Coil device and cooling mechanism

Abstract

To enable a coil to be cooled with a simple configuration.SOLUTION: A coil device 1 comprises a coil 10, a housing 30 enclosing coil 10, and a cooling mechanism 50 for cooling the coil 10. The cooling mechanism 50 having a porous structure having a plurality of fine pores, includes a water absorption member 51 in thermal contact with an outer face 33b of the housing 30, and a water supply mechanism 52 configured to supply the water absorption member 51 with water W.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a coil device and a cooling mechanism. [Background technology]

[0002] Patent Document 1 discloses a technique for cooling a coil device. The contactless power transfer device described in Patent Document 1 has a liquid-type cooling mechanism. Specifically, this contactless power transfer device includes a coil, a housing that houses the coil, a flow path formed inside the top plate of the housing, and a pump that circulates liquid through the flow path in the housing. Heat generated by the coil is absorbed by the liquid flowing through the flow path in the housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-228123 Summary of the Invention [Problem to be solved by the invention]

[0004] However, providing such a cooling mechanism requires the provision of a flow path in the housing, and additional equipment such as a pump to circulate the liquid through the flow path, which increases the size and complexity of the device configuration, potentially increasing the burden of inspection and maintenance of the device and raising costs.

[0005] The present disclosure describes a coil device and a cooling mechanism that can cool a coil with a simple configuration. [Means for solving the problem]

[0006] The coil device of the present disclosure comprises a coil, a housing that houses the coil, and a cooling mechanism for cooling the coil, the cooling mechanism being formed by a porous structure including a plurality of pores and having a water absorption member that is in thermal contact with the outer surface of the housing, and a water supply mechanism configured to supply water to the water absorption member.

[0007] In this coil device, the water-absorbing member, which has a porous structure, absorbs water supplied from a water supply mechanism. Because this water-absorbing member is in thermal contact with the outer surface of the housing, heat generated by the coil housed in the housing is transferred to the water-absorbing member. The water absorbed by the water-absorbing member then evaporates, absorbing heat from the surrounding area and cooling the housing and the coil inside the housing. This configuration makes it possible to cool the coil simply by supplying water to the water-absorbing member, without requiring an additional device such as a pump to circulate the coolant.

[0008] In some embodiments, the water absorbing member may be removably attached to the outer surface of the housing, which allows for easy maintenance such as replacement of the water absorbing member, thereby improving maintainability.

[0009] In some embodiments, the housing has a base and a cover that faces the base with the coil interposed therebetween and defines an internal space for accommodating the coil between the base and the cover, and the water-absorbing member may be disposed on the outer surface of the cover in a portion that overlaps with the coil in the opposing direction of the base and the cover. In this case, the water-absorbing member is disposed in a portion that is particularly likely to become hot, making it possible to effectively cool the housing and the coil inside the housing.

[0010] In some embodiments, the water supply mechanism may include a water storage unit disposed around the housing and having a water storage space for storing water, and a delivery unit configured to deliver the water stored in the water storage space to the water absorption member. In this case, the water supply mechanism that supplies water to the water absorption member can be easily realized.

[0011] In some embodiments, the transfer section may include a separate water-absorbent member having a porous structure including a plurality of pores, and the separate water-absorbent member may be in contact with the water storage space and the water-absorbent member. In this case, water stored in the water storage space is absorbed from the water storage space by the separate water-absorbent member and transferred from the separate water-absorbent member to the water-absorbent member. This configuration makes it easy to transfer water stored in the water storage space to the water-absorbent member.

[0012] In some embodiments, the transfer section includes a separate water-absorbent member having a porous structure including a plurality of pores and a deformable member attached to the separate water-absorbent member. The deformable member may be configured to be deformable from a first configuration in which the separate water-absorbent member is in contact with both the water storage space and the water-absorbent member to a second configuration in which the separate water-absorbent member is spaced apart from at least one of the water storage space and the water-absorbent member. When the deformable member is in the first configuration, the separate water-absorbent member is in contact with both the water storage space and the water-absorbent member, so that water in the water storage space is transferred to the water-absorbent member via the separate water-absorbent member. On the other hand, when the deformable member is in the second configuration, the separate water-absorbent member is spaced apart from at least one of the water storage space and the water-absorbent member, so that water in the water storage space is not transferred to the water-absorbent member. Therefore, with the above configuration, water can be supplied to the water-absorbent member only when it is necessary, and water supply to the water-absorbent member can be stopped when water supply to the water-absorbent member is not necessary. In this way, by stopping the supply of water to the water absorbing member when it is not necessary to supply water to the water absorbing member, it is possible to prevent water from being consumed more than necessary.

[0013] In some embodiments, the deformable member may be a heat-sensitive deformable member that is deformable in response to a temperature rise due to heat transfer from the coil or induction heating caused by a magnetic field generated by the coil, and may deform to the second form when the temperature of the deformable member is in a first temperature range, and to the first form when the temperature of the deformable member is in a second temperature range that is higher than the first temperature range. In this case, the first form and the second form can be automatically switched in response to the temperature of the coil, making it possible to easily realize a configuration that stops the supply of water to the water absorbing member when it is not necessary (for example, when the coil is not performing a contactless power supply operation).

[0014] In some embodiments, the separate water-absorbing member may be in thermal contact with the outer surface of the housing. In this case, heat generated by the coil housed in the housing is also transferred to the separate water-absorbing member, and the water absorbed by the separate water-absorbing member evaporates and absorbs heat from the surrounding area, thereby cooling the housing and the coil inside the housing. In other words, with this configuration, not only the water absorbed by the separate water-absorbing member but also the water absorbed by the separate water-absorbing member can be used to cool the housing and the coil inside the housing. This allows the coil to be cooled effectively.

[0015] In some embodiments, the water supply mechanism includes a tank having a storage space for storing water. The tank is provided with a flow path connecting the storage space and a water storage space through which water flows, and a valve provided in the flow path. The valve may be configured to open the flow path when the water level in the water storage space is below a reference water level. In this case, water can be automatically supplied from the storage space of the tank to the water storage space when the water level in the water storage space is insufficient. This prevents the water level in the water storage space from becoming insufficient and more reliably supplies water from the water storage space to the water absorbent member.

[0016] The cooling mechanism of the present disclosure is a cooling mechanism for cooling a coil used in a coil device, and includes a water-absorbing member that is formed of a porous structure including a plurality of pores and is capable of thermally contacting the outer surface of a housing that houses the coil, and a water supply mechanism that is configured to supply water to the water-absorbing member.

[0017] In this cooling mechanism, a water-absorbing member with a porous structure absorbs water supplied from a water supply mechanism. This water-absorbing member is placed in thermal contact with the outer surface of the housing, so that heat generated by the coil housed in the housing is transferred to the water-absorbing member. The water absorbed by the water-absorbing member then evaporates, absorbing heat from the surrounding area and cooling the housing and the coil inside the housing. This configuration makes it possible to cool the coil simply by supplying water to the water-absorbing member, without requiring an additional device such as a pump to circulate the coolant. [Effects of the Invention]

[0018] According to some aspects of the present disclosure, a coil device and a cooling mechanism capable of cooling a coil with a simple configuration are provided. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a contactless power supply system including a coil device according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing the coil device of FIG. [Figure 3] FIG. 3 is a plan view showing the coil device of FIG. [Figure 4] FIG. 4 is a cross-sectional view showing the coil device of FIG. [Figure 5] FIG. 5 is an enlarged perspective view of part A in FIG. [Figure 6] FIG. 6 is an enlarged perspective view of part B in FIG. [Figure 7] FIG. 7 is a perspective view showing a coil device according to a first modified example. [Figure 8] FIG. 8 is a perspective view showing the coil device shown in FIG. [Figure 9] FIG. 9 is a perspective view showing a coil device according to a second modified example. [Figure 10] FIG. 10 is a cross-sectional view showing the coil device shown in FIG. [Figure 11] Fig. 11(a) is a cross-sectional view showing a second configuration of the transfer section of the coil device according to the third modified example, and Fig. 11(b) is a cross-sectional view showing a first configuration of the transfer section shown in Fig. 11(a). [Figure 12] Fig. 12(a) is a cross-sectional view showing a second configuration of the delivery section of the coil device according to the fourth modified example, and Fig. 12(b) is a cross-sectional view showing a first configuration of the delivery section shown in Fig. 12(a). DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment in which a coil device according to the present disclosure is applied to a power transmission coil device that transmits power in a contactless power supply system will be described with reference to the drawings. In the description of the drawings, identical elements are denoted by the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0021] As shown in FIG. 1, the contactless power transfer system 100 includes a power transmitting coil device 1 (coil device) and a power receiving coil device 2. The contactless power transfer system 100 charges a battery mounted on a moving object V, such as a vehicle or a drone. The power transmitting coil device 1 is installed, for example, on an outdoor road surface G. The power transmitting coil device 1 may also be installed (buried) under the road surface G. The power transmitting coil device 1 generates a magnetic field by AC power supplied from a circuit. The power receiving coil device 2 is installed, for example, on the moving object V.

