Heating coil for high-frequency heating device

Abstract

[Problem] To provide a heating coil with which it is possible to: efficiently apply quenching treatment to a workpiece in a short time; effectively suppress a situation where a portion is excessively heated on account of the shape of the workpiece; prevent a decrease in mechanical strength of the workpiece; and, furthermore, easily control the depth of a cured layer due to quenching of the workpiece. [Solution] A heating coil 1 comprises: grounding parts 2a, 2b for attachment to electrodes; support parts 3a, 3b disposed to be respectively orthogonal to each of the grounding parts 2a, 2b; and a continuous annular heating part 4 arranged to connect tips of the supporting parts 3a, 3b. The heating coil 1 is provided with an attachment 21 having a shield body 26 which is interposed between the heating part 4 and the workpiece W and functions as a heat removal shield for reducing the degree of quenching of the workpiece W by the heating part 4.

Description

Heating coil for high frequency heating equipment

[0001] The present invention relates to a heating coil used in a high-frequency heating device for heating a workpiece by utilizing electromagnetic induction caused by a high-frequency current.

[0002] In order to increase the hardness of the surface of a metal workpiece (workpiece), the surface of the workpiece is heated to a temperature equal to or higher than the metal's transformation point (austenite transformation point) and then rapidly cooled (a process known as quenching). A widely used method for performing such quenching is to heat the workpiece by bringing a metal member (heating coil) through which a high-frequency current flows into close proximity to the surface of the workpiece using a high-frequency heating device. A known heating coil for use in such quenching is one disclosed in Patent Document 1, which has an annular coil made of a metal pipe fitted around the workpiece and connected to a conductive plate (copper plate) for supplying high-frequency power.

[0003] Japanese Patent Application Laid-Open No. 2020-115428

[0004] However, in the heating coils for the conventional high-frequency heating devices described above, current always flows in one direction inside the annular coil. Therefore, if a large amount of current flows inside the coil, the workpiece is overheated, the crystal grains of the hardened structure of the workpiece become coarse, and the toughness of the workpiece decreases, resulting in a decrease in mechanical strength. Conversely, if only a small amount of current flows inside the coil, the hardened layer depth of the workpiece becomes shallow, resulting in insufficient hardening. Therefore, with the heating coils for conventional high-frequency heating devices, it is difficult to control the depth of the hardened layer caused by hardening the workpiece.

[0005] The object of the present invention is to provide a practical heating coil that solves the problems of the heating coils for conventional high-frequency heating devices described above, that can efficiently harden a workpiece in a short time, that can effectively prevent the workpiece from being overheated due to its shape, that can prevent a decrease in the mechanical strength of the workpiece, and that can easily control the depth of the hardened layer formed by hardening the workpiece.

[0006] Among the present inventions, the invention described in claim 1 is a heating coil used in a high-frequency heating device for heating a workpiece by utilizing electromagnetic induction caused by high-frequency current, characterized in that it comprises a coil body having a pair of plate-shaped grounding portions for contacting electrodes through which high-frequency current is passed, a pair of plate-shaped support portions arranged perpendicular to each of the grounding portions, and a series of circumferential heating portions arranged to connect the tips of the support portions, and an attachment having a heat-removing shield interposed between the heating portions and the workpiece to reduce the degree of hardening of the workpiece by the heating portions.

[0007] The invention described in claim 2 is characterized in that, in the invention described in claim 1, the attachment is capable of changing the amount of the heat shield interposed between the heating part and the workpiece.

[0008] The invention described in claim 3 is characterized in that, in the invention described in claim 2, the heat shield is rotatably arranged relative to the center of the heating part, and the amount of intervention between the heating part and the workpiece can be changed by changing the rotational phase of the heat shield.

[0009] The heating coil for a high-frequency heating device described in claim 1 (hereinafter simply referred to as the heating coil) has a heat shield provided on the attachment that is interposed between the workpiece and the heating portion of the coil body, thereby reducing the magnetic flux generated by the high-frequency current and preventing the workpiece from being locally overheated (i.e., the effect of suppressing temperature rise in areas that are prone to overheating can be adjusted), making it possible to easily control the depth of the hardened layer caused by quenching the workpiece.

