US20010005296A1 - Spindle device having a dynamic-pressure-fluid bearing - Google Patents
Spindle device having a dynamic-pressure-fluid bearing Download PDFInfo
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- US20010005296A1 US20010005296A1 US09/781,425 US78142501A US2001005296A1 US 20010005296 A1 US20010005296 A1 US 20010005296A1 US 78142501 A US78142501 A US 78142501A US 2001005296 A1 US2001005296 A1 US 2001005296A1
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- United States
- Prior art keywords
- shaft
- create
- mist
- proof seal
- spindle device
- Prior art date
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Classifications
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- 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
- F16C33/741—Sealings of sliding-contact bearings by means of a fluid
- F16C33/743—Sealings of sliding-contact bearings by means of a fluid retained in the sealing gap
- F16C33/746—Sealings of sliding-contact bearings by means of a fluid retained in the sealing gap by a magnetic field
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- 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
- F16C17/02—Sliding-contact bearings for exclusively rotary movement for radial load only
- F16C17/026—Sliding-contact bearings for exclusively rotary movement for radial load only with helical grooves in the bearing surface to generate hydrodynamic pressure, e.g. herringbone grooves
-
- 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
- F16C17/00—Sliding-contact bearings for exclusively rotary movement
- F16C17/10—Sliding-contact bearings for exclusively rotary movement for both radial and 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
- F16C17/10—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
- 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
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B17/00—Guiding record carriers not specifically of filamentary or web form, or of supports therefor
- G11B17/02—Details
- G11B17/022—Positioning or locking of single discs
- G11B17/028—Positioning or locking of single discs of discs rotating during transducing operation
- G11B17/0282—Positioning or locking of single discs of discs rotating during transducing operation by means provided on the turntable
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
- G11B19/20—Driving; Starting; Stopping; Control thereof
- G11B19/2009—Turntables, hubs and motors for disk drives; Mounting of motors in the drive
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
- H02K5/167—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using sliding-contact or spherical cap bearings
- H02K5/1677—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using sliding-contact or spherical cap bearings radially supporting the rotor around a fixed spindle; radially supporting the rotor directly
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- 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 spindle device to be mounted to a disc driving apparatus for driving, e.g., discs, and more particularly to a structure of a spindle motor of an outer rotor type, which is formed by fixing rotor magnets within a hub that clamps magnetic discs.
- the track density of discs can be 8000 TPI (tracks per inch)-10000 TPI, which is converted to a track pitch as fine as 3 ⁇ m.
- the performance required of the motor mounted to the apparatus is to always accurately trace each track having such fine track pitch.
- This kind of motor has employed ball bearings in general; however, the rotation of ball bearings inevitably generates vibration.
- the level of vibration is measured to be as fine as ca. 0.15 ⁇ m based on NRRO (Non Repeatable Run Out), which is non repeatable sway of the hub of the motor. This vibration level is the minimum possible value for the ball bearings.
- NRRO Non Repeatable Run Out
- the motor comprises a fixed shaft, a sleeve that is supported and rotated by the shaft and a radial-dynamic-pressure-fluid bearing, or the motor comprises a fixed sleeve, a rotating shaft that is supported and rotated by the sleeve and the radial-dynamic-pressure-fluid bearing.
- FIG. 16 is a cross sectional view of this conventional motor.
- a shaft 501 is vertically fixed at the center of a bracket 504 , and a stator core 510 with wires wound thereon is mounted to the bracket 504 .
- a rotor magnet 506 is fixed to a rotor frame 505 so that the rotor magnet faces the stator core 510 .
- the rotor frame 505 is mounted to the hub 503 .
- a bushing 511 is fixed at a lower section of an inner rim of the hub 503 , and another bushing 512 is mounted to an outer rim of the bracket 504 .
- the bushing 511 faces the bushing 512 with a clearance in-between.
- the magnetic discs (not shown) are to be mounted around the hub 503 .
- Grooves (not shown) are provided inside of a sleeve 502 , the grooves produce dynamic pressure of lubricating fluid by the rotation of the sleeve 502 , which is rotatively supported by the fixed shaft 501 via lubricating fluid.
- Radial-dynamic-pressure-fluid bearings R 501 and R 502 are thus constructed.
- Axial dynamic pressure bearings A 501 and A 502 comprise both end faces of a fixed thrust ring 507 , a lower face of rotation thrust ring 508 and an upper face of the sleeve 502 .
- a groove 541 is provided on an outer circumference of a cap 509
- another groove 542 is provided on an inner circumference of the rotation thrust ring 508 .
- the lower rim of groove 541 is disposed at substantially the center of groove 542
- the upper rim of groove 542 is disposed at substantially the center of groove 541 .
- the upper and lower rims of each groove 541 and 542 face each other with some offset.
- the conventional motor employing the above dynamic-pressure-fluid bearing has a possible problem that the lubricating fluid might splash into a space where the magnetic discs are disposed.
- a magnetic head reads/writes data from/to the magnetic disc with little clearance between the head and disc.
- the space thus must be kept utmost clean because if the lubricating fluid splashes or flows into the space, serious problems such as a head crush, a head absorption, etc. will occur. (Hereinafter the above space is called the “clean space”.)
- the above conventional motor has provided a countermeasure against lubricating oil splashes by forming an oil pool using the grooves 541 and 542 to prevent the lubricating fluid from splashing out from the upper part of the motor; however, this countermeasure cannot prevent a mist of lubricating fluid from flowing out.
- the present invention aims to provide a reliable spindle device which avoids inconvenience such as a head crush or a head absorption by disposing a mist seal between the thrust-dynamic-pressure-fluid bearing and the clean space where magnetic discs are disposed.
- the mist seal prevents a mist of lubricating fluid from flowing out into the clean space where magnetic discs are disposed.
- the spindle device of the present invention comprises the following elements:
- a mist seal such as a viscous seal, a labyrinth seal, a magnetic fluid seal or the like disposed between the thrust-dynamic-pressure-fluid bearing and the clean space where the discs are disposed, and the mist seal blocks the mist of lubricating fluid from flowing out.
- the above structure can prevent the mist of lubricating fluid from splashing into the clean space by using the mist seal.
- an oil seal that prevents the lubricating fluid per se from flowing out, and an oil pool that prevents surplus lubricating fluid from flowing out are combined, whereby liquid lubricating fluid is prevented from flowing out into the clean space.
- This structure can further enhance a reliability of the spindle device.
- the spindle device has an advantageous sealing structure that can prevent the lubricating fluid of the dynamic-pressure-fluid bearing from splashing out into the clean space.
- sealing mechanisms between the dynamic-pressure-lubricating-fluid-bearing and the clean space oil seal (surface tension seal, centrifugal force seal) and mist seal (viscous seal, magnetic fluid seal, labyrinth seal).
