O
`Umted States Patent
`
`[19]
`
`US005694268A
`
`[11] Patent Number:
`
`5,694,268
`
`Dunfield et a1.
`
`.
`
`[45] Date of Patent:
`
`Dec. 2, 1997
`
`[54] SPINDLE MOTOR HAVING OVERMOLDED
`STATOR
`
`[75]
`
`Inventors: John Charles Dlmfield. Santa Cruz;
`.
`2:11;” Karl Heme’ Aptos‘ both °f
`'
`
`.
`[73] ”Sign”: smgamT§m°l°H1m°93wm
`Valle» Cahf~
`
`[21] App1.No.;550,175
`
`[22] Filed:
`
`Oct. 30, 1995
`
`[63]
`
`Int. Cl.
`[51]
`[52] US. Cl.
`
`Rented U-S- Application Data
`_
`.
`,
`Contmuatton—m—part of Ser. No. 386,883, Feb. 10, 1995.
`6
`.
`.
`............................. GllB 17/02,!13521E57/2144,
`..................................... 360/9837; 360/9903;
`310I67 R; 310/51; 310/254
`[58] Field of Search .............................. 360/9701. 98.01.
`360/9807, 98.08, 99.04. 99.08—99.12; 310/51,
`67 R. 254
`
`[56]
`
`References Cited
`BTEIIT
`CUI [EMT
`
`S
`D0
`US' P
`10/1928 Spreen ...................................... 310/51
`1,688,891
`310/51
`4/1969 Frohmuller et 81.
`3,438,407
`
`3,546,504 12/1970 Janssen et a1.
`310/51
`
`4,268,233
`5/1981 Fernstrfim
`-- 413/270
`4,647,803
`3/1987 von der Heide et 31.
`
`310,51
`4,672,250
`6/1987 Scitz ..........................
`
`313$
`..
`4,760,299
`7/1988 Dickie et a1.
`
`310,194
`4,816,710
`3/1989 Silvaggio e, 31.
`"310/67 R
`4,823,034
`4/1989 Wrobel
`.............
`
`4,965,476 10/1990 Lin ............................................ 310/51
`
`426*-
`
`
`
`1/1992 Jones ......................................... 310/91
`5,079,466
`3/1992 Ueki et a1.
`360/972
`5,097,366
`6/1992 Girault
`......
`310/90.5
`5,126,612
`$1133; graze -------
`-- 3603/f333
`3:333:23;
`gawa ..
`,
`8/1993 Fazekas .........
`310/51
`5,235,227
`8/1993 Katakura eta].
`....... 310/51
`5,241,229
`.. 360/9807
`5,352,947 10/1994 MacLeod ..........
`
`.. 360/9912
`5,367,418
`11/1994 Chessman eta].
`
`5,376,350 12/1994 Elsing et a1. .................. 310/67
`...... 360/9908
`5,457,583 10/1995 Hattori et a1.
`
`5/1996 Yamadaetal. .......... 360/9807
`5,519270
`11/1996 Dunfield etal. ..................... 360/9908
`5,579,183
`
`FOREIGN PATENT DOCUMENTS
`
`10/1967 Canada .................................... 310/70
`4/1991
`Japan.
`
`770/273
`3-89838 (A)
`4-168942
`Japan.
`6/1992
`(AA)
`Japan.
`9/19”
`4451542 (A)
`Japan.
`4-364340 (A) 121992
`2 154 072
`3/1935 United Kingdom .
`
`.
`'
`”mm WWW—Jefferson Evans
`Attorney Agent, 0' Fi'm—Wcsmm €113!“le & K5115“
`PA-
`AB TRA T
`7
`S
`C
`[5 ]
`A disc drive spindle motor for rotating at least one disc in a
`data storage device includes a base. a shaft. a rotor and 3
`stator. A bearing interconnects the rotor with the shaft and
`allows the rotor to rotate about the shaft. An overmold
`
`encapsulates at least a portion 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 acouan no1se 1n the storage devwe.
`
`31 Claims, 14 Drawing Sheets
`
`4|2
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET_HONDA_1013 -0001
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0001
`
`

