JP2001298899A - Dynamic pressure bearing motor and disk driving device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use free cutting stainless steel which is easy of cutting work as bearing material of a dynamic pressure bearing, form trenches in the bearing material by electromechanical machining, and obtain a superior bearing surface free from protrusions of cutting component. SOLUTION: Dynamic pressure trenches are formed on one out of a fixed bearing surface formed on a fixed member side and a rotary bearing surface formed on a rotating member side or on both of them, and the dynamic pressure bearing is constituted. The rotating member is supported rotatably to the fixed member by the dynamic pressure bearing. One or both of the fixed bearing surface and the rotary bearing surface are constituted of the free cutting stainless steal. The dynamic pressure trenches are formed by performing electromechanicai machining to the stainless steel, and acid treatment is performed to the forming surface of the trenches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing motor for rotatably supporting a rotating member with respect to a fixed member by using a dynamic pressure bearing, a hard disk drive device for rotating a recording disk using the motor, and a high-performance hard disk drive. The present invention relates to a disk drive such as a capacity floppy disk drive.

[0002]

2. Description of the Related Art Usually, disk drives such as a hard disk drive and a high-capacity floppy disk drive,
A clean chamber is constituted by a base member and a cover member, a recording disk is accommodated in a clean space in the clean chamber, and access to the recording disk is performed by a magnetic head supported by a head arm.

[0003] More specifically, at least a rotor hub of a spindle motor is rotatably accommodated in a clean chamber, and one or a plurality of recording disks are mounted in the rotatable hub. A head assembly including a voice coil motor is housed in a clean chamber, and the magnetic head at the tip of an arm rotated by the voice coil motor can be read and written by tracing the magnetic head to the recording disk surface. I have.

In this type of disk drive, it is necessary to prevent a crash caused by dust particles being caught between the head and the disk surface, and it is necessary to maintain a high level of cleanliness of the air in the clean chamber. , Not only to block the air from blocking the air,
It is necessary to suppress the generation of dust particles, so-called contamination, in the chamber. For this reason, stainless steel, which is less likely to rust than general steel or structural steel, is often used as a component in a clean chamber, for example, a shaft or a rotor hub of a spindle motor. But big.

[0005] Since parts used in precision machines such as disk drives such as hard disks are required to have high dimensional accuracy, the materials themselves are required to have excellent moldability. Above all, cutting is the most frequently used processing method, and free-cutting steel to which various free-cutting elements are added is often used in order to improve the machinability of the material. The above-mentioned stainless steel is a material that is relatively hard to cut, but sulfur (S), tellurium (Te), selenium (S)
The machinability is improved by adding e) and the like. Stainless steel containing 0.25% or more of sulfur as a free-cutting component is commonly used because it is inexpensive and can provide good machinability. This sulfur is mainly composed of manganese sulfide (MnS) and chromium sulfide (Cr
As present in steel as S).

On the other hand, in recent years, dynamic bearings having excellent high-speed rotation bearing characteristics have been attracting attention as bearing devices used for spindle motors and the like. In this dynamic pressure bearing, a predetermined bearing fluid is interposed between a fixed side and a rotation side which are relatively rotatably disposed, and a dynamic pressure groove provided on one or both of the fixed side and the rotation side is provided. A dynamic pressure is generated in the bearing fluid by the pumping action, and the rotary member is rotatably supported on the fixed member by the dynamic pressure.

The dynamic pressure groove in such a dynamic pressure bearing is formed into a predetermined groove shape such as a herringbone shape or a spiral shape on a fixed or rotating bearing surface. There is. In the electrolytic machining method, a non-workpiece whose dynamic pressure groove is electrolytically machined and an electrode tool having a groove-shaped electrode exposed portion corresponding to the dynamic pressure groove are arranged to face each other, and the non-workpiece and the electrode tool are electrolyzed. Connected to the positive electrode and the negative electrode of the power source for processing, respectively, by applying electricity while flowing the electrolytic solution between the electrode tool and the non-processed object, the non-processed object is eluted according to the groove shape, and the dynamic pressure groove is formed. I am getting it.

