Static eliminator and image forming 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 electrophotographic image forming apparatuses, a high transfer voltage is applied when a toner image is transferred to a sheet, which can cause the sheet to become charged after transfer. If the transferred sheet is not neutralized, it may electrostatically adhere to a previously stacked sheet on the discharge tray when discharged onto the discharge tray, resulting in stacking problems, or may electrostatically adhere to a sheet being transported toward the discharge tray, resulting in transport problems. To address this issue, image forming apparatuses are provided with a neutralization device that neutralizes the sheet after transfer (Patent Document 1). The neutralization device described in Patent Document 1 includes a contact-type neutralization device that can neutralize the sheet by contacting it, and a non-contact-type neutralization device that can neutralize the sheet without contacting it. The neutralization device described in Patent Document 1 neutralizes the sheet using either a contact-type neutralization device or a non-contact-type neutralization device, or both a contact-type neutralization device and a non-contact-type neutralization device, depending on the surface resistance of the sheet.

[0003] To achieve a high sheet static elimination effect using a contact-type static eliminator or a non-contact-type static eliminator, it is necessary to apply an optimal voltage for static elimination to each device (hereinafter referred to as the static elimination voltage). Because the surface resistance of a sheet varies depending on the type of sheet, the static elimination voltage of a contact-type static eliminator or a non-contact-type static eliminator is determined depending on 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 the time (e.g., humidity). Therefore, users had to measure the amount of charge on the sheet on which an image was 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] Japanese Patent Application Publication No. 2019-167169 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method in which the user actually measures the charge amount of the sheet and adjusts the neutralization voltage has the problem that the user's operations become cumbersome and it takes time to adjust the neutralization voltage.

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

[0007] The static eliminator according to one embodiment of the present invention includes: a static eliminator that eliminates charges that have been charged on a sheet by applying a voltage; When printing the sample sheet, The device is characterized by comprising: a control unit capable of executing a predetermined process of applying a first voltage to the discharge unit to discharge a first sheet stack from which a set number of sheets have been discharged, and, following the discharge of the first sheet stack, applying a second voltage different from the first voltage to the discharge unit to discharge a second sheet stack from which the set number of sheets have been discharged; and an input unit that accepts input to set either the first voltage or the second voltage as the voltage to be applied to the sheets by the discharge unit after the predetermined process has been executed. [Effects of the Invention]

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

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

[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 electrophotographic full-color printer. As shown in FIG. 1, the image forming apparatus 101 includes a printing device 102, a static eliminator 103, and a finisher 104. Note that, although an example in which the printing device 102, the static eliminator 103, and the finisher 104 are each configured in separate housings and then connected together has been shown here, this is not limiting. For example, the printing device 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, not shown, such as a document reading device connected to the printing device 102 or a personal computer. Sheets are supplied to the printing device 102 from cassettes 111 and 112 that can accommodate various types of sheets. Only the topmost sheet stored in the cassettes 111 and 112 is transported to a transport path 113. Examples of sheets include thin paper, regular 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 in yellow, magenta, cyan, and black. In the image forming stations 114, 115, 116, and 117, toner images are formed on the photosensitive drums of the respective stations. The toner images formed on the photosensitive drums are primarily transferred to an intermediate transfer belt 118, which serves as an image carrier, in response to a primary transfer voltage being applied to the primary transfer roller. Then, as the intermediate transfer belt 118 rotates clockwise, the toner images reach a secondary transfer portion T2. ​​The secondary transfer portion T2 is a transfer nip formed by the contact between an inner secondary transfer roller 119 and an outer secondary transfer roller 120. In response to a secondary transfer voltage being applied to the inner secondary transfer roller 119, which serves 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 along a conveyance 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 onto 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 nipped and conveyed through the fixing nip formed by these rollers, the toner is melted by the heat, and the melted toner image is pressed onto the sheet by the pressure.

[0014] After passing through the first fixing unit 121, the sheet is transported to a transport path 125 via a transport path 122. However, depending on the type of sheet, further melting and pressure bonding may be required for fixing. In such cases, the sheet is transported 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. After passing through the second fixing unit 123, the sheet is transported to a transport path 125 via a transport path 124. In a double-sided image formation 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 transported from the transport paths 122 and 124 to a reversing path 126, where the leading and trailing ends in the transport direction are swapped. The sheet is then transported to a transport path 113 via a double-sided transport path 127, where the toner image on the intermediate transfer belt 118 is secondarily transferred to the second side of the sheet at a secondary transfer unit T2.

