Recording device and recording method

Abstract

To provide a technique that can reduce curls of a sheet, in two-sided recording.SOLUTION: A recording device according to the present invention is provided with: conveying means that conveys a sheet; recording means that records an image on the sheet conveyed by the conveying means while discharging ink to the sheet; heating means that heats the sheet, conveyed by the conveying means and having the image recorded thereon by the recording means; and control means that controls heating performed to a second surface of the sheet by the heating means, on the basis of ink discharge amounts to a first surface of the sheet and ink discharge amounts to the second surface, in two-sided recording of recording an image on the second surface after recording an image on the first surface.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to recording technology. [Background technology]

[0002] In a method of ejecting ink onto a sheet to record an image, the sheet may curl due to the moisture contained in the ink. Therefore, a technique for heating the sheet to promote drying has been proposed. For example, Patent Document 1 discloses a technique for promoting drying by blowing hot air onto a sheet on which an image has been recorded. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2018 / 0050548 Summary of the Invention [Problem to be solved by the invention]

[0004] When recording images on both sides of a sheet, the difference in the amount of moisture in the ink on each side may cause the sheet to curl. Also, due to the configuration of the device, the drying ability of each side of the sheet may vary, causing the sheet to curl.

[0005] The present invention provides a technique for reducing sheet curl in double-sided recording. [Means for solving the problem]

[0006] According to the present invention, an ejection head that ejects ink onto a recording medium that is transported by a transport unit that transports the recording medium; a first heating means for heating the recording medium onto which the ink is discharged by the discharge head; a second heating means arranged downstream of the first heating means in a conveying direction of the recording medium by the conveying means, the second heating means heating the recording medium; Based on the amount of ink ejected onto the recording medium Fever As the quantity changes, The second heating meansA control means for controlling the amount of heat applied to the recording medium. picture, In the case of double-sided recording, in which both sides of the recording medium are recorded, the recording medium is conveyed by the conveying means so that each side of the recording medium is heated by the first heating means, and one side of the recording medium is heated by the second heating means. A recording device is provided. Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique for reducing curling of a sheet in the case of double-sided recording. [Brief description of the drawings]

[0008] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. 4 is a block diagram of a control unit of the main unit. [Figure 6] FIG. 3 is an explanatory diagram of the operation of the recording apparatus in FIG. 2. [Figure 7] FIG. 3 is an explanatory diagram of the operation of the recording apparatus in FIG. 2. [Figure 8] FIG. 3 is an explanatory diagram of the operation of the recording apparatus in FIG. 2. [Figure 9] FIG. 3 is an explanatory diagram of the operation of the recording apparatus in FIG. 2. [Figure 10] 1A and 1B are diagrams illustrating the degree of dryness of the front and back surfaces of a sheet using a drying acceleration unit. [Figure 11] 6A to 6C are flowcharts showing an example of processing by a control unit. [Figure 12] 13A is a flowchart showing another example of processing by the control unit, and FIG. 13B is an explanatory diagram showing an example of an area of ​​a sheet. [Figure 13] 6 is a flowchart showing an example of processing by a control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] First Embodiment <Recording system configuration> Fig. 1 is a front view of a recording system 1 according to an embodiment of the present invention. In each of the drawings including Fig. 1, an arrow X indicates the left-right direction, an arrow Y indicates the depth direction, and they are perpendicular to each other. An arrow Z indicates the up-down direction.

[0011] The recording system 1 includes a main unit 2 and a post-processing device 3. The main unit 2 in this embodiment is a device that constitutes a multifunction peripheral, and has a copying function, a scanner function, and a printer function. The main unit 2 includes a reading device 4, a recording device 5, and a feeding device 6, and an operation unit 7 is provided on the front of the main unit 2. The operation unit 7 is an input / output interface with the user, and includes, for example, hard keys and a display unit, or a touch panel that accepts user input and displays information, and also includes an output unit such as a sound generator.

[0012] The reading device 4 includes an ADF (automatic document feeder) and transports stacked documents and reads document images. The feeding device 6 is a device that feeds recording media to the recording device 5. In this embodiment, the recording media are sheets such as paper or film, and in particular cut sheets. The recording media may also be called sheets. The feeding device 6 includes a plurality of cassettes 6a on which sheets are stacked, and a feeding mechanism (not shown) that feeds sheets from the cassettes 6a to the recording device 5 on the transport path RT.

[0013] The recording device 5 records an image on a sheet. The recording device 5 includes a recording unit 30 that ejects ink onto a sheet to record an image, and drying acceleration units 40 and 50 that accelerate drying of the sheet. The recording device 5 will be described in detail later.

[0014] The post-processing device 3 is a finisher (sheet processing device) that is detachably attached to the side of the main body device 2 as an optional device and performs post-processing of sheets. Examples of post-processing include a stacking process in which sheets discharged from the recording device 5 are stacked on a tray 3a, a sorting process in which multiple sheets discharged from the recording device 5 are sequentially taken in and aligned to form a bundle, a stapling process in which the bundled sheets are stapled, a bookbinding process, and a hole punching process.

[0015] <Recording device configuration> 2 is an explanatory diagram showing the internal structure of the recording device 5. The recording device 5 includes a bottom wall 5a, an upper wall 5b, a right wall 5c, a left wall 5d, and a rear wall 5e as a frame that supports the internal mechanism. These walls define the internal space of the recording device 5. The internal space of the recording device 5 is further divided into an upper space SP2 and a lower space SP1 by a partition wall 5h. The spaces SP1 and SP2 are not separated airtight, but communicate with each other.

[0016] The bottom wall portion 5a has an opening 5f through which a sheet fed from the feeding device 6 passes. In addition, the right wall portion 5c has an opening 5g through which a sheet discharged to the post-processing device 3 passes. The left wall portion 5d and the right wall portion 5c may be supported in the form of a door that can be opened and closed for maintenance purposes.

