WO2013184931A1 - Puits de chaleur cinétique à écart thermique régulable - Google Patents

Puits de chaleur cinétique à écart thermique régulable Download PDF

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Publication number
WO2013184931A1
WO2013184931A1 PCT/US2013/044539 US2013044539W WO2013184931A1 WO 2013184931 A1 WO2013184931 A1 WO 2013184931A1 US 2013044539 W US2013044539 W US 2013044539W WO 2013184931 A1 WO2013184931 A1 WO 2013184931A1
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WIPO (PCT)
Prior art keywords
heat
rotating structure
rotating
stationary
bearing
Prior art date
Application number
PCT/US2013/044539
Other languages
English (en)
Inventor
Lino A. GONZALEZ
William R. SANCHEZ
Steven STODDARD
Original Assignee
CoolChip Technologies, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CoolChip Technologies, Inc. filed Critical CoolChip Technologies, Inc.
Publication of WO2013184931A1 publication Critical patent/WO2013184931A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F3/00—Plate-like or laminated elements; Assemblies of plate-like or laminated elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
    • F28F13/06—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media
    • F28F13/12—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media by creating turbulence, e.g. by stirring, by increasing the force of circulation
    • F28F13/125—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by affecting the pattern of flow of the heat-exchange media by creating turbulence, e.g. by stirring, by increasing the force of circulation by stirring
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
    • H01L23/467—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing gases, e.g. air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D2021/0019—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for
    • F28D2021/0028—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for cooling heat generating elements, e.g. for cooling electronic components or electric devices
    • F28D2021/0029—Heat sinks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

  • the present invention relates to heat-extraction and dissipation devices and methods and, more particularly, kinetic heat sinks for use with electronic components.
  • FIGS. 1 A, IB, and 1C show several examples of
  • the heat sink assemblies 100 generally extract heat 102 (see Figure 1C) from the thermal source 104 (i.e., the electric circuit or device) to a heat sink 106, and then rejects (i.e., dissipates) the heat into a thermal reservoir 108, which is generally ambient air.
  • the heat sink 106 may have fins 110 and be coupled with a fan 112 to increase the airflow across the fins 110.
  • a thermal mass with integrated fluid-directing structures (such as fins and/or fan blades) that rotates with respect to a stationary base mounted on or near the heated electric device.
  • a fluid refers to a substance that may flow and includes a liquid, a gas, or a combination of liquid and gas.
  • a first type of kinetic heat sink design provides a thermal transfer medium, including thin films or various thermal fluids (such as oils), between the stationary base and the rotating heat sink.
  • a kinetic heat sink apparatus has a stationary member that includes a base structure having both a first heat- conducting surface and a second heat-conducting surface to conduct heat therebetween.
  • the first heat-conducting surface is fixably mountable to a heat-generating component.
  • the kinetic heat sink also has a rotating structure rotatably coupled with the base structure. This rotating structure has a movable heat-extraction surface facing the second heat-conducting surface across a spatial gap.
  • the rotating structure is configured to transfer heat from the second heat-conducting surface to a thermal reservoir communicating with the rotating structure.
  • the rotating structure and stationary member has at least two pairs of opposing surfaces configured to form a first thrust and second opposing thrust to maintain the spatial gap within a pre-specified range during rotation of the rotating structure. At least one surface of each of the pair of opposing surfaces may have at least one surface with hydrodynamic features thereon to generate the thrust.
  • Each pair of the two pairs of opposing surfaces may form a hydrodynamic bearing (e.g., a spiral groove bearing, a step bearing, a sector step bearing, a Rayleigh step bearing, a thrust inward-pumping bearing, a thrust outward-pumping bearing, and a herringbone thrust bearing).
  • the kinetic heat sink also may have an electric motor assembly.
  • the stationary member may include stationary motor component fixably affixed thereto.
  • the rotating structure may include a rotating motor component.
  • the stationary motor component and the rotating motor component may include the pair of opposing surfaces to generate thrust.
  • the stationary base structure and the rotating structure may be made of different thermal-conducting thermal material (e.g., copper, aluminum, silver, nickel, iron, zinc, and combinations thereof).
  • the kinetic heat sink apparatus may include a sensor to provide a feedback signal to a controller.
  • the sensor may sense a distance of the spatial gap or a thermal quantity of one or more of the heat-generating component, the stationary base structure, and the rotating structure.
  • the controller may vary the rotating speed of the electric motor assembly based upon the feedback signal.
