JP2001254732A - Dynamic pressure bearing, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and miniaturize a dynamic pressure bearing, and to obtain the excellent dynamic pressure characteristic. SOLUTION: Conductive pieces formed of flakes which are residual powder produced when machining a flexible bearing sleeve 13 are dispersed in the lubricating fluid which is generally used, inexpensive and excellent in bearing characteristic, the lubricating fluid conductive thereby is poured in a bearing space between a rotary shaft 21 formed of a conductive material and the bearing sleeve 13, and the rotary shaft 21 side and the bearing sleeve 13 side are electrically connected to each other by one or a plurality of conductive pieces P formed of flakes which are residual powder of the bearing sleeve 13.

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 device for supporting a shaft member and a bearing member rotatably relative to each other by a dynamic pressure of a predetermined lubricating fluid, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, magnetic disks, polygon mirrors,
A dynamic pressure bearing device using the dynamic pressure of a lubricating fluid is being adopted to support various types of rotating bodies such as optical disks at high speed, and the development of the dynamic pressure bearing device is being rapidly carried out. For example, in the case where a magnetoresistive magnetic head (hereinafter, referred to as an MR head) is employed for high-density recording of a magnetic disk, a dynamic head provided with a countermeasure for preventing charge destruction of the MR head. There have been various proposals for pressure bearing devices.

As one example, in a dynamic pressure bearing device described in Japanese Patent Application Laid-Open No. 7-64991, a high-speed rotation of a magnetic disk is provided by providing a conductive bearing member and a sleeve and using a conductive lubricating fluid. Is caused to flow to the base side through the conductive bearing member and sleeve, and the conductive lubricating fluid, thereby reducing the potential difference between the magnetic disk and the magnetic head so as to prevent discharge. I have. At this time, a magnetic fluid or a lubricating oil provided with a special conductive additive is used as the conductive lubricating fluid.

[0004] As another means for preventing charge destruction of the MR head, conductivity is ensured by means such as arranging a magnetic fluid seal separately from the bearing member to remove unnecessary charges from the magnetic disk. Has also been proposed.

[0005]

However, in the case of using a magnetic fluid or a lubricating oil to which a special conductive additive is added as in the above-described conventional apparatus, the viscosity of the lubricating fluid may increase. In addition, there is a problem that the physical properties of the lubricating fluid are reduced due to a decrease in thermal stability or the like, and good bearing characteristics may not be obtained. In addition,
The use of a very special lubricating oil has to be expensive.

In the case of using a magnetic fluid seal,
Since a large mounting space is required, there is a problem that the entire apparatus becomes large.

Accordingly, the present invention provides a dynamic pressure bearing device and a method of manufacturing the same which can be reduced in size by a simple and inexpensive structure and can obtain good dynamic pressure characteristics. Aim.

[0008]

According to a first aspect of the present invention, there is provided a hydrodynamic bearing device wherein a shaft member and a bearing member are disposed so as to face each other and rotate relative to each other, and the shaft member. And a hydrodynamic bearing surface formed on each of both opposing surfaces of the bearing member, a hydrodynamic pressure generating groove provided on at least one of these hydrodynamic bearing surfaces, and an opposing gap between the hydrodynamic bearing surfaces. And a lubricating fluid that is injected into and generates a dynamic pressure by the pressurizing action of the dynamic pressure generating groove, wherein each of the shaft member and the bearing member is formed of a conductive material, And, the member on one side of the shaft member and the bearing member is formed from a material having more flexibility than the member on the other side,
Conductive strips having the same degree of flexibility as the above-mentioned flexible material are dispersed in the lubricating fluid so that the lubricating fluid has conductivity.

Further, in the dynamic pressure bearing device according to the second aspect,
The conductive strip according to claim 1 is formed of a strip having a long side in the thickness direction, and contains the same component as the flexible material.

Further, in the dynamic pressure bearing device according to the third aspect, the conductive strip according to the first aspect includes a conductive strip having at least one side having a size smaller than a size of a facing gap between the two dynamic pressure bearing surfaces. .

Further, in the hydrodynamic bearing device according to the fourth aspect, in the conductive strip according to the first aspect, a side portion having a dimension longer in a thickness direction is opposed to the two hydrodynamic bearing surfaces. Includes those with dimensions comparable to or greater than the dimensions of the gap.

On the other hand, in the dynamic bearing device according to the fifth aspect,
A shaft member and a bearing member that are arranged so as to rotate relative to each other while facing each other; a dynamic pressure bearing surface formed on each of the opposed surfaces of the shaft member and the bearing member; A dynamic pressure generating groove provided on at least one side,
A lubricating fluid that is injected into the opposing gap between the two hydrodynamic bearing surfaces and generates a dynamic pressure by the pressurizing action of the dynamic pressure generating groove; Each is formed of a conductive material, and one of the shaft member and the bearing member is formed of a material having more flexibility than the other member, and the lubricating fluid includes In addition, a predetermined amount of residual processing powder of a member made of a flexible material among the shaft member and the bearing member is dispersed so that the lubricating fluid has conductivity.

