Inkjet printing apparatus, sheet drying apparatus, and sheet drying method

Abstract

To efficiently dry ink while normally continuing sheet conveyance without deforming a sheet when drying ink discharged to a cut sheet.SOLUTION: An ink jet printer 1 comprises: a conveyance part 2 which conveys a cut sheet P; an ink discharge part 16 which forms an image by discharging ink when the sheet P passes through a prescribed position; a first heat source part 30 which is provided on the downstream side of the ink discharge part 16 and dries an ink discharge surface of the sheet P; and a second heat source part 40 which is arranged so as to be opposed to the first heat source part 30 and heats the sheet P by contacting a rear surface of the sheet P being the opposite side of the ink discharge surface. The first heat source part 30 discharges an electromagnetic wave to heat the ink discharge surface of the sheet P with the radiation heat. With this, both surfaces of the sheet P can be uniformly heated without floating the cut sheet P.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inkjet printing apparatus, a sheet drying apparatus, and a sheet drying method, and particularly to a technique for heating a sheet to dry ink and fix it to the sheet after forming an image on a cut sheet by an inkjet method.

Background Art

[0002] An inkjet printing apparatus that discharges ink onto a sheet to form an image fixes the ink to the sheet by performing a drying process after discharging the ink onto the sheet. In the drying process, a process of heating the sheet to dry the ink is performed.

[0003] In recent years, in this type of inkjet printing apparatus, an increase in the conveyance speed of the sheet has been demanded, and a sheet on which an image is formed by ink passes through the drying process section in a short time. Therefore, the amount of heat required to dry the ink is increasing.

[0004] In addition, in recent years, from the viewpoint of environmental problems and the like, the demand for water-based ink is increasing rather than solvent-based ink. Since water-based ink requires a higher amount of heat for drying than solvent-based ink, when using water-based ink, it is necessary to heat the sheet with an even higher amount of heat.

[0005] Conventionally, an inkjet printing apparatus has been proposed that increases the amount of heat by heating the sheet from both the front and back sides of the sheet (for example, Patent Document 1). In this conventional technology, the back side of a roll-shaped printing paper is closely held against a heating conveyance belt to heat the back side of the printing paper, and a configuration is adopted in which hot air is blown onto the front side of the printing paper to dry the ink by hot air.

[0006] Also conventionally, a technique has been proposed in which printing paper is wound around a heat roller and the back side of the printing paper is heated by the heat roller to dry the ink (for example, Patent Document 2).

Prior Art Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-46272 [Patent Document 2] Japanese Patent Application Publication No. 8-290560 [Overview of the project] [Problems that the invention aims to solve]

[0008] By the way, in the prior art described in Patent Document 1, the sheet from which the ink is ejected is made of roll-shaped printing paper. With a roll-shaped sheet, a constant tension is applied in the direction of sheet transport, so no problem occurs even if hot air is blown onto the surface side of the sheet from above.

[0009] However, if the sheets are not in roll form but are cut to a predetermined size, such as A4, blowing hot air to dry the ink can cause the sheets to lift off the heated conveyor belt, preventing normal sheet transport and increasing the likelihood of jams. Furthermore, when the sheets lift off the heated conveyor belt, the underside of the sheet is not heated properly, preventing even heating of both sides of the sheet. This can cause deformation of the sheet, such as curling due to temperature differences, potentially degrading the quality of the printed material.

[0010] Furthermore, the prior art described in Patent Document 2 heats only the back surface of the sheet, making it impossible to heat both the front and back surfaces of the sheet evenly. Therefore, even with this prior art, there is a possibility that the sheet may deform due to the temperature difference between the front and back surfaces.

[0011] Therefore, the present invention has been made to solve the above problems, and aims to provide an inkjet printing apparatus, a sheet drying apparatus, and a sheet drying method that can efficiently dry the ink dispensed onto a cut sheet without deforming the sheet and while continuing normal sheet transport. [Means for solving the problem]

[0012] To achieve the above objective, the invention according to claim 1 is an inkjet printing apparatus comprising: a transport unit for transporting a cut sheet; an ink ejection unit for ejecting ink to form an image when the sheet passes a predetermined position; and a unit provided downstream of the ink ejection unit for drying the ink ejection surface of the sheet. To achieve this, electromagnetic waves are emitted to heat the ink ejection surface with radiant heat. A first heat source unit, and a second heat source unit positioned opposite the first heat source unit, which contacts the back surface of the sheet on the side opposite the ink ejection surface to heat the sheet, A blower unit provided downstream of the first heat source unit, and a wall unit provided between the heating region by the first heat source unit and the blowing region by the blower unit, Equipped with, The wall portion is a barrier that prevents air from the blower portion from flowing into the heating region. This configuration is characterized by the following features.

