Neutralization apparatus and image formation apparatus

Abstract

To provide a neutralization apparatus which allows a user to determine a suitable neutralization voltage in a simple process.SOLUTION: One unit of sample sheets are neutralized under the same neutralization voltage, and sample output for exhausting the same to an exhaust tray is executed (S4 to S8). After the output of the one unit of sample sheets, the neutralization voltage is changed (S13, S4), and other sample sheets in one unit are neutralized under the neutralization voltage after the change and are exhausted to the exhaust tray. In this way, since the sheet bundles of the sample sheets neutralized under the different neutralization voltages in one unit are loaded on the exhaust tray, a user can actually confirm the loading conditions and the conveyance conditions of the sample sheets by comparing plural parts of the sheet bundles. Then, the user can set a high neutralization voltage with a high sheet neutralization effect (S10 to S12). With this simple process, the user can set an optimum neutralization voltage in accordance with the charge quantity on the sheets after copying.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a static eliminator that eliminates static electricity from a sheet, and an image forming apparatus including the static eliminator. [Background technology]

[0002] In an electrophotographic image forming apparatus, a high transfer voltage is applied when a toner image is transferred to a sheet, so that the sheet after the transfer may become charged. If the sheet after the transfer is not de-electrified, when the sheet is discharged to the discharge tray, it may electrostatically adhere to the sheet previously stacked on the discharge tray, causing a stacking failure, or the sheet being conveyed toward the discharge tray may electrostatically adhere to the sheet during the conveyance, causing a conveyance failure. Therefore, the image forming apparatus is provided with a de-electrification device that de-electrifies the sheet after the transfer (Patent Document 1). The de-electrification device described in Patent Document 1 has a contact type de-electrification device that can de-electrify the sheet by contacting it, and a non-contact type de-electrification device that can de-electrify the sheet without contacting it. In the de-electrification device described in Patent Document 1, the sheet is de-electrified using a contact type de-electrification device or a non-contact type de-electrification device, or both a contact type de-electrification device and a non-contact type de-electrification device, depending on the difference in the surface resistance of the sheet.

[0003] To obtain a high sheet static elimination effect using a contact static eliminator or a non-contact static eliminator, it is necessary to apply an optimal voltage for static elimination to each (hereinafter referred to as static elimination voltage). Since the surface resistance of a sheet differs depending on the type of sheet, the static elimination voltage of a contact static eliminator or the static elimination voltage of a non-contact static eliminator is determined according to the type of sheet. However, the amount of charge on the sheet after transfer can vary depending on the voltage value of the transfer voltage applied to transfer the toner image to the sheet and the environment at that time (e.g. humidity, etc.). Therefore, the user needs to measure the amount of charge on the sheet on which an image has been formed and adjust the static elimination voltage based on the measured amount of charge on the sheet. [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 method in which the user actually measures the amount of charge on the sheet and adjusts the charge removal voltage, there are problems in that the user's operations become cumbersome and it takes time to adjust the charge removal voltage.

[0006] The present invention has been made in consideration of the above problems, and has an object to provide a static eliminator and an image forming apparatus that enable a user to set an appropriate static elimination voltage through a simple process. [Means for solving the problem]

[0007] The static elimination device according to one embodiment of the present invention is characterized in that it comprises: a static elimination unit that eliminates charges accumulated on a sheet by applying a voltage; a control unit capable of executing a predetermined process of applying a first voltage to the static elimination unit to discharge a first sheet bundle from which a set number of sheets have been de-electrified, and, following the discharge of the first sheet bundle, applying a second voltage different from the first voltage to the static elimination unit to discharge a second sheet bundle from which the set number of sheets have been de-electrified; and an input unit that accepts an input to set either the first voltage or the second voltage as the voltage to be applied to the sheets by the static elimination unit after the predetermined process is performed. Effect of the Invention

[0008] According to the present invention, a user can set an appropriate static elimination voltage through a simple process. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a block diagram showing a control system of the image forming apparatus. [Diagram 3] FIG. 2 is a schematic diagram showing a contact type static eliminator. [Figure 4](a) is a schematic diagram showing the non-contact static electricity removing device before the sheet passes, and (b) is a schematic diagram showing the non-contact static electricity removing device after the sheet passes. [Diagram 5] 4 is a flowchart showing a static elimination voltage adjustment process according to the first embodiment. [Figure 6] 1A is a diagram showing an adjustment mode screen, and FIG. 1B is a diagram showing a screen for inputting the number of sheets per copy. [Figure 7] FIG. 13 is a diagram showing a sample sheet to be output. [Figure 8] 1A is a diagram showing an adjustment value input screen, and FIG. 1B is a diagram showing an adjustment value confirmation screen. [Figure 9] 10 is a flowchart showing a static elimination voltage adjustment process according to a second embodiment. [Figure 10] FIG. 13 is a diagram showing a sample confirmation screen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [First embodiment] <Image forming device> The image forming apparatus of this embodiment will be described below. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIG. 1. The image forming apparatus 101 shown in FIG. 1 is a tandem-type full-color printer of an electrophotographic system. As shown in FIG. 1, the image forming apparatus 101 includes a printing apparatus 102, a static eliminator 103, and a finisher 104. Note that, in this example, the printing apparatus 102, the static eliminator 103, and the finisher 104 are configured in separate housings and are connected to each other, but this is not limiting. For example, the printing apparatus 102 and the static eliminator 103 may be provided in the same housing.

