JP3744170B2 - Color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an image forming apparatus such as a copying machine, a printer, or a fax machine, in which a plurality of sets of charging means, image exposing means, and developing means are arranged around an image forming body to generate a toner image during one rotation of the image forming body. The present invention relates to an electrophotographic color image forming apparatus that superimposes and forms a color image.
[0002]
[Prior art]
Conventionally, as a method for forming a multicolor image, the same number of image forming bodies as those required for image formation, charging means, developing means, etc. are provided, and a single color toner image formed on each image forming body is transferred. A color image forming apparatus that forms a color image by superimposing on a material, a color image forming apparatus that rotates an image forming body a plurality of times and repeats charging, image exposure, and development for each color, or a similar image 2. Description of the Related Art A color image forming apparatus that forms a color image by sequentially performing charging, image exposure, and development for each color within one rotation of a formed body is known.
[0003]
However, each of the image forming apparatuses described above includes the same number of image forming bodies, charging means, developing means, etc. as the number of colors required for image formation, and a single color toner image formed on each image forming body is superimposed on a transfer material to form a color. A color image forming apparatus for forming an image has a disadvantage that the volume of the apparatus is increased because it requires transport of a plurality of image forming bodies and transfer materials. On the other hand, the image forming body is rotated a plurality of times to charge and image each color. A color image forming apparatus that repeats exposure and development to form a color image has a limitation that the size of the formed image is limited to the surface area of the image forming body, although the volume is reduced.
[0004]
In that respect, a color image forming device that forms a color image by sequentially performing charging, image exposure, and development for each color within one rotation of the image forming body has no restrictions on the size of the image and enables high-speed image formation. There are advantages such as. Further, for example, Japanese Patent Laid-Open No. 5-307307 proposes a device in which a light-transmitting substrate is used as a substrate of an image forming body and an image exposure unit is arranged inside the image forming body to reduce the size of the apparatus. .
[0005]
On the other hand, as a photoreceptor layer of an image forming body used in a color image forming apparatus, an OPC photoreceptor (organic photoreceptor) is generally used as being inexpensive and stable.
[0006]
[Problems to be solved by the invention]
However, in the color image forming apparatus according to the above proposal, the pre-charging exposure means for removing the optical memory of the image forming body is arranged opposite to the cleaning means so as to irradiate the cleaning means with the light, but the image is formed. When an OPC photoconductor is used as the forming body, the OPC photoconductor has a slow charge transfer speed and takes a time (about 0.05 to 0.2 sec) until the potential is lowered. Furthermore, the potential change due to temperature change is also large. For this reason, unlike an inorganic photoconductor such as a Se photoconductor, it is necessary to reduce the potential from the pre-charging exposure unit to the charging unit at the most upstream position in the rotation direction of the image forming body arranged close to the pre-charging exposure unit. Become. That is, the apparatus needs to be set so that the potential should be sufficiently lowered before the exposed portion of the image forming body by uniform exposure enters the charging unit position from the uniform exposure position by the pre-charging exposure unit. There is a problem of increasing the size.
[0007]
On the other hand, when the charge potential of the image forming body is reduced to about ½ or less by uniform exposure of the pre-charging exposure means (photostatic discharge), the inside of the cleaning means that is repelled and difficult to adhere due to the same polarity as the image forming body The electric repulsion of the toner with the image forming body in which the potential is lowered is weakened. In other words, the toner inside the cleaning unit easily adheres to the image forming body, the toner inside the cleaning unit adheres to the image forming body, is transported to the outside, and is scattered. There arises a problem that image contamination occurs due to contamination of the means and toner adhesion to the image forming body.
[0008]
  The present invention improves the above-mentioned problems, reduces the size of the apparatus, and forms a toner image inside the cleaning unit due to a decrease in potential (photostatic discharge) of the image forming member after uniform exposure by the pre-charging exposure unit. To provide a color image forming apparatus that prevents adhesion to a forming body and prevents internal contamination, charging means, and image contamination caused by toner inside a cleaning unit adhering to an image forming body and being carried to the outside.EyesTarget.
[0015]
[Means for Solving the Problems]
  The object is to provide a plurality of charging means, image exposing means and developing means on the peripheral surface of the image forming body, and repeating charging, image exposing and developing during one rotation of the image forming body. A color toner image is formed by superimposing a plurality of toner images on the peripheral surface, the color toner image is transferred onto a recording material by a transfer unit, and the color toner image on the recording material is fixed by a fixing unit. In the color image forming apparatus in which the transfer residual toner on the image forming body is cleaned by a cleaning unit, an organic photoconductor is used for the image forming body, and the image forming body is uniformly exposed to pre-exposure. Means in the cleaning means, and in the step from the uniform exposure position of the pre-charge exposure means to the charging means at the most upstream position in the rotation direction of the image forming body, the exposure at the uniform exposure position A color image forming apparatus, wherein the exposed portion on the image forming body is moved out of the cleaning means until the charged potential V1 of the portion is attenuated to (V1) / 2. Achieved byThe
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. The description of the present application does not limit the technical scope of the claims or the meaning of the terms. In addition, the following assertive description in the embodiment of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention. In the following description, a color image forming method is employed in which a color toner image formed on an image forming body is once transferred to an intermediate transfer body and then transferred to a recording material from the intermediate transfer body. A color toner image on the image forming body may be directly transferred to a recording material without using a body. Therefore, in this description, the transfer process using the intermediate transfer member as a transfer unit will be described, but the present invention is also applicable to a transfer process in which a transfer member that transfers directly from an image forming member to a recording material is used as a transfer unit.
[0019]
An image forming process and mechanisms of an embodiment of a color image forming apparatus common to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional configuration diagram of an embodiment of a color image forming apparatus common to the present invention, and FIG. 2 is a diagram illustrating a configuration of an image exposure unit in FIG. 1 and a mounting method to a support member. 3 is a perspective view of FIG. 2, and FIG. 4 is a cross-sectional configuration diagram of the image forming body of FIG.
[0020]
According to FIGS. 1 to 4, the photosensitive drum 10 as an image forming body is provided with a translucent material on the outer periphery of a cylindrical substrate formed of a translucent member such as glass or translucent acrylic resin. A conductive layer and a photoconductor layer of an organic photosensitive layer (OPC) are formed. The photosensitive drum 10 is rotated in the direction indicated by the arrow in FIG. 1 with the translucent conductive layer grounded by power from a driving source (not shown).
