Image forming apparatus

Abstract

To provide an image forming apparatus that can reduce the frequency of replacing a waste toner container.SOLUTION: A color copying machine as an image forming apparatus has an operation panel as setting means that allows a user to set a discharge image to be formed on paper as a sheet. When determining that a refresh operation is required, the image forming apparatus detects whether the sheet has a margin part where an image for toner discharge set by the user can be formed. When the sheet has the margin part, the image forming apparatus forms the image for toner discharge H set by the user in the margin part.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] Conventionally, there is known an image forming apparatus provided with refresh execution means for executing a refresh operation of forming a toner ejection image on a sheet and forcibly consuming the toner in the developing device at a predetermined timing.

[0003] In Patent Document 1, as the above-described image forming apparatus, a toner ejection image made of invisible toner is transferred from an image carrier to a sheet and formed on the sheet, and a toner ejection image made of visible toner is not transferred to the sheet but removed from the image carrier by a cleaning device. The visible toner that constituted the toner ejection image removed by this cleaning device is stored in a waste toner container as waste toner.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there has been a possibility that the replacement frequency of the waste toner container for storing waste toner increases.

Means for Solving the Problems

[0005] In order to solve the above-described problems, the present invention provides an image forming apparatus provided with refresh execution means for forming a toner ejection image on a sheet and forcibly consuming the toner in the developing device at a predetermined timing, wherein the toner ejection image has setting means set by a user.

Effects of the Invention

[0006] According to the present invention, the replacement frequency of the waste toner container can be reduced.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

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Figure 8

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Figure 10

Figure 11

Best Mode for Carrying Out the Invention

[0008] Hereinafter, the best mode for carrying out the present invention will be described based on the drawings. It should be noted that those skilled in the art can easily modify and change the present invention within the scope of the claims to form other embodiments, and these modifications and changes are included in the scope of the claims. The following description is an example of the best mode in the present invention and does not limit the scope of the claims.

[0009] FIG. 1 is a schematic front view showing a perspective view of the overall configuration of a color copier as an example of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an in-body paper discharge type color copier using an electrophotographic method, which is exemplified as an image forming apparatus according to an embodiment of the present invention. In the figure, the Z direction is the vertical direction, the Y direction in the figure is the front-rear direction (also the axial direction) of the apparatus, and the X direction in the figure indicates the left-right direction of the apparatus.

[0010] This color copier 1 includes a schematic box-shaped apparatus main body 10 that is the housing of the entire image forming apparatus, and an image reading unit 2 that is disposed above the apparatus main body 10 and reads an image of an original. Further, the color copier 1 has an image forming unit 3 that is disposed inside the apparatus main body and records and forms an image on a sheet of paper, which is an example of a sheet, based on image information read by the image reading unit 2 or transmitted from an external device such as a personal computer.

[0011] Further, it has a paper discharge space 12 as a discharge space for discharging a sheet of paper on which an image is recorded between the image reading unit 2 and the image forming unit 3. Also, at the lowermost part of the apparatus main body 10, a paper feeding unit 4 for feeding a sheet (which means a sheet-like recording medium including copy paper, a resin sheet for OHP, thick paper, postcards, etc., and will be hereinafter described generically as "paper") to a paper conveyance path as a sheet conveyance path is disposed. Further, above the image forming unit 3, a paper discharge unit for discharging a sheet of paper on which an image is recorded to the paper discharge space 12 is provided, and a paper conveyance path 6 is provided between the paper feeding unit 4 and the paper discharge unit 5.

[0012] The image reading unit 2 has a contact glass 20 as an original table on which an original is placed. Further, a light source 21 that is disposed directly below the contact glass 20 and applies light to the original while moving, an imaging lens 22 that forms an image of the reflected light from the original, and an image sensor 23 such as a CCD as a reading means that is disposed at the imaging position and reads the original image are provided. Furthermore, the image reading unit 2 also has a plurality of mirrors and the like that guide the reflected light from the original to the imaging lens 22 while reflecting it.

[0013] Further, above the image reading unit 2, a pressure plate 24 for pressing the document placed on the contact glass 20 is provided. Instead of this pressure plate 24, an automatic document feeder (ADF) for automatically feeding the document to the contact glass 20 may be installed.

[0014] The image forming unit 3 includes four process cartridges 11Y, 11C, 11M, and 11K corresponding to four colors of toner, namely yellow, cyan, magenta, which are the three primary colors of color materials, and black. Further, the image forming unit 3 is provided below these four process cartridges 11Y, 11C, 11M, and 11K, and includes a writing unit 34 for writing a latent image on each photosensitive drum described later. The image forming unit 3 also includes four toner bottles 31Y, 31C, 31M, and 31K for storing fresh toner of the color corresponding to each process cartridge 11Y, 11C, 11M, and 11K. After the toner image formed by each process cartridge 11Y, 11C, 11M, and 11K is once transferred, a transfer unit 32 for transferring it to the paper, a fixing unit 33 for fixing the toner image to the paper, and the like are also provided.

[0015] The process cartridges 11Y, 11C, 11M, and 11K are configured to be detachable from the apparatus main body 10. The process cartridges 11Y, 11C, 11M, and 11K are arranged in the order of yellow, cyan, magenta, and black from the upstream side along the moving direction (arrow Xa in the figure) of the outer peripheral surface of the intermediate transfer belt 32a described later. Each process cartridge 11Y, 11C, 11M, and 11K has a photosensitive drum 7Y, 7C, 7M, and 7K which is a latent image carrier that rotates in a clockwise direction when viewed from the front. Further, centering around the photosensitive drum, it has a charging device, developing devices 30Y, 30C, 30M, and 30K, a cleaning device, and the like.

