Dielectric heating device

Abstract

To prevent an unnecessary electromagnetic field generated from a coil to prevent a reduction in the heating efficiency of an object to be heated in a dielectric heating device.SOLUTION: A dielectric heating device comprises: a first electrode and a second electrode that face an object to be heated and are applied with AC voltage; and a coil that is electrically connected in series with the first electrode. The direct distance between one end and the other end of the coil is equal to or less than the direct distance between the center and one end of the coil in a direction of a magnetic path of the coil.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a dielectric heating device.

Background Art

[0002] Patent Document 1 discloses a dielectric heating device including an electromagnetic wave generation unit having a first electrode, a second electrode, and a coil electrically connected to the first electrode. This dielectric heating device generates an electric field between the first electrode and the second electrode by applying a high-frequency voltage to the first electrode and the second electrode, and heats and dries the ink attached to the recording medium by dielectric heating by the generated electric field. The coil plays roles such as adjusting the resonance frequency of the electromagnetic wave generation unit, impedance matching, and strengthening the electric field generated between the electrodes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, there may be a case where it is desired to increase the inductance of the coil for the purpose of adjusting the resonance frequency of the electromagnetic wave generation unit or the like. In this case, the inductance of the coil can be easily increased by increasing the number of turns or the cross-sectional area of the coil. However, increasing the number of turns or the cross-sectional area of the coil causes the coil to become larger, and there is a risk that the range of unnecessary electromagnetic fields generated from the coil when a voltage is applied becomes larger. If the output of the power output to the electromagnetic wave generation unit is reduced to suppress such unnecessary electromagnetic fields, there is a risk that the heating efficiency of the object to be heated decreases.

Means for Solving the Problems

[0005] According to one embodiment of the present disclosure, a dielectric heating device is provided. This dielectric heating device comprises a first electrode and a second electrode facing an object to be heated and to which an alternating voltage is applied, and a coil electrically connected in series with the first electrode. The linear distance between one end and the other end of the coil is less than or equal to the linear distance between the center of the coil and the one end in the magnetic path direction of the coil. [Brief explanation of the drawing]

[0006] [Figure 1] This is a perspective view showing the schematic configuration of the dielectric heating device in the first embodiment. [Figure 2] This is a perspective view showing the schematic configuration of the electrode unit in the first embodiment. [Figure 3] This is a front view of the electrode unit in the first embodiment. [Figure 4] This is a perspective view showing the schematic configuration of the electrode unit in the second embodiment. [Figure 5] This is a top view of the electrode unit in the second embodiment. [Figure 6] This is a front view of the electrode unit in the second embodiment. [Figure 7] This is a side view of the electrode unit in the second embodiment. [Figure 8] This is a perspective view showing the schematic configuration of the electrode unit in the third embodiment. [Figure 9] This figure shows a cross-section perpendicular to the magnetic path direction of the core. [Modes for carrying out the invention]

[0007] A. First Embodiment: Figure 1 is a perspective view showing the schematic configuration of the dielectric heating device 100 in the first embodiment. Figure 1 shows arrows indicating the mutually orthogonal X, Y, and Z directions. The X and Y directions are parallel to the horizontal plane, and the Z direction is along the vertically upward direction. In other figures, arrows indicating the X, Y, and Z directions are shown as appropriate, so that the directions shown correspond to those in Figure 1. In the following description, when specifying the direction, the direction indicated by the arrow in each figure will be denoted as "+" and the opposite direction as "-", and positive and negative signs will be used in the direction notation. Hereafter, the +Z direction will also be referred to as "up" and the -Z direction as "down". In this specification, orthogonal includes the range of 90° ± 10°.

[0008] The dielectric heating device 100 comprises an electrode unit 20 for heating the material to be heated (OH), a voltage application unit 80 for applying an AC voltage to the electrode unit 20, and a control unit 500. Furthermore, the dielectric heating device 100 in this embodiment comprises a transport unit 200 for transporting the material to be heated (OH) and a case unit 300 for housing the electrode unit 20.

[0009] In this embodiment, the dielectric heating device 100 heats the material to be heated (OH) within the case section 300 by an electric field generated from the electrode unit 20 while transporting the material to be heated (OH) by the transport section 200. In this embodiment, the dielectric heating device 100 dries the material to be heated (OH) by heating a sheet-like printing medium coated with a liquid. Examples of printing media include paper, cloth, and film. Examples of liquids coated on the printing medium include water and various inks mainly composed of organic solvents. The liquid is applied to the printing medium by a liquid ejection device such as an inkjet printer.