[0021]
In the present invention, the photoconductive layer of the photoconductive drum, which is the imaging point of the exposure beam for image exposure, has a wavelength that can provide an appropriate contrast with respect to the light attenuation characteristics (photo carrier generation) of the photoconductive layer. What is necessary is just to have the amount of exposure light. Therefore, the light transmittance of the light-transmitting substrate of the photosensitive drum in this embodiment does not need to be 100%, and may have a characteristic that a certain amount of light is absorbed when the exposure beam is transmitted. Need only be able to provide an appropriate contrast. As the material of the translucent substrate, an acrylic resin, particularly polymerized using a methacrylic acid methyl ester monomer is preferably used because it is excellent in translucency, strength, accuracy, surface property, etc. Other general optical members, etc. Various translucent resins such as acrylic, fluorine, polyester, polycarbonate, polyethylene terephthalate, etc. used in the above can be used. Moreover, as long as it has translucency with respect to exposure light, you may color. As the translucent conductive layer, indium tin oxide (ITO), tin oxide, lead oxide, indium oxide, copper iodide, a metal thin film that maintains translucency, such as Au, Ag, Ni, and Al is used. As the film formation method, a vacuum deposition method, an active reaction deposition method, various sputtering methods, various CVD methods, a dip coating method, a spray coating method, or the like is used. In addition, various organic photosensitive layers (OPC) are used as the photoconductor layer.
[0022]
Examples of preferable image forming bodies are shown below.
[0023]
After synthesizing the plastic material monomer and adding a catalyst for polymerization, it is poured into a cylindrical mold, sealed and fixed with a side plate, and rotated at high speed while being appropriately heated in an oil bath or hot water tank. To promote uniform polymerization. After the polymerization is completed, the resultant is cooled, and the obtained translucent resin substrate is taken out of the mold and cut. If necessary, a transparent resin substrate for a photosensitive drum of an image forming apparatus is manufactured through a finishing process (centrifugal weight). legal).
[0024]
As a material of a translucent resin base material of translucent plastic molded by centrifugal polymerization, polymerized using a methacrylic acid methyl ester monomer as described above is most effective in translucency, strength, accuracy, surface properties, etc. In addition, other polyethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, polyimide, polyester, polyvinyl chloride, or a copolymer thereof may be used. In the centrifugal polymerization method, since the roundness is determined by the mold used for molding, a highly accurate substrate can be obtained. Further, the uneven thickness changes depending on the rotation unevenness and viscosity during polymerization and the heating conditions during polymerization.
[0025]
As the conductive layer, conductive in which conductive fine particles made of indium tin oxide (ITO), tin oxide, lead oxide, indium oxide, alumina, copper iodide, Au, Ag, Ni, Al, etc. are mixed with a resin. Resin is used, and as a film forming method, a dip coating method, a spray coating method or the like is preferably used.
[0026]
The organophotoreceptor layer has a two-layer structure that is functionally separated into a charge generation layer (CGL) mainly composed of a charge generation material (CGM) and a charge transport layer (CTL) mainly composed of a charge transport material (CTM). The photoreceptor layer. The organic photoreceptor layer having a two-layer structure has a thin CGL, and therefore has a good image exposure light transmittance and is suitable for the present invention. The organic photoreceptor layer may have a single layer structure containing a charge generation material (CGM) and a charge transport material (CTM) in one layer, and the single layer structure or the two layer structure of the photoreceptor layer. Usually contains a binder resin.
[0027]
In the photosensitive drum having the two-layered organic photosensitive layer, CGM contained in CGL includes azo pigments, azulenium pigments, phthalocyanine pigments, and perylene-based pigments that are sensitive to light sources such as LEDs and LDs. Among them, a copper phthalocyanine pigment, a titanyl phthalocyanine pigment, or the like is preferably used as the CGM of the OPC photoreceptor that is sensitive to red to infrared light (600 nm to 850 nm).
[0028]
As the binder resin used for CGL, polyvinyl butyral resin or polycarbonate resin is used, which is excellent in sensitivity, potential change during repeated use, and the like. These binder resins can be used alone or as a mixture of two or more.
[0029]
As the solvent or dispersion medium used for forming CGL, a ketone-based or halogen-based solvent is preferably used, and sensitivity, potential change during repeated use, and the like are further improved. These solvents may be used alone or as a mixed solvent of two or more.
[0030]
The weight ratio of CGM and binder resin in the CGL is 100: 1 to 1000, and the film thickness of the CGL is 0.01 to 10 μm. The coating methods for forming the CGL include blade coating and wire coating. There are various coating methods such as bar coating, spray coating, dip coating, and slide hopper coating.
[0031]
Next, as the CTM contained in the CTL, hydrazone compounds, styryl compounds, benzidine compounds, stilbene compounds, and the like are used.
[0032]
The binder resin used in the CTL can be selected from a wide range of insulating resins in a timely manner, and preferred binder resins include silicon-alkyd resins, phenol-formaldehyde resins, poly-N-vinylcarbazole, An insulating resin such as polysilane can be used, and these binder resins can be used alone or in combination of two or more.
[0033]
The blending ratio of the binder resin and CTM is 1:10 to 500, and more preferably 1:20 to 150. The film thickness of CTL is set to 1 to 100 μm, and more preferably 5 to 50 μm.
[0034]
As a coating method, a method similar to CGL can be used.
[0035]
An intermediate layer is provided between the organic photoreceptor layer and the conductive layer as necessary. Examples of the intermediate layer include a vinyl acetate vinyl acetate copolymer, a vinyl acetate vinyl maleic acid copolymer, ethyl cellulose, carboxymethyl cellulose, and copolymer. The resin layer is 0.01 to 2 μm thick, such as a type or modified type alcohol-soluble polyamide resin.
[0036]
By using the plastic cylindrical translucent resin substrate made by the above manufacturing method, the thickness is uniform, the cylindrical substrate is excellent in cylindricity and roundness, and the defocus of image exposure light is reduced. No photoreceptor drum is provided.
[0037]
The scorotron charger 11 as the charging means, the exposure optical system 12 as the image exposing means, and the developing device 13 as the developing means described below are yellow (Y), magenta (M), cyan (C) and black, respectively. Used in the image forming process of each color of (K), and in this embodiment, they are arranged in the order of Y, M, C, K with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG.
[0038]
Reference numeral 12A denotes a pre-charge exposure unit as a pre-charge exposure unit using, for example, a light emitting diode, for removing the optical memory of the organic photosensitive layer of the photosensitive drum 10, and is attached to the support member 20 as a cleaning unit to be described later. The cleaning blade 101 provided in the cleaning device 100 on the downstream side in the rotation direction of the photosensitive drum 10 from the contact position with the photosensitive drum 10 faces the cleaning device 100 with the photosensitive drum 10 interposed therebetween. It is arrange | positioned inside.
