Drying equipment, printing system

Abstract

This invention provides a drying apparatus and a printing system for protecting an alternating current (AC) electric field generating unit. The drying apparatus dries a conveyed medium and includes: a support portion supporting the conveyed medium; an AC electric field generating unit that generates an AC electric field; a detection portion that detects the moisture content of the medium; and a control portion. The AC electric field generating unit has: a first electrode and a second electrode arranged opposite to and adjacent to the medium supported by the support portion; a high-frequency voltage generating unit that generates a high-frequency voltage to the first and second electrodes; and a conductor electrically connecting the first and second electrodes to the high-frequency voltage generating unit. The detection portion is located downstream or upstream of the first and second electrodes in the conveying direction. The control portion controls the AC electric field generating unit based on the detection result of the detection portion.

Description

Technical Field

[0001] This invention relates to a drying apparatus and a printing system. Background Technology

[0002] Previously, as shown in Patent Document 1, there was a known drying apparatus that included a heating section that irradiates electromagnetic waves onto a liquid sprayed onto a medium.

[0003] However, in devices that heat objects by irradiating them with electromagnetic waves, such as the aforementioned drying device, there is a problem that the electromagnetic wave generating unit malfunctions when heating is continued in a state where there is no moisture or other substances contained in the object.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2017-114001 Summary of the Invention

[0005] The drying apparatus is for drying a conveyed medium, comprising: a support portion for supporting the conveyed medium; an alternating current (AC) electric field generating portion for generating an AC electric field; a detection portion for detecting the moisture content of the medium; and a control portion, wherein the AC electric field generating portion has: a first electrode and a second electrode arranged opposite to and adjacent to the medium supported by the support portion; a high-frequency voltage generating portion for generating a high-frequency voltage to the first electrode and the second electrode; and a conductor electrically connecting the first electrode, the second electrode, and the high-frequency voltage generating portion. The detection portion is located at least one downstream or upstream of the first electrode and the second electrode in the conveying direction. The control portion controls the AC electric field generating portion based on the detection result of the detection portion.

[0006] The printing system includes the aforementioned drying device and a printing device for coating a liquid onto a medium, wherein the drying device dries the medium coated with the liquid that has passed through the printing device. Attached Figure Description

[0007] Figure 1 This is a schematic diagram illustrating the structure of a printing system.

[0008] Figure 2 This is a schematic diagram showing the structure of the alternating current electric field generating unit.

[0009] Figure 3 This is a schematic diagram showing the structure of the alternating current electric field generating unit.

[0010] Figure 4 This is a schematic diagram showing the structure of the air supply section.

[0011] Figure 5AThis is a schematic diagram illustrating the structure of the detection unit (ultrasonic sensor).

[0012] Figure 5B This is a schematic diagram illustrating the structure of another detection unit (ultrasonic sensor).

[0013] Figure 6 This is a schematic diagram illustrating the structure of the detection unit (capacitance sensor).

[0014] Figure 7 This is a schematic diagram illustrating the structure of the detection unit (optical sensor).

[0015] Figure 8 This is a schematic diagram illustrating the structure of the detection unit (optical sensor).

[0016] Figure 9 This is a block diagram showing the structure of the control unit of the drying device.

[0017] Figure 10 This is a block diagram showing the structure of the control unit of the drying device. Detailed Implementation

[0018] First, the structure of printing system 1 will be explained.

[0019] like Figure 1 As shown, the printing system 1 includes: a holding device 2, a winding device 3, a printing device 10, and a drying device 20.

[0020] The holding device 2 is a device for holding a roll 5 formed by winding a sheet-like medium M. The holding device 2 has a holding shaft 7 for holding the roll 5. The holding shaft 7 is configured to be rotatable, for example. As the holding shaft 7 rotates, the medium M is unwound from the roll 5. The medium M is, for example, a sheet of paper, cloth, or other similar material.

[0021] The winding device 3 is a device for winding up the medium M that is unwound from the holding device 2. The winding device 3 has a winding shaft 8 for winding up the medium M. The winding shaft 8 is configured to be rotatable. By driving the winding shaft 8 to rotate, the medium M is wound up. As a result, the winding shaft 8 holds the roll 9 formed by winding up the medium M. In this embodiment, the medium M is unwound from the roll 5 held on the holding shaft 7 by driving the winding shaft 8 to rotate.

[0022] The medium M is conveyed by being wound by the winding device 3. The medium M is conveyed from the holding device 2, via the printing device 10 and the drying device 20, toward the winding device 3. The conveying direction of the medium M is from the holding device 2 toward the winding device 3 (parallel to the +Y direction). The medium M has a surface MA and a back surface MB, which is the opposite side of the surface MA.

[0023] The printing apparatus 10 is an apparatus that applies a liquid (e.g., ink) to a medium M to perform printing on the medium M. The printing apparatus 10 is, for example, an inkjet printer that records (prints) images such as text, photographs, and graphics by ejecting ink onto the medium M.

[0024] The printing device 10 is located between the holding device 2 and the winding device 3 in the conveying direction. The printing device 10 is positioned upstream of the drying device 20 in the conveying direction. That is, the medium M unwound from the holding device 2 passes sequentially through the printing device 10 and the drying device 20.

[0025] The printing apparatus 10 includes: an impression plate 11, a printing section 12, and a control section 13.

[0026] The imprint plate 11 is a plate-shaped component. The imprint plate 11 supports the medium M being transported. The imprint plate 11 supports the medium M from below. The imprint plate 11 is in contact with the back surface MB of the medium M.

[0027] The printing section 12 is positioned opposite the printing plate 11. The printing section 12 is located above the printing plate 11. The printing section 12 includes a head 15 and a carriage 16.

[0028] The head 15 is positioned opposite the impression plate 11. The head 15 is located above the impression plate 11. The head 15 sprays liquid toward the surface MA of the medium M supported on the impression plate 11. As a result, an image is printed on the medium M. The liquid sprayed by the head 15 is, for example, a water-based ink with water as the solvent.

