Movable quenching device

Abstract

A moving quenching device for moving quenching a shaft-shaped body in which a large-diameter section having a relatively large outer diameter and a small-diameter section having a relatively small outer diameter are connected via a stepped section, the moving quenching device being provided with: a plurality of split coils which are arranged annularly around a central axis and through which a high-frequency current flows; and a coil drive unit that causes the split coils to approach and separate from each other with respect to the central axis, each of the split coils being provided with a plurality of convex coil parts having a shape that protrudes in a direction away from the central axis when viewed along the central axis. Each of the convex coil portions is disposed so that at least a portion thereof overlaps each other in the direction in which the central axis extends, and so that the convex coil portions overlap each other in the radial direction centered on the central axis in a line-of-sight line along the central axis.

Description

Technical Field

[0001] The present disclosure relates to a mobile quenching apparatus. Background Art

[0002] Conventionally, the fatigue strength of the shaft-shaped body is improved by traverse hardening of the shaft-shaped body by induction heating. The traverse hardening mentioned here refers to quenching while moving the coil component or the like relative to the shaft-shaped body in the axial direction.

[0003] Specifically, the coil is moved along the outer peripheral surface in the longitudinal direction of the shaft-shaped body while a current is passed through the coil, thereby induction heating the shaft-shaped body. Then, a coolant is blown to the outer peripheral surface just after heating, so that the shaft-shaped body is quickly cooled and quenched. Here, in the case where the shaft-shaped body is a stepped shaft having a step portion in which the outer diameter changes from a large diameter to a small diameter, or from a small diameter to a large diameter at a midway position in the longitudinal direction, in order to maintain the heating efficiency, it is necessary to appropriately adjust the air gap between the outer peripheral surface of the shaft-shaped body and the coil.

[0004] One of the device structures capable of such adjustment is a method of forming a coil using a plurality of split coils. Specifically, a plurality of split coils are arranged along the circumferential direction of the shaft-like body, and these split coils are connected in series with a power supply. Then, while the current from the power supply flows to each split coil, these split coils are moved along the length direction of the shaft-like body. Then, before the split coils are about to reach the step portion, each split coil is brought close to or separated from the outer peripheral surface of the shaft-like body according to the change in the outer diameter of the shaft-like body, so that the air gap is maintained approximately constant.

[0005] The following patent document 1 discloses a conventional high-frequency induction heating device using such a split coil. The device is equipped with a high-frequency induction heating coil as a split coil. The high-frequency induction heating coil for heating the shaft-shaped component adopts "a high-frequency induction heating coil for heating the shaft-shaped component, which is used for high-frequency induction heating of the arc portion formed between the flange portion and the shaft portion and the outer peripheral surface of the shaft portion in the shaft-shaped component having a flange portion and a shaft portion erected at the center of the flange portion, wherein a pair of high-frequency induction heating coil components are provided, which are respectively arranged at positions opposite to each other across the axis of the shaft-shaped component, and are arranged opposite to the arc portion and the shaft portion at a position separated from the arc portion and the shaft portion of the shaft-shaped component, and the pair of high-frequency induction heating coil components are respectively formed with curved coil portions that are curved in a manner protruding in a direction away from the axis of the shaft-shaped component."

[0006] According to this device, it is described that "by using a pair of high-frequency induction heating coil components, the pair of high-frequency induction heating coil components can be arranged correspondingly to all various shaft-shaped members having different outer peripheral surface diameters."

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2008-150640 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] However, in the conventional mobile quenching device including the above-mentioned device, the number of turns of the split coil is one turn, and the number of turns cannot be increased to multiple turns for structural reasons. This is because, when the number of turns of the split coil is increased by overlapping multiple split coils along the length direction of the shaft-like body, the step portion of the shaft-like body where the outer diameter changes cannot be properly mobile quenched. For example, in the mobile quenching of the step portion from the large diameter portion to the small diameter portion, the split coil cannot be brought close to the small diameter portion before the entirety of the split coils overlapping in the length direction of the shaft-like body passes through the large diameter portion. Therefore, the portion of the split coil that ends the heating of the large diameter portion and reaches the front side of the traveling direction of the small diameter portion is inductively heated in a state with a wide air gap between it and the outer peripheral surface of the small diameter portion, which is not preferred from the viewpoint of heating efficiency and poor quenching.

[0012] On the other hand, in the moving quenching of the step portion from the small diameter portion to the large diameter portion, the portion of the split coils overlapping in the longitudinal direction of the shaft-shaped body located on the rear side in the traveling direction cannot pass over the step portion unless the portion located on the front side in the traveling direction quickly moves away from the outer peripheral surface of the small diameter portion before the portion located on the front side in the traveling direction reaches the large diameter portion, even if the small diameter portion is still being heated. Therefore, this is still an undesirable result from the viewpoint of heating efficiency and poor quenching.

[0013] For the reasons described above, the split coils in the past cannot have multiple turns, but usually have one turn. In the case of one turn, the current flowing through the split coil needs to be much higher than that in the case of multiple turns, which easily causes problems such as overheating and short circuit of the split coil.

[0014] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a mobile quenching device capable of performing mobile quenching on a stepped shaft while suppressing overheating and short circuit of split coils accompanied by a large current.

[0015] Technical solutions for solving technical problems

[0016] In order to solve the above-mentioned problems, the present disclosure proposes the following means.

[0017] (1) A mobile quenching device according to one aspect of the present disclosure is a device for performing mobile quenching on a shaft-shaped body, the shaft-shaped body being formed by connecting a large diameter portion having a relatively large outer diameter and a small diameter portion having a relatively small outer diameter via a step portion, the mobile quenching device comprising:

[0018] A plurality of split coils are arranged in a ring shape around the central axis and through which high-frequency current flows; and

[0019] a coil driving unit that moves each of the split coils toward and away from the central axis,

[0020] Each of the split coils includes a plurality of convex coil portions, each of which has a shape that convexly projects in a direction away from the central axis when viewed along the central axis;

[0021] Each of the convex coil portions is configured such that:

[0022] In the extension direction of the central axis, at least a portion overlaps with each other, and,

[0023] In a line of sight along the central axis, they overlap in a radial direction centered on the central axis.

[0024] According to the mobile quenching device described in (1) above, if a high-frequency current is supplied to each of the split coils on the basis of arranging a plurality of split coils around the shaft-shaped body, the high-frequency current flows through a plurality of convex coil portions that are arranged to overlap at least partially in the extension direction of the central axis and overlap in the radial direction centered on the central axis in the line of sight along the central axis. As a result, each convex coil portion is electromagnetically induced with the shaft-shaped body, thereby heating the shaft-shaped body.

