Image forming device

Abstract

To provide an image formation apparatus which can suppress wasteful toner consumption and excellently remove filming.SOLUTION: An image formation apparatus comprises: an image carrier such as an intermediate transfer belt; a transfer member such as a secondary transfer roller which transfers a toner image on the image carrier to a recording medium such as a sheet; and a cleaning member such as a cleaning blade which cleans the surface of the image carrier. The image formation apparatus forms a toner image pattern such as a toner pattern for scraping that is not transferred to the recording medium on the image carrier. The input toner amount of the toner image pattern input to the cleaning member is set on the basis of a background contamination toner amount adhering to the image carrier surface.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Conventionally, there has been known an image forming apparatus 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 that forms a toner image pattern on the image carrier that is not transferred to the recording medium.

[0003] Patent document 1 describes an image forming device that forms a toner image pattern to remove filming from an intermediate transfer belt, which serves as an image carrier, and inputs this toner image pattern into the contact portion of a cleaning member with the image carrier. Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is a problem in that it is not possible to suppress unnecessary toner consumption and to sufficiently remove filming. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus 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 that forms a toner image pattern on the image carrier that is not transferred to the recording medium, the image forming apparatus comprising: an input toner amount to be input to the cleaning member for the toner image pattern based on an amount of background smear toner adhering to the image carrier, the input toner amount being determined based on the temperature and humidity of the apparatus; The toner image forming apparatus further includes an adhesion amount detecting means disposed opposite to the surface of the image carrier and detecting the amount of toner adhesion of the toner image, and the amount of input toner in a first region of the toner image pattern corresponding to the position of the adhesion amount detecting means is made larger than the amount of input toner in other regions in a direction perpendicular to the surface movement direction of the image carrier. It is characterized by the following. [Effects of the Invention]

[0006] According to the present invention, it is possible to suppress unnecessary toner consumption and to effectively remove filming. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a tandem color copying machine that is an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 4 is a schematic diagram illustrating an image quality adjustment pattern on an intermediate transfer belt. [Figure 3] 5A and 5B are schematic diagrams showing an example of an image quality adjustment pattern formed on an intermediate transfer belt when image adjustment is performed in parallel with a printing operation. [Figure 4] 5A and 5B are diagrams illustrating the positions where toner patterns are formed on the intermediate transfer belt. [Figure 5] FIG. 10 is a diagram for explaining the amount of toner input to a cleaning blade of a conventional toner scraping pattern. [Figure 6] 5A and 5B are diagrams for explaining setting of the input toner amount of the scraping toner pattern according to the present embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example in which the target input toner amount is increased in a high-temperature, high-humidity environment. [Figure 8] 10 is a schematic diagram showing an example of a scraping toner pattern in which the amount of input toner in an area corresponding to the arrangement position of an optical sensor is increased. FIG. [Figure 9] FIG. 10 is a diagram illustrating the width of an opposing region of a toner scraping pattern. [Figure 10] Schematic diagram of the reference plate used to measure the sensor spot diameter. [Figure 11] FIG. 10A is a diagram showing an example of the acquired specular reflection output, and FIG. 10B is a diagram showing an example of the acquired diffuse reflection output. [Figure 12] 10 is a graph showing the detection results of the amount of light reflected from the intermediate transfer belt by an optical sensor within the paper passing area and the detection results of the amount of light reflected from the intermediate transfer belt by an optical sensor outside the paper passing area. [Figure 13] FIG. 10 is a diagram showing an example of a timing chart of a cleaning operation. [Figure 14]FIG. 10 is a diagram showing an example of a timing chart in which a scraping toner pattern passes through the secondary transfer nip before a pre-sheet-feed cleaning operation. [Figure 15] FIG. 10 is a diagram showing an example of a timing chart for passing a scraping toner pattern through a secondary transfer nip during a pre-sheet-feed cleaning operation. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0009] FIG. 1 is a schematic diagram of a tandem color copying machine (hereinafter simply referred to as a copying machine) which is an image forming apparatus according to this embodiment. 1, a tandem color copier 1 (hereinafter simply referred to as the copier) as an image forming apparatus includes a document transport unit 3 that transports a document to a document reading unit, and a document reading unit 4 that reads image information from the document. The copier also includes a paper output tray 5 on which output images are stacked, and a paper feed unit 7 that stores paper P as a recording medium.

[0010] The copier 1 also includes registration rollers 9 (timing rollers) that adjust the transport timing of the paper P, and photosensitive drums 11Y, 11M, 11C, and 11BK, which serve as latent image carriers on which toner images of each color (yellow, magenta, cyan, and black) are formed. The copier 1 also includes a charging device 12 that uniformly charges the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK, and a writing unit (exposure unit) 6 that emits laser light based on input image information and writes electrostatic latent images onto each photosensitive drum 11Y, 11M, 11C, and 11BK. The copier 1 also includes a developing device 13 that develops the electrostatic latent images written on each photosensitive drum 11Y, 11M, 11C, and 11BK. The copying machine 1 also includes a primary transfer bias roller 14 that transfers the toner images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK onto the paper P in an overlapping manner.

[0011] The copier 1 also includes an intermediate transfer belt 17 as an image carrier onto which multiple color toner images are transferred in superimposed layers, and a secondary transfer roller 18 as a transfer member for transferring the color toner images on the intermediate transfer belt 17 onto paper P. The copier 1 also includes a fixing device 20 that fixes unfixed images on paper P, and a toner container 28 that stores toner of each color (yellow, cyan, magenta, and black) to be supplied to the developing device 13. The copier 1 also includes a belt cleaning device 30 that removes toner (untransferred toner) adhering to the surface of the intermediate transfer belt 17. The copier 1 also includes a waste toner collection container 80 in which untransferred toner removed by the belt cleaning device 30 or the like is collected as waste toner.

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

[0013] More specifically, the document reader 4 scans the image of the document on the contact glass while irradiating it with light emitted from an illumination lamp, and the light reflected from the document is imaged on a color sensor via a group of mirrors and a lens. The color image information of the document is read by the color sensor in units of RGB (red, green, and blue) color separation light, and then converted into electrical image signals. Furthermore, the image processor performs color conversion processing, color correction processing, spatial frequency correction processing, etc. based on the RGB color separation image signals, thereby obtaining color image information of yellow, magenta, cyan, and black.

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

[0015] Meanwhile, the four photoconductor drums 11Y, 11M, 11C, and 11BK each rotate clockwise in FIG. 1. First, the surfaces of the photoconductor 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 photoconductor drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK reach the respective laser beam irradiation positions.

[0016] In the writing unit 6, laser beams corresponding to the image signals are emitted from four light sources, one for each color. Each laser beam passes through a separate optical path for each color component: yellow, magenta, cyan, and black (this is the exposure process).

