JPH11212421A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner in a cleaning means from sticking on an image formation body owing to a potential drop (photoelectrostatic discharging) by providing an exposed part on the image forming body so that the exposed part moves to a position other than the cleaning means until the electrostatic charging potential of the exposed part at a uniform exposure position has optical attenuation down to a specific value. SOLUTION: So that the toner in the cleaning device 100 is not carried out sticking on a photosensitive drum 10 to scatter, the exposed part of the photosensitive drum 10 needs to have reached the end part P12 on the side of the scorotron electrostatic charger 11 of the cleaning casing 104 of the cleaning device 100. Namely, when the exposed part of the photosensitive drum 10 passes by the end part P12 on the side of the scorotron electrostatic charger 11, the potential needs to be larger than 1/2 and must not drop as the toner sticks on the photosensitive drum 10 and is carried out of the cleaning device 100 to scatter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., in which a plurality of sets of charging means, image exposing means and developing means are arranged around the image forming body. The present invention relates to an electrophotographic color image forming apparatus that forms a color image by superimposing toner images during one rotation.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a multi-color image, a single color image formed on each image forming body is provided with the same number of image forming bodies, charging means, developing means and the like as the number of colors required for image formation. Color image forming apparatus that forms a color image by superimposing the toner image on a transfer material, or a color image forming apparatus that rotates the image forming body a plurality of times and repeats charging, image exposure, and development for each color to form a color image Alternatively, there is known a color image forming apparatus which forms a color image by sequentially performing charging, image exposure, and development for each color within one rotation of the image forming body.

However, each of the above image forming apparatuses is provided with the same number of image forming bodies, charging means, developing means, etc. as the number of colors required for image formation, and superposes a single color toner image formed on each image forming body on a transfer material. A color image forming apparatus that forms a color image together has a drawback that the volume of the apparatus is increased due to the necessity of transporting a plurality of image forming bodies and a transfer material. A color image forming apparatus that forms a color image by repeating charging, image exposure, and development has a limitation that although the volume is reduced, the size of the formed image is limited to the surface area of the image forming body or less. .

In this regard, a color image forming apparatus which 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 restriction on the size of the image and has a high speed image. There are advantages such as enabling formation. Further, an apparatus in which a light-transmitting substrate is used as a substrate of an image forming body and an image exposing means is arranged inside the image forming body to reduce the size of the apparatus has been proposed, for example, in Japanese Patent Application Laid-Open No. 5-307307. .

On the other hand, as a photosensitive layer of an image forming body used in a color image forming apparatus, an OPC photosensitive body (organic photosensitive body) is generally used as an inexpensive and stable one.

[0006]

However, in the color image forming apparatus proposed above, the pre-charging exposure means for removing the optical memory of the image forming body is opposed to the cleaning means so as to irradiate the inside of the cleaning means with light. When the OPC photosensitive member is used as an image forming member, the OPC photosensitive member has a low charge moving speed, and it takes time (about 0.05 to 0.2 sec) until the potential decreases. Further, a potential change due to a temperature change is large. For this reason, unlike an inorganic photoreceptor such as a Se photoreceptor, 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 member arranged close to the pre-charging exposure unit. Become. That is, from the uniform exposure position by the pre-charging exposure unit, it is necessary to set the potential to be sufficiently lowered before the exposed portion of the image forming body by the uniform exposure enters the charging unit position. There is a problem that the size is increased.

On the other hand, the charging potential of the image forming body due to the uniform exposure of the pre-charging exposure means drops to about １ ／ or less (light elimination).
Then, the electric repulsion of the toner inside the cleaning means, which has the same polarity as that of the image forming body and is hardly adhered due to repulsion, with the image forming body having a reduced potential is weakened. That is, the toner inside the cleaning means easily adheres to the image forming body, and the toner inside the cleaning means adheres to the image forming body and is carried outside and scattered. There arises a problem that image stains occur due to stains on the means and toner adhesion to the image forming body.

The present invention solves the above problems, reduces the size of the apparatus, and reduces the potential inside the cleaning means due to a decrease in the potential of the image forming body after uniform exposure by the pre-charging exposure means (light removal). A color image forming apparatus that prevents toner from adhering to an image forming body, and prevents in-machine dirt, charging means dirt, and image dirt caused by toner inside the cleaning means adhering to the image forming body and being carried outside. The primary purpose is to provide.

In the color image forming apparatus according to the above-mentioned proposal, uniform exposure is performed on the image forming body so as to facilitate transfer of the color toner image on the image forming body, and pre-transfer exposure is performed to remove the charge on the image forming body. However, when an OPC photosensitive member is used as an image forming member, the OPC photosensitive member has a low charge moving speed and a time (0.05 to 0.2 sec.) Until the potential decreases.
About). Further, a potential change due to a temperature change is large. For this reason, unlike an inorganic photoreceptor such as a Se photoreceptor, a time is required for lowering the potential from the uniform exposure by the pre-transfer exposure means to the transfer position by the transfer means. That is, it is necessary to set the transfer position to a position where the potential should be sufficiently lowered from the uniform exposure position by the pre-transfer exposure means, so that there is a problem that the apparatus becomes large.

On the other hand, the charge potential of the image forming body due to the uniform exposure of the pre-transfer exposure means drops to about 1/2 or less (photo-elimination).
Then, the electrical adhesion of the color toner image on the image forming body to the image forming body is reduced, and the toner is scattered, thereby causing a problem that the inside of the apparatus is stained by the toner. Further, in an apparatus in which the image exposing means is provided outside the image forming body, there is also a problem that the image exposing means is stained by scattering of toner.

The present invention also solves the above-mentioned problems, reduces the size of the apparatus, and reduces the adhesive force due to the potential drop (light neutralization) of the image forming body after uniform exposure by the pre-transfer exposure means. A color image that prevents contamination of the color toner image on the formed image forming body due to toner scattering, and also prevents contamination of the image exposing means due to toner scattering when the image exposing means is provided outside the image forming body. Providing forming equipment second
The purpose of.

Also, in the color image forming apparatus according to the above-mentioned proposal, the image forming body is uniformly exposed to remove residual charges on the image forming body so as to easily remove the transfer residual toner on the image forming body. Although an exposure unit before cleaning is used, if an OPC photoconductor is used as an image forming body,
The charge transfer speed of the PC photoreceptor is slow, and it takes time (about 0.05 to 0.2 sec) until the potential drops. Further, a potential change due to a temperature change is large. For this reason, unlike an inorganic photoreceptor such as a Se photoreceptor, from the uniform exposure by the pre-cleaning exposure unit to the cleaning position by the cleaning blade of the cleaning unit that contacts the image forming body and cleans the transfer residual toner on the image forming body. Requires a time to lower the potential. In other words, it is necessary to set the cleaning blade contact position at a position where the potential should be sufficiently lowered from the uniform exposure position by the pre-cleaning exposure unit, so that there is a problem that the apparatus becomes large.

On the other hand, when the charged potential of the image forming body by the uniform exposure of the pre-cleaning exposure means is reduced to about １ ／ or less (light elimination), the transfer residual toner on the image forming body is charged to the image forming body. This causes a problem that the adhesive force is reduced and the toner is scattered, and the inside of the apparatus is stained with the toner. Further, in an apparatus in which the image exposing means is provided outside the image forming body, there is also a problem that the image exposing means is stained by scattering of toner.

