Manufacturing method for induction heating coil

Abstract

To provide an induction heating coil which is manufactured using a metal lamination molding method without tilting a central axis of an induction heating coil with respect to a horizontal direction during molding and capable of attaining reduction of a pressure loss in a cooling passage and improvement of cooling capability.SOLUTION: An induction heating coil 10 is manufactured by a metal lamination molding method and includes at least one ring-like part 11, 12. Cooling passages 20 and 21 extending in a coil circumferential direction are formed in the ring-like parts 11 and 12. The cooling passages 20 and 21 include hexagonal passages of which the cross-sectional shape in the case of cutting in a coil axial direction is a hexagon having two apexes in both ends inside and outside of a coil radial direction and which are formed continuously in the coil circumferential direction. In the cross-sectional shape of the hexagonal passage, angles θ1, θ2, θ3 and θ4 of inclining two straight lines A1-A4 forming a V shape with respect to a coil diameter 60 in each of both the ends in the coil radial direction are equal to or smaller than 45 degrees.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an induction heating coil made by metal additive manufacturing, which reduces pressure loss in the cooling channels and improves cooling capacity. [Background technology]

[0002] Patent Document 1 describes the production of an induction heating coil having an internal cooling channel by metal additive manufacturing (metal 3D printer molding method). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-10876 A Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing an induction heating coil by metal additive manufacturing, a support may be required in the cooling channel to prevent deformation depending on the cross-sectional shape of the cooling channel. For example, when the cross section of the cooling channel has a straight line that coincides with the horizontal direction at the top end of the cooling channel in the metal lamination direction, for example, when the cross-sectional shape of the cooling channel is rectangular, a support is required inside.

[0005] The completed induction heating coil induces heating of the object to be heated placed inside the coil while cooling water flows through the cooling flow path. In order to reduce the electrical resistance of the induction heating coil and maintain its magnetic performance, it is better for the temperature of the induction heating coil itself to be low. If the above support is formed in the cooling flow path, it will lead to pressure loss of the cooling water in the cooling flow path, which will increase energy loss, and the cooling water will not flow smoothly, which will cause a decrease in the cooling capacity of the induction heating coil.

[0006] On the other hand, when the induction heating coil is molded by the metal additive manufacturing method, it is possible to tilt the central axis of the induction heating coil at an angle of 45 degrees with respect to the horizontal direction. In this case, even if the cross-sectional shape of the cooling flow path is rectangular, the rectangular cross-sectional shape is tilted at 45 degrees during molding, so that a straight line that coincides with the horizontal direction is not formed at the upper end of the cooling flow path in terms of the metal additive manufacturing direction. Therefore, it is possible to prevent the formation of a support for preventing the shape of the upper end from collapsing inside the cooling flow path. However, in this case, when the total thickness in the axial direction is smaller than the length of the coil diameter, which is the diameter of the coil, due to a small number of turns of the induction heating coil, the length of the inclined end face in the thickness direction as viewed from above becomes large in the planar shape of the induction heating coil as it is molded. This increases the planar area of ​​the induction heating coil. In addition, in metal additive manufacturing, an external support extending downward from the outer surface is formed to prevent the outer shape of the induction heating coil from collapsing during molding, so it is not possible to mold multiple induction heating coils in a vertically stacked state. For this reason, the planar area of ​​one induction heating coil becomes larger during molding, which may reduce the number of induction heating coils that can be formed at one time in a limited molding space. This may lead to an increase in the cost of each induction heating coil when multiple induction heating coils are manufactured at the same time.

[0007] The object of the present invention is to obtain an induction heating coil that can be manufactured using a metal additive manufacturing method without tilting the central axis of the induction heating coil relative to the horizontal direction during molding, and that can reduce pressure loss in the cooling flow path and improve cooling capacity. [Means for solving the problem]

[0008] The induction heating coil of the present invention is an induction heating coil made by a metal additive manufacturing method and having at least one ring-shaped portion, wherein a cooling flow passage extending in a coil circumferential direction is formed in the ring-shaped portion, and the cooling flow passage has a cross-sectional shape when cut along the coil axial direction that is a hexagon with two vertices at both ends in the coil radial direction, and includes a hexagonal flow passage formed continuously in the coil circumferential direction, and in the cross-sectional shape of the hexagonal flow passage, at each end in the coil radial direction, the angle at which the two straight lines forming a V-shape are inclined with respect to the coil diameter is 45 degrees or less.

