Charge elimination device, image forming system, and charge adjustment device

Abstract

The invention discloses a charge eliminating apparatus, an image forming system, and a charge adjusting apparatus. An electric charge eliminating apparatus includes an electric charge eliminating member for eliminating an electric charge of a sheet while clamping and transporting the sheet, a voltage applying unit for applying a voltage to the electric charge eliminating member, and a detecting unit for detecting the voltage applied to the electric charge eliminating member or a current flowing through the electric charge eliminating member. The controller measures an amount of charged charge of the sheet based on a detection result of the detection unit when the sheet passes through the charge elimination member.

Description

Technical Field

[0001] The present disclosure relates to a charge elimination device for eliminating charges of a sheet, an image forming system for forming an image on a sheet, and a charge adjustment device for adjusting a charge distribution on a sheet. Background Art

[0002] In Japanese Patent Application Laid-Open No. 2019-167169, a charge elimination device is disclosed which uses a charge elimination roller (contact type charge eliminator) in contact with a sheet and a non-contact type charge eliminator of a corona type to eliminate charges of the sheet. In Japanese Patent Application Laid-Open No. 2019-156603, a charging processing device which performs a charging process (charge elimination) of a sheet and is provided with a surface potential sensor for detecting a surface potential of the sheet, and adjusts a voltage to be applied to a charging roller based on a measurement value of the surface potential sensor.

[0003] In a conventional configuration, due to a surface potential sensor additionally deployed for the purpose of detecting a surface potential of a sheet, the number of components increases. Therefore, it is desired to enable detection of a charged amount or a surface potential of a sheet with a simpler configuration, or to enable control corresponding to the charged amount or the surface potential of the sheet. Summary of the Invention

[0004] Accordingly, an object of the present disclosure is to provide a charge elimination device, an image forming system, and a charge adjustment device which can detect a charged amount of a sheet with a simpler configuration or perform control based on the charged amount. According to one aspect of the present invention, there is provided a charge elimination device including: a charge elimination member configured to eliminate charges of a sheet while clamping and conveying the sheet; a voltage application unit configured to apply a voltage to the charge elimination member; a detection unit configured to detect a voltage applied to the charge elimination member or a current flowing through the charge elimination member; and a controller configured to measure a charged amount of the sheet based on a detection result of the detection unit when the sheet passes through the charge elimination member.

[0005] More features of the present invention will become clear from the following description of exemplary embodiments with reference to the drawings. Brief Description of the Drawings

[0006] Figure 1 is a schematic diagram of an image forming system according to Embodiment 1.

[0007] Figure 2 is a schematic diagram of a charge elimination device according to Embodiment 1.

[0008] Figure 3 It is a schematic view of a conveying guide according to Embodiment 1.

[0009] Figure 4 It is a block diagram of a control system according to Embodiment 1.

[0010] Figure 5 It is a flowchart illustrating a control method according to Embodiment 1.

[0011] Figure 6 Part (a) is a graph illustrating the relationship between the charged amount of the sheet and the detection voltage according to Embodiment 1, and Figure 6 Part (b) is a graph illustrating the relationship between the detection voltage and the charge elimination voltage according to Embodiment 1.

[0012] Figure 7 It is a view illustrating an operation part for charge elimination according to Embodiment 2.

[0013] Figure 8 It is a flowchart illustrating a control method according to Embodiment 2.

[0014] Figure 9 It is a view illustrating an example of screen display according to Embodiment 2. Detailed Description of the Invention

[0015] Hereinafter, embodiments according to the present disclosure will be described with reference to the accompanying drawings.

[0016] [Embodiment 1]

[0017] Figure 1 It is a schematic view illustrating an image forming system 400 according to Embodiment 1. The image forming system 400 includes an image forming apparatus 100 (printer) and a charge elimination apparatus 300 connected to the image forming apparatus 100. The image forming system 400 forms an image on a sheet S and discharges the sheet S as a product (printed product). As the sheet S as a recording material (recording medium), various sheet materials of different sizes and materials can be used, for example, papers such as plain paper and thick paper, sheet materials with surface treatment such as coated paper, special-shaped sheets such as envelopes and index paper, sheet materials made of plastic, cloth, etc. Examples of sheet materials made of plastic include synthetic paper whose main raw material is synthetic resin and sheets for overhead projectors (OHT).

[0018] The charge elimination device 300 is a device (static eliminator) having a charge elimination function of eliminating (reducing) the charge of the sheet S discharged from the image forming system 400. The charge elimination device 300 may be referred to as a charge adjustment device for adjusting the charged state of the sheet S discharged from the image forming system 400. The charge elimination device 300 may have functions other than the charge elimination function (for example, a de-curling function for correcting the curl of the sheet S). In addition, the charge elimination device 300 in the present embodiment is deployed as a device independent of the image forming device 100. However, the charge elimination device 300 may be incorporated into the housing of the image forming device 100.

[0019] The image forming system 400 may include optional devices other than the charge elimination device 300. Examples of the optional devices include a high-capacity feeding device (optional feeder) that supplies the sheet S to the image forming device 100 and a sheet processing device (finisher) that applies a process such as a binding process to the sheet S on which an image is formed by the image forming device 100.

[0020] <Image forming device>

[0021] Figure 1 The schematic configuration of the image forming device 100 is illustrated. The image forming device 100 includes an image forming section 101 as an intermediate transfer type electrophotographic mechanism. The image forming section 101 includes four processing units 11Y, 11M, 11C, and 11K respectively including photosensitive drums 1Y, 1M, 1C, and 1K, and a transfer unit 15 including an intermediate transfer belt 6 and a secondary transfer roller 9.

[0022] Each processing unit includes a photosensitive drum as an image bearing member (latent image bearing member), a charging device, an exposure device, and a developing device as processing sections that act on the photosensitive drum to perform each process in the electrophotographic process. That is, the processing unit 11Y includes the photosensitive drum 1Y, the charging device 2Y, the exposure device 3Y, and the developing device 4Y. The processing unit 11M includes the photosensitive drum 1M, the charging device 2M, the exposure device 3M, and the developing device 4M. The processing unit 11C includes the photosensitive drum 1C, the charging device 2C, the exposure device 3C, and the developing device 4C. The processing unit 11K includes the photosensitive drum 1K, the charging device 2K, the exposure device 3K, and the developing device 4K.

[0023] Each of the photosensitive drums 1Y, 1M, 1C, and 1K is rotationally driven in a predetermined rotation direction A. The processing units 11Y, 11M, 11C, and 11K have substantially the same configuration, except that the toners as developers accommodated in the developing devices 4Y, 4M, 4C, and 4K are different from each other.

[0024] The transfer unit 15 includes an intermediate transfer belt 6 as an intermediate transfer member, a secondary transfer roller 9 as a transfer member (secondary transfer member), primary transfer rollers 5Y, 5M, 5C, and 5K, a plurality of rollers 20, 21, 22, 23, 24, and 25, and a belt cleaner 12. The intermediate transfer belt 6 is stretched over the plurality of rollers 20, 21, 22, 23, 24, and 25. The primary transfer rollers 5Y, 5M, 5C, and 5K are disposed on the inner surface side of the intermediate transfer belt 6 and at positions corresponding to the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. A primary transfer portion is formed between the primary transfer rollers 5Y, 5M, 5C, and 5K and the corresponding photosensitive drums 1Y, 1M, 1C, and 1K. The roller 20 is a tension roller that applies an appropriate tension to the intermediate transfer belt 6. The roller 22 is a drive roller that rotationally drives the intermediate transfer belt 6 in a predetermined rotation direction G. The secondary transfer roller 9 contacts the outer surface of the intermediate transfer belt 6 and is disposed to sandwich the intermediate transfer belt 6 together with the opposed roller 21 (secondary transfer opposed roller). A secondary transfer portion T2, which is a transfer portion for transferring the toner image to the sheet S, is formed as a clamping portion between the secondary transfer roller 9 and the intermediate transfer belt 6.

[0025] The image forming apparatus 100 is provided with a transfer power source 10 as a voltage application unit to form a bias electric field in the secondary transfer portion T2 for transferring the toner image. In the present embodiment, the secondary transfer roller 9, which is the outer roller of the secondary transfer portion T2, is electrically connected to the transfer power source 10, and a predetermined transfer voltage is applied thereto from the transfer power source 10. The transfer voltage is a voltage having a polarity opposite to the normal charging polarity of the toner used for image formation. On the other hand, the opposed roller 21, which is the inner roller of the secondary transfer portion T2, is electrically connected to the ground potential GND (such as a metal frame) of the image forming apparatus 100. Incidentally, the inner roller of the secondary transfer portion T2 may be connected to the transfer power source 10, and the outer roller of the secondary transfer portion T2 may be connected to the ground potential GND. In this case, a transfer voltage having a polarity same as the normal charging polarity of the toner is applied to the inner roller.

