Image forming system and printing method

Abstract

To accurately detect a sheet size or a sheet shape, and prevent a reduction in productivity.SOLUTION: An image forming system comprises: a reading unit 50 including a reading sensor 51 that optically reads a sheet conveyed through a conveyance path 341; and a control unit that controls the reading unit 50. The reading unit 50 can execute a plurality of reading modes including at least a first reading mode and a second reading mode different from the first reading mode, and performs reading of the sheet in any one of the reading modes selected according to print settings. When there is a switch from the first reading mode to the second reading mode during formation of images on the sheet to be continuously conveyed, the control unit changes a conveyance condition for the sheet from a first conveyance condition to a second conveyance condition, in regard to the conveyance of a sheet to be conveyed after the switch.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming system and a printing method. [Background technology]

[0002] There is a technology in image forming devices that detects the size of paper and corrects the image according to this detected size (for example, Patent Document 1). In the image forming device disclosed in Patent Document 1, the size measurement unit is positioned sufficiently upstream of the image forming unit, so that the image position correction set based on the measurement results of the size measurement unit is reflected in the detected paper.

[0003] Furthermore, in Patent Document 1, the paper width is measured by detecting the position of the side edges of the paper (the position of the right edge and the position of the left edge in the conveying direction) using a contact image sensor (CIS) that measures the paper width as a size measurement unit (paragraph 0013). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-238544 Summary of the Invention [Problem to be solved by the invention]

[0005] Image forming devices use a wide variety of paper types, including dark colored paper in addition to white paper. While the image forming device described above uses a CIS to detect the positions of both edge portions of the paper, there is a risk that accurate detection will not be possible with colored paper because sufficient contrast may not be obtained at the edge positions.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide an image forming system that can accurately detect the size or shape of paper and suppress a decrease in productivity. [Means for solving the problem]

[0007] The above object of the present invention can be achieved by the following means.

[0008] (1) a paper feed unit that feeds paper; a conveying unit that conveys paper in a conveying path; a reading unit including a reading sensor that optically reads the paper conveyed through the conveyance path; an image forming unit that is located downstream of the reading unit in the conveyance path and that forms an image on the conveyed paper; a control unit, the reading unit is capable of executing a plurality of reading modes including at least a first reading mode and a second reading mode different from the first reading mode, and reads the paper in one of the reading modes selected in accordance with print settings; The control unit, when switching from the first reading mode to the second reading mode while forming an image on continuously transported paper, changes the paper transport conditions for the paper transported after the switching from the first transport conditions to second transport conditions different from the first transport conditions.

[0009] (2) The image forming system according to (1) above, wherein the reading unit executes the reading mode according to the color of the paper to be read.

[0010] (3) The reading unit includes a background unit disposed opposite the reading sensor across the conveyance path, the background unit having a plurality of background surfaces of different colors that become the background of the paper when reading, The image forming system according to (1) or (2), wherein the switching of the reading mode is switching of the background surface.

[0011] (4) The image forming system according to (3), wherein the reading unit switches the background surface depending on the color of the paper to be read.

[0012] (5) The image forming system according to (1), wherein the control unit, under the second transport condition, makes the transport speed of the paper in the transport path faster than the transport speed of the paper under the first transport condition.

[0013] (6) The image forming system described in (1) or (5) above, wherein the control unit, under the second transport condition, makes the stop time of the paper at the temporary stop position in the transport path shorter than the stop time of the paper under the first transport condition.

[0014] (7) An image forming system as described in (1) or (5) above, wherein the control unit, under the second transport condition, shortens the paper spacing between the paper and the preceding and succeeding papers in the transport path compared to the paper spacing under the first transport condition.

[0015] (8) The image forming system described in (1) above, wherein the control unit, when switching from the first reading mode to the second reading mode, sets the second transport conditions and / or sets the number of sheets of paper to which the second transport conditions are continuously applied based on the switching time required for switching.

[0016] (9) a paper feed unit that feeds paper; a conveying unit that conveys paper in a conveying path; a reading unit including a reading sensor that optically reads the paper conveyed through the conveyance path; an image forming unit that forms an image on the transported paper downstream of the reading unit in the transport path, the reading unit is capable of executing a plurality of reading modes including at least a first reading mode and a second reading mode different from the first reading mode, and a step (a) of selecting one of the reading modes according to a print setting; (b) reading the paper in the selected reading mode; (c) forming an image on the continuously conveyed paper; a step (d) of changing the paper transport conditions from the first transport conditions to the second transport conditions for transporting the paper transported after the switching from the first reading mode to the second reading mode during the execution of the step (c); A printing method that performs a process including:

[0017] (10) The printing method according to (9) above, wherein in the step (a), the reading mode is selected according to the color of the paper to be read. [Effects of the Invention]