[0010] The heating coil described in claim 2 can adjust the amount of magnetic flux generated by the high-frequency current by changing the amount of heat shield of the attachment placed between the heating portion of the coil body and the workpiece, so that the depth of the hardened layer caused by quenching the workpiece can be controlled (fine-tuned) with great precision.

[0011] The heating coil described in claim 3 can change the amount of heat shield interposed between the heating part and the workpiece by changing the rotational phase of the heat shield of the attachment, so that the depth of the hardened layer caused by quenching the workpiece can be very easily controlled simply by changing the rotational phase of the heat shield of the attachment.

[0012] 1 is a perspective view of a heating coil; a front view of a heating coil; a plan view of a heating coil; a left side view of a heating coil; a right side view of a heating coil; an explanatory diagram showing a vertical cross section of a heating coil (a is a cross section taken along line A-A in FIG. 3, and b is an enlarged view of part α in a); a perspective view of an attachment; an explanatory diagram showing an attachment with a connecting member removed (a is a plan view, and b is a front view); an explanatory diagram (cross section taken along line A-A in FIG. 3) showing the heating coil in use; an explanatory diagram (plan view) showing how to change (adjust) the position of the heat shield of the attachment.

[0013] 1 to 6 show a heating coil 1, which includes a coil body 11 including a metal base 5 integrally formed of a copper alloy (high copper alloy) and an insulating plate 16 formed in a sheet shape from an insulating and heat-resistant synthetic resin (fluororesin), and an attachment 21 having a shield 26 interposed between a heating portion 4 of the metal base 5 of the coil body 11 and a workpiece (work) to function as a heat shield for reducing the degree of hardening of the workpiece by the heating portion 4.

[0014] <Structure of Metal Base> The metal base 5 of the coil body 11 is formed by a modeling method using a three-dimensional printer, and has grounding portions 2a, 2b for contacting the electrodes of a high-frequency power supply, a series of circumferential heating portions 4 for heating the workpiece by induction heating, and support portions 3a, 3b for supporting the heating portions 4 at positions spaced apart from the grounding portions 2a, 2b. The metal base 5 has dimensions of length (front-to-back) × width (width) × height = 300 mm × 150 mm × 100 mm (the lengths of the maximum portions of the length, width, and height).

[0015] The heating unit 4 is designed to heat a workpiece inserted therein and has a ring-like (annular) shape with its base end split into left and right halves. An upper heating region 13a is formed on the left side of the base end of the heating unit 4, and is arc-shaped at an angle of approximately 45°. The upper heating region 13a is connected to a lower heating region 15, which is arc-shaped at an angle of approximately 120°, via a first vertical body 17 extending vertically. An upper heating region 13b is formed on the right side of the base end of the heating unit 4, and is arc-shaped at an angle of approximately 30°. The upper heating region 13b is connected to a middle heating region 14, which is arc-shaped at an angle of approximately 30°, via a third vertical body 19 extending vertically. The middle heating region 14 is further connected to the lower heating region 15 via a second vertical body 18 extending vertically. The upper heating zones 13a and 13b, the middle heating zone 14, and the lower heating zone 15 are arranged so that their longitudinal direction (the direction of the arc) is horizontal. The lower surface of the lower heating zone 15 has a tapered surface 20 that tapers downward (see FIG. 6). The length from the center of the heating unit 4 to the outer periphery of the lower heating zone 15, which is the outermost part, is approximately 75 mm.

[0016] Furthermore, inside the heating unit 4 (i.e., inside the left and right upper heating regions 13a, 13b, middle heating region 14, lower heating region 15, first vertical body 17, second vertical body 18, and third vertical body 19), a cooling medium flow path 6 is provided in a hollow shape for cooling the heating unit 4 itself by flowing a cooling medium (water, etc.). The left and right separated portions of the base end of the heating unit 4 are connected to the tips (tips at the bottom ends) of the left and right support parts 3a, 3b, respectively.

[0017] The support portions 3a, 3b are formed as a pair of flat rectangular parallelepipeds (plates) on the left and right, and are arranged adjacent to each other on the left and right, with one plate surface facing the other, spaced a predetermined distance (approximately 2 mm) apart. The upper front portions of the support portions 3a, 3b are chamfered in an arc shape. A coolant flow path (not shown) is formed inside (at the lower edge) of each support portion 3a, 3b, so as to communicate with the coolant flow path 6 inside the heating portion 4.

