Charging Coil for High-Power Medium- and Long-Distance Wireless Transmission and Its Preparation Method

Abstract

The present invention discloses a charging coil for high-power medium- and long-distance wireless transmission and a preparation method thereof, including a circuit board. An upper-layer circuit wiring A is provided on the upper surface of the circuit board, and a lower-layer circuit wiring B is provided on the lower surface. The upper-layer circuit wiring A is formed by winding patch copper wires that sequentially surround outward from the center of the circuit board along the counterclockwise / clockwise direction in a double-wire manner to the edge of the circuit board; the starting ends of both wires penetrate the circuit board to reach the lower surface of the circuit board. The starting end of one path of patch copper wires is connected to an energy port through patch copper wires of the same specification as it and via a capacitor module, and the end of this path of patch copper wires penetrates the circuit board and is connected to the starting end of the other path of patch copper wires through patch copper wires to form the lower-layer circuit wiring B; the end of the other path of patch copper wires extends to a grounding port and is connected to the grounding port. Metal strips / tubes are fixed along the lines on the patch copper wires of the upper-layer circuit wiring A and the lower-layer circuit wiring B. The problem of high heat dissipation of the charging coil is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless electromagnetism and energy, and relates to a charging coil for high-power medium and long-distance wireless transmission and a preparation method thereof. Background Art

[0002] Wireless power transmission technology originated from the experiment conducted by Tesla in 1891: an electromagnetic energy transmission channel is formed by an electromagnetic transmitter and an electromagnetic wave receiver. This technology was improved and published by the Massachusetts Institute of Technology in 2007 and has received extensive attention. The electromagnetic technology most similar to it is the wireless data communication transmission technology (such as: 3G, 4G, WiFi) well-known and used by the public. The principle of wireless data transmission is similar to that of wireless power transmission. The difference is that data transmission mainly uses far field plane waves, while wireless power transmission uses near field electromagnetic waves. With the prosperity and wide use of mobile data terminals, wireless power transmission has been re-focused by the business community after 2000. In the field of technology research, wireless power transmission is mainly divided into two development directions: the technical exploration in the cutting-edge and frontier fields relying on laboratories; the research and development of practical technologies focusing on the consumer field.

[0003] At present, the technologies in the market application field are mainly divided into: 1. Ultra-short distance electromagnetic wave resonance transmission. Theoretically, this is based on the principle of a traditional transformer, and the electromagnetic field transmitters at both ends are fine-tuned to the resonance frequency band to achieve radio inductive resonance transmission of electrical energy (System of transmission of electrical energy. US645576 A). 2. Relatively long-distance wireless power transmission by means of electromagnetic wave transmission. This technology mainly uses the array gain achieved by a high-frequency antenna array to improve the transmission efficiency between the antenna transmitting array and the receiving antenna in a specific direction, such as Wattup of PowerCast. Compared with the relatively mature wireless data transmission technology, the wireless power transmission technology is still in its initial stage, with a short effective transmission distance (a few centimeters), a complex circuit structure, and a high cost.

[0004] At present, the existing QI technical standard is mainly used for mobile phone wireless charging: it consists of a wound coil and a magnetic core, which results in a relatively large volume, a transmission efficiency of 50% - 70%, easy heat generation inside the mobile phone; low penetration ability, resulting in a transmission distance of 3 - 5 mm, a charging power of 5 - 10 watts, and in addition, the transmitting coil and the receiving coil need to be strictly aligned. Many disadvantages of such technologies seriously restrict the application prospects of wireless charging in mobile phones, tablets, wearable devices, etc.

[0005] Due to its working principle, the electromagnetic induction method used in Qi technology must use a copper wire coil and a magnetic core to work together to improve the transmission efficiency. This results in a relatively large volume and high heat dissipation of the Qi charging module inside the mobile phone. For devices with limited space such as mobile phones, tablets, and wearable devices, the volume of the wireless charging receiving module inside the device must be small enough to ensure high transmission efficiency. With the increasing power of mobile phones, tablets, and wearable devices, the transmission power also needs to be larger and larger to meet the demand for fast charging. To improve the user experience of the product and maintain requirements such as a long transmission distance and low heat dissipation, these need to be comprehensively considered. All of these require a new concept for design. Summary of the Invention

[0006] An object of an embodiment of the present invention is to provide a charging coil for high-power medium and long-distance wireless transmission, so as to solve problems such as a large volume of the existing charging coil module, low transmission efficiency, low transmission power, short transmission distance, and high heat dissipation.

