JP2011186176A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus enabling a user to surely understand an amount of the wear of a photoreceptor being an image carrier, and capable of obtaining a stable image until its life ends. <P>SOLUTION: The image forming apparatus includes: the photoreceptor 11 that carries an electrostatic latent image; an electrifying device 20 that is disposed in contact with or in the vicinity of the photoreceptor 11 and electrifies a surface of the photoreceptor 11; an exposure device 12 that exposes the surface of the photoreceptor 11 to write the electrostatic latent image; a developing device 30 that develops the latent image formed on the surface of the photoreceptor 11 so as to become a visible image with a toner; a transfer device 60 that transfers the visible image on the surface of the photoreceptor 11 to an intermediate transfer belt 61; and a cleaning device 40 that is disposed at a downstream side of the transfer device 60 and cleans the toner on the surface of the photoreceptor 11. The image forming apparatus includes a waste toner collecting container 44 for collecting a waste toner conveyed from the cleaning device 40, and is provided with a waste toner amount detection means 46 for detecting a waste toner amount in the waste toner collecting container 44 to estimate the amount of the wear of the photoreceptor 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine, and more particularly to an image forming apparatus that suppresses the occurrence of an abnormal image associated with a decrease in the film thickness of an image carrier.

In recent electrophotographic image forming apparatuses, an organic photoreceptor (OPC) is generally used as an image carrier. A resin is used for the material of the organic photoreceptor, and it can be manufactured at a relatively low cost.
The structure of the photoconductor is generally a laminated type structure of an undercoat layer, a charge generation layer (CGL), and a charge transport layer (CTL) from the side of a conductive metal tube such as aluminum as a base material. Have. However, the CTL serving as the surface layer of the photoconductor wears when a high electric field is applied due to charging or when it is rubbed against the developing means or the cleaning device. When the photoconductor is worn and the film thickness is reduced, an abnormal image such as a background stain occurs due to a local decrease in the surface potential of the photoconductor.
If the photoconductor wears and the photoconductor film thickness decreases, the post-exposure potential rises, making it impossible to obtain an image with a stable density such as a thin image. Further, in the contact or proximity charging method, an abnormal image such as a charging failure due to dielectric breakdown occurs.
Therefore, in order to provide a stable image from the initial stage of the photoconductor to the end of its life, it is necessary to accurately grasp the wear amount of the photoconductor and set the optimum image forming conditions according to the film thickness of the photoconductor. .

Until now, it has been found that the wear amount of the photoreceptor greatly contributes to the image area ratio. This is because the toner that has not been completely transferred by the transfer means remains on the photosensitive member and is collected by the cleaning device, but the toner input to the cleaning device acts as an abrasive and promotes wear of the photosensitive member. Conceivable.
Therefore, the amount of toner input to the cleaning device has a large contribution rate to photoconductor wear. In addition, a tandem type image forming apparatus having a plurality of developing devices has a phenomenon called reverse transfer in which a toner image once transferred to a transfer unit is partially transferred to a photosensitive member of a developing device downstream. Yes, the amount of toner input to the cleaning device is not accurate only by pixel information. Therefore, since the wear amount of the photoconductor can be predicted more reliably, the wear amount of the photoconductor can be reduced if the toner amount input to the cleaning device can be grasped so that it can be used without waste until the life of the photoconductor. It is necessary to know for sure.
To provide an image forming apparatus and a process cartridge that do not generate an abnormal image until the lifetime of the photoreceptor.

Therefore, for the above necessity, for example, in Patent Document 1, at the time of measuring the film thickness of the image carrier by measuring the current flowing through the image carrier, at least one member in contact with the image carrier is image-bearing. A method for measuring the film thickness of an image carrier separated from the body is disclosed. However, it is necessary to separate the photoconductor, which requires a cam and a motor, and there is a problem that the image forming apparatus becomes large.
Further, Patent Document 2 includes a replaceable toner image carrier having a surface layer formed by laminating a plurality of layers, and the surface layer is formed by increasing the cumulative rotational speed of the toner image carrier. Of the layers, the layers on the surface side wear sequentially, and the layers adjacent to each other have different layer thickness reduction ratios relative to the cumulative rotational speed of the toner image carrier, and this image forming apparatus Further includes a change detection unit that detects a change in a reduction rate of the layer thickness in the surface layer with respect to the cumulative rotational speed of the toner image carrier, and the toner image carrier based on a detection result of the change detection unit. An image forming apparatus having a replacement time detection unit for detecting the replacement time is disclosed. However, since it is difficult to accurately measure the impedance of the charging member depending on the surrounding environment and the degree of contamination of the charging member, there is a problem that an error in the film thickness of the photosensitive member becomes large.
In Cited Document 3, the measuring means for measuring the operating amount of the photoconductor, the calculating means for calculating the integrated operating amount of the photoconductor, and the first storing the integrated operating amount calculated by the calculating means. The storage means, the second storage means for storing the wear life limit of the photoconductor, the accumulated operation amount stored by the first storage means and the wear life limit stored by the second storage means are compared. Determination means for determining the wear life of the photoconductor, and environment detection means having at least one of a temperature detector and a humidity detector, and the calculation means includes operation amount information based on the measurement means, An image forming apparatus is disclosed that calculates an integrated operating amount of the photoconductor from environmental information based on the environment detection means. However, in the case of the tandem type, the influence of the reverse transfer toner amount is particularly large in the downstream image forming unit, and there is a problem that it is difficult to accurately grasp the photoconductor wear only with the image information.

Further, in Patent Document 4, in an image forming apparatus including an image carrier, a charging unit that charges the image carrier, and a current detection unit that detects a charging current flowing through the charging unit, a change in charging current from an initial state is disclosed. An image forming apparatus having a changing unit that detects the amount of wear of the image carrier from the amount and changes the control target value of the charging current according to the amount of wear is disclosed. However, since the current flowing through the charging means is easily affected by the surrounding environment and the current value is likely to change, there is a problem that it is difficult to accurately determine the wear amount of the photoconductor.
In Patent Document 5, torque measuring means for measuring the driving torque of the photoconductor, rotation amount measuring means for measuring the rotation amount of the photoconductor, measurement values of the torque measuring means, and measurement of the rotation amount measuring means. An image forming apparatus having a wear amount estimating means for estimating a wear amount of a photoconductor based on a value and a control system correcting means for correcting an image forming control system based on the estimated wear amount is disclosed. Yes. However, since the torque of the photoconductor is greatly affected by the developing unit, the cleaning blade, and the transfer unit, the torque distribution is different, so that it is difficult to accurately determine only the photoconductor torque.
Further, in Patent Document 6, the use state grasping means for grasping the application condition of the voltage applied from the charger to the image carrier and the number of cycles of the image carrier, and the use state grasping means. Life coefficient determining means for determining a life coefficient of the image carrier from the application conditions and the past use history of the image carrier, the life coefficient determined by the life coefficient determiner, and the life of the image carrier. There is disclosed an image forming apparatus provided with a lifetime integrated amount calculating means for calculating the lifetime of the image carrier based on the number of cycles. However, although the amount of wear of the photoconductor is converted from the number of cycles of the photoconductor, there is a problem that the amount of wear cannot be accurately determined because it is greatly affected by the image area ratio and the like.

  Therefore, the present invention has been made in view of the above problems, and the problem is that the wear amount of the photoconductor as the image carrier can be reliably grasped, and a stable image can be obtained until the end of its lifetime. An image forming apparatus is provided.

