Image formation control method and image formation device

Abstract

To prevent shrinkage of a sheet from having a negative impact on correction of a center position of an edge detection part based on test images formed on both sides of the sheet.SOLUTION: A processor 80 acquires a pair of first lateral edge positions when a first face of a target sheet is a printing face (S5). The processor 80 acquires a pair of second lateral edge positions when a second face of the target sheet is a printing face (S8). The processor 80, among a plurality of first scale images formed on the first face of the target sheet, acquires matching scale information that specifies a matched scale image in which a position in a width direction and one of a plurality of second scale images formed on the second face of the target sheet match each other (S10). The processor 80 sets a reference center position according to the ratio of an interval between the pair of second lateral edge positions to an interval between the pair of first lateral edge positions as well as the matching scale information (S12).SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an image formation control method and an image forming apparatus capable of adjusting the position of an image to be printed in accordance with the detection results of the positions of both edges in the width direction of a sheet being conveyed. [Background technology]

[0002] An image forming apparatus may include an edge detection unit capable of detecting the positions of both ends in the width direction of a conveyed sheet. The edge detection unit is disposed upstream of a printing device in the sheet conveying direction.

[0003] It is known that the image forming device identifies a sheet center position, which is the center position in the width direction of the sheet, based on the detection results of the edge detection unit, and adjusts the width direction position of the image to be printed in accordance with the sheet center position (see, for example, Patent Document 1).

[0004] Furthermore, it is known that the image forming device forms a test image including a plurality of scale images on both sides of a sheet in order to correct the deviation of the center position of the edge detection unit in the width direction (for example, see Patent Document 1). In this case, the image forming device corrects the deviation of the center position of the edge detection unit according to the overlapping state of the plurality of scale images on both sides of the sheet when the sheet is transparent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-116885 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, there are cases where the image forming apparatus includes a drying device that dries the ink image formed on the sheet by heating it.

[0007] In the case where the test images are formed on both sides of the sheet, a first test chart is formed on the first side of the sheet, and then the sheet passes through the drying device, and the sheet passes through the edge detection unit, and a second test image is formed on the second side of the sheet.

[0008] When the temperature of the drying device is high, the sheet may shrink due to passing through the drying device, and therefore, when the temperature of the drying device is high, the first test image is formed on a first side of the sheet before shrinkage, and the second test image is formed on a second side of the sheet after shrinkage.

[0009] The shrinkage of the sheet adversely affects the correction of the deviation of the center position of the edge detection unit based on the test images formed on both sides of the sheet.

[0010] An object of the present invention is to provide an image forming control method and an image forming apparatus that can prevent shrinkage of a sheet due to passing through a drying device from adversely affecting the correction of the central position of the edge detection unit based on test images formed on both sides of the sheet. [Means for solving the problem]

[0011] An image forming control method according to one aspect of the present invention is a method for controlling an image forming apparatus. The image forming apparatus includes a sheet conveying device, a printing device, a drying device, and an edge detection unit. The sheet conveying device conveys a sheet along a conveying path. The printing device forms an image on the sheet by ejecting ink onto the sheet conveyed along the conveying path. The drying device is disposed downstream of the printing device in a sheet conveying direction, has a heater for heating the sheet, and dries the ink on the sheet. The edge detection unit is disposed upstream of the printing device in the sheet conveying direction, and detects a pair of lateral edge positions that are positions of both ends of the sheet in a width direction intersecting the sheet conveying direction. The image forming control method includes, when an operation mode is a first mode, a processor causing the sheet conveying device to execute a process of conveying the target sheet in a state in which a first surface of the target sheet is a printing surface. The image forming control method further includes, when the operation mode is a first mode, the processor acquiring a pair of first lateral edge positions that are detection results of the edge detection unit when the target sheet is conveyed in a state in which the first surface of the target sheet is a printing surface. The image formation control method further includes the processor causing the printing device to execute a process of forming a first test image on the first surface of the target sheet, the first test image including a plurality of first scale images arranged at a first interval in the width direction based on a center position of the pair of first horizontal edge positions. The image formation control method further includes the processor causing the sheet conveying device to execute a process of conveying the target sheet in a state in which the second surface of the target sheet is the printing surface. The image formation control method further includes the processor acquiring a pair of second horizontal edge positions that are the detection results of the edge detection unit when the target sheet is conveyed in a state in which the second surface of the target sheet is the printing surface. The image formation control method further includes the processor causing the printing device to execute a process of forming a second test image on the second surface of the target sheet, the second test image including a plurality of second scale images arranged at a second interval in the width direction based on a center position of the pair of second horizontal edge positions.The image formation control method further includes the processor acquiring matching scale information that identifies a matching scale image among the plurality of first scale images formed on the target sheet, the matching scale image having a position in the width direction that matches one of the plurality of second scale images.The image formation control method further includes the processor setting a reference center position according to the matching scale information and a sheet width ratio that is a ratio of the distance between the pair of second horizontal edge positions to the distance between the pair of first horizontal edge positions.The image formation control method further includes the processor, when the operation mode is the second mode, correcting the position in the width direction of the image to be printed according to a difference between the center position of the pair of horizontal edge positions detected by the edge detection unit and the reference center position, and then causing the printing device to execute a process of forming the image to be printed on the sheet.