[0018] The image forming system according to the present invention is capable of executing a plurality of reading modes, including at least a first reading mode and a second reading mode different from the first reading mode. The system includes a reading unit that reads the paper sheets using one of the reading modes selected according to print settings. When the first reading mode is switched to the second reading mode during image formation on continuously transported paper sheets, the control unit changes the paper transport conditions for the paper sheets transported after the switch from the first transport conditions to second transport conditions different from the first transport conditions. This allows for accurate detection of paper size or paper shape and minimizes productivity degradation. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing a schematic configuration of an image forming system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing a hardware configuration of the image forming system. [Figure 3] FIG. 2 is a schematic diagram showing the main configuration of a reading unit in the present embodiment. [Figure 4] FIG. 2 is a schematic diagram showing the main configuration of a reading unit. [Figure 5] 10 is a table for explaining the conditions for using each surface of the background portion. [Figure 6] 10 is a table for explaining the conditions for using each surface of the background portion. [Figure 7A] 10 is a flowchart showing a background surface switching process and a printing process in the present embodiment. [Figure 7B] 7B is a subroutine flowchart showing the processing of step S120 in FIG. 7A. [Figure 7C] 7B is a subroutine flowchart showing the processing of step S130 in FIG. 7A. [Figure 8] 1 is an example of a print job. [Figure 9] 10 is an example of a table showing the switching time required to switch from the reading mode for the previous sheet to the reading mode for the next sheet. [Figure 10] 10 is a table showing examples of first and second transport conditions. [Figure 11] 10 is a timing chart showing a timing delay process and a recovery process by transport control when the reading mode is switched. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the scope of the present invention is not limited to the disclosed embodiments. In the description of the drawings, identical elements are given the same reference numerals, and redundant description will be omitted. Furthermore, the dimensional ratios of the drawings are exaggerated for convenience of explanation and may differ from the actual ratios. In the drawings, the up-down direction (vertical direction) is defined as the Z direction, the front and rear directions of the image forming system or reading device are defined as the Y direction, and the direction perpendicular to these Y and Z directions is defined as the X direction. The X direction is also referred to as the paper transport direction. The Y direction is also referred to as the width direction. In this embodiment, paper includes printing paper (hereinafter simply referred to as paper) and various films.

[0021] Fig. 1 is a diagram showing a schematic configuration of an image forming system 1000 according to this embodiment. Fig. 2 is a block diagram showing a hardware configuration of the image forming system 1000. As shown in Fig. 1, the image forming system 1000 includes an image forming apparatus 10, a paper feeder 20, a reader 30, and a post-processing apparatus 40, which are mechanically and electrically connected to one another.

[0022] (Image forming apparatus 10) The image forming apparatus 10 forms an image on a sheet 90 that is fed from an upstream paper feeder 20 and sent via a reading device 30. The image forming apparatus 10 also forms an image on a sheet 90 that is fed from its own paper feed unit.

[0023] The image forming apparatus 10 includes a control unit 11, a storage unit 12, an image forming unit 13, a conveying unit 14, a paper feeding unit 15, an operation panel 18, a communication unit 19, etc. These are connected to each other via signal lines such as a bus for exchanging signals. Note that in Fig. 2, the signal lines connecting some of the components of the image forming apparatus 10, such as the storage unit 12 and the operation panel 18, are omitted (connections to the control unit 31 of the reading device 30, which will be described later, etc., are also omitted).

[0024] (Control unit 11) The control unit 11 is composed of a CPU, ROM, RAM, etc., and executes various processes by executing programs stored in the ROM or in the storage unit 12 described below, and controls each unit of the device and performs various arithmetic processes in accordance with the programs. The control unit 11 functions as a print control unit 111, a reading device control unit 112, an other device control unit 113, and a correction value calculation unit 114. The functions of these sub-control units 111 to 114 will be described later.

[0025] (Storage unit 12) The memory unit 12 includes an auxiliary memory unit such as a hard disk that stores various programs and data in advance. The memory unit 12 also stores information about the paper stored in each paper feed tray (such as trays 155, 255, and 256, described below) in association with the paper feed tray. The paper information includes information about the paper brand, size (paper width, paper length), paper color, basis weight, and paper type (gloss coated paper, matte coated paper, plain paper, high-quality paper, rough paper, etc.). The memory unit 12 may also store a paper brand, a determination model (determination model algorithm) used to determine control parameters, and a paper profile. The memory unit 12 also stores the switching time required to switch the background unit 56, the paper interval (paper spacing) associated with switching to a paper feed tray (such as trays 255 and 256, described below), and the paper interval (paper spacing) for each paper size. Here, the sheet interval time refers to the interval (measured in transport time) between the rear end of the previous sheet 90 and the front end of the next sheet 90. The memory unit 12 also stores conditions for executing stabilization processing for the image forming unit 13. For example, the stabilization processing is executed when a predetermined event occurs, such as the power being turned on, or every predetermined number of prints (for example, every 1,000 sheets).

[0026] (Image forming unit 13) Image forming unit 13 forms an image, for example, by electrophotography. Image forming unit 13 includes writing units (laser exposure units) corresponding to the respective basic colors of Y (yellow), M (magenta), C (cyan), and K (black), photosensitive drums, and developing units containing two-component developers consisting of toner and carrier for each color. Image forming unit 13 also includes an intermediate transfer belt, a secondary transfer unit, and a fixing unit. Toner images formed on the photosensitive drums by the developing units for each color are superimposed on the intermediate transfer belt and transferred to paper 90 conveyed in the secondary transfer unit. The toner images on paper 90 are fixed to paper 90 by applying heat and pressure in a fixing unit downstream.

[0027] A density sensor that optically detects the density of the toner patches formed on the intermediate transfer belt is disposed in the image forming unit 13. In the stabilization process, a plurality of patch images with different colors and gradations (densities) are printed on the intermediate transfer belt based on the evaluation chart data stored in the memory unit 12, the reflection density of these images is detected by the density sensor, and the image formation conditions are adjusted based on the obtained data.

[0028] (Transport unit 14, paper feed unit 15) The transport unit 14 includes transport paths 141, 142, etc. The paper feed unit 15 includes multiple paper feed trays 155. The transport path 141 includes multiple pairs of transport rollers provided along the transport path, and a drive motor (not shown) that drives these pairs of transport rollers. The paper feed unit 15 includes a feed roller that feeds the topmost sheet of paper 90 stacked in the paper feed tray 155, and feeds the sheets 90 in the paper feed tray one by one to the downstream transport path. The upstream side of the transport path 141 is connected to a transport path 341 of the reading device 30.

