Litz wire connection structure and coil unit

Abstract

To provide a litz wire connection structure and a coil unit capable of reducing power loss by reducing contact resistance between a litz wire and a wiring board.SOLUTION: A litz wire connection structure for connecting a litz wire 21 formed by twisting a plurality of wires to a wiring board 9 includes a terminal member 22 having a board fixing portion 23 fixed to the wiring board 9 and a holding portion 24 holding an end portion of the litz wire 21, and the end of the litz wire 21 dipped in melted solder and impregnated with the solder Y is held by the holding portion 24 of the terminal member 22 fixed to the wiring board 9, and the end of the litz wire 21 is connected to the wiring board 9 by attaching the solder Y so as to cover the end of the litz wire 21 and the holding portion 24.SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] The present invention relates to a litz wire connection structure and a coil unit. [Background technology]

[0002] In recent years, contactless charging systems have been attracting attention as a method for charging the onboard batteries of electric vehicles. In contactless charging systems, power is transmitted between a power-transmitting coil unit installed on the ground and a power-receiving coil unit installed in the electric vehicle, thereby charging the battery installed in the electric vehicle.

[0003] Patent Document 1 discloses a coil unit (power supply coil unit) used in the above-mentioned contactless charging system. This coil unit has a box-shaped case, and a control unit and a coil connected to the control unit are arranged side by side in the space inside the case. The coil of the coil unit used in such a contactless charging system often uses a litz wire formed by twisting together multiple insulating-coated wires to prevent an increase in winding resistance due to the skin effect. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-233107 Summary of the Invention [Problem to be solved by the invention]

[0005] A conventional method for connecting a litz wire to a wiring board is to use a screw terminal, in which the end of the litz wire is crimped to one end of a terminal member that is fixed to the wiring board with a screw by fusing (caulking), thereby connecting the litz wire to the wiring board.

[0006] However, because litz wire is made by twisting together multiple wires, crimping joints using fusing can cause unstable contact points between the terminal member and the litz wire, increasing contact resistance. Furthermore, the contact resistance between the terminal member, the wiring board, and the fixing screws is also significant, which, combined with other factors, results in significant power loss at the connection points of the litz wire.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a litz wire connection structure and coil unit that can reduce the contact resistance between the litz wire and the wiring board, thereby reducing power loss. [Means for solving the problem]

[0008] The litz wire connection structure according to the first aspect of the present invention is a litz wire connection structure for connecting a litz wire made of multiple twisted wires to a wiring board, and is provided with a terminal member having a board fixing portion fixed to the wiring board and a clamping portion for clamping the end of the litz wire.The end of the litz wire, which has been immersed in molten solder and soaked with solder, is clamped by the clamping portion of the terminal member fixed to the wiring board, and solder is applied so as to cover the end of the litz wire and the clamping portion, thereby connecting the end of the litz wire to the wiring board. [Effects of the Invention]

[0009] According to the litz wire connection structure of the present invention, the end of the litz wire is dipped in molten solder and soaked in the solder, and is then clamped by a terminal member fixed to a wiring board, so that the solder is interposed between the litz wire and the terminal member. Furthermore, by covering the end of the litz wire and the clamped portion of the terminal member with solder, the contact portion between the litz wire and the terminal member is stabilized, reducing contact resistance and therefore power loss. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a planar perspective view of the coil unit according to the embodiment. [Figure 2] FIG. 2 is a bottom perspective view of the coil unit according to the embodiment. [Figure 3] FIG. 2 is a side view of the coil unit according to the embodiment. [Figure 4] FIG. 2 is an exploded perspective view of the coil unit according to the embodiment. [Figure 5] FIG. 2 is a planar perspective view of the case body according to the embodiment. [Figure 6] FIG. 2 is a plan view of the case body according to the embodiment. [Figure 7] FIG. 2 is a bottom perspective view of the case body according to the embodiment. [Figure 8] FIG. 2 is a bottom view of the case body according to the embodiment. [Figure 9] FIG. 2 is a perspective plan view of a first cover member according to the embodiment. [Figure 10] FIG. 4 is a plan view of a first cover member according to the present embodiment. [Figure 11] FIG. 4 is a bottom perspective view of a first cover member according to the embodiment. [Figure 12] FIG. 4 is a perspective plan view of a second cover member according to the embodiment. [Figure 13] FIG. 4 is a bottom perspective view of a second cover member according to the embodiment. [Figure 14] FIG. 2 is a planar perspective view of the coil case according to the embodiment. [Figure 15] FIG. 2 is a plan view of the coil case according to the embodiment. [Figure 16] FIG. 2 is a bottom perspective view of the coil case according to the embodiment. [Figure 17] FIG. 2 is a bottom view of the coil case according to the embodiment. [Figure 18] 1 is an enlarged perspective view showing a connection structure between a litz wire and a wiring board according to an embodiment of the present invention. FIG. [Figure 19] 19 is a cross-sectional view of the terminal member taken along line XIX-XIX in FIG. 18. [Figure 20] FIG. 2 is a cross-sectional view of the device case taken along line XX-XX in FIG. [Figure 21]2 is a cross-sectional view of the device case taken along line XXI-XXI in FIG. 1. [Figure 22] 21 is a cross-sectional view of a device case corresponding to FIG. 20, showing a modification of the recessed and protruding portions according to the present embodiment. FIG. [Figure 23] 23 is a cross-sectional view of the device case corresponding to FIG. 22, showing a modification of the first support portion and the second support portion according to the present embodiment. FIG. [Figure 24] 1 is a schematic diagram of a contactless charging system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A contactless charging system 100 according to an embodiment of the present invention and a coil unit 1 used in the contactless charging system 100 will be described below with reference to Figs. 1 to 24. In this embodiment, for convenience of explanation, the directions indicated by up-down, left-right, and front-rear arrows appropriately shown in each figure will be defined as the up-down direction, left-right direction, and front-rear direction, respectively. Also, in each figure, some reference numerals may be omitted to make the drawings easier to understand.