  • the stationary base structure may form in part, or be part of, a vapor chamber and/or a heat pipe.
  • a kinetic heat sink includes a base plate and an impeller.
  • the base plate is adapted to fixably mount to a heat-generating component.
  • the impeller is adapted to rotate in relation to the base plate across a gap of less than 20 micrometers.
  • the impeller has an impeller plate and a plurality of fins extending therefrom.
  • the impeller plate forms the gap with the base plate.
  • the fins form channels therebetween.
  • the kinetic heat sink further includes a spindle motor adapted to cause the impeller to rotate.
  • the spindle motor has a stationary portion affixed to the base plate and a rotating portion affixed to the impeller. Portions of the stationary portion and rotating portion form fluid-dynamic bearings.
  • the base plate conductively draws heat from the heat-generating component and transfers a substantial portion of the drawn heat across the gap to the impeller.
  • the gap is regulated, in part, by thrusts formed in opposing direction by the fluid-dynamic bearings, and the impeller receives the transferred heat and rejects the transferred heat to ambient fluid communicating with the impeller by directing the ambient fluid through the channels.
  • the kinetic heat sink may be configured to operate with substantially low- friction between the heat-extraction surface and the second heat-conducting surface when at rest.
  • a portion of the heat-extraction surface may form a low- friction contact with the second heat-conducting surface via a low-friction insert disposed therebetween.
  • the surfaces or insert may include a low- friction coating (i.e., having a friction coefficient less than 0.5).
  • the low-friction surface may be non-abradable. Examples of coatings, includes ceramics, such as metal-doped ceramics, Teflon, and graphite (e.g., diamond like carbon (DLC)).
  • the insert may form, or be part of, a roller bearing or a ball bearing.
  • the kinetic heat sink has a first portion of the heat-extraction surface forming the spatial gap with the second surface when at rest, while a second portion of the heat- extraction surface is in contact with the stationary base structure when at rest.
  • a method of dissipating heat from an electronic device includes providing a stationary structure having a first and second heat-conducting surface.
  • the stationary structure is thermally coupled to the electronic device at the first heat-conducting surface to drawn heat from the electronic device.
  • the stationary structure conducts the drawn heat from the first heat-conducting surface to the second heat-conducting surface.
  • the method then includes rotating a rotating structure having a heat-extraction surface facing the second heat-conducting surface across a spatial gap.
  • the rotation substantially transfers heat from the second heat-conducting surface to the rotating structure and rejects the transferred heat from the rotating structure to a thermal reservoir in communication with the rotating structure.
  • the method then includes generating thrusts on the rotating structure as a result of the rotation of the rotating structure. The thrusts are in opposing direction to maintain the spatial gap within a pre-specified range.
  • the method may include varying the rotation of the rotating structure, including a rate of rotation, to maintain the spatial gap within a pre-specified range.
  • the method may also include measuring a thermal quantity associated with at least one of the stationary structure, the stationary structure, the spatial gap, and the electronic device and using the measured thermal quantity to vary the rotation of the rotating structure.
  • FIGS 1 A-C show various examples of conventional heat sinks
  • Figures 2A-2E schematically show examples of a spatial gap of an apparatus for dissipating heat according to a preferred embodiment
  • FIG. 3B schematically shows the apparatus of Figures 2A-2E with alternate embodiments of the motor assembly
  • Figure 4 schematically shows a detailed diagram of the motor assembly and apparatus of Figure 3A according to an embodiment
  • Figure 5A schematically shows a cross sectional view of a kinetic heat sink according to an embodiment.
  • Figure 5B schematically shows a perspective view of the kinetic heat sink of Figure 5A
  • Figure 6A schematically shows a diagram of the fluid dynamic bearing of the kinetic heat sink of Figure 5A in accordance with illustrative embodiments of the invention
  • Figure 6B schematically shows a picture of the fluid dynamic bearing of Figure 6A disassembled
  • Figure 6C schematically shows a picture of a cross-sectional view of the rotor housing of Figure 6B;
  • Figure 6D schematically shows an exploded view of the fluid dynamic bearing of
  • Figure 8A schematically shows an apparatus with hydrodynamic surfaces in the spatial gap according to another embodiment
  • Figure 9 is a diagram of a pressure profile for the step-sector bearing of Figure 8B;
  • Figure 10A illustratively shows a diagram of stationary base structure having included a spiral groove hydrodynamic bearing
  • Figure 13 a method according to a preferred embodiment of the invention.