[0011] The printing device 102 forms a toner image on a sheet based on image data sent from an external device, such as a document reading device connected to the printing device 102 or a personal computer (not shown). Sheets are supplied to the printing device 102 from cassettes 111 and 112 capable of accommodating various sheets. Only the topmost sheet among the sheets accommodated in the cassettes 111 and 112 is transported to a transport path 113. Examples of the sheet include sheet materials such as thin paper, plain paper, thick paper, rough paper, textured paper, and coated paper.

[0012] The printing device 102 has image forming stations 114, 115, 116, and 117 that form images of yellow, magenta, cyan, and black. In the image forming stations 114, 115, 116, and 117, a toner image is formed on the photosensitive drum of each station. The toner image formed on the photosensitive drum is primarily transferred to an intermediate transfer belt 118 as an image carrier in response to a primary transfer voltage being applied to the primary transfer roller. Then, the intermediate transfer belt 118 rotates clockwise, so that the toner image reaches a secondary transfer portion T2. ​​The secondary transfer portion T2 is a transfer nip portion formed by abutting a secondary transfer inner roller 119 and a secondary transfer outer roller 120, and in response to a secondary transfer voltage being applied to the secondary transfer inner roller 119 as a transfer member by a power source (not shown), the toner image on the intermediate transfer belt 118 (on the image carrier) is secondarily transferred to a sheet conveyed through a conveying path 113. The image forming stations 114 , 115 , 116 , and 117 and the primary transfer roller constitute an image forming section 190 that forms a toner image on the intermediate transfer belt 118 .

[0013] The toner image secondarily transferred to the sheet is fixed to the sheet by applying heat and pressure by the first fixing unit 121. The first fixing unit 121 includes a pressure roller and a heating roller, and when the sheet is sandwiched and conveyed through a fixing nip portion formed by these rollers, the toner is melted by the heat, and the melted toner image is pressed onto the sheet by pressure.

[0014] The sheet that has passed through the first fixing unit 121 is conveyed to a conveying path 125 through a conveying path 122. However, depending on the type of sheet, further melting and pressure bonding may be required for fixing, and such a sheet is conveyed to a second fixing unit 123. The second fixing unit 123 has the same configuration as the first fixing unit 121 described above, and fixes the toner image to the sheet by applying heat and pressure. The sheet that has passed through the second fixing unit 123 is conveyed to a conveying path 125 through a conveying path 124. Here, in the case of a double-sided image forming mode in which a toner image is formed on both sides of a sheet, after the toner image is formed on the first side, the sheet is conveyed from the conveying paths 122 and 124 to a reversing path 126, where the leading edge and the trailing edge in the conveying direction are swapped. Thereafter, the sheet is conveyed to a conveying path 113 through a double-sided conveying path 127, and the toner image on the intermediate transfer belt 118 is secondarily transferred to the second side of the sheet at a secondary transfer section T2.

[0015] The sheet conveyed to the conveying path 125 is delivered from the printing device 102 via the conveying path 128 to the charge removing device 103 disposed downstream of the secondary transfer portion T2 in the sheet conveying direction. In the image forming device 101, a high secondary transfer voltage is applied when a toner image is secondarily transferred to the sheet, so that the sheet becomes charged after the transfer. If the sheet is charged, the sheet may electrostatically adhere to a conveying guide or the like during conveyance, causing a conveyance failure, or when the sheet is discharged to the discharge tray (135, 136), the sheet may electrostatically adhere to sheets already stacked on the discharge tray (135, 136), causing a stacking failure. Therefore, in order to remove the charge from the charged sheet and to eliminate the charge, the image forming device 101 of this embodiment is provided with the charge removing device 103. The static eliminator 103 has a contact static eliminator 129 and a non-contact static eliminator 131, and as described below, a static elimination voltage is applied to the contact static eliminator 129 and the non-contact static eliminator 131 to remove electric charges from the sheet after secondary transfer.

[0016] The finisher 104 is capable of stacking a large volume of sheets, and is provided with an upper tray 135 as a second discharge section and a lower tray 136 as a first discharge section as discharge trays for discharging sheets. The upper tray 135 is disposed vertically above the lower tray 136. A sheet transported from the printing device 102 to the finisher 104 is discharged to the upper tray 135 via a transport path 132 and a transport path 133, or is discharged to the lower tray 136 via a transport path 132 and a transport path 134. The transport path (132, 133) leading to the upper tray 135 and the transport path (132, 134) leading to the lower tray 136 share the same route as the transport path 132, and the routes of the transport paths 133 and 134 beyond the transport path 132 are different. The transport paths 132, 133, and 134 are formed by guide members (180, 181) that guide the sheet P toward the upper tray 135 and the lower tray 136. The guide members (180, 181) are molded from, for example, resin.

[0017] Transport sensors 137, 138, and 139 that detect the passage of a sheet are disposed along the transport paths 132, 133, and 134, respectively, and the detection results are sent to the printing device 102. Based on the detection results, the printing device 102 (CPU 203 for details, see FIG. 2 described later) detects that a transport jam, in which the sheet gets stuck during transport, has occurred in the finisher 104 if it does not detect the passage of the leading or trailing end of the sheet even after a predetermined time has elapsed.

