Ferrite tile voltage reduction

Abstract

A system for reducing the voltage between tiles in a wireless power transfer (WPT) assembly is disclosed. The system includes a core comprising a plurality of magnetically permeable elements arranged adjacent one another; a housing at least partially containing the core, the housing comprising a conductive portion; and at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.

Description

P0482PCT-W-NPR1 / 000469-0015-W01FERRITE TILE VOLTAGE REDUCTIONRelated Application

[0001] This present disclosure is related to WiTricity Corp, docket number P0486US-W- PRO1 (U.S. Patent Application 63 / 733,052 filed on 12 December 2024), the disclosure of which is incorporated by reference herein in their entirety.Field of the Invention

[0002] The technical field relates generally to wireless power transfer, and more specifically to devices, systems, and methods related to wireless power transfer. More particularly, the present disclosure relates to magnetic coupling structures and winding arrangements used in wireless power transfer systems, and in particular inductive power transfer (IPT) systems.Background

[0003] Wireless power transfer (WPT) for charging electric vehicles is described in detail in patents such as U.S. Patents 8,933,594, titled “Wireless energy transfer for vehicles,” and 9,561,730, titled “Wireless power transmission in electric vehicles,” which are incorporated here by reference in their entirety. More specifically, these patents refer to inductive WPT between a ground-based unit of a wireless charging station and a vehicle-based unit, herein also simply referred to as the ground unit or ground assembly and the vehicle unit or vehicle assembly, respectively.

[0004] Efficient and regulatory compliant WPT for electric vehicles requires a WPT coil in the vehicle unit to be aligned with a WPT coil in the ground unit within a specified tolerance zone. Some standards specify a tolerance zone of + / - 75 mm in x-direction (vehicle longitudinal axis) and + / - 100 mm in y-direction (vehicle lateral axis). Therefore, one aspect of WPT for charging electric vehicles to be addressed is assisting a user or an autonomous driving system to park and align the vehicle within the relatively tight tolerance zone sometimes also referred to as “charging spot”. Such park assist system may also include guidance of the user or the autonomous driving system in steering the vehicle towards the ground unit.

[0005] A further aspect of WPT for electric vehicle charging to be addressed is establishing wireless communications between the vehicle and the wireless charging station from which the vehicle is attempting to charge. Standard compliant WPT for electric vehicles, requires the wireless charging station to communicate with the vehicle via a wireless communication network for purposes of WPT system control and other WPT-related functions (e.g., for the safety of the system). This communication is based on WiFi IEEE 802.1 lx using standardized protocols enabling interoperability. Establishing wireless communications may be particularly difficult in a parking facility with multiple wireless charging stations at which multiple EVs may be attempting to park at the same time. It is necessary to disambiguate the connections - that is, make sure that each vehicle is in communication with the wireless charging station it is attempting to use for charging, and not another e.g., neighboring station. This disambiguation is part of a process referred to as pairing and shall ensure that a wireless communication node (e.g., a WiFi client) associated to the vehicle communicates with a wireless communication node (e.g., a WiFi access point) associated to the right wireless charging station.Summary

[0006] A WPT system may utilize inductive power transfer to transfer power between WPT units of the WPT system, such as between respective WPT units of a ground assembly and a vehicle assembly of a WPT system for charging EVs. For example, a WPT unit may be configured to transmit electrical power to another WPT unit, or receive from another WPT unit, power via the establishment of an electromagnetic near field, that is perceived by a receiving WPT unit positioned within a region near to the transmitting WPT unit. In some cases, such as grid to vehicle (G2V) charging, power is initially provided by a primary power source, for example, an electrical grid, to the transmitting WPT unit (e.g., a ground WPT unit), which in turn inductively transfers it to the receiving WPT unit (e.g., a vehicle WPT unit) to store it in a secondary source, for example, a power storage such as a battery of a vehicle. Similar principles apply for vehicle to everything (V2X) energy transfer. Irrespective of the direction of the energy transfer, the induction coils of the WPT units will typically be positioned close to each other and substantially aligned so as to achieve a strong degree of electromagnetic coupling and thus efficient energy transfer.

[0007] In most cases, a WPT unit includes a physical core made of a material having a high electromagnetic permeability. A commonly used material is ferrite, which is highly permeable to electromagnetic fields and can be used to help control the electromagnetic fieldproduced by an induction coil. Some approaches provide backing an induction coil with a ferrite structure. An advantage of using a ferrite core in a transmitting WPT is that the magnetic flux can be concentrated in the direction of a receiving WPT. A secondary goal of the ferrite structure is to protect electronics and reduce the exposure of lossy metals to the electromagnetic field, thus increasing efficiency of the WPT.

[0008] In some approaches, a WPT unit comprises a housing (e.g., made of plastic and / or metal), a multi -turn induction coil (e.g., made of stranded Litz wire) and a ferrite structure, along with associated electronics. In some instances, the multi-turn induction coil sits upon or underneath the ferrite structure in the housing. Furthermore, in some cases, the multi-turn coil and the ferrite structure may be embedded in a non-conducting non-magnetic material, for example, a resin. As a result, the overall thickness of the WPT unit is dependent on the stacking of the thicknesses of the above components. In particular, when considering the physical requirements for the power transfer of a WPT system for charging EVs, the overall thickness of a WPT unit may be in the region of around 100mm. As such, it is desirable to minimize the overall thickness of a WPT and improve the implementation of WPT units, e.g., in ground assemblies and vehicle assemblies of WPT systems for EV charging.