[0025] Furthermore, when each segmented coil is moved along the length direction of the shaft-shaped body, when the step portion is crossed from the small diameter portion toward the large diameter portion, the coil driving unit causes each segmented coil to leave the outer peripheral surface of the small diameter portion, so that all convex coil portions can be simultaneously arranged at positions corresponding to the outer peripheral surface of the large diameter portion. Then, the large diameter portion is subjected to moving quenching following the small diameter portion.

[0026] On the other hand, when crossing the step from the large diameter portion to the small diameter portion, after each convex coil portion passes the position of the large diameter portion, the coil driving unit makes each split coil close to the outer peripheral surface of the small diameter portion, so that all convex coil portions can be arranged at the position corresponding to the outer peripheral surface of the small diameter portion at the same time. Then, the small diameter portion is subjected to mobile quenching following the large diameter portion.

[0027] In either of the above cases, since each convex coil portion is configured to overlap at least a portion of each other in the extension direction of the central axis and overlap in the radial direction centered on the central axis in the line of sight along the central axis, the positions of all convex coil portions in the extension direction of the central axis in the moving direction are always consistent. As a result, the overall thickness of each convex coil portion can be made thinner than when they are overlapped in the direction of the central axis, thereby eliminating the problems caused by overlapping each convex coil portion in the direction of the central axis. In this way, mobile quenching based on multiple turns of split coils can be performed, so the current value of the high-frequency current flowing through each split coil can be significantly reduced compared to the case of one turn.

[0028] (2) In the mobile quenching device described in (1) above, the following structure may be adopted:

[0029] Each of the split coils further comprises:

[0030] A connecting portion electrically connecting the convex coil portions;

[0031] A first lead portion electrically connected to one end side of each of the convex coil portions around the central axis and extending in the radial direction; and

[0032] A second conductor portion is electrically connected to the other end side of each of the convex coil portions around the central axis and extends in the radial direction.

[0033] The first lead portion and the second lead portion are arranged to overlap with the connection portion in the direction of the central axis.

[0034] According to the mobile quenching device described in (2) above, by overlapping the first and second wire portions that do not contribute to induction heating with the originally existing connection portion in the direction along the central axis, the portion that is not induction heated in the circumferential direction of the shaft-like body can be reduced. That is, if the first and second wire portions are to be arranged in the gaps between the split coils, it is necessary to expand the non-heating range generated between these split coils, but by arranging the first and second wire portions at positions other than the gaps between the split coils, the intervals between the gaps between the split coils can be narrowed. In this way, it is possible to suppress uneven heating in the circumferential direction of the shaft-like body and perform uniform heating.

[0035] (3) In the mobile quenching device described in (2) above, the following structure may be adopted:

[0036] Each of the split coils is a double-turn coil having an inner convex coil portion and an outer convex coil portion as each convex coil portion, wherein the inner convex coil portion is relatively close to the central axis and the outer convex coil portion is relatively far from the central axis;

[0037] The first conductor portion has a first bent portion that is bent in a direction toward the central axis side from a position of the outer circumferential side convex coil portion and connected to the one end side of the inner circumferential side convex coil portion;

[0038] The second lead portion includes a second bent portion bent from the other end side toward the one end side, and a third bent portion bent from the second bent portion toward the other end side of the outer peripheral side convex coil portion to be connected.

[0039] According to the mobile quenching device described in (3) above, the first wire portion can be connected to the inner convex coil portion by bypassing the outer convex coil portion using the first bent portion. In addition, the second wire portion can be connected to the outer convex coil portion by bypassing the connecting portion using a combination of the second bent portion and the third bent portion. Therefore, the first wire portion and the second wire portion can overlap on the connecting portion without interfering with other parts.

[0040] (4) In the mobile quenching device described in (2) above, the following structure may be adopted:

[0041] Each of the split coils is a three-turn coil having a first convex coil portion, a second convex coil portion, and a third convex coil portion arranged in sequence in a direction away from the central axis as each of the convex coil portions;

[0042] The first lead portion and the second lead portion overlap the connection portion connecting the first convex coil portion and the second convex coil portion and the connection portion connecting the second convex coil portion and the third convex coil portion in a direction along the central axis.

[0043] According to the mobile quenching device described in (4) above, the first wire portion and the second wire portion will not enter the gap between the adjacent split coils, so the interval between the split coils can be narrowed. As a result, the circumferential heating unevenness of the shaft body can be suppressed and uniform heating can be performed. On this basis, by setting it as a three-turn coil, the current value of the high-frequency current flowing through each split coil can be further reduced.

[0044] (5) In the mobile quenching device described in (1) above, the following structure may be adopted:

[0045] Each of the split coils is a three-turn coil having a first convex coil portion, a second convex coil portion, and a third convex coil portion arranged in sequence in a direction away from the central axis as each of the convex coil portions;

[0046] Each of the split coils comprises:

[0047] a first connecting portion connecting the first convex coil portion and the second convex coil portion;

[0048] a second connecting portion connecting the second convex coil portion and the third convex coil portion;

[0049] A first wire portion, which is electrically connected to the first convex coil portion and extends in the radial direction; and

[0050] a second wire portion, which is electrically connected to the third convex coil portion and extends toward the radial direction;

[0051] At least a portion of the first lead portion and the second lead portion is offset from the first connection portion and the second connection portion in a circumferential direction around the central axis.

[0052] According to the mobile quenching device described in (5) above, since at least a portion of the first wire portion and the second wire portion is deviated from the first connecting portion and the second connecting portion in the circumferential direction, the arrangement interval between the first connecting portion and the second connecting portion in the direction along the central axis can be narrowed. As a result, the overall thickness of the split coil can be thinned, so it is difficult to cause problems related to interference between each split coil and the step portion when the axial body is moved and heated while passing through the step portion. On this basis, by setting it as a three-turn coil, the current value of the high-frequency current flowing through each split coil can be further reduced.

[0053] (6) In the moving quenching device described in any one of (1) to (3) above, the number of each of the split coils may be two or three.

[0054] According to the moving quenching device described in (6), the number of regions that do not contribute to induction heating formed between adjacent segmented coils is minimized, thereby suppressing heating unevenness in the circumferential direction of the shaft body and more reliably performing uniform heating.

[0055] Effects of the Invention

[0056] According to the transfer hardening apparatus of each of the above aspects, it is possible to transfer harden the stepped shaft while suppressing overheating and short circuit of the split coils caused by a large current. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1This is a side view schematically showing a portion of the mobile quenching device according to the first embodiment of the present disclosure.

[0058] Figure 2 This is a perspective view of one of the split coils provided in the moving quenching device as viewed from below. The opening angle between the first conductor portion and the second conductor portion is 180°, but in this figure, the opening angle is narrowed using a break line for the sake of explanation.