[0018] <Image forming device control system> Next, the control system of the image forming apparatus 101 will be described using FIG. 2 with reference to FIG. 1. First, the control system of the printing apparatus 102 will be described. As shown in FIG. 2, the printing apparatus 102 is composed of a communication interface (I / F) 201, a hard disk drive (HDD) 202, a central processing unit (CPU) 203, a memory 204, an operation unit 205, and a display 206. Furthermore, the printing apparatus 102 includes a laser exposure unit 207, an image creating unit 208, a fixing unit 209, a feeding unit 210, and an image reading unit 211. Each of the components is connected via a system bus 213.

[0019] The communication interface 201 is connected to the static eliminator 103 via a communication cable 229, and input / output of control instructions, data, and the like is performed between the printer 102 and the static eliminator 103. The communication interface 201 is also connected to an external device such as a computer (not shown), and input / output of various data is performed between the printer 102 and the static eliminator 103. The HDD 202 as a storage unit is a storage device in which control programs and data are stored. The CPU 203 as a control unit executes, for example, an image forming process (second mode) and a static elimination voltage adjustment process (first mode, see FIG. 5 described later) (not shown) based on the control program and the like stored in the HDD 202, and controls the entire image forming apparatus 101 accordingly. The memory 204 stores the control programs and image data required when the CPU 203 executes various processes, and also functions as a temporary work area for data.

[0020] An operation unit 205 as an input unit accepts various setting inputs and operation instructions from a user. A display 206 as a display unit can display setting information of the image processing apparatus, the processing status of an image forming job, and various screens described later. This display 206 may be a touch panel that allows a user to touch a software key on the screen to execute various operations that are assigned in advance to the operated software key.

[0021] The laser exposure unit 207 is a device that performs primary charging and laser exposure to irradiate the photosensitive drum with laser light in order to transfer a toner image. In the laser exposure unit 207, first, primary charging is performed to charge the surface of the photosensitive drum to a uniform negative potential. Next, the laser light emitted from the laser driver is irradiated onto the photosensitive drum while the reflection angle is adjusted by a polygon mirror, whereby the negative charge at the portion of the photosensitive drum surface irradiated with the laser light is neutralized, and an electrostatic latent image is formed on the photosensitive drum.

[0022] The image forming unit 208 is a device for transferring toner onto a sheet, and is composed of a developing unit, a transfer unit, a toner supply unit, etc., and transfers the toner on the photosensitive drum onto a sheet. 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 positive voltage is applied to the primary transfer roller to transfer the toner on the surface of the photosensitive drum onto the intermediate transfer belt 118, and a negative voltage is applied to the secondary transfer inner roller 119 to transfer the toner on the intermediate transfer belt 118 onto the sheet, performing primary transfer. The fixing unit 209 is a device for melting and fixing the toner on the sheet to the sheet by heat and pressure, and is composed of a heater, a heating roller, a pressure roller, etc. The feeding unit 210 is a device for transporting the sheet, and the sheet feeding and transporting operations are controlled by rollers and various sensors.

[0023] Next, a control system of the static eliminator 103 will be described. The static eliminator 103 is composed of a communication interface (I / F) 221, a static elimination high voltage control unit 222, an attachment / detachment control unit 223, and a non-contact static elimination high voltage control unit 224, and each of the components is connected via a system bus 225. The communication interface 221 is connected to the printing device 102 via a communication cable 229, and communication is performed between the printing device 102 and the static eliminator 103 to send and receive control instructions, data, and the like.

[0024] 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 the static elimination voltage of the contact static elimination device 129 by the static elimination high voltage power supply 230 (see FIG. 3 described later). The attachment / detachment control unit 223 controls the movement between a contact position where the static elimination roller 130a and the static elimination roller 130b of the contact static elimination device 129 are in contact with each other by a contact / detachment mechanism (not shown) and a non-contact position where they are not in contact. The non-contact static elimination high voltage control unit 224 controls the static elimination voltage of the non-contact static elimination device 131 by the non-contact static elimination high voltage power supply 240 (see FIG. 4(a) described later).

[0025] Next, the control system of the finisher 104 will be described. The finisher 104 is composed of a communication interface (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 interface 231 is connected to the static eliminator 103 via a communication cable 239, and communication is performed between the finisher 104 and the static eliminator 103 to transmit and receive control instructions and data. The CPU 232 performs various controls required for discharging the sheet 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 can perform control to divide and transport the sheet conveyed from the static eliminator 103 to an upper tray 135 and a lower tray 136 based on a control instruction from the CPU 232.

[0026] Next, the contact type static eliminator 129 and the non-contact type static eliminator 131 provided in the static eliminator 103 as a static eliminator will be described with reference to Fig. 1 and Fig. 3 to Fig. 4(b). Fig. 3 is a schematic diagram showing the contact type static eliminator 129. Fig. 4(a) is a schematic diagram showing the non-contact type static eliminator 131 before the sheet passes, and Fig. 4(b) is a schematic diagram showing the non-contact type static eliminator 131 after the sheet passes.

[0027] In this embodiment, a negative voltage is applied to the inner secondary transfer roller 119 as a secondary transfer voltage. Therefore, when the sheet passes through the secondary transfer portion T2, the surface of the sheet on the side of the inner secondary transfer roller 119 is negatively charged, and the reverse surface of the sheet on the opposite side is positively charged by dielectric polarization. If the sheet is transported to the finisher 104 while still being charged, the sheet may be electrostatically attracted to a transport guide or the like during transport, causing a transport failure. Alternatively, when the sheet is discharged to the discharge tray (135, 136), the sheet may be electrostatically attracted to sheets already stacked on the discharge tray (135, 136), causing a stacking failure, or the stacked sheets may stick to each other due to electrostatic force. Therefore, in this embodiment, the charge is removed from the sheet by the static eliminator 103 to eliminate static electricity. The static eliminator 103 has two static eliminators, a contact static eliminator 129 and a non-contact static eliminator 131, and these static eliminators are arranged side by side in the sheet transport direction.

