JP2001065551A - Liquid dynamic pressure bearing, motor, and rotor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid dynamic pressure bearing causing less wear and damage to a member at the time of resting and at a low speed rotation of a rotor while providing excellent durability. SOLUTION: This liquid dynamic pressure bearing is provided with a stator part 10 comprising a cylindrical supporting hole 11a opened at one end, a rotor part 20 comprising a shaft 21 relatively rotatably provided in the supporting hole 11a, magnetic fluid F laying between the stator part 10 and the shaft 21 in the supporting hole 11a of the stator part 10, dynamic pressure generating grooves 25a, 25b, 25c to generate dynamic pressure between the stator part 10 and the shaft 21 by involving the magnetic fluid F at the time of relative rotation of the shaft 21 to the stator part 10, and magnets M1, M2 magnetically attracting the magnetic fluid F to an adjacent part of the shaft 21 to the stator part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a liquid dynamic pressure bearing,
Motor, and rotating body device, more specifically, a liquid dynamic pressure bearing that can obtain good durability, less wear and damage of members at rest or at low speed rotation, motor,
And a rotator device.

[0002]

2. Description of the Related Art Conventionally, liquid dynamic pressure bearings have been used as bearings for spindle motors in various disk devices such as hard disk drives, rotary polygon mirror devices such as printers, and other rotating devices. FIG. 4 is a cross-sectional view showing a motor using such a liquid dynamic pressure bearing. As shown in FIG. 4, the liquid dynamic pressure bearing is fixed to a rotating body side and rotates with a rotating body (rotor). Side member) 120 and a bearing member (stator side member) 110 fixed to the non-rotating body side. One of the member 120 on the rotor side and the member 110 on the stator side (the member 110 on the stator side in FIG. 4) has a hollow portion 1.
11a, and the other (in FIG. 4, the rotor side member 12
0) is formed with a shaft portion 122 which is housed coaxially in the hollow portion 111a. One of the peripheral surface of the hollow portion 111a and the peripheral surface of the shaft portion 122 has a dynamic pressure generating means (in FIG. 4, dynamic pressure generating grooves 125a, 125b,
125c) is provided. The gap between the hollow portion 111a and the shaft 122 is filled with a liquid S such as oil. Then, when the rotor-side member 120 rotates during rotation of the rotating body, the dynamic pressure generating grooves 125a, 125b, 125c
As a result, the S liquid is caught between the two bearing members 110 and 120, and a dynamic pressure is generated. When the rotation speed exceeds a predetermined value, the rotor side member 120 is brought into non-contact with the stator side member 120 due to the dynamic pressure. Supported in state. Such a liquid dynamic pressure bearing and a motor using the liquid dynamic pressure bearing are:
There is an advantage that the friction between the member 120 on the rotor side and the member 110 on the stator side during high-speed rotation is small, and good durability can be obtained.

[0003]

In the above-described liquid dynamic pressure bearing, since the rotor-side member 120 is supported by the stator-side member 110 in a non-contact manner during rotation, the liquid dynamic pressure bearing has a structure in which the peripheral surface of the hollow portion 111a is rotated. The shaft portion 122 is formed smaller by a predetermined size, and a gap of a predetermined size is provided between the peripheral surface of the hollow portion 111a and the peripheral surface of the shaft portion 122. Therefore, in a state where no dynamic pressure is generated or in an insufficient state, such as at the time of non-rotation or immediately after the start of rotation, when there is an external vibration or the motor is tilted, FIG.
As shown in (2), the member 120 on the rotor side may be greatly inclined with respect to the member 110 on the stator side. For example, in a hard disk drive, the rotor portion supported by the rotor-side member 120 and the hard disk carried by the rotor portion are tilted with the inclination of the rotor-side member 120, and the hard disk contacts the reading head and causes the reading head to move. Damage to the member, such as damage, may occur. Also, if rotation is started while the rotor-side member 120 is tilted with respect to the stator-side member 110, sufficient dynamic pressure is not generated during low-speed rotation, so that the rotor-side member 120 It rotates while sliding on the member 110. Therefore, the rotor-side member 120 and the stator-side member 110 may be worn or damaged due to contact with each other, which may cause a decrease in the function of the fluid dynamic pressure bearing or a decrease in durability such as deterioration of the members.