The present invention also solves the above problems, reduces the size of the apparatus, and reduces the potential of the image forming body after uniform exposure by the pre-cleaning exposure means (light elimination). To prevent in-machine contamination caused by toner scattering of transfer residual toner on the image forming body having weakened adhesion to the image forming body, and to prevent image scattering means from scattering due to toner scattering when the image exposing means is provided outside the image forming body. It is a third object of the present invention to provide a color image forming apparatus which also prevents the occurrence of the image.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to dispose a plurality of charging means, image exposing means and developing means on a peripheral surface of an image forming body so that charging, image exposing and image forming operations are performed during one rotation of the image forming body. The development is repeated, a plurality of toner images are superimposed on the peripheral surface of the image forming member to form a color toner image, the color toner image is transferred onto a recording material by a transfer unit, and the color toner image is transferred onto the recording material by a fixing unit. A color image forming apparatus for fixing a color toner image to form a color image, and cleaning a transfer residual toner on the image forming body by a cleaning unit, using an organic photoconductor for the image forming body,
A pre-charging exposure unit for uniformly exposing the image forming body is provided in the cleaning unit, and in a step from a uniform exposure position of the pre-charging exposure unit to a charging unit at a most upstream position in a rotation direction of the image forming body, The exposed portion on the image forming body is set to move out of the cleaning unit until the charged potential V1 of the exposed portion at the uniform exposure position is lightly attenuated to (V1) / 2. A first aspect of the present invention is achieved by a color image forming apparatus.

Further, 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 repeat 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 of the image forming body, the color toner image is transferred onto a recording material by a transfer unit, and the color toner image on the recording material is transferred by a fixing unit. In a color image forming apparatus for fixing and forming a color image, an organic photoreceptor is used for the image forming body, and a pre-transfer exposing means for uniformly exposing the image forming body is provided. In the process from the exposure position to the transfer means, the exposed portion on the image forming body is transferred to the transfer portion until the charged potential V2 of the exposed portion at the uniform exposure position is attenuated to (V2) / 2. This is achieved by a color image forming apparatus characterized by being set so as to move into the means (second invention).

Further, 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 repeat 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 of the image forming body, the color toner image is transferred onto a recording material by a transfer unit, and the color toner image on the recording material is transferred by a fixing unit. In a color image forming apparatus for fixing and forming a color image and cleaning the transfer residual toner on the image forming body by a cleaning blade provided in a cleaning unit, an organic photoconductor is used for the image forming body, A pre-cleaning exposure means for uniformly exposing the formed body is provided, and in a step from the uniform exposure position of the pre-cleaning exposure means to the cleaning means, the charged potential V3 of the exposed portion at the uniform exposure position is ( V3) It is set that the exposed portion on the image forming body is moved into the cleaning means before the light is attenuated to / 2. It is accomplished by a color image forming apparatus according to claim (third invention).

[0018]

Embodiments of the present invention will be described below. The description of the present application does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope. In the following description, a color image forming method of temporarily transferring a color toner image formed on an image forming body to an intermediate transfer body and then transferring the color toner image from the intermediate transfer body to a recording material is used. It is also possible to directly transfer a color toner image on an image forming body to a recording material without using a body. Therefore, in this description, the transfer step using the intermediate transfer member as a transfer unit will be described. However, the present invention is also applied to a transfer step in which a transfer member that directly transfers an image forming member onto a recording material is used as a transfer unit.

FIG. 1 shows an image forming process and each mechanism of an embodiment of a color image forming apparatus common to the present invention.
This will be described with reference to FIG. FIG. 1 is a sectional configuration diagram of an embodiment of a color image forming apparatus common to the present invention, and FIG. 2 is a diagram showing a configuration of an image exposure unit of FIG. 1 and a method of attaching to a support member. FIG. 3 is a perspective view of FIG. 2, and FIG. 4 is a sectional view of the image forming body of FIG.

As shown in FIGS. 1 to 4, a photosensitive drum 10 as an image forming body is provided on the outer periphery of a cylindrical base formed of a light-transmitting member such as glass or light-transmitting acrylic resin. A photoconductive layer and a photoconductor layer of an organic photosensitive layer (OPC) are formed. The photosensitive drum 10 is rotated in a direction indicated by an arrow in FIG. 1 in a state where the light-transmitting conductive layer is grounded by power from a driving source (not shown).

According to the present invention, in the photoconductor layer of the photosensitive drum, which is the image forming point of the exposure beam for image exposure, an appropriate contrast is given to the light attenuation characteristics (photocarrier generation) of the photoconductor layer. It is sufficient that the exposure light amount has a wavelength that can be obtained. Therefore, the light transmittance of the light-transmitting substrate of the photosensitive drum in the present embodiment does not need to be 100%, but may be such that a certain amount of light is absorbed when the exposure beam is transmitted. Should just provide an appropriate contrast. Acrylic resin,
In particular, those obtained by polymerization using a methacrylic acid methyl ester monomer are preferably used because they are excellent in light transmission, strength, precision, surface properties, etc., but are used for other general optical members such as acrylic, fluorine, polyester, polycarbonate, Various translucent resins such as polyethylene terephthalate can be used. Further, as long as it has a light-transmitting property with respect to the exposure light, it may be colored. As the light-transmitting conductive layer, indium tin oxide (ITO), tin oxide, lead oxide, indium oxide, copper iodide, Au, Ag, N
A light-transmissive metal thin film made of i, Al, or the like is used. As a film forming method, a vacuum deposition method, an active reactive deposition method,
Various sputtering methods, various CVD methods, dip coating methods, spray coating methods, and the like are used. Various organic photosensitive layers (OPC) are used as the photoconductor layer.

The following are examples of preferred image forming bodies.

After adding a catalyst for synthesizing and polymerizing the plastic material monomer, pour it into a cylindrical mold, seal it tightly with a side plate, fix it properly in an oil bath or a hot water tank and heat it at high speed. To promote uniform polymerization. After completion of the polymerization, the mixture is cooled, the obtained translucent resin substrate is taken out of the mold, cut and, if necessary, subjected to a finishing step to produce a transparent resin substrate for the photosensitive drum of the image forming apparatus (centrifugal weight). legal).

As the material of the light-transmitting resin substrate of the light-transmitting plastic molded by centrifugal polymerization, as described above, a material obtained by polymerizing a methacrylic acid methyl ester monomer is used. In addition, polyethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, polyimide, polyester, polyvinyl chloride, or the like, or a copolymer thereof can 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. In addition, uneven thickness varies depending on rotation unevenness and viscosity during polymerization and heating conditions during polymerization.

As the conductive layer, indium tin oxide (I
TO), tin oxide, lead oxide, indium oxide, alumina,
A conductive resin obtained by mixing a resin and conductive fine particles made of copper iodide, Au, Ag, Ni, Al, or the like is used. As a film forming method, a dip coating method, a spray coating method, or the like is preferably used. .

The organic photoreceptor layer comprises a charge generating material (CGM)
And a charge transport layer (CTL) containing a charge transport material (CTM) as a main component. The organic photoreceptor layer having a two-layer structure has a low CGL, and thus has good transparency of image exposure light 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 may have the single-layer structure or the two-layer structure. Usually contains a binder resin.

