JP2003278743A - Dynamic pressure bearing, spindle motor and recording disc drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite dynamic pressure bearing constituted of a thrust bearing part by liquid and a radial bearing part by gas realizing higher speed rotation by further improving stability of a rotating member in the radial direction. <P>SOLUTION: The dynamic pressure bearing installed on a stationary part of the rotating device is furnished with a stationary member 2 having a shaft 8 and the rotating member 3 on which a through hole through which the shaft 8 is inserted through a small clearance. A thrust bearing part 36 is constituted of a thrust small clearance between the shaft 8 and the rotating member 3 and liquid held in the small clearance. A radial bearing part 35 is constituted of a radial small clearance between the shaft 8 and the rotating member 3 and gas held in the small clearance. The radial bearing part 35 is arranged above in the axial direction of the thrust bearing part 36, and both ends of the shaft 8 are supported by a base plate 9 and a plate 45. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing, and more particularly to
The present invention relates to a composite dynamic bearing in which a liquid thrust bearing portion and a gas radial bearing portion are mixed. The present invention further relates to a spindle motor and a recording disk drive device in which the dynamic pressure bearing is adopted.

[0002]

2. Description of the Related Art A recording disk drive device such as a hard disk has a spindle motor for rotation drive arranged concentrically with the recording disk in the device. This spindle motor mainly includes a stationary member to which an armature coil is fixed, a rotating member to which a rotor magnet facing the coil is fixed, and a bearing mechanism that rotatably supports the rotating member on the stationary member. ing.

As the bearing mechanism, a dynamic pressure bearing is adopted for the purpose of speeding up and low vibration (noise). The dynamic pressure bearing has a radial bearing portion and a thrust bearing portion, and each of the bearing portions has, for example, a minute gap between opposed surfaces on which a groove for dynamic pressure generation is formed, and oil retained in the gap. It is composed of a lubricating fluid. The liquid dynamic bearing using oil as the lubricating fluid has the following problems. First, there is a risk that oil will leak not only to the outside of the bearing but also to the outside of the motor during high-speed rotation, and the recording disk will be contaminated. Secondly, since the volume of oil changes when the temperature changes, oil tends to leak at high temperatures. Thirdly, the bearing rigidity, particularly the radial rigidity, tends to change due to the change in oil viscosity.

On the other hand, there is provided an air dynamic pressure bearing using air as a lubricating fluid. The pneumatic dynamic bearing has a simple structure because there is no concern about leakage of the lubricating fluid and the sealing mechanism is not required. Further, it has an advantage that the rigidity does not change in a wide temperature range. However, the air dynamic pressure bearing has the following problems. That is, the air dynamic pressure has weaker damping characteristics than the oil dynamic pressure,
The braking force is hard to work against vibration or irregular movement, resulting in continuous vibration or unnecessary contact sliding between members. As a result, in particular, sliding failure is likely to occur in the thrust bearing portion at the time of starting / stopping, and the bearing performance is likely to deteriorate due to wear of the bearing surface.

Therefore, a so-called composite type hydrodynamic bearing has been developed in which liquid is used as the lubricating fluid in the thrust bearing portion and gas is used as the lubricating fluid in the radial bearing portion. In this composite type hydrodynamic bearing, by combining each bearing with each lubricating fluid, the problems of the conventional hydrodynamic bearing using a single type of lubricating fluid are solved, and as a result, optimum performance is realized. There is.

For example, US Pat. No. 6,071,014 discloses such a composite type dynamic pressure bearing. US Patent Bulletin
6,07,014 of FIGS. 3, 6, 7 and 8 disclose a fixed shaft type dynamic pressure bearing, and FIGS. 9 and 10 disclose a shaft rotating type dynamic pressure bearing. In the shaft fixed type dynamic pressure bearing of FIGS. 3, 6, 7 and 8, the thrust bearing portion is arranged axially above the radial bearing portion. The shaft-rotational dynamic pressure bearings of FIGS. 9 and 10 disclose a structure in which the thrust bearing portion is arranged axially below the radial bearing portion. The shaft-fixed dynamic pressure bearing means that the center shaft is fixed to the stationary member, and the shaft-rotation-type dynamic pressure bearing means that the center shaft is fixed to the rotating member.

