JP2008169454A - Spline shaft, heat treatment method and heat treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treatment method for a spline shaft having a stepped part formed therein. <P>SOLUTION: When induction-hardening the spline shaft 200, this heat treatment method includes induction-heating a large-diameter part 250 only with a low-frequency wave and a spline part 210 with a combined wave of the low-frequency wave and a high-frequency wave, respectively. In this way, the method can appropriately heat each of a rising part 251, a tooth bottom 212 and a tooth top 211, and can form a hardened layer 270 having predetermined hardness down to sufficient depth on each of these parts. Here, the spline shaft is heated in a fixed position or while moving, with the low-frequency wave. Thereby, the large-diameter part 250 is not damaged by overheat, but is heated down to appropriate depth as well as a corner part 251R of the bottom of the rising part 251. In addition, in a step of supplying two waves of different frequencies to the spline part, which starts after an induction heating coil has passed through the rising part 251, the tooth bottom 212 is heated with the low-frequency wave and the tooth top 211 is heated with the high-frequency wave, so that the whole surface of the spline part 210 can be heated down to the appropriate depth. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat treatment of a spline shaft using induction heating. In particular, the present invention relates to a heat treatment of a spline shaft having an irregular shape and having a stepped portion or a protruding portion protruding from the axial direction of the shaft.

Conventionally, an induction heating apparatus that heats a workpiece by supplying electric power of two different frequencies to the induction heating coil is known. By heating the workpiece with such an induction heating device and then cooling, induction hardening is performed. (For example, Patent Documents 1 and 2).
In Patent Document 1, two-frequency power is simultaneously supplied to one induction heating coil, and the two-frequency power distribution or heating time is arbitrarily changed to adjust the heating depth of the workpiece.

Further, in Patent Document 2, two-frequency power from two power sources is supplied to one induction heating coil, and the output from the two power sources to the coil is switched by a control device according to the heating part, and the tooth surface of the rack portion in the rack bar・ Moving quenching is performed on the back and the shaft adjacent to the rack.
Specifically, when heating the shaft portion, a high frequency is selected from a high frequency and a low frequency, and the shaft portion is heated at a high frequency. On the other hand, when heating the rack portion, high frequency power and low frequency power are simultaneously supplied to the coil. Thus, a hardened and hardened layer having a predetermined hardness is formed at a predetermined depth on the surface of the rack bar including the tooth bottom and the tooth tip of the rack portion.

  Here, as a workpiece, there is a spline shaft having a deformed spline portion whose distance from the shaft center is not constant, and it is necessary to heat while giving rotation, and thus a coil corresponding to each tooth of such a deformed spline shaft is not manufactured. . Even if the spline portion is not deformed, a normal coil does not correspond to the teeth of the spline if the spline portion is not a module standard.

JP 2003-342633 A (FIGS. 5 and 6) Japanese Patent Laying-Open No. 2004-315851 (FIG. 3, paragraphs 0018 to 0020)

Although the spline part may be heat-treated by the methods of Patent Documents 1 and 2, a spline in which a stepped part is formed at a position adjacent to the spline part and rises with respect to the tooth bottom and has the same height as the tooth tip. Heat treatment of the shaft is difficult due to the fact that such a stepped portion does not enter the inside of an induction heating coil that is annular or the like and the following circumstances.
The stepped portion is, for example, a rolled end portion of the spline portion, or a brim-like shape, and the spline shaft heat treatment in which such a stepped portion is formed has the following problems.

(1) In the case of using a single quenching method and hairpin type coil It is necessary to balance the temperature rise in each part of the tooth tip, the bottom of the tooth, and the stepped portion with respect to the shaft axis direction. Even if the maximum frequency band is used, it is impossible. That is, due to the synergistic effect of the vertical axis current and the proximity effect along the axial direction of the shaft, the temperature rise at the tooth tip and the rising portion is strong, so that the heating depth at the tooth bottom is insufficient.

(2) When using a single quenching method and a turn-type coil The diameter of the step is as large as the maximum diameter of the spline part (tooth tip part), so the corner of the rising part with respect to the shaft axis direction (R part) ) Cannot be designed to be a one-turn coil facing. That is, the temperature rise is insufficient in the vicinity of a substantially right angle corner formed by the stepped portion and the tooth bottom. On the other hand, thermal stress concentrates at the leading end of the rising portion, causing melting damage.

(3) When using a moving quenching method and a hairpin type coil As in (1), since a sufficient temperature rise cannot be obtained at the root, the heating depth of the bottom is insufficient.

(4) In the case of moving quenching method and use of turn type coil Even if the coil of 1 turn moves, it does not oppose the R part as in (2), so the R part of the rising part becomes insufficient in temperature rise, and R The tip of the part melts down.

  In other words, the spline portion may be heat-treated by the methods of Patent Documents 1 and 2, but the heat treatment of the spline shaft having the stepped portion is extremely difficult.

  It is an object of the present invention to provide a heat treatment method and a heat treatment apparatus, and a heat treated heat treated spline shaft with respect to a spline shaft in which a step portion is formed.

  In the heat treatment method of the present invention, a spline shaft having a spline portion having a tooth crest and a tooth bottom and a stepped portion that is continuous with an axial end portion of the spline portion and rises from the tooth bottom is provided in the circumferential direction of the spline shaft. A heat treatment method in which heating is performed by an induction heating coil surrounded by quenching, and the spline shaft is opposite to the step portion along the axial direction of the spline shaft from the step portion side with respect to the induction heating coil. The induction heating coil and the spline shaft are provided so as to be relatively movable so as to move to the side, and the stepped portion intersects the rising portion from the tooth bottom and extends substantially along the axial direction of the spline shaft Starting with the induction heating coil facing the part, the low frequency power alone of the two frequency powers with different frequencies A low frequency supply step for supplying to the induction heating coil, and a two frequency supply step for combining the low frequency power with a high frequency power higher than the low frequency power to supply the induction heating coil with the low frequency power. The frequency supplying step has a stationary time in which the spline shaft and the induction heating coil are placed in a stationary state without relative movement while the induction heating coil faces the axial direction portion or the rising portion. After the time, the spline shaft and the induction heating coil are relatively moved until at least the rising portion passes through the induction heating coil, and the induction heating coil is moved through the low frequency supply step and the two frequency supply step. Quenching is performed by continuously supplying a coolant to the portion of the spline shaft that has passed.