[0004] In addition, even when there is no external vibration or the like,
At the time of non-rotation, as shown in FIG.
The zero end pushes the oil apart due to its own weight or the like, and becomes substantially in contact with the member 110 on the stator side in the axial direction. Therefore, even when the rotation is started, the member 120 on the rotor side rotates while being in contact with the member 120 on the stator side until a sufficient dynamic pressure is generated. As a result, the rotor-side member 120 and the stator-side member 110 may be worn or damaged due to contact with each other, which may cause a decrease in durability such as a decrease in the function of the dynamic pressure dynamic pressure bearing or deterioration of the members. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has low wear and damage to members at rest or at low speed rotation, and can provide a good dynamic durability. , A motor, and a rotating body device.

[0006]

According to the present invention, there is provided an outer cylindrical member having a cylindrical hollow portion having an open end, and a rotating member which is rotatable in the hollow portion of the outer cylindrical member with respect to the outer cylindrical member. A hollow or solid columnar member disposed as possible, a fluid interposed between the outer cylinder member and the columnar member in the hollow portion of the outer cylinder member, and a fluid interposed between the columnar member and the outer cylinder member. A liquid dynamic pressure bearing comprising a dynamic pressure generating means for generating a dynamic pressure between the outer cylindrical member and the columnar member by entraining the fluid during relative rotation, wherein the fluid is a magnetic fluid; The object described above is achieved by providing a liquid dynamic pressure bearing provided with a magnet for magnetically attracting the magnetic fluid in a vicinity of at least one of the cylindrical member and the columnar member. 1
Configuration). In the liquid dynamic pressure bearing of the present invention, the magnet provided on at least one of the cylindrical member and the columnar member sucks the magnetic fluid, and the portion where the magnet is provided and the other portion opposed to the magnet are provided. The state where the magnetic fluid has entered between the opposing portions is maintained. Therefore, contact between the cylindrical member and the columnar member at these portions is avoided, and wear and damage due to the contact are suppressed.

In the liquid dynamic pressure bearing according to the first aspect of the present invention, the magnet includes a peripheral surface of a hollow portion of the outer cylindrical member and a peripheral surface of the columnar member facing the peripheral surface. At least one can be provided (second
Configuration). In the liquid dynamic pressure bearing of the present invention having the second configuration, the state in which the magnetic fluid has entered between the peripheral surface of the hollow portion of the outer cylindrical member and the peripheral surface of the columnar member facing the peripheral surface is maintained. You. Then, even if a force acts in a direction in which the columnar member inclines with respect to the hollow portion of the cylindrical member due to external vibration or impact, the magnetic fluid pushes the columnar member back against this force. Therefore, contact between the peripheral surface of the hollow portion of the outer cylindrical member and the peripheral surface of the columnar member facing the peripheral surface is avoided, and the columnar member is held at a predetermined position on the outer cylindrical member. Therefore,
Wear and damage due to contact between the peripheral surface of the hollow portion of the cylindrical member and the peripheral surface of the columnar member facing the peripheral surface are avoided, and wear and damage due to the start of rotation from the contact state are also avoided. In the liquid dynamic pressure bearing according to the first configuration of the present invention, the magnet is provided on one of a peripheral surface of a hollow portion of the outer cylindrical member and a peripheral surface of the columnar member facing the peripheral surface. In addition, the other of the other, the opposing peripheral surface facing the magnet may be made of a non-magnetic member (third configuration).

In the first, second, and third liquid dynamic pressure bearings according to the present invention, the magnet includes a bottom portion of the hollow portion of the outer cylindrical member, and It can be provided on at least one of the opposite ends of the columnar member (fourth configuration). In the liquid dynamic pressure bearing of the present invention having the fourth configuration, the state in which the magnetic fluid enters between the bottom surface of the hollow portion of the outer cylindrical member and the end of the columnar member facing the bottom surface is maintained. Is done. And
Due to the weight of the columnar member and the outer cylindrical member or the load from the outside, vibration or impact, even if the columnar member exerts a force to advance to the bottom side of the hollow portion of the cylindrical member, the magnetic fluid resists this force, Push back the columnar member. Therefore, contact between the bottom surface of the hollow portion of the outer cylindrical member and the end of the columnar member facing the bottom surface is avoided. Therefore, wear and damage due to contact between the bottom surface of the hollow portion of the cylindrical member and the end of the columnar member facing the bottom surface are avoided, and wear and damage due to the start of rotation from the contact state are avoided. You. The first configuration of the present invention, the second configuration
In the liquid dynamic pressure bearing according to the third, fourth, and fourth configurations, the magnet is provided at a bottom portion of the hollow portion of the outer cylindrical member, and at an end of the columnar member facing the bottom portion. An opposing flat surface portion provided on one of them and facing the magnet on the other side may be made of a non-magnetic member (fifth configuration).

