Dielectric heating device

Abstract

To uniformly heat a heating object with a longer length.SOLUTION: A dielectric heating device 10 comprises a power supply circuit 4 that supplies a high-frequency power generated in a power supply part 1 to an opposing long electrode 5. The power supply circuit 4 includes a first step line path 41 and a second step line path 42 that are hierarchically connected to between the power supply part 1 and the electrode 5. The first step line path 41 is divided into two at a left and a right of a long direction of the electrode 5 in an output end SP1 of the power supply part 1, and each tip end is corresponded to a center position of a dimension of 1 / 2 of a long direction of the electrode 5. The second step line path 42 is divided into two at the left and the right of the long direction of the electrode 5 in each tip end of the first step line path 41. Each tip end is corresponded to the center position of a dimension of 1 / 4 of the long direction of the electrode 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an apparatus for dielectric heating a heating object disposed between opposing electrodes with high-frequency power.

Background Art

[0002] Conventionally, there has been a demand for applying dielectric heating to a longer object, but uniform heating in the length direction is not easy, and various countermeasures have been studied. For example, there is known a high-frequency heating apparatus for manufacturing a laminate by applying an adhesive between a plurality of thin-layer wooden boards, laminating them, and integrally bonding them by dielectric heating (for example, Patent Document 1). Patent Document 1 describes that when a long electrode is employed to manufacture a longer laminate, a multi-point power feeding method is adopted in consideration of the distribution of the high-frequency electric field. Specifically, small electrode plates are arranged in series at predetermined intervals, and individual high-frequency oscillation circuits are connected to each of them, and the high-frequency heating operation is alternately switched to perform a heating and bonding process over the entire length.

[0003] Non-Patent Documents 1 and 2 describe that when a high-frequency voltage is applied to a long electrode, the voltage at a position away from the power feeding point becomes higher and reaches a maximum at the end portion or the like. Further, since the amount of heat generation with respect to the heating object is proportional to the square of the voltage, it is shown that the voltage in the electrode plane is preferably more uniform in suppressing heating unevenness. And in order to equalize the voltage, a two-point power feeding configuration and the voltage gradient characteristics in that case are shown. Also, depending on the case where the electrode is long with respect to the wavelength used, the product processing conditions, and the required accuracy for the heating balance in the length direction, there is a limit to the voltage equalization in the length direction with two-point power feeding. Therefore, for example, a four-point power feeding type is configured, and an apparatus has been proposed in which every other two points are alternately switched in time division or the workpiece is shifted by 1 / 4 dimension to perform the heating operation over the entire length.

[0004] Patent Document 2 proposes a high-frequency dielectric heating device in which high-voltage electrodes and ground electrodes are alternately arranged opposite each other to form multiple heating layers, and in order to minimize the difference in the length of the electrical circuits from the power supply to the high-voltage electrodes of each layer, the electrical circuits between them are configured in a so-called tournament shape, and the voltage applied to the high-voltage electrodes of each layer is made almost equal, that is, equivalent heating is made possible in each heating layer (see paragraphs 0022 to 0024, Figures 6, 8 to 10). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-276309 [Patent Document 2] Japanese Patent Publication No. 2019-75363 [Non-patent literature]

[0006] [Non-Patent Document 1] Kanemichi Tomoda, "Electric Heating Classroom: High-Frequency Dielectric Heating Devices and Applications," pp. 58-67, "Electric Heating" No. 70, 1993. [Non-Patent Document 2] Dielectric Heating Expert Committee, "Technical Standards for High-Frequency Wood Processing," No. 38(1)-(18), "Technical Report of the Institute of Electrical Engineers of Japan," February 1960. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] As shown in Patent Document 1, in the configuration in which the electrode plate is divided into multiple parts and arranged, multiple high-frequency oscillation circuits are required, resulting in a structurally larger design. Furthermore, as shown in Non-Patent Documents 1 and 2, when a multi-point power supply structure is adopted to suppress voltage unevenness, the dimensions of the long laminated timber products can vary in multiple or even diverse sizes, making it impractical to use a two-point power supply structure as exemplified in Non-Patent Documents 1 and 2. In addition, while the heating balance problem can be improved to some extent by incorporating a switching device in the four-point power supply system, the pressurized state of the workpiece pressing section must be released once during the process of shifting the workpiece during switching, and consideration must be given to the impact on cycle time and the switching schedule.

[0008] Furthermore, the tournament shape shown in Patent Document 2 relates to the electrical circuit between the power source and the individual high-voltage electrodes of each layer, and power is supplied to each high-voltage electrode at a single point on the edge of the high-voltage electrode. This differs from a system that supplies power to multiple points on a single electrode surface to adjust the voltage uniformly across the surface.

[0009] The present invention has been made in view of the above, and provides a dielectric heating device that enables the most uniform heating possible for longer objects by using a hierarchical power supply line. [Means for solving the problem]

[0010] The dielectric heating apparatus according to the present invention includes a power supply circuit that supplies high-frequency power generated by a power supply unit to opposing long electrodes, the power supply circuit having at least a first-stage line and a second-stage line connected hierarchically between the power supply unit and the electrodes, the first-stage line being branched into two at the output terminal of the power supply unit to the left and right in the longitudinal direction of the electrodes, with each end corresponding to the center position of half the length of the electrodes in the longitudinal direction, taking into account a predetermined dimension, and the second-stage line being branched into two at each end of the first-stage line to the left and right in the longitudinal direction of the electrodes, with each end corresponding to the center position of one-quarter the length of the electrodes in the longitudinal direction.

[0011] According to the present invention, the first-stage and second-stage transmission lines constitute a so-called two-tiered tournament power supply circuit. In the configuration where the second-stage transmission line is connected to the electrodes, high-frequency power is supplied to the center position of each quarter of the length of the electrodes, thereby suppressing differences in voltage levels on the electrode surface and enabling uniform heating. Furthermore, in the configuration where the second-stage transmission line constitutes an intermediate transmission line in the power supply circuit and the final-stage transmission line is connected to the electrodes, the differences in voltage levels on the electrode surface are suppressed in the final-stage transmission line connected to the electrodes because each end of the second-stage transmission line is divided and arranged in the length of the electrodes.

