Induction heating device and liquid ejection system

Abstract

The present disclosure relates to an induction heating device and a liquid ejection system. A technique is provided in which a liquid adhering to a medium can be uniformly dried without using a sensor that measures the water content in the induction heating device. The induction heating device includes a first heater that has a first electrode and a second electrode that oppose the medium to which a liquid containing water is adhered, and a first coil that is electrically connected in series to the first electrode, and that heats the liquid to dry it, and a voltage application unit that applies an alternating voltage of a predetermined drive frequency to the first electrode and the second electrode. The first heater is configured such that a difference between a resonance frequency of the first heater and the drive frequency in a case where the water content of the medium is in a first range is smaller than a difference between a resonance frequency of the first heater and the drive frequency in a case where the water content is in a second range that is less than the first range, and the amount of heat in the case where the water content is in the first range is greater than the amount of heat in the case where the water content is in the second range.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an induction heating device and a liquid ejection system. BACKGROUND

[0002] As for the induction heating device, in Patent Literature 1, there is disclosed a technology of measuring the water content of a conveyance by a plurality of sensors, and individually controlling the power of a high-frequency electric field applied to a plurality of electrodes provided at positions corresponding to the plurality of sensors, in accordance with each measurement result. By this technology, it is possible to uniformly dry the conveyance.

[0003] Patent Literature 1: Japanese Patent Application Publication No. 2018-9754

[0004] However, in the technology of Patent Literature 1, in order to control the power of the high-frequency electric field applied to the electrodes, it is necessary to provide sensors for measuring the water content of the conveyance. SUMMARY

[0005] According to a first aspect of the present disclosure, there is provided an induction heating device. The induction heating device includes a first heater that has a first electrode and a second electrode that oppose a medium to which a liquid containing water is attached, and a first coil that is electrically connected in series to the first electrode, and that heats the liquid to dry it, and a voltage application unit that applies an alternating voltage of a predetermined drive frequency to the first electrode and the second electrode. The first heater is configured such that a difference between a resonance frequency of the first heater when a water content of the medium is in a first range and the drive frequency is smaller than a difference between a resonance frequency of the first heater when the water content is in a second range that is less than the first range and the drive frequency, and a heating amount when the water content is in the first range is greater than a heating amount when the water content is in the second range.

[0006] According to a second aspect of the present disclosure, there is provided a liquid ejection system. The liquid ejection system includes the induction heating device of the above aspect, and a liquid ejection unit that ejects and applies the liquid to the medium, the first heater heating the medium to which the liquid is applied by the liquid ejection unit. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a schematic view that shows an outline structure of a liquid ejection system.

[0008] Figure 2 is a perspective view that shows an outline structure of an induction heating device.

[0009] Figure 3 is a perspective view that shows an outline structure of a heater.

[0010] Figure 4 is an explanatory diagram showing a circuit configuration of the induction heating device.

[0011] Figure 5 is a schematic diagram showing an electric circuit formed by the heater and the liquid on the medium.

[0012] Figure 6 is an equivalent circuit diagram of the induction heating device.

[0013] Figure 7 is an explanatory diagram showing a relationship between the degree of drying and the first resonance frequency.

[0014] Figure 8 is an explanatory diagram showing a relationship between the degree of drying and the amount of heating based on the first heater.

[0015] Figure 9 is a schematic diagram showing adjustment of the thickness of the first electrode, the thickness of the second electrode.

[0016] Figure 10 is a schematic diagram showing adjustment of the distance between the first electrode and the second electrode.

[0017] Figure 11 is a schematic diagram showing adjustment of the width of the first electrode, the width of the second electrode.

[0018] BRIEF DESCRIPTION OF DRAWINGS

[0019] 20: heater; 30: first heater; 31: first electrode; 32: second electrode; 33: connecting member; 34: first coil; 35: first electric wire; 40: second heater; 41: third electrode; 42: fourth electrode; 44: second coil; 80: voltage application section; 81: switching circuit; 82: switching element; 83: Zener diode; 100: induction heating device; 110: substrate; 150: direct current power supply; 180: second control section; 200: liquid ejection system; 205: liquid ejection device; 210: liquid ejection section; 250: first control section; 320: conveyance section; 321: first conveyance section; 322: second conveyance section; 323: roller. DETAILED DESCRIPTION

[0020] A. First Embodiment:

[0021] Figure 1 is a schematic diagram showing a schematic structure of the liquid ejection system 200 as the first embodiment. In Figure 1 , arrows showing X, Y, Z directions orthogonal to each other are shown. The X direction and the Y direction are directions parallel to a horizontal plane, and the Z direction is a direction along a vertical upward direction. The arrows showing the X, Y, Z directions are also shown in the directions illustrated in other drawings. Figure 1The corresponding modes are appropriately illustrated. In the following description, in the case of determining the direction of the orientation, the direction indicated by the arrow in each figure is set to "+" and the opposite direction thereof is set to "-", and the positive and negative signs are used in the direction mark. Hereinafter, the +Z direction is also referred to as "up" and the -Z direction is referred to as "down". In addition, in the present specification, the orthogonality includes a range of 90° ± 10°.

[0022] The liquid ejection system 200 includes the induction heating device 100 having the heater 20, the liquid ejection device 205, and a conveyance section 320. The liquid ejection system 200 in the present embodiment conveys the medium Md by the conveyance section 320, ejects and applies a liquid containing water to the medium Md by the liquid ejection device 205, and dries the liquid applied to the medium Md by the heater 20 of the induction heating device 100. It can be said that the liquid ejection device 205 applies the liquid heated by the heater 20 to the medium Md.

[0023] As the medium Md, for example, paper, cloth, film, or the like is used. The cloth used as the medium Md is, for example, formed by weaving fibers such as cotton, hemp, polyester, silk, rayon, or a fiber obtained by blending them. In the present embodiment, a sheet-shaped cotton cloth is used as the medium Md. As the liquid applied to the medium Md, for example, various inks mainly containing water are used. In the present embodiment, an aqueous ink mainly containing water is used as the liquid. In the present specification, the main component of the liquid means a substance included in the liquid at a rate of 50% or more in terms of mass. In other embodiments, as the liquid, for example, any liquid such as a sample of various coloring materials, electrode materials, biological organic matter, inorganic matter, lubricating oil, resin liquid, etching liquid, or the like can be used in addition to the ink.

[0024] The conveyance section 320 conveys the medium Md. In the present embodiment, the conveyance section 320 is configured as a roller mechanism that conveys the medium Md by a driving roller 323. The conveyance section 320 has a first conveyance section 321 provided to the liquid ejection device 205 and a second conveyance section 322 provided to the induction heating device 100. The first conveyance section 321 and the second conveyance section 322 each have the roller 323 and a not-illustrated driving section configured of a motor or the like for driving the roller 323. The first conveyance section 321 is disposed at a position in the +Y direction of the second conveyance section 322. In the present embodiment, the first conveyance section 321 and the second conveyance section 322 convey the sheet-shaped medium Md in the -Y direction. In other embodiments, the conveyance section 320 can be configured as a belt mechanism that conveys the medium Md by driving a belt, for example.

