Conveyor device

Abstract

The present application provides a conveying device. In the conveying device, the number of media for correcting curling is suppressed and the media is prevented from contacting the processing unit. The conveying device includes: an adsorption conveying unit having a conveying member for conveying the media and an adsorption unit for causing the conveying member to adsorb the media, and configured to face the processing unit for processing the media; a curling correction unit disposed at a position upstream of the processing unit and the adsorption conveying unit in the conveying direction of the media, and correcting the curling of the media to prevent the front end of the media from contacting the processing unit; and a control unit that controls the curling correction unit to correct the curling of the first medium and omit the curling correction for at least a part of the media after the second medium when the media is continuously conveyed by the adsorption conveying unit.

Description

Technical Field

[0001] The present invention relates to a conveying device. Background Art

[0002] Conventionally, in an image forming apparatus, when printing, it is required to convey a medium such as paper to a printing unit in an appropriate state. For example, in an inkjet type image forming apparatus, when a paper in a curled state (end rising shape) in which the front end portion protrudes more toward the inkjet head side than the central portion in the conveying direction is conveyed to the printing unit, the front end portion of the paper may come into contact with the inkjet head. When the paper comes into contact with the inkjet head, there is a risk of damage to the nozzle portion of the inkjet head or ink stains adhering to the paper.

[0003] In response to this, a method for correcting the curl of paper is known. For example, in order not to correct the curl in thick paper or the like but to correct the curl in plain paper, a paper curl correction device has been proposed. The paper curl correction device includes: a curl correction path having a curl correction mechanism; a path not having a curl correction mechanism; a path switching mechanism that guides the paper to any one of the two paths; and a control mechanism that switches the path switching mechanism according to the setting of each paper feeding mechanism that supplies the paper (for example, refer to Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-247526 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, in a conveying device that conveys a medium such as paper, an adsorption conveying unit that adsorbs the medium may be arranged to face a printing unit that prints on the medium. In the case where the adsorption conveying unit has an attracting portion that attracts the medium and a conveying member such as a conveyor belt that adsorbs the medium by attracting air through the attracting portion, in a state where the first medium among a plurality of continuously conveyed media is conveyed by the conveying member, the suction holes of the conveying member are open without being blocked by the previous medium, so the adhesion force between the conveying member and the medium is small. Therefore, when the medium has the above-described end rising shape, the printing unit may be damaged due to contact between the medium and the printing unit, or ink stains may adhere to the medium. It should be noted that in the case where another processing unit such as an inspection unit is arranged to face the adsorption conveying unit, there is also a risk of damage to a processing unit other than the printing unit. In addition, the same problem occurs when the medium is adsorbed to the conveying member by an adsorption method other than suction adsorption using an attracting portion that attracts air in the adsorption conveying unit, such as electrostatic adsorption.

[0009] On the other hand, in a state where the medium is conveyed by the conveying member after the second sheet, since the suction holes of the conveying member are blocked by the previous medium, breakage of the above-described processing unit is less likely to occur.

[0010] It should be noted that, for example, a curl correction unit for correcting the curl of the medium sandwiches the medium using a pair of a soft roller and a hard roller to correct the curl of the medium. However, when correcting the curl of the medium by such a pair of rollers, wrinkles extending in the conveying direction may be generated on the medium, or image unevenness may be generated due to fluctuations in the conveying speed. In addition, the portions at the widthwise ends of the soft roller that sandwich the medium are worn. When the soft roller is worn, the curl correction effect is reduced. Further, in the conveyance of the medium by a soft roller such as this, the rotational resistance of the roller is large, and the power consumption of the apparatus becomes large.

[0011] An object of the present invention is to provide a conveying device that can prevent the medium from coming into contact with the processing unit while suppressing the number of media whose curls are corrected.

[0012] Means for Solving the Problem

[0013] In one aspect, a conveying device includes: an adsorption conveyance unit having a conveying member for conveying a medium and an adsorption unit for causing the conveying member to adsorb the medium, the adsorption conveyance unit being disposed to face a processing unit that processes the medium; a curl correction unit disposed at a position upstream of the processing unit and the adsorption conveyance unit in the conveying direction of the medium, and correcting the curl of the medium to prevent the front end of the medium from coming into contact with the processing unit; and a control unit that controls the curl correction unit such that, when the medium is continuously conveyed by the adsorption conveyance unit, the curl of the first sheet of the medium is corrected, and the curl correction of at least a part of the second sheet and subsequent sheets of the medium is omitted.

[0014] Advantages of the Invention

[0015] According to the above aspect, it is possible to prevent the medium from coming into contact with the processing unit while suppressing the number of media whose curls are corrected. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a diagram showing a schematic configuration of an image forming apparatus including a conveying device according to one embodiment.

[0017] Figure 2 FIG. is an enlarged view of a part of a curl correction unit and the like in an image forming apparatus according to one embodiment.

[0018] Figure 3 FIG. is a diagram showing a control configuration of an image forming apparatus according to one embodiment.

[0019] Figure 4A It is a cross-sectional view of the crimping state showing the operation of the curl correction unit in one embodiment.

[0020] Figure 4B It is a cross-sectional view of the separation state showing the operation of the curl correction unit in one embodiment.

[0021] Figure 5A It is a diagram showing the crimping state with respect to the first sheet in the operation of the curl correction unit in one embodiment.

[0022] Figure 5B It is a diagram showing the separation state with respect to the sheets after the second sheet in the operation of the curl correction unit in one embodiment.

[0023] Figure 6 It is a diagram showing the operation of the curl correction unit during double-sided printing of sheets in one embodiment.

