WO2025154187A1 - Induction heating device - Google Patents

Abstract

An induction heating device (10) comprises: an induction coil (1) that includes at least two coils; a high-frequency power supply (2) that supplies currents of mutually different phases to each of the at least two coils; and a conveyance device (3) that conveys a heating subject (4). When a current is supplied to the induction coil (1), a shifting magnetic field is formed on the surface of the heating subject (4), and the shifting direction (Y) of the shifting magnetic field is different from the conveyance direction (X) of the heating subject (4).

Description

induction heating device

This disclosure relates to an induction heating device.

Drying furnaces are used to heat the object to be heated (hereinafter also referred to as the workpiece) in drying processes such as drying paint on metal plates and drying coatings on battery electrodes. One of the drying methods used in drying furnaces is the induction heating (IH) method. Induction heating devices that use induction heating for drying pass high-frequency current through a coil placed close to the workpiece, inducing eddy currents inside the workpiece, and heat the workpiece with Joule heat from the eddy current. The induction heating device disclosed in Patent Document 1 has multiple coils of different shapes placed at different positions in the direction in which the workpiece is transported. This allows heating power to be applied to different points as the workpiece is transported.

Japanese Unexamined Patent Publication No. 63-175374

However, with conventional technology, the distribution of heating power applied by each coil is uneven, making it difficult to achieve a sufficiently uniform temperature distribution in the workpiece.

The objective of this disclosure is to provide an induction heating device that can heat an object so that the temperature distribution is uniform.

An induction heating device according to one aspect of the present disclosure includes:
an induction coil including at least two coils;
A high frequency power supply that supplies currents of different phases to each of the at least two coils;
A conveying device that conveys the object to be heated,
When the current is supplied to the induction coil, a moving magnetic field is generated on the surface of the object to be heated,
The moving direction of the traveling magnetic field is different from the transport direction of the object to be heated.

The present disclosure provides an induction heating device that can heat an object so that the temperature distribution is uniform.

1 is a diagram illustrating a schematic configuration of an induction heating device according to a first embodiment. 4 is a cross-sectional view showing an induction coil and a workpiece as viewed from the conveying direction. FIG. 1 is a diagram showing a schematic distribution of eddy currents generated in a workpiece by a current flowing through an induction coil; FIG. 4 is a diagram showing a schematic diagram of a time-averaged distribution of heating power applied to a workpiece. 11 is a cross-sectional view showing a schematic cross section of an induction heating device (specifically, an induction coil and a workpiece) according to a second embodiment, the cross section being perpendicular to the workpiece transport direction. FIG. 11 is a cross-sectional view showing a schematic cross section of an induction heating device (specifically, an induction coil and a workpiece) according to embodiment 3, the cross section being perpendicular to the workpiece transport direction. FIG. 11 is a cross-sectional view showing a schematic cross section of an induction heating device (specifically, an induction coil and a workpiece) according to embodiment 4, perpendicular to the workpiece transport direction. FIG.

The induction heating device according to the embodiment will be described in detail below with reference to the drawings.

Embodiment 1.
FIG. 1 is a diagram illustrating a schematic configuration of an induction heating device 10 according to a first embodiment.
The induction heating device 10 includes an induction coil 1 , a high-frequency power source 2 , a conveying device 3 , a temperature sensor 5 , and a controller 6 .

The induction coil 1 is positioned at a predetermined distance above the workpiece 4. The workpiece 4 is the object to be heated in the induction heating device 10. The workpiece 4 is, for example, a flat workpiece or a thin foil-like workpiece.

The conveying device 3 conveys the workpiece 4 at a predetermined speed in the conveying direction X. The conveying direction X is also referred to as the "first direction."

Induction coil 1 includes at least two coils. In the example shown in FIG. 1, induction coil 1 is composed of a first coil 1A, a second coil 1B, and a third coil 1C. First coil 1A, second coil 1B, and third coil 1C partially overlap each other. A current of a predetermined frequency is supplied from high-frequency power source 2 to each of first coil 1A, second coil 1B, and third coil 1C.