[0010] The control unit 500 is composed of a computer comprising a CPU, a memory unit, and an input / output interface for inputting and outputting signals to and from the outside. The control unit 500 controls each of the above-mentioned transport unit 200 and voltage application unit 80, etc., to heat the material OH to be heated in the dielectric heating device 100. In other embodiments, the control unit 500 may be composed of, for example, a combination of multiple circuits.

[0011] In this embodiment, the conveying unit 200 has two roller units 205 and a drive unit (not shown) which is composed of a motor or the like that drives the roller units 205. The conveying unit 200 conveys the sheet-like heated material OH by driving the roller units 205. In other embodiments, the conveying unit 200 may be composed of, for example, a belt for supporting and conveying the heated material OH and a drive unit that drives the belt.

[0012] The case portion 300 is made of a metallic material and blocks radiation waves from the electrode unit 20 housed inside. More specifically, the case portion 300 blocks radiation waves by generating an electromagnetic field that weakens them through eddy currents generated on the walls of the case portion 300 when radiation waves are emitted from the electrode unit 20. "Blocking of radiation waves" by the case portion 300 means that the intensity of the electromagnetic field radiated from the electrode unit 20 to the outside of the case portion 300 is kept below a predetermined standard value. This standard value is determined based on regulatory values ​​stipulated in guidelines on electromagnetic field exposure limits in each country and region.

[0013] In this embodiment, the case portion 300 is made of zinc and has a rectangular parallelepiped shape. Each face of the case portion 300 is made of a wire mesh formed by plain weaving zinc wires vertically and horizontally, and has a plurality of openings 315 partitioned by the wires. 1Here, only the opening 315 provided on the +X direction side surface of the case portion 300 among the openings 315 is shown, and the openings 315 provided on other surfaces are omitted. In other embodiments, each surface of the case portion 300 may be constituted by, for example, a wire mesh obtained by twill weaving wires, expanded metal, perforated metal, or the like. Also, the case portion 300 may be formed of, for example, carbon steel, aluminum, or the like.

[0014] The object to be heated OH is inserted into the case portion 300 through the insertion port 312 provided on the +Y direction side surface of the case portion 300 while being conveyed by the conveying portion 200. Then, the object to be heated OH is heated by the electrode unit 20 in the case portion 300 while being conveyed in the same manner, and then is sent out of the case portion 300 through the delivery port 314 provided on the -Y direction side surface of the case portion 300.

[0015] FIG. 2 is a perspective view showing a schematic configuration of the electrode unit 20 in the present embodiment. FIG. 3 is a front view of the electrode unit 20 in the present embodiment. The electrode unit 20 includes a first electrode 30, a second electrode 40, and a coil 50 electrically connected in series with the first electrode 30.

[0016] Both the first electrode 30 and the second electrode 40 are electrically connected to the voltage application unit 80 shown in FIG. 1. In the present embodiment, the first electrode 30 is electrically connected to the voltage application unit 80 through the first electric wire 75, the first connection portion 76, the coil 50, the second connection portion 77, the second electric wire 78, and the inner conductor 70 of the coaxial cable. The second electrode 40 is electrically connected to the voltage application unit 80 through a connection member 43 disposed above the second electrode 40 and an outer conductor of a coaxial cable not shown. In FIG. 3, the connection member 43 is omitted.

[0017] The first electrode 30 and the second electrode 40 are conductors and are formed of, for example, metal, alloy, conductive oxide, or the like. The first electrode 30 and the second electrode 40 may be formed of the same material as each other or may be formed of different materials. The first electrode 30 and the second electrode 40 may be disposed, for example, on a substrate or the like formed of a material having a low dielectric loss tangent and low conductivity for the purpose of maintaining their postures and strengths, or may be supported by other members.

[0018] As shown in FIG. 2, the first electrode 30 in the present embodiment has a boat shape with the Y direction as the longitudinal direction and the X direction as the short-side direction. The lower surface of the first electrode 30 has a curved surface shape convex in the -Z direction. The first electrode 30 has an oval shape elongated in the Y direction when viewed along the Z direction. The first electrode 30 has an arc shape convex in the -Z direction when viewed along the X direction. Also, the first electrode 30 has an arc shape convex in the -Z direction when viewed along the Y direction. Therefore, the end portions of the first electrode 30 in the longitudinal direction and the short-side direction are located at positions in the +Z direction relative to the central portion of the first electrode 30.