[0007]

Problems to be Solved by the Invention US Pat. No. 6,071,01
The hydrodynamic bearings shown in FIGS. 3, 6, 7 and 8 in FIG. 4 have a common point that the thrust bearing portion is arranged axially above the radial bearing portion. Therefore, the center of gravity of the rotating member is the radial bearing portion. It is distant from the center of the axis of the above in the axial direction. In such a structure, the stability of the rotary member in the radial direction is reduced, and the rotary member is liable to swirl largely. Specifically, in such a structure, when an oscillating force that exceeds the posture maintaining ability acts on the rotary member from the outside, non-uniform displacement in the axial direction occurs in the axially upper and lower portions of the radial bearing portion, As a result, the rotary member is tilted about its axis. Since the exciting force changes, the tilt angle also changes accordingly, and the tilt angle also has an angular velocity. A gyro moment is generated in the rotating member by this angular velocity.

Due to such a gyro effect, the rotating member is largely swung, and RRO (Repeatable Run-Ou)
t: Repeatable shake component) and NRRO (Non Repeatable Run-
Out: Non-repetitive shake component) worsens. As a result, swing vibration occurs in the recording disk, the magnetic head is not correctly positioned with respect to the recording disk, and accurate reading and writing of information becomes impossible. Furthermore, the peripheral surfaces may contact each other on the upper side of the radial bearing portion. That is, if the radial stability of the rotary member is reduced, it is difficult to rotate the dynamic pressure bearing at high speed.

9 and 10 of US Pat. No. 6,071,014
In the dynamic pressure bearing shown in Fig. 7, the thrust bearing portion is arranged axially below the radial bearing portion, and the center of gravity of the rotating member is located in the vicinity of the axial center of the radial bearing. The stability of the rotating member in the radial direction is improved as compared with, and high speed rotation becomes possible. However, since the dynamic pressure bearings shown in FIGS. 9 and 10 employ the shaft rotation type structure, it cannot be said that the radial direction stability of the rotating member is sufficiently obtained. Therefore, it is difficult to rotate the dynamic pressure bearing at a higher speed.

An object of the present invention is to improve the stability in the radial direction of a rotating member in a composite type dynamic pressure bearing composed of a thrust bearing portion made of liquid and a radial bearing portion made of gas, thereby enabling further high speed rotation. To do.

[0011]

A dynamic pressure bearing according to claim 1 is mounted on a stationary portion of a rotating device,
A stationary member having a shaft and a rotating member having a through hole through which the shaft is inserted through a minute gap are provided. A thrust bearing portion is constituted by the thrust minute gap between the shaft and the rotating member and the liquid held in the minute gap. The radial bearing portion is configured by the radial minute gap between the shaft and the rotating member and the gas held in the minute gap. The radial bearing portion is arranged axially above the thrust bearing portion, and both ends of the shaft are supported by stationary portions.

In this dynamic pressure bearing, the rotary member rotates with respect to the shaft, and dynamic pressure for supporting the shaft is generated in the thrust bearing portion and the radial bearing portion. The dynamic pressure is generated by the gas in the radial bearing portion, and the dynamic pressure is generated by the liquid in the thrust bearing portion. Since the lubricating fluid suitable for each bearing is adopted in this way, optimum performance is realized.

Further, since the radial bearing portion is arranged axially above the thrust bearing portion, the center of gravity of the rotating member can be located near the center of the radial bearing in the axial direction, whereby the radial direction of the rotating member is increased. The posture holding ability including the inclination of can be maximized. As a result, stable high speed rotation becomes possible. Furthermore, since this dynamic pressure bearing adopts a double-end type fixed shaft structure in which both ends of the shaft, which is the central shaft, are fixed to the stationary part of the rotating device, only one end of the shaft rotation type is used. In comparison with a cantilever type fixed shaft type dynamic pressure bearing that is fixed to a stationary member, the supporting stability is improved and the shaft is less likely to vibrate. As a result, the stability of the rotary member in the radial direction is further improved, and higher speed rotation is possible. The rotating device refers to a motor on which the dynamic pressure bearing is mounted, a drive device including the motor, and the like.

As described above, by combining the structure in which the radial bearing portion is arranged axially above the thrust bearing portion and the double-supported type fixed shaft type structure, the radial stability of the rotary member is improved. Has a synergistic effect of being significantly improved. According to a second aspect of the present invention, in the first aspect, the center of gravity of the rotating member is substantially coincident with the axial center of the radial bearing portion.