The temperature sensor 5 measures the temperature of the measurement area 7, which is the measurement target on the workpiece 4. The measurement results measured by the temperature sensor 5 are transmitted to the controller 6, which acquires the measurement results. Specifically, a sensor signal S1 indicating the measurement results is transmitted from the temperature sensor 5 to the controller 6. The controller 6 receives the sensor signal S1 from the temperature sensor 5. The measurement results are, for example, the temperature of a part of the measurement area 7 or the temperature distribution of the measurement area 7.

The controller 6 controls the current supplied from the high frequency power supply 2 to the first coil 1A, the second coil 1B, and the third coil 1C. Specifically, the controller 6 receives a sensor signal S1 obtained from the temperature sensor 5, and transmits a control signal S2 to the high frequency power supply 2 based on the sensor signal S1, thereby controlling the high frequency power supply 2.

For example, the controller 6 controls the high-frequency power supply 2 to change the phase of the current supplied to at least one of the at least two coils in accordance with the measurement results.

FIG. 2 is a cross-sectional view showing a schematic view of the induction coil 1 and the workpiece 4 as viewed from the conveying direction X. As shown in FIG.
The induction coil 1 is disposed at a predetermined distance d from the workpiece 4. In the example shown in FIG. 2, the distance d is the shortest distance from the workpiece 4 to each coil. The first coil 1A, the second coil 1B, and the third coil 1C are offset from each other in the width direction Y of the workpiece 4. In the cross section shown in FIG. 2, a part of the first coil 1A is disposed adjacent to a part of the third coil 1C, and the second coil 1B is disposed across the first coil 1A and the third coil 1C. The winding density of each coil may be uniform or different.

The high frequency power supply 2 supplies currents of different phases to the at least two coils.
When the high frequency power supply 2 supplies current to the first coil 1A, the second coil 1B, and the third coil 1C, the current supplied to the second coil 1B has a phase lead of 90 degrees or a phase lag of 90 degrees with respect to the phase of the current supplied to the first coil 1A and the phase of the current supplied to the third coil 1C. For example, with respect to the phase of the first coil 1A, a current with a phase lag of 90 degrees is supplied to the second coil 1B, and a current with a phase lag of 180 degrees is supplied to the third coil 1C. The amplitude of the current supplied to each coil may be the same, or currents with different amplitudes may be supplied to each coil. When the amplitude of the current supplied to each coil is the same, each current is a quadrature two-phase AC current.

FIG. 3 is a diagram showing a schematic distribution of eddy currents generated in the workpiece 4 by the current flowing through the induction coil 1. As shown in FIG.
The phase of the current flowing through the second coil 1B lags behind the phase of the current flowing through the first coil 1A by 90 degrees, and the phase of the current flowing through the third coil 1C lags behind the phase of the current flowing through the first coil 1A by 180 degrees. Therefore, if K is the amplitude of the current, f is the frequency, and t is time, the current flowing through the first coil 1A can be described as Ia = Kcos(2πft), the current flowing through the second coil 1B can be described as Ib = Kcos(2πft-π/2), and the current flowing through the third coil 1C can be described as Ic = Kcos(2πft-π).

When a current is supplied to the induction coil 1, a moving magnetic field is formed on the surface of the workpiece 4. Specifically, when currents of different phases are passed through the first coil 1A, the second coil 1B, and the third coil 1C, a moving magnetic field that progresses in the width direction Y of the workpiece 4 is formed on the surface of the workpiece 4. The width direction Y of the workpiece 4 is a direction different from the transport direction X of the workpiece 4. In other words, the movement direction of the moving magnetic field is a direction different from the transport direction X of the workpiece 4. The width direction Y is also referred to as the "moving direction Y" or "second direction".

In the example shown in FIG. 1, the direction of movement of the moving magnetic field is perpendicular to the conveying direction X.

When the phase of the current in the first coil 1A is 0 degrees, an eddy current distribution is generated in the workpiece 4 as shown by the solid line in Figure 3. As time passes, when the phase of the current flowing in the first coil 1A becomes 90 degrees, the distribution of eddy currents generated in the workpiece 4 becomes the distribution shown by the dashed line in Figure 3. In this way, over time, the distribution of eddy currents becomes a traveling wave that moves in the width direction Y of the workpiece 4.

The phase velocity of the moving magnetic field is faster than the transport speed of the workpiece 4. The transport speed of the workpiece 4 is the speed at which the transport device 3 transports the workpiece 4. Since the frequency f of the current supplied to each coil from the high frequency power source 2 is typically about 1 kHz to 20 MHz, the phase velocity of this traveling wave is sufficiently faster than the transport speed. Therefore, the distribution of the magnitude of the eddy currents, when averaged over time, is uniform in the width direction Y, which is the direction of the traveling wave.

