Image forming apparatus
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-04-13
- Publication Date
- 2026-04-07
AI Technical Summary
Conventional image forming apparatuses face issues with image defects on perforated sheets due to burrs causing toner scattering during the transfer process.
The apparatus includes a display section that provides information on the front and back sides of perforated sheets, guiding users to set them correctly to prevent image defects by ensuring the burr side faces away from the image transfer surface, and an optional back stain elimination control to manage toner adherence on the secondary transfer roller.
Prevents image defects and back staining by correctly orienting perforated sheets and managing toner adherence, thereby improving image quality and reducing defects on perforated sheets.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present invention relates to an electrophotographic image forming apparatus such as a printer, a copier, a facsimile, or a multifunction machine. [Background technology]
[0002] The image forming apparatus is equipped with a cassette or a manual feed tray in which sheets can be set, and can form images on various sheets of different sizes and types that are conveyed from the cassette or the manual feed tray. As the sheets, perforated sheets (hereinafter, referred to as perforated sheets) may be used (Patent Document 1). [Prior art documents] [Patent documents]
[0003] [Patent Document 1] Patent Publication No. 2022-71751 Summary of the Invention [Problem to be solved by the invention]
[0004] However, in the past, when an image was formed on a perforated sheet, there was a risk that image defects would easily occur on the sheet. This is because, in the case of a perforated sheet, unevenness called burrs occurs on one side of the sheet when the perforations are processed, and when a toner image is transferred to the one side with the burrs, the toner is likely to scatter due to the burrs.
[0005] SUMMARY OF THE PRESENT DISCLOSURE In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of suppressing image defects caused by burrs in a perforated sheet when an image is formed on the sheet. [Means for solving the problem]
[0006] An image forming apparatus according to one embodiment of the present invention comprises an image forming unit that forms a toner image on an image carrier, a transfer unit that transfers the toner image formed on the image carrier to a sheet, a setting unit in which a perforated sheet can be set, a transport unit that can transport a sheet from the setting unit to the transfer unit, and a display unit that displays and allows selection of the types of sheets that can be set in the setting unit, and is characterized in that when a perforated sheet is selected as the sheet to be set in the setting unit, the display unit is capable of displaying information regarding the front and back of the sheet when the sheet is set in the setting unit. Effect of the Invention
[0007] According to the present invention, when forming an image on a perforated sheet, the user can set the perforated sheet in the setting section by referring to the information regarding the front and back displayed on the display section so as to prevent image defects caused by curling of the sheet. [Brief description of the drawings]
[0008] [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 control block diagram showing a control configuration of the image forming apparatus. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] 1A is a cross-sectional view of a perforated sheet, and FIG. 1B is an enlarged view of a burr in the perforated sheet, illustrating toner scattering caused by burrs. [Figure 7] 5A and 5B are diagrams for explaining toner adhesion to the outer secondary transfer roller. [Figure 8] FIG. [Figure 9] 5 is a timing chart for explaining the back stain elimination control. [Figure 10] FIG. 11 is a diagram showing a process flow relating to mode setting of back stain elimination control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] <Image forming device> The image forming apparatus of this embodiment will be described with reference to FIG. 1. The image forming apparatus 100 is a tandem-type full-color printer of an electrophotographic system. The image forming apparatus 100 has image forming units Pa, Pb, Pc, and Pd that form images of yellow, magenta, cyan, and black, respectively. The image forming apparatus 100 forms a toner image on a sheet S based on image data sent from an external device 1000 such as a document reading device (not shown) connected to the image forming apparatus 100 or a personal computer. Examples of the sheet S include sheet materials such as plain paper, thick paper, rough paper, textured paper, and coated paper.
[0010] The conveying process of the sheet S in the image forming apparatus 100 will be described. The sheet S can be set by being stacked in a cassette 10 serving as a setting unit. Alternatively, the sheet S can be set by being stacked on a manual feed tray 17 serving as a setting unit. The sheet S set in the cassette 10 or the manual feed tray 17 is sent out by a supply roller 13 in accordance with the image formation timing. The manual feed tray 17 is provided so as to be openable and closable, and may be opened and closed at the user's discretion.