[0016] The charging device uniformly charges the outer peripheral surfaces of the photosensitive drums 7Y, 7C, 7M, and 7K by performing a charging process. The developing devices 30Y, 30C, 30M, and 30K visualize the electrostatic latent images formed by the writing unit 34 described below on the respective photosensitive drums 7Y, 7C, 7M, and 7K into monochromatic toner images with toner of corresponding colors. The cleaning device cleans and collects the transfer residual toner remaining on the outer peripheral surfaces of the photosensitive drums 7Y, 7C, 7M, and 7K after transfer.

[0017] The writing unit 34 includes a polygon mirror, an fθ lens, etc. The writing unit 34 scans while irradiating laser light from a laser light emitting device based on image information input from the image reading unit 2, a personal computer, an external scanner, etc. Then, the outer peripheral surfaces of the uniformly charged photosensitive drums 7Y, 7C, 7M, and 7K are selectively exposed, the surface potential of the irradiated portions is lowered, and an electrostatic latent image is formed on the photosensitive drums.

[0018] The toner bottles 31Y, 31C, 31M, and 31K are individually filled with the new toner of the four colors respectively. The toner of each color in the toner bottles 31Y, 31C, 31M, and 31K is supplied to the developing devices 30Y, 30C, 30M, and 30K of the respective process cartridges 11Y, 11C, 11M, and 11K through a conveyance path.

[0019] The transfer unit 32 has an endless belt intermediate transfer belt 32a made of a multi-layer structure of an elastic resin as an intermediate transfer body. This intermediate transfer belt 32a is supported and stretched (meaning spanned in a state of being tensioned, the same hereinafter) by a plurality of rollers. Specifically, it is supported and stretched by four support rollers 32b, 32c, 32d, 32e, four primary transfer rollers 32f, and a secondary transfer roller 32g.

[0020] The support roller 32b serves as a driving roller connected to the driving means, and has a function of rotationally driving the intermediate transfer belt 32a in the direction of arrow Xa in the figure. A secondary transfer roller 32g is disposed (which means arranging or positioning and providing, the same hereinafter) at a position facing the support roller 32b (hereinafter referred to as "driving roller 32b") with the intermediate transfer belt 32a interposed therebetween. In the vicinity of the support roller 32c, a cleaning device 32h is provided for scraping and cleaning the residual toner adhering to the outer peripheral surface of the intermediate transfer belt 32a.

[0021] Each primary transfer roller 32f is arranged at a position slightly shifted downstream in the conveyance direction of the intermediate transfer belt 32a from the facing position where the center-to-center distance is the shortest distance and they are in contact with each other with the photosensitive drums 7Y, 7C, 7M, 7K and the intermediate transfer belt 32a interposed therebetween, taking into account image degradation due to void discharge. Each primary transfer roller 32f functions as a transfer bias (transfer voltage) application means of the contact application method. Specifically, each primary transfer roller 32f is connected to a bias power supply and is configured to be able to apply a primary transfer bias from the back surface (inner peripheral surface) of the intermediate transfer belt 32a (which means applying a voltage, the same hereinafter).

[0022] The secondary transfer roller 32g is biased by a biasing means and is pressed against the intermediate transfer belt 32a on the outer periphery of the driving roller 32b, and is configured to form a secondary transfer nip between the driving roller 32b. And the driving roller 32b serves as a contact-type transfer bias application means connected to a bias power supply. Also, the secondary transfer roller 32g may serve as a transfer bias application means, and in that case, a transfer bias of the opposite polarity to the toner image to be transferred is applied.

[0023] The fixing unit 33 includes a fixing roller 33a, a fixing belt 33c which is an endless belt stretched between the fixing roller 33a and the heating roller 33b, and a pressure roller 33d as a pressing member. The pressure roller 33d is in pressure contact with (which means pressing contact, the same hereinafter) the fixing belt 33c and forms a fixing nip between the fixing belt 33c. Heat and pressure are applied to the paper conveyed through the paper conveyance path 6 described later in this fixing nip, and the toner image transferred at the secondary transfer nip of the transfer unit 32 described above melts and adheres to the paper and is fixed.

[0024] The paper feeding unit 4 includes paper feeding cassettes 40, 41 which accommodate and stock predetermined papers of different sizes as sheets and can be pulled out from the apparatus main body 10, and paper feeding rollers 42, 43 which are in pressure contact with the stocked papers from above with a predetermined pressure. The paper feeding unit 4 is configured to send out the papers respectively accommodated in the paper feeding cassettes 40, 41 to the paper conveyance path 6 described later by the paper feeding rollers 42, 43 based on a control signal from the control means.

[0025] In addition, the paper feeding unit 4 is provided with a manual feed tray 44 on which an arbitrary paper within a range of a predetermined size and dimension that can be conveyed is placed, and a paper feeding roller 45 for sending out this paper. The paper feeding unit 4 can send out the paper placed on the manual feed tray 44 to the paper conveyance path 6 described later by rotationally driving the paper feeding roller 45.

[0026] The paper discharging unit 5 has a paper discharge tray 5a formed by an inclined surface on the apparatus main body 10 below the paper discharge space 12 between the aforementioned toner bottles 31Y, 31C, 31M, 31K and the image reading unit 2. The paper discharging unit 5 also includes a pair of paper discharge rollers 5b and the like for discharging (ejecting) the paper that has passed through the fixing unit 33 to the paper discharge tray 5a from the paper conveyance path 6 described later. Thus, the color copying machine 1 of this embodiment is a paper discharging unit of an in-body paper discharging type having a function of stacking the papers discharged by the pair of paper discharge rollers 5b on the paper discharge tray 5a.