  • FIG. 2A schematically shows an example of a kinetic heat sink 200 (also referred to as "apparatus 200") for dissipating heat 202 according to various embodiments.
  • the apparatus 200 includes a stationary member, having a base structure 204 (also referred as a "stationary base structure 204"), and a rotating structure 206 that cooperate to transfer heat from a heat generating component.
  • the stationary base structure 204 has a first heat-conducting surface 208 and a second heat-conducting surface 210 to conduct heat therebetween.
  • the stationary base structure 204 may be mountable at the first heat- conducting surface 208 to a heat-generating component 212.
  • the first heat-conducting surface 208 and the second heat-conducting surface 210 may form the footprint of the apparatus 200.
  • the rotating structure 206 which is rotatably coupled to the stationary base structure 204, has a heat-extraction surface 216 facing the second heat-conducting surface 210 across a spatial gap 218.
  • the heat-extraction surface 216 may face some or all portions of the second heat-conducting surface 210.
  • the rotating structure 206 rotates with respect to the stationary base structure 204 to transfer heat from the second heat- conducting surface 204 to a thermal reservoir 220 (e.g., the environment) communicating with the rotating structure 206.
  • the term "thermal reservoir” (or “thermal energy reservoir” and “thermal bath”) refers to a fluid having a heat capacity intended for heat to flow.
  • the rotating structure 206 may have additional flow-directing structures 214 (e.g., blades or fins) to reject the heat to the thermal reservoir 220.
  • Figure 2A and others simply show two planar surfaces 210 and 216. It is contemplated, however, that various embodiments may configure those surfaces 210 and 216 with non-planar surfaces, including grooves, channels, and recesses (shown in subsequent figures). Similarly, it is contemplated that the various embodiments may configure those surfaces 210 and 216 as an angled region 224 defined by angle 226 (as shown in Figure 2B, for example). The angle region may be over a portion of the two planar surfaces 210 and 216 and may be located on the outer circumferential portion of the planar surfaces 210 and 216 (as shown) or, alternatively, in the inner circumferential portion.
  • surfaces of the rotating structure 206 and the stationary base structure 204 generate a (axial) thrust and an opposing (axial) thrust to vary and/or maintain the spatial gap 218 within a prescribed distance.
  • thrust is a tangible force resulting from fluid flowing over a tangible surface.
  • Such surfaces may be part of the heat-extraction surface 216 and/or the second heat-conducting surface 210.
  • the rotating structure 206 transfers heat from the second heat-conducting surface 210 to the thermal reservoir 220 as a result of enhanced heat transfer properties resulting from the rotating structure 206 rotatably moving with respect to the stationary base structure 204.
  • a portion of the heat at the second heat-conducting surface may dissipate directly to the thermal reservoir through convection and radiation mechanisms (i.e. , thermal leakage).
  • the term "substantially transfers” refers to transferring a non-negligible amount of heat that is beyond the thermal leakage mechanisms.
  • a majority of heat is transferred from the second heat-conducting surface 210 to the thermal reservoir 220 through the rotating structure 206.
  • thermal resistance value depends on the application. For example, for a small heat source (i.e., heat watt output), a higher thermal resistance value may suffice. For such small heat sources, a small kinetic heat sink may be employed. Conversely, for larger heat sources, a low thermal resistance may be preferred to prevent the temperature at the heat source from getting too hot. In general, a thermal resistance across the gap of 25 percent or less of the total thermal resistance should provide satisfactory results.
  • the thermal resistance of the spatial gap is inversely proportional to surface area of the spatial gap.
  • the rotating structure 206 may include fluid-directing structures 214 including, for example, fins and blades, to reject heat into the thermal reservoir 220.
  • the rotating structure 206 may be configured as an impeller or other members that radiate heat with an enhanced surface area.
  • the rotating structure 206 includes a fluid-directing structure to direct air.
  • a fluid-directing structure to direct air.
  • the rotating structure 206 may have a higher fluid velocity flowing through it, thereby enhancing its heat transfer properties.
  • the kinetic heat sink may have a smaller form factor as compared to conventional blower with heat sinks. This also means that the kinetic heat sink 200 may rotate at a slower rate, thus saving energy, while providing comparable thermal dissipation performance.
  • illustrative embodiments also reduce unintended acoustics resulting from the rotation, and should reduce the accumulation of dust that typically gathers on conventional heat sink designs.
  • the kinetic heat sink 200 may be used with any of a variety of different heat-generating components 212.