Further, in the dynamic bearing device according to the sixth aspect,
A shaft member and a bearing member that are arranged so as to rotate relative to each other while facing each other; a dynamic pressure bearing surface formed on each of the opposed surfaces of the shaft member and the bearing member; A dynamic pressure generating groove provided on at least one side,
A lubricating fluid that is injected into the opposing gap between the two hydrodynamic bearing surfaces and generates a dynamic pressure by the pressurizing action of the dynamic pressure generating groove; Each is formed of a conductive material, and the one side member provided with the dynamic pressure generating groove is formed of a material having more flexibility than the other side member, and the lubricating fluid includes The processing residual powder of the member on which the dynamic pressure generating groove is formed is dispersed in a predetermined amount for obtaining conductivity.

Further, in the hydrodynamic bearing device according to the seventh aspect, the lubricating fluid according to the first, fifth, or sixth aspect comprises a fluid having an insulating property.

Further, in the hydrodynamic bearing device according to the present invention, the processing residue powder according to the above-mentioned claim 5 or 6 has at least one side having a size smaller than a size of an opposing gap between the two hydrodynamic bearing surfaces. including.

According to a ninth aspect of the present invention, in the hydrodynamic bearing device according to the fifth or sixth aspect, the side having the maximum length is substantially equal to the gap between the dynamic pressure bearing surfaces. Or include those with large dimensions.

According to a tenth aspect of the present invention, the shaft member according to the first or fifth or sixth aspect is made of stainless steel, and the bearing member is made of a copper-based alloy.

Further, in the method of manufacturing a hydrodynamic bearing device according to the eleventh aspect, the shaft member and the bearing member which are arranged so as to rotate relative to each other while facing each other, and to the both opposing surfaces of the shaft member and the bearing member. Each of the formed dynamic pressure bearing surfaces, a dynamic pressure generation groove provided on at least one of the two dynamic pressure bearing surfaces, and a dynamic pressure generating groove which is injected into an opposing gap between the two dynamic pressure bearing surfaces to form the dynamic pressure bearing surface. A lubricating fluid that generates dynamic pressure by the pressurizing action of the pressure generating groove, wherein the shaft member and the bearing member are each formed of a conductive material, and the shaft member and the bearing member are formed of a conductive material. While the one member of the bearing member is formed from a material having more flexibility than the member on the other side, the processing residue of the member made of the flexible material of the shaft member and the bearing member is formed. The flexible Advance by a predetermined amount remaining on the surface of the member, upon injection of the lubricating fluid, and dispersing the processed residual powder in the lubricating fluid, and so as to impart conductivity to the lubricating fluid.

Furthermore, in the method of manufacturing a dynamic pressure bearing device according to the twelfth aspect, the shaft member and the bearing member are disposed so as to rotate relative to each other while facing each other, and both opposing surfaces of the shaft member and the bearing member. A dynamic pressure bearing surface respectively formed on the
Hydrodynamic pressure generating grooves provided on at least one of the two dynamic pressure bearing surfaces, and are injected into opposing gaps between the two dynamic pressure bearing surfaces, and the dynamic pressure is generated by the pressurizing action of the dynamic pressure generating grooves. And a method of manufacturing a hydrodynamic bearing device having a lubricating fluid that generates a fluid, wherein each of the shaft member and the bearing member is formed of a conductive material, and the member on one side of the shaft member and the bearing member is formed. , While forming from a material having more flexibility than the member on the other side, processing residual powder at the time of processing of the member having the dynamic pressure generating groove of the fixed member and the rotating member, on the surface of the member A predetermined amount is left, and at the time of injection of the lubricating fluid, the above-mentioned processing residue is dispersed in the lubricating fluid to impart conductivity to the lubricating fluid.

In the method of manufacturing a dynamic pressure bearing device according to a thirteenth aspect, the shaft member according to the eleventh or twelfth aspect is formed of stainless steel, and the bearing member is formed of a copper-based alloy. I have.

Further, in the method for manufacturing a dynamic pressure bearing device according to the fourteenth aspect, the eleventh aspect uses a lubricating oil having an insulating property as the lubricating fluid.

On the other hand, in the method of manufacturing a hydrodynamic bearing device according to the present invention, at least one side of the processing remnant according to the present invention is smaller than a gap between the hydrodynamic bearing surfaces. Are kept.

In the method of manufacturing a dynamic pressure bearing device according to a sixteenth aspect of the present invention, the maximum length side of the processing residue according to the eleventh or twelfth aspect is substantially equal to the gap size between the dynamic pressure bearing surfaces. Large dimensions are left.

In the method of manufacturing a hydrodynamic bearing device according to a seventeenth aspect, the member that retains the processing residue according to the sixteenth aspect is subjected to ultrasonic cleaning after the processing, so that the small-size processing residue remains. I try to make it.

