JP2007205369A - Fluid bearing device and spindle motor equipped therewith, and record regenerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing type rotating device adaptable into a smaller size and a lower profile while preventing the splash or leakage of lubricating fluid to the outside of a bearing. <P>SOLUTION: The fluid bearing type rotating device 30 is provided for rotating a shaft as the axis of rotation arranged in a bearing hole 1a formed in a central portion of a sleeve 1. A vent hole 5b is provided in part of a ring seal cap 5 covering the sleeve 1 at its axial upper end face, and a recessed portion 1d as a bottomed hole is formed in a position on the sleeve 1 corresponding to the vent hole 5b. Capillary pressure in a gap E between the sleeve 1 and the seal cap 5 is greater than capillary pressure in a gap D between the position on the sleeve 1 where the recessed portion 1d is formed and the position on the seal cap 5 where the vent hole 5b is formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device mounted on a spindle motor that rotationally drives a recording disk such as a magnetic disk or an optical disc, and more particularly, to a hydrodynamic bearing device that can cope with the miniaturization of a spindle motor and the same. The present invention relates to a spindle motor and a recording / reproducing apparatus.

In recent years, a spindle motor that rotates and drives a recording disk such as a magnetic disk or an optical disk is required to have high performance and reliability for rotating the disk with high accuracy.
In the hydrodynamic bearing included in the hydrodynamic bearing device, when bubbles are mixed into the lubricating fluid inside the bearing, the bubbles contained in the lubricating fluid expand due to the reduced pressure environment during the transportation of the aircraft and the temperature rise of the bearing and the usage environment, There is a risk that the bearing performance will deteriorate and oil will scatter. For this reason, a hydrodynamic bearing device has been developed that forcibly circulates a lubricating fluid filled in the bearing and positively discharges bubbles to the outside (see Patent Document 1).
In the hydrodynamic bearing device disclosed in Patent Document 1, the flange is formed integrally with the shaft and is inserted through the sleeve. One side of the sleeve is closed by a thrust plate, and the other side is covered by a cover plate to form an upper reservoir between the sleeve and the sleeve. And the communicating hole connects the flange space and the upper reservoir. Further, a radial bearing is formed on the inner peripheral surface of the sleeve. A thrust sub bearing is formed on the upper surface of the flange, and a thrust main bearing is formed on the lower surface of the flange.

By the asymmetrical radial bearing portion included in the hydrodynamic bearing device, a lubricating fluid circulation path is formed in the hydrodynamic bearing device in the order of the radial bearing, the thrust sub-bearing, the outer periphery of the flange, the communication hole, the upper pool space, and the radial bearing. . At this time, the bubbles contained in the lubricating fluid are sequentially discharged into the upper pool space by the circulation of the lubricating fluid. And since the axial direction dimension becomes narrow toward the inner peripheral side, an air bubble is isolate | separated from lubricating fluid by capillary action and exhausted from a ventilation hole.
WO2004 / 094848 A1 (Internationally released on November 4, 2004)

However, the conventional hydrodynamic bearing device has the following problems.
That is, recent information recording devices (particularly hard disk devices) have been installed not only for personal computers but also for HDD recorders and car navigation systems, and are also used for HDD movies and HDD portable audio as portable devices. It is becoming. Recently, it has begun to be installed in mobile phones. As described above, HDDs are being developed for portable use and the like, and HDD spindle motors are also required to respond to downsizing and thinning such as 0.85 inches and 1.0 inches. It has been.
For this reason, even if the conventional bubble discharging technology in the hydrodynamic bearing device disclosed in the above publication is applied as it is in order to satisfy the above-mentioned demand for reduction in size and thickness, it may be difficult to function sufficiently. I came.
Specifically, the hydrodynamic bearing device disclosed in the above publication has the following configuration as the top cover structure.
That is, the shaft and the flange are integrally fixed and constitute a part of the rotation side member. The shaft and the flange may be processed integrally.
One end of the sleeve is closed by a thrust plate, and a cover plate is attached to the other end.

A radial dynamic pressure groove is formed in one of the gaps between the shaft and the sleeve, and constitutes a radial bearing.
A thrust dynamic pressure groove is formed in one of the gaps between the flange and the sleeve, and constitutes a thrust sub-bearing.
A thrust dynamic pressure groove is formed in one of the gaps between the flange and the thrust plate, and constitutes a thrust main bearing.
The cover plate and the sleeve form a fluid reservoir between them.
The sleeve is formed with a communication passage that communicates the outer peripheral portion of the flange or the thrust sub-bearing gap with the fluid reservoir.
In the initial stage of production, the lubricating fluid is held in the radial bearing gap, the thrust sub-bearing gap, the thrust main bearing gap, the flange outer peripheral portion, the communication path, and the fluid reservoir.
Lubricating fluid is actively circulated in the bearing, and bubbles existing in the bearing are moved to the fluid reservoir and discharged through the ventilation path. At this time, the circulating force of the lubricating fluid is generated in the direction toward the flange by providing the radial bearing with asymmetry in the axial direction.
A recess is provided between the ventilation path and the fluid reservoir. This is because the bearing is subject to shock during manufacturing and use, the lubricating fluid expands due to a rise in temperature, and the bubbles expand due to decompression or a rise in temperature, causing the lubricating fluid to scatter and leak out of the bearing. It is for preventing. In the initial stage of manufacture, the oil is removed after the shaft order oil so that the lubricating fluid does not exist in the ventilation path and the recess.

In the configuration as described above, when the motor is reduced in size and thickness, the axial dimension is limited, the size of the recess formed below the ventilation path is reduced, and the portion formed with the recess is formed. The difference in size to the upper surface of the sleeve from the unexposed portion becomes small (in the worst case, it becomes 0).
This is synonymous with the fact that the difference in capillary pressure between the fluid reservoir and the recess is eliminated, and as a result, a problem such that the seepage of the lubricating fluid into the recess is likely to occur.
For this reason, the bearing may be impacted during manufacture and use, the lubricating fluid may expand due to a rise in temperature, or the bubbles may expand due to decompression or a rise in temperature. It becomes easy to do.
SUMMARY OF THE INVENTION An object of the present invention is to provide a hydrodynamic bearing device capable of responding to the miniaturization and thinning of the device while preventing the occurrence of lubrication fluid scattering and leakage to the outside of the bearing, a spindle motor equipped with the hydrodynamic bearing device, and recording / reproduction To provide an apparatus.

A hydrodynamic bearing device according to a first invention includes a sleeve, a shaft, a lubricating fluid, an annular seal cap, a first space, and a second space. The sleeve has a bearing hole. The shaft is disposed so as to be relatively rotatable in the bearing hole, and serves as a rotating shaft. The lubricating fluid is filled in a gap formed between the sleeve and the shaft. The seal cap is fixed to one side in the axial direction of the sleeve, and a ventilation port for discharging bubbles contained in the lubricating fluid is formed. The first space is formed between the surface on the other axial side of the portion of the seal cap where the ventilation port is formed and the surface on the one axial side of the sleeve. The second space is formed between the surface on the other side in the axial direction of the portion of the seal cap where the ventilation port is not formed and the surface on the one side in the axial direction of the sleeve. The sleeve further includes a recess formed at a position facing the ventilation port formed in a part of the seal cap, and the capillary pressure in the first space is smaller than the capillary pressure in the second space.
Here, in a hydrodynamic bearing device in which a lubricating fluid is filled in a gap formed between a shaft and a sleeve, a seal cap and a sleeve that are attached so as to cover the upper surface of the sleeve on one end side of the shaft Capillary pressure in the space (second space) for storing the lubricating fluid formed between the caps and the capillary pressure in the space (first space) formed between the vent and the sleeve formed in a part of the seal cap And the capillary pressure in the first space is configured to be smaller than the capillary pressure in the second space.

