Dielectric heating device

Abstract

A dielectric heating device capable of suppressing a decrease in heating efficiency of an object being heated by suppressing unnecessary electromagnetic fields generated by a coil. The dielectric heating device comprises a first electrode and a second electrode facing the object to be heated and to which an AC 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 the linear distance between the center of the coil and one end in the direction of the magnetic circuit.

Description

Technical Field

[0001] The present application relates to dielectric heating devices. Background Art

[0002] Patent Document 1 discloses a dielectric heating device comprising a first electrode, a second electrode, and an electromagnetic wave generator, wherein the electromagnetic wave generator includes a coil electrically connected to the first electrode. This dielectric heating device generates an electric field between the first and second electrodes by applying a high-frequency voltage to the first and second electrodes. This generated electric field generates dielectric heating to heat and dry ink adhered to the recording medium. The coil performs various functions, including adjusting the resonant frequency of the electromagnetic wave generator, matching impedance, and strengthening the electric field generated between the electrodes.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-8055

[0004] Patent Document 1 describes a case where the inductance of a coil is increased for purposes such as adjusting the resonant frequency of the electromagnetic wave generator. In this case, the inductance of the coil can be easily increased by increasing the number of turns and cross-sectional area of ​​the coil. However, increasing the number of turns and cross-sectional area of ​​the coil results in a larger coil, which carries the risk of increasing the range of the unnecessary electromagnetic field generated by the coil when voltage is applied. To suppress such unnecessary electromagnetic fields, reducing the power output to the electromagnetic wave generator risks reducing the heating efficiency of the heated object. Summary of the Invention

[0005] According to one embodiment of the present application, a dielectric heating device is provided. The dielectric heating device includes: a first electrode and a second electrode facing an object to be heated and to which an AC 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 the linear distance between the center of the coil in the direction of the magnetic circuit and the one end. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a perspective view showing a schematic configuration of the dielectric heating device in the first embodiment.

[0007] Figure 2 It is a perspective view showing a schematic configuration of an electrode unit in the first embodiment.

[0008] Figure 3 It is a front view of the electrode unit in the first embodiment.

[0009] Figure 4 It is a perspective view showing a schematic configuration of an electrode unit in the second embodiment.

[0010] Figure 5 It is a top view of the electrode unit in the second embodiment.

[0011] Figure 6 It is a front view of the electrode unit in the second embodiment.

[0012] Figure 7 It is a side view of the electrode unit in the second embodiment.

[0013] Figure 8 It is a perspective view showing a schematic configuration of an electrode unit in a third embodiment.

[0014] Figure 9 This is a diagram showing a cross section of the core body perpendicular to the magnetic path direction.

[0015] Description of Reference Numerals

[0016] 20, 20b, 20c…electrode unit; 30…first electrode; 40…second electrode; 43…connecting component; 50, 50b, 50c…coil; 51, 51b…one end; 52, 52b…the other end; 53…central portion; 55…core; 56…winding wire; 59…hollow portion; 70…inner conductor; 75, 75b…first electric wire; 76, 76b…first connecting portion; 77, 77b…second connecting portion; 78, 78b…second electric wire; 80…voltage applying portion; 100…dielectric heating device; 110…substrate; 200…conveying portion; 205…roller portion; 300…housing portion; 312…insertion port; 314…delivery port; 315…opening portion; 500…control portion. DETAILED DESCRIPTION

[0017] A. First embodiment:

[0018] Figure 1 It is a perspective view showing a schematic configuration of a dielectric heating device 100 in the first embodiment. Figure 1 The arrows showing the X, Y, and Z directions are perpendicular to each other. The X and Y directions are parallel to the horizontal plane, and the Z direction is the vertically upward direction. The arrows showing the X, Y, and Z directions are also in the same direction as shown in the other figures. Figure 1 The corresponding method is appropriately illustrated. In the following description, when specifying the direction of a direction, the direction indicated by the arrow in each figure is "+", and the opposite direction is "-", and the positive and negative signs are used in the direction description. Hereinafter, the +Z direction is also referred to as "up" and the -Z direction is referred to as "down". In addition, in this specification, the term "vertical" means including the range of 90°±10°.

[0019] The dielectric heating device 100 includes an electrode unit 20 for heating an object to be heated OH, a voltage applying 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 includes a conveying unit 200 for conveying the object to be heated OH and a housing 300 for housing the electrode unit 20.