The features of the present invention, which is a means for solving the above problems, are listed below.
An image forming apparatus of the present invention includes an image carrier that carries an electrostatic latent image, a charging device that is disposed in contact with or in proximity to the image carrier and charges the surface of the image carrier, and the image carrier. An exposure device that exposes the surface of the body and writes an electrostatic latent image; a developing device that visualizes the latent image formed on the surface of the image carrier with toner; and a visible image on the surface of the image carrier. In an image forming apparatus comprising: a transfer device that transfers to a transfer member; and a cleaning device that is disposed downstream of the transfer device and cleans toner on the surface of the image carrier, waste toner conveyed from the cleaning device A waste toner collecting container for collecting is provided, and a waste toner amount detecting means for detecting the amount of waste toner in the waste toner collecting container is provided to estimate the wear amount of the image carrier.
The image forming apparatus of the present invention is further characterized in that the control of image formation is changed based on the estimated wear amount of the image carrier.
The image forming apparatus of the present invention is further characterized in that the voltage applied to the charging device is changed based on the estimated amount of wear of the image carrier.
The image forming apparatus according to the present invention further estimates the image carrier when applying a bias in which an alternating current component is superimposed on a direct current component to a charging device arranged in a non-contact manner or close to the image carrier. The target current value of the AC component is changed based on the wear amount.
The image forming apparatus of the present invention is further characterized in that the output of the exposure apparatus is changed based on the estimated wear amount of the image carrier.
The image forming apparatus of the present invention is further characterized in that the voltage applied to the developing device is changed based on the estimated amount of wear of the image carrier.
Further, the image forming apparatus of the present invention is further characterized in that the condition for the static eliminator disposed downstream of the cleaning device is changed based on the estimated amount of wear of the image carrier.
Further, the image forming apparatus of the present invention further performs at least one change from the charging device, the exposure device, the developing device, the static eliminator, and the transfer device based on the estimated wear amount of the image carrier. Features.
The image forming apparatus of the present invention further includes a process cartridge that integrally supports at least the image carrier, the charging device, and the cleaning device, and is detachable from the image forming apparatus main body. .

  When the image forming apparatus of the present invention, which is a means for solving the above problems, reduces the image density by reducing the film thickness of the photoconductor, and an abnormal image due to an afterimage or abnormal discharge due to the charging device is likely to occur. However, there is a specific effect that an optimum condition can be determined according to the amount of wear of the photoconductor, and an image determined until the end of its life can be provided.

1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing a configuration around an image carrier. 6 is a graph showing the relationship between waste toner amount and photoreceptor wear amount. 6 is a graph showing the amount of waste toner of each image forming unit and the amount of wear of each photoconductor. 3 is a graph showing the relationship between the amount of waste toner of an image forming unit and the amount of photoconductor wear. 6 is a graph showing the amount of waste toner of an image forming unit and the amount of wear of each photoconductor. FIG. 3 is a diagram illustrating a configuration of waste toner amount detection means used by the image forming apparatus of the present invention. 2A and 2B are diagrams for explaining the operation of a waste toner amount detection unit used by the image forming apparatus of the present invention, in which FIG. 1A shows a state where there is no waste toner in a waste toner collection container, and FIG. FIG. 2 is a diagram illustrating a configuration of waste toner amount detection means used by the tandem type image forming apparatus of the present invention. It is a block diagram showing control in the image forming apparatus of the present invention. It is a graph which shows the relationship between the CTL film thickness of a photoreceptor, and the electric potential after exposure. It is a graph which shows the relationship between the CTL film thickness of a photoreceptor, and the electric potential after exposure. It is a graph which shows the relationship between the CTL film thickness of a photoconductor and the electric potential after exposure when the output of a laser beam is changed.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings. In the following, a copier capable of forming a full-color image employing a tandem method will be described as the image forming apparatus. However, the image forming apparatus according to the present invention is not limited to the illustrated one, and may be a printer, a facsimile machine, It can be applied to various devices such as a composite device.
The basic configuration and operation of the copying machine will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a configuration around the image carrier.
A paper feeding device 80 having a paper feeding cassette 81 for storing paper as a recording material is provided below the image forming apparatus 1, and the image forming unit 2 is disposed above the paper feeding device 80. The image forming unit 2 includes a plurality of image carriers (hereinafter, referred to as “photosensitive members”) 11Y, 11M, 11C, and 11K (hereinafter, referred to as the photosensitive member 11 unless it is particularly necessary to specify a color). Four image forming units 10 serving as image forming means, here in the form of a process cartridge 10. An intermediate transfer belt 61 as an intermediate transfer member constituted by a flexible endless belt wound around a plurality of support rollers 65 and 66, and an exposure that is a latent image forming apparatus that forms a latent image on each photoconductor 11. A device 12 and a fixing device 70 for fixing a toner image on a sheet are provided.
Between the paper feeding cassette 81 and the fixing device 70, the paper is transported by the calling roller 21 that takes out the paper from the paper feeding cassette 81 one by one, and the registration roller 83 that feeds the paper to the transfer device 60 in a timely manner. A path is formed.

The space between the support rollers 65 and 66 of the intermediate transfer belt 61 corresponds to the lower belt running side of this belt. The intermediate transfer belt 61 is provided with a secondary transfer roller 63 serving as a secondary transfer device facing a support path at a portion facing the support roller 66, and cleaning the belt surface at a portion facing the support roller 65. A belt cleaning device 64 is provided.
The image forming unit 10 is disposed below the intermediate transfer belt 61 by being disposed so as to face the lower running side. Each image forming unit 10 includes a photoreceptor 11 in contact with the intermediate transfer belt 61. Around each photoconductor 11, a charging device 20 including a charging roller 21, a developing device 30 including a developing sleeve, and a cleaning device 40 including a cleaning blade 41 are disposed. A primary transfer roller 62 as a transfer device 60 that performs primary transfer is provided inside the intermediate transfer belt 61 at a position where each photoconductor 11 is in contact with the intermediate transfer belt 61.
In this example, the image forming unit 10 basically has the same structure, and only the structure of one image forming unit 10 is shown. The difference in each image forming unit 10 is that the color of the toner as the developer stored in each developing device 30 is different.

Although not shown, the exposure device 12 in the image forming apparatus 1 of the present invention deflects a polygon mirror by a cylinder lens serving as a first imaging system through a condenser lens for a laser beam emitted from a light source (LD (laser diode)). A linear image is formed in the vicinity of the reflection surface, and the laser beam is scanned by rotating the polygon mirror. The laser beam deflected and scanned by the polygon mirror is narrowed down to a predetermined spot diameter in the main scanning and sub-scanning directions by the fθ lens serving as the second imaging system, and scans the photosensitive member 11 at a constant speed. As a result, an invisible electrostatic latent image is formed on the charged photoreceptor 11. Further, the intensity and diameter of the laser beam are controlled by the current value of the LD and the light emission time. These change the line width, potential, and the like of the electrostatic latent image formed.
As shown in FIG. 2, the image forming apparatus 1 according to the present invention is provided with a static elimination device 13. The static eliminator 13 irradiates the surface of the photoconductor 11 with light to remove charges on the surface of the photoconductor 11. Although the photoconductor 11 is used as a light source having sensitivity, other light neutralization means can be applied as long as the residual charge can be removed. It is also possible to use an optical static elimination device using an LED, an organic EL or the like as a light source. Further, a discharge charger using a thin wire such as tungsten or molybdenum may be used.

The charging device 20 in the image forming apparatus 1 of the present invention includes a charging roller 21 configured by coating a medium resistance elastic layer on the outside of a conductive metal core as a charging member. The charging roller 21 is connected to a power source (not shown) and is applied with a predetermined direct current voltage (DC) and / or alternating current voltage (AC). The charging roller 21 that discharges ions uses an elastic resin roller as a material. In addition, the charging roller 21 may contain an inorganic conductive material such as carbon black or an ionic conductive material in order to adjust electric resistance.
In addition, the charging roller 21 is disposed with a small gap with respect to the photoreceptor 11. This minute gap is set by, for example, winding a spacer member having a certain thickness around the non-image forming regions at both ends of the charging roller 21 to bring the surface of the spacer member into contact with the surface of the photoreceptor 11. can do. Further, the charging roller 21 may be brought into contact without being brought close to the photosensitive member. The photosensitive member 11 can be charged by discharging at a portion that is in a roller shape and is close to the photosensitive member 11. Further, by making them close and not in contact with each other, it is possible to suppress the occurrence of contamination due to the transfer residual toner of the charging roller 21. In addition, the charging roller 21 is provided with a charging cleaner roller (not shown) that contacts the surface of the charging roller 21 for cleaning.