[0013] The invention according to claim 2 is an inkjet printing apparatus according to claim 1, characterized in that the transport unit has a belt transport unit that transports the back side of the sheet by adhering it to the surface of the belt.

[0014] The invention according to claim 3 is an inkjet printing apparatus according to claim 2, wherein the second heat source unit heats the belt and heats the back surface of the sheet by heat conduction from the belt.

[0015] The invention according to claim 4 is an inkjet printing apparatus according to claim 3, characterized in that the second heat source unit comprises a heat source plate that contacts the back surface of the belt.

[0016] The invention according to claim 5 is an inkjet printing apparatus according to claim 3, wherein the belt is stretched over a plurality of rollers, and the second heat source unit heats the rollers to heat the belt.

[0017] The invention according to claim 6 is configured such that, in the inkjet printing apparatus of claim 1, the first heat source unit is a UV heater that emits ultraviolet rays.

[0018] The invention according to claim 7 is configured such that, in the inkjet printing apparatus of claim 1, the first heat source unit is a halogen heater.

[0019] The invention according to claim 8 is configured such that, in the inkjet printing apparatus of claim 1, the ink ejection unit ejects aqueous ink.

[0022] Claim 9 The invention according to claim 17 further includes a control unit that controls the amount of heat applied to the sheet by each of the first heat source unit and the second heat source unit in the inkjet printing apparatus according to any one of claims 1 to 8, and the control unit determines the amount of heat of each of the first heat source unit and the second heat source unit based on at least one of the type of the sheet, the amount of ink ejected onto the sheet, and the type of the ink.

[0023] Claim 10 The invention according to claim 23 further includes a control unit that controls the amount of heat applied to the sheet by each of the first heat source unit and the second heat source unit in the inkjet printing apparatus according to any one of claims 1 to 8, and when ink is ejected onto the second surface of the sheet after ink is ejected onto the first surface of the sheet, the control unit reduces the amount of heat of each of the first heat source unit and the second heat source unit compared to when ink is ejected onto the first surface.

[0024] Claim 11 The invention according to claim 29 is a sheet drying device, including a transport unit that transports a cut sheet with ink ejected onto its surface, and a heater that heats the ink ejection surface of the sheet while the sheet is being transported. To achieve this, electromagnetic waves are emitted to heat the ink ejection surface with radiant heat.A first heat source unit, and a second heat source unit that is disposed opposite to the first heat source unit and contacts the back surface of the sheet on the opposite side of the ink ejection surface to heat the sheet. A blower unit provided downstream of the first heat source unit, and a wall unit provided between the heating region by the first heat source unit and the blowing region by the blower unit, It is provided with The wall portion is a barrier that prevents air from the blower portion from flowing into the heating region. It is a configuration characterized by this.

[0025] Claim 12 The invention according to [claim number] is a sheet drying method, which includes a step of conveying a sheet cut in a state where the ink ejection surface on which ink is ejected faces upward, and driving a first heat source unit disposed above the ink ejection surface of the sheet while the sheet is being conveyed The first heat source emits electromagnetic waves to heat the ink ejection surface with radiant heat. and driving a second heat source unit disposed so as to contact the back surface of the sheet on the opposite side of the ink ejection surface of the sheet to heat the back surface of the sheet. A step of driving a blower unit provided downstream of the first heat source unit and blowing air from the blower unit to promote drying of the ink ejection surface heated by the first heat source unit, It has A wall is provided between the heating region by the first heat source and the air blowing region by the air blowing unit, and the step of blowing air from the air blowing unit to promote drying of the ink ejection surface is performed such that the air from the air blowing unit does not flow into the heating region by the wall. It is a configuration characterized by this.

Effect of the Invention

[0026] According to the present invention, when drying the ink ejected onto the cut sheet, the sheet can be dried efficiently while continuously and normally conveying the sheet without deforming the sheet.

