Image forming apparatus and image forming system

Abstract

To provide a technique for performing image formation processing that does not inhibit an effect of liquid application when image formation processing is performed at a liquid application position on a medium used for binding processing accompanied by liquid application.SOLUTION: An image forming apparatus that forms an image on a medium to which liquid is applied and conveys the medium to a medium processing apparatus that performs binding processing on a medium bundle including at least one medium to which liquid has been applied includes: an image forming unit that forms an image on the medium; an image overlap detection unit that detects whether or not an image is formed so as to overlap a liquid application position corresponding to a part of the medium to which liquid is applied; an image density acquisition unit that acquires an image density of an image portion for which overlap is detected; and a target value calculation unit that calculates a target value of the image density of the image portion when forming an image including the image portion for which overlap is detected. The image forming unit adjusts the image density of the image portion in accordance with the target value and forms the image.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Media processing devices are known that perform a binding process to form a stack (sheet bundle) of sheet-like media on which images are formed. Also known are media processing devices that perform a "staple-less" binding process without using metal staples (staples) in order to conserve resources and reduce environmental impact. These media processing devices are equipped with a crimping unit that can perform so-called "crimp binding," in which the sheet bundle is clamped and pressure-deformed between concave and convex binding teeth. Paper is a widely known example of sheet-like media. Therefore, in this specification, when describing a sheet bundle, a "paper bundle" consisting of multiple sheets of paper as media will be used as an example.

[0003] 2. Description of the Related Art Devices are known that have a function of applying a liquid to a position where binding processing is performed in advance to make it easier for staples or binding teeth to bite into a stack of paper sheets, in order to improve binding strength.

[0004] In applying liquid as a pre-processing step prior to the binding process, a device is also known that can adjust the amount of liquid applied in accordance with fluctuations in external factors that affect the binding strength (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0005] When performing binding processing on a portion of a paper stack made up of multiple media bundled together, even if the amount of liquid applied is adjusted as in the media processing device disclosed in Patent Document 1, if an image is formed on the portion where liquid is applied, the liquid application state will not be as intended.

[0006] In other words, if an image is formed in the area where liquid is applied, the effect of applying the liquid will not be as intended due to the influence of the image, which will have an impact that reduces the binding strength, thereby reducing the binding quality.

[0007] The present invention aims to provide a technology for performing image formation processing that does not hinder the effect of liquid application when performing image formation processing at a liquid application position on a medium used in a binding process that involves liquid application. [Means for solving the problem]

[0008] In order to solve the above problem, one aspect of the present invention is an image forming device that forms an image on a medium to which liquid has been applied and then transports the medium to a medium processing device that performs a binding process on a media bundle containing at least one medium to which liquid has been applied, the image forming device comprising: an image forming unit that forms an image on the medium; an image overlap detection unit that detects whether the image is formed so as to overlap at a liquid application position corresponding to a portion of the medium to which the liquid is applied; an image density acquisition unit that acquires the image density of the image portion where the overlap is detected; and a target value calculation unit that calculates a target value of the image density of the image portion when forming an image including the image portion where the overlap is detected, and is characterized in that the image forming unit adjusts the image density of the image portion in accordance with the target value and forms the image. [Effects of the Invention]

[0009] According to the present invention, when an image forming process is performed at a liquid application position on a medium used in a binding process involving the application of liquid, the image forming process can be performed in a manner that does not impede the effect of the liquid application. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing the overall configuration of an image forming system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the internal structure of a post-processing device according to an embodiment of the present invention. [Figure 3]FIG. 4 is a schematic diagram of the edge binding processing section as viewed from the upstream side in the conveyance direction. [Figure 4] FIG. 2 is a hardware configuration diagram of a control block that controls the operation of the image forming apparatus according to the embodiment. [Figure 5] FIG. 1 is a functional block diagram of an image forming system according to an embodiment of the present invention. [Figure 6] 5A to 5C are diagrams for explaining an outline of image forming processing according to the present embodiment. [Figure 7] 10 is a flowchart illustrating an example of image forming and binding processing according to the present embodiment. [Figure 8] 5 is a flowchart of a first example of image forming processing according to the present embodiment. [Figure 9] 10 is a flowchart of a second example of image forming processing according to the present embodiment. [Figure 10] 10 is a flowchart of a third example of image forming processing according to the present embodiment. [Figure 11] 10 is a flowchart of a fourth example of image forming processing according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First embodiment] An image forming system 1 according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of the image forming system 1. The image forming system 1 has the function of forming an image on paper P as a sheet-like medium and performing predetermined post-processing on the paper P on which the image has been formed. As shown in FIG. 1, the image forming system 1 is configured to link an image forming device 2 as the image forming device according to the present invention and a post-processing device 3 as a medium processing device. The post-processing device 3 is a device that processes the paper P on which the image has been formed in the image forming device 2.

