Moving hardening device and moving hardening method

Abstract

This traverse hardening device performs traverse hardening on a shaft-like body in which a large-diameter portion having a relatively large outer diameter and a small-diameter portion having a relatively small outer diameter are contiguous via a stepped portion, and comprises: a plurality of first coil sections arranged in a first position on a traverse central line, in an annular shape around the traverse central line; a plurality of second coil sections arranged in a second position different from the first position on the traverse central line, in an annular shape around the traverse central line; a first coil section driving unit that moves each of the first coil sections toward and away from the traverse central line; a second coil section driving unit that moves each of the second coil sections toward and away from the traverse central line; and a control unit that controls the first coil section driving unit and the second coil section driving unit.

Description

[Technical Field]

[0001] The present disclosure relates to a moving quenching apparatus and a moving quenching method. [Background technology]

[0002] Conventionally, shaft-shaped bodies have been subjected to traverse hardening by induction heating to increase their fatigue strength. Traverse hardening here refers to hardening while moving a coil member or the like in the axial direction relative to the shaft-shaped body. Specifically, the shaft-shaped body is induction-heated by passing a current through the coil while moving the coil along the outer peripheral surface in the longitudinal direction of the shaft-shaped body. Then, immediately after heating, a coolant is sprayed onto the outer peripheral surface to rapidly cool and harden the shaft-shaped body. Here, if the shaft-shaped body is a stepped shaft having a stepped portion where the outer diameter changes from large to small or from small to large at a position midway along its longitudinal direction, it is necessary to appropriately adjust the air gap between the outer peripheral surface of the shaft-shaped body and the coil in order to maintain heating efficiency.

[0003] One device configuration that enables such adjustment is one in which the coil is composed of multiple split coils. Specifically, multiple split coils are arranged in a line in the circumferential direction of the shaft-shaped body and connected in series to a power source. Then, while a current from the power source is passed through each split coil, the split coils are moved in the longitudinal direction of the shaft-shaped body. Then, just before each split coil reaches the step, the split coils are moved toward or away from the outer peripheral surface of the shaft-shaped body in accordance with changes in the outer diameter of the shaft-shaped body, thereby maintaining the air gap at a substantially constant value.

[0004] A conventional high-frequency induction heating device using this type of split coil is disclosed in Patent Document 1 below. The device includes a high-frequency induction heating coil as a split coil. This high-frequency induction heating coil is configured as follows: "A high-frequency induction heating coil for heating a shaft-shaped member having a flange portion and a shaft portion erected at the center of the flange portion, for high-frequency induction heating a rounded portion formed between the flange portion and the shaft portion where they intersect and an outer peripheral surface of the shaft portion, the high-frequency induction heating coil comprising a pair of high-frequency induction heating coil components arranged at positions facing each other across the axis of the shaft-shaped member and arranged at positions facing the rounded portion and the shaft portion of the shaft-shaped member at a distance from the rounded portion and the shaft portion, and each of the pair of high-frequency induction heating coil components is formed with a bent coil portion bent so as to protrude in a direction away from the axis of the shaft-shaped member." According to this device, "by using a pair of high-frequency induction heating coil components, it becomes possible to arrange the pair of high-frequency induction heating coil components in correspondence with all of the various types of shaft-shaped members having different outer diameters." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2008-150640 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional traveling hardening devices, including the above-mentioned device, have a single-turn split coil, and structurally, the number of turns cannot be increased to multiple turns. This is because, if the number of turns were increased by stacking multiple split coils along the longitudinal direction of the shaft-shaped body, the stepped portion where the outer diameter of the shaft-shaped body changes would not be properly travel-hardened. For example, in traveling hardening of the stepped portion from the large-diameter portion to the small-diameter portion, the split coil cannot be brought close to the small-diameter portion until the entire overlapping split coil along the longitudinal direction of the shaft-shaped body has passed through the large-diameter portion. Therefore, the portion of the split coil that is located forward in the traveling direction after heating the large-diameter portion and reaching the small-diameter portion is induction-heated while a large air gap remains between the coil and the outer circumferential surface of the small-diameter portion, which is undesirable from the standpoints of heating efficiency and uneven heating.

[0007] On the other hand, in the moving hardening 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 that is on the rear side in the traveling direction cannot overcome the step portion unless the portion on the front side in the traveling direction is quickly moved away from the outer surface of the small diameter portion before it reaches the large diameter portion, even if the small diameter portion is still being heated. Therefore, again, this results in undesirable results from the viewpoint of heating efficiency and uneven heating.

[0008] For the reasons explained above, split coils up until now have not been able to have multiple windings, and have usually been configured with a single winding. In the case of a single winding, the current flowing through the split coil must be significantly higher than in the case of a multiple winding, which can easily cause problems such as overheating or short circuits in the split coil.

[0009] The present disclosure has been made in consideration of the above circumstances, and aims to provide a moving hardening device and a moving hardening method that can perform moving hardening on a stepped shaft while suppressing overheating and short circuits in split coils that occur due to large currents. [Means for solving the problem]

[0010] In order to solve the above problems, the present disclosure proposes the following aspects. (1) A moving quenching device according to one aspect of the present disclosure includes: An apparatus for performing moving hardening on a shaft-shaped body in which a large diameter portion having a relatively large outer diameter and a small diameter portion having a relatively small outer diameter are connected via a step portion, a plurality of first split coils arranged annularly around the center line of movement at a first position on the center line of movement; a plurality of second divided coils arranged annularly around the center line of movement at a second position on the center line of movement that is different from the first position; a first divided coil driving unit that moves each of the first divided coils toward or away from the center line of movement; a second split coil driving unit that moves each of the second split coils toward or away from the center line of movement; a control unit that controls the first divided coil driving unit and the second divided coil driving unit; Equipped with.

