JP2016117554A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device which can suppress sticking and repulsion between laminated sheets.SOLUTION: An image formation device 1A comprises: an image formation part 11 which forms an image on a sheet P; a fixation part 3 which fixes an image on the sheet P on which the image is formed by the image formation part 11; a potential detection part 4 which detects the potential of the sheet P on which the image is fixed by the fixation part 3; and an electrification part 5 which electrifies the sheet P on which the image is fixed by the fixation part 3, and controls the potential of the next sheet P by the electrification part 5 on the basis of the potential of the preceding sheet P detected by the potential detection part 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus that forms an image by transferring a toner image onto a sheet.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses are known as printers, copying machines, and the like. In such an image forming apparatus, when an image is formed or a sheet is conveyed, static electricity may be generated on the sheet to be charged. When discharging and stacking charged sheets outside the apparatus, a stacking failure may occur due to a repulsive force or adsorption force generated between the sheets.

  To solve this problem, a technology has been proposed in which a charging unit is provided for charging the paper before stacking, and a correction voltage corresponding to the potential of the paper before stacking is applied to the charging unit to charge the paper. (For example, see Patent Documents 1 and 2).

JP 2009-001418 A JP 2013-227088 A

  In the image forming apparatus, the latent image formed on the photosensitive drum is developed by developing with toner, and the visualized toner image is primarily transferred from the photosensitive drum to the transfer belt, and then primary transferred to the transfer belt. The transferred toner image is secondarily transferred to a sheet, whereby an image is formed on the sheet.

  In the secondary transfer unit, for example, a positive voltage is applied from the back side of the paper in order to transfer the toner image onto the paper. As a result, the sheet that has passed through the secondary transfer portion is charged with the negative electrode on the image forming surface side to which the toner is transferred and with the positive electrode on the back surface.

  FIG. 7 is an explanatory diagram showing a conventional problem. When printing is performed on both sides of the sheet P, first, as shown in FIG. 7A, when the toner image is transferred to one side P10, the other side P11 side which is the opposite side of the image forming side + Charge E11 is applied to the toner layer P10a transferred on the one surface P10 side. The + charge E11 moves in the paper P toward the -charge E12.

  As shown in FIG. 7B, when the paper P is reversed and the toner image is transferred to the other surface P11, + charge E21 is given to the toner layer P10a on the one surface P10 side, and the other surface P11 is transferred. The negative charge E22 is given to the toner layer P11a transferred on the side. If left in this state, partial inquiries of + charge E21 and −charge E12, −charge E12 and + charge E11, + charge E11 and −charge E22 occur, and one side P10 and the other side P11 of the paper P are generated. Is charged to the opposite polarity.

  Further, as shown in FIG. 7C, by stacking the paper P, the + charge E21 on the toner layer P10a side and the -charge E22 on the toner layer P11a side face each other with the gap G interposed therebetween, and the reverse polarity charge As a result, −charge E22 gradually moves to the surface side, and a high-density charge portion is formed on the surface side. As a result, a force attracting each other is generated between the stacked sheets P, and the sheets P stick to each other.

  In the technology for charging a sheet by applying a correction voltage corresponding to the potential of the sheet before stacking to the charging unit, the potential of the sheet stacked later can be controlled in accordance with the potential of the sheet stacked first. Since this is not possible, there is a possibility that the sheets will stick to each other or may be charged with a polarity such that the sheets will repel each other.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of suppressing sticking and repulsion between stacked sheets.

  In order to solve the above-described problem, the invention according to claim 1 is directed to an image forming unit that forms an image on a sheet, a fixing unit that fixes an image on a sheet on which an image is formed by the image forming unit, Based on the potential detection means for detecting the potential of the fixed paper, the charging means for charging the paper on which the image is fixed by the fixing means, and the potential of the preceding paper detected by the potential detection means, And an image forming apparatus including a control unit that controls the potential of the image forming apparatus.

  According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the potential detecting unit is provided downstream of the charging unit in the sheet transport direction.

