JP2002081440A - Dynamic pressure bearing device and spindle motor comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To level a holding amount of lubricant held at each bearing part for rotating stably when a pair of radial dynamic pressure bearing parts separated by an air intervening part and a pair of thrust dynamic pressure bearing parts next to the radial dynamic pressure bearing parts respectively are constituted. SOLUTION: Each of the pair of radial dynamic pressure bearing parts 28a, 28b is placed next to each of the pair of thrust dynamic pressure bearing parts 32a, 32b respectively. The pair of thrust dynamic pressure bearing parts is functioned such that each of them is pumped to the adjoining radial dynamic pressure bearing part side for the lubricant 24 held in thrust small gaps respectively. An expanding gap part 19a of which a gap size between an outer circumferential face of a thrust plate 4a and a plate facing inner circumferential face 18c changes circumferentially and continuously and an opening is made outward in an axial direction is formed in a part, in a circumferential direction at a gap in a radial direction of an outer circumference of the thrust plate 4a. At least one lubricant communicating passage 34 adapted to communicate between each of outer circumferential end parts of the pair of thrust small gaps is formed on a sleeve body 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a pair of thrust plates, a pair of thrust dynamic pressure bearing portions provided in relation to each of the two thrust plates, and an arrangement between the two thrust dynamic pressure bearing portions. The present invention relates to a dynamic pressure bearing device provided with a pair of radial dynamic pressure bearing portions and a spindle motor including the dynamic pressure bearing device.

[0002]

2. Description of the Related Art As a bearing means for rotatably supporting a motor rotor, a dynamic pressure bearing device having a pair of thrust plates has been known.
No. 217735. In this hydrodynamic bearing device, a pair of thrust plates is fixed to both ends of a fixed shaft, and a thrust load applied to the motor in a thrust direction is applied to both thrust plates and a thrust surface of a rotating body (rotor) opposed to the thrust plates in the axial direction. A pair of radial bearings, which form a pair of thrust bearing portions for supporting by a dynamic pressure, and further support, by dynamic pressure, a radial load applied to a motor by an outer peripheral surface of a shaft and a radial surface of a rotating body radially opposed to the shaft. A bearing portion is formed.

[0003] One and the other of a pair of thrust bearing portions are:
A lubricating liquid such as oil is continuously held in one of the thrust bearing portions and one of the radial bearing portions, and the other thrust bearing portion and the other radial bearing portion are adjacent to each other. The lubricating liquid is continuously held by the radial bearing portion, and an air intervening portion that divides one and the other is provided between the pair of radial bearing portions.

[0004] The dynamic pressure generating grooves of the pair of thrust bearing portions are provided with a lubricating liquid held in a minute gap between the thrust plate and the thrust surface of the rotor, and a transfer pressure radially inward when the rotor rotates. A spiral groove that generates
Further, the dynamic pressure generating grooves of the pair of radial bearings serve as a transfer pressure in the direction of the adjacent thrust bearing during rotation of the rotor with respect to the lubricating liquid held in the minute gap between the shaft and the radial surface of the rotor. The herringbone groove is formed in an unbalanced shape in the axial direction in which the generation occurs.

In this prior art, the thrust bearing is configured such that when the rotor rotates, the outer end of the spiral groove of each thrust bearing is exposed due to the radial inward movement of the lubricating liquid, and the thrust plate is further formed. A tapered seal portion whose interval gradually increases radially outward between the axially inner surface and the thrust surface of the rotor, wherein the interface between the lubricating liquid and the outside air is located at the tapered seal portion. Have been.

[0006]

SUMMARY OF THE INVENTION
By using a spiral groove as a groove for generating dynamic pressure in the thrust bearing, the lubricating liquid retained in the thrust bearing is pumped radially inward of the thrust bearing, and is also supplied to the radially outer end of the thrust bearing. By arranging the tapered seal portion, leakage of the lubricating liquid to the outside of the bearing is prevented. However, in such a configuration, the lubricating liquid is retained in the thrust bearing part by the tapered seal part. However, when the motor rotates, centrifugal force acts on the lubricating liquid in the outer circumferential direction with the rotation of the rotor. It is difficult to completely seal the liquid. That is, at the molecular level of the lubricating fluid, the lubricating fluid is lubricated from the bearing along the thrust surface of the thrust plate and the rotor constituting the thrust bearing, and along the surface of the shaft and sleeve in the radial dynamic pressure bearing. A so-called migration phenomenon that attempts to diffuse into a portion where no liquid exists (exists) occurs.

[0007] The above-mentioned migration phenomenon does not become constant at each bearing due to the material, surface accuracy, etc. of the members that come into contact with the lubricating liquid, and the amount of lubricating liquid dissipated differs between the bearings. If the lubricating fluid held in one bearing and the lubricating fluid held in the other bearing are completely separated after assembling the motor, a difference occurs in the amount of lubricant held between the one and the other bearings, and It will be in a balanced state.
The imbalance in the amount of retained lubricating fluid between the one and the other bearings also occurs due to a work error or the like when the lubricant is injected into the bearings. In addition, when the motor is installed so that the shaft is in the vertical direction, gravity acts on the lubricating fluid held in the upper radial bearing toward the gas intervening part, and the migration phenomenon is promoted and the lubricating fluid is promoted. Leakage and dissipation increases.