[0011] The sheet S sent out by the supply roller 13 is conveyed to the registration roller 12 arranged in the conveying section 114 capable of conveying the sheet S. Then, after the registration roller 12 performs skew correction and timing correction on the sheet S, the sheet S is sent to the secondary transfer section T2. The secondary transfer section T2 is a transfer nip section formed by the secondary transfer inner roller 14 and the secondary transfer outer roller 11, and a toner image is transferred onto the sheet in response to a secondary transfer voltage applied by a power source 90 to the secondary transfer outer roller 11 as a transfer section. Although only one cassette 10 is shown in FIG. 1, there may be multiple cassettes 10. The conveying section 114 conveys the sheet S from the cassette 10 or the manual feed tray 17 to the secondary transfer section T2.
[0012] The process of forming an image sent to the secondary transfer unit T2 at the same timing as the process of conveying the sheet S to the secondary transfer unit T2 described above will be described. First, the image forming units Pa, Pb, Pc, Pd, and Pe for each color are configured almost the same, except that the toners used in the developing devices 1a, 1b, 1c, and 1d are yellow (Y), magenta (M), cyan (C), and black (K). Therefore, the following description will be given of the black image forming unit Pd as a representative, and the description of the other image forming units Pa, Pb, and Pc will be omitted.
[0013] The image forming section Pd is mainly composed of a developing device 1d, a charging device 2d, a photosensitive drum 3d, a photosensitive drum cleaner 4d, an exposure device 5d, a primary transfer roller 6d, and the like. The surface of the rotating photosensitive drum 3d is uniformly charged in advance by the charging device 2d, and then an electrostatic latent image is formed on the surface of the photosensitive drum 3d by the exposure device 5d, which is driven based on a signal of image information. Next, the electrostatic latent image formed on the photosensitive drum 3d is developed into a toner image by the developing device 1d using a developer. Then, the toner image formed on the photosensitive drum 3d is primarily transferred onto the intermediate transfer belt 80 in response to the application of a primary transfer voltage to the primary transfer roller 6d, which is disposed with the photosensitive drum 3d and the intermediate transfer belt 80 sandwiched therebetween. A small amount of primary transfer residual toner remaining on the photosensitive drum 3d is collected by the photosensitive drum cleaner 4d.
[0014] The intermediate transfer belt 80 as an image carrier is stretched by the inner secondary transfer roller 14 and tension rollers 15 and 16, and is driven in the direction of the arrow R2. In this embodiment, the tension roller 16 also serves as a drive roller for driving the intermediate transfer belt 80. The image forming processes of each color, which are processed in parallel by the image forming units Pa to Pd, are performed at a timing when the image is sequentially superimposed on the toner image of the upstream color that has been primarily transferred onto the intermediate transfer belt 80. As a result, a full-color toner image is finally formed on the intermediate transfer belt 80, and is carried by the intermediate transfer belt 80 and conveyed to the secondary transfer unit T2. The secondary transfer residual toner after passing through the secondary transfer unit T2 is removed from the intermediate transfer belt 80 by the belt cleaner 22. In this embodiment, the image forming units Pa to Pd, the intermediate transfer belt 80, the rollers (14, 15, 16), the outer secondary transfer roller 11, and the like constitute an image forming unit 150 capable of forming a toner image on the sheet S.
[0015] Through the above-described conveying process and image forming process, the timing of the sheet S and the full-color toner image coincides at the secondary transfer section T2, and the secondary transfer is performed. After that, the sheet S is conveyed to the fixing device 50, where heat and pressure are applied to fix the toner image on the sheet. The fixing device 50 clamps and conveys the sheet S on which the toner image has been formed, and applies heat and pressure to the sheet S, thereby fixing the toner image to the sheet S. That is, the toner of the toner image formed on the sheet S is melted and mixed by the heat and pressure, and is fixed to the sheet S as a full-color image. The sheet S on which the toner image has been fixed is discharged to a discharge tray 95 provided outside the main body of the image forming apparatus 100. Alternatively, if another post-process unit (not shown), such as a finisher device, is connected to the main body of the image forming apparatus 100, the sheet S on which the toner image has been fixed is conveyed to the post-process unit. The finisher device performs, for example, a punching process for making holes in the sheet S, or a stapling process for bundling and staple multiple sheets S.
