JP2019159051A - Image formation device, image defect reducing method, and computer program - Google Patents

Abstract

To reduce the occurrence of a defect of an image due to a remaining lubricant with a mechanism simpler than the conventional art.SOLUTION: An image formation device includes an image carrier 2A that forms a toner image using toner and receives a lubricant for separating toner. For each of a plurality of regions arranged in the longitudinal direction of the image carrier 2A in a page as a printing object, the percentage of the toner amount required for printing the part of the region in the page corresponding to the size of the region is calculated. Then, when the difference between a maximum value and minimum value of percentages of the plurality of regions exceeds a threshold, the image carrier 2A is electrified using an AC voltage higher than that when the difference does not exceed the threshold.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a technique for reducing problems such as noise in an electrophotographic image forming apparatus.

  An electrophotographic image forming apparatus is widely used. Such an image forming apparatus is provided with an image carrier. When a toner image of an image to be printed is formed on an image carrier, the image carrier is charged and toner is supplied to the image carrier. Then, the toner image is transferred from the image carrier to a sheet or a transfer belt. The toner remaining on the image carrier is removed by a cleaning blade.

  A lubricant is mixed in the toner so that the toner is easily transferred from the image carrier to a transfer belt or the like.

  Since the lubricant is scraped off from the image carrier together with the toner by the cleaning blade, the residual amount of the lubricant may become non-uniform in the longitudinal direction of the image carrier after cleaning.

  Then, when the image carrier is charged in order to newly form a toner image, a potential difference is generated between a portion where the residual amount of the lubricant is large and a portion where the lubricant is small. This difference may cause problems such as noise in the toner image.

  Therefore, the following techniques have been proposed as techniques for solving the problems caused by the residual lubricant.

  According to the technique described in Patent Document 1, a solid lubricant consisting of a plurality of small pieces divided in the longitudinal direction of the photosensitive member is provided for contact with the lubricant applying means for each small piece. The contact pressure can be arbitrarily changed. Then, an appropriate lubricant is applied according to the toner input amount by changing the contact / separation of the lubricant or the contact pressure according to the toner input amount.

  According to the technique described in Patent Document 2, a power supply device that applies an AC voltage to the charging roller of the image forming unit and an AC peak-to-peak voltage changing unit that changes the AC peak-to-peak voltage (Vp-p) applied by the power supply device. Place. The AC peak-to-peak voltage changing means increases the AC peak-to-peak voltage (Vpp) as the image area ratio of the photosensitive drum decreases, and decreases the AC peak-to-peak voltage (Vp-p) as the image area ratio increases.

  According to the technique described in Patent Literature 3, an electrophotographic system is provided in which a lubricant application device that applies a lubricant to an image carrier such as a photosensitive drum is mounted, and an AC voltage is applied to a charging unit that charges the photosensitive drum. In the image forming apparatus, the AC peak-to-peak voltage (Vp-p) applied to the charging unit is changed in accordance with the fluctuation of the lubricant consumption. The lubricant application device is a mechanism for scraping off the rod-shaped solid lubricant with a brush roller and applying it to the photosensitive drum, and the AC peak-to-peak voltage (Vp-p) applied to the charging means in the initial use of the brush roller. Increase it, decrease it in the initial use of the lubricant, and decrease it according to the usage time of the brush roller.

JP 2007-147917 A JP 2012-177866 A JP 2013-44871 A

  However, according to the technique described in Patent Document 1, since the means for applying the lubricant must be controlled in accordance with the input image, the mechanism becomes complicated and large.

  According to the technique described in Patent Document 2 or Patent Document 3, the amount of lubricant on the entire photosensitive drum (image carrier) can be adjusted, but depending on the difference in the amount of lubricant in the longitudinal direction on the photosensitive drum. The occurrence of defects cannot be suppressed.

  The present invention has been made in view of such problems, and an object thereof is to reduce the occurrence of image defects due to remaining lubricant by a simpler mechanism than in the past.

  An image forming apparatus according to an aspect of the present invention includes: an image carrier on which a toner image is formed with toner and a lubricant for separating the toner is supplied; and the image carrier of a page to be printed Calculating means for calculating, for each of a plurality of regions arranged in the longitudinal direction of the body, a ratio of the amount of the toner necessary for printing a portion of the region of the page with respect to the width of the region; When the difference between the maximum value and the minimum value of the ratios of the respective areas of the image area exceeds a threshold value, the charging unit charges the image carrier using an AC voltage stronger than when the difference does not exceed the threshold value. And removing means for removing the toner and the lubricant remaining on the image carrier after the toner image is transferred from the image carrier to another medium.

