US20010046336A1 - Hydrodynamic bearing device - Google Patents
Hydrodynamic bearing device Download PDFInfo
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- US20010046336A1 US20010046336A1 US09/245,308 US24530899A US2001046336A1 US 20010046336 A1 US20010046336 A1 US 20010046336A1 US 24530899 A US24530899 A US 24530899A US 2001046336 A1 US2001046336 A1 US 2001046336A1
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- Prior art keywords
- dynamic pressure
- pressure generating
- stationary
- generating portion
- rotary sleeve
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- 239000012530 fluid Substances 0.000 claims abstract description 38
- 230000001050 lubricating effect Effects 0.000 claims abstract description 37
- 238000010276 construction Methods 0.000 abstract description 6
- 230000035939 shock Effects 0.000 description 7
- 238000004804 winding Methods 0.000 description 4
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000010696 ester oil Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C17/00—Sliding-contact bearings for exclusively rotary movement
- F16C17/10—Sliding-contact bearings for exclusively rotary movement for both radial and axial load
- F16C17/102—Sliding-contact bearings for exclusively rotary movement for both radial and axial load with grooves in the bearing surface to generate hydrodynamic pressure
- F16C17/107—Sliding-contact bearings for exclusively rotary movement for both radial and axial load with grooves in the bearing surface to generate hydrodynamic pressure with at least one surface for radial load and at least one surface for axial load
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C17/00—Sliding-contact bearings for exclusively rotary movement
- F16C17/04—Sliding-contact bearings for exclusively rotary movement for axial load only
- F16C17/045—Sliding-contact bearings for exclusively rotary movement for axial load only with grooves in the bearing surface to generate hydrodynamic pressure, e.g. spiral groove thrust bearings
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/02—Parts of sliding-contact bearings
- F16C33/04—Brasses; Bushes; Linings
- F16C33/06—Sliding surface mainly made of metal
- F16C33/10—Construction relative to lubrication
- F16C33/1025—Construction relative to lubrication with liquid, e.g. oil, as lubricant
- F16C33/106—Details of distribution or circulation inside the bearings, e.g. details of the bearing surfaces to affect flow or pressure of the liquid
- F16C33/107—Grooves for generating pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/72—Sealings
- F16C33/74—Sealings of sliding-contact bearings
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2370/00—Apparatus relating to physics, e.g. instruments
- F16C2370/12—Hard disk drives or the like
Definitions
- the present invention relates to a hydrodynamic bearing device for use in an office automation system and an audio-visual system.
- Hydrodynamic bearing devices are generally used in rotary head cylinders for tabletop VTRs and camera-incorporated VTRs, in polygon scanner motors for laser copiers, and in recording medium rotation drivers for floppy disk devices and hard disk devices.
- the hard disk devices have higher memory capacities and higher data transfer speeds. This requires a disk rotating device for use in a recording apparatus of this type to be capable of high-speed and high-precision rotation.
- a hydrodynamic bearing device as disclosed in U.S. Pat. No. 5,504,637 is used for a rotary main shaft of the recording apparatus.
- the hydrodynamic bearing device has a construction as shown in FIG. 5.
- the hydrodynamic bearing device includes a stationary shaft 1 and a rotary sleeve 2 supported around the stationary shaft 1 .
- the stationary shaft 1 has a proximal end fixed to a lower casing 3 .
- Hard disks 4 are fitted around the rotary sleeve 2 .
- Dynamic pressure generating grooves 6 are provided in an outer circumferential portion of the stationary shaft 1 in a radial-side dynamic pressure generating portion 5 defined between the stationary shaft 1 and the rotary sleeve 2 .
- a stationary thrust ring 9 is attached to a distal end of the stationary shaft 1 by an extension shaft 8 formed with a male thread portion 7 threaded with the stationary shaft 1 .
- the rotary sleeve 2 has a recessed portion 10 provided in association with the stationary thrust ring 9 .