- the dynamic-pressure-lubricating-fluid-bearing holds the lubricating fluid using the surface tension seal, and the centrifugal force seal restores the lubricating fluid, further, the mist seal prevents the mist of lubricating fluid from splashing.
- This sealing process effectively prevents the lubricating fluid from flowing and splashing out into the clean space. A part of this arrangement can be omitted depending on the motor construction.
- the oil pool and grooves in addition to the above sealing process contribute to preventing the fluid from flowing as well as splashing out not only in a continuous operation but also in an intermittent operation, at rest at a high temperature or with a change in orientation.
- the thrust-dynamic-pressure-fluid bearings are disposed on both the upper and lower sections of the radial-dynamic-pressure-fluid bearing, whereby a longer bearing span for the radial-dynamic-pressure-fluid bearing can be obtained, and the rigidity is increased. As a result, the dynamic-pressure-fluid bearing can be well-balanced.
- the spindle device of the present invention allows no flow-out of the lubricating fluid, the bearing is always filled with the lubricating fluid, which substantially extends a life span of the magnetic disc driving apparatus.
- FIG. 1 is a cross section of a motor used in a first exemplary embodiment of the present invention.
- FIG. 2 is an enlarged view of an upper portion of the motor used in the first exemplary embodiment of the present invention.
- FIG. 3 is an enlarged view of a lower portion of the motor used in the first exemplary embodiment of the present invention.
- FIG. 4 details the inside of a sleeve used in the first exemplary embodiment of the present invention.
- FIG. 5 details a thrust-dynamic-pressure-fluid bearing used in the first exemplary of the present invention.
- FIG. 6 is an enlarged view of a lower portion of a motor used in a second exemplary embodiment of the present invention.
- FIG. 7 is a cross section of a motor used in third exemplary embodiment of the present invention.
- FIG. 8 is an enlarged view of a lower portion of the motor used in the third exemplary embodiment of the present invention.
- FIG. 9 is a cross section of a motor used in a fourth exemplary embodiment of the present invention.
- FIG. 10 is a cross section of a motor used in a fifth exemplary embodiment of the present invention.
- FIG. 11 is an enlarged view of an upper portion of the motor used in the fifth exemplary embodiment of the present invention.
- FIG. 12 is a cross section of a motor used in a sixth exemplary embodiment of the present invention.
- FIG. 13 is an enlarged view of an upper portion of the motor used in the sixth exemplary embodiment of the present invention.
- FIG. 14 is a cross section of a motor used in a seventh exemplary embodiment of the present invention.
- FIG. 15 is a cross section of a motor used in an eighth exemplary embodiment of the present invention.
- FIG. 16 is a cross section of a conventional motor.
- FIG. 1 is a cross section of a motor used in a first exemplary embodiment of the present invention.
- FIG. 2 is an enlarged view of an upper portion of the motor.
- FIG. 3 is an enlarged view of a lower portion of the motor.
- FIG. 4 details the inside of sleeve used in the first exemplary embodiment.
- FIG. 5 details the thrust-dynamic-pressure-fluid bearing used in the first exemplary embodiment.
- a shaft 1 is vertically fixed at the center of a bracket 4 , for which screw holes and protruded sections are provided so that the bracket can be mounted to the disc driving apparatus.
- a core holder 12 is also provided in the bracket 4 .
- a stator core 11 of coiled wires is mounted on the outer circumference of the core holder 12 so that the stator core 11 is situated opposite to a cylindrical rotor magnet 6 via a narrow clearance.
- Magnetic discs (not shown) are mounted on an outer circumference of a hub 3 .
- the cylindrical rotor magnet 6 is mounted via a cylindrical rotor frame 5 .
- a sleeve 2 is mounted on another circumference of the hub 3 .
- Grooves 17 are provided inside the sleeve 2 , the grooves 17 produce dynamic pressure of lubricating fluid (not shown) through rotation of the sleeve 2 .
- the sleeve 2 is rotatively supported by the fixed shaft 1 via lubricating fluid, and forms the radial dynamic-fluid-bearings R 1 and R 2 .
- a rotation thrust ring 8 On the upper end face of sleeve 2 , a rotation thrust ring 8 is fixed, and rotatively supported via the lubricating fluid by a thrust ring 7 which is fixed on the fixed shaft 1 , thereby forming a thrust-dynamic-pressure-fluid bearing A 1 .
- the rotation thrust ring 8 has grooves 18 which produce dynamic pressure in the lubricating fluid. These grooves 18 can be provided on the fixed thrust ring 7 instead of on the rotation thrust ring 8 .
- a rotation thrust ring 10 On the lower end face of sleeve 2 , a rotation thrust ring 10 is fixed, and rotatively supported via the lubricating fluid by a thrust ring 9 which is fixed to an end portion of bracket 4 , thereby forming a thrust-dynamic-pressure-fluid bearing A 2 .
- the rotation thrust ring 10 has grooves (similar to the grooves 18 of one rotation thrust ring 8 ) which produce dynamic pressure in the lubricating fluid. These grooves can be provided on fixed thrust ring 9 instead of on the thrust ring 10 .
- a seal member 13 is fixed to the sleeve 2 so as to sandwich the ring 8 between the seal member 13 and the sleeve 2 .
- a tapered centrifugal force seal 16 and an oil pool 30 are provided on the seal member 13 .
- the inner circumference of hub 3 faces the outer circumference of fixed thrust ring 7 via a small clearance 15 , this small clearance preferably ranging from 0.03 to 0.05 mm.
- a viscous seal 14 is formed on the inner circumference of hub 3 .
- the viscous seal 14 employs a screw to be rotated for drawing air in from the clean space 29 .
- An example of the viscous seal has the following structure and mechanism.
- the screw In a cylindrical space, the screw is provided on an inner or outer circumference that forms the cylindrical space.
- the screw rotates to produce pressure so that air flows from the clean space where the discs are disposed toward the thrust-dynamic-pressure-fluid bearing, whereby the mist of the lubricating fluid is prevented from splashing into the clean space 29 .
- centrifugal force seal 21 On the lower circumference of sleeve 2 , a tapered centrifugal force seal 21 is provided. An example of a mechanism of the centrifugal force seal is now will bedescribed.
- the centrifugal force is proportional to a radius from a rotating center, and based on this principle, when the motor is driven, the lubricating fluid flows toward the dynamic-pressure-fluid bearing by utilizing the taper. A liquid of the lubricating fluid is thus prevented from flowing out.
- the centrifugal force seal 21 is disposed on the outer circumference of the rotative sleeve 2 .
- the lower outer circumference of sleeve 2 faces the inner circumference of core holder 12 via a small clearance 20 , this small clearance preferably ranging from 0.03 to 0.05 mm.
- Another viscous seal 19 is formed on the lower outer circumference of sleeve 2 .