[0027] The paper conveyance path 6 has a normal conveyance path 6a of a vertical conveyance system (vertical path system) that conveys from the paper feeding unit 4 provided at the lower part of the apparatus main body 10 upward to the paper discharging unit 5 provided at the upper part of the apparatus main body 10. Also, it has a reverse conveyance path 6b for reversing the paper for double-sided printing. These conveyance paths can be switched by a switching claw 6c, and the paper is guided to the reverse conveyance path 6b by this switching claw 6c. The paper guided to the reverse conveyance path 6b is conveyed above 6e of the reverse conveyance path 6b by a pair of reverse conveyance rollers 6d, and then is reversed in a switch-back manner by the reversal of the pair of reverse conveyance rollers 6d. Thereafter, it is conveyed to the normal conveyance path 6a in front of a pair of registration rollers 6f described later.

[0028] A plurality of pairs of conveyance rollers are provided in the normal conveyance path 6a and the reverse conveyance path 6b at intervals corresponding to the minimum paper size, and the paper is conveyed by rotating while sandwiching the paper with these pairs of conveyance rollers. Also, a pair of registration rollers 6f is provided below the secondary transfer nip in the normal conveyance path 6a, and the timing for conveying the paper to the secondary transfer nip based on a command from the control means is adjusted by this pair of registration rollers 6f.

[0029] Also, on the left side in the drawing of the paper feeding cassette 40, a waste toner container 18 for accommodating the waste toner removed by the cleaning devices of the respective process cartridges 11Y, 11C, 11M, 11K and the waste toner removed by the cleaning device 32h of the transfer unit 32 is disposed.

[0030] When the consumption of toner in the developing device is small, there are many old toners that remain in the developing device and deteriorate. When there are many old toners, image mottling and wormholes are likely to occur, and the image quality deteriorates. Therefore, in order to suppress such a decrease in image quality, the color copier 1 performs a refresh operation (also referred to as a forced consumption operation) of forcibly consuming the toner in the developing device 30 at a predetermined timing, discharging the old toner, replacing it with new toner, and keeping the toner in the developing device in a fresh state.

[0031] Conventionally, when a refresh operation is executed, a predetermined latent image pattern is formed on the surface of the photoreceptor drum 7. By attaching and developing the toner in the developing device 30 to this latent image pattern, the old toner in the developing device 30 is discharged and the toner in the developing device 30 is refreshed.

[0032] The developed discharge pattern image is not transferred to the paper, but is removed by the cleaning device of the process cartridge 11 and becomes waste toner, which is stored in the waste toner container 18. As a result, there was a problem that when images with a low image area ratio continued and the refresh operation occurred frequently, the waste toner container 18 would quickly become full and the replacement frequency would increase. Also, conventionally, the refresh operation was performed after the printing job was completed, and since extra image formation was performed by the refresh operation, it was one of the factors contributing to the reduction of the life of the process cartridge 11.

[0033] It is conceivable to reduce the replacement frequency of the waste toner container 18 by forming the discharge pattern image on the paper and not making the toner constituting the discharge pattern image into waste toner. However, the discharge pattern formed on the paper may deteriorate the visual impression of the printed image on the paper (the image printed based on the image data received from a personal computer, a document reading unit, etc.) or may not be to the user's preference, and there is a risk that the user may be dissatisfied with the image for toner discharge.

[0034] Therefore, in the present embodiment, the discharge image formed on the paper can be set by the user. As a result, it is possible to form a discharge image that does not deteriorate the impression of the printed image or a discharge image that matches the user's preference on the paper, and it is possible to suppress the user from being dissatisfied with the discharge image formed on the paper. Hereinafter, the characteristic parts of the present embodiment will be described with reference to the drawings. In the present embodiment, the user is not limited to the user who actually uses the color copier 1, and includes, for example, the representative of the department to which the user belongs or the administrator of the color copier 1.

[0035] FIG. 2 is a functional block diagram regarding the refresh operation of the color copier 1. As shown in FIG. 2, the color copier 1 includes a control unit 60 as control means. The control unit 60 includes a CPU 60a, a ROM 60b, a RAM 60c, a printer control unit 63, an image reading control unit 64, a storage control unit 65, an operation panel control unit 61, and a communication control unit 68. Further, the control unit 60 includes a refresh execution unit 62, a margin detection unit 66, an image area cumulative average calculation unit 67, and a pixel acquisition unit 69. Each unit constituting the control unit 60 is connected by a bus.

[0036] The control unit 60 controls the entire color copier 1. The CPU 60a starts the OS by a boot program stored in the ROM 60b. Then, the CPU 60a executes control programs stored in the storage 51 and the ROM 60b on the OS. The RAM 60c is used as a temporary storage area such as the main memory and work area of the CPU 60a.

[0037] The printer control unit 63 of the control unit 60 functions as an interface for the CPU 60a to control each hardware of the image forming unit 3 (process cartridge, transfer unit 32, writing unit 34, fixing unit 33, etc.). The image reading control unit 64 functions as an interface for the CPU 60a to control the image reading unit 2.

[0038] The storage control unit 65 functions as an interface for the CPU 60a to control the storage 51, which is storage means provided in the color copier 1.

[0039] The storage 51 is a readable and writable non-volatile storage device such as an HDD. Programs for controlling the entire color copier 1, various application programs, data for managing consumable parts, etc. are stored in this storage 51. Further, the storage 51 also stores image data for toner ejection registered by the user, paper size information stocked in the paper feed cassettes 40, 41, the image area cumulative average value calculated by the image area cumulative average calculation unit 67, etc.