[0012] As shown in FIG. 24, a contactless charging system 100 is a system for charging an electric vehicle 200, such as an electric vehicle or a plug-in hybrid vehicle. In the contactless charging system 100, power is transmitted between a power transmitting coil unit 1A disposed on the ground and a power receiving coil unit 1B disposed in the electric vehicle 200, thereby charging a battery 300 mounted on the electric vehicle 200. The power is transmitted by arranging a primary coil 2 housed in the power transmitting coil unit 1A and a secondary coil 2 housed in the power receiving coil unit 1B opposite each other, and transmitting power by utilizing electromagnetic induction between the coils. Specifically, AC power is supplied from an external power supply device 400 to the power transmitting coil unit 1A, causing an induced current to flow in the primary coil 2, generating a magnetic field. The generated magnetic field reaches the secondary coil 2, and an induced current flows in the secondary coil 2, thereby transmitting power.

[0013] Next, we will explain the coil units 1A and 1B that make up the contactless charging system 100 configured as described above. In the following, when the power receiving side coil unit 1B is not distinguished from the power transmitting side coil unit 1A, they will be simply referred to as coil unit 1.

[0014] 1 to 4, the coil unit 1 includes a box-shaped device case 3 that houses a coil 2 (described later) and other components. The device case 3 includes a case main body 4 in which storage spaces S1 and S2 that house the coil 2 and other components are formed, and a first cover member 5 and a second cover member 6 that close openings 41 and 42 of the case main body 4.

[0015] As shown in FIGS. 5 to 8, the case body 4 has a predetermined width in the front-rear and left-right directions and is formed in a box shape that is flat in the up-down direction. The case body 4 is made of a non-magnetic material such as aluminum, for example, aluminum die-casting. The case body 4 includes a front wall 4A, a rear wall 4B, a left wall 4C, a right wall 4D, a top wall 4E, a bottom wall 4F, and a partition wall 4G. The partition wall 4G extends in the front-rear direction so as to connect the middle portion of the front wall 4A to the middle portion of the rear wall 4B. The top wall 4E is integrally connected to and connected to the upper end of the partition wall 4G, the upper ends of the front wall 4A and the rear wall 4B to the right of the partition wall 4G, and the upper end of the right wall 4D. The bottom wall 4F is integrally connected to the lower end of the partition wall 4G, the lower ends of the front wall 4A and the rear wall 4B to the left of the partition wall 4G, and the lower end of the left wall 4C. In the case body 4, the top, bottom, left, and right cross sections of the upper wall 4E, the partition wall 4G, and the bottom wall 4F are crank-shaped.

[0016] In the case body 4, a first storage space S1 that opens downward is formed by the top wall 4E, the partition wall 4G, the right wall 4D, the front wall 4A, and the rear wall 4B. In addition, a second storage space S2 that opens upward is formed by the bottom wall 4F, the partition wall 4G, the left wall 4C, the front wall 4A, and the rear wall 4B. In the case body 4, the partition wall 4G divides the internal space (storage space) of the case body 4 into two, left and right, spaces that open in opposite directions.

[0017] In the case body 4, a first housing space S1 formed on the right side of the partition wall 4G houses a coil case 7 that holds the coil 2 and the ferrite core 8 (see FIG. 4). A second housing space S2 formed on the left side of the partition wall 4G houses a wiring board 9 to which the coil 2 is connected (see FIG. 4). Although not shown, the wiring board 9 mainly mounts a resonant circuit section, a control section, and a power conversion section. The resonant circuit section includes a capacitor (resonant capacitor) connected in series or in parallel with the coil 2. The control section monitors the charging power. The power conversion section includes a rectifier section, and converts received high-frequency AC power into predetermined DC power and supplies it to the battery 300 installed in the electric vehicle 200.

[0018] In the case body 4, the first storage space S1 formed on the right side of the partition wall 4G has a first opening 41 that opens downward. Furthermore, the second storage space S2 formed on the left side of the partition wall 4G has a second opening 42 that opens upward. In the case body 4, the first opening 41 of the first storage space S1 and the second opening 42 of the second storage space S2 are provided separately on opposing side surfaces (4E, 4F) of the case body 4. Therefore, the case body 4 has a crank-shaped structure with a step between the first storage space S1 and the second storage space S2 due to the partition wall 4G.

[0019] 1 to 23 show the power receiving coil unit 1B mounted on the electric vehicle 200, so the first housing space S1 opens downward facing the counterpart (power transmitting) coil unit 1A installed on the ground. In the power transmitting coil unit 1A, the first housing space S1 opens upward facing the power receiving coil unit 1B.

[0020] 7 and 8, the first storage space S1 is a rectangular box-shaped storage space that opens downward in the device case 3, and its side walls are formed by the front wall 4A, rear wall 4B, right wall 4D, and partition wall 4G of the case main body 4. These walls 4A, 4B, 4D, and 4G are integrally formed with a plurality of first bosses 43 for fixing the first cover member 5 to the case main body 4. The plurality of first bosses 43 protrude from the walls 4A, 4B, 4D, and 4G toward the inside of the first storage space S1 and are formed in a columnar shape with the axial direction extending vertically. The outer periphery of the first cover member 5 is fixed to the case main body 4 via the plurality of first bosses 43.

[0021] As shown in FIGS. 9 to 11, the first cover member 5 is a plate-like member made of resin having a predetermined width in the front-rear and left-right directions and a predetermined thickness in the up-down direction. The first cover member 5 is disposed below the case body 4 (see FIG. 4) and is configured to close the first opening 41 of the first housing space S1 by attaching it to the case body 4. A plurality of first mounting holes 51 are formed on the outer periphery of the first cover member 5, penetrating the first cover member 5 in the up-down direction. The plurality of first mounting holes 51 correspond to the plurality of first bosses 43 provided in the first housing space S1, respectively. The first cover member 5 is attached to the case body 4 by inserting screws 52 (see FIGS. 2 and 3) into the first mounting holes 51 and screw holes (female threads) formed in the first bosses 43.

[0022] As shown in FIG. 11 , a cover-side recess 53 is formed on the underside 5B of the first cover member 5 at a position corresponding to the first mounting hole 51. The cover-side recess 53 is a cylindrical recess recessed upward, and the first mounting hole 51 is formed on the bottom surface. The screw 52 inserted into the first mounting hole 51 from the outside of the first cover member 5 is inserted into the cover-side recess 53 and does not protrude from the underside 5B of the first cover member 5. Therefore, in the power-receiving-side coil unit 1B mounted on the electric vehicle 200, the underside 5B of the first cover member 5, which forms the bottom surface of the electric vehicle 200, can be made flat, preventing a decrease in the aerodynamic performance of the vehicle's underside. Furthermore, contact between the screw 52 and pebbles bouncing off the road surface or obstacles that enter the underside of the vehicle while driving can be reduced.

