Image formation control method and image formation device

Abstract

To accurately set a center position in a width direction of an area in which an edge of a sheet is detected on the basis of a test image formed on the sheet with no need for visual image confirmation.SOLUTION: A processor 80 forces a sheet conveyance device 3 to execute processing for conveying a target sheet in a state where a specific face on which first test images G1 including a plurality of black patch images G11 arrayed stepwise is a printing face (S7). The processor 80 forces data of second test images G2 including a plurality of segment images G21 corresponding to the plurality of black patch images G11 to be supplied to an image processing device 53 as reference image data, and acquires information for a test interference position where a masking area corresponding to the plurality of black patch images G11 interfere with each other (S10). The processor 80 sets a reference center position according to the test interference position (S11).SELECTED DRAWING: Figure 8

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 sheet being conveyed. 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 in the width direction in the edge detection area (for example, see Patent Document 1). In this case, the image forming device corrects the deviation of the center position of the edge detection area according to the overlapping state of the plurality of scale images on both sides of the sheet when the sheet is transparent.

[0005] The overlapping state of the plurality of scale images on both sides of the sheet is visually confirmed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-116885 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the overlapping state of the plurality of scale images on both sides of the sheet is visually confirmed, a mistake in the visual confirmation may adversely affect the correction of the deviation of the center position of the edge detection region.

[0008] An object of the present invention is to provide an image forming control method and an image forming apparatus that can accurately set the widthwise center position of the area where the edge of the sheet is detected based on a test image formed on the sheet without the need for visual confirmation of the image. [Means for solving the problem]

[0009] An image formation 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 black reference member, an image sensor unit, and an image processing device. The sheet conveying device conveys a sheet along a conveying path. The printing device forms an image on the sheet conveyed along the conveying path. The black reference member has a black reference surface arranged along a width direction intersecting the sheet conveying direction in a state facing a detection area upstream of the printing device in the sheet conveying direction in the conveying path. The image sensor unit is arranged along the width direction in a state facing the reference surface via the detection area, emits detection light toward the reference surface, detects the amount of reflected light of the detection light, and outputs a plurality of line image data each including a plurality of pixel data representing the amount of detected light corresponding to a plurality of unit areas divided in the width direction in the detection area. The image processing device executes image processing based on the plurality of line image data. The image processing device can execute an area detection process to detect a pair of lateral edge positions, which are positions of both ends in the width direction of the sheet passing through the detection area, a sheet area, which is an area within a rectangular outline of the sheet, and a mask area, which is a portion in the sheet area where the detected light amount is lower than a reference light amount. The image processing device can also execute an interference position identification process to identify a position of an interference portion that overlaps with the mask area in a reference image represented by supplied reference image data. The image formation control method further includes the processor causing the sheet conveying device to execute a first conveying process, when the operation mode is a first mode, to convey the target sheet in a state in which a blank specific surface of the target sheet becomes a printing surface. The image formation control method further includes the processor acquiring information on a pair of first lateral edge positions, which are the pair of lateral edge positions detected by the image processing device when the first conveying process is being executed. The image formation control method further includes the processor causing the printing device to execute a process to form a first test image including a plurality of black patch images on the specific surface when the first conveying process is being executed.The image formation control method further includes the processor causing the sheet conveying device to execute a second conveying process in which the target sheet is conveyed in a state in which the specific surface on which the first test image is formed becomes a print surface. The image formation control method further includes the processor acquiring information on a pair of second horizontal edge positions that are the pair of horizontal edge positions detected by the image processing device when the second conveying process is executed. The image formation control method further includes the processor supplying data of a second test image that corresponds to the plurality of black patch images and includes a plurality of line segment images each of which is a line segment along the sheet conveying direction to the image processing device as the reference image data, and acquiring information on a test interference position that is the position of the interference part identified by the image processing device based on the mask area corresponding to the second conveying process and the data of the second test image. The image formation control method further includes the processor setting a reference center position that is the center position in the width direction of the image sensor unit according to the test interference position. The image formation control method further includes, when the operating mode is the second mode, the processor executing a width position correction process to correct the width direction position of the image to be printed each time the sheet is transported in accordance with a difference between the center position of the pair of horizontal edge positions detected by the image processing device and the reference center position each time the sheet is transported.The image formation control method further includes the processor supplying data of the image to be printed that has been subjected to the width position correction process to the image processing device as the reference image data, and executing a mask process to replace pixels in the image to be printed that correspond to the position of the interference portion identified by the image processing device with non-print pixels.The image formation control method further includes the processor causing the printing device to execute a process of forming the image to be printed that has been subjected to the width position correction process and the mask process on the sheet.The plurality of black patch images in the first test image are arranged in a stepped manner in the width direction at a pitch of a reference length with the center position of the pair of first horizontal edge positions as a reference with the positions of the black patch images in the sheet transport direction being shifted sequentially, and are rectangular black painted images each having a width of the reference length. The plurality of line segment images in the second test image are arranged in the width direction at equal intervals smaller than the reference length with the center position of the pair of second horizontal edge positions as a reference, and an end of each of the plurality of line segment images is formed at a position overlapping a corresponding one of the plurality of black patch images in the sheet transport direction.