[0025] As described in the first aspect of the present invention,
Disperse conductive strips consisting of flakes having the same degree of flexibility as flexible members in lubricating fluids that are generally used at low cost and have good bearing properties, thereby improving conductivity. Since the applied lubricating fluid is used by injecting it into the bearing gap between the shaft member and the bearing member made of a conductive material, special conductive lubrication, which is expensive and has difficulties in bearing characteristics as in the past, is used. It is not necessary to use a fluid or a large-sized magnetic fluid seal. As a result, good dynamic pressure characteristics can be obtained while simplifying and downsizing the configuration.

At this time, as in the invention described in claim 2,
If the conductive strip made of the flakes is assumed to contain the same components as the material of the flexible member, the conductive strips made of the flake may damage the shaft member and the bearing member. As a result, smooth rotation characteristics can be obtained and the life of the device can be prolonged.

Further, if the conductive strip having at least one side smaller than the dimension of the bearing gap is included as in the third aspect of the present invention, the conductive strip in the bearing gap becomes smaller. It moves freely while being oriented in the direction of low resistance, and easily rotates in the gap between the dynamic pressure bearing surfaces, further reducing damage to the shaft member and the bearing member.

Further, if the long side portion of the conductive strip includes a dimension approximately equal to or larger than the dimension of the bearing gap, as in the invention according to claim 4, the above-mentioned bearing gap can be reduced. The frequency of contact with the inner wall is increased, and good conductivity is obtained.

Further, claim 5 or 6 or 11 or 12
As in the invention described above, processing residue of a shaft member or a bearing member made of a conductive material is dispersed in a lubricating fluid, and the lubricating fluid imparted with the conductivity is thereby supplied to a bearing between the shaft member and the bearing member. If it is used by injecting it into the gap, there is no need to use a special conductive lubricating fluid that is difficult and has a problem with bearing characteristics as in the past, or a large magnetic fluid seal. And good dynamic pressure characteristics can be obtained.

At this time, if an insulative lubricating fluid that is inexpensive and has excellent bearing characteristics is used, the cost can be further reduced.

Further, if the conductive strips include a conductive strip having at least one side smaller than the dimension of the bearing gap, the conductive strip in the bearing gap may be included. The piece moves freely while being oriented in the direction of low resistance, and easily rotates in the gap between the dynamic pressure bearing surfaces, further reducing damage to the shaft member and the bearing member.

Furthermore, if the long side portion of the conductive strip includes a dimension approximately equal to or larger than the dimension of the bearing gap as in the ninth or sixteenth aspect of the present invention, The frequency of contact with the inner wall portion of the gap is increased, and the conductivity is reliably obtained.

Further, the shaft member is made of stainless steel as in the invention according to claim 10 or 13,
If the bearing member is made of a copper-based alloy, the basic structure of the dynamic pressure bearing device can be a simple and ordinary structure.

Further, if only a relatively large dimension that easily damages the shaft member and the bearing member is removed by performing ultrasonic cleaning after processing, the shaft member can be removed. Only the micro-sized processing residue having a thickness of, for example, about 1 μm or less, which hardly damages the bearing member, is efficiently left on the surface of the workpiece.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. Prior to that, the overall structure of a hard disk drive (HDD) to which the present invention is applied will be described with reference to the drawings.

The entirety of the shaft-rotating HDD spindle motor shown in FIG.
And a rotor set 20 as a rotating member attached to the stator set 10 from above in the figure. Among them, the stator set 10 has a fixed frame 11 screwed to a fixed base (not shown). The fixed frame 11 is formed of an aluminum-based metal material to reduce the weight. However, an inner peripheral side of an annular bearing holder 12 formed so as to stand substantially at the center of the fixed frame 11. A bearing sleeve 13 as a fixed bearing member formed in a hollow cylindrical shape is joined to the bearing holder 12 by press fitting or shrink fitting. The bearing sleeve 13 is formed of a copper-based alloy material such as phosphor bronze in order to facilitate drilling of a small diameter hole.

A stator core 14 made of a laminated body of electromagnetic steel sheets is fitted on the outer peripheral mounting surface of the bearing holder 12. A drive coil 15 is wound around each salient pole portion provided on the stator core 14.

Further, a rotation shaft 21 constituting the above-mentioned rotor set 20 is rotatably inserted into a center hole provided in the bearing sleeve 13. The rotating shaft 21 in the present embodiment is formed from a predetermined stainless steel. That is, the bearing sleeve 13 as the bearing member is formed of a material having more flexibility than the rotating shaft 21 as the shaft member.

The dynamic pressure surface formed on the inner peripheral wall of the bearing sleeve 13 is disposed so as to radially oppose the dynamic pressure surface formed on the outer peripheral surface of the rotary shaft 21. A radial dynamic pressure bearing portion RB is formed in a small bearing gap. More specifically, the dynamic pressure surface on the bearing sleeve 13 side and the dynamic pressure surface on the rotary shaft 21 side of the radial dynamic pressure bearing portion RB are circumferentially opposed to each other with a small gap of several μm. A lubricating fluid having a composition described below is injected into the bearing space formed by the minute gap so as to be continuous in the axial direction.

