Title of the invention: Induction heating method for metal strips and induction heating equipment thereof Technical field [0001] 　The present invention relates to an induction heating method for a metal strip traveling in the longitudinal direction and an induction heating facility thereof. In particular, the present invention provides an induction heating method for a metal strip that can uniformly heat the metal strip by suppressing overheating at the end in the width direction and can quickly respond to changes in the position of the strip due to meandering or the like. Regarding the induction heating equipment. Background technology [0002] 　Induction heating is a heating method that uses the principle of electromagnetic induction to generate an eddy current in an object to be heated and heats the object with Joule heat, and is widely used because of its low heat loss and high efficiency. .. There are roughly two methods for induction heating of metal strips. One of them is to pass a high-frequency current through an induction coil that surrounds the width direction of the metal strip to allow magnetic flux to penetrate in the longitudinal direction of the metal strip, and this magnetic flux is used within the width cross section of the metal strip. This is an LF (Longitudinal Flux induction heating) method (hereinafter referred to as LF method) in which an induced current that circulates around the metal strip is heated. In the other one, a metal strip is placed between the induction coils (good conductors) around which the primary coil is wound, and the magnetic flux generated by passing a current through the primary coil is passed through the plate surface of the metal strip. This is a TF (Transverse Flux induction heating) method (hereinafter referred to as TF method) in which an induced current is generated on the plate surface of the metal strip to heat the metal strip. [0003] 　Generally, in the LF method induction heating, the relationship between the current penetration depth δ and the current frequency f (δ (mm) = 5.03 × 10 5 √ (ρ / μr ・ f), ρ (Ωm): resistivity, μr : Specific magnetic permeability · f: Frequency (Hz)), there are some problems. For example, when the thickness of the metal strip is thin, there is a problem that an induced current is not generated unless the frequency f of the current is increased. Further, in the case of a non-magnetic metal strip or a metal strip that is magnetic at room temperature exceeding the Curie temperature, the current permeation depth δ becomes deep, so that an induced current does not occur if the metal strip is thin. There is. On the other hand, in the TF method induction heating, the metal strip can be heated regardless of the plate thickness and regardless of whether it is magnetic or non-magnetic. However, in the TF method, if the opposing induction coils are not close to each other, the heating efficiency is low, and overheating occurs at the end of the metal strip, making uniform heating in the plate width direction difficult. [0004] 　Based on the advantages and disadvantages of such an induction heating method, Patent Document 1 discloses a technique related to the TF method as a technique capable of controlling the heating temperature distribution over the entire width including the edge of the metal strip regardless of whether it is magnetic or non-magnetic. Patent Document 2 describes a technique having the characteristics of both the LF method and the TF method. [0005] 　For example, Patent Document 1 describes a technique for disposing a plurality of mutually independent magnetic cores (magnetic rods) on the back surface of a TF type induction coil. As a result, the position of the magnetic core can be changed according to the width of the metal strip, and the temperature uniformity in the width direction of the metal strip can be obtained by using the electromagnetic shielding plate (screen) in combination. [0006] 　In Patent Document 2, instead of winding a large number of induction coils around the width direction of the metal strip as in the LF method, one winding of the induction coil is formed on the front surface and the back surface of the metal strip, respectively. A technique for providing two or more sets of induction coils for rotating in a direction shifted in position is described. As a result, an induced current that orbits in the surface of the metal strip as in the TF method is generated. Further, in Patent Document 2, the shape of the induction coil is made to be inclined toward the end in the width direction, a magnetic core is used in combination, the induction coil is moved in the width direction, and the like. A technique for avoiding overheating of the widthwise end of the strip is described. [0007] 　Further, for example, Patent Document 3 describes a technique for heating a traveling metal strip by utilizing such induction heating. [0008] 　In Patent Document 3, in order to regulate the path line and control meandering, an induction heating device (inductor) is used in the traveling direction of a metal strip (strip-shaped metal material) on which a non-magnetic roll having an insulating surface is traveling. The technique of arranging the front and back is described. As a result, even a magnetic material can be stably heated without being attracted to the inductor, and meandering can be controlled to prevent an increase in the heating temperature deviation. [0009] 　In the technique described in Patent Document 3 above, the metal strip is wound based on the position in the width direction of the metal strip detected by using the position detection device provided on the upstream side or the downstream side of the induction heating device. The roll is moving. As a result, the