[0009] In some WPT units, ferrite tiles are used to guide the magnetic flux from the coil and increase the coupling between the vehicle assembly and ground assembly. One of the design constraints is to minimize the distance in between the tiles to reduce losses and to increase coupling. A contradicting requirement is to increase the distance in between the tiles due to isolation requirements and improved performance reliant on increased spacing between tiles.

[0010] In some WPT units, high voltages are used. The high voltage present between ferrite tiles can lead to arcing between the tiles, which can result in malfunctions, degradation of the ferrite tiles, and other issues with operation.

[0011] To mitigate these issues, examples of the present disclosure reduce the inter-tile voltages and therefore lead to better system performance while reducing cost and complexity. This may be accomplished by adding electrically conductive pads between the ferrite tiles and the metal housing of the assembly.

[0012] In one aspect of the present disclosure, a power transfer unit is described. The power transfer unit may be, for example, a ground unit of a GA or a vehicle unit of a VA of a WPT system for wirelessly charging an electric vehicle. The power transfer unit may include a core comprising a plurality of magnetically permeable elements (e.g., ferrite tiles) arranged adjacent one another. The power transfer unit may also include a housing at least partiallycontaining the core, the housing comprising a conductive portion (e.g., a back plate). The power transfer system may also include at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.

[0013] In some examples, the power transfer unit further comprises one or more windings in magnetic association with the core, the windings being at least partially contained within the housing and configured to cause a capacitive coupling between the plurality of magnetically permeable elements in operation.

[0014] In some examples, the conductive element of the power transfer unit is formed from a conductive elastomeric material. This may include conductive rubber, or another type of flexible metallic material. Additionally, this may include a metallic sprung tang.

[0015] In some examples, the thickness of the conductive element may be greater than the space between the core and the housing in an uncompressed state. That is, the conductive element may be compressed between the core and housing when the core and housing are assembled together.

[0016] In some examples, the conductive element may be configured to reduce a voltage between adjacent magnetically permeable elements during operation of the power transfer unit.

[0017] In some examples, the conductive element may be configured to span an interface between adjacent magnetically permeable elements of the core.

[0018] In some examples, the conductive element may be provided in between adjacent magnetically permeable elements of the core.

[0019] In some examples, the housing is configured to apply a clamping force to the conductive element when the power transfer unit is in an assembled configuration.

[0020] In some examples, an electrically conductive adhesive is provided between the conductive element and the conductive portion of the housing, and / or between the conductive element and a respective magnetically permeable element.

[0021] In another aspect, a ground unit for a wireless power transfer system for wirelessly charging a vehicle is described. The ground unit includes a core comprising a plurality of magnetically permeable elements arranged adjacent one another; a housing at least partially containing the core, the housing comprising a conductive portion; and at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.

[0022] In another aspect, a vehicle unit for a wireless power transfer system for wirelessly charging a vehicle is described. The vehicle unit includes a core comprising a plurality of magnetically permeable elements arranged adjacent one another; a housing at least partially containing the core, the housing comprising a conductive portion; and at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.Brief Description of the Drawings

[0023] The above and other objects and advantages of the disclosure will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0024] FIG. 1 illustrates an example parking facility with multiple wireless charging stations for use by electric vehicles in accordance with some examples of the disclosure;

[0025] FIG. 2 illustrates a hierarchical block diagram of an example wireless power transfer system for wireless electric vehicle charging, in accordance with some examples of the disclosure;

[0026] FIGS. 3A-B illustrate perspective views of an example WPT unit being assembled, in accordance with some examples of the disclosure;

[0027] FIG. 4 illustrates an exploded view of a portion of the WPT unit, in accordance with some examples of the disclosure;

[0028] FIG. 5 illustrates a simplified block diagram of a side perspective view of select portions of the WPT unit, in accordance with some examples of the disclosure;

[0029] FIG. 6 illustrates a bottom plan view of the WPT unit, showing example positioning of the conductive elements on the ferrite tiles, in accordance with some examples of the disclosure;

[0030] FIG. 7 illustrates a top plan view of the WPT unit of FIG. 6 in an assembled form, in accordance with some examples of the disclosure; and

[0031] FIG. 8 illustrates a side view of the WPT unit of FIG. 7 taken along a line passing through a middle of the WPT unit, in accordance with some examples of the disclosure.Detailed Description

