JPH1069143A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the divergence of focus by thermally expanding a holding member which is arranged between an image forming body and a supporting member and for holding an image forming element, to set the center of the image forming element in the middle position between the image forming body and the supporting member. SOLUTION: A metallic casing 12d and the holding member 12c provided in an exposure unit 12, the supporting member 20 for the exposure unit 12, the substrate of a photoreceptor drum 10 as the image forming body, etc., are thermally expanded by the generation of heat by the LED 121 as a light emitting element of the exposure unit 12. When the linear expansion coefficients of the prism of the supporting member 20, the holding member 12c and the substrate of the photoreceptor drum 10 are defined as α11, α12 and α13, and α13 is >=α11, α12 is >=α11. Thus, even if variation in temp. caused by the generation of the heat from an exposure element occurs, the divergence of the focus of the image forming element hardly occurs.

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., which forms an image by forming a charging means, an image exposing means and a developing means around an image forming body. Related to an image forming apparatus.

[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, 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 an image forming body is also known.

However, each of the above image forming apparatuses is provided with the same number of image forming members, charging means, developing means and the like as the number of colors required for image formation, and superimposes a single-color toner image formed on a photosensitive member on a transfer material. A color image forming apparatus that forms a color image has a drawback that the volume of the apparatus is increased due to the need to transport a plurality of image forming bodies and a transfer material.On the other hand, the charging of each color by rotating the image forming body a plurality of times is required. A color image forming apparatus that forms a color image by repeating image exposure and development,
Although the volume is reduced, there is a restriction that the size of the formed image is limited to the surface area of the photoconductor 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.

In order to reduce the size of the apparatus, a plurality of light emitting elements, for example, LEDs are arranged in an array as an exposure element, and a light converging light is used as an image forming element for imaging light emitted from the light emitting element. An image exposure unit using a transmission body (trade name: Selfoc lens) is used.

[0006]

However, in the apparatus according to the above proposal, it is necessary that the supporting member for supporting the image exposing means and the image forming body, which are arranged along the central axis, be positioned and maintained with high precision. There is a light emitting element as a light source of image exposure light of an exposure element provided in the image exposure means, for example, a light emitting element such as an LED. The supporting member thermally expands in the radial direction of the central axis of the image forming body, and its diameter changes. Further, the position of the imaging element (Selfoc lens) which is attached to the support member and held by the holding member provided in the image exposing means also changes due to the thermal expansion of the holding member. The focus of the lens deviates from the depth of focus and defocus occurs,
There is a problem that image blur occurs.

[0007] The inventors of the present invention conducted an experiment on the defocus of the SELFOC lens due to the thermal expansion.
2 shows the change of the MTF of the exposure optical system of the image exposure means, and FIG. 13 shows the change of the MTF of the exposure optical system using the selfoc lens. Distance b, Selfoc lens 5
When both the distance a and the distance a between the image forming body 510 and the image forming body 510 increase or decrease, the change of the MTF on the image forming body 510 by the selfoc lens 512 is small, that is, the depth of focus. Is defocused, and it is difficult to cause defocus, but if one of them increases and the other decreases, the image forming body 510 by the selfoc lens 512 is used.
It was confirmed that the MTF changes greatly above, the depth of focus is shallow, and the focus shift is large.

When both distances increase or decrease as compared with the case where one of them increases and the other decreases, the depth of focus is about 5 to 10 times deeper.

An object of the present invention is to provide an image forming apparatus which captures the above problems and phenomena, and is less likely to cause a focus shift of an image forming element even when a temperature change occurs due to heat generated from an exposure element used in an image exposure means. With the goal.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus having a holding member for holding an exposure element having a plurality of light emitting elements arranged in an array and an imaging element for forming an image of light emitted from the light emitting elements. Exposure means are provided on a support member that supports the image exposure means and are disposed inside a cylindrical image forming body. The image exposure means perpendicularly intersects the central axis of the image formation body with respect to the image formation body. In an image forming apparatus that performs image exposure, when the linear expansion coefficient of the support member is α11, the linear expansion coefficient of the holding member is α12, and the linear expansion coefficient of the image forming body is α13, when α13 ≧ α11, This is achieved by an image forming apparatus characterized by satisfying α12 ≧ α11 (first invention).

Further, the above object is to provide an image exposing means having a holding member for holding an exposing element in which a plurality of light emitting elements are arranged in an array and an imaging element for forming an image of light emitted from the light emitting element. The image exposing unit is provided on a support member that supports the image exposing unit, and is disposed inside a cylindrical image forming unit. The image exposing unit performs image exposure on the image forming unit perpendicular to a central axis of the image forming unit. In the image forming apparatus, when the linear expansion coefficient of the support member is α11, the linear expansion coefficient of the holding member is α12, and the linear expansion coefficient of the image forming body is α13, α13 <
In the case of α11, this is achieved by an image forming apparatus characterized by satisfying α12 <α11 (second invention).

Further, the object is to provide an image exposing means having a holding member for holding an exposing element in which a plurality of light emitting elements are arranged in an array and an imaging element for forming an image of light emitted from the light emitting element. The image exposing unit is provided on a support member that supports the image exposing unit, and is disposed outside the cylindrical image forming unit. The image exposing unit performs image exposure on the image forming unit perpendicular to the central axis of the image forming unit. In the image forming apparatus, when the linear expansion coefficient of the support member is α21, the linear expansion coefficient of the holding member is α22, and the linear expansion coefficient of the image forming body is α23, α21>
In the case of α23, the image forming apparatus is characterized in that α22> α23 is satisfied (third invention).