[0009] According to the induction heating coil of the present invention, the cross-sectional shape of the hexagonal flow path of the cooling flow path when cut along the coil axis direction is a hexagon. As a result, when the induction heating coil is molded by metal additive manufacturing with the coil central axis aligned horizontally, the cross-sectional shape when the hexagonal flow path is cut along a plane including the coil central axis along the vertical direction, or along a plane parallel to the coil central axis along the vertical direction, is a hexagon having a V-shaped portion at the upper end consisting of two straight lines inclined with respect to the horizontal direction. In addition, in the cross-sectional shape when the hexagonal flow path is cut along the coil axis direction, the angle at which the two straight lines forming the V-shape at both ends in the coil radial direction are inclined with respect to the coil diameter is 45 degrees or less. Therefore, it is possible to prevent the shape from collapsing at the upper part of the hexagonal flow path without forming a support inside the hexagonal flow path. Therefore, it is possible to reduce or eliminate the support in the cooling flow path, thereby reducing the pressure loss in the cooling flow path and improving the cooling capacity. Furthermore, in this case, it is possible to improve the molding efficiency when molding the induction heating coil without inclining the central axis of the induction heating coil with respect to the horizontal direction. Effect of the Invention

[0010] According to the present invention, an induction heating coil can be obtained that is manufactured using a metal additive manufacturing method without tilting the central axis of the induction heating coil relative to the horizontal direction during molding, thereby reducing pressure loss in the cooling flow path and improving cooling capacity. [Brief description of the drawings]

[0011] [Figure 1A] 1 is a diagram showing an induction heating device incorporating an induction heating coil according to an embodiment, as viewed obliquely from above. [Figure 1B] FIG. 1B is a view of the induction heating device of FIG. 1A as seen obliquely from below. [Diagram 2] 2 is a perspective view showing an induction heating coil taken out from the induction heating device of FIG. 1. [Diagram 3] 3 is a view of the induction heating coil of FIG. 2 as viewed in the direction of arrow A of FIG. 2. [Figure 4] 3A to 3C are diagrams showing the cross section BB of FIG. 2 and cross sections at multiple positions of a hexagonal flow passage of a cooling flow passage. [Diagram 5] FIG. 4 is a perspective view including a cross section CC of FIG. [Figure 6] 4(a) is a cross-sectional view taken along line CC in FIG. 3, and (b) is an enlarged view of part D in (a). [Figure 7] 4 is a cross-sectional view of FIG. 3 taken along line E-E. [Figure 8] 1 is a perspective view showing a state immediately after forming a plurality of induction heating coils in a manufacturing method of an induction heating coil according to an embodiment. FIG. [Figure 9] This is an image showing the conditions under which support is required when using metal additive manufacturing. [Figure 10] 11A and 11B are diagrams illustrating disadvantages when the cross-sectional shape of a cooling flow passage in a ring-shaped portion of an induction heating coil is circular in the first example of the comparative example. [Figure 11] 13A and 13B are diagrams illustrating disadvantages when the cross-sectional shape of a cooling flow passage in a ring-shaped portion of an induction heating coil is rectangular in a second example of the comparative example. [Figure 12] 13A and 13B are diagrams illustrating disadvantages when the cross-sectional shape of the cooling flow passage in the ring-shaped portion of the induction heating coil is pentagonal in the third comparative example. [Figure 13] 1A and 1B are diagrams showing the inconvenience that occurs when manufacturing a plurality of induction heating coils with their central axes inclined relative to the horizontal direction. [Figure 14] FIG. 1 is a diagram showing the cross-sectional shapes of the cooling passages of the induction heating coils of an example and comparative examples 1 to 3 used in a temperature analysis when the induction heating coil is cooled with cooling water. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an induction heating coil according to an embodiment of the present invention will be described. First, an induction heating device 100 incorporating an induction heating coil 10 will be described with reference to Figs. 1A and 1B. Figs. 1A and 1B are views of the induction heating device 100 as viewed obliquely from above and below when installed. In Figs. 1A and 1B, the side of the induction heating device 100 where the induction heating coil 10 is located is the front side, the side where the back faces of the lead parts 101 and 102, which are attachment parts for a fixed part (not shown) of the induction heating device 100, face the bottom side, and the right and left sides of the induction heating device 100 as viewed from the front side of Fig. 1A are the right side and the left side, respectively.

[0013] The induction heating device 100 is used to perform high-frequency hardening or the like on an object to be heated, such as a shaft, and heats the object to be heated by induction heating it using electric power from a commercial power source or the like, thereby performing heat treatment on the object to be heated.

[0014] Moreover, the induction heating coil 10 of the induction heating device 100 is manufactured by a metal additive manufacturing method using a metal material such as copper, which has excellent electrical conductivity.

[0015] The induction heating device 100 includes lead portions 101 and 102, a plurality of pipes 110, 111, 112, and 113, and an induction heating coil 10. AC power is supplied to the lead portions 101 and 102 from a power source, and the AC power is supplied to the induction heating coil 10.