[0032] FIG. 1 illustrates an example of a parking facility 100 providing wireless charging services in parking spots 150a and 150b, including a plurality of WPT systems suitable foruse in systems and methods of the present disclosure. Two wireless charging-enabled vehicles, 102a, 102b integrating WPT vehicle units 130a, 130b are each parked over a WPT ground unit, 120a, 120b. Both vehicle unit and ground unit include a WPT coil (not shown) sometimes also referred to as an induction coil configured to wirelessly transfer power based on the Faraday induction principle. Both vehicle unit and ground unit also include respective portions of a position detection system. In some implementations, the ground units are surface mounted on the floor. In other implementations, the ground units are flush mount with the floor or buried in the ground (e.g., in the asphalt). The power converters 140a, 140b convert power received by WPT vehicle units 130a, 130b to a form suitable for charging the vehicle’s traction battery (not shown). In some examples and as described in U.S. Patent US 9,561,730 B2, the power converters 140a, 140b may be integrated with power converters used for plug-in charging of the vehicle, commonly called on-board chargers (OBC), or other on-board vehicle components. The WPT ground units 120a, 120b are shown linked to external power converters 110a, 110b, each connected to a power supply bus 118. In some implementations, the power converters 110a, 110b are configured and mounted as a “wall box.” In other implementations, the power converters or parts thereof are integrated into the WPT ground units. The power supply bus 118 is in turn connected to a central power distribution unit 114. In some implementations and operations, the central power distribution unit 114 receives power from a power utility 112 sometimes referred to as “power grid” and provides DC power to the bus 118, and the power converters 110a, 110b are inverters, such as the multi-level inverter described in provisional U.S. Application 18 / 486,830, filed October 13, 2023, and incorporated here by reference. The power converters 110a, 110b, provide low-frequency (LF) power signals, such as the 85 kHz signals used for WPT according to the SAE J2954 standard, to the WPT ground units 120a, 120b, to turn into LF magnetic fields for WPT. In other examples, the power distribution unit 114 provides the LF signals directly to each WPT ground unit, and power converters 110a, 110b are simpler or not present. In yet other examples, the power distribution unit 114 and bus 118 are not present, and the power converters 110a, 110b are each connected directly to the power utility 112 and convert AC power from the utility to LF power for wireless power transfer. The combination of a WPT ground unit (e.g., 120a), a power converter (e.g., 110a), and any other ground-side electronics (not shown) constitutes a wireless charging station (e.g., 104a) as indicated in FIG. 1. In some cases, the WPT ground units 120a, 120b are also referred to as Ground Assembly Resonators (GAR) or ground assembly pads, and the wireless charging station is also referred to as a Ground Assembly (GA) or Electric Vehicle Supply Equipment (EVSE).Analogously, the WPT vehicle units 130a, 130b are sometimes referred to as Vehicle Assembly Resonators (VAR) or vehicle assembly pads and the combination of a WPT vehicle unit (e.g., 130a) and a power converter (e.g., 140a) and any other vehicle-side electronics (not shown) constitutes a Vehicle Assembly (VA) (e.g., 106a, 106b). Each of the power connections shown may be bi-directional, allowing the vehicles to discharge power from their batteries to the power utility 112 in a vehicle-to-grid (V2G), or other load in a vehicle-to-home (V2H), vehicle-to-vehicle (V2V) or similar arrangement (generally V2X).

[0033] FIG. 1 also illustrates vehicles 102a, 102b, and power distribution unit 114 providing wireless communication units 146a, 146b, and 116, respectively. The wireless communication unit 116 may be configured to wirelessly communicate with the vehicles 102a and 102b e.g., based on a Wi-Fi IEEE 802.1 lx standard. In SAE standard conformant wireless charging systems, this communication is used for exchanging data between the GA and VA for purposes of WPT control and safety. Further, the power distribution unit 114 provides an interface 119 configured to communicate with external entities (e.g., a charging operation center) via a communication backhaul (not shown). This backhaul may rely on radio communications (e.g., via communication unit 116), power line communications (e.g., via power utility 112), or any other line communications including fiber optical. In the example parking facility 100, wireless communication unit 116 is configured to serve multiple vehicles. In other parking facilities, each of the wireless charging stations 104a, 104b provide a wireless communication unit (not shown) configured to communicate with the respective vehicles 102a, 102b.

[0034] Beside the WPT coil, the WPT ground units 120a, 120b or the WPT vehicle units 130a, 130b, or both may include various sensors and detection systems (not shown). For example, they may include systems for detecting a positional relationship between the vehicle unit and the ground unit. The positional relationship is needed to guide the vehicle to the charging spot, to mutually align the vehicle-side and groundside WPT coils within the specified tolerance, and for pairing of a vehicle with a wireless charging station as needed to establish communication between the right entities in multiple vehicle multiple charging station scenarios. The ground unit may also include sensors and detection systems to determine presence of a foreign object that has the potential to heat up by induction heating or any hazardous events caused by an incandescent object on the surface of the ground unit. Further, it may include sensors and a detection system for determining presence of a living object e.g., a hand of a person or animals approaching a critical space beneath the vehicle where electromagnetic field exposure exceeds certain limits (e.g., based on IEEE or ICNIRPguidelines). Moreover, the ground unit may include sensors and a detection system for determining a presence of the vehicle or a type of the vehicle. In some implementations, sensors and detection systems or parts thereof may be external to the ground unit or vehicle unit. The systems and methods disclosed herein may improve the process of positioning the vehicle, e.g., vehicle 102a, 102b, relative to a charging spot. Additionally or alternatively, systems and methods disclosed herein may improve wireless communications between the vehicle and the wireless charging station from which the vehicle is attempting to charge.

