Cases for wireless power transmitters and wireless power receivers

Abstract

The present invention addresses the problem of providing a carbon fiber-reinforced composite material that, while having an electromagnetic shielding property in a high frequency band, allows electromagnetic waves in a low frequency band to pass therethrough.　The present invention is a carbon fiber-reinforced composite material, wherein the ratio SEM300K / SEM1G of the value SEM300K (dB) at 300 kHz to the value SEM1G (dB) at 1 GHz, which are magnetic field shielding effectiveness values measured by the KEC method, is 0.50 or lower.

Description

[Technical Field]

[0001] The present invention relates to a carbon fiber reinforced composite material, particularly one suitable for a case for a wireless power feeder and a case for a wireless power receiver. [Background technology]

[0002] Wireless charging, which allows gadgets such as smartphones to be charged without being connected to a wired cord, has become widespread. Wireless charging methods include, for example, electromagnetic induction and magnetic resonance, which supply power from a transmitting antenna to a receiving antenna via a magnetic field, and it is important that the materials used for the cases of wireless power transmitters and receivers are transparent to the magnetic field in the frequency range used for wireless power transmission / reception.

[0003] The frequency band used for wireless charging is generally 110 kHz to 205 kHz for electronic devices such as smartphones, and although commercial use for electric buses and EVs is limited, development using frequencies from 20 kHz to 250 kHz is underway (see, for example, Patent Document 1), and the case material of wireless power transmitters / receivers must be able to transmit magnetic fields in the low frequency band of 300 kHz or less.

[0004] Generally, cases for wireless power supply / receivers use materials that do not have shielding properties across all frequency bands. Typical materials include glass fiber reinforced resin materials, ceramics, and glass plates, and housings for wireless power supply devices and wireless power receivers that combine these materials to achieve both cost and mechanical properties such as strength and impact resistance have been proposed (see, for example, Patent Document 2). However, in order to use a combination of materials, it is necessary to use adhesives for bonding and joining. The process became complicated, and it was difficult to reduce costs to the level required by the market.

[0005] Furthermore, as control technology becomes more advanced, CPUs and GPUs that generate strong high-frequency noise have become common, making it increasingly important for cases for wireless power transmitters and receivers to be able to block high-frequency noise.

[0006] In summary, there is a market demand for materials that have a certain level of mechanical properties while simultaneously achieving low-frequency band transparency and high-frequency shielding properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-193430 [Patent Document 2] Japanese Patent Application Publication No. 2019-122184 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a carbon fiber reinforced composite material that has electromagnetic wave shielding properties in the high frequency band while allowing electromagnetic waves in the low frequency band to pass through. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0010] That is, the present invention is directed to a magnetic field shielding effect measured by the KEC method and defined by the following formula (1) at 300 kHz, SE M300K (dB) and SE at 1GHz M1G (dB) SE M300K / SE M1G is 0.50 or less. SE M =20×log 10 (H0 / H X ) …Formula (1) Here, SE M : Magnetic field shielding effect (dB) H0: Spatial magnetic field strength (A / m) when no carbon fiber reinforced composite test specimen is installed H X : Spatial magnetic field strength (A / m) when a test piece cut into a square with sides of 150 mm of the carbon fiber reinforced composite material to be measured is placed.

[0011] The present invention also relates to a laminated carbon fiber composite material formed by laminating at least two layers of the carbon fiber composite material of the present invention, wherein the two layers of carbon fiber composite material are a combination of at least two selected from the following three types: those made using a continuous fiber substrate, those made using a discontinuous fiber substrate, and those made by injection molding.

[0012] The present invention also provides a laminated composite material obtained by combining the carbon fiber composite material of the present invention with another resin material in the thickness direction.

[0013] The present invention also provides a case for a wireless power feeder, which constitutes part of the wireless power feeder, and in which the carbon fiber reinforced composite material of the present invention is disposed in at least a portion that covers a power feed portion of the wireless power feeder.

[0014] The present invention also relates to a case for a wireless power receiver, which constitutes part of the wireless power receiver, and in which the carbon fiber reinforced composite material of the present invention is disposed in at least a portion that covers the power receiving portion of the wireless power feeder. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a carbon fiber reinforced composite material that has electromagnetic wave shielding properties in the high frequency band while being permeable to electromagnetic waves in the low frequency band used in wireless power supply / reception, and a case for a wireless power supply device and a case for a wireless power receiver that use this carbon fiber composite material. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing an example of a carbon fiber reinforced composite material according to the present invention. [Figure 2] FIG. 2 is a perspective view showing an example of a carbon fiber reinforced composite material according to the present invention. [Figure 3] FIG. 3 is a perspective view showing an example of a carbon fiber reinforced composite material according to the present invention. [Figure 4] FIG. 4 is a perspective view showing an example of a carbon fiber reinforced composite material according to the present invention. [Figure 5] FIG. 5 is a perspective view showing an example of a wireless power feeder using a case for a wireless power feeder according to the present invention. [Figure 6] FIG. 6 is a perspective view showing an example of a wireless power feeder using a case for a wireless power feeder according to the present invention. [Figure 7] FIG. 7 is a perspective view showing (a) the front side and (b) the back side of an example of a wireless power feeder using a case for a wireless power feeder according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in more detail below. In the present invention, "or more" means the same as or larger than the indicated numerical value. Furthermore, "or less" means the same as or smaller than the indicated numerical value.

[0018] As the resin used in the carbon fiber reinforced composite material of the present invention, a thermosetting resin or a thermoplastic resin can be preferably used.

[0019] The thermosetting resin may be any resin that undergoes a crosslinking reaction due to heat to form at least a partial three-dimensional crosslinked structure. Examples of such thermosetting resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, benzoxazine resins, phenolic resins, urea resins, melamine resins, and thermosetting polyimide resins. Modified versions of these resins and blends of two or more of these resins may also be used. The thermosetting resin may be self-curing upon heating, or may contain a curing agent or a curing accelerator. Among thermosetting resins, epoxy resins are preferred because of their excellent balance of mechanical properties and low shrinkage upon curing.

