WO2014055118A1

WO2014055118A1 - Magnetic flux guide component

Info

Publication number: WO2014055118A1
Application number: PCT/US2013/031130
Authority: WO
Inventors: Joshua K. Schwannecke; Kaitlyn J. TURNER; Benjamin C. Moes
Original assignee: Access Business Group International Llc
Priority date: 2012-10-02
Filing date: 2013-03-14
Publication date: 2014-04-10
Also published as: CN103714938A; TW201415501A

Abstract

A laminated flux guide with a cover layer and a thermally conductive layer disposed on opposite sides of a plurality of alternating layers of high permeability and electrically insulating materials. The thermally conductive layer may be a metal, such as aluminum. The present invention also provides a method of manufacturing including the general steps of: providing a plurality of rolls of high permeability material; providing a roll of thermally conductive material, providing a roll of cover material; applying an electrically insulating adhesive between adjacent layers of the high permeability material; feeding the high permeability material layers with the applied adhesive into pressure rollers to form a pre-laminate; feeding the thermally conductive layer, the pre-laminate and the cover layer into pressure rollers to join them under pressure into a final laminate and cutting the final laminate into the desired shape.

Description

MAGNETIC FLUX GUIDE COMPONENT

BACKGROUND OF THE INVENTION

[0001] The present invention relates to magnetic flux guides and methods for manufacturing magnetic flux guides.

[0002] Magnetic flux guides, sometimes referred to as flux concentrators, flux focusers, flux intensifies, flux diverters, flux controllers, flux reflectors and other names, are generally known and have been used in controlling the flow of magnetic fields in applications such as inductive heating and inductive power transfer applications. Flux guides typically help to control the flow of magnetic fields by providing a high magnetic permeability flow path. By providing a high permeability flow path, a flux guide provides a path of least resistance and can affectively draw in more of the magnetic field. This can intensify the magnetic field in certain areas and can assist in increasing efficiency in power. Without a flux guide, the magnetic field is more likely to spread around and intersect with any electrically conductive surroundings. In some circumstances, a magnetic flux shield can be a type of magnetic flux concentrator.

[0003] As noted above, flux guides are typically formed from materials having a relatively high magnetic permeability. A wide variety of high permeability materials are available for us in flux guides. For example, soft magnetic materials, such as ferrite, are often used in manufacturing flux guides. Ferrite flux concentrators are dense structures typically made by mixing iron oxide with oxides or carbonates of one or more metals such as nickel, zinc or manganese. The main drawbacks of ferrite flux concentrators are that they are often brittle and tend to warp when manufactured in thin cross sections. Ferrites also typically have a low saturation flux density and therefore become saturated easily and thus are no longer significantly more permeable to magnetic fields than air in the presence of other magnetic fields, which may be undesirable in some applications.

[0004] Another soft magnetic material sometimes used in manufacturing flux concentrators is magneto dielectric materials ("MDM"). These materials are made from soft magnetic material and dielectric material, which serves as a binder and electric insulator of the particles. MDM flux concentrators come in two forms: formable and solid. Formable MDM is putty-like and is intended to be molded to fit the geometry of the coil. Solid MDM is produced by pressing a metal powder and a binder with subsequent thermal treatment. The characteristics of an MDM flux concentrator vary based on, among other things, binder percentage. Typically, the less binder the higher the permeability. However, in conventional arrangements, less binder translates to more metal on metal contact, and therefore more eddy currents forming during use of the flux concentrator. Although MDM flux concentrators may be manufactured with a thin profile, it is difficult to manufacture an MDM flux concentrator with all of the desired magnetic and thermal characteristics due to the competing effects of varying the binder percentage.

[0005] Although the soft magnetic materials discussed above provide higher permeability than ambient air and are generally effective flux guides, materials with higher permeability can be even more effective in many types of applications. For example, alternative soft magnetic materials incorporating a "high permeability materials" (i.e. relative magnetic permeability in excess of 100 with typical values in the range of 1 ,000-70,000+), such as various types of amorphous metal, metal glass and nanocrystaline metal are suitable for use in the manufacture of high performance flux guides. Although these materials can provide dramatic gains in magnetic permeability over other soft magnetic materials, they suffer from some potential disadvantages. First, they are typically highly electrically conductive, which can lead to the production of eddy currents and undesirable heating within the material. To address heating concerns, laminated flux guide have been developed. A typical laminated flux guide 200 includes a plurality of thin layers of a high permeability material 202 separated from one another by thin electrically insulating layers 204 (See, for example, Fig. 1). Further, each layer of high permeability material may be separated into narrow strips that are spaced apart to provide electrically isolated adjacent strips. The combined affect of the insulating layers and the division of the material into strips can significantly limit eddy currents, and consequently limit heat production. Second, these high permeability materials are also prone to oxidation. To address this concern, it is known to cover the exposed major surfaces of the material with a material that acts as a vapor barrier 206. Further, high permeability materials can be relatively brittle and are susceptible to cracking or breaking. Protective outer layers, such as layer 206, may help to reduce the problems resulting from cracks in the material. For example, outer layers of PET may hold the cracked material together and reduce the chances that pieces of the material will break off.

