JP2003172338A - Bearing having conducting function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing suppressing the generation of diffusion and scattering of conductive fluid, in the bearing conducting between a rotating member and a fixing member through the conductive fluid. <P>SOLUTION: The conductive fluid 103 contacting with a small diameter portion 102a is diffused in an opening portion 106 direction due to getting wet and the like with the small diameter portion 102a surface, a large diameter portion 102b is provided in a position before the conductive fluid 103 reaches the opening portion 106, so that a creepage distance of a conducting pin 102 surface led to the opening portion 106 is decreased, and a recessed portion 101 is actually blocked by the large diameter portion 102b while leaving a minute clearance. Magnetic force generated by a magnet 104 acts on the conductive fluid 103 structured by magnetic material, and the conductive fluid 103 is pulled close to the magnet 104, so that the conductive fluid 103 is securely held in a recessed portion 101. Force diffusing the conductive fluid 103 is prevented, so that the conductive fluid 103 is prevented from diffusing or scattering from an opening portion of the recessed portion 101 to the outside. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure having a conduction function.

[0002]

2. Description of the Related Art Since a spindle motor or the like used for driving a hard disk drive is required to rotate at a high speed, static electricity is generated due to the effect of friction between a rotating member forming the motor and air. The static electricity generated and accumulated inside the motor is discharged when the amount of electric charge becomes large, and the motor or a hard disk device equipped with the motor is damaged by the electrostatic discharge. In particular, in a spindle motor having an air dynamic pressure bearing in which a rotating side member and a fixed side member that constitute a motor are combined in a non-contact manner, the rotating side member and the fixed side member do not come into contact with each other. Since the ground path cannot be provided, the occurrence of equipment damage due to the accumulation and discharge of static electricity is more remarkable.

Therefore, as a bearing structure provided with an earth path for removing static electricity, for example, an actual flat plate 7-3274 is used.
No. 6 discloses that a conductive fluid is magnetically held in a recess provided in the end face of a fixed shaft, and a pin member provided in an opposed portion is brought into contact with the conductive fluid, so that static electricity is generated through the conductive fluid. A structure for escaping is disclosed.

[0004]

However, in the above-mentioned conventional structure, due to the wettability between the conductive fluid and the inner wall surface of the concave portion holding the conductive fluid or the pin member surface in contact with the conductive fluid, There is a problem that the conductive fluid held by the magnetic force diffuses while wetting the surface of the pin member or the inner wall surface of the concave portion which relatively rotates in the conductive fluid, and further scatters due to centrifugal force or the like.

The present invention has been made in view of the above,
An object of the present invention is to provide a bearing having a conduction function for electrically connecting a rotating side member and a fixed side member via a conductive fluid, in which the conductive fluid does not diffuse or scatter outside the bearing. To do.

[0006]

The invention according to claim 1 is a bearing having a rotating side member and a stationary side member,
One of the rotating-side member and the stationary-side member is provided with a concave portion that opens upward and holds a conductive fluid at least on the bottom, and the other member is provided with a cylindrical portion, and the concave portion and the cylindrical portion. Is provided on or near the center axis of rotation, the cylindrical portion is rotatably inserted into the inside of the concave portion from above the concave portion, and the cylindrical portion is a conductive fluid held in the concave portion. It is characterized in that a diffusion preventing structure for the conductive fluid is provided in at least one of the columnar portion and the recess.

According to a second aspect of the present invention, in the bearing according to the first aspect, the cylindrical portion has a large diameter portion having a diameter smaller than the inner diameter of the recess and a diameter smaller than the large diameter portion, and A small diameter portion having the same central axis as a large diameter portion, and the order of inserting into the recess is such that the large diameter portion is inserted after the small diameter portion is inserted, and the small diameter portion contacts the conductive fluid. It is characterized by doing.

