Image forming apparatus and program

Abstract

To provide an image forming apparatus that can prevent the occurrence of an image defect when forming an image on a perforated sheet.SOLUTION: An image forming apparatus starts "perforation detection control" when using a perforated sheet (S3), and causes a recording material reading unit to read the perforated sheet on which a toner image is not formed to acquire perforation positions on the perforated sheet (S5). When the perforation positions are "OK" (YES in S7), the image forming apparatus stores "perforation pattern information" as information on the positions of perforations (S8). Subsequently, the image forming apparatus starts an image forming job on the perforated sheet according to an instruction to start the image forming job (S9). At that time, the image forming apparatus performs "perforated image control" according to the "perforation pattern information" (S10). In the "perforated image control," the image forming apparatus does not form a toner image in a perforated area of the perforated sheet where turn-up occurs, and forms the toner image in an area other than the perforated area.SELECTED DRAWING: Figure 5

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, and a program therefor. [Background technology]

[0002] The image forming apparatus is equipped with a cassette or a manual feed tray on which sheets can be set, and forms images by transferring a toner image onto various sheets conveyed from the cassette or the manual feed tray. In some cases, the sheets used are perforated sheets (referred to as perforated sheets) (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 case of perforated sheets, unevenness called burrs occurs in the sheet when the perforations are processed, and there is a risk of image defects occurring when a toner image is formed on the perforated sheet.

[0005] In view of the above-mentioned problems, an object of the present invention is to provide an image forming apparatus and a program capable of suppressing the occurrence of image defects when forming an image on a perforated sheet. [Means for solving the problem]

[0006] An image forming apparatus according to one embodiment of the present invention is an image forming apparatus capable of forming an image on a perforated sheet, and is characterized in that it comprises an acquisition unit that acquires information regarding a perforation formation area formed on the perforated sheet, an image forming unit that forms an image on the perforated sheet in accordance with image data, and a control unit that controls the image forming unit so that an image is not formed in the perforation formation area when there is an image to be formed by the image forming unit in accordance with the image data in the perforation formation area.

[0007] An image forming apparatus according to one embodiment of the present invention is an image forming apparatus capable of forming an image on a perforated sheet, and is characterized in that it comprises an image carrier that carries a toner image, an image forming unit that forms a toner image to be carried on the image carrier, a transfer unit that transfers the toner image carried on the image carrier to a sheet, a transport unit that transports the sheet to the transfer unit, an acquisition unit that acquires information regarding a perforation formation area formed on the perforated sheet, and a control unit that, when the sheet on which the toner image is formed is a sheet on which perforations are formed in a direction intersecting the transport direction of the sheet and there is a toner image formed in the perforation formation area, controls the transfer unit to apply a first voltage to areas other than the perforation formation area and to apply a second voltage, which is smaller in absolute value than the first voltage, to the transfer unit to the perforation formation area.

[0008] An image forming apparatus according to one embodiment of the present invention is an image forming apparatus capable of forming an image on a perforated sheet, and is characterized in that it comprises a receiving unit that receives information relating to a perforation formation area formed on the perforated sheet, and a display unit that displays the perforations in accordance with the information relating to the perforation formation area.

[0009] A program according to one embodiment of the present invention is characterized in that it causes an information processing device to execute a reception process for receiving information relating to a perforation formation area formed on a perforated sheet, and a display process for displaying the perforation in accordance with the information relating to the perforation formation area. Effect of the Invention

[0010] According to the present invention, when an image is formed on a perforated sheet, the occurrence of image defects can be suppressed. [Brief description of the drawings]

[0011] [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] 4 is a flowchart showing image processing according to the first embodiment. [Figure 6] FIG. 13 is a diagram for explaining detection of perforations. [Figure 7] 11A to 11D are diagrams for explaining the calculation of the perforation pattern, showing (a) a two-dimensional luminance image, (b) a two-dimensional binary image, (c) a Hough transform formula, (d) a Hough transform image, (e) a histogram of the Hough transform image, (f) a two-dimensional histogram, and (g) a perforation pattern image. [Figure 8] FIG. 13 is a diagram showing a display screen of a perforation pattern. [Figure 9] (a) Schematic diagram showing a perforated area where burrs have occurred, (b) A diagram for explaining toner transfer at the perforated area, (c) A diagram showing a halftone image, and (d) A diagram showing an image defect that has occurred on a perforated sheet. [Figure 10] 1A is a diagram showing a perforated region, FIG. 1B is a diagram showing an image pattern after an image signal has been changed, and FIG. 1C is a diagram showing an image formed on a perforated sheet based on the image pattern after the image signal has been changed. [Figure 11]FIG. 13 is a diagram showing a warning screen that warns of a mismatch between the perforation pattern and the divided print pattern. [Figure 12] FIG. 13 is a diagram showing a perforation acquisition screen. [Figure 13] FIG. 13A is a diagram showing the perforation pattern input screen when a divided print pattern is selected, and FIG. 13B is a diagram showing the perforation pattern input screen when a divided print pattern is not selected. [Figure 14] FIG. 1A is a diagram showing the cut and tie portions; FIG. 1B is a diagram for explaining toner transfer at the cut portion; FIG. 1C is a diagram for explaining toner transfer at the tie portion; and FIG. 1D is a diagram showing an image defect that occurs on a perforated sheet. [Figure 15] 10 is a flowchart showing image processing according to a second embodiment. [Figure 16] Regarding the second embodiment, (a) is a diagram showing a cut area where a toner image is not formed, (b) is a diagram showing an image pattern after the image signal has been changed, and (c) is a diagram showing an image formed on a perforated sheet based on the image pattern after the image signal has been changed. [Figure 17] (a) A diagram showing an image formed on a perforated sheet with an image ratio of 30%, (b) A diagram showing an image formed on a perforated sheet with an image ratio of 50%, and (c) A diagram showing an image formed on a perforated sheet with an image ratio of 80%. [Figure 18] 13 is a flowchart showing image processing according to a third embodiment. [Figure 19] 4 is an enlarged view of the vicinity of the secondary transfer nip portion. [Figure 20] 10A and 10B are diagrams showing toner scattering when the secondary transfer voltage is 1000V and 700V, respectively. [Figure 21] 13 is a flowchart showing image processing according to a fourth embodiment. [Figure 22] FIG. 13A shows a secondary transfer voltage applied when the direction in which the perforations are formed is perpendicular to the conveying direction, and FIG. 13B shows a secondary transfer voltage applied when the direction in which the perforations are formed is the conveying direction, in the fourth embodiment. [Diagram 23] 13A and 13B are diagrams illustrating a secondary transfer voltage applied when the direction of perforations is perpendicular to the transport direction and in the transport direction in the fourth embodiment. [Figure 24] FIG. 1 is a schematic diagram showing an image forming apparatus having a document reading device. [Diagram 25] 1A is a diagram showing a selection screen for selecting a method for reading a perforated sheet, and FIG. 1B is a diagram showing a setting screen for a perforated sheet. [Figure 26] FIG. 1 is a schematic diagram showing a direct transfer type image forming apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [First embodiment] <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, for example, a document reading device 800 (see FIG. 24) connected to the image forming apparatus 100 or an external device 1000 such as a personal computer. Examples of the sheet S include sheet materials such as plain paper, thick paper, rough paper, textured paper, and coated paper.

[0013] The conveying process of the sheet S in the image forming apparatus 100 will be described. The sheet S can be set in a form stacked in the cassette 10. Alternatively, the sheet S can be set in a form stacked in the manual feed tray 17. The sheet S set in the cassette 10 or the manual feed tray 17 as a setting unit is sent out by a supply roller 13 in accordance with the image formation timing. The cassette 10 and the manual feed tray 17 are provided so as to be openable and closable, and may be opened and closed at the user's discretion. Although not shown in the figure, the cassette 10 and the manual feed tray 17 are each equipped with a paper detection sensor, which can detect whether or not the sheet S is set in the cassette 10 or the manual feed tray 17.

