Drying equipment, printing systems

Abstract

To protect an AC electric field generation section.SOLUTION: A drying apparatus dries a medium to be conveyed. The drying apparatus includes: a support section which supports the conveyed medium; an AC electric field generation section which generates AC electric field; a detection section which detects moisture contents contained in the medium; and a control section. The AC electric field section has a first electrode and a second electrode which are arranged to face the medium supported by the support section and are arranged to be adjacent to each other, a high frequency voltage generation section which generates high frequency voltage to the first electrode and the second electrode, and a conductor which electrically connects the first and second electrodes with the high frequency voltage generation section. The detection section is arranged on at least one of a conveyance direction downstream or upstream of each of the first electrode and the second electrode. The control section controls the AC electric field generation section according to the detection result of the detection section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drying device and a printing system. [Background technology]

[0002] 2. Description of the Related Art As disclosed in Patent Document 1, a drying device is known that includes a heating unit that irradiates electromagnetic waves onto a liquid discharged onto a medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-114001 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a device that irradiates electromagnetic waves to heat an object, such as the drying device described above, if heating is continued in an environment in which there is no moisture or the like contained in the object, there is a problem that the generating unit that generates the electromagnetic waves will break down. [Means for solving the problem]

[0005] The drying device is a drying device that dries a medium being transported, and includes a support section that supports the medium being transported, an AC electric field generating section that generates an AC electric field, a detection section that detects the amount of moisture contained in the medium, and a control section, wherein the AC electric field generating section is arranged opposite the medium supported on the support section and includes a first electrode and a second electrode that are arranged adjacent to each other, a high-frequency voltage generating section that generates a high-frequency voltage to the first electrode and the second electrode, and a conductor that electrically connects the first electrode and the second electrode to the high-frequency voltage generating section, and the detection section is arranged at least either downstream or upstream in the transport direction of the first electrode and the second electrode, and the control section controls the AC electric field generating section in accordance with the detection result of the detection section.

[0006] The printing system includes the drying device described above and a printing device that applies a liquid to a medium, and the drying device dries the medium on which the liquid has been applied by the printing device. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a printing system. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of an AC electric field generating unit. [Diagram 3] FIG. 2 is a schematic diagram showing the configuration of an AC electric field generating unit. [Figure 4] FIG. [Figure 5A] FIG. 2 is a schematic diagram showing the configuration of a detection unit (ultrasonic sensor). [Figure 5B] FIG. 13 is a schematic diagram showing the configuration of another detection unit (ultrasonic sensor). [Figure 6] FIG. 2 is a schematic diagram showing the configuration of a detection unit (capacitive sensor). [Figure 7] FIG. 2 is a schematic diagram showing the configuration of a detection unit (optical sensor). [Figure 8] FIG. 2 is a schematic diagram showing the configuration of a detection unit (optical sensor). [Figure 9] FIG. 4 is a block diagram showing the configuration of a control unit of the drying device. [Figure 10] FIG. 4 is a block diagram showing the configuration of a control unit of the drying device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] First, the configuration of the printing system 1 will be described. As shown in FIG. 1, the printing system 1 includes a holding device 2, a winding device 3, a printing device 10, and a drying device 20.

[0009] The holding device 2 is a device that holds a roll body 5 on which a sheet-like medium M is wound up. The holding device 2 has a holding shaft 7 that holds the roll body 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 body 5. The medium M is, for example, a sheet of paper, fabric, or the like.

[0010] The winding device 3 is a device that winds up the medium M unwound from the holding device 2. The winding device 3 has a winding shaft 8 that winds up the medium M. The winding shaft 8 is configured to be driven to rotate. The winding shaft 8 winds up the medium M by being driven to rotate. As a result, the winding shaft 8 holds a roll body 9 that is formed by winding up the medium M. In this embodiment, the winding shaft 8 is driven to rotate, causing the medium M to be unwound from the roll body 5 held by the holding shaft 7.

[0011] The medium M is transported by being wound around the winding device 3. The medium M is transported from the holding device 2 toward the winding device 3 via the printing device 10 and the drying device 20. The transport direction of the medium M is the direction from the holding device 2 toward the winding device 3 (the direction following the +Y direction). The medium M has a front side MA and a back side MB, which is the surface opposite to the front side MA.

[0012] The printing device 10 is a device that applies liquid (e.g., ink) to a medium M to print on the medium M. The printing device 10 is, for example, an inkjet printer that records (prints) images such as characters, photographs, and figures by ejecting ink onto the medium M.

[0013] The printing device 10 is located between the holding device 2 and the winding device 3 in the transport direction. The printing device 10 is disposed upstream in the transport direction of the drying device 20. That is, the medium M fed from the holding device 2 passes through the printing device 10 and then the drying device 20.

[0014] The printing apparatus 10 includes a platen 11, a printing unit 12, and a control unit 13.

[0015] The platen 11 is a plate-shaped member. The platen 11 supports the medium M being transported. The platen 11 supports the medium M from below. The platen 11 comes into contact with the rear surface MB of the medium M.

[0016] The printing unit 12 faces the platen 11. The printing unit 12 is located above the platen 11. The printing unit 12 includes a head 15 and a carriage 16.

[0017] The head 15 faces the platen 11. The head 15 is located above the platen 11. The head 15 ejects liquid toward the surface MA of the medium M supported by the platen 11. As a result, an image is printed on the medium M. The liquid ejected by the head 15 is, for example, a water-based ink that uses water as a solvent.

[0018] When the head 15 ejects liquid onto the medium M, the amount of moisture contained in the medium M increases. That is, the head 15 ejects liquid onto the medium M, thereby subjecting the medium M to a process that increases the amount of moisture contained in the medium M.