[0035] FIG. 2 is a hierarchical block diagram of an example WPT system 200 for wireless electric vehicle charging. At the top hierarchy level, the system 200 comprises a GA 204 and a VA 206 that may refer to the wireless charging station 104a and the VA 106a, respectively, of FIG. 1. The next lower level shows the GA 204 composed of a GA power conversion & control unit 210 and a WPT ground unit 220 (e.g., 120a of FIG. 1) and various connections between these blocks. Splitting the GA into two blocks implies implementations where the GA power conversion & control unit and the ground unit are physically separated (as illustrated in FIG. 1) and interconnected via a several meters long multiwire cable herein referred to as GA feeder cable (not shown). However, it should not exclude implementations where the GA power conversion & control unit is entirely or partially integrated in the ground unit forming one physical unit with a common housing (not shown).

[0036] At the third level, the GA power conversion & control unit includes a GA power converter 212 (e.g., 110a of FIG. 1), a GA controller 214, and a GA wireless communication unit 216 (e.g., 116 of FIG. 1). The ground unit 220 integrates a GA WPT coil 222 as well as various functions as needed for Foreign Object Detection (FOD), Living Object Detection (LOD), Vehicle Detection (VD), and Position Detection (PD) as previously discussed with reference to FIG. 1. In the example of FIG. 2, these functions are provided by a FOD unit 224, a LOD unit 226, and a GA PD unit 228, each configured and connected to the GA controller for exchanging data and control. In some implementations such as described in Patent US 11,914,094 and incorporated here by reference, these functions share or partially share one common hardware platform referred to as a multi-purpose detection system.

[0037] In an implementation conforming with the SAE standard, the GA wireless communication unit 216 is a WiFi Access Point providing an air interface to a Wireless Local Area Network (WLAN) of a parking facility. Certain parking facilities (e.g., parking facility 100 of FIG. 1) provide a central WiFi access point associated to multiple GAs. In such implementations, the GA wireless communication unit 216 is external to the GA 204. Inanother implementation, the GA wireless communication unit is integral part of the ground unit 220.

[0038] The GA WPT coil 222 may include a tuning & impedance matching network (not shown) forming a resonant circuit and the ground-unit is referred to as the GAR as previously mentioned. In other implementations, the tuning & impedance matching network or parts thereof are included in the GA power converter 212. Further, the GA controller 214 interfaces to the GA power converter 212 and the GA wireless communication unit 216 for data exchange and system control. It also provides a data interface 219 (e.g., Ethernet) to communicate with a system external entity e.g., via a backbone network as mentioned with reference to FIG. 1. Moreover, the GA power converter 212 disposes a power interface 218 for feeding or receiving AC or DC power as discussed with reference to FIG. 1.

[0039] At the second level, FIG. 2 shows the VA 206 composed of a WPT vehicle unit 230 (e.g., 106a of FIG. 1) connected to a VA power conversion & control unit 240. At a third level, the VA power conversion & control unit 240 comprises a VA power converter 242 (e.g., 140a of FIG. 1), a VA controller 244, and a VA wireless communication unit 246 (e.g., 146a of FIG. 1). The vehicle unit 230 comprises a VA WPT coil 232 and a VA PD unit 238, the vehicle-side counterpart of the GA PD unit 228 interfacing with the VA controller for data exchange and control. Splitting the VA into two blocks implies implementations where the VA power conversion & control unit and the vehicle unit are physically separated (as illustrated in FIG. 1) and interconnected via a multiwire cable herein referred to as VA feeder cable (not shown). However, this should not exclude implementations where the VA power conversion & control unit 240 is entirely or partially integrated in the vehicle unit 230 forming one physical unit with a common housing (not shown).

[0040] In a standard-conforming implementation, the VA wireless communication unit 246 is a WiFi Client. As with the GA wireless communication unit, the VA wireless communication unit may be external to the VA 206, e.g., mounted anywhere on the vehicle or parts or it may be partially or fully integrated into the vehicle unit.

[0041] In some implementations, the VA WPT coil 232 includes a tuning & impedance matching network (not shown) forming a resonant circuit and the vehicle unit is referred to as the VAR as previously mentioned. Further, the VA controller interfaces to the VA power converter and the VA wireless communication unit for data exchange and control. It also provides a line communication interface 249, e.g., a CAN bus interface to communicate with an external vehicle onboard entity. Moreover, the VA power converter disposes a powerinterface 248 for feeding or receiving DC power as previously discussed with reference to FIG. 1.

[0042] FIGS. 3A and 3B depict part of an example process for manufacturing a WPT unit, in accordance with some implementations of the disclosure. The WPT unit comprises a coil assembly 302, a casing 304 and a circuit assembly 306 (which comprises, for instance, a thermal pad 310).

[0043] Coil assembly 302 comprises one or more coils (e.g., a power transfer coil, one or more positioning coils), a ferrite array and one or more spacer pads (illustrated and described in further detail below with respect to FIGS. 4-8). The power transfer coil is supported by the ferrite array, which is in turn supported by the one or more spacer pads, which are in turn supported by the internal surface of casing 304, more specifically by parts of the internal surface of casing 304, which are levelled at a same level that is above the range of levels corresponding to recesses present in the internal surface of casing 304.

[0044] The power transfer coil is a planar multi-turn coil (for example, made of a Litz wire) having a first terminal lead (for example, outer terminal lead 312a) and a second terminal lead (for example, inner terminal lead 312b), wherein the planar multi -turn coil and the first terminal lead are located within a same first plane. The first terminal lead is located outside the planar multi -turn coil and consecutive to the most external turn of the multi -turn coil. The second terminal lead is initially located inside the planar multi-turn coil, in an unoccupied space, delineated by the most internal turn of the multi-turn coil, consecutive to the second terminal lead. Then, the second terminal lead is pulled to be in the vicinity of the first terminal lead, such that the second terminal lead is almost within the first plane. In effect, the second terminal lead passes slightly below the planar multi -turn coil.

