(12) United States Patent
`Neal
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006362554Bl
`US 6,362,554 Bl
`Mar.26,2002
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) STATOR ASSEMBLY
`
`(75)
`
`Inventor: Griffith D. Neal, Alameda, CA (US)
`
`(73) Assignee: Encap Motor Corporation, Alameda,
`CA(US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/470,429
`
`(22) Filed:
`
`Dec. 22, 1999
`
`Related U.S. Application Data
`( 60) Provisional application No. 60/146,446, filed on Jul. 29,
`1999.
`Int. Cl? .................................................. H02K 1/12
`(51)
`(52) U.S. Cl. ........................... 310/254; 310/43; 29/596;
`264/272.2
`(58) Field of Search .............................. 310/43, 51, 89,
`310/254; 29/596, 606; 264/272.13, 272.2
`
`BE
`DE
`EP
`EP
`
`891.258
`25 39 492 A1
`0 747 943 A2
`0 883 171 A1
`
`3/1982
`3/1977
`2/1998
`12/1998
`
`(List continued on next page.)
`
`OTHER PUBLICATIONS
`
`U.S. application No. 09/470,428, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,432, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,430, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,434, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,427, filed Dec. 22, 1999, copy
`of claims enclosed.
`
`(List continued on next page.)
`
`Primary Examiner-Joseph Waks
`(74) Attorney, Agent, or Firm-Steven P. Shurtz; Brinks
`Hofer Gilson & Liane
`
`(56)
`
`References Cited
`
`(57)
`
`ABSTRACT
`
`U.S. PATENT DOCUMENTS
`
`6/1971 Frescura .. .. ... ... ... ... ... .. . 36/708
`3,590,328 A
`1!1972 Zimmerman et a!. ......... 310/93
`3,638,055 A
`4/1975 Dochterman et a!. ....... 291!598
`3,874,073 A
`.............. 310/179
`3/1976 Kristen et a!.
`3,942,054 A
`9/1976 Schwider eta!. ........... 427/104
`3,979,530 A
`4,128,527 A * 12/1978 Kinjo et a!.
`.................. 310/43
`4,352,897 A * 10/1982 Ogata et a!. ................ 523/220
`4,387,311 A * 6/1983 Kobayashi et a!.
`........... 310/43
`............... 310/87
`1!1985 Fukushi et a!.
`4,492,889 A
`2/1986 Haar et a!. ................ 310/68 R
`4,572,979 A
`
`(List continued on next page.)
`
`FOREIGN PATENT DOCUMENTS
`
`A high speed spindle motor is constructed from a stator
`assembly that includes a stator having multiple conductors
`that create a plurality of magnetic fields when electrical
`current is conducted by the conductors and a body of a phase
`change material, such as a thermoplastic, substantially
`encapsulating the stator. A rotatable hub having a magnet
`connected thereto is in operable proximity to the stator. The
`high speed motor also includes a shaft, a bearing surround(cid:173)
`ing the shaft and one of the bearing or shaft being fixed to
`the stator assembly and the other of the bearing or shaft
`being fixed to the rotatable hub. Hard disc drives using the
`motor, and methods of developing and constructing the
`motor and hard disc drives are also disclosed.
`
`BE
`
`870.878
`
`1!1979
`
`12 Claims, 13 Drawing Sheets
`
`PETITIONERS' EXHIBIT 1104
`
`PAGE 1 OF 26
`
`