positional relationship between the metal strip and the induction heating device in the width direction is controlled within a certain range. [0010] 　In addition, other techniques for controlling the positional relationship between the metal strip and the induction heating device in the width direction with respect to the meandering of the metal plate are described in, for example, Patent Documents 4 to 6. [0011] 　Patent Document 4 describes that the center line in the width direction of the metal strip (strip) is detected, and the amount of deviation from the position where the center line should be located is detected. Further, Patent Document 4 describes a technique for controlling the position of an induction heating device (electromagnet device) so as to follow the deviation amount according to the deviation amount of the center line or the edge of the metal strip. [0012] 　Further, Patent Document 5 describes that an induction heating device (conductor coil) facing a metal strip (metal plate) is horizontally reciprocated in the width direction of the metal plate with a predetermined period and amplitude. For example, Patent Document 5 describes a technique for following and moving the amplitude center of a conductor coil to a metal plate center line whose position fluctuates in the plate width direction during continuous traveling. [0013] 　Further, in Patent Document 6, the coil of the induction heating device (induction heating coil device) follows the movement of the flat plate in the width direction based on the detection signal of the detector that detects the movement amount of the metal strip (flat plate) in the width direction. Techniques for controlling to do so are described. Prior art literature Patent documents [0014] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-008838 Patent Document 2: Japanese Patent Application Laid-Open No. 2008-288200 Patent Document 3: Japanese Patent Application Laid-Open No. 11-251048 Patent Document 4: Japanese Patent Application Laid-Open No. 2001-0068666 Patent Document 5: Special Fairness No. 6-037676 Patent Document 6: Jikken No. 6-022950 Outline of the invention Problems to be solved by the invention [0015] 　Here, in Patent Document 3, although the position detection device is provided on the upstream side or the downstream side of the induction heating device, the position detection device is substantially located on the upstream side of the induction heating device as shown in FIGS. 1 and 4. It only discloses the examples that have been placed. Therefore, for example, due to the high temperature metal fume, there is a problem when the position detection device must be arranged on the downstream side of the induction heating device, such as the outlet side of the hot dip galvanizing device where it is difficult to install the sensors. No solution is offered. That is, when the position detection device is arranged on the downstream side of the induction heating device, only the position in the width direction after the metal strip has passed through the induction heating device is known, so that the metal strip and the induction heating device when passing through the induction heating device are known. It is not always easy to properly control the positional relationship with and in the width direction. [0016] 　On the other hand, when the induction heating method of the metal strip is the TF method described in Patent Document 1 or the induction heating method described in Patent Document 2, the metal strip and the induction heating device are used. It is required to control the positional relationship in the width direction of the above with high accuracy. This is because these induction heating methods (excluding the induction heating method using a solenoid coil) are sensitive to the accuracy of the temperature at the end of the metal strip in the width direction and require highly accurate control. Therefore, even when the position detection device is arranged on the upstream side of the induction heating device, the metal strip when passing through the induction heating device due to the distance between the position detection device and the induction heating device It is not always easy to control the positional relationship in the width direction with the induction heating device with sufficient accuracy. [0017] 　Further, based on the position of the metal strip detected by the position detection device described in Patent Documents 3 to 6, the positional relationship between the metal strip and the induction heating device is controlled by using general PID control. That is not always easy. In such control, various factors that can affect the meandering of the metal strip (material of the metal strip, temperature distribution, tension distribution, shape of the metal strip (plate thickness, plate width, presence / absence of plate joint, etc.)) When a complicated meandering occurs due to the above, it is difficult to deal with the complicated meandering by mere tracking based on the detection result as described in Patent Documents 3 to 6. [0018] 　Therefore, in the present invention, when inducing and heating a metal strip that is continuously conveyed, it is possible to control the positional relationship between the induction heating apparatus and the metal strip with high accuracy while minimizing restrictions on the device arrangement. One of the purposes is to provide a new and improved induction heating method for metal strips and an induction heating facility thereof. Means to solve problems [0019] 　According to a certain aspect of the present invention, it is an induced heating method of a metal strip, which heats a metal strip continuously transported by using an induced heating device arranged at a first position on a transport line. The step of detecting the amount of displacement of the widthwise center line of the metal strip from the predetermined reference line at the second position different from the first position on the transport line, and the function representing the time-series change of the amount of displacement Based on the step of calculating the estimated displacement of the widthwise centerline of the metal strip at the first position by extrapolating the displacement temporally and spatially, and based on the estimated displacement, the metal strip. A method for inducing heating of a metal strip is provided, which comprises a step of controlling the relative positional relationship between the induction heating device and the metal strip in the width direction of the metal strip. 　