Image forming apparatus

Abstract

To provide an image forming apparatus that can reduce unnecessary toner consumption and satisfactorily remove filming.SOLUTION: A toner pattern Kp for scraping that is a toner image pattern not transferred to a recording medium is partitioned into a plurality of areas K1-K8 in an orthogonal direction orthogonal to a surface movement direction of an intermediate transfer belt 17 that is an image carrier. An input toner amount of respective areas of the toner pattern Kp for scraping input to the cleaning member is set based on a cumulative toner amount input to portions of the cleaning member corresponding to the areas from when the previous toner image pattern is input to the cleaning member until the present time.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] Conventionally, an image forming apparatus is known that includes an image carrier, a transfer member that transfers a toner image on the image carrier to a recording medium, and a cleaning member that cleans the surface of the image carrier, and forms a toner image pattern that is not transferred to the recording medium on the image carrier.

[0003] Patent Document 1 describes setting the toner amount of a solid toner band as a toner image pattern to be formed based on the toner amount consumed in forming a toner image transferred to a recording medium from the time when the solid toner band was formed last time to the current time.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there has been a problem that sufficient removal of filming cannot be achieved while suppressing wasteful toner consumption.

Means for Solving the Problems

[0005] In order to solve the above-described problems, the present invention provides an image forming apparatus including an image carrier, a transfer member that transfers a toner image on the image carrier to a recording medium, and a cleaning member that cleans the surface of the image carrier, and forms a toner image pattern that is not transferred to the recording medium on the image carrier. An adhesion amount detection means is provided which is disposed opposite to the surface of the image carrier and detects the toner adhesion amount of the toner image. The toner image pattern is divided into a plurality of regions in a direction orthogonal to the surface movement direction of the image carrier, and the input toner amount of each region input to the cleaning member of the toner image pattern is set based on the cumulative toner amount input to the location of the cleaning member corresponding to the region from the time when the previous toner image pattern was input to the cleaning member to the current time. The input toner amount with respect to the cumulative toner amount in the region of the toner image pattern corresponding to the adhesion amount detection region of the adhesion amount detection means is larger than that in other regions. It is characterized by the above.

Effects of the Invention

[0006] According to the present invention, it is possible to suppress wasteful toner consumption and to satisfactorily remove filming.

Brief Description of the Drawings

[0007]

Figure 1

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Figure 5

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Figure 11

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the redundant description will be simplified or omitted as appropriate.

[0009] FIG. 1 is a schematic configuration diagram of a tandem color copier (hereinafter simply referred to as a copier), which is an image forming apparatus according to the present embodiment. In FIG. 1, a tandem color copier 1 (hereinafter simply referred to as a copier) as an image forming apparatus includes a document conveyance unit 3 that conveys a document to a document reading unit, and a document reading unit 4 that reads image information of the document. The copier also includes a paper discharge tray 5 on which an output image is stacked, and a paper supply unit 7 that houses a sheet of paper P as a recording medium.

[0010] The copier 1 also includes a registration roller 9 (timing roller) that adjusts the conveyance timing of the sheet of paper P, and photosensitive drums 11Y, 11M, 11C, 11BK as latent image carriers on which toner images of respective colors (yellow, magenta, cyan, black) are formed. The copier 1 also includes a charging device 12 that uniformly charges the surfaces of the respective photosensitive drums 11Y, 11M, 11C, 11BK, and a writing unit (exposure unit) 6 that emits laser light based on input image information and writes an electrostatic latent image on the respective photosensitive drums 11Y, 11M, 11C, 11BK. The copier 1 also includes a developing device 13 that develops the electrostatic latent image written on the respective photosensitive drums 11Y, 11M, 11C, 11BK. The copier 1 also includes a primary transfer bias roller 14 that overlaps and transfers the toner image formed on the respective photosensitive drums 11Y, 11M, 11C, 11BK onto the sheet of paper P.

[0011] Further, the copying machine 1 includes an intermediate transfer belt 17 as an image carrier on which toner images of a plurality of colors are superposed and transferred, and a secondary transfer roller 18 as a transfer member for transferring the color toner image on the intermediate transfer belt 17 onto the paper P. The copying machine 1 also includes a fixing device 20 for fixing the unfixed image on the paper P, and toner containers 28 containing toner of each color (yellow, cyan, magenta, black) for supplying to the developing device 13. The copying machine 1 further includes a belt cleaning device 30 for removing the toner (untransferred toner) adhering to the surface of the intermediate transfer belt 17. Additionally, the copying machine 1 includes a waste toner collection container 80 for collecting the untransferred toner removed by the belt cleaning device 30 or the like as waste toner.

[0012] Hereinafter, the operation during normal color image formation in the image forming apparatus will be described. First, the original document is conveyed from the document table by the conveying rollers of the document conveying unit 3 and placed on the contact glass of the document reading unit 4. Then, in the document reading unit 4, the image information of the original document placed on the contact glass is optically read.

[0013] Specifically, the document reading unit 4 scans the image of the original document on the contact glass while irradiating light emitted from the illumination lamp, and forms an image of the light reflected by the original document on the color sensor via a mirror group and a lens. The color image information of the original document is read by the color sensor for each color-separated light of RGB (red, green, blue), and then converted into an electrical image signal. Further, based on the RGB color-separated image signals, the image processing unit performs processes such as color conversion processing, color correction processing, and spatial frequency correction processing to obtain color image information of yellow, magenta, cyan, and black.

[0014] The image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 6. Then, laser light L (see FIG. 2) based on the image information of each color is emitted from the writing unit 6 toward the surfaces of the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK, respectively.