[0011] According to the moving hardening device described in (1) above, while moving each of the first and second divided coils in a state where they are stacked around the shaft-shaped body in a direction along the center line of movement, a high-frequency current is passed through each of the first and second divided coils, which then causes electromagnetic induction between each of the first and second divided coils and the shaft-shaped body, thereby inductively heating the shaft-shaped body. When the shaft-shaped body is induction-heated while moving in this manner, if each of the first split coils induction-heats the stepped portion while each of the second split coils induction-heats the small-diameter portion, the control unit drives the first split-coil drive unit to gradually move the position of each of the first split coils radially outward of the shaft-shaped body. This movement allows each of the first split coils to move along the outer peripheral surface without interfering with the stepped portion, while each of the second split coils remains aligned with the periphery of the small-diameter portion. Furthermore, when each second split coil induction heats the stepped portion and each first split coil induction heats the large diameter portion at the same time, the control unit drives the second split coil drive unit to gradually move the position of each second split coil radially outward of the shaft-shaped body, so that each first split coil can be kept aligned with the periphery of the large diameter portion while each second split coil can be moved along the outer circumferential surface of the stepped portion without interfering with the stepped portion. On the other hand, when induction heating is performed from the large diameter portion over the stepped portion to the small diameter portion, the above procedure is reversed: the first split coil driving unit brings each first split coil close to the outer peripheral surface of the shaft-shaped body, and the second split coil driving unit brings each second split coil close to the outer peripheral surface of the shaft-shaped body. The movements of these first and second split coils approaching the shaft-shaped body are performed individually depending on the outer diameter of the portion to be induction heated by these first and second split coils.

[0012] This eliminates the problem of interference with the shaft-shaped body that occurs when the first and second divided coils are stacked in the direction of the moving centerline. As a result, moving hardening can be achieved using divided coils with multiple turns (first and second divided coils), making it possible to significantly reduce the high-frequency current value passed through each divided coil compared to when each coil is a single turn. The number of coils for heating the shaft-shaped body is not limited to two, i.e., each of the first and second split coils. Three or more split coils may be stacked in the direction of the center line of movement. In this case, it is preferable to also employ three or more split coil drive units, the same number as the number of split coils.

[0013] (2) In the moving hardening device described in (1) above, the following configuration may be adopted: further comprising a high frequency power source; The control unit individually controls the current value of the high frequency current flowing from the high frequency power supply to each of the first divided coils and the current value of the high frequency current flowing from the high frequency power supply to each of the second divided coils.

[0014] According to the moving hardening device described in (2) above, the control unit individually controls the current value in each of the first divided coils and the current value in each of the second divided coils, so that the current value can be adjusted to suit the heating location of the shaft-shaped body. For example, when heating a corner formed at the connection between the stepped portion and the large diameter portion with each of the first divided coils, the current value in each of the first divided coils can be set higher, so that the corner can be sufficiently heated without reducing the moving speed of each of the first divided coils. One possible method for heating the corners to a higher temperature is to slow down the speed at which each of the first split coils passes through the corners. However, this would require slowing down the movement of the cooling ring that cools the shaft-shaped body after heating, which would prevent the cooling ring from moving at a constant speed in the axial direction and result in uneven cooling. In contrast, this embodiment has the advantage of not requiring a slowdown in the movement speed, which avoids such problems.

[0015] (3) In the moving hardening device described in (2) above, the following configuration may be adopted: further comprising a variable resistor that electrically connects the first split coils and the second split coils and allows the high-frequency current from the high-frequency power supply to flow; The control unit distributes and supplies the high frequency current from the high frequency power supply to each of the first divided coils and each of the second divided coils while controlling the variable resistor.

[0016] According to the moving hardening device described in (3) above, the control unit controls the variable resistors, so that the current value of the high-frequency current flowing through each of the first divided coils and the current value of the high-frequency current flowing through each of the second divided coils can be adjusted to either different values ​​or the same value. Thus, high-frequency currents according to the heating locations of the shaft-shaped body can be set for each of the first divided coils and each of the second divided coils.

[0017] (4) A moving quenching method according to one aspect of the present disclosure includes: A method for performing moving hardening on a shaft-shaped body having a large diameter portion with a relatively large outer diameter and a small diameter portion with a relatively small outer diameter connected via a step portion, comprising: performing the moving hardening on the shaft-shaped body using a plurality of first divided coils arranged annularly around the center line of movement at a first position on the center line of movement and a plurality of second divided coils arranged annularly around the center line of movement at a second position on the center line of movement; During the moving hardening, the first divided coils and the second divided coils are individually moved toward and away from the outer circumferential surface of the shaft-shaped body.

[0018] The moving hardening method described in (4) above can achieve the same effect as the moving hardening device described in (1) above. Therefore, it is possible to solve the problem of interference with the shaft-shaped body that occurs when each of the first and second divided coils is stacked in the direction of the moving center line. As a result, moving hardening can be achieved using divided coils with multiple turns (first and second divided coils), making it possible to significantly reduce the high-frequency current value flowing through each divided coil compared to when each coil has only one turn.

[0019] (5) In the moving hardening method described in (4) above, the current value of the high-frequency current passed through each of the first split coils and the current value of the high-frequency current passed through each of the second split coils may be individually controlled during the moving hardening.

