Static eliminator and image forming system

Abstract

To provide a static eliminator that improves the productivity.SOLUTION: The static eliminator includes: a static eliminating member that contacts a conveyed sheet and eliminates static from the sheet by applying a voltage; a moving part that moves the static eliminating member between a contact position where it contacts the sheet and an evacuation position where it is separated from the sheet; and a control part that executes static elimination processing by the static eliminating member for a first type of sheet (synthetic paper) and does not execute static elimination processing by the static eliminating member for a second type of sheet (plain paper) which is different from the first type of sheet. In a mixed job in which the first type of sheet and the second type of sheet are transported together, the control part executes first processing (Fig.9(d)) for the first type of sheet, in which the static elimination member is positioned at the contact position and a voltage is applied to the static elimination member to remove static from the sheet, and executes second processing (Fig.9(d)) for the second type of sheet, in which the static elimination member is positioned at the contact position and a voltage is not applied to the static elimination member to remove static from the sheet.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a static eliminator that eliminates static electricity from a sheet-like recording material, and to an image forming system to which the static eliminator is applied. [Background technology]

[0002] Conventionally, in an electrophotographic image forming apparatus, a high voltage is applied to a sheet during image formation, and therefore, the sheet may become charged after image formation. As a result, there is a risk that the sheet may be electrostatically attracted to the conveying path in the apparatus, causing conveying failure, or that the electrostatic force generated between the sheets when stacking the sheets discharged outside the apparatus may cause stacking failure. To address such problems, a static eliminator that removes static electricity from the sheet has been proposed. As a static eliminator, for example, one having two static eliminators, a contact static eliminator that contacts the sheet being conveyed and a non-contact static eliminator that is provided downstream in the conveying direction from the contact static eliminator, has been developed (see Patent Document 1).

[0003] In this static elimination device, the pair of static elimination rollers used in the contact type static eliminator wears out every time a sheet is neutralized, and there is a risk that the static elimination capability will decrease after long-term use. Therefore, the pair of static elimination rollers are made movable between a contact position where they contact each other and a retracted position where they are spaced apart, and in order to prevent roller wear, the pair of static elimination rollers are positioned in the retracted position when a sheet that does not require static elimination is passed through. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-167169 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the static elimination device described in the above-mentioned Patent Document 1, when a sheet that does not require static elimination is passed through, the static elimination roller pair is positioned at the retracted position. It takes time to move the static elimination roller pair from the contact position to the retracted position, or from the retracted position to the contact position. For this reason, when an image forming job is executed in which sheets of a type that require static elimination and sheets of a type that do not require static elimination are mixed, the static elimination roller pair moves from the contact position to the retracted position, or from the retracted position to the contact position, when the type of sheet is changed. As a result, the time between sheets becomes longer than when the same type of sheets are continuously static eliminated, and there is a possibility that productivity will decrease.

[0006] An object of the present invention is to provide a static eliminator and an image forming system that can improve productivity. [Means for solving the problem]

[0007] The static elimination device of the present invention includes a static elimination member that comes into contact with a transported sheet and eliminates static electricity from the sheet by applying a voltage to the sheet, a moving unit that moves the static elimination member to a contact position where it comes into contact with the sheet and a retracted position away from the sheet, and a control unit that performs a static elimination process using the static elimination member on a first type of sheet, but does not perform a static elimination process using the static elimination member on a second type of sheet different from the first type, and is characterized in that, in a mixed job in which the first type of sheet and the second type of sheet are transported, the control unit performs a first process for the first type of sheet, in which the static elimination member is positioned at the contact position and a voltage is applied to the static elimination member to eliminate static electricity from the sheet, and performs a second process for the second type of sheet, in which the static elimination member is positioned at the contact position and a voltage is not applied to the static elimination member to eliminate static electricity from the sheet.

[0008] The image forming system of the present invention is characterized by comprising: an image forming apparatus that forms an image on a sheet; and the above-described static elimination apparatus that receives the sheet on which an image has been formed by the image forming apparatus and eliminates static electricity therefrom. Effect of the Invention

[0009] According to the present invention, productivity can be improved. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an image forming system according to an embodiment. [Diagram 2] FIG. 2 is a control block diagram showing a control system of the image forming system according to the embodiment. [Diagram 3] 1 is a cross-sectional view showing a contact-type static eliminator according to an embodiment. [Figure 4] 1A and 1B are cross-sectional views showing a non-contact static eliminator according to an embodiment of the present invention, in which FIG. 1A shows a state before static elimination of a sheet, and FIG. [Diagram 5] 4A and 4B are side views showing the attachment / detachment mechanism according to the embodiment, in which FIG. [Figure 6] 11 is a flowchart showing a detachment operation in the attachment / detachment mechanism according to the embodiment. [Figure 7] 10 is a flowchart showing an attachment operation in the attachment / detachment mechanism according to the embodiment. [Figure 8] 1 is a table showing a relationship between the type of sheet and the applied voltage of a contact static eliminator and a non-contact static eliminator according to an embodiment. [Figure 9] 1 is a time chart showing the de-electrification process of a sheet row according to an embodiment, where (a) shows a sheet row of plain paper, (b) shows a sheet row of synthetic paper, (c) shows a comparative example of a mixed sheet row, (d) shows a second process of the mixed sheet row, and (e) shows a third process of the mixed sheet row. [Figure 10] 10 is a flowchart showing a processing procedure of a mounting / detachment mode switching operation according to the embodiment. [Figure 11] 4 is a flowchart showing a procedure of a static elimination process according to the embodiment. [Figure 12] FIG. 13 is a plan view showing an operation switching screen of a display according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present embodiment will be described below with reference to the drawings. First, the schematic configuration of an image forming system 1 according to the present embodiment will be described with reference to FIG. 1. The dimensions, materials, relative positions, etc. of the components of the image forming system 1 are not intended to limit the scope of the present invention unless otherwise specified. In addition, in this embodiment, a full-color copying machine equipped with multiple photosensitive drums is applied as the image forming device 2 of the image forming system 1. However, the present invention is not limited to this, and can also be applied to a monochrome or mono-color copying machine or printer equipped with one photosensitive drum.