- An opening of the recessed portion 10 is virtually closed by a rotary thrust ring 12 which has at its center a center hole 11 of a diameter greater than the outer diameter of the extension shaft 8 .
- the rotary thrust ring 12 is fixed to the rotary sleeve 2 by a screw 13 .
- a thrust-side dynamic pressure generating portion 14 defined by the recessed portion 10 of the rotary sleeve 2 , the stationary thrust ring 9 and the rotary thrust ring 12 , dynamic pressure generating grooves 15 , 16 are provided in upper and lower faces of the stationary thrust ring 9 .
- the thrust-side dynamic pressure generating portion 14 and the radial-side dynamic pressure generating portion 5 are filled with a lubricating fluid.
- a stator winding 17 is disposed around a proximal end portion of the stationary shaft 1 on the lower casing 3 .
- a magnet 18 is provided on an inner circumferential surface of the rotary sleeve 2 as opposing to the stator winding 17 .
- the extension shaft 8 is fixed to an upper casing 19 by a screw 20 .
- the hard disks 4 are rotated at a high speed via the rotary sleeve 2 in a sealed space defined between the lower casing 3 and the upper casing 19 upon energization of the stator winding 17 .
- the lubricating fluid 21 Due to expansion of the lubricating fluid and a centrifugal force, the lubricating fluid 21 is liable to scatter out of the radial-side dynamic pressure generating portion 5 as indicated by 22 in FIG. 6, or scatter out of a gap between the extension shaft 8 and the rotary thrust ring 12 as indicated by 23 , thereby causing lockup or seizure of a motor.
- a conventional technical approach to the prevention of the scattering of the lubricating fluid from the open end of the thrust-side dynamic pressure generating portion is to reduce the radial spacing of the gap as much as possible.
- the hydrodynamic bearing device of the present invention is characterized in that a radial spacing of a gap at an open end of a thrust-side dynamic pressure generating portion is set greater than a spacing of the thrust-side dynamic pressure generating portion as measured with respect to the thrust direction.
- a hydrodynamic bearing device which comprises a stationary shaft having opposite ends at least one of which is fixed and a rotary sleeve supported rotatably about the stationary shaft and is adapted to pump a lubricating fluid between the stationary shaft and the rotary sleeve for non-contact rotation of the device, wherein the stationary shaft is provided with a stationary thrust ring, wherein the rotary sleeve has a recessed portion defined by faces thereof opposed to upper and lower faces and outer circumferential surface of the stationary thrust ring, wherein the lubricating fluid is filled in a gap defined between the stationary thrust ring and the recessed portion, wherein the following expression is satisfied:
- ⁇ L t+ 10 ⁇ m to 30 ⁇ m [ 10 ⁇ m ⁇ L ⁇ t ⁇ 30 ⁇ m]
- t is a thickness of the stationary thrust ring and ⁇ L is a height of the recessed portion.
- the hydrodynamic bearing device is characterized in that the stationary shaft is supported at its fixed opposite ends, that a radial-side dynamic pressure generating portion is defined between the stationary shaft and the rotary sleeve and a thrust-side dynamic pressure generating portion is defined between the stationary thrust ring and the recessed portion and disposed on one side of the radial-side dynamic pressure generating portion, that the radial-side dynamic pressure generating portion and the thrust-side dynamic pressure generating portion are filled with the lubricating fluid, and that a radial spacing ⁇ d of a gap at an open end of the thrust-side dynamic pressure generating portion satisfies the following expression:
- a hydrodynamic bearing device which comprises a stationary shaft supported at its fixed opposite ends and a rotary sleeve supported rotatably about the stationary shaft and is adapted to pump a lubricating fluid between the stationary shaft and the rotary sleeve for non-contact rotation of the device, wherein the stationary shaft is provided with a stationary thrust ring, wherein the rotary sleeve has a recessed portion defined by faces thereof opposed to upper and lower faces and outer circumferential surface of the stationary thrust ring, wherein a radial-side dynamic pressure generating portion is defined between the stationary shaft and the rotary sleeve and a thrust-side dynamic pressure generating portion is defined between the stationary thrust ring and the recessed portion and disposed on one side of the radial-side dynamic pressure generating portion, wherein the radial-side dynamic pressure generating portion and the thrust-side dynamic pressure generating portion are filled with the lubricating fluid, wherein a radial-side dynamic pressure generating portion and the thrust-side dynamic pressure generating
- t is a thickness of the stationary thrust ring and ⁇ L is a height of the recessed portion.