[0016] The lead portions 101 and 102 are disposed opposite each other with a sheet-like insulator (not shown) therebetween, and are formed in a symmetrical shape.

[0017] Each of the lead portions 101, 102 has a vertical plate portion 105 connected to the inner end in the left-right direction and extending in the up-down direction and forward, and an outer water passage 107 connected to the outer surface of the vertical plate portion 105. One end of the outer water passage 107 is led out upward from the upper end of the rear end of the vertical plate portion 105. The other end of the outer water passage 107 is connected by a plurality of pipes 110, 111 to form a cooling passage, and the lead portion 101 is cooled by flowing cooling water inside the cooling passage.

[0018] FIG. 2 is a perspective view showing the induction heating coil 10 taken out from the induction heating device 100. FIG. 3 is a view of the induction heating coil 10 as seen in the direction of the arrow A in FIG. 2. Referring to FIGS. 1A, 1B, 2, and 3, in the induction heating coil 10, the upper first ring-shaped portion 11 and the lower second ring-shaped portion 12 are disposed facing each other so that the coil central axis O, which is the central axis, coincides. Each of the ring-shaped portions 11 and 12 has a rectangular cross-sectional shape along the coil axis direction, and is formed into a substantially annular shape in which the entirety is divided at a portion in the coil circumferential direction. A first linear portion 13 that protrudes outward in the coil radial direction is formed at one end in the circumferential direction of the first ring-shaped portion 11. The front end of the vertical plate portion 105 on the lead portion 101 side is joined to the outer surface of the first linear portion 13. A second linear portion 14 that protrudes outward in the coil radial direction is formed at the other end in the circumferential direction of the second ring-shaped portion 12 from near the protruding position of the first linear portion 13. A front end of a vertical plate portion 105 on the lead portion 102 side is joined to the outer surface of the second linear portion 14.

[0019] Mounting protrusions 15 protruding outwardly are formed at multiple positions on the outer circumferential surface of each of the ring-shaped portions 11 and 12. The induction heating coil 10 is attached to a fixing member (not shown) that fixes the induction heating coil 10 by bolts (not shown) that pass through the mounting protrusions 15.

[0020] Furthermore, as will be described in detail later, cooling channels 20, 21 for flowing cooling water inside the induction heating coil 10 are formed inside the induction heating coil 10. The cooling channels 20, 21 are formed along the circumferential direction in each of the first ring-shaped portion 11 and the second ring-shaped portion 12. The part of the cooling channel 20 formed in the first ring-shaped portion 11 and the part of the cooling channel 21 formed in the second ring-shaped portion 12 are connected at a joint portion 16 (FIG. 1A) between the other circumferential end of the first ring-shaped portion 11 and one circumferential end of the second ring-shaped portion 12. One end of the cooling channel 20 opens at the rear end of the first straight portion 13. The other end of the cooling channel 21 opens at the rear end of the second straight portion 14. With the induction heating coil 10 connected to the lead portion 101, one end of the cooling channel 20 opening at the rear end of the first straight portion 13 is connected to one end of a pipe 112 arranged adjacent to the outer surface of the lead portion 101. In the cooling flow passage 21, one end of a pipe 113 arranged adjacent to the outer surface of the lead portion 102 is connected to the other end that opens at the rear end of the second straight portion 14.

[0021] Furthermore, the thickness D1 (FIG. 2) of the induction heating coil 10 in the direction of the coil central axis O is smaller than the length D2 (FIG. 2) in the coil radial direction. This allows the space required for manufacturing the induction heating coil 10 to be reduced when the coil central axis O is aligned horizontally as described below.

[0022] When the induction heating device 100 is in use, cooling water is supplied from a water tank (not shown) to one of the two pipes 112, 113, and the cooling water flows through the inside of the induction heating coil 10 and is then discharged from the other of the two pipes 112, 113. This cools the induction heating coil 10.

[0023] When the induction heating device 100 is in use, a ring-sheet-shaped insulator (not shown) is placed between the first and second ring-shaped portions 11, 12, a first terminal plate (not shown) connected to a power source is connected to the lead portion 101, and a second terminal plate (not shown) connected to a power source is connected to the lead portion 102. AC power is supplied from the power source to the lead portion 101 via the terminal plates, causing a high-frequency AC current to flow through the induction heating coil 10. This allows the induction heating device 100 to perform high-frequency hardening of an object to be heated that is inserted inside the induction heating coil 10.