[0023] In the device case 3, in order to improve the sealing performance of the first housing space S1, a sealant X is applied to the opposing surfaces of the wall portions 4A, 4B, 4D, and 4G of the case main body 4 that constitute the sidewall portion of the first housing space S1 and the first cover member 5. As shown in FIGS. 7 and 8 , a recess 44 is formed in the lower end surface (the surface to which the sealant X is applied) of the wall portions 4A, 4B, 4D, and 4G that constitute the sidewall portion of the first housing space S1 of the case main body 4. The recess 44 is disposed inward of the first boss portion 43 in the wall portions 4A, 4B, 4D, and 4G, and is formed in a linear shape extending around the outer periphery of the first opening 41. As shown in FIG. 20 , the recess 44 is formed in the shape of a rectangular groove that opens toward the first cover member 5 (downward), and has a pair of opposing side surfaces 441 and a bottom surface 442 that connects the upper ends of the pair of side surfaces 441.

[0024] 9 and 10, a protrusion 54 is formed on the peripheral edge (portion to which the sealing material X is applied) of the upper surface 5A of the first cover member 5. The protrusion 54 is arranged on the peripheral edge of the upper surface 5A of the first cover member 5, inside the first mounting hole 51, and is configured as a linear protrusion that extends all the way around along the peripheral edge of the upper surface 5A. As shown in FIG. 20, the protrusion 54 stands on the upper surface 5A of the first cover member 5 toward the case main body 4 (upper side), and has a rectangular cross section in a direction perpendicular to the extending direction that is slightly smaller than the recess 44.

[0025] When attaching the first cover member 5 to the case body 4, the recess 44 of the case body 4 is filled with the sealant X, and then the first cover member 5 is attached to the case body 4 so that the protrusion 54 of the first cover member 5 is inserted into the recess 44 of the case body 4. When the first cover member 5 is attached to the case body 4 in this manner, as shown in FIG. 20 , a portion of the sealant X in the recess 44 is pressed by the protrusion 54 and pushed out of the recess 44, and the sealant X becomes interposed between the lower end surfaces of the walls 4A, 4B, 4D, and 4G of the case body 4 and the upper surface 5A of the first cover member 5. A portion of the sealant X also remains in the recess 44, and the sealant X becomes interposed between the pair of side surfaces 441 and the bottom surface 442 that constitute the recess 44 and each surface that constitutes the protrusion 54. The sealant X is, for example, a silicone-based wet sealant that is filled in the recess 44 in a liquid state and hardens to become an elastic rubber-like material.

[0026] There are two main reasons for the above-described configuration in which the protrusion 54 of the first cover member 5 is inserted into the recess 44 formed on the case body 4 side. The first reason is to increase the area of ​​the joint between the case body 4 and the first cover member 5 and to enhance the joint strength between the case body 4 and the first cover member 5 by the sealant X. This prevents the first housing space S1 from opening even if a portion of the first cover member 5 separates from the case body 4 when the difference in linear expansion and contraction between the metal case body 4 and the resin first cover member 5 becomes large. The second reason is that by interposing the elastic sealant X between the recess 44 and the protrusion 54, the difference in linear expansion and contraction between the case body 4 and the resin first cover member 5 can be efficiently absorbed in multiple directions by the elastic deformation of the sealant X.

[0027] The second reason will be explained in detail. For example, when a vehicle is cooled in a cold region, the first cover member 5 made of resin, which has a larger linear expansion coefficient, shrinks more than the metal case body 4, and an external force may act on the first cover member 5 in a direction that separates the first cover member 5 from the first opening 41 of the case body 4. In this case, the sealant X near the side surface 441 of the recessed portion 44 elastically deforms to follow the side surface of the protruding portion 54 of the first cover member 5, and therefore, the difference in linear expansion and contraction can be absorbed while maintaining the hermetic seal between the case body 4 and the first cover member 5. On the other hand, for example, when the vehicle is hot immediately after driving, the first cover member 5 made of resin expands more than the metal case body 4, and the separation distance t1 between one side surface of the protruding portion 54 of the first cover member 5 and the side surface of the recessed portion 44 may become smaller. The sealing material X near the side surface 441 of the recess 44 elastically deforms so as to be pushed toward the bottom surface 442 of the recess 44, so that the difference in linear expansion and contraction can be absorbed while maintaining the sealing property between the case main body 4 and the first cover member 5.

[0028] 20 , when the first cover member 5 is attached to the case body 4, the distance t2 between the tip of the protrusion 54 and the bottom surface 442 of the recess 44 is set to be larger than the distance t1 between the side surface of the protrusion 54 and the side surface of the recess 44. This configuration is intended to efficiently absorb the difference in expansion and contraction between the case body 4 and the first cover member 5. That is, as described above, it is expected that the relative positional relationship between the side surface of the protrusion 54 of the first cover member 5 and the side surface 441 of the recess 44 will change significantly as the difference in linear expansion and contraction between the case body 4 and the first cover member 5 increases. If the positional relationship between the side surface of the protrusion 54 and the side surface 441 of the recess 44 changes significantly, there is a risk that the difference in expansion and contraction will not be fully absorbed by the spaces on both sides of the side surfaces of the protrusion 54. Therefore, the sealing layer on the bottom surface 442 side of the recess 44, which is in communication with the spaces on both sides of the side surfaces of the protrusion 54, is made thicker by increasing the separation distance t2 between the tip of the protrusion 54 and the bottom surface 442 of the recess 44. By making the sealing layer on the bottom surface 442 side of the recess 44 thicker, even in a state where the difference in expansion and contraction cannot be fully absorbed in the spaces on both sides of the side surfaces of the protrusion 54, the sealing material X can be efficiently deformed, and therefore the difference in expansion and contraction between the case body 4 and the first cover member 5 can be efficiently absorbed.

[0029] Furthermore, the walls 4A, 4B, 4D, and 4G of the case body 4 that form the first housing space S1 have inclined surfaces 45 formed by chamfering the corners on the first housing space S1 side. This configuration aims to improve the airtightness of the first housing space S1. The inclined surfaces 45 are inclined so that the gap between the inclined surfaces 45 and the opposing surface (top surface 5A) of the first cover member 5 increases toward the inside of the first housing space S1. Therefore, when liquid sealant X is filled into the recess 44 and the first cover member 5 is attached to the case body 4, the sealant X pushed by the protrusions 54 from the inside of the recess 44 toward the first housing space S1 remains between the inclined surfaces 45 and the top surface 5A of the first cover member 5, forming a thick sealing layer. This improves the airtightness of the first housing space S1. Furthermore, by retaining excess sealant X between the inclined surfaces 45 and the first cover member 5, the sealant X is prevented from flowing into the first housing space S1.