[0012] An image forming apparatus according to another aspect of the present invention includes the sheet conveying device, the printing device, the drying device, the edge detection unit, and the processor. Effect of the Invention

[0013] According to the present invention, it is possible to provide an image forming control method and an image forming apparatus that can prevent shrinkage of a sheet due to passing through a drying device from adversely affecting the correction of the central position of the edge detection unit based on test images formed on both sides of the sheet. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. [Diagram 3] FIG. 3 is a plan view of the edge sensor in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a first surface of a target sheet on which a first test image is formed by the image forming apparatus according to the embodiment. [Diagram 5] FIG. 5 is a diagram showing an example of the second surface of the target sheet on which a second test image is formed by the image forming apparatus according to the embodiment. [Figure 6] FIG. 6 is an enlarged view of a portion of the first surface of the target sheet on which the first test image is formed. [Figure 7] FIG. 7 is a flowchart showing an example of a procedure for the central position calibration process in the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0016] [Configuration of image forming apparatus 10] The image forming apparatus 10 according to the embodiment includes a sheet storage unit 1, a sheet conveying device 3, and a printing device 4.

[0017] The sheet transport device 3 includes a sheet feeding mechanism 30, a plurality of pairs of transport rollers 31, a first belt transport device 32, and a second belt transport device 33. The sheet feeding mechanism 30 feeds the sheet 9 in the sheet storage unit 1 to a main transport path 301.

[0018] Some of the plurality of pairs of conveying rollers 31 convey the sheet 9 along the main conveying path 301 , and further send the sheet 9 to the first belt conveying device 32 .

[0019] The first belt conveying device 32 takes over from the multiple conveying roller pairs 31 to convey the sheet 9, and sends the sheet 9 to the second belt conveying device 33. The second belt conveying device 33 takes over from the first belt conveying device 32 to convey the sheet 9, and further sends the sheet 9 to a subsequent conveying path 302.

[0020] Some of the multiple pairs of transport rollers 31 transport the sheet 9 along a rear transport path 302, and further send the sheet 9 to a rear stage. For example, the rear stage is a discharge tray or a post-processing device.

[0021] In addition, some of the multiple transport roller pairs 31 may transport the sheet 9 from the rear transport path 302 to the reversing transport path 303. The sheet transport device 3 also includes a reversing mechanism 34 that reverses the sheet 9 in the reversing transport path 303 and returns it to the main transport path 301.

[0022] Each of the main conveying path 301, the rear conveying path 302, and the reversing conveying path 303 is a part of the conveying path of the sheet 9. In addition, the belts of each of the first belt conveying device 32 and the second belt conveying device 33 are also a part of the conveying path of the sheet 9.

[0023] The printing device 4 executes a printing process on the sheet 9 conveyed by the first belt conveying device 32. The printing process is a process of forming an image on the sheet 9.

[0024] In this embodiment, the printing device 4 executes the printing process by an inkjet method. That is, the printing device 4 forms an image on the sheet 9 by ejecting ink onto the sheet 9. The ink is an example of a developer.

[0025] The printing device 4 includes a plurality of ink heads 41 corresponding to inks of different colors and a plurality of ink supply units 42. Specifically, the printing device 4 includes four ink heads 41 and four ink supply units 42 corresponding to yellow, magenta, cyan, and black.

[0026] Each of the ink heads 41 has a plurality of ejection nozzles 41a that eject ink. The ink heads 41 are fixed at positions facing the conveyor belt 321 of the first belt conveyor device 32. The ink supply units 42 each contain ink of a different color and supply the ink to the ink heads 41.

[0027] The first belt conveying device 32 conveys the sheet 9 on which the image is formed to the second belt conveying device 33.

[0028] The printing device 4 forms an image on a first side of the sheet 9 when the sheet 9 is transported for the first time by the first belt transport device 32. The printing device 4 forms an image on a second side of the sheet 9 when the sheet 9, which has passed through the reversing transport path 303, is transported for the second time by the first belt transport device 32.