  According to the present invention, in the moving quenching method, a time is set for placing the stepped portion when heating the stepped portion, and after the start of heating and cooling at the low frequency alone, the rising portion of the stepped portion is the induction heating coil. Since the induction heating by two frequencies is started at the timing after passing through, the temperature of the rising part of the stepped part and the tooth bottom and tooth crest of the spline part are appropriately increased, and the rising part, the tooth bottom, and A hardened and hardened layer having a predetermined hardness can be formed on each tooth crest with a sufficient quenching depth. Since stationary heating is performed after stationary heating and the coolant is sprayed onto the heated portion that has passed through the induction heating coil in the spline shaft, there is no problem in raising the temperature of the stepped portion.

Here, due to stationary heating / moving heating at low frequency in the low frequency supply process, the portion adjacent to the induction heating coil in the stepped portion is not melted by overheating, and the corner corner (R portion) at the base end of the rising portion Appropriate heating depth can be obtained over the entire rising portion including.
In addition, in the two-frequency supply process that starts after the rising portion has passed through the induction heating coil, the tooth bottom is heated by the low frequency and the tooth crest is heated by the high frequency. Heating depth is obtained.
That is, the spline shaft in the present invention has irregularities between the root and the step portion in addition to the irregularities between the tooth crest and the tooth bottom, and the distance from the induction heating coil varies depending on each part. The temperature can be raised to a predetermined temperature, and a hardened and hardened layer having a sufficient hardness and curing depth can be formed on each surface of each part. In other words, the heating depth can be controlled while the surface temperature is constant.
In this way, taking advantage of the features of high-frequency heating and low-frequency heating, step heating is performed by low-frequency stationary heating, workpiece (spline shaft) movement start, cooling start, and two-frequency synthesis heating start. In the spline shaft in which the portion is formed, both the spline portion and the step portion can be appropriately quenched.
The spline shaft and the induction heating coil can be moved relative to each other by moving the spline shaft with respect to the fixed position of the induction heating coil or with the induction heating coil with respect to the fixed position of the spline shaft. There are things to move.

The induction heating coil may be a one-turn or multi-turn annular coil.
Further, the step portion corresponds to, for example, a portion having a diameter larger than the diameter of the spline portion, and includes a protruding portion that rises from the bottom of the spline portion. Furthermore, the rising portion of the stepped portion refers to a portion that rises with respect to the axial direction of the spline shaft, and may rise not only from the tooth bottom of the spline portion but also from the tooth crest. The rising portion only needs to protrude from the tooth bottom of the spline shaft, and the rising angle with respect to the axis of the spline shaft is not limited.

  In the heat treatment method of the present invention, it is preferable that the spline shaft having the spline portion deformed is a heat treatment target.

  According to the present invention, the effect of the present invention is achieved because a deformed spline shaft, which is deformed, does not produce a coil corresponding to each tooth, and cannot obtain a predetermined heating depth by heating at a single frequency, is processed. Can stand out.

  In the heat treatment method of the present invention, the low frequency supply step relatively moves the spline shaft and the induction heating coil at a lower speed than a relative movement speed between the spline shaft and the induction heating coil in the two frequency supply step. Preferably, the low-speed moving time includes a timing at which the position of the spline shaft facing the induction heating coil shifts from the rising portion to the spline portion.

According to the present invention, the temperature of the stepped portion is more reliably increased due to the slow moving speed, and in particular, the rising speed of the rising portion when passing through the induction heating coil is low. A temperature rise at the corner can be obtained more sufficiently.
Here, by adjusting the time of the low-speed moving time and the moving speed, the heating depth of the rising portion can be adjusted.

  In the heat treatment method of the present invention, it is preferable that the low frequency supplying step is continued for a predetermined time after the rising portion has passed through the induction heating coil.

  According to the present invention, the edge portion on the rising portion side of the spline portion is heated not at a high frequency but at a low frequency, thereby preventing overheating of the surface of the rising portion.

  The heat treatment apparatus of the present invention includes a spline shaft having a spline portion having a tooth crest and a tooth bottom and a stepped portion that is continuous with an axial end portion of the spline portion and rises from the tooth bottom in the circumferential direction of the spline shaft. A heat treatment apparatus for heating by an induction heating coil that surrounds the spline shaft, wherein the spline shaft moves from the stepped portion side to the opposite side of the stepped portion along the axial direction of the spline shaft with respect to the induction heating coil. As described above, a moving device that enables relative movement of the induction heating coil and the spline shaft, a low-frequency output device that outputs low-frequency power out of two-frequency powers having different frequencies, and a higher frequency than the low-frequency power A high-frequency output device that outputs a high-frequency power and a portion of the spline shaft that has passed through the induction heating coil. A cooling device for supplying the induction heating coil, the low-frequency power is supplied alone, or the low-frequency power and the high-frequency power are combined and supplied to the induction heating coil. From the state in which the induction heating coil and the axial direction portion that intersects the rising portion from the tooth bottom and extends substantially along the axial direction of the spline shaft and the induction heating coil face each other at the step portion, the side opposite to the step portion of the spline shaft The low-frequency electric power is output until the end portion of the spline shaft passes through the induction heating coil, and the high-frequency output device is different from the stepped portion of the spline shaft after the rising portion has passed through the induction heating coil. The high-frequency power is output until the opposite end passes through the induction heating coil, and the moving device is guided to the axial portion or the rising portion. Predetermined fixed time in a state where the heat coil is opposed, characterized in that a stationary state and the induction heating coil and the spline shaft without relative movement.

