JP4917819B2 - Induction heating method using step heating and induction heating apparatus using the heating - Google Patents

Description

  The present invention provides, for example, an induction heating method using stepped heating and its heating in order to reduce the temperature difference due to thickness difference in the return process using induction heating in the constant velocity joint outer ring and to make the hardness uniform. It is related with the induction heating apparatus used.

  In the heat treatment of the constant velocity joint outer ring, a tempering method using high frequency induction heating is used.

In such tempering of the constant velocity joint outer ring, as described in (Patent Document 1), for example, as shown in FIG. 4, a workpiece (outer ring) is placed inside a heating solenoid coil (round shape) 1. 2 is placed (fixed with jigs 3, 4 and the like), and then the work 2 is induction heated by passing a high-frequency current through the heating coil 1. At this time, the magnitude and frequency of the high-frequency current flowing through the coil 1 vary depending on the product. Then, when the work 2 is raised to a predetermined temperature by induction heating, the high-frequency current is stopped, and after holding for a certain time, the work 2 is cooled with cooling water to complete the tempering.
Japanese Patent Laid-Open No. 05-9588

  However, in the above tempering method, when the tripod type constant velocity joint outer ring is subjected to heat treatment, the hardness after tempering becomes uneven at thick and thin portions, or near and far from the solenoid coil. There is.

  In other words, the tripod type constant velocity joint outer ring, as shown in FIG. 6, has a track groove 12 formed on the cylindrical inner surface of the outer ring with opposed roller guide surfaces 13 extending in the axial direction. Are formed at intervals of 120 degrees. The roller guide surfaces 13 facing each other are connected by the large inner diameter portion 5, and each track groove 12 has a shape connected by the small inner diameter portion 6.

  Here, when the outer ring of this shape is placed in the heating solenoid coil (round shape) 1 and induction-heated and quenched, the temperature of the large inner diameter portion 5 is higher than that of the smaller inner diameter portion 6. Get higher. The reason why the unevenness of the heating is caused is that, for example, the thickness of the workpiece is not uniform and the distance between the workpiece and the solenoid coil 1 is different between the large inner diameter portion 5 and the small inner diameter portion 6.

  Thus, if the heating time is the same for the portion cured by quenching, the amount of decrease in hardness increases as the heating temperature increases. Therefore, the hardness of the large inner diameter portion 5 after tempering is lower than that of the small inner diameter portion 6.

  Therefore, when trying to obtain a specified hardness at the small inner diameter portion 6 (the constant velocity joint outer ring defines the hardness after tempering based on the strength of the product), the temperature of the larger inner diameter portion 5 than the small inner diameter portion 6 is increased. Therefore, there is a problem that the hardness of the large inner diameter portion 5 is at a specified lower limit or lower than a specified value.

However, in addition to this, as shown in the current-time curve of FIG. 7, there is also a major cause that the high-frequency current is continuously supplied to the heating coil 1. That is, since the supply of the high-frequency current to the heating coil 1 is performed once on and off, the temperature rise curve as shown in FIG. Become. As described above, since the temperature difference at the end of heating becomes very large, when the small inner diameter portion 6 enters the required temperature region T1-T2, the large inner diameter portion 5 deviates from the temperature region T1-T2. It is.
Therefore, the object of the present invention is to reduce the temperature difference of the workpiece (particularly, tripod type constant velocity joint outer ring that generates a temperature difference between the parts during induction heating) 2 and to reduce variation in partial hardness reduction due to tempering. In other words, the hardness after tempering can be kept uniform.

  In order to solve the above-described problems, the present invention provides a method using step heating in which a high-frequency current is supplied to an induction heating coil for heating a workpiece in a plurality of times and the workpiece is heated stepwise to a tempering temperature. Adopted.

  By adopting such a method, the high-frequency current continuously supplied is supplied to the induction heating coil in a plurality of times, and energy is given to the workpiece by repeating the on / off a plurality of times. By doing so, for example, the temperature of the large inner diameter portion rises faster than that of the small inner diameter portion during the on period, but during the off period, the large inner diameter portion is thin and the heat is dissipated to lower the temperature. At this time, since the small inner diameter portion is thick, it is difficult for the temperature to decrease, and there is also heat conduction from the large inner diameter portion, and the temperature difference from the large inner diameter portion is reduced. By repeating this several times, both the large inner diameter portion and the small inner diameter portion are brought into the temperature range necessary for tempering.

  In addition, a high-frequency power source that supplies a high-frequency current to the induction heating coil that heats the workpiece, and a high-frequency current that is supplied from the power source to the induction heating coil are supplied in multiple steps, and the workpiece is heated stepwise to the tempering temperature. The structure provided with the control apparatus to perform can be employ | adopted.

  By adopting such a configuration, the control device controls the high frequency power supply, and supplies the high frequency current to the induction heating coil so as to be repeatedly turned on and off in a plurality of times. Then, for example, during the ON period, the temperature of the large inner diameter portion rises faster than that of the small inner diameter portion, but during the OFF period, the large inner diameter portion is thin, so that heat is released and the temperature decreases. At this time, since the small inner diameter portion is thick, it is difficult for the temperature to decrease, and there is also heat conduction from the large inner diameter portion, and the temperature difference from the large inner diameter portion is reduced. By repeating this several times, both the large inner diameter portion and the small inner diameter portion are brought into the temperature range necessary for tempering.