In the liquid dynamic pressure bearing having the first to fifth configurations of the present invention, the magnet may be a permanent magnet (sixth configuration).

In the liquid dynamic pressure bearing having the first to fifth configurations of the present invention, an energizing means for supplying electricity to the electromagnet using the magnet as an electromagnet; An energization control unit that controls intermittent energization of the electromagnet by the energization unit in accordance with the relative rotation can be provided (seventh configuration).

The present invention achieves the above object by providing a motor provided with a liquid dynamic pressure bearing having any one of the first to seventh configurations. Further, the present invention achieves the above object by providing a rotating body device including the motor of the present invention and a rotating body rotated by the motor.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an axial sectional view showing an embodiment of a motor of the present invention provided with an embodiment of the liquid dynamic pressure bearing of the present invention.

The motor according to the present embodiment is used for a hard disk drive (HDD). As shown in FIG. 1, a motor includes a stator portion 10 including a tubular portion 11 as an outer tubular member, and a motor as a columnar member. A rotor unit 20 having a shaft 22 and supporting a hard disk and rotating, and a driving unit 30 for rotating the rotor unit 20 while being supported by the stator unit 10 are provided.

The stator section 10 includes the tubular section 11, a base section 12, and a locking ring 13. Base 1
2 has a shape in which a substantially central portion of one surface side is depressed to form a cylindrical central hole, and a substantially central portion of the base portion 12 also functions as a part of the outer cylinder member of the present invention. Has become.
A cylindrical depression is formed at the bottom of the center hole, and the columnar magnet M1 is fitted and fixed in the depression. Thus, the bottom surface of the center hole of the base 12 is formed by the end surface of the columnar magnet M1. Further, a depression near the bottom of the peripheral portion of the center hole is formed around the bottom, and a cylindrical magnet M2 is fitted and fixed in the depression. Thus, the inner peripheral surface near the bottom of the center hole of the base portion 12 is formed by the cylindrical magnet M2. The tubular portion 11 is formed to extend perpendicularly to the one surface of the base portion 12 from a peripheral portion of the central hole of the base portion 12, and a side opposite to the base portion 12 of the tubular portion 11 is opened. ing. The hollow portion of the cylindrical portion 11 and the center hole of the base portion 12 form a support hole 11a whose end opposite to the base portion 12 is open. The locking ring 13 has a disk shape having a hole in the center.
The support hole 11a is fitted on the inner peripheral surface of the open end.

The rotor section 20 is made of SU as a non-magnetic member.
It is formed of an S member, and includes a hub 21 and a shaft 22. The hub portion 21 has a disk-shaped portion 21a having a hole in the center, and an annular portion 21b extending from the outer peripheral edge of the disk-shaped portion 21a at right angles to the disk-shaped portion 21a. A hard disk is coaxially mounted and fixed on the outer peripheral surface of the annular portion 21b, and is rotated together with the annular portion 21b. One end of the shaft portion 22 is inserted and fixed in the hole of the disc-shaped portion 21a. Shaft part 2
2 is an annular part 2 with respect to the disk upper part 21a of the hub part 21.
On the same side as 1b, it is arranged coaxially with the disc-shaped portion 21a and the annular portion 21b of the hub portion 21. The other end of the shaft 22 (the end not fixed to the disc-shaped portion 21a)
Is formed with a disk-shaped plate portion 22a extending over the entire circumference of the shaft portion 22 by a predetermined distance. The shaft portion 22 of the rotor portion 20 is mounted in the support hole 11a of the stator portion 10 with the plate portion 22a facing the base portion 12. In this state, the shaft 22
The hole of the locking ring 13 of the stator portion 10 is inserted,
The plate portion 22a of the shaft portion 22 is housed in the support hole 11a. As a result, the rotor unit 20 is rotatably supported by the stator unit 10. Hub 21
The inner peripheral surface of the annular portion 21b is the cylindrical portion 1 of the stator portion 10.
1, facing the outer peripheral surface.