[0029] When head 15 sprays liquid into medium M, the water content of medium M will increase. That is, head 15 performs a process on medium M to increase the water content of medium M by spraying liquid into medium M.

[0030] The carriage 16 is mounted on the head 15. The carriage 16 is opposite to the imprint plate 11. The carriage 16 is located above the imprint plate 11. The carriage 16 reciprocates relative to the medium M being transported in the X-axis direction. That is, the carriage 16 reciprocates above the imprint plate 11 in a manner that spans the width direction of the medium M.

[0031] The printing apparatus 10 is a serial printer in which the head 15 reciprocates relative to the medium M. Alternatively, the printing apparatus 10 may also be a line printer in which the head 15 ejects liquid simultaneously across the width of the medium M.

[0032] The control unit 13 controls each drive unit of the printing apparatus 10. The control unit 13 includes a CPU, a memory, a control circuit, and an I / F (interface). The CPU is an arithmetic processing unit. The memory is a storage device that stores the CPU's program or working area, and includes storage elements such as RAM and EEPROM. When recording data is obtained from an external source such as an information processing terminal via the I / F, the CPU controls the drive units of the printing unit 12, etc., via the control circuit.

[0033] The control unit 13 is capable of communicating with the holding device 2, the winding device 3, and the drying device 20. The control unit 13 receives signals from the holding device 2, the winding device 3, and the drying device 20, or sends signals to the holding device 2, the winding device 3, and the drying device 20 (control unit 100) as needed.

[0034] Alternatively, in the printing apparatus 10, a pretreatment section for applying a pretreatment liquid to the surface MA of the medium M can be disposed upstream of the printing section 12 in the transport direction. By pretreating the medium M before printing in the pretreatment section, the permeability of the liquid sprayed onto the medium M during printing can be improved, thereby improving the printing quality such as color development of the image printed on the medium M, as well as the durability of the medium M.

[0035] Next, the structure of the drying device 20 will be described.

[0036] The drying device 20 is a device for drying the conveyed medium M. The drying device 20 is disposed downstream of the printing device 10 in the conveying direction and dries the medium M that has been coated with liquid by the printing device 10.

[0037] like Figure 1 As shown, the drying device 20 includes: a support 21, an alternating current generating unit 30, a detection unit 40, and a control unit 100.

[0038] The support portion 21 supports the conveyed medium M. In this embodiment, a pair of conveyor rollers 21a and 21b are provided. Each conveyor roller 21a and 21b extends in the direction along the X-axis. One conveyor roller 21a is positioned upstream in the conveying direction relative to the other conveyor roller 21b. Each conveyor roller 21a and 21b supports the back surface MB of the medium M. Each conveyor roller 21a and 21b is a driven roller and rotates drivenly in conjunction with the winding action of the medium M performed by the winding device 3.

[0039] The alternating current (AC) electric field generating unit 30 is a component for drying the medium M. Specifically, the AC electric field generating unit 30 performs the following process: by generating an AC electric field, it heats the moisture contained in the medium M and reduces the moisture content of the medium M. That is, the AC electric field generating unit 30 heats the liquid applied to the medium M supported on the support unit 21, thereby drying the medium M. The AC electric field generating unit 30 is disposed between the conveyor rollers 21a and 21b in the conveying direction.

[0040] The alternating current field generating unit 30 heats the liquid by generating an alternating current field of 2.4 GHz. Alternatively, for example, Joule heating formed by eddy currents generated in the liquid coated on the medium M by generating an alternating current field of 3 MHz to 300 MHz, or dielectric heating formed by friction based on molecular vibrations that generate an alternating current field of 300 MHz to 30 GHz, may be used. Among these, generating an alternating current field of 10 MHz to 20 GHz is preferred.

[0041] like Figure 2 As shown, the alternating current electric field generating unit 30 has a plurality of generators 33 for generating an alternating current electric field. The plurality of generators 33 are arranged to extend in the direction along the X-axis. The dimension of the plurality of generators 33 in the direction along the X-axis is longer than the dimension of the medium M in the direction along the X-axis. The plurality of generators 33 are arranged in a plurality of columns in the direction along the X-axis.

[0042] Furthermore, multiple generators 33 are disposed within the housing 37 to prevent the alternating electric field generated by the multiple generators 33 from affecting the outside. The housing 37 is a box with an opening at the bottom. The multiple generators 33 are arranged facing the opening of the housing 37 in a manner opposite to the surface MA of the medium M supported on the support 21.

[0043] Furthermore, preferably, the distance between the -Z direction end of the housing 37 and the medium M along the Z-axis is approximately 1mm to 20mm. This prevents the user's fingers or other objects from entering between the housing 37 and the medium M.

[0044] Furthermore, an electric field detection sensor 36 is mounted on the housing 37. In this embodiment, the electric field detection sensor 36 is configured to include a pair of electric field detection antennas for detecting alternating current electric fields. The electric field detection sensor 36 is positioned opposite the medium M along the Z-axis. The electric field detection sensor 36 is disposed at the end of the housing 37. Specifically, one of the pair of electric field detection antennas is disposed at a corner of the housing 37, and the other electric field detection antenna is disposed at a corner diagonally opposite the corner of the housing 37 where one electric field detection antenna is disposed. In this manner, the electric field detection sensor 36 is disposed such that the electric field detection antennas are separated from the generator 33, and it is capable of detecting changes in the alternating current electric field generated by the alternating current electric field generating unit 30.

[0045] like Figure 3 As shown, the generator 33 includes a first electrode 81, a second electrode 82, and a conductor 83. The first electrode 81 is a rectangular plate when viewed in planar view. The first electrode 81 faces the medium M supported on the support portion 21. The first electrode 81 is positioned above the medium M. The second electrode 82 is a hollow rectangular plate surrounding the first electrode 81 when viewed in planar view. The second electrode 82 faces the medium M supported on the support portion 21. The second electrode 82 is positioned above the medium M. The first electrode 81 and the second electrode 82 are arranged adjacent to each other.