[0015] The sheet transported to the transport path 125 is handed over from the printing device 102 via the transport path 128 to the static eliminator 103, which is disposed downstream of the secondary transfer unit T2 in the sheet transport direction. In the image forming device 101, a high secondary transfer voltage is applied when a toner image is secondarily transferred to the sheet, causing the sheet to become charged after transfer. If the sheet is charged, the sheet may electrostatically adhere to a transport guide or the like during transport, resulting in transport problems, or when the sheet is discharged onto the discharge trays (135, 136), the sheet may electrostatically adhere to sheets already stacked on the discharge trays (135, 136), causing stacking problems. Therefore, the image forming device 101 of this embodiment is provided with the static eliminator 103 to remove the charge from the charged sheet and eliminate the charge. The static eliminator 103 has a contact static eliminator 129 and a non-contact static eliminator 131, and as will be described later, a static elimination voltage is applied to the contact static eliminator 129 and the non-contact static eliminator 131 to remove charge from the sheet after secondary transfer.

[0016] The finisher 104 is capable of stacking a large number of sheets, and is provided with an upper tray 135 as a second discharge unit and a lower tray 136 as a first discharge unit 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 are different. The conveying 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 arranged along the transport paths 132, 133, and 134, respectively, and the detection results are sent to the printing device 102. Based on these detection results, the printing device 102 (CPU 203 for details, see FIG. 2 described later) detects that a transport jam has occurred in the finisher 104, where the sheet has become stuck during transport, if the printing device 102 does not detect the passage of the leading or trailing edge of the sheet 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 while referring 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, an HDD (Hard Disk Drive) 202, a CPU (Central Processing Unit) 203, memory 204, an operation unit 205, and a display 206. The printing apparatus 102 further includes a laser exposure unit 207, an image creation 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 inputs and outputs control instructions, data, and the like between the printing apparatus 102 and the static eliminator 103. The communication interface 201 is also connected to an external device such as a computer (not shown), and inputs and outputs various types of data to and from the external device. The HDD 202, which serves as a storage unit, is a storage device in which control programs and data are stored. The CPU 203, which serves as a control unit, executes, for example, an image formation process (second mode) and a static elimination voltage adjustment process (first mode, see FIG. 5, which will be described later), not shown, based on the control programs and the like stored in the HDD 202, and accordingly controls the entire image forming apparatus 101. The memory 204 stores the control programs and image data required when the CPU 203 performs various processes, and also functions as a temporary data work area.

[0020] An operation unit 205 serving as an input unit accepts various setting inputs and operation instructions from the user. A display 206 serving 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 enables the user to execute various operations pre-assigned to the software keys on the screen by touching the software keys.

[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, primary charging is first performed to charge the surface of the photosensitive drum to a uniform negative potential. Next, laser light emitted from a laser driver is irradiated onto the photosensitive drum while the reflection angle is adjusted by a polygon mirror, thereby neutralizing the negative charge at the point on the photosensitive drum surface where the laser light was irradiated, 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, creating a visible image. In the transfer unit, a primary transfer is performed by applying a positive voltage to the primary transfer roller to transfer the toner on the surface of the photosensitive drum to the intermediate transfer belt 118, and a secondary transfer is performed by applying a negative voltage to the secondary transfer inner roller 119 to transfer the toner on the intermediate transfer belt 118 to the sheet. The fixing unit 209 is a device for melting and fixing the toner on the sheet to the sheet using heat and pressure, and is composed of a heater, a heating roller, a pressure roller, etc. The feed unit 210 is a device for transporting sheets, and the sheet feeding and transport operations are controlled by rollers and various sensors.