[0030] As shown in FIGS. 7 and 8, a central boss 47 protruding downward is disposed on the underside of the upper wall 4E of the case body 4 at the center of the first housing space S1. The central boss 47 (first support portion) is formed in a cylindrical shape with its axis extending vertically. The central portion of the first cover member 5 is fixed to the case body 4 via the central boss 47. As shown in FIG. 21, a recess 46 recessed upward is formed in the center of the underside of the central boss 47. The recess 46 forms the lower end of the central boss 47 into a cylindrical shape. A female screw hole is also formed in the center of the recess 46. When the first cover member 5 is attached to the case body 4, the lower end surface of the central boss 47 abuts against the opposing surface (upper surface 5A) of the first cover member 5 to support the first cover member 5 from inside the first housing space S1. An annular recess 471 is formed in the lower end surface (the surface facing the first cover member 5) of the central boss 47. The recess 471 is formed in a rectangular groove shape that opens toward the first cover member 5 (downward), and the inside of the recess 471 is filled with a seal material X.

[0031] 9 and 10, a cylindrical protrusion 59 is formed on the upper surface 5A of the first cover member 5 at a position facing the central boss portion 47 (the center position of the upper surface 5A). A screw hole 55 penetrating in the vertical direction is formed in the center of the protrusion 59. As shown in FIG. 21, the first cover member 5 is fixed to the case body 4 by inserting the protrusion 59 of the first cover member 5 into the recess 46 of the central boss portion 47 of the case body 4 and threading a screw 52 inserted through the screw hole 55 into the female threaded hole of the recess 46. A cover-side recess 53 is formed on the lower surface 5B of the first cover member 5 at a position corresponding to the protrusion 59 and the screw hole 55. The cover-side recess 53 has the same configuration as the cover-side recess 53 provided in the first cover member 5 corresponding to the first mounting hole 51, and therefore a description thereof will be omitted. The screws 52 inserted into the screw holes 55 from the outside of the first cover member 5 are inserted into the cover-side recesses 53 and do not protrude from the lower surface 5B of the first cover member 5.

[0032] As shown in FIGS. 9 and 10 , an annular convex portion 56 is integrally formed on the upper surface 5A of the first cover member 5 so as to surround the protrusion 59. As shown in FIG. 21 , the convex portion 56 extends upward from the upper surface 5A of the first cover member 5 and has a rectangular cross section perpendicular to the extending direction. The first cover member 5 is attached to the case body 4 by inserting the convex portion 56 into the recess 471 of the case body 4 (central boss portion 47) filled with the sealing material X, with the sealing material X interposed between the upper surface 5A of the first cover member 5 and the lower end surface of the central boss portion 47. When the first cover member 5 is attached to the case body 4 in this manner, a portion of the sealing material X in the recess 471 is pressed by the convex portion 56 and pushed out of the recess 471, and the sealing material X is interposed between the lower end surface of the central boss portion 47 and the upper surface 5A of the first cover member 5. A portion of the sealant X remains in the recess 471, and the sealant X is interposed between each surface constituting the recess 471 and each surface constituting the protrusion 56. This allows the case body 4 and the first cover member 5 to be tightly attached to each other via the sealant X, ensuring airtightness of the first housing space S1 and absorbing the difference in linear expansion and contraction between the case body 4 and the first cover member 5.

[0033] As shown in FIGS. 9 and 10 , a cylindrical second support portion 57 protruding upward is formed on the top surface 5A of the first cover member 5 at a position radially outward of the annular protrusion 56. The second support portion 57 is formed in a double cylindrical shape with an inner wall 571 formed in a cylindrical shape with the screw hole 55 at its center and an outer wall 572 formed in a cylindrical shape and extending upward from the top surface 5A radially outward of the inner wall 571. The inner wall 571 and the outer wall 572 are connected by a plurality of ribs 573, forming a lattice-like configuration when viewed from the axial direction. As shown in FIG. 21 , when the first cover member 5 is attached to the case body 4, the second support portion 57 is nested with the central boss portion 47 (first support portion) of the case body 4 inside. At this time, the upper end of the second support portion 57 abuts against the opposing surface of the case body 4 (the lower surface of the upper wall portion 4E), supporting the case body 4 from inside the first housing space S1. The central boss portion 47 and the second support portion 57, which are nested, are located within the central space of the coil 2 when the coil 2 is housed in the first housing space S1.

[0034] As described above, the coil 2 is held in the coil case 7 and accommodated in the first accommodation space S1 of the case main body 4. As shown in FIGS. 14 to 17 , the coil case 7 is a plate-like resin member having a predetermined width in the front-rear and left-right directions and a predetermined thickness in the up-down direction, and is formed into a rectangular shape when viewed from the up-down direction. A rectangular opening 71 is formed in the center of the coil case 7, penetrating the coil case 7 in the up-down direction. When the coil case 7 is accommodated in the first accommodation space S1, the central boss portion 47 of the case main body 4 and the second support portion 57 of the first cover member 5 are disposed inside the opening 71. The upper surface of the coil case 7 forms a core fixing surface 7A to which multiple ferrite cores 8 are fixed. The core fixing surface 7A is partitioned into a grid pattern by multiple partition walls 72, and a rectangular plate-shaped ferrite core 8 is fixed to each of the compartments.

[0035] A coil insertion hole 73 that passes through the coil case 7 in the vertical direction is formed outside the opening 71 of the coil case 7. One end 2A (see FIG. 4) of the coil 2 held on the lower surface side of the coil case 7 is inserted into the coil insertion hole 73 and drawn out toward the core fixing surface 7A of the coil case 7. One end 2A of the coil 2 drawn out toward the core fixing surface 7A is inserted into and held in a groove-shaped first coil guide portion 74A provided on the left end side of the core fixing surface 7A of the coil case 7.