In the above configuration, the displacement amount of the width direction center line of the metal strip from the transport line width direction center line is extrapolated temporally and spatially, and the position where the displacement amount is detected is downstream of the induction heating device. The estimated displacement amount of the widthwise center line of the induction heating device can be calculated in the same manner in both the case of the side and the case of the upstream side. Therefore, the device for detecting the displacement amount may be arranged on either the upstream side or the downstream side of the induction heating device, and the constraint on the device arrangement is minimized in that respect. Further, by using the estimated displacement amount at the position of the induction heating device, the positional relationship between the induction heating device and the metal strip can be controlled with high accuracy. [0020] 　In the above-mentioned induction heating method for metal strips, the second position may be located on the downstream side of the first position. [0021] 　In the above-mentioned induction heating method for metal strips, the second position may be located upstream of the first position. [0022] 　In the above-mentioned induction heating method for the metal strip, the steps for detecting the displacement are the step for measuring the temperature distribution in the range including at least one end in the width direction of the metal strip at the second position, and the temperature distribution. It may include a step of converting the position of the widthwise end of the metal strip appearing as a temperature drop into a displacement amount. [0023] 　In the above-mentioned induction heating method for the metal strip, the steps for calculating the estimated displacement amount are the step of converting the time-series change of the displacement amount into a function, and the transport speed of the metal strip, the first position and the second position. It may include the step of calculating the estimated displacement at the first time based on the distance between and the function and the displacement at the first time. 　In this case, in the above-mentioned induction heating method of the metal strip, the displacement amount at the second time after the first time is compared with the estimated displacement amount calculated based on the displacement amount at the first time. It may further include a step to update the function based on the result. 　Further, in this case, the above-mentioned induction heating method for the metal strip may further include a step of applying an external force to suppress the displacement in the width direction to the metal strip according to the tendency of the function. [0024] 　In the above-mentioned induction heating method for metal strips, the step of controlling the relative positional relationship may include a step of moving the induction heating device and / or a part thereof in the width direction of the metal strips. [0025] 　According to another aspect of the present invention, it is an induction heating facility for a metal strip, which includes an induction heating device arranged at a first position on a transfer line for the metal strip to be continuously conveyed. Based on a detection unit that detects the amount of displacement of the widthwise center line of the metal strip at a second position different from the first position on the line from a predetermined reference line, and a function that represents the time-series change of the amount of displacement. , The estimated displacement amount calculation unit that calculates the estimated displacement amount of the widthwise center line of the metal strip at the first position by extrapolating the displacement amount temporally and spatially, and the metal based on the estimated displacement amount. Provided is an induction heating facility for a metal strip, which includes a relative position control unit for controlling a relative positional relationship between the induction heating device and the metal strip in the width direction of the strip. [0026] 　In the above-mentioned induction heating facility for metal strips, the second position may be located on the downstream side of the first position. [0027] 　In the above-mentioned induction heating facility for metal strips, the second position may be located upstream of the first position. [0028] 　In the above metal strip induction heating equipment, the detector measures the temperature distribution at the second position, including at least one end in the width direction of the metal strip, and as a temperature drop in the temperature distribution. The position of the widthwise end of the appearing metal strip may be converted into a displacement amount. [0029] 　In the above-mentioned induction heating facility for the metal strip, the estimated displacement amount calculation unit has a function of converting the time-series change of the displacement amount into a function, and the transfer speed of the metal strip, the first position and the second position. The estimated displacement at the first time may be calculated based on the distance between them, the function, and the displacement at the first time. 　