[0007] Another object of an embodiment of the present invention is to provide a preparation method for a charging coil for high-power medium and long-distance wireless transmission.

[0008] The technical solution adopted in an embodiment of the present invention is that a charging coil for high-power medium and long-distance wireless transmission includes a circuit board. An upper circuit wiring A is provided on the upper surface of the circuit board, and a lower circuit wiring B is provided on the lower surface of the circuit board; the upper circuit wiring A is formed by winding patch copper wires that sequentially surround outward in a double line from the center of the upper surface of the circuit board in a counterclockwise or clockwise direction to one side edge of the surface of the circuit board; the starting ends of the double lines of the upper circuit wiring A both penetrate the circuit board to reach the lower surface of the circuit board. The starting end of one path of patch copper wire is connected to an energy port through a patch copper wire of the same specification as it and via a capacitor module, and the end of this path of patch copper wire penetrates the circuit board and is connected to the starting end of the other path of patch copper wire through a patch copper wire of the same specification as it to form the lower circuit wiring B; the end of the other path of patch copper wire extends to a grounding port and is connected to the grounding port; metal strips or metal tubes are fixed along the lines of the patch copper wires of the upper circuit wiring A and the lower circuit wiring B.

[0009] Further, the width of the metal strip or the outer diameter of the metal tube is equal to the width of the patch copper wires of the upper circuit wiring A and the lower circuit wiring B;

[0010] The line spacing of the metal strip or the metal tube is equal to the line spacing of the upper circuit wiring A and the lower circuit wiring B;

[0011] The metal tube is made of a copper tube, and the metal strip is made of a copper strip.

[0012] Further, the line widths of the upper circuit wiring A and the lower circuit wiring B are both 2 ± 1.5 mm, and the line spacings are both 3.25 ± 2 mm. The line bends at the turning points are arranged in an arc shape.

[0013] Further, the circuit board is a rigid or flexible board with a dielectric constant less than 5 and a thickness less than 5 mm, and its length and width are both less than 15 cm.

[0014] Further, a coolant with a large conductivity difference and high impedance flows in the metal pipes welded on the upper circuit wiring A and the lower circuit wiring B, and the metal pipe welded on the upper circuit wiring A passes through the circuit board and is connected to the metal pipe welded on the lower circuit wiring B.

[0015] Further, the coolant with a large conductivity difference and high impedance is supplied by an external heat dissipation device connected to the transmission coil to form a closed-loop circuit;

[0016] The external heat dissipation device consists of a water pump, a radiator, an inlet pipe, a first outlet pipe and a second outlet pipe. The coolant outlet of the water pump is connected to the coolant inlet of the coil through the inlet pipe. The coolant outlet of the coil is connected to the coolant inlet of the radiator through the first outlet pipe for heat dissipation. The coolant outlet of the radiator is connected to the coolant inlet of the water pump through the second outlet pipe.

[0017] Further, the coolant inlet of the coil is the nozzle of the metal pipe at the connection between the upper circuit wiring A and the grounding port, and the coolant outlet of the coil is the nozzle of the metal pipe at the connection between the pin of the capacitor module not connected to the energy port and the lower circuit wiring B; or the coolant inlet of the coil is the nozzle of the metal pipe at the connection between the pin of the capacitor module not connected to the energy port and the lower circuit wiring B, and the coolant outlet of the coil is the nozzle of the metal pipe at the connection between the upper circuit wiring A and the grounding port;

[0018] The water pump uses a micropump;

[0019] The coolant with a large conductivity difference and high impedance uses liquid nitrogen;

[0020] The inlet pipe, the first outlet pipe and the second outlet pipe all use rubber hoses, and their inner diameters are less than or equal to the inner diameter of the metal pipe on the transmission coil.