[0026] The image forming apparatus 100 further includes a housing portion 63 (storage, cassette) for housing the sheet S, a feeding unit 64 for feeding the sheet S, and alignment rollers 8 for performing alignment (position alignment) of the sheet S. In addition, the image forming apparatus 100 includes a pre-fixing conveyance device 41 for conveying the sheet S that has passed through the secondary transfer portion T2, a fixing device 40 for fixing the toner image to the sheet S, and a pair of discharge rollers 42 as a discharge unit for discharging the sheet S to the outside of the image forming apparatus 100.

[0027] The feeding unit 64 includes, for example, a pickup roller 65 that picks up the uppermost sheet S from the accommodating portion 63 in the sheet feeding direction, and a pair of separating rollers 66 that convey the picked-up sheet S while separating the sheets S one by one. The pair of separating rollers 66 includes a conveying roller that conveys the uppermost sheet S in the sheet conveying direction, and a separating roller that contacts the conveying roller and forms a separating clamping portion together with the conveying roller. The separating roller prevents the sheets S other than the uppermost sheet S from passing through the separating clamping portion by applying a frictional force to the sheet S in the separating clamping portion, thereby preventing a plurality of sheets S from being conveyed. The separating roller is an example of a separating member for separating the sheets S, and for example, an elastic member (rubber pad) having a pad shape can be used as the separating member.

[0028] The fixing device 40 is a heat fixing type device that includes a fixing clamping portion in which the toner image on the sheet S is heated while the sheet S is clamped and conveyed. The fixing device 40 includes a heating member that contacts the surface of the sheet S on which the toner image is formed, a pressing member that forms the fixing clamping portion together with the heating member, and a heat source that heats the heating member. For the heating member and the pressing member, for example, a belt member stretched over a plurality of rollers or a rigid roller member can be used. For the heat source, for example, a halogen lamp or an IH type induction heating mechanism can be used.

[0029] In addition, the image forming apparatus 100 is further provided with a user operation portion 102 that serves as a user interface of the image forming system 400. The user operation portion 102 includes a display portion such as a liquid crystal panel that displays information to the user and an input portion such as a touch panel function of the liquid crystal panel and physical buttons that receives inputs of information from the user. The user can set execution conditions and setting information of the image forming operation for the image forming system 400 by operating the user operation portion 102. The setting information is attribute information of the sheet S accommodated in the accommodating portion 63, such as size, material, and brand, for example. The execution conditions of the image forming operation include, for example, the value of the transfer voltage.

[0030] When an execution instruction for image formation is input from the user, the control portion of the image forming apparatus 100 starts an image forming job, which is a series of tasks of forming an image on and outputting a product while conveying the sheets S one by one. Hereinafter, a series of operations of forming an image on the sheet S by the image forming apparatus 100 is referred to as an image forming operation. The image forming job includes an image forming operation on at least one sheet S.

[0031] In an image forming operation, toner images of each color are formed in the processing units 11Y, 11M, 11C, and 11K. Specifically, the photosensitive drums 1Y, 1M, 1C, and 1K are rotationally driven, and the charging devices 2Y, 2M, 2C, and 2K uniformly charge the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. The exposure devices 3Y, 3M, 3C, and 3K expose the photosensitive drums 1Y, 1M, 1C, and 1K based on the image information input together with the execution instruction, and electrostatic latent images are respectively formed on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K. The developing devices 4Y, 4M, 4C, and 4K supply yellow, magenta, cyan, and black toner to the photosensitive drums 1Y, 1M, 1C, and 1K, respectively, to develop the electrostatic latent images into toner images of each color.

[0032] Incidentally, in the present embodiment, the reverse development type is used. That is, after the charging device charges the surface of the photosensitive drum to the same polarity as the normal charging polarity of the toner, the potential of the exposed area exposed by the exposure device decays, and the toner adheres to the exposed area during development.

[0033] The toner images formed in each of the processing units 11Y, 11M, 11C, and 11K are primary-transferred from the photosensitive drums 1Y, 1M, 1C, and 1K to the intermediate transfer belt 6 in the primary transfer section. A transfer voltage having a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer rollers 5Y, 5M, 5C, and 5K by constant voltage control.

[0034] In the present embodiment, the primary transfer rollers 5Y, 5M, 5C, and 5K are conductive rollers including a core metal and a conductive elastic layer formed on the outer peripheral side of the core metal. The elastic layer is made of, for example, ion-conductive foam rubber. The ion-conductive foam rubber is a foam rubber material in which a conductive agent exhibiting ionic conductivity is dispersed. As the conductive agent and the foam rubber material, known materials for the transfer roller can be used. For each of the primary transfer rollers, for example, a roller having an outer diameter of 15 mm to 20 mm and a resistance value of 1E+5 to 1E+8 Ω when a voltage of 2 kV is applied under environmental conditions of 23°C and 50% RH can be appropriately used.

[0035] The intermediate transfer belt 6 is rotationally driven at a predetermined circumferential speed (processing speed) equal to the circumferential speeds of the photosensitive drums 1Y, 1M, 1C, and 1K. In the present embodiment, the circumferential speed is from 150 to 470 mm / second. By transferring a toner image of another color onto the toner image transferred on the upstream side of the primary transfer section while the intermediate transfer belt 6 is rotating, a full-color toner image is formed on the intermediate transfer belt 6. The full-color toner image is carried by the intermediate transfer belt 6 and conveyed toward the secondary transfer section T2.

[0036] In parallel with the formation of the toner image in the image forming section 101, the feeding unit 64 feeds the sheet S one by one toward the image forming section 101. In synchronization with the timing at which the toner image on the intermediate transfer belt 6 is conveyed to the secondary transfer section T2, the fed sheet S is conveyed by the registration rollers 8 to the secondary transfer section T2. Then, the toner image is transferred (secondary transfer) from the intermediate transfer belt 6 to the sheet S in the secondary transfer section T2.

[0037] In the present embodiment, the secondary transfer roller 9 is a conductive roller including a core metal and a conductive elastic layer formed on the outer peripheral side of the core metal. The elastic layer is made of, for example, ion-conductive foam rubber. The ion-conductive foam rubber is a foam rubber material in which a conductive agent exhibiting ionic conductivity is dispersed. As the conductive agent and the foam rubber material, known materials for transfer rollers can be used. For the secondary transfer roller 9, for example, a roller having an outer diameter of from 20 mm to 25 mm and a resistance value of from 1E+5 to 1E+8 Ω when a voltage of 2 kV is applied under environmental conditions of 23°C and 50% RH can be suitably used.

[0038] In addition, the opposing roller 21 is a conductive rubber roller including a core metal and an elastic layer of conductive foam rubber formed on the outer peripheral side of the core metal. The conductive foam rubber is a foam rubber material in which a conductive agent exhibiting electronic conductivity is dispersed. As the conductive agent and the foam rubber material, known materials for transfer rollers can be used. For the opposing roller 21, for example, a roller having an outer diameter of from 20 mm to 22 mm and a resistance value of from 1E+5 to 1E+8 Ω when a voltage of 50 V is applied under environmental conditions of 23°C and 50% RH can be suitably used.

[0039] During secondary transfer, a transfer voltage having a polarity opposite to the normal charging polarity of the toner is applied from the transfer power supply 10 to the secondary transfer roller 9 by constant voltage control. The transfer voltage is, for example, from +1 kV to +7 kV, and is automatically adjusted so that a current of from +40 μA to +120 μA flows from the secondary transfer roller 9 to the opposing roller 21. By the application of the transfer voltage, a bias electric field is formed in the secondary transfer section T2, in which the potential of the secondary transfer roller 9 becomes a polarity opposite to the normal charging polarity of the toner with respect to the intermediate transfer belt 6. By this bias electric field, an electrostatic force in the direction approaching the secondary transfer roller 9 acts on the toner on the intermediate transfer belt 6. Then, the toner image is transferred to the sheet S by the transfer of the toner from the intermediate transfer belt 6 to the sheet S passing through the secondary transfer section T2.

[0040] Incidentally, immediately before the secondary transfer section T2, a conveying guide 11 is provided to improve the positioning accuracy of the sheet S with respect to the intermediate transfer belt 6. In addition, the transfer residual toner remaining on the intermediate transfer belt 6 and not transferred to the sheet S is collected by the belt cleaner 12 and reused for image formation.

