JP2000308297A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion in potential difference by interposing a potential difference lightening member, which consists of metallic material where the trend of ionization on an electrochemical row exists in middle position to each of heterogeneous metals constituting a rotary shaft bearing member and a rotary hug, at the junction face between the rotary shaft bearing member and the rotary hub. SOLUTION: The energy difference between a bearing sleeve 21 and a rotary hub 22 consisting of heterogeneous metals, that is, the potential difference between both the fellow members 21 and 22 is relaxed and reduced by the potential difference lightening member A which is interposed between both members 21 and 22, and consists of metallic material where the trend of ionization on electrochemical row to fresh water lies midway between that of copper material and that of aluminum metallic material. This necks the occurrence or progress of potential difference corrosion. This potential difference corrosion preventive action becomes remarkable, especially in the case where the bearing sleeve 21 consisting of copper metallic material and the rotary hub 22 consisting of aluminum metallic material are joined with each other, and the energy difference (potential difference) between the joined members has become large thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor having a component in which dissimilar metal members are joined.

[0002]

2. Description of the Related Art In recent years, a spindle motor for rotating a recording medium disk has been rapidly reduced in size and thickness, and accordingly, a bearing member (bearing sleeve) supporting a shaft has been changed. , Such as a rotating hub for mounting a recording medium disk and a metal material different from the metal material forming the fixed frame. This is because, even if the diameter of the bearing sleeve is reduced due to miniaturization, a metal having good workability is adopted as a metal material constituting the bearing sleeve so that the inner diameter portion can be particularly well processed. For example, the rotating hub and fixed frame for mounting the recording medium disk are made of lightweight aluminum-based metal,
On the other hand, for the bearing sleeve, a copper-based metal that can be easily processed is used. In this case, a bearing sleeve made of a dissimilar metal material is integrally joined to the rotating hub or the fixed frame by press fitting, shrink fitting, or the like.

[0003]

However, in such a spindle motor in which dissimilar metal materials are integrally joined, when an electrolyte having a large dielectric constant, for example, water enters the joint portion, the dissimilar metal materials are interposed. A local battery is formed, and the local battery may cause anodic dissolution, resulting in so-called potential difference corrosion. The portion where such potential difference corrosion occurs eventually becomes dust and scatters, causing damage to the recording medium disk and the head. Therefore, devices that require cleanliness,
For example, in a hard disk drive (HDD), it is desired to reliably prevent the occurrence of the above-mentioned potential difference corrosion.

Accordingly, the present invention provides a spindle motor capable of favorably preventing potential difference corrosion between a bearing member (bearing sleeve) made of dissimilar metal material and another member with a simple configuration. The purpose is to:

[0005]

In order to achieve the above object, according to the first aspect of the present invention, the fixed shaft is rotatably supported on the outer peripheral side of the fixed shaft with predetermined bearing means interposed therebetween. A spindle comprising: a substantially cylindrical rotating bearing member; and a rotating hub for mounting a recording medium disk concentrically and integrally joined to the rotating bearing member, wherein the rotating bearing member and the rotating hub are made of different kinds of metal materials. In the motor, at the joint surface between the rotary bearing member and the rotary hub, a metal whose ionization tendency on the electrochemical row exists at an intermediate position with respect to each of the different metals forming the rotary bearing member and the rotary hub. A potential difference reducing member made of a material is interposed.

According to a second aspect of the present invention, the rotary bearing member according to the first aspect is made of a copper-based metal material, the rotary hub is made of an aluminum-based metal material, and the potential difference reducing member is made of a nickel-based metal. Made of material.

Further, according to the third aspect of the present invention, the potential difference reducing member according to the first aspect is applied to at least one of the joining surfaces of the rotary bearing member and the rotary hub in a layer by plating, vapor deposition, or painting. Is being worn.