`

`US 6,362,554 Bl
`Page 2
`
`U.S. PATENT DOCUMENTS
`4,679,313 A *
`4,760,299 A *
`4,801,833 A
`4,853,576 A
`4,858,073 A
`4,868,970 A *
`4,954,739 A *
`5,008,572 A *
`5,036,580 A
`5,073,735 A
`5,075,585 A
`5,121,021 A
`5,134,327 A
`5,142,103 A
`5,147,982 A
`5,206,554 A
`5,268,607 A
`5,334,897 A
`5,345,129 A
`5,382,852 A
`5,396,210 A
`5,400,218 A
`5,414,317 A
`5,461,772 A
`5,500,780 A
`5,506,458 A
`5,541,787 A
`5,548,458 A
`5,558,445 A
`5,579,188 A
`5,587,617 A
`5,598,048 A
`5,610,463 A
`5,619,083 A
`5,619,389 A
`5,621,372 A
`5,633,545 A
`5,666,242 A
`5,668,427 A
`5,672,927 A
`5,675,196 A
`5,694,268 A
`5,698,919 A
`5,728,600 A
`5,729,404 A
`5,742,450 A
`5,751,085 A *
`5,751,514 A
`5,766,535 A
`5,783,888 A
`5,806,169 A
`5,814,412 A
`5,850,318 A
`5,880,179 A *
`5,881,447 A
`5,942,824 A *
`5,958,466 A
`5,973,424 A
`5,982,247 A
`5,990,583 A
`
`Schultz et a!. ................ 29!596
`Dickie eta!. ................. 310/91
`Dye ........................... 310/239
`Mayumi eta!. ............ 310/239
`Gregory ..................... 361!708
`Schultz et a!. ................ 29!596
`Schultz et a!. .............. 310/156
`Marshall et a!. .............. 310/45
`Fox eta!. ..................... 29/605
`Takagi ......................... 310/71
`............ 310/89
`Teruyama et a!.
`Ward .......................... 310/154
`Sumi et a!. ................... 310/43
`Stine ......................... 174/52.2
`Steffen ...................... 174/52.2
`Perrot .................. 310/40 MM
`McManus .................... 310/89
`Ineson et a!. . . . . . . . . . . . . . . . . . 310/89
`Molnar ....................... 310/156
`Yuhi et a!. ............ 310/40 MM
`Purohit et a!.
`................ 336/60
`Val
`............................ 361!709
`Reid eta!. .................. 310/239
`Puri ............................ 29/605
`Boutaghou et a!. ...... 360/99.08
`Pace et a!. ................ 310/67 R
`Jabbari et a!.
`........... 360/97.01
`Pelstring et a!. ......... 360/99.08
`Chen et a!.
`................. 389/132
`Dunfield et a!.
`......... 360/99.08
`Dunfield et a!.
`........... 310/90.5
`Dunfield et a!.
`........... 310/90.5
`Dunfield et a!.
`........... 310/90.5
`Dunfield et a!.
`........... 310/90.5
`Dunfield et a!.
`... ... ... 360/98.07
`Purohit . ... ... .. ... ... ... ... .. . 336/60
`............ 310/670
`Albrecht et a!.
`Edwards et a!.
`. . . . . . . . . . . . 360/265
`Morita ....................... 310/216
`Viskochil .................... 310/194
`Huang et a!. ............. 310/67 R
`Dunfield et a!.
`.......... 310/67 R
`Obara ......................... 310/90
`Saxelby, Jr. eta!. .... 264/272.11
`......... 360/99.08
`Dunfield et a!.
`Moser ..................... 360/99.08
`Hayashi ....................... 310/90
`Hyde eta!. .............. 360/97.01
`Ong ...................... 264/272.15
`...................... 310/91
`Yamano
`Trago et a!.
`.................. 29!596
`Terada et a!. ............... 428/958
`......... 360/99.08
`Dunfield et a!.
`Ito et a!. ..................... 523/433
`Molnar ........................ 29/598
`Shioya et a!. .............. 310/90.5
`Ong ........................... 425/127
`.... 360/97.01
`Engelberber et a!.
`Imada et a!. .................. 310/43