Brief Description of the Drawings

[0027] [Figure 1] It is a diagram showing a configuration example of an inkjet printing apparatus. [Figure 2] It is a diagram showing a detailed configuration example of a drying unit. [Figure 3] It is a diagram showing the relationship between temperature and saturated water vapor amount. [Figure 4] It is a diagram showing a configuration example of a control unit. [Figure 5] It is a diagram showing an example of reference information. [Figure 6] It is a flowchart showing an example of a processing procedure by a control unit. [Figure 7] It is a diagram showing another configuration example of a drying unit.

Mode for Carrying Out the Invention

[0028] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In the embodiments described below, elements common to all are denoted by the same reference numerals, and redundant explanations of these elements will be omitted.

[0029] (First Embodiment) Figure 1 shows an example of the configuration of an inkjet printing apparatus 1 in the first embodiment of the present invention. The inkjet printing apparatus 1 is a device that transports a sheet P that has been pre-cut to a predetermined size such as A4 size, and ejects ink as the sheet P passes a predetermined position to form an image. This inkjet printing apparatus 1 comprises a paper feeding unit 4, a positioning unit 5, an image forming unit 6, a drying unit 7, a sheet reversing unit 8, and a discharge unit 9, and a transport unit 2 for transporting the sheet P is provided inside each of these units. The inkjet printing apparatus 1 also includes a control unit 3 that controls the operation of each unit.

[0030] The transport unit 2 transports the sheet P by roller transport using pairs of rollers or by belt transport using a belt. Inside the inkjet printing device 1, a first path 2a and a second path 2b are provided as paths for transporting the cut sheet P. The first path 2a is a transport path for forming an image on the sheet P. The second path 2b is a path for inverting the sheet P, and is a transport path for inverting the front and back sides of the sheet P, which has an image formed on the first surface (front), and supplying it back to the first path 2a.

[0031] The paper feeding unit 4 includes a tray 11 for loading sheets P that have been pre-cut to a predetermined size, such as A4 size, a pickup roller 12, and a paper feed roller 13. The pickup roller 12 joins with the sheet P located on the top of the multiple sheets P loaded in the tray 11 and feeds the sheet P toward the paper feed roller 13. The paper feed roller 13 feeds the sheet P fed by the pickup roller 12 toward the first path 2a.

[0032] The alignment unit 5 supplies the sheet P, which is fed by the paper feeding unit 4, to the image forming unit 6. The alignment unit 5 is equipped with a timing roller 14. The alignment unit 5 aligns the sheet P by bringing its leading edge into contact with the timing roller 14, and drives the timing roller 14 at a predetermined timing to supply the sheet P to the image forming unit 6. As a result, the image forming unit 6 can eject ink in accordance with the timing at which the sheet P is supplied from the alignment unit 5, and form an appropriate image on the sheet P.

[0033] The image forming unit 6 includes a belt 15 for transporting the sheet P and an ink ejection unit 16 that ejects ink when the sheet P transported by the belt 15 passes a predetermined position. By driving the ink ejection unit 16 based on the image data to be printed, an image is formed on the sheet P.

[0034] The belt 15 is an endless belt and is stretched between a pair of rollers 17 and 18 located on the upstream and downstream sides. Numerous tiny holes are formed on the surface of the belt 15, and air is drawn in through these tiny holes by a blower (not shown). The image forming unit 6 holds the back side of the sheet P supplied from the alignment unit 5 to the surface of the belt 15 by suction and conveys it downstream in the conveying direction.

[0035] The ink ejection unit 16 is equipped with multiple ejection heads. Each ejection head ejects ink of a specific color, such as Y (yellow), M (magenta), C (cyan), and K (black). The ink ejection unit 16 drives each ejection head individually based on image data to eject ink of each color onto the first surface of the sheet P, thereby forming a color image. For example, the ink ejected by the ink ejection unit 16 may be either water-based ink or non-water-based ink (including solvent-based ink, oil-based ink, and UV-curing ink).

[0036] The drying unit 7 is located downstream of the image forming unit 6 and functions as a sheet drying device. The drying unit 7 heats the sheet P on which the ink has been ejected in the image forming unit 6, thereby drying the ink and fixing it to the sheet P. The drying unit 7 includes a belt 21 for transporting the sheet P, a first heat source unit 30, a second heat source unit 40, an air blower unit 50, and a wall unit 55.