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

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

[0019] Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color have been formed reach positions facing the developing devices 13. Then, toner of each color is supplied from each developing device 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (the developing process).

[0020] After the development process, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK each reach a position facing the intermediate transfer belt 17, which serves as an image carrier. At each of these positions, a primary transfer bias roller 14 is installed so as to abut against the inner circumferential surface of the intermediate transfer belt 17. Then, at the position of the primary transfer bias roller 14, the toner images of each color formed on the photosensitive 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 photoconductor drums 11Y, 11M, 11C, and 11BK each reach a position facing cleaning unit 15. Then, cleaning unit 15 removes and collects untransferred toner remaining on photoconductor drums 11Y, 11M, 11C, and 11BK (cleaning process). The untransferred toner removed and collected by cleaning unit 15 is transported as waste toner to waste toner collection container 80 via a transport path and collected. Thereafter, the surfaces of photoconductor drums 11Y, 11M, 11C, and 11BK pass through a charge removal unit, and the series of image formation processes on photoconductor drums 11Y, 11M, 11C, and 11BK is completed.

[0022] Meanwhile, intermediate transfer belt 17 (image carrier), onto which the toner of each color on photosensitive drums 11Y, 11M, 11C, and 11BK has been primarily transferred (carried) in layers, travels counterclockwise in FIG. 1 and reaches a position facing secondary transfer roller 18. Secondary transfer roller 18 abuts against intermediate transfer belt 17 to form a secondary transfer nip. In this secondary transfer nip, the color toner image carried on intermediate transfer belt 17 is secondarily transferred onto paper P (secondary transfer process).

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

[0024] After the secondary transfer step, the surface of the intermediate transfer belt 17 reaches the position of the belt cleaning device 30. The belt cleaning device 30 has a cleaning blade 31 as a cleaning member. The cleaning blade 31 removes toner (untransferred toner) adhering to the intermediate transfer belt 17. The toner removed by the cleaning blade is transported as waste toner via a transport path to a waste toner collection container 80 and collected.

[0025] Here, the paper P transported between the intermediate transfer belt 17 and the secondary transfer roller 18 (secondary transfer nip) is transported from the paper feed unit 7 via the registration rollers 9 and the like. More specifically, the paper P is fed by a paper feed roller 8 from a paper feed unit 7 that stores the paper P, passes through a conveyance guide, and is then guided to a registration roller 9. The paper P that has reached the registration roller 9 is conveyed in time 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 a fixing roller and a pressure roller. After the fixing process, the paper P is then discharged as an output image outside the device body by a paper discharge roller and stacked on the paper discharge tray 5, completing the image formation process.

[0027] In addition, the copier 1 is provided with a temperature sensor 42 disposed around the black photosensitive drum 11BK, and a temperature and humidity sensor 41 disposed near the paper transport path from the paper feed roller 8 to the registration roller 9. The copier 1 grasps the device environment based on the detection results of these temperature sensor 42 and temperature and humidity sensor 41, and performs various controls according to the device environment. The temperature and humidity sensor may also be disposed near the cleaning blade 31. By disposing the temperature and humidity sensor near the cleaning blade 31, the amount of filming on the intermediate transfer belt under the environmental conditions within the device can be accurately grasped, as will be described later, and is therefore preferable.

[0028] This copying machine performs a process control at a predetermined timing in order to stabilize image quality despite environmental changes and the passage of time. FIG. 2 is a schematic diagram illustrating the image quality adjustment pattern on the intermediate transfer belt.

[0029] The image quality adjustment pattern is a gradation pattern and is made up of a plurality of toner patches with different image densities. The image quality adjustment patterns are formed at positions (the center and both ends in the width direction) of the intermediate transfer belt 17 facing the optical sensor. In the example shown in Figure 2, image quality adjustment patterns for black, cyan, magenta, and yellow are formed from top to bottom.

[0030] The optical sensor unit 40 has a plurality of optical sensors 40R, 40C, and 40F as adhesion amount detection means arranged at predetermined intervals in the belt width direction of the intermediate transfer belt 17. Each optical sensor detects the amount of toner adhesion by outputting a signal corresponding to the light reflectance of the intermediate transfer belt 17 and the image quality adjustment patterns PtK, PtC, PtM, and PtY on the intermediate transfer belt 17. The copier 1 adjusts image creation conditions such as the development bias Vb based on the detected toner adhesion amount.

[0031] The optical sensors 40R and 40F, which are arranged to face the widthwise end regions of the intermediate transfer belt 17, are located outside the paper passage area. This allows the copier to perform image quality adjustments such as image density adjustment during printing. Specifically, as shown in FIG. 3, an image quality adjustment pattern is formed outside the paper passage area, and the optical sensors 40R and 40F detect the amount of toner adhesion on the image quality adjustment pattern. Then, based on the amount of toner adhesion detected by the optical sensors 40R and 40F, the developing bias and the like are adjusted to adjust the image density and the like.

[0032] The toner base components, silica or titanium oxide added to the toner, and other so-called external additives of the toner are transferred from the photosensitive 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. Furthermore, if the surface of the photosensitive drum 11 has a lubricant application section that applies a lubricant, various components contained in the lubricant, in addition to the external additives of the toner, are also transferred from the photosensitive drum 11 to the intermediate transfer belt 17. The external additives of the toner and the lubricant may interact with each other, causing filming on 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 adhere to the intermediate transfer belt 17, causing paper dust filming.

[0033] Such filming on the intermediate transfer belt 17 occurs when external pressure (mainly contact pressure with the photosensitive drum) on the intermediate transfer belt 17 causes filming substances, such as silica and other external toner additives and various components contained in lubricants, to adhere to the intermediate transfer belt 17. If filming occurs on the intermediate transfer belt 17, when a full solid image or halftone image is output, toner does not adhere to the areas corresponding to the filming, resulting in abnormal images such as white spots, so-called blank areas.

[0034] Furthermore, when filming occurs, the glossiness of the belt decreases. Therefore, when filming occurs in the area of ​​the intermediate transfer belt 17 facing the optical sensors 40R, 40C, and 40F, the output signal changes, making it impossible to properly detect the amount of gradation pattern adhesion on the intermediate transfer belt. Another problem is that uneven filming causes the output of the optical sensor to become unstable, making it impossible to properly adjust the image.

[0035] Furthermore, filming may reduce the cleaning performance of the cleaning blade 31. In the belt width direction, gradation patterns with a large amount of adhesion per unit area are often input to the positions of the cleaning blade 31 corresponding to the positions of the optical sensors 40R, 40C, and 40F. Therefore, if filming occurs in the areas of the intermediate transfer belt 17 facing the optical sensors 40R, 40C, and 40F, there is a higher risk of poor cleaning (toner passing through) when the gradation patterns are input to the cleaning blade 31.