[0013] The object of the present invention is to provide an image exposing means having a holding member for holding an exposing element in which a plurality of light emitting elements are arranged in an array and an image forming element for imaging light emitted from the light emitting element. The image exposing unit is provided on a support member that supports the image exposing unit, and is disposed outside the cylindrical image forming unit. The image exposing unit performs image exposure on the image forming unit perpendicular to the central axis of the image forming unit. In the image forming apparatus, when the linear expansion coefficient of the support member is α21, the linear expansion coefficient of the holding member is α22, and the linear expansion coefficient of the image forming body is α23, α21 ≦
In the case of α23, this is achieved by an image forming apparatus characterized by satisfying α22 ≦ α23 (fourth invention).

[0014]

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.

Embodiment 1 An image forming process and a configuration of an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus according to a first embodiment of the image forming apparatus, FIG. 2 is an enlarged cross-sectional view of a main part of the image exposure unit of FIG. 1, and FIG. FIG. 4 is a perspective view of FIG.
FIG. 4A is a diagram illustrating a state of thermal expansion between an image forming body and an image exposing unit according to the first embodiment, and FIG. 4A illustrates a linear expansion coefficient of a supporting member of the image exposing unit. FIG. 4B is a diagram showing the above case, FIG. 4B is a diagram showing a case where the linear expansion coefficient of the image forming body is smaller than the linear expansion coefficient of the support member of the image exposure unit, and FIG. 6 is a cross-sectional view illustrating a support structure of the image forming body, FIG. 7 is a front view illustrating a support structure of the intermediate transfer belt, and FIG. 8 is a front view illustrating the intermediate transfer belt. It is a side view which shows the support structure of a belt.

According to FIGS. 1 to 4 and 6, the photosensitive drum 10, which is a cylindrical image forming member, is a cylindrical member formed of, for example, a glass material or a translucent member of a translucent acrylic resin. A light-transmitting conductive layer and an organic photoconductor layer (OPC) are formed on the outer periphery of a transparent light-transmitting substrate, and the conductive layer is grounded, and the conductive layer is grounded. Rotated clockwise.

In the present embodiment, the photoconductor layer of the photoreceptor drum only needs to have an exposure sensitivity capable of generating an appropriate contrast with respect to image exposure light. Accordingly, the light transmittance of the substrate made of glass or light-transmitting resin of the photosensitive drum in the present embodiment does not need to be 100%, and has such characteristics that a certain amount of light is absorbed when the exposure beam is transmitted. It does not matter. As the material of the light-transmitting substrate, an acrylic resin other than a glass material, in particular, a polymer obtained by polymerization using a methyl methacrylate monomer is preferably used because of its excellent transparency, strength, accuracy, surface properties, and the like. Various light-transmitting resins such as fluorine, polyester, polycarbonate, and polyethylene terephthalate used for general optical members and the like can be used. The light-transmitting substrate may be colored as long as it has a light-transmitting property with respect to exposure light. The refractive index of these resins is approximately 1.5.

As a method of manufacturing a substrate using a light-transmitting resin, a high-precision element cylinder can be formed by a centrifugal polymerization method. This production method is to synthesize a plastic material monomer, add a catalyst for polymerization, pour it into a cylindrical mold, seal and fix it with side plates, rotate it, and heat it moderately Promotes uniform polymerization. After completion of the polymerization, the substrate 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 substrate for a photosensitive drum of an image forming apparatus (centrifugal polymerization method).

As the material of the transparent plastic substrate molded by centrifugal polymerization, those obtained by polymerization using a methyl methacrylate monomer as described above are the best in terms of transparency, strength, precision, surface properties and the like. , Other polyethyl methacrylate, polybutyl methacrylate,
Polyethyl acrylate, polybutyl acrylate, polystyrene, polyimide, polyester, polyvinyl chloride, or the like, or a copolymer thereof, or the like can be used. In the centrifugal polymerization method, 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.

By using a plastic cylindrical light-transmitting resin substrate produced by the above-mentioned production method, the thickness is uniform, the cylindrical substrate has excellent cylindricity and roundness, and is superior to glass material. A photosensitive drum that is easy to manufacture and that is easy to provide is provided.

Next, as a method for forming the light-transmitting conductive layer, a vacuum evaporation method, an active reaction evaporation method, various sputtering methods, and various CVD methods are used to form indium tin oxide (IT).
O), alumina, tin oxide, lead oxide, indium oxide, copper iodide, or a thin film of a light-transmitting material such as Au, Ag, Ni, or Al is used. Preferably, a conductive resin layer or the like made of the above-mentioned transparent conductive (for example, ITO) fine particles and a binder resin is used by a dip coating method, a spray coating method, or the like. In this case, in order to enhance the translucency, the fine particles constituting the layer are controlled to be about 500 Å or less in the Rayleigh scattering (scattering by fine particles having a size of 1/10 or less of the exposure wavelength) region where there is almost no light scattering. Is preferred. In particular, as a main constituent material,
It is preferable to use conductive fine particles having a primary particle diameter of 400 angstroms or less and a particle radius distribution controlled to ± 100 angstroms or less.

As the photoconductor layer, various organic photoconductor layers (OPC) having a two-layer structure composed of a charge generation layer and a charge transport layer or a single layer structure can be used.

Reference numeral 11 denotes a scorotron charger serving as a charger for corona discharge. The scorotron charger 11 charges the organic photosensitive layer of the photosensitive drum 10 by a grid maintained at a predetermined potential and a corona discharge by a discharge electrode. To apply a uniform potential to the photosensitive drum 10.

An exposure unit 12 as an image exposure means for each color includes a photosensitive drum 10 on a substrate 122 as an exposure system.
A linear exposure element 12a in which a plurality of LEDs (light emitting diodes) 121 as light emitting elements arranged in a main scanning direction parallel to the axis of the light emitting element 12a, and a light converging light transmitter (image forming element) The selfoc lens 12b is fixed to the holding member 12c by, for example, an adhesive shown by a black circle in FIGS. 2 and 3, and the exposure element 12a is formed by an adhesive shown by a black circle, for example. The holding member 12c is fixed to the metal casing 12d by, for example, an adhesive indicated by a black circle while the exposure element 12a and the selfoc lens 12b are positioned and fixed to a metal casing 12d as a metal member having good heat conductivity. The exposure unit 12 is fixed and configured.