- the viscous seal 19 employs a screw that rotates to draw air in from the clean space 29 through the space where the stator core 11 and rotor magnet 6 are disposed.
- the above structure allows the centrifugal force seals 16 and 21 to prevent liquid lubricating fluid from flowing out, and allows the viscous seals 14 and 19 to prevent lubricating fluid mist from splashing out into the clean space.
- a small annular space is provided between the outer circumference of the ring 10 and the inner circumference of core holder 12 , whereby a surface tension seal 24 is formed to provide an oil seal. Further, an oil pool 22 is disposed on the core holder 12 . These arrangements reinforce the prevention of the flowing out of the lubricating fluid.
- the lubricating fluid is filled into the radial-dynamic-pressure-fluid bearings R 1 and R 2 as well as the thrust-dynamic-pressure-fluid bearings A 1 and A 2 when the spindle device is assembled.
- the lubricating fluid concentrates on the centers of R 1 , R 2 , A 1 and A 2 .
- surplus fluid does not have a constant flow, and sometimes splashes due to the centrifugal force.
- bubbles are incidentally entrapped in the lubricating fluid. The bubbles grow due to temperature changes, or concentrate and grow in a lower pressure section in the bearings due to the rotation. The growth of the bubbles pushes up the fluid to cause splashing.
- the spindle device of the present invention can prevent the fluid from flowing and splashing out into the clean space 29 thanks to a combination of the mist seal, oil seal and oil pool.
- FIG. 6 is an enlarged view of a lower portion of a motor used in the second exemplary embodiment of the present invention.
- grooves (not shown, but similar to the grooves 17 in FIG. 4) are provided inside the sleeve 52 . These grooves generate dynamic pressure through rotation.
- the sleeve 52 is rotatively supported via the lubricating fluid by the fixed shaft 1 , thereby forming the radial-dynamic-pressure-fluid bearing R 2 .
- This embodiment differs from the first exemplary embodiment only in the following point: a tapered centrifugal force seal 25 has a larger taper angle than that in the first exemplary embodiment.
- the tapered seal 25 is disposed as an oil seal on the lower outer circumference of the sleeve 52 .
- the fluid is subject to flowing out due to gravity.
- a larger taper angle is thus preferably employed for the centrifugal force seal 25 to expand the space. This structure further assures the prevention of fluid flow-out.
- FIG. 7 is a cross section of a motor used in the third exemplary embodiment of the present invention.
- FIG. 8 is an enlarged view of a lower portion of the motor.
- FIGS. 7 and 8 this embodiment differs from the first and second exemplary embodiments in the following points:
- the stator core 11 of coiled wires is mounted to a bracket 54
- a mount collar 62 is mounted at the center of an inner circumference of the bracket 54 .
- the shaft 1 is fixed at the center of the mount collar 62
- a thrust ring 60 is fixed at the end face of the mount collar 62 .
- Grooves for generating dynamic pressure are provided on either the thrust ring 60 or a rotating ring 10 mounted to the sleeve 52 .
- the thrust-dynamic-pressure-fluid bearing A 2 is formed by the fixed thrust ring 60 and the rotation thrust ring 10 via the lubricating fluid. This structure can also prevent the fluid from flowing out as already discussed in connection with the first and second exemplary embodiments.
- FIG. 9 is a cross section of a motor used in the fourth exemplary embodiment of the present invention.
- This embodiment differs from the first exemplary embodiment in the following points: On a bracket 104 , an airtight seal 26 is disposed to seal the screw holes and the like provided on the bracket 104 . A small annular space is provided between the inner circumference of hub 3 and the outer circumference of bracket 104 whereby a labyrinth seal 27 is formed to provide a mist seal.
- the labyrinth seal thus comprises a small clearance and an expansion room, this small clearance preferably ranging from 0.05 to 0.1 mm.
- a room 28 where the rotor core 11 coiled by wires and the rotor magnet 6 are disposed, is the expansion room, and the annular space between the hub 3 and the bracket 104 is the small clearance. Air flow energy is consumed in the expansion room 28 , and the air flow rate through the small clearance decreases substantially, which prohibits the mist of lubricating fluid from splashing into the clean space 29 .
- FIG. 10 is a cross section of a motor used in the fifth exemplary embodiment of the present invention.
- FIG. 11 is an enlarged view of an upper portion of the motor.
- a mount collar 212 is mounted to the inner center of a bracket 204 .
- a shaft 301 is vertically fixed at the center of the mount collar 212 .
- protrusion sections and screw holes are provided to mount the spindle device to the disc driving apparatus.
- a stator core 211 of coiled wires is mounted to face a rotor magnet 206 via a narrow clearance.
- Magnetic discs (not shown) are to be mounted on the outer circumference of a hub 203 .
- the cylindrical rotor magnet 206 is mounted to the inner circumference of hub 203 via a cylindrical rotor frame 205 .
- a magnetic shield panel 210 is mounted on the inner circumference of hub 203 .
- a sleeve 202 is mounted to another inner circumference of hub 203 .
- Grooves (not shown, but similar to grooves 17 in FIG. 4) are provided inside the sleeve 202 for generating dynamic pressure in lubricating fluid through rotation.
- the sleeve 202 is rotatively supported by the fixed shaft 301 via the lubricating fluid, and thereby forms radial-dynamic-pressure-fluid bearings R 201 and R 202 .
- a thrust ring 207 is mounted to a top screw 201 to be fixed so that the ring 207 can be kept coaxial with the shaft 301 .
- the fixed thrust ring 207 employs grooves on both sides for generating dynamic pressure in the lubricating fluid.
- a thrust bearing A 202 is formed and rotatively supported between the sleeve 202 and a lower face of the fixed thrust ring 207 via the lubricating fluid.
- a rotation thrust ring 208 is mounted to the sleeve 202 above the thrust ring 207 .
- a thrust-dynamic-pressure-fluid bearing A 201 is formed and rotatively supported between the upper face of thrust ring 207 and the lower face of thrust ring 208 via the lubricating fluid.
- top screw 201 faces the inner circumference of a member 209 for forming a viscous seal 213 via a small annular space 214 .
- the viscous seal 213 is provided above the rotation thrust ring 208 .
- a screw is provided inside the member 209 , and thereby forms the viscous seal 213 . The screw rotates to draw air in from the clean space 29 so that the viscous seal 213 can prevent the lubricating fluid from splashing.
- a small annular space 219 is formed between the sleeve 202 and the fixed thrust ring 207 , and is filled with the lubricating fluid, which is held by surface tension. Further a small annular space 220 is formed between the outer circumference of top screw 201 and the inner circumference of rotation thrust ring 208 . The small space 220 is filled with the lubricating fluid, which is held by surface tension.
- top screw 201 can be that of fixed shaft 301 .
- An oil pool 217 is disposed between the thrust ring 208 and the member 209 so that surplus fluid on the inner circumference of the ring 208 travels on the surface of the ring 208 to the oil pool 217 due to centrifugal force.