[0025] In the present embodiment, the liquid discharge device 205 is configured as an inkjet printer that performs printing by discharging and applying ink as a liquid to the medium Md. Therefore, it can also be said that the liquid discharge system 200 is configured as a printing system provided with the inkjet printer. The liquid discharge device 205 has the liquid discharge section 210 that discharges and applies a liquid to the medium Md, and the first control section 250. Hereinafter, the first control section 250 will also be simply referred to as the control section.

[0026] The liquid discharge section 210 is configured as a liquid discharge head of a piezoelectric method or a thermal method, for example, and has one or a plurality of unillustrated head chips. Each head chip has a flow path through which a liquid flows, and a nozzle for discharging a liquid. The color of ink discharged from each head chip can be the same or different. Furthermore, the liquid discharge section 210 can be configured to be capable of reciprocating in a direction orthogonal to the Z direction and intersecting the Y direction with respect to the medium Md by means of an unillustrated carriage, or can be configured as a so-called line head that is fixed in position without reciprocating with respect to the medium Md.

[0027] The ink used as a liquid in the present embodiment is a pigment ink containing a resin. The resin contained in the ink has the effect of firmly fixing a pigment to the medium Md via itself. Such a resin is used in a state in which 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, an acrylic resin, a styrene acrylic resin, a fluorene resin, a polyurethane resin, a polyolefin resin, a rosin-modified resin, a terpene resin, a polyester resin, a polyamide resin, an epoxy resin, a vinyl chloride resin, a vinyl chloride-vinyl acetate copolymer, an ethylene-vinyl acetate resin, or the like can be used. Two or more of these resins can also be used in combination. Such a resin is also referred to as a synthetic resin.

[0028] The first control section 250 is configured by a computer provided with one or a plurality of processors, a storage device, and an input / output interface that performs input and output of signals with the outside. The first control section 250 in the present embodiment discharges and adheres a liquid to the medium Md while carrying the medium Md by controlling the liquid discharge section 210 and the second carrying section 322. In other embodiments, the first control section 250 can also be configured by a combination of a plurality of circuits, for example.

[0029] Figure 2 is a perspective view that shows the schematic structure of the induction heating device 100 in the first embodiment. As Figure 1 and Figure 2As shown, the induction heating device 100 includes: a heater 20 for heating and drying a liquid coated on a medium Md; a voltage application unit 80 for applying an alternating current voltage to the heater 20; and a second control unit 180. In this embodiment, the induction heating device 100 heats the liquid adhering to the medium Md by the alternating current electric field generated by the heater 20 while transporting the medium Md via the second transport unit 322, thereby drying the liquid adhering to the medium Md. In the induction heating device 100, for example, a blower for generating airflow may be provided. By providing such a blower, the drying of the liquid adhering to the medium Md and the cooling of the medium Md after drying can be promoted.

[0030] like Figure 2 As shown, the induction heating device 100 in this embodiment, serving as heater 20, includes a first heater 30 and a second heater 40. The first heater 30 includes a first electrode 31, a second electrode 32, and a first coil 34. The second heater 40 includes a third electrode 41, a fourth electrode 42, and a second coil 44. Hereinafter, the first heater 30 and the second heater 40 will sometimes be referred to simply as heater 20 without distinction.

[0031] The first electrode 31 and the second electrode 32 are opposite to the medium Md. Additionally, the third electrode 41 and the fourth electrode 42 are also opposite to the medium Md. In this embodiment, the first electrode 31 and the second electrode 32, and the third electrode 41 and the fourth electrode 42 are respectively opposite to the medium Md being transported along the first direction in a second direction orthogonal to the first direction. In this embodiment, the first direction is the -Y direction. The second direction is a direction that includes both the direction along one side of the same axis and its opposite direction; in this embodiment, it is the Z direction. That is, in this embodiment, the first electrode 31 and the second electrode 32, and the third electrode 41 and the fourth electrode 42 are opposite to the medium Md being transported by the second transport unit 322 along the -Y direction in the Z direction.

[0032] In this embodiment, the first heater 30 and the second heater 40 are arranged along a third direction. The third direction is a direction orthogonal to the first direction and intersecting the second direction. The third direction is a direction that includes both the direction along one side of the same axis and its opposite direction; in this embodiment, it is the X direction.

[0033] The voltage application section 80 is electrically connected to the first heater 30, and applies an alternating voltage of a predetermined drive frequency f0 to the first electrode 31 and the second electrode 32. In addition, in the present embodiment, the voltage application section 80 is electrically connected to the second heater 40, and applies an alternating voltage of the drive frequency f0 to the third electrode 41 and the fourth electrode 42. In the present embodiment, the first heater 30 and the second heater 40 are electrically connected in parallel to each other. One of the potentials applied to the first electrode 31 or the second electrode 32, and one of the potentials applied to the third electrode 41 or the fourth electrode 42 can also be a reference potential. The reference potential is a constant potential that becomes a reference for a high-frequency voltage, and is, for example, a ground potential.

[0034] In the present embodiment, a high-frequency voltage is applied to each electrode of each heater 20. In the present specification, "high frequency" refers to a frequency of 1 MHz or more. More specifically, in the present embodiment, as the drive frequency f0, one of the industrial scientific and medical (ISM) band, that is, 13.56 MHz is used. In addition, since the dielectric loss tangent of water reaches a maximum near 20 GHz, by applying a high-frequency voltage of 2.45 GHz, 5.8 GHz in the ISM band to each electrode of each heater 20, it is possible to more efficiently heat a liquid adhering to the medium Md. On the other hand, from the viewpoint of heating the ink, even in the case where the drive frequency f0 is relatively low, such as 13.56 MHz, 40.68 MHz, a good heating efficiency can be obtained. The reason for this is that, in the case where the drive frequency f0 is 13.56 MHz, 40.68 MHz, the dielectric loss tangent of water in the ink is low, and on the other hand, it is easy to generate Joule heat generated as a resistance of a pigment component or the like in the ink.

[0035] The second control section 180 is also composed of a computer, like the above-described first control section 250. In the present embodiment, the second control section 180 controls the above-described second conveyance section 322.

[0036] Figure 3 is a perspective view showing the outline structure of the heater 20 in the present embodiment. More specifically, in Figure 3 the outline structure of the first heater 30 is shown. As described above, the first heater 30 has the first electrode 31, the second electrode 32, and the first coil 34. In addition, although not shown, in the present embodiment, the third electrode 41, the fourth electrode 42, and the second coil 44 of the above-described second heater 40 each have the same structure as the first electrode 31, the second electrode 32, and the first coil 34.