[0006] Although a marked improvement over many other conventional types of flux guides, there remains a need for a flux guide that can provide even greater control over magnetic fields, and that can be manufactured simply and inexpensively.

SUMMARY OF THE INVENTION

[0007] The present invention provides a laminated flux guide having a cover layer and a thermally conductive layer disposed on opposite sides of a plurality of alternating layers of high permeability material and electrically insulating material. In one embodiment, the thermally conductive layer is also electrically conductive. In one embodiment, the thermally conductive layer is a thin layer of high thermal conductivity metal. In one embodiment, the metal may be aluminum.

[0008] In one embodiment, a layer of insulting material is disposed between each layer of high permeability layer and over the outermost high permeability layers. The insulating material may be selected to provide good electrically insulating properties, while providing limited thermal insulation. In one embodiment, the insulating layers are formed from a thin layer of polyethylene terephthalaie ("PET"). In one embodiment, the insulating layers may be a material that functions as an electrically insulating material and as an adhesive for joining adjacent layers of high permeability material. For example, the insulating layers may be a pressure sensitive adhesive or a heat activated adhesive. In other embodiments, a separate adhesive may be used to join the layers of high permeability material and layers of insulating material.

[0009] In one embodiment, the cover layer is formed from a material that has good vapor barrier properties to reduce or eliminate oxidation of the outermost layer of high permeability layers. The cover layer may be selected to provide good strength and flexibility properties to help hold the laminated flux guide together even if one or more of the high permeability layers becomes cracked or broken. In one embodiment, the cover layer is formed from a layer of PET or other polymers.

[0010] In one embodiment, each high permeability layer includes a plurality of strips of high permeability material that are spaced apart to create electrical isolation between adjacent strips. The width of the strips may be selected to prevent the development of excessive eddy currents when the flux guide is subject to expected magnetic fields. As a manufacturing expedient, the interior insulating layers may be cut or otherwise divided into electrically isolated strips along with the high permeability layers.

[0011] In those embodiments, in which the thermally conductive layer is electrically conductive, the thermally conductive layer may be cut and separated into electrically isolated strips or otherwise configured to reduce the amount of continuous material. This can reduce eddy currents and minimize the associated losses in the thermal conductive layer.

[0012] In one embodiment, the laminated flux guide may be coupled to a heat sink. For example, the thermally conductive layer may be joined to a heat sink or to a heat pipe that carries heat to a heat sink. The thermally conductive layer may be joined directly to the heat sink or heat pipe, or a layer of electrically insulating material may be disposed between them. In embodiments that include an intermediate electrically insulating layer, the insulating material may be selected to provide minimal thermal insulation.

[0013] In another aspect, the present invention provides a method for manufacturing a laminated flux guide including the general steps of: providing a plurality of rolls of high permeability material; providing a roll of thermally conductive material, providing a roll of a cover material; applying an adhesive material between adjacent layers of the high permeability material, the adhesive material capable of functioning as an electrically insulating material; feeding the high permeability materials with the applied adhesive into a set of pressure rollers to join the various layers under pressure to form a pre-laminate; feeding the thermally conductive layer, the pre-laminate and the cover material into a set of pressure rollers to join them under pressure into a final laminate and cutting the final laminate into the desired shape. In one embodiment, the thermally conductive material is a roll of a thin layer of aluminum or other metal.

[0014] In one embodiment, each layer of high permeability material may include a plurality of narrow strips of material that are spaced apart to create electrical isolation between adjacent strips. In such embodiments, the method may include the steps of: cutting the pre-laminate into longitudinally extending strips; separating adjacent strips to provide electrical isolation between strips and maintaining the separation between the strips during formation of the final laminate, such that the strip are in electrical isolation from one another in the final laminate.

[0015] In one embodiment, the method includes the step of annealing the high permeability material. The high permeability material may be annealed at essentially any point in the manufacturing process, such as before or after it is wrapped into a roll, and before or after the material is cut into narrow strips. In embodiments that incorporate an adhesive/insulating material that is not damaged by annealing, the high permeability material may be annealed after the pre-laminate is formed. In embodiments that incorporate a final insulating layer and thermally conductive layer that are not damaged by annealing, the high permeability material may be annealed after the final laminate is formed.

[0016] In one embodiment, the method includes the step of applying an adhesive (or cement) between adjacent layers. For example, the method may include the step of applying pressure sensitive adhesive or heat activated adhesive to at least one of the mating surfaces at each layer. The adhesive may be applied to a material before it is formed into a roll. Alternatively, the adhesive may be applied to a material after it is taken off of the roll. For example, the method may include the step of applying an adhesive to at least one of the mating surfaces just prior to the materials entering the pressure rollers. When a heat activated adhesive is used, the method may further include the step of applying heat to the laminate to activate the adhesive. The heating step may be carried out by heating one or more of the pressure rollers, or by an external source of heat. In some embodiments, the adhesive may both join adjacent layers of high permeability material and function as an electrically insulating material.