[0029] 1, 3 to 5, a conveying direction D1 is a sheet conveying direction. The sheet conveying direction is a direction in which a sheet 9 is conveyed by a sheet conveying device 3. A width direction D2 is a direction intersecting the conveying direction D1. The width direction D2 is a main scanning direction in the printing process, and the conveying direction D1 is a sub-scanning direction in the printing process.

[0030] The printing device 4 further includes a drying device 43 having a heater 431 that heats the sheet 9. The drying device 43 is disposed downstream of the printing device 4 in the transport direction D1.

[0031] The drying device 43 has a heater 431 that heats the sheet 9. The drying device 43 dries the ink on the sheet 9 transported by the second belt transport device 33.

[0032] The drying device 43 further includes a fan 432. The fan 432 sends the air heated by the heater 431 to the sheet 9 on the second belt conveying device 33. The drying device 43 further includes a temperature sensor 430 that detects the temperature inside the drying device 43.

[0033] The image forming apparatus 10 further includes an operation device 801, a display device 802, and a control device 8 (see FIG. 1).

[0034] The operation device 801 detects operations by a person. For example, the operation device 801 includes a plurality of operation buttons and a touch panel. The display device 802 can display various information. For example, the display device 802 is a panel display device such as a liquid crystal display panel.

[0035] As shown in FIG. 2, the control device 8 includes a central processing unit (CPU) 80, a random access memory (RAM) 81, a secondary storage device 82, a communication device 83, and the like.

[0036] The CPU 80 executes various control and data processing operations by executing computer programs. The RAM 81 temporarily stores the computer programs executed by the CPU 80 and various data.

[0037] The secondary storage device 82 is a computer-readable non-volatile storage device. The secondary storage device 82 stores the computer programs executed by the CPU 80 and various data. For example, one or both of a flash memory and a hard disk drive are adopted as the secondary storage device 82.

[0038] The communication device 83 executes communication with other devices such as the host device 7 through the network 70. The CPU 80 executes communication with other devices through the communication device 83. The host device 7 is an information processing device that requests the image forming apparatus 10 to perform the print process.

[0039] The CPU 80 includes a plurality of processing modules that are realized by executing the computer programs, including a main control unit 8a and a print control unit 8b (see FIG. 2).

[0040] The main control unit 8a executes start control for starting various processes in response to an operation on the operation device 801 or a processing request received through the communication device 83, and the like.

[0041] The print control unit 8b controls the sheet transporting device 3 and the printing device 4. The print control unit 8b controls the sheet transporting device 3, thereby controlling the transport of the sheet 9.

[0042] Furthermore, the print control unit 8b causes the printing device 4 to execute the print process in synchronization with the conveyance of the sheet 9. Furthermore, the print control unit 8b executes control to supply power to the heater 431 of the drying device 43 and control to operate the fan 432 when the print process is executed for the image to be printed.

[0043] The image forming apparatus 10 further includes an edge detection device 5 (see FIGS. 1 and 3). The edge detection device 5 is disposed upstream of the printing device 4 in the transport direction D1.

[0044] The edge detection device 5 detects a pair of lateral edge positions E1 (see FIG. 3) which are positions of both ends in the width direction D2 of the sheet 9 conveyed by the sheet conveying device 3. The edge detection device 5 is an example of an edge detection section.

[0045] In this embodiment, the edge detection device 5 includes a line sensor 51, a line light source 52, and an edge detection circuit 53 (see FIGS. 1 and 3).

[0046] The line sensor 51 and the line light source 52 are disposed along the width direction D2 (see FIG. 3). The line sensor 51 and the line light source 52 are disposed opposite each other across the main transport path 301 (see FIG. 1).

[0047] The line sensor 51 has a plurality of photoelectric conversion elements arranged along the width direction D2. The line sensor 51 outputs line data including a plurality of pixel data corresponding to a plurality of positions in the width direction D2. The plurality of image data represent the amount of light received by the plurality of photoelectric conversion elements.

[0048] The sheet 9 blocks the light from the line light source 52 toward the line sensor 51 when passing through a detection region between the line sensor 51 and the line light source 52 .

[0049] The edge detection circuit 53 is a device that realizes the processing of the line data by hardware. For example, the edge detection circuit 53 is configured by an ASIC (Application Specific Integrated Circuit) or a DSP (Digital Signal Processor).

[0050] The amount of light received by the line sensor 51 is smaller in a portion corresponding to the width of the sheet 9 than in other portions. The edge detection circuit 53 detects a pair of horizontal edge positions E1 by edge detection processing on the line data.

[0051] The edge detection device 5 described above is a transmission type light detection device. On the other hand, a reflection type light detection device may be adopted as the edge detection device 5.

[0052] In the reflective photodetection device, the line sensor 51 and the line light source 52 are arranged side by side on one side of the detection area. The reflective photodetection device further includes a black reference member arranged opposite the line sensor 51 across the detection area.

