JPH1169725A - Spindle motor and rotator unit employing spindle motor as drive source for rotator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a spindle motor employing a hydrodynamic bearing or a rotator unit employing a spindle motor as the drive source for a rotator in which an electrostatic prevention means having low contact friction, simple structure and reliable earth is interposed between the rotor and the stator. SOLUTION: In a rotary shaft spindle motor, a storing hole 12 is made at the lower end of a rotary shaft 9 having upper end bonded with a hub 10. A conductive fluid 13, e.g. a conductive grease, produced by admixing a grease with micro particles of metal is injected into the storing hole 12. A needle-like earth member 17 comprises an earth needle 18 having a forward end buried in the conductive grease 13, and a disc-like supporting part bonded to a base plate 1. The rotary section, i.e., the hub 10, is earthed to a fixed section, i.e., the base plate 1, through the rotary shaft 9, the conductive fluid 13, and the needle-like earth member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the prevention of static electricity in a spindle motor provided with an air dynamic pressure bearing or a rotating device using the spindle motor as a driving source of a rotating member.

[0002]

2. Description of the Related Art Pneumatic dynamic bearings are widely used in spindle motors, especially spindle motors for hard disk drives. This is because an air dynamic bearing is light, clean, and smoothly rotates, is resistant to heat and cold, and has a long lasting characteristic, and is therefore extremely suitable for a bearing of a rotating machine for information equipment. The outline of the structure of the air dynamic pressure bearing is as follows. There are two types of air dynamic pressure bearings: radial dynamic pressure bearings and thrust dynamic pressure bearings. As shown in FIG. 2, the radial air dynamic pressure bearing includes a cylindrical bearing member 4 having a dynamic pressure generating groove G, for example, a herringbone groove formed on an outer peripheral surface, and a cylindrical bearing member having an inner peripheral surface having a smooth surface. 4 and a cylindrical bearing member 3 inserted with a predetermined narrow gap therebetween. Contrary to FIG. 2, the dynamic pressure generating groove G may be formed on the cylindrical bearing member side. As shown in FIG. 3, the thrust air dynamic pressure bearing is opposed to the thrust pressing members 5 and 6 formed with dynamic pressure generating grooves G, for example, herringbone grooves, with a predetermined narrow gap therebetween. And a disc-shaped thrust member (not shown) whose opposing surface is a smooth surface. Contrary to FIG. 3, the dynamic pressure generating groove G may be formed on the disc-shaped thrust member side. An air dynamic pressure bearing used in a spindle motor is usually a combination of a radial dynamic pressure bearing and a thrust dynamic pressure bearing.

[0005] By the way, as a head of a hard disk device of a high storage capacity type, an MR head using a magnetoresistive element whose electric resistance changes according to a change in a magnetic field is currently the mainstream. However, in the case of the MR head, unless the hard disk is mounted and the hub that rotates at high speed is grounded, the MR head may be damaged by static electricity generated in the hard disk. This is due to the basic structure that the air dynamic pressure bearing has the structure as described above and makes solid contact at startup and stop unless special measures are taken, but the shaft does not contact the bearing during operation. Is what you do. Therefore, grounding may be performed, but grounding a hub that rotates at high speed is not easy. Conventionally, as shown in FIG. 5, for example, a concave portion is provided at the lower end of a rotating shaft 9 having a hub coaxially fixed at the upper end, and an earth support plate 19 fixed to an opposing portion of a base plate opposing the concave portion. ,
At the lower end of the rotating shaft 9, a concave portion was also provided at a position corresponding to the concave portion, and a static electricity preventing means was constituted by a ground metal ball 18 held in mechanical contact with these concave portions.
There is a so-called metal contact type static electricity preventing means.