In the photoreceptor drum having the two-layered organic photoreceptor layer, the CGM contained in the CGL may be an azo pigment, an azulenium pigment, a phthalocyanine pigment which is sensitive to light from a light source such as an LED or an LD. , A perylene pigment is used, and red to infrared light (600 nm
Copper phthalocyanine pigments, titanyl phthalocyanine pigments, and the like are preferably used as the CGM of the OPC photoreceptor that is sensitive to light of about 850 nm.

As a binder resin used for CGL, a polyvinyl butyral resin or a polycarbonate resin is used, which is excellent in sensitivity, potential change upon repeated use, and the like. These binder resins can be used alone or as a mixture of two or more.

As a solvent or a dispersion medium used for forming CGL, a ketone-based or halogen-based solvent is preferably used, and the sensitivity, the potential change upon repeated use, and the like are further improved. In addition, these solvents can be used alone or as a mixed solvent of two or more kinds.

The weight ratio of CGM to the binder resin in the CGL is 100: 1 to 1000, the thickness of the CGL is 0.01 to 10 μm, and the coating method for forming the CGL is a blade. There are various coating methods such as coating, wire bar coating, spray coating, dip coating and slide hopper coating.

Next, as the CTM contained in the CTL, hydrazone compounds, styryl compounds, benzidine compounds, stilbene compounds and the like are used.

As the binder resin used in the CTL, a wide range of insulating resins can be appropriately selected and used, and preferred binder resins are silicon-alkyd resin, phenol-formaldehyde resin, poly-N- Insulating resins such as vinyl carbazole and polysilane can be mentioned, and these binder resins can be used alone or in combination of two or more.

The mixing ratio of the binder resin and CTM is 1:
It is set to 10 to 500, and more preferably 1:20 to 150. The thickness of the CTL is set to 1 to 100 μm.
~ 50 μm is preferred.

As a coating method, a method similar to CGL can be used.

If necessary, an intermediate layer is provided between the organic photoreceptor layer and the conductive layer. Examples of the intermediate layer include polyvinyl chloride vinyl acetate copolymer, vinyl acetate vinyl acetate maleate copolymer, ethyl cellulose, carboxymethyl cellulose. And a resin layer having a thickness of 0.01 to 2 μm, such as a copolymer type or modified type alcohol-soluble polyamide resin.

By using a plastic cylindrical translucent resin substrate produced by the above-described production method, the thickness is uniform, the cylindrical substrate has excellent cylindricity and roundness, and the image exposure light A photosensitive drum without a focus shift is provided.

A scorotron charger 11 as a charging unit described below, an exposure optical system 12 as an image exposure unit,
Developing devices 13 as developing means include yellow (Y), magenta (M), cyan (C) and black (K), respectively.
In the present embodiment, Y, M, C, and K are arranged in this order with respect to the rotation direction of the photosensitive drum 10 indicated by an arrow in FIG.

Reference numeral 12A denotes a pre-charging exposure device as a pre-charging exposure device using, for example, a light emitting diode for removing the optical memory of the organic photoreceptor layer of the photoreceptor drum 10, and is attached to the support member 20 and will be described later. A cleaning blade 101 provided in a cleaning device 100 serving as a cleaning unit is provided at a position downstream of the contact position of the cleaning blade 101 with the photosensitive drum 10 in the rotation direction of the photosensitive drum 10.
The cleaning device 100 is disposed inside the photosensitive drum 10 with the “0” therebetween.

Scorotron charger 11 as charging means
Is mounted so as to face and be close to the photosensitive drum 10 in a direction perpendicular to the moving direction of the photosensitive drum 10 as an image forming body (the direction perpendicular to the plane of FIG. 1). Using a control grid maintained at a predetermined potential with respect to the body layer and a wire electrode as a corona discharge electrode, for example, a corona discharge having the same polarity as the toner performs a charging action (in the present embodiment, negative charging) to perform a photosensitive operation. A uniform potential is applied to the body drum 10. As the corona discharge electrode, a needle-like or saw-tooth-like electrode can also be used.

After the optical memory is removed by removing the charge of the pre-charging exposure unit 12A or removing the charge of the corona remover (not shown),
For example, uniform charging is performed by the Y scorotron charger 11 of the first color.

An exposure optical system 12 as an image exposure means for each of the colors Y, M, C and K has a plurality of exposure systems arranged on a substrate 122 in a main scanning direction parallel to the axis of the photosensitive drum 10. LED (light emitting diode) 12 as a light emitting element
1 are arranged in an array, and a light converging light transmitter (trade name, Selfoc lens) 12b as an imaging element. The Selfoc lens 12b is mounted on a lens holder 12c, for example. 2 and FIG. 3, the exposure element 12a is fixed to a metal casing 12d as a holding member of the exposure element having good thermal conductivity by, for example, an adhesive indicated by a black circle. With the 12a and the SELFOC lens 12b positioned, the lens holder 12c is fixed to the metal casing 12d with, for example, an adhesive indicated by a black circle to form the exposure optical system 12. By using the metal casing 12d, the heat generated in the exposure element 12a portion is quickly transmitted and diffused, which affects the displacement between the exposure elements 12a due to thermal expansion and the fluctuation in the amount of light.
Uneven temperature distribution and temperature rise are prevented.

Although the holding member of the exposure element is a metal casing as a preferred example, the holding member is not necessarily limited to the metal member, but may be a casing made of resin or the like.

As the light emitting element, FL (phosphor emission), EL (electroluminescence), PL (plasma discharge) and the like are used.

The exposure optical system 12 for each color uses a spacer block 12e as a wedge-shaped block member. The main scanning direction with respect to the photosensitive drum 10 and the sub-scanning direction with respect to the rotation direction of the photosensitive drum 10 are previously performed by a jig or the like. The metal casing 12d and the spacer are provided on a support member 20 using a pipe-shaped hollow member such as a cylindrical pipe or a square pipe, which is a common support for the image exposure means for each color. The block 12e and the spacer block 12e and the support member 20 are fixed to each other with an adhesive indicated by a black circle in FIGS. 2 and 3, for example. With the exposure optical system 12 for each color held, the center axis of the support member 20 is aligned with the center axis of the photosensitive drum 10 so that the support member 20
0. Therefore, image exposure of the photosensitive drum 10 by the exposure optical system 12 is performed perpendicular to the central axis of the photosensitive drum 10.

The distance between the inner peripheral surface of the support member 20 and the outer peripheral surface of the substrate of the photoreceptor drum 10 is adjusted by the exposure optical system 1.
2, the bottom surface of the exposure optical system 12 has a circumferential surface which is always located outside the inner circumferential surface of the support member 20. The support member 20 does not need to break the cylindrical surface, the strength is maintained, and the exposure optical system 12 can be reliably held at a predetermined imaging position.

A storage unit (not shown), such as an RA, which is read by an image scanner or inputted by an external signal or the like.
The image signal of each color stored in M is sequentially read from the storage unit through the control unit of the apparatus main body, and input as an electric signal to the exposure optical system 12 for each color, and the LED 121
Are emitted by, for example, a pulse width modulation method (PWM method). The emission wavelength of the light emitting element used in this embodiment is in the range of 600 to 900 nm.