[0017] The present invention provides a simple and effective flux guide capable of providing a high degree of control over magnetic fields, while also providing improved thermal management. The use of alternating plies of high permeability material and electrically insulating material reduces eddy currents, and consequently reduces heat generation. Subdividing each high permeability layer into strips also reduces eddy currents and heat generation. The outer thermally conductive layer provides a structure for extracting heat from the laminated flux guide. When coupled, directly or indirectly, to a heat sink or heat pipe, the thermally conductive layer can provide an affective route for removing heat form the laminated flux guide. The cover layer helps to hold the laminated flux guide together even if one or more of the sometimes brittle high permeability layers becomes broken or fractured. The cover layer may also provide a vapor barrier that protects the underlying high permeability layer from oxidation. The manufacturing method of the present invention provides a simple, inexpensive and highly repeatable method for manufacturing a flux guide. The use of rolls of material reduces complexity associated with the supply of materials to the laminating equipment. The use of one or more set of pressure rollers provides uniform lamination using simple and highly reliable equipment.

[0018] These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings.

[0019] Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention may be implemented in various other embodiments and of being practiced or being carried out in alternative ways not expressly disclosed herein. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the invention to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the invention any additional steps or components that might be combined with or into the enumerated steps or components.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Fig. 1 is a side view of a laminated flux guide according to the prior art.

[0021] Fig. 2 is a side view of a laminated flux guide according to the present invention.

[0022] Fig. 3 is a representational view showing manufacture of a flux guide in accordance with the present invention.

[0023] Fig. 4 is a side view showing a flux guide coupled to a heat sink.

[0024] Fig. 5 is a side view showing a flux guide coupled to a heat sink via a heat pipe.

[0025] Fig. 6 is a representational view comparing performance of a prior art laminated flux guide with a laminated flux guide in accordance with the present invention. DESCRIPTION OF THE CURRENT EMBODIMENT

[0026] A laminated flux guide in accordance with an embodiment of the present invention is shown in Fig. 2. The laminated flux guide 10 generally includes a cover layer 15 and thermally conductive outer layer 16 that are disposed on opposite sides of an arrangement of alternating layers of high permeability material 12a-d and electrically insulating material 14a-c. The number of alternating layers may vary. The cover layer 15 may be a thin layer of material that is capable of holding the laminated flux guide together and providing a vapor barrier that protects the underlying layer of high permeability material. The thermally conductive layer 16 may be a thin layer of metal or other thermally conductive material that is also capable of holding the laminated flux guide together and providing a vapor barrier that protects the overlying layer of high permeability material, along with providing a thermal flow path for moving thermal energy out of the flux guide. For example, the thermally conductive layer may be coupled directly or indirectly to a heat sink 30 or a heat pipe 32 capable of extracting thermal energy (See Figs. 4 and 5). The thermally conductive layer 16 may also be electrically conductive, thereby allowing the thermally conductive layer 16 to also function as a shield to the magnetic field.

[0027] The present invention is described in the context of a laminated flux guide configured for use with electronic devices that are charged wirelessly via magnetic or electromagnetic fields. In this context, the laminated flux guide is intended to assist in control of the magnetic flux associated with the supply of wireless power. The present invention is, however, well-suited for use in other applications where it may be desirable to control the flow of a magnetic field. Directional terms, such as "vertical," "horizontal," "top," "bottom," "upper," "lower," "inner," "inwardly," "outer" and "outwardly," are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation(s). It should also be noted that the thicknesses of the various layers of the laminated flux guide 10 are exaggerated in the figures to facilitate disclosure.

[0028] The laminated flux guide 10 of Fig. 2 generally includes a high permeability portion 20 and a thermally conductive portion 22. The high permeability portion 20 includes a plurality of layers of high permeability material 12a-d that are separated by a plurality of layers of electrically insulating material 14a-c. An additional layer of electrically insulating material 14d may be disposed between the thermally conductive layer 16 and the adjacent layers of high permeability material 12d. In the illustrated embodiment, there are four layers of high permeability material, but the number of layers may vary from application to application as desired. For example, with greater magnetic fields, it may be desirable to increase the number of layers, and with lesser magnetic fields, it may be desirable to reduce the number of layers. [0029] The layers of high permeability material 12a-d may be manufactured from soft magnetic materials incorporating "high permeability materials." More specifically, the high permeability layers may be manufactured from one or more materials having a relative magnetic permeability in excess of 100, with typical values in the range of 1 ,000-70,000+. For example, the high permeability material may be a type of amorphous metal, metal glass and nanocrystaline metal that is suitable for use in the manufacture of high performance flux guides. One suitable material is a soft magnetic material containing amorphous and nanocrystalline alloy available from Vacuumschmelze GmbH & Co. KG under the brand name VITROPERM, such as VITROPERM 800. In the illustrated embodiment, each layer of high permeability material is manufactured from the same material and is of approximately the same thickness (0.0008 inches). However, the type and thickness of the high permeability material may vary from layer to layer if desired.

