Dielectric heating device
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SEIKO EPSON CORP
- Filing Date
- 2022-07-13
- Publication Date
- 2026-08-04
Smart Images
Figure 0007899619000001 
Figure 0007899619000002 
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Abstract
Description
[Technical Field]
[0001] This disclosure relates to a dielectric heating apparatus. [Background technology]
[0002] Regarding dielectric heating devices, Patent Document 1 describes a device that heats and dries a conveyed object by a dielectric heating method by applying a high-frequency electric field to the conveyed object using multiple electrodes. [Prior art documents] [Patent Documents]
[0003] [Patent Document 1] Japanese Patent Publication No. 2018-9754 [Overview of the project] [Problems that the invention aims to solve]
[0004] In apparatuses that heat and dry conveyed materials, such as the one described in Patent Document 1, the conveyed material may become over-dried downstream in the conveying direction, for example, when the conveying speed is relatively slow or the electrode size is relatively large. [Means for solving the problem]
[0005] According to one embodiment of the present disclosure, a dielectric heating device is provided. This dielectric heating device comprises a transport unit for transporting media in a transport direction, an electrode unit having a first electrode and a second electrode facing the media transported by the transport unit, and drying the media by dielectric heating, a voltage application unit for applying an AC voltage to the first electrode and the second electrode, and a control unit for controlling the transport unit. The second electrode has a first portion and a second portion that sandwich the first electrode in the transport direction, the first portion is positioned upstream of the second portion in the transport direction, and the first electrode and the second electrode are formed such that the amount of heating of the media due to the electric field formed between the first electrode and the first portion is greater than the amount of heating of the media due to the electric field formed between the first electrode and the second portion. [Brief explanation of the drawing]
[0006] [Figure 1] A schematic diagram showing the general configuration of a dielectric heating device. [Figure 2] A perspective view showing the schematic configuration of the electrode unit in the first embodiment. [Figure 3] A top view showing the first electrode, the second electrode, and the media. [Figure 4] A schematic diagram illustrating the thickness of the first and second parts. [Figure 5] A schematic diagram illustrating the circuit formed by the electrode unit and the media. [Figure 6] A perspective view showing the schematic configuration of the electrode unit in the second embodiment. [Figure 7] A schematic diagram illustrating the width of the first and second parts. [Figure 8] A perspective view showing the schematic configuration of the electrode unit in the third embodiment. [Figure 9] A schematic diagram illustrating the first and second distances. [Modes for carrying out the invention]
[0007] A. First Embodiment: Figure 1 is a schematic diagram showing the general configuration of a dielectric heating device 100 as a 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°. The plane along the X and Y directions will also be referred to as the "XY plane".
[0008] The dielectric heating device 100 comprises a transport unit 320 for transporting media Md, an electrode unit 30 for drying media Md by dielectric heating, a voltage application unit 80 for applying an AC voltage to the electrode unit 30, and a control unit 250. The dielectric heating device 100 dries media Md by transporting it with the transport unit 320 and heating it with an AC electric field generated from the electrode unit 30. When we say "heating media Md with an AC electric field," this includes not only heating media Md itself with an AC electric field, but also heating any adhering substances such as liquids or solids on the media Md with an AC electric field. The electrode unit 30 is also called a heater.
[0009] For example, paper, cloth, or film can be used as the media Md. The cloth used as the media Md is formed by weaving fibers such as cotton, linen, polyester, silk, rayon, or blends thereof. In this embodiment, a sheet of cotton cloth is used as the media Md.
[0010] In this embodiment, the dielectric heating device 100 dries the medium Md coated with the liquid discharged by a liquid discharge device (not shown). As such a liquid, for example, various inks mainly composed of water are used. In this embodiment, an aqueous ink mainly composed of water is used as the liquid. In this specification, the main component of the liquid refers to a substance among the substances contained in the liquid whose mass fraction is 50% or more. In other embodiments, as the liquid, in addition to ink, for example, any liquid such as various coloring materials, electrode materials, samples such as biological organic and inorganic substances, lubricating oil, resin liquid, etching liquid, etc. may be used.
[0011] The ink used as the liquid in this embodiment is a pigment ink containing resin. The resin contained in the ink has the effect of firmly fixing the pigment on the medium Md through itself. Such a resin is used, for example, in a state where a resin that is hardly soluble or insoluble in a solvent such as water is made into fine particles and dispersed in the solvent, that is, in an emulsion state or a suspension state. As such a resin, for example, acrylic resin, styrene-acrylic resin, fluorene resin, urethane resin, polyolefin resin, rosin-modified resin, terpene resin, polyester resin, polyamide resin, epoxy resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, ethylene vinyl acetate resin, etc. can be used. Two or more of these resins may be used in combination. Such a resin is also called a resin.
[0012] The conveyance unit 320 is configured as a roller mechanism that conveys the medium Md by driving the roller 323. The conveyance unit 320 drives the roller 323 by the driving force of a driving unit (not shown) composed of a motor or the like under the control of the control unit 250. In this embodiment, the conveyance unit 320 conveys the medium Md in the -Y direction. In other embodiments, the conveyance unit 320 may be configured as a belt mechanism that conveys the medium Md by driving a belt, for example.
[0013] The control unit 250 is composed of a computer including one or more processors, a storage device, and an input / output interface for inputting and outputting signals to and from the outside. In other embodiments, the control unit 250 may be composed of, for example, a combination of multiple circuits.