[0019] The second electrode 40 is flat in the X and Y directions and has an oval annular shape elongated in the Y direction. The second electrode 40 is disposed so as to surround the first electrode 30 when viewed along the Z direction. That is, in the present embodiment, the first electrode 30 is disposed inside the ring of the second electrode 40 when viewed along the Z direction. Thereby, the electrode unit 20 in the present embodiment has a point-symmetrical shape centered on the center points of the first electrode 30 in the X and Y directions when viewed along the Z direction.

[0020] The first electrode 30 and the second electrode 40 are both positioned on a substrate 110 that is arranged parallel to the X and Y directions. More specifically, the first electrode 30 is positioned so that the central portion of its lower surface in the X and Y directions is in contact with the upper surface of the substrate 110. The second electrode 40 is positioned so that its lower surface is in contact with the upper surface of the substrate 110. Therefore, in this embodiment, the central portion of the lower surface of the first electrode 30 and the lower surface of the second electrode 40 are positioned on the same plane.

[0021] In this embodiment, the substrate 110 is made of glass. The substrate 110 prevents liquids such as ink applied to the heated material OH from adhering to the first electrode 30 and the second electrode 40, and also prevents lint from the heated material OH, if it is a cloth, from adhering to the first electrode 30 and the second electrode 40. In other embodiments, the substrate 110 may be made of alumina, for example.

[0022] An AC voltage is applied to the first electrode 30 and the second electrode 40 by the voltage application unit 80 shown in Figure 1. In this embodiment, the voltage application unit 80 is configured as a high-frequency power supply including a high-frequency voltage generation circuit and outputs a high-frequency voltage. The voltage application unit 80 is composed of, for example, a crystal oscillator, a PLL (Phase Locked Loop) circuit, and a power amplifier. The voltage application unit 80 amplifies the high-frequency signal generated by the PLL circuit with the power amplifier and supplies power to the electrode unit 20 via a coaxial cable or the like, thereby applying a high-frequency voltage to the first electrode 30 and the second electrode 40. One of the potentials applied to the first electrode 30 or the second electrode 40 may be a reference potential. A reference potential is a constant potential that serves as a reference for the high-frequency voltage, for example, the ground potential. In this specification, high-frequency voltage refers to an AC voltage with a frequency of 1 MHz or higher.

[0023] When an alternating current voltage is applied to the first electrode 30 and the second electrode 40, an electromagnetic field with a wavelength λ0 corresponding to the frequency f0 of the applied alternating current voltage is generated from the first electrode 30 and the second electrode 40. The strength of this electromagnetic field is very strong in the vicinity of the first electrode 30 and the second electrode 40, and very weak at a distance. In this specification, the electromagnetic field generated in the vicinity of the first electrode 30 and the second electrode 40 by the application of an alternating current voltage is also called the "nearby electromagnetic field." "Nearby" of the first electrode 30 and the second electrode 40 refers to the range where the distance from the first electrode 30 and the second electrode 40 is 1 / 2π or less of the wavelength of the generated electromagnetic field. The range further than "nearby" is also called "far." In this specification, the electromagnetic field generated far from the first electrode 30 and the second electrode 40 by the application of an alternating current voltage is also called the "far electromagnetic field." The far electromagnetic field corresponds to the electromagnetic field used for communication by general communication antennas, etc.

[0024] The electromagnetic field generated from the electrode unit 20 has a wavelength λ0 corresponding to the frequency f0 of the AC voltage applied to the electrode unit 20. Therefore, for example, when the material to be heated OH contains water, the dielectric loss tangent of water is maximum around 20 GHz, so by applying high-frequency voltages of 2.45 GHz or 5.8 GHz in the ISM band to the electrode unit 20, the material to be heated OH can be heated more efficiently in the dielectric heating device 100. Furthermore, from the perspective of heating ink, good heating efficiency can be obtained even if the frequency f0 is low, for example, 40.68 MHz, which is one of the ISM bands. This is because at 40.68 MHz, the dielectric loss tangent of water in the ink is low, while Joule heat is more easily generated due to the electrical resistance of the pigment components in the ink.

[0025] The frequency f0 of the electromagnetic field generated from the electrode unit 20, that is, the resonant frequency of the electrode unit 20, is determined based on the capacitance and inductance of the electrode unit 20. For example, if the distance between the first electrode 30 and the second electrode 40 is increased within the "neighborhood" range to increase the heating range of the object OH to be heated by the electrode unit 20, the capacitance of the electrode unit 20 decreases as the first electrode 30 and the second electrode 40 are considered as individual electrode plates constituting a single capacitor. As a result, the resonant frequency of the electrode unit 20 increases. Therefore, to maintain the resonant frequency of the electrode unit 20 even when the distance between the first electrode 30 and the second electrode 40 is increased, it is necessary to increase the inductance of the electrode unit 20 by increasing the inductance of the coil 50, thereby lowering the resonant frequency.

