Heating system based on same-frequency coupling magnetic field

Abstract

The invention discloses a heating system based on a same-frequency coupling magnetic field, and relates to the field of thermoplastic composite material repairing. The heating device comprises a heating device body, the heating device body is a sheet-shaped shell with a certain thickness, the lower end face of the shell is a heating face, a plurality of coils which are arranged in a stacked mode from bottom to top are arranged in the shell, an insulating layer is arranged between every two adjacent coils, and the areas of the coils are sequentially reduced from bottom to top. The device can adapt to composite material products of different structural types, the induction heating technology can achieve rapid heating of materials, and the repairing speed is increased.

Description

Technical Field

[0001] The present invention relates to the field of repairing thermoplastic composites, and particularly to a heating system based on a co-frequency coupling magnetic field. Background Art

[0002] Carbon fiber thermoplastic composites have high specific strength, specific stiffness, and excellent fatigue resistance and corrosion resistance. Therefore, they are widely used in fields such as aerospace, automobiles, and pressure vessels, and have become key components and standardized products for power structures, fuel systems, and energy storage and transportation. However, during the service process of carbon fiber composite products, they will withstand various harsh environments and complex loads, and it is inevitable to generate multi-scale and multi-type damages inside them (such as resin matrix cracks, fiber fractures, fiber-resin debonding, fiber pull-outs, interlayer delamination, etc.). This is likely to cause the gradual expansion of micro-scale damages, leading to severe damage to the material, seriously affecting the service reliability, safety, and service life of the structure. Therefore, during the use of the material, it is necessary to repair the damaged location in a timely manner to ensure the safety of the use of carbon fiber composite products and improve the service life of the products.

[0003] Traditional heating technologies for repairing carbon fiber composite products mainly use infrared, hot air, and resistance heating methods. These methods all have the problems of large equipment floor area, long heating cycles, and the need for a specific working environment during repair. In particular, it is extremely difficult to repair large-sized and non-removable carbon fiber composite products (such as aircraft fuselages, wind turbine blades, etc.). Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a heating system based on a co-frequency coupling magnetic field, including a heating device. The heating device is a sheet-shaped housing with a certain thickness. The lower end surface of the housing is the heating surface. Inside the housing, there are several coils arranged in a stacked manner from bottom to top. There is an insulating layer between adjacent coils, and the areas of the coils gradually decrease from bottom to top.

[0005] Further, the housing is a flexible rubber housing.

[0006] Further, the sheet-shaped housing includes a first housing and a second housing, and the first housing and the second housing are joined together to form a sealed sheet-shaped housing.

[0007] Further, the coils are independent disc-shaped structures, and the winding directions of the coils are the same. The winding density of the coils gradually decreases from the inside to the outside.

[0008] Further, the distance L between the nth turn of the wire and the (n - 1)th turn of the wire of the coil is:

[0009]

[0010] Among them, N is the target number of turns of the coil, and a is the wire diameter of the wire used.

[0011] Furthermore, a first coil and a second coil are provided inside the housing, and the first coil is located below the second coil.

[0012] Furthermore, the relationship between the current I1 passed through the first coil and the current I2 passed through the second coil is: C·I1 = I2, where C is the current coefficient; the current coefficient C is:

[0013]

[0014] Among them, S1 is the area of the first coil, S2 is the area of the second coil, I1 is the current intensity in the first coil, f1 is the frequency applied in the first coil, and l is the distance between the first coil and the second coil.

[0015] Furthermore, the heating system includes a vacuum pressure device. An annular groove is formed on the side surface where the first housing and the second housing are joined together, and the vacuum pressure device is connected to the annular groove through a vacuum tube.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] The present invention is small in size and portable. The heating device as a whole is a soft rubber pad, which can adapt to composite products with different structural types, and the induction heating technology can achieve rapid heating of the material and improve the repair rate.

