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

Abstract

The invention relates to a charge eliminating device, an image forming system, and a charge adjusting device. The charge eliminating device includes a charge eliminating member, a voltage applying unit, and a setting unit for setting a value of a voltage applied to the charge eliminating member by the voltage applying unit. The controller executes a changing process in which a value of a voltage to be output by the voltage applying unit is changed from a value of a voltage set by the setting unit during execution of a charge eliminating operation in which charges of a plurality of sheets are continuously eliminated by the charge eliminating member. A selection unit selects a first mode in which the change processing is performed during execution of the charge elimination operation or a second mode in which the change processing is performed during execution of the charge elimination operation. The change processing is not executed during execution of the charge cancellation operation and the voltage applying unit outputs a voltage based on the value set by the setting unit.

Description

Technical Field

[0001] The present invention relates to a charge eliminating device for eliminating the charge of a sheet, an image forming system for forming an image on a sheet, and a charge adjusting device for adjusting the charge of a sheet. Background Art

[0002] In Japanese Patent Application Laid-Open No. 2019-167169, a charge eliminating device provided with a contact type charge eliminating member in contact with a sheet, which is a charge eliminating roll, and a non-contact type charge eliminating device that does not contact the sheet, which is a corona tube type charge eliminator, is disclosed. In this document, it is disclosed that the charge eliminating voltage to be applied to the charge eliminating roll is determined based on the surface potential of the sheet actually measured by using a surface potentiometer (potential detector).

[0003] Since the work of measuring the surface potential of the sheet and adjusting the charge eliminating voltage may be cumbersome for the user, a function of automatically correcting the charge eliminating voltage during the execution of the operation has been considered. However, it can be assumed that there are cases where the user does not want the automatic correction of the charge eliminating voltage, or cases where the value of the automatically corrected charge eliminating voltage may deviate from the appropriate value. Summary of the Invention

[0004] An object of the present invention is to provide a charge eliminating device, an image forming system, and a charge adjusting device that can apply a voltage to a charge eliminating member in an appropriate manner.

[0005] According to an aspect of the present invention, there is provided a charge eliminating device including: a charge eliminating member configured to eliminate the charge of a sheet in contact with the sheet; a voltage applying unit configured to apply a voltage to the charge eliminating member; a setting unit configured to set a value of the voltage applied by the voltage applying unit to the charge eliminating member; a controller capable of performing a change process during the execution of a charge eliminating operation in which the charges of a plurality of sheets are continuously eliminated by the charge eliminating member, and in the change process, the voltage to be output by the voltage applying unit is changed from the voltage set by the setting unit; and a selection unit configured to select a first mode or a second mode, in the first mode, the change process is performed during the execution of the charge eliminating operation, and in the second mode, the change process is not performed during the execution of the charge eliminating operation and the voltage applying unit outputs a voltage based on the value set by the setting unit.

[0006] According to another aspect of the present invention, there is provided an image forming system including an image forming apparatus configured to form an image on a sheet, and a charge eliminating device configured to eliminate the charge of the sheet on which the image is formed by the image forming apparatus. The charge eliminating device includes: a charge eliminating member configured to eliminate the charge of the sheet in contact with the sheet; a voltage applying unit configured to apply a voltage to the charge eliminating member; a setting unit configured to set a value of the voltage applied by the voltage applying unit to the charge eliminating member; a controller capable of performing a change process during the execution of a charge eliminating operation in which the charges of a plurality of sheets are continuously eliminated by the charge eliminating member, and in the change process, the value of the voltage to be output by the voltage applying unit is changed from the value of the voltage set by the setting unit; and a selection unit configured to select a first mode or a second mode. In the first mode, the change process is performed during the execution of the charge eliminating operation, and in the second mode, the change process is not performed during the execution of the charge eliminating operation and the voltage applying unit outputs a voltage based on the value set by the setting unit.

[0007] According to another aspect of the present invention, there is provided a charge adjusting device including: a charge applying member configured to apply a charge to a sheet in contact with the sheet; a voltage applying unit configured to apply a voltage to the charge applying member; a setting unit configured to set a value of the voltage applied by the voltage applying unit to the charge applying member; a controller capable of performing a change process during the execution of a charge applying operation in which the charge applying member continuously applies charges to a plurality of sheets, and in the change process, the value of the voltage to be output by the voltage applying unit is changed from the value of the voltage set by the setting unit; and a selection unit configured to select a first mode or a second mode. In the first mode, the change process is performed during the execution of the charge applying operation, and in the second mode, the change process is not performed during the execution of the charge applying operation and the voltage applying unit outputs a voltage based on the value set by the setting unit.

[0008] Further features of the present invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic diagram of an image forming system according to Embodiment 1.

[0010] Figure 2Schematic diagram of the charge elimination device according to Embodiment 1.

[0011] Figure 3 Schematic diagram of the conveyance guide according to Embodiment 1.

[0012] Figure 4 Diagram illustrating the operation portion for charge elimination according to Embodiment 1.

[0013] Figure 5 Block diagram of the control system according to Embodiment 1.

[0014] Figure 6 Flowchart illustrating the control method (automatic adjustment) according to Embodiment 1.

[0015] Figure 7 Diagram illustrating an example of the transition of the charge elimination current and the charge elimination voltage in Embodiment 1.

[0016] Figure 8 Flowchart illustrating the control method (manual adjustment) according to Embodiment 1.

[0017] Figure 9 Explanatory diagram regarding the measurement of the surface potential of the sample sheet.

[0018] Figure 10 Diagrams including examples of screen displays of the operation portion according to Embodiment 1 in Part (a), Part (b), Part (c), and Part (d).

[0019] Figure 11 Explanatory diagram of the control corresponding to the environmental moisture amount in Embodiment 2.

[0020] Figure 12 Explanatory diagram of the control corresponding to the number of sheets continuously passing through in Embodiment 2.

[0021] Figure 13 Diagram illustrating an example of the screen display of the operation portion according to Embodiment 2. Detailed Description of the Invention

[0022] Hereinafter, embodiments according to the present disclosure will be described with reference to the accompanying drawings.

[0023] [Embodiment 1]

[0024] In Figure 1In this case, a schematic diagram of an image forming system 400 according to Embodiment 1 is illustrated. The image forming system 400 includes an image forming apparatus 100 (printer) and a charge eliminating device 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 (print product). As the sheet S (which is 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 to which a surface treatment is applied such as coated paper, sheet materials of special shapes such as envelopes and index paper, and sheet materials made of plastic, cloth, etc. Examples of the sheet material made of plastic include synthetic paper whose main raw material is a synthetic resin and a sheet for an overhead projector (OHT).

[0025] The charge eliminating device 300 is a device (static eliminator) having a charge eliminating function that eliminates (reduces) the charge of the sheet S discharged from the image forming system 400. The charge eliminating device 300 can be referred to as a charge adjusting device for adjusting the charged state of the sheet S discharged from the image forming system 400. The charge eliminating device 300 may have functions other than the charge eliminating function (for example, a de-curling function for correcting the curling of the sheet S). In addition, in the present embodiment, the charge eliminating device 300 is deployed as a device independent of the image forming apparatus 100. However, the charge eliminating device 300 may be incorporated in the housing of the image forming apparatus 100.

[0026] The image forming system 400 may include optional devices other than the charge eliminating device 300. Examples of the optional devices include a high-capacity feeding device (optional feeder) for feeding the sheet S to the image forming apparatus 100, and a sheet processing device (trimmer) for applying a process such as a binding process to the sheet S on which the image forming apparatus 100 forms an image.

[0027] <Image Forming Apparatus>

[0028] Figure 1 The schematic configuration of the image forming apparatus 100 is illustrated. The image forming apparatus 100 includes an image forming section 101, which is an intermediate transfer type electrophotographic mechanism. The image forming section 101 includes four processing units 11Y, 11M, 11C, and 11K, and a transfer unit 15. The four processing units 11Y, 11M, 11C, and 11K respectively include photosensitive drums 1Y, 1M, 1C, and 1K, and the transfer unit 15 includes an intermediate transfer belt 6 and a secondary transfer roller 9.

[0029] 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 portions that act on the photosensitive drum to perform each process in electrophotographic processing. 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.

[0030] Each of the photosensitive drums 1Y, 1M, 1C, and 1K is rotationally driven in a predetermined rotational 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.

[0031] The transfer unit 15 includes an intermediate transfer belt 6 as an intermediate transfer member, a secondary transfer roller 9 as a transfer portion (secondary transfer portion), 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 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 rotational 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 opposing roller 21 (secondary transfer opposing roller). A secondary transfer portion T2 as a transfer portion where the toner image is transferred to the sheet S is formed as a sandwiching portion between the secondary transfer roller 9 and the intermediate transfer belt 6.

[0032] An image forming apparatus 100 is provided with a transfer power source 10 which is a voltage application member for forming a bias electric field for transferring a toner image in a secondary transfer portion T2. In the present embodiment, a secondary transfer roller 9 (which is an 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, a counter roller 21 (which is an 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 the same polarity as the normal charging polarity of the toner is applied to the inner roller.

[0033] The image forming apparatus 100 further includes a storage portion 63 (storage device, cassette) for storing a sheet S, a feeding unit 64 for feeding the sheet S, and a registration roller 8 for performing registration (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 onto the sheet S, and a discharge roller pair 42 as a discharge unit for discharging the sheet S to the outside of the image forming apparatus 100.

[0034] The feeding unit 64 includes, for example, a pickup roller 65 for picking up the uppermost sheet S from the storage portion 63 in the feeding direction, and a separation roller pair 66 for conveying the picked-up sheet S while separating the sheets S one by one. The separation roller pair 66 includes a conveyance roller for conveying the uppermost sheet S in the sheet conveyance direction, and a separation roller that contacts the conveyance roller and forms a separation clamping portion together with the conveyance roller. The separation roller prevents sheets S other than the uppermost sheet S from passing through the separation clamping portion by applying a frictional force to the sheet S in the separation clamping portion, thereby preventing multiple sheets S from being conveyed. The separation roller is an example of a separation member for separating the sheet S, and for example, an elastic member (rubber gasket) having a gasket shape may be used as the separation member.