[0039]
A scorotron charger 11 as a charging means is attached in close proximity to the photosensitive drum 10 in a direction orthogonal to the moving direction of the photosensitive drum 10 as an image forming body (in the direction perpendicular to the paper surface in FIG. 1). The control grid maintained at a predetermined potential with respect to the above-described organic photoreceptor layer of the body drum 10 and, for example, a wire electrode as a corona discharge electrode, and charging action by corona discharge having the same polarity as the toner (in this embodiment) Is negatively charged), and a uniform potential is applied to the photosensitive drum 10. As the corona discharge electrode, other needle-like or saw-toothed electrodes can be used.
[0040]
After the optical memory is removed by charge removal of the pre-charge exposure unit 12A or charge removal by a corona charge remover (not shown), uniform charging is performed by, for example, the first color Y scorotron charger 11.
[0041]
The exposure optical system 12 as image exposure means for each color of Y, M, C, and K is a plurality of light emitting elements arranged on the substrate 122 as an exposure system in the main scanning direction parallel to the axis of the photosensitive drum 10. The LED (light emitting diode) 121 is a linear exposure element 12a arranged in an array, and a light converging light transmission body (trade name, Selfoc lens) 12b as an imaging element. The lens holder 12c is fixed with, for example, an adhesive indicated by a black circle in FIGS. 2 and 3, and the exposure element 12a is attached to a metal casing 12d as a holding member for the exposure element having good thermal conductivity by an adhesive indicated by a black circle, for example. In a state where the exposure element 12a and the SELFOC lens 12b are positioned, the lens holder 12c is bonded to the metal casing 12d by a black circle, for example. Exposure optical system 12 is constructed is fixed by. By using the metal casing 12d, the heat generated in the exposure element 12a is quickly transmitted and diffused, and the non-uniformity of the exposure element 12a affects the positional deviation and light quantity fluctuation between the exposure elements 12a due to thermal expansion. Temperature distribution and temperature rise are prevented.
[0042]
The exposure element holding member is a metallic casing as a preferred example. However, the exposure element holding member is not necessarily limited to a metallic member, and may be a resin casing.
[0043]
In addition, FL (phosphor light emission), EL (electroluminescence), PL (plasma discharge), or the like is used as the light emitting element.
[0044]
The exposure optical system 12 for each color uses a spacer block 12e as a wedge-shaped block member, and positions the main scanning direction with respect to the photosensitive drum 10 and the sub-scanning direction of the rotating direction of the photosensitive drum 10 with a jig or the like in advance. A metal casing 12d, a spacer block 12e, and a support member 20 using a pipe-shaped hollow member such as a cylindrical pipe or a square pipe, which is a common support of image exposure means for each color, adjusted to the state of being exposed. However, the spacer block 12e and the support member 20 are fixed to each other with, for example, an adhesive indicated by black circles in FIGS. With the exposure optical system 12 for each color being held, the support member 20 is disposed inside the photoconductive drum 10 with the central axis of the support member 20 aligned with the central axis of the photoconductive drum 10. Therefore, image exposure by the exposure optical system 12 is performed on the photosensitive drum 10 perpendicularly to the central axis of the photosensitive drum 10.
[0045]
Further, the distance between the inner peripheral surface of the support member 20 and the outer peripheral surface of the substrate of the photosensitive drum 10 is larger than the height of the exposure optical system 12 and the distance to the image forming position, that is, the bottom surface of the exposure optical system 12. Has a circumferential surface whose size is always positioned outside the inner circumferential surface of the support member 20, so that the support member 20 does not need to break the cylindrical surface, and the exposure optical system 12 is maintained in strength. Can be reliably held at a predetermined imaging position.
[0046]
An image signal of each color which is read by an image scanner or inputted by an external signal or the like and stored in a RAM (not shown), for example, RAM, is sequentially read out from the storage unit through the control unit of the apparatus main body and exposed for each color. Each is input as an electrical signal to the optical system 12, and the LED 121 emits light by, for example, a pulse width modulation method (PWM method). The light emission wavelength of the light emitting element used in this embodiment is in the range of 600 to 900 nm.
[0047]
As described above, each exposure optical system 12 is attached to the support member 20 that is a common support using a pipe-shaped hollow member, and is accommodated in the base of the photosensitive drum 10, and the substrate of each exposure optical system 12 The lead wire WA of the LED 121 is provided through the connector C drawn from 122 and attached to the lower end of the metal casing 12d. The lead wires WA for the respective colors are drawn out from the insertion holes 20H and bundled, passed through the hollow portion of the support member 20, and drawn out from the insertion holes 30H of the side substrate 30 to the outside of the substrate. In addition, the support member 20 is attached with the above-described pre-charge exposure unit 12A as a pre-charge exposure unit, a pre-transfer exposure unit 12B as a pre-transfer exposure unit, and a pre-cleaning exposure unit 12C as a pre-cleaning exposure unit. Each of the lead wires (not shown) housed in the base body of the body drum 10 passes through the hollow portion of the support member 20 and is drawn out from the insertion hole 30H of the side substrate 30 to the outside of the substrate.
[0048]
After the connection between the connector C and the lead wire WA, each insertion hole 20H is closed together with the lead wire WA from the inner peripheral side of the support member 20 with the seal member S, thereby intruding scattered toner and dust into the exposure optical system 12. Is prevented. Further, the insertion hole 20H is filled with an adhesive or an elastic member such as urethane foam or rubber material to prevent intrusion of toner or dust. As the sealing material S, for example, a curable silicone rubber sheet is used, and each insertion hole 20H is closed by an adhesive or the like, whereby airtightness is maintained. As a result, the lead wire WA is easily connected to the fixed electrode PA along the inner peripheral surface of the support member 20 without being strongly bent. Further, the holding member of the exposure element is not subjected to stress due to the lead wire WA and does not come off due to bending of the lead wire WA or the like.
[0049]
The support member 20 that is a common support for each exposure optical system 12 is a thin hollow member formed of a light metal material such as aluminum or stainless steel, preferably a cylindrical pipe or a square pipe. As a result, the weight of the support member 20 using a metallic hollow member can be reduced and the heat capacity can be reduced, the weight of the image forming portion can be reduced, the heat capacity can be reduced, the heat conductivity can be improved, and the temperature adjustment efficiency can be improved. It has been. Also, cylinders and prismatic pipes are resistant to mechanical deformation.