Further, according to the present invention, a fixed frame, a substantially cylindrical fixed bearing member integrally joined to the fixed frame, and a predetermined bearing means on the inner peripheral side of the fixed bearing member. A rotating shaft rotatably supported with a rotating shaft interposed therebetween, and a rotating hub for mounting a recording medium disk fixedly fitted to the rotating shaft, wherein the fixed frame and the fixed bearing member are made of dissimilar metal materials. In the spindle motor, the ionization tendency in the electrochemical row is at an intermediate position on the joint surface between the fixed frame and the fixed bearing member, as compared with each of the dissimilar metals constituting the fixed frame and the fixed bearing member. A potential difference reducing member made of an existing metal material is interposed.

On the other hand, in the invention according to claim 5, the fixed bearing member according to claim 4 is made of a copper-based metal material, the fixed frame is made of an aluminum-based metal material, and the potential difference reducing member is made of a nickel-based metal. Made of material.

Further, in the invention according to claim 6, the potential difference reducing member according to claim 4 is coated on at least one side of the fixed frame and the fixed bearing member in a layer by plating, vapor deposition or painting. Is being worn.

Further, in the invention according to claim 7, the potential difference reducing member according to claim 1 or 4 is made of a passive film.

Further, in the invention according to claim 8, the passive film according to claim 1 or 4 is made of the metal material itself of the member on which the passive film is formed or another metal material.

According to the ninth aspect of the present invention, there is provided a fixed shaft, a substantially cylindrical rotating bearing member rotatably supported on the outer peripheral side of the fixed shaft with predetermined bearing means interposed therebetween, and the rotating bearing. A rotating hub for mounting a recording medium disk concentrically integrally joined to a member, wherein the rotating bearing member and the rotating hub are made of different kinds of metal materials. An insulating resin-coated film is interposed on the joint surface.

According to the tenth aspect of the present invention, the insulative resin-coated coating according to the ninth aspect of the present invention is such that the insulating resin coating film is continuous from a joint surface between the rotary bearing member and the rotary hub to an external exposed surface continuous with the joint surface. While being formed
A part of the joint surface between the rotating bearing member and the rotating hub is partially cut away so as to electrically conduct the part.

Further, according to the eleventh aspect of the present invention, the fixed frame, the substantially cylindrical fixed bearing member integrally joined to the fixed frame, and the predetermined bearing means on the inner peripheral side of the fixed bearing member. A rotating shaft rotatably supported by an intervening shaft; and a rotating hub for mounting a recording medium disk fitted and fixed to the rotating shaft. The fixed frame and the fixed bearing member are made of different kinds of metal materials. In the spindle motor, at the joint surface between the fixed frame and the fixed bearing member,
An insulating resin-coated film is interposed.

Further, in the twelfth aspect of the present invention,
The insulating resin-coated film according to claim 11, which is formed continuously from a joint surface between the fixed frame and the fixed bearing member to an externally exposed surface continuous with the joint surface, and is fixed to the fixed frame. Partially cut away portions are provided so as to electrically conduct a part of the joint surfaces with the bearing member.

According to the first aspect of the present invention having such a configuration, the energy difference between the rotary bearing member and the rotary hub made of dissimilar metals, that is, the potential difference between the two members, is set between the two members. It is alleviated and reduced by the intervening potential difference reducing member, and as a result, the occurrence or progress of the potential difference corrosion is prevented.

According to the second or fifth aspect of the present invention, the effect of preventing potential difference corrosion is achieved by a rotating bearing member or fixed bearing member made of a copper-based metal material and a rotating hub or fixed frame made of an aluminum-based metal material. This is particularly effective in the case where are joined, that is, when the energy difference (potential difference) between the joined members becomes large.

At this time, if the potential difference reducing member is formed by a plating layer or a passive film as described in the third, sixth, seventh or eighth aspect of the present invention, the potential difference reducing member having a good function can be easily provided. It can be formed.

According to the fourth aspect of the present invention, the energy difference between the fixed bearing member made of dissimilar metal and the rotary hub, that is, the potential difference between the two members is reduced by the potential difference reducing member interposed between the two members. Therefore, the occurrence or progress of the potential difference corrosion is prevented.

At this time, if the potential difference reducing member is formed by the plating layer or the passive film as in the invention of claim 5, 6, 7 or 8, the potential difference reducing member having a good function can be easily provided. It can be formed.