The invention described in claim 3 is the invention according to claim 1 or 2.
In the bearing described above, the cylindrical portion has a large-diameter portion having a diameter smaller than the inner diameter of the recess and a small-diameter portion having a diameter smaller than that of the large-diameter portion and having the same central axis as the large-diameter portion. The peripheral surfaces of the large diameter portion and the small diameter portion are continuously connected by a tapered surface or a curved surface similar thereto, and the insertion order of the large diameter portion is such that the large diameter portion is inserted. The small-diameter portion is inserted later, and the large-diameter portion comes into contact with the conductive fluid.

According to a fourth aspect of the invention, in the bearing according to any one of the first to third aspects, the inner diameter of the recess is at a predetermined position near the opening of the recess into which the columnar portion is inserted. It is characterized in that a portion that is smaller than the inner diameter of the concave portion at a position farther from the opening than the predetermined position and larger than the diameter of the cylindrical portion is provided.

According to a fifth aspect of the present invention, in the bearing according to any one of the first to fourth aspects, the conductive fluid is made of a magnetic material, and a magnet is provided inside the recess.
The conductive fluid is magnetically retained inside the recess.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a vertical sectional view of an example in which a bearing according to an embodiment of the present invention is applied to an air dynamic pressure bearing of a spindle motor for driving a magnetic disk.
As shown in FIG. 1, a dynamic pressure bearing spindle motor includes a bracket 1 which is a fixed member, a shaft 2, a radial bearing member 3, thrust plates 4 and 5, a hub 7 which is a rotating member, a radial sleeve 6 and a hub 7. It is provided with a rotor magnet 8 and a stator 9 as magnetic drive means for rotationally driving. Since air is present between the radial bearing member 3 and the radial sleeve 6, the radial dynamic pressure bearing HB
1 and comprises thrust plates 4 and 5 and a radial sleeve 6.
Thrust dynamic pressure bearing H
Configure B2.

The bracket 1 is an annular member that constitutes the base of the dynamic pressure bearing motor, and the through hole 1 is formed in the central portion.
1 is formed. The back surface of the flange portion of the bracket 1 is fixed to a housing (not shown) of the hard disk and is grounded. The shaft 2 is, for example, a cylindrical member made of metal such as stainless steel, and the through hole 11 of the bracket 1 with the upper end protruding from the bracket 1.
It is supported by internal fitting. A cylindrical radial bearing member 3 is fixed to the upper outer peripheral surface of the shaft 2, and two disk-shaped thrust plates 4 and 5 are attached to both upper and lower end surfaces of the radial bearing member 3. A cylindrical radial sleeve 6 is rotatably mounted on the outer peripheral surface of the radial bearing member 3 between the thrust plates 4 and 5.

Herringbone grooves 41 and 51 having a depth of several μm and having a V shape for generating a dynamic pressure between the radial sleeve 6 and the opposing surfaces 4a and 5a of the thrust plates 4 and 5. Are formed. Opposed surface 4a of thrust plates 4 and 5
A thrust dynamic pressure bearing HB2 is formed between the upper and lower end surfaces of the radial sleeve 6 and 5a. The outer peripheral surface 3a of the radial bearing member 3 has a "dimple" for generating dynamic pressure between the radial bearing member 3 and the radial sleeve 6.
A herringbone groove 31 having a square shape and a depth of several μm is formed. A radial dynamic pressure bearing HB1 is formed between the outer peripheral surface of the radial bearing member 3 and the inner peripheral surface of the radial sleeve 6. The radial sleeve 6 is rotatably supported with respect to the shaft 2 and the thrust plates 4 and 5 via a radial dynamic pressure bearing HB1 and a thrust dynamic pressure bearing HB2.