[0030] In the embodiment of Fig. 2, each high permeability layer 12a-d includes a plurality of strips of high permeability material that are spaced apart to create electrical isolation between adjacent strips. For example, in the illustrated embodiment, the overall width of the laminated flux guide 10 is approximately 2.5 inches and there are 20 strips of approximately 0.125 inches. The width of the strips may be selected to prevent the development of excessive eddy currents (and excessive heat) when the laminated flux guide 10 is subject to expected magnetic fields, but the width may vary from application to application depending on a variety of factors. For example, wider strips may be used when the magnetic field is smaller, the system is capable of quickly extracting heat from the laminated flux guide 10 and/or the system is capable of withstanding greater heat. On the other hand, narrower strips may be used when the magnetic field is greater, the system is not capable of extracting heat as quickly and/or the system is capable of withstanding less heat. Although the high permeability layers 12a-d are divided into strips in the illustrated embodiment, the present invention may be implemented with undivided high permeability layers 12a-d in some applications.

[0031] As noted above, electrically insulating layers 14a-c are positioned between each layer of high permeability material 12a-d to provide electrical isolation between adjacent layers. The principle purpose of insulating layers 14a-c in this embodiment is to separate the high permeability layers 12a-d and thereby reduce eddy currents that might be generated by the magnetic field. The insulating layers 14a-c may be manufactured from essentially any electrically insulating material. However, in the embodiment of Fig. 2, the insulating layers 14a-c are manufactured from a material that is capable of both electrically isolating adjacent layers and adhesively joining the layers. For example, the insulating layers 14a-c may be a pressure sensitive adhesive that joins adjacent layers and is applied thick enough to create electrical isolation. In the illustrated embodiment, the insulating layers 14a-c are a pressure sensitive adhesive, such as acrylic, having a thickness of about 0.001 inches. As another example, the insulating layers 14a-c may be a heat activated adhesive that is has sufficient strength to hold the layers together and is of sufficient thickness to provide electrical isolation. As yet another example, each insulating layer 14a-c may be a layer of polymer that is capable of bonding adjacent layers of high permeability material 12a-d as it cures. It may also be desirable to use an electrically insulating material that has only limited thermal insulating properties. With materials that have greater thermal conductivity, the laminated flux guide 10 may be capable of more quickly dissipating heat generated internally. Alternatively, the insulating layers 14a-c may be manufactured from materials that are not capable of readily joining adjacent layers of high permeability material 12a-d. In such applications, a separate adhesive may be disposed between the high permeability layers 12a-d and the insulating layers 14a-c. For example, in embodiments of this type, the insulating layers 14a-c may be formed from a thin layer of polyethylene terephthalate ("PET") and the various layers 12a-d and 14a-c may be joined by a pressure sensitive adhesive or a heat activated adhesive (not shown).

[0032] As shown in Fig. 2, insulating layer 14d may be applied to an outer surface of high permeability layers 12d. This insulating layer 14d may be manufactured from the same material as insulating layers 14a-c, but may be manufactured from different materials is desired. In this embodiment, the insulating layer 14d is manufactured from a material selected to electrically isolate the outer surface of high permeability layer 12d and the thermally conductive layer 16. If the thermally conductive layer 16 does not have good vapor barrier properties, the insulating layer 14d may be manufactured from a material that also has good vapor barrier properties to reduce or eliminate oxidation of high permeability layer 12d. As with the other insulating layers 14a-c, insulating layer 14d may be manufactured from a material that is capable of both electrically isolating adjacent layers and adhesively joining the layers, or from a material that requires a separate adhesive to join the layers. For example, the insulating layers 14a-c may be a pressure sensitive adhesive that joins adjacent layers and is applied thick enough to create electrical isolation between thermally conductive layer 16 and high permeability layer 12d, a heat activated adhesive or a layer of polymer that is capable of bonding thermally conductive layer 16 to high permeability layer 12d. In the illustrated embodiment, insulating layer 14d is pressure sensitive adhesive, such as acrylic, having a thickness of approximately 0.001 inches.

[0033] Although not shown, an insulating layer may be applied to the outer surface of the thermally conductive layer 16 to provide electrical isolation between the thermally conductive layer 16 and the heat sink or heat pipe. For example, a thin layer of PET may be applied to the outer surface of the thermally conductive layer 16.

[0034] Referring again to Fig. 2, cover layer 15 may be applied to the outer surface of high permeability layer 12a. The cover layer 15 may be manufactured from a material selected to provide a vapor barrier over high permeability layer 12a and to hold together the laminated flux guide 10 even if one or more of the high permeability layers 12a-d break or fracture. The cover layer 15 may be a vapor barrier that reduces or eliminates oxidation of high permeability layer 12d. For example, the cover layer 15 may be formed from a thin layer of PET, PVC other similar flexible, but strong, polymers. The inner surface of the cover layer 15 may be coated with an adhesive, such as a pressure sensitive adhesive or a heat activated adhesive.