As described above, each of the exposure optical systems 12 is a support member 2 which is a common support using a pipe-shaped hollow member.
0, is housed inside the base of the photoconductor drum 10, is drawn out from the substrate 122 of each exposure optical system 12, and is provided with a lead wire WA of the LED 121 through a connector C mounted at one lower end of the metal casing 12d. . The lead wire WA for each color is drawn out and bundled through the insertion hole 20H, passes through the hollow portion of the support member 20, and is drawn out of the side plate 30 through the insertion hole 30H. The support member 20 also includes a pre-charge exposure unit 12A as a pre-charge exposure unit and a pre-transfer exposure unit 12B as a pre-transfer exposure unit described above.
A pre-cleaning exposure unit 12C as a pre-cleaning exposure unit is mounted and accommodated inside the substrate of the photoreceptor drum 10, and has a lead wire (not shown).
Is inserted through the hollow portion of the support member 20 and the insertion hole 3 of the side substrate 30 is formed.
It is drawn out of the substrate from 0H.

Each of the insertion holes 20H is connected to the connector C and the lead wire W.
A, after the connection with the sealing member S
With this, the lead wire WA is closed together with the lead wire WA, thereby preventing the scattered toner and dust from entering the exposure optical system 12. Further, an adhesive or an elastic member such as urethane foam or a rubber material is filled in the insertion hole 20H to prevent intrusion of toner or dust. As the sealing material S, for example, a hardening type silicone rubber sheet is used, and each insertion hole 20H is closed by an adhesive or the like, thereby maintaining airtightness. 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 does not receive the stress due to the lead wire WA and does not come off due to bending of the lead wire WA.

The support member 20, which is a common support for the exposure optical systems 12, is a thin hollow member made of a light metal material such as aluminum or stainless steel, preferably a cylindrical pipe or a square pipe. Accordingly, the weight and the heat capacity of the supporting member 20 using the metallic hollow member are reduced, and the weight of the image forming unit is reduced, the heat capacity is small, the heat conductivity is good, and the temperature control is achieved. Efficiency is increased. In addition, cylindrical and prismatic pipes are also resistant to mechanical deformation.

13 is yellow (Y), magenta (M),
Developing devices as developing means for accommodating cyan (C) and black (K) developers, each having a developing sleeve 130 that rotates in the same direction while maintaining a predetermined gap with respect to the peripheral surface of the photosensitive drum 10. ing.

Each of the above-mentioned developing units makes the electrostatic latent image on the photosensitive drum 10 formed by the above-described charging by the scorotron charger 11 and image exposure by the exposure optical system 12 non-contact by applying a developing bias voltage. Develop reversely in the state of.

The original image is temporarily stored in an image reading apparatus separate from the present apparatus as an image read by an image sensor or an image edited by a computer as an image signal for each of Y, M, C and K colors. And stored.

After the start of the image recording, the photosensitive drum 10 is rotated counterclockwise by the start of the photosensitive member drive motor, and at the same time, the optical memory of the photosensitive drum 10 is removed by uniform exposure of the pre-charging exposure unit 12A. The application of a potential to the photosensitive drum 10 is started by the charging action of the scorotron charger 11 (Y).

After a potential is applied to the photosensitive drum 10, exposure by an electric signal corresponding to a first color signal, that is, an image signal of yellow (Y) is started in the exposure optical system 12 (Y), and the exposure of the drum is started. An electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer on the surface by rotational scanning.

The latent image is reversal-developed by the developing device 13 (Y) in a state where the developer on the developing sleeve is not in contact with the developer, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 is further provided with a potential on the yellow (Y) toner image by the charging action of the scorotron charger 11 (M) for the second color, and the second color of the exposure optical system 12 (M). Exposure is performed using an electric signal corresponding to the color signal of magenta (M), that is, the image signal of magenta (M), and the magenta (M) ) Are sequentially formed to be superimposed.

By the same process, the cyan (C) toner image corresponding to the third color signal is further formed by the third color scorotron charger 11 (C), the exposure optical system 12 (C) and the developing device 13 (C). And a scorotron charger 11 (K) for the fourth color, an exposure optical system 12 (K), and a developing device 13
(K), a black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed.
A color toner image is formed on the peripheral surface within one rotation.

The photosensitive drum 1 by each of these exposure optical systems
The exposure of the organic photosensitive layer of No. 0 is performed from the inside of the drum through a substrate that is transparent to the above-mentioned exposure wavelength. Therefore, the exposure of the images corresponding to the second, third, and fourth color signals is performed without any influence from the previously formed toner image, and is equivalent to the image corresponding to the first color signal. It is possible to form an electrostatic latent image. At the time of the developing action by each developing device, a developing bias to which a direct current or a further alternating current is applied is applied to the developing sleeve 130, and a jumping development is performed by a one-component or two-component developer accommodated in the developing device, and the developing sleeve 130 is subjected to a transparent development. Non-contact reversal development is performed on the photosensitive drum 10 that grounds the photoconductive layer.

Thus, the photosensitive drum 1 as an image forming body
The residual charge of the photosensitive drum 10 is removed by uniform exposure of a pre-transfer exposure device 12B as a pre-transfer exposure means using, for example, a light emitting diode to remove the residual charge of the organic photosensitive layer of No. 0. The color toner image whose adhesion to the photosensitive drum 10 has been weakened by the removal of the charge is temporarily transferred to the peripheral surface of the intermediate transfer belt 14 as an intermediate transfer unit. The transfer unit in the present embodiment is an intermediate transfer belt 1
4 and an earth roller 14A and an intermediate transfer roller 14B described below.

The 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 at 10 ⁸ to 10 ¹² Ω · cm.
And a resistance value of 10 ¹⁰ to 10 ¹⁶ Ω as a toner filming preventing layer on the outside of the rubber substrate.
-It has a two-layer structure in which a fluorine coating having a thickness of 5 to 50 µm is performed in cm. This layer also preferably has a similar semiconductivity. 0.1-0.5m thickness instead of rubber belt base
m, a semiconductive polyester, polystyrene, polyethylene, polyethylene terephthalate, or the like can also be used. An intermediate transfer belt 14 is stretched between an earth roller 14A, an intermediate transfer roller 14B, a guide roller 14C, a drive roller 14D, and a tension roller 14E, and the photosensitive drum 1 is driven by power transmitted to the drive roller 14D.
The sheet is circulated clockwise in synchronization with the peripheral speed of zero.

The intermediate transfer belt 14 has a central portion of a portion stretched between an earth roller 14A and an intermediate transfer roller 14B, which is in contact with the peripheral surface of the photosensitive drum 10 and has a photosensitive drum 1
The transfer portion TE of the color toner image on the intermediate transfer belt 14 to the intermediate transfer belt 14 is formed. On the other hand, the belt surface on the outer periphery of the guide roller 14C contacts the transfer roller 15 as a transfer member to transfer the recording paper P from the intermediate transfer belt 14 to the recording paper P. Is formed.

After the photosensitive drum 10 with the color toner image adhered to the peripheral surface is neutralized by the uniform exposure of the pre-transfer exposure unit 12B, first, the photosensitive drum 10 and the intermediate transfer belt 14 At a contact point (transfer section TE) between the transfer rollers, the toner is sequentially transferred onto the peripheral surface 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. That is, the color toner image on the drum is conveyed to the transfer area without scattering the toner by the guide of the grounded earth roller 14A, and is transferred to the intermediate transfer roller 14B.
The transfer is efficiently performed on the intermediate transfer belt 14 side by applying a bias voltage of about 3 kV.