[0024] In this example, the induction heating coil 10 is made by metal additive manufacturing. The manufactured induction heating coil 10 is joined to the lead portion 101 by brazing. In the "metal additive manufacturing" method, a process of laying metal powder in a thin layer and a process of selectively melting the layered metal powder with laser light from a laser irradiation device and solidifying it by coagulation are repeated, so that the multiple solidified metal layers are bonded in a stacked state to manufacture the induction heating coil 10.

[0025] When the induction heating coil 10 is manufactured by the metal additive manufacturing method in this way, it is necessary to form an external support on the outside of the induction heating coil 10 to prevent the shape from collapsing. In addition, depending on the cross-sectional shape of the cooling flow path, it is necessary to form a support inside the cooling flow path. The external support can be easily removed by machining after the induction heating coil is manufactured. On the other hand, the support formed inside the cooling flow path cannot be easily removed. This may result in the support remaining inside the cooling flow path. This leads to a pressure loss of the cooling water in the cooling flow path, which increases energy loss, and also causes the cooling water to flow less smoothly, which reduces the cooling capacity of the induction heating coil. For these reasons, in the induction heating coil 10 of this example, the internal support is not required by improving the shape of the cooling flow paths 20 and 21.

[0026] The cooling flow paths 20, 21 of the induction heating coil 10 will be described in detail with reference to Figs. 4 to 8. Fig. 4 shows a cross section taken along line BB in Fig. 2 and schematic cross sections of the cooling flow paths at a plurality of positions. Fig. 5 is a perspective view including a cross section taken along line CC in Fig. 3. Fig. 6(a) is a cross section taken along line CC in Fig. 3, and Fig. 6(b) is an enlarged view of part D in Fig. 6(a). Fig. 7 is a cross section taken along line EE in Fig. 3.

[0027] As shown in Figs. 4 to 7, cooling channels 20 and 21 are formed inside the induction heating coil 10. The cooling channels 20 and 21 include ring-shaped channel portions 22 and 23 formed in the first ring-shaped portion 11 and the second ring-shaped portion 12, and linear channel portions 31 and 32 formed in the first linear portion 13 and the second linear portion 14. As shown in Figs. 5 and 6, the ring-shaped channel portions 22 and 23 of each ring-shaped portion 11 and 12 are connected to each other at the joint portion 16 of the two ring-shaped portions 11 and 12 by a connecting channel portion 28. Here, in the portions of each ring-shaped channel portion 22 and 23 of the cooling channels 20 and 21 except for the portion that coincides with the connecting channel portion 28 in the coil circumferential direction, a hexagonal channel that is a channel portion with a hexagonal cross section is formed continuously in the coil circumferential direction of the corresponding ring-shaped portion 11 and 12.

[0028] The outer shape of the second ring-shaped portion 12 has a tapered surface 40 formed on one axial side of the inner surface, and a cylindrical surface 41 formed on the other axial side, but the entire axial direction may be a cylindrical surface, similar to the cylindrical surface 42 formed on the inner surface of the first ring-shaped portion 11.

[0029] The cross-sectional shape of the hexagonal flow path when cut along the direction of the coil central axis O, which is the coil axis, (shape of the cross section in the coil axial direction), for example as shown in FIG. 4, is a hexagon with two vertices P1 and P2 at both the inner and outer ends in the direction of the coil diameter 60.

[0030] 6, in the shape of the hexagonal flow channel in the coil axial direction cross section, the angles θ1, θ2, θ3, θ4 at which the two straight lines A1, A2, A3, A4 forming a V shape at each end in the coil diameter 60 direction are inclined with respect to the coil diameter 60 are each 45 degrees or less. This makes it unnecessary to form a support inside the hexagonal flow channel to prevent deformation when forming the induction heating coil 10 by aligning the coil central axis O with the horizontal direction, as described below.

[0031] Further, as shown in FIG. 5 and FIG. 6, in the portion where the two ring-shaped flow passage portions 22, 23 are connected by the connecting flow passage portion 28, the pentagonal portions 43, 44, each having a pentagonal cross section having a shape of one side with respect to the coil diameter 60 of the hexagonal flow passage, are connected by the connecting flow passage portion 28. The connecting flow passage portion 28 connects the outer ends of the pentagonal portions 43, 44 to each other at the outer wall portion 29 on the outer side in the coil radial direction, and connects the inner ends of the pentagonal portions 43, 44 to each other at the inner wall portion 30 on the inner side in the coil radial direction. At this time, the outer wall portion 29 has an inclined surface that is inclined inward in the coil radial direction from the first ring-shaped flow passage portion 22 toward the second ring-shaped flow passage portion 23 with respect to the axial direction of the coil central axis O. As a result, when the induction heating coil 10 is formed so that the coil central axis O coincides with the horizontal direction and each straight portion 13, 14 and the connecting flow passage portion 28 are located at the upper end in the metal lamination direction, the inner surface of the outer wall portion 29, which is the upper end of the connecting flow passage portion 28, is inclined with respect to the horizontal direction. Therefore, when the length of the outer wall portion 29 in the coil circumferential direction is short, it becomes unnecessary to form a support inside the connecting flow passage portion 28 to prevent the shape from collapsing.