[0036] The filming can be scraped off by toner remaining at the contact point between the cleaning blade 31 and the surface of the intermediate transfer belt 17 (hereinafter referred to as the "cleaning point") and 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 of the toner surface remaining at the cleaning point and the pressure of the cleaning blade 31 acting on the toner.

[0037] Therefore, in order to suppress filming on the intermediate transfer belt 17, the copier 1 forms a scraping toner pattern on the intermediate transfer belt 17 at a predetermined timing. Then, by inputting this scraping toner pattern into the cleaning blade 31, a sufficient amount of toner is allowed to remain at the cleaning location. As a result, filming on the intermediate transfer belt 17 is effectively scraped off by the toner remaining at the cleaning location, and defects such as abnormal images such as whiteouts can be suppressed.

[0038] FIG. 4 is a diagram for explaining the positions of the gradation patterns serving as image quality adjustment patterns and the scraping toner patterns formed on the intermediate transfer belt 17 when three sheets are printed consecutively in a normal image forming operation. The gradation pattern, which is an image quality adjustment pattern, is formed at a position outside the width of the paper that passes through the secondary transfer nip indicated by "2." in FIG. The positions where the scraping toner pattern is formed include the position "1." in Figure 4, before the first sheet of paper enters the secondary transfer nip, the position in the non-image forming area at the rear end of the sheet that passes through the secondary transfer nip, "3.", the position between sheets, "4.", and the position "5." after the final sheet of paper has passed through the secondary transfer nip. The scraping toner pattern is a strip-shaped pattern that is long in the belt width direction (main scanning direction), and extends outside the paper passing area.

[0039] 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, preventing the scraping toner pattern from being transferred to the secondary transfer roller 18 or paper P.

[0040] The background toner adhering to areas other than the toner-adhered areas of the latent image on the photosensitive drum (in negative-positive development of this embodiment, the exposed areas correspond to the toner-adhered areas of the latent image, and in positive-positive development, the non-exposed areas correspond to the toner-adhered areas of the latent image) adheres from the photosensitive drum to areas other than the toner image on the intermediate transfer belt 17. This background toner adhering to areas other than the toner image on the intermediate transfer belt 17 is input to the cleaning blade 31. The background toner input to the cleaning blade 31 also scrapes off filming on the intermediate transfer belt 17. As a result, the amount of filming on the intermediate transfer belt 17 varies depending on the amount of background toner input to the cleaning blade 31.

[0041] FIG. 5 is a diagram for explaining the amount of toner input to the cleaning blade 31 of the conventional toner scraping pattern. The black bars in FIG. 5 indicate the amount of smear toner input to the cleaning blade 31 over a predetermined period of time, and the amount of smear toner input to the cleaning blade 31 increases as the temperature and humidity increase. The bar graph to the right of the bar graph showing the amount of background smear toner is the target input toner amount, which is the amount of toner input to the cleaning blade 31 that can effectively remove filming that has occurred on the intermediate transfer belt within the specified period.

[0042] Conventionally, the amount of input toner input to the cleaning blade 31 of the scraping toner pattern was set without considering the scraping of filming caused by background toner. In other words, conventionally, the scraping toner pattern was formed so that the input toner amount of the scraping toner pattern was the target input toner amount. As a result, excess toner was input to the cleaning blade compared to the actual amount of filming on the intermediate transfer belt 17, resulting in unnecessary toner consumption. In particular, in a high-temperature, high-humidity environment, the amount of background toner increases, and the amount of filming scraped off by this background toner is greater than in a low-temperature, low-humidity environment or a normal-temperature, normal-humidity environment. Therefore, unnecessary toner consumption increases in a high-temperature, high-humidity environment.

[0043] Therefore, in this embodiment, the input toner amount of the scraping toner pattern is set based on the amount of background smear toner input to the cleaning blade 31 .

[0044] FIG. 6 is a diagram for explaining how to set the input toner amount of the scraping toner pattern in this embodiment. The input toner amount of the scraping toner pattern is calculated by estimating the amount of background smear toner input to the cleaning blade from the time the previous scraping toner pattern was formed to the present time, and subtracting the estimated amount of background smear toner from the target input toner amount. The amount of background smear toner is estimated based on the printing operation time and the environmental conditions at that time. For example, the amount of background smear toner is estimated by multiplying the printing operation time by a predetermined coefficient (amount of background smear toner input to the cleaning blade per unit time) based on the temperature and humidity inside the device during printing operation. Since the amount of background smear toner increases as the temperature and humidity increase, the value of the coefficient is minimum in a low-temperature, low-humidity environment and maximum in a high-temperature, high-humidity environment.

[0045] Here, the amount of background smear toner per unit time was calculated by driving the device for a predetermined time under the same conditions as during image formation, except that no exposure was performed, and calculating the amount of background smear toner per short time from the amount of toner input to the cleaning blade during this predetermined time.

[0046] The environment inside the device is classified into a low-temperature, low-humidity environment, a normal-temperature, normal-humidity environment, or a high-temperature, high-humidity environment based on the temperature and humidity detected by the temperature and humidity sensor 41. The temperature may also be the temperature measured by the temperature sensor 42. The temperature and humidity inside the device may be the average values ​​detected by the temperature and humidity sensor 41 and the temperature sensor 42 during printing operation, or may be the temperature and humidity detected at a predetermined timing during printing operation. In the above description, the amount of background smear toner is calculated by dividing the environment inside the apparatus into three environments: low temperature and low humidity environment, normal temperature and normal humidity environment, and high temperature and high humidity environment. However, the environment inside the apparatus may be divided into more detailed environments. Alternatively, the amount of smear toner per unit time may be calculated by detecting the smear toner with an optical sensor. Specifically, the device is driven for a predetermined time under the same conditions as those for image formation except that no exposure is performed, and the amount of smear toner per unit time is calculated from the amount of toner detected by the optical sensor during this predetermined time.

[0047] For example, when forming a scraping toner pattern at "1. Position before the first sheet of paper to the secondary transfer nip" in Figure 4, the input toner amount for the scraping toner pattern is set based on the amount of background smear toner calculated based on the temperature and humidity during the previous printing operation.

[0048] Also, for example, when forming a scraping toner pattern at "5. Position after the final paper has passed through the secondary transfer nip" in Figure 4, the input toner amount of the scraping toner pattern is set based on the amount of background smear toner calculated based on the temperature and humidity during the current printing operation.

[0049] For example, when forming scraping toner patterns at 4. "position between sheets" and "5. position after the final sheet has passed through the secondary transfer nip" in Fig. 4, the input toner amount for the scraping toner pattern is set as follows: That is, the input toner amount for the scraping toner pattern is set based on the amount of background smear toner calculated based on the temperature and humidity at the time of image formation on the paper.