[0012] The image forming device 2 is a device that forms an image on a sheet P and conveys the sheet P with the image formed thereon to the post-processing device 3. The image forming device 2 includes a storage tray that stores the sheet P, a conveying unit that conveys the sheet P stored in the storage tray, an image forming unit 100 that forms an image on the sheet P conveyed by the conveying unit, and an image formation control unit 110 that controls the operation of the entire image forming device 2 including the image forming unit 100.

[0013] In the following description, the image forming method applied to the image forming unit 100 is an electrophotographic method. That is, the embodiment of the present invention will be described on the premise of a method in which an image is formed on paper P by transferring and fixing an image developing material (toner) onto paper P. However, the image forming unit 100 according to the embodiment of the present invention may be an inkjet method in which an image is formed by ejecting ink onto a medium (paper P).

[0014] Regardless of the image formation method, or even if it is a method other than these, the image formation process executed in the image forming unit 100 according to this embodiment is premised on the process of applying liquid to paper P on which an image has been formed. In other words, when the liquid application process is performed on a portion of paper P on which an image has been formed, and a factor that inhibits the effect of the application of the liquid is generated in the image formation process, the image formation process is executed in a way that reduces the inhibiting factor, which is one of the features according to this embodiment.

[0015] For example, in the case of an electrophotographic system, when an image is formed at a liquid application position, toner adheres to that position. When liquid is subsequently applied, the toner becomes a factor that hinders the penetration of the liquid. Since the liquid application process aims to improve the binding strength in the subsequent binding process, if the amount of liquid application is constant regardless of the amount of toner adhered, the amount of toner adhered can be a factor that affects the binding strength.

[0016] In addition, for example, in the case of an inkjet method, when an image is formed at a liquid application position, liquid ink adheres to that position. This can be a factor that inhibits the liquid signal and affects the binding strength.

[0017] In this embodiment, it is detected whether the image formation process is one that creates factors that hinder the penetration of the pre-adjusted amount of liquid application into the paper P, and the parameters used in the image formation process are corrected to reduce the factors that hinder the effect of liquid application, and image formation is performed based on the corrected parameters.

[0018] The post-processing device 3 also includes an end-stitching processing unit 25 that receives the sheets P (sheets P on which images have been formed) discharged by the image forming device 2 and binds a plurality of sheets P into a sheet bundle Pb. In Fig. 1, an example of a transport path from the image forming unit 100 to the end-stitching processing unit 25 in the image forming system 1 is shown by a dashed line.

[0019] FIG. 2 is a diagram showing the internal structure of the post-processing device 3 according to the first embodiment. The post-processing device 3 performs predetermined post-processing on sheets P on which images have been formed by the image forming device 2. The post-processing according to this embodiment is a binding process that serves as a "pressure binding process" that binds a bundle of multiple sheets P (a sheet bundle) on which images have been formed without using staples. Hereinafter, the bundle of sheets P will be referred to as a "sheet bundle Pb" as a medium bundle. More specifically, the binding process according to this embodiment is a so-called "pressure binding" that pressurizes and deforms the sheet bundle Pb at the binding position. Note that the binding processes that can be performed by the post-processing device 3 include an end binding process that binds the ends of the sheet bundle Pb and a saddle binding process that binds the center of the sheet bundle Pb.

[0020] The post-processing device 3 includes conveyance roller pairs 10-19 (conveyance section) and a switching claw 20. The conveyance roller pairs 10-19 convey the paper P supplied from the image forming device 2 inside the post-processing device 3. More specifically, the conveyance roller pairs 10-13 convey the paper P along a first conveyance path Ph1. Furthermore, the conveyance roller pairs 14-15 convey the paper P along a second conveyance path Ph2. Furthermore, the conveyance roller pairs 16-19 convey the paper P along a third conveyance path Ph3.

[0021] The first transport path Ph1 is a path that leads from the supply port of the paper P from the image forming device 2 to the discharge tray 21. The second transport path Ph2 is a path that branches off from the first transport path Ph1 between the pairs of transport rollers 11 and 14 in the transport direction, and leads to the discharge tray 26 through the internal tray 22. The third transport path Ph3 is a path that branches off from the first transport path Ph1 between the pairs of transport rollers 11 and 14 in the transport direction, and leads to the discharge tray 30.