[0022] The power transmitting coil device 1 transmits power contactlessly to the power receiving coil device 2 of the moving object V that has arrived at the power supply position (i.e., the position where the power transmitting coil device 1 and the power receiving coil device 2 face each other) by utilizing magnetic coupling between coils such as a magnetic field resonance method or an electromagnetic induction method. As a result, the power receiving coil device 2 receives power. Note that the contactless power supply method is not limited to one that utilizes magnetic coupling, and may be, for example, an electric field resonance method.

[0023] As shown in FIGS. 2 and 3, the power transmitting coil device 1 includes a power transmitting coil 10 (coil), a housing 30, and a cooling mechanism 50. The housing 30 is, for example, a flat, box-shaped member. The housing 30 houses at least the power transmitting coil 10. As shown in FIG. 4, the housing 30 includes a base 31 and a cover 32. The base 31 is a rectangular, plate-shaped member placed on a road surface G. The power transmitting coil 10 is installed on the base 31. The base 31 ensures the rigidity of the power transmitting coil device 1 as a whole. The base 31 is formed, for example, from a non-magnetic, electrically conductive material. The base 31 may be formed, for example, from aluminum, which is a metal material with low magnetic permeability. By selecting such a material for the base 31, the base 31 can block leakage of a leakage magnetic field to the outside.

[0024] The cover 32 has, for example, a rectangular box shape with an open bottom. The cover 32 is disposed opposite the base 31 across the power transmitting coil 10 and is airtightly attached to the base 31 so as to cover the power transmitting coil 10. The gap between the base 31 and the cover 32 is sealed, for example, with a sealant. The cover 32 may be removably attached to the base 31 or may be permanently fixed. The space enclosed (defined) by the base 31 and the cover 32 defines an internal space R1 for accommodating the power transmitting coil 10. The cover 32 protects the power transmitting coil 10 and other components accommodated within the internal space R1. The cover 32 is made of, for example, a non-magnetic and non-conductive material. The cover 32 may be made of, for example, a resin material such as FRP (Fiber Reinforced Plastic).

[0025] As shown in FIG. 4 , the cover 32 has a top wall 33 that faces the base 31 across the power transmission coil 10, and a side wall 34 that extends from the periphery of the top wall 33 to the base 31. The top wall 33 is a rectangular plate that is slightly smaller than the base 31. The top wall 33 includes an inner surface 33a that faces the inside of the housing 30 and an outer surface 33b that faces the outside of the housing 30. The inner surface 33a and the outer surface 33b are, for example, flat surfaces that extend parallel to each other. The normal directions of the inner surface 33a and the outer surface 33b coincide with, for example, the facing direction D1 between the base 31 and the cover 32. Note that, in the following description, the base 31 side in the facing direction D1 may be referred to as "bottom," and the cover 32 side in the facing direction D1 may be referred to as "top."

[0026] The sidewall 34 includes an inner surface 34a facing the inside of the housing 30 and an outer surface 34b facing the outside of the housing 30. The inner surface 34a and the outer surface 34b are, for example, planes extending parallel to each other and extending in a direction intersecting the inner surface 33a and the outer surface 33b. The outer surface 34b of the sidewall 34 and the outer surface 33b of the top wall 33 form the outer surface of the housing 30. The sidewall 34 also includes an inclined portion P1 that slopes downward from the top wall 33 and widens outward, and a standing portion P2 that extends downward from the lower end of the inclined portion P1. The inclined portion P1 is inclined to connect the top wall 33 and the water storage space R2 of the water moat 53 provided around the periphery of the housing 30. Therefore, rainwater, etc. dripping onto the outer surface 34b of the inclined portion P1 flows down the outer surface 34b and is guided to the water storage space R2. The standing portion P2 extends linearly from the lower end of the inclined portion P1 along the facing direction D1 and stands perpendicular to the cover 32. The standing portion P2 is disposed at a position where it comes into contact with the annular wall portion 53b of the moat 53, for example.

[0027] The power transmitting coil 10 generates a magnetic field using AC power supplied from a circuit. The power transmitting coil 10 is formed, for example, by a conductor wound in a spiral shape on the same plane. The power transmitting coil 10 is, for example, a circular coil. In a circular coil, the conductor is wound in a winding direction so as to surround a winding axis (coil axis). The winding axis coincides, for example, with the normal direction to the inner surface 33a and the outer surface 33b of the top wall 33. The power transmitting coil 10 may be a single-layer or multi-layer coil as long as the conductor is wound in a spiral shape. The shape of the power transmitting coil 10 as viewed in the winding axis direction can be various, such as rectangular, circular, or elliptical. The conductor may be, for example, a Litz wire made by twisting together multiple insulated conductor wires, or a Litz wire that reduces high-frequency resistance due to the skin effect. The conductor may be, for example, a solid wire made of copper or aluminum.

[0028] As shown in FIG. 4 , the power transmission coil 10 is fitted into a groove in a bobbin 11, which is, for example, a flat-plate member. The bobbin 11 is made of a non-magnetic and non-conductive material. The bobbin 11 may be made of, for example, silicone or polyphenylene sulfide resin. The position of the power transmission coil 10 within the housing 30 is determined by fixing the bobbin 11 to a base 31. A ferrite plate 12 is provided between the bobbin 11 and the base 31. The ferrite plate 12 is, for example, a rectangular flat-plate ferrite core. The ferrite plate 12 is a magnetic material that directs and concentrates magnetic field lines generated by the power transmission coil 10. The ferrite plate 12 is held by a coil holding member 13. The coil holding member 13 is, for example, a hollow member, and the ferrite plate 12 is disposed in the hollow portion of the coil holding member 13.

[0029] The cooling mechanism 50 shown in FIG. 2 is provided to cool the power transmission coil 10. The cooling mechanism 50 includes a water supply spacer 51 capable of absorbing water W and a water supply mechanism 52 configured to supply water W to the water supply spacer 51. The water supply spacer 51 is a water-absorbing member having a porous structure with a plurality of pores. The pores are formed inside the water supply spacer 51 and open on the surface of the water supply spacer 51. The water supply spacer 51 has the water-absorbing property capable of absorbing water W due to the presence of the plurality of pores. Here, "water" may be water containing substances such as additives and / or impurities, or pure water that does not contain such substances. Examples of "water" include tap water, rainwater, river water, groundwater, and distilled water. The water supply spacer 51 may have water-retentive properties that allow it to retain absorbed moisture. For example, the water supply spacer 51 may be a sponge made of silicone, cellulose, or the like. The porous structure of the water supply spacer 51 may be formed by overlapping a plurality of fibers. For example, the water supply spacer 51 may be a nonwoven fabric made of rayon fiber, etc. In this embodiment, a case where a silicone sponge is used as the water supply spacer 51 is exemplified.

[0030] As shown in FIG. 2, the water supply spacer 51 has, for example, a rectangular plate shape (a rectangular parallelepiped) and is arranged to overlap the housing 30. Specifically, as shown in FIGS. 3 and 4, the water supply spacer 51 is arranged to cover the outer surface 33b of the cover 32. More specifically, the water supply spacer 51 is arranged to cover a portion of the outer surface 33b that overlaps with the power transmitting coil 10 in the facing direction D1. In this embodiment, the water supply spacer 51 covers the entire outer surface 33b, but this does not necessarily have to be the case. For example, the water supply spacer 51 may cover only a portion of the outer surface 33b, including the portion that overlaps with the power transmitting coil 10 in the facing direction D1. The area of ​​the water supply spacer 51 as viewed from the facing direction D1 may be the same as or smaller than the area of ​​the outer surface 33b. Alternatively, the area of ​​the water supply spacer 51 as viewed from the facing direction D1 may be larger than the area of ​​the outer surface 33b. The thickness of the water supply spacer 51 may be, for example, 1 mm or more and 5 mm or less.