In this case, the estimated displacement amount calculation unit further compares the displacement amount at the second time after the first time with the estimated displacement amount calculated based on the displacement amount at the first time. You may update the function based on it. 　Further, in this case, the induction heating facility for the metal strip may further include an external force applying portion that applies an external force to suppress the displacement in the width direction to the metal strip according to the tendency of the function. [0030] 　In the above-mentioned induction heating equipment for metal strips, the induction heating device includes an actuator for moving the induction heating device in the width direction of the metal strip and / or an actuator for moving a part of the induction heating device in the width direction of the metal strip. The relative position control unit may transmit a control signal to each actuator. Effect of the invention [0031] 　As described above, according to the present invention, when inductively heating a metal strip that is continuously conveyed, the positional relationship between the induction heating device and the metal strip is determined while minimizing restrictions on the device arrangement. It can be controlled with high accuracy. A brief description of the drawing [0032] FIG. 1 is a side view showing a schematic configuration of an induction heating facility according to a first embodiment of the present invention. FIG. 2 is a diagram showing an arrangement example of an induction heating device and a temperature scanner using an electromagnetic shielding plate in the induction heating equipment shown in FIG. FIG. 3A shows that the widthwise centerline Fc of the induction heating device and the widthwise centerline Sc of the steel strip S are aligned with the widthwise centerline Lc of the transport line in the induction heating facility according to the first embodiment of the present invention. It is a figure explaining the state of matching with a plan view. FIG. 3B is a plan view illustrating a state in which the center line Sc in the width direction of the steel strip S deviates from the state of FIG. 3A. FIG. 4 is a graph showing an example of a temperature distribution measured by the temperature scanner shown in FIG. FIG. 5A is a diagram for explaining a method of calculating an estimated displacement amount in the width direction of a steel strip according to the first embodiment of the present invention. FIG. 5B is a diagram for explaining a method of calculating an estimated displacement amount in the width direction of a steel strip according to the first embodiment of the present invention. FIG. 6 is a flowchart showing an example of the steps of the induction heating method according to the first embodiment of the present invention. FIG. 7A is a flowchart showing a specific example of the process of the induction heating method according to the first embodiment of the present invention. FIG. 7B is a flowchart showing a specific example of the process of the induction heating method according to the first embodiment of the present invention. FIG. 8 is a diagram showing a modified example of moving the entire induction heating device in the induction heating facility shown in FIG. FIG. 9 is a diagram showing an arrangement example of an induction heating device and a temperature scanner provided with a divided magnetic core in the induction heating equipment according to the second embodiment of the present invention. FIG. 10 is a diagram showing a schematic configuration of an induction heating facility according to a third embodiment of the present invention. FIG. 11A is a flowchart showing an example of a process of an induction heating method according to a third embodiment of the present invention. FIG. 11B is a flowchart showing an example of a process of an induction heating method according to a third embodiment of the present invention. Mode for carrying out the invention [0033] 　Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted. [0034] 　(First Embodiment) 　FIG. 1 is a side view showing a schematic configuration of an induction heating facility 10 according to a first embodiment of the present invention. As shown in FIG. 1, the induction heating equipment 10 includes an induction heating device 11 and a control device 12. The induction heating device 11 is a TF type induction heating device that heats the steel strip S that is continuously transported, and is arranged at a position P1 on the transport line of the steel strip S. The steel strip S is an example of a metal strip in this embodiment. The control device 12 includes a temperature scanner 121 as an example of the sensor and an arithmetic unit 122. The temperature scanner 121 is arranged at a position P2 on the transport line of the steel strip S, which is a position different from the position P1 in the transport direction. In the following description, the upstream side and the downstream side are defined according to the direction in which the steel strip S is transported and flows on the transport line of the steel strip S. According to this definition, the position P2 of the temperature scanner 121 may be on the downstream side of the position P1 of the induction heating device 11 on the transport line of the steel strip