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

The exposure unit 12 for each color uses a wedge-shaped sticking member 21 and a photosensitive drum 10 using a tool or the like in advance.
The main scanning direction of the photosensitive drum 10 and the sub-scanning direction of the rotation of the photosensitive drum 10 are adjusted so as to be positioned. Is attached with adhesive. The support member 20 is disposed inside the photoconductor drum 10 with the center axis of the support member 20 aligned with the center axis of the photoconductor drum 10 while holding the exposure unit 12 for each color. Therefore, image exposure of the photosensitive drum 10 by the exposure unit 12 is performed perpendicular to the central axis of the photosensitive drum 10.

The photosensitive drum 10 has an outer diameter of 60-18.
A support member having a diameter of 40 to 160 mm is used as the support member 20.

The central position C1-C1 of the selfoc lens 12b is located at the center of the image forming position of the image exposure light on the photosensitive drum 10 and the distance D1 between the LED 121 of the exposure element 12a.
Is set.

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 unit 12 for each color, and the LED 12
1 is 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.

LE as Light Emitting Element of Exposure Unit 12
Due to the heat generated by D121, the metal casing 12d provided in the exposure unit 12, the holding member 12c, the support member 20 of the exposure unit 12, the base of the photosensitive drum 10 as an image forming body, and the like are thermally expanded.

The radius of the prism of the supporting member 20 is D (mm),
The linear expansion coefficient is α11, the height from the metal casing 12d of the holding member 12c to the mounting position of the selfoc lens 12b is L (mm), the linear expansion coefficient is α12, and the radius of the base of the photosensitive drum 10 is R1 (mm). , The linear expansion coefficient is α13
When the temperature rises by ΔT, the center position C1-C1 of the Selfoc lens 12b is preferably (α13 × R1-α11 × D) / 2 = α12 × L, and ΔT × ((α13 × R1-α11 × D) / 2-α12 ×
L) ≦ ± 50 (μm) is preferable for preventing defocus. That is,
It is preferable to keep the change from the center position within 50 μm.

As shown in FIG. 4A, α13 ≧ α11
In the case of, for example, as described above, a resin member having a linear expansion coefficient of 80 to 180 × 10 ⁻⁶ ° C. ⁻¹ such as polyethylene, polystyrene, or polymethyl methacrylate is used as the substrate of the photoreceptor drum 10, and the support member 20 is used. As iron material (linear expansion coefficient 11.7 to 15 × 10 ^-6 ° C. ^-1 ), copper material (linear expansion coefficient 16.7 to 20 × 10 ^-6 ℃ ^-1 ) or aluminum material (linear expansion coefficient 23 to 29 × 10 ⁻⁶ ° C. ⁻¹ ) is used, the thermal expansion of the photoconductor drum 10 is expanded more than the thermal expansion of the support member 20, and the photoconductor drum 10 and the support member 20 move to the position indicated by the dotted line in the direction of the arrow. Inflated.

The thermal expansion of the support member 20 causes the exposure element 12
The position of the LED 121 a is also moved to the position indicated by the dotted line, and the center position of the selfoc lens 12b indicated by C1-C1 attached to the holding member 12c is added to the thermal expansion of the support member and moved to the position C2-C2. You.

The height L of the holding member 12c is about 8 to 10 mm, and at least L≪D. Therefore, the self-locking member is located at the center of the distance D2 between the thermal expansion position of the photosensitive drum 10 and the LED 121. The holding member 12 is positioned such that the center position C2-C2 of the lens 12b is in the direction of the thick arrow.
A member having a linear expansion coefficient α12 of α11 or more is preferably used as the holding member 12c so that the height L of c is thermally expanded (thermal expansion is ΔT × L × α12) (α12 ≧ α1).
1).

As described above, the thermal expansion of the image forming body and the supporting member for supporting the image exposure means caused by the rise of the environmental temperature and the heat generated by the light emitting element as the light source of the image exposure light of the exposure element provided in the image exposure means. The holding member, which is arranged between the image forming body and the support member and holds the imaging element, is thermally expanded so that the center of the imaging element is set at an intermediate position between the image forming body and the support member, and the defocus is caused. Is prevented.

As shown in FIG. 4B, α13 <
In the case of α11, for example, Pyrex glass (with a linear expansion coefficient of 3.
Glass materials such as ^{0 to} 3.6 × 10 ⁻⁶ ° C. ⁻¹ ) and quartz glass (linear expansion coefficient: 0.4 × 10 ⁻⁶ ° C. ⁻¹ ) are used. ~ 29 × 10 ^-6
When the temperature (° C.- ¹ ) is used, the thermal expansion of the support member 20 is larger than the thermal expansion of the photoconductor drum 10, and the photoconductor drum 10 and the support member 20 are thermally expanded to the position indicated by the dotted line in the direction of the arrow. .

Due to the thermal expansion of the support member 20, the exposure element 12
The position of the LED 121 a is moved to the position indicated by the dotted line, and the center position of the SELFOC lens 12b indicated by C1-C1 attached to the holding member 12c is added to the thermal expansion of the support member and moved to the position C3-C3. You.

The height L of the holding member 12c is about 8 to 10 mm, and at least L≪R1, so that the self-locating member is located at the center of the distance D3 between the thermal expansion position of the photosensitive drum 10 and the LED 121. The holding member 1 is positioned such that the center position C3-C3 of the lens 12b is in the direction of the thick arrow.
Although it is necessary that 2c be thermally contracted, it is impossible to contract it, so that a member having a linear expansion coefficient α12 smaller than α11 is preferably used as the holding member 12c (α12 <α11). Therefore, it is particularly preferable to use an Invar alloy (36% nickel alloy, linear expansion coefficient 0 to ¹ × 10 ⁻⁶ ° C. ⁻¹ ) having the smallest linear expansion coefficient as the holding member 12 c.