  According to the present invention, substantially in the same manner as the heat treatment method described above, when the stepped portion is heated, the stepped portion is in a stationary state, and following the start of heating and cooling at a low frequency alone, the rising portion of the stepped portion is set to the induction heating coil. Induction heating by two frequencies is started at a timing after the passage of the. As a result, a hardened hardened layer having a predetermined hardness can be formed with a sufficient quenching depth on each of the rising portion of the stepped portion, the tooth bottom, and the tooth crest, and the spline shaft on which the stepped portion is formed can be quenched. Can be done appropriately.

  In the heat treatment apparatus of the present invention, it is preferable that the spline shaft having the spline portion having an irregular shape is a heat treatment target.

  According to the present invention, as described above, the effect of the present invention can be emphasized because the modified spline shaft is treated.

  In the heat treatment apparatus according to the present invention, the moving device may be configured so that the spline shaft is opposed to the spline shaft at a predetermined low speed moving time including a timing at which the position of the spline shaft facing the induction heating coil shifts from the rising portion to the spline portion. It is preferable that the relative movement speed with the induction heating coil is lower than the relative movement speed between the spline shaft and the induction heating coil at other times.

  According to this invention, since the moving speed when the induction heating coil passes through the rising portion is low, the temperature rise at the corner portion of the rising portion base end can be more sufficiently obtained.

  In the heat treatment apparatus of the present invention, it is preferable that the cooling device ejects the cooling liquid from a direction inclined with respect to the axial direction of the spline shaft.

  According to this aspect of the invention, the coolant injection angle is oblique to the axial direction of the spline shaft, so that the coolant is sufficiently applied to the entire rising portion including the corner portion of the rising portion base end. That is, the stepped portion and the end portion of the spline portion are each rapidly cooled by the cooling liquid spray angle, so that a hardened and hardened layer having a predetermined hardness can be more reliably formed.

  The spline shaft of the present invention is a spline shaft having a spline portion having a tooth crest and a tooth bottom, and a stepped portion that is continuous with an axial end portion of the spline portion and rises from the tooth bottom, Can be moved relative to the induction heating coil so as to move to the opposite side of the step portion along the axial direction of the spline shaft, and along the circumferential direction of the spline shaft by the induction heating coil. A quench-hardened layer is formed by being heated and cooled, and the quench-hardened layer is formed in the stepped portion by low-frequency power of two frequencies having different frequencies supplied to the induction heating coil. From the axial portion that intersects the rising portion from the tooth bottom and extends substantially along the axial direction of the spline shaft, the spline shaft A low-frequency curing pattern formed to include the corners between the rising portion and the root, and the root, up to the end opposite to the stepped portion, and more than the low-frequency power A two-frequency curing formed from the axial end to the other end of the spline portion including the tooth ridges by high frequency power that is combined with the low frequency power and supplied to the induction heating coil. And a pattern.

  According to the present invention, two frequencies are used in substantially the same manner as in the heat treatment method and the heat treatment apparatus, and each of the rising portion of the stepped portion, the tooth bottom, and the tooth crest is determined by the low frequency hardening pattern and the high frequency hardening pattern. A hardened hardened layer is formed with a sufficient hardened depth. Thereby, induction heating hardening of the spline shaft in which the level | step-difference part was formed is attained.

  In the spline shaft of the present invention, it is preferable that the spline portion has an irregular shape.

  According to the present invention, the effect of the present invention is enhanced by application to a deformed spline shaft that is deformed and does not produce a coil corresponding to each tooth and that cannot obtain a predetermined heating depth by heating at a single frequency. be able to.

  In the spline shaft of the present invention, it is preferable that the step portion is formed with a diameter equal to or greater than or equal to the tooth crest of the spline portion over the entire circumferential direction of the spline portion.

According to the present invention, the spline shaft has a stepped portion that protrudes substantially equal to or more than the tooth crest of the spline portion, but it is difficult to achieve a predetermined heating depth in each part. It is preferable to apply the present invention, and the effect of the present invention can be highlighted here.
In addition, since the level | step-difference part is formed in the large diameter by the diameter equal to or more than a tooth | gear, this level | step-difference part can be favorably hold | maintained with a jig etc.

  According to the present invention described above, a heat treatment method and a heat treatment apparatus, and a heat treated spline shaft with a step can be realized with respect to the spline shaft in which the step portion is formed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1. Overall configuration of heat treatment equipment]
FIG. 1 is a circuit diagram showing a schematic configuration of an induction heating apparatus 100 provided in the heat treatment apparatus in the present embodiment. Here, this heat treatment apparatus is for quenching the surface of the spline shaft 200 shown in FIG. 2 and FIG. 3 by induction heating and cooling. In addition to the induction heating apparatus 100 of FIG. It is configured with a device.

[2. Configuration of induction heating device]
In FIG. 1, reference numeral 100 denotes an induction heating apparatus as a heat treatment apparatus. The induction heating apparatus 100 is an apparatus for induction heating and quenching the spline shaft 200 using two different frequencies.
The induction heating apparatus 100 supplies the induction heating coil 110 that induction-heats the spline shaft 200, the first transformer 120 as a transformer, and the induction heating coil 110 with power having a frequency of 1 kHz or more and less than 50 kHz, for example. A low frequency output device 140 for induction heating, and a high frequency output device 130 for supplying the induction heating coil 110 with a high frequency power higher than the frequency of the low frequency output device 140, for example, high frequency power of 10 kHz to 400 kHz to the induction heating coil 110 for heating. , And control means 150.

  Induction heating coil 110 is connected in series to high-frequency output device 130 and low-frequency output device 140. The induction heating coil 110 is supplied with electric power of a predetermined frequency from each of the high-frequency output device 130 and the low-frequency output device 140 and induction-heats the spline shaft 200.

The first transformer 120 is connected to the high frequency output device 130 and the low frequency output device 140 and is connected to the induction heating coil 110, and supplies AC power of a predetermined frequency to the induction heating coil 110.
The first transformer 120 has, for example, a small self-inductance, that is, an air-core coupling type, and the secondary winding 122 and the tertiary winding 123 on the secondary side are wound once. The inductance values of the winding 122 and the tertiary winding 123 and the inductance value of the induction heating coil 110 are set to be substantially the same. In the first transformer 120, the induction heating coil 110 is connected between one end side of the secondary winding 122 and the other end side of the tertiary winding 123.