[0024] Figure 7 It is a diagram showing the operation of the curl correction unit when the width of the continuously conveyed sheet widens midway in one embodiment.

[0025] Explanation of reference numerals

[0026] 10: Image forming apparatus;

[0027] 11: Sheet feeding unit;

[0028] 13: Printing unit;

[0029] 14: Inkjet head;

[0030] 15: Sheet discharging unit;

[0031] 16: Under-head conveying unit (adsorption conveying unit);

[0032] 17: Conveyor belt;

[0033] 17a: Conveying surface;

[0034] 22: Suction fan (adsorption unit);

[0035] 30: Diagonal correction conveying device;

[0036] 31: First roller;

[0037] 32: Second roller;

[0038] 34: Sheet contact portion;

[0039] 36: Sheet adsorption guide roller;

[0040] 37: Sheet floating detection device;

[0041] 40: Curling correction unit;

[0042] 41: First roller;

[0043] 42: Second roller;

[0044] 44: Paper contact part;

[0045] 50: Control unit;

[0046] P: Paper (medium);

[0047] T1: Paper supply side conveying path;

[0048] T2: Circulation conveying path;

[0049] T3: Paper discharge side conveying path. Detailed implementation mode

[0050] Hereinafter, a conveying device according to an embodiment of the present invention will be described with reference to the drawings.

[0051] Figure 1 is a diagram showing a schematic structure of an image forming apparatus 10 including a conveying device according to an embodiment of the present invention.

[0052] Figure 2 is an enlarged view showing a part of the curling correction unit 40 and the like of the image forming apparatus 10.

[0053] Figure 3 is a diagram showing a control structure of the image forming apparatus 10.

[0054] The image forming apparatus 10 is an inkjet printing apparatus that ejects ink from an inkjet head 14 of a printing unit 13 onto a paper P as an example of a medium to perform printing. Figure 1 The double-dashed line in indicates the conveyance path of the paper P in the image forming apparatus 10, and a plurality of rollers and the like are provided along the conveyance path to convey the paper P. The image forming apparatus 10 includes Figure 3 the control unit 50 shown below, and the conveyance, curling correction, printing, and other operations of the paper P described below are performed based on the control of the control unit 50.

[0055] As Figure 1 shown, the image forming apparatus 10 includes a paper supply unit 11, and unprinted papers P are stacked on a paper supply tray (not shown) provided in the paper supply unit 11. When printing is performed, the paper P is sent from the paper supply unit 11 to the circulation conveyance path T2 via the paper supply side conveyance path T1. The circulation conveyance path T2 is formed in a ring shape, and the paper P can be conveyed in the reverse direction by the reversing unit 12 to reverse the front and back sides.

[0056] Inside the image forming apparatus 10, a printing unit 13 is provided for performing printing processing on the sheet P fed to the circulation conveyance path T2. The printing unit 13 includes a plurality of inkjet heads 14, and ink is ejected from each inkjet head 14 onto the sheet P conveyed on the circulation conveyance path T2 to perform printing. By reversing the travel direction of the sheet P by means of the reversing unit 12 in the middle of the circulation conveyance path T2, printing can be performed on both the front and back sides of the sheet P.

[0057] Below the inkjet head 14, a sub-head conveyance unit 16 is arranged to face the inkjet head 14 (printing unit 13). The sheet P is adsorbed and held by the sub-head conveyance unit 16 and conveyed at a predetermined speed, and ink is ejected from the inkjet head 14 to perform printing. The width direction of the sheet P conveyed by the sub-head conveyance unit 16 is defined as the main scanning direction F1 (refer to Figure 6 and Figure 7 ), and the conveyance direction of the sheet P perpendicular to the main scanning direction F1 is defined as the sub-scanning direction F2. The side where the paper feed side conveyance path T1 (paper feed unit 11) is located in the sub-scanning direction F2 is defined as the upstream side of sheet conveyance, and the side where the paper discharge side conveyance path T3 (paper discharge unit 15) is located is defined as the downstream side of sheet conveyance. It should be noted that the printing unit 13 is an example of a processing unit for processing the sheet P. As this processing unit, it can also be an inspection unit for inspecting the sheet P, etc.

[0058] The sub-head conveyance unit 16 includes a conveyor belt 17, a belt drive roller 18, and a plurality of driven rollers 19, 20, 21.

[0059] The conveyor belt 17 is an annular (loop) belt-like body stretched between the belt drive roller 18 and the plurality of driven rollers 19, 20, 21, and a substantially horizontal conveyance surface 17a is formed between the belt drive roller 18 and the driven roller 19. The conveyance surface 17a forms a part of the circulation conveyance path T2, and the sheet P fed from the paper feed side conveyance path T1 is placed on the conveyance surface 17a.

[0060] The belt drive roller 18 is driven to rotate by the Figure 3 shown belt drive unit 51. The belt drive unit 51 includes a motor as an example of an actuator, a transmission mechanism for transmitting the driving force of the motor to the belt drive roller 18, and the like. When the belt drive roller 18 rotates, the driving force is transmitted to the conveyor belt 17, and the conveyor belt 17 rotates while being guided by the driven rollers 19, 20, 21, causing the sheet P on the conveyance surface 17a to move from the upstream side to the downstream side in the sub-scanning direction F2. The driven rollers 19, 20, 21 rotate following the belt drive roller 18 via the conveyor belt 17.