[0028] <Contact static eliminator> As shown in Fig. 3, the contact-type static elimination device 129 (contact-type static elimination section) has two opposing static elimination rollers 130a, 130b. The static elimination roller 130a is grounded, and a static elimination voltage is applied to the static elimination roller 130b by a static elimination high-voltage power supply 230. When the static elimination roller 130a is in contact with the front surface of the sheet and the static elimination roller 130b is in contact with the rear surface of the sheet, a negative static elimination voltage is applied by the static elimination high-voltage power supply 230, and the positive charge present on the rear surface of the sheet is removed. As a result, when the positive charge present on the rear surface of the sheet decreases, the negative charge present on the front surface of the sheet also decreases accordingly. The contact-type static elimination device 129 applies a voltage directly by contacting the sheet P, and therefore a high static elimination effect can be obtained.

[0029] <Non-contact static eliminator> Although the contact type static eliminator 129 described above provides a high static elimination effect, the potentials of the front and back surfaces of the sheet P after static elimination (hereinafter referred to as surface potential) are prone to variation. In order to make the surface potential of the sheet P, which has become uneven due to static elimination by the contact type static eliminator 129, approximately uniform, the non-contact type static eliminator 131 is disposed downstream of the contact type static eliminator 129 in the conveying direction of the sheet P. The non-contact type static eliminator 131 can generally eliminate the remaining charge of the sheet after static elimination by the contact type static eliminator 129 in a non-contact state. In this embodiment, an AC corotron type is used as the non-contact type static eliminator 131.

[0030] As shown in FIG. 4(a), the non-contact static electricity removal device 131 (non-contact static electricity removal section) has a discharge wire 140 and an earth electrode 141, and a positive static electricity removal voltage is applied to the discharge wire 140 by a non-contact static electricity removal high-voltage power supply 240. When a positive static electricity removal voltage is applied to the discharge wire 140, a corona discharge occurs in the discharge wire 140, and a positive charge is generated. Then, as shown in FIG. 4(b), the positive charge generated in the discharge wire 140 is attracted to the negative charge on the sheet surface by electrostatic force. As a result, the negative charge on the sheet surface is removed. On the other hand, the positive charge on the back surface of the sheet is attracted to the earth electrode 141, which is grounded and has a potential of "0", and is thereby removed. The effect of eliminating static electricity on sheet P by such a non-contact static eliminator 131 is smaller than that by the contact static eliminator 129; however, since the non-contact static eliminator 131 can reduce the variation in the surface potential of sheet P after static elimination, the surface potential of sheet P after passing through the non-contact static eliminator 131 becomes approximately uniform.

[0031] <Static charge removal voltage> Incidentally, the amount of charge on the sheet P after the secondary transfer differs depending on the type of sheet. Therefore, in this embodiment, in order to obtain a charge removal effect on the sheet P, a predetermined reference voltage to be applied to each of the contact-type charge removal device 129 and the non-contact-type charge removal device 131 can be set according to the type of sheet in accordance with a reference voltage table shown in Table 1. The reference voltage table is stored in advance in, for example, the HDD 202 (see FIG. 2) of the printing device 102. [Table 1]

[0032] As shown in Table 1, the reference voltage table sets the reference voltage of the contact-type static eliminator 129 and the reference voltage of the non-contact-type static eliminator 131 for each type of sheet (paper type). In the reference voltage table of Table 1, the reference voltage of the contact-type static eliminator 129 is set to "0 volts" for "plain paper" and "thick paper," "-100 volts" for "coated paper," and "-800 volts" for "synthetic paper." On the other hand, the reference voltage of the non-contact-type static eliminator 131 is set to "800 volts" for all of "plain paper," "thick paper," "coated paper," and "synthetic paper."

[0033] However, in the past, even if the sheet P was neutralized by applying the reference voltage, there were cases where a sufficient neutralization effect was not obtained. This is because the charge amount of the sheet P after the secondary transfer varies depending on the voltage value of the secondary transfer voltage and the environment at that time (for example, humidity, temperature, etc.). In consideration of this point, in this embodiment, a plurality of sample sheets (sheet stacks) are outputted by applying different neutralization voltages to sheets that have passed through the secondary transfer portion T2 under the same image forming conditions, and the user can adjust the neutralization voltage by comparing the plurality of sheet stacks that have actually been outputted. Hereinafter, the "neutralization voltage adjustment process" of this embodiment that realizes this will be described with reference to FIGS. 1 and 2 and with reference to FIGS. 5 to 8(b).

[0034] <Static charge removal voltage adjustment process> 5 is a flowchart showing the static elimination voltage adjustment process according to the first embodiment. The static elimination voltage adjustment process (mode) is executed by the CPU 203 in response to, for example, the user selecting the "adjustment mode."

