KR100810477B1 - Fluid bearing device - Google Patents

Abstract

(assignment)

Provided is a fluid bearing device capable of achieving low rotational fluctuations and high reliability without lengthening an axial length of a bearing.

(Solution)

A shaft (1, 51) and a sleeve (9, 59) into which the shaft is inserted and a lubricating fluid (20) interposed in the gap between the shaft and the sleeve, so that the shaft can rotate relatively freely with respect to the sleeve. It is supported and provided with annular seal rings 4 and 54 at the end of the sleeve, and at least one of the inner circumferential surfaces 4a and 54a of the seal ring and the outer circumferential surfaces 1a and 91b of the shaft opposite thereto is a gap between each other. To the inclined surfaces 4a and 54a in the direction of extension as it is moved away from the sleeve to form a tapered seal portion TS that prevents leakage of lubricating fluid, and at the same time, the thermal expansion coefficient of the sleeve and shaft Formed of larger material.

Shaft, sleeve, fluid bearing

Description

Fluid Bearing Device {FLUID BEARING DEVICE}

1 is a cross-sectional view of a motor equipped with an embodiment in the fluid bearing device of the present invention.

2 is an enlarged cross-sectional view illustrating the main part of the fluid bearing device of the present invention.

It is an expanded sectional view explaining the principal part in the temperature rising state in the fluid bearing apparatus of this invention.

4 is a sectional view of a motor equipped with another embodiment in the fluid bearing device of the present invention.

Fig. 5 is a sectional view of a motor equipped with a conventional fluid bearing device.

* Description of the symbols for the main parts of the drawings *

1: shaft 1a: outer peripheral surface

2: hub 2a: outer peripheral surface

2b: center hole 2d: perimeter wall

2d1: inside 4: tapering

4a: 2nd taper surface (inner peripheral surface) 6: magnet

9: sleeve 9a: inner circumference

9b: end 9c: first tapered surface

9k: protruding wall 9t: cross section

13: motor base 13a: standing part

13a1: Inner circumference 13a2: Outer circumference

14: stator core 20: lubricating fluid

20a: liquid level (interface) 30: coil

31: thrust ring 32: thrust plate

50, 50A: motor 51: shaft

54: Taping 54a: 2nd taper surface (inner peripheral surface)

56: magnet 59: sleeve

59a: through hole 59a1: inner circumferential surface

59m1, 59m2: Peripheral groove (adhesive groove) 63 Motor base

63a: standing part 63a1: outer peripheral surface

63b: center hole 64: stator core

72: hub 72a: outer peripheral surface

72b: through hole 72b1: inner surface

72d: perimeter wall 72d1: inner surface

80: coil 91: cylindrical body

91a: outer peripheral surface 91b: first tapered surface

91t: end adh: glue

B: fluid bearing (device) S: stator

TS: Taper Seal R: Rotor

RB: Bearing (in radial direction) SB: Bearing (in thrust direction)

ds, d1, d2: diameter

Patent Document 1 Japanese Unexamined Patent Publication No. 2002-101610

Patent Document 2 Japanese Patent Application Laid-Open No. 8-210364

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid bearing device, and more particularly, to a fluid bearing device that is suitably mounted on a disk drive motor of a hard disk drive.

Patent Documents 1 and 2 are examples of motors equipped with conventional fluid bearing devices. The general form of such a motor is shown in FIG.

The motor 500 shown in this FIG. 5 is a disk drive motor of a hard disk drive, and is comprised by the stator S and the rotor R. As shown in FIG.

The stator S is fixed to the motor base J13 and the outer circumferential surface of the sleeve J9 and the standing portion J13a made of brass fixed to the inner circumferential surface of the standing portion J13a, which can stand in a circular shape at the center thereof. Configured stator core J14.

The rotor R comprises a hub J2 and a ring magnet J6 fixed to the hub J2.

A hard disk (not shown) is attached to the outer circumferential surface J2a of the hub J2.

In addition, the shaft J1 made of stainless steel is fixed to the center hole J2b of the hub J2.