  In the invention according to claim 3, the control means controls the voltage applied to the charging means based on the potential of the preceding paper detected by the potential detection means, and the charging means sets the applied voltage to the paper to be controlled. The image forming apparatus according to claim 1, wherein a corresponding current is applied.

  According to a fourth aspect of the present invention, the control means includes the paper information acquired by the paper information acquisition means, the image information acquired by the image information acquisition means, the environmental information acquired by the environmental information acquisition means, and the preceding detected by the potential detection means. The image forming apparatus according to claim 1, wherein the potential of the next sheet is controlled by the charging unit based on the potential of the sheet to be printed.

  According to the present invention, the surface potential of the preceding sheet is detected, and the detected potential is fed back to the charging control of the succeeding sheet, so that the charging control of the succeeding sheet is performed. As a result, appropriate charging control can be performed according to the potential of the sheets actually stacked, so that sticking when sheets are stacked can be suppressed and the repulsive force between the sheets can be reduced. .

1 is a configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a block diagram which shows an example of a charging part. 3 is a functional block diagram illustrating an example of a control function of the image forming apparatus according to the present exemplary embodiment. FIG. 5 is a flowchart illustrating an example of a charging operation in the image forming apparatus according to the present embodiment. FIG. 6 is an operation explanatory diagram illustrating a flow of a sheet in a charging operation of the image forming apparatus according to the present embodiment. 1 is a configuration diagram illustrating an example of an image forming system according to an exemplary embodiment. It is explanatory drawing which shows the conventional subject.

  Hereinafter, an embodiment of an image forming apparatus of the present invention will be described with reference to the drawings.

<Example of Configuration of Image Forming Apparatus of Embodiment>
FIG. 1 is a configuration diagram illustrating an example of an image forming apparatus according to the present embodiment. The image forming apparatus 1A is an electrophotographic image forming apparatus such as a copying machine. In this example, a plurality of photoconductors face a single intermediate transfer belt and are arranged in a vertical direction to form a full color image. This is a so-called tandem color image forming apparatus.

  The image forming apparatus 1 </ b> A includes a document reading unit 10, an image forming unit 11, a paper transport unit 2, a fixing unit 3, a potential detection unit 4, and a charging unit 5.

  The document reading unit 10 scans and exposes an image of a document with the optical system of the scanning exposure apparatus, reads the reflected light with a line image sensor, and obtains an image signal. The image forming apparatus 1A may have a configuration in which an automatic document feeder (not shown) that feeds a document is provided on the upper portion.

  The image forming unit 11 is an example of an image forming unit, and forms an image forming unit 11Y that forms a yellow (Y) image, an image forming unit 11M that forms a magenta (M) image, and a cyan (C) image. And an image forming unit 11BK that forms a black (BK) image.

  The image forming unit 11Y includes a photosensitive drum Y and a charging unit 12Y, an optical writing unit 13Y, a developing device 14Y, and a drum cleaner 15Y arranged around the photosensitive drum Y. Similarly, the image forming units 11M, 11C, and 11BK include the photosensitive drums M, C, and BK and the charging units 12M, 12C, and 12BK, the optical writing units 13M, 13C, and 13BK, the developing devices 14M, 14C, 14BK and drum cleaners 15M, 15C, 15BK are provided.

  The surface of the photosensitive drum Y is uniformly charged by the charging unit 12Y, and a latent image is formed on the photosensitive drum Y by scanning exposure by the optical writing unit 13Y. Further, the developing device 14Y develops the latent image on the photosensitive drum Y by developing with toner. As a result, an image (toner image) of a predetermined color corresponding to yellow is formed on the photosensitive drum Y.

  Similarly, the surface of the photosensitive drum M is uniformly charged by the charging unit 12M, and a latent image is formed on the photosensitive drum M by scanning exposure by the optical writing unit 13M. Further, the developing device 14M develops the latent image on the photosensitive drum M by developing with toner. As a result, a toner image of a predetermined color corresponding to magenta is formed on the photosensitive drum M.