[0029] The conveying section 14 conveys paper 90 fed from a paper feed tray 155 or the like. After an image is formed on the paper 90 conveyed along the conveying path 141 by the image forming section 13, the paper 90 is discharged onto the paper output tray 41 via the subsequent post-processing device 40. When performing double-sided printing, in which an image is also formed on the back side (second side) of the paper 90, the paper 90 with the image formed on one side is conveyed to a conveying path 142 for double-sided image formation located at the bottom of the device main body. The paper 90 conveyed to this conveying path 142 is turned over on a switchback path, and then merges with the conveying path 141 for single side, where an image is again formed on the other side of the paper 90 by the image forming section 13.

[0030] (Operation panel 18, etc.) The operation panel 18 includes a touch panel, a numeric keypad, a start button, a stop button, etc. The operation panel 18 displays the status of the image forming apparatus 10 or the image forming system 1000, and is used for inputting various settings and instructions from the user. The user can set the type of paper loaded in the paper feed trays 155, 255, etc., and the paper color information through the setting screen of the operation panel 18 (see FIG. 6 described later). The user can also set the following through the setting screen of the operation panel 18 or the setting screen of a print setting application running on a PC (personal computer) connected to and communicating with the image forming system 1000 (hereinafter referred to as the operation panel, etc.). (1) Paper size to be used as print settings, (2) Paper color information, and (3) Setting of paper image position correction, such as valid / invalid. Note that, hereinafter, the paper size and color information of the paper are also referred to as paper attribute information.

[0031] The communication unit 19 is an interface for communicating with a PC or other devices 20, 30, etc.

[0032] (Sub-control units 111 to 114) When a print job is input, the print control unit 111 executes the print job based on the print job setting information of the input print job. The print job is input based on instructions sent from the operation panel 18 or an external terminal such as a network-connected PC operated by the user.

[0033] The print control unit 111 controls the transport unit 14 (including drive motors for transport paths 141, 142, the fixing unit, etc.) and the paper feed unit 15 to control the feeding and transport of the paper 90. The print control unit 111 also instructs the reading device control unit 112 to read the paper 90 before image formation (reading instruction) according to the print job settings (whether image position correction is enabled). The print control unit 111 also calculates the time required to switch the background surface (see FIG. 4, described later) between reading modes (hereinafter referred to as the "switching time"). This switching time may be calculated based on the positional relationship (amount of rotation of 90 degrees or 270 degrees) between the current background surface (background surface 1, 2, paper passing surface) and the background surface to be switched, and the movement speed (rotation speed). Alternatively, a table describing the previous and next background surfaces and their switching times, previously stored in the storage unit 12, may be referenced (see, for example, FIG. 9, described later). Alternatively, the switching time may be acquired by inquiring of the control unit 31 of the reading device 30 via the reading device control unit 112. This switching time corresponds to the delay time dt.

[0034] In addition, the print control unit 111 compares the switching time with the current paper interval, and if the switching time is longer than the current paper interval, controls the image forming unit 13 and / or the paper feeding unit 255, etc., to increase the image formation timing or paper interval.

[0035] In addition, the print control unit 111 controls the image forming unit 13, controls the image forming timing according to the image forming conditions and the paper position based on the paper position correction value calculated by the correction value calculation unit 114 described below, and adjusts the vertical and horizontal magnification (hereinafter referred to as position correction control).

[0036] As will be described below, position correction control is performed on at least either the first surface (front side) or the second surface (back side) depending on the placement position of at least the reading unit 50. The placement conditions of the reading unit 50 will differ depending on the length or speed of the conveying path of the reading device 30 itself, or whether other devices are connected between the reading device 30 and the image forming apparatus 10. (1) Possible placement conditions for both the first and second sides For example, if the reading unit 50 is positioned sufficiently upstream of the image forming unit 13 (similar to, for example, JP 2014-238544 A) and is positioned in a way that allows for image correction timing, position correction control is performed on the paper 90 that has been read. Specifically, if the reading unit 50 is positioned such that (b) comes after (a) below, position correction control is performed when forming an image on the first and / or second side of the paper 90 that has been read. (a) The timing when preparation for image formation reflecting position correction control is completed based on the image data (hereinafter referred to as read data) obtained by the reading unit 50 of the reading device 30 reading the paper 90, and (b) the timing when image formation on the paper 90 begins. (2) Placement conditions only available on the second side Furthermore, if the placement conditions of the reading device 30 are such that the image correction timing is not in time, image formation is performed that reflects position correction control when forming an image on the second side (rear side) of the read paper 90 during double-sided image formation in order to align the image registration on the front and back sides.

[0037] The reading device control unit 112 controls the reading device 30 in response to an execution instruction request (reading instruction) from the print control unit 111. In response to the execution instruction request, the reading device 30 executes measurement of paper characteristics using the reading unit 50 and various other sensors included in the reading device 30. Furthermore, when the reading device 30 reads the paper 90, the reading device control unit 112 acquires the read data generated by the reading device 30.

[0038] The other device control unit 113 controls the sheet feeding device 20 and the post-processing device 40. Specifically, the other device control unit 113 communicates with the sheet feeding device 20 to send and receive information such as the sheet feeding tray to be used and the timing of sheet transport. Specifically, the other device control unit 113 sends information such as the timing of sheet transport and setting information for post-processing of the sheets to be transported to the post-processing device 40.

