JP2001025208A - Hydrodynamic pressure bearing motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent undesirable inclination of a shaft member caused by the clearance of a dynamic pressure generating part in the course of a standstill in a hydraulic dynamic pressure bearing motor, whose rotor is stuck to and integrated with the shaft member of a dynamic pressure bearing. SOLUTION: This hydrodynamic pressure bearing motor is composed of a dynamic pressure bearing provided with a shaft member 1 and a cylindrical supporting member 4 and an annular lid member 5, a cup-shaped hub 6, rotor magnets 7, a stator coil 8, and a motor board 9. A part of a back yoke 10 being one of the constituent members of a rotor is made of an annular magnetic member 12, and an annular inclination preventing permanent magnet 11 is fitted to the motor board 9 being one of the constituent members of a stator, and an inclination preventing means which always draws the rotor side toward the stator side by magnetic attracting force to an extent of practically not exerting influence on thrust dynamic pressure, is provided with.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid dynamic bearing motor in which a rotating body is integrally fixed to a shaft member of a dynamic pressure bearing, and more particularly, to a shaft member caused by a clearance of a dynamic pressure generating portion during a stop. The present invention relates to prevention of occurrence of undesired inclination. Here, a fluid dynamic bearing motor is a gas dynamic bearing using a gas such as air or an inert gas as a lubricant, or a liquid dynamic bearing using a liquid such as water, oil, or liquid helium as a lubricant. It is a motor provided.

[0002]

2. Description of the Related Art As shown in FIG. 5, for example, a fluid dynamic bearing motor is provided with a hydrodynamic bearing having a shaft member 1, a cylindrical receiving member 4 and an annular lid member 5 and concentrically fixed to the shaft member 1. And a rotor magnet 7 attached to the inner peripheral surface of the skirt portion of the cup-shaped hub 6
And a stator coil 8 attached to the outer peripheral surface of the cylindrical receiving member 4 so as to face the rotor magnet 7, and a motor substrate 9 on which the cylindrical receiving member 4 is erected.

A shaft member 1 is a shaft member with a flange in which a cylindrical portion 2 and a ring-shaped flange portion 3 are integrally formed. A radial dynamic pressure generating groove G1 such as a herringbone groove is formed on the lower outer peripheral surface of the cylindrical portion 2, and a thrust dynamic pressure generating groove G2 such as a herringbone groove is formed on the upper surface and the lower surface of the flange portion 3, respectively. I have.

In the fluid dynamic bearing motor shown in FIG. 5, the radial dynamic pressure is applied to a radial bearing gap formed by the lower outer peripheral surface of the cylindrical portion 2 and the inner peripheral surface of the small diameter cylindrical portion of the stepped cylindrical receiving member 4. appear. Further, the thrust dynamic pressure is generated by a first thrust bearing gap formed by the upper surface of the ring-shaped flange portion 3 and the lower surface of the annular lid member 5, the lower surface of the ring-shaped flange portion 3, and the step portion of the stepped cylindrical receiving member 4. Respectively generated in the second thrust bearing gap formed by the above.

[0005] Incidentally, the clearance of the bearing clearance, that is, the clearance required to generate dynamic pressure is determined by the size of the bearing,
Depends on rotation speed and viscosity of lubricating oil
m to 50 μm. Because of this clearance, the shaft member 1 tilts in the cylindrical receiving member 4 during the stop. When the shaft member 1 is tilted while stopped, the edge of the lower end of the cylindrical portion 2 comes into contact with the inner peripheral surface or the bottom surface of the small-diameter cylindrical portion of the cylindrical receiving member 4. Also, when the shaft member 1 is tilted while stopped, the upper and lower edges of the ring-shaped flange 3 come into contact with the lower surface of the annular lid member 5, the step of the cylindrical receiving member 4, and the inner peripheral surface of the large-diameter cylindrical portion. I do. It is common that some of these contacts occur simultaneously. The contact condition determines the inclination of the shaft member.

Referring to FIG. 4 which is a partially enlarged sectional view of a conventional fluid dynamic bearing motor, a radial bearing gap R
4 and the interval β between the thrust bearing gaps R1 and R3 are generally 5 μm to 50 μm. Further, the minute gaps R2 and R5 functioning as a lubricating oil reservoir or a circulation path have the same size. Therefore, when the shaft member 1 is tilted as described above during the stop, the horizontal plane of the hard disk support surface 6b of the cup-shaped hub 6 is separated from the center of the rotation axis, so that it is larger than the vicinity of the shaft as apparent from the dotted line in the drawing. You will lean. When such a bearing motor is used in a hard disk drive, if such a tilt of the shaft member occurs, the head may come into contact with the surface of the hard disk and cause a damage accident.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fluid dynamic bearing motor in which a rotating body is integrated with a shaft member. The purpose is to prevent the members from tilting. It is another object of the present invention to provide a simple and inexpensive means for preventing inclination of a shaft member used in the fluid dynamic bearing motor.