[0017] The recording apparatus 5 includes a transport unit 20, a recording unit 30, drying promotion units 40 and 50, a straightening unit 60, and an exhaust unit .

[0018] <Transport unit> The transport unit 20 is a mechanism for transporting a sheet along a transport path RT. In this embodiment, the transport path RT is a path along which a sheet is transported, with the opening 5f as the upstream end and the opening 5g as the downstream end. The transport path RT includes main paths RT1 and RT2, a switchback path RT3, and a reversing path RT4. The main paths RT1 and RT2 are paths that connect the opening 5f to the opening 5g through the midpoint M1, and the main path RT1 is from the opening 5f to the midpoint M1, and the main path RT2 is from the midpoint M1 to the opening 5g. The main paths RT1 and RT2 are paths that transport a sheet in the left direction →upward direction →right direction, and the sheet passes through the recording unit 30 →drying promotion unit 40 →drying promotion unit 50 →correction unit 60 in this order. In the case of single-sided recording in which only one side of the sheet is recorded, the sheet is transported through the main paths RT1 and R2.

[0019] The switchback path RT3 and the reversing path RT4 are paths along which the sheet after one-side printing is transported in the case of double-sided printing, where both sides of the sheet are printed. The switchback path RT3 forms a path from the midpoint M1 to the main path RT2. The reversing path RT4 is a path from the midpoint M1 to the junction M2 on the main path RT1, and by passing through the reversing path RT4, the sheet is reversed and returned to the main path RT1.

[0020] In the following description, when referring to the downstream side and the upstream side, the conveying direction of the sheet on the conveying path RT is used as a reference.

[0021] The transport unit 20 includes a drive mechanism that applies a transport force to the sheet and a guide that guides the transport of the sheet along the transport path RT, and a part of the drive mechanism is shown in FIG. 2. The drive mechanism includes a plurality of transport rollers 21 driven by a drive source such as a motor. A driven roller or a spur is disposed opposite each transport roller 21. The sheet is transported while being sandwiched between the transport roller 21 and the driven roller or the spur. The spur is disposed in a region downstream of the recording unit 30 so as to contact the recording surface side in order to maintain the quality of the recorded image. The guide includes guide members 22 to 24. The guide member 24 is supported by the left wall portion 5d. A part of the transport path RT is formed between the guide member 23 and the guide member 24, and a part of the path RT1 is formed between the guide member 22 and the guide member 24.

[0022] The transport unit 20 also includes path switching units 25 and 26. The path switching units 25 and 26 are units that switch the guide path of the sheet, and are operated by a driving source such as an electromagnetic solenoid or a motor. In the case of single-sided recording, the path switching units 25 and 26 guide the sheet from the main path RT1 to the main path RT2, and in the case of double-sided recording, the path switching units 25 and 26 guide the sheet from the main path RT1 to the switchback path RT3, and guide the switched-back sheet to the reversal path RT4. FIG. 3 shows the path switching manner of the path switching units 25 and 26. Each of the path switching units 25 and 26 includes a rotatable flap, and switches the path depending on the position of the flap. The position indicated by the solid line is the position in the case of single-sided recording, and the position indicated by the dashed line is the position in the case of double-sided recording.

[0023] <Recording unit> Returning to Fig. 2, the recording unit 30 includes a recording head 31, which is an inkjet head that ejects ink onto a sheet to form an image (ink image). The ink ejected by the recording head 31 is stored in a plurality of ink storage sections T. An ink storage section T is provided for each type of ink, and the types of ink are, for example, color types such as yellow, magenta, cyan, and black.

[0024] A recording head 31 is provided for each type of ink. In this embodiment, each recording head 31 is a full line head extending in the Y direction, and nozzles are arranged in a range that covers the width of the image recording area of ​​a sheet of the maximum size that can be used. The recording head includes a lower surface that faces the sheet via a minute gap (for example, a few mm), and this lower surface forms an ink ejection surface with nozzles opening therein.

[0025] Each nozzle is provided with an ejection element. The ejection element is, for example, an element that generates pressure in the nozzle to eject ink in the nozzle, and known inkjet head technology can be applied to the ejection element. Examples of the ejection element include an element that ejects ink by generating film boiling in the ink using an electro-thermal converter to form bubbles, an element that ejects ink using an electro-mechanical converter, and an element that ejects ink using static electricity. By using an ejection element that uses an electro-thermal converter, high-speed and high-density recording can be performed.

[0026] The recording unit 30 may be a serial type recording unit in which a recording head mounted on a carriage moves back and forth in the width direction of the sheet to perform recording. The ink to be ejected may be one type, such as black ink only. The recording mode of the recording unit 30 may be selectable between a single ink recording mode and a multiple ink recording mode. The ink may mainly contain a coloring agent (dye or pigment) and a solvent component. The solvent component may be either a water-based material or an oil-based material. As the dye, for example, a water-soluble dye represented by direct dye, acid dye, basic dye, reactive dye, food coloring, etc. is preferable, and any dye may be used as long as it gives an image that satisfies the required performance such as fixability, color development, clarity, stability, light resistance, etc., when combined with the above-mentioned recording medium. As the pigment, carbon black, etc. is preferable. A method of using a pigment and a dispersant in combination, a method of using a self-dispersing pigment, or a method of microencapsulation are also possible. In addition, various additives such as a solvent component, a solubilizer, a viscosity adjuster, a surfactant, a surface tension adjuster, a pH adjuster, and a resistivity adjuster can be added to the ink as necessary. Also, instead of providing a recording head 31 for each type of ink, a single recording head may be provided with nozzles for each type of ink.