[0008]

By the way, when forming a dynamic pressure groove in a component of a dynamic pressure bearing, when the groove processing is performed by rolling or cutting, burrs or fluffs occur on the processed surface.
It is very difficult to remove them, and many man-hours are required. On the other hand, in the groove machining by electrolytic machining, no burr or fluff is generated on the machined surface of ordinary stainless steel or the like.

However, when the above-described easy-cuttable stainless steel, which is easy to cut, is used, the free-cutting component on the surface of the free-cuttable stainless steel is not electrolytically processed, but becomes a projection of several microns to several tens of microns. Remains. If used as it is, the projections become particles and may enter the sliding portion of the bearing, causing a serious problem in lubrication.

The present invention has been made in consideration of such problems of the prior art, and an object of the present invention is to provide a free-cutting stainless steel which is easy to cut by a dynamic pressure bearing. A hydrodynamic bearing motor and a disk drive device using the same, which can be used as a bearing material, subjected to groove processing by electrolytic processing on the bearing material, and can obtain a good bearing surface free of protrusions of free-cutting components. Is to provide.

[0011]

In order to achieve the above object, in a dynamic bearing motor according to the present invention, a fixed bearing surface provided on a fixed member side and a rotary bearing surface provided on a rotating member side are provided. A dynamic pressure bearing is formed by forming a dynamic pressure groove in one or both of the above, and a dynamic pressure bearing motor which rotatably supports a rotating member with respect to a fixed member by the dynamic pressure bearing.
One or both of the fixed bearing surface and the rotating bearing surface on which the dynamic pressure grooves are formed are made of free-cutting stainless steel, and the free-cutting stainless steel is subjected to electrolytic processing to form the dynamic pressure grooves. An acid treatment is performed on the surface on which the dynamic pressure grooves are formed (claim 1).

One or both of the fixed bearing surface and the rotary bearing surface constituting the dynamic pressure bearing are made of a free-cutting stainless steel, and are machined to a desired shape by utilizing the free-cutting property. Thereafter, a dynamic pressure groove is formed by electrolytic machining on one or both of the fixed bearing surface and the rotating bearing surface. Although the free-cutting component does not dissolve after electrolytic machining and remains in a projecting shape on the bearing surface with the dynamic pressure groove, the free-cutting component is preferentially dissolved by acid-treating the surface on which the dynamic pressure groove is formed. And the stainless steel surface is cleaned to remove various scale stains generated during processing. Thereby, high corrosion resistance peculiar to the stainless steel material is exhibited, and at the same time, occurrence of contamination due to particles composed of free-cutting components is prevented.

In this case, the acid treatment is desirably performed with an aqueous acid solution capable of removing dirt, rust and scale remaining on the surface of the free-cutting stainless steel, and is preferably performed mainly with a nitric acid solution.

[0014] The pickled stainless steel has improved corrosion resistance and can completely remove free-cutting components to prevent contamination due to particles. When treated, highly corrosive hydrogen sulfide (H2S) or sulfur itself is generated and may adhere to or remain on members. Since these gases may have a significant effect on the head and media in the disk drive, it is desirable to carry out a neutralization treatment or a baking treatment after the acid treatment.

[0015] The pickled stainless steel is preferably subjected to a chromate treatment immediately after the neutralization treatment (or before the neutralization treatment or the baking treatment, if any) (claim 4), and the corrosion resistance is further improved. be able to.

Prior to the acid treatment of the surface on which the dynamic pressure grooves are formed, the surface may be oxidized. Since the protrusions of the free-cutting component generated by the electrolytic processing are oxidized by the oxidation treatment as a pre-treatment of the acid treatment, the protrusions are easily removed in the subsequent acid treatment, and a good movement without the protrusions is obtained. A processed surface of the press groove can be obtained.

If the recording disk accommodated in the clean chamber of the disk drive device is configured to be rotated by the above-mentioned dynamic pressure bearing motor (claim 5), particle contamination from the bearing portion is effectively suppressed. Accordingly, the clean environment in the clean chamber is maintained, and read / write errors on the recording disk can be minimized.

[0018]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing a configuration of a main part of a disk drive device equipped with a dynamic pressure bearing motor (spindle motor 1) of the present invention. FIG. 2 is a radial bearing of the spindle motor 1 of FIG. FIG. 3 is a cross-sectional view showing a dynamic pressure groove formed in a portion, and FIG. 3 is a schematic configuration diagram schematically showing an electrolytic processing apparatus for forming a dynamic pressure groove in a radial bearing portion.