[0041] The sheet S that has passed through the secondary transfer section T2 is conveyed by the pre-fixing conveyance device 41 to the fixing device 40, and the toner image undergoes a fixing process performed by the fixing device 40. The fixing process is a process in which while the sheet S is clamped and conveyed in the clamping section of the fixing device 40, the toner image on the sheet S is heated and pressed. For example, the pre-fixing conveyance device 41 carries and conveys the sheet S on an endless rubber belt. For the rubber belt, ethylene propylene diene monomer (EPDM) with a width ranging from 100 mm to 110 mm and a thickness ranging from 1 mm to 3 mm can be used. Additionally, the rubber belt has holes with a diameter ranging from 3 mm to 7 mm, and by generating a negative pressure inside the rubber belt using a fan, the sheet S can be stably carried on the rubber belt.

[0042] The sheet S that has passed through the fixing device 40 is discharged by the discharge roller pair 42 toward the charge elimination device 300.

[0043] The above-described intermediate transfer type image forming section 101 is an example of an image forming unit that forms an image on the sheet S. For example, the image forming unit can be a direct transfer type electrophotographic unit. In this case, the toner image formed on the photosensitive drum serving as an image bearing member is directly transferred from the photosensitive drum to the sheet S in a transfer clamping section (transfer section) where the photosensitive drum and the transfer roller face each other. In the transfer clamping section, a bias electric field is formed, in which the potential of the transfer roller becomes a polarity opposite to the normal charging polarity of the toner with respect to the photosensitive drum.

[0044] <Charge elimination device>

[0045] Figure 2 is a schematic view of the charge elimination device 300 in the present embodiment. The charge elimination device 300 is provided with a charge elimination roller pair 51 serving as a contact type charge eliminator, an ion generator section 52 serving as a non-contact type charge eliminator, and a high voltage power supply 55.

[0046] The charge elimination roller pair 51 includes a charge elimination counter roller 51a (second counter roller) that contacts the first surface Sa of the sheet S and a charge elimination roller 51b that contacts the second surface Sb opposite to the first surface Sa of the sheet S. The charge elimination roller 51b is a contact type charge elimination member that contacts the conveyed sheet S and eliminates the charge of the sheet S. The charge elimination counter roller 51a contacts the charge elimination roller 51b, and a charge elimination clamping section serving as a clamping section between the charge elimination roller 51b and the charge elimination counter roller 51a is formed. The charge elimination roller pair 51 performs charge elimination of the sheet S while clamping and conveying the sheet S in the charge elimination clamping section.

[0047] The charge elimination counter roll 51a is connected to the ground potential GND. The charge elimination counter roll 51a is electrically connected to, for example, the metal frame of the charge elimination device 300. The charge elimination roll 51b is connected to the high-voltage power supply 55. The high-voltage power supply 55 is a voltage application unit that applies a voltage (charge elimination voltage) to the charge elimination roll 51b to perform charge elimination of the sheet S.

[0048] In addition, it can be configured such that the charge elimination roll 51b is deployed to contact the first surface Sa of the sheet S, and the charge elimination counter roll 51a is deployed to contact the second surface Sb of the sheet S. In this case, the voltage applied to the charge elimination roll 51b becomes the opposite polarity to the voltage applied to the charge elimination roll 51b in the present embodiment.

[0049] In the present embodiment, the charge elimination roll 51b is a conductive roll including a core metal and a conductive elastic layer formed on the outer peripheral side of the core metal. The elastic layer is made of, for example, ion-conductive foam rubber. The ion-conductive foam rubber is a foam rubber material in which a conductive agent exhibiting ionic conductivity is dispersed. For the conductive agent and the foam rubber material, known materials can be used. For the charge elimination roll 51b, for example, a roll having an outer diameter from 20 mm to 25 mm and a resistance value from 1E+5 to 1E+8 Ω when a voltage of 2 kV is applied under environmental conditions of 23°C and 50% RH can be appropriately used. The charge elimination counter roll 51a is made of stainless steel (SUS), and for the charge elimination counter roll 51a, a roll having an outer diameter from 20 mm to 25 mm is used. Incidentally, as the charge elimination roll 51b, a roll made of a metal material such as stainless steel can be used.

[0050] The ion generator section 52 has a first ion generator 52a facing the first surface of the sheet S and a second ion generator 52b facing the second surface of the sheet S. Each of the first ion generator 52a and the second ion generator 52b includes electrode needles, and by applying a voltage to the electrode needles, corona discharge is generated from the tips of the needles, so that the air around the tips of the needles is ionized. Then, the charge on the surface of the sheet S is neutralized by the generated ions, and the charge of the sheet S is eliminated.

[0051] As the ion generator section 52 in the present embodiment, the bar-type ion generator IZS40 (manufactured by SMC Corporation) is deployed above and below the sheet conveyance path as the first ion generator 52a and the second ion generator 52b. The conveyance guides 53a and 53b that form the sheet conveyance path in the ion generator section 52 are made of a resin synthesized from, for example, PC (polycarbonate) and ABS (acrylonitrile-butadiene-styrene). The volume resistivity of the conveyance guides 53a and 53b is, for example, 1×10 14 Ωcm. In addition, as Figure 3As shown, for each of the conveyance guides 53a and 53b, a plurality of holes 530 are formed so that the ions emitted from the first ion generator 52a and the second ion generator 52b are not physically shielded. The plurality of holes 530 are arranged side by side in the sheet width direction perpendicular to the sheet conveyance direction Cv.

[0052] The above-described first ion generator 52a and second ion generator 52b are examples of non-contact type charge eliminators, and other non-contact type charge eliminators can be used. For example, a corona tube type or high-pressure chamber type charge eliminator that eliminates the charge of a sheet by corona discharge from a discharge wire can be used. Additionally, the non-contact type charge eliminator is not necessarily provided on both sides of the conveyance path. For example, the charge elimination device 300 may have a configuration in which only the first ion generator 52a, which is a non-contact type charge eliminator, is included. Further, in a case where the charge of the sheet S can be sufficiently eliminated by the charge elimination roller 51b, the non-contact type charge eliminator can be omitted.

[0053] For the sheet S conveyed from the image forming apparatus 100 to the charge elimination device 300, first, most of its charge is removed (substantially removed) by the charge elimination clamping portion of the charge elimination roller pair 51. Specifically, the charge elimination voltage is set to a polarity opposite to the transfer voltage applied to the secondary transfer roller 9. The value of the charge elimination voltage is set in the range from -1 kV to -6 kV.

[0054] Immediately after passing through the secondary transfer portion T2 ( Figure 1 ), generally, the first surface Sa of the sheet S that has contacted the intermediate transfer belt 6 is charged to a negative polarity, and the second surface Sb that has contacted the secondary transfer roller 9 is charged to a positive polarity. By applying a charge elimination voltage having a polarity opposite to the transfer voltage to the charge elimination roller 51b, a current flows between the charge elimination roller 51b and the charge elimination counter roller 51a, such that positive charges are supplied to the first surface Sa of the sheet S and negative charges are supplied to the second surface Sb. In this way, a current flows through the sheet S in the charge elimination clamping portion by applying the charge elimination voltage to the charge elimination roller 51b, and the charged amount of the sheet S, which is the amount of charge carried on the first surface Sa and the second surface Sb of the sheet S, is reduced.

[0055] The sheet S that has passed through the charge elimination roller pair 51 is further subjected to charge elimination in the ion generator portion 52. Specifically, by irradiating ions from the first ion generator 52a and the second ion generator 52b, the residual charges on the first surface Sa and the second surface Sb of the sheet S are neutralized, and the charged amount of the sheet S is further reduced. The sheet S that has passed through the ion generator portion 52 is discharged to the outside of the charge elimination device 300.

[0056] <Method for Detecting Charged Electric Quantity and Method for Controlling Charge Elimination Voltage>

[0057] In this embodiment, a detection mode for detecting the charged electric quantity using the charge elimination roller 51b can be executed. In other words, the control circuit 200 can execute a normal mode (first mode) and a detection mode (second mode). In the normal mode, charge elimination of the sheet S (the sheet S to be a product) is performed. In the detection mode, the charged electric quantity of the sheet S (the sheet S for measurement) is detected. The detection mode is a mode in which the charged electric quantity of the sheet is detected based on the detection result of the voltage detection circuit 55V (detection unit) when the sheet passes through the charge elimination roller 51b (charge elimination member).