[0036] The lower surface of the coil case 7 serves as a coil fixing surface 7B for fixing the coil 2. A coil accommodating groove 76 having a spiral shape is formed in the coil fixing surface 7B. The coil accommodating groove 76 is, for example, a rectangular groove that opens downward, and the wire that forms the coil 2 is inserted inside. In this embodiment, the coil 2 is made of a litz wire 21 to prevent an increase in winding resistance due to the skin effect. The litz wire 21 is formed by twisting together a plurality of wires (thin wires) that are insulated. When inserted into the coil accommodating groove 76 of the coil case 7, the coil 2 is formed into a spiral shape. In this manner, the spiral coil 2 is disposed on the coil fixing surface 7B (surface) of the coil case 7. One end 2A of the coil 2, which is disposed on the central space side of the coil 2, is drawn out to the core fixing surface 7A on the upper surface side through the coil insertion hole 73 described above. On the other hand, the other end 2A of the coil 2, which is positioned radially outward, is inserted into and held in the second coil guide portion 74B which extends from the end of the coil accommodating groove 76 to the left end side of the coil fixing surface 7B.

[0037] A plurality of coil case side bosses 75 are integrally formed on the outer periphery of the coil case 7 and on the inner surface of the opening 71. The coil case 7 is fixed to the upper wall 4E of the case body 4 via the plurality of coil case side bosses 75. The upper wall 4E is provided with case body side bosses 48 at positions facing the coil case side bosses 75 of the coil case 7 (see FIG. 8). The coil case 7 is fixed within the first housing space S1 of the case body 4 by inserting screws (not shown) into the coil case side bosses 75 and the case body side bosses 48.

[0038] As shown schematically in Fig. 8, in the coil case 7 fixed in the first housing space S1 of the case body 4, both end portions 2A, 2A of the coil 2 held by the first coil guide portion 74A and the second coil guide portion 74B extend toward the partition wall portion 4G constituting the left wall portion of the first housing space S1 and are guided into the second housing space S2 through an insertion hole 49 formed in the partition wall portion 4G. Both end portions 2A, 2A of the coil 2 guided into the second housing space S2 are connected to a mounting surface 9A on the upper surface of a wiring board 9 accommodated in the second housing space S2 via terminal members 22 (see Fig. 18). The detailed configuration of the terminal members 22 will be described later.

[0039] The insertion hole 49 is formed across the partition wall 4G and bottom wall 4F of the case body 4, penetrating the partition wall 4G in the left-right direction to connect the first storage space S1 and the second storage space S2, and penetrating the bottom wall 4F in the up-down direction to connect the second storage space S2 and the outside. The insertion hole 49 is positioned inside the recess 44 extending along the first opening 41 of the case body 4. Therefore, when the first cover member 5 is attached to the case body 4, the periphery of the insertion hole 49 is sealed with the sealing material X, preventing water droplets and the like from entering the inside of the device case 3 from the outside through the insertion hole 49.

[0040] As described above, the case body 4 is die-cast, and the insertion hole 49 has a portion that opens in the vertical direction. Therefore, it can be formed using a die-cast mold consisting only of upper and lower molds. Therefore, a mold that requires lateral insertion and removal is not required, simplifying the mold configuration. When the first cover member 5 is attached to the case body 4, the lower side of the insertion hole 49 is blocked by a protrusion 58 protruding from the left end portion 5L of the first cover member 5 (see FIGS. 10 and 2). The surface of the bottom wall portion 4F is formed with a step portion 4H that conforms to the shape of the left end portion 5L of the first cover member 5. When the left end portion 5L of the first cover member 5 is placed over the underside of the partition wall portion 4G, the step portion 4H of the bottom wall portion 4F fits into the step portion 4H of the bottom wall portion 4F to position the first cover member 5, and the underside of the bottom wall portion 4F and the underside 5B of the first cover member 5 are flush with each other.

[0041] 18 and 19, a connection structure between the litz wire 21 and the wiring board 9 at both end portions 2A, 2A of the coil 2 will be described. In this embodiment, the end portions of the litz wire 21 are connected to the wiring board 9 via terminal members 22.

[0042] A conventional method for fixing the end of a litz wire to a wiring board is to crimp the end of the litz wire to one end of a terminal member that is screwed to the wiring board by fusing (caulking). This type of crimping of the litz wire to the terminal member by fusing can cause power loss due to contact resistance, especially in litz wires formed by twisting multiple wires together, because the crimped joint between each wire and the terminal member 22 becomes unstable. Furthermore, significant contact resistance exists between the terminal member, wiring board, and fixing screws, which also results in power loss.

[0043] As shown in FIG. 18 , the terminal member 22 is made of a metal plate-like member and includes a substrate fixing portion 23 fixed to the wiring substrate 9 and a clamping portion 24 formed integrally with the substrate fixing portion 23 and clamping the end of the litz wire 21. The substrate fixing portion 23 is made of a long, plate-like member having a predetermined thickness in the vertical direction, and its lower surface is placed on the mounting surface 9A of the upper surface of the wiring substrate 9. The end of the litz wire 21 is placed on the upper surface of the substrate fixing portion 23 with the longitudinal direction of the substrate fixing portion 23 aligned with the extension direction of the litz wire 21. The substrate fixing portion 23 is formed with a pair of legs 231 extending toward the wiring substrate 9 at each of one and the other longitudinal ends. The pair of legs 231 are inserted into through holes 91 that penetrate the wiring substrate 9 in the vertical direction and soldered to be mounted on the wiring substrate 9.

[0044] The clamping portion 24 has a pair of arms 241 formed integrally on both sides of the substrate fixing portion 23 in the short direction. The pair of arms 241 extend from the substrate fixing portion 23 toward the opposite side (upward) of the leg portion 231 and are disposed on both sides of the litz wire 21 placed on the substrate fixing portion 23. The base ends of the pair of arms 241 protruding from the substrate fixing portion 23 extend along the circumferential direction of the litz wire 21, and the tip ends are bent away from each other to form introduction portions 241A that taper and widen. The ends of the litz wire 21 are attached to the terminal member 22 in a pre-soldering process after being immersed in molten solder Y to allow the solder Y to soak into the spaces between the wire members (see FIG. 19). At this time, the end of the litz wire 21 is inserted between the introduction portion 241A, elastically deforming the pair of arms 241 so as to spread the introduction portion 241A, and is inserted inside the pair of arms 241. When the litz wire 21 passes through the introduction portion 241A, the pair of arms 241 that were spread apart return to their original positions and clamp the end of the litz wire 21. In this embodiment, pairs of clamping portions 24 are provided at two locations along the longitudinal direction of the substrate fixing portion 23, but the number of pairs of arms 241 can be changed as appropriate, and may be one, three, or more. The terminal member 22 connects the end of the litz wire 21 to the wiring board 9 by applying solder Y to cover the end of the litz wire 21 and the pair of arms 241 (clamping portions 24) while the pair of arms 241 clamp the end of the litz wire 21, which has been coated with solder Y in the pre-soldering process.