[0020] The dielectric heating device 100 of this embodiment heats the object OH by an electric field generated by the electrode unit 20 within the housing 300 while transporting the object OH via the transport unit 200. In this embodiment, the dielectric heating device 100 heats a sheet-like printing medium coated with a liquid as the object OH, and dries the object OH. For example, paper, cloth, film, etc. can be used as the printing medium. For example, various inks mainly composed of water or an organic solvent can be used as the liquid applied to the printing medium. For example, the liquid is applied to the printing medium by a liquid ejection device such as an inkjet printer.

[0021] The control unit 500 is comprised of a computer equipped with the following components: a CPU, a storage unit, and an input / output interface for external signal input and output. The control unit 500 controls various components, such as the transport unit 200 and the voltage application unit 80, to heat the object OH in the dielectric heating device 100. In other embodiments, for example, the control unit 500 may be comprised of a combination of multiple circuits.

[0022] The conveyor unit 200 in this embodiment includes a drive unit (not shown) composed of two rollers 205 and a motor that drives the rollers 205. The conveyor unit 200 conveys the sheet-like object to be heated OH by driving the rollers 205. In other embodiments, for example, the conveyor unit 200 may be composed of a belt that supports and conveys the object to be heated OH and a drive unit that drives the belt.

[0023] The housing 300 is formed of a metal material and is used to block radiation waves from the electrode unit 20 housed therein. Specifically, the housing 300 generates an electromagnetic field within the housing 300 that weakens the radiation waves emitted from the electrode unit 20 by generating eddy currents on the walls of the housing 300, thereby blocking the radiation waves. "Blocking radiation waves" by the housing 300 means that the housing 300 controls the intensity of the electromagnetic field radiated from the electrode unit 20 to the outside of the housing 300 to below a predetermined baseline value. This baseline value is determined based on regulatory values ​​specified in national and regional guidelines regarding exposure limits to electromagnetic fields.

[0024] The housing 300 in this embodiment is made of lead and has a rectangular outer shape. Each surface of the housing 300 is made of a metal mesh with lead wires in a plain weave, and has a plurality of openings 315 divided by the wires. Figure 5 In the figure, only the openings 315 provided on the surface of the housing 300 on the +X direction side are shown; the openings 315 provided on other surfaces are omitted. In other embodiments, for example, the surfaces of the housing 300 may be formed of a wire mesh with a twill weave, expanded metal mesh, perforated metal sheet, or the like. Furthermore, for example, the housing 300 may be formed of carbon steel, aluminum, or the like.

[0025] The object to be heated OH is inserted into the housing 300 through an insertion port 312 provided on the surface of the housing 300 on the +Y direction side while being transported by the transport unit 200. Thereafter, the object to be heated OH is heated by the electrode unit 20 in the housing 300 while being similarly transported, and is then delivered to the outside of the housing 300 through a delivery port 314 provided on the surface of the housing 300 on the -Y direction side.

[0026] Figure 2 It is a perspective view showing a schematic configuration of the electrode unit 20 in this embodiment. Figure 3 2 is a front view of the electrode unit 20 in this 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 .

[0027] The first electrode 30 and the second electrode 40 are both Figure 1 In this embodiment, the first electrode 30 is electrically connected to the voltage applying unit 80 via the first wire 75, the first connecting portion 76, the coil 50, the second connecting portion 77, the second wire 78, and the inner conductor 70 of the coaxial cable. The second electrode 40 is electrically connected to the voltage applying unit 80 via the connecting member 43 arranged on the upper portion of the second electrode 40, the outer conductor of the coaxial cable not shown, etc. It should be noted that Figure 3 , the connecting component 43 is omitted.

[0028] The first electrode 30 and the second electrode 40 are conductive materials, such as metals, alloys, or conductive oxides. The first electrode 30 and the second electrode 40 may be formed of the same material or different materials. For example, to maintain their posture and strength, the first electrode 30 and the second electrode 40 may be disposed on a substrate, for example, made of a material with low dielectric loss and low conductivity, or may be supported by other components.