[0021] Another technical solution adopted in the embodiment of the present invention is a preparation method of a charging coil for high-power medium- and long-distance wireless transmission, which is carried out according to the following steps:

[0022] Step S1: Simulate, adjust and optimize the physical parameters of the upper circuit wiring A and the lower circuit wiring B, namely the line width, the line spacing and the bending angle of the arc-shaped setting at the corner, and determine the optimal physical parameters of the upper circuit wiring A and the lower circuit wiring B;

[0023] Step S2: According to the optimal physical parameters of the upper-layer circuit wiring A and the lower-layer circuit wiring B, etch the upper-layer circuit wiring A and the lower-layer circuit wiring B on the circuit board, and then weld metal strips or metal tubes on the patch copper wires of the etched upper-layer circuit wiring A and the lower-layer circuit wiring B.

[0024] Further, in step S1, first etch the upper-layer circuit wiring A and the lower-layer circuit wiring B on the circuit board according to certain physical parameters to prepare a patch copper wire coil, measure its transmission efficiency, and then use simulation software to simulate and optimize the physical parameters of the upper-layer circuit wiring A and the lower-layer circuit wiring B. Prepare an optimized patch copper wire coil according to the optimized physical parameters of the upper-layer circuit wiring A and the lower-layer circuit wiring B and measure its transmission efficiency. Repeat the processes of simulation optimization, etching, and measuring the transmission efficiency until the physical parameters of the upper-layer circuit wiring A and the lower-layer circuit wiring B that maximize the transmission efficiency of the patch copper wire coil are obtained, and use them as the optimal physical parameters of the upper-layer circuit wiring A and the lower-layer circuit wiring B.

[0025] The thickness of the metal strip or metal tube in step S2 is greater than or equal to the skin depth.

[0026] Further, in step S2, a mold is used for auxiliary fixation, and metal strips or metal tubes are directly welded along the lines on the patch copper wires according to the wiring of the etched upper-layer circuit wiring A and the lower-layer circuit wiring B on the circuit board, so that within a distance of 1 mm to 10 cm, welding a capacitor module can generate electromagnetic resonance coupling with a transmission efficiency higher than 85% and a bandwidth of 1.5 MHz at 6.78 MHz.

[0027] The beneficial effects of the embodiments of the present invention are as follows: In order to reduce the temperature rise problem of high transmission power and obtain higher transmission efficiency, metal strips or metal tubes are arranged on the patch copper wires, and the thickness of the metal strips or metal tubes meets the skin depth. The outer layer of the metal strip or metal tube transmits energy or data, and the inner layer dissipates heat, effectively slowing down the temperature rise speed and reducing the temperature saturation critical value, so that charging can be quickly completed before the over-temperature value. At the same time, the increase of metal can generate a stronger magnetic field, which not only increases the heat conduction ability of the charging coil but also improves the transmission efficiency of the coil. Energy transmission with a power greater than or equal to 500 W and a transmission distance of 1 mm to 10 cm can be carried out, and the length and width of the circuit board are less than 15 cm, and the transmission efficiency reaches 90 - 95%. This effectively solves the problems of the existing charging coil module, such as large volume, low transmission efficiency, low transmission power, short transmission distance, and high heat dissipation. For energy transmission with a power greater than 500 W, metal tubes are arranged on the patch copper wires, and a coolant with poor conductivity and high impedance flows in the metal tubes. Under the action of an external heat circulation device, the coolant conducts the heat energy on the metal tubes to the outside, effectively dissipating heat for high-power charging coils. Moreover, while improving the coupling transmission efficiency, the coils of the embodiments of the present invention do not affect the circuit design parameters. Brief Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 is a schematic structural diagram of the charging coil according to an embodiment of the present invention.

[0030] Figure 2 is a schematic diagram of the upper-layer circuit wiring A of the charging coil according to an embodiment of the present invention.

[0031] Figure 3 is a simulation effect diagram of the charging coil according to an embodiment of the present invention.

[0032] Figure 4 is a diagram showing the relationship between various indicators of the transmission coil.

[0033] Figure 5 is a comparison diagram of the transmission efficiency between the coil according to an embodiment of the present invention and the coil without using metal strips or metal tubes for wiring.

