Sheet drying apparatus and image forming system including the same

Abstract

To provide a sheet drying apparatus which can set dry performance appropriate to characteristics of a sheet to be dried, and to provide an image forming system including the sheet drying apparatus.SOLUTION: A sheet drying apparatus includes a conveyance portion, a drying portion, a heater voltage power supply, and a control portion. The conveyance portion conveys a sheet having an image formed on it with inks containing moisture. The drying portion has a heater which is arranged facing the conveyance portion and heats and dries the sheet by using the heater. The heater voltage power supply applies an alternating-current voltage to the heater. The control portion controls the heater voltage power supply. The control portion can change a duty of the alternating-current voltage applied to the heater from an initial set value to an adjusted set value.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a sheet drying device for drying a sheet on which an image is printed by an inkjet recording device or the like, and an image forming system including the same.

Background Art

[0002] Conventionally, as a recording device such as a facsimile machine, a copying machine, or a printer, an inkjet recording device that discharges ink onto a sheet to form an image has been widely used. Further, a sheet drying device that heats and dries a sheet (paper) to which ink has been attached by an inkjet recording device is known.

[0003] In a sheet drying device that dries a sheet using an infrared heater, the drying performance (irradiation intensity of infrared rays) required to sufficiently dry a wide variety of sheets varies depending on the amount of ink per unit area attached to the sheet. That is, the higher the amount of ink per unit area, the higher the drying performance (irradiation intensity of the heater) needs to be increased.

[0004] In the conventional configuration, since the heater can only be switched between the on state and the off state, it is not possible to set a fine irradiation illuminance according to the sheet that is the object to be dried. Therefore, when the ink is changed or depending on the type of sheet, an optimal setting cannot be made, and a large-scale operation such as heater replacement has been required.

[0005] As a method of controlling the drying ability according to the amount of ink per unit area, for example, Patent Document 1 discloses a printing device and a printing method that perform control to extend the drying period of a printing medium as the amount of ink per unit area increases.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the configuration of Patent Document 1, a printed medium with an image printed thereon is conveyed in the forward direction and sent out to a drying area. When the printed medium fits within the drying area, the printed medium is conveyed in the reverse direction to wind it back (feeding and drying process). Then, after drying the printed medium in the drying area, the leading edge of the printed medium is prepared for printing the next image. Therefore, it is necessary to return the printed medium to the upstream side, resulting in problems such as a slow printing speed or a large machine size.

[0008] In view of the above problems, an object of the present invention is to provide a sheet drying device capable of setting appropriate drying performance according to the characteristics of a sheet as an object to be dried, and an image forming system including the same.

Means for Solving the Problems

[0009] A first configuration of the present invention to achieve the above object is a sheet drying device including a conveyance unit, a drying unit, a heater voltage power supply, and a control unit. The conveyance unit conveys a sheet on which an image is formed with ink containing moisture. The drying unit has a heater disposed opposite to the conveyance unit, and dries the sheet by heating the sheet using the heater. The heater voltage power supply applies an alternating voltage to the heater. The control unit controls the heater voltage power supply. The control unit can change the Duty of the alternating voltage applied to the heater from an initial setting value to an adjusted setting value.

Effects of the Invention

[0010] According to the first configuration of the present invention, by changing the Duty of the alternating voltage applied to the heater from the initial setting value to the adjusted setting value, it is possible to adjust the Duty necessary and sufficient for drying the sheet. Therefore, the sheet can be stably dried without being affected by factors such as the type of sheet and the printing rate, and unnecessary power consumption can also be reduced.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0012] [1. Configuration of an Image Forming System including a Sheet Drying Device] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the internal configuration of an image forming system 200 including the sheet drying device 10 of the present invention. FIG. 2 is a side cross-sectional view around the drying unit 40 of the sheet drying device 10 according to an embodiment of the present invention. With reference to FIGS. ① and ②, an image forming system 200 composed of an image forming device 100 and a sheet drying device 10 will be described.

