JP2023092255A - High-frequency induction heating system and high-frequency induction heating method - Google Patents

Abstract

To provide a high-frequency induction heating device including a matching portion capable of optimizing the load-side impedance viewed from a power supply with respect to the load impedance and a high-frequency induction heating method.SOLUTION: A high-frequency induction heating device 1 includes a high frequency power supply 2, a heating coil 4 connected to the high frequency power source 2, and a matching portion 3 provided between the high frequency power supply 2 and the heating coil 4, and the matching portion 3 includes a matching transformer 5, a capacitor 6, and a plurality of electromagnetic contactors 7 as switching means for selecting the number of turns of a primary winding 5a of the matching transformer 5, and when a workpiece W is heated, the number of turns of the primary winding 5a of the matching transformer 5 is switched according to the change in the physical properties of the workpiece W due to the heating of the workpiece W, and the impedance on the load side viewed from the high frequency power supply 2 is optimized.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a high-frequency induction heating apparatus and a high-frequency induction heating method having a matching section capable of optimizing a load impedance viewed from a high-frequency power source.

2. Description of the Related Art Induction heating using electromagnetic induction is known as a method for heating a conductive object such as a metal. Induction heating uses an alternating magnetic field generated around a coil by supplying high-frequency current from a high-frequency power supply. In induction heating, magnetic flux is supplied to the object to be heated by the alternating magnetic field, and an induced current (eddy current) is generated in the object to be heated. Due to the heat generated by the eddy current and the electrical resistance of the object to be heated, the object itself generates heat and is heated. Therefore, it has the feature of being able to raise the temperature at high speed and with good efficiency. Taking advantage of such features, high-frequency induction heating has been widely used in various fields in recent years. On the other hand, in order to realize carbon neutrality, attention has been focused on reducing the amount of electric power, and reduction of the amount of electric power has become one of the issues in high-frequency induction heating.

For example, Patent Literature 1 discloses a high-frequency heating apparatus capable of obtaining maximum power output for various objects to be heated (steel plates) having different load impedances. Among them, a plurality of secondary windings of the matching transformer are prepared in a state that can be switched by switching the intermediate contact, and the secondary winding of the matching transformer is switched according to the load impedance that varies depending on the heated object. , a technology that can extract the maximum output from the power supply even if the load impedance of the steel plate changes.

JP-A-11-167980

In the switchgear disclosed in Patent Document 1, the number of turns on the secondary side of the matching transformer can be selected according to various objects to be heated, so that the object to be heated can be heated with maximum efficiency. On the other hand, for example, when the object to be heated is a ferromagnetic material, when the temperature of the object to be heated reaches the Curie temperature during heating, the physical properties change from a ferromagnetic material to a paramagnetic material. Due to this change in physical properties, the magnetic coupling between the heating coil and the object to be heated becomes weaker, and the load impedance becomes lower. may become. High-frequency induction heating is used to efficiently heat the object to be heated, which affects the load impedance and changes the physical properties of the object. In addition, in order to stabilize the load impedance, it is necessary to optimize the load impedance seen from the high-frequency power source before and after the change in the physical properties of the object to be heated. However, Patent Document 1 does not pay attention to changes in the load impedance during heating due to changes in the physical properties of the object to be heated. It can be said that it is difficult. Even if the load impedance change during heating can be handled, the secondary winding switching means of Patent Document 1 is a complicated mechanism using an air cylinder, and switching takes time, which affects the heating capacity. may come out. Furthermore, since the high-frequency heating device of Patent Document 1 obtains the maximum power output, it is conceivable that it will be in an overheated state.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a high-frequency induction heating apparatus and a high-frequency induction heating method having a matching section capable of optimizing the load impedance viewed from a high-frequency power source.

In order to achieve the above object, the invention according to claim 1 is a high-frequency induction heating apparatus comprising a high-frequency power supply capable of outputting at an arbitrary frequency and a heating coil connected to the high-frequency power supply, the high-frequency power supply and A matching section is provided between the heating coil and the matching section includes a matching transformer, a capacitor, and switching means for arbitrarily selecting the number of turns of the primary winding of the matching transformer.
According to the second aspect of the invention, there is provided a high-frequency power supply capable of outputting at an arbitrary frequency, a heating coil connected to the high-frequency power supply, and a matching transformer, a capacitor, and a matching power supply provided between the high-frequency power supply and the heating coil. A high-frequency induction heating method for heating an object to be heated using a high-frequency induction heating device comprising a matching unit including switching means for arbitrarily selecting the number of turns of a primary winding of a transformer, The number of turns of the primary side winding of the matching transformer is switched according to the change in the heated object due to the heating of the heated object, and the impedance on the load side viewed from the high frequency power supply is optimized.