[0053] In the reflective photodetector, the portion of the line sensor 51 that corresponds to the width of the sheet 9 receives a larger amount of light than other portions. In the reflective photodetector, the edge detection circuit 53 also detects a pair of horizontal edge positions E1 by edge detection processing on the line data.

[0054] In the image forming apparatus 10, the center position of the detection area in the width direction D2 is set as a reference center position SC1 (see FIG. 3). The reference center position SC1 is a position that corresponds to a specific one of the plurality of pixel data of the line data.

[0055] The reference center position SC1 corresponds to a print center position which is the center position in the width direction D2 of the print width area. The print width area is an area in the width direction D2 where the printing device 4 can form an image.

[0056] In the following description, the center position between the pair of lateral edge positions E1 is referred to as a sheet center position PC1 (see FIGS. 4 and 5). The sheet center position PC1 is the center position in the width direction D2 of the sheet 9 passing through the detection area.

[0057] The state in which the sheet center position PC1 coincides with the reference center position SC1 is a state in which the sheet 9 is conveyed at a pre-estimated position in the width direction D2.

[0058] The print control unit 8b executes a width position correction process every time one sheet 9 is conveyed. The width position correction process is a process for correcting the position of the image to be printed in the width direction D2 in accordance with a position difference DX1 which is the difference between a sheet center position PC1 and a reference center position SC1 (see FIG. 3).

[0059] The print control unit 8b executes the width position correction process for each sheet 9, and then causes the printing device 4 to execute the print process for the image to be printed whose position in the width direction D2 has been corrected. As a result, the image to be printed is formed at an appropriate position in the width direction D2 on the sheet 9.

[0060] However, if the reference center position SC1 in the edge detection device 5 is misaligned with respect to the print center position in the printing device 4, the image to be printed will be formed at a position offset to one side in the width direction D2 of the sheet 9.

[0061] The plurality of processing modules of the CPU 80 further includes a calibration unit 8c. The print control unit 8b and the calibration unit 8c execute a center position calibration process (see FIG. 7) to be described later. The center position calibration process is a process for correcting a deviation of a reference center position SC1 from the print center position.

[0062] In the following description, the sheet 9 used in the central position calibration process is referred to as a target sheet 9x (see FIGS. 4 and 5).

[0063] In the central position calibration process, the calibration unit 8c causes the printing device 4 to perform a process of forming a first test image G1 on a first surface 9a of the target sheet 9x, and a process of forming a second test image G2 on a second surface 9b of the target sheet 9x (see Figures 4 and 5).

[0064] The first test image G1 includes a plurality of first scale images G11 arranged at a first interval P1 in the width direction D2 (see FIG. 4). The first test image G1 further includes a plurality of discrimination value images G12 corresponding to the plurality of first scale images G11.

[0065] The second test image G2 includes a plurality of second scale images G21 arranged at second intervals P2 in the width direction D2 (see FIG. 5). The second intervals P2 are larger than the first intervals P1 by one pixel.

[0066] The multiple identification value images G12 are images that represent values ​​that identify the multiple first scale images G11, respectively.

[0067] As described later, the calibration unit 8c corrects the deviation of the reference center position SC1 according to the overlapping state of the multiple scale images G11, G21 on both sides of the target sheet 9x when the target sheet 9x is see-through.

[0068] Incidentally, the image forming apparatus 10 includes a drying device 43 that dries the ink image formed on the sheet 9 by heating it.

[0069] When the first test image G1 and the second test image G2 are formed on the target sheet 9x, after the first test image G1 is formed on the first surface 9a of the target sheet 9x, the target sheet 9x passes through the drying device 43. Furthermore, the target sheet 9x that has passed through the drying device 43 passes the position of the edge detection device 5, and the second test image G2 is formed on the second surface 9b of the target sheet 9x.

[0070] When the temperature of the drying device 43 is high, the target sheet 9x may shrink due to passing through the drying device 43. Therefore, when the temperature of the drying device 43 is high, the first test image G1 is formed on the first surface 9a of the target sheet 9x before shrinkage, and the second test image G2 is formed on the second surface 9b of the target sheet 9x after shrinkage.

[0071] The shrinkage of the target sheet 9x adversely affects the correction of the deviation of the reference center position SC1 based on the first test image G1 and the second test image G2 formed on both sides of the target sheet 9x.

[0072] The central position calibration process in this embodiment includes a process for preventing contraction of the target sheet 9x caused by passing through the drying device 43 from adversely affecting the correction of the reference central position SC1.

[0073] In this embodiment, the main control unit 8a switches the operation mode of the image forming apparatus 10 from the normal mode to the calibration mode when a calibration start operation is detected by the operation device 801. The initial state of the operation mode is the normal mode.