[0013] The image forming device 100 is an inkjet recording type printer, and includes a paper feeding unit 2 disposed below the image forming device 100, an image forming unit 3 disposed above the paper feeding unit 2, and a paper feeding unit 4 that feeds the paper P accommodated in the paper feeding unit 2 to the image forming unit 3.

[0014] Note: In the translation of line , the "①" and "②" in the original text seem to be incorrect references and should be "1" and "..." respectively. I translated them as "1" and "2" according to the context. If there are other specific requirements or corrections, please let me know.The image forming unit 3 includes a recording unit 3a having a plurality of recording heads and a printing conveyance unit 3b disposed opposite to the recording unit 3a. The printing conveyance unit 3b includes an endless printing conveyance belt 5 wound around a plurality of rollers including a drive roller. The sheet P conveyed by the sheet feeding unit 4 passes below the recording unit 3a while being adsorbed and held on the printing conveyance belt 5 by a sheet suction unit (not shown) provided inside the printing conveyance belt 5. The sheet P on which a predetermined image is recorded by the image forming unit 3 is discharged from the discharge roller pair 6 and carried into the sheet drying device 10.

[0015] The image forming apparatus 100 includes an operation panel 101 and a main body control unit 102. The operation panel 101 is an operation unit for receiving various setting inputs. For example, the user can operate the operation panel 101 to input sheet size information. Also, by operating the operation panel 101, the number of sheets to be printed can be input and the start of a printing job can be instructed. The main body control unit 102 supervises the operations of the entire image forming apparatus 100 and controls each part of the image forming apparatus 100.

[0016] The sheet drying device 10 is disposed adjacent to the image forming apparatus 100 and dries the ink on the sheet P discharged from the image forming apparatus 100. The sheet drying device 10 includes a first conveyance unit 20, a preliminary drying unit 30, a drying unit 40, a suction fan unit 50, and a second conveyance unit 70.

[0017] The first conveyance unit 20 includes a drive roller 21a, a driven roller 21b, and a conveyance belt 22. The conveyance belt 22 is wound around the drive roller 21a disposed on the downstream side with respect to the conveyance direction of the sheet P (from right to left in FIG. 1, hereinafter simply referred to as the conveyance direction) and the driven roller 21b disposed on the upstream side.

[0018] Sheet suction parts 23a and 23b are disposed inside the conveyance belt 22. The conveyance belt 22 is formed with a number of suction holes (not shown) through which a suction wind for sucking the sheet P onto the conveyance belt 22 by negative pressure suction by the sheet suction parts 23a and 23b passes.

[0019] Belt cooling fans 24 are arranged at two locations below the conveyor belt 22. Further, a belt temperature sensor 25 is arranged in contact with and separated from the lower surface of the conveyor belt 22. The belt cooling fan 24 blows cooling air onto the conveyor belt 22 when the temperature detected by the belt temperature sensor 25 reaches a predetermined temperature or higher.

[0020] The preliminary drying unit 30 is arranged immediately downstream of the sheet inlet 61 in the conveying direction, and preliminarily dries the ink on the paper P carried in from the sheet inlet 61. The preliminary drying unit 30 includes a paper blowing fan 31 and a paper blowing duct 32 for blowing air onto the paper P from above.

[0021] The drying unit 40 is arranged adjacent to the downstream side of the preliminary drying unit 30 in the conveying direction, and dries the ink on the paper P that has passed through the preliminary drying unit 30. The drying unit 40 includes two heating units 41 arranged so as to face the upper surface of the conveyor belt 22.

[0022] The suction fan unit 50 sucks the water vapor generated from the paper P passing through the drying unit 40. The suction fan unit 50 includes a suction fan 51 that sucks the air containing water vapor in the drying unit 40, and a separation fan 52 that blows separation air for separating the paper P from the conveyor belt 22. The suction fan unit 50 communicates with the space between the conveyor belt 22 and the heating unit 41 via the first duct 53, and communicates with the exhaust port 60 formed in the upper part of the sheet drying device 10 via the second duct 54.