[0012] Furthermore, the first-stage transmission line includes a first-stage two-branch line arranged parallel to the longitudinal direction of the electrode from the output terminal of the power supply unit, and a first-stage connecting line extending from the first-stage two-branch line toward the surface of the electrode. This configuration makes it easy to manufacture a power supply line with balanced impedance.

[0013] Furthermore, in the first stage two-way branch circuit, each of the ends coincides with the center position of half the length of the electrode in the longitudinal direction. This configuration facilitates impedance adjustment.

[0014] Furthermore, the first-stage two-branch circuit has each of its ends offset by a predetermined adjustment dimension from the center position of half the length of the electrode in the longitudinal direction. This configuration makes it possible to manufacture a power supply line with adjusted impedance balance, enabling uniform heating for longer workpieces. Also, since the impedance balance is adjusted in the first-stage two-branch circuit rather than the final stage, it becomes easier to adjust the balance over the entire longitudinal direction. The adjustment dimension can be set in advance through testing or other means.

[0015] Furthermore, the shapes of the first and second stage transmission lines are symmetrical with respect to the longitudinal center of the electrode. With this configuration, if the workpiece is symmetrical in the longitudinal direction, the circuit design can be easily carried out by configuring a symmetrical power supply circuit accordingly.

[0016] Each tip of the final-stage line connected to the electrode, which is the final stage hierarchically, has a multi-point power supply shape branched in the width direction of the electrode. According to this configuration, the difference in voltage level is suppressed also in the width direction of the electrode, and the temperature balance on the front surface of the workpiece is made more uniform.

[0017] Further, the power supply circuit further has a third-stage line. The third-stage line is bifurcated left and right in the longitudinal direction of the electrode at each tip of the second-stage line, and each tip corresponds to the center position of each 1 / 8 dimension in the longitudinal direction of the electrode. According to this configuration, although the power supply circuit is provided with at least two stages, for an object such as a workpiece with strict uniform heating conditions, by further providing a third-stage line, it becomes possible to meet the requirement for maintaining the quality of the heat-treated product.

Advantages of the Invention

[0018] According to the present invention, by performing multi-point power supply to the electrode surface via at least the first-stage line and the second-stage line connected hierarchically, it becomes possible to perform as uniform heating as possible even for a longer workpiece.

Brief Description of the Drawings

[0019] [Figure 1] It shows a schematic circuit diagram of a dielectric heating device according to the present invention. (A) is a so-called tournament type of two-layer (four-point power supply) type according to the first embodiment, and (B) is a so-called tournament type of three-layer (eight-point power supply) type according to the second embodiment. [Figure 2] It is a diagram showing Comparative Example A1. (A) is a perspective view showing the right half (as viewed from the central power supply port SP1) of the power supply circuit and the electrode, (B) is a partial view showing a longitudinal section of the central part of the electrode, (C) is a top view showing the right half of the electrode, and (D) is a temperature distribution diagram in the entire longitudinal direction of the heating object (workpiece). [Figure 3] It is a diagram showing Comparative Example B1. (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram in the entire longitudinal direction of the workpiece. [Figure 4]A diagram showing Comparative Example C1, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 5] A diagram showing Comparative Example D1, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 6] A diagram showing Comparative Example E1, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 7] A diagram showing Comparative Example H1, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 8] A diagram showing Comparative Example H3, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 9] A diagram showing Comparative Example I1, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 10] A diagram showing Example F1, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 11] A diagram showing Example G1, where (A) is a perspective view showing the right half of the power supply circuit and the electrode, (B) is a top view showing the right half of the electrode, and (C) is a diagram showing the temperature distribution over the entire longitudinal direction of the workpiece. [Figure 12] A chart showing the power supply forms and temperature uniformity for all comparative examples. [Figure 13] A chart showing the power supply forms and temperature uniformity for all examples. [Figure 14] A chart showing a summary of the limiting length of the workpiece with respect to the power supply form and temperature uniformity for each individual comparative example. [Figure 15] This diagram shows a summary of the workpiece limit length for each power supply configuration and temperature uniformity in the respective examples. [Figure 16] Figures 14 and 15 correspond to a diagram that summarizes the limit length of the workpiece when the temperature uniformity is kept within 15°C. [Figure 17] Figures 14 and 15 correspond to a diagram that summarizes the limit length of the workpiece when the temperature uniformity is kept within 30°C. [Figure 18] Figure 11 shows another embodiment of the power supply circuit, and is a partial perspective view showing a tournament power supply structure with respect to the width direction of the electrodes, where the connection paths connected to the electrodes are located. [Modes for carrying out the invention]

[0020] Figure 1 shows a schematic circuit diagram of the dielectric heating apparatus according to the present invention. (A) is a two-tier (four-point power supply) type of the so-called tournament type according to the first embodiment, and (B) is a three-tier (eight-point power supply) type of the so-called tournament type according to the second embodiment. For the sake of explanation, the housing structure surrounding the apparatus is omitted in Figure 1.

[0021] The dielectric heating device 10 comprises a power supply unit 1, a power supply circuit 4, and electrodes 5 as its main components. The power supply unit 1 includes a high-frequency oscillator 2 and a matching unit 3. Although omitted in Figure 1, it generally includes a processor and a control unit that comprehensively controls the heating operation and matching adjustment operation. The high-frequency oscillator 2 generates a predetermined high-frequency power and supplies it to the electrodes 5 via the matching unit 3 and power supply circuit 4.