[0035] As shown in FIG. 5, the CPU 203 displays an "adjustment mode screen" on the display 206 (S1). FIG. 6(a) shows the "adjustment mode screen." As shown in FIG. 6(a), a "cassette selection button" is displayed on the "adjustment mode screen." By operating the "cassette selection button," the user can specify which of the cassettes 111 and 112 contains the target sheet P for sample output. For example, when the "cassette 1" button is operated, the cassette 111 is specified, and when the "cassette 2" button is operated, the cassette 112 is specified. Note that the cassettes 111 and 112 may be associated in advance with the types of sheets that can be contained therein. In this case, the type of sheets is automatically determined when the cassettes 111 and 112 are specified.

[0036] Then, when the user operates the "Next" button, the screen of the display 206 transitions from the "adjustment mode screen" to the "number of sheets per copy input screen" shown in FIG. 6(b). As shown in FIG. 6(b), the "number of sheets per copy input screen" displays numeric keys. The user can input the number of samples per copy by operating the numeric keys "0-9". FIG. 6(b) shows an example in which the number button "5" is operated and the number of samples "5" is displayed. Here, the number of samples per copy (set number) is the number of sample sheets to be output under the same image forming conditions without changing the static elimination voltage. The input number of samples per copy is stored in the memory 204 by the CPU 203.

[0037] In addition, the "number of sheets per copy input screen" displays a "start adjustment" button, and when the user operates the "start adjustment" button, the CPU 203 proceeds to the process of step S2 shown in FIG. 5 to start sample output. The CPU 203 sets the variable "Step" to "1" (S2). The variable "Step" is used to output sample sheets with different static elimination voltages under the same image forming conditions, and sample sheets (sheet stacks) of the sample number per copy are output for each variable "Step". Then, the CPU 203 acquires page information to be used for the sample output (S3). The page information includes the type of sheet. The CPU 203 determines the static elimination voltage of the contact static elimination device 129 and the static elimination voltage of the non-contact static elimination device 131 (S4). Note that the method of acquiring the type of sheet is not limited to acquiring the page information.

[0038] A method for determining the neutralization voltage of the contact-type neutralization device 129 will now be described. The CPU 203 determines the reference voltage of the contact-type neutralization device 129 in accordance with the "Reference Voltage Table" in Table 1, based on the type of sheet included in the page information. The CPU 203 also determines an "adjustment value" in accordance with the "adjustment table" shown in Table 2, based on the value of the variable "Step." The adjustment table is stored in advance in the printing device 102, for example, in the HDD 202 (see FIG. 2). [Table 2]

[0039] Then, the CPU 203 obtains the neutralization voltage of the contact-type neutralizer 129 from the reference voltage determined based on the type of sheet and the adjustment value determined based on the value of the variable "Step". For example, when the type of sheet is "coated paper", the reference voltage of the contact-type neutralizer 129 is determined to be "-100 volts" (see Table 1). When the variable "Step" is "1", the adjustment value is determined to be "-10" (first adjustment value) (see Table 2). As shown in the "adjustment table" of Table 2, in this embodiment, the voltage is offset by "-25V" per adjustment value "1". Therefore, when the variable "Step" is "1", the neutralization voltage of the contact-type neutralizer 129 becomes "+150 volts (-100+(+250))" (first voltage) obtained by offsetting the voltage adjustment amount "+250V (-10×-25)" from the reference voltage "-100 volts".

[0040] A method for determining the neutralization voltage of the non-contact static eliminator 131 will be described. In this embodiment, the neutralization voltage for the non-contact static eliminator 131 is the reference voltage determined based on the type of sheet, without using an adjustment value determined based on the value of the variable "Step". For example, when the type of sheet is "coated paper", the reference voltage of the non-contact static eliminator 131 is determined to be "800 volts" (see Table 1), and therefore the neutralization voltage of the non-contact static eliminator 131 is "800 volts" regardless of the value of the variable "Step".

[0041] Returning to the explanation of Fig. 5, the CPU 203 sets the variable "number of prints" to "1" (S5). The variable "number of prints" is used to output sample sheets under the same image forming conditions without changing the static elimination voltage so as not to exceed the input number of samples per copy.

[0042] The CPU 203 executes a sample output using the sheet P (S6). At this time, the printing device 102 is operated under the same image forming conditions as in normal image forming processing. Thereafter, in the static eliminator 103 to which the sheet P has been handed over from the printing device 102, the static elimination voltage of the contact static eliminator 129 and the static elimination voltage of the non-contact static eliminator 131 are applied to eliminate static electricity from the sheet P. After static elimination, the sheet P is transported to the finisher 104 and discharged to the discharge tray (135, 136) as a sample sheet.

[0043] The CPU 203 judges whether the variable "number of prints" is equal to or greater than the number of samples per copy (e.g., 5 sheets) stored in the memory 204 (S7). If the variable "number of prints", i.e., the number of sample sheets outputted under the same image forming conditions without changing the static elimination voltage, is less than the number of samples per copy (NO in S7), the CPU 203 increments the variable "number of prints" (S8) and returns to the process of step S6. Thereafter, the CPU 203 repeats the processes of steps S6 to S8 until the variable "number of prints" becomes equal to or greater than the number of samples per copy, and executes sample output using a plurality of sheets P. As a result, a plurality of sample sheets (the number of samples per copy) that have been static-eliminated under the same image forming conditions with the same static elimination voltage are stacked on the upper tray 135 or the lower tray 136 as a first sheet bundle, a second sheet bundle, etc.