[0058] In addition, in the detection mode in this embodiment, the value of the charge elimination voltage in the normal mode is determined such that the charge elimination voltage to be applied to the charge elimination roller 51b to eliminate the charge of the sheet S is a value corresponding to the charged electric quantity of the sheet S. In other words, the control circuit 200 can implement the normal mode (first mode) of performing charge elimination of the sheet S (the sheet S to be a product) and a mode (second mode, adjustment mode) of automatically determining the value of the charge elimination voltage. In the detection mode in this embodiment, based on the detection result of the voltage detection circuit 55V (detection unit) when the sheet passes through the charge elimination roller 51b (charge elimination member), the value of the charge elimination voltage to be applied to the charge elimination roller 51b (charge elimination member) by the high-voltage power supply 55 (voltage application unit) in the normal mode is determined.

[0059] Incidentally, the charged electric quantity of the sheet S is usually proportional to the surface potential of the sheet S. In addition, the charged electric quantity of the sheet S can be expressed as the electric quantity per unit area on the surface of the sheet (surface charge density). Therefore, the "charged electric quantity" of the sheet S in the following description can be replaced with the surface potential of the sheet S or the surface charge density of the sheet S.

[0060] For example, before an image is formed on the sheet S to be a product, when an image formation job is input, the detection mode is automatically executed. Alternatively, based on the operation of the user on the user operation unit 102, the detection mode can be executed as an operation independent of the image formation job.

[0061] Hereinafter, the voltage applied from the high-voltage power supply 55 to the charge elimination roller 51b in the detection mode is referred to as "high voltage for detection", and is distinguished from the charge elimination voltage applied from the high-voltage power supply 55 to the charge elimination roller 51b in the normal mode.

[0062] In Figure 4In [the figure], a block diagram of a control circuit 200 according to the present embodiment is illustrated. The control circuit 200 is an example of a control unit that controls the operation of the charge elimination device 300. The control circuit 200 may be installed on the main component of the charge elimination device 300, or part or all of the functions of the control circuit 200 may be installed in the image forming apparatus 100.

[0063] As Figure 4 shown in [the figure], the control circuit 200 includes a CPU 201, a RAM 210, and a ROM 220. The CPU 201 is an execution component that reads and executes a control program. The RAM 210 provides a working area when the CPU 201 executes the control program. The ROM 220 is an example of a memory section that stores various types of information such as setting information related to the control of the charge elimination device 300. In addition, the control circuit 200 is connected to the user operation section 102, the charge elimination operation section 54, the high-voltage power supply 55, and the transfer power supply 10. The charge elimination operation section 54 will be described in detail in Embodiment 2.

[0064] More specifically, the CPU 201 obtains information such as information related to an image forming job (job information), the value of the current flowing through the charge elimination roller 51b when a charge elimination voltage is applied to the charge elimination roller 51b (referred to as the charge elimination current), and the value of the transfer voltage output by the transfer power supply 10, and stores this information in the RAM 210. Here, the job information is, for example, attribute information of the sheet S input by the user via the user operation section 102 and used for the current image forming job. In the case of the period during which the sheet S is passing through the charge elimination clamping section (during sheet passing), the value of the charge elimination current corresponds to the amount of charge supplied from the charge elimination roller 51b to the sheet S per unit time.

[0065] During the period when the sheet S for detection passes through the charge elimination clamping section and during the periods before and after this period, the CPU 201 causes the high-voltage power supply 55 to apply a high voltage for detection to the charge elimination roller 51b. Based on the detection result of the current detection circuit 55A or the voltage detection circuit 55V when the sheet S for detection passes through the charge elimination roller 51b, the CPU 201 determines the voltage (charge elimination voltage) to be applied to the charge elimination roller 51b by the high-voltage power supply 55 when the charge elimination roller 51b eliminates the charge of the sheet S.

[0066] In this embodiment, the high-voltage power supply 55 can perform output control with constant voltage control in the range from 0 kV to -6 kV and constant current control in the range from 0 μA to -100 μA. Additionally, a voltage detection circuit 55V and a current detection circuit 55A are provided to the high-voltage power supply 55. The voltage detection circuit 55V can detect the value of the voltage applied from the high-voltage power supply 55 to the charge elimination roller 51b, and the current detection circuit 55A can detect the current flowing through the charge elimination roller 51b due to the application of the voltage from the high-voltage power supply 55.

[0067] The voltage detection circuit 55V and the current detection circuit 55A are examples of detection units that detect the voltage applied to the charge elimination member or the current flowing through the charge elimination member. As described below, in this embodiment, control mainly performed using the voltage detection result of the voltage detection circuit 55V.

[0068] (Control Flow)

[0069] Will be based on Figure 5 The flowchart in describes the control process executed by the control circuit 200. Hereinafter, unless otherwise specified, the execution entity of each process in this flow is the CPU 201.

[0070] In this embodiment, by operating the user operation section 102, the user can instruct the control circuit 200 to execute the detection mode as an independent operation of the image forming job. When an instruction for executing the image forming job or the detection mode is input to the image forming system 400, the processing of this flow starts. First, the CPU 201 obtains the job information set via the user operation section 102 (S10). In the job information, there is information indicating whether the current job is an image forming job or the detection mode.

[0071] If the current job is an image forming job (S11N), the CPU 201 operates the charge elimination device 300 in the normal mode (S12). That is, the CPU 201 causes the high-voltage power supply 55 to apply a charge elimination voltage to the charge elimination roller 51b so as to eliminate the charge of the sheet S on which the image is formed by the image forming device 100 in the charge elimination clamping portion. The value of the charge elimination voltage is, for example, the value recorded in the RAM 210 in the previously executed detection mode. If the detection mode has not been executed, or if an operation for resetting the value recorded in the RAM 210 has been performed, then for the value of the charge elimination voltage, the value in the table pre-stored in the ROM 220 is used. The operation for resetting the value recorded in the RAM 210 is, for example, turning off the charge elimination device 300.

[0072] If the current job is the detection mode (S11Y), the CPU 201 causes the image forming apparatus 100 to form an image (image for testing) on the sheet S in a process similar to the normal image forming operation. On the other hand, during the period when the first sheet S in the image forming job passes through the charge elimination holding portion and during the periods before and after this period, the CPU 201 causes the high-voltage power supply 55 to apply a high voltage for detection to the charge elimination roller 51b (S13). In the present embodiment, for example, the high voltage for detection is applied by constant current control at a preset current value within the range from -10 μA to -30 μA. Then, the fluctuation of the voltage value when the sheet S passes through the charge elimination holding portion during the period when the high voltage for detection is applied is measured (S14).

[0073] The amount of fluctuation of the voltage value when the sheet S passes through the charge elimination holding portion is referred to as the "detection voltage". That is, the detection voltage is a value obtained by subtracting the detection value of the voltage detection circuit 55V when the sheet S does not pass through the charge elimination holding portion from the detection value of the voltage detection circuit 55V when the sheet S passes through the charge elimination holding portion (charge elimination roller 51b) in a state where a voltage is applied to the charge elimination roller 51b by constant current control.

[0074] The CPU 201 records the detection voltage obtained in S14 as a detection result in the RAM 210. Then, the CPU 201 calculates the amount of charged electric charge and the value of the charge elimination voltage of the sheet S based on the detection voltage obtained in S14 and the charged charge conversion table and the charge elimination voltage conversion table stored in the ROM 220 ( Figure 4 ).

[0075] The value of the charge elimination voltage obtained in S16 is recorded in the RAM 210 as an adjustment value of the charge elimination voltage. When an image forming job is input after the detection mode is executed and the charge elimination device 300 operates in the normal mode, the charge elimination voltage is applied from the high-voltage power supply 55 to the charge elimination roller 51b using the adjustment value of the charge elimination voltage recorded in the RAM 210 (S12).

[0076] In this way, the voltage detection circuit 55V as the detection unit detects the voltage applied to the charge elimination roller 51b (charge elimination member). The control circuit 200 (control unit) calculates the amount of charged electric charge of the sheet S based on the amount of fluctuation of the voltage detected by the voltage detection circuit 55V when the sheet passes through the charge elimination roller 51b in a state where a voltage is applied to the charge elimination roller 51b in the detection mode (second mode). Accordingly, the charge elimination device 300 can automatically detect the amount of charged electric charge of the sheet S.

[0077] In addition, the control circuit 200 (control unit) determines the value of the charge elimination voltage for the normal mode (first mode) based on the amount of fluctuation of the voltage detected by the voltage detection circuit 55V when the sheet passes through the charge elimination roller 51b in a state where a voltage is applied to the charge elimination roller 51b in the detection mode (second mode). Accordingly, the charge elimination voltage is automatically set to a value suitable for performing charge elimination of the sheet S according to the charged amount of the sheet S.

