JPH11119508A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the change of a gap between an image forming body and the developer carrying member of a developing means caused by temperature change to be small by providing a specified condition among the raidus of curvature of the developer carrying member of the developing means, the radius of curvature of a position regulating member for regulating the gap between the image forming body and the developer carrying member and the coefficient of linear expansion of the developer carrying member. SOLUTION: A butting roller 130A functioning as the position regulating member provided at both side ends of a developing sleeve 130 coaxially with the sleeve 130 is made abut on the outer periphery part of a flange member 10A holding a photoreceptor drum 10. When it is assumed that the radius of curvature of the sleeve 130 of a developing device is r1 (μm), the raidus of curvature of the roller 130A functioning as the position regulating member for regulating the gap between the drum 10 and the sleeve 130 is r2(μm), the coefficient of linear expansion of the sleeve 130 is α1(/ deg.C) and the coefficient of linear expansion of the roller 130A is α2(/ deg.C), the condition expressed by an expression |r2×α2-r1×α1|<3(μm/ deg.C) is provided.

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. .

[0005]

However, when forming a superimposed color toner image in the color image forming apparatus according to the above-mentioned proposal, the developing sleeves (developer conveying members) of a plurality of developing means and the image forming body are changed due to a temperature change. And the gaps between the color toners vary, and the amount of adhered color toner changes, resulting in image defects such as loss of color balance.

Further, in the above-described color image forming apparatus, since the image forming body using the translucent resin base is adopted, the image forming body and the developing sleeve are caused to expand and contract by the temperature change. In this case, there arises a problem that the gap changes and an image defect occurs. For example, in the case of performing non-contact development in which the prescribed gap between the image forming body and the developing sleeve is about 500 μm, the allowable width is ± 60 μm. I want to suppress the occurrence of image defects even when the temperature changes from room temperature (20 ° C.) to ± 20 ° C. in an actual use environment.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color image forming apparatus which solves the above problems and suppresses a change in a gap between an image forming body and a developer conveying member of a developing means due to a temperature change.

[0008]

The object of the present invention is to provide a plurality of charging means and developing means on the outer peripheral surface of the image forming body, and a plurality of image exposing means on the inner peripheral surface of the image forming body. To be charged,
In a color image forming apparatus that repeats image exposure and development to form a color toner image by superimposing a plurality of toner images on the peripheral surface of the image forming body, a radius of curvature of a developer conveying member of the developing unit is r1 (μm ), The radius of curvature of the position regulating member for regulating the gap between the image forming body and the developer conveying member is r2 (μm), the linear expansion coefficient of the developer conveying member is α1 (/ ° C.), and the position is When the linear expansion coefficient of the regulating member is α2 (/ ° C.), | r2 × α2−r1 × α1 | <3 (μm / ° C.) is achieved by the color image forming apparatus (first example). Invention).

It is another object of the present invention to dispose a plurality of charging means and developing means on the outer peripheral surface of the image forming body, and a plurality of image exposing means on the inner peripheral surface of the image forming body. In a color image forming apparatus that repeats exposure and development to form a color toner image by superimposing a plurality of toner images on the peripheral surface of the image forming body, a first position regulating member is provided for the developing unit, and a second position controlling member is provided for the second unit. A position regulating member is provided on each of the image forming bodies, and the first position regulating member and the second position regulating member are brought into contact with each other to reduce a gap between the developer conveying member of the developing unit and the image forming body. The radius of curvature of the image forming body is ra (μm), the radius of curvature of the developer conveying member is rb (μm), the radius of curvature of the first position regulating member is rc (μm). The radius of curvature of the position regulating member 2 is r
d (μm), and the linear expansion coefficient of the image forming body is αa (/
° C), and the linear expansion coefficient of the developer conveying member is αb (/
° C), and the linear expansion coefficient of the first position regulating member is αc (/
° C), and the linear expansion coefficient of the second position regulating member is αd (/
° C), | ra × αa + rb × αb-rc × αc-rd × αd |
<3 (μm / ° C.) is achieved by a color image forming apparatus (second invention).

[0010]

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.