[0010] An image forming apparatus according to another aspect of the present invention includes the sheet transport device, the printing device, the black reference member, the image sensor unit, the image processing device, and the processor. Effect of the Invention

[0011] According to the present invention, it is possible to provide an image forming control method and an image forming apparatus that can accurately set the widthwise center position of the area where the edge of the sheet is detected based on a test image formed on the sheet without the need for visual confirmation of the image. [Brief description of the drawings]

[0012] [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 configuration diagram of a sheet measuring device in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a plan view of an image sensor unit and a black reference member provided in the sheet measuring device of the image forming apparatus according to the embodiment. [Diagram 5] FIG. 5 is a diagram showing an example of a first test image formed on a target sheet in the image forming apparatus according to the embodiment. [Figure 6] FIG. 6 is a diagram showing an example of a second test image represented by reference image data supplied to a sheet measuring device in the image forming apparatus according to the embodiment. [Figure 7] FIG. 7 is an enlarged view of a portion of the first test image and the second test image. [Figure 8] FIG. 8 is a flowchart showing an example of a procedure for the central position calibration process in the image forming apparatus according to the embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of a procedure of a second test image data supply process in the image forming apparatus according to the application example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] 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.

[0014] [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.

[0015] 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.

[0016] 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 .

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] It should be noted that the printing device 4 may be a device that executes the printing process using another method, such as an electrophotographic method.

[0026] The first belt conveying device 32 conveys the sheet 9 on which the image is formed to the second belt conveying device 33.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The image forming apparatus 10 further includes an operation device 801, a display device 802, and a control device 8 (see FIG. 1).

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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).

[0039] 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.

[0040] 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.

[0041] 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.

[0042] The image forming apparatus 10 further includes a sheet measuring device 5 (see FIGS. 1, 3, and 4). The sheet measuring device 5 is disposed upstream of the printing device 4 in the conveying direction D1.

[0043] In the following description, an area of ​​the main transport path 301 corresponding to the sheet measuring device 5 is referred to as a detection area A1 (see FIGS. 1, 3, and 4). The detection area A1 is an area on the upstream side of the printing device 4 in the transport direction D1 (see FIG. 1).

[0044] [Configuration of sheet measuring device 5] The sheet measuring device 5 includes a black reference member 51, an image sensor unit 52, and an image processing circuit 53 (see FIGS. 1 and 3).

[0045] The black reference member 51 and the image sensor unit 52 are disposed along the width direction D2 (see FIG. 4). The black reference member 51 and the image sensor unit 52 are disposed opposite each other across the detection area A1 (see FIGS. 1 and 3).

[0046] The black reference member 51 has a black reference surface 51a (see FIG. 3). The reference surface 51a is disposed along the width direction D2 in a state facing the detection area A1.

[0047] The image sensor unit 52 is disposed along the width direction D2 in a state facing the reference surface 51a across the detection area A1 (see FIGS. 3 and 4). The image sensor unit 52 includes a light emitting portion 5a, a lens 5b, and an image sensor 5c (see FIG. 3).

[0048] The light emitting unit 5a emits detection light toward the reference surface 51a. The lens 5b collects the reflected light of the detection light onto the light receiving unit of the image sensor 5c.

[0049] The image sensor 5c is a line sensor having a plurality of photoelectric conversion elements arranged along the width direction D2. The image sensor 5c detects the amount of reflected light and sequentially outputs a plurality of line image data, each of which includes a plurality of pixel data.

[0050] The plurality of pixel data represent detected light intensities corresponding to a plurality of unit regions divided in the detection area A1 in the width direction D2. The plurality of image data represent received light intensities of the plurality of photoelectric conversion elements, respectively.