[0014] The voltage application unit 80 is electrically connected to the electrode unit 30 and applies an alternating voltage with a predetermined drive frequency f0 to the first electrode 31 and the second electrode 32 of the electrode unit 30 described later. In the present embodiment, the voltage application unit 80 is configured as a high-frequency power supply including a high-frequency voltage generation circuit and has a crystal oscillator, a PLL (Phase Locked Loop) circuit, and a power amplifier, which are not shown respectively. In other embodiments, the voltage application unit 80 may be configured as an inverter including a switching circuit having a switching element such as a transistor. One of the potentials applied to the first electrode 31 or the second electrode 32 may be a reference potential. The reference potential is a fixed potential serving as a reference for the high-frequency voltage and is, for example, the ground potential.
[0015] In the present embodiment, a high-frequency voltage is applied to each electrode of the electrode unit 。In this specification, "high frequency" refers to a frequency of 1 MHz or higher. More specifically, in the present embodiment, 13.56 MHz, which is one of the Industrial Scientific and Medical (ISM) bands, is used as the drive frequency f0. Since the dielectric loss tangent of water becomes maximum around 20 GHz, by applying a high-frequency voltage of 2.45 GHz or 5.8 GHz in the ISM band to each electrode of the electrode unit 30, the medium Md can be heated more efficiently. On the other hand, from the perspective of heating the ink, even when the drive frequency f0 is relatively low, such as 13.56 MHz or 40.68 MHz, good heating efficiency can be obtained. The reason for this is that when the drive frequency f0 is 13.56 MHz or 40.68 MHz, although the dielectric loss tangent of water in the ink is low, Joule heat generated by treating the dye component in the ink as an electrical resistance is likely to occur.
[0016] Figure 2 is a perspective view showing the schematic configuration of the electrode unit 30 in this embodiment. As shown in Figure 1, in this embodiment, the dielectric heating device 100 has two electrode units 30 arranged side by side along the X direction. As shown in Figures 1 and 2, the electrode unit 30 has a first electrode 31 and a second electrode 32. The electrode unit 30 in this embodiment also has a coil 34. In other embodiments, the number of electrode units 30 may be one or three or more. Also, each electrode unit 30 does not have to be arranged side by side along the X direction, but may be arranged arbitrarily.
[0017] The first electrode 31 and the second electrode 32 face the media Md being transported in the transport direction. In this embodiment, the transport direction is the -Y direction. Therefore, in this embodiment, the +Y direction side corresponds to the upstream side of the transport direction, and the -Y direction side corresponds to the downstream side of the transport direction. In the following, the first electrode 31 and the second electrode 32 face the media Md. Direction The direction in which this occurs is also called the opposing direction. The opposing direction includes both the direction along the same axis and the opposite direction, and in this embodiment, it is the Z direction.
[0018] The first electrode 31 and the second electrode 32 are conductors and are formed from, for example, metals, alloys, conductive oxides, etc. The first electrode 31 and the second electrode 32 may be formed from the same material or from different materials. The first electrode 31 and the second electrode 32 may be placed on a substrate or the like made of a material with low dielectric loss tangent or conductivity, for example, to maintain their orientation and strength, or they may be supported by other members.
[0019] The first electrode 31 and the second electrode 32 are arranged such that the shortest distance between the first electrode 31 and the second electrode 32 is one-tenth or less of the wavelength of the electromagnetic field output from the electrode unit 30. As shown in Figure 2, the first electrode 31 in this embodiment is X The direction is the longitudinal direction, YIt has a boat-shaped form with its shorter side facing outwards. The lower surface of the first electrode 31 has a curved shape that is convex in the -Z direction. When viewed along the Z direction, the first electrode 31 has an elongated oval shape that is longer in the X direction. The second electrode 32 is flattened in the X and Y directions and has an elongated oval annular shape that is longer in the X direction. When viewed along the Z direction, the second electrode 32 is arranged to surround the first electrode 31. As will be described later, the second electrode 32 has a first part 36 and a second part 37 that sandwich the first electrode 31 from each other in the transport direction.
[0020] As shown in Figures 1 and 2, the first electrode 31 and the second electrode 32 are both positioned on a substrate 110 that is parallel to the XY plane. More specifically, the first electrode 31 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 32 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 31 and the lower surface of the second electrode 32 are positioned on the same plane.
[0021] As shown in Figure 1, in this embodiment, the first electrode 31 and the second electrode 32 are positioned above the media Md. Therefore, in this embodiment, the lower surfaces of the first electrode 31 and the second electrode 32 face the upper surface of the media Md. The substrate 110 described above is positioned between the media Md and the first electrode 31 and the second electrode 32.
[0022] In this embodiment, the substrate 110 is made of glass. The substrate 110 prevents liquids such as ink applied to the media Md from adhering to the first electrode 31 and the second electrode 32, and also prevents lint from the media Md from adhering to the first electrode 31 and the second electrode 32 if the media Md is cloth. In other embodiments, the substrate 110 may be made of alumina, for example.
[0023] Let's return to the explanation of Figure 2. In this embodiment, the first electrode 31 is electrically connected to the voltage application unit 80 via the electric wire 35, the coil 34, and the internal conductor IC1 of the coaxial cable. The second electrode 32 is electrically connected to the voltage application unit 80 via a connecting member 33 located on the upper part of the second electrode 32, or via the external conductor of the coaxial cable (not shown).