[0020] Examples of thermoplastic resins include polyolefin resins such as polyethylene (PE) resin and polypropylene (PP) resin, polyethylene terephthalate (PET) resin, polyamide (PA) resin, polyphenylene sulfide (PPS) resin, and copolymer resins, modified resins, and alloys thereof. Among these, polypropylene resins are preferred in terms of the light weight of the resulting molded product, polyamide resins in terms of mechanical properties and moldability, and polyphenylene sulfide resins in terms of heat resistance.

[0021] Examples of the carbon fiber in the carbon fiber reinforced composite material of the present invention include polyacrylonitrile (PAN)-based, rayon-based, and pitch-based carbon fibers. Of these, PAN-based carbon fibers are preferred because of their excellent balance between strength and elastic modulus.

[0022] The form of the carbon fibers in the carbon fiber reinforced composite material of the present invention may be, for example, a sheet / tape form in which the carbon fibers are aligned in one direction, a woven fabric form, a knitted fabric form, a nonwoven fabric form, or a short fiber additive form.

[0023] When the carbon fibers in the carbon fiber composite material of the present invention are discontinuous fibers, the number average fiber length L n It is preferable that L is 0.1 mm or more and 50 mm or less. nBy making the thickness 0.1 mm or more, it is possible to effectively improve the electromagnetic wave shielding performance in the high frequency band. n By setting the diameter to 50 mm or less, the moldability of the carbon fiber reinforced composite material is improved, allowing it to be formed into complex shapes.

[0024] The carbon fiber reinforced composite material of the present invention was measured using 114 10 mm × 10 mm test pieces, and the volume fraction of the contained fibers, Vf, defined by the following formula (2) i The average value Vf defined by the following formula (3) ave By adjusting the value within this range, it is possible to obtain a material that has excellent strength and elastic modulus while also having electromagnetic wave shielding properties in the high frequency band. Vf i =(W bi / ρf) / {W bi / ρf+(W ai -W bi ) / ρr} ...Equation (2) Vf ave =ΣVf i / n …Formula (3) Vf i : Fiber volume fraction of each test piece W ai : Mass of each test piece before heat treatment (g) W bi : Mass (g) of each test piece after heat treatment at 600°C for 30 minutes ρf: density of carbon fiber (g / cm 3 ) ρr: density of matrix resin (g / cm 3 ) Vf ave : Average fiber volume fraction n: total number of test pieces (114 pieces) σ Vf : Standard deviation of fiber volume fraction.

[0025] The carbon fiber reinforced composite material of the present invention has a Vf i The standard deviation σ is defined by the following formula (4) Vf Vf ave Divided by σ Vf / Vf aveis preferably 0.0001 or more and 0.5 or less. σ Vf =(ΣVf i 2 / n-Vf ave 2 ) 1 / 2 ...Formula (4) Here, Vf i : Fiber volume fraction of each test piece Vf ave : Average fiber volume fraction n: total number of test pieces (114 pieces) σ Vf : Standard deviation of fiber volume fraction σ Vf / Vf ave By making the ratio 0.5 or less, the variation in the carbon fiber volume content in the material is small, and a carbon fiber reinforced composite material having stable and excellent electromagnetic wave shielding properties in the high frequency band can be obtained.

[0026] Also, σ Vf / Vf ave is preferably 0.0001 or more. Vf / Vf ave By setting the value to 0.0001 or more, it can be achieved with general-purpose materials, and costs can be reduced.

[0027] The carbon fiber reinforced composite material of the present invention has a Vf i Regarding the minimum value Vf min It is preferable that Vf is 0.05 or more. min By making the value 0.05 or more, it is possible to obtain a carbon fiber reinforced composite material that does not transmit electromagnetic waves locally and that is stable and has excellent electromagnetic wave shielding properties in the high frequency band.

[0028] Also, Vf min It is preferable that Vf is 0.85 or less. min By keeping the ratio at 0.85 or less, the amount of carbon fiber used can be reduced, making the product cheaper.

[0029] The carbon fiber reinforced composite material of the present invention can also be a laminate in which multiple thin layers of carbon fiber reinforced composite material are laminated. The laminate structure of the carbon fiber reinforced composite material can be obtained by laminating prepregs. When the carbon fibers have a fixed fiber direction, such as long fibers, a cross-lamination method can be used, in which layers are alternately laminated in two mutually perpendicular directions. A quasi-isotropic lamination method can also be preferably used, in which the fiber direction of a certain layer is set to 0° and layers are laminated in the order of -45°, 0°, 45°, and 90°. In addition to long fiber prepregs, the above-mentioned cross-lamination method and quasi-isotropic lamination method can also be used for carbon fiber reinforced composite materials such as woven prepregs and carbon fiber sheet molding compounds (CF-SMC).

[0030] The carbon fiber reinforced composite material of the present invention has a magnetic field shielding effect measured by the KEC method and defined by the following formula (1) at 300 kHz, SE M300K (dB) and SE at 1GHz M1G (dB) SE M300K / SE M1G is less than 0.50. SE M =20×log 10 (H0 / H X ) …Formula (1) Here, SE M : Magnetic field shielding effect (dB) H0: Spatial magnetic field strength (A / m) when no carbon fiber reinforced composite test specimen is installed H X : Spatial magnetic field strength (A / m) when a test piece cut into a square with sides of 150 mm of the carbon fiber reinforced composite material to be measured is placed.

[0031] Magnetic field shielding effect SE in the present invention M"dB" is a physical quantity that indicates the degree to which a carbon fiber composite material shields against magnetic fields generated by electronic devices, etc. The larger this value, the smaller the magnetic field that penetrates the carbon fiber composite material, and the higher the magnetic field shielding effect. By changing the frequency of the antenna coil that generates this magnetic field, the frequency of the magnetic field can be changed, and the frequency characteristics of the magnetic field shielding effect can be measured.