[0022] In this embodiment, the high-frequency oscillator 2 outputs high-frequency power at a frequency of 13.56 MHz and a predetermined output level. The frequency and output level can be appropriately selected depending on the material and size of the object to be heated (workpiece W) and the application. For example, frequencies from several MHz to several hundred MHz can be used, and practically, a high-frequency range including 13.56 MHz, 27.12 MHz, and 40.6 MHz can be applied. The output level can preferably be several hundred W to several tens of kilowatts, depending on the application. The matching unit 3 is composed of, for example, an LC circuit, and uses the measurement results of a known matching sensor (not shown) to change at least one component of the LC in conjunction with the impedance change to achieve impedance matching between the power supply side and the load side, thereby maintaining efficient dielectric heating. The output terminal of the power from the power supply unit 1 is shown as the power supply port SP1 in the left-right direction, i.e., in the longitudinal direction of the electrode 5, in Figures 1(A), 10(A), and 11(A). In Figure 1, the output terminal of the power supply unit 1 corresponds to the center of the electrode 5 in the longitudinal direction.

[0023] The electrode 5 comprises a pair of opposing plate-shaped upper electrodes 51 and lower electrodes 52 having predetermined dimensions in the longitudinal direction (left-right direction in Figure 1). In this embodiment, the upper electrode 51 is the positive electrode and the lower electrode 52 is the negative electrode. Preferably, one of the upper electrode 51 and the lower electrode 52 is configured to be able to move up and down by a lifting mechanism (not shown), and clamps the workpiece W to be heated with the required pressure. As the workpiece W, for example, two wooden boards (upper workpiece W1, lower workpiece W2) are used, and an adhesive is applied in the middle of their thickness direction to laminate them, and a laminated material is manufactured by integrally bonding them by dielectric heating under pressure between the upper electrode 51 and the lower electrode 52.

[0024] In the first embodiment shown in Figure 1(A), the power supply circuit 4 has a structure in which a first-stage transmission line 41 and a second-stage transmission line 42, both made of metal plates, are connected in a hierarchical manner. In the second embodiment, the dielectric heating device 10' shown in Figure 1(B) has a structure in which a third-stage transmission line 43, also made of metal plates, is connected in a hierarchical manner to the first-stage transmission line 41 and the second-stage transmission line 42. In both embodiments, the ends of each final-stage transmission line are connected to the electrode 51. Hereinafter, the first-stage transmission line 41, the second-stage transmission line 42, and the third-stage transmission line 43 will be referred to as tournament type or tournament power supply, as appropriate.

[0025] In Figure 1(A), the first-stage line 41 is branched into two, one to the left and one to the right in the longitudinal direction of the electrode 5 (the left-right direction in Figure 1), and each branch has a length extending from the branching point to the center position of half the length of the longitudinal direction of the electrode 5. More specifically, the first-stage line 41 is branched into two at the power supply port SP1, which is the output terminal of the power supply unit 1, i.e., at the center in the longitudinal direction of the electrode 5, and has two branched lines 411 that extend parallel to the left and right in the longitudinal direction of the electrode 5, and connecting lines 412 that extend from each end of the two branched lines 411 toward the electrode 5 by a predetermined length, for example, taking into account the insulation distance.

[0026] The second-stage track 42 is divided into two branches at the left and right ends of the first-stage track 41, extending to the left and right in the longitudinal direction of the electrode 5, and each branch has a length extending to the center position of a dimension of 1 / 4 of the longitudinal direction of the electrode 5. More specifically, the second-stage track 42 is divided into two branches 421 at the end of the connecting path 412 of the first-stage track 41 and extends parallel to the left and right in the longitudinal direction of the electrode 5, and connecting paths 422 extend from each end of the two branches 421 toward the electrode 5 by a predetermined length.

[0027] In the first embodiment, each end of the connecting path 422 of the second stage line 42 is connected to four locations on the surface of the upper electrode 51, starting from the left side in the longitudinal direction, at the center positions of each 1 / 4 dimension in the longitudinal direction of the electrode 5, i.e., 1 / 8, 3 / 8, 5 / 8, and 7 / 8 (hereinafter referred to as 4-point tournament power supply as needed).

[0028] The dielectric heating device 10' of the second embodiment shown in Figure 1(B) includes a third line 43. The third line 43 has two branch lines 431 that are branched at the ends of each connection line 422 of the second line 42 and extended parallel to the left and right in the longitudinal direction of the electrode 5, and connection lines 432 that are extended by a predetermined length from each end of the two branch lines 431 toward the electrode 5. In the second embodiment, the ends of each connection line 432 of the third line 43 are connected to eight locations on the surface of the upper electrode 51, starting from the left side in the longitudinal direction, at the center positions of each 1 / 8 dimension in the longitudinal direction of the electrode 5, i.e., 1 / 16, 3 / 16, 5 / 16, 7 / 16, 9 / 16, 11 / 16, 13 / 16, and 15 / 16 (hereinafter referred to as 8-point tournament power supply as needed).

[0029] Here, the aforementioned Non-Patent Documents 1 and 2 describe that when high-frequency power is applied to a certain position (feed point) on a long electrode surface, the voltage on the electrode surface is lowest at the feed point, gradually increases as it moves away from the feed point, reaches its maximum voltage at the furthest edge, and is more easily heated. Furthermore, "Saburo Kumagai, Sanji Fujimoto, Industrial Electronic Devices Series 22 "High-Frequency Heating Device", pp. 47-50, Nikkan Kogyo Shimbun, published in 1966" states that, generally, the degree of heating at any point along the longitudinal direction of the electrode surface is determined by the square of the ratio between the feed point voltage (lowest level) V1 and the maximum voltage Vm, and this corresponds to the square of the cosine of the ratio of the length l (L) of the object to be heated to its internal wavelength λ (i.e., 2πl / λ), that is, (V1 / Vm) 2 =cos 2 It is stated that this can be expressed as (2πl / λ). Therefore, if uniform heating is to be achieved along the longitudinal direction of the electrode, for example within 80%, the cosine value should be 0.9, meaning the length l of the object to be heated should be about λ / 14. For example, in the case of common wood (such as pine), the dielectric wavelength λ is 16.47m at a high frequency of 13.56MHz, and from this, λ / 14 is 1.177m. This means that in order to uniformly heat this wood, the length is limited to 1.177m with single-point feeding, and if power is supplied to the intermediate part excluding both ends of the electrode, it will appear symmetrically on both sides, i.e., twice as long, 2.354m. If the workpiece is even longer, it can be handled by increasing the number of power supply points (by applying multi-point feeding).