In the developing device 30 in the image forming apparatus 1 of the present invention, a developing sleeve (not shown) having a magnetic field generating unit is arranged at a position facing the photoconductor 11. Below the developing sleeve, a stirring / conveying screw having a mechanism for mixing toner introduced from a toner bottle (not shown) with the developer and pumping the toner to the developing sleeve 32 while stirring is provided. The two-component developer composed of the toner and the magnetic carrier conveyed by the developing sleeve 32 is regulated to a predetermined developer layer thickness by the regulating member 33 and is carried on the developing sleeve 32. The developing sleeve carries and carries the developer while supplying the toner to the photoconductor 11 while moving in the same direction at a position facing the photoconductor 11. At this time, a developing bias is applied to the developing sleeve 33 from a power source as output means (not shown). In the positive-positive development method in the image forming apparatus 1 of the present invention, the electrostatic charge image having a size sufficient to supply toner to the electrostatic latent image formed on the photosensitive member 11 with laser light is the same as the charge of the toner. A polar development bias is applied.
In addition, toner cartridges for each color in which unused toner is stored are detachably stored in a space above the photoconductor 11. Toner is supplied to each developing device 30 as necessary by toner conveying means such as a mono pump or air pump (not shown). A toner cartridge for black toner that is highly consumed can be set to have a particularly large capacity.

Further, the image forming apparatus 1 is provided with a lubricant application device 50 for applying a lubricant to the photoreceptor 11. The lubricant application device 50 includes a solid lubricant 52 housed in a fixed case, and a brush roller 51 that contacts the solid lubricant 52 to scrape the lubricant and apply it to the photoconductor 11. In addition, although not shown, a lubricant application blade for leveling the lubricant applied by the brush roller 51 may be provided. The solid lubricant 52 is formed in a rectangular parallelepiped shape and is urged toward the brush roller by a pressure spring 53. The solid lubricant 52 is scraped off and consumed by the brush roller 51, and the thickness of the solid lubricant 52 decreases with time. However, since the solid lubricant 52 is pressurized by the pressure spring 53, it is always in contact with the brush roller. The brush roller applies the lubricant scraped off while rotating to the surface of the photoreceptor 11.
A lubricant application device having a similar function may be provided for the intermediate transfer belt 61.
As the lubricant, a dry solid hydrophobic lubricant can be used. In addition to zinc stearate, metal compounds having fatty acid groups such as stearic acid, oleic acid, and palmitic acid can also be used. Further, waxes such as candelilla wax, carnauba wax, rice wax, wax, ooba oil, beeswax, and lanolin can be used.
In the image forming apparatus 1 of the present invention, the lubricant application unit 50 is provided. In FIG. 2, the lubricant application device 50 is provided in the cleaning device 40. May be.

The cleaning device 40 includes a mechanism in which the cleaning blade 41 abuts and separates from the photoconductor 11, and can be arbitrarily abutted and separated by the control unit of the image forming apparatus main body. The cleaning blade is brought into contact with the photoconductor 11 in a counter manner, whereby toner remaining on the photoconductor 11 and additives such as talc, kaolin and calcium carbonate adhering to the recording member are removed from the photoconductor 11. Remove and clean. The removed toner or the like is transported and stored in a waste toner collection container 44 through a waste toner collection path 43 by a waste toner collection coil 42.
Further, the waste toner collecting container 44 is provided with waste toner amount detecting means 46 for detecting the amount of waste toner in the waste toner collecting container 44. This will be described later.

The transfer device 60 transfers an intermediate transfer belt 61 on which toner images are stacked, a primary transfer roller 62 that transfers and stacks the toner images on the photoreceptor 11 to the intermediate transfer belt 61, and transfers the stacked toner images to the recording medium 6. A secondary transfer roller 63 and the like are provided. Further, the transfer device 60 is a portion facing the secondary transfer roller 63, and is provided inside the intermediate transfer belt 61 so that a support roller 653 serving as a facing member faces.
A primary transfer roller 62 that primarily transfers a toner image formed on the photoconductor 11 onto the intermediate transfer belt 61 is disposed at a position facing each photoconductor 11 with the intermediate transfer belt 61 interposed therebetween. The primary transfer roller 62 is connected to a power source (not shown), and is applied with a predetermined direct current voltage (DC) and / or alternating current voltage (AC). As the polarity of the voltage to be applied, the polarity is opposite to the polarity of the charge of the toner, and primary transfer is performed by drawing and moving from the photoreceptor 11 to the intermediate transfer belt 61 side. The primary transfer roller 62 is preferably semiconductive by containing an inorganic conductive material such as carbon black and an ionic conductive material in order to adjust electric resistance. Even if the resistance value of the primary transfer roller 62 is different, the transfer efficiency is hardly changed. However, if the image area ratio is different, the transfer efficiency is greatly different, so that the transfer efficiency cannot be stably maintained. This is because the current flows preferentially to the portion where the toner is not present in the transfer nip portion. As a result, when the image area ratio is small, the transfer voltage value becomes low and the electric field necessary for transfer cannot be obtained sufficiently. is there. In particular, when the resistance value of the primary transfer roller 62 is low, the influence of the resistance value of the toner interposed in the transfer portion becomes large. When constant current control is employed in this way, it is desirable to use a primary transfer roller 62 having a high resistance value. However, if the resistance value exceeds 5 × 10 ⁸ Ω, a toner image is formed due to current leakage. The risk of disturbance is increased.

Therefore, it is preferable to use a primary transfer roller having a resistance value in the range of 1 × 10 ⁵ Ω to 5 × 10 ⁸ Ω. The phenomenon that the current flows preferentially to the portion where the toner does not intervene is not only due to the above-described toner resistance, but also the primary transfer voltage applied to the metal core provided at the center of the primary transfer roller 62 and the photosensitive member 11. This is also because the transfer current tends to flow toward the larger potential difference because the portion where the toner is not developed is larger than the portion where the toner is developed. This is because the toner image is the same as the charging polarity of the photoconductor 11, and the toner is developed on the photoconductor 11 where the photoconductor potential is removed by receiving the image exposure of the photoconductor 11, thereby forming a toner image on the photoconductor 11. This occurs in the case of the image forming apparatus 1 that performs this. The photosensitive member potential is high where the toner image is not formed and the photosensitive member potential is low where the toner image is formed, but the transfer potential is opposite to the photosensitive member potential, so the primary transfer voltage and the photosensitive member potential The difference is larger at the portion where the toner is not developed than at the portion where the toner is developed. In this case, the resistance value of the primary transfer roller 62 is desirably in the range of 5 × 10 ⁷ Ω to 5 × 10 ⁸ Ω.