[0059] Figure 3 is a diagram showing a state in which the small diameter portion of the shaft body is inductively heated by the split coil, and is Figure 1 A-A view.

[0060] Figure 4 It means that the split coil has reached Figure 1 A diagram showing a state in which the large diameter portion of the shaft-shaped body is inductively heated at the position of the BB cross section.

[0061] Figure 5 1 is a flowchart showing the transfer quenching method in this embodiment.

[0062] Figure 6 is a diagram showing a state in which a small diameter portion of a shaft-shaped body is inductively heated by a mobile quenching device according to a second embodiment of the present disclosure, and is Figure 1 A-A view.

[0063] Figure 7 This is a diagram of one of the split coils of the mobile quenching device of the third embodiment of the present disclosure, viewed from below. (a) is a perspective view showing the appearance of the split coil, and (b) is a perspective view showing the flow of coolant and current. The opening angle between the first wire portion and the second wire portion is 180°, but in this figure, the opening angle is narrowed using a fracture line for illustration.

[0064] Figure 8 This is a diagram of one of the split coils of the mobile quenching device of the fourth embodiment of the present disclosure, viewed from below. (a) is a perspective view showing the appearance of the split coil, and (b) is a perspective view showing the flow of coolant and current. The opening angle between the first wire portion and the second wire portion is 180°, but in this figure, the opening angle is narrowed using a fracture line for illustration.

[0065] Fig. 9 is a diagram showing the simulation results of the mobile quenching device, and is Figure 1 A longitudinal cross-sectional view of the C portion of FIG. (a) shows a conventional example, and (b) shows an embodiment. DETAILED DESCRIPTION

[0066] Hereinafter, an embodiment of the mobile quenching device disclosed in the present invention will be described based on the accompanying drawings. Figure 1 The upper side of the paper along the central axis CL is referred to as the upper direction, the lower side of the paper is referred to as the lower direction, and the upper and lower directions of the paper are collectively referred to as the length direction. In addition, the radial direction of the axial body W centered on the central axis CL is sometimes referred to as the radial direction, and the circumferential direction of the axial body W is referred to as the circumferential direction.

[0067] [First embodiment]

[0068] <Mobile quenching equipment>

[0069] First, use Figures 1 to 4 , the structure of the mobile quenching device of the first embodiment is described. Here, Figure 1 This is a side view schematically showing a portion of the mobile quenching device. Figure 2 This is a perspective view of one of the split coils included in the moving quenching device as viewed from below. Figure 3 is a diagram showing a state in which the small diameter portion of the shaft body is inductively heated by the split coil, and is Figure 1 A-A view. Figure 4 It means that the split coil has reached Figure 1 A diagram showing a state in which the large diameter portion of the shaft-shaped body is inductively heated at the position of the BB cross section.

[0070] Figure 1 The traverse hardening device 1 shown is a device for performing traverse hardening on an axle for a railway vehicle or an axial body W such as a ball screw using a high-frequency current.

[0071] First, the shaft-like body W is described. The shaft-like body W is a stepped shaft having a large diameter portion W1, a step portion W2, a small diameter portion W3, a step portion W4, and a large diameter portion W5 coaxially arranged in sequence from the bottom to the top in the longitudinal direction thereof. The large diameter portions W1 and W5 are cylinders with a circular cross section, and have the largest outer diameter in the entire shaft-like body W. The small diameter portion W3 is a cylinder with a circular cross section, and has a smaller outer diameter than the large diameter portions W1 and W5. The step portion W2 has a truncated cone shape connecting the upper end of the large diameter portion W1 and the lower end of the small diameter portion W3. The outer diameter of the step portion W2 gradually decreases from the same outer diameter as the large diameter portion W1 toward the upper direction, and then becomes equal to the outer diameter of the lower end of the small diameter portion W3. The step portion W4 has an inverted truncated cone shape connecting the upper end of the small diameter portion W3 and the lower end of the large diameter portion W5. The outer diameter of the step portion W4 gradually increases upward from the same outer diameter as the upper end of the small diameter portion W3, and then becomes equal to the outer diameter of the lower end of the large diameter portion W5. The large diameter portion W1, the step portion W2, the small diameter portion W3, the step portion W4, and the large diameter portion W5 share the central axis CL. When the outer diameters of the large diameter portions W1 and W5 are assumed to be 100%, the outer diameter of the small diameter portion W3 is, for example, 80% to 90%.

[0072] The shaft-shaped body W is formed of a conductive material such as carbon steel or low-alloy steel containing 95% by weight or more of iron (Fe) as a ferrite phase.

[0073] like Figure 1 As shown, the mobile quenching device includes a support unit 10 , an induction heating unit 20 , a cooling unit 30 , a moving unit 40 , a control unit 50 , and a power source 60 .

[0074] like Figure 1 As shown, the support portion 10 includes a lower center 11 and an upper center 12. The lower center 11 coaxially supports the large diameter portion W1 of the shaft-like body W from below. The upper center 12 coaxially supports the large diameter portion W5 of the shaft-like body W from above. The lower center 11 and the upper center 12 support the shaft-like body W in a manner such that its center axis CL is along the up-down direction and one end side (the side with the large diameter portion W1) of the shaft-like body W is at the bottom and the other end (the side with the large diameter portion W5) is at the top. Between these lower centers 11 and upper centers 12, the shaft-like body W is configured to be rotatable around the center axis CL. The lower center 11 and the upper center 12 that support the shaft-like body W in this way rotate the shaft-like body W around the center axis CL when receiving a driving force from a shaft-like body rotating motor (not shown) provided in the support portion 10.

[0075] like Figure 1 As shown, the induction heating unit 20 includes a plurality of split coils 21 and a coil support 28 .

[0076] In this embodiment, two split coils 21 are used. The two split coils 21 have the same structure as each other, so Figure 2 One of them will be described, and the description of the other will be omitted as it has the same structure.

[0077] like Figure 2 As shown, the split coil 21 includes a convex coil portion 22 , a connecting portion 23 , a first conductor portion 24 , and a second conductor portion 25 .

[0078] like Figure 2 as well as Figure 3 As shown, the convex coil portion 22 is a double-turn coil having an inner circumferential convex coil portion 22a located relatively close to the center axis CL and an outer circumferential convex coil portion 22b located relatively far from the center axis CL.

[0079] Both the inner convex coil portion 22a and the outer convex coil portion 22b have arc shapes that convex in a direction away from the center axis CL when viewed along the center axis CL. Alternatively, an L-shape or a V-shape may be used instead of the arc shape.