[0026] In this embodiment, the first electrode 30 and the second electrode 40 are arranged such that the shortest distance between them is less than or equal to one-tenth of the wavelength λ0 of the electromagnetic field. This allows the electric field density of the electromagnetic field generated from the first electrode 30 and the second electrode 40 to be attenuated in the vicinity of the first electrode 30 and the second electrode 40. Therefore, by appropriately maintaining the distance between the object to be heated OH and the first electrode 30 and the second electrode 40, the object to be heated OH can be efficiently heated by the electric field generated in the vicinity of the first electrode 30 and the second electrode 40, while suppressing the radiation of the far-field electromagnetic field from the first electrode 30 and the second electrode 40. In particular, in this embodiment, since the second electrode 40 is arranged to surround the first electrode 30 when viewed along the Z direction, the radiation of the far-field electromagnetic field from the first electrode 30 and the second electrode 40 can be further suppressed. Furthermore, if the second electrode 40 is arranged to surround the first electrode 30 when viewed along the Z direction, then even if the outer shapes of the first electrode 30 and the second electrode 40 when viewed along the Z direction are circular, rectangular, or other polygonal shapes, the radiation of the far-field electromagnetic field from the first electrode 30 and the second electrode 40 can be suppressed.

[0027] Furthermore, in this embodiment, as described above, since the electrode unit 20 has a point-symmetric shape with respect to the center point of the first electrode 30 in the X and Y directions when viewed along the Z direction, the radiation of far-field electromagnetic fields from the first electrode 30 and the second electrode 40 can be further suppressed.

[0028] As shown in Figure 3, in this embodiment, one end 51 of the coil 50 is electrically connected in series with the first electrode 30 via a first connection part 76 and a first wire 75, and the other end 52 is electrically connected in series with the voltage application unit 80 via a second connection part 77 and a second wire 78. When the voltage application unit 80 applies an AC voltage to the electrode unit 20, a high voltage is generated at one end 51 of the coil 50. This increases the strength of the electric field generated from the first electrode 30 and the second electrode 40. Furthermore, by increasing the inductance of the coil 50, the Q value of the coil 50 increases, which further increases the strength of the electric field generated from the first electrode 30 and the second electrode 40. The Q value is also called the quality factor.

[0029] As shown in Figure 3, the straight-line distance d1 between one end 51 and the other end 52 of the coil 50 is less than or equal to the shortest straight-line distance d2 between the central part 53 and the one end 51. The central part 53 refers to the central portion of the coil 50 in the magnetic path direction Dm. The distance in the magnetic path direction Dm from the end 51 side of the coil 50 to the central part 53 is equal to the distance in the magnetic path direction Dm from the end 52 side of the coil 50 to the central part 53. The magnetic path direction Dm also refers to the direction of the magnetic path formed within the coil 50 when the coil 50 is energized. The magnetic path direction Dm reverses depending on the sign of the voltage applied to the coil 50. When the straight-line distance d1 is less than or equal to the straight-line distance d2, the one end 51 and the other end 52 are closer to each other compared to when the straight-line distance d1 is greater than the straight-line distance d2. Therefore, when an AC voltage is applied to the coil 50, the electromagnetic field irradiated from one end 51 of the coil 50 is more easily guided to the other end 52 of the coil 50, and the electromagnetic field irradiated from the other end 52 is more easily guided to the one end 51.

[0030] In coil 50, if the linear distance d1 is greater than the linear distance d2, increasing the inductance of coil 50 to adjust the resonant frequency of the electrode unit 20 or to strengthen the electric field generated from the first electrode 30 and the second electrode 40 may increase the strength of the unwanted electromagnetic field generated from coil 50 when a voltage is applied. Also, increasing the number of turns or cross-sectional area of ​​coil 50 to increase its inductance will increase the size of coil 50, which may increase the range of the unwanted electromagnetic field generated from coil 50 when a voltage is applied. As a method to suppress such unwanted electromagnetic fields, for example, reducing the output of AC power to the first electrode 30 and the second electrode 40 can be considered. However, reducing the output of AC power will decrease the heating efficiency of the heated material OH, so for example, it may take a long time to heat and dry the heated material OH. In this embodiment, as described above, since the linear distance d1 is less than or equal to the linear distance d2, even if the inductance of coil 50 is increased, the unwanted electromagnetic field generated from coil 50 can be suppressed without reducing the output of AC power.