[0018] Meanwhile, each grounding portion 2a, 2b is formed as a pair of flat rectangular parallelepipeds (plates) and is arranged adjacent to the left and right with their inner sides facing each other and a predetermined distance (approximately 2 mm) apart. The inner edges of each grounding portion 2a, 2b are connected to the base edges of the left and right support portions 3a, 3b, and the plate surfaces of each grounding portion 2a, 2b are perpendicular to the plate surfaces of the support portions 3a, 3b. Cylindrical discharge pipes 7a and injection pipes 7b are provided near the center (approximately the center in the height direction) of the back surface of each grounding portion 2a, 2b, respectively, and these discharge pipes 7a and injection pipes 7b are connected to cooling medium flow paths (not shown) formed vertically inside each grounding portion 2a, 2b. Furthermore, the cooling medium flow path inside each grounding portion 2a, 2b is connected (communicates) with the cooling medium flow path (not shown) inside each support portion 3a, 3b at the lower end of each grounding portion 2a, 2b.

[0019] Furthermore, a sheet-like insulating plate 16 having a predetermined thickness (approximately 2.0 mm) is sandwiched between the left and right grounding portions 2a, 2b of the metal base 5, between the left and right support portions 3a, 3b, and between the left and right base end portions of the heating portion 4, and in this state, the left and right support portions 3a, 3b and the insulating plate 16 are fastened together by screw members (bolts and nuts) 10, 10 inserted through screw holes (not shown). Note that these screw members 10, 10 fasten the support portions 3a, 3b and the insulating plate 16 together via bushings (not shown) made of insulating and heat-resistant synthetic resin (glass epoxy resin), so that the support portions 3a, 3b are not electrically connected to each other via the screw members 10, 10.

[0020] <Metal Substrate Manufacturing Method> The metal substrate 5 described above can be integrally formed by a modeling method based on three-dimensional data using a three-dimensional printer (hereinafter referred to as a three-dimensional additive manufacturing method). Formation by such a three-dimensional additive manufacturing method is preferable because it allows for long-term use without damage even under high-output conditions, allows for reproducible production of identical characteristics at the time of manufacture, and produces a lightweight metal substrate 5 that is easy to handle. Examples of such three-dimensional additive manufacturing methods include a modeling method (partial deposition of conductive powder layers) that repeatedly lays, melts (by irradiation with a laser such as a semiconductor laser, carbon dioxide laser, excimer laser, YAG laser, or fiber laser), solidifies, and stacks a conductive material powder based on three-dimensional data, or a modeling method (melt extrusion deposition of conductive material) that stacks a molten conductive material based on three-dimensional data. The partial deposition of conductive powder layers is preferable as a three-dimensional additive manufacturing method because it enables the easy production of metal substrates 5 with complex shapes and structures.

[0021] In addition, copper, brass, silver, etc. can be suitably used as conductive materials used as raw materials in three-dimensional additive manufacturing methods. Among these conductive materials, copper is preferred because it reduces material costs, enables metal substrates to be manufactured inexpensively and easily using a three-dimensional printer, and improves the conductivity of the metal substrate, resulting in high heat generation efficiency through electromagnetic induction. When using copper as the conductive material, pure copper can be used, but alloys containing copper in smaller proportions of iron, tin, nickel, titanium, beryllium, zirconium, chromium, silicon, etc. (high-copper alloys) are preferred because they enhance laser absorption and promote temperature rise. Furthermore, among these copper alloys, copper-chromium alloys containing chromium in copper are more preferred because they effectively increase the strength of the metal substrate while maintaining high manufacturing efficiency using a three-dimensional printer. Copper alloys containing chromium and zirconium in a predetermined proportion are particularly preferred.

[0022] <Structure of attachment> Figure 7 shows the attachment 21, which is composed of a support member 22 to which a shield member 24 (shield body 26) is fixed so that its position can be adjusted, and a pair of left and right connecting members 23a, 23b for attaching the support member 22 to the coil main body 11.