[0023] In addition, a plurality of outside air introduction fans 63 for taking in outside air are arranged at appropriate positions inside the sheet drying device 10. Sheet detection sensors 64 and 65 are arranged at the upstream and downstream parts of the first conveying unit 20, respectively. The sheet detection sensors 64 and 65 detect that the paper P has passed through the sheet inlet 61 and the sheet outlet 62.

[0024] By the rotational drive of the drive roller 21a, the conveyor belt 22 rotates counterclockwise, causing the paper P carried in from the sheet inlet 61 to sequentially pass through the preliminary drying section 30 and the drying section 40, and be discharged outside the sheet drying device 10 from the sheet outlet 62, or be carried into the second conveying section 70.

[0025] The second conveying section 70 is disposed below the drying section 40 and the preliminary drying section 30 with the first conveying section 20 interposed therebetween. The second conveying section 70 includes a reversing conveyance path 70a for reversing the front and back surfaces of the paper P with the ink dried, and a duplex conveyance path 70b for returning the paper P with the front and back surfaces reversed to the image forming apparatus 100 when performing duplex printing on the paper P.

[0026] An arc-shaped retracting path 71 is provided on the downstream side (the left side in FIG. 1) of the suction fan unit 50 with respect to the conveying direction. The retracting path 71 retracts and stocks the paper P (waste paper) that has become unnecessary due to printing defects or the like in the image forming apparatus 100.

[0027] [2. Configuration of Sheet Drying Device] FIG. 3 is an enlarged view of the drying section 40 in FIG. 2. The drying section 40 includes a heating unit 41 and a warm air fan 42 (see FIG. 2). Two sets of heating units 41 are arranged along the conveying direction (arrow X direction). The heating unit 41 includes a heater 43 and a reflector 44. The heating unit 41 is movable between a heating position (the position in FIG. 3) facing the conveyor belt 22 and a separated position (see FIG. 10) separated from the conveyor belt 22.

[0028] The heater 43 is rod-shaped and extends in the sheet width direction (the direction orthogonal to the paper surface in FIG. 3, hereinafter simply referred to as the width direction) that is horizontally orthogonal to the conveying direction. A plurality (12 in this embodiment) of heaters 43 are arranged in parallel along the conveying direction in the heating unit 41. In this embodiment, an infrared heater is used as the heater 43.

[0029] The reflector 44 is a U-shaped reflector in a side view that is arranged to surround each heater 43 from above. The infrared rays emitted from the heater 43 are reflected downward by the inner surface of the reflector 44 and irradiated onto the paper P carried and conveyed by the conveyor belt 22. As a result, the moisture in the ink on the paper P evaporates and dries, and the ink is fixed on the paper P.

[0030] The hot air fan 42 is arranged above the heating unit 41. More specifically, the hot air fan 42 is arranged to blow air upward toward the reflector 44. The air blown onto the reflector 44 by the hot air fan 42 is heated when passing through the gap of each reflector 44 to become hot air, and flows into the gap (drying space) between the heating unit 41 and the conveyor belt 22.

[0031] If there is steam or water vapor in the gap between the heating unit 41 and the conveyor belt 22, the infrared rays emitted from the heater 43 and reflected by the reflector 44 will be absorbed by the steam or water vapor, and the drying ability of the ink on the paper P will be inhibited. Therefore, by blowing hot air into the gap between the heating unit 41 and the conveyor belt 22 by the hot air fan 42 to disperse and remove the steam or water vapor generated from the paper P, the drying property of the ink by the infrared rays can be maintained.

[0032] A first duct 53 for sucking the steam or water vapor generated from the paper P together with air is provided between the drying unit 40 and the suction fan unit 50. The first duct 53 extends from the gap between the heating unit 41 and the conveyor belt 22 to the suction fan 51 in the suction fan unit 50.

[0033] Drying unit temperature sensors 75 are arranged at two locations facing the two heating units 41 of the drying unit 40. The drying unit temperature sensors 75 detect the temperature inside the drying unit 40. The detection results are transmitted to the control unit 90 (see FIG. 4).