[0027] <Drying acceleration unit> A sheet on which an image is recorded by the recording unit 30 may expand due to the liquid content of the ink, causing undulations. Such a sheet can cause paper jams in the recording device 5 and deteriorate the stackability / alignment in the post-processing device 3. By promoting the drying of the sheet, it is possible to suppress the expansion of the sheet due to the liquid content of the ink. The recording device 5 of this embodiment is equipped with multiple drying promotion units 40 and 50 that have different sheet drying methods. The liquid content of the ink contains a certain amount of moisture.

[0028] The drying promotion unit 40 is disposed downstream of the recording unit 30 and promotes drying of the sheet without contacting the sheet by blowing hot air onto the sheet. The structure of the drying promotion unit 40 will be described with reference to Figs. 2 and 3.

[0029] The drying promotion unit 40 includes a hollow body 41 that defines an internal space, and a fan 42 and a heating element 43 that are arranged inside the hollow body 41. The hollow body 41 has an air intake 41a on its right side. A wall portion 41b that forms the left side of the hollow body 41 is a guide wall portion that also serves as a sheet conveying guide, and is extended in the Y direction so as to cover the width of a maximum size sheet. The guide wall portion 41b has a C-shaped cross section (cross section on the XZ plane) and has a wall surface that faces the guide members 22 to 24. A part of the conveying path RT is formed between this wall surface and the guide members 22 to 24, and a midpoint M1 is also set. A number of hot air blowing holes N that communicate with the internal space of the hollow body 41 are formed in the guide wall portion 41b.

[0030] The fan 42 is an electric fan, such as a sirocco fan, driven by a motor. The fan 42 introduces air into the hollow body 41 from the intake port 41a. The introduced air increases the air pressure inside the hollow body 41, and the air inside the hollow body 41 is blown out of the hollow body 41 from the blowing hole N. There may be only one fan 42, or multiple fans 42 may be arranged side by side in the Y direction.

[0031] The heating element 43 heats the air introduced into the hollow body 41 from the intake port 41a by the fan 42. In this embodiment, the heating element 43 is a rod-shaped heating element such as an infrared lamp heater, and is extended in the Y direction. A plurality of heating elements 43 are arranged in the Z direction. The plurality of heating elements 43 are disposed between the fan 43 and the intake port 41a, and the air introduced into the hollow body 41 from the intake port 41a is heated as it passes through the heating elements 43. The drying promotion unit 40 is provided with a temperature sensor 44, and the operation of the heating element 43 is controlled based on the detection result of the temperature sensor 44.

[0032] With this configuration, the drying promotion unit 40 blows hot air from the blowing holes N as the airflow is indicated by the arrow in Fig. 3. This heats the sheet passing through the transport path RT, promotes evaporation of the liquid contained in the ink image on the sheet, and promotes drying of the sheet.

[0033] The drying acceleration unit 50 is disposed downstream of the drying acceleration unit 40 and is a heating and fixing device that comes into contact with the sheet to heat the sheet and accelerate the drying of the sheet. The structure of the heating and fixing device will be described with reference to FIG.

[0034] The drying promotion unit 50 includes a heating element 51 and a roller 56, which are extended in the Y direction to cover the width of the maximum size sheet. The heating element 51 includes a support member 53 that supports a heating element 54, which is a heat source. The heating element 54 is, for example, a ceramic heater, and is extended in the Y direction. The temperature of the heating element 54 is detected by a temperature sensor 55, typically a thermistor, and the operation of the heating element 54 is controlled based on the detection result.

[0035] The support member 53 also supports the film 52. The film 52 is cylindrically shaped and extends in the Y direction. The film 52 is supported by the support member 53 so as to be rotatable around the support member 53, and is interposed between the roller 56 and the heating element 54. The film 52 is, for example, a single-layer film or a composite film having a thickness of 10 μm to 100 μm. In the case of a single-layer film, the material is, for example, PTFE, PFA, or FEP. In the case of a composite film, the film has a layered structure in which, for example, a layer of polyimide, polyamideimide, PEEK, PES, PPS, or the like is covered or coated with PTFE, PFA, FEP, or the like.

[0036] The configuration of the heating element 51 is not limited to this structure, and may be, for example, a structure in which a heating element such as a halogen heater is provided inside a hollow metal core shaft, and the periphery of the core shaft is covered with an elastic material such as silicone rubber.

[0037] Roller 56 is configured by covering the peripheral surface of core metal 56a with elastic body 56b such as silicone rubber. Roller 56 is pressed against heating element 51 with a predetermined pressing force, and a nip portion is formed between roller 56 and heating element 51. Roller 56 is rotated by a motor as a drive source, and film 52 rotates along with roller 56. With this configuration, the sheet is heated while being transported in the nip portion, and the drying of the sheet can be promoted.

[0038] In this embodiment, the sheet is dried in two stages by the drying acceleration units 40 and 50, but only one of the drying acceleration units may be provided.

[0039] <Correctional Unit> The straightening unit 60 is a mechanism for straightening the curvature (here, curl) of the sheet. In the present embodiment, the straightening unit 60 includes a large diameter driving roller 61 and a small diameter driven roller 62. The driving roller 61 is a roller in which the periphery of a core metal is covered with an elastic body such as silicone rubber. The driven roller 62 is a metal roller. The driving roller 61 and the driven roller 62 are pressed against each other. When the sheet passes between the driving roller 61 and the driven roller 62, these rollers apply pressure to the sheet, so that the curl of the sheet can be straightened. The straightening unit 60 can apply a straightening force to the sheet in a direction that makes the sheet convex upward, for example. In this case, the sheet having a downward convex curl can be straightened to a flatter shape by the straightening unit 60.