[0031] The lower surface 51a of the water supply spacer 51 is in thermal contact with the outer surface 33b of the cover 32. Here, "thermal contact" refers to two components being in direct contact or indirect contact via another component, allowing heat conduction between the two components. In this embodiment, the lower surface 51a of the water supply spacer 51 is in direct contact with the outer surface 33b of the cover 32 and is in close contact with the outer surface 33b. However, the lower surface 51a of the water supply spacer 51 may be in indirect contact with the outer surface 33b of the cover 32 via, for example, a thermally conductive foreign object (e.g., a metal foreign object) that may adhere to the outer surface 33b. In other words, the foreign object may be present between the lower surface 51a and the outer surface 33b. In this embodiment, the lower surface 51a of the water supply spacer 51 is not bonded to the outer surface 33b of the cover 32, and is therefore easily removable from the housing 30. However, the lower surface 51a of the water supply spacer 51 may be bonded to the outer surface 33b with an adhesive or the like, and may be made unremovable from the housing 30.

[0032] The water supply spacer 51 absorbs water W supplied from the water supply mechanism 52, thereby maintaining the presence of water W on the outer surface 33b of the cover 32. Because the water supply spacer 51 has a porous structure, it has the function of diffusing the water W inside the water supply spacer 51 by capillary action. As a result, the water supply spacer 51 can cause the water W to be present over a wide area on the outer surface 33b of the cover 32. Because the water supply spacer 51 is in thermal contact with the outer surface 33b of the cover 32, heat generated by the power transmission coil 10 housed in the housing 30 is transferred via the cover 32 to the water W absorbed in the water supply spacer 51. At this time, the water W in the water supply spacer 51 evaporates and absorbs heat from the surroundings, thereby cooling the housing 30 and the power transmission coil 10 inside the housing 30. Specifically, the housing 30 is directly cooled by the heat absorbed from the housing 30, and accordingly, heat from the power transmission coil 10 is transferred to the housing 30, thereby indirectly cooling the power transmission coil 10. Therefore, supplying water W to the water supply spacer 51 on the outer surface 33b of the cover 32 has the effect of cooling the power transmission coil 10. If a foreign object is present between the joint portion 54 and the outer surface 34b, the effect of cooling the foreign object is also obtained.

[0033] From the viewpoint of efficiently obtaining the cooling effect of the water supply spacer 51 on the power transmission coil 10, it is suitable for the water supply spacer 51 to be heat resistant. Here, heat resistance means that the water supply spacer 51 has a property that makes it difficult for the water supply spacer 51 to undergo plastic deformation when the temperature of the housing 30 rises. The heat resistance of the water supply spacer 51 allows the water supply spacer 51 to maintain a wide range of thermal contact with the outer surface 33b of the cover 32, thereby enabling efficient cooling of the housing 30 and the power transmission coil 10 inside the housing 30. Furthermore, because electromagnetic coupling between the power transmission coil device 1 and the power receiving coil device 2 occurs through the cover 32 and the water supply spacer 51 on the cover 32, it is suitable for the water supply spacer 51 to be made of a nonmagnetic and nonconductive material that does not affect electromagnetic coupling, so that contactless power transfer can be performed with high efficiency.

[0034] As shown in FIG. 2, water supply mechanism 52 includes water moat 53, joint 54, tank 55, and sensor 56. Water moat 53 is a water storage unit provided to store water W to be supplied to water supply spacer 51. Examples of water W stored in water moat 53 include water supplied from tank 55 and rainwater. Water moat 53 is, for example, a tray-shaped member capable of accommodating housing 30. Water moat 53 may be made of a nonmagnetic and nonconductive material (e.g., FRP) that does not affect electromagnetic coupling. As shown in FIG. 4, water moat 53 includes a rectangular plate-shaped bottom 53a and an annular wall 53b that extends from the periphery of bottom 53a and surrounds the center of bottom 53a.

[0035] The bottom 53a has an area slightly larger than that of the housing 30 when viewed from the facing direction D1. The base 31 of the housing 30 is placed on the center of the bottom 53a. The annular wall 53b is arranged to surround the housing 30 placed on the bottom 53a. The annular wall 53b has a rectangular ring shape when viewed from the facing direction D1. The annular wall 53b is, for example, provided perpendicular to the bottom 53a and along the facing direction D1. The space surrounded by the bottom 53a and the annular wall 53b forms a water storage space R2 for storing water W. The water storage space R2 is, for example, located lower than the water supply spacer 51 on the outer surface 33b of the cover 32. In other words, the water storage space R2 is located on the bottom 53a side relative to the water supply spacer 51 in the facing direction D1. The water storage space R2 is a rectangular parallelepiped space that is open upward (i.e., toward the water supply spacer 51 in the facing direction D1). The spacing between the annular wall portions 53b, i.e., the distance between the two wall portions that make up the annular wall portion 53b, may be set to, for example, 22 mm.

[0036] The joint portion 54 is provided as a transfer portion that transfers the water W stored in the water storage space R2 to the water supply spacer 51. The joint portion 54 is a water-absorbent member (another water-absorbent member) formed with a porous structure having a plurality of pores, and, like the water supply spacer 51, has water-absorbency that allows it to absorb water W. Like the water supply spacer 51, the joint portion 54 may have water-retentive properties and heat resistance in addition to water absorption, and may be non-magnetic and non-conductive. The joint portion 54 may be formed of the same material as the water supply spacer 51, or may be formed of a different material from the water supply spacer 51. In this embodiment, the joint portion 54 is formed of a rayon fiber nonwoven fabric, as an example. The joint portion 54 may also be formed of the same silicone-based sponge as the water supply spacer 51.

[0037] The joint portion 54 has, for example, a rectangular sheet shape. As shown in FIGS. 4 and 5, the joint portion 54 extends upward from the water storage space R2 to the water supply spacer 51 outside the housing 30, connecting the water storage space R2 and the water supply spacer 51. The lower end 54b of the joint portion 54 (i.e., one end on the water storage space R2 side in the facing direction D1) is in contact with the water storage space R2. The lower end 54b of the joint portion 54 in contact with the water storage space R2 means that the lower end 54b of the joint portion 54 is disposed inside the water storage space R2. Specifically, the lower end 54b of the joint portion 54 is in a position where it can come into contact with the water W stored in the water storage space R2, i.e., a position lower than the lowest water level (reference water level) of the water W stored in the water moat 53. In this embodiment, the lower end 54b of the joint part 54 is positioned so as to contact the bottom 53a of the water moat 53, but it does not necessarily have to be positioned so as to contact the bottom 53a. For example, the lower end 54b of the joint part 54 may be spaced apart in the facing direction D1 from the bottom 53a of the water moat 53 within a range that allows it to contact the water W in the water storage space R2.

[0038] The upper end 54a of the joint portion 54 (i.e., the other end on the water supply spacer 51 side in the facing direction D1) is, for example, in contact with the side surface 51b of the water supply spacer 51. The upper end 54a of the joint portion 54 may be in contact with the upper surface 51c of the water supply spacer 51. The upper surface 51c of the water supply spacer 51 is located opposite the lower surface 51a and faces away from the power transmission coil 10 in the facing direction D1. The side surface 51b of the water supply spacer 51 is a surface that connects the lower surface 51a and the upper surface 51c in the facing direction D1. The joint portion 54 is in thermal contact with, for example, the inclined portion P1 of the side wall 34 of the cover 32 between the water storage space R2 and the water supply spacer 51. Specifically, the joint portion 54 is in direct contact with the outer surface 34b of the inclined portion P1 and is in close contact with the outer surface 34b. The joint portion 54 may be in indirect contact with the outer surface 34b via, for example, a thermally conductive foreign object that may adhere to the outer surface 34b. In other words, the foreign object may be present between the joint portion 54 and the outer surface 34b. The lower end 54b and the upper end 54a of the joint portion 54 may be joined to the bottom 53a of the water moat 53 and the side surface 51b of the water supply spacer 51, respectively.