[0051] The unit areas are areas obtained by dividing a detection area A1 having a longitudinal direction in a width direction D2 at a predetermined resolution. The reference center position SC1 is a position corresponding to a specific one of the pixel data of each of the line data.

[0052] All of the plurality of pixel data in each of the line image data obtained when the sheet 9 is not present in the detection area A1 represent the amount of light reflected by the reference surface 51a, and are data that are below a predetermined reference light amount.

[0053] On the other hand, in each of the line image data obtained when the sheet 9 passes through the detection area A1, the data of the area among the multiple pixel data corresponding to the width of the sheet 9 is brightness data corresponding to the surface condition of the sheet 9.

[0054] The image processing circuit 53 is a device that realizes image processing based on the multiple line data by hardware. For example, the image processing circuit 53 is configured with an ASIC (Application Specific Integrated Circuit) or a DSP (Digital Signal Processor). The image processing circuit 53 is an example of an image processing device.

[0055] The image processing circuit 53 is capable of executing an area detection process and an interference position identification process based on the plurality of line image data sequentially output from the image sensor unit 52 .

[0056] The area detection process is a process for detecting a pair of lateral edge positions E1, a sheet area, and a mask area. The pair of lateral edge positions E1 are the positions of both ends of the sheet 9 in the width direction D2 passing through the detection area A1 (see FIG. 4). The sheet area is an area within the rectangular outline of the sheet 9.

[0057] The image processing circuit 53 detects a pair of horizontal edge positions E1 by edge detection processing in the width direction D2 for each of the line data.

[0058] Furthermore, the image processing circuit 53 detects the leading edge and trailing edge of the sheet 9 by edge detection processing in the conveying direction D1 for each of the line data. The image processing circuit 53 specifies the sheet area based on the detection results of the pair of horizontal edge positions E1, the leading edge of the sheet 9, and the trailing edge of the sheet 9.

[0059] Furthermore, the image processing circuit 53 specifies, as the mask region, a portion of the sheet region where the detected light amount is lower than the reference light amount.

[0060] When an opening 90 such as a punch hole is formed in the sheet 9, a part of the reference surface 51a is exposed to the image sensor unit 52 through the opening 90 (see FIG. 4). Therefore, the area of ​​the opening 90 in the sheet 9 is detected as the mask area.

[0061] The interference position identifying process is executed when the reference image data is supplied to the image processing circuit 53. The interference position identifying process is a process for identifying a position of an interference part that overlaps with the mask area in a reference image represented by the supplied reference image data. In the following description, the position of the interference part identified by the image processing circuit 53 is referred to as an interference position.

[0062] In the image forming apparatus 10, a reference center position SC1 that indicates the center position in the width direction D2 of the detection area A1 is set in advance (see FIG. 4).

[0063] 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.

[0064] 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 FIG. 4). The sheet center position PC1 is the center position in the width direction D2 of the sheet 9 passing through the detection area A1.

[0065] 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.

[0066] The print control unit 8b executes the width position correction process and the mask process every time one sheet 9 is conveyed.

[0067] The widthwise 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. 4).

[0068] The mask process is a process in which the data of the image to be printed that has been subjected to the width position correction process is supplied as the reference image data to the image processing circuit 53, and pixels in the image to be printed that correspond to the interference positions are replaced with non-print pixels. The non-print pixels are pixels that are not drawn with ink.

[0069] The area detection process, the interference position identification process, the width position correction process, and the mask process must be completed while the sheet 9 is transported from the detection area A1 to the position of the printing device 4. The area detection process and the interference position identification process are realized by hardware to increase the speed.

[0070] The print control unit 8b causes the printing device 4 to execute the print process on the image to be printed that has been subjected to the width position correction process and the mask process for each sheet 9. As a result, the image to be printed is formed at an appropriate position in the width direction D2 on the sheet 9. Furthermore, ejection of ink into the area of ​​the opening 90 of the sheet 9 is avoided.

[0071] However, if the reference center position SC1 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.

[0072] 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. 8) 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.

[0073] In a conventional device, in order to correct the deviation of the reference central position SC1, a test image including a plurality of scale images may be formed on both sides of the sheet 9. In this case, the conventional device corrects the deviation of the reference central position SC1 according to the overlapping state of the plurality of scale images on both sides of the sheet 9 when the sheet 9 is transparent.

[0074] The overlapping state of the plurality of scale images on both sides of the sheet 9 is visually confirmed.