[0034] FIG. 4 is a block diagram showing an example of a control path of the sheet drying apparatus 10 of the present embodiment. Here, among the control paths of the sheet drying apparatus 10, parts necessary for implementing the present invention will be mainly described.

[0035] The control unit 90 includes at least a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only storage unit, a RAM (Random Access Memory) 93 as a readable and writable storage unit, a temporary storage unit 94 that temporarily stores data necessary for controlling each part of the sheet drying apparatus 10, and a plurality (here, two) of I / Fs (interfaces) 96 that transmit control signals to each device in the sheet drying apparatus 10 and receive input signals from the operation unit 80.

[0036] The ROM 92 stores a control program for the sheet drying apparatus 10, data such as numerical values necessary for control, and data that will not be changed during the use of the sheet drying apparatus 10. The RAM 93 stores necessary data generated during the control of the sheet drying apparatus 10 and data temporarily required for the control of the sheet drying apparatus 10. Also, the RAM 93 (or ROM 92) stores the relationship between the printing rate of the image formed on the sheet P and the duty of the heater 43, which is used for the duty control of the heater 43. The counter 95 accumulates and counts the number of sheets P carried in.

[0037] Further, the control unit 90 transmits control signals to each part and device in the sheet drying apparatus 10 from the CPU 91 through the I / F 96. Also, signals indicating the state and input signals from each part and device are transmitted to the CPU 91 through the I / F 96. Examples of the parts and devices controlled by the control unit 90 include, for example, the first conveyance unit 20, the preliminary drying unit 30, the drying unit 40, the suction fan unit 50, the second conveyance unit 70, the sheet detection sensors 64a and 64b, the operation unit 80, the drying unit temperature sensor 64, the voltage control circuit 84, and the like.

[0038] The voltage control circuit 84 is connected to the fan drive voltage power supply 85 and the heater voltage power supply 86, and operates these power supplies according to the output signal from the control unit 90. Each of these power supplies, according to the control signal from the voltage control circuit 84, applies a predetermined voltage to the belt cooling fan 24 of the conveying unit 20 and the warm air fan 42 in the heating unit 41 for the fan drive voltage power supply 85, and to the heater 43 in the heating unit 41 for the heater voltage power supply 86.

[0039] The operation unit 80 is provided with a liquid crystal display unit 81 and LEDs 82 indicating various states. The user can operate the stop / clear button of the operation unit 80 to stop the drying of the paper P, and operate the reset button to return the various settings of the sheet drying device 10 to the default state. The liquid crystal display unit 81 is configured to indicate the state of the sheet drying device 10, display the drying status of the paper P, and the number of sheets of paper P loaded. The various settings of the sheet drying device 10 may also be made from the operation panel 101 of the image forming apparatus 100 or a personal computer.

[0040] The external temperature and humidity sensor 83 detects the temperature and humidity outside the sheet drying device 10. The detection result is transmitted to the control unit 90. The external temperature and humidity sensor 83 is arranged at a location that is not easily affected by the heat of the preliminary drying unit 30 and the drying unit 40 within the sheet drying device 10.

[0041] [3. Duty Adjustment of the Alternating Voltage Applied to the Heater] The drying performance (infrared irradiation intensity) of the heater 43 required for drying the paper P varies depending on the type, size, and thickness of the paper P. It also varies depending on the amount of ink used for image recording in the image forming apparatus 100. Therefore, it may be difficult to stably dry the paper P only by adjusting the infrared irradiation intensity by turning the heater 43 on and off.

[0042] Therefore, in this embodiment, based on the output information regarding the characteristics of the paper P, the Duty of the alternating voltage applied to the heater 43 is adjusted. Specifically, information regarding the output information regarding the characteristics of the paper P (type, size, thickness, and printing rate of the paper P) is input from the image forming apparatus 100. The control unit 90 changes the Duty of the alternating voltage applied to the heater 43 from the default (initial setting value) to a predetermined adjustment setting value according to the input output information regarding the characteristics of the paper P.