[0023] Next, we will explain the control system of the static eliminator 103. 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 these 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 carried out 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 received from the CPU 203 via a communication cable 229. The static elimination high voltage control unit 222 controls the static elimination voltage of the contact static eliminator 129 by the static elimination high voltage power supply 230 (see FIG. 3 described later). The attachment / detachment control unit 223 controls the movement of the static elimination roller 130a and the static elimination roller 130b of the contact static eliminator 129 between a contact position where they come into contact and a non-contact position where they do not come into contact, using a contact / separation mechanism not shown. The non-contact static elimination high voltage control unit 224 controls the static elimination voltage of the non-contact static eliminator 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 these 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 send and receive control instructions, data, and the like. The CPU 232 performs various controls required for sheet discharge in accordance with 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 separate and transport sheets 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 using Fig. 3 to Fig. 4(b) with reference to Fig. 1. 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 the secondary transfer voltage. Therefore, when a sheet passes through the secondary transfer portion T2, the surface of the sheet facing the inner secondary transfer roller 119 is negatively charged, and the back surface of the sheet on the opposite side is positively charged due to dielectric polarization. If the charged sheet is transported to the finisher 104, the sheet may electrostatically adhere to a transport guide or the like during transport, resulting in transport problems. Alternatively, when the sheet is discharged onto the discharge tray (135, 136), the sheet may electrostatically adhere to sheets already stacked on the discharge tray (135, 136), resulting in stacking problems, or the stacked sheets may stick to each other due to electrostatic force. Therefore, in this embodiment, the static eliminator 103 is used to remove charge from the sheet and eliminate static electricity. The static eliminator 103 has two static eliminators: a contact static eliminator 129 and a non-contact static eliminator 131. These static eliminators are arranged side by side in the sheet transport direction.

[0028] <Contact static eliminator> As shown in FIG. 3, contact-type static eliminator 129 (contact-type static eliminator unit) has two opposing static eliminator rollers 130a and 130b. Static eliminator roller 130a is grounded, and static eliminator roller 130b has a static elimination voltage applied thereto by static elimination high-voltage power supply 230. When static eliminator roller 130a is in contact with the front surface of the sheet and static eliminator roller 130b is in contact with the back surface of the sheet, a negative static elimination voltage is applied by static elimination high-voltage power supply 230, and the positive charge present on the back surface of the sheet is removed. As a result, when the positive charge present on the back surface of the sheet decreases, the negative charge present on the front surface of the sheet also decreases accordingly. Contact-type static eliminator 129 applies a voltage directly to contact sheet P, thereby achieving a high static elimination effect.

[0029] <Non-contact static eliminator> Although the contact-type static eliminator 129 described above has a high static elimination effect, variations tend to occur in the electric potential (hereinafter referred to as surface potential) on the front and back surfaces of the sheet P after static elimination. Therefore, in order to substantially uniform the surface electric potential of the sheet P that has become uneven due to static elimination by the contact-type static eliminator 129, the non-contact static eliminator 131 is disposed downstream of the contact-type static eliminator 129 in the conveyance direction of the sheet P. The non-contact static eliminator 131 can generally eliminate residual charges on the sheet in a non-contact state after static elimination by the contact-type static eliminator 129. In this embodiment, an AC corotron type non-contact static eliminator 131 is used.

[0030] As shown in FIG. 4(a), the non-contact static eliminator 131 (non-contact static eliminator unit) has a discharge wire 140 and an earth electrode 141, and a positive static elimination voltage is applied to the discharge wire 140 by a non-contact static elimination high-voltage power supply 240. When a positive static elimination voltage is applied to the discharge wire 140, a corona discharge occurs in the discharge wire 140, generating a positive charge. 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. This eliminates the negative charge on the sheet surface. 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 eliminated. Although the effect of such a non-contact type static eliminator 131 on the sheet P is smaller than that of the contact type static eliminator 129, the non-contact type static eliminator 131 can reduce the variation in the surface potential of the sheet P after static elimination, so that the surface potential of the sheet P after passing through the non-contact type static eliminator 131 becomes approximately uniform.

[0031] <Static elimination voltage> Incidentally, the amount of charge on the sheet P after secondary transfer differs depending on the type of sheet. Therefore, in this embodiment, in order to obtain a neutralization effect on the sheet P, a predetermined reference voltage to be applied to each of the contact-type static eliminator 129 and the non-contact-type static eliminator 131 can be set according to the type of sheet in accordance with the 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 apparatus 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 "cardboard," "-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," "cardboard," "coated paper," and "synthetic paper."