  An image forming apparatus according to another aspect of the present invention includes: an image carrier on which a toner image is formed with toner and supplied with a lubricant for separating the toner; and Calculating means for calculating, for each of a plurality of regions arranged in the longitudinal direction of the image carrier, a ratio of the amount of the toner necessary for printing a portion of the region of the page with respect to the width of the region; The first number of times that the difference between the maximum value and the minimum value of the ratios of each of the plurality of regions exceeds the threshold value is more than a predetermined number of times than the second number of times that the difference does not exceed the threshold value. After entering the state, the charging means for charging the image carrier using an alternating voltage stronger than usual, and the toner image is transferred from the image carrier to another medium and then remains on the image carrier. Remove the toner and the lubricant Having a removal means for the.

  Preferably, the charging unit charges the image carrier using the AC voltage until the predetermined number of printed pages is reached after the state is reached.

  According to the present invention, it is possible to reduce the occurrence of image defects due to the remaining lubricant by a simpler mechanism than before.

1 is a diagram illustrating an example of a network system having an image forming apparatus. 2 is a diagram illustrating an example of a hardware configuration of an image forming apparatus. FIG. FIG. 3 is a diagram illustrating an example of a configuration of a print unit. 3 is a diagram illustrating an example of a configuration of a toner image forming unit. It is a figure for demonstrating the example of the malfunction of the image by a lubricant. 2 is a diagram illustrating an example of a functional configuration of an image forming apparatus. FIG. It is a figure which shows the example of a division area. It is a flowchart explaining the example of the flow of a mode switching process. 10 is a flowchart illustrating an example of the overall processing flow related to printing in the image forming apparatus. It is a figure which shows the example of how the lubricant is supplied. It is a figure which shows the modification of a division area.

  FIG. 1 is a diagram illustrating an example of a network system having an image forming apparatus 1. FIG. 2 is a diagram illustrating an example of a hardware configuration of the image forming apparatus 1. FIG. 3 is a diagram illustrating an example of the configuration of the print unit 10i. FIG. 4 is a diagram illustrating an example of the configuration of the toner image forming unit 2. FIG. 5 is a diagram for explaining an example of an image defect caused by a lubricant.

  An image forming apparatus 1 shown in FIG. 1 is an apparatus generally called an MFP (Multi Function Peripherals) or a multifunction peripheral, and is an apparatus that integrates functions such as copying, PC printing, facsimile, and scanning.

  The PC print function is a function for receiving image data from a personal computer, a tablet computer, a server, or the like, and printing the image on a recording medium (hereinafter referred to as “sheet”) such as paper or film. It may also be called “network printer function” or “network printing function”.

  As shown in FIG. 2, the image forming apparatus 1 includes a CPU (Central Processing Unit) 10a, a RAM (Random Access Memory) 10b, a ROM (Read Only Memory) 10c, an auxiliary storage device 10d, an operation panel 10e, an NIC (Network Interface). Card) 10f, facsimile unit 10g, scan unit 10h, print unit 10i, and the like.

  The NIC 10f communicates with a personal computer, tablet computer, server, or the like via a communication line using a protocol such as TCP / IP (Transmission Control Protocol / Internet Protocol).

  The facsimile unit 10g exchanges image data with a facsimile terminal using a protocol such as G3 via a public telephone line.

  The operation panel 10e includes a key input unit 10e1 and a touch panel display 10e2 (see FIG. 3).

  The key input unit 10e1 is a so-called hardware keyboard, and includes a numeric keypad, a start key, a stop key, a function key, and the like.

  The touch panel display 10e2 includes a screen for giving a message or an instruction to the user, a screen for inputting a processing type and processing conditions desired by the user, a screen showing a result of processing executed by the CPU 10a, and the like. indicate.

  The user can input data and commands to the image forming apparatus 1 by operating the key input unit 10e1 or the touch panel display 10e2 while viewing these screens.

  The scan unit 10h reads an image written on a sheet set on the platen glass and generates image data.

  In addition to the image read by the scan unit 10h, the print unit 10i prints an image indicated by image data received from another apparatus on a sheet by an electrophotographic method. Hereinafter, a case where a tandem color print engine is used as the print unit 10i will be described as an example.