Specifically, since the concave portion is formed in the portion of the sleeve facing the vent of the seal cap, the gap between the sleeve and the seal cap that forms the first space corresponding to the vent portion is the first. It is formed to be larger than the gap between the sleeve forming the two spaces and the seal cap.
Usually, when providing a difference in the capillary pressure in the first space and the second space in this way, by forming a recess on the seal cap side where the ventilation port is formed and providing a difference in the size of the gap, The lubricant fluid was prevented from splashing or leaking out from the ventilation port. However, in order to meet the recent demand for thinner spindle motors, it is required to reduce the thickness of the seal cap that constitutes the hydrodynamic bearing device, and it becomes difficult to form a sufficient recess directly under the ventilation port. ing. On the other hand, in order to reduce the thickness of the hydrodynamic bearing device while maintaining the thickness of the seal cap in order to form a sufficient recess in the seal cap, it is necessary to reduce the thickness on the sleeve side. However, in this case, by reducing the thickness on the sleeve side, the length of the radial bearing becomes too short, which may reduce the performance and reliability of the fluid dynamic bearing device.
Therefore, in the hydrodynamic bearing device of the present invention, a recess is formed in a portion on the sleeve side facing the ventilation port formed in the seal cap, and the first space of the ventilation port portion is made wider than the second space, so that each space There is a difference in the capillary pressure.

As a result, it is not necessary to form a recess on the seal cap side, or the depth of the recess can be reduced, and the thickness on the sleeve side can be maintained, thereby preventing deterioration in performance and reliability. The hydrodynamic bearing device can be thinned.
The hydrodynamic bearing device according to the second invention is the hydrodynamic bearing device according to the first invention, wherein a third space is formed between the side surface of the shaft and the inner peripheral surface of the seal cap. . The capillary pressure in the third space is larger than the capillary pressure in the first space and the second space.
Here, the space (third space) between the shaft and the seal cap has a smaller gap than the first and second spaces, and the capillary pressure is higher on the first space side than on the third space side. It is larger than space.
As a result, it is possible to prevent the lubricating fluid filled in the gap between the shaft and the sleeve from moving to the ventilating port side and scattering or leaking out of the lubricating fluid from the ventilating port.
A hydrodynamic bearing device according to a third invention is the hydrodynamic bearing device according to the first or second invention, wherein a fourth space is formed between the sleeve and a portion on the innermost peripheral side of the seal cap. ing. The capillary pressure in the fourth space is larger than the capillary pressure in the first space and the second space.

Here, of the space formed between the sleeve and the seal cap, the space (fourth space) formed between the innermost peripheral portion of the annular seal cap and the sleeve is the first space. The gap is smaller than the second space, and the capillary pressure in the fourth space is larger than the capillary pressure in the first and second spaces.
Thereby, it is possible to prevent the lubricating fluid filled in the gap between the shaft and the sleeve from moving to the ventilation port side and scattering or leaking out of the lubricating fluid from the ventilation port.
Further, the capillary pressure in the fourth space is made larger than the capillary pressure in the space between the shaft and the seal cap (third space), so that the lubricating fluid is scattered or leaked from between the shaft and the seal cap. Can also be suppressed.
A hydrodynamic bearing device according to a fourth invention is the hydrodynamic bearing device according to any one of the first to third inventions, wherein a fifth space is formed between the shaft and the sleeve, The capillary pressure in the fifth space is larger than the capillary pressure in the first space and the second space.
Here, the space (fifth space) formed between the shaft and the sleeve has a smaller gap than the first and second spaces, and the capillary pressure in the fifth space is the first and second spaces. It is larger than the capillary pressure of the two spaces.

Thereby, it is possible to prevent the lubricating fluid filled in the gap between the shaft and the sleeve from moving to the ventilation port side and scattering or leaking out of the lubricating fluid from the ventilation port.
Furthermore, the capillary pressure in the fifth space is more than the capillary pressure in the space between the seal cap and the seal cap (third space) and in the space between the innermost peripheral side of the seal cap and the sleeve (fourth space). By enlarging, it is possible to suppress the scattering and leakage of the lubricating fluid from between the shaft and the seal cap.
A hydrodynamic bearing device according to a fifth aspect of the present invention is the hydrodynamic bearing device according to any one of the first to fourth aspects of the present invention, in the vicinity of a substantially central portion on at least one of the side surface of the shaft and the inner peripheral side of the sleeve. A substantially annular groove portion is provided, and a sixth space is formed between the groove portion and the shaft or sleeve. The capillary pressure in the sixth space is larger than the capillary pressure in the first space and the second space.
Here, of the space formed between the shaft and the sleeve, the space formed between the groove and the sleeve formed in the vicinity of the substantially central portion of at least one of the outer periphery of the shaft and the sleeve bearing hole (sixth) The space) is smaller than the first and second spaces, and the capillary pressure of the sixth space is larger than the capillary pressure of the first and second spaces.

Thus, the upper and lower radial bearings formed in the gap between the shaft and the sleeve can perform their functions without interfering with each other via the lubricating fluid.
Further, the capillary pressure in the sixth space is more than the capillary pressure in the space between the seal cap and the seal cap (third space) and in the space between the innermost peripheral side of the seal cap and the sleeve (fourth space). By enlarging, it is possible to suppress the scattering and leakage of the lubricating fluid from between the shaft and the seal cap.
A hydrodynamic bearing device according to a sixth invention is the hydrodynamic bearing device according to any one of the first to fifth inventions, wherein the concave portion formed in the sleeve is tapered so as to increase toward the seal cap side. have.
Here, the concave portion formed on the sleeve-side surface forming the first space has a tapered shape in which the opening increases toward the seal cap side.
Thereby, the lubricating fluid can be made difficult to enter the concave portion located directly below the ventilation port due to the relationship with the surface tension of the lubricating fluid on the surface of the sleeve facing the seal cap. As a result, in addition to attracting the lubricating fluid in a predetermined direction by capillary pressure, the use of the above-described configuration further prevents the lubricating fluid from scattering and leaking from the vent of the seal cap formed above the recess. It can be effectively suppressed.