[0035] The fixing device 40 is a heat fixing type device, which 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 for heating 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 may be used. For the heat source, for example, a halogen lamp or an IH type induction heating mechanism may be used.

[0036] In addition, the image forming apparatus 100 is further provided with a user operation section 102, which is a user interface of the image forming system 400. The user operation section 102 includes a display unit 102a (such as a liquid crystal panel) for displaying information to the user and an input section (such as physical buttons and the touch panel function of the liquid crystal panel) for receiving inputs of information from the user. The user can set setting information and execution conditions of the image forming operation for the image forming system 400 by operating the user operation section 102. The setting information is attribute information of the sheet S accommodated in the accommodation section 63, such as, for example, size, material, and brand name. The execution conditions of the image forming operation include, for example, the value of the transfer voltage.

[0037] When an execution instruction for image formation is input from the user, the control section of the image forming apparatus 100 starts an image forming job, which is a series of tasks in which an image is formed on the sheet S while the sheet S is conveyed one by one and the product is output. Hereinafter, the series of operations for 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 for at least one sheet S.

[0038] In the 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.

[0039] 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 is attenuated, and the toner adheres to the exposed area during development.

[0040] The toner images formed in each of the processing units 11Y, 11M, 11C, and 11K are transferred from the photosensitive drums 1Y, 1M, 1C, and 1K to the intermediate transfer belt 6 at once 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.

[0041] In this embodiment, the primary transfer rollers 5Y, 5M, 5C, and 5K are conductive rollers, which include 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 foamed rubber. The ion-conductive foamed rubber is a foamed rubber material in which a conductive agent exhibiting ion conductivity is dispersed. For the conductive agent and the foamed rubber material, known materials for transfer rollers can be used. For each of the primary transfer rollers, for example, a roller with an outer diameter of from 15 to 20 mm and a resistance value of from 1×10 5 to 1×10 8 Ω can be suitably used when a voltage of 2 kV is applied under environmental conditions of 23°C and 50% RH.

[0042] The intermediate transfer belt 6 is rotationally driven at a predetermined circumferential speed (processing speed), which is equal to the circumferential speeds of the photosensitive drums 1Y, 1M, 1C, and 1K. In this embodiment, the circumferential speed is from 150 to 470 mm / sec. As the intermediate transfer belt 6 rotates, toner images of other colors are transferred onto the toner image transferred on the upstream side of the primary transfer portion, and 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 portion T2.

[0043] In parallel with the formation of the toner image in the image forming section 101, the feeding unit 64 feeds the sheets S one by one toward the image forming section 101. The fed sheet S is conveyed to the secondary transfer portion T2 by the registration roller 8 synchronously with the timing when the toner image on the intermediate transfer belt 6 is transferred to the secondary transfer portion T2. Then, the toner image is transferred (secondary transfer) from the intermediate transfer belt 6 to the sheet S in the secondary transfer portion T2.

[0044] In this embodiment, the secondary transfer roller 9 is a conductive roller, which includes 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 foamed rubber. The ion-conductive foamed rubber is a foamed rubber material in which a conductive agent exhibiting ion conductivity is dispersed. For the conductive agent and the foamed rubber material, known materials for transfer rollers can be used. For the secondary transfer roller 9, for example, a roller with an outer diameter of from 20 to 25 mm and a resistance value of from 1×10 5 to 1×10 8 Ω can be suitably used when a voltage of 2 kV is applied under environmental conditions of 23°C and 50% RH.

[0045] In addition, the counter roller 21 is a conductive roller, which includes 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. For the conductive agent and the foam rubber material, known materials used for transfer rollers can be used. For the counter roller 21, for example, a roller with an outer diameter of 20 to 22 mm and a resistance value of 1×10 5 to 1×10 8 Ω when a voltage of 50 V is applied under environmental conditions of 23°C and 50% RH can be appropriately used.

[0046] During the secondary transfer, through constant voltage control, 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. The transfer voltage is, for example, from +1 to +7 kV, and is automatically adjusted so that a current of +40 to +120 μA flows from the secondary transfer roller 9 to the counter roller 21. By applying the transfer voltage, a bias electric field is formed in the secondary transfer portion T2, where 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. Through 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 toner being transferred from the intermediate transfer belt 6 to the sheet S passing through the secondary transfer portion T2.

[0047] Incidentally, in front of the secondary transfer portion T2, a conveyance 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 without being transferred to the sheet S is collected by the belt cleaner 12 and reused for image formation.

[0048] The sheet S that has passed through the secondary transfer portion T2 is conveyed to the fixing device 40 by the pre-fixing conveyance device 41, and the fixing device 40 performs a fixing process on the toner image. The fixing process is a process in which the toner image on the sheet S is heated and pressed while the sheet S is held and conveyed in the holding portion of the fixing device 40. The pre-fixing conveyance device 41 conveys the sheet S while carrying it on, for example, an endless rubber belt. For the rubber belt, ethylene propylene diene monomer (EPDM) with a width of 100 to 110 mm and a thickness of 1 to 3 mm can be used. In addition, the rubber belt has holes with a diameter of 3 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.

[0049] The sheet S that has passed through the fixing device 40 is discharged toward the charge elimination device 300 by the discharge roller pair 42.

[0050] The above-described image forming section 101 of the intermediate transfer type is an example of an image forming member that forms an image on the sheet S, and the image forming member can be, for example, a direct transfer type electrophotographic unit. In this case, the toner image formed on the photosensitive drum as an image bearing member is directly transferred from the photosensitive drum to the sheet S in a transfer nip (transfer section) where the photosensitive drum and the transfer roller face each other. In the transfer nip, 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.

[0051] <Charge eliminating device>

[0052] Figure 2 is a schematic diagram of the charge eliminating device 300 in the first embodiment. In the present embodiment, the charge eliminating device 300 is connected to the downstream side of the image forming device 100. The charge eliminating device 300 performs charge elimination (reduction of static charges on the sheet surface) of the sheet S while receiving the sheet S on which an image has been formed by the image forming device 100 and conveying the sheet S in the sheet conveying direction Cv. That is, the charge eliminating device 300 performs a charge eliminating operation of continuously eliminating the charges of a plurality of sheets in an image forming operation of forming images on a plurality of sheets. By performing charge elimination of the sheet S, it becomes possible to prevent the sheets discharged and stacked from the image forming system 400 from sticking to each other due to electrostatic adsorption force, and to suppress the occurrence of deterioration in alignment of the sheets caused by sticking between the sheets. The charge eliminating device 300 is provided with a charge eliminating roller pair 51 as a contact type charge eliminator and an ionizer section 52 as a non-contact type charge eliminator.

[0053] The charge eliminating roller pair 51 includes a charge eliminating opposing roller 51a that contacts the first surface Sa of the sheet S and a charge eliminating roller 51b that contacts the second surface Sb opposite to the first surface Sa of the sheet S. The charge eliminating roller 51b is a contact type charge eliminating member that contacts the conveyed sheet S and eliminates the charge of the sheet S. The charge eliminating opposing roller 51a contacts the charge eliminating roller 51b, and forms a charge eliminating nip as a clamping portion between the charge eliminating roller 51b and the charge eliminating opposing roller 51a. The charge eliminating roller pair 51 performs charge elimination of the sheet S while clamping and conveying the sheet S in the charge eliminating nip.

[0054] The charge eliminating opposing roller 51a is connected to the ground potential GND. The charge eliminating opposing roller 51a is electrically connected to, for example, the metal frame of the charge eliminating device 300 and is electrically grounded. The charge eliminating roller 51b is connected to a high voltage power supply 55. The high voltage power supply 55 is a voltage applying component that applies a voltage (charge eliminating voltage) for performing charge elimination of the sheet S to the charge eliminating roller 51b.

[0055] Incidentally, it can be configured that the charge elimination roller 51b is deployed to contact the first surface Sa of the sheet S, and the charge elimination counter roller 51a is deployed to contact the second surface Sb of the sheet S. In that case, the voltage applied to the charge elimination roller 51b becomes the opposite polarity to the voltage applied to the charge elimination roller 51b in the present embodiment.

[0056] In the present embodiment, the charge elimination roller 51b 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 ion conductivity is dispersed. For the conductive agent and the foam rubber material, known materials can be used. For the charge elimination roller 51b, for example, a roller with an outer diameter of from 20 to 25 mm and a resistance value of from 1×10 5 to 1×10 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 roller 51a is made of stainless steel (SUS), and for the charge elimination counter roller 51a, a roller with an outer diameter of from 20 to 25 mm is used. Incidentally, for the charge elimination roller 51b, a roller made of a metal such as stainless steel can be used.

[0057] The ionizer section 52 includes a first ionizer 52a facing the first surface of the sheet S and a second ionizer 52b facing the second surface of the sheet S. Each of the first ionizer 52a and the second ionizer 52b includes electrode needles, and by applying a voltage to the electrode needles, corona discharge is generated from the tips of the needles, thereby ionizing the air around the tips of the needles. Then, the charges on the surface of the sheet S are neutralized by the generated ions, and the charges of the sheet S are eliminated.