[0046] Conductor 83 electrically connects the first electrode 81 and the second electrode 82 to the high-frequency voltage generating unit 91 that generates a high-frequency voltage. Conductor 83 has a coaxial cable 84 and a coil 85. The coaxial cable 84 has an inner conductor 84A and an outer conductor 84B. The inner conductor 84A is connected to the first electrode 81 via the coil 85, and electrically connects the high-frequency voltage generating unit 91 and the first electrode 81. The outer conductor 84B is connected to the second electrode 82, and electrically connects the high-frequency voltage generating unit 91 and the second electrode 82. As an example of winding, the coil 85 is connected between the first electrode 81 and the inner conductor 84A of the coaxial cable 84, and preferably, is positioned as close as possible to the first electrode 81.

[0047] The minimum separation distance between the first electrode 81 and the second electrode 82 is less than one-tenth of the wavelength of the AC electric field output from the AC electric field generating unit 30. Furthermore, the first electrode 81 and the second electrode 82 are point-symmetrical about the center of the first electrode 81. Therefore, since the electric field generated between the first electrode 81 and the second electrode 82 cancels out the electric field generated at the point-symmetrical position, almost all of the AC electric field generated when a high-frequency voltage is applied is attenuated near the first electrode 81 and the second electrode 82. This reduces the intensity of electromagnetic waves traveling from the first electrode 81 and the second electrode 82 to distant locations. In other words, the AC electric field generated by the AC electric field generating unit 30 is very strong near the first electrode 81 and the second electrode 82, but becomes very weak at a distance.

[0048] Such a generator 33 can generate an AC electric field in a concentrated range, for example, 3 mm to 3 cm, in the vicinity of the first electrode 81 and the second electrode 82 by appropriately controlling the frequency band of the generated AC electric field, and is less susceptible to the influence of the AC electric field beyond this range.

[0049] Furthermore, in the generator 33, the alternating current field can be concentrated near the first electrode 81 and the second electrode 82, thereby improving the heating efficiency of the liquid sprayed onto the medium M supported by the support portion 21, and thus improving the drying efficiency of the medium M. On the other hand, it makes it less likely for an alternating current field to be generated at locations away from the first electrode 81 and the second electrode 82, thereby eliminating the need for excessive configuration of components for suppressing the alternating current field, and thus improving the operability of the drying apparatus 20. In addition, it can prevent the drying apparatus 20 from becoming too large.

[0050] like Figure 1 As shown, the opposing surfaces of the first electrode 81 and the second electrode 82 in the generator 33, which face the medium M, are covered by a cover 34. The cover 34 is positioned below the generator 33. Because the generator 33 is covered by the cover 34, the adhesion of foreign matter to the first electrode 81 and the second electrode 82 is suppressed.

[0051] The cover 34 is formed of a material that allows the alternating electric field generated from the alternating electric field generating unit 30 to pass through. Specifically, the cover 34 is formed of glass. However, it is not limited to this; for example, it may be formed of a resin with permeability, such as a cyclic olefin copolymer. Preferably, it is a material that is not easily affected by dielectric heating. The surface of the cover 34 in the -Z direction has an uneven shape, so that the alternating electric field generated from the alternating electric field generating unit 30 converges toward the medium M supported on the support unit 21.

[0052] Furthermore, the drying device 20 includes an adjustment mechanism 88 that allows the generator 33 and the cover 34 to move in the direction along the Z-axis. Figure 4 Therefore, the distance between generator 33 and medium M can be adjusted. The adjustment mechanism 88 can be, for example, a linkage mechanism or a rack and pinion mechanism. Therefore, depending on the type of medium M, the type of liquid ejected from head 15, etc., the distance between generator 33 and medium M can be easily adjusted.

[0053] like Figure 4 As shown, the drying apparatus 20 includes an air supply section 90 that supplies air to the generator 33 (first electrode 81 and second electrode 82). The air supply section 90 is mounted on the housing 37. The air supply section 90 includes a first channel 94A, a second channel 94B, a first air supply fan 94C, and a second air supply fan 94D.

[0054] The first channel 94A is a channel extending along the Z-axis between the outer edge of the generator 33 and the housing 37, adjacent to the generator 33. The second channel 94B is a channel extending along the Z-axis on the -Y side of the generator 33, adjacent to the generator 33.

[0055] A first air supply fan 94C is positioned at the upper end of the first channel 94A. The first air supply fan 94C is a fan that supplies air from the outside of the housing 37 into the first channel 94A. A second air supply fan 94D is positioned at the upper end of the second channel 94B of the housing 37. The second air supply fan 94D is a fan that supplies air from the second channel 94B to the outside of the housing 37.

[0056] Air is drawn in from outside the housing 37 by the first air supply fan 94C and supplied to the first channel 94A, and air is supplied to the outside of the housing 37 from the second channel 94B by the second air supply fan 94D. Thus, the gas flows from the first channel 94A, through the bottom of the cover 34, and through the second channel 94B. In this way, the air supply unit 90 supplies air to the generator 33, which includes the coil 85, the first electrode 81, and the second electrode 82. As a result, the generator 33, including the coil 85, the first electrode 81, and the second electrode 82, is cooled.

[0057] Furthermore, the gas supplied by the first blower fan 94C is heated by the generator 33. The heated gas is blown onto the medium M supported on the support 21. As a result, the liquid coated on the medium M is heated, thereby promoting the drying of the medium M.

[0058] The detection unit 40 detects the moisture content of the medium M. In this embodiment, the detection unit 40 detects the moisture content of the ink in the medium M that has passed through the printing apparatus 10. The detection unit 40 is disposed at least one downstream or upstream of the first electrode 81 and the second electrode 82 in the conveying direction.

[0059] like Figure 1 As shown, the detection unit 40 in this embodiment includes an ultrasonic sensor 41 and capacitance sensors 43 and 44. Although this embodiment uses only one ultrasonic sensor 41, it can also include two or more. Furthermore, while two capacitance sensors 43 and 44 are provided, it can also include three or more, or only one.

[0060] In addition, the detection unit 40 of this embodiment also includes an optical sensor 45.