`Terada et a!. ................. 310/43
`
`7/1987
`7/1988
`1!1989
`8/1989
`8/1989
`9/1989
`9/1990
`4/1991
`8/1991
`12/1991
`12/1991
`6/1992
`7/1992
`8/1992
`9/1992
`4/1993
`12/1993
`8/1994
`9/1994
`1!1995
`3/1995
`3/1995
`5/1995
`10/1995
`3/1996
`4/1996
`7/1996
`8/1996
`9/1996
`11/1996
`12/1996
`1!1997
`3/1997
`4/1997
`4/1997
`4/1997
`5/1997
`9/1997
`9/1997
`9/1997
`10/1997
`12/1997
`12/1997
`3/1998
`3/1998
`4/1998
`5/1998
`5/1998
`6/1998
`7/1998
`9/1998
`9/1998
`12/1998
`3/1999
`3/1999
`8/1999
`9/1999
`10/1999
`11/1999
`11/1999
`
`6,002,185 A
`6,019,516 A
`6,020,661 A
`6,034,841 A
`6,043,583 A
`6,071,014 A
`
`* 12/1999 Nakao et a!.
`................. 310/43
`2/2000 Leuthold et a!. . . . . . . . . . . . . 384/107
`.................. 310/43
`2/2000 Trago et a!.
`3/2000 Albrecht et a!.
`. ... ... .. ... ... 36/43
`3/2000 Kurosawa eta!. .......... 310/254
`. . . . . . . . . . . . . . . . . . . 384/110
`6/2000 Lee et a!.
`
`FOREIGN PATENT DOCUMENTS
`
`FR
`JP
`JP
`JP
`JP
`su
`su
`wo
`wo
`wo
`wo
`
`2 647 958
`5336722
`10070870
`410271719
`11082508
`1334297
`1494148
`wo 92/06532
`wo 96/20501
`wo 96/33533
`wo 97/39870
`
`12/1990
`12/1993
`3/1998
`10/1998
`3/1999
`8/1987
`7/1989
`4/1992
`7/1996
`10/1996
`10/1997
`
`OTHER PUBLICATIONS
`
`U.S. application No. 09/470,431, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,433, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,425, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,426, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/470,424, filed Dec. 22, 1999, copy
`of claims enclosed.
`U.S. application No. 09/738,268, filed Dec. 15, 2000, copy
`of application as originally filed enclosed.
`Product Information from Dupont Engineering Polymers
`entitled "Electrical/Electronic Thermoplastic Encapsula(cid:173)
`tion," (no date), Publ. Reorder No.: H-58633 (R, 96.7), 20
`pages.
`The Epoxy lite Corporation, article from the Internet entitled
`"Vacuum Pressure Impregnation (VPI) Systems", Nov. 19,
`1999,
`<http://www.epoxylite.com/EpoxyliteEquipmen(cid:173)
`t.htm>, 3 pages.
`Buchanan Motor Works, Inc., article from the Internet
`entitled "Epoxy Seal-Prevents Down Time and Keeps
`Equipment Running Longer," Jul. 14, 1999, <http://www.b(cid:173)
`mwworks.com/VIP.htm>, 1 page.
`Neeltran Inc., article from the Internet entitled "Vacuum
`Pressure Impregnation (VPI)", Nov. 19, 1999, <http://ww(cid:173)
`w.neeltran. thomasregister.com/olc/neeltran/neel9 .htm>
`2
`pages.
`LNP Engineering Plastics, Press Release entitled "LNP
`Introduces First-Ever Line of Thermally Conductive Com(cid:173)
`pounds," Jan. 28, 1999 (2 pages).
`LNP Engineering Plastics, Advertisement entitled "Kon(cid:173)
`duit™ Thermally Conductive Composites," undated (2
`pages).
`* cited by examiner
`
`PAGE 2 OF 26
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 26, 2002
`Mar. 26, 2002
`
`Sheet 1 of 13
`Sheet 1 0f 13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`
`
`\
`
`PAGE 3 OF 26
`
`PAGE 3 OF 26
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 26, 2002
`Mar. 26, 2002
`
`Sheet 2 of 13
`Sheet 2 0f 13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`
`
`.
`(.? -
`
`PAGE 4 OF 26
`
`PAGE 4 OF 26
`
`