[0058] As the ionizer section 52 in the present embodiment, rod-type ionizers IZS40 (manufactured by SMC Corporation) are deployed above and below the sheet conveying path as the first ionizer 52a and the second ionizer 52b. The conveying guides 53a and 53b forming the sheet conveying path in the ionizer section 52 are made of a resin synthesized from, for example, PC (polycarbonate) and ABS (acrylonitrile-butadiene-styrene). The volume resistivity of the conveying guides 53a and 53b is, for example, 1×10 14 Ωcm. In addition, as shown in Figure 3 , a plurality of holes 530 are formed in each of the conveying guides 53a and 53b so that the ions emitted from the first ionizer 52a and the second ionizer 52b are not physically blocked. The plurality of holes 530 are deployed side by side in the sheet width direction perpendicular to the sheet conveying direction Cv.

[0059] The above-described first ionizer 52a and second ionizer 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 scorotron type charge eliminator that eliminates the charge of a sheet by corona discharge from a discharge wire can be used. Further, the non-contact type charge eliminators are not necessarily provided on both sides of the conveyance path. For example, the charge elimination device 300 may be configured to include only the first ionizer 52a as a non-contact type charge eliminator. Further, when 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.

[0060] For the sheet S conveyed from the image forming apparatus 100 to the charge elimination device 300, first, most of its charge is removed (roughly 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.

[0061] In the secondary transfer section T2 ( Figure 1 ), generally, the sheet S is charged such that the first surface Sa of the sheet S that has contacted the intermediate transfer belt 6 becomes negative and the second surface Sb that has contacted the secondary transfer roller 9 becomes positive. 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, by applying a charge elimination voltage to the charge elimination roller 51b, a current flows through the sheet S in the charge elimination clamping portion, and the amount of charged electricity of the sheet S, which is the amount of charges carried on the first surface Sa and the second surface Sb of the sheet S, is reduced.

[0062] The sheet S that has passed through the charge elimination roller pair 51 is further charge-eliminated in the ionizer section 52. Specifically, by irradiating ions from the first ionizer 52a and the second ionizer 52b, the residual charges on the first surface Sa and the second surface Sb of the sheet S are neutralized, and the amount of charged electricity of the sheet S is further reduced. The sheet S that has passed through the ionizer section 52 is discharged to the outside of the charge elimination device 300.

[0063] Incidentally, the amount of charged electricity of the sheet S and the surface potential of the sheet S are generally proportional. Further, the amount of charged electricity of the sheet S can be expressed as the amount of charges per unit area of the sheet surface (surface charge density). Therefore, the "amount of charged electricity" 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.

[0064] <Charge elimination voltage adjustment switch>

[0065] The charge elimination device 300 is provided with an operation part 54 for charge elimination, and the operation part 54 for charge elimination can perform an operation of changing the operation conditions of the charge elimination device 300. In Figure 4 FIG., an enlarged view of the operation part 54 for charge elimination is illustrated. The operation part 54 for charge elimination is an example of an input part for a user to input a value of the voltage to be applied by a high voltage power supply 55 (voltage application part) to a charge elimination roller 51b (charge elimination member).

[0066] The operation part 54 for charge elimination includes a change-over switch 54a and a voltage adjustment switch 54b. By operating the change-over 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 ) that 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.

[0067] The value of the charge elimination voltage can be fixed at a value preset according to the category of the sheet S. For example, in the case of a plastic film or synthetic paper, it is known that those sheets are likely to be more strongly dielectrically polarized in the secondary transfer part than ordinary paper and the amount of electric charge of the sheet S becomes larger. Therefore, in the case of using a plastic film or synthetic paper as the sheet S, it can be considered to preset the value of the charge elimination voltage according to the category of the sheet S so that the charge elimination voltage is a voltage higher (so that its absolute value is larger) than the case of using ordinary paper as the sheet S. However, even for sheets S in the same category, due to differences in resistance, thickness, and usage environment caused by differences in specific materials, there are cases where the appropriate value of the charge elimination voltage fluctuates. Therefore, in the present embodiment, it is configured that the value of the charge elimination voltage is adjustable.

[0068] The voltage adjustment switch 54b in the present embodiment includes a display part 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 digit in the corresponding place increases, and when the - button is pressed, the digit in the corresponding place decreases.

[0069] The value displayed in the display section is the value obtained by displaying the absolute value of the charge elimination voltage in two digits with a unit of 0.1 kV. That is, the set value of the charge elimination voltage is 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. 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.

[0070] Incidentally, when the display is set to "00" by the voltage adjustment switch 54b, the set value of the charge elimination voltage becomes 0 V (0.0 kV). In this case, the state of the high voltage power supply 55 becomes the same state as when the changeover switch 54a is turned off. This state can also be referred to as a state where the high voltage power supply 55 applies 0 V to the charge elimination roller 51b.

[0071] Incidentally, the display type and input type of the value of the charge elimination voltage are not limited to the above types. 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 numerical value indicating the level of the charge elimination voltage (e.g., in 10 levels) may be displayed. The value of the charge elimination voltage may be displayed, for example, on the screen of the user operation section 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 numerical input may be provided to the operation section 54 for charge elimination, or input may be made by touch panel operation of the user operation section 102, or it may be configured to receive input via an external computer. The user operation section 102 that can display a screen for inputting the charge elimination voltage is another example of an input component for the user to input the value of the charge elimination voltage to be applied by the high voltage power supply 55 (voltage application component) to the charge elimination roller 51b (charge elimination member).

[0072] <Factors causing appropriate fluctuations in the charge elimination voltage>

[0073] Incidentally, when a voltage is continuously applied to the charge elimination roller 51b, the resistance value of the charge elimination roller 51b changes. For example, as in this embodiment, when a conductive roller containing an ion conductive agent is used as the charge elimination roller 51b, the distribution of the conductive agent in the roller deviates due to continuous energization, and the resistance value changes. In this case, if the set value of the charge elimination voltage set via the operation section 54 for charge elimination in the state before the resistance value of the charge elimination roller 51b changes is continued to be used, there is a possibility that the charge elimination roller 51b cannot properly eliminate the charge of the sheet S. That is, due to the change in the resistance value of the charge elimination roller 51b, the charge application (supply) ability from the charge elimination roller 51b to the sheet S is affected, so there will be an excess or deficiency in the amount of charge actually supplied to the sheet S compared to the amount of charge required to eliminate the charge of the sheet S.

[0074] In addition, due to the environmental conditions (especially temperature and humidity) of the environment in which the charge elimination device 300 is installed, the value of the transfer voltage applied in the secondary transfer section T2 and / or the resistance value of the sheet S (the possibility of charge accumulation on the sheet surface) also change. Therefore, there will be an excess or deficiency in the amount of charge actually supplied to the sheet S compared to the amount of charge required to eliminate the charge of the sheet S.

[0075] <Automatic correction of charge elimination voltage>

[0076] In this embodiment, in order to cope with the possibility of excess or deficiency in the charge elimination ability of the charge elimination roller 51b due to the above factors, a function (automatic correction function) that performs feedback control is provided, which automatically corrects the charge elimination voltage during the execution of the operation.

[0077] In Figure 5 FIG., a block diagram of the control circuit 200 related to the control of the charge elimination voltage is illustrated. The control circuit 200 is an example of a control component that controls the operation of the charge elimination device 300. The control circuit 200 can be installed in the main component of the charge elimination device 300, or a part or all of the control circuit 200 can be installed in the image forming device 100.

[0078] As Figure 5As 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 work area when the CPU 201 executes the control program. The ROM 220 is an example of a memory part that memorizes 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 a user operation part 102, an operation part 54 for charge elimination, a high-voltage power supply 55, and a transfer power supply 10. Inside the high-voltage power supply 55, a current detection circuit 55a for detecting the current supplied from the high-voltage power supply 55 to the charge elimination roller 51b is provided. The current detection circuit 55a serves as a current detection component for detecting the current flowing through the charge elimination roller 51b (charge elimination member).

[0079] The CPU 201 acquires information such as information related to an image formation job (job information), a set value of the charge elimination voltage, a value of the current flowing through the charge elimination roller 51b when the charge elimination voltage is applied (referred to as the charge elimination current), and a value of the transfer voltage output by the transfer power supply 10, and memorizes 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 part 102 and used for the current image formation job. The set value of the charge elimination voltage is a value set by the user through the operation of the operation part 54 for charge elimination. The value of the charge elimination current is a value detected by the current detection circuit 55a. In the case of the period when the sheet S is passing through the charge elimination clamping part (during paper 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. The CPU 201 calculates a corrected charge elimination voltage based on the information stored in the RAM 210 and the control conditions described below and stored in the ROM 220, and performs feedback control that controls the output of the high-voltage power supply 55 based on the corrected charge elimination voltage.

[0080] In addition, the control circuit 200 is connected to an environment sensor 13 for detecting the environmental conditions of the installation environment (the space around the installed device) of the charge elimination device 300 (image formation system 400). The control using the environment sensor 13 will be described in Embodiment 2. In addition, in the ROM 220, control parameters for controlling the charge elimination voltage and various types of tables are stored.

[0081] will be described according to Figure 6 the flowchart in the figure describes the control process of the charge elimination voltage executed by the control circuit 200. Hereinafter, unless otherwise specified, the execution subject of each process in this flow is the CPU 201.

[0082] When an image formation job is input to the image forming system 400, the processing of this flow starts. First, the CPU 201 checks that the method of setting the charge elimination voltage is any one of three modes (automatic correction, manual setting, media setting) that the image forming apparatus 100 of this embodiment can execute (S0).

[0083] The automatic correction mode is an example of the first mode in which the value of the voltage output from the high voltage power supply 55 (voltage application component) automatically changes during the execution of the job. Both the manual setting mode and the media setting mode are examples of the second mode in which the value of the voltage output from the high voltage power supply 55 (voltage application component) does not automatically change during the execution of the job, but outputs a voltage based on the value input through the operation section 54 for charge elimination or the user operation section 102 (input component).