- a groove 218 facing the oil pool 217 is provided on the top screw 201 . If centrifugal force pushes the surplus fluid on the inner circumference of the ring 208 to flow out, the groove 218 can prevent the flow from traveling to the clean space 29 .
- the motor is kept upside down, the surplus fluid travels along the top screw 201 and reaches the head thereof. If the motor is driven in this attitude, the fluid will splash into the clean space; however, the groove 218 can block the surplus fluid from travelling down to the head.
- a tapered centrifugal force seal 225 is disposed on the lower outer circumference of sleeve 202 .
- the seal 225 is disposed on the outer circumference of the rotating body, i.e., sleeve 202 , to prevent the lubricating fluid from flowing out.
- An oil pool 221 is disposed between the sleeve 202 and the magnetic shield plate 210
- another oil pool 226 is disposed between the rotor frame 205 and the magnetic shield panel 210 .
- Surplus fluid in the lower part of sleeve 202 flows out to the outer circumference of sleeve 202 ; however, the flow is blocked by the centrifugal force seal 225 .
- the oil pool 221 can block the flow-out from the lower part of sleeve 202 . And yet, if the surplus fluid travels on the magnetic shield panel 210 due to centrifugal force accompanied by rotation, the oil pool 226 can block the flow from flowing out to the clean space 29 .
- a narrow clearance can be provided to the oil pools 221 and 226 so that the lubricating fluid can be held by surface tension even if the motor is repeatedly started and stopped.
- the oil pools 221 and 226 are, in addition to other seals, preventive measures against draining the fluid into the clean space 29 , and these oil pools further prevent the lubricating fluid from flowing out.
- FIG. 12 is a cross section of a motor used in the sixth exemplary embodiment of the present invention.
- FIG. 13 is an enlarged view of an upper portion of the motor.
- this embodiment differs from the fifth exemplary embodiment in the following points:
- a magnetic fluid seal holder 309 is fixed to the sleeve 202 .
- a magnetic fluid seal 314 is fixed to the holder 309 , and the seal 314 holds magnetic fluid 313 with magnetic force.
- the magnetic fluid seal 314 comprises the following elements:
- the magnetic fluid seal 314 is formed by being encircled with these elements.
- the magnetic fluid 313 as shown in FIG. 13, completely clogs a small clearance between the outer circumference of the top screw 201 and an end face of the magnetic member 316 opposite to the outer circumference.
- the following magnetic path is formed. Magnetic flux produced by the magnet 315 travels through the magnetic member 316 , magnetic fluid 313 and top screw 201 , and arrives at the magnet 315 again via a small clearance between the outer circumference of the top screw 201 and an end face of the magnetic member 317 opposite to the outer circumference.
- This magnetic path can hold the magnetic fluid 313 , whereby the mist of the lubricating fluid is prevented from splashing out from the inner rim of ring 208 into the clean space 29 .
- a room 318 formed by the seal 314 is substantially airtight, the magnetic fluid 313 could possibly be blown out due to a temperature change or a pressure difference.
- This possible blow-out can be avoided by the following measures: (a) decreasing the capacity of the airtight room 318 , and (b) providing a small annular clearance 220 between the ring 208 and the top screw 201 to obtain surface tension which can hold the lubricating fluid. The height of the lubricating fluid surface thus changes, which balances pressures, whereby the blow-out is avoided.
- the capacity of the airtight room 318 is preferably less than a capacity enclosed by the inner circumference of the rotation thrust ring and the outer circumference of the top screw.
- the top screw can be incorporated into the fixed shaft.
- FIG. 14 is a cross section of a motor used in the seventh exemplary embodiment of the present invention.
- an airtight seal 222 is disposed to seal the screw holes and the like provided in the bracket 304 .
- a small annular space is provided between the inner circumference of hub 203 and the outer circumference of bracket 304 whereby a labyrinth seal 223 is formed to provide a mist seal.
- an expansion room 224 where a stator core 211 and a rotor magnet 206 are disposed, consumes air flow, and the air flow rate through the labyrinth seal decreases substantially, which prevents the mist of lubricating fluid from splashing into the clean space 29 .
- FIG. 15 is a cross section of a motor used in the eighth exemplary embodiment of the present invention.
- this embodiment differs from the seventh exemplary embodiment in the following point: A magnetic fluid seal 314 is provided, which reinforces the preventive measures against the splash-out of the mist fluid from above the motor.
- combinations of mist seals, oil seals and oil pools can prevent the lubricating fluid from flowing out into the clean space, whereby a reliable spindle device can be realized.
- the mist seal prevents a mist of the lubricating fluid from splashing out, the oil seal prohibits the lubricating fluid per se from flowing out, and the oil pool is a measure to prevent surplus lubricating fluid from flowing out.
- the spindle device of the present invention can be used not only in the magnetic disc driving apparatus, but also other disc driving apparatuses for optical discs, CD-ROMs, MDs, DVDs and others. Further, the spindle device also can be used in other apparatuses, and therefore, the spindle device has a great advantage in industrial applications.
Abstract
Description
- The present invention relates to a spindle device to be mounted to a disc driving apparatus for driving, e.g., discs, and more particularly to a structure of a spindle motor of an outer rotor type, which is formed by fixing rotor magnets within a hub that clamps magnetic discs.
- One of the distinctive trends in computer systems is that memory capacities are becoming larger and larger due to the extending of computer networks, popularity of engineering work stations, utilization of data bases and the like. Further, the most common magnetic disc driving apparatus built in computer systems as a memory apparatus has been changed from the 5.25-inch disc drive to the 3.5-inch disc drive, which proves the demand for memory apparatus to be made more compact and slim in size. The demands of magnetic disc driving apparatus, such as the demands for larger capacity, smaller and slimmer size, naturally lead to demands for a spindle motor (hereinafter called simply a “motor”) mounted to the disc driving apparatus to be of higher accuracy and smaller size. The higher accuracy, among others, is strongly demanded.
- Along with the technology advancement, a memory capacity of the magnetic disc has increased, and the track density of discs can be 8000 TPI (tracks per inch)-10000 TPI, which is converted to a track pitch as fine as 3 μm. The performance required of the motor mounted to the apparatus is to always accurately trace each track having such fine track pitch. This kind of motor has employed ball bearings in general; however, the rotation of ball bearings inevitably generates vibration. The level of vibration is measured to be as fine as ca. 0.15 μm based on NRRO (Non Repeatable Run Out), which is non repeatable sway of the hub of the motor. This vibration level is the minimum possible value for the ball bearings. When this vibration occurs, a magnetic head deviates from a track by the displacement component due to the vibration. This deviation has a harmful influence on read/write operation, and the conventional apparatus employing the ball bearings thus allows almost no margin to meet the required performance.
