Induction heating coil and manufacturing method thereof

Abstract

To provide an induction heating coil capable of reducing power loss.SOLUTION: An induction heating coil according to an embodiment includes a coil portion that is curved in an arc around an object to be heated and that induction-heats the object to be heated, and a cooling water passage that is provided in the coil portion and extends along the circumferential direction of the coil portion and through which cooling water can circulate, and the thickness of an inner wall of the coil portion that faces the object to be heated is thicker than the thickness of an outer wall that faces the inner wall across the cooling water passage. A cooling fin may be formed in the cooling water passage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an induction heating coil and a method for manufacturing the same. [Background technology]

[0002] Patent Document 1 discloses a forging device that includes, as a heating element, a high-frequency induction heating coil formed of a copper coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-181589 A Summary of the Invention [Problem to be solved by the invention]

[0004] A continuous high-frequency induction heating device in which multiple induction heating coils are arranged concentrically is known. The multiple induction heating coils are connected to high-frequency power sources consisting of corresponding inverters. In general, a matching unit including a capacitor is provided between the induction heating coil and the high-frequency power source. In such a high-frequency induction heating device, power loss occurs in the induction heating coil, the high-frequency power source, the matching unit, etc. Therefore, while the high-frequency induction heating device can heat the material in a short time, there is a problem that a large amount of power is required.

[0005] The present invention has been made in view of such problems, and an object of the present invention is to provide an induction heating coil capable of reducing power loss and a manufacturing method thereof. [Means for solving the problem]

[0006] An induction heating coil according to one embodiment of the present disclosure has a coil section that is curved in an arc around an object to be heated and inductively heats the object to be heated, and a cooling water passage provided within the coil section and extending circumferentially of the coil section, through which cooling water can be circulated, wherein the thickness of an inner wall of the coil section facing the object to be heated is thicker than the thickness of an outer wall facing the inner wall across the cooling water passage.

[0007] In one embodiment, cooling fins may be formed within the cooling water passage.

[0008] In one aspect, the fin may divide the cooling water channel into a plurality of passages, and the fin may be provided with an opening that connects the plurality of passages.

[0009] In one aspect, the coil portion is formed from a pipe having a square cross-section, the inner wall of which is spirally curved so as to fit along the outer peripheral surface of a cylindrical object to be heated, and the cooling water passage may consist of a hollow portion of the pipe.

[0010] A method for manufacturing an induction heating coil according to one aspect of the present disclosure includes a step of dividing and shaping an induction heating coil by a metal additive manufacturing method, the induction heating coil having a coil section that is curved in an arc around an object to be heated and that induces heating of the object to be heated, and a cooling water channel that is provided within the coil section and extends circumferentially of the coil section, through which cooling water can be circulated, wherein the thickness of an inner wall of the coil section that faces the object to be heated is thicker than the thickness of an outer wall that faces the inner wall across the cooling water channel, and a step of brazing the divided induction heating coil. Effect of the Invention

[0011] According to the present invention, it is possible to provide an induction heating coil capable of reducing power loss and a manufacturing method thereof. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a schematic configuration of an induction heating coil according to a first embodiment. [Diagram 2] 2 is a cross-sectional view taken along a cutting plane P1 in FIG. [Diagram 3] FIG. 11 is a perspective view showing a schematic configuration of an induction heating coil according to a second embodiment. [Figure 4] 4 is a cross-sectional view taken along a cutting plane P2 in FIG. 3. [Diagram 5] FIG. 13 is an enlarged view of a portion of an induction heating coil according to a modified example. [Figure 6] 5A to 5C are diagrams illustrating a manufacturing method of an induction heating coil according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, in each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary. In the following embodiments, when the number, quantity, amount, range, etc. of each element is mentioned, it is not limited to the mentioned number, unless it is specifically stated or clearly specified in principle. In addition, the structures, etc. described in the following embodiments are not necessarily essential to the technical idea of ​​the present disclosure, unless it is specifically stated or clearly specified in principle.

[0014] The present disclosure relates to an induction heating coil used in a hot forging line that heats a heating object such as a metal part by electromagnetic induction. The induction heating coil is incorporated in a high-frequency induction heating device that heats a material from room temperature to 1200° C., for example. From the viewpoint of productivity, a continuous high-frequency induction heating device in which multiple induction heating coils are arranged coaxially is often used as the high-frequency induction heating device.