[0030] (Comparative Examples and Examples) Next, we will describe the power supply methods for the comparative examples and examples, and the simulation experimental results of their heating temperatures. The temperature distribution of the workpiece W was analyzed using the simulation software Femtet® (manufactured by Murata Software Co., Ltd.).

[0031] Figures 2 to 9 show representative examples for each comparative example group, and Figures 10 and 11 show representative examples for each embodiment group. Figure 12 is a table showing the power supply configuration and temperature uniformity of all comparative examples in each comparative example group, and Figure 13 is a table showing the power supply configuration and temperature uniformity of all embodiments in each embodiment group. Figure 14 is a table summarizing the limit length of the workpiece for each comparative example's power supply configuration and temperature uniformity, and Figure 15 is a table summarizing the limit length of the workpiece for each embodiment's power supply configuration and temperature uniformity.

[0032] The tests in the comparative examples and examples will be described in order below. The simulation test conditions were as follows: upper and lower workpieces W1 and W2: "pine" wood, dielectric constant: 1.8 except for some parts, heating time: 10 minutes, electrode width: 800 mm, workpiece width: 400 mm, workpiece height (electrode spacing): 200 mm, initial temperature: 25°C, output: 100 KW, frequency: 13.56 MHz, wavelength in air (dielectric constant: 1): 22.124 m, quarter wavelength: 5.531 m. Various adhesives can be used, but here a water-based polymer isocyanate adhesive with a curing temperature of 60°C was used. This adhesive allows for uniform bonding with a temperature variation of, for example, within 20%. In the heating test at 100°C described later, a resocinol resin adhesive with a curing temperature of 80°C was applied.

[0033] Furthermore, as shown in Figures 11 and 12, the evaluation item "uniformity" was represented by ◎, ○, △, and ×. Temperature variation was calculated as the sum of the difference (percentage) between the average temperature and the minimum temperature and the difference (percentage) between the average temperature and the maximum temperature. Based on the calculation results, ◎ was defined as within 10%, ○ as within 15%, △ as within 20% (all above indicating "uniformity"), and × as exceeding 20% ​​("uniformity" not present).

[0034] (1) Test of Comparative Example Group A Comparative Example A is a two-point power supply configuration in which power is supplied to each central position that divides the electrode in the longitudinal direction into two equal parts. Comparative Example A1 in Figure 2 has an electrode length of 12m and a workpiece length of 11m. (A) is a perspective view showing the right half (viewed from the central power supply port SP1) of the power supply circuit and electrode, (B) is a partial view showing the longitudinal section of the central part of the electrode, (C) is a top view showing the right half of the electrode, and (D) is a temperature distribution diagram over the entire longitudinal direction of the object to be heated (workpiece). In Comparative Example A1, the temperature rose from an initial temperature of 25°C to 34°C near the center, while it rose to 68°C near both the left and right ends. The temperature variation exceeded 20%, as indicated by 78.9% in No. A1 in the first row of Figure 12, and the "uniformity" item in the figure is indicated by an "x".

[0035] Furthermore, in Figure 12, in Comparative Example A2, with an electrode length of 9m and a workpiece length of 8.25m, the temperature variation exceeded 20%, and the "uniformity" item in the figure is indicated by an "x". In Figure 12, in Comparative Example A4, with an electrode length of 12m and a workpiece length of 8.25m, the temperature variation also exceeded 20%, and the "uniformity" item in the figure is indicated by an "x".

[0036] In Figure 12, for Comparative Example A3, with an electrode length of 6m and a workpiece length of 5.5m, the temperature variation was within 20%, and the "uniformity" item in the figure is indicated by a circle (○). Also in Figure 12, for Comparative Example A5, with an electrode length of 12m and a workpiece length of 5.5m, the temperature variation was within 20%, and the "uniformity" item in the figure is indicated by a circle (○). Based on these results, it is considered that uniform heating is possible with two-point power supply if the workpiece length is 5.5m or less.

[0037] (2) Tests of Comparative Example Group B Comparative Example B is a four-point power supply configuration in which power is supplied to each of the four central positions of the electrode. More specifically, in the power supply circuit B1, a power supply plate b0 is arranged parallel to the electrode 5 from a power supply port SP1 on the central side, and a connecting path b1 extends vertically from the power supply plate b0 to the upper electrode and is connected to the upper electrode. In Comparative Example B1 in Figure 3, the electrode length is 12m and the workpiece length is 11m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire longitudinal direction of the workpiece. In Comparative Example B1, the temperature rose by 21°C near the center, while it rose by 74°C near both the left and right ends, resulting in a temperature variation of over 20%, and the "uniformity" item in the figure is indicated by an "x".

[0038] Furthermore, in Figure 12, in Comparative Example B2, the electrode length was 12m and the workpiece length was 8.25m; in Comparative Example B3, the electrode length was 12m and the workpiece length was 5.5m; and in Comparative Example B4, the electrode length was 9m and the workpiece length was 8.25m. In all cases, the temperature variation exceeded 20%, and the "uniformity" item in the figure was marked with an "X". As a result of these findings, it is considered that uniform heating cannot be achieved even for a workpiece length of 5.5m with the four-point power supply configuration shown in Figure 3.

[0039] (3) Tests of Comparative Example Group C Comparative Example C differs from the configuration of power supply circuit B1 in that the two central connection paths c1 have a narrow, elongated shape and are bent in the planar direction, for example, by repeatedly bending into a rectangular shape to form a longer length. In this example, the central connection path c1 is formed to be twice as long in the longitudinal direction, for example, with a width dimension of 1 / 4 that of connection path b1 (see Figure 3). By making the central connection path c1 longer, the inductance L component is increased, balancing the impedance with the connection path c1 at the end. Comparative Example C1 in Figure 4 has an electrode length of 12m and a workpiece length of 11m, (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram over the entire longitudinal direction of the workpiece. In comparative example C1, the temperature rose by 35°C near the center, while it rose by 52°C near both ends. The temperature variation exceeded 20%, and the "uniformity" item in the chart is indicated by an "X".