- Recently, a motor has been proposed in order to improve the accuracy, lower the noise level, and extend the product life. The motor comprises a fixed shaft, a sleeve that is supported and rotated by the shaft and a radial-dynamic-pressure-fluid bearing, or the motor comprises a fixed sleeve, a rotating shaft that is supported and rotated by the sleeve and the radial-dynamic-pressure-fluid bearing.
- The motor employing the dynamic-pressure-fluid bearing is disclosed in Japanese Patent Application unexamined publication No. H06-178489.
- FIG. 16 is a cross sectional view of this conventional motor. In FIG. 16, a
shaft 501 is vertically fixed at the center of abracket 504, and astator core 510 with wires wound thereon is mounted to thebracket 504. Arotor magnet 506 is fixed to arotor frame 505 so that the rotor magnet faces thestator core 510. Therotor frame 505 is mounted to thehub 503. Abushing 511 is fixed at a lower section of an inner rim of thehub 503, and anotherbushing 512 is mounted to an outer rim of thebracket 504. The bushing 511 faces the bushing 512 with a clearance in-between. The magnetic discs (not shown) are to be mounted around thehub 503. - Grooves (not shown) are provided inside of a
sleeve 502, the grooves produce dynamic pressure of lubricating fluid by the rotation of thesleeve 502, which is rotatively supported by thefixed shaft 501 via lubricating fluid. Radial-dynamic-pressure-fluid bearings R501 and R502 are thus constructed. Axial dynamic pressure bearings A501 and A502 comprise both end faces of a fixedthrust ring 507, a lower face ofrotation thrust ring 508 and an upper face of thesleeve 502. Agroove 541 is provided on an outer circumference of a cap 509, and anothergroove 542 is provided on an inner circumference of therotation thrust ring 508. The lower rim ofgroove 541 is disposed at substantially the center ofgroove 542, and the upper rim ofgroove 542 is disposed at substantially the center ofgroove 541. The upper and lower rims of eachgroove - The conventional motor employing the above dynamic-pressure-fluid bearing has a possible problem that the lubricating fluid might splash into a space where the magnetic discs are disposed. In this space, a magnetic head reads/writes data from/to the magnetic disc with little clearance between the head and disc. The space thus must be kept utmost clean because if the lubricating fluid splashes or flows into the space, serious problems such as a head crush, a head absorption, etc. will occur. (Hereinafter the above space is called the “clean space”.)
- The above conventional motor has provided a countermeasure against lubricating oil splashes by forming an oil pool using the
grooves - The present invention aims to provide a reliable spindle device which avoids inconvenience such as a head crush or a head absorption by disposing a mist seal between the thrust-dynamic-pressure-fluid bearing and the clean space where magnetic discs are disposed. The mist seal prevents a mist of lubricating fluid from flowing out into the clean space where magnetic discs are disposed.
- The spindle device of the present invention comprises the following elements:
- (a) a bracket comprising a fixed shaft and a stator core on which wire is wound,
- (b) a hub to which discs are mounted,
- (c) a rotor magnet mounted to the hub and facing the stator core,
- (d) a sleeve fixed to the hub and rotatively supported by the fixed shaft via the lubricating fluid,
- (e) thrust-dynamic-pressure-fluid bearings disposed on both end faces of the sleeve, and
- (f) a mist seal such as a viscous seal, a labyrinth seal, a magnetic fluid seal or the like disposed between the thrust-dynamic-pressure-fluid bearing and the clean space where the discs are disposed, and the mist seal blocks the mist of lubricating fluid from flowing out.
- The above structure can prevent the mist of lubricating fluid from splashing into the clean space by using the mist seal.
- Further, an oil seal that prevents the lubricating fluid per se from flowing out, and an oil pool that prevents surplus lubricating fluid from flowing out are combined, whereby liquid lubricating fluid is prevented from flowing out into the clean space. This structure can further enhance a reliability of the spindle device.
- The spindle device according to the present invention has an advantageous sealing structure that can prevent the lubricating fluid of the dynamic-pressure-fluid bearing from splashing out into the clean space. There are the following sealing mechanisms between the dynamic-pressure-lubricating-fluid-bearing and the clean space: oil seal (surface tension seal, centrifugal force seal) and mist seal (viscous seal, magnetic fluid seal, labyrinth seal). The dynamic-pressure-lubricating-fluid-bearing holds the lubricating fluid using the surface tension seal, and the centrifugal force seal restores the lubricating fluid, further, the mist seal prevents the mist of lubricating fluid from splashing. This sealing process effectively prevents the lubricating fluid from flowing and splashing out into the clean space. A part of this arrangement can be omitted depending on the motor construction.
- The oil pool and grooves in addition to the above sealing process contribute to preventing the fluid from flowing as well as splashing out not only in a continuous operation but also in an intermittent operation, at rest at a high temperature or with a change in orientation.
- The thrust-dynamic-pressure-fluid bearings are disposed on both the upper and lower sections of the radial-dynamic-pressure-fluid bearing, whereby a longer bearing span for the radial-dynamic-pressure-fluid bearing can be obtained, and the rigidity is increased. As a result, the dynamic-pressure-fluid bearing can be well-balanced.
- Since the spindle device of the present invention allows no flow-out of the lubricating fluid, the bearing is always filled with the lubricating fluid, which substantially extends a life span of the magnetic disc driving apparatus.
- FIG. 1 is a cross section of a motor used in a first exemplary embodiment of the present invention.
- FIG. 2 is an enlarged view of an upper portion of the motor used in the first exemplary embodiment of the present invention.
- FIG. 3 is an enlarged view of a lower portion of the motor used in the first exemplary embodiment of the present invention.
- FIG. 4 details the inside of a sleeve used in the first exemplary embodiment of the present invention.
- FIG. 5 details a thrust-dynamic-pressure-fluid bearing used in the first exemplary of the present invention.
- FIG. 6 is an enlarged view of a lower portion of a motor used in a second exemplary embodiment of the present invention.
- FIG. 7 is a cross section of a motor used in third exemplary embodiment of the present invention.
- FIG. 8 is an enlarged view of a lower portion of the motor used in the third exemplary embodiment of the present invention.
- FIG. 9 is a cross section of a motor used in a fourth exemplary embodiment of the present invention.
- FIG. 10 is a cross section of a motor used in a fifth exemplary embodiment of the present invention.
- FIG. 11 is an enlarged view of an upper portion of the motor used in the fifth exemplary embodiment of the present invention.
- FIG. 12 is a cross section of a motor used in a sixth exemplary embodiment of the present invention.
- FIG. 13 is an enlarged view of an upper portion of the motor used in the sixth exemplary embodiment of the present invention.
- FIG. 14 is a cross section of a motor used in a seventh exemplary embodiment of the present invention.
- FIG. 15 is a cross section of a motor used in an eighth exemplary embodiment of the present invention.