[0044] On the other hand, if the variable "number of prints" is equal to or greater than the number of samples per copy (YES in S7), CPU 203 determines whether or not the variable "Step" is equal to or greater than the threshold "number of copies output" (S9). In this embodiment, the number of copies output is set to "21 copies" because the adjustment value is changed in 21 steps from "-10 to +10" as shown in the adjustment table of Table 2. If the variable "Step" is less than the threshold "number of copies output" (NO in S9), CPU 203 increments the variable "Step" (S13) and returns to the process of step S4.

[0045] As described above, the CPU 203 determines the "adjustment value" according to the "adjustment table" shown in Table 2 based on the value of the variable "Step", and therefore, each time the variable "Step" is incremented by 1, the neutralization voltage of the contact-type neutralization device 129 is offset by "-25V". For example, when the variable "Step" is "2", the adjustment value is determined to be "-9" (second adjustment value) (see Table 2). Therefore, the neutralization voltage of the contact-type neutralization device 129 when the variable "Step" is "2" is "+125V (-100+(+225))" (second voltage) obtained by offsetting the voltage adjustment amount "+250V (-9×-25)" from the reference voltage "-100V". In this way, by executing the sample output, sample sheets with the sample number of "5 sheets" per copy are output in "21 copies" (number of output copies) under the same image forming conditions but with different neutralization voltages. That is, the CPU 203 can execute a predetermined process for outputting a plurality of sheet bundles neutralized with different neutralization voltages.

[0046] FIG. 7 shows an example of sample sheets output by the above-mentioned sample output. As shown in FIG. 7, for each variable "Step" (1 to 21), sample sheets are output under the same image forming conditions without changing the static elimination voltage, resulting in "21 copies" of sample sheets, with "5 sheets" per copy, that is, a total of "105 sheets (21 copies x 5 sheets)" of sample sheets. When the sample sheets per copy are output to the output tray (135, 136), the user removes the stack of sample sheets from the output tray (135, 136). When removing the stack of sample sheets from the output tray (135, 136), the user checks the loading state of the sample sheets on the output tray (135, 136) and the transport state of the sample sheets.

[0047] It is preferable that the sample sheets are separated into sets of one copy and loaded on each of the upper tray 135 and the lower tray 136. It is preferable that a toner image of information related to the static elimination voltage is formed on the sample sheets by the printing device 102. In the example shown in Fig. 7, as an example of information related to the static elimination voltage, a toner image of the same adjustment value is formed on each set of sample sheets.

[0048] Returning to the explanation of FIG. 5, if the variable "Step" is equal to or greater than the threshold "number of copies to be output" (YES in S9), the CPU 203 displays an "adjustment value input screen" on the display 206 (S10). Then, the CPU 203 determines whether or not an adjustment value has been input by the user (S11). The CPU 203 waits for the process until the adjustment value is input by the user (NO in S11). In this way, by displaying the "adjustment value input screen" on the display 206, the CPU 203 prompts the user to input an adjustment value for adjusting the reference voltage described above in order to allow the user to set the static elimination voltage that the contact static elimination device 129 applies to the sheet after the execution of a predetermined process. If the adjustment value has been input by the user (YES in S11), the CPU 203 stores the adjustment value input by the user in the HDD 202 in response to the adjustment value being confirmed by the user (S12), and ends the process.

[0049] FIG. 8(a) shows the "adjustment value input screen." As shown in FIG. 8(a), the "adjustment value input screen" displays numeric keys. The user can input an adjustment value by operating the numeric keys "0-9." FIG. 8(a) shows an example in which the numeric keypad "8" is operated and an adjustment value "8" is displayed. The user checks the sample sheets for each set discharged to the discharge tray (135, 136) (see FIG. 7), and inputs an adjustment value from the "adjustment value input screen" based on the adjustment value image-formed on the sample sheet that is determined to have the highest static elimination effect. After inputting the adjustment value, the user operates the "Next" button to confirm the adjustment value.

[0050] The adjustment value thus determined is used to determine the neutralization voltage of the contact-type neutralization device 129 when neutralizing the sheet P that has been subjected to normal image formation processing. For example, if the adjustment value is "-9" when the sheet type is "synthetic paper", the neutralization voltage of the contact-type neutralization device 129 becomes "-575 volts (-800 + (+225))", which is obtained by offsetting the voltage adjustment amount "+250V (-9 x -25)" from the reference voltage "-800 volts".

[0051] In the case of this embodiment, the user can confirm the confirmed adjustment value by displaying the "adjustment value confirmation screen" shown in Fig. 8(b) on the display 206. As shown in Fig. 8(b), the "adjustment value confirmation screen" displays the adjustment value input by the user on the above-mentioned "adjustment value input screen" and stored in the HDD 202.

[0052] Furthermore, if a sheet transport failure or sheet stacking failure occurs during normal image formation processing, the user can display an "adjustment value confirmation screen" on the display 206 to confirm the adjustment value stored in the HDD 202. The user can then adjust the static elimination voltage to a voltage value that is unlikely to cause a sheet transport failure or sheet stacking failure during normal image formation processing by performing the above-mentioned "static elimination voltage adjustment process" and changing the adjustment value from the "adjustment value input screen." Note that, in addition to the adjustment value, the "adjustment value confirmation screen" may display, as image formation conditions stored in the HDD 202, for example, an image position adjustment value, a secondary transfer voltage adjustment value, and a gloss adjustment value.