Further, according to the ninth and eleventh aspects of the present invention having the above-described structure, between the rotating bearing member made of dissimilar metal and the rotating hub or the joint surface between the fixed frame and the fixed bearing member. Since the space between the electrodes is electrically insulated by the resin coating film, a local battery is not formed, and as a result, the occurrence or progress of potential difference corrosion is prevented.

At this time, according to the tenth or twelfth aspect of the present invention, since the resin coating film is continuously formed from the joining surface to the externally exposed surface which is continuous with the joining surface, the electrolytic solution such as water or the like is formed. Can be satisfactorily prevented from forming a local battery even if it adheres to the outside exposed side of the bonding surface. In addition, the grounding of the rotating member is performed through a part of the electrically conductive joint surface, so that even if static electricity is generated in the rotating member, static elimination is performed smoothly.

[0024]

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

The fixed shaft type HDD spindle motor shown in FIG. 1 is entirely composed of a stator set 1 as a fixed member.
0 and a rotor set 20 as a rotating member assembled to the stator set 10 from above in the figure. The stator set 10 has a fixed frame 11 screwed to a fixed base (not shown), and a hollow cylindrical bearing holder 12 is integrally formed at a substantially central portion of the fixed frame 11. The bearing core 12 has a stator core 14 fitted on the outer peripheral surface thereof. This stator core 1
A drive coil 15 is wound around each of the salient pole portions 4.

A fixed shaft 16 made of stainless steel (SUS420J2) is fixed to a substantially central portion of the fixed frame 11 so as to protrude upward. The fixed shaft 16 is disposed concentrically with the bearing holder 12, and the upper end of the fixed shaft 16 is screwed to a fixed base (not shown). A bearing sleeve 21 as a rotary bearing member constituting the rotor set 20 is rotatably mounted on the outer peripheral side of the fixed shaft 16, and is not shown on the outer peripheral side of the bearing sleeve 21. A rotating hub 22 for mounting a recording medium such as a magnetic disk is joined thereto.

That is, at the upper end portion of the bearing sleeve 21, a substantially cylindrical joining large-diameter portion 20a formed so as to protrude radially outward is disposed.
A joint hole 22a formed through the center of the rotary hub 22 is integrally joined to the outer peripheral surface of the joint large diameter portion 20a by press-fitting or shrink fitting. At this time, the rotary hub 22 is formed of an aluminum-based metal material for weight reduction, and has a substantially cylindrical body 22a for mounting a recording medium disk (not shown) on the outer periphery. An annular drive magnet 22c is attached to the inner peripheral wall of the body 22a via a back yoke 22b. This annular drive magnet 22c is
The stator core 14 is disposed in proximity to the outer peripheral end face of the stator core 14 so as to face the end face annularly.

On the other hand, the bearing sleeve 21 is formed of a copper-based material to facilitate drilling and the like, and an inner peripheral wall portion of a center hole provided in the bearing sleeve 21 has:
A pair of bearing projections 21a, 21a are formed at a predetermined interval in the axial direction. And each of these bearing projections 21
a, 21a, the dynamic pressure surface formed on the inner peripheral wall surface is opposed to the dynamic pressure surface formed on the outer peripheral surface of the fixed shaft 16 so as to be opposed to each other. Radial dynamic pressure bearing portions RBa, RBb. More specifically, the dynamic pressure surface on the bearing sleeve 21 side and the dynamic pressure surface on the fixed shaft 16 side of the pair of radial dynamic pressure bearing portions RBa, RBb are circumferentially opposed to each other with a small interval of several μm. In addition, a lubricating fluid such as oil, a magnetic fluid, or air is injected into the bearing space having the minute intervals so as to be continuous in the axial direction.

The above-mentioned pair of radial dynamic pressure bearing portions RB
a, RBb, the bearing sleeve 21
Fluid reservoir 21 in which the inner peripheral wall of the center hole of
b is formed, and a sufficient amount of lubricating fluid is stored in the fluid reservoir 21b.