[0050] As can be seen from Figure 6, the input toner amount of the scraping toner pattern is calculated by subtracting the calculated amount of background smear toner from the target input toner amount. This target input toner amount is the input toner amount determined in advance through experiments or the like to effectively remove filming from the intermediate transfer belt. Then, based on the calculated input toner amount, the length of the scraping toner pattern in the surface movement direction of the intermediate transfer belt and / or the amount of toner adhesion per unit area are set.

[0051] 6, the sum of the amount of background smear toner and the amount of input toner input to the cleaning blade by the scraping toner pattern becomes the target input toner amount. This reduces unnecessary toner consumption and effectively removes filming from the intermediate transfer belt 17. As a result, unnecessary toner consumption can be reduced and abnormal images such as white spots caused by filming can be prevented.

[0052] Furthermore, in a high-temperature, high-humidity environment, the amount of stick-slip of the cleaning blade 31 increases, which may worsen filming. Therefore, as shown in Figure 7, the target toner amount when the internal environment of the device is a high-temperature, high-humidity environment (27°C, 80%) may be set to be greater than the target toner amount when the internal environment is a low-temperature, low-humidity environment (10°C, 15%) or a normal-temperature, normal-humidity environment (23°C, 54%). 6, when the target input toner amount is the same under each environment, the frequency of forming the scraping toner pattern may be changed depending on the environment within the device. That is, in a high-temperature, high-humidity environment, the frequency of forming the scraping toner pattern is set higher than in a low-temperature, low-humidity environment (10°C, 15%) and a normal-temperature, normal-humidity environment (23°C, 54%). This makes it possible to prevent filming from worsening under a high-temperature, high-humidity environment.

[0053] Filming has a greater impact on the accuracy of detecting the amount of adhesion by the optical sensors 40R, 40C, and 40F than on abnormal images such as white spots caused by filming, and even a small amount of filming can reduce the accuracy of detecting the amount of adhesion. Therefore, it is preferable to increase the amount of toner input to the cleaning blade 31 at the locations of the intermediate transfer belt 17 facing the optical sensors 40R, 40C, and 40F compared to other locations, in order to scrape off more filming. Therefore, it is preferable to increase the amount of toner input to the areas of the scraping toner pattern corresponding to the positions of the optical sensors 40R, 40C, and 40F.

[0054] FIG. 8 is a schematic diagram showing an example of a scraping toner pattern Kp in which the amount of input toner in the areas corresponding to the positions of the optical sensors 40R, 40C, and 40F is increased. As shown in Figures 8(a) and 8(b), the scraping toner pattern Kp is a band-shaped pattern having a length from the optical sensor 40F at one end of the belt width direction to the optical sensor 40R at the other end, and has a length greater than or equal to the paper passing area T of the intermediate transfer belt 17.

[0055] 8A, the length of the scraping toner pattern Kp in the surface movement direction of the intermediate transfer belt 17 in the facing region P1 where it faces the optical sensors 40R, 40C, and 40F is longer than the length in the surface movement direction of the non-facing region P2. For example, the scraping toner pattern shown in FIG. 8A is obtained by increasing the length in the belt movement direction in the facing region P1 by a predetermined amount from the scraping toner pattern set based on the input toner amount calculated based on the amount of background toner. This makes it possible to increase the amount of input toner input to the areas of the cleaning blade 31 corresponding to the positions of the optical sensors 40R, 40C, and 40F in the belt width direction compared to the amount of input toner input to other areas.

[0056] 8(b), the amount of toner adhesion in the facing region P1 of the scraping toner pattern Kp may be made greater than the amount of toner adhesion in the non-facing region P2. The scraping pattern shown in FIG. 8(b) is obtained by adding a predetermined value to the amount of toner adhesion in the facing region P1 from the scraping toner pattern set using the input toner amount calculated based on the amount of background toner. In FIG. 8(b) as well, the amount of input toner input to the portions of the cleaning blade 31 corresponding to the positions of the optical sensors 40R, 40C, and 40F in the belt width direction can be made greater than the amount of input toner input to other portions.

[0057] Increasing the amount of toner input to the cleaning blade 31 at the locations corresponding to the optical sensors 40R, 40C, and 40F in the belt width direction allows the toner to remain longer at the cleaning locations of the cleaning blade 31. This enhances the effectiveness of removing toner filming on the intermediate transfer belt. As a result, filming can be effectively removed from the areas of the intermediate transfer belt 17 facing the optical sensors 40R, 40C, and 40F, preventing a decrease in the accuracy of detecting the amount of toner adhesion.

[0058] On the other hand, the amount of input toner to areas of the cleaning blade 31 other than those corresponding to the positions of the optical sensors 40R, 40C, and 40F (hereinafter referred to as non-corresponding areas) is less than that to the areas corresponding to the positions of the optical sensors 40R, 40C, and 40F. For the non-corresponding areas, it is sufficient to remove filming on the intermediate transfer belt to a level where abnormal images such as white spots due to filming do not occur. The impact of filming on abnormal images such as white spots is less than the reduction in the accuracy of toner adhesion detection due to filming. Therefore, even if some filming remains on the intermediate transfer belt, abnormal images such as white spots due to filming can be suppressed. Therefore, even with a small amount of input toner, filming on the intermediate transfer belt can be reduced to a level where abnormal images such as white spots due to filming do not occur.

[0059] In this way, by varying the amount of toner input to the cleaning blade 31 in the belt width direction using the scraping toner pattern, the following advantages can be obtained: Compared to when the amount of toner input to the cleaning blade 31 is the same in the belt width direction, unnecessary toner consumption can be reduced, and the occurrence of abnormal images and a decrease in the accuracy of detecting the amount of adhered toner can be suppressed.

[0060] FIG. 9 is a diagram illustrating the width of the opposing region P1 of the scraping toner pattern Kp. The width of the facing region P1 of the toner scraping pattern Kp is set to the size of the optical sensor lens 40a and is set to be equal to or larger than the sensor spot diameter, which is the detection range of the optical sensor. This allows the input toner input to the cleaning blade to effectively remove filming at least within the detection range of the optical sensor on the intermediate transfer belt 17. This prevents a decrease in the accuracy of the optical sensor's toner adhesion amount detection. Furthermore, by setting the width of the facing region P1 of the toner scraping pattern Kp to the size of the optical sensor lens 40a, toner waste can be reduced compared to when the width exceeds the size of the optical sensor lens 40a.