As described above, with respect to the thermal expansion of the image forming body and the supporting member, the holding member for holding the image forming element is thermally expanded so that the center of the image forming element approaches the intermediate position between the image forming body and the supporting member. In addition, defocus is prevented. Further, by using an Invar alloy having the smallest linear expansion coefficient as the holding member, there is almost no thermal expansion of the holding member holding the imaging element, and the image forming body and the supporting member are supported by the image forming body and the supporting member. The holding member is thermally expanded so that the center of the imaging element is closest to the intermediate position of the member, thereby preventing defocus.

In the exposure unit 12, the SELFOC lens 12b has a linear expansion coefficient of 0.4 to 3.6 × 1.
Since a glass material of about 0 ^-6 ° C ^-1 is used, and the substrate 122 and the metal casing 12d of the LED 121 are thin, the amount of thermal expansion is extremely small. One in which the center position of the Selfoc lens 12b is determined by adding the thermal expansion of the Selfoc lens 12b, and one in which the position of the LED 121 is determined by adding the thermal expansion of the substrate 122 and the metal casing 12d of the LED 121 The present invention also includes a case in which the holding member 12c and the metal casing 12d are used integrally as a holding member and the holding member is thermally expanded.

In particular, as described with reference to FIG.
When 13 <α11, it is preferable to use an Invar alloy having the smallest linear expansion coefficient as the material of the metal casing 12d. Thereby, there is almost no thermal expansion of the holding member holding the image forming element, and the center of the image forming element is located closest to the intermediate position between the image forming body and the supporting member with respect to the thermal expansion of the image forming body and the supporting member. The holding member is thermally expanded, thereby preventing defocus.

As shown in FIG. 5, each of the exposure units 12 is mounted on a support member 20 provided as an exposure unit support means and housed inside the substrate of the photosensitive drum 10. The lead wire 12A of the LED 121 provided on the support member 20 on the front side
Hole 20B and each window 20A are drawn out to the outside.

13 (Y), 13 (M), 13 (C) and 13 (K) are developments containing yellow (Y), magenta (M), cyan (C) and black (K) developers, respectively. The developing device includes a developing sleeve 130 that rotates in the same direction as the photosensitive drum 10 in a developing region while maintaining a predetermined gap with respect to the peripheral surface of the photosensitive drum 10.

Each of the developing units is in a non-contact state by applying a developing bias voltage to the electrostatic latent image formed on the photosensitive drum 10 by the charging by the scorotron charger 11 and the image exposure by the exposure unit 12. To reverse development.

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

When the image recording starts, the photosensitive drum driving motor starts to rotate the photosensitive drum 10 in the counterclockwise direction, and at the same time, the charging action of the scorotron charger 11 (Y) starts applying a potential to the photosensitive drum 10. Is done.

After the photosensitive drum 10 is applied with a potential, the exposure unit 12 (Y) starts exposure with an electric signal corresponding to a first color signal, ie, a yellow (Y) image signal, and rotates the drum. By scanning, an electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer on the surface.

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 in accordance with the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 further applies a scorotron charger 11 on the yellow (Y) toner image.
A potential is applied by the charging action of (M), and exposure is performed by an electric signal corresponding to the second color signal of the exposure unit 12 (M), that is, an image signal of magenta (M).
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 unit 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), exposure unit 12 (K) and developing unit 13 (K)
As a result, a black (K) toner image corresponding to the fourth color signal is sequentially superposed, and a color toner image is formed on the peripheral surface within one rotation of the photosensitive drum 10.

The exposure of the organic photosensitive layer of the photosensitive drum 10 by each of the exposure units 12 is performed from the inside of the drum through a substrate 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 operation by each developing device, the developing sleeve 130
Is applied with a developing bias to which a direct current or a further alternating current is applied, and a jumping development is performed by a one-component or two-component developer contained in the developing device. Non-contact reversal development is performed.

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 has a thickness of 0.5 to 2.0.
mm, an endless rubber belt having a resistance of 10 ⁸ to 10 ¹² Ω · cm of silicon rubber or urethane rubber, and a resistance value of 10 ¹⁰ to 10 ¹⁶ Ωcm, thickness 5
It has a two-layer structure with a 50 μm fluorine coating. This layer also preferably has a similar semiconductivity. Instead of the rubber belt substrate, semiconductive polyester, polystyrene, polyethylene, polyethylene terephthalate or the like having a thickness of 0.1 to 0.5 mm can be used. The intermediate transfer belt 14 is stretched between the rollers 14A, 14B, 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. Has formed.

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 at first. 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 a transfer 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, where the color toner image on the intermediate transfer belt 14 is formed. The sheet is fed to the transfer area of the transfer roller 15 in synchronization with the conveyance.

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 that of the toner of 1 to 3 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.

The photosensitive drum 10 and the intermediate transfer belt 14 have cleaning devices 100 and 14 respectively.
No. 0 is provided, and the blades provided are always in pressure contact with each other, the remaining adhered toner is removed, and the peripheral surface is always kept in a clean state.

According to FIG. 5 and FIG.
Reference numeral 0 denotes a pair of front and rear members fixed to the support shaft 30 of the photoreceptor drum 10.
Both ends are adjusted so that the distance to the photosensitive surface is in a predetermined positional relationship via a wedge-shaped sticking member 21, and is fixed to the adjustment position by bonding.