[0075] However, when the overlapping state of the plurality of scale images on both sides of the sheet 9 is visually confirmed, there is a risk that an error in the visual confirmation will adversely affect the correction of the deviation of the reference center position SC1.

[0076] The image forming apparatus 10 has a configuration for accurately setting the center position of the detection area A1 in the width direction D2 based on the test image formed on the sheet 9 without the need for visual confirmation of the image. The configuration will be described below.

[0077] In the following description, the sheet 9 used in the central position calibration process is referred to as a target sheet 9x (see FIGS. 5 to 7).

[0078] 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.

[0079] 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.

[0080] When the operating mode is the normal mode, the print control unit 8b executes two processes, the width position correction process and the mask process, on the image to be printed for each sheet 9, and then causes the printing device 4 to execute the print process on the image to be printed that has been subjected to the two processes.

[0081] The mask processing for the image to be printed is the mask processing based on the interference position obtained by the interference position specifying processing using the data of the image to be printed as the reference image data.

[0082] As described above, the position of the image to be printed in the width direction D2 is corrected by the width position correction process. Furthermore, the mask process prevents ink from being ejected onto the reference surface 51a of the black reference member 51.

[0083] The calibration mode is an example of a first mode, and the normal mode is an example of a second mode.

[0084] [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.

[0085] 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.

[0086] 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.

[0087] <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.

[0088] 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.

[0089] <Process S2> In step S2, the calibration unit 8c judges whether or not the temperature of the drying device 43 satisfies the temperature tolerance condition.

[0090] 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.

[0091] The temperature tolerance condition is determined in order to prevent the target sheet 9x from shrinking due to passing through the drying device 43.

[0092] The calibration unit 8c shifts the process to step S3 when the temperature of the drying device 43 does not satisfy the temperature tolerance condition. On the other hand, the calibration unit 8c shifts the process to step S4 when the temperature of the drying device 43 satisfies the temperature tolerance condition.

[0093] <Process S3> In step S3, the calibration unit 8c executes an error notification for notifying predetermined error information through the display device 802.

[0094] For example, the error information is information indicating that the temperature of the drying device 43 does not satisfy the temperature tolerance condition, and indicating what the user should do to make the temperature of the drying device 43 satisfy the temperature tolerance condition.

[0095] 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 temperature of the drying device 43 satisfies the temperature tolerance condition.

[0096] When the temperature of the drying device 43 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.

[0097] The processes from step S4 onward described below are performed on the condition that the temperature of the drying device 43 satisfies the temperature tolerance condition.

[0098] <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 specific surface 9a of the target sheet 9x becomes the print surface.

[0099] The specific side 9a of the target sheet 9x that is the target of the first conveying process is a blank side on which no image is formed. During the first conveying process, the processes of steps S5 and S6 are performed.

[0100] <Process S5> In step S5, the calibration unit 8c acquires data on the pair of first lateral edge positions detected by the sheet measuring device 5 at the timing when the target sheet 9x passes through the detection area A1.

[0101] The pair of first lateral edge positions is a pair of lateral edge positions E1 obtained by the area detection process of the sheet measuring device 5 when the target sheet 9x is transported by the first transport process.

[0102] After executing the process of step S5, the calibration unit 8c shifts the process to step S6.

[0103] <Process S6> 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 black patch images G11 on a specific surface 9a of the target sheet 9x (see FIGS. 5 and 7).

[0104] The plurality of black patch images G11 in the first test image G1 are rectangular black-filled images each having a width of a first length L1 (see FIGS. 5 and 7). The first length L1 is a predetermined reference length.

[0105] In this embodiment, data representing a first reference test image is stored in advance in the secondary storage device 82. The first reference test image includes a plurality of black patch images G11 arranged in a stepped manner at a pitch of a first length L1 in the width direction D2 with the reference center position SC1 as a reference, with the positions in the transport direction D1 being sequentially shifted.

[0106] The black patch images G11 are arranged in a stepped manner, successively shifted from the first side to the second side in the width direction D2 toward the upstream side in the transport direction D1 (see FIG. 5). In the examples shown in FIGS. 5 to 7, the first side in the width direction D2 is the right side in the paper, and the second side in the width direction D2 is the left side in the paper.

[0107] In step S6, the print control unit 8b executes the width position correction process on the first reference test image.

[0108] 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 center position SC1 in accordance with the difference between the sheet center position PC1 in the center of the pair of first horizontal edge positions obtained in step S5 and the reference center position SC1.

