* cited by examiner
`
`Primary Examiner 7 Quang T Van
`(74) Attorney, Agent, or Firm iBrinks Ilofer Gilson &
`Lione; Steven P. Shurtz
`
`(57)
`
`ABSTRACT
`
`
`
`ELECTROMAGNETIC DEVICE WITH
`INTEGRATED FLUID FLOW' PATH
`
`Inventor: Griffith D. Neal, Alameda, CA (US)
`
`Assignee: Encap Technologies Inc.,Ala1neda, CA
`(US)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC. 154(b) by 1171 days.
`
`11/489,911
`
`Jul. 19, 2006
`
`Prior Publication Data
`
`US 2008/0029506 A1
`
`Feb. 7, 2008
`
`Int. Cl.
`(2006.01)
`H053 6/10
`(2006.01)
`II02K 9/20
`US. Cl.
`........................... .. 219/628; 310/54; 310/43
`Field of Classification Search ................ .. 219/628;
`310/43, 54, 55, 67 R, 89, 90, 156.23; 165/104.14,
`165/212, 214, 272.4, 285, 311; 62/101
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,678,881 A *
`7/1987 Griffith ....................... .. 219/631
`5,534,097 A *
`7/1996 Fasano etal.
`. .............. .. 156/214
`
`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, includes one or more electrical
`conductors. A monolithic body of phase change material
`substantially encapsulates the conductors or an inductor, At
`least one liquid—tight coolant channel is also substantially
`encapsulated within the body 01' 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.
`
`27 Claims, 14 Drawing Sheets
`
`(12) United States Patent
`(10) Patent No.:
`US 7,928,348 B2
`Neal
`(45) Date of Patent:
`Apr. 19, 2011
`
`US007928348B2
`
`............. .. 440/89 R
`8/2004 Nakata et a1.
`.
`.. 310/156.23
`3/2006 Johnson et al.
`. . . . . . . .
`. . .. 264/489
`4/2007 Huang et a1.
`. ,
`
`FOREIGN l’Alel DOCUMle S
`63118559 A *
`5/1988
`
`
`
`6,783,413 B2 *
`2006/0055264 A1 *
`2007/0075463 A1 *
`
`JP
`
`Petitioners' Exhibit 1001, pg. 1
`
`

`

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`
`US. Patent
`
`Petitioners' Exhibit 1001, pg. 2
`
`

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`US. Patent
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`Petitioners' Exhibit 1001, pg. 3
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`Apr. 19, 2011
`
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`

`

`US 7,928,348 B2
`
`1
`ELECTROMAGNETIC DEVICE WITH
`INTEGRATED FLUID FLOW PATH
`
`
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to electromagnetic
`devices that include heat exchange mechanisms. It relates
`particularly to motors, generators, transfomiers, 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 motor/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.
`BACKGRO U N J.) OF THE IN VENTION
`
`
`
`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— '
`porated by reference, further disclose some ofthese concepts.
`An example of a conventional 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 rising 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.
`An important factor in motor design is the lowering of the
`operating temperature of the motor. Increased motor tem-
`perature affects the electrical efliciency 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 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.
`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 airpast 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
`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
`pump. The problem with liquids, however, is getting them in
`contact with hot motor surfaces without damaging the motor,
`
`2
`and their collecting tlrerrr 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 ifthere 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 dam aging 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 corn-
`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 housing,
`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 THE INVENTION
`
`'
`
`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. Errcap sulating 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 an electromagnetic field-
`functioning device for heating a fluid comprising at least one
`electrical conductor that generates heat when in use; a mono-
`lithic body of injection molded thermoplastic material sub—
`stantially encapsulating the at least one conductor; and a lluic
`pathway in the monolithic body, with at least one fluid inle
`and at least one fluid outlet to the pathway to allow for pas sage
`of fluid through the pathway, the outlet directing the fluid to a
`place of usage wherein heat picked up by the fluid as i
`transfers through the device is put to functional use.
`In a second aspect, the invention is an electromagnetic
`field-functioning device for heating a fluid comprising at leas
`one electrical conductor that generates heat when in use; a
`monolithic body of injection molded thermoplastic inateria
`substantially encapsulating the at least one conductor; and a
`fluid pathway in the monolithic body, with at least one fluic
`inlet and at least one fluid outlet to the pathway to allow for
`passage of fluid through the pathway, the outlet directing the
`fluid to a place ofusage wherein heat picked up by the fluid as
`it transfers through the device is put to functional use, anc
`further wherein the monolithic body completely surrounds
`the device except for the inlet and the outlet.
`In a third aspect, the invention is an electromagnetic field-
`l'unctioning device for heating a fluid comprising at least one
`electrical conductor and at least one inductor that generates
`heat when in use; a monolithic body of injection molded
`thermoplastic material substantially encapsulating the at least
`one inductor; and a 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 fluid through the pathway, the
`
`Petitioners' Exhibit 1001, pg. 16
`
`

