`United States Patent
`Dunfield et al.
`
`i»
`
`US005694268A
`(11) Patent Number:
`[45] Date of Patent:
`
`5,694,268
`Dec. 2, 1997
`
`[54] SPINDLE MOTOR HAVING OVERMOLDED
`STATOR
`Inventors: John Charles Dunfield, Santa Cruz;
`.
`cumer Karl Heine, Aptos, both of
`’
`
`[75]
`
`.
`[73] Assignee: Seagate Technology, Inc., Scotts
`Valley, Calif.
`
`[21] Appl. No.: 550,175
`
`[22] Filed:
`
`Oct. 30, 1995
`
`Related U.S. Application Data
`oo.
`[63] Continuation-in-part of Ser. No. 386,883, Feb. 10, 1995.
`6
`.
`[52]
`Tint. CLS occcccsscenee G11B 17/02; OK524;
`[52] US. C1.ceeeecnsesccnsecnnesenneenes 360/98.07; 360/99.08;
`310/67 R; 310/51; 310/254
`[58] Field of Search o....ssccsccseessen 360/97.01, 98.01,
`360/98.07, 98.08, 99.04, 99.08-99.12; 310/51,
`67R,254
`
`:
`
`[56]
`
`5,079,466
`1/1992 Jomes cecrseccssccesvncvscceseeeseerecereeee 310/91
`5,097,366
`3/1992 Ueki et al.
`vee 360/97.2
`5,126,612
`6/1992 Girault......
`vee 310/90.5
`520786 woo Frage seseees
`“ 50eee
`F
`gawa ..
`oes
`5.235.227
`8/1993 Fazekas ........
`"310/51
`5,241,229
`8/1993 Katakura et al.
`csscsssscsssssssssneee 310/51
`5,352,947 10/1994 MacLeod .........
`. 360/98.07
`5,367,418
`11/1994 Chessman et al.
`.. 360/99.12
`5,376,850 12/1994 Elsing et al.
`.ssssssssosssssssssssnssean 310/67
`5,457,588 10/1995 Hattori et al. osccsscessseseen: 360/99.08
`
`5/1996 Yamada et al. escosscecssecees 360/98.07
`5,519,270
`11/1996 Dunfield et ab. ccc 360/99.08
`5,579,188
`
`
`
`FOREIGN PATENT DOCUMENTS
`TIOZT3 YO/1967 Canada ceeceessscessecccsssnneseeeenene 310/70
`3-89838 (A)
`4/1991
`Japan .
`4-168942
`(AA)
`4.251342 (A)
`Japan.
`9/1992
`Japan .
`4-364340 (A) 12/1992
`2154072
`8/1985 United Kingdom .
`
`6/1992
`
`Japan .
`
`.
`;
`Primary Examiner—Jefferson Evans
`Attorney, Agent, or Firm—Westman, Champlin & Kelly,
`PA.
`ABSTRACT
`7
`s
`[57]
`Cc
`References Cited
`A disc drive spindle motor for rotating at least one disc in a
`ATENT
`CUMENT.
`data storage device includes a base, a shaft, a rotor and a
`s
`US.P
`DO
`stator. A bearing interconnects the rotor with the shaft and
`1,688,891 LO/1928 Spreen ......sssssessseessnssesersesseaeee 310/51
`allows the rotor to rotate about the shaft. An overmold
`3,438,407
`4/1969 Frohmuller etal.
`310/51
`
`3,546,504 12/1970 Janssen etal.....
`encapsulates at least a portion of the stator and provides the
`a 310/51
`4,268,233
`5/1981 Femstrém ..............0
`
`stator with a smooth external surface. The overmold
`-- 418270
`4,647,803
`3/1987 von der Heide et al.
`“ee areas
`mechanically isolates the stator from the base and damps
`4,672,250—G/19B7 Seitz «0...ceeeccsccnees
`
`“
`sympathetic vibrations in the stator structure to reduce the
`a 310/91
`.
`:
`.
`os
`:
`4,760,299
`7/1988 Dickie et al.