[0078] (Reasons for being able to detect the charged amount)

[0079] The reasons for being able to determine the charged amount of the sheet S based on the amount of fluctuation (detection voltage) of the voltage value of the high voltage used for detection when the sheet S passes through the charge elimination clamping portion (charge elimination roller 51b) will be described. The sheet S is affected by an electric field in the secondary transfer portion T2. In the secondary transfer portion T2, an electric field is formed such that the potential of the secondary transfer roller 9 becomes a polarity opposite to the normal charging polarity of the toner with respect to the intermediate transfer belt 6. Hereinafter, it is assumed that the normal charging polarity of the toner is negative. In the secondary transfer portion T2, the side of the surface (first surface Sa, image surface) of the sheet S with the toner image transferred thereon has a negative polarity, and the side of its back surface (second surface Sb, non-image surface) is affected by an electric field with a positive polarity.

[0080] In the case where the resistance value of the sheet S is low, for example, the positive charges supplied from the secondary transfer roller 9 to the second surface Sb of the sheet S can move through the sheet S in the thickness direction and leave from the first surface Sa to reach the intermediate transfer belt 6. As a result, in the case where the resistance value of the sheet S is low, most of the positive charges supplied to the second surface Sb of the sheet S leave and reach the intermediate transfer belt 6 in addition to the positive charge amount required for transferring the toner image. Therefore, in the case where the resistance value of the sheet S is low, the charged amounts of the first surface Sa and the second surface Sb of the sheet S do not become large values.

[0081] However, in the case where the resistance value of the sheet S is high, the positive charges supplied from the secondary transfer roller 9 to the second surface Sb of the sheet S may remain on the second surface Sb. On the first surface Sa of the sheet S, in response to the positive charges on the second surface Sb, dielectric polarization occurs, and negative charges are distributed on the first surface Sa. In addition, in the case where the resistance value of the sheet S is high, after the sheet S leaves the secondary transfer portion T2, the charged amounts on the first surface Sa and the second surface Sb are still maintained without experiencing a large amount of attenuation.

[0082] Incidentally, examples of the sheet S with a high resistance value are sheets made of synthetic resins such as plastic films and synthetic papers. These sheets are typical examples of sheets that highly require charge elimination to be performed by the charge elimination device 300. This is because, for these sheets, if charge elimination is not performed, the sheets are discharged onto a discharge tray or the like while the amount of electric charge carried on the sheet surface remains large, and the sheets may adhere to each other due to electrostatic adsorption force.

[0083] The relationship between voltage and current when the charged sheet S passes through the charge elimination clamping portion in a state where voltage is applied to the charge elimination roller 51b is different from the relationship between voltage and current when the uncharged sheet S passes through the charge elimination clamping portion. That is, the applied voltage required to apply a current at a specific current value to the charge elimination roller 51b while the sheet S is passing through the charge elimination clamping portion varies according to the resistance value of the sheet S, the amount of electric charge carried on the sheet S, and the polarity of the charge.

[0084] For example, consider the following case: In a state where the sheet S is charged such that the first surface Sa carries negative charge and the second surface Sb carries positive charge, negative charge is supplied to the charge elimination roller 51b (a high voltage for detecting negative polarity is applied). In this case, the sheet S acts as a capacitor, and when the sheet S passes through the charge elimination clamping portion, the charges stored on the first surface Sa and the second surface Sb are released. As a result, more charges are likely to move along the potential gradient generated by applying voltage to the charge elimination roller 51b. That is, if the applied voltage is constant, the current flowing through the charge elimination roller 51b increases due to the current caused by the charges on the surface of the sheet when the sheet S passes through the charge elimination clamping portion.

[0085] In other words, the applied voltage required to apply a current at a predetermined current value to the charge elimination roller 51b while the sheet S passes through the charge elimination clamping portion varies according to the amount of electric charge carried on the sheet S. The applied voltage required to apply a current at a predetermined current value (e.g., -20 μA) to the charge elimination roller 51b when a sheet in which the first surface Sa is charged to negative polarity and the second surface Sb is charged to positive polarity passes through the charge elimination clamping portion becomes lower than the applied voltage required to apply the same current value to the charge elimination roller 51b when the uncharged sheet S passes through the charge elimination clamping portion. Conversely, the applied voltage required to apply a current at a predetermined current value to the charge elimination roller 51b when a sheet S in which the first surface Sa is charged to positive polarity and the second surface Sb is charged to negative polarity passes through the charge elimination clamping portion becomes higher than the applied voltage required to apply the same current value to the charge elimination roller 51b when the uncharged sheet S passes through the charge elimination clamping portion.

[0086] (Relationship between detection voltage and amount of electric charge carried)

[0087] In Figure 6 Part (a), preliminary research results are shown for the relationship between the amount of fluctuation (detection voltage) of the voltage value of the high voltage used for detection when the sheet S passes through the charge elimination clamping portion and the charged amount of the sheet S. Here, a sheet with a high resistance value (synthetic paper) is charged with a pre-specified charged amount by a charging unit prepared separately from the charge elimination device 300. Figure 6 In part (a), the horizontal axis represents the charged amount of the sheet as a charge density (the amount of charge per unit area of the sheet surface). And the detection voltage (vertical axis) is measured when the charged sheet passes through the charge elimination clamping portion.

[0088] In the present embodiment, in the ROM 220 ( Figure 4 ) in the control circuit 200, a charged charge conversion table indicating the correspondence between the detection voltage and the charged amount shown in Figure 6 part (a) is stored. In S14 of the above process ( Figure 5 ), the CPU 201 can determine the charged amount of the sheet S by using the detection voltage obtained when the sheet S passes through the charge elimination clamping portion and referring to the charged charge conversion table. In other words, the control circuit 200 (control unit) includes the ROM 220 (storage portion) that stores information indicating the correspondence between the amount of fluctuation of the voltage and the charged amount of the sheet S. In addition, the control circuit 200 detects the charged amount of the sheet S based on the amount of fluctuation of the voltage detected by the voltage detection circuit 55V (detection unit) and the information in the ROM 220.

[0089] Incidentally, in the present embodiment, the information indicating the correspondence between the detection voltage and the charged amount is prepared in the form of a table. However, it can be configured such that the charged amount is represented as a function with the detection voltage as a variable, and the coefficients of the function are stored in the ROM 220 as control parameters.

[0090] (Relationship between detection voltage and charge elimination voltage)

[0091] In Figure 6 part (b), preliminary research results are shown for the relationship between the amount of fluctuation (detection voltage) of the voltage value of the high voltage used for detection when the sheet S passes through the charge elimination clamping portion and the value of the charge elimination voltage suitable for eliminating the charge of the sheet S. Similar to the case of Figure 6 part (a), a sheet with a high resistance value (synthetic paper) is charged with a pre-specified charged amount by a charging unit prepared separately from the charge elimination device 300. Figure 6 In part (b), the horizontal axis represents the detection voltage when the charged sheet passes through the charge elimination clamping portion.Figure 6 The vertical axis in part (b) represents the value of the charge elimination voltage corresponding to the amount of electric charge carried by the sheet S.

[0092] In the present embodiment, in the ROM 220 ( Figure 4 ) in the control circuit 200, the charge elimination voltage conversion table indicating the correspondence between the detection voltage and the charge elimination voltage shown in part (b) of Figure 6 is stored. In step S14 of the above process ( Figure 5 ), the CPU 201 can determine the value of the charge elimination voltage by using the detection voltage obtained when the sheet S passes through the charge elimination clamping portion and referring to the charge elimination voltage conversion table. In other words, the control circuit 200 (control unit) includes the ROM 220 (storage portion) that stores information indicating the correspondence between the amount of voltage fluctuation and the value of the voltage to be applied to the charge elimination roller 51b (charge elimination member). In addition, the control circuit 200 determines the value of the voltage applied to the charge elimination roller 51b by the high-voltage power supply 55 (voltage application unit) in the normal mode based on the amount of voltage fluctuation detected by the voltage detection circuit 55V (detection unit) and the information in the ROM 220.

[0093] Incidentally, in the present embodiment, the information indicating the correspondence between the detection voltage and the charge elimination voltage is prepared in the form of a table. However, it can be configured such that the charge elimination voltage is represented as a function of the detection voltage as a variable, and the coefficients of the function are stored in the ROM 220 as control parameters.

