JP6531495B2 - Charge adjustment device, image forming apparatus and image forming system - Google Patents

Description

  The present invention relates to a charge adjustment device, an image forming apparatus and an image forming system.

2. Description of the Related Art Conventionally, there has been known an image forming apparatus which fixes a color material on a recording medium such as paper to form an image. In such an image forming apparatus, the recording medium may be charged due to friction or the like in the conveyance process of the recording medium at the time of image formation, and the recording media stacked after the image formation may stick to each other.
On the other hand, Patent Document 1 discloses a technique for preventing sticking of recording media stacked one another by applying charge to the recording medium in an amount corresponding to the charge state of the recording medium and removing the charge. .

JP, 2009-196774, A

  However, in the above-described conventional techniques, it is difficult to completely discharge the recording medium by the application of charges. For this reason, when the recording medium is folded and stacked after charge application, the opposing surfaces stick together when the opposing surfaces of the recording media facing each other are in a charged state attracting each other at the time of stacking. There is.

  An object of the present invention is to provide a charge adjusting device, an image forming apparatus, and an image forming system capable of suppressing sticking of recording media which are folded and stacked after fixing of a color material.

In order to achieve the above object, the invention of the charge adjustment device according to claim 1 is:
A charge adjusting device which is connected to a post-processing apparatus for folding and stacking recording media, applies charge to the recording medium to which the coloring material is fixed, and supplies the charge to the post-processing apparatus,
A charge giving unit for giving a charge to the recording medium;
The amount of charge to be applied to each of a plurality of areas of the recording medium divided by the folding position where the recording medium is folded in the post-processing apparatus is determined, and the determined charge amount is applied by the charge applying unit. Control unit, and
Equipped with
The control unit determines, for each of the plurality of regions, the coverage of one surface of the region and the coverage of the other surface, based on the coverage indicating the amount of the color material fixed to the region. The amount of applied charge is determined based on the ratio of

In order to achieve the above object, the invention of the charge adjustment device according to claim 2 is:
A charge adjusting device which is connected to a post-processing apparatus for folding and stacking recording media, applies charge to the recording medium to which the coloring material is fixed, and supplies the charge to the post-processing apparatus,
A charge giving unit for giving a charge to the recording medium;
The amount of charge to be applied to each of a plurality of areas of the recording medium divided by the folding position where the recording medium is folded in the post-processing apparatus is determined, and the determined charge amount is applied by the charge applying unit. Control unit, and
Equipped with
The control unit
The amount of applied charge is determined for each of the plurality of regions based on the coverage indicating the amount of the color material fixed to the regions;
Based on the coverage of the opposite area of the recording medium or the other recording medium facing below the one area of the recording medium at the time of stacking by the post-processing apparatus with respect to one area of the plurality of areas. , Determine the amount of applied charge,
The amount of applied charge is determined based on the amount of charge applied to the opposite region with respect to the one region .

The invention according to claim 3 is the charge adjustment device according to claim 2.
The control unit is characterized in that, for each of the plurality of regions, the amount of applied charge is determined based on a ratio of the coverage of one surface of the region to the coverage of the other surface.

The invention according to claim 4 is the charge adjustment device according to claim 1 ;
The control unit is configured to, with respect to one of the plurality of areas, an opposing area of the recording medium or another recording medium that faces the lower side of the one area of the recording medium at the time of stacking by the post-processing device. The amount of applied charge is determined based on the coverage.

The invention according to claim 5 is the charge adjustment device according to claim 4.
The control unit is characterized in that the amount of applied charge is determined based on the amount of charge applied to the opposite region with respect to the one region.

The invention according to claim 6 is the charge adjustment device according to claim 1 or 2
A charge amount measurement unit configured to measure a charge amount of each of the plurality of regions;
The control unit is characterized in that the applied charge amount is determined based on the measurement result by the charge amount measurement unit.

In order to achieve the above object, the invention of an image forming apparatus according to claim 7 is:
An image forming unit for fixing a color material on a recording medium to form an image;
The charge adjusting device according to any one of claims 1 to 6, which applies a charge to a recording medium to which a color material is fixed by the image forming unit.
It is characterized by having.

In order to achieve the above object, the invention of an image forming system according to claim 8 is:
An image forming apparatus for fixing a color material on a recording medium to form an image;
The charge adjusting device according to any one of claims 1 to 6, which applies a charge to a recording medium to which a color material is fixed by the image forming device.
A post-processing device that folds and stacks the recording medium to which the charge has been applied;
It is characterized by having.

  According to the present invention, there is an effect that the sticking of the recording medium which is folded and laminated after the fixing of the color material can be suppressed.

FIG. 1 is a diagram showing a schematic configuration of an image forming system. FIG. 2 is a block diagram showing the main functional configurations of an image forming apparatus, a charge control apparatus and a post-processing apparatus. It is a schematic diagram which shows the structure of a charge provision part. FIG. 7 is a schematic view showing an example of an aspect of a folding process on a sheet by a folding unit. It is a figure which shows the relationship between the coverage of each surface of a paper, and an electric current value. It is a lookup table which shows the field and the field of the coverage acquisition object corresponding to a charge control object field. 5 is a flowchart showing a control procedure of image formation processing. It is a flowchart which shows the control procedure of charge adjustment processing. It is a flowchart which shows the control procedure of a charge adjustment setting acquisition process. It is a flowchart which shows the control procedure of area | region division number and a folding position acquisition process. It is a flowchart which shows the control procedure of an electric current value setting acquisition process. FIG. 6 is a schematic view showing an example of the charged state of the sheet before and after charge adjustment processing. It is a figure explaining the sticking control effect of the sheets by electric charge adjustment processing. It is a figure explaining the sticking control effect of the opposing surface of the same paper by electric charge adjustment processing. It is a block diagram showing the main functional composition of the image forming device concerning a modification.

  Hereinafter, embodiments of a charge adjustment device, an image forming apparatus, and an image forming system of the present invention will be described based on the drawings.

FIG. 1 is a view showing a schematic configuration of an image forming system 1 according to an embodiment of the present invention.
The image forming system 1 includes an image forming device 2, a charge adjustment device 3, and a post-processing device 4.

The image forming apparatus 2 is an apparatus for forming an image on a sheet (recording medium) by an electrophotographic method. The image forming apparatus 2 conveys the sheet on which the image is formed to the charge adjustment device 3.
The charge adjusting device 3 is a device that applies an electric charge to the sheet delivered from the image forming device 2 to adjust the electric charge that the sheet is charged. The charge adjusting device 3 conveys the sheet whose charge has been adjusted to the post-processing device 4.
The post-processing device 4 is a device that performs predetermined folding processing on the sheet delivered from the charge adjustment device 3 and stacks the sheet on the sheet discharge trays 434 and 435. The post-processing device 4 may be configured to perform decurling processing, stapling processing, punching processing, bookbinding processing and the like in addition to the folding processing.
The image forming apparatus 2, the charge adjustment apparatus 3 and the post-processing apparatus 4 are configured to be removable from adjacent apparatuses.

  FIG. 2 is a block diagram showing the main functional configurations of the image forming apparatus 2, the charge adjustment apparatus 3 and the post-processing apparatus 4.