  As shown in FIG. 3, the print unit 10 i mainly includes an image forming unit 17 and a transport unit 18.

  The image forming unit 17 includes a toner bottle 17B, a stirring blade 17C, a toner image forming unit 2, an intermediate transfer belt 17E, an intermediate transfer belt cleaner 17F, a waste toner box 17G, and the like. An image to be printed on a sheet is formed as follows by each unit of the image forming unit 17.

  The toner bottle 17B, the stirring blade 17C, and the toner image forming unit 2 are provided for each color of cyan, magenta, yellow, and black. Hereinafter, the cyan toner bottle 17B, the stirring blade 17C, and the toner image forming unit 2 will be described as examples.

  The toner bottle 17B stores supplemental cyan toner. The stirring blade 17C supplies cyan toner to the toner image forming unit 2 from the toner bottle 17B.

  The toner image forming unit 2 forms a toner image of an image to be printed as follows and transfers it to the intermediate transfer belt 17E.

  As shown in FIG. 4, the toner image forming unit 2 includes an image carrier 2A, a charging device 2B, an exposure device 2C, a developing device 2D, an intermediate transfer device 2E, a cleaning unit 2F, and the like.

  The image carrier 2A may be called a “photosensitive drum” or a “photosensitive drum”. Image carrier 2A rotates in the direction of arrow M1.

  The charging device 2B includes a charging roller 2B1, an application circuit 2B2, and the like. Then, the entire portion of the surface of the image carrier 2A facing the charging roller 2B1 is charged as follows.

  The application circuit 2B2 applies a constant voltage obtained by superimposing an AC voltage on a DC negative voltage to the charging roller 2B1. The charging roller 2B1 charges the image carrier 2A while rotating in the direction of the arrow M2.

  The charging device 2 </ b> B is provided with two modes, a normal mode and an adjustment mode, as modes of alternating voltage strength (hereinafter referred to as “voltage mode”). In the normal mode, the application circuit 2B2 superimposes an AC voltage Vo having a predetermined strength on the DC voltage. However, in the adjustment mode, the strength of the alternating voltage is increased from that in the normal mode and superimposed. Therefore, the image carrier 2A is charged more strongly in the adjustment mode than in the normal mode. The default voltage mode is the normal mode.

  The exposure device 2C irradiates light onto the surface of the image carrier 2A according to the image to be printed, thereby forming (creating) an electrostatic latent image corresponding to this image on the surface of the image carrier 2A. . In particular, the exposure apparatus 2C forms an electrostatic latent image corresponding to a cyan component (pixel) in the image.

  The developing device 2D includes a developing roller 2D1, an application circuit 2D2, a screw 2D3, a toner tank 2D4, and the like, and forms a cyan toner image on the image carrier 2A by placing cyan toner on the surface of the image carrier 2A. To do.

  In the toner tank 2D4, cyan toner and carrier are mixed and stored at a certain ratio. The toner is appropriately replenished from the toner bottle 17B. Further, a lubricant is provided in the toner tank 2D4 so that the toner easily moves from the image carrier 2A to the intermediate transfer belt 17E and the toner remaining on the image carrier 2A is easily separated from the intermediate transfer belt 17E. It has been added. Lubricants are sometimes called “lubricants”.

  The application circuit 2D2 applies a constant voltage obtained by superimposing an AC voltage on a DC negative voltage to the developing roller 2D1.

  The screw 2D3 adheres toner and developer to the developing roller 2D1 with a carrier interposed therebetween. The developing roller 2D1 rotates in the direction of the arrow M3. Then, the toner adhering to the surface of the developing roller 2D1 moves to the portion of the electrostatic latent image formed on the image carrier 2A. As a result, a toner image is formed on the image carrier 2A. The lubricant also moves to the surface of the image carrier 2A together with the toner.

  The intermediate transfer belt 17E passes between the intermediate transfer device 2E and the image carrier 2A, and moves in the direction of the arrow M4 in accordance with the speed at which the surface of the image carrier 2A moves due to the rotation of the image carrier 2A. .

  The intermediate transfer device 2E includes a transfer roller 2E1, an application circuit 2E2, and the like, and transfers the toner image formed on the image carrier 2A to the intermediate transfer belt 17E as follows.

  The application circuit 2E2 applies a DC positive voltage to the transfer roller 2E1. Then, the surface of the transfer roller 2E1 is positively charged.