The hard disk drive as a disk drive shown in FIG. 1 constitutes a clean chamber 8 which forms a clean space 6 sealed from the outside by a base 2 and a cover member 4 which covers the upper surface of the base 2. In the clean space 6, a recording disk 12 rotated by a spindle motor 10 is accommodated, and a head assembly including a magnetic head for reading and writing data from and to the recording disk 12 and a voice coil motor are accommodated.

The spindle motor 10 is a dynamic pressure bearing motor, and includes a support cylinder 14 provided on the base member 2 and a cylindrical sleeve member 16 fitted and fixed to the support cylinder 14.
The cover 18, which closes the lower surface opening of the support cylinder 14, and the stator 20, which is externally fitted and fixed to the support cylinder 14, constitute a motor fixing member. A rotor hub 22 as a rotating member of the motor includes a hub member 24 on which the recording disk 12 is mounted, a shaft 26 integrally fixed to the center of rotation of the hub member 24, and a hub member which is radially opposed to the stator 20. The hub member 2 is composed of a cylindrical rotor magnet 28 and the like mounted on the inner surface of the outer peripheral wall of the hub member 2.
4, a plurality of recording disks 1 mounted on the outer surface of the outer peripheral wall
2 (two sheets in the figure) are fixed to the hub member 24 by the clamp member 30 screwed to the shaft 26, and rotate integrally with the rotor hub 22.

The rotating member is rotatably supported by a fixed member via a radial dynamic pressure bearing 32 and a thrust dynamic pressure bearing 34. In the radial dynamic pressure bearing 32, the inner peripheral surface of the support member 16 and the outer peripheral surface of the shaft 26 are opposed to each other via a radial bearing gap, and the radial bearing gap is filled with a lubricating fluid 36 such as oil. Is formed by forming a dynamic pressure groove 32a for generating a radial load supporting pressure on one or both of the bearing surfaces (the inner peripheral surface of the support member 16 which is a fixed-side bearing surface in the figure). The dynamic pressure groove 32a is formed in a herringbone shape as shown in FIG. 2, and the dynamic pressure for moving the lubricating fluid 36 toward the thrust dynamic pressure bearing 34 as shown by an arrow A in FIG. It is unbalanced in the axial direction to occur. The formation of the dynamic pressure groove 32a in the support member 16 is performed by electrolytic processing described later.

The thrust bearing 34 fills the thrust bearing gap between the upper surface of the support member 16 and the inner ceiling surface of the hub member axially facing the support member 16 with the lubricating fluid 36 and forms a thrust bearing gap. One or both of the surfaces (in the figure, the inner ceiling surface of the hub member 24 that is the rotation-side bearing surface)
Is formed by forming a dynamic pressure groove 34a for generating a thrust load supporting pressure. This dynamic pressure groove 34a is formed in a spiral shape, and rotates when the rotor hub 22 rotates as shown in FIG.
As shown by the arrow B, a dynamic pressure for moving the lubricating fluid 36 inward in the radial direction is generated.

The radial bearing gap of the radial dynamic pressure bearing 32 and the thrust bearing gap of the thrust dynamic pressure bearing 34 are continuous, and are continuously filled with the lubricating fluid 36. The dynamic pressure generated by the radial dynamic pressure groove 32a And the dynamic pressure generated by the thrust dynamic pressure groove 34a, the radial dynamic pressure bearing 3
The pressure is highest at a position closer to the thrust dynamic pressure bearing 34 than the center in the axial direction of No. 2, and the pressure gradually decreases from the maximum pressure point toward the opposite side of the radial dynamic pressure bearing 32 from the thrust dynamic pressure bearing 34. On the other hand, the pressure distribution of the lubricating fluid 36 is obtained such that the pressure decreases as the position approaches the thrust dynamic pressure bearing 34 from the maximum pressure point and the pressure gradually decreases from the inner peripheral portion to the outer peripheral portion in the thrust dynamic pressure bearing 34. , Radial loads and thrust loads.