[0029] like Figure 2As shown, the first electrode 30 in this embodiment has a boat-like shape with the Y direction as the long side direction and the X direction as the short side direction. The lower surface of the first electrode 30 has a curved surface shape that is convex in the -Z direction. The first electrode 30 has an elliptical shape that is longer in the Y direction when viewed along the Z direction. The first electrode 30 has an arc shape that is convex in the -Z direction when viewed along the X direction. In addition, the first electrode 30 has an arc shape that is convex in the -Z direction when viewed along the Y direction. Therefore, the end portions of the first electrode 30 in the long side direction and the end portions in the short side direction are located closer to the +Z direction than the central portion of the first electrode 30.

[0030] The second electrode 40 has a ring shape that is flat in the X and Y directions and long in the Y direction. The second electrode 40 is arranged so as to surround the first electrode 30 when viewed in the Z direction. That is, in this embodiment, the first electrode 30 is arranged within the ring of the second electrode 40 when viewed in the Z direction. As a result, the electrode unit 20 in this embodiment has a point-symmetrical shape centered on the center point of the first electrode 30 in the X and Y directions when viewed in the Z direction.

[0031] The first electrode 30 and the second electrode 40 are both disposed on the substrate 110, which is arranged parallel to the X and Y directions. More specifically, the first electrode 30 is disposed such that the center of the lower surface of the first electrode 30 in the X and Y directions contacts the upper surface of the substrate 110. The second electrode 40 is disposed such that the lower surface of the second electrode 40 contacts the upper surface of the substrate 110. Therefore, in this embodiment, the center of the lower surface of the first electrode 30 and the lower surface of the second electrode 40 are disposed on the same plane.

[0032] In this embodiment, the substrate 110 is formed of glass. The substrate 110 prevents liquids such as ink applied to the heated object OH from adhering to the first and second electrodes 30 and 40, and prevents lint from adhering to the first and second electrodes 30 and 40 if the heated object OH is cloth. In other embodiments, for example, the substrate 110 may be formed of aluminum oxide.

[0033] Depend on Figure 1The voltage applying unit 80 shown in the figure applies an AC voltage to the first electrode 30 and the second electrode 40. The voltage applying unit 80 in this embodiment is configured as a high-frequency power supply including a high-frequency voltage generating circuit, and outputs a high-frequency voltage. For example, the voltage applying unit 80 is composed of a quartz oscillator, a PLL (Phase Locked Loop) circuit, and a power amplifier. The voltage applying unit 80 amplifies the high-frequency signal generated in the PLL circuit with a power amplifier, and supplies power to the electrode unit 20 via a coaxial cable, etc., 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 also be a reference potential. The so-called reference potential refers to a constant potential that serves as a reference for the high-frequency voltage, such as a ground potential. It should be noted that in this specification, the so-called high-frequency voltage refers to an AC voltage with a frequency of 1 MHz or more.

[0034] Application of an AC voltage to the first and second electrodes 30, 40 generates an electromagnetic field having a wavelength λ0 corresponding to the frequency f0 of the applied AC voltage. The intensity of this electromagnetic field is very strong near the first and second electrodes 30, 40 and very weak far away. In this specification, the electromagnetic field generated near the first and second electrodes 30, 40 by the application of the AC voltage is also referred to as the "near electromagnetic field." "Near" the first and second electrodes 30, 40 refers to a range within which the distance from the first and second electrodes 30, 40 is less than ½π of the wavelength of the generated electromagnetic field. A range further than "near" is also referred to as "far away." Furthermore, in this specification, the electromagnetic field generated far away from the first and second electrodes 30, 40 by the application of the AC voltage is also referred to as the "far away electromagnetic field." Far away electromagnetic fields correspond to electromagnetic fields typically used in communications using communication antennas, etc.

[0035] The electromagnetic field generated by 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 heated object OH contains water, the dielectric loss of the water reaches its maximum at around 20 GHz. Therefore, by applying high-frequency voltages of 2.45 GHz and 5.8 GHz in the ISM band to the electrode unit 20, the heated object OH can be heated more efficiently in the dielectric heating device 100. Furthermore, from the perspective of heating the ink, even at a low frequency such as 40.68 MHz, which is part of the ISM band, good heating efficiency can be achieved. This is because at 40.68 MHz, the dielectric loss of the water in the ink is low, making it easier for Joule heat generated by the pigment components in the ink, etc., to act as resistors.