[0061] The ultrasonic sensor 41 is positioned upstream of the generator 33 (first electrode 81 and second electrode 82) in the conveying direction.

[0062] like Figure 5A As shown, the ultrasonic sensor 41 has a transmitting unit 41a and a receiving unit 41b. The transmitting unit 41a and the receiving unit 41b are configured to clamp the medium M being transported. The transmitting unit 41a and the receiving unit 41b are configured to clamp the medium M being transported from both above and below. That is, the medium M is transported through the transmitting unit 41a and the receiving unit 41b.

[0063] The transmitting unit 41a is positioned above the receiving unit 41b (in the +Z direction). The transmitting unit 41a transmits ultrasonic waves toward the receiving unit 41b. That is, the transmitting unit 41a transmits ultrasonic waves downwards (in the -Z direction). Therefore, when the medium M is located between the transmitting unit 41a and the receiving unit 41b, the ultrasonic waves transmitted from the transmitting unit 41a will irradiate the medium M. At this time, the ultrasonic waves transmitted from the transmitting unit 41a irradiate the medium M before drying. When the medium M is not located between the transmitting unit 41a and the receiving unit 41b, the ultrasonic waves transmitted from the transmitting unit 41a directly irradiate the receiving unit 41b.

[0064] The receiving unit 41b receives the ultrasonic waves transmitted by the transmitting unit 41a. Therefore, when the medium M is located between the transmitting unit 41a and the receiving unit 41b, the receiving unit 41b receives the ultrasonic waves transmitted from the transmitting unit 41a and passing through the medium M. At this time, the receiving unit 41b receives the ultrasonic waves that have passed through the medium M before drying. When the medium M is not located between the transmitting unit 41a and the receiving unit 41b, the receiving unit 41b directly receives the ultrasonic waves transmitted from the transmitting unit 41a.

[0065] The ultrasonic waves transmitted from the transmitting unit 41a are attenuated as they pass through the medium M. Therefore, when the medium M is located between the transmitting unit 41a and the receiving unit 41b, the intensity of the ultrasonic waves received by the receiving unit 41b is lower than when the medium M is not located between the transmitting unit 41a and the receiving unit 41b. Furthermore, the degree of attenuation of the ultrasonic waves passing through the medium M varies depending on the density, thickness, and other factors of the medium M.

[0066] The transmittance of the ultrasonic wave relative to the medium M is detected based on the intensity of the ultrasonic wave received by the receiving unit 41b when the medium M is located between the transmitting unit 41a and the receiving unit 41b, and the intensity of the ultrasonic wave received by the receiving unit 41b when the medium M is not located between the transmitting unit 41a and the receiving unit 41b. The transmittance of the ultrasonic wave relative to the medium M refers to the proportion of the ultrasonic wave that passes through the medium M relative to the ultrasonic wave transmitted by the transmitting unit 41a.

[0067] There is a correlation between the transmittance of ultrasound waves relative to medium M and the basis weight of medium M. For example, the greater the transmittance of ultrasound waves relative to medium M, the smaller the basis weight of medium M. Conversely, the smaller the transmittance of ultrasound waves relative to medium M, the greater the basis weight of medium M. In this way, the basis weight of medium M can be detected based on the transmittance of ultrasound waves relative to medium M. Therefore, the ultrasonic sensor 41 is a sensor for detecting the basis weight of medium M. The control unit 100 calculates the basis weight of medium M based on the signal transmitted from the ultrasonic sensor 41.

[0068] Alternatively, a structure can be added that calculates the thickness of the medium M based on the signal transmitted from the ultrasonic sensor 41.

[0069] Specifically, such as Figure 5B As shown, the transmitting unit 41a and the receiving unit 41b are positioned above the medium M. Ultrasonic waves are transmitted from the transmitting unit 41a toward the medium M, and the receiving unit 41b receives the ultrasonic waves reflected by the medium M. Furthermore, a support body 49 is provided on the back surface MB side of the medium M, which reflects the ultrasonic waves transmitted from the transmitting unit 41a. This support body 49 has a support surface that supports the medium M. Thus, the ultrasonic waves transmitted from the transmitting unit 41a are reflected on the surface MA of the medium M and the support surface, and the receiving unit 41b receives the ultrasonic waves reflected on the surface MA of the medium M and the support surface. Then, the time from when the transmitting unit 41a transmits the ultrasonic waves until the ultrasonic waves reflected on the surface MA of the medium M are received, and the time difference between when the transmitting unit 41a transmits the ultrasonic waves until the ultrasonic waves reflected on the support surface are received, are detected. By converting this time difference into a distance, the thickness of the medium M can be detected.

[0070] like Figure 1As shown, the capacitance sensor 43 is positioned upstream of the generator 33 (first electrode 81 and second electrode 82) in the conveying direction, and the capacitance sensor 44 is positioned downstream of the generator 33 (first electrode 81 and second electrode 82) in the conveying direction.

[0071] like Figure 6 As shown, the capacitance sensor 43 is positioned slightly below the medium M. The capacitance sensor 43 contacts the medium M from below. By contacting the medium M, the capacitance sensor 43 detects the capacitance of the medium M. The capacitance sensor 43 detects the capacitance of the medium M before drying, based on the alternating current field generating unit 30.

[0072] The capacitance sensor 43 has a holding part 51 and an electrode pair 52. The holding part 51 holds the electrode pair 52. The shape of the holding part 51 is, for example, cuboid or rectangular.

[0073] The electrode pair 52 protrudes from the upper surface of the holding portion 51 in the +Z direction. The electrode pair 52 contacts the conveyed medium M. In this embodiment, the electrode pair 52 contacts the back surface MB of the medium M. Therefore, compared with the case where the electrode pair 52 contacts the surface MA of the medium M, the possibility of damaging the printed surface MA can be reduced.

[0074] The electrode pair 52 forms part of the oscillation circuit of the capacitance sensor 43. The electrode pair 52 consists of two electrodes 54. An alternating current (AC) voltage is applied between the two electrodes 54. That is, the capacitance sensor 43 detects the capacitance between the two electrodes 54. When the two electrodes 54 are in contact with the dielectric M, an AC voltage will flow through the dielectric M. Thus, the capacitance sensor 43 detects the capacitance of the dielectric M in contact with the electrode pair 52.