[0015] Embodiment 1. Fig. 1 is a perspective view showing a schematic configuration of an induction heating coil according to embodiment 1. Fig. 1 shows one of a plurality of induction heating coils used in a continuous high-frequency induction heating device. In Fig. 1, the induction heating coil 10 is arranged so that a mounting portion 20 for mounting to the high-frequency induction heating device is on the lower side. The induction heating coil 10 is fixed to the high-frequency induction heating device by a bolt (not shown) that penetrates the mounting portion 20.

[0016] First, a high-frequency induction heating device incorporating an induction heating coil 10 will be described. High-frequency induction heating devices are used, for example, in hot forging of engine parts and chassis parts of automobiles. Hot forging is a method in which a billet is heated to a temperature required for forging that is equal to or higher than the recrystallization temperature (for example, 1200°C), and the billet is shaped by applying pressure with a die or the like to obtain a forged product of a predetermined shape. The billet is a rod-shaped metal material of a predetermined length according to the shape of the forged product. In the example shown in FIG. 1, a cylindrical billet is used as the heating object (hereinafter referred to as the workpiece W).

[0017] The induction heating coil 10 is made of a metal material such as copper that has excellent electrical conductivity. The high-frequency induction heating device passes a current through the induction heating coil 10 while passing the workpiece W through the induction heating coil 10. As a result, Joule heat is generated on the surface of the workpiece W, and the workpiece W itself heats up and is induction heated. The workpiece W is introduced into the induction heating coil 10 by, for example, continuously pushing out a plurality of workpieces W in a state where they are aligned in series.

[0018] FIG. 2 is a cross-sectional view taken along the cutting plane P1 of FIG. 1. As shown in FIG. 2, the induction heating coil 10 includes a coil portion 11 and a cooling water passage 12. The coil portion 11 is formed from a pipe having a square cross section. The cooling water passage 12 is formed from a hollow portion of the pipe. The portion of the coil portion 11 facing the workpiece W is defined as an inner circumferential wall 13. The portion facing the inner circumferential wall 13 across the cooling water passage 12 is defined as an outer circumferential wall 14. The inner circumferential wall 13 and the outer circumferential wall 14 are connected by two side walls 15. The internal space surrounded by the inner circumferential wall 13, the outer circumferential wall 14, and the two side walls 15 constitutes the cooling water passage 12.

[0019] As shown in Figs. 1 and 2, the coil portion 11 is curved in an arc shape around the workpiece W. Specifically, the inner peripheral wall 13 of the coil portion 11 is disposed so as to face the outer peripheral surface of the workpiece W. The coil portion 11 is curved in a spiral shape so that the inner peripheral wall 13 follows the outer peripheral surface of the cylindrical workpiece W. Here, in Fig. 1, the direction perpendicular to the rotation plane of the coil portion 11 is defined as the z direction. Also, the left-right direction of the coil portion 11 in Fig. 1 is defined as the x direction, and the up-down direction is defined as the y direction. A tunnel-shaped space extending in the z direction is formed in the coil portion 11. The workpiece W is introduced into the tunnel-shaped space formed by the coil portion 11.

[0020] As shown in Fig. 2, a cooling water passage 12 is provided inside the coil portion 11. The cooling water passage 12 is capable of circulating cooling water inside the induction heating coil 10. The cooling water passage 12 extends along the circumferential direction of the coil portion 11. Both ends of the cooling water passage 12 are connected to a pipe 16 serving as an inlet (IN) of the cooling water and a pipe 17 serving as an outlet (OUT) of the cooling water, respectively.

[0021] In the example shown in Fig. 1, two sets of pipes 16 and pipes 17 are provided. That is, in this example, the cooling water passage 12 in the coil section 11 is divided into two. The high-frequency induction heating device can circulate cooling water through either one or both of the two cooling water passages 12 according to a cooling requirement based on the temperature of the coil section 11, etc. Note that all of the cooling water passages 12 in the coil section 11 may be continuous, or only one set of pipes 16 and pipes 17 may be provided. The number of pipes 16 and pipes 17 is not particularly limited.

[0022] When the high-frequency induction heating device is in use, cooling water is supplied from a tank (not shown) to pipe 16. The cooling water supplied to pipe 16 flows inside induction heating coil 10 and is then discharged from pipe 17. This causes induction heating coil 10 to be cooled.

[0023] The power loss P when current flows through the induction heating coil 10 is P=I 2It is determined by R. Here, I is the current (A) and R is the resistance (Ω). Furthermore, resistance R is expressed as R = L / S × ρ, where L is the length of the coil, S is the cross-sectional area of ​​the coil, and ρ is the resistivity of the coil. Electrical conductivity σ = 1 / ρ. Therefore, in order to reduce power loss P, it is necessary to reduce resistance R. If the length L of the induction heating coil 10 is constant, then in order to reduce R, it is possible to (1) increase S or (2) reduce ρ.