[0019] The carriage 16 carries the head 15. The carriage 16 faces the platen 11. The carriage 16 is located above the platen 11. The carriage 16 moves back and forth in a direction along the X-axis relative to the medium M being transported. In other words, the carriage 16 moves back and forth above the platen 11 across the width direction of the medium M.

[0020] The printing device 10 is a serial printer in which the head 15 moves back and forth relative to the medium M. Note that the printing device 10 may also be a line-type printer in which the head 15 ejects liquid across the width of the medium M all at once.

[0021] The control unit 13 controls each driving unit of the printing device 10. The control unit 13 includes a CPU, a memory, a control circuit, and an I / F (interface). The CPU is an arithmetic processing device. The memory is a storage device that secures an area for storing programs for the CPU or a working area, and has memory elements such as RAM and EEPROM. When recording data, etc. is acquired from an external device such as an information processing terminal via the I / F, the CPU controls driving units such as the printing unit 12 via the control circuit.

[0022] 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, and transmits signals to the holding device 2, the winding device 3, and the drying device 20 (control unit 100) as necessary.

[0023] In the printing device 10, a pretreatment section that applies a pretreatment liquid to the surface MA of the medium M may be disposed upstream of the printing unit 12 in the transport direction. Pretreatment of the medium M before printing in the pretreatment section improves the permeability of the liquid ejected onto the medium M during printing, and improves the print quality, such as the color development of the image printed on the medium M, and the durability of the medium M.

[0024] Next, the configuration of the drying device 20 will be described. The drying device 20 is a device that dries the transported medium M. The drying device 20 is disposed downstream of the printing device 10 in the transport direction, and dries the medium M on which liquid has been applied by the printing device 10. As shown in FIG. 1, the drying device 20 includes a support section 21, an AC electric field generating section 30, a detection section 40, and a control section 100.

[0025] The support unit 21 supports the medium M to be transported. In this embodiment, it includes a pair of transport rollers 21a, 21b. Each of the transport rollers 21a, 21b extends in a direction along the X-axis. One of the transport rollers 21a is disposed upstream in the transport direction relative to the other transport roller 21b. Each of the transport rollers 21a, 21b supports the back surface MB of the medium M. Each of the transport rollers 21a, 21b is a driven roller, and rotates in response to the winding operation of the medium M by the winding device 3.

[0026] The AC electric field generating unit 30 dries the medium M. Specifically, the AC electric field generating unit 30 generates an AC electric field to heat the moisture contained in the medium M and perform a process to reduce the amount of moisture contained in the medium M. In other words, the AC electric field generating unit 30 heats the liquid applied to the medium M supported by the support unit 21, and dries the medium M. The AC electric field generating unit 30 is disposed between the transport roller 21a and the transport roller 21b in the transport direction.

[0027] The AC electric field generating unit 30 heats the liquid by generating an AC electric field of 2.4 GHz. Note that, for example, Joule heat due to eddy currents generated in the liquid applied to the medium M by generating an AC electric field of 3 MHz to 300 MHz, or dielectric heating due to friction caused by molecular vibrations by generating an AC electric field of 300 MHz to 30 GHz may be used, and among these, it is preferable to generate an AC electric field of 10 MHz to 20 GHz.

[0028] 2, the AC electric field generating unit 30 has a plurality of generators 33 that generate an AC electric field. The plurality of generators 33 are arranged extending in a 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 rows in the direction along the X-axis. In order to prevent the AC electric field generated by the multiple generators 33 from affecting the outside, the multiple generators 33 are disposed in a housing 37. The housing 37 is a box-shaped body with an open bottom. The multiple generators 33 are disposed facing the opening of the housing 37 so as to face the surface MA of the medium M supported by the support portion 21. The distance in the direction along the Z axis between the -Z direction end of the housing 37 and the medium M is preferably about 1 mm to 20 mm. This makes it possible to prevent the user's fingers from entering between the housing 37 and the medium M.

[0029] The housing 37 is also equipped with an electric field detection sensor 36. In this embodiment, the electric field detection sensor 36 is configured to include a pair of electric field detection antennas that detect an AC electric field. The electric field detection sensor 36 faces the medium M in a direction along the Z axis. The electric field detection sensor 36 is disposed at an end of the housing 37. In detail, 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 the one electric field detection antenna is disposed. In this way, the electric field detection sensor 36 is disposed such that the electric field detection antenna is located at a position separated from the generator 33, and can detect a change in the AC electric field generated by the AC electric field generating unit 30.

[0030] As shown in FIG. 3, the generator 33 has a first electrode 81, a second electrode 82, and a conductor 83. The first electrode 81 is a rectangular flat plate in a plan view. The first electrode 81 faces the medium M supported by the support portion 21. The first electrode 81 is disposed above the medium M. The second electrode 82 is a hollowed-out rectangular flat plate surrounding the first electrode 81 in a plan view. The second electrode 82 faces the medium M supported by the support portion 21. The second electrode 82 is disposed above the medium M. The first electrode 81 and the second electrode 82 are disposed adjacent to each other.

[0031] The conductor 83 electrically connects the first electrode 81 and the second electrode 82 to a high-frequency voltage generating unit 91 that generates a high-frequency voltage. The 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 to 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 to the second electrode 82. The coil 85, which is an example of a winding, is connected between the first electrode 81 and the inner conductor 84A of the coaxial cable 84, and is preferably disposed as close as possible to the first electrode 81.