The toner image laminated on the intermediate transfer belt 61 is secondarily transferred to the recording member by the secondary transfer roller 63. Similar to the primary transfer roller 62, the secondary transfer roller 63 is connected to a power source (not shown) and is applied with a predetermined DC voltage (DC) and / or AC voltage (AC). The polarity of the voltage to be applied is opposite to the polarity of the charge of the toner, and the secondary transfer is performed by drawing the intermediate transfer belt 61 toward the recording member that has been conveyed.
The secondary transfer roller 63 includes a cylindrical metal core made of metal, an elastic layer formed on the outer peripheral surface of the metal core, and a surface layer made of a resin material formed on the outer peripheral surface of the elastic layer. Has been.
The metal constituting the metal core is not particularly limited. For example, a metal material such as stainless steel or aluminum is used. Generally, a rubber material is used for the elastic layer formed on the cored bar to form a rubber layer. This is because the secondary transfer roller 63 is required to have an elastic function in order to deform the secondary transfer roller 63 and secure a secondary transfer nip portion, and the JIS-A hardness is 70 [ °] The following is desirable.
In addition, since the cleaning blade 22 is used as a cleaning means for the secondary transfer roller 63, if the elastic layer is too soft, the contact state of the cleaning blade 22 becomes unstable and an appropriate cleaning angle cannot be obtained. Therefore, the hardness of the elastic layer is preferably JIS-A 40 [°] or more.
In addition, since the secondary transfer roller 63 cannot perform the function of transferring a toner image to a recording medium when an insulator is used, it is preferably a foamed resin agent having a conductive function and a thickness of 2 mm to 10 mm. As a material imparting a conductive function, EPDM or Si rubber in which carbon black is dispersed, NBR having an ionic conductive function, urethane rubber, or the like may be used.
Since most of the foamed resin agents used for the elastic layer have high chemical affinity for the toner and a large friction coefficient, the functions required for the surface layer with which the cleaning blade 22 is in contact are low friction coefficient, toner separation. Since the moldability is required, the surface layer of the secondary transfer roller 63 is used by adjusting the resistance by adding a resistance control material to the fluororesin resin.
Further, since the secondary transfer roller 63 rotates in contact with the intermediate transfer belt 10, if a minute linear velocity difference occurs between the intermediate transfer belt 10 and the secondary transfer roller 63, the intermediate transfer belt 10. It will affect the driving of the. Accordingly, since the surface layer of the secondary transfer roller 63 is required to have slipperiness with the intermediate transfer belt 10 (reducing friction with the intermediate transfer belt 10), the friction coefficient of the outermost surface of the surface layer is 0.4 or less. It is desirable to set so that
The intermediate transfer belt 61 is provided with an intermediate transfer belt cleaning device 64 that cleans the surface of the intermediate transfer belt 61 after the secondary transfer.
In addition, the support roller 653 includes a mechanism for contacting / separating with the intermediate transfer belt 61 and can be arbitrarily contacted / separated by the control unit of the main body of the image forming apparatus 1.

The intermediate transfer belt 61 is composed of single layer or multiple layers of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), etc., and is made of conductive material such as carbon black. The volume resistivity is adjusted to be in the range of 10 ⁸ to 10 ¹² Ωcm, and the surface resistivity is adjusted to be in the range of 10 ⁹ to 10 ¹³ Ωcm. If necessary, a release layer may be coated on the surface of the intermediate transfer belt 61. As materials used for the coating, ETFE (ethylene-tetrafluoroethylene copolymer),
PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PVF (vinyl fluoride), etc. Although a fluororesin can be used, it is not limited to this.
The volume resistivity and surface resistivity were measured by connecting an HRS probe (inner electrode diameter 5.9 mm, ring electrode inner diameter 11 mm) to a high resistivity meter (manufactured by Mitsubishi Chemical Co., Ltd .: Hiresta IP). The measured value 10 seconds after applying the voltage of 100V (surface resistivity is 500V) to the front and back of the was used.

  In the image forming apparatus 1 configured as described above, the four image forming units 10 are provided so as to face the intermediate transfer belt 61, and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 61. The image forming time is greatly reduced as compared with a type in which a single four-color developing device is used to transfer a toner image on an intermediate transfer belt and then transfer it onto a sheet. In addition, since the stacking unit is formed on the upper portion of the image forming apparatus 1, the stacking unit does not jump out from the image forming apparatus 1, and the installation area and the occupied area are reduced.

On the other hand, the photoconductor 11 used in the image forming apparatus 1 of the present invention is a metal such as amorphous silicone or selenium, or an organic photoconductor. As an organic photoreceptor (hereinafter simply referred to as “photoreceptor”) 11, a photosensitive layer having a resin layer in which a filler is dispersed, a charge generation layer and a charge transport layer on a conductive support, and a filler is dispersed on the surface thereof. A protective layer.
The photosensitive layer may be a single-layered photosensitive layer containing a charge generation material and a charge transport material, but a laminated type composed of a charge generation layer and a charge transport layer is excellent in sensitivity and durability.
In the charge generation layer (CGL), a pigment having charge generation ability is dispersed in a suitable solvent together with a binder resin, if necessary, using a ball mill, attritor, sand mill, ultrasonic wave, etc. It is formed by applying to and drying. As binder resin, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, poly-N-vinylcarbazole, polyacrylamide, polyvinyl benzal, polyester Phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone and the like. The amount of the binder resin is suitably 0 to 500 parts by mass, preferably 10 to 300 parts by mass with respect to 100 parts by mass of the charge generating material.
The charge transport layer (CTL) can be formed by dissolving or dispersing a charge transport material and a binder resin in a suitable solvent, and applying and drying the solution on the charge generation layer. Charge transport materials include hole transport materials and electron transport materials. As the binder resin, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, Polyvinylidene chloride, polyarate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol Examples thereof include thermoplastic or thermosetting resins such as resins and alkyd resins.
In addition, a protective layer may be provided on the photosensitive layer. By providing a protective layer and improving durability, it is possible to use the photoconductor 11 with high sensitivity and no abnormal defects.
Materials used for the protective layer include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, Examples thereof include resins such as polybutylene terephthalate, polycarbonate, polyarylate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten, polypropylene, polyvinylidene chloride, and epoxy resin. Of these, polycarbonate or polyarylate can be most preferably used. Other protective layers include fluorine resins such as polytetrafluoroethylene, silicone resins, and inorganic fillers such as titanium oxide, tin oxide, potassium titanate, and silica for the purpose of improving wear resistance. What disperse | distributed the filler etc. can be added. The filler concentration in the protective layer varies depending on the type of filler used and also on the electrophotographic process conditions using the photoreceptor 11, but is preferably 5% by mass or more in the ratio of filler to the total solid content on the outermost layer side of the protective layer. 10 mass% or more and 50 mass% or less, Preferably about 30 mass% or less is favorable.
An undercoat layer can be provided between the conductive support and the photosensitive layer. The undercoat layer is mainly composed of a resin. Since the photosensitive layer is coated with a solvent thereon, it is preferable to use a resin having a high solvent resistance with respect to the organic solvent. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin. Further, a metal oxide fine powder pigment exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the undercoat layer in order to prevent moire and reduce residual potential.

The surface of the organic photoreceptor 11 is worn when printing is performed, and as the wear progresses, the entire thickness of the photoreceptor 11 is reduced, and the charged potential is different from the initial set value. An abnormal image such as a charging failure such as becoming dirty or a background stain occurs.
A cleaning device 40 using a cleaning blade 41 is generally used as a means for removing transfer residual toner from the surface of the photoreceptor. However, the cleaning blade 41 is pressed against the surface of the photoconductor, which is one of the causes of wear on the surface of the photoconductor.
Further, the toner staying at the edge of the cleaning blade 41 acts as an abrasive. Therefore, the polishing action increases as the amount of toner input to the edge portion of the cleaning blade 41 increases. Accordingly, it has been found that the amount of wear on the surface of the photosensitive member varies greatly depending on the amount of residual toner transferred to the cleaning blade 41. If the amount of residual toner is large, the amount of wear increases, and if the amount of residual toner is small. The amount of wear is reduced.
The untransferred toner is toner that has been transferred onto the surface of the photoconductor by the transfer device 60 and is not completely transferred, but remains on the photoconductor, but the toner that is transferred from the photoconductor 11 to the transfer device 60. Since the ratio is constant, the amount of toner remaining after transfer is determined by the image area ratio printed by the user.

Therefore, it is known that the wear on the surface of the photoreceptor has a correlation with the image area. The wear amount of the photoconductor 11 was measured under the condition where the image area ratio was varied. The photoreceptor 11 used here is not provided with a protective layer in order to clarify the action of wear (hereinafter the same).
Ricoh's imagio MP C2200 image forming device was remodeled to print an image with an image area ratio varied in order to change the amount of residual transfer toner input to the cleaning device that cleans the photoconductor. Wear evaluation was performed.
The evaluation conditions are as follows.
1) Image area ratio 2% 5% 20% 50%
2) Printing conditions Continuous printing 3) Number of printed sheets 20000 4) Photoconductor Prototype photoconductor A
In addition, the photoconductor wear measuring method was measured using FISCHERSCOPE · mms manufactured by FISCHER.
24 measurement points were measured in the longitudinal direction, and the wear amount of the photoconductor 11 was calculated from the difference from the initial value of the photoconductor.