[0024] When an AC voltage with a driving frequency f0 is applied to the first electrode 31 and the second electrode 32, an electromagnetic field with a wavelength corresponding to the driving frequency f0 is generated from the first electrode 31 and the second electrode 32. The strength of this electromagnetic field is very strong in the vicinity of the first electrode 31 and the second electrode 32, and very weak at a distance. Hereafter, the electromagnetic field generated in the vicinity of the first electrode 31 and the second electrode 32 by the application of the AC voltage will also be called the "nearby electromagnetic field". "Nearby" of the first electrode 31 and the second electrode 32 refers to the range where the distance from the first electrode 31 and the second electrode 32 is 1 / 2π or less of the wavelength of the generated electromagnetic field. The range further than "nearby" will also be called "far". The electromagnetic field generated far from the first electrode 31 and the second electrode 32 by the application of the AC voltage will also be called the "far electromagnetic field". The far electromagnetic field corresponds to the electromagnetic field used for communication using general communication antennas, etc. Furthermore, the electric field formed in the vicinity of the first electrode 31 and the second electrode 32 is also called the near-field electric field.
[0025] As described above, the first electrode 31 and the second electrode 32 are arranged such that the shortest distance between them is less than one-tenth of the wavelength of the electromagnetic field. This allows the density of the electromagnetic field generated from the first electrode 31 and the second electrode 32 to be attenuated in the vicinity of the first electrode 31 and the second electrode 32. Therefore, by appropriately maintaining the distance between the media Md and the first electrode 31 and the second electrode 32, the media Md can be efficiently heated by the electric field generated in the vicinity of the first electrode 31 and the second electrode 32 while suppressing the radiation of far-field electromagnetic fields from the first electrode 31 and the second electrode 32. In particular, in this embodiment, since the second electrode 32 is arranged to surround the first electrode 31 when viewed along the Z direction, the radiation of far-field electromagnetic fields from the first electrode 31 and the second electrode 32 can be further suppressed.
[0026] In this embodiment, one end of the coil 34 is electrically connected in series with the first electrode 31 via the electric wire 35, and the other end is electrically connected in series with the voltage application unit 80 shown in Figure 1. In this embodiment, the coil 34 is composed of a solenoid coil and is arranged so that its length is aligned with the Z direction. The shape, length, cross-sectional area, number of turns, material, etc. of the coil 34 are selected, for example, according to the driving frequency f0, and to achieve impedance matching between the electrode unit 30 and the voltage application unit 80. In other embodiments, one end of the coil 34 may be connected in series with the second electrode 32 instead of the first electrode 31.
[0027] When the voltage application unit 80 applies an AC voltage to the electrode unit 30, a high voltage is generated at one end of the coil 34. This increases the strength of the electric field generated from the first electrode 31 and the second electrode 32. Preferably, the coil 34 is arranged so that the distance between one end of the coil 34 and the first electrode 31 is as small as possible. If the distance between one end of the coil 34 and the first electrode 31 is large, the high voltage generated at one end of the coil 34 may generate an electric field between the coil 34 and the first electrode 31, or between the wire 35 and the second electrode 32, which does not contribute to heating the media Md, potentially reducing the effect of increasing the strength of the near-field electric field generated from the first electrode 31 and the second electrode 32. In contrast, by reducing the distance between one end of the coil 34 and the first electrode 31, the generation of such an electric field that does not contribute to heating the media Md can be suppressed, thereby effectively increasing the strength of the electric field that contributes to heating the media Md. In other embodiments, for example, the first electrode 31 may be formed in a meander shape to allow it to perform a function similar to that of the coil 34.
[0028] Figure 3 is a top view showing the first electrode 31 and the second electrode 32 and the media Md in this embodiment. In Figure 3, the substrate 110 is omitted. As shown in Figures 2 and 3, the first portion 36 of the second electrode 32 described above is located upstream of the second portion 37 in the transport direction. More specifically, in this embodiment, the first portion 36 is the portion of the annularly formed second electrode 32 surrounding the first electrode 31 as described above, located on the +Y direction side of the first electrode 31. The second portion 37 is the portion of the second electrode 32 located on the -Y direction side of the first electrode 31.
[0029] In this embodiment, the thickness t1 of the first portion 36 is greater than the thickness t2 of the second portion 37. In this specification, thickness t1 refers to the average thickness of the first portion 36, and thickness t2 refers to the average thickness of the second portion 37. The average thickness of a portion is measured by measuring the thickness of 10 or more points in that portion and calculating the arithmetic mean of each thickness. In this embodiment, the first portion 36 and the second portion 37 are formed such that their thicknesses are uniform in the Z direction.
[0030] The first electrode 31 and the second electrode 32 are formed such that the first heating amount of the electrode unit 30 is greater than the second heating amount of the electrode unit 30. The first heating amount refers to the amount of heating of the media Md by the first electric field, which represents the near-field electric field formed between the first electrode 31 and the first part 36. The second heating amount refers to the amount of heating of the media Md by the second electric field, which represents the near-field electric field formed between the first electrode 31 and the second part 37.