  The image forming apparatus 2 includes a control unit 20 having a CPU 201 (Central Processing Unit), a RAM 202 (Random Access Memory), and a ROM 203 (Read Only Memory), a storage unit 21, an operation unit 22, a display unit 23, and a communication unit. 24, an interface 25, a scanner 26, an image processing unit 27, an image forming unit 28, a transport unit 29 and the like. The control unit 20 is connected to the storage unit 21, the operation unit 22, the display unit 23, the communication unit 24, the interface 25, the scanner 26, the image processing unit 27, the image forming unit 28 and the transport unit 29 via the bus 2 b. .

  The CPU 201 reads out and executes a control program stored in the ROM 203 and performs various arithmetic processing.

  The RAM 202 provides the CPU 201 with a working memory space and stores temporary data.

  The ROM 203 stores various control programs executed by the CPU 201, setting data, and the like. Note that instead of the ROM 203, a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

  The control unit 20 including the CPU 201, the RAM 202, and the ROM 203 integrally controls each part of the image forming apparatus 2 in accordance with the various control programs described above. For example, the control unit 20 causes the conveyance unit 29 to convey the sheet, and causes the image forming unit 28 to form an image on the sheet based on the image data stored in the storage unit 21.

  The storage unit 21 is configured by a dynamic random access memory (DRAM) or the like, and stores image data acquired by the scanner 26, image data input from the outside via the communication unit 24, and the like. Note that these image data and the like may be stored in the RAM 202.

  The operation unit 22 includes input devices such as a touch panel disposed on the operation keys and the screen of the display unit 23, converts an input operation to these input devices into an operation signal, and outputs the operation signal to the control unit 20.

  The display unit 23 includes a display device such as an LCD (Liquid crystal display), and displays an operation screen and the like indicating the state of the image forming system 1 and the content of the input operation to the touch panel.

  The communication unit 24 communicates with a computer or another image forming apparatus on the network according to a control signal from the control unit 20 to transmit and receive image data and the like.

  The interface 25 is a means for transmitting and receiving data to and from the charge adjustment device 3, and is configured of, for example, any of various serial interfaces.

  The scanner 26 reads an image formed on a sheet, generates image data including monochrome image data for each of R (red), G (green) and B (blue) color components, and stores the image data in the storage unit 21.

  The image processing unit 27 includes, for example, a rasterization processing unit, a color conversion unit, a gradation correction unit, and a halftone processing unit, performs various image processing on the image data stored in the storage unit 21 and stores the image data in the storage unit 21 Let

  The image forming unit 28 forms an image on a sheet based on the image data stored in the storage unit 21. The image forming unit 28 includes four sets of an exposure unit 281, a photosensitive member 282, and a developing unit 283 respectively corresponding to C (cyan), M (magenta), Y (yellow) and K (black) color components. . The image forming unit 28 further includes a transfer member 284, a secondary transfer roller 285, and a fixing unit 286.

The exposure unit 281 includes an LD (Laser Diode) as a light emitting element. The exposure unit 281 drives the LD based on the image data, irradiates the photosensitive member 282 to be charged with laser light and exposes it, and forms an electrostatic latent image on the photosensitive member 282. The developing unit 283 forms toner (color material) of a predetermined color (any one of C, M, Y and K) by the developing roller charged on the exposed photosensitive member 282 and forms the photosensitive member 282 on the photosensitive member 282. Develop the electrostatic latent image.
The images (monochrome images) formed by the toners of C, M, Y and K on the four photosensitive members 282 corresponding to C, M, Y and K are sequentially superimposed on the transfer member 284 from the respective photosensitive members 282. And transferred. Thus, a color image having C, M, Y, and K as color components is formed on the transfer member 284. The transfer body 284 is an endless belt wound around a plurality of transfer body transport rollers, and rotates according to the rotation of each transfer body transport roller.
The secondary transfer roller 285 transfers the color image on the transfer body 284 onto the sheet fed from the sheet feed tray 2a. Specifically, by applying a predetermined transfer voltage to the secondary transfer roller 285 that holds the sheet and the transfer body 284, the toner forming a color image on the transfer body 284 is attracted to the sheet side and the sheet is transferred to the sheet. Transcribed.

  The fixing unit 286 performs a fixing process of fixing the toner on the sheet by heating and pressurizing the sheet on which the toner has been transferred. The fixing unit 286 is provided with a pair of rollers including a heating roller and a pressure roller which sandwich the sheet. The heating roller is heated to a predetermined target temperature (for example, a temperature within the range of 180 ° C. or more and 200 ° C. or less) by a heater as a heating source. The pressure roller is biased toward the heating roller by an elastic member (not shown). The sheet on which the image formed of the toner is transferred by the secondary transfer roller 285 passes through the nip portion of the heating roller and the pressure roller, and the image formed of the toner is fixed to the sheet.

  The transport unit 29 includes a plurality of sheet transport rollers that transport the sheet by rotating in a state where the sheet is nipped, and transports the sheet along a predetermined transport path. The transport unit 29 includes a reversing mechanism 291 that reverses the front and back of the sheet on which the fixing process has been performed by the fixing unit 286 and transports the sheet to the secondary transfer roller 285. In the image forming apparatus 2, when forming an image on both sides of the sheet, the reversing mechanism 291 reverses the front and back of the sheet, and after the image is formed on both sides, the sheet is transported to the charge adjustment device 3. When an image is formed on only one side of the sheet, the sheet on which the image is formed on one side is conveyed to the charge adjustment device 3 without the front and back sides of the sheet being reversed by the reversing mechanism 291.

  The charge adjustment device 3 includes a control unit 30 having a CPU 301, a RAM 302, and a ROM 303, interfaces 31, 33, a charge applying unit 32, a transport unit 34, and the like. The control unit 30 is connected to the interfaces 31 and 33, the charge application unit 32, and the transport unit 34 via the bus 3b.

The configurations of the CPU 301, the RAM 302, and the ROM 303 are the same as the configurations of the CPU 201, the RAM 202, and the ROM 203. The RAM 302 stores, as temporary data, an area division number Nmax, coverages x, y, z, and folding positions F1, F2 described later, for example. The ROM 303 stores, as setting data, for example, a lookup table (FIG. 6) for acquiring a detection target area of the coverage z described later, and setting values used for the current value setting acquisition processing.
The control unit 30 including the CPU 301, the RAM 302, and the ROM 303 integrally controls the respective units of the charge adjustment device 3 in accordance with various control programs. For example, the control unit 30 acquires settings relating to charge application from temporary data stored in the RAM 302 and setting values stored in the ROM 303, and charges the sheet by the charge application unit 32 based on the settings. Let

  The interfaces 31 and 33 are means for transmitting and receiving data to and from the image forming apparatus 2 and the post-processing apparatus 4, respectively, and are configured by, for example, any of various serial interfaces.

FIG. 3 is a schematic view showing the configuration of the charge applying unit 32. As shown in FIG.
The charge applying unit 32 applies a voltage to the sheet P having the toner fixed thereon and conveyed from the image forming apparatus 2 to apply an electric charge. The charge applying unit 32 includes a first conductive rubber roller 321, a second conductive rubber roller 322 disposed to face the first conductive rubber roller 321, and the first and second conductive rubber rollers 321 and 322. And a power supply 323 for applying a voltage between them. The first and second conductive rubber rollers 321 and 322 convey the sheet P by rotating while holding the sheet P in the nip portion.

