JPH08194357A - Color image forming device - Google Patents

Abstract

PURPOSE: To provide a small-sized and lightweight photoreceptor drum having a transparent substrate capable of maintaining roundness and straightness even by the press-contacts of a developing unit and a cleaning device. CONSTITUTION: A transparent substrate 101 is formed with optical glass or transparent acrylic resin and the upper limit of the thickness (T) of the substrate is made to be 8mm shorter than the optical path length of the image forming side of the 'Selfoc (R)' lense of an included image exposing means and the lower limit of the inner diameter (D) of the substrate is made to be 60mm diameter required for including the image exposing means. Besides, the thickness (T) is set to be between 3mm and 8mm and the inner diameter (D) is set to be between 60mm and 200mm diameter by obtaining them from many results of image forming experiments concerning to the lower limit of the thickness (T) and the upper limit of the inner diameter (D).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention arranges a plurality of charging, image exposing and developing means on the peripheral surface of a drum-shaped image forming body to superpose toner on the image forming body during one rotation of the image forming body. The present invention relates to an electrophotographic color image forming apparatus that also forms a color toner image.

[0002]

2. Description of the Related Art As a method for forming a multicolor image, a monochromatic toner image formed on each photoconductor is intermediately transferred by equipping the photoconductor with the same number of images as necessary, a charger and a developing device. A device that creates a color image by overlaying it on the body (A)
An apparatus (B) for forming a color image by repeating charging, image exposure and development for each color by rotating one photoreceptor a plurality of times, or similarly, charging and image exposure for each color within one rotation of one photoreceptor. An apparatus (C) and the like for forming a color image by sequentially performing development are known.

However, the above-mentioned device (A) has a drawback that the volume of the device is increased because a plurality of photoconductors and intermediate transfer members are required, while the device (B) has a charging means, an image exposing means and a photoconductor. However, there is a restriction that the size of the formed image is limited to the surface area of the photoconductor or less.

[0004]

The above-mentioned device (C) for forming a color image is characterized in that the size of the image is not restricted and the image can be formed within a short time, but the periphery of the image forming body is charged. Since it is necessary to arrange a plurality of sets of means for image exposure and development, there is a limit to downsizing of the image forming body and thus the apparatus. On the other hand, there is also proposed an apparatus in which a transparent member is used as the base of the image forming body, the image exposing means is housed therein, and image exposure is performed from the inside so as to downsize the image forming body. .

However, in this case, since the substrate of the image forming body is placed in the optical path of the image exposure, thermal expansion due to the rise of the environmental temperature or heat generation of the light source of the image exposure, or distortion and uneven rotation due to the pressure contact of the developing means and the cleaning means. Due to the influence of (3), there is a problem in that the registration between the superimposed images may fluctuate or the image may be out of focus to cause color misregistration, resulting in deterioration of image quality.

As a result of solving and improving this point, the present invention provides
To provide a color image forming apparatus capable of forming a high-quality color image at high speed by realizing a transparent image forming body having sufficient strength against external force and capable of responding to temperature changes. It is intended.

[0007]

The above-described object is to provide a charging means for performing a plurality of charges on the peripheral surface of a rotating drum-shaped image forming body, an image exposing means for forming a latent image, and the latent image forming means. A developing means for visualizing an image is provided, and charging, image exposure, and development are repeated during one rotation of the image forming body to form a toner image so that the toner images are collectively formed on a transfer material. In a color image forming apparatus that transfers by
The image forming body is provided with a photosensitive layer on the outer periphery of a transparent substrate, and is subjected to image exposure from the inside. The transparent substrate has a thickness of 3 mm to 8 mm and an inner diameter of φ60 mm to φ200 mm. This is achieved by an image forming apparatus.

[0008]

In the present invention, as the cylindrical transparent member forming the substrate of the image forming body, optical glass from the viewpoint of transparency or a transparent acrylic resin material from the viewpoint of moldability is preferably used.