[0023] The support member 22 is made of ceramic and has a flat cylindrical shape with a constant width (i.e., a constant inner diameter (196 mmφ) and outer diameter (225 mmφ)) and an integral height (approximately 15 mm). Elongated insertion holes 31, 31 with a constant vertical width are provided on the left and right sides, penetrating between the inner and outer walls. An angle indicator 34 is formed on the left surface of the support member 22, indicating the rotation angle (rotation phase) of the shield member 24 (shield body 26) relative to the center, with eight scales provided at 5° angular intervals. Furthermore, screw holes 33, 33 for attaching the connection members 23a, 23b are drilled on the left and right sides of the base end side of the support member 22 (the attachment side of the connection members 23a, 23b).

[0024] On the other hand, the shield member 24 is made of ceramic and has a shape in which a ring-shaped (strip-shaped) shield body 26 with a constant width and a central angle of 90° protrudes inward from the lower end of a flat, cylindrical abutment body 25. The abutment body 25 has an outer diameter (approximately 195 mmφ) that is slightly smaller than the inner diameter (196 mmφ) of the support member 22, and a thickness of approximately 5.0 mm. Therefore, when the attachment 21 is attached to the coil body 11, the inner wall of the abutment body 25 faces the outer peripheral surface of the lower heating region 15 of the heating unit 4, at a distance of approximately 15 mm (see FIG. 3, etc.).

[0025] Two cylindrical (rod-shaped) male screw members 27, 27 are provided on the left and right outer sides of the abutment body 25, respectively, at a predetermined angle (approximately 25°) apart and detachably (by screwing) so as to protrude radially from the center of the abutment body 25. The male screw members 27, 27 on the left and right base ends of the abutment body 25 are arranged symmetrically with respect to the center of the abutment body 25. Meanwhile, the shield body 26 is formed in the shape of a plate-like annular ring (band) with a constant thickness, and is provided at its tip with a tapered portion 32 whose diameter gradually increases from top to bottom. The shield body 26 is provided integrally with the lower end of the inner wall of the abutment body 25 so that its surface (upper surface) is horizontal.

[0026] Meanwhile, the left and right connecting members 23a, 23b are each formed by fastening, using screws, metal connecting bodies 30a, 30b, which are L-shaped and have a rectangular prism shape, to the upper surface of a metal vertical body 29. A screw hole (not shown) for screwing in the support member 22 is drilled in the lower end surface of the vertical body 29, and a screw hole (not shown) for screwing in the coil body 11 (metal substrate 5) is drilled in the base end side of each connecting body 30a, 30b.

[0027] The attachment 21 is formed by fitting the annular abutment body 25 of the shield member 24 into the annular support member 22, threading two male screw members 27 onto the left and right outer sides of the abutment body 25 using the horizontally elongated insertion holes 31 in the support member 22, and screwing nuts 28 onto the distal ends of the male screw members 27, thereby integrating the support member 22 and the shield member 24 (see FIG. 6 ). The attachment 21 is then integrally assembled to the support member 22 thus integrated with the shield member 24 by threading a pair of connecting members 23 a, 23 b onto the support member 22, which is thus integrated with the shield member 24, using the left and right screw holes 33 on the proximal side so that the inner surfaces of the connecting members 30 a, 30 b are closely facing each other.

[0028] The attachment 21 is screwed to the left and right support portions 3a and 3b of the coil body 11 (metal base 5) by utilizing screw holes (not shown) on the base end sides of the connecting bodies 30a and 30b of the left and right connecting members 23a and 23b, and the support member 22 and the shield member 24 (contact body 25 and shield body 26) are arranged concentrically outside the heating portion 4 of the metal base 5. As shown in Figure 6, the tip portion (tapered portion 32) of the shield body 26 of the shield member 24 is closely opposed to the underside of the tapered surface 20 (underside of a part of the tapered surface 20) of the lower heating region 15 of the heating portion 4 of the metal base 5.