An image forming process and each mechanism of a color image forming apparatus according to an embodiment of 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, FIG. 2 is a diagram illustrating a configuration of an image exposure unit and a method of attaching the image exposure unit to a support member, and FIG.
FIG. 4 is a perspective view of FIG. 2, FIG. 4 is a cross-sectional configuration diagram of the image forming body of FIG. 2, and FIG. 5 is an enlarged view of the position regulating member and the developer conveying member of FIG.

According to FIGS. 1 to 4, a photosensitive drum 10 as a drum-shaped image forming member is, for example, a cylindrical light-transmitting resin base formed of a light-transmitting member made of a light-transmitting acrylic resin. Is provided inside, and a translucent conductive layer and an organic photoreceptor layer (OPC) are formed on the outer periphery of the substrate.
It is rotated in the direction shown by the arrow in FIG.

In the present embodiment, it is sufficient that the photoconductive layer of the photosensitive drum has an exposure light amount capable of giving an appropriate contrast. Therefore, the light transmittance of the light-transmitting resin substrate of the photosensitive drum in the present embodiment does not need to be 100%, and may have a characteristic such that a certain amount of light is absorbed when the exposure beam is transmitted. . As the material of the light-transmitting substrate, an acrylic resin, particularly one polymerized using a methyl methacrylate monomer, has a light-transmitting property, strength,
Although it is excellent in accuracy, surface properties, and the like, it is preferably used, but various translucent resins such as fluorine, polyester, polycarbonate, polyethylene terephthalate, and the like used for other general optical members can be used. Also,
It may be colored as long as it has a property of transmitting the exposure light. The refractive index of these resins is approximately 1.5. As a method for forming the light-transmitting conductive layer, indium tin oxide (ITO), alumina, tin oxide, lead oxide, indium oxide can be formed by a vacuum evaporation method, an active reaction evaporation method, various sputtering methods, and various CVD methods. , Copper iodide, Au, Ag, Ni,
A light-transmitting thin film made of Al or the like is used,
A conductive resin composed of the above-mentioned metal fine particles and a binder resin is used by a dip coating method, a spray coating method or the like. Further, as the photoconductor layer, various organic photoreceptor layers (O
PC) can be used.

Preferred examples of the image forming body are shown below.

After adding a catalyst for synthesizing and polymerizing the plastic material monomer, the mixture is poured into a cylindrical mold, sealed and fixed with a side plate, rotated at high speed, and heated appropriately. Promotes 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 a material for the light-transmitting resin substrate of a 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 generation 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-based pigment, an azulenium pigment, a phthalocyanine-based 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 the binder resin used for the 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 sensitivity and potential change upon repeated use 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.

The binder resin used in the CTL can be selected from a wide range of insulating resins as appropriate, and is preferably used as a binder resin such as a silicon-alkyd resin, a phenol-formaldehyde resin, or a poly-N- resin. 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 maleic acid copolymer, ethyl cellulose and 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 light-transmitting resin substrate produced by the above-mentioned manufacturing 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.

Reference numeral 11 denotes a scorotron charger as a charging means, which performs a charging action on the above-mentioned organic photoreceptor layer of the photoreceptor drum 10 by a grid maintained at a predetermined potential and corona discharge by a discharge wire. 10 is given a uniform potential.

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 a metal member, but may be a casing made of resin or the like.

As the light emitting element, FL (fluorescent light emission), EL (electroluminescence), PL (plasma discharge), etc. are used.

The exposure optical system 12 for each color uses a spacer block 12e as a wedge-shaped block member, and a main scanning direction with the photosensitive drum 10 and a sub-scanning direction with respect to the rotation direction of the photosensitive drum 10 by a jig or the like in advance. 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 determined 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 input 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 attached to the support member 20 using a pipe-shaped hollow member, is accommodated in the base of the photosensitive drum 10, and is exposed from the substrate 122 of each of the exposure optical systems 12. Drawn out metal casing 12d
LED1 through connector C attached to the lower end of the
21 lead wires WA are provided. Lead wire W for each color
A is pulled out of the insertion hole 20H and bundled, and the support member 2
The through-hole 30H is drawn out of the side board 30 through the through hole 30H.

Each insertion hole 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.

A thin hollow member made of a light metal material such as aluminum or stainless steel, preferably a cylindrical pipe or a square pipe, is used as the support member 20 which is a common support for each exposure optical system 12. 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.