[0037] The first electrode 31 and the second electrode 32 are conductors, such as those formed of metals, alloys, or conductive oxides. The first electrode 31 and the second electrode 32 can be formed of the same material or different materials. For example, to maintain their orientation and strength, the first electrode 31 and the second electrode 32 can be disposed on a substrate or other material formed of a material with a low dielectric loss tangent and low conductivity, or they can be supported by other components.

[0038] 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 output from the first heater 30. In this embodiment, the first electrode 31 has a boat-shaped form with both its long and short sides. The lower surface of the first electrode 31 has a curved shape convex in the -Z direction. The first electrode 31 has an elliptical shape when viewed along the Z direction. The second electrode 32 has a flattened elliptical ring shape in both the X and Y directions. The second electrode 32 is arranged to surround the first electrode 31 when viewed along the Z direction. The first electrode 31 and the second electrode 32 are arranged such that the long side of the first electrode 31 is parallel to the long side of the second electrode 32.

[0039] like Figure 1 as well as Figure 2 As shown, both the first electrode 31 and the second electrode 32 are disposed on a substrate 110 arranged parallel to the X and Y directions. More specifically, the first electrode 31 is disposed such that the central portion of its lower surface in the X and Y directions contacts the upper surface of the substrate 110. The second electrode 32 is disposed such that its lower surface contacts 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 disposed on the same plane. Furthermore, in this embodiment, the substrate 110 is commonly provided for the first heater 30 and the second heater 40.

[0040] like Figure 1 As shown, in this embodiment, the first electrode 31 and the second electrode 32 are disposed above the dielectric Md. Therefore, in this embodiment, the lower surfaces of the first electrode 31 and the second electrode 32 face the upper surface of the dielectric Md. The substrate 110 is disposed between the dielectric Md and the first electrode 31 and the second electrode 32. Similarly, the third electrode 41 and the fourth electrode 42 are disposed above the dielectric Md in a manner that faces the dielectric Md in the Z direction.

[0041] In this embodiment, the substrate 110 is formed of glass. With the substrate 110, it is possible to suppress the case where a liquid such as ink applied on the medium Md adheres to the first electrode 31 and the second electrode 32, and the case where, in the case where the medium Md is cloth, the pile of the medium Md adheres to the first electrode 31 and the second electrode 32. In this embodiment, the substrate 110 also suppresses the adhesion of a liquid and a pile toward the third electrode 41 and the fourth electrode 42 of the second heater 40, as with the above. In other embodiments, the substrate 110 may, for example, also be formed of alumina.

[0042] Returning to Figure 3 An explanation is given. In this embodiment, the first electrode 31 is electrically connected to the voltage application section 80 via the first electric wire 35, the first coil 34, and the inner conductor IC1 of the coaxial cable. The second electrode 32 is electrically connected to the voltage application section 80 via the connection member 33 disposed on the upper portion of the second electrode 32, the outer conductor of the coaxial cable, and the like, which are not shown.

[0043] By applying an alternating voltage of the drive frequency f0 to the first electrode 31 and the second electrode 32, an electromagnetic field having a wavelength corresponding to the drive 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 is very weak at a distance. In this specification, the electromagnetic field generated in the vicinity of the first electrode 31 and the second electrode 32 by the application of the alternating voltage is also referred to as a "vicinity electromagnetic field". The "vicinity" of the first electrode 31 and the second electrode 32 refers to a range in which the distance from the first electrode 31 and the second electrode 32 becomes 1 / 2π or less of the wavelength of the generated electromagnetic field. A range farther than the "vicinity" is also referred to as a "distance". In this specification, the electromagnetic field generated at a distance from the first electrode 31 and the second electrode 32 by the application of the alternating voltage is also referred to as a "distance electromagnetic field". The distance electromagnetic field corresponds to an electromagnetic field used in communication based on a general communication antenna or the like.

[0044] As described above, the first electrode 31 and the second electrode 32 are arranged in such a manner that the shortest distance therebetween becomes 1 / 10 or less of the wavelength of the electromagnetic field. Thereby, the density of the electromagnetic field generated from the first electrode 31 and the second electrode 32 can be attenuated in the vicinity of the first electrode 31 and the second electrode 32. Therefore, by appropriately maintaining the distance between the medium Md and the first electrode 31 and the second electrode 32, the liquid adhered to the medium Md can be effectively heated using the electric field generated in the vicinity of the first electrode 31 and the second electrode 32 while suppressing the emission of the far electromagnetic field from the first electrode 31 and the second electrode 32. In particular, in the present embodiment, the second electrode 32 is arranged in such a manner as to surround the first electrode 31 when viewed in the Z direction, and thus the emission of the far electromagnetic field from the first electrode 31 and the second electrode 32 can be further suppressed.

[0045] In the present embodiment, one end of the first coil 34 is electrically connected in series with the first electrode 31 via the first electric wire 35, and the other end is electrically connected in series with the voltage application unit 80. In the present embodiment, the first coil 34 is constituted by a solenoid coil and is arranged in such a manner that the length direction thereof is along the Z direction. The shape, length, cross-sectional area, number of turns, material, and the like of the first coil 34 are selected, for example, in accordance with the drive frequency fo, and further in such a manner as to achieve impedance matching of the first heater 30 and the voltage application unit 80. Further, although not illustrated, in the present embodiment, one end of the second coil 44 is electrically connected with the third electrode 41 via the second electric wire, and the other end is electrically connected in series with the voltage application unit 80. In other embodiments, one end of the first coil 34 can not be connected in series with the first electrode 31, but can be connected in series with the second electrode 32. Further, likewise, one end of the second coil 44 can not be connected in series with the third electrode 41, but can be connected in series with the fourth electrode 42. Figure 1 Figure 2 In the present embodiment, one end of the first coil 34 is electrically connected in series with the first electrode 31 via the first electric wire 35, and the other end is electrically connected in series with the voltage application unit 80. In the present embodiment, the first coil 34 is constituted by a solenoid coil and is arranged in such a manner that the length direction thereof is along the Z direction. The shape, length, cross-sectional area, number of turns, material, and the like of the first coil 34 are selected, for example, in accordance with the drive frequency fo, and further in such a manner as to achieve impedance matching of the first heater 30 and the voltage application unit 80. Further, although not illustrated, in the present embodiment, one end of the second coil 44 is electrically connected with the third electrode 41 via the second electric wire, and the other end is electrically connected in series with the voltage application unit 80. In other embodiments, one end of the first coil 34 can not be connected in series with the first electrode 31, but can be connected in series with the second electrode 32. Further, likewise, one end of the second coil 44 can not be connected in series with the third electrode 41, but can be connected in series with the fourth electrode 42.