In this configuration, the sleeve J9 is axially supported through the fluid bearing in the thrust direction and the radial direction of the shaft J1, whereby the rotor R is supported so as to be able to rotate freely with respect to the stator S. .

The radial fluid bearing comprises an outer circumferential surface J1a of the shaft J1, an inner circumferential surface J9a of the sleeve J9 and a lubricating fluid 20 filled in the gap thereof. This lubricating fluid 20 is also shared by the fluid bearing of the thrust direction which is not shown in figure.

A tapered seal portion JTS for sealing this lubricating fluid 20 is formed at an end portion on the side of the hub J2 in the sleeve J9, and an inner circumferential surface J9a of the sleeve J9 and a shaft J1 opposite thereto. Is formed as the outer peripheral surface J1a.

In addition, the filling amount of the lubricating fluid 20 is defined such that the liquid surface 20a is positioned at the tapered seal portion JTS.

However, the motor 500 using the above-mentioned fluid bearing has a shaft J1 using the pressure of the lubricating fluid 20 generated by the rotation of the rotor R in which the bearing inside is filled with the lubricating fluid 20. Is supported so as to rotate freely in a non-contact state such as the sleeve J9.

In addition, although the tapered seal part JTS for sealing the lubricating fluid 20 is formed in the open end part of the fluid bearing, this taper seal part JTS has a lubricating fluid () by the temperature rising according to the rotation of the rotor R. 20) is formed in a shape that does not overflow even when expanded.

In other words, the tapered seal portion JTS has a shape in which the lubricating fluid 20 is accumulated by a predetermined capacity.

This expansion will be described by way of example.

The thermal expansion coefficient of the shaft J1 made of stainless steel is 10.5 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the sleeve J9 made of brass is 17 × 10 ⁻⁶ / ° C.

In addition, the upper limit temperature of use of the motor 500 is 80 degreeC normally, and when the temperature rises from 25 degreeC which is normal temperature to this upper limit temperature, the amount of temperature increase will be 55 degreeC.

This fluid bearing is a stainless steel shaft with an outer diameter of 4.0000 mm and a length of 20.000 mm in a brass sleeve J9 having a hole diameter of 4.0050 mm and a depth of 21.000 mm at a temperature of 25 ° C. The capacity J1 is inserted and the volume (volume of the gap except the tapered seal portion JTS) for holding the lubricating fluid 20 is 13.227 kPa.

When the temperature rises from room temperature to 80 ° C, the diameter of the hole of the sleeve J9 changes to 4.0087 mm, the outer diameter of the shaft J1 changes to 4.0023 mm, and the capacity increases to 13.431 kPa to 1.0154 times. This increase is 1.54%.

On the other hand, the tapered seal portion JTS is formed at 25 ° C. at room temperature, with a minimum diameter of 4.0050 mm, a maximum diameter of 4.2050 mm, and an axial length of 2.1000 mm, with a capacity of 1.4091 kPa.

When the temperature rises from room temperature to 80 ° C., the capacity increases by 1.0153 times to 1.4306 kPa. This increase is 1.53%.

On the other hand, since the thermal expansion coefficient of the oil generally used as the lubricating fluid 20 is 8 × 10 ⁻⁶ / ° C., when the temperature rises from 25 ° C. to 80 ° C. at room temperature, the temperature increase amount is 55 ° C. The volume increase is therefore 4.40%.

In this way, the increase in the capacity (or volume) due to the temperature increase is greater than the increase in the capacity of the combined capacity increase of the capacity of the tapered seal portion JTS except for the tapered seal portion JTS and the increase in the capacity of the tapered seal portion JTS. Since the volume increase amount of is large, the liquid surface 20a of the lubricating fluid 20 rises in the taper seal part JTS with temperature increase.

Specifically, if the distance from the end surface J9b of the sleeve J9 in FIG. 5 to the liquid surface 20a at 25 ° C at room temperature is 1.100 mm, when the temperature rises to 80 ° C, the lubricating fluid 20 ) Subtracting the increase in the total capacity to hold the lubricating fluid from its volume expansion is 0.3824 kPa, and the liquid level rises 0.479 mm, so that the tapered seal portion does not overflow even if this liquid level rises. The axial length of (JTS) is set.