  The transfer roller 2E1 rotates in the direction of the arrow M5. Since the toner is positively charged, the toner image is separated from the surface of the image carrier 2A and travels toward the surface of the transfer roller 2E1. Then, it adheres to the intermediate transfer belt 17E. As a result, the toner image is transferred to the intermediate transfer belt 17E.

  The cleaning unit 2F includes a cleaning blade 2F1, a waste toner tray 2F2, and the like.

  The cleaning blade 2F1 separates (removes) the toner remaining on the surface of the image carrier 2A by scraping off the toner from the surface. The separated toner (so-called waste toner) is stored in a waste toner tray 2F2. The lubricant is also scraped off and stored in the waste toner tray 2F2. When the voltage mode is the adjustment mode, the image carrier 2A is more strongly charged than when the voltage mode is the normal mode. Therefore, the lubricant is more easily scraped off in the adjustment mode than in the normal mode. As a result, the non-uniformity in the amount of lubricant in the longitudinal direction of the image carrier 2A is more easily reduced than in the past.

  The toner bottles 17B, the stirring blades 17C, and the toner image forming unit 2 for magenta, yellow, and black have the same role as those for cyan, and the magenta, yellow, and black toner images are transferred to the intermediate transfer belt 17E. Transcript to.

  In this way, cyan, magenta, yellow, and black toner images are superimposed on the intermediate transfer belt 17E.

  By the way, when the toner is separated, the surface of the image carrier 2A may be scraped off together with the toner. The portion where the toner remains is easily scraped off. Therefore, the surface of the image carrier 2A is worn unevenly. When the surface of the image carrier 2A is deviated and worn in the longitudinal direction, the amount of lubricant remaining may become non-uniform in the longitudinal direction of the image carrier 2A as shown in FIG.

  Then, when the image carrier 2A is charged in order to newly form a toner image, a potential difference is generated between a portion where the remaining amount of the lubricant is large and a portion where the lubricant is small. Due to this difference, problems such as noise occur in the toner image as shown in FIG. A method for suppressing this problem will be described later.

  Returning to FIG. 3, the transport unit 18 includes a paper feed tray 18A, a paper feed roller 18B, a registration roller 18C, a secondary transfer roller 18D, a heating roller 18E, a pressure roller 18F, a paper discharge roller 18G, a manual feed tray 18H, The manual feed roller 18J and the vertical transport rollers 18K and 18L are configured. Each unit of the conveyance unit 18 conveys the sheet and fixes the toner image on the sheet as follows.

  A large number of sheets for printing an image are set in the paper feed tray 18A. Usually, a standard copy paper is set.

  The paper feed roller 18B sends out the sheet set on the paper feed tray 18A to the transport path 3.

  The vertical conveyance roller 18K conveys the sheet fed from the paper feed tray 18A to the registration roller 18C.

  On the manual feed tray 18H, about 1 to about a dozen sheets are set for so-called manual feed printing. Although it is possible to set the same type of sheet as the sheet set in the sheet feeding tray 18A, different types of sheets are mainly set.

  The manual sheet feeding roller 18J sends out the sheet set on the manual sheet feeding tray 18H to the conveyance path 3.

  The vertical conveyance roller 18L conveys the sheet fed from the manual feed tray 18H to the registration roller 18C.

  The registration roller 18C temporarily stops the sheet conveyed by the paper feed roller 18B or the manual paper feed roller 18J, and sends it to the secondary transfer roller 18D at a predetermined timing.

  The secondary transfer roller 18D transfers the toner image superimposed on the intermediate transfer belt 17E onto the sheet sent from the registration roller 18C.

  The heating roller 18E heats the sheet on which the toner image is transferred. The pressure roller 18F presses the sheet on which the toner image is transferred. As a result, the toner image is fixed on the sheet. The heating roller 18E and the pressure roller 18F are generally referred to as “fixing rollers”.

  The paper discharge roller 18G sends the sheet on which the toner image is fixed to a predetermined position (paper discharge tray or bin).

  The intermediate transfer belt cleaner 17F of the image forming unit 17 separates toner remaining on the intermediate transfer belt 17E without being transferred to the sheet from the intermediate transfer belt 17E. The separated toner (so-called waste toner) is stored in a waste toner box 17G.

  Returning to FIG. 2, the ROM 10c or the auxiliary storage device 10d stores a program for realizing the above-described functions. In particular, in the present embodiment, a print control program 10P (see FIG. 6) is stored.