[0061] A plurality of suction holes (not shown) penetrating the front and back surfaces are formed in the conveyor belt 17. The under-head conveying unit 16 is provided with a suction fan 22 below the conveying surface 17a between the belt driving roller 18 and the driven roller 19. The suction fan 22 is Figure 3 driven to rotate by the fan driving unit 52 shown, and an air flow from above toward below is generated by the rotation of the suction fan 22. When the suction fan 22 is rotated, a force (negative pressure) for sucking air from the space above the conveying surface 17a through the plurality of suction holes is generated, and the paper P is adsorbed and held on the conveying surface 17a by the negative pressure acting on the suction holes. By driving the belt driving roller 18 to rotate while driving the suction fan 22, the paper P can be conveyed while being adsorbed and held on the conveying surface 17a.

[0062] Here, the under-head conveying unit 16 is an example of an adsorption conveying unit, which includes a conveyor belt 17 as an example of a conveying member for conveying the paper P and a suction fan 22 as an example of an adsorption unit for adsorbing the paper P to the conveyor belt 17. The adsorption conveying unit is arranged to face a processing unit (printing unit 13) that processes the paper P. It should be noted that the adsorption unit is preferably an adsorption unit such as a suction fan 22 that sucks air, but other adsorption methods such as electrostatic adsorption can also be used.

[0063] The flap 23 provided on the downstream side of the under-head conveying unit 16 switches whether the paper P circulates in the circulation conveying path T2 or moves to the paper discharge side conveying path T3. The printed paper P in the printing unit 13 is sent to the paper discharge side conveying path T3 continuous with the circulation conveying path T2. A paper discharge unit 15 is arranged at the outlet portion of the paper discharge side conveying path T3, and a paper discharge tray (not shown) provided in the paper discharge unit 15 recovers the printed paper P.

[0064] It should be noted that Figure 1 only one paper supply side conveying path T1 and one paper discharge side conveying path T3 are shown respectively, but it is also possible to have a plurality of paper supply side conveying paths and a plurality of paper discharge side conveying paths connected to the circulation conveying path T2. For example, it can also be configured to provide a plurality of paper supply trays corresponding to a plurality of paper sizes, and the plurality of paper supply side conveying paths corresponding to each paper supply area merge midway.

[0065] As Figure 2As shown in the figure, it can be said that the skew correction conveying device 30 located on the upstream side in the sub-scanning direction F2 constitutes the upstream conveying mechanism, and the under-head conveying unit 16 (conveyor belt 17) located on the downstream side constitutes the downstream conveying mechanism. In addition, these upstream and downstream conveying mechanisms function as part of the conveying device. The conveying device only needs to include, for example, an adsorption conveying unit such as the under-head conveying unit 16, a curl correction unit 40, and a control unit 50. In addition, the conveying device is integrally provided in the image forming apparatus 10 and includes a control unit 50 that controls the overall operation of the image forming apparatus 10, but it may also include a control unit that only controls the operation of the conveying device (at least the curl correction unit 40). In addition, the conveying device may not be integrally provided in the image forming apparatus 10, but may be arranged as a single unit, or integrally provided in other parts such as an inspection device.

[0066] As Figure 2 shown, a skew correction conveying device 30 for conveying the paper after correcting the skew of the paper P is arranged on the upstream side of the under-head conveying unit 16. A paper guiding unit 25A, 25B for guiding the paper P to the skew correction conveying device 30 is arranged near the skew correction conveying device 30. The paper P sent from the paper feeding unit 11 along the paper feeding side conveying path T1 passes between the paper guiding units 26A, 26B and between the paper guiding units 25A, 25B and is guided to the skew correction conveying device 30. In addition, the paper P circulating in the circulation conveying path T2 passes between the paper guiding units 27A, 27B and between the paper guiding units 25A, 25B and is guided to the skew correction conveying device 30.

[0067] The skew correction conveying device 30 is composed of a pair of rollers (positioning rollers) separately arranged above and below the paper conveying path (circulation conveying path T2). More specifically, the skew correction conveying device 30 includes a first roller 31 located above and a second roller 32 located below. The first roller 31 has a paper contact portion 34 with a diameter larger than that of the shaft portion 33 on the outer diameter side of the shaft portion 33 extending in the main scanning direction F1. Although not shown, a plurality of such paper contact portions 34 are arranged at a predetermined interval in the main scanning direction F1.

[0068] The outer peripheral surface of the second roller 32 contacts the outer peripheral surface of the paper contact portion 34. The second roller 32 is formed of a harder material than the paper contact portion 34. The materials of the second roller 32 and the paper contact portion 34 can be arbitrarily selected. As an example, the paper contact portion 34 can be made of rubber and the second roller 32 can be made of metal.

[0069] The first roller 31 and the second roller 32 are respectively supported so as to be rotatable about an axis facing the main scanning direction F1, and are Figure 3It is rotated by the positioning roller driving unit 53 shown. The positioning roller driving unit 53 is composed of a motor as an example of an actuator, a transmission mechanism for transmitting the driving force of the motor, etc., and rotates the first roller 31 and the second roller 32 at the same speed.

[0070] When printing is performed in the printing unit 13, the control unit 50 controls the rotation and stop of the first roller 31 and the second roller 32 through the positioning roller driving unit 53. The rotation directions of the first roller 31 and the second roller 32 when being driven are the forward conveying direction for moving the paper P from the upstream side to the downstream side.