[0039] As described above, the lower end 54b of the joint portion 54 is positioned so that it can come into contact with the water W in the water storage space R2, and therefore the lower end 54b of the joint portion 54 is immersed in the water W in the water storage space R2. As a result, the water in the water storage space R2 is absorbed into the joint portion 54 and moves to the upper end 54a of the joint portion 54 by capillary action. The water W that has moved to the upper end 54a of the joint portion 54 is then delivered to the water supply spacer 51, which is in contact with the upper end 54a. The water W delivered to the water supply spacer 51 is used to cool the transmission coil 10. When the water W in the water supply spacer 51 evaporates during cooling of the transmission coil 10, further water is supplied from the water storage space R2 to the water supply spacer 51 via the joint portion 54, and the water supply spacer 51 is maintained in a state in which it contains the water W. In other words, the cooling effect on the transmission coil 10 is maintained.

[0040] Because the joint portion 54 is in thermal contact with the outer surface 34b of the cover 32, the water W absorbed by the joint portion 54 can also be used to cool the transmission coil 10, similar to the water W absorbed by the water supply spacer 51. Therefore, in this embodiment, the joint portion 54 has both the function of transferring the water W in the water storage space R2 to the water supply spacer 51 and the function of cooling the transmission coil 10. In this embodiment, as shown in FIG. 2 , one joint portion 54 is disposed on the outer surface 34b of the cover 32, but multiple joint portions 54 may be disposed on the outer surface 34b of the cover 32.

[0041] When the porous structure of the joint portion 54 is formed by overlapping a plurality of fibers as in the present embodiment, the direction of the fibers may be from the lower end 54b to the upper end 54a of the joint portion 54. In this case, the water W in the water storage space R2 can be easily moved from the lower end 54b to the upper end 54a, and the joint portion 54 can more effectively perform the function of transferring the water W in the water storage space R2 to the water supply spacer 51.

[0042] The longitudinal length of the joint portion 54 (i.e., the length from the upper end 54a to the lower end 54b) is set to be at least equal to or greater than the distance between the water storage space R2 and the side surface 51b of the water supply spacer 51. The lateral width of the joint portion 54 is set to be smaller than the width of the outer surface 33b of the top wall 33 in the same direction (i.e., the length of one side of the outer surface 33b), for example. As an example, the lateral width of the joint portion 54 is 0.05 times the width of the outer surface 33b of the top wall 33. The thickness of the joint portion 54 is set to be smaller than the spacing between the annular wall portions 53b, i.e., the distance between the two wall portions that make up the annular wall portion 53b.

[0043] As shown in FIG. 4, the tank 55 is a water supply tank having a storage space R3 for storing water W to be supplied to the water storage space R2. The storage space R3 of the tank 55 is provided, for example, at a higher position than the water storage space R2. The storage space R3 and the water storage space R2 are connected by a pipe 57 (flow path). A pressure adjustment valve 58 (valve) is provided in the middle of the pipe 57. The pressure adjustment valve 58 opens and closes the flow path of the pipe 57 to maintain the fluid pressure in the pipe 57 at a constant pressure. When the fluid pressure in the pipe 57 is lower than a reference pressure, the pressure adjustment valve 58 is maintained in a closed state, closing the flow path of the pipe 57. On the other hand, when the water level in the water storage space R2 drops and the fluid pressure in the pipe 57 becomes equal to or higher than the reference pressure, the pressure adjustment valve 58 is opened, opening the flow path of the pipe 57. The amount of water in the storage space R3 is set to be greater than the amount of water in the water storage space R2.

[0044] Here, the fluid pressure in the pipe 57 is determined according to the relationship between the water level in the storage space R3 and the water level in the water storage space R2. The water level in the storage space R3 is, for example, always maintained constant. Therefore, the reference pressure may be the fluid pressure in the pipe 57 when the water level in the water storage space R2 is at the reference water level. The reference water level may be the reference water level of the water W stored in the water storage space R2. For example, the reference water level may be set to half (i.e., 0.5 times) the height of the top end of the annular wall portion 53b, based on the height of the bottom portion 53a of the water moat 53. In this case, when the water level in the water storage space R2 is higher than the reference water level, the fluid pressure in the pipe 57 is lower than the reference pressure, and the pressure adjustment valve 58 is closed. On the other hand, when the water level in the water storage space R2 is lower than the reference water level, the fluid pressure in the pipe 57 is higher than the reference pressure, and the pressure adjustment valve 58 is opened. In this case, water W is supplied from the accommodation space R3 to the water storage space R2 so that the water level in the water storage space R2 becomes higher than the reference water level. Note that the pressure regulating valve 58 may be set to a closed state, i.e., the supply of water from the accommodation space R3 to the water storage space R2 is stopped, when the water W is supplied to the water storage space R2 up to a height 0.8 times the height of the upper end of the annular wall portion 53b, based on the height of the bottom portion 53a of the water moat 53.

[0045] The sensor 56 shown in FIG. 2 is a water level sensor that detects the water level in the water storage space R2. Specifically, the sensor 56 detects whether water W is stored in the water storage space R2. When water W is not stored in the water storage space R2 (i.e., when the water storage space R2 is empty), the sensor 56 outputs a warning signal notifying that water W is not stored in the water storage space R2. For example, when water W is not stored in the storage space R3 of the tank 55 (i.e., when the storage space R3 is empty), the water storage space R2 is in a state where water W is not stored. When this warning signal is output, a notification may be sent to the user notifying that water needs to be supplied to the storage space R3 of the tank 55, or the contactless power supply operation of the power transmitting coil device 1 and the power receiving coil device 2 may be stopped.

[0046] As shown in Figure 6, a drain pipe 60 is provided on the sloped portion P1 of the side wall 34 of the cover 32. The drain pipe 60 is configured to guide rainwater and other water that drips onto the outer surface 34b of the sloped portion P1 to the water storage space R2 of the moat 53. Specifically, the drain pipe 60 extends from the outer surface 34b of the sloped portion P1 to the water storage space R2 of the moat 53. The rainwater and other water that flows over the outer surface 34b passes through the drain pipe 60 and is guided to the water storage space R2.

[0047] The following describes the functions and effects achieved by the power transmission coil device 1 and the cooling mechanism 50 described above. In the power transmission coil device 1, as described above, the water supply spacer 51 is in thermal contact with the outer surface of the housing 30. Therefore, heat generated by the power transmission coil 10 housed in the housing 30 is transferred to the water supply spacer 51. At this time, the water W absorbed by the water supply spacer 51 evaporates and absorbs heat from the surroundings, thereby cooling the housing 30 and the power transmission coil 10 therein. Therefore, the power transmission coil device 1 can cool the power transmission coil 10 with a simple configuration that supplies water W to the water supply spacer 51, without requiring an additional device such as a pump for circulating a coolant. This prevents the device configuration from becoming larger and more complicated due to the need for the cooling mechanism 50. As a result, it is possible to prevent an increase in the burden of inspection and maintenance of the device, and thus prevent an increase in costs.

[0048] As in this embodiment, the water supply spacer 51 may be removably attached to the outer surface 33b of the cover 32. In this case, maintenance work such as replacing the water supply spacer 51 can be easily performed, thereby improving maintainability.

[0049] As in the present embodiment, the water supply spacer 51 may be disposed on the outer surface 33b of the cover 32 in a portion that overlaps with the power transmission coil 10 in the opposing direction D1 between the base 31 and the cover 32. In this case, the water supply spacer 51 is disposed in a portion that is particularly likely to become hot, and therefore the housing 30 and the power transmission coil 10 inside the housing 30 can be effectively cooled.

[0050] As in this embodiment, the water supply mechanism 52 may include a water trench 53 having a water storage space R2 for storing water W, and a joint portion 54 configured to transfer the water W stored in the water storage space R2 to the water supply spacer 51. In this case, the water supply mechanism 52 that supplies water W to the water supply spacer 51 can be easily realized.

[0051] As in this embodiment, the joint portion 54 may be in contact with the water storage space R2 and the water supply spacer 51. In this case, the water W stored in the water storage space R2 is absorbed from the water storage space R2 into the joint portion 54 and transferred from the joint portion 54 to the water supply spacer 51. According to this configuration, a configuration for transferring the water W stored in the water storage space R2 to the water supply spacer 51 can be easily realized.

[0052] As in the present embodiment, the joint 54 may be in thermal contact with the outer surface 33b of the cover 32. In this case, heat generated by the power transmission coil 10 housed in the housing 30 is also transferred to the joint 54, and the water W absorbed by the joint 54 evaporates and absorbs heat from the surrounding area, thereby cooling the housing 30 and the power transmission coil 10 inside the housing 30. In other words, with this configuration, not only the water W absorbed by the water supply spacer 51 but also the water W absorbed by the joint 54 can be used to cool the housing 30 and the power transmission coil 10 inside the housing 30. This makes it possible to effectively cool the power transmission coil 10.