[0014] The sheet S sent out by the supply roller 13 is conveyed to the registration roller 12. After the registration roller 12 performs skew correction and timing correction on the sheet S, the sheet S is conveyed to the secondary transfer nip portion T2. ​​The secondary transfer nip portion T2 is a transfer nip portion 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 portion. Although only one cassette 10 is shown in FIG. 1, there may be multiple cassettes 10. A conveying portion 114 that conveys the sheet S conveys the sheet S from the cassette 10 or the manual feed tray 17 to the secondary transfer nip portion T2.

[0015] The process of forming an image sent to the secondary transfer nip T2 at the same timing as the process of conveying the sheet S to the secondary transfer nip T2 described above will be described. First, the image forming units Pa, Pb, Pc, and Pd 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.

[0016] 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.

[0017] 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 while contacting the photosensitive drums 3a to 3d. 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 nip portion T2. ​​The secondary transfer residual toner after passing through the secondary transfer nip portion T2 is removed from the intermediate transfer belt 80 by the belt cleaner 22.

[0018] 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 nip T2, and secondary transfer is performed. Thereafter, 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 a post-processing device (not shown) such as a finisher 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-processing device. The finisher performs, for example, a punching process for making holes in the sheet S, or a stapling process for bundling and staple multiple sheets S.

[0019] Although not shown in the figure, outside the main body of the image forming apparatus 100, pre-processing devices such as a sheet supplying device that supplies a large amount of stored sheets S one by one to the image forming apparatus 100, and a perforation processing device that perforates the sheets S and supplies them to the image forming apparatus 100 may be connected.

[0020] <Recording material reading section> In the main body of the image forming apparatus 100, a recording material reading unit 131 is disposed upstream of a secondary transfer nip portion T2 of a conveying path 132 along which the sheet S is conveyed and downstream of the cassette 10 and the manual feed tray 17 with respect to the conveying direction of the sheet S by the conveying unit 114. The recording material reading unit 131 has an LED array 131a, a CIS (Contact Image Sensor) 131b, and a contact glass 131c, and is capable of acquiring an optical image of the sheet S conveyed along the conveying path 132 by the conveying unit 114. The LED array 131a irradiates light toward the sheet S conveyed onto the contact glass 131c by the conveying unit 114. The LED array 131a has a plurality of white LEDs arranged in a width direction intersecting the conveying direction of the sheet S and intersecting the vertical direction, and irradiates light so that the amount of irradiation light is approximately uniform. The CIS receives light reflected by the sheet S in response to the irradiation of light by the LED array 131a and forms an image on a photoelectric conversion element or the like to obtain an optical image or a height image of the sheet S. The contact glass 131c transmits the irradiation light irradiated from the LED array 131a toward the sheet S and the reflected light reflected by the sheet S in response to the irradiation of light.

[0021] In addition to the above-mentioned CIS type one-dimensional sensor, the recording material reading unit 131 may use a reduction optical type (CCD type) one-dimensional sensor, a one-dimensional height sensor, a two-dimensional area camera, or the like. The recording material reading unit 131 may also be used in common with other image detection sensors, such as sensors for product inspection, automatic density control, registration control, and the like. However, when these sensors are used in common, it is preferable that the contrast for obtaining the perforation positions of the perforated sheet S is smaller than that when the sensors detect the detection target. Therefore, when a sensor is used in common, it is preferable that a dedicated mode is provided in which the light amount of the LED array 131a of the recording material reading unit 131 is set to a small value or the contrast is set to a low value in order to obtain the perforation positions of the perforated sheet S.

[0022] <Developer> In the image forming apparatus 100 of 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. Known colorants may be used for yellow (Y), magenta (M), cyan (C), and black (K).

[0023] 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.

[0024] <Control Unit> As shown in Fig. 1, image forming apparatus 100 includes a control unit 101. The control configuration of image forming apparatus 100 by control unit 101 will be described using Fig. 2 with reference to Fig. 1. In addition to those shown in Fig. 2, various devices such as each unit constituting image forming apparatus 100 and drive sources (motors, power sources, etc.) for operating each unit are connected to control unit 101. However, since this is not the main point of the invention, illustration and description of those will be omitted here.

[0025] 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. The ROM 103 stores various programs such as image forming jobs.

[0026] The control unit 101 has an interface unit 105 as an acquisition unit, and can acquire various data via the interface unit 105, such as various data input from the operation unit 110, information set in a communicatively connected external device 1000, and image data transmitted from a document reading device 800 (described below). The data acquired by the control unit 101 is stored in a RAM 104. The RAM 104 can also temporarily store results of arithmetic processing associated with the execution of various programs. In this embodiment, the external device 1000 can output the perforation positions of the perforated sheet as information relating to the perforation formation area.

[0027] Image forming apparatus 100 includes an operation unit 110 having a display unit 111 (see FIG. 1), and operation unit 110 is connected to control unit 101. Control unit 101 can display various screens presenting various programs and various data on display unit 111, and also accepts inputs for starting various programs and inputs of various data in response to user operations from operation unit 110. Operation unit 110 as an input unit (reception unit) allows a user to input perforation positions of perforated sheet S (referred to as perforated sheet S) as information relating to the perforation formation area, as will be described later (see FIGS. 12 and 13).

[0028] When the control unit 101 receives a command to start an image forming job, it controls the image forming units Pa to Pd to form an image on the sheet S. At that time, the control unit 101 controls the power source 90 to change the secondary transfer voltage applied to the outer secondary transfer roller 11. As will be described in detail later, when forming a toner image on the perforated sheet S, the control unit 101 can execute a mode in which a toner image is not formed in a predetermined area including the perforation position (called the perforation area), but a toner image is formed in an area other than the perforation area.

[0029] <Operation section> Next, 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 various screens including various buttons, switches, etc. as software keys that can be operated by touch.

[0030] 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.

[0031] 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, etc. The reset key 1105 is used, for example, when canceling the type of sheet S that has been set.

[0032] <Sheet selection screen> A "sheet selection screen" is displayed on display unit 111 of operation unit 110. The "sheet selection screen" is displayed on display unit 111, for example, when the user operates a sheet type selection button from a "menu screen" (not shown) displayed on display unit 111, or when the user opens cassette 10 or manual feed tray 17. The "sheet selection screen" will be described with reference to FIG. 4.

[0033] As shown in FIG. 4, the "sheet selection screen" displays in a dialog box 1201 the types of sheets S on which images can be formed by the image forming apparatus 100, which are stored in advance in the ROM 103 (see FIG. 2), in a selectable manner. Here, "plain paper," "thick paper," and "perforated paper" (perforated sheet) are displayed, but the user can scroll the screen displayed in the dialog box 1201 to display other types on which images can be formed. The user can select the type of sheet S from the multiple types displayed in the dialog box 1201. The selected type of sheet S is confirmed by operating a confirmation button 1203. The user may then input the size, thickness, surface characteristics, and the like of the perforated sheet S to be used as paper settings in the conventional manner.

[0034] As already mentioned, conventionally, when a toner image is transferred to a perforated sheet S, unintended discharge occurs in a specific area where burrs have occurred, and there is a risk of toner being transferred to an unintended location, resulting in image defects such as a change in the color of the toner image. In view of this, in this embodiment, when forming an image on a perforated sheet S, a toner image is not formed in the perforated area including the perforation position where burrs have been formed.

[0035] The image processing of this embodiment will be described below with reference to Fig. 2 and Fig. 5 to Fig. 10(c). This image processing starts when the user selects and confirms "perforated paper" (perforated sheet S) on the "sheet selection screen" (see Fig. 4) displayed on the display unit 111.