  The surface of the photosensitive drum C is uniformly charged by the charging unit 12C, and a latent image is formed on the photosensitive drum C by scanning exposure by the optical writing unit 13C. Further, the developing device 14C develops the latent image on the photosensitive drum C by developing with toner. As a result, a toner image of a predetermined color corresponding to cyan is formed on the photosensitive drum C.

  The surface of the photosensitive drum BK is uniformly charged by the charging unit 12BK, and a latent image is formed on the photosensitive drum BK by scanning exposure by the optical writing unit 13BK. Further, the developing device 14BK develops the latent image on the photosensitive drum BK by developing with toner. As a result, a toner image of a predetermined color corresponding to black is formed on the photosensitive drum BK.

  The images formed on the photosensitive drums Y, M, C, and BK are sequentially moved to predetermined positions on the intermediate transfer belt 16 that is a belt-like intermediate transfer member by the primary transfer rollers 17Y, 17M, 17C, and 17BK. Transcribed.

  The image composed of each color transferred onto the intermediate transfer belt 16 is transferred by the secondary transfer unit 18 to the paper P conveyed at a predetermined timing by the paper conveyance unit 2. The secondary transfer unit 18 forms a transfer nip 19 by the secondary transfer roller 18a being disposed in pressure contact with the intermediate transfer belt 16, and transfers the image onto the paper P while conveying the paper P.

  In the secondary transfer unit 18, a positive voltage is applied from the back side of the paper P by the secondary transfer roller 18 a in order to transfer the toner image onto the paper P. As a result, the sheet P that has passed through the secondary transfer portion 18 is charged with the negative electrode on the image forming surface side to which the toner is transferred and with the positive electrode on the back surface.

  In this example, the paper transport unit 2 includes a plurality of paper feed trays 21 and a paper feed unit 21 a that feeds the paper P stored in the paper feed tray 21. The paper transport unit 2 also includes a main transport path 23 through which the paper P fed from the paper feed tray 21 is transported, and a reverse transport path 24 that reverses the front and back of the paper P.

  The main transport path 23 constitutes a transport path from the paper feed tray 21 to the paper discharge tray 25. When the external paper feed tray 22, which is called a manual feed tray, is opened and used, the transport path from the external paper feed tray 22 joins the main transport path 23 upstream from the junction of the main transport path 23 and the reverse transport path 24. To do.

  The sheet conveyance unit 2 corrects the inclination of the sheet P called skew and the deviation of the position in the width direction of the sheet P perpendicular to the conveyance direction with respect to the sheet P conveyed on the main conveyance path 23. Is provided. The paper transport unit 2 also includes a loop roller 27 that abuts the paper against the registration roller 26.

  The registration roller 26 is composed of a pair of rollers facing each other with the paper P conveyed through the main conveyance path 23, and includes a shaft orthogonal to the conveyance direction of the paper P and rotates along the conveyance direction of the paper P To do.

  The loop roller 27 is composed of a pair of rollers facing each other with the paper P conveyed through the main conveyance path 23 interposed therebetween, and is provided on the upstream side of the registration roller 26 with respect to the conveyance direction of the paper P. The loop roller 27 includes an axis orthogonal to the conveyance direction of the paper P, and conveys the paper P by rotating along the conveyance direction of the paper P.

  In a state where the registration roller 26 is stopped, the paper P is conveyed by the loop roller 27, the leading end of the paper P is abutted against the nip portion 26a formed by the contact portion of the pair of rollers, and is curved called a loop. By conveying the paper P until it reaches the state, the inclination in the direction along the surface of the paper P is corrected.

  After the inclination of the paper P is corrected, the registration roller 26 is rotationally driven along the transport direction of the paper P, whereby the paper P is nipped and transported. Further, the position of the sheet P in the width direction is corrected by moving the registration roller 26 in the width direction of the sheet P perpendicular to the conveyance direction of the sheet P. As described above, a series of sheet position correction operations for correcting the deviation of the position in the width direction while transporting the sheet P is referred to as registration swing.

