JP2002061638A - Dynamic pressure type bearing device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wear resistance of a bearing surface. SOLUTION: A shaft member 2 is rotated by a driving plate 21, while supporting an outer peripheral surface of a shaft 2a of the shaft member 2 by a shoe 20. The shoe 20 is made of a hard material such as carbide alloy and combax, and the surface hardness of a supporting surface of the shoe 20 is larger than that of an outer peripheral surface of the shaft 2a. A rotating grinding wheel 22 is pressed on an end surface of a thrust plate 2b of the rotating shaft member 2 to carry out grinding work of the thrust plate 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dynamic pressure bearing device. This bearing device is particularly suitable for information equipment such as HD
D, FDD, etc., magnetic disk drive, CD-ROM, DV
It is suitable for supporting a spindle motor such as an optical disk device such as a D-ROM, a magneto-optical disk device such as an MD or MO, or a polygon scanner motor of a laser beam printer (LBP).

[0002]

2. Description of the Related Art Spindle motors for various information devices are required to have high rotational accuracy, high speed, low cost, low noise, and the like. One of the components that determine these required performances is a bearing that supports the spindle of the motor.In recent years, as this type of bearing, the use of a dynamic pressure bearing having characteristics excellent in the required performance has been studied. Or they are actually used.

For example, in a dynamic pressure type bearing device incorporated in a spindle motor of a disk device such as an HDD, a radial bearing portion that rotatably supports a shaft member in a radial direction in a non-contact manner, and a non-rotatable shaft member rotatably in a thrust direction. Thrust bearings for contact and support are provided, and as these bearings,
A dynamic pressure bearing having a groove (dynamic pressure groove) for generating dynamic pressure on a bearing surface is used. The dynamic pressure groove of the radial bearing portion is formed on the inner peripheral surface (radial bearing surface) of the housing or the bearing member or the outer peripheral surface of the shaft member, and the dynamic pressure groove of the thrust bearing portion is formed on the thrust plate provided on the shaft member. It is formed on both end surfaces or on a surface (thrust bearing surface) opposed thereto.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dynamic pressure bearing device as described above in which the radial bearing surface and the thrust bearing surface are prevented from being worn, and this type of dynamic pressure bearing device has excellent bearing performance. Is to be maintained for a long time.

[0005]

To achieve the above object, the present invention provides a shaft member having a bottomed cylindrical housing, a shaft portion inserted into the housing, and a thrust plate provided on the shaft portion. And a radial bearing portion for supporting the shaft portion in a non-contact manner in the radial direction by the dynamic pressure action of the fluid generated in the radial bearing gap, and a thrust for supporting the thrust plate in the thrust direction by the dynamic pressure action of the fluid generated in the thrust bearing gap. A method of manufacturing a dynamic pressure bearing device having a bearing portion, wherein after grinding an outer peripheral surface of a shaft portion, the outer peripheral surface of the shaft portion is supported by a support member having a surface hardness greater than the surface. The present invention also provides a configuration including a step of grinding the end face of the thrust plate.

In the above configuration, it is possible to provide a configuration in which the shaft is rotated to cause sliding between the outer peripheral surface of the shaft and the support member.

Further, the present invention provides a cylindrical housing with a bottom, a shaft member inserted into the housing and having a shaft and a thrust plate provided on the shaft, and a dynamic pressure of a fluid generated in a radial bearing gap. A dynamic pressure bearing device comprising: a radial bearing portion that supports a shaft portion in a non-contact manner in a radial direction by an action; and a thrust bearing portion that supports a thrust plate in a non-contact manner in a thrust direction by a dynamic pressure action of a fluid generated in a thrust bearing gap. Then, the outer peripheral surface of the shaft portion has a circumferential grinding stitch, and
The micro projections constituting the surface roughness are smoothed, and the end face of the thrust plate has a cross-shaped grinding line.

In the above configuration, the axial surface roughness of the outer peripheral surface of the shaft portion is 0.04 μm or less as an arithmetic mean deviation Ra specified in ISO4287 / 1, and the circumferential surface roughness of the end face of the thrust plate is arithmetic. 0.04 μm or less in average deviation Ra,
Preferably, it is 0.01 μm or less.

[0009]

Embodiments of the present invention will be described below.

FIG. 1 shows an example of the configuration of a spindle motor for information equipment incorporating a dynamic pressure bearing device 1 according to this embodiment. The spindle motor is used in a disk drive device such as an HDD, and includes a dynamic pressure bearing device 1 that rotatably supports a shaft member 2 in a non-contact manner, a disk hub 3 mounted on the shaft member 2, Motor stator 4 and motor rotor 5 opposed to each other via a gap
And The stator 4 is mounted on the outer circumference of the casing 6, and the rotor 5 is mounted on the inner circumference of the disk hub 3. The housing 7 of the dynamic pressure bearing device 1 is mounted on the inner periphery of the casing 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator 4 is energized, the rotor 5 is rotated by the exciting force between the stator 4 and the rotor 5, whereby the disk hub 3 is rotated.
And the shaft member 2 rotates integrally.