At the lower end of the shaft 26, a retaining member 38 having a diameter larger than the inner peripheral surface of the support member 16 constituting the bearing surface of the radial dynamic pressure bearing 32 is fixed, and the shaft 26 is detached from the support member 16. Has been prevented. A back pressure is always applied to the rotor hub 22 in the axially downward direction by a magnetic force or the like, and the inner ceiling surface of the hub member 24 is urged in a direction in which it contacts the upper surface of the support member 16.

The hub member 24 and the support member 16 are formed of a free-cutting stainless steel having good cutting properties, and after being cut into a desired shape, the radial dynamic pressure grooves 32 are formed on the respective bearing surfaces.
a and the thrust dynamic pressure groove 34a are formed by electrolytic processing.

FIG. 3 shows that the radial dynamic pressure grooves 3
2 shows an overall configuration of an electrolytic processing apparatus for forming 2a.

The workpiece to be machined, that is, the support member 16 of the spindle motor 10 described with reference to FIG. The supporting member 16 is subjected to electrolytic processing under predetermined processing conditions. As the processing conditions of the electrolytic processing, for example, a processing voltage of 10 V, a processing current of 10 A, a processing time (time for turning on the switch means 46) of 3 seconds, the support member 16
The gap between the machining surface of the tool electrode 44 and the electrode surface of the tool electrode 44 is set to 0.1 mm, and a dynamic pressure groove having a desired shape with a depth of 10 μm is formed under such machining conditions.

During electrolytic processing, the circulation pump 48 is operated,
The electrolyte 52 in the electrolyte tank 50 is supplied to the processing chamber 42, the electrolyte 52 flows between the support member 16 and the tool electrode 44, and is returned from the processing chamber 42 into the electrolyte tank 50. Thus, the electrolyte 52 is circulated. When the switch means 46 is turned on for a predetermined time (processing time), a DC power supply (pulse power supply) is applied from the processing power supply 54 to the supporting member 16 and the tool electrode 44, and the supporting member 16,
A current flows between the tool electrodes 44, and the surface of the support member 16 facing the exposed electrode of the tool electrode 44 elutes into the electrolytic solution 52, and a dynamic pressure groove having a shape corresponding to the exposed electrode is formed.

The on / off of the switch means 46 is controlled by an energization control circuit 56.
The current flowing between the tool electrode 44 and the
And the energization control circuit 56 according to the detected value.
As a result, the ON time of the switch means 46 is finely adjusted, and the quality is always stable even when the amount of eluted material mixed into the electrolytic solution 52, the change in the flow rate at the processing position of the electrolytic solution 52, the change in various other processing conditions, and the like. Groove processing can be performed. The reference numerals 60 and 62 denote sections connected to the positive power supply terminal and the negative power supply terminal of the processing power supply 54, which are electrically connected to the support member 16 and the tool electrode 44, respectively.

The support member 16 made of free-cutting stainless steel is formed into a predetermined shape, and then a dynamic pressure groove 32a is formed by the above-described electrolytic processing apparatus. The protrusions remain without completely dissolving. For this reason, the support member 16 grooved by electrolytic processing is subjected to an acid treatment centering on the inner peripheral surface (dynamic pressure bearing surface).

That is, the supporting member 16 which has been grooved by the electrolytic processing is pickled with a nitric acid aqueous solution to remove projections made of free-cutting components such as manganese sulfide which are difficult to be processed in the electrolytic processing. Thereby, high corrosion resistance peculiar to the present stainless steel is exhibited, and generation of contamination due to particles is prevented.

In the acid treatment, the concentration of nitric acid is 5% to 2%.
It is good to carry out at a relatively low concentration of 0%, but it is not limited to this. That is, any other solution that can remove free-cutting components from the surface of the free-cutting stainless steel can be used. For example, an aqueous solution of sulfuric acid, hydrochloric acid, hydrofluoric acid, or the like can be used.

As described above, the stainless steel subjected to the acid treatment can improve the corrosion resistance and prevent the particle contamination, but it is necessary to remove the sulfur-containing gas generated during the acid treatment. It is preferable that the support member 16 after the acid treatment is subjected to an alkali neutralization treatment or a baking treatment, so that the corrosion resistance is enhanced.

Here, the neutralization treatment is to neutralize the hydrogen sulfide generated from the free-cutting component using an aqueous solution of sodium hydroxide, potassium hydroxide or the like.
C., preferably at 120.degree. C. for several hours to remove sulfur gas. Support member 1 that has been subjected to such processing
No. 6 does not generate these sulfur-containing gases, which increases the corrosion resistance of the steel itself and can also prevent corrosion of the head and media in the apparatus.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the gist of the present invention.