On the other hand, the transfer paper P as a recording material is carried out by the operation of the paper feed roller 17 of a paper feed cassette (not shown) and fed to the timing roller 18 so that the intermediate transfer belt 1 is moved.
Transfer roller 15 in synchronization with the transport of the color toner image on
The paper is fed to the transfer area.

The transfer roller 15 is connected to the intermediate transfer belt 14.
Is rotated in a counterclockwise direction in synchronism with the peripheral speed of the transfer paper P, and the fed transfer paper P is positioned in a transfer area formed by a nip portion between the transfer roller 15 and the guide roller 14C in the ground state. The color toner images are sequentially transferred onto the transfer paper P by applying a bias voltage having a polarity opposite to that of the toner of 1 to 2 kV to the transfer roller 15 in close contact with the color toner image on the transfer belt 14.

The transfer roller 15 is connected to the intermediate transfer belt 14.
Is rotated in a counterclockwise direction in synchronization with the peripheral speed of the transfer paper P, and the fed transfer paper P is transferred in a transfer area formed by a nip portion between the transfer roller 15 and the guide roller 14C in the ground state. The color toner images are sequentially transferred onto the transfer paper P by applying a bias voltage having a polarity opposite to that of 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.

The transfer paper P to which the color toner image has been transferred is neutralized, conveyed to the fixing device 91 via the conveyance plate 19, and pinched and conveyed between the heat roller 91A and the pressure roller 91B to be heated. After the toner is fused and fixed, the toner is discharged to the outside of the apparatus via a discharge roller 92.

The untransferred toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to a pre-cleaning exposure unit 12 as a pre-cleaning exposure unit using, for example, a light emitting diode.
The cleaning blade 101 made of a rubber material which is weakened in adhesion to the photosensitive drum 10 from which electricity has been removed by C, and is in a cleaning device 100 which is a means for cleaning the image bearing member or is always in contact with the photosensitive drum 10. The toner is scraped off into the cleaning device 100 by the screw 102, and is collected by the screw 102 into a waste toner container (not shown). Furthermore, in order to eliminate the history of the photoconductor up to the previous printing, for example, a pre-charging exposure unit 12A using a light emitting diode is used.
After the optical memory is removed by removing the charge of the corona remover (not shown) or the corona remover (not shown), the next color image is formed by receiving the uniform charge by the Y scorotron charger 11. Further, 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.

In general, the outer diameter of the photosensitive drum 10 depends on the size of the apparatus and the limitations of the plurality of scorotron chargers 11, the plurality of developing devices 13, the cleaning device 100, and the like provided on the outer peripheral surface of the photosensitive drum 10. A drum having a diameter between 50 mm and 200 mm is preferably used.
The thickness of the substrate is 2 mm to 10 m corresponding to the drum diameter.
On the other hand, the supporting member 20 for supporting these photosensitive drums 10 has a smaller diameter by the exposure optical system 12 and its image forming distance, and has an outer diameter of 20 mm in the case of a cylindrical pipe.
By setting the thickness of the support member 20 to 0.5 mm to 5 mm corresponding to the outer diameter, the strength is sufficient and the exposure optical systems 12 can be installed on the support member 20 with a margin. Becomes possible.

According to FIG. 4 and FIG.
Reference numeral 0 denotes a photosensitive drum that supports the flange members 10A and 10B 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. 10 to flange member 10
A is rotatably supported by the power of a driving gear G that meshes with an internal gear 10G provided on the inner peripheral surface of A.

When the support member 20 supports the photosensitive drum 10, the concave portions on both end surfaces, ie, the inner peripheral surfaces, are the protrusions provided on the side substrate 30 of the apparatus main body, ie, the engaging portions 3 projecting from the inner surface.
1 and is fixed between the side substrates 30 by being inserted. When the support member 20 is held, the engagement pin 32 provided on the outer peripheral surface of the engagement portion 31 of the one side substrate 30 engages with the notch 20A on the end surface of the support member 20, and the fixing angle of the support member 20 is regulated. Each exposure optical system 12 is set at a predetermined position with respect to the apparatus main body, and a scorotron charger 1 as a charging unit disposed along the peripheral surface of the photosensitive drum 10.
The correct positional relationship is maintained with respect to the developing device 1 and the developing device 13 as the developing means.

The support member 20 is provided on the photosensitive drum 10.
A disk member 22 is coaxially and integrally provided on the side opposite to the side on which the internal gear 10G is provided, and the disk member 22 serves as a support member for supporting one bearing B2 provided between the photosensitive drum 10 and the disk member 22. Is also used.

The first aspect of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is an explanatory diagram of the arrangement of the pre-charging exposure unit and the pre-cleaning exposure unit. FIG. 6 is a diagram showing the potential decay of the image forming body due to the uniform exposure of the pre-charging exposure unit.

According to FIG. 5 or FIG.
2A denotes an exposure position on the photosensitive drum 10, a contact position of the cleaning blade 101 attached to the blade holder 103 and provided in the cleaning device 100 with the photosensitive drum 10, and a cleaning casing 104 of the cleaning device 100. The end of the scorotron charger 11 side (the center of the photosensitive drum 10 and the cleaning device 100
Of the Y-scorotron charger 11 at the most upstream position in the rotation direction of the photosensitive drum 10
(A point where the straight line connecting the four end portions intersects with the surface of the photosensitive drum 10) P12, and faces the cleaning device 100 with the photosensitive drum 10 interposed therebetween.
0. As described above, the scorotron charger 11 for Y at the most upstream position in the rotation direction of the photosensitive drum 10 is provided near the cleaning device 100 downstream of the cleaning device 100 in the rotation direction of the photosensitive drum 10.

When the uniform exposure is performed by setting the image forming position on the photosensitive layer on the substrate surface by the pre-charging exposure unit 12A, the photosensitive member 10 is exposed to the highest charging potential V1 of the exposed portion. The charging with the optical memory on the body drum 10 is performed by charging the electric potential V of the portion to be exposed by light attenuation due to uniform exposure.
1 is sufficiently reduced and the potential reduction rate is 90% or more, that is, V1 × in which the potential is sufficiently reduced.
It is necessary to perform charging after the charge becomes 0.1 or less.
In the case of an organic photoreceptor, the charge transfer speed is slow, and the potential reduction time tends to be longer than that of the inorganic photoreceptor.

Assuming that the time from the uniform exposure of the pre-transfer exposure device 12A to the potential V1 × 0.1 is T11, the image forming position P11 of the pre-charge exposure device 12A and the photosensitive drum 10 The end of the side plate 11a serving as a shield member of the Y scorotron charger 11 at the most upstream position in the rotation direction on the side of the pre-charge exposure unit 12A (the center of the photosensitive drum 10 and the end of the side plate 11a on the pre-charge exposure unit 12A side). Point of intersection of the straight line connecting the two and the surface of the photosensitive drum 10) P1
Assuming that the distance on the peripheral surface of the photoconductor drum 10 from the photoconductor 3 is L11 and the peripheral speed of the photoconductor drum 10 is v, (L11) / v> T11. As a result, the potential of the portion to be exposed can be sufficiently lowered, and favorable charging is performed.