Furthermore, on at least one side of both the dynamic pressure surfaces of the bearing sleeve 13 and the rotating shaft 21, for example, a herringbone-shaped radial dynamic pressure generating groove (not shown) is divided into two blocks in the axial direction. The lubricating fluid is pressurized by the pumping action of the radial dynamic pressure generating groove during rotation to generate a dynamic pressure, and the dynamic pressure of the lubricating fluid causes the dynamic pressure of the lubricating fluid and the rotating shaft 21 to be described later. The rotating hub 22 is axially supported in the radial direction.

On the other hand, a capillary seal portion RS is arranged at the upper end in the drawing of the bearing space constituting each of the radial dynamic pressure bearing portions RB. The capillary seal portion RS has a configuration in which the above-described bearing gap is gradually enlarged toward the outer side of the bearing by an inclined surface formed on the rotating shaft 21 or the bearing sleeve 13 side.
It is formed to have a gap size of μm to 300 μm. The liquid level of the lubricating fluid is located in the capillary seal portion RS regardless of whether the motor rotates or stops.

Further, the rotary hub 22, which constitutes the rotor set 20 together with the rotary shaft 21, is formed of a substantially cup-shaped member made of aluminum-based metal so that a recording medium such as a magnetic disk (not shown) is mounted. , The rotary hub 22
Of the rotary shaft 21
Are integrally joined by press fitting or shrink fitting.

The rotary hub 22 has a substantially cylindrical body 22a on which a recording medium disk is mounted on the outer periphery, and a back yoke 22b The annular drive magnet 22c is attached via the. This annular drive magnet 22c
Are disposed close to each other so as to annularly face the outer peripheral end face of the stator core 14 described above.

On the other hand, a disc-shaped thrust plate 23 is fixed to the tip of the rotating shaft 21 at the lower end in the figure. The thrust plate 23 is disposed so as to be accommodated in a cylindrical recessed portion formed in the center of the bearing sleeve 13 at the lower end in the drawing, and in the recessed portion of the bearing sleeve 13. The dynamic pressure surface provided on the upper side surface of the thrust plate 23 in the drawing is opposed to the dynamic pressure surface provided on the bearing sleeve 13 so as to be close to the axial direction. A dynamic pressure generating groove having an appropriate shape is formed on at least one of the two opposing dynamic pressure surfaces, and an opposing gap is formed between the two dynamic pressure surfaces of the thrust plate 23 and the bearing sleeve 13. The thrust dynamic pressure bearing portion SBa is formed.

Further, a counter plate 16 made of a relatively large-diameter disc-shaped member is arranged so as to be close to the lower dynamic pressure surface of the thrust plate 23 in the figure. The counter plate 16 is fixed so as to close the lower end side opening of the bearing sleeve 13, and includes a dynamic pressure surface provided on the upper surface side of the counter plate 16 in the drawing and the above-described thrust plate 2.
3 also in the close opposing gap between the lower dynamic pressure surface in the drawing and
By forming the dynamic pressure generating groove having an appropriate shape, a lower thrust dynamic pressure bearing portion SBb is formed.

As described above, the two dynamic pressure surfaces on the thrust plate 23 side, which constitute a set of thrust dynamic pressure bearing portions SBa, SBb arranged adjacent to each other in the axial direction, the bearing sleeve 13 and the counter opposed thereto. The two dynamic pressure surfaces on the plate 16 side are disposed axially opposite each other with a small gap of several μm therebetween, and a lubricating fluid having a composition described later is filled in the bearing space formed by the small gap with the thrust. It is injected so as to be continuous in the axial direction via the outer peripheral passage of the plate 23.

Further, at least one of the dynamic pressure surfaces of the thrust plate 23 and the dynamic pressure surfaces of the bearing sleeve 13 and the counter plate 16 is provided with a herringbone-shaped thrust dynamic pressure generating groove (not shown). The lubricating fluid is pressurized by the pumping action of the thrust dynamic pressure generating groove to generate a dynamic pressure during rotation, and the dynamic pressure of the lubricating fluid causes The rotating shaft 21 and the rotating hub 22 described above
Are axially supported in the thrust direction.

Here, as described above, the bearing sleeve 13 of the stator set 10 and the rotating shaft 21 of the rotor set 20 are formed of conductive materials such as stainless steel and phosphor bronze (copper-based alloy). The material of the bearing sleeve 13 as the bearing member is more flexible than the rotating shaft 21 as the shaft member. And, the processing residual powder when finishing the inner peripheral surface of the bearing sleeve 13 having flexibility is dispersed in the lubricating fluid.