[0008]

In order to solve the above first and second problems, a dynamic pressure bearing having a shaft member and a receiving member as basic constituent members, and a hydrodynamic bearing concentrically fixed to the shaft member. A cup-shaped hub that is a rotating body, a rotor magnet attached to the inner peripheral surface of the cup-shaped hub, a stator coil attached to an outer peripheral surface of the receiving member facing the rotor magnet, and the receiving member A fluid dynamic pressure bearing motor comprising an upright motor substrate, a part of a rotor component including the cup-shaped hub is formed of a magnetic material, and a tilt preventing permanent magnet is attached to a stator component,
An anti-tilt means is provided which constantly draws the rotor side to the stator side with a magnetic attraction force that does not substantially affect the thrust dynamic pressure.

Further, the rotor constituting member made of the magnetic material is realized by the cup-shaped hub itself made of a magnetic material. Further, the rotor component member made of the magnetic material is realized by an annular magnetic material member arranged at or near an end face of the skirt portion of the cup-shaped hub, and the tilt preventing permanent magnet is attached to the motor substrate. It was realized with a ring-shaped permanent magnet. Further, an annular magnetic body integrally formed with a back yoke fixedly inserted by fixing a rotor constituent member formed of the magnetic body between an inner peripheral surface of the cup-shaped hub and an outer peripheral surface of the rotor magnet. The permanent magnet for preventing inclination is realized by an annular permanent magnet attached to a motor substrate.

[0010]

FIG. 1 is a longitudinal sectional view of a fluid dynamic bearing motor according to an embodiment of the present invention, and FIG. 2 is a cross sectional view of FIG. A dynamic pressure bearing having a lid member 5, a cup-shaped hub 6 which is a rotating body concentrically fixed to the shaft member 1, and an inner peripheral surface of a skirt portion 6 a of the cup-shaped hub 6 via a back yoke 10. It comprises a rotor magnet 7 attached, a stator coil 8 attached to the outer peripheral surface of the cylindrical receiving member 4 so as to face the rotor magnet 7, and a motor board 9 on which the cylindrical receiving member 4 is erected. I have. The annular lid member 5 is a member that also functions as a thrust holding member. The permanent magnet 11 attached to the motor substrate 9 is a permanent magnet for preventing the shaft member from being tilted, which is employed in the present invention.

The shaft member 1 is a flanged shaft member in which a cylindrical portion 2 and a ring-shaped flange portion 3 are integrally formed. A radial dynamic pressure generating groove G1 such as a herringbone groove is formed on the lower outer peripheral surface of the cylindrical portion 2, and a thrust dynamic pressure generating groove G2 such as a herringbone groove is formed on the upper surface and the lower surface of the flange portion 3, respectively. I have.

The tilt preventing magnet 11 is an annular permanent magnet magnetized in the direction of the rotation axis, and is attached to the upper surface of the motor substrate 9 so as to face the lower end surface of the skirt portion 6a of the cup-shaped hub 6. . The inclination preventing magnet 11 may be a magnet in which a plurality of permanent magnet pieces magnetized in the rotation axis direction are annularly arranged at predetermined positions on the upper surface of the motor substrate 9 at equal intervals.

In the present embodiment, the magnetic member 12 which is attached to the end face of the skirt portion 6a of the cup-shaped hub 6 in the vicinity of the inclination preventing permanent magnet 11 or in the vicinity thereof is formed integrally with the back yoke 10. Is a magnetic annular member. In other words, the magnetic member 12 constitutes the counter electrode portion of the tilt preventing permanent magnet 11 formed on the back yoke 10. The original back yoke 10 is a magnetic annular member that functions as a magnetic path forming a magnetic circuit of the fluid dynamic bearing motor. The rotor magnet 7 composed of a plurality of arc-shaped permanent magnets is fitted and fixed to the inner peripheral surface of the back yoke 10. The magnetization direction of the rotor magnet 7 is a radial direction.

The directions of the magnetic poles of the inclination preventing permanent magnet 11 are as follows.
It corresponds to the direction of the magnetic pole of the rotor magnet 7. That is, if the inner side of the rotor magnet 7 is the N pole and the outer side is the S pole, the direction of the magnetic pole of the inclination preventing permanent magnet 11 is determined so that the upper side is the S pole and the lower side is the N pole. In short, the inclination preventing permanent magnet 11 is attached to the motor substrate 9 which is a stator constituent member in the direction of the magnetic pole which attracts the rotor magnet 7 mutually.

[0015] Tilt preventing permanent magnet 11 and magnetic member 12
In the means for preventing tilting of the shaft member according to the present invention, which is arranged close to each other as described above, the tilt preventing permanent magnet 11 always draws the magnetic member by magnetic attraction. By the way, since the magnetic attraction acts in the opposite direction to the thrust dynamic pressure, its magnitude is naturally weak enough not to substantially affect the thrust dynamic pressure.