[0045] Casing 304 is electrically conductive and comprises aluminum (although other appropriate materials are envisaged). The internal surface of casing 304 comprises a region to accommodate coil assembly 302, a plurality of recesses and a groove running along a perimeter of said internal surface. A largest recess of the plurality of recesses accommodates circuit assembly 306. The groove initially accommodates a sealing compound 308. Sealing compound 308 comprises a glue, which is then cured (for example, via exposure to a light of given wavelength range) to become a gasket, e.g., to enable sealing between the casing 304 and a cover assembled to the casing 304. Additionally, the internal surface of casing 304 comprises threaded holes (for example, threaded hole 305). For the sake of clarity, in the FIGS., each occurrence of several recurrent items (e.g., guiding pins 303, threaded holes 305in casing 304, holes in the frame, bolts, etc.) may not be labelled. For instance, only a few examples of threaded hole 305 are labelled using numbering ‘305’on FIGS. 3A-B.

[0046] In a first assembly step associated with FIG. 3A, one or more guiding pins 303 (e.g., hollow or solid) are inserted into one or more threaded holes 305 of the plurality of threaded holes extending into an internal surface 315 of casing 304. The one or more threaded holes are positioned within the perimeter region of the internal surface of casing 304. Using the one or more guiding pins 303, a coil assembly 302 is placed on the internal surface of casing 304, more specifically within, e.g., in-board of, the perimeter region of the internal surface of casing 304.

[0047] In a next assembly step associated with FIG. 3B, the one or more guiding pins 303 are removed and replaced by one or more fasteners (for example, bolts) to fasten coil assembly 302 to the internal surface of casing 304. In some instances, the one or more guiding pins 303 are hollow and each of the one or more guiding pins 303 can accommodate a fastener (such as a bolt 314) to fasten coil assembly 302 to the internal surface of casing 304.

[0048] The assembly process includes further steps which are not illustrated in the FIGS., including subjecting the coil assembly 302 to electromagnetic tests to determine whether the electromagnetic behavior of coil assembly 302 is as expected. Additional steps may include connecting the first and second terminal leads to the circuit assembly, adding additional components, glues, and / or other materials, and attaching a cover.

[0049] FIG. 4 illustrates an exploded view of the coil assembly (e.g., coil assembly 302), which may be inserted into the casing or housing (e.g., casing 304). The coil assembly includes polyimide film strips 402 (e.g., Pi film), which are configured to be affixed to the top of the Differential-Inductive-Positioning-System (DIPS) wires 414 and 426.

[0050] The coil assembly also includes a transfer coil 404 (e.g., a Litz coil), having first and second terminals (not labeled). The power transfer coil 404 is the primary coil for transmitting and / or receiving power. The power transfer coil 404 comprises a plurality of windings and may be in magnetic association with the core or ferrite array 412 discussed below. It should be appreciated that while the power transfer coil 404 is illustrated as a Litz wire, one or more other types of coils or wires may be used. In the illustrated example, the power transfer coil 404 is affixed to a coil-ferrite spacer 408 by a layer of glue 406. The glue 406 may comprise an epoxy or AB glue, such as weld bond 6102. In some examples, a different material may be used to affix the power transfer coil 404 to the coil-ferrite spacer 408, or the coil-ferrite spacer may be omitted.

[0051] Positioned below the coil-ferrite spacer 408 is another adhesion layer 410, used to affix the coil-ferrite spacer 408 to the ferrite array 412. The adhesion layer 410 may comprise a layer of tape or glue, such as 3M 468MP adhesive tape. In the case that the coil-ferrite spacer is omitted, one of the glue 406 and the adhesion layer 410 may omitted, with a single material adhering the coil 404 directly to the ferrite array 412 while controlling their spacing and providing electrical insulation, if required.

[0052] In some examples, the ferrite array 412 may be referred to as a “core.” The ferrite array or core 412 may comprise any suitable magnetically permeable material, such as ferrite. As shown in FIG. 4, the ferrite array 412 comprises a plurality of tiles arranged in a plane. The illustrated number of tiles is 16, however it should be appreciated that fewer or more tiles may be used as well. Additionally, the illustrated example shows the tiles of the ferrite array 412 arranged in a 4x4 grid. However, it should be appreciated that other orientations and arrangements may be used as well, including both symmetrical arrangements (e.g., as shown in FIG. 4) as well as asymmetrical arrangements. The shape of each tile of the ferrite array 412 may be the same, or there may be one or more different shaped tiles. In some examples, the comer and / or edge tiles may have different shapes than the interior tiles. Additionally, one or more interior tiles may have a different shape than other tiles, so as to accommodate other components of the system, for example.