  These programs are loaded into the RAM 10b and executed by the CPU 10a. A hard disk, SSD (Solid State Drive), or the like is used as the auxiliary storage device 10d.

  The print control program 10P is a computer program for printing an image on a sheet. Further, according to the print control program 10P, noise generated in the printed matter due to unevenness of the lubricant can be reduced as compared with the conventional case. Hereinafter, this mechanism will be described.

  FIG. 6 is a diagram illustrating an example of a functional configuration of the image forming apparatus 1. FIG. 7 is a diagram illustrating an example of the divided region 4. FIG. 8 is a flowchart illustrating an example of the flow of mode switching processing.

  According to the print control program 10P, the counter storage unit 101, the flag storage unit 102, the rasterization unit 103, the coverage calculation unit 104, the image formation control unit 105, the counter update unit 106, the mode switching unit 107, and the like illustrated in FIG. 6 are realized. The

  The counter storage unit 101 stores a set of first counter 5A, second counter 5B, and third counter 5C for each color of CMYK (cyan, magenta, yellow, black). How to use these counters will be described later. The initial values of these counters are all “0”.

  The flag storage unit 102 stores one new flag 5F for each of cyan, magenta, yellow, and black. The new product flag 5F indicates whether or not the image carrier 2A of the corresponding color is new. “1” means a new article, and “0” means not a new article. The default value of any new flag 5F is “1”.

  When a job with printing such as a copy job, a fax reception job, or a PC print job is given, the rasterizing unit 103 or the mode switching unit 107 prints an image on a sheet or reduces the trouble caused by remaining lubricant. Is executed as follows.

  The rasterizing unit 103 converts the image data received by the NIC 10f or the facsimile unit 10g or the image data generated by the scan unit 10h into CMYK bitmap data. That is, rasterization is performed. If the image data is for a document consisting of a plurality of pages, it is converted into bitmap data for each page.

  The coverage calculation unit 104 calculates the coverage (coverage rate) R of each color in each divided region 4 of each page based on the bitmap data obtained by the rasterization unit 103.

  As shown in FIG. 7, the “divided area 4” is obtained by dividing the entire page into a plurality of parts along the sheet traveling direction. Therefore, the divided regions 4 are arranged along the longitudinal direction of the image carrier 2A. Hereinafter, a case where each page is equally divided into three will be described as an example. Further, each divided area 4 of one page is described separately from the “divided area 4A”, “divided area 4B”, and “divided area 4C” from the left.

The “coverage R” of a certain color in a certain divided area 4 of a certain page is a ratio of the dots of that color in the divided area 4 to the entire divided area 4. That is, the coverage R is calculated by the following equation (1).
R (cr, p, k) = (D (cr, p, k) / W (p, k)) × 100 (%) (1)
However, crε {cyan, magenta, yellow, black}.
p is a page number.
D (cr, p, k) is the total area of cr colored dots in the kth divided region 4 from the left of the pth page.
W (p) is the area of the entire kth divided region 4 from the left of the pth page.

Based on the bitmap data obtained by the rasterizing unit 103, the image forming control unit 105 performs toner image forming units for cyan, magenta, yellow, and black so that one page is printed on one sheet. 2 parts are controlled.

  Hereinafter, the processing of the image formation control unit 105 will be described by taking as an example the case of controlling each part of the cyan toner image forming unit 2 in order to print the kth page of an original composed of N pages (N ≧ 2).

  The image forming control unit 105 sets the image carrier 2A, the charging roller 2B1, the developing roller 2D1, the screw 2D3, and the transfer roller 2E1 of the cyan toner image forming unit 2 at a predetermined speed and a predetermined speed. Rotate in the direction of.

  Further, the image formation control unit 105 controls the application circuit 2B2 so that a DC voltage and an AC voltage having a strength of Vpp are superimposed on the charging roller 2B1. Currently, when the voltage mode is the normal mode, Vpp is Vo. On the other hand, when the voltage mode is the adjustment mode, Vo is increased by Va. That is, Vpp = Vo + Va. Va is, for example, 500 volts. The switching of the voltage mode will be sequentially described later.

  Further, the image formation control unit 105 controls the application circuit 2D2 so that a constant voltage is applied to the developing roller 2D1 so that the surface potential of the developing roller 2D1 becomes a predetermined potential. The application circuit 2E2 is controlled so that a positive DC voltage is applied to the transfer roller 2E1.

