Coil unit

Abstract

To obtain a coil unit which can inhibit stress from concentrating on a part of a coil due to heat expansion during energization.SOLUTION: A coil unit 1 is arranged on the ground or an electric vehicle in a non-contact charging system. The coil unit 1 includes: a flat plate-like coil case 50; a coil 2 which is housed in a coil housing groove 54 formed in a spiral form on a surface of the coil case 50, and is arranged in a spiral form on the surface of the coil case 50; and a device case 10 which houses the coil case 50 and the coil 2. The coil 2 contacts with side surfaces 541 at both sides in a width direction of the coil housing groove 54 in a state that the coil 2 is housed in the coil housing groove 54. A depth H of the coil housing groove 54 is set larger than a coil diameter D of the coil 2. A deflection margin H1 is provided that allows deflection of the coil 2 in a depth direction of the coil housing groove 54 when the coil 2 is extended by heat expansion.SELECTED DRAWING: Figure 12

Description

Technical Field

[0004] ,

[0001] The present invention relates to a coil unit.

Background Art

[0002] As disclosed in Patent Documents 1 and 2, a non-contact charging system is known that transmits power between a power transmission-side coil unit disposed on the ground and a power reception-side coil unit disposed on an electric vehicle, and charges a battery mounted on the electric vehicle. In the coil units of these non-contact charging systems, in order to hold a coil formed in a spiral shape, it has been proposed to form a spiral coil accommodation groove in a coil case (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the coil unit of the non-contact charging system, since the coil for power transmission thermally expands inside the coil accommodation groove due to heat generation during energization, there is a problem that stress concentrates on a part of the coil due to the resulting bending of the coil.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a coil unit capable of suppressing stress concentration on a part of the coil due to thermal expansion during energization.

Means for Solving the Problems

[0006] A coil unit according to a first aspect of the present invention is a coil unit located on the ground or on an electric vehicle in a contactless charging system that transmits power between a power-transmitting coil unit located on the ground and a power-receiving coil unit located on an electric vehicle to charge a battery mounted on the electric vehicle, and comprises a flat coil case, a coil housed in a spiral-shaped coil housing groove formed on the surface of the coil case and arranged spirally on the surface of the coil case, and a device case that houses the coil case and the coil, wherein the coil, while housed in the coil housing groove, abuts against the sides on both sides in the width direction of the coil housing groove, the depth of the coil housing groove is set to be greater than the coil diameter of the coil, and a deflection allowance is provided to allow the coil to deflect in the depth direction of the coil housing groove when the coil expands due to thermal expansion. [Effects of the Invention]

[0007] In the coil unit according to the present invention, a spiral-shaped coil housing groove is formed on the surface of a flat coil case, and by housing the coil in the coil housing groove, the coil is arranged in a spiral shape on the surface of the coil case. Here, when energized, the coil will bend due to thermal expansion caused by heat generation. By bringing the coil into contact with the sides on both sides in the width direction of the coil housing groove while it is housed in the coil housing groove, the bending in the groove width direction can be restricted, and the movement of the coil along the extension direction of the groove can be promoted. Furthermore, the depth of the coil housing groove is set to be greater than the coil diameter, and a deflection allowance is provided to allow bending in the depth direction of the coil housing groove. In this configuration, when the coil expands due to thermal expansion, the movement of the coil along the extension direction of the groove can be promoted, and bending in the depth direction of the groove can be allowed within the coil housing groove. Therefore, the stress caused by suppressing the bending of the coil in the R portion of the coil housing groove is relieved by bending in the depth direction of the groove, and local bending of the coil can be suppressed. This makes it possible to suppress the concentration of stress in a part of the coil due to thermal expansion when energized. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view of a coil unit according to an embodiment, with a portion of it disassembled. [Figure 2] This is a bottom-side perspective view of a coil unit according to an embodiment, with a portion of it disassembled. [Figure 3] This is a bottom view of the case body according to the embodiment. [Figure 4] This is a bottom view of the core case according to the embodiment. [Figure 5] This is a magnified view of a core case and the core housed within it. [Figure 6] Figure 5 is a partial cross-sectional view of the coil unit along the line VI-VI. [Figure 7] This is a partial cross-sectional view of the coil unit along line VII-VII in Figure 5. [Figure 8] Figure 5 is a partial cross-sectional view of the coil unit along the line VIII-VIII. [Figure 9] This is a bottom view of the coil case containing the coil. [Figure 10] Figure 9 is a cross-sectional view of the coil case along line XX. [Figure 11] This is a schematic diagram illustrating the stress generation mechanism of a coil within a coil housing groove. [Figure 12] This is an enlarged cross-sectional view of the coil housing groove according to the embodiment, cut in a direction perpendicular to the extending direction, and is a schematic diagram showing the state of the coil before and after it is housed in the groove. [Figure 13] This is a perspective view of the bottom side of the circuit board case containing the sensor board. [Figure 14] This is a schematic diagram of the contactless charging system according to this embodiment. [Figure 15] This is a block diagram of a coil unit according to this embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, the non-contact charging system 100 according to an embodiment of the present invention and the coil unit 1 used in the non-contact charging system 100 will be described with reference to FIGS. 1 to 15. However, the present invention is not limited to the following embodiments. In this embodiment, for convenience of explanation, the directions indicated by the arrows of up and down, left and right, and front and back appropriately shown in each figure are defined as the up-down direction, left-right direction, and front-back direction, respectively, and will be described. Also, in each figure, some reference numerals may be omitted for easy viewing of the drawings.