[0071] More specifically, when guiding the paper P along the paper guiding portions 25A and 25B to the skew correction conveying device 30, the control unit 50 stops the rotation of the first roller 31 and the second roller 32. The front end of the paper P abuts against the first roller 31 (paper contact portion 34) and the second roller 32 in the stopped state, and the paper P is slack. When the paper P in a state inclined with respect to the standard paper conveying direction (sub-scanning direction F2) reaches the skew correction conveying device 30, the paper P whose progress is restricted by the stopped first roller 31 and second roller 32 is pressed from behind, so that the front end of the paper P is parallel to the axial directions of the first roller 31 and the second roller 32. That is, the skew of the paper P is corrected.

[0072] Next, at a predetermined time point when the skew correction is completed, the control unit 50 controls the positioning roller driving unit 53 to drive the first roller 31 and the second roller 32 to rotate. The paper P after skew correction enters between the driven-rotating first roller 31 (paper contact portion 34) and the second roller 32, and the paper P is conveyed downstream by the frictional force generated by the first roller 31 and the second roller 32. Immediately after the conveyance of the paper P downstream is completed, the control unit 50 controls the positioning roller driving unit 53 to stop the rotation of the first roller 31 and the second roller 32, and prepares for the skew correction of the next paper P to be conveyed to the skew correction conveying device 30. In this way, after the skew correction conveying device 30 corrects the skew of the paper P, the paper P is conveyed to the head-down conveying unit 16 located on the downstream side of the skew correction conveying device 30.

[0073] It should be noted that the control unit 50 has a processor (such as a CPU: Central Processing Unit) that functions as an arithmetic processing device for controlling the overall operation of the image forming apparatus 10, and controls each part of the image forming apparatus 10. As described above, the control unit 50 also functions as a control unit for at least controlling the conveying device of the curl correction unit 40. In addition, the control unit 50 determines the number of cycles and the presence or absence of cycles of the medium M in the skew correction conveying device 30, and controls the flap 23 and the like.

[0074] The storage unit 55 includes, for example, a ROM (Read Only Memory), which is a read-only semiconductor memory with a predetermined control program pre-recorded therein, and a RAM (Random Access Memory), which is a semiconductor memory that can be written to and read from at any time and is used as a working storage area as needed when the processor executes various control programs, and other memories.

[0075] The interface unit 56 transmits and receives various information to and from external devices. For example, the interface unit 56 receives a printing job (printing data) from a user terminal.

[0076] In addition, the image forming apparatus 10 may include a scanner that reads an image of an original, an input unit that accepts various operations by a user (e.g., setting of skew correction), and an operation panel that functions as an example of a display unit.

[0077] As Figure 2 shown, a sheet adsorption guide roller 36 that constitutes a downstream conveyance mechanism together with the under-head conveyance unit 16 is provided near the driven roller 19 of the under-head conveyance unit 16. The sheet adsorption guide roller 36 is located directly above the conveyance surface 17a of the conveyor belt 17 and functions as a sheet guide that easily presses and adsorbs and holds the sheet P toward the conveyance surface 17a side.

[0078] The sheet P that has reached the printing unit 13 through the diagonal correction conveyance device 30 is conveyed below the inkjet head 14 while being in close contact with the conveyance surface 17a without floating upward. In particular, when the sheet P has a curl in which the front end (front portion) in the sub-scanning direction F2 protrudes more upward than the central portion, forming an end-rising shape (a downward convex shape when the sheet P is viewed from the side), the front end of the sheet P that has floated up from the conveyance surface 17a may come into contact with the inkjet head 14. In this case, there is a risk of damage to the head surface of the inkjet head 14 that comes into contact with the sheet P, or ink adhering to the sheet P from the inkjet head 14 and contaminating the sheet P.

[0079] As Figure 2As shown, a paper floating detection device 37 is disposed on the downstream side of the paper adsorption guide roller 36 and on the upstream side of the inkjet head 14. The paper floating detection device 37 is composed of a known sensor or the like located above the conveying surface 17a, and detects the floating of the paper P from the conveying surface 17a. A detection signal from the paper floating detection device 37 is input to the control unit 50. When the floating of the paper P from the conveying surface 17a is detected via the paper floating detection device 37, the control unit 50 stops the conveyance of the paper P and performs preventive processing such as bringing the paper P into contact with the inkjet head 14 and preventing paper jams of the paper P. However, when the paper conveyance is at high speed, it is difficult to stop the paper P in the floating state before it reaches the inkjet head 14. In addition, when the printing is stopped every time the floating of the paper P is detected, the printing efficiency deteriorates.

[0080] In order to make it difficult for the paper P to float from the conveying surface 17a, the image forming apparatus 10 of the present embodiment includes a curl correction unit 40 that corrects curls such as the upward shape of the end portion of the paper P. The curl correction unit 40 is disposed at a position upstream of the printing unit 13 and the under-head conveyance unit 16 in the conveyance direction (sub-scanning direction F2) of the paper P, and corrects the curl of the paper P to prevent the front end of the paper P from coming into contact with the processing unit.

[0081] The curl correction unit 40 gives the paper P a shape in which the end portion in the sub-scanning direction F2 is lower than the central portion, thereby preventing the curl of the end portion rising shape that is likely to come into contact with the inkjet head 14.

[0082] The curl correction unit 40 is composed of a pair of rollers (decurling rollers) separately disposed on both sides of the paper conveyance path (circulation conveyance path T2). More specifically, the curl correction unit 40 has a first roller 41 located above and a second roller 42 located below.