[0074] The central position calibration process is executed when the operation mode is the calibration mode. When the central calibration process is completed, the main control unit 8a returns the operation mode from the calibration mode to the normal mode.

[0075] When the operating mode is the normal mode, the print control unit 8b executes the width position correction process for each sheet 9, and then causes the printing device 4 to execute the print process for the image to be printed whose position in the width direction D2 has been corrected.

[0076] The calibration mode is an example of a first mode, and the normal mode is an example of a second mode.

[0077] [Central position calibration process] An example of the procedure of the central position calibration process will be described below with reference to the flowchart shown in FIG.

[0078] The central position calibration process is an example of a process for realizing an image formation control method for controlling the image forming apparatus 10. The CPU 80 is an example of a processor for realizing the image formation control method.

[0079] In the following description, S1, S2, ... represent identification codes of a plurality of steps in the central position calibration process. In the central position calibration process, the process of step S1 is executed first.

[0080] <Process S1> In step S1, the print control unit 8b executes control to stop the power supply to the heater 431 of the drying device 43.

[0081] After executing the process of step S1, the print control unit 8b shifts the process to step S2. The processes after step S2 are executed in a state where the power supply to the heater 431 is stopped.

[0082] <Process S2> In step S2, the calibration unit 8c judges whether the image forming apparatus 10 is in an acceptable state in which a predetermined acceptable condition is satisfied, or in a non-acceptable state in which the acceptable condition is not satisfied.

[0083] In this embodiment, the permissible conditions include a temperature permissible condition regarding the temperature of the drying device 43 and a thickness permissible condition regarding the thickness of the target sheet 9x.

[0084] The temperature tolerance condition is a condition that the temperature detected by the temperature sensor 430 of the drying device 43 does not exceed a preset tolerance temperature. In step S2, the calibration unit 8c acquires the temperature detected by the temperature sensor 430, and further determines whether the detected temperature satisfies the temperature tolerance condition.

[0085] The thickness tolerance condition is a condition that thickness information representing the thickness of the target sheet 9x does not exceed a preset tolerance thickness. In step S2, the calibration unit 8c acquires the thickness information stored in the secondary storage device 82, and further determines whether the thickness information satisfies the thickness tolerance condition.

[0086] The thickness information is stored in the secondary storage device 82 in a state associated with the sheet storage unit 1. The calibration unit 8c acquires, from the secondary storage device 82, the thickness information corresponding to the sheet storage unit 1 that is the supply source of the target sheet 9x.

[0087] For example, the thickness information is information that indicates the basis weight of the target sheet 9x, and the allowable thickness is a preset upper allowable limit value of the basis weight of the target sheet 9x.

[0088] The temperature tolerance condition is determined in order to avoid excessive shrinkage of the target sheet 9x due to the target sheet 9x passing through the drying device 43. The thickness condition is determined in order to avoid a situation in which the second test image G2 cannot be viewed from the first surface 9a side of the target sheet 9x when the target sheet 9x is transparent.

[0089] The calibration unit 8c determines that the image forming apparatus 10 is in the permissible state when both the temperature permissible condition and the thickness permissible condition are satisfied, whereas the calibration unit 8c determines that the image forming apparatus 10 is in the non-permissible state when at least one of the temperature permissible condition and the thickness permissible condition is not satisfied.

[0090] When the calibration unit 8c determines that the image forming device 10 is in the non-permissible state, the calibration unit 8c shifts the process to step S3. On the other hand, when the calibration unit 8c determines that the image forming device 10 is in the permissible state, the calibration unit 8c shifts the process to step S4.

[0091] <Process S3> In step S3, the calibration unit 8c executes an error notification for notifying predetermined error information through the display device 802.

[0092] For example, the error information is information that indicates that the image forming apparatus 10 does not satisfy the permissible condition, and indicates what the user should do to make the image forming apparatus 10 satisfy the permissible condition.

[0093] After performing the process of step S3, the calibration unit 8c ends the central position calibration process. Note that the calibration unit 8c may repeat the processes of steps S2 and S3 until the image forming apparatus 10 satisfies the permissible condition.

[0094] If the temperature detected by the temperature sensor 430 does not satisfy the temperature tolerance condition, the print control unit 8b may operate the fan 432 while stopping the power supply to the heater 431 of the drying device 43. This promotes cooling of the drying device 43.

[0095] The processes from step S4 onwards are carried out on the condition that both the temperature tolerance condition and the thickness tolerance condition are satisfied.

[0096] <Process S4> In step S4, the print control unit 8b causes the sheet conveying device 3 to execute a first conveying process for conveying the target sheet 9x in a state in which the first surface 9a of the target sheet 9x becomes the printing surface.