The result is shown in FIG.
FIG. 3 is a graph showing the relationship between the waste toner amount and the photoreceptor wear amount.
As shown in FIG. 3, it was found that as the image area ratio increases as the amount of waste toner increases, the amount of wear on the photoconductor also increases in proportion thereto.
As described above, the transfer residual toner is collected as waste toner in the waste toner collecting container 44, and therefore, there is a correlation between the amount of waste toner that is the amount of toner input to the cleaning device 40 and the amount of wear of the photoconductor 11. Therefore, by detecting the amount of waste toner collected in the waste toner collection container 44, the wear amount of the photoconductor can be determined.

As described above, if the transfer residual toner is only determined by the image area ratio to be printed by the user, it is possible to predict the approximate transfer residual toner amount by storing the image information printed by the image forming apparatus 1. it can.
However, in the tandem type image forming apparatus 1, not only the transfer residual toner but also the reverse transfer toner of the upstream developing device 30 is input as the toner input to the cleaning device 40. Reverse transfer is a tandem type in which a toner image formed on an image carrier such as the photoreceptor 11 is sequentially transferred to an intermediate transfer member such as an intermediate transfer belt 61, and toner images of a plurality of colors are formed on the intermediate transfer member. In the color image forming apparatus 1, a part of the toner primarily transferred by the image forming unit 10 on the upstream side of the intermediate transfer member returns to the image carrier of the image forming unit 10 on the downstream side. Yes, it causes color mixing, image distortion, and dirt.
In other words, even if the image information printed by the image forming apparatus 1 is accumulated, the toner that is actually input to the cleaning device 40 differs depending on each image forming unit 10. Further, the toner input amount to the actual cleaning device 40 increases as the image forming unit 10 is downstream.
In addition, the amount of reverse transfer toner varies depending on the overlap of toner on the intermediate transfer belt 61 and the surrounding environment, so that it is difficult to predict. Therefore, directly checking the toner amount input to the cleaning device 40 of each image forming unit 10 can minimize the error.
Since the toner input to the cleaning device 40 is collected in a waste toner collecting container, the wear state of the photoconductor 11 can be predicted by detecting the amount of waste toner. Based on the waste toner amount information obtained from the waste toner amount detection means 46, the wear amount of the photoreceptor 11 is estimated by a photoreceptor wear amount estimation means (not shown) provided in the image forming apparatus 4. .

Next, the image area ratio of each image forming unit 10 was set to 20%, and the amount of wear of the photosensitive member when 20000 sheets were printed was measured.
As the image forming apparatus 1, a Ricoh imagio MP C2200 image forming apparatus is modified, and the yellow image forming unit 10Y, the magenta image forming unit 10M, the cyan image forming unit 10C, and the black image from the upstream side with respect to the rotation direction of the intermediate transfer belt 61. The image forming unit 10K is provided, and the downstream transfer image forming unit 10 has a larger input amount of reverse transfer toner. That is, the amount of toner input to the photoconductor cleaning device 40 increases as the image forming unit is located on the downstream side.
Table 1 shows the amount of waste toner of each image forming unit 10 and the amount of wear of the photoconductor 11.

FIG. 4 is a graph showing the amount of waste toner of each image forming unit and the amount of wear of each photoconductor.
FIG. 5 is a graph showing the relationship between the waste toner amount of the image forming unit and the photoreceptor wear amount.
As shown in FIG. 4, it can be seen that a part of the toner primarily transferred by the image forming unit 10 on the upstream side of the intermediate transfer belt 61 is more than the image forming unit 10 on the downstream side. As a result, the amount of waste toner collected by the black toner image forming unit 10K located on the most downstream side is the largest.
Further, in FIG. 5, it can be seen that the wear amount of the photoconductor 11 increases in proportion to the amount of waste toner, as in the graph shown in FIG.
Thus, a good correlation was obtained between the amount of waste toner discharged from each image forming unit 10 and the amount of wear of the photoconductor 11.

In addition, the Ricoh imagio MP C2200 image forming apparatus was actually remodeled to confirm the amount of waste toner and the amount of photoconductor wear for each number of printed sheets.
The evaluation conditions are as follows.
Evaluation conditions 1) Image area ratio 5%
2) Printing conditions 2 sheets / time 3) Photoconductor Prototype photoconductor A

図６は、作像ユニットの廃トナー量とそれぞれの感光体の摩耗量を示すグラフである。
表２、図６の結果より、８００００枚印刷時に地肌汚れが発生しており、感光体の寿命に達したといえる。よって、６００００枚までが安定して感光体の使用できる枚数とすると、感光体寿命時の廃トナー量は１０５．２ｇになった場合となる。 Table 2 shows the amount of waste toner of the image forming unit 10 and the amount of wear of the photoconductor 11.

FIG. 6 is a graph showing the amount of waste toner of the image forming unit and the amount of wear of each photoconductor.
From the results of Table 2 and FIG. 6, it can be said that the background stain has occurred at the time of printing 80000 sheets, and the life of the photoreceptor has been reached. Accordingly, assuming that the number of sheets of the photoconductor that can be used stably is up to 60,000, the amount of waste toner at the time of the life of the photoconductor becomes 105.2 g.

FIG. 7 is a diagram showing a configuration of waste toner amount detection means used by the image forming apparatus of the present invention.
As shown in FIG. 7, in the waste toner collecting container 44, as a waste toner amount detecting means 46, a light emitting element (LED and a light receiving element (photodiode (PD) or phototransistor (PTr)) as a light emitting part 461 are provided. Then, sensor light is emitted from the light emitting element and received by the light receiving element.
Further, as shown in FIG. 7, in order to detect the amount of waste toner, a transparent transmission window 47 that allows light to pass through the waste toner collection container 44 in the front-rear or left-right direction is provided, and the transmission window 47 can be transmitted. A light emitting unit 461 and a light receiving unit 462 are disposed outside the waste toner collecting container 44. Further, the waste toner amount detection means 46 is provided with a plurality of light emitting units 461, light receiving units 462, and transmission windows 47, so that the waste toner collection container 44 has a light emission depending on whether light is received by each light receiving unit 462. The amount of collected waste toner can be detected.
The detection of the amount of toner in the waste toner collection container 44 by the waste toner amount detection means 46 is not limited to the detection by the optical sensor, but a pressure sensor and a strain sensor are provided under the waste toner collection container 44. The weight of the waste toner may be measured.

In order to determine the life of the photoconductor based on the amount of waste toner in the waste toner collection container 44, it is necessary to detect the amount of waste toner by the waste toner amount detection means 46. A transparent transmission window 47 that allows light to pass through the waste toner collection container 44 in the front-rear or left-right direction is provided, and a light-emitting unit 461 and a light-receiving unit 462 are arranged outside the waste toner collection container 44 so that the transmission window 47 can be transmitted. Then, whether or not a predetermined amount of waste toner has been collected in the waste toner collection container 44 can be confirmed based on whether or not the light receiving unit 462 receives light.
If the amount of waste toner at the lifetime of the photoreceptor is 105.2 g, the bulk density of the waste toner is 0.4 g / cm ³ , so the volume of waste toner is 105.2 / 0.4 = 263 cm ³ . Become. For example, if the bottom area of the waste toner collecting container 44 is 100 cm ² , the amount of waste toner reaches the end of the life of the photoconductor 11 when the height becomes 263/100 = 2.63 cm. A quantity detecting means 46 may be provided.
8A and 8B are diagrams for explaining the operation of the waste toner amount detecting means used in the image forming apparatus of the present invention. FIG. 8A is a state where there is no waste toner in the waste toner collecting container, and FIG. It is a figure of the state where light does not reach.
Since the wear rate varies depending on the diameter and material of the photoconductor 11, the relationship between the photoconductor wear rate and the waste toner amount in the image forming apparatus 1 is confirmed, and the waste toner amount detection means 46 determines the waste toner amount at the time of the photoconductor life. It is necessary to set it so that it can be detected. Therefore, as shown in (b), when a predetermined amount of waste toner is collected and stored in the waste toner collecting container 44 from the state of (a), the light does not reach the light receiving unit. It is determined that the photoconductor 11 has reached an amount of wear that generates an abnormal image.
Therefore, the image forming apparatus 1 of the present invention can estimate the amount of wear of the photoconductor 11 by detecting the amount of waste toner by the waste toner amount detection unit 46, and also estimate the life of the photoconductor 11 associated therewith. be able to.