That is, as shown in FIG. 2, the lubricating fluid A has an insulating property with a volume resistivity of 1 × 10 ⁻¹² Ω · cm or more as a dispersed base oil material A1 of the lubricating fluid A. Ester oil, hydrocarbon type (poly α-olefin,
Mineral oil), ether-based, fluorine-based, etc. insulating lubricating oils, and the insulating dispersed base oil material A
1, a large number of residual powder A2 of the bearing sleeve 13 described above is dispersed. The lubricating fluid A is given conductivity by the dispersed processing residue powder A2.

At this time, the residual powder A2 of the bearing sleeve 13 remains on the processed surface when the inner peripheral wall surface of the bearing sleeve 13 is finished or when the dynamic pressure generating groove is rolled. However, at the time of assembling the motor, the above-described dispersed base oil material A1 of the insulating lubricating oil A is injected into the bearing gap, and at the same time, the residual machining powder A2 on the bearing sleeve 13 is removed from the bearing sleeve 13. It is arranged by being naturally dispersed in the insulating lubricating oil A1 in the gap.

That is, in the processing step of the bearing sleeve 13, first, a bearing hole having an inner diameter of 2.998 mm is formed through the material of the bearing sleeve 13, and a bearing hole of the bearing sleeve material is formed. A dynamic pressure generating groove having a depth of about 8 μm is plastically formed on the inner peripheral wall surface by using a ball rolling tool or the like. The above-mentioned residual processing powder A2 remains on the surface of the plastically processed dynamic pressure generating groove. Then, the inner peripheral wall surface of the bearing hole of the bearing sleeve material is also processed to an inner diameter of 2.998 mm, thereby removing a raised portion such as a burr generated during plastic working of the dynamic pressure generating groove. I do. After that, the inner diameter of the bearing hole is finished with 3.000 mm, that is, 1 μm
Perform cutting work with the processing allowance. On the surface of the finished bearing sleeve material, processing residue including the processing residue A2 having a thickness of about 1 μm remains.

Further, after the above-described processing steps are completed, the surface of the bearing sleeve material is ultrasonically cleaned using a predetermined solvent and water. Generally, ultrasonic cleaning has a high removal rate for relatively large particles, but has a poor removal rate for small attached particles of about 1 μm. Therefore, the surface of the bearing sleeve material after the above-described ultrasonic cleaning step has a thickness of 1 μm.
Only the processing residue A2 consisting of conductive strips having a small thickness of not more than m remains, and the processing residue larger than A2 is removed.

At this time, the processing residue powder A2 composed of the conductive strip mainly has a shape corresponding to the cutting processing at the processing margin of 1 μm described above, and is shown in FIG. As shown in the figure, the shape is formed in a piece having a long side with respect to the thickness, such as a generally disc-like shape (a), a needle-like shape (b), and a thin plate-like shape (c). The thickness of the piece is formed to be 1 μm or less. Further, in the residual processing powder A2, at least one of the sides of the piece is smaller than the bearing clearance dimension (for example, 3 to 5 μm) between the bearing sleeve 13 and the rotating shaft 21 described above. It is configured to be able to move freely by being oriented in the direction of low resistance in the bearing gap.

Further, as indicated by reference symbol A2 'in FIG. 4, in the above-mentioned residual machining powder A2, a side portion longer in the thickness direction is defined by the bearing clearance dimension (3 to 5 μm). The same or larger dimensions are included. Since the frequency of contact with the inner wall portion of the bearing gap is increased, the processing residual powder A2 ′ having these long sides has conductivity reliably obtained by including the processing residual powder A2 ′ as described later. It is supposed to be.

As described above, in the present embodiment, when the dispersed base oil material A1, which is an insulative lubricating fluid generally used at low cost and with good bearing characteristics, is injected, the remaining processing of the flexible bearing sleeve 13 is performed. Powder, that is, a lubricating fluid A having conductivity by dispersing a conductive strip A2 made of flakes in the insulating lubricating fluid A1, and the lubricating fluid having the conductivity. A is used in a bearing gap formed between the rotating shaft 21 made of a conductive material and the bearing sleeve 13. At this time, the conductive strip A2, which is a flaky body, which is the residual powder of the bearing sleeve 13 described above, freely moves around in the bearing gap along the flow of the lubricating fluid, and the rotating shaft 21 and the bearing sleeve 13 Contact and separation are repeated with respect to each surface. For example, as shown in FIG. A contact state is established such that the surface and the surface of the bearing sleeve 13 are connected, whereby the rotating shaft 21 and the bearing sleeve 13 are electrically connected to each other. As a result, electric charges generated by high-speed rotation of the magnetic disk and the like Is discharged, the potential difference between the magnetic disk and the magnetic head is reduced, and discharge is prevented.