[0040] Furthermore, in Figure 12, in Comparative Example C2, the electrode length was 12m and the workpiece length was 8.25m, and in Comparative Example C3, the electrode length was 12m and the workpiece length was 5.5m. In both cases, the temperature variation was within 20%, and the "uniformity" item in the figure is indicated by △ and ○. Based on these results, it is considered that uniform heating is possible to some extent for workpiece lengths of 8.25m or less by adjusting the impedance balance (applied voltage balance) of the connection path c1 between the end and center sides with four-point power supply. In this case, the shape design and manufacturing of the connection path d1 become complex.

[0041] (4) Tests of Comparative Example Group D Comparative Example D differs from the shape of the power supply circuit C1 in that the two central connection paths d1 have the same width dimension as the end connection paths d1. By making the central connection path d1 rectangular and elongated, the inductance L component is increased, balancing the impedance with the end connection paths d1. The central connection path d1 is formed to be four times longer in the longitudinal direction than the end connection paths d1. Comparative Example D1 in Figure 5 has an electrode length of 12m and a workpiece length of 11m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire longitudinal direction of the workpiece. In Comparative Example D1, the temperature rose by 38°C near the center, while it rose by 48°C near both the left and right ends. The temperature variation exceeded 20%, and the "uniformity" item in the figure is indicated by an "x".

[0042] Furthermore, in Figure 12, for Comparative Example D2, the electrode length was 12m and the workpiece length was 8.25m; for Comparative Example D3, the electrode length was 12m and the workpiece length was 5.5m; and for Comparative Example D4, the electrode length was 12m and the workpiece length was 2.75m. In all cases, the temperature variation was within 20%, and the "uniformity" item in the figure is indicated by a circle (○). Based on these results, it is considered that uniform heating is possible for workpieces with a length of 8.25m or less by adjusting the impedance balance of the connection path d1 between the end and center sides with a four-point power supply. In this case, the design and manufacturing of the shape of the connection path d1 becomes complex.

[0043] (5) Tests of Comparative Example Group E Comparative Example Group E includes Comparative Examples E1-E3 and Comparative Examples E4-E6. In Comparative Examples E1-E3, the central connecting path e1 is set to a predetermined length Δ from the intermediate position O, which is 1 / 4 of the length of the original electrode, and in this example, it is uniformly set to 120 cm towards the end. In Comparative Examples E4-E6, the position of the connecting path e1 is set according to the length of the workpiece W.

[0044] First, in Comparative Example E1 in Figure 6, the electrode length is 12m and the workpiece length is 11m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire longitudinal direction of the workpiece. In Comparative Example E1, the temperature rose by 36°C near the center, while it rose by 49°C near both the left and right ends. The temperature variation exceeded 20%, and the "uniformity" item in the figure is indicated by an "x". Also, in Figure 12, Comparative Example E2 had an electrode length of 12m and a workpiece length of 8.25m, and Comparative Example E3 had an electrode length of 12m and a workpiece length of 5.5m. In both cases, the temperature variation exceeded 20%, and the "uniformity" item in the figure is indicated by an "x". As a result of the above, it was found that even with a four-point power supply, and by changing the central connection path e1 to the end by 120 cm compared to comparative examples B1 to B3, uniform heating could not be achieved, just as in the cases of comparative examples B1 to B3.

[0045] Next, in Figure 12, Comparative Example E4 has an electrode length of 12m and a workpiece length of 8.25m, with the central connection path e1 adjusted 200mm towards the center from its original midpoint position at 1 / 4 of the electrode length. Comparative Example E4 had a temperature variation exceeding 20%, and the "Uniformity" item in the figure is indicated by ×. Comparative Example E5 has an electrode length of 12m and a workpiece length of 5.5m, with the central connection path e1 adjusted 400mm towards the center from its original midpoint position at 1 / 4 of the electrode length. Comparative Example E5 had a temperature variation of 20% or less, and the "Uniformity" item in the figure is indicated by △. Comparative Example E6 has an electrode length of 9m and a workpiece length of 8.25m, with the central connection path e1 adjusted 800mm towards the end from its original midpoint position at 1 / 4 of the electrode length. Comparative Example E6 showed a temperature variation of less than 20%, and the "uniformity" item in the figure is indicated by a circle (○). Based on these results, it is considered that uniform heating is possible for workpieces W with a length of 8.25m or less by adjusting the central connection path e1 by an appropriate length to either the end or the center, depending on the length of the workpiece W. In this case, adjusting the mounting position of the connection path e1 according to the workpiece length becomes complex.

[0046] (6) Test of Comparative Example Group H Comparative Example Group H includes Comparative Examples H1, H2 and Comparative Examples H3, H4. Comparative Examples H1 and H2 are powered from a single point in the center, while Comparative Examples H3 and H4 are powered from a single point in the end.

[0047] First, in Comparative Example H1 in Figure 7, the electrode length is 6m and the workpiece length is 5.5m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire longitudinal direction of the workpiece. In Comparative Example H1, the temperature rose by 34°C near the center, while it rose by 56°C near both ends. The temperature variation exceeded 20%, and the "uniformity" item in the figure is indicated by ×. In addition, in Comparative Example H2 in Figure 12, the electrode length is 3m and the workpiece length is 2.75m. The temperature variation was within 20%, and the "uniformity" item in the figure is indicated by ◎.

[0048] Next, in Comparative Example H3 in Figure 8, the electrode length was 3m and the workpiece length was 2.75m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire longitudinal direction of the workpiece. In Comparative Example H3, the temperature rose by 29°C on the power supply side and by 57°C on the other end side, resulting in a temperature variation exceeding 20%, and the "uniformity" item in the figure is indicated by ×. Also, in Figure 12, in Comparative Example H4, the electrode length was 1.625m and the workpiece length was 1.375m, and the temperature variation was within 20%, and the "uniformity" item in the figure is indicated by ○. As a result of these findings, uniform heating was possible with single-point power supply when the workpiece W was 2.75m or less.