`

`U.S. Patent
`
`Mar.26,2002
`
`Sheet 3 of 13
`
`US 6,362,554 Bl
`
`FIG.4
`
`II _/ 15 44
`.
`13
`
`FIG.6
`
`110 J
`
`PAGE 5 OF 26
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 26,2002
`Mar. 26, 2002
`
`Sheet 4 of 13
`Sheet 4 0f 13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`0
`
`
`
`L()
`
`<.9 -
`LL
`
`PAGE 6 OF 26
`
`PAGE 6 OF 26
`
`

`

`U.S. Patent
`
`Mar. 26, 2002
`
`Sheet 5 of 13
`
`US 6,362,554 Bl
`
`f'(cid:173)
`
`c_rj -LL
`
`PAGE 7 OF 26
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 26, 2002
`Mar. 26,2002
`
`Sheet 6 0f 13
`Sheet 6 of 13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`
`
`-LL
`
`PAGE 8 OF 26
`
`PAGE 8 OF 26
`
`

`

`U.S. Patent
`US. Patent
`
`Mar.26,2002
`Mar. 26, 2002
`
`Sheet 7 0f 13
`Sheet 7 of 13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`NE
`
`Ex.
`
`7
`
`Aa o
`I")¢l
`
`m I
`
`“\““\
`I,”
`"
`d
`
`Zu/
`
`
`
`OJ .
`(.9
`LL
`
`PAGE 9 OF 26
`
`m—EAWIWl-flr
`
`§§§§Wa\Vé‘
`§§§“é—m“V‘all?"zL
`90k‘9kw§§
`
`m2.
`
`-(
`
`.9
`LL
`
`PAGE 9 OF 26
`
`
`
`
`
`
`