[0034] Figure 6(a) is a schematic diagram of the magnetic field distribution of the coil without using metal strips or metal tubes for wiring.

[0035] Figure 6(b) is a schematic diagram of the magnetic field distribution of the coil according to an embodiment of the present invention.

[0036] Figure 7 is a structural block diagram of the external heat dissipation device according to an embodiment of the present invention.

[0037] In the figure, 1. circuit board, 2. upper-layer circuit wiring A, 3. through hole, 4. lower-layer circuit wiring B, 5. energy port, 6. grounding port, 7. capacitor module, 11. upper-layer first through hole, 12. upper-layer second through hole, 13. upper-layer third through hole, 21. lower-layer first through hole, 22. lower-layer second through hole, 23. lower-layer third through hole, 8. water pump, 9. radiator, 10. water inlet pipe, 14. first water outlet pipe, 15. second water outlet pipe. Detailed Embodiments

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0039] The charging coil structure for high-power medium- and long-distance transmission is as follows Figures 1-2 shown, including a circuit board 1. An upper-layer circuit wiring A2 is provided on the upper surface of the circuit board 1, and a lower-layer circuit wiring B4 is provided on the lower surface of the circuit board 1; the upper-layer circuit wiring A2 is formed by winding patch copper wires that sequentially and outwardly surround in a counterclockwise direction from the center of the upper surface of the circuit board 1 to one side edge of the surface of the circuit board 1 in a double-wire manner; the starting ends of the double wires of the upper-layer circuit wiring A2 both penetrate the circuit board 1 to reach the lower surface of the circuit board 1. The starting end of one path of patch copper wires is connected to the energy port 5 through patch copper wires of the same specification as it and via a capacitor module 7, and the end of this path of patch copper wires penetrates the circuit board 1 and is connected to the starting end of the other path of patch copper wires through patch copper wires of the same specification as it, forming the lower-layer circuit wiring B4; the end of the other path of patch copper wires extends to the ground port 6 and is connected to the ground port 6. Specifically, the end of one path of copper wires in the double wires reaches the lower surface of the circuit board 1 through a through hole 3 (via hole) that penetrates the upper and lower surfaces of the circuit board 1. One end of the through hole 3 on the upper surface of the circuit board 1 is the upper-layer first through hole 11, and one end of it on the lower surface of the circuit board 1 is the lower-layer first through hole 21. The patch copper wires passing through the through hole 3 reach the lower-layer first through hole 21 on the lower surface of the circuit board 1. An upper-layer second through hole 12 and an upper-layer third through hole 13 are provided at the center of the upper surface of the circuit board 1, and a lower-layer second through hole 22 and a lower-layer third through hole 23 are provided at the center of the lower surface of the circuit board 1. The upper-layer second through hole 12 and the lower-layer second through hole 22 are vertically penetrated, and the upper-layer third through hole 13 and the lower-layer third through hole 23 are vertically penetrated. The starting end of one path of patch copper wires in the double wires of the upper-layer circuit wiring A2 sequentially passes through the upper-layer second through hole 12 and the lower-layer second through hole 22, and is connected to the starting end of the patch copper wires on the lower surface of the circuit board 1 passing through the through hole 3 through patch copper wires of the same specification. The starting end of the other path of patch copper wires in the double wires sequentially passes through the upper-layer third through hole 13 and the lower-layer third through hole 23, and is connected to one end of the capacitor module 7 through patch copper wires of the same specification. The other end of the capacitor module 7 is connected to the energy port 5 through patch copper wires of the same specification, and the energy port 5 is connected to an external cable. And metal strips or metal tubes are fixed along the lines of the patch copper wires of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4.