[0010] As shown in FIG. 14, the non-contact 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 non-contact charging system 100, power is transmitted between the power transmission side coil unit 1A disposed on the ground and the power reception side coil unit 1B disposed on the electric vehicle 200, and the battery 300 mounted on the electric vehicle 200 is charged. The power transmission method is to arrange the primary coil 2 accommodated in the power transmission side coil unit 1A and the secondary coil 2 accommodated in the power reception side coil unit 1B to face each other, and utilize electromagnetic induction between the coils to transmit power. Specifically, by supplying alternating current power from the commercial power supply 400 to the power transmission side coil unit 1A, an induced current flows through the primary coil 2 to generate a magnetic field. The generated magnetic field reaches the secondary coil 2, and power is transmitted when an induced current flows through the secondary coil 2.

[0011] Hereinafter, the configuration will be described centering on the power reception side coil unit 1B disposed on the electric vehicle 200. Also, when the power transmission side coil unit 1A and the power reception side coil unit 1B are not distinguished, they will be simply described as the coil unit 1.

[0012] FIG. 15 is a block diagram showing the main part of the power reception side coil unit 1B. As shown in this figure, the coil unit 1B has a coil 2, a power supply circuit unit 3, a power conversion unit 4, a control unit 5, and a sensor coil unit 6. The power supply circuit unit 3 generates a control power supply that supplies the control unit 5 using the alternating current power received from the power transmission side coil unit 1A.

[0013] The power conversion unit 4 has a rectifying unit 4A including a plurality of switching elements. The rectifying unit 4A converts the AC power received from the power transmission side coil unit 1A into DC power and stores it in the battery 300.

[0014] The control unit 5 has a function of generating various control signals for the coil unit 1B. Specifically, the control unit 5 includes a charge control unit 5A, a sensor control unit 5B, and a system monitoring control unit 5C. The charge control unit 5A controls the power to be charged into the battery 300. The sensor control unit 5B has a function of diagnosing the relative positional relationship between the power transmission side coil unit 1A and the power reception side coil unit 1B. In an example of the present embodiment, by controlling the energization of the sensor coil unit 6, the relative positional relationship between the sensor coil unit 6 (not shown) provided in the power reception side coil unit 1A is diagnosed by the electromagnetic induction action therebetween. Thus, in the electric vehicle 20, alignment between the power transmission side coil unit 1A and the power reception side coil unit 1B can be performed based on the diagnosis result of the sensor control unit 5B.

[0015] In the coil unit 1B, each of the above-described components of the coil 2, the power supply circuit unit 3, the power conversion unit 4, the control unit 5, and the sensor coil unit 6 is housed in the device case 10. As shown in FIGS. 1 and 2, the device case 10 has a case body 12 in which accommodation spaces S1 and S2 for accommodating the coil 2 and the like are formed, and a first cover member 14 and a second cover member 16 that close the openings 121 and 122 of the case body 12.

[0016] The case body 12 is made of a metal material such as iron or aluminum alloy, has a predetermined width in the front-to-back and left-to-right directions, and is formed in a box shape that is flattened in the vertical direction. The case body 12 includes a front wall 12A, a rear wall 12B, a left wall 12C, a right wall 12D, an upper wall 12E, a bottom wall 12F, and a dividing wall 12G. The dividing wall 12G extends in the front-to-back direction so as to connect the middle part of the front wall 12A and the middle part of the rear wall 12B. The upper wall 12E is integrally provided, connected to the upper end of the dividing wall 12G, the upper ends of the front wall 12A and rear wall 12B to the right of the dividing wall 12G, and the upper end of the right wall 12D. The bottom wall 12F is integrally connected to the lower end of the partition wall 12G, the lower ends of the front wall 12A and rear wall 12B to the left of the partition wall 12G, and the lower end of the left wall 12C. In the case body 12, the upper wall 12E, partition wall 12G, and bottom wall 12F have crank-shaped cross-sections in the upper, lower, left, and right directions. Therefore, in the case body 12, the partition wall 12G divides the internal space (storage space) of the case body 12 into two sections, left and right, and these left and right internal spaces open to each other in opposite directions.

[0017] In the case body 12 with this configuration, a first housing space S1 is formed, the side wall portion of which is composed of a bottom wall portion 12F, a dividing wall portion 12G, a left wall portion 12C, a front wall portion 12A, and a rear wall portion 12B. The first housing space S1 has a first opening 121 that opens upward, and the first opening 121 is closed by a rectangular plate-shaped first cover member 14 made of the same metal material as the case body 12. A wiring board 9 to which the coil 2 is connected is housed inside the first housing space S1. The power supply circuit portion 3, power conversion portion 4, and control portion 5 described above are mounted on this wiring board 9.

[0018] Furthermore, the case body 12 has a second storage space S2 formed therein, the side wall portion of which is composed of an upper wall portion 12E, a dividing wall portion 12G, a right wall portion 12D, a front wall portion 12A, and a rear wall portion 12B. The second storage space S2 has a second opening 122 that opens downward, and the second opening 122 is closed by a second cover member 16 made of resin material. This second cover member 16 is formed in the shape of a flat rectangular box that opens upward. The second cover member 16 is screw-fixed to the case body 12 at its outer edge and the center of its bottom surface via a plurality of boss portions (reference numerals omitted) that are integrally formed on the side wall portion and the central part of the bottom wall portion (upper wall portion 12E) of the second storage space S2.

[0019] A core case 20, formed in a grid-like structure, is housed inside the second housing space S2. The core case 20 is fixed to the upper wall portion 12E of the case body 12. Furthermore, a core 40 (not shown in Figure 2), a coil case 50, a coil 2, and a substrate case 60 are stacked in this order on the core case 20 fixed to the upper wall portion 12E and housed in the second housing space S2. The second housing space S2 of the case body 12 and the core case 20, core 40, coil case 50, coil 2, and substrate case 60 housed in the second housing space S2 will be described in detail below.

[0020] (Case body) Figure 3 is a bottom view of the case body 12 as seen from below. The bottom side of the case body 12 shown in this figure is positioned facing upwards on the workbench 80 (see Figure 7, etc.) in a work process in which components are assembled inside the second storage space S2 on the workbench 80.