`.....
`. 310/194
`generation of acoustic noise in the storage device.
`4,816,710
`3/1989 Silvaggioet al.
`4,823,034
`4/1989 Wrobel
`.............
`4,965,476 LO/E99O Lim ....esssessesssssensseesseassnenceesscenes 310/51
`
`31 Claims, 14 Drawing Sheets
`
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`Am. Hondav. IV II - IPR2018-00619
`PETHONDA_1013-0001
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0001
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`
`
`U.S. Patent
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`5,694,268
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`Dec. 2, 1997
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`U.S. Patent
`
`Dec. 2, 1997
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`Sheet 3 of 14
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`US. Patent
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`Dec. 2, 1997
`
`Sheet 5 of 14
`
`5,694,268
`
`
`
`Am. Hondav. IV II - IPR2018-00619
`PETHONDA_1013-0006
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0006
`
`
`
`Dec. 2, 1997
`
`Sheet 6 of 14
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`5,694,268
`
`U.S. Patent
`
`Am. Hondav. IV II - IPR2018-00619
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`PET HONDA_ 1013-0007
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0007
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`
`
`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 7 of 14
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`5,694,268
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`Dec.2, 1997
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`Sheet 8 of 14
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0009
`
`
`
`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 9 of 14
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`5,694,268
`
`
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`Am. Hondav. IV II - IPR2018-00619
`PETHONDA_1013-0010
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0010
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`US. Patent
`
`Dec. 2, 1997
`
`Sheet 10 of 14
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`5,694,268
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`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 11 of 14
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`5,694,268
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`Am. Hondav. IV II - IPR2018-00619
`PETHONDA_1013-0012
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0012
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`
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`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 12 of 14
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`5,694,268
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`US. Patent
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`Dec. 2, 1997
`
`Sheet 13 of 14
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`5,694,268
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`
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`Am. Hondav. IV II - IPR2018-00619
`PETHONDA_1013-0014
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0014
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`U.S. Patent
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`Dec. 2, 1997
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`Sheet 14 of 14
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`5,694,268
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`Am. Honda v. IV II - IPR2018-00619
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`5,694,268
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`1
`SPINDLE MOTOR HAVING OVERMOLDED
`STATOR
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application is a continuation-in-part of U.S. Ser. No.
`08/386,883. filed Feb. 10, 1995.
`BACKGROUND OF THE INVENTION
`
`Thepresent invention relates generally to the field of disc
`drive spindle motors for data storage devices and, more
`particularly, to a spindle motor in which the stator has a
`resilient overmold to isolate the stator from a base of the
`storage device.
`Disc drive data storage devices, known as “Winchester”
`type disc drives, are well-known in the industry. In a
`Winchester disc drive, digital data are written to and read
`from a thin layer of magnetizable material on the surface of
`rotating discs. Write and read operations are performed
`through a transducer which is carried in a slider body. The
`slider and transducer are sometimescollectively referred to
`as a head, and typically a single head is associated with each
`disc surface. The heads are selectively moved under the
`control of electronic circuitry to any one of a plurality of
`circular, concentric data tracks on the disc surface by an
`actuator device. Each slider body includes a self-acting
`hydrodynamic air bearing surface. As the disc rotates, the
`disc drags air beneath the air bearing surface, which devel-
`opsa lifting force that causes the slider to lift and fly several
`microinches above the disc surface.
`
`In the current generation of disc drive products, the most
`commonly used type of actuator is a rotary moving coil
`actuator. The discs themselves are typically mounted in a
`“stack” on the hub structure of a brushless DC spindle
`motor. The rotational speed of the spindle motor is precisely
`controlled by motor drive circuitry which controls both the
`timing and the power of commutation signals directed to the
`stator windings of the motor.
