JP2003239985A - Pivot unit for magnetic disc device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pivot unit for a magnetic disc device provided with a ball bearing filling a proper amount of grease to prevent the grease from adhering to a rolling element and prevent the grease from leaking to the outside so as to reduce cost by preventing torque fluctuation of the magnetic disc de vice. <P>SOLUTION: A cage 20 is constituted in such a way that the rolling element 22 retained by a plurality of pairs of claws 28, 28 is stored in each pocket 26 in a no-load condition. A grease collection part 32 is formed in a basic part positioned between pockets 26. A bottom face of each grease collection part 32 is formed as a flat face which has a large area and has a circular arc shape in which its outer profile has radius of curvature R1 larger than diameter of outer periphery r1 (R1>r1) of a claw part 28 and a circular arc shape in which its inner profile has radius of curvature R2 smaller than diameter of inner periphery r2 (R2<r2) of the claw part 28. Moreover, wall parts 34, 36 rising in the same direction as the direction in which the claw 28 is formed are formed on the bottom face and at outer profile and inner profile of each grease collection part 32. <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 pivot unit of a magnetic disk device, and more particularly to improvement of a ball bearing that rotatably supports a rotary carriage on a rotary shaft.

[0002]

2. Description of the Related Art As a pivot unit for rotatably supporting a rotary carriage of a magnetic disk device, for example, a technique described in Japanese Patent No. 2901254 is known.
In the technique of this publication, a rotary carriage (hereinafter, carriage) is rotatably mounted on a single rotary shaft having a shaft provided in the vertical direction via two radial ball bearings. The two radial ball bearings are arranged vertically separated from each other in the axial direction. The inner ring fitted to the rotating shaft, the outer ring fitted to the carriage, and the inner ring and outer ring raceways are housed and held in a cage. And a plurality of rolling elements arranged so as to be rollable. A pair of shield plates (referred to as an upper shield plate and a lower shield plate) that close the rolling elements from above and below are arranged in the space between the inner ring and the outer ring of each radial ball bearing. A grease pool is formed between the lower shield plate of the radial ball bearing arranged at the upper part and the rolling element, and between the upper shield plate of the radial ball bearing arranged at the lower part and the rolling element, and the grease pool is filled with grease. Is enclosed. That is, a grease reservoir is provided on the side facing each other of the two radial ball bearings to fill the grease.

According to the above construction, even if the grease having increased fluidity at high temperature leaks out from the grease reservoir,
Since the grease reservoirs are located between the two radial ball bearings that are separated from each other in the axial direction, they do not leak to the outside of the carriage and can be prevented from adhering to the magnetic disk surface.

[0004]

By the way, the above-mentioned 2
The amount of grease required for smooth lubrication of individual radial ball bearings is sufficient to allow a small amount of oil to flow on the raceways of the inner and outer rings, but the grease pool of the radial ball bearings placed above must be If the excess grease flowing out of the bearings adheres to the rolling elements of the radial ball bearings placed at the bottom, torque unevenness will occur in the radial ball bearings,
Torque fluctuations may occur in the magnetic disk device.

Further, in the conventional radial ball bearing, anticipating that the enclosed grease will flow out, 10 to 30% of the bearing space volume surrounded by the outer peripheral surface of the inner ring, the inner peripheral surface of the outer ring, and the shield plate. A large amount of grease, that is, a large amount of grease, is filled. If this is done, the filled grease is likely to adhere to the rolling elements, and torque unevenness is likely to occur in the radial ball bearing as described above.

[0006] Further, as the production of high-mix low-volume products has advanced, the demand for cost reduction of magnetic disk devices has become stronger. However, the radial ball bearing of the magnetic disk device described above has a pair of shield plates as constituent members, and has poor assembly workability, which is an obstacle to cost reduction. The present invention has been made in view of the above circumstances, and is provided with a ball bearing in which an appropriate amount of grease is sealed so that it does not adhere to the rolling elements and does not leak to the outside. It is an object of the present invention to provide a pivot unit for a magnetic disk device that can prevent the cost while reducing the cost.

[0007]

According to a first aspect of the present invention, there is provided a pivot unit for a magnetic disk device, wherein a rotary carriage for a magnetic disk device is provided on an upper and a lower part of a rotary shaft arranged with its axis oriented vertically. It is rotatably supported via individual ball bearings, and each ball bearing has a plurality of rolling elements housed and held in pockets of the cage so as to be rollable on the raceways of the inner ring and the outer ring. In the pivot unit of the magnetic disk device, wherein the retainer is provided with a plurality of pairs of pawls at predetermined intervals in the circumferential direction on the one end surface of the annular body, and a pocket is provided between each pair of pawls. The cage is
A plurality of recesses are formed on the end face of the adjacent pockets facing upwards from the intermediate position, and these recesses serve as a grease reservoir in which grease is filled.