[0053] As in this embodiment, the pressure regulating valve 58 may be configured to open the flow path of the piping 57 when the water level in the water storage space R2 is equal to or lower than the reference water level. In this case, when the water level in the water storage space R2 is insufficient, water can be automatically supplied from the accommodation space R3 of the tank 55 to the water storage space R2. This makes it possible to prevent the water level in the water storage space R2 from becoming insufficient, and makes it possible to more reliably supply water from the water storage space R2 to the water supply spacer 51.

[0054] Although one embodiment of the present disclosure has been described above, the present invention is not limited to the above embodiment.

[0055] <First Modification> 7 and 8 show a power transmission coil device 1A according to a first modified example. The power transmission coil device 1A according to this modified example differs from the power transmission coil device 1 according to the above embodiment in the shape of the water supply spacer. A cooling mechanism 50A of the power transmission coil device 1A according to this modified example has a water supply spacer 51A instead of the water supply spacer 51 according to the above embodiment. Unlike the water supply spacer 51, the water supply spacer 51A has an annular shape when viewed from the facing direction D1. As shown in FIG. 8, the water supply spacer 51A is arranged to cover the area directly above the power transmission coil 10. In other words, the water supply spacer 51A is arranged to cover the portion of the outer surface 33b of the cover 32 that faces the power transmission coil 10 in the facing direction D1 (see FIG. 4).

[0056] The portion of the outer surface 33b facing the power transmission coil 10 in the facing direction D1 (i.e., directly above the power transmission coil 10) is close to the power transmission coil 10, which is a heat source, and therefore the heat from the power transmission coil 10 is easily transferred to the portion, which is prone to become particularly hot. Therefore, by having the water supply spacer 51A have an annular shape as in this modification, the water supply spacer 51A can be arranged to mainly cover the area directly above the power transmission coil 10, which is prone to become particularly hot, thereby making it possible to effectively cool the housing 30 and the power transmission coil 10. Furthermore, with this configuration, the amount of material used for the water supply spacer 51A can be reduced, and manufacturing costs can be kept low, compared to when the water-absorbing member is shaped to cover the entire outer surface 33b of the cover 32.

[0057] The cooling mechanism 50A of the power transmission coil device 1A has multiple (two in this modification) joints 54A as transfer sections that transfer water W from the water moat 53 to the water supply spacer 51A. Each joint 54A has the same configuration as the joint 54 according to the above embodiment. As shown in FIGS. 7 and 8, each joint 54A is arranged, for example, point-symmetrically with respect to the center of the power transmission coil 10. Like the joint 54 according to the above embodiment, each joint 54A is arranged so as to contact the water storage space R2 of the water moat 53 and the water supply spacer 51A, and transfers the water W in the water storage space R2 to the water supply spacer 51A. By providing multiple joints 54A as transfer sections that transfer water W from the water moat 53 to the water supply spacer 51A, more paths (flow paths) can be secured for transferring water W from the water moat 53 to the water supply spacer 51A, allowing more water W to be supplied to the water supply spacer 51A. This allows the housing 30 and the power transmission coil 10 to be cooled more effectively.

[0058] In this modification, the water supply spacer 51A is made of sponge, but the water supply spacer 51A may also be made of the same nonwoven fabric as the joint portion 54A. When the porous structure of the water supply spacer 51A is formed by overlapping multiple fibers, the fibers may be oriented along the radial direction of the annular water supply spacer 51A. In this case, the water absorbed by the joint portion 54A can be more easily transported from the outside to the center of the water supply spacer 51A. In other words, the water supply spacer 51A can more effectively diffuse water W within itself.

[0059] <Second Modification> 9 and 10 show a power transmission coil device 1B according to a second modification. The power transmission coil device 1B according to this modification differs from the power transmission coil device 1 according to the above embodiment in the shape of the housing. The power transmission coil device 1B according to this modification includes a housing 30B instead of the housing 30 according to the above embodiment. As shown in FIG. 10, a side wall 34B of the housing 30B is formed perpendicular to the top wall 33 and extends linearly along the facing direction D1. That is, the side wall 34B does not have a portion corresponding to the inclined portion P1 according to the above embodiment. The side wall 34B is spaced a predetermined distance from the annular wall portion 53b, for example. The cooling mechanism 50B of the power transmission coil device 1B according to this modification also includes multiple (two in this modification) joint portions 54B as transfer portions that transfer water W from the water moat 53 to the water supply spacer 51. Each joint portion 54B has the same configuration as the joint portion 54 according to the above embodiment, for example. As shown in FIG. 9, the joints 54B are arranged, for example, point-symmetrically with respect to the center of the power transmission coil 10 (see FIG. 3).

[0060] As shown in FIG. 10 , unlike the joint portion 54 according to the above embodiment, the joint portion 54B does not contact the outer surface 34b of the side wall 34B of the cover 32. In other words, the joint portion 54B is spaced apart from the outer surface 34b of the side wall 34B. The lower end 54b of the joint portion 54B contacts the water storage space R2 (specifically, the bottom 53a) of the water moat 53 and is immersed in the water W in the water storage space R2. The upper end 54a of the joint portion 54B extends upward from the water storage space R2 and contacts the side surface 51b of the water supply spacer 51. Therefore, water in the water storage space R2 is absorbed into the joint portion 54B from the lower end 54b and moves to the upper end 54a of the joint portion 54B by capillary action. The water that has moved to the upper end 54a is then transferred to the water supply spacer 51, which is in contact with the upper end 54a. This configuration also achieves the same effects as the above embodiment.

[0061] <Third Modification> 11(a) and 11(b) show a power transmission coil device 1C according to a third modified example. The power transmission coil device 1C according to this modified example differs from the power transmission coil device 1 according to the above embodiment in the configuration of the transfer section that transfers the water W from the water moat 53 to the water supply spacer 51. The power transmission coil device 1C according to this modified example has a joint section 54C instead of the joint section 54 according to the above embodiment, and a deformable member 65 attached to the joint section 54C, as the transfer section that transfers the water W from the water moat 53 to the water supply spacer 51. In addition, in the power transmission coil device 1C according to this modified example, the side surface 51b of the water supply spacer 51 is positioned so as to protrude slightly outward from the top wall 33 when viewed from the facing direction D1.

[0062] The deformable member 65 is a heat-sensitive deformable member that can deform, for example, in response to heat transfer from the power transmission coil 10 or a temperature rise due to induction heating caused by a magnetic field generated by the coil. In this modified example, a case in which the deformable member 65 deforms in response to heat transfer from the power transmission coil 10 will be described. The deformable member 65 includes a spring 61 and support portions 62 and 63 attached to the spring 61. The spring 61 is made of a shape memory alloy. Examples of shape memory alloys include Ti (titanium)-Ni (nickel) alloys. The spring 61 is attached, for example, to the outer surface 34b of the inclined portion P1 of the side wall 34 of the cover 32 via the support portions 62 and 63. The support portions 62 and 63 are, for example, plate-shaped members that stand upright on the outer surface 34b of the inclined portion P1. The support portions 62 and 63 are arranged on the outer surface 34b so as to face each other along the facing direction D1.

[0063] The support portion 62 is disposed below the support portion 63 (i.e., closer to the base 31 in the facing direction D1 than the support portion 63). The spring 61 is disposed so as to be sandwiched between the support portions 62, 63 and extends along the facing direction D1. The lower end of the spring 61 is fixed to the upper surface of the support portion 62, and the upper end of the spring 61 is fixed to the lower surface of the support portion 63. The side surface of the support portion 62 is fixed to the outer surface 34b of the inclined portion P1. Meanwhile, the side surface of the support portion 63 is slidable relative to the outer surface 34b of the inclined portion P1. Therefore, the position of the lower end of the spring 61 is fixed, while the position of the upper end of the spring 61 is movable. The support portions 62, 63 are thermally conductive and transfer heat transferred from the power transmission coil 10 to the cover 32 to the spring 61.