[0035] Although not shown, a second cover layer may be applied to the outer surface of the thermally conductive layer 16 to provide the laminated flux guide 10 with additional strength and integrity. This may be particularly beneficial if the thermally conductive layer 16 includes a plurality of separated strips, as described in an alternative embodiment below. When the thermally conductive layer 16 includes separated strips, an additional cover layer on the bottom of the laminated flux guide 10 may help to hold the entire assembly together, and may also help to provide a vapor barrier that protects the high permeability layers from oxidation.

[0036] The thermally conductive portion 22 generally includes a layer of thermally conductive material 16. As shown in Fig. 2, the thermally conductive layer 16 is disposed adjacent to insulating layer 14d in the illustrated embodiment. The thermally conductive layer 16 may be a thin layer of high thermal conductivity metal or other material that is has sufficient thermal conductivity. In the illustrated embodiment, the thermally conductive material has a thermal conductivity in the range of 200 to 500 W/(M*K), but it may be essentially any material with thermal conductivity greater than that of the ambient material for the related environment, such as air in many typical environments. For example, in some applications, the thermally conductive material may be a thermally conductive polymer. The amount of thermal conductivity desired may vary from application to application depending on a variety of factors, such as the environment and the amount of heat generated in the laminated flux guide 10. For example, less thermal conductivity may be necessary when less heat is generated, the environment is capable of quickly extracting heat from the thermally conductive layer and/or the electronic device in which the laminated flux guide 10 is installed is capable of withstanding relatively high heat. On the other hand, more thermal conductivity may be required when the flux guide generates more heat, the environment is not capable of quickly extracting heat from the thermally conductive layer and/or the associated electronic device is capable of withstanding relatively low heat. In the illustrated embodiment, the thermally conductive layer is a thin layer of aluminum having a thickness of approximately 0.01 to 0.25 inches. This range is merely exemplary and the thickness of the thermally conductive layer may be thicker or thinner in some applications. To facilitate manufacture of the laminated flux guide 10 using the methods described below, the layer of aluminum may be thin enough to allow it to be provided in a roll, but that is not strictly necessary. Aluminum is well-suite for this particular application because it has high thermal conductivity, good mechanical strength, is flexible and light weight and is an effective vapor barrier. Although aluminum may provide the best combination of characteristics for many typical applications, the high thermal conductivity layer may be formed of other materials, such as other metals or other materials with high thermal conductivity.

[0037] In the illustrated embodiment, the thermally conductive layer 16 is also electrically conductive. This allows the thermally conductive layer 16 to function as a shield that provides further control over the magnetic flux. For example, when electrically conductive, the magnetic field may induce eddy currents in the thermally conductive layer. This may, in effect, reduce or eliminate passage of the magnetic field through the thermally conductive layer, thereby shielding from the magnetic field objects in the environment on the opposite side of the thermally conductive layer. For example, Fig. 6 shows a representative comparison of the magnetic field M in a prior art laminated flux guide 200 (left) having no thermally conductive layer and laminated flux guide 10 (right), which includes a thermally conductive layer 16 that is electrically conductive. In this representation, the laminated flux guides 200 and 10 are positioned adjacent to an inductive transmitting coil C that is generating a magnetic field M. As can be seen, with prior art laminated flux guide 200, the magnetic field M extends below the lowermost extreme of the flux guide 200. However, with laminated flux guide 10, thermally conductive layer 16 functions as a shield that prevents the magnetic field M from extending beyond the thermally conductive layer 16. The improved magnetic performance of the laminated flux guide is attributable to the diamagnetic effect in the thermally and electrically conductive material 16, for example aluminum or copper. This illustration shows that laminated flux guide 10 can be configured to shield objects, including metal (e.g., steel) objects, positioned below the laminated flux guide 10 from the magnetic field M. It should also be noted that the laminated flux guide 10 may be incorporated into a remote device that is receiving inductive power from a wireless power supply. In such applications, the laminated flux guide may be positioned adjacent the receiving coil opposite the transmitting coil. More specifically, the laminated flux guide 10 may be positioned with cover layer 15 adjacent the receiver coil and the thermally conductive layer 16 on the opposite side. In such applications, the thermally conductive layer 16 may function as a shield that helps to contain the magnetic field transmitted by the transmitter coil. Although the thermally conductive layer 16 of the illustrated embodiment has good electrical conductivity properties, the thermally conductive layer 16 may be manufactured from a material with low electrical conductivity parameters, such as a thermally conductive polymer. This alternative may be implemented where it is desirable to limit eddy currents and the associated heat loss resulting from conductive materials.

[0038] In those applications where the thermally conductive layer 16 is electrically conductive, but it is desirable to limit heat generated by eddy currents, the thermal conductive layer 16 may be slit or divided into electrically isolated strips to reduce the amount of continuous material, which can reduce eddy current and minimize thermal losses in the thermal conductive layer. As discussed above in connection with the high permeability layers 12a-d, the number and width of strip in the thermally conductive layer 16 may vary from application to application depending on a variety of factors, but will likely be selected to be narrow enough to prevent the development of excessive eddy currents (and excessive heat) when the laminated flux guide 10 is subject to expected magnetic fields.