In actual design, the shape of the tapered seal should be set in consideration of not only the liquid level rise but also the fluctuation of the dimension during mass production, the decrease in the amount of liquid due to the evaporation of the lubricating fluid, and the liquid surface fluctuation due to the external impact. do.

However, since the thickness of the motor is strictly prescribed, for example, when mounted on a hard disk drive, such as 7.5 mm or less, when the axial length of the tapered seal portion is increased, the bearing span in the thrust direction is shortened by that amount. There was a problem that the rotational fluctuation of the rotor is increased due to the increased load applied.

In order to solve this problem, a configuration in which the material of the sleeve is made of a material having a larger coefficient of thermal expansion than other members is also studied.

According to this configuration, as the temperature increases, the inner diameter of the sleeve is expanded and the capacity of the tapered seal portion is increased to suppress the liquid level rise of the lubricating fluid, but the lubricating fluid holding portions other than the tapered seal portion, that is, the shaft and the sleeve Because of the small gap, the gap between is greatly expanded, the bearing rigidity is lowered, and the rotational swing of the rotor is increased.

Therefore, the problem to be solved by the present invention is to provide a fluid bearing device that can achieve high reliability without rotational fluctuations without increasing the axial length of the bearing.

[Means for solving the problem]

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention has the following structures as means.

That is, the lubricating fluid interposed between the shafts 1 and 51, the sleeves 9 and 59 in which the shafts 1 and 51 are inserted, and the gap between the shafts 1 and 51 and the sleeves 9 and 59. A fluid bearing device (B) having a (20) and supporting the shafts (1, 51) so as to be freely rotatable relative to the sleeves (9, 59), wherein the sleeves (9, 59) At least an inner peripheral surface 4a, 54a of the seal ring 4, 54 and an outer peripheral surface 1a, 91b of the shaft 1, 51 opposite thereto provided with an annular seal ring 4, 54 at an end thereof. One side is formed with the inclined surfaces 4a and 54a in the extending direction as the gap between them is separated from the sleeves 9 and 59 to form a tapered seal portion TS that prevents leakage of the lubricating fluid 20. In addition, the sealing rings 4 and 54 have a coefficient of thermal expansion greater than that of the sleeves 9 and 59 and the shafts 1 and 51. It is a fluid bearing device 50, 50A characterized by being formed of a material.

An embodiment of the present invention will be described with reference to Figs.

<First Embodiment>

The motor 50 equipped with the fluid bearing device of the first embodiment shown in FIG. 1 is a disk drive motor used for a hard disk drive, and is composed of a stator S and a rotor R. As shown in FIG.

The stator S is formed of brass sleeves fixed to the inner circumferential surface 13a1 of the standing portion 13a, which can stand in a ring shape at the motor base 13 and its center portion, and the outer circumferential surface of the standing portion 13a. It comprises a ring-shaped stator core 14 fixed to 13a2. This stator core 14 is provided with the some protrusion pole which is not shown in figure, and the coil 30 is wound by each protrusion pole.

The rotor R comprises a cup-shaped hub 2 and a ring-shaped magnet 6 fixed to the inner surface 2d1 of the outermost circumferential wall 2d.

A hard disk (not shown) is attached to the outer circumferential surface 2a of the hub 2.

A shaft 1 made of stainless steel is fixed to the center hole 2b of the hub 2.

The shaft 1 is axially supported through the fluid bearing device B in the radial direction and the thrust direction at the same time as being inserted into the sleeve 9.

This fluid bearing device B is comprised from the radial bearing RB and the thrust bearing SB.

The radial bearing RB comprises an outer circumferential surface 1a of the shaft 1, an inner circumferential surface 9a of the sleeve 9, and a lubricating fluid 20 filled in the gap thereof.

The bearing SB in the thrust direction has an end 9b formed at the lower end of FIG. 1 in the sleeve 9, and a thrust ring 31 fixed to the end of the shaft 1 and received at the end 9b. Thrust plate 32 fixed to the end 9b and sealing the opening end of the sleeve 9 and the gap between these members, that is, the sleeve 9 and the thrust plate 32 and the thrust ring 31 and the shaft 1 It is configured to include a lubricating fluid 20 filled in the gap between the tip surface of the ().