[0004]

However, the antistatic means grounded using the metal ball 18 for grounding as shown in FIG. 5 essentially reduces the friction between the metal ball 18 and the upper and lower recesses holding it. There is a problem that the smooth rotation of the air dynamic pressure bearing having a low load capacity is hindered. In other words, it hinders the largest feature of the air dynamic pressure bearing, that is, the non-contact bearing. Accordingly, the present invention provides an antistatic means having a small contact friction and a simple structure provided between a hub serving as a rotating part and a base plate serving as a fixed part in a spindle motor employing an air dynamic pressure bearing. is there.

[0005]

SUMMARY OF THE INVENTION In a shaft rotary spindle motor according to the present invention, or a rotating body device using the spindle motor as a driving source of a rotating body, a reservoir hole is formed at a lower end of a shaft, and the reservoir hole is formed in the reservoir hole. A needle-like grounding member is fixed to a portion of the base plate facing the lower end of the shaft by injecting the conductive fluid so that the tip thereof is rotatably buried in the conductive fluid. An antistatic means in which the earth is constituted by the earth member and the conductive fluid is provided. Similarly, in a shaft rotary type spindle motor, a needle-like ground member is fixed to a lower end of a shaft, and a reservoir hole is formed in a portion of a base plate facing the lower end of the shaft, and a tip of the needle-like ground member is formed in the reservoir hole. Was injected with a conductive fluid so as to be rotatably buried therein, and provided with an antistatic means in which the needle-like ground member and the conductive fluid constituted an earth.

Further, in the fixed shaft type spindle motor according to the present invention, or a rotating body device using the spindle motor as a driving source of a rotating body, a reservoir is formed at an upper end of a shaft, and a conductive fluid is filled in the reservoir. A needle-shaped grounding member is fixed to the hub at a position facing the upper end of the shaft so as to be rotatably buried in the conductive fluid. An antistatic means was provided, which constituted a ground with the fluid. Similarly, in the fixed shaft type spindle motor, a needle-like ground member is fixed to the upper end of the shaft, and a reservoir hole is formed in a facing portion of the hub facing the upper end of the shaft, and the tip of the needle-like ground member is formed in the reservoir hole. Was injected with a conductive fluid so as to be rotatably buried therein, and provided with an antistatic means in which the needle-like ground member and the conductive fluid constituted an earth.

[0007]

In the spindle motor provided with the antistatic means according to the present invention, or in a rotating device using the spindle motor as a driving source of the rotating body, the needle-shaped ground member and the conductive grease such as the conductive grease as described above. Since the antistatic means is composed of the reservoir hole into which the fluid is injected,
The hub on which the high-speed rotating hard disk is mounted is reliably grounded to the base plate via the needle-shaped ground member and the conductive fluid whose tip end is rotatably buried, and the head is statically charged. No longer damaged. Since the frictional force between the tip of the ground member and the conductive fluid is extremely small, the spindle motor rotates smoothly.

[0008]

FIG. 1 shows an embodiment of a shaft rotation type spindle motor according to the present invention. In FIG. 1, 1 is a base plate, 2 is a cylindrical support member erected on the base plate 1, 3 is a cylindrical bearing member coaxially supported by the cylindrical support member 2, and 4 is a cylindrical bearing member 3.
The cylindrical bearing member 5, which is inserted and arranged coaxially with a predetermined narrow gap therebetween, is disposed with a predetermined narrow gap from the upper surface of the cylindrical bearing member 4, and is fixed to the upper end of the cylindrical support member 2. The doughnut-shaped upper thrust holding member 6 is disposed at a predetermined narrow gap from the lower surface of the cylindrical bearing member 4, and is fixed to the lower end of the cylindrical support member 2; A stator coil attached to the outer peripheral surface of the cylindrical support member 2; a rotor magnet 8 which generates a rotational force in cooperation with the stator coil 7; a shaft 9 press-fitted and fixed coaxially with the cylindrical bearing member 4; 1
Reference numeral 0 denotes a substantially cup-shaped hub which is coaxially fixed to the upper end of the shaft 9 and has a rotor magnet 8 attached to the inner peripheral surface thereof.