The time from the uniform exposure until the potential of the photosensitive drum 10 becomes (1/2) × V1 is T.
It is assumed to be 12. When the potential V1 of the photosensitive drum 10 is reduced to (１ ／) × V1 or less (light elimination) due to the uniform exposure of the pre-charging exposure unit 12A, the photosensitive drum 10 has the same polarity as the photosensitive drum 10 and is repelled so that it is difficult to adhere. The electrical repulsion of the toner inside the cleaning device 100 with the photoreceptor drum 10 in which the potential has been reduced is weakened. That is, the cleaning device 1
00, the toner inside the cleaning device 100 easily adheres to the photosensitive drum 10, and the toner inside the cleaning device 100 adheres to the photosensitive drum 10 and is carried outside to scatter.
The potential of the photosensitive drum 10 is set to (1/2) so as not to cause the inside of the apparatus, the Y scorotron charger 11 disposed close to the cleaning device to be stained, and the image stain due to toner adhesion to the photosensitive drum 10. ) × V1 until the exposed portion on the photosensitive drum 10 is at the end of the cleaning casing 104 of the cleaning device 100 on the side of the scorotron charger 11 (the center of the photosensitive drum 10 and the rotation direction of the photosensitive drum 10 in the rotation direction). It is necessary that the straight line connecting the end of the cleaning casing 104 on the side of the scorotron charger 11 of the upstream position Y intersects with the surface of the photosensitive drum 10) P12. That is, the photosensitive drum 1
When the exposed portion 0 passes through the end P12 of the cleaning casing 104 on the side of the scorotron charger 11, the potential is higher than (1/2) × V1 and the toner is
It is necessary that the toner does not drop so as to adhere to the outside of the cleaning device 100 and be scattered from the peripheral surface of the photosensitive drum 10. Therefore, the peripheral speed v of the photosensitive drum 10
In contrast, a side plate 11a as a shield member of the Y scorotron charger 11 at the image forming position P11 of the pre-charging exposure device 12A and the most upstream position in the rotation direction of the photosensitive drum 10
Drum 1 with the end P13 on the side of the pre-charging exposure unit 12A
The distance on the 0 circumferential surface is L11, the image forming position P11 of the pre-charging exposure unit 12A, and the Y at the most upstream position in the rotation direction of the photosensitive drum 10
Of the cleaning casing 104 on the side of the scorotron charger 11 (the end of the cleaning casing 104 on the side of the scorotron charger 11 of Y at the most upstream position in the rotation direction of the photosensitive drum 10 with respect to the cleaning device 100 and the center of the photosensitive drum 10). (L12) / v <T12, where L12 is the distance between the straight line connecting to and the surface of the photosensitive drum 10) P12 on the peripheral surface of the photosensitive drum 10. In general, an organic photoreceptor has T12 ≦ (T1
1) / 2, the above conditional expression, T11 <(L11)
From / v, the above equation is transformed into L12 <(1/2) × L11. This condition is a preferable condition in which the exposed position does not cause toner scattering after leaving the cleaning unit and the potential is sufficiently lowered at the charging position. Further, the cleaning device 100 and the scorotron charger 11 can be arranged close to each other, so that the diameter of the photosensitive drum 10 can be reduced, and the device can be downsized.

Further, as shown in FIG. 5, a DC of the same polarity as the toner (minus polarity in the present embodiment) is applied to the end of the cleaning casing 104 close to the photosensitive drum 10 on the Y scorotron charger 11 side. A toner scattering shielding member 104a to which a voltage cleaning casing bias E1 is applied is provided, and the toner scattered from above the photosensitive drum 10 inside the cleaning device 100 or the toner scattered in the cleaning unit is outside the cleaning casing 104 of the cleaning device 100. To prevent scattering.

As described above, the device can be downsized,
The toner inside the cleaning means is prevented from adhering to the image forming body due to the potential decrease (light elimination) of the image forming body after uniform exposure by the pre-charging exposure means, and the toner inside the cleaning means adheres to the image forming body. Then, contamination inside the apparatus, contamination of the charging means, and image contamination caused by being carried outside are prevented.

The second invention according to claim 4 or 5 will be described with reference to FIG. 7 and FIG. FIG. 7 is an explanatory view of the arrangement of the pre-transfer exposure means, and FIG. 8 is a diagram showing the potential decay of the image forming body due to uniform exposure of the pre-transfer exposure means.

According to FIG. 7 or FIG.
2B, the exposure position on the photosensitive drum 10 is set such that the end of the K developing device 13 provided at the most downstream position in the rotation direction of the photosensitive drum 10 on the side of the intermediate transfer belt 14 (the center of the photosensitive drum 10 and K Point P2 where the straight line connecting the end of the developing device 13 with the intermediate transfer belt 14 and the surface of the photosensitive drum 10 intersects
Roller 14A that stretches the belt 3 and the intermediate transfer belt 14
(The center of the photosensitive drum 10 and the earth roller 1)
4A and a point P22 where the straight line connecting the center of 4A intersects with the surface of the photosensitive drum 10). As described above, the transfer unit in the present embodiment is the intermediate transfer belt 14.
And an intermediate transfer roller 14A. The intermediate transfer belt 14 includes an earth roller 14A and an intermediate transfer roller 14B.
The central portion of the portion stretched between the photosensitive drum 10 and the peripheral surface of the photosensitive drum 10 is in contact with the photosensitive drum 10 to form a transfer portion TE of the color toner image on the photosensitive drum 10 to the intermediate transfer belt 14.

When the image-forming position is set on the photosensitive layer on the surface of the substrate by the pre-transfer exposure device 12B and the image exposure is performed, the highest charged potential V2 of the exposed portion of the photosensitive drum 10 is set to The transfer with the electric charge on the drum 10 is
The photosensitive drum 1 at the exposed portion due to light attenuation due to uniform exposure
The operation is performed after the charging potential V2 at a place where there is no color toner image on 0 is sufficiently reduced and the potential reduction rate is 90% or more, that is, the potential is sufficiently reduced to V2 × 0.1 or less. It is necessary to perform the transfer afterwards. In the case of an organic photoreceptor, the charge transfer speed is slow, and the potential reduction time tends to be longer than that of the inorganic photoreceptor.

Assuming that the time from when uniform exposure is performed by the pre-transfer exposure device 12B until the potential reaches V2 × 0.1 is T21, the image forming position P21 of the pre-transfer exposure device 12B and the transfer When the distance on the peripheral surface of the photosensitive drum 10 from the position (transfer section TE) is L21, and the peripheral speed of the photosensitive drum 10 is v, (L21) / v> T21. Thereby, the potential of the exposed portion can be sufficiently lowered, and good transfer can be performed.