[0080] The inner circumference side convex coil portion 22a and the outer circumference side convex coil portion 22b are as follows. Figure 1 As shown, they are arranged at the same position relative to each other in the extension direction of the center axis CL. That is, with respect to the inner circumferential side convex coil portion 22a and the outer circumferential side convex coil portion 22b, in the extension direction, the positions of their upper surfaces are the same as each other, and the positions of their lower surfaces are also the same as each other. In addition, the relative positions of the inner circumferential side convex coil portion 22a and the outer circumferential side convex coil portion 22b in the extension direction may be completely consistent as in the present embodiment, or there may be some deviations. However, from the viewpoint of heating efficiency, it is preferred as in Figure 1 Exactly the same as shown.

[0081] On the other hand, Figure 3 As shown, when observed from the line of sight along the central axis CL, these inner convex coil portions 22a and outer convex coil portions 22b are arranged overlappingly with a gap g1 in the radial direction centered on the central axis CL. That is, the positions of one end side of the inner convex coil portion 22a and the outer convex coil portion 22b in the circumferential direction are the same. Similarly, the positions of the other end side of the inner convex coil portion 22a and the outer convex coil portion 22b in the circumferential direction are also the same. Moreover, these inner convex coil portions 22a and the outer convex coil portions 22b cover a range of about 180° on the outer circumferential surface of the axial body W, and induction heating is performed on this range.

[0082] On the other hand, Figure 1As shown, in the length direction along the central axis CL, the upper and lower positions of the inner convex coil portion 22a and the outer convex coil portion 22b are consistent. That is, the upper surface of the inner convex coil portion 22a and the upper surface of the outer convex coil portion 22b are in the same position along the length direction of the central axis CL. Similarly, the lower surface of the inner convex coil portion 22a and the lower surface of the outer convex coil portion 22b are also in the same position along the length direction of the central axis CL.

[0083] The connecting portion 23 electrically and mechanically connects the inner circumferential side convex coil portion 22a and the outer circumferential side convex coil portion 22b. That is, when one of the inner circumferential side convex coil portion 22a and the outer circumferential side convex coil portion 22b in the circumferential direction is regarded as one end side and the other as the other end side, the other end side of the inner circumferential side convex coil portion 22a is connected to the one end side of the outer circumferential side convex coil portion 22b.

[0084] Use the Figure 3 The split coil 21 on the right side of the paper will be described in more detail. The connecting portion 23 includes straight portions 23a, 23b and a reverse winding portion 23c.

[0085] The straight portion 23a is connected to the inner convex coil portion 22a at the upper end of the paper as the other end side, and is a portion extending straightly generally toward the outside in the radial direction. The straight portion 23b is connected to the outer convex coil portion 22b at the lower end of the paper as the one end side, and is a portion extending straightly generally toward the outside in the radial direction.

[0086] The reverse winding portion 23c has a shape that is convex in the direction away from the central axis CL when viewed along the central axis CL, and connects the ends of the straight portions 23a and 23b. The reverse winding portion 23c has an arc shape that shares the central axis CL between the inner convex coil portion 22a and the outer convex coil portion 22b. Moreover, the position of the reverse winding portion 23c in the direction of the central axis CL is the same as that of the inner convex coil portion 22a and the outer convex coil portion 22b.

[0087] The reverse winding portion 23c is arranged with a gap g2 relative to the outer peripheral surface of the outer peripheral side convex coil portion 22b. The gap g2 is much wider than the gap g1. The reverse winding portion 23c is a portion for returning the flow of current so that the flow direction of the high-frequency current between the inner peripheral side convex coil portion 22a and the outer peripheral side convex coil portion 22b is the same. That is, induction heating is performed by the high-frequency current flowing through the inner peripheral side convex coil portion 22a and the outer peripheral side convex coil portion 22b.

[0088] The first conductor portion 24 is Figure 2 as well as Figure 3As shown in the figure, the inner circumferential convex coil portion 22a is electrically and mechanically connected at the lower end of the paper as the one end side, and extends straightly approximately toward the radial outside. Moreover, the first wire portion 24 is arranged to overlap below the straight portion 23b. That is, when viewed from above along the center axis CL, the first wire portion 24 overlaps directly below the straight portion 23b. Therefore, Figure 3 In comparison with the case where the first conductor portion 24 is interposed between, for example, one straight portion 23 b and the other straight portion 23 a of a pair of split coils 21 , the gap between the split coils 21 can be narrowed.

[0089] The shaft body W cannot be inductively heated in the straight portions 23a and 23b and the gap therebetween. Therefore, by not arranging the first lead portion 24 in the gap as in the present embodiment, the non-heating range in the circumferential direction of the shaft body W can be narrowed to suppress uneven quenching.

[0090] like Figure 2 As shown, the first wire portion 24 has a first bent portion 24a that is bent toward a direction toward the central axis CL side more than the position of the outer convex coil portion 22b and connected to the one end side of the inner convex coil portion 22a. That is, after passing directly below the outer convex coil portion 22b, the first wire portion 24 is bent upward at a right angle at the first bent portion 24a, thereby connecting directly below the inner convex coil portion 22a. In this way, according to the first bent portion 24a, the first wire portion 24 can be connected to the inner convex coil portion 22a without causing interference by bypassing the outer convex coil portion 22b.

[0091] like Figure 2 As shown, the second wire portion 25 has a second curved portion 25a that is bent from the other end side toward the one end side and a third curved portion 25b that is bent from the second curved portion 25a to the other end side of the outer peripheral side convex coil portion 22b and connected. That is, the second wire portion 25 is bent in the second curved portion 25a from the lower part of the straight portion 23a toward the lower position of the outer peripheral side convex coil portion 22b in the horizontal direction. Then, the second wire portion 25 is bent in the third curved portion 25b toward the lower surface of the outer peripheral side convex coil portion 22b and connected. In this way, according to the second curved portion 25a and the third curved portion 25b, the second wire portion 25 can be connected to the outer peripheral side convex coil portion 22b without causing interference by bypassing the straight portion 23a.

[0092] The second conductor portion 25 is Figure 3As shown in FIG. 1 , the second conductor portion 25 is electrically and mechanically connected to the outer convex coil portion 22b at the upper end of the paper as the other end side, and extends straightly approximately toward the radial outside. Moreover, the second conductor portion 25 is arranged to overlap below the straight portion 23a. That is, when viewed from above along the center axis CL, the second conductor portion 25 overlaps directly below the straight portion 23a. Therefore, Figure 3 Compared with the case where the second wire portion 25 is sandwiched between one straight portion 23a and the other straight portion 23b of each split coil 21, the gap between the split coils 21 can be narrowed. As a result, the non-heating range in the circumferential direction of the shaft-shaped body W can be narrowed for the above-mentioned reasons, thereby suppressing quenching unevenness.