[0032] In the present invention, the magnetic field shielding effect is measured using the KEC method standardized by the Kansai Electronics Industry Development Center (KEC) General Incorporated Association.

[0033] Through intensive research by the inventors, it has become clear that the magnetic field shielding properties of carbon fiber composite materials increase monotonically with frequency. In particular, the magnetic field shielding effect SE at 300 kHz M300K If it can be confirmed that the magnetic field shielding effect SE at 1 GHz is low, it can be said that it can be used for wireless power supply / reception applications that use lower frequency bands. M1G If the resistance is high, it is possible to sufficiently shield high frequency noise including magnetic and electric fields in the near field and electromagnetic waves in the far field.

[0034] The carbon fiber reinforced composite material of the present invention is M300K and SE M1G SE M300K / SE M1G It is important that SE is 0.50 or less. M300K / SE M1G By setting the value to 0.50 or less, preferably 0.20 or less, and more preferably 0.10 or less, it is possible to transmit electromagnetic waves in a low frequency band for wireless charging while maintaining electromagnetic wave shielding properties in a high frequency band.

[0035] Materials that satisfy these ranges can selectively transmit low-frequency electromagnetic waves used in wireless power supply / reception and can shield high-frequency electromagnetic waves that block high-frequency magnetic fields that cause noise, making them suitable for use as construction materials for cases for wireless power supply devices or cases for wireless power receivers.

[0036] Also, SE M300K / SE M1G is 1.0 x 10 -6 It is preferable to set it to SE or higher. M300K / SE M1G to 1.0 x 10 -6 By setting the above, it is possible to achieve the above with general-purpose materials, and costs can be reduced.

[0037] Also, SE M300k It is preferable that SE is 10 dB or less. M300K By keeping this at 10 dB or less, low-frequency electromagnetic waves for wireless charging can be effectively transmitted.

[0038] Also, SE M300K is 1.0 x 10 -2 It is preferable to set the SE M300K to 1.0 x 10 -2 By achieving a value of 100 dB or more, it can be achieved using general-purpose materials, and costs can be reduced.

[0039] Also, SE M1G It is preferable that SE is 20 dB or more. M300K By setting the value to 20 dB or more, high frequency noise can be effectively blocked.

[0040] Also, SE M1G It is preferable that SE is 200 dB or less. M1G By keeping the loss to 200 dB or less, it can be achieved using general-purpose materials, and costs can be reduced.

[0041] The carbon fiber reinforced composite material of the present invention is preferably at least one selected from the following three types: one made using a continuous fiber reinforced substrate, one made using a discontinuous fiber reinforced substrate, and one made by injection molding. By adopting such an embodiment, a carbon fiber reinforced composite material that has electromagnetic wave shielding properties in the high frequency band and is capable of transmitting electromagnetic waves in the low frequency band used for wireless power feeding / reception can be effectively obtained while maintaining mechanical properties, moldability, etc.

[0042] The carbon fiber reinforced composite material of the present invention is preferably in the form of a plate, which can efficiently cover a wireless power supply / receive system. Specific plate shapes include flat plates, corrugated plates, hat-shaped plates, hollow boards, cylinders, hollow cones, polygonal tubes, hollow polygonal cones, hollow spheres, and partial shapes thereof. Furthermore, bosses or ribs can be added to the above-mentioned plate shapes.

[0043] Even when a carbon fiber reinforced composite material of the present invention is in a form other than a plate, for example, in the form of pellets, it can be preferably used as long as the molded product formed from it is in the form of a plate.

[0044] 1 shows a perspective view of a flat carbon fiber reinforced composite material 1 as an example of a plate shape. A flat plate is preferable because it has excellent storage efficiency during transportation.

[0045] 2 shows a perspective view of a carbon fiber reinforced composite material 2 having a partial shape of an elliptical cylinder as an example of a plate shape. A partial shape of a cylinder can be easily used for molded products having curved surfaces.

[0046] 3 shows a perspective view of a carbon fiber reinforced composite material 3 having a partial polygonal cylindrical shape as an example of a plate shape. This shape can efficiently cover a three-dimensional wireless power supply / receive system.

[0047] The carbon fiber reinforced composite material of the present invention preferably has a 10-point average thickness t of 0.1 mm or more and 10 mm or less at its thinnest point. By setting t to 0.1 mm or more, excellent electromagnetic wave shielding properties in the high frequency band are achieved. Furthermore, by setting t to 10 mm or less, excellent lightness is achieved and material costs can be further reduced.

[0048] In the case of a carbon fiber reinforced composite material of a constant thickness as shown in Figures 1 to 3, the thinnest part can be selected arbitrarily. On the other hand, in the case of a carbon fiber reinforced composite material 4 which is a flat plate with ribs as shown in Figure 4, the 10-point average thickness t of the thinnest part is measured not at the ribs 5 but at the flat plate 6.

[0049] When the carbon fiber reinforced composite material of the present invention is in the form of a plate, the 10-point average thickness t (mm) of the thinnest part is raised to the 1 / 2 power, the average carbon fiber volume content Vf ave 1 / 2 power, the average fiber length L (mm) of the carbon fiber to the 1 / 4 power, the specific gravity ρ (g / mm 3 ) product ρ(Vf ave ) 1 / 2 L 1 / 4 t 1 / 2 But 0.4×10 -3 (g / mm 9 / 4 ) or more. ave ) 1 / 2 L 1 / 4 t 1 / 2 to 0.4×10 -3 (g / mm 9 / 4 ) or more, SE M300K / SE M1G can be effectively reduced to 0.50 or less.

[0050] Also, ρ(Vf ave ) 1 / 2 L 1 / 4 t 1 / 2 is 10 x 10 -3 (g / mm 9 / 4 ) or less. ave ) 1 / 2 L 1 / 4 t 1 / 2 10 x 10 -3 (g / mm 9 / 4 ) or less, it is lightweight.