[0036] The frequency f0 of the electromagnetic field generated by the electrode unit 20, i.e., 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 "nearby" range in order to expand the heating range of the heated object OH by the electrode unit 20, the capacitance of the first electrode 30 and the second electrode 40, when considered as electrode plates forming a capacitor, decreases, and therefore the capacitance of the electrode unit 20 decreases. Consequently, the resonant frequency of the electrode unit 20 increases. Therefore, for example, in order to maintain the resonant frequency of the electrode unit 20 while increasing the distance between the first electrode 30 and the second electrode 40, it is necessary to increase the inductance of the coil 50, thereby increasing the inductance of the electrode unit 20 and lowering the resonant frequency.

[0037] In this embodiment, the first electrode 30 and the second electrode 40 are arranged so that the shortest distance between them is less than one-tenth of the wavelength λ0 of the electromagnetic field. This allows the electric field density of the electromagnetic field generated by the first and second electrodes 30, 40 to be attenuated near the first and second electrodes 30, 40. Therefore, by appropriately maintaining the distance between the object to be heated OH and the first and second electrodes 30, 40, the object to be heated OH can be effectively heated by the electric field generated near the first and second electrodes 30, 40, while suppressing the radiation of the distant electromagnetic field from the first and second electrodes 30, 40. In particular, in this embodiment, the second electrode 40 is arranged so as to surround the first electrode 30 when viewed in the Z direction, thereby further suppressing the radiation of the distant electromagnetic field from the first and second electrodes 30, 40. It should be noted that if the second electrode 40 is configured so as to surround the first electrode 30 when viewed along the Z direction, for example, the outer shapes of the first electrode 30 and the second electrode 40 when viewed along the Z direction are polygonal shapes such as circular, rectangular, etc., the radiation of distant electromagnetic fields from the first electrode 30 and the second electrode 40 can also be suppressed.

[0038] In addition, in this embodiment, as described above, the electrode unit 20 has a point-symmetrical shape centered on the center point of the first electrode 30 in the X and Y directions when viewed along the Z direction, so the radiation of the distant electromagnetic field from the first electrode 30 and the second electrode 40 can be further suppressed.

[0039] like Figure 3As shown, in this embodiment, one end 51 of the coil 50 is electrically connected in series with the first electrode 30 via the first connection portion 76 and the first wire 75, and the other end 52 is electrically connected in series with the voltage application portion 80 via the second connection portion 77 and the second wire 78. By applying an AC voltage to the electrode unit 20 by the voltage application portion 80, a high voltage is generated at the one end 51 of the coil 50. As a result, the intensity of the electric field generated by the first electrode 30 and the second electrode 40 can be increased. It should be noted that by increasing the inductance of the coil 50, the Q value of the coil 50 is increased, thereby further increasing the intensity of the electric field generated by the first electrode 30 and the second electrode 40. The Q value is also called the quality factor.

[0040] like Figure 3 As shown, the straight-line distance d1 between one end 51 and the other end 52 of the coil 50 is less than the shortest straight-line distance d2 between the center portion 53 and the one end 51. The so-called center portion 53 refers to the central part of the coil 50 in the magnetic circuit direction Dm of the coil 50. The distance from the end of the coil 50 on the side of the one end 51 to the center portion 53 in the magnetic circuit direction Dm is equal to the distance from the end of the coil 50 on the side of the other end 52 to the center portion 53 in the magnetic circuit direction Dm. In addition, the so-called magnetic circuit direction Dm refers to the direction of the magnetic circuit formed in the coil 50 due to the passage of electricity to the coil 50. The magnetic circuit direction Dm reverses depending on the sign of the voltage applied to the coil 50. When the straight-line distance d1 is less than the straight-line distance d2, the one end 51 and the other end 52 are closer to each other than when the straight-line distance d1 is greater than the straight-line distance d2. Therefore, when an AC voltage is applied to coil 50 , it becomes easy to guide the electromagnetic field irradiated from one end 51 of coil 50 to the other end 52 of coil 50 , and it becomes easy to guide the electromagnetic field irradiated from the other end 52 to one end 51 .