The magnetic attraction generated by the means for preventing the inclination of the shaft member is weak enough not to substantially affect the thrust dynamic pressure. However, when the fluid dynamic bearing motor stops, the thrust dynamic pressure disappears. The magnetic member 12 is drawn toward the inclination preventing permanent magnet 11 by the magnetic attraction. Accordingly, the skirt portion 6a of the cup-shaped hub 6 to which the magnetic member 12 is fixed is uniformly drawn to the inclination preventing permanent magnet 11 over the entire circumference. Therefore, the shaft member 1 to which the cup-shaped hub 6 as the rotating body is concentrically and integrally fixed is stationary without tilting in the cylindrical receiving member 4.

In short, in the fluid dynamic bearing motor provided with the shaft member inclination preventing means according to the present invention, when the motor is stopped, the rotor descends straight on the stator. Therefore, the head and the hard disk supported by the cup-shaped hub 6 do not come into contact when stopped.

Although the magnetic member 12 is an annular magnetic member formed integrally with the back yoke 10 in the present embodiment, it may be formed separately from the back yoke 10. Further, in the fluid dynamic bearing motor in which the cup-shaped hub 6 itself is formed of a magnetic material, it is only necessary to dispose the inclination preventing permanent magnet 11 at a predetermined position of the stator member, and the magnetic member 12 is specially formed. No need to provide.

In this embodiment, the inclination preventing permanent magnet 11 is attached to the motor board 9, but may be attached to another stator component. For example, the cylindrical receiving member 4
A permanent magnet 11 for preventing tilting may be attached to the upper end portion of the cover and the upper surface of the annular lid member 5. In this case, the annular magnetic member 12 is attached to the lower surface of the horizontal portion of the hub 6.

[0020]

The present invention provides a fluid dynamic bearing motor in which a cup-shaped rotating body is integrally fixed to a shaft member, with a magnetic attraction force having a magnitude that does not substantially affect the thrust dynamic pressure. Because it is always attracted,
When the motor is stopped, the rotor comes down straight, and the shaft member comes to rest without tilting into the receiving member.

Therefore, in the hard disk drive provided with the fluid dynamic bearing motor, the hard disk does not contact the head when stopped. In addition, the means for preventing the shaft member from tilting according to the present invention is configured by providing a ring-shaped permanent magnet on the stator side and forming a part of the rotor constituent member including the cup-shaped hub with a magnetic material. It can be realized at a low price with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of a fluid dynamic bearing motor according to the present invention.

FIG. 2 is a cross-sectional view of the fluid dynamic bearing motor of FIG.

FIG. 3 is a perspective view of a shaft member with a flange of the fluid dynamic bearing motor of FIG. 1;

FIG. 4 is a partially enlarged longitudinal sectional view of a conventional fluid dynamic bearing motor.

FIG. 5 is a longitudinal sectional view of a conventional fluid dynamic bearing motor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 shaft member with flange 2 cylindrical portion 3 ring-shaped flange portion 4 cylindrical receiving member 5 annular lid member 6 cup-shaped hub 6a skirt portion of cup-shaped hub 7 rotor magnet 8 stator coil 9 motor substrate 10 back yoke 11 permanent for inclination prevention Magnet 12 annular magnetic member

Continuing from the front page (72) Inventor Naoki Kawawada 1-8-8 Nakase, Mihama-ku, Chiba City, Chiba Prefecture Inside Seiko Instruments Inc. (72) Inventor Koji Nitori 1-8-8 Nakase, Mihama-ku, Chiba City, Chiba Seiko Instruments Inc. Company F term (reference) 3J011 AA04 AA20 BA09 CA02 5H607 BB01 BB14 BB17 BB25 CC01 DD01 DD03 EE10 GG02 GG12 GG15

Claims (4)

[Claims] 1. A dynamic pressure bearing having a shaft member and a receiving member as basic constituent members, a cup-shaped hub as a rotating body fixed concentrically to the shaft member, and an inner peripheral surface of the cup-shaped hub. A fluid dynamic bearing motor comprising: a mounted rotor magnet, a stator coil opposed to the rotor magnet on an outer peripheral surface of the receiving member, and a motor substrate on which the receiving member is erected. A part of the rotor component including the hub is formed of a magnetic material,
A fluid having a tilt preventing means for attaching a permanent magnet for preventing inclination to the stator constituent member, and constantly attracting the rotor side to the stator side with a magnetic attraction force that does not substantially affect the thrust dynamic pressure. Dynamic bearing motor. 2. The fluid dynamic bearing motor according to claim 1, wherein the rotor component member formed of the magnetic material is the cup-shaped hub. 3. The rotor component member formed of the magnetic material is an annular magnetic material member disposed at or near an end surface of a skirt portion of the cup-shaped hub, and the tilt preventing permanent magnet is provided on a motor substrate. 2. The fluid dynamic bearing motor according to claim 1, wherein the motor is a ring-shaped permanent magnet attached. 4. An annular member integrally formed with a back yoke interposed and fixed between an inner peripheral surface of the cup-shaped hub and an outer peripheral surface of the rotor magnet. 2. The fluid dynamic bearing motor according to claim 1, wherein said permanent magnet for preventing inclination is an annular permanent magnet attached to a motor substrate.