[0083] The first roller 41 has a paper contact portion 44 having a diameter larger than that of the shaft portion 43 on the outer diameter side of the shaft portion 43 extending in the main scanning direction F1. Although not shown, a plurality of paper contact portions 44 are arranged at a predetermined interval in the main scanning direction F1. The paper contact portion 44 is formed of a soft material (such as an elastic body like sponge) that can be elastically deformed. The second roller 42 is a cylindrical shaft member having a diameter smaller than that of the paper contact portion 44 of the first roller 41, and is formed of a material (such as metal) harder than the paper contact portion 44. That is, the paper contact portion 44 constitutes the soft portion in the curl correction unit 40, and the second roller 42 constitutes the hard portion in the curl correction unit 40.

[0084] The first roller 41 is capable of performing an operation of changing the axial distance (approaching and separating) relative to the second roller 42. When the first roller 41 approaches the second roller 42, depending on the difference in hardness and diameter between the paper contact portion 44 and the second roller 42 (the second roller 42 is harder and has a smaller diameter), the second roller 42 enters a position inside the outer shape of the paper contact portion 44 in the free state (initial state), and the paper contact portion 44 is pressed into the inner diameter side (shaft portion 43 side) by the second roller 42 and becomes a crimped state after elastic deformation ( Figure 4A ). When the first roller 41 is separated from the second roller 42, the pressing of the second roller 42 on the paper contact portion 44 is released, and it becomes a separated state in which the deformation of the paper contact portion 44 is released ( Figure 4B ).

[0085] The first roller 41 and the second roller 42 are each supported so as to be rotatable about an axis oriented in the main scanning direction F1, and are driven to rotate by the Figure 3 shown uncurling roller drive unit 54. The uncurling roller drive unit 54 is composed of a motor as an example of an actuator, a transmission mechanism for transmitting the driving force of the motor, etc., and rotates the first roller 41 and the second roller 4 at the same speed. In addition, the uncurling roller drive unit 54 moves the curling correction unit 40 between a crimped state ( Figure 4A ) and a separated state ( Figure 4B ).

[0086] When printing is performed in the printing unit 13, the control unit 50 controls the uncurling roller drive unit 54 to make the curling correction unit 40 enter a crimped state, and drives the first roller 41 and the second roller 42 to rotate through the uncurling roller drive unit 54. The rotation directions of the first roller 41 and the second roller 42 at this time are the forward conveying direction for moving the paper P from the upstream side to the downstream side.

[0087] When the paper P passes between the driven-rotating first roller 41 (paper contact portion 44) and the second roller 42, the paper P is shaped so as to be a convex shape facing upward along the outer surface of the hard second roller 42 (refer to Figure 4A ). Therefore, the paper P conveyed from the curling correction unit 40 toward the printing unit 13 travels in a state where the front end portion in the sub-scanning direction F2 does not face upward (does not become an end-rising shape) and curling is suppressed, and reaches the position of the head-under conveying unit 16. The paper P that reaches the head-under conveying unit 16 is pressed against the conveying surface 17a of the conveyor belt 17 by the paper adsorption guide roller 36, and is conveyed downstream while being adsorbed by the conveyor belt 17. Then, the inkjet head 14 ejects ink onto the paper P held on the conveying surface 17a to perform printing. It should be noted that when correcting the curling of the paper P, when the front end of the paper P passes through the curling correction unit 40, the curling correction unit 40 is operated in a crimped state ( Figure 4A) is sufficient. However, when the curling correction unit 40 moves from the crimping state ( Figure 4A ) to the separated state ( Figure 4B ) during the conveyance of a sheet of paper P, wrinkles may occur in the paper P.

[0088] For the paper P with the curling whose end rising shape is suppressed by the curling correction unit 40, the front end in the sub-scanning direction F2 does not float from the conveyor belt 17 and come into contact with the inkjet head 14, and is conveyed by the conveyor belt 17 while being appropriately held on the conveying surface 17a. Thereby, damage to the inkjet head 14 or ink contamination of the paper P is not caused, and printing can be performed with excellent printing quality.

[0089] When the paper conveyance speed of the diagonal correction conveyance device 30 is set to V1 and the paper conveyance speed of the under-head conveyance unit 16 is set to V2, the control unit 50 controls the driving of the positioning roller driving unit 53 and the belt driving unit 51 during the printing operation so that V1 > V2.

[0090] Although it also depends on the type of the paper P, the distance from the diagonal correction conveyance device 30 to the conveyor belt 17 in the sub-scanning direction F2 is smaller than the length of the general paper P used in the image forming apparatus 10. Therefore, the paper P reaches the conveying surface 17a of the conveyor belt 17 while maintaining the state of being clamped between the first roller 31 (paper contact portion 34) and the second roller 32 of the diagonal correction conveyance device 30. Here, when V1 < V2, the paper P is sharply stretched by the conveyor belt 17, so that the conveyance accuracy of the paper P becomes unstable, and there is a risk of print misregistration and uneven printing. In contrast, by setting V1 > V2, the conveyance of the paper P from the diagonal correction conveyance device 30 to the under-head conveyance unit 16 is stable, and the movement of the paper P that deteriorates the printing quality can be prevented.

[0091] When V1 > V2 is set, the paper conveyance amount based on the diagonal correction conveyance device 30 per unit time is larger than the paper conveyance amount based on the under-head conveyance unit 16 per unit time. Due to this difference in the paper conveyance amount, slack of the paper P is generated between the diagonal correction conveyance device 30 and the under-head conveyance unit 16. In other words, it is necessary to appropriately slack the paper P between the diagonal correction conveyance device 30 and the under-head conveyance unit 16. For example, if the structure hinders the slack of the paper P conveyed from the diagonal correction conveyance device 30, the paper P cannot smoothly travel toward the printing unit 13, or the paper P is bent.

