USOO7683509B2
`
`(12) United States Patent
`(10) Patent N0.:
`US 7,683,509 B2
`Neal
`(45) Date of Patent:
`Mar. 23, 2010
`
`ELECTROMAGNETIC DEVICE WITH OPEN,
`NON-LINEAR HEAT TRANSFER SYSTEM
`
`Inventor: Griffith D. Neal, Alameda, CA (US)
`
`6,903,471 132*
`6,986,647 132 r
`7,186,093 B2 *
`7,196,439 132 *
`
`6/2005
`1/2006
`3/2007
`3/2007
`
`Ai'imitsu et a1.
`Jones et a1.
`Goshi
`...... ..
`Pierret et a1.
`
`............. ,. 310/59
`417/357
`417/53
`................ .. 310/58
`
`Assignee: Encap Technologies Inc., Alameda, CA
`(US)
`
`* cited by examiner
`
`Electromagnetic components are provided with a heat
`exchange mechanism. For example, a fluid-cooled electro-
`magnetic field—functioning device, such as a motor, generator,
`transformer, solenoid or relay, comprises one or more elec-
`trical conductors. A monolithic body of phase change mate-
`rial substantially encapsulates the conductors or an inductor.
`At least onc liquid-tight coolant channel is also substantially
`encapsulated Within the body of phase change material. The
`coolant channel may be part of a heat pipe or cold plate. The
`coolant channel may be made by molding a conduit into the
`body, using a “lost wax” molding process, or injecting gas
`into the molten phase change material while it is in the mold.
`The coolant channel may also be formed at the juncture
`between the body and a cover over the body.
`
`\
`
`Primary ExamineriMichael C Zarroli
`(74)A ttomey, Agem, orFirmiBrinks Hofer Gilson & Lione;
`Steven P. Shurtz
`
`(57)
`
`ABSTRACT
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 661 days.
`
`11/489,914
`
`Jul. 19, 2006
`
`Prior Publication Data
`
`US 2008/0017354 A1
`
`Jan. 24, 2008
`
`Int. Cl.
`(2006.01)
`H02K 11/00
`US. Cl.
`......................... .. 310/54; 310/58; ISO/65.1
`Field of Classification Search ................. .. 310/54,
`310/52, 43, 58759, 64,
`ISO/65.1
`See application file for complete search history.
`References Cited
`
`US. PATENT DOCUMENTS
`
`5,072,145 A *
`
`12/1991 Davisetal.
`
`................. ..3lO/54
`
`16 Claims, 14 Drawing Sheets
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`inlet and fluid outlet.
`
`The present invention utilizes aspects ofApplicant’ s earlier
`inventions, some ofwhich are repeated herein. U.S. Pat. Nos.
`6,362,554; 6,753,682 and 6,911,166, which are hereby incor-
`poratcd by reference, further disclose some ofthese concepts.
`An example of a conventional motor 1 is shown in FIG. 1.
`he 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 cormector 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.
`An important factor in motor design is the lowering of the
`operating temperature of the motor. Increased motor tem-
`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 Arrhenius equation predicts that the failure rate of an
`electrical device is exponentially related to its operating tem-
`perature. 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. One
`drawback with existing motor designs is their limited effec-
`tive dissipation of the heat, and difliculty 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.
`
`US 7,683,509 B2
`
`2
`liquids in particular, typically have a high enough heat capac—
`ity that they can be used to carry away heat. For example, a
`water pump driven by a motor uses the water to cool the
`plunp. The problem with liquids, however, is getting them in
`contact with hot motor surfaces without damaging the motor,
`and then collecting them to carry them away. Thus, a need
`exists for an improved motor that includes an effective and
`practical way of using a liquid to carry heat away from the
`motor. Also, a need exits for improved methods of cooling
`other electromagnetic components.
`Also, there are times when the heat generated by operation
`of the electrical device, such as a motor, could be put to a
`beneficial use if there were a way to confine a fluid used in a
`heat transfer relationship with the device so that it could be
`directed to a point of desired use. Thus, if liquids or gasses
`could be channeled in such a way that they picked up heat
`from an electromagnetic device without damaging the device,
`and then carried that heat to a place where the heat was
`desired, that would be a great benefit.