[0020] The moving quenching method described in (5) above can achieve the same effect as the moving quenching device described in (2) above. Therefore, moving quenching can be performed while keeping the moving speed of each of the first and second divided coils constant, and the moving speed of the cooling ring that follows them can also be kept constant, thereby suppressing uneven cooling. [Effects of the Invention]

[0021] According to the moving hardening device and the moving hardening method according to the above aspects, it is possible to perform moving hardening on a stepped shaft while suppressing overheating and short-circuiting of the split coils due to a large current. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a side view showing a schematic cutaway view of a moving quenching device according to an embodiment of the present disclosure; [Figure 2] 2A and 2B are diagrams showing a pair of first split coils provided in the moving hardening device as viewed from above, taken along the arrow AA in Fig. 1. Fig. 2A shows a state in which the distance between the first split coils is narrowed to inductively heat the small diameter portion, and Fig. 2B shows a state in which the distance between the first split coils is widened to inductively heat the large diameter portion. [Figure 3]4 is a circuit diagram schematically showing electrical connections between a high-frequency power supply and the first and second split coils. FIG. [Figure 4] 4 is a flowchart showing a moving hardening method according to the embodiment. [Figure 5] 1. This is a diagram showing a state in which a shaft-shaped body is quenched while moving through a step portion, and is a vertical cross-sectional view of part B in FIG. 1. Moving quenching is performed in the order of (a), (b), and (c). [Figure 6] 2A and 2B are diagrams showing the results of a simulation of a moving hardening device, and are longitudinal cross-sectional views of a portion including part B in Fig. 1. (a) shows a conventional example, and (b) shows an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of a moving hardening device and a moving hardening method according to the present disclosure will be described below with reference to the drawings. In the following description, the direction along the central axis CL of the shaft-shaped body W may be referred to as the longitudinal direction, the radial direction of the shaft-shaped body W centered on the central axis CL may be simply referred to as the radial direction, and the circumferential direction of the shaft-shaped body W may be simply referred to as the circumferential direction. Furthermore, a moving center line, which is the center line of each of the first and second divided coils provided in the moving hardening device, will be used to indicate the direction in which each of the first and second divided coils moves. This moving center line is a straight line that coincides with the central axis CL. Furthermore, in FIG. 1, the upper side of the drawing along the moving center line may be simply referred to as the upper side, and the lower side of the drawing may be simply referred to as the lower side.

[0024] <Mobile hardening equipment> First, the configuration of the moving hardening device of this embodiment will be described with reference to Figures 1 to 3. Here, Figure 1 is a side view showing a schematic cutaway view of a part of the moving hardening device. Figure 2 is a view of a pair of first split coils provided in the moving hardening device as seen from above, as viewed from the arrow AA in Figure 1. Figure 3 is a circuit diagram showing the electrical connection between a high-frequency power supply and the first and second split coils.

[0025] The traverse hardening apparatus 1 shown in FIG. 1 is an apparatus that performs traverse hardening on a shaft-shaped body W such as an axle for a railway vehicle or a ball screw by using a high frequency current. First, we will explain the shaft-shaped body W. The shaft-shaped body W is a stepped shaft having a large diameter portion W1, a stepped portion W2, a small diameter portion W3, a stepped portion W4, and a large diameter portion W5 arranged coaxially in this order from bottom to top in the longitudinal direction. The large diameter portions W1 and W5 are cylindrical with a circular cross section and have the largest outer diameter within the entire shaft-shaped body W. The small diameter portion W3 is also cylindrical with a circular cross section and has a smaller outer diameter than the large diameter portions W1 and W5. The stepped portion W2 has a truncated conical 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 stepped portion W2 gradually decreases upward from the same outer diameter as the large diameter portion W1, and finally becomes equal to the outer diameter of the lower end of the small diameter portion W3. The stepped portion W4 has an inverted truncated conical shape connecting the upper end of the small diameter portion W1 and the lower end of the large diameter portion W5. The outer diameter of the step portion W4 gradually increases upward from the outer diameter equal to the outer diameter of 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 a central axis CL. When the outer diameter dimensions of the large diameter portions W1 and W5 are taken as 100%, the outer diameter dimension of the small diameter portion W3 is, for example, 80% to 90%. The shaft-shaped body W is made of a conductive material such as carbon steel or low-alloy steel containing 95% by weight or more of iron (Fe), which is a ferrite phase.

[0026] As shown in FIG. 1, the moving hardening 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 supply 60.

[0027] As shown in FIG. 1 , the support unit 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-shaped body W from below. The upper center 12 coaxially supports the large-diameter portion W5 of the shaft-shaped body W from above. The lower center 11 and upper center 12 support the shaft-shaped body W so that its central axis CL is aligned vertically, with one end of the shaft-shaped body W (the side with the large-diameter portion W1) at the bottom and the other end (the side with the large-diameter portion W5) at the top. The shaft-shaped body W is disposed between the lower center 11 and upper center 12 so as to be rotatable about the central axis CL. When the lower center 11 and upper center 12 support the shaft-shaped body W in this manner, they rotate the shaft-shaped body W about the central axis CL when they receive a driving force from a shaft-shaped body rotation motor (not shown) provided in the support unit 10.

[0028] As shown in FIG. 1, the induction heating unit 20 has a plurality of coils and a coil support base . In this embodiment, two coils, an upper coil 21 and a lower coil 22, are used as the multiple coils. The upper coil 21 and the lower coil 22 have the same configuration. Therefore, the upper coil 21 will be described first below, and the lower coil 22 will be given the same reference numeral as the upper coil 21, and a duplicated description will be omitted. Note that the coils that heat the shaft-shaped body W are not limited to the two coils, the upper coil 21 and the lower coil 22. Three or more coils may be stacked in the direction of the center line of movement.

[0029] 2(a), the upper coil 21 has a pair of split coils 21A arranged in an annular shape around the center line of movement (central axis CL). Each split coil 21A has a coil main body 21a, a first conductor portion 21b, and a second conductor portion 21c. The coil main body 21a has an arc shape that is convex in the radial direction about the central axis CL. The inner peripheral surface of the coil main body 21a is a concave arc surface centered on the central axis CL, and is disposed with a certain gap g in the circumferential direction from the outer peripheral surface of the small diameter portion W3. The coil main body 21a induction heats a range of approximately half the circumference (180° portion) in the circumferential direction of the shaft-shaped body W. Note that instead of an arc shape, the coil main body 21a may have an L-shape or V-shape that is convex in the direction away from the central axis CL. The first conductor portion 21b is electrically and mechanically connected to one end of the coil body portion 21a and extends straight outward in the radial direction. The second conductor portion 21c is electrically and mechanically connected to the other end of the coil body portion 21a and extends straight outward in the radial direction. The first conductor portion 21b and the second conductor portion 21c extend along a common straight line.