[0031] When comparing the first heating amount and the second heating amount, for example, a cotton cloth with a liquid applied to its entire surface to a roughly uniform thickness is prepared as media Md, and the temperature of the first media portion Mp1 and the temperature of the second media portion Mp2 are compared when the media Md is heated by the electrode unit 30 without being transported. More specifically, if the first heating amount is greater than the second heating amount, the temperature of the first media portion Mp1 when the media Md is heated in this way will be higher than the temperature of the second media portion Mp2. The first media portion Mp1 refers to the portion of the media Md located between the first electrode 31 and the first portion 36 when viewed along the Z direction, as shown by the dashed line and hatching in Figure 3. Similarly, the second media portion Mp2 refers to the portion of the media Md located between the first electrode 31 and the second portion 37 when viewed along the Z direction.
[0032] When a portion of the media Md is heated by the electrode unit 30, the amount of heating increases as the strength of the near-field electric field acting on that portion increases. Therefore, by increasing the strength of the electric field acting on the liquid attached to the first media portion Mp1, or decreasing the strength of the electric field acting on the liquid attached to the second media portion Mp2, the amount of heating in the first portion can be made relatively larger than the amount of heating in the second portion. Note that increasing the strength of the near-field electric field acting on the liquid attached to a portion of the media Md corresponds to increasing the density of electric field lines passing through that liquid when the near-field electric field is represented by electric field lines. In particular, since the liquid attached to the sheet-like media Md is usually distributed so as to spread along the planar direction of the media Md, the amount of heating in a portion of the media Md can be effectively increased by increasing the density of electric field lines along the planar direction of the media Md near that portion.
[0033] Figure 4 is a schematic diagram illustrating the thickness t1 of the first portion 36 and the thickness t2 of the second portion 37. Figure 4 schematically shows the state when the liquid Lq attached to the media Md is heated by the electrode unit 30. In Figure 4, the electric field Eq1 acting on the liquid Lq attached to the first media portion Mp1 and the electric field Eq2 acting on the liquid Lq attached to the second media portion Mp2 are represented by dashed lines. In Figure 4, the thicker the dashed line, the stronger the electric field represented by that dashed line. As shown in Figures 2 and 4, in this embodiment, the second electrode 32 is formed such that the thickness t1 of the first portion 36 in the Z direction is thicker than the thickness t2 of the second portion 37 in the Z direction, thereby achieving a first heating amount that is greater than the second heating amount. More specifically, as shown in Figure 4, in this embodiment, by making the thickness t1 thicker than the thickness t2, the strength of the electric field Eq1 is stronger than the strength of the electric field Eq2.
[0034] Figure 5 is a schematic diagram illustrating the circuit formed by the electrode unit 30 and the liquid Lq adhering to the media Md in this embodiment. As shown in Figure 5, the first electrode 31 and the second electrode 32 of the electrode unit 30 can each be considered as electrode plates constituting a single capacitor.
[0035] The resistor R shown in Figure 5 a This represents the resistance of electrode unit 30. Resistance R a This includes the internal resistance of the voltage application section 80 and the parasitic resistance of the coil 34. Inductance L a This represents the inductance of electrode unit 30. Inductance L a This includes the inductance of coil 34 and the parasitic inductance of each electrode of electrode unit 30. Capacitance C a This represents the capacitance of electrode unit 30. Capacitance C a This includes the parasitic capacitance of coil 34 and the capacitance between each electrode of electrode unit 30. Resistor R b This represents the electrical resistance of the liquid Lq attached to the media Md. Capacitance Cb1 represents the parasitic capacitance between the first electrode 31 and the liquid Lq. Capacitance C b2 represents the parasitic capacitance between the second electrode 32 and the liquid Lq. Capacitance C b is capacitance C b1 and C b2 is expressed as the sum of them. Capacitance C a and capacitance C b The sum of and corresponds to the capacitance of the electrode unit 30.
[0036] The resonance frequency f1 of the electrode unit 30 when drying the liquid applied to the medium Md is expressed as the resonance frequency of the electrode unit 30 in the circuit formed by the electrode unit 30 and the liquid Lq attached to the medium Md shown in FIG. 5. As the water content of the medium Md decreases with the progress of drying, the capacitance C a decreases, so the resonance frequency f1 increases with the progress of drying. Hereinafter, such a change in the resonance frequency f1 with the progress of drying is also referred to as a shift of the resonance frequency f1. When the resonance frequency f1 shifts, the difference between the driving frequency f0 and the resonance frequency f1 changes, so the impedance of the electrode unit 30 changes. Therefore, the shift of the resonance frequency f1 affects the heating amount of the entire electrode unit 30. For example, when the driving frequency f0 is set to be equal to the resonance frequency f1 when the water content of the medium Md is sufficiently large, the shift of the resonance frequency f1 increases the difference between the resonance frequency f1 and the driving frequency f0, and the impedance of the electrode unit 30 increases. Therefore, in this case, the shift of the resonance frequency f1 contributes to a decrease in the heating amount of the entire electrode unit 30.
[0037] In this embodiment, the electrode unit 30 is configured such that the first sensitivity to the resonant frequency f1 is higher than the second sensitivity. The first sensitivity refers to the sensitivity of the electrode unit 30 to changes in the water content of the media Md between the first electrode 31 and the first portion 36 at the resonant frequency f1. The second sensitivity refers to the sensitivity of the electrode unit 30 to changes in the water content of the media Md between the second electrode 32 and the second portion 37 at the resonant frequency f1. More specifically, the first sensitivity corresponds to the sensitivity of the resonant frequency f1 to changes in the water content of the first media portion Mp1. The second sensitivity corresponds to the sensitivity of the resonant frequency f1 to changes in the water content of the second media portion Mp2. As described above, a shift in the resonant frequency f1 affects the heating amount of the entire electrode unit 30. Therefore, by making the first sensitivity higher than the second sensitivity, the sensitivity of the heating amount of the entire electrode unit 30 to changes in the water content of the first media portion Mp1 can be made higher than the sensitivity to changes in the water content of the second media portion Mp2.