[0097] When the first transfer process is being performed, the processes of steps S5 and S6 are performed.

[0098] <Process S5> In step S5, when the target sheet 9x passes through the detection area, the calibration unit 8c acquires data on a pair of first horizontal edge positions from the edge detection device 5. The pair of first horizontal edge positions are detection results of the edge detection device 5 when the target sheet 9x is transported with the first surface 9a of the target sheet 9x as the print surface.

[0099] After executing the process of step S5, the calibration unit 8c shifts the process to step S6.

[0100] <Process S6> In step S6, the print control unit 8b causes the printing device 4 to execute a process of forming a first test image G1 on the first surface 9a of the target sheet 9x.

[0101] In step S6, the print control unit 8b executes the widthwise position correction process on a first test image G1 including a plurality of first scale images G11 arranged at first intervals P1 in the width direction D2 with respect to a preset reference center position SC1.

[0102] That is, the print control unit 8b corrects the position of the first test image G1 in the width direction D2 based on the reference central position SC1 in accordance with the difference between the center position of the pair of first horizontal edge positions obtained in step S5 and the reference central position SC1.

[0103] The plurality of first scale images G11 includes a first reference scale image G110 (see FIG. 4). The first reference scale image G110 is one of the plurality of first scale images G11 that is located at the center in the width direction D2.

[0104] In the first test image G1 before the widthwise position correction process is performed, the first reference scale image G110 is located at the reference center position SC1.

[0105] In step S6, the print control unit 8b causes the print device 4 to execute a process of forming the first test image G1, which has been subjected to the width position correction process, on the first surface 9a of the target sheet 9x.

[0106] In the first test image G1 after the width position correction process, the first reference scale image G110 is located at the sheet center position PC1 corresponding to the pair of first horizontal edge positions. The sheet center position PC1 corresponding to the pair of first horizontal edge positions is the center position between the pair of first horizontal edge positions.

[0107] That is, in step S6, the print control unit 8b causes the print device 4 to execute a process of forming a first test image G1 including a plurality of first scale images G11 arranged at a first interval P1 in the width direction D2 based on the center position of the pair of first horizontal edge positions.

[0108] After executing the process of step S6, the print control unit 8b shifts the process to step S7.

[0109] <Process S7> In step S7, the print control unit 8b causes the sheet conveying device 3 to execute a second conveying process for conveying the target sheet 9x in a state in which the second surface 9b of the target sheet 9x becomes the print surface.

[0110] In this embodiment, the sheet conveying device 3 can automatically perform a second conveying process following the first conveying process by inverting and conveying the target sheet 9x on which the first test image G1 is formed.

[0111] When the sheet conveying device 3 does not include a reverse conveying mechanism, in step S7, the main control unit 8a notifies a target sheet set message through the display device 802. The target sheet set message is a message that prompts the user to set the target sheet 9x in the sheet storage unit 1 so that the second surface 9b of the target sheet 9x becomes the print surface.

[0112] When the operation device 801 detects a start conveying operation corresponding to the target sheet set message, the print control unit 8b causes the sheet conveying device 3 to execute the second conveying process for the target sheet 9x set in the sheet storage unit 1.

[0113] When the second transfer process is being performed, the processes of steps S8 and S9 are performed.

[0114] <Process S8> In step S8, when the target sheet 9x passes through the detection area, the calibration unit 8c acquires data on a pair of second horizontal edge positions from the edge detection device 5. The pair of second horizontal edge positions are detection results of the edge detection device 5 when the target sheet 9x is transported with the second surface 9b of the target sheet 9x as the print surface.

[0115] After executing the process of step S8, the calibration unit 8c shifts the process to step S9.

[0116] <Process S9> In step S9, the print control unit 8b causes the print device 4 to execute a process of forming a second test image G2 on the second surface 9b of the target sheet 9x.

[0117] In step S9, the print control unit 8b executes the widthwise position correction process on a second test image G2 including a plurality of second scale images G21 arranged at second intervals P2 in the width direction D2 with reference to a preset reference center position SC1.

[0118] That is, the print control unit 8b corrects the position in the width direction D2 of the second test image G2 based on the reference central position SC1 in accordance with the difference between the center position of the pair of second horizontal edge positions obtained in step S8 and the reference central position SC1.

[0119] The plurality of second scale images G21 includes a second reference scale image G210 (see FIG. 5). The second reference scale image G210 is one of the plurality of second scale images G21 that is located at the center in the width direction D2.

[0120] In the second test image G2 before the widthwise position correction process is performed, the second reference scale image G210 is located at the reference center position SC1.