[0024] In the first embodiment, (1) an example in which the cross-sectional area S of the induction heating coil 10 is increased will be described. Normally, when an AC current is passed through the induction heating coil 10, a bias in the current density occurs within the conductor cross section due to the self-inductance and skin effect of the induction heating coil 10. Specifically, it is known that the current concentrates on the inner diameter side of the induction heating coil 10. For this reason, the inventors devised a method of increasing the cross-sectional area of ​​the inner diameter side of the induction heating coil 10.

[0025] 2, the thickness of the inner peripheral wall 13 of the coil portion 11 facing the workpiece W is thicker than the thickness of the outer peripheral wall 14 facing the inner peripheral wall 13 across the cooling water passage 12. In the first embodiment, the thickness of the side wall 15 and the outer peripheral wall 14 is 3 mm, whereas the thickness of the inner peripheral wall 13 is 8 mm.

[0026] Moreover, the width of the inner circumferential wall 13 in the z direction is wider than the width of the outer circumferential wall 14 in the z direction. In this example, the width of the inner circumferential wall 13 in the z direction is 17 mm, whereas the width of the outer circumferential wall 14 in the z direction is 15 mm. Furthermore, the gap between adjacent inner circumferential walls 13 is narrower than the gap between adjacent outer circumferential walls 14. In this example, the gap between the inner circumferential walls 13 is 6 mm, whereas the gap between the outer circumferential walls 14 is 8 mm.

[0027] Therefore, the cross-sectional area of ​​the inner circumferential wall 13 at the cut surface P1 is larger than the cross-sectional area of ​​the outer circumferential wall 14. For this reason, compared to the conventional case in which the thicknesses of the inner circumferential wall 13, the outer circumferential wall 14, and the side wall 15 are constant (3 mm), the width of the cooling water passage 12 in the x direction is smaller in the embodiment. In this way, by making the cross-sectional area of ​​the inner circumferential wall 13, which has a large effect on the heat generation of the induction heating coil 10, larger than the cross-sectional area of ​​the outer circumferential wall 14, it is possible to reduce power loss.

[0028] Manufacturing method The induction heating coil 10 described above is manufactured by metal additive manufacturing using a metal material such as copper. Metal additive manufacturing is a method that repeats a process of laying metal powder in thin layers and a process of selectively melting the layered metal powder with laser light from a laser irradiation device and solidifying it by coagulation. The induction heating coil 10 is formed by bonding multiple solidified metal layers in a stacked state.

[0029] The induction heating coil 10 can be manufactured using a metal 3D printer. FIG. 6 is a diagram for explaining a manufacturing method of an induction heating coil according to an embodiment. As shown in FIG. 6, the induction heating coil 10 is manufactured by combining two parts 1, for example. Each part 1 has a configuration in which arc-shaped pipes are arranged in a spiral shape in multiple stages. That is, the part 1 has a shape in which the induction heating coil 10 is divided into two.

[0030] As shown on the left side of Fig. 6, a pair of parts 1 is formed in a metal 3D printer. By brazing the joints of this pair of parts 1, an induction heating coil 10 can be formed, as shown on the right side of Fig. 6. For the brazing material, JIS silver brazing material (BAG-1A: composition Ag: 50%, Cu: 15.5%, Zn: 16.5%, Cd: 18%, conductivity 25%) can be used.

[0031] Embodiment 2. Fig. 3 is a perspective view showing a schematic configuration of an induction heating coil according to embodiment 2. For the sake of explanation, Fig. 3 shows a state in which part of side wall 15 of coil portion 11 has been removed. Fig. 4 is a cross-sectional view taken along cutting plane P2 in Fig. 3.

[0032] In the second embodiment, the above-mentioned (2) example of reducing the resistivity ρ of the induction heating coil 10 will be described. It is generally known that the resistivity ρ of the induction heating coil 10 (conductor) increases as the temperature increases. For this reason, the resistivity ρ can be reduced by suppressing the temperature rise of the induction heating coil 10 itself.

[0033] For this purpose, as shown in Fig. 3, cooling fins 18 are provided inside the cooling water channel 12. As shown in Fig. 4, two fins 18 extend in the x direction on the cross section P2. The fins 18 divide the cooling water channel 12 into a plurality of passages. In the second embodiment, the cooling water channel 12 is divided into three passages by the two fins 18. The thickness of the fins 18 is, for example, 0.8 mm.