[0022] The switching claw 20 is disposed at a branching position of the first transport path Ph1 and the second transport path Ph2. The switching claw 20 is configured to be switchable between a first position where the sheet P is discharged to the discharge tray 21 via the first transport path Ph1, and a second position where the sheet P transported along the first transport path Ph1 is guided to the second transport path Ph2. Furthermore, when the rear end of the sheet P that has entered the second transport path Ph2 passes the pair of transport rollers 11, the pair of transport rollers 14 is rotated in the reverse direction, thereby guiding the sheet P to the third transport path Ph3. The post-processing device 3 also includes multiple sensors that detect the position of the sheet P on each of the transport paths Ph1, Ph2, and Ph3. The multiple sensors are indicated by solid triangles (▲) in FIG. 2.

[0023] The post-processing device 3 includes a discharge tray 21. The discharge tray 21 holds the paper sheets P discharged through the first conveying path Ph1. Of the paper sheets P supplied from the image forming device 2, the paper sheets P that are not to be bound are discharged to the discharge tray 21.

[0024] The post-processing device 3 also includes an internal tray 22 as a loading tray, an end fence 23, side fences 24L and 24R, an edge-stitching processing unit 25, and a discharge tray 26. The internal tray 22, the end fence 23, the side fences 24L and 24R, and the edge-stitching processing unit 25 perform edge-stitching processing on a sheet bundle Pb made up of a plurality of sheets P transported from the second transport path Ph to the internal tray 22. The sheet bundle Pb that has been edge-stitched is discharged to the discharge tray 26 from the sheets P supplied from the image forming device 2. The "edge-stitching processing" referred to here includes a "parallel binding processing" in which binding processing is performed along one side of the sheet bundle Pb that is parallel to the main scanning direction, a "diagonal binding processing" in which binding processing is performed at a corner of the sheet bundle Pb, and a "vertical binding processing" in which binding processing is performed along one side of the sheet bundle Pb that is parallel to the transport direction of the sheet bundle Pb.

[0025] Hereinafter, the direction in which the paper P is transported from the transport roller pair 15 toward the end fence 23 is defined as the "transport direction." Furthermore, the thickness direction of the paper P and the direction perpendicular to the transport direction are defined as the "main scanning direction (width direction of the paper P)."

[0026] The internal tray 22, which serves as a loading tray, temporarily loads multiple sheets of paper P that are transported in sequence along the second transport path Ph2. The end fence 23 aligns the position of the sheets of paper P or the sheet bundle Pb loaded on the internal tray 22 in the transport direction. The side fences 24L and 24R align the position of the sheets of paper P or the sheet bundle Pb loaded on the internal tray 22 in the main scanning direction. The edge binding processing unit 25 binds the edges of the sheet bundle Pb that have been aligned by the end fence 23 and the side fences 24L and 24R. Then, the transport roller pair 15 discharges the sheet bundle Pb that has undergone edge binding processing onto the discharge tray 26.

[0027] The edge binding processing unit 25 has a processing function of applying liquid to at least one sheet P of the multiple sheets P that make up the sheet bundle Pb to be bound, at a position where the binding processing is to be performed, before the binding processing is performed. Hereinafter, applying a liquid containing water to the sheet P or the sheet bundle Pb will be referred to as "liquid application," and the processing for applying the liquid will be referred to as "liquid application processing."

[0028] The liquid used in "liquid application" is, more specifically, a liquid compound of hydrogen and oxygen, represented by the chemical formula HO, as its main component. As long as it is in a liquid state, its temperature does not matter, and it can be so-called warm water or hot water. Furthermore, it is not limited to pure water, but can also be purified water, or it can contain ionized salts. The metal ion content can also be of any hardness, from so-called soft water to ultra-hard water.

[0029] In addition to the main ingredient, additives may be added. It may contain residual chlorine, which is used in tap water, and it is also desirable to add colorants, penetrants, pH adjusters, preservatives such as phenoxyethanol, and drying inhibitors such as glycerin. Furthermore, inks used in inkjet printers and water-based pens also contain water, so these may also be used as "liquid application."

[0030] The liquid is not limited to those specifically mentioned here, and any "water" in the broad sense, such as hypochlorous acid water or an ethanol solution diluted for disinfection, will also work, but if the only purpose is to function as a pressure binding agent, tap water, which is easy to obtain and manage, can be used. Furthermore, using a liquid whose main component is water, such as the examples given above, can improve the binding strength of the paper stack Pb more than using a liquid whose main component is not water.

[0031] [Outline of binding process involving liquid application] An example of how to perform binding processing involving liquid application will now be described with reference to Fig. 3. The liquid application unit 31 and the pressure-bonding unit 32 are integrated by a base member 48 and are installed so as to be capable of reciprocating movement in the main scanning direction. As shown in Fig. 3(A), the standby position HP is a position that is offset in the width direction from the paper P or paper stack Pb placed on the internal tray 22. Also, as shown in Figs. 3(B) and 3(C), the liquid application unit 31 and the pressure bonding unit 32 that constitute the end binding processing unit 25 are configured to be able to move to the binding position B1.