FIG. 4 is a diagram showing a schematic diagram of the time-averaged distribution of the heating power applied to the workpiece 4. As shown in FIG.
As described above, the distribution of eddy currents becomes a traveling wave, which repeatedly moves at high speed in the width direction Y, thereby realizing a uniform distribution of heating power in the width direction Y on a time average, as shown by the solid line in Fig. 4. Also, the distribution of heating power can be changed by changing the phase difference between the first coil 1A and the second coil 1B.

The dashed line in Figure 4 shows a schematic diagram of the heating power distribution when the phase difference between the first coil 1A and the second coil 1B is 45 degrees. Compared to when the phase difference is 90 degrees, the heating power distribution is larger on the first coil 1A side and smaller on the third coil 1C side. On the other hand, when the phase difference between the first coil 1A and the second coil 1B is 135 degrees, the heating power distribution is smaller on the first coil 1A side and larger on the third coil 1C side.

In this way, by controlling the phase of the current in the second coil 1B, it is possible to control the distribution of the heating power. The controller 6 controls the phase of the current in the second coil 1B based on the information (e.g., temperature distribution) of the measurement area 7 measured by the temperature sensor 5, and by controlling the distribution of the heating power, the uniformity of the temperature distribution of the workpiece 4 is maintained.

As described above, by passing currents of different phases through the first coil 1A, second coil 1B, and third coil 1C that make up the induction coil 1, traveling waves of a moving magnetic field and eddy current distribution that progress in the width direction Y of the workpiece 4 are formed, and the workpiece 4 can be heated uniformly in the width direction Y. Furthermore, by the controller 6 controlling the phase of the second coil 1B based on information about the workpiece 4 measured by the temperature sensor 5 (e.g., temperature distribution), it is possible to maintain the uniformity of the temperature distribution of the workpiece 4.

As described above, according to the first embodiment, it is possible to provide an induction heating device 10 capable of heating the workpiece 4 so that the temperature distribution of the workpiece 4 is uniform.

Embodiment 2
Fig. 5 is a cross-sectional view that shows a schematic cross section of the induction heating device 10 (specifically, the induction coil 1 and the workpiece 4) according to the second embodiment, perpendicular to the conveying direction X of the workpiece 4. In the example shown in Fig. 5, the cross section perpendicular to the conveying direction X of the workpiece 4 is also a cross section along the moving direction Y of the moving magnetic field.

In the second embodiment, the arrangement of each coil of the induction coil 1 differs from that of the first embodiment. In the induction coil 1, the first coil 1A and the third coil 1C are adjacent to each other, and the second coil 1B is arranged so as to straddle a part of the first coil 1A and a part of the third coil 1C. The winding densities of these coils may be uniform or may be different.

The current supplied to the second coil 1B has a phase lead or lag of 90 degrees based on the phase of the current supplied to the first coil 1A and the phase of the current supplied to the third coil 1C. For example, a current with a phase lag of 90 degrees based on the phase of the first coil 1A is supplied to the second coil 1B, and a current with a phase lag of 180 degrees based on the phase of the first coil 1A is supplied to the third coil 1C. The amplitude of the current supplied to each coil may be the same, or currents of different amplitudes may be supplied to each coil. When the amplitude of the current supplied to each coil is the same, the current is a quadrature two-phase AC current.

Each coil of the induction coil 1 is disposed away from the workpiece 4. The distance from the first coil 1A to the workpiece 4, the distance from the second coil 1B to the workpiece 4, and the distance from the third coil 1C to the workpiece 4 are different from one another. In the example shown in FIG. 5, in a cross section of the induction heating device 10 perpendicular to the conveying direction X of the workpiece 4, when the distance between the end of the induction coil 1 (the first coil 1A in FIG. 5) in the moving direction Y of the moving magnetic field and the workpiece 4 is d1, the distance between the center of the induction coil 1 (the boundary between the first coil 1A and the third coil 1C in FIG. 5) in the moving direction Y and the workpiece 4 is d3, and the distance between the intermediate portion (the second coil 1B in FIG. 5) between the center of the induction coil 1 in the moving direction Y and the end of the induction coil 1 in the moving direction Y and the workpiece 4 is d2, the relationship between the distances d1, d2, and d3 satisfies d1>d2 and d3>d2.