[0041] In the case of 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 and strengthen the electric field generated by the first and second electrodes 30 and 40, for example, risks increasing the intensity of the unnecessary electromagnetic field generated by coil 50 when voltage is applied. Furthermore, increasing the number of turns and cross-sectional area of ​​coil 50 to increase its inductance increases the size of coil 50, thereby increasing the range of the unnecessary electromagnetic field generated by coil 50 when voltage is applied. For example, reducing the AC power output to the first and second electrodes 30 and 40 is a conceivable method for suppressing such unnecessary electromagnetic fields. However, reducing the AC power output reduces the heating efficiency of the heated object OH, potentially requiring a longer time to heat and dry the heated object OH. In this embodiment, as described above, the linear distance d1 is less than the linear distance d2. Therefore, even when the inductance of coil 50 is increased, the unnecessary electromagnetic field generated by coil 50 can be suppressed without reducing the AC power output.

[0042] It should be noted that, for example, the cross-sectional area and number of turns of the coil 50 are preferably determined from the perspective of achieving impedance matching between the electrode unit 20 and the voltage applying unit 80, in addition to the aforementioned perspectives of adjusting the resonant frequency and strengthening the electric field. Furthermore, the magnetic path length and material of the coil 50 are preferably also selected from the same perspective.

[0043] In this embodiment, if Figure 2 as well as Figure 3 As shown, the coil 50 is formed in a ring shape as a whole in such a way that a ring-shaped magnetic circuit is formed in the coil 50 when viewed along the X direction. In more detail, the winding wire 56 of the coil 50 is formed in a spiral shape that runs along the circumference. Thus, the coil 50 is formed in a ring shape as a whole in such a way that a ring-shaped magnetic circuit is formed in the coil 50 when viewed along the X direction. In addition, the cross-section perpendicular to the magnetic circuit direction Dm of the coil 50 has a circular shape. The shape of the coil 50 in this embodiment is also referred to as a donut shape, a ring shape, or a circle shape. It should be noted that, Figure 2 as well as Figure 3 Although a part of the winding wire 56 of the coil 50 is omitted in FIG. 1 , the winding wire 56 is actually wound in a spiral shape so that the intervals between the winding wires 56 in the magnetic path direction Dm are substantially constant.

[0044] In addition, in this embodiment, Figure 3The linear distance d3 between the first electrode 30 and one end 51 of the coil 50 shown in FIG is less than the linear distance d4 between the first electrode 30 and the central portion 53. This allows the one end 51 of the coil 50 to be closer to the first electrode 30 than when the linear distance d3 is greater than the linear distance d4. This prevents the generation of electromagnetic fields that do not contribute to heating the object OH between the coil 50 and the first electrode 30, or between the first electric wire 75, the first connecting portion 76, and the second electrode 40. Furthermore, this effectively increases the strength of the electric fields generated by the first and second electrodes 30, 40.

[0045] According to 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 the linear distance d2 between the center portion 53 of the coil 50 and the one end 51. Consequently, when an AC voltage is applied, it becomes easier to guide the electromagnetic field radiated from the one end 51 of the coil 50 to the other end 52 of the coil 50, and easier to guide the electromagnetic field radiated from the other end 52 of the coil 50 to the one end 51 of the coil 50. Therefore, even when the coil 50 is increased in size due to an increase in the number of turns and cross-sectional area, the generation of unnecessary electromagnetic fields from the coil 50 can be suppressed. Consequently, there is no need to reduce the power output to the first electrode 30 and the second electrode 40 to suppress the generation of unnecessary electromagnetic fields from the coil 50, thereby preventing a decrease in the heating efficiency of the object to be heated OH.

[0046] Furthermore, according to the present embodiment, the coil 50 is formed in an annular shape so as to form an annular magnetic path within the coil 50. Therefore, it is possible to more effectively suppress unnecessary electromagnetic fields generated from the coil 50.

[0047] 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 the linear distance d4 between the first electrode 30 and the central portion 53. Consequently, the distance between the one end 51 of the coil 50 and the first electrode 30 is closer than when the linear distance d3 is greater than the linear distance d4. Consequently, the generation of unnecessary electromagnetic fields between the first electrode 30 and the coil 50 that do not contribute to heating the object OH can be suppressed. Furthermore, this effectively increases the strength of the electric fields generated by the first electrode 30 and the second electrode 40 via the coil 50.