`One difficulty encountered in the design of electrical com—
`ponents is that various components need to withstand expo-
`sure to solvents and particulates. The environmental agents
`can corrode the conductors or inductors in the component. In
`pumps used for movement of corrosive agents, this can be a
`particular problem. In hybrid electric vehicles where the
`motor or generator resides inside ofthe transmission ho using,
`stray metallic debris generated from the transmission gears
`may be thrown into the windings, damaging them to the point
`that the device no longer works.
`
`
`
`BRIEF SUMMARY OF 1H i INV iN 1 ION
`
`
`
`Electromagnetic devices have been invented which over—
`come many of the foregoing problems. In one class of
`devices, a heat transfer fluid flows through the device. In
`another class of devices, a heat transfer fluid is contained
`within the device. Encapsulating portions of the device at the
`same time a heat exchange mechanism is provided may pro-
`vide the additional benefit of protecting the parts from corro-
`sive or otherwise damaging environments.
`In a first aspect, the invention is a fluid-cooled electromag-
`netic field-functioning device comprising at least one electri-
`cal conductor; a monolithic body of injection molded ther-
`moplastic material substantially encapsulating the at least one
`conductor; and a non-linear heat transfer fluid pathway in the
`monolithic body, with at least one fluid inlet and at least one
`fluid outlet to the pathway to allow for passage ofheat transfer
`fluid through the pathway.
`In a second aspect, the invention is a fluid-cooled electro-
`magnetic field-fiJnctioning device comprising at least one
`conductor and at least one inductor; a monolithic body of
`injection molded thermoplastic material substantially encap-
`sulating the at least one inductor, and a non-linear heat trans-
`fer fluid pathway in the monolithic body, with at least one
`fluid inlet and at least one fluid outlet to the pathway to allow
`for pas sage of heat transfer fluid through the pathway.
`In a third aspect the invention is a fluid-cooled electromag-
`netic field-functioning device comprising at least one electri-
`cal conductor; a monolithic body of injection molded ther—
`moplastic material substantially encapsulating the at least one
`conductor; and a non-linear heat transfer fluid pathway in the
`monolithic body, with at least one fluid inlet and at least one
`fluid outlet to the pathway to allow for passage ofheat transfer
`fluid through the pathway, and wherein the monolithic body
`completely covers the exterior of the device except for fluid
`
`1
`ELECTROMAGNETIC DEVICE WITH OPEN,
`NON-LINEAR HEAT TRANSFER SYSTEM
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to electromagnetic
`devices that include heat exchange mechanisms. It relates
`particularly to motors, generators, transfonners, relays and
`solenoids that are cooled by a fluid coolant. The devices can
`be used in various electronic products, such as a motor for
`hard disc drive or other consumer electronic device, a pump
`motor, a rnotor/generator used in a hybrid electric vehicle, a
`motor used in an air blower and a solenoid used in a fuel
`injector or liquid flow valve.
`In addition to the present application, Applicant has filed
`four other applications with similar disclosures but different
`claims. Those applications are as follows: application Ser.
`No. 11/485,822; application Ser. No. 11/489,911; application
`Ser. No. 11/489,912; and application Ser. No. 11/489,913.
`BACKGROI \]
`) OF THE INVENTION
`
`,_
`
`
`
`Electromagnetic devices used in electrical products may
`need to be cooled to remove heat generated by operation of
`the device. It is well known that a fluid in the environment of
`the device can be used to aid cooling. As an example, a
`method of cooling a motor is to include a fan on the motor
`shaft. The fan then blows air past the motor. Air, however, has
`a fairly low heat capacity, and thus cannot carry away as much
`heat as is sometime generated by the motor. Also, in some
`applications there is no place to mount a fan. Other fluids, and
`
`Petitioners' Exhibit 1001, pg. 16
`
`

`

`US 7,683,509 B2
`
`BRIEF DESCRIPTION OF SEVERAL VIEWS OF
`
`4
`
`
`THE DRAW \lGS
`
`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-
`tive view of a high speed motor in accordance with a first
`embodiment of the present invention.