A hydrodynamic bearing device according to a seventh invention is the hydrodynamic bearing device according to any one of the first to sixth inventions, wherein the sleeve is a symmetrical position of the recess about the rotation axis of the shaft in plan view. And a communication hole formed along the direction of the rotation axis of the shaft.
Here, the recess formed in the sleeve is provided at a position that is symmetric with respect to the communication hole that becomes the circulation path of the lubricating fluid.
Thereby, since a recessed part and a ventilation port exist in the most distant position with respect to a communicating hole, generation | occurrence | production of scattering, leakage, etc. of a lubricating fluid from a ventilation port can be suppressed more effectively. .
A hydrodynamic bearing device according to an eighth invention is the hydrodynamic bearing device according to any one of the first to seventh inventions, wherein the sleeve is configured by combining an inner sleeve and an outer sleeve. And a recessed part is formed by combining an inner sleeve and an outer sleeve.
Here, in a sleeve configured by combining an inner sleeve and an outer sleeve, a recess is formed when these are combined.
Thereby, a notch etc. are formed with respect to at least one of an inner sleeve and an outer sleeve, and when these are combined, a desired recessed part can be formed easily. As a result, it is not necessary to form a recess by processing or the like after forming the sleeve, so that the manufacturing cost can be reduced.

A hydrodynamic bearing device according to a ninth aspect of the present invention is the hydrodynamic bearing device according to any one of the first to eighth aspects of the invention, wherein the lubricating fluid pool space formed between the seal cap and the sleeve is The size of the gap changes in the circumferential direction around the rotation axis of the shaft.
Here, the accumulation space of the lubricating fluid formed between the seal cap and the sleeve is configured such that the gap is changed in the circumferential direction.
As a result, when the rotating side of the hydrodynamic bearing device is rotated, the performance of the hydrodynamic bearing device is reduced by suppressing the movement of the air surrounded by the lubricating fluid existing directly under the ventilation port. Can be prevented.
A hydrodynamic bearing device according to a tenth aspect of the present invention is the hydrodynamic bearing device according to any one of the first to ninth aspects, wherein the seal cap is centered on the rotational axis of the shaft on the surface facing the sleeve. The taper surface has a smaller gap with the sleeve toward the inner side in the radial direction of the circle.
Here, the surface on the seal cap side, which forms the lubricating fluid pool space including the first and second spaces, together with the sleeves arranged opposite to each other, is inclined downward toward the radially inner side of the circle centering on the rotation axis. is doing.

As a result, the lubricating fluid that circulates along with the bubbles through the communication hole is separated into bubbles and the lubricating fluid by capillary action due to the inclined portion, and the communication hole is maintained with the smallest gap portion at the innermost periphery maintaining the gap. The lubricating fluid can be circulated to the end even if the lubricating fluid is reduced.
A hydrodynamic bearing device according to an eleventh invention is the hydrodynamic bearing device according to any one of the first to tenth inventions, and is formed on at least one of a side surface of the shaft and an inner peripheral surface of the sleeve. The radial dynamic pressure generating groove is formed to be asymmetric in the direction of the rotation axis of the shaft.
Here, the radial dynamic pressure generating groove formed on at least one of the shaft and the sleeve is formed to be asymmetric in the axial direction of the shaft.
Thereby, in the radial bearing portion, since the circulation force of the lubricating fluid can be generated, the bubbles contained in the lubricating fluid are circulated to the second space through the communication hole, where the bubbles are separated and are effective from the ventilation port. Can be discharged.
A hydrodynamic bearing device according to a twelfth invention is the hydrodynamic bearing device according to any one of the first to eleventh inventions, wherein a radial bearing portion is provided between a side surface of the shaft and an inner peripheral surface of the sleeve. One is formed.

Here, one radial bearing portion formed on at least one of the opposing surfaces of the shaft and the sleeve is provided.
Thereby, a highly reliable hydrodynamic bearing device can be obtained while constituting a thin device such as a so-called single bearing.
A spindle motor according to a thirteenth aspect includes the hydrodynamic bearing device according to any one of the first to twelfth aspects.
A recording / reproducing apparatus according to a fourteenth aspect includes the spindle motor according to the thirteenth aspect.

According to the hydrodynamic bearing device according to the first aspect of the invention, the hydrodynamic bearing device can be thinned while preventing deterioration in performance and reliability.
According to the hydrodynamic bearing device according to the second aspect of the invention, the lubricating fluid filled in the gap between the shaft and the sleeve moves to the ventilation port side, and the lubricating fluid scatters or leaks from the ventilation port. Can be suppressed.
According to the hydrodynamic bearing device of the third aspect of the invention, the lubricating fluid filled in the gap between the shaft and the sleeve moves to the ventilation port side, and the lubricating fluid scatters or leaks from the ventilation port. This can be suppressed.
According to the hydrodynamic bearing device of the fourth aspect of the invention, the lubricating fluid filled in the gap between the shaft and the sleeve moves to the ventilation port side, and the lubricating fluid scatters or leaks from the ventilation port. This can be suppressed.
According to the hydrodynamic bearing device according to the fifth aspect of the invention, the lubricating fluid filled in the gap between the shaft and the sleeve moves to the ventilation port side, and the lubricating fluid scatters or leaks out from the ventilation port. This can be suppressed.
According to the hydrodynamic bearing device according to the sixth aspect of the present invention, the scattering and leakage of the lubricating fluid from the vent of the seal cap formed above the recess can be further effectively suppressed.

According to the hydrodynamic bearing device pertaining to the seventh aspect of the invention, it is possible to more effectively suppress the occurrence of scattering, leakage, etc. of the lubricating fluid from the ventilation port.
According to the hydrodynamic bearing device according to the eighth aspect of the invention, by forming a notch or the like in at least one of the inner sleeve and the outer sleeve, a desired recess can be easily formed when these are combined. it can.
According to the fluid dynamic bearing device of the ninth invention, it is possible to prevent the performance of the fluid dynamic bearing device from being deteriorated.
According to the hydrodynamic bearing device according to the tenth aspect of the invention, the air surrounded by the lubricating fluid existing directly under the ventilation port moves radially outward due to centrifugal force or the like with rotation in the hydrodynamic bearing device. This can be suppressed.
According to the hydrodynamic bearing device pertaining to the eleventh aspect of the invention, the bubbles contained in the lubricating fluid can be effectively discharged from the ventilation port.
With the hydrodynamic bearing device according to the twelfth aspect of the invention, a highly reliable hydrodynamic bearing device can be obtained while constituting a thin device.
According to the spindle motor of the thirteenth aspect, the spindle motor can be reduced in thickness while preventing the performance and reliability from being lowered.

  According to the recording / reproducing apparatus of the fourteenth aspect, the recording / reproducing apparatus can be thinned while preventing the performance and reliability from being lowered.

A spindle motor equipped with a hydrodynamic bearing device according to an embodiment of the present invention will be described below with reference to FIGS.
In the following description, the vertical direction in FIG. 1 is expressed as “axial direction”, the upward direction as “axial upper side” (axial one side), and the downward direction as “axial downward” (axial other side). However, these do not limit the mounting state of the actual fluid bearing mechanism (fluid bearing device) 40.
[Configuration of the entire spindle motor 30]
As shown in FIG. 1, the spindle motor 30 according to the present embodiment is a device for rotationally driving a recording disk (recording medium) 11, and mainly includes a rotating member 31, a stationary member 32, and a fluid bearing mechanism. 40.
The rotating member 31 mainly has a hub 7 on which the recording disk 11 is mounted and a rotor magnet 9.
The hub 7 is integrated with the shaft 2 by press-fitting adhesion to the shaft 2 or integral molding of both members. Further, the hub 7 is provided with a disk mounting portion 7a for mounting two recording disks 11 on the outer peripheral portion on the lower side in the axial direction by integral molding.
The rotor magnet 9 is fixed to the inner peripheral surface of the hub 7 and constitutes a magnetic circuit together with a stator 10 described later.