- FIG. 16 is a cross section of a conventional motor.
- Exemplary embodiments of the present invention are detailed hereinafter by referring to the attached drawings.
- FIG. 1 is a cross section of a motor used in a first exemplary embodiment of the present invention. FIG. 2 is an enlarged view of an upper portion of the motor. FIG. 3 is an enlarged view of a lower portion of the motor. FIG. 4 details the inside of sleeve used in the first exemplary embodiment. FIG. 5 details the thrust-dynamic-pressure-fluid bearing used in the first exemplary embodiment.
- In FIG. 1 through FIG. 5, a
shaft 1 is vertically fixed at the center of abracket 4, for which screw holes and protruded sections are provided so that the bracket can be mounted to the disc driving apparatus. Acore holder 12 is also provided in thebracket 4. Astator core 11 of coiled wires is mounted on the outer circumference of thecore holder 12 so that thestator core 11 is situated opposite to acylindrical rotor magnet 6 via a narrow clearance. - Magnetic discs (not shown) are mounted on an outer circumference of a
hub 3. On the inner circumference of thehub 3, thecylindrical rotor magnet 6 is mounted via acylindrical rotor frame 5. Asleeve 2 is mounted on another circumference of thehub 3.Grooves 17 are provided inside thesleeve 2, thegrooves 17 produce dynamic pressure of lubricating fluid (not shown) through rotation of thesleeve 2. Thesleeve 2 is rotatively supported by the fixedshaft 1 via lubricating fluid, and forms the radial dynamic-fluid-bearings R1 and R2. - On the upper end face of
sleeve 2, arotation thrust ring 8 is fixed, and rotatively supported via the lubricating fluid by athrust ring 7 which is fixed on the fixedshaft 1, thereby forming a thrust-dynamic-pressure-fluid bearing A1. The rotation thrustring 8 hasgrooves 18 which produce dynamic pressure in the lubricating fluid. Thesegrooves 18 can be provided on the fixedthrust ring 7 instead of on the rotation thrustring 8. On the lower end face ofsleeve 2, arotation thrust ring 10 is fixed, and rotatively supported via the lubricating fluid by athrust ring 9 which is fixed to an end portion ofbracket 4, thereby forming a thrust-dynamic-pressure-fluid bearing A2. The rotation thrustring 10 has grooves (similar to thegrooves 18 of one rotation thrust ring 8) which produce dynamic pressure in the lubricating fluid. These grooves can be provided on fixedthrust ring 9 instead of on thethrust ring 10. - On the upper side of the rotation thrust
ring 8, aseal member 13 is fixed to thesleeve 2 so as to sandwich thering 8 between theseal member 13 and thesleeve 2. On theseal member 13, a taperedcentrifugal force seal 16 and anoil pool 30 are provided. The inner circumference ofhub 3 faces the outer circumference offixed thrust ring 7 via asmall clearance 15, this small clearance preferably ranging from 0.03 to 0.05 mm. On the inner circumference ofhub 3, aviscous seal 14 is formed. Theviscous seal 14 employs a screw to be rotated for drawing air in from theclean space 29. - An example of the viscous seal has the following structure and mechanism. In a cylindrical space, the screw is provided on an inner or outer circumference that forms the cylindrical space. The screw rotates to produce pressure so that air flows from the clean space where the discs are disposed toward the thrust-dynamic-pressure-fluid bearing, whereby the mist of the lubricating fluid is prevented from splashing into the
clean space 29. - On the lower circumference of
sleeve 2, a taperedcentrifugal force seal 21 is provided. An example of a mechanism of the centrifugal force seal is now will bedescribed. The centrifugal force is proportional to a radius from a rotating center, and based on this principle, when the motor is driven, the lubricating fluid flows toward the dynamic-pressure-fluid bearing by utilizing the taper. A liquid of the lubricating fluid is thus prevented from flowing out. - For a better effect, the
centrifugal force seal 21 is disposed on the outer circumference of therotative sleeve 2. - The lower outer circumference of
sleeve 2 faces the inner circumference ofcore holder 12 via asmall clearance 20, this small clearance preferably ranging from 0.03 to 0.05 mm. Anotherviscous seal 19 is formed on the lower outer circumference ofsleeve 2. Theviscous seal 19 employs a screw that rotates to draw air in from theclean space 29 through the space where thestator core 11 androtor magnet 6 are disposed. - The above structure allows the centrifugal force seals16 and 21 to prevent liquid lubricating fluid from flowing out, and allows the
viscous seals - A small annular space is provided between the outer circumference of the
ring 10 and the inner circumference ofcore holder 12, whereby asurface tension seal 24 is formed to provide an oil seal. Further, anoil pool 22 is disposed on thecore holder 12. These arrangements reinforce the prevention of the flowing out of the lubricating fluid. - The lubricating fluid is filled into the radial-dynamic-pressure-fluid bearings R1 and R2 as well as the thrust-dynamic-pressure-fluid bearings A1 and A2 when the spindle device is assembled. When the motor is rotated, the lubricating fluid concentrates on the centers of R1, R2, A1 and A2. However, surplus fluid does not have a constant flow, and sometimes splashes due to the centrifugal force. When the spindle device is assembled, bubbles are incidentally entrapped in the lubricating fluid. The bubbles grow due to temperature changes, or concentrate and grow in a lower pressure section in the bearings due to the rotation. The growth of the bubbles pushes up the fluid to cause splashing. When the spindle device is left at a high temperature atmosphere for a long period, the lubricating fluid is more likely to leak. In these cases, the spindle device of the present invention can prevent the fluid from flowing and splashing out into the
clean space 29 thanks to a combination of the mist seal, oil seal and oil pool. - FIG. 6 is an enlarged view of a lower portion of a motor used in the second exemplary embodiment of the present invention. In FIG. 6, grooves (not shown, but similar to the
grooves 17 in FIG. 4) are provided inside thesleeve 52. These grooves generate dynamic pressure through rotation. Thesleeve 52 is rotatively supported via the lubricating fluid by the fixedshaft 1, thereby forming the radial-dynamic-pressure-fluid bearing R2. This embodiment differs from the first exemplary embodiment only in the following point: a taperedcentrifugal force seal 25 has a larger taper angle than that in the first exemplary embodiment. The taperedseal 25 is disposed as an oil seal on the lower outer circumference of thesleeve 52. In the lower part ofsleeve 52, in particular, the fluid is subject to flowing out due to gravity. A larger taper angle is thus preferably employed for thecentrifugal force seal 25 to expand the space. This structure further assures the prevention of fluid flow-out. - FIG. 7 is a cross section of a motor used in the third exemplary embodiment of the present invention. FIG. 8 is an enlarged view of a lower portion of the motor.