[0008] As described above, when an unbalance occurs in the amount of retained lubricating fluid between one bearing portion and the other bearing portion, the groove for generating dynamic pressure of the bearing portion having the smaller retained amount of lubricating liquid is formed. When exposed to the outside air and the generated dynamic pressure is reduced, a difference occurs in the bearing rigidity between the one and the other bearing portions, which may make it difficult to obtain stable rotation of the motor. In addition, leakage and dissipation of the lubricating liquid from the bearing due to the migration phenomenon and the like cause early depletion of the lubricating liquid retained in the bearing, which causes a deterioration in durability and reliability of the motor.

The present invention has been made in consideration of such problems of the prior art, and an object of the present invention is to form a pair of radial dynamic pressure bearing portions separated by a gas intervening portion. In this case, the amount of the lubricating liquid held in each bearing portion can be made uniform, and a stable rotation can be obtained. The dynamic pressure bearing device which can be used for a long time, and a spindle motor using the same The purpose is to provide.

[0010]

In order to achieve the above object, in a dynamic bearing device according to the present invention, a shaft and two radially outwardly projecting portions are provided at two positions separated in the axial direction of the shaft. A pair of disc-shaped thrust plates, a radial bearing surface opposed to the outer peripheral surface of the shaft between the pair of thrust plates via a radial minute gap, and a thrust minute gap on an axially inner surface of the pair of thrust plates facing each other. A sleeve body having a through hole formed by continuously forming a pair of thrust bearing surfaces opposed to each other through an inner peripheral surface of a pair of thrust plates opposed to each other via a radial gap on an outer peripheral surface of the pair of thrust plates; A pair of thrust presses having a lubricating liquid continuously held in the radial minute gap, the thrust minute gap and the radial gap. An annular gas intervening portion communicating with the outside of the bearing is formed at a substantially central portion in the axial direction of the radial minute gap between the shafts, and at least one of the outer peripheral surface of the shaft and the radial bearing surface is formed at the upper and lower portions in the axial direction of the gas intervening portion. A pair of radial dynamic pressure bearings is formed by forming a dynamic pressure generating groove for generating a dynamic pressure with respect to the lubricating fluid, and a pair of thrust plates are axially inwardly disposed in the axially inner portions of the pair of thrust plates. At least one of the inner surface and the thrust bearing surface is formed with a dynamic pressure generating groove for generating a dynamic pressure on the lubricating liquid to form a pair of thrust dynamic pressure bearing portions, and one of the pair of radial dynamic pressure bearing portions And the other is disposed adjacent to each other on one and the other of the pair of thrust dynamic pressure bearings, and the pair of thrust dynamic pressure bearings is adjacent to the lubricating liquid held in the thrust minute gap. Pumping to the radial dynamic pressure bearing portion side, and pumping the lubricating fluid held in the radial minute gap to the adjacent thrust dynamic pressure bearing portion side in each of the pair of radial dynamic pressure bearing portions. In the radial gap, an enlarged gap portion in which a radial gap dimension between the outer peripheral surface of the thrust plate and the plate-facing inner peripheral surface continuously changes in the circumferential direction and is opened outward in the axial direction. Is formed at a part in the circumferential direction, and at least one lubricating fluid communication passage communicating between the outer peripheral ends of the pair of thrust minute gaps is provided in the sleeve body. 1).

In the hydrodynamic bearing device having such a configuration, when the shaft and the sleeve body rotate relative to each other, the radial dynamic pressure bearing portion and the thrust dynamic pressure bearing portion which are arranged adjacent to each other are respectively lubricated. It functions to pump the liquid to the adjacent dynamic pressure bearing part side, and the pressure of the lubricating liquid becomes highest between adjacent dynamic pressure bearing parts or at each part of the dynamic pressure bearing part adjacent thereto, and the radial load and thrust load Is supported. The centrifugal force acts on the lubricating liquid in the thrust dynamic pressure bearing in addition to the pumping force in the direction toward the radial dynamic pressure bearing, and there is a concern that the lubricating liquid may diffuse outward in the radial direction with a migration phenomenon. ,
A radially outer side of the thrust dynamic pressure bearing portion has a plate-facing inner peripheral surface facing the outer peripheral surface of the thrust plate, and is formed on both facing surfaces (continuous with the thrust minute gap).
Since the lubricating liquid is held in the radial gap, there is no fear of leakage and dissipation of the lubricating liquid.

At this time, if air bubbles are contained in the lubricating liquid, the air bubbles in the lubricating liquid are transferred from the high pressure part to the low pressure part along the pressure gradient, so that the thrust dynamic pressure bearing part It moves to the gas interposition part side of the outer peripheral direction and the radial dynamic pressure bearing part, and is removed to the outside in the axial direction from between the thrust plate and the plate-facing inner peripheral surface of the sleeve body. Be eliminated.

In the enlarged gap portion formed in the radial gap on the outer periphery of the thrust plate, the radial gap dimension continuously changes in the circumferential direction, and a tapered region is formed. A meniscus can be formed at an arbitrary position in the enlarged gap portion, functioning as a buffer region, and forming a taper seal portion in a form balanced with the boundary surface of the lubricating liquid on the radial dynamic pressure bearing portion side.