[0094] (Difference between the high voltage for detection and the charge elimination voltage)

[0095] The voltage (high voltage for detection) applied to the charge elimination roller 51b to determine the amount of electric charge carried by the sheet S and the charge elimination voltage is subject to different voltage controls from the voltage (charge elimination voltage) applied to the charge elimination roller 51b to perform charge elimination of the sheet S. Here, "different voltage controls" means that at least one of the control type of the voltage (constant current control or constant voltage control) and the presence or absence of a change in the voltage value according to the detection result of the detection unit is different.

[0096] In the present embodiment, the charge elimination voltage is controlled by constant voltage control. This is because it is easier to stably perform charge elimination of the sheet S. For example, in constant voltage control, it is not necessary to change the output voltage value according to the width of the sheet S (the length of the sheet in the sheet width direction perpendicular to the sheet conveyance direction Cv).

[0097] Meanwhile, the high voltage for detection is controlled by constant current control. Additionally, the high voltage for detection is a preset value (a predetermined value stored in the ROM 220) regardless of the detection result of the voltage detection circuit 55V (detection unit), while the value of the charge elimination voltage changes based on the detection result of the voltage detection circuit 55V.

[0098] To appropriately perform charge elimination of the sheet S, the charge elimination voltage is changed according to the charged amount of the sheet S. Conversely, for the purpose of evaluating the charged amount of the sheet S, it is acceptable that the high voltage for detection is a predetermined value. Moreover, by fixing the high voltage for detection to a predetermined value, it becomes easier to conduct preliminary studies such as a charged charge conversion table.

[0099] In the case of controlling the high voltage for detection by constant voltage control, the detection result may change due to factors other than the charged amount, for example, a change in the resistance value of the charge elimination roller 51b. That is, even if the relationship between the detection result (current value or its fluctuation amount) and the charged amount or the charge elimination voltage when applying the high voltage for detection by constant voltage control is determined through preliminary studies, the result of the preliminary studies may deviate when the charge elimination device 300 is used over a long period.

[0100] Furthermore, in the case of controlling the high voltage for detection by constant voltage control using the same voltage value as the charge elimination voltage, there may be a situation where, depending on the value of the charge elimination voltage, the current flowing through the charge elimination roller 51b becomes substantially 0A when the sheet S passes through the charge elimination clamping portion. In this case, the fluctuation of the current value corresponding to the charged amount of the sheet S may be buried in the noise (the signal-to-noise ratio (S / N) becomes low), and it may become difficult to appropriately evaluate the charged amount of the sheet S and set the charge elimination voltage according to the charged amount. Additionally, in the case of controlling the high voltage for detection by constant voltage control using the same voltage value as the charge elimination voltage, there may be a situation where, depending on the value of the charge elimination voltage, the current flowing through the charge elimination roller 51b becomes very large when the sheet S passes through the charge elimination clamping portion. In this case, it may become difficult to perform appropriate control because the current exceeds the detectable range of the current detection circuit 55A.

[0101] Therefore, by using constant current control for the high voltage for detection, it is less likely to encounter the above-mentioned troubles.

[0102] <Image in the detection mode>

[0103] The sheet S used for testing in the detection mode (second mode) can be either a pure white sheet S on which no toner image is transferred in the image forming apparatus 100 or a sheet S on which a test pattern is transferred in the image forming apparatus 100. The pure white sheet S is a sheet output when the image forming apparatus 100 performs a normal image forming operation based on image data with a printing ratio (toner coverage rate) of 0%. The test pattern is a toner image (pattern image for testing) set in advance for testing. The test pattern is output by the image forming apparatus 100 performing a normal image forming operation based on the image data for the test pattern stored in the ROM 220 in advance.

[0104] The advantage of using the pure white sheet S in the detection mode is that the charged amount of the sheet S in a state where only the sheet S on which no toner image is transferred exists can be detected. Therefore, for example, when an image forming job of printing an image at a low printing ratio is performed after the detection mode, the value of the charge elimination voltage can be made more accurate.

[0105] The advantage of using the sheet S on which the test pattern is transferred in the detection mode is that the charged amount of the sheet S in a state where a toner image of an image printed at a printing ratio close to that of an image output under normal usage conditions is transferred can be detected. Therefore, for example, when an image forming job of printing a general image (for example, an image mainly composed of text) is performed after the detection mode, the value of the charge elimination voltage can be made more accurate.

[0106] Incidentally, regardless of whether the pure white or the test pattern is used in the detection mode, when the test sheet S passes through the secondary transfer portion T2 in the image forming apparatus 100, it is assumed that the same transfer voltage as during normal image formation is applied to the secondary transfer roller 9. That is, in the detection mode (second mode), the control circuit 200 detects the charged amount of the sheet by using the sheet that has passed through the transfer portion of the image forming apparatus in a state where the same bias electric field as when transferring the toner image is formed. Accordingly, it becomes possible to detect the charged amount of the sheet S charged in the transfer portion under the same conditions as normal image formation and make the value of the charge elimination voltage more accurate.

[0107] <Overview of the present embodiment>

[0108] As described above, in the present embodiment, the charged amount of the sheet S is detected by using the charge elimination roller 51b itself, which is a contact type charge elimination member. In other words, the control circuit 200 (control unit) detects the charged amount of the sheet based on the detection result of the voltage detection circuit 55V (detection unit) when the sheet passes through the charge elimination roller 51b (charge elimination member).

[0109] Therefore, compared with a case where, for example, a non-contact type surface potential sensor is separately deployed from a charge elimination member, it becomes possible to provide a charge elimination device capable of detecting the charged amount of a sheet and an image forming system provided with the charge elimination device with a simpler configuration.

[0110] In the present embodiment, since it is not necessary to deploy an additional surface potential sensor to detect the charged amount of the sheet S, it becomes possible to reduce the deployment cost and space required when adding a surface potential sensor.

[0111] In addition, in the present embodiment, by using the charge elimination roller 51b itself which is a contact type charge elimination member, the value of the charge elimination voltage is determined based on the detection result of the voltage or current when a high voltage for detection is applied thereto. In other words, the control circuit 200 (control unit) determines the value of the voltage (charge elimination voltage) to be applied to the charge elimination roller 51b (charge elimination member) by the high voltage power supply 55 (voltage application unit) to eliminate the charge of the sheet based on the detection result of the voltage detection circuit 55V (detection unit) when the sheet passes through the charge elimination roller 51b (charge elimination member).

[0112] Therefore, compared with a case where, for example, a non-contact type surface potential sensor is separately deployed from a charge elimination member, it becomes possible to provide a charge elimination device capable of determining the value of the charge elimination voltage according to the charged amount of a sheet and an image forming system provided with the charge elimination device with a simpler configuration.

[0113] In addition, in the present embodiment, since the value of the charge elimination voltage is determined based on the detection result of the voltage detection circuit 55V (detection unit), it becomes possible to reduce the burden of the adjustment work of the charge elimination voltage performed by the user. The adjustment work of the charge elimination voltage performed by the user means a series of operations such as (1) the user causes the image forming system 400 to discharge a sheet for testing, (2) the user manually measures the charged amount of the discharged sheet for testing using a surface potentiometer, and (3) the user increases or decreases the set value for the charge elimination voltage by operating the user interface of the charge elimination device 300 or the image forming system 400 according to the measurement result until the charged amount of the sheet for testing becomes small enough.

[0114] <Modification Example>

[0115] In this embodiment, an example of controlling the high voltage for detection by constant current control is described. However, the high voltage for detection can be controlled by constant voltage control. That is, it can be configured such that the amount of fluctuation of the current value when the sheet S passes through the charge elimination clamping portion in a state where a preset predetermined voltage is applied to the charge elimination roller 51b is used as the detection current, and based on the detection current, the charged charge amount and the charge elimination voltage of the sheet S are determined. In this case, a table or the like indicating the relationship between the detection current and the charged charge amount or the charge elimination voltage of the sheet S (corresponding to Figure 6 parts (a) and (b)) is obtained through preliminary research and stored in the ROM 220.

[0116] In addition, the relationship between the detection voltage detected by using the charge elimination roller 51b and the charged charge amount or the charge elimination voltage of the sheet S may vary depending on the material (type) and thickness (basis weight) of the sheet S. Therefore, the calculation method of the charged charge amount and the charge elimination voltage of the sheet S based on the detection voltage can be changed according to at least one of the material or thickness of the sheet S. Accordingly, it becomes possible to determine the charged charge amount and the charge elimination voltage of the sheet S with higher accuracy. Specifically, it can be configured such that a conversion table of the charged charge amount according to the material and / or thickness of the sheet S ( Figure 4 the paper type table and / or the paper thickness table in) is pre-stored in the ROM 220, and the CPU 201 refers to this conversion table based on the information of the sheet S included in the job information. Instead of the conversion table, parameters (coefficients of calculation formulas) capable of realizing the conversion of the charged charge amount according to the material and thickness of the sheet S can be prepared. In addition, a table indicating the relationship between the detection voltage and the charged charge amount and the charge elimination voltage (charged charge conversion table and charge elimination voltage conversion table) can be prepared for each of the type and thickness of the sheet S.