[0061] In this embodiment, the optical sensor used is equipped with a light receiving element that receives diffusely reflected light and a light receiving element that receives specularly reflected light. Thus, the optical sensor that receives both specularly reflected light and diffusely reflected light has two types of sensor spot diameters: a specular reflection spot diameter and a diffuse reflection spot diameter. The width of the opposing region P1 of the scraping toner pattern Kp is set wider than both the specular reflection spot diameter and the diffuse reflection spot diameter.

[0062] Here, the measurement of the sensor spot diameter of the optical sensor will be described. Figure 10 shows a reference plate 100 used to measure the sensor spot diameter, with the upper part of the figure being a specular reflection substrate portion 100a made of glass and the lower part being a diffuse reflection substrate portion 100b made of resin with a roughened surface. The measurement range of this reference plate is placed opposite the optical sensor, and scanning is performed downward in the drawing at 0.1 mm intervals from a position of +5 mm from the measurement range, to obtain the specular reflection output V01 and the diffuse reflection output V02.

[0063] 11(a) shows an example of the acquired specular reflection output V01, and FIG. 11(b) shows an example of the acquired diffuse reflection output V02. The horizontal axis in the figure represents the distance from the boundary between the specular reflection substrate portion 100a and the diffuse reflection substrate portion 100b of the reference plate 100, with the specular reflection substrate portion side being positive and the diffuse reflection substrate portion side being negative.

[0064] As can be seen from FIG. 11(a), when the entire specular reflection spot is on the specular reflection substrate portion 100a, the specular reflection output V01 of the optical sensor indicates a maximum value V01(max). Then, as the reference plate 100 is scanned, part of the specular reflection spot falls on the diffuse reflection substrate portion 100b. This causes the specular reflection output V01 to decrease. As the reference plate 100 is further scanned, the proportion of the specular reflection spot that is occupied by the diffuse reflection substrate portion 100b increases, and the specular reflection output V01 decreases accordingly. Then, when the entire specular reflection spot falls on the diffuse reflection substrate portion 100b, the specular reflection output V01 indicates a minimum value V01(min).

[0065] 9(b), when the entire diffuse reflection spot is on the specular reflection substrate portion 100a, the diffuse reflection output V02 of the optical sensor indicates a minimum value V02(min). Then, as the reference plate is scanned and part of the diffuse reflection spot enters the diffuse reflection substrate portion 100b, the diffuse reflection output V02 gradually increases. Then, when the entire diffuse reflection spot enters the diffuse reflection substrate portion 100b, the diffuse reflection output V02 indicates a maximum value V02(max).

[0066] To calculate the specular reflection spot diameter φV01(D), first, the maximum specular reflection output value V01(max) is calculated by averaging the 10 points in the region (+5.0 to +4.0 mm) indicated by the dotted line X1 in Figure 11(a) where the specular reflection substrate portion 100a of the reference plate 100 is detected. Next, the minimum specular reflection output value V01(min) is calculated by averaging the 10 points in the region (-4.0 to -5.0 mm) indicated by the dotted line X2 in Figure 11(a) where the diffuse reflection substrate portion 100b of the reference plate 100 is detected.

[0067] Next, the first distance PV01(D1) at which the specular reflected light output is equal to or less than (V01(max)-V01(min))×0.9+V01(min) is calculated. Also, the first distance PV01(D2) at which the specular reflected light output is equal to or less than (V01(max)-V01(min))×0.1+V01(min) is calculated. Then, the specular reflected spot diameter φV01(D) is calculated using the following equation 1. φV01(D)=|PV01(D1)-PV01(D2)| (Formula 1)

[0068] The calculation of the diffuse reflection spot diameter φV02(D) is basically the same as the calculation of the specular reflection spot diameter. That is, first, the minimum diffuse reflection output value V02(min) is determined by calculating the average value at 10 points in the region (+5.0 to +4.0 mm) indicated by the dotted line Y2 in FIG. 9(b) where the specular reflection substrate portion 100a of the reference plate 100 is detected. Next, the maximum diffuse reflection output value V02(max) is determined by calculating the average value at 10 points in the region (-4.0 to -5.0 mm) indicated by the dotted line Y1 in FIG. 11(b) where the diffuse reflection substrate portion 100b of the reference plate 100 is detected.

[0069] Next, the first distance PV02(D1) at which the diffuse reflected light output is equal to or less than (V02(max)-V02(min))×0.1+V02(min) is calculated. Also, the first distance PV01(D2) at which the diffuse reflected light output is equal to or less than (V02(max)-V02(min))×0.9+V02(min) is calculated. Then, the diffuse reflected spot diameter φV02(D) is calculated using the following equation 2. φV02(D)=|PV02(D1)-PV02(D2)| (Formula 2)

[0070] FIG. 12 is a graph showing the detection results of the amount of light reflected from the intermediate transfer belt 17 by the optical sensor 40C within the paper passing area and the detection results of the amount of light reflected from the intermediate transfer belt 17 by the optical sensor 40F (40R) outside the paper passing area. As can be seen from FIG. 12, the optical sensor 40F (40R) outside the paper passing area has a worse detection result than the optical sensor 40C outside the paper passing area before the toner pattern for scraping is input to the cleaning blade.

[0071] This is because, within the paper-passing area, residual toner that has not been transferred to the paper and remains on the intermediate transfer belt 17 is input to the cleaning blade 31, and this residual toner scrapes off filming on the intermediate transfer belt. On the other hand, outside the paper-passing area, no residual toner is generated, and no filming is scraped off by the residual toner. Therefore, the amount of filming outside the paper-passing area is greater than within the paper-passing area. As a result, it is thought that the optical sensor 40F (40R) outside the paper-passing area received less reflected light from the intermediate transfer belt before inputting the toner pattern for scraping to the cleaning blade, resulting in worse results than the optical sensor 40C within the paper-passing area.

[0072] Thus, the amount of filming outside the paper-passing area is greater than that inside the paper-passing area. Therefore, after inputting the same scraping toner pattern to each opposing area P1, the amount of reflected light received by the optical sensor 40F (40R) outside the paper-passing area may not be fully recovered, resulting in poor detection accuracy. Therefore, increasing the amount of input toner in each opposing area P1 is one way to ensure good detection accuracy for the optical sensor 40F (40R) outside the paper-passing area. However, the amount of input toner in the opposing area P1 of the optical sensor 40C inside the paper-passing area is excessive compared to the amount of filming on the intermediate transfer belt, resulting in unnecessary toner consumption.

[0073] Therefore, the amount of input toner in opposing regions P1 at both ends of the belt width direction of the scraping toner pattern, which faces the optical sensors 40F and 40R outside the paper passing area, may be made larger than the amount of input toner in region P1 facing the optical sensor 40C inside the paper passing area. Specifically, for the scraping toner pattern Kp shown in Figures 8(a) and 8(b), the length in the belt movement direction of region P1 facing the optical sensors 40F and 40R outside the paper passing area is made longer than the length in the belt movement direction of region P1 facing the optical sensor 40C inside the paper passing area. Alternatively, the amount of toner adhesion in region P1 facing the optical sensors 40F and 40R outside the paper passing area is made larger than the amount of toner adhesion in region P1 facing the optical sensor 40C inside the paper passing area.