Here, as shown in FIG. 3, the sheet P supplied to the charge imparting unit 32 has a positive charge only on the first surface Pa of the first surface Pa (front surface) and the second surface Pb (back surface). ing. This is because an image is formed on the first surface Pa of the sheet P earlier than the second surface Pb, and the toner 51 is fixed, and then the conveyance processing at the time of image formation with respect to the second surface Pb is performed on the first surface Pa. This is because static electricity is generated on the toner 51. Therefore, while the positive charge is retained only on the first surface Pa of the sheet P, the second surface Pb on which the toner 52 is fixed is generally hardly charged.
In the present specification and the drawings, the number of signs “+” represents the amount of positive charge on the sheet P. For example, the amount of charges on the first surface Pa before the toner 51 is fixed and the charges are applied by the charge applying unit 32 is represented by four “+”, and the amount of charges relatively smaller is smaller than this. It shall be represented by "+".

The first conductive rubber roller 321 is connected to the power source 323, and the second conductive rubber roller 322 is grounded. When a positive voltage is applied from the power supply 323 to the first conductive rubber roller 321 while the first and second conductive rubber rollers 321 and 322 are transporting the sheet P, the first and second conductive properties are obtained. A current flows between the rubber rollers 321 and 322, and a positive charge is applied to the second surface Pb (rear surface) of the sheet P. Also, at this time, the same amount of negative charge as the positive charge applied from the first conductive rubber roller 321 is induced to the second conductive rubber roller 322, and the positive charge of the first surface Pa (surface) of the paper P is A part (or all) forms a charge pair Cp with the negative charge induced in the second conductive rubber roller 322 to cancel the charge. The charge applying unit 32 operates with the application voltage of the power supply 323 controlled so that the current value becomes a predetermined value. That is, the charge applying unit 32 is controlled at constant current.
In the present embodiment, the outer peripheral surfaces of the first and second conductive rubber rollers 321 and 322 are made of NBR (acrylonitrile butadiene rubber) having ion conductivity. The outer circumferential surfaces of the first and second conductive rubber rollers 321 and 322 may be made of a conductive material other than the ion conductive material, such as a metal.

  The transport unit 34 includes a plurality of sheet transport rollers configured to transport the sheet by rotating in a state in which the sheet is nipped, and transports the sheet along a predetermined transport path including the charge applying section 32.

  The post-processing device 4 includes a control unit 40 having a CPU 401, a RAM 402, and a ROM 403, an interface 41, a folding unit 42, a conveyance unit 43, and the like. The control unit 40 is connected to the interface 41, the folding unit 42, and the transport unit 43 via the bus 4b.

  The configurations of the CPU 401, the RAM 402, and the ROM 403 are the same as the configurations of the CPU 201, the RAM 202, and the ROM 203. The control unit 40 generally controls each part of the post-processing device 4 in accordance with various control programs.

  The interface 41 is means for transmitting and receiving data with the charge adjustment device 3 or with the image forming device 2 via the charge adjustment device 3 and is constituted by any of various serial interfaces, for example.

The folding unit 42 folds the sheet delivered from the charge adjustment device 3 and conveyed to the conveyance path 432 in a predetermined folding mode and causes the sheet to be stacked on the sheet discharge trays 434 and 435. The folding mode is selected from, for example, half folding (center folding), outer folding, and inner folding.
The folding unit 42 includes folding rollers 423, 424, 425, pushing plates 421, 422, and the like.
The pressing plate 421 is a plate-like member for pressing the sheet P on the conveyance path 432 toward the nip portion of the folding rollers 423 and 424 at a predetermined folding position. The predetermined folding position is, for example, the central portion of the sheet P when the folding mode is two-fold, and approximately 1/3 from the end of the sheet P when the folding mode is three-fold or three-fold. Or 2/3 position. The sheet P pushed into the nip portion of the folding rollers 423 and 424 by the pushing plate 421 is drawn into the nip portion in a state where the folding position is at the top, and the sheet P of the folding rollers 423 and 424 passes through the nip portion. It is folded and creased by pressure. When the folding mode is half folding, the sheet P folded by the folding rollers 423 and 424 is conveyed to the sheet discharge tray 434 as it is and stacked.
The pressing plate 422 is a nip of the folding rollers 424 and 425 at a predetermined folding position (for example, approximately 2/3 or 1/3 from the end) when the folding mode is outer tri-fold or inner tri-fold. It is a plate-like member which is pushed toward the part. The sheet P pushed into the nip portion of the folding rollers 424 and 425 by the pushing plate 422 is drawn into the nip portion in a state where the folding position is at the top, and the sheet P of the folding rollers 424 and 425 passes the nip portion. It is folded and creased by pressure. The sheet P folded and folded in three by the folding rollers 423 and 424 is conveyed to the sheet discharge tray 435 and stacked.
The configuration of the folding unit 42 is not limited to the above, and the sheet P may be folded in two or three, and may be stacked on the sheet discharge trays 434 and 435.
When the folding process is not performed on the sheet P, the sheet P delivered from the charge adjustment device 3 is stacked on the sheet discharge tray 433 through the conveyance path 431.

FIG. 4 is a schematic view showing an example of the form of the folding process on the sheet P by the folding unit 42. As shown in FIG. FIGS. 4 (a) to 4 (c) respectively show half-folded, three-folded and three-folded modes.
As shown in FIG. 4A, in the case of folding in half, the sheet P is such that the second surface Pb is inward at a distance F1 from the leading edge of the sheet P (hereinafter referred to as a folding position F1). It is broken. The sheet P is divided into the first area R1 and the second area R2 by the folding position F1, and after being folded, the second surface Pb of the first area R1 and the second surface Pb of the second area R2 face each other. . In addition, when two-folded sheets P are stacked, the first surface Pa of the first area R1 is the second area R2 of the sheet P processed in front of the sheet P (hereinafter referred to as a front sheet). It faces the first surface Pa of
Further, as shown in FIG. 4B, in the case of outer folding, the sheet P is such that the second surface Pb is inward at a position F1 from the leading edge of the sheet P (folding position F1). The sheet P is folded so that the first surface Pa is inward at a position F2 (folding position F2) from the leading edge of the sheet P. The sheet P is divided into a first area R1, a second area R2 and a third area R3 by the folding positions F1 and F2, and after being folded, the second surface Pb of the first area R1 and the second surface R2 of the second area R2 The two faces Pb face each other, and the first face Pa of the second region R2 faces the first face Pa of the third region. Further, in the case where the outer-folded paper P is stacked, the first surface Pa of the first region R1 faces the second surface Pb of the third region R3 of the front paper.
Further, as shown in FIG. 4C, in the case of inner folding, the sheet P is folded so that the second surface Pb is inward at the folding position F1 and at the folding position F2. The sheet P is divided into the first area R1, the second area R2, and the third area R3 by the folding positions F1 and F2, and after being folded, the second surface Pb of the first area R1 and the second surface of the third area R2 One surface Pa is opposed, and the second surface Pb of the second region R2 and the second surface Pb of the third region are opposed. In addition, when the inner three-folded sheet P is stacked, the first surface Pa of the first area R1 faces the first surface Pa of the second area R2 of the front sheet.
Hereinafter, the area of the sheet P divided by the folding position F1 and / or the folding position F2 in any of the folding modes is also referred to as an area R.

  The transport unit 43 includes a plurality of sheet transport rollers that transport the sheet P by rotating in a state in which the sheet is nipped, and transports the sheet P along a predetermined transport path including the transport paths 431 and 432.