The two recording disks 11 are fitted on the outer peripheral side of the hub 7 via an annular spacer 12, and are placed on the disk placing portion 7a. Further, the recording disk 11 is pressed down on the lower side in the axial direction by a clamper 13 fixed to the upper side in the axial direction of the shaft 2 by a screw 14 and is sandwiched between the clamper 13 and the disk mounting portion 7a. Yes.
As shown in FIG. 1, the stationary member 32 mainly includes a base 8 and a stator 10 fixed to the base 8.
The base 8 is fixed to a housing of a recording disk drive device (not shown) and constitutes a base portion of the spindle motor 30.
The stator 10 opposes the rotor magnet 9 attached to the inner peripheral surface of the hub 7 on the outer peripheral side of the opening formed in the substantially central portion of the base 8 in order to arrange a spindle motor 30 to be described later. It is arranged at the position to do.
The hydrodynamic bearing mechanism 40 is fixed to an opening formed at a substantially central portion of the base 8 and supports the rotating member 31 in a rotatable state with respect to the stationary member 32. The hydrodynamic bearing mechanism 40 will be described in detail later.
[Configuration of Fluid Bearing Mechanism 40]
As shown in FIG. 2, the hydrodynamic bearing mechanism 40 mainly includes a sleeve 1, a shaft 2, a flange 3, a thrust plate 4, a seal cap 5, and oil (lubricating fluid) 6 as a lubricating fluid. It is configured as follows. Of these, the sleeve 1, the thrust plate 4 and the seal cap 5 constitute a stationary member, and the shaft 2 and the flange 3 constitute a rotating member.

(Sleeve 1)
The sleeve 1 is a substantially cylindrical member extending in the axial direction and formed of pure iron, stainless steel, copper alloy, sintered metal, or the like, and is fixed to the base 8 by adhesion or the like. The sleeve 1 is formed with a substantially circular opening at the lower end in the axial direction, and a thrust plate 4 is fixed so as to close the opening. The sleeve 1 and the thrust plate 4 form a bearing hole 1a.
Further, the sleeve 1 has an annular recess 1c at the lower end in the axial direction, and an outer peripheral portion of the flange 3 described later is accommodated in a space between the recess 1c and the thrust plate 4. .
Furthermore, the sleeve 1 has a concave portion 1d at a position facing a ventilation port 5b formed in a seal cap 5 described later. And this recessed part 1d and the communicating hole G mentioned later are arrange | positioned in the symmetrical position by stopping the rotating shaft of the shaft 2 in planar view (refer Fig.5 (a) and FIG.5 (b)).
The relationship such as the magnitude of capillary pressure in the gap formed between the sleeve 1 and the seal cap 5 will be described in detail later.
Further, a communication hole G is formed in the sleeve 1. Specifically, as shown in FIGS. 1 and 2, the communication hole G is a through hole extending along the axial direction, and connects the upper surface and the lower surface of the sleeve 1. The communication hole G is formed to communicate with a position facing the thrust sub-bearing portion including the thrust dynamic pressure generating groove 3b formed in the flange 3. Thereby, by suppressing the dimension of the spindle motor 30 in the radial direction, the spindle motor can be reduced in size and thickness.

A plurality of communication holes G may be provided in the circumferential direction.
(Shaft 2)
The shaft 2 is a cylindrical member extending in the axial direction, and supports the hub 7 in a state of being rotatable with respect to the stationary member 32. Specifically, the shaft 2 is disposed so as to be rotatable relative to the inner peripheral side of the bearing hole 1a formed by the sleeve 1 and the thrust plate 4 via a gap. A hub 7 is fixed to the shaft 2 at the end on the upper side in the axial direction.
The shaft 2 has a plurality of radial dynamic pressure generating grooves 2b on the outer peripheral surface thereof. For this reason, a radial bearing portion 21 including the radial dynamic pressure generating groove 2b is formed between the sleeve 1 and the shaft 2. The radial dynamic pressure generating groove 2b has, for example, a herringbone shape that is asymmetric in the vertical direction in the axial direction. The shaft 2 including the rotating member 31 is supported in a direction substantially perpendicular to the axial direction by the support pressure generated in the radial bearing portion 21.
The shaft 2 is made of, for example, stainless steel. Further, the radial dynamic pressure generating groove 2 b formed on the outer peripheral surface of the shaft 2 may be formed on the inner peripheral surface side of the sleeve 1.

(Flange 3)
The flange 3 is a disk-shaped member, and is fixed to an end portion on the lower side in the axial direction of the shaft 2. The flange 3 has a plurality of thrust dynamic pressure generating grooves 3a and 3b on the upper surface in the axial direction and the lower surface in the axial direction. Therefore, a thrust bearing portion 22 including thrust dynamic pressure generating grooves 3a and 3b is formed between the flange 3, the sleeve 1, and the thrust plate 4.
The thrust dynamic pressure generating grooves 3a and 3b have, for example, a spiral shape.
The shaft 2 and the rotating member 31 are supported in the axial direction by the support pressure generated in the thrust bearing portion 22.
The shaft 2 and the flange 3 may be integrally formed, and the thrust dynamic pressure generating grooves 3a and 3b may have a herringbone shape.
(Thrust plate 4)
As described above, the thrust plate 4 is attached to the inner peripheral side of the annular recess 1 c formed on the lower side in the axial direction of the sleeve 1. The thrust plate 4 forms a thrust bearing portion 22 between the axially lower surface of the flange 3 attached to the axially lower side of the shaft 2.

(Seal cap 5)
The seal cap 5 is an annular member that is fixed to the upper end of the sleeve 1 in the axial direction, and includes a fixing portion 5a and a ventilation port 5b.
The fixing portion 5a is a cylindrical member fixed to the sleeve 1, and is attached so as to be fitted into an annular step portion formed at an outer peripheral end portion on the axial upper side of the sleeve 1.
The ventilation port 5b is a hole that penetrates the surface intersecting the axial direction of the seal cap 5 in the vertical direction, and is formed at a position facing the recess 1d formed on the upper end surface in the axial direction of the sleeve 1 in the seal cap 5. ing.
An annular oil reservoir H is formed between the seal cap 5 and the sleeve 1, and the inner peripheral portion of the oil reservoir H communicates with the radial bearing 21.
(Oil 6)
The oil 6 includes a gap formed between the sleeve 1 including the radial bearing portion 21 and the thrust bearing portion 22, the shaft 2, the flange 3, and the thrust plate 4, a communication hole G formed in the sleeve 1, and the shaft of the sleeve 1. An oil reservoir H or the like formed between the upper end surface in the direction and the seal cap 5 is filled.