[0050]
Reference numeral 13 denotes a developing unit serving as a developing unit that accommodates yellow (Y), magenta (M), cyan (C), and black (K) developers, each having a predetermined gap with respect to the peripheral surface of the photosensitive drum 10. A developing sleeve 130 that rotates in the same direction is provided.
[0051]
Each of the developing devices described above is configured so that the electrostatic latent image formed on the photosensitive drum 10 formed by charging by the scorotron charger 11 and image exposure by the exposure optical system 12 is in a non-contact state by applying a developing bias voltage. Reverse development.
[0052]
The document image is stored in the memory once as an image signal for each color of Y, M, C, and K, in an image reading device separate from the present device, and an image read by the image sensor or an image edited by a computer. Stored.
[0053]
At the start of image recording, the photosensitive drum 10 is rotated counterclockwise by the start of the photosensitive drum drive motor. At the same time, the optical memory of the photosensitive drum 10 is removed by uniform exposure by the pre-charge exposure unit 12A, and then the scorotron charging is performed. Application of a potential to the photosensitive drum 10 is started by the charging action of the device 11 (Y).
[0054]
After a potential is applied to the photosensitive drum 10, exposure by an electrical signal corresponding to the first color signal, that is, the yellow (Y) image signal is started in the exposure optical system 12 (Y), and the drum is rotated and scanned. An electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer on the surface.
[0055]
The latent image is reversed and developed by the developing device 13 (Y) in a state where the developer on the developing sleeve is not in contact, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.
[0056]
Next, a potential is applied to the photosensitive drum 10 by the charging action of the second color scorotron charger 11 (M) on the yellow (Y) toner image, and the second color signal of the exposure optical system 12 (M). That is, exposure is performed with an electric signal corresponding to the magenta (M) image signal, and magenta (M) toner is formed on the yellow (Y) toner image by non-contact reversal development by the developing unit 13 (M). Images are formed by sequentially overlapping.
[0057]
By a similar process, a cyan (C) toner image corresponding to the third color signal is also obtained by the third color scorotron charger 11 (C), exposure optical system 12 (C), and developer 13 (C). A black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed by the color scorotron charger 11 (K), the exposure optical system 12 (K), and the developing device 13 (K). A color toner image is formed on the peripheral surface within one rotation of the drum 10.
[0058]
The exposure of the organic photosensitive layer of the photosensitive drum 10 by each of these exposure optical systems is performed from the inside of the drum through a light-transmitting substrate with respect to the exposure wavelength described above. Accordingly, the exposure of the image corresponding to the second, third, and fourth color signals is performed without any influence of the previously formed toner image, and is equivalent to the image corresponding to the first color signal. An electrostatic latent image can be formed. In the developing operation by each developing device, a developing bias applied with direct current or further alternating current is applied to the developing sleeve 130, and jumping development is performed with a one-component or two-component developer contained in the developing device. Non-contact reversal development is performed on the photosensitive drum 10 that grounds the photoconductive layer.
[0059]
Thus, for example, the pre-transfer exposure unit 12B as a pre-transfer exposure unit using a light-emitting diode for removing residual charges in the organic photosensitive layer of the photo-sensitive drum 10 as the image forming body is uniformly exposed by the pre-transfer exposure unit 12B. After the residual charge is removed, the color toner image whose adhesion to the photosensitive drum 10 is weakened by the removal of the residual charge is once transferred to the peripheral surface of the intermediate transfer belt 14 as an intermediate transfer unit. The transfer means in the present embodiment is constituted by an intermediate transfer belt 14, an earth roller 14A and an intermediate transfer roller 14B described below.
[0060]
An intermediate transfer belt 14 as an intermediate transfer member is an endless rubber belt having a thickness of 0.5 to 2.0 mm, and is made of silicon rubber or urethane rubber 10.⁸-10¹²A semiconductive substrate having a resistance value of Ω · cm and a resistance value of 10 as a toner filming preventing layer on the outside of the rubber substrate.^Ten-10¹⁶It is made into 2 layer structure which carried out fluorine coating of 5-50 micrometers in thickness with (omega | ohm) * cm. This layer is also preferably semi-conductive. Semiconductive polyester, polystyrene, polyethylene, polyethylene terephthalate, etc. having a thickness of 0.1 to 0.5 mm can be used instead of the rubber belt substrate. The intermediate transfer belt 14 is stretched between the ground roller 14A, the intermediate transfer roller 14B, the guide roller 14C, the drive roller 14D, and the tension roller 14E, and is synchronized with the peripheral speed of the photosensitive drum 10 by the power transmitted to the drive roller 14D. Then, it is circulated and conveyed in the clockwise direction.
[0061]
The intermediate transfer belt 14 is in contact with the peripheral surface of the photosensitive drum 10 at the center of the portion stretched between the ground roller 14A and the intermediate transfer roller 14B, and the intermediate transfer belt 14 for the color toner image on the photosensitive drum 10. On the other hand, the belt surface on the outer periphery of the guide roller 14C is in contact with the transfer roller 15 as a transfer member to form a transfer area from the intermediate transfer belt 14 to the recording paper P.
[0062]
The photosensitive drum 10 with the color toner image attached to the peripheral surface is neutralized by uniform exposure by the pre-transfer exposure device 12B, and then first contacted between the photosensitive drum 10 and the intermediate transfer belt 14. The toner images are sequentially transferred to the peripheral surface side of the intermediate transfer belt 14 by applying a bias voltage having a polarity opposite to that of the toner to the intermediate transfer roller 14B at (transfer portion TE). That is, the color toner image on the drum is conveyed to the transfer area without being scattered by the guide of the grounded ground roller 14A, and efficiently applied to the intermediate transfer belt 14 side by applying a bias voltage of 1 to 3 kV to the intermediate transfer roller 14B. Transcribed.
[0063]
On the other hand, the transfer sheet P as a recording material is unloaded and fed to the timing roller 18 by the operation of the sheet feeding roller 17 of a sheet feeding cassette (not shown), and is synchronized with the conveyance of the color toner image on the intermediate transfer belt 14. Then, the paper is fed to the transfer area of the transfer roller 15.
[0064]
The transfer roller 15 is rotated counterclockwise in synchronization with the peripheral speed of the intermediate transfer belt 14, and the fed transfer paper P is between the transfer roller 15 and the guide roller 14C in the grounding state. In the transfer area formed by the nip portion, the color toner image is transferred onto the transfer paper P in sequence by applying a bias voltage opposite to the toner of 1 to 2 kV to the transfer roller 15 in close contact with the color toner image on the intermediate transfer belt 14. Is done.