On the other hand, the photosensitive drum 10 has flange members 10A and 10B provided at both ends thereof rotatably supported by the support member 20 via bearings B, respectively, and is driven by a gear 10G provided in the flange member 10B. The support shaft 30 in the fixed state is rotated around the rotation center.

The photosensitive drum 10 and each of the exposure units 12 are coaxially integrated as a unit around the support shaft 30, and are formed in a U-shape with the support shaft 30 supporting the unit. The image forming unit 300 is supported by bearings between the symmetrical front and rear drum support plates 40 that are integrally connected.

The drum support plate 40 is provided at its front and rear connection portions with rail members 50 as hanging means using metal members such as iron or aluminum. The rail members 50 are provided in the apparatus main body. The support shaft 3 is inserted into and engaged with the guide member 60 to be in a suspended state.
0 means that the photosensitive drum 10 and each of the exposure units 12 are located at substantially predetermined setting positions.

Further, when the support shaft 30 is inserted to a regular position, the shaft end 30B protruding from the rear drum support plate 40 from the suspended state described above has a seat provided on the rear plate 71 as an apparatus substrate. 72, and a shaft end 30A protruding from the front drum support plate 40 is supported by a screw member 82 taperedly fitted to a receiving seat 81 provided on the drum support substrate 80, so that the photosensitive drum 10
Is accurately regulated to a regular set position, and the gear 10G meshes with the driving gear, while each exposure unit 12 further has a through pin P1 of the shaft end 30B formed in the receiving seat 72. By being engaged with the V-shaped groove, it is accurately regulated at a predetermined angular position with respect to the apparatus main body, and becomes a fixed state.

Thereafter, the lead wire 12A of the LED 121 provided in each exposure unit 12 is connected to the support member 2 on the front side.
The holes 20B and the windows 20A are connected to the power supply unit through the notches 40A of the drum support plate 40. The windows 20A through which the lead wires 12A pass are sealed so that toner and the like do not enter inside.

The upper and lower reference holes H1 of the drum supporting substrate 80 are engaged with a pair of reference pins P2 of the front plate 70 as a front device substrate, and the mounting positions thereof are determined. The scorotron charger 11 having a plurality of windows 80A and having the above-described rod shape is inserted from the outside of the drum supporting substrate 80, and the photosensitive drum 10 is fixed thereto. Is set at a predetermined interval position, and is fixed and supported by screwing with the electrodes connected.

Therefore, when the screw member 82 is removed in a state where each scorotron charger 11 has been removed through the window 80A, the drum supporting substrate 80 only releases the screw holes at a plurality of positions. 70.

From this state, the drum support plate 40
Is pulled out by sliding the rail member 50 under the guidance of the guide member 60, the image forming unit 300 in which the photosensitive drum 10 and each of the exposure units 12 are integrated moves in the horizontal direction, and the image of the front side plate 70 as an apparatus substrate is formed. It is possible to take it out of the apparatus main body from the opening hole 70A as the formed body opening.

Prior to the start of the operation of attaching and detaching the photosensitive drum 10 supported by the drum support plate 40 to and from the apparatus main body, the respective pressure contact operations of the intermediate transfer belt 14 and the blades arranged around the photosensitive drum 10 are performed. Is already released, the cleaning device 100 is 1 to 10 m
m, and the photosensitive drum 10
Are retracted to a position of about 30 to 50 mm at which the developing device 13 can be pulled out in the same direction as a pulling-out direction of the photosensitive drum 10, which will be described later. Shall be attributed to the state.

According to FIG. 7 and FIG.
Reference numerals 4A to 14D denote each of the front and rear belt support plates 4 formed integrally in a U-shape while the intermediate transfer belt 14 is stretched by the bias of the tension roller T.
5 between the bearings.

The belt support plate 45 is further formed in a U-shape, and the cleaning device 140 is disposed between the asymmetrical front and rear belt support substrates 85 which are integrally connected.
And are integrated together.

The front belt support substrate 85 is provided with a reference hole H2 as a suspending means on the upper and lower rising portions 85A, while the rear belt support substrate 85 is provided on the rear surface with a pair of reference pins P4 also serving as the suspending means. And a reference pin P provided with the reference hole H2 of the front plate 70 on the front side.
On the other hand, the intermediate transfer belt 14 is set at a predetermined position by fixing the above-mentioned reference pin P4 with an upper screw engaged with a reference hole H3 provided in a rear side plate 71 as a rear device board. A first transfer area for transferring a toner image from the photosensitive drum 10 to the intermediate transfer belt 14 by pressing against the peripheral surface of the photosensitive drum 10, and further pressing the intermediate transfer belt by pressing the transfer roller 15. A second transfer area for transferring the toner image to the transfer material is formed from 14.

The belt support substrate 85 is provided on the front and rear side plates 7.
0 and 71 are supported on a front side of the apparatus main body via a pair of guide rails 200 which can be extended and contracted in two steps called an accuride rail (trade name).

The belt support substrate 85 has a pair of front and rear guide plates 86 provided on the left and right sides, respectively, sandwiching the movable portion 200A of the guide rail 200 slidably in the vertical direction. The movable part 200A
However, in the vertical direction, the abutting plate 87 can be lowered until it abuts against the movable portion 200A.

The above-mentioned belt support substrate 85 is released from the engagement of the above-mentioned reference pins and the respective reference holes by a slight operation of being pulled out to the entire surface of the apparatus main body after releasing the screw fixing member, and is slightly lowered. Therefore, in a state where each of the abutting plates 87 is mounted on the movable portion 200A, the guide rail 200 is extended to a large extent from the opening 70A serving as the image forming body opening of the front side plate 70 to the front surface of the apparatus main body. .
As a result, the intermediate transfer belt 14 is retracted from the peripheral surface of the photosensitive drum 10 and is pulled out in a state where the pressure contact is released. Even when the belt is re-mounted, the guide rail 200 returns from the extended state and guides the tapered portion of each reference pin. As a result, the photosensitive drum 10 is slightly moved upward, and the operation of returning to the state of being pressed against the photosensitive drum 10 is automatically and reliably performed.