[0040] In this embodiment, the widths and line spacings of the patch copper wires of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 are equal, with the width being 2 ± 1.5 mm and the line spacing being 3.25 ± 2 mm. The outer diameter of the copper tube / the width of the copper strip and the line spacing are equal to the width and line spacing of the patch copper wire. Additionally, in the embodiment of the present invention, all the turning points of the charging coil are arranged in an arc shape, and the bending angle, that is, the angle of bending, is 30 - 85°, ensuring the transmission efficiency. This is because when the turning points of the copper tube / copper strip are set at right angles, the transmission efficiency will be reduced by 10 - 15%. The circuit board 1 is a rigid or flexible board with a dielectric constant less than 5 and a thickness less than 5 mm, and its length and width are both less than 15 cm. The capacitor module 7 can be installed and encapsulated into various capacitor groups with specifications of 0402, 0603, 0805, 1206, 1812, 2010, 2225, and 2512 according to the size of the capacitor bank.

[0041] While improving the transmission efficiency, this embodiment conducts heat dissipation, making the time to reach the over-temperature value longer and ensuring that charging can be quickly completed before the over-temperature value. Copper tubes with a diameter of 3 mm and a thickness of 0.8 mm (i.e., an inner diameter of 2.2 mm) are welded on the patch copper wires of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 of the circuit board 1. The obtained coil can complete the charging of a 48V battery with a capacity of 10 Ah within 2 hours under an energy transmission power of 250W, and its temperature will not exceed the standard temperature index of 80°C for products in the general consumer market. When the coil thickness, that is, the wall thickness of the copper tube or the thickness of the copper strip, is 2.5 - 3 mm, its energy transmission power can reach 500W. In this embodiment, the thickness of the copper tube and the copper strip is not limited, and it is specifically set according to requirements and only needs to meet the skin depth.

[0042] When the energy transmission power is greater than or equal to 500W, there will inevitably be an over-temperature problem in the system. To solve this problem, in the embodiment of the present invention, on the basis of using copper tubes for energy transmission and heat dissipation, while increasing the outer diameter and thickness of the copper tubes, a coolant with a poor conductivity and a high impedance (such as liquid nitrogen) is circulated in the copper tubes welded on the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4, and the copper tube welded on the upper-layer circuit wiring A2 passes through the circuit board 1 and is connected to the copper tube welded on the lower-layer circuit wiring B4. This coolant with a poor conductivity and a high impedance is supplied by an external heat dissipation device connected to the charging coil to form a closed-loop circuit. Figure 7As shown in the figure, the external heat dissipation device is composed of a water pump 8, a radiator 9, a water inlet pipe 10, a first water outlet pipe 14, and a second water outlet pipe 15. The coolant outlet of the water pump 8 is connected to the coolant inlet of the coil through the water inlet pipe 10. The coolant outlet of the coil is connected to the coolant inlet of the radiator 9 through the first water outlet pipe 14 for heat dissipation. The coolant outlet of the radiator 9 is connected to the coolant inlet of the water pump 8 through the second water outlet pipe 15. The coolant inlet of the coil is the copper pipe nozzle at the connection of the upper-layer circuit wiring A2 and the grounding port 6, and the coolant outlet of the coil is the copper pipe nozzle at the connection of the pin of the capacitor module 7 not connected to the energy port 5 and the lower-layer circuit wiring B4; or the coolant inlet of the coil is the copper pipe nozzle at the connection of the pin of the capacitor module 7 not connected to the energy port 5 and the lower-layer circuit wiring B4, and the coolant outlet of the coil is the copper pipe nozzle at the connection of the upper-layer circuit wiring A2 and the grounding port 6. The water pump 8 uses a micropump, and the water inlet pipe 10, the first water outlet pipe 14, and the second water outlet pipe 15 all use rubber hoses, and their inner diameters are less than or equal to the inner diameter of the metal pipe on the transmission coil. Through the water pump 8, the radiator 9, the coolant with a large conductivity difference or high impedance, and the formed closed-loop circuit, the heat exchange and heat dissipation of the copper pipe are realized, and the recycling of the coolant is realized.

[0043] In the embodiment of the present invention, the patch copper wire between the capacitor module 7 and the energy port 5 can be shortened, so that the capacitor module 7 is close to the energy port 5. Then, the coolant circulation loop is formed from the copper pipe above the capacitor module 7 to the copper pipe at the grounding port 6. The temperature influence of the shortened patch copper wire (close to the energy port 5) is infinitely suppressed and can be ignored.