[0016] <Developer> In this embodiment, a two-component developer containing a toner and a carrier is used as the developer. The toner contains a binder resin, a colorant, and a release agent. The binder resin may be a known one. For example, a vinyl copolymer such as a styrene-(meth)acrylic copolymer, a polyester resin, a hybrid resin in which a vinyl copolymer and a polyester are chemically bonded, an epoxy resin, a styrene-butadiene copolymer, or other resin may be used. The colorants may be known for yellow (Y), magenta (M), cyan (C), and black (K).
[0017] Examples of the release agent include aliphatic hydrocarbon waxes such as low molecular weight polyethylene wax, low molecular weight olefin copolymer wax, microcrystalline wax, Fischer-Tropsch wax, and paraffin wax, oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, and block copolymers thereof; waxes containing fatty acid esters as the main component such as carnauba wax and montan acid ester wax, ester waxes which are synthetic reaction products of higher fatty acids and higher alcohols such as behenyl behenate and behenyl stearate, and partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax.
[0018] <Control configuration of image forming apparatus> Next, the control configuration of the image forming apparatus 100 will be described using Fig. 2 while referring to Fig. 1. Note that various devices such as a motor and a power supply are connected to the control unit 101 in addition to those shown in Fig. 2, but since they are not the main point of the invention, their illustration and description will be omitted here.
[0019] The control unit 101 has a central processing unit (CPU) 102, a read only memory (ROM) 103, and a random access memory (RAM) 104, and controls the entire image forming apparatus 100. Various programs such as image forming jobs are stored in the ROM 103. Various data such as image data acquired from the operation unit 110 or an external device 1000 (see FIG. 1) are stored in the RAM 104.
[0020] For example, when the control unit 101 receives a command to start an image forming job, the control unit 101 executes an image forming program stored in the ROM 103 to control the image forming units Pa to Pd to form an image on the sheet S. In addition, in the case of this embodiment, as described later, when the number of sheets S on which images have been formed reaches a threshold value, the control unit 101 can execute a voltage control program (back stain elimination control) for repeatedly switching the polarity and applying a voltage to the outer secondary transfer roller 11 without passing the sheet S. At that time, the power source 90 for applying a voltage to the outer secondary transfer roller 11 is controlled by the control unit 101. The RAM 104 can also temporarily store the results of calculations and the like associated with the execution of various programs.
[0021] The image forming apparatus 100 includes an operation unit 110 having a display unit 111 (see FIG. 1), and the operation unit 110 is connected to a control unit 101. The control unit 101 can display various screens presenting various programs and various data on the display unit 111, and also accepts inputs for starting various programs and inputting various data from the operation unit 110 in response to user operations.
[0022] <Operation section> The operation unit 110 will be described with reference to Fig. 3. As shown in Fig. 3, the operation unit 110 has a display unit 111, such as a liquid crystal monitor, and hardware keys. The display unit 111 may be a touch panel that can be operated by the user by touch, and can display a screen including various buttons, switches, etc. as software keys that can be operated by touch. In the case of this embodiment, the display unit 111 displays a "sheet selection screen" (see Fig. 4) and a "sheet setting screen" (see Fig. 5), which will be described later, and the like.
[0023] The hardware keys include, for example, a setting key 1102, a power saving key 1103, a group of hard keys 1104, a reset key 1105, a stop key 1106, and a start key 1107. The start key 1107 has a function of instructing the start of, for example, reading and printing (copying) an image of an original document, and other operations. The start key 1107 has a built-in two-color LED, green and red (not shown), which indicates that an operation can be started when lit green and that an operation cannot be started when lit red. The stop key 1106 has a function of temporarily pausing an operation such as image formation that is in progress. The group of hard keys 1104 includes, for example, a numeric keypad, a clear key, and an authentication key.
[0024] The power saving key 1103 has a function of switching the image forming apparatus 100 from the normal mode to a sleep mode in which the image forming apparatus 100 waits in a power-saving state, or of returning the image forming apparatus 100 from the sleep mode to the normal mode. That is, when the power saving key 1103 is pressed by the user in the normal mode, the image forming apparatus 100 switches to the sleep mode, and when the power saving key 1103 is pressed by the user in the sleep mode, the image forming apparatus 100 switches to the normal mode. The setting key 1102 is used, for example, when setting the type of sheet S. The reset key 1105 is used, for example, when canceling the type of sheet S that has been set.