- the hydrodynamic bearing device comprises: a stationary shaft having a proximal end fixed to a casing; a rotary sleeve supported rotatably about the stationary shaft and having an open portion provided adjacent one end thereof in association with a distal end of the stationary shaft, the opening having a diameter greater than a diameter of the stationary shaft, the rotary sleeve having an outer circumference to which a load member is attached; a stationary thrust ring of a disk shape having a through-hole at its center and attached to the distal end of the stationary shaft, the stationary thrust ring having a lower face opposed to a bottom of the open portion of the rotary sleeve and an outer circumferential surface opposed to an inner circumferential surface of the open portion; an extension shaft having a proximal end threaded with the distal end of the stationary shaft thereby fixing the stationary thrust ring to the stationary shaft; and a rotary thrust ring of a disk shape
- the hydrodynamic bearing device according to claim 2 , 3 or 4 is characterized in that ⁇ d is 10 ⁇ m to 30 ⁇ m.
- FIG. 1 is a sectional view illustrating a hydrodynamic bearing device according to one embodiment of the present invention
- FIG. 2 is an enlarged view illustrating major portions of the hydrodynamic bearing device of the embodiment
- FIG. 3 is an enlarged view illustrating major portions of the hydrodynamic bearing device of the embodiment
- FIG. 4 is a graph showing a relation of a thrust spacing of a gap versus a shock resistance according to the embodiment
- FIG. 5 is a sectional view of a conventional hydrodynamic bearing device
- FIG. 7 is an enlarged view illustrating major portions of the hydrodynamic bearing device of FIG. 6.
- FIGS. 1 to 4 An embodiment of the present invention will hereinafter be described with reference to FIGS. 1 to 4 .
- FIG. 1 shows a hydrodynamic bearing device for use in a hard disk device.
- This hydrodynamic bearing device is illustrated as having a construction such that a stationary shaft is supported at its opposite ends, but the stationary shaft may be cantilevered.
- the hydrodynamic bearing device shown in FIG. 1 has substantially the same construction as the conventional one shown in FIG. 5 with some specific portions thereof being different.
- components having like functions are denoted by like reference characters.
- a proximal end of the stationary shaft 1 is fixed to a lower casing 3 by a screw 24 .
- a stationary thrust ring 9 is fixed to a distal end of the stationary shaft 1 by an extension shaft 8 .
- the rotary sleeve 2 has a recessed portion 10 which is defined by faces thereof opposed to lower and upper faces and outer circumferential surface of the stationary thrust ring 9 .
- a radial-side dynamic pressure generating portion 5 is defined between the stationary shaft 1 and the rotary sleeve 2
- a thrust-side dynamic pressure generating portion 14 is defined between the stationary thrust ring 9 and the recessed portion 10 and provided on one side of the radial-side dynamic pressure generating portion 5 .
- Dynamic pressure generating grooves 6 are provided on an outer circumferential portion of the stationary shaft 1 in the radial-side dynamic pressure generating portion 5 .
- Dynamic pressure generating grooves 15 and 16 are provided in upper and lower faces, respectively, of the stationary thrust ring 9 in the thrust-side dynamic pressure generating portion 14 .
- a radial spacing ⁇ d of a gap at an open end of the thrust-side dynamic pressure generating portion 14 is set as satisfying the following expression:
- a lubricating fluid 21 is filled in the radial-side dynamic pressure generating portion 5 and the thrust-side dynamic pressure generating portion 14 .