[0092] The image forming apparatus 10 includes a curling correction unit 40 as a curling suppression conveyance mechanism between the diagonal correction conveyance device 30 as an upstream-side conveyance mechanism and the under-head conveyance unit 16 and the paper adsorption guide roller 36 as downstream-side conveyance mechanisms. As Figure 2As shown, in the sub-scanning direction F2 which is the paper conveyance direction, the curl correction unit 40 is located near the downstream side adjacent to the skew correction conveyance device 30. More specifically, a part of the paper contact portion 34 in the skew correction conveyance device 30 and the paper contact portion 44 in the curl correction unit 40 are in a positional relationship of overlapping in the sub-scanning direction F2 which is the paper conveyance direction.

[0093] When the curl amount of the end of the paper P in the main scanning direction F1 exceeds 2 mm and protrudes from the reference position of the paper surface, the paper P is guided by the paper guide portions 25A and 25B, and thus is conveyed to the curl correction unit 40 in a state where the protrusion amount is 2 mm. In the curl correction unit 40, if the crimping area of the first roller 41 and the second roller 42 with respect to the paper P is spaced 2 mm from the end of the paper width, even if the paper P is in a state where the protrusion amount is 2 mm, the end of the paper width will not be crimped, so that wear of the first roller 41 and the second roller 42 can be prevented. Therefore, in the curl correction unit 40, by setting a blank of 2 mm from the end of the paper width for crimping, wear of the rollers 41 and 42 can be prevented, and a practically sufficient curl suppression effect can be obtained.

[0094] Regarding the operation of the image forming apparatus 10, matters that are repetitive to the above description will be appropriately omitted from the description.

[0095] First, when the control unit 50 is input with an instruction to execute a printing job, it determines whether the curl correction unit 40 is in a separated state. When the curl correction unit 40 is in a separated state, the control unit 50 instructs the de-curling roller drive unit 54 to move the first roller 41 closer to the second roller 42, so that the curl correction unit 40 becomes a crimped state. On the other hand, when the curl correction unit 40 is in a crimped state, the control unit 50 instructs the de-curling roller drive unit 54 to drive the first roller 41 and the second roller 42 to rotate, so that the curl correction unit 40 performs preliminary rotation.

[0096] Then, the control unit 50 performs a paper conveyance operation of conveying the paper P from the paper supply unit 11 to the printing unit 13 and a printing process in the printing unit 13.

[0097] The paper conveyance operation is performed by the driving rotation of the first roller 31 and the second roller 32 by the positioning roller driving unit 53 (repeated skew correction in the roller stopped state and roller driving after skew correction), the driving rotation of the first roller 41 and the second roller 42 by the de-curling roller driving unit 54, the driving rotation of the conveyor belt 17 by the belt driving unit 51, etc. In addition, the control unit 50 drives the suction fan 22 by the fan driving unit 52, and conveys the paper P while sucking and holding it on the conveying surface 17a of the conveyor belt 17. The printing process is performed by ejecting ink from the inkjet head 14 onto the paper P conveyed on the conveying surface 17a based on a printing job. The printed paper P is conveyed to the paper discharge unit 15 and recovered.

[0098] Here, in the case of conveying a plurality of sheets of paper P for a single printing job, in the case of continuously executing a plurality of printing jobs, etc., the paper P is continuously conveyed by the under-head conveying unit 16. It should be noted that the case where the paper P is continuously conveyed is, for example, the case where the under-head conveying unit 16 simultaneously conveys at least the rear end of the previous paper P and at least the front end of the subsequent paper P.

[0099] When the paper P is continuously conveyed by the under-head conveying unit 16, as Figure 5A shown, when the first sheet of paper P1 enters the conveying surface 17a of the conveyor belt 17, the suction holes of the conveyor belt 17 are not blocked by the previous paper P and are open. Therefore, when the adhesion force between the conveyor belt 17 and the first sheet of paper P1 becomes small and the first sheet of paper P1 becomes the above-mentioned end-rising shape, the first sheet of paper P1 comes into contact with the inkjet head 14 (printing unit 13), causing damage to the inkjet head 14 or ink stains adhering to the first sheet of paper P1.

[0100] In response to this, when the first sheet of paper P1 passes through the curling correction unit 40, the control unit 50 preferably instructs the de-curling roller driving unit 54 to move the first roller 41 closer to the second roller 42 as described above, so that the curling correction unit 40 becomes a crimped state, that is, the curling correction unit 40 is controlled to correct the curling of the first sheet of paper P1.

[0101] On the other hand, as Figure 5B shown, when the second sheet (the second sheet and subsequent sheets) of paper P2 enters the conveying surface 17a of the conveyor belt 17, at least a part of the suction holes of the conveyor belt 17 is blocked by the previous first sheet of paper P1. Therefore, the adhesion force between the conveyor belt 17 and the second sheet of paper P2 becomes large, and even if the curling is not corrected, there is less risk of damage to the inkjet head 14 or ink stains adhering to the second sheet of paper P2 due to the contact between the second sheet of paper P2 and the inkjet head 14 (printing unit 13).

[0102] Therefore, the control unit 50 preferably controls the de-curling roller driving unit 54 (curling correction unit 40) to omit curling correction for the sheets P after the second sheet P2. It should be noted that, for example, a mode in which curling correction for the sheets P after the second sheet is omitted when the sheet P is continuously conveyed by the under-head conveyance unit 16, a mode in which curling correction is performed for all the sheets P, and a mode in which curling correction for all the sheets P is omitted can be set in the printing operation or the operation panel of the image forming apparatus 10. In this case, the control unit 50 controls the curling correction unit 40 based on the set mode.