[0030] The pair of split coils 21A having the above configuration, by combining two coil main bodies 21a, form one heating coil arranged coaxially around the shaft-shaped body W. When induction heating the small diameter portion W3, the relative position between the pair of split coils 21A is narrowed, so that the pair of coil main bodies 21a are arranged around the small diameter portion W3 with the gap g therebetween. On the other hand, when induction heating the large diameter portions W1 and W5 as shown in Figure 2(b), the relative position between the pair of split coils 21A is widened so that the pair of coil main body portions 21a are arranged around the large diameter portions W1 and W5. When induction heating the step portions W2 and W4, the relative position between the pair of split coils 21A is widened or narrowed according to the change in the outer diameter of the step portions, so that the pair of coil main body portions 21a are arranged around the step portions W2 and W4. When adjusting the relative position between the pair of split coils 21A in accordance with the outer diameter of the heated portion of the shaft-shaped body W, the adjustment is made so that the gap g is minimized within a range that does not interfere with the heated portion. The above is an explanation of the upper coil 21, but in order to distinguish between the split coil 21A and the split coil of the lower coil 22, in the following explanation, the split coil of the lower coil 22 will be given the symbol 22A.

[0031] 1, the upper coil 21 and the lower coil 22 are coaxially arranged such that the upper coil 21 overlaps the lower coil 22. That is, the coil main bodies 21a of the upper coil 21 are arranged coaxially on top of the coil main bodies 21a of the lower coil 22. Note that the circumferential arrangement of the lower coil 22 and the upper coil 21 may be such that the first conductor portion 21b and the second conductor portion 21c of the lower coil 22 and the first conductor portion 21b and the second conductor portion 21c of the upper coil 21 overlap each other in a plan view.

[0032] Alternatively, the first conductor portions 21b and the second conductor portions 21c of the lower coil 22 may be arranged so as not to overlap with the first conductor portions 21b and the second conductor portions 21c of the upper coil 21 in a plan view. In this case, gaps (non-heated areas) formed between the first conductor portions 21b of the lower coil 22 and gaps (non-heated areas) formed between the second conductor portions 21c of the lower coil 22 can be covered by heating the coil main body portions 21a of the upper coil 21. Conversely, the gaps (non-heated areas) formed between the first conductor portions 21b of the upper coil 21 and gaps (non-heated areas) formed between the second conductor portions 21c of the upper coil 21 can also be covered by heating the coil main body portions 21a of the lower coil 22.

[0033] Furthermore, although the upper coil 21 and the lower coil 22 are each divided into two coils, the number of divisions is not limited to two and may be three or more. For example, if the number of divisions is three, one divided coil will heat an angular range of approximately 120° in the circumferential direction of the shaft-shaped body W.

[0034] The upper coil 21 and the lower coil 22 described above are manufactured by bending and brazing hollow tubes with a rectangular cross section, and are electrically conductive. The ends of the first conductor portion 21b and the second conductor portion 21c are electrically and mechanically connected to a current transformer 61 of a power supply 60 shown in FIG. 1. The current transformer 61 passes a high-frequency current through the upper coil 21 and the lower coil 22. The upper coil 21 and the lower coil 22 can be cooled by flowing a cooling liquid through the pipes thereof.

[0035] 1, the coil support base 28 supports the upper coil 21 and the lower coil 22 coaxially with the shaft-shaped body W, with the upper coil 21 and the lower coil 22 overlapping in the direction of extension of the center line of movement. The coil support base 28 has a first guide portion and a second guide portion (not shown), a first divided coil driving portion 28a and a second divided coil driving portion 28b, and a support base main body 28c. The first and second guide portions, the first and second split coil driving portions 28a and 28b are fixed to the support base main body 28c. The support base main body 28c is connected to and supported by a current transformer 61 (described later) via a stay 28d.

[0036] 2(a) and 2(b), the first guide portion guides the split coils 21A of the upper coil 21 so that they can move toward and away from each other. An example of the first guide portion is a linear guide laid along the moving toward and away from each other direction. The first split coil driving unit 28a applies a driving force to each split coil 21A to move them closer to or farther away from each other. The first split coil driving unit 28a can be a combination of a stepping motor and a ball screw. In this embodiment, each split coil 21A is provided with one first split coil driving unit 28a, but this configuration is not limited thereto. A single first split coil driving unit 28a may be used as a common driving source to move the pair of split coils 21A closer to or farther away from each other.

[0037] Similar to the first guide portion, the second guide portion also guides the split coils 22A of the lower coil 22 so that they can move toward and away from each other. An example of the second guide portion is a linear guide laid along the moving toward and away from each other direction. The second split coil drive unit 28b applies a driving force to each split coil 22A to move them closer to or farther away from each other. A combination of a stepping motor and a ball screw can be used as the second split coil drive unit 28b. While one second split coil drive unit 28b is provided for each split coil 22A in this embodiment, the present invention is not limited to this configuration. Alternatively, one second split coil drive unit 28b may be used as a common drive source to move a pair of split coils 22A closer to or farther away from each other.

[0038] As shown in FIG. 1, the cooling unit 30 includes a cooling ring 31, a cooling ring support stay 32, and a coolant circulation pump 33. The cooling ring 31 is formed in an annular shape. An internal space 31a is formed within the cooling ring 31. A plurality of nozzles 31b communicating with the internal space 31a are formed on the inner peripheral surface of the cooling ring 31 and spaced apart from one another in the circumferential direction. A shaft-shaped body W is inserted coaxially within the cooling ring 31. The cooling ring 31 is disposed below each of the split coils 21. The cooling ring 31 is connected to 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 sprayed toward the shaft-shaped body W through a plurality of nozzles 31b, cooling the shaft-shaped body W.