[0039] The laminated flux guide 10 of the present invention may be coupled to other heat management components to remove heat from the system. For example, in the embodiment of Fig. 4, the laminated flux guide 10 is coupled to a heat sink 30, and in Fig. 5, the laminated flux guide 10 is coupled to a heat pipe 32 that is, in turn, coupled to a heat sink 30. The heat sink 30 and heat pipe 32 may be essentially any heat sink or heat pipe, including any conventional heat sink or heat pipe capable of providing the desired heat dissipation within the packaging constraints of the application. The thermally conductive layer 16 may be joined directly to the heat sink 30 or heat pipe 32, or a layer of electrically insulating material (not shown) may be disposed between them. When joined directly to the heat sink 30 or heat pipe 32, the thermally conductive layer 16 may be joined to the heat sink 30 or heat pipe 32 by a thermally conductive adhesive, such as a thermally conductive silicone adhesive, epoxy adhesive or transfer tape. In embodiments that include an intermediate electrically insulating layer, the insulating material may be any of the insulating materials discussed above in connection with layers 14a-d.

[0040] In another aspect, the present invention provides a method for manufacturing a laminated flux guide 10. One embodiment of this method is described in connection with Fig. 3, which is a schematic representation of a manufacturing system for manufacturing laminated flux guide 10 in accordance with one embodiment of this manufacturing method. The method generally includes the steps of: providing a plurality of rolls of high permeability material; providing a roll of thermally conductive material, providing a roll of a final insulating material; applying an adhesive material between adjacent layers of the high permeability material, the adhesive material capable of functioning as an electrically insulating material; feeding the high permeability materials with the applied adhesive into a set of pressure rollers to join the various layers under pressure to form a pre-laminate; feeding the thermally conductive layer, the pre-laminate and the final insulating material into a set of pressure rollers to join them under pressure into a final laminate and cutting the final laminate into the desired shape. In the illustrated embodiment, the high permeability material is a soft magnetic material containing amorphous and nanocrystalline alloy available from Vacuumschmelze GmbH & Co. KG under the brand name VITROPERM, such as VITROPERM 800. The high permeability layers may, however, be other high permeability materials capable of being supplied in a roll. In the illustrated embodiment, the thermally conductive material is a roll of a thin layer of aluminum, but other material may be used as discussed above.

[0041] Referring now to Fig. 3, the manufacturing system 100 includes a plurality of rolls 102a-d of high permeability material that supply the high permeability material for layers 12a-d. During manufacture, four webs 104a-d of high permeability material are drawn from the four rolls 102a-d to form the four high permeability layers 12a-d.

[0042] In this embodiment, the insulating layers 14b-e are formed from an insulating material that adheres and electrically insulates the high permeability layers 12a-d. To this end, the manufacturing system 100 of this embodiment includes an inline applicator 108 located downstream from rolls 102a-d. The applicator 108 is configured to apply an insulating/adhesive material to the appropriate surfaces of webs 104a-d. More specifically, in this embodiment, the applicator 108 applies a layer of insulating/adhesive material to the undersurfaces of webs 104a-d as the webs pass from the rolls 102a-d to the pressure rollers 106a-b (discussed below). The insulating/adhesive material may alternatively be applied to the upper surfaces of webs 104b-d, or to both the undersurfaces of webs 104a-d and the upper surfaces of webs 104b-d. The applicator 108 may include sprayers, rollers or other mechanisms capable of applying the insulating material to the webs 104a-d. In this embodiment, the insulating material may be a pressure sensitive adhesive, a heat activated adhesive or a polymer capable of insulating and bonding together adjacent webs 104a-d. In some applications, it may be desirable to apply an insulating material to the bottom surface of web 104d after the pressure rollers 106a-b. This insulating material may be used to form insulating layer 14d to join and electrically isolate the thermally conductive layer 16 from high permeability layer 12d. The insulating material used for this layer may be the same as or differ from the material used to form insulating layers 14a-c.

[0043] In this embodiment, the high permeability webs 104a-d with applied insulating material are next joined together to form a pre-laminate 110. The webs 104a-d and insulating material may be joined by pressure and possibly heat. As shown in Fig. 3, the coated webs 104a-d are fed into a pair of pressure rollers 106a-b. The pressure rollers 106a-b are configured to apply the correct amount of pressure, and possibly heat, to cause the insulating/adhesive material to join the webs 104a-d into the pre-laminate 110. In applications where heat is applied, one or both of the rollers 106a-b may be heated or a separate source of heat may be incorporated into the system. For example, heat lamps or radiant heaters may be positioned before the pressure rollers 106a-b to apply the correct amount of heat to activate or otherwise help the insulating material to adhesively join adjacent layers and form into the insulating layers 14a-d. In some applications, it may be desirable to provide the bottom pressure roller 106b with a non-stick coating to prevent build-up of insulating material on the bottom pressure roller 106b. [0044] In the illustrated embodiment, the pre-laminate 110 is divided into include a plurality of longitudinally-extending narrow strips that are spaced apart to create electrical isolation between adjacent strips. In this embodiment, the pre-laminate 110 is cut into strips and the strips are spaced- apart in an inline slitting station 112 located downstream from the pressure rollers 106a-b. However, the high permeability material layers and possibly the insulating layers may be divided into strips at other times. For example, the rolls of high permeability material may be pre-slit or they may be slit in an inline station before the webs 104a-b are fed into the pressure rollers 106a-b. The strips remain spaced apart during formation of the final laminate 120, such that the strips are in electrical isolation from one another in the final laminate 120.