With this dynamic pressure bearing, the stability of the rotary member in the radial direction is further improved, and high speed rotation is possible. According to a third aspect of the present invention, in the hydrodynamic bearing according to the first or second aspect, the radial bearing portion is composed of first and second radial bearing portions arranged in the axial direction, and the center of gravity of the rotating member is the first and the second. It is arranged between the two radial bearing portions in the axial direction.

In this dynamic pressure bearing, the stability of the rotary member in the radial direction is further improved and high speed rotation becomes possible. A spindle motor according to claim 4 is the dynamic pressure bearing according to any one of claims 1 to 3, a stator coil fixed to a stationary member, and a stator fixed to a rotating member so as to face the stator coil. And a rotor magnet for generating a rotating magnetic field in cooperation with the coil.

Since this spindle motor uses the above-mentioned dynamic pressure bearing, high speed rotation can be realized. Claim 5
According to a fourth aspect of the spindle motor of the present invention, the stator coil and the rotor magnet are opposed to each other in the radial direction, and at least a part of the thrust bearing portion is overlapped in the axial direction in the opposed axial direction range.

In this spindle motor, as compared with the case where a magnetic circuit is formed below the thrust bearing portion, for example,
The axial length of the motor can be shortened. A recording disk drive device according to claim 6 is a housing, a spindle motor according to claim 4 fixed to the inside of the housing, a disk-shaped recording medium fixed to a rotating member capable of recording information, An information access unit for writing or reading information at a required position on the recording medium is provided.

Since this recording disk drive device uses the above-mentioned spindle motor, high-speed rotation can be realized.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION 1. First Embodiment (1) Overall Motor Structure FIG. 1 shows a spindle motor 1 as an embodiment of the present invention.
3 is a vertical cross-sectional view schematically showing the schematic configuration of FIG. The spindle motor 1 is a spindle motor for driving a recording disk, and constitutes a part of a recording disk driving device such as a hard disk.

OO shown in FIG. 1 is the rotation axis of the spindle motor 1. Further, in the description of the present embodiment, the upper and lower sides of FIG. 1 are referred to as “up and down in the axial direction” for convenience, but the direction in the actual mounting state of the spindle motor 1 is not limited. In FIG. 1, this spindle motor 1
Mainly includes a stationary member 2, a rotating member 3, and a bearing mechanism 4 for rotatably supporting the rotating member 3 on the stationary member 2.

The stationary member 2 includes a shaft 8 and a shaft 8
And a base plate 9 fixed to the lower end of the. The rotating member 3 includes a shaft 8 and a base plate 9
It is composed of a hub 26 and the like which is rotatably supported by the disk and fixedly holds a recording disk 83 (described later). The bearing mechanism 4 is a dynamic pressure bearing that utilizes a lubricating fluid, and more specifically, a complex dynamic pressure bearing that uses gas for the radial bearing portion and liquid for the thrust bearing portion. Further, the fluid dynamic pressure bearing in the first embodiment has a double-end type fixed shaft structure in which both ends of the shaft, which is the central shaft, are supported by the stationary portion of the device.

The spindle motor 1 is further provided with a stator 6 composed of a stator core and a coil fixed to the stationary member 2, and a rotor magnet 7 fixed to the rotating member 3. And a magnetic circuit portion for applying a rotational force. (2) The stationary member shaft 8 is a cylindrical member extending in the axial direction,
It is composed of a large-diameter upper portion 15 and a small-diameter lower portion 16. On the outer peripheral surface 15a of the upper portion 15, two radial dynamic pressure generating grooves 17 and 18 arranged in the axial direction are formed. In this embodiment, the radial dynamic pressure generating groove 1 is used.
Reference numerals 7 and 18 are herringbone shapes formed symmetrically.
The outer diameter of the lower portion 16 is smaller than that of the upper portion 15, and the lower end of the lower portion 16 is fitted and fixed in the center hole 9a of the base plate 9. Further, the upper portion 15 is fixed to the plate 45 with screws. In this way, the shaft 8 is supported at both ends by being fixed to the other stationary portion at the upper and lower ends in the axial direction. The plate 45 constitutes, for example, a part of the housing of the hard disk device to which the spindle motor 1 is attached, and the base plate 9 is fixed to a part of the housing.

In this embodiment, both ends of the shaft 8 are supported by being fixed to other stationary parts, but one end of the shaft 8 is formed integrally with the base plate 9. Alternatively, the base plate 9 may have a structure formed integrally with the housing. In that case, the upper part 15 is divided so that the thrust plate 21 described later can be assembled. There is a need to. Even in that case, the shaft is supported by both ends with both ends supported.