[0031] Furthermore, it is preferable that the cross-sectional area and number of turns of the coil 50 be determined not only from the perspective of adjusting the resonant frequency and strengthening the electric field as described above, but also from the perspective of achieving impedance matching between the electrode unit 20 and the voltage application unit 80. It is also preferable that the magnetic path length and material of the coil 50 be selected from the same perspective.

[0032] In this embodiment, the coil 50 is formed in an annular shape overall, as shown in Figures 2 and 3, such that an annular magnetic path is formed within the coil 50 when viewed along the X direction. More specifically, the windings 56 of the coil 50 are formed in a spiral shape that progresses along the circumference. As a result, the coil 50 is formed in an annular shape overall, such that an annular magnetic path is formed within the coil 50 when viewed along the X direction. Furthermore, the cross-section of the coil 50 perpendicular to the magnetic path direction Dm is circular. The shape of the coil 50 in this embodiment is also called a donut shape, toroidal shape, or torus shape. Note that in Figures 2 and 3, a portion of the windings 56 of the coil 50 is omitted, but in reality, the windings 56 are wound in a spiral shape such that the spacing between the windings 56 in the magnetic path direction Dm is approximately constant.

[0033] Furthermore, in this embodiment, the linear distance d3 between the first electrode 30 and one end 51 of the coil 50, as shown in Figure 3, is less than or equal to the linear distance d4 between the first electrode 30 and the central portion 53. As a result, compared to the case where the linear distance d3 is greater than the linear distance d4, the distance between one end 51 of the coil 50 and the first electrode 30 becomes shorter, which suppresses the generation of an electromagnetic field that does not contribute to the heating of the heated material OH between the coil 50 and the first electrode 30, or between the first electric wire 75 or the first connection portion 76 and the second electrode 40. Moreover, this effectively increases the strength of the electric field generated from the first electrode 30 and the second electrode 40.

[0034] In the dielectric heating device 100 of the first embodiment described above, the linear distance d1 between one end 51 and the other end 52 of the coil 50 is less than or equal to the linear distance d2 between the central part 53 of the coil 50 and one end 51. As a result, when an AC voltage is applied, the electromagnetic field irradiated from one end 51 of the coil 50 is more easily guided to the other end 52 of the coil 50, and the electromagnetic field irradiated from the other end 52 of the coil 50 is more easily guided to one end 51 of the coil 50. Therefore, even if the number of turns or cross-sectional area of ​​the coil 50 is increased and the coil 50 becomes larger, unwanted electromagnetic fields generated from the coil 50 can be suppressed. Consequently, it is not necessary to reduce the output power of the first electrode 30 and the second electrode 40 in order to suppress unwanted electromagnetic fields generated from the coil 50, and thus a decrease in the heating efficiency of the heated object OH can be suppressed.

[0035] Furthermore, according to this embodiment, the coil 50 is formed in a ring shape so as to form an annular magnetic path within the coil 50. Therefore, unwanted electromagnetic fields generated from the coil 50 can be suppressed more effectively.

[0036] Furthermore, according to this embodiment, the linear distance d3 between the first electrode 30 and one end 51 of the coil 50 is less than or equal to the linear distance d4 between the first electrode 30 and the central portion 53. As a result, the distance between one end 51 of the coil 50 and the first electrode 30 becomes shorter compared to the case where the linear distance d3 is greater than the linear distance d4. Therefore, it is possible to suppress the generation of an unwanted electromagnetic field between the first electrode 30 and the coil 50 that does not contribute to the heating of the material OH. In addition, as a result, the coil 50 can effectively increase the strength of the electric field generated from the first electrode 30 and the second electrode 40.

[0037] B. Second Embodiment: Figure 4 is a perspective view showing the schematic configuration of the electrode unit 20b in the second embodiment. Figure 5 is a top view of the electrode unit 20b in the second embodiment. Figure 6 is a front view of the electrode unit 20b in the second embodiment. Figure 7 is a side view of the electrode unit 20b in the second embodiment. Note that the connecting member 43 is omitted in Figures 5 to 7. Also, in Figures 4 and 6, a part of the winding 56 is omitted, similar to Figures 2 and 3 described in the first embodiment. In this embodiment, unlike the first embodiment, the entire coil 50b is positioned above the first electrode 30. The configuration of the electrode unit 20b and dielectric heating device 100 in the second embodiment is the same as in the first embodiment unless specifically described.