[0064] Similar to the above embodiment, the joint portion 54C has a rectangular sheet shape. The lower end 54b of the joint portion 54C contacts the water W in the water storage space R2 of the water moat 53. Specifically, the lower end 54b of the joint portion 54C contacts the bottom 53a of the water moat 53. The joint portion 54C extends upward from the water storage space R2, crosses the spring 61, and extends to the upper surface of the support portion 63. The upper end 54a of the joint portion 54C is located on the upper surface of the support portion 63 and faces the lower surface 51a of the water supply spacer 51 in the facing direction D1. The upper end 54a of the joint portion 54C is joined to the upper surface of the support portion 63, for example. From the lower end 54b to the upper end 54a of the joint portion 54C, the joint portion 54C contacts the side surfaces of the supports 62 and 63, but does not contact the spring 61. The joint portion 54C may be joined to the side surfaces of the support portions 62 and 63. The heat of the cover 32 is transferred to the spring 61 via the support portions 62 and 63.

[0065] The temperature of the spring 61 changes depending on the temperature of the power transmission coil 10 due to the influence of heat transfer from the power transmission coil 10. The spring 61 deforms depending on the temperature of the power transmission coil 10 and has two different shapes. When the temperature of the power transmission coil 10 is a normal temperature, not a high temperature, the temperature of the spring 61 also becomes a normal temperature corresponding to the temperature of the power transmission coil 10. In this case, as shown in FIG. 11( a), the spring 61 is in a compressed state and assumes a non-water supply shape (second shape) in which it is significantly separated from the lower surface 51a of the water supply spacer 51 in the facing direction D1. In the non-water supply shape, the support portion 63 above the spring 61 is separated from the lower surface 51a of the water supply spacer 51 in the facing direction D1 by a predetermined distance, which is smaller than the thickness of the joint portion 54C. Therefore, the joint portion 54C on the support portion 63 does not contact the lower surface 51a of the water supply spacer 51 and is separated from the lower surface 51a. That is, in the non-water supply mode, the joint portion 54C is in contact with the water W in the water storage space R2 but is not in contact with the water supply spacer 51 (i.e., is separated from the water supply spacer 51). In this case, the water W absorbed by the joint portion 54C from the water storage space R2 is not transferred to the water supply spacer 51, and therefore water is not supplied to the water supply spacer 51.

[0066] On the other hand, when the temperature of the power transmission coil 10 is high, the heat of the power transmission coil 10 is transferred to the spring 61, and the temperature of the spring 61 also becomes high. In this case, as shown in FIG. 11(b), the spring 61 is stretched and deforms from the non-water supply configuration to the water supply configuration (first configuration) in which the spring 61 is close to the lower surface 51a of the water supply spacer 51. In the water supply configuration, the joint portion 54C on the support portion 63 is in contact with the lower surface 51a of the water supply spacer 51. That is, in the water supply configuration, the joint portion 54C is in contact with both the water W in the water storage space R2 and the water supply spacer 51. In this case, the water W absorbed by the joint portion 54C from the water storage space R2 is transferred to the water supply spacer 51, and water is supplied to the water supply spacer 51.

[0067] In other words, when the temperature of the spring 61 is in the first temperature range, as shown in FIG. 11(a), the spring 61 is in the non-water-supplying configuration in which the joint portion 54C is not in contact with the water supply spacer 51, and water is not supplied to the water supply spacer 51. On the other hand, when the temperature of the spring 61 is in the second temperature range, as shown in FIG. 11(b), the spring 61 transforms from the non-water-supplying configuration to the water-supplying configuration in which the joint portion 54C is in contact with both the water storage space R2 and the water supply spacer 51, and water is supplied to the water supply spacer 51. The first temperature range is a temperature range of the spring 61 corresponding to a temperature range of the power transmission coil 10 that does not require cooling. The temperature of the spring 61 falls within the first temperature range when the power transmission coil 10 is not performing a contactless power supply operation, or when the power transmission coil 10 is performing a contactless power supply operation but is not high enough to require cooling. The first temperature range is, for example, below 50°C. The second temperature range is a temperature range of the spring 61 corresponding to the temperature range of the power transmission coil 10 in a high temperature state, and is higher than the first temperature range. The temperature of the spring 61 falls into the second temperature range when the power transmission coil 10 becomes so hot due to the contactless power feeding operation that cooling is required. The second temperature range is, for example, 50°C or higher. Note that when the temperature of the power transmission coil 10 drops from the second temperature range to the first temperature range, the spring 61 transforms from the water supply form to the non-water supply form.

[0068] In the power transmission coil device 1C according to this modification, the spring 61 is configured to change from the non-water supply state to the water supply state in accordance with the temperature of the power transmission coil 10. Therefore, water is supplied to the water supply spacer 51 only when water needs to be supplied to the water supply spacer 51 (i.e., when the power transmission coil 10 needs to be cooled), and the water supply to the water supply spacer 51 is stopped when water does not need to be supplied to the water supply spacer 51 (i.e., when the power transmission coil 10 does not need to be cooled). In this way, by stopping the water supply to the water supply spacer 51 when cooling of the power transmission coil 10 is not required, it is possible to prevent the water W from being consumed more than necessary. Furthermore, in the power transmission coil device 1C according to this modification, the non-water supply state and the water supply state can be automatically switched between in accordance with the temperature of the power transmission coil 10, and therefore a configuration can be easily realized in which the water supply to the water supply spacer 51 is stopped when cooling of the power transmission coil 10 is not required. In this modified example, a configuration has been described in which the lower end 54b of the joint portion 54C is always in contact with the water W in the water storage space R2 when the spring 61 is in the non-water supply form, but conversely, the upper end 54a of the joint portion 54C may also be in constant contact with the water supply spacer 51.

[0069] As described above, the spring 61 may be thermally deformed in response to a temperature rise due to induction heating caused by the magnetic field generated by the power transmission coil 10. When the power transmission coil 10 performs a contactless power supply operation (during contactless power supply), the spring 61 is disposed near the power transmission coil 10, and an eddy current is generated in the spring 61 by the magnetic field generated by the power transmission coil 10. The Joule heat of the eddy current heats the spring 61, causing a temperature rise (heat generation). This heating principle is called induction heating. The temperature rise of the spring 61 due to this induction heating causes the spring 61 to transform from the non-water-supplying configuration to the water-supplying configuration, thereby enabling the spring 61 to enter a water-supplying state in which water is supplied to the water supply spacer 51. Therefore, the spring 61 can transform from the non-water-supplying configuration to the water-supplying configuration and enter the water-supplying state when either the condition of the spring 61 being thermally deformed due to heat transfer from the high-temperature power transmission coil 10 or the condition of the spring 61 being thermally deformed due to a temperature rise caused by induction heating is satisfied.

[0070] When the spring 61 is thermally deformed due to heat transfer from the power transmitting coil 10, the timing at which the spring 61 switches from the non-water supply mode to the water supply mode due to thermal deformation corresponds to the timing at which the temperature of the power transmitting coil 10 becomes high enough to require cooling, as described above. In this case, the spring 61 switches between the non-water supply mode and the water supply mode in accordance with the change in temperature of the power transmitting coil 10. On the other hand, when the spring 61 is thermally deformed in response to a temperature increase due to induction heating, the timing at which the spring 61 switches from the non-water supply mode to the water supply mode due to thermal deformation corresponds to the timing at which the power transmitting coil 10 starts a contactless power supply operation. When contactless power supply starts, the temperature of the spring 61 rises from the first temperature range to the second temperature range due to induction heating caused by the magnetic field generated by the power transmitting coil 10, and the spring 61 switches from the non-water supply mode to the water supply mode. Then, at the timing when the power transmitting coil 10 ends contactless power feeding, the temperature of the spring 61 drops from the second temperature range to the first temperature range, and the spring 61 switches from the water supply mode to the non-water supply mode. Therefore, if the spring 61 is thermally deformed due to heat transfer from the power transmitting coil 10, the spring 61 switches between the non-water supply mode and the water supply mode at the timing when the power transmitting coil 10 starts and ends the contactless power feeding operation. In this case, even if the temperature of the power transmitting coil 10 is not high enough to require cooling, the spring 61 may switch from the non-water supply mode to the water supply mode at the timing when the power transmitting coil 10 starts contactless power feeding.

[0071] <Fourth Modification> 12(a) and 12(b) show a power transmission coil device 1D according to a fourth modification. The power transmission coil device 1D according to this modification differs from the power transmission coil device 1 according to the above embodiment in the configuration of the transfer section that transfers the water W from the water moat 53 to the water supply spacer 51. The power transmission coil device 1D according to this modification has a joint section 54D and a deformable member 75 attached to the joint section 54D, instead of the joint section 54 according to the above embodiment, as the transfer section that transfers the water W from the water moat 53 to the water supply spacer 51. In addition, in the power transmission coil device 1D according to this modification, the side surface 51b of the water supply spacer 51 is positioned so as to protrude slightly outward from the top wall 33 when viewed from the facing direction D1.