On the outer peripheral surface of the plate portion 22a, two rows of diagonal grooves 25a are formed around the entire periphery of the plate portion 22 as dynamic pressure generating means for generating a dynamic pressure in the radial direction. Further, an opposing plane (the plane on the hub 22 side) of the plate portion 22a opposing the locking ring 13 and an opposing plane (the hub portion 2) opposing the base portion 12 of the plate portion 22a.
2), each of which has a herringbone groove 25 as a dynamic pressure generating means for generating a dynamic pressure in the thrust direction.
b, 25c are formed.

In the support hole 11a, a space between the shaft portion 22 and the stator portion 10 is filled with a magnetic fluid F for lubrication and for generating a dynamic pressure. As the magnetic fluid F, a conventionally used magnetic fluid of a fluid bearing, such as a commonly used ferromagnetic fine powder such as magnetite, which is surface-treated with a surfactant and dispersed in water, alkylnaphthalene, diester, or the like, is used. What is used as can be used.

The motor section 30 is fixed to the outer peripheral wall of the cylindrical section 11 of the stator section 10 and forms a stator coil 31 that forms a rotating magnetic field that rotates around the outer peripheral wall when energized, and an annular section 21b of the rotor section 20. And a rotor magnet 32 fixed coaxially with the annular portion 21b on the inner peripheral wall of the rotor. The rotor magnet 32 is a cylindrical inner peripheral multipole magnet, and is disposed so that the position in the thrust direction is substantially the same as the rotating magnetic field formed by the stator coil 31. The rotor magnet 32 is formed by the stator coil 31. The rotor 20 is rotated by the rotating magnetic field.

FIG. 2 is a cross-sectional view showing a state where the motor of this embodiment is stopped. In the motor of the present embodiment having the above-described configuration, when the stator coil 31 is not energized and no rotating magnetic field is formed, the magnetic fluid F
Is attracted to the columnar magnet M1. Therefore, FIG.
As shown in FIG. 5, the magnetic fluid F enters between the plate portion 22a of the rotor portion 20 and the base portion 12 against the drop of the rotor portion 20 due to its own weight, and the magnetic fluid F contains the cylindrical magnet M2. Therefore, the magnetic fluid F enters the space between the shaft 22 and the peripheral wall of the support hole 11a against the shaft 22. Then, even if the rotor unit 20 attempts to drop toward the base 12 (in the direction of arrow A in the figure) due to its own weight or the like, the shaft 22 is pushed back by the magnetic fluid F. Further, even if the shaft portion 22 of the rotor portion 20 is inclined by external vibration or impact and a part of the shaft 22 approaches the peripheral wall of the support hole 11a, the shaft 22 is pushed back to the magnetic fluid F. Therefore, the rotor unit 20 is always held in a non-contact state with the stator unit 10.

When a rotating magnetic field is generated in which the stator coil 31 is energized, the rotating magnetic field energizes the rotor magnet 32, and the shaft 22 starts rotating. As the shaft 22 rotates, the entire rotor section 20 rotates. I do. With the rotation of the shaft portion 22, the herringbone grooves 25b and 25c allow the two flat surfaces of the plate portion 22a to be interposed between the flat surface of the locking ring 13 and the end surface of the base portion 12 opposed thereto. A liquid dynamic pressure in the thrust direction is generated. Further, along with the rotation of the shaft portion 22, a liquid dynamic pressure in the radial direction is generated between the outer peripheral surface of the plate portion 22a and the peripheral surface of the support hole 11a by the two hatched grooves 25a.

At the time of low-speed rotation, the generated liquid dynamic pressure is small. Then, as in the case of the stop, the magnetic fluid F is attracted by the columnar magnet M1 and the cylindrical magnet M2, and enters between the plate portion 22a of the rotor portion 20 and the base portion 12, whereby the plate portion 22a , And maintain a non-contact state with the base portion 12. Then, even if the shaft portion 22 of the rotor portion 20 is inclined by external vibration or impact, and a part of the shaft 22 approaches the peripheral wall of the support hole 11a, the shaft 22 is pushed back by the magnetic fluid F, and It rotates without contact with the hole 11a. Therefore, there is no fear of wear and damage due to contact friction between the rotor section 20 and the stator section 10.