[0038] In this embodiment, the water content in a portion of media Md is expressed as the mass of water contained per unit volume of that portion. In other embodiments, for example, the water content in a portion may be expressed as the volume of water contained per unit volume of that portion, or as the ratio of the mass or volume of water to a reference value of mass or volume.
[0039] When comparing the first sensitivity and the second sensitivity, first, a cotton cloth with a liquid applied to its entire surface in a substantially uniform thickness is prepared as the first sample, and the resonance frequency ft0 is measured when the first sample is heated by the electrode unit 30 without being transported. Next, a cotton cloth with a liquid applied to its entire surface in a substantially uniform thickness is prepared as the second sample, excluding the portion corresponding to the first media portion Mp1, and the resonance frequency ft1 is measured when the second sample is heated by the electrode unit 30 without being transported. The difference between this resonance frequency ft1 and the resonance frequency ft0 corresponds to the first sensitivity. Similarly, the same process is performed on the surface excluding the portion corresponding to the second media portion Mp2. With thickness A cotton cloth soaked in liquid Sample 3The first sample is prepared and heated by the electrode unit 30 in the same way, and the resonant frequency ft2 is measured. The difference between this resonant frequency ft2 and the resonant frequency ft0 corresponds to the second sensitivity. When ink is used as the liquid Lq as in this embodiment, the first sample described above can be prepared, for example, by solid printing the liquid over the entire surface of the cotton cloth using an inkjet printer. Solid printing means printing so that dots are formed for all pixels that make up the image, and no background color of the media Md remains. The second and third samples can be prepared in the same way by solid printing the liquid over the surface of the cotton cloth, excluding the parts corresponding to the first media part Mp1 and the second media part Mp2. The resonant frequencies ft0 to ft2 are calculated, for example, based on the inductance and capacitance of the electrode unit 30 measured using a network analyzer.
[0040] As shown in Figure 4, the first sensitivity can be increased by increasing the ratio of the strength of the electric field Eq1 acting on the first media portion Mp1 to the strength of the electric field En1 that does not act on the first media portion Mp1. Increasing the ratio of the electric field Eq1 to the strength of the electric field En1 corresponds to increasing the proportion of electric field lines that pass through the liquid Lq attached to the first media portion Mp1 among the electric field lines representing the first electric field. Furthermore, the second sensitivity can be decreased by decreasing the ratio of the strength of the electric field Eq2 acting on the second media portion Mp2 to the strength of the electric field En2 that does not act on the second media portion Mp2.
[0041] In this embodiment, the second electrode 32 is formed such that the thickness t1 shown in Figures 2 and 4 is greater than the thickness t2, thereby achieving a higher first sensitivity to the resonant frequency f1 compared to the second sensitivity. Generally, increasing the thickness t1 can increase the density of electric field lines passing through the liquid Lq on the first media portion Mp1, and thus increase the ratio of the electric field Eq1 to the strength of the electric field En1. However, if the thickness t1 is made too thick, the number of electric field lines that do not pass through the liquid Lq on the first media portion Mp1 increases, which may reduce the ratio of the electric field Eq1 to the strength of the electric field En1. In this embodiment, the thickness t1 is preferably 1.5 times or more the thickness t2, and more preferably 3 times or more. Furthermore, the thickness t1 is preferably 10 times or less the thickness t2, and more preferably 8 times or less the thickness t2.
[0042] According to the dielectric heating device 100 of the first embodiment described above, the electrode unit 30 has a first portion 36 and a second portion 37 that sandwich the first electrode 31 from each other in the transport direction of the media Md, the first portion 36 is positioned upstream of the second portion 37 in the transport direction, and the first electrode 31 and the second electrode 32 are formed such that the first heating amount, which represents the amount of heating of the media Md by the first electric field formed between the first electrode 31 and the first portion 36, is larger than the second heating amount, which represents the amount of heating of the media Md by the second electric field formed between the first electrode 31 and the second portion 37. As a result, the amount of heating of the media Md by the electrode unit 30 is greater upstream in the transport direction of the media Md, and the amount of heating of the media Md by the electrode unit 30 is smaller downstream in the transport direction. Therefore, it is possible to suppress the media Md from drying out too much due to heating by the electrode unit 30 downstream in the transport direction. Furthermore, since it is not necessary to measure the water content of the media Md, it is possible to prevent the media Md from drying out too much further downstream in the transport direction, even without installing a sensor to measure the water content near the first electrode 31 or the second electrode 32.