[0072] The deformable member 75 is a heat-sensitive deformable member that can deform, for example, in response to heat transfer from the power transmission coil 10 or a temperature increase due to induction heating caused by a magnetic field generated by the coil. In this modified example, a case in which the deformable member 75 deforms in response to heat transfer from the power transmission coil 10 will be described. The deformable member 75 includes a bimetal formed by bonding together two metal plates 71 and 72 having different thermal expansion coefficients (thermal expansion rates), and a support portion 73 that supports the bimetal. The support portion 73 is fixed, for example, directly above the wall portion of the annular wall portion 53b that faces the cover 32, on the outer surface 34b of the cover 32 (specifically, directly above the erected portion P2 of the side wall 34 of the cover 32). The metal plates 71 and 72 extend upward from the support portion 73 along the facing direction D1. The lower ends of the metal plates 71 and 72 (i.e., one end on the support portion 73 side in the facing direction D1) are fixed to the support portion 73. The upper ends of the metal plates 71 and 72 (i.e., the other ends on the support portion 73 side in the facing direction D1) are free ends that are not fixed to any member. The support portion 73 has thermal conductivity and transfers heat transferred from the power transmission coil 10 to the cover 32 to the metal plates 71 and 72.

[0073] The metal plates 71 and 72 are stacked in a transverse direction D2 that intersects with the opposing direction D1. The transverse direction D2 is a direction along the radial direction of the power transmission coil 10 when viewed from the opposing direction D1. The metal plate 72 is located closer to the cover 32 than the metal plate 71 in the transverse direction D2. The outer surface 72a of the metal plate 72 faces the cover 32 in the transverse direction D2, and the outer surface 71a of the metal plate 71 faces the opposite side from the cover 32 in the transverse direction D2. The outer surfaces 71a and 72a form outer surfaces of a bimetal. The metal plate 71 has a first thermal expansion coefficient. The metal plate 72 has a second thermal expansion coefficient that is greater than the first thermal expansion coefficient. Materials defined in JIS C2530-1993 "Electrical Bimetals" may be used as the material of the metal plates 71 and 72 (bimetal materials), for example. The bimetal may be configured by bonding three or more metal plates together. For example, the bimetal may further include another metal plate bonded to the outer surface 72a of the metal plate 72. In this case, the other metal plate may have a third thermal expansion coefficient greater than the second thermal expansion coefficient.

[0074] Similar to the above embodiment, the joint portion 54D has a rectangular sheet shape. The lower end 54b of the joint portion 54D contacts the water W in the water storage space R2 of the water moat 53. Specifically, the lower end 54b of the joint portion 54D contacts the bottom 53a of the water moat 53. The joint portion 54D extends upward from the water storage space R2, from the outer surface 71a of the metal plate 71, around the upper ends of the metal plates 71 and 72, and extends to a position where it reaches the outer surface 72a of the metal plate 72. The upper end 54a of the joint portion 54D is located on the outer surface 72a of the metal plate 72. The upper end 54a of the joint portion 54D is joined to the outer surface 72a of the metal plate 72, for example. The joint portion 54D contacts the metal plates 71 and 72 along the path from the lower end 54b to the upper end 54a of the joint portion 54D.

[0075] The temperatures of the metal plates 71 and 72 change depending on the temperature of the power transmission coil 10 due to the influence of heat transfer from the power transmission coil 10. The metal plates 71 and 72 deform depending on the temperature of the power transmission coil 10 and have two different shapes. When the temperature of the power transmission coil 10 is a normal temperature, not a high temperature, the metal plates 71 and 72 also become at a normal temperature corresponding to the temperature of the power transmission coil 10. In this case, as shown in FIG. 12( a), the metal plates 71 and 72 assume a non-water supply shape (second shape) in which they extend linearly upward from the support portion 73. In the non-water supply shape, the upper ends of the metal plates 71 and 72 are spaced a predetermined distance from the side surface 51b of the water supply spacer 51 in the cross direction D2, and this predetermined distance is smaller than the thickness of the joint portion 54D. Therefore, the joint portion 54D on the outer surface 72a of the metal plate 72 does not contact the side surface 51b of the water supply spacer 51 and is spaced apart from the side surface 51b. That is, in the non-water supply mode, the joint portion 54D is in contact with the water W in the water storage space R2 but is not in contact with the water supply spacer 51 (i.e., is separated from the water supply spacer 51). In this case, the water W absorbed by the joint portion 54D from the water storage space R2 is not transferred to the water supply spacer 51, and therefore water is not supplied to the water supply spacer 51.

[0076] On the other hand, when the temperature of the power transmission coil 10 is high, the heat of the power transmission coil 10 is transferred to the metal plates 71 and 72, causing the temperatures of the metal plates 71 and 72 to also become high. In this case, as shown in FIG. 12( b), the metal plates 71 and 72 transform from the non-water-supply configuration to a water-supply configuration (first configuration) in which they are curved from the support portion 73 toward the side surface 51b of the water supply spacer 51. Specifically, because the thermal expansion coefficient of the metal plate 72 is greater than that of the metal plate 71, as the temperature of the power transmission coil 10 increases, the metal plate 72 expands more than the metal plate 71. As a result, the metal plates 71 and 72 curve toward the side surface 51b of the water supply spacer 51, and the joint portion 54D on the outer surface 72a of the metal plate 72 comes into contact with the side surface 51b of the water supply spacer 51. That is, in the water-supply configuration, the joint portion 54D is in contact with both the water W in the water storage space R2 and the water supply spacer 51. In this case, the water W absorbed from the water storage space R2 into the joint portion 54D is transferred to the water supply spacer 51, and thus water is supplied to the water supply spacer 51.

[0077] In other words, when the temperature of the metal plates 71, 72 is within the first temperature range, as shown in FIG. 12(a), the metal plates 71, 72 are in the non-water-supplying configuration in which the joint portion 54D is not in contact with the water supply spacer 51, and water is not supplied to the water supply spacer 51. On the other hand, when the temperature of the metal plates 71, 72 is within the second temperature range, as shown in FIG. 12(b), the metal plates 71, 72 are transformed from the non-water-supplying configuration to the water-supplying configuration in which the joint portion 54D is in contact with both the water storage space R2 and the water supply spacer 51, and water is supplied to the water supply spacer 51. The first temperature range is the temperature range of the metal plates 71, 72 that corresponds to the temperature range of the power transmission coil 10 that does not require cooling. The temperatures of the metal plates 71, 72 are within the first temperature range when the power transmission coil 10 is not performing a contactless power supply operation, or when the power transmission coil 10 is performing a contactless power supply operation but is not high enough to require cooling. The first temperature range is, for example, below 50°C. The second temperature range is a temperature range of the metal plates 71, 72 corresponding to the temperature range of the power transmission coil 10 in a high temperature state, and is higher than the first temperature range. The temperature of the power transmission coil 10 falls into the second temperature range when the power transmission coil 10 becomes so hot due to the contactless power feeding operation that cooling is required. The second temperature range is, for example, 50°C or higher. Note that the metal plates 71, 72 change from the water supplying form to the non-water supplying form when the temperature of the power transmission coil 10 drops from the second temperature range to the first temperature range.

[0078] In the power transmission coil device 1D according to this modification, the metal plates 71, 72 are configured to change from the non-water supply state to the water supply state in accordance with the temperature of the power transmission coil 10. Therefore, water is supplied to the water supply spacer 51 only when it is necessary to supply water to the water supply spacer 51 (i.e., when it is necessary to cool the power transmission coil 10), and the water supply to the water supply spacer 51 is stopped when it is not necessary to supply water to the water supply spacer 51 (i.e., when it is not necessary to cool the power transmission coil 10). In this way, by stopping the water supply to the water supply spacer 51 when it is not necessary to cool the power transmission coil 10, it is possible to prevent the water W from being consumed more than necessary. Furthermore, in the power transmission coil device 1D according to this modification, it is possible to automatically switch between the non-water supply state and the water supply state in accordance with the temperature of the power transmission coil 10, and therefore it is possible to easily realize a configuration in which the water supply to the water supply spacer 51 is stopped when it is not necessary to cool the power transmission coil 10. In this modified example, a configuration has been described in which the lower end 54b of the joint portion 54D is always in contact with the water W in the water storage space R2 when the metal plates 71, 72 are in the non-water supply form, but conversely, the upper end 54a of the joint portion 54D may also be in constant contact with the water supply spacer 51.