`FIG. 4 is a cross—sectional view ofthe high speed motor of
`FIG. 3.
`FIG. 5 is a schematic drawing ofa mold used to make the
`encapsulated stator of the motor of FIG. 3.
`FIG. 6 is a schematic drawing of the mold of FIG. 5 in a
`closed position.
`FIG. 7 is an exploded, partial cross-sectional and perspec-
`tive View of a high speed motor in accordance with a second
`embodiment of the present invention.
`FIG. 8 is a cross—sectional view ofa high speed motor in
`accordance with a third embodiment ofthe present invention.
`FIG. 9 is a cross-sectional view of a high speed motor in
`accordance with a fourth embodiment of the present inven-
`tion.
`FIG. 10 is aperspective view ofa stator, shaft andcoldplate
`used in a fifth embodiment of the present invention.
`FIG. 11 is an exploded view of a hard disc drive of the
`present invention using the components of FIG. 10.
`FIG. 12 is a perspective, partially cross—sectional View of a
`motor/generator for an electric vehicle using a liquid cooling
`channel.
`FIG. 13 is a cross sectional View ofthe motor/generator of
`FIG. 12.
`FIG. 14 is an exploded and partial cross sectional View of
`the motor/generator of FIG. 12.
`FIG. 15 is an enlarged cross-sectional view ofa portion of
`the motor/generator of FIG. 12.
`FIG. 16 is a cross—sectional view of a motor in accordance
`with a seventh embodiment of the invention.
`FIG. 17 is a cross-sectional view of a transfonner in accor-
`dance with the invention.
`FIG. 18 is a cross—sectional view ofa solenoid used in a fuel
`injector in accordance with the invention.
`FIG. 19 is a cross-sectional View taken along line 19-19 of
`FIG. 18.
`FIG. 20 is a cross-sectional view ofa solenoid flow valve in
`accordance with the invention.
`FIG. 21 is a perspective view ofa heat transfer fluid con-
`finement member used in tie valve of FIG. 20.
`
`magnetic field, which in turn induces an electrical current in
`
`
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`
`AND PR 4 F E RRED E MBODIMENTS OF THE
`IN VEN'I'ION
`
`
`
`The term “electromagnetic field-functioning device” as
`used in the present application includes electromagnetic
`devices that include one or more electrical conductors and use
`an electromagnetic field as part of the function of the device.
`In some embodiments, the device includes a moving part, and
`there is a relationship between movement of the moving part
`and flow of current in the conductors involving one or more
`magnetic fields. For example, in some devices, such as a
`motor or solenoid, current in the one or more conductors
`generates one or more magnetic fields, which generate a force
`that causes movement of the moving part. In other devices,
`such as a generator,
`the moving part generates a moving
`
`3
`In another aspect, the invention is a fluid—cooled electro—
`magnetic field-functioning device comprising one or more
`electrical conductors, a heat transfer fluid confinement mem-
`ber; and a monolithic body ofphase change material substan-
`tially encapsulating both the one or more conductors and the
`heat transfer fluid confinement member.
`
`5
`
`In yet another aspect the invention is a fluid-cooled elec-
`tromagnetic device comprising an assembly comprising i) an
`inductor in operable proximity to at least one conductor that
`creates at least one magnetic field when electrical current is
`conducted by the conductor; and ii) a body of a phase change
`material substantially encapsulating the conductor; and at
`least one liquid-tight coolant chamiel substantially encapsu-
`lated within the body of phase change material.
`In still another aspect the invention is a fluid-cooled elec-
`tromagnetic field-functioning device comprising an inductor
`and at least one conductor that creates at least one magnetic
`field when electrical current is conducted by the conductor; a
`heat transfer fluid confinement member containing a heat
`transfer fluid; and a monolithic body ofphase change material
`substantially encapsulating at least one ofthe inductor and the
`at least one conductor, the monolithic body being in themial
`contact with the heat transfer fluid.