[0048] B. Second embodiment:

[0049] Figure 4 It is a perspective view showing a schematic configuration of an electrode unit 20 b in the second embodiment. Figure 5 It is a plan view of the electrode unit 20b in the second embodiment. Figure 6It 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. Figures 5 to 7 , the connecting member 43 is omitted. Figure 4 as well as Figure 6 In the first embodiment, Figure 2 as well as Figure 3 Similarly, a portion of the winding wire 56 is omitted. Unlike the first embodiment, the coil 50b in this embodiment is entirely disposed above the first electrode 30. The configurations of the electrode unit 20b and the dielectric heating device 100 in the second embodiment, except for portions not specifically described, are the same as those in the first embodiment.

[0050] like Figures 4 to 7 As shown, in this embodiment, the coil 50b is arranged above the first electrode 30 so that the entire coil 50b overlaps with 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 elliptical shape that is larger than the coil 50b in the X and Y directions, and the coil 50b is arranged inside the outer contour of the first electrode 30.

[0051] In this embodiment, if Figure 6 As shown, one end 51b of the coil 50b is located closer to the first electrode 30 than the center position of the coil 50b in the Z direction, that is, the center position Pc. In other words, the straight-line distance d3 between the one end 51b and the first electrode 30 is shorter than the straight-line distance d5 between the first electrode 30 and the center position Pc. More specifically, the one end 51b is located at the lower end of the coil 50b, that is, the position closest to the first electrode 30 within the coil 50b. In addition, as shown in FIG. Figures 5 to 7 As shown, in this embodiment, the first wire 75b is arranged in the +X direction of the coil 50b. The first connector 76b is provided so as to extend in the -X direction from the first wire 75b to the one end 51b of the coil 50b. The second wire 78b is arranged in the -X direction of the coil 50b. The second connector 77b is provided so as to extend in the +X direction from the second wire 78b to the other end 52b of the coil 50b.

[0052] Because one end 51b is positioned closer to the first electrode 30 than the center position Pc, the generation of unnecessary electric fields that do not contribute to heating the object OH between the coil 50b and the first electrode 30, or between the first electric wire 75b, the first connecting portion 76b, and the second electrode 40, can be further suppressed. Furthermore, this further increases the intensity of the electric fields generated by the first and second electrodes 30, 40. In particular, in this embodiment, the one end 51b is positioned at the lower end of the coil 50b, further suppressing the generation of unnecessary electromagnetic fields between the first electric wire 75b, the first connecting portion 76b, and the second electrode 40.

[0053] 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 prevents the formation of an unnecessary electromagnetic field between the coil 50b and the second electrode 40 that does not contribute to the heating of the heated object OH. In particular, in this embodiment, the second electrode 40 is arranged so as to surround the first electrode 30 when viewed along the Z direction. Therefore, for example, when projected onto a plane perpendicular to the Z direction, if there is a portion of the coil 50b that is not covered by the first electrode 30, an unnecessary electromagnetic field is likely to form between the portion and the second electrode 40. Therefore, when projected onto a plane perpendicular to the Z direction, the coil 50b is covered by the first electrode 30, which can more effectively prevent the formation of an unnecessary electromagnetic field between the coil 50b and the second electrode 40.

[0054] C. Third embodiment:

[0055] Figure 8 It is a perspective view showing a schematic configuration of an electrode unit 20 c in the third embodiment. Figure 8 In the first embodiment, Figure 2 as well as Figure 3 Similarly, a portion of the winding wire 56 is omitted. In this embodiment, the coil 50c has a core 55, unlike the first embodiment. The electrode unit 20c and the dielectric heating device 100 in the third embodiment are the same as those in the first embodiment except for the parts not specifically described.

[0056] The winding wire 56 of the coil 50c in this embodiment is wound around the core 55. The core 55 is also called a winding core.

[0057] In this embodiment, the core 55 is formed of resin or ceramic. This reduces the iron loss of the core 55 compared to, for example, an iron core formed of carbon steel or the like. Consequently, heat generation and power loss caused by the iron loss of the core 55 can be reduced. It should be noted that in other embodiments, the core 55 may also be formed of an iron core. In this case, the inductance of the coil 50c can be further increased compared to a core 55 formed of resin or ceramic.