[0093] Each split coil 21 described above is manufactured by bending and brazing a hollow tube having a square cross section, and has electrical conductivity. Figure 1 The current transformer 61 of the power supply 60 shown is electrically and mechanically connected. The current transformer 61 allows a high-frequency current to flow through each segmented coil 21.

[0094] Furthermore, each of the split coils 21 can be cooled by allowing a coolant to flow through the tube thereof.

[0095] return Figure 1 The coil support 28 supports a pair of split coils 21 coaxially with the shaft body W. The coil support 28 includes a guide portion (not shown) for guiding a pair of split coils 21 to approach and separate from each other freely, and a coil drive portion (not shown) for making these split coils 21 approach and separate relative to the center axis CL. For example, a linear guide can be used as the guide portion, and a combination of a stepping motor and a ball screw can be used as the coil drive portion. The coil support 28 is connected and supported by a moving portion 40 described later via a stay 28a.

[0096] like Figure 1 As shown, the cooling unit 30 includes a cooling ring 31 , a cooling ring support stay 32 , and a coolant circulation pump 33 .

[0097] The cooling ring 31 is formed in a ring shape. An internal space 31a is formed in the cooling ring 31. A plurality of nozzles 31b are formed on the inner peripheral surface of the cooling ring 31 and are separated from each other in the circumferential direction and communicate with the internal space 31a. The shaft-shaped body W is coaxially inserted into the cooling ring 31. The cooling ring 31 is arranged below each of the split coils 21.

[0098] The cooling ring 31 is connected and supported by a coolant circulation pump 33 via a cooling ring support stay 32. The coolant circulation pump 33 supplies a coolant L such as water into the internal space 31a of the cooling ring 31. The coolant L supplied to the internal space 31a is ejected toward the shaft body W through a plurality of nozzles 31b, thereby cooling the shaft body W.

[0099] Figure 1 The moving part 40 shown has a supporting plate 41 , a pinion 42 , a motor 43 and a rack 44 .

[0100] The coil support 28, the current transformer 61, the cooling ring 31, and the coolant circulation pump 33 are fixed to the support plate 41. The pinion 42 is rotatably fixed to the support plate 41. The motor 43 for driving the pinion 42 to rotate is mounted on the support plate 41.

[0101] The support plate 41 is connected to the rack 44 via a guide rail (not shown). The support plate 41 is movable relative to the rack 44 in the vertical direction by the guide rail. The pinion 42 is meshed with the teeth of the rack 44. Therefore, when the control unit 50 drives the motor 43, the pinion 42 rotates, and the support plate 41 moves upward or downward relative to the rack 44.

[0102] The control unit 50 includes a calculation circuit and a memory (not shown). The memory stores a control program for driving the calculation circuit and the like.

[0103] The control unit 50 is connected to the current transformer 61, the coil driving unit, the motor 43, the coolant circulation pump 33, and the shaft-shaped body rotating motor, and controls them.

[0104] For example, when the small diameter portion W3 of the shaft body W is subjected to moving quenching, the control unit 50 controls the coil driving unit so that Figure 3 As shown, the arrangement interval between the pair of split coils 21 is minimized. On the other hand, when the large diameter portions W1 and W5 of the shaft body W are subjected to movement quenching, the coil driving portion is controlled by the control portion 50, as shown in FIG. Figure 4 As shown, the gap between the pair of split coils 21 is maximized.

[0105] When the step portions W2 and W4 of the shaft body W are subjected to movement quenching, the control unit 50 controls the coil driving unit to open and close the pair of split coils 21 in accordance with the change in diameter of the step portions W2 and W4 in the longitudinal direction along the central axis CL.

[0106] <Mobile quenching method>

[0107] Next, the transfer quenching method according to the present embodiment will be described.

[0108] Figure 5 1 is a flowchart showing the transfer quenching method in this embodiment.

[0109] The shaft-shaped body W is supported in advance by the support portion 10 so that the central axis CL is along the up-down direction.

[0110] First, in the arrangement step S1, the control unit 50 drives the motor 43 to arrange the pair of split coils 21 below the large diameter portion W5. Thereafter, the control unit 50 controls the shaft-shaped body rotating motor to rotate the shaft-shaped body W around the central axis CL.

[0111] Next, the control unit 50 drives the current transformer 61 to flow a high-frequency current through each segmented coil 21. Furthermore, the control unit 50 drives the coolant circulation pump 33 to spray the coolant L from the plurality of nozzles 31b of the cooling ring 31 toward the shaft-shaped body W. Furthermore, the control unit 50 controls the coil driving unit to open the gap between the pair of segmented coils 21 in accordance with the outer diameter of the large diameter portion W5.

[0112] When the arrangement step S1 is completed, the process proceeds to the first quenching step S2 .

[0113] In the next first quenching step S2, the control unit 50 drives the motor 43 to move the split coils 21 and the cooling ring 31 upward as a whole. At this time, between the two split coils 21, the large diameter portion W5 is inductively heated from its lower end to its upper end. Figure 4 As shown by the black arrow, the current first flows from the first conductor portion 24 through the inner circumferential side convex coil portion 22a, then flows through the outer circumferential side convex coil portion 22b via the connecting portion 23, and then flows to the second conductor portion 25. Figure 4 The coolant indicated by the white arrow also flows in the same manner as the high-frequency current, thereby cooling each segment coil 21 .

[0114] On the other hand, in the large diameter portion W5 of the shaft-shaped body W, eddy current flows on the surface by the high frequency current flowing through the inner circumference side convex coil portion 22a and the outer circumference side convex coil portion 22b, and the eddy current is inductively heated. Then, when each segment coil 21 passes through the cooling ring 31 next, the coolant L is blown to the outer circumference of the heated large diameter portion W5. As a result, the heated large diameter portion W5 is rapidly cooled and quenched.

[0115] In the next split coil diameter reduction step S3, the step portion W2 gradually reduced in diameter upward is induction heated. In the first quenching step, the interval between the split coils 21 is kept constant, but in this split coil diameter reduction step, the interval between the split coils 21 is gradually narrowed. That is, when the step portion W2 between the two split coils 21 is induction heated from the lower end to the upper end, the control unit 50 controls the coil driving unit so that the air gap with the step portion W2 is maintained constant and the interval between the two split coils 21 is narrowed.

[0116] At this time, in the step portion W2 of the shaft-shaped body W, eddy current flows on the surface of the high-frequency current flowing through the inner circumferential side convex coil portion 22a and the outer circumferential side convex coil portion 22b, and induction heating is performed by the eddy current. Moreover, when each segmented coil 21 passes through the cooling ring 31 next, the coolant L is blown to the outer circumferential surface of the heated step portion W2. As a result, the heated step portion W2 is rapidly cooled and quenched.