Next, the charge adjusting operation performed in the charge adjusting device 3 of the image forming system 1 having the above configuration will be described.
In the charge adjustment device 3 of the present embodiment, in order to suppress sticking between the sheets of paper P to be subjected to folding processing and stacked in the post-processing device 4 and between facing surfaces in the same sheet of paper P, The amount of charge (the amount of applied charge) based on the coverage of the first surface Pa and the second surface Pb in the region R is applied to each region R divided at the folding position, and the charge is adjusted. Here, the coverage refers to the amount of toner fixed on the image formable area of the first surface Pa (second surface Pb) of the area R (hereinafter also referred to as charge adjustment target area) to which charge is applied and adjusted. , C, M, Y, and K is a value that is represented as 100% when the toner of any of the colors C, M, Y, and K is fixed on the entire image formable area. In other words, the coverage is a value obtained by adding the printing rates for C, M, Y, and K toners. Therefore, for example, when toners of all colors C, M, Y and K are applied to the entire image formable area, the coverage is 400%. For example, toners of colors C and M can be formed out of the image formable area. When each is given in the range of 25%, the coverage is 50%. There is a positive correlation between the amount of toner fixed to the sheet P and the amount of charge on the surface on which the toner is fixed after image formation by the image forming apparatus 2. In this specification, the coverage of the first side Pa of the sheet P is referred to as coverage x, and the coverage of the second side is referred to as coverage y.

  In the charge adjusting device 3, the control unit 30 controls the first and second conductive rubber rollers of the charge applying unit 32 based on the ratio of the coverage x of the first surface Pa to the coverage y of the second surface Pb in a certain region R. Determine the current value flowing between 321 and 322. Also, this current value corresponds to the amount of charge applied to the region R. Therefore, the control unit 30 determines the amount of applied charge by determining the current value. The charge applying unit 32 applies a constant charge amount to the region R under constant current control with the current value thus determined and set.

FIG. 5 is a view showing the relationship between the coverage of each side of the sheet P and the current value.
As shown in FIG. 5, when the coverage x and the coverage y satisfy y ≧ 2.5 x, the current value flowing between the first and second conductive rubber rollers 321 and 322 of the charge application unit 32 is the first. One current value (20 μA in this embodiment).
Further, when y ≧ 1.67x and y <2.5x hold, the current value is set to the second current value (40 μA in the present embodiment).
Further, in the case where y か つ 0.4x and y <1.67x hold, the current value is set to a third current value (50 μA in the present embodiment).
When y <0.4x holds, the current value is set to the fourth current value. In the present embodiment, the fourth current value is a value of the second surface Pb of a region R (hereinafter referred to as a facing region) facing the lower side of the charge adjustment target region when the sheets P are stacked by the post-processing device 4. When the coverage (referred to as coverage z in the present specification) is 100% or less, it is 70 μA, and when it exceeds 100%, it is (80-Iz) μA. Here, Iz is a current value set for the facing area.

FIG. 6 is a look-up table showing the area R and the surface of coverage z acquisition target corresponding to the charge adjustment target area.
In the look-up table of FIG. 6, the opposing regions are provided to the charge adjustment target regions (the first region R1 to the third region R3) in the respective folding modes (no folding, two folds, three outer folds, three inner folds). And the opposite surface is shown, and the area R of coverage z acquisition target and the second surface of the opposite region which is a surface are shown. In the charge adjustment device 3, when y <0.4x holds in the charge adjustment target region, the region R for acquisition of coverage z corresponding to the charge adjustment target region and the surface are referred to by this lookup table, and the reference result is The coverage z is obtained accordingly.

  Next, a control procedure by the control units 20, 30, and 40 in the case where the image forming process including the charge adjustment process according to the above-described charge adjustment operation is performed will be described.

FIG. 7 is a flowchart showing the control procedure of the image forming process.
The image forming process is started when an image forming instruction including image data is input from the computer or the like on the network via the communication unit 24 of the image forming apparatus 2 to the control unit 20 and stored in the storage unit 21. The image formation command includes information on the number Mmax of sheets P forming an image, the folding mode of the sheet P, and the folding position F1 (F2).
When the image forming process is started, the control unit 20 of the image forming apparatus 2 operates each unit of the image forming apparatus 2 to form an image on one side or both sides of the sheet P (step S101). That is, the control unit 20 causes the image forming unit 28 to apply toner to the sheet P based on the image data stored in the storage unit 21 and causes the fixing unit 286 to fix the toner on the sheet P. The control unit 20 executes the step S101 on the number of sheets P designated in the image formation command to form an image. The control unit 20 causes the transport unit 29 to transport the sheet P on which the image is formed to the charge adjustment device 3.

  The control unit 30 of the charge adjustment device 3 executes charge adjustment processing described later on the sheet P delivered from the image forming device 2 (step S102). The control unit 30 causes the conveyance unit 34 to convey the sheet P subjected to the charge adjustment processing to the post-processing device 4.

  The control unit 40 of the post-processing device 4 causes the folding unit 42 to execute the folding process on the sheet P delivered from the charge adjustment device 3 (step S103). That is, the control unit 40 causes the folding unit 42 to execute the folding process in accordance with the folding mode and the folding position F1 (F2) designated in the image forming command. The control unit 40 executes the process of step S103 for each of the sheets P specified in the image formation command.

The control unit 40 of the post-processing device 4 causes the conveyance unit 43 to stack the sheets P on which the folding process has been performed on the paper discharge trays 434 and 435 (step S104).
When the process of step S104 ends, the control units 20, 30, and 40 end the image forming process.

FIG. 8 is a flowchart showing a control procedure of charge adjustment processing.
When the charge adjustment processing (step S102 in FIG. 7) is started, the control unit 30 of the charge adjustment device 3 substitutes 1 into a variable M indicating the number of processed sheets of paper P and stores it in the RAM 302 (step S201).

  Control unit 30 executes charge adjustment setting acquisition processing described later (step S202). In the charge adjustment setting acquisition process, the setting of the area division number Nmax of the sheet P according to the folding mode and the current value for each area R are acquired and stored in the RAM 302.

  The control unit 30 substitutes 1 into a variable N indicating the number of the area R of the sheet P, and stores the variable N in the RAM 302 (step S203). Hereinafter, the N-th area R of the sheet P is referred to as an N-th area.

  The control unit 30 determines whether the leading end of the sheet P has reached the nip portion of the first and second conductive rubber rollers 321 and 322 of the charge application unit 32 (step S204). If it is determined that the leading end of the sheet P has not reached the nip portion ("No" in step S204), the control unit 30 executes the process of step S204 again.

  When it is determined that the leading end of the sheet P has reached the nip portion ("Yes" in step S204), the control unit 30 charges the charge applying portion with the current value set for the Nth area of the sheet P. Charge is applied to the Nth area of the sheet P by the step S 32 (step S 205).

  The control unit 30 determines whether the N-th area of the sheet P has passed through the nip portion of the first and second conductive rubber rollers 321 and 322 of the charge application unit 32 (step S206). If it is determined that the N-th region of the sheet P has not passed through the nip portion (“No” in step S206), the control unit 30 shifts the process to step S205 and continues using the charge applying unit 32. Charge is applied to the Nth region.

  When it is determined that the Nth area of the sheet P has passed through the nip portion ("Yes" in step S206), the control unit 30 determines whether the variable N is equal to the area division number Nmax of the sheet P. It discriminates (step S207).

  If it is determined that the variable N is different from the area division number Nmax ("No" in step S207), the control unit 30 substitutes (N + 1) for the variable N and stores it in the RAM 302 (step S208). When the process of step S208 ends, the control unit 30 shifts the process to step S205.