[0015] On one hand, the four photoreceptor drums 11Y, 11M, 11C, and 11BK are each rotating in the clockwise direction in FIG. 1. First, the surfaces of the photoreceptor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portions facing the charging device 12 (charging process). In this way, a charging potential is formed on the surfaces of the photoreceptor drums 11Y, 11M, 11C, and 11BK. Then, the surfaces of the charged photoreceptor drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of their respective laser lights.

[0016] In the writing unit 6, laser lights corresponding to the image signals are emitted from the four light sources respectively for each color. Each laser light will pass through a different optical path for each of the yellow, magenta, cyan, and black color components (exposure process).

[0017] The laser light corresponding to the yellow component is irradiated onto the surface of the first photoreceptor drum 11Y from the left side of the paper surface. At this time, the laser light of the yellow component is scanned in the rotation axis direction (main scanning direction) of the photoreceptor drum 11Y by a high-speed rotating polygon mirror. In this way, an electrostatic latent image corresponding to the yellow component is formed on the surface of the photoreceptor drum 11Y after being charged by the charging device 12.

[0018] Similarly, the laser light corresponding to the magenta component is irradiated onto the surface of the second photoreceptor drum 11M from the left of the paper surface, and an electrostatic latent image corresponding to the magenta component is formed. The laser light of the cyan component is irradiated onto the surface of the third photoreceptor drum 11C from the left of the paper surface, and an electrostatic latent image of the cyan component is formed. The laser light of the black component is irradiated onto the surface of the fourth photoreceptor drum 11BK from the left of the paper surface, and an electrostatic latent image of the black component is formed.

[0019] After that, the surfaces of the photoreceptor drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color are formed reach the positions facing the developing devices 13 respectively. Then, toners of each color are supplied from each developing device 13 onto the photoreceptor drums 11Y, 11M, 11C, and 11BK, and the latent images on the photoreceptor drums 11Y, 11M, 11C, and 11BK are developed (developing process).

[0020] After the developing process, the surfaces of the photoreceptor drums 11Y, 11M, 11C, and 11BK reach the opposing portions with the intermediate transfer belt 17 as the image carrier respectively. Here, at each opposing portion, a primary transfer bias roller 14 is installed so as to contact the inner peripheral surface of the intermediate transfer belt 17. And at the position of the primary transfer bias roller 14, the toner images of each color formed on the photoreceptor drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and primarily transferred onto the intermediate transfer belt 17 (this is the primary transfer process).

[0021] After the transfer process, the surfaces of the photoreceptor drums 11Y, 11M, 11C, and 11BK reach the opposing positions with the cleaning unit 15 respectively. And at the cleaning unit 15, the untransferred toner remaining on the photoreceptor drums 11Y, 11M, 11C, and 11BK is removed and recovered (this is the cleaning process). Note that the untransferred toner removed and recovered by the cleaning unit 15 is conveyed and recovered as waste toner into the waste toner recovery container 80 via the conveyance path. Thereafter, the surfaces of the photoreceptor drums 11Y, 11M, 11C, and 11BK pass through the charge removal unit, and a series of image forming processes on the photoreceptor drums 11Y, 11M, 11C, and 11BK are completed.

[0022] On the other hand, the intermediate transfer belt 17 (image carrier) on which the toner images of each color on the photoreceptor drums 11Y, 11M, 11C, and 11BK are superposed and primarily transferred runs in the counterclockwise direction in FIG. 1 and reaches the opposing position with the secondary transfer roller 18. The secondary transfer roller 18 contacts the intermediate transfer belt 17 to form a secondary transfer nip which is a transfer nip. At this secondary transfer nip, the color toner image carried on the intermediate transfer belt 17 is secondarily transferred onto the paper P (this is the secondary transfer process).

[0023] A secondary transfer bias is applied to the opposing roller 18A that faces the secondary transfer roller 18 via the intermediate transfer belt 17, and the secondary transfer roller 18 is electrically grounded. When secondarily transferring the color toner image on the intermediate transfer belt 17 onto the paper P, a transfer bias of the negative polarity, which is the normal charging polarity of the toner, is applied to the opposing roller 18A, and the negatively charged toner of the normal charge on the intermediate transfer belt is repulsively transferred onto the paper P.

[0024] The surface of the intermediate transfer belt 17 after the secondary transfer process reaches the position of the belt cleaning device 30. The belt cleaning device 30 has a cleaning blade 31 as a cleaning member. The toner (untransferred toner) attached to the intermediate transfer belt 17 is removed by this cleaning blade 31. The toner removed by the cleaning blade is conveyed via a conveyance path and recovered as waste toner in the waste toner collection container 80.

[0025] Here, the paper P conveyed between the intermediate transfer belt 17 and the secondary transfer roller 18 (the secondary transfer nip) is conveyed from the paper feed unit 7 via the registration roller 9 and the like. Specifically, the paper P fed by the paper feed roller 8 from the paper feed unit 7 that stores the paper P is guided to the registration roller 9 after passing through a conveyance guide. The paper P that has reached the registration roller 9 is conveyed in synchronization toward the secondary transfer nip.

[0026] The paper P onto which the full-color image has been transferred in the secondary transfer process is then guided to the fixing device 20. In the fixing device 20, the color image is fixed onto the paper P at the nip between the fixing roller and the pressure roller. Then, the paper P after the fixing process is discharged outside the apparatus body as an output image by the discharge roller, stacked on the discharge tray 5, and a series of image forming processes is completed.

[0027] In order to stabilize the image quality with respect to environmental variations and over time, this copying machine performs control called process control at a predetermined timing. FIG. 2 is a schematic diagram for explaining a pattern for image quality adjustment on the intermediate transfer belt.