[0039] The moving unit 40 shown in FIG. 1 includes a support plate 41, a pinion gear 42, a motor 43, and a rack 44. The support base body 28c, the current transformer 61, the cooling ring 31, and the coolant circulation pump 33 are fixed to a support plate 41. A pinion gear 42 is rotatably fixed to the support plate 41. A motor 43 that rotates and drives the pinion gear 42 is attached to the support plate 41.

[0040] The support plate 41 is connected to the rack 44 via a guide rail (not shown). The guide rail allows the support plate 41 to move up and down relative to the rack 44. The pinion gear 42 meshes with the teeth of the rack 44. Therefore, when the control unit 50 drives the motor 43, the pinion gear 42 rotates, and the support plate 41 moves up or down relative to the rack 44.

[0041] 3, the upper coil 21 and the lower coil 22 are connected in parallel to a power supply 60. That is, one end of the upper coil 21 (one end of each split coil 21A) and one end of the lower coil 22 (one end of each split coil 22A) are electrically connected via a variable resistor 62. A slider 63a connected to a wiring 63 extending from one end of the power supply 60 is electrically connected to the variable resistor 62. The other end of the upper coil 21 (the other end of each split coil 21A) and the other end of the lower coil 22 (the other end of each split coil 22A) are electrically connected via a wire 64. The other end of the power supply 60 is electrically connected to this wire 64 via a wire 65.

[0042] According to the above configuration, current from the power supply flows through the wiring 63 and the variable resistor 62 to the upper coil 21 and the lower coil 22. At this time, the control unit 50 controls the slider 63a, thereby adjusting the value of the current flowing through the upper coil 21 and the value of the current flowing through the lower coil 22. Therefore, depending on the location of the shaft-shaped body W to be heated, the value of the current flowing through the upper coil 21 and the value of the current flowing through the lower coil 22 can be made the same or different.

[0043] The control unit 50 includes an arithmetic circuit and a memory (not shown). The memory stores a control program for driving the arithmetic circuit. The control unit 50 is connected to and controls the current transformer 61, the first split coil drive unit 28a, the second split coil drive unit 28b, the slider 63a, the coolant circulation pump 33, the motor 43, and the shaft-shaped body rotation motor.

[0044] For example, when performing moving hardening on the small diameter portion W3 of the shaft-shaped body W, the control unit 50 controls the first split coil drive unit 28a and the second split coil drive unit 28b to minimize the arrangement distance between the pair of split coils 22A as shown in Fig. 2(a). On the other hand, when performing moving hardening on the large diameter portions W1, W5 of the shaft-shaped body W, the control unit 50 controls the first split coil drive unit 28a and the second split coil drive unit 28b to maximize the distance between the pair of split coils 22A as shown in Fig. 2(b). In addition, when the step portions W2 and W4 of the axial body W are subjected to moving hardening, the control unit 50 controls the first split coil driving unit 28a and the second split coil driving unit 28b, thereby opening and closing the space between the pair of split coils 21A and the space between the pair of split coils 22A in accordance with the change in diameter of the step portions W2 and W4 in the longitudinal direction along the central axis CL.

[0045] <Sliding hardening method> Next, the moving hardening method of this embodiment will be described. FIG. 4 is a flowchart showing the moving hardening method according to this embodiment. The shaft-shaped body W is supported in advance by the support portion 10 so that the central axis CL is aligned in the vertical direction.

[0046] First, in the placement step S1, the control unit 50 drives the motor 43 to place the upper coil 21 and the lower coil 22 below the large diameter portion W1. Then, the control unit 50 controls the shaft-shaped body rotation motor to rotate the shaft-shaped body W around the central axis line CL. Next, the control unit 50 drives the current transformer 61 to pass a high-frequency current through the upper coil 21 and the lower coil 22. At this time, the control unit 50 controls the slider 63a to make the current value passed through the upper coil 21 and the current value passed through the lower coil 22 the same.

[0047] Furthermore, the control unit 50 drives the coolant circulation pump 33 to spray the coolant L from the multiple nozzles 31b of the cooling ring 31 toward the shaft-shaped body W. The control unit 50 also starts supplying the coolant to each of the upper coil 21 and the lower coil 22 to cool them. Furthermore, the control unit 50 controls the first split coil driving unit 28a and the second split coil driving unit 28b to open the gaps between each split coil 21A of the upper coil 21 and the gaps between each split coil 22A of the lower coil 22 to match the outer diameter dimension of the large diameter portion W1. When the arrangement step S1 is completed, the process proceeds to the first quenching step S2.

[0048] In the subsequent first quenching step S2, the control unit 50 drives the motor 43 to move the upper coil 21 and the lower coil 22 upward together. As a result, the large diameter portion W1 is induction-heated by the upper coil 21 and the lower coil 22 from its lower end toward its upper end. That is, the high-frequency current flowing through the upper coil 21 and the lower coil 22 causes eddy currents to flow on the surface of the large diameter portion W1 of the shaft-shaped body W, and these eddy currents inductively heat the large diameter portion W1. At this time, because the current value supplied to the upper coil 21 is the same as the current value supplied to the lower coil 22, the amount of heat imparted to the shaft-shaped body W by the upper coil 21 and the lower coil 22 is the same. Then, when the cooling ring 31 passes after the lower coil 22, the coolant L is sprayed onto the outer peripheral surface of the heated large diameter portion W1, thereby rapidly cooling and quenching the heated large diameter portion W1.