[0074] This makes it possible to suppress unnecessary consumption of toner, effectively remove filming on the area of ​​the intermediate transfer belt 17 facing the optical sensor, and suppress a decrease in the accuracy of detecting the amount of adhered toner.

[0075] As described above, when the scraping toner pattern passes through the secondary transfer nip, a positive bias is applied to the opposing roller 18A. This electrostatically attracts negatively charged toner to the intermediate transfer belt 17, preventing the toner from moving to the secondary transfer roller 18. However, at this time, the oppositely charged toner of the positively charged scraping toner pattern and the positively charged background toner are electrostatically transferred to the secondary transfer roller 18, causing the secondary transfer roller 18 to become contaminated with the toner. In addition, the surface layer of the secondary transfer roller 18 is made of a foaming agent such as sponge and contains many microscopic cells. Therefore, the negatively charged normally charged toner of the scraping toner pattern is also scraped off by the secondary transfer roller 18 at the secondary transfer nip and adheres to the secondary transfer roller 18.

[0076] If the secondary transfer roller 18 becomes soiled with toner in this way, the tolerance for backside soiling that soils the back side of the paper P decreases, and when a toner image is transferred onto the paper P, toner may adhere to the back side of the paper P, causing backside soiling.

[0077] Therefore, it is conceivable to provide a contact / separation mechanism that moves the secondary transfer roller 18 toward and away from the intermediate transfer belt 17, and when the toner pattern for scraping is input to the cleaning blade 31, the contact / separation mechanism separates the secondary transfer roller 18 from the intermediate transfer belt 17. However, providing a contact / separation mechanism increases the number of parts, which may increase the cost and size of the device.

[0078] Therefore, it is preferable to perform a cleaning operation to clean the secondary transfer roller 18 before the first sheet passes through the secondary transfer nip during an image forming operation or after the last sheet passes through the secondary transfer nip.

[0079] FIG. 13 is a diagram showing an example of a timing chart of the cleaning operation. 13, cleaning operations are performed from the start of the printing operation until the first sheet passes through the secondary transfer nip (hereinafter, the cleaning operation performed at this timing is referred to as the pre-sheet cleaning operation). Additionally, cleaning operations are performed from the end of the printing operation until the last sheet passes through the secondary transfer nip (hereinafter, the cleaning operation performed at this timing is referred to as the post-sheet cleaning operation).

[0080] When the cleaning operation is performed, a negative bias and a positive bias are alternately applied to the opposing roller 18A to form an alternating electric field at the secondary transfer nip. By forming an alternating electric field, toner adhering to the secondary transfer roller 18 can be efficiently cleaned by a hopping effect. Here, the hopping effect refers to the effect of toner moving back and forth between the secondary transfer roller 18 and the intermediate transfer belt 17, making it easier for the toner on the secondary transfer roller 18 to move to the intermediate transfer belt 17. By forming an alternating electric field in this way, toner of both polarities adhering to the secondary transfer roller 18 can be moved to the intermediate transfer belt 17, effectively cleaning the surface of the secondary transfer roller 18. This reduces backside contamination of paper.

[0081] The period of negative and positive application that forms the alternating electric field is the period during which the secondary transfer roller 18 rotates once. In the pre-paper-passing cleaning operation, after negative and positive application are performed three times, the bias is temporarily set to zero and then the negative bias is applied again. The length of the negative bias that is applied again is adjusted depending on the timing of the paper feed. It is not necessary to temporarily set the bias to zero.

[0082] The cleaning operation after paper feed involves one cycle of negative application followed by positive application. Note that the cleaning operation is not limited to the above, and negative application followed by positive application may be performed four or more times. Also, the bias value for the first and second negative application followed by positive application does not have to be constant (the bias may be gradually amplified or attenuated).

[0083] When performing the cleaning operation in this way, it is preferable to form the scraping toner pattern so that the scraping toner pattern passes through the secondary transfer nip at at least one of the following timings A to C. Timing A: Before paper feed cleaning operation Timing B: Pre-feed cleaning in progress Timing C: Cleaning operation after paper feed

[0084] By forming the scraping toner pattern so that the scraping toner pattern passes through the secondary transfer nip at any of the above timings A to C, it is possible to suppress backside contamination of the paper.

[0085] FIG. 14 is a diagram showing an example of a timing chart in which the scraping toner pattern passes through the secondary transfer nip before the pre-sheet-passage cleaning operation at timing A. 14, a pre-sheet-passing cleaning operation is performed after the scraping toner pattern passes through the secondary transfer nip. As a result, the toner that adheres to the secondary transfer nip when the scraping toner pattern passes through the secondary transfer nip is moved to the intermediate transfer belt by the pre-sheet-passing cleaning operation, thereby cleaning the secondary transfer roller 18. Therefore, the paper can be passed through the secondary transfer nip with an increased margin for backside contamination of the secondary transfer roller 18, effectively suppressing backside contamination of the paper.

[0086] FIG. 15 is a diagram showing an example of a timing chart for timing B: passing the scraping toner pattern through the secondary transfer nip during the pre-paper-passage cleaning operation. As shown in Figure 15(a), the scraping pattern may be divided into multiple parts and passed through the secondary transfer nip in accordance with the timing of positive bias application and zero bias during the pre-sheet-passing cleaning operation. Alternatively, as shown in Figure 15(b), the scraping toner pattern may be passed through the secondary transfer nip in accordance with the timing of the first positive bias application during the pre-sheet-passing cleaning operation. Alternatively, as shown in Figure 15(c), the scraping toner pattern may be passed through the secondary transfer nip in accordance with the timing of the first positive bias application during the cleaning operation.

[0087] Incidentally, during the timing C: post-paper-passage cleaning operation, the scraping toner pattern is also caused to pass through the secondary transfer nip in accordance with the timing of positive bias application during the pre-paper-passage cleaning operation and zero bias.

[0088] 15(a) to 15(c), by passing the scraping toner pattern through the secondary transfer nip in accordance with the timing of application of the positive bias voltage during the cleaning operation, the scraping toner pattern passes through the secondary transfer nip without being transferred to the secondary transfer roller 18. Therefore, the scraping toner pattern can be input to the cleaning location, and the toner remaining in the cleaning location can scrape off filming on the intermediate transfer belt 17.