According to the present invention, it is possible to optimize the impedance on the load side as seen from the high-frequency power source. It is possible to heat the object while it is in the same state, and the object to be heated can be heated with high efficiency. In addition, since it is possible to suppress the peak output and the decrease in output, it leads to a stable power supply, which leads to a reduction in the rated capacity of the power panel, and the size of the power panel can be reduced, so it can be used for space-saving equipment. can be provided.

1 is a circuit diagram showing a high frequency induction heating device of the present invention; FIG. It is explanatory drawing which shows a workpiece|work shape and a temperature measurement location. 1 is a circuit diagram showing a conventional high-frequency induction heating device; FIG. 7 is a graph showing changes in primary power and work temperature when a conventional high-frequency induction heating apparatus is used; 4 is a graph showing changes in primary power and work temperature when the high-frequency induction heating apparatus of the present invention is used. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the high frequency induction heating system using the high frequency induction heating apparatus of this invention, Comprising: (a) is a perspective view, (b) is the side view seen from the unloading side.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a circuit diagram showing a high frequency induction heating apparatus of the present invention.
A high-frequency induction heating device 1 includes a high-frequency power source 2, a matching section 3, and a heating coil 4, as shown in FIG. A high-frequency induction heating apparatus 1 is used for heating an object to be heated (hereinafter referred to as work W) having conductivity such as metal.
The high-frequency power supply 2 can output a high-frequency current of an arbitrary frequency with a predetermined amount of current.
By energizing the heating coil 4 with a high-frequency current from the high-frequency power supply 2, magnetic flux is supplied to the workpiece W by the magnetic field generated around the heating coil 4, and the magnetic flux induces an eddy current in the workpiece W. The eddy current and the The workpiece W is directly heated by the heat generated by the electrical resistance of the workpiece W.

The matching section 3 includes a matching transformer 5 and a capacitor 6 . A capacitor 6 is provided in series with the heating coil 4 . A resonance circuit can be configured by appropriately selecting the inductance of the heating coil 4, the capacitance of the capacitor 6, and the frequency of the high-frequency current. By using a resonance circuit, the amplitude of the high-frequency current applied to the heating coil 4 can be maximized.
The matching transformer 5 includes a primary winding 5a and a secondary winding 5b, and the secondary winding 5b has a predetermined number of turns. On the other hand, the primary winding 5a is formed with a predetermined number of turns, and on the winding, as a switching means, a copper bar tapped every desired number of turns and an electromagnetic contactor 7 connected to each copper bar are provided. is provided. Each electromagnetic contactor 7 is switchable. Here, a case is illustrated in which the magnetic contactors 7a and 7b are provided at positions with two different numbers of turns.

Hereinafter, the heating test results of the work W using the high-frequency induction heating apparatus 1 of the present invention and the conventional high-frequency induction heating apparatus 10 not belonging to the present invention will be shown, and the heating method of the work W using the high-frequency induction heating apparatus 1. will be explained.
FIG. 2 is an explanatory diagram showing a workpiece shape and temperature measurement points. FIG. 3 is a circuit diagram showing a conventional high-frequency induction heating device. FIG. 4 is a graph showing changes in primary power and work temperature when a conventional high-frequency induction heating apparatus is used. FIG. 5 is a graph showing changes in primary power and work temperature when the high-frequency induction heating apparatus of the present invention is used.
In the following explanation of the results of the heating test, as shown in FIG. Measurement was performed at (measurement point F). Note that iron, which is the material of the work W, has a Curie point at about 770° C., and when it exceeds the Curie point, it changes from a ferromagnetic material to a paramagnetic material.

In the heating test of the workpiece W, after the heating range of the workpiece W was placed within the heating coil 4 , a high frequency current was applied to the heating coil 4 from the high frequency power source 2 to heat the workpiece W by induction heating of the heating coil 4 . From the start of heating until the target temperature of 1100° C. was measured at the measurement point F, the temperature at the measurement point F and the primary power in the high-frequency induction heating device were measured.