`

`U.S. Patent
`US. Patent
`
`Mar.26,2002
`
`Sheet 8 of 13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`<.0
`L()
`
`B.aJO_0—I:_m7,w.\L%ma0%
`
`0
`.
`<..9
`LL
`
`Zm
`
`"““““‘A—uM"‘.’““““.I"“‘““".
`2..\M“i““‘
`‘4'“
`
`\figr/J7/.gWumi‘
`0A\.h
`
`
`
`mmmwho90
`
`Q
`.0
`<.0
`~
`W
`
`9(
`
`“\“\K.Wfikm$gA
`
`05
`
`050%ma
`
`:OE
`
`.
`<..9
`LL
`
`PAGE 10 0F 26
`
`PAGE 10 OF 26
`
`
`
`
`
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 26, 2002
`Mar. 26,2002
`
`Sheet 9 0f 13
`Sheet 9 of 13
`
`US 6,362,554 Bl
`
`FIG. 12
`
`
`
`PAGE 11 OF 26
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 26, 2002
`Mar.26,2002
`
`Sheet 10 0f 13
`Sheet 10 of 13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`FlG.l4
`
`‘
`
`\
`
`V W”!
`mmk
`(Ina‘
`
`"an
`
`844
`
`848
`
`PAGE 12 0F 26
`
`PAGE 12 OF 26
`
`

`

`U.S. Patent
`
`Mar.26,2002
`
`Sheet 11 of 13
`
`US 6,362,554 Bl
`
`
`
`L!)l
`
`. I
`
`- .
`(.9
`lL
`
`PAGE 13 OF 26
`
`

`

`Sheet 12 of 13
`
`US 6,362,554 Bl
`
`Mar.26,2002
`
`U.S. Patent
`FIG. 17
`
`912
`
`916
`
`FIG. 19
`
`FIG. 18
`
`PAGE 14 OF 26
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 26, 2002
`hdar.26,2002
`
`Sheet 13 of 13
`Sheet13 0f13
`
`US 6,362,554 Bl
`US 6,362,554 B1
`
`FJG. 20
`~
`I
`
`I
`
`
`
`1102
`
`PAGE 15 0F 26
`
`PAGE 15 OF 26
`
`