[0117] [Embodiment 2]

[0118] In Embodiment 1, a configuration in which the control circuit 200 automatically determines the value of the charge elimination voltage is described. In Embodiment 2, a configuration in which presenting the determination result of the charged charge amount of the sheet S and the adjustment of the charge elimination voltage to the user is left to the user will be described. Hereinafter, it is assumed that elements having the same reference numerals as those in Embodiment 1 are provided with substantially the same configuration and operation as those described in Embodiment 1, and mainly the parts different from Embodiment 1 will be described.

[0119] <Charge elimination voltage adjustment switch>

[0120] The charge elimination device 300 in this embodiment is provided with a charge elimination operation portion 54 capable of performing an operation for changing the operation conditions of the charge elimination device 300. In Figure 7In [the figure], an enlarged view of the charge elimination operation section 54 is shown. The charge elimination operation section 54 is an example of an input unit (setting unit) that allows a user to input (set) the value of the voltage to be applied to the charge elimination roller 51b (charge elimination member) by the high-voltage power supply 55 (voltage application unit).

[0121] The charge elimination operation section 54 includes a changeover switch 54a and a voltage adjustment switch 54b. By operating the changeover switch 54a, the user can switch between the output (ON) and the stop output (OFF) of the charge elimination voltage of the high-voltage power supply 55 ( Figure 2 ), which applies the charge elimination voltage to the charge elimination roller 51b. The voltage adjustment switch 54b allows the user to adjust the value of the charge elimination voltage.

[0122] The value of the charge elimination voltage can be fixed at a preset value according to the type of the sheet S. For example, in the case of a plastic film or synthetic paper, it is known that these sheets are likely to be more strongly dielectrically polarized in the secondary transfer section than ordinary paper, and the amount of charge of the sheet S is likely to become larger. Therefore, in the case of using a plastic film or synthetic paper as the sheet S, it is possible to consider presetting the value of the charge elimination voltage according to the type of the sheet S so that the charge elimination voltage is a higher voltage (in terms of its absolute value) than in the case of using ordinary paper as the sheet S. However, even for sheets S of the same type, there are cases where the appropriate value of the charge elimination voltage fluctuates due to differences in resistance, thickness, and usage environment caused by differences in specific materials. Therefore, in the present embodiment, it is configured such that the user can adjust the value of the charge elimination voltage.

[0123] The voltage adjustment switch 54b in the present embodiment includes a display section that displays the value of the charge elimination voltage in two digits and buttons (+ button and - button) for increasing or decreasing the value of the charge elimination voltage. When the + button is pressed, the corresponding digit increases, and when the - button is pressed, the corresponding digit decreases.

[0124] The value displayed in the display section is the absolute value of the charge elimination voltage displayed as a two-digit number in units of 0.1 kV. That is, the set value of the charge elimination voltage is the value obtained by multiplying the value displayed in the display section of the voltage adjustment switch 54b by -0.1 kV. For example, when “45” is displayed in the display section of the voltage adjustment switch 54b, the set value of the charge elimination voltage is -4.5 kV. Starting from this state, when the - button in the tens place is pressed once and the + button in the units place is pressed twice, the display changes to “37” and the value of the charge elimination voltage is set to -3.7 kV.

[0125] Incidentally, when the display is set to "00" using the voltage adjustment switch 54b, the value of the charge elimination voltage is set to 0 V (0.0 kV). In this case, the state of the high-voltage power supply 55 becomes the same as the state when the changeover switch 54a is turned off. This state can also be referred to as a state in which the high-voltage power supply 55 applies 0 V to the charge elimination roller 51b.

[0126] Incidentally, the display type and input type of the value of the charge elimination voltage are not limited to those described above. Instead of displaying the upper two digits of the value of the charge elimination voltage, the value of the charge elimination voltage itself may be displayed, or a value indicating the level of the charge elimination voltage in, for example, 10 levels may be displayed. The value of the charge elimination voltage may be displayed, for example, on the screen of the user operation unit 102 or on the screen of an external computer communicably connected to the image forming system 400. As an input type of the value of the charge elimination voltage, a numeric keypad for numeric input may be provided in the charge elimination operation unit 54, or may be operated via the touch panel of the user operation unit 102, or may be configured to receive input via an external computer. The user operation unit 102 is another example of an input unit (setting unit) that allows a user to input (set) the value of the voltage to be applied by the high-voltage power supply 55 (voltage application unit) to the charge elimination roller 51b (charge elimination member).

[0127] The configurations of the image forming system 400 and the charge elimination device 300 in the present embodiment are the same as those in the first embodiment. That is, in the present embodiment, by operating the user operation unit 102, the user can instruct the control circuit 200 to execute the adjustment mode as an independent operation of the image forming job. However, instead of automatically determining the value of the charge elimination voltage after determining the charged amount of the sheet S, in the present embodiment, it is configured to display the obtained charged amount of the sheet S on the screen of the user operation unit 102 and request the user to input the value of the charge elimination voltage.

[0128] (Control Flow)

[0129] The control process executed by the control circuit 200 in the present embodiment will be described based on the Figure 8 flowchart shown below. Since the processing from S10 to S15 is the same as that in the first embodiment, the description thereof will be omitted. After determining the charged amount of the sheet S in S15, the CPU 201 displays the charged amount on the screen of the user operation unit 102 (S16'), and waits for input from the user. In Figure 9In this case, an example of the screen display in S16' is illustrated. On the display 102a which is the display part of the user operation part 102, information 102b indicating the charged amount of the sheet S and information 102c prompting the user to input the value of the charge elimination voltage are displayed. The user operates the charge elimination operation part 54 based on the screen display and inputs the value of the charge elimination voltage according to the charged amount of the sheet (S17). The CPU 201 stores the value input by the user as the new charge elimination voltage value in the RAM 210 (S18) and ends the adjustment mode.

[0130] Incidentally, the display 102a of the user operation part 102 is an example of a display unit that displays information to the user, and can be configured to be equivalent to, for example, Figure 9 The information displayed in the screen in is displayed on an external computer communicably connected to the control circuit 200. The external computer can be the user's smart phone or tablet.

[0131] In addition, the information displayed on the screen in S16' is not limited to the numerical value of the charged amount of the sheet S itself, but can be other information related to the charged amount of the sheet S. For example, since the charged amount (surface charge density) of the sheet S is proportional to the surface potential of the sheet S, the value displayed on the screen in S16' can be the surface potential of the sheet S.

[0132] <Overview of this embodiment>

[0133] As described above, in this embodiment, the charged amount of the sheet S is detected by using the charge elimination roller 51b itself which is a contact type charge elimination member. In other words, the control circuit 200 (control unit) detects the charged amount of the sheet based on the detection result of the voltage detection circuit 55V (detection unit) when the sheet passes through the charge elimination roller 51b (charge elimination member).

[0134] Therefore, as in Embodiment 1, compared with the case of using, for example, a non-contact type surface potential sensor separately deployed from the charge elimination member, it becomes possible to provide a charge elimination device capable of detecting the charged amount of a sheet and an image forming system provided with the charge elimination device with a simpler configuration.

[0135] In addition, in this embodiment, the charged amount detected by using the charge elimination roller 51b is displayed on the display 102a of the user operation part 102. That is, the charge elimination device 300 is also provided with a display 102a (display unit) for displaying information. In the detection mode (second mode), the control circuit 200 (control unit) displays information about the charged amount of the sheet detected based on the detection result of the voltage detection circuit 55V (detection unit) on the display 102a.

[0136] Accordingly, it becomes possible to inform the user of the charged state of the sheet S without using a surface potential sensor. In addition, by being configured to allow the user to input the value of the charge elimination voltage via the charge elimination operation section 54 (input unit) based on the screen display, the load of the adjustment operation for the user can be reduced as compared with the case where the user manually measures the charged amount using a surface potentiometer.