`
`A further aspect of the invention is a method of making a I
`fluid—cooled electromagnetic field—functioning device com—
`prising the steps ofproviding a core assembly comprising an
`inductor and at least one conductor that creates at least one
`magnetic field when electrical current is conducted by the
`conductor, substantially encapsulating at least one of the
`inductor and the at least one conductor in a body of phase
`change material; providing a heat transfer Iluid confinement
`chamber in the body of phase change material; and, adding a
`heat transfer fluid to the confinement chamber and sealing the
`chamber to retain the heat transfer fluid in the chamber.
`
`In another aspect the invention is a method of cooling an
`electromagnetic field -functioning device wherein the electro-
`magnetic field—functioning device comprises one or more
`electrical conductors and a monolithic body of phase change
`material substantially encapsulating the one or more conduc-
`tors, wherein a heat transfer fluid flows through a confined
`path substantially within the body ofphase change material to
`transfer heat away from the conductors.
`In one embodiment, a motor can be cooled by using a heat
`pipe embedded in a body of phase change material that also
`substantially encapsulates parts of the motor. In another
`embodiment, a motor can be cooled by pas sing liquid through
`a coolant channel encased in the body of phase change mate-
`rial also substantially encapsulating the motor component,
`The body of phase change material provides a path for the ,
`heat to be transferred from the stator to the liquid coolant,
`where it can be carried away. The liquid is also confined, so
`that it does not contact other parts of the motor or get ran-
`domly discharged from the motor. Besides motors, other elec-
`tromagnetic field function devices may be made with coolant
`chamiels. The flow path or chamber for the coolant may be
`formed by injecting gas into the molten thermoplastic after it
`has been injected into a mold but before it solidifies to form
`the body encapsulating the motor component, or component
`of other electromagnetic field—functioning devices. The fore—
`going and other features, and the advantages ofthe 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 ofthe inven—
`tion and do not limit the scope of the invention. which is
`defined by the appended claims and equivalents thereof.
`
`Petitioners' Exhibit 1001, pg. 17
`
`

`

`US 7,683,509 B2
`
`5
`the one or more conductors. In some devices, like transform—
`ers, current conducted by the one or more conductors creates
`a magnetic field, and the magnetic field induces a current in a
`second conductor coupled to the magnetic field.
`The term “heat transfer fluid” as used in the present appli-
`cation includes both liquids and gases, as well as combina-
`tions thereof. While liquids typically have a higher heat
`capacity per unit volume, and will therefore be more fre—
`quently used in the present invention, gases, such as air, may
`also serve as heat transfer Iuids.
`
`maimer such that the faces of the poles are exposed and are
`
`6
`the body 14 and stator 20 are rigidly fixed together, and
`behave as a single component with respect to harmonic oscil-
`lation vibration.
`The body 14 is preferably formed of a phase change mate-
`rial, 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: temperature 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 encap-
`sulate a stator. Preferred temperature activated phase change
`materials will be changed from a liquid to a solid at a tem—
`perature in the range of about 200 to 7000 F. The most pre-
`ferred temperature aetivated phase change materials are ther-
`rnoplastics. The preferred thermoplastic will become molten
`at a temperature at which it is injection—moldable, and then
`‘ will be solid at normal operating 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 mate-
`rials may be classified as thermosetting materials.
`As shown in FIG. 4, a shaft 16 is connected to the hub or
`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 (FIG. 3), and terminals comprising a connector
`26 for cormecting 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.
`The heat pipe 62 is positioned in the body 14 so that one end
`is near the stator 20, which will be the high-temperature
`region. The other end has one face that is not covered by the
`phase change material. This face is located ust below the hub
`12, so that air currents created by the spimiing hub can convey
`heat away from the exposed face, which serves as the low-
`temperature region. The heat pipe 62 is substantially encap—
`sulated in the body 14, as the body 14 surrounds almost all of
`the heat pipe 62 except for the minor exposed face, and the
`body 14 and heat pipe 62 are rigidly fixed together, and
`behave as a single component with respect to harmonic oscil-
`lation vibration.