[0039] The correction value calculation unit 114 acquires read data obtained by reading the paper 90 before image formation from the reading device control unit 112, and detects the length and shape characteristics of each side (length and width) of the paper 90 from the acquired read data (hereinafter, the detected characteristics will also be simply referred to as "paper size"). The correction value calculation unit 114 calculates an image position correction value from the difference between the detected paper size and the paper size in the print settings. The calculated image position correction value is sent to the print control unit 111. As described above, the print control unit 111 performs position correction control to match the paper position according to this image position correction value.

[0040] (Paper feeder 20) 1 and 2, paper feeder 20 includes conveying section 24 and paper feed section 25. In addition to conveying section 24 and paper feed section 25, paper feeder 20 also includes a control section, a storage section, and a communication section (none of which are shown), which are interconnected via signal lines such as a bus for exchanging signals.

[0041] The paper feed unit 25 includes a plurality of paper feed trays 255 and a manual feed tray 256. The paper feed trays 255 are automatically numbered from tray 1 to tray n based on a predetermined rule. The transport unit 24 and the paper feed unit 25 have the same functions as the transport unit 14 and the paper feed unit 15, and feed paper 90 placed in the paper feed tray 255 or the like one sheet at a time and transport the paper to a transport path 241. The transport path 241 is connected to the subsequent transport path 341. The paper 90 fed from the paper feed tray 255 or the like and transported along the transport path 241 is transported to the downstream reading device 30, where the paper characteristics such as the paper size are measured, and an image is formed on the paper by the image forming device 10 further downstream.

[0042] (Post-processing device 40) The post-processing device 40 performs post-processing on the paper sheets 90 sent from the image forming device 10 and ejects them in accordance with the settings of the print job. The post-processing device 40 includes paper output trays 41 and 42, a post-processing unit 43, and a conveying path 441. The post-processing device 40 also includes a control unit, a memory unit, a conveying unit, and a communication unit (none of which are shown), which are connected to each other via signal lines such as a bus for exchanging signals. The paper output trays 41 and 42 are selected in accordance with the settings of the print job. The conveying path 441 is connected to the upstream conveying path 141. The post-processing unit 43 performs at least one of post-processing processes, including stapling, punching, cutting, folding, and binding, on the paper sheets 90 on which an image has been formed.

[0043] (Reader 30) Next, the reading device 30 will be described. As shown in Fig. 2, the reading device 30 includes a control unit 31, a storage unit 32, a conveying unit 34, a communication unit 39, a reading unit 50, etc. The control unit 31, the storage unit 32, the conveying unit 34, and the communication unit 39 each have the same hardware configuration as the control unit 11, the storage unit 12, the conveying unit 14, and the communication unit 19 of the image forming apparatus 10 described above, and therefore a description thereof will be omitted.

[0044] (Reading unit 50) An overview of the reading unit 50 will be described below with reference to FIGS. 3 to 6. FIGS. 3 and 4 are schematic diagrams showing the main components of the reading unit 50. FIG. 3(a) is a top view, and FIG. 3(b) is a side view. The reading unit 50 includes a reading sensor 51, a background unit 56, and a switching mechanism 57. The reading sensor 51 is a one-dimensional line sensor having multiple photoelectric conversion elements lined up in the Y direction, and reads one-dimensional images. The reading sensor 51 also has optical elements such as light-emitting elements and lens arrays arranged along the row of photoelectric conversion elements. During reading, the light-emitting elements irradiate the paper 90 on the conveying path 341 with uniform light in the extension direction of the row. When the reading unit 50 reads the paper 90, read data corresponding to one sheet of paper is generated.

[0045] The background unit 56 has a polygonal cross-section and a rectangular prism shape with its axis extending in the Y direction. In the example shown in FIG. 4 etc., the background unit 56 has a quadrangular prism shape with four faces 561 to 564. The switching mechanism 57 is composed of a drive source and a rotation mechanism such as gears, and switches the background face facing the reading sensor 51 by controlling the rotation position of the background unit 56. For example, the switching mechanism 57 has a servo motor or a stepping motor, and rotates the background unit 56 clockwise in FIG. 4 around the rotation axis by a predetermined angle (an integer multiple of 90 degrees) and stops it at that position.

[0046] 3(b) and 4, the background section 56 is disposed opposite the reading sensor 51 across the conveying path 341. The background section 56 is disposed in a cutout portion of a lower guide plate that constitutes the conveying path 341. The surface of the background section 56 that faces the reading sensor 51 among four surfaces 561 to 564 is switched by a switching mechanism 57.

[0047] The configuration of the background unit 56 is not limited to the example shown in FIG. 4 and other examples, and other configurations may be used. For example, four surfaces are arranged in the X direction on a plate-shaped background unit 56. Then, the switching mechanism 57 slides the background unit 56 a predetermined amount back and forth in the X direction, thereby switching the surface facing the reading sensor 51. As another example, the background unit 56 may be configured as a device that can electrically switch the density of the display surface, such as electronic paper. In this case, the density (brightness) of the surface facing the reading sensor 51 is switched by electrical control.

[0048] 3(a), the reading area of the reading sensor 51 in the Y direction ranges from y0 to y100, which is wider than the maximum paper width of the paper 90 that can be conveyed in the image forming system 1000. Also, in the Y direction, the center c1 of the conveyance of the paper 90 and the center c1 of the reading area of the reading sensor 51 are aligned.