[0018] The following will further illustrate the concept, specific structure and technical effects of the present invention with reference to the drawings to fully understand the purpose, features and effects of the present invention. Description of the Drawings

[0019] Figure 1 is a schematic diagram of the overall structure of a specific embodiment of the present invention;

[0020] Figure 2 is a schematic longitudinal sectional view of the first coil and the second coil of the heating device in a specific embodiment of the present invention;

[0021] Figure 3 is a schematic diagram of the structure of the first coil in a specific embodiment of the present invention;

[0022] Figure 4 is a schematic diagram of the structure of the first housing in a specific embodiment of the present invention;

[0023] Figure 5 is a schematic diagram of the structure of the vacuum pressure device in a specific embodiment of the present invention;

[0024] Figure 6It is a schematic structural diagram of a dual-channel induction heater according to a specific embodiment of the present invention;

[0025] Figure 7 It is a schematic structural principle diagram of a traditional heating coil according to a specific embodiment of the present invention;

[0026] Figure 8 It is a schematic diagram of the heating effect according to a specific embodiment of the present invention; Figure 8 a is the heating effect diagram using a traditional heating coil, Figure 8 b is the heating effect diagram using the heating coil of this embodiment. Specific Embodiments

[0027] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0028] As Figure 1 shown, in a specific embodiment, a heating system based on a same-frequency coupled magnetic field is provided, including a vacuum pressure device 1, a dual-channel induction heater 2, and a heating device 3. The heating device 3 is used to directly act on the area to be heated. The dual-channel induction heater is used to control the heating device 3 and adjust the temperature and heating time of the heating device 3. The vacuum pressure device 1 is used to adjust the pressure inside the heating device 3 to make the heating device 3 closely fit on the surface of the composite material product, providing surface pressure for the carbon fiber thermoplastic composite material.

[0029] As Figure 2As shown, the heating device 3 is a sheet-shaped housing with a certain thickness. The lower end face of the sheet-shaped housing is the heating surface. A coil disk is arranged inside the sheet-shaped housing. The sheet-shaped housing is a soft high-temperature resistant rubber housing, and its rubber material can be fluororubber, silicone rubber, neoprene rubber, etc. In application, the sheet-shaped heating device 3 does not need to be limited to the plane heating condition, but can also be applied to the heating of irregular surfaces such as arc surfaces, and has good high-temperature resistance characteristics. When the working temperature is about 350°C, the rubber material will not undergo a phase change reaction after heating and can be reused multiple times. Compared with the traditional large heating device 3, the total weight of the heating device 3 is only about 10 kilograms. The sheet-shaped heating device 3 is convenient to move, and can be operated by a single person during the working process. It can be applied to the repair of the surfaces of large curved parts such as the aircraft fuselage and wind turbine blades. During the working process, the heating device 3 can be laid at the position to be repaired, and the application is more flexible, greatly improving the applicable range of the thermoplastic composite material repair; in actual application, the specific material of the housing can be selected according to needs, as long as it can achieve softness, high-temperature resistance, and will not undergo a phase change reaction when the heating temperature is about 350°C.

[0030] The coil disk is the heating element of the heating device 3. Coils are arranged in the housing in a stacked manner from bottom to top. And an insulating layer 307 is provided between adjacent coils. The area of the coils decreases from bottom to top. The number of coils can be adjusted according to needs. However, if the number of coil layers is too many, the distance between the topmost coil and the object to be heated is too large, and the generated magnetic field decays cubically with the increase of the distance, and the magnetic field intensity acting on the material drops severely, resulting in a waste of energy. Therefore, in this embodiment, it includes a first coil 301 and a second coil 302 arranged in a stacked manner from bottom to top. The two coils are independent disk-shaped structures, and the structures of the first coil 301 and the second coil 302 are the same, and the winding directions of the first coil 301 and the second coil 302 are also the same. The two coils are heated by the same-frequency heating method, and the heat is transmitted through the housing to complete the repair operation. In order to monitor the heating temperature of the coils, a temperature sensor is provided in the housing.

[0031] In a specific embodiment, the first coil 301 and the second coil 302 are rectangular coils. In the specific application process, other shapes can also be used, such as circular shapes, etc. The wire for winding the coils is copper wire, and the copper wire is a stranded wire, or can also be wound with single-strand enameled wire and silk-covered wire.

[0032] In this embodiment, both the first coil 301 and the second coil 302 are planar disk-shaped coils, and the magnetic fields they generate belong to planar magnetic fields. The intensity of the magnetic field is directly related to the number of turns and the diameter of the coil. The larger the diameter and the more the number of turns, the higher the intensity. However, the coil diameter in the central region of the coil structure is small, resulting in a weak magnetic field intensity and poor internal heating uniformity. Therefore, the winding density of the coils in this embodiment gradually decreases from the inside to the outside. As Figure 3 shown, increasing the internal coil density and the number of turns of the coil can increase the magnetic field intensity. Since the outer coil has a large diameter, reducing the number of turns of the coil makes the overall magnetic field intensity inside and outside close, which can improve the heating uniformity.