[0032] When manufacturing the induction heating coil 10, the induction heating coil 10 is first modeled in 3D using a computer, and the data of the 3D model is divided into two-dimensional images, which are multiple layer images obtained by slicing the image of the induction heating coil 10 at predetermined intervals in the vertical direction. The computer models the induction heating coil 10 using a metal additive manufacturing device based on the multiple two-dimensional images. At this time, a metal powder layer having a thickness corresponding to each layer image is laid, and a laser beam is irradiated to the part to be modeled to melt and solidify the metal powder. The multiple metal layers are laminated and bonded vertically to form the induction heating coil 10. The induction heating coil 10 after modeling is brazed to the lead parts 101 and 102 to manufacture the induction heating device 100. The completed induction heating device 100 is attached to a high-frequency hardening facility.

[0033] FIG. 8 is a perspective view showing a state immediately after the formation of a plurality of induction heating coils 10 in the manufacturing method of the induction heating coil 10. As shown in FIG. 8, the induction heating coil 10 is manufactured by metal additive manufacturing with the coil central axis O aligned horizontally. At this time, the thickness D1 of the induction heating coil 10 in the direction of the coil central axis O is smaller than the length D2 in the coil radial direction, so that the formation space for formation can be made small. For this reason, as shown in FIG. 8, many induction heating coils 10 (four in the illustrated example) can be formed in a limited formation space in the direction of the coil central axis O, and a plurality of rows (two rows in the illustrated example) can be arranged in the horizontal direction with one row being one row. At this time, an external support 61 for preventing deformation is formed on the lower side of the outer surface of the induction heating coil 10, but the external support 61 can be easily removed by machining after the induction heating coil 10 is formed.

[0034] Furthermore, in the present embodiment, in the manufacture of each induction heating coil 10, the coil central axis O coincides with the horizontal direction as shown in FIG. 8, so that the front-rear direction of the induction heating coil 10 shown in FIG. 2 to FIG. 7 is the up-down direction with respect to the metal lamination direction (the up-down direction when the metal is laminated). In this case, in the induction heating coil 10 of this example, the cross-sectional shape of the hexagonal flow path formed in the ring-shaped parts 11 and 12 of the cooling flow paths 20 and 21 when cut along the coil axis direction is a hexagon with two vertices P1 and P2 at both the inner and outer ends in the coil radial direction, and is formed continuously in the coil circumferential direction. As a result, when the induction heating coil 10 is molded by the metal additive manufacturing method in the posture of FIG. 8, the cross-sectional shape when the hexagonal flow path is cut along the up-down direction when the metal is laminated, along a plane including the coil central axis O or parallel to the coil central axis O, is the same as the cross-sectional shape cut in the front-rear direction, such as the cross-sectional shapes in the front-rear direction of FIG. 4, the coil axial direction cross-sections 1 and 2, and the cross-sectional shapes in FIG. 5 to FIG. 7. As a result, the cross-sectional shape becomes a hexagon having V-shaped portions at the top and bottom ends in the metal lamination direction, each V-shaped portion being made up of two straight lines A1 to A4 (FIG. 6) that are inclined with respect to the horizontal direction.

[0035] In addition, in a cross-sectional shape when the hexagonal flow path is cut along the coil axis direction, the angle at which the two straight lines A1 to A4 forming the V shape at both ends in the coil radial direction is inclined to the coil diameter 60 is 45 degrees or less. As a result, in a cross-sectional shape cut along the vertical direction during metal lamination when forming the induction heating coil 10 in the above-mentioned posture, the angle at which the two straight lines A1, A2 of the V shape forming the upper end of the hexagon are inclined to the vertical direction is also 45 degrees or less.

[0036] For example, in the coil axial cross section 1 in Fig. 4 and the cross section of the front end of each ring-shaped flow passage section 22, 23 in Fig. 6, the cross section when cut along a plane including the coil central axis O in the front-rear direction, i.e., the vertical direction when the metal is laminated, coincides with the cross section in the coil radial direction. In this case, as shown in Fig. 6(b), the angles θ1, θ2 of the two straight lines A1, A2 of the V-shape at the upper end of the hexagonal flow passage when the metal is laminated in the cross section are inclined with respect to the vertical direction when the metal is laminated in the cross section of 45 degrees or less. This makes it possible to prevent deformation without forming a support inside the above cross section of the hexagonal flow passage, as described later.