The thickness of the transparent substrate is limited to a thickness that can be accommodated in the optical path of the optical system of the image exposure means contained therein depending on the length of the optical path on the image forming side. For example, when an image is formed by a SELFOC lens using an LED as a light source, the lens tip 3
Since the image is formed at a position of -10 mm, the thickness of the transparent substrate is also limited by this. Further, the inner diameter of the image forming body is not less than a size sufficient for accommodating each image exposing means, and at the same time, the mechanical temperature can be maintained without being distorted or deformed even when the above-mentioned developing means or the like is subjected to pressure contact. Must be the size of Further, from the viewpoint of reducing the uneven rotation of the image forming body, it is preferable that the moment of inertia is large, but if it is large, the load on the drive system becomes large, which causes a problem.

With respect to an image forming body including many such restrictions, the inventor of the present invention creates a large number of transparent substrates having different thicknesses and inner diameters and incorporates them in a color image forming apparatus to actually form a color image. By judging the image quality,
It was confirmed that the thickness and the inner diameter of the substrate of the image forming body satisfying the above conditions were within the limits of 3 to 8 mm in thickness and 60 to 200 mm in inner diameter.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

Reference numeral 10 denotes a drum-shaped image forming body, that is, a photosensitive drum, in which an organic photosensitive layer (OPC) formed of a transparent conductive layer is applied to the outer periphery of a substrate formed of a transparent member such as optical glass or transparent acrylic resin. Then, it is rotated clockwise while being grounded.

Reference numeral 11 denotes a scorotron charger, which is a charging means. The scorotron charger 11 performs a charging operation on the above-mentioned organic photoreceptor layer of the photoreceptor drum 10 by a grid held at a predetermined potential and a corona discharge by a discharge wire. A uniform electric potential is applied to the drum 10.

Reference numeral 12 denotes an exposure optical system which is an image exposure means, and includes LEDs, FL, EL and P arranged in the axial direction of the photosensitive drum 10.
It is composed of a light emitting element such as L and a SELFOC lens. The image signals of the respective colors read by the separate image reading device are sequentially taken out from the memory and input to the exposure optical systems 12 as electric signals. The emission wavelengths of the light emitting devices used in this example have the same wavelength and are in the range of 500 to 900 nm.

Each of the exposure optical systems 12 described above is attached to a common columnar support member 20, and each exposure optical system 12
As shown in FIG. 4, (Y), 12 (M), 12 (C), and 12 (K) are arranged at equal intervals and are housed inside the base body of the photosensitive drum 10. The exposure optical system 12 includes an L
It may be composed of a combination of optical shutter members such as CD, LISA, and PLZT, and an imaging lens such as SELFOC lens.

13Y, 13M, 13C and 13K are yellow (Y), magenta (M), cyan (C) and black (K).
The developing device, which is a developing means for accommodating each developer, includes a developing sleeve 130 that rotates in the same direction with a predetermined gap from the peripheral surface of the photosensitive drum 10.

Each of the developing devices 13 does not contact the electrostatic latent image on the photosensitive drum 10 formed by the charging by the charging device 11 and the image exposure by the exposure optical system 12 by applying a developing bias voltage. Reverse development in the state.

Next, the process of the color image forming apparatus in this apparatus will be described.

In the image reading apparatus which is separate from this apparatus, the original image is an image read by the image pickup device or an image edited by a computer is once used as an image signal for each color of Y, M, C and K. Stored and stored in memory.

When the image recording is started, the photoconductor drive motor is rotated to rotate the photoconductor drum 10 in the clockwise direction, and at the same time, the charging action of the charger 11 (Y) starts applying the potential to the photoconductor drum 10. To be done.

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

The latent image is reversely developed by the developing device 13 (Y) with the developer on the developing sleeve in a non-contact state, and a yellow (Y) toner image is formed according to the rotation of the photosensitive drum 10.

Then, the photosensitive drum 10 is further given a potential on the yellow (Y) toner image by the charging action of the charger 11 (M), and the second color signal of the exposure optical system 12 (M), that is, Image exposure is performed by an electric signal corresponding to the magenta (M) image signal, and non-contact reversal development by the developing device 13 (M) causes the magenta (M) toner on the yellow (Y) toner image. The images are sequentially superimposed and formed.