Further, on at least one side of both the dynamic pressure surfaces of the bearing sleeve 21 and the fixed shaft 16, for example, a herringbone-shaped radial dynamic pressure generating groove (not shown) is divided into two blocks in the axial direction. When rotating, the lubricating fluid is pressurized by the pumping action of the radial dynamic pressure generating groove to generate a dynamic pressure, and the rotating hub 22 is radially moved by the dynamic pressure of the lubricating fluid. It is configured to be axially supported in the direction.

Further, each of the above-mentioned radial dynamic pressure bearing portions RBa,
At both ends in the axial direction of the bearing space constituting RBb,
A capillary seal portion is arranged so as to sandwich these radial dynamic pressure bearing portions RBa and RBb in the axial direction. Each of these capillary seal portions is such that the gap between the fixed shaft 16 and the fixed shaft 16 is gradually enlarged by an inclined surface formed on the bearing sleeve 21 side, and is disposed inside the bearing. The gap size of the formed capillary seal portion is, for example, 20
It is set from μm to 300 μm. Each of these capillary seal portions is configured such that the liquid level of the lubricating fluid is positioned regardless of whether the motor rotates or stops.

Further, a disc-shaped thrust ring 23 is fixed to a tip portion (upper end portion in the figure) of the fixed shaft 16. The thrust ring 23 is arranged so as to be accommodated in a cylindrical recess formed in the center of the bearing sleeve 21 at the upper end in the drawing, and the thrust ring 23 is provided in the recess of the bearing sleeve 21. A lower thrust dynamic pressure bearing portion SBa is formed by a dynamic pressure surface in which the bearing sleeve 21 and the bearing sleeve 21 face each other in the axial direction.

Further, a counter plate 24 made of a large disc-shaped member is fixed to the upper end of the bearing sleeve 22 so as to be close to the upper dynamic pressure surface of the thrust ring 23 in the figure. An upper thrust dynamic pressure bearing portion SBb is formed by the dynamic pressure surface provided on the lower surface side of the plate 24 in the drawing and the above-described dynamic pressure surface on the thrust ring 23 side.

More specifically, in the pair of thrust dynamic pressure bearing portions SBa and SBb disposed adjacent to each other in the axial direction, the two dynamic pressure surfaces on the thrust ring 23 side, the bearing sleeve 21 and the counter plate 24 opposed thereto. The two dynamic pressure surfaces are axially opposed to each other with a very small interval of several μm, and a lubricating fluid such as oil, magnetic fluid, air, etc. It is injected so as to be continuous in the axial direction via the outer peripheral passage of the ring 23.

Further, on at least one side of the dynamic pressure surfaces of the thrust ring 23 and the dynamic pressure surfaces of the bearing sleeve 21 and the fixed shaft 16, for example, a herringbone-shaped thrust dynamic pressure generating groove (not shown) is provided. 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 is generated by the dynamic pressure of the lubricating fluid. The rotary hub 22 is configured to be axially supported in the thrust direction.

In this embodiment, as described above, the bearing sleeve 21 is formed of a copper-based material, and the rotary hub 22 integrally joined to the bearing sleeve 21 is formed of an aluminum-based metal material. These dissimilar metals are joined together to form an integral rotating body, but these bearing sleeve 21 and rotating hub 22
A potential difference reducing member A is interposed on the joint surface between the first and second members.
The potential difference reducing member A is made of a metal material, for example, a nickel material, whose ionization tendency in the electrochemical row with respect to fresh water is located between a copper-based material and an aluminum-based metal material. At least one of the bonding surfaces is applied in a layer by plating, vapor deposition, or painting.

In such an embodiment, the energy difference between the bearing sleeve 21 and the rotary hub 22, which are formed by joining dissimilar metals, that is, the potential difference between the two members 21 and 22 is determined by the two members 21 and 22. The potential difference is reduced or reduced by the potential difference reducing member A interposed therebetween, so that the occurrence or progress of the potential difference corrosion is prevented. This potential difference corrosion preventing action is achieved, in particular, by joining the bearing sleeve 21 made of a copper-based metal material and the rotating hub 22 made of an aluminum-based metal material, as in the present embodiment, to reduce the energy difference (potential difference) between the joined members. It is remarkably obtained when it is large.