[0045] The first notable feature of the above configuration is that the end of the litz wire 21, which has been soaked in solder Y, is clamped between a pair of arm portions 241 (clamping portions 24) of the terminal member 22, stabilizing the contact portion between the terminal member 22 and the litz wire 21. Since each wire material constituting the litz wire 21 is clamped between the pair of arm portions 241 while covered with solder Y in the pre-soldering process, each wire material of the litz wire 21 does not come into direct contact with the pair of arm portions 241, but is clamped with the solder Y from the pre-soldering process interposed between the pair of arm portions 241. This reduces the contact resistance between the litz wire 21 and the terminal member 22, thereby reducing power loss.

[0046] Second, by applying solder Y so as to cover the end of the litz wire 21 and the clamping portion 24, the solder Y can be reliably interposed between the litz wire 21 and the terminal member 22. This makes it possible to achieve a connection state similar to that achieved when the end of the litz wire 21 (each wire) is directly soldered to the wiring board 9, thereby improving the mechanical joint strength between the litz wire 21 and the terminal member 22 and further stabilizing the contact between the litz wire 21 and the terminal member 22 (wiring board 9), thereby reducing contact resistance. Furthermore, because the litz wire 21 is clamped by the terminal member 22, stress on the solder caused by vehicle vibrations and shocks can be reduced.

[0047] The second housing space S2 of the case body 4 will be described below with reference to FIGS. 5 and 6. The second housing space S2 is a rectangular box-shaped housing space that opens upward of the case body 4. The side walls of the second housing space S2 are formed by the front wall 4A, rear wall 4B, left wall 4C, and partition wall 4G of the case body 4. These walls 4A, 4B, 4C, and 4G are integrally formed with a plurality of second bosses 50 for fixing the second cover member 6 to the case body 4. The second housing space S2 accommodates a wiring board 9 and a resonant choke (not shown) for optimizing transmission efficiency. Two connector mounting portions 501 and 502 are formed in the left wall 4C that constitutes the left wall of the second housing space S2. The connector mounting portions 501 and 502 are formed in a cylindrical shape that protrudes from the left wall 4C to the outside of the case body 4. The housing 11A of the input connector 11 and the housing 12A of the output connector 12 are mounted inside the left wall 4C (see FIG. 1). The housings 11A and 12A are each provided with a connection terminal (not shown), which is connected to the mounting surface 9A of the wiring board 9. The input-side connector 11 is connected to a cable connector that is electrically connected to a power source (not shown), etc. The output-side connector 12 is connected to a cable connector that is electrically connected to the battery 300 of the electric vehicle 200, and supplies the power received by the coil 2 to the battery 300 of the electric vehicle 200.

[0048] 12 and 13, the second cover member 6 is a metal plate-like member having a predetermined width in the front-rear and left-right directions and a predetermined thickness in the up-down direction. The second cover member 6 is disposed above the case body 4 and is configured to close the second opening 42 of the second housing space S2 by attaching it to the case body 4. A plurality of second mounting holes 61 are formed on the outer periphery of the second cover member 6, penetrating the second cover member 6 in the up-down direction. The plurality of second mounting holes 61 correspond to a plurality of second bosses 50 provided on each wall portion that forms the second housing space S2. The second cover member 6 is attached to the case body 4 by inserting screws 62 into the second mounting holes 61 and the second bosses 50.

[0049] An accommodating recess 63 is formed on the underside of the second cover member 6 by press-molding the upper surface of the second cover member 6 so that it protrudes upward. The accommodating recess 63 is a rectangular box-shaped accommodating space that opens downward, and accommodates various circuit elements such as capacitors mounted on the wiring board 9, as well as resonant chokes that optimize transmission efficiency.

[0050] A notable feature of the second housing space S2 is the fixed position of the right end portion 6R of the second cover member 6. As described above, in the case body 4, the partition wall 4G that separates the first housing space S1 and the second housing space S2 is integrally formed with a first boss portion 43 that attaches the first cover member 5 to the case body 4 and a second boss portion 50 that attaches the second cover member 6 to the case body 4. Therefore, as shown in FIG. 3, the right end portion 6R side (position end side) of the second cover member 6 is disposed so as to cover the upper surface side of the partition wall 4G, and the left end portion 5L side of the first cover member 5 and the right end portion 6R side of the second cover member 6 are attached to the case body 4 in a state where they are overlapped vertically with the partition wall 4G in between.

[0051] (Action and effect) As described above, in the coil unit 1 of this embodiment, the coil 2 and the wiring board 9 connected to the coil 2 are housed inside the device case 3. The case body 4 of this device case 3 has a first housing space S1 and a second housing space S2 partitioned by a partition wall 4G. The coil 2 is housed in the first housing space S1, and the wiring board 9 is housed in the second housing space S2. In the case body 4, the first housing space S1 opens facing the mating coil unit, and the second housing space S2 opens on the opposite side from the first housing space. Therefore, the case body 4 is formed into a crank shape with a step between the first housing space S1 and the second housing space S2 by the partition wall 4G. This increases the cross-sectional rigidity and improves the strength of the case body 4. Furthermore, the first opening 41 of the first housing space S1, in which the coil 2 is housed, is reduced in size, allowing the first cover member 5 to be miniaturized, thereby also improving the strength of the device case 3 as a whole. In this way, the coil unit 1 of the present invention improves the strength of the device case 3.

[0052] In this embodiment, a first boss 43 for fixing the first cover member 5 and a second boss 50 for fixing the second cover member 6 are integrally provided on both side surfaces of the partition wall 4G. As a result, as shown in Fig. 3, the left end 5L side (one end side) of the first cover member 5 and the right end 6R side (one end side) of the second cover member 6 are attached to the case body in an overlapping state with the partition wall 4G in between. Therefore, the case body 4 can be made more compact than in a configuration in which the first cover member 5 and the second cover member 6 are fixed side by side on the same surface of the case body 4.