[0046] ​The high voltage is generated at the one end of the first coil 34 by the voltage application section 80 applying an alternating voltage to the first heater 30. Thereby, the strength of the electric field generated from the first electrode 31 and the second electrode 32 can be increased. Further, the first coil 34 is preferably arranged in such a manner that the distance between the one end of the first coil 34 and the first electrode 31 is as small as possible. In the case where the distance between the one end of the first coil 34 and the first electrode 31 is far, the high voltage generated at the one end of the first coil 34 generates an electric field between the first coil 34 and the first electrode 31 or between the first electric wire 35 and the second electrode 32, which is not helpful for the heating of the medium Md, and the effect of increasing the strength of the electric field generated from the first electrode 31 and the second electrode 32 can be reduced. In contrast, by shortening the distance between the one end of the first coil 34 and the first electrode 31, the generation of such an electric field, which is not helpful for the heating of the medium Md, can be suppressed, and thus the strength of the electric field generated from the first electrode 31 and the second electrode 32 can be effectively increased. Similarly, the second coil 44 can increase the strength of the electric field generated from the third electrode 41 and the fourth electrode 42. Further, in other embodiments, for example, the first electrode 31 and the third electrode 41 can be made to function as a coil by being formed in a meandering shape.

[0047] Figure 4 is an explanatory diagram showing the circuit structure of the induction heating device 100 in the present embodiment. In Figure 4 , a part of the circuit structure of the induction heating device 100 is omitted for easy understanding of the technology. As Figure 4 shown, the voltage application section 80 is configured as an inverter having a switching circuit 81. The switching circuit 81 is electrically connected to the direct-current power supply 150, the first heater 30, and the second heater 40. The switching circuit 81 switches the direct-current voltage of the direct-current power supply 150 to an alternating voltage of the drive frequency fo and outputs the alternating voltage to the first heater 30 and the second heater 40.

[0048] In this embodiment, the switching circuit 81 is configured as a full-bridge inverter, having four switching elements 82 and Zener diodes 83 for overvoltage protection corresponding to each switching element 82. In this embodiment, the switching elements 82 are N-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). In other embodiments, the switching elements 82 may be, for example, bipolar transistors, insulated-gate transistors, turn-off thyristors, etc. Furthermore, in addition to Zener diodes 83, or in place of Zener diodes 83, the switching circuit 81 may appropriately include PN junction diodes, etc. Moreover, the switching circuit 81 may be configured as a phase-shifted full-bridge inverter, or as a half-bridge inverter, for example.

[0049] Each switching element 82 repeatedly switches a portion of the switching circuit 81 on and off according to the control signal input to its gate. Through the operation of the switching elements 82, the switching circuit 81 converts the DC voltage of the DC power supply 150 into an AC voltage with a driving frequency f0. This applies an AC voltage with driving frequency f0 to the first heater 30 and the second heater 40.

[0050] In this embodiment, alternating current voltages with a 180° phase reversal are applied to the first heater 30 and the second heater 40, respectively. More specifically, as... Figure 4 As shown, the first electrode 31 of the first heater 30 and the fourth electrode 42 of the second heater 40 are connected to the switching circuit 81 in phase, and the second electrode 32 of the first heater 30 and the fourth electrode 42 of the second heater 40 are also connected to the switching circuit 81 in phase, thereby applying AC voltages with a 180° phase reversal to the first heater 30 and the second heater 40 respectively. In this way, by applying AC voltages with a 180° phase reversal to adjacent heaters 20, radiation waves from adjacent heaters 20 that do not contribute to the heating of the medium Md can be mutually attenuated.

[0051] Figure 5 This is a schematic diagram illustrating the circuit formed by the heater 20 in this embodiment and the liquid Lq attached to the medium Md. Figure 6 This is an equivalent circuit diagram of the induction heating device 100 in this embodiment. More specifically, Figure 5 The circuit formed by the first heater 30 and the liquid Lq is shown. Additionally, Figure 6 This is equivalent to a circuit that only considers the first heater 30 in the case of the first heater 30 and the second heater 40. In Figure 5 as well as Figure 6In the circuit shown, the first electrode 31 and the second electrode 32 of the first heater 30 can each be considered as electrode plates constituting a capacitor. Furthermore, although not shown in the diagram, it is also possible to form a capacitor using the second heater 40 and the liquid Lq. Figure 5 The circuit shown is the same as the circuit shown. Additionally, considering only the second heater 40 of the first heater 30 and the second heater 40, the circuit is the same. Figure 6 The circuit shown is the same.

[0052] Figure 5 as well as Figure 6 R shown a This indicates the resistance of the first heater 30. In resistor R... a It includes the internal resistance of the voltage application section 80 and the parasitic resistance of the first coil 34. Figure 6 The L shown a This represents the inductance of the first heater 30. Inductance L... a Including Figure 5 The inductance L of the first coil 34 shown c And the parasitic inductance of each electrode of the first heater 30. Figure 5 as well as Figure 6 C shown a This represents the capacitance of the first heater 30. In capacitance C... a This includes the parasitic capacitance of the first coil 34 and the capacitance between the electrodes of the first heater 30. Figure 5 as well as Figure 6 R shown b This represents the resistance of the liquid Lq attached to the medium Md. Figure 5 C shown b1 This represents the parasitic capacitance between the first electrode 31 and the liquid Lq. Figure 5 C shown b2 This represents the parasitic capacitance between the second electrode 32 and the liquid Lq. Figure 6 C shown b Represented as parasitic capacitance C b1 And C b2 The sum of the two. Additionally, the capacitance C... a With capacitor C b The sum is equivalent to the capacitance of the first heater 30.

[0053] Drying is achieved by heating the liquid Lq on the medium Md, reducing the water content of the medium Md, and thus reducing the capacitance C of the first heater 30. a And the resistance R of the liquid Lq bchanges. More specifically, as the water contained in the liquid Lq on the medium Md decreases in amount accompanying the progress of drying, the thickness of the water contained in the liquid Lq decreases, and thus the capacitance of the capacitor composed of the first electrode 31 and the second electrode 32 decreases, so the capacitance C a decreases. The reason for this is that the dielectric constant of the water contained in the liquid Lq is higher than the dielectric constant of vacuum. In addition, as the water contained in the liquid Lq decreases in mass ratio accompanying the progress of drying, the electrical conductivity of the liquid Lq decreases, so the resistance R b increases. Furthermore, in fact, the capacitance C b also decreases due to the drying of the liquid Lq, but the decrease amplitude thereof is very small compared to the decrease amplitude of the capacitance C a and the increase amplitude of the resistance R b , and thus can be ignored.