[0045] In the illustrated embodiment, the method includes the step of annealing the high permeability material. The high permeability material may be annealed at essentially any point in the manufacturing process, such as before or after it is wrapped into a roll, and before or after the material is cut into narrow strips. In embodiments that incorporate an adhesive/insulating material that is not damaged by annealing, the high permeability material may be annealed after the pre-laminate is formed. In embodiments that incorporate a cover layer and thermally conductive layer that are not damaged by annealing, the high permeability material may be annealed after the final laminate is formed. In the illustrated embodiment, the high permeability material is annealed before it is wrapped into roll 102a-d. In applications where it is desirable to anneal the high permeability material later, an inline annealing station may be incorporated into the manufacturing system 100. For example, an annealing station may be located downstream from the rolls 102a-d and upstream from the applicator 108.

[0046] After the pre-laminate 110 is cut into strips and separated, a cover layer 15 is applied to the top of the pre-laminate 110 and the thermally conductive layer 16 is applied to the bottom of the pre-laminate 110. In this embodiment, the cover layer 15 and thermally conductive layer 16 are applied to the pre-laminate 110 simultaneously. Referring now to Fig. 3, the cover layer 15 is provided in a roll 114 that is position to allow the cover layer 15 to be drawn from the roll and secured to the pre-laminate 110 by a second set of pressure rollers 116a-b. For example, the cover layer 15 of the illustrated embodiment may be a roll of PET. In this embodiment, the cover layer 15 is provided in advance with an adhesive layer for joining the cover layer 15 the top surface of the pre-laminate. For example, a pressure sensitive adhesive or a heat activated adhesive may be applied to the bottom surface of the PET before it is wrapped into roll 114. The adhesive may alternatively be applied to the cover layer 15 after the material is drawn off of the roll 114. For example, an adhesive applicator (not shown) may be disposed between the roll 114 and the second pressure rollers 116a-b. Similarly, the thermally conductive layer 16 is provided in a roll 118. The roll 118 may be position to feed the thermally conductive material onto the bottom surface of the pre-laminate 110 prior to second rollers 116a-b. The insulating layer 14d may be used to secure the thermally conductive layer 16 to the pre-laminate 110. For example, the amount of pressure or heat required to activate the adhesive in insulating layer 14d may be supplied by or at second rollers 116a-b. Although in this embodiment the cover layer 15 and thermally conductive layer 16 are applied using a second set of pressure rollers 116a-b, one or both may alternatively be applied using the first pressure roller 106a-b. For example, in alternative embodiments, the high permeability layers 12a-d may be separated into strips, and the cover layer 15 and thermally conductive layer 16 may be fed into the assembly of webs before the first pressure rollers 106a-b. With this alternative embodiment, a single set of pressure rollers may combine all of the layers simultaneously to form the continuous web of final laminate 120.

[0047] After the various layers have been joined by second rollers 116a-b, the webs 104a-d, insulating layers 14a-d, cover layer 15 and thermally conductive layer 16 collectively form a continuous web of final laminate 120. This continuous web of final laminate 120 may next be cut to form the final laminated flux guide 10. In the illustrated embodiment, the continuous web of final laminate 120 is cut into laminated flux guides 10 at cutting station 122. The cutting station 122 cuts the web in a lateral direction to divide the continuous web into discrete segments corresponding to the desired size of the laminated flux guide 10. If the continuous web is wider than the desired dimensions of the laminated flux guide 10, then the cutting station 122 can also be configured to perform longitudinal cuts, as well. For example, the continuous web of final laminate 120 may be configured to be twice as wide as the desired width of the laminated flux guide 10. In such applications, the cutting station may, in addition to the lateral cut, perform a longitudinal cut that divides the web 120 in half laterally. The cutting station 122 may include essentially any equipment capable of cutting the web of final laminate 120 into individual laminated flux guides 10. For example, the cutting station 122 may include a conventional die cutting machine. Alternatively, the cutting step may be performed by adding cutting blades to the second set of pressure rollers 116a-b.

[0048] In some applications, it may be desirable to separate the thermally conductive layer 16 into separate strips. Although not shown, this may be done by introducing the thermally conductive layer 16 into the manufacturing process prior to the first set of pressure rollers 106a-b. In such applications, the thermally conductive layer 16 will be included in the pre-laminate 110 and the inline slitting station 112 will cut and separate the thermally conductive layer 16 along with the remaining parts of the pre-laminate 110.