[0021] As shown in Figure 3, the case body 12 has a plurality of protrusions 18 that protrude from the upper wall portion 12E within the second housing space S2. The plurality of protrusions 18 are arranged radially around the central part of the upper wall portion 12E. Each protrusion 18 is formed as if a part of the upper wall portion 12E has been pushed out, and is formed in a rectangular tubular shape that protrudes into the second housing space S2. Each protrusion 18 is configured to contact the core 40 through the through hole 24 of the core case 20 when the core case 20, which will be described later, is fixed to the upper wall portion 12E. In addition, screw holes 17 are formed on the surface of the plurality of protrusions 18 that faces the core case 20. Female threads are formed on the inner circumferential surface of the screw holes 17, and metal screws 34 (see Figure 5, etc.), which will be described later, are screwed into them.

[0022] Multiple insertion slots 19 are formed on the central and outer sides of the upper wall portion 12E where the multiple protrusions 18 are not located. The insertion slots 19 are formed as if a part of the upper wall portion 12E has been pushed out, and consist of rectangular recesses that are recessed in the depth direction (above the coil unit 1) of the second housing space S2. Columnar fixing legs 66 (see Figure 7), provided on the substrate case 60 (described later), are inserted into these insertion slots 19.

[0023] (Core case) Figure 4 is a bottom view of the core case 20 as seen from below. The bottom side of the core case 20 shown in this figure is positioned facing upwards on the workbench 80, for example, in a work process where assembly is performed inside the second storage space S2 on the workbench 80.

[0024] As shown in Figure 4, the core case 20 is a resin plate-like member having a predetermined width in the front-to-back and left-to-right directions and a predetermined thickness in the up-to-down direction. A rectangular opening 22 is formed in the central part of the core case 20, penetrating it vertically. Multiple through holes 24 are formed around the opening 22, penetrating the core case 20 vertically. The multiple through holes 24 are arranged radially around the opening 22 and correspond to the protrusions 18 provided on the case body 12. The core case 20 is fixed to the upper wall portion 12E of the case body 12 using metal screws 34 (metal screws), which will be described later. Once the core case 20 is fixed to the case body 12, the protrusions 18 protruding from the upper wall portion 12E are inserted through each of the multiple through holes 24. In other words, the core case 20 with this configuration can be described as being formed in a lattice frame shape as a whole.

[0025] The core case 20 has a plurality of first fixing parts 26 inside the through hole 24, and is fixed to the upper wall portion 12E (protrusion 18) of the case body 12 via the plurality of first fixing parts 26 (see Figure 7). In addition, a plurality of second fixing parts 28 are provided on the outside of the through hole 24, i.e., on the outer and inner circumference (periphery of the opening 22) of the core case 20. The core case 20 is fixed to the coil case 50 and the substrate case 60, which are stacked on top of the core case 20, via the plurality of second fixing parts 28 (see Figure 8). The outer and inner circumference of the core case 20 are further provided with a plurality of adhesive filling parts 30. For example, the plurality of adhesive filling parts 30 consist of four adhesive filling parts 30 that protrude outward from the outer circumference of the core case 20 and two adhesive filling parts 30 that protrude inward from the inner circumference of the core case 20. Each adhesive filling part 30 is formed in the shape of a rectangular frame into which adhesive can be filled. The adhesive filling section 30 is filled with adhesive Y while the columnar fixing legs 66 provided on the substrate case 60 (described later) are inserted through it. In this configuration, the case body 12, the core case 20, and the substrate case 60 are bonded and fixed to each other via the adhesive filling section 30 (see Figure 8). Details of each fixing part will be described later.

[0026] The lower surface of the core case 20 is divided into a grid pattern by wall sections 32 that are discontinuously erected to surround each through-hole 24. Each section separated by the wall sections 32 constitutes a core housing section, and a flat core 40 (see Figure 5) is housed inside each section. As a result, multiple cores 40 are arranged radially around the opening 22 of the core case 20. Each core 40 is positioned to cover the through-hole 24.

[0027] Figure 5 shows the arrangement of multiple cores 40 as seen from the bottom of the core case 20. Figure 6 shows a cross-section of the coil unit 1 when cut along the line VI-VI in Figure 5. The cross-section in Figure 6 is illustrated assuming an assembly process inside the second housing space S2, and shows the top-down relationship when the case body 12 is placed on a workbench 80 and the core case 20, cores 40, coil case 50, coils 2, and substrate case 60 are stacked in this order from the bottom of the paper.

[0028] As shown in Figures 5 and 6, each core 40 is composed of a rectangular plate-shaped ferrite core. Multiple cores 40 are arranged on the lower surface of the core case 20 (the surface opposite to the surface facing the upper wall portion 12E of the case body 12). When each core 40 is housed, multiple wall portions 32 are arranged to surround the core 40. The cores 40 are also positioned to block the through-holes 24 formed in the core case 20. The depth of the through-holes 24 is set to be approximately the same as the height of the protrusions 18 of the case body 12, and when the protrusions 18 are inserted through the through-holes 24, the height of the protrusions 18 is set to be approximately the same as the height of the lower surface of the core case 20. Therefore, when the through-holes 24 are blocked by the cores 40, the protrusions 18 inserted through the through-holes 24 come into contact with the cores 40. This creates a heat dissipation path that transfers the heat generated in the cores 40 to the case body 12 via the protrusions 18, thereby increasing the cooling efficiency of the cores.