`

`US 6,362,554 Bl
`
`1
`STATOR ASSEMBLY
`
`REFERENCE TO EARLIER FILED
`APPLICATION
`
`The present application claims the benefit of the filing
`date under 35 U.S.C. §119(e) of provisional U.S. patent
`application Ser. No. 60/146,446, filed Jul. 29, 1999, which
`is hereby incorporated by reference.
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to a high speed
`motor. It relates particularly to a spindle motor such as used
`in a hard disc drive, and to the construction and arrangement
`of the body of the spindle motor to align and retain the
`respective component parts of the motor, as well as stator
`assemblies used in the motors and hard disc drives using the
`motors, and methods of developing and manufacturing high
`speed motors.
`
`BACKGROUND OF THE INVENTION
`
`30
`
`2
`the parts, as well as the overall tolerance that relates to the
`alignment of the parts relative to one another.
`In an effort to enable increased motor speed, some hard
`disc manufacturers have turned to the use of hydrodynamic
`5 bearings. These hydrodynamic bearings, however, have dif(cid:173)
`ferent aspect ratios from conventional bearings. An example
`of a different aspect ratio may be found in a cylindrical
`hydrodynamic bearing in which the length of the bearing is
`greater than it's diameter. This results in more susceptibility
`10 to problems induced by differing coefficients of thermal
`expansion than other metals used in existing spindle motors,
`making it difficult to maintain dimensional consistency over
`the operating temperature that the drive sees between the
`hydrodynamic bearings and other metal parts of the motor.
`15 Hydrodynamic bearings have less stiffness than conven(cid:173)
`tional ball bearings so they are more susceptible to imprecise
`rotation when exposed to vibrations or shock.
`An important characteristic of a hard drive is the amount
`of information that can be stored on a disc. One method to
`20 store more information on a disc is to place data tracks more
`closely together. Presently this spacing between portions of
`information is limited due to vibrations occurring during the
`operation of the motor. These vibrations can be caused when
`the stator windings are energized, which results in vibrations
`25 of a particular frequency. These vibrations also occur from
`harmonic oscillations in the hub and discs during rotation,
`caused primarily by non-uniform size media discs.
`An important factor in motor design is the lowering of the
`operating temperature of the motor. Increased motor tem(cid:173)
`perature affects the electrical efficiency of the motor and
`bearing life. As temperature increases, resistive loses in wire
`increase, thereby reducing total motor power. Furthermore,
`the Arhennius equation predicts that the failure rate of an
`electrical device is exponentially related to its operating
`temperature. The frictional heat generated by bearings
`increases with speed. Also, as bearings get hot they expand,
`and the bearing cages get stressed and may deflect, causing
`non-uniform rotation and the resultant further heat increase,
`non-uniform rotation requiring greater spacing in data
`tracks, and reduced bearing life. One drawback with existing
`motor designs is their limited effective dissipation of the
`heat, and difficulty in incorporating heat sinks to aid in heat
`dissipation. In addition, in current motors the operating
`temperatures generally increase as the size of the motor is
`decreased.
`Manufacturers have established strict requirements on the
`outgassing of materials that are used inside a hard disc drive.
`These requirements are intended to reduce the emission of
`materials onto the magnetic media or heads during the
`operation of the drive. Of primary concern are glues used to
`attach components together, varnish used to insulate wire,
`and epoxy used to protect steel laminations from oxidation.
`In addition to such outgassed materials, airborne particu(cid:173)
`late in a drive may lead to head damage. Also, airborne
`particulates in the disc drive could interfere with signal
`transfer between the read/write head and the media. To
`reduce the effects of potential airborne particulate, hard
`drives are manufactured to exacting clean room standards
`and air filters are installed inside of the drive to reduce the
`contamination levels during operation.
`Heads used in disc drives are susceptible to damage from
`electrical shorts passing through a small air gap between the
`media and the head surface. In order to prevent such shorts,
`some hard drives use a plastic or rubber ring to isolate the
`spindle motor from the hard drive case. A drawback to this
`design is the requirement of an extra component.
`
`35
`
`40
`
`45
`
`Computers commonly use disc drives for memory storage
`purposes. Disc drives include a stack of one or more
`magnetic discs that rotate and are accessed using a head or
`read-write transducer. Typically, a high speed motor such as
`a spindle motor is used to rotate the discs.
`An example of a conventional spindle motor 1 is shown
`in FIG. 1. The motor 1 includes a base 2 which is usually
`made from die cast aluminum, a stator 4, a shaft 6, bearings
`7 and a disc support member 8, also referred to as a hub. A
`magnet 3 and flux return ring 5 are attached to the disc
`support member 8. The stator 4 is separated from the base 2
`using an insulator (not shown) and attached to the base 2
`using a glue. Distinct structures are formed in the base 2 and
`the disc support member 8 to accommodate the bearings 7.
`One end of the shaft 6 is inserted into the bearing 7
`positioned in the base 2 and the other end of the shaft 6 is
`placed in the bearing 7 located in the hub 8. A separate
`electrical connector 9 may also be inserted into the base 2.
`Each of these parts must be fixed at predefined tolerances
`with respect to one another. Accuracy in these tolerances can
`significantly enhance motor performance.
`In operation, the disc stack is placed upon the hub. The
`stator windings are selectively energized and interact with
`the permanent magnet to cause a defined rotation of the hub.
`As hub 8 rotates, the head engages in reading or writing
`activities based upon instructions from the CPU in the
`computer.
`Manufacturers of disc drives are constantly seeking to 50
`improve the speed with which data can be accessed. To an
`extent, this speed depends upon the speed of the spindle
`motor, as existing magneto-resistive head technology is
`capable of accessing data at a rate greater than the speed
`offered by the highest speed spindle motor currently in 55
`production. The speed of the spindle motor is dependent
`upon the dimensional consistency or tolerances between the
`various components of the motor. Greater dimensional con(cid:173)
`sistency between components leads to a smaller gap between
`the stator 4 and the magnet 3, producing more force, which 60
`provides more torque and enables faster acceleration and
`higher rotational speeds. One drawback of conventional
`spindle motors is that a number of separate parts are required
`to fix motor components to one another. This can lead to
`stack up tolerances which reduce the overall dimensional 65
`consistency between the components. Stack up tolerances
`refers to the sum of the variation of all the tolerances of all
`
`PAGE 16 OF 26
`
`