  The reverse conveyance path 24 branches from the main conveyance path 23 on the downstream side of the fixing unit 3, and includes a switching gate 23 a at a branch point between the main conveyance path 23 and the reverse conveyance path 24. The reverse conveyance path 24 includes a first reverse conveyance path 24 a that branches from the main conveyance path 23 and extends in a substantially horizontal direction below the main conveyance path 23. In the first reverse conveyance path 24a, the conveyance direction of the paper P is reversed from the arrow D1 direction to the arrow D2 direction.

  The reverse conveyance path 24 is branched upward from the first reverse conveyance path 24a with respect to the conveyance direction indicated by the arrow D2, and from the second reverse conveyance path 24b and the second reverse conveyance path 24b that bend in a substantially U shape. And a third reverse conveyance path 24c extending along the first reverse conveyance path 24a. Further, the reverse conveyance path 24 includes a fourth reverse conveyance path 24 d that bends in a substantially U shape from the third reverse conveyance path 24 c and joins the main conveyance path 23.

  In the image forming apparatus 1A, an image is formed on the surface of the paper P that has been transported through the main transport path 23 and has passed through the transfer nip portion 19 and the fixing portion 3 and directed upward. When images are formed on both sides of the sheet P, the sheet P on which an image is formed on one side facing upward is conveyed from the main conveyance path 23 to the first reverse conveyance path 24 a of the reverse conveyance path 24. The image forming surface faces downward.

  The sheet P transported to the first reverse transport path 24a is transported from the second reverse transport path 24b to the third reverse transport path 24c, so that the image forming surface faces upward. Then, the sheet P transported to the third reverse transport path 24c is transported from the fourth reverse transport path 24d to the main transport path 23, so that the image forming surface faces downward. As a result, the paper P is turned upside down, and an image can be formed on the other side facing upward.

  The fixing unit 3 is an example of a fixing unit, and performs a fixing process for fixing the image on the paper P on which the image is transferred. The fixing unit 3 includes a fixing roller 31 and a fixing roller 32 as a pair of fixing members arranged in pressure contact with each other, and a fixing nip portion 33 is formed by the fixing roller 31 and the fixing roller 32 being pressed against each other.

  The fixing unit 3 includes a fixing heater 34 that heats the fixing roller 31 as a heating unit that heats the fixing member. The fixing heater 34 is turned on by energization, and for example, a halogen lamp can be used. The fixing unit 3 conveys the paper P and fixes the image on the paper P by performing pressure fixing with the pair of fixing rollers 31 and 32 and heat fixing with the fixing heater 34.

  The potential detection unit 4 is an example of a potential detection unit. The potential detection unit 4 is provided on the main transport path 23 so as to face one surface of the paper P on the downstream side of the fixing unit 3 with respect to the transport direction of the paper P and passes through the fixing unit 3 The potential of the upper surface, which is one surface of the sheet P, is detected.

  The charging unit 5 is an example of a charging unit. The charging unit 5 is provided on the downstream side of the fixing unit 3 with respect to the conveyance direction of the paper P in the main conveyance path 23, and charges the paper P that has passed through the fixing unit 3. To control the potential.

  The potential detection unit 4 and the charging unit 5 are provided with the potential detection unit 4 on the downstream side of the charging unit 5 in the conveyance direction of the paper P. As a result, the potential of the paper P whose surface potential has been changed by the charging unit 5 can be detected by the potential detection unit 4.

  FIG. 2 is a configuration diagram illustrating an example of the charging unit. The charging unit 5a shown in FIG. 2A includes a pair of charging rollers 50a and a charging roller 50b that face each other with the sheet P conveyed through the main conveyance path 23 therebetween. The charging roller 50 a and the charging roller 50 b have an axis orthogonal to the transport direction of the paper P, and rotate along the transport direction of the paper P.