When the rotation reaches the high-speed rotation stage, the liquid dynamic pressure increases with the rotation. As shown in FIG. 1, this dynamic pressure causes the plate portion 22a to move in the thrust direction and the radial direction with respect to the support hole 11a. At a predetermined position, and rotates at a high speed without contacting the base 13 and the cylindrical portion 11.

As described above, in the motor of the present embodiment, the magnetic fluid F is used as the fluid for generating the dynamic pressure, and the magnet (the columnar magnet M1) is provided on the bottom of the support hole 11a and on the peripheral edge from the bottom. , The cylindrical magnet M2) is buried, so that the magnetic fluid F is attracted by the columnar magnet M1 and the cylindrical magnet M2, and between the plate portion 22a and the base portion 12 of the rotor portion 20, and Portion 22a and support hole 11
a. Therefore, the plate portion 22
When a approaches the peripheral wall of the support hole, the plate portion 22a is pushed back by the magnetic fluid, and the plate portion 22a is fixed to the stator portion 10 (the base portion 12, the cylindrical portion 11, the locking ring 13).
, And a state of being substantially coaxially supported with the cylindrical portion 11. Therefore, even when stationary or rotating at a low speed, wear and damage of the member are small, deformation of the groove for generating dynamic pressure and deterioration of the member can be avoided, and good durability can be obtained.

In the motor according to the present embodiment, since the rotor portion 20 is made of a non-magnetic member, the peripheral surface facing the columnar magnet M1 fixed to the stator portion 10 is a non-magnetic member. . Therefore, the cylindrical magnet M1 and the rotor section 20 do not attract each other, and the rotor section 20 can be rotated with a small driving force without requiring an extra rotating force. Further, since the rotor member is made of a non-magnetic member, the opposing flat portion facing the cylindrical magnet M2 fixed to the stator portion 10 is a non-magnetic member. Therefore, the cylindrical magnet M2 and the rotor section 20 do not attract each other, and no extra rotational force is required.
The rotor unit 20 can be rotated with a small driving force.

Next, as one embodiment of the rotating device of the present invention, a rotating device using the above-described motor will be described. FIGS. 3A and 3B are views showing a hard disk drive as one embodiment of the rotating device of the present invention, wherein FIG. 3A is a perspective view, and FIG. 3B is an axial sectional view. As shown in FIG. 3, the rotator device (hard disk drive) includes the motor 1 of the above-described embodiment, and the base 12 of the stator 10 of the motor 1 is fitted and fixed to the frame F of the hard disk drive. It is supposed to be.
The hard disk 80 is supported on the periphery of the annular portion 21 b of the hub 21 and is rotated together with the rotor 20.

In the hard disk drive of the present embodiment, the rotor 20 of the motor 1 that carries and rotates the hard disk 80 is kept in a non-contact state with the stator 10 even when the motor 1 is stationary or rotating at a low speed. With little wear and damage and good durability can be obtained. Further, even when the rotor section 20 is stationary or rotating at a low speed, the rotor section 20 is kept in a non-contact state with the stator section 10 and is hardly tilted by external impact or vibration. There is no contact, and there is little wear and damage on the hard disk and the read head. From this point, good durability can be obtained.

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the gist of the present invention. For example, in the above-described embodiment, the permanent magnets (the columnar magnet M1 and the cylindrical magnet M2) are disposed on the bottom of the support hole 11a and the peripheral surface near the bottom. Even if it is arranged only at the bottom and the contact between the bottom of the support hole 11a and the plate portion 22a is mainly avoided, it is arranged near the bottom of the periphery of the support hole 11a and The contact with 22a may be mainly avoided. In the above-described embodiment and the modification, the cylindrical magnet M2 is disposed near the bottom of the peripheral surface of the support hole 11a. However, the cylindrical magnet M2 is used together with the cylindrical magnet M2 or instead of the cylindrical magnet M2. A cylindrical magnet may be provided near the locking ring 13 on the peripheral surface of the support hole 11a. In the above-described embodiment and each of the modifications, the circumferential surface of the support hole 11a is provided with magnets over the entire circumference by the cylindrical magnet M2. However, a plurality of magnets are provided in the circumferential direction of the circumferential surface. You may. In this case, it is desirable that all adjacent magnets are arranged at equal intervals. In the above-described embodiment and each modified example, the bottom of the support hole 11a is substantially entirely covered with the columnar magnet M1.
Is fixed, but a plurality of magnets may be provided at the center of the bottom or at the periphery. In this case, it is desirable that the magnets arranged on the peripheral edge are all arranged at equal distances from each other.