The hub 7 has a cylindrical shape with a lid and an upper cylindrical portion 7
1 and a lower cylindrical portion 72 having a diameter larger than that of the upper cylindrical portion 71. The upper cylindrical portion 71 and the lower cylindrical portion 72 are integrated by a step portion 73. The radial sleeve 6 is attached to the inner peripheral surface of the upper cylindrical portion 71. On the outer peripheral surface of the upper cylindrical portion 71, a plurality of magnetic disks D, for example, three magnetic disks D are arranged in the vertical direction.
One is installed. An annular rotor magnet 8 in which N poles and S poles are alternately arranged on the inner peripheral surface of the lower cylindrical portion 72.
Are attached so as to face the stator 9 fixed to the bracket 1.

The operation of the dynamic pressure bearing spindle motor configured as described above will be described. When an exciting current is applied to the coil of the stator 9, a magnetic force is generated between the rotor magnet 8 and the stator 9, and the magnetic force causes the hub 7 to rotate. When the radial sleeve 6 rotates together with the hub 7, dynamic pressure is generated in the radial dynamic pressure bearing HB1 and at the same time dynamic pressure is generated in the thrust dynamic pressure bearing HB2, and the rotary side member rotates in a non-contact manner with the fixed side member.

When the rotating member rotates, static electricity is generated due to friction with air, and the rotating member and the magnetic disk D attached to the rotating member are charged. When the rotating member continues to rotate, the amount of electrostatic charge increases and the magnetic disk D
And the magnetic head DH are discharged. By this discharge,
The magnetic head DH may be damaged.

In the bearing according to the first embodiment, the shaft 2
A cylindrical recess 101 is provided at the upper end of the, and an axially magnetized magnet 104 is provided in the lower inside of the recess 101, and a conductive fluid (magnetic fluid) made of a magnetic material is provided.
103 is held inside the recess 101 above the magnet 104. Further, a conduction pin 102 is provided on the center axis of rotation of the hub 7 so as to be rotatably fitted in the recess 101. The conduction pin 102 has the recess 1
01 in contact with the conductive fluid 103 held therein.
In this case, static electricity generated in the rotation side member and the magnetic disk D attached to the rotation side member causes the hub 7, the conduction pin 102, the conductive fluid 103, the recess 101, the shaft 2,
The electricity is removed through the ground path that passes through the bracket 1.

FIG. 2 is an enlarged view of a conduction mechanism portion 100 composed of a recess 101, a conduction pin 102, a conductive fluid 103, a magnet 104 and the like. The conduction pin 102 has a concave portion 101.
Of the large diameter portion 102b having a smaller diameter than the inner diameter of the
A small diameter portion 102a similar to 02b is provided.

The conductive fluid 103 is held in the recess 101 at a position in contact with the small diameter portion 102a. The conductive fluid 103 in contact with the small diameter portion 102a diffuses toward the opening 106 due to wetting with the surface of the small diameter portion 102a, but the large diameter portion 102b is located before the conductive fluid 103 reaches the opening 106. Is provided,
The creepage distance of the surface of the conduction pin 102 up to the opening 106 increases, and the recess 101 has a large diameter portion 102b.
It is effectively closed by leaving a small gap. further,
A magnet 104 is attached to the conductive fluid 103 composed of a magnetic material.
The magnetic force generated by the
Since it is pulled in the direction of 04, it is strongly held in the recess 101. Further, the force of the conductive fluid 103 attempting to diffuse is hindered, so that the conductive fluid 103 may not reach the recess 101.
It can be prevented from diffusing or scattering from the opening portion to the outside. Further, the conduction pin 102 is made of a magnetic material, and the conduction pin 102, the conductive fluid (magnetic fluid) 103, and the magnet 10 are used.
If a magnetic circuit passing through 4 is configured, the conductive fluid (magnetic fluid) 103 is further strongly retained.

Incidentally, as shown in FIG. 3, the large diameter portion 102b is formed.
May be extended to reach the hub 7 as it is.