[0075] The electrode pair 52 comes into contact with the medium M after the liquid has been sprayed from the nozzle 15. Therefore, the capacitance sensor 43 detects the capacitance of the medium M containing moisture.

[0076] An alternating voltage flows from the two electrodes 54 to the medium M, causing a change in the capacitance between the two electrodes 54. This change in capacitance is largely influenced by the amount of water contained in the medium M in contact with the electrodes 54. This is because water has a higher dielectric constant than media such as paper or cloth. Therefore, for example, when the medium M contains a higher amount of water, the change in capacitance between the two electrodes 54 is larger. When the medium M contains a lower amount of water, the change in capacitance between the two electrodes 54 is smaller. Thus, there is a correlation between the change in capacitance between the two electrodes 54 and the amount of water contained in the medium M.

[0077] The change in capacitance between the two electrodes 54 is affected by the weight of the medium M in contact with the two electrodes 54. For example, when the weight of medium M is large, the change in capacitance between the two electrodes 54 is larger. When the weight of medium M is small, the change in capacitance between the two electrodes 54 is smaller.

[0078] The holding part 51 can be adjusted in position along the X and Z axes by means of screws or the like. This allows adjustment of the position of the electrode pair 52 to ensure reliable contact between the electrode pair 52 and the dielectric M. Consequently, capacitance can be measured with high accuracy.

[0079] Another capacitance sensor 44 is positioned below the dielectric M. The capacitance sensor 44 contacts the dielectric M from below. By contacting the dielectric M, the capacitance sensor 44 detects the capacitance of the dielectric M. Since the structure of the capacitance sensor 44 is the same as that of the capacitance sensor 43, further description is omitted. The capacitance sensor 44 detects the capacitance of the dried dielectric M based on the alternating current field generating unit 30.

[0080] Based on the above, the water content contained in the medium M can be detected with high accuracy using the ultrasonic sensor 41 and the capacitance sensors 43 and 44. The control unit 100 can also calculate the water content contained in the medium M based on the signals transmitted from the ultrasonic sensor 41 and the capacitance sensor 43.

[0081] The optical sensor 45 detects the amount of water contained in the medium M. Specifically, the optical sensor 45 detects the amount of water on the surface MA.

[0082] Optical sensor 45 is positioned upstream of generator 33 in the conveying direction. Optical sensor 45 is opposite to the conveyed medium M. Optical sensor 45 is positioned above medium M.

[0083] like Figure 7 as well as Figure 8 As shown, the optical sensor 45 includes a housing 71, a light source 72, and a light-receiving part 73. Furthermore, the optical sensor 45 has a light-shielding part 74. The optical sensor 45 is a reflective type optical sensor.

[0084] The housing 71 houses the light source 72, the light-receiving part 73, and the light-shielding part 74. The housing 71 is, for example, rectangular or cuboid in shape. The housing 71 has an opening 75. The opening 75 is located on the side of the housing 71 opposite to the medium M. That is, the opening 75 is located at the bottom of the housing 71. The interior and exterior of the housing 71 communicate through the opening 75.

[0085] Light source 72 emits light. Light source 72 emits light with a peak wavelength that is the absorption wavelength of water. Light source 72 is configured, for example, to emit light with a peak wavelength containing a peak wavelength of 900 nm or more and 2100 nm or less. The light source 72 of this embodiment emits near-infrared light.

[0086] Light source 72 shines light downwards. Therefore, light source 72 shines light onto medium M. Light source 72 shines light onto medium M after liquid has been applied to the head 15. At this time, light source 72 shines light onto the surface MA of medium M.

[0087] Light source 72 has one or more light-emitting elements. Light source 72 may have multiple light-emitting elements. Specifically, light source 72 has multiple light-emitting elements with different peak wavelengths. The light-emitting elements are, for example, LEDs. Light source 72 may have, for example, a first light-emitting element 76 and a second light-emitting element 77. Light source 72 may also have three or more light-emitting elements.

[0088] The first light-emitting element 76 is, for example, a light-emitting element that emits light with a peak wavelength of 940 nm. 940 nm is the absorption wavelength of water. The second light-emitting element 77 is, for example, a light-emitting element that emits light with a peak wavelength of 1450 nm. 1450 nm is the absorption wavelength of water. Both the first light-emitting element 76 and the second light-emitting element 77 can be light-emitting elements that emit light with a peak wavelength that is the absorption wavelength of water. For example, the peak wavelength can also be 1800 nm, 1940 nm, or 2100 nm.

[0089] The light-receiving section 73 receives light emitted by the light source 72. The light-receiving section 73 includes, for example, a light-receiving element, such as a photodiode. The light-receiving section 73 receives light that travels from the light source 72 in the detection optical path L1, or light that travels from the light source 72 in the reference optical path L2. That is, the light emitted by the light source 72 travels through the detection optical path L1 or the reference optical path L2 and thus enters the light-receiving section 73.

[0090] The detection optical path L1 is a path through which light emitted from the light source 72 is reflected on the medium M and then incident on the light-receiving part 73. The detection optical path L1 is... Figure 7 The solid line in the middle shows that... Figure 8 The optical path is shown in double-dotted lines. The detection optical path L1 extends through the opening 75 inside and outside the housing 71. After extending from the light source 72 to the medium M, the detection optical path L1 extends from the medium M to the light-receiving part 73.

[0091] The light traveling in the detection optical path L1 first passes from the light source 72 through the opening 75 and strikes the medium M. Then, the light traveling in the detection optical path L1 strikes the surface MA of the medium M. The light struck on the surface MA of the medium M is reflected. The light reflected from the surface MA of the medium M passes through the opening 75 and enters the light-receiving part 73. In this way, the light emitted by the light source 72 travels in the detection optical path L1. As a result, the light-receiving part 73 receives the light reflected from the medium M.