In the example shown in FIG. 5, distance d1 is the shortest distance between the end of induction coil 1 (first coil 1A in FIG. 5) and workpiece 4, distance d2 is the shortest distance between the middle part of induction coil 1 and the end (second coil 1B in FIG. 5) and workpiece 4, and distance d3 is the shortest distance between the center of induction coil 1 (the boundary between first coil 1A and third coil 1C in FIG. 5) and workpiece 4.

This makes it possible to achieve a more uniform distribution of heating power by weakening the eddy currents at the ends and center of the workpiece 4, where eddy currents flow easily, and strengthening the eddy currents in the middle area, where eddy currents do not flow easily.

Embodiment 3
Fig. 6 is a cross-sectional view that shows a schematic cross section of the induction heating device 10 (specifically, the induction coil 1 and the workpiece 4) according to the third embodiment, perpendicular to the conveying direction X of the workpiece 4. In the example shown in Fig. 6, the cross section perpendicular to the conveying direction X of the workpiece 4 is also a cross section along the moving direction Y of the moving magnetic field.

In embodiment 3, the arrangement of each coil of the induction coil 1 differs from embodiment 1. The first coil 1A, second coil 1B, and third coil 1C are arranged in the width direction Y of the workpiece 4 in the order of first coil 1A, second coil 1B, and third coil 1C. The first coil 1A is arranged so as to straddle a part of the second coil 1B and a part of the third coil 1C. The second coil 1B is arranged so as to straddle a part of the first coil 1A and a part of the third coil 1C. The third coil 1C is arranged so as to straddle a part of the first coil 1A and a part of the second coil 1B.

The current supplied to each coil of the induction coil 1 is a three-phase AC current. The current supplied to the second coil 1B has a phase lead or lag of 120 degrees based on the phase of the current supplied to the first coil 1A and the phase of the current supplied to the third coil 1C. For example, a current with a phase lag of 120 degrees based on the phase of the first coil 1A is supplied to the second coil 1B, and a current with a phase lead of 120 degrees based on the phase of the first coil 1A is supplied to the third coil 1C. The amplitude of the current supplied to each coil may be the same, or currents of different amplitudes may be supplied to each coil. By supplying three-phase AC current to coils that are offset from each other in the width direction Y, a moving magnetic field that moves in the width direction Y is formed.

In the example shown in FIG. 6, in a cross section of the induction heating device 10 perpendicular to the transport direction X of the workpiece 4, when the distance between the end of the induction coil 1 (first coil 1A and third coil 1C in FIG. 6) in the width direction Y and the workpiece 4 is d1, the distance between the center of the induction coil 1 (the boundary between the first coil 1A and the third coil 1C in FIG. 6) in the width direction Y and the workpiece 4 is d3, and the distance between the intermediate portion between the center of the induction coil 1 in the width direction Y and the end of the induction coil 1 in the width direction Y (second coil 1B in FIG. 6) and the workpiece 4 is d2, the relationship between the distances d1, d2, and d3 satisfies d1>d2 and d3>d2.

In the example shown in FIG. 6, distance d1 is the shortest distance between the end of induction coil 1 (first coil 1A and third coil 1C in FIG. 6) and workpiece 4, distance d2 is the shortest distance between the intermediate portion between the center of induction coil 1 and the end of induction coil 1 in width direction Y (second coil 1B in FIG. 6) and workpiece 4, and distance d3 is the shortest distance between the center of induction coil 1 (the boundary between first coil 1A and third coil 1C in FIG. 6) and workpiece 4.

In a cross section of the induction heating device 10 perpendicular to the transport direction X of the workpiece 4, the winding density of the central part of the induction coil 1 in the moving direction Y of the moving magnetic field (in FIG. 6, the part where the first coil 1A and the third coil 1C face each other) is smaller than the winding density of the intermediate part (in FIG. 6, the second coil 1B) between the central part of the induction coil 1 in the moving direction Y of the moving magnetic field and the end of the induction coil 1 in the moving direction Y of the moving magnetic field.