[0049] In some applications, it may be desirable to add a bottom cover layer (not shown) over the outer surface of the thermally conductive layer 16. This may be particularly beneficial when the thermally conductive layer 16 has been divided into separate strips. In such applications, the bottom cover layer may cooperate with the top cover layer 15 to hold together the laminated flux guide 10. The bottom cover layer (not shown) may be added to the final laminate 120 by introducing the bottom cover layer prior to the second set of pressure rollers 116a-b. For example, a roll (not shown) of the bottom cover layer material may be positioned to allow the bottom cover material to be drawn into a position along the outer surface of the thermally conductive layer 16 prior to the materials entering the second set of pressure rollers 116a-b. This will allow the bottom cover layer to be joined into the final laminate 120 by the second set of pressure rollers 116a-b. If desired, the top cover layer 16 and the bottom cover layer (not shown) may be sized to extend beyond the intermediate layers so that that top cover layer 16 and the bottom cover layer may be joined together along at least portions of their periphery. In applications where it is desirable to join the top and bottom cover layers around their entire periphery, the top and bottom cover layers may be applied after the continuous web of final laminate 120 is cut at cutting station 118.

[0050] The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Further, the disclosed embodiments include a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles "a," "an," "the" or "said," is not to be construed as limiting the element to the singular.

Claims

CLAIMS The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A laminated flux guide comprising:

a plurality of layers of high permeability material;

a plurality of layers of electrically insulating material, said layers of high permeability material and said layers of insulating material arranged in alternating layers; and

a thermally conducting layer disposed adjacent to said alternating layers.

2. The flux guide of claim 1 wherein each of said plurality of layers of high permeability material includes a plurality of electrically isolated strips.

3. The flux guide of claim 2 wherein said thermally conductive layer is a layer of metal.

4. The flux guide of claim 2 wherein said thermally conductive layer is a layer of aluminum.

5. The flux guide of claim 4 further including a cover layer adjacent to said alternating layers, wherein said cover layer and said thermally conductive layer are disposed on opposite sides of said alternating layers, said cover layer providing a vapor barrier.

6. The flux guide of claim 5 wherein each of said plurality of layers of insulating material is an adhesive.

7. The flux guide of claim 6 further including a layer of electrically insulating material disposed between said alternating layers and said thermally conductive layer.

8. An assembly comprising:

an inductive coil configured to generate or receive a magnetic field; and

a laminated flux guide disposed adjacent to said inductive coil, said laminated flux guide having:

a permeability portion including alternating layers of high permeability material and electrically insulating material; and

a thermally conductive layer disposed adjacent to said permeability portion opposite said inductive coil.

9. The assembly of claim 8 wherein said thermally conductive layer is a layer of metal.

10. The assembly of claim 8 wherein said thermally conductive layer is a layer of aluminum.

11. The assembly of claim 9 further including a cover layer adjacent to said permeability portion, wherein said cover layer and said thermally conductive layer are disposed on opposite sides of said permeability portion.

12. The assembly of claim 11 wherein each of said layers of electrically insulating material is an adhesive bonding adjacent pairs of said layers of high permeability material.

13. The assembly of claim 12 further including a layer of electrically insulating material disposed between said permeabilty portion and said thermally conductive layer.

14. The assembly of claim 8 wherein each of said layers of high permeability material includes a plurality of electrically isolated strips.

15. The assembly of claim 14 wherein said thermally conductive layer includes a plurality of electrically isolated strips.

16. A method of manufacturing a laminated flux guide, comprising the steps of:

providing a plurality of rolls of high permeability material, each of the rolls including a continuous web of the high permeability material;

providing an electrically insulating layer between the continuous webs;

feeding the webs and insulating layers into pressure rollers to form a pre-laminate;

providing a continuous roll of thermally conductive material;

providing a continuous roll of a cover material; and

feeding the thermally conductive material, the pre-laminate and the cover material into pressure rollers to form a final laminate.

17. The method of claim 16 further including the step of dividing the pre-laminate into electrically isolated strips.

18. The method of claim 17 wherein said dividing step includes the steps of slitting the pre-laminate into a plurality of strips and separating the strips a sufficient distance to provide electrical isolation between adjacent strips.

19. The method of claim 18 wherein the thermally conductive layer is a metal.

20. The method of claim 18 wherein the thermally conductive layer is aluminum.

21. The method of claim 16 wherein adjacent pairs of the continuous webs having a pair of mating surfaces; and

wherein said step of providing an insulating layer between the continuous webs includes appying an electrically insulating adhesive to at least one of each pair of mating surfaces.

22. The method of claim 16 wherein said step of providing an insulating layer between the continuous webs includes the steps of:

providing a plurality of rolls of insulating material, each of the rolls of insulating material including a continuous web of an electrically insulating material; positioning a layer of insulating material between each pair of adjacent webs of high permeability material prior to said step of feeding the webs and insulating layers into pressure rollers to form a pre-laminate.

23. The method of claim 22 wherein each adjacent pair of the high permeability continuous webs and the insulating layer continuous webs have a pair of mating surfaces; and

wherein said step of providing an insulating layer includes the steps of applying an adhesive to at least one of each pair of mating surfaces.

24. The method of claim 16 further including the step of cutting the final laminate into laminated flux guides.