[0043] Furthermore, in this embodiment, the electrode unit 30 is configured such that the first sensitivity of the electrode unit 30 to changes in the water content of the media Md heated by the electric field formed between the first electrode 31 and the first portion 36 is higher than the second sensitivity to changes in the water content of the media Md heated by the electric field formed between the first electrode 31 and the second portion 37. With this configuration, the sensitivity of the total heating amount of the electrode unit 30 to changes in the water content of the first media portion Mp1 can be made higher than the sensitivity to changes in the water content of the second media portion Mp2. As a result, for example, by setting the drive frequency f0 to match the resonance frequency f1 when the water content of the media Md is sufficiently large, the amount of heating in the first media portion Mp1 can be increased when the water content of the first media portion Mp1 is relatively large, and the water content of the first media portion Mp1 can be reduced further. Conversely, if the moisture content of the first media portion Mp1 is lower, the amount of heating in the first media portion Mp1 can be reduced, thereby preventing over-drying of the first media portion Mp1. When heating the media Md while it is being transported, the portion that is first heated by the electrode unit 30 as the first media portion Mp1 becomes the second media portion Mp2. Therefore, by doing as described above, the likelihood of drying the second media portion Mp2 without excess or deficiency increases, regardless of whether the moisture content of the first media portion Mp1 is relatively high or low. As a result, the media Md can be dried more uniformly.
[0044] Furthermore, in this embodiment, the thickness t1 of the first portion 36 is greater than the thickness t2 of the second portion 37. Therefore, by making the thickness t1 greater than the thickness t2, it is easy to achieve that the first heating amount is greater than the second heating amount. Also, by making the thickness t1 greater than the thickness t2, it is easy to achieve that the first sensitivity at the resonant frequency f1 is higher than the second sensitivity.
[0045] B. Second Embodiment: Figure 6 is a perspective view showing the schematic configuration of the electrode unit 30b in the second embodiment. In Figure 6, the electric wire 35, coil 34, and internal conductor IC1 are omitted. In this embodiment, unlike the first embodiment, the second electrode 32b is formed such that the width w1 of the first part 36b in the transport direction is smaller than the width w2 of the second part 37b in the transport direction. The configuration of the electrode unit 30b and dielectric heating device 100 in the second embodiment is the same as in the first embodiment unless otherwise described.
[0046] As described above, in this embodiment, width w1 is smaller than width w2. In this specification, width w1 refers to the average width of the first part 36b, and width w2 refers to the average width of the second part 37b. The average width of a part is measured by measuring the widths of 10 or more points in that part and calculating the arithmetic mean of each width. In this embodiment, because width w1 is smaller than width w2, the second electrode 32b has a shape that is asymmetric with respect to a straight line along the X direction that bisects the first electrode 31 in the Y direction when viewed along the Z direction, and a shape that is asymmetric with respect to the center point of the first electrode 31 in the X and Y directions. Also, in this embodiment, because width w1 is smaller than width w2, the first heating amount is made larger than the second heating amount. In this embodiment, the first part 36b and the second part 37b are formed to have uniform widths w1 and w2 over the X direction, respectively. b The thickness t1 and the second part 37 b The thickness t2 is the same in each case.
[0047] Figure 7 is a schematic diagram illustrating the width w1 of the first portion 36b and the width w2 of the second portion 37b. Similar to Figure 4 described in the first embodiment, Figure 7 schematically shows the state when the liquid Lq adhering to the media Md is heated by the electrode unit 30b. Similar to Figure 4, the electric fields Eq1, Eq2, En1, and En2 are shown by dashed lines in Figure 7. As shown in Figure 7, in this embodiment, by making the width w1 smaller than the width w2, the intensity of the electric field Eq1 is stronger than the intensity of the electric field Eq2. More specifically, the smaller width w1 concentrates the electric field lines from the first portion 36b toward the first electrode 31 and from the first electrode 31 toward the first portion 36b over a narrower area, thereby increasing the intensity of the electric field Eq1. In this embodiment, the width w 2 is width w 1 It is preferable that it be 1.5 times or more, and more preferable that it be 2 times or more. Also, the width w 2 is width w 1 It is preferable that it is 8 times or less, and more preferable that it is 6 times or less.
[0048] Furthermore, in this embodiment, the width w1 is made smaller than the width w2 of the second electrode 32 b The formation of this structure results in a first sensitivity at resonant frequency f1 being higher than the second sensitivity. More specifically, as described above, the smaller width w1 causes the electric field lines from the first portion 36b toward the first electrode 31 and from the first electrode 31 toward the first portion 36b to concentrate over a narrower area in the first portion 36b, thereby increasing the strength of the electric field Eq1 relative to the strength of the electric field En1.
[0049] According to the second embodiment described above, the width w1 of the first portion 36b of the second electrode 32b is smaller than the width w2 of the second portion 37b. Therefore, by making the width w1 smaller than the width w2, it is easy to achieve that the first heating amount is larger than the second heating amount. Furthermore, by making the width w1 smaller than the width w2, it is also easy to achieve that the first sensitivity of the resonant frequency f1 is higher than the second sensitivity.
[0050] C. Third Embodiment: Figure 8 is a perspective view showing the schematic configuration of the electrode unit 30c in the third embodiment. In Figure 8, as with Figure 2 described in the second embodiment, the electric wire 35, coil 34, and internal conductor IC1 are omitted. In this embodiment, unlike the first and second embodiments, the first distance d1 in the transport direction between the first electrode 31 and the first portion 36c of the second electrode 32c is shorter than the second distance d2 in the transport direction between the first electrode 31 and the second portion 37. The configuration of the electrode unit 30c and dielectric heating device 100 in the third embodiment is the same as in the first embodiment unless otherwise described.