A thrust plate 21 is fixed to the lower side portion 16 with a space between the upper surface of the base plate 9 and the lower surface of the upper side portion 15. The thrust plate 21 is an annular and disk-shaped member, and has flat upper thrust surfaces 22 and lower thrust surfaces 23 on both sides in the axial direction. Further, a plurality of grooves 24 extending in the axial direction are formed on the inner peripheral edge of the thrust plate 21. The groove 24 forms a through hole together with the outer peripheral surface of the lower portion 16, and the through hole penetrates both axial direction sides of the thrust plate 21 described later to allow gas to flow between the radial bearing portion 35 and the motor external space. Function as a gas flow hole.

The base plate 9 is a disk-shaped member, and has an outer peripheral cylindrical portion 9b on the outer peripheral side thereof, on which the stator 6 is mounted on the inner peripheral surface. (3) Rotating member The rotating member 3 is composed of a plurality of tubular members fixed to each other, and is mainly composed of the hub 26, the sleeve 27, and the thrust bearing portion constituting member 28.

The hub 26 is a cylindrical member extending in the axial direction, and a plurality of recording disks 83 are fixed to the outer peripheral surface of the hub 26 via spacers. Further, the rotor magnet 7 is fixed to the lower portion of the outer peripheral surface of the hub 26. The rotor magnet 7 faces the inner peripheral side of the stator 6 in the radial direction with a minute gap. When the stator 6 is energized, torque acts on the rotating member 3 due to electromagnetic interaction between the stator 6 and the rotor magnet 7. The structure in which the rotor magnet 7 is arranged on the inner peripheral side of the stator 6 is called an inner rotor type magnetic circuit unit.

The sleeve 27 is a member for forming a radial bearing portion described later, and is a thick-walled tubular member fixed to the upper portion of the inner peripheral surface of the hub 26. The sleeve 27 is
It is a member for forming a minute gap with the outer peripheral surface 15a of the upper portion 15 of the shaft 8. The sleeve 27 corresponds to the upper portion 15 of the shaft 8. That is, the radial inner peripheral surface 27a of the sleeve 27 is radially opposed to the outer peripheral surface 15a of the upper portion 15 with a minute gap therebetween.

The thrust bearing portion constituting member 28 includes a hub 26.
It is a cylindrical member fixed to the lower part of the inner peripheral surface of the surface. The thrust bearing portion constituting member 28 is a member for forming a minute gap between the thrust bearing surface forming member 28 and the thrust surfaces 22, 23 of the thrust plate 21. The thrust bearing component member 28 is the first member 2
9 and the second member 30. First member 2
9, the outer peripheral surface is fixed to the inner peripheral surface of the hub 26. A disk-shaped portion 29a is provided on the axially upper side of the inner peripheral surface of the first member 29.
Are integrally formed. The disc-shaped portion 29 a projects inward in the radial direction from the main body portion, and is located on the upper portion 1 of the shaft 8.
It is arranged between the lower end surface 15b of the No. 5 and the upper thrust surface 22 of the thrust plate 21. As a result, the lower thrust surface 29b of the disk-shaped portion 29a and the thrust plate 2
A minute gap is secured between the upper thrust surface 22 and the upper thrust surface 22, and they are axially opposed to each other. Disk-shaped part 29a
The thrust dynamic pressure generating groove 3 is formed on the lower thrust surface 29b.
2 is formed. The second member 30 is a disc-shaped member fixed to the lower portion of the inner peripheral surface of the first member 29. The second member 30 is arranged near the lower portion of the thrust plate 21. Therefore, the upper thrust surface 3 of the second member 30
0a and a lower thrust surface 23 of the thrust plate 21 are provided with a minute gap, which are opposed to each other in the axial direction. A thrust dynamic pressure generating groove 33 is formed on the upper thrust surface 30a of the second member 30. In this embodiment, the thrust dynamic pressure generating grooves 32 and 33 are herringbone shaped symmetrically formed.

(4) Bearing Mechanism The bearing mechanism 4 is a dynamic pressure bearing for rotatably supporting the rotating member 3 with respect to the stationary member 2 via a lubricating fluid.
The bearing mechanism 4 includes a radial bearing portion 35 that uses air as a lubricating fluid and a thrust bearing portion 36 that uses oil as a lubricating fluid.