The high-frequency output device 130 includes first oscillating means 131, a second transformer 132, and a first capacitor C1. The first oscillation means 131 includes a first converter 131A, a first smoothing capacitor Cf1, and a first inverter 131B.
The first converter 131A is a forward conversion circuit using, for example, various bridge rectifier circuits, and is connected to the commercial AC power source e to convert the AC of the commercial AC power source e into DC. The converted DC current is appropriately smoothed through the first smoothing capacitor Cf1 and output to the first inverter 131B.
The first inverter 131B is, for example, a voltage source inverter, and converts the direct current input via the first smoothing capacitor Cf1 into the above-described high-frequency alternating current having a predetermined frequency. The primary winding 132A of the second transformer 132 is connected in series between the output terminals of the first inverter 131B.

In the high-frequency output device 130, the series circuit of the first capacitor C1 and the primary winding 121 of the first transformer 120 is connected in series between the output terminals of the secondary winding 132B of the second transformer 132. Connected and configured.
That is, the first capacitor C1 enters a series resonance state by the high-frequency power output from the first inverter 131B and supplied through the second transformer 132, and the induction heating coil 110 induction-heats the spline shaft 200. .
The first capacitor C1 compensates for the reactive power of the first transformer 120 and the induction heating coil 110, and the low-frequency component of the AC power fed back from the low-frequency output device 140 by the first transformer 120. Attenuate.
Then, as described above, the high-frequency output device 130 supplies high-frequency power having a frequency of 10 kHz or more and 400 kHz or less to the induction heating coil 110 via the first transformer 120, and by series resonance with the first capacitor C <b> 1. The spline shaft 200 is induction-heated.

  Here, when the frequency of the high-frequency power supplied by the high-frequency output device 130 is lower than 10 kHz, there is a possibility that good quenching cannot be obtained particularly on the uneven heating surface of the spline portion of the spline shaft. On the other hand, if the frequency is higher than 400 kHz, it may be difficult to obtain good induction heating. For this reason, it is preferable to set the frequency supplied by the high-frequency output device 130 in the range of 10 kHz to 400 kHz.

The low-frequency output device 140 includes a second oscillation unit 141, a reactor L1, a second capacitor C2, a third transformer 142, a third capacitor C3, and a fourth capacitor C4. ing.
Similarly to the high-frequency output device 130, the second oscillation means 141 includes a second converter 141A, a second smoothing capacitor Cf2, and a second inverter 141B.
The second converter 141A is a forward conversion circuit using, for example, various bridge rectifier circuits, and is connected to the commercial AC power source e to convert the AC of the commercial AC power source e into DC. The converted DC current is appropriately smoothed through the second smoothing capacitor Cf2 and output to the second inverter 141B. The second inverter 141B is, for example, a voltage source inverter, and converts the direct current input via the second smoothing capacitor Cf2 into the low-frequency alternating current described above.

In the low-frequency output device 140, a series circuit of the reactor L1, the second capacitor C2, and the primary winding 142A of the third transformer 142 is connected between the output terminals of the second inverter 141B. ing. In the low frequency output device 140, a series circuit of a third capacitor C3 and a fourth capacitor C4 is connected between the secondary windings 142B of the third transformer 142. The connection point between the third capacitor C3 and the fourth capacitor C4 is connected to the ground.
Further, in the low-frequency output device 140, the output terminal of the secondary winding 142B of the third transformer 142 is connected to the other of the secondary winding 122 of the first transformer 120 and one of the tertiary windings 123. Has been. In the low-frequency output device 140, the reactor L1 attenuates the high-frequency feedback component of the high-frequency output device 130 to form a series resonance circuit.
In addition, the third capacitor C3 and the fourth capacitor C4 use the reactive power of the first transformer 120 in which the secondary side of the first transformer 120 has a low inductance in order to bypass the low-frequency alternating current. To compensate.
Then, as described above, the low-frequency output device 140 supplies low-frequency power having a frequency of 1 kHz or more and less than 50 kHz to the induction heating coil 110, and causes the spline shaft 200 to be generated by series resonance of the reactor L1 and the second capacitor C2. Induction heating.

  Here, when the frequency of the low-frequency power supplied by the low-frequency output device 140 is lower than 1 kHz, it may be difficult to obtain good induction heating. On the other hand, when it becomes higher than 50 kHz, there is a possibility that good induction heating from the surface of the spline shaft 200 to the inside cannot be obtained. Therefore, the frequency supplied by the low frequency output device 140 is preferably 1 kHz or more and less than 50 kHz.

The control means 150 controls the operation of the high frequency output device 130 and the low frequency output device 140. The control means 150 includes operation means (not shown) for setting the magnitude of AC power supplied from the high frequency output device 130 and the low frequency output device 140 to the induction heating coil 110 by an input operation by an operator. Specifically, the operation means includes an operation means having an operation knob that can be input by an operator, for example. The maximum output of the high-frequency output device 130 and the low-frequency output device 140 is 100%, and is 0% or more and 100%. When the operation knob is input within the following range, the high-frequency output device 130 and the low-frequency output device 140 are set to have constant current control, and AC power is set to a current value corresponding to the input value that has been input. input.
And the control means 150 is made to supply the alternating current power by the high frequency output device 130 to the induction heating coil 110 by electric current constant control in the state where an electric current value becomes fixed with the set output ratio.
Furthermore, the control means 150 supplies the alternating current power by the low frequency output device 140 to the induction heating coil 110 at the output ratio similarly set by the constant current control.

  These high-frequency AC power and low-frequency AC power can be supplied independently, and can be supplied by appropriately combining high-frequency and low-frequency. Then, when synthesizing the high frequency and the low frequency and supplying the AC power, the control unit 150 corrects the set value of the high frequency output device 130 based on a predetermined formula and controls the AC power to be supplied in a constant state. To do. Since the current control is constant, the set value and the supplied current value are directly proportional to each other. For example, when the maximum standard value is 10000 A, if the set value is 9%, it is about 900 A, and if it is 50%. If it is about 5000A, 100%, it will be about 10000A.

