JP2608203B2 - Induction heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating apparatus for forging, and more particularly, to a method in which a material to be heated is stopped in a heating coil during processing of the material to be heated. The present invention relates to an induction heating device capable of uniformly heating a heating material to a predetermined temperature and performing a forging process.

[0002]

2. Description of the Related Art As a conventional apparatus of this type, an apparatus described in "Industrial Heating" Vol. 27, No. 4 (published by the Japan Industrial Furnace Association in 1990) is known. The high-performance billet heater (induction heating device) described in this publication will be described with reference to FIGS. As shown in FIG. 4, the induction heating device includes a heating coil 3 for a low-temperature region for heating a material to be heated (a billet) 2 by high-frequency power from a high-frequency inverter device 1, and a billet heated by the heating coil 3. A high-temperature heating coil 5 for heating the heating coil 2 to a predetermined temperature by high-frequency power from a high-frequency inverter device 4; and a pinch roller mechanism 6 for continuously transporting the billets 2 in both the heating coils 3, 5. It is configured. The induction heating device includes a motor 7 for driving the pinch roller mechanism 6, a speed control device 8 for controlling the rotation speed of the motor 7, and a control device 9 for controlling the speed control device 8 and the high-frequency inverter devices 1 and 4, respectively. And

Next, the operation will be described. First, the normal operation will be described. During the normal operation, the billet 2
The pinch roller mechanism 6 continuously conveys the sheet through the heating coil 3 for the low temperature region and the heating coil 5 for the high temperature region, and heats and raises it to a predetermined temperature (usually around 1200 ° C.) during the conveyance. It is discharged from the induction heating device and transported to a post-process (press device) not shown. During the normal operation, the billets 2 in the heating coils 3 and 5 are in the state shown in FIG.
The temperature reaches a predetermined temperature from room temperature through a smooth heating process shown in FIG. The heating pattern is determined by power supply from the high-frequency inverter devices 1 and 4 to the heating coils 3 and 5 based on the control of the control device 9 including a heat-retaining operation described later.

Next, the operation at the time of abnormality will be described.
During the continuous operation of the induction heating device, if there is a failure or the like in the press device in the subsequent process and the operation is stopped, the transport of the billet 2 from the induction heating device is immediately stopped. That is, the pinch roller mechanism 6 is stopped via the motor 7 based on the stop command from the speed control device 8 based on the command from the control device 9 to stop the conveyance of the billet 2, and the high frequency inverter devices 1, 4 The power supply to the heating coils 3 and 5 is stopped. And if the failure of the press device recovers,
Restart operation. When the operation is resumed, each heating coil 3,
The temperature inside 5 has decreased as shown in FIG. 5B, and the longer the time until resumption, the greater the temperature decrease. Therefore, the temperature of the billet 2 discharged from the heating coil 5 for the high temperature region when the operation of the induction heating device is restarted has not reached the regular temperature (around 1200 ° C. in FIG. 5). Cannot be performed, and the billet 2 is discharged by a bypass device (not shown) before the press device. At this time, the induction heating device is set in a heat-retaining operation state as described later.

In order to carry out the heat-retaining operation of the induction heating device, while the pinch roller mechanism 6 is stopped and the billet 2 is kept stationary, first, only the high-frequency inverter device 4 for the high-temperature region is activated and the heating coil 5 is turned on. Supply high frequency power. Thereby, the billet 2 inside the heating coil 5 for the high temperature region is heated to increase the temperature. At the time of heating, the heating coil 5 for the high-temperature region has a reduced temperature rise and is close to parallel in consideration of temperature equalization. Therefore, when the billet 2 in the stationary state is heated, the billet 2 approaches a normal temperature rising curve. When the temperature of the billet 2 reaches the normal temperature rising curve shown in FIG.
Based on this command, the speed controller 8 operates to output a transport command to the motor 7 to rotate the pinch roller mechanism 6 to restart the transport of the billet 2. Time to resume 10
In a short time of about one minute, the degree of temperature decrease of the billet 2 in the heating coil 3 for the low temperature region is small, and after the operation is resumed, the billet 2 is kept at a predetermined temperature until it is discharged from the heating coil 5 for the high temperature region. The temperature is raised to a temperature close to.