[0084] As described above, in this embodiment, as the second mode, two control modes are prepared: a control mode (manual setting mode) in which the charge elimination voltage is determined regardless of the type of sheet, and a control mode (media setting mode) in which the charge elimination voltage is determined based on the type of sheet. However, it is not limited thereto, and it may be configured such that the control circuit 200 can execute one of a plurality of control modes including at least one of the manual setting mode and the media setting mode.

[0085] (Manual setting mode)

[0086] In the case of the manual setting mode, the CPU 201 acquires the set value of the charge elimination voltage previously adjusted by the user (Sa1). An example of the adjustment process of the charge elimination voltage by the user will be described below, and it is assumed here that the adjusted set value is previously stored in a memory unit such as the RAM 210. In the manual setting mode, regardless of the type of sheet used for the job, the value of the charge elimination voltage set through the operation section 54 for charge elimination before the start of the job is applied. The CPU 201 causes the high voltage power supply 55 to output the charge elimination voltage with the set value acquired in Sa1, and causes the charge elimination roller 51b to eliminate the charge of the sheet S (Sa2).

[0087] In addition, the set value of the charge elimination voltage can be changed during the execution of the job. That is, during the execution of a job (continuous printing job) of continuously forming an image on a plurality of sheets S, when the user changes the set value of the charge elimination voltage by operating the voltage adjustment switch 54b of the operation section 54 for charge elimination or when the user switches the ON / OFF of the transfer switch 54a, the CPU 201 continues the job based on the changed setting. In other words, in the manual setting mode which is an example of the second mode, when the operation section 54 (input component) for charge elimination is operated after the start of the job, the CPU 201 changes the value of the voltage to be output by the high voltage power supply 55 (voltage application component) from the value input through the operation section 54 before the start of the job to the value input through the operation section 54 after the start of the job.

[0088] In Sa3, the CPU 201 determines whether the current sheet S is the last sheet in the image forming job, and if the current sheet S is not the last sheet (Sa3N), the CPU 201 returns the process to Sa1 and repeats the same process for the subsequent sheets S. If the current sheet S is the last sheet (Sa3Y), the CPU 201 ends the process.

[0089] (Media setting mode)

[0090] In the case of the media setting mode, the CPU 201 acquires job information and checks the type of the sheet S to be used for the current job (Sb1). Then, the CPU 201 acquires the set value of the charge elimination voltage corresponding to the sheet S to be used for the current job from the set information (media information) set in advance for each type of sheet (Sb2). The setting of the media information by the user will be described below, and here, it is assumed that the media information for each type of sheet (which includes the set value of the charge elimination voltage) is stored in the RAM 210 in advance. The RAM 210 is an example of a memory unit that memorizes the value of the voltage preset for each type of sheet by the user operation section 102 (input component). The CPU 201 causes the high voltage power supply 55 to output the charge elimination voltage at the set value acquired in Sb2, and causes the charge elimination roller 51b to eliminate the charge of the sheet S (Sb3). In other words, in the media setting mode which is an example of the second mode, the CPU 201 determines the value of the voltage to be output by the high voltage power supply 55 (voltage application device) based on the type of the sheet used in the job by referring to the information memorized in the memory unit.

[0091] In Sb4, the CPU 201 determines whether the current sheet S is the last sheet in the image forming job, and if the current sheet S is not the last sheet (Sb4N), then the CPU 201 returns the process to Sb3 and repeats the same process for the subsequent sheets S. If the current sheet S is the last sheet (Sb4Y), then the CPU 201 ends the process.

[0092] (Auto - correction mode)

[0093] In the case of the auto - correction mode, the CPU 201 changes the charge elimination voltage based on the detection result of the current detection circuit 55a when the sheet S passes through the charge elimination clamping portion (change process). In other words, in the auto - correction mode (the first mode), the CPU 201 changes the value of the voltage to be output by the high - voltage power supply 55 (voltage application component) based on the detection result of the current detection circuit 55a (current detection component) when the sheet S passes through the charge elimination roller 51b. Hereinafter, the specific control mode of the auto - correction mode in the present embodiment will be described.

[0094] First, the CPU 201 acquires job information (Sc1). In the image forming apparatus 100, the image forming operation starts based on the job information. On the other hand, to prepare for the charge elimination process in the charge elimination apparatus 300, the CPU 201 acquires the set value of the charge elimination voltage (Sc2). The set value of the charge elimination voltage acquired in Sc2 is, for example, a value pre - input by the user through the operation portion 54 (voltage adjustment switch 54b) for charge elimination. The CPU 201 determines the set value of the charge elimination voltage acquired in Sc2 as the value of the charge elimination voltage (initial charge elimination voltage) to be output by the high - voltage power supply 55 during the period immediately after the start of the image forming job (Sc3).

[0095] Hereinafter, the current value detected by the current detection circuit 55a from when the leading end of the sheet S enters the charge elimination clamping portion in the sheet conveyance direction Cv until the trailing end of the sheet S leaves the charge elimination clamping portion is referred to as the charge elimination current during the paper passing period of the sheet S. For the first few sheets S in an image forming operation, by applying an initial charge elimination voltage (a predetermined voltage value) to the charge elimination roller 51b, it is considered that the charge elimination current during the paper passing period becomes a value that can appropriately eliminate the charge of the sheet S. However, for example, during the execution of an image forming operation for outputting a very large number of sheets S, due to fluctuations in the resistance of the charge elimination roller 51b caused by the above reasons, there is a possibility that the charge of the sheet S cannot be appropriately eliminated. In the present embodiment, although the ionizer portion 52 disposed downstream of the charge elimination roller 51b also performs charge elimination, the amount of charged charge that the ionizer portion 52 can eliminate is less than the amount of charged charge of the charge elimination roller 51b. Therefore, when the charge elimination roller 51b cannot appropriately eliminate the charge of the sheet S, there is a possibility that the charge of the sheet S cannot be appropriately eliminated before the sheet S is discharged from the charge elimination device 300.

[0096] Therefore, in the present embodiment, the following control is performed: in this control, the measured value of the charge elimination current for the first predetermined number N of sheets in an image forming operation is memorized as the initial charge elimination current, and the value of the charge elimination voltage thereafter is corrected based on the initial charge elimination current.

[0097] The number of sheets S for measuring the initial charge elimination current (the predetermined number N of sheets) is preferably configured to be two or more in order to reduce the influence of variations in each sheet S. In the present embodiment, the predetermined number N of sheets is set to three, however, it can be set to a number other than three.

[0098] The CPU 201 acquires the charge elimination current (Sc4) during the paper passing period of each of the sheets S while counting which sheet the current sheet S conveyed to the charge elimination device 300 is among the sheets (where the sheet S first conveyed to the charge elimination device 300 from the start of the image forming operation is the first sheet). Then, if the current sheet S corresponds to the predetermined number of sheets from the start of the operation (Sc5Y), the initial charge elimination current I0 is calculated based on the values of the charge elimination currents of the sheets S from the first sheet to the predetermined number of sheets (Sc6). In the present embodiment, the average value of the values of the charge elimination currents of the sheets S from the first sheet to the predetermined number of sheets is defined as the initial charge elimination current I0.

[0099] The initial charge elimination current I0 is the target value (target current value) of the charge elimination current (controlled variable, control amount) during the execution of an image forming operation. That is, in the present embodiment, based on the detection result of the current detection circuit 55a when the sheet S passes through the charge elimination roller 51b (charge elimination member) in a state where a voltage is applied to the charge elimination roller 51b at a predetermined voltage value by the high voltage power supply 55 after the start of the operation, the target value of the charge elimination current is determined.

[0100] Furthermore, after calculating the initial charge elimination current I0, the CPU 201 calculates a threshold Ith (Sc7) for determining whether to perform correction of the charge elimination voltage. The threshold Ith is a quantity (unit: μA) that defines the degree to which the charge elimination current during the passage of the paper deviates from the initial charge elimination current I0 when performing correction of the charge elimination voltage.

[0101] In the present embodiment, the value of the threshold Ith is determined by the following method. The set value of the charge elimination voltage set via the operation section 54 for charge elimination is defined as V0 (kV). The initial charge elimination current is defined as I0. When the unit digit value in the voltage adjustment switch 54b changes by one, the variable step of the charge elimination voltage is defined as ΔV (kV). In this case, the threshold Ith is calculated by the following equation.

[0102] Ith = |I0 / V0 × ΔV|

[0103] In other words, the threshold Ith in the present embodiment is defined as the absolute value of the value calculated by multiplying the value (calculated by dividing the initial charge elimination current I0 by the set value V0 of the charge elimination voltage) by the variable step ΔV of the charge elimination voltage corresponding to the minimum adjustment unit of the voltage adjustment switch 54b. For example, when the initial charge elimination current I0 is -40 μA, the set value V0 of the initial charge elimination voltage is -4.0 kV, and the variable step ΔV of the charge elimination voltage is -0.1 kV, the threshold Ith is 1.0 μA.

[0104] In the case where the current sheet S is a sheet after a predetermined number of sheets from the start of the operation, the CPU 201 acquires the charge elimination current I(Sc8) during the sheet passing period of the current sheet S. Then, the CPU 201 compares the absolute value of the difference between the charge elimination current I during the sheet passing period and the initial charge elimination current I0 with the above-mentioned threshold Ith (Sc9). If the absolute value of the difference between I and I0 is greater than the threshold Ith (Sc9Y), then the CPU 201 determines that the value of the charge elimination voltage needs to be corrected, and corrects the value of the charge elimination voltage so that the charge elimination current is closer to the target value (I0) (Sc10). If the absolute value of the difference between I and I0 is the threshold Ith or less (Sc9N), then the CPU 201 determines that the value of the charge elimination voltage does not need to be corrected and maintains the value of the charge elimination voltage.