[0037] The belt 21 is an endless belt and is stretched across three rollers 22, 23, and 24. Numerous tiny holes are formed on the surface of the belt 21, and air is drawn in through these tiny holes by a blower (not shown). The drying unit 7 holds the back side of the sheet P supplied from the image forming unit 6 by adsorption to the surface of the belt 21 and transports it downstream in the transport direction. The drying unit 7 then heats the sheet P to dry the ink while the sheet P is being transported by the belt 21. The detailed configuration of the drying unit 7 will be described later.

[0038] The sheet reversal unit 8 receives the ink-dried sheet P from the drying unit 7 and supplies it to the discharge unit 9. The sheet reversal unit 8 is also equipped with a switchback roller 25, which can guide the sheet P to the second path 2b without supplying it to the discharge unit 9. That is, the switchback roller 25 supplies the sheet P from the first path 2a to the second path 2b when double-sided printing on the sheet P is specified. The second path 2b is formed from the sheet reversal unit 8 through the drying unit 7 and the image forming unit 6 to the alignment unit 5. Therefore, the sheet P guided to the second path 2b is transported along the second path 2b with the rear end of the sheet becoming the front end, and then transported again along the first path 2a at the alignment unit 5.

[0039] The discharge unit 9 includes a discharge roller 26 and a tray 27, and the sheet P supplied from the sheet reversing unit 8 is discharged onto the tray 27 by the discharge roller 26.

[0040] As described above, the inkjet printing apparatus 1 of this embodiment can transport the sheet P cut by the transport unit 2 and form an image on one or both sides of the sheet P with ink ejected by the ink ejection unit 16.

[0041] Figure 2 shows a detailed example of the configuration of the drying section 7. As shown in Figure 2, a sheet P on which an image G has been formed by the image forming section 6 is transported to the drying section 7. This sheet P is transported in the direction of arrow F1 within the drying section 7. That is, the sheet P entering the drying section 7 is held by adsorption on the surface of the belt 21, and the rollers 22 and 23 move the belt 21 in a circulating manner, thereby transporting it downstream in the transport direction F1.

[0042] The first heat source unit 30 is positioned upstream of the sheet P in the conveying direction F1 in the drying unit 7, and is located opposite the ink discharge surface of the sheet P being conveyed by the belt 21. The first heat source unit 30 is equipped with a light source 31 that emits electromagnetic waves 32. This light source 31 irradiates the ink discharge surface of the sheet P with electromagnetic waves 32 to impart radiant energy, heating the ink discharge surface with radiant heat. By heating the ink discharge surface with radiant heat, the sheet P does not lift off the surface of the belt 21, and the belt 21 can continue to convey the sheet P normally. Therefore, the possibility of jams occurring in the drying process by the drying unit 7 can be reduced.

[0043] The light source 31 of the first heat source unit 30 is, for example, a UV heater (ultraviolet lamp) that emits ultraviolet light, a halogen heater (halogen lamp), or an infrared heater (infrared lamp). Here, the radiant energy emitted by the light source 31 increases as the wavelength of the electromagnetic wave 32 becomes shorter. Therefore, in order to efficiently heat the ink ejection surface of the sheet P with radiant heat, it is most preferable to use a UV heater as the light source 31. That is, by using a UV heater, it is possible to raise the ink ejection surface of the sheet P to a predetermined temperature in a short time. The next most preferred light source 31 after the UV heater is a halogen heater.

[0044] The second heat source unit 40 is positioned opposite the first heat source unit 30 and heats the sheet P by contacting the side of the sheet P opposite to the ink ejection surface (the back side). In other words, the drying unit 7 heats both the front and back sides of the sheet P simultaneously, so that no temperature difference occurs between the front and back sides.

[0045] The second heat source unit 40 includes a heat source plate 41 that contacts the back side of the belt 21 that holds the sheet P by suction. The belt 21 slides in contact with the upper surface of the heat source plate 41 to transport the sheet P. The heat source plate 41 is, for example, a metal plate, and is provided with a plurality of heaters 42 arranged at predetermined intervals along the transport direction F1 of the sheet P inside it. The heat source plate 41 is heated by these plurality of heaters 42, and heats the back side of the sheet P by heat conduction through the belt 21.

[0046] Furthermore, the upper surface of the heat source plate 41 is provided with multiple holes for drawing in air. Therefore, even when the belt 21 moves while in contact with the upper surface of the heat source plate 41, the sheet P remains held in place by suction on the surface of the belt 21.