[0032] The binding position B1 is a position facing the paper P or paper stack Pb placed on the internal tray 22, and is a position where liquid application and pressure binding are performed. In other words, the standby position HP and the binding position B1 are positions spaced apart in the main scanning direction. Furthermore, the liquid application unit 31 according to this embodiment is disposed adjacent to the pressure bonding unit 32, and is closer to the binding position B1 than the pressure bonding unit 32 at the standby position HP.

[0033] The liquid application unit 31 is configured to be movable in the main scanning direction together with the pressure bonding unit 32 by transmitting the driving force of the edge binding processing unit movement motor. The position (liquid application position) where the liquid application unit 31 applies liquid to the paper P or the paper stack Pb corresponds to the binding position B1 where pressure binding by the pressure bonding unit 32 is to be performed.

[0034] The liquid application position, where the liquid application unit 31 applies liquid to the sheets P, is specified in advance. That is, when a job including a binding process involving liquid application is executed, liquid application is performed at binding position B1 on at least one sheet of paper P on which an image is formed in the job. Therefore, in a job including a binding process involving liquid application, the liquid application performed in a later stage of the image formation process may overlap the image formation area on at least one sheet of paper P. The image formation control unit 110 can determine the image portion to be formed within the image formation area, and can also determine the position (binding position B1) of the binding process to be performed in a later stage in an image formation job that includes an instruction for binding. That is, in the image forming device 2, the image formation control unit 110 can identify the position where the liquid application process and the binding process to be performed in a later stage will be performed on the sheets P at the stage where image formation is about to be performed, and can therefore determine the image portion to be formed at this position.

[0035] [Control configuration (hardware) of image forming device 2] Fig. 4 is a hardware configuration diagram of the control configuration of the image forming apparatus 2 according to this embodiment. As shown in Fig. 7, the image forming apparatus 2 has a configuration in which a CPU (Central Processing Unit) 111, a RAM (Random Access Memory) 112, a ROM (Read Only Memory) 113, an HDD (Hard Disk Drive) 114, and an I / F 115 are connected via a common bus 119.

[0036] The CPU 111 is a computing unit that controls the overall operation of the image forming apparatus 2. The RAM 112 is a volatile storage medium that can read and write information at high speed, and is used as a work area when the CPU 111 processes information. The ROM 113 is a read-only nonvolatile storage medium that stores programs such as firmware. The HDD 114 is a nonvolatile storage medium that can read and write information and has a large storage capacity, and stores an OS (Operating System), various control programs, application programs, etc.

[0037] The image forming apparatus 2 processes a control program stored in the ROM 113, an information processing program (application program) loaded into the RAM 112 from a storage medium such as the HDD 114, and the like using the arithmetic functions of the CPU 111. This processing constitutes a software control unit including various functional modules of the post-processing device 3. The combination of the software control unit thus constituted and the hardware resources installed in the image forming apparatus 2 constitutes a functional block that realizes the functions of the image forming apparatus 2. In other words, the CPU 111, RAM 112, ROM 113, and HDD 114 constitute an image formation control unit 110 that controls the operation of the image forming apparatus 2.

[0038] The I / F 105 is an interface that connects a pair of transport rollers 151 that transports the paper P, an image forming unit 100 that forms an image on the paper P, and an operation panel 120 to the common bus 109 .

[0039] As shown in FIG. 1, the image forming apparatus 2 includes an operation panel 120. The operation panel 120 includes an operation unit that accepts operations from a user and a display (notification unit) that notifies the user of information. The operation unit includes, for example, hard keys, a touch panel superimposed on the display, etc. The operation panel 120 acquires information from the user through the operation unit and provides the information to the user through the display. Note that the notification unit is not limited to a display, and may be an LED lamp, a speaker, etc.

[0040] Fig. 5 is a functional block diagram illustrating an example of a control configuration realized in the image forming apparatus 2. Fig. 5 illustrates an example of a functional configuration realized when a control program is executed in the image forming control unit 110 provided in the image forming apparatus 2. The image forming control unit 110 is broadly composed of a controller unit 1110 and an engine unit 1120. The controller unit 1110 sends print information from a controller control management unit 1111, which manages image formation requests (print requests) from users, to the engine unit 1120 and requests printing. This print request corresponds to a request for image formation.

[0041] The engine unit 1120 performs image formation and paper P transport processing according to the print information using an engine control management unit 1121. When binding processing is performed in the subsequent stage, a binding request from the image formation control unit 110 is notified to the post-processing image formation control unit 110b of the post-processing device 3 via the engine unit 1120.

[0042] In response to the request, the post-processing device 3 performs binding processing under the post-processing image formation control section 110b.