FIG. 2 shows the dynamic pressure type bearing device 1.
The dynamic pressure type bearing device 1 includes a cylindrical housing 7 having a cylindrical inner peripheral surface 7 a, a cylindrical bearing member 8 fixed to the inner peripheral surface 7 a of the housing 7, the shaft member 2, and a bearing. A main component is a seal member 10 for sealing the upper end surface side of the member 8 (opening side of the housing 7).

The housing 7 is formed of, for example, brass, and has a cylindrical side portion 7b and a bottom portion 7c.
In addition, in this embodiment, the side part 7b and the bottom part 7c of the housing 7 are made into an integral structure, but they may be made into separate structures.

The shaft member 2 is made of, for example, stainless steel (SU
S420J2) and the like, and includes a shaft portion 2a and a thrust plate 2b integrally or separately provided on the shaft portion 2a. The shaft portion 2a is inserted into the inner peripheral surface 8a of the bearing member 8 with a predetermined radial bearing gap S5, and the thrust plate 2b
Are the lower end surface 8b of the bearing member 8 and the bottom surface 7c of the housing 7.
1 is accommodated in the space between the two. Between the upper end surface 2b1 of the thrust plate 2b and the lower end surface 8b of the bearing member 8, and between the lower end surface 2b2 of the thrust plate 2b and the bottom surface 7c of the housing 7.
1 respectively, a predetermined thrust bearing clearance S
3, S4 is provided.

The bearing member 8 is made of, for example, a porous material,
It is made of an iron-based sintered metal, and its pores are impregnated with lubricating oil or lubricating grease to form an oil-impregnated bearing. A dynamic pressure groove is formed in a region of the inner peripheral surface 8a of the bearing member 8 to be a radial bearing surface. When the shaft member 2 rotates, a dynamic pressure action is generated in the radial bearing gap S5, and the shaft portion 2a of the shaft member 2 is rotatably and non-contactly supported in the radial direction by a lubricating oil film formed in the radial bearing gap S5. Is done. As a result, a radial bearing 11 that rotatably supports the shaft member 2 in the radial direction in a non-contact manner is configured. The dynamic pressure groove may be formed on the outer peripheral surface of the shaft portion 2a of the shaft member 2.

The upper end surface 2b1 of the thrust plate 2b or the lower end surface 8b of the bearing member 8, and the lower end surface 2b of the thrust plate 2b
A dynamic pressure groove is formed in each of the regions b2 and the thrust bearing surface of the bottom surface 7c1 of the housing 7. Shaft member 2
Rotates, a dynamic pressure action is generated in the thrust bearing gaps S3 and S4, and the thrust plate 2b of the shaft member 2 is rotatably non-contacted in the thrust direction by the oil film of the lubricating oil formed in the thrust bearing gaps S3 and S4. Supported. As a result, a thrust bearing portion 12 that rotatably supports the shaft member 2 in the thrust direction in a non-contact manner is configured.

The shape of the hydrodynamic grooves on the radial bearing surface and the thrust bearing surface can be arbitrarily selected, and any of the well-known herringbone type, spiral type, step type, multi-arc type, or the like can be selected. Can be used in appropriate combination.

In the above configuration, the surface hardness of the outer peripheral surface of the shaft portion 2a is larger than that of the inner peripheral surface 8a of the bearing member 8, and the surface hardness of both end surfaces 2b1, 2b2 of the thrust plate 2b is lower than that of the bearing member 8. It is larger than the end face 8b and the bottom face 7c1 of the housing 7. For example, the shaft member 2 is subjected to a surface hardening treatment such as plating, carburizing, nitriding, carbonitriding, and other heat treatments, and the surface hardness of the outer peripheral surface of the shaft portion 2a and the both end surfaces 2b1 and 2b2 of the thrust plate 2b. Is Vickers hardness and HV50
It is adjusted to 0 or more, preferably about HV 500 to 550.

The surface roughness of the outer peripheral surface of the shaft portion 2a is smaller than that of the inner peripheral surface 8a of the bearing member 8, and the surface roughness of both end surfaces 2b1 and 2b2 of the thrust plate 2b is smaller than the lower surface 8b of the bearing member 8. And smaller than the bottom surface 7c1 of the housing 7.

The shaft member 2 is manufactured, for example, in the mode described below.

First, the shaft 2a and the thrust plate 2b are made of steel.
After shaping the shaft member 2 integrally having the shaft member 2 and subjecting the shaft member 2 to a surface hardening treatment, the outer peripheral surface of the shaft portion 2a is ground.