Accordingly, the photosensitive drum 10 is attached to the intermediate transfer belt 14 by a very simple attaching / detaching operation of the belt supporting substrate 85.
Can be taken out without interfering with the image forming apparatus, and furthermore, a process of taking out jammed paper staying in the conveyance path by pulling out the belt support substrate 85, replacing the intermediate transfer belt 14,
Maintenance such as inspection can be easily performed.

Prior to the operation of pulling out the belt support substrate 85 from the apparatus main body, the pressing action of the transfer roller against the roller 14C for stretching the intermediate transfer belt 14 is released in advance, and after returning to a predetermined set position, the belt support substrate 85 is returned again. Placed in pressure contact.

Embodiment 2 Regarding a second embodiment of the image forming apparatus of the present invention, FIG.
This will be described with reference to FIG. FIG. 9 illustrates a second example of the image forming apparatus.
1 is a cross-sectional configuration diagram of a color image forming apparatus according to an embodiment;
FIG. 10 is an enlarged sectional view of a main part of the image exposure means of FIG.
FIG. 11 is a view showing a state of thermal expansion between the image forming body and the image exposing means of the second embodiment, and FIG. 11A shows the linear expansion coefficient of the image forming body and the supporting member of the image exposing means. FIG. 11B is a diagram showing a case where the linear expansion coefficient of the image forming body is equal to or less than the linear expansion coefficient of the support member of the image exposure unit.

In the first embodiment, the exposure unit 12 as the image exposure means has been described as being provided inside the photosensitive drum 10 as the image forming body. Photoconductor drum 1 as body
The image exposure process is performed by providing an exposure unit 12 as an image exposure unit outside the image exposure unit 0, and an image forming process similar to that of the embodiment described with reference to FIG. 1 is performed. Members having the same functions and shapes as those of the first embodiment are denoted by the same reference numerals.

The photosensitive drum 10a, which is an image forming body, is obtained by forming a photosensitive layer such as an a-Si layer or an organic photosensitive layer (OPC) on the outer periphery of a cylindrical substrate, for example. The substrate and the conductive layer are rotated counterclockwise as shown by arrows in FIG. 9 in a state where they are grounded.

An exposure unit 12 as an image exposure means for each color includes a photosensitive drum 10 on a substrate 122 as an exposure system.
A linear exposure element 12a in which a plurality of LEDs (light emitting diodes) 121 as light emitting elements arranged in a main scanning direction parallel to the axis of a are arranged in an array, and a light converging light transmitter as an imaging element. (Trade name, Selfoc lens) 12b, and the Selfoc lens 12b is a holding member 12c.
For example, the exposure element 12a is fixed by an adhesive indicated by a black circle in FIG.
In a state where the exposure element 12a and the selfoc lens 12b are positioned.
The exposure unit 12 is configured by fixing the holding member 12c to d by, for example, an adhesive indicated by a black circle.

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

The exposure unit 12 for each color uses the wedge-shaped sticking member 21 and the photosensitive drum 10 in advance by a jig or the like.
The main scanning direction and the sub-scanning direction of the rotation of the photosensitive drum 10a are adjusted so as to be positioned, and attached to a cylindrical support member 20a as a common support with an adhesive. The support member 20a is an exposure unit 1 for each color.
2, the support member 20a is arranged outside the photosensitive drum 10a with the central axis of the support member 20a aligned with the central axis of the photosensitive drum 10a. Therefore, image exposure of the photosensitive drum 10a by the exposure unit 12 is performed perpendicular to the central axis of the photosensitive drum 10a.

The outer diameter of the photosensitive drum 10a is 60-1.
The support member 20a has an outer diameter of 80 to 200 mm.

The center position C1-C of the selfoc lens 12b is located at the center between the image forming position of the image exposure light on the photosensitive drum 10a and the distance D1 between the LED 121 of the exposure element 12a.
1 is set.

A storage unit (not shown), for example, 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 unit 12 for each color, and the LED 12
1 is 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.

LE as Light Emitting Element of Exposure Unit 12
Due to the heat generated by D121, the metal casing 12d provided in the exposure unit 12, the holding member 12c, the support member 20a of the exposure unit 12, the base of the photosensitive drum 10a as an image forming body, and the like are thermally expanded.

The radius of the cylindrical support member 20a is R2 (m
m), the radius of the prism of the support member 20 is R2 (mm), the coefficient of linear expansion is α11, and the metal casing 12 of the holding member 12c is
The height from d to the mounting position of the selfoc lens 12b is L (mm), the linear expansion coefficient is α21, and the photosensitive drum 10
When the radius of the substrate is R3 (mm) and the linear expansion coefficient is α23, the center position C1-C1 of the Selfoc lens 12b is (α21 × R2-α23 × R3) / 2 with respect to a temperature rise of ΔT. = Α22 × L, ΔT × ((α21 × R2−α23 × R3) / 2−α22
× L) ≦ ± 50 (μm) is preferable for preventing defocus. That is,
It is preferable to keep the change from the center position within 50 μm.

As shown in FIG. 11A, α21> α2
In the case of 3, for example, an aluminum material (linear expansion coefficient: 23 to 29 × 10 ⁻⁶ ° C. ⁻¹ ) is used as the support member 20, and an iron material (linear expansion coefficient: 11.7) is used as the base of the photosensitive drum 10.
~ 15 × 10 ^-6 ° C ^-1 ), the supporting member 20
Is expanded more than the thermal expansion of the photoconductor drum 10, and the support member 20 and the photoconductor drum 10 are thermally expanded to the position indicated by the dotted line in the direction of the arrow.

