bearing outer ring rotates with respect to the housing (creep phenomenon). Normally, small diameter holes 3b and 4b are provided in the bearing outer ring, and detent pins 16 and 17
To prevent rotation of the bearing outer ring.

FIG. 1 shows details of the configuration of the bearing 3 and the housing portion 5a. FIG. 2A is a cross-sectional view in the lateral direction of the bearing 3 and the housing 5a, and FIG. 2B is an AOB cross-sectional view thereof. The symbols in the figure are used for the same meaning as described above.

The outer race 3a of the bearing 3 is pressed by a U-shaped spring 7 against two flat portions 5b and 5c provided in a part of the housing portion 5a. The U-shaped spring 7 is set so as to press near the center of the bearing 3, and the bearing outer ring 3a is
Are surely brought into contact with the flat portions 5b and 5c. This makes it possible to obtain a spindle that can rotate with high precision for a long period of time. The flat portions 5b and 5c of the housing portion 5a can be accurately processed by a machine tool such as an NC milling machine.

In addition, in FIG. 1 (a), the gap between the housing portion 5a and the bearing outer ring 3a is inevitable in consideration of the movement allowance of the U-shaped spring 7 and the stability of the rotating shaft 2 when the spring is damaged. Preferred dimensions are calculated. As an example, within 3% of the bearing outer ring diameter, more preferably 0.05% of the bearing outer ring diameter
It is desirable to set it to about 2%.

FIG. 3 shows another embodiment of the present invention. In this embodiment,
While the housing portion 5a of the above-described embodiment is configured by an arc and a flat portion, the housing portion 5a is configured by only a pair of flat portions 5d and 5e. The bearing 3 is pressed by the spring 15 against the flat portions 5d and 5e. The present embodiment is functionally almost the same as the above-described embodiment, and a spindle capable of rotating with high precision for a long period of time can be obtained. In addition, since the housing portion is composed of only a flat portion, manufacture is easy,
It has the advantage of being cheap.

FIG. 4 shows an embodiment in which two U-shaped springs 18 and 19 are used. According to this embodiment as well, a spindle capable of rotating with high precision for a long period of time can be obtained as in the above-described embodiment. In addition, the force applied to the bearing outer ring 3a comes from a total of four directions, i.e., two directions due to the spring and two directions due to the reaction force from the housing flat surfaces 5b, 5c. There is an advantage that it is lower than that.

FIG. 5 shows that the bearing outer ring 3a is
9 shows another embodiment of the means for pressing the first and second members. In the present embodiment, a screw 20 is attached via a coil spring 21 to a screw hole provided in the bearing outer ring 3a. Due to the extension force of the coil spring 21, the bearing outer ring 3a is pulled leftward in the drawing, and is pressed against the housing portion flat portions 5d and 5e. According to this embodiment as well, a spindle capable of rotating with high precision for a long period of time can be obtained as in the above-described embodiment.

Each of the above embodiments is shown as one embodiment of the present invention, and various modifications other than those shown here are possible. Further, these embodiments can be appropriately combined.

〔The invention's effect〕

As described above, according to the present invention, the so-called Hertzian contact stress can be extremely reduced, so that the wear (small motion wear) between the bearing outer ring and the housing due to the long-term spindle rotation can be reduced. This has a remarkable effect that a contact stress between the bearing outer ring and the bearing housing can be extremely reduced, and a high-precision spindle assembly free of wear between the two can be realized.

[Brief description of the drawings]

FIG. 1 is a view showing details of a bearing portion which is a main part of a spindle assembly showing an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a spindle portion of a magnetic disk device including the spindle assembly of the embodiment. 3 to 5 are plan views showing another embodiment of the present invention, and FIG. 6 is a plan view showing the prior art. 1: magnetic disk, 2: rotating shaft, 3, 4: ball bearing, 5, 6: base,
5a, 6a: housing part, 5b to 5e: flat part, 7, 8, 18, 19: U-shaped spring, 11: thrust spring, 14, 15, 21: spring.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor, Takemasa Shimizu 2880 Kozu, Kozuhara, Odawara City, Kanagawa Prefecture Inside the Odawara Plant, Hitachi, Ltd. Inside the factory (56) References JP-A-63-206954 (JP, A) JP-A-61-136017 (JP, A) Jikai Sho 61-44023 (JP, U)

Claims (8)

(57) [Claims] 1. A spindle assembly having a rotating shaft, a plurality of bearings rotatably supporting the rotating shaft, and a housing supporting the bearing, wherein at least one of the housings has two flat portions. The bearing outer shaft is configured to be pressed against the flat portion by pressing means, and the length of the contact portion between the flat portion and the bearing outer ring is substantially equal to the length of the bearing outer ring in the rotation axis direction. A spindle assembly characterized by being equalized. 2. A spindle set according to claim 1, wherein two flat portions are formed on both sides of said housing, and said bearing outer ring is pressed against said flat portion by pressing means. Three-dimensional. 3. The spindle assembly according to claim 1, wherein a gap between the bearing outer ring and the housing is 0.05 to 2% of a diameter of the bearing outer ring. 4. The spindle assembly according to claim 1, wherein a compression spring is used as said pressing means. 5. The spindle assembly according to claim 4, wherein a plurality of compression springs are used as said pressing means. 6. A spindle assembly according to claim 4, wherein a U-shaped spring is used as said pressing means. 7. A spindle assembly according to claim 1, wherein a tension spring is used as said pressing means. 8. The spindle assembly according to claim 7, wherein a plurality of tension springs are used as said pressing means.