[0049] (7) Tests of Comparative Example Group I Comparative Example I is an 8-point power supply type in which power is supplied to each of the eight equally divided centers of the electrode 5 via connection paths i1 of the same length. In Comparative Example I1 in Figure 9, the electrode length is 12m and the workpiece length is 11m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire longitudinal direction of the workpiece. In Comparative Example I1, the temperature rose by 6°C near the center and by 85°C at the ends, resulting in a temperature variation exceeding 20%, and the "uniformity" item in the figure is indicated by an "x". Also, in Figure 12, Comparative Example I2 is the case with an electrode length of 12m and a workpiece length of 8.25m, and Comparative Example I3 is the case with an electrode length of 12m and a workpiece length of 5.5m. In both cases, the temperature variation exceeded 20%, and the "uniformity" item in the figure is indicated by an "x". Comparative Example I4 involved an electrode length of 6m and a workpiece length of 5.5m. Unlike Comparative Example I3, the temperature variation was within 20%, and the "uniformity" item in the figure is indicated by a circle (○). As a result of these findings, it was found that with 8-point power supply, uniform heating is not possible even with a workpiece length of 5.5m when the electrode is as long as 12m.

[0050] (8) Test of Example Group F In Example F, the electrode 5 is divided into four equal parts along its length, and power is supplied to each center in the same manner as in Figure 1(A), i.e., a four-point tournament power supply. In Example F1 in Figure 10, the electrode length is 12m and the workpiece length is 11m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire length of the workpiece. In Example F1, the temperature rose by 47°C near the center and by 43°C at the ends, with a temperature variation of less than 10%, and the "uniformity" item in the figure is indicated by ◎.

[0051] In Figure 13, Example F2, with an electrode length of 12m and a workpiece length of 8.25m, had a temperature variation within 20%, and the "Uniformity" item in the chart was indicated by △. In Figure 13, Example F3, with an electrode length of 12m and a workpiece length of 5.5m, had a temperature variation within 20%, and the "Uniformity" item in the chart was indicated by ○. In Figure 13, Example F4, with an electrode length of 12m and a workpiece length of 11m, and the workpiece material having twice the dielectric constant εr of the workpiece in Example F1, had a temperature variation exceeding 20%, and the "Uniformity" item in the chart was indicated by ×. In Figure 13, Example F5, with an electrode length of 12m and a workpiece length of 2.75m, had a temperature variation within 20%, and the "Uniformity" item in the chart was indicated by ◎. In Figure 13, Example F6, with an electrode length of 13m and a workpiece length of 12m, showed a temperature variation of less than 20%, and the "uniformity" item in the chart was marked with a circle (○). In Figure 13, Example F7, with an electrode length of 14m and a workpiece length of 13m, showed a temperature variation exceeding 20%, and the "uniformity" item in the chart was marked with a cross (×). In Figure 13, Example F8, an improved version of Example F7, with an electrode length of 14m and a workpiece length of 13m, was moved 100mm towards the center from the midpoint of the two-way branch line 421 (as indicated by the arrow in Figure 10(A)), as shown in Figure 10(A). The temperature variation was less than 20%, and the "uniformity" item in the chart was marked with a triangle (△). In Example F8, instead of adjusting the connection position with electrode 5, impedance balance was achieved by adjusting the connection point between the first-stage transmission line 41 and the second-stage transmission line 42, making it possible to achieve temperature balance as much as possible even when the workpiece is long. As a result, with the 4-point tournament power supply, uniform heating is possible even when the workpiece is 13m long.

[0052] In addition, an example was added to evaluate "uniformity" with respect to other heating temperatures, using a workpiece with the same configuration and shape as Example F1 (electrode length 12m, workpiece length 11m), heated to approximately 100°C in the same heating time. In this additional example, a power level 1.66 times higher (=70°C / 45°C) was applied compared to Example F1. The result was an average temperature increase of 74.67°C, with a maximum of 78.99°C near the center and a minimum of 72.37°C over a wide area towards the edges. The temperature variation was within 20%, and the "uniformity" item in the figure corresponds to ○. Furthermore, the difference between the maximum and minimum temperatures was also 1.66 times that of Example F1, confirming a correlation between the power level and the maximum and minimum temperature difference. Note that 70°C is a heating temperature range that can be applied to wood bonding, etc., and 100°C is a heating temperature range that can be applied to wood bonding as well as wood drying.

[0053] (9) Test of Group G of Examples In Example G, the electrode 5 was divided into eight equal parts, and the same eight-point tournament power supply as in Figure 1(B) was applied to each center. In Example G1 in Figure 11, the electrode length was 12m and the workpiece length was 11m. (A) is a perspective view showing the right half of the power supply circuit and electrode, (B) is a top view showing the right half of the electrode, and (C) is a temperature distribution diagram along the entire longitudinal direction of the workpiece. In Example G1, the temperature was 39°C near the center and rose to around 44°C over a wide area at the edges. The temperature variation was within 20%, and the "uniformity" item in the figure is indicated by ◎.

[0054] In Figure 13, Example G2 had an electrode length of 12m and a workpiece length of 11m, and the workpiece material had twice the dielectric constant εr of the workpiece in Example G1. However, the temperature variation was within 20%, and the "uniformity" item in the figure is marked with a circle (○). This is because, in Example F4, which also had an electrode length of 12m and a workpiece length of 11m and the workpiece material had twice the dielectric constant εr, the "uniformity" was marked with a cross (×). However, in Example G2, the impedance balance was further improved by the 8-point tournament power supply, resulting in improved uniformity.

[0055] In Figure 13, Example G3 has an electrode length of 12m and a workpiece length of 11m, and the workpiece material has a dielectric constant εr three times that of the workpiece in Example G1. In this case, the temperature variation exceeds 20%, and the "uniformity" item in the figure is indicated by an "X". This is thought to be because the dielectric constant εr of the workpiece was tripled, resulting in a 1 / 3 reduction in the wavelength within the workpiece, i.e., a 1 / 3 reduction in the range of uniform heating.

[0056] In Figure 13, in Example G4, with an electrode length of 15m and a workpiece length of 14m, the temperature variation exceeded 20%, and the "Uniformity" item in the figure is indicated by an "X".