[0032] The minimum distance between the first electrode 81 and the second electrode 82 is 1 / 10 or less of the wavelength of the AC electric field output from the AC electric field generating unit 30. The first electrode 81 and the second electrode 82 are symmetrical with respect to the center of the first electrode 81. As a result, the electric field generated between the first electrode 81 and the second electrode 82 cancels out the electric field generated at the point-symmetric position, so that most of the AC electric field generated when the high frequency voltage is applied can be attenuated in the vicinity of the first electrode 81 and the second electrode 82. As a result, the intensity of the electromagnetic wave reaching a distant location from the first electrode 81 and the second electrode 82 can be reduced. That is, the AC electric field generated from the AC electric field generating unit 30 is very strong in the vicinity of the first electrode 81 and the second electrode 82 and very weak in the distant location.

[0033] By appropriately controlling the frequency band of the AC electric field generated by such a generator 33, the AC electric field can be generated in a concentrated manner in an area near the first electrode 81 and the second electrode 82, for example, in an area of ​​3 mm to 3 cm, making it difficult for the AC electric field to have an effect beyond that area. Furthermore, in the generator 33, an AC electric field can be concentrated in the vicinity of the first electrode 81 and the second electrode 82, improving the efficiency of heating the liquid discharged onto the medium M supported by the support portion 21 and improving the drying efficiency of the medium M. On the other hand, it is possible to make it difficult for an AC electric field to be generated in a position separated from the first electrode 81 and the second electrode 82, eliminating the need to excessively dispose members for suppressing the AC electric field, and improving the workability of the drying device 20. Also, it is possible to prevent the drying device 20 from becoming large.

[0034] 1, the surfaces of the first electrode 81 and the second electrode 82 in the generator 33 that face the medium M are covered with a cover 34. The cover 34 is disposed below the generator 33. Since the generator 33 is covered with the cover 34, adhesion of foreign matter to the first electrode 81 and the second electrode 82 is suppressed.

[0035] The cover 34 is made of a material that transmits the AC electric field generated by the AC electric field generating unit 30. Specifically, the cover 34 is made of glass. However, the cover 34 is not limited to this, and may be made of a resin having transparency, such as a cyclic olefin copolymer, and a material that is not easily affected by dielectric heating is preferable. The surface of the cover 34 on the -Z direction side is uneven, and the AC electric field generated by the AC electric field generating unit 30 can be converged toward the medium M supported by the support unit 21.

[0036] The drying device 20 also includes an adjustment mechanism 88 (FIG. 4) that can move the generator 33 and the cover 34 in the direction along the Z axis. This makes it possible to adjust the distance between the generator 33 and the medium M. The adjustment mechanism 88 may be, for example, a link mechanism or a rack-and-pinion mechanism. This makes it possible to easily adjust the distance between the generator 33 and the medium M depending on the type of medium M, the type of liquid ejected from the head 15, etc.

[0037] 4, the drying device 20 includes an air blower 90 that blows air to the generator 33 (the first electrode 81 and the second electrode 82). The air blower 90 is mounted on the housing 37. The air blower 90 has a first passage 94A, a second passage 94B, a first blower fan 94C, and a second blower fan 94D.

[0038] The first passage 94A is a passage that extends in the direction along the Z axis so as to be adjacent to the generator 33 between the generator 33 and the outer edge of the housing 37. The second passage 94B is a passage that extends in the direction along the Z axis so as to be adjacent to the generator 33 on the -Y direction side of the generator 33.

[0039] The first blower fan 94C is disposed at the upper end of the first passage 94A. The first blower fan 94C is a fan that blows air from the outside of the housing 37 to the first passage 94A. The second blower fan 94D is disposed at the upper end of the second passage 94B of the housing 37. The second blower fan 94D is a fan that blows air from the second passage 94B to the outside of the housing 37.

[0040] By driving the first blower fan 94C, air is taken in from outside the housing 37 and sent to the first passage 94A, and by driving the second blower fan 94D, air is sent from the second passage 94B to the outside of the housing 37. As a result, the gas flows from the first passage 94A, passes under the cover 34, and passes through the second passage 94B. In this way, the blower 90 sends air to the generator 33 including 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. Furthermore, the gas sent to the first blower fan 94C is heated by the generator 33. The heated gas is blown onto the medium M supported by the support portion 21. As a result, the liquid applied to the medium M is heated, and the drying of the medium M can be promoted.

[0041] The detection unit 40 detects the amount of moisture contained in the medium M. The detection unit 40 of this embodiment detects the amount of moisture contained in the ink of the medium M that has passed through the printing device 10. The detection unit 40 is disposed at least either downstream or upstream of the first electrode 81 and the second electrode 82 in the transport direction.

[0042] 1, the detection unit 40 of this embodiment includes an ultrasonic sensor 41 and capacitance sensors 43 and 44. Although this embodiment includes one ultrasonic sensor 41, two or more may be included. Also, although two capacitance sensors 43 and 44 are included, three or more may be included, or only one may be included. In addition, the detection unit 40 of this embodiment further includes an optical sensor 45.

[0043] The ultrasonic sensor 41 is disposed upstream of the generator 33 (the first electrode 81 and the second electrode 82) in the conveying direction. 5A, the ultrasonic sensor 41 has a transmitter 41a and a receiver 41b. The transmitter 41a and the receiver 41b are disposed so as to sandwich the medium M being transported therebetween. The transmitter 41a and the receiver 41b are disposed so as to sandwich the medium M being transported from above and below. In other words, the medium M is transported by passing between the transmitter 41a and the receiver 41b.