[0053] As described above, in this embodiment, the neutralization voltage adjustment process is performed, and a set of sample sheets consisting of a plurality of sheets output by applying the same neutralization voltage is stacked on the discharge tray (135, 136). In the neutralization voltage adjustment process, the same neutralization voltage is applied under the same image forming conditions to output the sample sheets in sets of one copy, so that the user can actually check the stacking state of the sample sheets and the conveying state of the sample sheets. In addition, in the neutralization voltage adjustment process, the neutralization voltage is changed to output a plurality of copies of the sample sheets. Therefore, the user can compare the plurality of copies of the sample sheets output with different neutralization voltages and specify a sample sheet that has a higher neutralization effect on the sheet. The user can adjust the neutralization voltage to a voltage value that obtains a higher neutralization effect on the sheet by inputting information (adjustment value) regarding the neutralization voltage applied when the specified sample sheet is output. In this way, in this embodiment, the user can set an optimal neutralization voltage according to the charge amount of the sheet after transfer with a simple process.

[0054] [Second embodiment] Next, a second embodiment will be described with reference to Figs. 9 and 10 while also referring to Figs. 1 and 2. Fig. 9 is a flowchart showing the static elimination voltage adjustment process of the second embodiment. Fig. 10 is a diagram showing a "sample confirmation screen" displayed on the display 206. In the static elimination voltage adjustment process shown in Fig. 9, the same processes as those in the static elimination voltage adjustment process of the above-mentioned first embodiment (see Fig. 5) are given the same step numbers, and the description thereof will be simplified or omitted.

[0055] As shown in Fig. 9, in the static elimination voltage adjustment process of the second embodiment, similarly to the static elimination voltage adjustment process of the first embodiment, sample output is performed using a plurality of sheets P (steps S1 to S8). As a result, a plurality of sample sheets (the number of sample sheets per copy) output under the same image forming conditions without changing the static elimination voltage are stacked on the output tray (135, 136). The number of sample sheets per copy can be input by the user from the "number of sheets per copy input screen" shown in Fig. 6(b) described above (for example, 5 sheets).

[0056] If the variable "print count" is equal to or greater than the number of samples per copy (YES in S7), that is, every time a copy of sample sheets is discharged to the discharge tray (135, 136), the CPU 203 temporarily suspends the sample output (S6) and displays a "sample confirmation screen" on the display 206 (S21). As shown in Fig. 10, the "sample confirmation screen" displays a message urging the user to confirm the copy of sample sheets loaded on the discharge tray (135, 136). The "sample confirmation screen" also displays an "OK button" and an "NG button".

[0057] CPU 203 determines whether or not either the "OK button" or the "NG button" on the "sample confirmation screen" has been operated (S22). CPU 203 waits for processing until either the "OK button" or the "NG button" is operated by the user (NO in S22). If either the "OK button" or the "NG button" has been operated by the user (YES in S22), CPU 203 determines whether or not the operated button is the "OK button" (S23).

[0058] When the user operates the "OK button" (YES in S23), the CPU 203 stores the adjustment value (see Table 2) corresponding to the value of the variable "Step" at that time in the HDD 202 (S24), and ends the process. That is, each time a set of sample sheets is discharged to the discharge trays (135, 136), the user can check whether there are any transport or stacking problems with those sheets, and input the adjustment value by operating the "OK" button.

[0059] On the other hand, if the user operates the "NG button" (NO in S23), CPU 203 determines whether or not the variable "Step" is equal to or greater than the threshold "number of copies to be output" (S25). In this embodiment, as shown in the adjustment table of Table 2, the adjustment value is changed in 21 steps from "-10 to +10", so the number of copies to be output is set to "21 copies". If the variable "Step" is equal to or greater than the threshold "number of copies to be output" (YES in S25), CPU 203 ends the process. In this case, CPU 203 displays an error on display 206 to the effect that the adjustment value cannot be set.

[0060] If the variable "Step" is less than the threshold "number of output copies" (NO in S25), the CPU 203 increments the variable "Step" (S26). As described above, the CPU 203 determines the "adjustment value" in accordance with the "adjustment table" shown in Table 2 based on the value of the variable "Step", so that the static elimination voltage of the contact-type static eliminator 129 is offset by "-25V" each time the variable "Step" is incremented by 1. Then, the CPU 203 returns to the process of step S4, resumes the temporarily stopped sample output (S6), and outputs "one copy" of a new sample sheet with a sample number of "five sheets" based on the offset static elimination voltage.

[0061] In addition, the user can adjust the neutralization voltage to a better level by comparing the sheet bundles. For this reason, it is preferable to output at least two sets of sheet bundles as samples for comparison, and then allow the user to operate the "OK button" and "NG button" on the "sample confirmation screen" described above. That is, when the neutralization voltage adjustment process of the second embodiment is performed, if the "NG button" is operated after the second set of sheet bundle is discharged, an incremented voltage (third voltage) is applied to the contact-type neutralization device 129 to output "one copy" (third sheet bundle) of sample sheets with a new sample number of "five sheets".

[0062] As described above, in the second embodiment, similarly to the first embodiment, the neutralization voltage adjustment process is executed, and a set of sample sheets consisting of a plurality of sheets output by applying the same neutralization voltage is stacked on the discharge tray (135, 136). However, in the second embodiment, unlike the first embodiment, the user checks the stacking state of the sample sheets and the conveying state of the sample sheets, and when it is determined that the sample sheet has a higher neutralization effect, the neutralization voltage at the time of outputting the sample sheet is stored. That is, the user can input information (adjustment value) regarding the neutralization voltage without waiting for multiple copies of the sample sheets to be output with different neutralization voltages. Thus, in the second embodiment, the user can set the optimal neutralization voltage according to the charge amount of the sheet after transfer with a simple process, and in addition, compared to the first embodiment, there is no need to output sample sheets unnecessarily, and the user can reduce the time required for setting the neutralization voltage.