S. [0035] 　The arithmetic unit 122 performs various arithmetic operations and controls in the induction heating facility 10. The arithmetic unit 122 realizes a part or all of the functions as a detection unit, an estimated displacement amount calculation unit, and a relative position control unit, which will be described later. [0036] 　Although it is shown in FIG. 1 that the steel strip S is conveyed in the horizontal direction, such an illustration does not limit the arrangement of the metal strips in the embodiment of the present invention. In other embodiments, the metal strip may be transported in the vertical direction. [0037] 　FIG. 2 is a plan view showing an arrangement example of the induction heating device 11 and the temperature scanner 121 using the electromagnetic shielding plate 112 in the induction heating facility 10 shown in FIG. As shown in FIG. 2, the induction heating device 11 includes an induction coil 111, an electromagnetic shielding plate 112, and an actuator 113 for moving the electromagnetic shielding plate 112 in the width direction of the steel strip S indicated by an arrow in the drawing. .. The electromagnetic shielding plate 112 partially shields the magnetic flux generated by the induction coil 111 at the widthwise end portion of the steel strip S. The actuator 113 is connected to the arithmetic unit 122 included in the control device 12 shown in FIG. 1, and moves the electromagnetic shielding plate 112 according to the control signal transmitted by the arithmetic unit 122. The electromagnetic shielding plate 112 is arranged at the correct position with respect to the steel strip S, specifically, at a position that covers only an appropriate width from the widthwise end of the steel strip S, thereby blocking the magnetic flux and blocking the steel strip. It is possible to prevent overheating caused by an increase in the density of eddy currents at the widthwise end of S. The details of the control for moving the electromagnetic shielding plate 112 by using the actuator 113 and arranging it at the correct position will be described later. [0038] 　On the other hand, the temperature scanner 121 is an example of a sensor that measures the temperature distribution in the range including the steel strip S at the position P2. In the illustrated example, the temperature scanner 121 is described as measuring the temperature while a single sensor moves in the width direction of the steel strip S, but in another example, the temperature scanner 121 measures the transport line width. The temperature sensor itself, which is fixed above the position of the center line of the direction and is built in the housing of the temperature scanner 121, is swung at different angles in the width direction as necessary to measure the entire width direction. You may use the thing. Further, in the illustrated example, the range in which the temperature scanner 121 measures the temperature distribution includes both ends in the width direction of the steel strip S, but in the other example, the temperature is taken into consideration in consideration of the symmetry in the width direction. The range in which the scanner 121 measures the temperature distribution may include only one end in the width direction of the steel strip S. [0039] 　Further, the temperature scanner 121 may be fixed independently of the induction heating device 11. In this case, the temperature scanner 121 may measure the temperature of the steel strip S regardless of the movement of the induction heating device 11. Since the temperature scanner 121 is fixed independently of the induction heating device 11, noise due to the influence of vibration or the like from the induction heating device 11 is reduced. As a result, the detection accuracy of the temperature scanner 121 is improved. Further, the temperature scanner 121 may be provided at a position separated from the induction heating device 11 by a predetermined distance. In this case, the temperature scanner 121 may measure the temperature of the steel strip S regardless of the movement and installation position of the induction heating device 11. Since the temperature scanner 121 is provided apart from the induction heating device 11, noise due to the influence of vibration, magnetic field, etc. from the induction heating device 11 is reduced. As a result, the detection accuracy of the temperature scanner 121 is further improved. Here, the distance between the temperature scanner 121 and the induction heating device 11 is not particularly limited as long as it does not affect the estimation of the displacement amount at the second position P2 described later. [0040] 　Here, in FIG. 2, the width direction center line Lc (thin line in FIG. 2) of the design transport line, the width direction center line Fc of the induction heating device 11 (medium thick line in FIG. 2), and the steel strip are shown. The width direction center line Sc (thick line in FIG. 2) of S is shown. The width direction center line is a line that passes through the midpoint of each width direction length and extends in a direction orthogonal to the width direction when the transport line, the induction heating device 11, or the steel strip S is viewed in a plan view. Is. As shown in FIGS. 2 and 3A, the induction heating device 11 is designed so that these widthwise center lines Lc, Fc, and Sc coincide with each other as an ideal state. However, in reality, as shown in FIG. 3B, due to the meandering of the steel strip S, the widthwise center line Sc of the steel strip S becomes the widthwise centerline Lc of the transport line and the widthwise center of the induction heating device 11. It deviates from the line Fc. Then, the problem occurs because the electromagnetic