[0036] <Image processing> When "perforated paper" is selected on the "sheet selection screen", as shown in Fig. 5, the control unit 101 refers to the paper library stored in the ROM 103 and checks the selected perforated sheet S (S1). The paper library is a table that stores in advance paper information such as image formation conditions corresponding to the sizes and thicknesses of various sheets including the perforated sheet S, and setting positions where various sheets can be set. The control unit 101 determines one of the cassette 10 to the manual feed tray 17 as a setting position where the perforated sheet S can be set based on the paper information in the paper library (S2).

[0037] Although not shown, when the perforated sheet S is not set in the cassette 10 or the manual feed tray 17, the control unit 101 displays on the display unit 111 that the perforated sheet S should be set in the determined set position of either the cassette 10 or the manual feed tray 17. The user sets the perforated sheet S in the cassette 10 or the manual feed tray 17 according to the display. On the other hand, when the perforated sheet S is set in the cassette 10 or the manual feed tray 17, the control unit 101 continues the process if the set cassette 10 or the manual feed tray 17 is the determined set position, and displays a warning on the display unit 111 that the set position is incorrect if it is not the determined set position. The control unit 101 may also display on the display unit 111, together with the warning, that the perforated sheet S should be set in the correct set position of either the determined cassette 10 or the manual feed tray 17.

[0038] The control unit 101 starts "perforation detection control" for the perforated sheet S set in the cassette 10 or the manual feed tray 17 (S3), and causes the conveying unit 114 to convey the perforated sheet S from the cassette 10 or the manual feed tray 17 to the recording material reading unit 131 (S4). The control unit 101 then causes the recording material reading unit 131, which serves as an acquisition unit, to read the perforated sheet S on which no toner image is formed, thereby acquiring the perforation position (S5), and causes the display unit 111 to display the acquired perforation position (a perforation pattern image, which will be described in detail later) (S6).

[0039] <Getting perforation position> Here, acquisition of the perforation positions of the perforated sheet S will be described with reference to Fig. 6 to Fig. 7(e). When the recording material reading unit 131 reads the perforated sheet S on which no toner image is formed, the recording material reading unit 131 detects one-dimensional luminance information in the main scanning direction by the CIS 131b (see Fig. 1) (Figs. 6(a-1) to (a-4)) and sends this one-dimensional luminance information together with time information to the control unit 101.

[0040] As shown in the upper diagram of FIG. 6, when the perforations are formed in the main scanning direction of the exposure devices 5a to 5d, smooth one-dimensional luminance information (FIG. 6(a-1)) is detected at the sub-scanning positions of the non-perforations, and one-dimensional luminance information (FIG. 6(a-2)) with repeated light and dark (convex and concave on the main scanning luminance graph) is detected at the sub-scanning positions of the perforations. In the one-dimensional luminance image, the parts corresponding to the perforations are darker images than the non-perforations. Also, as shown in the lower diagram of FIG. 6, when the perforations are formed in the sub-scanning direction of the exposure devices 5a to 5d, smooth one-dimensional luminance information (FIG. 6(a-3)) is detected at the sub-scanning positions of the gaps between the perforations, and one-dimensional luminance information (FIG. 6(a-4)) with dark parts (concave on the main scanning luminance graph) is detected at the sub-scanning positions corresponding to the perforations. Although not shown here, if the perforations are formed diagonally to the main scanning direction, brightness information in the main scanning direction can be obtained such that the pitch, number, and position in the main scanning direction of the perforations change depending on the position in the sub-scanning direction and the angle of the perforations.

[0041] The width of the perforations is 0.2 to 0.3 mm, including the burrs formed by the perforation process, and the pitch of the perforations is several mm apart. From this, it can be seen that the resolution of the input image for detecting the perforations is 100 dpi (spatial resolution 0.25 mm) or more, and preferably 300 dpi (spatial resolution 0.085 mm) or more. Therefore, a CIS 131b (see FIG. 1) with a scanning direction resolution of 300 dpi is used, and the conveying speed of the conveying unit 114 is adjusted so that the resolution in the sub-scanning direction is equivalent to 300 dpi.

[0042] The control unit 101 then obtains a two-dimensional luminance image (FIGS. 6(b-1) and (b-2)) of the perforated sheet S by integrating the one-dimensional luminance information sent from the recording material reading unit 131 based on time information, and detects straight line components that are candidates for perforations based on this two-dimensional luminance image. In this embodiment, the Hough transform is used as a method for detecting straight line components. An overview of the Hough transform will be described. The Hough transform transforms a straight line on the xy coordinate system as shown in Equation 1 and describes it using two variables, θ and ρ. x×cosθ+y×sinθ=ρ… Formula 1

[0043] Here, "θ" is the angle of the line, and "ρ" is the distance from the origin. The Hough transform is used to calculate the distance "ρ" for a line on the xy coordinate system at a certain angle "θ". When the angle of the line and angle "θ" on the xy coordinate system match, all points on the line on the xy coordinate system will be at a specific distance "ρ". When the angle of the line and angle "θ" do not match, the points on the line on the xy coordinate system will be distributed over a variety of distances "ρ". Using this relationship, the parameters "θ" and "ρ" of the line can be calculated.

[0044] The procedure for detecting a straight line will be described with reference to Fig. 7(a) to Fig. 7(e). As shown in Fig. 7(a), the case where the control unit 101 obtains Fig. 6(b-1) as a two-dimensional luminance image of the perforated sheet S will be described as an example. Note that a feature of the Hough transform is that it has no singular point in the angle of the straight line (i.e., the inclination does not diverge to infinity), so that straight lines of any angle can be detected. Therefore, although the case where the perforations are parallel to the main scanning direction will be described as an example here, similar processing can be performed even when the perforations are parallel to the sub-scanning direction or when the perforations are oblique and have an angle to the main scanning direction.

[0045] First, the control unit 101 performs binarization processing on the two-dimensional luminance image (FIG. 7(a)) and converts it into the two-dimensional binary image shown in FIG. 7(b). In this embodiment, the binarization processing is performed using an algorithm of Otsu's method, and dark parts of the two-dimensional luminance image are converted to "1" and light parts are converted to "0". This is to make areas that may be points on a line passing through the perforation "1" and areas that may not be a line passing through the perforation "0". Note that the binarization processing is not limited to Otsu's method. Furthermore, if necessary, the two-dimensional luminance image may be processed using a LOG filter or a differential filter before performing the binarization processing.

[0046] Next, prepare an image for Hough transform of the same size as the converted 2D binary image. If a point on the xy coordinate system is expressed as ij(xi, yj), the value of the distance "ρijn" at a certain angle "θn" can be written as Equation 2 in the above formula 1. xi×cosθn+yj×sinθn=ρijn … Formula 2

[0047] 7(c) shows an image in which distance "ρ" is calculated from equation (2) for a point on the xy coordinate system at a certain angle "θ". However, here, the following are set: "0≦i≦4000 (pix)", "0≦j≦5800 (pix)", "-90≦θ≦90 (°), 1° intervals", and "0≦ρ≦7100 (pix), rounded off to the nearest whole number". When the maximum size of sheet S on which an image can be formed by image forming apparatus 100 is "13×19 inches", the maximum values ​​of "i" and "j" are set to be larger than the maximum size at 300 dpi, and the maximum value of distance "ρ" is set to be larger than the length of the diagonal of sheet S.

[0048] Next, in order to calculate ρ of pixels that may be perforations, the control unit 101 multiplies the Hough transform image (Fig. 7(c)) by the two-dimensional binarized image (Fig. 7(b)) for each pixel to calculate the distance "ρ'" (Fig. 7(d)). With this process, the distance "ρ'" of points that may be on the straight line of the perforation remains the distance "ρ", while the distance "ρ'" of points that may not be on the straight line of the perforation becomes "0". Looking at Fig. 7(d), the value of the distance "ρ'" (image brightness) is constant at an angle parallel to the main scanning direction (90° in this case), and the value of the distance "ρ'" varies when the angle is not parallel to the main scanning direction.