[0037] On the other hand, the cross-sectional shapes of the front and rear sides of each of the ring-shaped flow passage sections 22, 23 in FIG. 4 and FIG. 7 do not match the cross-sectional shapes in the coil axis direction, and the length of the ring-shaped flow passage sections 22, 23 in the front and rear direction increases by the distance in the left and right direction from the coil central axis O. At this time, the flow passage width w of the ring-shaped flow passage sections 22, 23 in the direction parallel to the coil central axis O is constant even if the ring-shaped flow passage sections 22, 23 are moved left and right from the coil central axis O, so the shape of the front and rear cross section is generally elongated in the front and rear direction compared to the coil axis direction cross section 1. For this reason, the angle at which the two straight lines of the V-shape at the upper end of the front and rear cross section of the hexagonal flow passage are inclined with respect to the vertical direction when the metal is laminated is 45 degrees or less, which is smaller than the angle in the case of the coil axis direction cross section 1. As a result, the cross section of the hexagonal flow passage along the vertical direction when the metal is laminated is small, 45 degrees or less, even in the cross section including the coil central axis O. This makes it possible to prevent deformation in any cross section along the vertical direction when laminating metal of the hexagonal flow path, without forming a support inside, as described below.

[0038] FIG. 9 is an image showing the conditions under which a support is required by the metal additive manufacturing method. As shown in FIG. 9, in the metal additive manufacturing method, a laser beam 63 is irradiated to a part to be molded with a thin layer of metal powder 62 laid, and the metal powder 62 is melted and solidified to form a layered melted and solidified part 65. In FIG. 9, the melted and solidified part 65 is shown by a part with sand. The metal powder 62 whose overall shape is not fixed is located at a position adjacent to the melted and solidified part 65. At this time, when forming an inclined surface Sa inclined with respect to the horizontal direction by the stacked layers of the melted and solidified part 65, if the self-supporting angle θk, which is the angle at which the inclined surface Sa is inclined with respect to the vertical direction, becomes larger than 45 degrees, the shape collapse is likely to occur depending on the size of the inclined surface Sa. For this reason, when the self-supporting angle θk is larger than 45 degrees and the inclined surface Sa is relatively large, it is necessary to form a support for supporting the inclined surface Sa as a part of the melted and solidified part.

[0039] In this embodiment, as described above, in the hexagonal flow channel, the angle at which the two straight lines of the V-shape at the upper end when the metal is laminated is inclined with respect to the vertical direction is 45 degrees or less. This makes it possible to prevent the shape of the upper part of the hexagonal flow channel from collapsing without forming supports inside the hexagonal flow channel. Therefore, the supports in the cooling flow channels 20 and 21 can be reduced or eliminated, thereby reducing the pressure loss in the cooling flow channels 20 and 21 and improving the cooling capacity.

[0040] FIG. 10 is a diagram showing the inconvenience when the cross-sectional shape of the cooling flow passage 71 in the ring-shaped portion 70 of the induction heating coil is circular in the first example of the comparative example. In the comparative example of FIG. 10, as in the embodiment, the induction heating coil is manufactured by metal additive manufacturing with the coil central axis aligned horizontally. In the comparative example of FIG. 10, the cross-sectional shape of the cooling flow passage 71 in the ring-shaped portion 70 is circular. In this case, when the inner diameter of the cross-sectional shape of the cooling flow passage is relatively large, for example, when the circular inner diameter D3 of the cooling flow passages 20 and 21 is 5 mm or more, it is desirable to form the support 72 in order to improve the shape accuracy. In addition, when the induction heating coil 10 is formed of a material with high thermal conductivity such as a copper material, when the inner diameter D3 of the cooling flow passage 71 is small, for example, even if the inner diameter D3 of the cooling flow passages 20 and 21 is 4 mm, heat is easily transferred to the metal powder adjacent to the melt-solidified portion, and molding defects are likely to occur at the upper end of the cooling flow passage with a circular cross section, so it is desirable to form the support 72.

[0041] FIG. 11 is a diagram showing a disadvantage in the case where the cross-sectional shape of the cooling flow passage 75 in the ring-shaped parts 73, 74 of the induction heating coil 10a is rectangular in the second example of the comparative example. In the comparative example of FIG. 11, as in the embodiment, the induction heating coil 10a is manufactured by metal additive manufacturing with the coil central axis O aligned horizontally. In the comparative example of FIG. 11, the cross-sectional shape of the cooling flow passage 75 in the ring-shaped parts 73, 74 is rectangular. In this case, in the cross-sectional shape cut in the vertical direction of the metal lamination direction of the cooling flow passage 75, the upper end becomes a straight line aligned with the horizontal direction, so that the self-supporting angle θk shown in FIG. 9 becomes 90 degrees. For this reason, a support is required. For example, as shown in FIG. 11, a plurality of ring-shaped supports 76 are formed inside the cooling flow passage 75.