That is, the control unit 150 includes a conversion value acquisition unit (not shown), a processing unit, and the like as programs. By supplying AC power from the high frequency output device 130 and the low frequency output device 140 in a state where the high frequency and the low frequency are combined, the permeability of the spline shaft 200 changes, and a high frequency corresponding to the changing permeability. The impedance in the high-frequency output device 130 on the side decreases, and the AC power supplied from the high-frequency output device 130 decreases.
Thereby, the conversion value acquisition unit calculates a correction value as a conversion value for correcting the power to decrease to a state before superimposition, and based on the correction value calculated by the conversion value acquisition unit, The processing means controls the high-frequency output device 130 to supply AC power having a current value according to the converted corrected setting.

[3. (Spline shaft configuration)
Next, the structure of the spline shaft which is a workpiece | work of the heat processing apparatus of this embodiment is demonstrated.
FIG. 2 is an external side view of the spline shaft 200. The spline shaft 200 includes a spline portion 210 having a tooth crest 211 and a tooth bottom 212, and a substantially cylindrical shaft portion 290 held by a jig or the like. Here, the shaft portion 290 has a large-diameter portion 250 as a stepped portion protruding in the axial direction of the spline shaft 200 on the side continuous with the spline portion 210.
In this embodiment, the spline shaft 200 is made of S35C steel and is formed by cold forging. Moreover, although the maximum diameter of the spline part 210 is 20 mm, the material and diameter of the spline shaft 200 are not limited thereto.

3A is a longitudinal sectional view showing the spline portion 210 and the large diameter portion 250 of the spline shaft 200, and FIG. 3B is a plan view of the spline shaft 200. FIG.
As shown in FIG. 3 (B), the spline portion 210 has an irregular shape, and two tooth teeth 211 are arranged in close proximity to each other, and tooth bases 212A and 212B having different shapes are formed on each tooth tooth 211. It is formed between. Each of these bottoms 212A and 212B has a different distance from the center of the axis, and it is necessary to form a hardened hardened layer having a predetermined quenching depth on both of these bottoms 212A and 212B. When it is not necessary to distinguish between these tooth bottoms 212 </ b> A and 212 </ b> B, they are collectively referred to as a tooth bottom 212. Hereinafter, the axial direction of the spline shaft 200 is referred to as S.

As shown in FIG. 3B, the large diameter portion 250 has a diameter substantially equal to the tooth crest 211 of the spline portion 210, and as shown in FIG. 3A, the rising portion rises from the tooth bottom 212. 251 and an axial portion 252 that intersects the rising portion 251 and substantially extends along the axial direction S.
The rising portion 251 rises at a substantially right angle with respect to the tooth bottom 212, for example, at a height of about 5 mm, and an R portion 251R is formed at the proximal end of the rising portion.

[4. Outline of heat treatment of spline shaft)
Next, an outline of induction heating and quenching of the spline shaft 200 will be described with reference to FIG.
That is, the spline shaft 200 is disposed on the inner peripheral side of the induction heating coil 110 of the induction heating device 100 (FIG. 1), and the spline shaft 200 is axially moved with respect to the induction heating coil 110 while being rotated by a moving device (not shown). Move along S.
As shown in FIG. 4, the heat treatment start position of the spline shaft 200 is a position where the axial portion 252 faces the inner peripheral surface 110A of the induction heating coil 110. From the state of FIG. When the end of the spline portion 210 opposite to the large diameter portion 250 passes through the inner peripheral surface 110A of the induction heating coil 110, the heating of the spline shaft 200 is finished.

Here, the induction heating coil 110 has an annular shape and a width of 6 mm, and is integrated with a cooling device that injects cooling water (quenching water). In FIG. 4, reference numeral 115 denotes a cooling water injection hole. In this embodiment, a large number of injection holes 115 are arranged in a staggered manner in four rows along the circumferential direction of the induction heating coil 110, and the cooling width is 20.0 mm or more. ing.
In the present embodiment, the injection angle of the injection hole 115 is set to about 30 ° with respect to the axial direction S so that the cooling water is applied to the entire rising portion 251 including the R portion 251R.

[5. (Hardening pattern of spline shaft)
The spline shaft 200 of the present embodiment is induction-heated and quenched by a heat treatment apparatus including the induction heating apparatus 100 (FIG. 1) described above.
FIG. 5 shows the spline shaft 200 that has been quenched, and (A) and (B) are cross-sectional views taken along lines AA and BB in FIG. 2, respectively.
A hardened and hardened layer 270 is formed along the axial direction S on the surface of the spline shaft 200. In FIG. 5, reference numeral 280 denotes a base of the spline shaft 200.

The quench hardening layer 270 is formed by the low frequency curing pattern 271 formed by supplying the low frequency power from the low frequency output device 140 (FIG. 1) and the high frequency power supplied by the high frequency output device 130 (FIG. 1). And a high-frequency curing pattern 272. In FIG. 5, the low frequency curing pattern 271 is shown in light gray (light gray), and the high frequency curing pattern 272 is shown in dark gray (dark gray).
Here, the frequency of the low frequency power supplied to the induction heating coil 110 by the low frequency output device 140 is 10 kHz in the present embodiment, and the frequency of the high frequency power supplied to the induction heating coil 110 by the high frequency output device 130 is the present embodiment. The form is 200 kHz.

  The low-frequency curing pattern 271 is formed with a predetermined quenching depth including the R portion 251R and the tooth bottom 212. On the other hand, the high-frequency hardening pattern 272 does not include both the rising portion 251 and the tooth bottom 212, and is located outside the low-frequency hardening pattern 271 at a quenching depth shallower than the low-frequency hardening pattern 271. Is formed.

[6. Heat treatment process for spline shaft]
Next, a heat treatment method for the spline shaft 200 having the curing patterns 271 and 272 as shown in FIG. 5 will be described with reference to FIGS. 4 and 6 to 8.
The heat treatment apparatus including the induction heating apparatus 100 described above quenches the spline shaft 200 from the large diameter portion 250 side using two frequencies of low frequency and high frequency, but the induction heating coil 110 applies low frequency power for a predetermined time from the start of the process. After that, the low frequency and the high frequency are synthesized and supplied to the induction heating coil 110.