[0043] The engine unit 1120 includes an image overlap detection unit 1122 and an image correction unit 1123. The image overlap detection unit 1122, which serves as an image overlap detection unit, has the function of determining whether an image formed in the image forming process has a portion that overlaps with the binding position, based on print image information and binding request information, and notifying the engine control management unit 1121 of the determination result.

[0044] The engine control management unit 1121 as an image density acquisition unit acquires the image density of the image portion corresponding to the overlapping portion of each of the plurality of sheets P to be bound.

[0045] The image correction unit 1123 as a target value calculation unit calculates a target value of image density for uniforming the image density of image portions that overlap at the binding position on each of the multiple sheets of paper P to be bound, in image formation processing of the image portions. The target value of image density is control data for uniforming the image density of image portions that are determined to overlap on each sheet of paper P, even if different images are formed on each sheet of paper P.

[0046] That is, when the image forming process is an electrophotographic process, the image correcting unit 1123 calculates a correction value so that the toner density of overlapping image portions becomes uniform.

[0047] According to the image forming device 2 equipped with the above functional blocks, stable binding quality can be provided in the binding process involving the application of liquid without adjusting the amount of liquid applied taking into account the amount of toner adhered to the paper P.

[0048] 6A and 6B are diagrams illustrating an example of an image forming process implemented in the above-described functional block diagram. As shown in Fig. 6A, the image forming process will be described using an example in which a binding process for forming a single sheet bundle Pb using three sheets P (first sheet P1, second sheet P2, and third sheet P3) is scheduled for a later stage. It is assumed that an image is to be formed on each of the portions (Lp1, Lp2, and Lp3) of each sheet P that correspond to the binding position.

[0049] 6(B), when the image density of the image portion (Gp1, Gp2, Gp3) corresponding to the binding position differs in the image formed on each sheet P, that is, when the same amount of liquid is applied to the image portion overlapping the binding position, the effect will be different. If the effect of applying liquid differs for each sheet P that makes up a single sheet bundle Pb, this can cause a decrease in binding strength and may result in a decrease in binding quality.

[0050] 6(C), if the image density of the image portion corresponding to the binding position B1 is adjusted and the amount of toner adhered to this portion is made approximately uniform, a similar effect can be expected even if the amount of liquid applied by the liquid application operation is the same. Therefore, in the image forming apparatus 2 according to this embodiment, when a job including a medium process in which a liquid application process is performed in a subsequent stage is executed, a target value of image density is set for the portion in the image forming process of each sheet P that overlaps with the liquid application position in the subsequent stage so that the image density of that portion is approximately uniform on each sheet P.

[0051] In the image forming process executed in the image forming apparatus 2 according to the present embodiment described below, several examples of the method for calculating the target value of image density (method for correcting image density) are assumed.

[0052] In the first embodiment, the image density of the image portion (the image overlapping with the binding position) of the first sheet P (the sheet P corresponding to the first page) constituting the sheet bundle Pb is set as the target value for the image density of the image portion of the other sheets P of the sheet bundle Pb.

[0053] In a second embodiment, under the control of the image forming control unit 110, an overlap determination process is executed based on the print image information until the image writing process, which is a process for generating the image to be formed on the paper P by the image forming unit 100 from the print image information, is started, and the moving average value of the image density of the overlapping image portion obtained is set as the target value of the image density.

[0054] In a third embodiment, an overlap determination process is performed based on the print image information until the image writing process is started, and the lightest image density among the image densities of the overlapping image portions is set as the target value for the image density of the image portions of the entire paper stack Pb.

[0055] In a fourth embodiment, an overlap determination process is performed based on the print image information until the image writing process is started, and the darkest image density among the image densities of the overlapping image portions is set as the target value for the image density of the image portions of the entire paper stack Pb.

[0056] [Common binding process flow] The following describes the flow of media processing executed in the image forming system 1 according to an embodiment of the present invention. Fig. 7 illustrates the flow of image formation and binding processing, which includes the image forming processing executed in the image forming device 2 constituting the image forming system 1 and the binding processing accompanied by a liquid application operation executed in the post-processing device 3.

[0057] First, an image writing process is executed based on a target image density as a process for forming an image on a sheet P based on print image information (S701). In step S701, an image is formed using a target value of image density stored in the storage means of the image formation control unit 110. Then, the sheet P on which the image has been formed is transported to the post-processing device 3 (S702).

[0058] The post-processing control unit 100b included in the post-processing device 3 determines whether or not sheets P equivalent to the number of sheets that make up the sheet bundle Pb to be formed in the binding process have been conveyed (S703). If the number of sheets P has not reached the number of sheets that make up the sheet bundle Pb (the number of sheets to be bound) (S703: NO), the image writing process ends and image writing process for the next sheet P is started. If the number of sheets P has reached the number of sheets that make up the sheet bundle Pb (the number of sheets to be bound) (S703: YES), the binding process is executed (S704).