[0012] [Image formation system] 1 is a cross-sectional view showing a configuration of a main part of an image forming system 1 according to the present embodiment. The image forming system 1 includes an image forming device 2 that forms an image to be printed on a sheet S, a static eliminator 3, and a finisher 4.

[0013] The image forming apparatus 2 has feeding decks 11 and 12, an image forming unit 10, a fixing unit 20, a display 206, and the like. Each of the feeding decks 11 and 12 is capable of storing various types of sheets S. Each of the feeding decks 11 and 12 is capable of separating only the uppermost sheet S of the stored sheets S and transporting it to the transport path 13. The display 206 displays the printing status of the image forming system 1 and information for settings.

[0014] The fixing section 20 is provided to fix the toner image to the sheet S, and has a first fixing unit 21 and a second fixing unit 23. The first fixing unit 21 has a heating roller and a pressure roller, and the sheet S passes between the rollers to melt and press the toner, thereby fixing the toner image to the sheet S. The sheet S that has passed through the first fixing unit 21 is conveyed to a conveying path 25 through a conveying path 22. If further melting and pressing are required for fixing depending on the type of the sheet S, after passing through the first fixing unit 21, the sheet S is conveyed to the second fixing unit 23 using the upper conveying path, where additional melting and pressing are performed. Thereafter, the sheet S is conveyed to the conveying path 25 through a conveying path 24. When the image formation mode is double-sided printing, the sheet S is conveyed to a sheet inversion path 26, inverted by the sheet inversion path 26, and conveyed to a double-sided conveying path 27, where the image is transferred to the second side opposite to the first side by a secondary transfer roller 19.

[0015] The static eliminator 3 receives the sheet S on which an image has been formed by the image forming apparatus 2 and eliminates static electricity. The static eliminator 3 has a conveying path 28 that receives the sheet S that has passed through the conveying path 25, and a contact static eliminator 29 and a non-contact static eliminator 31 that eliminate static electricity from the received sheet S. The static eliminator 3 applies a high voltage to the contact static eliminator 29 and the non-contact static eliminator 31 to eliminate static electricity from the sheet S. The sheet S that has passed through the contact static eliminator 29 and the non-contact static eliminator 31 and has been subjected to static elimination processing is conveyed to the finisher 4. That is, the non-contact static eliminator 31 is an example of a non-contact static eliminator, and is disposed downstream of the static eliminator roller pair 30 in the sheet conveying direction, and eliminates static electricity from the sheet S conveyed from the static eliminator roller pair 30 in a non-contact manner.

[0016] The finisher 4 is a sheet stacking device capable of stacking a large amount of sheets S transported from the static eliminator 3. The finisher 4 has a transport path 35 that receives the sheets S transported from the static eliminator 3, and a stack tray 37 that continuously stacks the sheets S on the transport path 35. The transport path 35 is provided with transport sensors 32, 33, 34, and 36 that detect the passage of the sheets S. If the transport sensors 32, 33, 34, and 36 do not detect the leading end or trailing end of the sheet even after a predetermined time has elapsed, the finisher 4 determines that a jam has occurred in the finisher 4, and notifies the image forming apparatus 2 of the occurrence of the jam.

[0017] [Image formation system control system] 2 is a block diagram showing the system configuration of the image forming system 1. First, a control system of the image forming apparatus 2 will be described. The image forming apparatus 2 has a communication I / F 201, a HDD 202, a CPU 203, a memory 204, an operation unit 205, a display 206, a laser exposure unit 207, an image forming unit 10, a fixing unit 20, and a feeding unit 210. Each of the components is connected via a system bus 213.

[0018] The communication I / F 201 is connected to the static eliminator 3 via a communication cable 229, and communication is performed to control each device. The HDD 202 is a storage device in which programs and data are stored. The CPU 203 comprehensively controls image processing and printing based on the programs and the like stored in the HDD 202. In this embodiment, the CPU 203 is an example of a control unit, and controls the contact static eliminator 29 and the non-contact static eliminator 31. The memory 204 stores programs and image data required when the CPU 203 performs various processes, and operates as a work area.

[0019] The operation unit 205 accepts various setting inputs and operation instructions from the user. The display 206 displays setting information of the image forming apparatus 2, the processing status of a print job, and the like. The user can set the type of sheets accommodated in each of the feeding decks 11 and 12 via the operation unit 205. The user can also set, via the operation unit 205, whether or not static elimination is required for any type of sheet. Alternatively, instead of a user setting, the CPU 203 may automatically set whether or not static elimination is required based on the type of sheet set for the sheet accommodated in each of the feeding decks 11 and 12.

[0020] The laser exposure unit 207 performs primary charging and laser exposure to irradiate the photosensitive drum with laser light in order to transfer the toner image. In the laser exposure unit 207, primary charging is first performed to charge the surface of the photosensitive drum to a uniform negative potential. Next, the laser driver irradiates the photosensitive drum with laser light while adjusting the reflection angle with a polygon mirror. This neutralizes the negative charge in the irradiated area, forming an electrostatic latent image.