[0044] In the embodiment of the present invention, the water-transporting function of the copper pipe is skillfully utilized, so that a small-sized high-wattage copper pipe coil can use general water-cooling equipment. The water-cooling equipment fills the copper pipe at the hot spot with coolant through a soft rubber water pipe, and the coolant circulates through the soft rubber water pipe and goes to the external radiator 9 to take away the heat energy. Furthermore, at this time, the high-frequency electricity will select the physical surface with low impedance and flow within the skin surface, so it will not have a negative impact on the performance of the high-frequency coil. Therefore, the heat dissipation method of welding copper pipe + coolant can effectively solve the over-temperature problem of systems with a working power of 500 watts or more up to tens of thousands of watts, such as the over-temperature problems of charging systems for electric buses (power 100 - 150 kW), electric vehicles (power 20 - 50 kW), etc.

[0045] When wiring the coil in this embodiment, the following steps are carried out:

[0046] Step S1: Simulate and adjust the physical parameters such as the line width, line spacing, and the bending angle of the arc-shaped setting at the corner of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 to determine the optimal physical parameters of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4. Specifically, first etch the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 on the circuit board 1 according to certain physical parameters to form a patch copper wire coil, measure its transmission efficiency, and then use simulation software to simulate and optimize the physical parameters of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4. Prepare an optimized patch copper wire coil according to the optimized physical parameters of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 and measure its transmission efficiency. Repeat the simulation optimization, etching, and measurement of the transmission efficiency until the physical parameters of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 that maximize the transmission efficiency of the patch copper wire coil are obtained, and use them as the optimal physical parameters of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4.

[0047] Step S2: According to the optimal physical parameters of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4, etch the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 on the circuit board 1, and then weld metal strips or metal tubes along the lines of the etched patch copper wires of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4. Specifically, use a mold for auxiliary fixation and directly weld metal strips or metal tubes along the lines of the etched patch copper wires of the upper-layer circuit wiring A2 and the lower-layer circuit wiring B4 on the circuit board 1 according to the wiring.

[0048] Using a mold for auxiliary fixation, directly weld copper tubes or copper strips on the patch copper wire coil according to the wiring of the patch copper wire coil. Without further fine-tuning, it can have the characteristics of good heat dissipation, high efficiency, and long transmission distance. The inductance value of the coil must be able to reach the degree of resonant coupling. After optimization and adjustment, the inductance value of the coil is in the range of 1 - 1500 pf, so that within a distance of 1 mm to 10 cm, the coil only needs the capacitor module 7 to generate high-efficiency electromagnetic resonance coupling at 6.78 MHz within the effective design distance. The coupling effect is as Figure 3 shown, which is the simulation result diagram of the charging coil of the embodiment of the present invention. Among them, the transmission coefficient of about 0.8 MHz bandwidth is 97.4%, and the transmission efficiency is 97.4 2 = 95%; the transmission coefficient of 1.3 MHz bandwidth is 94.8%, and the transmission efficiency is 94.8 2 = 90%; the transmission coefficient of 1.5 MHz bandwidth is 92.2%, and the transmission efficiency is 92.2 2 = 85%. Currently, no other design can achieve such wide-frequency and high-efficiency energy transmission. Figure 3Among them, curve S1,1 is the curve of the reflection coefficient of the transmitting coil port varying with frequency, curve S2,2 is the curve of the reflection coefficient of the receiving coil port varying with frequency, curve S1,2 is the curve of the reverse transmission coefficient varying with frequency, and S2,1 is the curve of the forward transmission coefficient varying with frequency.

[0049] The outer diameter of the metal tube or the width of the metal strip is equal to the width of the patch copper wire on the circuit board 1. The thickness of the metal strip needs to be ensured outside the skin depth range, that is, the thickness of the metal strip should be greater than the skin depth. And through appropriate thickness design and adjustment, the system can be quickly charged before the over-temperature value.