In the above structure, the rotor R is supported so that it may rotate freely with respect to the stator S. As shown in FIG.

Next, the taper seal part TS of the fluid bearing device B is explained in full detail.

In the fluid bearing B of the embodiment, the tapered seal portion TS has a shaft 1 and a sleeve 9 and a protruding wall 9k protruding axially from the outer circumferential portion of the sleeve 9 and It is comprised by the tapering ring 4 fixed to the cross section 9t of the sleeve 9. This tapering 4 is fixed by the end face 9t and the adhesive adh1, and is fixed by the protrusion wall 9k by the transient adhesive adh2.

The adhesive adh1 may use, for example, an anaerobic adhesive suitable for surface bonding.

The adhesive adh2 is cured by being piled up at the corners, and for example, an epoxy adhesive having a small volume change can be used.

Moreover, the recessed part 4k which thins the thickness of an axial direction is formed in the part to which the adhesive agent adh2 which is the outer peripheral side of the tapering ring 4 is apply | coated.

Thereby, since the adhesive agent adh2 does not protrude from the upper surface 4t of the tapering ring 4, the thickness of the axial direction of the motor 50 does not increase by the adhesive agent adh2.

Moreover, by fixing the tapering ring 4 so that the outer peripheral surface of the tapering ring 4 abuts on the inner peripheral face of the protruding wall 9k, the center position of the tapering ring 4 can be matched with high precision.

In such a fixing method, when the tapering ring 4 expands due to an increase in temperature due to the rotation of the rotor R, the inner ring of the tapering ring 4 expands and is deformed so as to increase in thickness.

Therefore, peeling does not arise in the adhesive surface between the end surfaces 9t of the sleeve 9, etc. by the tapering ring 4. As shown in FIG.

The structure of the part containing this tapering 4 is demonstrated concretely using FIG. This figure is a figure explaining the state in normal temperature.

In FIG. 2, the tapered seal portion TS has a large diameter as it faces the end face 9t on the end face 9t side of the outer circumferential face 1a of the shaft 1 and the inner circumferential face 9a of the sleeve 9. It is comprised by the 1st taper surface 9c inclined so that it may be formed, and the 2nd taper surface 4a which inclines so that it may become large diameter as it falls from the sleeve 9, and is the inner peripheral surface of the tapering ring 4. As shown in FIG.

That is, in the taper seal part TS, it is formed so that the space | interval of radial direction of the inner peripheral surface 4a of the tapering ring 4 and the outer peripheral surface 1a of the shaft 1 may expand | separate from the sleeve 9, and is expanded.

The lubricating fluid 20 is filled in the quantity in which the liquid surface 20a is located in the middle of the taper seal part TS.

Next, the thermal expansion of each member is explained in full detail.

The shaft 1 is made of martensitic stainless steel, the sleeve 9 is made of copper alloy, the tapering ring 4 is made of aluminum, and the coefficient of thermal expansion is

Shaft (1): 10.5 × 10 ^-6 / ℃

Sleeve (9): 17 × 10 ^-6 / ℃

Taper ring (4): 23.5 × 10 ^-6 / ° C.

That is, the taper ring 4 is formed of a material having a larger coefficient of thermal expansion than the shaft 1 and the sleeve 9.

In addition, ester oil is used as lubricating fluid 20, and the thermal expansion coefficient is 8 * 10 <^-6> / degreeC.

Here, each member is formed so that it may become the following dimensions at normal temperature 25 degreeC.

That is, the outer diameter ds of the shaft 1: Φ4.0000mm

In the 2nd taper surface 4a which is an inner peripheral surface of the tapering ring 4,

Minimum Inner Diameter (d1) (Inner Diameter of Sleeve Side): Φ4.0050mm

Maximum outer diameter (d2) (inside diameter of sleeve): Φ4.2050mm

Therefore, when the temperature of each member becomes 80 degreeC by the temperature rising according to the rotation of the rotor R, since the temperature increment is 55 degreeC, each dimension changes to the direction which becomes large as follows. Here, the subscript " ₍₈₀₎ " is appended to the code | symbol for a distinction, and this elevated temperature state is demonstrated using FIG.