  • the heat-generating component 212 may include, among other things, a circuit board having electric components generating and/or transferring heat thereon, a semiconductor device, a thermal mass (i.e., a heat sink), a power circuit including a power switch such as a IGBT, and/or an electric circuit packaging surface (ceramic or plastic).
  • heat-extraction and heat-spreading devices may be employed between the first heat-conducting surface 208 and the second heat-conducting surface 210. Heat-extraction and heat-spreading devices are generally utilized to
  • Heat-extraction and heat-spreading devices may include, for example, heat pipes and fluid pumping systems.
  • FIG 3A shows another heat sink embodiment, this time identified by reference 300.
  • This figure shows more specific components of the device than those shown in Figure 2A, including a motor assembly 302, 304.
  • the stationary base structure 204 has heat- conducting surfaces to conduct heat from the heat-generating component 212 to the rotating structure 206.
  • the rotating structure 206 is rotatably coupled to the stationary base structure 204 though the motor assembly.
  • the motor assembly includes a motor-stationary component 302 and a motor-rotating component 304.
  • the motor-stationary component 302 may include a stator (i.e., electrical windings and armature) and a housing.
  • the motor-rotating i.e., electrical windings and armature
  • component 304 may include a rotor shaft and components attached thereon, including, for example, permanent magnets (in some embodiments).
  • the motor-stationary component 302 preferably is fixably coupled to the stationary base structure 204 and thus, may be considered part of the stationary member.
  • the motor-rotating component 304 may be fixably coupled or coupled via a gear to the rotating structure 206.
  • the motor-stationary component 302 and the motor-rotating component 304 preferably are generally concentrically located between the rotating structure 206 and the stationary base structure 204.
  • the apparatus 300 may include a controller 306 to regulate the rotation speed of the rotating structure 206 by regulating the current or voltage provided to the electrical winding.
  • the electrical winding is part of the motor-stationary component 302.
  • the controller 306 may include a control circuit, a driver, and corresponding signal processing circuitries.
  • the controller 306 may be mounted within or on the stationary base structure 204.
  • the control circuit may be configured to provide pulse-width modulation, frequency, phase, torque, and/or amplitude control.
  • the apparatus 300 may also include a sensor 308 to provide feedback signals for the controller 306.
  • the feedback signals may be based upon the speed, temperature, or clearance of the spatial gap.
  • the speed may be of the rotation speed of the rotating structure 206 and/or of the motor.
  • the temperature may be of the heat-generating component 212, the stationary base structure 204, the rotating structure 206, spatial gap 218 and/or the motor.
  • the sensor 308 may be a capacitive-based sensor, a thermocouple, and/or an infrared detector and may output an electrical signal that is un-scaled or offset and merely have some correlation to the temperature value. It should be apparent to those skilled in the art that various controllers and control schemes may be utilized to regulate the heat dissipating apparatus based upon temperature, rotation speed, and clearance gap.
  • FIG. 3B shows another example of an apparatus with a motor assembly according to an alternative embodiment. Rather than the motor assembly being located proximal to or near the axis of rotation, the motor-stationary component 302 (having the electrical windings) is located distally to the rotor axis.
  • parts of the motor-stationary component 302 may be located on top of the rotating structure 206 or within the stationary base structure 204.
  • direct-current and alternating-current based motor may be employed.
  • examples of direct- current (DC) based motors may include brushed DC motors, permanent-magnet electric motors, brushless DC motors, switched reluctance motors, coreless DC motors, universal motors, and examples of alternating-current (AC) based motors may include single-phase synchronous motors, poly-phase synchronous motors, AC induction motors, and stepper motors.
  • the motor assembly may include an integrated motor controller, such as a servo motor. The motor may operate based upon pulse-width modulation scheme or direct current control.
  • Hydrodynamic bearings i.e., self-acting bearings
  • a thin film of fluid including gas, such as air, or liquid, such as oils and thin films
  • the thin film of fluid is created by the relative motion of two mating surfaces separated by a small distance.
  • a velocity-induced pressure gradient is generally formed across the clearance between the two mating surfaces.
  • Hydrodynamic bearings generally include topographical features formed onto at least one of the mating surfaces. Among other things, the
  • topographical features may be characterized as spiral grooves of a step bearing.
  • Spiral groove bearings may be configured as a thrust inward-pumping bearing, a thrust outward- pumping bearing, and a herringbone thrust bearing.
  • FIG. 5A and 5B show another example of a kinetic heat sink/apparatus 500 according to an illustrative embodiment of the invention.