The radial bearing portion 35 is composed of first and second radial bearing portions 38, 39 which are vertically arranged in the axial direction. The first radial bearing portion 38 is composed of a portion of the outer peripheral surface 15a of the shaft 8 in which the radial dynamic pressure generating groove 17 is formed, a radial inner peripheral surface 27a of the sleeve 27, and air existing in a minute gap therebetween. ing. The second radial bearing portion 39 is composed of a portion of the outer peripheral surface 15a of the shaft 8 where the radial dynamic pressure generating groove 18 is formed, a radial inner peripheral surface 27a of the sleeve 27, and air existing in a minute gap therebetween. There is.

The thrust bearing portion 36 is composed of first and second thrust bearing portions 41 and 42 which are vertically arranged in the axial direction. The first thrust bearing portion 41 is composed of a lower thrust surface 29b of the thrust bearing portion constituting member 28, an upper thrust surface 22 of the thrust plate 21, and oil present in a minute gap between them. The second thrust bearing portion 42 includes the upper thrust surface 30 a of the thrust bearing portion constituting member 28 and the lower thrust surface 23 of the thrust plate 21.
And the oil present in the minute gap. A taper surface is formed at the inner peripheral edge of the lower thrust surface 29b and the inner peripheral edge of the upper thrust surface 30a so that a minute gap formed by each expands in the inner diameter direction, and a taper seal structure that regulates oil flow by a capillary force. Thus, the oil is retained in the minute gap.

The lower end of the second radial bearing portion 39 communicates with the through hole formed by the thrust plate 21 and the lower portion 16, communicates with the motor external space, and the first radial bearing portion 3
The upper end of 8 communicates with the motor outer space via the upper wall of the hub 26. As a result, the gas in the radial bearing portion 35 is configured to communicate with the motor external space without being mixed with the oil in the thrust bearing portion 36.
A partial negative pressure area is not formed in the area. In addition,
In a dynamic pressure bearing that uses gas as a lubricating fluid, if a pressure distribution including a negative pressure region smaller than atmospheric pressure is formed in the minute gap, it may cause deterioration of bearing characteristics. It is desirable that the regions are formed as little as possible. Therefore, in the present example, the radial bearing portion 35 is communicated with the motor external space that is almost equivalent to the atmospheric pressure.

In order to eliminate the negative pressure region, a vertical through hole connecting the upper end of the first radial bearing portion 38 and the lower end of the second radial bearing portion 39 is provided in the upper portion 15, and further the first and the first and second holes are formed. (2) A horizontal through hole connected to the vertical through hole is provided in an intermediate portion of the two radial bearing parts 38, 39, and the radial bearing part 35 communicates with the motor external space by the circulation hole composed of the vertical through hole and the horizontal through hole. It is also possible to eliminate the negative pressure region. In this case, the thrust plate 21 and the lower part 1
The through hole formed by 6 and 6 can be omitted, and in addition, the lower end of the radial bearing portion 35 can be prevented from flowing a gas by the oil of the thrust bearing portion 36, and as a result, in the radial bearing portion 35, It is possible to prevent the abrasion powder generated from flowing out to the space outside the motor.

The first and second radial bearing portions 38,
The herringbone-shaped groove of 39 may become asymmetric due to the symmetry breaking even if there is only a processing tolerance, but it may cause the generation of a negative pressure area. However, the circulation hole eliminates the negative pressure area. can do. Further, in this example, the upper end surface of the sleeve 27 forms a minute gap with the hub upper wall portion, and the lower end surface of the sleeve 27 forms a minute gap with the first member 29. In each case, the radial bearing portion 35 has a minute gap. Since the minute gaps communicate with the gaps, the minute gaps contain the abrasion powder generated in the radial bearing portion 35 and moved by the centrifugal force, and prevent the abrasion powder from flowing out to the motor external space.