The cylindrical bearing member 3 and the cylindrical bearing member 4 constitute a radial pneumatic dynamic pressure bearing, and either one of the inner peripheral surface of the cylindrical bearing member 3 and the outer peripheral surface of the cylindrical bearing member 4 is provided. Has a herringbone groove G as shown in FIG. Further, the upper end surface of the cylindrical bearing member 4 and the upper thrust holding member 5 constitute a first thrust air dynamic pressure bearing. Similarly, the lower end surface of the cylindrical bearing member 4 and the lower thrust holding member 6 also form the second thrust air bearing. Construct a dynamic pressure bearing. The spiral groove G as shown in FIG. 3 is formed on one of the upper end surface of the cylindrical bearing member 4 and the opposing surface of the upper thrust holding member 5 in the first thrust air dynamic pressure bearing. In the thrust air dynamic pressure bearing 2, it is formed on one of the lower end surface of the cylindrical bearing member 4 and the opposing surface of the lower thrust holding member 6.

The antistatic means includes a reservoir hole 12 drilled at the lower end of the shaft 9 along the central axis to the vicinity of the center, a conductive fluid 13 injected into the reservoir hole 12, and the ground needle 1.
A metal needle-like grounding member 17 whose tip is buried in the conductive fluid 13 and whose disk-shaped support portion is in electrical contact with the base plate 1 is fixed. As the conductive fluid 13, for example, a conductive grease obtained by mixing hard grease with metal fine particles is used. An annular first permanent magnet 15 is fixed to the lower end of the shaft 9, and an annular second permanent magnet 16 disposed on the needle side of the needle-like ground member with a polarity opposite to that of the first permanent magnet 15.
Is fixed. The first permanent magnet 15 and the second permanent magnet 16 constitute a magnetic bearing. In addition, these first
The space between the permanent magnet 15 and the second permanent magnet 16 is filled with a conductive magnetic fluid, and functions as sealing means for the conductive fluid 13.

In FIG. 1, the antistatic means has a needle-like grounding member 17 fixed to the base plate 1 on the fixed side, and a reservoir hole into which the conductive fluid 13 has been injected is formed in the rotating shaft 9 on the rotating side. However, these may be reversed as shown in FIG. That is, in FIG. 4, the needle-shaped earth member 17 is fixed to the lower end of the rotating shaft 9 on the rotating side, while the reservoir hole into which the conductive fluid 13 is injected is formed in the second earth member 19 on the fixed side. Is also good. The second ground member 19 is disposed to face the lower end of the rotating shaft 9 and is fixed to the base plate 1.

FIG. 6 shows an embodiment of a fixed shaft type spindle motor according to the present invention. The bearing used in the rotary shaft type spindle motor shown in FIG.
This is a combined dynamic pressure bearing comprising two radial air dynamic pressure bearings and two thrust air dynamic pressure bearings. On the contrary,
The bearing employed in the fixed shaft type spindle motor of FIG. 6 is a combined dynamic pressure bearing composed of one radial air dynamic pressure bearing and one thrust air dynamic pressure bearing. Accordingly, in FIG. 6, a thrust air dynamic pressure bearing includes a donut disk-shaped thrust holding member 21 fixed to the base plate 1 coaxially with the shaft 9, and the thrust holding member 21.
And a doughnut-shaped thrust bearing member 22 arranged at a predetermined narrow gap and fixed to the open end of the substantially cup-shaped hub 10 so as to face the thrust holding member 2.
A spiral groove G as shown in FIG. 3 is formed on one of the opposing surfaces of the first and thrust bearing members 22.