[0079] As described above, the metal plates 71 and 72 may be thermally deformed in response to a temperature rise due to induction heating caused by the magnetic field generated by the power transmission coil 10. When the power transmission coil 10 performs a contactless power supply operation (during contactless power supply), the metal plates 71 and 72 are disposed near the power transmission coil 10, and the magnetic field generated by the power transmission coil 10 generates eddy currents in the metal plates 71 and 72. The Joule heat of the eddy currents heats the metal plates 71 and 72, causing a temperature rise (heat generation). This heating principle is called induction heating. The temperature rise of the metal plates 71 and 72 due to this induction heating causes the metal plates 71 and 72 to deform from a non-water-supplying configuration to a water-supplying configuration, enabling them to enter a water-supplying state in which water is supplied to the water supply spacer 51. Therefore, when either of the following conditions is met: when the metal plates 71, 72 are thermally deformed due to heat transfer from the high-temperature transmission coil 10, or when the metal plates 71, 72 are thermally deformed due to a temperature rise caused by induction heating, the metal plates 71, 72 can be transformed from a non-water supply form to a water supply form and enter a water supply state.

[0080] When the metal plates 71, 72 are thermally deformed due to heat transfer from the power transmitting coil 10, the timing at which the metal plates 71, 72 switch from the non-water-supply mode to the water-supply mode due to thermal deformation corresponds to the timing at which the temperature of the power transmitting coil 10 becomes high enough to require cooling, as described above. In this case, the metal plates 71, 72 switch between the non-water-supply mode and the water-supply mode in response to changes in the temperature of the power transmitting coil 10. On the other hand, when the metal plates 71, 72 are thermally deformed in response to a temperature increase due to induction heating, the timing at which the metal plates 71, 72 switch from the non-water-supply mode to the water-supply mode due to thermal deformation corresponds to the timing at which the power transmitting coil 10 starts a contactless power supply operation. When contactless power supply starts, the temperature of the metal plates 71, 72 rises from the first temperature range to the second temperature range due to induction heating caused by the magnetic field generated by the power transmitting coil 10. As a result, the metal plates 71, 72 switch from the non-water-supply mode to the water-supply mode. Then, at the timing when the power transmitting coil 10 ends contactless power feeding, the temperatures of the metal plates 71, 72 drop from the second temperature range to the first temperature range, and the metal plates 71, 72 switch from the water supply mode to the water non-supply mode. Therefore, if the metal plates 71, 72 are thermally deformed in response to a temperature increase due to induction heating, the metal plates 71, 72 switch between the water non-supply mode and the water supply mode at the timing when the power transmitting coil 10 starts and ends the contactless power feeding operation. In this case, even if the temperature of the power transmitting coil 10 has not yet reached a high enough temperature to require cooling, the metal plates 71, 72 may switch from the water non-supply mode to the water supply mode at the timing when the power transmitting coil 10 starts contactless power feeding.

[0081] <Other variations> The coil device of the present disclosure may be applied to a contactless power transfer system for charging the battery of a mobile body other than a vehicle, such as an unmanned aerial vehicle (UAV) such as a drone. Furthermore, the coil device may be applied to a contactless power transfer system for charging the battery of a home appliance or the like other than a mobile body, or to an induction heating system or an eddy current testing system. The coil device according to the present disclosure may be applied to a power receiving coil device that receives power in a contactless power transfer system. Furthermore, the above-described power transmitting coil device is not limited to being installed on the road surface G, but may also be mounted on the mobile body. In this case, the power receiving coil device may be installed on the road surface G. Furthermore, the power transmitting coil device and the power receiving coil device are not limited to only transmitting or receiving power, but may also perform both transmitting and receiving power. Furthermore, a cooling mechanism constituted by a water absorbing member (water supply spacer) and a water supply mechanism may be applied to an existing coil device.

[0082] The coil of the present disclosure may be formed of a Litz wire wound helically (three-dimensionally) around a ferrite core. That is, the coil of the present disclosure may be a solenoid coil. In the cooling mechanism of the present disclosure, the water-absorbing member (water supply spacer) and the separate water-absorbing member (joint portion) serving as the transfer portion may both be made of nonwoven fabric or sponge. Furthermore, the water-absorbing member and / or the separate water-absorbing member may have a two-layer structure in which a nonwoven fabric and a sponge are overlapped. The shape of the water-absorbing member as viewed from the facing direction D1 is not limited to the rectangular or annular shape described above, and may be other shapes such as a circular or elliptical shape. In the cooling mechanism of the present disclosure, the water storage portion (water moat) does not need to be formed separately from the housing and may be formed directly on the outer periphery of the housing, for example. [Explanation of symbols]

[0083] 1, 1A, 1B, 1C, 1D Power transmission coil device (coil device) 10 Transmission coil (coil) 30,30B housing 31 Base 32 Cover 33b,34b External surface 50,50A,50B Cooling mechanism 51, 51A Water supply spacer (water absorption member) 54, 54A, 54B, 54C, 54D Joint part (separate water absorption material) 52 Water supply mechanism 53 Moat (reservoir) 55 Tank 57 Piping (flow path) 58 Pressure Regulating Valve 65,75 Deformed member D1 Opposite direction R1 interior space R2 Water storage space R3 Containment Space W water

Claims

1. A coil and A housing that houses a coil; A cooling mechanism for cooling the coil, The cooling mechanism includes: a water absorbing member having a porous structure including a plurality of pores and in thermal contact with an outer surface of the housing; A water supply mechanism configured to supply water to the water absorbing member, The water supply mechanism includes: a water storage section disposed around the housing and having a water storage space for storing the water; a transfer section configured to transfer the water stored in the water storage space to the water absorbing member, The delivery unit includes: Another water-absorbing member having a porous structure including a plurality of pores; a deformation member attached to the other water-absorbing member; A coil device, wherein the deformation member is configured to be deformable from a first form in which the other water-absorbing member is in contact with both the water storage space and the water-absorbing member, to a second form in which the other water-absorbing member is separated from at least one of the water storage space and the water-absorbing member.

2. The coil device according to claim 1 , wherein the water-absorbent member is removably attached to an outer surface of the housing.

3. the housing has a base and a cover that faces the base with the coil interposed therebetween and defines an internal space between the base and the cover for accommodating the coil; The coil device according to claim 1 , wherein the water absorbing member is disposed on an outer surface of the cover at a portion overlapping the coil in an opposing direction between the base and the cover.

4. The deformation member is a deformable heat-sensitive deformation member that can be deformed in response to heat transfer from the coil or a temperature rise due to induction heating caused by a magnetic field generated by the coil, and deforms to the second form when the temperature of the deformation member is in a first temperature range, and to the first form when the temperature of the deformation member is in a second temperature range that is higher than the first temperature range.The coil device described in any one of claims 1 to 3.

5. The coil device according to any one of claims 1 to 4, wherein the separate water-absorbing member is in thermal contact with an outer surface of the housing.

6. the water supply mechanism includes a tank having a storage space for storing the water; The tank is provided with a flow path that connects the accommodation space and the water storage space and through which the water flows, and a valve provided in the flow path, The coil device according to any one of claims 1 to 5, wherein the valve is configured to open the flow path when the water level in the water storage space is equal to or lower than a reference water level.

7. A cooling mechanism for cooling a coil used in a coil device, comprising: a water absorbing member having a porous structure including a plurality of pores and capable of being in thermal contact with an outer surface of a housing that accommodates the coil; A water supply mechanism configured to supply water to the water absorbing member, The water supply mechanism includes: a water storage section disposed around the housing and having a water storage space for storing the water; a transfer section configured to transfer the water stored in the water storage space to the water absorbing member, The delivery unit includes: Another water-absorbing member having a porous structure including a plurality of pores; a deformation member attached to the other water-absorbing member; A cooling mechanism, wherein the deformable member is configured to be deformable from a first form in which the other water-absorbing member is in contact with both the water storage space and the water-absorbing member, to a second form in which the other water-absorbing member is separated from at least one of the water storage space and the water-absorbing member.

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