According to a second aspect of the present invention, in the pivot unit of the magnetic disk according to the first aspect, the bottom surface of the grease reservoir has an arc shape whose outer radius is larger than the outer diameter of the claw. The inner surface of the bottom surface is formed into a flat surface having an arc shape with a radius of curvature smaller than the inner diameter of the claw. Further, the invention of claim 3 is the same as claim 2
In the pivot unit of the magnetic disk device described,
The outer and inner contours of the bottom surface of the grease reservoir are provided with wall portions that stand up in the same direction as the direction in which the claws are formed.

According to a fourth aspect of the present invention, in the pivot unit of the magnetic disk device according to any one of the first to third aspects, the space between the inner ring and the outer ring is provided above the upper ball bearing. One grease scattering prevention shield member that closes the space between the inner ring and the outer ring from below is arranged in the lower ball bearing.

Further, the invention of claim 5 is the same as claim 1.
In the pivot unit of the magnetic disk device described in any one of 1 to 4, the grease filling amount of the two ball bearings is 5 to 10% of the bearing space volume.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a pivot unit of a magnetic disk device according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration in which a rotary carriage (hereinafter, referred to as a carriage) 12 is fixed to a pivot unit 2.

The pivot unit 2 has a rotary shaft 4 provided with a shaft in the vertical direction and two rotary shafts 2 arranged at the upper and lower positions of the rotary shaft 4.
And a cylindrical housing 10 which is rotatably mounted via individual radial ball bearings 6 and 8,
The carriage 12 is fixed to the outer circumference of the housing with screws 14. The upper radial ball bearing 6 includes an inner ring 16 fitted to the rotating shaft 4 and an outer ring 18 fitted to the housing 10.
And a plurality of rolling elements 22 accommodated and held in the cage 20 and arranged for rolling on the raceways of the inner ring 16 and the outer ring 18.
And the rolling element 2 in the space between the inner ring 16 and the outer ring 18.
Shield plate 2 for preventing grease from scattering, which closes 2 from above
4 and.

The cage 20 is a crown-shaped member formed by injection molding using a synthetic resin or the like as a material. As shown in FIGS. 2 and 3, one end surface of the annular body is circumferentially spaced by a predetermined distance. A plurality of pockets 26 are formed open. The pocket 26 is partitioned by a base portion, and a pocket inlet 30 is formed by a pair of pawls 28, 28 extending in an arc shape from the base portion in the axial direction, and the pocket inlet 30 is held by the pair of pawls 28, 28. The moving body 22 is stored in each pocket 26 in an unloaded state.

Here, a recess is formed in the base portion located between the pockets 26, and this recess serves as a grease reservoir 32. As shown in FIGS. 3 and 4, the outer surface of the bottom surface of each grease reservoir 32 has an arc shape with a radius of curvature R1 (R1> r1) larger than the outer peripheral diameter r1 of the claw portion 28, and the inner surface thereof has a claw portion. 28 is formed as a flat surface having a large area in the shape of an arc having a radius of curvature R2 (R2 <r2) smaller than the inner peripheral diameter r2 of 28. Further, on the outer and inner contours of the bottom surface of each grease reservoir 32, wall portions 34 that stand up in the same direction as the direction in which the claws 28 are formed,
36 is formed.

In the upper radial ball bearing 6, 5 to 10% of the bearing space volume surrounded by the outer peripheral surface of the inner ring 16, the inner peripheral surface of the outer ring 18, the grease scattering prevention shield plate 24, and the grease reservoir 32. Is filled with grease.
On the other hand, the lower radial ball bearing 6 also has substantially the same configuration as the upper radial ball bearing 8, but as shown in FIG. 1, the rolling element 22 is closed from below in the space between the inner ring 16 and the outer ring 18. Shield plate 24 for preventing grease from scattering
Are arranged. In addition, the outer peripheral surface of the inner ring 16 and the outer ring 18
The grease is filled in 5 to 10% of the bearing space volume surrounded by the inner peripheral surface of the and the grease reservoir 32.