[0049] (Background surface 1, 2, paper passing surface, etc.) 5 and 6 are tables for explaining the conditions for using surfaces 561 to 564 of the background portion 56. These tables are stored in advance in the memory unit 12 or the memory unit 32. Background surfaces 1 and 2 (surfaces 561 and 562) are surfaces that are used when the reading setting in the reading unit 50 is enabled. Hereinafter, reading using background surface 1 may be referred to as reading mode 1, and reading using background surface 2 may be referred to as reading mode 2 (one of reading modes 1 and 2 corresponds to the first reading mode, and the other corresponds to the second reading mode).

[0050] Surface 561 is black or a color with a brightness equal to or less than a predetermined value (for example, L* in the CIELAB color space is 20 or less). Surface 561 is a first background surface (hereinafter also referred to as "background surface 1") that becomes the background of paper 90 when read by reading sensor 51. As shown in FIGS. 5 and 6, background surface 1 is used when the color information of paper 90 to be read is included in group 1 and the background color has a brightness difference with surface 561 that is greater than or equal to a predetermined value.

[0051] Surface 562 is white or a color with a brightness equal to or greater than a predetermined value (for example, L* in the CIELAB color space is equal to or greater than 70). Surface 562 is a second background surface (hereinafter also referred to as "background surface 2") that forms the background of paper 90 when read by reading sensor 51. As shown in FIGS. 5 and 6, background surface 2 is used when the color information of paper 90 to be read is included in group 2 and the background color has a brightness difference from surface 562 that is greater than or equal to a predetermined value.

[0052] The surface 563 is a calibration surface used for calibrating the reading sensor 51, which is performed periodically at a predetermined timing of the reading sensor 51. For example, the surface 563 is configured to have a white color within a specified range, and is used for adjusting the white balance and white level.

[0053] Surface 564 is used when reading is not performed (reading setting is disabled), and functions as a paper passing surface that covers the cutout portion of the lower guide plate of conveying path 341 when paper is passed.

[0054] (Background surface switching process, timing process, productivity recovery process and printing process) Next, various control processes associated with the background plane switching process executed in the image forming system 1000 according to this embodiment will be described with reference to FIGS. 7A to 7C and 8 to 11. FIG.

[0055] FIG. 7A is a flowchart showing the background surface switching process executed by the reading device 30 and the printing process executed by the image forming system 1000. FIGS. 7B and 7C are subroutine flowcharts showing the processes of steps S120 and S130 in FIG. 7A, respectively. FIG. 8 is an example of a print job to be executed, with the table in FIG. 8(a) showing a job list and FIG. 8(b) showing detailed information for job 1 in the job list. The print jobs in the job list are executed consecutively in order starting from job 1. For each job, the image forming system 1000 continuously transports multiple sheets of paper 90 according to the print settings, continuously reads images (according to the image position correction settings), and continuously forms images.

[0056] (Step S100) The print control unit 111 of the control unit 11 reads the first print job in the print job reservation list. In the example shown in Fig. 8, the first job 1 is read. The print job includes print settings and print data (document image data). As shown in Fig. 8, the print settings include at least the paper color (paper attribute information) for each page and the enable / disable (ON / OFF) setting for image position correction for each print job or each page.

[0057] (Step S110) The print control unit 111 acquires the page settings from the print settings of the currently executing print job.

[0058] (Step S120) The print control unit 111 performs a process for selecting a reading mode based on print settings or page settings. This process will be described with reference to the subroutine flowchart in FIG. 7B.

[0059] (Step S201) The print control unit 111 refers to the print settings or page settings and determines whether image position correction is enabled. If it is set to disabled, the print control unit 111 proceeds to step S202, and if it is set to enabled, the print control unit 111 proceeds to step S203. In the example of job 1 in FIG. 8, image position correction is set to "enabled."

[0060] (Step S202) The print control unit 111 selects a mode other than the reading mode. In this case, the passing paper side (side 564) is selected.

[0061] (Step S203) The print control unit 111 acquires the paper color (paper information) in the print settings and, with reference to the table in Fig. 6, determines whether this paper color is group 1 (light color) or group 2 (dark color). If the paper color is group 1, the print control unit 111 proceeds to step S204, and if the paper color is not group 1 (if the paper color is group 2), the print control unit 111 proceeds to step S205.

[0062] (Step S204) The print control unit 111 selects reading mode 1. In this case, background surface 1 (black) (surface 561) is selected. For example, in the example of job 1 in FIG. 8(b), in subjob 1-2, pages 2 to 31 have a white paper color (group 1), so background surface 1 (black) is selected.

[0063] (Step S205) The print control unit 111 selects reading mode 2. In this case, background surface 2 (white) (surface 562) is selected. For example, in the example of job 1 in FIG. 8(b), the paper color is gray (group 2) for page 1 of subjob 1-1 or page 32 of subjob 1-3. Therefore, background surface 2 (white) is selected, which corresponds to reading mode 2 selected in response to switching from paper feed tray 1 to paper feed tray 4. With this, the print control unit 111 ends the processing of FIG. 7B and returns to the processing from step S130 onwards in FIG. 7A.

[0064] (Step S130) The print control unit 111 acquires setting information for the current reading mode (background surface) from the reading device control unit 112 and determines whether the current reading mode is different from the reading mode selected in step S120 and whether a change in reading mode will occur. If a change in reading mode will occur, the print control unit 111 executes timing delay processing and recovery processing corresponding to the change. The recovery processing is processing that uses timing delay processing to make up for the delay, that is, processing by transport control (second transport control in FIG. 10, described below) to suppress a decrease in productivity. This processing will be explained using the subroutine flowchart in FIG. 7C.

[0065] (Timing delay processing: steps S301 to S304) (Step S301) If the reading mode is the same between the previous and next consecutive sheets and there is no switching, the print control unit 111 proceeds to step S305, and if there is a switching of the reading mode, the print control unit 111 proceeds to step S302.