[0034] 3, the fins 18 are provided with a plurality of openings 19. The openings 19 communicate a plurality of passages separated by the fins 18. In the second embodiment, the plurality of openings 19 are provided in each fin 18 so as to be aligned in the circumferential direction along the outer peripheral wall 14. In the second embodiment as well, the induction heating coil 10 can be manufactured by metal additive manufacturing, as in the first embodiment.

[0035] Typically, when the induction heating coil 10 is manufactured by metal additive manufacturing, it may be necessary to form a support to prevent deformation of the induction heating coil 10. Due to such limitations in the 3D printer, the fin 18 includes a base portion 18a and a branch portion 18b.

[0036] The base 18a extends from the inner peripheral wall 13 and is provided continuously in the circumferential direction. The openings 19 have a pentagonal shape in the top view in FIG. 3, with one side facing the outer peripheral wall 14. The branch portions 18b are disposed between adjacent openings 19. The branch portions 18b connect the base 18a and the outer peripheral wall 14. The branch portions 18b and the openings 19 are disposed so as to be alternately arranged along the circumferential direction of the outer peripheral wall 14.

[0037] As an example, when viewed from the z direction, base 18a has a shape in which the portion connected to branch 18b forms a mountain, and the apex of opening 19 on the base 18a side forms a valley. For example, branch 18b has a constant width in the circumferential direction. The circumferential width of opening 19 gradually narrows from outer peripheral wall 14 toward inner peripheral wall 13. However, the shape, number, and arrangement position of opening 19 are not particularly limited.

[0038] In the second embodiment, the thicknesses of the inner peripheral wall 13, the outer peripheral wall 14, and the side wall 15 are constant (3 mm). In this manner, by forming the fins 18 in the cooling water passage 12, it is possible to suppress the temperature rise of the induction heating coil 10 and reduce its resistivity ρ. In addition, by providing the openings 19 in the fins 18, it is possible to reduce the pressure loss of the cooling water in the cooling water passage 12 and smooth the flow of the cooling water.

[0039] Variations FIG. 5 is an enlarged view of a part of the induction heating coil according to the modified example. FIG. 5 shows a cross section of a square pipe forming the induction heating coil 10 cut in the xz plane. As shown in FIG. 5, it is also possible to combine the first embodiment and the second embodiment. That is, in the induction heating coil 10 shown in FIG. 5, the thickness of the inner peripheral wall 13 is thicker than the thickness of the outer peripheral wall 14. In addition, a fin 18 having an opening 19 is provided in the cooling water passage 12. With this configuration, it is possible to further reduce the current loss when a current flows through the induction heating coil 10. This makes it possible to reduce the power consumption in the hot forging line and suppress CO2 emissions.

[0040] As described above, according to the embodiment, by increasing the cross-sectional area of ​​the induction heating coil 10 and / or providing fins 18 inside the induction heating coil 10, it is possible to reduce current loss when current flows through the induction heating coil 10.

[0041] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0042] 10 Induction heating coil 11 Coil section 12 Cooling Channel 13 Inner wall 14 Peripheral wall 15 Side wall 16 Piping 17 Piping 18 Finn 18a base 18b Branch 19 Opening 20 Mounting part W work

Claims

1. A coil portion that is curved in an arc shape around an object to be heated and that induction heats the object to be heated; a cooling water passage provided in the coil portion and extending along a circumferential direction of the coil portion, through which cooling water can circulate; The thickness of an inner wall of the coil portion facing the object to be heated is thicker than the thickness of an outer wall facing the inner wall across the cooling water channel. Induction heating coil.

2. A cooling fin is formed in the cooling water passage.

2. The induction heating coil according to claim 1.

3. The fins divide the cooling water channel into a plurality of passages, The fin is provided with an opening that communicates with a plurality of passages.

3. The induction heating coil according to claim 2.

4. The coil portion is formed from a pipe having a square cross section, and the inner peripheral wall is curved in a spiral shape so as to fit along an outer peripheral surface of a cylindrical heating object, The cooling water channel is formed from a hollow portion of the pipe.

2. The induction heating coil according to claim 1.

5. By using metal additive manufacturing, A coil portion that is curved in an arc shape around an object to be heated and that induction heats the object to be heated; a cooling water passage provided in the coil portion and extending along a circumferential direction of the coil portion, through which cooling water can circulate; The thickness of an inner wall of the coil portion facing the object to be heated is thicker than the thickness of an outer wall facing the inner wall across the cooling water channel. A step of dividing and shaping an induction heating coil; A step of brazing the divided induction heating coil; Including, How induction heating coils are manufactured.

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