[0117] In the subsequent second quenching step S4, the small diameter portion W3 having the smallest outer diameter and being constant in the longitudinal direction is induction heated. In the above-mentioned split coil diameter reduction step, the intervals between the split coils 21 are gradually narrowed, but in this second quenching step, the intervals between the split coils 21 are kept constant in such a way that the intervals are minimized.

[0118] That is, when the small diameter portion W3 is inductively heated from the lower end to the upper end between the two split coils 21, the control unit 50 controls the coil driving unit to maintain the air gap with the small diameter portion W3 constant and the interval between the two split coils 21 constant. The configuration state of each split coil 21 at this time is Figure 3 .

[0119] On the other hand, in the small diameter portion W3 of the shaft-shaped body W, eddy current flows on the surface of the shaft-shaped body W by the high frequency current flowing through the inner circumference side convex coil portion 22a and the outer circumference side convex coil portion 22b, and induction heating is performed by the eddy current. Then, when each segment coil 21 passes through the cooling ring 31 next, the coolant L is blown to the outer peripheral surface of the heated small diameter portion W3. As a result, the heated small diameter portion W3 is rapidly cooled and quenched.

[0120] In the next split coil diameter expanding step S5, the stepped portion W4 gradually expanding upward is induction heated. In the second quenching step, the intervals between the split coils 21 are kept constant, but in this split coil diameter expanding step, the intervals between the split coils 21 are gradually expanded.

[0121] That is, when the step portion W4 is inductively heated from the lower end to the upper end between the two split coils 21 , the control unit 50 controls the coil driving unit to maintain a constant air gap with the step portion W4 and to expand the interval between the two split coils 21 .

[0122] On the other hand, in the step portion W4 of the shaft-shaped body W, eddy current flows on the surface by the high-frequency current flowing through the inner circumferential side convex coil portion 22a and the outer circumferential side convex coil portion 22b, and induction heating is performed by the eddy current. Moreover, when each segment coil 21 passes through the cooling ring 31 next, the coolant L is blown to the outer circumferential surface of the heated step portion W4. As a result, the heated step portion W4 is rapidly cooled and quenched.

[0123] In the subsequent third quenching step S6, the large diameter portion W5 having the largest outer diameter and being constant in the longitudinal direction is induction heated. In the above-mentioned split coil diameter expansion step, the intervals between the split coils 21 are gradually expanded, but in this third quenching step, the intervals between the split coils 21 are continuously maintained constant in a manner that the intervals are the largest.

[0124] That is, when the large diameter portion W5 is inductively heated from the lower end to the upper end between the two segmented coils 21, the control unit 50 controls the coil driving unit to maintain the air gap with the large diameter portion W5 constant and the interval between the two segmented coils 21 constant. The configuration state of each segmented coil 21 at this time is Figure 4 .

[0125] On the other hand, in the large diameter portion W5 of the shaft-shaped body W, eddy current flows on the surface by the high frequency current flowing through the inner circumference side convex coil portion 22a and the outer circumference side convex coil portion 22b, and induction heating is performed by the eddy current. Moreover, when each segment coil 21 passes through the cooling ring 31 next, the coolant L is blown to the outer circumference of the heated large diameter portion W5. As a result, the heated large diameter portion W5 is rapidly cooled and quenched.

[0126] Through the above-described steps, the shaft body W is quenched over its entire length, and all steps are completed. In addition, in the configuration step S1, the first quenching step S2, the split coil diameter reduction step S3, the second quenching step S4, the split coil diameter expansion step S5, and the third quenching step S6, the split coils 21 and the cooling ring 31 continue to move upward relative to the shaft body W without stopping, and the moving quenching is performed at the same time.

[0127] The shaft-shaped body W subjected to the movement quenching over the entire length has a higher hardness than that before the movement quenching.

[0128] [Second embodiment]

[0129] The following side reference Figure 6Next, a moving quenching device according to a second embodiment of the present disclosure will be described. Figure 6 1 is a diagram showing a state where the small diameter portion W3 of the shaft-shaped body W is inductively heated by the mobile quenching device of the present embodiment, and is Figure 1 In the following, the differences from the first embodiment are mainly described, and the other points are assumed to be the same as the first embodiment, and the repeated description is omitted.

[0130] In the mobile quenching device of this embodiment, by Figure 3 As can be seen from the comparison, the shape of each segment coil 21 is different from that of the first embodiment. That is, in the first embodiment, one segment coil 21 is used to induction heat the 180° circumferential range of the shaft body W. Figure 6 In the present embodiment shown, three split coils 21A are used. Each split coil 21A has the same structure as each other. Although it has a substantially similar structure to the split coil 21 of the first embodiment, it is different in that one split coil 21A is used to induction heat a 120° range in the circumferential direction of the shaft-shaped body W. That is, by arranging the three split coils 21A at equal intervals around the shaft-shaped body W, the entire 360° circumference of the shaft-shaped body W is induction heated.

[0131] Each split coil 21A has a convex coil portion 22 , a connecting portion 23 , a first conductor portion 24 , and a second conductor portion 25 , similarly to the split coil 21 described above.

[0132] like Figure 6 As shown, the convex coil portion 22 of this embodiment is also a double-turn coil, and has an inner convex coil portion 22a located relatively close to the center axis CL and an outer convex coil portion 22b located relatively far from the center axis CL.

[0133] The inner circumferential side convex coil portion 22 a and the outer circumferential side convex coil portion 22 b both have an arc shape that is convex in a direction away from the center axis CL when viewed along the center axis CL.

[0134] These inner convex coil portions 22a and outer convex coil portions 22b are the same as the first embodiment described above, and are arranged at the same position relative to each other in the extension direction of the central axis CL. In addition, the relative positions of the inner convex coil portions 22a and outer convex coil portions 22b in the extension direction may also deviate slightly, but from the perspective of heating efficiency, it is preferred that they are completely consistent as in the present embodiment.

[0135] Moreover, if Figure 6As shown, when viewed along the central axis CL, the inner circumference side convex coil portion 22a and the outer circumference side convex coil portion 22b are overlapped with each other with a gap in the radial direction around the central axis CL.

[0136] When the moving quenching device of this embodiment is used to induction heat the shaft-shaped body W, the three split coils 21A are made to approach and separate relative to the outer peripheral surface of the shaft-shaped body W in the radial direction according to the respective outer diameter dimensions of the large diameter portion W1, W5, the small diameter portion W3, and the step portions W2, W4, and moving quenching is performed simultaneously.