`The first Winchester disc drives to be produced were large
`cabinet models which included discs having a diameter of 14
`inches and AC induction spindle motors. These types of disc
`drives were commonly located in dedicated “computer
`rooms” with large mainframe computers, where environ-
`mental factors such as temperature and humidity could be
`carefully controlled. In this type of environment, the acous-
`tic noise generated by cooling fans and disc drive motors
`was of little concern, since the only persons directly in
`contact with the systems were maintenance personnel, who
`were generally not in the computer rooms for extended
`periods of time. The users of such systems were typically
`located at a remote location and communicated with the
`computer system via keyboards and display terminals which
`did not generate excessive amounts of acoustic noise.
`More recently, personal computers have become more
`popular and are commonly located within the work space of
`the system user. This has prompted an increase in awareness
`of acoustic noise generated by the disc drives located within
`the personal computers. In certain markets, such as Europe,
`the amountof acoustic noise allowable in the work placeis
`closely regulated. With this in mind, it has become common
`for system manufacturers to impose a “noise budget” on
`manufacturers of major system components, such as disc
`drives, which limits the amount of acoustic noise that such
`components can contribute to the overall noise of the
`system.
`Oneof the principal sources of noise in disc drive data
`storage devices is the spindle motor which drives the discs
`
`10
`
`15
`
`20
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`65
`
`2
`at a constant speed. Typical spindle motor speeds have been
`in the range of 3600 RPM.Current technology has increased
`spindle motor speeds to 4800 RPM, 7200 RPM and above.
`Analysis of various types of disc drives has broughtto light
`several different modes of acoustic noise generation which
`are attributable to the spindle motor and its control logic.
`One mode of noise generation is sympathetic vibration of
`the disc drive housing in responseto therotating mass of the
`spindle motor. Another mode of acoustic noise generation is
`electromagnetic disturbances caused by the excitation of the
`stator mass by the application and removal of the commu-
`tation pulses that are used to drive the motor and controlits
`speed. The commutation pulses are timed, polarization-
`selected DC current pulses which are directed to sequen-
`tially selected stator windings. The rapid rise and fall times
`of these pulsesact as a striking force and set up sympathetic
`vibrations in the stator structure.
`
`If the stator structure is rigidly connected to the disc drive
`housing, either directly or through a rigid material, these
`vibrations are coupled to the housing and generate resonant
`vibrations in the housing causing unacceptable levels of
`acoustic noise.
`
`Prior art attempts to reduce or eliminate noise include
`controlling the resonant frequency of the housing. and
`damping the vibration of the housing. In U.S. Pat. No.
`5,376,850, acoustic noise is reduced by uncoupling the
`stator from hard contact with the stationary portion of the
`shaft. A plurality of O-rings interposed radially between the
`stator andtheshaft of the spindle motor. Also, a non-metallic
`washer is positioned at one end of the shaft and an axial
`O-ring is positioned at the other end of the shaft.
`
`SUMMARY OF THE INVENTION
`
`The present invention is a disc drive spindle motor for
`rotating at least one disc in a data storage device. The motor
`includes a base, a stationary member, a rotor and a stator. A
`bearing interconnects the rotor with the stationary member
`and allows the rotor to rotate about the stationary member.
`An overmold encapsulates at least part of the stator and
`provides the stator with a smooth external surface. The
`overmold mechanically isolates the stator from the base and
`damps sympathetic vibrations in the stator structure to
`reduce the generation of acoustic noise in the storage device.
`The overmold provides a convenient structure for mount-
`ing the stator to the base. In one embodiment, the stator
`includes a plurality of phase windings which are disposed
`aboutthe stator and spaced apart by gaps. The overmoldfills
`the gaps and substantially encapsulatesthe stator. A plurality
`of mounting apertures extend in an axial direction through
`the overmold in the gaps between the phase windings. A
`mounting pin extends through each mounting aperture and
`has a distal end which can be attached to the base by
`heat-staking, for example.
`the overmold comprises at a
`In another embodiment,
`plurality of mounting ears extending from a circumference
`of the stator in a radial direction for connection to the base.
`The mounting ears can include a rigid material, such as
`plastic or metal, which is encapsulated by the overmold or
`exposed to provide a rigid yet isolated connection.