Here, a heating test of the workpiece W using the conventional high-frequency induction heating apparatus 10 will be described.
A conventional high-frequency induction heating apparatus 10 includes a high-frequency power source 20 with a rated capacity of 600 kW, a matching section 30, and a heating coil 4, as shown in FIG. The matching section 30 has a matching transformer 50 and a capacitor 6 .
FIG. 4 shows the heating test results of the workpiece W using the conventional high-frequency induction heating apparatus 10. As shown in FIG.
A high-frequency current was applied to the circuit from the high-frequency power supply 20 to heat the workpiece W. It can be seen that both the primary power and the temperature of the workpiece W are rising smoothly until about 15 seconds have passed since the start of heating. However, when the temperature at the measurement point F reaches around 770° C., which is the Curie point of iron, the primary power drops sharply. This is because when the temperature of the workpiece W reaches the Curie point, the physical properties of the workpiece W change from a ferromagnetic material to a paramagnetic material. This is probably because the output of the coil 4 decreased and the heating efficiency decreased. It is considered that the decrease in the output of the heating coil 4 is caused by the weakening of the magnetic coupling between the workpiece W and the heating coil 4, thereby decreasing the impedance of the heating coil 4 and decreasing the secondary voltage. The drop in primary power begins about 15 seconds after heating and continues until about 45 seconds have passed. After that, heating was continued, and when the measurement point F reached about 1100°C, that is, when about 60 seconds had passed since the start of heating, the operation of the high-frequency induction heating device 10 was stopped, and the heating of the workpiece W was completed.
In the heating test using the high-frequency induction heating device 10, the integrated power consumption during heating was about 6 kWh.

Next, a heating test of the workpiece W using the high-frequency induction heating apparatus 1 of the present invention will be described.
In the high frequency induction heating device 1, the rated capacity of the high frequency power source 2 is 400 kW. In the matching transformer 5, the positions on the primary winding 5a where the magnetic contactors 7a and 7b are provided are determined in advance according to changes in the secondary power before and after reaching the Curie temperature, which will be described later. A turn ratio with the winding 5b is calculated and set based on the result.
FIG. 5 shows the result of a heating test of the workpiece W using the high-frequency induction heating apparatus 1 of the present invention.
A high-frequency current was applied to the heating coil 4 from the high-frequency power supply 2 to heat the workpiece W. At the start of heating, the matching transformer 5 is connected to the electromagnetic contactor 7a. It can be seen that both the primary power and the temperature of the work W are rising smoothly until about 35 seconds have passed since the start of heating.
After about 35 seconds from the start of heating, the primary power becomes zero once, but during this time the circuit was switched from the electromagnetic contactor 7a to the electromagnetic contactor 7b. This is because the load impedance is optimized on the primary side of the matching transformer 5 so as to compensate for the decrease in the impedance of the workpiece when the workpiece W reaches the Curie temperature, thereby reducing the primary power. This is for stabilizing and ensuring a stable output of the heating coil 4 . By switching from the electromagnetic contactor 7a to the electromagnetic contactor 7b before the temperature of the work W reaches the Curie point and physical properties change, the work W is heated with a stable output without lowering the output of the heating coil 4. can do
After switching from the magnetic contactor 7a to the magnetic contactor 7b, the energization from the high-frequency power supply 2 is resumed, and after about 65 seconds from the start of heating, when the temperature reaches about 1100 ° C. at the measurement point F, high-frequency induction heating is performed. The operation of the apparatus 1 was stopped, and the heating of the workpiece W was finished.

In the heating test using the high-frequency induction heating apparatus 1 of the present invention, the integrated power consumption during heating was about 4.7 kWh. Here, when compared with the results of the heating test using the conventional high-frequency induction heating device 10 (rated capacity 600 kW), the use of the high-frequency induction heating device 1 (rated capacity 400 kW) reduces the rated capacity of the power supply. It can also be seen that the same heating as in the case of using a high-output power source can be performed. Also, it can be seen that the reduction in the output of the heating coil 4 due to changes in the physical properties of the workpiece W can be suppressed by switching the turns ratio of the primary side winding of the matching transformer 5 .