`

`US. Patent
`
`5,694,268
`
`
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0002
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 2 of 14
`
`5,694,268
`
` N.ON
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`Am. Honda V. IV 11 - IPR2018-00619
`
`PET_HONDA 1013 -0003
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0003
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 3 of 14
`
`5,694,268
`
`
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET HONDA 1013-0004
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0004
`
`

`

`
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0005
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 5 of 14
`
`5,694,268
`
`
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET_HONDA_1013 -0006
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0006
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 6 of 14
`
`5,694,268
`
`
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET HONDA 1013-0007
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0007
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 7 of 14
`
`5,694,268
`
`
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`Am. Honda V. IV 11 - IPR2018-00619
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`PET HONDA 1013—0008
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0008
`
`
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 8 of 14
`
`5,694,268
`
`
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET_HONDA_1013 -0009
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0009
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 9 of 14
`
`5,694,268
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0010
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 10 of 14
`
`5,694,268
`
`
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET_HONDA_1013—0011
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0011
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 11 of 14
`
`5,694,268
`
`
`
`Am. Honda V. IV 11 - IPR2018-00619
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`PET_HONDA_1013 —00 12
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0012
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 12 of 14
`
`5,694,268
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`PET_HONDA_1013-0013
`
`
`
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 13 of 14
`
`5,694,268
`
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`PET_HONDA_1013 -0014
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0014
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 14 of 14
`
`5,694,268
`
`
`
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`
`Am. Honda V. IV 11 - IPR2018-00619
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`PET HONDA 1013—0015
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`PET_HONDA_1013-0015
`
`

`

`5,694,268
`
`1
`SPINDLE MOTOR HAVING OVERMOLDED
`STATOR
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application is a continuation—in-part of US. Ser. No.
`08/386383. filed Feb. 10. 1995.
`BACKGROUND OF THE INVENTION
`
`The present 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 sometimes collectively 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-
`ops a lifting force that causes the slider to lift and fly sevm'al
`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 amount of acoustic noise allowable in the work place is
`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.
`One of the principal sources of noise in disc drive data
`storage devices is the spindle motor which drives the discs
`
`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 brought to light
`several diflerent 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 response to the rotating 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 control its
`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 pulses act 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 US. 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 and the shaft 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
`about the stator and spaced apart by gaps. The overmold fills
`the gaps and substantially encapsulates the stator. A plurality
`of mounting apertures extend in an axial direction through
`the overmold in the gaps between the phase windings. A
`mounu‘ng 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.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`35
`
`45
`
`SO
`
`55
`
`65
`
`Am. Honda V. IV 11 - IPR2018-00619
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`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0016
`
`

`

`5,694,268
`
`3
`
`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. 13 is 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. 16 is 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 overmolded stator 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 of a typical disc drive 10 in which the present
`invention is useful. Disc drive 10 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
`common in the industry. However. other arrangements of 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
`shown in FIG. I is of the type known as a rotary moving coil
`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 includes a stationary member 34. a hub or
`sleeve 36 and a stator 38. In the embodiment shown in 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. Shafl 34 includes fluid ports 54. 56 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
`
`15
`
`20
`
`25
`
`35
`
`45
`
`50
`
`55
`
`65
`
`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-
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET_HONDA_1013 -0017
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1013-0017
`
`