[0047] Furthermore, the second heat source unit 40 may adopt a configuration in which heaters 43 are provided inside the rollers 22 and 23, as shown in Figure 2. For example, the roller 22 may have multiple heaters 43 provided around the rotating shaft 22a at predetermined angular intervals, and the roller 23 may have multiple heaters 43 provided around the rotating shaft 23a at predetermined angular intervals. By providing heaters 43 not only in the heat source plate 41 but also inside the rollers 22 and 23, the second heat source unit 40 can efficiently heat the belt 21 to a predetermined temperature. However, whether or not to provide heaters 43 inside the rollers 22 and 23 is optional.

[0048] A blower unit 50 is provided downstream of the first heat source unit 30. The blower unit 50 is equipped with a blowing means 51 such as a fan or blower, and blows air 52 towards the sheet P that is being conveyed while being held in place by the belt 21. However, the amount of air blown by the blower unit 50 is set to a minute amount so as not to cause the sheet P, which is held in place by the belt 21, to lift off the belt 21. Therefore, even when passing below the blower unit 50, the sheet P does not lift off the belt 21 and maintains a good state of being held in place by the belt 21. This suppresses the occurrence of jams and also suppresses deformation such as curling of the sheet P.

[0049] The air blower unit 50 is provided to promote the drying of the ink ejection surface heated by the first heat source unit 30. For example, in the case of water-based ink, when the ink ejection surface is heated by the first heat source unit 30, the water contained in the ink evaporates. However, if the area near the ink ejection surface reaches the saturation water vapor amount, the evaporation of water will be suppressed. The air blower unit 50 introduces outside air to the area near the ink ejection surface by blowing air 52 onto the ink ejection surface, preventing the area near the ink ejection surface from reaching the saturation water vapor amount and thus promoting the drying of the ink.

[0050] Figure 3 shows the relationship between temperature and saturated water vapor amount. As shown in Figure 3, the saturated water vapor amount increases with increasing temperature and decreases with decreasing temperature. Here, the heating region R1 where the first heat source unit 30 is located becomes high temperature due to radiant heat from electromagnetic waves 32, resulting in a large saturated water vapor amount. Therefore, when the sheet P is passing through the heating region R1, it is unlikely that the area near the ink ejection surface will reach saturated water vapor amount due to ink evaporation. In contrast, the air blowing region R2 where the air blowing unit 50 is located is relatively low temperature because there is no radiant heat from electromagnetic waves 32, so the saturated water vapor amount decreases to a small value. Therefore, when the sheet P is transported downstream of the first heat source unit 30, there is a possibility that the area near the ink ejection surface will reach saturated water vapor amount due to ink evaporation. The air blowing unit 50 blows away evaporated moisture present near the ink ejection surface by blowing air 52 onto the ink ejection surface, preventing the area near the ink ejection surface from reaching saturated water vapor amount. This allows the ink ejection surface to be dried efficiently.

[0051] Furthermore, the air blower 50 may also be equipped with a heater 53, as shown in Figure 2. By providing the heater 53, the air blower 50 can send air 52 at a temperature higher than room temperature to the ink ejection surface. This increases the amount of saturated water vapor near the ink ejection surface, allowing the ink ejection surface to be dried more efficiently.

[0052] Furthermore, the heat source plate 41 is positioned to face not only the first heat source section 30 but also the air blowing section 50. In other words, the heat source plate 41 is provided across both the heating area R1 and the air blowing area R2. Therefore, even while the sheet P is being transported by the air blowing section 50, the heat source plate 41 can maintain the sheet P at a constant temperature.

[0053] The wall portion 55 is provided between the heating region R1 by the first heat source portion 30 and the air blowing region R2 by the air blowing portion 50. The wall portion 55 is a barrier to prevent the wind 52 from the air blowing portion 50 from flowing into the heating region R1. If wind 52 flows into the heating region R1, it will become a crosswind, which may cause the sheet P being conveyed in the heating region R1 to lift off the belt 21. The wall portion 55 prevents the generation of such a crosswind and suppresses the sheet P from lifting off the belt 21. The distance between the lower end of the wall portion 55 and the surface of the belt 21 should be at least sufficient to allow the sheet P on which the ink has been ejected to pass through.