Further, since the radial dynamic pressure generating groove 2b formed in the radial bearing portion 21 is asymmetric in the axial direction, the oil 6 circulates in the bearing by a circulating force in the axially lower direction.
As the oil 6, for example, low viscosity ester oil or the like can be used.
1 and 2, the oil 6 contains bubbles (air) 15. The bubbles 15 move to the oil reservoir H while the oil 6 is circulated, The air is discharged to the outside from the vent 5b formed in the seal cap 5 described above.
[Operation of spindle motor 30]
Here, the operation of the spindle motor 30 will be described.
In the spindle motor 30, when the stator 10 is energized, a rotating magnetic field is generated, and a rotational force is applied to the rotor magnet 9. Thereby, the rotating member 31 can be rotated together with the shaft 2 with the shaft 2 as the rotation center.
When the shaft 2 rotates, support pressures in the radial direction and the axial direction are generated in the dynamic pressure generating grooves 2b, 3a, 3b. Thereby, the shaft 2 is supported in a non-contact state with respect to the sleeve 1. That is, the rotating member 31 can be rotated in a non-contact state with respect to the stationary member 32, thereby realizing high-precision high-speed rotation of the recording disk 11.

<Configuration around the vent 5b>
As shown in FIG. 3, the ventilation port 5 b is disposed immediately above the recess 1 d formed on the upper end surface of the sleeve 1 in the seal cap 5.
The recess 1d is a bottomed hole having a depth of about 0.4 to 0.5 mm formed on the upper end surface of the sleeve 1 facing the ventilation port 5b. Further, as shown in FIG. 4 and the like, the recess 1d is tapered so that the opening area increases toward the upper side in the axial direction. Thereby, even when the oil 6 has moved to the vicinity of the recess 1d, the oil 6 can be made difficult to enter the recess 1d.
In the initial stage of the manufacturing process of the spindle motor 30, the oil 6 is placed in the bearing portion as shown in FIG. 5A so that the oil 6 does not exist in the vicinity of the oil reservoir H including the vent 5b and the recess 1d. It is preferably removed after oiling.
The oil 6 is usually removed by wiping or sucking the annular gap between the shaft 1 and the seal cap 5. However, in this method, the oil 6 may remain at the bottom of the concave portion 1d which is a bottomed hole. Therefore, in order to completely remove the oil 6, the oil 6 is sucked from the ventilation port 5b, and FIG. As shown, it is more preferable to remove the oil 6 from the vicinity of the recess 1d.

<Relationship between capillary pressures in the spindle motor 30>
In the present embodiment, as a result of performing a simulation on the magnitude of the capillary pressure in the gaps A to E (see FIG. 3) formed between the members in the spindle motor 30 having the above-described configuration, FIG. ).
As shown in FIG. 3, the gap A (fifth space) is the gap between the outer peripheral surface of the shaft 2 and the inner peripheral surface of the sleeve 1, and the gap B (fourth space) is the outermost surface of the seal cap 5. A gap between the inner peripheral portion and the upper end surface of the sleeve 1, the gap C (third space), is between the outer peripheral surface of the shaft 2 and the innermost peripheral surface of the seal cap 5 facing this. The gap, gap D (first space) is a gap, gap E (second space) between the surface of the seal cap 5 on which the ventilation port 5b is formed and the bottom surface of the recess 1d formed on the upper end surface of the sleeve 1. Means the gap between the surface of the seal cap 5 where the ventilation port 5b is not formed and the upper end surface of the sleeve 1 in the substantially horizontal plane.
The oil 6 circulates in the direction indicated by the arrow in FIG. 2 in the spindle motor 30 and the oil 6 tends to move toward the higher capillary pressure, so that the oil 6 is scattered or leaked outside the bearing. In order to prevent this, the capillary pressure in each gap needs to satisfy the following relationship.

That is, the capillary pressure in the gap A constituting the radial bearing portion 21 is maximum, and the capillary pressure in the gap C in contact with the outside air is smaller than the capillary pressure in the gap B corresponding to the outlet from the oil reservoir H. Or equivalent. Further, the capillary pressure in the gap E, that is, the oil reservoir H, needs to be smaller than the capillary pressure in the gap B. The capillary pressure in the gap D between the recess 1d formed on the upper end surface of the sleeve 1 and the ventilation port 5b portion of the seal cap 5 prevents the oil 6 from leaking out of the ventilation port 5b. It is best to keep it to a minimum.
The above relationship can be expressed as an expression as follows.
A> (B and C)>E> D Equation 1
E> D ... Formula 2
The capillary pressure in each of the gaps A to E can be calculated (defined) by the following relational expression.
(1) Capillary pressure due to the surface tension of the oil 6 in the gap E Capillary pressure due to the surface tension of the gas-liquid boundary surface Fe: Fe = 2 × π × De × γ × cos θ
Pressure Pe due to capillary pressure at gas-liquid interface: Pe = Fe / Ae
Area Ae: Ae = π × De × he
De: outer diameter of the portion having the gap De in the oil reservoir γ: surface tension θ: contact angle of the lubricating fluid Ae: opening area of the gas-liquid boundary surface (2) Capillary pressure due to the surface tension of the oil 6 in the gap D Capillary pressure Fd by the surface tension at the gas-liquid interface Fd: Fd = 2 × π × Dd × γ × cos θ
Pressure Pd due to capillary pressure at gas-liquid boundary surface: Pd = Fd / Ad
Area Ad: Ad = π × Dd × D
Dd: inner diameter of concave portion γ: surface tension θ: contact angle of lubricating fluid Ad: area of gas-liquid interface (3) Calculation example
When the surface tension γ = 30.6 dyne / cm and the contact angle θ = 13 deg, when the sleeve recess inner diameter = φ0.7 mm and the sleeve recess depth = 0.4 mm,
Pe = 561Pa
Pd = 140 Pa
Thus, it can be seen that the capillary pressure in the gap D connected to the ventilation port 5d is sufficiently smaller than the capillary pressure in the gap E (oil reservoir H).

In the spindle motor 30 of the present embodiment, as described above, the capillary pressure in each of the gaps A to E is configured to satisfy the magnitude relationship as shown in FIG. The oil 6 can be effectively prevented from scattering from the gap C between the outer peripheral surface 2 and the inner peripheral surface of the seal cap 5, the ventilation port 5b of the seal cap 5, and the like.
In particular, the ventilation port 5b formed in the seal cap 5 has a configuration in which the oil 6 is likely to be scattered or leaked out. Therefore, the magnitude relationship between the capillary pressures in the gap D and the gap E is as described above. It satisfies the relationship of formula (2), but is more preferable.
[Reference example]
In the hydrodynamic bearing device, in order to achieve a reduction in size and thickness while ensuring the magnitude relationship of the capillary pressure in each gap described above, a sufficiently large gap (recess) is provided on the seal cap 5 side as in the past. It is difficult to configure.
Here, FIG. 6A shows the capillary pressure simulation result of the hydrodynamic bearing device having a configuration in which no recess is formed on both the seal cap side and the sleeve upper end surface side.
Here, the capillary pressure in the gap D is equal to the capillary pressure in the gap E (oil reservoir).