[0059] [First Example] Next, a first embodiment of an image reading process for setting a target value of image density used in an image writing process will be described with reference to the flowchart in Fig. 8. The image forming control unit 110 first determines whether the job to be processed is a process including a binding process that involves liquid application (S801). If the job does not include a binding process that involves liquid application (S801: NO), the image reading process ends, and the image forming process is executed using the set target image density.

[0060] If the process includes a binding process involving liquid application (S801: YES), the print image information of the binding position B1, where the binding process to be executed later will be performed, is read to determine whether an image will be formed at that position (S802). Based on the information read in step S802, it is determined whether an image will be formed at the binding position B1 (S803). If an image is not formed at the binding position B1, that is, if there is no overlapping image at the binding position B1 (S803: NO), the image reading process ends.

[0061] If an image is formed at the binding position B1 and the target of judgment is the first sheet P (first page) that constitutes the paper stack Pb (S803: YES), the image density of the image portion formed at the binding position B1 on the first page sheet P that is the target of processing is obtained (S804).

[0062] Subsequently, the image density obtained in step S804 is stored as a target value in the storage means of the image formation control unit 110 (S805).

[0063] By using the target value saved by the above process as the target image density when executing the image forming process, it is possible to make the amount of toner adhered at the binding position B1 uniform for the multiple sheets P that make up one sheet bundle Pb. This makes it possible to stabilize the binding quality even if the amount of liquid applied to the sheets P on which images are formed at the binding position B1 is constant.

[0064] [Second Example] Next, a second embodiment of the image reading process for setting a target value of image density used in the image writing process will be described with reference to the flowchart in Fig. 9. The image forming control unit 110 first determines whether the job to be processed is a process including a binding process that involves liquid application (S901). If the job does not include a binding process that involves liquid application (S901: NO), the image reading process ends, and the image forming process is executed using the set target image density.

[0065] If the process includes a binding process involving the application of liquid (S901: YES), the print image information of the binding position B1, where the binding process to be executed later will be performed, is read to determine whether an image will be formed at that position (S902). Based on the information read in step S902, it is determined whether an image will be formed at the binding position B1 (S903). If an image is not formed at the binding position B1, that is, if there is no overlapping image at the binding position B1 (S903: NO), the image reading process ends.

[0066] When an image is formed at the binding position B1 and there is an overlapping image portion at the binding position B1 (S903: YES), the image density of the image portion formed at the binding position B1 on the paper P being processed is obtained (S904).

[0067] Next, a moving average is calculated using the image density obtained in step S904 (S905), and the calculated moving average value is stored in the storage means of the image formation control unit 110 as a target value of the image density (S906).

[0068] The target value saved by the above process is used as the target image density when the image forming process is executed. That is, for the multiple sheets P constituting one sheet bundle Pb, the moving average value of the image density obtained in the image reading process executed before the image writing process is executed is set as the target value based on the amount of toner adhesion at the binding position B1 (S905). This reduces variations in density of the image portion where the image is formed at the binding position B1 for each sheet P constituting one sheet bundle Pb, while stabilizing the binding quality even if the amount of liquid applied is constant.

[0069] [Third Example] Next, a third embodiment of the image reading process for setting a target value of image density used in the image writing process will be described with reference to the flowchart in Fig. 10. The image forming control unit 110 first determines whether the job to be processed is a process including a binding process that involves liquid application (S1001). If the job does not include a binding process that involves liquid application (S1001: NO), the image reading process ends, and the image forming process is executed using the set target image density.

[0070] If the process includes a binding process involving the application of liquid (S1001: YES), the print image information of the binding position B1, where the binding process to be executed later will be performed, is read to determine whether an image will be formed at the binding position B1 (S1002). Based on the information read in step S1002, it is determined whether an image will be formed at the binding position B1 (S1003). If an image is not formed at the binding position B1, that is, if there is no overlapping image at the binding position B1 (S1003: NO), the image reading process ends.

[0071] When an image is formed at the binding position B1 and there is an image portion that overlaps with the binding position B1 (S1003: YES), the image density of the image portion formed at the binding position B1 on the paper P being processed is obtained (S1004).

[0072] Next, the image density acquired in step S1004 is compared with the image density already acquired (the image density target value stored in the storage means of the image formation control unit 110) (S1005). If the comparison result shows that the acquired image density is smaller than the stored image density target value (S1005: YES), the image density target value stored in the storage means of the image formation control unit 110 is updated with the acquired image density (S1006).