[0025] <Sheet selection screen> In this embodiment, a "sheet selection screen" is displayed on display unit 111. The "sheet selection screen" is a screen that is displayed on display unit 111, for example, when a user operates a sheet type selection button from a "menu screen" (not shown) displayed on display unit 111, or when a user opens cassette 10 or manual feed tray 17. The "sheet selection screen" will be described with reference to FIG. 4.
[0026] As shown in FIG. 4, on the "sheet selection screen", types of sheets S on which images can be formed by image forming apparatus 100, which are stored in advance in ROM 103 (see FIG. 2), are displayed in a selectable dialog box 1201. Here, "plain paper", "cardboard", and "perforated paper" (perforated sheet) are displayed, but the user can scroll the screen displayed in dialog box 1201 to display other types on which images can be formed. The user can select the type of sheet S by touching any type from the multiple types displayed in dialog box 1201. The selected type of sheet S is confirmed by operating confirmation button 1203.
[0027] <Sheet set screen> Next, when the Confirm button 1203 is operated with "Perforated Paper" selected as the type of sheet S on the above-mentioned "Sheet Selection Screen", a "Sheet Setting Screen" is displayed on the display unit 111 as shown in Fig. 5. Note that Fig. 5 shows an example in which there are four cassettes 10.
[0028] As shown in FIG. 5, the "sheet setting screen" displays a warning screen 1301 and a setting mode screen 1302. The setting mode screen 1302 displays information regarding the front and back when setting the perforated sheet in the cassette 10 or the manual feed tray 17, indicating whether the surface of the perforated sheet on which unevenness caused by perforation processing, called burrs, is formed (hereinafter referred to as the burr surface) is to be set facing up or down. In other words, the information regarding the front and back is information to set the perforated sheet with the burr surface facing up or down. The front and back orientation of the perforated sheet is displayed so that the burr surface of the perforated sheet conveyed from the cassette 10 or the manual feed tray 17 to the secondary transfer unit T2 through the conveyance unit 114 does not become the image transfer surface (printing surface) onto which the toner image is transferred at the secondary transfer unit T2.
[0029] In this embodiment, as shown in FIG. 1, the sheet S set in the cassette 10 is conveyed to the secondary transfer section T2 with the front side of the sheet S facing down, i.e., inverted, when passing through the conveying section 114. Therefore, as a setting mode when setting the perforated sheet in the cassette 10, a message is displayed indicating that the burr surface (corresponding to the first surface in this case) should be set "up (front)". On the other hand, the sheet S set in the manual feed tray 17 is conveyed to the secondary transfer section T2 with the front side of the sheet S facing up, i.e., not inverted, when passing through the conveying section 114. Therefore, as a setting mode when setting the perforated sheet in the manual feed tray 17, a message is displayed indicating that the burr surface (corresponding to the second surface in this case) should be set "down".
[0030] As already mentioned, conventionally, when forming an image on a perforated sheet, there was a risk of image defects occurring when the toner image was transferred to the burred side. This is because toner is prone to scattering due to burrs during the secondary transfer of the toner image from the intermediate transfer belt 80 to the perforated sheet at the secondary transfer section T2. Here, the scattering of toner caused by burrs will be explained using Figures 6(a) and 6(b). Figure 6(a) is a cross-sectional view showing the perforated sheet, and Figure 6(b) is an enlarged view showing the burrs on the perforated sheet.
[0031] As shown in FIG. 6(a), burrs 201 are generated on the perforated sheet (S) during perforation. The burrs 201 of the perforated sheet are crushed by being sandwiched and conveyed by the secondary transfer section T2 when the perforated sheet passes through the secondary transfer section T2, and the "height h" of the burrs 201 becomes lower than before the passage. However, when the perforated sheet is sandwiched and conveyed to the secondary transfer section T2 with the burr surface of the perforated sheet facing the image transfer surface, the burrs 201 are not crushed sufficiently by the contact pressure of the inner secondary transfer roller 14 and the outer secondary transfer roller 11 (see FIG. 1), and a gap is generated between the burr surface and the intermediate transfer belt 80. A secondary transfer voltage is applied to the secondary transfer section T2, and discharge is likely to occur in the gap, so that toner is likely to scatter in the vicinity of the burrs 201.