  • the apparatus 500 includes a base plate spreader 502 adapted to mount onto the heat-generating component 212.
  • a fluid- dynamic bearing spindle motor 504 is affixed to the base plate spreader 502 and a kinetic heat sink impeller 506 to rotate the kinetic heat sink impeller 506 with respect to the base plate 502.
  • the kinetic heat sink impeller 506 includes the rotating base 222 (referred to as an impeller plate) and a plurality of flow-directing structures 214 (referred to as impellers).
  • the plurality of flow-directing structures 214 are configured to direct air flow through channels formed therebetween when the kinetic heat sink impeller 506 rotates to dissipate heat into ambient air.
  • FIG. 6A schematically shows a detailed diagram of the fluid-dynamic bearing 600 within the fluid dynamic bearing spindle motor 504 or within other similar embodiments.
  • the fluid dynamic bearing 600 includes an axial control component 602 and may include a radial control component 604.
  • the axial control component 602 may be incorporated into the rotor 404, the rotor housing 402, and the rotor cap 610.
  • the axial control component 602 controls the position of the rotor 404 situated on or along the direction of the axis 612.
  • the axial control component 602 may include a first control surface 614 to generate a thrust in a first direction 616, and a second (opposed) control surface 618 to generate a thrust in a second direction 620.
  • the first control surface 614 may be a part the rotor housing 402.
  • the second control surface 618 may be a part of the rotor cap 610. It should be apparent to those skilled in the art that the rotor cap 610 and the rotor housing 402 may be configured as a single unitary component.
  • Clearance between rotor 404 and/or the rotor housing 402 and rotor cap 610 at the axial control component 602 may vary during normal operation.
  • the clearance may be about 5-10 ⁇ or, more specifically, between about 2-4 ⁇ . Again, the application may dictate the required clearance.
  • clearance values are merely illustrative.
  • clearance values greater than about 5-10 ⁇ may be used for larger scale applications where the apparatus is larger than a few inches, and for low cost cooling applications having generally high variability in tolerances.
  • a shaft portion 628 embedded with a ring-shaped portion 630 at one end.
  • the shaft portion 628 and the ring-shaped portion 630 have included the journal (i.e., portions in contact with the bearing).
  • the rotor cap 610 is assembled to be flush between the stationary base structure 204 and the rotating structure 206 (see for example, Figures 5A, 5B).
  • the rotor cap 610 may be fixably attached to the stationary base structure 204 (such as, for example, by adhesives or by a factional fit).
  • the rotor cap 610 may preferably be made of a thermally conductive material to provide a parallel heat path between the stationary base structure 204 and the rotating structure 206.
  • Figure 6C shows a photo of a cut-away of the rotor housing 402 of Figure 6B, specifically of the radial control component 604.
  • the rotor housing 402 has included the fluid bearing 624 and 626 with herringbone groove patterns.
  • Figure 6D shows an exploded view of an alternate assembly of the fluid dynamic bearing 600 of Figure 6A.
  • the rotor housing 402 includes a casing component 632 and a bearing component 634.
  • the rotor 404 may be in direct contact only with the bearing component 634.
  • the bearing component 634 may be made of a different material and/or manufacturing process than the casing component 632. For example, a lower cost manufacturing process may be employed, such as casting, to form the casing component 632.
  • the through-hole may be machined to achieve a defined finish and/or tolerance.
  • the bearing component 634 may be fabricated with high tolerance techniques.
  • the bearing component 634 may be made, in part, of high strength and high toughness material to minimize its wear.
  • the fluid dynamic bearing 600 may be configured with a heat insulating structure embedded between the motor-stationary component and the stationary base structure, thereby insulating the electric motor assembly from the heat.
  • the rotor cap 610 made of a thermal insulating material (i.e., a ceramic) may form the heat insulating structure.
  • the rotor cap 610 may extend across both the motor-rotating
  • the motor assembly may be configured with cooling channels to direct air through the motor assembly when the motor-rotating component is rotatably moving.
  • FIG. 7A shows cut-views of fluid dynamic bearings according to an illustrative embodiment of the invention.
  • the fluid dynamic bearings include an axial control component and a radial control component, both of which may be incorporated into the rotor 404, rotor housing 402, and rotor cap 610.
  • the fluid bearing is shown as being a part of the rotor 404, rather than of the rotor housing 402 and the rotor cap 610.
  • the first control surface 614 is configured as a spiral groove bearing.