  Then, the image formation control unit 105 controls the exposure device 2C so that the surface of the image carrier 2A is irradiated in accordance with the image to be printed.

  Then, an electrostatic latent image of the image is formed on the surface of the image carrier 2A. A toner image is formed on the surface of the image carrier 2A where the electrostatic latent image is formed, and the toner image is transferred from the surface of the image carrier 2A to the intermediate transfer belt 17E.

  Thereafter, the toner remaining on the surface of the image carrier 2A is removed by the cleaning unit 2F.

  By the way, the voltage mode is switched by the mode switching unit 107 based on the value of the cyan first counter 5A, the second counter 5B, or the third counter 5C. The first counter 5A, the second counter 5B, and the third counter 5C are updated by the counter update unit 106.

  The switching of the voltage mode and the updating of these counters are performed according to the procedure shown in FIG. 8 before the image carrier 2A is charged by the charging device 2B for the image formation of the Kth page. In FIG. 8, “α”, “β”, and “γ” mean values of the first counter 5A, the second counter 5B, and the third counter 5C, respectively.

  When the current voltage mode is the normal mode (Yes in # 701 in FIG. 8), the counter update unit 106 determines that the cyan update for each of the divided areas 4A, 4B, and 4C of the Kth page is performed. If the difference between the maximum value and the minimum value of the coverage R is equal to or smaller than the threshold Th1, “1” is subtracted from each of the first counter 5A and the second counter 5B (# 702, # 703). However, if it is already “0”, it is not necessary to subtract. Hereinafter, this difference is referred to as “coverage difference D”. For example, if the coverage R of each of the divided areas 4A, 4B, and 4C is “12%”, “73%”, and “36%”, the coverage difference D is 73% −12% = 61%. .

  The threshold Th1 can be arbitrarily set by the user or the administrator. The same applies to other threshold values described later.

  If the coverage difference D exceeds the threshold Th1 (Yes in # 702) but does not exceed the threshold Th2 (No in # 705), the counter update unit 106 adds “1” to the second counter 5B ( # 706). If the coverage difference D exceeds the threshold Th2 (Yes in # 705), “1” is added to the first counter 5A (# 708).

  Note that threshold Th2> threshold Th1. The threshold value Th1 is, for example, “50%”. The threshold value Th2 is “100%”, for example.

  As a result of updating the second counter 5B, the value of the second counter 5B exceeds the threshold value Th4 (Yes in # 707), or as a result of updating the first counter 5A, the first counter 5A is updated. When the value exceeds the threshold Th3 (Yes in # 709), the mode switching unit 107 switches the voltage mode to the adjustment mode (# 710).

  Note that threshold Th4> threshold Th3. Further, the threshold value Th3 and the threshold value Th4 change according to the value of the new article flag 5F. When the value of the new product flag 5F is “1”, for example, “200” is used as the threshold Th3 and “300” is used as the threshold Th4. When the value of the new flag 5F is “0”, for example, “100” is used as the threshold Th3 and “200” is used as the threshold Th4. That is, both the threshold Th3 and the threshold Th4 are smaller when the new flag 5F is “0” than when the new flag 5F is “1”.

  When the voltage mode is switched to the adjustment mode, the counter update unit 106 adds “1” to the third counter 5C (# 711).

  Alternatively, even when the current voltage mode is the adjustment mode (No in # 701), the counter update unit 106 adds “1” to the third counter 5C (# 711).

  In this embodiment, the counter update unit 106 adds “1” before the toner image of the Kth page is transferred to the intermediate transfer belt 17E, but it may be added after the transfer.

  In this manner, the third counter 5C counts the number of pages on which the toner image has been transferred to the intermediate transfer belt 17E after switching to the adjustment mode most recently.

  When the value of the third counter 5C exceeds the threshold Th5 (Yes in # 712), the mode switching unit 107 switches the voltage mode to the normal mode (# 713). The counter updating unit 106 resets the values of the first counter 5A, the second counter 5B, and the third counter 5C to “0” (# 714). If the cyan new flag 5F stored in the flag storage unit 102 is “1” (# 715), it is updated to “0” (# 716). The threshold value Th5 is “200”, for example.

  In this way, the first counter 5A prints the total number of pages printed with the coverage difference D exceeding the threshold Th3 and the coverage difference D being equal to or less than the threshold Th1 after the switch to the adjustment mode most recently. Count the difference from the total number of pages you have selected.