[0029] Here, each core 40 housed in the core housing is sealed with sealing resin X. The sealing resin X is filled to seal the space between the core 40 and the lower surface of the core case 20, the space between the core 40 and the multiple wall portions 32, and the gaps between adjacent cores 40. These sealing resins X are filled in the process of housing the cores 40 in the core case 20. Specifically, after fixing the core case 20 to the upper wall portion 12E of the case body 12, sealing resin X is filled into the space formed between the inner surface 241 of the through hole 24 and the side surface of the protrusion 18 inserted through the through hole 24. Then, by stacking the cores 40 on the lower surface of the core case 20, the space between the cores 40 and the lower surface of the core case 20 is sealed. Furthermore, additional sealing resin X is filled into the gaps formed between the cores 40 and the multiple wall portions 32, and into the gaps formed between adjacent cores 40. In this configuration, the outer periphery of the core 40 is sealed with sealing resin X, so the sealing resin X acts as a buffer and absorbs shocks and vibrations input from the outside. Furthermore, even if the core 40 expands due to a rapid temperature change, the sealing resin X interposed between it and the core case 20 suppresses the generation of stress on the core 40. This enhances the protective performance of the core 40.

[0030] Since the inner surface 241 of the through hole 24 is inclined toward the inside of the through hole 24, the shape of the space formed between the inner surface of the through hole 24 and the side surface of the protrusion 18 becomes a tapered mortar shape. Therefore, when filling with the sealing resin X, the sealing resin X flows smoothly in the direction of gravity. Consequently, the structure is such that excess resin is less likely to be generated, and the amount of resin can be optimized. In addition, the formation of voids in the space can also be suppressed.

[0031] In this embodiment, a sheet-like heat dissipation member 42 is further placed both between the core 40 and the protrusion 18 of the case body 12, and between the core 40 and the coil case 50. This heat dissipation member 42 is constructed, for example, by applying a gel with excellent thermal conductivity to the surface of a sheet-like substrate. The heat dissipation member 42 with this configuration also functions as a cushioning material, similar to the sealing resin X.

[0032] (Securing the core case to the main case) Next, the fixing of the core case 20 to the case body 12 will be explained with reference to Figure 7. Figure 7 shows a cross-section of the coil unit 1 when cut along the line VII-VII in Figure 5. Note that, similar to Figure 6, the cross-section in Figure 7 is shown as being placed on a workbench 80, assuming a work process in which assembly is performed inside the second housing space S2.

[0033] As shown in Figure 7, the core case 20 and the upper wall portion 12E of the case body 12 are fixed together by metal screws 34 via a plurality of first fixing portions 26 provided inside the through-hole 24 of the core case 20. The first fixing portions 26 are made up of small plate-shaped pieces that protrude inward from the inner surface 241 of the through-hole 24. The first fixing portions 26 have mounting holes 261 formed through them at positions corresponding to the screw holes 17 formed in the protrusions 18 of the case body 12. The metal screws 34 are inserted through the mounting holes 261 of these first fixing portions 26. The metal screws 34 fix the core case 20 to the upper wall portion 12E of the case body 12 by screwing them into the screw holes 17 of the protrusions 18. In this configuration, since the metal screws 34 are positioned inside the through-hole 24, the metal screws 34 are positioned away from the ends of the core 40.

[0034] Here, since typical metal screws 34 are often made of ferromagnetic materials such as iron, they are easily magnetized by the magnetic field generated around the coil 2. Therefore, at the fixing point where the metal case body 12 and the core case 20 are fixed, if the metal screw 34 is placed near the end of the core 40, the magnetic flux generated at the inner or outer end of the coil will wrap around the end of the core and reach the metal screw 34, and the magnetized metal screw 34 may cause the case body 12 to be affected by magnetization. When the magnetic flux reaches the case body 12 in this way, if the case body 12 is made of a ferromagnetic material such as steel, the case body 12 will heat up due to induction heating caused by the electromagnetic induction action of the coil 2. In contrast, in this embodiment, the metal screw 34 can be placed at a position away from the end of the core 40, so that the heat generated in the case body 12 due to the electromagnetic induction action of the coil 2 as described above can be suppressed.

[0035] (Securing the coil case and circuit board case to the core case) Next, the fixing of the coil case 50 and the substrate case 60 to the core case 20 will be described with reference to Figure 8. Figure 8 shows a cross-section of the coil unit 1 when cut at the position of line VIII-VIII in Figure 5. Note that, as with Figures 6 and 7, the cross-section in Figure 8 is shown in a state where it is placed on a workbench 80, assuming a work process in which assembly is carried out inside the second housing space S2.

[0036] As shown in Figure 8, the coil case 50 and the substrate case 60 are stacked and fixed in this order on the core case 20. The coil case 50 and the substrate case 60 are fixed to the core case 20 via a plurality of second fixing parts 28 provided on the outside of the through hole 24 of the core case 20 using resin screws 44 (resin screws) and adhesive Y. The plurality of second fixing parts 28 are arranged along the outer and inner circumference (periphery of the opening 22) of the core case 20. Each second fixing part 28 constitutes a boss formed through the core case 20, and a female thread is formed on the inner surface into which the resin screw 44 is screwed. When the coil case 50 and the substrate case 60 are stacked on the core case 20, the first mounting part 52 formed on the coil case 50 is stacked on top of the second fixing part 28. Also, the second mounting part 64 formed on the substrate case 60 is stacked on top of the first mounting part 52.

[0037] The first mounting portion 52 of the coil case 50 has a recess 521 formed on the surface facing the second mounting portion 64, and a mounting hole 522 formed through the bottom surface of the recess 521. On the other hand, the second mounting portion 64 of the substrate case 60 has a fitting projection 641 formed on the surface facing the first mounting portion 52, a mounting hole 642 formed through the fitting projection 641, and an annular adhesive-filled wall portion 643 erected to surround the mounting hole 642.

[0038] The resin screw 44 is inserted from the substrate case 60 side through the mounting hole 642 of the second mounting portion 64 and the mounting hole 522 of the first mounting portion 52, and screwed into the second fixing portion 28 of the core case 20. In this state, the fitting projection 641 of the second mounting portion 64 is fitted into the recess 521 of the first mounting portion 52, so the mechanical strength of the joint made by the resin screw 44 is synergistically increased. In addition, the head of the resin screw 44 is housed inside the adhesive-filled wall portion 643 of the second mounting portion 64. Adhesive Y is filled into this adhesive-filled wall portion 643. As a result, the coil case 50 and the substrate case 60 are fixed to the core case 20, which is fixed to the case body 12, by the resin screw 44 and adhesive Y.