[0049] Then, the control unit 101 acquires a histogram (FIG. 7(e)) of a Hough transform image (FIG. 7(d)) ​​that may be a perforation in order to obtain the distribution of the distance "ρ" at the angle "θn". From FIG. 7(e), it can be seen that the distance "ρ" is concentrated at a certain value at an angle parallel to the main scanning direction (here, 90°), and the distance "ρ" is scattered at other angles. When the histogram (FIG. 7(e)) of the Hough transform image is acquired while changing the angle "θ" in the above-mentioned "-90≦θ≦90(°), 1° interval", a two-dimensional histogram of FIG. 7(f) is obtained. The value of the peak T(θt, ρt) of this two-dimensional histogram indicates the parameters of the estimated straight line. Using these parameters, the straight line present on the Hough transform image is expressed by Equation 3. Then, by reconverting Equation 3 into xy coordinates, Equation 4 is obtained. x×cosθt+y×sinθt=ρt…Equation 3 y=(1 / sinθt)×(-x×cosθt+ρt) … Equation 4

[0050] In this way, the control unit 101 obtains a perforation pattern image (FIG. 7(g)) of the perforation position expressed by Equation 4. The control unit 101 obtains "perforation pattern information" by further converting the x and y coordinates of the perforation pattern image (FIG. 7(g)) into the resolution of the output image of the image forming apparatus 100 (e.g., 1200 dpi).

[0051] Although the above describes an example of a perforation pattern image showing the position of one perforation, perforation pattern images showing multiple perforation positions can also be obtained in the same manner. In the case of multiple perforations, multiple peaks T(θt, ρt) of the above-mentioned two-dimensional histogram are detected, and perforation pattern images corresponding to each of the multiple peaks T are obtained. If a perforation pattern image cannot be obtained, the control unit 101 stores "perforation pattern error information" in the RAM 104. The method of straight line detection is not limited to the above-mentioned method.

[0052] Returning to the explanation of FIG. 5, if the control unit 101 can detect the perforation position, it displays a "perforation pattern display screen" on the display unit 111 (S6). Then, the control unit 101 judges whether the perforation pattern is "OK" or not according to the user input (S7). If the perforation pattern is not "OK" but "NG" (NO in S7), the control unit 101 returns to the process of step S3 and repeats the above-mentioned detection of the perforation position (steps S3 to S6).

[0053] FIG. 8 shows the "perforation pattern display screen" (see S6 in FIG. 5). As shown in FIG. 8, the "perforation pattern display screen" displays perforation pattern 112, a "Yes" button, and a "No" button. Control unit 101 creates perforation pattern 112 based on paper information in the paper library read from ROM 103 and "perforation pattern information," and displays it on display unit 111. The "Yes" button is a button that the user operates when the perforation position is correctly detected (OK) after viewing the displayed perforation pattern 112. The "No" button is a button that the user operates when the perforation position is not correctly detected (NG) after viewing the displayed perforation pattern 112.

[0054] Returning to the explanation of FIG. 5, if the perforation pattern image is "OK," that is, if the "Yes" button is operated (YES in S7), the control unit 101 stores "perforation pattern information" (perforation position) as information related to the perforation formation area in the RAM 104 (S8). The "perforation pattern information" stored in the RAM 104 is held until the next time the paper information of the corresponding cassette 10 or manual feed tray 17 is updated. Thereafter, the control unit 101 starts an image formation job on the perforated sheet S in response to a command to start the image formation job (S9). At that time, the control unit 101 performs "perforation image control" in accordance with the "perforation pattern information" stored in the RAM 104 (S10).

[0055] In the "perforated image control (mode)" of this embodiment, a toner image is not formed in the perforated area (perforated processing area) where burrs have occurred in the perforated sheet S, but a toner image is formed in the area other than the perforated area. To achieve this, the control unit 101 performs a modification process in which an image signal relating to a toner image to be formed in the perforated area in the acquired image data is modified, for example, to a solid white image signal, in accordance with the "perforated pattern information." Specifically, the control unit 101 superimposes the perforation pattern and a digital image pattern (PDF data, etc.) obtained by binarizing the acquired image data, and modifies the original digital image pattern to a digital image pattern in which the perforated area becomes solid white.

[0056] The "perforated line image control" will be described with reference to Figs. 9(a) to 10(c). Figs. 9(a) to 9(d) are diagrams for explaining image defects occurring at perforation positions. Fig. 9(a) shows a perforated region 200, and Fig. 9(b) is a diagram for explaining toner transfer in the perforated region 200. Fig. 9(c) is a diagram showing a halftone image, and Fig. 9(d) is a diagram showing an image defect occurring on the perforated sheet S.

[0057] In this embodiment, the perforations are formed in a direction perpendicular to the conveying direction of the perforated sheet S. However, the perforation image control of this embodiment is performed regardless of the direction in which the perforations are formed, for example, when the perforations are formed in the conveying direction of the perforated sheet S.

[0058] 9(a), a protrusion 201 called a burr is formed in the perforation region 200. This is because, when forming perforations in the sheet S, a perforation forming member such as a blade is pressed against one side of the sheet S, causing the side opposite to the side against which the perforation forming member is pressed to rise.

[0059] As shown in FIG. 9B, when the perforated sheet S is conveyed to the secondary transfer nip T2, the perforated sheet S is not in contact with the intermediate transfer belt 80 due to the convex portion 201 on the upstream and downstream sides of the conveying direction in the perforated region 200. In these regions a1 and a2, when a voltage is applied to transfer the toner image from the intermediate transfer belt 80, an unintended discharge may occur due to the gap between the sheet surface and the intermediate transfer belt 80. If this happens, the toner may fly in the regions a1 and a2, and the toner may be transferred to a position shifted from the predetermined transfer position, resulting in a transfer failure called scattering. As an example, when a halftone image with an image ratio of 50% as shown in FIG. 9C is formed, the image formed in the perforated region 200 may be disturbed, and there is a risk of a blurred image failure as shown in FIG. 9D.

[0060] 10(a) is a diagram showing a perforation area. The perforation area 200 is an area along the perforation, for example, a range of 1 mm on one side in a direction perpendicular to the perforation based on the perforation position. The perforation area 200 may be set by the user from the operation unit 110 to an appropriate length in a direction perpendicular to the perforation based on the perforation position.

[0061] Fig. 10(b) is a diagram showing an image pattern after the image signal has been changed by perforated image control, and Fig. 10(c) is a diagram showing an image formed on perforated sheet S based on the image pattern after the image signal has been changed. As shown in Fig. 10(b), the image data after the image signal has been changed has a solid white image signal with no image signal forming a toner image in perforated area 200, and has an image signal forming a toner image in areas other than the perforated area. By forming an image on perforated sheet S based on this image data after the image signal has been changed, as shown in Fig. 10(c), a toner image is not formed in perforated area 200, and a toner image is formed in areas other than the perforated area.

[0062] As described above, in this embodiment, when a toner image is formed on the perforated sheet S, a toner image is not formed in the perforation area 200 including the perforations, but is formed in the area other than the perforation area. In this way, even if an unintended discharge occurs in a specific area where burrs have occurred when a toner image is transferred to the perforated sheet S, since no toner image is formed in the specific area where burrs have occurred and there is no toner to scatter in the first place, there is no risk of the toner scattering and being transferred to an unintended location. Therefore, when a toner image is formed on the perforated sheet S, it is possible to suppress image defects caused by burrs on the perforated sheet S.