  • Figure 7B shows a portion of a fluid dynamic bearing having a first control surface 614 according to an illustrative embodiment of the invention.
  • the first control surface 614 is configured as a herringbone thrust bearing.
  • the second control surface may be configured as one of a spiral groove bearing and a herringbone thrust bearing.
  • the fluid dynamic bearing spindle motor 504 may include thrust fluid bearings 516 to both generate the gap thickness 218 and to confine the gap thickness 218 to a finite rage (less than 20 microns) for a wide range of rotational speeds, impeller weight/shape, and orientation of the apparatus.
  • the fluid dynamic bearings independently or in combinations with other fluid dynamic bearings may be configured to minimize the axial and radial movement of the heat-sink impeller 214.
  • the lift and/or thrust force generated by a hydrodynamic bearing may be expressed as:
  • Equation 2 K' ⁇ ⁇ er-R f nner) (Equation 2) where K' is a dimensionless function of the bearing topology based upon the type of features, the number of features, and the thickness and depth of the features; R ou ter and Rmnner are the radius of the bearing features; h is the clearance gap; ⁇ is the angular velocity; and ⁇ is the viscosity of fluid and/or medium.
  • hydrodynamic bearings may form varying thrusts based on a gap h between the bearing surface and an opposing surface.
  • the thrust i.e., opposing pressure
  • hydrodynamic bearing may be characterized as having an inherent feedback control loop.
  • two opposing hydrodynamic bearing may be arranged to maintain a pre-defined gap thickness.
  • Illustrative embodiments may use a number of different types of bearings, such as Rayleigh step thrust bearings, step-sector bearings, and spiral groove bearings (e.g., inward, outward, and/or herringbone).
  • Hydrodynamic bearings may include Rayleigh step thrust bearing and spiral groove bearings.
  • Rayleigh step bearings are generally angularly symmetric, and generate a repulsive force regardless of the direction of rotation.
  • a step- sector bearing employs a non-angularly symmetric design (see, e.g., figure 12B) and generally generate a repulsive force when rotating in the intended direction. Despite this, the force generated by a step-sector bearing is generally greater than that produced by a Rayleigh step bearing.
  • Step-sector bearings generally have a deep groove right after the land section, as compared to a Rayleigh bearing, to ensure that the pressure is equalized to the surrounding fluid pressure at that location.
  • Spiral groove bearings may be configured as a thrust inward-pumping bearing, a thrust outward-pumping bearing, and a herringbone thrust bearing.
  • Inward-pumping bearings are generally characterized as having fluid drawn inward from the outer perimeter.
  • Outward-pumping bearings are generally characterized as having fluid drawn from the inner diameter.
  • Herringbone thrust bearings are generally characterized as having both inward pumping and outward pumping actions.
  • the fluid dynamic bearing spindle motor 504 may rotate the heat sink impeller at high speeds. In a test setup, fluid dynamic bearing spindle motor was rotated at up to 12,000 revolutions per minutes (RPM).
  • the fluid dynamic bearing may be configured to provide dampening and/or stiffening effects as well as to account for thermal expansion effects.
  • the fluid dynamic bearing spindle motor 504 may include mechanical bearings, such as ball bearings and/or roller bearings.
  • the bearings may be used for both thrust and journal bearings (i.e., for radial alignment).
  • the fluid dynamic bearings and the mechanical bearings may be used independently or in combination for either of the axial alignment and for thrust.
  • the baseplate spreader 204 may be composed in part of a copper and/or aluminum disk and/or a vapor chamber.
  • at least two journal bearings may be used to control tilting and radial displacement of the rotor in the fluid dynamic bearing spindle motor.
  • two opposing thrust bearings which may be spiral, groove, or herringbone journal bearings, may be used to control the axial positioning.
  • the operating gaps between the rotor and the rotor casing in the fluid dynamic bearing spindle motor may be 2 to 3 microns in the radial direction, and 5 to 10 microns on each side of the thrust bearings.
  • Any number of different fluids may be used, such as oil (e.g. , ester oil), thin- film, ferro-fluid, and/or air may be used as the lubricant.
  • the thrust bearings in the fluid dynamic bearing spindle motor may provide an additional 5-10 micron gap.
  • the thrust generated, and thus the resulting gap thickness may depend in part on the operating characteristics of the heat sink impeller, including its rotational speed, effective weight, and orientation.
  • Figure 8A shows a diagram of kinetic heat sink/apparatus 800 according to another preferred embodiment of the present invention.