  FIG. 6 shows the timing of supplying low frequency and high frequency, respectively, and the timing of cooling (heat treatment cycle). The vertical axis of the graph in FIG. 6 indicates that the state where the axial portion 252 of the large diameter portion 250 faces the inner peripheral surface 110A of the induction heating coil 110 (FIG. 4) is the position “0”, and the spline shaft 200 is in the axial direction S. The horizontal axis of the graph indicates the elapsed time from the start of the heat treatment at the position “0”.

In other words, the heat treatment method for the spline shaft 200 is performed by synthesizing the low frequency and the high frequency at a predetermined timing with the low frequency supply step P1 for supplying the low frequency alone to the induction heating coil 110 for a predetermined time from the start time T0. And a two-frequency supply process P <b> 2 for supplying the heating coil 110.
Moreover, although the spline shaft 200 is moved along the axial direction S with respect to the induction heating coil 110 by a moving device (not shown), the moving speed at that time is set to a low speed halfway.
Further, a cooling process Q for injecting the cooling water to the spline shaft 200 is started after the processing start time T0 by the cooling device provided in the induction heating coil 110.

[Low frequency supply process]
In the low frequency supply process P1, the spline shaft 200 is placed in a stationary state without moving the spline shaft 200 with respect to the induction heating coil 110 for a predetermined stationary time T1 from the processing start T0, and thereafter, with respect to the induction heating coil 110 by a moving device (not shown). The spline shaft 200 is moved at a low speed (low speed movement time T2). Here, the low speed movement time T <b> 2 includes a timing at which the position of the spline shaft 200 facing the induction heating coil 110 shifts from the rising portion 251 to the spline portion 210.

And the injection of cooling water is started at a predetermined timing during the low speed movement time T2. This cooling is started at a timing immediately after the rising portion 251 (FIG. 4) passes through the inner peripheral surface 110A of the induction heating coil 110, so that the cooling water is prevented from splashing and the cooling water from the injection hole 115 rises. Sufficiently hooks the portion 251 and the axial portion 252. In the present embodiment, cooling is started at a position of about 7 mm, but the cooling start timing can be appropriately set according to the shape of the rising portion 251 and the like. By cooling at such timing, it is possible to prevent a tensile stress from being applied due to a delay in transformation at the time of cooling, and the occurrence of cracks in the axial portion 252 and the spline portion 210.
The cooling is performed by continuously injecting cooling water to the portion of the spline shaft 200 that has passed through the inner peripheral surface 110A of the induction heating coil 110 by the movement of the spline shaft 200.

After the low-speed moving time T2, the moving speed of the spline shaft 200 with respect to the induction heating coil 110 is increased, and induction heating with a low frequency is continuously performed.
That is, in the low frequency supply process P1, after the stationary heating, the moving heating is performed at a low speed for a predetermined time, and the delayed cooling is started. Here, the low frequency supply process P1 may be performed until the rising portion 251 passes through the induction heating coil 110. However, in the present embodiment, the spline portion 210 also after the rising portion 251 passes through the induction heating coil 110. Inductive heating with a low frequency alone is performed continuously for a predetermined time in which the inner peripheral surface 110A of the induction heating coil 110 faces the end of the coil.
In this embodiment, the stationary time is set within about 0.5 seconds, the moving speed at the low speed moving time T2 is set to about 5 mm / second, and the moving speed after the low speed moving time T2 is set to about 15 mm / second. These can be appropriately set according to the shape of the spline shaft 200 and the like.

A predetermined heating depth is obtained from the axial direction portion 252 to the rising portion 251 of the spline shaft 200 by the induction heating in the low-frequency supply process P1, and as a result of this induction heating quenching, as shown in FIG. A low frequency curing pattern 271 having a predetermined hardness and a predetermined quenching depth is formed in a region including the R portion 251R of the portion 251.
Note that the spline shaft 200 shown in FIG. 7 shows an example in which the spline portion 210 and the large diameter portion 250 are quenched by supplying only a low frequency alone. In this example, the tooth crest 211 has a large amount of undissolved ferrite due to insufficient temperature rise, and the hardness is insufficient. On the other hand, the center part including the axis of the spline part 210 was improper due to the subtle heating.

[Dual frequency supply process]
Subsequently, in the two-frequency supply process P2 (FIG. 6), the low-frequency and high-frequency are synthesized to move and heat the spline unit 210 (FIG. 4). In this embodiment, the two-frequency supply process P2 starts about 1.7 seconds after the processing start time T0, and after heating for about 3 seconds until the upper end of the spline part 210 passes through the induction heating coil 110, the low frequency supply process P2 The heating by each of the frequency output device 140 and the high frequency output device 130 (FIG. 1) is terminated.
In addition, the timing which starts 2 frequency supply process P2 can be suitably set according to the shape of the spline shaft 200, etc.
In addition, in the two-frequency supply process P2 using high frequency, the spline shaft 200 is moved at a relatively high speed of about 15 mm / sec in order to secure an unfired portion that does not reach the predetermined range including the axis of the spline portion 210. Move.

By this two-frequency supply process P2, as shown in FIG. 5, a low-frequency hardening pattern 271 on the tooth bottom 212 of the spline part 210 and a high-frequency hardening pattern 272 on the tooth crest 211 are formed.
Here, FIG. 8 shows an example in which the spline portion 210 and the large diameter portion 250 are quenched by supplying only a high frequency alone. In the case of FIG. 8, in the large diameter portion 250, the melting point is the closest to the induction heating coil 110 and the portion where the thermal stress is most concentrated by heat conduction, that is, the portion Z where the axial portion 252 and the rising portion 251 intersect. Loss (shown in black) will occur. On the other hand, in the present embodiment, the portion including the rising portion 251 and the axial direction portion 252 is heated at a low frequency in the low frequency supply step P1, and then from the spline portion 210 by a high frequency in the two frequency supply step P2. Heat. For this reason, as shown in FIG.