[0051] Examples of the precursor of the carbon fiber reinforced composite material of the present invention include prepreg, which is a continuous fiber substrate, and thermoplastic UD ( U ni D You can choose from a variety of materials, including directional tapes, thermoplastic stampable sheets with discontinuous fiber substrates, CF-SMC, and injection molding materials, based on your requirements for material properties and moldability.

[0052] Prepregs can be easily made by arranging fiber bundles or fiber cloth in a flat mold, then soaking it in thermosetting resin and pressing it.

[0053] The thermoplastic prepreg is not particularly limited, and can be easily produced in the same manner as the above prepreg, except that a thermoplastic resin is used instead of a thermosetting resin.

[0054] The thermoplastic UD tape is not particularly limited, but can be easily produced in the same manner as the unidirectional prepreg described above, except that a thermoplastic resin is used instead of a thermosetting resin.

[0055] As the carbon fiber reinforced composite material of the present invention, a discontinuous carbon fiber substrate can be used, which is obtained by depositing discontinuous carbon fibers and impregnating a nonwoven fabric with a resin.

[0056] The nonwoven fabric according to the present invention is produced by mechanically cutting chopped fibers to a predetermined fiber length using various mat production methods, including, but not limited to, carding, air-laid, and wet papermaking.

[0057] As the resin used in the discontinuous carbon fiber substrate of the present invention, various thermosetting resins and thermoplastic resins can be used, similar to prepregs and thermoplastic UD tapes.

[0058] The carbon fiber reinforced composite material of the present invention can be an injection molding material. One form of injection molding material is obtained by kneading a desired amount of thermoplastic resin (A) and chopped or continuous carbon fiber (B) in an extruder, extruding, and pelletizing the mixture. In such pellets, the fiber length in the pellet is shorter than the longitudinal length of the pellet, but the pellets of the present invention also include long fiber pellets.

[0059] Such long fiber pellets refer to those in which the fibers are arranged almost parallel to the longitudinal direction of the pellet, and the length of the fibers in the pellet is equal to or greater than the length of the pellet, as disclosed in Japanese Patent Publication No. 63-37694.

[0060] In the long fiber pellets, the resin may be impregnated into the fiber bundles or coated on the fiber bundles. In particular, in the case of resin-coated long fiber pellets, the fiber bundles may be pre-impregnated with a resin having the same viscosity (or lower molecular weight) as the coating resin or a resin having a lower viscosity (or lower molecular weight) than the coating resin.

[0061] When long fiber pellets are used for molding, the carbon fiber length in the molded product is longer than in pellets in which the fiber length in the pellet is shorter than the longitudinal length of the pellet, resulting in superior mechanical properties, and therefore they are more preferably used.

[0062] As with the thermoplastic UD tape, various thermoplastic resins can be used as the resin for the injection molding material of the present invention.

[0063] The carbon fiber reinforced composite material of the present invention can be molded into molded articles by various molding methods without any particular limitation, such as autoclave molding, oven heating molding, press molding, and injection molding.

[0064] The laminated carbon fiber composite material of the present invention is formed by laminating at least two layers of carbon fiber composite material, and is a combination of at least two selected from the following three types: those made using a continuous fiber substrate, those made using a discontinuous fiber substrate, and those made by injection molding.

[0065] Examples of laminated carbon fiber composite materials include UD hybrid materials that combine thermoplastic UD tape and injection molding materials, and hybrid materials made of CF-SMC and prepreg. Various combinations can be selected taking into consideration the required high-frequency shielding properties, mechanical properties, moldability, etc.

[0066] Furthermore, there are no particular limitations on the manufacturing method for molding a molded article made of a laminated carbon fiber reinforced composite material, and examples include a method of molding a prepared laminated carbon fiber reinforced composite material, a method of molding two types of carbon fiber reinforced composite materials separately and then bonding or joining them to form an integrated body, and a method of performing molding and integration simultaneously, such as insert molding.

[0067] The laminated composite material of the present invention is formed by combining the carbon fiber reinforced composite material of the present invention and another resin material in the thickness direction.

[0068] As the other resin material, at least one selected from a glass fiber reinforced resin material, an organic fiber reinforced resin material, and a filler reinforced resin material can be preferably used.

[0069] A specific example of a lamination combination in the laminated composite material of the present invention is a laminated material combining a thermoplastic prepreg and a glass fiber reinforced resin material. The addition of a thermoplastic prepreg not only provides electromagnetic shielding in the high frequency band while maintaining the low frequency band transparency of the glass fiber reinforced resin material, but also improves mechanical properties. Furthermore, when mechanical properties are required in only one direction, UD tape can be suitably used as the continuous fiber substrate for the carbon fiber.

[0070] Examples of combinations of thermosetting resin materials include prepreg and glass prepreg, prepreg and glass SMC, CF-SMC and glass prepreg, and CF-SMC and glass SMC. Examples of combinations of thermoplastic resin materials include thermoplastic prepreg and glass reinforced resin, injection molding resin and glass reinforced resin, etc. Other examples include combinations of thermoplastic and thermosetting systems.

[0071] Examples of the organic fibers that can be used include natural fibers, aramid fibers, polyester fibers, LCP fibers, "Kevlar" fibers, and Zylon fibers. Examples of the filler that can be used include carbon black, calcium carbonate, talc, and mica.

[0072] The carbon fiber reinforced composite material of the present invention can be suitably used for a portion of a case for a wireless power feeder that covers at least the power feeding portion, or a portion of a case for a wireless power receiver that covers at least the power receiving portion.

[0073] That is, the case for a wireless power feeder of the present invention is a case that constitutes part of the wireless power feeder, and has the carbon fiber reinforced composite material of the present invention disposed in at least the portion that covers the power feeding portion of the wireless power feeder.

[0074] Furthermore, the case for a wireless power receiver of the present invention is a case that constitutes part of a wireless power receiver, and has the carbon fiber reinforced composite material of the present invention disposed in at least a portion that covers the power receiving portion of the wireless power feeder.