`In another embodiment, the overmold has a circumferen-
`tial side wall opposite to the rotor having an annular raised
`projection. The projection is compressed between the stator
`and the base to secure the stator within the base. In yet
`another embodiment,
`the stator is adhered to the base
`through a polyester plastic film having first and second
`surfaces which carry a pressure sensitive adhesive.
`
`Am. Hondav. IV II - IPR2018-00619
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`5,694,268
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`While the present invention is useful in disc drive spindle
`motors having ball bearings, the present invention is par-
`ticularly useful in hydrodynamic bearing motors to reduce or
`eliminate pure vibration tones which become more notice-
`able with lower levels of background vibration. The over-
`molded stator can have an axial position which is within or
`below the hub, and can have a radial position which is
`internal or external to the rotor. The overmold provides the
`stator with an environmental seal having a smooth external
`surface which is substantially free of apertures. The over-
`mold can be cleaned more easily during production than a
`bare stator and therefore reduces impurities in the disc drive.
`The overmold provides a large surface area over which
`vibrations can be damped to reduce acoustic noise genera-
`tion. The overmold also allows a greater integration of parts
`which reduces the number of parts that must be assembled
`in the disc drive.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a top plan view of a disc drive data storage
`device, in accordance with the present invention.
`FIG. 2 is a sectional view of an isolated hydrodynamic
`bearing spindle motor in accordance with the present inven-
`tion.
`
`FIG. 3 is a fragmentary sectional view of an alternative
`attachment between the stator and the base in which the
`stator is partially isolated from the disc.
`FIG. 4 is a fragmentary sectional view of an alternative
`attachment between the stator and the base which includes
`two O-rings for isolation.
`FIG. 5 is a fragmentary sectional view of another alter-
`native attachment between the stator and the base which
`includes an O-ring located radially between the stator and
`the base and an O-ring located axially between the stator and
`the base.
`
`FIG.6 is a sectional view of a ball bearing spindle motor,
`in accordance with the present invention.
`FIG. 7 is a plan view of an overmolded stator in accor-
`dance with the present invention.
`FIG. 8 is a sectional view of the stator shown in FIG.7,
`taken along lines 7—7.
`FIG. 9 is a fragmentary sectional view of a spindle motor
`having the stator shown in FIGS.7 and 8.
`FIG. 10 is a sectional view of a fully encapsulated stator.
`FIG.11 is a sectional view of a overmolded stator having
`flux shields.
`
`FIG. 12 is a plan view of an overmolded stator having
`mounting ears.
`FIG. 13is a sectional view of the stator shown in FIG.12,
`taken along line 13—13.
`FIG.14 is a fragmentary sectional view of a spindle motor
`having the stator shown in FIGS. 12 and 13.
`FIG. 15 is a plan view of a overmolded stator having a
`rigid mounting ring formed within the overmolding.
`FIG.16is a sectional view of the stator shown in FIG. 15,
`taken along lines 16—16.
`FIG.17 is a fragmentary sectional view of a spindle motor
`having the stator shown in FIGS. 15 and 16.
`FIG. 18 is a sectional view of an overmolded stator with
`an annular projection.
`FIG.19 is a fragmentary sectional view of a spindle motor
`having the stator shown in FIG. 18.
`FIG.20 is a fragmentary sectional view of a spindle motor
`in which an overmolded stator is adhered to the base through
`a polyester plastic film.
`
`4
`FIG. 21 is a sectional view of an overmoldedstator in
`which the overmold is limited to an outer diameter of the
`stator.
`
`FIG.22 is a fragmentary sectional view of a spindle motor
`having an overmolded stator with a radial position that is
`internal to the rotor.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`The present invention is a spindle motor for a disc drive
`data storage device in which the stator is isolated from the
`base to reduce acoustic levels in the storage device. FIG. 1
`is a plan view ofa typical disc drive 1¢ in which the present
`inventionis useful. Disc drive 16 includes a housing base 12
`and a top cover 14. The housing base 12 is combined with
`top cover 14 to form a sealed environment to protect the
`internal components from contamination by elements from
`outside the sealed environment.