For example, in the above example, the radial bearing 3
Although the support member 16 in which the two dynamic pressure grooves 32a are formed has been described as an example, the present invention can be similarly applied to the hub member 24 in which the dynamic pressure grooves 34a of the thrust bearing portion 34 are formed. The hub member 24 is made of a free-cutting stainless steel, which is cut into a predetermined shape, and then the dynamic pressure groove 34a is formed by electrolytic processing.
May be subjected to an acid treatment. Of course, it is desired to perform an alkali neutralization treatment or a baking treatment after the acid treatment,
Further, an oxidation treatment is preferably performed as a pretreatment of the acid treatment.

[0037]

The hydrodynamic bearing motor and the disk drive using the same according to the present invention are constructed as described above and have the following effects. In the dynamic bearing motor according to the first aspect, one or both of the fixed bearing surface and the rotary bearing surface forming the dynamic pressure bearing, in which the dynamic pressure groove is formed, are formed of free-cutting stainless steel. Since the formation surface is subjected to an acid treatment after the formation of the dynamic pressure groove by the electrolytic processing, it is possible to remove the projections made of a free-cutting component which are difficult to be processed at the time of the electrolytic processing by the acid treatment. Particle contamination due to objects can be prevented, and stable bearing performance can be exhibited.

In the hydrodynamic bearing motor according to claims 2 and 3, neutralization treatment or baking with an alkali is performed after the acid treatment of the free-cutting stainless steel. It is possible to reliably remove the generated gas containing sulfur.

In the hydrodynamic bearing motor according to the fourth aspect, since the chromate treatment is performed immediately after the acid treatment, the corrosion resistance of the free-cutting stainless steel can be remarkably improved.

In the disk drive device according to the fifth aspect, since the recording disk is driven to rotate in the clean chamber by using the above-described dynamic bearing motor, particle contamination due to protrusions of free-cutting components is provided. Since there is no nation, no problem occurs in the access of the head to the recording disk, and high reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a hard disk drive including a dynamic bearing motor according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a dynamic pressure groove in the support member of FIG.

FIG. 3 is a schematic configuration diagram showing an electrolytic processing apparatus for processing the dynamic pressure groove of FIG. 2;

[Explanation of symbols]

 Reference Signs List 10 spindle motor 12 recording disk 16 support member 22 rotor hub 24 hub member 26 shaft 32 radial dynamic pressure bearing portion 32a dynamic pressure groove 34 thrust dynamic pressure bearing portion 34a dynamic pressure groove

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 5/16 H02K 5/16 Z (72) Inventor Hiromi Ishii 10 Nishitei Gokutomachi Nishitei, Ukyo-ku, Kyoto F-term in the Central Research Laboratories of Stock Company (Reference) GG12

Claims (5)

[Claims] 1. A dynamic pressure bearing is formed by forming a dynamic pressure groove on one or both of a fixed bearing surface provided on a fixed member side and a rotary bearing surface provided on a rotary member side. A dynamic pressure bearing motor rotatably supporting a rotating member with respect to a fixed member, wherein one or both of the fixed bearing surface and the rotating bearing surface in which the dynamic pressure grooves are formed are made of free-cutting stainless steel. A hydrodynamic bearing motor, wherein the dynamic pressure groove is formed by subjecting the free-cutting stainless steel to electrolytic processing, and the surface on which the dynamic pressure groove is formed is subjected to an acid treatment. 2. The hydrodynamic bearing motor according to claim 1, wherein the surface on which the hydrodynamic grooves are formed is subjected to a neutralization treatment with an alkali solution after the acid treatment. 3. The hydrodynamic bearing motor according to claim 1, wherein the surface on which the hydrodynamic grooves are formed is baked after the acid treatment. 4. The surface on which the dynamic pressure grooves are formed is subjected to a chromate treatment immediately after the acid treatment.
The dynamic pressure bearing motor according to any one of claims 1 to 3. 5. A disk drive comprising a recording chamber rotated by the hydrodynamic bearing motor according to claim 1 and a head for accessing said recording disk housed in a clean chamber.