[0044] The transmitter 41a is disposed above the receiver 41b (in the +Z direction). The transmitter 41a transmits ultrasonic waves toward the receiver 41b. That is, the transmitter 41a transmits ultrasonic waves downward (in the -Z direction). Therefore, when the medium M is located between the transmitter 41a and the receiver 41b, the ultrasonic waves transmitted from the transmitter 41a are irradiated onto the medium M. At this time, the ultrasonic waves transmitted from the transmitter 41a are irradiated onto the medium M before drying. When the medium M is not located between the transmitter 41a and the receiver 41b, the ultrasonic waves transmitted from the transmitter 41a are directly irradiated onto the receiver 41b.

[0045] 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 transmitted through the medium M. At this time, the receiving unit 41b receives the ultrasonic waves transmitted 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.

[0046] The ultrasonic waves transmitted from the transmitting unit 41a are attenuated by passing 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. Note that the degree of attenuation of the ultrasonic waves passing through the medium M varies depending on the density, thickness, etc. of the medium M.

[0047] The transmittance of the ultrasonic wave through 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 through the medium M is the ratio of the ultrasonic wave transmitted by the transmitting unit 41a to the ultrasonic wave transmitted by the medium M.

[0048] There is a correlation between the transmittance of ultrasonic waves through the medium M and the basis weight of the medium M. For example, the greater the transmittance of ultrasonic waves through the medium M, the smaller the basis weight of the medium M. The smaller the transmittance of ultrasonic waves through the medium M, the larger the basis weight of the medium M. In this manner, the basis weight of the medium M is detected based on the transmittance of ultrasonic waves through the medium M. Therefore, the ultrasonic sensor 41 is a sensor that detects the basis weight of the medium M. The control unit 100 calculates the basis weight of the medium M based on the signal transmitted from the ultrasonic sensor 41.

[0049] It should be noted that a configuration for calculating the thickness of the medium M based on the signal transmitted from the ultrasonic sensor 41 may be added. Specifically, as shown in FIG. 5B, the transmitter 41a and the receiver 41b are disposed above the medium M. The transmitter 41a transmits ultrasonic waves toward the medium M, and the receiver 41b receives the ultrasonic waves reflected by the medium M. A support 49 having a support surface for supporting the medium M is provided on the back surface MB side of the medium M where the ultrasonic waves transmitted from the transmitter 41a are reflected. As a result, the ultrasonic waves transmitted from the transmitter 41a are reflected by the front surface MA and the support surface of the medium M, and the receiver 41b receives the ultrasonic waves reflected by the front surface MA and the support surface of the medium M. Then, the difference between the time from when the transmitter 41a transmits ultrasonic waves to when it receives the ultrasonic waves reflected by the front surface MA of the medium M, and the time from when the transmitter 41a transmits ultrasonic waves to when it receives the ultrasonic waves reflected by the support surface, is detected. The thickness of the medium M can be detected by converting the time difference into a distance.

[0050] As shown in FIG. 1, the capacitance sensor 43 is arranged upstream of the generator 33 (first electrode 81 and second electrode 82) in the transport direction, and the capacitance sensor 44 is arranged downstream of the generator 33 (first electrode 81 and second electrode 82) in the transport direction.

[0051] 6, the capacitance sensor 43 is disposed below the medium M. The capacitance sensor 43 contacts the medium M from below. The capacitance sensor 43 detects the capacitance of the medium M by contacting the medium M. The capacitance sensor 43 detects the capacitance of the medium M before it is dried by the AC electric field generation unit 30.

[0052] The capacitance sensor 43 has a holder 51 and an electrode pair 52. The holder 51 holds the electrode pair 52. The holder 51 has a shape of, for example, a rectangular parallelepiped or a rectangular parallelepiped shape.

[0053] The electrode pair 52 protrudes in the +Z direction from the upper surface of the holding portion 51. The electrode pair 52 comes into contact with the medium M being transported. In this embodiment, the electrode pair 52 comes into contact with the back surface MB of the medium M. This reduces the risk of damaging the front surface MA to be printed, compared to when the electrode pair 52 comes into contact with the front surface MA of the medium M.

[0054] The electrode pair 52 constitutes a part of an oscillator circuit of the capacitance sensor 43. The electrode pair 52 is composed of two electrodes 54. An 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 come into contact with the medium M, an AC voltage flows through the medium M. As a result, the capacitance sensor 43 detects the capacitance of the medium M with which the electrode pair 52 comes into contact.

[0055] The electrode pair 52 comes into contact with the medium M after the liquid has been ejected by the head 15. Therefore, the capacitance sensor 43 detects the capacitance of the medium M that contains moisture.

[0056] When an AC voltage flows from the two electrodes 54 to the medium M, the capacitance between the two electrodes 54 changes. At this time, the change in capacitance between the two electrodes 54 is greatly affected by the amount of moisture contained in the medium M with which the two electrodes 54 come into contact. This is because the relative dielectric constant of water is large compared to the medium M in which paper, cloth, and the like are used. Therefore, for example, if the amount of moisture contained in the medium M is large, the change in capacitance between the two electrodes 54 becomes large. If the amount of moisture contained in the medium M is small, the change in capacitance between the two electrodes 54 becomes small. In this way, there is a correlation between the change in capacitance between the two electrodes 54 and the amount of moisture contained in the medium M.

[0057] The change in capacitance between the two electrodes 54 is affected by the basis weight of the medium M with which the two electrodes 54 contact. For example, if the basis weight of the medium M is large, the change in capacitance between the two electrodes 54 is large. If the basis weight of the medium M is small, the change in capacitance between the two electrodes 54 is small.