[0040] <Exhaust unit> The exhaust unit 70 is a unit that exhausts the air in the recording device 5 to the outside of the device. The recording device 5 of this embodiment is equipped with drying promotion units 40 and 50, which increase the temperature inside the device. In addition, these units act to evaporate the moisture of the ink. When recording is performed continuously on a large number of sheets, the humidity inside the device may increase. High humidity can cause the sheet to curve. The sheet is transported through a relatively long distance between the drying promotion unit 50 and the opening 5g, and is transported through the upper space SP2 where water vapor is likely to remain. In the space SP2, the sheet may be exposed to a high humidity atmosphere. The humidity inside the device can be reduced by exhausting the air in the space SP2 to the outside of the device using the exhaust unit 70.

[0041] The exhaust unit 70 of this embodiment has a structure in which the air in the space SP2 is naturally exhausted by a plurality of exhaust ducts 71 to 73. However, the exhaust unit 70 may be a type that forcibly exhausts the air in the device by a fan or the like. The structure of the exhaust unit 70 will be described with reference to Fig. 2 and Fig. 4. Fig. 4 is a plan view showing the periphery of the exhaust unit 70, and the upper wall portion 5b is not shown.

[0042] The exhaust duct 71 is a pipe member including an extension portion 71a extending in the Y direction and an extension portion 71b extending from the end of the extension portion 71a on the rear side in the Y direction to the right side in the X direction. The extension portion 71a is extended in the vicinity of the sheet discharge position in the drying promotion unit 50 and at a position lower than the main path RT2. The extension portion 71a is an air intake portion having a plurality of slits serving as air intakes formed in the upper left side and the bottom side. For example, air heated by the drying promotion unit 50 can be introduced from the slit in the upper left side, and for example, hot air blown out from the blowing hole N of the drying promotion unit 40 can be introduced from the slit in the bottom side. The extension portion 71a is extended across the back wall portion 5e, and its end on the rear side in the Y direction and the extension portion 71b are located outside the space SP2 (the rear side in the Y direction). The extension portion 71a may be extended at a position above the main path RT2.

[0043] The exhaust duct 72 is a pipe member including an extension portion 72a extending in the Y direction, a collection portion 72b extending to the right from the extension portion 72a, and an extension portion 72c extending from the right end of the collection portion 72b to the rear side in the Y direction. The extension portion 72a is provided near the sheet discharge position in the drying promotion unit 50 and at a position above the main path RT2. The bottom of the extension portion 72a is open to form an air intake port, through which, for example, air heated by the drying promotion unit 50 or water vapor in the space SP2 is introduced. The extension portion 72a crosses the upper wall portion 5b and protrudes above the upper wall portion 5b.

[0044] The collecting portion 72b has a triangular shape with a wider width on the extension portion 72a side in a plan view, and the entirety is located above the upper wall portion 5b. The collecting portion 72b collects the air introduced into the extension portion 72a at the center in the Y direction at its right end. The collected air flows into the extension portion 72c. The extension portion 72c is also located entirely above the upper wall portion 5b, and is partially bent and extended to the rear side of the rear wall portion 5e. At the rear side of the rear wall portion 5e, the extension portion 71b of the exhaust duct 71 is connected to the extension portion 72c of the exhaust duct 72, and their internal spaces are connected to each other. The extension portion 72c is connected to the exhaust duct 73.

[0045] Exhaust duct 73 is an exhaust member that extends in the X direction and opens to the rear side in the Y direction. The opening of exhaust duct 73 faces cover 8 that forms the exterior of the rear side of main body device 2. A large number of slits (louvers) 8a are formed in cover 8, and air that flows into exhaust duct 73 passes through the slits 8a and is exhausted to the outside of the main body device 2 from the rear side.

[0046] <Control unit> The control system of the main body device 2 will be described. FIG. 5 is a block diagram of the control unit 9 of the main body device 2. The control unit 9 includes a processing unit 10, a storage unit 11, a reading control unit 13, an image processing unit 14, a head control unit 15, an engine control unit 16, and a drying control unit 17. The processing unit 10 is a processor represented by a CPU (Central Processing Unit), and controls the operation of each unit of the main body device 2 in an integrated manner. The storage unit 11 is, for example, a storage device such as a ROM or a RAM. The storage unit 11 stores programs to be executed by the processing unit 10 and fixed data required for various operations of the main body device 2 (for example, data related to the type of sheets contained in each cassette 6a). The storage unit 11 also stores various setting data as a work area for the processing unit 10 or as a temporary storage area for various received data.

[0047] The reading control unit 13 controls the reading device 4. The image processing unit 14 performs image processing of image data handled by the main device 2. It converts the color space (e.g., YCbCr) of the input image data into a standard RGB color space (e.g., sRGB). The recording data obtained by these image processes is stored in the memory unit 11. The head control unit 15 controls the driving of the recording unit 30 in accordance with the recording data based on the control command received from the processing unit 10. The engine control unit 16 controls the conveyance of the sheet, etc. The drying control unit 17 controls the driving of the drying promotion units 40, 50. Each of these control units includes a processor such as a CPU, a storage device such as a RAM or ROM, and an interface with an external device.

[0048] The I / O 12 is an interface (I / F) for connecting the control unit 9 with the host device 18 and the post-processing device 3, and is a local I / F or a network I / F. The host device 18 is a device that serves as a supply source of image data for causing the recording device 5 to perform a recording operation. The host device 18 may be a general-purpose or dedicated computer, or may be a dedicated imaging device such as an image capture device having an image reader unit, a digital camera, or a photo storage device.

[0049] <Example of operation> An example of the recording operation of the recording device 5 under the control of the control unit 9 will be described with reference to Figs. 6 to 9. First, the operation when an image is recorded on one side of a sheet will be described with reference to Figs. 6 and 7. When an image is recorded on one side of a sheet, the path switching units 25 and 26 are set to the positions for one-sided recording (positions shown by solid lines in Fig. 3). The heating element 43 of the drying promotion unit 40 and the heating element 54 of the drying promotion unit 50 are maintained at a predetermined temperature in advance.