- the lubricating fluid to be herein used is composed of not less than 95% of an ester oil with the remaining not greater than 5% being a mineral oil, an olefin, a hydrocarbon or the like.
- the surface tension of the lubricating fluid is adjusted to 25 dyn/cm (at 29° C.).
- the stationary shaft 1 has a tapered portion 1 a having a diameter progressively decreasing toward the proximal end thereof, and the rotary sleeve 2 has a larger inner diameter portion 2 a provided in association with the tapered portion 1 a , the larger inner diameter portion having an inner diameter larger than the inner diameter of a portion of the rotary sleeve 2 facing to the radial-side dynamic pressure generating portion 5 .
- the lubricating fluid is not allowed into a space defined between the tapered portion 1 a of the stationary shaft 1 and the larger inner diameter portion 2 a of the rotary sleeve 2 due to the surface tension of the lubricating fluid.
- the rotary sleeve 2 is composed of a copper alloy or an aluminum alloy, and a magnetic steel plate 25 is interposed between the rotary sleeve 2 and a magnet 18 for suppression of magnetic leakage.
- the spacing be smaller.
- the spacing has a lower limit as expressed by the following expression in consideration of reliability of practical finishing accuracy.
- the spacing has an upper limit as expressed by the following expression in consideration of an allowable range for an intended 500G shock resistance.
- ⁇ L t+ 10 ⁇ m to 30 ⁇ m
- FIG. 4 shows measurement results which indicate the relationship of the spacing versus the shock resistance.
- ⁇ L t+ 20 ⁇ m to 40 ⁇ m
- the hydrodynamic bearing device of the present invention is arranged such that the radial spacing ⁇ d of the gap at the open end of the thrust dynamic pressure generating portion is set as satisfying the expression ⁇ d> ⁇ L ⁇ t, the scattering of the lubricating fluid can be obviated. Therefore, the hydrodynamic bearing device is particularly suitable for use in a hard disk device.
Abstract
Description
- The present invention relates to a hydrodynamic bearing device for use in an office automation system and an audio-visual system.
- Hydrodynamic bearing devices are generally used in rotary head cylinders for tabletop VTRs and camera-incorporated VTRs, in polygon scanner motors for laser copiers, and in recording medium rotation drivers for floppy disk devices and hard disk devices.
- Specifically, the hard disk devices have higher memory capacities and higher data transfer speeds. This requires a disk rotating device for use in a recording apparatus of this type to be capable of high-speed and high-precision rotation.
- To this end, a hydrodynamic bearing device as disclosed in U.S. Pat. No. 5,504,637 is used for a rotary main shaft of the recording apparatus.
- The hydrodynamic bearing device has a construction as shown in FIG. 5.
- The hydrodynamic bearing device includes a
stationary shaft 1 and arotary sleeve 2 supported around thestationary shaft 1. Thestationary shaft 1 has a proximal end fixed to alower casing 3. Hard disks 4 are fitted around therotary sleeve 2. - Dynamic
pressure generating grooves 6 are provided in an outer circumferential portion of thestationary shaft 1 in a radial-side dynamicpressure generating portion 5 defined between thestationary shaft 1 and therotary sleeve 2. - A
stationary thrust ring 9 is attached to a distal end of thestationary shaft 1 by anextension shaft 8 formed with amale thread portion 7 threaded with thestationary shaft 1. - The
rotary sleeve 2 has arecessed portion 10 provided in association with thestationary thrust ring 9. An opening of the recessedportion 10 is virtually closed by arotary thrust ring 12 which has at its center a center hole 11 of a diameter greater than the outer diameter of theextension shaft 8. Therotary thrust ring 12 is fixed to therotary sleeve 2 by ascrew 13. - In a thrust-side dynamic
pressure generating portion 14 defined by therecessed portion 10 of therotary sleeve 2, thestationary thrust ring 9 and therotary thrust ring 12, dynamicpressure generating grooves stationary thrust ring 9. The thrust-side dynamicpressure generating portion 14 and the radial-side dynamicpressure generating portion 5 are filled with a lubricating fluid. - A stator winding17 is disposed around a proximal end portion of the
stationary shaft 1 on thelower casing 3. Amagnet 18 is provided on an inner circumferential surface of therotary sleeve 2 as opposing to the stator winding 17. Theextension shaft 8 is fixed to anupper casing 19 by ascrew 20. - In the hydrodynamic bearing device having the aforesaid construction, the hard disks4 are rotated at a high speed via the
rotary sleeve 2 in a sealed space defined between thelower casing 3 and theupper casing 19 upon energization of the stator winding 17. - The rotation of the
rotary sleeve 2 about thestationary shaft 1 pumps the lubricating fluid so that therotary sleeve 2 can maintain non-contact rotation. - However, the aforesaid arrangement has the following drawback.