Such a rotating shaft 21 and the bearing sleeve 13
The electrical connection state between the two members 21 and 13 can be confirmed by measuring a temporal change in the electric resistance between the two members 21 and 13 as shown in FIG. 5, for example. That is, FIG. 3 shows the results obtained by measuring the electric resistance between the rotor and the stator based on the potential difference when the rotation speed is set to 7200 rpm. The potential difference (vertical axis) between the two members 21 and 13 is 10 MΩ. In the case of a non-conducting state having a resistance value far exceeding the above, the voltage is about 5 V. However, in the apparatus according to the above-described embodiment, time (horizontal axis)
With the passage of time, the potential frequently changes to zero potential, and has an average resistance of several MΩ. In general, it has been confirmed that a resistance value of about 10 MΩ or less is sufficient in order to avoid charging trouble. Therefore, in the present embodiment, the rotating shaft 21 and the bearing sleeve 13 are well connected. It was actually confirmed that it was done.

Therefore, according to the present embodiment, there is no need to use a special conductive lubricating fluid having a disadvantage in bearing characteristics as in the prior art, or a large-sized magnetic fluid seal, thereby simplifying the configuration of the entire apparatus. -Good dynamic pressure characteristics can be obtained at the same time as miniaturization. Actually, as a result of a sliding reliability test, no seizure, abrasion, or other performance problems were found.

In particular, in the present embodiment, since the conductive strip A2 made of a piece is formed of the same material as the flexible bearing sleeve 13, the conductive strip A2 made of a piece is used. However, the rotation shaft 21 and the bearing sleeve 13 are not damaged, so that smooth rotation characteristics can be obtained and the life of the device can be extended.

In addition, in the present embodiment, at least one side of each side of the conductive strip A2 made of a piece is made smaller than the dimension of the bearing gap between the hydrodynamic bearing surfaces. Because of the inclusion, as shown by the arrows in FIG.
The conductive strip A2 made of the above-mentioned flaky body rotates immediately after coming into contact with the rotating shaft 21 side or the bearing sleeve 13 side, so that the conductive strip A2 made of such a flaky body can easily rotate. Accordingly, damage to the rotating shaft 21 or the bearing sleeve 13 is more reliably reduced.

Further, the conductive strip A2 'as shown in FIG. 4, that is, the long side portion includes the same size as or larger than the size of the bearing gap between the dynamic pressure bearing surfaces. In this case, the rotating shaft 21 constituting the bearing clearance
Alternatively, the frequency of contact with the inner wall of the bearing sleeve 13 is increased, and good conductivity is reliably obtained.

Further, in the present embodiment, the rotating shaft 21
Since the bearing sleeve 13 is formed from a general material such as stainless steel or phosphor bronze, the basic structure of the hydrodynamic bearing device has an ordinary simple structure. Since an insulative lubricating oil that is inexpensive and has excellent bearing characteristics is used for the dispersion base material A1 of the lubricating fluid A, the cost can be further reduced.

In addition, in this embodiment, the bearing sleeve 1
By performing ultrasonic cleaning after the processing of step 3, the rotating shaft 2
1 and a relatively large-sized machining residue that easily damages the bearing sleeve 13 is removed, and only a small-sized machining residue having a thickness of, for example, about 1 μm or less is left on the surface of the bearing sleeve 13. And finely-processed residual powder A2 that makes it difficult to damage the rotating shaft 21 and the bearing sleeve 13.
Is very efficiently selected.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be moderately modified without departing from the gist thereof. Needless to say.

For example, in the above-described embodiment, the conductive strip A2 made of a piece is made of the same material as the bearing sleeve 13, but the material itself is different but the same degree as that of the bearing sleeve 13 having flexibility. A material having flexibility or a material partially containing a material having flexibility similar to that of the bearing sleeve 13 can also be employed. In addition, the conductive strip A2 made of a piece-like body does not necessarily need to have the same degree of flexibility as the bearing sleeve 13 as a bearing member. What is necessary is just to have the same flexibility as a member.

Further, the conductive strip A2 made of a flake in the above-described embodiment may contain spherical particles. Furthermore, the dispersed base oil material A1 of the lubricating fluid does not necessarily have to have insulating properties.

Further, the present invention can be similarly applied to a shaft-fixed type dynamic pressure bearing device different from the shaft rotation type as in the above-described embodiment.

The hydrodynamic bearing device according to the present invention is used for a hydrodynamic bearing device used in addition to the HDD motor as in the above-described embodiment, for example, a polygon mirror driving motor or a CD-ROM driving motor. The present invention can be similarly applied to a dynamic bearing device to be used.

[0068]

As described above, the present invention provides a lubricating fluid having good bearing characteristics, which is inexpensive and generally used, in the form of a flake having the same degree of flexibility as a member having flexibility. By dispersing conductive strips into a bearing gap between a shaft member made of a conductive material and a bearing member and using it, a special and expensive conventional bearing with difficulties in bearing characteristics is used. This eliminates the need to use a conductive lubricating fluid or a large magnetic fluid seal, thereby achieving a remarkable effect of obtaining good dynamic pressure characteristics while simplifying and miniaturizing the configuration. Play.

At this time, the invention according to claim 2 is characterized in that the conductive strip made of a flake is regarded as containing the same component as the material of the flexible member, and the conductive strip made of the flake is used. Since the piece does not damage the shaft member and the bearing member, and achieves smooth rotation characteristics and extends the life of the device, the above-described effects can be further improved.