[0058] The position of the holding unit 51 can be adjusted in the directions along the X-axis and Z-axis by a screw or the like. This allows the position of the electrode pair 52 to be adjusted so that the electrode pair 52 reliably contacts the medium M. This allows the capacitance to be detected with high accuracy.

[0059] The other capacitance sensor 44 is disposed below the medium M. The capacitance sensor 44 contacts the medium M from below. The capacitance sensor 44 detects the capacitance of the medium M by contacting the medium M. Note that the configuration of the capacitance sensor 44 is the same as that of the capacitance sensor 43, and therefore a description thereof will be omitted. The capacitance sensor 44 detects the capacitance of the medium M after it has been dried by the AC electric field generation unit 30.

[0060] From the above, the amount of moisture contained in the medium M is accurately detected based on the ultrasonic sensor 41 and the capacitance sensors 43 and 44. Based on the signal transmitted from the ultrasonic sensor 41 and the signal transmitted from the capacitance sensor 43, the control unit 100 may calculate the amount of moisture contained in the medium M.

[0061] The optical sensor 45 detects the amount of moisture contained in the medium M. In particular, the optical sensor 45 detects the amount of moisture on the surface MA. The optical sensor 45 is disposed upstream of the generator 33 in the transport direction. The optical sensor 45 faces the transported medium M. The optical sensor 45 is disposed above the medium M.

[0062] 7 and 8, the optical sensor 45 has a case 71, a light source 72, and a light receiving section 73. The optical sensor 45 also has a light blocking section 74. The optical sensor 45 is a reflective optical sensor.

[0063] Case 71 houses light source 72, light receiving unit 73, and light blocking unit 74. Case 71 is shaped, for example, like a rectangular parallelepiped. Case 71 has an opening 75. Opening 75 is provided on the surface of case 71 that faces medium M. In other words, opening 75 is provided in the lower part of case 71. The inside of case 71 communicates with the outside of case 71 via opening 75.

[0064] The light source 72 emits light. The light source 72 emits light whose peak wavelength is the absorption wavelength of water. The light source 72 is configured to emit light whose peak wavelength is included in the range of 900 nm to 2100 nm, for example. The light source 72 of this embodiment emits near-infrared light.

[0065] The light source 72 irradiates light downward. Therefore, the light source 72 irradiates light onto the medium M. The light source 72 irradiates light onto the medium M after the liquid has been applied by the head 15. At this time, the light source 72 irradiates light onto the surface MA of the medium M.

[0066] The light source 72 has one or more light-emitting elements that emit light. The light source 72 has a plurality of light-emitting elements. Specifically, the light source 72 has a plurality of light-emitting elements with different peak wavelengths. The light-emitting elements are, for example, LEDs. The light source 72 has, for example, a first light-emitting element 76 and a second light-emitting element 77. The light source 72 may have three or more light-emitting elements.

[0067] 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. The first light-emitting element 76 and the second light-emitting element 77 may be light-emitting elements that emit light whose peak wavelength is the absorption wavelength of water. For example, the peak wavelength may be 1800 nm, 1940 nm, or 2100 nm.

[0068] The light receiving unit 73 receives light emitted by the light source 72. The light receiving unit 73 includes, for example, a light receiving element. The light receiving element is, for example, a photodiode. The light receiving unit 73 receives light traveling from the light source 72 through the detection light path L1, or light traveling from the light source 72 through the reference light path L2. That is, the light emitted by the light source 72 is incident on the light receiving unit 73 by traveling through the detection light path L1 or the reference light path L2.

[0069] The detection light path L1 is an optical path along which light emitted by the light source 72 is reflected by the medium M and enters the light receiving unit 73. The detection light path L1 is an optical path indicated by a solid line in Fig. 7 and by a two-dot chain line in Fig. 8. The detection light path L1 extends between the inside and the outside of the case 71 through the opening 75. The detection light path L1 extends from the light source 72 to the medium M, and then extends from the medium M to the light receiving unit 73.

[0070] Light traveling along the detection optical path L1 first hits the medium M by passing through the opening 75 from the light source 72. At this time, the light traveling along the detection optical path L1 hits the surface MA of the medium M. The light that hits the surface MA of the medium M is reflected by the surface MA of the medium M. The light reflected by the surface MA of the medium M is incident on the light receiving unit 73 by passing through the opening 75. In this way, the light emitted by the light source 72 travels along the detection optical path L1. As a result, the light receiving unit 73 receives the light reflected by the medium M.

[0071] The reference optical path L2 is an optical path along which light emitted by the light source 72 enters the light receiving unit 73 without being reflected by the medium M supported by the platen 11. The reference optical path L2 is an optical path indicated by a two-dot chain line in FIG. 7 and a solid line in FIG. 8. The reference optical path L2 extends inside the case 71. The reference optical path L2 extends straight from the light source 72 to the light receiving unit 73 inside the case 71. Therefore, the light traveling along the reference optical path L2 enters the light receiving unit 73 directly from the light source 72. As a result, the light receiving unit 73 directly receives the light emitted by the light source 72.

[0072] The light shielding portion 74 is configured to shield the light emitted by the light source 72. The light shielding portion 74 has a shape of, for example, a flat plate or a flat plate-like shape. The light shielding portion 74 is located between the light source 72 and the light receiving portion 73 inside the case 71. The light shielding portion 74 is located, for example, so as to straddle the detection light path L1 and the reference light path L2. The light shielding portion 74 blocks the detection light path L1 or the reference light path L2. The light shielding portion 74 blocks the light emitted by the light source 72 by blocking the detection light path L1 or the reference light path L2.