[0050] State ST1 in Fig. 6 shows a state in which the sheet P fed from the feeding device 6 is transported by the transport unit 20 on the main path RT1 to the recording unit 30, and recording by the recording unit 30 is started. The recording unit 30 ejects ink onto the sheet P as shown by the arrows to record an image. The sheet P is transported toward the drying promotion unit 40. The drying promotion unit 40 starts operating, and blows hot air onto the sheet P being transported, as shown in state ST2 in Fig. 6. The hot air promotes drying of the sheet P that is wet with ink.

[0051] The sheet P is further transported on the main path RT2 toward the drying promotion unit 50. The drying promotion unit 50 starts operating, and as shown in state ST3 in FIG. 7, the roller 56 rotates to transport the sheet P, and the sheet P is heated by the heating element 51. The drying of the sheet P is further promoted.

[0052] 7, the sheet P is further transported on the main path RT2 toward the straightening unit 60. The straightening unit 60 starts operating, and the sheet P is discharged from the opening 5g to the post-processing device 3 while the curl of the sheet P is being straightened.

[0053] Next, the operation when recording images on both sides of a sheet will be described with reference to Figures 8 and 9. State ST11 in Figure 8 shows a state in which the sheet P fed from the feeding device 6 is transported by the transport unit 20 on the main path RT1 to the recording unit 30, and recording by the recording unit 30 is started. The recording unit 30 ejects ink onto the surface of the sheet P as shown by the arrow, to record an image. The path switching unit 26 is set to a position for double-sided recording (the position shown by the dashed line in Figure 3).

[0054] The sheet P is transported towards the drying promotion unit 40. The drying promotion unit 40 starts operating, and as shown in state ST12 in FIG. 8, blows hot air onto the transported sheet P. The hot air promotes the drying of the sheet P that is wet with ink. Guided by the path switching unit 26, the sheet P is not transported to the drying promotion unit 50 but is transported to the switchback path RT3. When the rear end of the sheet P passes the position of the path switching unit 25, the path switching unit 25 is set to a position for double-sided recording. Next, the transport unit 20 transports the sheet P in the reverse direction on the switchback path RT3 (switchback transport).

[0055] Guided by the path switching unit 25, the sheet P is transported to the reverse path RT4 as shown in state ST13 in Fig. 8. Then, the sheet P is returned to the main path RT1 as shown in state ST14 in Fig. 8. The path switching unit 25 is set to a position for single-sided recording (the position shown by the solid line in Fig. 3). The recording unit 30 ejects ink onto the back surface of the sheet P as shown by the arrow to record an image. The subsequent operations are the same as states ST2 to ST4 for single-sided recording.

[0056] <Example of drying control for double-sided printing> In the case of double-sided recording, a difference in the amount of moisture in the ink may occur between the front and back sides of the sheet P. This difference in moisture amount is a factor that causes the sheet P to curl. The difference in moisture amount is caused by the difference between the images recorded on the front and back sides of the sheet P (difference in the amount of ink) and the structure of the recording device 5 related to drying the sheet P, i.e., the difference in the drying ability of the drying promotion units 40 and 50 for the front side and the drying ability of the back side. The drying abilities of the drying promotion units 40 and 50 in this embodiment will be described. In the following description, the front side means the side of the two sides of the sheet P on which an image is recorded first, and the back side means the side on which an image is recorded later.

[0057] The drying promotion unit 40 of this embodiment is disposed on one side of the transport path RT of the sheet P, and is configured to blow hot air to only one side of the sheet P. Therefore, although the drying of both sides is promoted, the drying is promoted more on the side that is directly hit by the hot air. In the case of single-sided recording, hot air is blown to the image recording side of the sheet P. In the case of double-sided recording, hot air is blown to the front side when an image is recorded on the front side of the sheet P, and hot air is blown to the back side when an image is recorded on the back side.

[0058] In the drying promotion unit 50 of this embodiment, a heating element 51 (heating element 54) is disposed on one side of the transport path RT of the sheet P, and the heating element 51 contacts only one side of the sheet P to heat it. Therefore, although heat is applied to both sides of the sheet P to promote drying, drying is more promoted on the one side with which the heating element 51 directly contacts. In the case of single-sided recording, the heating element 51 contacts the image recording surface of the sheet P. In the case of double-sided recording, the heating element 54 faces the back surface of the sheet P, and the heating element 51 contacts only the back surface, and there is no stage where the heating element 51 contacts the front surface of the sheet P.

[0059] 10A and 10B show the difference in the degree of dryness on each side when the drying acceleration units 40 and 50 are driven under the same conditions on the front and back sides in double-sided printing.

[0060] Fig. 10(A) shows the difference in dryness due to hot air drying by the drying promotion unit 40. In the case of double-sided recording, after an image is recorded on the front side of the sheet P, the sheet P is switched back and transported on the switchback path RT3 (S12 in Fig. 8). In the case of this embodiment, even during this switchback transport, hot air is blown onto the front side of the sheet P by the drying promotion unit 40. On the other hand, after an image is recorded on the back side of the sheet P, the sheet P is transported to the drying promotion unit 50 without being transported on the switchback path RT3, as in the case of single-sided recording. Therefore, when comparing the front side and the back side, the front side tends to be drier.

[0061] 10B shows the difference in the degree of dryness caused by the heating and drying of the drying acceleration unit 50. In the case of double-sided recording, the heating element 51 comes into contact with only the back surface of the sheet P. Therefore, when comparing the front surface and the back surface, the back surface tends to be drier.

[0062] When the difference in the degree of dryness of each surface is examined for the combined dryness promotion units 40 and 50, the degree of dryness of the front surface tends to be higher due to the higher degree of dryness of the hot air.

[0063] Taking into account these tendencies of the drying promotion units 40 and 50 and the ability of the correction unit 60 to correct the curl of the sheet P, the curl of the sheet can be reduced by controlling the degree of dryness of each side of the sheet P according to the amount of ink ejected for the image recorded on each side.