[0032] As shown in FIG. 6B, the area crushed by the contact pressure of the inner secondary transfer roller 14 and the outer secondary transfer roller 11 is the "area ABC" surrounded by straight lines passing through the "height h" of the burr 201 in the "area 1" on the burr surface from the perforation 202 penetrating the front and back of the sheet in the conveying direction to a position separated by a small distance. On the other hand, the surface opposite the burr surface (hereinafter referred to as the non-burr surface) is the "area ADEB". The "area 1" depends on the "height h" of the burr 201 and the stiffness of the perforated sheet, but the inventors' study revealed that the gap generated when passing through the secondary transfer portion T2 is larger in the "area ABC" compared with the "area ADEB". Since a larger gap generates a stronger discharge, toner is more likely to scatter on the burr surface with the "area ABC". Therefore, an image defect in which the toner concentration is darker in a streak shape than other areas may occur around the perforation 202 on the burr surface.
[0033] As described above, the setting mode screen 1302 displays the setting mode of the perforated sheet that can prevent the toner from scattering separately for the cassette 10 and the manual feed tray 17, which have different transport modes to the secondary transfer portion T2.
[0034] Returning to FIG. 5, in addition to the setting mode screen 1302, the "sheet setting screen" displays a warning screen 1301 as information regarding the effect on the image formed on the perforated sheet. The warning screen 1301 displays a warning display indicating that an image defect will occur if the perforated sheet is set in an orientation opposite to the front and back orientation displayed on the setting mode screen 1302. The warning screen 1301 also displays a warning image indicating an image defect that may occur if the perforated sheet is set in an orientation opposite to the front and back orientation displayed on the setting mode screen 1302. The warning image is an image indicating an image defect that may occur due to burrs 201 of the perforated sheet.
[0035] As described above, in this embodiment, when "perforated paper" is selected as the sheet type, the "sheet setting screen" displayed on the display unit 111 displays a setting mode screen 1302 (see FIG. 5). The setting mode screen 1302 displays the front / back orientation of the perforated sheet, that is, whether the curled surface of the perforated sheet is set facing up or down when the perforated sheet is set in the cassette or manual feed tray. The front / back orientation of the perforated sheet is displayed so that the curled surface of the perforated sheet conveyed from the cassette 10 or manual feed tray 17 does not become the image transfer surface. In order to prevent image defects caused by curling when forming an image on the perforated sheet, the perforated sheet may be set in the cassette 10 or manual feed tray 17 so that the surface without the curl becomes the image transfer surface, and such setting modes are displayed separately for the cassette 10 and the manual feed tray 17 on the setting mode screen 1302. Therefore, if the user refers to the setting mode screen 1302 and sets the perforated sheet in the cassette 10 or the manual feed tray 17, image defects caused by burrs can be prevented.
[0036] Furthermore, the "sheet setting screen" displays a warning screen 1301 together with a setting mode screen 1302. The warning screen 1301 displays a warning display indicating that an image defect will occur if the perforated sheet is set in the opposite direction to the front and back orientation displayed on the setting mode screen 1302, and a warning image showing the image defect that may occur in such a case. By displaying the warning display and the warning image, it is possible to prevent the user from mistakenly setting the perforated sheet in the opposite direction to the front and back orientation displayed on the setting mode screen 1302.
[0037] <Other embodiments> Incidentally, even if the user sets the perforated sheet in the cassette 10 or the manual feed tray 17 according to the display on the setting mode screen 1302, back stains may occur on the sheet S when forming an image on another sheet S after forming an image on the perforated sheet. Back stains occur when toner adheres to the outer secondary transfer roller 11 at the secondary transfer section T2 during secondary transfer onto the perforated sheet, and the adhered toner stains the back surface of the sheet S.
[0038] FIG. 7 is a diagram for explaining toner adhesion to the secondary transfer outer roller 11 that occurs during secondary transfer to a perforated sheet, which causes back stains. As shown in FIG. 7, in the case of a perforated sheet (S), the toner T transferred from the intermediate transfer belt 80 may pass through the perforations 202 that penetrate the front and back of the sheet to the secondary transfer outer roller 11 side, and may adhere to the secondary transfer outer roller 11. After that, when another sheet S is conveyed in contact with the secondary transfer outer roller 11 to which the toner T is attached, the back surface of the sheet S is stained by the toner T. Such back stains do not occur when the amount of toner attached to the secondary transfer outer roller 11 is small, but when the amount of toner attached increases due to repeated secondary transfer to the perforated sheet and exceeds the allowable amount that the secondary transfer outer roller 11 can support, the back stains become apparent.