`
`The base and top cover arrangement shown in FIG.1 is
`commonin the industry. However, other arrangementsof the
`housing components have been frequently used, and the
`present invention is not limited to the configuration of the
`disc drive housing. For example, disc drives have been
`manufactured using a vertical split between two housing
`members. In such drives, that portion of the housing half
`which connects to the lower end of the spindle motor is
`analogous to base 12, while the opposite side of the same
`housing member, which is connected to or adjacent the top
`of the spindle motor, is functionally the same as the top
`cover 14.
`
`Disc drive 10 further includes a disc pack 16 which is
`mounted for rotation on a spindle motor (not shown) by a
`disc clamp 18. Disc pack 16 includes a plurality of indi-
`vidual discs which are mounted for co-rotation about a
`central axis. Each disc surface has an associated head 20
`which is mounted to disc drive 10 for communicating with
`the disc surface. In the example shown in FIG. 1, heads 20
`are supported by flexures 22 which are in turn attached to
`head mounting arms 24 of an actuator body 26. The actuator
`shownin FIG.1 is of the type knownas a rotary movingcoil
`actuator and includes a voice coil motor (VCM), shown
`generally at 28. Voice coil motor 28 rotates actuator body 26
`with its attached heads 20 about a pivot shaft 30 to position
`heads 20 over a desired data track along an arcuate path 32.
`While a rotary actuator is shown in FIG. 1, the present
`invention is also useful in disc drives having other types of
`actuators, such as linear actuators.
`FIG. 2 is a sectional view of a hydrodynamic bearing
`spindle motor 32 in accordance with the present invention.
`Spindle motor 32 includesa stationary member 34, a hub or
`sleeve 36 anda stator 38. In the embodiment shownin FIG.
`2, the stationary member is a shaft which is fixed and
`attached to base 12 through a nut 40 and a washer 42. Hub
`36 is interconnected with shaft 34 through a hydrodynamic
`bearing 37 for rotation about shaft 34. Bearing 37 includes
`a radial working surface 46 and axial working surfaces 48
`and 50. Shaft 34 includes fluid ports 54, $6 and 58 which
`supply hydrodynamic fluid 60 and assist in circulating the
`fluid along the working surfaces of the bearing. Hydrody-
`namic fluid 60 is supplied to shaft 34 by a fluid source (not
`shown) which is coupled to the interior of shaft 34 in a
`known manner.
`
`10
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`15
`
`20
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`25
`
`35
`
`45
`
`50
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`55
`
`65
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`Spindle motor 32 further includes a thrust bearing 45
`which forms the axial working surfaces 48 and 50 of
`hydrodynamic bearing 37. A counterplate 62 bears against
`working surface 48 to provide axial stability for the hydro-
`
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`dynamic bearing and to position hub 36 within spindle
`motor 32. An O-ring 64 is provided between counterplate 62
`and hub 36 to seal the hydrodynamic bearing. The seal
`prevents hydrodynamic fluid 60 from escaping between
`counterplate 62 and hub 36.
`Hub 36 includes a disc carrier member 66 which supports
`disc pack 16 (shown in FIG. 1)for rotation about shaft 34.
`Disc pack 16 is held on disc carrier member 66 by disc
`clamp 18 (also shown in FIG. 1). A permanent magnet 70 is
`attached to the outer diameter of hub 36, which acts as a
`rotor for spindle motor 32.
`Stator 38 is formed of a stack of stator laminations 72 and
`associated stator windings 74. In accordance with the
`present invention, stator 38 is mechanically isolated from
`base 12 through a resilient coupling. It has been found
`through experiments that hydrodynamic bearing motors are
`much quieter and in general have lower background vibra-
`tion levels than motors having ball bearings. Because the
`background vibration levels are less in a hydrodynamic
`bearing motor, vibration responses to electromagnetic dis-
`turbances become more noticeable since the responses are
`no longer hidden in the background. Therefore, it is desir-
`able to reduce or eliminate as far as possible the transfer of
`vibrations resulting from electromagnetic disturbances from
`the stator to the base.