[0006]

However, in the conventional induction heating apparatus, the temperature of the billet 2 discharged from the high-temperature heating coil 5 is raised to a state close to a predetermined temperature by performing a heat-retaining operation. However, the following problems still remain. That is, each of the heating coils 3 and 5 is generally divided into a plurality of blocks, and a coil is wound for each block as shown in FIG.
Since there is a portion that is not heated between the blocks, the billet 2 is not heated in these portions even during the warming operation, and the non-heated portion is still in a low temperature state even when the heated portion reaches a predetermined temperature. When the operation is resumed, the billet 2 is carried out from the heating coil 5 for the high-temperature region while partially forming a low-temperature state, and the billet 2 discharged out of the system increases. In addition, in general, the larger the capacity of the induction heating device, the longer the heating coils 3 and 5 and the number of blocks increases, resulting in an increase in the number of billets 2 discharged at a low temperature.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and the billet (heated material) is heated to a predetermined temperature as uniformly as possible when the operation is resumed after the stop to reduce the number of discharged materials. It is an object to provide an induction heating device that can be minimized.

[0008]

An induction heating apparatus according to the present invention comprises a first heating coil for heating a material to be heated by high frequency power from a first high frequency inverter, and a material to be heated heated by the first heating coil. Is heated to a predetermined temperature by high-frequency power from the second high-frequency inverter device.
In an induction heating device including a heating coil and a transfer device that continuously transfers the material to be heated in both of the heating coils, the material to be heated in the second heating coil when the second high-frequency inverter device is activated. And a movement command circuit for outputting a command to start the transfer device at a time when the temperature reaches an intermediate temperature between the temperature of the second heating coil and the final heating temperature and to transfer the transfer device by a distance shorter than the length of the second heating coil. It is.

[0009]

According to the present invention, the material to be heated is heated by the second heating coil during the heat retention operation, and the temperature of the material to be heated and the final heating temperature in the second heating coil when the second high-frequency inverter is started up. When the temperature reaches an intermediate temperature between the first heating coil and the second heating coil, the movement command circuit operates to start the transfer device, and the transfer device transfers the material to be heated by a distance shorter than the length of the second heating coil. By heating the low temperature portion of the material to uniformly heat the material to be heated to the final heating temperature, the number of materials to be heated discharged to the outside of the system can be reduced.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a first embodiment of the present invention; FIG. In each figure, FIG. 1 is a circuit diagram showing one embodiment of the induction heating apparatus of the present invention, and FIG. 2 is a pattern showing a heating pattern of a material to be heated when the induction heating apparatus shown in FIG. 1 is used. FIG. 3 and FIG. 3 are time charts showing a state of conveyance by the induction heating device shown in FIG.

As shown in FIG. 1, the induction heating apparatus according to the present embodiment has a first low-temperature region for heating a billet 2 by high-frequency power from a first high-frequency inverter 1 as in the prior art.
A heating coil 3; a second high-temperature heating coil 5 for heating the billet 2 heated by the first heating coil 3 to a predetermined temperature by high-frequency power from a second high-frequency inverter device 4; Billet 2 in 5
(Pinch roller mechanism) 6 for continuously transporting the paper, and a motor 7 for driving the pinch roller mechanism 6
And a speed control device 8 for controlling the rotational speed of the motor 7 and a control device 9 for controlling the speed control device 8 and the high-frequency inverter devices 1 and 4 respectively.

In the induction heating apparatus according to the present embodiment, the temperature detector 10 for measuring the temperature of the billet 2 in the second heating coil 5 and the activation of the second high-frequency inverter device 4 by the temperature detector 10 are provided. Temperature TS of billet 2 measured at time
And the final heating temperature (for example, around 1200 ° C. in the conventional example) TE input in advance and the intermediate temperature is calculated, and the pinch roller mechanism 6 is activated and the billet 2 And a movement command circuit 11 for outputting a command to convey a distance shorter than the length of the second heating coil 5. Further, the induction heating device of the present embodiment is provided with a pinch roller rotation number detector 12 for measuring the transport distance of the billet 2.

That is, the movement command circuit 11 stores the temperature TS of the billet 2 measured at the time of activation of the second high-frequency inverter device 4, and based on this temperature TS and the final heating temperature TE, the transfer during the stationary heating is performed. Temperature T of timing to perform
1, the intermediate temperature is calculated from T1 = (TS + TE) / 2, and when the temperature of the billet 2 in the second heating coil 5 reaches T1, a movement command is output to the speed control device 8 to pinch it via the motor 7. The roller mechanism 6 is configured to be driven to rotate. The transport distance of the billet 2 transported by the pinch roller mechanism 6 is measured by the pinch roller rotation speed detector 12 and exceeds the distance between the blocks of the second heating coil 5 (usually 20 to 50 mm). 1
It is transported by 00 mm. At this time, the movement command circuit 11 operates and outputs a stop command to the speed control device 8 to send the billet 2
Is stopped, and at that position, the billet 2 is heated by the second heating coil 5 to the low-temperature portion located between the blocks to the final heating temperature TE.