[0103] It should be noted that, as Figure 6 shown, in the case of performing double-sided printing on the sheet P, after printing the front side of the sheet P, the sheet P is conveyed in the Figure 1 shown circulation conveyance path T2, and the front and back sides are reversed by the reversing unit 12, so that there is a case where it is conveyed to the printing unit 13 again, for example, at an interval of four sheets P. In such a case, sometimes there is an interval of more than the amount of one sheet P between the time of printing the front side of the first sheet P ( Figure 6 one positive) and the time of printing the front side of the second sheet P (two positives), or between the time of printing the front side of the second sheet P (two positives) and the time of printing the front side of the third sheet P (three positives). Therefore, when printing the front side of the first sheet P (one positive) and when printing the front side of the second sheet P (two positives), it can be said that the sheet P is continuously conveyed by the under-head conveyance unit 16. Therefore, it is preferable that when printing the front sides of the first to third sheets P (one positive, two positives, and three positives), the control unit 50 controls (turns on) the curling correction unit 40 to correct the curling of the sheet P.

[0104] In addition, the control unit 50 may not omit the curl correction for all the sheets P after the second sheet continuously conveyed by the under-head conveying unit 16. For example, based on the type such as the thickness and material of the sheet P, the control unit 50 may determine the sheets P for which curl correction is to be performed and the sheets P for which curl correction is to be omitted. Alternatively, for the last sheet P continuously conveyed by the under-head conveying unit 16, since no subsequent sheet P is conveyed, especially when the front end comes out of the conveying surface 17a of the conveyor belt 17, the suction holes of the conveyor belt 17 are not blocked and are open, so that the adhesion force between the conveyor belt 17 and the last sheet P becomes smaller. Therefore, it is preferable to perform curl correction on the last sheet P continuously conveyed by the under-head conveying unit 16. However, since the sheet P adsorbed on the conveyor belt 17 is difficult to float, the last sheet P has a lower possibility of contacting the inkjet head 14 than the first sheet P. In addition, when the rear end of the last sheet P reaches around the middle position of the conveying surface 17a, as described above, the suction holes of the conveyor belt 17 are not blocked and are open, so that the suction force becomes weak, but at this time, the front end of the last sheet P is about to fall off from the conveying surface 17a. Therefore, the curl correction of the last sheet P may be omitted.

[0105] In addition, as Figure 7 shown, when the width in the width direction (main scanning direction F1) orthogonal to the conveying direction (sub-scanning direction F2) of the first to third sheets P is relatively narrow and the width of the fourth to sixth sheets P is relatively wide, even for the sheets P after the second sheet continuously conveyed, the width of the fourth sheet P (four-wide) is wider than the width of the previous sheet P (three-narrow) conveyed. Therefore, when entering the conveying surface 17a of the conveyor belt 17, compared with the case of continuously conveying sheets P of the same width, the suction holes of the conveyor belt 17 are open, and the adhesion force between the conveyor belt 17 and the fourth sheet P (four-wide) is likely to become smaller. Therefore, in such a case, the control unit 50 may control (turn on) the curl correction unit 40 to correct the curl of the fourth sheet P (four-wide).

[0106] When the printing operation is completed, the control unit 50 instructs the de-curling roller driving unit 54 to separate and move the first roller 41 from the second roller 42, so that the curl correction unit 40 is in a separated state. By making the curl correction unit 40 in a separated state in this way, after the printing is completed, the paper contact portion 44 is not pressed by the second roller 42 and is released, and deformation (permanent deformation) of the paper contact portion 44 can be prevented. It should be noted that due to a power outage or the like during the printing operation, it is also possible that the curl correction unit 40 remains in a crimped state and the printing stops. In this case, the paper contact portion 44 is in a state of being continuously pressed by the second roller 42 and deformed ( Figure 4A)。Here, when the preliminary rotation of the curl correction unit 40 is performed as described above before the execution of the next printing operation, the deformation of the paper contact portion 44 is flattened and a restoration action close to the original shape occurs. Assuming that paper conveyance is performed in a state where a concave permanent deformation has occurred in a part of the paper contact portion 44, the paper P cannot pass smoothly through the curl correction unit 40, and the paper conveyance accuracy decreases. In contrast, by the preliminary rotation of the curl correction unit 40, the shape of the paper contact portion 44 is restored, thereby preventing the decrease in paper conveyance accuracy.

[0107] It should be noted that although in the above description, the curl correction unit 40 constituted by a pair of rollers that sandwich the paper P from both sides is used, the structure of the curl correction unit 40 is not limited thereto. For example, a combination of a conveyor belt and a roller that presses the paper against the conveyor belt may be used instead of the curl correction unit 40 constituted by a pair of rollers.

[0108] In the present embodiment described above, the conveyance device includes a head-down conveyance unit 16 (an example of an adsorption conveyance unit), a curl correction unit 40, and a control unit 50. The head-down conveyance unit 16 has a conveyor belt 17 (an example of a conveyance member) that conveys the paper P (an example of a medium) and a suction fan 22 (an example of an adsorption unit) that adsorbs the paper P to the conveyor belt 17, and is arranged to face a printing unit 13 (an example of a processing unit) that performs printing (an example of a process) on the paper P. The curl correction unit 40 is arranged at a position upstream of the printing unit 13 and the head-down conveyance unit 16 in the conveyance direction (sub-scanning direction F2) of the paper P, and corrects the curl of the paper P to prevent the front end of the paper P from contacting the printing unit 13. When the paper P is continuously conveyed by the head-down conveyance unit 16, the control unit 50 controls the curl correction unit 40 to correct the curl of the first sheet of paper P and omit the curl correction for at least a part of the second and subsequent sheets of paper P.