- Due to expansion of the lubricating fluid and a centrifugal force, the
lubricating fluid 21 is liable to scatter out of the radial-side dynamicpressure generating portion 5 as indicated by 22 in FIG. 6, or scatter out of a gap between theextension shaft 8 and therotary thrust ring 12 as indicated by 23, thereby causing lockup or seizure of a motor. - Particularly, where the scattered lubricating fluid adheres onto the hard disks4, erroneous data reproduction may result.
- More specifically, a conventional technical approach to the prevention of the scattering of the lubricating fluid from the open end of the thrust-side dynamic pressure generating portion is to reduce the radial spacing of the gap as much as possible.
- Further, improvement in shock resistance with respect to the thrust direction is currently demanded. This demand is directed not only to a hydrodynamic bearing device constructed such that a stationary shaft is fixed at its opposite ends as described above, but also to a hydrodynamic bearing device constructed such that the stationary shaft is fixed only at its proximal end.
- It is therefore an object of the present invention to provide a hydrodynamic bearing device which has an improved construction to prevent a lubricating fluid from scattering out of a dynamic pressure generating portion.
- The hydrodynamic bearing device of the present invention is characterized in that a radial spacing of a gap at an open end of a thrust-side dynamic pressure generating portion is set greater than a spacing of the thrust-side dynamic pressure generating portion as measured with respect to the thrust direction.
- With this arrangement, the scattering of the lubricating fluid from the open end of the thrust-side dynamic pressure generating portion can be prevented even when the hydrodynamic bearing device is operated at a high rotation speed in a high temperature environment.
- In accordance with
claim 1 of the present invention, there is provided a hydrodynamic bearing device which comprises a stationary shaft having opposite ends at least one of which is fixed and a rotary sleeve supported rotatably about the stationary shaft and is adapted to pump a lubricating fluid between the stationary shaft and the rotary sleeve for non-contact rotation of the device, wherein the stationary shaft is provided with a stationary thrust ring, wherein the rotary sleeve has a recessed portion defined by faces thereof opposed to upper and lower faces and outer circumferential surface of the stationary thrust ring, wherein the lubricating fluid is filled in a gap defined between the stationary thrust ring and the recessed portion, wherein the following expression is satisfied: - ΔL=t+10 μm to 30 μm [10 μm≦ΔL −t≦30 μm]
- wherein t is a thickness of the stationary thrust ring and ΔL is a height of the recessed portion.