  If it is determined that the variable N is equal to the area division number Nmax ("Yes" in step S207), the control unit 30 determines the number M of sheets P forming the image designated by the image formation command and the variable M It is determined whether they are equal (step S209).

  If it is determined that the variable M is different from Mmax ("No" in step S209), the control unit 30 substitutes (M + 1) for the variable M and stores the same in the RAM 302 (step S210). When the process of step S210 is completed, the control unit 30 shifts the process to step S202.

  If it is determined that the variable M is equal to Mmax ("Yes" in step S209), the control unit 30 ends the charge adjustment process.

FIG. 9 is a flowchart showing a control procedure of charge adjustment setting acquisition processing.
When the charge adjustment setting acquisition process (step S202 in FIG. 8) is started, the control unit 30 determines whether the folding mode is set in the image forming command (step S301).

  If it is determined that the folding mode is not set in the image formation command (“No” in step S301), control unit 30 determines coverage x of the entire first surface Pa of sheet P and the entire second surface Pb. The coverage y is acquired (step S302). That is, the control unit 30 acquires the coverages x and y from the sum of the pixel values of the image data respectively corresponding to the C, M, Y and K color components and stores them in the RAM 302.

  The control unit 30 acquires the coverage z of the second surface Pb of the front sheet (step S303). That is, the control unit 30 acquires the coverage z related to the second surface Pb of the front sheet from the image data of the previous sheet processed one before as in step S302 and stores the coverage z in the RAM 302.

  Control unit 30 executes current value setting acquisition processing described later (step S304). When the process of step S304 ends, the control unit 30 ends the charge adjustment setting acquisition process.

  On the other hand, when it is determined that the folding mode is set in the image formation command ("Yes" in step S301), control unit 30 executes area division number and folding position acquisition processing described later (step S305). ). In the area division number and folding position acquisition process, the area division number Nmax and the folding position F1 (F2) are acquired and stored in the RAM 302.

  The control unit 30 substitutes 1 into a variable N indicating the number of the area R of the sheet P and stores the variable N in the RAM 302 (step S306).

  The control unit 30 acquires the coverage x of the first surface Pa and the coverage y of the entire second surface Pb related to the N-th region of the sheet P (step S307). That is, the control unit 30 determines whether the sum of pixel values of pixels included in the Nth area divided by the folding position F1 (F2) among the image data respectively corresponding to the C, M, Y and K color components is used. The coverage x, y of the area is acquired and stored in the RAM 302.

  Control unit 30 obtains coverage z of the second surface of the facing area corresponding to the Nth area (step S308). That is, the control unit 30 refers to the look-up table shown in FIG. 6 to specify the area R (facing area) and the surface of coverage z acquisition target, and the facing area among the image data related to the sheet including the facing area. The coverage z is acquired from the sum of the pixel values of the pixels included in and stored in the RAM 302.

  Control unit 30 executes a current value setting acquisition process described later (step S309).

  Control unit 30 determines whether or not variable N is equal to area division number Nmax (step S310).

  If it is determined that the variable N is different from the area division number Nmax (“No” in step S310), the control unit 30 substitutes (N + 1) for the variable N and causes the RAM 302 to store (N) (step S311). When the process of step S311 ends, the control unit 30 shifts the process to step S307.

  If it is determined that the variable N is equal to the area division number Nmax ("Yes" in step S310), the control unit 30 ends the charge adjustment setting acquisition process.

FIG. 10 is a flowchart showing the control procedure of the area division number and the folding position acquisition process.
When the area division number and the folding position acquisition process (step S305 in FIG. 9) are started, the control unit 30 determines the folding mode set in the image forming command (step S401).

  If it is determined in step S401 that the folding mode is half folding, the control unit 30 substitutes 2 for the variable Nmax (the number of area divisions Nmax) and stores it in the RAM 302 (step S402).

  The control unit 30 acquires the folding position F1 set in the image formation command and stores the folding position F1 in the RAM 302 (step S403).

  On the other hand, when it is determined in step S401 that the folding mode is three-fold (three-fold or three-fold), control unit 30 substitutes 3 into variable Nmax (number of area divisions Nmax) to RAM 302. It memorizes (Step S404).

The control unit 30 acquires the folding positions F1 and F2 set in the image forming command and stores the folding positions F1 and F2 in the RAM 302 (step S405).
When the process of step S403 or step S405 ends, the control unit 30 ends the area division number and folding position acquisition process.
In FIG. 10, the case where the folding mode is two-fold or three-fold is described as an example, but a folding mode of four or more may be included. In this case, the folding mode is appropriately selected. The corresponding processing is performed.

FIG. 11 is a flowchart showing a control procedure of the current value setting acquisition process.
When the current value setting acquisition process (steps S304 and S309 in FIG. 9) is started, the control unit 30 sets y ≧ between the coverage x of the first surface and the coverage y of the second surface stored in the RAM 302. It is determined whether the relationship of 0.4x is established (step S501).

  If it is determined that the relationship of y ≧ 0.4x is not established (“No” in step S501), the control unit 30 determines whether the coverage z stored in the RAM 302 satisfies z ≦ 100%. Is determined (step S505).

  When it is determined that the coverage z does not satisfy z ≦ 100% (“No” in step S505), the control unit 30 acquires the current value Iz set for the opposing region, and relates to the current value. The setting is set to (80−Iz) μA, and data indicating the setting is stored in the RAM 302 (step S506).

  If it is determined that the coverage z satisfies z ≦ 100% (“Yes” in step S505), the control unit 30 stores data representing the setting regarding the setting of the current value as 70 μA in the RAM 302 (step S507).

  If it is determined in step S501 that the relationship of y ≧ 0.4x is satisfied (“Yes” in step S501), control unit 30 determines whether the relationship of y ≧ 1.67x is satisfied (step S502).

  If it is determined that the relation of y ≧ 1.67x does not hold (“No” in step S502), the control unit 30 stores the data representing the setting regarding the setting of the current value as 50 μA in the RAM 302 ( Step S508).

  If it is determined that the relationship of y ≧ 1.67x is established (“Yes” in step S502), the control unit 30 determines whether the relationship of y2.52.5x is established (step S503).

  If it is determined that the relationship of y ≧ 2.5x does not hold (“No” in step S503), the control unit 30 stores the data representing the setting regarding the setting of the current value as 40 μA in the RAM 302 ( Step S509).

If it is determined that the relationship of y ≧ 2.5x is established (“Yes” in step S503), the control unit 30 stores the data representing the setting regarding the setting of the current value as 20 μA in the RAM 302 (step S504).
When one of the processes in steps S504 and S506 to S509 ends, the control unit 30 ends the current value setting acquisition process.

  Next, the change in the charged state before and after the above-described charge adjustment process will be described by taking the sheet P on which toner is formed in various patterns as an example.

FIG. 12 is a schematic view showing an example of the charged state of the sheet P before and after the charge adjustment processing.
FIGS. 12A to 12D show the charged states of the sheet before and after the charge adjustment processing in one region R of the sheet P on which the toner is formed in various patterns.