  Since the present invention is configured as described above, it is possible to reduce the temperature difference of the workpiece, for example, the temperature difference inside the cup of the constant velocity joint outer ring that is induction-heated, thereby reducing variation in the amount of partial hardness reduction due to tempering. As a result, the hardness after tempering can be kept uniform. As a result, the hardness standard of the product (for example, the large inner diameter portion and the small inner diameter portion of the outer ring) can be sufficiently satisfied, so that the strength of the product can be increased as compared with the case of tempering without using this stage heating.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  As shown in FIG. 1A, the induction heating device of this embodiment includes an induction heating coil 1, a high frequency power source 10, and a control device 11.

  In this embodiment, the induction heating coil 1 is a solenoid coil formed in a cylindrical shape by spirally winding a round coil so that the workpiece 2 can be arranged in the coil 1 as shown in FIG. Is formed. The induction heating coil 1 is connected to a high frequency power source 10.

  The high-frequency power source 10 is a transistor type inverter, and is composed of a main circuit and a control circuit. For example, a transistor such as an IGBT or a MOS-FET is used as a control element of the main circuit.

  The control circuit includes, for example, a PLC (sequencer) circuit and a drive circuit, and drives a transistor of the inverter by the drive circuit based on a preset value of frequency and power programmed in the PLC and an operation time thereof.

  Here, the control device 11 uses a programmable device such as a sequencer to control the high-frequency power supply 10 corresponding to the on / off heating cycle as shown in FIG.

  This embodiment is configured as described above, and the induction heating method of the present application will be described by setting the tripod type constant velocity joint outer ring as the work 2 in this induction heating device and describing the operation of the tempering cycle. .

  As shown in the cross-sectional views of FIG. 1B and FIG. 6, the workpiece 2 has track grooves 12 formed by the roller guide surfaces 13 facing each other, and the three track grooves 12 are formed at intervals of 120 degrees. ing. The roller guide surfaces 13 facing each other are connected by the large inner diameter portion 5, and each track groove 12 has a shape connected by the small inner diameter portion 6.

  As shown in FIG. 1A, the workpiece 2 is supported by a lower jig 4 and an upper center jig 3 and set inside the induction heating coil 1.

  Next, a high frequency current is supplied from the high frequency power source 10 to the coil 1 according to the program of the control device 11 to perform induction heating.

  That is, as shown in FIG. 2, the high-frequency current is supplied to the induction heating coil 1 in a plurality of times. That is, energy is given to the workpiece 2 by repeating ON / OFF several times. By doing so, the temperature of the large inner diameter portion 5 rises faster than the small inner diameter portion 6 during the on period, but during the off period, the large inner diameter portion 5 is thin and thus dissipates heat, thereby lowering the temperature. On the other hand, since the small inner diameter portion 6 is thick, it is difficult for the temperature to decrease, and there is thermal diffusion from the large inner diameter portion 5, and the temperature difference from the large inner diameter portion 5 is reduced. By repeating this several times, as shown in FIG. 3, it is possible to heat both the large inner diameter portion 5 and the small inner diameter portion 6 so as to enter the temperature range T1-T2 necessary for tempering.

  In this way, the workpiece 2 heated to a uniform temperature is cooled for a predetermined time after the heating is finished, and the processing is finished. Since the workpiece (outer ring) 2 that has been tempered in this manner can reduce the temperature difference inside the cup of the outer ring, it is possible to reduce variations in the amount of partial hardness reduction. As a result, the hardness after tempering can be kept uniform. Thereby, the hardness standard of the product can be sufficiently satisfied, so that the strength of the product can be increased as compared with the case of tempering without using this stage heating.

  The current-time curve varies depending on the type and shape of the product, and is set as appropriate through experiments and tests.

(A) Block diagram of embodiment, (b) Cross section of workpiece Action explanatory diagram of the embodiment Action explanatory diagram of the embodiment Explanatory drawing of conventional tempering Cross section of workpiece Partially enlarged sectional view of the workpiece of FIG. Action explanatory diagram of conventional example Action explanatory diagram of conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Induction heating coil 2 Workpiece | work 5 Large inside diameter part 6 Small inside diameter part 10 High frequency power supply 11 Control apparatus 12 Track groove 13 Roller guide surface

Claims (2)

A constant velocity joint outer ring having a thin large inner diameter portion serving as a track groove and a thick small inner diameter portion connecting the track groove is disposed in a cylindrical induction heating coil, and the constant velocity joint outer ring and induction are arranged. The heating coil is opened so that heat can be dissipated, and the induction heating coil is turned on when the temperature of the large inner diameter portion of the constant velocity joint outer ring rises, and the large inner diameter portion of the constant velocity joint outer ring dissipates heat and the temperature decreases. Induction heating tempering that supplies high-frequency currents divided into multiple times so as to repeat on and off during the off period, and heats both the large and small inner diameters of the constant velocity joint outer ring stepwise to the tempering temperature. Method. A constant velocity joint outer ring having a thin large inner diameter portion serving as a track groove and a thick small inner diameter portion connecting the track groove is disposed in a cylindrical induction heating coil, and the constant velocity joint outer ring and induction are arranged. A high-frequency power source that opens the space between the heating coils so as to dissipate heat and supplies a high-frequency current to the induction heating coil, and a high-frequency current from the power source to the induction heating coil increases the temperature of the large inner diameter portion of the constant velocity joint outer ring. period and, by radiating the large inner diameter portion of the outer race is supplied a plurality of times to repeat on and off at the time of off temperature decreases, the large inner diameter portion and the small of the constant velocity joint outer ring of the An induction heating device provided with a control device that heats both inner diameter portions step by step up to the tempering temperature.

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