`
`10
`
`15
`
`20
`
`25
`
`6
`A larger damping ratio is therefore preferred with hydrody-
`namic bearings.
`An example of a suitable material is a 70 durometer
`material such as Viton®, a patented polymer product of E.L
`DuPont de Nemours Co., of Wilmington, Del., which is
`subjected to 0.009 inches of radial compression. Other
`materials which provide suitable isolation and stiffness may
`also be used to isolate stator 38 from base 12. It has been
`found that some rubber materials contain silicone or sulfur
`which can be harmful to the various components in a disc
`drive. Therefore, rubber or mibber-like materials not con-
`taining silicone and sulfur are preferred.
`Resilient bridge 82 extends between an upper mounting
`surface 90 of stator 38 and an upper mounting surface 92 of
`base 12. Bolts 94 and 96 secure bridge $2 to base 12 and
`compress bridge 82 against the upper mounting surfaces 90
`and 92 in an axial direction to provide additional vertical
`stiffness for the resilient coupling betweenstator 38 and base
`12. The combination of O-ring 80 and resilient bridge 82
`clamps stator 38 rotationally and vertically with respect to
`base 12. The O-ring preferably has enough torsional stiffness
`so that as spindle motor 32 beginsto rotate, stator 38 is not
`allowed to rotate more than an insignificant amount. The
`combination of O-ring 80 and resilient bridge 82 provides
`sufficient vertical and torsional stiffness.
`
`35
`
`Resilient bridge 82 is preferably formed of a material
`Asshownin FIG.2, stator 38 is resiliently coupled to, but
`similar to that of O-ring 80. Resilient bridge 82 can be an
`mechanically isolated from, base 12. Stator 38 is coupled to
`annular ring, as shown in FIG.2, or can include one or more
`base 12 through an O-ring 80 andaresilient damping bridge
`30
`individual bridge pieces which extend between stator 38 and
`$2. O-ring 80 is compressed between a side surface 84 of
`stator 38 and a side surface 86 of base 12 such that stator 38
`base 12. In addition, bridge 82 can be formed as a washer
`which is secured to base 12 by a bolt, such as bolt 94 or 96.
`and base 12 are adjacent to, but spaced from, one another in
`The washer would have a tab that would extend between
`a radial direction with respect to a central axis 87. In one
`base 12 andstator 38. Resilient bridge 82 can also be formed
`embodiment, O-ring 860 is integrated in stator 38 to form an
`as a clamp of O-ring type material. Further, bridge 82 can be
`assembly whichfacilitates a low-cost approach to mounting
`compressed against the upper mounting surfaces 90 and 92
`the stator within base 12. For example, O-ring 80 can be
`integrated in an indentation (not shown) in stator 38 through
`in several ways. For example, resilient bridge 82 can be
`a vulcanizing process. O-ring 80 can also be integrated in
`compressed by bolt 94, as shown in FIG. 2, or can be
`compressed by a portion of top cover 14 (shown in FIG.1).
`stator 38 by over-molding the O-ring onto the stator. The
`The mounting surfaces 90 and 92 can also include associated
`O-ring material flows over the stator to form the desired
`grooves for accepting resilient bridge 82. In addition, resil-
`O-ring features and is then hardened at a selected tempera-
`ient bridge 82 can be integrated into the stator similar to
`ture and pressure. The vulcanizing process and the over-
`O-ring 80.
`molding process are controlled to provide the desired damp-
`ing and stiffness characteristics.
`In the embodiment shown in FIG.2, the spindle motor is
`a “below-hub” type motor in which stator 38 is positioned
`Base 12 includes a corresponding annular groove (not
`below hub 36, as opposed to within hub 36. In addition.
`labeled) which retains O-ring 80 under compression when
`stator 38 is located externally from hub 36 and is attached
`stator 38 is mounted within base 12. The annular groove
`directly to base 12. In this embodiment, O-ring 80 and
`within base 12 also assists in axially constraining O-ring 80.