At this time, in this embodiment, since the potential difference reducing member A is formed by plating, vapor deposition, or painting, a plating process or the like is simply added to a normal processing / assembly process. Thus, it is possible to easily provide the potential difference reducing member A having a good function.

On the other hand, the present invention can be similarly applied to a shaft rotation type spindle motor as shown in FIG. The shaft-rotating H shown in FIG.
The entire DD spindle motor includes a stator set 30 as a fixed member and a rotor set 40 as a rotating member assembled to the stator set 30 from above in the figure. The stator assembly 30 includes a fixed frame 31 screwed to a fixed base (not shown).
have. The fixed frame 31 is made of an aluminum-based metal material to reduce the weight. However, an inner side of an annular mounting portion 32 that is formed upright at a substantially central portion of the fixed frame 31 is provided. A bearing sleeve 33 as a fixed bearing member formed in a hollow cylindrical shape is integrally joined by press fitting or shrink fitting.

The bearing sleeve 33 is formed of a copper-based material for facilitating machining, and is fixedly joined to the bearing sleeve 33 integrally.
Is formed of an aluminum-based metal material as described above, and these dissimilar metals are joined together. A potential difference reducing member B is interposed on the joint surface between the bearing sleeve 33 and the fixed frame 31. The potential difference reducing member B is made of a metal material, for example, a nickel material, whose ionization tendency on the electrochemical column with respect to fresh water is located between the copper-based material and the aluminum-based metal material, and includes at least the bearing sleeve 33 and the fixed frame 31. It is formed from a passive body coating applied on one of the joining surfaces.

Such a passive body coating can be obtained, for example, by subjecting the joint surface of the bearing sleeve 33 or the fixed frame 31 to electroless nickel phosphorus plating and then leaving it to stand for a predetermined time. Alternatively, the metal material itself forming the fixed frame 31 may be formed as a passive body coating.

The outer peripheral surface of the bearing sleeve 33 is
The outer peripheral surface of the above-mentioned annular mounting portion 32 is formed so that the radial dimension thereof substantially coincides with the outer peripheral surface of the above-mentioned annular mounting portion 32. ing. This stator core 3
A drive coil 35 is wound around each of the salient pole portions provided in the motor 4.

A rotating shaft 41 made of stainless steel (SUS420J2) constituting the rotor set 40 is rotatably inserted into a center hole provided in the bearing sleeve 33. That is, the dynamic pressure surface formed on the inner peripheral wall of the bearing sleeve 33 is opposed to the dynamic pressure surface formed on the outer peripheral surface of the rotary shaft 41 so as to be close to the dynamic pressure surface, and is adjacent to the axial direction. A set of radial dynamic pressure bearing portions RBa, RBb is configured. More specifically,
In the pair of radial dynamic pressure bearing portions RBa and RBb, the dynamic pressure surface on the bearing sleeve 33 side and the dynamic pressure surface on the rotary shaft 41 side are circumferentially opposed to each other with a very small interval of several μm. A lubricating fluid such as oil, a magnetic fluid, or air is injected into the bearing space formed by the minute intervals so as to be continuous in the axial direction.

Further, on at least one side of both the dynamic pressure surfaces of the bearing sleeve 33 and the rotary shaft 41, for example, a herringbone-shaped radial dynamic pressure generating groove (not shown) is divided into two blocks in the axial direction. When rotating, the lubricating fluid is pressurized by the pumping action of the radial dynamic pressure generating groove to generate a dynamic pressure, and the dynamic pressure of the lubricating fluid causes the dynamic pressure to be described later together with the rotating shaft 41. The rotary hub 42 is configured to be axially supported in the radial direction.

That is, the rotary hub 42 which constitutes the rotor set 40 together with the rotary shaft 41 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 rotating hub 3
The three joint holes provided at the center portion are integrally joined to the upper end portion of the rotating shaft 41 in the figure by press-fitting or shrink fitting.