[0021] The image forming unit 10 is a device that forms a toner image and transfers the toner image to the sheet S, and is composed of a developing unit, a transfer unit, a toner supply unit, etc., and transfers the toner image on the photosensitive drum to the sheet S via the intermediate transfer belt 18. In the developing unit, negatively charged toner from a developing cylinder is attached to the electrostatic latent image on the surface of the photosensitive drum to make it visible. In the transfer unit, a primary transfer is performed in which a positive potential is applied to the primary transfer roller to transfer the toner image on the surface of the photosensitive drum to the intermediate transfer belt 18, and a secondary transfer is performed in which a positive potential is applied to the secondary transfer outer roller to transfer the toner image on the intermediate transfer belt 18 to the sheet S. The fixing unit 20 is a device that melts and fixes the toner on the sheet S to the sheet S by heat and pressure, and is composed of a first fixing unit 21 and a second fixing unit 23. The feeding unit 210 is a device that feeds the sheet S, and the feeding operation and conveying operation of the sheet S are controlled by rollers and various sensors.

[0022] Next, the control system of the static eliminator 3 will be described. The static eliminator 3 has a communication I / F 221, a static elimination high voltage control unit 222, an attachment / detachment control unit 223, a non-contact static elimination high voltage control unit 224, and the like, and each of the components is connected via a system bus 225. The communication I / F 221 is connected to the image forming apparatus 2 via a communication cable 229, and communication required for control is performed. The static elimination high voltage control unit 222, the attachment / detachment control unit 223, and the non-contact static elimination high voltage control unit 224 perform various controls based on control instructions from the CPU 203 received via the communication cable 229. The static elimination high voltage control unit 222 controls static elimination by the contact static eliminator 29. The attachment / detachment control unit 223 controls the attachment and detachment of the two static elimination rollers 30a and 30b by the attachment / detachment mechanism 150 (see FIGS. 5(a) and (b)). The non-contact static elimination high voltage control unit 224 controls static elimination by the non-contact static eliminator 31.

[0023] Next, the control system of the finisher 4 will be described. The finisher 4 has a communication I / F 231, a CPU 232, a memory 233, and a discharge control unit 234, and each of the components is connected via a system bus 235. The communication I / F 231 is connected to the static eliminator 3 via a communication cable 239, and communication required for control is performed. The CPU 232 performs various controls required for discharge according to a control program stored in the memory 233. The memory 233 is a storage device in which the control program is saved. The discharge control unit 234 controls the transport of the transported sheet S to the stack tray 37 based on an instruction from the CPU 232.

[0024] [Static eliminator] In this embodiment, the secondary transfer roller 19 applies a negative voltage, so that the upper surface of the sheet S is negatively charged, and the lower surface of the sheet S is positively charged due to dielectric polarization. Therefore, if the sheets S are stacked on the stack tray 37 without undergoing a static electricity removal process, the stacked sheets will stick to each other due to electrostatic force. To prevent the sheets S from sticking due to electrostatic force, in this embodiment, the charge on the surface of the sheet S is removed by a static electricity removal device 3. The static electricity removal device 3 has two static electricity removal units, a contact static electricity removal device 29 and a non-contact static electricity removal device 31 (see FIG. 1).

[0025] [Contact static eliminator] FIG. 3 is a cross-sectional view for explaining the charge removal process by the contact type charge removal device 29. The contact type charge removal device 29 is disposed upstream of the non-contact type charge removal device 31 in the sheet conveying direction, and has a pair of opposing charge removal rollers 30 disposed so as to contact each other. The charge removal roller pair 30 has, for example, charge removal rollers 30a, 30b made of sponge, and a rotating shaft 30c that rotatably supports the charge removal rollers 30a, 30b, and conveys and removes charge from the sheet S by sandwiching it. In this embodiment, the charge removal rollers 30a, 30b made of sponge are used, and therefore, they may be easily worn by rotating while being in contact with each other. In this embodiment, the charge removal rollers 30a, 30b are described as being made of sponge rollers, but the present invention is not limited to this, and one of the charge removal rollers 30a, 30b may be made of a metal roller.

[0026] The static elimination high voltage control section 222 (see FIG. 2) applies a negative voltage to the static elimination roller 30b using a static elimination high voltage board 230 as a voltage application section, thereby eliminating the positive charges present on the lower surface of the sheet S. The static elimination roller 30a is grounded. In this embodiment, the static elimination roller pair 30 is an example of a conveying section that conveys the sheet S, and is also an example of a static elimination member that comes into contact with the conveyed sheet S and eliminates static electricity from the sheet S by applying a voltage thereto. In addition to the static elimination roller pair 30, the static elimination device 3 has a plurality of conveying roller pairs for conveying the sheet in the conveying path 28.

[0027] When the positive charge on the lower surface of the sheet S is reduced, the negative charge on the upper surface of the dielectrically polarized sheet S is also reduced. The contact type static elimination device 29 contacts the sheet S and applies a voltage directly, so the static elimination effect is high. On the other hand, the surface potential of the sheet S after static elimination varies greatly, and static elimination tends to be uneven. The static elimination high voltage board 230, which is an example of the second board that applies a voltage to the static elimination roller pair 30, may have the same configuration as the high voltage board for use in the image forming system 1 other than static elimination. For example, the image forming device 2 has a high voltage board 101 (see FIG. 2), which is an example of the first board that applies a voltage to the development unit, transfer unit, etc. of the image forming section 10. The static elimination high voltage board 230 can be configured to have the same configuration as the high voltage board 101. In this case, the common configuration of the boards can reduce manufacturing costs.