[0063] <Other embodiments> In the above-mentioned first and second embodiments, the static elimination voltage of the contact static eliminator 129 is adjusted, but the present invention is not limited to this. For example, the static elimination voltage of the non-contact static eliminator 131 may be adjusted, or both the static elimination voltage of the contact static eliminator 129 and the static elimination voltage of the non-contact static eliminator 131 may be adjusted.

[0064] In the above-described first and second embodiments, the printing device 102 is an intermediate transfer type in which the toner image of each color is primarily transferred from the photosensitive drum of each color to the intermediate transfer belt 118, and then the composite toner image of each color is secondary-transferred collectively to a sheet, but the present invention is not limited to this. For example, the printing device 102 may be a direct transfer type in which the toner image on the photosensitive drum is directly transferred to the sheet by applying a voltage to a transfer roller disposed opposite the photosensitive drum and the conveying belt, with the sheet being conveyed by a conveying belt having a nip formed between the photosensitive drum and the conveying belt. [Explanation of symbols]

[0065] 103...discharge section (discharger), 118...image carrier (intermediate transfer belt), 119...transfer member (secondary transfer inner roller), 129...contact type discharge section (contact type discharger), 131...non-contact type discharge section (non-contact type discharger), 135...second discharge section (upper tray), 136...first discharge section (lower tray), 190...image forming section, 202...storage section (HDD), 203...control section (CPU), 205...input section (operation section), 206...display section (display), P...sheet, T2...transfer nip section (secondary transfer section)

Claims

1. a charge removing unit that removes electric charge from the sheet by applying a voltage; a control unit capable of executing a predetermined process of applying a first voltage to the static elimination unit to discharge a first sheet bundle from which a set number of sheets have been neutralized, and subsequently to the discharge of the first sheet bundle, applying a second voltage different from the first voltage to the static elimination unit to discharge a second sheet bundle from which the set number of sheets have been neutralized; and an input unit configured to receive an input for setting either the first voltage or the second voltage as a voltage to be applied to the sheet by the static electricity removing unit after the predetermined process is performed. A static eliminator characterized by the above.

2. a storage unit that stores a first adjustment value for adjusting a predetermined reference voltage determined for each type of sheet, and a second adjustment value different from the first adjustment value for adjusting the reference voltage, When the control unit applies the first voltage to the static elimination unit during the execution of the predetermined process, the control unit adjusts the reference voltage based on the first adjustment value and applies the adjusted reference voltage to the static elimination unit, and when the control unit applies the second voltage to the static elimination unit, the control unit adjusts the reference voltage based on the second adjustment value and applies the adjusted reference voltage to the static elimination unit.

2. The static eliminator according to claim 1 .

3. the input unit is capable of accepting an input of either the first adjustment value or the second adjustment value stored in the storage unit, The control unit adjusts the reference voltage based on either the first adjustment value or the second adjustment value input by the input unit and applies the adjusted reference voltage to the static eliminator.

3. The static eliminator according to claim 2.

4. a display unit capable of displaying either the first adjustment value or the second adjustment value input by the input unit, 4. The static eliminator according to claim 3.

5. An input unit capable of inputting the set number is provided.

2. The static eliminator according to claim 1 .

6. A first discharge portion; A second discharge section different from the first discharge section, the control unit, when executing the predetermined process, discharges the first sheet stack to the first discharge unit and discharges the second sheet stack to the second discharge unit.

2. The static eliminator according to claim 1 .

7. the charge eliminating section includes a contact type charge eliminating section that eliminates charge by contacting the sheet being transported, and a non-contact type charge eliminating section that is provided downstream of the contact type charge eliminating section in the sheet transport direction and eliminates residual charge of the sheet after the sheet has been neutralized by the contact type charge eliminating section in a non-contact state; The control unit controls a voltage applied to the contact-type static electricity removing unit.

2. The static eliminator according to claim 1 .

8. when there is no input from the input unit to set either the first voltage or the second voltage after the second sheet stack is discharged during the execution of the predetermined process, the control unit applies a third voltage to the static elimination unit to discharge a third sheet stack in which static electricity has been eliminated from the set number of sheets; the input unit is capable of receiving an input for setting the third voltage as a voltage to be applied to the sheets by the static electricity removing unit after the third sheet stack is discharged.

2. The static eliminator according to claim 1 .

9. an image carrier that carries a toner image; an image forming unit for forming a toner image on the image carrier; a transfer member that contacts the image carrier to form a transfer nip and transfers a toner image on the image carrier to a sheet passing through the transfer nip by application of a transfer voltage; and the static elimination device according to claim 1 , which is disposed downstream of the transfer nip portion in a sheet transport direction.

1. An image forming apparatus comprising:

10. the control unit, during execution of the predetermined process, causes the image forming unit to form a toner image of information related to the first voltage and transfer it to a sheet of the first sheet stack, and causes the image forming unit to form a toner image of information related to the second voltage and transfer it to a sheet of the second sheet stack.

10. The image forming apparatus according to claim 9,

Images