`the base 22 of the body 14 is
`Referring to FIGS. 3-4,
`generally connected to the hard drive case (not shown). Con-
`necting 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 . Altematively, other types ofmounting features such
`as connecting pins or legs may be formed as part of the base
`22, The connector 26 is preferably a 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 ofthe base
`(not shown). Alternatively the cormector may be a flexible
`circuit with copper pads allowing spring contact interc01mec-
`tion.
`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 con-
`tains an open central portion 32. The poles 21 extend radially
`outward from this central portion 32. Faces ofthe 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
`
`First Embodiment
`
`
`
`A first embodiment of a motor of the present invention is
`shown in FIGS. 2-4. The motor may be a “high speed” motor,
`meaning that the motor can operate at over 5,000 rpm. The
`motor 10 is designed for rotating a disc or stack of discs in a
`computer hard disc drive. Motor 10 is formed using an encap-
`sulation method which reduces the number of parts needed to
`manufacture the motor as compared with conventional
`motors used for disc drives, thereby reducing stack up toler-
`ances and manufacturing costs and producing other advan—
`tages discussed below.
`Referring to FIG. 2, a stator 20 is first constructed, using I
`conventional steel laminations 11 forming a magnetically
`inducible core 17 having a plurality of poles 21 thereon, and
`wire windings 15 which serve as conductors. The conductors
`induce or otherwise create a plurality ofma gnetic fields in the
`core when electrical current is conducted through the conduc-
`tors. In this embodiment, a magnetic field is induced in each
`of the poles 21.
`The stator 20 is then used to construct the rest of the motor
`10 (FIG. 3). The motor 10 includes a hub 12, which serves as
`a disc support member, the stator 20, a heat transfer fluid
`confinement member 62 and a body 14. Together the stator 20
`and body 14 make up a stator assembly 13. The heat transfer
`fluid confinement member 62 constitutes a heat pipe in the
`embodiment of FIGS. 2—4. The heat pipe has an annular
`shape. Heat pipes function by containing a fluid that carries
`heat from a high-temperature region to a low-temperature
`region, and then migrates back to the hi gh-temperature region
`to repeat the cycle. Many heat pipes include a liquid that
`vaporizes at the temperature encountered in the high-tem-
`perature region, and travels as a gas to the low-temperature
`region, where it condenses. The heat pipes preferably include
`an internal capillary structure, such as a wick, saturated with
`the working fluid. As heat is input at the high—temperature
`region (sometimes referred to as the evaporator), fluid is
`vaporized, creating a pressure gradient in the heat pipe. This 7
`pressure gradient forces the vaporto flow along the pipe to the
`low—temperature region, where it condenses, giving up its
`latent heat ofvaporization. The working fluid is then returned
`to the evaporator by the capillary forces developed in the wick
`structure. The heat pipe is sealed to prevent loss of the heat
`transfer fluid. A heat pipe is thus one example of a heat
`transfer fluid confinement member comprising a heat transfer
`fluid in a sealed system. Heat pipes can be built in a variety of
`shapes. The internal structure ofthe heat pipe 62 is not shown,
`but may be of any known arrangement, optimized for the
`expected operating temperature of the motor.
`The body 14 is preferably a monolithic body 14. Mono-
`lithic is defined as being formed as a singlepiece, The body 14
`substantially encapsulates the stator 20. Substantial encapsu-
`lation means that the body 14 either entirely surrounds the
`stator 20, or surrounds significant areas of the stator that may
`be exposed. However, substantial encapsulation means that
`
`Petitioners' Exhibit 1001, pg. 18
`
`

`

`molding apparatus suitable for use in the method comprises
`
`7
`surrounded by and aligned concentrically with respect to the
`disc support member 12. Alternatively, 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 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 shaped.