Here, the lubricating fluid held by the pair of radial dynamic pressure bearing portions separated by the air in the gas intervening portion and the thrust dynamic pressure bearing portion adjacent thereto is supplied to one radial dynamic pressure bearing portion and to the other. If there is a quantitative imbalance between the adjacent thrust dynamic pressure bearing and the other radial dynamic pressure bearing and the lubricating fluid held by the adjacent thrust dynamic pressure bearing, a pair of radial dynamic The surface tension of the lubricating fluid, the atmospheric pressure of the outside air, and the like held in each of the pressure bearing portion and the thrust dynamic pressure bearing portion adjacent to the pressure bearing portion attempt to balance each other, so that the lubricating fluid passes through the lubricant retaining portion of the communication passage. A moving pressure is generated from the bearing portion having a large holding amount to the bearing portion having a small amount, and the lubricating fluid is retained through a communication passage between the pair of radial dynamic pressure bearing portions and the thrust dynamic pressure bearing portion adjacent thereto. There redistribution to become uniform is performed, quantitative unbalance of the lubricating fluid is eliminated.

In the configuration of the present invention described above, the enlarged gap portion is formed by cutting off a part of the outer peripheral surface of the thrust plate except for a portion facing the thrust minute gap in the axial direction.
If it is formed between the cut surface and the inner peripheral surface facing the plate (Claim 2), it is possible to very easily form the main tapered shape in which the radial gap dimension changes continuously.

Further, in the configuration of the present invention described above,
As a dynamic pressure generating groove of the pair of radial dynamic pressure bearing portions, an unbalanced herringbone groove is formed in the axial direction so that a large dynamic pressure acts on the opposite side to the gas interposition portion, and a pair of thrust dynamic pressure bearing portions The pump-in type spiral groove in which the dynamic pressure acts in the shaft direction can be formed as the dynamic pressure generating groove (claim 3). According to this,
From the boundary surface of the lubricating fluid located on the radial dynamic pressure bearing side to the boundary surface of the lubricating fluid located on the thrust dynamic pressure bearing side, there is only one point where the dynamic pressure is maximal and there are points where the dynamic pressure is minimal. Therefore, even if bubbles are contained in the lubricating liquid, the lubricating liquid is automatically eliminated from the boundary surface of the lubricating liquid, which minimizes the pressure, to the atmosphere.

Further, in the above-mentioned structure, the sleeve body may include an outer sleeve having a cylindrical inner peripheral surface forming an inner peripheral surface facing the plate, a cylindrical outer peripheral surface having substantially the same diameter as the inner peripheral surface facing the plate, and a radial bearing. And an inner sleeve having a cylindrical inner peripheral surface forming a surface and being fitted inside the outer sleeve, and a communication path can be formed by cutting off a part of the outer peripheral portion of the inner sleeve in the axial direction. (Claim 4).
According to this configuration, the communication passage can be formed in the sleeve body only by fitting the inner sleeve, whose part of the outer peripheral portion has been cut off, to the outer sleeve, and the manufacture becomes extremely easy.

On the other hand, in the present invention described above, the sleeve body is provided with a pair of annular cover plates so as to close the openings at both ends of the through hole, and a radial direction is provided between the pair of cover plates and the pair of thrust plates. It is also possible to form an axial gap that increases inward (claim 5). At the time of relative rotation between the shaft and the sleeve body, the interface of the lubricating liquid on the thrust dynamic pressure bearing side exists in the radial gap on the outer periphery of the thrust plate or in the axial gap between the thrust plate and the cover plate. When the interface of the lubricating liquid is located in the gap, migration of the lubricating liquid is suppressed by the centrifugal force, and the interface of the lubricating liquid is stably maintained. Since this axial gap has a tapered shape that expands inward in the radial direction, it serves as a buffer area for storing the lubricating fluid axially outside the thrust dynamic pressure bearing portion. And the margin of the amount of the lubricating fluid can be expanded.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a dynamic bearing device and a spindle motor according to the present invention will be described with reference to the drawings, taking a spindle motor for driving a recording disk as an example. FIG. 1 is a cross-sectional view schematically showing a schematic configuration of a spindle motor according to one embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a dynamic pressure bearing portion of FIG. 1, and FIG. FIG. 4 is a plan view of a part of the state, FIG.
5 is a perspective view of a thrust plate, and FIG. 6 is a perspective view of an inner sleeve constituting a part of the sleeve body.

The spindle motor 1 for driving a recording disk shown in FIG. 1 is supported by a bracket 2 fixed to a base of the disk drive and a motor shaft hole 2a provided in the bracket 2 with a lower end fitted thereto. Shaft 4, a rotor 6 rotatable relative to the shaft 4, and a stator 8 fixed to the bracket 2 in a concentric arrangement with the shaft hole 2a.
And The rotor 6 has a recording disk D
A rotor hub 6a as a sleeve body for holding
A plurality of recording disks D are placed on a disk mounting portion 6ab formed on the rotor hub 6a with spacers 10 therebetween.
The laminated body is sandwiched between the disk mounting portion 6ab and the clamper 12 fixed to the outer peripheral portion of the upper end of the rotor hub 6a, and the recording disk D rotates integrally with the rotor hub 6a. .

A cylindrical rotor magnet 14 is fixed to the inner peripheral surface of the lower outer peripheral wall of the rotor hub 6a by bonding or the like, and the stator 8 is radially opposed to this. The stator 8 is configured by winding a multi-phase coil 8b around a magnetic pole portion (teeth) of a stator core 8a formed by laminating electromagnetic steel sheets. An annular yoke 16 for applying the magnetic attractive force of the rotor magnet 14 to the rotor 6 is fixed to the bracket 2 at a position facing the rotor magnet 14 in the axial direction. In the above description, the bracket 2 is fixed to the base of the disk drive. However, it is also possible to use a base-integrated spindle motor that directly fixes the shaft to the base of the disk drive.