By the same process, the toner image of cyan (C) corresponding to the third color signal is finally obtained by the charger 11 (C), the exposure optical system 12 (C) and the developer 13 (C), and finally. Black (K) corresponding to the fourth color signal by the charger 11 (K), the exposure optical system 12 (K) and the developing device 13 (K)
Toner images are sequentially superposed and formed on the photosensitive drum.
A color toner image is formed on the peripheral surface within one rotation of 10.

The color toner image thus formed on the peripheral surface of the photosensitive drum 10 is a transfer material which is conveyed from the paper feed cassette 15 in the transfer device 14A and is fed in synchronization with the driving of the timing roller 16. It is transferred onto the transfer paper.

The transfer paper on which the toner image has been transferred is a static eliminator.
In 14B, the charge is removed and the toner is separated from the peripheral surface of the drum. After the toner is fused and fixed in the fixing device 17, the toner is discharged through the paper discharge roller 18 onto the tray above the device.

On the other hand, the photosensitive drum 10 from which the transfer paper has been separated is cleaned by removing the residual toner in the cleaning device 19 to continue the formation of the toner image of the original image, or is temporarily stopped and the toner of the new original image is stopped. Wait for image formation.

The above-mentioned photosensitive drum 10 is, as shown in FIG.
Flange members 10A and 10B on both ends for engaging and fixing it
Is rotatably supported by being directly or indirectly borne by a drum shaft 110 which is erected and fixed to the main body of the apparatus, and a gear G integrated with the flange member 10B is driven by being meshed with a drive gear on the main body of the apparatus. It is designed to rotate at a constant speed in a predetermined direction.

The drum shaft 110 is integrally fixed by inserting the supporting member 20 for mounting and fixing each of the above-mentioned exposure optical systems 12 inside the photosensitive drum 10.

Each of the developing devices 13 is elastically biased toward the peripheral surface of the photoconductor drum 10 from the horizontal direction, and is provided at both axial ends of each developing sleeve 130 and has a rotatable abutment. A roller (not shown) is brought into pressure contact with a non-image area on the peripheral edge of the drum, so that the interval between the developing sleeve 130 and the peripheral surface of the drum, that is, the developing interval is set to a predetermined interval.

The cleaning device 19 keeps a cleaning blade in pressure contact with the peripheral surface of the photoconductor drum 10 to sequentially remove and clean residual toner of the toner image after transfer.

Therefore, the photosensitive drum 10 is subjected to an external force due to the pressure contact of the developing devices 13 and the cleaning device 19 even during the image exposure, and is also affected by the temperature rise due to the heat generation of the light source of each exposure optical system 12. There is.

As shown in the cross-sectional view of FIG. 3, the photosensitive drum 10 is a transparent drum substrate 101 formed of optical glass or transparent acrylic resin having a thickness T, and a transparent drum substrate 101 formed around the drum substrate 101. It is composed of a thin organic photosensitive layer 102 applied to a thickness of up to 50 μm, and the roundness and straightness of the photosensitive layer 102 are maintained by the mechanical strength of the drum substrate 101.

Since the exposure optical system 12 described above uses a SELFOC lens having an optical path length of 3 mm to 10 mm on the image forming side in view of the depth of focus and the brightness, the drum substrate 101 is Drum substrate 101 to fit within the optical path length
The upper limit of the thickness (T) is selected from the range of 3 mm to 8 mm and is preferentially determined.

Further, the inner diameter (D) of the drum base 101 described above.
Is a general lower limit value of a minimum diameter φ60 mm capable of accommodating each of the exposure optical system 12 and the supporting member 20 integrated with the drum shaft 110, while the upper limit value is the thickness selected in advance. In combination with (T), the maximum inner diameter (D) that can guarantee the mechanical strength of the photoconductor drum 10 is set by experiment.