[0109] The print control unit 8b sets the image whose position in the width direction D2 has been corrected by the width position correction process as a first test image G1.

[0110] The multiple black patch images G11 include a reference black patch image G110 (see FIGS. 5 and 7). The reference black patch image G110 is one of the multiple black patch images G11 located at the center in the width direction D2.

[0111] In the first reference test image, a specific side, which is one of the two sides of the reference black patch image G110, is located at the reference center position SC1. In the example shown in Figures 5 and 7, the specific side is the left side of the reference black patch image G110.

[0112] In the first test image G1 obtained by the width position correction process, the specific side edge of the reference black patch image G110 is located at a sheet center position PC1 in the middle of the pair of first horizontal edge positions (see FIG. 5).

[0113] That is, in the first test image G1 formed on a specific surface 9a of the target sheet 9x in step S6, the multiple black patch images G11 are arranged in a stepped manner in the width direction D2 at a pitch of a first length L1, based on the sheet center position PC1 in the center of the pair of first horizontal edge positions, with their positions in the conveying direction D1 sequentially shifted (see Figure 5).

[0114] After executing the process of step S6, the print control unit 8b shifts the process to step S7.

[0115] <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 specific surface 9a of the target sheet 9x on which the first test image G1 is formed becomes the print surface.

[0116] For example, 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 specific surface 9a of the target sheet 9x on which the first test image G1 is formed becomes the print surface.

[0117] 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.

[0118] When the second conveying process is performed, the plurality of black patch images G11 in the first test image G1 form pseudo regions of the openings 90 in the target sheet 9x.

[0119] That is, the image processing circuit 53 executes the area detection process corresponding to the second conveying process, and detects the areas of the multiple black patch images G11 as the mask areas.

[0120] After executing the process of step S7, the print control unit 8b shifts the process to step S8. During the second conveying process, the processes of steps S8 and S9 are executed.

[0121] <Process S8> In step S8, the calibration unit 8c acquires data on the pair of second lateral edge positions from the sheet measuring device 5 at the timing when the target sheet 9x passes through the detection area.

[0122] The pair of second lateral edge positions are a pair of lateral edge positions E1 obtained by the area detection process of the sheet measuring device 5 when the target sheet 9x is transported by the second transport process.

[0123] After executing the process of step S8, the calibration unit 8c shifts the process to step S9.

[0124] <Process S9> In step S9, the print control unit 8b supplies data of the second test image G2 including a plurality of line segment images G21 each having a line segment shape along the transport direction D1 to the image processing circuit 53 as the reference image data (see FIG. 6).

[0125] The line segment images G21 in the second test image G2 correspond to the black patch images G11 in the first test image G1, respectively. For convenience, the black patch images G11 in the first test image G1 are indicated by dashed lines in FIG.

[0126] The multiple line segment images G21 in the second test image G2 are arranged at equal intervals of a second length L2 in the width direction D2 with reference to a sheet center position PC1 in the middle of the pair of second horizontal edge positions.

[0127] The second length L2 is shorter than the first length L1. Specifically, the second length L2 is shorter than the first length L1 by the length of one pixel.

[0128] An end portion of each of the multiple line segment images G21 is formed at a position overlapping a corresponding one of the multiple black patch images G11 in the transport direction D1.

[0129] For example, the first end of each of the multiple line segment images G21 is formed at a position downstream in the conveying direction D1 with respect to all of the multiple black patch images G11 (see FIG. 6). The downstream side in the conveying direction D1 is the leading edge side of the target sheet 9x being conveyed.

[0130] On the other hand, the second end portion of each of the multiple line segment images G21 is formed at the center position in the transport direction D1 of the corresponding one of the multiple black patch images G11 (see FIG. 6).

[0131] In this embodiment, data representing a second reference test image is stored in advance in the secondary storage device 82. The second reference test image includes a plurality of line segment images G21 arranged at equal intervals of a second length L2 in the width direction D2 with respect to a reference central position SC1.

[0132] In step S9, the print control unit 8b executes the width position correction process on the second reference test image.

[0133] That is, the print control unit 8b corrects the position in the width direction D2 of the second reference test image based on the reference center position SC1 in accordance with the difference between the sheet center position PC1 in the center of the pair of second horizontal edge positions obtained in step S8 and the reference center position SC1.

[0134] The print control unit 8b sets the image whose position in the width direction D2 has been corrected by the width position correction process as a second test image G2.