[0029] <Method of using the heating coil> In the heating coil 1 configured as described above, the left and right grounding portions 2a, 2b of the metal base 5 are grounded to the electrodes, and as shown in Figure 9, the workpiece W is inserted inside the series of circumferential heating portions 4, and while rotating the workpiece W as necessary, an external power source (high-frequency power source) is turned on via the electrodes, thereby utilizing the electromagnetic induction phenomenon to heat (harden) the workpiece W. In addition, cooling medium (water) is injected from injection pipe 7b on the back of right-side grounding portion 2b, passes through the cooling medium flow path (not shown) inside right-side grounding portion 2b, the cooling medium flow path (not shown) of right-side support portion 3b, and the cooling medium flow path 6 of heating portion 4, and then passes through the cooling medium flow path (not shown) of left-side support portion 3a and the cooling medium flow path (not shown) of the left-side grounding portion, and is then drained from discharge pipe 7a on the back of left-side grounding portion 2a.By efficiently cooling heating portion 4, support portions 3a, 3b, and grounding portions 2a, 2b, damage due to melting of insulating plate 16 can be accurately prevented.

[0030] 9, the shield body 26 of the shield member 24 of the attachment 21 is interposed between the base end of the lower heating zone 15 of the heating part 4 of the metal substrate 5 and the workpiece W. Therefore, the amount of magnetic flux generated in the overlapping portion with the shield body 26 of the lower heating zone 15 is reduced, making it possible to effectively prevent the portion of the workpiece W adjacent to the lower heating zone 15 (the β portion in FIG. 9) from being overheated.

[0031] 10, the phase of the contact body 25 and the shield body 26 relative to the support member 22 (i.e., the degree of overlap with the lower heating region 15 of the heating unit 4) can be adjusted by loosening the bolts 28, 28, which are threaded into the male thread members 27, 27. By adjusting the phase of the contact body 25 and the shield body 26 in this manner, the degree of hardening of the portion of the workpiece W adjacent to the lower heating region 15 (the β portion in FIG. 9) can be adjusted.

[0032] <Effects of the Heating Coil> As described above, the heating coil 1 includes a coil body 11 (metal base 5) having a pair of plate-shaped grounding portions 2a, 2b for contacting the electrodes through which high-frequency current is passed, a pair of plate-shaped support portions 3a, 3b arranged perpendicular to the grounding portions 2a, 2b, and a series of circumferential heating portions 4 provided to connect the tips of the support portions 3a, 3b, and an attachment 21 having a shield body 26 interposed between the heating portions 4 and the workpiece W and functioning as a heat shield to reduce the degree of hardening of the workpiece W by the heating portions 4. Therefore, according to the heating coil 1, by interposing the shield body 26 provided on the attachment 21 between the workpiece W and the heating portions 4 (i.e., the lower heating region 15) of the coil body 11, it is possible to prevent the workpiece W from being locally overheated and to easily control the depth of the hardened layer formed by hardening the workpiece W.

[0033] Furthermore, since the attachment 21 of the heating coil 1 can change the amount of the shield body 26 between the heating section 4 and the workpiece W (i.e., the degree of overlap between the lower heating area 15 of the heating section 4 and the shield body 26), by changing this amount of interposition, the amount of magnetic flux generated by the high-frequency current can be adjusted, and the depth of the hardened layer caused by hardening the workpiece W can be controlled (fine-tuned) with extremely high precision.

[0034] Furthermore, the heating coil 1 has a shield body 26 that is rotatable relative to the center of the heating portion 4, and the amount of space between the heating portion 4 and the workpiece W can be changed by changing the rotational phase of the shield body 26. Therefore, simply by changing the rotational phase of the shield body 26, the depth of the hardened layer formed by quenching the workpiece W can be very easily controlled (finely adjusted).

[0035] Furthermore, since the heating coil 1 has the angle display unit 34 provided on the support member 22 of the attachment 21, the rotational phase of the shield body 26 relative to the support member 22 can be adjusted very accurately and very easily.

[0036] <Modifications of the heating coil> The heating coil according to the present invention is not limited to the aspects of the above-described embodiment, and the materials, shapes, structures, etc. of the coil body (metal base, grounding portion, support portion, heating portion), insulating plate, and attachments (support member, connecting member, shield member (shield body: heat removal shield)) can be appropriately modified as necessary within the scope of the present invention.

[0037] For example, the heating section of the heating coil is not limited to a top-bottom, multi-stage, circular ring-shaped structure in plan view (i.e., a structure in which peripheral bodies are arranged horizontally above and below and connected by vertical columnar bodies extending in the vertical direction) as in the above embodiment, but can also be changed to a simple circular ring or a ring-shaped body in which at least a portion has a shape other than an arc.