[0040] The operation panel control unit 61 functions as an interface for the CPU 60a to control the operation panel 50. The communication control unit 68 functions as an interface for controlling the external communication I / F 53 provided in the color copier 1. The operation panel 50 includes an input unit that receives user operation instructions such as a touch panel and hard keys, and a display unit such as an LCD and a CRT.

[0041] The pixel acquisition unit 69 acquires the number of pixels of each color printed on the paper based on the image data at a cycle of 0.1 seconds from the start of the development device drive, and the acquired number of pixels is temporarily stored in the print count memory. Note that the acquisition cycle of the number of pixels of each color is not limited to 0.1 seconds and can be appropriately set according to the configuration of the device.

[0042] The image area cumulative average calculation unit 67 calculates the cumulative average value of the image area of each color. The image area cumulative average is the average value of the image area over the past 100 seconds during the 0.1-second drive time of the development device. The calculation formula for the image area cumulative average is as follows.

[0043]

Equation

[0044] The above "image area cumulative average (i - 1)" is the cumulative average value of the image area before calculation (the previous one). Also, the above "image area (i)" is the latest image area. "Image area (i)" is calculated based on the number of pixels stored in the print count memory. The image area cumulative average is calculated each time the number of pixels stored in the print count memory is updated. During the printing job, the number of pixels is acquired at a cycle of 0.1 seconds, and the number of pixels in the print count memory is updated at 0.1-second intervals. Therefore, the cumulative average value of the image area of each color is also calculated at 0.1-second intervals.

[0045] In addition, when the developing device is new, until the pixel number acquisition for the 1st to 999th times, the execution determination of the refresh operation is not performed, and when the pixel number acquisition count reaches the 1000th time, the execution determination of the refresh operation is performed. When the developing device is new, since only new toner is contained, even if the refresh operation is not performed until the pixel number acquisition count reaches 1000, the deterioration of the image quality due to the deteriorated old toner does not occur.

[0046] In addition, until the pixel acquisition for the 1st to 999th times, the calculation of the accumulated average of the image area is performed by changing the "1000" in the above-mentioned number 1 to the current pixel acquisition count, so that the "accumulated average of the image area (i - 1)" can be used when calculating the accumulated average of the image area for the 1000th time. Also, until the pixel acquisition for the 1st to 999th times, the accumulated average of the image area may not be calculated, and when calculating the accumulated average of the image area for the 1000th time, the preset default "accumulated average of the image area (i - 1)" may be used. In such a configuration, although there is a possibility that the error from the actual usage situation increases until further use, there is an advantage that the control can be simplified.

[0047] The margin detection unit 66 detects whether there is a margin on the paper where an image for toner ejection can be formed. For example, when the accumulated average A(i) of the image area calculated by the image area accumulated average calculation unit 67 is equal to or less than the ejection threshold B, it is detected whether there is a margin on the paper where an image for toner ejection can be formed. The margin detection unit 66 functions as margin detection means.

[0048] Specifically, the margin detection unit 66 detects whether there is a margin on the paper where an image for toner ejection can be formed based on the margin area C calculated from the image data for toner ejection to be formed on the paper. For example, when the image for toner ejection to be formed on the paper is as shown in FIG. 3, the area within the frame indicated by the broken line in the figure is the margin area C. The margin area C is calculated, for example, when the user registers the image for toner ejection, and is stored in association with the image for toner ejection registered in the storage 51.

[0049] FIG. 4 is a diagram for explaining the blank detection range of the blank detection unit 66. The dotted line shown in FIG. 4 is the timing at which the pixel acquisition unit 69 acquires the number of pixels of each color. At the timings A1 to A5 in FIG. 4, the pixel acquisition unit 69 acquires the number of pixels, and the image area cumulative average calculation unit 67 calculates the image area cumulative average A(i). Specifically, at the timing of A1 in the figure, the number of pixels of each color in the range of B0 (the paper conveyance range in 0.1 seconds from the start of driving of the developing device) is acquired, and the image area (i) of the range of B0 is calculated by the image area cumulative average calculation unit 67. Then, the image area cumulative average A(i) is calculated based on the above formula 1. Also, at the timing of A2 in the figure, the number of pixels of each color in the range of B1 in the figure is acquired, and the image area (i) of the range of B1 and the image area cumulative average A(i) are calculated.

[0050] When the calculated image area cumulative average A(i) is equal to or less than the ejection threshold B, the blank detection unit 66 detects whether there is a blank area on the paper where an image for toner ejection can be formed. At the timing of A1 in the figure, it is detected whether there is a blank area on the paper in the range of B2 (hereinafter referred to as the blank detection range) where an image for toner ejection can be formed. At the timing of A2 in the figure, it is detected whether there is a blank area on the paper in the blank detection range of B3 in the figure where an image for toner ejection can be formed.

[0051] Specifically, the blank detection unit 66 detects whether there is a blank area on the paper where an image for toner ejection can be formed based on the intersheet length, the paper size, the printed image data, and the blank area C.

[0052] When the margin detection unit 66 detects that there is a margin on the paper where the toner ejection image can be formed, it sets this margin as the toner ejection image formation position. When there are multiple margins where the toner ejection image can be formed within the margin detection range, the margin detection unit 66 sets the margin on the most downstream side in the paper conveyance direction as the toner ejection image formation position. Also, when there are multiple margins where the toner ejection image can be formed at the same position in the paper conveyance direction and at different locations in the paper width direction, the margin on the most front side of the apparatus is set as the toner ejection image formation position.

[0053] In this way, it searches for whether there is a margin where the toner ejection image can be formed from the front side to the rear side of the apparatus on the downstream side in the sheet conveyance direction within the margin detection range. If there is no margin, it shifts the search range to the upstream side of the sheet and searches. When a margin where the toner ejection image can be formed is detected, the margin detection is terminated. With this control, margin detection can be performed. Therefore, the margin detection can be terminated at the time when the margin is detected, and the margin detection time can be shortened.