[0137] In addition, although three split coils 21A are used in this embodiment, it is also conceivable to further increase the number to 4 or more. However, if the number of coil divisions is increased excessively, the number of parts that do not contribute to heating will increase between the split coils, so it is actually preferable to stop before the division into three. In addition, when comparing the case of dividing the coil into three parts with the case of dividing it into two parts, the configuration of dividing it into two parts is more preferable for the same reason.

[0138] [Third Embodiment]

[0139] Below, while referring to Figure 7 Next, a moving quenching device according to a third embodiment of the present disclosure will be described. Figure 7 The following is a diagram of one of the split coils 21B of the mobile quenching device of the present embodiment as viewed from below. (a) is a perspective view showing the appearance of the split coil 21B, and (b) is a perspective view showing the flow of coolant and current. In addition, the following mainly describes the differences from the first embodiment, and the other points are assumed to be the same as the first embodiment and repeated descriptions are omitted.

[0140] In the first embodiment, each split coil 21 is a double-turn coil having two inner circumference side convex coil portion 22a and outer circumference side convex coil portion 22b. However, in the present embodiment, Figure 7 As shown in (a) and (b), a three-turn coil is used.

[0141] That is, the split coil 21B of the present embodiment has three convex coil portions 22p, 22q, and 22r arranged in sequence in a direction away from the center axis CL. The positions of the first convex coil portion 22p, the second convex coil portion 22q, and the third convex coil portion 22r along the direction of the center axis CL are the same as each other. In addition, the relative positions of the first convex coil portion 22p, the second convex coil portion 22q, and the third convex coil portion 22r in the extension direction of the center axis CL may also deviate slightly, but from the perspective of heating efficiency, it is preferred that they are completely consistent as in the present embodiment.

[0142] When viewed along the central axis CL, the first convex coil portion 22p, the second convex coil portion 22q, and the third convex coil portion 22r are overlapped with each other with gaps therebetween in the radial direction around the central axis CL.

[0143] The first convex coil portion 22p and the second convex coil portion 22q are connected by a connection portion 23p. Similarly, the second convex coil portion 22q and the third convex coil portion 22r are connected by a connection portion 23q.

[0144] On this basis, the first lead portion 24 and the second lead portion 25 overlap the connecting portions 23p and 23q in the direction along the central axis CL (the vertical direction on the paper), respectively.

[0145] According to the mobile quenching device of this embodiment, the first wire portion 24 and the second wire portion 25 do not enter the gap between the adjacent split coils 21B, so the interval between the split coils 21B can be narrowed. As a result, it is possible to suppress uneven heating of the circumferential direction of the shaft-shaped body W and perform uniform heating. On this basis, by setting it as a three-turn coil, the current value of the high-frequency current flowing through each split coil 21B can be further reduced.

[0146] [Fourth Embodiment]

[0147] Below, while referring to Figure 8 Next, a moving quenching device according to a fourth embodiment of the present disclosure will be described. Figure 8 This is a diagram of one of the split coils 21C of the mobile quenching device of this embodiment as viewed from below. (a) is a perspective view showing the appearance of the split coil 21C, and (b) is a perspective view showing the flow of coolant and current. In addition, the following mainly describes the differences from the third embodiment, and the other points are set to be the same as the third embodiment and repeated description is omitted.

[0148] The split coil 21C of this embodiment is also a three-turn coil like the split coil 21B of the third embodiment, but at least a portion of the first conductor portion 24 and the second conductor portion 25 are positioned away from the connection portions 23p and 23q in the circumferential direction around the central axis CL.

[0149] According to the mobile quenching device of this embodiment, the interval between the connection parts 23p and 23q in the direction along the central axis CL can be narrowed compared with the split coil 21B of the third embodiment. As a result, the overall thickness of each split coil 21C can be reduced, so it is difficult to cause the problem of interference between each split coil 21C and the step parts W2 and W4 when the shaft-shaped body W is moved and heated while passing through the step parts W2 and W4. On this basis, as in the third embodiment, by setting it as a three-turn coil, the current value of the high-frequency current flowing through each split coil 21C can be further reduced.

[0150] The following summarizes the above-described embodiments and modifications.

[0151] [1] A mobile quenching device according to one embodiment of the present disclosure is a device for performing mobile quenching on a shaft-shaped body (W), wherein the shaft-shaped body (W) is formed by connecting a large diameter portion (W1, W5) having a relatively large outer diameter and a small diameter portion (W3) having a relatively small outer diameter via a step portion (W2, W4), and the mobile quenching device comprises:

[0152] A plurality of split coils (21, 21A, 21B, 21C) are arranged in a ring shape around a central axis (CL) and pass a high-frequency current; and

[0153] a coil driving unit for moving each of the split coils (21, 21A, 21B, 21C) closer to and farther from the central axis (CL),

[0154] Each of the split coils (21, 21A, 21B, 21C) has a plurality of convex coil portions (22, 22a, 22b, 22p, 22q, 22r) having a shape that bulges away from the center axis (CL) when viewed along the center axis (CL);

[0155] Each of the convex coil portions (22, 22a, 22b, 22p, 22q, 22r) is configured such that:

[0156] In the extension direction of the central axis (CL), at least a portion overlaps with each other, and,

[0157] In the line of sight along the central axis (CL), they overlap in a radial direction centered on the central axis (CL).

[0158] [2] In the mobile quenching device described in [1] above,

[0159] Each of the split coils (21, 21A, 21B) further comprises:

[0160] A connecting portion (23) electrically connecting the convex coil portions (22, 22a, 22b, 22p, 22q, 22r);

[0161] a first lead portion (24) electrically connected to one end side of each of the convex coil portions (22, 22a, 22b, 22p, 22q, 22r) around the central axis (CL) and extending in the radial direction; and

[0162] A second conductor portion (25) is electrically connected to the other end side of each of the convex coil portions (22, 22a, 22b, 22p, 22q, 22r) around the central axis (CL) and extends in the radial direction.

[0163] The first conductor portion (24) and the second conductor portion (25) are arranged to overlap with the connection portion (23) in the direction of the central axis (CL).

[0164] [3] In the mobile quenching device described in [2] above,

[0165] Each of the split coils (21) is a double-turn coil having an inner convex coil portion (22a) and an outer convex coil portion (22b) as each convex coil portion, the inner convex coil portion is relatively close to the central axis, and the outer convex coil portion is relatively far from the central axis;

[0166] The first conductor portion (24) has a first bent portion (24a) which is bent in a direction toward the center axis (CL) side from the position of the outer convex coil portion (22b) and connected to the one end side of the inner convex coil portion (22a);

[0167] The second conductor portion (25) has: a second bent portion (25a) bent from the other end side toward the one end side; and a third bent portion (25b) bent from the second bent portion (25a) toward the other end side of the outer peripheral side convex coil portion (22b) to connect.