Reference numerals 13Y to 13K denote developing units as developing means for accommodating the respective developers of yellow (Y), magenta (M), cyan (C) and black (K). On the other hand, there is provided a developing sleeve 130 that rotates in the same direction while maintaining a predetermined gap.

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 contactless by applying a developing bias voltage. Develop reversely in the state of.

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

At the start of image recording, the photosensitive drum 10 is rotated counterclockwise by the start of the photosensitive member drive motor, and at the same time, the application of potential to the photosensitive drum 10 is started by the charging action of the scorotron charger 11 (Y). Is done.

After a potential is applied to the photosensitive drum 10, the exposure optical system 12 (Y) starts exposure with an electrical signal corresponding to a first color signal, ie, a yellow (Y) image signal, and the drum is exposed. 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, and a yellow (Y) toner image is formed according to the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 further applies a scorotron charger 11 on the yellow (Y) toner image.
The potential is given by the charging action of (M), and the exposure optical system 1
Exposure is performed with an electric signal corresponding to the second color signal of 2 (M), that is, the image signal of magenta (M), and the developing device 13
By the non-contact reversal development by (M), a magenta (M) toner image is sequentially superimposed on the yellow (Y) toner image.

The scorotron charger 11 (C), the exposure optical system 12 (C) and the developing device 13
(C) further forms a cyan (C) toner image corresponding to the third color signal, and the scorotron charger 11
(K), a black (K) toner image corresponding to the fourth color signal is sequentially superimposed by the exposure optical system 12 (K) and the developing device 13 (K), and is formed within one rotation of the photosensitive drum 10. Then, a color toner image is formed on the peripheral surface.

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.

The color toner image formed on the peripheral surface of the photosensitive drum 10 is once transferred onto the peripheral surface of the intermediate transfer belt 14 provided as an intermediate transfer means.

The intermediate transfer belt 14 serving 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. The intermediate transfer belt 14 has rollers 14A, 14B,
The photosensitive drum 10 is stretched between the rollers 14C and 14D, and is circulated clockwise in synchronization with the peripheral speed of the photosensitive drum 10 by the power transmitted to the roller 14D.

The intermediate transfer belt 14 has a roller 14A.
The belt surface between the roller 14B and the roller 14B is in contact with the peripheral surface of the photosensitive drum 10, while the belt surface on the outer periphery of the roller 14C is in contact with the transfer roller 15, which is a transfer member, to form a toner image transfer area at each contact point. ing.

The color toner image adhered to the peripheral surface of the photosensitive drum 10 is first subjected to intermediate transfer by applying a bias voltage having a polarity opposite to that of the toner to the roller 14B at the contact point with the intermediate transfer belt 14. The image is transferred to the peripheral surface of the belt 14. That is, the color toner image on the drum is conveyed to the transfer area without scattering the toner by the guidance of the roller 14A that is grounded,
The intermediate transfer belt 14 is applied by applying a bias voltage of kV.
It is efficiently transferred to the side.

On the other hand, the transfer paper P as the transfer material is carried out by the operation of the paper feed roller 17 of the paper feed cassette (not shown) and fed to the timing roller 18, and the color toner image on the intermediate transfer belt 14 is formed. Transfer roller 1 in synchronization with conveyance
No. 5 is fed to the transfer area.

The transfer roller 15 is connected to the intermediate transfer belt 14.
The transfer paper P fed in the counterclockwise direction is synchronized with the peripheral speed of the intermediate transfer in the transfer area formed by the nip portion between the transfer roller 15 and the roller 14C in the ground state. The color toner images are successively transferred onto the transfer paper P by applying a bias voltage of the opposite polarity to the toner of 1 to 2 kV to the transfer roller 15 in close contact with the color toner image on the 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, sandwiched and conveyed between the heat roller 91A and the pressure roller 91B, and heated. After the toner is fused and fixed, the toner is discharged to the outside of the apparatus via a discharge roller 92.

Cleaning devices 100 and 140 as cleaning means are installed on the photosensitive drum 10 and the intermediate transfer belt 14, respectively, and the blades of the respective devices are constantly pressed against each other to remove the remaining adhered toner. The surrounding surface is always kept clean.