This weakens the force to move the oil from the gap D in the portion of the seal cap where the ventilation port is formed to the gap where the ventilation port is not formed, so that the oil in the oil reservoir is easily removed from the ventilation port. It will be easy to leak out from the bearing outside.
FIG. 6B is a simulation of capillary pressure in a configuration in which a recess 1d is added to the sleeve 1, that is, a configuration according to an embodiment of the present invention.
According to this, the capillary pressure in the gap F is minimized, and it can be seen that the oil 6 existing in the gap E (oil reservoir H) is difficult to leak out from the ventilation port 5b.
[Features of hydrodynamic bearing device 40]
(1)
In the hydrodynamic bearing device 40 of the present embodiment, as shown in FIG. 3 and the like, in the hydrodynamic bearing device 40 that rotates with the shaft 2 disposed in the bearing hole 1a formed in the central portion of the sleeve 1 as the rotation axis, the sleeve A vent 5b is provided in a part of the annular seal cap 5 that covers the upper end surface in the axial direction of 1 and a recess 1d that is a bottomed hole is formed at a position facing the vent 5b in the sleeve 1. Has been. The capillary pressure in the gap E between the sleeve 1 and the seal cap 5 is such that the capillary in the gap D between the position of the sleeve 1 where the recess 1d is formed and the position of the seal cap 5 where the vent 5b is formed. Greater than pressure.

Thereby, the magnitude | size of the clearance gap D directly under the ventilation port 5b which leads to the seal cap 5 can be ensured larger than the magnitude | size of the clearance gap E between the seal cap 5 and the sleeve 1 in the other part. That is, it is possible to form a space where the capillary pressure is small at a portion communicating with the ventilation port 5b. For this reason, the capillary pressure in the gap D leading to the ventilation port 5b can be made smaller than before, and the occurrence of oil 6 scattering and leakage from the ventilation port 5b can be suppressed.
As a result, for example, even when a disk reproducing device such as an HDD motor on which the hydrodynamic bearing device 40 is mounted is reduced in size and thickness, the concave portion 1d necessary for reducing the capillary pressure is formed on the sleeve 1 side. Generation | occurrence | production of scattering of the oil 6 from the ventilation port 5b, leaking, etc. can be suppressed effectively, without reducing the performance as the fluid dynamic bearing device 40.
Further, since the recess 1d is provided on the surface of the sleeve 1 substantially opposite to the ventilation port 5b, even when the oil 6 moves to just below the ventilation port 5b due to thermal expansion when placed in a high temperature environment, The oil 6 is absorbed in the recess 1d. For this reason, generation | occurrence | production of the leakage of the oil 6 from the ventilation port 5b can be suppressed.
(2)
In the hydrodynamic bearing device 40 of the present embodiment, the capillary pressure in the gap C between the outer peripheral surface of the shaft 2 and the inner peripheral surface of the seal cap 5 shown in FIG. Greater than the capillary pressure at D and gap E.

That is, the capillary pressures in the gaps C, D, and E are configured to have a magnitude relationship of gap C> gap E> gap D.
As a result, the oil 6 can be attracted to the gap C side between the shaft 2 and the seal cap 5 by the capillary pressure, so that the oil 6 scatters or leaks from the ventilation port 5b formed in the seal cap 5. Can be suppressed.
(3)
In the hydrodynamic bearing device 40 of the present embodiment, the capillary pressure in the gap B between the axial upper end surface of the sleeve 1 shown in FIG. 3 and the inner peripheral side portion of the seal cap 5 is as shown in FIG. Furthermore, it is larger than the capillary pressure in the gap D and the gap E.
That is, the capillary pressures in the gaps B, C, D, and E are configured to have a magnitude relationship of (gap C and gap B)> gap E> gap D.
Accordingly, the oil 6 can be attracted to the gap B side between the sleeve 1 and the seal cap 5 by capillary pressure, so that the oil 6 scatters or leaks from the ventilation port 5b formed in the seal cap 5. Can be prevented.
Further, by configuring the capillary pressure in the gap B to be larger than the capillary pressure in the gap C, the oil 6 can be scattered from the gap C between the shaft 2 and the inner peripheral surface of the seal cap 5. Generation | occurrence | production of a leak etc. can be suppressed effectively.

(4)
In the hydrodynamic bearing device 40 of the present embodiment, the capillary pressure in the gap A between the outer peripheral surface of the shaft 1 and the inner peripheral surface of the sleeve 1 shown in FIG. And larger than the capillary pressure in the gap E.
That is, the capillary pressures in the gaps A, B, C, D, and E are configured to have a magnitude relationship of gap A> (gap B and gap C)> gap E> gap D.
Thereby, since the oil 6 can be attracted to the gap A side constituting the radial bearing portion 21 by the capillary pressure, the oil 6 is scattered or leaked from the ventilation port 5b formed in the seal cap 5. Can be prevented.
Further, by configuring the capillary pressure in the gap A to be larger than the capillary pressure in the gap B or the gap C, the oil 6 from the gap C between the shaft 2 and the inner peripheral surface of the seal cap 5 can be obtained. It is possible to effectively suppress the occurrence of scattering and leakage.
(5)
In the hydrodynamic bearing device 40 according to the present embodiment, as shown in FIG. 3 and the like, the recess 1d formed on the sleeve 1 side has an outer peripheral portion whose opening area increases from the bottom portion toward the seal cap 5 side. Tapered.

As a result, the oil 6 that has moved to the vicinity of the concave portion 1d on the upper surface of the sleeve 1 due to an impact, thermal expansion, or the like on the hydrodynamic bearing device 40 causes the angle at the boundary portion between the upper surface of the sleeve 1 and the tapered surface, The movement into the recess 1d can be suppressed by the relationship with the tension. As a result, it is possible to effectively prevent the oil 6 from being scattered or leaked from the ventilation port 5b formed immediately above the recess 1d.
(6)
In the hydrodynamic bearing device 40 according to the present embodiment, as shown in FIG. 5A and the like, the ventilation port 5b formed in the seal cap 5 and the recess 1d formed on the surface of the sleeve 1 opposed to the ventilation port 5b 6 is formed at a position facing the communication hole G formed in the sleeve 1 as a circulation path in a plan view.
As a result, the concave portion 1d is formed at a position farthest from the communication hole G for circulating the oil 6 on the upper and lower surfaces in the axial direction of the sleeve 1, so that the oil from the ventilation port 5b immediately above the concave portion 1d is formed. Generation | occurrence | production of 6 scattering, a leak, etc. can be suppressed effectively.
(7)
In the hydrodynamic bearing device 40 of this embodiment, as shown in FIG. 2 and the like, the radial dynamic pressure generating groove 2b formed on the outer peripheral surface of the shaft 1 is formed so as to be asymmetric in the axial direction (vertical direction). Yes.