[0053] In some examples, the assembly may include an adhesive layer positioned between adjacent tiles. That is, within the plane of the ferrite array 412, adjacent tiles may be separated by an adhesive material. In other examples, the ferrite array 412 may include a spacer material or non-adhesive layer positioned between adjacent tiles. The material selected to be positioned between adjacent tiles within the ferrite array 412 may be conductive, insulating, or somewhere in between. Additionally, the material between adjacent tiles may be a material that changes properties based on changes in temperature, pressure, current / voltage, etc. Further, in some examples multiple different materials may be used to separate adjacent tiles, such that a first set of adjacent tiles are separated by a first material, and a second set of adjacent tiles are separated by a second material. Still further, in some examples, two or more different materials may be used to separate adjacent tiles (e.g., both an adhesive material and a conductive material, for example). During operation of the assembly, the spacing and materials between adjacent tiles can exacerbate or reduce arcing between tiles, and / or cause hotspots to occur. Depending on the spacing and materials selected, certain portions of the tiles may experience different electrical environments, leading to hot spots. Additionally, the spacing and separator materials selected can affect whether arcing betweenadjacent tiles occurs, and / or the intensity of those arcs. For example, if adjacent tiles are spaced close together without a conductive adhesive separating them, arcing is likely to occur, which may also cause hot spots on the tiles at the points of contact of the arc.

[0054] The coil assembly of FIG. 4 also includes DIPS coils 414 and 426, held in place by a top DIPS wire holder 422 and a bottom DIPS wire holder 424. The assembly may also include a DIPS wire holder 420. The DIPS coils 414 and 426 may be used for positioning. In some instances, the one or more positioning coils 414 and 426 assist in the alignment of the receiving WPT unit relative to a transmitting WPT unit so as to enable power transfer from the transmitting WPT unit to the receiving WPT unit. The electromagnetic field generated by the power transfer coil 404 of the transmitting WPT unit may be sensed by the one or more coils of the receiving WPT unit and used to guide the receiving WPT unit to achieve the alignment between the receiving WPT unit and the transmitting WPT unit. In some instances, the receiving WPT unit is installed on a movable object (for example, a vehicle). The transmitting WPT unit is fastened to a stationary object (e.g., a floor, a wall). However, in some instances, the transmitting WPT unit may be installed on a movable object (for example, a vehicle), and the receiving WPT unit may be fastened to a stationary object (e.g., a floor, a wall).

[0055] The assembly of FIG. 4 also includes another layer of polyimide film 416, which may be affixed to the bottom of the DIPS wires 414 and 426.

[0056] The assembly may further include a set of conductive elements 418. Each of the conductive elements 418 may comprise a conductive elastomeric material, such as a conductive rubber. In the example shown in FIG. 4, a top face of each conductive element 418 is positioned to contact a bottom face of a respective tile of the ferrite array or core 412. A bottom face of each conductive element 418 is positioned to be in contact with the assembly housing, such as casing 304 shown in FIGS. 3A-B. The conductive elements 418 provide an electrical connection between the ferrite tiles of the ferrite array 412 and the casing 304, thereby reducing the voltage difference between adjacent tiles in the array.

[0057] A thickness of the conductive elements 418 may be selected such that each conductive element 418 is thicker than a space between the ferrite array or core 412 and the housing or casing 304 in an uncompressed state. The conductive element thickness may be selected such that when assembled, the conductive elements 418 are slightly compressed by the ferrite array 412 and housing, in order to provide a reliable physical and electrical connection between the ferrite array 412 and the housing via the conductive elements 418. In some examples, the casing or housing may be configured to apply a clamping force to theconductive elements 418 when the power transfer unit is in an assembled configuration. It should be understood that the assembly shown in FIGS. 3 A and 3B is inverted, showing the bottom of the assembly on the top of the figures. The inverted assembly is shown in this way to allow for easier illustration of various aspects described herein. Further, it should be appreciated that when fully assembled, the weight of the coil assembly on top may apply a compressive force to the conductive elements 418, thereby providing a good contact between the tiles, conductive elements, and the bottom housing.

[0058] In FIG. 4, the shape of each of the conductive elements 418 is generally rectangular. In some examples, the conductive elements may be 7mmx20mm, 15mmx20mm, or any other suitable size. Additionally or alternatively, in some examples, one or more conductive elements may be asymmetrical, so as to fit within the housing or casing (e.g., to allow other components to fit). The shape and size of one or more conductive elements, as well as the combined shape and size of all of the conductive elements as a whole, may be dependent upon a desired resistance and / or conductivity. The conductive elements 418 should be sized and shaped such that there is a low enough resistance from the ferrite tiles 412 to the housing to achieve a sufficient reduction in voltage between tiles in the array. A larger area for the conductive elements creates a lower resistance. Additionally, a higher conductivity (e.g., based on the material(s) selected for the conductive elements) may create a lower resistance. Too high of a conductivity may create eddy current losses, which can cause issues with operation of the WPT unit. Further, conductivity that is too low may increase the tile-to-tile voltage within the ferrite array, which can lead to arcing across adjacent tiles and damage to the WPT assembly. Mechanical effects may also play a role. For example, the size, shape, and positioning of the conductive elements 418 may be selected such that the ferrite tiles are supported sufficiently when pressure is applied to the top of the assembly.

[0059] In some examples, the assembly may also include an electrically conductive adhesive provided between the conductive elements 418 and the conductive portion of the housing (e.g., casing 304), and / or between the conductive element 418 and a respective magnetically permeable element of the array 412.