[0058] Figure 9 1 is a diagram showing a cross section perpendicular to the magnetic path direction Dm of the core body 55. Figure 9 As shown, the core body 55 in this embodiment has a hollow structure. In more detail, the core body 55 is formed with a circular hollow portion 59 along the circular magnetic circuit direction Dm. That is to say, the core body 55 has a tubular shape along the magnetic circuit direction Dm. As a result, the iron loss of the core body 55 can be suppressed. It should be noted that the effect obtained by providing the hollow portion 59 in the core body 55 is particularly large when the core body 55 is composed of an iron core. On the other hand, when the core body 55 is formed of resin or ceramic, there is also a situation where hysteresis loss and eddy current loss based on the core body 55 are generated. Therefore, by providing the hollow portion 59 in the core body 55, the iron loss of the core body 55 can be suppressed.

[0059] According to the third embodiment described above, the coil 50c includes the core 55. This makes it possible to easily form the coil 50c.

[0060] In addition, in this embodiment, the core body 55 is formed of resin or ceramics. Therefore, compared with the case where the core body 55 is an iron core, the iron loss of the core body 55 can be suppressed.

[0061] In addition, in this embodiment, the core body 55 has the hollow portion 59 along the magnetic path direction Dm. Therefore, the iron loss of the core body 55 can be suppressed.

[0062] D. Other implementation methods:

[0063] (D-1) In the above embodiment, the linear distance d3 between the first electrode 30 and the one end 51 of the coil 50 is less than the linear distance d4 between the first electrode 30 and the center portion 53. However, the linear distance d3 may be greater than the linear distance d4.

[0064] (D-2) In the above embodiment, the coil 50 is formed into a circular ring shape in such a way that a circular ring-shaped magnetic circuit is formed within the coil 50. In this regard, the coil 50 may not be formed into a circular ring shape. For example, the coil 50 may be formed into a polygonal ring shape as a whole in such a way that a polygonal ring-shaped magnetic circuit such as a rectangle is formed within the coil 50. Similarly, the coil 50 may be formed into an elliptical or elliptical ring shape as a whole in such a way that an elliptical or elliptical ring-shaped path is formed within the coil 50. It should be noted that when the coil 50 is formed into a ring shape, the end portion on the side of one end 51 of the coil 50 and the end portion on the side of the other end 52 of the coil 50 may be separated and arranged with a size that is approximately the average value of the spacing between the windings of the coil 50. In this case, for example, the average value of the spacing between the windings of the coil 50 can be calculated by dividing the average magnetic circuit length of the coil 50 by the number of windings of the coil 50. In addition, if the straight-line distance d1 is less than the straight-line distance d2, the coil 50 may not be formed into a ring shape. In this case, it is preferable that the end portion of the coil 50 on the one end 51 side and the end portion on the other end 52 side face each other. Figure 3 The angle difference between the direction Dm1 of the magnetic path on the side of one end 51 of the coil 50 and the direction Dm2 of the magnetic path on the side of the other end 52 is shown to be 10 degrees or less. In addition, the end of the coil 50 on the side of one end 51 is preferably arranged near the end of the coil 50 on the side of the other end 52, and the shortest distance between the end of the coil 50 on the side of one end 51 and the end of the coil 50 on the side of the other end 52 is preferably less than one tenth of the wavelength λ0.

[0065] (D-3) In the above embodiment, only a single electrode unit 20 is provided in the dielectric heating device 100. However, two or more electrode units 20 may be provided in the dielectric heating device 100.

[0066] (D-4) In the above embodiment, the second electrode 40 is arranged so as to surround the first electrode 30 when viewed along the Z direction. For example, the first electrode 30 may be arranged so as to surround the second electrode 40 when viewed along the Z direction. In addition, the first electrode 30 and the second electrode 40 may be arranged so as to be adjacent to each other when viewed along the Z direction, or so as to sandwich the heated object OH between the first electrode 30 and the second electrode 40 in the Z direction. It should be noted that even in these cases, by arranging the coil 50 so as to be covered by the first electrode 30 when projected onto a plane perpendicular to the Z direction, as in the second embodiment, it is possible to suppress the formation of an unnecessary electromagnetic field between the coil 50 and the second electrode 40. In this case, the shapes of the first electrode 30 and the second electrode 40 may be arbitrary, and may be circular, elliptical, rectangular, polygonal, or the like. In addition, the areas of the first electrode 30 and the second electrode 40 when viewed along the Z direction may be the same or different. It is preferred that the first electrode 30 and the second electrode 40 be arranged so as not to overlap each other when viewed along the Z direction.