[0063] Since the perforated region 200 is an area that is separated by a perforation, a toner image that would be difficult to convey to a user as information when separated is not formed in the perforated region 200. Therefore, even if the acquired image data includes image information related to a toner image to be formed in the perforated region 200 and such a toner image is not formed in the perforated region 200, the user will not feel inconvenienced.

[0064] As described above, a problem that may arise when forming an image on a perforated sheet S is the occurrence of image defects due to burrs, and in this embodiment, as a countermeasure against this problem, a toner image is not formed in the perforated area 200. However, since the perforation pattern varies depending on the user's application, it is difficult to accommodate all perforated sheets S with a uniform perforation pattern set in advance. Therefore, in this embodiment, by actually detecting the perforation pattern of the perforated sheet S using "perforation detection control", it is possible to prevent a toner image from being formed in the perforated area even for perforated sheets S with different perforation patterns. In this embodiment, if the perforation pattern image is "OK", "perforation image control" is performed to form a toner image in an area other than the perforated area without forming a toner image in the perforated area, but the user may be able to select in advance whether or not to form a toner image in the perforated area by operating the operation unit 110.

[0065] The perforated sheet S is often used for split printing (2in1, 4in1, etc.). For the perforated sheet S for split printing, the split position is often stored in advance in the paper library. When an image forming job for split printing is input, if the split position (split pattern) stored in the paper library does not match the detected perforation position (perforation pattern information), the toner image may not be formed even though it is not supposed to be formed in the perforation area. Therefore, when the split position stored in the paper library does not match the detected perforation position, it is preferable to display the "warning screen" shown in FIG. 11 on the display unit 111. For example, before the "Yes" button on the "perforation pattern display screen" shown in FIG. 8 is operated to start the image forming job (see S7 to S9 in FIG. 5), the control unit 101 may display the above-mentioned "warning screen" on the display unit 111.

[0066] As shown in Fig. 11, the "warning screen" displays an image of the detected perforation position (perforation pattern) and toner image, a warning of the mismatch between the division pattern and the perforation pattern, a message asking the user whether to start an image formation job, and a "Yes" button and a "No" button. If the "Yes" button is operated by the user, the image formation job is started even though the division pattern and the perforation pattern do not match, and the image data change process described above is performed, and an image is formed on the perforated sheet S. If the "No" button is operated by the user, for example, the process of obtaining the perforation position of the perforated sheet S may be performed again (S3 in Fig. 5).

[0067] In the above-described embodiment, when the perforation pattern is "NG" (S7 in FIG. 5 is NO), the control unit 101 unconditionally re-executes the "perforation detection control" (see S3 to S5) using the recording material reading unit 131, but this is not limited thereto. The user may be allowed to select whether or not to re-execute the "perforation detection control". FIG. 12 shows a "perforation acquisition screen" that allows the user to select whether or not to re-execute the "perforation detection control". The "perforation acquisition screen" may be displayed on the display unit 111, for example, when the perforation pattern is "NG", that is, when the "No" button on the "perforation pattern display screen" shown in FIG. 8 is operated.

[0068] As shown in Fig. 12, the "perforation acquisition screen" displays a message indicating that the perforation position could not be read, along with a "retry" button. By operating the "retry" button, the user can re-execute the "perforation detection control" using the recording material reading unit 131 (S3 to S5 in Fig. 5).

[0069] Here, if the perforation pattern is "NG", there is a possibility that the acquisition conditions of one-dimensional luminance image information in the recording material reading unit 131 (see FIG. 1) were not appropriate. Therefore, when re-executing the "perforation detection control", it is preferable to perform different control on the recording material reading unit 131 according to the in-plane average value of the above-mentioned two-dimensional binary image (FIG. 7(b)). For example, when the in-plane average value is low, that is, when there are many bright areas on the two-dimensional binary image, the reading contrast of the CIS 131b is low or the light amount of the LED array 131a is large, so when re-executing, it is preferable to increase the reading contrast or decrease the light amount of the LED array 131a. On the other hand, when the in-plane average value is high, that is, when there are many dark areas on the two-dimensional binary image, it is preferable to decrease the reading contrast or increase the light amount of the LED array 131a, so when re-executing, it is preferable to decrease the reading contrast or increase the light amount of the LED array 131a.

[0070] Returning to FIG. 12, the "perforation acquisition screen" displays a "manual setting" button in addition to the above. This is to allow the user to manually input the perforation position in cases where the perforation pattern is "NG" even after re-executing the "perforation detection control." When the user operates the "manual setting" button, the display on the display unit 111 transitions from the "perforation acquisition screen" to the "perforation setting screen" shown in FIG. 13(a) and FIG. 13(b).

[0071] As shown in FIG. 13(a), the "perforation setting screen" displays a plurality of selection buttons such as a "2in1" button and a "4in1" button that allow the user to select a basic perforation pattern according to the type of division printing (such as 2in1 or 4in1). The basic perforation patterns are stored in advance in the ROM 103 for each type of division printing. When the user operates any of the selection buttons, the control unit 101 acquires a perforation pattern (perforation position) according to the desired type of division printing from the ROM 103 and displays the acquired perforation pattern in the pattern section 122. The "perforation setting screen" then displays an adjustment dialog box 121 that allows the user to adjust the displayed perforation pattern together with the perforation pattern. The adjustment dialog box 121 has two sliders that move in the left and right directions. When the user operates these sliders, the coordinates of the division position, that is, the perforation position, is adjusted. When the user operates the "save perforation pattern" button, the adjusted perforation position is stored in the RAM 104.

[0072] As an example, Fig. 13(a) shows the perforation pattern when the "4in1" button is operated. In this case, the perforation pattern has "perforation 1" where the perforations are formed horizontally and "perforation 2" where the perforations are formed vertically, so the position of "perforation 1" is adjusted by the upper slider, and the position of "perforation 2" is adjusted by the lower slider. For example, moving the upper slider left and right moves "perforation 1" up and down, and moving the lower slider left and right moves "perforation 2" left and right.

[0073] As shown in FIG. 13(b), the "perforation setting screen" displays an "other" button in addition to the selection button. The "other" button is used when the user manually inputs an arbitrary perforation pattern other than the basic perforation patterns described above. The user can input an arbitrary perforation pattern by operating the "other" button and inputting coordinates using the numeric keypad or specifying two points on the pattern section 122. The input perforation pattern is displayed in the pattern section 122. In this case, the adjustment dialog box 121 has three sliders that allow the user to adjust the input perforation position in the "horizontal direction," "vertical direction," and "angle." The perforation position thus input is stored in the RAM 104 when the "save perforation pattern" button is operated by the user. The user may set the perforation area 200 by arbitrarily inputting the length in the direction perpendicular to the perforation based on the perforation position.

[0074] If the image forming apparatus 100 is not provided with the recording material reading unit 131, the perforation position cannot be obtained by the above-mentioned "perforation detection control" (S3 to S6 in FIG. 5). Therefore, if the recording material reading unit 131 is not provided, after the setting position of the perforated sheet S is determined (S2), the above-mentioned "perforation setting screen" is displayed on the display unit 111 to prompt the user to input the perforation position.

[0075] [Second embodiment] Next, a second embodiment will be described with reference to Figures 14(a) to 16. In the first embodiment described above, a toner image is not formed in the entire area of ​​the perforation region 200, but in the second embodiment, a toner image is formed in the tie portion of the perforation region 200, and a toner image is not formed in the area including the cut portion excluding the tie portion. In the second embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description will be simplified or omitted.

[0076] Fig. 14(a) is a diagram showing a cut portion and a tie portion of the perforated sheet S. Fig. 14(b) is a diagram for explaining toner transfer at the cut portion. Fig. 14(c) is a diagram for explaining toner transfer at the tie portion. Fig. 14(d) is a diagram showing an image defect occurring on the perforated sheet S.