At the center of the rotor hub 6a as a sleeve body, there is formed a through hole 18 which penetrates in the axial direction and has a stepped diameter extending outwardly at both ends in the axial direction. That is, the through hole 18 has a radial bearing surface 18a which is a cylindrical inner peripheral surface provided in the middle portion and a ring-shaped thrust bearing extending radially outward from both axial end edges of the radial bearing surface 18a. Surface 18b, and a plate-facing inner peripheral surface 18c which is a cylindrical inner peripheral surface extending outward in the axial direction from the outer peripheral edge of each of the thrust bearing surfaces 18b. A stepped opening 18d is provided with an enlarged diameter.

The above-described stepped through hole 18 can be easily formed by combining the outer sleeve 6a1 and the cylindrical inner sleeve 6a2 to form the rotor hub 6a as a sleeve body. The outer sleeve 6a1 has a two-stage cylindrical shape capable of holding the disk D on the outer periphery and mounting the rotor magnet 14 on the lower inner periphery, and having a constant inner diameter in the axial direction forming the plate-facing inner peripheral surface 18c on the inner periphery. A cylindrical inner peripheral surface is formed, and has a stepped opening 18d at the upper and lower ends of the cylindrical inner peripheral surface. Also, the inner sleeve 6a
Reference numeral 2 denotes a cylindrical outer peripheral surface having substantially the same outer diameter as the plate-facing inner peripheral surface 18c so that the inner peripheral surface of the outer sleeve 6a1 can be fitted tightly, and an axially constant inner diameter forming the radial bearing surface 18a. A cylindrical inner peripheral surface is formed. Then, by fitting the inner sleeve 6a2 to the inner peripheral surface of the outer sleeve 6a1, a step-shaped through hole 18 is formed in the sleeve body (rotor hub 6a) composed of the two sleeves 6a1 and 6a2, and the inner peripheral surface of the outer sleeve 6a1 is formed. Inner sleeve 6a
The outer surface in the axial direction from 2 is the inner peripheral surface 18c facing the plate.
At the same time, both end surfaces of the inner sleeve 6a2 become annular thrust bearing surfaces 18b, and the inner peripheral surface of the inner sleeve 6a2 becomes radial bearing surfaces 18a.

A disk-shaped upper thrust plate 4a and a lower thrust plate 4b, which protrude outward in the radial direction, are integrally attached to upper and lower portions of a portion of the shaft 4 protruding from the bracket 2, respectively. The inner sleeve 6a2 of the sleeve body is disposed between the surfaces of the thrust plates 4a and 4b facing each other, and the outer peripheral surface (upper and lower portions) between the thrust plates 4a and 4b of the shaft 4 is a radial bearing of the through hole 18. The thrust plate 4 faces the surface 18a in the radial direction with a radial minute gap therebetween.
a and 4b face each other in the axial direction with a thrust minute gap therebetween with respect to the thrust bearing surfaces 18b (both end surfaces of the inner sleeve 6a2) of the through hole 18.
The outer peripheral surfaces of both thrust plates 4a and 4b are radially opposed to both plate-facing inner peripheral surfaces 18c of through hole 18 with a radial gap therebetween.

As shown in FIG. 5, the thrust plates 4a and 4b have a part of the outer peripheral surface (two places at 180-degree point symmetrical positions around the axis) excluding the part facing the minute thrust gap in the axial direction. Cut surface 4a by D-cut
1, 4b1 are formed, and in the radial gap,
The cut surfaces 4a1, 4b1 and the plate-facing inner peripheral surface 18c
Thus, the enlarged gap portions 19a and 19b surrounded by are formed. These enlarged gap portions 19a and 19b are
Outer peripheral surface of thrust plate 4a, 4b, that is, cut surface 4a
The radial gap between the inner peripheral surface 18c and the inner peripheral surface 18c is continuously changed in the circumferential direction so as to gradually increase from both end positions of the cut surfaces 4a1 and 4b1 toward the center and outward in the axial direction. It is open.

On the axially outer sides of the thrust plates 4a, 4b, annular cover plates 7a, 7b respectively fitted in both stepped openings 18d are arranged so as to close both ends of the through hole 18 of the rotor hub 6a. An axial gap is formed between each of the axially outer surfaces of the thrust plates 4a and 4b, and the radially inwardly increasing gaps are formed between the axially outer surfaces. A gap is formed between the inner peripheral surfaces of the cover plates 7a and 7b and the outer peripheral surface of the shaft 4 so as to be sufficiently small so that the outflow resistance to the vapor of the lubricating liquid becomes large.

An annular concave portion 4c having a curved section is formed in a central portion between the thrust plates 4a and 4b on the outer peripheral surface of the shaft 4 and becomes deeper at the center and gradually becomes shallower toward both ends. Surface and inner sleeve 6a2
An annular gas intervening part 20 is formed between the inner peripheral surface and the inner peripheral surface. The gas intervening portion 20 is released outside the motor, that is, below the bracket 2 through a communication hole 22 formed inside the shaft 4. The radial minute gap between the outer peripheral surface of the shaft 4 and the radial bearing surface 18a, which is the inner peripheral surface of the inner sleeve 6a2, is separated by the gas intervening portion 20 and exists at two upper and lower locations. The minute gap and the thrust minute gap near the upper thrust plate 4a are continuous, and the lower radial minute gap and the thrust minute gap near the lower thrust plate 4b are continuous.