[0121] In step S9, the print control unit 8b causes the print device 4 to execute a process of forming the second test image G2, which has been subjected to the width position correction process, on the second surface 9b of the target sheet 9x.

[0122] In the second test image G2 after the width position correction process, the second reference scale image G210 is located at the sheet center position PC1 corresponding to the pair of second lateral edge positions. The sheet center position PC1 corresponding to the pair of second lateral edge positions is the center position between the pair of second lateral edge positions.

[0123] That is, in step S9, the print control unit 8b causes the print device 4 to execute a process of forming a second test image G2 including a plurality of second scale images G21 arranged at a second interval P2 in the width direction D2 based on the center position of the pair of second horizontal edge positions.

[0124] After executing the process of step S9, the print control unit 8b shifts the process to step S10.

[0125] <Process S10> In step S10, the calibration unit 8c executes a process for obtaining the coincident scale value.

[0126] The matching scale value is a numerical value that identifies a matching scale image G10 whose position in the width direction D2 coincides with one of a plurality of second scale images G21 among a plurality of first scale images G11 formed on the target sheet 9x (see FIG. 6).

[0127] In this embodiment, the corresponding scale value is a numerical value represented by a specific discrimination value image G120 corresponding to the corresponding scale image G10 among the plurality of discrimination value images G12. The corresponding scale value is an example of corresponding scale information.

[0128] 4, the numerical values ​​represented by the discrimination value images G12 increase by 1 from the first side to the second side in the width direction D2. Furthermore, the numerical value corresponding to the first reference scale image G110 is 0.

[0129] 4, 41 first scale images G11 are arranged at a first interval P1 in the width direction D2. Furthermore, 41 discrimination value images G12 are associated with the 41 first scale images G11 and represent integers from -20 to +20 arranged in order from the first side to the second side in the width direction D2.

[0130] 6, the matching scale image G10 is the fourth scale image on the second side of the plurality of first scale images G11 with respect to the first reference scale image G110. In this case, the matching scale value is 4.

[0131] In step S10, the proofreading unit 8c notifies the user through the display device 802 of a predetermined watermark request message.

[0132] The watermark request message includes a message requesting that the matching scale image G10 be identified by visually observing the target sheet 9x from the first surface 9a side through the watermark.

[0133] Furthermore, the watermark request message includes a message requesting input, via the operation device 801, of a numerical value represented by the specific identification value image G120 corresponding to the matching scale image G10.

[0134] The calibration unit 8c acquires, as the matching scale value, a numerical value input to the operation device 801 in response to the notification of the watermark request message.

[0135] The multiple discrimination value images G12 may be images representing multiple symbols, etc. In this case, the calibration unit 8c converts the symbols obtained in step S10 into numerical values ​​according to a preset conversion table.

[0136] After executing the process of step S10, the calibration unit 8c shifts the process to step S11.

[0137] <Process S11> In step S11, the calibration unit 8c derives a first sheet width and a second sheet width, and further derives a sheet width ratio that is the ratio of the second sheet width to the first sheet width.

[0138] The first sheet width is the distance between the pair of first lateral edge positions obtained in step S5, and the second sheet width is the distance between the pair of second lateral edge positions obtained in step S8.

[0139] When the first conveying process is performed and the target sheet 9x shrinks due to passing through the drying device 43, the sheet width ratio that is less than 1 is derived.

[0140] After executing the process of step S11, the calibration unit 8c shifts the process to step S12.

[0141] <Process S12> In step S12, the calibration unit 8c corrects the reference center position SC1 in accordance with the sheet width ratio and the corresponding scale value, and sets the corrected reference center position SC1 as a new reference center position SC1.

[0142] Specifically, the calibration unit 8c derives Y, which is the corrected pixel number of the reference center position SC1, by applying X, which is the coincident scale value, and R, which is the sheet width ratio, to the following formula (1): P in formula (1) is the first interval P1.

number

[0143] The reference center position SC1 is represented by a pixel position in the width direction D2. The calibration unit 8c corrects the original reference center position SC1 by the number of correction pixels and sets the new reference center position SC1. The calibration unit 8c records information about the corrected reference center position SC1 in the secondary storage device 82.

[0144] It should be noted that formula (1) is a formula that is adopted when the second interval P2 is one pixel larger than the first interval P1.

[0145] After executing the process of step S12, the calibration unit 8c ends the central position calibration process. When the central position calibration process ends, the main control unit 8a returns the operation mode from the calibration mode to the normal mode.

[0146] When the operation mode is the normal mode, the print control unit 8b executes the width position correction process for each sheet 9, and then causes the printing device 4 to execute the print process for the image to be printed whose position in the width direction D2 has been corrected. In the width position correction process, the corrected reference center position SC1 is used.