[0054] Also, among the multiple margins where the toner ejection image can be formed, the margin with the shortest distance from the paper edge may be set as the margin for forming the toner ejection image. This can separate the printed image, which is often formed near the center of the paper, from the toner ejection image, and can suppress the printed image from being less noticeable due to the toner ejection image.

[0055] When there are multiple margins where the toner ejection image can be formed, it may be possible to form the toner ejection image on all the margins. However, if there are too many toner ejection images, the toner ejection images may be more noticeable than the printed image. Therefore, as described above, it is preferable to form one toner ejection image within the margin range. This can suppress the appearance of the printed image from being impaired by the toner ejection image.

[0056] The refresh execution unit 62 shown in FIG. 2 determines whether to execute a refresh operation based on the image area cumulative average A(i) calculated by the image area cumulative average calculation unit 67 and the margin detection result of the margin detection unit 66. The refresh execution unit 62 functions as a refresh execution means.

[0057] The external communication I / F 53 shown in FIG. 2 communicates with an external device such as a PC (personal computer) via a network line or the like. The external communication I / F 53 receives image data for printing transmitted to the color copier by application software installed on the PC, and setting data such as an image for toner ejection formed in the margin of the paper. Also, an image for toner ejection can be registered from the application software installed on the PC, and the external communication I / F 53 also receives the registered image data for toner ejection. Further, the external communication I / F 53 transmits information regarding the state of the color copier, such as the toner remaining amount to be displayed on the application software and the paper size information stocked in the paper feed cassette, to the PC.

[0058] FIG. 5 is a diagram showing an example of a setting screen displayed on the display unit 50a of the operation panel 50. The screen shown in FIG. 5 is displayed, for example, by tapping "Adjustment / Management" from the setting top screen displayed by tapping the setting icon on the home screen displayed on the display unit 50a of the operation panel 50. By tapping "Waste Toner Save" on the setting screen shown in FIG. 5, the screen transitions to a registration screen for registering an image for toner ejection or a selection screen for selecting which of the registered images for toner ejection to set as the image for toner ejection.

[0059] Registration of the image for toner ejection is performed, for example, after setting a document having an image to be registered as the image for toner ejection in the image reading unit 2 and then operating the above-described registration screen to read the document with the image reading unit 2. The read image is displayed on the operation panel, and by operating the operation panel to specify the range of the image to be registered as the image for toner ejection, the image for toner ejection is registered.

[0060] For the registered image for toner ejection, a blank area C is calculated. When the calculated blank area C exceeds a predetermined area, a process is performed to reduce the registered image for toner ejection so that the blank area C is within the predetermined area. In the present embodiment, the predetermined area is about 10 [cm 2 . By making the blank area C of the image for toner ejection fall within the predetermined area in this way, it is possible to prevent a situation where the image for toner ejection is too large and hardly formed on the paper. Then, the registered image for toner ejection is stored in the storage 51 in association with the calculated blank area C.

[0061] FIG. 6 is a diagram showing an example of a selection screen displayed on the display unit of the operation panel 50. As shown in FIG. 6, on the selection screen, the image for toner ejection registered by the user and "no printing" where the image for toner ejection is not printed on the paper are displayed. When the user taps the registered image for toner ejection, the tapped image for toner ejection is set as the image for toner ejection to be formed in the margin of the paper during the refresh operation. In this way, the operation panel 50 functions as setting means for the user to set the image for toner ejection.

[0062] In FIG. 6, the logo mark or QR code (registered trademark) of the company registered by the user is displayed as the image for toner ejection to be set. For example, display marks such as "for home use" or "for in-house use", illustrations or patterns of animals or cars may be registered by default as the image for toner ejection.

[0063] On the other hand, when "no printing" is selected, in the same manner as in the prior art, a solid image toner ejection pattern in a strip shape is formed between papers or after the printing job is completed and removed by the cleaning device. In addition, it is also possible to register the toner ejection image and select the toner ejection image to be printed from the application software installed on the PC. Also, it may be possible to acquire and register the toner ejection image from a smartphone or USB memory.

[0064] FIG. 7 is a control flowchart of the refresh operation. First, when a print job is started (S1) and 0.1 second has elapsed since the start of driving the developing device (timing of A1 shown in FIG. 4), the pixel acquisition unit 69 acquires the number of pixels of each color and calculates the cumulative average A(i) of the image area of each color (S2).

[0065] When the calculated cumulative average A(i) of the image area exceeds the ejection threshold B (No in S3), a large amount of toner is consumed, there is little old toner in the developing device, and there is no need to update the toner in the developing device. Therefore, when the calculated cumulative average A(i) of the image area is equal to or greater than the ejection threshold B (No in S3), the refresh operation is not executed at this timing. In this embodiment, the ejection threshold B is 32.2 [cm 2 . This ejection threshold B is the cumulative average A of the image area when an image with an image area of about 5% is formed on A4 paper.

[0066] On the other hand, when the calculated cumulative average A(i) of the image area is less than or equal to the ejection threshold B (YES in S3), toner consumption is low, there is a lot of old toner in the developing device, image blotches and wormholes are likely to occur, and image quality may deteriorate. Therefore, if there is a margin on the paper where the toner ejection image can be formed, the refresh operation is performed to eject the old toner from the developing device.

[0067] Therefore, when the calculated accumulated average A(i) of the image area is less than or equal to the ejection threshold B (YES in S3), the margin detection unit 66 detects the presence or absence of a margin. Specifically, the margin area C corresponding to the toner ejection image set to be formed in the margin of the sheet is acquired from the storage 51 (S4). Next, the margin detection unit 66 detects whether there is a margin having an area equal to or larger than the margin area C within a predetermined margin detection range (the range of B2 in FIG. 4).