[0043] Figs. 5(a) to (c) are schematic diagrams showing examples of Duty settings of the alternating voltage waveform applied from the heater voltage power supply 86 to the heater 43. The heater 43 performs on / off control by taking 20 waves as one cycle starting from the zero-cross point, and reduces the number of waves according to the Duty. For example, in the case of a 50 Hz power supply, one cycle = 200 [ms].

[0044] Fig. 5(a) shows a waveform with a Duty of 100%, the number of waves is not reduced, and the on-interval is 20 / 20 waves (100%). Fig. 5(a) shows a waveform with a Duty of 90%, and by reducing 2 waves out of 20 waves as the off-interval, the on-interval becomes 18 / 20 waves (90%). Fig. 5(c) shows a waveform with a Duty of 50%, and by reducing 10 waves out of 20 waves as the off-interval, the on-interval becomes 10 / 20 waves (50%).

[0045] The Duty of the alternating voltage applied to the heater 43 is set according to the type, size, thickness, and printing rate (ratio of the ink adhesion area to the surface area) of the paper P. For example, when the paper P is offset coated paper that is more difficult to dry than plain paper and the printing rate is low (less than 30%), the Duty is set to 50%. If the printing rate is in the range of 30% to 100% of the maximum load of the image forming apparatus 100, the Duty setting is according to that ratio.

[0046] Also, when the paper P is plain paper, if the printing rate is low (less than 30%) and the paper P can be dried without turning on the heater 43, set the Duty to 0%. Also, if the printing rate is in the range of 30% to 100% of the maximum load capacity of the image forming apparatus 100, set the Duty to 50%.

[0047] Furthermore, it is also conceivable to adjust the Duty of the AC voltage waveform applied to the heater 43 according to the temperature and humidity environment inside and outside the sheet drying device 10. For example, in a high-temperature and low-humidity environment, since the paper P is easily dried, change the Duty to an adjustment setting value lower than the default (initial setting value). In a low-temperature and high-humidity environment, since the paper P is difficult to dry, change the Duty to an adjustment setting value higher than the default (initial setting value). Table 1 shows examples of Duty settings.

[0048]

Table 1

[0049] In the example shown in Table 1, menu setting values 1 to 7 with different Duty setting values of the AC voltage applied to the heater 43 are provided, and menu setting value 2 (Duty 50%) is the default (initial setting). The Duty is set in 7 steps of 0%, 50%, 60%, 70%, 80%, 90%, and 100%, and is set to increase as the menu setting value increases.

[0050] The Duty setting of the AC voltage applied to the heater 43 may be a manual setting or an automatic setting. In the case of manual setting, the user selects the menu setting value using the operation unit 80 of the sheet drying device 10 to set it to the desired adjustment setting value. In the case of manual setting, the user can change the Duty to a desired value for various papers, inks, and printing rates (ink loading amounts), enabling flexible response to the diversity of papers and inks.

[0051] In the case of automatic setting, based on the output information regarding the characteristics of the paper P (type, size, thickness, and printing rate of the paper P) transmitted from the image forming apparatus 100, the control unit 90 sets the optimal adjustment setting value. In the case of automatic setting, since it is not necessary for the user to perform operations such as test printing and test drying to change the settings, this leads to a reduction in working time.

[0052] Also, when manually setting the Duty, it is preferable to automatically return the Duty of the AC voltage applied to the heater 43 to the initial setting value from the adjustment setting value after the job is completed. This eliminates the possibility that the next job (drying process) will be executed with the adjustment setting value used in the previous job at the start.

[0053] FIG. 6 is a flowchart showing an example of Duty adjustment control of the heater 43 in the sheet drying apparatus 10 of the present embodiment. The control procedure for automatically adjusting the Duty of the AC voltage applied to the heater 43 will be described along the steps of FIG. 6 while referring to FIGS. 1 to 5 as necessary. In the initial state, it is assumed that the Duty of the heater 43 is set to the initial setting value (for example, 50%). Also, in the following description, the output information regarding the characteristics of the paper P is also simply referred to as the output information of the paper P.