[0065]
The transfer roller 15 is rotated counterclockwise in synchronization with the peripheral speed of the intermediate transfer belt 14, and the fed transfer paper P is between the transfer roller 15 and the guide roller 14C in the grounding state. In the transfer area formed by the nip portion, the color toner image is applied onto the transfer paper P in sequence by applying a bias voltage opposite to the 1 to 2 kV toner that is in close contact with the color toner image on the intermediate transfer belt 14. Transcribed.
[0066]
The transfer paper P that has received the transfer of the color toner image is de-charged, transported to the fixing device 91 via the transport plate 19, and sandwiched and transported between the heat roller 91A and the pressure roller 91B to heat the toner. After fixing, the paper is discharged to the outside of the apparatus via a paper discharge roller 92.
[0067]
The untransferred toner remaining on the peripheral surface of the photosensitive drum 10 after transfer weakens the adhesive force with the photosensitive drum 10 that has been neutralized by the pre-cleaning exposure device 12C as a pre-cleaning exposure unit using a light emitting diode, for example. Then, it is scraped off into the cleaning device 100 by a cleaning blade 101 made of a rubber material that is always in contact with the photosensitive drum 10, and is shown by a screw 102. It is collected in a waste toner container. Further, in order to eliminate the history of the photoconductor until the previous printing, the optical memory is removed by, for example, neutralization of the pre-charge exposure unit 12A using a light emitting diode or neutralization of a corona neutralizer (not shown), and then the Y scorotron charger 11 is used. Subsequently, the next color image is formed by receiving the uniform charging. The toner remaining on the peripheral surface of the intermediate transfer belt 14 after the transfer is cleaned by the intermediate transfer body cleaning device 140.
[0068]
In general, the outer diameter of the photosensitive drum 10 is 50 mm to 200 mm depending on the scale of the apparatus and the restrictions imposed by a plurality of scorotron chargers 11, a plurality of developing units 13, a cleaning device 100 and the like installed on the outer peripheral surface of the photosensitive drum 10. In this case, for the purpose of maintaining rigidity, the thickness of the substrate of the photosensitive drum 10 is set to 2 mm to 10 mm corresponding to the drum diameter, while these photosensitive members are used. The support member 20 that supports the drum 10 has a small diameter corresponding to the exposure optical system 12 and its imaging distance. In the case of a cylindrical pipe, the outer diameter is 20 to 160 mm, and the thickness of the support member 20 corresponds to the outer diameter. By setting the thickness to 0.5 mm to 5 mm, the exposure optical system 12 having sufficient strength can be installed on the support member 20 with a margin. The ability.
[0069]
According to FIGS. 4 and 2, the support member 20 is a flange member at the end of the photosensitive drum 10 via a bearing B1 held directly on the outer periphery and a bearing B2 held by a disk member 22 integrated with the support member 20. 10A and 10B are supported, and the photosensitive drum 10 is rotatably supported by the power of the drive gear G that meshes with the internal gear 10G provided on the inner peripheral surface of the flange member 10A.
[0070]
The support member 20 holds the photosensitive drum 10 in a state where the recesses, that is, the inner peripheral surfaces of both end faces are inserted by the engagement portions 31 that protrude from the protrusions, that is, the inner surfaces of the side substrate 30 of the apparatus main body. Then, it is fixed between the side substrates 30. When holding the support member 20, the engagement pin 32 provided on the outer peripheral surface of the engagement portion 31 of the one side substrate 30 is engaged with the notch 20 </ b> A on the end surface of the support member 20, thereby restricting the fixing angle of the support member 20. Each exposure optical system 12 is set at a predetermined position with respect to the apparatus main body, and the scorotron charger 11 as a charging unit and the developing unit 13 as a developing unit are disposed along the peripheral surface of the photosensitive drum 10. However, the correct positional relationship is maintained.
[0071]
Further, the support member 20 is provided with a disk member 22 coaxially and integrally on the side of the photosensitive drum 10 opposite to the side where the internal gear 10 </ b> G is provided, and the disk member 22 is provided between the photosensitive drum 10. It is also used as a support member for supporting one of the bearings B2.
[0072]
A first invention according to claims 1 to 3 will be described with reference to FIGS. FIG. 5 is an explanatory view of the arrangement of the pre-charging exposure means and the pre-cleaning exposure means, and FIG. 6 is a diagram showing the potential attenuation of the image forming body due to the uniform exposure of the pre-charging exposure means.
[0073]
According to FIG. 5 or FIG. 6, the pre-charge exposure device 12 </ b> A determines the exposure position on the photosensitive drum 10 with respect to the photosensitive drum 10 of the cleaning blade 101 attached to the blade holder 103 and provided in the cleaning device 100. The contact position and the end of the cleaning casing 104 of the cleaning device 100 on the side of the scorotron charger 11 (the center of the photoconductor drum 10 and the Y scorotron charger 11 at the most upstream position in the rotation direction of the photoconductor drum 10 with respect to the cleaning device 100) Of the photosensitive drum 10 facing the cleaning device 100 with the photosensitive drum 10 sandwiched between the straight line connecting the end of the cleaning casing 104 and the surface of the photosensitive drum 10. Arranged inside. As described above, the Y scorotron charger 11 at the most upstream position in the rotation direction of the photosensitive drum 10 is provided in the vicinity of the cleaning device 100 on the downstream side in the rotation direction of the photosensitive drum 10 of the cleaning device 100.
[0074]
With respect to the highest charged potential V1 of the exposed portion of the photosensitive drum 10 when the image forming position is set on the photosensitive layer on the substrate surface by the pre-charge exposure device 12A and uniform exposure is performed, the photosensitive drum 10 Charging with the optical memory above is performed after the charged potential V1 of the exposed portion is sufficiently lowered due to light attenuation by uniform exposure and the potential decrease rate becomes 90% or more, that is, the potential is sufficient. It is necessary to perform charging after V1 × 0.1 or less, which is decreased. In the case of an organic photoreceptor image forming body, the charge transfer speed is slow, and the potential drop time tends to be longer than that of the inorganic photoreceptor, and special attention must be paid.