[0068] If there is a margin having an area equal to or larger than the margin area C (YES in S5), a refresh operation is executed (S6). Specifically, the toner ejection image data set as the toner ejection image to be formed on the sheet is acquired from the storage 51. Then, the acquired toner ejection image data is added to the location where the toner ejection image of the print image data is to be formed to create processed image data. Then, based on the processed image data, a toner image is formed by the image forming unit 3, and the toner ejection image set by the user is formed in the margin portion within the range of B2 in FIG. 4. On the other hand, if there is no margin having an area equal to or larger than the margin area C (NO in S5), the refresh operation is not executed.

[0069] The above-described series of steps are executed at a cycle of 0.1 seconds until the print job is completed. In the example shown in FIG. 4, it is detected whether there is a margin where a toner ejection image can be formed in the range of B2 to B4.

[0070] FIG. 8 shows an example of forming a toner ejection image during continuous printing of four sheets. In the example shown in FIG. 8, in the ranges of B2 and B5, there is no margin where the toner ejection image H can be formed on the paper. As described with reference to FIG. 4, the margin detection unit 66 detects the presence or absence of a margin in the range of B2 when the accumulated average A(i) of the image area calculated at the timing of A1 in the figure is equal to or less than the ejection threshold B. Therefore, even when the accumulated average A(i) of the image area calculated at the timing of A1 is equal to or less than the ejection threshold B, since there is no margin where the toner ejection image is formed in the range of B2, the refresh operation is not performed. Similarly, even when the accumulated average A(i) of the image area calculated at the timing of A4 is equal to or less than the ejection threshold B, since there is no margin where the toner ejection image is formed in the range of B5, the refresh operation is not performed.

[0071] On the other hand, in the ranges of B3, B4, and B6 in the figure, there is a margin where the toner ejection image H can be formed. Among B3, B4, and B6, for the ranges of B3 and B4, since the accumulated average A(i) of the image area is equal to or less than the ejection threshold B, as shown in the figure, the toner ejection image is formed in the margin area of the paper. On the other hand, since the accumulated average A(i) of the image area calculated at the timing of A5 is equal to or greater than the ejection threshold B for all colors, the toner ejection image H is not formed in the margin area of the range of B6.

[0072] As described above, in the present embodiment, by forming the toner ejection image H on the paper, the toner constituting the toner ejection image does not become waste toner and is not collected in the waste toner container 18. Thereby, the replacement frequency of the waste toner container 18 can be reduced. Further, as described with reference to FIG. 6, the user can set the toner ejection image to be formed on the paper. Thereby, a toner ejection image that does not deteriorate the impression of the printed image or a toner ejection image according to the user's preference can be formed on the paper, and the user's dissatisfaction with the toner ejection image formed on the paper can be reduced.

[0073] Note that at the timing A0 of starting the driving of the developing device shown in FIG. 8, it may be determined whether or not to execute the refresh operation. In this case, the image area cumulative average calculation unit 67 calculates the image area cumulative average A(i) for each color at the end of the printing job and stores it in the storage 51. At the start of the printing job, the image area cumulative average A(i) for each color calculated at the end of this printing job is acquired from the storage 51. When there is a color for which the image area cumulative average A(i) is equal to or less than the ejection threshold B, the margin detection unit 66 detects whether there is a margin within the margin detection range of B1 where an image for toner ejection can be formed. Then, when the margin detection unit 66 detects that there is a formable margin, the refresh execution unit 62 executes the refresh operation and forms the image for toner ejection set by the user in the margin portion within the range of B1 in FIG. 8.

[0074] Also, the image density of the image for toner ejection may be made thinner than the image density of the printed image to make the image for toner ejection less conspicuous. Thereby, the influence of the image for toner ejection on the printed image can be reduced.

[0075] FIG. 9 is a diagram showing an example of forming an image for toner ejection in a double-sided printing job. FIG. 9 shows an example of forming printed images on three pages on two sheets of paper. This color copier 1 performs double-sided printing in an interleaving method. The interleaving method is a method in which an image is printed on the front side of the next sheet of paper between the printing on the front side and the printing on the back side of the sheet of paper. When forming printed images on three pages, no printed image is formed on the back side of the second sheet. In the present embodiment, when the image area cumulative average A(i) calculated at the timing of A4 or A5 in the figure is equal to or less than the ejection threshold B, an image for toner ejection is formed on the back side of the second sheet, which is originally blank.

[0076] In addition, a mode of forming an image for toner ejection only on the back surface of a blank sheet of paper and a mode of forming an image for toner ejection in the margin of a printed image may be provided, and the user may be allowed to switch between the modes. When the user selects the mode of forming an image for toner ejection only on the back surface of a blank sheet of paper, during a print job in which a printed image is formed on only one side, after the toner image of the front surface printed image is formed, the cumulative average value of the image area is calculated. If the calculated cumulative average value of the image area is less than the ejection threshold B, the sheet of paper on which the printed image is formed on the front surface is conveyed to the reverse conveyance path 6b, and the ejection image set by the user is formed on the back surface of the sheet of paper. At this time, the number of images for toner ejection formed on the back surface of the sheet of paper may be set based on the difference value between the calculated cumulative average value of the image area and the ejection threshold B.

[0077] By selecting the mode of forming an image for toner ejection only on the back surface of a blank sheet of paper, it is possible to prevent the appearance of the printed image formed on the front surface of the sheet from being impaired by the image for toner ejection. On the other hand, by selecting the mode of forming an image for toner ejection in the margin of the printed image, the productivity of a single-sided print job can be increased.