[0028] The pattern for image quality adjustment is a gradation pattern and is composed of a plurality of toner patches with different image densities. The pattern for image quality adjustment is formed at positions facing the optical sensor of the intermediate transfer belt 17 (the center in the width direction and both ends). In the example shown in FIG. 2, patterns for image quality adjustment of black, cyan, magenta, and yellow are formed from top to bottom.

[0029] The optical sensor unit 40 has optical sensors 40R, 40C, and 40F as a plurality of adhesion amount detection means arranged at predetermined intervals in the belt width direction of the intermediate transfer belt 17. Each optical sensor outputs a signal corresponding to the light reflectance of the intermediate transfer belt 17 and the patterns for image quality adjustment PtK, PtC, PtM, and PtY on the intermediate transfer belt 17, and detects the toner adhesion amount. The copying machine 1 adjusts imaging conditions such as the developing bias Vb based on the detected toner adhesion amount.

[0030] The optical sensors 40R and 40F arranged so as to face the width direction end regions of the intermediate transfer belt 17 are arranged outside the paper passage region. Therefore, the copying machine can perform image quality adjustment such as image density adjustment during the printing operation. Specifically, as shown in FIG. 3, a pattern for image quality adjustment is formed outside the paper passage region, and the toner adhesion amount of the pattern for image quality adjustment is detected by the optical sensors 40R and 40F. Then, based on the toner adhesion amount detected by the optical sensors 40R and 40F, the developing bias and the like are adjusted to adjust the image density and the like.

[0031] The base components of the toner, silica, titanium oxide added to the toner, and other so-called external additives of the toner are transferred from the photoreceptor drum 11 to the intermediate transfer belt 17. The external additives of the toner transferred to the intermediate transfer belt 17 may adhere to the intermediate transfer belt 17, causing filming on the intermediate transfer belt 17. Further, when there is a lubricant application unit for applying a lubricant to the surface of the photoreceptor drum 11, in addition to the external additives of the toner, various components contained in the lubricant are also transferred from the photoreceptor drum 11 to the intermediate transfer belt 17. Then, the external additives of the toner and the lubricant may interact with each other, worsening the filming of the intermediate transfer belt 17. Furthermore, at the secondary transfer nip, paper dust may be transferred from the paper P to the intermediate transfer belt 17 and adhered thereto, causing paper dust filming to occur.

[0032] Such filming of the intermediate transfer belt 17 is caused by the external pressure (mainly the contact pressure with the photoreceptor drum) on the intermediate transfer belt 17, causing filming substances such as external additives of the toner such as silica and various components contained in the lubricant to adhere. When filming occurs on the intermediate transfer belt 17, when a solid black image or a halftone image is output, toner does not adhere to the portion corresponding to the filming, resulting in abnormal images such as so-called white missing where it appears white.

[0033] Also, when filming occurs, the glossiness of the belt decreases. Therefore, when filming occurs in the opposing regions of the intermediate transfer belt 17 with the optical sensors 40R, 40C, and 40F, the output signal changes, and it becomes impossible to accurately detect the adhesion amount of the tone pattern on the intermediate transfer belt. There is also a problem that the output of the optical sensor is not stable due to unevenness in the filming state and correct image adjustment cannot be performed.

[0034] Furthermore, filming may reduce the cleaning performance of the cleaning blade 31. In the belt width direction, there is a high chance that a tone pattern with a large amount of adhesion per unit area is input at a position corresponding to the arrangement positions of the optical sensors 40R, 40C, and 40F of the cleaning blade 31. Therefore, when filming occurs in the area facing the optical sensors 40R, 40C, and 40F of the intermediate transfer belt 17, there is a high risk of cleaning failure (toner leakage) when the tone pattern is input to the cleaning blade 31.

[0035] The above-mentioned filming can be scraped off by the toner staying at the contact portion (hereinafter referred to as "cleaning portion") between the cleaning blade 31 and the surface of the intermediate transfer belt 17, and can be removed from the surface of the intermediate transfer belt 17. Specifically, the filming on the surface of the intermediate transfer belt is scraped off by the unevenness on the surface of the toner staying at the cleaning portion and the pressure of the cleaning blade 31 applied to the toner.

[0036] Therefore, in order to suppress the filming of the intermediate transfer belt 17, the copying machine 1 forms a scraping toner pattern on the intermediate transfer belt 17 at a predetermined timing. Then, by inputting this scraping toner pattern to the cleaning blade 31, a sufficient amount of toner stays at the cleaning portion.

[0037] FIG. 4 is a diagram for explaining the formation position of the toner pattern formed on the intermediate transfer belt 17 when three consecutive prints are performed in a normal image forming operation. As shown in FIG. 4, the formation positions of the toner pattern include 1. A position before the first sheet passed through the secondary transfer nip 2. Outside the width of the sheet passed through the secondary transfer nip 3. Between sheets 4. A position after the last sheet has passed through the secondary transfer nip and so on. 2. is the position where a gradation pattern, which is a pattern for image quality adjustment, is formed, and 1., 3., and 4. are the formation positions of the scraping toner pattern. The scraping toner pattern is a belt-shaped pattern that is long in the belt width direction (main scanning direction) and has the same width as the width of the toner image formation possible region where the toner image on the intermediate transfer belt 17 can be formed. In the present embodiment, the width of the toner image formation possible region of the intermediate transfer belt 17 is the length in the main scanning direction where toner can be supplied on the photoreceptor drum of the developing device 13, and is shorter than the belt width of the intermediate transfer belt.

[0038] When the scraping toner pattern on the intermediate transfer belt passes through the secondary transfer nip, a positive bias is applied to the opposing roller 18A. By applying a positive bias to the opposing roller 18A, the scraping toner pattern is electrostatically attracted to the intermediate transfer belt 17 so that the scraping toner pattern is not transferred to the secondary transfer roller 18 or the paper P.