`resilient damping bridge 82 are located at an outer diameter
`O-ring 80 can be formed as a continuousinternal ring or as
`of stator 38.
`one or more individual pieces of O-ring material positioned
`between stator 38 and base 12. O-ring 80 can have any
`suitable cross section, such as circular or rectangular.
`O-ring 80 can be formed of a rubber-like or plastic-like
`material having high stiffness and high vibration damping
`characteristics. In a preferred embodiment, O-ring 80 is
`formed of an approximately 40-75 durometer (Shore A)
`material having a damping ratio of at least 2 decibels in an
`acoustic frequency range of approximately 100 Hz to 10
`KHz. The material absorbs energy of acoustic vibrations and
`dissipates the energy as heat. In some embodiments, O-ring
`80 preferably has a dampingratio of at least 5 decibels. The
`preferred dampingratio depends on the type of bearing used,
`among other factors. With ball bearings, the background
`vibration level is higher. Electromagnetic disturbances are
`more hidden and require less damping. A damping ratio of
`2-3 decibels may be sufficient. With hydrodynamic
`bearings, electromagnetic disturbances are more noticeable.
`
`45
`
`35
`
`65
`
`FIG.3 is a fragmentary sectional view of a spindle motor
`which illustrates an alternative attachment between the
`stator and the base. In FIG. 3, stator 100 is attached to base
`102 through an O-ring 104 and a metallic C-clamp 106.
`C-clamp 106 provides sufficient vertical stiffness between
`stator 100 and base 102 but does not provide complete
`isolation betweenthe stator and the base as does the embodi-
`ment shownin FIG.2. Therefore, the embodiment shown in
`FIG. 2 is preferred over the embodiment shown in FIG.3.
`FIG.4 is a fragmentary sectional view of a spindle motor
`illustrating another alternative attachment betweenthe stator
`and the base. In FIG. 4,stator 110 is attached to base 112
`through two O-rings 114 and 116. O-rings 114 and 116 are
`located radially between stator 110 and 112. O-rings 114 and
`116 are separated from one another by a radius such that they
`form a couple which contributes to the vertical and torsional
`stiffness of stator 110 with respect to base 112. If the stator
`
`Am. Hondav. IV II - IPR2018-00619
`PETHONDA_1013-0018
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0018
`
`
`
`5,694,268
`
`7
`is rotated with respect to the base, the O-rings provide a
`restoring torque to overcomethe rotation. The O-rings also
`maintain vertical alignment of the stator by providing a
`restoring force in a vertical direction in response to vertical
`movement of the stator with respect to the base. In the
`embodiment shown in FIG.4, there is no need for a clamp
`or a bridge between stator 110 and base 112 since O-rings
`114 and 116 provide sufficient vertical and torsional stiff-
`ness.
`
`FIG. 5 is a fragmentary sectional view of a spindle motor
`which illustrates another embodiment of the present inven-
`tion. In FIG.5, stator 120 is resiliently coupled to base 122
`through O-rings 124 and 126. O-ring 124 is located radially
`between stator 120 and base 122. O-ring 124 is compressed
`betweenthe side walls of stator 120 and base 122 similar to
`the O-rings shown in FIGS. 2-4. O-ring 126 is located
`axially and compressed between a lower mounting surface
`128 of stator 120 and an opposing surface 130 of base 122.
`O-ring 126 provides additional stability and isolation. rect-
`angular.
`in
`invention is particularly useful
`While the present
`hydrodynamic bearing motors to reduce pure tone vibrations
`where the background vibration level is relatively low, the
`present invention is also useful in motors having ball bear-
`ings to reduceor eliminate the transfer of vibrations from the
`stator to the base.
`
`FIG.6 illustrates a spindle motor having ball bearings, as
`opposed to a hydrodynamic bearing. Spindle motor 15¢
`includes a shaft 152, a hub 154 and a stator 156. Shaft 152
`is a stationary shaft which is fixedly attached to a base 158.