The rotary hub 42 has a substantially cylindrical body 42a on which a recording medium disk is mounted on the outer periphery, and an annular drive magnet 42c is attached to the inner peripheral wall surface of the body 42a. I have. The annular drive magnet 42c is arranged in proximity to the outer peripheral end face of the stator core 34 so as to annularly oppose the above-mentioned.

On the other hand, a disc-shaped thrust ring 43 is fixed to the tip of the rotating shaft 41 at the lower end in the figure. The thrust ring 43 is disposed so as to be accommodated in a cylindrical recess formed in the center of the bearing sleeve 33 at the lower end in the figure, and the thrust ring 4 is disposed in the recess of the bearing sleeve 33.
The upper thrust dynamic pressure bearing portion SBa is formed by a dynamic pressure surface in which the bearing sleeve 3 and the bearing sleeve 33 face each other in the axial direction.

Further, a counter plate 44 made of a large disc-shaped member is fixed to the lower end side opening of the bearing sleeve 33 so as to be close to the upper dynamic pressure surface of the thrust ring 43 in the figure. A dynamic pressure surface provided on the illustrated upper surface side of the counter plate 44;
The lower thrust dynamic pressure bearing portion SBb is formed by the above-described thrust ring 43 side dynamic pressure surface.

More specifically, in the pair of thrust dynamic pressure bearing portions SBa, SBb disposed adjacent to each other in the axial direction, the two dynamic pressure surfaces on the thrust ring 43 side, the bearing sleeve 33 and the counter plate 44 opposed thereto. The two dynamic pressure surfaces are axially opposed to each other with a very small interval of several μm, and a lubricating fluid such as oil, magnetic fluid, air, etc. It is injected so as to be continuous in the axial direction through the outer peripheral passage of the ring 43.

Further, on at least one side of the dynamic pressure surfaces of the thrust ring 43 and the dynamic pressure surfaces of the bearing sleeve 33 and the counter plate 44, for example, a herringbone-shaped thrust dynamic pressure generating groove (not shown) is provided. 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 is generated by the dynamic pressure of the lubricating fluid. The rotary hub 42 is configured to be axially supported in the thrust direction.

In such an embodiment, the energy difference between the bearing sleeve 33 to which the dissimilar metals are joined and the fixed frame 31, that is, the potential difference between the two members 33, 31 is determined by the two members 33, 31. It is reduced and reduced by the potential difference reducing member B interposed therebetween,
The occurrence or progress of potentiometric corrosion is prevented. This potential difference corrosion preventing action is achieved by joining the bearing sleeve 33 made of a copper-based metal material and the fixed frame 31 made of an aluminum-based metal material to reduce the energy difference (potential difference) between the joining members, as in the present embodiment. It is remarkably obtained when it is large.

In the embodiment shown in FIG.
Instead of the potential difference reducing member A in the embodiment according to FIG. 1 described above, an insulating resin coating C is interposed on the joint surface between the bearing sleeve 21 and the rotary hub 22. This resin coating film C is continuously formed from the joint surface between the bearing sleeve 21 and the rotary hub 22 to the externally exposed surface of the bearing sleeve 21 extending to the upper side and the lower side in FIG. ing. On the inner side of the resin coating film C,
A part of the resin coating film C is formed so as to be cut out, and a part of the joint surface between the bearing sleeve 21 and the rotary hub 22 is electrically connected to the cut portion of the resin coating film C. Conducted.

In the embodiment having such a configuration, the bearing sleeve 21 made of dissimilar metal and the rotary hub 22 are electrically insulated by the resin coating film C, and therefore, as described in the prior art. No local cell is formed, which prevents the occurrence or progression of potential difference corrosion. In particular, in the present embodiment, since the resin coating film C is continuously formed over the externally exposed surface of the bearing sleeve 21 extending continuously to the joint surface, the electrolyte such as water is exposed to the externally exposed side of the joint surface. , The formation of a local battery is well prevented.