[0053] Furthermore, the first boss 43 and the second boss 50 are integrally formed on both sides of the partition wall 4G, thereby increasing the rigidity of the partition wall 4G. This effectively increases the rigidity of the crank-shaped portion of the case body 4, further improving the strength of the case body 4.

[0054] Furthermore, according to this embodiment, the partition wall portion 4G has an insertion hole 49 through which the coil 2 is inserted, so that the end portion 2A of the coil 2 can be routed inside the device case 3 and connected to the wiring board 9. Therefore, since no insertion hole communicating with the outside is formed in the device case 3, the waterproof performance of the inside of the device case 3 can be improved.

[0055] Furthermore, in this embodiment, the coil 2 is housed in a coil housing groove 76 formed in the coil fixing surface 7B (surface) of the coil case 7, and is arranged in a spiral shape on the surface of the coil case 7. Therefore, the coil 2 is held in the coil case 7 and can be prevented from shaking during use, so that the coil can be protected from vibrations while the electric vehicle 200 is running. Furthermore, because the coil 2 is arranged on the surface of the coil case 7, the coil case can be made thinner, and therefore the coil unit 1 can be made thinner and lighter.

[0056] In this embodiment, the case body 4 has recesses 44 formed on the surfaces of the walls (front wall 4A, rear wall 4B, right wall 4D, and partition wall 4G) that form the first housing space S1, facing the first cover member 5, and the recesses 44 are filled with a sealant X. The first cover member 5 has protrusions 54 formed on the surfaces facing the walls 4A, 4B, 4D, and 4G of the first housing space S1, and the protrusions 54 are inserted into the recesses 44, with the sealant X interposed between the walls 4A, 4B, 4D, and 4G. When the difference in linear expansion and contraction between the case body 4 and the first cover member 5 increases due to the installation environment of the coil unit 1, the sealant X interposed between the recesses 44 and the protrusions 54 deforms. Therefore, the difference in linear expansion and contraction can be efficiently absorbed in multiple directions, preventing the first housing space S1 from opening.

[0057] In this embodiment, the walls 4A, 4B, 4D, and 4G of the case body 4 are formed with inclined surfaces 45 formed by chamfering the corners on the first housing space S1 side, and the sealing material X extruded toward the first housing space S1 is retained by the inclined surfaces 45. Therefore, a thick sealing layer is formed on the inclined surfaces 45, which improves the airtightness of the first housing space S1, thereby improving the waterproof performance of the device case 3. Furthermore, because excess sealing material X is retained on the inclined surfaces 45 and prevented from flowing into the first housing space S1, components such as the coil 2 housed in the first housing space S1 can be protected from the sealing material X.

[0058] It is also possible to form a thick portion of the sealing material X between the case body 4 and the first cover member 5 by forming a step portion at the corner portion of the wall portions 4A, 4B, 4D, 4G on the first storage space S1 side, but by forming the corner portion into an inclined surface, the sealing material X can be extruded more smoothly.

[0059] Furthermore, in this embodiment, when the first cover member 5 is attached to the case body 4, as shown in Fig. 20, the distance t2 between the tip of the convex portion 54 of the first cover member 5 and the bottom surface 442 of the concave portion 44 of the case body 4 is set to be larger than the distance t1 between the side surface of the convex portion 54 and the side surface 441 of the concave portion 44. In other words, the thickness of the seal layer (sealing material) formed between the tip of the convex portion 54 and the bottom surface 442 of the concave portion is set to be larger than the thickness of the seal layer formed on both sides of the convex portion 54. Because the space on the bottom surface 442 side of the concave portion 44 communicates with the spaces on both sides of the convex portion 54, by making the seal layer on the bottom surface 442 side thicker, deformation of the spaces on both sides of the convex portion 54 due to the difference in linear expansion and contraction between the members can be efficiently absorbed.

[0060] In this embodiment, the central boss portion 47 (first support portion) formed on the case body 4 abuts against the first cover member 5, and the second support portion 57 formed on the first cover member 5 abuts against the case body 4, so that the case body 4 and the first cover member 5 support each other. When the first cover member 5 is attached to the case body 4, the central boss portion 47 and the second support portion 57 are nested. Therefore, by supporting the case body 4 and the first cover member 5 against each other, predetermined portions within the first housing space S1 where strength is reduced can be efficiently reinforced. As a result, the plate thicknesses of the case body 4 and the first cover member 5 can be reduced.

[0061] Furthermore, in this embodiment, the central boss portion 47 and the second support portion 57 are disposed within the central space of the coil 2 housed in the first housing space S1 of the case body 4. Therefore, in the first housing space S1 in which the coil 2 is housed, the central space of the coil 2, which has reduced strength, can be efficiently reinforced.

[0062] Furthermore, in this embodiment, when the first cover member 5 is attached to the case body 4, the central boss portion 47 of the case body 4 is nested within the second support portion 57. That is, the second support portion 57 of the first cover member 5 has an inner diameter large enough to accommodate the central boss portion 47 of the case body 4 therein, thereby supporting the opposing surface of the case body 4 over a wider area. Therefore, even when the case body 4 is formed from a relatively easy-to-form material such as aluminum, as in this embodiment, the strength of the case body 4 can be increased over a wider area, thereby achieving both strength and weight reduction. Furthermore, even when the case body 4 is die-cast, the strength weaknesses of die-casting can be compensated for by the structure, ensuring the required strength and improving dimensional accuracy and productivity.

[0063] In this embodiment, the second support portion 57 has a double-tube shape with an inner wall 571 and an outer wall 572, and has multiple ribs 573 between the inner wall 571 and the outer wall 572. This increases the support area of ​​the case body 4 provided by the second support portion 57, thereby more effectively reinforcing the case body 4. It is also possible to increase the support area for the case body 4 by making the second support portion 57 a single-layer tube and increasing its thickness. However, if this configuration is applied to a resin first cover member 5 as in this embodiment, not only will the weight of the first cover member 5 increase, but the increased thickness will also increase the likelihood of resin sink. In this embodiment, the second support portion 57 has a structure in which multiple ribs are formed on the inside of the double-tube shape, thereby suppressing an increase in the weight of the first cover member 5 and preventing resin sink.