[0057] In Figure 13, Example G5 is an improved version of Example G4, with an electrode length of 15m and a workpiece length of 14m. A characteristic of Example G5 is that, as shown for reference in Figure 11(A), when the connecting path 412 of the first stage line 41 is moved 200mm toward the end (as indicated by the arrow in Figure 11(A)) from the midpoint of the two-way branch line 421, the temperature variation is within 20%, and the "uniformity" item in the chart is improved to ◎. In this Example G5, it is thought that the impedance balance is further improved and uniformity is increased by adjusting the position of the first stage connecting path 412, that is, by adjusting the connection point between the first stage line 41 and the second stage line 42, without touching the connecting path 432.

[0058] In Figure 13, in Example G6, with an electrode length of 14m and a workpiece length of 13m, the temperature variation exceeded 20%, and the "Uniformity" item in the figure is indicated by ×. In Figure 13, in Example G7, with an electrode length of 13m and a workpiece length of 12m, the temperature variation was within 20%, and the "Uniformity" item in the figure is indicated by △.

[0059] In Figure 13, in Example G8, with an electrode length of 16m and a workpiece length of 15m, the temperature variation exceeded 20%, and the "Uniformity" item in the figure is indicated by an "X".

[0060] In Figure 13, Example G9 is an improved version of Example G8, with an electrode length of 16m and a workpiece length of 15m. A characteristic of Example G9 is that, as shown for reference in Figure 11(A), when the connecting path 412 of the first stage line 41 is moved 200mm toward the end (as indicated by the arrow in Figure 11(A)) from the midpoint of the two-way branch line 421, the temperature variation is within 20%, and the "uniformity" item in the figure is indicated by a circle. In this Example G9, it is thought that the impedance balance was further improved and uniformity increased by adjusting the position of the first stage connecting path 412, that is, by adjusting the connection point between the first stage line 41 and the second stage line 42, without touching the connecting path 432.

[0061] Next, we will discuss the comparative examples and examples summarized in Figures 14 and 15. In the comparative examples, under the operating frequency and dielectric constant of the workpiece, as shown in Figure 14(C), it was found that uniform heating was possible within a temperature variation of 20% for workpiece lengths up to 2.75m with single-point power supply and up to twice that length, 5.5m, with two-point power supply. Furthermore, in the four-point power supply, it was found that by adjusting the length and width dimensions and connection positions to the electrodes of the central connection paths c1, d1, and e1 in comparative examples C, D, and E, the inductance balance was achieved, enabling uniform heating up to approximately three times that length, 8.25m. In addition, among the eight-point power supply shown in comparative example I in Figure 9(A), comparative example I4 has a shorter electrode length of 6m compared to comparative example I3 with an electrode length of 12m. As a result, the spacing between each connection path i1 is shorter, the voltage rise between them is smaller, and as a result, temperature unevenness is reduced, making uniform heating possible for a workpiece length of 5.5m.

[0062] In contrast, as shown in Figure 15(C), the examples showed that uniform heating was possible up to 12m in the 4-point tournament power supply, and up to 13m in Example F8, where the branching point position was adjusted and impedance balancing was achieved, with uniform heating within 20% of the workpiece length. Furthermore, in the 8-point tournament power supply, uniform heating was possible up to 12m, and even at 14m and 15m by adjusting the branching point position as shown in Examples G5 and G9 and balancing impedance. Therefore, it became possible to apply uniform heating to longer workpieces compared to the same 4-point power supply shown in the comparative example.

[0063] Figures 14 and 15 above are charts comparing the limit lengths of workpieces in the comparative example and the example when 20% is used as the evaluation criterion for "uniformity." Here, we will examine and review the relationship between the limit lengths of workpieces between the comparative example and the example when the evaluation criterion is other than 20%. Figure 16 is a chart corresponding to Figures 14 and 15, showing a summary of the limit lengths of workpieces when temperature uniformity is within 15°C, and Figure 17 is a chart corresponding to Figures 14 and 15, showing a summary of the limit lengths of workpieces when temperature uniformity is within 30°C.

[0064] In the comparative example shown in Figure 16(A), with a workpiece length of 8.25m and power supply at four points (width and length adjustment), the temperature variation was 16.60% (see Figure 14). In the comparative example with a workpiece length of 5.5m and power supply at four points (position adjustment), the temperature variation was 17.20% (see Figure 14). In the case of Figure 14, both were marked as ○, but in the "uniformity" evaluation criterion of 15%, they shifted to ×. On the other hand, in the example shown in Figure 16(B) with a 4-point tournament power supply and a workpiece length of 8.25m, the temperature variation was 16.30% (see Figure 15), and in the example with a 4-point tournament (branch point adjustment) and a workpiece length of 13m, the temperature variation was 19.30% (see Figure 15), and in the example with an 8-point tournament power supply and a workpiece length of 12m, the temperature variation was 18.10% (see Figure 15). In the case of Figure 15, all of these were marked as ○, but in the "uniformity" evaluation criterion of 15%, they shifted to ×. Based on the above, in both the comparative example and the examples, in response to the change in the evaluation criterion from 20% to 15%, nearly uniform heating was maintained for short-length workpieces, while for long-length workpieces, such as 12m and 13m, some shifted from ○ to ×.

[0065] Next, in the comparative example shown in Figure 17(A), with a workpiece length of 11m and power supply at 4 points (length adjustment), the temperature variation was 22.5% (see Figure 14). In the comparative example with a workpiece length of 11m and power supply at 4 points (position adjustment), the temperature variation was 30.0% (see Figure 14). In both cases in Figure 14, an "X" was indicated, but in the "uniformity" evaluation criterion of 30%, it transitioned to a "○". On the other hand, in the example shown in Figure 17(B), with a workpiece length of 13m and power supply at 4 points, the temperature variation was 21.7% (see Figure 15). In the example with a workpiece length of 13m and power supply at 8 points, the temperature variation was 22.6% (see Figure 15). In both cases in Figure 15, an "X" was indicated, but in the "uniformity" evaluation criterion of 30%, it transitioned to a "○". Based on the above, in response to the change in the evaluation criterion from 20% to 30%, an extension in the workpiece limit length (from 8.25m to 11m) was observed in the comparative example for some heating methods, and an extension in the workpiece limit length (from 12m to 13m) was observed in some heating methods for the example. In both the comparative example and the example, it was found that the workpiece limit length for "uniformity" could be extended. Thus, because the workpiece limit length changes in a similar trend in the comparative example and the example depending on the level of the evaluation criterion for "uniformity," the workpiece limit length in the example can be made longer than in the comparative example.