[0051] As described above, in this embodiment, the first distance d1 is shorter than the second distance d2. In this embodiment, the first distance d1 refers to the average value of the distance in the transport direction between the first electrode 31 and the first part 36c, and the second distance d2 refers to the average value of the distance in the transport direction between the first electrode 31 and the second part 37. The average value of the distance is measured by measuring the distances at 10 or more points and calculating the arithmetic mean of each distance. In this embodiment, because the first distance d1 is smaller than the second distance d2, the second electrode 32c has a shape that is asymmetric with respect to a straight line along the X direction that bisects the first electrode 31 in the Y direction when viewed along the Z direction, and a shape that is asymmetric with respect to the center point of the first electrode 31 in the X and Y directions. Furthermore, in this embodiment, because the first distance d1 is smaller than the second distance d2, it is realized that the first heating amount is larger than the second heating amount. Thus, forming the first electrode 31 and the second electrode 32c such that the first heating amount is greater than the second heating amount also includes setting the relative positions of the first electrode 31 and the second electrode 32c such that the first heating amount is greater than the second heating amount. In this embodiment, the first electrode 31 and the first portion 36c are arranged with a constant first distance d1 across the X direction, and the first electrode 31 and the second portion 37 are arranged with a constant second distance d2 across the X direction. In this embodiment, the thickness t1 of the first portion 36c and the thickness t2 of the second portion 37 are the same, and the width w1 of the first portion 36c and the width w2 of the second portion 37 are the same.
[0052] Figure 9 is a schematic diagram illustrating the first distance d1 and the second distance d2. Similar to Figure 4 described in the first embodiment, Figure 9 shows the liquid Lq adhering to the media Md in the electrode unit 30 c This figure schematically shows the state when the material is being heated. In Figure 9, as in Figure 4, the electric fields Eq1, Eq2, En1, and En2 are shown by dashed lines. As shown in Figure 9, in this embodiment, by making the first distance d1 smaller than the second distance d2, the strength of the electric field Eq1 is stronger than the strength of the electric field Eq2.
[0053] Furthermore, in this embodiment, the first sensitivity of the resonant frequency f1 is higher than the second sensitivity because the first distance d1 is smaller than the second distance d2. Generally, by making the first distance d1 shorter and the second distance d2 longer, the density of electric field lines passing through the liquid Lq on the first media portion Mp1 can be increased, and the ratio of the electric field Eq1 to the strength of the electric field En1 can be increased. However, if the first distance d1 is made too short compared to the second distance d2, the area of the first media portion Mp1 in the XY plane becomes relatively smaller than the area of the second media portion Mp2 in the XY plane, which may result in the first sensitivity being lower than the second sensitivity. In this embodiment, the first distance d1 is preferably 0.25 times or more the second distance d2, and more preferably 0.35 times or more. Also, the first distance d1 is preferably 0.75 times or less the second distance d2, and more preferably 0.6 times or less.
[0054] According to the third embodiment described above, the first distance d1 between the first electrode 31 and the first portion 36c is shorter than the second distance d2 between the first electrode 31 and the second portion 37. Therefore, by making the first distance d1 shorter than the second distance d2, it is easy to achieve that the first heating amount is larger than the second heating amount. Furthermore, by making the first distance d1 shorter than the second distance d2, it is also easy to achieve that the first sensitivity of the resonant frequency f1 is higher than the second sensitivity.
[0055] D. Other embodiments: (D-1) In the above embodiment, for example, the first heating amount may be greater than the second heating amount by combining two or more of the following: making the thickness t1 thicker than the thickness t2, making the width w1 smaller than the width w2, and making the first distance d1 shorter than the second distance d2.
[0056] (D-2) In the above embodiment, for example, the first heating amount may be made higher than the second heating amount by adjusting the thickness of the first electrode 31. For example, the first heating amount may be made higher than the second heating amount by making the thickness of the first electrode 31 on the +Y side half larger than the thickness of the first electrode 31 on the -Y side half.
[0057] (D-3) In the above embodiment, the electrode unit 30 is configured such that the first sensitivity at the resonant frequency f1 is higher than the second sensitivity, but it is not necessary to configure it in this way.
[0058] (D-4) In the above embodiment, the first electrode 31 has a boat shape, but it does not have to have a boat shape, and may have a flat plate shape or a rod shape, for example. Also, in the above embodiment, the first electrode 31 has an oval shape when viewed along the Z direction, but it does not have to have an oval shape, and may have a circular shape, a rectangular shape, or other polygonal shape, for example.
[0059] (D-5) In the above embodiment, the second electrode 32 is arranged to surround the first electrode 31 when viewed along the Z direction. However, the second electrode 32 does not have to be arranged to surround the first electrode 31 when viewed along the Z direction. For example, the second electrode 32 may be composed of two rod-shaped electrodes or two flat plate-shaped electrodes of the same potential that sandwich the first electrode 31 in the transport direction. In this case, of the portions of each electrode constituting the second electrode 32 that sandwich the first electrode 31 in the transport direction, the portion located upstream in the transport direction corresponds to the first portion 36, and the portion located downstream corresponds to the second portion 37.
[0060] (D-6) In the above embodiment, the electrode unit 30 may be configured to reciprocate in the X direction, for example. For example, the electrode unit 30 may be supported by a drive unit (not shown) configured by a belt mechanism or a ball screw mechanism, and reciprocate in the X direction.