[0089] During this cleaning operation, the reversely charged toner of the scraping toner pattern that has been electrostatically moved to the secondary transfer roller and the normally charged toner that has been mechanically scraped off by the secondary transfer roller 18 are moved to the intermediate transfer belt 17. Therefore, although the amount is less than in the case of timing A above, the toner of the scraping toner pattern that has adhered to the secondary transfer roller 18 can be removed to some extent, and the margin for back staining can be increased to a level where no back staining occurs on the paper.

[0090] Furthermore, the travel distance of the intermediate transfer belt 17 from the start to the end of the printing operation can be made shorter at the timings B and C than at the timing A. Therefore, the lifespan of components can be shortened at the timings B and C than at the timing A, and therefore these are preferable.

[0091] 15A, the pre-sheet-passing cleaning operation can form a toner scraping pattern by applying a positive voltage multiple times, which has the advantage that the amount of toner input to the cleaning blade 31 by the toner scraping pattern can be more easily adjusted to the set input toner amount.

[0092] Therefore, forming the scraping toner pattern at the timing B (during the pre-feed cleaning operation) is most preferable from the viewpoint of the advantages of suppressing an increase in the travel distance of the intermediate transfer belt and making it easier to achieve the target input toner amount. Therefore, the basic setting is the timing B. Then, when the set input toner amount is large and cannot be achieved with timing B alone, the scraping toner pattern is formed at timing B and timing A, or timing B and timing C.

[0093] As described above, in a high-temperature, high-humidity environment, the amount of stick-slip of the cleaning blade 31 increases, which may worsen filming. Therefore, in a low-humidity environment or a normal-temperature, normal-humidity environment, the scraping toner pattern is formed at timing B. On the other hand, in a high-temperature, high-humidity environment, it is preferable to form the scraping toner pattern at timing B and timing A, or timing B and timing C, thereby increasing the frequency of forming the scraping toner pattern.

[0094] Although the above description has been given of an embodiment in which the present invention is applied to an intermediate transfer image forming apparatus, the present invention can also be applied to a direct transfer image forming apparatus in which a toner image on a photosensitive drum is directly transferred to a recording medium such as paper. In this direct transfer image forming apparatus, the image carrier corresponds to the photosensitive drum, the transfer member corresponds to a transfer roller that contacts the photosensitive drum to form a transfer nip, and the cleaning member corresponds to a photosensitive cleaning blade that cleans the surface of the photosensitive drum.

[0095] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) In an image forming apparatus that 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, and that forms a toner image pattern such as a scraping toner pattern Kp on the image carrier that is not transferred to the recording medium, the amount of input toner to be input to the cleaning member for the toner image pattern is set based on the amount of background toner adhering to the surface of the image carrier. When toner accumulates at the contact area between the cleaning member and the image carrier, the accumulated toner scrapes off filming from the image carrier, thereby removing the filming from the image carrier. The background toner adhering to areas of the image carrier other than the toner image is input to the contact area, and the background toner scrapes off the filming from the surface of the image carrier. Therefore, the amount of filming on the surface of the image carrier varies depending on the amount of background toner input to the cleaning member. Conventionally, the input toner amount for the toner image pattern was set without taking into consideration the scraping off of filming caused by the above-mentioned background smear toner, so that excessive toner was input to the cleaning member compared to the actual amount of filming on the image carrier, resulting in unnecessary toner consumption. On the other hand, in aspect 1, the input toner amount of the toner image pattern is set based on the amount of background smear toner, so that an amount of toner corresponding to the amount of filming on the surface of the image carrier can be input to the cleaning member, thereby suppressing unnecessary toner consumption and enabling the filming on the surface of the image carrier to be effectively removed.

[0096] (Aspect 2) In the first embodiment, the amount of smear toner is determined based on the environmental conditions of the apparatus. According to this, as described in the embodiment, the amount of background smear toner changes depending on environmental conditions such as temperature and humidity inside the device. Therefore, by determining the amount of background smear toner based on the environmental conditions of the device, the amount of background smear toner can be calculated with high accuracy.

[0097] (Aspect 3) In the first or second embodiment, the greater the amount of background smear toner, the smaller the input toner amount is set. According to this, as explained in the embodiment, unnecessary toner consumption can be suppressed and filming on the image carrier such as the intermediate transfer belt 17 can be effectively removed.

[0098] (Aspect 4) In any of the first to third aspects, the timing of forming the toner image pattern is changed based on the environmental conditions of the device. As described in the embodiment, the likelihood of filming varies depending on the environmental conditions within the device. Therefore, by changing the timing of forming a toner image pattern, such as a scraping toner pattern, based on the environmental conditions of the device, it is possible to input toner to a cleaning member, such as a cleaning blade, at the optimal timing, thereby reducing toner waste and suppressing filming.

[0099] (Aspect 5) In any of aspects 1 to 4, a transfer member such as secondary transfer roller 18 contacts an image carrier such as intermediate transfer belt 17 to form a transfer nip, and the image forming operation to form an image on a recording medium such as paper includes a pre-paper cleaning operation in which any adhering matter adhering to the transfer member is moved to the image carrier and the transfer member is cleaned before the first recording medium reaches the transfer nip, and a post-paper cleaning operation in which any adhering matter adhering to the transfer member is moved to the image carrier and the transfer member is cleaned after the last recording medium leaves the transfer nip, and the timing of forming the toner image pattern is set so that the toner image pattern passes through the transfer nip at at least one of the following times 1 to 3 during the image forming operation. Timing 1: Before the start of pre-feed cleaning operation Timing 2: Pre-feed cleaning in progress Timing 3: During cleaning after paper feed This makes it possible to suppress back contamination of the recording medium, as described in the embodiment.

[0100] (Aspect 6) In the fifth embodiment, in a high-temperature, high-humidity environment, a toner image pattern is formed so that the toner image pattern passes through the transfer nip at timing 2, timing 1, or timing 3. As a result, as described in the embodiment, it is possible to increase the frequency of forming toner image patterns such as scraping toner patterns in high-temperature, high-humidity environments where filming is likely to worsen, and it is possible to effectively suppress filming on image carriers such as the intermediate transfer belt 17 in high-temperature, high-humidity environments.

[0101] (Aspect 7) In any of aspects 1 to 6, an adhesion amount detection means such as an optical sensor is provided, which is arranged opposite the surface of an image carrier such as intermediate transfer belt 17 and detects the amount of toner adhesion in a toner image, and in a direction perpendicular to the surface movement direction of the image carrier, the input toner amount in a first area such as area P1 corresponding to the position of the adhesion amount detection means for a toner image pattern such as a scraping toner pattern Kp is made larger than the input toner amount in other areas. This allows more filming to be scraped off from areas of an image carrier, such as an intermediate transfer belt, facing an adhesion amount detection means, such as an optical sensor, than from areas not facing the adhesion amount detection means. This allows filming to be removed more effectively from areas of the image carrier facing the adhesion amount detection means than from areas not facing the adhesion amount detection means, and reduces filming from areas of the image carrier facing the adhesion amount detection means than from areas not facing the adhesion amount detection means. This effectively reduces detection errors by the adhesion amount detection means, which are more susceptible to the influence of filming than image abnormalities caused by filming. Furthermore, compared to a toner image pattern in which the amount of input toner input to the cleaning member in a direction perpendicular to the surface movement direction of the image carrier is constant, the amount of toner consumed by the toner image pattern can be reduced while suppressing detection errors by the adhesion amount detection means.