`The phase change material used to make the body 14 is
`preferably a thermally conductive but non-electrically con-
`ductive plastic. In addition, the plastic preferably includes
`ceramic filler particles that enhance the thermal conductivity
`of the plastic so that it has a coefficient of thermal expansion
`similar to that ofthe heat pipe. I11 that way, as the encapsulated
`product changes temperature, either from cooling after been
`molded, or heating during operation, the body 14 will stay in
`close contact with the heat pipe, but will not expand faster and
`cause pressure on the heat pipe, or thermal hardening of the
`walls ofthe heat pipe. Ifthe thermoplastic body and heat pipe
`were to separate, thch would be a significant barrier to ther-
`mal conductivity across that juncture.
`Apreferred form ofplastic is polyphenyl sulfide (PPS) sold I
`under the trade name “Konduit” by General Electric Plastics.
`Grade OTF-ZlZ-ll PPS is particularly preferred. Examples
`of other suitable thermoplastic resins include, but are not
`limited to,
`themioplastic resins such as 6,6—polyamide,
`6-polyamide, 4,6-polyamide, 2,12-polyamide, 6,12-polya-
`mide, and polyamides containing aromatic monomers, poly-
`butylene terephthalate, polyethylene terephthalate, polyeth-
`ylene naphthalate, polybutylene naphthalate,
`aromatic
`polyesters, liquid crystal polymers. polycyclohexane dim-
`ethylol terephthalate, copolyetheresters, polyphenylene sul-
`fide, polyacylics, polypropylene, polyethylene, polyacetals,
`polymcthylpcntcnc,
`polycthcrimidcs,
`polycarbonate,
`polysulfone, polyethersulfone, polyphenylene oxide, poly—
`styrene, styrene copolymer, mixtures and 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, andpolycarbon—
`ate 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 contacts the
`lower support portion 44. The inner surfaces 52 of the bear-
`ings 18 contact the shaft 16. The bearings are preferably
`annular shaped. The inner surfaces 52 of the bearings 18 may
`be press fit onto the sha'" 16. A glue may also be used. The
`outer surface 50 of the bearings 18 may be press fit into the
`interior portion 30 ofthe body 14. A glue may also be used.
`The bearings in the embodiment shown in FIGS. 3—4 are ball
`bearings. Alternatively ot 1er types ofbearings, such as hydro-
`dynamic or combinations of hydrodynamic and magnetic
`bearings, may be used. The bearings are typically made of
`stainless steel.
`The shaft 16 is concentrically disposed within the interior
`portion 30 ofthe body 14. The bearings 18 surround portions
`of the shaft 16. As described above, the inner surfaces 52 of
`the bearings are in contact with the shaft 16. The shaft 16
`includes a top portion 54 and a bottom portion 56. The top
`portion 54 of the shaft 16 is fixed to the hub 12. The bottom
`portion 54 of the shaft 16 is free to rotate inside the lower
`
`,
`
`
`
`US 7,683,509 B2
`
`8
`bearing. Thus, in this embodiment, the shaft 16 is freely
`rotatable relative to the body 14. The shaft 16 is preferably
`cylindrical shaped. The shaft 16 may be made of stainless
`steel.
`Referring to FIG. 4, the hub 12 is concentrically disposed
`around the body 14. The hub 12 is fixed to the shaft 16 and is
`spaced apart from the body 14. The hub 12 includes a flux
`return ring 58 and the magnet 28. The flux return ring 58 is
`glued to the disc support member. The magnet 28 is glued to
`the hub 12. As shown in FIG. 4, the magnet 28 concentrically
`surrounds the portion of the body 14 that includes the stator
`20. In this embodiment the magnet 28 and stator 20 are
`generally coplanar when the motor 10 is assembled.
`The magnet 28 is preferably a sintcrcd part and is one solid
`piece. The magnet 28 is placed in a magnetizer which puts a
`plurality of discrete North and South poles onto the magnet
`28, dependant on the ntunber ofpoles 21 on the stator 20. The
`flux return ring 58 is preferably made of a magnetic steel. The
`hub is preferably made of aluminum. Also, the hub may be
`‘ made of a magnetic material to replace the flux return ring.
`As shown in FIGS. 3 and 4, the heat pipe may compri se just
`one circumferential loop. Of course multiple heat pipes or
`pipe loops could be provided in the body 14.
`
`Operation of the First Embodiment
`In op