[0039] As shown in Figure 7, the fixing legs 66 extending from the substrate case 60 towards the case body 12 are inserted into the adhesive-filled section 30 provided in the core case 20. The tip of the fixing legs 66 is inserted into the insertion opening 19 formed in the upper wall 12E of the case body 12. The internal space of the adhesive-filled section 30 is then filled with adhesive Y. As a result, the case body 12, the core case 20, and the substrate case 60 are bonded and fixed to each other via the adhesive-filled section 30.

[0040] Incidentally, the fixing points formed via the second fixing portion 28 of the core case 20 fix the outer and inner ends of the core case 20, coil case 50, and substrate case 60 to each other. The positions of these fixing points are located near the inner and outer ends of the coil 2 housed in the coil case 50. Therefore, as described above, if metal screws are placed at the positions of these fixing points, the case body 12 may generate heat due to induction heating caused by the electromagnetic induction action of the coil 2. In contrast, in this embodiment, the heat generation of the case body 12 is suppressed by fixing these ends of the core case 20, coil case 50, and substrate case 60 to each other with resin screws 44 and adhesive Y. Furthermore, by using resin screws 44 and adhesive Y in combination, the joint strength of these fixing points can be made equivalent to that of screw fastening with metal screws.

[0041] In this embodiment, the opposing surfaces of the core case 20 and the coil case 50, and the opposing surfaces of the coil case 50 and the substrate case 60 are further fixed with adhesive Y. As shown in Figure 7, on the opposing surfaces of the core case 20 and the coil case 50, a linear adhesive groove 46 is formed on the opposing surface on the core case 20 side. This adhesive groove 46 is arranged along the outer circumference of the core case 20. On the other hand, on the opposing surface on the coil case 50 side, a linear projection 48 is arranged along the outer circumference of the case. After filling the adhesive groove 46 of the core case 20 with adhesive Y, the coil case 50 is placed on top of the core case 20, so that the linear projection 48 of the coil case 50 is inserted into the adhesive groove 46 of the core case 20. With this configuration, the coil case 50 is bonded and fixed to the core case 20 with its movement in the groove width direction restricted by the adhesive groove 46.

[0042] The same applies to the opposing surfaces of the coil case 50 and the substrate case 60. On the opposing surface of the coil case 50, a linear adhesive groove 46 is arranged along the outer circumference of the case, and on the opposing surface of the substrate case 60, a linear projection 48 is arranged along the outer circumference of the case. After filling the adhesive groove 46 of the coil case 50 with adhesive Y, the substrate case 60 is placed on top of the coil case 50, thereby inserting the linear projection 48 of the substrate case 60 into the adhesive groove 46 of the coil case 50.

[0043] In this way, the coil case 50 and the substrate case 60, which are stacked on top of the core case 20, have their movement in the groove width direction restricted by the adhesive groove 46, thereby suppressing displacement between the cases due to external shocks and vibrations. The vertical relationship between the adhesive groove 46 and the linear protrusion 48 provided on the opposing surfaces between each case may be reversed from that of this embodiment. For example, between the core case 20 and the coil case 50, the linear protrusion 48 may be placed on the core case side and the adhesive groove 46 may be formed on the coil case 50 side.

[0044] (Coil case) Next, the coil 2 and coil case 50 will be described in detail with reference to Figures 9 and 10. Figure 9 is a bottom view of the coil case 50 as seen from below. The bottom side of the core case 20 shown in this figure is the side that is positioned facing upwards on the workbench 80 during the assembly process inside the second housing space S2. Figure 10 shows a cross-section of the coil case cut at the position of line XX in Figure 9.

[0045] As shown in Figures 9 and 10, the coil case 50 is a resin plate-shaped member having a predetermined width in the front-rear and left-right directions and a predetermined thickness in the vertical direction. A rectangular opening 51 is formed in the central part of the coil case 50, penetrating the coil case 50 in the vertical direction. The upper surface of the coil case 50 faces the core case 20 when assembled. The upper surface of the coil case 50 is formed in a flat planar shape, and the linear protrusions 48 described above are formed on each of the four sides that constitute the outer periphery. In addition, the above-described plurality of first mounting portions 52 are provided along the outer periphery and inner periphery (the periphery of the opening 51) of the coil case 50.

[0046] The lower surface of the coil case 50 faces the substrate case 60 when assembled. The aforementioned adhesive grooves 46 are formed along the outer and inner circumferences of the lower surface of the coil case 50. In addition, a spiral-shaped coil housing groove 54 is formed between the adhesive grooves 46 on the outer circumference and the adhesive grooves 46 on the inner circumference.

[0047] As an example, the coil housing groove 54 is formed in the shape of a rectangular groove opening on the substrate case 60 side (downward side), and the wire material forming the coil 2 is inserted into the inside. In this embodiment, the coil 2 is made of Litz wire 24 to prevent an increase in winding resistance due to the skin effect. The Litz wire 24 is formed by twisting together multiple wires (thin wires), and when inserted into the coil housing groove 54 of the coil case 50, it forms a spiral-shaped coil 2. In this way, the coil 2 is arranged in a spiral shape on the surface of the coil case 50. Regarding the ends 2A and 2B of the coil 2, one end 2A, which is located on the central space side of the coil 2, is pulled out from the end 54A on the central space side of the coil housing groove 54 through the opening 51 of the coil case 50 to the left end of the upper surface of the coil case 50. On the other hand, the other end 2B on the outer circumference side of the coil 2 is pulled out from the end 54B on the outer circumference side of the coil housing groove 54 to the left end of the lower surface of the coil case 50. When the coil case 50, in which the coil 2 is arranged in this manner, is housed in the second housing space S2 of the case body 12, both ends 2A and 2B of the coil 2 extend toward the partition wall portion 12G of the case body 12, which constitutes the left wall portion of the second housing space S2, and are guided into the first housing space S1 through the insertion hole 13 (see Figure 3) formed in the partition wall portion 12G. Both ends 2A and 2B of the coil 2 guided into the first housing space S1 are connected to the wiring board 9 housed in the first housing space S1.