  Further, the second counter 5B has the total number of pages printed in a state where the coverage difference D is larger than the threshold Th2 and equal to or smaller than the threshold Th3 after the switching to the adjustment mode most recently, and the coverage difference D is equal to or smaller than the threshold Th1. Count the difference from the total number of pages printed in status.

  Then, the image forming control unit 105 performs the image forming process for the Kth page according to the voltage mode as described above.

  The rasterizing unit 103 or the mode switching unit 107 similarly performs the above-described processing for colors other than cyan, that is, magenta, yellow, and black.

  FIG. 9 is a flowchart illustrating an example of the overall processing flow related to printing in the image forming apparatus 1.

  Next, the overall processing flow of the image forming apparatus 1 will be described with reference to the flowchart of FIG. The image forming apparatus 1 executes processing according to the procedure shown in FIG. 9 based on the print control program 10P.

  The image forming apparatus 1 resets all of the setting values of unused, that is, new ones of the cyan, magenta, yellow, and black image carriers 2A (Yes in # 721, # 722). The set values that have already been used are left as they are (No in # 721).

  When the image forming apparatus 1 receives a job accompanied by printing (Yes in # 723), the image forming apparatus 1 executes a process for printing as follows.

  The image forming apparatus 1 rasterizes each page of the document to be printed (# 724), and calculates the coverage R of each color in each divided area 4 of each page (# 725). Then, the following processing is performed for each page (# 726 to # 730).

  The image forming apparatus 1 performs a process for appropriately switching the voltage mode (# 726). The procedure of this process is as described above with reference to FIG.

  If the current voltage mode is the normal mode (Yes in # 727), the image carrier 2A is charged using an alternating voltage of normal strength (Vo), and the target page is printed (# 728). . On the other hand, in the adjustment mode (No in # 727), the image carrier 2A is charged using an AC voltage stronger than usual (with a strength of (Vo + Va)), and the target page is printed (#). 729).

  The image forming apparatus 1 appropriately executes the processes of steps # 721 to # 730 while continuing to provide the printing service (Yes in # 730).

  According to the present embodiment, it is possible to more easily reduce the occurrence of image defects due to the remaining lubricant.

  FIG. 10 is a diagram showing an example of how the lubricant is supplied. FIG. 11 is a diagram illustrating a modified example of the divided region 4.

  In the present embodiment, the AC voltage is increased by the same strength both in the case where the first counter 5A exceeds the threshold Th3 and in the case where the second counter 5B exceeds the threshold Th4. That is, in both cases, the same value was used as Va. However, a higher value may be used as Va when the first counter 5A exceeds the threshold Th3 than when the second counter 5B exceeds the threshold Th4. For example, if the new product flag 5F is “1”, “800” is used as Va when the first counter 5A exceeds the threshold Th3, and “700” when the second counter 5B exceeds the threshold Th4. May be used. If the new flag 5F is “0”, “700” is used when the first counter 5A exceeds the threshold Th3, and “500” is used when the second counter 5B exceeds the threshold Th4. Good.

  In this embodiment, the same value is used as Va regardless of the temperature and humidity around the image forming apparatus 1 or in the vicinity of the heating roller 18E. However, when this temperature or humidity is higher than the normal (predetermined) temperature or humidity, the AC voltage may be set lower than normal. Then, the lubricant tends to remain on the image carrier 2A than usual. Therefore, in this case, the timing for switching to the adjustment mode may be advanced. That is, in this case, the threshold Th3 and the threshold Th4 may be set lower than usual.

  Alternatively, the threshold Th3 and the threshold Th4 may be lowered as the process speed or the printing speed increases. The threshold Th3 and the threshold Th4 may be lowered as the toner charge amount is higher. The threshold Th3 and the threshold Th4 may be lowered as the surface of the image carrier 2A is rougher. The threshold Th3 and the threshold Th4 may be lowered as the primary transfer current increases.

  In the present embodiment, there is no relationship between the threshold Th3 and the threshold Th5, but both may be related. For example, the threshold value Th5 may be increased as the threshold value Th3 is larger (that is, as the timing for switching to the adjustment mode is later). Similarly, the threshold Th5 may be increased as the threshold Th4 is increased.