The thermal expansion of the support member 20 causes the exposure element 12
The position of the LED 121 a is moved to the position indicated by the dotted line, and the center position of the SELFOC lens 12b indicated by C1-C1 attached to the holding member 12c is moved to the C4-C4 position according to the thermal expansion of the supporting member.

The height L of the holding member 12c is approximately 8 to 10 mm, and at least L≪R3. The holding member 12 is positioned so that the center position C4-C4 of the lens 12b is in the direction of the thick arrow.
It is preferable to use a member having a linear expansion coefficient α22 larger than α23 as the holding member 12c so that the height L of c is thermally expanded (thermal expansion is ΔT × L × α22) (α22>
α23).

As described above, the thermal expansion of the image forming body and the supporting member for supporting the image exposing means due to the rise of the environmental temperature and the heat generation of the light emitting element as the light source of the image exposing light of the exposing element provided in the image exposing means. The holding member, which is arranged between the image forming body and the support member and holds the imaging element, is thermally expanded so that the center of the imaging element is set at an intermediate position between the image forming body and the support member, and the defocus is caused. Is prevented.

Further, as shown in FIG.
If ≦ α23, for example, an iron material (linear expansion coefficient of 11.7 to 15 × 10 ⁻⁶ ° C. ⁻¹ ) or an invar alloy (36% nickel alloy, linear expansion coefficient of 0 to ¹ × 10) is used as the support member 20.
^-6 ° C. ^-1) is used, if the aluminum material (linear expansion coefficient 23~29 × 10 ^-6 ℃ ^-1) was used as a substrate of the photosensitive drum 10, the thermal expansion of the photosensitive drum 10 is a support member The support member 20 and the photoconductor drum 10 are thermally expanded to a position indicated by a dotted line in the direction of the arrow in FIG.

The thermal expansion of the support member 20 causes the exposure element 12
The position of the LED 121 a is moved to the position indicated by the dotted line, and the center position of the SELFOC lens 12b indicated by C1-C1 attached to the holding member 12c is moved to the C5-C5 position according to the thermal expansion of the support member.

The height L of the holding member 12c is about 8 to 10 mm, and at least L≪R2. Therefore, the self-locking member is located at the center of the distance D5 between the thermal expansion position of the photosensitive drum 10 and the thermal expansion position of the LED 121. The holding member 1 is positioned such that the center position C5-C5 of the lens 12b is in the direction of the thick arrow.
2c is required to be thermally contracted, but cannot be contracted. Therefore, it is preferable to use a member having a linear expansion coefficient α22 of α23 or less as the holding member 12c (α
22 ≦ α23). Therefore, as the holding member 12c, an invar alloy (36% nickel alloy,
It is particularly preferable to use a coefficient of linear expansion of 0 to ¹ × 10 ⁻⁶ ° C. ^-1 ).

As described above, with respect to the thermal expansion of the image forming body and the supporting member, the holding member for holding the image forming element is thermally expanded so that the center of the image forming element approaches the intermediate position between the image forming body and the supporting member. In addition, defocus is prevented. Further, by using an Invar alloy having the smallest linear expansion coefficient as the holding member, there is almost no thermal expansion of the holding member holding the imaging element, and the image forming body and the supporting member are supported by the image forming body and the supporting member. The holding member is thermally expanded so that the center of the imaging element is closest to the intermediate position of the member, thereby preventing defocus.

In the above embodiment, the coefficient of linear expansion of the selfoc lens 12b is 0.4 to 3.6 × 10 ^-6 ° C ^-1.
Glass material is used, and a substrate 122 of the LED 121 is used.
Since the metal casing 12d has a small thickness, the amount of thermal expansion is extremely small, and the description has been made without considering the thermal expansion of the mutual members. However, by adding the thermal expansion of the selfoc lens 12b, the center position of the selfoc lens 12b is determined. The present invention also includes a structure in which the position of the LED 121 is determined by adding the thermal expansion of the substrate 122 of the LED 121 and the metal casing 12d. The present invention also includes a case in which a member integrally formed with the casing 12d is used as a holding member and the holding member is thermally expanded.

In particular, as described with reference to FIG.
When α21 ≦ α23, it is preferable to use an Invar alloy having the smallest linear expansion coefficient for the material of the metal casing 12d. Thereby, there is almost no thermal expansion of the holding member holding the image forming element, and the center of the image forming element is located closest to the intermediate position between the image forming body and the supporting member with respect to the thermal expansion of the image forming body and the supporting member. The holding member is thermally expanded, thereby preventing defocus.

According to the first and second embodiments, even if a temperature change occurs due to heat generated from the exposure element used in the image exposure means, the distance between the light emitting element and the imaging element, and the distance between the imaging element and the image forming body can be reduced. The present invention provides an image forming apparatus in which a difference due to thermal expansion of the image forming apparatus is suppressed to a small value, a focus shift is small, and an image blur is less likely to occur.

In the above embodiment, the case where the image is formed by directly transferring the image from the image forming body to the transfer material without using the intermediate transfer means in FIGS. 1 and 9 is also included in the present invention. Of course.

[0101]

According to the first aspect of the present invention, there is provided a support for supporting an image forming body or an image exposing means due to a rise in environmental temperature or heat generation of a light emitting element as a light source of image exposing light of an exposing element provided in the image exposing means. In response to the thermal expansion of the member, the holding member, which is disposed between the image forming body and the support member and holds the image forming element, is heated so that the center of the image forming element is set at an intermediate position between the image forming body and the supporting member. It is expanded and defocus is prevented.

According to the second aspect, the holding member for holding the image forming element brings the center of the image forming element closer to an intermediate position between the image forming body and the supporting member against thermal expansion of the image forming body and the supporting member. Thermal expansion to prevent defocus.