As the movement command circuit 11, for example, a commercially available programmable controller or the like can be used. As the pinch roller rotation speed detector 12, for example, a combination of a rotary encoder or a proximity switch and a rotating disk is used. Can be used.

Next, the operation of the induction heating apparatus according to the present embodiment will be described with reference to FIGS. During normal operation, as shown in FIG. 2A, the billet 2 is heated and heated according to the same heating pattern as in the prior art, and when the press device is stopped due to a failure or the like, the induction heating device is stopped as in the prior art, and the temperature detector 10 is stopped. The temperature of the billet 2 in the heating coil 5 measured by the method shown in FIG.

[0016] In Thus, at the time of resuming operation of the press, induction command to that effect to the heating apparatus is outputted, the induction heating device from the control device 9 based on the this Directive to the first high-frequency inverter unit 4 When a start command is output and high-frequency power is supplied to the second heating coil 5, the second heating coil 5 starts heating and increasing the temperature of the billet 2, and the temperature detector 10 measures the temperature TS of the billet 2. Movement command circuit 1
1 stores the temperature TS measured by the temperature detector 10, and stores this temperature TS and a preset final heating temperature T
An intermediate temperature T1 is calculated based on E. When the temperature detector 10 measures the temperature T1, a drive command is output to the speed control device 8 as shown in FIG. Is driven to transport the billet 2 by 100 mm and stop. At this stop position, the first heating coil 3 and the second heating coil 5 heat the low-temperature portions of the respective billets 2, that is, the non-heating portions between the blocks of the heating coil 5 to the final heating temperature TE, as shown in FIG. 3C. In the normal operation, the subsequent billet 2 is heated in the normal state. The billet 2 discharged from the outlet of the second heating coil 5 according to the moving distance (100 mm) during the stationary heating is too low in temperature to be pressed and discharged outside the system. Is usually 100 to 200 mm, the number of billets 2 discharged out of the system is about 1 to 2 and the number of billets 2 in a normal heating coil is 20.
The loss of one or two billets 2 does not pose a problem in operation when compared with the fact that there are about 50 billets 2.

As described above, according to the present embodiment, the billet 2 in the heating coil 5 is conveyed and the non-heating portion located between the blocks of the heating coil 5 is heated during the stationary heating in the heat keeping operation. By heating the billet 2 to the final heating temperature TE (1200 ° C.) while minimizing the uneven heating of the billet 2, the billet 2 can be supplied to the press machine in the next step. In this case, the degree of heating in each block is not uniform in one block. Therefore, even if the billet 2 is moved during the still heating, the billet 2 cannot be brought into a completely uniform heating state. On the other hand, it is a temperature variation within an allowable range of about 30 ° C. at most, and does not cause any problem in an actual process.

In the above embodiment, the temperature T1 at which the billet 2 is moved during the stationary heating is set as the temperature T1.
The average value of the static heating start temperature TS and the final heating temperature TE is taken, but the temperature T1 may be any temperature approximately intermediate between these temperatures.

[0019]

As described above, according to the present invention, when the operation is restarted after the stop, the material to be heated is heated to a predetermined temperature with as little unevenness as possible to minimize the number of discharged materials to be heated. A possible induction heating device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an induction heating apparatus according to the present invention.

FIG. 2 is a pattern diagram showing a heating pattern of a material to be heated when the induction heating device shown in FIG. 1 is used.

FIG. 3 is a time chart showing a state of conveyance by the induction heating device shown in FIG. 1;

FIG. 4 is a circuit configuration diagram showing an example of a conventional induction heating device.

5 is a pattern diagram showing a heating pattern of a material to be heated when the induction heating device shown in FIG. 4 is used.

FIG. 6 is an explanatory diagram illustrating a block configuration of a heating coil of the induction heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st high frequency inverter apparatus 2 Billet (material to be heated) 3 1st heating coil (for low temperature area) 4 2nd high frequency inverter apparatus 5 2nd heating coil (for high temperature area) 11 Move command circuit

Claims (1)

(57) [Claims] 1. A first heating coil for heating a material to be heated by high-frequency power from a first high-frequency inverter, and a material heated by the first heating coil is predetermined by high-frequency power from a second high-frequency inverter. In an induction heating device including a second heating coil for heating to a temperature and a transfer device for continuously transferring the material to be heated in both of the heating coils, the second heating is performed when the second high-frequency inverter is started. A movement command circuit for starting the transfer device at the time when the temperature reaches an intermediate temperature between the temperature of the material to be heated in the coil and the final heating temperature, and outputting a command to transfer a distance shorter than the length of the second heating coil. An induction heating device characterized by being provided.