In the above-described embodiment and each modified example,
The columnar magnet M1 and the cylindrical magnet M2 are exposed and are in direct contact with the magnetic fluid F, but are buried inside the rotor section 10 and are not in contact with the magnetic fluid. The magnetic fluid may be sucked through the device.

In the above embodiment and each of the modifications,
Permanent magnets (cylindrical magnets M1 and cylindrical magnets M2) are provided as magnets for magnetically attracting the magnetic fluid F, but are not limited thereto.
An electromagnet can be used for at least one of the first and cylindrical magnets M2. For example, an electromagnet may be provided on both the bottom and the peripheral surface of the support hole 11a. One or more electromagnets may be provided at the bottom of the support hole 11a, and a cylindrical magnet M2 may be provided at the peripheral surface of the support hole 11a. Further, a columnar magnet M1 may be arranged at the bottom of the support hole 11a, and a plurality of electromagnets may be arranged at the peripheral surface of the support hole 11a. When a permanent magnet is used, the manufacturing cost can be reduced.
Since the rotor is rotated while the magnets are attracted by the permanent magnet, large power consumption may be required. In the case of an electromagnet, an energizing unit that supplies electricity to the electromagnet may use an energizing unit that supplies electricity to the stator coil 31. In addition, by providing an energization control unit that controls the intermittent operation of the energization unit that supplies electricity to the electromagnet, for example, the energization control unit can connect the energization unit when the rotor is rotating or when the rotation speed is equal to or greater than a predetermined number of rotations. By cutting and connecting to the energizing means only when the rotor is not rotating or only at a predetermined number of rotations or less, it is possible to avoid suction of the magnetic fluid F during rotation and to efficiently generate dynamic pressure or reduce power consumption. Can be suppressed.

In the above-described embodiment and each of the modifications, the dynamic pressure generating means (herringbone grooves 25b, 25c
And the diagonal grooves 25a) are formed in the rotor portion 20. One of the dynamic pressure generating means for generating a dynamic pressure in the thrust direction and the dynamic pressure generating means for generating a dynamic pressure in the radial direction is provided. Both may be formed in the stator part 10 (the base part 12 and the locking ring 13).

In the above-described embodiment and each modified example,
The dynamic pressure generating means includes dynamic pressure generating grooves 25a, 25b, 25c.
However, instead of the groove, a plurality of segments may be provided on the shaft 21 or the stator 10. Further, the shape of the dynamic pressure generating grooves 25a, 25b, 25c is not limited to the above-mentioned one. For example, the dynamic pressure generating grooves 25a may be replaced with diagonal grooves, spiral grooves, or herring grooves. Bone grooves and other shaped grooves may be formed. Also, as grooves 25b and 25c for generating dynamic pressure,
Instead of the herringbone groove, a spiral groove or other various grooves may be formed. The rotor magnet 32 may be a permanent magnet or an electromagnet. Further, when the rotor magnet 32 is a permanent magnet, even if a plurality of magnets are fixed to the inner peripheral wall of the cylindrical member 22, the N pole and the S pole are alternately formed in the direction around the inner peripheral surface. A cylindrical magnet having a multi-polarity may be coaxially fixed to the inner peripheral wall of the cylindrical member 22.

The motor of the above-described embodiment is of an outer rotor type in which the rotor magnet 32 is arranged radially outward with respect to the stator coil 31, but is not limited to this. Motor. Further, an axial gap type motor can be used instead of the radial gap type. In the present specification, “rotation” when the rotor unit 20 rotates means relative rotation with respect to the stator unit 10. Therefore, the present invention also includes a motor or a rotating body device in which the rotor unit 20 is fixed to an external member and the stator unit 10 rotates externally.

In the above-described embodiment and each modified example,
The hard disk device supports a plurality of disks and rotates. However, the hard disk device may support only one disk and rotate. In the above-described embodiment and each of the modifications, the rotator device is a hard disk drive, but is not limited to this.
Other disk drives such as a D-ROM drive, a rotary polygon mirror device in which a polygon mirror is attached to a spindle of a spindle motor, and other devices can be used.