  The charging unit 5a includes a voltage applying unit 51 having a power source for applying a voltage to the charging roller 50a and the charging roller 50b, and is configured to be able to apply a DC voltage or an AC superimposed voltage to the charging roller 50a and the charging roller 50b.

  In the charging unit 5a, a positive voltage is applied to the charging roller 50a in contact with the surface, which is one surface of the paper P, under the controlled arbitrary current value and voltage value by the control of the voltage application unit 51, and the other surface A negative voltage is applied to the charging roller 50b in contact with the back surface. Further, a negative voltage is applied to the charging roller 50a in contact with the front surface of the paper P, and a positive voltage is applied to the charging roller 50b in contact with the back surface. As a result, an electric current of an arbitrary direction and an arbitrary value is applied to the paper P that is sandwiched between the charging roller 50a and the charging roller 50b and passes between them.

  The charging unit 5b illustrated in FIG. 2B includes a pair of discharge electrodes 52a and a discharge electrode 52b that are opposed to each other with the sheet P conveyed through the main conveyance path 23 interposed therebetween. The charging unit 5b includes a voltage applying unit 53 having a power source for applying a voltage to the discharge electrode 52a and the discharge electrode 52b, and is configured to be able to apply a DC voltage or an AC superimposed voltage to the discharge electrode 52a and the discharge electrode 52b.

  Under the control of the voltage application unit 53, the charging unit 5b applies a positive voltage at an arbitrary controlled current value and voltage value to the discharge electrode 52a facing the surface which is one surface of the paper P. A negative voltage is applied to the discharge electrode 52b facing the back surface, which is the surface. Further, a negative voltage is applied to the discharge electrode 52a facing the front surface of the paper P, and a positive voltage is applied to the discharge electrode 52b facing the back surface. As a result, a current having an arbitrary direction and an arbitrary value is applied to the paper P passing between the discharge electrode 52a and the discharge electrode 52b.

<Example of Control Function of Image Forming Apparatus of Present Embodiment>
FIG. 3 is a functional block diagram illustrating an example of a control function of the image forming apparatus according to the present embodiment. Here, FIG. 3 illustrates a control function related to an operation of controlling the surface potential of the paper P stacked after image formation.

  The image forming apparatus 1A includes a control unit 100 that performs a series of controls for feeding paper P, forming an image, and discharging the paper. The control unit 100 is an example of control means, and includes a microprocessor called CPU and MPU, and memory such as RAM and ROM as storage means.

  The normal operation of forming an image on the paper P by the image forming apparatus 1A will be described. The control unit 100 controls the paper transport unit 2 to transport the paper P. The control unit 100 controls the image forming unit 11 based on the image data acquired from the document by the document reading unit 10 or the image data acquired from the outside to form an image on the paper P. Further, the control unit 100 controls the fixing unit 3 to fix the image on the paper P, and discharges the paper P on which the image is formed.

  When performing continuous paper feeding, the control unit 100 detects the potential of the upper surface of the paper P discharged to the paper discharge tray 25 with the potential detection unit 4 and stores it in the storage unit 110. The control unit 100 uses a predetermined arithmetic expression or a table in which the detection potential and the applied current, the detection potential and the applied voltage, or the detection potential, the applied current, and the applied voltage are associated with each other. One of the set current and the set voltage for controlling the current, or both the set current and the set voltage are calculated. That is, the control unit 100 suppresses sticking of the succeeding sheet P to the preceding sheet P based on the potential of the preceding sheet P detected by the potential detecting unit 4 and stored in the storage unit 110, and A set current and a set voltage are calculated so as to reduce the repulsion between sheets. The set current and the set voltage may be values that cause the surface potential of the paper P to approach 0, or values that cancel the potential of the preceding paper P.

  The control unit 100 controls the charging unit 5 with the set current and the set voltage calculated according to the sign of the surface potential of the paper P and the magnitude of the potential, and controls the surface potential of the subsequent paper P. In the charging unit 5a having the configuration shown in FIG. 2A, the control unit 100 controls the voltage application unit 51 with the set current and the set voltage calculated according to the positive / negative of the surface potential of the paper P and the magnitude of the potential. Control.