In the experiment, as shown in Table 1 and the graph of FIG. 5, optical glass (indicated by symbol G) and transparent acrylic resin (indicated by symbol G) having different combinations of thickness (T) and inner diameter (D) were used. By forming a photosensitive drum 10 of various sizes by a plurality of drum substrates 101 (denoted by the symbol P), actually incorporating the image forming apparatus into an image forming apparatus, performing image formation, and evaluating the image quality of the image obtained thereby. Drum substrate 10 that is not affected by distortion or deformation due to external force
The upper limit of the inner diameter (D) of 1 is obtained.

As a result, when the thickness (T) is selected from the range of 3 mm to 8 mm as shown in the section of Example of Table 1, the evaluation is good even if the upper limit of the inner diameter (D) is φ200 mm. ◯), the thickness (T) as shown in the comparative example section
Is less than 3 mm, the inner diameter (D) is the lower limit of φ60 mm
If the value is smaller, the evaluation is somewhat poor (△), and if the upper limit of the inner diameter (D) is larger than φ200 mm, the evaluation is significantly poor (×) even if the thickness (T) is selected from the range of 3 mm to 8 mm. ) Is determined. Therefore the drum base
It has been clarified that the values of the thickness (T) and the inner diameter (D) of 101 are preferably determined within the region surrounded by the broken line in the graph of FIG.

[0038]

[Table 1]

In this way, the photoconductor drum 10 whose mechanical strength against external force is guaranteed has each exposure optical system 12 included therein as shown in FIG.
Common support members so that the central angles θ are equal as shown in
By arranging it on top of 20, even if the peripheral surface length is extended due to thermal expansion, the relationship of equal intervals is maintained, so the resist accuracy in superimposing the toner images is maintained, and therefore the image can be dealt with even when the environmental temperature changes. The image quality of can be guaranteed.

[0040]

According to the present invention, the problem of distortion and deformation of the photoconductor drum due to the pressure contact of the plurality of developing devices and the cleaning device is solved, and a plurality of toner images are superposed with high precision by one rotation of the photoconductor drum. It is also possible to downsize the photoconductor drum by effectively utilizing the space occupied by multiple exposure optical systems. As a result, it is a practically extremely useful color image that can form a high-quality image at high speed while being compact. Forming equipment has been provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of a color image forming apparatus of the present invention.

FIG. 2 is a vertical sectional view showing the configuration of a photosensitive drum.

FIG. 3 is a lateral cross-sectional view of a main part of a photosensitive drum.

FIG. 4 is an explanatory diagram showing a layout of an exposure optical system.

FIG. 5 is a graph showing the distribution of the thickness and inner diameter of the substrate of the photosensitive drum.

[Explanation of symbols]

 10 Photosensitive drum 10A, 10B Flange member 101 Drum base 102 Photosensitive layer 110 Drum shaft 11 Charging device 12 Exposure optical system 13 Developing device 14A Transfer device 14B Static eliminator 15 Paper feed cassette 16 Timing roller 17 Fixing device 18 Paper ejection roller 19 Cleaning Device 20 Support member

Claims (5)

[Claims] 1. A circumferential surface of a rotating drum-shaped image forming body,
A charging means for performing a plurality of charging operations, an image exposure means for forming a latent image, and a developing means for developing the latent image are provided, and the charging is performed during one rotation of the image forming body.
In a color image forming apparatus in which image exposure and development are repeated to form toner images in a superimposed manner, and then the toner images are collectively transferred to a transfer material, the image forming body includes a photosensitive layer on the outer periphery of a transparent substrate. A color image forming apparatus for performing image exposure from one side, wherein the transparent substrate has a thickness of 3 mm to 8 mm and an inner diameter of 60 mm to 200 mm. 2. The color image forming apparatus according to claim 1, wherein the image forming body is made of transparent glass or plastic. 3. The color image forming apparatus according to claim 1, wherein the image forming body forms an image by pressing the developing means against a peripheral surface of the image forming body. 4. The color image forming apparatus according to claim 1, wherein the image exposing unit is held on a common support. 5. The color image forming apparatus according to claim 4, wherein the image exposure units are arranged at equal intervals.