[0135] The multiple line segment images G21 include a reference line segment image G210 (see FIG. 6). The reference line segment image G210 is one of the multiple line segment images G21 that is located in the center in the width direction D2.

[0136] In the second reference test image, the reference line segment image G210 is located at a reference center position SC1. Meanwhile, in the second test image G2 obtained by the width position correction process, the reference line segment image G210 is located at a sheet center position PC1 in the center between the pair of second horizontal edge positions (see FIG. 6).

[0137] That is, in step S9, a plurality of line segment images G21 corresponding to the reference image data supplied to the image processing circuit 53 are arranged at equal intervals of a second length L2 in the width direction D2 based on the sheet center position PC1 in the center of the pair of second horizontal edge positions.

[0138] After executing the process of step S9, the print control unit 8b shifts the process to step S10.

[0139] <Process S10> In step S10, the calibration unit 8c acquires information on a test interference position from the image processing circuit 53. The test interference position is the interference position identified by the image processing circuit 53 based on the mask area corresponding to the second conveying process and data of the second test image G2.

[0140] As described above, the mask area corresponding to the second conveying process is an area of ​​the plurality of black patch images G11 in the first test image G1. Therefore, the test interference position is a position where a part of the plurality of black patch images G11 interferes with a part of the plurality of line segment images G21.

[0141] In this embodiment, the calibration unit 8c acquires a target test interference position Px1, which is the test interference position on the most downstream side in the transport direction D1, from the image processing circuit 53 (see FIG. 7).

[0142] When the reference center position SC1 coincides with the print center position, the position where the reference black patch image G110 and the reference line segment image G210 interfere is identified as the target test interference position Px1 (see FIG. 6).

[0143] However, when the reference central position SC1 is shifted toward the first side in the width direction D2 relative to the print central position, the first test image G1 is formed at a position shifted toward the second side in the width direction D2 further than the state in which the reference black patch image G110 and the reference line segment image G210 interfere with each other.

[0144] Similarly, when the reference central position SC1 is shifted toward the second side in the width direction D2 relative to the print central position, the first test image G1 is formed at a position shifted toward the first side in the width direction D2 further than the state in which the reference black patch image G110 and the reference line segment image G210 interfere with each other.

[0145] In the example shown in Figure 7, the target test interference position Px1 is a position where one of the multiple black patch images G11 that is arranged second on the first side of the reference black patch image G110 in the width direction D2 interferes with one of the multiple line segment images G21 that is arranged second to the right of the reference line segment image G210 in the width direction D2.

[0146] In this embodiment, the difference between the first length L1 and the second length L2 is the length of one pixel, so Fig. 7 shows an example in which the reference center position SC1 is shifted two pixels to the left in the width direction D2 from the print center position.

[0147] That is, the calibration unit 8c can derive the direction and magnitude of the deviation of the reference center position SC1 from the print center position by identifying which of the multiple line segment images G21 the target test interference position Px1 corresponds to.

[0148] After executing the process of step S10, the calibration unit 8c shifts the process to step S11.

[0149] <Process S11> In step S11, the calibration unit 8c corrects the reference central position SC1 in accordance with the target test interference position Px1, and sets the corrected reference central position SC1 as a new reference central position SC1.

[0150] Specifically, the line segment images G21 are assigned with a number of identification values ​​that increase by 1 according to the arrangement order from the first side to the second side in the width direction D2. Among the identification values, the value corresponding to the reference line segment image G210 is 0.

[0151] When the number of line segment images G21 is (2N+1), the plurality of identification values ​​are integers ranging from −N to +N. In the example shown in Fig. 7, the value corresponding to the target test interference position Px1 among the plurality of identification values ​​is −2.

[0152] In step S11, the calibration unit 8c specifies the value corresponding to the target test interference position Px1 from among the plurality of identification values ​​as the correction pixel number of the reference central position SC1.

[0153] 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.

[0154] After executing the process of step S11, 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.

[0155] When the operation mode is the normal mode, the print control unit 8b executes the width position correction process and the mask process for each sheet 9. In the width position correction process, the corrected reference center position SC1 is used. Furthermore, in the normal mode, the print control unit 8b causes the printing device 4 to execute a process of forming, on the sheet 9, the image to be printed that has been subjected to the width position correction process and the mask process.

[0156] By executing the central position calibration process, it is possible to accurately set the reference central position SC1 based on the test image formed on the target sheet 9x without the need for visual confirmation of the image.