  As a result, a positive voltage is applied to the charging roller 50a in contact with the front surface of the paper P according to the set current and the set voltage, for example, at a predetermined current value and voltage value, and a negative voltage is applied to the charging roller 50b in contact with the back surface. When applied, the surface potential of the paper P is controlled. Further, a negative voltage is applied to the charging roller 50a in contact with the front surface of the paper P, and a positive voltage is applied to the charging roller 50b in contact with the back surface, whereby the surface potential of the paper P is controlled.

  In the charging unit 5b configured as shown in FIG. 2B, the control unit 100 controls the voltage application unit 53 with the set current and the set voltage calculated according to the sign of the surface potential of the paper P and the magnitude of the potential. Control.

  As a result, a positive voltage is applied to the discharge electrode 52a facing the front surface of the sheet P according to the set current and the set voltage, for example, with a predetermined current value and voltage value, and a negative voltage is applied to the discharge electrode 52b facing the back surface. A voltage is applied to control the surface potential of the paper P. Further, a negative voltage is applied to the discharge electrode 52a facing the front surface of the paper P, and a positive voltage is applied to the discharge electrode 52b facing the back surface, so that the surface potential of the paper P is controlled.

  In addition, the control unit 100 uses the paper information such as the paper type, basis weight, and size of the paper P acquired by the paper information acquisition unit 101, the image information such as coverage acquired by the image information acquisition unit 102, and the environment information acquisition unit 103. Based on the acquired environmental information such as the temperature and humidity of the installation location, the set current and the set voltage calculated according to the surface potential of the paper P and the magnitude of the potential are corrected.

  The paper information acquisition unit 101 is an example of a paper information acquisition unit, and detects the size of the paper P set in the operation unit 101a as an operation unit for selecting the basis weight, size, paper type, and the like of the paper P. And a paper size detection sensor 101b.

  The image information acquisition unit 102 is an example of an image information acquisition unit, and generates coverage information by calculating a toner consumption amount for each page by an image forming operation. The environment information acquisition unit 103 is an example of an environment information acquisition unit, and includes a temperature sensor 103a that detects the temperature of the installation location of the image forming apparatus 1A, a humidity sensor 103b that detects the humidity of the installation location of the image forming apparatus 1A, and the like. . The operating environment such as temperature and humidity may be set by the operation unit 101a.

  Here, the correction value may be calculated using all of the paper information acquired by the paper information acquisition unit 101, the image information acquired by the image information acquisition unit 102, and the environment information acquired by the environment information acquisition unit 103. However, the correction value may be calculated by combining any information or a plurality of information. For example, since the surface potential is higher in high temperature and high humidity than in low temperature and low humidity, the applied voltage or applied current is set according to the surface potential.

<Example of Operation of Image Forming Apparatus of Present Embodiment>
FIG. 4 is a flowchart showing an example of the charging operation in the image forming apparatus of the present embodiment. FIG. 5 is an operation explanatory diagram showing the flow of paper in the charging operation of the image forming apparatus of the present embodiment. The potential detection and charging operation in the image forming apparatus 1A of the present embodiment will be described with reference to each drawing. Here, in FIG. 5, the charging unit 5a shown in FIG. 2A will be described as an example of the charging unit 5, but the same applies to the charging unit 5b shown in FIG. 2B.

  The control unit 100 determines whether or not the image forming job is executed in steps SA1 and SA2 in FIG. 4, and waits until the image forming job is started. When the image forming job is started, the control unit 100 controls the paper transport unit 2 to transport the paper P in step SA3 in FIG. Further, the control unit 100 controls the image forming unit 11 based on the image data acquired from the document by the document reading unit 10 or the image data acquired from the outside in Step SA4 in FIG. Primary transfer of the image. Then, the image primarily transferred to the intermediate transfer belt 16 is secondarily transferred to the paper P by the secondary transfer unit 18.