[0077] As shown in FIG. 14(a), the perforated sheet S has a cut portion CU where a hole is formed by perforation processing, and a tie portion TI where no hole is formed between the cut portions CU along the direction of perforation. When the perforated sheet S is conveyed to the secondary transfer nip portion T2, as shown in FIG. 14(b), a convex portion 201 called a burr is formed in the cut portion CU, and therefore regions a1 and a2 that do not contact the intermediate transfer belt 80 due to the convex portion 201 are formed on the upstream and downstream sides of the conveyance direction of the perforated sheet S. In these regions a1 and a2, when a voltage is applied to transfer a toner image from the intermediate transfer belt 80, an unintended discharge may occur due to the gap between the sheet surface and the intermediate transfer belt 80. This causes the toner to fly in the regions a1 and a2, and the toner is transferred to a position shifted from the specified transfer position, resulting in a transfer failure called scattering.

[0078] 14(c), the above-mentioned convex portion 201 is not formed in the tie portion TI, so no gap occurs between the sheet surface and the intermediate transfer belt 80 in the tie portion TI, and no transfer failure such as scattering occurs. Therefore, as an example, when a halftone image with an image ratio of 50% is formed, as shown in FIG. 14(d), a blurred image failure occurs in the region 210 near the cut portion CU in the perforation region 200, but no such image failure occurs in the other region 220 including the tie portion TI.

[0079] Fig. 15 is a flowchart showing image processing of the second embodiment. Note that the same steps in the image processing shown in Fig. 15 as those in the image processing of the first embodiment described above (see Fig. 5) are given the same step numbers, and the explanation will be simplified or omitted. As shown in Fig. 15, in the second embodiment as well, the control unit 101 performs the above-mentioned "perforation detection control" (S3 to S6) to obtain the perforation positions of the perforated sheet S.

[0080] If the perforation pattern image is "OK" (YES in S7), the control unit 101 detects the positions of the cut portion CU and the tie portion TI in the "perforation pattern information" (S21). As described above, the control unit 101 obtains "perforation pattern information" by further converting the x and y coordinates of the perforation pattern image (FIG. 7(g)) into the resolution of the output image of the image forming apparatus 100 (for example, 1200 dpi). Then, the control unit 101 detects the positions of the cut portion CU and the tie portion TI along the lines of the perforation pattern image (FIG. 7(g)) by applying the two-dimensional binary image acquired in FIG. 7(b) at each position. That is, on the perforation pattern image (FIG. 7(g)), the areas where the two-dimensional binary image is a dark area (1) are determined to be cut portions CU, and the areas where the two-dimensional binary image is a light area (0) are determined to be tie portions TI. The control unit 101 stores the positions of the cut portion CU and the tie portion TI together with the "perforation pattern information" in the RAM 104 (S8).

[0081] Thereafter, the control unit 101 starts an image formation job on the perforated sheet S in response to a command to start the image formation job (S9). At that time, the control unit 101 performs "perforation image control" in accordance with the "perforation pattern information" stored in the RAM 104, the positions of the cut portions CU, and the positions of the tie portions TI (S10). In the "perforation image control" of this embodiment, a toner image is not formed in the area including the cut portions CU, and a toner image is formed in the area other than the area including the cut portions CU.

[0082] FIG. 16(a) shows an area 230 including the cut portion CU. The perforation area 200 is an area, for example, 1 mm on one side, along the perforation in a direction perpendicular to the perforation based on the perforation position. FIG. 16(b) shows an image pattern after the image signal is changed by the perforation image control, and FIG. 16(c) shows an image formed on the perforated sheet S based on the image pattern after the image signal is changed. As shown in FIG. 16(b), the image data after the image signal change has a solid white image signal without an image signal for forming a toner image for the area 230 (first area) including the cut portion CU in the perforation area 200, and has an image signal for forming a toner image for the area 240 (second area) other than the area including the cut portion CU. By forming an image on the perforated sheet S based on this image data after the image signal change, as shown in FIG. 16(c), a toner image is not formed in the area 230 including the cut portion CU, and a toner image is formed in the area 240 other than the area including the cut portion CU.

[0083] As described above, in the second embodiment, when a toner image is formed on the perforated sheet S, a toner image is not formed in the region 230 including the cut portion CU in the perforated region 200, and a toner image is formed in the region 240 other than the region including the cut portion CU. In this way, by simply not forming a portion of the toner image formed in the perforated region 200, image defects caused by burrs on the perforated sheet S can be suppressed, thereby reducing the impact of not forming a toner image.

[0084] [Third embodiment] As described above, in the first embodiment, a toner image is not formed in the entire perforated region 200, and in the second embodiment, a toner image is not formed in the region 230 including the cut portion CU in the perforated region 200, but this is not limited thereto. For example, when the density of the toner image is high, image defects are not noticeable even if unintended discharge occurs due to burrs.

[0085] Therefore, in the third embodiment, the image ratio of the toner image is used, and when the image ratio is equal to or less than a threshold value and the density of the toner image is deemed low, the toner image is not formed in the above-mentioned area, and when the image ratio is greater than the threshold value and the density of the toner image is deemed high, the toner image is formed in the above-mentioned area. The third embodiment will be described below with reference to Figures 17(a) to 18.

[0086] 17(a), 17(b), and 17(c) show output images when toner images with image ratios of 30%, 50%, and 80%, respectively, are formed over the entire area of ​​the perforated sheet S. In the case of the output images with image ratios of 30% and 50%, the user could confirm the blurred image (also called a scattered image) caused by the above-mentioned scattering, which causes the image formed in the perforated area 200 to be distorted. On the other hand, in the case of the output image with an image ratio of 80%, the user could not confirm the blurred image. This is because, when the image ratio is high, as shown in the above-mentioned FIG. 9(b), even if unintended discharge occurs in the areas a1 and a2 that do not contact the intermediate transfer belt 80 and toner is transferred to a position shifted from the specified transfer position, there is a high possibility that toner is already present at the shifted transfer position, and the image is unlikely to become blurred.

[0087] Fig. 18 is a flowchart showing image processing of the third embodiment. Note that the same steps in the image processing shown in Fig. 18 as those in the image processing of the first embodiment described above (see Fig. 5) are given the same step numbers, and the explanation will be simplified or omitted. As shown in Fig. 18, in the third embodiment as well, the control unit 101 performs the above-mentioned "perforation detection control" (S3 to S6) to obtain the perforation positions of the perforated sheet S.

[0088] If the perforation pattern image is "OK" (YES in S7), the control unit 101 calculates the average image ratio of the toner image formed in the perforation area 200 in the "perforation pattern information" (S31). As described above, the control unit 101 obtains "perforation pattern information" by further converting the x and y coordinates of the perforation pattern image (FIG. 7(g)) into the resolution of the output image of the image forming apparatus 100 (for example, 1200 dpi). The control unit 101 applies the two-dimensional binarized image acquired in FIG. 7(b) at each position along the line of the perforation pattern image (FIG. 7(g)), superimposes the perforation pattern and a digital image pattern (PDF data, etc.) obtained by binarizing the acquired image data, and calculates the average image ratio from the brightness information of the digital image pattern of the perforation area 200. The control unit 101 stores the "average image ratio" together with the "perforation pattern information" in the RAM 104 (S8).

[0089] Thereafter, the control unit 101 starts an image formation job on the perforated sheet S in response to a command to start the image formation job (S9). At that time, the control unit 101 determines whether the "average image ratio" stored in the RAM 104 is equal to or less than a threshold value (S32). If the "average image ratio" is equal to or less than the threshold value (YES in S32), the control unit 101 performs "perforation image control" to form an image (S10). If the "average image ratio" is greater than the threshold value (NO in S32), the control unit 101 performs image formation without performing "perforation image control".