FIG. 12A shows an example in which the coverage x of the first surface Pa and the coverage y of the second surface Pb are both 150% in the region R where the sheet P is present. In this case, in the state before the charge adjustment processing, as shown in FIG. 3, the first surface Pa is positively charged while the second surface Pb is not charged. Then, in this case, since the relationship of y0.40.4x and y <1.67x is satisfied, charge is applied to the region R under the condition of a current value of 50 μA by the charge applying unit 32. As a result, a positive charge is imparted to the second surface Pb, while a negative charge is imparted to the first surface Pa to form a charge pair with a part of the positive charge that has been charged, thereby canceling the charge. As a result, the charge amount of the first surface Pa after the charge adjustment processing is approximately halved, and the first surface Pa and the second surface Pb have a substantially equal amount of positive charge.
FIG. 12B shows the case where the coverage x of the first surface Pa is 150% and the coverage y of the second surface Pb is 0% in the region R where the sheet P is present. In this case, since the relationship of y <0.4x is satisfied, charges are applied to the region R under the condition of a current value of 70 μA by the charge applying unit 32 (coverage z is 100% or less). Here, since the toner is not fixed to the second surface Pb, the second surface Pb is in a state closer to the conductor as compared with the state in which the toner is fixed. Therefore, even if a positive charge is applied to the second surface Pb by the charge applying unit 32, the charge does not stay on the second surface, and the second surface Pb after charge adjustment processing is hardly charged. Become. On the other hand, a sufficient amount of negative charges is imparted to the first surface Pa by the charge imparting portion 32, and positive charges form charge pairs, almost all the charges are cancelled, and the first surface Pa after charge adjustment processing is also , Almost uncharged.
FIG. 12C shows the case where the coverage x of the first surface Pa is 0% and the coverage y of the second surface Pb is 150% in the region R where the sheet P is present. In this case, since the relationship of y ≧ 2.5x is satisfied, the charge application unit 32 applies charges to the region R under the condition of a current value of 20 μA. As a result, a small amount of positive charge is applied to the second surface Pb, and the second surface Pb after charge adjustment processing is slightly positively charged. On the other hand, in the first surface Pa, the charge applied for the same reason as the second surface Pb in FIG. 12B does not stay, and the first surface Pa after charge adjustment processing is hardly charged It becomes.
FIG. 12D shows the case where the coverage x of the first surface Pa and the coverage y of the second surface Pb are both 0% in the region R where the sheet P is present. Also in this case, since the relationship of y ≧ 2.5x is satisfied, the charge applying unit 32 applies charges to the region R under the condition of the current value of 20 μA. In this case, since no toner is fixed on the first surface Pa and the second surface Pb, the applied charge does not stay. Therefore, the first surface Pa and the second surface Pb after the charge adjustment processing are hardly charged.
The relationship between the coverage x, y of the sheet P and the current value shown in FIG. 5 is determined such that the charged state of the sheet P before and after the charge adjustment processing is as shown in FIGS. 12 (a) to 12 (d). .

  Next, the sticking suppression effect of the paper P by the above-described charge adjustment processing will be described by taking the case where the paper P is folded in two and stacked, as an example.

FIG. 13 is a view for explaining the sticking suppression effect between the sheets P by the charge adjustment processing.
13 (a) to 13 (f) show an embodiment in which each of the lower sheet P and the upper sheet P is folded in two and stacked, charging of the sheets before charge adjustment processing, after charge adjustment processing, and at the time of lamination is performed. It shows the state. Further, the coverage x (y) is 150% in the area R where toner is drawn on the paper P, and the coverage x (y) is 0% in the area R where toner is not drawn. Therefore, the state of each area R of each sheet P described in FIGS. 13A to 13F is the same as that in any one of FIGS. The setting of the values is the same as that of the corresponding one of FIGS. 12 (a) to 12 (d) unless otherwise specified.

In FIG. 13A, the coverages x and y of the second region R2 of the lower sheet P are 150% and 0%, respectively, which correspond to FIG. 12B. Further, the coverages x and y of the first area R1 of the upper sheet P of the sheet P are both 150%, which corresponds to FIG. 12 (a). The coverages x and y of the first area R1 of the lower sheet P and the second area R2 of the upper sheet P are both 0%, which corresponds to FIG.
Therefore, in the example of FIG. 13A, at the time of stacking after charge adjustment processing, the opposing surface of the lower sheet P is not charged, and the opposing surface of the upper sheet P has a half charge amount. It becomes a state of being positively charged by an amount corresponding to two "+". In this state, the amount of induced charge (negative charge) generated on the facing surface of the lower sheet P is small, and the sheets P hardly adhere to each other. As described above, by the charge adjustment processing, a suitable charged state is realized such that the opposing surfaces of the sheet P do not stick to each other.
Although charge is applied to the first area R1 of the lower sheet P and the second area R2 of the upper sheet P under the condition of a current value of 20 μA, the toner is not fixed and the electric charge does not stay. The charged state does not change. In the following description of FIGS. 13 (b) to 13 (f), the setting of the charging state and the current value according to the first area R1 of the lower sheet P and the second area R2 of the upper sheet P is shown in FIG. The description is omitted because it is the same as

  In FIG. 13B, the first area R1 of the upper sheet P of the paper corresponds to FIG. 12A, and the other area corresponds to FIG. Therefore, at the time of stacking after charge adjustment processing, the opposing surface of the lower sheet P is not charged, and the opposing surface of the upper sheet P is positively charged in amounts corresponding to two “+” s. It becomes a state. Thus, the preferred charged state is realized.

  13C, the second area R2 of the lower sheet P corresponds to FIG. 12A, and the first area R1 of the upper sheet P corresponds to FIG. 12C. Therefore, at the time of stacking, the opposing surface of the lower sheet P is positively charged by an amount corresponding to two “+”, and the opposing surface of the upper sheet P is not charged. Thus, the preferred charged state is realized.

  In FIG. 13D, the second area R2 of the lower sheet P and the first area R1 of the upper sheet P correspond to FIG. 12C. Therefore, when stacked, the opposing surfaces of the upper and lower sheets of paper P are in a state where they do not carry an electric charge. Thus, the preferred charged state is realized.

13E, the second area R2 of the lower sheet P corresponds to FIG. 12A, and the first area R1 of the upper sheet P corresponds to FIG. 12B. Here, y ≧ 0.4x is not satisfied for the first area R1 of the upper sheet P (“No” in step S501 of FIG. 11), and the coverage z (the second area R2 of the lower sheet P) is satisfied. Since the coverage of the second surface Pb does not satisfy z ≦ 100% (“No” in step S505 in FIG. 11), the setting of the current value is (80−Iz) μA (step S506 in FIG. 11). In this example, since Iz (the current value of the second area R2 of the lower sheet P) is 50 μA, the current value of the first area R1 of the upper sheet P is (80−50) = 30 μA. As described above, when the coverage z exceeds 100%, the current value is set such that the sum of the current value set for the opposing region and the current value regarding the current charge adjustment target region is constant at 80 μA. It is set. Thereby, the sticking at the time of lamination | stacking by the electric charge of excessive amount being provided to the paper P can be suppressed.
As a result, after charge adjustment processing and at the time of stacking, the first surface Pa of the first region R1 (the surface facing the lower sheet P) of the upper sheets P is positive for the amount corresponding to three “+”. It becomes charged. In addition, the opposing surface of the lower sheet P (the first surface Pa of the second region R2) is in a state of being positively charged by an amount corresponding to two “+”. This state is a state in which sticking does not occur because both opposing surfaces are positively charged. Therefore, a suitable charge state is realized by the charge adjustment process.