[0109] However, in a state where the first sheet P among a plurality of continuously conveyed sheets P is conveyed by the conveyor belt 17 (an example of a conveying member), for example, in the case of performing suction based on air, the suction holes of the conveyor belt 17 are not blocked by the previous sheet P and are open, so the adhesion force between the conveyor belt 17 and the sheet P is small. Therefore, when the sheet P is curled (for example, an end rising shape), the printing unit 13 may be damaged due to contact between the sheet P and the printing unit 13, or ink stains may adhere to the sheet P. On the other hand, in a state where the second and subsequent sheets P are conveyed by the conveyor belt 17, the suction holes of the conveyor belt 17 are blocked by the previous sheet P, so it is not easy to cause the above-mentioned damage to the printing unit 13. Therefore, it is possible to omit curl correction for the second and subsequent sheets P. It should be noted that the same can be said when the suction unit adsorbs the sheet P to the conveyor belt 17 by other suction methods such as electrostatic adsorption instead of the suction fan 22 and other suction units that suck air. Therefore, according to the present embodiment, it is possible to prevent the sheet P (an example of a medium) from contacting the printing unit 13 (an example of a processing unit) while suppressing the number of sheets P (an example of a medium) whose curl is corrected.

[0110] Moreover, when curl correction is performed on all the sheets P, especially on all the sheets P, wrinkles extending in the conveying direction of the sheet P that are likely to occur when correcting the curl by sandwiching the sheet P between a soft roller (for example, the sheet contact portion 44 of the first roller 41) and a hard roller (for example, the second roller 42), and image unevenness caused by fluctuations in the conveying speed may occur, but the generation of these wrinkles and image unevenness can be suppressed. In addition, especially when performing curl correction using a soft roller such as a soft roller, the roller will wear, the curl correction effect will decrease, or the power consumption will increase due to the large rotational resistance of the roller. However, by omitting curl correction for at least a part of the second and subsequent sheets P, it is possible to prevent wear and save power.

[0111] In addition, in the present embodiment, the control unit 50 controls the curl correction unit 40 to correct the curl of the second and subsequent sheets P when the sheets P are continuously conveyed by the head-down conveying unit 16 and the width of the sheet P in the width direction (main scanning direction F1) orthogonal to the conveying direction (sub-scanning direction F2) of the sheet P is wider than the previous conveyed sheet P (for example Figure 7 three narrow) wide sheet P (for example, four wide).

[0112] In this way, when the sheet P whose width is wider than the previous sheet P enters the conveying surface 17a of the conveyor belt 17, compared with the case where the previous sheet P has the same width, the suction holes of the conveyor belt 17 are more likely to open, etc., and the adhesion force with the conveyor belt 17 is likely to become smaller. Therefore, by performing curl correction on the sheet P whose width is wider than the previous sheet P, it is possible to more reliably prevent damage to the printing unit 13 or ink stains from adhering to the sheet P.

[0113] In addition, the present invention is not limited to the above-described embodiments themselves, and constituent elements can be modified and embodied within the scope of not departing from the gist thereof at the implementation stage. Further, by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments, various inventions can be formed. For example, all the constituent elements shown in the above-described embodiments can be appropriately combined. Of course, various modifications and applications can be made within the scope of not departing from the gist of the invention. Hereinafter, the invention described in the technical solution at the initial filing of this application is noted.

[0114] [Note 1]

[0115] A conveying device, characterized in that

[0116] the conveying device includes:

[0117] an adsorption conveying unit having a conveying member for conveying a medium and an adsorption unit for causing the conveying member to adsorb the medium, the adsorption conveying unit being arranged to face a processing unit for processing the medium;

[0118] a curl correction unit arranged at a position upstream of the processing unit and the adsorption conveying unit in the conveying direction of the medium, and correcting the curl of the medium to prevent the front end of the medium from contacting the processing unit; and

[0119] a control unit that controls the curl correction unit to correct the curl of the first sheet of the medium and omit curl correction for at least a part of the second and subsequent sheets of the medium when the medium is continuously conveyed by the adsorption conveying unit.

[0120] [Note 2]

[0121] The conveying device according to Technical Solution 1, characterized in that the control unit controls the curl correction unit to correct the curl of the second and subsequent sheets of the medium when the medium is continuously conveyed by the adsorption conveying unit and the width of the medium in the width direction orthogonal to the conveying direction of the medium is wider than that of the previous sheet of the medium conveyed.

Claims

1. A conveying device, characterized in that, the conveying device includes: an adsorption conveying part having a conveying member for conveying a medium and an adsorption part for making the conveying member adsorb the medium, and the adsorption conveying part is arranged to face a processing part for processing the medium; a curling correction part arranged at a position upstream of the processing part and the adsorption conveying part in the conveying direction of the medium, and correcting the curling of the medium to prevent the front end of the medium from contacting the processing part; and a control part that controls the curling correction part to correct the curling of the first medium and omit the curling correction for at least a part of the media after the second medium when the medium is continuously conveyed by the adsorption conveying part, the control part controls the curling correction part to correct the curling of the media after the second medium and having a width in the width direction orthogonal to the conveying direction of the medium wider than that of the previous conveyed medium when the medium is continuously conveyed by the adsorption conveying part.

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