[0039] The cleaning blade 31 receives the transfer residual toner remaining on the intermediate transfer belt without being secondarily transferred to the paper. The filming of the intermediate transfer belt is also scraped off by the transfer residual toner input to the cleaning blade 31. The transfer residual toner input to the cleaning blade 31 is not uniform in the belt width direction (main scanning direction). In the belt width direction, at locations where the image area ratio of the image transferred to the paper is high, a large amount of transfer residual toner is input, but at locations where the image area ratio is low, the amount of input transfer residual toner is small. As a result, in the belt width direction of the intermediate transfer belt, the amount of filming removal by the transfer residual toner is different, and the amount of filming on the intermediate transfer belt is different in the belt width direction.

[0040] In the conventional toner pattern for scraping, the length in the belt conveyance direction (sub-scanning direction) was constant in the belt width direction, and the toner adhesion amount per unit area was also constant in the belt width direction. Therefore, the amount of input toner to the cleaning blade 31 was constant in the belt width direction. Thus, in a location where the input of residual transfer toner in the belt width direction was large and the filming amount was small, excessive toner was input to the cleaning blade 31 by the scraping toner pattern, resulting in wasted toner consumption. On the other hand, in a location where the input of residual transfer toner in the belt width direction was small and the filming amount was large, the amount of input toner to the cleaning blade by the scraping toner pattern was insufficient, and there was a possibility that sufficient filming removal could not be achieved.

[0041] Therefore, as shown in FIG. 5, this copying machine divides the scraping toner pattern Kp into a plurality of regions, and sets the amount of toner input to the cleaning blade 31 in each region based on the amount of toner input to the location of the cleaning blade corresponding to that region.

[0042] In the example shown in this FIG. 5, the scraping toner pattern is divided into eight regions K1 to K8, and the length in the belt conveyance direction (sub-scanning direction) in each region is changed according to the amount of toner input to the location of the cleaning blade 31 corresponding to that region. In FIG. 5, in the locations of the intermediate transfer belt 17 corresponding to the regions K1 and K8 at both ends of the scraping toner pattern Kp, no toner image to be transferred to the paper is formed. Therefore, there is no residual transfer toner input to the locations of the cleaning blade 31 corresponding to the regions K1 and K8. Accordingly, in the locations corresponding to these regions K1 and K8, since the scraping of filming by the residual transfer toner is not performed, there is a possibility that a large amount of filming occurs. Thus, the regions K1 and K8 have the maximum value for the amount of input toner to the cleaning blade 31, and the belt width direction length of the regions K1 and K8 of the scraping toner pattern is made the longest.

[0043] At locations corresponding to regions K5 to K7 of the toner pattern Kp for scraping the intermediate transfer belt 17, a photo toner image G2 with a high image area ratio is formed. Therefore, at these locations, a large amount of residual transfer toner is generated, and the amount of residual transfer toner input to the cleaning blade 31 is large. Thus, at these locations, the filming of the intermediate transfer belt 17 is to some extent scraped off by the residual transfer toner input to the cleaning blade 31. Therefore, the amount of filming of the intermediate transfer belt 17 is small. Thus, at these locations, even if the amount of input toner input to the cleaning blade 31 is small, the filming of the intermediate transfer belt 17 can be sufficiently removed. Therefore, for regions K5 to K7 of the scraping toner pattern Kp, the amount of input toner is set small, and the length in the belt width direction is shortened.

[0044] At locations corresponding to regions K2 to K3 of the toner pattern Kp for scraping the intermediate transfer belt 17, a character toner image G1 with a low image area ratio is formed. Therefore, at these locations, the residual transfer toner is small. Thus, at these locations, the filming of the intermediate transfer belt 17 is not much removed by the residual transfer toner input to the cleaning blade 31. Therefore, for regions K2 to K3 of the scraping toner pattern, the amount of input toner is set relatively large, and the length in the belt width direction is set between regions K1, K8 and regions K5 to K7.

[0045] At locations corresponding to region K4 of the toner pattern Kp for scraping the intermediate transfer belt 17, a part of the character toner image G1 and a part of the photo toner image G2 are formed. Therefore, the image area ratio at that location is higher than that of the location corresponding to regions K2 to K3 and lower than that of the location corresponding to regions K5 to K7. Therefore, the amount of residual transfer toner input to the cleaning blade 31 is also an amount between the amount of residual transfer toner at the location corresponding to regions K2 to K3 and the amount of residual transfer toner at the location corresponding to regions K5 to K7. Accordingly, for region K4 of the scraping toner pattern Kp, the amount of input toner is set between the amount of input toner in regions K2 to K3 and the amount of input toner in regions K5 to K7.

[0046] The toner used to form the scraping toner pattern Kp is preferably the toner with the highest scraping effect for filming among the toners of Y, M, C, and K. If there is no difference in the scraping effect for filming, at least one of the toners of Y, M, C, and K may be used. Also, since a toner with less deterioration has no dropout of external additives and the like and has a high scraping effect, it is preferably a K-color toner with a high usage frequency and few toners remaining in the developing device for a long time and few deteriorated toners to form the scraping toner pattern.

[0047] In this way, by setting the input toner amounts of regions K1 to K8 based on the amount of residual transferred toner input to the locations corresponding to the respective regions K1 to K8 of the scraping toner pattern of the cleaning blade 31, the following effects can be obtained. That is, it is an effect that can suppress wasteful toner consumption and can satisfactorily suppress filming on the intermediate transfer belt 17.