[0042] Fig. 12 is a diagram showing an inconvenience caused when the cross-sectional shape of the cooling flow passage 79 in the ring-shaped portions 77, 78 of the induction heating coil 10b is a pentagon in a third comparative example. In the comparative example of Fig. 12, as in the embodiment, the induction heating coil 10b is manufactured by metal additive manufacturing with the coil central axis O aligned horizontally.

[0043] In the comparative example of Fig. 12, the cross-sectional shape of the cooling flow passage 79 at the ring-shaped portions 77, 78 is a pentagon having a V-shaped apex at the inner peripheral end in the coil radial direction. In this case, a V-shaped portion is formed at the upper end of the cross section of the cooling flow passage 20, 21 on the lower side in the metal lamination direction, so there is a possibility that a support is not required as in the embodiment. However, the upper end of the cross section of the cooling flow passage 20, 21 on the upper side in the metal lamination direction is a straight line that coincides with the horizontal direction, so multiple supports 80 are required inside the flow passage.

[0044] 10 to 12, support is required, or support is required depending on the size. This may increase pressure loss in the cooling channel and reduce cooling capacity.

[0045] Fig. 13 is a diagram showing the inconvenience that occurs when manufacturing a plurality of induction heating coils 10c with the coil central axis O inclined with respect to the horizontal direction. As shown in Fig. 13, in any of the comparative examples of Figs. 10 to 12, metal additive manufacturing may be performed with the coil central axis O inclined, for example, by 45 degrees with respect to the horizontal direction. In this case, even if the cross-sectional shape of the cooling flow path is rectangular or circular as in the comparative example of Fig. 11, during modeling, a straight line coinciding with the horizontal direction is not formed at the upper end of the cooling flow path in the metal lamination direction, and therefore it may be possible to prevent the formation of a support inside the cooling flow path to prevent deformation of the upper end.

[0046] On the other hand, when the induction heating coil 10c is molded in the state of FIG. 13, if the total thickness in the axial direction is small compared to the length of the coil diameter due to a small number of turns of the induction heating coil 10c, the length of the inclined end face in the thickness direction when viewed from above in the plan view shape of the induction heating coil 10c when molded becomes large. This results in a large plan view area of ​​the induction heating coil 10c. In addition, in metal additive manufacturing, an external support 61 extending downward from the outer surface is formed to prevent the outer shape of the induction heating coil 10 from collapsing during molding, so it is not possible to mold multiple induction heating coils 10c in a state where they are stacked in the vertical direction. For this reason, the plan view area of ​​one induction heating coil 10 when molded becomes large, and the number of induction heating coils 10c that can be formed at one time in a limited molding space decreases. In the case of FIG. 13, as a result of considering manufacturing multiple induction heating coils 10 of the same size in a space similar to that of the embodiment of FIG. 8, it was found that only four induction heating coils 10c, half the number of induction heating coils 10c in the case of FIG. 8, could be manufactured. This may lead to an increase in the cost of each induction heating coil 10c when multiple induction heating coils 10c are manufactured at the same time.

[0047] In the embodiment shown in FIGS. 1 to 8, it is possible to eliminate any of the inconveniences in the comparative example in FIGS. 10 to 12 and the manufacturing method in FIG.

[0048] Next, the results of a temperature analysis performed by CAE will be described, in which the maximum coil temperatures when high-frequency hardening was performed while cooling with cooling water was performed using the induction heating coil 10 of the example having the same shape as the embodiment and the induction heating coils 10d, 10e, and 10f of the comparative examples 1 to 3.

[0049] FIG. 14 shows the cross-sectional shapes of the cooling passages 20 (21), 81 to 83 of the induction heating coils 10, 10d, 10e, 10f of the embodiment (a) and comparative examples 1 to 3 ((b) to (d)) used in the above temperature analysis. The cooling passage 81 of comparative example 1 has an elliptical cross-sectional shape cut in the coil radial direction. The cooling passage 82 of comparative example 2 has a rectangular cross-sectional shape cut in the coil radial direction. The cooling passage 83 of comparative example 3 has a triangular cross-sectional shape cut in the coil radial direction. It is assumed that no support is formed inside any of comparative examples 1 to 3.