[0028] [Non-contact static eliminator] 4 is a cross-sectional view illustrating the charge removal process by the non-contact charge removal device 31. In order to adjust the surface potential of the sheet S that has become uneven due to the charge removal process by the contact charge removal device 29, the charge removal device 3 of this embodiment is provided with the non-contact charge removal device 31. The non-contact charge removal device 31 is an example of a non-contact charge removal section, and removes charge from the sheet S conveyed by the charge removal roller pair 30 in a non-contact manner. As shown in FIG. 4(a), the non-contact charge removal device 31 has a discharge wire 40 and an earth electrode 41. When a positive voltage is applied to the discharge wire 40 from the non-contact charge removal high voltage board 240, a positive charge is generated by corona discharge.

[0029] As shown in FIG. 4(b), the positive charge generated by applying a voltage to the discharge wire 40 is attracted to the negative charge on the upper surface of the sheet S by electrostatic force and neutralized. As a result, the negative charge on the upper surface of the sheet S is neutralized. The positive charge on the lower surface of the sheet S is attracted to the earth electrode 41, which has a zero potential, and neutralized. The effect of neutralizing the surface of the sheet S by the non-contact type neutralizing device 31 is smaller than that by the contact type neutralizing device 29, but the surface potential of the sheet S after neutralization is less variable and neutralization is uniform. Therefore, it is possible to adjust the surface potential of the sheet S, whose potential has become uneven due to neutralization by the contact type neutralizing device 29. In this embodiment, an AC corotron type is used as the non-contact type neutralizing device, but an ionizer may be used.

[0030] [Determining the voltage of the static eliminator] In this embodiment, the static eliminator 3 has both the contact static eliminator 29 and the non-contact static eliminator 31, but both are not always used when eliminating static electricity from the sheet S. For sheets S such as plain paper having a small current resistance, static elimination can be performed sufficiently by the non-contact static eliminator 31 alone. On the other hand, for sheets S having a large current resistance such as synthetic paper, static elimination is performed using both the contact static eliminator 29 and the non-contact static eliminator 31. FIG. 8 is a table showing the voltages applied by the contact static eliminator 29 and the non-contact static eliminator 31 according to the type of sheet. This table is stored in the HDD 202, and the CPU 203 refers to this table when applying a high voltage, and instructs the static elimination high voltage control unit 222 and the non-contact static elimination high voltage control unit 224 to apply a high voltage via the communication I / F 201.

[0031] [Detachable mechanism] The pair of charge removing rollers 30 provided in the contact type charge removing device 29 may be worn every time the sheet S is conveyed, and the charge removing ability may be reduced. Therefore, in this embodiment, the charge removing rollers 30a, 30b are movable between a contact position where the charge removing rollers 30a, 30b contact the sheet S and a retracted position away from the sheet S. As shown in Figs. 5(a) and 5(b), the charge removing device 3 includes an attachment / detachment mechanism 150, which is an example of a moving unit that moves the charge removing rollers 30a, 30b between the contact position and the retracted position. As a result, when charge removal is performed only by the non-contact type charge removing device 31, the charge removing device 3 can position the charge removing rollers 30a, 30b at the retracted position. In this specification, the switching of the charge removal rollers 30a, 30b between the contact position and the retracted position is referred to as attachment and detachment, positioning them at the contact position is referred to as the attachment operation, the state in which they are positioned at the contact position is referred to as the attachment state, positioning them at the retracted position is referred to as the detachment operation, and the state in which they are positioned at the retracted position is referred to as the detachment state.

[0032] 5(a) and (b) are cross-sectional views of an attachment / detachment mechanism 150 that attaches and detaches the pair of static electricity removing rollers 30. As shown in Figs. 5(a) and (b), the attachment / detachment mechanism 150 is attached to the static electricity removing roller 30a. The attachment / detachment mechanism 150 has a swing arm 151 that swings around a swing fulcrum 152. As shown in Fig. 5(a), when an attachment / detachment motor (not shown) is driven in the forward direction to rotate the swing arm 151 in the R1 direction, the static electricity removing roller 30a comes into contact with the static electricity removing roller 30b (contact position), completing the attachment operation of the static electricity removing rollers 30a and 30b.

[0033] On the other hand, as shown in FIG. 5B, when the mounting / detaching motor is driven in the reverse direction, the swing arm 151 rotates in the R2 direction, and the charge removing roller 30a pushes in the mounting / detaching sensor 153, which is a push switch provided on the upper part of the mounting / detaching mechanism 150. When the mounting / detaching sensor 153 is turned on, the CPU 203 determines that the charge removing roller pair 30 is located at the retreat position, stops the mounting / detaching motor, and completes the removal operation of the charge removing roller 30a and the charge removing roller 30b. In this embodiment, during the mounting / detaching operation of the charge removing roller pair 30, the grounded charge removing roller 30a moves, and the charge removing roller 30b connected to the charge removing high voltage board 230 does not move, but this is not limited to this. For example, the charge removing roller 30b may move, and the charge removing roller 30a may not move. Alternatively, both the charge removing rollers 30a and 30b may move.