In general, the outer diameter of the photosensitive drum 10 depends on the size of the apparatus and the restrictions imposed by 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.

With the support member 20 supporting the photosensitive drum 10, the concave portions at 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.

Referring to FIGS. 5 and 4, the photosensitive drum 10
On the outer periphery with the flange members 10A and 10B
Abutting rollers 130A as position regulating members provided on both side ends of the developing sleeves 130 are coaxially abutted, whereby the positions of the developing sleeves 130 as the developer conveying members are regulated. A predetermined gap is set between the peripheral surface of the photosensitive drum 10 and the peripheral surface of the photosensitive drum 10.

The radius of curvature of the developing sleeve 130 of the developing unit 13 is r1 (μm), and the photosensitive drum 10 and the developing sleeve 1
The radius of curvature of the abutting roller 130A as a position regulating member for regulating the gap between the abutment roller 30 and r30 is r2 (μm), the linear expansion coefficient of the developing sleeve 130 is α1 (/ ° C.),
When the linear expansion coefficient of A is α2 (/ ° C.), | r2 × α2-r1 × α1 | <3 (μm / ° C.)

For example, when the developing sleeve 130 has a radius of curvature of 1
0 mm silicone rubber (linear expansion coefficient 20 to 40 × 10
^-6 / ° C), and the abutting roller 130A has a radius of curvature of 10.5 m.
m of ABS resin (linear expansion coefficient: 60 to 130 × 10 ⁻⁶ /
° C) and the value of the above equation is 0.23 to 1.2. Even if the temperature change occurs at normal temperature (20 ° C) ± 20 ° C, the variation width of the gap between the photosensitive drum 10 and the developing sleeve 130 is ±
24 μm, which is within ± 60 μm of the allowable width.
Image defects can be prevented.

As another example, the developing sleeve 130
With stainless steel having a radius of curvature of 20 mm (linear expansion coefficient 14.7
× 10 ^-6 / ° C) and the abutting roller 130A with a radius of curvature of 2
A 0.5 mm POM (polyoxymethylene) resin (coefficient of linear expansion: 80 × 10 ⁻⁶ / ° C.) is used, the value of the above equation is set to 1.3, and even if the temperature change occurs at room temperature (20 ° C.) ± 20 ° C. The variation width of the gap between the photosensitive drum 10 and the developing sleeve 130 is ± 26 μm, which is within ± 60 μm of the allowable width, so that image defects can be prevented.

In the above, the abutting roller 130A does not abut against the flange members 10A and 10B of the photosensitive drum 10,
A configuration in which the photosensitive drum 10 directly abuts on both side ends may be adopted.

A second example of maintaining the gap between the image forming body and the developer conveying member will be described with reference to FIG. FIG. 6 is a diagram illustrating a second example of maintaining a gap between the image forming body and the developer conveying member.

In the second example, as shown in FIG. 6, the abutting roller 130A is used as a first position restricting member, and the positioning member 1 is used as a second position restricting member that freely rotates on the support member 20.
30B, and the abutting roller 130A is positioned by the positioning member 130.
B, a developing sleeve 130 serving as a developer conveying member
And a predetermined gap between the photoconductor drum 10 as an image forming body.

The radius of curvature of the photosensitive drum 10 is set to ra (μ
m), the radius of curvature of the developing sleeve 130 is rb (μm),
The radius of curvature of the abutting roller 130A is rc (μm), the radius of curvature of the positioning member 130B is rd (μm), the linear expansion coefficient of the photosensitive drum 10 is αa (/ ° C.), and the developing sleeve 130
When the linear expansion coefficient is αb (/ ° C.), the linear expansion coefficient of the abutting roller 130A is αc (/ ° C.), and the linear expansion coefficient of the positioning member 130B is αd (/ ° C.), | ra × αa + rb × αb− rc × αc−rd × αd |
<3 (μm / ° C).