[0054] When a print command for the paper P is input from the main control unit 102 of the image forming apparatus 100, the output information of the paper P is input to the control unit 90 of the sheet drying apparatus 10 together with the drying start command for the paper P (step S1). Among the output information of the paper P, information regarding the type of the paper P such as the size, thickness, and surface smoothness of the paper P is input from the operation panel 101 (see FIG. 1) of the image forming apparatus 100. For example, the manufacturer, product name, product number, etc. of the paper P may be stored in advance in the main control unit 102 in association with the information regarding the type of the corresponding paper P. Thereby, the main control unit 102 can recognize the information regarding the type of the paper P to be used only by the user selecting the manufacturer, product name, product number, etc. of the paper P from the operation panel 101.

[0055] Information regarding the printing rate of the paper P is calculated by the main control unit 102 based on the image data transmitted from a host device such as a personal computer and input to the control unit 90.

[0056] Based on the input output information of the paper P, the control unit 90 determines whether it is necessary to adjust the duty of the AC voltage applied to the heater 43 (step S2). If it is determined that duty adjustment is necessary (Yes in step S2), the control unit 10 changes the duty of the AC voltage applied to the heater 43 from the initial setting value to the adjusted setting value (step S3).

[0057] For example, when the size and thickness of the paper P increase, the amount of heat required for drying the paper P increases. Also, when the paper P is coated paper with high surface smoothness, the ink is more difficult to dry compared to the case of plain paper, so the amount of heat required for drying the paper P increases. Therefore, when the size and thickness of the paper P are large or when the paper P is coated paper, the duty is set to an adjusted setting value larger than the initial setting value.

[0058] On the other hand, when the size and thickness of the paper P are small or when the paper P is plain paper, the duty is set to an adjusted setting value smaller than the initial setting value. The adjustment amount from the initial setting value of the duty is determined based on a table defining the relationship between the type, size, and thickness of the paper P and the corresponding duty. [[ID=…]]

[0059] Also, when the printing rate of the paper P increases, the moisture content of the paper P increases, so the amount of heat required for drying the paper P increases. Therefore, when the printing rate is higher than the reference printing rate (e.g., 30%), the duty is set to an adjusted setting value larger than the initial setting value. On the other hand, when the printing rate is lower than the reference printing rate, the adjusted setting value is smaller than the initial setting value. The adjustment amount from the initial setting value of the duty is determined based on a table defining the relationship between the printing rate and the corresponding duty.

[0060] Furthermore, in conjunction with the duty adjustment of the AC voltage applied to the heater 43, the air volume of the hot air fan 42 and the belt cooling fan 24 is also adjusted (step S4). For example, when the duty is set to an adjustment setting value larger than the initial setting value, the air volume of the hot air fan 42 is increased to enhance the drying ability of the paper P. Also, the air volume of the belt cooling fan 24 is decreased to utilize the heat of the conveyance belt 22 for drying the paper P. When the duty is set to an adjustment setting value smaller than the initial setting value, the air volume of the hot air fan 42 is decreased to suppress power consumption.

[0061] If it is determined that duty adjustment is not necessary (No in step S2), the control unit 90 does not change the duty from the initial setting value and proceeds to the next step without adjusting the air volumes of the hot air fan 42 and the belt cooling fan 24.

[0062] Next, the control unit 90 determines whether Duty = 0% was selected in step S3 (step S5). If Duty = 0% is not selected (No in step S5), the heater 43 is turned on to start preheating (step S6). At this time, an AC voltage is applied to the heater 43 using the adjustment setting value set in step S3.