Further, the radial pneumatic dynamic pressure bearing has a cylindrical bearing member 4 coaxially fixed to a fixed shaft 9 and the cylindrical bearing member 4 inserted coaxially and arranged with a predetermined narrow gap therebetween. The cylindrical bearing member 3 is fixed to the inner peripheral surface of the substantially cup-shaped hub 10 and has one of the outer peripheral surface of the cylindrical bearing member 4 and the inner peripheral surface of the cylindrical bearing member 3. A herringbone groove G as shown in FIG. 3 is formed. The stator coil 7 is mounted near the upper end of the fixed shaft. A rotor magnet 8 that generates a rotational force in cooperation with the stator coil 7 faces the stator coil 7 on the inner peripheral surface of the substantially cup-shaped hub 10. Attached.

The static electricity preventing means provided in the fixed shaft type spindle motor shown in FIG. 6 also forms a ground by the needle-shaped ground member 17 and the conductive fluid 13. That is, a reservoir hole 12 formed along the central axis is formed at the upper end of the fixed shaft 9, and a conductive fluid 13 such as conductive grease is injected into the reservoir hole 12. A needle-like grounding member 17 in which the tip of a grounding needle 18 is buried in the fluid 13 is fixed to the center of the bottom of the substantially cup-shaped hub coaxially with the shaft 9. With such a configuration, static electricity preventing means for the fixed spindle motor is realized. Conversely, the needle-shaped ground member 17 is fixed to the fixed side, and the reservoir hole 20 into which the conductive fluid 13 is injected.
The static electricity prevention means for the fixed spindle motor in which the disc-shaped ground member 19 formed with the above is fixed to the rotation side can be realized.

[0015]

According to the present invention, there is provided a spindle motor having an air dynamic pressure bearing provided with an antistatic means having a needle-shaped earth member and a reservoir hole into which a conductive fluid is injected as described above. is there. Therefore, the spindle motor according to the present invention reliably grounds the hub on which the high-speed rotating hard disk is mounted to the base plate via the needle-like ground member and the conductive fluid. In this case, the contact friction between the tip of the needle of the needle-like ground member and the conductive fluid is compared with the contact friction between the metal contacts existing in the spindle motor having the conventional metal contact type antistatic means. Since it is extremely small, it does not hinder the feature of a non-contact bearing of an air dynamic pressure bearing. In addition, the static electricity prevention means composed of the needle-like ground member and the reservoir hole into which the conductive fluid is injected has a simple structure, so that it is easy to manufacture and requires almost no maintenance, and further increases the cost of the spindle motor. Can hardly be a factor.

[Brief description of the drawings]

FIG. 1 is a sectional view of a rotary shaft type spindle motor having an air dynamic pressure bearing according to an embodiment of the present invention.

FIG. 2 is a diagram showing a basic structure of a radial air dynamic pressure bearing.

FIG. 3 is a diagram showing a basic structure of a thrust air dynamic pressure bearing.

FIG. 4 is a diagram showing an example of an antistatic means constituted by a needle-like earth member used in the present invention and a reservoir hole into which a conductive fluid is injected.

FIG. 5 is a view showing an example of a conventional metal contact type static electricity preventing means.

FIG. 6 is a sectional view of a fixed shaft type spindle motor provided with an air dynamic pressure bearing according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base plate 2 Cylindrical support member 3 Cylindrical bearing member 4 Cylindrical bearing member 5 Donut board-like upper thrust holding member 6 Donut board-like lower thrust holding member 7 Stator coil 8 Rotor magnet 9 Shaft 10 Hub 11 Clamping center hole 12 Reservoir 13 Conductive fluid 14 Conductive magnetic fluid 15 First permanent magnet 16 Second permanent magnet 17 Needle-like ground member 18 Ground needle 19 Disc-like ground member 20 Reservoir 21 Thrust holding member 22 Thrust bearing member

[Procedure amendment]