`

`US 6,362,554 Bl
`
`4
`BRIEF DESCRIPTION OF SEVERAL VIEWS OF
`THE DRAWINGS
`
`5
`
`3
`Another example of a spindle motor is shown in U.S. Pat.
`No. 5,694,268 (Dunfield et al.) (incorporated herein by
`reference). Referring to FIGS. 7 and 8 of this patent, a stator
`200 of the spindle motor is encapsulated with an overmold
`209. The overmolded stator contains openings through
`which mounting pins 242 may be inserted for attaching the
`stator 200 to a base. U.S. Pat. No. 5,672,972 (Viskochil)
`(incorporated herein by reference) also discloses a spindle
`motor having an overmolded stator. One drawback with the
`overmold used in these patents is that it has a different 10
`coefficient of linear thermal expansion ("CLTE") than the
`corresponding metal parts to which it is attached. Another
`drawback with the overmold is that it is not very effective at
`dissipating heat. Further, the overmolds shown in these
`patents are not effective in dampening some vibrations 15
`generated by energizing the stator windings.
`U.S. Pat. No. 5,806,169 (Trago) (incorporated herein by
`reference) discloses a method of fabricating an injection
`molded motor assembly. However, the motor disclosed in
`Trago is a step motor, not a high speed spindle motor, and 20
`would not be used in applications such as hard disc drives.
`Thus, a need exists for an improved high speed spindle
`motor, having properties that will be especially useful in a
`hard disc drive, overcoming the aforementioned problems.
`
`BRIEF SUMMARY OF THE INVENTION
`
`25
`
`FIG. 1 is an exploded, partial cross-sectional and perspec-
`tive view of a prior art high speed motor.
`FIG. 2 is a perspective view of a stator used in a first
`embodiment of the present invention.
`FIG. 3 is an exploded, partial cross-sectional and perspec(cid:173)
`tive view of a high speed motor in accordance with the first
`embodiment of the present invention.
`FIG. 4 is a cross-sectional view of the high speed motor
`of FIG. 3.
`FIG. 5 is an exploded, partial cross-sectional and perspec(cid:173)
`tive view of a high speed motor in accordance with a second
`embodiment of the present invention.
`FIG. 6 is a cross-sectional view of the high speed motor
`shown in FIG. 5.
`FIG. 7 is an exploded, partial cross-sectional and perspec(cid:173)
`tive view of a high speed motor in accordance with a third
`embodiment of the present invention.
`FIG. 8 is an exploded, partial cross-sectional and perspec(cid:173)
`tive view of a high speed motor in accordance with a fourth
`embodiment of the present invention.
`FIG. 9 is a cross-sectional view of a high speed motor in
`accordance with a fifth embodiment of the present invention.
`FIG. 10 is a cross-sectional view of a high speed motor in
`accordance with a sixth embodiment of the present inven(cid:173)
`tion.
`FIG. 11 is a cross-sectional view of a high speed motor in
`accordance with a seventh embodiment of the present inven(cid:173)
`tion.
`FIG. 12 is a perspective view of the inserts used in the
`35 high speed motor of FIG. 11.
`FIG. 13 is a cross-sectional view of a high speed motor in
`accordance with an eighth embodiment of the present inven(cid:173)
`tion.
`FIG. 14 is an exploded, partial cross-sectional and per(cid:173)
`spective view of a high speed motor in accordance with the
`ninth embodiment of the present invention.
`FIG. 15 is a drawing of a mold used to make the
`encapsulated stator of FIG. 3.
`FIG. 16 is a drawing of the mold of FIG. 15 in a closed
`position.
`FIG. 17 is an exploded and partial cross sectional view of
`components used in a pancake motor, a tenth embodiment of
`the invention.
`FIG. 18 is a cross-sectional view of a high speed motor in
`accordance with an eleventh embodiment of the invention.
`FIG. 19 is a perspective view of a stator and shaft used in
`a twelfth embodiment of the present invention.
`FIG. 20 is an exploded and partial cross sectional view of
`55 a hard disc drive of the present invention.
`
`30
`
`40
`
`A high speed motor has been invented which overcomes
`many of the foregoing problems. In addition, unique stator
`assemblies and other components of a high speed motor
`have been invented, as well as methods of manufacturing
`and developing motors and hard disc drives. In one aspect,
`the invention is a high speed spindle motor comprising: a
`stator assembly, including a stator having multiple conduc(cid:173)
`tors that create a plurality of magnetic fields when electrical
`current is conducted by the conductors; and a body of a
`phase change material substantially encapsulating the stator;
`a rotatable hub having a magnet connected thereto in oper(cid:173)
`able proximity to the stator; a shaft; a bearing around the
`shaft; and one of the shaft or bearing being fixed to the stator
`assembly and the other of the shaft or bearing being fixed to
`the rotatable hub.
`In another aspect the invention is a stator assembly
`comprising a) a magnetically inducible core; b) a plurality of
`conductors in proximity to the core such that magnetic fields 45
`are induced in the core when electrical current is conducted
`through the conductors; and c) a body of a phase change
`material substantially encapsulating the core and
`conductors, the phase change material having a coefficient of
`linear thermal expansion approximately the same as the 50
`coefficient of linear thermal expansion of the core.
`In another aspect the invention is a stator assembly
`comprising: a) a stator having multiple conductors that
`create a plurality of magnetic fields when electrical current
`is conducted through the conductors; and b) a body of phase
`change material substantially encapsulating the conductors,
`the phase change material having a thermal conductivity of
`at least 0.7 watts/meter0 K. and a dielectric strength of at
`least 250 volts/mil.
`The invention provides the foregoing and other features, 60
`and the advantages of the invention will become further
`apparent from the following detailed description of the
`presently preferred embodiments, read in conjunction with
`the accompanying drawings. The detailed description and
`drawings are merely illustrative of the invention and do not 65
`limit the scope of the invention, which is defined by the
`appended claims and equivalents thereof.
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`AND PREFERRED EMBODIMENTS OF THE
`INVENTION
`
`First Embodiment
`A first embodiment of a high speed motor of the present
`invention is shown in FIGS. 2-4. By "high speed" it is meant
`that the motor can operate at over 5,000 rpm. The spindle
`motor 10 is designed for rotating a disc or stack of discs in
`a computer hard disc drive. Motor 10 is formed using an
`encapsulation method which reduces the number of parts
`
`PAGE 17 OF 26
`
`