[0073] If the comparison result shows that the acquired image density is greater than the stored image density target value (S1005: NO), the image reading process is terminated without updating the image density target value stored in the memory means of the image formation control unit 110, and the image formation process is performed using the set target image density.

[0074] The target value stored by the above process is used as the target image density when the image forming process is executed. That is, the image density value when the density is lowest among the toner adhesion amounts at the binding position B1 of the multiple sheets P that make up one bundle of sheets Pb is used as the target image density (S1006). As a result, when the image writing process corresponding to each sheet P that makes up one bundle of sheets Pb is executed, the image portion at the binding position B1 is formed using the target image density stored at that time. This makes it possible to reduce variations in the density of the image portion formed on the sheets P that make up one bundle of sheets Pb. As a result, it is possible to stabilize the binding quality even if the amount of liquid applied is constant.

[0075] [Fourth Example] Next, a fourth embodiment of the image reading process for setting a target value of image density used in the image writing process will be described with reference to the flowchart in Fig. 11. The image forming control unit 110 first determines whether the job to be processed is a process including a binding process that involves liquid application (S1101). If the job does not include a binding process that involves liquid application (S1101: NO), the image reading process ends, and the image forming process is executed using the set target image density.

[0076] If the process includes a binding process involving the application of liquid (S1101: YES), the print image information of the binding position B1, where the binding process to be executed later will be performed, is read to determine whether an image will be formed at that position (S1102). Based on the information read in step S1102, it is determined whether an image will be formed at the binding position B1 (S1103). If an image is not formed at the binding position B1, that is, if there is no overlapping image at the binding position B1 (S1103: NO), the image reading process ends.

[0077] When an image is formed at the binding position B1 and there is an image portion that overlaps with the binding position B1 (S1103: YES), the image density of the image portion formed at the binding position B1 on the paper P being processed is obtained (S1104).

[0078] Next, the image density acquired in step S1104 is compared with the image density already acquired (the image density target value stored in the storage means of the image formation control unit 110) (S1105). If the comparison result shows that the acquired image density is greater than the stored image density target value (S1105: YES), the image density target value stored in the storage means of the image formation control unit 110 is updated with the acquired image density (S1106).

[0079] If the comparison result shows that the acquired image density is smaller than the stored image density target value (S1105: NO), the image reading process is terminated without updating the image density target value stored in the memory means of the image forming control unit 110, and the image forming process is performed using the set target image density.

[0080] The target value stored by the above process is used as the target image density when executing the image forming process. That is, the image density value at the highest density among the toner adhesion amounts at the binding position B1 of the multiple sheets P that make up one bundle of sheets Pb is used as the target image density (S1106). As a result, when executing the image writing process corresponding to each sheet P that makes up one bundle of sheets Pb, the image portion at the binding position B1 is formed using the target image density stored at that time. This makes it possible to reduce variations in the density of the image portion formed on the sheets P that make up one bundle of sheets Pb. As a result, it is possible to stabilize the binding quality even if the amount of liquid applied is constant.

[0081] As described above, according to the image forming apparatus 2 according to each example of this embodiment, in an image forming process in which a binding process involving liquid application is performed at a later stage, the amount of toner adhered to the image portion corresponding to the binding position B1 is made uniform, thereby maintaining the effect of applying liquid to the multiple sheets P that make up one sheet bundle Pb and stabilizing the binding quality. Furthermore, the image gap around the binding portion can be reduced.

[0082] As already explained, the control method by the image formation control unit 110 described above is realized by cooperation between the hardware resources of a computer and a program as computer software. That is, the control method is a method executed by a computer by causing an arithmetic unit, a storage unit, an input unit, an output unit, and a control unit to operate in cooperation based on the program. The program may also be written to a storage unit or a storage medium, etc., and distributed, or distributed via a telecommunications line, etc.

[0083] Furthermore, the present invention is not limited to the above-described exemplary embodiments, and various modifications are possible without departing from the technical gist thereof. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims.