[0048] FIG. 6 is a block diagram regarding the setting of the input toner amount for each region of the scraping toner pattern Kp. As shown in FIG. 6, the control unit 100 includes an image forming controller 101, a cumulative input toner amount calculation unit 102, a storage unit 103, an input toner amount setting unit 104, a scraping toner pattern setting unit 105, and the like.

[0049] The image forming controller 101 controls the writing unit 6, charging devices and developing devices of each color, etc., and forms a toner image based on the input image data by controlling these. The storage unit 103 is composed of a known non-volatile memory such as an HDD or a flash memory. The storage unit 103 stores the cumulative input toner amount of each location input to the locations corresponding to the respective regions K1 to K8 of the scraping toner pattern of the cleaning blade 31 from the previous formation of the scraping toner pattern to the current time.

[0050] The cumulative input toner amount calculation unit 102 calculates the cumulative input toner amount from the previous scraping toner pattern formation to the current time at the location corresponding to each area of the scraping toner pattern Kp of the cleaning blade 31. Image data to be formed on the paper is input to the cumulative input toner amount calculation unit 102. The cumulative input toner amount calculation unit 102 obtains the image area ratio at the location corresponding to each area K1 to K8 of the scraping toner pattern Kp of the cleaning blade 31 based on this image data. Then, from the obtained image area ratio at each location, the toner adhesion amount of the solid toner image on the intermediate transfer belt obtained in advance, and the assumed secondary transfer rate, the remaining transfer toner amount at each location is estimated. This estimated remaining transfer toner amount at each location is integrated into the cumulative input toner amount at each location stored in the storage unit 103 as the input toner amount input to each location of the cleaning blade in the current image forming operation.

[0051] The toner adhesion amount of the solid toner image on the intermediate transfer belt can be obtained by forming a solid toner image on the intermediate transfer belt and detecting the adhesion amount of the solid toner image with an optical sensor. As the assumed secondary transfer rate, a fixed value obtained in advance may be used, or it may be changed based on factors affecting the secondary transfer rate, such as the degree of toner deterioration, the use environment, and the image area ratio. Also, a test pattern consisting of a solid image may be periodically formed on the paper, and the test pattern formed on the paper may be read by a scanner or the like to obtain the secondary transfer rate. Further, optical sensors may be arranged in an array between the secondary transfer nip and the cleaning blade 31, and the remaining transfer toner amount input to each location corresponding to each area K1 to K8 of the cleaning blade 31 may be detected by the optical sensors.

[0052] In addition to the transferred residual toner, an image quality adjustment pattern such as a gradation pattern is input to the cleaning blade 31. Therefore, the cumulative input toner amount calculation unit 102 also integrates the toner amount of the image quality adjustment pattern input to the cleaning blade 31 into the cumulative input toner amount. The toner amount of the image quality adjustment pattern is grasped as follows. The cumulative input toner amount calculation unit 102 grasps from the formation position of the image quality adjustment pattern in which region of the scraping toner pattern Kp the image quality adjustment pattern is formed. For example, as shown in FIG. 3, when the image quality adjustment pattern is formed at a position facing the rear optical sensor 40R and a position facing the front optical sensor 40F, it is grasped that the image quality adjustment pattern is formed at a position corresponding to the regions K1 and K8.

[0053] The image quality adjustment pattern is input to the cleaning blade 31 as it is without secondary transfer. Therefore, the input toner amount is calculated from the toner adhesion amount per unit area of the image quality adjustment pattern detected by the optical sensor and the area of the image quality adjustment pattern, and integrated into the cumulative input toner amount. Further, the toner adhesion amount per unit area of the image quality adjustment pattern may be estimated from the image formation conditions (charging bias, exposure amount, development bias, etc.) when forming the image quality adjustment pattern.

[0054] The input toner amount setting unit 104 sets the input toner amounts for the respective regions K1 to K8 of the scraping toner pattern Kp. Specifically, when forming the scraping toner pattern Kp, the input toner amount setting unit 104 reads out the cumulative input toner amounts at the respective locations from the storage unit 103. Then, based on the cumulative input toner amounts at the read-out respective locations, the input toner amounts for the respective regions K1 to K8 of the scraping toner pattern Kp are set. For example, the cumulative input toner amount is subtracted from the target toner amount of the scraping toner pattern to set the input toner amounts to the cleaning blade 31 for the respective regions K1 to K8.

[0055] The scraping toner pattern setting unit 105 sets the belt conveyance direction lengths of the respective regions K1 to K8 based on the input toner amounts of the respective regions K1 to K8 set by the input toner amount setting unit 104. Then, it constructs scraping toner pattern data with the belt conveyance direction lengths set for each region, and transmits the scraping toner pattern data to the image forming controller 101. The image forming controller 101 controls the writing unit 6 and the like based on the scraping toner pattern data to form a scraping toner pattern Kp as shown in FIG. 5 on the intermediate transfer belt 17. Further, after forming the scraping toner pattern Kp, it resets the cumulative input toner amount stored in the storage unit 103.

[0056] FIG. 7 is a diagram for explaining an example of forming the scraping toner pattern Kp at the position between sheets of paper and after the last sheet has passed through the secondary transfer nip. As shown in FIG. 7, the image transferred onto the first sheet of paper is the same as the image shown in FIG. 5, but in FIG. 7, an image quality adjustment pattern Pt is formed outside the paper passage area. Therefore, the toner amount of this image quality adjustment pattern Pt is integrated into the cumulative input toner amounts at the locations corresponding to the regions K1 and K8 of the scraping toner pattern Kp. Accordingly, the belt conveyance direction lengths of the regions K1 and K8 of the scraping toner pattern Kp formed between the first and second sheets of paper are shorter than those in FIG. 5, and the input toner amounts of the regions K1 and K8 are reduced.