[0054] The resonance frequency of the heater 20 at the time when the liquid applied to the medium Md is dried is expressed as Figure 5 , Figure 6 the resonance frequency of the heater 20 in the equivalent circuit shown in FIG. 6. Thus, the resonance frequency of the heater 20 changes according to the progress of drying. More specifically, as described above, as the capacitance C a decreases due to the decrease in the amount of water accompanying the progress of drying, the resonance frequency of the heater 20 increases accompanying the progress of drying. Hereinafter, the change in the resonance frequency of the heater 20 accompanying such progress of drying will also be referred to as the shift of the resonance frequency. In addition, the change amplitude of the resonance frequency caused by the shift of the resonance frequency will also be referred to as the shift amount of the resonance frequency. In addition, the resonance frequency of the first heater 30 at the time when the liquid applied to the medium Md is dried will also be referred to as the first resonance frequency fl. Likewise, the resonance frequency of the second heater 40 at the time when the liquid applied to the medium Md is dried will also be referred to as the second resonance frequency f2.

[0055] The first heater 30 is configured to satisfy a first condition that a difference between the first resonance frequency fl and the drive frequency fo in a case where the moisture content of the medium Md is in a first range is smaller than a difference between the first resonance frequency fl and the drive frequency fo in a case where the moisture content is in a second range that is smaller than the first range. The case where the moisture content of the medium Md is in the first range, the second range refers to a case where the amount of water contained per unit volume of a first portion of the medium Md, which forms the above-described equivalent circuit with the first heater 30, is in the first range, the second range. The "amount of water" in this case is represented by the mass of water in the present embodiment, but in other embodiments, for example, it can also be represented by the mass, the proportion of the volume with respect to the mass, the volume of water. Hereinafter, unless otherwise specified, the "moisture content of the first portion" refers to the "moisture content per unit volume of the first portion". In the present embodiment, the first portion corresponds to a portion located between the first electrode 31 and the second electrode 32 when viewed in the Z direction. This "portion between the first electrode 31 and the second electrode 32" includes the portion in which the first electrode 31 and the second electrode 32 are provided.

[0056] In addition, in the present embodiment, the second heater 40 is configured to satisfy a third condition that a difference between the second resonance frequency f2 and the drive frequency fo in a case where the moisture content of the medium Md is in a third range is smaller than a difference between the second resonance frequency f2 and the drive frequency fo in a case where the moisture content is in a fourth range that is smaller than the third range, by being configured in the same manner as the first heater 30. The case where the moisture content of the medium Md is in the third range, the fourth range refers to a case where the amount of water contained per unit volume of a second portion of the medium Md, which forms the above-described equivalent circuit with the second heater 40, is in the third range, the fourth range. Hereinafter, unless otherwise specified, the "moisture content of the second portion" refers to the "moisture content per unit volume of the second portion". In the present embodiment, the second portion corresponds to a portion located between the third electrode 41 and the fourth electrode 42 when viewed in the Z direction. The "portion between the third electrode 41 and the fourth electrode 42" includes the portion in which the third electrode 41 and the fourth electrode 42 are provided.

[0057] Figure 7 is a graph that shows the relationship between the degree of drying and the first resonance frequency fl. In Figure 7 a schematic graph in which the horizontal axis is the degree of drying and the vertical axis is the first resonance frequency fl is shown. Figure 7The "degree of drying" in the above expression indicates a difference between the current water content in the first portion of the medium Md and the water content at the drying start point. The water content at the drying start point is calculated, for example, as a difference between the mass per unit volume of the first portion at the drying start point and a drying mass indicating the mass per unit volume of the first portion at the drying completion point. The drying mass is calculated, for example, as the mass in the case where the medium Md is sufficiently dried. The first resonance frequency fl is calculated, for example, based on the inductance and the capacitance of the first heater 30 determined using a network analyzer.

[0058] Since Figure 7 The degree of drying in the above expression and the water content in the first portion have a negative correlation, and thus it can also be said that Figure 7 The above expression indicates the relationship between the water content in the first portion and the first resonance frequency fl. In this way, since the water content is correlated with the degree of drying, it is also possible to determine the size of the water content at two timings at which the progress of drying is different from each other by comparing the size of the degree of drying at the respective timings, instead of directly comparing the size of the water content at the respective timings. Further, the "degree of drying" can be expressed, for example, by the ratio of the current water content of the first portion to the water content at the drying start point, the inverse of the current water content of the first portion, or the drying time in the case where the liquid applied to the first portion is dried under certain conditions.

[0059] In the present embodiment, the first heater 30 is configured such that the first resonance frequency fl coincides with the drive frequency fo in the case where the water content in the first portion of the medium Md is a full-coat equivalent water content corresponding to the water content in the case where the medium Md is fully coated with the liquid. The case where the medium Md is fully coated with the liquid means a state in which the liquid is applied without a gap in the range of at least a portion of one side of the medium Md. In more detail, the full-coat equivalent water content in the present embodiment is defined as the water content per unit volume in the first portion of the medium Md immediately after full-coat printing of multiple colors is performed on the medium Md by the liquid ejection section 210. The full-coat printing means printing in which dots are formed on all pixels constituting an image, in a manner that does not leave a portion of the background color of the medium Md. In the present embodiment, the full-coat equivalent water content is calculated, for example, as a difference between the mass per unit volume of the first portion at the drying start point and a drying mass indicating the mass per unit volume of the first portion at the drying completion point. Figure 7In the present embodiment, the degree of drying is zero, and the water content at the time point of the start of drying is equivalent to the full-coat equivalent water content. Thus, in the present embodiment, in the case where the water content in the first portion of the medium Md at the start of drying is below the full-coat equivalent water content, the greater the drying proceeds, that is, the lower the water content in the first portion, the greater the difference between the first resonance frequency fl and the drive frequency fo. In the case where the first resonance frequency fl coincides with the drive frequency fo, the first resonance frequency fl and the drive frequency fo can not be completely coincident. More specifically, the first resonance frequency fl and the drive frequency fo coincide within a range of ±1.0% of the difference between the first resonance frequency fl and the drive frequency fo with respect to the drive frequency fo, more preferably within a range of ±0.5%, and further preferably within a range of ±0.1%. Furthermore, in other embodiments, the full-coat equivalent water content can be defined, for example, as the water content per unit volume in the first portion of the medium Md after the full-coat printing of a single color such as black has just been performed on the medium Md by the liquid ejection section 210.

[0060] Figure 8 is a diagram indicating the relationship between the degree of drying and the amount of heating based on the first heater 30. In Figure 8 , a schematic graph is shown in which the horizontal axis is set as the degree of drying and the vertical axis is set as the amount of heating based on the first heater 30. The first heater 30 is configured to satisfy a second condition in which the amount of heating in the case where the water content of the first portion is in the first range is greater than the amount of heating in the case where the water content of the first portion is in the second range. More specifically, in the present embodiment, as shown in Figure 8 , the greater the drying proceeds, that is, the lower the water content of the first portion, the smaller the amount of heating based on the first heater 30. Furthermore, regarding the magnitude of the amount of heating based on the first heater 30 in each of the case where the water content is in the first range and the case where the water content is in the second range, for example, the magnitude can be compared by comparing the temperature in the case where a cotton cloth having the water content in the first range and the second range is heated from the same temperature for the same time with the same power output. In addition, in the present embodiment, the second heater 40 is configured similarly to the first heater 30, and thus is configured to satisfy a fourth condition in which the amount of heating in the case where the water content of the second portion is in the third range is greater than the amount of heating in the case where the water content of the second portion is in the fourth range.