[0105] For example, consider the case where the initial charge elimination current I0 is -40 μA, the set value V0 of the initial voltage is -4.0 kV, the variable step ΔV of the charge elimination voltage is -0.1 kV, and the threshold Ith is 1.0 μA. In this case, if the charge elimination current I during the sheet passing period of the current sheet S is a value less than -41 μA or greater than -39 μA, then correction of the charge elimination voltage is performed (Sc10). Assume the case where the charge elimination current I in the fourth sheet S is -42 μA. The absolute value of the difference from the initial charge elimination current I0 is 2 (μA), which is greater than the threshold Ith. Therefore, the charge elimination voltage is corrected so that the absolute value of the charge elimination current becomes smaller. The correction step of the charge elimination voltage is defined as, for example, the variable step ΔV of the charge elimination voltage corresponding to the minimum adjustment unit of the voltage adjustment switch 54b. That is, the value of the charge elimination voltage to be applied to the charge elimination roller 51b by the high voltage power supply 55 is corrected from -4.0 kV, which is the set value V0 of the initial voltage, to -3.9 kV, which is a voltage only 0.1 kV lower.

[0106] Incidentally, in the present embodiment, regardless of the magnitude of the absolute value of the difference between the detected charge elimination current I and the initial charge elimination current I0, the correction step of the charge elimination voltage is configured as a fixed value (0.1 kV). However, the correction step may vary depending on the absolute value of the difference between I and I0.

[0107] Thereafter, the CPU 201 determines whether the current sheet S is the last sheet in the image forming operation. If the current sheet S is not the last sheet (Sc11N), then the CPU 201 returns the process to Sc8 and repeats the same process for the subsequent sheets S. If the current sheet S is the last sheet (Sc11N), then the CPU 201 ends the process.

[0108] (Example of the transition of the charge elimination voltage and the charge elimination current)

[0109] In Figure 7 , an example of the transition of the charge elimination voltage and the charge elimination current in the case where the above control is executed is illustrated. For the first few sheets S immediately after the start of the image forming operation, an initial charge elimination voltage is applied at a set value V0 of the charge elimination voltage, and the charge elimination current during the passage of the sheet is the initial charge elimination current I0. However, as time passes, the value of the charge elimination current deviates from the initial charge elimination current I0.

[0110] In Figure 7 the example in, for the m-th sheet S from the start of the operation, the absolute value of the charge elimination current Im during the passage of the sheet is greater than the absolute value of the initial charge elimination current I0, and the difference therebetween is greater than the threshold Ith. In this case, after the m-th sheet S leaves the charge elimination nip and before the (m + 1)-th sheet S enters the charge elimination nip, correction of the charge elimination voltage ( Figure 6 Sc10 in) is performed. The charge elimination voltage is corrected so that the charge elimination current becomes closer to the initial charge elimination current I0, that is, in this case, corrected to a voltage value lower than the initial charge elimination voltage (V0) so that the absolute value of the charge elimination current becomes smaller. As a result, the charge elimination current I_(m + 1) of the (m + 1)-th sheet S becomes a value closer to the initial charge elimination current I0.

[0111] In the present embodiment, correction of the charge elimination voltage is performed based on a comparison between the detection result of the charge elimination current during the passage of the sheet and the target value of the charge elimination current during the passage of the sheet. This is because, by using the charge elimination current during the passage of the sheet, it becomes possible to uniquely determine the current value for appropriately eliminating the charge of the charged sheet S. The magnitude of the current flowing through the charge elimination nip when the sheet S does not pass through the charge elimination nip (during no-sheet passage) does not take into account the electromotive force caused by the charge of the sheet S. Therefore, particularly in the case of using a sheet S having a high resistance such as a plastic film or synthetic paper, it may be difficult to appropriately correct the charge elimination voltage. On the contrary, by performing feedback control based on the detection result of the charge elimination current during the passage of the sheet, it becomes possible to correct the charge elimination voltage depending on the resistance value of the charge elimination roller 51b and the charged amount of the sheet S.

[0112] In this manner, in the automatic correction mode, based on the detection result of the charge elimination current when the previous sheet in the job passes through the charge elimination nip, feedback control is performed, and this feedback control changes the set value of the charge elimination voltage for the subsequent sheet passing through the charge elimination nip after the previous sheet. As a result, in a continuous printing job, it becomes possible to maintain the magnitude of the charge elimination voltage at an appropriate value and make it less likely for adhesion between sheets to occur.

[0113] In addition, through the automatic correction mode, compared with the case where the user manually performs the adjustment work of the charge elimination voltage, it becomes possible to reduce the work burden on the user.

[0114] <Manual setting of charge elimination voltage>

[0115] In the manual setting mode, an example of a method for the user to manually set the set value of the charge elimination voltage will be described. In the manual setting mode, the user inputs the set value of the charge elimination voltage into the charge elimination device 300 by operating the user operation unit 102 or the operation unit 54 for charge elimination, and the control circuit 200 causes the high-voltage power supply 55 to output the charge elimination voltage based on the input set value.

[0116] Manually adjusting the charge elimination voltage has the following advantages, for example. First, fine adjustment corresponding to various types of media can be performed. When the value of the charge elimination voltage set in the automatic correction mode is expected to deviate from the appropriate value, such as when using sheets S made of multiple materials with different properties (such as label sheets and laminated sheets) and sheets S with different physical properties on their front and back surfaces, the manual setting mode can appropriately handle those situations. In addition, due to the content of the image to be formed on the sheet S (for example, in the case where an extreme image such as pure coloring on the entire surface of the sheet persists), the value of the charge elimination voltage set in the automatic correction mode is expected to deviate from the appropriate value. However, the manual setting mode can also appropriately handle such a situation.

[0117] Second, the manual setting mode can handle the situation where the target value (intended use of the product) of the output result varies depending on the user. The general advantage of performing charge elimination on the sheet S is to prevent the sheets S from sticking to each other and facilitate the handling of the sheets S in subsequent post-processing. On the other hand, charge elimination of the sheet S also has the advantage, for example, of making it easier to turn the pages of the final product after the sheets S are bound into a book and reducing the peeling sound. Depending on the intended use of the sheet S as a product, there are cases where the way of performing charge elimination on the sheet S should be different. In such a case, with the manual setting mode, the user can adjust the charge elimination voltage depending on the intended use.

[0118] Figure 8This is a flowchart showing the method for setting the charge elimination voltage in the manual setting mode. Incidentally, this flowchart is only an example, and in practice, a method determined by each user can be executed, and the criteria and timing for determining the values are not limited to those shown in the figure.

[0119] First, in S201, sample output is executed. This can be executed by an instruction for executing a mode (adjustment mode) for causing the image forming system 400 to output a sheet S for adjustment as a sample, or by extracting a part of the sheet S discharged as a product during the execution of a normal operation as a sample. In addition, on the conveyance path of the sheet S in the image forming system 400, a measurement section for measuring the surface potential of the sheet S can be provided.

[0120] In S202, the surface potential of the sample sheet S is measured. For the measurement of the surface potential, for example, the measurement device (surface potentiometer) shown in Figure 9 is used. In this case, the sheet S is placed on a ground plate 71 to be used as a reference, and by measuring the surface potential of the opposing section 72, the potential difference between the front and back surfaces of the sheet S is measured.

[0121] Here, the threshold value of the potential difference between the front and back surfaces that satisfies the quality of the product is defined as Vs. In the measurement result in S202, if the potential of the first surface Sa is +Vs or more with respect to the potential of the second surface Sb ( Figure 2 ), it is determined that the charge elimination voltage is excessive (S203Y), and the set value of the charge elimination voltage is decreased (S204). That is, by operating the user operation section 102 or the operation section 54 for charge elimination, as the set value of the charge elimination voltage, the user inputs a value whose absolute value is smaller than the absolute value of the current set value. Then, sample output is executed again (S205), and the process returns to S202 to perform measurement.

[0122] Conversely, in the measurement result in S202, if the potential of the first surface Sa is -Vs or less with respect to the potential of the second surface Sb ( Figure 2 ), it is determined that the charge elimination voltage is insufficient (S206Y), and the set value of the charge elimination voltage is increased (S207). That is, by operating the user operation section 102 or the operation section 54 for charge elimination, as the set value of the charge elimination voltage, the user inputs a value whose absolute value is larger than the absolute value of the current set value. Then, sample output is executed again (S208), and the process returns to S202 to perform measurement.

[0123] In the measurement results in S202, repeat the adjustment as described above until the potential difference between the front and the back is within the range of ±Vs, and if the potential difference between the front and the back is within this range (S203N, S206N), then the adjustment is completed (S209).

[0124] <Selection of Charge Elimination Voltage Setting Mode>

[0125] Using Figure 10 Parts (a) to (d) of, the configuration that allows the user to select the charge elimination voltage setting mode will be described. Figure 10 Parts (a) to (d) of are examples of the screens displayed on the display unit 102a ( Figure 1 ) of the user operation section 102.

[0126] Figure 10 The screen of part (a) is displayed, for example, by opening the setting screen (user mode) of the function of the setting image forming system 400 from the state where the main screen is displayed on the display unit 102a and further selecting an item related to the adjustment of the charge elimination voltage. In the present embodiment, by pressing Figure 10 any one of the buttons B1 to B3 shown in the screen of part (a) of, the user can selectively set the charge elimination voltage setting method from the automatic correction mode, the manual setting mode, or the medium setting mode. When the button B1 of "Adjustment Switch" is pressed, the manual setting mode is selected. When the button B2 of "Medium Setting" is pressed, the medium setting mode is selected. When the button B3 of "Automatic Correction" is pressed, the automatic correction mode is selected.

[0127] In this way, the display unit 102a that displays the screen allowing the user to select the charge elimination voltage setting method is an example of a selection component for the user to select the mode executed by the multi-mode selection control circuit 200 (control component).