That is, each dimension at 80 degreeC which heated up,

Outer diameter of shaft 1 (ds ₈₀ ): Φ4.0023mm

Of the second tapered surface 4c Minimum inner diameter (d1 ₍₈₀₎ ): Φ 4.0 102 mm

Maximum inner diameter d2 ₍₈₀₎ of the second tapered surface 4c: Φ 4.2104 mm.

In addition, as described above, the tapering ring 4 is fixed to the end surface 9t of the sleeve 9 by the adhesive adh1 and is fixed by the protruding wall 9k and the adhesive adh. When the tapering ring 4 expands due to the temperature rising due to the rotation of R), as shown by the arrow in FIG. 3, the tapering ring 4 expands and deforms in the direction of increasing thickness.

By this dimensional change, the volume of the tapered seal portion TS is expanded by 1.0294 times from 1.4091 mm to 1.4505 mm. This increase is 2.94%.

This is about a 2x increase over the volume increment 1.53% shown in the prior example.

On the other hand, the capacity (gap) for holding the lubricating fluid 20 of the fluid bearing device B, other than the tapered seal portion TS, is also increased (expanded) in the same way, but this is because the shaft 1 of stainless steel Since it is a combination with the sleeve 9, the capacity increment is 1.54% as in the prior art.

In addition, the volume of the lubricating fluid 20 is increased by 4.40%.

Summarizing the increments of the capacities and volumes due to the expansion of each member and the lubricating fluid, the liquid surface 20a of the lubricating fluid 20 has a 0.466 mm displacement (rising) when the temperature rises from the normal temperature of 25 ° C to 80 ° C. However, this is 0.013 mm less with respect to 0.479 mm, which is the displacement (rising) amount of the conventional example.

Therefore, with respect to the conventional structure in which the taper ring 4 is not used as the taper seal portion TS, the axial length thereof can be shortened by 0.013 mm, that is, the thickness of the motor 50 on which the fluid bearing B is mounted. It can be thinned 0.013mm.

As can be seen from the above-mentioned contents, the material of the tapering ring 4 is so preferable that its thermal expansion coefficient is large.

For example, when POM (polyacetal) is used, the coefficient of thermal expansion is greater than that of aluminum because the coefficient of thermal expansion is 90 × 10 ⁻⁶ / ° C., in which case other members, dimensions, and the like are used at 80 ° C. under the same conditions. If the liquid level displacement (rising) is found, it is 0.326 mm. Therefore, this displacement amount is 0.140 mm smaller than the displacement amount when aluminum is used.

That is, it becomes possible to further shorten the thickness of the motor on which the fluid bearing device B is mounted by 0.140 mm.

According to the structure described in detail above, the lubricating fluid in the taper seal part TS, without widening the filling gap of the lubricating fluid 20 other than the taper seal part TS in the fluid bearing apparatus B too much. Since the holding capacity of 20 can be further increased, the liquid level rise of the lubricating fluid 20 at the time of temperature increase can be suppressed and the axial length of the fluid bearing device B can be shortened.

In addition, since the bearing span does not need to be shortened, the bearing rigidity does not deteriorate accordingly, and the rotational fluctuation of the rotor R does not increase.

In addition, since the gap between the shaft 1 and the sleeve 9 does not greatly expand, the reduction in the bearing rigidity is suppressed and the rotational fluctuation of the rotor R does not increase.

Second Embodiment

Next, the 2nd Example of the fluid bearing apparatus of this invention is described in detail using FIG.

The motor 50A on which the fluid bearing device of the second embodiment shown in FIG. 4 is mounted is a disk drive motor used for a hard disk drive, and is composed of a stator S and a rotor R. As shown in FIG.

The motor 50 of the first embodiment has a configuration in which the sleeve 9 fixed to the motor base 13 is configured to axially rotate the shaft 1 freely, but the motor 50A of this second embodiment has a shaft. One end of the 51s is fixed to the motor base 63, and the rotor R including the sleeve 59 rotates with respect to the shaft 51s.