[0090] For example, as shown in Table 1, if the average image ratio is greater than the threshold value "80%", "perforation image control" is not performed, and if the average image ratio is equal to or less than the threshold value "80%", "perforation image control" is performed. When "perforation image control" is performed, as described above, a toner image is not formed in the perforation area 200, and a toner image is formed in areas other than the perforation area. Alternatively, with respect to the perforation area 200, a toner image is not formed in the area 230 including the cut portion CU, and a toner image is formed in the area 240 other than the area including the cut portion CU. [Table 1]

[0091] As described above, in the third embodiment, when the density of the toner image is deemed to be low, "perforated image control" is implemented to prevent a toner image from being formed in the perforated area 200 or the area 230 including the cut portion CU. In this way, by simply not forming a toner image only when the density of the toner image is low, it is possible to suppress image defects caused by burrs on the perforated sheet S, thereby reducing the impact of not forming a toner image.

[0092] [Fourth embodiment] Next, a fourth embodiment will be described with reference to Figs. 19 to 22. Fig. 19 is an enlarged view of the vicinity of the secondary transfer nip T2. When the sheet S reaches the secondary transfer nip T2, if a secondary transfer voltage (Vt1) is applied to the outer secondary transfer roller 11 by the power source 90, the toner image on the intermediate transfer belt 80 is transferred to the sheet S. The secondary transfer voltage is, for example, "1000V".

[0093] Fig. 20(a) is a diagram showing toner scattering when the secondary transfer voltage is "1000 V," and Fig. 20(b) is a diagram showing toner scattering when the secondary transfer voltage is "700 V." As shown in Fig. 20(a) and Fig. 20(b), whether the secondary transfer voltage is "1000 V" or "700 V," toner may fly in areas a1 and a2 that do not contact the intermediate transfer belt 80, causing scattered images.

[0094] However, when the secondary transfer voltage is "700V", the amount of toner that flies is smaller than when it is "1000V". This is because when the secondary transfer voltage is low, the electric field formed in areas a1 and a2 in the secondary transfer nip T2 is smaller than when the secondary transfer voltage is high, and discharge is less likely to occur in areas where the gap between the intermediate transfer belt 80 and the perforated sheet S is large. Conversely, when the secondary transfer voltage is high, the electric field formed in areas a1 and a2 is larger, and discharge occurs in areas where the gap between the intermediate transfer belt 80 and the perforated sheet S is large, causing more toner to fly, and therefore scattering images are more likely to occur.

[0095] In consideration of this point, in the fourth embodiment, when forming an image on a perforated sheet S, the secondary transfer voltage applied to the outer secondary transfer roller 11 is made smaller in absolute value than when forming an image on a sheet S other than a perforated sheet, making it less likely for scattered images to occur.

[0096] Fig. 21 is a flowchart showing image processing of the fourth embodiment. Note that the same steps in the image processing shown in Fig. 21 as those in the image processing of the first embodiment described above (see Fig. 5) are given the same step numbers, and the explanation will be simplified or omitted. As shown in Fig. 21, in the fourth embodiment as well, the control unit 101 performs the above-mentioned "perforation detection control" (S3 to S6) to obtain the perforation positions of the perforated sheet S.

[0097] If the perforation pattern image is "OK" (YES in S7), the control unit 101 stores the "perforation pattern information" in the RAM 104 (S8). After that, the control unit 101 starts an image formation job on the perforated sheet S in response to a command to start the image formation job (S9). At that time, the control unit 101 performs "secondary transfer voltage control" when the perforated sheet S passes through the secondary transfer nip portion T2 (S41).

[0098] The "secondary transfer voltage control" will be described. FIG. 22(a) is a diagram showing a second transfer voltage applied to a perforated sheet S in which the perforations are formed in a direction perpendicular to the conveying direction. FIG. 22(b) is a diagram showing a second transfer voltage applied to a perforated sheet S in which the perforations are formed in the conveying direction. FIG. 23 is a diagram showing a second transfer voltage applied to a perforated sheet S in which the perforations are formed in a direction perpendicular to the conveying direction and in the conveying direction. In FIGS. 22(a) to 23, the perforated area 200 of the perforated sheet S is shown in the upper row, and the secondary transfer voltage Vt1 is shown in the lower row. Also, the arrow X in the diagram indicates the conveying direction of the perforated sheet S.

[0099] 22(a), in the case of a perforated sheet S in which the direction in which the perforations are formed is perpendicular to the conveying direction, a secondary transfer voltage Vt1 of "1000 V" is normally applied to the areas other than the perforated area 200 (other than the area in which the perforations are formed). If a toner image is formed in the perforated area 200, a voltage of "700 V", which is smaller in absolute value than normal, is applied to the perforated area 200. If no toner image is formed in the perforated area 200, a voltage of "1000 V", the same as that applied to the areas other than the perforated area 200, is applied to the perforated area 200.

[0100] 22(b), in the case of a perforated sheet S in which the direction of perforations is the transport direction, the perforations are formed from the leading edge to the trailing edge in the transport direction. Therefore, regardless of whether or not there is a toner image formed in the perforated region 200, a secondary transfer voltage Vt1 of "700 V" is applied from the leading edge to the trailing edge of the perforated sheet S. Here, the secondary transfer voltage "700 V" is a voltage value at which no transfer failure occurs even if the secondary transfer voltage Vt1 is lower than normal in areas other than the perforated region 200.

[0101] 23, for the perforated sheet S in which the perforations are formed in a direction perpendicular to the conveying direction and in the conveying direction, a secondary transfer voltage Vt1 of "500V" is applied to the perforated region 200. In addition, in the conveying direction in which the perforated region 200A is formed, a secondary transfer voltage Vt1 of "700V" (corresponding to a third voltage) that is smaller in absolute value than the normal "1000V" (corresponding to a first voltage) and larger in absolute value than the "500V" (corresponding to a second voltage) applied to the perforated region 200 is applied to the perforated sheet S from the leading end to the trailing end excluding the perforated region 200.

[0102] In order to suppress image defects due to scattering, it is preferable to lower the secondary transfer voltage Vt1. Therefore, in the case of the perforated sheet S shown in FIG. 23, in which the direction of perforation is perpendicular to the conveying direction and the conveying direction, it is possible to apply "500V" as the secondary transfer voltage Vt1 from the leading edge to the trailing edge of the perforated sheet S, including the perforated area 200. However, if "500V" is applied from the leading edge to the trailing edge of the perforated sheet S, there is a risk of transfer defects occurring in areas other than the perforated areas 200 and 200A due to the low secondary transfer voltage Vt1. For this reason, the secondary transfer voltage Vt1 is set not to be lower than "700V" at which no transfer defects occur in areas other than the perforated area 200 in the conveying direction.

[0103] 23, in the fourth embodiment, the secondary transfer voltage Vt1 "500 V" is applied only to the perforated region 200, and the secondary transfer voltage Vt1 "700 V" is applied to the region other than the perforated region 200 in the transport direction. By lowering the secondary transfer voltage applied to the perforated region 200 in this manner, unintended discharge is less likely to occur in the area where burrs are formed, and image defects due to scattering in the perforated region 200 can be suppressed without causing transfer defects in regions other than the perforated region 200.

[0104] <Other embodiments> In the above-described first to fourth embodiments, the perforation positions of the perforated sheet S are obtained using the recording material reading unit 131 disposed in the image forming apparatus 100, but the present invention is not limited to this. Some image forming apparatuses do not include the recording material reading unit 131. Even in such cases, as shown in FIG. 24, a separate document reading device 800 is often attached to the image forming apparatus 100A. Therefore, instead of the recording material reading unit 131, the document reading device 800 may be used to obtain the perforation positions of the perforated sheet S.