[0034] [Dropping and putting on] Next, the procedure of the detachment operation and the attachment operation of the pair of static electricity removing rollers 30 will be described with reference to the flowcharts shown in FIGS. 6 and 7. FIG. 6 is a flowchart of the detachment operation. When the detachment operation is started, the CPU 203 instructs the attachment / detachment control unit 223 to perform the detachment operation of the pair of static electricity removing rollers 30 via the communication I / F 201. When the attachment / detachment control unit 223 receives the instruction of the detachment operation from the CPU 203, it drives the attachment / detachment motor in reverse at a predetermined speed to start the detachment operation (S1). When the detachment operation is started, the CPU 203 obtains the output of the attachment / detachment sensor 153 via the communication I / F 201. The CPU 203 determines whether the attachment / detachment sensor 153 is on or not (step S2). When the CPU 203 determines that the attachment / detachment sensor 153 is not on (No in step S2), it again determines whether the attachment / detachment sensor 153 is on or not (step S2). When the CPU 203 determines that the attachment / detachment sensor 153 is in the ON state (Yes in step S2), the CPU 203 stops the attachment / detachment motor (step S3) and ends the detachment operation.

[0035] FIG. 7 is a flowchart of the attachment operation. When the CPU 203 starts the attachment operation, it instructs the attachment / detachment control unit 223 to start the attachment operation via the communication I / F 201. When the attachment / detachment control unit 223 receives the instruction of the attachment operation from the CPU 203, it drives the attachment / detachment motor in the forward direction at a predetermined speed to start the attachment operation (S4). When the attachment operation starts, the CPU 203 judges whether or not 600 msec has elapsed since the attachment / detachment motor started to be driven (S5). When the CPU 203 judges that 600 msec has not elapsed (No in step S5), it judges again whether or not it has elapsed (step S5). When the CPU 203 judges that 600 msec has elapsed (Yes in step S5), the CPU 203 instructs the attachment / detachment control unit 223 to end the attachment operation via the communication I / F 201. When the attachment / detachment control unit 223 receives the instruction of the attachment operation end from the CPU 203, it stops the attachment / detachment motor (S6) and ends the attachment operation. By following the above-mentioned procedure, it is possible to switch the attached and detached states of the charge eliminating rollers 30a and 30b using the attachment / detachment mechanism 150, thereby suppressing wear of the charge eliminating rollers 30a and 30b.

[0036] [Operation for sheets that require static elimination and sheets that do not] Next, the operation for sheets that require and do not require static elimination by the contact static eliminator 29 will be described with reference to Figs. 9(a) to (e). Here, synthetic paper is used as an example of a sheet that requires static elimination by the contact static eliminator 29. Also, plain paper is used as an example of a sheet that does not require static elimination by the contact static eliminator 29. Furthermore, a sheet row in which synthetic paper and plain paper are mixed in an image forming job (hereinafter also simply referred to as a job) is called a mixed sheet row. Also, a job in which different types of sheets such as synthetic paper and plain paper are transported is called a mixed job. In this embodiment, a sheet that requires static elimination is a first type of sheet (synthetic paper), and a sheet that does not require static elimination is a second type of sheet (plain paper) different from the first type.

[0037] Fig. 9(a) is a time chart showing the operation in a job of plain paper that does not require static elimination by the contact-type static eliminator 29, and Fig. 9(b) is a time chart showing the operation in a job of synthetic paper that requires static elimination by the contact-type static eliminator 29. Figs. 9(c) to (e) are mixed jobs in a mixed sheet row of plain paper that requires static elimination and synthetic paper that does not, Fig. 9(c) is a comparative example, and Figs. 9(d) and (e) are time charts showing the operation of this embodiment.

[0038] FIG. 9(a) is a time chart of a job for five sheets of plain paper that does not require static elimination. That is, the job shown in FIG. 9(a) is an example of a second job in which only sheets of a type that does not require static elimination are transported. Since the non-contact static elimination device 31 performs static elimination on all sheets, the non-contact static elimination high voltage board 240 keeps the high voltage on from the start to the end of the job. Since plain paper with a small current resistance does not require static elimination by the contact static elimination device 29, the static elimination high voltage board 230 keeps the high voltage off and the static elimination roller pair 30 facing the attachment / detachment mechanism 150 in a de-energized state. By de-energizing the static elimination roller pair 30 in this way, it is possible to prevent wear of the static elimination roller pair 30. In this way, in the second job in which only sheets of a type that does not require static elimination are transported, the CPU 203 executes a third process in which the static elimination roller pair 30 is not neutralized by moving the attachment / detachment mechanism 150 to the retreat position. That is, the CPU 203 does not execute the charge elimination process by the charge elimination roller pair 30 for the second type of sheet that does not require charge elimination.

[0039] FIG. 9B is a time chart of a job for five sheets of synthetic paper that require static elimination. That is, the job shown in FIG. 9B is an example of a first job in which only sheets of a type that require static elimination are transported. Since synthetic paper with a large current resistance requires static elimination by the contact type static elimination device 29, the high voltage of the static elimination high voltage board 230 is turned on and the static elimination roller pair 30 facing the attachment / detachment mechanism 150 is turned on. In this way, in the first job in which only sheets of a type that require static elimination are transported, the CPU 203 performs a first process of eliminating static electricity from the sheet by applying a voltage to the static elimination roller pair 30 with the static elimination roller pair 30 positioned at the contact position. That is, the CPU 203 performs a static elimination process by the static elimination roller pair 30 for the first type of sheet that requires static elimination. T1 shown in FIG. 9B etc. is the minimum sheet-to-sheet time required for image formation and sheet transport on plain paper and synthetic paper.

[0040] 9C is a time chart showing the operation of a comparative example in a mixed job of synthetic paper that requires static elimination and plain paper that does not require static elimination. Here, it is assumed that a mixed sheet row in which a first type of sheet (synthetic paper) and a second type of sheet (plain paper) are mixed and transported is transported.