`

`
`
`US 7,928,348 B2
`
`4
`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 of the invention,
`will become further apparent from he following detailed
`description of the presently preferred embodiments, read in
`conjunction with the accompanying drawings. The detailed
`description and drawings are merely i lustrative of the inven-
`tion and do not limit the scope of the invention, which is
`delined by the appended claims and equivalents thereof.
`BRIEF DESCRIPTION OF SEVERAL VIEWS OF
`THE DRAWINGS
`
`
`
`'
`
`used in the present application includes electromagnetic
`
`3
`outlet directing the fluid to a place of usage wherein heat
`flicked up by the fluid as it transfers through the device is put
`0 functional use.
`In a fourth aspect, the invention is a fluid conveying mecha-
`nism comprising an electromagnetic field—functioning device
`iaving at least one electrical conductor; a monolithic body of
`injection molded themioplastic material substantially encap—
`sulating the at least one conductor; and a fluid pathway in the
`monolithic body, with at least one of a fluid inlet into the
`3athway and a fluid outlet from the pathway being formed in
`he body of injection molded therrnopla stic, and the pathway
`hrough the body being confined within the body.
`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-
`Jer; and a monolithic body ofphase change material sub stan-
`ially encap sulating both the one or more conductors and the
`ieat transfer fluid confinement member.
`In yet another aspect the invention is a fluid-cooled elec-
`romagnetic 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 lluid confinement member containing a heat
`transfer fluid; and a monolithic body ofphase change material
`substantially encapsulating at least one of the inductor and the
`at least one conductor, the monolithic body being in thermal
`contact with the heat transfer fluid.
`A fiu‘ther aspect of the invention is a method of making a
`fluid—cooled electromagnetic field—fiinctioning device com—
`prising the steps of providing 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 fluid 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 ofphase change material that also
`substantially encapsulates parts of the motor. In another
`embodiment, a motor can be cooled by passing liquid through
`a coolant channel encased in the body ofphase 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
`channels. The flow path or chamber for the coolant may be
`
`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 of the high speed motor of
`FIG. 3.
`FIG. 5 is a schematic drawing of a 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 of the present invention.
`FIG. 9 is a cross-sectional view ofa high speed motor in
`accordance with a fourth embodirrient of the present inven—
`tion.
`FIG. 10 is a perspective View ofa stator, shaft and cold plate
`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 transformer in accor—
`dance with the invention.
`FIG. 18 is a cross—sectional View ofa solenoid usedin 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 of a heat transfer fluid con-
`finement member used in the valve ofFIG. 20.
`
`.
`
`
`DETAILED DESCRIPTION OF TI IE DRAWINGS
`AND PREFERRED EMBODIMENTS OF THE
`INVENTION
`
`The term “electromagnetic field-functioning device” as
`
`Petitioners' Exhibit 1001, pg. 17
`
`