Next, as shown conceptually in FIG. 3, the driving member 21 rotates the shaft member 2 while supporting the outer peripheral surface of the shaft portion 2a with the shoe 20. Note that the shoe 20 is formed of a hard material such as a cemented carbide or a CONVAX, and the surface hardness of the support surface is larger than the outer peripheral surface of the shaft portion 2a. Then, the rotating grindstone 22 is pressed against the end surface (the upper end surface 2b1 in the example shown in the figure) of the thrust plate 2b of the rotating shaft member 2, and the end surface of the thrust plate 2b is ground.

As schematically shown in FIG. 4, the outer peripheral surface of the shaft portion 2a of the shaft member 2 that has undergone the above-described manufacturing process has a circumferential grinding line and has a roughness of the surface. The minute projections are smoothed by sliding on the support surface of the shoe 20. The axial surface roughness of the outer peripheral surface of the shaft portion 2a is ISO4287 /
The calculated average deviation Ra specified in 1 is not more than 0.04 μm, and the root mean square angle Δq specified in ISO4287 / 1 is not more than 2.0. The upper end surface 2b1 and the lower end surface 2b2 of the thrust plate 2b have cross-shaped grinding stitches formed by combining rotation of the shaft member 2 and rotation of the grindstone 22 (cross hatched surface). The circumferential surface roughness of the upper end surface 2b1 and the lower end surface 2b2 of the thrust plate 2b is I
The calculated average deviation Ra defined in SO4287 / 1 is 0.
It is 0.4 μm or less, preferably 0.01 μm or less.

[0023]

According to the present invention, the wear of the radial bearing surface constituting the radial bearing portion and the thrust bearing surface constituting the thrust bearing portion is suppressed, and the excellent bearing performance of this type of dynamic pressure type bearing device is extended. Can be maintained over time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor having a hydrodynamic bearing device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a dynamic pressure bearing device according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram illustrating a manufacturing process of a shaft member.

FIG. 4 is a view schematically showing a shaft manufactured in the manufacturing process shown in FIG. 3;

[Explanation of symbols]

 Reference Signs List 1 dynamic pressure bearing device 2 shaft member 2a shaft portion 2b thrust plate 2b1 upper end surface 2b2 lower end surface 7 housing 8 bearing member 11 radial bearing portion 12 thrust bearing portion

Claims (6)

[Claims] A bottomed cylindrical housing, a shaft member inserted into the housing and having a shaft portion and a thrust plate provided on the shaft portion, and a dynamic pressure action of a fluid generated in a radial bearing gap. Manufactures a dynamic pressure bearing device including a radial bearing portion that supports a shaft portion in a non-contact manner in a radial direction and a thrust bearing portion that supports the thrust plate in a non-contact manner in a thrust direction by a dynamic pressure action of a fluid generated in a thrust bearing gap. After grinding the outer peripheral surface of the shaft portion, grinding the end surface of the thrust plate while supporting the outer peripheral surface of the shaft portion with a support member having a surface hardness greater than the surface. A method of manufacturing a dynamic pressure bearing device including a step of performing. 2. The method of manufacturing a dynamic pressure bearing device according to claim 1, wherein the rotation of the shaft portion causes sliding between an outer peripheral surface of the shaft portion and a support member. 3. The axial surface roughness of the outer peripheral surface of the shaft portion is 0.04 μm or less in arithmetic mean deviation Ra, and the circumferential surface roughness of the end face of the thrust plate is 0.1 in arithmetic mean deviation Ra.
The method for manufacturing a dynamic pressure bearing device according to claim 1 or 2, wherein the thickness is not more than 04 µm. 4. A dynamic pressure bearing device manufactured by the manufacturing method according to claim 1. 5. A housing having a bottomed cylindrical shape, a shaft member inserted into the housing and having a shaft portion and a thrust plate provided on the shaft portion, and a dynamic pressure effect of a fluid generated in a radial bearing gap. A dynamic pressure bearing device comprising: a radial bearing portion for supporting a shaft portion in a non-contact manner in a radial direction; and a thrust bearing portion for supporting the thrust plate in a non-contact manner in a thrust direction by a dynamic pressure action of a fluid generated in a thrust bearing gap. The outer peripheral surface of the shaft portion has a circumferential grinding stitch, and
A dynamic pressure bearing device, wherein minute projections constituting the surface roughness are smoothed, and an end face of the thrust plate has a cross-shaped grinding line. 6. The axial surface roughness of the outer peripheral surface of the shaft portion is not more than 0.04 μm in arithmetic mean deviation Ra, and the circumferential surface roughness of the end face of the thrust plate is 0.1 in arithmetic mean deviation Ra. The dynamic pressure type bearing device according to claim 5, wherein the diameter is not more than 04 µm.