[0105] The document reading device 800 as a document reading section is disposed on the upper part of the image forming apparatus 100A, and has an image reading section 801 that reads an image on a sheet S, and an ADF (Auto Document Feeder) 802 that automatically transports the sheet S to the image reading section 801. The image reading section 801 can irradiate light onto the sheet S on a document table 803 using an LED array 801a, receive reflected light from the sheet S of the irradiated light, and obtain an optical image or height image of the sheet S using a CIS 801b. The method of obtaining the perforation position using the document reading device 800 is the same as that of the recording material reading section 131 described above, and therefore will not be described here.

[0106] When the perforation positions of the perforated sheet S are obtained using the document reading device 800, it is preferable to display a screen on the display unit 111 that prompts the user to place the perforated sheet S on the document reading device 800 at the time of "perforation detection control start" (see S3 in Fig. 5). Fig. 25(a) is a "selection screen" that prompts the user to select a method for reading the perforated sheet S using the document reading device 800, and Fig. 25(b) is an "installation screen" that instructs the user on the installation position to set the perforated sheet S.

[0107] As shown in FIG. 25(a), the "selection screen" displays a "paper stand" button and an "ADF" button. The "paper stand" button is for acquiring the perforation position of the perforated sheet S placed on the paper stand 803, and the "ADF" button is for acquiring the perforation position by automatically conveying the perforated sheet S set in the ADF 802 to the paper stand 803. When either the "paper stand" button or the "ADF" button is operated by the user, the screen of the display unit 111 transitions from the "selection screen" to the "installation screen" shown in FIG. 25(b). In FIG. 25(b), as an example, the ADF 802 is displayed as the installation position of the perforated sheet S when the "ADF" button on the "selection screen" is operated. Although not shown, when the "paper stand" button on the "selection screen" is operated, the paper stand 803 is displayed as the installation position of the perforated sheet S. The user installs the perforated sheet S on the ADF 802 or the paper stand 803 according to the displayed installation position.

[0108] In addition, if perforated sheet S has already been placed on ADF 802 or document tray 803, a screen may be displayed on display unit 111 informing the user that perforated sheet S has been placed on ADF 802 or document tray 803, based on the detection results of a sheet detection sensor (not shown), so that the user can confirm this.

[0109] As shown in FIG. 24, the perforation positions of the perforated sheet S may be obtained from an external device 1000 such as a personal computer connected to the image forming apparatus 100A. In this case, a two-dimensional luminance image of the perforated sheet S read by an external scanner is sent from the external device 1000 to the image forming apparatus 100A. Alternatively, the display unit of the external device 1000 may display the above-mentioned "perforation setting screen" (see FIGS. 13(a) and 13(b)), and the perforation positions input by the user on the "perforation setting screen" may be sent from the external device 1000 to the image forming apparatus 100A. The control unit 101 causes the external device 1000 as an information processing device to execute a receiving step of receiving information on the formation area of ​​the perforations formed on the perforated sheet, and a display step of displaying the perforations according to the information on the formation area of ​​the perforations.

[0110] In the above-described first and second embodiments, the image forming apparatus is configured to perform primary transfer of the toner images of each color from the photosensitive drums 3a to 3d of each color onto the intermediate transfer belt 80, and then secondary transfer of the composite toner images of each color collectively onto the sheet S, but the present invention is not limited thereto. For example, as shown in FIG. 26, the image forming apparatus may be of a direct transfer type in which the toner images on the photosensitive drums are directly transferred onto the sheet S by applying a voltage to transfer rollers 6a to 6d arranged opposite the photosensitive drums 3a to 3d and the conveying belt 900, for the sheet S conveyed by the conveying belt 900 in which a nip portion is formed between the photosensitive drums 3a to 3d. [Explanation of symbols]

[0111] 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 (100A)...Image forming device, 101...Control section, 105...Acquisition section (interface section), 110...Input section (reception section, operation section), 111...Display section, 114...Conveying section, 131...Acquisition section (recording material reading section), 132...Conveying path, 800...Document reading section (document reading device), 1000...Information processing device (external device), Pa, Pb, Pc, Pd...Image forming section, S...Sheet (perforated sheet)

Claims

1. An image forming apparatus capable of forming an image on a perforated sheet, An acquisition unit that acquires information regarding a perforation formation area formed on a perforated sheet; an image forming unit that forms an image on the perforated sheet in accordance with image data; and a control unit that controls the image forming unit so as not to form an image in the perforation formation area when the image is to be formed by the image forming unit in accordance with the image data in the perforation formation area.

1. An image forming apparatus comprising:

2. the image forming unit includes an image carrier that carries a toner image, and a transfer unit that transfers the toner image carried on the image carrier onto a sheet; A setting section in which a perforated sheet can be set; a conveying unit that conveys the perforated sheet set in the setting unit toward the transfer unit, The acquisition unit is disposed upstream of the transfer unit and downstream of the setting unit in a conveying path along which the perforated sheet is conveyed in a sheet conveying direction, and reads perforations formed on the perforated sheet.

2. The image forming apparatus according to claim 1,

3. An input unit capable of inputting information regarding a perforation formation area formed on a perforated sheet, The acquisition unit acquires information regarding a perforation formation area input by the input unit.

2. The image forming apparatus according to claim 1,

4. The acquisition unit acquires information regarding a perforation formation area formed on a perforated sheet from an external device connected to the image forming apparatus.

2. The image forming apparatus according to claim 1,

5. A display unit displays the position of the perforation formed on the perforated sheet in accordance with the information regarding the perforation formation area acquired by the acquisition unit.

2. The image forming apparatus according to claim 1,

6. The control unit controls the image forming unit so that, when an average image ratio of an image to be formed in the perforation formation area is equal to or less than a threshold value, an image is not formed in the perforation formation area, and, when the average image ratio is greater than the threshold value, an image is formed in the perforation formation area.

2. The image forming apparatus according to claim 1,

7. The perforation formation region includes a cut portion in which a hole is formed by perforation processing and a tie portion in which a hole is not formed, When there is an image to be formed by the image forming unit in accordance with the image data in the perforation formation area, the control unit controls the image forming unit so that an image is not formed in the cut portion of the perforation formation area, and an image is formed in the tie portion.

2. The image forming apparatus according to claim 1,

8. An image forming apparatus capable of forming an image on a perforated sheet, an image carrier that carries a toner image; an image forming unit that forms a toner image to be carried on the image carrier; a transfer section for transferring the toner image carried on the image carrier onto a sheet; a conveying section that conveys a sheet to the transfer section; An acquisition unit that acquires information regarding a perforation formation area formed on a perforated sheet; and a control unit that, when the sheet on which the toner image is formed is a sheet on which perforations are formed in a direction intersecting the sheet conveying direction and there is a toner image formed in an area where the perforations are formed, applies a first voltage to the transfer unit to an area other than the area where the perforations are formed, and controls to apply a second voltage, the absolute value of which is smaller than the first voltage, to the transfer unit to the area where the perforations are formed.

1. An image forming apparatus comprising:

9. When a perforation is also formed in the transport direction, the control unit applies a third voltage to the transfer unit, the third voltage being smaller in absolute value than the first voltage and larger in absolute value than the second voltage, to an area excluding an area where the perforation is formed in the transport direction.

9. The image forming apparatus according to claim 8,

10. An image forming apparatus capable of forming an image on a perforated sheet, a receiving unit that receives information regarding a perforation formation area formed on the perforated sheet; A display unit that displays the perforation according to information about the perforation formation area.

1. An image forming apparatus comprising:

11. In the information processing device, A receiving step of receiving information regarding a perforation formation area formed on the perforated sheet; A display step of displaying a perforation in accordance with information regarding a formation area of ​​the perforation. A program characterized by:

Images