[0033] However, in the past, even when a reference voltage was applied to neutralize the sheet P, sufficient neutralization effects were not always achieved. This is because the amount of charge on the sheet P after secondary transfer varies depending on the voltage value of the secondary transfer voltage and the environment at the time (e.g., humidity, temperature, etc.). In consideration of this, in this embodiment, multiple sample sheets (sheet stacks) are output by applying different neutralization voltages to sheets that have passed through the secondary transfer portion T2 under the same image forming conditions. The user can then adjust the neutralization voltage by comparing the multiple sheet stacks that have actually been output. The "neutralization voltage adjustment process" of this embodiment, which achieves this, will be described below with reference to FIGS. 1 and 2 and using FIGS. 5 to 8(b).

[0034] <Static elimination voltage adjustment process> 5 is a flowchart showing the static elimination voltage adjustment process of the first embodiment. The static elimination voltage adjustment process (mode) is executed by the CPU 203 in response to, for example, the user selecting "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 sheet P to be sample-printed. 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 previously associated 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] When the user presses the "Next" button, the screen on 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), a numeric keypad is displayed on the "number of sheets per copy input screen." The user can input the number of samples per copy by operating the number buttons "0-9" on the numeric keypad. 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] Furthermore, the "Number of Sheets per Copy Input Screen" displays a "Start Adjustment" button. 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 sheet type is not limited to acquiring page information.

[0038] The 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 the "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 calculates the neutralization voltage of the contact-type neutralization device 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 neutralization device 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 "-25 V" per adjustment value "1." Therefore, when the variable "Step" is "1," the neutralization voltage of the contact-type neutralization device 129 is "+150 volts (-100 + (+250))" (first voltage), which is obtained by offsetting the reference voltage of "-100 volts" by the voltage adjustment amount "+250 V (-10 × -25)."

[0040] A method for determining the neutralization voltage of the non-contact static eliminator 131 will be described. In this embodiment, the reference voltage determined based on the type of sheet is used as the neutralization voltage for the non-contact static eliminator 131 without using an adjustment value determined based on the value of the variable "Step". For example, if 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 sample sheets per copy.

[0042] The CPU 203 executes sample output using the sheet P (S6). At this time, the printing device 102 operates under the same image forming conditions as in normal image forming processing. Thereafter, the static eliminator 103 to which the sheet P is handed over from the printing device 102 applies the static elimination voltage of the contact static eliminator 129 and the static elimination voltage of the non-contact static eliminator 131 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 trays (135, 136) as a sample sheet.

[0043] The CPU 203 determines whether the variable "number of prints" is equal to or greater than the number of sample sheets 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 output under the same image forming conditions without changing the static elimination voltage, is less than the number of sample sheets per copy (NO in S7), the CPU 203 increments the variable "number of prints" (S8) and returns to the processing of step S6. Thereafter, the CPU 203 repeats the processing of steps S6 to S8 until the variable "number of prints" becomes equal to or greater than the number of sample sheets per copy, and executes sample output using multiple sheets P. As a result, multiple sample sheets (the number of sample sheets per copy) that have been neutralized with the same static elimination voltage under the same image forming conditions 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 the variable "Step" is equal to or greater than the threshold "Number of Output Copies" (S9). 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 output copies is set to "21 copies". If the variable "Step" is less than the threshold "Number of Output Copies" (NO in S9), CPU 203 increments the variable "Step" (S13) and returns to the processing of step S4.

[0045] 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." Therefore, each time the variable "Step" is incremented by 1, the static elimination voltage of the contact-type static eliminator 129 is offset by "-25 V." For example, when the variable "Step" is "2," the adjustment value is determined to be "-9" (second adjustment value) (see Table 2). Therefore, when the variable "Step" is "2," the static elimination voltage of the contact-type static eliminator 129 becomes "+125 volts (-100 + (+225))" (second voltage), which is obtained by offsetting the voltage adjustment amount "+250 V (-9 × -25)" from the reference voltage "-100 volts." In this way, by executing sample output, for example, 21 copies (number of output copies) of sample sheets with a sample number of "5 sheets" per copy are output under the same image formation conditions but with different static elimination voltages. That is, the CPU 203 can execute a predetermined process for outputting a plurality of sheet bundles that have been neutralized with different neutralization voltages.