According to a third aspect of the present invention, the conductive strip in the bearing gap can be freely moved by including at least one side of the conductive strip having a size smaller than the dimension of the bearing gap. Since the damage to the shaft member and the bearing member is further reduced, the above-described effects can be further enhanced.

Furthermore, the invention according to claim 4 is characterized in that the long side portion of the conductive strip includes one having a size approximately equal to or larger than the size of the bearing gap, so that the frequency of contact of the bearing gap with the inner wall portion is increased. , And good conductivity is surely obtained, so that the above-described effects can be further improved.

Further, claim 5 or 6 or 11 or 12
According to the invention described above, by dispersing a residual powder of machining of a shaft member or a bearing member made of a conductive material in a lubricating fluid, by injecting and using it in a bearing gap between the shaft member and the bearing member, This eliminates the need for special conductive lubricating fluids, which are expensive and has difficulties in bearing characteristics, as well as large magnetic fluid seals. This has a remarkable effect that dynamic pressure characteristics can be obtained.

At this time, the invention according to claim 7 or 14 is designed to further reduce the cost by using an insulated lubricating fluid which is inexpensive and has excellent bearing characteristics. The above effects can be further improved.

According to the present invention, at least one side of the conductive strip is smaller than the dimension of the bearing gap, so that the conductive strip in the bearing gap can be freely formed. Since the movable member can be moved to further reduce damage to the shaft member and the bearing member, the above-described effect can be further enhanced.

Further, as in the invention according to claim 9 or 16, by including a conductive strip having a long side portion having a size approximately equal to or larger than the size of the bearing gap,
Since the frequency of contact with the inner wall portion of the bearing gap is increased to ensure conductivity, the above-described effect can be further improved.

Further, according to the tenth and thirteenth aspects of the present invention, the shaft member is made of stainless steel and the bearing member is made of a copper-based alloy, so that the basic structure of the hydrodynamic bearing device can be made simple and ordinary. With the configuration, the above-described effects can be further improved.

Further, according to the seventeenth aspect of the present invention, by performing ultrasonic cleaning after processing, only relatively large dimensions that easily damage the shaft member and the bearing member are removed, and the shaft member and the bearing member are damaged. Since only a very small processing residue, which is difficult, for example, having a thickness of about 1 μm or less, is efficiently left on the surface of the workpiece, the above-described effects can be further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view showing an example of the entire structure of a hard disk drive (HDD) including a shaft rotation type dynamic pressure bearing device according to an embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view showing an enlarged bearing clearance of the dynamic pressure bearing device shown in FIG. 1;

FIG. 3 is an enlarged cross-sectional explanatory view showing another example of the residual machining powder contained in the bearing gap of the dynamic pressure bearing device.

FIG. 4: Residual powder A2, A2 ′ contained in lubricating fluid A
It is an external appearance perspective explanatory view showing the example of a shape.

FIG. 5 is a diagram illustrating a time (horizontal axis) change of a potential (vertical axis) between a shaft member and a bearing member over time;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Stator set (fixing member) 13 Bearing sleeve (bearing member) 20 Rotor set (rotating member) 21 Rotating shaft 22 Rotating hub A Lubricating fluid A1 Dispersed base oil material A2, A2 'Processing residue

Claims (17)