[0075] The cases for wireless power feeders and wireless power receivers of the present invention are molded and used from the carbon fiber reinforced composite material of the present invention, and in addition to being able to transmit magnetic fields in the frequency range used for wireless power feeding / receiving and shielding against high-frequency noise, they can also absorb external impacts and be lightweight, thereby satisfying the required properties.

[0076] In the case for a wireless power feeder of the present invention, by arranging the carbon fiber reinforced composite material of the present invention at least in the portion directly above the coil of the power feeding portion of the wireless power feeder, and by arranging the carbon fiber reinforced composite material of the present invention at least in the portion directly above the coil of the power receiving portion of the wireless power feeder, it is possible to suppress high frequency noise while preventing a decrease in power transmission efficiency.

[0077] Figure 5 shows an example of a wireless power feeder 7 for gadgets. A power feeding coil 9 is housed in a main body 8, and the main body is covered with a top panel 10. The entire surface of this top panel 10 is made of a carbon fiber reinforced composite material, and gadgets such as smartphones can be placed on top to charge them.

[0078] An example of a wireless power supply device 11 for gadgets is shown in Figure 6. The main body 12 and power supply coil 13 have the same configuration as in Figure 4, but the top plate is made up of an outer periphery 14 made of aluminum that blocks power transmission, and a center part 15 made of carbon fiber reinforced composite material that does not interfere with power transmission.

[0079] In this way, in the case for a wireless power feeder of the present invention, the carbon fiber reinforced composite material of the present invention is disposed in at least the power feeding portion, but if a single material is desired to simplify the manufacturing process, the carbon fiber reinforced composite material of the present invention can be used for the entire case for a wireless power feeder.

[0080] Examples of devices that have a wireless power receiver include gadgets such as smartphones, Wi-Fi routers, digital cameras, wearable devices, personal computers, and tablet devices, general industrial equipment such as power tools, lighting equipment, compressors, and vacuum cleaners, mobility devices such as electric cars, electric buses, electric motorcycles, electrically assisted bicycles, robots, and electric heavy machinery, and healthcare devices such as electric toothbrushes, electric shavers, heart rate monitors, electrocardiographs, and life log tools. For small gadgets such as smartphones, it is also preferable that the case for the wireless power feeder also serves as the housing for the device that has the wireless power receiver.

[0081] The wireless power feeder according to the present invention may be a wireless power feeder for charging the above-mentioned devices.

[0082] Figure 7 shows an example of a smartphone 16 that supports wireless charging. The case of the smartphone 16 is composed of three parts: a frame 18, a screen 19, and a back panel 20, which houses a power receiving coil 17. The back panel 20, which comes into contact with the top panel of the wireless power supply device, is made of a carbon fiber reinforced composite material. [Example]

[0083] The present invention will now be described in detail with reference to examples, although the present invention is not limited to these examples.

[0084] <Evaluation and measurement methods> (1) Evaluation of magnetic field shielding effect From each of the molded plates obtained in the examples and comparative examples, square pieces with sides of 150 mm were cut out to serve as test pieces for measuring the shielding effect. Using a shielding property measuring device (manufactured by Microwave Factory Co., Ltd.) conforming to the KEC method, the magnetic field shielding effect at 300 kHz, defined by the following formula (1), SE M300K (dB) and SE at 1GHz M1G The number of measurements, n, was set to 2, and the average value was used. SE M =20×log 10 (H0 / H X ) …Formula (1) Here, SE M : Magnetic field shielding effect (dB) H0: Spatial magnetic field strength (A / m) when no carbon fiber reinforced composite test specimen is installed H X : Spatial magnetic field strength (A / m) when a carbon fiber reinforced composite test specimen is placed.

[0085] (2) Measurement of carbon fiber volume fraction Vf From the test piece for measuring the shielding effect, 144 square test pieces for measuring Vf, each 10 mm on a side, were cut out uniformly, leaving the four edges of the test piece. The weight W of each test piece, defined by the following formula (2), was calculated. ai After measuring, each test piece was heated in air at 600°C for 30 minutes to burn off the thermoplastic resin component, and the mass W of the remaining carbon fiber was bi The fiber volume fraction Vf of each test piece was calculated using the following formula: i , calculate the carbon fiber volume content, and the minimum value is Vf min In addition, the standard deviation σ defined by the following formula (4) Vf The average value Vf defined by the following formula (3) ave Divided by σ Vf / Vfave was calculated. Vf i =(W bi / ρf) / {W bi / ρf+(W ai -W bi ) / ρr} ...Equation (2) Vf ave =ΣVf i / n …Formula (3) σ Vf =(ΣVf i 2 / n-Vf ave 2 ) 1 / 2 ...Formula (4) Here, Vf i : Fiber volume fraction of each test piece W ai : Mass of each test piece before heat treatment (g) W bi : Mass (g) of each test piece after heat treatment at 600°C for 30 minutes ρf: density of carbon fiber (g / cm 3 ) ρr: density of matrix resin (g / cm 3 ) Vf ave : Average fiber volume fraction n: total number of test pieces (114 pieces) σ Vf : Standard deviation of fiber volume fraction.

[0086] (3) Number average fiber length L of carbon fibers n A square with a side length of 50 mm was cut out from the molded plate obtained in the Examples or Comparative Examples, and the matrix resin was thoroughly dissolved in a solvent that dissolves the matrix resin, and then separated from the carbon fibers by filtration. If no solvent was available to dissolve the matrix resin, the cut molded plate was heated at 600°C for 30 minutes to burn off the matrix resin and separate the carbon fibers. Four hundred of the separated carbon fibers were randomly selected, and their lengths were measured using an optical microscope in 1-μm increments from 1 μm to 50 mm, to determine the fiber length L. i The number average fiber length L was calculated using the following formula: nHowever, carbon fibers with a fiber length of 50 mm or more were treated as 50 mm so that they could be measured using a commonly available optical microscope. L n =ΣL i / n Here, L n : Number average fiber length (mm) L i : Fiber length of each fiber (mm) (i=1, 2, 3, 400) n: number of fibers (400).