[0049] In the subsequent second quenching process S3, the stepped portion W2, which gradually decreases in diameter toward the top, is induction-heated. In the first quenching process, the spacing between the split coils 21A and 22A in each of the upper coil 21 and the lower coil 22 was kept constant. However, in this second quenching process S3, the spacing between the split coils 21A and 22A is gradually narrowed. That is, when the stepped portion W2 is induction-heated from its lower end toward its upper end, the control unit 50 controls the first split coil driving unit 28a and the second split coil driving unit 28b to narrow the spacing between the split coils 21A and 22A so as to maintain a constant air gap with the stepped portion W2. At this time, the high-frequency current flowing through each of the split coils 21A, 22A causes eddy currents to flow on the surface of the stepped portion W2 of the shaft-shaped body W, which inductively heats the stepped portion W2. Furthermore, when the cooling ring 31 passes after each of the split coils 21A, 22A, coolant L is sprayed onto the outer peripheral surface of the heated stepped portion W2. This causes the heated stepped portion W2 to be rapidly cooled and quenched.

[0050] In the subsequent third quenching process S4, the small diameter portion W3, which has the smallest outer diameter and is constant along the longitudinal direction, is induction heated. In the second quenching process S3, the spacing between the split coils 21A and 22A is gradually narrowed, but in this third quenching process S4, the spacing between the split coils 21A and 22A is kept constant so as to be minimum. That is, when the small diameter portion W3 is induction heated from its lower end to its upper end, the control unit 50 controls the first split coil drive unit 28a and the second split coil drive unit 28b to maintain a constant distance between the split coils 21A and between the split coils 22A so that the air gap with the small diameter portion W3 is maintained constant. The arrangement of the split coils 21A at this time is shown in FIG. 2(a). Meanwhile, in the small diameter portion W3 of the shaft-shaped body W, eddy currents flow on the surface due to the high-frequency current flowing through each of the split coils 21A and 22A, and this eddy current causes induction heating. Then, when the cooling ring 31 passes after each of the split coils 21A and 22A, coolant L is sprayed onto the outer peripheral surface of the heated small diameter portion W3. This causes the heated small diameter portion W3 to be rapidly cooled and quenched.

[0051] In the subsequent fourth quenching process S5, the step portion W4, which gradually increases in diameter toward the top, is induction heated. In the third quenching process S4, the spacing between the split coils 21A and 22A was kept constant, but in this fourth quenching process S5, the spacing between the split coils 21A and 22A is gradually increased. That is, when the step portion W4 between the two split coils 21A is induction heated from its lower end to its upper end, the control unit 50 controls the first split coil driving unit 28a and the second split coil driving unit 28b to increase the spacing between each split coil 21A and each split coil 22A so that the air gap with the step portion W4 is maintained constant. Meanwhile, in the stepped portion W4 of the shaft-shaped body W, eddy currents flow on the surface due to the high-frequency current flowing through each of the split coils 21A and 22A, and this eddy current causes induction heating. Furthermore, when the cooling ring 31 passes after each of the split coils 21A and 22A, coolant L is sprayed onto the outer peripheral surface of the heated stepped portion W4. This causes the heated stepped portion W4 to be rapidly cooled and quenched.

[0052] In the subsequent fifth quenching process S6, the large diameter portion W5, which has the largest outer diameter and is constant along the longitudinal direction, is induction heated. In the fourth quenching process S5, the spacing between the split coils 21A and 22A was gradually increased, but in this fifth quenching process S6, the spacing between the split coils 21A and 22A is kept constant so that it is maximized. That is, when the large diameter portion W5 is induction heated from its lower end to its upper end, the control unit 50 controls the first split coil driving unit 28a and the second split coil driving unit 28b to maintain a constant distance between the split coils 21A and 22A so that the air gap with the large diameter portion W5 is maintained constant. The arrangement of the split coils 21A and 22A at this time is shown in FIG. 2(b). Meanwhile, in the large diameter portion W5 of the shaft-shaped body W, eddy currents flow on the surface due to the high-frequency currents flowing through the split coils 21A and 22A, and the large diameter portion W5 is induction-heated by these eddy currents. Furthermore, when the cooling ring 31 passes after each split coil 21, coolant L is sprayed onto the outer peripheral surface of the heated large diameter portion W5. This causes the heated large diameter portion W5 to be rapidly cooled and quenched.

[0053] Through the above-described steps S1 to S6, the shaft-shaped body W is quenched over its entire length, and all steps are completed. The shaft-shaped body W that has been subjected to the rolling quenching over its entire length has increased hardness compared to before the rolling quenching was performed.

[0054] In the traveling hardening method of the present disclosure, the control unit 50 controls the first divided coil driving unit 28a and the second divided coil driving unit 28b individually during the process in which the upper coil 21 and the lower coil 22 move from the large diameter portion W1 through the stepped portion W2 to the small diameter portion W3, and during the process in which the upper coil 21 and the lower coil 22 move from the small diameter portion W3 through the stepped portion W4 to the large diameter portion W5. As a result, the upper coil 21 and the lower coil 22 can be moved independently toward and away from the outer peripheral surface of the shaft-shaped body W, and therefore, as shown in FIG. 5, the upper coil 21 and the lower coil 22 can be moved along the outer peripheral surface while responding to changes in the outer diameter of the shaft-shaped body W.

[0055] FIG. 5 is a diagram showing the process from the small diameter section W3 through the step section W4 to the large diameter section W5, and shows a state in which (a) the small diameter section W3 is heated by both the upper coil 21 and the lower coil 22, (b) the small diameter section W3 is heated by the lower coil 22 while the step section W4 is heated by the upper coil 21, and (c) the large diameter section W5 is heated by both the upper coil 21 and the lower coil 22.

[0056] First, as shown in Fig. 5(a), when induction heating the small diameter portion W3, the control unit 50 controls the first divided coil drive unit 28a and the second divided coil drive unit 28b to bring both the upper coil 21 and the lower coil 22 close to the outer circumferential surface of the small diameter portion W3 so that equal air gaps are maintained. As a result, the inner circumferential surfaces of the upper coil 21 and the lower coil 22 are positioned at equal distances from the center line of movement (center axis CL). Then, in this state, moving quenching is performed while the upper coil 21 and the lower coil 22 are moved upward. As described above, in FIG. 5(a), the third quenching step S4 using the upper coil 21 and the third quenching step S4 using the lower coil 22 are performed simultaneously in parallel.