[Submission date] April 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

The antistatic means comprises a reservoir hole 12 drilled at the lower end of the shaft 9 along the central axis to near the center, a conductive fluid 13 injected into the reservoir hole 12, and a tip of the ground needle 18 which is electrically conductive. A metal needle-like grounding member 17 buried in the fluid 13 and fixed so that its disk-shaped support portion is in electrical contact with the base plate 1. As the conductive fluid 13, for example, a conductive grease obtained by mixing hard grease with metal fine particles is used.
An annular first permanent magnet 15 is fixed to the lower end of the shaft 9, and the first permanent magnet 15 is attached to the needle side of the needle-shaped ground member.
An annular second permanent magnet 16 arranged in a polarity opposite to the above is fixed. The first permanent magnet 15 and the second permanent magnet 16 constitute a magnetic bearing. The space between the first permanent magnet 15 and the second permanent magnet 16 is filled with a conductive magnetic fluid 14 , and functions as a sealing unit for the conductive fluid 13.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

Further, the radial pneumatic dynamic pressure bearing has a cylindrical bearing member 4 coaxially fixed to a fixed shaft 9, and the cylindrical bearing member 4 is inserted coaxially and arranged with a predetermined narrow gap. The cylindrical bearing member 3 is fixed to the inner peripheral surface of the substantially cup-shaped hub 10 and has one of the outer peripheral surface of the cylindrical bearing member 4 and the inner peripheral surface of the cylindrical bearing member 3. A herringbone groove G as shown in FIG. 2 is formed. The stator coil 7 is mounted near the upper end of the fixed shaft. A rotor magnet 8 that generates a rotational force in cooperation with the stator coil 7 faces the stator coil 7 on the inner peripheral surface of the substantially cup-shaped hub 10. Attached.

Claims (5)

[Claims] 1. A spindle motor in which a rotor is supported on a stator by a pneumatic bearing, a needle-shaped grounding member is fixed to one of a center portion of the rotor and a portion of the stator opposed thereto, and the needle-shaped ground member is fixed to the other. A static electricity preventing means is provided which forms a reservoir hole into which a conductive fluid in which the tip of the grounding member is rotatably buried is injected, and which forms an earth with the needle-like grounding member and the conductive fluid. Spindle motor. 2. An air dynamic pressure bearing is constituted by at least two members of a cylindrical bearing member into which a shaft is press-fitted and fixed and a cylindrical bearing member into which the cylindrical bearing member is inserted, and a hub is coaxial with the shaft. And the cylindrical bearing member is a shaft rotating spindle motor fixed to a base plate, wherein a needle-like ground member is fixed to one of a lower end of the shaft and an opposing portion of the base plate opposed thereto, and On the other hand, a reservoir hole into which a conductive fluid in which the tip of the needle-like ground member is rotatably buried is formed, and the needle-like ground member and the conductive fluid constitute a ground. Spindle motor with anti-static means. 3. An air dynamic pressure bearing is constituted by at least two members, a cylindrical bearing member into which a shaft is press-fitted and fixed, and a cylindrical bearing member into which the cylindrical bearing member is inserted. In a fixed shaft type spindle motor in which a hub is coaxially fixed and the shaft is fixed to a base plate, a needle-shaped ground member is fixed to an upper end of the shaft and one of opposing portions of the hub facing the shaft, and On the other hand, a reservoir hole into which a conductive fluid in which the tip of the needle-like ground member is rotatably buried is formed, and the needle-like ground member and the conductive fluid constitute a ground. Spindle motor with anti-static means. 4. The spindle motor according to claim 1, wherein the conductive fluid is conductive grease obtained by mixing fine powder metal with hard grease. 5. A spindle motor in which a rotor is supported on a stator by an air dynamic bearing, wherein a needle-like ground member is fixed to one of a center portion of the rotor and a portion of the stator opposed to the center portion, and the other end has a needle-like ground member. The tip of the needle-like earth member is formed with a reservoir hole into which a conductive fluid is rotatably buried, and the needle-like earth member and the conductive fluid form an earth. A rotating body device using the provided spindle motor as a driving source of the rotating body.