(Second Embodiment) The second embodiment basically has the same configuration as that of the first embodiment, and has a conduction mechanism section 100.
The configuration of is different. FIG. 4 is a diagram showing a configuration example of the conduction mechanism unit 100 according to the second embodiment. The conductive pin 102 has a large-diameter portion 10 having a diameter smaller than the inner diameter of the recess 101.
2c and a small diameter portion 102d having a diameter smaller than that of the large diameter portion 102c and having the same central axis as that of the large diameter portion 102c. The peripheral surfaces of the large diameter portion 102c and the small diameter portion 102d are connected by a tapered surface 102e. Cage, recess 1
The gap formed with the inner wall of the inner wall 01 is continuously enlarged toward the opening 106.

The conductive fluid 103 is held in the recess 101 at a position in contact with the large-diameter portion 102c.
The interface 03 is located on the tapered surface 102e. The conductive fluid 103 in contact with the large diameter portion 102c tends to diffuse toward the opening 106 due to wetting with the surface of the large diameter portion 102c. However, the conductive fluid 103 is held by the surface tension, and does not diffuse beyond the large diameter portion 102c toward the opening 106. Therefore, the conductive fluid 103 can be prevented from diffusing or scattering from the opening 106 of the recess 101 to the outside.

Although the large-diameter portion 102c and the small-diameter portion 102d are connected by a taper in FIG. 4, another shape, specifically, a curved surface approximate to a tapered surface may be used.

(Third Embodiment) The third embodiment basically has the same configuration as that of the first embodiment, and has a conduction mechanism section 100.
The configuration of is different. FIG. 8 is a diagram showing a configuration example of the conduction mechanism unit 100 according to the third embodiment. A lid-shaped portion 105 is provided at a predetermined position near the opening 106 of the recess 101, and a lid opening 107 having an inner diameter larger than the diameter of the conduction pin 102 is provided at the center of the lid-shaped portion 105.
The conduction pin 102 penetrates through the lid opening 107 to form the recess 101.
Conductive fluid 1 inserted into the cavity and held in the recess 101
We are in contact with 03.

In this case, the conductive fluid 103 is filled with the concave portion 101.
Although it tends to diffuse upward in the concave portion 101 due to the wetting of the inner wall surface of the inside of the concave portion 101 and the like, the lid-shaped portion 105 is provided before the conductive fluid 103 reaches the opening portion 106. As the creepage distance of becomes longer,
Since the lid opening portion 107 is closed with a minute gap left between the lid opening portion 107 and the conduction pin 102, the conductive fluid 103 is not covered by the lid opening portion 10.
7 is prevented, so that it does not reach the opening 106 and leaks to the outside of the recess 101.

As shown in FIG. 9, the lid portion 105
May be integrated with the opening 106.

(Other Modifications) As shown in FIG. 6, the structure of the conduction pin 102 has a large diameter portion 102c (FIG. 4) according to the second embodiment and a large diameter portion according to the second embodiment. A configuration in which 102b (FIG. 2) is combined may be used.

In the first to third embodiments, the magnet is provided inside the recess to hold the magnetic conductive fluid by magnetic force. However, the magnet is not provided and the magnet is not provided. It may be configured to hold. For example, the embodiment of FIG. 4 corresponds to the configuration of FIG. 5 and the embodiment of FIG. 6 corresponds to the configuration of FIG. 7, and can be held by the surface tension of the conductive fluid or the like. In this case, the conductive fluid need not be a magnetic material.

Further, in the case of holding the magnetic conductive fluid by magnetic force, the end face of the conduction pin 102, that is, the face facing the magnet 104 arranged at the bottom of the recess 101 is flat or slightly concave in the center. It is desirable to make it a dull shape. For example, when the end face of the conduction pin 102 is formed in a concave shape at the center, a conductive fluid holding mechanism as shown in FIG. 10 can be constructed. The magnetic conductive fluid is arranged along the magnetic field and, at the same time, has a needle-like shape with a sharp tip due to the repulsive force of the conductive fluids. By contacting this tip with the concave portion of the conductive pin 102, scattering due to centrifugal force is caused. It can be kept small and the contact surface pressure can be adjusted automatically.