[Stationary cooling]
Finally, stationary cooling is performed for about 10 seconds, and induction heating quenching of the spline shaft 200 is completed.

[7. Hardness distribution]
FIG. 9 shows the hardness distribution in the hardened and hardened layer 270 of the spline shaft 200 after the completion of quenching shown in FIG. Here, the circles and triangles correspond to the respective parts of the spline shaft 200 shown in FIG. 5 and the like, the white circle indicates the hardness of the tooth bottom 212A, the white triangle indicates the hardness of the tooth bottom 212B, and the black circle Indicates the hardness of the tooth crest 211, and the white square indicates the hardness of the R portion 251R. As shown in FIG. 9, in each part of these spline shafts 200, the surface hardness after quenching was about 600 HV, and the quenching depth was about 2 mm.

[8. Effects of this embodiment]
According to the present embodiment as described above, the following effects can be obtained.
(1) The low frequency supply process P1 and the two frequency supply process P2 are performed by the heat treatment apparatus provided with the induction heating apparatus 100, and the low frequency alone or the combination of the low frequency and the high frequency is performed according to each part of the spline shaft 200. By performing induction heating respectively, the rising portion 251 of the large diameter portion 250 and the tooth bottom 212 and the tooth crest 211 of the spline portion 210 are appropriately heated. As a result, the hardened and hardened layer 270 having a predetermined hardness can be formed with a sufficient quenching depth on each of the rising portion 251, the tooth bottom 212, and the tooth crest 211.

By the stationary heating / moving heating at the low frequency in the low frequency supply process P1, the portion adjacent to the induction heating coil 110 in the large diameter portion 250 is not melted by overheating, and the R portion 251R at the base of the rising portion 251 is included. An appropriate heating depth can be obtained over the entire rising portion 251.
In addition, in the two-frequency supply process P2 that starts after the induction heating coil 110 passes through the rising portion 251, the tooth bottom 212 is heated by the low frequency and the tooth crest 211 is heated by the high frequency. Appropriate heating depth can be obtained throughout.
That is, by making use of the features of high-frequency heating and low-frequency heating, both the spline portion 210 and the large diameter portion 250 can be appropriately quenched in the spline shaft in which the large diameter portion 250 is formed.

(2) The low frequency supply process P1 has a low speed movement time T2, and the movement speed when the induction heating coil 110 passes through the rising portion 251 is low, so that the rising at the R portion 251R at the base of the rising portion 251 is increased. The temperature can be obtained more sufficiently.

(3) Since the low frequency supply process P1 is continued for a predetermined time after the induction heating coil 110 passes through the rising part 251, the edge part on the rising part 251 side of the spline part 210 is not heated at high frequency. Overheating of the rising portion 251 can be prevented.

(4) Since the injection angle by the cooling device mounted on the induction heating coil 110 is inclined with respect to the axial direction of the spline shaft 200, the rising portion 251 including the R portion 251R at the base end of the rising portion 251 Sufficient cooling water is applied. Thereby, each of the end portions of the large diameter portion 250 and the spline portion 210 is rapidly cooled, and the hardened and hardened layer 270 having a predetermined hardness can be more reliably formed.

[Modification of the present invention]
FIG. 10 shows a workpiece (hardened object) 9 according to a modification of the present invention. That is, the work 9 includes a gear portion 90 having a tooth crest 91 and a tooth bottom 92 and a flange portion 95 having a diameter equivalent to that of the tooth crest 91, and toward the base end side of the rising portion 951 rising from the tooth bottom 92. This is the same as the above-described spline shaft 200 in that it is difficult to quench.
Such induction heating and quenching of the workpiece 9 is also performed by the above-described low frequency using the heat treatment apparatus including the induction heating apparatus 100 (FIG. 1) having the induction heating coil 110 (FIG. 4) and the workpiece moving apparatus. It can be performed by substantially the same method as the supply process P1 and the dual frequency supply process P2 (FIG. 6).

Here, the frequency used for induction heating can be appropriately selected based on the rising dimension of the flange portion 95 and the like. The general formula used for this frequency selection is shown.

δ: depth of penetration of eddy current (position where current density is 36.8% of surface) (cm)
ρ: Workpiece resistivity (Ω · cm)
μ: relative permeability of workpiece (magnetic material: μ> 1, non-magnetic material: μ = 1)
f: Frequency (Hz)

  That is, the heat treatment method and the heat treatment apparatus of the present invention can be used for various works including uneven portions such as tooth crests and tooth bottoms and portions rising from the recessed portions.

Further, the low frequency and high frequency supplied to the induction heating coil are not limited to the above-described example, and can be appropriately set according to the shape, size, material, and the like of the workpiece. In addition, stationary heating time, cooling start timing, relative movement speed of induction heating coil and workpiece, movement speed switching timing, timing to synthesize low frequency and high frequency, low frequency single heating time, low frequency / high frequency synthesis Of course, the heating time, the coil width, the cooling water injection angle, and the like are not limited to the above-described example, and can be appropriately set according to the shape, dimensions, material, and the like of the workpiece.
In addition to the low frequency and the high frequency, other frequencies different from these two frequencies may be used. It is also possible to examine induction heating by combining these plural frequencies individually or in combination of two or more.

Although the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

The schematic structure circuit diagram of the induction heating apparatus in the embodiment of the present invention. The external appearance side view of the spline shaft which is a workpiece | work in the said embodiment. The longitudinal cross-sectional view and top view of the said spline shaft. The figure for demonstrating the outline of the induction heating hardening of the said spline shaft. The figure which shows the hardening hardening pattern of the said spline shaft. The figure which shows the heat processing cycle in the said embodiment. The figure which shows the hardening pattern at the time of heat-processing only at low frequency tentatively. The figure which shows the hardening pattern at the time of heat-processing only with a high frequency. The figure which shows the hardness distribution in each site | part of the said spline shaft. The figure which shows the modification of this invention.