[0050] In the triangular cooling channel 83 of Comparative Example 3, as in the embodiment, even when the coil central axis is aligned horizontally and manufactured by metal additive manufacturing, the upper end of the cross-sectional shape cut in the vertical direction of the metal lamination direction of the cooling channel 83 can be a straight line that is greatly inclined with respect to the horizontal direction, so there is a possibility that a support will not be necessary. On the other hand, in Comparative Example 1, when the coil central axis is aligned horizontally and manufactured by metal additive manufacturing, a support is necessary unless the inner diameter of the cross-sectional shape of the cooling channel 81 is reduced. In Comparative Example 2, when the coil central axis is aligned horizontally and manufactured by metal additive manufacturing, a support is necessary.

[0051] On the other hand, the above temperature analysis revealed that the maximum temperatures of the induction heating coils 10, 10d, 10e, and 10f were 88.0°C in the embodiment, 84.6°C in the comparative example 1, 80.6°C in the comparative example 2, and 91.3°C in the comparative example 3. Therefore, in the embodiment and the comparative examples 1 and 2, the maximum temperatures of the induction heating coils 10, 10d, and 10e were within the allowable range, but in the comparative example 3, the temperature of the induction heating coil 10f rose significantly and exceeded the allowable range. This is considered to be due to the reduction in the area ratio of the cooling flow path 83 in the cross-sectional shape of the induction heating coil. Therefore, when the cross-sectional shape of the cooling flow path 83 is triangular as in the comparative example 3, it is difficult to improve the cooling capacity, unlike the embodiment.

[0052] Also, unlike the embodiment, if the cross-sectional shape of the cooling flow passage is a polygon having more corners than a hexagon, the self-supporting angle θk becomes larger than 45 degrees or the cross-sectional shape approaches a circle, so unless the coil central axis is tilted relative to the horizontal direction during molding, a support is required inside the cooling flow passage depending on the size of the cross-sectional shape of the cooling flow passage. This may reduce the cooling capacity of the induction heating coil and increase pressure loss. According to the embodiment, since no support is formed in the hexagonal flow passages of the cooling flow passages 20 and 21, it is possible to improve the cooling capacity of the induction heating coil and reduce pressure loss.

[0053] In the above embodiment, the induction heating coil 10 has two ring-shaped portions 11 and 12. However, the present invention is not limited to this, and the number of ring-shaped portions may be one or three or more. [Explanation of symbols]

[0054] 10, 10a, 10b, 10c, 10d, 10e, 10f induction heating coil, 11 first ring-shaped portion, 12 second ring-shaped portion, 13 first straight portion, 14 second straight portion, 15 mounting protrusion, 16 joint portion, 20, 21 cooling flow path, 22, 23 ring-shaped flow path portion, 28 connecting flow path portion, 29 outer wall portion, 30 inner wall portion, 31, 32 straight flow path portion, 40 tapered surface, 41, 42 cylindrical surface, 60 coil diameter, 61 external support, 62 metal powder, 63 laser light, 65 melting and solidifying portion, 70 ring-shaped portion, 71 cooling flow path, 72 support, 73, 74 ring-shaped portion, 75 cooling flow path, 76 support, 77, 78 ring-shaped portion, 79 cooling flow path, 80 support, 81, 82, 83 Cooling flow passage, 100 induction heating device, 101, 102 lead section, 105 vertical plate section, 107 outer water passage, 110, 111, 112, 113 piping.

Claims

1. 1. A method for manufacturing an induction heating coil made by metal additive manufacturing and having at least one ring-shaped portion, comprising: The ring-shaped portion includes a cooling passage extending in a coil circumferential direction, the cooling flow passage has a cross-sectional shape, when cut along the coil axial direction, of a hexagon having two vertices at both inner and outer ends in the coil radial direction, and has a hexagonal flow passage formed continuously in the coil circumferential direction, When forming the induction heating coil, a plurality of metal layers are laminated so that the coil central axis is aligned horizontally; When the plurality of metal layers are laminated, in the cross-sectional shape of the hexagonal flow path, at each of both ends in the coil radial direction, the inclination angle of two straight lines forming a V shape with respect to the coil radial direction is 45 degrees or less. How induction heating coils are manufactured.

2. The at least one ring-shaped portion includes two ring-shaped portions, Each of the two ring-shaped portions includes the cooling passage having the hexagonal passage, The cooling passages are connected to each other by a connecting passage portion formed at a portion provided at a joint of the two ring-shaped portions, The connecting flow path portion is formed so that an outer wall portion connecting the outer ends of the cooling flow paths that become the upper ends during the molding has an inclined surface that is inclined inward in the coil radial direction from one cooling flow path to the other cooling flow path in the axial direction of the coil central axis. A method for manufacturing the induction heating coil according to claim 1.

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