[0073] The light blocking portion 74 is configured to be switched between a first state S1 and a second state S2. The light blocking portion 74 shown in Fig. 7 is in the first state S1. The light blocking portion 74 shown in Fig. 8 is in the second state S2.

[0074] The light shielding portion 74 is switched between a first state S1 and a second state S2, for example, by being displaced. The light shielding portion 74 is configured to rotate about a rotation axis 78 that is a virtual axis. The light shielding portion 74 is switched between the first state S1 and the second state S2 by rotating about the rotation axis 78. The light shielding portion 74 is supported by the case 71 in a state in which it is rotatable about the rotation axis 78, for example.

[0075] The light shielding portion 74 has a through hole 79. When the light shielding portion 74 is in the first state S1, the through hole 79 is located on the detection light path L1. Therefore, when the light shielding portion 74 is in the first state S1, the light traveling from the light source 72 along the detection light path L1 passes through the through hole 79 and enters the light receiving portion 73. That is, when the light shielding portion 74 is in the first state S1, the light emitted by the light source 72 is permitted to travel along the detection light path L1. Also, when the light shielding portion 74 is in the first state S1, the through hole 79 is not located on the reference light path L2. That is, when the light shielding portion 74 is in the first state S1, the light shielding portion 74 does not permit the light emitted by the light source 72 to travel along the reference light path L2. Thus, the first state S1 of the light shielding portion 74 is a state in which the light shielding portion 74 does not block the detection light path L1 and the light shielding portion 74 blocks the reference light path L2.

[0076] When the light shielding portion 74 is in the second state S2, the through hole 79 is located on the reference light path L2. Therefore, when the light shielding portion 74 is in the second state S2, the light traveling from the light source 72 through the reference light path L2 is incident on the light receiving portion 73 by passing through the through hole 79. That is, when the light shielding portion 74 is in the second state S2, the light emitted by the light source 72 is allowed to travel through the reference light path L2. Also, when the light shielding portion 74 is in the second state S2, the through hole 79 is not located on the detection light path L1. That is, when the light shielding portion 74 is in the second state S2, the light shielding portion 74 does not allow the light emitted by the light source 72 to travel through the detection light path L1. Thus, the second state S2 of the light shielding portion 74 is a state in which the light shielding portion 74 blocks the detection light path L1 and does not block the reference light path L2.

[0077] The light blocking unit 74 switches between a first state S1 and a second state S2 to determine the optical path along which the light emitted by the light source 72 travels. The control unit 100 switches the light blocking unit 74 between the first state S1 and the second state S2.

[0078] When light from the light source 72 is irradiated onto the medium M, that is, when the light traveling along the detection light path L1 hits 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, if the medium M contains a large amount of moisture, more light will be absorbed by the medium M. Conversely, if the medium M contains a small amount of moisture, less light will be absorbed by the medium M.

[0079] The light receiving unit 73 receives the light traveling along the detection light path L1, thereby detecting the intensity of the light reflected by the medium M. The light receiving unit 73 receives the light traveling along the reference light path L2, thereby detecting the intensity of the light irradiated onto the medium M by the light source 72. The reflectance of the light with respect to the medium M is detected based on the intensity of the light traveling along the detection light path L1 and the intensity of the light traveling along the reference light path L2. Here, the reflectance of the light with respect to the medium M is the ratio of the light reflected by the medium M to the light irradiated onto the medium M.

[0080] There is a correlation between the light reflectance of the medium M and the amount of moisture contained in the medium M. For example, the higher the light reflectance of the medium M, the lower the amount of moisture contained in the medium M. The lower the light reflectance of the medium M, the higher the amount of moisture contained in the medium M. In this way, the amount of moisture contained in the medium M is detected based on the light reflectance of the medium M. Therefore, the optical sensor 45 is a sensor that detects the amount of moisture contained in the medium M after printing. The optical sensor 45 can particularly accurately detect the amount of moisture on the surface MA. The control unit 100 may calculate the amount of moisture contained in the medium M based on the signal transmitted from the optical sensor 45.

[0081] The optical sensor 45 mainly detects the amount of moisture contained in the front surface MA of the medium M, while the capacitance sensors 43, 44 mainly detect the amount of moisture contained in the back surface MB of the medium M and inside the medium M. Therefore, the optical sensor 45 and the capacitance sensors 43, 44 accurately detect the amount of moisture contained in the medium M.

[0082] When the head 15 ejects liquid onto the medium M, there are cases where most of the liquid remains on the surface MA of the medium M. In this case, by referring to the detection results of the capacitance sensor 43, it can be seen that the increase in the amount of moisture contained in the medium M is small compared to the amount of liquid ejected by the head 15. On the other hand, by referring to the detection results of the capacitance sensor 43 and the detection results of the optical sensor 45, it can be seen that the increase in the amount of moisture contained in the medium M is large compared to the amount of liquid ejected by the head 15, because liquid remains on the surface MA of the medium M. From the above, it can be seen that the medium M has the characteristic of being difficult to absorb liquid. In this way, the characteristics of the medium M can be seen based on the detection results of the capacitance sensor 43 and the detection results of the optical sensor 45. The optical sensor 45 may be disposed downstream in the transport direction from the generator 33. In this manner, the amount of moisture on the surface MA of the medium M after drying can be detected.