According to the third aspect, the holding member for holding the imaging element has almost no thermal expansion, and the imaging element is located at an intermediate position between the image forming body and the supporting member with respect to the thermal expansion of the image forming body and the supporting member. The thermal expansion of the holding member is performed to bring the center of the lens closest to the center, thereby preventing defocusing.

According to the fourth aspect of the present invention, the supporting member for supporting the image forming body and the image exposing means due to a rise in the environmental temperature and the heat generated by the light emitting element as a light source of the image exposing light of the exposing element provided in the image exposing means. In response to thermal expansion, a holding member that is disposed between the image forming body and the support member and holds the image forming element is thermally expanded so as to set the center of the image forming element at an intermediate position between the image forming body and the supporting member. In addition, defocus is prevented.

According to the fifth aspect, the holding member for holding the image forming element brings the center of the image forming element closer to an intermediate position between the image forming body and the supporting member against the thermal expansion of the image forming body and the supporting member. Thermal expansion to prevent defocus.

According to the sixth aspect, the holding member for holding the imaging element has almost no thermal expansion, and the thermal expansion of the image forming body and the supporting member causes the imaging element to be located at an intermediate position between the image forming body and the supporting member. The thermal expansion of the holding member is performed to bring the center of the lens closest to the center, thereby preventing defocusing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus according to a first embodiment of the image forming apparatus.

FIG. 2 is an enlarged sectional view of a main part of the image exposure means of FIG.

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

FIG. 4 is a diagram illustrating a state of thermal expansion between the image forming body and the image exposure unit according to the first embodiment.

FIG. 5 is a front view showing a support structure of the image forming body.

FIG. 6 is a sectional view showing a support structure of the image forming body.

FIG. 7 is a front view showing a support structure of the intermediate transfer belt.

FIG. 8 is a side view showing a support structure of the intermediate transfer belt.

FIG. 9 is a sectional configuration diagram of a color image forming apparatus according to a second embodiment of the image forming apparatus.

FIG. 10 is an enlarged sectional view of a main part of the image exposure means of FIG. 9;

FIG. 11 is a diagram illustrating a state of thermal expansion between an image forming body and an image exposure unit according to a second embodiment.

FIG. 12 is a diagram illustrating an exposure optical system of an image exposure unit.

FIG. 13 shows M of an exposure optical system using a selfoc lens.
It is a figure showing change of TF.

[Explanation of symbols]

 10, 10a Photoreceptor drum 11 Scorotron charger 12 Exposure unit 12a Exposure element 12b Selfoc lens 12c Holding member 12d Metal casing 13 Developing device 14 Intermediate transfer belt 20, 20a Support member 121 LED 122 Substrate

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kuki Nagase Konica Corporation, 2970 Ishikawacho, Hachioji-shi, Tokyo Inventor Masayasu Onodera 2970 Ishikawacho, Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Toshihide Miura 5-14-14 Midoricho, Koganei-shi, Tokyo

Claims (6)

[Claims] 1. An image exposure device comprising: a light exposure device having a plurality of light emitting devices arranged in an array; and an image exposure device having a holding member for holding an imaging device for imaging light emitted from the light emitting device. An image forming apparatus is provided on a supporting member for supporting the image forming apparatus, and is arranged inside the cylindrical image forming body, and performs image exposure on the image forming body by the image exposing means perpendicularly to a central axis of the image forming body. The linear expansion coefficient of the support member is α11,
An image forming apparatus, wherein when the linear expansion coefficient of the holding member is α12 and the linear expansion coefficient of the image forming body is α13, when α13 ≧ α11, α12 ≧ α11. 2. An image exposure device comprising: a light exposure device having a plurality of light emitting devices arranged in an array; and an image exposure device having a holding member for holding an image forming device for imaging light emitted from the light emitting device. An image forming apparatus is provided on a supporting member for supporting the image forming apparatus, and is arranged inside the cylindrical image forming body, and performs image exposure on the image forming body by the image exposing means perpendicularly to a central axis of the image forming body. The linear expansion coefficient of the support member is α11,
An image forming apparatus, wherein when the linear expansion coefficient of the holding member is α12, and when the linear expansion coefficient of the image forming body is α13, when α13 <α11, α12 <α11. 3. The holding member has a linear expansion coefficient α12 of 1 ×.
The image forming apparatus according to claim 2, wherein the image forming apparatus is an Invar alloy having a temperature of 10 ^-6 ° C ^-1 or less. 4. An image exposing means having a holding member for holding an exposing element in which a plurality of light emitting elements are arranged in an array and an image forming element for imaging light emitted from the light emitting element. An image forming apparatus is provided on a supporting member for supporting the image forming apparatus, and is disposed outside the cylindrical image forming body, and performs image exposure on the image forming body by the image exposing means in a direction perpendicular to a central axis of the image forming body. The linear expansion coefficient of the support member is α21,
An image forming apparatus, wherein when the linear expansion coefficient of the holding member is α22 and the linear expansion coefficient of the image forming body is α23, when α21> α23, α22> α23. 5. An image exposure device comprising: an exposure device having a plurality of light emitting devices arranged in an array and a holding member for holding an image forming device for forming an image of light emitted from the light emitting device. An image forming apparatus is provided on a supporting member for supporting the image forming apparatus, and is disposed outside the cylindrical image forming body, and performs image exposure on the image forming body by the image exposing means in a direction perpendicular to a central axis of the image forming body. The linear expansion coefficient of the support member is α21,
An image forming apparatus, wherein, when the linear expansion coefficient of the holding member is α22 and the linear expansion coefficient of the image forming body is α23, when α21 ≦ α23, α22 ≦ α23. 6. The holding member has a linear expansion coefficient α22 of 1 ×.
The image forming apparatus according to claim 5, wherein the image forming apparatus is an Invar alloy having a temperature of 10 ^-6 ° C ^-1 or less.