[0087] (4) Measurement of the average thickness at 10 points The thickness t of the molded plate obtained in the example or comparative example under an atmosphere of 23°C i was measured 10 times with a micrometer, and the 10-point average thickness t was calculated using the following formula. t=Σt i / 10[mm] Here, t: 10-point average thickness (mm) ti: measured thickness at ith time (mm) n: Number of measurement points (10 points) <Materials used> The materials and components used in each example and comparative example are as follows:

[0088] [Carbon fiber (A)] A-1: Toray Industries, Inc. "Torayca (registered trademark)" thread T700S-12K.

[0089] [Polyamide 6 resin (B)] B-1: Amilan (registered trademark) CM1017, manufactured by Toray Industries, Inc.

[0090] [Polyamide 6 film (C)] C-1: A predetermined amount of polyamide 6 resin (B-1) was placed on a stainless steel plate, spacers of a predetermined thickness were placed around it, and another stainless steel plate was placed on top of it with the spacer sandwiched between them. The mixture was pressed at 250°C and 1 MPa for 5 minutes to obtain a polyamide 6 film (C-1).

[0091] [Carbon fiber reinforced composite material D] D-1: Toray Industries, Inc., "TORAYCA (registered trademark)" prepreg P6055F-16 D-2: Toray Industries, Inc., "TORAYCA (registered trademark)" prepreg P3252S-12.

[0092] D-3: Stampable sheet A discontinuous carbon fiber mat with isotropic fiber orientation was obtained by uniformly dispersing chopped yarns obtained by cutting carbon fiber A-1 to a fiber length of 12.5 mm using a rotary cutter. Next, a laminate of discontinuous carbon fiber mat and polyamide 6 film B-1, adjusted to a thickness of 2 mm and a carbon fiber volume content of 35%, was placed in a press-molding flat mold cavity preheated to above the melting temperature of the thermoplastic resin. The mold was closed, a pressure of 3 MPa was applied, and the mold was held for 180 seconds. The cavity temperature was then cooled to 50 ° C. while maintaining the pressure, resulting in a stampable sheet D-3 in which the discontinuous carbon fiber substrate was impregnated with the thermoplastic resin. The thickness of the stampable sheet was adjusted using a 2 mm thick spacer.

[0093] D-4: Stampable sheet Stampable sheet D-4 was obtained in the same manner as D-3, except that carbon fiber A-1 was expanded to a width of 25 mm using a vibrating rod vibrating at 10 Hz, then slit into 5 mm intervals using a disc-shaped dividing blade, and then cut to a fiber length of 12.5 mm.

[0094] D-5, D-6, D-7: Short fiber pellets A twin-screw extruder (JSW TEX-30α type, screw diameter 30 mm, die diameter 5 mm, barrel temperature 290°C, screw rotation speed 150 rpm) was used to obtain a specified Vf ave (D-5 Vf ave is 0.22, Vf of D-6 ave is 0.14, Vf of D-7 aveCarbon fiber A-1 and polyamide 6 resin B-1 were kneaded so that the viscosity was 0.04), and the molten resin was discharged from the die opening while degassing through a downstream vacuum vent. The resulting strand was cooled and then cut with a cutter to obtain short fiber pellets D-5 to D-7 of carbon fiber reinforced composite material.

[0095] D-8: Stampable sheet Stampable sheet D-8 was obtained in the same manner as D-4, except that carbon fiber A-1 was cut to a fiber length of 1 mm, and the thickness was adjusted to 0.5 mm and the carbon fiber volume content was adjusted to 20%.

[0096] D-9: Stampable sheet Stampable sheet D-9 was obtained in the same manner as D-4, except that carbon fiber A-1 was cut to a fiber length of 1 mm, and the thickness was adjusted to 0.4 mm and the carbon fiber volume content to 12%.

[0097] D-10: Thermoplastic UD tape Carbon fiber A-1 was prepared and continuously fed into a carbon fiber bundle through a yarn guide. Polyamide 6 resin B-1 was supplied at a fixed rate from a filled feeder into the impregnation die, allowing the carbon fiber bundle to be impregnated. The carbon fiber bundle impregnated with polyamide 6 resin B-1 was then continuously drawn through the nozzle of the impregnation die using a take-up roll. The bundle passed through a cooling roll, allowing the polyamide 6 resin B-1 to cool and solidify. The resulting thermoplastic UD tape was wound onto a winder. The thickness of the resulting thermoplastic UD tape was 0.3 mm, and the carbon fibers were aligned in one direction. The fiber volume fraction in the thermoplastic UD tape was 50 vol%.

[0098] [Glass fiber reinforced resin material (E)] E-1: Epoxy glass plate, thickness 2mm E-2: Glass fiber reinforced nylon 6 resin (Toray Industries, Inc. "Amilan (registered trademark)" CM1011G-30).

[0099] [Example 1] Carbon fiber reinforced composite material D-1 was cut to the specified dimensions in the carbon fiber orientation direction (0° direction) and in a direction shifted 45 degrees to the right from the carbon fiber orientation direction (45° direction), and then fabricated into a 16-layer quasi-isotropic ([-45 / 0 / +45 / 90] 2S ) to obtain a laminate. This laminate was exposed to a curing atmosphere to obtain a molded plate in which the matrix resin was cured. This plate was then left to stand in a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50% for 24 hours, after which it was subjected to evaluation. The results are shown in Table 1.

[0100] [Example 2] A molded plate was obtained and evaluated in the same manner as in Example 1, except that carbon fiber reinforced composite material D-2 was used. The results are shown in Table 1.

[0101] [Example 3] The stacking pattern is 48 layers pseudo-isotropic ([-45 / 0 / +45 / 90] 6S A molded plate was obtained in the same manner as in Example 1, except that the temperature was changed to 100°C, and the molded plate was subjected to evaluation. The results are shown in Table 1.

[0102] [Comparative Example 1] The glass fiber reinforced resin material E-1 was left to stand for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 23° C. and a relative humidity of 50%, and then subjected to evaluation. The results are shown in Table 1.