[0168] [4] In the mobile quenching device described in [2] above,

[0169] Each of the split coils (21B) is a three-turn coil having a first convex coil portion (22p), a second convex coil portion (22q), and a third convex coil portion (22r) arranged in sequence in a direction away from the central axis (CL) as each of the convex coil portions (22p, 22q, 22r);

[0170] The first conductor portion (24) and the second conductor portion (25) overlap with the connecting portion (23p) connecting the first convex coil portion (22p) and the second convex coil portion (22q) and the connecting portion (23q) connecting the second convex coil portion (22q) and the third convex coil portion (22r) in the direction along the center axis (CL).

[0171] [5] In the mobile quenching device described in [1] above,

[0172] Each of the split coils (21C) is a three-turn coil having a first convex coil portion (22p), a second convex coil portion (22q), and a third convex coil portion (22r) arranged in sequence in a direction away from the central axis (CL) as each of the convex coil portions (22p, 22q, 22r);

[0173] Each of the split coils (21C) comprises:

[0174] a first connecting portion (23p) connecting the first convex coil portion (22p) and the second convex coil portion (22q);

[0175] a second connecting portion (23q) connecting the second convex coil portion (22q) and the third convex coil portion (22r);

[0176] A first wire portion (24) electrically connected to the first convex coil portion (22p) and extending in the radial direction; and

[0177] A second wire portion (25) electrically connected to the third convex coil portion (22r) and extending in the radial direction;

[0178] At least a portion of the first conductor portion (24) and the second conductor portion (25) is offset from the first connection portion (23p) and the second connection portion (23q) in a circumferential direction centered on the central axis (CL).

[0179] [6] In the mobile quenching device described in any one of [1] to [5] above,

[0180] The number of each of the split coils (21, 21A, 21B, 21C) is two or three.

[0181] [Example]

[0182] The following describes simulation results of a comparative example of induction heating by a conventional moving quenching device using a one-turn split coil and an example of induction heating by a moving quenching device using the split coil 21 according to the first embodiment.

[0183] Fig. 9 is a graph showing the simulation results, Figure 1 A longitudinal section view of the C portion. (a) shows a conventional example, and (b) shows an embodiment. In this simulation, the outer diameter of the large diameter portion W5 is set to 200 mm, and the outer diameter of the small diameter portion W3 is set to 170 mm. The material of the axial body W is set to carbon steel. In addition, the current value required for heating to approximately the same temperature is calculated. As a result, the required current value is 45000A in the comparative example of one turn and 24750A in the embodiment of two turns. In this way, it can be confirmed that the current value is greatly reduced in the embodiment compared with the comparative example.

[0184] Industrial Applicability

[0185] According to the movement hardening device of the present disclosure, it is possible to carry out movement hardening on a stepped shaft while suppressing overheating and short circuit of the split coils caused by a large current.

[0186] Description of Reference Numerals

[0187] 21, 21A, 21B, 21C split coil

[0188] 22 Convex coil part

[0189] 22a Inner circumference side convex coil portion

[0190] 22b Outer circumferential side convex coil portion

[0191] 22p First convex coil portion

[0192] 22q Second convex coil portion

[0193] 22r Third convex coil portion

[0194] 23 connection part,

[0195] 23p connecting part (first connecting part)

[0196] 23q connection part (second connection part)

[0197] 24 First conductor section

[0198] 24a First bend

[0199] 25 Second conductor section

[0200] 25a Second bend

[0201] 25b Third bend

[0202] CL Centerline

[0203] W Axis

[0204] W1, W5 large diameter part

[0205] W2, W4 step part

[0206] W3 Trail Section

Claims

1. A mobile quenching device, characterized in that: The invention is a device for performing mobile quenching on a shaft-shaped body, wherein the shaft-shaped body is formed by connecting a large diameter portion with a relatively large outer diameter and a small diameter portion with a relatively small outer diameter via a step portion, and the mobile quenching device comprises: A plurality of split coils are arranged in a ring shape around the central axis and through which high-frequency current flows; and a coil driving unit that moves each of the split coils toward and away from the central axis, Each of the split coils includes a plurality of convex coil portions, each of which has a shape that convexly projects away from the central axis when viewed along the central axis; Each of the convex coil portions is configured such that: In the extension direction of the central axis, at least a portion overlaps with each other, and, In a line of sight along the central axis, they overlap in a radial direction centered on the central axis.

2. The mobile quenching device according to claim 1, characterized in that: Each of the split coils further comprises: A connecting portion electrically connecting the convex coil portions; A first conductor portion, which is electrically connected to one end side of each of the convex coil portions around the central axis and extends toward the radial direction; as well as A second conductor portion is electrically connected to the other end side of each of the convex coil portions around the central axis and extends in the radial direction. The first lead portion and the second lead portion are arranged to overlap with the connection portion in the direction of the central axis.

3. The mobile quenching device according to claim 2, characterized in that: Each of the split coils is a double-turn coil having an inner convex coil portion and an outer convex coil portion as each convex coil portion, wherein the inner convex coil portion is relatively close to the central axis and the outer convex coil portion is relatively far from the central axis; The first conductor portion has a first bent portion that is bent in a direction toward the central axis side from a position of the outer circumferential side convex coil portion and connected to the one end side of the inner circumferential side convex coil portion; The second lead portion includes a second bent portion bent from the other end side toward the one end side, and a third bent portion bent from the second bent portion toward the other end side of the outer peripheral side convex coil portion to be connected.

4. The mobile quenching device according to claim 2, characterized in that: Each of the split coils is a three-turn coil having a first convex coil portion, a second convex coil portion, and a third convex coil portion arranged in sequence in a direction away from the central axis as each of the convex coil portions; The first lead portion and the second lead portion overlap the connection portion connecting the first convex coil portion and the second convex coil portion and the connection portion connecting the second convex coil portion and the third convex coil portion in a direction along the central axis.

5. The mobile quenching device according to claim 1, characterized in that: Each of the split coils is a three-turn coil having a first convex coil portion, a second convex coil portion, and a third convex coil portion arranged in sequence in a direction away from the central axis as each of the convex coil portions; Each of the split coils comprises: a first connecting portion connecting the first convex coil portion and the second convex coil portion; a second connecting portion connecting the second convex coil portion and the third convex coil portion; a first wire portion, which is electrically connected to the first convex coil portion and extends toward the radial direction; as well as a second wire portion, which is electrically connected to the third convex coil portion and extends toward the radial direction; At least a portion of the first lead portion and the second lead portion is offset from the first connection portion and the second connection portion in a circumferential direction around the central axis.

6. The mobile quenching device according to any one of claims 1 to 5, characterized in that: The number of each of the split coils is two or three.

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