[0060] While the conductive elements 418 are shown in FIG. 4 as being conductive rubber, it should be appreciated that alternatives may be used as well. For example, in some examples, the conductive elements may comprise metallic or conductive sprung tangs, which are configured to create an electrical connection between respective ferrite tiles and the conductive housing. In other examples, a different compressible conductive material or element may be used, in order to create the electrical connection. The conductive elementsmay be configured to reduce a voltage different between adjacent magnetically permeable elements (e.g., ferrite tiles) during operation of the power transfer unit. In some embodiments, the conductive elements may comprise conductive tape, or another conductive element positioned between adjacent tiles. In some embodiments, the conductive elements may comprise a conductive epoxy with a filler material such as silver or nickel. The conductive elements may also or alternatively comprise a conductive silicone with a filler material, or a conductive carbon adhesive material. Further, combinations of the above, and / or other materials, may be used instead.

[0061] In some examples, one or more conductive elements 418 are configured to span an interface between adjacent magnetically permeable elements of the core. That is, one or more conductive elements 418 may be in contact with two or more ferrite tiles of the array 412 and may span the gap between the tiles. The conductive element may then contact two or more ferrite tiles and the casing or housing.

[0062] In still other examples, one or more conductive elements 418 may be positioned in the gap between adjacent ferrite tiles, in contact with the sides or edges of adjacent tiles. The conductive elements may be positioned in the same plane as the ferrite array 412, and one or more of the conductive elements 418 may be positioned in the gaps between adjacent tiles, rather than below the tiles. The conductive elements may then contact two or more ferrite tiles. Additionally, the conductive elements may or may not also contact the casing or housing.

[0063] FIG. 5 illustrates a side view simplified block diagram of a portion of the WPT assembly, such as the assemblies shown in FIGS. 3A-B and 4. The assembly 500 includes a coil 504, a coil-ferrite spacer 508, ferrite tiles 512, conductive elements 518, and an aluminum enclosure 530.

[0064] The coil 504 may be similar or identical to the coil 404 described above with respect to FIG. 4. The coil 504 may be a Litz coil and may comprise the primary coil for transmitting and / or receiving power. The coil 504 may comprise a plurality of windings (e.g., four are shown in FIG. 5). The coil 504 may be separated from the ferrite array 512 by a coil-ferrite spacer 508. The ferrite array 512 (also referred to as the core) may be similar or identical to the ferrite array 412 described above. The ferrite array 512 may comprise a plurality of ferrite tiles that are spaced apart from one another, such that each tile is not in contact with the adjacent tiles. Below each tile of the ferrite array 512 is a conductive element 518, which may be similar or identical to the conductive elements 418 described above. The conductive elements 518 may provide an electrical and physical connection between the ferrite array 512and the housing 530. The housing 530 may be an electrically conductive material, such as aluminum.

[0065] FIGS. 6, 7, 8 show an example charging pad assembly 600 bottom view (FIG. 6), top view (FIG. 7), and sectional side view (FIG. 8) respectively. The assembly 600 may include a coil 604, a coil-ferrite spacer 608, a ferrite array 612, a plurality of conductive elements 618, and a housing 630 (shown in FIG. 7). The coil 604 may be similar or identical to the coils 404 and 504 described above with respect to FIGS. 4 and 5. Additionally, the coil-ferrite spacer 608 may be similar or identical to the spacers 408 and 508 described above, the ferrite array 612 may be similar or identical to the arrays 412 and 512 described above, the conductive elements 618 may be similar or identical to the conductive elements 418 and 518 described above, and the housing 630 may be similar or identical to the housing 530 and / or 304 described above.

[0066] The systems, devices, and processes discussed above are intended to be illustrative and not limiting. One skilled in the art would appreciate that the actions of the processes discussed herein may be omitted, modified, combined, and / or rearranged, and any additional actions may be performed without departing from the scope of the invention. Furthermore, it should be noted that the features and limitations described in any one example may be applied to any other example herein, and flowcharts or examples relating to one example may be combined with any other example in a suitable manner, done in different orders, or done in parallel. In addition, the systems and methods described herein may be performed in realtime. It should also be noted that the systems and / or methods described above may be applied to, or used in accordance with, other systems and / or methods.