(5) Operation When the coil of the stator 6 is energized, the magnetic circuit portion of the stator 6 and the rotor magnet 7 causes the rotating member 3 to move together with the recording disk 83 via the radial bearing portion 35 and the thrust bearing portion 36. In the supported state, it rotates with respect to the shaft 8. At this time, in the radial bearing portion 35, the air in the gap between the outer peripheral surface 15a of the shaft 8 and the radial inner peripheral surface 27a of the sleeve 27 is shaped like a herringbone-shaped radial dynamic pressure generating groove 17, 18 in rotation. The radial load supporting pressure is generated due to the action toward the curved portion (central portion). That is, by maximizing the supporting pressure of the bent portion, the thrust bearing portion 36 is formed with a pair of maximum supporting pressure portions on both sides in the axial direction of the thrust plate 21. Further, in the thrust bearing portion 36, the lubricating oil in the gap between the thrust plate 21 and the circular concave portion of the thrust bearing portion constituting member 28 causes the herringbone-shaped thrust dynamic pressure generating grooves 32, 33 to have a dogleg-shaped bent portion. Thrust load supporting pressure is generated due to the action toward (central portion). That is, by maximizing the supporting pressure of the bent portion, the radial bearing portion 35 is formed with a pair of maximum supporting pressure portions in the axial direction.

(6) Effects Advantages of being a composite type dynamic pressure bearing Since the radial bearing portion 35 is a gas dynamic pressure bearing, the change in rigidity is small in a wide temperature range. Further, since the seal structure is not required, the structure is simplified, and the problem of lack of lubricating fluid is solved, so that the life is extended.

Since the thrust bearing portion 36 has oil dynamic pressure, the required bearing rigidity can be obtained even at low speed starting and stopping compared to pneumatic dynamic pressure, and sliding failure in the thrust bearing portion is less likely to occur. Therefore, the life of the bearing member in the thrust bearing portion is improved. Effects due to the positional relationship between the radial bearing and thrust bearing
As a result, since the radial bearing portion 35 is arranged axially above the thrust bearing portion 36, the center of gravity of the rotating member 3 moves axially downward as compared with the conventional case, and the radial bearing portion 3 moves.
5 can be located near the center in the axial direction. As a result, the posture holding ability including the inclination of the rotary member 3 in the radial direction can be maximized, and the speed of the rotary member 3 can be increased.

In this embodiment, the rotary member 3 is actually used.
The center of gravity G of is substantially coincident with the axial center of the radial bearing portion 35. In other words, as in this embodiment, the radial bearing portion 35 has two first and second radial bearing portions 35 arranged in the axial direction.
In the case where it is composed of the radial bearing portions 38 and 39, the center of gravity position G of the rotating member 3 is set to the first and second radial bearing portions 3.
It is located between 8 and 39. Therefore,
The rotating member 3 is supported by the first and second radial bearing portions 38 and 39 above and below the center of gravity G even if a load tilting in the radial direction about the center of gravity G acts. The posture holding ability of the robot becomes maximum, and the speed can be further increased.

Further, the thrust bearing portion 36 is arranged axially below the radial bearing portion 35, and is further enclosed in the spindle motor 1 by the base plate 9. Since the thrust bearing portion 36 is arranged inside the spindle motor 1 as described above, even if the oil leaks from the thrust bearing portion 36 due to an impact from the outside, the oil remains in the base plate 9 of the spindle motor 1. ing. Therefore, the inside of the recording disk drive device such as the hard disk device is less likely to be contaminated.

Further, the axial width of the thrust bearing portion 36 (that is, the wall thickness of the first member 29) has a positional relationship including the axial width of the magnetic circuit described above. As a result, the axial length of the motor can be shortened as compared with a case where such a positional relationship is not taken, for example, when a magnetic circuit is formed below the thrust bearing portion 36. Further, since the thrust bearing portion 36 is located below the radial bearing portion 35, the hub 2 located above the radial bearing portion 35.
The upper wall portion of 6 can have a simple shape.

Effect of shaft fixing structure Since the bearing mechanism 4 adopts the shaft fixing type structure, the supporting stability is improved and the shaft is less likely to vibrate as compared with the shaft rotating type dynamic pressure bearing. ing. Furthermore, since this bearing mechanism 4 is a double-supported type in which both ends of the shaft 8 are supported by the base plate 9 and the plate 45, vibrations on the shaft 8 are less likely to occur even under conditions of high speed and high load. If this is a conventional cantilever type, under the conditions of high speed and high load, the free end side of the shaft swings around and the vibration of the shaft becomes large, and the RR of the upper recording disk increases.
There are problems that ONRO is deteriorated and that contact wear occurs at the upper portion of the radial bearing portion.