Further, in the first to third embodiments, an example in which the bearing according to the present invention is applied to an air dynamic pressure bearing of a spindle motor for driving a magnetic disk is shown. However, a rotating body such as a generator, a wind turbine, a turbine, etc. The bearing is not limited to the bearing of the motor as long as it is a bearing to support. Further, although the present invention is applied to the dynamic pressure bearing, other types of bearings such as bearings may be used.
Further, the concave portion 101 may be provided on the rotating side member, and the conduction pin 102 may be provided on the fixed side member.

[0031]

As described above, according to the present invention, a bearing having a conduction function for electrically connecting a rotating side member and a fixed side member via a conductive fluid is provided. It is possible to provide a bearing that does not diffuse or scatter outside the bearing.

Further, according to the present invention, the rotating side member can rotate without generating contact resistance with the fixed side member. In addition, static electricity generated by friction with air due to the rotation of the rotating side member passes through the earth path from the rotating side member to the fixed side member through the cylindrical portion, the conductive fluid, and the recess. The electricity is removed. Also,
Since the relative speed between the rotating side member and the fixed side member that rotates is the position on or near the center axis of rotation where the cylindrical portion and the recess are provided,
The viscous resistance generated by the contact between the cylindrical portion and the conductive fluid is minimized. Further, since the conductive fluid diffusion preventing structure is provided in at least one of the columnar portion and the concave portion, the conductive fluid held in the concave portion is prevented from diffusing and scattering outside the concave portion. It

Further, according to the present invention, in the case where the conductive fluid in contact with the small diameter portion diffuses toward the opening of the recess along the surface of the cylindrical portion due to the wetting of the surface of the cylindrical portion or the like. Even if there is, the large diameter portion having a diameter larger than the small diameter portion is provided before the conductive fluid reaches the opening portion of the recess, so that the opening from the position where the conductive fluid is held is changed to the opening portion. As the creeping distance of the surface of the columnar portion reaching becomes large and the concave portion is closed by the large diameter portion leaving a minute gap, it is possible to prevent the conductive fluid from diffusing or scattering outside from the opening portion of the concave portion. Can be achieved.

Further, according to the present invention, the conductive fluid in contact with the large-diameter portion is wetted on the surface of the cylindrical portion having the large-diameter portion and the small-diameter portion, so that the conductive fluid flows along the surface of the cylindrical portion. Even when attempting to diffuse toward the opening of the recess, the large-diameter portion is continuously connected to the small-diameter portion by a tapered surface or a curved surface similar thereto, so that the conductive fluid is It is held by tension and does not diffuse toward the opening. Therefore, it is possible to prevent the conductive fluid from diffusing or scattering from the opening of the recess to the outside.

Further, according to the present invention, even when the conductive fluid held in the recess is diffused toward the opening of the recess due to the wetting of the inner wall surface of the recess or the like, the conductive fluid is not formed near the opening. Since the inner diameter of the concave portion is smaller than the inner diameter of the concave portion at a position farther from the opening than the specific position and larger than the diameter of the cylindrical portion, a portion where the conductive fluid is held is The creepage distance on the inner wall surface of the recess reaching the opening becomes large. Further, since the opening of the recess is closed with a minute gap left between the opening and the cylindrical portion, it is possible to prevent the conductive fluid from diffusing or scattering outside from the opening of the recess.

Further, according to the present invention, the conductive fluid is a conductive magnetic fluid composed of a magnetic material, and the conductive magnetic fluid is retained in the recess by a magnetic force. The magnetic force acts on the conductive magnetic fluid that tends to diffuse toward the opening of the recess due to the wetting of the surface of the cylindrical portion or the wetting of the inner wall surface of the recess, etc. It is possible to prevent the conductive magnetic fluid from diffusing or scattering from the opening of the recess to the outside.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a dynamic pressure bearing spindle motor according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a conduction mechanism section according to the first embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a conduction mechanism section according to the first embodiment of the present invention.