shielding plate 112 shown in FIG. 2 is not arranged at the correct position with respect to the steel strip S. Specifically, for example, overheating occurs because the width covered by the electromagnetic shielding plate 112 becomes smaller at one end in the width direction of the steel strip S, or the end portion is not covered by the electromagnetic shielding plate 112. At the other end, the width covered by the electromagnetic shielding plate 112 becomes large, so that heating becomes insufficient. As described above, by moving the electromagnetic shielding plate 112 as shown in FIG. 2, for example, even when the widthwise center line Sc of the steel strip S is displaced as shown in FIG. 3B, the electromagnetic shielding plate 112 Can maintain the correct position with respect to the steel strip S and prevent overheating and insufficient heating. [0041] 　Normally, the center line Sc of the steel strip S and the center line Fc of the induction heating device 11 are set so as to coincide with a predetermined reference line. Here, as an example of the predetermined reference line, it is the center line Lc of the designed transport line. However, the profile of the in-furnace roll of the heat treatment furnace has changed due to the unsteady transition of the in-furnace temperature and the steel plate temperature of the heating furnace. Along with this, the contact state between the steel strip S and the roll in the furnace changes, the tension distribution in the steel strip S changes, and the tension distribution occurs in the steel strip S in the process of heating and cooling. The center line Sc of is often deviated from the center line Lc of the transport line. As a result, the center line Fc of the induction heating device 11 deviates from the center line Sc of the steel strip S. [0042] 　When the induction heating device 11 is of the TF method, the position where the magnetic flux is concentrated affects the heating temperature distribution of the steel strip S sensitively. Therefore, in order to obtain a desired heating temperature distribution, the center line Sc of the steel strip S is used. It is necessary to always align with the center line Fc of the induction heating device as much as possible. The alignment method predicts the position of the center line Sc of the steel strip S in advance, and controls the movement of the induction heating device 11 so as to align the center line Sc of the steel strip S with the center line Fc of the induction heating device 11. Alternatively, if there is a meandering control device for the steel strip S, the meandering of the steel strip S may be controlled so that the center line Sc of the steel strip S always matches the center line Fc of the induction heating device 11. [0043] 　Therefore, the present inventors diligently observed the state of the meandering of the steel strip S when examining the control of the induction heating facility 10 to cope with the meandering of the steel strip S. As a result, the present inventors have found that the meandering of the steel strip S often has a periodic component. Furthermore, the present inventors have focused on the fact that meandering is represented by various functions including long-period and short-period periodic functions, and these functions can be used to deal with meandering of the steel strip S. I came up with the idea of ​​controlling the induction heating equipment 10. [0044] 　Hereinafter, the control of the position of the electromagnetic shielding plate 112 in the induction heating device 11 according to the present embodiment will be further described with reference to FIGS. 4, 5A and 5B. FIG. 4 is a graph showing an example of the temperature distribution measured by the temperature scanner shown in FIG. As shown in FIG. 4, in the induction heating facility 10, the steel strip S after heating in the induction heating device 11 has a high temperature, while the ambient temperature is normal temperature or a cooled copper plate or the like is placed on the back surface of the steel strip S. By installing the steel strip S, the ends E1 and E2 appear in the temperature distribution as temperature drop portions corresponding to both ends in the width direction of the steel strip S (shown as the x-axis in the graph of FIG. 4). The arithmetic unit 122 converts the positions of the ends E1 and E2 into the displacement amount Δx from the design width direction center line Sc of the width direction center line Sc of the steel strip S. [0045] 　More specifically, the arithmetic unit 122 specifies the center line Sc in the width direction of the steel strip S as the midpoint of the positions of the ends E1 and E2 in the width direction of the steel strip S as the detection unit, and determines the center line Sc in the width direction of the steel strip S. The displacement amount Δx is sequentially calculated by using the width direction center line Sc as the position difference from the width direction center line Lc of the transport line. In this example, the predetermined reference line is the widthwise centerline Lc of the transport line (which also coincides with the widthwise centerline Fc of the induction heating device 11). The widthwise center line Lc of the transport line is also the center position of the measurement range of the temperature scanner 121. [0046] 　On the other hand, for example, when the width direction center line Lc of the transport line and the width direction center line Fc of the induction heating device 11 do not match, the predetermined reference line may be the width direction center line Fc of the induction heating device 11. .. In this example, the arithmetic unit 122 sequentially calculates the displacement amount Δx as