[0034]

As described above, according to the liquid dynamic pressure bearing, the motor, and the rotating device of the present invention, the wear and damage of the members at the time of stationary or low-speed rotation are small, and good durability is obtained. It is possible to get.

[Brief description of the drawings]

FIG. 1 is an axial sectional view showing an embodiment of a motor of the present invention provided with a liquid dynamic pressure bearing of the present invention.

FIG. 2 is an axial sectional view showing a state when the motor of FIG. 1 is stopped.

FIG. 3 is a diagram showing a hard disk drive as one embodiment of the rotating body device of the present invention, wherein (a) is a perspective view,
(B) is an axial sectional view.

FIG. 4 is an axial sectional view showing a prior art motor provided with a prior art liquid dynamic pressure bearing.

FIG. 5 is an axial sectional view showing a state of the prior art motor of FIG. 4 when the motor is stopped.

FIG. 6 is an axial sectional view showing a state of the conventional motor of FIG. 4 when stopped.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor 10 Stator part 11 Cylindrical part 11a Support hole (hollow part) 12 Base part 13 Locking ring 20 Rotor part 21 Hub part 21a Disk-shaped part 21b Annular part 22 Shaft part 22a Plate part 25a Diagonal groove 25b Herringbone groove 25c Herringbone groove 30 Drive unit 31 Stator coil 32 Rotor magnet 80 Hard disk M1 Column magnet M2 Cylindrical magnet F Magnetic fluid

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Naoki Kawawada 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba SII Micro Precision Co., Ltd. (72) Inventor Atsushi Ota 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba No. S-AI Micro Precision Co., Ltd. F-term (reference) 3J011 AA04 BA04 CA02 JA03 KA04 MA22 RA04 5H607 AA04 BB14 BB17 BB25 CC01 DD03 EE10 GG12 GG15 KK03

Claims (9)

[Claims] An outer cylindrical member having a cylindrical hollow portion having an open end; and a hollow or rotatable member disposed in the hollow portion of the outer cylindrical member so as to be rotatable relative to the outer cylindrical member. A solid columnar member, a fluid interposed between the outer cylinder member and the columnar member in the hollow portion of the outer cylinder member, and at the time of relative rotation of the columnar member with respect to the outer cylinder member,
A liquid dynamic pressure bearing comprising: a dynamic pressure generating unit configured to generate a dynamic pressure between the outer cylinder member and the columnar member by entraining the fluid; wherein the fluid is a magnetic fluid; A liquid dynamic pressure bearing, comprising: a magnet that magnetically attracts the magnetic fluid in a portion close to at least one of the other of the columnar members. 2. The method according to claim 1, wherein the magnet is provided on at least one of a peripheral surface of a hollow portion of the outer cylindrical member and a peripheral surface of the columnar member facing the peripheral surface. Liquid dynamic pressure bearing. 3. The magnet is provided on one of a peripheral surface of a hollow portion of the outer cylindrical member and a peripheral surface of the columnar member facing the peripheral surface, and opposes the magnet of the other. 2. The liquid dynamic pressure bearing according to claim 1, wherein the opposed peripheral surface portion is made of a non-magnetic member. 4. The apparatus according to claim 1, wherein the magnet is provided on at least one of a bottom surface of the hollow portion of the outer tubular member and an end of the columnar member facing the bottom surface. The liquid dynamic pressure bearing according to claim 3. 5. The magnet is provided on one of a bottom surface portion of the hollow portion of the outer cylindrical member and an end portion of the columnar member facing the bottom surface portion, and opposes the other of the magnets. The liquid dynamic pressure bearing according to any one of claims 1 to 3, wherein the opposed flat portion is made of a non-magnetic member. 6. The liquid dynamic pressure bearing according to claim 1, wherein the magnet is a permanent magnet. 7. An electromagnet, wherein the magnet is an electromagnet, and energizing means for supplying electricity to the electromagnet; and intermittent energization of the electromagnet by the energizing means in accordance with relative rotation of the columnar member with respect to the outer cylindrical member. The liquid dynamic pressure bearing according to any one of claims 1 to 5, further comprising an energization control means for controlling. 8. A motor comprising the liquid dynamic pressure bearing according to claim 1. Description: 9. A rotating body device comprising: the motor according to claim 8; and a rotating body rotated by the motor.