The upper thrust minute gap and the radial minute gap, and the lower thrust minute gap and the radial minute gap are each filled with a lubricating liquid 24 such as oil, etc., continuously to these adjacent minute gaps. The interface of the lubricating liquid 24 on the radial minute gap side is located at both ends of the gas interposing part 20 facing the gas interposing part 20 when the rotor 6 is stopped, and the interface on the thrust minute gap side is the thrust plates 4a, 4b. Is located in the radial gap on the outer periphery or the axial gap between the thrust plates 4a, 4b and the cover plates 7a, 7b.

The radial dynamic pressure generating grooves 26a and 26a are respectively formed on the radial bearing surfaces 18a facing the two minute radial gaps.
26b are formed. This radial dynamic pressure generating groove 26
a and 26b are formed by arranging in the circumferential direction a plurality of herringbone grooves that are unbalanced in the axial direction (the inner herringbone groove is longer than the outer axial direction), as schematically shown by a broken line in FIG. Gas intervening part 2 from axial center of radial minute gap
4 is configured to generate a large dynamic pressure on the opposite side,
Thus, a pair of radial dynamic pressure bearing portions 28a and 28b that support a radial load on the shaft 4 are formed. The thrust bearing surface 18b facing the small gap between the thrusts has a thrust dynamic pressure generating groove 30a, respectively.
30b are formed. This thrust dynamic pressure generating groove 30
a and 30b are formed by arranging pump-in type spiral grooves in the circumferential direction so that dynamic pressure acts in the inner diameter direction, that is, the direction toward the shaft 4, as schematically shown by broken lines in FIG. A pair of thrust dynamic pressure bearing portions 32a and 32b for supporting a thrust load on the shaft 4 are formed.

The radial dynamic pressure generating grooves 26a and 26b are not limited to the radial bearing surface 18a, but the shaft
May be formed on the outer peripheral surface, or may be formed on both surfaces thereof. Similarly, the thrust dynamic pressure generating grooves 30a, 3
0b is not limited to the thrust bearing surface 18b, and may be formed on the axially inner surfaces of the thrust plates 4a and 4b opposed thereto, or may be formed on both surfaces thereof.

Here, as described above, the upper radial dynamic pressure bearing portion 28a and the lower radial dynamic pressure bearing portion 28b
The upper thrust dynamic pressure bearing portion 32a and the lower thrust dynamic pressure bearing portion 32b are respectively disposed adjacent to each other, and each of the pair of thrust dynamic pressure bearing portions 32a and 32b is provided with respect to the lubricating liquid 24 held in the thrust minute gap. This serves to pump the radial dynamic pressure bearings 28a, 28b adjacent to each other, and a pair of radial dynamic pressure bearings 2
8a and 28b respectively provide the thrust dynamic pressure bearing portions 32a and 32b with respect to the lubricating liquid 24 held in the radial minute gap by the adjacent thrust dynamic pressure bearing portions 32a and 32b.
It is set to pump with a pumping ability greater than b.

The rotor hub 6a1 as the sleeve member is provided with two axial communication paths 34 communicating between the outer peripheral ends of the pair of thrust minute gaps at symmetrical positions opposed to each other with the axial center line interposed therebetween. I have. This communication path 34
As shown in FIG. 6, two D-cut surfaces 6a2x in the axial direction formed by cutting off a part of the outer peripheral surface of the inner sleeve 6a2 to a thickness of about 50 μm to 100 μm, and the cylindrical inner peripheral surface of the outer sleeve 6a1 And a lubricating liquid 2 which is substantially crescent shaped and is filled in both thrust minute gaps.
A part of the lubricating fluid 4 flows into and is held in the communication passage 34 by capillary action, and the lubricating liquid 24 in both the thrust bearing portions 32a and 32b continues through the communication passage 34. This communication passage 3
4 can also be formed by forming a V-shaped or concave groove in the axial direction on the outer peripheral surface of the inner sleeve 6a2.

In the spindle motor using the hydrodynamic bearing device configured as described above, when the motor is stopped, the upper radial dynamic pressure bearing portion 28a and the thrust dynamic pressure bearing portion 32a adjacent to each other are continuously filled. Lubricating liquid 24,
And a lower radial dynamic pressure bearing portion 28b adjacent to each other.
And the lubricating liquid 24 continuously filled in the thrust dynamic pressure bearing portion 32b has one interface thereof in the gas intervening portion 20.
And the other interface is located in a radial gap between the outer peripheral surfaces of the thrust plates 4a, 4b and the plate-facing inner peripheral surface 18c of the sleeve body. Lubricating liquid 24 in radial gap
As shown in FIG. 3, a part thereof is an enlarged gap portion 19a,
19b flows from both ends thereof to form an interface in the tapered region, and settles in a span substantially equal to the span of the interface facing the gas intervening portion 20. At this time, the lubricating liquid 24 is held in the communication passage 34 that communicates between the outer peripheral ends of the two thrust minute gaps, and the lubricating liquid 24 in the upper and lower bearings continues.