[0078] In addition, the user may be able to set a paper area where an image for toner ejection is not to be formed. FIG. 10 is a diagram showing an example of an image for toner ejection prohibited area setting screen displayed on the display unit 50a of the operation panel 50. The hatched portion shown in FIG. 10 is the image for toner ejection prohibited area of the sheet of paper. The user taps an image corresponding to the area where the ejection image is not to be formed, thereby setting the image for toner ejection prohibited area. The set image for toner ejection prohibited area is stored in the storage 51. In this way, the operation panel 50 functions as an area setting means.

[0079] When the margin detection unit 66 detects whether there is a margin on the paper where an image for toner ejection can be formed, it acquires the toner ejection image prohibited area from the storage 51. Then, based on the acquired toner ejection image prohibited area, the margin detection unit 66 sets a margin detection range and detects whether there is a margin where an image for toner ejection can be formed within the set margin detection range.

[0080] Depending on the printed image, if an image for toner ejection is formed in the margin in the upper half of the paper, it may deteriorate the impression of the printed image. Also, for example, the margin in the lower half or the horizontal half of the paper is laid out as a margin for taking notes, and in some cases, it is not desired to form an image for toner ejection in the margin for notes. As shown in FIG. 10, by enabling the user to set the toner ejection image prohibited area, it is possible to suppress the deterioration of the impression of the printed image due to the image for toner ejection. Also, it is possible to suppress the formation of an image for toner ejection in the margin for notes.

[0081] FIG. 11 is a diagram showing a modified example of the refresh operation. In FIG. 11, when the printing job of A7 in the figure ends, the image area cumulative average A(i) is calculated. When the image area cumulative average A(i) is equal to or less than the ejection threshold B, a toner ejection pattern Hp to be removed by the cleaning device is formed on the photosensitive drum. Note that the ejection threshold at the end of the printing job may be different from the ejection threshold B during the printing job.

[0082] This toner ejection pattern Hp is, for example, one having an image area equal to or greater than the difference value between the image area cumulative average A(i) and the ejection threshold. Thereby, it is possible to satisfactorily suppress the deterioration of the quality of the printed image due to deteriorated old toner during the next printing.

[0083] As described above, the preferred embodiments of the present invention have been explained. However, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims, unless otherwise particularly limited in the above description.

[0084] What has been described above is an example, and each of the following aspects has specific effects. (Aspect 1) An image forming apparatus such as a color copier 1 provided with refresh execution means such as a refresh execution unit 62 that forms an image for toner ejection on a sheet such as paper and executes a refresh operation for forcibly consuming the toner in the developing device at a predetermined timing, and the image for toner ejection is set by setting means such as an operation panel 50 set by the user. When an image for toner ejection composed of visible toner is formed on a sheet, the image for toner ejection may deteriorate the visual impression of a printed image (an image printed based on image data received from a personal computer, scanner, etc.) or may not match the user's preference, and the user may be dissatisfied with the image for toner ejection composed of visible toner formed on the sheet. Therefore, in Patent Document 1, the image for toner ejection composed of visible toner is removed by cleaning means for cleaning the surface of the image carrier without being transferred to the sheet, and the visible toner that constituted the removed image for toner ejection is stored in a waste toner container as waste toner. Therefore, if the toner forced consumption operation frequently occurs, such as when a printed image with a low image area ratio follows, the waste toner container may quickly become full and the replacement frequency may increase. On the other hand, in Aspect 1, the user can set the image for toner ejection to be formed on the sheet to an image for toner ejection that does not deteriorate the visual impression of a printed image, such as a company logo mark, a QR code (registered trademark), a pattern, etc., or an image for toner ejection that suits the user's preference, and it is possible to suppress the user from being dissatisfied with the ejected image composed of visible toner formed on the sheet together with the printed image. In addition, by forming an image for toner ejection composed of visible toner on the sheet, it is possible to suppress the toner constituting the image for toner ejection from becoming waste toner and being stored in the waste toner container. As a result, the time until the waste toner container becomes full can be extended, and the replacement frequency of the waste toner container can be reduced.

[0085] (Aspect 2) In Aspect 1, it includes storage means such as a storage 51 that stores the image for toner ejection set by the user, and margin detection means such as a margin detection unit 66 that detects whether there is a margin on the sheet where the ejection image can be formed. The toner forced consumption operation such as the refresh operation forms an image for toner ejection on the margin portion of the sheet. The refresh execution means such as the refresh execution unit 62 executes the refresh operation when the cumulative average value of the image area within a predetermined time (in this embodiment, 0.1 seconds) during the driving of the developing device is less than the threshold value, and the margin detection means detects that there is a margin on the sheet where the ejection image can be formed. According to this, as described in the embodiment, it is possible to form the image for toner ejection set by the user on the margin portion of the sheet, and suppress the printed image formed on the sheet by the image for toner ejection from being damaged.

[0086] (Aspect 3) In Aspect 2, the refresh execution means such as the refresh execution unit 62 forms a toner ejection pattern Hp that is not transferred to the sheet on the image carrier such as the photosensitive drum after the completion of the printing job when the cumulative average value of the image area within a predetermined time (0.1 second in this embodiment) during the driving of the developing device is less than the threshold value at the end of the printing job. According to this, as described with reference to FIG. 11, it is possible to satisfactorily suppress the deterioration in the quality of the printed image due to the deteriorated old toner during the next printing.