  The control unit 100 conveys the paper P onto which the image has been transferred to the fixing unit 3, and controls the fixing unit 3 to fix the image on the paper P in step SA5 in FIG. In step SA6 of FIG. 4, the control unit 100 determines whether the image forming job is double-sided printing and the back side is printed. When determining that there is printing on the back surface, the control unit 100 transports the paper P to the reverse transport path 24, reverses the front and back, and returns it to the main transport path 23 in step SA7 in FIG.

  The control unit 100 determines in step SA6 in FIG. 4 that the image forming job is single-sided printing and there is no printing on the back side, or the image forming job is double-sided printing. If it is determined that the back side is not printed, it is determined in step SA8 whether the sheet P is the first sheet.

  When the control unit 100 determines that the sheet P is the first sheet, the potential of the first sheet P (1) on which the image is fixed is shown in FIG. 5A in step SA9 in FIG. The sheet is conveyed to the detection unit 4, and the surface potential of the paper P (1) is detected by the potential detection unit 4 and stored in the storage unit 110. Then, the control unit 100 discharges the paper P (1) for which image formation and surface potential detection have been completed to the paper discharge tray 25 in Step SA10 of FIG.

  In step SA11, the control unit 100 determines whether there is a next sheet. If it determines that there is a next sheet, the control unit 100 returns to step SA3 in FIG. If it is determined that there is no next sheet, the image forming job is terminated.

  When the control unit 100 determines that the sheet P is the second or subsequent sheet, the control unit 100 uses a predetermined arithmetic expression or a table in which the detection potential, the applied current, and the applied voltage are associated with each other in Step SA12 in FIG. Then, based on the potential of the preceding paper P detected and stored by the potential detection unit 4, sticking of the succeeding paper P to the preceding paper P is suppressed, and repulsion between the papers is reduced. Calculate the set current and set voltage.

  Then, the control unit 100 controls the charging unit 5 with the set current and the set voltage calculated according to the sign of the surface potential of the preceding paper P and the magnitude of the potential, and the surface potential of the subsequent paper P is determined. Control.

  The control unit 100 conveys the paper P whose potential is controlled by the charging unit 5 to the potential detection unit 4 in step SA9 in FIG. 4, detects the surface potential of the paper P by the potential detection unit 4, and stores it in the storage unit 110. Remember. Then, the control unit 100 discharges the paper P, on which image formation, potential control, and surface potential detection have been completed, to the paper discharge tray 25 in step SA10 in FIG.

  For example, when the sheet P is the second sheet, 2 subsequent to the sheet P (1) based on the potential of the preceding first sheet P (1) detected and stored by the potential detection unit 4. A set current and a set voltage are calculated so that sticking of the sheet P (2) is suppressed and repulsion between sheets is reduced.

  As shown in FIG. 5B, the control unit 100 conveys the second sheet P (2) to the charging unit 5a, and the surface potential of the preceding first sheet P (1) is positive or negative. The voltage application unit 51 is controlled with the set current and the set voltage calculated according to the magnitude of the potential, and the surface potential of the second sheet P (2) is controlled.

  The control unit 100 conveys the second sheet P (2) whose potential is controlled by the charging unit 5a to the potential detection unit 4 as shown in FIG. 5C, and changes the surface potential of the sheet P (2). It is detected by the potential detection unit 4 and stored in the storage unit 110. Then, the control unit 100 discharges the paper P (2) on which image formation, potential control, and surface potential detection have been completed to the paper discharge tray 25.

  Thereafter, based on the potential detected from the preceding n−1 sheet P (n−1) by the potential detection unit 4, as shown in FIG. 5D, the nth sheet immediately after by the charging unit 5a. As shown in FIG. 5E, the charging control is performed on the P (n), and the potential detection of the paper P (n) and the detected potential storage control are performed by the potential detecting unit 4 as shown in FIG. 5E. The sheet P (n) is discharged and the next sheet P (n + 1) is charged based on the detected potential of the sheet P (n).