[0033] The distance L between the nth turn of copper wire and the (n - 1)th turn in the coil is:

[0034]

[0035] where N is the target number of turns of the coil, and a is the diameter of the copper wire used.

[0036] To further improve the heating uniformity, the area of the first coil 301 is larger than that of the second coil 302, and the shapes of the first coil 301 and the second coil 302 are similar. In this embodiment, when the coils are rectangular coils, the ratio of the side length of the second coil 302 to the side length of the first coil 301 is 1 / 3 - 1 / 2. When the coils are circular coils, the ratio of the radius of the second coil 302 to the diameter of the first coil 301 is 1 / 3 - 1 / 2. The size difference between the two coils is to increase the concentration of energy at the center of the coil, which can further enhance the central energy and the outer circle energy.

[0037] Due to the difference in size between the first coil 301 and the second coil 302, to improve the heating uniformity, the current I1 passed through the first coil 301 and the current I2 passed through the second coil 302 satisfy the following relationship:

[0038] C·I1 = I2;

[0039] where C is the current coefficient; the current coefficient C is:

[0040]

[0041] where S1 is the area of the first coil 301; S2 is the area of the second coil 302; I1 is the current intensity in the first coil 301, in unit A; f1 is the frequency applied in the first coil 301, in unit kHz; l is the distance between the first coil 301 and the second coil 302, in unit mm.

[0042] In order to protect and carry two coils, in this embodiment, the sheet-shaped housing includes a first housing 303 and a second housing 304. The first housing 303 and the second housing 304 are combined to form a sealed sheet-shaped housing. In this embodiment, the first housing 303 is located at the lower part, and the second housing 304 is located at the upper part. The upper end surface and the lower end surface of the second housing 304 are both smooth planes. The upper end surface of the first housing 303 is recessed downward to form two interconnected annular grooves 307. Due to the existence of the annular grooves 307, a rubber boss 308 is formed in the middle of the first housing 303 relative to the annular grooves 307. The first coil 301 and the second coil 302 are located on the rubber boss 308. When the first housing 303 and the second housing 304 are combined, the upper surface of the rubber boss 308 and the lower surface of the second housing 304 tightly fix the first coil 301 and the second coil 302 inside the housing.

[0043] In a specific embodiment, as Figure 4 shown, the first housing 303 and the second housing 304 can adopt an integrally injection-molded overall structure. The first housing 303 and the second housing 304 are pressed and formed, and intermediate components such as the first coil 301, the second coil 302, and the temperature sensor are all integrally injection-molded in the middle.

[0044] Since the heating device 3 is in a flexible sheet-shaped structure, the sheet-shaped structure makes the pressure between the heating device 3 and the plane to be repaired slightly insufficient. In order to combine portability and heating effect, as Figure 5 shown, in this embodiment, the vacuum pressure device 1 includes a vacuum button 101 starting device, a vacuum pumping port 102, a pressurizing port 103, a vacuum pressure test port 104, a vacuum pressure gauge 105, a vacuum pump 106, a vacuum tube 107, a vacuum test tube 108, and a pressurizing tube 109. Correspondingly, a pressure sensor 305 is provided in the housing to monitor the pressure inside the housing in real time through the pressure sensor 305.

[0045] The vacuum pressure device 1 is communicated with the inside of the sheet-shaped housing through a vacuum tube. As Figure 1 shown, in this embodiment, two air circulation holes are opened on the second housing 304, and the air circulation holes are located at the annular grooves 307, so that the vacuum pressure device 1 is communicated with the annular grooves 307 through a vacuum tube. During the working process, a rubber pad is laid on the damaged part of the composite material, the vacuum pressure channel is opened, the rubber pad is tightly attached to the surface of the composite material product to provide surface pressure for the carbon fiber thermoplastic composite material, and then the induction heating channel is opened to provide energy for the induction coil to heat the carbon fiber composite material to make it solidify and form, completing the repair of the damaged position of the thermoplastic carbon fiber composite material.

[0046] As Figure 6As shown, the dual-channel induction heater includes a power input port 201, a load power supply port 202, a load power supply port 203, a display 204, a temperature sensor port 205, a start button 206, a power supply 207, power output lines 208 and 209. An adjustment circuit is provided inside the dual-channel induction heater. By receiving data from the temperature sensor and the pressure sensor, it adjusts the output voltage, current, and vacuum pumping control signal, and adjusts data such as the heating temperature of the heating device 3 and the vacuum pumping pressure inside the housing. The adjustment circuit can be implemented using an adjustment circuit in the prior art and will not be elaborated here.