[0064] The degree of dryness of each side of the sheet P, that is, the difference in the amount of moisture between the front and back sides of the sheet P, can be controlled by controlling the drying acceleration units 40 and 50 according to the amount of ink ejected for the image recorded on each side. Either of the drying acceleration units 40 and 50 can be controlled, but the drying acceleration unit 50 has better responsiveness than the drying acceleration unit 40 in that the heating element 51 contacts the image recording surface. In this embodiment, the difference in the amount of moisture between the front and back sides of the sheet P is controlled by controlling the heating of the image recording surface of the sheet P by the drying acceleration unit 50. FIGS. 11(A) to 11(C) are flowcharts showing an example of this control. The process in the figures is a control process for the drying acceleration units 40 and 50 executed by the drying control unit 17 in the case of double-sided recording.

[0065] Referring to FIG. 11(A), in S1, drying control of the front surface of the sheet P is executed. FIG. 11(B) is a flow chart thereof. In S11, the ink ejection amount α for forming an image on the front surface of the sheet P is acquired. The ejection amount α may be calculated, for example, by the image processing unit 14 or the head control unit 15, and the calculation result may be acquired by the drying control unit 17. As another example, the drying control unit 17 may calculate the ejection amount α from image data or recording data. The ejection amount α may be calculated, for example, by counting the number of ink ejections actually ejected by the recording head 31. Alternatively, the ejection amount α may be an estimated value calculated from the image data or recording data.

[0066] In S12, the hot air drying conditions are set to predetermined standard values. The hot air drying conditions are driving conditions of the drying acceleration unit 40, for example, at least one of the heat value of the heating element 43 and the air volume of the fan 42. In S13, the drying acceleration unit 40 is driven according to the conditions set in S12, and hot air drying of the sheet P transported to the drying acceleration unit 40 is performed. As a result, hot air is blown onto the image formed on the front surface of the sheet P, promoting drying of the ink. In parallel with the processing of S12, the sheet P is transported to the switchback path RT3 (ST12 in FIG. 8), and then transported to the reversing path RT4 (ST13 in FIG. 9).

[0067] Returning to FIG. 11(A), in S2, drying control of the back surface of the sheet P is executed. FIG. 11(C) is a flow chart thereof. In S21, the ink ejection amount β for forming an image on the back surface of the sheet P is acquired. As with the ejection amount α, the ejection amount β may be calculated, for example, by the image processing unit 14 or the head control unit 15, and the calculation result may be acquired by the drying control unit 17. As another example, the drying control unit 17 may calculate it from image data or recording data. Also, as with the ejection amount α, the ejection amount β may be calculated, for example, by counting the number of ink ejections actually ejected by the recording head 31, or may be an estimated value calculated from the image data or recording data.

[0068] In addition, the ejection amount α and the ejection amount β may be the ink ejection amount for the entire image recorded on the front and back surfaces of the sheet P, or may be the ink ejection amount for the image recorded on the front and back surfaces of a predetermined area of ​​the sheet P.

[0069] In S22, the ink ejection amount α acquired in S11 is compared with the ink ejection amount β acquired in S21, and it is determined whether the difference (β-α) exceeds a threshold value. The threshold value is a value for determining whether the difference will cause a large curl in the sheet P, and can be set by prior experimentation. The threshold value may be a fixed value, or a variable value that changes depending on the recording conditions (e.g., the material and thickness of the sheet P). The threshold value may be 0, in which case only the magnitude relationship between the ink ejection amount α and the ink ejection amount β will be determined.

[0070] If the difference does not exceed the threshold, it is assumed that no significant curl will occur in the sheet P, and the process proceeds to S23. If the difference exceeds the threshold, it is assumed that the amount of ink ejected on the back side of the sheet P is excessive compared to the amount of ink moisture on the front side of the sheet P, and that a significant curl may occur in the sheet P, and the process proceeds to S24.

[0071] In S23, the hot air drying conditions and the heat drying conditions are set to predetermined standard values. The heat drying conditions are driving conditions of the drying promotion unit 50, and are at least one of the heat generation amount of the heating element 54 and the conveying speed of the sheet P (the rotation speed of the roller 56). On the other hand, in S24, the hot air drying conditions are set to a predetermined standard value, but the heat drying conditions are set to a strong value. The strong value is a value at which the degree of heating of the sheet P is increased from the standard value. For example, the heat generation amount of the heating element 54 is increased, or the conveying speed of the sheet P passing through the drying promotion unit 50 is slowed, or both of these are used. The setting of S24 heats the back side of the sheet P more strongly by the drying promotion unit 50 than the setting of S23, and therefore the drying is promoted. This allows the difference in moisture amount between the front and back sides of the sheet P to be within a predetermined range (a range where no large curl occurs).

[0072] In S25, the drying acceleration unit 40 is driven under the conditions set in S23 or S24, and hot air drying is performed on the sheet P transported to the drying acceleration unit 40. As a result, hot air is blown onto the image formed on the back surface of the sheet P, accelerating the drying of the ink. In S26, the drying acceleration unit 50 is driven under the conditions set in S23 or S24, and heat drying is performed on the sheet P transported to the drying acceleration unit 50. As a result, the back surface of the sheet P is heated, accelerating the drying of the ink.

[0073] As described above, according to this embodiment, the difference in moisture amount between the front and back surfaces of the sheet P can be kept within a predetermined range by switching the heating and drying conditions between standard and strong values ​​based on the ink ejection amount α on the front surface and the ink ejection amount β on the back surface of the sheet P. Therefore, curling of the sheet P can be reduced in the case of double-sided printing.