[0048] (Condition of the coil housed within the coil housing groove) Next, the state in which the coil 2 is housed in the coil housing groove 54 of the coil case 50 will be described. In this embodiment, the dimensions of the depth H and width W of the coil housing groove 54 are set considering the thermal expansion of the coil 2 when energized.

[0049] Figure 11 schematically shows a coil housing groove 500 as a comparative example, rather than the coil housing groove 54 of this embodiment. In the coil housing groove 500, the arc-shaped R portion is indicated by the reference numeral "501", and the straight portion extending linearly from one end of the R portion 501 is indicated by the reference numeral "502". The coil housing groove 500 as a comparative example is formed in a spiral shape on the surface of the coil case (reference numerals omitted). The dimension of the coil housing groove 500 in the groove width direction is set to be larger than the coil diameter D of the coil 2 housed inside. Therefore, when the coil 2 is housed in the coil housing groove 500, a gap exists between the side surface 511, which is arranged opposite to the coil in the groove width direction, and the coil 2. The coil diameter D referred to here is the outer diameter dimension of the coil 2 before it is housed in the coil housing groove 500.

[0050] First, with reference to Figure 11, the mechanism of stress generated in the coil 2 housed in the coil housing groove 500 will be explained. Assuming heat generation during energization, if a rapid temperature change is applied to the coil 2, the coil 2, which has thermally expanded within the coil housing groove 500, will bend, which can cause localized bending of the coil 2. The inventors discovered that the cause of such localized bending is that, in the case of a spiral-shaped coil 2, there is a difference in how the coil 2 bends between the part housed in the R-shaped section 501 of the coil housing groove 500 and the part housed in the straight section 502.

[0051] In other words, in the R-section 501 of the coil housing groove 500, the coil 2 housed inside is bent along the curvature of the R-section. Therefore, although the coil 2 tries to extend in the direction of extension due to thermal expansion, the deflection of the coil 2 is restricted by the curvature of the R-section 501. On the other hand, in the straight section 502 of the coil housing groove 500, when the coil 2 housed inside extends in the direction of extension due to thermal expansion, it is parallel to the side surface 511 and the wall which are arranged opposite each other in the groove width direction within the coil housing groove 500, making it difficult to restrict the deflection of the coil 2. Therefore, in the straight section 502, the same stress as in the R-section 501 does not occur in the coil 2, so the deflection of the coil 2 during thermal expansion is not restricted, and the amount of deflection in the straight section 502 is greater than the amount of deflection that occurs in the R-section 501. As a result, the amount of deflection of the coil 2 changes significantly, especially at the boundary between the R-section 501 and the straight section 502, resulting in localized bending of the coil 2.

[0052] Therefore, the inventor devised a method to alleviate the stress on the coil 2 within the coil housing groove 54 by defining the depth H and width W of the coil housing groove 54 relative to the coil diameter D.

[0053] The coil housing groove 54 according to this embodiment will now be described in detail with reference to Figure 12. As shown in this figure, the coil housing groove 54 is formed in a rectangular groove shape by a pair of side surfaces 541 arranged opposite each other in the groove width direction and a bottom surface 542 connecting the pair of side surfaces 541. When the substrate case 60 is placed on top of the coil case 50, the opening 543 of the coil housing groove 54 is closed by the opposing surface of the substrate case 60. Note that the shape of the coil housing groove is not limited to a rectangular groove shape. For example, the bottom surface of the groove may be composed of an arc-shaped curved surface.

[0054] In this embodiment, the depth H of the coil housing groove 54 is set to be greater than the coil diameter D of the coil 2. Also, the width W of the coil housing groove 54 is set to be smaller than the coil diameter D.

[0055] By setting the depth H of the coil housing groove 54 to be greater than the coil diameter D of the coil 2, a deflection allowance H1 is provided within the coil housing groove 54 that allows for deflection of the coil 2 in the depth direction during thermal expansion. Therefore, it is possible to allow the coil 2, which has expanded due to thermal expansion, to deflect in the depth direction of the coil housing groove 54, thereby preventing part or all of the coil 2 from falling out of the coil case 50.

[0056] On the other hand, by setting the width W of the coil housing groove 54 to be smaller than the coil diameter D, the coil 2 abuts against the side surfaces 541 on both sides in the width direction of the coil housing groove 54 while housed within the coil housing groove 54. In this state, the coil 2 is housed in an elliptical shape with the diameter in the depth direction of the coil housing groove 54 as its major axis. By housing the coil 2 in the coil housing groove 54 in this elliptical shape, the deflection of the coil 2 in the width direction of the coil housing groove 54 can be suppressed.

[0057] In this configuration, the pair of side surfaces 541 can restrict the coil 2, which expands due to thermal expansion, from bending in the groove width direction. Furthermore, by guiding both sides of the coil 2 with the pair of side surfaces 541, it is possible to encourage the coil 2, which expands due to thermal expansion, to move along the extending direction of the coil housing groove 54.

[0058] In this way, when the coil 2 expands due to electrical current, it is possible to promote the movement of the coil 2 along the direction of extension of the groove and to allow deflection in the depth direction of the groove within the coil housing groove 54. Therefore, the stress caused by the suppression of deflection of the coil 2 in the R portion of the coil housing groove 54 is relieved by deflection in the depth direction of the groove, making it less likely for the coil 2 to bend locally. In addition, during the assembly process, the front and back of the coil case 50 can be turned inside out while the coil 2 is held in the coil housing groove 54.