FIG. 9 is a diagram showing the configuration of waste toner amount detection means used by the tandem type image forming apparatus of the present invention.
Each waste toner collection container 44K, 44C, 44M, 44Y is provided with a partition in order to collect only the waste toner from each image forming unit 10K, 10C, 10M, 10Y. But you can.
Further, a leveling member 481 is provided to level the waste toner collected in each of the waste toner collection containers 44K, 44C, 44M, and 44Y, and leveled by a gear 482 provided outside to improve the accuracy of detection of the waste toner. Can be improved.

Therefore, in the image forming apparatus 1 of the present invention, the waste toner amount detection means 46 detects the waste toner amount in the waste toner collection container 44 and changes the image formation control. For image formation, as described above, at least one change is made from the charging device 20, the exposure device 12, the developing device 30, the charge removal device 13, and the transfer device 60 arranged around the photoreceptor 11. .
FIG. 10 is a block diagram showing control in the image forming apparatus of the present invention.
It controls the output device of the charging device 20, the exposure device 12, the developing device 30, the charge eliminating device 13 and the transfer device 60 around the photoconductor 11 that performs image formation. The signal from the light receiving unit 462 of the waste toner amount detection unit 46 is signal-processed by an image carrier wear amount estimation unit (not shown) in the image forming apparatus 1 to estimate the wear amount of the photoconductor.
The charging device 20, the exposure device 12, the developing device 30, the neutralization device 13, and the transfer device 60 are controlled based on the amount of wear of the photosensitive member, depending on the amount of wear.

In the image forming apparatus 1 of the present invention, the voltage applied to the charging device 20 is changed based on the estimated wear amount of the photoconductor 11.
When the charge transport layer (CTL) of the photoconductor 11 is thinned, the capacitance of the photoconductor 11 is increased, so that the charging potential is lowered and the sensitivity is lowered. Also, due to local wear, background stains are likely to occur due to a decrease in potential on the surface of the photoreceptor.
Increasing the background potential according to the amount of wear of the photoconductor 11 suppresses the generation of background stains. The background potential referred to here is a difference between a charging potential of an unexposed portion (white portion) on the surface of the photoreceptor and a voltage applied to the developing device 30. When this value is increased, an electric field acts on the toner in the direction from the photoconductor 11 to the developing device 30, so that the movement of the toner to the background portion can be prevented, so that the background stain is improved.
Accordingly, the DC bias (DC) and / or AC voltage (AC) applied to the charging roller 21 is calculated based on the estimated wear amount of the photosensitive member 11 by the charging bias calculating means, and the charging bias and charging bias are calculated. The AC current value and the like are controlled by a power source that is an output means, the voltage and current value are determined, and a DC voltage (DC) and / or an AC voltage (AC) is applied.

Using the modified Ricoh imagio MP C2200 image forming apparatus 1, the film thickness and background contamination of the charge transport layer (CTL) of the photoreceptor 11 were confirmed.
Here, the conditions are as follows.
1.1) Conditional trial photoconductor A
2) CTL thickness 26μm (equivalent to initial film thickness)
2.1) Prototype photoconductor B
2) CTL thickness 21μm
3.1) Trial photoconductor C
2) CTL thickness 19μm
The background stain on the photoconductor 11 was measured by changing the background potential. For the background stain, the toner adhered to the white portion on the photoconductor 11 was collected from the white portion on the photoconductor 11 using a transparent tape, and the image density of the tape was measured.

FIG. 11 is a graph showing the relationship between the CTL thickness of the photoreceptor and the background stain.
As shown in FIG. 11, when the background potential at the initial stage of the photoconductor is 150 V, the background stain is deteriorated when the CTL thickness is 19 μm. However, even if the CTL thickness is 19 μm, if the background potential is set to 180 V, the background dirt is improved.
Therefore, the background stain can be improved by increasing the background potential when the wear amount of the photoconductor 11 reaches a predetermined wear amount. As a method of increasing the background potential, it is possible to increase the charging potential of the photoconductor 11 by increasing the bias applied to the charging device 20.

Further, in the image forming apparatus 1 according to the present invention, when a bias in which an AC component is superimposed on a DC component is applied to the charging device 20 disposed in a non-contact manner or close to the photoconductor 11, the estimated wear of the photoconductor 11 is estimated. Based on the amount, the target current value of the AC component is changed.
The method in which a small gap is formed between the photosensitive member 11 and the charging roller 21 is effective against contamination of the charging roller 21 because the charging roller 21 is not in contact with the photosensitive member 11, and the life of the charging roller 21 is increased. Is possible. However, when the photoconductor 11 and the charging roller 21 are close to each other, a slight gap variation affects the uniformity of charging. Therefore, in order to uniformly charge the photoconductor 11, the applied bias is a DC component. It is desirable to superimpose the AC component. The charging roller 11 is preferably controlled by constant current because the resistance varies under the influence of temperature and humidity. However, when the thickness of the photoconductor 11 is reduced, the peak-to-peak potential is increased in order to obtain the same charging current value.

表３に示すように、この結果より、帯電装置２０への交流成分のピークトゥピーク電位が大きくなると感光体１１がフィルミングしたり、異常放電による異常画像が発生する。よって、感光体１１の膜厚が変動すると帯電装置２０の目標電流値の制御変更する必要がある。 Using the modified Ricoh imagio MP C2200 image forming apparatus 1, the CTL thickness of the photoconductor 11, the AC component to the charging device 20, and the occurrence of filming were confirmed.

As shown in Table 3, from this result, when the peak-to-peak potential of the alternating current component to the charging device 20 is increased, the photoconductor 11 is filmed or an abnormal image is generated due to abnormal discharge. Therefore, when the film thickness of the photoconductor 11 varies, it is necessary to change the control of the target current value of the charging device 20.

Using a modified Ricoh imagio MP C2200 image forming apparatus 1, due to abnormal discharge when the CTL film thickness of the photoreceptor 11 and the AC target current value of the AC component in which the AC component of the charging AC component becomes constant are shaken. The occurrence of abnormal images was confirmed.
In addition, the abnormal image here has an abnormal discharge point-like shape.
Here, the conditions are as follows.
1.1) Conditional trial photoconductor A
2) CTL thickness 26μm (equivalent to initial film thickness)
2.1) Prototype photoconductor B
2) CTL thickness 21μm
3.1) Trial photoconductor C
2) CTL thickness 19μm

表４に示すように、異常放電による異常画像は、帯電の交流成分のピークトゥピーク電位と相関があり、帯電の交流成分のピークトゥピーク電位が２１８０Ｖｐ−ｐ以上となると発生する。よって、感光体１１の寿命時まで帯電の交流成分のピークトゥピーク電位が２１８０Ｖｐ−ｐを越えないように制御する必要がある。よって、感光体１１の推定される摩耗量に応じて帯電の交流成分の電流の目標値の制御を変更する。
ここで、例えば、帯電の交流成分の電流の目標値を、電荷輸送層（以下、「ＣＴＬ」と記す。）厚さが２６μｍの時には７００μＡ、ＣＴＬ厚さが２１μｍの時には６５０μＡ、ＣＴＬ厚さが１９μｍの時には６００μＡとなるように感光体の推定摩耗量に達したときに変更するようにすればよい。
これは、実験から得られたパラメータを割り当てても良いし、演算装置で比例式に基づいて摩耗量に対して帯電の交流成分の電流の目標値を変更できるようにしてもよい。

As shown in Table 4, an abnormal image due to abnormal discharge has a correlation with the peak-to-peak potential of the alternating current component of charging, and is generated when the peak-to-peak potential of the alternating current component of charging becomes 2180 Vp-p or more. Therefore, it is necessary to control so that the peak-to-peak potential of the alternating current component of charging does not exceed 2180 Vp-p until the lifetime of the photoconductor 11. Therefore, the control of the target value of the current of the alternating current component of charging is changed according to the estimated wear amount of the photoconductor 11.
Here, for example, the target value of the current of the alternating current component of charging is 700 μA when the charge transport layer (hereinafter referred to as “CTL”) thickness is 26 μm, and 650 μA when the CTL thickness is 21 μm, and the CTL thickness is When it is 19 μm, it may be changed to 600 μA when the estimated wear amount of the photoreceptor is reached.
For this, a parameter obtained from an experiment may be assigned, or the target value of the current of the alternating current component of charging may be changed with respect to the amount of wear based on a proportional expression by an arithmetic unit.