[0103] [Example 4] The carbon fiber reinforced composite material D-3 was left to stand in a constant temperature and humidity chamber adjusted to a temperature of 23° C. and a relative humidity of 50% for 24 hours, and then subjected to evaluation. The results are shown in Table 2.

[0104] [Example 5] The carbon fiber reinforced composite material D-4 was left to stand for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50%, and then subjected to evaluation. The results are shown in Table 2.

[0105] [Examples 6 to 8] Carbon fiber reinforced composite materials D-5 to D-7 were molded into plates using an injection molding machine (SE75DUZ-C250 manufactured by Sumitomo Heavy Industries, Ltd.) under conditions of a cylinder temperature of 300°C and a mold temperature of 80°C. The obtained test specimens were left to stand in a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50% for 24 hours before being subjected to evaluation. The results are summarized in Table 3.

[0106] [Example 9] The carbon fiber reinforced composite material D-8 was left to stand in a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50% for 24 hours, and then subjected to evaluation. The results are shown in Table 4.

[0107] [Example 10] The carbon fiber reinforced composite material D-9 was left to stand in a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50% for 24 hours, and then subjected to evaluation. The results are shown in Table 4.

[0108] [Example 11] The carbon fiber reinforced composite material D-10 was left to stand in a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50% for 24 hours, and then subjected to evaluation. The results are shown in Table 5.

[0109] [Example 12] A 0.3 mm thick carbon fiber reinforced composite material D-10 was placed over the entire surface of one side of a 3 mm thick injection mold for flat plates, and then glass fiber reinforced resin material E-2 was injection molded to obtain a 3 mm thick laminate. The resulting laminate was left to stand in a constant temperature and humidity chamber adjusted to 23°C and 50% RH for 24 hours before being evaluated. The results are shown in Table 5.

[0110] [Table 1]

[0111] [Table 2]

[0112] [Table 3]

[0113] [Table 4]

[0114] [Table 5]

[0115] As described above, Examples 1 to 12 are SE M300K / SE M1G are all 0.50 or less, allowing the low frequencies used in wireless charging to pass through while shielding the high frequencies that are a source of noise.

[0116] Furthermore, the carbon fiber reinforced composite materials of Examples 1 to 7 and 9 to 12 were particularly excellent in wireless charging efficiency.

[0117] Furthermore, the carbon fiber reinforced composite material of Example 8 was superior to Comparative Example 1 in wireless charging efficiency, although not as good as Examples 1 to 7 and 9 to 12.

[0118] On the other hand, Comparative Example 1 had poor wireless charging efficiency. [Industrial Applicability]

[0119] The carbon fiber reinforced composite material of the present invention has shielding properties in near magnetic fields, such that it can transmit low frequencies used in wireless charging while shielding high frequencies that are a source of noise, and therefore can be suitably used for cases for wireless power feeders / receivers. [Explanation of symbols]

[0120] 1. Flat carbon fiber reinforced composite material 2 Carbon fiber reinforced composite material with a partial shape of an elliptical cylinder 3 Carbon fiber reinforced composite material with a polygonal cylindrical part shape 4. Carbon fiber reinforced composite material of ribbed plate 5. Ribs 6 Flat plate part 7. Wireless power supply for gadgets (the entire top surface is made of carbon fiber reinforced composite material) 8 Wireless power supply unit 9 Power supply coil 10. Top plate 11 Wireless power supply for gadgets (part of the top surface is made of carbon fiber reinforced composite material) 12 Wireless power supply unit 13 Power supply coil 14 Periphery of the top plate 15 Center of top plate 16 Smartphones that support wireless charging 17 Receiving coil 18 frames 19 screens 20 Rear Panel

Claims

1. A case constituting a part of a wireless power feeder, the case comprising: The magnetic field shielding effect measured by the KEC method and defined by the following formula (1) is the value SE at 300 kHz. Ｍ３００Ｋ (dB) and SE at 1 GHz Ｍ１Ｇ (dB) SE Ｍ３００Ｋ / SE Ｍ１Ｇ is 0.50 or less, and the SE M300K is 10 dB or less. A case for a wireless power supply with the above. SE Ｍ = 20 × log １０ (H ０ / H Ｘ ) ··· Equation (1) Here, SE Ｍ : Magnetic field shielding effect (dB) H ０ : spatial magnetic field strength (A / m) when no test piece of carbon fiber reinforced composite material is placed H Ｘ : Spatial magnetic field strength (A / m) when a test piece cut into a square with sides of 150 mm from the carbon fiber reinforced composite material to be measured is placed

2. The SE Ｍ１Ｇ The case for a wireless power supply according to claim 1 , wherein the impedance is 20 dB or more.

3. The volume fraction Vf of the contained fibers, which is defined by the following formula (2), was measured from 114 test pieces of the carbon fiber reinforced composite material, each having a size of 10 mm x 10 mm. ｉ The standard deviation σ defined by the following formula (4) Ｖｆ is the average value Vf defined by the following formula (3) ａｖｅ Divided by σ Ｖｆ / Vf ａｖｅ The case for a wireless power supply according to claim 1 or 2, wherein the value of the resistance is 0.5 or less. Vf ｉ = (W ｂｉ / ρf) / {W ｂｉ / ρf + (W ａｉ - W ｂｉ ) / ρr} ··· Equation (2) Vf ａｖｅ =ΣVf ｉ / n ・・・Form (3) s Ｖｆ =(SVf ｉ ２ / n-Vf ａｖｅ ２ ) １／２ ・・・formula (4) Here, Vf ｉ : Fiber volume fraction of each test piece W ａｉ : Mass (g) of each test piece before heat treatment W ｂｉ : Mass (g) of each test piece after heat treatment at 600 ° C. for 30 minutes ρf: density of carbon fiber (g / cm ３ ) ρr: density of matrix resin (g / cm ３ ) Vf ａｖｅ : Average fiber volume fraction n: total number of test pieces (114 pieces) σ Ｖｆ : Standard deviation of fiber volume fraction