[0057] From the formation of the previous scraping toner pattern to the formation of the scraping toner pattern formed between the second and third sheets of paper, only the transfer residual toner of the toner image transferred to the second sheet of paper is input to the cleaning blade 31. There is no toner input to the cleaning blade 31 at the locations corresponding to the regions K1, K7, and K8 of the cleaning blade 31 from the previous time to this time. Therefore, the input toner amount in the regions K1, K7, and K8 becomes the target input toner amount, and the length in the belt conveyance direction is maximized. Also, the image area ratio of the character toner image G1 at the locations corresponding to the regions K2 and K3 is higher than the image area ratio of the character toner image G1 at the locations corresponding to the regions K5 and K6. Therefore, more transfer residual toner is input to the locations corresponding to the regions K2 and K3 of the cleaning blade 31 than to the locations corresponding to the regions K5 and K6. Consequently, since the cumulative toner amount at the locations corresponding to the regions K2 and K3 is larger than that at the locations corresponding to the regions K5 and K6, the length of the regions K2 and K3 in the belt conveyance direction is shorter than the length of the regions K5 and K6 in the belt conveyance direction.

[0058] On the third sheet of paper, an image is formed only at the locations corresponding to the regions K6 and K7. Therefore, only the locations corresponding to the regions K6 and K7 of the cleaning blade 31 are input with toner from the formation of the previous scraping toner pattern Kp to the formation of the current scraping toner pattern. Thus, for the scraping toner pattern formed at the position after the final sheet has passed through the secondary transfer nip, the input toner amount set only for the regions K6 and K7 is less than the target input toner amount, and the length in the belt conveyance direction becomes shorter.

[0059] FIG. 8 is a diagram for explaining an embodiment of forming a scraping toner pattern Kp at the position after the final sheet has passed through the secondary transfer nip. In the configuration shown in FIG. 8, compared with the configuration shown in FIG. 7, the formation frequency of the scraping toner pattern Kp is lower. Therefore, compared with the configuration shown in FIG. 7, the set target input toner amount is larger.

[0060] In FIG. 8, the remaining toner amount of the toner image transferred onto the first to third sheets of paper and the toner amount of the image quality adjustment pattern Pt are integrated as the cumulative input toner amount. The scraping toner pattern Kp is formed by setting the input toner amounts for each of the regions K1 to K8 based on the cumulative input toner amount at the location corresponding to each region and the target input toner amount. Then, based on the set input toner amounts for each region, the belt conveyance direction lengths for each region are set, and the scraping toner pattern Kp as shown in FIG. 8 is formed.

[0061] FIG. 9 is a diagram for explaining an embodiment in which a scraping toner pattern is formed at a position before the first sheet of paper passed through the secondary transfer nip. In the case shown in FIG. 9, the remaining toner amount and the toner amount of the image quality adjustment pattern Pt input to the cleaning blade 31 during the previous printing operation are integrated as the cumulative input toner amount, and based on this cumulative input toner amount, the input toner amounts for each of the regions K1 to K8 are set. Then, based on the set input toner amounts for each of the regions K1 to K8, the belt conveyance direction lengths for each of the regions K1 to K8 are set, and the scraping toner pattern Kp as shown in FIG. 9 is formed.

[0062] The remaining toner amount of the image transferred onto the first to third sheets of paper shown in FIG. 9 and the toner amount of the image quality adjustment pattern Pt are integrated as the cumulative input toner amount. This cumulative input toner amount is used for setting the input toner amounts for each of the regions K1 to K8 of the scraping toner pattern Kp formed at a position before the first sheet of paper during the next printing operation.

[0063] The decrease in the detection accuracy of the adhesion amount of the optical sensors 40R, 40C, and 40F due to filming has a higher degree of influence of filming than abnormal images such as white spots due to filming, and there is a risk that the detection accuracy of the adhesion amount will decrease even with a small amount of filming. Therefore, at the locations where the optical sensors 40R, 40C, and 40F of the intermediate transfer belt 17 face, it is preferable to increase the amount of toner input to the cleaning blade 31 compared to other locations to scrape off more filming. Therefore, it is preferable to perform weighting so that the input toner amount increases for the region corresponding to the arrangement positions of the optical sensors 40R, 40C, and 40F of the scraping toner pattern Kp.

[0064] FIG. 10 is a diagram for explaining an embodiment in which weighting is performed so that the input toner amount increases for the region corresponding to the arrangement positions of the optical sensors 40R, 40C, and 40F of the scraping toner pattern Kp. In FIG. 10, the region K1, the region K4, and the region K8 of the scraping toner pattern Kp correspond to the arrangement positions of the optical sensors 40R, 40C, and 40F. The cumulative input toner amount in the example shown in FIG. 10 is the same as that in the example shown in FIG. 8, but the belt conveyance direction lengths of the regions K1, K4, and K8 corresponding to the arrangement positions of the optical sensors 40R, 40C, and 40F are longer than those of the scraping toner pattern shown in FIG. 8. This is because for the regions K1, K4, and K8, the input toner amount calculated based on the cumulative input toner amount and the target input toner amount is multiplied by a preset weighting coefficient α (α > 1) to increase the input toner amount. As a result, for these regions K1, K4, and K8, even if the cumulative input toner amount is the same as that of other regions, the set input toner amount becomes larger than that of other regions, and the belt conveyance direction length becomes longer.

[0065] Thus, for regions K1, K4, and K8, by weighting the input toner amount to increase it, the areas facing the optical sensors 40R, 40C, and 40F of the intermediate transfer belt 17 are less likely to be filmed compared to other areas. Therefore, it is possible to suppress a decrease in the detection accuracy of the toner adhesion amount due to filming.