The stator S is comprised including the motor base 63 and the annular stator core 64 fixed to the outer peripheral surface 63a1 of the annular standing part 63a formed in this motor base 63. As shown in FIG.

This stator core 64 is provided with the some protrusion pole which is not shown in figure, and the coil 80 is wound by each protrusion pole.

A shaft core 51s made of stainless steel is fixed to the center hole 63b of the motor base 63, and a cylindrical cylindrical body 91 is fixed to the outer circumferential surface of the shaft core 51s. Since the shaft core 51s and the cylindrical body 91 are integrated, it can be seen as the shaft 51 including this cylindrical body 91.

The rotor R has a ring-shaped yoke 56Y fixed to an annular hub 72 having a through hole 72b and an inner surface 72d1 of a circumferential wall 72d thereof, and a ring shape fixed to an inner circumferential surface thereof. And a magnet 56M.

On the outer circumferential surface 72a of the hub, a hard disk (not shown) is mounted.

The sleeve 59 is attached to the inner surface 72b1 of the through hole 72b of the hub 72.

In the sleeve 59, a cylindrical body 91 is inserted into the through hole 59a, which is axially supported by the sleeve 59 via the fluid bearing device B in radial and thrust directions. do.

In the above structure, the rotor R is supported so that it may rotate freely with respect to the stator S. As shown in FIG.

The fluid bearing device B comprises an inner circumferential surface 59a1 of the through hole 59a of the sleeve 59, an outer circumferential surface 91a of the cylindrical body 91, and a lubricating fluid 20 filled in these gaps. do.

The tapered seal portion TS of the fluid bearing B is formed in pairs on both end sides of the sleeve 59.

Specifically, the tapered seal portion TS is formed on the inner circumferential surface 59a1 of the sleeve 59 and on both end portions 91t of the outer circumferential surface 91a of the cylindrical body 91, and is directed to each end portion 91t. As the inner peripheral surface of the first tapered surface 91b inclined so as to be small in diameter and the pair of tapering rings 54 fixed by adhesion to both end surfaces 59t of the sleeve 59, the small diameter as it is separated from the sleeve 59 It is comprised by the 2nd taper surface 54a inclined so that it may be formed.

The tapering ring 54 is also fixed by adhesion to the inner circumferential surface of the annular wall 59k extending in the axial direction from the outer circumferential surface of the sleeve 59. Thereby, the center position of the tapering ring 54 can be matched with high precision.

In Fig. 4, peripheral grooves 59m1 and 59m2 in cross-sectional triangles formed in the inner circumferential surface and the inner corner of the annular wall 59k in the sleeve 59 have an adhesive for keeping the adhesive for adhering the tapering 54 well. Home.

The inclination is set so that the 1st taper surface 91b and the 2nd taper surface 54a may have a clearance gap and oppose each other so that the clearance gap of the radial direction may enlarge as it falls from the sleeve 59. As shown in FIG.

The lubricating fluid 20 is filled in the quantity in which the liquid surface 20a is located in the middle of the taper seal part TS.

In such a configuration, the cylindrical body 91 is made of the same material as the shaft core 51, and the tapering ring 54 is thermally expanded than the cylindrical body 91 and the sleeve 59 using the same materials as those of the first embodiment. It is formed of a material with a large coefficient.

Thereby, as the temperature increases, the second tapered surface 54a of the tapering ring 54 greatly expands in the large radial direction, so that the capacity of the tapered seal portion TS increases to match the volume expansion of the lubricating fluid 20, The liquid level rise of the lubricating fluid 20 liquid level 20a by the temperature rising according to the rotation of the rotor R becomes small.

Therefore, also in this 2nd Example, like the 1st Example, the length of the taper seal part TS in the axial direction can be shortened, and the thickness of the motor 50 equipped with this fluid bearing apparatus B is provided. You can thin that much.

That is, this fluid bearing device B does not widen the filling gap of the lubricating fluid 20 other than the taper seal part TS, and maintains the holding capacity of the lubricating fluid 20 in the taper seal part TS. Since it increases significantly, the liquid level rise of the lubricating fluid 20 at the time of temperature increase can be suppressed, and the axial length of the fluid bearing apparatus B can be shortened.