[0064] 21 , in this embodiment, a screw hole 55 is formed in the center of the second support portion 57, and a screw 52 is inserted into the screw hole 55 to fix the first cover member 5 to the case main body 4. Therefore, the central boss portion 47 and the center portion of the second support portion 57 can be fixed and reinforced with the screw 52. Furthermore, an annular protrusion 56 formed in the second support portion 57 so as to surround the screw hole 55 is inserted into the opposing annular recess 471 of the case main body 4 via the sealing material X, thereby ensuring waterproof performance around the screw hole 55. Therefore, a coil unit 1 can be obtained that has sufficient strength and excellent waterproof performance.

[0065] In this embodiment, to connect the litz wire 21 constituting the coil 2 to the wiring board 9, the end of the litz wire 21 is immersed in molten solder Y in a pre-soldering process and impregnated with the solder Y. The end is then sandwiched between the terminal member 22 fixed to the wiring board 9. Therefore, the solder Y is interposed between the litz wire 21 and the terminal member 22. As a result, compared to a configuration in which the litz wire 21 and the terminal member 22 are directly contacted and crimped, for example, the contact portion between the litz wire 21 and the terminal member 22 is stabilized, thereby reducing contact resistance. Furthermore, by applying the solder Y so as to cover the sandwiched portion 24 of the litz wire 21 and the terminal member 22, the mechanical fixing strength between the litz wire 21 and the terminal member 22 can be easily ensured without increasing contact resistance. Furthermore, because the litz wire 21 is sandwiched between the terminal member 22, stress on the solder caused by vehicle vibrations and impacts can be reduced.

[0066] In addition, in this embodiment, the clamping portion 24 of the terminal member 22 clamps the litz wire 21 with a pair of elastically deformable arms 241, so the clamping portion 24 can clamp a plurality of different diameter litz wires 21. Therefore, a plurality of different diameter litz wires 21 can be connected to the wiring board 9 using a common terminal member 22, which allows for standardization of components and provides a connection structure with excellent versatility.

[0067] Below, various modifications that can also be applied to the above embodiment will be explained. Note that the same components as those in the above embodiment will be given the same numbers and explanations thereof will be omitted.

[0068] In the above embodiment, recesses 44 are formed in the walls 4A, 4B, 4D, and 4G of the case body 4, and protrusions 54 are formed in the first cover member 5 on the opposing surfaces of the walls 4A, 4B, 4D, and 4G that form the side walls of the first housing space S1. However, the present invention is not limited to this. For example, as shown in a modified example in FIG. 22(A), protrusions 500 may be formed in the walls 4A, 4B, 4D, and 4G of the case body 4 and inserted into recesses 503 formed on the opposing surfaces of the first cover member 5. Furthermore, in the above embodiment, the recesses 44 formed in the case body 4 have a rectangular groove shape, but the present invention is not limited to this. For example, as shown in FIG. 22(B), a protrusion 602 having a hemispherical cross section may be inserted into a groove-shaped recess 600 having a hemispherical cross section. Alternatively, as shown in a modified example in FIG. 22(C), a trapezoidal protrusion 702 may be inserted into a groove-shaped recess 700 having a trapezoidal cross section. Alternatively, a triangular projection may be inserted into a groove-shaped recess having a triangular cross section.

[0069] Furthermore, in the above embodiment, the central boss portion 47 (first support portion) and the second support portion 57 are configured so that the central boss portion 47 protruding from the case body 4 is nested inside the second support portion 57, but the present invention is not limited to this. As shown in a modified example in FIG. 23 , the second support portion 900 protruding from the first cover member 5 may be nested inside the central boss portion 800 (first support portion). The central boss portion 800 (first support portion) according to the modified example shown in this figure is formed in a cylindrical shape protruding from the upper wall portion 4E of the case body 4 toward the first cover member 5. A cylindrical protrusion protruding downward is formed in the center of the central boss portion 800, and a female screw hole is formed in the center of the protrusion. A rectangular groove-shaped annular recess 802 is formed on the surface of the central boss portion 800 facing the first cover member 5, and an annular protrusion 902 protruding from the first cover member 5 is inserted into the recess 802 with a sealing material X interposed therebetween. On the other hand, the second support part 900 according to the modified example is disposed inside an annular protrusion 902 formed to surround the screw hole 55 formed in the center of the first cover member 5, and is formed in a cylindrical shape that protrudes from the first cover member 5 toward the case body 4. The second support part 900 has a double cylindrical shape with an inner wall 904 formed to surround the periphery of the screw hole 55 and an outer wall 906 arranged coaxially radially outside the inner wall 904, and has a plurality of ribs 908 between the inner wall 904 and the outer wall 906. When the first cover member 5 is attached to the case body 4, the second support part 900 is disposed inside the first support part 800 in a nested manner, and the second support part 57 abuts against the case body 4 to support the case body 4.

[0070] Furthermore, in the above embodiment and each modified example, a coil unit for a contactless charging system using a magnetic field resonance method has been described, but the coil unit of the present invention is not limited to this, and may also be applied to a contactless charging system using an electromagnetic induction method. [Explanation of symbols]

[0071] 1 coil unit (1A, 1B) 2 coils 3 Equipment case 9. Wiring board 21 Litz wire 22 Terminal member 23 Board fixing part 24 Clamping part 100 Contactless power supply system 200 electric vehicles 241 Arm 300 Battery Y solder

Claims

1. A litz wire connection structure for connecting a litz wire, which is made by twisting together a plurality of insulatingly coated wires, to a wiring board, a terminal member having a substrate fixing portion fixed to the wiring substrate and a clamping portion for clamping an end of the Litz wire; the clamping portion has a pair of elastically deformable arms extending from both sides of the substrate fixing portion along the circumferential direction of the litz wire, The arms have leading ends formed thereon that are bent away from each other to form tapered introduction sections, A litz wire connection structure in which the end of the litz wire, which has been immersed in molten solder and soaked with solder, is clamped between a pair of arm portions of the terminal member fixed to the wiring board, and solder is applied so as to cover the end of the litz wire and the clamping portion, thereby connecting the end of the litz wire to the wiring board.

2. A coil unit disposed on the ground or on an electric vehicle in a contactless charging system that transmits power between a power transmission coil unit disposed on the ground and a power receiving coil unit disposed on an electric vehicle, and charges a battery mounted on the electric vehicle, a coil formed by twisting together a plurality of insulating coated wires into a spiral litz wire; a wiring board to which the coil is electrically connected; an apparatus case that accommodates the coil and the wiring board therein, A coil unit in which the end of the coil and the wiring board are connected by the Litz wire connection structure according to claim 1.

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