the detection unit by using the width direction center line Sc of the steel strip S as the position difference from the width direction center line Fc of the induction heating device 11. [0047] 　As another example from the above, the arithmetic unit 122 may calculate the displacement amount Δx by comparing the positions of the ends E1 and E2 with the reference end positions of the steel strip S. In this case, in order to calculate the displacement amount Δx, information on the reference end position of the steel strip S, specifically, information on the width of the steel strip S in addition to the widthwise center line Lc of the transport line is required. The range in which the temperature scanner 121 measures the temperature distribution may include only one end in the width direction of the steel strip S. [0048] 　5A and 5B are diagrams for explaining a method of calculating an estimated displacement amount in the width direction of a steel strip according to the first embodiment of the present invention. As shown in FIG. 5A, the arithmetic unit 122 accumulates the displacement amount Δx (Δx, Δx + 1, Δx + 2, ...) In the width direction of the steel strip S from time to time with respect to the time t, and changes the displacement amount Δx in time series. The approximate function f (t) of is obtained by a method such as time series analysis or function approximation. The method of this conversion is not particularly limited, for example, approximating with a trigonometric function that minimizes the error when it has periodicity. The time-series change of the displacement amount Δx in the width direction of the steel strip S, that is, the meandering of the steel strip S often occurs periodically. Therefore, the approximate function f (t) can be obtained relatively easily by accumulating the displacement amount Δx in a relatively short time. If the approximate function f (t) is estimated, it becomes possible to predict the displacement amount Δx2 at an arbitrary position in the longitudinal direction of the steel strip S at a future time t2 from the displacement amount Δx1 at a certain time t1. Further, if the approximate function f (t) is estimated, it is possible to predict the displacement amount Δx2 at an arbitrary position in the longitudinal direction of the steel strip S at the past time t3 from the displacement amount Δx1 at a certain time t1. .. The estimation of the displacement amount Δx2 at an arbitrary position in the longitudinal direction at the present or past time by the approximate function f (t) will be further described below. [0049] 　As shown in FIG. 5B, the arithmetic unit 122 at the upstream position P1 at the same time t1 based on the displacement amount Δx1 in the width direction of the steel strip S detected at the downstream position P2 at the time t1. The estimated displacement of the steel strip S is calculated. Here, FIG. 5B shows the distance d in the transport direction between the position P1 and the position P2, and the transport speed v of the steel strip S. The displacement amount Δx2 of the steel strip S generated at the upstream position P1 at time t1 is observed at the downstream position P2 after the lapse of time (d / v) obtained by dividing the distance d by the transport speed v. Should be. Therefore, in the time-series change of Δx shown in FIG. 5A, if t2 = t1 + d / v, the displacement amount Δx2 at the future time t2 at the downstream position P2 is the upstream position P1 at the current time t1. Is equal to the estimated displacement at. [0050] 　On the other hand, at the current time t1, the displacement amount Δx2 of the steel strip S generated at the downstream position P1 is observed at the upstream position P2, which is traced back by the time (d / v) obtained by dividing the distance d by the transport speed v. It should have been done. Therefore, in the time series change of Δx, if t3 = t1-d / v, the displacement amount Δx2 at the past time t3 at the upstream position P2 is estimated at the downstream position P1 at the current time t1. Equal to the amount of displacement. [0051] 　In this way, the arithmetic unit 122 has a steel strip S at the position P1 that cannot be directly measured from the time-series change of the displacement amount Δx at the measurable position P2 on the upstream side or the downstream side of the induction heating device 11. The estimated displacement in the width direction can be calculated. [0052] 　In the transportation of the steel strip S, the transportation speed v may fluctuate. At this time, the arithmetic unit 122 may calculate an average value from the transition of the value of the transport speed v within a predetermined time and use it as the average transport speed vavg in the above calculation. Here, the transition of the transport speed v is detected by a line speedometer (not shown) provided at a predetermined position on the transport line. The position where the line speedometer is provided is not particularly limited as long as it is a position where the average transfer speed v can be detected. For example, the line speedometer may be provided in the vicinity of the second position P2 where the displacement amount is measured. [0053] 　As described above, in the present embodiment, the arithmetic unit 122 as the estimated displacement amount calculation unit is positioned by extrapolating the displacement amount Δx in the width direction of the steel strip S detected at the position P2 in a temporal and spatial manner. The estimated displacement amount of the steel strip S in the width direction in P1 is calculated. Further, the arithmetic unit 122 as the relative position control unit controls the relative positional relationship between the induction heating