  According to the image forming apparatus 1A of the present embodiment, the surface potential of the preceding sheet P is detected, and this detected potential is fed back to the calculation of the set current and set voltage for charging control of the succeeding sheet P. Then, the charging control of the subsequent paper P is performed.

  As a result, appropriate charging control can be performed according to the potential of the sheets actually stacked, so that sticking when sheets are stacked is suppressed, and the repulsive force between the sheets is reduced, so that Handling properties such as movement can be improved.

  The potential detection unit 4 is provided on the downstream side of the charging unit 5 in the transport direction of the paper P. As a result, the sheet potential can be detected and stored after the surface potential is changed by the charging control by the charging unit 5, so that more accurate feedback control is possible.

  Further, the charging unit 5 includes both the charging unit 5a having the configuration shown in FIG. 2A and the charging unit 5b having the configuration shown in FIG. 2B. Value current can be added. Thereby, the paper P can be controlled to a target potential.

  Also, paper information such as the paper type, basis weight, and size of the paper P acquired by the paper information acquisition unit 101, image information such as coverage acquired by the image information acquisition unit 102, and the installation location acquired by the environment information acquisition unit 103 Based on environmental information such as temperature and humidity, the set current and the set voltage calculated according to the sign of the surface potential of the preceding paper P and the magnitude of the potential are corrected.

  As the coverage increases, the charge amount of the toner layer increases, and the sticking force between the stacked sheets after paper discharge increases. As the basis weight increases, the charge amount increases, and the sticking force between the stacked sheets after paper discharge increases. When the room temperature and humidity increase, the sticking force between the stacked sheets after paper discharge increases.

  In this way, the sticking force between papers varies depending on the environment such as coverage, basis weight, paper type, temperature and humidity, etc., so by correcting the set current and set voltage in feedback control in consideration of these, coverage , Charging control according to sticking force that varies depending on basis weight, paper type, environment, and the like becomes possible.

<Example of image forming system>
FIG. 6 is a configuration diagram showing an example of the image forming system of the present embodiment. In the image forming apparatus 1A of the present embodiment, the potential detecting unit 4 and the charging unit 5 are provided in the apparatus. On the other hand, the charging device 111 including the potential detection unit 4 and the charging unit 5 is provided in the rear stage of the image forming apparatus 1B independently of the image forming apparatus 1B, and the rear of the relay conveying apparatus 112, the sheet binding apparatus 113, and the like. An image forming system 115 used in combination with the processing device 114 may be configured. In the image forming system, the charging device may be provided in the device arranged at the last stage.

  The present invention is applied to an image forming apparatus that charges a sheet and transfers a toner image.

  DESCRIPTION OF SYMBOLS 1A, 1B ... Image forming apparatus, 2 ... Paper conveyance part, 3 ... Transfer part, 4 ... Potential detection part, 5 ... Charging part, 100 ... Control part

Claims (4)

An image forming unit that forms an image on a sheet; a fixing unit that fixes an image on a sheet on which an image is formed by the image forming unit;
A potential detecting means for detecting the potential of the paper on which the image is fixed by the fixing means;
Charging means for charging the paper on which the image is fixed by the fixing means;
An image forming apparatus comprising: a control unit that controls the potential of the next sheet by the charging unit based on the potential of the preceding sheet detected by the potential detection unit. The image forming apparatus according to claim 1, wherein the potential detection unit is provided downstream of the charging unit in a sheet conveyance direction. The control means controls the voltage and current applied to the charging means based on the potential of the preceding paper detected by the potential detection means, and the charging means responds to the applied voltage to the paper to be controlled. The image forming apparatus according to claim 1, wherein an electric current is applied. The control means is based on the paper information acquired by the paper information acquisition means, the image information acquired by the image information acquisition means, the environmental information acquired by the environment information acquisition means, and the potential of the preceding paper detected by the potential detection means. The image forming apparatus according to claim 1, wherein the potential of the next sheet is controlled by the charging unit.

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