  • At least one of the heat-extraction surface 216 and the second heat-conducting surface 210 are configured with a plurality of surface features 802 configured to maintain the spatial gap 218 when the rotating structure 206 is rotatably moving.
  • the plurality of surface features may form a hydrodynamic bearing (e.g., a Rayleigh step bearing and/or a spiral groove bearing).
  • Figure 8B shows a diagram of rotating structure 206 having a hydrodynamic bearing, specifically, a Rayleigh step bearing 804.
  • a Rayleigh step bearing is generally characterized as having topographic surface features of alternating land regions 806 and groove regions 808.
  • a profile 810 of the Rayleigh step bearing is provided, where ho is the spatial gap 218 and S h is the depth of the groove region.
  • Step bearings such as Rayleigh step bearings, generally operate through the principle of fluid being compressed resulting from a motion between two parallel bodies. As the two parallel bodies move, the fluid is forced to move between the groove and the land regions; the forced fluid results in a force that may be configured to repel in either clockwise or counterclockwise direction of movement.
  • Figure 9 is a diagram of a pressure profile 902 for the Rayleigh step bearing of Figure 8B.
  • the geometry of the Rayleigh step bearing 804 is characterized by Bi (the length of the land region), B 2 (the length of the groove region), B (the length of the each step bearing), ho (the spatial gap between the rotating and the stationary structure), and hi-ho (the depth of the groove region).
  • the pressure from the forced fluid is normalized to be zero.
  • a repulsion force is created by the compressed fluid, which linearly increases the pressure.
  • the pressure reaches a maximum pressure, P max , at the end of the groove region at position 906. Then, the pressure profile linearly drops back to the initial starting pressure, P 0 , at position 908.
  • Figure 10A shows a picture of the stationary base structure 204 having included a hydrodynamic bearing, specifically, a spiral groove bearing 1002 on the second heat- conducting surface 210.
  • Figure 10B shows a zoomed-in image of the stationary base structure 204 of Figure 10A.
  • the spiral groove bearings 1002 between land regions 1004 act as an outward pumping bearing.
  • the average groove depth may vary up to 7 ⁇ .
  • the fluid dynamic bearing when at rest, may be configured to provide a very small clearance between certain portions of the baseplate 204 and the impeller plate 222. Some other portions of the opposing components 204 and 222, however, may have no such clearance at rest. If there is no clearance, then there is some degree of friction during startup, and also during operation (e.g., if subjected to a shock). Illustrative embodiments therefore minimize the contact region of the fluid dynamic bearing to other components in the spindle motor 504, effectively reducing start-up friction. This consequently improves the efficiency and the operating performance of the kinetic heat sink 200.
  • the apparatus 500 may include a low-friction insert 518.
  • the fluid dynamic bearing spindle motor 504 may control the tilting of the heat-sink impeller 214 relative to the baseplate spreader 204 (as a baseplate spreader) during operation, the rotating and stationary surfaces of the heat sink may make contact at low rotational speed and/or when a large external shock is introduced.
  • the contact may result in a high start-up power/torque in order to rotate the heat-sink impeller 214.
  • the insert 518 may be configured to minimize wear or damage and may lower the high start-up power/torque.
  • the insert 518 may be made from a variety of low friction materials, and/or may be placed closer to the axis of rotation than shown (the figure shows it at the maximum diameter), provided that the tolerances are such that the rotating and stationary surfaces do not make contact anywhere except for the region where the insert is present.
  • Figure 5B shows a cross sectional view of the apparatus 500 of Figure 5 A.
  • the insert 518 or the surfaces surrounding the gap thickness 218 may include a coating.
  • the coating may be hard (i.e., non-abradable) and may provide a low- friction contact.
  • the coating may be composed in part of at least electro-less nickel, a diamond-like coating, hardened steel, and/or dry film lubrication (e.g., tungsten disulfide, WS 2 ).
  • the low- friction insert may be placed either on the rotating surface and/or on the stationary surface such that a portion of the insert extends out with respect to either of the surfaces.
  • the insert When placed at a perimeter of a 4-inch diameter rotating structure, the insert may be configured to protrude up to some amount, such as about 7 ⁇ from the underlying surface.
  • Figure 11 shows an exploded diagram of the apparatus 500. Further shown are the components of the motor assembly 504, including the rotor 404, rotor cap 610, rotor housing 402, stator windings 406, permanent magnets 406, and a retaining cap 1102.