For example, the photosensitive drum 10 is set to have a radius of curvature of 60.
mm acrylic resin (linear expansion coefficient 45 to 70 × 10 ⁻⁶ /
° C), the developing sleeve 130 is made of aluminum having a radius of curvature of 10 mm (linear expansion coefficient: 23.6 × 10 ^-6 / ° C), and the abutting roller 130A is made of ABS having a radius of curvature of 10.5 mm.
Resin (coefficient of linear expansion: 60 to 130 × 10 ⁻⁶ / ° C.), positioning member 130B made of stainless steel (linear expansion coefficient: 14.7 × 10 ⁻⁶ / ° C.) having a radius of curvature of 60 mm, and the value of the above equation is set to 2. 0 to 2.5, temperature change is normal temperature (20 ° C)
Even when the temperature is ± 20 ° C., the variation width of the gap between the photosensitive drum 10 and the developing sleeve 130 is ± 50 μm, which is within ± 60 μm of the allowable width, so that an image defect can be prevented.

As another example, the photosensitive drum 10 is made of acrylic resin having a radius of curvature of 40 mm (linear expansion coefficient of 45 to 7).
0 × 10 ⁻⁶ / ° C.) and the developing sleeve 130 is made of silicone rubber having a radius of curvature of 8 mm (linear expansion coefficient 20 to 40 × 10 6
^-6 / ° C), and the abutting roller 130A has a radius of curvature of 8 mm.
AI (polyamide imide) resin (linear expansion coefficient 34 to 40)
× and 10 ^-6 / ℃), brass curvature radius 40.5mm positioning member 130B (linear expansion coefficient 17.5 × 10 ^-6 /
° C) and the value of the above equation is 0.93 to 2.1, and even if the temperature change occurs at room temperature (20 ° C) ± 20 ° C, the width of change of the gap between the photosensitive drum 10 and the developing sleeve 130 is Since it is ± 42 μm, which is within ± 60 μm of the allowable width, image defects can be prevented.

[0070]

According to the present invention, a change in the gap between the image forming body and the developer conveying member of the developing means due to a temperature change is suppressed to a small extent, and an image defect is prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an embodiment of a color image forming apparatus.

FIG. 2 is a diagram illustrating a configuration of an image exposure unit 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. 2;

FIG. 5 is an enlarged view of a position regulating member and a developer conveying member of FIG. 4;

FIG. 6 is a diagram illustrating a second example of maintaining a gap between the image forming body and the developer conveying member.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 20 support member 130 developing sleeve 130A abutting roller 130B positioning member

Claims (2)

[Claims] 1. A plurality of charging means and developing means on an outer peripheral surface of an image forming body, and a plurality of image exposing means on an inner peripheral surface, wherein charging, image exposing and developing are performed during one rotation of the image forming body. repetition,
In a color image forming apparatus for forming a color toner image by superimposing a plurality of toner images on a peripheral surface of the image forming body, a radius of curvature of a developer conveying member of the developing unit is set to r1 (μ).
m), the radius of curvature of the position regulating member for regulating the gap between the image forming body and the developer conveying member is r2 (μm);
When the linear expansion coefficient of the developer conveying member is α1 (/ ° C.) and the linear expansion coefficient of the position regulating member is α2 (/ ° C.), | r2 × α2-r1 × α1 | <3 (μm / ° C.) And a color image forming apparatus. 2. A method according to claim 1, wherein a plurality of charging means and developing means are provided on an outer peripheral surface of the image forming body, and a plurality of image exposing means are provided on an inner peripheral surface of the image forming body. repetition,
In a color image forming apparatus for forming a color toner image by superimposing a plurality of toner images on a peripheral surface of the image forming body, a first position regulating member is used as the developing unit, and a second position regulating member is used as the image. The first position regulating member and the second position regulating member are respectively provided on the formed body, and abut on the first position regulating member and the second position regulating member to regulate a gap between the developer conveying member of the developing means and the image forming body; The radius of curvature of the image forming body is ra (μm), the radius of curvature of the developer conveying member is rb (μm), the radius of curvature of the first position regulating member is rc (μm), and the radius of curvature of the second position regulating member is The radius of curvature is rd (μm), the linear expansion coefficient of the image forming body is αa (/ ° C.), the linear expansion coefficient of the developer conveying member is αb (/ ° C.), and the linear expansion coefficient of the first position regulating member is Is αc (/ ° C.), and the linear expansion coefficient of the second position regulating member is αd. / ° C.) to time, | ra × αa + rb × αb-rc × αc-rd × αd |
<3 (μm / ° C.).