`

`US 7,928,348 B2
`
`5
`devices that include one or more electrical conductors anduse
`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 cturent 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
`magnetic field, which in turn induces an electrical current in
`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 lluids.
`
`'
`
`control circuit board residing on the outer surface of the base
`
`6
`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. Morro-
`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
`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 teln—
`perature in the range of about 200 to 7008 F. The most pre-
`ferred temperature activated 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 nomial 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 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.
`The heat pipe 62 is positioned inthe 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
`c ' phase change material. This face is locatedj ust below the hub
`12, so that air currents created by the spinning hub can convey
`heat away from the exposed face, which serves as the low—
`ternperature 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.
`Referring to FIGS. 3-4, the base 22 of the body 14 is
`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
`
`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 ofparts 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
`conventional steel laminations 11 forming a magnetically
`inducible core 17 having a plurality ofpoles 21 thereon, and
`wire windings 15 which serve as conductors. The conductors
`induce or otherwise create a plurality ofmagnetie fields in the
`core when electrical current is conducted through the conduc-
`tors. In this embodiment, a magnetic field is induced in each
`ofthe 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
`luid 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
`1eat from a high-temperature region to a low-temperature
`region, and then migrates back to the hi gh —temperature region
`0 repeat the cycle. Many heat pipes include a liquid that
`vaporizes at the temperature encountered in the high—tem—
`oerature 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
`he 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
`oressure gradient forces the vapor to flow along the pipe to the
`ow-temperature region, where it condenses, giving tip its
`atent heat ofvaporization. The working fluid is then returned
`0 the evaporator by the capillary forces developed in the wick
`structure. The heat pipe is sealed to prevent loss of the heat
`ransfer fluid. A heat pipe is thus one example of a heat
`ransfer fluid confinement member comprising a heat transfer
`
`
`
`Petitioners' Exhibit 1001, pg. 18
`
`

`

`US 7,928,348 B2
`
`8
`bearings. Alternatively other 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 of the 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
`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 sintered 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 011 the number ofpoles 21 on the stator 20. The
`flux return ring 58 is preferably made ofa 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 sejust
`one circumferential loop, Of course multiple heat pipes or
`pipe loops could be provided in the body 14.
`
`Operation of the First Embodiment
`
`In operation, the motor shown in FIGS. 3-4 is driven by
`supplying electrical pulses to the connector 26. These pulses
`are used to selectively energize the windings 15 around the
`stator 20 poles 21. This results in a moving magnetic field,
`This magnetic field interacts with the magnetic field gener-
`ated by the magnet 28 in a manner that causes the magnet 28
`to rotate about the body 14. As a resul , the hub 12 begins to
`rotate along with the shaft 16. The bearings 18 facilitate the
`rotation of the shaft 16.
`The coolant is captive to the system and continuously recir-
`culates through the hollow structure 0 the heat pipe 62.
`
`Method of Making the First Embodiment
`
`7
`(not shown). Alternatively the connector may be a flexible
`circuit with copperpads allowing spring contact interconnec-
`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
`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, 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
`similarto that ofthe heat pipe. In 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 of the heat pipe. If the thermoplastic body and heat pipe
`were to separate, there would be a significant barrier to ther-
`mal conductivity across that juncture.
`Apreferred form ofplastic is polyphenyl sulfide (PPS) sold
`under the trade name “Konduit” by General Electric Plastics.
`
`Grade OTF-2l2-ll PPS is particularly preferred. Examples
`of other suitable thermoplastic resins include, but are not
`imited to,
`thermoplastic resins such as 6,6-polyamide,
`6-polyamide, 4,6-polyamide, 2,12-polyamide, 6,12-polya-
`mide, and polyamides containing aromatic monomers, poly-
`)utylene terephthalate, polyethylene terephthalate, polyeth-
`ylene napththalate, polybutylene napththalate, aromatic
`oolyesters, liquid crystal polymers, polycyclohexane dim-
`ethylol terephthalate, copolyetheresters, polyphenylene sul—
`ide, polyacylics, polypropylene, polyethylene, polyacetals,
`oolymethylpentene,
`polyetherimides,
`polycarbonate,
`Jolysulfone, polyethersulfone, polyphenylene oxide, poly-
`
`flows in, pins 76 are withdrawn so that the plastic completely
`
`'
`
` styrene,