[0083] Next, the configuration of the control unit 100 of the drying device 20 will be described. As shown in FIG. 9, the control unit 100 controls each driving unit of the drying device 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 device. The memory 102 is a storage device that secures an area for storing a program of the CPU 101 or a working area, and has storage elements such as a RAM and an EEPROM. When the CPU 101 acquires drying treatment data or the like from an external device such as an information processing terminal via the I / F 104, the CPU 101 controls the AC electric field generating unit 30, the blower 90, the adjustment mechanism 88, the detection unit 40 (ultrasonic sensor 41, electrostatic capacitance sensors 43 and 44, and optical sensor 45), and the electric field detection sensor 36 via the control circuit 103. The control unit 100 can also control the holding device 2 and the winding device 3 in cooperation with the control unit 13.

[0084] The control unit 100 controls the AC electric field generating unit 30 in accordance with the detection result of the detection unit 40. For example, when the amount of moisture contained in the medium M reaches a threshold based on the detection data detected by the detection unit 40, the control unit 100 drives the AC electric field generating unit 30. On the other hand, when the amount of moisture contained in the medium M does not reach the threshold, that is, when the amount of moisture contained in the medium M is small, the control unit 100 stops driving the AC electric field generating unit 30. As a result, the medium M, which has a low moisture content and is dry, is not heated, and therefore a breakdown in the AC electric field generating unit 30 can be avoided.

[0085] Furthermore, the control unit 100 regulates the driving of the AC electric field generating unit 30 based on a signal from the electric field detection sensor .

[0086] As shown in FIG. 10, the AC electric field generating unit 30 has a monitoring circuit 92 in addition to the generator 33 and a high-frequency voltage generating unit 91.

[0087] The high frequency voltage generating unit 91 is connected to the generator 33. More 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 generates an AC electric field from the first electrode 81 and the second electrode 82 by outputting the high frequency voltage to the first electrode 81 and the second electrode 82.

[0088] The high frequency voltage generating unit 91 has 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 is a circuit that generates a high frequency voltage based on a generation instruction signal from the control unit 100 and outputs the high frequency voltage to the amplifier circuit 91b. The amplifier circuit 91b is a circuit that 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 the high frequency voltage to the generator 33. The high frequency voltage generating unit 91 supplies, for example, power of 3 kW or less to the generator 33.

[0089] 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 result of monitoring the high frequency voltage to the control unit 100.

[0090] 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 rectifies and smoothes the high frequency voltage from the high frequency voltage generator 91 to convert it into direct current and outputs it to the comparator circuit 92b.

[0091] 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 a reference voltage, and when the signal output from the rectifier circuit 92a exceeds the reference voltage, outputs a signal indicating that the signal has exceeded the reference voltage to the control unit 100.

[0092] Using the characteristic that abnormal heating of the coil 85 changes the electrical resistance, i.e., impedance, of the coil 85, the monitoring circuit 92 monitors the high frequency voltage input to the generator 33, and when the high frequency voltage exceeds a reference voltage, it estimates that the temperature of the coil 85 has risen, detecting the occurrence of abnormal heating in the generator 33. In particular, the temperature of the generator 33 may rise due to heat generation by the coil 85, and if the temperature fluctuation of the coil 85 can be grasped, it is possible to detect abnormal heating of the generator 33. More specifically, the coil 85 is made of copper. The electrical resistance of copper changes significantly in response to temperature changes, and a temperature rise of about 50°C can be detected even with a simple circuit.

[0093] In the monitoring circuit 92, the rectifier circuit 92a uses a diode for rectification and a capacitor for smoothing, and the comparator circuit 92b uses a Zener diode for generating a reference voltage. Even if the frequency of the AC electric field generated by the generator 33 changes due to aging or the like, the monitoring circuit 92 can detect the occurrence of an abnormality in the generator 33 because the electrical resistance of the generator 33, particularly the electrical resistance of the coil 85, changes. The monitoring circuit 92 detects a change in the impedance of the generator 33 including the conductor 83, the first electrode 81, and the second electrode 82, and detects the temperature of at least one of the conductor 83, the first electrode 81, and the second electrode 82 based on the detected change.

[0094] If the restrictive conditions are met when printing is to be started, the control unit 100 halts the start of printing. If the restrictive conditions are met when printing is started and is in progress, the control unit 100 halts printing. This makes it possible to avoid a breakdown in the AC electric field generating unit 30.

[0095] In the present embodiment, the printing system 1 has been described as an example, but the present invention is not limited to this. For example, the printing device 10 may be replaced with another processing device that applies liquid to the medium M. In this case, the same effect as described above can be obtained. Moreover, the same effect as above can be obtained even with the drying device 20 alone, instead of the printing system 1. That is, the breakdown of the AC electric field generating unit 30 can be avoided.

[0096] Next, another embodiment will be described. The AC electric field generating unit 30 in the drying device 20 of the above embodiment is configured to generate an AC electric field of one type of frequency band, but is not limited to this. It may be configured to be capable of selectively generating an AC electric field of any one of a plurality of types of frequency bands of AC electric fields. 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 of a first frequency band and a second AC electric field generating unit that generates an AC electric field of a second frequency band, and the control unit 100 drives the first AC electric field generating unit or the second AC electric field generating unit depending on the detection result of the detection unit 40.

[0097] For example, the first AC electric field generating unit generates an AC electric field in a first frequency band of 915 MHz, and the 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 first system of generators and a high-frequency voltage generating unit for generating an AC electric field in the first frequency band. The second AC electric field generating unit includes a second system of generators and a high-frequency voltage generating unit for generating an AC electric field in the second frequency band. The generators of the first system and the generators of the second system are alternately arranged so as to be adjacent to each other. This makes it possible to suppress variation in the intensity of the AC electric field per unit area of ​​the medium M.