4. The volume fraction Vf of the contained fibers, which is defined by the following formula (2), was measured from 114 test pieces of the carbon fiber reinforced composite material, each having a size of 10 mm x 10 mm. ｉ Regarding the minimum value Vf ｍｉｎ The case for a wireless power supply according to any one of claims 1 to 3, wherein is 0.05 or more. Vf ｉ = (W ｂｉ / ρf) / {W ｂｉ / ρf + (W ａｉ - W ｂｉ ) / ρr} ··· Equation (2) Here, Vf ｉ : Fiber volume fraction of each test piece W ａｉ : Mass (g) of each test piece before heat treatment W ｂｉ : Mass (g) of each test piece after heat treatment at 600 ° C. for 30 minutes ρf: density of carbon fiber (g / cm ３ ) ρr: density of matrix resin (g / cm ３ )

5. 5. The case for a wireless power supply device according to claim 1, wherein the carbon fiber reinforced composite material is at least one selected from the group consisting of a continuous fiber reinforced substrate, a discontinuous fiber reinforced substrate, and an injection molded carbon fiber reinforced composite material.

6. The carbon fiber reinforced composite material is in a plate shape, and the 10-point average thickness t (mm) of the thinnest part of the carbon fiber reinforced composite material is the 1 / 2 power, the average carbon fiber volume content Vf ａｖｅ 1 / 2 power, the number average fiber length L of the carbon fiber ｎ (mm) to the 1 / 4 power, specific gravity ρ of carbon fiber (g / mm ３ ) product ρ(Vf ａｖｅ ) １／２ L １／４ t １／２ But 0.4 x 10 －３ (g / mm ９／４ 6. The case for a wireless power supply according to claim 1, wherein the number of wires is 1 or more.

7. A case constituting a part of a wireless power receiver, the case comprising: a part covering at least a power receiving part of the wireless power receiver; The magnetic field shielding effect measured by the KEC method and defined by the following formula (1) is the value SE at 300 kHz. Ｍ３００Ｋ (dB) and SE at 1 GHz Ｍ１Ｇ (dB) SE Ｍ３００Ｋ / SE Ｍ１Ｇ is 0.50 or less, and the SE M300K is 10 dB or less. A case for a wireless receiver with a SE Ｍ = 20 × log １０ (H ０ / H Ｘ ) ··· Equation (1) Here, SE Ｍ : Magnetic field shielding effect (dB) H ０ : spatial magnetic field strength (A / m) when no test piece of carbon fiber reinforced composite material is placed H Ｘ : Spatial magnetic field strength (A / m) when a test piece cut into a square with sides of 150 mm from the carbon fiber reinforced composite material to be measured is placed

8. The SE Ｍ１Ｇ The case for a wireless power receiver according to claim 7 , wherein the impedance is 20 dB or more.

9. The volume fraction Vf of the contained fibers, which is defined by the following formula (2), was measured from 114 test pieces of the carbon fiber reinforced composite material, each having a size of 10 mm x 10 mm. ｉ The standard deviation σ defined by the following formula (4) Ｖｆ is the average value Vf defined by the following formula (3) ａｖｅ Divided by σ Ｖｆ / Vf ａｖｅ The case for a wireless power receiver according to claim 7 or 8, wherein the value of the resistance is 0.5 or less. Vf ｉ = (W ｂｉ / ρf) / {W ｂｉ / ρf + (W ａｉ - W ｂｉ ) / ρr} ··· Equation (2) Vf ａｖｅ =ΣVf ｉ / n ・・・Form (3) s Ｖｆ =(SVf ｉ ２ / n-Vf ａｖｅ ２ ) １／２ ・・・formula (4) Here, Vf ｉ : Fiber volume fraction of each test piece W ａｉ : Mass (g) of each test piece before heat treatment W ｂｉ : Mass (g) of each test piece after heat treatment at 600 ° C. for 30 minutes ρf: density of carbon fiber (g / cm ３ ) ρr: density of matrix resin (g / cm ３ ) Vf ａｖｅ : Average fiber volume fraction n: total number of test pieces (114 pieces) σ Ｖｆ : Standard deviation of fiber volume fraction

10. The volume fraction Vf of the contained fibers, which is defined by the following formula (2), was measured from 114 test pieces of the carbon fiber reinforced composite material, each having a size of 10 mm x 10 mm. ｉ Regarding the minimum value Vf ｍｉｎ The case for a wireless power receiver according to any one of claims 7 to 9, wherein is 0.05 or more. Vf ｉ = (W ｂｉ / ρf) / {W ｂｉ / ρf + (W ａｉ - W ｂｉ ) / ρr} ··· Equation (2) Here, Vf ｉ : Fiber volume fraction of each test piece W ａｉ : Mass (g) of each test piece before heat treatment W ｂｉ : Mass (g) of each test piece after heat treatment at 600 ° C. for 30 minutes ρf: density of carbon fiber (g / cm ３ ) ρr: density of matrix resin (g / cm ３ )

11. The case for a wireless power receiver according to any one of claims 7 to 10, wherein the carbon fiber reinforced composite material is at least one selected from the group consisting of a continuous fiber reinforced substrate, a discontinuous fiber reinforced substrate, and an injection molded carbon fiber reinforced composite material.

12. The carbon fiber reinforced composite material is in a plate shape, and the 10-point average thickness t (mm) of the thinnest part of the carbon fiber reinforced composite material is the 1 / 2 power, the average carbon fiber volume content Vf ａｖｅ 1 / 2 power, the number average fiber length L of the carbon fiber ｎ (mm) to the 1 / 4 power, specific gravity ρ of carbon fiber (g / mm ３ ) product ρ(Vf ａｖｅ ) １／２ L １／４ t １／２ But 0.4 x 10 －３ (g / mm ９／４ 12. The case for a wireless power receiver according to claim 7, wherein the number of wires is equal to or greater than 1.

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