At this time, in this embodiment, since a part of the joint surface is electrically connected, the rotary hub 22 is grounded through the conductive portion. Therefore, even if static electricity is generated in the rotary hub 22, the static elimination is performed smoothly, and damage to the head due to static electricity is prevented.

Such a resin coating film C can be similarly applied to the shaft rotation type spindle motor shown in FIG.
If the same resin coating film C is formed between the third frame 3 and the fixed frame 31, the same operation and effect can be obtained.

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 variously modified without departing from the gist thereof. Needless to say.

For example, the potential difference reducing member interposed at the joint can obtain the same operation and effect as those of the above-described embodiments.

The present invention can be similarly applied to any portion where different kinds of metals are joined together. For example, the embodiment shown in FIG. In the embodiment, the rotating shaft 41 and the rotating hub 42
It is also possible to interpose a potential difference reducing member at the junction with the above.

Further, the present invention can be similarly applied to a dynamic bearing device used other than the above-described motor, for example, a polygon mirror driving motor or a CD-ROM driving motor.

[0060]

As described above, the first or fourth aspect of the present invention provides a rotating or fixed bearing member made of a dissimilar metal,
Since it is configured to prevent the occurrence or progress of potential difference corrosion by interposing a potential difference reducing member that reduces or reduces the potential difference, which is the energy difference between the two members, between the rotating hub or the fixed frame, In particular, the use environment of a device requiring cleanliness, such as a hard disk drive (HDD), can be made favorable, and the reliability of the device can be improved.

According to a second aspect of the present invention, a rotary bearing member or a fixed bearing member made of a copper-based metal material is joined to a rotary hub or a fixed frame made of an aluminum-based metal material. As described above, since the present invention is applied to a case where the energy difference (potential difference) between the joining members becomes large, the above-described effect can be obtained as a particularly remarkable one.

Further, according to the third, sixth, seventh or eighth aspect of the present invention, the potential difference reducing member having a good function can be easily formed by forming the potential difference reducing member by a plating layer or a passive film. Since it is made possible, productivity can be improved in addition to the effects described above.

On the other hand, according to the ninth or eleventh aspect of the present invention, a local battery is provided by interposing an insulating resin coating film between a rotating or fixed bearing member made of dissimilar metal and a rotating hub or a fixed frame. Since it is configured not to be formed and to prevent the occurrence or progress of the potential difference corrosion, the use environment of a device requiring cleanliness such as a hard disk drive (HDD) is particularly suitable. And the reliability of the device can be improved.

According to the tenth and twelfth aspects of the present invention, an electrolytic solution such as water is exposed to the outside of the joint surface by forming a resin coating film continuously from the joint surface to the continuous outside exposed surface. Even if it adheres to the side, the formation of a local battery is prevented well, and the rotating member side is grounded through a part of the electrically conductive joint surface, so that the above-mentioned effect is further improved. In addition to this, the static electricity generated in the rotating member can be smoothly removed, and the safety and reliability of the device can be further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing an example of a fixed-shaft hard disk drive motor (HDD) to which the present invention is applied.

FIG. 2 is an explanatory cross-sectional view showing an example of a shaft-rotating hard disk drive motor (HDD) to which the present invention is applied.

FIG. 3 is a cross-sectional explanatory view corresponding to FIG. 1, showing another embodiment of the present invention.

[Description of Signs] 10, 30 Stator set 20, 40 Rotor set 11, 31 Fixed frame 12 Bearing holder 16, 41 Shaft 21, 33 Bearing sleeve (bearing member) 22 Rotating hub 23 Thrust rings RBa, RBb Radial dynamic pressure bearing portion SBa, SBb Thrust dynamic pressure bearing A, B Potential difference reducing member C Resin coating

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayuki Narita 5329 Shimosuwa Town, Suwa County, Nagano Prefecture Inside Sankyo Seiki Seisakusho Co., Ltd. (72) Inventor Tokio Tago 5329 Shimo Suwa Town, Suwa County, Nagano Prefecture Sankyo Seiki Seisakusho Co., Ltd. (72) Inventor Takehiko Yazawa 5329 Shimosuwa-cho, Suwa-gun, Nagano F-term (reference) in Sankyo Seiki Seisakusho Co., Ltd. BB25 CC01 DD02 DD03 DD16 EE17 GG07 GG09 GG12 GG15 5H621 BB07 GA01 GA04 HH05 JK08 JK10 JK15 JK19