In the image forming apparatus 1 of the present invention, the output of the exposure device 12 is changed based on the estimated wear amount of the photoconductor 11.
When the film thickness of the photoconductor 11 is reduced, the potential after exposure increases. When the post-exposure potential increases, the potential difference from the bias applied to the development becomes smaller, so that the developing ability is lowered and the image density is lowered. Therefore, if the output of the exposure device 12 is changed according to the estimated wear amount of the photoconductor 11, the target post-exposure potential can be obtained, and the target image density can be obtained.
Using a modified Ricoh imagio MP C2200 image forming apparatus 1, the relationship between the CTL film thickness of the photoconductor 11 and the post-exposure potential when the laser output was constant was confirmed.
Here, the conditions are as follows.
1.1) Conditional trial photoconductor A
2) CTL thickness 26μm (equivalent to initial film thickness)
2.1) Prototype photoconductor B
2) CTL thickness 21μm
3.1) Trial photoconductor C
2) CTL thickness 19μm
4). Dark part potential 600V
The result is shown in FIG.
FIG. 12 is a graph showing the relationship between the CTL film thickness of the photoreceptor and the post-exposure potential.
Here, a sufficient exposure amount is obtained when the CTL thickness is 26 μm, but the post-exposure potential increases as the CTL thickness decreases. Therefore, the potential after exposure increases as the film thickness of the photoconductor 11 decreases as described above.
For each CTL thickness, increasing the laser output can lower the post-exposure potential.

Further, it was confirmed that the post-exposure potential could be lowered to the same potential as the CTL layer 26 μm (corresponding to the initial film thickness) by increasing the laser output for the photoreceptor 11 having a CTL thickness of 21 μm and 19 μm.
FIG. 13 is a graph showing the relationship between the CTL film thickness of the photoreceptor and the post-exposure potential when the output of the laser beam is changed.
As a result, the potential difference in developing the toner can be made constant even if the photoconductor 11 is worn without changing the bias applied to the development. Therefore, the image density can be stabilized by changing the control of the laser beam output in the exposure device 12 until the lifetime of the photoconductor 11.
For this, a parameter obtained from an experiment may be assigned, or the control of the target value of the exposure apparatus 12 may be changed with respect to the wear amount based on a calculation formula by an arithmetic unit.

表５に示すように、感光体１１のＣＴＬ厚が薄くなるにつれて、同じ現像バイアスでも画像濃度が低下している。 In the image forming apparatus 1 of the present invention, the voltage applied to the developing device 30 is changed based on the estimated wear amount of the photoconductor 11.
As the film thickness of the photoconductor 11 decreases, the post-exposure potential increases. When the post-exposure potential rises, the potential difference from the bias applied to the developing device 30 decreases, so that the developing ability of the developing device 30 decreases and the image density decreases. Therefore, by increasing the voltage applied to the developing device 30 in accordance with the estimated amount of wear of the photoconductor 11, the potential difference of the post-exposure potential between the developing device 30 and the photoconductor 11 is made constant from the beginning, so that the photoconductor. Even if 11 is worn, the image density can be kept constant.
The relationship between the black solid image density when the CTL film thickness of the photoconductor 11 and the bias applied to the developing device 30 are made constant using the modified Ricoh imagio MP C2200 image forming apparatus 1 is shown.
Here, the conditions are as follows.
1.1) Conditional trial photoconductor A
2) CTL thickness 26μm (equivalent to initial film thickness)
2.1) Prototype photoconductor B
2) CTL thickness 21μm
3.1) Trial photoconductor C
2) CTL thickness 19μm
4). Dark part potential 600V
Measuring instrument X-rite 938

As shown in Table 5, as the CTL thickness of the photoconductor 11 decreases, the image density decreases even with the same developing bias.

表６に示すように、現像に必要な電位差が得られることから、目標の画像濃度１．４０異常とすることができる。これは、実験から得られたパラメータを割り当てても良いし、演算装置で比例式に基づいて摩耗量に対して、現像装置３０における現像バイアスの制御を変更できるようにしてもよい。 As described above, the target image density is 1.40 or more. However, when the CTL thickness of the photoconductor 11 is 21 μm or less, the image density is 1.40 or less. However, when the CTL thickness is 21 μm and 19 μm, the bias applied to the developing device 30 is increased to 500 V and 550 V, respectively.

As shown in Table 6, since a potential difference necessary for development can be obtained, the target image density of 1.40 can be determined to be abnormal. For this, a parameter obtained from an experiment may be assigned, or the control of the developing bias in the developing device 30 may be changed with respect to the wear amount based on a proportional expression by the arithmetic device.

Further, in the image forming apparatus 1 of the present invention, the condition for the static eliminator 13 disposed downstream of the cleaning device 40 is changed based on the estimated wear amount of the photoconductor 11.
When the film thickness of the photoconductor 11 is reduced, a phenomenon of an afterimage in which an image is written on the photoconductor 11 by the exposure device 12 and an image appears after one turn of the photoconductor 11 occurs. After the portion where the photoconductor 11 is written by the exposure device 12 passes through the transfer device 60, a positive charge remains on the photoconductor 11 due to the transfer bias, and even if that portion is charged by the next charging device 20. The potential of the exposed portion exposed by the laser beam is in a slightly low state. Therefore, the potential difference appears as an image. By using the charge eliminating device 13, it is possible to remove the charge on the photoconductor after the transfer, and it is possible to uniformly charge the next charge, so that the afterimage is improved.
However, when the film thickness of the photoconductor 11 is reduced, the setting conditions of the static eliminator 13 set in accordance with the photoconductor 11 having a short initial use time become insufficient, and a potential difference remains on the photoconductor 11. It will remain. Therefore, by increasing the charge removal capability under the set conditions of the charge removal device 13 from the photoconductor 11 having a short initial use time in accordance with the wear amount of the photoconductor 11, a stable image with no afterimage can be obtained until the lifetime.

Table 7 shows the result of changing the conditions of the static eliminator with respect to the CTL thickness of the photoconductor 11 and the occurrence of afterimages using the modified Ricoh imagio MP C2200 image forming apparatus 1.
This time, a static elimination lamp was used for the static elimination device 13. The input current was changed as a method of changing the illuminance of the static elimination lamp.
Here, the conditions are as follows.
1. Static elimination lamp specifications
Peak wavelength: 660 ± 20 nm
Illuminance: 27 to 120 mW / m ²
Photoconductor prototype photoconductor A CTL thickness 26μm (equivalent to initial film thickness)
Prototype photoconductor B CTL thickness 21μm
Prototype photoconductor C CTL thickness 19μm
Dark part potential 600V

表７に示すように、感光体膜厚が薄くなると残像を改善するための除電ランプ１３の入力電流を大きくする必要がある。よって、感光体１１の推定摩耗量に応じて、除電ランプ１３の入力電流を大きくすることで、残像のない安定した画像を得ることができる。
これは、実験から得られたパラメータを割り当てても良いし、演算装置で比例式に基づいて摩耗量に対して除電装置１３に印加する電圧を制御を変更することができるようにしてもよい。除電装置１３としては、除電ランプの他にチャージャでもよい。

As shown in Table 7, it is necessary to increase the input current of the static elimination lamp 13 for improving the afterimage as the photosensitive member film thickness decreases. Therefore, by increasing the input current of the static elimination lamp 13 in accordance with the estimated wear amount of the photoconductor 11, a stable image with no afterimage can be obtained.
For this, a parameter obtained from an experiment may be assigned, or the calculation device may be able to change the control of the voltage applied to the static eliminator 13 with respect to the wear amount based on a proportional expression. The static eliminator 13 may be a charger in addition to the static eliminator lamp.