Thereby, in the radial bearing 21, the circulating force of the oil 6 in the axial direction can be generated. As a result, even with the thin hydrodynamic bearing device 40, the oil 6 can be circulated efficiently to prevent performance degradation caused by oil deterioration or leakage.
(8)
In the hydrodynamic bearing device 40 of the present embodiment, as shown in FIG. 2 and the like, one radial bearing portion 21 is provided on the outer peripheral surface of the shaft 2. In other words, the radial bearing portion 21 is a so-called single bearing.
Thereby, since the length of the radial bearing part 21 formed in the outer peripheral surface of the shaft 2 may be short, the hydrodynamic bearing device 40 can be reduced in thickness.
[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.
(A)
In the embodiment described above, an example in which the concave portion 1d is formed only on the surface on the sleeve 1 side facing the ventilation port 5b in order to form a space where the capillary pressure is small in a portion communicating with the ventilation port 5b has been described. However, the present invention is not limited to this.

For example, as shown in FIG. 7, in addition to the concave portion 1d on the sleeve 1, the hydrodynamic bearing device 90 has a concave portion 55d formed on the surface side of the ventilation port 55b facing the sleeve 1 on the seal cap 55 side. Also good.
Even in this case, since the size of the gap leading to the ventilation port 5b can be ensured larger than the other gaps (gap B to gap E shown in FIG. 3), the oil 6 is scattered or leaked in the same manner as described above. Etc. can be suppressed.
Further, since the size of the concave portion 55d on the seal cap 55 side can be reduced by the amount of the concave portion 1d formed on the sleeve 1, the hydrodynamic bearing device 90 can be thinned.
(B)
In the embodiment described above, an example in which the shape of the back surface side of the seal cap 5 that forms the oil reservoir H with the sleeve 1 is formed by surfaces that are substantially perpendicular to each other has been described. However, the present invention is not limited to this.
For example, as shown in FIG. 8, the hydrodynamic bearing in which the portion near the shaft 2 in the seal cap 65 is formed with a tapered portion 65 e so that a gap for forming the oil reservoir portion H increases radially outward. The device 91 may be used.

In this case, since the capillary pressure in the space connected to the ventilation port 65b can be made smaller than that in the other spaces, it is possible to suppress the occurrence of oil 6 splattering or leaking out as described above. Furthermore, by making the surfaces of the seal cap 65 on the sleeves 61a and 61b side tapered, it is possible to prevent the lump of air existing immediately below the ventilation port 65b from moving due to rotation.
(C)
In the said embodiment, the sleeve 1 was demonstrated and demonstrated with the example comprised by the single block. However, the present invention is not limited to this.
For example, as shown in FIG. 8, a hydrodynamic bearing device 91 in which an inner sleeve 61 b and an outer sleeve 61 a are combined to form one sleeve may be used.
In this case, when the inner sleeve 61b and the outer sleeve 61a are combined, it is more preferable that the concave portion 61d is formed on the upper end surface side facing the ventilation port 65b of the seal cap 65. Accordingly, after forming the sleeves 61a and 61b, it is not necessary to form the recess 61d by processing or the like. Therefore, the recesses necessary for securing the capillary pressure magnitude relationship while reducing the manufacturing cost of the sleeves 61a and 61b. 61d can be formed easily. Further, by forming a notch on the side where the inner sleeve 61b and the outer sleeve 61a are adjacent to each other (in the example shown in FIG. 8, the inner sleeve 61b side), a recess can be formed when the two members are combined. Therefore, workability at the time of processing is improved as compared with the case of forming a hole.

(D)
In the embodiment described above, an example in which the concave portion 1d is formed near the radial center of the upper end surface in the axial direction of the sleeve 1 has been described. However, the present invention is not limited to this.
For example, as shown in FIGS. 9 (a) and 9 (b), a notch 72a may be formed in the radially outer end portion of the sleeve 71 and used as a recess.
(E)
In the said embodiment, the example which provided the one radial bearing part 21 in the outer peripheral surface of the flat shaft 2 was demonstrated and demonstrated. However, the present invention is not limited to this.
For example, as shown in FIG. 10, a hydrodynamic bearing in which a groove (groove portion) 81 a is formed in a substantially central portion in the axial direction on the outer peripheral surface of the sleeve 81, and radial bearing portions are formed in the upper and lower portions in the axial direction of the groove 81 a. The device 92 may be used. In this case, as shown in FIG. 10, the capillary pressure in the gap A1 corresponding to the groove 81a is smaller than that of the gap A, but the groove 81a is designed so that the capillary pressure is larger than other gaps. Functions as a separation groove for the upper and lower radial dynamic pressure generating grooves, and the upper and lower radial bearings formed in the gap between the shaft and the sleeve do not interfere with each other via the lubricating fluid and perform their functions. The same effect as described above can be obtained.

(F)
In the above-described embodiment, an example in which the shape of the oil reservoir H formed between the sleeve 1 and the seal cap 5 is an annular shape has been described. However, the present invention is not limited to this.
For example, as shown in FIGS. 10 and 11, the sleeve 83 may be such that the depth h of the annular portion forming the recess 83d changes in the circumferential direction.
(G)
In the embodiment described above, an example in which the shape of the recess 1d formed on the sleeve 1 side is substantially circular in plan view has been described. However, the present invention is not limited to this.
For example, the shape of the concave portion in plan view may be a polygonal shape such as a substantially square shape.
(H)
In the said embodiment, the example using the shaft 2 with the flange 3 was given and demonstrated. However, the present invention is not limited to this.
For example, the present invention can be similarly applied to a hydrodynamic bearing device using a flangeless shaft.

(I)
In the said embodiment, the oil 6 was used and demonstrated as a lubricating fluid. However, the present invention is not limited to this.
For example, high fluidity grease or ionic liquid can be used instead of oil.
(J)
In the above embodiment, the configuration in which only one communication hole G is formed in the sleeve 1 has been described as an example. However, the present invention is not limited to this.
For example, a hydrodynamic bearing device in which a plurality of communication paths are formed with respect to the sleeve may be used.
(K)
In the said embodiment, in order to generate | occur | produce a circulating force, the radial dynamic-pressure generation | occurrence | production groove | channel 2b which comprises the radial bearing part 21 was demonstrated and demonstrated as an example in the axial direction. However, the present invention is not limited to this.
For example, the lower bearing or both of the radial bearings may be formed asymmetrically, or the radial bearing may be one of the upper and lower single bearings.
Further, the circulation force may be generated not in the radial bearing but in the thrust bearing.

(L)
In the embodiment described above, an example in which the recess 1 d formed on the upper end surface of the sleeve 1 faces the ventilation port 5 b formed in the seal cap 5 has been described. However, the present invention is not limited to this.
For example, the structure which a part of ventilation opening and a part of recessed part overlap in planar view may be sufficient.
(M)
In the said embodiment, the shape of the ventilation port 5b formed in the seal cap 5 demonstrated and demonstrated the example which is substantially circular in planar view. However, the present invention is not limited to this.
For example, it may be a polygonal shape such as a quadrangle.
However, from the viewpoint of workability of the ventilation port, it is often substantially circular as in the above embodiment.
(N)
In the above embodiment, the present invention has been described with reference to an example in which the present invention is applied to the spindle motor 30 and the spindle motor 1 including the same. However, the present invention is not limited to this.