The time from when uniform exposure is performed until the potential of the photosensitive drum 10 becomes (1/2) × V2 is T.
22. The color toner image existing in the vicinity of the photosensitive drum 10 due to the uniform exposure of the pre-transfer exposure unit 12B does not scatter instantaneously, and does not scatter until the electric adhesion decreases due to the potential drop. When the potential drop from the image exposure is substantially 以下 or less, that is, the potential drops (light elimination) to (以下) × V2 or less, toner scattering from the toner image occurs. For this reason, the photosensitive member is prevented from being stained by the toner scattered due to the potential drop, and from being stained by the pre-transfer exposing device 12B when it is disposed outside the photosensitive drum 10 indicated by a dotted line in FIG. Until the potential of the drum 10 attenuates to (１ ／) × V2, the exposed portion on the photosensitive drum 10 connects the center position of the ground roller 14A (connects the center of the photosensitive drum 10 and the center of the ground roller 14A). (The point where the straight line intersects the surface of the photosensitive drum 10). That is, when the exposed portion of the photosensitive drum 10 passes through the center position P22 of the ground roller 14A on which the intermediate transfer belt 14 is stretched, the potential is larger than (1/2) × V2, and the potential decreases as the toner scatters. It is necessary that there is not. Accordingly, with respect to the peripheral speed v of the photosensitive drum 10, the distance on the peripheral surface of the photosensitive drum 10 between the image forming position P21 of the pre-transfer exposure device 12B and the transfer position (transfer section TE) of the transfer means is L21. The end of the transfer means on the upstream side in the rotation direction of the pre-exposure unit 12B and the photosensitive drum 10, that is, the center position of the ground roller 14A (a straight line connecting the center of the photosensitive drum 10 and the center of the ground roller 14A, Assuming that the distance on the peripheral surface of the photosensitive drum 10 from the point P22 on the peripheral surface of the photosensitive drum 10 is L22, the following formula is established. Generally, an organic photoreceptor has T22 ≦ (T2
1) / 2, the above conditional expression, T21 <(L21)
From / v, the above equation is transformed into L12 <(1/2) × L11. This condition is a preferable condition in which 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 unit 13 and the intermediate transfer belt 14 can be arranged close to each other, so that the diameter of the photosensitive drum 10 can be reduced, and the apparatus can be downsized.

As described above, the device can be downsized,
Before the color toner image on the image forming body whose adhesion has been weakened is scattered due to the potential decrease (light elimination) of the image forming body after uniform exposure by the pre-transfer exposure means, the color on the image forming body is reduced. The transfer of the toner image is performed, thereby preventing the inside of the apparatus from being stained due to toner scattering. Further, in the case where the pre-transfer exposure means is provided outside the image forming body, the contamination of the image exposure means due to toner scattering is also prevented.

A third aspect of the present invention will be described with reference to FIGS. 9 and 5. FIG. 9 is a diagram showing the potential decay of the image forming body due to uniform exposure of the pre-cleaning exposure unit.

According to FIG. 5 or FIG. 9, the pre-cleaning exposure unit 12C sets the exposure position on the photosensitive drum 10 to
The center position of the intermediate transfer roller 14B (the photosensitive drum 10) which stretches the intermediate transfer belt 14 provided at the upstream position in the rotation direction of the photosensitive drum 10 with respect to the cleaning device 100.
And a straight line connecting the center of the intermediate transfer roller 14B and
(Point of intersection with the surface of the photoreceptor drum 10) P33 and an end of the cleaning device 100 on the intermediate transfer belt 14 side.

The highest charged potential V of the exposed portion of the photosensitive drum 10 when the image exposure is performed by setting the image forming position on the photosensitive layer on the substrate surface by the pre-cleaning exposure unit 12C.
On the other hand, in the cleaning in a state in which electric charges are present on the photosensitive drum 10, the charge potential V3 of the exposed portion is sufficiently reduced due to light attenuation by uniform exposure, and the potential reduction rate becomes 90% or more. It is necessary to perform cleaning, that is, to perform cleaning after the potential has decreased to V3 × 0.1 or less. In the case of an organic photoreceptor, the charge transfer speed is slow, and the potential reduction time tends to be longer than that of the inorganic photoreceptor. In the case of an organic photoreceptor image forming body, the moving speed of the charge is slow,
The potential drop time tends to be longer compared to the inorganic photoreceptor,
Special attention must be paid.

The time from the uniform exposure of the pre-cleaning exposure unit 12C until the potential becomes V3 × 0.1 is T
31, the distance between the image forming position P31 of the pre-cleaning exposure device 12C and the contact position of the cleaning blade 101 of the cleaning device 100 on the photosensitive drum 10 is L31, and the photosensitive drum 10 Let (L31) / v> T31 be the peripheral speed of v. As a result, the exposed portion can be sufficiently lowered in potential, and good cleaning is performed.

The time from the uniform exposure until the potential of the photosensitive drum 10 becomes (1/2) × V3 is T.
32. The transfer residual toner adhering to the photoreceptor drum 10 due to the uniform exposure of the pre-cleaning exposure unit 12C does not instantaneously scatter and does not scatter until the electric adhesion decreases due to the potential drop. When the potential drop of the photosensitive drum 10 due to the uniform exposure of the pre-cleaning exposure unit 12C is substantially 以下 or less, that is, the potential becomes (１ ／) × V3 or less, toner scattering from transfer residual toner occurs. For this reason, the photoconductor is prevented from being stained by the toner scattered due to the potential drop or the pre-cleaning exposure device 12C when the photoconductor is disposed outside the photoconductor drum 10 shown by a dotted line in FIG. The exposed portion on the photosensitive drum 10 has reached the end P32 of the cleaning casing 104 of the cleaning device 100 on the intermediate transfer belt 14 side before the potential of the drum 10 attenuates to (1/2) × V3. Is required. That is, the exposed portion of the photosensitive drum 10 is the end portion P32 of the cleaning casing 104 on the intermediate transfer belt 14 side.
Is passed, the potential is higher than (1/2) × V1, and the residual toner is attached to the photosensitive drum 10 and carried to the inside of the cleaning device 100, and decreases as the toner scatters from the peripheral surface of the photosensitive drum 10. It is necessary that you do not. Accordingly, the image forming position P31 of the pre-cleaning exposure unit 12C and the cleaning device 10 are determined with respect to the peripheral speed v of the photosensitive drum 10.
The distance on the peripheral surface of the photosensitive drum 10 between the cleaning blade 101 and the contact position of the cleaning blade 101 with the photosensitive drum 10 is L3.
1. The image forming position P31 of the pre-cleaning exposure device 12C and the cleaning device 10 upstream of the photosensitive drum 10 in the rotation direction.
0 of the cleaning casing 104 (the center of the photosensitive drum 10 and the cleaning casing 104 on the intermediate transfer belt 14 side at the most upstream position in the rotation direction of the photosensitive drum 10).
Assuming that the distance on the peripheral surface of the image forming body between the straight line connecting the end and the point of intersection with the surface of the photosensitive drum 10) P32 is L32, then (L32) / v <T32. In general, an organic photoreceptor has T32 ≦ (T3
1) / 2, the above conditional expression, T31 <(L31)
The above equation is transformed from L / v to L32 <(1/2) × L31. This is a preferable condition that the toner is not scattered until the exposure position enters the cleaning unit, and the potential is sufficiently lowered at the cleaning position of the cleaning blade 101 in contact with the photosensitive drum 10. Also,
As a result, the diameter of the photosensitive drum 10 is reduced, and the size of the apparatus is reduced.