[0067] All of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0068] Each feature disclosed in this specification (including any accompanying claims, abstract, and drawings), may be replaced by alternative features serving the same, equivalent, or similar purpose unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0069] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers, or steps.Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0070] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0071] This specification discloses embodiments which include, but are not limited to, the following:1. A power transfer unit of a wireless power transfer (WPT) system for wirelessly charging an electric vehicle, the power transfer unit comprising: a core comprising a plurality of magnetically permeable elements arranged adjacent one another; a housing at least partially containing the core, the housing comprising a conductive portion; and at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.2. The power transfer unit of item 1, comprising one or more windings in magnetic association with the core, the windings being at least partially contained within the housing and configured to cause a capacitive coupling between the plurality of magnetically permeable elements in operation.3. The power transfer unit of item 1, wherein the conductive element is formed from a conductive elastomeric material.4. The power transfer unit of item 2, wherein a thickness of the conductive element in an uncompressed state is greater than the space between the core and the housing.5. The power transfer unit of item 1, wherein the conductive element is configured to reduce a voltage between adjacent magnetically permeable elements during operation of the power transfer unit.6. The power transfer unit of item 1, wherein the conductive element is configured to span an interface between adjacent magnetically permeable elements of the core.7. The power transfer unit of item 1, wherein the conductive element is provided in between adjacent magnetically permeable elements of the core.8. The power transfer unit of item 1, wherein the housing is configured to apply a clamping force to the conductive element when the power transfer unit is in an assembled configuration.9. The power transfer unit of item 1, wherein an electrically conductive adhesive is provided between the conductive element and the conductive portion of the housing, and / or between the conductive element and a respective magnetically permeable element.10. A ground unit for a wireless power transfer system for wirelessly charging a vehicle comprising: a core comprising a plurality of magnetically permeable elements arranged adjacent one another; a housing at least partially containing the core, the housing comprising a conductive portion; and at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.11. The ground unit of item 10, comprising one or more windings in magnetic association with the core, the windings being at least partially contained within the housing and configured to cause a capacitive coupling between the plurality of magnetically permeable elements in operation.12. The ground unit of item 10, wherein the conductive element is formed from a conductive elastomeric material.13. The ground unit of item 11, wherein a thickness of the conductive element in an uncompressed state is greater than the space between the core and the housing.14. The ground unit of item 10, wherein the conductive element is configured to reduce a voltage between adjacent magnetically permeable elements during operation of the power transfer unit.15. The ground unit of item 10, wherein the conductive element is configured to span an interface between adjacent magnetically permeable elements of the core.16. The ground unit of item 10, wherein the conductive element is provided in between adjacent magnetically permeable elements of the core.17. The ground unit of item 10, wherein the housing is configured to apply a clamping force to the conductive element when the power transfer unit is in an assembled configuration.18. The ground unit of item 10, wherein an electrically conductive adhesive is provided between the conductive element and the conductive portion of the housing, and / or between the conductive element and a respective magnetically permeable element.19. A vehicle unit for a wireless power transfer system for wirelessly charging a vehicle comprising: a core comprising a plurality of magnetically permeable elements arranged adjacent one another; a housing at least partially containing the core, the housing comprising a conductive portion; and at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.20. The vehicle unit of item 19, comprising one or more windings in magnetic association with the core, the windings being at least partially contained within the housing and configured to cause a capacitive coupling between the plurality of magnetically permeable elements in operation.21. The vehicle unit of item 19, wherein the conductive element is formed from a conductive elastomeric material.22. The vehicle unit of item 20, wherein a thickness of the conductive element in an uncompressed state is greater than the space between the core and the housing.23. The vehicle unit of item 19, wherein the conductive element is configured to reduce a voltage between adjacent magnetically permeable elements during operation of the power transfer unit.24. The vehicle unit of item 19, wherein the conductive element is configured to span an interface between adjacent magnetically permeable elements of the core.25. The vehicle unit of item 19, wherein the conductive element is provided in between adjacent magnetically permeable elements of the core.26. The vehicle unit of item 19, wherein the housing is configured to apply a clamping force to the conductive element when the power transfer unit is in an assembled configuration.27. The vehicle unit of item 19, wherein an electrically conductive adhesive is provided between the conductive element and the conductive portion of the housing, and / or between the conductive element and a respective magnetically permeable element.28. A vehicle comprising the vehicle unit of item 19.

Claims

What is Claimed is:

1. A power transfer unit of a wireless power transfer (WPT) system for wirelessly charging an electric vehicle, the power transfer unit comprising: a core comprising a plurality of magnetically permeable elements arranged adjacent one another; a housing at least partially containing the core, the housing comprising a conductive portion; and at least one conductive element provided in a space between the core and the housing and configured to electrically couple a respective magnetically permeable element of the core to the conductive portion of the housing.

2. The power transfer unit of claim 1, comprising one or more windings in magnetic association with the core, the windings being at least partially contained within the housing and configured to cause a capacitive coupling between the plurality of magnetically permeable elements in operation.

3. The power transfer unit of claim 1 or claim 2, wherein the conductive element is formed from a conductive elastomeric material.

4. The power transfer unit of claim 3, wherein a thickness of the conductive element in an uncompressed state is greater than the space between the core and the housing.

5. The power transfer unit of any one of claims 1 to 4, wherein the conductive element is configured to reduce a voltage between adjacent magnetically permeable elements during operation of the power transfer unit.

6. The power transfer unit of any one of claims 1 to 5, wherein the conductive element is configured to span an interface between adjacent magnetically permeable elements of the core.

7. The power transfer unit of any one of claims 1 to 6, wherein the conductive element is provided in between adjacent magnetically permeable elements of the core.

8. The power transfer unit of any one of claims 1 to 7, wherein the housing is configured to apply a clamping force to the conductive element when the power transfer unit is in an assembled configuration.

9. The power transfer unit of any one of claims 1 to 8, wherein an electrically conductive adhesive is provided between the conductive element and the conductive portion of the housing, and / or between the conductive element and a respective magnetically permeable element.

10. A ground unit for a wireless power transfer system for wirelessly charging a vehicle, the ground unit comprising the power transfer unit of any one of claims 1 to 9.

11. A vehicle unit for a wireless power transfer system for wirelessly charging a vehicle, the vehicle unit comprising the power transfer unit of any one of claims 1 to 9.

12. A vehicle comprising the vehicle unit of claim 11.

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