[0075]
Assuming that the time from the uniform exposure of the pre-transfer exposure unit 12A to the potential V1 × 0.1 is T11, the imaging position P11 of the pre-charge exposure unit 12A and the rotation direction of the photosensitive drum 10 are the maximum. A pre-charging exposure device 12A side end of the side plate 11a as a shield member of the Y scorotron charger 11 at the upstream position (a straight line connecting the center of the photosensitive drum 10 and the end of the side plate 11a on the pre-charging device 12A side). And the point on the surface of the photosensitive drum 10 with respect to P13 is L11, and the peripheral speed of the photosensitive drum 10 is v.
(L11) / v> T11
And As a result, the potential of the exposed portion can be sufficiently lowered, and good charging is performed.
[0076]
Also, T12 is the time from the uniform exposure until the potential of the photosensitive drum 10 becomes (1/2) × V1. When the potential V1 of the photosensitive drum 10 is reduced to (1/2) × V1 or less (photostatic discharge) by uniform exposure of the pre-charge exposure device 12A, the same polarity as that of the photosensitive drum 10 makes it difficult to repel and adhere. In addition, the electric repulsion between the toner in the cleaning device 100 and the photosensitive drum 10 in which the potential is lowered is weakened. That is, the toner inside the cleaning device 100 is likely to adhere to the photosensitive drum 10, and the toner inside the cleaning device 100 adheres to the photosensitive drum 10 and is transported to the outside to be scattered and close to the cleaning device. The potential of the photoconductor drum 10 is attenuated to (1/2) × V1 so that the Y scorotron charger 11 disposed in this manner and the image stain due to toner adhesion to the photoconductor drum 10 do not occur. Further, the exposed portion on the photosensitive drum 10 is the end of the cleaning casing 104 of the cleaning device 100 on the scorotron charger 11 side (the center of the photosensitive drum 10 and the Y scorotron charging at the most upstream position in the rotational direction of the photosensitive drum 10). The point where the straight line connecting the end of the cleaning casing 104 on the side of the device 11 intersects the surface of the photosensitive drum 10) P It is necessary to have reached the 2. That is, when the exposed portion of the photosensitive drum 10 passes through the end P12 of the cleaning casing 104 on the scorotron charger 11, the potential is set to be larger than (1/2) × V1, and the toner adheres to the photosensitive drum 10 for cleaning. It is necessary that it is not lowered to the extent that it is carried outside the apparatus 100 and scattered from the peripheral surface of the photosensitive drum 10. Therefore, with respect to the circumferential speed v of the photosensitive drum 10, the image forming position P11 of the pre-charging exposure device 12A and the side plate 11a as a shield member of the Y scorotron charger 11 at the most upstream position in the rotation direction of the photosensitive drum 10 are used. The distance on the circumferential surface of the photosensitive drum 10 from the pre-charging exposure device 12A side end portion P13 is L11, and the imaging position P11 of the pre-charging exposure device 12A and the Y scorotron charger at the most upstream position in the rotation direction of the photosensitive drum 10. 11 side cleaning casing 104 end (a straight line connecting the center of the photoconductor drum 10 and the end of the cleaning casing 104 on the Y scorotron charger 11 side at the most upstream position in the rotation direction of the photoconductor drum 10 with respect to the cleaning device 100) When the distance between the surface of the photosensitive drum 10 and the surface of the photosensitive drum 10 is L12,
(L12) / v <T12
And In general, organic photoreceptors have T12 ≦ (T11) / 2, and the above equation is modified from the previous conditional expression, T11 <(L11) / v.
L12 <(1/2) × L11
It becomes. This condition is a preferable condition that the toner does not scatter after the exposed position leaves the cleaning means, and the potential is sufficiently lowered at the charging position. Further, the cleaning device 100 and the scorotron charger 11 can be disposed close to each other, the diameter of the photosensitive drum 10 can be reduced, and the size of the device can be reduced.
[0077]
Further, as shown in FIG. 5, at the Y scorotron charger 11 side, the end of the cleaning casing 104 adjacent to the photosensitive drum 10 is cleaned with a DC voltage having the same polarity as the toner (negative polarity in the present embodiment). A toner scattering shielding member 104 a to which the casing bias E <b> 1 is applied is provided, and the toner scattered from the photosensitive drum 10 inside the cleaning device 100 or scattered from the cleaning unit is scattered outside the cleaning casing 104 of the cleaning device 100. To prevent that.
[0078]
As a result, the apparatus is downsized, and the toner in the cleaning unit is prevented from adhering to the image forming body due to the potential drop (photostatic discharge) of the image forming body after uniform exposure by the pre-charging exposure unit. In-machine contamination, charging device contamination, and image contamination caused by toner inside the cleaning unit adhering to the image forming body and being carried to the outside are prevented.
[0079]
  The second invention will be described with reference to FIGS. FIG. 7 is an explanatory view of the arrangement of the pre-transfer exposure means, and FIG. 8 is a diagram showing the potential attenuation of the image forming body by the uniform exposure of the pre-transfer exposure means.
[0080]
According to FIG. 7 or FIG. 8, the pre-transfer exposure device 12B has the intermediate transfer belt of the K developing device 13 provided at the most downstream position in the rotation direction of the photosensitive drum 10 at the exposure position on the photosensitive drum 10. 14 side end (a point where the straight line connecting the center of the photosensitive drum 10 and the end of the K developing device 13 on the side of the intermediate transfer belt 14 intersects the surface of the photosensitive drum 10) P23 and the intermediate transfer belt 14 are stretched. And the center position of the earthing roller 14A (a point where the straight line connecting the center of the photosensitive drum 10 and the center of the earthing roller 14A intersects the surface of the photosensitive drum 10) P22. As described above, the transfer unit in the present embodiment includes the intermediate transfer belt 14 and the intermediate transfer roller 14A, and the intermediate transfer belt 14 has a central portion stretched between the ground roller 14A and the intermediate transfer roller 14B. A transfer portion TE of the color toner image on the photosensitive drum 10 to the intermediate transfer belt 14 is formed in contact with the peripheral surface of the photosensitive drum 10.
[0081]
On the photosensitive drum 10 with respect to the highest charged potential V2 of the exposed portion of the photosensitive drum 10 when the image exposure is performed by setting the imaging position on the photosensitive layer on the substrate surface by the pre-transfer exposure device 12B. In the transfer in the state where there is an electric charge, the charged potential V2 of the exposed portion of the photosensitive drum 10 where there is no color toner image is sufficiently lowered due to light attenuation by uniform exposure, and the potential decrease rate is 90% or more. In other words, it is necessary to carry out the transfer after V2 × 0.1 or less where the potential is sufficiently lowered. In the case of an organic photoreceptor image forming body, the charge transfer speed is slow, and the potential drop time tends to be longer than that of the inorganic photoreceptor, and special attention must be paid.