[0066] (Step S302) The print control unit 111 calculates the switching time (hereinafter also referred to as delay time dt) required to switch the background surface between reading modes. FIG. 9 is an example of a table showing the switching time required to switch from the reading mode for the previous sheet to the reading mode for the next sheet. The switching time from reading mode 1 to reading mode 2 is time x1 (e.g., 0.5 seconds). The switching time from reading mode 2 to reading mode 1 is time x3 (e.g., 1.0 seconds), which is longer than time x1. Furthermore, if the previous sheet is in a mode other than the reading mode (paper passing side), the reading mode for the next sheet can be switched to while the previous sheet (one or several sheets) is being transported (passing) through the reading unit 50 (particularly the reading area). Therefore, the switching time is essentially zero. The print control unit 111 adds this delay time dt to the required reduction time rt. The required reduction time rt is initially set to zero and is reset at the start of the print job.

[0067] (Step S303) The print control unit 111 controls the switching mechanism 57 by the control unit 31 through the reading device control unit 112 to switch to the reading mode (background side) selected in step S120. For example, the print control unit 111 switches to the paper side if a mode other than the reading mode (paper side) is selected in step S120 (S202), and switches to background side 1 if reading mode 1 (background side 1) is selected in step S120 (S204).

[0068] (Step S304) The print control unit 111 waits for image formation preparation during the switching time required to switch the reading mode. That is, the print control unit 111 delays the image formation timing during the switching time. The delay delays the paper feed timing of the paper (next paper) and also delays the image formation start timing (writing timing) for this paper 90.

[0069] It should be noted that the print control unit 111 may exceptionally not delay the image formation timing in the following cases. (1) When the switching time is less than the paper interval time. The paper interval is set differently depending on the paper size. For example, it is short for A4, A3, and letter, and long for other sizes. It is even longer for non-standard size paper (non-JIS standard). Therefore, if the paper interval time according to the paper size is longer than the switching time, the processing of step S304 (delay processing due to waiting) is not necessary. (2) When switching time is less than paper tray change time. When different paper trays are used for the previous and next sheets, a delay occurs (paper tray change time) that lengthens the time between sheets before and after the paper tray change due to the positional relationship of the paper tray being changed. The distance to a specific position on the transport path (e.g., image formation position, registration roller position, etc.) differs depending on the paper tray. For example, consider the following cases (2a) and (2b). (2a) When switching to a later paper feed tray after detecting that the previous paper feed tray is out of paper (out of paper). (2b) When the distance to the new paper feed tray is longer than that of the previous paper feed tray (i.e., when switching to a paper feed tray located further upstream), the difference in the transport distance between the two paper feed trays increases the distance between the last sheet from the previous paper feed tray and the first sheet from the new paper feed tray (the changeover time increases). (3) When image stabilization processing is performed between the previous and next sheets: In this case, the time required for image stabilization processing is sufficiently longer than the switching time, so the processing (waiting) of step S304 is not necessary.

[0070] (Recovery process: steps S306 to S308) (Step S305) The print control unit 111 determines whether the current required reduction time rt is greater than 0, and if it is greater than 0, proceeds to step S306, and if it is equal to or less than 0 (zero), proceeds to step S308. As described above, this required reduction time rt has an initial value of zero, to which the delay time dt has been added by the processing in step S302.

[0071] (Step S306) The print control unit 111 sets the transport conditions to second transport conditions. That is, if the transport conditions were the first transport conditions up until then, the print control unit 111 changes the transport conditions for the paper transported after the reading mode is switched from the first transport conditions to second transport conditions that are different from the first transport conditions. On the other hand, if the transport conditions were the second transport conditions up until then, the print control unit 111 continues to use the second transport conditions.

[0072] FIG. 10 is a table showing examples of first and second transport conditions. The first transport condition is a transport condition for normal mode, and the second transport condition is a transport condition that improves productivity more than the first transport condition. Item a is the interval (gap) between continuously transported sheets. Item b is the pause time (standard time) at the registration roller position as a pause position. The registration roller is a roller located immediately upstream of the image forming position (secondary transfer roller) on the transport path, and the image timing and the paper transport timing are synchronized by fine-tuning the pause length at the registration roller. Items c to e are the transport speeds for paper feeding, image formation, and paper discharge, respectively. Item c is the transport speed of a device upstream of the image forming device 10. The transport speed for image formation in item d is mainly the transport speed on the transport path of the image forming device 10 (and the process speed of the image forming unit 13). Item e is the transport speed of a device downstream of the image forming device 10. As the second transport condition, all or some of the items a to e may be applied. For example, only items a and b, or only items c and e may be applied, or items a, b, d, and e may be applied. In the following description and in FIG. 11 described later, it is assumed that items a and b are applied.

[0073] (Step S307) The print control unit 111 performs a subtraction process on the required time to be reduced rt. By changing from the first transport condition to the second transport condition, the time that can be reduced is subtracted from the required time to be reduced rt. For example, in FIG. 10, when items a and b are applied, a reduction of 80 msec is possible, which is the sum of the contribution of item a (60 msec) and the contribution of item b (20 msec). The print control unit 111 subtracts this 80 msec of the reduced time st from the required time to be reduced rt.

[0074] (Step S308) The print control unit 111 sets the transport conditions to the first transport conditions. In other words, if the transport conditions were the second transport conditions up until that point, the print control unit 111 changes the paper transport conditions from the second transport conditions to the normal first transport conditions. This is because the first transport conditions allow for more stable transport. With this, the print control unit 111 ends the processing of FIG. 7C and returns to the processing from step S140 onwards in FIG. 7A.