When the coil current is applied to the stator 8, the rotor 6
Starts rotating, the relative rotation of the sleeve body with respect to the shaft 4 causes the pair of radial dynamic pressure bearing portions 28a, 28
b and a pair of thrust dynamic pressure bearing portions 32a and 32b generate dynamic pressure, and the rotor 6 is rotatably supported. In the radial dynamic pressure bearing portions 28a and 28b, the pressure peak of the lubricating liquid 24 held in the radial minute gap according to the unbalanced shape of the dynamic pressure generating grooves 26a and 26b is adjacent to the thrust dynamic pressure bearing portions 32a and 32b. At the same time, a pumping force acts on the lubricating liquid 24 in the radial minute gap in a direction toward the adjacent thrust dynamic pressure bearing portions 32a, 32b. On the other hand, in the thrust dynamic pressure bearing portions 32a, 32b, the dynamic pressure generating grooves are formed. The pumping force in the direction toward the adjacent radial dynamic pressure bearings 28a, 28b acts on the lubricating liquid 24 in the thrust minute gap according to the spiral groove shapes of 30a, 30b. In this case, the radial dynamic pressure bearing portion 28
a, 28b is the thrust dynamic pressure bearing portion 32
Since the pumping force is set to be larger than the pumping forces a and 32b, the lubricating liquid 24 in the radial minute gap is pushed into the thrust minute gap side, and as shown in FIG. With a part of the generating grooves 26a and 26b exposed, the radial-side pumping force and the thrust-side pumping force are balanced.

In this balanced state, part of the lubricating liquid 24 in the radial minute gap is pushed into the thrust minute gap side, so that the lubricating liquid 24
a, flows radially outward through the radial gap outside of 4b,
As shown in FIG. 3, when the seal portions are set by enlarging the span of the interface at both ends of the enlarged gap portions 19 a and 19 b and settle down, and when the lubricating liquid 24 flows in a large amount, the enlarged gap portions 19 a and 19 b are set. From the radial gaps other than the above, the fluid flows from the outer peripheral side toward the inner peripheral side into the axial gap between the thrust plates 4a, 4b and the cover plates 7a, 7b, and is held in this tapered region.

Radial dynamic pressure bearings 28a, 28b and thrust dynamic pressure bearings 32a, 32b adjacent thereto, respectively.
The lubricating liquid 24 is continuously held between the lubricating liquid 24 and the boundary between one lubricating liquid 24 (the boundary with the outside air held in the gas intervening portion 20) and the other lubricating liquid 24 (thrust). The dynamic pressure reaches a maximum at only one point until reaching the boundary between the plates 4a, 4b and the cover plates 7a, 7b at a certain gap (a boundary surface with outside air), and the pressure gradually increases from this position toward both boundary surfaces. Therefore, if air bubbles are contained in the lubricating liquid 24, the air bubbles are automatically transferred in the direction of low pressure. Will be eliminated during.

As described above, each of the dynamic pressure bearing portions 28a, 28
Bubbles generated in the lubricating fluid 24 held by the b, 32a, 32b sequentially move to the low pressure side and are released to the atmosphere from the boundary surfaces of the respective lubricating fluids 24, so that the bubbles stay in the lubricating fluid 24. This prevents bubbles from thermally expanding when the motor temperature rises, and prevents the lubricating liquid 24 from leaking out of the bearing. When the interface of the lubricating liquid 24 on the motor external side is located in the axial gap between the thrust plates 4a, 4b and the cover plates 7a, 7b, the lubricating liquid 24 at this position is rotated when the rotor 6 rotates. Since the centrifugal force acts and the lubricating liquid 24 tries to move in a direction opposite to the direction in which the lubricating liquid 24 leaks, the leakage of the lubricating liquid 24 is effectively prevented. In addition, the gap between the cover plates 7a and 7b and the shaft 4 is set to be sufficiently small, and the outflow resistance of the vapor of the lubricating liquid 24 is large, so that the lubricating liquid 24 fills the vicinity of the boundary with the atmosphere. The vapor pressure of the lubricating liquid 24 can be kept high, and the evaporation of the lubricating liquid 24 can be minimized.

By the way, the dynamic pressure bearing device as described above,
That is, the lubricating liquid 24 is applied to the upper radial dynamic pressure bearing 2.
8a and a thrust dynamic pressure bearing portion 32a, and a lower radial dynamic pressure bearing portion 28b and a thrust dynamic pressure bearing portion 32b. Even if the same amount of the lubricating liquid 24 is sealed under the conditions, there is a possibility that the lubricating liquid 24 moves to one side depending on the long-term use, and the amount of the lubricating liquid 24 becomes excessive or insufficient. For example, when a spindle motor using a hydrodynamic bearing device is used in a state where the shaft 4 is vertical, the two regions are divided into upper and lower portions. 4 can migrate down the surface. Alternatively, when the rotor 6 rotates, the liquid interface on the gas intervening portion 20 side of the upper radial dynamic pressure bearing portion 28a is at a position corresponding to the radial dynamic pressure generating groove 26a, and is affected by the unevenness of the dynamic pressure groove during rotation. There is a situation where continuous vibration is applied to the lubricating liquid boundary surface. In this case, the inclination of the dynamic pressure generating groove 26a is very gentle, and it is unlikely that a serious change occurs immediately at the lubricating liquid interface. However, droplets are generated stochastically, and the accumulated amount is overlooked during long-term use. It may be possible to reach an impossible level.