`

`US 6,362,554 Bl
`
`5
`needed to manufacture the motor as compared with conven(cid:173)
`tional motors used for disc drives, thereby reducing stack up
`tolerances and manufacturing costs and producing other
`advantages discussed below.
`Referring to FIG. 2, a stator 20 is first constructed, using
`conventional steel laminations 11 forming a magnetically
`inducible core 17 having a plurality of salient poles 21
`thereon, and wire windings 15 which serve as conductors.
`The conductors induce or otherwise create a plurality of
`magnetic fields in the core when electrical current is con(cid:173)
`ducted through the conductors. In this embodiment, a mag(cid:173)
`netic field is induced in each of the poles 21.
`The stator 20 is then used to construct the rest of the
`spindle motor 10 (FIG. 3). The spindle motor 10 includes a
`hub 12, which serves as a disc support member, the stator 20
`and a body 14. Together the stator 20 and body 14 make up
`a stator assembly 13. The body 14 is preferably a monolithic
`body 14. Monolithic is defined as being formed as a single
`piece. The body 14 substantially encapsulates the stator 20.
`Substantial encapsulation means that the body 14 either
`entirely surrounds the stator 20, or surrounds almost all of it
`except for minor areas of the stator that may be exposed.
`However, substantial encapsulation means that the body 14
`and stator 20 are rigidly fixed together, and behave as a
`single component with respect to harmonic oscillation vibra(cid:173)
`tion.
`The body 14 is preferably formed of a phase change
`material, meaning a material that can be used in a liquid
`phase to envelope the stator, but which later changes to a
`solid phase. There are two types of phase change materials
`that will be most useful in practicing the invention: tem(cid:173)
`perature activated and chemically activated. A temperature
`activated phase change material will become molten at a
`higher temperature, and then solidify at a lower temperature.
`However, in order to be practical, the phase change material
`must be molten at a temperature that is low enough that it
`can be used to encapsulate a stator. Preferred temperature
`activated phase change materials will be changed from a
`liquid to a solid at a temperature in the range of about 200
`to 700° F. The most preferred temperature activated phase
`change materials are thermoplastics. The preferred thermo(cid:173)
`plastic will become molten at a temperature at which it is
`injection-moldable, and then will be solid at normal oper(cid:173)
`ating temperatures for the motor. An example of a phase
`change material that changes phases due to a chemical
`reaction, and which could be used to form the body 14, is an
`epoxy. Other suitable phase change materials may be clas(cid:173)
`sified as thermosetting materials.
`As shown in FIG. 4, a shaft 16 is connected to the hub or 50
`disc support member 12 and is surrounded by bearings 18,
`which are adjacent against the body 14. A rotor or magnet 28
`is fixed to the inside of the hub 12 on a flange so as to be in
`operable proximity to the stator. The magnet 28 is preferably
`a permanent magnet, as described below. The body 14
`includes a base 22. In addition, mounting features, such as
`apertures 25, and terminals comprising a connector 26 for
`connecting the conductors to an external power source are
`formed as a part of the stator assembly. The terminals 26 are
`partially encapsulated in the body 14.
`Referring to FIGS. 3-4, the base 22 of the body 14 is
`generally connected to the hard drive case (not shown).
`Connecting members (not shown), such as screws, may be
`used to fix the base 22 to the hard drive case, using holes 25
`as shown in FIG. 3. Alternatively, other types of mounting
`features such as connecting pins or legs may be formed as
`part of the base 22. The connector 26 is preferably a
`
`6
`through-hole pin type of connector 26 and is coupled
`through the hard drive case to the control circuit board
`residing on the outer surface of the base (not shown).
`Alternatively the connector may be a flexible circuit with
`5 copper pads allowing spring contact interconnection.
`The stator 20 is positioned in the body 14 generally in a
`direction perpendicular to an interior portion 30. Referring
`to FIG. 2, the stator 20 is preferably annular in shape and
`contains an open central portion 32. The poles 21 extend
`10 radially outward from this central portion 32. Faces of the
`poles 21 are positioned outward relative to the central
`portion 32 of the stator 20. The body 14 is molded around
`the stator 20 in a manner such that the faces of the poles are
`exposed and are surrounded by and aligned concentrically
`with respect to the disc support member 12. Alternatively,
`15 the poles may be totally encapsulated in body 14 and not be
`exposed.
`Referring to FIG. 4, the body 14 has an upper portion 40
`that extends upwardly from the stator 20. The upper portion
`40 is also preferably annular shaped. The body 14 includes
`20 the interior portion 30. The interior portion 30 is generally
`sized and shaped to accommodate the bearings 18. The
`interior portion 30 includes an upper support portion 42 and
`a lower support portion 44. In the embodiment illustrated in
`FIG. 4 the interior portion 30 is preferably cylindrically
`25 shaped.
`The phase change material used to make the body 14 is
`preferably a thermally conductive but non-electrically con(cid:173)
`ductive plastic. In addition, the plastic preferably includes
`ceramic filler particles that enhance the thermal conductivity
`30 of the plastic. A preferred form of plastic is polyphenyl
`sulfide (PPS) sold under the tradename "Konduit" by LNP.
`Grade OTF-212 PPS is particularly preferred. Examples of
`other suitable thermoplastic resins include, but are not
`limited to, thermoplastic resins such as 6,6-polyamide,
`35 6-polyamide, 4,6-polyamide, 12,12-polyamide, 6,12-
`polyamide, and polyamides containing aromatic monomers,
`polybutylene terephthalate, polyethylene terephthalate,
`polyethylene napththalate, polybutylene napththalate, aro(cid:173)
`matic polyesters, liquid crystal polymers, polycyclohexane
`40 dimethylol terephthalate, copolyetheresters, polyphenylene
`sulfide, polyacylics, polypropylene, polyethylene,
`polyacetals, polymethylpentene, polyetherimides,
`polycarbonate, polysulfone, polyethersulfone, polyphe(cid:173)
`nylene oxide, polystyrene, styrene copolymer, mixtures and
`45 graft copolymers of styrene and rubber, and glass reinforced
`or impact modified versions of such resins. Blends of these
`resins such as polyphenylene oxide and polyamide blends,
`and polycarbonate and polybutylene terephthalate, may also
`be used in this invention.
`Referring to FIG. 4, the bearings 18 include an upper
`bearing 46 and a lower bearing 48. Also, each bearing 18 has
`an outer surface 50 and an inner surface 52. The outer
`surface 50 of the upper bearing contacts the upper support
`portion 42 and the outer surface 50 of the lower bearing 48
`55 contacts the lower support portion 44. The inner surfaces 52
`of the bearings 18 contact the shaft 16. The bearings are
`preferably an