[0061] The increase in the shift amount of the first resonance frequency fl accompanying the progress of drying contributes to the reduction in the amount of heating based on the first heater 30. The reason for this is that the impedance of the first heater 30 is further increased by making the difference between the first resonance frequency fl and the drive frequency fo greater. On the other hand, the use Figure 5 and Figure 6This describes the resistance R of the liquid Lq on the medium Md caused by the increase in water content during drying. b The increase in resistance R contributes to an increase in the heating amount based on the first heater 30. The reason for this is that by increasing the resistance R... b In the equivalent circuit, the current flowing through the resistive component of the liquid Lq decreases, thus increasing the Q value in the equivalent circuit. In this embodiment, the reduction in heating caused by the shift in the first resonant frequency f1 exceeds the reduction caused by the resistance R. b The increase in heating amount caused by the increase constitutes the first heater 30, thereby satisfying the second condition.

[0062] By further increasing Figure 5 as well as Figure 6 The capacitor C in the equivalent circuit shown b The ratio of capacitance to that of the first heater 30 increases the offset of the first resonant frequency f1. This allows the capacitance C to... b The larger ratio of the capacitance to the capacitance of the first heater 30 is equivalent to increasing the effect of the dielectric constant of the liquid Lq on the nearby electric field formed in the region near the first electrode 31 and the second electrode 32, which is equivalent to increasing the proportion of electric field lines passing through the liquid Lq when the nearby electric field is represented by electric field lines.

[0063] Figure 9 This is a schematic diagram illustrating the adjustment of the thickness t1 of the first electrode 31 and the thickness t2 of the second electrode 32. For example... Figure 9 As shown, the offset of the first resonant frequency f1 can be adjusted by adjusting the thicknesses t1 and t2. More specifically, in order to increase the offset of the first resonant frequency f1, that is, to increase the proportion of electric field lines Eq that supply liquid Lq, the thicknesses t1 and t2 are adjusted by relatively increasing the number of electric field lines Eq relative to the number of electric field lines En that cannot supply liquid Lq. Figure 9 This illustrates an example of increasing the proportion of the electric field line Eq by increasing the thicknesses t1 and t2. Generally speaking, such as... Figure 9 As shown, by further increasing the thicknesses t1 and t2, the number of electric field lines Eq can be further increased. However, if the thicknesses t1 and t2 are too thick, there is a possibility that the proportion of electric field lines Eq decreases due to the increase in the number of electric field lines En. In this embodiment, the thicknesses t1 and t2 are preferably adjusted to, for example, 0.1 mm or more and 2.0 mm or less.

[0064] Figure 10 This diagram illustrates the adjustment of the distance d between the first electrode 31 and the second electrode 32. Furthermore, Figure 10 The thicker dashed arrows in the diagram indicate that there are more power lines than the thinner dashed arrows. Figure 10An example of increasing the shift of the first resonance frequency fl by shortening the distance d in a range in which the proportion of the electric power line En passing through the liquid Lq is increased. By adjusting the distance d as shown in Figure 10 , it is also possible to adjust the shift of the first resonance frequency fl.

[0065] Figure 11 is a diagram illustrating adjustment of the width Wl of the first electrode 31 and the width W2 of the second electrode 32. As shown in Figure 11 , by adjusting the width Wl and the width W2, it is also possible to adjust the shift of the first resonance frequency fl. In this case, by making the width Wl and the width W2 narrower, it is easy to concentrate the electric power line En around the liquid Lq, and thus it is possible to increase the number of the electric power lines En and to increase the shift of the first resonance frequency fl. Figure 11 An example of increasing the shift of the first resonance frequency fl by making the width W2 narrower is shown.

[0066] In addition, for example, it is possible to reduce the increase in the amount of heat caused by the increase in the resistance R b by reducing the parasitic resistance of the first coil 34 while keeping the inductance. The reason for this is that, as shown in Figure 5 and Figure 6 , the resistance R a in the equivalent circuit becomes smaller, and thus the Q value in the equivalent circuit becomes larger, and the resistance R b relatively becomes smaller in helping the Q value in the equivalent circuit. In this case, for example, by increasing the diameter of the winding of the first coil 34 and increasing the distance between the windings of the first coil 34, it is possible to reduce the parasitic resistance of the first coil 34. In addition, as described above, by configuring the voltage application unit 80 with the switching circuit 81, it is possible to reduce the internal resistance of the voltage application unit 80 compared to the case in which the voltage application unit 80 is configured with a high-frequency power supply circuit having an analog amplifier such as a class-B amplifier or a transformer, and thus it is possible to reduce the resistance R Figure 5 and Figure 6 in the equivalent circuit shown in a . Thus, it is also possible to reduce the increase in the amount of heat caused by the increase in the resistance R b .

[0067] In this way, by reducing the resistance R bIn a case where the increase in the amount of heating caused by the increase in the amount of the liquid is large, it is more preferable that the first heater 30 be configured in such a manner that the amount of heating of the liquid by the first heater 30 after the completion of drying of the medium Md becomes equal to or less than the amount of cooling of the liquid. The timing of the completion of drying of the medium Md is, for example, set to a timing at which the water content of the first portion of the medium Md becomes equal to or less than a predetermined water content. The amount of cooling of the liquid is, for example, the amount of cooling taking into account cooling based on the blower in a case where the blower is provided as described above. Thus, it is possible to suppress excessive heating of the medium Md after the completion of drying.

[0068] According to the inductive heating device 100 in the first embodiment described above, the first heater 30 is configured such that, in a case where the water content of the medium Md is in the first range, the difference between the resonance frequency of the first heater 30 and the drive frequency fo is smaller than the difference between the resonance frequency of the first heater 30 and the drive frequency fo in a case where the water content is in a second range that is less than the first range, and the amount of heating of the first heater 30 in the case where the water content is in the first range is greater than the amount of heating in the case where the water content is in the second range. Thus, even if the output of the alternating-current power applied to the first heater 30 is not controlled based on the water content of the medium Md, it is possible to heat the medium Md with a greater amount of heating by the first heater 30 in a case where the water content is in the first range that is greater than the second range, and it is possible to heat the medium Md with a smaller amount of heating by the first heater 30 in a case where the water content is in the second range that is less than the first range. Therefore, it is possible to uniformly dry the liquid adhering to the medium Md without providing a sensor that measures the water content of the medium Md.