[0061] (D-7) In the above embodiment, a frequency of 13.56 MHz is used as the driving frequency f0. However, the driving frequency f0 does not have to be 13.56 MHz; for example, other ISM band frequencies such as 40.68 MHz, 2.45 GHz, or 5.8 GHz may be used. Furthermore, the driving frequency f0 does not have to be a high frequency as long as it is a frequency that can heat the liquid attached to the media Md by the electrode unit 30. In this case, the driving frequency f0 is preferably, for example, 100 kHz or more and less than 1 MHz.
[0062] 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.
[0063] (1) According to one embodiment of the present disclosure, a dielectric heating device is provided. This dielectric heating device comprises a transport unit for transporting media in a transport direction, an electrode unit having a first electrode and a second electrode facing the media transported by the transport unit, and for drying the media by dielectric heating, a voltage application unit for applying an AC voltage to the first electrode and the second electrode, and a control unit for controlling the transport unit. The second electrode has a first part and a second part that sandwich the first electrode in the transport direction, the first part is positioned upstream of the second part in the transport direction, and the first electrode and the second electrode are formed such that the amount of heating of the media by the electric field formed between the first electrode and the first part is greater than the amount of heating of the media by the electric field formed between the first electrode and the second part. In this configuration, the amount of heating of the media by the electrode unit becomes greater upstream in the media transport direction, and the amount of heating of the media by the electrode unit becomes smaller downstream in the transport direction. Therefore, it is possible to suppress excessive drying of the media by heating by the electrode unit downstream in the transport direction.
[0064] (2) In the above embodiment, the distance in the transport direction between the first electrode and the first part may be shorter than the distance in the transport direction between the first electrode and the second part. 2 By making the distance between the parts shorter than the distance in the transport direction, it is easy to ensure that the amount of heating of the media due to the electric field formed between the first electrode and the first part is greater than the amount of heating of the media due to the electric field formed between the first electrode and the second part.
[0065] (3) In the above embodiment, the thickness of the first portion in the direction in which the first electrode and the second electrode face the media may be thicker than the thickness of the second portion in the same direction. With this embodiment, by making the thickness of the first portion thicker than the thickness of the second portion, it is possible to easily achieve that the amount of heating of the media due to the electric field formed between the first electrode and the first portion is greater than the amount of heating of the media due to the electric field formed between the first electrode and the second portion.
[0066] (4) In the above embodiment, the width of the first portion in the transport direction may be smaller than the width of the second portion in the transport direction. With this embodiment, by making the width of the first portion smaller than the width of the second portion, it is possible to easily achieve that the amount of heating of the media due to the electric field formed between the first electrode and the first portion is greater than the amount of heating of the media due to the electric field formed between the first electrode and the second portion.
[0067] (5) In the above embodiment, the electrode unit may be configured such that the sensitivity of the resonant frequency of the electrode unit to changes in the moisture content of the media heated by the electric field formed between the first electrode and the first part is higher than the sensitivity to changes in the moisture content of the media heated by the electric field formed between the first electrode and the second part. With this embodiment, the sensitivity of the total heating amount of the electrode unit to changes in the moisture content of the media heated by the electric field formed between the first electrode and the first part can be made higher than the sensitivity to changes in the moisture content of the media heated by the electric field formed between the first electrode and the second part. As a result, the possibility of drying the media more uniformly is increased. [Explanation of symbols]
[0068] 30, 30b, 30c... Electrode unit, 31... First electrode, 32, 32b, 32c... Second electrode, 33... Connecting member, 34... Coil, 35... Electric wire, 36, 36b, 36c... First part, 37, 37b... Second part, 80... Voltage application unit, 100... Dielectric heating device, 110... Substrate, 250... Control unit, 320... Transport unit, 323... Roller
Claims
1. A transport unit that transports media in the transport direction, An electrode unit having a first electrode and a second electrode facing the media being transported by the transport unit, which dries the media by dielectric heating, A voltage application unit that applies an AC voltage to the first electrode and the second electrode, The system comprises a control unit for controlling the transport unit, The second electrode has a first portion and a second portion that sandwich the first electrode in the transport direction, The first portion is positioned upstream of the second portion in the transport direction. The first electrode and the second electrode are formed such that the amount of heating of the media due to the electric field formed between the first electrode and the first portion is greater than the amount of heating of the media due to the electric field formed between the first electrode and the second portion. A dielectric heating device in which the second electrode is arranged to surround the first electrode when viewed along the direction opposite to the medium.
2. A dielectric heating apparatus according to claim 1, A dielectric heating device in which the distance between the first electrode and the first portion in the transport direction is shorter than the distance between the first electrode and the second portion in the transport direction.
3. A dielectric heating apparatus according to claim 1, A dielectric heating device wherein the thickness of the first portion in the direction in which the first electrode and the second electrode face the media is greater than the thickness of the second portion in the same direction.
4. A dielectric heating apparatus according to claim 1, A dielectric heating device wherein the width of the first portion in the transport direction is smaller than the width of the second portion in the transport direction.
5. A dielectric heating apparatus according to any one of claims 1 to 4, A dielectric heating device wherein the electrode unit is configured such that the sensitivity of the electrode unit's resonant frequency to changes in the water content of the media heated by the electric field formed between the first electrode and the first portion is higher than the sensitivity to changes in the water content of the media heated by the electric field formed between the first electrode and the second portion.