[0082]
Assuming that the time until the potential becomes V2 × 0.1 after the uniform exposure of the pre-transfer exposure device 12B is T21, the imaging position P21 of the pre-transfer exposure device 12B and the transfer position (transfer) of the transfer means are as follows. Portion TE) on the circumferential surface of the photosensitive drum 10 is L21, and the circumferential speed of the photosensitive drum 10 is v.
(L21) / v> T21
And As a result, the potential of the exposed portion can be sufficiently lowered, and good transfer can be performed.
[0083]
Also, T22 is the time from when the uniform exposure is performed until the potential of the photosensitive drum 10 becomes (1/2) × V2. The color toner image existing in the vicinity of the photosensitive drum 10 by the uniform exposure of the pre-transfer exposure device 12B does not scatter instantaneously, and does not scatter until the electric adhesive force decreases due to a potential drop. When the potential drop from the image exposure is about ½ or less, that is, when the potential is lowered to (½) × V2 or less (photostatic discharge), toner scattering from the toner image occurs. Therefore, the photosensitive member is prevented from being contaminated by the toner scattered due to the potential drop or the pre-transfer exposure device 12B when disposed outside the photosensitive drum 10 indicated by a dotted line in FIG. Until the potential of the drum 10 is attenuated to (1/2) × V2, the exposed portion on the photosensitive drum 10 connects the center position of the earth roller 14A (the center of the photosensitive drum 10 and the center of the earth roller 14A). It is necessary to reach the point (P22) where the straight line and the surface of the photosensitive drum 10 intersect. That is, when the exposed portion of the photosensitive drum 10 passes the center position P22 of the earth roller 14A that stretches the intermediate transfer belt 14, the potential is larger than (1/2) × V2 and decreases as the toner scatters. It is necessary not to. Therefore, with respect to the circumferential speed v of the photosensitive drum 10, the distance on the circumferential surface of the photosensitive drum 10 between the imaging position P21 of the pre-transfer exposure device 12B and the transfer position (transfer portion TE) of the transfer means is L21. The transfer means end on the upstream side of the pre-exposure device 12B and the photosensitive drum 10, that is, the center position of the ground roller 14A (the straight line connecting the center of the photosensitive drum 10 and the center of the ground roller 14A, and the photosensitive drum). 10) When the distance on the circumferential surface of the photosensitive drum 10 from P22 is L22,
(L22) / v <T22
And In general, an organic photoreceptor has T22 ≦ (T21) / 2, and the above expression is modified from the previous conditional expression, T21 <(L21) / v.
L12 <(1/2) × L11
It becomes. This condition is a preferable condition that the toner does not scatter before the exposure position enters the transfer means, and the potential is sufficiently lowered at the transfer position. Further, the K developing device 13 and the intermediate transfer belt 14 can be disposed close to each other, the diameter of the photosensitive drum 10 can be reduced, and the apparatus can be downsized.
[0084]
As a result, the size of the apparatus is reduced, and the color toner image on the image forming body whose adhesion is weakened due to a decrease in potential (photostatic discharge) of the image forming body after uniform exposure by the pre-transfer exposure means. Prior to the scattering, the color toner image on the image forming body is transferred to prevent internal contamination caused by the scattering of the toner. Further, when the pre-transfer exposure means is provided outside the image forming body, the image exposure means is prevented from being contaminated by toner scattering.
[0085]
  The third invention will be described with reference to FIG. 9 and FIG. FIG. 9 is a diagram showing the potential attenuation of the image forming body by uniform exposure by the pre-cleaning exposure means.
[0086]
According to FIG. 5 or FIG. 9, the pre-cleaning exposure device 12C moves the exposure position on the photosensitive drum 10 to the intermediate transfer belt 14 provided upstream of the cleaning device 100 in the rotational direction of the photosensitive drum 10. The center position of the intermediate transfer roller 14B to be stretched (the point where the straight line connecting the center of the photosensitive drum 10 and the center of the intermediate transfer roller 14B intersects the surface of the photosensitive drum 10) P33 and the intermediate transfer belt 14 of the cleaning device 100. It is provided between the side ends.
[0087]
On the photosensitive drum 10 with respect to the highest charged potential V3 of the exposed portion of the photosensitive drum 10 when the image exposure is performed by setting the imaging position on the photosensitive layer on the substrate surface by the pre-cleaning exposure device 12C. Cleaning in a state where there is electric charge is performed after the charged potential V3 of the exposed portion is sufficiently lowered due to light attenuation due to uniform exposure and the potential decrease rate becomes 90% or more, that is, the potential is sufficiently decreased. It is necessary to perform cleaning after V3 × 0.1 or less. In the case of an organic photoreceptor image forming body, the charge transfer speed is slow, and the potential drop time tends to be longer than that of the inorganic photoreceptor, and special attention must be paid. In the case of an organic photoreceptor image forming body, the charge transfer speed is slow, and the potential drop time tends to be longer than that of the inorganic photoreceptor, and special attention must be paid.
[0088]
Assuming that the time until the potential becomes V3 × 0.1 after the uniform exposure of the pre-cleaning exposure unit 12C is T31, the imaging position P31 of the pre-cleaning exposure unit 12C and the cleaning blade 101 of the cleaning device 100 When the distance on the circumferential surface of the photosensitive drum 10 to the contact position with the photosensitive drum 10 is L31, and the circumferential speed of the photosensitive drum 10 is v,
(L31) / v> T31
And As a result, the potential of the exposed portion can be sufficiently lowered and good cleaning can be performed.