[0066] When setting the evaluation criteria for "uniformity," for example, in the case of "thawing," it is desirable to set the temperature variation to be small, while in the case of "drying," since electricity is absorbed where there is moisture, a certain degree of temperature variation is acceptable, and these factors should be taken into consideration when setting the criteria.

[0067] Figure 18 shows another embodiment of the power supply circuit of Figure 11, and is a partial perspective view showing a tournament power supply structure in the width direction of the electrode 51, with the connection path 4320 connected to the electrode 51. When the length of the object to be heated is long, for example, 10 m, the width dimension may also be 600 to 1000 mm, or even around 20000 mm. With this width, voltage changes in the width direction, i.e., heating variations in the width direction, become a problem not only in the length direction of the electrode 51, but also in the width direction, and it is desirable to adopt a multi-point power supply, preferably a tournament power supply structure, in the width direction.

[0068] In Figure 18, a connecting path 4320 is formed at the end of the third-stage line 43. The connecting path 4320 has a tournament power supply structure. The connecting path 4320 includes a vertical surface portion 4321 extending from above the midpoint of the width direction of the electrode 51 toward the electrode 51 surface, and two branched pieces 4322 that branch out in the width direction from the lower end of the vertical surface portion 4321, with each end extending to the center position of half the width of the electrode 51. It also includes a one-way connecting piece 432f that extends toward the electrode 51 surface from the end of the two-way connecting piece 4322 that extends toward one side in the width direction, and a other-way connecting piece 432b that extends toward the electrode 51 surface from the end of the two-way connecting piece 4322 that extends toward the other side in the width direction.

[0069] By employing the connection path 4320, variations in voltage levels in the width direction of the electrodes can be suppressed. In Figure 18, a tournament power supply structure is used at each end of the third-stage transmission line 43, but it may also be used at each end of the second-stage transmission line 42. In addition to the two-point or four-point tournament power supply structure, a multi-point power supply method including two-point power supply, as shown in the comparative example above, may also be applied in the width direction, provided that a more uniform voltage can be supplied in the width direction.

[0070] The present invention is applicable not only to the dielectric heating bonding of laminated materials described in the first and second embodiments, but also to dielectric heating treatments in general for long objects that require uniform heating in the longitudinal direction. For example, if the object to be heated is a long object where uneven heating is a problem, the present invention can be applied not only to the bonding of laminated materials, but also to bonding, drying, alteration, and thawing of various objects to be heated.

[0071] Furthermore, although this embodiment shows 4-point tournament power supply and 8-point tournament power supply, a multi-point power supply configuration including 16-point tournament power supply may be used depending on the range of uniform heating required for the heating purpose, etc. Moreover, if the shape of the workpiece is not symmetrical in the longitudinal direction, the shape of the electrodes or the tournament shape of the power supply circuit do not need to be symmetrical in the longitudinal direction. The position and spacing of connection paths 412, etc. can be designed in advance according to the amount of heat required, and used accordingly to always maintain a balanced heating environment. [Explanation of Symbols]

[0072] 10,10' Dielectric heating device 1 Power supply section 4. Power supply circuit 41 First level track 42 Second level track 43 Third level track 411, 421, 431 2-way junction 412,422,432,4320 connecting lines 5 electrodes 51 Upper electrode 52 Lower electrode Double job W1 Upper Work W2 Lower Work

Claims

1. It is equipped with a power supply circuit that supplies high-frequency power generated in the power supply unit to opposing electrodes that are long in the left-right direction, The power supply circuit has a first-stage line and a second-stage final-stage line, both made of metal plates, which are connected in a hierarchical manner between the power supply unit and the electrodes. The power supply unit has an output terminal that outputs the high-frequency power corresponding to the center position in the longitudinal direction of the electrode, The first stage of the track is divided into two equal parts in the left and right directions around the branching point, and the two ends of the two branched metal plates correspond to the center positions of each half length along the longitudinal direction of the electrode. The final stage track is divided equally in the left and right directions around a branching point, and each of the two ends of the metal plate of the first stage track is branched into two, and the four ends of the two branched metal plates are connected to the center position of the electrode, each one-quarter of the length of the electrode, in a dielectric heating device.

2. A power supply circuit is provided that supplies high-frequency power generated in the power supply unit to opposing electrodes that are long in the left-right direction, The power supply circuit has a first-stage line, a second-stage line, and a third-stage final-stage line, each made of a metal plate, which are connected in a hierarchical manner between the power supply unit and the electrodes. The power supply unit has an output terminal that outputs the high-frequency power corresponding to the center position in the longitudinal direction of the electrode, The first stage of the track is divided into two equal parts in the left and right directions around the branching point, and the two ends of the two branched metal plates correspond to the center positions of each half length along the longitudinal direction of the electrode. The second stage of the track is divided equally in the left and right directions around the branching point, with each of the two ends of the metal plate of the first stage of the track branching into two, and the four ends of the two branched metal plates correspond to the center position of each 1 / 4 dimension in the longitudinal direction of the electrode. The dielectric heating device is such that the final stage track is equally divided in the left and right directions around the branching point, with each of the four left and right ends of the metal plate of the second stage track branching into two, and the eight left and right ends of the branched metal plate are connected to the center position of the electrode, each one-eighth of the length in the longitudinal direction.

3. The dielectric heating apparatus according to claim 1 or 2, wherein the tip of each metal plate of the final stage line has a multi-point power supply shape that branches in the width direction of the electrode.

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