According to the pivot unit 2 of the magnetic disk device having the above-described structure, the cage 20 of the two radial ball bearings 6 and 8 has a plurality of concave shapes facing upward between the plurality of pockets 26. The grease reservoirs 32 are formed. Each grease reservoir 32 has a bottom surface having a large area, and the walls 34 and 36 are formed on the outer and inner contours of the bottom surface. Almost all of the grease specified for the enclosed amount of 100% can be enclosed in the grease reservoir 32. Therefore, the filled grease is less likely to adhere to the rolling elements 22, and torque unevenness does not occur in the radial ball bearings 6 and 8, so that torque fluctuations of the magnetic disk device can be prevented.

Further, since most of the grease in the upper radial ball bearing 6 is enclosed in the grease reservoir 32, it becomes difficult for the grease to leak from the upper radial ball bearing 6 to the lower radial ball bearing 8. Since the leaked grease does not adhere to the rolling elements 22 of the lower radial ball bearing 8, torque unevenness of the lower radial ball bearing 8 can also be prevented.

Also, two radial bearing ball bearings 6 and 8
Since the grease is filled in the grease reservoir 32, it becomes difficult for the grease to flow to the lower part, and the shield plates facing each other unlike the conventional device are not required, which reduces the number of parts and improves the assembly workability. Therefore, the cost of the magnetic disk device can be reduced.

[0019]

As described above, according to the pivot unit of the magnetic disk drive of the present invention, the cage capable of enclosing a proper amount of grease so that the grease does not adhere to the rolling elements and does not leak to the outside. By providing the ball bearing having the above, it is possible to prevent the torque fluctuation of the magnetic disk device and reduce the cost of the magnetic disk device.

[Brief description of drawings]

FIG. 1 is an axial cross-sectional view showing a pivot unit of a magnetic disk device according to the present invention.

FIG. 2 is a perspective view showing a main part of a cage of a ball bearing that constitutes a pivot unit.

FIG. 3 is a view showing a cage of a ball bearing in an axial direction.

FIG. 4 is a view taken along the line VI-VI of FIG.

[Explanation of symbols] 2 Pivot unit 4 Rotating shaft 6, 8 Radial ball bearing (ball bearing) 10 Housing 12 Carriage (rotary type carriage) 16 Inner ring 18 Outer ring 20 Cage 22 Rolling element 24 Grease scattering prevention shield plate (grease scattering) Preventing shield member) 26 pocket 28 claw 30 pocket inlet 32 grease reservoir 34, 36 wall r1 outer diameter r2 of claw inner diameter R2 of claw inner radius R1 outer radius of curvature of grease reservoir R2 inside bottom of grease reservoir Radius of curvature

Continued front page    F term (reference) 3J101 AA02 AA32 AA62 BA25 BA44                       CA14 EA31 EA63 FA32 GA53                 5D068 AA01 BB01 CC12 GG05

Claims (5)

[Claims] 1. A rotary type carriage for a magnetic disk device is rotatably supported by a rotary shaft arranged with its axis oriented in the vertical direction via two ball bearings, an upper ball bearing and a lower ball bearing. The bearing has a plurality of rolling elements housed and held in pockets of a cage so as to be rollable on raceways of an inner ring and an outer ring, and the cage has a predetermined interval in a circumferential direction of one end surface of an annular body. In a pivot unit of a magnetic disk device having a plurality of pairs of claws provided with a pocket and a pocket provided between each pair of claws, a plurality of the cages are provided on an end surface of the adjacent pocket facing upward in the middle position. Pivot unit for a magnetic disk drive, wherein the concave portions are formed, and these concave portions serve as a grease reservoir in which grease is filled. 2. The bottom surface of the grease reservoir has an outer shape of an arc shape having a radius of curvature larger than an outer diameter of the claw, and an inner shape of the bottom surface has an arc shape of a radius of curvature smaller than an inner diameter of the claw. The pivot unit for a magnetic disk according to claim 1, wherein the pivot unit is a flat surface. 3. The pivot of the magnetic disk drive according to claim 2, wherein the outer and inner contours of the bottom surface of the grease reservoir are provided with wall portions that rise in the same direction as the direction in which the claws are formed. unit. 4. The grease scattering prevention shield member for closing the space between the inner ring and the outer ring from above is arranged in the upper ball bearing, and the inner ring and the lower ball bearing are arranged in the lower ball bearing. 4. A pivot unit for a magnetic disk drive according to claim 1, wherein one grease scattering prevention shield member is arranged to close the space between the outer rings from below. 5. The grease filling amount of the two ball bearings is
The pivot unit of the magnetic disk device according to any one of claims 1 to 4, wherein the bearing space volume is 5 to 10%.