- In FIGS. 7 and 8, this embodiment differs from the first and second exemplary embodiments in the following points: The
stator core 11 of coiled wires is mounted to abracket 54, and amount collar 62 is mounted at the center of an inner circumference of thebracket 54. Theshaft 1 is fixed at the center of themount collar 62, and athrust ring 60 is fixed at the end face of themount collar 62. Grooves for generating dynamic pressure are provided on either thethrust ring 60 or arotating ring 10 mounted to thesleeve 52. The thrust-dynamic-pressure-fluid bearing A2 is formed by the fixedthrust ring 60 and therotation thrust ring 10 via the lubricating fluid. This structure can also prevent the fluid from flowing out as already discussed in connection with the first and second exemplary embodiments. - FIG. 9 is a cross section of a motor used in the fourth exemplary embodiment of the present invention.
- This embodiment differs from the first exemplary embodiment in the following points: On a
bracket 104, anairtight seal 26 is disposed to seal the screw holes and the like provided on thebracket 104. A small annular space is provided between the inner circumference ofhub 3 and the outer circumference ofbracket 104 whereby alabyrinth seal 27 is formed to provide a mist seal. - In general, the labyrinth seal thus comprises a small clearance and an expansion room, this small clearance preferably ranging from 0.05 to 0.1 mm. Namely, a
room 28, where therotor core 11 coiled by wires and therotor magnet 6 are disposed, is the expansion room, and the annular space between thehub 3 and thebracket 104 is the small clearance. Air flow energy is consumed in theexpansion room 28, and the air flow rate through the small clearance decreases substantially, which prohibits the mist of lubricating fluid from splashing into theclean space 29. - FIG. 10 is a cross section of a motor used in the fifth exemplary embodiment of the present invention. FIG. 11 is an enlarged view of an upper portion of the motor.
- In FIGS. 10 and 11, a
mount collar 212 is mounted to the inner center of abracket 204. Ashaft 301 is vertically fixed at the center of themount collar 212. On thebracket 204, protrusion sections and screw holes are provided to mount the spindle device to the disc driving apparatus. On the outer circumference ofbracket 204, astator core 211 of coiled wires is mounted to face arotor magnet 206 via a narrow clearance. - Magnetic discs (not shown) are to be mounted on the outer circumference of a
hub 203. Thecylindrical rotor magnet 206 is mounted to the inner circumference ofhub 203 via acylindrical rotor frame 205. On the inner circumference ofhub 203, amagnetic shield panel 210 is mounted for preventing leakage of magnetic flux. Asleeve 202 is mounted to another inner circumference ofhub 203. Grooves (not shown, but similar togrooves 17 in FIG. 4) are provided inside thesleeve 202 for generating dynamic pressure in lubricating fluid through rotation. Thesleeve 202 is rotatively supported by the fixedshaft 301 via the lubricating fluid, and thereby forms radial-dynamic-pressure-fluid bearings R201 and R202. - On the upper end of the fixed
shaft 301, athrust ring 207 is mounted to atop screw 201 to be fixed so that thering 207 can be kept coaxial with theshaft 301. The fixedthrust ring 207 employs grooves on both sides for generating dynamic pressure in the lubricating fluid. A thrust bearing A202 is formed and rotatively supported between thesleeve 202 and a lower face of the fixedthrust ring 207 via the lubricating fluid. Arotation thrust ring 208 is mounted to thesleeve 202 above thethrust ring 207. A thrust-dynamic-pressure-fluid bearing A201 is formed and rotatively supported between the upper face ofthrust ring 207 and the lower face ofthrust ring 208 via the lubricating fluid. - The outer circumference of
top screw 201 faces the inner circumference of amember 209 for forming aviscous seal 213 via a smallannular space 214. Theviscous seal 213 is provided above therotation thrust ring 208. A screw is provided inside themember 209, and thereby forms theviscous seal 213. The screw rotates to draw air in from theclean space 29 so that theviscous seal 213 can prevent the lubricating fluid from splashing. - A small
annular space 219 is formed between thesleeve 202 and the fixedthrust ring 207, and is filled with the lubricating fluid, which is held by surface tension. Further a smallannular space 220 is formed between the outer circumference oftop screw 201 and the inner circumference ofrotation thrust ring 208. Thesmall space 220 is filled with the lubricating fluid, which is held by surface tension. - This surface tension prevents the lubricating fluid from flowing out, and further prevents the mist thereof from splashing above the
rotation thrust ring 208. The outer circumference oftop screw 201 can be that of fixedshaft 301. - An
oil pool 217 is disposed between thethrust ring 208 and themember 209 so that surplus fluid on the inner circumference of thering 208 travels on the surface of thering 208 to theoil pool 217 due to centrifugal force. Agroove 218 facing theoil pool 217 is provided on thetop screw 201. If centrifugal force pushes the surplus fluid on the inner circumference of thering 208 to flow out, thegroove 218 can prevent the flow from traveling to theclean space 29. When the motor is kept upside down, the surplus fluid travels along thetop screw 201 and reaches the head thereof. If the motor is driven in this attitude, the fluid will splash into the clean space; however, thegroove 218 can block the surplus fluid from travelling down to the head. - A tapered
centrifugal force seal 225 is disposed on the lower outer circumference ofsleeve 202. For better effect, theseal 225 is disposed on the outer circumference of the rotating body, i.e.,sleeve 202, to prevent the lubricating fluid from flowing out. Anoil pool 221 is disposed between thesleeve 202 and themagnetic shield plate 210, and anotheroil pool 226 is disposed between therotor frame 205 and themagnetic shield panel 210. Surplus fluid in the lower part ofsleeve 202 flows out to the outer circumference ofsleeve 202; however, the flow is blocked by thecentrifugal force seal 225. If the surplus fluid still travels on the outer circumference ofsleeve 202 to flow out, theoil pool 221 can block the flow-out from the lower part ofsleeve 202. And yet, if the surplus fluid travels on themagnetic shield panel 210 due to centrifugal force accompanied by rotation, theoil pool 226 can block the flow from flowing out to theclean space 29. A narrow clearance can be provided to the oil pools 221 and 226 so that the lubricating fluid can be held by surface tension even if the motor is repeatedly started and stopped. - The oil pools221 and 226 are, in addition to other seals, preventive measures against draining the fluid into the
clean space 29, and these oil pools further prevent the lubricating fluid from flowing out. - FIG. 12 is a cross section of a motor used in the sixth exemplary embodiment of the present invention. FIG. 13 is an enlarged view of an upper portion of the motor. In FIGS. 12 and 13, this embodiment differs from the fifth exemplary embodiment in the following points: Above the
rotation thrust ring 208, a magneticfluid seal holder 309 is fixed to thesleeve 202. Amagnetic fluid seal 314 is fixed to theholder 309, and theseal 314 holdsmagnetic fluid 313 with magnetic force. - The