[0084] [Aspects of the present invention] The contents of the present invention are as follows, for example. <1> An image forming apparatus that forms an image on a medium to which a liquid has been applied and then conveys the medium to a medium processing device that performs a binding process on a medium bundle including at least one medium to which a liquid has been applied, an image forming unit that forms an image on the medium; an image overlap detection unit that detects whether the image is formed so as to overlap at a liquid application position corresponding to a portion of the medium to which the liquid is applied; an image density acquisition unit that acquires the image density of the image portion where the overlap is detected; a target value calculation unit that calculates a target value of the image density of the image portion in which the overlap is detected when forming an image including the image portion; Equipped with the image forming unit adjusts the image density of the image portion in accordance with the target value and forms the image; The image forming apparatus is characterized by the above. <2> The image density acquisition unit acquiring an image density of the image portion of a first medium among the media constituting the medium bundle and for which an overlap of the liquid application position with respect to the image portion has been detected; the target value calculation unit sets the image density on the first medium as the target value; The aforementioned <1> 2. The image forming apparatus according to claim 1, wherein: <3> The target value calculation unit the moving average of the densities of the image portions of the media constituting the medium bundle, which are detected as overlapping of the liquid application positions with the image portions, acquired by the image density acquisition unit until image formation is started, is set as the target value; The aforementioned <1> or the above <2> 2. The image forming apparatus according to claim 1, wherein: <4> The target value calculation unit the target value is set to the lightest density of the image portion of the media constituting the medium bundle, among the media for which the overlap of the liquid application position with the image portion has been detected and acquired by the image density acquisition unit before image formation is started; The aforementioned <1> and the above <3> 10. The image forming apparatus according to claim 9, wherein the first and second electrodes are arranged parallel to each other. <5> The target value calculation unit the target value is set to the highest density among the densities of the image portions acquired by the image density acquisition unit before image formation is started among the media constituting the medium bundle and for which overlapping of the liquid application position with the image portion has been detected; The aforementioned <1> and the above <4> 10. The image forming apparatus according to claim 9, wherein the first and second electrodes are arranged parallel to each other. <6> The above-mentioned <1 to <5>, which are provided with an image forming unit that forms an image on the medium. <5> an image forming apparatus according to any one of the preceding items; a media processing device that performs predetermined processing on the plurality of media on which images have been formed by the image forming device; The image forming system is characterized by comprising: [Explanation of symbols]

[0085] 1: Image forming system 2: Image forming device 3: Post-processing device 10: Transport roller pair 11: Pair of conveying rollers 12: Pair of conveying rollers 13: Pair of conveying rollers 14: Pair of conveying rollers 15: Pair of conveying rollers 16: Pair of conveying rollers 17: Transport roller pair 18: Pair of conveying rollers 19: Pair of conveying rollers 20: Switching claw 21: Output tray 22: Internal tray 23: End fence 24L: Side fence 24R: Side fence 25: Processing section 26: Output tray 28: Processing section 30: Output tray 31: Liquid application unit 32: Crimping section 48: Base material 100: Image forming unit 100b: Post-processing control unit 105: Interface 109: Common bus 110: Image formation control unit 110b: Post-processing image formation control unit 111:CPU 112:RAM 113:ROM 114: HDD 115: Interface 119: Common bus 120: Operation panel 151: conveying roller pair 1110: Controller section 1111: Controller control management unit 1120: Engine section 1121: Engine control management unit 1122: Image overlap detection unit 1123: Image correction unit [Prior art documents] [Patent documents]

[0086] [Patent Document 1] Japanese Patent Application Publication No. 2023-111840

Claims

1. An image forming apparatus that forms an image on a medium to which a liquid has been applied and then conveys the medium to a medium processing device that performs a binding process on a medium bundle including at least one medium to which a liquid has been applied, an image forming unit that forms an image on the medium; an image overlap detection unit that detects whether the image is formed so as to overlap at a liquid application position corresponding to a portion of the medium to which the liquid is applied; an image density acquisition unit that acquires the image density of the image portion where the overlap is detected; a target value calculation unit that calculates a target value of the image density of the image portion in which the overlap is detected when forming an image including the image portion; Equipped with the image forming unit adjusts the image density of the image portion in accordance with the target value and forms the image; An image forming apparatus characterized by:

2. The image density acquisition unit acquiring an image density of the image portion of a first medium among the media constituting the medium bundle and for which an overlap of the liquid application position with respect to the image portion has been detected; the target value calculation unit sets the image density on the first medium as the target value; The image forming apparatus according to claim 1 .

3. The target value calculation unit and setting the moving average of the densities of the image portions of the media constituting the medium bundle, the image densities of the media being detected as overlapping with the image portions, the moving average being acquired by the image density acquisition unit until image formation is started, as the target value. The image forming apparatus according to claim 1 .

4. The target value calculation unit the target value is set to the lightest density of the image portion of the media constituting the medium bundle, among the media for which the overlap of the liquid application position with the image portion has been detected and acquired by the image density acquisition unit before image formation is started; The image forming apparatus according to claim 1 .

5. The target value calculation unit the target value is set to the highest density among the densities of the image portions acquired by the image density acquisition unit before image formation is started among the media constituting the medium bundle and for which overlapping of the liquid application position with the image portion has been detected; The image forming apparatus according to claim 1 .

6. The image forming apparatus according to claim 1 , further comprising an image forming unit that forms an image on the medium; a media processing device that performs predetermined processing on the plurality of media on which images have been formed by the image forming device; An image forming system comprising:

Images