[0047] In a specific embodiment, the power of the power supply 207 is generally between 2.5 - 5 KW, and the power can be adjusted. The load power supply ports 202 and 203 output the same current and frequency to enhance the energy output in the central region.

[0048] In a specific embodiment, the overall outer diameter of the first coil 301 is 350 mm, and the overall outer diameter of the second coil 302 is 250 mm. The second coil 302 is laid 2 - 8 mm below the first coil 301. The annular groove 307 is located 25 mm from the outer edge of the first coil 301. The width range of the groove is 15 - 35 mm, the depth is 5 mm - 15 mm, and the distance from the edge of the second housing 304 is 35 mm. For repairing carbon fiber composite materials with different resin matrices, the control temperatures are different. For PEEK material as the matrix, when the temperature sensor 306 collects a value reaching 320 °C, the dual-channel induction heater 22 is regulated to output a current to maintain the temperature at 320 °C. At the same time, when the number of material plies is 3 or less, the dual-channel induction heater 22 is turned off after maintaining the temperature for 35 seconds. If PP material is used, when the temperature sensor 306 collects a value reaching 180 °C, if PE material is used, when the temperature sensor 306 collects a value reaching 165 °C is sufficient, and the temperature holding time is the same as that of the PEEK material. Before the dual-channel induction heater 22 heats, vacuum pumping is first performed. When the relative true vacuum reaches 0.6, the start button 206 is pressed. The relative vacuum degree linearly rises with the change of the relative temperature. When the relative temperature is 1, the relative medium vacuum degree is 1.

[0049] In a specific embodiment, the carbon fiber composite material is heated by a traditional coil and the heating coil described in the above embodiment. The traditional coil is a uniformly wound spiral coil, as Figure 7 shown. The wire diameters and materials of the coils in the two schemes are the same, and the number of turns of the coils in the two schemes is the same. The heating effect diagrams are as Figure 8As shown, the heating effect of the helical coil wound in the traditional uniform manner is as shown in Figure a. The surface temperature field of the material is mainly concentrated in the middle area of the coil, and the numerical value of the temperature field decreases rapidly during the outward diffusion process. The uniformity of the temperature field is poor, especially the temperature value in the central area is low, and it is difficult to achieve the uniformity of the temperature field within the effective heating range. However, the heating effect of the induction heating method of the present application is as shown in Figure b. It can be seen that the uniformity of the temperature field in the central area is significantly improved, and the overall temperature gradient of the material decreases, effectively improving the uniformity of the temperature field distribution within the effective heating range.

[0050] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A heating system based on a co-frequency coupled magnetic field, characterized in that It includes a heating device. The heating device is a sheet-shaped housing with a certain thickness. The lower end face of the housing is the heating surface. Inside the housing, there are several coils arranged in a stacked manner from bottom to top. An insulating layer is provided between adjacent coils, and the area of each coil decreases sequentially from bottom to top.

2. The heating system based on a co-frequency coupled magnetic field according to claim 1, wherein The housing is a flexible rubber housing.

3. The heating system based on the co-frequency coupled magnetic field according to claim 2, wherein The sheet-shaped housing includes a first housing and a second housing. The first housing and the second housing are joined together to form a sealed sheet-shaped housing.

4. The heating system based on the co-frequency coupled magnetic field according to claim 1, wherein The coils are independent disc-shaped structures, and the winding directions of all coils are the same. The winding density of the coils decreases sequentially from inside to outside.

5. The heating system based on a co-frequency coupled magnetic field according to claim 4, wherein The distance L between the nth turn of wire and the (n - 1)th turn of wire of the coil is: Where N is the target number of turns of the coil, and a is the wire diameter of the wire used.

6. The heating system based on a co-frequency coupled magnetic field according to claim 4, characterized in that, Inside the housing, there are a first coil and a second coil. The first coil is located below the second coil.

7. The heating system based on the co-frequency coupled magnetic field according to claim 1, wherein The relationship between the current I1 passed through the first coil and the current I2 passed through the second coil is: C·I1 = I2, where C is the current coefficient; the current coefficient C is: Where S1 is the area of the first coil, S2 is the area of the second coil, I1 is the current intensity in the first coil, f1 is the frequency applied in the first coil, and l is the distance between the first coil and the second coil.

8. The heating system based on the co-frequency coupled magnetic field according to claim 1, wherein, The heating system includes a vacuum pressure device. An annular groove is provided on the side where the first housing and the second housing are joined together. The vacuum pressure device is connected to the annular groove through a vacuum tube.

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