[0128] In the case of selecting the manual setting mode ( Figure 10 part (b) of), as the set value of the charge elimination voltage, for example, use the value of the charge elimination voltage adjusted according to the aforementioned flowchart ( Figure 8 ) ( Figure 6 Sa1 to Sa3 in). In the flowchart in Figure 8 , the charge elimination voltage is adjusted based on the potential difference between the front and the back of the sheet S measured by the surface potentiometer. However, for example, the user can check the degree of adhesion between the sheets S by touching with his or her hand, and gradually adjust the value of the charge elimination voltage so that the adhesion force becomes smaller.

[0129] One advantage of the manual setting mode is that the user can easily track the set value of the charge elimination voltage. When the environment where the image forming system 400 is installed and the environmental conditions for job execution are stable and the content of the job is regular, by fixing the set value of the charge elimination voltage, it becomes possible to reduce the occurrence of problems caused by the unintentional deviation of the charge elimination voltage from the appropriate value.

[0130] Incidentally, in the manual setting mode, the set value of the charge elimination voltage can be changed dynamically (i.e., during job execution). For example, during the execution of a continuous printing job, a sheet S can be taken out as a sample and measured by a surface potentiometer, and the set value of the charge elimination voltage can be changed based on the measurement result or the output / stop output of the charge elimination voltage can be switched. In addition, according to the timing of switching the operation mode of the image forming system 400 during the job, a change in the set value of the charge elimination voltage, etc., can be performed.

[0131] In the case of selecting the medium setting mode ( Figure 10 part (c)), in the setting screen for performing the setting for each type of sheet, the user can input the set value of the charge elimination voltage, the basis weight, and the surface properties of the sheet S, and the input values are reflected when the job is executed ( Figure 6 Sb1 to Sb4 in). In this case, for example, for each type of sheet, by pre-calculating and setting the appropriate value of the charge elimination voltage according to the flowchart in Figure 9 , appropriate charge elimination can be performed even when the same type of sheet S is used over multiple days.

[0132] In the case of selecting the automatic correction mode ( Figure 10 part (d)), as described above, the set value of the charge elimination voltage is automatically determined by feedback control based on the detection result of the charge elimination current during the passage of the paper ( Figure 6 Sc1 to Sc11 in). The advantage of this mode is that it can reduce the burden on the user when adjusting the charge elimination voltage. In addition, except for the sheet S for the product, there is no need to output the sheet S for the sample, and it becomes possible to automatically correct the charge elimination voltage in response to fluctuations in environmental conditions, etc. Therefore, there are cases where the automatic correction mode is suitable, for example, when using the same type of synthetic paper (sheet with high resistance) and performing a continuous printing job over a long period of time.

[0133] (Example of modification)

[0134] In the present embodiment, as a method for setting the charge elimination voltage, a configuration of three modes in which an automatic correction mode, a manual setting mode, and a medium setting mode can be selected is exemplified. However, the present invention is not limited thereto, and the charge elimination device 300 and the image forming system 400 may have a configuration in which only two of the above three modes can be selected as the method for setting the charge elimination voltage. For example, the charge elimination device 300 and the image forming system 400 may have a configuration in which either the automatic correction mode or the manual setting mode is selected as the method for setting the charge elimination voltage. Further, the charge elimination device 300 and the image forming system 400 may have a configuration in which one mode can be selected from one or more of the above three modes and modes other than the above three modes as the method for setting the charge elimination voltage.

[0135] In addition, in the present embodiment, only when Figure 10 the button B3 of "automatic correction" is selected on the screen in part (a) of Figure 10 the function of automatically correcting the charge elimination voltage by the charge elimination device 300 during operation (automatic correction function of the charge elimination voltage) is enabled. When

[0136] other buttons B1 and B2 are selected on the screen in part (a) of

[0137] the automatic correction function of the charge elimination voltage is disabled. In other words, by operating to select the mode of the method for setting the charge elimination voltage, the enabling / disabling of the automatic correction function of the charge elimination voltage is performed. However, the present invention is not limited thereto. For example, on the display unit 102a of the user operation unit 102, a screen including a table (checkbox, button, etc.) may be displayed, and the enabling / disabling of the automatic correction function of the charge elimination voltage can be switched by the table (checkbox, button, etc.). In this case, for example, when a checkmark is entered in the checkbox, the automatic correction mode is set, and when the checkbox is not checked, the manual setting mode or the medium setting mode is set according to the user's selection. Further, the state in which a checkmark is entered in the checkbox (the state in which the automatic correction function is enabled) corresponds to the state in which the first mode is selected, and the state in which the checkbox is not checked (the state in which the automatic correction function is disabled) corresponds to the state in which the second mode is selected.

[0136] The user operation unit 102 configured to allow the user to select the mode of the method for setting the charge elimination voltage via the screen display is an example of a selection component, and the selection component is not limited thereto. For example, it may be configured that by operating an external computer communicably connected to the image forming system 400, the mode of the method for setting the charge elimination voltage can be changed. In this case, the control circuit 200 configured to receive an instruction related to mode selection from the external computer serves as the selection component.

[0137] In addition, in the automatic correction mode, by passing a test sheet S different from the sheet S to be the product, and based on the detection result of the current or voltage when the test sheet S passes through the charge elimination clamping portion, the set value of the charge elimination voltage obtained at the start of the operation can be automatically obtained ( Figure 6 Sc2 in). For example, after forming a test image on the test sheet S by an operation similar to the normal image forming operation, while controlling the voltage application to the charge elimination roller 51b by constant current control, the change in the voltage applied to the charge elimination roller 51b when the test sheet S passes through the charge elimination clamping portion is measured. Since the charge on the surface of the sheet S acts as an electromotive force in the charge elimination clamping portion, the amount of charged charge of the sheet S can be observed as the change in the applied voltage. And based on the relationship between the change amount of the applied voltage and the amount of charged charge and the relationship between the amount of charged charge and the appropriate value of the charge elimination voltage, which are predetermined and stored in the ROM 220, the set value of the charge elimination voltage is determined.

[0138] [Embodiment 2]

[0139] Hereinafter, Embodiment 2 will be described. The charge elimination device 300 in the present embodiment is provided with a function of automatically correcting the charge elimination voltage in a control mode different from the automatic correction mode in Embodiment 1. Hereinafter, unless otherwise described, elements having the same reference numerals as those in Embodiment 1 are considered to provide substantially the same configuration and function as those described in Embodiment 1, and the parts different from Embodiment 1 will be mainly described.

[0140] As described below, in the present embodiment, as the modes for performing automatic correction of the charge elimination voltage, three modes of a current detection mode, a number-of-sheets-passed mode, and an environmental condition mode can be selected. The current detection mode, the number-of-sheets-passed mode, and the environmental condition mode are all examples of the first mode, which automatically changes the value of the voltage to be output by the high-voltage power supply 55 (voltage application component) during the execution of the operation.

[0141] As described above, in the present embodiment, as the first mode, three control modes of a current detection mode, a number-of-sheets-passed mode, and an environmental condition mode are provided. However, it is not limited thereto, and the control circuit 200 can be configured to be able to execute one of a plurality of control modes including at least one of the current detection mode, the number-of-sheets-passed mode, and the environmental condition mode.

[0142] In addition to the manual setting mode and the medium setting mode in Embodiment 1, the charge elimination device 300 in this embodiment is also capable of executing a current detection mode, a number-of-sheets-passed mode, and an environmental condition mode. However, the charge elimination device 300 may be configured to be capable of executing only the current detection mode, the number-of-sheets-passed mode, and the environmental condition mode (or even only a part thereof).

[0143] <Correction of Charge Elimination Voltage Corresponding to the Number of Sheets Passed>

[0144] In this embodiment, the resistance value of the charge elimination roller 51b fluctuates according to the number of sheets S passed since the start time of the operation (the number of sheets passed continuously). This is mainly due to the fact that by the charge elimination roller 51b contacting the sheet S heated by the fixing device 40, the temperature of the charge elimination roller 51b, which is at a normal temperature before the start of the operation, gradually rises during the operation. As the temperature of the charge elimination roller 51b rises, the resistance value of the charge elimination roller 51b becomes lower, and the current flowing therethrough tends to increase when the same charge elimination voltage is applied.

[0145] For this reason, the control circuit 200 ( Figure 5 ) in this embodiment is configured in a selectable mode (number-of-sheets-passed mode), in which control is performed to gradually decrease the set value of the charge elimination voltage according to the number of sheets passed continuously during the operation. In other words, in the number-of-sheets-passed mode, which is an example of the first mode, the control circuit 200 (control component) changes the value of the voltage to be output by the high-voltage power supply 55 (voltage application device) based on the number of sheets conveyed during the execution of the operation.

[0146] Figure 12 is a diagram showing an example of the relationship between the number of sheets passed continuously and the setting ratio of the charge elimination voltage. The setting ratio of the charge elimination voltage is the ratio that represents the value of the charge elimination voltage (the appropriate value of the charge elimination voltage) suitable for performing charge elimination of the sheet S with respect to the appropriate value of the charge elimination voltage at the start of the operation as a reference (100%). Here, it is assumed that data (parameters of a table or conversion formula) corresponding to Figure 12 is stored in advance in the ROM 220 of the control circuit 200. In addition, since this relationship varies depending on the type of the sheet S, it is preferable to prepare multiple sets of data for each type of sheet (or for each category into which the sheet types are classified). However, regardless of the physical properties of the sheet S, generally, the setting ratio of the charge elimination voltage gradually decreases depending on the number of sheets passed continuously.

[0147] For example, in the case of the relationship between the number of sheets passing continuously and the set ratio of the charge elimination voltage as shown in Figure 12 when the number of sheets passing continuously reaches 100, the set value of the charge elimination voltage becomes 80% of the initial charge elimination voltage. For example, in the case where the charge elimination voltage is set to 4.0 kV by the operation unit 54 for charge elimination and a continuous printing job is started in a state where the paper passing history mode ( Figure 13 button B5 in ) is selected, a charge elimination voltage of 3.2 kV is applied to the 100th sheet and subsequent sheets S.