[0046] FIG. 7 shows an example of sample sheets output by the above-described sample output. As shown in FIG. 7, for each variable "Step" (1 to 21), sample sheets are output under the same image formation conditions without changing the static elimination voltage, resulting in "21 copies" of "5 sheets per copy," for a total of "105 sheets (21 copies x 5 copies)" of sample sheets. When the sample sheets corresponding to the number of samples per copy have been output onto the output trays (135, 136), the user removes the stack of sample sheets from the output trays (135, 136). When removing the stack of sample sheets from the output trays (135, 136), the user checks the stacking status of the sample sheets on the output trays (135, 136), the transport status of the sample sheets, etc.

[0047] It is preferable that the sample sheets are stacked in sets of one copy on each of the upper tray 135 and the lower tray 136. It is also preferable that a toner image of information relating 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 relating 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 processing to end until the user inputs an adjustment value (NO in S11). By displaying the "adjustment value input screen" on the display 206 in this way, the CPU 203 prompts the user to input an adjustment value for adjusting the reference voltage, so that the user can set the neutralization voltage to be applied to the sheet by the contact-type neutralization device 129 after the execution of a predetermined processing. If the adjustment value has been input by the user (YES in S11), the CPU 203 stores the user-inputted adjustment value in the HDD 202 in response to the user's confirmation of the adjustment value (S12), and ends the processing.

[0049] FIG. 8(a) shows the "adjustment value input screen." As shown in FIG. 8(a), a numeric keypad is displayed on the "adjustment value input screen." The user can input an adjustment value by operating the number buttons "0 to 9" on the numeric keypad. FIG. 8(a) shows an example in which the number button "8" is operated and the adjustment value "8" is displayed. The user checks the sample sheets for each set discharged to the output trays (135, 136) (see FIG. 7), and inputs an adjustment value on the "adjustment value input screen" based on the adjustment value for the 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 a sheet P that has undergone normal image formation processing. For example, if the sheet type is "synthetic paper" and the adjustment value is "-9", the neutralization voltage of the contact-type neutralization device 129 will be "-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 this embodiment, the user can confirm the confirmed adjustment values ​​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 values ​​that were input by the user on the above-mentioned "adjustment value input screen" and stored in the HDD 202.

[0052] Furthermore, if a sheet transport error or sheet stacking error occurs during normal image formation processing, the user can display the "adjustment value confirmation screen" on the display 206 and check the adjustment value stored in the HDD 202. Then, by performing the above-mentioned "static elimination voltage adjustment process" and changing the adjustment value on the "adjustment value input screen," the user can adjust the static elimination voltage to a voltage value that is less likely to cause a sheet transport error or sheet stacking error during normal image formation processing. In addition to the adjustment value, the "adjustment value confirmation screen" may also display image formation conditions stored in the HDD 202, such as an image position adjustment value, a secondary transfer voltage adjustment value, and a gloss adjustment value.

[0053] As described above, in this embodiment, by executing the static elimination voltage adjustment process, a set of sample sheets consisting of multiple sheets output by applying the same static elimination voltage is stacked on the output tray (135, 136). In the static elimination voltage adjustment process, the same static elimination voltage is applied under the same image formation conditions to output the sample sheets one by one, allowing the user to actually check the stacking state of the sample sheets, the transport state of the sample sheets, and so on. Furthermore, in the static elimination voltage adjustment process, multiple sets of sample sheets are output by changing the static elimination voltage. Therefore, the user can compare multiple sets of sample sheets output at different static elimination voltages and identify sample sheets that have achieved a higher sheet static elimination effect. The user can input information (adjustment value) regarding the static elimination voltage applied when outputting the identified sample sheets, thereby adjusting the static elimination voltage to a voltage value that achieves a higher sheet static elimination effect. As described above, in this embodiment, the user can set the optimal static elimination voltage according to the charge amount of the sheet after transfer through a simple process.

[0054] [Second embodiment] Next, a second embodiment will be described using Fig. 9 and Fig. 10 with reference to Fig. 1 and Fig. 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 first embodiment described above (see Fig. 5) are assigned the same step numbers, and their explanations will be simplified or omitted.