Explanation of symbols

100 Induction heating device 110 Induction heating coil 115 Injection hole 130 High frequency output device 140 Low frequency output device 200 Spline shaft 210 Spline part 211 Tooth crest 212 Tooth bottom 212A Tooth bottom 212B Tooth bottom 250 Large diameter part (step part)
251 Rising part 251R R part (corner corner)
252 Axial direction part 270 Quench hardening layer 271 Low frequency curing pattern 272 High frequency curing pattern P1 Low frequency supply process P2 Two frequency supply process S Axial direction T1 Fixed time T2 Low speed movement time

Claims (11)

An induction heating coil that surrounds a spline shaft having a spline portion having a tooth crest and a tooth bottom and a stepped portion that is continuous with the axial end portion of the spline portion and rises from the tooth bottom along the circumferential direction of the spline shaft. A heat treatment method for heating and quenching,
Relative movement of the induction heating coil and the spline shaft so that the spline shaft moves from the stepped portion side to the opposite side of the stepped portion along the axial direction of the spline shaft with respect to the induction heating coil Possible,
The stepped portion starts with the induction heating coil facing the axial portion that intersects the rising portion from the tooth bottom and extends substantially along the axial direction of the spline shaft. A low frequency supply step of supplying low frequency power alone to the induction heating coil;
A two-frequency supply step of combining the low-frequency power with the high-frequency power higher than the low-frequency power and supplying the high-frequency power to the induction heating coil,
The low-frequency supply step has a stationary time for placing the spline shaft and the induction heating coil in a stationary state in a state where the induction heating coil faces the axial direction portion or the rising portion, After this settling time, the spline shaft and the induction heating coil are relatively moved until at least the rising portion passes through the induction heating coil,
A heat treatment method for a spline shaft, wherein quenching is performed by continuously supplying a coolant to the portion of the spline shaft that has passed through the induction heating coil through the low frequency supply step and the dual frequency supply step. . In the heat processing method of the spline shaft of Claim 1,
A spline shaft heat treatment method, characterized in that a spline shaft having a spline portion having an irregular shape is a heat treatment target. In the heat processing method of the spline shaft of Claim 1 or 2,
The low frequency supply step has a low speed movement time for relatively moving the spline shaft and the induction heating coil at a lower speed than the relative movement speed of the spline shaft and the induction heating coil in the two frequency supply step,
The low-speed moving time includes a timing at which the position of the spline shaft facing the induction heating coil shifts from the rising portion to the spline portion. In the heat processing method of the spline shaft in any one of Claim 1 to 3,
The low-frequency supplying step is continued for a predetermined time after the rising portion has passed through the induction heating coil. An induction heating coil that surrounds a spline shaft having a spline portion having a tooth crest and a tooth bottom and a stepped portion that is continuous with the axial end portion of the spline portion and rises from the tooth bottom along the circumferential direction of the spline shaft. A heat treatment apparatus for heating,
Relative movement of the induction heating coil and the spline shaft so that the spline shaft moves from the stepped portion side to the opposite side of the stepped portion along the axial direction of the spline shaft with respect to the induction heating coil A mobile device to enable;
A low-frequency output device that outputs low-frequency power out of two-frequency power having different frequencies;
A high-frequency output device that outputs high-frequency power that is higher in frequency than the low-frequency power;
A cooling device that supplies a cooling liquid to a portion of the spline shaft that has passed through the induction heating coil,
The induction heating coil is supplied with the low frequency power alone, or the low frequency power and the high frequency power are combined and supplied,
The low-frequency output device is configured so that the induction heating coil faces the axial portion that intersects the rising portion from the tooth bottom at the stepped portion and extends substantially along the axial direction of the spline shaft. Until the end on the opposite side of the step portion passes through the induction heating coil,
The high-frequency output device outputs the high-frequency power after the rising portion passes through the induction heating coil until the end of the spline shaft opposite to the stepped portion passes through the induction heating coil. ,
The moving device is in a stationary state without relative movement of the spline shaft and the induction heating coil for a predetermined stationary time with the induction heating coil facing the axial direction portion or the rising portion. Spline shaft heat treatment equipment. In the heat processing apparatus of the spline shaft of Claim 5,
A spline shaft heat treatment apparatus, characterized in that a spline shaft having a spline portion having an irregular shape is a heat treatment target. The heat treatment apparatus for a spline shaft according to claim 5 or 6,
The moving device is configured such that the position of the spline shaft facing the induction heating coil is relative to the spline shaft and the induction heating coil during a predetermined low-speed moving time including a timing at which the rising portion shifts to the spline portion. A heat treatment apparatus for a spline shaft, wherein the movement speed is lower than the relative movement speed between the spline shaft and the induction heating coil at other times. In the heat processing apparatus of the spline shaft in any one of Claim 5 to 7,
The cooling apparatus sprays the cooling liquid from a direction inclined with respect to the axial direction of the spline shaft. A spline shaft having a spline portion having a tooth crest and a tooth bottom, and a stepped portion that is continuous with an axial end portion of the spline portion and rises from the tooth bottom,
It is possible to move relative to the induction heating coil so as to move from the step portion side to the side opposite to the step portion along the axial direction of the spline shaft,
A quench-hardened layer is formed by being heated and cooled along the circumferential direction of the spline shaft by the induction heating coil,
The quench-hardened layer is
An axial portion extending substantially along the axial direction of the spline shaft by crossing the rising portion from the tooth bottom at the stepped portion due to the low frequency power of the two frequencies of different frequencies supplied to the induction heating coil. To the end of the spline shaft opposite to the stepped portion, the corner portion between the rising portion and the tooth bottom, and the low frequency curing pattern formed including the tooth bottom, respectively.
From the one end of the spline portion in the axial direction to the other end by the high-frequency power that is higher than the low-frequency power and is combined with the low-frequency power and supplied to the induction heating coil. A spline shaft, comprising: a formed dual-frequency curing pattern. The spline shaft according to claim 9,
The spline shaft is characterized in that the spline portion has an irregular shape. The spline shaft according to claim 9 or 10,
The spline shaft is characterized in that the stepped portion is formed with a diameter equal to or greater than or equal to or equal to the tooth crest of the spline portion over the entire circumferential direction of the spline portion.