In the example shown in FIG. 6, the winding density of the first coil 1A and the third coil 1C is smaller than the winding density of the second coil 1B. This weakens the eddy currents at the ends and center of the workpiece 4, where eddy currents tend to flow, and strengthens the eddy currents in the middle portion (second coil 1B in FIG. 6), where eddy currents tend not to flow, thereby achieving a more uniform distribution of heating power.

According to the third embodiment, a uniform distribution of heating power can be achieved by using a moving magnetic field using three-phase AC.

Embodiment 4
Fig. 7 is a cross-sectional view that shows a schematic cross section of the induction heating device 10 (specifically, the induction coil 1 and the workpiece 4) according to the fourth embodiment, perpendicular to the transport direction X of the workpiece 4. In the example shown in Fig. 7, the cross section perpendicular to the transport direction X of the workpiece 4 is also a cross section along the movement direction Y of the moving magnetic field.

In embodiment 4, the arrangement of each coil of induction coil 1 differs from embodiment 1. As in each of the above embodiments, induction coil 1 has a first coil 1A, a second coil 1B, and a third coil 1C. In the moving direction Y of the moving magnetic field, the end of first coil 1A and the end of third coil 1C face each other. When viewed in a direction perpendicular to the moving direction Y of the moving magnetic field and the transport direction X, the center of second coil 1B in the moving direction Y of the moving magnetic field is located halfway between the center of first coil 1A in the moving direction Y of the moving magnetic field and the center of third coil 1C in the moving direction Y of the moving magnetic field.

In the example shown in FIG. 7, the first coil 1A and the third coil 1C are adjacent to each other in the moving direction Y of the moving magnetic field, and the second coil 1B is disposed on the opposite side of the workpiece 4 to the first coil 1A and the third coil 1C. The winding densities of these coils may be uniform or may be different.

The current supplied to the second coil 1B has a phase lead or lag of 90 degrees based on the phase of the current supplied to the first coil 1A and the phase of the current supplied to the third coil 1C. For example, a current with a phase lag of 90 degrees based on the phase of the first coil 1A is supplied to the second coil 1B, and a current with a phase lag of 180 degrees based on the phase of the first coil 1A is supplied to the third coil 1C. The amplitude of the current supplied to each coil may be the same, or currents of different amplitudes may be supplied to each coil. When the amplitude of the current supplied to each coil is the same, the current is a quadrature two-phase AC current.

In this way, a moving magnetic field is formed in the same way as in embodiment 1, the eddy current distribution becomes a traveling wave, and a uniform distribution of heating power can be generated as a time average. Furthermore, since the second coil 1B does not have any intersections with other coils, the induction coil 1 can be easily positioned.

The features of each embodiment described above can be combined with each other, and each embodiment allows for modification of components or omission of components.

Various aspects of the present disclosure are summarized below as appendices.
(Appendix 1)
an induction coil including at least two coils;
A high frequency power supply that supplies currents of different phases to each of the at least two coils;
A conveying device that conveys the object to be heated,
When the current is supplied to the induction coil, a moving magnetic field is generated on the surface of the object to be heated,
The induction heating device, characterized in that a moving direction of the traveling magnetic field is different from a transport direction of the object to be heated.
(Appendix 2)
2. The induction heating device according to claim 1, wherein the moving direction of the moving magnetic field is perpendicular to the conveying direction.
(Appendix 3)
3. The induction heating device according to claim 1, wherein a phase speed of the moving magnetic field is faster than a transport speed of the object to be heated.
(Appendix 4)
A temperature sensor that measures the temperature of the object to be heated;
and a controller for acquiring a measurement result measured by the temperature sensor,
The induction heating device according to any one of appendix 1 to 3, wherein the controller controls the high-frequency power supply so as to change a phase of a current supplied to at least one of the at least two coils in accordance with a result of the measurement.
(Appendix 5)
In a cross section of the induction heating device perpendicular to the transport direction, when a distance between an end of the induction coil in the movement direction and the object to be heated is d1, a distance between a center of the induction coil in the movement direction and the object to be heated is d3, and a distance between an intermediate portion between the center of the induction coil in the movement direction and the end of the induction coil in the movement direction and the object to be heated is d2,
The induction heating device according to any one of claims 1 to 4, wherein d1>d2 and d3>d2 are satisfied.
(Appendix 6)
6. The induction heating device according to claim 1, wherein in a cross section of the induction heating device perpendicular to the transport direction of the object to be heated, a winding density of a central portion of the induction coil in the movement direction is smaller than a winding density of an intermediate portion between the central portion of the induction coil and an end of the induction coil in the movement direction.
(Appendix 7)
the induction coil includes a first coil, a second coil, and a third coil;
In the moving direction, an end of the first coil and an end of the third coil face each other,
The induction heating device according to any one of claims 1 to 6, characterized in that, when viewed in a direction perpendicular to the movement direction and the conveying direction, a center of the second coil in the movement direction is located midway between a center of the first coil in the movement direction and a center of the third coil in the movement direction.
(Appendix 8)
The induction heating device described in Appendix 7, characterized in that the second coil is arranged on the opposite side of the object to be heated to the first coil and the third coil.
(Appendix 9)
9. The induction heating device according to claim 7 or 8, wherein the current supplied to the second coil has a phase lead of 90 degrees or a phase lag of 90 degrees based on the phase of the current supplied to the first coil and the phase of the current supplied to the third coil.
(Appendix 10)
9. The induction heating device according to claim 7 or 8, wherein the current supplied to the second coil has a phase lead of 120 degrees or a phase lag of 120 degrees based on the phase of the current supplied to the first coil and the phase of the current supplied to the third coil.