[0148] As the period during which the image forming system 400 does not execute a job (the period during which no sheet S is transferred to the charge elimination device 300, the standby period) becomes longer, the temperature of the charge elimination roller 51b gradually approaches the normal temperature. Therefore, after the previous job is completed, the value of the charge elimination voltage at the start of the next job is set to a value close to 100% of the set ratio depending on the length of the standby period. In other words, in the case where the next job starts immediately after the previous job is completed, the value of the charge elimination voltage at the start of the next job is applied based on the set ratio according to the number of sheets passing continuously in the previous job. On the other hand, in the case where the next job starts after sufficient time has passed since the completion of the previous job, for the value of the charge elimination voltage at the start of the next job, regardless of the number of sheets passing continuously in the previous job, for example, the value of the initial charge elimination voltage set by the operation unit 54 for charge elimination (the value with a set ratio of 100%) is applied.

[0149] <Correction of Charge Elimination Voltage Corresponding to Environmental Conditions>

[0150] In addition, even when the type of the sheet S is the same, the appropriate value of the charge elimination voltage fluctuates because the resistance value of the sheet S changes depending on the environmental conditions (especially the environmental moisture content) of the environment where the charge elimination device 300 is installed.

[0151] In the present embodiment, in the case where the automatic correction function is enabled, the environmental condition mode ( Figure 13 button B4 in ) can be selected. In this environmental condition mode, the set value of the charge elimination voltage is automatically determined based on the environmental conditions. In other words, in the environmental condition mode as an example of the first mode, the control circuit 200 (control component) changes the value of the voltage to be output by the high voltage power supply 55 (voltage application unit (component)) based on the detection result of the environmental sensor 13 (environmental detection component).

[0152] In the environmental condition mode of the present embodiment, simply, as the set value of the charge elimination voltage, a value corresponding to the environmental moisture content and set in advance is applied, and control based on the detection result of the charge elimination current during the paper passing history or the job is not performed.

[0153] Figure 11 is a graph showing the relationship between the set value of the charge elimination voltage and the environmental moisture content (weight absolute humidity, unit: g / kg). Here, it is assumed that data (parameters of a table or conversion formula) corresponding to Figure 11 is stored in the ROM 220 of the control circuit 200 in advance. When performing a job in the environmental condition mode, based on the environmental information detected by the environmental sensor 13, by referring to the data in the ROM 220, the control circuit 200 determines the set value of the charge elimination voltage. When the environmental information changes during the job, at any time, the set value of the charge elimination voltage is changed based on the detected environmental information.

[0154] In this way, by automatically correcting the set value of the charge elimination voltage based on the detection result of the environmental sensor 13, charge elimination of the sheet S can be performed with an appropriate charge elimination voltage corresponding to the environmental conditions.

[0155] <Selection of the method for setting the charge elimination voltage>

[0156] In the present embodiment, the user can select the method for setting the charge elimination voltage from the above three modes. Figure 13 is an example of a selection screen for selecting the method for setting the charge elimination voltage. By operating the screen shown on the display unit 102a ( Figure 1 ) of the user operation section 102, the user can select any one of the three modes: the environmental condition mode, the number of sheets passed mode, or the current detection mode. Figure 13

[0157] For example, when the "Automatic correction" button B3 is selected on the setting screen ( Figure 10 part (a)) of the charge elimination voltage setting method described in Embodiment 1, the selection screen shown in Figure 13 is displayed. Incidentally, when the charge elimination device 300 is configured not to include the functions of the manual setting mode and the medium setting mode, the screen shown in Figure 13 can be displayed instead of the setting screen in part (a) of Figure 10 .

[0158] ​If the “Ambient Temperature and Humidity” button B4 is pressed, the above-mentioned ambient condition mode is selected, and in this ambient condition mode, the value of the charge elimination voltage corresponding to the ambient conditions is applied. For example, after starting a continuous printing operation on the image forming system 400 in the early morning (in a state where the device is cooled), even when the temperature and humidity gradually rise during the operation, at any time, the charge elimination voltage corresponding to the ambient moisture content is applied. Thereby, it becomes possible to reduce the possibility that the charge elimination voltage becomes excessive or insufficient due to changes in the ambient conditions during the operation.

[0159] If the “Paper Passing History” button B5 is pressed, the above-mentioned number mode of the passed sheets is selected, and this number mode of the passed sheets corrects the charge elimination voltage corresponding to the number of sheets continuously passed during the operation. For example, when a large number of sheets S pass intermittently in bundles of dozens of sheets, the change in the appropriate value of the charge elimination voltage during the continuous passing of dozens of sheets constituting a single bundle can be regarded as a certain pattern (such as the pattern shown in Figure 12 . In such a case, there are cases where the number mode of the passed sheets is appropriate. On the other hand, in the following current detection mode, errors may occur in the first few sheets S before the correction of the charge elimination voltage starts and / or in the second half of the continuous paper passing.

[0160] If the “Current Detection” button B6 is pressed, the current detection mode is selected, and in this current detection mode, the charge elimination voltage is automatically corrected based on the detection result of the charge elimination current during the operation. The content of the control in the current detection mode is the same as that in the automatic correction mode in Embodiment 1 ( Figure 6 Sc1 to Sc11 in). For example, in a continuous printing operation using the same type of synthetic sheet, with the current detection mode, it becomes possible to more appropriately cope with changes in the resistance of the charge elimination roller 51b during the operation and / or changes in the resistance of the synthetic paper due to ambient conditions.

[0161] In this way, in the present embodiment, it is configured that the user can select the automatic correction mode of the charge elimination voltage. Thereby, it becomes possible for the user to select the mode that he or she considers most appropriate according to the specific usage situation, so as to improve the usability and reduce the adhesion between sheets by performing charge elimination with a more appropriate magnitude of the charge elimination voltage. Moreover, it becomes possible to reduce the man-hours of manual handling (separation work by hand) for eliminating the adhesion between sheets and improve the handling quality in the post-processing process, thus making it easier to cope with various sheet materials including synthetic sheets, film sheets, and label sheets.

[0162] [Embodiment 3]

[0163] In Embodiments 1 and 2, whether to enable the automatic correction function of the charge elimination voltage and which one of a plurality of modes to select in the case of performing automatic correction (hereinafter collectively referred to as the mode selection of the charge elimination voltage) are determined by the user's selection. The mode selection of the charge elimination voltage can be performed automatically (i.e., regardless of the user's selection) based on the type of the sheet S or other conditions.

[0164] In the present embodiment, it is assumed that information related to the physical properties of the sheet S (medium information) is input in advance for each type of the sheet via the user operation unit 102 and stored in a memory unit such as the ROM 220 or the RAM 210. The medium information is configured to at least include information indicating the volume resistivity of the sheet S or information related to the volume resistivity of the sheet S (its material, thickness, etc.).

[0165] Not limited to the method of inputting the medium information via the user operation unit 102, it can be configured that a medium sensor capable of automatically determining the physical properties of the sheet S is provided to the charge elimination device 300 or the image forming system 400, and the medium information is obtained based on the detection result of the medium sensor. The medium sensor can be, for example, an ultrasonic type sensor that uses ultrasonic waves to determine the thickness (basis weight) of the sheet S, an optical type sensor that irradiates light and determines the surface properties of the sheet S based on the amount of reflected light, or a combination of the ultrasonic type and the optical type.

[0166] The control circuit 200 obtains the medium information corresponding to the type of the sheet S to be used for the current job. Condition data representing whether to enable the automatic correction function of the charge elimination voltage and which one of a plurality of modes to select in the case of performing automatic correction is, for example, stored in the ROM 220 in advance. The control circuit 200 refers to the condition data, performs the mode selection of the charge elimination voltage, and applies any one of the charge elimination voltage setting methods described in Embodiments 1 and 2.

[0167] The mode selection of the charge elimination voltage corresponding to the type of the sheet S is performed, for example, based on the thickness of the high-resistance layer of the sheet S. If the sheet S has a high-resistance layer with a thickness of 100 μm or more, then the automatic correction mode in Embodiment 1 is selected. If the sheet S has a high-resistance layer with a thickness less than 100 μm or the sheet S does not have a high-resistance layer, then the medium setting mode or the manual setting mode is selected. The high-resistance layer mentioned here is composed of a volume resistivity of 1×10 12A layer made of a material of [[Ωcm]] or greater, and a surface treatment layer (coating layer) such as PI (polyimide) falls within it. For example, a sheet S having a pulp layer of 120 μm coated with a PI layer of 30 μm has a high-resistance layer of less than 100 μm, so the dielectric setting mode or the manual setting mode is selected, and a fixed value of the charge elimination voltage set in advance is applied. In this way, the control circuit 200 in the present embodiment serves as a selection component that selects any one of multiple modes based on the type of sheet to be used in the job.

[0168] (Example of modification)

[0169] In Embodiment 3, an example of automatically performing mode selection of the charge elimination voltage based on the type of sheet S (especially the thickness of the high-resistance layer) is described. However, mode selection of the charge elimination voltage can be automatically performed based on other conditions.

[0170] As an example, mode selection of the charge elimination voltage can be automatically performed based on the environmental conditions (environmental moisture content) detected by the environmental sensor 13 ( Figure 5 ). For example, it can be configured that in a low-humidity environment, since a relatively high charge elimination voltage is required and the appropriate value of the charge elimination voltage may fluctuate due to a slight change in the moisture content, the automatic correction mode is selected. Conversely, in a high-humidity environment, the dielectric setting mode or the manual setting mode is selected. In this case, the control circuit 200 serves as a selection component that selects any one of multiple modes based on the detection result of the environmental sensor 13 (environmental detection component).