[0059] Here, an example of the coil diameter D of coil 2 and the dimensions of the coil housing groove 54 is shown below. The coil diameter D is the outer diameter of coil 2 before it is housed in the coil housing groove 54. The coil diameter D varies depending on the capacity range of the non-contact charging system (coil unit), but one example is 3.1 mm to 3.6 mm. The coil deflection allowance H1 is set within the allowable range of electrical performance because deflection of coil 2 leads to a decrease in electrical performance. An example of a setting value for the coil deflection allowance H1 is about 0.3 mm. The depth of the coil housing groove 54 is the coil diameter D plus the coil deflection allowance H1.

[0060] The width W of the coil housing groove 54 is preferably set to be smaller than the coil diameter D of the coil 2, with the difference between the width W of the coil housing groove 54 and the coil diameter D of the coil 2 being within the range of 0.1 mm to 0.3 mm, and more preferably set to 0.2 mm (the width W of the coil housing groove 54 is set to be 0.1 mm smaller on each side than the coil diameter D).

[0061] When the coil 2 is constructed of Litz wire, the type of covering material 21 covering the surface is not particularly limited. For example, the covering material 21 may be made of an insulating film material containing polyester, such as Mylar Litz wire, or it may be made of fibers containing polyester, such as those. When the covering material 21 is made of an insulating film material, it is preferable in that the insulation distance of the coil 2 can be easily secured and the coil case 50 can be made smaller. Furthermore, when the covering material 21 is made of fibers, it is preferable in that it can be deformed more flexibly compared to film-covered Litz wire, thus suppressing localized stress on the coil 2 during thermal expansion. In one example of this embodiment, the covering material 21 of the coil 2 is made of polyester fibers.

[0062] (Circuit board case) Next, the details of the substrate case 60 will be described with reference to Figure 13. The substrate case 60 is a resin plate-shaped member having a predetermined width in the front-to-back and left-to-right directions and a predetermined thickness in the vertical direction. A rectangular opening 62 is formed in the central part of the substrate case 60, penetrating the substrate case 60 in the vertical direction. The upper surface of the substrate case 60 faces the coil case 50 when assembled. The upper surface of the substrate case 60 is formed in a flat planar shape and is configured to close the opening 543 of the coil housing groove 54 described above. In addition, the linear protrusions 48 described above are formed on each of the four sides that constitute the outer periphery of the upper surface of the substrate case 60. Furthermore, the plurality of second mounting parts 64 described above are provided along the outer periphery and inner periphery (the periphery of the opening 62) of the substrate case 60.

[0063] The outer and inner periphery (the periphery of the opening 62) of the substrate case 60 are further provided with the aforementioned multiple fixing legs 66. Each fixing leg 66 is formed in a columnar shape and extends from the substrate case 60 towards the case body 12.

[0064] The lower surface of the circuit board case 60 faces the second cover member 16 when assembled. The surface of the lower part of the circuit board case 60 is divided into a grid pattern by a plurality of ribs 68 that protrude toward the second cover member 16. The tips of the ribs 68 are configured to support the second cover member 16 from the inside of the case body 12 when the second cover member 16 is placed on top of the circuit board case 60.

[0065] Furthermore, the sensor substrate 70 is housed within the compartment partitioned by the ribs 68. The sensor coil section 6, whose energization is controlled by the sensor control unit 5B described above, is mounted on the sensor substrate 70. With this configuration, the sensor substrate 70 is surrounded by the ribs 68, thus protecting the sensor substrate 70 from external impacts.

[0066] The components of the coil unit 1, including the core case 20, core 40, coil case 50, coil 2, and substrate case 60, have been described above. These components can be assembled in this order into the second housing space S2 of the case body 12.

[0067] Specifically, the case body 12 is placed on the workbench 80 (see Figure 7, etc.) with the second opening 122 of the second storage space S2 facing upwards, and then the core case 20 is fixed to the upper wall portion 12E. After housing the core 40 in the core case 20 and sealing it with sealing resin X, the coil case 50 is stacked on top and assembled. The coil case 50 may be placed on top of the core case 20 with the coil 2 already held in place, or the coil case 50 may be placed on top of the core case 20 and then the coil 2 may be placed in the coil housing groove 54. After that, the substrate case 60 is placed on top of the coil case 50, and the core case 20, coil case 50 and substrate case 60 are fixed using resin screws 44 and adhesive Y. Finally, the second opening 122 is closed with the second cover member 16, completing the assembly into the second storage space S2.

[0068] (Mechanism of action and effect) In the second housing space S2 of the case body 12, a core case 20 housing a flat core 40 is fixed to the case body 12, and the core 40, coil case 50, and coil 2 are stacked on top of the core case 20 in this order. With this configuration, the core 40 of the coil unit 1 is housed in a core case 20 which is provided separately from the coil case 50, so it can be fixed to the case body 12 without being affected by the coil case 50. This makes it possible to suppress stress on the core 40. In addition, since the core 40, coil case 50, and coil 2 are stacked on top of the core case 20 in this order, it becomes possible to assemble them to the case body 12 by working from one direction, simplifying the assembly process.

[0069] In the core case 20, each core 40 is housed surrounded by the wall portion 32 of the core case 20, and the space inside the wall portion 32 is sealed with sealing resin X. Therefore, the sealing resin X is interposed between the core 40 and the wall portion 32, and the sealing resin X acts as a buffer to absorb deformation caused by thermal expansion of the core 40. It also protects the core 40 from external impacts.

[0070] A protrusion 18 on the case body 12 contacts the core 40 through a through-hole 24 in the core case 20. As a result, heat generated in the core 40 is efficiently transferred to the case body 12 via the protrusion 18, thereby improving the cooling efficiency of the core 40.