[0039] Therefore, instead of the warning display or warning image as shown in Fig. 5, a warning display indicating that backside stains may occur on the sheet S or a warning image showing backside stains on the sheet S may be displayed on the warning screen of the above-mentioned "sheet setting screen" (see Fig. 5). Such a warning screen of the "sheet setting screen" is shown in Fig. 8.
[0040] 8, the "sheet setting screen" displays a warning screen 1303 along with the above-mentioned setting mode screen 1302 (not shown). The warning screen 1303 displays a warning message indicating that back stains may occur on the back surface of the sheet S due to image formation on the perforated sheet. The warning screen 1303 also displays a warning image indicating the back stains that may occur on the back surface of the sheet S due to image formation on the perforated sheet.
[0041] Furthermore, the warning screen 1303 displays a selection screen 1304 for allowing the user to select whether the back stain elimination control for suppressing back stains is to be executed in an "image quality priority mode" or a "productivity priority mode". By referring to the warning display and the warning image, the user can select either the "image quality priority mode" or the "productivity priority mode" depending on the degree of back stains. In the case of the selection screen 1304 shown in FIG. 8, when "Yes" is selected, the back stain elimination control is set to the "image quality priority mode", and when "No" is selected, the back stain elimination control is set to the "productivity priority mode". In other words, the selection screen 1304 displays information regarding whether the "image quality priority mode" can be executed.
[0042] The back stain elimination control will be described. Back stains can be suppressed by executing "back stain elimination control." In "back stain elimination control," the sheet S is not passed through the secondary transfer portion T2, and an operation of repeatedly switching the polarity of a voltage at a predetermined cycle and applying it to the secondary transfer outer roller 11 is executed for a predetermined time, so that the toner adhering to the secondary transfer outer roller 11 is returned to the intermediate transfer belt 80. By returning the toner adhering to the secondary transfer outer roller 11 to the intermediate transfer belt 80, back stains are less likely to occur on the back surface of the sheet S. The toner returned to the intermediate transfer belt 80 is removed from the intermediate transfer belt 80 by the belt cleaner 22.
[0043] Fig. 9 is a timing chart for explaining the back stain elimination control. Fig. 9 shows an example in which the image forming speed is "435 mm / s", the outer diameter of the secondary transfer outer roller 11 is "20 mm", and the cycle of the secondary transfer outer roller 11 is "144 ms". The back stain elimination control is executed by interrupting the image forming job being executed when the number of images formed on the sheet S reaches a threshold value, or is executed after the image forming job is finished and before the successive image forming job is started.
[0044] In the example shown in FIG. 9, the back stain elimination control (mode) applies a voltage of 500V absolute value by alternately switching between negative polarity (first polarity) and positive polarity (second polarity) for each rotation period of the secondary transfer outer roller 11, three times within a predetermined time. The reason for alternately switching the polarity of the voltage between positive and negative polarities is that the polarity of the toner attached to the secondary transfer outer roller 11 can be either normally charged or reversely charged, and both types of toner are returned from the secondary transfer outer roller 11 to the intermediate transfer belt 80. However, since image formation on the sheet S cannot be performed during the execution of the back stain elimination control, the productivity of the image forming apparatus 100 decreases. Therefore, as a "productivity priority mode" (first mode) for preventing the productivity of the image forming apparatus 100 from decreasing, the back stain elimination control is executed once for every "1000" sheets of the sheet S on which images are formed.
[0045] 8, the selection screen 1304 is a screen that allows the user to select whether to execute the "productivity priority mode" when the number of images formed on the above-mentioned sheets S reaches a first number (e.g., 1000 sheets) or to execute the "image quality priority mode." The "image quality priority mode" (second mode) is executed when the number of images formed on the sheets S reaches a second number (e.g., 100 sheets) that is less than the first number.
[0046] In this "image quality priority mode", productivity is lower than in the "productivity priority mode", but the toner adhering to the secondary transfer outer roller 11 is returned to the intermediate transfer belt 80 more frequently, and the amount of toner adhering to the secondary transfer outer roller 11 can be reduced, thereby suppressing back stains on the sheet S. In other words, it is possible to give priority to the quality of the sheet S (image quality priority) rather than to the printing speed (productivity priority). Note that in the "image quality priority mode", the number of times the polarity of the secondary transfer voltage is switched in the back stain elimination control may be increased to be greater than the number of times (e.g., three times) in the "productivity priority mode", so that more toner is returned from the secondary transfer outer roller 11 to the intermediate transfer belt 80.