[0038] Furthermore, the heating coil is not limited to the above embodiment, in which a single cooling medium downflow path (mainly for cooling the heating portion itself) is provided within the heating portion of the metal base, but can be modified to have multiple cooling medium downflow paths within the heating portion (for example, a separate cooling medium downflow path with cooling medium injection holes for cooling the workpiece). Incidentally, providing two types of cooling medium downflow paths in this manner has the advantage of more efficiently cooling the workpiece after heating and the heating portion itself. Furthermore, the heating coil is not limited to the above embodiment, in which a single cooling medium downflow path is provided so that the cooling medium injected from one side of the heating portion passes through the support portion on the same side to the heating portion, then passes through the support portion on the opposite side and is discharged from the ground portion on the opposite side. The cooling medium downflow path may be divided into left and right sections, for example.

[0039] Furthermore, the heating coil is not limited to one in which the metal base is formed by a modeling method based on three-dimensional data using a three-dimensional printer, as in the above embodiment, but may also be one in which the metal base (all or part) is formed by another modeling method (for example, a brazing method, etc.).

[0040] Furthermore, the heating coil is not limited to an attachment in which the entire attachment (i.e., the shielding member, the support member, and the connecting member) is made of ceramics, as in the above embodiment, and at least a portion of the attachment may be made of a material other than ceramics (for example, a synthetic resin having insulating and heat-resistant properties, such as polyacetal (POM), polyphenylene sulfide (PPS), or polyether ether ketone (PEEK)).

[0041] Furthermore, the heating coil is not limited to the above embodiment in which the heat shield (shield body) rotates around the center of the heating portion of the metal base to change the amount of space between the heating portion and the workpiece (i.e., the degree of overlap with the heating portion (lower heating area)), but can also be changed to one in which the heat shield slides in a radial direction relative to the center of the heating portion of the metal base (i.e., the heat shield slides toward or away from the workpiece) to change the amount of space between the heating portion and the workpiece (i.e., the degree of overlap with the heating portion).

[0042] In addition, the heating coil according to the present invention is not limited to the above-described embodiment in which the pair of grounding portions and the pair of supporting portions are insulated by an insulating plate made of a fluororesin (PTFE, PFA, FEP, ETFE, PCTFE, ECTFE, PVDF), but may be changed to a configuration in which the pair of grounding portions and the pair of supporting portions are insulated by an insulating plate made of other synthetic resins such as POM, PPS, PEEK, or ceramics that have insulating and heat-resistant properties.

[0043] In addition, the heating coil according to the present invention can be modified as appropriate depending on the shape and size of the coil body and attachments, the type (material) and thickness of the insulating plate, the number of bolts for clamping the insulating plate, the structure for attaching the attachments to the coil body, etc., depending on the shape of the workpiece to be hardened, etc.

[0044] The heating coil according to the present invention has the excellent effects as described above, and can therefore be suitably used as a member for heating a workpiece by utilizing electromagnetic induction.

[0045] DESCRIPTION OF SYMBOLS 1. Heating coil 2a, 2b. Grounding portion 3a, 3b. Support portion 4. Heating portion 5. Metal substrate 11. Coil body 15. Lower heating region 16. Insulating plate 21. Attachment 22. Support member 23a, 23b. Connection member 24. Shield member 26. Shield body (heat shield) 34. Angle display portion

Claims

1. A heating coil used in a high-frequency heating device for heating a workpiece by utilizing electromagnetic induction caused by high-frequency current, comprising: a coil body having a pair of plate-shaped grounding portions for contacting electrodes through which high-frequency current is passed, a pair of plate-shaped supporting portions arranged so as to be perpendicular to each of the grounding portions, and a series of circumferential heating portions provided to connect the tips of the supporting portions; and an attachment having a heat shield interposed between the heating portions and the workpiece to reduce the degree of hardening of the workpiece by the heating portions.

2. The heating coil according to claim 1, wherein the attachment is capable of changing the amount of the heat shield disposed between the heating portion and the workpiece.

3. A heating coil as described in claim 2, characterized in that the heat shield is rotatably arranged relative to the center of the heating portion, and the amount of space between the heating portion and the workpiece can be changed by changing the rotational phase of the heat shield.

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