Claims (12)

[Claims] 1. A fixed shaft, a substantially cylindrical rotating bearing member rotatably supported on the outer peripheral side of the fixed shaft via a predetermined bearing means, and integrally and concentrically joined to the rotating bearing member. A rotary hub for mounting a recording medium disk, wherein the rotary bearing member and the rotary hub are made of different metal materials. A spindle motor characterized in that a potential difference reducing member made of a metal material having an ionization tendency on an electrochemical line at an intermediate position is interposed for each of the dissimilar metals constituting the member and the rotating hub. 2. The rotary bearing member according to claim 1, wherein the rotary bearing member is made of a copper-based metal material, the rotary hub is made of an aluminum-based metal material, and the potential difference reducing member is made of a nickel-based metal material. Spindle motor. 3. The method according to claim 1, wherein the potential difference reducing member is applied in a layered manner to at least one of the joining surfaces of the rotating bearing member and the rotating hub by plating, vapor deposition, or painting. Spindle motor. 4. A fixed frame, a substantially cylindrical fixed bearing member integrally joined to the fixed frame, and an inner peripheral side of the fixed bearing member rotatably supported via predetermined bearing means. A rotating shaft, and a rotating hub for mounting a recording medium disk fixedly fitted to the rotating shaft, wherein the fixed frame and the fixed bearing member are made of different kinds of metal materials. On the joint surface with the fixed bearing member, a potential difference reducing member made of a metal material having an ionization tendency in an intermediate position on the electrochemical column as compared with each of the dissimilar metals constituting the fixed frame and the fixed bearing member. A spindle motor, wherein a spindle motor is interposed. 5. The fixed bearing member is made of a copper-based metal material, the fixed frame is made of an aluminum-based metal material, and the potential difference reducing member is made of a nickel-based metal material. Spindle motor. 6. The electric potential difference reducing member according to claim 1, wherein at least one side of the fixed frame and the fixed bearing member has a joint surface.
5. The spindle motor according to claim 4, wherein the spindle motor is coated in a layer by plating, vapor deposition, or painting. 7. The spindle motor according to claim 1, wherein the potential difference reducing member is made of a passive film. 8. The spindle motor according to claim 1, wherein the passivation film is made of a metal material itself of the member on which the passivation film is formed or another metal material. 9. A fixed shaft, a substantially cylindrical rotating bearing member rotatably supported on the outer peripheral side of the fixed shaft via a predetermined bearing means, and integrally concentrically joined to the rotating bearing member. A rotating hub for mounting a recording medium disk, wherein the rotating bearing member and the rotating hub are made of different kinds of metal materials, wherein a joint surface between the rotating bearing member and the rotating hub has an insulating property. A spindle motor having a resin coating film interposed. 10. The insulating resin coating film is formed continuously from a joint surface between the rotary bearing member and the rotary hub to an externally exposed surface continuous with the joint surface. 10. The spindle motor according to claim 9, wherein a part of the joint surface with the rotary hub is partially cut out so as to electrically conduct the part. 11. A fixed frame, a substantially cylindrical fixed bearing member integrally joined to the fixed frame, and rotatably supported on the inner peripheral side of the fixed bearing member via predetermined bearing means. A rotating shaft, and a rotating hub for mounting a recording medium disk fixedly fitted to the rotating shaft, wherein the fixed frame and the fixed bearing member are made of different kinds of metal materials. A spindle motor, wherein an insulating resin coating film is interposed on a joint surface with a fixed bearing member. 12. The insulating resin-coated film is formed continuously from a joint surface between the fixed frame and the fixed bearing member to an externally exposed surface continuous with the joint surface, and is fixed to the fixed frame. 12. The spindle motor according to claim 11, wherein a part of the joint surface with the bearing member is cut out so as to electrically conduct a part thereof.