device 11 and the steel strip S at the position P1 based on the estimated displacement amount. Specifically, the arithmetic unit 122 transmits a control signal to the actuator 113 shown in FIG. 2 based on the estimated displacement amount, and the actuator 113 moves the electromagnetic shielding plate 112 according to the control signal. [0054] 　(Example of Steps of First Embodiment) 　FIG. 6 is a flowchart showing an example of steps of the induction heating method according to the first embodiment of the present invention described above. According to the example shown in FIG. 6, first, the displacement amount Δx1 of the steel strip S at the second position P2 is detected by the detection unit (step S11). Specifically, the temperature scanner 121 detects the position of the end portion of the steel strip S in the width direction, and the arithmetic unit 122 sets the transfer speed v and the distance d between the first position P1 and the second position P2. The displacement amount Δx of the steel strip S is calculated based on. Next, the calculation device 122 as the estimated displacement amount calculation unit is based on the approximate function f (t), the transport speed v, the distance d between the first position P1 and the second position P2, and the displacement amount Δx. The displacement amount is extrapolated temporally and spatially, and the estimated displacement amount Δx2 at the first position P1 is calculated (step S12). At this time, the approximate function f (t) is a function representing the time-series change of the displacement amount Δx. Subsequently, the relative positional relationship between the induction heating device 11 and the steel strip S is controlled based on the estimated displacement amount Δx2 at the first position P1 (step S13). Specifically, for example, the actuator 112A moves the induction heating device 11 to a predetermined position based on the control signal transmitted from the arithmetic unit 122 as the relative position control unit. [0055] 　(Specific Examples of Steps of the First Embodiment) 　FIGS. 7A and 7B are flowcharts showing specific examples of the steps of the induction heating method according to the first embodiment of the present invention described above. In the example shown in FIG. 7A, first, the initial setting of the induction heating facility 10 is performed (step S101). In the initial setting, in the induction heating device 11, the electromagnetic shielding plate 112 is initially arranged according to the width of the steel strip S. Further, in the control device 12, a value such as a distance d between the first position P1 and the second position P2 is initially set in the arithmetic unit 122. As the distance d, for example, the distance between the electromagnetic shielding plate 112 and the temperature scanner 121 in the transport direction may be set. After that, the steel strip S is started to be conveyed by a conveying device such as a roll (omitted in FIG. 1), a high frequency current is supplied to the induction coil 111, and the induction heating of the steel strip S is started (step). S102). [0056] 　After the start of the induction heating of the steel strip S, the temperature scanner 121 measures the temperature distribution in the width direction of the steel strip S at the position P2 before and after the induction heating device 11, for example, on the downstream side (step S103). Subsequently, the arithmetic unit 122 converts the positions of the ends E1 and E2 appearing in the temperature distribution into the displacement amount Δx in the width direction of the steel strip S (step S104). After repeating the above steps S103 and S104 for a predetermined time (step S105), the arithmetic unit 122 estimates an approximate function f (t) representing a time-series change of the displacement amount Δx (step S106). The method of estimating the approximate function is not particularly limited. For example, the approximation function may be estimated using a known mathematical approximation method. The estimated approximate function may be, for example, one trigonometric function or the like, or may be a combination of a plurality of trigonometric functions or the like having different periods, amplitudes, and the like. [0057] 　As shown in FIG. 7B, after the approximate function f (t) is estimated in step S106, the arithmetic unit 122 detects the displacement amount Δx based on the measurement result of the temperature distribution as in steps S103 and S104 (step). S107, S108), the steel at the position P1 of the induction heating device 11 based on the displacement amount Δx, the approximate function f (t), the transport speed v, and the distance d between the first position P1 and the second position P2. The estimated displacement amount of the band S is calculated (step S109). Further, the arithmetic unit 122 determines the movement amount of the electromagnetic shielding plate 112 of the induction heating device 11 or the induction heating device 11 based on the calculated estimated displacement amount (step S110), and outputs a control signal corresponding to the movement amount to the actuator. It is transmitted to 113 (step S111). The electromagnetic shielding plate 112 or the induction heating device 11 is moved by the operation of the actuator 113 that has received the control signal (step S112). [0058] 　Since the repetition time of steps S107 to S112 described above differs depending on the approximation function, the optimum time may be determined while tuning. [0059] 　After the elapse of the predetermined time in step S113, the arithmetic unit 122 calculates the displacement amount Δx detected in the nth steps S107 and S108 included in the above repetition in the mth (m