[0147] By executing the center position calibration process, the reference center position SC1 is corrected to reflect the sheet width ratio (see step S12). The sheet width ratio represents a shrinkage rate of the target sheet 9x caused by passing through the drying device 43.

[0148] Therefore, by employing the central position calibration process, it is possible to prevent the contraction of the target sheet 9x caused by passing through the drying device 43 from adversely affecting the correction of the reference central position SC1.

[0149] By adopting the image forming apparatus 10, even if the central position calibration process is performed without waiting until the temperature of the drying device 43 drops to room temperature, shrinkage of the target sheet 9x is prevented from adversely affecting the correction of the reference central position SC1. [Explanation of symbols]

[0150] 1: Sheet storage area 3: Sheet transport device 4: Printing device 5: Edge detection device 8: Control device 9a: First side of the target sheet 9b: Second side of the target sheet 9x: Target sheet 10: Image forming device 43:Drying equipment 51: Line sensor 52: Line light source 53: Edge detection circuit 430: Temperature sensor 431: Heater 801: Operating device 802:Display device G1: First test image G10: Matching scale image G11: First scale image G110: First reference scale image G12: Identification value image G120: Specific identification value image G2: Second test image G21: Second scale image G210: Second reference scale image

Claims

1. a sheet conveying device that conveys a sheet along a conveying path; a printing device that forms an image on the sheet by ejecting ink onto the sheet transported along the transport path; a drying device that is disposed downstream of the printing device in a sheet conveying direction, the drying device having a heater that heats the sheet and dries the ink on the sheet; an edge detection unit that is disposed upstream of the printing device in the sheet transport direction and detects a pair of lateral edge positions that are positions of both ends of the sheet in a width direction intersecting the sheet transport direction, the image formation control method comprising: a processor, when the operation mode is a first mode, causing the sheet conveying device to execute a process of conveying the target sheet in a state in which a first surface of the target sheet becomes a print surface; The processor acquires a pair of first lateral edge positions that are detection results of the edge detection unit when the target sheet is transported with the first surface of the target sheet being a print surface; The processor causes the printing device to execute a process of forming a first test image on the first surface of the target sheet, the first test image including a plurality of first scale images arranged at a first interval in the width direction based on a center position of the pair of first horizontal edge positions; the processor causes the sheet transport device to execute a process of transporting the target sheet in a state in which a second surface of the target sheet becomes a print surface; The processor acquires a pair of second lateral edge positions that are detection results of the edge detection unit when the target sheet is transported in a state in which the second surface of the target sheet is a print surface; The processor causes the printing device to execute a process of forming a second test image on the second surface of the target sheet, the second test image including a plurality of second scale images arranged at a second interval in the width direction based on a center position of the pair of second lateral edge positions; The processor acquires matching scale information that identifies one of the plurality of first scale images formed on the target sheet, the one having a position matching with one of the plurality of second scale images in the width direction; The processor sets a reference center position in accordance with a sheet width ratio, which is a ratio of an interval between the pair of second lateral edge positions to an interval between the pair of first lateral edge positions, and the coincidence scale information; An image forming control method including, when the operating mode is a second mode, causing the processor to correct the widthwise position of the image to be printed in accordance with the difference between the center position of the pair of horizontal edge positions detected by the edge detection unit and the reference center position, and then causing the printing device to execute a process of forming the image to be printed on the sheet.

2. The image formation control method according to claim 1 , further comprising the processor executing control to stop power supply to the heater of the drying device when the operation mode is the first mode.

3. the image forming apparatus further includes a temperature sensor for detecting a temperature of the drying device; The image forming control method of claim 1 or claim 2, wherein the processor, when the operating mode is the first mode, causes the sheet conveying device to execute a process of conveying the target sheet, provided that the detected temperature of the temperature sensor does not exceed a predetermined allowable temperature.

4. The method further includes, when the operation mode is the first mode, acquiring thickness information representing a thickness of the target sheet, The image forming control method of claim 1 or claim 2, wherein when the operating mode is the first mode, the processor causes the sheet conveying device to execute a process of conveying the target sheet, on condition that the thickness information satisfies a predetermined tolerance condition.

5. a sheet conveying device that conveys a sheet along a conveying path; a printing device that forms an image on the sheet by ejecting ink onto the sheet transported along the transport path; a drying device that is disposed downstream of the printing device in a sheet conveying direction, the drying device having a heater that heats the sheet and dries the ink on the sheet; an edge detection unit that is disposed upstream of the printing device in the sheet transport direction and detects a pair of lateral edge positions that are positions of both ends of the sheet in a width direction intersecting with the sheet transport direction; 3. An image forming apparatus comprising: a processor that realizes the image forming control method according to claim 1.

Images