[0054] In this way, the drying unit 7 heats the ink discharge surface of the sheet P with radiant heat from the first heat source unit 30, so the sheet P does not lift up, and the normal transport of the sheet P can continue. Furthermore, since the drying unit 7 heats both the front and back surfaces of the sheet P simultaneously with the first heat source unit 30 and the second heat source unit 40, it can heat evenly without creating a temperature difference between the front and back surfaces. Therefore, this drying unit 7 is configured to effectively prevent jamming and deformation of the sheet P during drying. In addition, the drying unit 7 can efficiently dry the ink by using a UV heater or a halogen heater as the light source 31 of the first heat source unit 30. In particular, using a UV heater allows for a large amount of heat to be applied during drying, which contributes to increasing the transport speed of the sheet P and has the advantage of efficiently drying even water-based inks.

[0055] Next, the configuration of the control unit 3 will be described. Figure 4 shows an example of the configuration of the control unit 3. The control unit 3 comprises a CPU 60 and a storage unit 61. The CPU 60 is a hardware processor that reads and executes the program 62 stored in the storage unit 61. The storage unit 61 is a storage device composed of a hard disk drive (HDD) or a solid state drive (SSD), and it stores the program 62 and reference information 63 in advance.

[0056] The CPU 60 functions as a job control unit 64 by executing program 62. The job control unit 64 comprehensively controls the execution of print jobs in the inkjet printing apparatus 1 and controls the operation of each of the parts described above. Specifically, the job control unit 64 controls the operation of forming an image on the sheet P based on the image data to be printed. This job control unit 64 includes a drying control unit 65.

[0057] The drying control unit 65 controls the drying process of the sheet P by the drying unit 7. Specifically, the drying control unit 65 controls the operation of the first heat source unit 30, the second heat source unit 40, and the blower unit 50. In particular, the drying control unit 65 can adjust the amount of heat applied to the sheet P by controlling the first heat source unit 30 and the second heat source unit 40, respectively. At this time, the drying control unit 65 reads the reference information 63 stored in the storage unit 61 and controls the first heat source unit 30 and the second heat source unit 40, respectively, based on the reference information 63.

[0058] Figure 5 shows an example of reference information 63. As shown in Figure 5, the reference information 63 records control parameters (heat quantity) for controlling the first heat source unit 30 and the second heat source unit 40 according to the ink type, sheet type, and the amount of ink dispensed onto the sheet P. For example, in the case of water-based ink, more heat is required for drying than for solvent-based ink (non-water-based ink), so the amount of heat supplied by the first heat source unit 30 and the second heat source unit 40 is set to be higher than that for solvent-based ink. Also, in the case of thick paper, more heat is required for drying than for thin paper, so the amount of heat supplied by the first heat source unit 30 and the second heat source unit 40 is set to be higher than that for thin paper. Furthermore, when the amount of ink is large, more heat is required to dry the ink compared to when the amount is small, so the amount of heat supplied by the first heat source unit 30 and the second heat source unit 40 is set to be higher than when the amount of ink is small.

[0059] Furthermore, since the first heat source 30 directly heats the surface of the sheet P with radiant heat, the temperature gradient on the surface of the sheet P becomes relatively steep, whereas the second heat source 40 heats the back surface of the sheet P with heat conduction via the belt 21, resulting in a relatively gentle temperature gradient on the back surface of the sheet P. In order to suppress the occurrence of temperature differences due to such differences in temperature gradients, reference information 63 is set so that the amount of heat supplied by the second heat source 40 is higher than the amount of heat supplied by the first heat source 30.

[0060] The drying control unit 65 determines control parameters (heat quantity) according to the ink type, sheet type, and ink quantity based on the reference information 63 described above, and drives and controls the first heat source unit 30 and the second heat source unit 40, respectively. Here, the amount of ink discharged onto the sheet P can be calculated based on the image data to be printed. The drying control unit 65 determines whether the calculated amount of ink is greater than a predetermined amount and determines the control parameters based on the reference information 63. Alternatively, the drying control unit 65 may determine the control parameters of the first heat source unit 30 and the second heat source unit 40 based on at least one of the ink type, sheet type, and ink quantity.