[0038] As shown in Figures 4 to 7, in this embodiment, the coil 50b is positioned above the first electrode 30 such that the entire coil 50b overlaps the first electrode 30 when viewed along the Z direction. In other words, when projected onto the XY plane perpendicular to the Z direction, the coil 50b is covered by the first electrode 30. More specifically, in this embodiment, the first electrode 30 has an oval shape with dimensions larger than the coil 50b in the X and Y directions, and the coil 50b is positioned inside the outer casing of the first electrode 30.

[0039] In this embodiment, as shown in Figure 6, one end 51b of the coil 50b is positioned closer to the first electrode 30 than the central position Pc, which is the center of the coil 50b in the Z direction. That is, the linear distance d3 between the end 51b and the first electrode 30 is shorter than the linear distance d5 between the first electrode 30 and the central position Pc. More specifically, the end 51b is positioned at the lower end of the coil 50b, that is, the position of the coil 50b closest to the first electrode 30. Also, as shown in Figures 5 to 7, the first wire 75b in this embodiment is positioned in the +X direction of the coil 50b. The first connection part 76b is provided so as to extend from the first wire 75b toward the one end 51b of the coil 50b in the -X direction. The second wire 78b is positioned in the -X direction of the coil 50b. The second connection part 77b is provided so as to extend from the second wire 78b toward the other end 52b of the coil 50b in the +X direction.

[0040] Because one end 51b is positioned closer to the first electrode 30 than the central position Pc, it is possible to further suppress the generation of unwanted electric fields that do not contribute to the heating of the heated material OH between the coil 50b and the first electrode 30, or between the first wire 75b or the first connection part 76b and the second electrode 40. Furthermore, this makes it possible to further increase the strength of the electric fields generated from the first electrode 30 and the second electrode 40. In particular, in this embodiment, since one end 51b is positioned at the lower end of the coil 50b, it is possible to further suppress the generation of unwanted electromagnetic fields between the first wire 75b or the first connection part 76b and the second electrode 40.

[0041] According to the second embodiment described above, when projected onto a plane perpendicular to the Z direction, the coil 50b is covered by the first electrode 30. This suppresses the formation of an unwanted electromagnetic field between the coil 50b and the second electrode 40 that does not contribute to the heating of the heated material OH. In particular, in this embodiment, since the second electrode 40 is arranged to surround the first electrode 30 when viewed along the Z direction, for example, if there is a portion of the coil 50b that is not covered by the first electrode 30 when projected onto a plane perpendicular to the Z direction, an unwanted electromagnetic field is likely to be formed between that portion and the second electrode 40. Therefore, by having the coil 50b covered by the first electrode 30 when projected onto a plane perpendicular to the Z direction, the formation of an unwanted electromagnetic field between the coil 50b and the second electrode 40 can be suppressed more effectively.

[0042] C. Third Embodiment: Figure 8 is a perspective view showing the schematic configuration of the electrode unit 20c in the third embodiment. In Figure 8, as with Figures 2 and 3 described in the first embodiment, a portion of the winding 56 is omitted. In this embodiment, unlike the first embodiment, the coil 50c has a core 55. The configuration of the electrode unit 20c and dielectric heating device 100 in the third embodiment is the same as in the first embodiment unless otherwise described.

[0043] In this embodiment, the winding 56 of the coil 50c is wound around the core 55. The core 55 is sometimes also called the winding core.

[0044] In this embodiment, the core 55 is formed of resin or ceramics. This suppresses iron loss in the core 55 compared to, for example, a case where the core 55 is an iron core made of carbon steel or the like. Therefore, heat generation and power loss due to iron loss in the core 55 can be suppressed. In other embodiments, the core 55 may be made of an iron core, in which case the inductance of the coil 50c can be increased compared to a case where the core 55 is made of resin or ceramics.

[0045] Figure 9 shows a cross-section of the core 55 perpendicular to the magnetic path direction Dm. As shown in Figure 9, the core 55 in this embodiment has a hollow structure. More specifically, the core 55 has an annular hollow section 59 formed along the annular magnetic path direction Dm. In other words, the core 55 has a pipe-like shape along the magnetic path direction Dm. This suppresses iron loss in the core 55. The effect of providing the hollow section 59 in the core 55 is particularly large when the core 55 is made of an iron core. On the other hand, even when the core 55 is made of resin or ceramics, hysteresis loss and eddy current loss may occur due to the core 55, so providing the hollow section 59 in the core 55 can suppress iron loss in the core 55.