  In FIG. 13F, the second area R2 of the lower sheet P and the first area R1 of the upper sheet P correspond to FIG. 12B. Therefore, when stacked, the opposing surfaces of the upper and lower sheets of paper P are in a state where they do not carry an electric charge. Thus, the preferred charged state is realized.

FIG. 14 is a diagram for explaining the sticking suppression effect of the facing surface of the same sheet P by the charge adjustment processing.
FIGS. 14 (a) to 14 (f) show the charged states of the sheet before charge adjustment processing, after charge adjustment processing, and at the time of lamination in an embodiment in which the sheets P are folded in two and stacked. Further, the state of each region R of each sheet P described in FIGS. 14A to 14F is the same as any one of FIGS. 12A to 12D, and the current of each region R is also the same. The setting of the values is the same as that of the corresponding one of FIGS. 12 (a) to 12 (d) unless otherwise specified.

  In FIG. 14A, the first area R1 of the sheet P corresponds to FIG. 12C, and the second area R2 corresponds to FIG. Therefore, at the time of stacking after charge adjustment processing, the opposite surface of the first region R1 to the second region R2 bears a positive charge corresponding to one “+”, and the first region of the second region R2 The opposite surface to the region R1 is in a state of being positively charged by an amount corresponding to two "+". Therefore, a suitable charged state is realized such that the facing surfaces of the same sheet P do not stick.

  In FIG. 14B, the first area R1 of the sheet P corresponds to FIG. 12D, and the second area R2 corresponds to FIG. Therefore, at the time of lamination after charge adjustment processing, the opposite surface of the first region R1 is not charged, and the opposite surface of the second region R2 is positively charged in amounts corresponding to two “+” s. It will be Thus, the preferred charged state is realized.

In FIG. 14C, the first area R1 of the sheet P corresponds to FIG. 12A, and the second area R2 corresponds to FIG. 12B. Therefore, at the time of stacking after charge adjustment processing, the opposing surface of the first region R1 is positively charged in an amount corresponding to two “+”, and the opposing surface of the second region R2 is in a non-charged state. Become. Thus, the preferred charged state is realized.
In the second region R2 in FIG. 14C, y ≧ 0.4x is not satisfied, and the coverage z (coverage of the second surface Pb of the first region R1) does not satisfy z ≦ 100%. The setting of the current value is (80−Iz) μA. In this example, since Iz (current value related to the second region R2) is 50 μA, the current value related to the first region R1 is (80−50) = 30 μA.

  In FIG. 14D, the first area R1 and the second area R2 of the sheet P correspond to FIG. 12B. Therefore, in the stacking after the charge adjustment processing, the facing surfaces of the first region R1 and the second region R2 are both in a state in which they do not carry a charge. Thus, the preferred charged state is realized.

  In FIG. 14 (e), the first area R1 of the sheet P corresponds to FIG. 12 (a), and the second area R2 corresponds to FIG. 12 (c). Therefore, at the time of stacking after charge adjustment processing, the opposing surface of the first region R1 bears a positive charge corresponding to two “+” s, and the opposing surface of the second region R2 has one “+”. "Is positively charged in a corresponding amount. Thus, the preferred charged state is realized.

  In FIG. 14F, the first area R1 and the second area R2 of the sheet P correspond to those of FIG. 12C. Therefore, in the stacking after the charge adjustment processing, the facing surfaces of the first region R1 and the second region R2 are both in a state of being positively charged in an amount corresponding to one “+”. Thus, the preferred charged state is realized.

When charge adjustment processing is not performed in the example shown in FIGS. 13 and 14, for example, two sheets P of the upper and lower sheets are processed in the state before the charge adjustment processing shown in FIGS. 13 (b) and 13 (c). When the sheet P is folded and stacked, one of the facing surfaces of the sheet P has a positive charge corresponding to four “+” s, and the other is in a non-charged state. In this case, a large amount of negative induced charge is generated on the opposite surface on the other side, and it sticks to the opposite surface on one side.
On the other hand, in the present embodiment, the charge adjustment process is relaxed by the charge adjustment process based on the common algorithm not based on the toner formation pattern, and the sheet P of any toner formation pattern as shown in FIGS. Also, the charged state is realized such that the opposing surfaces do not stick to each other.

  In FIGS. 13 and 14, although the case where the folding mode is two-fold is described as an example, the charge adjustment processing is performed according to the algorithm of the present embodiment also in other folding modes such as outer folding and inner folding. As a result, a suitable charged state is realized such that the opposite surface of the sheet P does not stick.

  As described above, the charge adjustment device 3 according to the present embodiment is connected to the post-processing device 4 that folds and stacks the sheets P, applies charge to the sheet P on which the toner is fixed, and then the post-processing device 4 Of the sheet P divided by the charge application unit 32 for applying charges to the sheet P and the folding position F1 (F2) at which the sheet P is folded in the post-processing apparatus 4 The control unit 30 determines the amount of charge to be applied to each of the plurality of regions R, and causes the charge applying unit 32 to apply the determined amount of applied charge. With such a configuration, it is possible to apply the charge of the applied charge amount separately determined to each area R according to the folding mode of the sheet P in the post-processing device 4, and the charged state of each area R Can be in such a state that the facing surfaces do not stick when folded and stacked. As a result, it is possible to suppress the sticking of the sheet P which is folded and stacked after the fixing of the toner.

  In addition, the control unit 30 determines the amount of applied charge for each of the plurality of regions R based on the coverage indicating the amount of toner fixed to the region. As a result, it is possible to estimate the amount of applied charge according to the amount of charge carried by the region R by estimating the amount of charge carried by the region R of the paper P without directly measuring it. As a result, it is possible to realize a suitable charged state that does not cause the facing surfaces of the sheets of paper P to be folded and stacked to stick, and to suppress sticking more effectively.

  Further, the control unit 30 determines the amount of applied charge for each of the plurality of regions R based on the ratio of the coverage x on one side of the region R to the coverage y on the other side. Thus, based on a common algorithm that does not depend on the formation pattern of the toner on one surface and the other surface of the region R, the amount that can suppress sticking between the region R and the opposing surface during lamination is A charge can be applied to the region R.

  Further, the control unit 30 controls the sheet P or the other sheet P facing the lower side of the one area R of the sheet P at the time of stacking by the post-processing device 4 with respect to one area R of the plurality of areas. Based on the coverage z of the opposing area, the amount of applied charge is determined. As a result, a charge of an amount according to the charged state of the opposite surface when folded and stacked is applied to the region R of the paper P and the charge is adjusted, so sticking of the paper P to be folded and stacked Can be suppressed more reliably.

  Further, the control unit 30 determines the amount of applied charge for one region R based on the amount of charge applied to the opposite region. As a result, it is possible to suppress the sticking of the sheet P due to the application of an excessive amount of charge to the pair of regions facing each other when being folded and stacked.

  Further, the image forming system 1 according to the present embodiment applies an electric charge to the sheet P on which the toner is fixed by the image forming apparatus 2 and the image forming apparatus 2 that fixes the toner on the sheet P to form an image. The apparatus includes a charge adjustment device 3 and a post-processing device 4 that folds and stacks sheets P to which charge has been applied. As a result, it is possible to suppress sticking of the sheets P which are folded and stacked after fixing of the toner in the image forming system 1.

(Modification)
Next, modifications of the above embodiment will be described.
In the present modification, the configuration of the charge adjustment device 3 in the image forming system 1 according to the above embodiment is included in the image forming device 2. The other points are the same as those of the above-described embodiment, and therefore, the differences from the above-described embodiment will be described below.