- In accordance with
claim 2 of the present invention, the hydrodynamic bearing device according toclaim 1 is characterized in that the stationary shaft is supported at its fixed opposite ends, that a radial-side dynamic pressure generating portion is defined between the stationary shaft and the rotary sleeve and a thrust-side dynamic pressure generating portion is defined between the stationary thrust ring and the recessed portion and disposed on one side of the radial-side dynamic pressure generating portion, that the radial-side dynamic pressure generating portion and the thrust-side dynamic pressure generating portion are filled with the lubricating fluid, and that a radial spacing Δd of a gap at an open end of the thrust-side dynamic pressure generating portion satisfies the following expression: - Δd>ΔL−t
- In accordance with
claim 3 of the present invention, there is provided a hydrodynamic bearing device which comprises a stationary shaft supported at its fixed opposite ends and a rotary sleeve supported rotatably about the stationary shaft and is adapted to pump a lubricating fluid between the stationary shaft and the rotary sleeve for non-contact rotation of the device, wherein the stationary shaft is provided with a stationary thrust ring, wherein the rotary sleeve has a recessed portion defined by faces thereof opposed to upper and lower faces and outer circumferential surface of the stationary thrust ring, wherein a radial-side dynamic pressure generating portion is defined between the stationary shaft and the rotary sleeve and a thrust-side dynamic pressure generating portion is defined between the stationary thrust ring and the recessed portion and disposed on one side of the radial-side dynamic pressure generating portion, wherein the radial-side dynamic pressure generating portion and the thrust-side dynamic pressure generating portion are filled with the lubricating fluid, wherein a radial spacing Δd of a gap at an open end of the thrust-side dynamic pressure generating portion satisfies the following expression: - Δd>ΔL−t
- wherein t is a thickness of the stationary thrust ring and ΔL is a height of the recessed portion.
- In accordance with claim4 of the present invention, the hydrodynamic bearing device according to
claim - In accordance with
claim 5 of the present invention, the hydrodynamic bearing device according toclaim - FIG. 1 is a sectional view illustrating a hydrodynamic bearing device according to one embodiment of the present invention;
- FIG. 2 is an enlarged view illustrating major portions of the hydrodynamic bearing device of the embodiment;
- FIG. 3 is an enlarged view illustrating major portions of the hydrodynamic bearing device of the embodiment;
- FIG. 4 is a graph showing a relation of a thrust spacing of a gap versus a shock resistance according to the embodiment;
- FIG. 5 is a sectional view of a conventional hydrodynamic bearing device; and
- FIG. 7 is an enlarged view illustrating major portions of the hydrodynamic bearing device of FIG. 6.
- An embodiment of the present invention will hereinafter be described with reference to FIGS.1 to 4.
- FIG. 1 shows a hydrodynamic bearing device for use in a hard disk device.
- This hydrodynamic bearing device is illustrated as having a construction such that a stationary shaft is supported at its opposite ends, but the stationary shaft may be cantilevered.
- The hydrodynamic bearing device shown in FIG. 1 has substantially the same construction as the conventional one shown in FIG. 5 with some specific portions thereof being different. In these figures, components having like functions are denoted by like reference characters.
- Referring to FIG. 1, a proximal end of the
stationary shaft 1 is fixed to alower casing 3 by ascrew 24. Astationary thrust ring 9 is fixed to a distal end of thestationary shaft 1 by anextension shaft 8. - The
rotary sleeve 2 has arecessed portion 10 which is defined by faces thereof opposed to lower and upper faces and outer circumferential surface of thestationary thrust ring 9. A radial-side dynamicpressure generating portion 5 is defined between thestationary shaft 1 and therotary sleeve 2, and a thrust-side dynamicpressure generating portion 14 is defined between thestationary thrust ring 9 and the recessedportion 10 and provided on one side of the radial-side dynamicpressure generating portion 5. Dynamicpressure generating grooves 6 are provided on an outer circumferential portion of thestationary shaft 1 in the radial-side dynamicpressure generating portion 5. Dynamicpressure generating grooves stationary thrust ring 9 in the thrust-side dynamicpressure generating portion 14. - Provided that the