[0137] <Modification Example>

[0138] In the present embodiment, the charged amount of the sheet S before charge elimination by the charge elimination roller 51b is detected in the adjustment mode. However, it may be configured to detect the charged amount of the sheet S after charge elimination by the charge elimination roller 51b. For example, the charge elimination device 300 may be provided with a circulating conveyance path to convey the sheet S that has passed through the charge elimination clamping portion again toward the charge elimination clamping portion. When the sheet S passes through the charge elimination clamping portion for the first time, a charge elimination voltage is applied to the charge elimination roller 51b to perform charge elimination of the sheet S. And when the sheet S passes through the charge elimination clamping portion for the second time, a detection voltage is obtained by applying a high voltage for detection to the charge elimination roller 51b. In this configuration, the information S102b displayed on the screen in S16' is the charged amount of the sheet S after charge elimination by the charge elimination roller 51b. In addition, the processes from S13 to S18 can be automatically (or based on an instruction from the user) repeated until the charged amount of the sheet S after charge elimination becomes a sufficiently low value.

[0139] [Other Embodiments]

[0140] In each of the above embodiments, the charge elimination device 300 that performs charge elimination of the sheet S is described. However, the charge elimination device 300 has a function as a charge adjustment device that adjusts the charged state of the sheet S by supplying charge to the sheet S via the charge elimination roller 51b as a charge supply member. The charge adjustment device does not necessarily reduce (eliminate) the charged amount of the sheet S. For example, in a state where the sheets S are stacked after being processed by the charge adjustment device, the charge adjustment device can adjust the charged amount of each surface of the sheet S such that the opposing surfaces of the overlapping sheets are charged to the same polarity state. Specifically, the charge adjustment device applies a voltage to every other sheet among a plurality of sheets so that the static electrode polarity on the sheet surface is reversed. In this case, by charging the opposing surfaces of the overlapping sheets to the same polarity, it becomes possible to reduce the adhesion between the sheets due to the electrostatic force. In addition, by applying the control described in each embodiment to the control of the voltage to be applied to the charge elimination roller 51b as a charge supply member, it becomes possible to more appropriately adjust the charged state of the sheet S.

[0141] In addition, in each of the above-described embodiments, the charge elimination roller 51b described as a roller member is exemplified as a contact-type charge elimination member that contacts the sheet S. However, the contact-type charge elimination member is not limited thereto, and may be, for example, a brush member in which conductive fibers or an elongated conductive sheet member contacts the sheet S.

[0142] In addition, in each of the above-described embodiments, it is described that the charge of the sheet S mainly appears in the transfer portion of the electrophotographic process. However, it is not limited thereto, and in an image forming system such as an inkjet type other than the electrophotographic type, the charge of the sheet S may appear due to frictional charging or peeling charging caused by friction and / or peeling of a conveying guide, a conveying roller, and / or a conveyor belt, etc. Therefore, the present technology can be applied to an image forming system of a type other than the electrophotographic type.

[0143] In addition, in Embodiment 1 and Embodiment 2, the determination of the value of the charge elimination voltage and the screen display of the charged amount are described as examples of the control according to the charged amount of the sheet S. However, it is not limited thereto, and the charged amount of the sheet S detected by using the charge elimination roller 51b (or a quantity related to the charged amount of the sheet S such as a detection voltage) can be used for other controls. For example, in the case where the charged amount of the sheet S exceeds a predetermined threshold, a warning may also be displayed to the user.

[0144] (Other Embodiments)

[0145] The present disclosure can also be implemented by the following process: supplying a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device reading and executing the program. In addition, the present invention can also be implemented by a circuit (for example, an ASIC) that implements one or more functions.

[0146] According to the present disclosure, it becomes possible to provide a charge elimination device, an image forming system, and a charge adjustment device that can detect the charged amount of a sheet with a simpler configuration or perform control according to the charged amount of the sheet.

[0147] Although the present invention has been described with reference to exemplary embodiments, it is to be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims will be given the broadest interpretation to encompass all such modifications as well as equivalent structures and functions.

Claims

1. A charge elimination device, comprising: a charge eliminating member configured to eliminate charges of the sheet while pinching and conveying the sheet; a voltage applying unit configured to apply a voltage to the charge eliminating member; a detection unit configured to detect a voltage applied to the charge eliminating member or a current flowing through the charge eliminating member; as well as A controller configured to measure the amount of electrified charge of the sheet based on a detection result of the detection unit when the sheet passes through the charge eliminating member.

2. The charge eliminating device according to claim 1, wherein: The controller is capable of operating in a first mode in which the voltage applying unit applies a voltage to the charge eliminating member to eliminate the charge of the sheet, and in a second mode in which an amount of charged charge of the sheet is measured based on a detection result of the detection unit.

3. The charge eliminating device according to claim 2, wherein: The detection unit detects a voltage applied to the charge eliminating member, and wherein the controller measures the amount of electrified charge of the sheet based on the voltage detected by the detection unit when the sheet passes through the charge eliminating member in the second mode.

4. The charge eliminating device according to claim 3, wherein: The controller includes a memory portion configured to store information indicating a correspondence between a voltage and an amount of charged charge of a sheet, and measures the amount of charged charge of the sheet based on an amount of fluctuation in the voltage detected by the detection unit and the information of the memory portion.

5. The charge eliminating device according to claim 2, wherein: The controller measures the amount of electrified charge of the sheet by using the sheet to which the toner image is not transferred in the transfer portion of the image forming apparatus in the second mode.

6. The charge eliminating device according to claim 2, wherein: The controller measures the amount of electrified charge of a sheet by using the sheet to which a toner image for a test is transferred in a transfer portion of the image forming apparatus in the second mode.

7. The charge eliminating device according to claim 2, wherein: The controller measures the charged charge amount of the sheet by using the sheet having passed through the transfer portion in a state where the same bias electric field as when the toner image is transferred is formed in the second mode. 8 . The charge eliminating device according to claim 1 , further comprising a display configured to display information on the amount of electrification charge of the sheet material measured and detected based on the detection result of the detection unit. 9 . The charge-eliminating device according to claim 1 , further comprising an operation section that allows a user to input a value of a voltage applied to the charge-eliminating member by the voltage applying unit.

10. The charge eliminating device according to claim 1, wherein: The relationship between the amount of electrified charge of the sheet and the detection result of the detection unit is changed according to at least one of the thickness of the sheet and the material of the sheet.

11. The charge eliminating device according to claim 1, wherein: The charge eliminating member is a roller pair composed of a roller member to which a voltage is applied by the voltage applying unit and an opposing roller which is electrically grounded and configured to nip and convey a sheet together with the roller member.

12. A charge elimination device, comprising: a charge eliminating member configured to eliminate charges of the sheet while pinching and conveying the sheet; a voltage applying unit configured to apply a voltage to the charge eliminating member; a detection unit configured to detect a voltage applied to the charge eliminating member or a current flowing through the charge eliminating member; as well as A controller configured to determine a value of a voltage to be applied by the voltage applying unit to the charge eliminating member in order to eliminate the charge of the sheet based on a detection result of the detection unit when the sheet passes through the charge eliminating member.

13. The charge eliminating device according to claim 12, wherein: The controller is capable of performing operations in a first mode in which the voltage applying unit applies a voltage to the charge eliminating member so as to eliminate the charge of the sheet, and in a second mode in which a value of the voltage to be applied to the charge eliminating member by the voltage applying unit in the first mode is determined based on a detection result of the detection unit.

14. The charge eliminating device according to claim 13, wherein: The detection unit detects a voltage applied to the charge eliminating member, and wherein the controller determines, in the second mode, a value of a voltage to be applied to the charge-eliminating member by the voltage applying unit in the first mode based on a voltage detected by the detecting unit when a sheet passes through the charge-eliminating member.

15. The charge eliminating device according to claim 14, wherein: The controller includes a memory portion configured to store information indicating a correspondence relationship between a voltage detected by the detection unit in the second mode and a value of a voltage to be applied to the charge eliminating member in the first mode.

16. The charge eliminating device according to claim 12, wherein: The charge eliminating member is a roller pair composed of a roller member to which a voltage is applied by the voltage applying unit and an opposing roller which is electrically grounded and configured to nip and convey a sheet together with the roller member.

17. An image forming system comprising: an image forming device configured to form an image on a sheet; as well as The charge-eliminating device according to claim 1, wherein the charge-eliminating device eliminates charges of a sheet on which an image is formed by the image forming device.

18. A charge adjustment device, comprising: a charge supply member configured to supply charge to the sheet while clamping and conveying the sheet; a voltage applying unit configured to apply a voltage to the charge supply member; a detection unit configured to detect a voltage applied to the charge supply member or a current flowing through the charge supply member; as well as A controller is configured to measure the amount of electrified charge of the sheet based on a detection result of the detection unit when the sheet passes through the charge supply member.

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