[0063] Next, the control unit 90 determines whether the drying unit 40 has reached a predetermined temperature or higher based on the detection result of the drying unit temperature sensor 75 (step S7). If the drying unit 40 has reached a predetermined temperature or higher (Yes in step S7), the printing process on the paper P by the image forming apparatus 100 and the drying process of the paper P by the sheet drying apparatus 100 are started (step S8). Note that if Duty = 0% was selected in step S5 (Yes in step S5), the printing process on the paper P by the image forming apparatus 100 and the drying process of the paper P by the sheet drying apparatus 100 are immediately started with the heater 43 turned off (step S8).

[0064] Based on the detection signal from the sheet detection sensor 64, the control unit 90 counts the number of sheets P carried into the sheet drying device 10 by the counter 95 (step S9). The control unit 90 determines whether a predetermined number of sheets P have been carried in and the drying process has ended (step S10).

[0065] If the drying process is continuing (No in step S10), it returns to step S9 to continue counting the number of sheets carried in. If the drying process has ended (Yes in step S10), the heater 43 is turned off and the process ends.

[0066] According to the control example shown in FIG. 6, based on the output information of the sheet P, the Duty of the AC voltage applied to the heater 43 is changed to the adjusted set value. Therefore, the sheet P can be stably dried without being affected by the type, size, thickness, printing rate, etc. of the sheet P, and unnecessary power consumption can also be reduced.

[0067] Also, when adjusting the Duty of the AC voltage applied to the heater 43, by changing the air volume of the warm air fan 42 and the belt cooling fan 24 in conjunction with the change in Duty, the sheet P can be dried more efficiently and the power consumption can also be reduced.

[0068] Also, by performing preheating of the drying unit 40 using the adjusted set value of Duty, when the Duty is set to an adjusted set value smaller than the initial set value, overheating of the drying unit 40 can be suppressed. Also, when the Duty is set to an adjusted set value larger than the initial set value, the startup time of the drying unit 40 can be shortened.

[0069] In the control example shown in FIG. 6, the air volumes of the hot air fan 42 and the belt cooling fan 24 are adjusted (step S4) in accordance with the Duty adjustment (step S3) of the AC voltage applied to the heater 43. However, only the air volume of either the hot air fan 42 or the belt cooling fan 24 may be adjusted in accordance with the Duty adjustment, or only the Duty may be adjusted without adjusting the air volumes of the hot air fan 42 and the belt cooling fan 24.

[0070] Also, in the control example shown in FIG. 6, the Duty adjustment of the AC voltage applied to the heater 43 is performed based on the output information of the sheet P. However, the Duty adjustment may be performed based on the temperature and humidity environment outside the sheet drying device 10 detected by the off-machine temperature and humidity sensor 83.

[0071] For example, when it is determined from the detection result of the off-machine temperature and humidity sensor 83 that the external environment is a high temperature and low humidity environment, the sheet P is likely to dry. Therefore, the control unit 90 changes the Duty to an adjustment setting value smaller than the initial setting value. When it is determined that the environment is a low temperature and high humidity environment, since the sheet P is difficult to dry, the control unit 90 may change the Duty to an adjustment setting value larger than the initial setting value.

[0072] Furthermore, the initial setting value of the Duty may be made changeable. For example, when only printing with a high printing rate is performed in the image forming apparatus 100, or when only coated paper is used as the sheet P, the initial setting value of the Duty is set to 60% to 100% in advance. As a result, the automatic adjustment control of the Duty is not frequently executed, and the control load on the control unit 90 can be reduced.

[0073] In addition, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, in the above-described embodiment, as an example of the image forming system, a configuration in which the sheet drying device 10 is connected to the image forming apparatus 100, which is an inkjet printer, is shown. However, it goes without saying that the sheet drying device 10 can be used independently without being connected to the image forming apparatus 100.

Industrial Applicability

[0074] The present invention can be used in a sheet drying device for drying a sheet on which an image is printed by an inkjet recording device or the like. By using the present invention, it is possible to provide a sheet drying device capable of setting appropriate drying performance according to the characteristics of the sheet to be dried, and an image forming system including the same.