stationary thrust plate 9 has a thickness t and therecessed portion 10 has a height ΔL as shown in FIG. 2, a radial spacing Δd of a gap at an open end of the thrust-side dynamic pressure generating portion 14 (see FIG. 3) is set as satisfying the following expression: - Δd>ΔL−t
- A lubricating
fluid 21 is filled in the radial-side dynamicpressure generating portion 5 and the thrust-side dynamicpressure generating portion 14. The lubricating fluid to be herein used is composed of not less than 95% of an ester oil with the remaining not greater than 5% being a mineral oil, an olefin, a hydrocarbon or the like. The surface tension of the lubricating fluid is adjusted to 25 dyn/cm (at 29° C.). - In a gap between the
rotary sleeve 2 and thestationary shaft 1 on the lower side of the radial-side dynamicpressure generating portion 5 in FIG. 1, thestationary shaft 1 has a taperedportion 1 a having a diameter progressively decreasing toward the proximal end thereof, and therotary sleeve 2 has a largerinner diameter portion 2 a provided in association with the taperedportion 1 a, the larger inner diameter portion having an inner diameter larger than the inner diameter of a portion of therotary sleeve 2 facing to the radial-side dynamicpressure generating portion 5. Thus, the lubricating fluid is not allowed into a space defined between thetapered portion 1 a of thestationary shaft 1 and the largerinner diameter portion 2 a of therotary sleeve 2 due to the surface tension of the lubricating fluid. - The
rotary sleeve 2 is composed of a copper alloy or an aluminum alloy, and amagnetic steel plate 25 is interposed between therotary sleeve 2 and amagnet 18 for suppression of magnetic leakage. - With this arrangement, upon energization of a stator winding17, hard disks 4 are rotated at a high speed via the
rotary sleeve 2 in a sealed space S defined between thelower casing 3 and anupper casing 19. Therotary sleeve 2 is rotated about thestationary shaft 1, whereby the lubricating fluid is pumped to cause therotary sleeve 2 to maintain non-contact rotation. - It was confirmed that, where a
spacing 26 between an upper face of thestationary thrust plate 9 and a lower face of arotary thrust ring 12 in the thrust-side dynamicpressure generating portion 14 during rotation is 5 μm and a spacing between a lower face of thestationary thrust ring 9 and a face of therotary sleeve 2 opposed thereto is 10 μm, the optimum performance is ensured. This is expressed as follows: - ΔL=t+15 μm
- For improvement of shock resistance with respect to the thrust direction, it may be preferred that the spacing be smaller. However, it was found that the spacing has a lower limit as expressed by the following expression in consideration of reliability of practical finishing accuracy.
- ΔL=t+10 μm
- Further, the spacing has an upper limit as expressed by the following expression in consideration of an allowable range for an intended 500G shock resistance.
- ΔL=t+30 μm
- Therefore, the allowable range of the spacing is expressed as follows:
- ΔL=t+10 μm to 30 μm
- FIG. 4 shows measurement results which indicate the relationship of the spacing versus the shock resistance.
- When the intended shock resistance level is lowered in a practically acceptable range without an increase in the finishing accuracy, the allowable range of the spacing is expressed as follows:
- ΔL=t+20 μm to 40 μm
- Scattering of the lubricating fluid from the open end of the thrust-side dynamic pressure generating portion to the outside was checked during the operation with the spacing26 between the upper face of the
stationary thrust ring 9 and the lower face of therotary thrust ring 12 being set to 5 μm, with the expression ΔL=t+15 μm being satisfied, and with the radial spacing Δd of the gap at the open end being set to 30 μm which prevents the lubricating fluid from flowing into the gap by the surface tension of the lubricating fluid herein used, as shown in FIG. 3. As a result, no fluid scattering was observed. It was found that the allowable range of the radial spacing d is as follows: - Δd>ΔL−t
- As described above, the hydrodynamic bearing device of the present invention is arranged such that: the stationary shaft is provided with the stationary thrust ring; the rotary sleeve has the recessed portion which is defined by the faces thereof opposed to the lower and upper faces and outer circumferential surface of the stationary thrust ring; the lubricating fluid is filled in the gap between the stationary thrust ring and the recessed portion; and the expression ΔL =t+10 μm to 30 μm is satisfied wherein t is the thickness of the stationary thrust ring and ΔL is the height of the recessed portion. Therefore, the hydrodynamic bearing device has a practically acceptable range of shock resistance with respect to the thrust direction.