`Shaft 152 is also attached to the inner races of ball bearings
`16@ and 162. Hub 154 is attached to the outer races of
`bearings 160 and 162 for rotation about shaft 152. Hub 154
`includes a disc carrying member 164 which carries a plu-
`rality of magnetic discs (not shown) for rotation about shaft
`152. Hub 154 also carries a permanent magnet 166 which
`forms a rotor for spindle motor 150.
`As in the embodiments shown in FIGS. 2-5, stator 156
`can be attached to base 158 through one or moreresilient
`couplings, such as O-ring 168. Spindle motor 150 can also
`include a resilient damping ring or tab 170 for providing
`additional vertical stiffness between stator 156 and base 158.
`As discussed above, damping ring or tab 170 is optional.
`Alternatively, spindle motor 150 can be provided with a
`metallic C-clamp as shown in FIG.3, two O-rings as shown
`in FIG. 4, or an additional O-ring located between the
`bottom of stator 156 and base 158.
`FIGS. 1-6 illustrate embodiments in which the stator is
`positioned external to the hub such that the O-rings are
`positioned along the outer diameter of the stator. However,
`the O-rings can also be positioned along the inner diameter
`of the stator in embodiments in which the stator is attached
`to the base about the stator’s inner diameter.
`
`FIG. 7 is a plan view of a stator in which the resilient
`coupling is integrated with the stator by overmolding the
`coupling onto the stator. FIG. 8 is a sectional view of the
`stator, taken along lines 8—8 of FIG. 7. Stator 200 includes
`a stator lamination 202 comprising a back-iron 204 and a
`plurality of teeth 206c—206/, which extend inward from
`back-iron 204 toward a central axis 207. Teeth 206a—206/
`are disposed about a circumference 222 of stator 200. A
`plurality of phase windings 208a—-208/ are wound on stator
`teeth 2062-2061, respectively, for magnetic communication
`with an internal rotor (not shown). Phase windings
`208a—208! can have a number of winding configurations,
`such as those discussed in Dunfield et al. U.S. Ser. No.
`
`8
`08/469,643, entitled IRONLESS HYDRODYNAMIC
`SPINDLE MOTOR,filed Jun. 6, 1995, and Dunfield et al.
`U.S. Ser. No. 08/400,661, entitled HYDRODYNAMIC
`SPINDLE MOTOR HAVING DISTRIBUTED
`WINDINGS, filed Mar. 8, 1995, which are hereby incorpo-
`rated by reference.
`A flexible printed circuit (FPC 210 carries a plurality of
`conductors 212 which are electrically connected to start and
`finish winding terminations 214, 216,218 and 226. Termi-
`nations 214,216, and 218 and 220 are electrically connected
`to phase windings 208¢-208/, in a known manner.
`Back-iron 204, stator teeth 206a—206/ and windings
`208a—208/ are overmolded by a resilient rubber-like or
`plastic-like material. Gaps 224a—224l are formed between
`each phase winding 208a—208/. Overmold 209 substantially
`encapsulates stator 200 and fills gaps 224a—224/ such that
`stator 200 has a smooth external surface which is substan-
`tially free of apertures, indentations or open cavities. This
`provides an environmental seal and a surface which can be
`cleaned much more easily during assembly than a rough and
`uneven surface provided by an exposed stator. Each of the
`stator lamination teeth 206a—206/ remain exposed at an
`inner diameter surface 236 along circumference 222 for
`closer communication with the rotor. In one embodiment,
`overmold 209 has a minimum thickness of approximately
`0.25 mm around the various features of stator 200.
`
`the overmold material
`In a preferred embodiment,
`includes a 70 durometer rubber-like material having char-
`acteristics similar to the O-rings discussed with reference to
`FIG. 2. Other rubber-like and plastic-like materials can also
`be used in the present invention. The overmolding process
`integrates the resilient coupling with the stator. The over-
`mold material flows over the stator to form the desired
`overmolding features and is then hardened at a selected
`temperature and pressu