[0061] Next, an example of a specific control operation by the control unit 3 will be described. Figure 6 is a flowchart showing an example of a processing procedure by the control unit 3, and mainly shows a processing procedure for controlling the operation of the drying unit 7. This process starts, for example, when the control unit 3 starts executing a print job. When the control unit 3 starts this process, it refers to the reference information 63 and determines the amount of heat of the first heat source unit 30 (step S10) and the amount of heat of the second heat source unit 40 (step S11). Then the control unit 3 starts driving the first heat source unit 30 (step S12) and starts driving the second heat source unit 40 (step S13). At this time, the control unit 3 also starts driving the blower unit 50. As a result, irradiation of electromagnetic waves 32 starts in the heating region R1 and heating of the belt 21 starts.

[0062] Subsequently, the control unit 3 waits until the sheet P on which the image has been formed has passed through the drying unit 7 (step S14). When the sheet P has passed through the drying unit 7 (YES in step S14), the control unit 3 determines whether or not double-sided printing is specified for the sheet P (step S15). If double-sided printing is specified (YES in step S15), the control unit 3 reduces the heat output of the first heat source unit 30 (step S16) and also reduces the heat output of the second heat source unit 40 (step S17). In the case of double-sided printing, after the sheet P on which the image has been formed has passed through the drying unit 7, it is transported back to the first path 2a via the second path 2b, and an image is formed on the second side (back side) of the same sheet P. When the sheet P on which the image has been formed has passed through the drying unit 7, the temperature of the sheet P is higher than room temperature, and if the same amount of heat is applied when the image is formed on the second side as on the first side, scorching or ink blistering (bubbles) may occur. To prevent this, the control unit 3 reduces the heat output of the first heat source unit 30 and the second heat source unit 40 when ink is ejected to the second side during double-sided printing compared to when ink is ejected to the first side.

[0063] The control unit 3 reduces the heat output of the first heat source unit 30 and the second heat source unit 40, and then waits until the sheet P, on which the image is formed on the second surface, passes through the drying unit 7 (step S18). Once the sheet P has passed through the drying unit 7 (YES in step S18), the control unit 3 terminates the operation of the first heat source unit 30 (step S19) and also terminates the operation of the second heat source unit 40 (step S20). In addition, if it is determined in step S15 that double-sided printing is not specified (NO in step S15), the control unit 3 performs the processes in steps S18 and S19 and terminates the operation of the first heat source unit 30 and the second heat source unit 40. This completes the processing by the control unit 3.

[0064] In addition, Figure 6 illustrates the processing procedure when one sheet P is fed from the paper feed unit 4, but multiple sheets P may be fed continuously from the paper feed unit 4. In that case, the control unit 3 should repeat the above-described process each time a sheet P is fed by the paper feed unit 4.

[0065] (Second Embodiment) Next, a second embodiment of the present invention will be described. In the first embodiment described above, an example configuration was described in which the drying unit 7 is equipped with an air blower 50. As described above, the air blower 50 prevents the vicinity of the ink discharge surface from reaching the saturated water vapor amount and promotes the drying of the ink, and is therefore particularly effective when the ink discharged from the ink discharge unit 16 is water-based ink. However, the ink discharged by the ink discharge unit 16 is not limited to water-based ink, and non-water-based ink may also be used. When the ink is non-water-based ink, the drying unit 7 may adopt a configuration that does not include the air blower 50 described in the first embodiment. In this embodiment, an example of such a configuration will be described.

[0066] Figure 7 shows an example of the configuration of the drying section 7 in the second embodiment. The drying section 7 shown in Figure 7 does not have the air blower section 50 and wall section 55 described in the first embodiment. That is, the first heat source section 30 and the second heat source section 40 are approximately the same length in the conveying direction F1 of the sheet P. With this configuration, while the sheet P is being conveyed by the belt 21, the first heat source section 30 can heat the ink discharge surface of the sheet P with radiant heat, and the second heat source section 40 can heat the back side of the sheet P with heat conduction via the belt 21. Therefore, instead of the configuration of the drying section 7 described in the first embodiment, the configuration shown in Figure 7 may be adopted.

[0067] (modified version) Preferred embodiments of the present invention have been described above. However, the present invention is not limited to those described in the above embodiments, and various modifications are applicable.

[0068] For example, in the above embodiment, an example configuration was described in which the inkjet printing apparatus 1 is capable of double-sided printing on a sheet P. However, the inkjet printing apparatus 1 is not limited to an apparatus capable of double-sided printing; it may be an apparatus capable of single-sided printing only.