[0050] The transmission distance is related to the size of the coil and the strength of the magnetic field. At the same frequency, area and transmission power, a strong electromagnetic field can effectively couple and convert, and the transmission efficiency is high. At the same time, for a coil with a large area, the magnetic field is large and the corresponding distance is far. Therefore, it is relatively difficult to make the coil area small while the transmission distance is large. The length and width of the coil in this application are both less than 15 cm. At a distance of 1 mm to 10 cm, the coil only needs the capacitor module 7 to generate high-efficiency electromagnetic resonance coupling at 6.78 MHz within the effective design distance. The effect is shown in Figure 3 , the transmission efficiency of the current charging device is generally 70%, and the best can reach 85%. However, the transmission efficiency of the charging coil in this embodiment reaches 90 - 95%.

[0051] Figure 4 Describes the relationship between the transmission coil and its electromagnetic characteristics and transmission characteristics. Among them, a represents power VS temperature, b represents multi-layer design VS temperature, c represents size VS efficiency, d represents distance VS efficiency, e represents frequency VS size, f represents frequency VS efficiency, and g represents all indicators VS cost. From Figure 4 It can be seen that the higher the transmission power, the higher the coil temperature; the more layers of the coil, the lower the surface temperature; the larger the coil size, the higher the transmission efficiency; the farther the distance between the coils, the lower the transmission efficiency; the higher the operating frequency, the smaller the coil size, and there is no direct relationship between the operating frequency and the transmission efficiency; the higher each indicator, the higher the cost. Therefore, it can be seen that there are contradictory relationships among many indicators (cost, efficiency, difficulty, size, distance, etc.), which restrict each other. And it is very difficult to achieve a better balance among the indicators. However, the embodiment of the present invention can obtain an ideal effect with simple processing and has a low cost.

[0052] Figure 5 Is a comparison chart of the transmission efficiency of the coil in the embodiment of the present invention and the coil without using metal strip or metal tube wiring. From Figure 5It can be seen that between 6 and 7.1 MHz (including 6.78 MHz), the coil transmission efficiency of the embodiment of the present invention is greater than that of the coil without using metal strip or metal tube wiring. Fig. 6(a) is a schematic diagram of the magnetic field distribution of the coil without using metal strip or metal tube wiring, and Fig. 6(b) is a schematic diagram of the magnetic field distribution of the coil of the embodiment sold to you. It can be seen from Fig. 6(a) and Fig. 6(b) that the magnetic field distribution of the coil of the embodiment of the present invention is more intensive, stable and uniform. Moreover, the electromagnetic energy of the embodiment of the present invention is strictly restricted near the coil, especially between the coils, especially in the core area, which is also the special point of the present invention. After measurement, at a distance of 15 cm, the electromagnetic energy is strictly confined.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A charging coil for high-power medium- and long-distance wireless transmission, characterized in that, It includes a circuit board (1). An upper-layer circuit wiring A (2) is provided on the upper surface of the circuit board (1), and a lower-layer circuit wiring B (4) is provided on the lower surface of the circuit board (1). The upper-layer circuit wiring A (2) is formed by winding patch copper wires that sequentially and outwardly surround in a double-line manner from the center of the upper surface of the circuit board (1) along the counterclockwise or clockwise direction to one side edge of the surface of the circuit board (1). The starting ends of the double lines of the upper-layer circuit wiring A (2) both penetrate the circuit board (1) to reach the lower surface of the circuit board (1). The starting end of one path of patch copper wires is connected to the energy port (5) through patch copper wires of the same specification as it and via a capacitor module (7). And the end of this path of patch copper wires penetrates the circuit board (1) and is then connected to the starting end of the other path of patch copper wires through patch copper wires of the same specification as it, forming the lower-layer circuit wiring B (4). The end of the other path of patch copper wires extends to the ground port (6) and is connected to the ground port (6). Metal strips or metal tubes are fixed along the lines of the patch copper wires of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4). Coolant with a poor conductivity and a high impedance flows in the metal tubes welded on the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4). And the metal tubes welded on the upper-layer circuit wiring A (2) penetrate the circuit board (1) and are connected to the metal tubes welded on the lower-layer circuit wiring B (4). The coolant with a poor conductivity and a high impedance is supplied by an external heat dissipation device connected to the transmission coil to form a closed-loop circuit. The external heat dissipation device consists of a water pump (8), a radiator (9), a water inlet pipe (10), a first water outlet pipe (14), and a second water outlet pipe (15). The coolant outlet of the water pump (8) is connected to the coolant inlet of the coil through the water inlet pipe (10). The coolant outlet of the coil is connected to the coolant inlet of the radiator (9) through the first water outlet pipe (14) for heat dissipation. The coolant outlet of the radiator (9) is connected to the coolant inlet of the water pump (8) through the second water outlet pipe (15). The circuit board (1) is a rigid or flexible board with a dielectric constant less than 5 and a thickness less than 5 mm, and its length and width are both less than 15 cm.