[0157] [Application example] Next, an application example of the image forming apparatus 10 will be described with reference to FIG.

[0158] When the central position calibration process is performed, power supply to the heater 431 of the drying device 43 is stopped. Furthermore, the processes after step S4 in the central position calibration process are performed on the condition that the temperature of the drying device 43 satisfies the temperature tolerance condition.

[0159] However, there are cases where it is required to set the permissible temperature of the temperature permissible condition to a relatively high temperature in order to shorten the time for the adjustment process of the image forming apparatus 10. In this case, there is a risk that the target sheet 9x may shrink due to the heat received from the heater 431 in the first conveying process.

[0160] [Second test image data supply process] The flowchart shown in FIG. 9 shows an example of the procedure of a second test image data supply process which is an application example of the process executed in step S9 of FIG.

[0161] In the following description, steps S91 to S93 represent identification codes of three steps in the second test image data supplying process. In the second test image data supplying process, the process of step S91 is executed first.

[0162] <Process S91> In step S91, the calibration unit 8c derives a first sheet width and a second sheet width, and further derives a sheet width ratio which is the ratio of the second sheet width to the first sheet width.

[0163] 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.

[0164] 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.

[0165] After executing the process of step S91, the calibration unit 8c shifts the process to step S92.

[0166] When the sheet width ratio exceeds 1, the proofreading unit 8c outputs an error notification and then ends the second test image data supply process and the center position proofreading process.

[0167] <Process S92> In step S92, the calibration unit 8c derives the line spacing by correcting the second length L2 corresponding to the first length L1 by the sheet width ratio. The line spacing is the spacing in the width direction D2 between the multiple line segment images G21 in the second test image G2. The second length L2 is an example of a reference spacing.

[0168] When the target sheet 9x on which the first test image G1 is formed shrinks, the dimension of each black patch image G11 in the width direction D2 and the pitch of the black patch images G11 in the width direction D2 become smaller according to the shrinkage rate of the target sheet 9x.

[0169] The process of step S92 is a process of correcting the intervals in the width direction D2 of the multiple line segment images G21 so as to match the dimensions in the width direction D2 of the multiple black patch images G11.

[0170] After executing the process of step S92, the calibration unit 8c shifts the process to step S93.

[0171] <Process S93> In step S93, the calibration unit 8c generates data for a second test image G2 including a plurality of line segment images G21 arranged at the line spacing in the width direction D2 based on the center position of the pair of second horizontal edge positions obtained in step S8.

[0172] Furthermore, the calibration unit 8c supplies the data of the generated second test image G2 to the image processing circuit 53 as the reference image data.

[0173] After executing the process of step S93, the proofreading unit 8c ends the second test image data supply process. Then, the proofreading unit 8c executes the processes of step S10 and after (see FIG. 8).

[0174] By executing the second test image data supply process, the reference center position SC1 is corrected to reflect the sheet width ratio (see steps S10 and S11). The sheet width ratio represents a shrinkage rate of the target sheet 9x due to passing through the drying device 43.

[0175] Therefore, by adopting this application example, 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 center position SC1.

[0176] By adopting this application example, 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]

[0177] 1: Sheet storage area 3: Sheet transport device 4: Printing device 5: Sheet measuring device 8: Control device 9a: Specific surface of target sheet 9x: Target sheet 10: Image forming device 43:Drying equipment 51: Black reference member 51a: Reference surface 52: Image sensor unit 53: Image processing circuit 430: Temperature sensor 431: Heater 801: Operating device 802:Display device G1: First test image G11: Black patch image G110: Reference black patch image G2: Second test image G21: Line image G210: Reference line image