1 Induction coil, 1A First coil, 1B Second coil, 1C Third coil, 2 High frequency power source, 3 Conveyor, 4 Workpiece (object to be heated), 5 Temperature sensor, 6 Controller, 7 Measurement area, 10 Induction heating device, S1 Sensor signal, S2 Control signal, X Conveyor direction, Y Width direction (direction of movement of moving magnetic field)

Claims (10)

an induction coil including at least two coils;
A high frequency power supply that supplies currents of different phases to each of the at least two coils;
A conveying device that conveys the object to be heated,
When the current is supplied to the induction coil, a moving magnetic field is generated on the surface of the object to be heated,
The induction heating device, characterized in that a moving direction of the traveling magnetic field is different from a transport direction of the object to be heated. The induction heating device according to claim 1, characterized in that the moving direction of the moving magnetic field is perpendicular to the conveying direction. The induction heating device according to claim 1 or 2, characterized in that the phase speed of the moving magnetic field is faster than the transport speed of the object to be heated. A temperature sensor that measures the temperature of the object to be heated;
and a controller for acquiring a measurement result measured by the temperature sensor,
4. The induction heating device according to claim 1, wherein the controller controls the high frequency power supply so as to change a phase of a current supplied to at least one of the at least two coils in accordance with a result of the measurement. In a cross section of the induction heating device perpendicular to the transport direction, when a distance between an end of the induction coil in the movement direction and the object to be heated is d1, a distance between a center of the induction coil in the movement direction and the object to be heated is d3, and a distance between an intermediate portion between the center of the induction coil in the movement direction and the end of the induction coil in the movement direction and the object to be heated is d2,
The induction heating device according to claim 1 , wherein d1>d2 and d3>d2 are satisfied. 6. The induction heating device according to claim 1, wherein in a cross section of the induction heating device perpendicular to the transport direction of the object to be heated, a winding density in a central portion of the induction coil in the movement direction is smaller than a winding density in an intermediate portion between the central portion of the induction coil and an end portion of the induction coil in the movement direction. the induction coil includes a first coil, a second coil, and a third coil;
In the moving direction, an end of the first coil and an end of the third coil face each other,
7. The induction heating device according to claim 1, wherein, when viewed in a direction perpendicular to the moving direction and the conveying direction, a center of the second coil in the moving direction is located midway between a center of the first coil in the moving direction and a center of the third coil in the moving direction. The induction heating device according to claim 7, characterized in that the second coil is disposed on the opposite side of the object to be heated from the first coil and the third coil. An induction heating device according to claim 7 or 8, characterized in that the current supplied to the second coil has a 90 degree lead phase or a 90 degree lag phase based on the phase of the current supplied to the first coil and the phase of the current supplied to the third coil. An induction heating device according to claim 7 or 8, characterized in that the current supplied to the second coil has a phase lead of 120 degrees or a phase lag of 120 degrees based on the phase of the current supplied to the first coil and the phase of the current supplied to the third coil.