Next, an image forming operation will be described.
When the image forming operation starts, first, the waste toner amount detection means 46 starts to detect the amount of waste toner in the waste toner storage container 44. At this time, the amount of waste toner is detected, and the amount of wear of the photoconductor 11 is estimated. When the estimated amount of wear does not require changing the image forming conditions, the following image forming operation is started.
The photoconductor 11 of each image forming unit 10 is rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductor 11 is uniformly charged to a predetermined polarity by the charging roller 21. The surface of each charged photoconductor 11 is irradiated with laser light L from the exposure device 12 to form an electrostatic latent image on each surface. At this time, for example, the image information that is read by the reading device 3 that reads the document and is exposed to each photoconductor 11 by the arithmetic unit is a single color obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. Image information. The electrostatic latent image formed in this manner is visualized as a toner image by toner stored in each developing device 30 when passing between each photoconductor 11 and the developing device 30.
One of the plurality of support rollers 65, 66 around which the intermediate transfer belt 61 is wound is driven to rotate counterclockwise by a driving device (not shown), thereby driving the intermediate transfer belt 61 to travel, The roller is driven to rotate. To the intermediate transfer belt 61 that travels in this manner, the toner images of the respective colors formed by the respective image forming units 10 are sequentially superimposed and transferred by the primary transfer roller 62, and a full-color toner image is formed on the surface of the intermediate transfer belt 61. Supported.
Residual toner adhering to the surface of each photoconductor 11 after the toner image is transferred is removed from the surface of each photoconductor 11 by the cleaning device 40, and the surface of the photoconductor 11 is discharged by a static eliminator (not shown). Initialization prepares for the next image formation.
On the other hand, the paper fed from the paper feed tray 81 is sent to the transport path, and the roller 66 and the secondary transfer roller 66 are timed by the registration roller pair 83 disposed on the paper feed side from the secondary transfer roller 63. Feed to the nip. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt 61 is applied to the secondary transfer roller 66, whereby the toner image on the surface of the intermediate transfer belt 61 is collectively put on the sheet. And transcribe. The sheet on which the toner image has been transferred is conveyed to the fixing device 70, and heat and pressure are applied when passing through the fixing device 70 to melt and fix the toner image. Then, the sheet on which the toner image is fixed, that is, the printed sheet, is conveyed to a discharge roller 84 positioned at the end of the conveyance path provided near the upper part of the image forming apparatus 1 and configured on the upper part of the image forming apparatus 1. Discharge to the loading section. The toner remaining on the intermediate transfer belt 61 after the toner image is transferred to the paper is removed by the belt cleaning device 64 and cleaned.

On the other hand, when it is determined that the estimated wear amount needs to change the image forming conditions, the charging unit 20, the developing device 30, the exposure device 12, and the charge eliminating device 13 are controlled by the control unit in the image forming apparatus 1. The optimum conditions are determined according to the amount of wear of the photoconductor 11, the control is changed, and the image forming operation is performed. At this time, it is possible to appropriately determine which device is to be controlled.
The above description is an image forming operation when a full-color image is formed on a sheet. However, a single-color image can be formed using any one of the image forming units 10 of the image forming unit 2, or 2 A color or three-color image may be formed. Further, when monochrome printing is performed using the image forming apparatus 1 of the present embodiment, an electrostatic latent image is formed only on the photoconductor 11K of the black image forming unit 10 and transferred to a sheet by the intermediate transfer device 60. Then, the image may be fixed by the fixing device 70.
The image forming unit 10 is a so-called process cartridge, and the photosensitive member 11, the developing device 30, the cleaning device 40, and the charging device 20 are integrated.

  As described above, in the image forming apparatus 1 of the present invention, the image density is reduced by reducing the film thickness of the photoconductor 11, and an abnormal image due to an afterimage or abnormal discharge due to the charging device is likely to occur. In order to remedy these problems, the charging device 20, the developing device 30, the exposure device 12, and the charge removal device 13 determine the optimum conditions according to the amount of wear of the photoconductor 11, and the photosensitive device The film thickness of the body 11 is worn, and a comprehensively stable image can be provided until the lifetime.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 3 Reading apparatus 10 Image forming unit / process cartridge 11 Photoconductor 12 Exposure apparatus 13 Static elimination charger 20 Charging apparatus 21 Charging roller 30 Developing apparatus 31 Toner replenishing unit 32 Developing sleeve 33 Restricting member 40 Cleaning apparatus 41 Cleaning blade 42 Recovery roller 43 Waste toner recovery path 44 Waste toner recovery container 45 Waste toner discharge port 46 Waste toner amount detection means 461 Light emission part 462 Light reception part 47 Transmission window 481 Leveling member 482 Gear 50 Lubricant application means 51 Brush roller 52 Solid lubricant 53 Compression spring 60 Transfer device 61 Intermediate transfer belt 62 Primary transfer roller 63 Secondary transfer roller 64 Belt cleaning device 65, 66 Support roller 70 Fixing device 80 Paper feed device 81 Paper feed cassette 82 Paper feed roller 83 Registration roller 84 Paper discharge roller

Japanese Patent Laid-Open No. 08-220935 JP 2005-266056 A JP-A-10-161487 JP 2008-107571 A JP 2006-267972 A JP 2004-101837 A

Claims (9)

An image carrier for carrying an electrostatic latent image;
A charging device disposed in contact with or in proximity to the image carrier to charge the surface of the image carrier;
An exposure device that exposes the surface of the image carrier and writes an electrostatic latent image;
A developing device that visualizes the latent image formed on the surface of the image carrier with toner;
A transfer device for transferring a visible image on the surface of the image carrier to a transfer target;
A cleaning device disposed downstream of the transfer device and cleaning toner on the surface of the image carrier,
The image forming apparatus includes:
A waste toner collecting container for collecting waste toner conveyed from the cleaning device;
An image forming apparatus comprising: a waste toner amount detection unit configured to detect a waste toner amount in a waste toner collection container, and estimating an abrasion amount of the image carrier. The image forming apparatus according to claim 1.
The image forming apparatus includes:
An image forming apparatus, wherein control of image formation is changed based on an estimated amount of wear of the image carrier. The image forming apparatus according to claim 1, wherein
The image forming apparatus includes:
An image forming apparatus, wherein the voltage applied to the charging device is changed based on the estimated wear amount of the image carrier. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus includes:
When applying a bias in which an alternating current component is superimposed on a direct current component to a charging device arranged in non-contact with or close to the image carrier,
An image forming apparatus, wherein the current target value of the AC component is changed based on the estimated wear amount of the image carrier. The image forming apparatus according to claim 1,
The image forming apparatus includes:
An image forming apparatus comprising: changing an output of an exposure apparatus based on an estimated wear amount of the image carrier. The image forming apparatus according to claim 1,
The image forming apparatus includes:
An image forming apparatus, wherein a voltage applied to a developing device is changed based on an estimated amount of wear of the image carrier. The image forming apparatus according to claim 1,
The image forming apparatus includes:
An image forming apparatus characterized in that, based on an estimated amount of wear of the image carrier, a condition for a static eliminator disposed downstream of a cleaning device is changed. The image forming apparatus according to claim 1, wherein
The image forming apparatus includes:
An image forming apparatus, wherein at least one change is made from a charging device, an exposure device, a developing device, a charge removal device, and a transfer device based on the estimated wear amount of the image carrier. The image forming apparatus according to claim 1,
The image forming apparatus includes:
An image forming apparatus comprising: a process cartridge that integrally supports at least an image carrier, a charging device, and a cleaning device, and is attachable to and detachable from an image forming apparatus main body.

Images