[0098] When generating an AC electric field of a first frequency band, the control unit 100 controls the high frequency voltage generating unit of the first system to generate an AC electric field of the first frequency band from the generator of the first system. When generating an AC electric field of a second frequency band, the control unit 100 controls the high frequency voltage generating unit of the second system to generate an AC electric field of the second frequency band from the generator of the second system.

[0099] Therefore, the AC electric field generating unit 30 can selectively generate one of a plurality of types of AC electric fields with different frequencies, and depending on the frequency, change the heating depth in the thickness direction of the liquid ejected onto the medium M. This allows the medium M to be efficiently dried by heating the liquid depending on the state of the medium M, such as by changing the frequency depending on the amount of moisture contained in the medium M. [Explanation of symbols]

[0100] 1...printing system, 2...holding device, 3...winding device, 10...printing device, 12...printing unit, 13...control unit, 20...drying device, 21...support unit, 21a...transport roller, 21b...transport roller, 30...AC electric field generating unit, 33...generator, 34...cover, 36...electric field detection sensor, 37...housing, 40...detection unit, 41...ultrasonic sensor, 41a...transmitter, 41b...receiver, 43...capacitive sensor, 44...capacitive sensor, 45...optical sensor, 49...support, 51...holding unit, 52...electrode pair, 54...electrode, 71...case, 72...light source, 73...light receiver, 74...light shielding unit, 75...opening, 7 6...first light-emitting element, 77...second light-emitting element, 78...rotating shaft, 79...through hole, 81...first electrode, 82...second electrode, 83...conductor, 84...coaxial cable, 84A...inner conductor, 84B...outer conductor, 85...coil, 88...adjusting mechanism, 90...blower section, 91...high-frequency voltage generating section, 91a...high-frequency voltage generating circuit, 91b...amplifier circuit, 92...monitoring circuit, 92a...rectifier circuit, 92b...comparison circuit, 94A...first passage, 94B...second passage, 94C...first blower fan, 94D...second blower fan, 100...control section, 101...CPU, 102...memory, 103...control circuit, 104...I / F, M...medium.

Claims

1. A drying device for drying a medium being conveyed, comprising: A support portion that supports the medium to be transported; An AC electric field generating unit that generates an AC electric field; A detection unit that detects the amount of moisture contained in the medium; A control unit, The AC electric field generating unit is A first electrode is disposed opposite to and adjacent to the medium supported by the support portion. a first electrode and a second electrode; a high frequency voltage generating unit that generates a high frequency voltage to the first electrode and the second electrode; a conductor electrically connecting the first electrode and the second electrode to the high frequency voltage generating unit; , the detection unit is disposed upstream of the first electrode and the second electrode in a transport direction, The control unit, in response to a detection result of the detection unit, When the amount of moisture contained in the medium reaches a threshold value, the AC electric field generating unit is driven, If the amount of moisture contained in the medium does not reach the threshold value, the AC electric field generating unit is driven. A drying device that controls the AC electric field generating unit to stop it.

2. The drying device according to claim 1, The first electrode and the second electrode have opposing surfaces facing the medium that are permeable to the AC electric field. A drying device covered with a removable cover.

3. The drying device according to claim 1 or 2, A drying device comprising: an air blowing unit that blows air to the first electrode and the second electrode.

4. The drying device according to any one of claims 1 to 3, The detection unit is A capacitance sensor having an electrode pair and detecting capacitance of the medium in contact with the electrode pair. and, a transmitter that transmits ultrasonic waves; and a transducer that is disposed opposite the transmitter via the medium. and a receiving unit that receives the ultrasonic waves transmitted by the transmitting unit. drying equipment.

5. The drying device according to claim 4, The electrode pair is provided on a surface of the medium opposite to a surface facing the first electrode and the second electrode. Contact, drying device.

6. A drying device according to claim 5, The detection unit irradiates light onto a surface of the medium facing the first electrode and the second electrode. A light source and a light receiving unit that receives light emitted by the light source, and a reflectance of the light with respect to the medium is measured. The drying device includes an optical sensor for detecting the temperature of the drying device.

7. A drying device as claimed in claim 6, the optical sensor has a light blocking portion disposed between the light source and the light receiving portion, The light blocking portion is The light emitted by the light source is reflected by the medium and enters the light receiving unit. The light emitted by the light source is incident on the light receiving section without being reflected by the medium without blocking a certain detection light path. a first state in which the reference light path is blocked; a second state in which the detection light path is blocked and the reference light path is not blocked; It is configured as follows: The optical sensor detects an intensity of light reflected by the medium in the first state. and based on the intensity of the light irradiated onto the medium detected in the second state, A drying device that detects the reflectance of light against a surface.

8. The drying device according to any one of claims 1 to 7, The AC electric field generating unit is a first AC electric field generating unit that generates an AC electric field of a first frequency band; a second AC electric field generating unit that generates an AC electric field of a second frequency band, The control unit is The first AC electric field generating unit or the second AC electric field generating unit is connected to the detection result of the detection unit. A drying device that drives the drying section.

9. A drying device according to any one of claims 1 to 8, The AC electric field generating unit includes a monitoring circuit that monitors the high frequency voltage from the high frequency voltage generating unit. Has The monitoring circuit responds to changes in impedance of the conductor, the first electrode, and the second electrode. Based on the temperature, the temperature of at least one of the conductor, the first electrode, and the second electrode is detected. Know, The control unit controls the temperature of at least one of the conductor, the first electrode, and the second electrode. and when the degree of drying reaches a threshold value, the driving of the AC electric field generating unit is stopped.

10. A drying device according to any one of claims 1 to 9; a printing device that applies a liquid to a medium; The drying device dries the medium on which the liquid is applied by the printing device. Printing system.

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