[0057] In the following FIG. 5(b), a fourth quenching step S5 is carried out following the third quenching step S4. That is, the upper coil 21, which has completed induction heating up to the top end of the small diameter portion W3, is gradually moved radially outward by the first split coil driving unit 28a in response to instructions from the control unit 50, thereby performing moving hardening on the stepped portion W4. During this moving hardening, the control unit 50 controls the air gap formed between the inner peripheral surface of the upper coil 21 and the outer peripheral surface of the stepped portion W4 to be always kept constant. After moving hardening up to the top end of the stepped portion W4, the upper coil 21 reaches the periphery of the lower end of the large diameter portion W5.

[0058] Meanwhile, the lower coil 22 continues to perform induction heating of the small diameter portion W3 while being maintained at a position a fixed distance from the center line of movement (center axis CL) until it reaches the upper end of the small diameter portion W3. Then, after completing induction heating up to the upper end of the small diameter portion W3, the lower coil 22 is gradually moved radially outward by the second split coil driving unit 28b in response to instructions from the control unit 50, while performing moving hardening on the stepped portion W4. During this moving hardening, the control unit 50 controls the air gap formed between the inner peripheral surface of the lower coil 22 and the outer peripheral surface of the stepped portion W4 so that it is always kept constant. As described above, in FIG. 5(b), the third quenching step S4 using the lower coil 22 and the fourth quenching step S5 using the upper coil 21 are carried out simultaneously in parallel.

[0059] Next, in FIG. 5(c), a fifth quenching step S6 is performed. That is, the control unit 50 controls the first divided coil driving unit 28a and the second divided coil driving unit 28b to bring both the upper coil 21 and the lower coil 22 close to the outer circumferential surface of the large diameter portion W5 so that equal air gaps are maintained. As a result, the inner circumferential surfaces of the upper coil 21 and the lower coil 22 are positioned at equal distances from the center line of movement (center axis CL). Then, in this state, the upper coil 21 and the lower coil 22 are moved upward to perform moving quenching. As described above, in FIG. 5(c), the fifth quenching step S6 for the upper coil 21 and the fifth quenching step S6 for the lower coil 22 are performed simultaneously in parallel.

[0060] The above describes the process of heating from the small diameter section W3 through the step section W4 to the large diameter section W5, but the process of heating from the large diameter section W1 through the step section W2 to the small diameter section W3 is also performed by moving quenching while individually adjusting the radial positions of the upper coil 21 and the lower coil 22 using the control unit 50. That is, in the second quenching process S3, the upper coil 21, which has completed induction heating up to the top end of the large diameter portion W1, is gradually moved radially inward by the first split coil driving unit 28a in response to instructions from the control unit 50, thereby performing moving quenching on the stepped portion W2. During this moving quenching, the control unit 50 controls the air gap formed between the inner peripheral surface of the upper coil 21 and the outer peripheral surface of the stepped portion W2 to be always kept constant. After moving quenching up to the top end of the stepped portion W2, the upper coil 21 reaches the periphery of the lower end of the small diameter portion W3.

[0061] Meanwhile, the lower coil 22 continues to perform induction heating of the large diameter portion W5 while being maintained at a position a fixed distance from the center line of movement (center axis CL) until it reaches the upper end of the large diameter portion W5. Then, after completing induction heating up to the upper end of the large diameter portion W5, the lower coil 22 is gradually moved radially inward by the second split coil driving unit 28b in response to instructions from the control unit 50, while performing moving hardening on the stepped portion W2. During this moving hardening, the control unit 50 controls the air gap formed between the inner peripheral surface of the lower coil 22 and the outer peripheral surface of the stepped portion W2 so that it is always kept constant. As described above, the first quenching step S2 using the lower coil 22 and the second quenching step S3 using the upper coil 21 are carried out simultaneously in parallel.

[0062] In the arrangement step S1 to the fifth quenching step S6 described above, moving quenching is performed while continuously moving each of the split coils 21A, 22A, and cooling ring 31 upward relative to the shaft-shaped body W. Therefore, for example, when moving from the fourth quenching step S5 to the fifth quenching step S6, moving quenching is performed while maintaining a constant moving speed of each of the split coils 21A, 22A, and cooling ring 31. At this time, there are some portions that require a sufficient amount of heat, such as the corner e formed between the stepped portion W4 and the large diameter portion W5 shown in FIG. 5(a). When heating such a location, it is possible to slow down the moving speed of the upper coil 21 and the lower coil 22 as they pass by. However, in that case, the movement of the cooling ring 31 that moves following it also becomes slower, so the moving speed of the cooling ring 31 cannot be made constant in the direction of the central axis CL, resulting in uneven cooling.

[0063] In contrast, in the moving hardening device of this embodiment, as shown in Fig. 3, the control unit 50 individually controls the current value in each split coil 21A and the current value in each split coil 22A, so that each current value can be adjusted to an appropriate value for the heating location of the shaft-shaped body W. For example, when heating the corner e with each split coil 21A, the current value in each split coil 21A can be set higher, so that the corner can be sufficiently heated without reducing the moving speed of each split coil 21A. Therefore, with this moving hardening device, it is not necessary to reduce the moving speed of the upper coil 21, and the above-mentioned uneven cooling does not occur.