[0046] According to the third embodiment described above, the coil 50c has a core 55. This makes it easy to form the coil 50c.

[0047] Furthermore, in this embodiment, the core 55 is formed of resin or ceramics. Therefore, iron loss in the core 55 can be suppressed compared to the case where the core 55 is made of iron.

[0048] Furthermore, in this embodiment, the core 55 has a hollow portion 59 along the magnetic path direction Dm. Therefore, iron loss in the core 55 can be suppressed.

[0049] D. Other embodiments: (D-1) In the above embodiment, the linear distance d3 between the first electrode 30 and one end 51 of the coil 50 is less than or equal to the linear distance d4 between the first electrode 30 and the central portion 53. In contrast, the linear distance d3 may be greater than the linear distance d4.

[0050] (D-2) In the above embodiment, the coil 50 is formed in an annular shape so as to form an annular magnetic path within the coil 50. However, the coil 50 does not have to be formed in an annular shape. For example, the entire coil 50 may be formed in a polygonal annular shape so as to form an annular magnetic path of a polygon such as a rectangle within the coil 50. Similarly, the entire coil 50 may be formed in an oval or elliptical annular shape so as to form an annular path of an oval or elliptical shape within the coil 50. When the coil 50 is formed in an annular shape, the end on the 51 side of the coil 50 and the end on the 52 side may be spaced apart by a distance approximately equal to the average distance between the windings of the coil 50. In this case, the average distance between the windings of the coil 50 may be calculated, for example, by dividing the average magnetic path length of the coil 50 by the number of turns of the coil 50. Also, the coil 50 does not have to be formed in an annular shape if the straight-line distance d1 is less than or equal to the straight-line distance d2. In this case, it is preferable that the end on the 51 side of the coil 50 and the end on the 52 side face each other. Furthermore, it is preferable that the angular difference between the direction Dm1 of the magnetic path at one end 51 of the coil 50 shown in Figure 3 and the direction Dm2 of the magnetic path at the other end 52 is 10° or less. Also, it is preferable that the end at one end 51 of the coil 50 is located near the end at the other end 52, and that the shortest distance between the end at one end 51 and the end at the other end 52 of the coil 50 is 10 minutes of the wavelength λ0. 1 The following is more preferable:

[0051] (D-3) In the above embodiment, the dielectric heating device 100 is provided with only a single electrode unit 20. In contrast, the dielectric heating device 100 may be provided with two or more electrode units 20.

[0052] (D-4) In the above embodiment, the second electrode 40 is arranged to surround the first electrode 30 when viewed along the Z direction. In contrast, for example, the first electrode 30 may be arranged to surround the second electrode 40 when viewed along the Z direction. The first electrode 30 and the second electrode 40 may also be arranged to be adjacent to each other when viewed along the Z direction, or they may be arranged so that the heated material OH is sandwiched between the first electrode 30 and the second electrode 40 in the Z direction. Even in these cases, the formation of an unwanted electromagnetic field between the coil 50 and the second electrode 40 can be suppressed by arranging the coil 50 so that when projected onto a plane perpendicular to the Z direction, the coil 50 is covered by the first electrode 30, similar to the second embodiment. In this case, the shapes of the first electrode 30 and the second electrode 40 may be arbitrary, and may be circular, oval, rectangular, polygonal, etc. Also, when viewed along the Z direction, the areas of the first electrode 30 and the second electrode 40 may be the same or different. Preferably, the first electrode 30 and the second electrode 40 are arranged so that they do not overlap when viewed along the Z direction.

[0053] (D-5) In the above embodiment, the electrode unit 20 may be configured to reciprocate in a direction intersecting the direction in which the heated material OH is conveyed. For example, the electrode unit 20 may be supported by a drive unit (not shown) composed of a belt mechanism or a ball screw mechanism, and reciprocate in the X direction.

[0054] (D-6) In the above embodiment, a high-frequency voltage is applied to the electrode unit 20. However, the frequency of the AC voltage applied to the electrode unit 20 does not have to be high frequency, as long as it is a frequency that can heat the object to be heated OH. In this case, the frequency of the AC voltage is preferably, for example, 100 kHz or more and less than 1 MHz.