FIG. 4 is a vertical sectional view of a conduction mechanism section according to a second embodiment of the present invention.

FIG. 5 is a vertical cross-sectional view of a conduction mechanism section according to a second embodiment of the present invention.

FIG. 6 is a vertical sectional view of a conduction mechanism section according to a third embodiment of the present invention.

FIG. 7 is a vertical cross-sectional view of a conduction mechanism section according to a third embodiment of the present invention.

FIG. 8 is a vertical cross-sectional view of a conduction mechanism section according to a fourth embodiment of the present invention.

FIG. 9 is a vertical sectional view of a conduction mechanism section according to a fourth embodiment of the present invention.

FIG. 10 is a vertical cross-sectional view of a conduction mechanism portion according to another modification of the present invention.

[Explanation of symbols]

1 bracket 11 Bracket through hole 2 shafts 3 Radial bearing members 31 herringbone groove 3a outer peripheral surface 4 Thrust plate 41 Herringbone groove 4a Thrust plate facing surface 5 Thrust plate 51 herringbone groove 5a Thrust plate facing surface 6 radial sleeve 7 hub 8 rotor magnet 9 stator 71 Upper cylindrical part 72 Lower cylindrical part 73 Step 100 conduction mechanism 101 recess 102 Conduction pin (cylindrical part) 102a small diameter part 102b Large diameter part 102c Large diameter part 102e Tapered surface 103 conductive fluid 104 magnet 105 Lid 106 opening 107 lid opening D magnetic disk DH magnetic head HB1 radial dynamic pressure bearing HB2 thrust dynamic pressure bearing

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3J011 AA20 BA02 BA08 CA02 EA10                       KA02 KA03                 5H605 BB05 BB14 BB19 CC04 DD09                       EB02 EB06 EB15 EB28                 5H607 BB01 BB07 BB09 BB14 BB17                       BB25 CC01 DD03 DD16 GG01                       GG02 GG09 GG12 GG15

Claims (5)

[Claims] 1. A bearing having a rotating side member and a fixed side member, the recess having an opening upward in at least one of the rotating side member and the fixed side member and holding a conductive fluid in at least a bottom portion. And a columnar portion is provided on the other member, and the recess and the columnar portion are provided on or near the rotation center axis, and the columnar portion is rotatable from above the recess to the inside thereof without contact. The columnar portion is in contact with the conductive fluid held in the recess, and at least one of the columnar portion and the recess is provided with a diffusion preventing structure for the conductive fluid. Bearing. 2. The cylindrical portion has a large-diameter portion having a diameter smaller than the inner diameter of the recess and a small-diameter portion having a diameter smaller than that of the large-diameter portion and having the same central axis as the large-diameter portion. The bearing according to claim 1, wherein the large diameter portion is inserted after the small diameter portion is inserted, and the small diameter portion comes into contact with the conductive fluid. 3. The cylindrical portion has a large-diameter portion having a diameter smaller than the inner diameter of the recess and a small-diameter portion having a diameter smaller than that of the large-diameter portion and having a central axis similar to that of the large-diameter portion. The peripheral surfaces of the large diameter portion and the small diameter portion are continuously connected by a tapered surface or a curved surface similar thereto, and the insertion order of the large diameter portion is such that the large diameter portion is inserted. 3. The bearing according to claim 1, wherein the small diameter portion is inserted later, and the large diameter portion comes into contact with the conductive fluid. 4. At the predetermined position near the opening of the recess where the cylindrical portion is inserted, the inner diameter of the recess is smaller than the inner diameter of the recess at a position farther from the opening than the predetermined position, The bearing according to any one of claims 1 to 3, further comprising a portion having a diameter larger than a diameter of the portion. 5. The conductive fluid is made of a magnetic material, a magnet is provided inside the recess, and the conductive fluid is magnetically retained inside the recess. The bearing according to any one of 1.