[0102] (Aspect 8) In aspect 7, an adhesion amount detection means such as an optical sensor is arranged in the perpendicular direction outside the paper passing area of ​​an image carrier such as the intermediate transfer belt 17, and inside the paper passing area, and a toner image pattern such as the scraping toner pattern Kp is a band-shaped pattern whose length in the perpendicular direction is longer than the paper passing area of ​​the image carrier, and the input toner amount in the first area corresponding to the arrangement position of the adhesion amount detection means outside the paper passing area is greater than the input toner amount in the first area corresponding to the arrangement position of the adhesion amount detection means inside the paper passing area. According to this, the amount of filming outside the paper passing area is likely to be greater than the amount of filming inside the paper passing area, as explained with reference to Fig. 12. Therefore, by making the input toner amount in the first area corresponding to the arrangement position of the adhesion amount detection means outside the paper passing area greater than the input toner amount in the first area corresponding to the arrangement position of the adhesion amount detection means inside the paper passing area, it is possible to suppress unnecessary consumption of toner and effectively remove filming in the area of ​​the intermediate transfer belt facing the adhesion amount detection means outside the paper passing area.

[0103] (Aspect 9) In the seventh or eighth aspect, the length of the first region in the orthogonal direction is equal to or greater than the length in the orthogonal direction of the adhesion amount detection range of the adhesion amount detection means such as an optical sensor. 9, this allows the input toner input to a cleaning member such as a cleaning blade to effectively remove filming at least within the detection range of an adhesion amount detection means such as an optical sensor on an image carrier such as the intermediate transfer belt 17. This makes it possible to prevent a decrease in the accuracy of toner adhesion amount detection by the adhesion amount detection means.

[0104] (Aspect 10) In any of the first to ninth embodiments, the length of a toner image pattern such as the scraping toner pattern kp in the surface movement direction of an image carrier such as the intermediate transfer belt 17 is set based on the input toner amount. This allows the amount of toner input to the cleaning member for the toner image pattern such as the scraping toner pattern Kp to be the set input toner amount.

[0105] (Aspect 11) In any one of the first to tenth aspects, the amount of toner adhesion per unit area of ​​the toner image pattern is set based on the input toner amount. This allows the amount of toner input to the cleaning member for the toner image pattern such as the scraping toner pattern Kp to be the set input toner amount. [Explanation of symbols]

[0106] 1: Copy machine 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 40a: Lens 41: Temperature and humidity sensor 42: Temperature sensor 80:Waste toner collection container 100: Reference plate 100a: Regular reflection substrate portion 100b: Diffuse reflection substrate part Kp: Toner scraping pattern P:Paper P1: Opposing area P2: Non-opposing area Pt: Image quality adjustment pattern T:Paper passing area [Prior art documents] [Patent documents]

[0107] [Patent Document 1] Japanese Patent Application Publication No. 2018-120183

Claims

1. an image carrier; a transfer member that transfers the toner image on the image carrier to a recording medium; a cleaning member for cleaning the surface of the image carrier; an image forming apparatus for forming a toner image pattern on an image carrier that is not transferred to a recording medium, setting an input toner amount of the toner image pattern to be input to the cleaning member based on an amount of background smear toner adhering to the surface of the image carrier, the amount being determined based on the temperature and humidity of the apparatus; an adhesion amount detection means disposed opposite to the surface of the image carrier and detecting the amount of toner adhesion of the toner image; An image forming apparatus characterized in that, in a direction perpendicular to the surface movement direction of the image carrier, the amount of input toner in a first area of ​​the toner image pattern corresponding to the position of the adhesion amount detection means is made larger than the amount of input toner in other areas.

2. In the image forming apparatus according to claim 1, The image forming apparatus is characterized in that the input toner amount is set to be smaller as the amount of background smear toner increases.

3. 3. The image forming apparatus according to claim 1, An image forming apparatus characterized in that the timing of forming the toner image pattern is changed based on environmental conditions of the apparatus.

4. 4. The image forming apparatus according to claim 1, the transfer member contacts the image carrier to form a transfer nip; The image forming operation for forming an image on the recording medium includes a pre-sheet-passing cleaning operation for moving deposits adhering to the transfer member to the image carrier before the first recording medium reaches the transfer nip and cleaning the transfer member, and a post-sheet-passing cleaning operation for moving deposits adhering to the transfer member to the image carrier after the last recording medium leaves the transfer nip and cleaning the transfer member, an image forming apparatus, characterized in that the timing of forming the toner image pattern is set so that the toner image pattern passes through a transfer nip at at least one of the following timings 1 to 3 during an image forming operation: Timing 1: Before the start of pre-sheet feeding cleaning operation Timing 2: During pre-feed cleaning Timing 3: During cleaning after paper feed

5. 5. The image forming apparatus according to claim 4, In a high-temperature, high-humidity environment, the image forming apparatus forms the toner image pattern so that the toner image pattern passes through the transfer nip at timing 2, timing 1, or timing 3.

6. In the image forming apparatus according to any one of claims 1 to 5, the adhesion amount detection means are arranged outside a paper passing area of ​​the image carrier, which is outside the paper passing area of ​​the image carrier, and inside the paper passing area in the perpendicular direction; the toner image pattern is a belt-shaped pattern whose length in the orthogonal direction is longer than a paper passing area of ​​the image carrier, An image forming apparatus characterized in that the input toner amount of the first area corresponding to the arrangement position of the adhesion amount detection means outside the paper passing area is made larger than the input toner amount of the first area corresponding to the arrangement position of the adhesion amount detection means inside the paper passing area.

7. 7. The image forming apparatus according to claim 1, The image forming apparatus is characterized in that the length of the first region in the perpendicular direction is equal to or greater than the length of an adhesion amount detection range of the adhesion amount detection means in the perpendicular direction.

8. 8. The image forming apparatus according to claim 1, an image forming apparatus, wherein a length of a toner image pattern in a surface movement direction of the image carrier is set based on the input toner amount;

9. 9. The image forming apparatus according to claim 1, an amount of toner adhered per unit area of ​​the toner image pattern based on the amount of input toner;

Images