[0074] In this embodiment, two types of values, standard (S23) and strong (S24), can be set as the heat drying conditions, but three or more types of values ​​may be set. For example, three types, standard, medium strong, and strong, may be set, and one of them may be selected depending on the magnitude of the difference between the ink ejection amount α and the ink ejection amount β. The multiple types of heat drying conditions may be defined by a combination of the heat generation amount of the heating element 54 and the conveying speed of the sheet P. For example, the standard setting may be heat generation amount: standard and conveying speed: standard, the medium strong setting may be heat generation amount: strong and conveying speed: standard, and the strong setting may be heat generation amount: strong and conveying speed: slow.

[0075] In this embodiment, the hot air drying conditions are standard in both S23 and S24, but may be changed based on the ink ejection amount α and the ink ejection amount β, as in the case of the heat drying conditions. For example, in S24, a strong value may be set as the hot air drying condition. This setting may be at least one of increasing the heat generation amount of the heating element 43 and increasing the air volume of the fan 42.

[0076] In addition, in this embodiment, the hot air drying conditions for the surface of the sheet P are always set to standard values ​​(S12), but may be changed according to the ink ejection amount α. For example, when the ink ejection amount α is significantly small, the moisture difference between the ink ejection amount α and the ink ejection amount β is expected to be large, so the hot air drying conditions may be set to a weak value. The weak value is a value at which the dryness of the sheet P is weaker than the standard value. For example, the heat generation amount of the heating element 43 may be reduced, or the air volume of the fan 42 may be reduced, or both may be used. Conversely, when the ink ejection amount β is significantly large, the moisture difference between the ink ejection amount α and the ink ejection amount β is expected to be large, so the hot air drying conditions may be set to a strong value. The strong value is a value at which the dryness of the sheet P is stronger than the standard value. For example, the heat generation amount of the heating element 43 may be increased, or the air volume of the fan 42 may be increased, or both may be used.

[0077] Furthermore, in the case of double-sided recording, the heating control of the sheet P in the drying acceleration unit 50 may be performed by keeping the heat generation amount of the heating element 54 constant and changing only the conveying speed of the sheet P (the rotation speed of the roller 56) according to the magnitude of the difference between the ink ejection amount α and the ink ejection amount β. For example, when the difference is large, the conveying speed is relatively slowed down to increase the amount of heat input to the back surface of the sheet P, and when the difference is small, the conveying speed is relatively fasted to reduce the amount of heat input to the back surface of the sheet P while improving the throughput. In the processing example of FIG. 11C, the conveying speed can be set to two types in the processing of S23 and S24, but the present invention is not limited to this, and three or more conveying speeds may be set according to the magnitude of the difference between the ink ejection amount α and the ink ejection amount β.

[0078] Second Embodiment Generally, curling of the sheet P is likely to occur locally, such as at the peripheral edge of the sheet P. Therefore, the process of S24 in the first embodiment may be performed only when there is a high possibility that curling will occur locally on the sheet P. Fig. 12(A) shows an example of the process of S2 in Fig. 11(A) in this embodiment, which is another example of the process example in Fig. 11(C). Below, only the process in the process example in Fig. 12(A) that differs from the process example in Fig. 11(C) will be described.

[0079] In this embodiment, if it is determined in S22 that the difference (β-α) between the ink ejection amount α and the ink ejection amount β exceeds the threshold value, the curl condition is determined in S31. The curl condition is a condition for determining whether or not a curl will occur locally on the sheet P, and in this embodiment, it is determined based on the ink ejection amount on the front and back sides of a specified area of ​​the sheet P. Fig. 12(B) shows an example of an area that is the subject of the determination. In most cases, curling occurs in the peripheral portion of the sheet P due to a difference in moisture amount between the front and back sides of the sheet P. In the example of Fig. 12(B), areas P1 at the four corners of the sheet P are subject to the determination.

[0080] In S31, the ink ejection amount on the front side and the ink ejection amount on the back side in each of the four regions P1 are compared. If the difference between the two in any one of the regions P1 is equal to or greater than a predetermined threshold, it is determined that the curl condition is met (curling may occur).

[0081] In S32, if it is determined in S31 that the curl condition is satisfied, the process proceeds to S24, and if it is determined that the curl condition is not satisfied, the process proceeds to S23. The other processes are the same as those in the process example of FIG.

[0082] According to this embodiment, when it is suspected that curling will occur locally, control (S24) is executed to reduce the difference in moisture amount between the front and back surfaces of the sheet P, so that it is possible to prevent unnecessary changes to the drying control.

[0083] <Third embodiment> As described above, in the configuration example of the recording device 5 of the first embodiment, in the case of double-sided recording, when the difference in the degree of dryness of each side is examined by the combined total of the drying promotion units 40 and 50, the degree of dryness of the front side tends to be higher due to the high degree of hot air dryness (in the case of standard settings). If the ink moisture content of the back side of the sheet P is greater than that of the front side, the image on the front side that was originally planned to be recorded may be swapped with the image on the back side. By swapping, the moisture content of the front side of the sheet P will be greater than that of the back side. However, because the drying ability of the front side is high, the difference in the moisture content between the front and back sides can be kept within a predetermined range with standard settings. Moreover, the opportunities for increasing heating (S24) can be reduced, and power consumption can be reduced.

[0084] 13 is a flowchart showing an example of a process for switching the images recorded on the front and back sides of a sheet P. The switching process in the figure is executed, for example, by the processing unit 10 or the image processing unit 14 before starting recording on the sheet P. In the following description, the image that is initially scheduled to be recorded on the front side of the sheet P is referred to as image A, and the image that is initially scheduled to be recorded on the back side is referred to as image B.

[0085] In S41, the ink ejection amount α of image A to be recorded on the front side of sheet P and the ink ejection amount β of image B to be recorded on the back side are calculated from their image data or recording data. In S42, the ink ejection amount α calculated in S41 is compared with the ink ejection amount β, and if the relationship of threshold value X<β-α≦threshold value Y is satisfied, the process proceeds to S43, and if not, the process ends (the images are not swapped). In S43, the relationship between the front and back sides of sheet P and images A and B is swapped. That is, it is set that image B is recorded on the front side of sheet P and image A is recorded on the back side.