[Claims] 1. A shaft member and a bearing member which are arranged so as to rotate relative to each other while facing each other, dynamic pressure bearing surfaces respectively formed on both opposing surfaces of the shaft member and the bearing member, A lubricating oil which is injected into the opposing gap between the hydrodynamic bearing surfaces provided on at least one side of the bearing surface and the hydrodynamic bearing surfaces and generates dynamic pressure by the pressurizing action of the hydrodynamic generating groove. And a fluid, wherein each of the shaft member and the bearing member is formed of a conductive material, and one member of the shaft member and the bearing member is more than the member of the other side. Also formed from a material having flexibility, the lubricating fluid is a conductive strip having the same degree of flexibility as the material having flexibility so that the lubricating fluid has conductivity. Characterized by being distributed Dynamic bearing device to be. 2. The method according to claim 1, wherein the conductive strip is formed of a piece having a long side in a thickness direction and contains the same component as the material having flexibility. The dynamic pressure bearing device according to claim 1. 3. The hydrodynamic bearing device according to claim 1, wherein the conductive strip has a dimension at least one side of which is smaller than a dimension of an opposing gap between the two hydrodynamic bearing surfaces. 4. The conductive strip has a side having a dimension longer in a thickness direction than a dimension of a facing gap between the two hydrodynamic bearing surfaces. The dynamic pressure bearing device according to claim 1, wherein: 5. A shaft member and a bearing member arranged so as to rotate relative to each other while facing each other, a dynamic pressure bearing surface formed on each of both opposing surfaces of the shaft member and the bearing member, and these two dynamic pressures. A lubricating oil which is injected into the opposing gap between the hydrodynamic bearing surfaces provided on at least one side of the bearing surface and the hydrodynamic bearing surfaces and generates dynamic pressure by the pressurizing action of the hydrodynamic generating groove. And a fluid, wherein each of the shaft member and the bearing member is formed of a conductive material, and one member of the shaft member and the bearing member is more than the member of the other side. The lubricating fluid is formed of a flexible material, and the lubricating fluid is made of a flexible material of the shaft member and the bearing member so that the lubricating fluid has conductivity. A certain amount of powder is dispersed Dynamic pressure bearing device, characterized in that it is. 6. A shaft member and a bearing member arranged so as to rotate relative to each other while facing each other, a dynamic pressure bearing surface formed on each of both opposing surfaces of the shaft member and the bearing member, and these two dynamic pressures. A lubricating oil which is injected into the opposing gap between the hydrodynamic bearing surfaces provided on at least one side of the bearing surface and the hydrodynamic bearing surfaces and generates dynamic pressure by the pressurizing action of the hydrodynamic generating groove. And a fluid, wherein each of the shaft member and the bearing member is formed of a conductive material, and one of the members provided with the dynamic pressure generating groove is more than the other member. The lubricating fluid is also formed of a material having flexibility, and the lubricating fluid is formed by dispersing a predetermined amount of processing residual powder of the member in which the dynamic pressure generating groove is formed, in order to obtain conductivity. Characteristic hydrodynamic bearing device. 7. The hydrodynamic bearing device according to claim 1, wherein the lubricating fluid is a fluid having an insulating property. 8. The dynamic pressure bearing device according to claim 5, wherein the processing residual powder includes at least one side having a size smaller than a size of an opposing gap between the two hydrodynamic bearing surfaces. 9. The processing residue powder according to claim 5, wherein a side portion having a maximum length has a size substantially equal to or larger than a gap size between the hydrodynamic bearing surfaces. Dynamic bearing device. 10. The dynamic pressure bearing device according to claim 1, wherein the shaft member is made of stainless steel, and the bearing member is made of a copper-based alloy. 11. A shaft member and a bearing member arranged so as to rotate relative to each other while facing each other, a dynamic pressure bearing surface formed on each of both opposing surfaces of the shaft member and the bearing member, and these two dynamic pressures. A lubricating oil which is injected into the opposing gap between the hydrodynamic bearing surfaces provided on at least one side of the bearing surface and the hydrodynamic bearing surfaces and generates dynamic pressure by the pressurizing action of the hydrodynamic generating groove. And a method of manufacturing a hydrodynamic bearing device having a fluid, wherein each of the shaft member and the bearing member is formed of a conductive material, and one member of the shaft member and the bearing member is formed on the other side. While being formed from a material having more flexibility than the member, a predetermined amount of residual processing powder of a member made of a material having flexibility among the shaft member and the bearing member is left on the surface of the flexible member. Every lubricating fluid A method of manufacturing a hydrodynamic bearing device, characterized in that at the time of pouring, the above-mentioned processing residue is dispersed in a lubricating fluid to impart conductivity to the lubricating fluid. 12. A shaft member and a bearing member arranged so as to rotate relative to each other while facing each other, a dynamic pressure bearing surface formed on each of both opposing surfaces of the shaft member and the bearing member, and these two dynamic pressures. A lubricating oil which is injected into the opposing gap between the hydrodynamic bearing surfaces provided on at least one side of the bearing surface and the hydrodynamic bearing surfaces and generates dynamic pressure by the pressurizing action of the hydrodynamic generating groove. And a method of manufacturing a hydrodynamic bearing device having a fluid, wherein each of the shaft member and the bearing member is formed of a conductive material, and one member of the shaft member and the bearing member is formed on the other side. While being formed from a material having more flexibility than the member, a predetermined amount of processing residual powder is left on the surface of the fixed member and the rotating member during processing of the member having the dynamic pressure generating groove formed thereon. In addition, the lubrication A method of manufacturing a hydrodynamic bearing device, characterized in that at the time of injecting a fluid, the residual machining powder is dispersed in a lubricating fluid to impart conductivity to the lubricating fluid. 13. The method according to claim 11, wherein the shaft member is formed of stainless steel, and the bearing member is formed of a copper-based alloy. 14. The lubricating fluid according to claim 11, wherein a lubricating oil having an insulating property is used.
13. A method for manufacturing a dynamic pressure bearing device according to item 12. 15. The dynamic dynamic bearing according to claim 11, wherein at least one side of the processing residue remains smaller than a gap between the dynamic pressure bearing surfaces. Manufacturing method of pressure bearing device. 16. The machine tool according to claim 11, wherein the longest side portion of the machining residue has a size approximately equal to or larger than a gap between the dynamic pressure bearing surfaces. Of manufacturing a dynamic pressure bearing device. 17. The hydrodynamic bearing device according to claim 16, wherein the member for retaining the machining residue is subjected to ultrasonic cleaning after machining to retain the machining residue of the small size. Production method.