[0089]
Also, T32 is the time from when the uniform exposure is performed until the potential of the photosensitive drum 10 becomes (1/2) × V3. The transfer residual toner adhering to the photosensitive drum 10 by the uniform exposure of the pre-cleaning exposure device 12C does not scatter instantly and does not scatter until the electric adhesion force decreases due to the potential drop. When the potential drop of the photosensitive drum 10 due to the uniform exposure by the pre-cleaning exposure device 12C is about ½ or less, that is, the potential becomes (½) × V3 or less, toner scattering from the transfer residual toner occurs. For this reason, the photosensitive member is prevented from being contaminated by the toner scattered by the potential drop or the pre-cleaning exposure device 12C when disposed outside the photosensitive drum 10 indicated by a dotted line in FIG. The exposed portion on the photosensitive drum 10 has reached the end P32 on the intermediate transfer belt 14 side of the cleaning casing 104 of the cleaning device 100 until the potential of the drum 10 is attenuated to (1/2) × V3. Is required. That is, when the exposed portion of the photosensitive drum 10 passes the end P32 on the intermediate transfer belt 14 side of the cleaning casing 104, the potential is larger than (1/2) × V1, and the transfer residual toner adheres to the photosensitive drum 10. Therefore, it is necessary that it is not lowered enough to be carried into the cleaning device 100 and scattered from the peripheral surface of the photosensitive drum 10. Therefore, on the circumferential surface of the photosensitive drum 10 between the imaging position P31 of the pre-cleaning exposure device 12C and the contact position of the cleaning blade 101 of the cleaning device 100 with respect to the photosensitive drum 10 with respect to the circumferential speed v of the photosensitive drum 10. L31, the image forming position P31 of the pre-cleaning exposure device 12C and the end of the cleaning casing 104 of the cleaning device 100 upstream of the rotation direction of the photosensitive drum 10 (the center of the photosensitive drum 10 and the rotation direction of the photosensitive drum 10). When the distance on the circumferential surface of the image forming body between the straight line connecting the end of the cleaning casing 104 on the intermediate transfer belt 14 side in the upstream position and the surface of the photosensitive drum 10) P32 is L32,
(L32) / v <T32
And Also, in general, the organic photoconductor is T32 ≦ (T31) / 2, and the above equation is modified from the previous conditional expression, T31 <(L31) / v.
L32 <(1/2) × L31
It becomes. This condition is a preferable condition in which the toner does not scatter until the exposed position enters the cleaning unit, and the potential is sufficiently lowered at the cleaning position of the cleaning blade 101 that contacts the photosensitive drum 10. This also reduces the diameter of the photoconductive drum 10 and reduces the size of the apparatus.
[0090]
Further, as shown in FIG. 5, a cleaning casing bias having a DC voltage having the same polarity as the toner (in this embodiment, a negative polarity) at the end of the cleaning casing 104 adjacent to the photosensitive drum 10 on the intermediate transfer belt 14 side. A toner scattering shielding member 104b to which E2 is applied is provided, so that the toner scattered from the photosensitive drum 10 inside the cleaning device 100 or the toner scattered in the cleaning unit is scattered outside the cleaning casing 104 of the cleaning device 100. To prevent. 5 is provided at the end of the cleaning casing 104 on the intermediate transfer belt 14 side in place of the toner scattering shielding member 104b, so that the toner is scattered outside the cleaning casing 104 of the cleaning device 100. It is also possible to prevent this.
[0091]
As a result, the size of the apparatus is reduced, and the transfer residual toner is scattered on the image forming body in which the adhesion force is weakened due to a decrease in the potential of the image forming body after the uniform exposure by the pre-cleaning exposure means (photostatic discharge). Is housed inside the cleaning means, and contamination inside the apparatus caused by scattering of transfer residual toner is prevented. In addition, when the image exposure means is provided outside the image forming body, the contamination of the image exposure means due to toner scattering is also prevented.
[0092]
The first to third inventions described above may be employed individually or in combination, and by using them in combination, a comprehensive result can be obtained.
[0093]
【The invention's effect】
According to the first to third aspects, the size of the apparatus is reduced, and the toner image forming body inside the cleaning unit is reduced by the potential reduction (photostatic discharge) of the image forming unit after uniform exposure by the pre-charging exposure unit. Is prevented, and contamination inside the apparatus, contamination of the charging unit and image contamination caused by the toner inside the cleaning unit adhering to the image forming body and being carried to the outside are prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of an embodiment of a color image forming apparatus common to the present invention.
2 is a diagram showing a configuration of an image exposure unit in FIG. 1 and a method of attaching to a support member. FIG.
FIG. 3 is a perspective view of FIG. 2;
4 is a cross-sectional configuration diagram of the image forming body of FIG. 1. FIG.
FIG. 5 is an explanatory diagram of the arrangement of pre-charging exposure means and pre-cleaning exposure means.
FIG. 6 is a diagram showing potential attenuation of an image forming body by uniform exposure by a pre-charging exposure means.
FIG. 7 is an explanatory diagram of an arrangement of pre-transfer exposure means.
FIG. 8 is a diagram showing potential attenuation of an image forming body by uniform exposure by a pre-transfer exposure unit.
FIG. 9 is a diagram showing potential attenuation of an image forming body by uniform exposure by a pre-cleaning exposure unit.
[Explanation of symbols]
10 Photosensitive drum
11 Scorotron charger
12 Exposure optics
12A Pre-charge exposure device
12B Pre-transfer exposure device
12C Exposure device before cleaning
13 Developer
14 Intermediate transfer belt
14A Earth roller
14B Intermediate transfer roller
100 Cleaning device
101 Cleaning blade
104 Cleaning casing
104a, 104b Toner scattering shielding member
E1, E2 Cleaning casing bias

Claims (3)

A plurality of charging means, image exposing means, and developing means are arranged on the peripheral surface of the image forming body, and charging, image exposure, and development are repeated during one rotation of the image forming body, and a plurality of charging means, image exposing means, and developing are repeated on the peripheral surface of the image forming body. A color toner image is formed by superimposing the toner images, and the color toner image is transferred onto a recording material by a transfer unit, and the color toner image on the recording material is fixed by a fixing unit to form a color image. In the color image forming apparatus for cleaning the transfer residual toner on the image forming body by a cleaning unit,
While using an organic photoreceptor for the image forming body,
A pre-charging exposure means for uniformly exposing the image forming body is provided in the cleaning means;
In the step from the uniform exposure position of the pre-charge exposure unit to the charging unit at the most upstream position in the rotation direction of the image forming body, the charged potential V1 of the exposed portion at the uniform exposure position is (V1) / 2. A color image forming apparatus, wherein an exposed portion on the image forming body is set to move out of the cleaning means before light attenuation.   2. The color image forming apparatus according to claim 1, wherein a cleaning casing bias having the same polarity as the toner is applied to the end of the cleaning unit on the charging unit side at the most upstream position in the rotation direction of the image forming body. The distance on the peripheral surface of the image forming body between the pre-charging exposure unit and the cleaning unit end on the charging unit side at the most upstream position in the rotation direction of the image forming body is L12, the pre-charging exposure unit and the pre-charging exposure unit side When the distance on the peripheral surface of the image forming body from the charging means end at the most upstream position in the rotation direction of the image forming body is L11,
L12 <(1/2) × L11
The color image forming apparatus according to claim 1, wherein the color image forming apparatus is a color image forming apparatus.

Images