[0064] The gist of each of the embodiments and modifications described above will be summarized below. [1] A moving quenching device according to one aspect of the present disclosure includes: An apparatus for performing moving hardening on a shaft-shaped body (W) in which a large diameter portion (W1, W5) having a relatively large outer diameter and a small diameter portion (W3) having a relatively small outer diameter are connected via a step portion (W2, W4), a plurality of first divided coils (21A) arranged in a circular shape around the center line of movement at a first position on the center line of movement; a plurality of second split coils (22A) arranged annularly around the center line of movement at a second position on the center line of movement that is different from the first position; a first split coil driving unit (28a) that moves each of the first split coils (21A) toward or away from the center line of movement; a second split coil driving unit (28b) that moves each of the second split coils (22A) toward or away from the center line of movement; a control unit (50) that controls the first split coil driving unit (28a) and the second split coil driving unit (28b); Equipped with.

[0065] [2] In the moving hardening device described in [1] above, the following configuration may be adopted: further comprising a high frequency power source (60); The control unit (50) individually controls the current value of the high-frequency current flowing from the high-frequency power supply (60) to each of the first split coils (21A) and the current value of the high-frequency current flowing from the high-frequency power supply (60) to each of the second split coils (22A).

[0066] [3] In the moving hardening device described in [2] above, the following configuration may be adopted: further comprising a variable resistor (62) that electrically connects the first split coils (21A) and the second split coils (22A) and passes the high-frequency current from the high-frequency power source (60); The control unit (50) distributes and supplies the high-frequency current from the high-frequency power supply (60) to each of the first split coils (21A) and each of the second split coils (22A) while controlling the variable resistor (62).

[0067] [4] A moving quenching method according to one aspect of the present disclosure includes: A method for performing moving quenching on a shaft-shaped body (W) in which a large diameter portion (W1, W5) having a relatively large outer diameter and a small diameter portion (W3) having a relatively small outer diameter are connected via a step portion (W2, W4), comprising: the moving quenching of the shaft-shaped body (W) using a plurality of first divided coils (21A) arranged annularly around the moving center line at a first position on the moving center line, and a plurality of second divided coils (22A) arranged annularly around the moving center line at a second position on the moving center line; During the moving hardening, the first split coils (21A) and the second split coils (22A) are individually moved toward and away from the outer circumferential surface of the shaft-shaped body (W).

[0068] [5] In the moving hardening method described in [4] above, during the moving hardening, the current value of the high-frequency current passed through each of the first split coils (21A) and the current value of the high-frequency current passed through each of the second split coils (22A) may be individually controlled. [Example]

[0069] Below, we will explain the results of simulations of a comparative example in which induction heating was performed using a moving hardening device with a conventional one-turn split coil, and an example in which induction heating was performed using a moving hardening device with split coils 21A and 22A based on the first embodiment described above. 6 is a diagram showing the results of the simulation, and is a longitudinal cross-sectional view of a portion including part B in FIG. 1. (a) shows a conventional example, and (b) shows an example. In this simulation, the outer diameter of the large diameter portion W5 was set to 200 mm, and the outer diameter of the small diameter portion W3 was set to 170 mm. The material of the shaft-shaped body W was carbon steel.

[0070] As a result of the simulation, in the comparative example shown in Figure 6(a), the maximum heating temperature at corner e was 1287°C. The current value passed through the coil was 28000 A to 45000 A. The time required to complete moving quenching of a predetermined length was 131 seconds. On the other hand, in the example shown in Figure 6(b), the maximum heating temperature at corner e was 1278°C. The current values ​​passed through each coil were 12600 A to 20250 A. The time required to complete moving quenching of a predetermined length was 132 seconds. From the above results, it was confirmed that the maximum current required to perform the same heating was half in the example using a two-turn coil compared to the comparative example using a one-turn coil, and the current value could be significantly reduced. [Industrial Applicability]

[0071] According to the moving hardening device and moving hardening method disclosed herein, it is possible to perform moving hardening on a stepped shaft while suppressing overheating and short circuits in the split coils that may occur due to large currents. [Explanation of symbols]

[0072] 21A 1st split coil 22A Second split coil 28a First split coil drive unit 28b Second split coil drive unit 50 control section 60 High frequency power supply 62 Variable resistor W-shape body W1, W5 Large diameter section W2, W4 step W3 Small diameter section

Claims

1. An apparatus for performing moving hardening on a shaft-shaped body in which a large diameter portion having a relatively large outer diameter and a small diameter portion having a relatively small outer diameter are connected via a step portion, a plurality of first split coils arranged annularly around the center line of movement at a first position on the center line of movement; a plurality of second divided coils arranged annularly around the center line of movement at a second position on the center line of movement that is different from the first position; a first divided coil driving unit that moves each of the first divided coils toward or away from the center line of movement; a second divided coil driving unit that moves each of the second divided coils toward or away from the center line of movement; a control unit that controls the first divided coil driving unit and the second divided coil driving unit; A moving hardening device comprising:

2. Further comprising a radio frequency power source; The control unit individually controls a current value of a high-frequency current flowing from the high-frequency power source to each of the first split coils and a current value of a high-frequency current flowing from the high-frequency power source to each of the second split coils; 2. The moving hardening device according to claim 1.

3. further comprising a variable resistor that electrically connects the first divided coils and the second divided coils and allows the high frequency current from the high frequency power source to flow; the control unit distributes and supplies the high-frequency current from the high-frequency power supply to each of the first split coils and each of the second split coils while controlling the variable resistor; 3. The moving hardening device according to claim 2.

4. A method for performing moving hardening on a shaft-shaped body having a large diameter portion with a relatively large outer diameter and a small diameter portion with a relatively small outer diameter connected via a step portion, comprising: the moving hardening of the shaft-shaped body using a plurality of first divided coils arranged annularly around the center line of movement at a first position on the center line of movement and a plurality of second divided coils arranged annularly around the center line of movement at a second position on the center line of movement; During the moving hardening, the first divided coils and the second divided coils are individually moved toward and away from the outer circumferential surface of the shaft-shaped body; A moving hardening method characterized by the above.

5. During the moving hardening, the current value of the high frequency current flowing through each of the first divided coils and the current value of the high frequency current flowing through each of the second divided coils are individually controlled.

5. The method for travelling hardening according to claim 4.

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