- Since the hydrodynamic bearing device of the present invention is arranged such that the radial spacing Δd of the gap at the open end of the thrust dynamic pressure generating portion is set as satisfying the expression Δd>ΔL−t, the scattering of the lubricating fluid can be obviated. Therefore, the hydrodynamic bearing device is particularly suitable for use in a hard disk device.
Claims (7)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP10-026275 | 1998-02-09 | ||
JP10-26275 | 1998-02-09 | ||
JP10026275A JPH11230163A (en) | 1998-02-09 | 1998-02-09 | Fluid bearing device |
Publications (2)
Publication Number | Publication Date |
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US20010046336A1 true US20010046336A1 (en) | 2001-11-29 |
US6357916B2 US6357916B2 (en) | 2002-03-19 |
Family
ID=12188745
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/245,308 Expired - Fee Related US6357916B2 (en) | 1998-02-09 | 1999-02-05 | Hydrodynamic bearing device |
Country Status (3)
Country | Link |
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US (1) | US6357916B2 (en) |
JP (1) | JPH11230163A (en) |
SG (1) | SG73611A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2006059205A1 (en) * | 2004-12-01 | 2006-06-08 | Minebea Co., Ltd. | Fluid dynamic pressure bearing device, spindle motor provided with the fluid dynamic pressure bearing device, and recording disk drive device |
US20140077643A1 (en) * | 2012-09-14 | 2014-03-20 | Samsung Electro-Mechanics Co., Ltd. | Spindle motor |
Families Citing this family (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3907031B2 (en) * | 2000-03-10 | 2007-04-18 | 株式会社ジェイテクト | Thrust dynamic pressure bearing |
US20020025090A1 (en) | 2000-03-29 | 2002-02-28 | Ikunori Sakatani | Fluid bearing device |
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US5559382A (en) * | 1992-10-01 | 1996-09-24 | Nidec Corporation | Spindle motor |
JPH06333331A (en) | 1993-05-20 | 1994-12-02 | Matsushita Electric Ind Co Ltd | Disk rotating device |
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JP3558710B2 (en) * | 1994-12-02 | 2004-08-25 | 日本電産株式会社 | Electric motor |
JP3625884B2 (en) * | 1994-12-05 | 2005-03-02 | 日本電産株式会社 | Motor with hydrodynamic bearing |
JP2641035B2 (en) | 1994-12-16 | 1997-08-13 | 日本電産株式会社 | Motor with hydrodynamic bearing |
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-
1998
- 1998-02-09 JP JP10026275A patent/JPH11230163A/en not_active Withdrawn
-
1999
- 1999-02-05 US US09/245,308 patent/US6357916B2/en not_active Expired - Fee Related
- 1999-02-08 SG SG1999000359A patent/SG73611A1/en unknown
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WO2006059205A1 (en) * | 2004-12-01 | 2006-06-08 | Minebea Co., Ltd. | Fluid dynamic pressure bearing device, spindle motor provided with the fluid dynamic pressure bearing device, and recording disk drive device |
US20080095480A1 (en) * | 2004-12-01 | 2008-04-24 | Minebea Co., Ltd. | Fluid Dynamic Pressure Bearing Device, Spindle Motor Provided with the Fluid Dynamic Pressure Bearing Device, and Recording Disk Drive Device |
US7661882B2 (en) | 2004-12-01 | 2010-02-16 | Minebea Co., Ltd. | Fluid dynamic pressure bearing device, spindle motor provided with the fluid dynamic pressure bearing device, and recording disk drive device |
US20140077643A1 (en) * | 2012-09-14 | 2014-03-20 | Samsung Electro-Mechanics Co., Ltd. | Spindle motor |
CN103683628A (en) * | 2012-09-14 | 2014-03-26 | 三星电机株式会社 | Spindle motor |
Also Published As
Publication number | Publication date |
---|---|
JPH11230163A (en) | 1999-08-27 |
SG73611A1 (en) | 2000-06-20 |
US6357916B2 (en) | 2002-03-19 |
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