[0071] The core case 20 and the coil case 50 are fixed together at multiple fixing points at the ends located on the inner and outer circumference sides of the coil 2. In this embodiment, since each of these fixing points is secured by a resin screw 44, it is possible to suppress the magnetic flux generated by the coil 2 from reaching the case body 12. Therefore, even if the case body 12 is made of a ferromagnetic material such as steel, it is possible to suppress the heat generation of the case body 12 due to the electromagnetic induction action of the coil 2. Furthermore, since the fixing is done using resin screws 44 and adhesive Y, the joint strength of the fixing part can be made equivalent to that of screw fastening with metal screws.

[0072] The coil case 50 and the core case 20 are fixed to each other by filling an adhesive groove 46 formed on the core case 20 side with adhesive Y and inserting a linear protrusion 48 formed on the core case 20 side into the adhesive groove 46. This suppresses displacement between the cases due to external shocks and vibrations.

[0073] In the circuit board case 60, the sensor circuit board 70 is surrounded by ribs 68, thus protecting the sensor circuit board 70 from external impacts. In addition, the second cover member 16 is supported from the inside of the coil unit 1 by the grid-like ribs 68, preventing the second cover member 16 from cracking due to external loads.

[0074] The circuit board case 60 is fixed to the case body 12 by adhesive Y via columnar fixing legs 66 that extend toward the case body 12. This allows the core case 20 and coil case 50, which are positioned between the case body 12 and the sensor circuit board 70, to be held stably, and prevents displacement of the core 40 and coil 2 due to external shocks or vibrations during operation.

[0075] In this embodiment, a spiral-shaped coil housing groove 54 is formed on the surface of a flat coil case 50, and by housing the coil 2 in the coil housing groove 54, the coil 2 is arranged in a spiral shape on the surface of the coil case 50.

[0076] The coil housing groove 54 is configured such that its side surfaces 541 on both sides in the width direction contact the side surfaces of the coil 2 housed inside. Furthermore, the depth H of the coil housing groove 54 is set to be greater than the coil diameter D of the coil 2, and a deflection allowance H1 is provided to allow the coil 2 to deflect in the depth direction of the coil housing groove 54 when the coil 2 expands due to thermal expansion.

[0077] Here, when the coil 2 is energized, it will bend due to thermal expansion caused by heat generation. By bringing the coil 2 into contact with the side surfaces 541 on both sides in the width direction of the coil housing groove 54 while it is housed in the coil housing groove 54, the bending in the groove width direction can be restricted, and the movement of the coil 2 along the extension direction of the groove can be promoted. By providing a bending allowance H1, when the coil 2 expands due to thermal expansion, the movement of the coil 2 along the extension direction of the coil housing groove 54 can be promoted, and bending in the depth direction of the groove can be allowed within the coil housing groove 54. In this configuration, the stress caused by the suppression of bending of the coil 2 in the R portion of the coil housing groove 54 is relieved by bending in the depth direction of the groove, and local bending of the coil 2 can be suppressed. This makes it possible to suppress the concentration of stress in a part of the coil 2 due to thermal expansion when energized.

[0078] Furthermore, the width W of the coil housing groove 54 is set to be smaller than the coil diameter D, causing the shape of the housed coil 2 to be deformed into an elliptical shape with the diameter in the depth direction of the coil housing groove 54 as its major axis. This makes it possible to more effectively promote the movement of the coil 2 along the extending direction of the coil housing groove 54.

[0079] Since coil 2 is composed of Litz wire covered with polyester fibers, it can deform more flexibly compared to Litz wire covered with a film, such as Mylar Litz wire. This effectively suppresses localized stress on parts of coil 2 caused by bending during thermal expansion.

[0080] By closing the opening 543 of the coil housing groove 54 with the substrate case 60 (coil case cover), it is possible to suppress the portion of the coil housing groove 54 that has bent in the depth direction from popping out of the groove and bending when the coil 2 undergoes thermal expansion. [supplementary explanation]

[0081] In the above embodiment, the focus was on the receiving coil unit 1B located in the electric vehicle 200, but the configuration of the present invention can also be applied to the transmitting coil unit 1A located on the ground side. [Explanation of Symbols]

[0082] 1 coil unit (1A, 1B) 2 coils 10 Device Cases 50 Coil Cases 54 Coil housing groove 60 PCB case (coil case cover) 100 contactless charging systems 200 Electric Vehicles 300 batteries D coil diameter Depth of the coil housing groove H1 Flexibility W width of coil housing groove

Claims

1. A coil unit located on the ground or in an electric vehicle in a contactless charging system that transmits power between a power-transmitting coil unit located on the ground and a power-receiving coil unit located in an electric vehicle, and charges a battery mounted in the electric vehicle, A flat coil case, A coil is housed in a coil housing groove formed in a spiral shape on the surface of the coil case, and the coil is arranged in a spiral shape on the surface of the coil case, The device comprises the coil case and the device case for housing the coil, The coil, while housed within the coil housing groove, abuts against the side surfaces on both sides in the width direction of the coil housing groove. By setting the depth of the coil housing groove to be greater than the coil diameter of the coil, a deflection allowance is provided within the coil housing groove to allow the coil to deflect in the depth direction of the coil housing groove when the coil expands due to thermal expansion. The width of the coil housing groove is set to be smaller than the coil diameter of the coil. A coil unit in which the coil is housed in the coil housing groove in an elliptical shape with the diameter in the depth direction of the coil housing groove as its major axis, and when the coil expands due to thermal expansion, movement in the direction of extension of the coil housing groove is permitted.

2. The coil unit according to claim 1, wherein the width of the coil housing groove is set to be smaller than the coil diameter, with the difference between the width of the coil and the coil diameter being within the range of 0.1 mm to 0.3 mm.

3. The coil unit according to claim 1 or 2, wherein the coil is made of litz wire covered with polyester fibers.

4. The coil unit according to claim 1 or 2, further comprising a coil case cover attached to the coil case and closing the opening of the coil housing groove.

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