[0171] As another example, it can be configured that mode selection of the charge elimination voltage is automatically performed based on the measured value of the current flowing through the charge elimination roller 51b or the secondary transfer roller 9. For example, if the measured current value of the charge elimination roller 51b is a certain value or less, the application of the automatic correction mode can be stopped because the error in the automatic correction mode may become large. In this case, the control circuit 200 serves as a selection component that selects any one of multiple modes based on the detection result of the current detection circuit 55a (current detection component) that detects the current flowing through the charge elimination roller 51b (charge elimination member).

[0172] As yet another example, in the case where the automatic correction function of the charge elimination voltage is disabled (second mode), when the difference between the current set value of the charge elimination voltage and the appropriate value of the charge elimination voltage calculated based on the detection result of the charge elimination current during the passage of the sheet exceeds a predetermined allowable range, a notification can be executed. This notification means notifying the user of information prompting the user to reset the charge elimination voltage via the operation section 54 for charge elimination or the user operation section 102 so as to appropriately perform the charge elimination of the sheet S. For the method of notification, a screen display on the user operation section 102 or a sound from the user operation section 102 can be used, or a screen display on an external computer connected to the image forming system 400 or a sound from an external computer connected to the image forming system 400 can be used. In this modified example, for instance, when the user accurately knows the state of the product, it is advantageous to be able to eliminate the charged state of the product while reducing the burden on the user.

[0173] [Other Embodiments]

[0174] In each of the above embodiments, the charge elimination device 300 that performs the charge elimination of the sheet S has been 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 application member. Such a charge adjustment device performs a charge application operation of continuously applying charge to a plurality of sheets in an image forming operation of performing image formation on the plurality of sheets. The charge adjustment device may be a device that does not necessarily reduce (does not eliminate) the amount of charged electric charge 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 may be a device that adjusts the amount of charged electric charge on each surface of the sheet S such that the surfaces of the overlapping sheets facing each other are in a state of being charged with the same polarity. Specifically, the charge adjustment device applies a voltage to every other sheet among the plurality of sheets so that the static electrode polarity of the sheet surface is reversed. In this case, by having the surfaces of the overlapping sheets facing each other charged with the same polarity, it becomes possible to reduce the adhesion between the sheets due to the electrostatic force. Further, 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 application member, it becomes possible to more appropriately adjust the charged state of the sheet S.

[0175] In addition, in each of the above embodiments, as an example of the charge elimination member of the contact type that contacts the sheet S, the charge elimination roller 51b as a roller member has been described. However, the charge elimination member of the contact type is not limited thereto, and may be, for example, a brush member in which its conductive fibers or elongated conductive sheet blocks contact the sheet S.

[0176] In addition, in each of the above-described embodiments, the charging of the sheet S is described as mainly occurring in the transfer portion of the electrophotographic process. However, not limited thereto, in an image forming system other than the electrophotographic type (such as an inkjet type), the charging of the sheet S may occur due to friction and / or peeling with a conveyance guide, a conveyance roller, and / or a conveyor belt, etc., by triboelectric charging or peeling charging. Therefore, the present technology can be applied to an image forming system of a type other than the electrophotographic type.

[0177] (Other Embodiments)

[0178] The present invention can also be implemented by a program that realizes one or more functions of the above-described embodiments being supplied to a system or device via a network or a storage medium and being read and executed by one or more processors in a computer of the system or device. In addition, the present invention can also be implemented by a circuit (e.g., ASIC) that realizes one or more functions.

[0179] According to the present invention, it becomes possible to provide a charge elimination device, an image forming system, and a charge adjustment device that can apply a voltage to a charge elimination member in an appropriate type.

[0180] Embodiments of the present disclosure can also be implemented by a computer of a system or device that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a 'non-transitory computer-readable storage medium') to perform one or more functions of the above-described embodiments and / or includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing one or more functions of the above-described embodiments, and by a method executed by the computer of the system or device by, for example, reading and executing the computer-executable instructions from the storage medium to perform one or more functions of the above-described embodiments and / or controlling one or more circuits to perform one or more functions of the above-described embodiments. The computer may include one or more processors (e.g., central processing unit (CPU), microprocessing unit (MPU)), and may include a network of individual computers or individual processors to read and execute the computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, one or more of a hard disk, a random access memory (RAM), a read only memory (ROM), a storage device of a distributed computing system, an optical disc (such as a compact disc (CD), a digital versatile disc (DVD), or a Blu-ray disc (BD) TM ), a flash device, a memory card, etc.

[0181] Although the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be accorded the broadest interpretation so as to cover all such modifications and equivalent structures and functions.

Claims

1. A charge elimination device, comprising: a charge eliminating member configured to eliminate charges of the sheet material while in contact with the sheet material; a voltage applying unit configured to apply a voltage to the charge eliminating member; a setting unit configured to set a value of a voltage applied by the voltage applying unit to the charge eliminating member; a controller capable of executing, during execution of a charge eliminating operation in which charges of a plurality of sheets are successively eliminated by the charge eliminating member, a changing process in which a voltage to be output by the voltage applying unit is changed from the voltage set by the setting unit; as well as a selection unit configured to select a first mode in which the changing process is performed during execution of the charge eliminating operation or a second mode in which the changing process is not performed during execution of the charge eliminating operation and the voltage applying unit outputs a voltage based on the value set by the setting unit. 2 . The charge-eliminating device according to claim 1 , wherein the selection unit is a display unit configured to display a screen for a user to select the first mode or the second mode. 3 . The charge-eliminating device according to claim 1 , wherein the selection unit selects the first mode or the second mode based on a type of sheet.

4. The charge-eliminating device according to claim 1 , further comprising an environment detection unit configured to detect an environmental condition of an environment in which the charge-eliminating device is installed. The selection unit selects the first mode or the second mode based on the detection result of the environment detection unit.

5. The charge-eliminating device according to claim 1 , further comprising a detection unit configured to detect a voltage applied to the charge-eliminating member or a current flowing through the charge-eliminating member, The selection unit selects the first mode or the second mode based on the detection result of the detection unit.

6. The charge-eliminating device according to claim 1 , further comprising a current detection unit configured to detect a current flowing through the charge-eliminating member, wherein in the changing process, the controller changes the voltage to be output by the voltage applying unit based on a detection result of the current detecting unit when the sheet passes through the charge eliminating member.

7. The charge-eliminating device according to claim 1 , further comprising an environment detection unit configured to detect an environmental condition of an environment in which the charge-eliminating device is installed. wherein in the changing process, the controller changes a value of a voltage to be output by the voltage applying unit based on a detection result of the environment detecting unit during execution of the charge eliminating operation. 8 . The charge-eliminating device according to claim 1 , wherein in the changing process, the controller changes a value of a voltage to be output by the voltage applying unit based on the number of sheets conveyed during execution of the charge-eliminating operation.

9. The charge-eliminating device according to claim 1 , wherein the setting unit includes an input unit configured for a user to input a value of a voltage to be applied to the charge-eliminating member by the voltage applying unit, and In the second mode, the controller causes the voltage applying unit to output a voltage at a value input through the input unit before the charge erasing operation is started, regardless of the type of the sheet.

10. The charge-eliminating device according to claim 9, wherein in the second mode, when the input unit is operated after the charge-eliminating operation is started, the controller changes the value of the voltage to be output by the voltage applying unit from a value input through the input unit before the charge-eliminating operation is started to a value input through the input unit after the charge-eliminating operation is started.

11. The charge-eliminating device according to claim 1 , further comprising an input unit configured to allow a user to input a value of a voltage applied to the charge-eliminating member by the voltage applying unit, and a memory unit configured to memorize a value of a voltage preset by the input unit for each type of sheet material, In the second mode, the setting unit determines a value of the voltage to be output by the voltage applying unit by referring to information memorized in the memory unit based on the type of the sheet.

12. The charge-eliminating device according to claim 1 , wherein in the second mode, when a difference between a value of a voltage output by the voltage applying unit during execution of the charge-eliminating operation and a value calculated by the controller as a voltage value suitable for application to the charge-eliminating member during execution of the charge-eliminating operation exceeds a predetermined allowable range, the controller notifies a user of information prompting a user to reset the voltage to be applied to the charge-eliminating member.

13. An image forming system comprising an image forming device for forming an image on a sheet, and a charge erasing device for erasing charge of the sheet on which the image is formed by the image forming device, The charge elimination device comprises: a charge eliminating member configured to eliminate charges of the sheet material while in contact with the sheet material; a voltage applying unit configured to apply a voltage to the charge eliminating member; a setting unit configured to set a value of a voltage applied by the voltage applying unit to the charge eliminating member; a controller capable of executing, during execution of a charge eliminating operation in which charges of a plurality of sheets are successively eliminated by the charge eliminating member, a changing process in which a value of a voltage to be output by the voltage applying unit is changed from a value of the voltage set by the setting unit; as well as a selection unit configured to select a first mode in which the changing process is performed during execution of the charge eliminating operation or a second mode in which the changing process is not performed during execution of the charge eliminating operation and the voltage applying unit outputs a voltage based on the value set by the setting unit.

14. A charge adjustment device, comprising: a charge applying member configured to apply a charge to the sheet material in contact with the sheet material; a voltage applying unit configured to apply a voltage to the charge applying member; a setting unit configured to set a value of a voltage applied by the voltage applying unit to the charge applying member; a controller capable of executing, during execution of a charge applying operation in which the charge applying member continuously applies charge to a plurality of sheets, a changing process in which a value of a voltage to be output by the voltage applying unit is changed from a value of the voltage set by the setting unit; as well as A selection unit configured to select a first mode or a second mode, in which the change process is performed during the execution of the charge application operation, and in which the change process is not performed during the execution of the charge application operation and the voltage application unit outputs a voltage based on the value set by the setting unit.

Images