[0055] As shown in Fig. 9, in the static elimination voltage adjustment process of the second embodiment, sample output is performed using a plurality of sheets P in the same manner as in the static elimination voltage adjustment process of the first embodiment (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 trays (135, 136). The number of sample sheets per copy can be input by the user (for example, 5 sheets) from the "Number of sheets per copy input screen" shown in Fig. 6(b) described above.

[0056] If the variable "number of prints" is equal to or greater than the number of sample sheets per copy (YES in S7), that is, every time a copy of sample sheets is discharged onto 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 prompting the user to confirm the copy of sample sheets stacked on the discharge tray (135, 136). The "sample confirmation screen" also displays an "OK button" and an "NG button."

[0057] The CPU 203 determines whether or not either the "OK button" or the "NG button" on the "sample confirmation screen" has been operated (S22). The 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), the CPU 203 determines whether or not the operated button is the "OK button" (S23).

[0058] If 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 onto the discharge trays (135, 136), the user can check whether there are any transport or stacking errors in 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 processing. In this case, CPU 203 displays an error on display 206 indicating 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", and therefore, each time the variable "Step" is incremented by 1, the static elimination voltage of the contact-type static eliminator 129 is offset by "-25 V". Then, the CPU 203 returns to the processing 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] The user can adjust the neutralization voltage to a better level by comparing the sheet bundles. Therefore, 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, and a new set of sample sheets (a third sheet bundle) with a sample number of "five sheets" is output.

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

[0063] <Other embodiments> In the first and second embodiments described above, 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 first and second embodiments described above, the printing device 102 is an intermediate transfer type in which a toner image of each color is primarily transferred from the photosensitive drum of each color to the intermediate transfer belt 118, and then a composite toner image of each color is secondarily 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 a toner image on a photosensitive drum is directly transferred to a sheet by applying a voltage to a transfer roller disposed opposite the photosensitive drum and the conveying belt, with a nip formed between the sheet and the photosensitive drum. [Explanation of symbols]

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

Claims

1. a charge removal unit that removes electric charges from the sheet by applying a voltage; a control unit that is 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 when outputting a sample sheet, and subsequently 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; an input unit that receives an input for setting either the first voltage or the second voltage as the voltage to be applied to the sheet by the static eliminator after the predetermined process is executed. A static eliminator characterized by:

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 that is different from the first adjustment value for adjusting the reference voltage; When the control unit is executing the predetermined process, if the first voltage is to be applied to the static eliminator, the control unit adjusts the reference voltage based on the first adjustment value and applies the adjusted voltage, and when the second voltage is to be applied to the static eliminator, the control unit adjusts the reference voltage based on the second adjustment value and applies the adjusted voltage.

2. The static eliminator according to claim 1.

3. the input unit is capable of accepting 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 of sheets; 2. The static eliminator according to claim 1.

6. A first discharge section; a second discharge section different from the first discharge section, the control unit, when executing the predetermined process, discharges the first sheet bundle to the first discharge unit and discharges the second sheet bundle 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 comes into contact with the sheet being conveyed to eliminate charge, and a non-contact type charge eliminating section that is provided downstream of the contact type charge eliminating section in the sheet conveyance direction and that eliminates residual charge of the sheet in a non-contact state after the sheet has been neutralized by the contact type charge eliminating section, The control unit controls a voltage applied to the contact-type static eliminator.

2. The static eliminator according to claim 1.

8. when the control unit performs the predetermined process, if there is no input from the input unit to set either the first voltage or the second voltage after the second sheet bundle is discharged, the control unit applies a third voltage to the static eliminator to discharge the third sheet bundle from which the set number of sheets have been neutralized; 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 eliminator 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 that forms a toner image on the image carrier; a transfer member that contacts the image carrier to form a transfer nip and transfers the toner image on the image carrier to a sheet passing through the transfer nip by application of a transfer voltage; the static elimination device according to claim 1 , which is disposed downstream of the transfer nip portion in a sheet conveyance direction, An image forming apparatus characterized by:

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 bundle, 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 bundle.

10. The image forming apparatus according to claim 9,

Images