2. The charging coil for high-power medium- and long-distance wireless transmission according to claim 1, wherein The width of the metal strip or the outer diameter of the metal tube is equal to the width of the patch copper wires of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4). The line spacing of the metal strip or the metal tube is equal to the line spacing of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4). The metal tube is made of copper tube, and the metal strip is made of copper strip.

3. The charging coil for high-power medium- and long-distance wireless transmission according to claim 1, wherein The line widths of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4) are both 2 ± 1.5 mm, and the line spacings are both 3.25 ± 2 mm. The turning points of their lines are set in an arc shape.

4. The charging coil for high-power medium- and long-distance wireless transmission according to claim 1, wherein The coolant inlet of the coil is the pipe orifice of the metal tube at the connection of the upper-layer circuit wiring A (2) and the ground port (6), and the coolant outlet of the coil is the pipe orifice of the metal tube at the connection of the pin of the capacitor module (7) not connected to the energy port (5) and the lower-layer circuit wiring B (4). Alternatively, the coolant inlet of the coil is the nozzle of the metal tube at the connection between the pin of the capacitor module (7) not connected to the energy port (5) and the lower-layer circuit wiring B (4), and the coolant outlet of the coil is the nozzle of the metal tube at the connection between the upper-layer circuit wiring A (2) and the ground port (6); The water pump (8) is a micropump; The coolant with poor conductivity and high impedance is liquid nitrogen; The water inlet pipe (10), the first water outlet pipe (14) and the second water outlet pipe (15) are all made of rubber hoses, and their inner diameters are less than or equal to the inner diameter of the metal tube on the transmission coil.

5. The preparation method of the charging coil for high-power medium- and long-distance wireless transmission according to any one of claims 1 to 4, characterized in that, It is carried out according to the following steps: Step S1: Simulate, adjust and optimize the physical parameters of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4), namely the line width, the line spacing and the bending angle of the arc-shaped setting at the corner, and determine the optimal physical parameters of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4); Step S2: According to the optimal physical parameters of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4), etch the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4) on the circuit board (1), and then weld metal strips or metal tubes on the patch copper wires of the etched upper-layer circuit wiring A (2) and lower-layer circuit wiring B (4).

6. The preparation method of the charging coil for high-power medium- and long-distance wireless transmission according to claim 5, characterized in that In step S1, first, the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4) are etched on the circuit board (1) according to certain physical parameters to prepare a patch copper wire coil, and its transmission efficiency is measured. Then, a simulation software is used to simulate, adjust and optimize the physical parameters of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4). According to the optimized physical parameters of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4), an optimized patch copper wire coil is prepared and its transmission efficiency is measured. The simulation optimization and etching measurement of the transmission efficiency are carried out in a cycle until the physical parameters of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4) that maximize the transmission efficiency of the patch copper wire coil are obtained, and they are used as the optimal physical parameters of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4); The thickness of the metal strip or metal tube in step S2 is greater than or equal to the skin depth.

7. The preparation method of the charging coil for high-power medium- and long-distance wireless transmission according to claim 6, characterized in that, Step S2 is to use a mold for auxiliary fixation, and directly weld metal strips or metal tubes along the lines on the patch copper wires according to the wiring of the upper-layer circuit wiring A (2) and the lower-layer circuit wiring B (4) etched on the circuit board (1), so that within a distance of 1 mm to 10 cm, welding the capacitor module (7) can generate electromagnetic resonance coupling with a transmission efficiency higher than 85% and a bandwidth of 1.5 MHz at 6.78 MHz.

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