magnetic fluid seal 314 comprises the following elements: - (a) a ring-
shape magnet 315 having N and S poles on respective ends; - (b) ring-shape
magnetic members shape magnet 315; and - (c)
magnetic fluid 313. - The
magnetic fluid seal 314 is formed by being encircled with these elements. - The
magnetic fluid 313, as shown in FIG. 13, completely clogs a small clearance between the outer circumference of thetop screw 201 and an end face of themagnetic member 316 opposite to the outer circumference. In this case, the following magnetic path is formed. Magnetic flux produced by themagnet 315 travels through themagnetic member 316,magnetic fluid 313 andtop screw 201, and arrives at themagnet 315 again via a small clearance between the outer circumference of thetop screw 201 and an end face of themagnetic member 317 opposite to the outer circumference. This magnetic path can hold themagnetic fluid 313, whereby the mist of the lubricating fluid is prevented from splashing out from the inner rim ofring 208 into theclean space 29. - Because a
room 318 formed by theseal 314 is substantially airtight, themagnetic fluid 313 could possibly be blown out due to a temperature change or a pressure difference. This possible blow-out can be avoided by the following measures: (a) decreasing the capacity of theairtight room 318, and (b) providing a smallannular clearance 220 between thering 208 and thetop screw 201 to obtain surface tension which can hold the lubricating fluid. The height of the lubricating fluid surface thus changes, which balances pressures, whereby the blow-out is avoided. The capacity of theairtight room 318 is preferably less than a capacity enclosed by the inner circumference of the rotation thrust ring and the outer circumference of the top screw. The top screw can be incorporated into the fixed shaft. - FIG. 14 is a cross section of a motor used in the seventh exemplary embodiment of the present invention. In FIG. 14, on a
bracket 304, anairtight seal 222 is disposed to seal the screw holes and the like provided in thebracket 304. A small annular space is provided between the inner circumference ofhub 203 and the outer circumference ofbracket 304 whereby alabyrinth seal 223 is formed to provide a mist seal. In the same manner as the fourth exemplary embodiment shows, anexpansion room 224, where astator core 211 and arotor magnet 206 are disposed, consumes air flow, and the air flow rate through the labyrinth seal decreases substantially, which prevents the mist of lubricating fluid from splashing into theclean space 29. - FIG. 15 is a cross section of a motor used in the eighth exemplary embodiment of the present invention. In FIG. 15, this embodiment differs from the seventh exemplary embodiment in the following point: A
magnetic fluid seal 314 is provided, which reinforces the preventive measures against the splash-out of the mist fluid from above the motor. - According to the present invention, combinations of mist seals, oil seals and oil pools can prevent the lubricating fluid from flowing out into the clean space, whereby a reliable spindle device can be realized. The mist seal prevents a mist of the lubricating fluid from splashing out, the oil seal prohibits the lubricating fluid per se from flowing out, and the oil pool is a measure to prevent surplus lubricating fluid from flowing out.
- The spindle device of the present invention can be used not only in the magnetic disc driving apparatus, but also other disc driving apparatuses for optical discs, CD-ROMs, MDs, DVDs and others. Further, the spindle device also can be used in other apparatuses, and therefore, the spindle device has a great advantage in industrial applications.
- Although illustrated and described herein with reference to certain specific embodiments, the present invention is not limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.
Claims (20)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US09/781,425 US6301074B2 (en) | 1997-09-12 | 2001-02-13 | Spindle device having a dynamic-pressure-fluid bearing |
US09/931,411 US6404586B2 (en) | 1997-09-12 | 2001-08-17 | Spindle device having a dynamic-pressure-fluid bearing |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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JP9-248037 | 1997-09-12 | ||
JP24803797 | 1997-09-12 | ||
US09/151,734 US6219199B1 (en) | 1997-09-12 | 1998-09-11 | Spindle device having a dynamic-pressure-fluid bearing |
US09/781,425 US6301074B2 (en) | 1997-09-12 | 2001-02-13 | Spindle device having a dynamic-pressure-fluid bearing |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US09/151,734 Division US6219199B1 (en) | 1997-09-12 | 1998-09-11 | Spindle device having a dynamic-pressure-fluid bearing |
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US09/931,411 Division US6404586B2 (en) | 1997-09-12 | 2001-08-17 | Spindle device having a dynamic-pressure-fluid bearing |
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US20010005296A1 true US20010005296A1 (en) | 2001-06-28 |
US6301074B2 US6301074B2 (en) | 2001-10-09 |
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US09/151,734 Expired - Lifetime US6219199B1 (en) | 1997-09-12 | 1998-09-11 | Spindle device having a dynamic-pressure-fluid bearing |
US09/781,425 Expired - Lifetime US6301074B2 (en) | 1997-09-12 | 2001-02-13 | Spindle device having a dynamic-pressure-fluid bearing |
US09/931,411 Expired - Fee Related US6404586B2 (en) | 1997-09-12 | 2001-08-17 | Spindle device having a dynamic-pressure-fluid bearing |
Family Applications Before (1)
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US09/151,734 Expired - Lifetime US6219199B1 (en) | 1997-09-12 | 1998-09-11 | Spindle device having a dynamic-pressure-fluid bearing |
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US09/931,411 Expired - Fee Related US6404586B2 (en) | 1997-09-12 | 2001-08-17 | Spindle device having a dynamic-pressure-fluid bearing |
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US (3) | US6219199B1 (en) |
CN (1) | CN1089962C (en) |
SG (1) | SG92616A1 (en) |
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1998
- 1998-09-02 SG SG9803398A patent/SG92616A1/en unknown
- 1998-09-11 US US09/151,734 patent/US6219199B1/en not_active Expired - Lifetime
- 1998-09-11 CN CN98119175A patent/CN1089962C/en not_active Expired - Lifetime
-
2001
- 2001-02-13 US US09/781,425 patent/US6301074B2/en not_active Expired - Lifetime
- 2001-08-17 US US09/931,411 patent/US6404586B2/en not_active Expired - Fee Related
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US6741007B2 (en) * | 2001-07-27 | 2004-05-25 | Beacon Power Corporation | Permanent magnet motor assembly having a device and method of reducing parasitic losses |
US6746151B2 (en) | 2002-01-14 | 2004-06-08 | Seagate Technology Llc | Parallel capillary seal for a disk drive |
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US8130086B2 (en) * | 2007-06-07 | 2012-03-06 | Samsung Electro-Mechanics Co., Ltd. | Linear vibration generator |
Also Published As
Publication number | Publication date |
---|---|
CN1089962C (en) | 2002-08-28 |
SG92616A1 (en) | 2002-11-19 |
US6301074B2 (en) | 2001-10-09 |
US6219199B1 (en) | 2001-04-17 |
US6404586B2 (en) | 2002-06-11 |
US20020003678A1 (en) | 2002-01-10 |
CN1211846A (en) | 1999-03-24 |
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