[0075] (Step S140) The print control unit 111 reads out the print data of the specified page based on the print settings, and sends an instruction to the image forming unit 13 to prepare for image formation on the next sheet 90 .

[0076] (Step S150) The print control unit 111 sends an instruction to the paper feed unit 25 of the paper feed device 20, via the other device control unit 113, to start feeding the next sheet of paper 90 from the paper feed tray 255 specified in accordance with the print settings. The paper feed unit 25 feeds the paper 90 from the specified paper feed tray 255 and transports it along the transport path 241. For example, in the example of subjob 1-2 of job 1 in FIG. 8, the paper 90 is fed from tray 1.

[0077] (Step S160) The print control unit 111 refers to the print settings and determines whether image position correction is enabled. If it is set to disabled, the print control unit 111 proceeds to step S220, and if it is set to enabled, the print control unit 111 proceeds to step S170. In the example of job 1 in FIG. 8, image position correction is set to "enabled."

[0078] (Step S170) The print control unit 111 instructs the reading device 30 to read the paper 90 before image formation via the reading device control unit 112. The reading unit 50 reads the designated paper 90 in accordance with the timing at which the paper 90 is transported to the reading area of the transport path 341, and generates read data (image data).

[0079] (Step S210) The reading device control unit 112 acquires the read data generated by the reading in step 21 from the reading device 30 and temporarily stores it in the storage unit 12. The reading device control unit 112 then notifies the correction value calculation unit 114 of this. The correction value calculation unit 114 recognizes the edge of the paper 90 from the read data and recognizes the lengths and shapes of the four sides of the paper 90. In this case, when reading in step S170, the background surface that serves as the background of the paper 90 when reading and that is arranged opposite the reading sensor 51 (reading sensor) is set to a background surface of a color that contrasts highly with the paper color of the paper 90. Therefore, the correction value calculation unit 114 can accurately recognize the edge of the paper 90 from the read data.

[0080] The correction value calculation unit 114 recognizes the paper size from the recognized lengths or shapes of the four sides, and calculates an image position correction value from the difference between the recognized paper size and the paper size in the print settings.

[0081] The correction value calculation unit 114 notifies the print control unit 111 of the calculated image position correction value via the reading device control unit 112. In job 1 shown in Fig. 8, the print control unit 111 uses the calculated image position correction value as a correction value for the image formation position on the back side (second surface) to align the image registration on the front and back sides (first and second surfaces). The print control unit 111 notifies the image forming unit 13 of the image formation position correction value and sets it.

[0082] (Step S220) The print control unit 111 sends an instruction to the image forming unit 13 to form an image on the next sheet 90. The image forming unit 13 forms an image on the sheet surface using the instructed print data. When forming this image, the image position of at least one of the first and second sides is finely adjusted based on the image position correction value.

[0083] (Step S230) Print control unit 111 checks the print settings, and if there is a next page in the print job being executed, returns the process to step S110 and repeats the subsequent processes. On the other hand, if there is no next page, the process proceeds to step S240.

[0084] (Step S240) The print control unit 111 checks the print job reservation list, and if there is a next print job, returns the process to step S100 and repeats the subsequent processes. On the other hand, if there is no next print job, the operation of the device is stopped and the process ends (END).

[0085] As described above, the image forming system according to this embodiment includes a reading unit equipped with a reading sensor that optically reads paper conveyed along a conveyance path, and the reading unit is capable of executing a plurality of reading modes, including at least a first reading mode and a second reading mode different from the first reading mode. When the first reading mode is switched to the second reading mode during image formation on continuously conveyed paper, the paper conveyance conditions for the paper conveyed after the switch are changed from the first conveyance conditions to the second conveyance conditions. This configuration enables accurate detection of paper size or paper shape and minimizes productivity degradation.

[0086] (Example of operation) Next, referring to FIG. 11, an example of actual operation in the processes of FIGS. 7A to 7C will be described. FIG. 11 is a timing chart showing timing delay processing and recovery processing by transport control accompanying switching of the reading mode. The horizontal axis indicates time, and the vertical axis indicates the status of each element. Time t0 is the timing when the print job starts to be executed. The timing chart shown in FIG. 11 corresponds to pages 1 to 34 of job 1. Pages 1 and 32 use gray paper, so reading mode 2 is applied. Pages 2 to 31 and 33 to 34 use blank paper, so reading mode 1 is applied. Then, delay processing (corresponding to step S304 in FIG. 7C) accompanying switching of the reading mode is performed between pages 1 and 2, between pages 31 and 32, and between pages 32 and 33. Delay processing is performed during the periods t to t3 and t6 to t8, and recovery processing is performed from times t3 to t5 and after time t6. Each time the delay process is performed, the required time to be reduced rt increases (corresponding to step S302). As shown in Fig. 9, when switching from reading mode 2 to 1, the required time to be reduced rt increases by time x3 (corresponding to delay time dt) (times t2 and t7 in Fig. 11). When switching from reading mode 1 to 2, the required time to be reduced rt increases by time x1 (corresponding to delay time dt) (time t6 in Fig. 11).

[0087] As the required reduction time rt becomes greater than 0, the transport control is changed from the first transport control to the second transport control (time t2). From the second page onwards, the required reduction time rt decreases by the reduction time rt for each page printed by switching to the second transport control (step S307). On the 11th page, the required reduction time rt becomes zero (end of recovery), and transport control thereafter returns to the first transport control (time t5). From the 32nd page onwards (time t6 onwards), the delay process and recovery process associated with switching the reading mode are repeated. The print control unit 111 may set the number of sheets to which the second transport condition is continuously applied based on the required reduction time rt and the reduction time rt according to the set second transport condition.