[0055] E. Other forms: This disclosure is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit. For example, this disclosure can also be implemented in the following forms. The technical features in the embodiments described below that correspond to the technical features in each of the forms described below can be replaced or combined as appropriate in order to solve some or all of the problems of this disclosure, or to achieve some or all of the effects of this disclosure. Furthermore, if such technical features are not described as essential in this specification, they can be deleted as appropriate.

[0056] (1) According to one embodiment of the present disclosure, a dielectric heating device is provided. This dielectric heating device comprises a first electrode and a second electrode facing an object to be heated and to which an alternating voltage is applied, and a coil electrically connected in series with the first electrode. The straight-line distance between one end and the other end of the coil is less than or equal to the straight-line distance between the center of the coil and the one end in the magnetic path direction of the coil. In this configuration, when an AC voltage is applied, the electromagnetic field irradiated from one end of the coil is more easily guided to the other end of the coil, and the electromagnetic field irradiated from the other end of the coil is more easily guided to the one end of the coil. Therefore, even if the number of turns or cross-sectional area of ​​the coil is increased and the coil becomes larger, unwanted electromagnetic fields generated from the coil can be suppressed. Consequently, it is not necessary to reduce the output power of the first and second electrodes in order to suppress unwanted electromagnetic fields generated from the coil, and thus the decrease in the heating efficiency of the object being heated can be suppressed.

[0057] (2) In the above embodiment, the coil may be formed in a ring shape so as to form a ring-shaped magnetic path within the coil. With this embodiment, unwanted electromagnetic fields generated from the coil can be suppressed more effectively.

[0058] (3) In the above configuration, when the coil is projected onto a plane perpendicular to the direction in which the object to be heated and the first electrode face each other, the coil may be covered by the first electrode. With this configuration, it is possible to suppress the formation of an unwanted electromagnetic field between the coil and the second electrode that does not contribute to heating the object to be heated.

[0059] (4) In the above embodiment, the linear distance between the first electrode and one end may be less than or equal to the linear distance between the first electrode and the central part. With this embodiment, the distance between one end of the coil and the first electrode becomes shorter compared to the case where the linear distance between the first electrode and one end of the coil is greater than the linear distance between the first electrode and the central part. Therefore, it is possible to suppress the generation of an unwanted electromagnetic field between the first electrode and the coil that does not contribute to heating the object to be heated.

[0060] (5) In the above embodiment, the coil may have a core. With this embodiment, the coil can be easily formed.

[0061] (6) In the above embodiment, the core may be made of resin or ceramics. With this embodiment, iron loss of the core can be suppressed compared to the case in which the core is made of iron.

[0062] (7) In the above embodiment, the core may have a hollow portion along the direction of the magnetic path. This embodiment can suppress iron loss in the core. [Explanation of symbols]

[0063] 20, 20b, 20c… ​​Electrode unit, 30… First electrode, 40… Second electrode, 43… Connecting member, 50, 50b, 50c… Coil, 51, 51b… One end, 52, 52b… Other end, 53… Central part, 55… Core, 56… Winding, 59… Hollow part, 70… Internal conductor, 75, 75b… First wire, 76, 76b… First connection part, 77, 77b… Second connection part, 78, 78b… Second wire, 80… Voltage application part, 100… Dielectric heating device, 110… Substrate, 200… Transport part, 205… Roller part, 300… Case part, 312… Insertion opening, 314… Outlet, 315… Opening, 500… Control unit

Claims

1. A first electrode and a second electrode facing the object to be heated, to which an AC voltage is applied, The device comprises a coil electrically connected in series with the first electrode, The straight-line distance between one end and the other end of the coil is less than or equal to the straight-line distance between the central part of the coil and the one end in the magnetic path direction of the coil. When the object to be heated and the first electrode are projected onto a plane perpendicular to the opposing direction, the coil is covered by the first electrode. A dielectric heating device in which the second electrode is arranged to surround the first electrode when viewed along the opposing direction.

2. A dielectric heating apparatus according to claim 1, A dielectric heating device wherein the coil is formed in a ring shape so as to form a ring-shaped magnetic path within the coil.

3. A dielectric heating apparatus according to claim 1 or 2, A dielectric heating device in which the linear distance between the first electrode and one end is less than or equal to the linear distance between the first electrode and the central portion.

4. A dielectric heating apparatus according to any one of claims 1 to 3, The coil is a dielectric heating device having a core.

5. A dielectric heating apparatus according to claim 4, The aforementioned core is formed of resin or ceramics, in a dielectric heating device.

6. A dielectric heating apparatus according to claim 4 or 5, The core is a dielectric heating device having a hollow portion along the direction of the magnetic path.

Images