[0069] Furthermore, in the above embodiment, an inkjet printing apparatus 1 capable of forming a color image on a sheet P by ejecting ink of multiple colors from an ink ejection unit 16 was described. However, the inkjet printing apparatus 1 is not limited to one capable of forming color images, and may be an apparatus capable of forming only monochrome images. [Explanation of symbols]

[0070] 1. Inkjet printing device 2. Conveying section 3. Control Unit 7. Drying section (sheet drying device) 16. Ink ejection section 21 belt 22,23 Rollers 30 1st heat source section 31 Light source (heater) 40 Second heat source section 41 Heat source plate 50 Air blower 55 Wall P Sheet

Claims

1. A conveying unit that transports the cut sheets, An ink ejection unit that ejects ink to form an image when the sheet passes a predetermined position, A first heat source unit is provided downstream of the ink ejection unit and emits electromagnetic waves to dry the ink ejection surface of the sheet, thereby heating the ink ejection surface with radiant heat. A second heat source is positioned opposite the first heat source and contacts the back surface of the sheet on the side opposite the ink ejection surface to heat the sheet, A blower unit provided downstream of the first heat source unit, A wall portion is provided between the heating region by the first heat source and the air blowing region by the air blowing unit, Equipped with, The inkjet printing apparatus is characterized in that the wall portion is a barrier that prevents air from the blower portion from flowing into the heating region.

2. The inkjet printing apparatus according to claim 1, characterized in that the conveying unit has a belt conveying unit that conveys the back side of the sheet by adhering it to the surface of a belt.

3. The inkjet printing apparatus according to claim 2, characterized in that the second heat source heats the belt and heats the back surface of the sheet by heat conduction from the belt.

4. The inkjet printing apparatus according to claim 3, characterized in that the second heat source unit comprises a heat source plate that contacts the back surface of the belt.

5. The aforementioned belt is stretched across multiple rollers, The inkjet printing apparatus according to claim 3, characterized in that the second heat source heats the roller and heats the belt.

6. The inkjet printing apparatus according to claim 1, characterized in that the first heat source is a UV heater that emits ultraviolet light.

7. The inkjet printing apparatus according to claim 1, characterized in that the first heat source is a halogen heater.

8. The ink ejection unit is characterized by ejecting water-based ink, as described in claim 1.

9. A control unit that controls the amount of heat supplied to the sheet by the first heat source unit and the second heat source unit, respectively. Furthermore, The inkjet printing apparatus according to any one of claims 1 to 8, characterized in that the control unit determines the amount of heat in the first heat source unit and the second heat source unit based on at least one of the type of sheet, the amount of ink discharged onto the sheet, and the type of ink.

10. A control unit that controls the amount of heat supplied to the sheet by the first heat source unit and the second heat source unit, respectively. Furthermore, The inkjet printing apparatus according to any one of claims 1 to 8, characterized in that when ink is ejected to the second side of the sheet after ink has been ejected to the first side of the sheet, the control unit reduces the heat output of the first heat source and the second heat source compared to when ink was ejected to the first side.

11. A transport unit that transports cut sheets with ink ejected onto the surface, While the sheet is being transported, a first heat source unit emits electromagnetic waves to heat the ink ejection surface of the sheet by radiant heat, A second heat source is positioned opposite the first heat source and contacts the back surface of the sheet on the side opposite the ink ejection surface to heat the sheet, A blower unit provided downstream of the first heat source unit, A wall portion is provided between the heating region by the first heat source and the air blowing region by the air blowing unit, Equipped with, The sheet drying apparatus is characterized in that the wall portion is a barrier that prevents air from the blowing portion from flowing into the heating region.

12. A process of transporting a cut sheet with the ink ejection surface facing upwards, While the sheet is being transported, a first heat source unit positioned above the ink ejection surface of the sheet is driven, and electromagnetic waves are emitted from the first heat source unit to heat the ink ejection surface with radiant heat, and a second heat source unit positioned to contact the back surface of the sheet on the opposite side of the ink ejection surface is driven to heat the back surface of the sheet. A step of driving a blower unit provided downstream of the first heat source unit and blowing air from the blower unit to promote drying of the ink ejection surface heated by the first heat source unit, It has, A wall is provided between the heating region by the first heat source and the air blowing region by the air blowing unit. A sheet drying method characterized in that the step of blowing air from the blowing unit to promote drying of the ink ejection surface is prevented from flowing the air from the blowing unit into the heating region by the wall.

Images