[0067] (D-5) In the above embodiment, the electrode unit 20 may be configured to be reciprocally movable in a direction intersecting the direction in which the object to be heated 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 reciprocated in the X direction.

[0068] (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 need not be high frequency as long as it can heat the object OH. For example, the frequency of the AC voltage in this case is preferably greater than 100 kHz and less than 1 MHz.

[0069] E. Other methods:

[0070] The present application is not limited to the above-mentioned embodiments and can be implemented in various ways without exceeding the scope of its main purpose. For example, the present application can also be implemented in the following ways. In order to solve part or all of the problems of the present application, or to achieve part or all of the effects of the present application, the technical features in the above-mentioned embodiments corresponding to the technical features in the various methods described below can be appropriately replaced or combined. In addition, if the technical feature is not described as an essential technical feature in this specification, it can be appropriately deleted.

[0071] (1) According to one embodiment of the present application, a dielectric heating device is provided. The dielectric heating device includes: a first electrode and a second electrode facing an object to be heated and to which an AC 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 the linear distance between the center of the coil in the direction of the magnetic circuit and the one end of the coil.

[0072] With this configuration, when an AC voltage is applied, it becomes easier to direct the electromagnetic field radiated from one end of the coil to the other end, and easier to direct the electromagnetic field radiated from the other end to the one end of the coil. Therefore, even when the coil size increases due to an increase in the number of turns and cross-sectional area, the generation of unnecessary electromagnetic fields from the coil can be suppressed. Consequently, there is no need to reduce the power output to the first and second electrodes to suppress the generation of unnecessary electromagnetic fields from the coil, thereby minimizing the reduction in heating efficiency of the object being heated.

[0073] (2) In the above aspect, the coil may be formed in an annular shape so as to form an annular magnetic path within the coil. According to this aspect, it is possible to more effectively suppress unnecessary electromagnetic fields generated by the coil.

[0074] (3) In the above embodiment, the coil may be covered by the first electrode when projected onto a plane perpendicular to the relative direction of the object to be heated and the first electrode. This embodiment can suppress the formation of an unnecessary electromagnetic field between the coil and the second electrode that does not contribute to heating the object to be heated.

[0075] (4) In the above embodiment, the linear distance between the first electrode and the one end may be less than the linear distance between the first electrode and the central portion. According to this embodiment, the distance between the one end of the coil and the first electrode is closer than when the linear distance between the first electrode and the one end of the coil is greater than the linear distance between the first electrode and the central portion. Therefore, it is possible to suppress the generation of an unnecessary electromagnetic field between the first electrode and the coil that does not contribute to heating the object.

[0076] (5) In the above embodiment, the coil may include a core. According to this embodiment, the coil can be easily formed.

[0077] (6) In the above embodiment, the core body may be formed of resin or ceramic. According to such an embodiment, the core body can suppress the iron loss of the core body compared to the case where the core body is an iron core.

[0078] (7) In the above embodiment, the core body may have a hollow portion along the magnetic path direction. According to such an embodiment, the iron loss of the core body can be suppressed.

Claims

1. A dielectric heating device, characterized in that: have: The first electrode and the second electrode face the object to be heated and are applied with an AC voltage; and a coil electrically connected in series with the first electrode, A linear distance between one end and the other end of the coil is less than a linear distance between a center portion of the coil in a magnetic path direction and the one end.

2. The dielectric heating device according to claim 1, characterized in that The coil is formed in an annular shape so as to form an annular magnetic circuit inside the coil.

3. The dielectric heating device according to claim 1 or 2, characterized in that When the coil is projected onto a plane perpendicular to the relative direction of the object to be heated and the first electrode, the coil is covered by the first electrode.

4. The dielectric heating device according to claim 1 or 2, characterized in that A straight-line distance between the first electrode and the one end is less than a straight-line distance between the first electrode and the central portion.

5. The dielectric heating device according to claim 1 or 2, characterized in that: The coil has a core.

6. The dielectric heating device according to claim 5, characterized in that The core body is formed of resin or ceramic.

7. The dielectric heating device according to claim 5, characterized in that The core body has a hollow portion along the direction of the magnetic circuit.

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