In the hydrodynamic bearing device according to the present invention, the excess and deficiency of the lubricating liquid 24 in the two regions as described above, that is, the quantitative imbalance of the lubricating liquid 24 is automatically corrected. And the lubricating fluid 2 in the two separated areas
In order to always properly maintain the amount of No. 4, a communication passage 34 is provided for communicating between the outer peripheral ends of the thrust minute gaps of both thrust dynamic pressure bearing portions 32 a and 32 b. In other words, when there is a quantitative imbalance of the lubricating liquid 24 in the two regions of the upper dynamic pressure bearing portions 28a and 32a and the lower dynamic pressure bearing portions 28b and 32b, the two In accordance with the difference in the internal pressure of the lubricating liquid 24 in the region, the region where the amount of the lubricating liquid 24 is retained (the region where the internal pressure of the lubricating liquid 24 is small) (the region where the internal pressure of the lubricating liquid 24 is Large area) to communication path 3
The lubricating liquid 24 is supplied and redistributed through 4, and settles in a balanced state in which the spans of the respective interfaces in the two regions are substantially equal. Therefore, even if the lubricating liquid 24 leaks downward from the lubricating liquid boundary surface of the radial dynamic pressure bearing portion located at the upper part for some reason, the proper distribution of the lubricating liquid 24 is always achieved through the communication path 34, The excess lubricating liquid 24 in the radial dynamic pressure bearing portion and the thrust dynamic pressure bearing portion located at the lower portion is transferred to the upper portion and adjusted.

On the other hand, when the rotor 6 rotates, the lubricating liquid boundary surfaces on the thrust dynamic pressure bearing portions 32a and 32b settle down with substantially equal spans. Since the surface is located in the radial minute gap, its span is the same, but the lubricating liquid 24 fills the radial minute gap with a different dimension due to factors such as gravity acting on the lubricating liquid 24.

At the time of initial injection of the lubricating liquid 24 into each of the two divided regions, considerable devising is necessary to evenly distribute the lubricating liquid 24 to both regions.
Although there is a possibility of complicating the manufacturing system of this kind of dynamic pressure bearing device, as described above, the redistribution of the lubricating liquid 24 in the two regions is automatically performed by the communication passage 34 formed in the sleeve body. Accordingly, the injection of the lubricating liquid 24 can be performed very easily without skill, and the simplification of the manufacturing system is realized.

Although the embodiment of the recording disk drive motor according to the present invention has been described above, the present invention is not limited to such an embodiment, and various modifications and corrections can be made without departing from the scope of the present invention. Is possible.

[0043]

As described above, the present invention has the above-mentioned structure.
The following effects are obtained. According to the hydrodynamic bearing device according to the first aspect, one radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion adjacent thereto and the other radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion adjacent thereto are provided. When a quantitative imbalance occurs between the lubricating fluid and the retained lubricating fluid, a difference in the internal pressure of the lubricating fluid induces a moving pressure from a side having a larger retained amount to a side having a smaller retained amount, and a pair of thrust minute gaps Redistribution is performed through the communication passage communicating between the outer peripheral portions of the lubricating fluid until the retained amount of the lubricating fluid becomes uniform, and the lubricating fluid retained in each radial dynamic pressure bearing portion and the thrust dynamic pressure bearing portion adjacent thereto is The quantitative imbalance between them is eliminated, and stable rotation of the motor can be obtained.

In the radial gap between the thrust plate forming the pair of thrust dynamic pressure bearings and the sleeve body, an enlarged gap portion whose radial gap dimension continuously changes in the circumferential direction is formed. Therefore, a tapered region at the interface of the lubricating fluid on the thrust dynamic pressure bearing portion side can be formed in the enlarged gap portion, and the span can be arbitrarily set with the interface of the lubricating fluid present on the radial dynamic pressure bearing portion side (gas interposed portion side). A seal portion that can be set to a predetermined value can be formed, and at the same time, a buffer region for the lubricating liquid can be secured.

According to the hydrodynamic bearing device of the second aspect,
Since the enlarged gap is formed by cutting off a part of the outer peripheral surface of the thrust plate, it is very easy to form the enlarged gap in which the radial gap dimension changes continuously.

According to the dynamic pressure bearing device of the third aspect,
In the lubricating fluid from the boundary surface of the lubricating fluid on the radial dynamic pressure bearing side to the boundary surface of the lubricating fluid on the thrust dynamic pressure bearing side, only one maximum point of the dynamic pressure is set, and there is no minimum point. Because it can be set, even if air bubbles are contained in the lubricating liquid, these air bubbles are automatically transferred to the boundary surface of the lubricating liquid where the pressure is minimized and eliminated to the atmosphere, and stable bearing performance is achieved. can get.

According to the dynamic pressure bearing device of the fourth aspect,
The sleeve body is composed of the outer sleeve and the inner sleeve, and a part of the outer peripheral part of the inner sleeve is cut off in the axial direction to form the communication path, so that the communication path is very easily formed in the sleeve body. It can be formed, and manufacturing can be facilitated.

According to the dynamic pressure bearing device of the fifth aspect,
In order to form an axial gap that becomes larger inward in the radial direction between the pair of cover plates provided on the sleeve body and the axially outer surfaces of the pair of thrust plates,
The buffer area for storing the lubricating fluid axially outside the thrust dynamic pressure bearing portion can be further expanded to increase the amount margin, and the lubricant overflowing from the radial gap on the outer peripheral surface of the thrust plate during rotation of the rotor can be removed by this shaft. By containing the lubricant in the directional gap, the outflow of the lubricant to the outside of the bearing due to the centrifugal force acting on the lubricant in this portion can be reliably suppressed.