[0069] In addition, in the present embodiment, the voltage application section 80 applies an alternating voltage of the drive frequency f0 to the third electrode 41 and the fourth electrode 42 of the second heater 40, and the second heater 40 is configured such that the difference between the resonance frequency of the second heater 40 when the water content of the medium Md is in the third range and the drive frequency f0 is smaller than the difference between the resonance frequency of the second heater 40 when the water content is in the fourth range that is less than the third range and the drive frequency f0, and the amount of heating of the second heater 40 when the water content is in the third range is greater than the amount of heating when the water content is in the fourth range. Thus, in the second heater 40 as well, as in the case of the first heater 30, even if the output of the alternating electric power applied to the second heater 40 is not controlled based on the water content of the medium Md, the medium Md can be heated with a greater amount of heating when the water content is in the third range that is greater than the fourth range, and the medium Md can be heated with a smaller amount of heating when the water content is in the fourth range that is less than the third range. Therefore, in the configuration in which the first heater 30 and the second heater 40 are provided, even if the output of the electric power applied to the first heater 30 and the output of the electric power applied to the second heater 40 are not controlled separately, the liquid adhering to the medium Md can be dried uniformly.

[0070] In addition, in the present embodiment, the first heater 30 and the second heater 40 are arranged in a third direction that is orthogonal to the Z direction as the first direction and intersects the Y direction as the second direction. Therefore, it is possible to suppress the deviation in the degree of drying of the medium Md in the third direction.

[0071] In addition, in the present embodiment, the voltage application section 80 has a switching circuit 81 that converts a direct-current voltage of the direct-current power supply 150 into an alternating voltage of the drive frequency f0 by switching. Thus, compared to a case in which the voltage application section 80 is configured by a high-frequency power supply circuit having an analog amplifier and a transformer, it is possible to reduce the internal resistance of the voltage application section 80, and thus it is possible to improve the possibility of improving the power efficiency. In addition, since it is possible to reduce the increase in the amount of heating caused by the increase in the resistance R b of the liquid adhering to the medium Md accompanying the progress of drying, it is possible to further increase the amount of heating when the water content is in the first range relative to the amount of heating when the water content is in the second range.

[0072] Further, in the present embodiment, the first heater 30 is configured so that the first resonance frequency fl coincides with the drive frequency fo when the water content is equal to the full-coat equivalent water content. Thus, in a case where the liquid on the medium Md whose water content is equal to or less than the full-coat equivalent water content is dried by the first heater 30, the more the drying proceeds, the more the difference between the first resonance frequency fl and the drive frequency fo can be increased. Therefore, the deviation of the degree of drying of the medium Md can be further suppressed.

[0073] B. Other Embodiments

[0074] (B-1) In the above-described embodiment, the induction heating device 100 is provided with the first heater 30 and the second heater 40. In contrast, the induction heating device 100 may, for example, be provided with only the first heater 30. Further, the induction heating device 100 may, for example, be provided with one or a plurality of other heaters 20 in addition to the first heater 30 and the second heater 40.

[0075] (B-2) In the above-described embodiment, the voltage application unit 80 applies the alternating voltage of the drive frequency fo to the first heater 30 and the second heater 40. In contrast, for example, two voltage application units 80 that are separately configured may apply the alternating voltage of the drive frequency fo to the first heater 30 and the second heater 40, respectively.

[0076] (B-3) In the above-described embodiment, the voltage application unit 80 is configured as an inverter having a switching circuit 81 that converts the direct current voltage of the direct current power supply 150 into the alternating voltage of the drive frequency fo. In contrast, the voltage application unit 80 may, for example, be configured by a high-frequency power supply circuit having an analog amplifier and a transformer, and not have the switching circuit 81.

[0077] (B-4) In the above-described embodiment, the first heater 30 is configured so that the first resonance frequency fl coincides with the drive frequency fo when the water content is equal to the full-coat equivalent water content. In contrast, the first heater 30 may, for example, be configured so that the first resonance frequency fl coincides with the drive frequency fo when the water content is equal to a water content that is less than the full-coat equivalent water content, as long as the first heater 30 is configured to satisfy the first condition and the second condition. Similarly, the second heater 40 may, for example, be configured so that the second resonance frequency f2 coincides with the drive frequency fo when the water content is equal to the full-coat equivalent water content, as long as the second heater 40 is configured to satisfy the third condition and the fourth condition.

[0078] (B-5) In the above-described embodiment, the second electrode 32 is arranged so as to surround the first electrode 31 when viewed in the Z direction. In contrast, for example, the first electrode 31 and the second electrode 32 can be arranged so as to be adjacent to each other when viewed in the Z direction, or can be arranged so as to sandwich the medium Md in the Z direction with the first electrode 31 and the second electrode 32. In this case, the shapes of the first electrode 31 and the second electrode 32 can be arbitrary, and can be circular, elliptical, rectangular, polygonal, or the like. Further, the areas of the first electrode 31 and the second electrode 32 when viewed in the Z direction can be the same as each other or different. It is preferable that the first electrode 31 and the second electrode 32 be arranged so as not to overlap with each other when viewed in the Z direction. Likewise, the third electrode 41 and the fourth electrode 42 can be arranged so as to be adjacent to each other when viewed in the Z direction, or can be arranged so as to sandwich the medium Md in the Z direction with the third electrode 41 and the fourth electrode 42.

[0079] (B-6) In the above-described embodiment, the medium Md is continuously transported from the liquid ejecting device 205 toward the induction heating device 100. In this case, the transport unit 320 can have, for example, only a transport unit common to the induction heating device 100 and the liquid ejecting device 205. Further, the medium Md can not be continuously transported from the liquid ejecting device 205 toward the induction heating device 100. For example, the medium Md on which liquid is applied by the liquid ejecting device 205 can be temporarily wound in a roll shape, and then moved toward the induction heating device 100 by a robot or the like. In this case, in the induction heating device 100, for example, the medium Md wound in a roll shape can be unwound, and the medium Md can be transported and heated by the second transport unit 322 or the like.

[0080] (B-7) In the above-described embodiment, the heater 20 can be configured to be reciprocally movable in the third direction. For example, the heater 20 can be supported by a not-illustrated drive unit configured of a belt mechanism or a ball screw mechanism, and can be reciprocally moved in the X direction.

[0081] (B-8) In the above-described embodiment, a frequency of 13.56 MHz is used as the drive frequency f0. In contrast, a frequency of 13.56 MHz can not be used as the drive frequency f0, and, for example, a frequency of 40.68 MHz, 2.45 GHz, 5.8 GHz, or the like of another ISM band can be used. Further, the drive frequency f0 can not be a high frequency as long as the medium Md on which liquid is attached can be heated by the heater 20. In this case, the drive frequency f0 is, for example, preferably 100 kHz or more and less than 1 MHz.

[0082] (B-9) In the above-described embodiments, the induction heating device 100 is assembled to the liquid ejection system 200. In contrast, the induction heating device 100 can not be assembled to the liquid ejection system 200, and for example, the induction heating device 100 can be used alone.