[0066] Note that by making the target input toner amounts of regions K1, K4, and K8 of the scraping toner pattern Kp larger than the target toner input amounts of other regions, the input toner amounts of these regions K1, K4, and K8 may be increased.

[0067] FIG. 11 is a diagram for explaining an embodiment in which the toner adhesion amount per unit area of each region K1 to K8 of the scraping toner pattern Kp is set based on the set input toner amount. Even in the configuration shown in FIG. 11, toner amounts corresponding to the filming amount are input to the locations corresponding to each of regions K1 to K8 of the cleaning blade 31, suppressing wasteful consumption of toner and enabling good removal of filming.

[0068] Note that in the above description, the scraping toner pattern is divided into eight regions, but the number of regions to be divided may be appropriately determined according to the configuration of the apparatus and the like. Also, in the above description, an embodiment in which the present invention is applied to an image forming apparatus using an intermediate transfer method has been described, but the present invention can also be applied to an image forming apparatus using a direct transfer method in which a toner image on a photoreceptor drum is directly transferred to a sheet as a recording medium. For this direct transfer method image forming apparatus, the image carrier corresponds to the photoreceptor drum, the transfer member corresponds to a transfer roller that abuts against the photoreceptor drum to form a transfer nip, and the cleaning member corresponds to a photoreceptor cleaning blade that cleans the surface of the photoreceptor.

[0069] What has been described above is an example, and specific effects are achieved for each of the following aspects. (Aspect 1) An image forming apparatus includes an image carrier such as an intermediate transfer belt 17, a transfer member such as a secondary transfer roller 18 that transfers a toner image on the image carrier to a recording medium such as paper, and a cleaning member such as a cleaning blade 31 that cleans the surface of the image carrier. In the image forming apparatus that forms a toner image pattern such as a scraping toner pattern Kp that is not transferred to the recording medium on the image carrier, the toner image pattern is divided into a plurality of regions K1 to K8 in a direction orthogonal to the surface movement direction of the image carrier. The input toner amount of each region input to the cleaning member of the toner image pattern is set based on the cumulative toner amount such as the cumulative input toner amount input to the location of the cleaning member corresponding to the region from the time when the previous toner image pattern was input to the cleaning member until the current time. When toner stays at the contact portion of the cleaning member with the image carrier, the filming of the image carrier is scraped off by the staying toner, and the filming of the image carrier is removed. When forming an image on the recording medium, the transfer residual toner remaining on the image carrier without being transferred to the recording medium is input to the cleaning member, and the filming is scraped off by the transfer residual toner input to the cleaning member. However, the toner amount of the toner image transferred to the recording medium often varies from each other in the direction orthogonal to the surface movement direction of the image carrier. As a result, the amount of transfer residual toner input to the cleaning member varies from each other in the orthogonal direction. Therefore, in the orthogonal direction, the filming amount on the surface of the image carrier varies in the orthogonal direction according to the amount of transfer residual toner input to the cleaning member. In Patent Document 1, where the toner image pattern is a solid toner band and the toner amount is constant in the orthogonal direction, in a portion where the amount of toner input to the cleaning member from the time when the previous toner image pattern was input to the cleaning member until the current time is large and filming is small, the toner input with respect to the filming amount is excessive, resulting in wasteful consumption of toner. On the other hand, in a portion where the amount of toner input to the cleaning member from the time when the previous toner image pattern was input to the cleaning member until the current time is small and filming cannot be sufficiently removed, the amount of toner input with respect to the filming amount is insufficient, causing a problem that sufficient filming removal cannot be achieved. In contrast, in this aspect, the toner image pattern is divided into a plurality of regions, and the amount of input toner to the cleaning member in each divided region is set based on the amount of toner input to the location corresponding to each region of the cleaning member from the time when the previous toner image pattern was input to the cleaning member until the current time. Thereby, according to the toner image pattern, it is possible to input the amount of toner corresponding to the filming amount at each location in the orthogonal direction of the image carrier to the cleaning member, suppress wasteful toner consumption, and satisfactorily remove the filming on the surface of the image carrier.

[0070] (Aspect 2) In Aspect 1, the cumulative toner amount such as the cumulative input toner amount at each location is calculated based on the amount of residual transfer toner at each location remaining on the image carrier without being transferred to at least the recording medium. According to this, as described in the embodiment, as the toner input to the location of the cleaning member corresponding to the region from the time when the previous toner image pattern was input to the cleaning member until the current time, there is residual transfer toner. Therefore, by using the amount of residual transfer toner, the cumulative toner amount can be grasped well.

[0071] (Aspect 3) In Aspect 2, the amount of residual transfer toner at each location is calculated based on the image area information of each location of the toner image transferred to the recording medium, the toner adhesion amount per unit area of the solid toner image on the image carrier, and the transfer rate. According to this, as described in the embodiment, the amount of residual transferred toner at each location input to the cleaning member can be estimated.

[0072] (Aspect 4) In Aspect 2 or 3, the cumulative toner amount such as the cumulative input toner amount at each location is the total value of the toner amount at each location of the image quality adjustment pattern Pt formed on the image carrier such as the intermediate transfer belt 17 and the residual transferred toner at each location. According to this, the cumulative toner amount can be grasped well.

[0073] (Aspect 5) In Aspect 4, the toner amount at each location of the image quality adjustment pattern is calculated based on the formation position in the orthogonal direction of the image quality adjustment pattern, the image area ratio of the image quality adjustment pattern, and the toner adhesion amount per unit area of the image quality adjustment pattern. As described in the embodiment, the toner amount of the image quality adjustment pattern at each location input to the cleaning member can be estimated.