Further, since the shaft 8 is of a double-support type, the rotating member 3 can be held in a state in which no trouble is caused even when external vibration or shock is applied. Since the shaft 8 is divided into a large-diameter upper portion 15 that constitutes the radial bearing portion 35 and a small-diameter lower portion 16 that constitutes the thrust bearing portion 36, the diameter of the radial bearing portion 35 is set sufficiently large. It is possible,
Sufficient dynamic pressure can be generated even at low speed rotation. At the same time, the members forming the thrust bearing portion 36 can be arranged within the same diameter as the members forming the radial bearing portion 35, so that the bearing mechanism 4 becomes compact in the radial direction.

(7) Configuration of Hard Disk Device The embodiment of the recording disk driving spindle motor 1 according to the present invention has been described above, but a hard disk device as a recording disk driving device including the spindle motor 1 according to the present invention will be described. An example will be explained. FIG. 4 is a schematic diagram showing the internal configuration of a general hard disk device 80. The inside of the casing 81 forms a clean space in which dust and the like are extremely small, and the spindle motor 1 having the disk-shaped recording disk 83 for storing information installed therein is installed therein. There is. In addition, a magnetic head moving mechanism 87 for reading and writing information from and to the recording disk 83 is arranged inside the housing 81. The magnetic head moving mechanism 87 includes a head 86 for reading and writing information on the recording disk, and this head. And an actuator section 84 for moving the head and the arm to a desired position on the disk.

2. Second Embodiment The spindle motor shown in FIG. 3 has the same basic structure as the spindle motor of the above embodiment. Therefore, only the different points will be described here. In this embodiment, the rotor magnet 7 is arranged on the outer peripheral side of the stator 6, which is called an outer rotor type magnetic circuit section. The configuration of this magnetic circuit section will be described below.

Unlike the above embodiment, the lower portion of the hub 26 does not extend in the axial direction to the outer peripheral side of the thrust bearing portion 36, but has a disk shape extending to the outer peripheral side. Further, on the outer peripheral edge of the disk-shaped portion, the cylindrical portion 2 extending downward in the axial direction is formed.
6a is formed. The tubular portion 26a is close to the outer circumferential side tubular portion 9b of the base plate 9 on the inner circumferential side. The rotor magnet 7 is mounted on the inner peripheral surface of the tubular portion 26a.

The base plate 9 has an inner cylindrical portion 9c.
Are formed. The inner peripheral side tubular portion 9c extends in the axial direction from the main body portion and is arranged close to the outer peripheral side of the thrust bearing portion 36. The stator 6 is fixed to the outer peripheral surface of the inner peripheral side tubular portion 9c and is arranged on the inner peripheral side of the rotor magnet 7. On the outer peripheral surface of the first member 29 of the thrust bearing portion constituting member 28, a concave portion 29c for accommodating the inner peripheral side tubular portion 9c and a part of the stator 6 is formed.

The outer rotor type described above is made possible by the fact that the thrust bearing portion 36 is arranged axially below the radial bearing portion 35, so that there is no restriction imposed by the radial bearing portion, and the thrust bearing portion 36 is not restricted. This is because a relatively large space can be secured on the outer peripheral side and the magnetic circuit section is arranged there. When the outer rotor type is adopted in this way, it is advantageous in terms of leakage magnetic flux, and winding to the stator 6 is facilitated, so that cost reduction can be realized.

3. Other Embodiments The present invention is not limited to the above embodiments, and various changes or modifications can be made without departing from the scope of the present invention. For example, in each bearing in the above-described embodiment, the dynamic pressure generating groove may be formed in the member on the opposite side, or may have a different shape. Further, each bearing may have a structure in which the dynamic pressure generating groove is not formed.

The spindle motor according to the present invention can be adopted not only in the hard disk recording device but also in other recording disk driving devices, polygon mirror driving devices for laser beam printers, color wheel driving devices used in projectors, and the like. .

[0051]

In the dynamic pressure bearing according to the first aspect of the invention, the rotary member rotates with respect to the shaft, and the dynamic pressure for supporting the shaft is generated in the thrust bearing portion and the radial bearing portion. The dynamic pressure is generated by the gas in the radial bearing portion, and the dynamic pressure is generated by the liquid in the thrust bearing portion. Since the lubricating fluid suitable for each bearing is adopted in this way, optimum performance is realized.

Further, since the radial bearing portion is arranged axially above the thrust bearing portion, the center of gravity of the rotating member is near the axial center of the radial bearing (that is, the portion having the largest radial bearing rigidity). positioned. As a result, the stability of the rotary member in the radial direction is improved, and high-speed rotation is possible. Furthermore, this dynamic pressure bearing
Since the shaft fixed type structure is adopted, the support stability is improved and the shaft is less likely to vibrate as compared with the shaft rotating type dynamic pressure bearing. Furthermore, since this dynamic pressure bearing is a double-sided type in which both ends of the shaft are supported by the stationary portion of the rotating device, the shaft does not vibrate. As a result, the radial stability of the rotating member is further improved,
Higher speed rotation is possible.