For example, as shown in FIG. 12, the hydrodynamic bearing mechanism 40 and the spindle motor 30 having the above-described configuration are mounted, and information recorded on the recording disk 11 is reproduced by the recording head 95a, The present invention can also be applied to a recording / reproducing apparatus 95 that records information.
Thereby, it is possible to obtain a recording / reproducing apparatus that can cope with a reduction in size and thickness without degrading performance and quality.
(O)
In the said embodiment, the example which employ | adopted the system which circulates the oil 6 was given and demonstrated. However, the present invention is not limited to this.
For example, the relationship between the capillary pressure in the gap D and the capillary pressure in the gap E may be a system that does not circulate oil.

  The hydrodynamic bearing device of the present invention has the effect of being able to reduce the thickness while preventing a decrease in reliability. Therefore, the reliability using an optical recording medium, a magneto-optical recording medium, a magnetic recording medium, or the like as a recording medium. The present invention can be widely applied to a hydrodynamic bearing device mounted on a spindle motor suitable for in-vehicle use and portable use.

A sectional view showing composition of a spindle motor carrying a fluid dynamic bearing device concerning one embodiment of the present invention. FIG. 2 is a schematic longitudinal sectional view of the periphery of a hydrodynamic bearing mechanism 40 included in the hydrodynamic bearing device of FIG. FIG. 3 is a schematic cross-sectional view showing a schematic configuration of the hydrodynamic bearing mechanism of FIG. 2. FIG. 4 is an enlarged view of a portion X included in FIG. 3. (A), (b) is a top view which shows the positional relationship of a communicating hole, a vent hole, a recessed part, and air when the fluid bearing mechanism of FIG. 2 is seen from the top. (A) is a graph which shows the magnitude relationship of the capillary pressure of each clearance gap in the conventional hydrodynamic bearing apparatus in which the recessed part is not formed in the sleeve upper end surface. (B) is a graph which shows the magnitude relationship of the capillary pressure of each clearance gap in the hydrodynamic bearing apparatus of FIG. Sectional drawing which shows schematic structure of the hydrodynamic bearing apparatus which concerns on other embodiment of this invention. Sectional drawing which shows schematic structure of the hydrodynamic bearing apparatus which concerns on further another embodiment of this invention. The top view and side view which show the schematic shape of the sleeve mounted in the hydrodynamic bearing apparatus which concerns on further another embodiment of this invention. Sectional drawing which shows schematic structure of the hydrodynamic bearing apparatus which concerns on further another embodiment of this invention. The perspective sectional view showing the shape of the sleeve contained in the hydrodynamic bearing device concerning other embodiments of the present invention. The internal sectional view showing the composition of the recording / reproducing apparatus concerning other embodiments of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sleeve 1a Bearing hole 1d Recess 2 Shaft 2b Radial dynamic pressure generating groove 3 Flange 3a, 3b Thrust dynamic pressure generating groove 4 Thrust plate 5 Seal cap 5a Fixing part 5b Ventilation port 6 Oil (lubricating fluid)
7 Hub 8 Base 9 Rotor magnet 10 Stator 11 Recording disk 15 Air bubbles (air)
21 Radial bearing portion 22 Thrust bearing portion 30 Fluid bearing device 31 Rotating member 32 Static member 40 Fluid bearing mechanism 55 Seal cap 55b Ventilation port 55d Recess 61a Outer sleeve 61b Inner sleeve 61d Recess 65 Seal cap 65b Ventilation port 65e Taper portion 71 Sleeve 71a Groove 72a Notch (concave)
81 Sleeve 81a Groove (groove)
81d recess 83 sleeve 83d recess 90 fluid dynamic bearing device 91 fluid dynamic bearing device 92 fluid dynamic bearing device 95 recording / reproducing device 95a recording head A gap (fifth space)
B gap (4th space)
C Clearance (third space)
D Clearance (first space)
E Clearance (second space)
G Communication hole H Oil reservoir h Depth

Claims (14)

A sleeve having a bearing hole;
A shaft disposed in a relatively rotatable state in the bearing hole;
A lubricating fluid filled in a gap formed between the sleeve and the shaft;
A seal cap fixed to one side of the sleeve in the axial direction and having a ventilation opening;
A first space formed between the surface on the other axial side of the portion of the seal cap where the ventilation port is formed and the surface on the one axial side of the sleeve;
A second space formed between the surface on the other side in the axial direction of the portion where the ventilation port in the seal cap is not formed and the surface on the one side in the axial direction of the sleeve;
With
The sleeve further includes a recess formed at a position facing the ventilation port formed in a part of the seal cap,
The capillary pressure in the first space is smaller than the capillary pressure in the second space,
Fluid bearing device. A third space is formed between the side surface of the shaft and the inner peripheral surface of the seal cap,
The capillary pressure in the third space is greater than the capillary pressure in the first space and the second space,
The hydrodynamic bearing device according to claim 1. A fourth space is formed between the sleeve and the innermost peripheral portion of the seal cap,
The capillary pressure in the fourth space is greater than the capillary pressure in the first space and the second space,
The hydrodynamic bearing device according to claim 1. A fifth space is formed between the shaft and the sleeve,
The capillary pressure in the fifth space is greater than the capillary pressure in the first space and the second space,
The hydrodynamic bearing device according to any one of claims 1 to 3. Having a substantially annular groove portion in the vicinity of a substantially central portion of at least one of the side surface of the shaft and the inner peripheral side of the sleeve;
A sixth space is formed between the groove and the shaft or the sleeve,
The capillary pressure in the sixth space is larger than the capillary pressure in the first space and the second space,
The hydrodynamic bearing device according to any one of claims 1 to 4. The recess formed in the sleeve has a tapered shape that increases toward the seal cap.
The hydrodynamic bearing device according to any one of claims 1 to 5. The sleeve further includes a communication hole formed along the rotation axis direction of the shaft at a symmetrical position of the recess centered on the rotation axis of the shaft in plan view.
The hydrodynamic bearing device according to any one of claims 1 to 6. The sleeve is configured by combining an inner sleeve and an outer sleeve,
The recess is formed by combining the inner sleeve and the outer sleeve.
The hydrodynamic bearing device according to claim 1. In the accumulation space of the lubricating fluid formed between the seal cap and the sleeve, the size of the gap changes in the circumferential direction around the rotation axis of the shaft.
The hydrodynamic bearing device according to claim 1. The seal cap has a tapered surface on a surface facing the sleeve, in which a gap between the sleeve and the sleeve becomes smaller toward a radially inner side of a circle centering on the rotation axis of the shaft.
The hydrodynamic bearing device according to any one of claims 1 to 9. A radial dynamic pressure generating groove formed on at least one of the side surface of the shaft and the inner peripheral surface of the sleeve is formed to be asymmetric in the rotation axis direction of the shaft.
The hydrodynamic bearing device according to claim 1. One radial bearing portion is formed between the side surface of the shaft and the inner peripheral surface of the sleeve.
The hydrodynamic bearing device according to any one of claims 1 to 11. The hydrodynamic bearing device according to any one of claims 1 to 12, comprising:
Spindle motor. A spindle motor according to claim 13 is provided.
Recording / playback device.

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