[0074] (Aspect 6) In any one of Aspects 1 to 5, the length in the orthogonal direction of the toner image pattern such as the scraping toner pattern Kp is the length in the orthogonal direction of the toner image formation region where the toner image of the image carrier such as the intermediate transfer belt 17 can be formed. According to this, the filming of the toner image formation region of the image carrier can be removed.

[0075] (Aspect 7) In any one of Aspects 1 to 6, it is arranged to face the surface of the image carrier such as the intermediate transfer belt 17, and is provided with adhesion amount detection means such as optical sensors 40R, 40C, 40F for detecting the toner adhesion amount of the toner image, and the input toner amount with respect to the cumulative toner amount in the region of the toner image pattern (in this embodiment, regions K1, K4, K8) corresponding to the adhesion amount detection region of the adhesion amount detection means is larger than that of other regions. According to this, as described in the embodiment, filming at a location facing the adhesion amount detection means such as the optical sensors 40R, 40C, and 40F of the image carrier such as the intermediate transfer belt 17 can be scraped off by the toner of the toner image pattern input to the cleaning member more than other locations. Thereby, filming at a location facing the adhesion amount detection means of the image carrier can be satisfactorily removed, and the detection error of the adhesion amount detection means can be suppressed.

[0076] (Aspect 8) In any of Aspects 1 to 7, based on the set input toner amount, the length in the surface movement direction of the image carrier in each region of the toner image pattern is determined. According to this, the toner amount input to the location of the cleaning member corresponding to each region of the toner image pattern such as the scraping toner pattern Kp can be made the set input toner amount.

[0077] (Aspect 9) In any of Aspects 1 to 7, based on the set input toner amount, the toner adhesion amount per unit area in each region of the toner image pattern is set. According to this, the toner amount input to the location of the cleaning member corresponding to each region of the toner image pattern such as the scraping toner pattern Kp can be made the set input toner amount.

Explanation of Signs

[0078] 1: Copier 17: Intermediate transfer belt 18: Secondary transfer roller 18A: Opposing roller 30: Belt cleaning device 31: Cleaning blade 40: Optical sensor unit 40C: Optical sensor 40F: Optical sensor 40R: Optical sensor 100: Control unit 101: Image formation controller 102: Cumulative input toner amount calculation unit 103: Memory unit 104: Input toner amount setting unit 105: Scraping toner pattern setting unit G1: Character toner image G2: Photo toner image Kp: Scraping toner pattern P: Paper Pt: Image quality adjustment pattern

Prior art documents

Patent documents

[0079]

Patent Document 1

Claims

1. An image carrier, A transfer member for transferring the toner image on the image carrier to a recording medium, A cleaning member for cleaning the surface of the image carrier, and In an image forming apparatus for forming a toner image pattern that is not transferred to the recording medium on the image carrier, It is provided with adhesion amount detection means that is disposed opposite to the surface of the image carrier and detects the toner adhesion amount of the toner image, The toner image pattern is divided into a plurality of regions in a direction orthogonal to the surface movement direction of the image carrier, The input toner amount of each region input to the cleaning member of the toner image pattern is set based on the cumulative toner amount input to the location of the cleaning member corresponding to the region from the time when the previous toner image pattern was input to the cleaning member until the current time, An image forming apparatus, characterized in that the input toner amount with respect to the cumulative toner amount of the region of the toner image pattern corresponding to the adhesion amount detection region of the adhesion amount detection means is larger than that of other regions.

2. In the image forming apparatus according to Claim 1, An image forming apparatus, characterized in that the length of each region of the toner image pattern in the surface movement direction of the image carrier is set based on the set input toner amount.

3. In the image forming apparatus according to Claim 1, An image forming apparatus, characterized in that the toner adhesion amount per unit area of each region of the toner image pattern is set based on the set input toner amount.

4. An image carrier, A transfer member for transferring the toner image on the image carrier to a recording medium, A cleaning member for cleaning the surface of the image carrier, and In an image forming apparatus for forming a toner image pattern that is not transferred to the recording medium on the image carrier, The toner image pattern is divided into a plurality of regions in a direction orthogonal to the surface movement direction of the image carrier, The input toner amount of each region input to the cleaning member of the toner image pattern is set based on the cumulative toner amount input to the location of the cleaning member corresponding to the region from the time when the previous toner image pattern was input to the cleaning member until the current time, An image forming apparatus, characterized in that the length of each region of the toner image pattern in the surface movement direction of the image carrier is set based on the set input toner amount.

5. In the image forming apparatus according to any one of Claims 1 to 4, An image forming apparatus, wherein the cumulative toner amount at each position is calculated based on at least the amount of residual transfer toner at each position remaining on the image carrier without being transferred to the recording medium.

6. In the image forming apparatus according to claim 5, the amount of residual transfer toner at each position is calculated based on the image area information at each position of the toner image transferred to the recording medium, the toner adhesion amount per unit area of the solid toner image on the image carrier, and the transfer rate. An image forming apparatus characterized by that.

7. In the image forming apparatus according to claim 5 or 6, the cumulative toner amount at each position is the total value of the toner amount at each position of the image quality adjustment pattern formed on the image carrier and the residual transfer toner at each position. An image forming apparatus characterized by that.

8. In the image forming apparatus according to claim 7, the toner amount at each position of the image quality adjustment pattern is calculated based on the formation position in the orthogonal direction of the image quality adjustment pattern, the image area ratio of the image quality adjustment pattern, and the toner adhesion amount per unit area of the image quality adjustment pattern. An image forming apparatus characterized by that.

9. In the image forming apparatus according to any one of claims 1 to 8, the length in the orthogonal direction of the toner image pattern is the length in the orthogonal direction of the toner image forming region where the toner image can be formed on the image carrier. An image forming apparatus characterized by that.

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