As described above, in the high-frequency induction heating method using the high-frequency induction heating apparatus 1 of the present invention, when heating the work W, the impedance of the work W decreases due to the change in the physical properties of the work W in the temperature range where the work W changes in physical properties. That is, by changing the number of turns of the primary side winding 5a of the matching transformer 5 of the matching section 3 by switching the electromagnetic contactor 7 according to the decrease in the load impedance, the load impedance is optimized on the primary side of the matching transformer 5. is performed. By optimizing the impedance, it is possible to optimize the primary power and ensure stable output of the heating coil 4 . Therefore, since it is possible to suppress the peak output and the decrease in output, it leads to stable power supply, which leads to lowering the rated capacity of the power panel, and the size of the power panel can be reduced. can be provided.

The high-frequency induction heating device 1 of the above embodiment includes a high-frequency power source 2 and a heating coil 4 connected to the high-frequency power source 2, and a matching section 3 between the high-frequency power source 2 and the heating coil 4. includes a matching transformer 5 , a capacitor 6 , and a plurality of electromagnetic contactors 7 as switching means for selecting the number of turns of the primary winding 5 a of the matching transformer 5 .
Further, in the high-frequency induction heating method of the above embodiment, when the high-frequency induction heating apparatus 1 is used to heat the work W, the primary The number of turns of the side winding 5a is switched to optimize the impedance on the load side as viewed from the high frequency power supply 2. FIG.
According to the high-frequency induction heating apparatus 1 and the high-frequency induction heating method configured in this manner, the impedance on the load side viewed from the high-frequency power source 2 can be optimized. On the other hand, it is possible to heat the work W in a stable state with a high power input to the work W, so that the work W can be heated with high efficiency. In addition, since it is possible to suppress the peak output and the decrease in output, it leads to a stable power supply, which leads to a reduction in the rated capacity of the power panel, and the size of the power panel can be reduced, so it can be used for space-saving equipment. can be provided.

Finally, a high-frequency induction heating system for workpieces W using the high-frequency induction heating apparatus 1 and the high-frequency induction heating method of the present invention will be described.
6A and 6B are explanatory diagrams of a high-frequency induction heating system using the high-frequency induction heating apparatus of the present invention, in which (a) is a perspective view and (b) is a side view seen from the unloading side.
The high-frequency induction heating system S includes a high-frequency induction heating device 1, an articulated manipulator M having a gripping portion M1 for gripping a workpiece W, a workpiece loading table 8 for accommodating the workpiece W before heat treatment, a heating A workpiece unloading table 9 for storing the workpiece W after processing is provided.
Here, the high-frequency induction heating device 1 has a heating coil 4 arranged therein so as to extend in the vertical direction. It is assumed that it is inserted from below into the heating coil 4 inside it via.

First, the manipulator M grips the non-heated end of the unheated workpiece W stored in the workpiece loading table 8 with the grip part M1, and moves the workpiece downward in the high-frequency induction heating apparatus 1 so that the longitudinal direction of the workpiece is Move it so that it faces the vertical direction.
Next, the workpiece W is inserted into the high-frequency induction heating device 1 from below. At this time, the heated range of the workpiece W is inserted into the heating coil 4 provided inside the high-frequency induction heating apparatus 1 .
After that, according to the high-frequency induction heating method, the workpiece W is heated to a predetermined temperature and heat-treated.
After the heating is finished, the manipulator M moves the heat-treated work W to the work unloading table 9, and the heat-treated work W is unloaded.
The work unloading table 9 may be a device itself for performing post-processes such as molding, or may be connected to a device for performing post-processes. It may be a system that transports to an apparatus for performing.

The present invention has been described above based on the illustrated examples, and the technical scope thereof is not limited thereto.
For example, the number of switching points of the switching means in the matching section is not limited as long as the impedance can be adjusted according to changes in the object to be heated. Therefore, in addition to a combination of a tap and an electromagnetic contactor that switches by setting the number of turns in advance, a mechanism such as a variable transformer that can arbitrarily change the number of turns may be used. Furthermore, the number of turns of the primary winding of the matching transformer for impedance adjustment performed in the high-frequency induction heating method may be changed any number of times. In addition, the number of turns may be switched manually, or may be automatically changed under arbitrary conditions such as elapsed time.
Also, the material and shape of the work can be arbitrarily set. However, when using a material that has the ability to change physical properties due to temperature changes, it is desirable to check the temperature at which physical properties change and the change in load impedance before and after the change in physical properties before heating with a high-frequency induction heating device.
In addition, the high-frequency induction heating equipment collects data in advance not only for changes in the physical properties of the workpiece, but also for impedance changes due to changes in the material, shape, temperature, power consumption, amount of workpiece inserted into the heating coil, etc. This can be handled by determining the number of turns of the primary side winding of the matching transformer and switching the number of turns during induction heating.
Further, the high-frequency induction heating system may include the high-frequency induction heating device of the present invention, and any robot related to inserting a workpiece into the high-frequency induction heating device is not limited to the above-described articulated manipulator, and various mechanisms may be used. of robots can be adopted. Furthermore, the workpiece may be inserted into the high-frequency induction heating device using, for example, a cylinder without using the robot. In addition, in the above description, the direction in which the high-frequency induction heating device is installed is the direction in which the work is inserted from below. can be set arbitrarily. In addition, sensors such as a thermometer, a power meter, etc., which can be interlocked with the switching of the number of windings of the matching transformer, may be mounted.