[0041] When switching from synthetic paper to plain paper, the switching operation to the detached state by the attachment / detachment mechanism 150 begins after the rear end of the synthetic paper passes the contact-type static eliminator 29. The time required for the attachment / detachment mechanism 150 to switch the static elimination roller pair 30 to the detached state is longer than the inter-sheet time (T1) of the synthetic paper. For this reason, the inter-sheet time (T2) must be set longer than T1 so that the next synthetic paper arrives at the contact-type static eliminator 29 after waiting for the inter-sheet time (T1) of the static elimination roller pair 30 to switch to the detached state. In addition, the high voltage switching operation by the static elimination high voltage board 230 falls within the inter-sheet time (T1) of the synthetic paper, so it only needs to be performed before the leading edge of the plain paper arrives at the contact-type static eliminator 29.

[0042] Similarly, when switching from plain paper to synthetic paper, the attaching / detaching mechanism 150 starts switching to the attached state after the trailing edge of the plain paper passes the contact-type static elimination device 29. The time required for the attaching / detaching mechanism 150 to switch the static elimination roller pair 30 to the attached state is longer than the sheet interval (T1) of plain paper. Therefore, the sheet interval (T2) must be set longer than T1 so that the next synthetic paper arrives at the contact-type static elimination device 29 after waiting for the static elimination roller pair 30 to switch to the attached state. In addition, the high voltage switching operation by the static elimination high voltage board 230 falls within the sheet interval (T1) of plain paper, so it may be performed before the leading edge of the synthetic paper arrives at the contact-type static elimination device 29. In this way, when a first type sheet (synthetic paper) is conveyed to the static elimination roller pair 30, the CPU 203 executes a first process of applying a voltage to the static elimination roller pair 30 while the static elimination roller pair 30 is positioned at the contact position to eliminate static electricity from the sheet.

[0043] In the comparative example, in a mixed job in which sheets that require static electricity removal and sheets that do not require static electricity removal are mixed, there is a problem that switching due to the attachment and detachment operation takes time, and there is a risk of productivity decreasing. Therefore, in the case of the mixed job as described above, even for sheets that do not require static electricity removal, the attachment and detachment mechanism 150 is left in the attached state and only the high voltage output from the static electricity removal high voltage board 230 is switched to the off state, thereby suppressing a decrease in productivity.

[0044] Fig. 9(d) is a time chart showing the operation in this embodiment for the same mixed job as Fig. 9(c). When switching from synthetic paper that requires static elimination to plain paper that does not require static elimination, the attachment / detachment mechanism 150 maintains the attached state, and the static elimination high voltage board 230 starts switching the high voltage after the rear end of the synthetic paper passes the contact type static elimination device 29. The operation of switching from the static elimination high voltage ON state to the static elimination high voltage OFF state falls within the sheet interval (T1), so there is no need to leave an interval between sheets to wait for the high voltage to be switched.

[0045] Similarly, when switching from plain paper to synthetic paper, the attachment / detachment mechanism 150 maintains the attached state, and the high voltage switching operation by the static elimination high voltage board 230 begins after the rear end of the plain paper has passed the contact type static elimination device 29. The operation of switching the static elimination high voltage from the OFF state to the ON state falls within the sheet-to-sheet time (T1) for plain paper, so there is no need to leave an interval between sheets to wait for the high voltage to be switched.

[0046] Thus, in this embodiment, in a mixed job in which sheets that require static elimination and sheets that do not require static elimination are mixed, the attached state is maintained, and only the high voltage output by the static elimination high voltage board 230 of the contact type static elimination device 29 is switched. That is, in a mixed job, the CPU 203 executes a first process for a first type of sheet (synthetic paper) by applying a voltage to the static elimination roller pair 30 with the static elimination roller pair 30 positioned at the contact position to eliminate static electricity from the sheet. On the other hand, the CPU 203 executes a second process for a second type of sheet (plain paper) by not applying a voltage to the static elimination roller pair 30 with the static elimination roller pair 30 positioned at the contact position to eliminate static electricity from the sheet. This makes it possible to prevent a decrease in productivity.

[0047] 9(e) is a time chart showing the operation of this embodiment in a mixed job of synthetic paper that requires static elimination and plain paper that does not, showing the case where plain paper that does not require static elimination follows. When switching from synthetic paper that requires static elimination to plain paper that does not require static elimination, the attachment / detachment mechanism 150 maintains the attached state, and the static elimination high voltage board 230 starts switching the high voltage after the rear end of the synthetic paper has passed the contact type static elimination device 29. The operation of switching from the static elimination high voltage ON state to the static elimination high voltage OFF state falls within the sheet interval (T1), so there is no need to leave an interval between sheets to wait for the high voltage to be switched.

[0048] However, if plain paper that does not require static elimination is subsequently fed in succession, the static elimination roller pair 30 will continue to wear out. Therefore, here, the switching operation to the detached state by the attachment / detachment mechanism 150 is started after the trailing end of the fifth sheet of plain paper passes the contact-type static eliminator 29. The time required for the attachment / detachment mechanism 150 to switch the static elimination roller pair 30 to the detached state is longer than the sheet interval time (T1) for plain paper. For this reason, the sheet interval (T2) is opened so that the next synthetic paper can arrive at the contact-type static eliminator 29 after waiting for the static elimination roller pair 30 to enter the attached state.