[0083] C. Other Modes:

[0084] The present disclosure is not limited to the above-described embodiments, and can be implemented in various ways without departing from the gist thereof. For example, the present disclosure can also be implemented by the following modes. In order to solve part or all of the problems of the present disclosure, or in order to achieve part or all of the effects of the present disclosure, the technical features of the above-described embodiments corresponding to the technical features in each of the following modes can be appropriately replaced, combined. In addition, the technical features can be appropriately deleted in the specification as long as they are not described as essential features.

[0085] (1) According to a first mode of the present disclosure, an induction heating device is provided. The induction heating device includes a first heater that has a first electrode and a second electrode that oppose a medium to which a liquid containing water is attached, and a first coil that is electrically connected in series to the first electrode, and that heats the liquid to dry it, and a voltage application unit that applies an alternating voltage of a predetermined drive frequency to the first electrode and the second electrode. The first heater is configured such that a difference between a resonance frequency of the first heater when a water content of the medium is in a first range and the drive frequency is smaller than a difference between a resonance frequency of the first heater when the water content is in a second range that is less than the first range and the drive frequency, and a heating amount when the water content is in the first range is greater than a heating amount when the water content is in the second range.

[0086] According to such a mode, even if the output of the alternating current power applied to the first heater is not controlled based on the water content of the medium, the medium can be heated with a greater heating amount by the first heater when the water content is in the first range that is greater than the second range, and the medium can be heated with a smaller heating amount by the first heater when the water content is in the second range that is less than the first range. Therefore, the liquid attached to the medium can be uniformly dried without providing a sensor that measures the water content of the medium.

[0087] (2) In the above-described aspect, the induction heating device can further include a second heater having a third electrode and a fourth electrode facing the medium, and a second coil electrically connected in series to the third electrode, and the voltage application unit can apply an alternating voltage of the drive frequency to the third electrode and the fourth electrode, and the second heater can be configured such that a difference between a resonance frequency of the second heater when the water content is in a third range and the drive frequency is smaller than a difference between a resonance frequency of the second heater when the water content is in a fourth range smaller than the third range and the drive frequency, and a heating amount when the water content is in the third range is larger than a heating amount when the water content is in the fourth range. According to this aspect, in the aspect in which the first heater and the second heater are provided, even if the output of the power applied to the first heater and the output of the power applied to the second heater are not individually controlled, the liquid adhering to the medium can be uniformly dried.

[0088] (3) In the above-described aspect, the first electrode, the second electrode, the third electrode, and the fourth electrode can each face the medium being conveyed in a first direction, and the first heater and the second heater can be arranged in a third direction orthogonal to the first direction and intersecting the second direction. According to this aspect, the degree of drying of the liquid on the medium in the third direction can be suppressed from being uneven.

[0089] (4) In the above-described aspect, the voltage application unit can include a switching circuit that converts a direct-current voltage of a direct-current power source into an alternating voltage of the drive frequency by switching. According to this aspect, compared to a case in which the voltage application unit is configured by, for example, a high-frequency power source circuit including an analog amplifier and a transformer, the voltage application unit can be more likely to be downsized, and the power efficiency can be more likely to be improved.

[0090] (5) In the above-described aspect, the first heater can be configured such that, when the water content corresponds to a water content in a case in which the medium is fully coated with the liquid, a resonance frequency of the first heater coincides with the drive frequency. According to this aspect, when the liquid on the medium having a water content lower than the water content in the case in which the medium is fully coated with the liquid is dried by the first heater, the more the drying proceeds, the more the difference between the resonance frequency of the first heater and the drive frequency can be increased. Thus, the degree of drying of the liquid on the medium can be further suppressed from being uneven.

[0091] (6) According to a second aspect of the present disclosure, there is provided a liquid ejection system. The liquid ejection system includes the induction heating device according to the above aspect, and a liquid ejection section that ejects and applies the liquid to the medium, the first heater heating the medium to which the liquid is applied by the liquid ejection section.

[0092] (7) According to a third aspect of the present disclosure, there is provided a liquid ejection device including a first electrode and a second electrode that face a medium to which a liquid containing water is attached and to which an alternating voltage of a predetermined drive frequency is applied, and a first coil that is electrically connected in series to the first electrode, the liquid ejection device applying the liquid heated by a heater to the medium, the heater being configured such that a difference between a resonance frequency in a case where a water content of the medium is in a first range and the drive frequency is smaller than a difference between a resonance frequency in a case where the water content is in a second range smaller than the first range and the drive frequency, and a heating amount in the case where the water content is in the first range is larger than a heating amount in the case where the water content is in the second range. The liquid ejection device includes a conveyance section that conveys the medium, a liquid ejection section that ejects and applies the liquid to the medium, and a control section that controls the conveyance section and the liquid ejection section.

Claims

1. An induction heating device, characterized by, Possessing: a first heater having a first electrode and a second electrode opposed to a medium to which a liquid containing water is attached, and a first coil electrically connected in series to the first electrode, the first heater heating the liquid to dry it; and a voltage application section applying an alternating voltage of a predetermined drive frequency to the first electrode and the second electrode, the first heater being configured so that: a difference between a resonance frequency of the first heater and the drive frequency when a water content of the medium is in a first range is smaller than a difference between a resonance frequency of the first heater and the drive frequency when the water content is in a second range that is less than the first range, and a heating amount when the water content is in the first range is greater than a heating amount when the water content is in the second range.

2. The inductive heating device according to claim 1, wherein: the inductive heating device possesses a second heater having a third electrode and a fourth electrode opposed to the medium, and a second coil electrically connected in series to the third electrode, the second heater heating the liquid to dry it, the voltage application section applies an alternating voltage of the drive frequency to the third electrode and the fourth electrode, the second heater is configured so that: a difference between a resonance frequency of the second heater and the drive frequency when a water content of the medium is in a third range is smaller than a difference between a resonance frequency of the second heater and the drive frequency when the water content is in a fourth range that is less than the third range, and a heating amount when the water content is in the third range is greater than a heating amount when the water content is in the fourth range.

3. The inductive heating device according to claim 2, wherein: the first electrode, the second electrode, the third electrode, and the fourth electrode are respectively opposed to the medium being carried in a first direction in a second direction orthogonal to the first direction, the first heater and the second heater are arranged in a third direction orthogonal to the first direction and intersecting the second direction.

4. The inductive heating device according to claim 1, wherein: the voltage application section has a switching circuit that converts a direct voltage of a direct current power source into an alternating voltage of the drive frequency by switching.

5. The inductive heating device according to claim 1, wherein: the first heater is configured so that, when the water content corresponds to a water content in a case where the medium is fully coated with the liquid, a resonance frequency of the first heater coincides with the drive frequency.

6. A liquid ejection system, characterized by, Possessing: the inductive heating device according to any one of claims 1 to 5; and a liquid ejection section that ejects and applies the liquid to the medium, the first heater heats the medium to which the liquid is applied by the liquid ejection section.

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