1 High-frequency induction heating device 2 High-frequency power supply 3 Matching part 4 Heating coil 5 Matching transformer 5a Primary winding 5b Secondary winding 7 ..Electromagnetic contactor (switching means), W..Work (object to be heated), _N1..Number of turns of primary winding, _N2..Number of turns of secondary winding.

The present invention relates to a high-frequency induction heating system and a high-frequency induction heating method using a high-frequency induction heating apparatus having a matching section capable of optimizing the load impedance viewed from a high-frequency power supply.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a high-frequency induction heating system and a high-frequency induction heating method using a high-frequency induction heating apparatus having a matching section capable of optimizing the load impedance viewed from the high-frequency power source.

In order to achieve the above object, the invention according to claim 1 provides a high frequency induction heating apparatus having a high frequency power supply capable of outputting at an arbitrary frequency and a heating coil connected to the high frequency power supply , and a heating object holding an object to be heated. A high-frequency induction heating system comprising a manipulator having a gripping portion for performing a high-frequency induction heating, a work loading table for storing an object to be heated before heat treatment, and a work unloading table for storing an object to be heated after heat treatment , The induction heating device comprises a matching section between the high-frequency power source and the heating coil, the matching section including a matching transformer, a capacitor, and switching means for arbitrarily selecting the number of turns of the primary winding of the matching transformer. The heating coil is arranged to extend vertically in the high-frequency induction heating device, and the manipulator grips one end of the object to be heated accommodated in the work loading table, The number of turns of the primary winding of the matching transformer is switched according to changes in the object to be heated as the object to be heated is heated while the heating coil is inserted from one end of the heating coil and heat treatment is performed by high-frequency induction heating, It is characterized by optimizing the impedance on the load side as seen from the high frequency power supply .
The invention according to claim 2 has a high-frequency power supply capable of outputting at an arbitrary frequency, and a heating coil connected to the high-frequency power supply. and a switching means for arbitrarily selecting the number of turns of the primary winding of the matching transformer, wherein the heating coil is arranged to extend vertically in the high frequency induction heating device. Equipped with a heating device, a manipulator having a gripping part for gripping an object to be heated, a work loading table for storing the object to be heated before heat treatment, and a work unloading table for storing the object to be heated after heat treatment A high-frequency induction heating method for heating an object to be heated using a high-frequency induction heating system , wherein a manipulator grips one end of the object to be heated accommodated in a work loading table and holds the other end of the object to be heated. is inserted from one end of the heating coil, and the number of turns of the primary winding of the matching transformer is switched according to changes in the object to be heated accompanying the heating of the object during the heat treatment by high-frequency induction heating. is performed to optimize the impedance on the load side as viewed from the high-frequency power supply.

Claims (2)

A high-frequency induction heating device comprising a high-frequency power supply capable of outputting at an arbitrary frequency and a heating coil connected to the high-frequency power supply,
A matching section is provided between the high-frequency power source and the heating coil,
A high-frequency induction heating apparatus, wherein the matching unit includes a matching transformer, a capacitor, and switching means for arbitrarily selecting the number of turns of the primary winding of the matching transformer. a high-frequency power supply capable of outputting at any frequency; a heating coil connected to the high-frequency power supply; a matching transformer provided between the high-frequency power supply and the heating coil; a capacitor; and a primary winding of the matching transformer. A high-frequency induction heating method for heating an object to be heated by using a high-frequency induction heating device comprising a matching unit including switching means for arbitrarily selecting the number of turns of a wire,
The number of turns of the primary side winding of the matching transformer is switched according to the change in the object to be heated accompanying the heating of the object to be heated, and the impedance on the load side viewed from the high frequency power supply is optimized. A high-frequency induction heating method characterized by:

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