[0092] Reference optical path L2 is the optical path that enters the light-receiving part 73 when the light emitted from the light source 72 is not reflected by the medium M supported on the imprint plate 11. Figure 7 The text is incomplete and contains numerous errors. A direct translation isn't possible without further context. Figure 8 The light path is shown in solid lines. The reference light path L2 extends inside the housing 71. Inside the housing 71, the reference light path L2 extends straight from the light source 72 to the light receiving part 73. Therefore, light traveling in the reference light path L2 directly enters the light receiving part 73 from the light source 72. Thus, the light receiving part 73 directly receives the light emitted by the light source 72.

[0093] The light-shielding part 74 is configured to block the light emitted by the light source 72. The shape of the light-shielding part 74 is, for example, a flat plate or a plate-like structure. The light-shielding part 74 is located inside the housing 71 between the light source 72 and the light-receiving part 73. The light-shielding part 74 is provided, for example, across the detection optical path L1 and the reference optical path L2. The light-shielding part 74 blocks the detection optical path L1 or the reference optical path L2. By blocking the detection optical path L1 or the reference optical path L2, the light-shielding part 74 blocks the light emitted by the light source 72.

[0094] The light-shielding part 74 is configured to switch between a first state S1 and a second state S2. Figure 7 The light-shielding part 74 shown is in the first state S1. Figure 8 The light-shielding part 74 shown is in the second state S2.

[0095] The light-shielding part 74 switches between a first state S1 and a second state S2, for example, by displacement. The light-shielding part 74 is configured to rotate about a rotation axis 78, which is an imaginary axis. The light-shielding part 74 switches between the first state S1 and the second state S2 by rotating about the rotation axis 78. The light-shielding part 74 is supported by the housing 71, for example, in a state where it can rotate about the rotation axis 78.

[0096] The light-shielding part 74 has a through hole 79. When the light-shielding part 74 is in the first state S1, the through hole 79 is located on the detection optical path L1. Therefore, when the light-shielding part 74 is in the first state S1, light traveling from the light source 72 in the detection optical path L1 passes through the through hole 79 and enters the light-receiving part 73. That is, when the light-shielding part 74 is in the first state S1, it allows light emitted by the light source 72 to travel in the detection optical path L1. Furthermore, when the light-shielding part 74 is in the first state S1, the through hole 79 is not located on the reference optical path L2. That is, when the light-shielding part 74 is in the first state S1, it does not allow light emitted by the light source 72 to travel in the reference optical path L2. Thus, the first state S1 of the light-shielding part 74 is a state in which the light-shielding part 74 does not block the detection optical path L1, but the light-shielding part 74 blocks the reference optical path L2.

[0097] When the light-shielding part 74 is in its second state S2, the through-hole 79 is located on the reference optical path L2. Therefore, when the light-shielding part 74 is in its second state S2, light traveling from the light source 72 in the reference optical path L2 passes through the through-hole 79 and enters the light-receiving part 73. That is, when the light-shielding part 74 is in its second state S2, it allows light emitted by the light source 72 to travel in the reference optical path L2. Furthermore, when the light-shielding part 74 is in its second state S2, the through-hole 79 is not located on the detection optical path L1. That is, when the light-shielding part 74 is in its second state S2, it does not allow light emitted by the light source 72 to travel in the detection optical path L1. Thus, the second state S2 of the light-shielding part 74 is a state in which the light-shielding part 74 blocks the detection optical path L1 but does not block the reference optical path L2.

[0098] The light-shielding section 74 determines the optical path of the light emitted by the light source 72 by switching between a first state S1 and a second state S2. The control unit 100 switches the light-shielding section 74 between the first state S1 and the second state S2.

[0099] When light from the light source 72 shines onto the medium M, that is, when light traveling in the detection optical path L1 strikes the medium M, a portion of the light is absorbed by the medium M. In particular, the near-infrared light emitted by the light source 72 is easily absorbed by water. Therefore, when the medium M contains a higher water content, more light is absorbed by the medium M. Conversely, when the medium M contains a lower water content, less light is absorbed by the medium M.

[0100] By receiving light traveling in the detection optical path L1 through the light-receiving unit 73, the intensity of the light reflected on the medium M can be detected. By receiving light traveling in the reference optical path L2 through the light-receiving unit 73, the intensity of the light irradiated onto the medium M by the light source 72 can be detected. Based on the intensity of the light traveling in the detection optical path L1 and the intensity of the light traveling in the reference optical path L2, the reflectivity of the light relative to the medium M can be detected. Here, the reflectivity of the light relative to the medium M refers to the proportion of light reflected on the medium M relative to the light irradiated onto the medium M.

[0101] There is a correlation between the reflectivity of light relative to medium M and the amount of water contained in medium M. For example, the greater the reflectivity of light relative to medium M, the less water contained in medium M. The smaller the reflectivity of light relative to medium M, the more water contained in medium M. Thus, the amount of water contained in medium M can be detected based on the reflectivity of light relative to medium M. Therefore, optical sensor 45 is a sensor for detecting the amount of water contained in the printed medium M. Optical sensor 45 is particularly capable of detecting the amount of water on surface MA with good accuracy. Control unit 100 can also calculate the amount of water contained in medium M based on the signal transmitted from optical sensor 45.

[0102] The optical sensor 45 primarily detects the amount of water contained in the surface MA of the medium M, while the capacitive sensors 43 and 44 primarily detect the amount of water contained in the back surface MB and the interior of the medium M. Therefore, by using the optical sensor 45 and the capacitive sensors 43 and 44, the amount of water contained in the medium M can be detected with good accuracy.

[0103] When head 15 sprays liquid onto medium M, sometimes most of the liquid remains on the surface MA of medium M. In this case, referring to the detection results of capacitance sensor 43, it can be determined that the increase in the amount of water contained in medium M is small relative to the amount of liquid sprayed by head 15. On the other hand, referring to the detection results of capacitance sensor 43 and optical sensor 45, since liquid remains on the surface MA of medium M, it can be determined that the increase in the amount of water contained in medium M is large relative to the amount of liquid sprayed by head 15. Based on the above, it can be determined that medium M has the characteristic of not easily absorbing liquid. In this way, based on the detection results of capacitance sensor 43 and optical sensor 45, the characteristics of medium M can be determined.