[0047] Fig. 10 shows a process flow relating to the mode setting of the back stain elimination control described above. As described above, when "perforated paper" is selected as the type of sheet S on the "sheet selection screen" (see Fig. 4) displayed on the display unit 111 (S1) and the confirm button 1203 is operated, the "sheet setting screen" is displayed on the display unit 111. The "sheet setting screen" displays the above-mentioned setting mode screen 1302 (see Fig. 5) and a warning screen 1303 (see Fig. 8) that displays a warning of light stains (S2). The warning screen 1303 displays the selection screen 1304 as described above.
[0048] Depending on whether "Yes" or "No" is selected on the selection screen 1304 of the "Sheet Setting Screen", the back stain elimination control mode is selected (S3). If the "image quality priority mode" is selected (YES in S3), the back stain elimination control is set to be executed once per "100 sheets" of image formation on the sheet S (S4). If the "productivity priority mode" is selected (NO in S3), the back stain elimination control is set to be executed once per "1000 sheets" of image formation on the sheet S (S5).
[0049] As described above, the warning screen 1303 displays the selection screen 1304 together with a warning display indicating that back stains may occur on the back surface of the sheet S due to image formation on the perforated sheet and a warning image showing the back stains that may occur on the back surface of the sheet S. The selection screen 1304 is a screen for allowing the user to select whether the back stain elimination control is to be executed in the "image quality priority mode" or the "productivity priority mode." By selecting the "image quality priority mode," the user can prevent back stains from occurring on the sheet S. [Explanation of symbols]
[0050] 10... setting section (cassette), 11... transfer section (secondary transfer outer roller), 17... setting section (manual feed tray), 80... image carrier (intermediate transfer belt), 90... power supply, 100... image forming apparatus, 111... display section, 114... conveying section, Pa to Pd... image forming section, S... sheet
Claims
1. An image forming apparatus capable of forming a toner image on a sheet having perforations and protrusions formed around holes created by the perforations, The loading section where the sheets are loaded, A transport path through which the sheets loaded on the loading section are transported, An image forming unit that forms a toner image on an image carrier, A transfer unit that transfers a toner image from the image carrier to a sheet transported along the transport path, The system includes a display unit that displays guidance regarding the orientation in which the sheet is placed on the loading section, depending on the surface of the sheet having the protrusions. An image forming apparatus characterized by the following:
2. The display unit displays a selection screen for selecting the type of sheet to be placed on the loading unit from a plurality of types of sheets, The aforementioned multiple types of sheets include the perforated sheet and other sheets that are not perforated. The image forming apparatus according to feature 1.
3. The display unit displays the guidance when the sheet with perforations is selected on the selection screen. The image forming apparatus according to feature 2.
4. The transfer unit transfers a toner image to a sheet at the transfer nip, The transport path has a U-shaped route between the loading section and the transfer nip. The guidance indicates that the sheet should be placed on the loading area so that the side of the sheet with the protrusion faces upward. The image forming apparatus according to feature 1.
5. The transfer unit transfers a toner image to a sheet at the transfer nip, The transport path has a straight path between the loading section and the transfer nip. The guidance indicates that the sheet should be placed on the loading area such that the side of the sheet with the protrusion faces downward. The image forming apparatus according to feature 1.
6. The loading section includes a cassette and a manual feed tray, The guidance indicates that the sheet should be placed in the cassette such that the side of the sheet with the protrusion faces the first side, and that the sheet should be placed in the manual feed tray such that the side of the sheet with the protrusion faces the second side opposite to the first side. The image forming apparatus according to feature 1.
7. The display unit further displays a warning screen that notifies that toner stains have occurred on the back of the sheet. The image forming apparatus according to feature 1.
8. A power supply for applying voltage to the transfer unit, The system includes a control unit capable of executing a removal control mode for removing toner adhering to the transfer unit, During the removal control mode, the control unit performs the operation of alternately applying a voltage of a first polarity and a voltage of a second polarity, which is the opposite polarity to the first polarity, to the transfer unit using the power supply for a predetermined period of time. The image forming apparatus according to feature 1.