As described above, by combining the structure in which the radial bearing portion is arranged axially above the thrust bearing portion and the double-end type fixed shaft type structure, the radial stability of the rotary member is improved. Has a synergistic effect of being significantly improved. In the hydrodynamic bearing according to claim 2, in claim 1, the center of gravity of the rotating member substantially coincides with the center of the radial bearing portion in the axial direction, so that the stability of the rotating member in the radial direction is further improved, and high speed is achieved. It becomes possible to rotate.

According to another aspect of the dynamic pressure bearing of the present invention,
Or 2, the radial bearing portion is composed of first and second radial bearing portions arranged in the axial direction, and the center of gravity of the rotating member is arranged between the first and second radial bearing portions in the axial direction. Further, the radial stability of the rotating member is further improved, and high-speed rotation becomes possible. In the spindle motor according to the fourth aspect, since the above dynamic pressure bearing is used, high speed rotation can be realized.

According to the spindle motor of the fifth aspect,
The stator coil and the rotor magnet are opposed to each other in the radial direction, and at least a part of the thrust bearing portion is overlapped in the axial direction in the opposing axial direction range. The axial length of the motor can be shortened as compared with the case where a circuit is formed.

In the recording disk drive device according to the sixth aspect, since the spindle motor described above is used in the fourth or fifth aspect, high speed rotation can be realized.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a spindle motor adopting a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG. 1 and is a schematic vertical cross-sectional view around a thrust bearing portion.

FIG. 3 is a schematic vertical cross-sectional view of a spindle motor that employs a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a general hard disk device.

[Explanation of symbols]

1 Spindle motor 2 stationary members 3 rotating members 4 Bearing mechanism 8 shafts 26 hubs 27 Sleeve 35 radial bearing 36 Thrust bearing

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02K 21/16 H02K 21/16 M 5 H621 21/22 21/22 MF term (reference) 3J011 AA08 AA12 BA04 BA06 CA03 JA02 KA02 KA03 MA02 MA12 3J102 AA08 BA04 BA17 BA18 CA02 CA05 CA09 FA27 FA30 GA03 5D109 BA14 BA20 BB05 BB13 BB18 BB21 BB22 5H605 AA04 BB05 BB19 CC04 DD05 DD09 EB08 5H607 AO04 BB01 BB14 BB17 CC01 DD15GG01H14 A01 04A15 04 JK19

Claims (6)

[Claims] 1. A dynamic pressure bearing mounted on a stationary portion of a rotating device, comprising: a stationary member having a shaft; and a rotating member having a through hole through which the shaft is inserted through a minute gap. A thrust bearing portion is formed by a minute gap in the thrust direction between the shaft and the rotating member and a liquid held in the minute gap, and a minute gap in the radial direction between the shaft and the rotating member and the minute gap. A radial bearing portion is formed by the gas retained in the axial direction, the radial bearing portion is disposed axially above the thrust bearing portion, and both ends of the shaft are supported by the stationary portion. , Dynamic pressure bearing. 2. The hydrodynamic bearing according to claim 1, wherein the center of gravity of the rotating member is substantially coincident with the axial center of the radial bearing portion. 3. The radial bearing portion is composed of first and second radial bearing portions arranged in the axial direction, and the center of gravity of the rotating member is between the axial directions of the first and second radial bearing portions. The hydrodynamic bearing according to claim 1 or 2, which is arranged. 4. The dynamic pressure bearing according to claim 1, a stator fixed to the stationary member, a stator fixed to the rotating member so as to face the stator, and a stator cooperating with the stator. A spindle motor including: a rotor magnet that works to generate a rotating magnetic field. 5. The spindle according to claim 4, wherein the stator and the rotor magnet are opposed to each other in the radial direction, and at least a part of the thrust bearing portion is overlapped in the axial direction in the opposed axial direction range. motor. 6. A housing, the spindle motor according to claim 4 fixed to the inside of the housing, a disk-shaped recording medium fixed to the rotating member, capable of recording information, and the recording. A recording disk drive device comprising: an information access unit for writing or reading information at a required position on a medium.