[0086] The threshold values ​​X and Y are set based on the difference in hot air drying capacity for the front and back sides of the sheet P in the standard settings of the drying control. In detail, the threshold value X is a value that can keep the difference in moisture amount between the front and back sides within a predetermined range with the standard settings as long as the value of β-α is equal to or less than the threshold value X. The threshold value Y is a value that can keep the difference in moisture amount between the front and back sides within a predetermined range only with increased heating control by the drying promotion unit 50 when the value of β-α exceeds the threshold value Y.

[0087] 11A to 11C of the first embodiment and the process of Fig. 12A of the second embodiment can be applied even when the images on the front and back sides are swapped by the process of Fig. 13. In this case, the ink ejection amount α is the ink ejection amount for recording image B on the front side of sheet P, and the ink ejection amount β is the ink ejection amount for recording image A on the back side of sheet P. Then, the threshold value Y of S42 in Fig. 13 can be applied as the threshold value for the process of S22.

[0088] In this embodiment, in the case of double-sided recording, if it is expected that the difference in moisture amount between the front and back sides after recording will slightly exceed a predetermined range, the difference in moisture amount can be kept within the predetermined range by switching the images in S43. In this case, it is not necessary to change the setting of the heat drying control. And, if it is expected that the difference in moisture amount between the front and back sides after recording will greatly exceed the predetermined range, the difference in moisture amount can be kept within the predetermined range by changing the setting of the heat drying control in S24.

[0089] In this embodiment, the image replacement process shown in FIG. 13 is used in combination with the setting change (S24) of the heat drying control shown in FIG. 11(C) or FIG. 12(A). However, as a modified example, the setting change of the heat drying control may not be performed (the standard setting is used), and the difference in the moisture amount between the front and back surfaces of the sheet P may be reduced only by the image replacement process shown in FIG. 13. In this case, the process of S42 only needs to determine whether the value of β-α exceeds the threshold value X. According to this modified example, when the difference in the moisture amount of the sheet P is large, the curl of the sheet P may not be reduced, but when the difference in the moisture amount is small, the curl of the sheet P may be reduced. In addition, since there is no need to change the setting of the hot air / heat drying control, it is possible to simplify the process and reduce the power consumption associated with increased heating.

[0090] <Other embodiments> The present invention can also be realized by a process in which a program for realizing one or more functions of the above-mentioned embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0091] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0092] 5 Recording device, 9 Control unit, 20 Transport unit, 30 Recording unit, 40 Drying promotion unit, 50 Drying promotion unit, P sheet

Claims

1. an ejection head that ejects ink onto a recording medium that is transported by a transport unit that transports the recording medium; a first heating means for heating the recording medium onto which the ink is discharged by the discharge head; a second heating means arranged downstream of the first heating means in a conveying direction of the recording medium by the conveying means, the second heating means heating the recording medium; a control unit that controls the amount of heat applied to the recording medium by the second heating unit so that the amount of heat changes based on the amount of ink ejected onto the recording medium, In the case of double-sided recording, in which both sides of the recording medium are recorded, the recording medium is conveyed by the conveying means so that each side of the recording medium is heated by the first heating means, and one side of the recording medium is heated by the second heating means. A recording apparatus comprising:

2. 2. The recording device according to claim 1, The control means changes the amount of heat by changing the output of the second heating means. A recording apparatus comprising:

3. 2. The recording device according to claim 1, the first heating means has an air outlet hole, and heats the recording medium by blowing hot air through the air outlet hole onto the recording medium; A recording apparatus comprising:

4. 2. The recording device according to claim 1, The control means calculates the ink amount based on image data. A recording apparatus comprising:

5. 2. The recording device according to claim 1, the control means calculates the amount of ink by counting the number of ink ejections from the ejection head; A recording apparatus comprising:

6. 3. The recording device according to claim 2, the control means controls an output of the second heating means based on the amount of ink and the type of the recording medium. A recording apparatus comprising:

7. 3. The recording device according to claim 2, The second heating means includes a heating element, The control means controls the output of the second heating means by changing the heat generation amount of the heating element. A recording apparatus comprising:

8. A recording method in a recording device comprising: an ejection head which ejects ink onto a recording medium transported by a transport means which transports the recording medium; a first heating means which heats the recording medium onto which ink has been ejected by the ejection head; and a second heating means which is disposed downstream of the first heating means in a transport direction of the recording medium by the transport means and which heats the recording medium, a control step of controlling the amount of heat applied to the recording medium by the second heating means so that the amount of heat changes based on the amount of ink ejected onto the recording medium; In the case of double-sided recording, in which both sides of the recording medium are recorded, the recording medium is conveyed by the conveying means so that each side of the recording medium is heated by the first heating means, and one side of the recording medium is heated by the second heating means. A recording method comprising:

9. The recording method according to claim 8, In the control step, the amount of heat is changed by changing an output of the second heating means. A recording method comprising:

10. The recording method according to claim 9, the first heating means has an air outlet hole, and heats the recording medium by blowing hot air through the air outlet hole onto the recording medium; A recording method comprising:

11. The recording method according to claim 8, In the control step, the ink amount is calculated based on image data. A recording method comprising:

12. The recording method according to claim 8, In the control step, the amount of ink is calculated by counting the number of ink ejections from the ejection head. A recording method comprising:

13. The recording method according to claim 9, In the control step, an output of the second heating means is controlled based on the amount of ink and the type of the recording medium. A recording method comprising:

14. The recording method according to claim 9, The second heating means includes a heating element, In the control step, the output of the second heating means is controlled by changing the heat generation amount of the heating element. A recording method comprising:

Images