[0104] Alternatively, the optical sensor 45 can be positioned downstream of the generator 33 in the conveying direction. If this is done, the moisture content on the surface MA of the dried medium M can be detected.

[0105] Next, the structure of the control unit 100 of the drying device 20 will be described.

[0106] like Figure 9 As shown, the control unit 100 controls each drive unit of the drying apparatus 20. The control unit 100 includes a CPU 101, a memory 102, a control circuit 103, and an I / F (interface) 104. The CPU 101 is an arithmetic processing unit. The memory 102 is a storage device that stores the program of the CPU 101 or the working area, and has storage elements such as RAM (Random Access Memory) and EEPROM (Electrically Erasable Programmable Read-Only Memory). When drying processing data is obtained from an external source such as an information processing terminal via the I / F 104, the CPU 101 controls the AC electric field generator 30, the air supply unit 90, the adjustment mechanism 88, the detection unit 40 (ultrasonic sensor 41, capacitance sensors 43 and 44, optical sensor 45), and the electric field detection sensor 36 via the control circuit 103. Furthermore, the control unit 100 can work in conjunction with the control unit 13 to control the holding device 2 and the winding device 3.

[0107] The control unit 100 controls the alternating current field generating unit 30 based on the detection results from the detection unit 40. For example, based on the detection data detected by the detection unit 40, the control unit 100 drives the alternating current field generating unit 30 when the water content in the medium M reaches a threshold. On the other hand, when the water content in the medium M does not reach the threshold, that is, when the water content in the medium M is low, the drive of the alternating current field generating unit 30 is stopped. Thus, since heating is not applied to the medium M, which has low water content and is dry, malfunctions of the alternating current field generating unit 30 can be avoided.

[0108] Furthermore, the control unit 100 limits the driving of the AC electric field generating unit 30 based on the signal from the electric field detection sensor 36.

[0109] like Figure 10 As shown, in addition to the generator 33 and the high-frequency voltage generator 91, the AC electric field generating unit 30 also has a monitoring circuit 92.

[0110] The high-frequency voltage generating unit 91 is connected to the generator 33. Specifically, the high-frequency voltage generating unit 91 is connected to the first electrode 81 and the second electrode 82 via the conductor 83. The high-frequency voltage generating unit 91 generates a high-frequency voltage to the first electrode 81 and the second electrode 82, and by outputting the high-frequency voltage to the first electrode 81 and the second electrode 82, it generates an alternating electric field on the first electrode 81 and the second electrode 82.

[0111] The high-frequency voltage generating unit 91 includes a high-frequency voltage generating circuit 91a and an amplifier circuit 91b. The high-frequency voltage generating circuit 91a is connected to the control unit 100 and the amplifier circuit 91b. The high-frequency voltage generating circuit 91a generates a high-frequency voltage based on a generation instruction signal from the control unit 100 and outputs it to the amplifier circuit 91b. The amplifier circuit 91b amplifies the high-frequency voltage generated by the high-frequency voltage generating circuit 91a based on the generation instruction signal from the control unit 100 and outputs it to the generator 33. The high-frequency voltage generating unit 91 supplies, for example, power of 3 kW or less to the generator 33.

[0112] The monitoring circuit 92 is connected to the high-frequency voltage generating unit 91 and the control unit 100. The monitoring circuit 92 monitors the high-frequency voltage from the high-frequency voltage generating unit 91 and outputs the monitoring result to the control unit 100.

[0113] The monitoring circuit 92 includes a rectifier circuit 92a and a comparator circuit 92b. The rectifier circuit 92a is connected to the high-frequency voltage generator 91 and the comparator circuit 92b. The rectifier circuit 92a converts the high-frequency voltage from the high-frequency voltage generator 91 into DC by rectifying and smoothing it, and outputs it to the comparator circuit 92b.

[0114] The comparator circuit 92b is connected to the rectifier circuit 92a and the control unit 100. The comparator circuit 92b compares the signal output from the rectifier circuit 92a with the reference voltage, and outputs a signal indicating that the signal exceeds the reference voltage to the control unit 100 when the signal output from the rectifier circuit 92a exceeds the reference voltage.

[0115] The monitoring circuit 92 utilizes the characteristic that the resistance, or impedance, of coil 85 changes due to abnormal heating to monitor the high-frequency voltage input to generator 33. When this high-frequency voltage exceeds a reference voltage, it infers that the temperature of coil 85 has risen and detects any abnormal heating related to generator 33. Specifically, since there are cases where the temperature of generator 33 rises due to heating of coil 85, abnormal heating of generator 33 can be detected if the temperature fluctuation of coil 85 can be monitored. In detail, coil 85 is made of copper. Copper's resistance changes significantly with temperature; a temperature rise of around 50°C can be detected even with a simple circuit.

[0116] In the monitoring circuit 92, a diode for rectification and a capacitor for smoothing are used in the rectifier circuit 92a, and a Zener diode is used in the comparator circuit 92b to generate a reference voltage. Furthermore, even when the frequency of the AC electric field generated by the generator 33 changes due to aging or other factors, the monitoring circuit 92 can detect abnormalities related to the generator 33 because the resistance of the generator 33, particularly the resistance of the coil 85, changes. The monitoring circuit 92 detects changes in the impedance of the generator 33, including the conductor 83, the first electrode 81, and the second electrode 82, and based on the detected changes, detects the temperature of at least one of the conductor 83, the first electrode 81, and the second electrode 82.

[0117] If the limiting conditions are met when printing begins, the control unit 100 will stop printing. If the limiting conditions are met when printing has begun or is in progress, the control unit 100 will stop printing. This prevents malfunctions of the AC electric field generating unit 30.

[0118] Furthermore, although this embodiment uses printing system 1 as an example, it is not limited thereto. For example, the printing device 10 can be replaced with other processing devices that apply liquid to the medium M. Even in such an manner, the same effects described above can be obtained.