`

`5,694,268
`
`5
`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). Apermanent 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 larninations 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 desirv
`able to reduce or eliminate as far as possible the transfer of
`vibrations resulting from electromagnetic disturbances from
`the stator to the base.
`
`As shown in FIG. 2. stator 38 is resiliently coupled to. but
`mechanically isolated from. base 12. Stator 38 is coupled to
`base 12 through an O-ring 80 and a resilient damping bridge
`82. 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
`and base 12 are adjacent to. but spaced from, one another in
`a radial direction with respect to a central axis 87. In one
`embodiment, O-ring 80 is integrated in stator 38 to form an
`assembly which facilitates a low-cost approach to mounting
`the stator within base 12. For example. O-ring 80 can be
`integrated in an indentation (not shown) in stator 38 through
`a vulcanizing process. O-ring 80 can also be integrated in
`stator 38 by over—molding the O-ring onto the stator. The
`O-ring material flows over the stator to form the desired
`O-ring features and is then hardened at a selected tempera-
`ture and pressure. The vulcanizing process and the over-
`molding process are controlled to provide the desired darnp—
`ing and stiffness characteristics.
`Base 12 includes a corresponding annular groove (not
`labeled) which retains O-ring 80 under compression when
`stator 38 is mounted within base 12. The annular groove
`within base 12 also assists in axially constraining O—ring 80.
`O—ring 80 can be formed as a continuous internal ring or as
`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 stifl’ness 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 approximawa 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 damping ratio of at least 5 decibels. The
`preferred damping ratio 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.
`
`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 EL
`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 rubber-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 82 to base 12 and
`compress bridge 82 against the upper mounting surfaces 90
`and 92 in an axial direction to provide additional vertical
`stilfness for the resilient coupling between stator 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 begins to rotate. stator 38 is not
`allowed to rotate more than an insignificant amount. The
`combination of O-ring 80 and resilient bridge 82 provides
`suflicient vertical and torsional stiffness.
`
`Resilient bridge 82 is preferably formed of a material
`similar to that of O—ring 80. Resilient bridge 82 can be an
`annular ring. as shown in FIG. 2. or can include one or more
`individual bridge pieces which extend between stator 38 and
`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.
`The washer would have a tab that would extend between
`
`base 12 and stator 38. Resilient bridge 82 can also be formed
`as a clamp of O—ring type material. Further. bridge 82 can be
`compressed against the upper mounting surfaces 90 and 92
`in several ways. For example. resilient bridge 82 can be
`compressed by bolt 94. as shown in FIG. 2. or can be
`compressed by a portion of top cover 14 (shown in FIG. 1).
`The mounting surfaces 90 and 92 can also include associated
`grooves for accepting resilient bridge 82. In addition. resil—
`ient bridge 82 can be integrated into the stator similar to
`O—ring 80.
`In the embodiment shown in FIG. 2. the spindle motor is
`a “below-hub” type motor in which stator 38 is positioned
`below hub 36. as opposed to within hub 36. In addition.
`stator 38 is located externally from hub 36 and is attached
`directly to base 12. In this embodiment. O-ring 80 and
`resilient damping bridge 82 are located at an outer diameter
`of stator 38.
`
`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 between the stator and the base as does the embodi-
`ment shown in 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 between the 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
`stiflness of stator 110 with respect to base 112. If the stator
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
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`55
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`65
`
`Am. Honda V. IV 11 - IPR2018-00619
`
`PET_HONDA_1013 -001 8
`
`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 overcome the 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 suflicient vertical and torsional stifl—
`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 12A is compressed
`between the 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 reduce or 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 150
`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
`160 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 more resilient
`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 206a—2061. which extend inward from
`back-iron 204 toward a central axis 207. Teeth 20641—2061
`
`are disposed about a circumference 222 of stator 200. A
`plurality of phase windings 208a—2081 are wound on stator
`teeth 206a—206l. respectively, for magnetic communication
`with an internal rotor (not shown). Phase windings
`208a—208l 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 220. Termi-
`nations 214.216. and 218 and 220 are electrically connected
`to phase windings 208a—2081. in a lmown manner.
`Back-iron 204. stator teeth 206a—206l and windings
`208a—2081 are overmolded by a resilient rubber-like or
`plastic-like material. Gaps 224a—224l are formed between
`each phase winding 208a—208L Overmold 209 substantially
`encapsulates stator 200 and fills gaps 224a—2241 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 smface 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—206l 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 dtn'ometer 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 overrnolding process
`integrates the resilient coupling with the stator. The over-
`mold material flows over the stator to form the desired
`
`ov