[0049] In this manner, in this embodiment, in a mixed job in which sheets requiring and not requiring static elimination are mixed, if sheets not requiring static elimination are consecutive, the state is switched to the destaticization state. That is, when the second type of sheet (plain paper) exceeds a predetermined number (here, five sheets) of sheets, the CPU 203 can execute a third process in which the sheets are not destaticized by moving the static elimination roller pair 30 to a retreat position by the attachment / detachment mechanism 150. That is, the CPU 203 executes a first mode (see FIG. 9(e)) in which the first process, the second process, and the third process are executed by switching between them. This makes it possible to prevent a decrease in productivity while suppressing wear of the static elimination roller pair 30. Note that, in this embodiment, the predetermined number of sheets, which is a threshold value for switching between processes, is set to five sheets, but is not limited to this. This predetermined number can be set based on the life of the charge removing rollers 30a, 30b of the charge removing roller pair 30. For example, if the charge removing rollers 30a, 30b are made of long-life materials, the number may be more than five.

[0050] [Attachment / detachment mode switching operation] Next, the operation flow of the attachment / detachment mode switching of this embodiment will be described with reference to the flowchart shown in FIG. 10. The process shown in this flowchart is executed by the CPU 203. When the CPU 203 is instructed to start the attachment / detachment mode switching operation, it judges whether or not the corresponding page is a sheet that requires static elimination (step S10). When the CPU 203 judges that the sheet requires static elimination (Yes in step S10), it clears the sheet number counter (step S11). Here, the sheet number counter counts the number of sheets that do not require static elimination and have been processed in the attached state, and the judgment process will be described later. The CPU 203 instructs the attachment / detachment control unit 223 to perform the attachment operation of the attachment / detachment mechanism 150 (step S12). The attachment / detachment control unit 223 performs the attachment operation of the flowchart shown in FIG. 6 and sets the static elimination roller pair 30 to the attached state.

[0051] On the other hand, when the CPU 203 determines that the sheet does not require static elimination (No in step S10), it determines whether the sheet is in an attached state (step S13). When the CPU 203 determines that the sheet is not in an attached state (No in step S13), it maintains the detached state and ends the process. When the CPU 203 determines that the sheet is in an attached state (Yes in step S13), it increments the sheet number counter by one (step S14). Then, the CPU 203 determines whether the sheet number counter has exceeded 5 (step S15). When the CPU 203 determines that the sheet number counter has not exceeded 5 (five or less) (No in step S15), it maintains the attached state and ends the process. When the CPU 203 determines that the sheet number counter has exceeded 5 (Yes in step S15), it instructs the attachment / detachment control unit 223 to perform a detaching operation of the attachment / detachment mechanism 150 (step S16), and ends the process.

[0052] In this way, when the second type of sheets (plain paper) exceeding a predetermined number (e.g., five sheets) are continuously transported to the discharging roller pair 30, the CPU 203 executes a third process of moving the discharging roller pair 30 to the retracted position by the attachment / detachment mechanism 150 (step S16). In this embodiment, when five sheets of plain paper, which is the predetermined number, are continuously transported to the discharging roller pair 30, the CPU 203 switches from the second process to the third process from the sixth sheet onwards.

[0053] In the present embodiment, the CPU 203 switches from the second process to the third process from the sixth sheet when a predetermined number of five plain papers are continuously transported to the static electricity removing roller pair 30, but this is not limited to the above. For example, if the CPU 203 knows the contents of the mixed sheet row in advance, it knows that there are five or more consecutive plain papers, so it may switch from the second process to the third process from any number of consecutive plain papers, such as the first or second sheet. In other words, when the CPU 203 determines that more than a predetermined number of second type sheets are continuously transported to the static electricity removing roller pair 30, it can switch from the second process to the third process from any number of consecutive sheets.

[0054] [Operation flow of this embodiment] Next, the control flow of this embodiment will be described with reference to the flowchart shown in FIG. 11. In this embodiment, when a predetermined number of sheets not requiring static elimination are consecutive in a mixed job, the static elimination roller pair 30 is set to a detached state. That is, the CPU 203 executes a first mode (see FIG. 9(e)) in which a first process, a second process, and a third process are switched and executed. The process shown in this flowchart is executed by the CPU 203. When the CPU 203 starts a job, it instructs the non-contact static elimination high voltage control unit 224 to apply a high voltage via the communication I / F 201, and applies a voltage to the non-contact static elimination device 31 (step S21). The CPU 203 executes the attach / detach switching operation of the static elimination roller pair 30 shown in the flowchart of FIG. 10 (step S22). The CPU 203 judges whether the sheet requires static elimination (step S23).

[0055] When the CPU 203 determines that the sheet requires static elimination (Yes in step S23), it instructs the static elimination high voltage control unit 222 to apply a negative voltage to the static elimination roller pair 30 (step S24). On the other hand, when the CPU 203 determines that the sheet does not require static elimination (No in step S23), it instructs the static elimination high voltage control unit 222 to turn off the high voltage of the static elimination roller pair 30 (step S25).

[0056] Next, the CPU 203 determines whether or not the trailing end of the sheet has passed through the contact-type static eliminator 29 (step S26). If the CPU 203 determines that the trailing end of the sheet has not passed through the contact-type static eliminator 29 (No in step S26), it again determines whether or not the trailing end of the sheet has passed through the contact-type static eliminator 29 (step S26). If the CPU 203 determines that the trailing end of the sheet has passed through the contact-type static eliminator 29 (Yes in step S26), it determines whether or not there is a subsequent sheet (step S27).