In addition, since the bearing span does not need to be shortened, the rotational fluctuation of the rotor R is not increased without causing a decrease in bearing rigidity.

In addition, since the gap between the shaft 51 and the sleeve 59 does not extend significantly, the reduction in bearing rigidity is suppressed and the rotational fluctuation of the rotor R does not increase.

It goes without saying that only one side of the pair of tapered rings 54 may be made of a material having a larger coefficient of thermal expansion than the other member.

As mentioned above, each Example described in detail shows the outstanding effect also in low temperature.

Referring to the operation in a low temperature environment, the lubricating fluid 20 is thermally contracted under such an environment to reduce its volume.

On the other hand, since each of the tapering rings 4 and 54 has a larger coefficient of thermal expansion than the other members (shafts 1 and 51 and the sleeves 9 and 59) as described above, the tapering seals ( The degree of reduction of the capacity of TS) becomes large.

Accordingly, the liquid level drop due to the volume shrinkage of the lubricating fluid 20 is suppressed, so that the liquid level does not reach the tapered seal portion TS (the liquid surface is not positioned on the tapered seal portion TS), so-called lubrication oil is cut off at the dynamic pressure generating portion or the like. This can be prevented from occurring.

As described above, the fluid bearing device B according to the present invention is very hard to be affected by the temperature change, and can maintain the initial function for a long time, and has a very high reliability.

As can be seen from the description of each embodiment described in detail above, the change of the liquid surface position of the lubricating fluid in the tapered seal portion TS according to the temperature change can be arbitrarily set according to the setting of the coefficient of thermal expansion and the dimension of each member. .

In each Example, although the example which suppressed liquid level rise by temperature rising was shown, it can also be set so that a liquid level hardly changes by temperature rising, and it can also be set so that a liquid level may fall.

In any case, even if the temperature changes, the liquid level can be kept in the tapered seal portion TS and the displacement can be minimized. Therefore, the axial length of the fluid bearing device is shortened, and as a result, the fluid bearing device is mounted. The axial length (thickness) of one motor can be shortened (thinned).

Each embodiment of the present invention is not limited to the above-described configuration and sequentially, and needless to say, modifications may be made without departing from the gist of the present invention.

Although each embodiment has described the example in which the fluid bearing device is mounted on the disk drive motor of the hard disk drive, it is not limited to this use, and it is possible to mount it on all the motors using the fluid bearing.

Although the example of oil was demonstrated as lubricating fluid, it is, of course, not limited to this.

The fluidity of the lubricating fluid is not particularly limited, but may be semi-fluid. In that case, you may interpret it as including an interface with the liquid surface in an Example.

In the first embodiment, an example in which the tapered surface of the tapered seal portion TS is formed only on the tapered ring 4 side has been described, but the present invention is not limited thereto, and the shaft 1 facing the tapered ring 4 is not limited thereto. You may also form in the side. In addition, you may form a taper surface only in the shaft 1 side.

In either case, the gap in the radial direction between the inner circumferential surface 4a of the tapering ring 4 and the outer circumferential surface 1a of the shaft 1 may be formed so as to extend toward the hub 2 side.

According to the present invention, the rotational fluctuation is small and high reliability can be obtained without increasing (long) the axial length of the bearing.

Claims (1)

Shaft, The sleeve with this shaft inserted, And a lubricating fluid interposed between the shaft and the sleeve, A fluid bearing device for supporting said shaft so as to be able to rotate relatively freely with respect to said sleeve, An annular seal ring at the end of the sleeve, At least one of an inner circumferential surface of the seal ring and an outer circumferential surface of the shaft opposite thereto is an inclined surface in which a gap between the inner circumferential surface of the seal ring and the outer circumferential surface of the shaft extends as it is detached from the sleeve, thereby causing leakage of the lubricating fluid. And at the same time forming the tapered seal portion for preventing the damage, the sealing ring is formed of a material whose thermal expansion coefficient is greater than the thermal expansion coefficient of the sleeve and the shaft.

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