FIG. 15 is a block diagram showing the main functional configuration of the image forming apparatus 2 according to the present modification.
The image forming apparatus 2 according to the present modification includes a control unit 20 having a CPU 201, a RAM 202, and a ROM 203, a storage unit 21, an operation unit 22, a display unit 23, a communication unit 24, an interface 25, a scanner 26, and The image processing unit 27, the image forming unit 28, the transport unit 29, the charge applying unit 32, and the like are provided. Each of these components has the same configuration and function as the components given the same reference numerals in the above embodiment, and the detailed description will be omitted. The control unit 20 and the transport unit 29 have the configuration and functions of the control unit 30 and the transport unit 34 of the charge adjustment device 3 of the above embodiment, in addition to the configuration and functions of the above embodiment. Further, the interface 25 exchanges data with the post-processing device 4.
In this modification, the charge adjustment process on the sheet P by the charge adjusting device 3 described in the above embodiment is performed in the image forming apparatus 2 under the control of the control unit 20 of the image forming apparatus 2.

  Note that only a part of the charge adjustment device 3 may be included in the image forming device 2. For example, the control unit 20 of the image forming apparatus 2 includes only the configuration and functions of the control unit 30 of the charge adjusting apparatus 3, and the charge adjusting operation on the sheet P by the charge adjusting apparatus 3 is performed by the control unit 20 of the image forming apparatus 2 You may go under control.

Further, as shown in FIG. 15, the image forming apparatus 2 of the present modification may include the charge amount measuring unit 35. The charge amount measuring unit 35 measures the amount of charge carried on each of the plurality of regions R of the sheet P and outputs the measured value to the control unit 20. The image forming apparatus 2 performs charge adjustment using the measurement value of the charge amount by the charge amount measurement unit 35 instead of the aspect in which the current value related to the charge adjustment processing is determined based on the coverage in the region R as in the above embodiment. You may determine the electric current value which concerns on a process.
The charge amount measurement unit 35 may be included in the charge amount adjustment device 3 according to the embodiment.

  As described above, in the image forming apparatus 2 according to the present modification, the image forming unit 28 which fixes the toner on the sheet P to form an image, and the charge on the sheet P on which the toner is fixed by the image forming unit 28 And a configuration related to the charge adjustment device 3 to be applied. According to such a configuration, the image forming apparatus 2 can perform charge adjustment processing that suppresses sticking of the sheets P folded and stacked after image formation.

  Further, the image forming apparatus 2 (or the charge adjustment device 3 according to the above embodiment) according to the present modification includes the charge amount measuring unit 35 that measures the charge amount of each of the plurality of regions R The unit 20 (30) determines the amount of applied charge based on the measurement result by the charge amount measuring unit 35. Accordingly, the charge of the sheet P can be more appropriately adjusted based on the measurement value of the charge amount that the sheet P is actually carrying.

The present invention is not limited to the above embodiment and modifications, and various modifications are possible.
For example, although the above-mentioned embodiment and modification explained the example which gives electric charge to paper P by the 1st and 2nd conductive rubber rollers 321 and 322, it is not the meaning limited to this. For example, the configuration may be such that the charge is applied by spraying a cation and / or an anion as a charge on the paper P using an ionizer. In addition, a voltage may be applied to the sheet P by a charge applying unit having a shape different from that of the first and second conductive rubber rollers 321 and 322. As such an electric charge provision part, a pair of electrode substrate arrange | positioned across the paper P, for example is mentioned.

  In the above embodiment and modification, the charge adjusting device 3 processes the sheet P on which the toner is fixed in the image forming device 2 as an example. However, the present invention is not limited to this. Alternatively, the sheet P may be directly supplied to the charge adjusting device 3 without the image forming device 2 and the charge adjusting process may be performed on the sheet P.

  In the embodiment and the modification, the electrophotographic image forming apparatus 2 is described as an example, but the system of the image forming apparatus 2 is not limited to this, and, for example, the recording medium transported by the transport apparatus Alternatively, the image forming apparatus may be an inkjet type image forming apparatus that discharges ink (color material) from the recording head and solidifies the discharged ink.

  Although some embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and the equivalents thereof. .

Reference Signs List 1 image forming system 2 image forming apparatus 28 image forming unit 3 charge adjusting device 30 control unit 32 charge applying unit 321, 322 conductive rubber roller 323 power source 4 post-processing device P sheet (recording medium)
R, R1, R2, R3 area F1, F2 folding position x, y, z coverage

Claims (8)

A charge adjusting device which is connected to a post-processing apparatus for folding and stacking recording media, applies charge to the recording medium to which the coloring material is fixed, and supplies the charge to the post-processing apparatus,
A charge giving unit for giving a charge to the recording medium;
The amount of charge to be applied to each of a plurality of areas of the recording medium divided by the folding position where the recording medium is folded in the post-processing apparatus is determined, and the determined charge amount is applied by the charge applying unit. Control unit, and
Equipped with
The control unit determines, for each of the plurality of regions, the coverage of one surface of the region and the coverage of the other surface, based on the coverage indicating the amount of the color material fixed to the region. A charge adjusting device, wherein the amount of applied charge is determined based on a ratio of . A charge adjusting device which is connected to a post-processing apparatus for folding and stacking recording media, applies charge to the recording medium to which the coloring material is fixed, and supplies the charge to the post-processing apparatus,
A charge giving unit for giving a charge to the recording medium;
The amount of charge to be applied to each of a plurality of areas of the recording medium divided by the folding position where the recording medium is folded in the post-processing apparatus is determined, and the determined charge amount is applied by the charge applying unit. Control unit, and
Equipped with
The control unit
The amount of applied charge is determined for each of the plurality of regions based on the coverage indicating the amount of the color material fixed to the regions;
Based on the coverage of the opposite area of the recording medium or the other recording medium facing below the one area of the recording medium at the time of stacking by the post-processing apparatus with respect to one area of the plurality of areas. , Determine the amount of applied charge,
A charge adjusting device, wherein the amount of applied charge is determined based on the amount of charge applied to the opposite region with respect to the one region.   The control unit may determine, for each of the plurality of regions, the amount of applied charge based on a ratio of the coverage of one surface of the region to the coverage of the other surface. Charge regulator as described in. The control unit is configured to, with respect to one of the plurality of areas, an opposing area of the recording medium or another recording medium that faces the lower side of the one area of the recording medium at the time of stacking by the post-processing device. based on the coverage, the charge controller according to claim 1, wherein the determining the grant amount of charge.   5. The charge adjustment device according to claim 4, wherein the control unit determines the amount of applied charge based on the amount of charge applied to the opposite region with respect to the one region. A charge amount measurement unit configured to measure a charge amount of each of the plurality of regions;
Wherein the control unit, the charge controller according to claim 1 or 2, characterized in that to determine the grant amount of charge based on a measurement result by the charge amount measuring unit. An image forming unit for fixing a color material on a recording medium to form an image;
The charge adjusting device according to any one of claims 1 to 6, which applies a charge to a recording medium to which a color material is fixed by the image forming unit.
An image forming apparatus comprising: An image forming apparatus for fixing a color material on a recording medium to form an image;
The charge adjusting device according to any one of claims 1 to 6, which applies a charge to a recording medium to which a color material is fixed by the image forming device.
A post-processing device that folds and stacks the recording medium to which the charge has been applied;
An imaging system comprising:

Images