  • the retaining cap 1102 fixably retains the rotor 404 with the impellers 214.
  • FIG 12A shows an apparatus 1200 according to an alternative embodiment.
  • the apparatus 1200 includes the various aspects of apparatus 800 (figure 8A) and further includes an active control schemes to help regulate the spatial gap distance during operation and at start-up.
  • the stationary base structure 204 includes an output 1202 to introduce actively pumped fluid (including, e.g., air) into the spatial gap 218.
  • the actively pumped fluid may be introduced at inlet 1204 and may be provided by a fluid pump 1206.
  • the actively pumped fluid may have a pressure as low as 0.5 psig.
  • Figure 12B shows a photo of the apparatus 1200 of Figure 12A.
  • the apparatus 1200 may be configured to introduce the actively pumped fluid only at the startup to reduce the factional contact at the spatial gap 218. As a result, upon the heat sink impeller reaching a sufficient speed for the fluid bearings 802 to produce self-regulating thrust, the actively pumped fluid may be stopped. Similarly, the actively pumped fluid may be introduced during shutdown.
  • the rotating structure 206 When at rest, the rotating structure 206 may be seated against the base structure
  • the spatial gap 218 may have a distance of 5-10 microns.
  • the fluid-directing structure 214 While rotating, the fluid-directing structure 214 (e.g., impeller) also rotates causing the fluid in the channels between the fluid- directing structures 214 to move. As the fluid moves, heat from the fluid-directing structure 214 is rejected to the moving fluid and dispels into the thermal reservoir 108. As a result, heat is drawn from the heat-generating component 212, spread across the base structure 204, transferred from the base structure 204 to the rotating structure 206 across the spatial gap 218, and spread from the heat-extraction surface 216 to the fluid-directing structures 214.
  • the fluid-directing structure 214 e.g., impeller
  • FIG 14 schematically illustrates this step by showing a diagram of a heat-flow model of the apparatus according to the preferred embodiment of the invention.
  • the heat generated by the heat-generating component 212 is characterized as Q c hi P -
  • the resistance of the base structure 204 may be characterized as & Rbase, linear and Rbase,spread.
  • the movement of fluid from the rotation of the rotating structure 206 may be model as a sheering loss that generates heat (Qshear).
  • the motor assembly 302, 304 also generates heat (Q mo tor) from the rotation.
  • the heat from the motor (Q mot0 r) is modeled to be a part of the base structure 204 to be transferred to the rotating structure 206.
  • the controller 306 determines whether to continue to cool the heat-generating component 212. This may be based on a control signal or power being applied to the kinetic heat sink.
  • the controller 306 may vary the rotation speed of the motor-rotating component 304 or the power output thereto based on temperature (e.g., at the heat-generating component 212 or various components of the kinetic heat sink) or distance of the spatial gap 314. Of course, various control schemes may be employed to rotatably move the rotating structure with respect to the stationary base structure.
  • the process concludes at step 1308, in which the kinetic heat sink is de-energized. To that end, the controller 306 may reduce power to the motor assembly 302, 304, or power may be removed to the controller.
  • the rotating structure 206 slows to a stop forming a contact with a portion of the base structure 204 or de-energize to a low-friction state.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)

Abstract

La présente invention concerne un appareil et un procédé permettant de refroidir un élément générateur de chaleur comprenant une structure de base stationnaire et une structure rotative. Selon l'invention, la structure de base stationnaire peut être montée au niveau de la première surface thermoconductrice sur l'élément générateur de chaleur ou à proximité de celui-ci. La structure de base stationnaire comporte une première et une seconde surface thermoconductrice afin que de la chaleur soit conduite entre celles-ci. La structure rotative est couplée de manière rotative à la structure de base stationnaire. La structure rotative comporte une surface d'extraction de chaleur située en regard de la seconde surface thermoconductrice sur l'ensemble d'un écart spatial. En conséquence du mouvement en rotation de la structure rotative, la structure rotative transfère sensiblement la chaleur à partir de la seconde surface thermoconductrice vers un réservoir thermique se trouvant en communication avec la structure rotative. En outre, en conséquence du mouvement en rotation de la structure rotative, au moins deux surfaces de la structure rotative et/ou de la structure de base stationnaire génèrent une poussée et une poussée inverse afin de faire varier et/ou maintenir l'écart spatial.
PCT/US2013/044539 2012-06-07 2013-06-06 Puits de chaleur cinétique à écart thermique régulable WO2013184931A1 (fr)

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