Claims

1. a sheet conveying device that conveys a sheet along a conveying path; a printing device for forming an image on the sheet conveyed along the conveying path; a black reference member having a black reference surface arranged along a width direction intersecting with the sheet transport direction in a state facing a detection area on an upstream side of the sheet transport path with respect to the printing device in the sheet transport direction; an image sensor unit disposed along the width direction in a state facing the reference surface across the detection area, emitting detection light toward the reference surface and detecting an amount of reflected light of the detection light, and outputting a plurality of line image data each including a plurality of pixel data representing an amount of detected light corresponding to a plurality of unit areas divided in the width direction in the detection area; an image processing device that performs image processing based on the plurality of line image data; and the image processing device is capable of executing an area detection process for detecting a pair of lateral edge positions that are positions of both ends in the width direction of the sheet passing through the detection area, a sheet area that is an area within a rectangular outline of the sheet, and a mask area that is a portion in the sheet area where the detected light amount is lower than a reference light amount; Furthermore, the image processing device is capable of executing an interference position identification process for identifying a position of an interference part overlapping with the mask region in a reference image represented by the supplied reference image data, a processor, when the operation mode is a first mode, causing the sheet conveying device to execute a first conveying process for conveying the target sheet in a state in which a blank specific side of the target sheet becomes a print side; The processor acquires information on a pair of first lateral edge positions, which are the pair of lateral edge positions detected by the image processing device when the first conveying process is being performed; the processor causes the printing device to execute a process of forming a first test image including a plurality of black patch images on the specific surface while the first conveying process is being executed; the processor causes the sheet conveying device to execute a second conveying process of conveying the target sheet in a state in which the specific side on which the first test image is formed becomes a print side; The processor acquires information on a pair of second lateral edge positions, which are the pair of lateral edge positions detected by the image processing device when the second conveying process is being performed; and The processor supplies data of a second test image, which corresponds to the plurality of black patch images and includes a plurality of line segment images each having a line segment shape along the sheet conveying direction, to the image processing device as the reference image data, and acquires information on a test interference position, which is the position of the interference portion specified by the image processing device based on the mask area corresponding to the second conveying process and the data of the second test image; The processor sets a reference center position, which is a center position in the width direction of the image sensor unit, according to the test interference position; When the operation mode is the second mode, the processor executes a width position correction process to correct the width direction position of the image to be printed each time the sheet is transported in accordance with a difference between the center position of the pair of lateral edge positions detected by the image processing device and the reference center position each time the sheet is transported; The processor supplies the data of the image to be printed that has been subjected to the width position correction process to the image processing device as the reference image data, and executes a mask process to replace pixels in the image to be printed that correspond to the position of the interference portion identified by the image processing device with non-print pixels; and causing the printing device to execute a process of forming, on the sheet, the image to be printed that has been subjected to the width position correction process and the mask process, the plurality of black patch images in the first test image are arranged in a stepped manner at a pitch of a reference length in the width direction with the center position of the pair of first horizontal edge positions as a reference, with the positions of the black patch images in the sheet conveying direction being shifted sequentially, and each of the black patch images is a rectangular black filled image having a width of the reference length, an image forming control method in which the multiple line segment images in the second test image are arranged at equal intervals in the width direction that are smaller than the reference length, based on the center position of the pair of second horizontal edge positions, and each end of the multiple line segment images is formed at a position that overlaps with a corresponding one of the multiple black patch images in the sheet transport direction.

2. the printing device forms an image on the sheet by ejecting ink onto the sheet; When the image forming apparatus further includes a drying device that is disposed downstream of the printing device in the sheet conveying direction, has a heater that heats the sheet, and dries the ink on the sheet, The processor derives a line interval, which is the interval in the width direction of the plurality of line segment images, by correcting a reference interval corresponding to the reference length by a ratio of the interval between the pair of second horizontal edge positions to the interval between the pair of first horizontal edge positions; The image forming control method of claim 1, further comprising: the processor generating data for the second test image including the plurality of line segment images arranged at the line spacing in the width direction based on the center position of the pair of second lateral edge positions.

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 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. a sheet conveying device that conveys a sheet along a conveying path; a printing device for forming an image on the sheet conveyed along the conveying path; a black reference member having a black reference surface arranged along a width direction intersecting with the sheet transport direction in a state facing a detection area on an upstream side of the sheet transport path with respect to the printing device in the sheet transport direction; an image sensor unit disposed along the width direction in a state facing the reference surface across the detection area, emitting detection light toward the reference surface and detecting an amount of reflected light of the detection light, and outputting a plurality of line image data each including a plurality of pixel data representing an amount of detected light corresponding to a plurality of unit areas divided in the width direction in the detection area; an image processing device capable of executing an area detection process to detect a pair of lateral edge positions which are the positions of both ends in the width direction of the sheet passing through the detection area, a sheet area which is an area within the rectangular outline of the sheet, and a mask area which is a portion in the sheet area where the detected light amount is lower than a reference light amount by executing image processing based on the plurality of line image data, and further capable of executing an interference position identification process to identify a position of an interference portion which overlaps with the mask area in a reference image represented by the supplied reference image data; 3. An image forming apparatus comprising: a processor that realizes the image forming control method according to claim 1.

Images