[0088] The above-described configuration of the reading device 30 and the image forming system 1000 equipped with the same has been described as the main configuration for explaining the features of the above embodiment, but is not limited to the above configuration and can be variously modified within the scope of the claims. Furthermore, configurations equipped in general image forming systems are not excluded.

[0089] (Variation) In the above-described embodiment, the second transport control is based on a fixed transport condition. However, multiple types of second transport control may be applied depending on various conditions. For example, in the example of FIG. 11, at time t5, the required reduction time rt becomes a negative value by subtracting the reduction time rt through recovery processing. In such a case, the second transport conditions set in the reduction mode may be partially relaxed so that the total value becomes exactly zero. For example, in the example of FIG. 11, the print control unit 111 fine-tunes the transport conditions for the 11th page, just before the negative value, by widening the paper spacing and lengthening the registration stop time compared to the previous transport conditions. As a result, the total value for the 11th page becomes exactly zero.

[0090] Furthermore, the print control unit 111 estimates the total value of the delay time dt that will occur when the print job starts. Then, the print control unit 111 may set the second transport conditions to be looser within a settable range so that this can be recovered as soon as possible by the time the print job ends. For example, in the example of FIG. 11, the delay time dt up to that point is resolved (recovered) by the 11th page, so the second transport conditions are set to be looser so that this can be resolved by the 31st page. For example, in the example shown in FIG. 10, instead of applying both items a and b, only one of them may be applied. Furthermore, if only one of them is applied during the period in which recovery is possible (depending on the number of pages), the paper spacing may be widened or the registration stop time may be extended.

[0091] Furthermore, the means and methods for performing various processes in the reading device 30 and image forming system 1000 according to the above-described embodiment can be realized by either a dedicated hardware circuit or a programmed computer. The above-described programs may be provided by a computer-readable recording medium such as a USB memory or a DVD (Digital Versatile Disc)-ROM, or may be provided online via a network such as the Internet. In this case, the programs recorded on the computer-readable recording medium are typically transferred and stored in a storage unit such as a hard disk. The above-described programs may be provided as standalone application software or may be incorporated into the software of the device as a function of the device. [Explanation of symbols]

[0092] 1000 Image Forming System 10 Image forming device 11 Control section 111 Printing control unit 112 Reader control unit 113 Other device control section 114 Correction value calculation unit 12 Storage section 13 Image forming unit 20 Paper feeder 24 Conveyor 25 Paper feed section 30 Reading device 31 Control Unit 32 Storage section 34 Conveying section 341 Transport Path 39 Communications Department 40 Aftertreatment device 50 Reading unit 51 Reading sensor 56 Background section 561 Background surface 1 562 Background surface 2 563 Calibration Surface 564 Paper passing side 57 Switching mechanism

Claims

1. a paper feed unit that feeds paper; a conveying unit that conveys paper in a conveying path; a reading unit including a reading sensor that optically reads the paper conveyed through the conveyance path; an image forming unit that is located downstream of the reading unit in the conveyance path and that forms an image on the conveyed paper; a control unit, the reading unit is capable of executing a plurality of reading modes including at least a first reading mode and a second reading mode different from the first reading mode, and reads the paper in one of the reading modes selected in accordance with print settings; The control unit, when switching from the first reading mode to the second reading mode while forming an image on continuously transported paper, changes the paper transport conditions for the paper transported after the switching from the first transport conditions to second transport conditions different from the first transport conditions.

2. The image forming system according to claim 1 , wherein the reading unit executes the reading mode according to the color of the paper to be read.

3. the reading unit includes a background unit disposed opposite the reading sensor across the transport path, the background unit having a plurality of background surfaces of different colors that become backgrounds of the paper when reading; 3. The image forming system according to claim 1, wherein the switching of the reading mode is a switching of the background surface.

4. The image forming system according to claim 3 , wherein the reading unit switches the background surface depending on the color of the paper to be read.

5. The image forming system according to claim 1 , wherein the control unit makes the transport speed of the paper in the transport path under the second transport condition faster than the transport speed of the paper under the first transport condition.

6. 6. The image forming system of claim 1, wherein the control unit, under the second transport condition, makes the stop time of the paper at the temporary stop position in the transport path shorter than the stop time of the paper under the first transport condition.

7. 6. The image forming system of claim 1, wherein the control unit, under the second transport condition, makes the paper spacing between the paper sheets in the transport path shorter than the paper spacing between the paper sheets in the first transport condition.

8. 2. The image forming system of claim 1, wherein the control unit, when switching from the first reading mode to the second reading mode, sets the second transport conditions and / or sets the number of sheets of paper to which the second transport conditions are continuously applied based on the switching time required for switching.

9. a paper feed unit that feeds paper; a conveying unit that conveys paper in a conveying path; a reading unit including a reading sensor that optically reads the paper conveyed through the conveyance path; an image forming unit that forms an image on the transported paper downstream of the reading unit in the transport path, the reading unit is capable of executing a plurality of reading modes including at least a first reading mode and a second reading mode different from the first reading mode, and a step (a) of selecting one of the reading modes in accordance with a print setting; (b) reading the paper in the selected reading mode; (c) forming an image on the continuously conveyed paper; a step (d) of changing the paper transport conditions from the first transport conditions to the second transport conditions for transporting the paper transported after the switching from the first reading mode to the second reading mode during the execution of the step (c); A printing method that performs a process including:

10. 10. The printing method according to claim 9, wherein in said step (a), said reading mode is selected according to the color of the paper to be read.

Images