[0057] When the CPU 203 determines that there is a succeeding sheet (Yes in step S27), it executes the operation from step S22 again. When the CPU 203 determines that there is no succeeding sheet (No in step S27), it instructs the static elimination high voltage control unit 222 to turn off the high voltage, and turns off the negative voltage applied to the static elimination roller pair 30 (step S28). The CPU 203 instructs the attachment / detachment control unit 223 to perform a detachment operation (step S29). The attachment / detachment control unit 223 executes the detachment operation shown in the flowchart of FIG. 6, and switches the static elimination roller pair 30 to the detached state. Here, if the static elimination roller pair 30 is already in the detached state, the detachment operation does not need to be performed. The CPU 203 instructs the non-contact static elimination high voltage control unit 224 to turn off the high voltage via the communication I / F 201, turns off the high voltage of the non-contact static elimination high voltage board 240 (step S30), and ends the job.

[0058] As described above, according to the static eliminator 3 of this embodiment, when a mixed sheet row containing sheets that require static elimination and unnecessary sheets is neutralized, when switching from a sheet that requires static elimination to an unnecessary sheet, the static elimination roller pair 30 is conveyed in the attached state without applying a voltage. This eliminates the need for the static elimination roller pair to move between the contact position and the retracted position, making it possible to reduce downtime due to the attachment and detachment operation and improve productivity.

[0059] Furthermore, according to the static elimination device 3 of this embodiment, when a predetermined number of sheets that do not require static elimination are continuously conveyed to the static elimination roller pair 30, the attachment / detachment mechanism 150 moves the static elimination roller pair 30 to a retracted position. This prevents the static elimination roller pair 30 from being maintained in contact with each other more than necessary, thereby preventing a shortened lifespan due to wear, and improves productivity in a mixed job of sheets that require static elimination and sheets that do not.

[0060] In the above-described embodiment, when a predetermined number or more of sheets that do not require static elimination are consecutively laid in a mixed job, the pair of static elimination rollers 30 is set to a deactivated state. That is, the CPU 203 executes the first mode (see FIG. 9(e)) in which the first process, the second process, and the third process are switched and executed, but this is not limited to the above. For example, the on state may be maintained during a mixed job. That is, the CPU 203 may execute the second mode (see FIG. 9(d)) in which the first process and the second process are switched and executed, regardless of the number of consecutive sheets that do not require static elimination. In this case, productivity can be further improved.

[0061] Also, the first mode (see FIG. 9E) and the second mode (see FIG. 9D) may be switched by the user depending on the purpose. In that case, for example, as shown in FIG. 12, an operation switching screen is displayed on the display 206. A button 206a for prioritizing productivity and a button 206b for prioritizing life are displayed on the display 206. When the user presses the button 206a, the second mode is executed, and when the user presses the button 206b, the first mode is executed. Alternatively, when the user presses the button 206b, a comparative example (see FIG. 9C) in which the pair of static elimination rollers 30 is in a non-discharged state for sheets that do not require static elimination, regardless of the number of consecutive sheets, may be executed. That is, the display 206 is an example of an input unit, and a selection result between the first mode and the second mode is input. The CPU 203 executes either the first mode or the second mode based on the selection result input to the display 206. [Explanation of symbols]

[0062] 1... image forming system, 2... image forming apparatus, 3... static electricity removal device, 30... static electricity removal roller pair (static electricity removal member), 30a, 30b... static electricity removal roller, 31... non-contact static electricity removal device (non-contact static electricity removal section), 150... attachment / detachment mechanism (movement section), 203... CPU (control section), 206... display (input section), S... sheet

Claims

1. A static elimination member that contacts the conveyed sheet and applies a voltage to eliminate static electricity from the sheet, A moving part moves the static elimination member between a contact position where it is in contact with the sheet and a retracted position where it is separated from the sheet. The system includes a control unit capable of performing a first process of removing static electricity from the sheet by applying a voltage to the static electricity removal member while the static electricity removal member is positioned at the contact position, and a second process of not removing static electricity from the sheet by not applying a voltage to the static electricity removal member while the static electricity removal member is positioned at the contact position. The control unit, In a mixed loading job in which a sheet of type 1 and a sheet of type 2 different from the first type are transported, the first processing is performed on the sheet of type 1, and the second processing is performed on the sheet of type 2. In the mixed loading job, when the second type of sheet is continuously transported to the static elimination member in a predetermined number of sheets, the moving unit can move the static elimination member to the retracted position, thereby enabling a third process in which the sheets are not statically eliminated. A static elimination device characterized by the following features.

2. The control unit switches from the second process to the third process when a predetermined number of sheets of the second type are continuously transported to the static elimination member in the mixed loading job. The static elimination device according to feature 1.

3. The control unit, in the mixed loading job, determines that a predetermined number of sheets of the second type are continuously transported to the static elimination member, and switches from the second process to the third process. The static elimination device according to feature 1.

4. The control unit, A first mode that performs the first process, the second process, and the third process, A second mode that performs the first process and the second process, The static elimination device according to feature 1.

5. The system includes an input unit that receives the selection result between the first mode and the second mode, The control unit executes either the first mode or the second mode based on the selection result input to the input unit. The static elimination device according to feature 4.

6. The control unit executes the first process in a first job in which only sheets of the first type are transported, and executes the third process in a second job in which only sheets of the second type are transported. The static elimination device according to feature 1.

7. The unit is positioned downstream of the static elimination member in the sheet transport direction and includes a non-contact static elimination unit that removes static electricity from the sheet being transported from the static elimination member without contact. The static elimination device according to feature 1.

8. The static elimination member is a pair of static elimination rollers having rollers made of sponge. The static elimination device according to feature 1.

9. An image forming apparatus that forms an image on a sheet, The static elimination device comprises a static elimination device according to any one of claims 1 to 8, which receives a sheet on which an image has been formed by the image forming apparatus and removes static electricity, An image forming system characterized by the following features.

Images