Explanation of Signs

[0075] 10 Sheet drying device 20 First conveying unit (conveying unit) 22 Conveying belt 24 Belt cooling fan 30 Preliminary drying unit 40 Drying unit 41 Heating unit 42 Warm air fan 43 Heater 44 Reflector 50 Suction fan unit 61 Sheet inlet 62 Sheet outlet 64, 65 Sheet detection sensors 70 Second conveying unit 75 Drying unit temperature sensor 80 Operation unit (input unit) 83 External temperature and humidity sensor 85 Fan drive voltage power supply 86 Heater voltage power supply 87 Unit lifting mechanism 90 Control unit 100 Image forming device 200 Image forming system P Paper (sheet)

Claims

1. A conveying unit that conveys a sheet on which an image is formed with ink containing moisture, A drying unit having a heater disposed opposite to the conveying unit, and drying the sheet by heating the sheet using the heater, A heater voltage power supply that applies an alternating voltage to the heater, A control unit that controls the heater voltage power supply, In a sheet drying device provided with: The control unit is characterized in that the duty of the alternating voltage applied to the heater can be changed from an initial setting value to an adjusted setting value. A sheet drying device.

2. The control unit automatically changes the duty from the initial setting value to the adjusted setting value based on output information regarding the characteristics of the sheet. The sheet drying device according to claim 1.

3. The output information regarding the characteristics of the sheet includes at least one of the type, size, thickness, and printing rate of the sheet. The sheet drying device according to claim 2.

4. A temperature and humidity detection sensor that detects the temperature and humidity inside or outside the sheet drying device is provided, The control unit automatically changes the duty from the initial setting value to the adjusted setting value based on the temperature and humidity detected by the temperature and humidity detection sensor. The sheet drying device according to claim 1.

5. An input unit that selects any one of a plurality of duties as an adjusted setting value is provided, When any one of the plurality of duties is selected as the adjusted setting value by the input unit, the control unit changes the duty of the alternating voltage applied to the heater to the adjusted setting value. The sheet drying device according to claim 1.

6. When any one of the plurality of duties is selected as the adjusted setting value by the input unit and the alternating voltage is applied to the heater using the selected adjusted setting value to perform the drying process of the sheet, the control unit returns from the adjusted setting value to the initial setting value after the execution of the drying process. The sheet drying device according to claim 5.

7. The input unit is characterized in that any one of the plurality of duties can be selected as the initial setting value. The sheet drying device according to claim 5.

8. Before the execution of the drying process of the sheet, the control unit can execute preliminary heating in which the alternating voltage is applied to the heater to heat the drying unit until it reaches a predetermined temperature or higher. The sheet drying device according to claim 1, wherein when the control unit changes the Duty from the initial set value to the adjustment set value, the control unit applies the AC voltage to the heater using the adjustment set value to perform the preliminary heating.

9. The sheet drying device according to claim 8, wherein when the adjustment set value is 0%, the control unit performs the drying process without performing the preliminary heating.

10. The drying unit includes a plurality of the heaters that are infrared heaters, a plurality of reflectors that surround the heaters from the direction opposite to the conveying unit, and a heating unit having the same, a hot air fan that is disposed on the side opposite to the conveying unit with the heating unit interposed therebetween and blows hot air heated when passing through the gap of the reflector toward the conveying unit, and is provided with the same. The sheet drying device according to claim 1, wherein when the Duty is changed to the adjustment set value, the control unit changes the air volume of the hot air fan according to the adjustment set value.

11. The conveying unit includes a conveying belt that adsorbs and conveys the sheet, and a belt cooling fan that cools the conveying belt, and is provided with the same. The sheet drying device according to claim 1, wherein when the Duty is changed to the adjustment set value, the control unit changes the air volume of the belt cooling fan according to the adjustment set value.

12. An image forming apparatus that forms an image using ink containing moisture on a sheet, and the sheet drying device according to any one of claims 1 to 11, which is connected to the downstream side of the image forming apparatus in the conveying direction, and an image forming system including the same.

Images