According to the dynamic pressure bearing device of the sixth aspect,
Since the spindle motor is provided with the hydrodynamic bearing device according to claims 1 to 5, there is no leakage of the lubricating liquid, and stable rotation of the rotor is realized for a long period of time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a spindle motor showing one embodiment of the present invention.

FIG. 2 is an enlarged view of a part of the dynamic pressure bearing portion of FIG.

FIG. 3 is a plan view of a part of FIG. 1 with a cover plate removed.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a perspective view of the thrust plate of FIG. 1;

FIG. 6 is a perspective view of the inner sleeve of FIG. 1;

[Explanation of symbols]

 Reference Signs List 4 Shaft 4a, 4b Thrust plate 4a1, 4b1 Cutting surface 6 Rotor 6a Rotor hub (sleeve body) 6a1 Outer sleeve 6a2 Inner sleeve 7a, 7b Cover plate 18 Through hole 18a Radial bearing surface 18b Thrust bearing surface 18c Thrust plate facing inner peripheral surface 19a , 19b Partial gap portion 20 Gas intervening portion 24 Lubricating liquid 26a, 26b Radial dynamic pressure generating groove 28a, 28b Radial dynamic pressure bearing portion 30a, 30b Thrust dynamic pressure generating groove 32a, 32b Thrust dynamic pressure bearing portion 34 Communication path

Continued on front page F-term (reference) 3J011 AA07 AA12 BA04 BA06 CA03 JA02 KA02 KA03 LA05 MA03 MA12 MA24 MA27 5H605 AA03 BB05 BB19 CC03 CC04 CC05 CC10 EB06 EB17 EB28 EB31 GG04 5H607 BB01 BB14 BB17 CC01 GG12 GG17

Claims (6)

[Claims] 1. A shaft, a pair of disk-shaped thrust plates protruding radially outward at two locations separated in the axial direction of the shaft, and an outer periphery of the shaft between the pair of thrust plates A pair of thrust bearing surfaces opposed to each other through a minute radial gap, a pair of thrust bearing surfaces opposed to each other through a minute axial gap between the axially inner surfaces of the pair of thrust plates facing each other, and an outer periphery of the pair of thrust plates A sleeve body having a through-hole formed by continuously forming a plate-facing inner peripheral surface opposing each other via a radial gap on a surface thereof; and a sleeve body continuous with the radial minute gap, the thrust minute gap, and the radial gap. An axial direction of the radial minute gap between the pair of thrust plates. An annular gas intervening portion communicating with the outside of the bearing is formed at the center portion, and at the upper and lower portions in the axial direction of the gas interposing portion, at least one of the outer peripheral surface of the shaft and the radial bearing surface with respect to the lubricating liquid. A pair of radial dynamic pressure bearing portions are formed by forming a dynamic pressure generating groove for generating dynamic pressure, and an axially inner surface of the pair of thrust plates is formed on an axially inner portion of the pair of thrust plates. A groove for generating dynamic pressure for generating a dynamic pressure on the lubricating liquid is formed on at least one of the thrust bearing surfaces to form a pair of thrust dynamic pressure bearing portions, and one of the pair of radial dynamic pressure bearing portions is provided. And the other is disposed adjacent to each other on one and the other of the pair of thrust dynamic pressure bearing portions, and the pair of thrust dynamic pressure bearing portions are each provided with the lubricating fluid held in the thrust minute gap. On the other hand, the pair of radial dynamic pressure bearing portions function to pump the lubricating fluid held in the radial minute gap with the adjacent thrust motion. In the radial gap, the radial gap between the outer peripheral surface of the thrust plate and the plate-facing inner peripheral surface continuously changes in the circumferential direction and the axial line is formed. An enlarged gap portion opened outward in the direction is formed at a part in the circumferential direction, and the sleeve body has at least a lubricating liquid communication passage communicating between respective outer peripheral ends of the pair of thrust minute gaps. A hydrodynamic bearing device, wherein one is provided. 2. The enlarged gap portion cuts off a part of the outer peripheral surface of the thrust plate excluding a portion facing the thrust minute gap in an axial direction, thereby forming a gap between the cut surface and the inner peripheral surface facing the plate. The dynamic pressure bearing device according to claim 1, which is formed between the bearings. 3. A herringbone groove, which is unbalanced in the axial direction, is formed in the pair of radial dynamic pressure bearing portions as a dynamic pressure generating groove so that a large dynamic pressure acts on a side opposite to the gas intervening portion. 3. The dynamic pressure bearing device according to claim 1, wherein the pair of thrust dynamic pressure bearing portions are formed with a pump-in type spiral groove on which dynamic pressure acts in the shaft direction as a dynamic pressure generating groove. 4. . 4. The sleeve body includes an outer sleeve having a cylindrical inner peripheral surface forming the plate-facing inner peripheral surface, a cylindrical outer peripheral surface having substantially the same diameter as the plate-facing inner peripheral surface, and the radial bearing surface. And an inner sleeve that has a cylindrical inner peripheral surface and that is fitted inside the outer sleeve. The communication path is formed by cutting off a part of the outer peripheral portion of the inner sleeve in the axial direction. The dynamic pressure bearing device according to claim 1. 5. The sleeve body is provided with a pair of annular cover plates so as to close openings at both ends of the through hole, and a radially inner portion is provided between the pair of cover plates and the pair of thrust plates. The hydrodynamic bearing device according to any one of claims 1 to 4, wherein an axial gap that increases in a direction toward the direction is formed. 6. A spindle motor comprising the dynamic pressure bearing device according to claim 1.