  In the present embodiment, as shown in FIG. 7, the image forming apparatus 1 is provided with the three divided regions 4, but only two or four or more may be provided. Further, the width may be different for each divided region 4. Generally, as shown in FIG. 10, the lubricant is more easily supplied on the upstream side than on the downstream side. Therefore, as shown in FIG. 11, the divided area 4 may be provided so that the upstream side is narrower than the downstream side.

  The page width length L1 (length in the longitudinal direction of the image carrier 2A) may be shorter than the width length L2 of the region on the image carrier 2A where the toner image is formed. In such a case, the image forming apparatus 1 may consider the page width to be the length L2 and divide it into the divided areas 4.

  In this embodiment, the case where the toner and the lubricant are simultaneously supplied to the image carrier 2A has been described as an example. However, the present invention can be applied to a case where the toner and the lubricant are supplied separately.

  In addition, the configuration of the entire image forming apparatus 1 or each unit, the content of processing, the order of processing, and the like can be appropriately changed in accordance with the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 104 Coverage calculation part (calculation means)
105 Image formation controller (charging means)
2A Image carrier 2B Charging device (charging means)
2F Cleaning unit (removal means)

Claims (11)

An image carrier on which a toner image is formed with toner and a lubricant for separating the toner is supplied;
For each of a plurality of regions arranged in the longitudinal direction of the image carrier of the page to be printed, the amount of the toner necessary for printing a portion of the region of the page with respect to the width of the region A calculating means for calculating a ratio;
When the difference between the maximum value and the minimum value of the ratio of each of the plurality of regions exceeds a threshold value, the image carrier is charged using a stronger AC voltage than when the difference does not exceed the threshold value. Charging means;
Removing means for removing the toner and the lubricant remaining on the image carrier after the toner image is transferred from the image carrier to another medium;
An image forming apparatus comprising: An image carrier on which a toner image is formed with toner and a lubricant for separating the toner is supplied;
For each of a plurality of regions arranged in the longitudinal direction of the image carrier of the page to be printed, the amount of the toner necessary for printing a portion of the region of the page with respect to the width of the region A calculating means for calculating a ratio;
The first number of times that the difference between the maximum value and the minimum value of the ratios of each of the plurality of regions exceeds the threshold value is more than a predetermined number of times than the second number of times that the difference does not exceed the threshold value. A charging means for charging the image carrier using an alternating voltage stronger than usual after entering the state;
Removing means for removing the toner and the lubricant remaining on the image carrier after the toner image is transferred from the image carrier to another medium;
An image forming apparatus comprising: The charging means charges the image carrier using the AC voltage until the predetermined number of printed pages is reached after entering the state.
The image forming apparatus according to claim 2. The predetermined number of times is smaller as the threshold value is larger.
The image forming apparatus according to claim 2. The predetermined number of times is smaller as the temperature or humidity around the image forming apparatus or the fixing unit is higher.
The image forming apparatus according to claim 2. The predetermined number of times is smaller as the printing speed is faster,
The image forming apparatus according to claim 2. The predetermined number of times is smaller as the charge amount of the toner is larger.
The image forming apparatus according to claim 2. The predetermined number of times is less as the surface of the image carrier is rougher.
The image forming apparatus according to claim 2. The plurality of regions are narrower as they are closer to the lubricant supplier.
The image forming apparatus according to claim 1. An image defect reduction method in an image forming apparatus having an image carrier on which a toner image is formed with toner and a lubricant for separating the toner is supplied,
For each of a plurality of regions arranged in the longitudinal direction of the image carrier of the page to be printed, the amount of the toner necessary for printing a portion of the region of the page with respect to the width of the region Calculate the percentage,
When the difference between the maximum value and the minimum value of the ratio of each of the plurality of regions exceeds a threshold value, the image carrier is charged using a stronger AC voltage than when the difference does not exceed the threshold value. ,
An image defect reduction method characterized by the above. A computer program used in an image forming apparatus having a toner image formed with toner and an image carrier to which a lubricant for separating the toner is supplied,
In the image forming apparatus,
For each of a plurality of regions arranged in the longitudinal direction of the image carrier of the page to be printed, the amount of the toner necessary for printing a portion of the region of the page with respect to the width of the region Run the calculation process to calculate the percentage,
When the difference between the maximum value and the minimum value of the ratio of each of the plurality of regions exceeds a threshold value, the image carrier is charged using a stronger AC voltage than when the difference does not exceed the threshold value. Execute charging process,
A computer program characterized by the above.

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