[0119] Furthermore, even if it is not the printing system 1, but the drying device 20 alone, the same effect can be achieved. That is, malfunctions of the alternating current generating unit 30 can be avoided.

[0120] Next, other implementation methods will be described.

[0121] Although the AC electric field generating unit 30 in the drying apparatus 20 of the above embodiment is configured to generate an AC electric field of one frequency band, it is not limited to this. It may also be configured to selectively generate an AC electric field of any one of multiple frequency bands.

[0122] That is, the AC electric field generating unit 30 of the drying device 20 includes a first AC electric field generating unit that generates an AC electric field in a first frequency band and a second AC electric field generating unit that generates an AC electric field in a second frequency band. The control unit 100 drives the first AC electric field generating unit or the second AC electric field generating unit according to the detection result of the detection unit 40.

[0123] For example, a first AC electric field generating unit generates an AC electric field in a first frequency band of 915 MHz, and a second AC electric field generating unit generates an AC electric field in a second frequency band of 2.4 GHz. In this case, the first AC electric field generating unit includes a generator for a first system for generating the AC electric field in the first frequency band and a high-frequency voltage generating unit. The second AC electric field generating unit includes a generator for a second system for generating the AC electric field in the second frequency band and a high-frequency voltage generating unit. The generators for the first system and the second system are alternately arranged in an adjacent manner. As a result, deviations in the intensity of the AC electric field relative to the unit area of ​​the dielectric M can be suppressed.

[0124] When generating an AC electric field in the first frequency band, the control unit 100 controls the high-frequency voltage generating unit of the first system and causes the generator of the first system to generate an AC electric field in the first frequency band. When generating an AC electric field in the second frequency band, the control unit 100 controls the high-frequency voltage generating unit of the second system and causes the generator of the second system to generate an AC electric field in the second frequency band.

[0125] Therefore, the alternating current generating unit 30 can selectively generate any one of a variety of alternating current fields with different frequencies, thereby varying the heating depth of the liquid sprayed onto the medium M in the thickness direction according to its frequency. Thus, by changing the frequency and other parameters in accordance with the water content contained in the medium M, the liquid can be heated according to the state of the medium M, thereby effectively drying the medium M.

[0126] Symbol Explanation

[0127] 1…Printing system; 2…Holding device; 3…Rolling device; 10…Printing apparatus; 12…Printing section; 13…Control section; 20…Drying device; 21…Support section; 21a…Conveyor roller; 21b…Conveyor roller; 30…AC electric field generating section; 33…Generator; 34…Cover; 36…Electrical field detection sensor; 37…Casing; 40…Detection section; 41…Ultrasonic sensor; 41a…Transmitting section; 41b…Receiving section; 43…Capacitive sensor; 44…Capacitive sensor; 45…Optical sensor; 49…Support body; 51…Holding section; 52…Electrode pair; 54…Electrode; 71…Housing; 72…Light source; 73…Light receiving section; 74…Light shielding section; 75…Opening; 76…First… Light-emitting element; 77…Second light-emitting element; 78…Rotation shaft; 79…Through hole; 81…First electrode; 82…Second electrode; 83…Conductor; 84…Coaxial cable; 84A…Internal conductor; 84B…External conductor; 85…Coil; 88…Adjustment mechanism; 90…Air supply unit; 91…High-frequency voltage generating unit; 91a…High-frequency voltage generating circuit; 91b…Amplification circuit; 92…Monitoring circuit; 92a…Rectifier circuit; 92b…Comparison circuit; 94A…First channel; 94B…Second channel; 94C…First air supply fan; 94D…Second air supply fan; 100…Control unit; 101…CPU; 102…Memory; 103…Control circuit; 104…I / F; M…Medium.

Claims

1. A drying apparatus for drying a conveyed medium, comprising: A support portion that supports the medium being transported; The alternating current electric field generating unit generates an alternating current electric field. The detection unit detects the amount of water contained in the medium. Control Department The alternating electric field generating unit has: The first electrode and the second electrode are arranged opposite to the medium supported by the support portion and arranged adjacent to each other. A high-frequency voltage generating unit generates a high-frequency voltage toward the first electrode and the second electrode; A conductor that electrically connects the first electrode, the second electrode, and the high-frequency voltage generating unit. The detection unit is positioned upstream of the first electrode and the second electrode in the transport direction. The control unit controls the AC electric field generating unit in a manner that, based on the detection result of the detection unit, it drives the AC electric field generating unit when the water content in the medium reaches a threshold, and stops driving the AC electric field generating unit when the water content in the medium does not reach the threshold.

2. The drying apparatus as described in claim 1, wherein, The opposing surfaces of the first electrode and the second electrode, which are opposite to the dielectric, are covered by a shield that allows the alternating electric field to pass through.

3. The drying apparatus as described in claim 1 or claim 2, wherein, It has an air supply unit that supplies air to the first electrode and the second electrode.

4. The drying apparatus as claimed in claim 1, wherein, The detection unit includes: A capacitance sensor having an electrode pair and detecting the capacitance of the medium in contact with the electrode pair; An ultrasonic sensor has a transmitting part and a receiving part, the transmitting part transmitting ultrasonic waves, and the receiving part being configured to face the transmitting part through a medium and receive the ultrasonic waves transmitted by the transmitting part.

5. The drying apparatus as described in claim 4, wherein, The electrode pair comes into contact with a surface that is opposite to the surface of the medium that is opposite to the surfaces of the first electrode and the second electrode.

6. The drying apparatus as claimed in claim 1, wherein, The alternating electric field generating unit includes: The first AC electric field generating unit generates an AC electric field in the first frequency band; The second alternating current electric field generating unit generates an alternating current electric field in the second frequency band. The control unit drives either the first AC electric field generating unit or the second AC electric field generating unit based on the detection result of the detection unit.

7. A printing system comprising: The drying apparatus according to any one of claims 1 to 6; A printing apparatus that applies a liquid to a medium. The drying apparatus dries the medium that has been coated with the liquid by the printing apparatus.

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