[0087] (Aspect 4) In Mode 2 or 3, when there are a plurality of margins on a sheet such as paper where the toner ejection image can be formed, the margin on the most downstream side in the sheet conveyance direction is set as the margin for forming the toner ejection image. According to this, as described in the embodiment, it is possible to perform margin detection by starting margin detection from the downstream side in the conveyance direction of the sheet and ending the margin detection when the margin is detected, and it is possible to shorten the time for margin detection.

[0088] (Mode 5) In Mode 4, when there are a plurality of margins where the toner ejection image can be formed at the same position in the sheet conveyance direction but at different positions in the width direction of the sheet, the margin on the most front side of the apparatus is set as the margin for forming the toner ejection image. According to this, as described in the embodiment, it is possible to perform margin detection by detecting the margin while searching from the front side to the rear side of the sheet of the apparatus and ending the margin detection when the margin is detected, and it is possible to shorten the time for margin detection.

[0089] (Mode 6) In Claim 2 or 3, when there are a plurality of margins on the sheet where the toner ejection image can be formed, the margin with the shortest distance from the end of the sheet is set as the margin for forming the toner ejection image. According to this, as described in the embodiment, it is possible to separate the printed image, which is often formed near the center of the sheet, from the toner ejection image, and it is possible to suppress the printed image from being less noticeable due to the toner ejection image.

[0090] (Mode 7) In any one of Modes 1 to 6, a toner ejection image prohibition area for prohibiting the formation of the toner ejection image is provided with area setting means such as an operation panel 50 set by the user. According to this, as described with reference to FIG. 10, it is possible to prevent the toner ejection image from being formed in a location where the toner ejection image for the sheet, such as the margin for memo, is not desired to be formed. As a result, it is possible to suppress the user from feeling dissatisfied with the toner ejection image formed on the sheet.

[0091] (Aspect 8) In any of Aspects 1 to 7, the refresh execution means such as the refresh execution unit 62 forms the toner ejection image set by the user on the back surface of the sheet on which the printed image is formed only on the front surface. According to this, as described in the embodiment, by forming the toner ejection image on the back surface of the sheet on which the printed image is not formed, the appearance of the printed image formed on the front surface of the sheet is not impaired by the toner ejection image.

[0092] (Aspect 9) In Aspect 8, it includes a mode of forming the toner ejection image set by the user on the back surface of the sheet such as paper on which the printed image is formed only on the front surface, and a mode of forming the toner ejection image set by the user in the margin portion of the surface of the sheet on which the printed image is formed. According to this, when it is not desired for the appearance of the printed image to be impaired by the toner ejection image, the mode of forming the toner ejection image set by the user on the back surface of the sheet such as paper on which the printed image is formed only on the front surface can be selected, and when productivity is high, the mode of forming the toner ejection image set by the user in the margin portion of the surface of the sheet on which the printed image is formed can be selected.

Explanation of Reference Numerals

[0093] 1: Color copier 3: Image forming unit 7: Photoconductor drum 11: Process cartridge 18: Waste toner container 30: Developing device 34: Writing unit 40: Paper feed cassette 41: Paper feeding cassette 50: Operation panel 50a: Display unit 51: Storage 53: External communication I / F 60: Control unit 61: Operation panel control unit 62: Refresh execution unit 63: Printer control unit 64: Image reading control unit 65: Storage control unit 66: Margin detection unit 67: Image area cumulative average calculation unit 68: Communication control unit 69: Pixel acquisition unit H: Ejected image Hp: Ejection pattern

Prior art documents

Patent documents

[0094]

Patent Document 1

Claims

1. An image forming apparatus including a refresh execution means for forming an image for toner ejection on a sheet and executing a refresh operation for forcibly consuming toner in a developing device at a predetermined timing, wherein the image for toner ejection has setting means set by a user.

2. In the image forming apparatus according to claim 1, a storage means for storing the image for toner ejection set by the user; a margin detection means for detecting whether there is a margin on the sheet where the image for toner ejection can be formed, wherein the refresh operation forms the image for toner ejection in the margin portion of the sheet, and the refresh execution means executes the refresh operation when the cumulative average value of the image area within a predetermined time during driving of the developing device is less than a threshold value and the margin detection means detects that there is a margin on the sheet where the image for toner ejection can be formed.

3. In the image forming apparatus according to claim 2, when the cumulative average value of the image area within a predetermined time during driving of the developing device is less than a threshold value at the end of a printing job, the refresh execution means forms a toner ejection pattern that is not transferred to the sheet on the image carrier after the printing job ends.

4. In the image forming apparatus according to claim 2, when there are a plurality of margins on the sheet where the image for toner ejection can be formed, the margin on the most downstream side in the sheet conveyance direction is set as the margin for forming the image for toner ejection.

5. In the image forming apparatus according to claim 4, when there are a plurality of margins where the image for toner ejection can be formed at different positions in the width direction of the sheet at the same position in the sheet conveyance direction, the margin on the most front side of the apparatus is set as the margin for forming the toner ejection image.

6. In the image forming apparatus according to claim 2, when there are a plurality of margins on the sheet where the image for toner ejection can be formed, the margin with the shortest distance from the end of the sheet is set as the margin for forming the toner ejection image.

7. In the image forming apparatus according to claim 1, An image forming apparatus, comprising area setting means for setting, by the user, a toner ejection image prohibition area that prohibits formation of the toner ejection image. **Claim 8** In the image forming apparatus according to claim 1, the refresh execution means forms the toner ejection image set by the user on the back surface of a sheet on which a printed image is formed only on the front surface. **Claim 9** In the image forming apparatus according to claim 8, the image forming apparatus includes a mode of forming the toner ejection image set by the user on the back surface of a sheet on which a printed image is formed only on the front surface, and a mode of forming the toner ejection image set by the user in a margin portion of the surface on which the printed image of the sheet is formed.

Images