Further, as shown in FIG. 5, a DC voltage of the same polarity as that of the toner (in this embodiment, a minus polarity) is applied to the end of the cleaning casing 104 close to the photosensitive drum 10 on the intermediate transfer belt 14 side. Toner scattering shielding member 1 to which cleaning casing bias E2 is applied
The cleaning device 104 is provided to prevent the toner scattered from the photosensitive drum 10 inside the cleaning device 100 and the toner scattered in the cleaning unit from being scattered outside the cleaning casing 104 of the cleaning device 100. Also,
Intermediate transfer belt 1 in place of toner scattering shielding member 104b
At the end of the cleaning casing 104 on the fourth side, a cleaning roller 105 shown by a dashed line in FIG.
4 can also be prevented from scattering outside.

As described above, the device can be downsized,
The scattering of the untransferred toner on the image forming body whose adhesion has been weakened due to the potential decrease (light elimination) of the image forming body after the uniform exposure by the pre-cleaning exposure unit is stored in the cleaning unit, and the untransferred toner is stored in the cleaning unit. Dirt caused by scattering of air is prevented. Further, when the image exposing means is provided outside the image forming body, the image exposing means is prevented from being stained by scattering of toner.

The above first to third aspects of the present invention may be employed individually or in combination, and a good overall result can be obtained by employing them in combination. .

[0093]

According to the first to third aspects of the present invention, the size of the apparatus is reduced, and the toner inside the cleaning means due to the potential decrease (light elimination) of the image forming body after uniform exposure by the pre-charging exposure means. Is prevented from adhering to the image forming body, and the in-machine contamination, the contamination of the charging unit, and the image contamination caused by the toner inside the cleaning means adhering to the image forming body and being carried outside are prevented.

According to the fourth or fifth aspect, the size of the apparatus is reduced, and the adhesive force is weakened due to the potential decrease (light elimination) of the image forming body after uniform exposure by the pre-transfer exposure means. Before the color toner image on the image forming body is scattered, the color toner image on the image forming body is transferred, so that the in-machine contamination caused by the toner scattering is prevented. Further, in the case where the pre-transfer exposure means is provided outside the image forming body, the contamination of the image exposure means due to toner scattering is also prevented.

According to the sixth to eighth aspects, the image forming apparatus is reduced in size, and the adhesion of the image forming body after the uniform exposure by the pre-cleaning exposure means is reduced due to a decrease in the potential (light elimination). Scattering of the transfer residual toner on the formed body is housed in the cleaning means, and contamination in the apparatus caused by scattering of the transfer residual toner is prevented. Further, when the image exposing means is provided outside the image forming body, the image exposing means is prevented from being stained by scattering of toner.

Further, the first aspect according to claims 1 to 3 above.
Invention, the second invention according to claim 4 or 5, and claim 6.
Overall good results can be obtained by using the three inventions of the third invention according to (8) to (8) in combination.

[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.

FIG. 2 is a diagram showing a configuration of an image exposure unit of FIG. 1 and a method of attaching the image exposure unit to a support member.

FIG. 3 is a perspective view of FIG. 2;

FIG. 4 is a cross-sectional configuration diagram of the image forming body of FIG. 1;

FIG. 5 is an explanatory diagram of an arrangement of a pre-charging exposure unit and a pre-cleaning exposure unit.

FIG. 6 is a diagram illustrating a potential decay of an image forming body due to uniform exposure of a pre-charging exposure unit.

FIG. 7 is an explanatory diagram of an arrangement of a pre-transfer exposure unit.

FIG. 8 is a diagram illustrating a potential decay of an image forming body due to uniform exposure of a pre-transfer exposure unit.

FIG. 9 is a diagram illustrating a potential decay of an image forming body due to uniform exposure of a pre-cleaning exposure unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Photoreceptor drum 11 Scorotron charger 12 Exposure optical system 12A Pre-charge exposure unit 12B Pre-transfer exposure unit 12C Pre-cleaning exposure unit 13 Developing unit 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 (8)

[Claims] A plurality of charging means, an image exposing means, and a developing means provided on a peripheral surface of the image forming body, and charging, image exposing, and developing are repeated 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 of the recording medium, 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 a color image forming apparatus that forms an image and cleans transfer residual toner on the image forming body by a cleaning unit, an organic photoconductor is used for the image forming body, and before the image forming body is uniformly exposed to light. An exposing unit is provided in the cleaning unit, and in a step from the uniform exposure position of the pre-charging exposing unit to the charging unit at the most upstream position in the rotation direction of the image forming body, the exposure at the uniform exposing position is performed. The charged potential V1 of the exposed portion is (V1)
The color image forming apparatus is set so that a portion to be exposed on the image forming body is moved out of the cleaning unit before the light is attenuated to / 2. 2. A color image forming apparatus according to claim 1, wherein a cleaning casing bias having the same polarity as that of the toner is applied to the end of the cleaning means on the charging means side at the most upstream position in the rotation direction of the image forming body. . 3. A distance L12 on the peripheral surface of the image forming body between the pre-charging exposure means and an end of the cleaning means on the charging means side at the most upstream position in the rotation direction of the image forming body, and L2, The distance on the peripheral surface of the image forming body from the end of the charging means at the most upstream position in the rotation direction of the image forming body on the pre-charging exposure means side is represented by L
The color image forming apparatus according to claim 1, wherein when L is 11, L 12 <(１ ／) × L 11. 4. A plurality of charging means, an image exposing means and a developing means are provided on a peripheral surface of the image forming body, and charging, image exposing and developing are repeated 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 of the recording medium, 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 a color image forming apparatus for forming an image, an organic photoreceptor is used for the image forming body, and a pre-transfer exposure unit for uniformly exposing the image forming body is provided, and In the step of reaching the transfer means, the exposed part on the image forming body moves into the transfer means until the charged potential V2 of the exposed part at the uniform exposure position is attenuated to (V2) / 2. The feature is that it is set to Color image forming apparatus. 5. A distance L22 on the peripheral surface of the image forming body between the pre-transfer exposure means and an end of the transfer means on the upstream side in the rotation direction of the image forming body, and a transfer position of the pre-transfer exposure means and the transfer means. 5. The color image forming apparatus according to claim 4, wherein L22 <(１ ／) × L21, where L <b> 21 is a distance on the peripheral surface of the image forming body. 6. A plurality of charging means, an image exposing means and a developing means are provided on a peripheral surface of the image forming body, and charging, image exposing and developing are repeated 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 of the recording medium, 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 a color image forming apparatus for forming an image and cleaning the transfer residual toner on the image forming body by a cleaning blade provided in a cleaning unit, an organic photoreceptor is used for the image forming body, and the image forming body is formed on the image forming body. Providing a pre-cleaning exposure unit for performing uniform exposure, wherein in the step from the uniform exposure position of the pre-cleaning exposure unit to the cleaning unit, Wherein the exposed portion on the image forming member is moved into the cleaning means until the charged potential V3 of the exposed portion is lightly attenuated to (V3) / 2. Image forming device. 7. The color image forming apparatus according to claim 6, wherein a cleaning casing bias having the same polarity as that of the toner is applied to an upstream end of the cleaning unit in the rotation direction of the image forming body. 8. A distance L32 on the peripheral surface of the image forming body between the pre-cleaning exposure unit and the end of the cleaning unit upstream in the rotation direction of the image forming unit, and the image formation of the pre-cleaning exposure unit and the cleaning blade. The color image forming apparatus according to claim 6, wherein L32 <(１ ／) × L31, where L <b> 31 is a distance on the peripheral surface of the image forming body from the contact position with the body. .