JP2003295571A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent color mixture due to scattered toner. <P>SOLUTION: In the constitution of a black fixed developing device plus a 3-color rotary developing device, during a black developing operation, the rotary rotates at constant intervals. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording type image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus for forming a color image by superposing toner images of a plurality of colors, a conventional intermediate transfer member as shown in FIG. 4 has been used for the purpose of obtaining a color image without color shift. An image forming apparatus using is proposed.

This image forming apparatus comprises an electrophotographic photosensitive member 50.
A charging means 51, an exposing means 52, and a developing means 53 are arranged around the circumference of, and a toner image is formed by sequentially performing charging, exposing and developing steps for each color according to the image information decomposed into each color.
It is superposed on the intermediate transfer member 54 and is conveyed by the transfer roller 55.
A color image is formed on the transfer material 56 such as paper conveyed by.

As the developing means 53, a rotation switching type yellow developing device 53y, a magenta developing device 53m,
Rotating developing means 5 including three color toners of the cyan developing device 53c
3a and fixed developing means 53b having a fixed black developing device.

The rotation developing means 53a of the rotation switching type.
Does not need to have different developing device shapes that occur when they are sequentially arranged around the electrophotographic photoconductor 50, and the color toner developing devices can be rotationally switched, so that the apparatus can be downsized. There are advantages.

Further, the fixed developing means 53b has an advantage that the capacity of the black toner which is generally consumed much can be increased.

[0007]

However, the following problems may occur in the image forming apparatus having the above structure.

Generally, the toner in the developing device is scattered due to deterioration of the toner tribo due to deterioration, and the scattered toner is accumulated on the surface of the developer carrying member of another developing device, so that the tint variation due to color mixing occurs. And then there is a problem. In particular, when the fixed developing device is arranged upstream of the other developing device as in the above configuration, there may occur a problem that a large amount of toner scattered from the upstream fixed developing device is accumulated in the downstream developing device. It was

Therefore, as a measure against the above problem, Japanese Patent Laid-Open No. 4-5
It is known from Japanese Laid-Open Patent Publication No. 1026 and the like that toner scattering can be prevented by applying a bias to a developer regulating member of a developing device. In addition, Japanese Patent Laid-Open No. 07-02
It is known from JP-A-07533 that it is possible to collect scattered toner by installing a fan near the developing device. Further, it is known from Japanese Patent Application Laid-Open No. 09-269655 to cover the surface of the rotary developing means with a cover to prevent contamination by scattered toner, but any of these methods are costly and not practical.

[0010]

The above problems can be solved by the image forming apparatus according to the present invention. That is, an image carrier, a charging device that charges the image carrier by applying a charging bias, an image information writing device that forms an electrostatic latent image on the charged surface of the image carrier, and the static image. An image forming apparatus comprising: a fixed developing unit for developing an electrostatic latent image with a developer; and a developing unit for developing by a rotary developing unit that rotatably supports at least two developing units,
While the fixed developing device is performing the developing operation, the rotary developing device is rotated without performing the developing operation, thereby reducing the tint variation due to the color mixture of the developers and forming a high quality color image. You can

[0011]

While the fixed developing means is performing the developing operation, the rotating developing means rotates without performing the developing operation, so that the scattered toner is accumulated on the specific developing device located downstream of the fixed developing means. By preventing and uniformly depositing on all the developing devices of the rotary developing means, it is possible to reduce the tint variation due to the color mixture of the developers and form a high quality color image.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) First, referring to FIG.
The electrophotographic image forming apparatus according to the first embodiment of the present invention will be described with reference to FIG. 1 is an overall schematic explanatory view of the electrophotographic image forming apparatus, and FIG. 2 is a schematic explanatory view of the constitution of the developing means.

In the electrophotographic image forming apparatus according to the present embodiment, as shown in FIG. 1, a photoconductor drum 1 which is an electrophotographic photoconductor in which a photosensitive layer made of an organic photoconductor is formed on a cylindrical substrate. It is rotatably attached at a predetermined peripheral speed in the direction of arrow A in FIG. In this embodiment, the outer diameter is 5
A photosensitive layer made of an organic photosensitive material is formed in the shape of a 0 mm aluminum cylinder, and a surface protective layer for improving the releasability of the toner and preventing abrasion of the photosensitive layer is provided.

The peripheral surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a charging roller 2 which is a charging means. Then, the charged surface is modulated (turned on) in response to the pixel signal of the image information output from the exposure unit 3 and input from the image signal generating device such as an image reading device or a personal computer (not shown) via the print interface. By scanning exposure with the laser beam 4 that has been turned on / off), an electrostatic latent image of image information is formed. Reference numeral 5 denotes a laser light reflection mirror, which deflects the output laser light 4 from the exposure means 3 with respect to the photosensitive drum 1.

Reference numeral 6 denotes a developing means, which is a fixed developing means having a rotary developing means 6a of a switching type of a yellow toner developing device 6Y, a magenta toner developing device 6M and a cyan toner developing device 6C, and a black toner developing device 6B for black. 6b. In this embodiment, black is a magnetic one-component toner, and the other three colors are a two-component developer containing a magnetic carrier and a non-magnetic toner.

The rotation developing means 6a is a rotation supporting device 6
1 is rotatably supported in the direction of arrow B in FIG. 1, and the above-described color toner developing devices 6Y, 6M, and 6C sequentially face the photoconductor drum 1 to perform development with toner of each color. The rotation developing means 6a is the main body 7 of the apparatus.
In contrast, it is configured as a detachable process cartridge, and when the toner in each of the color toner developing units 6Y, 6M and 6C is used up, the rotary developing means 6a can be replaced to form an image again. Further, the rotating means 6a is always present at a fixed position (home position) except during the copying operation (FIG. 9). Further, the rotating means 6a has a configuration in which it is in the home position even when the color toner development described above is completed. In the home position of this embodiment, when the opposing position of the photosensitive drum and the developing sleeve during the developing operation is 0 °, the yellow developing device 6Y is present at the upstream position of 60 ° and the magenta developing device is located at the downstream position of 60 °. 6M
Is present, and the cyan developing device 6C is present at the 180 ° upstream position.

On the other hand, the fixed developing means 6b has a developing device which contains a large amount of black toner, and is constructed as a process cartridge like the rotary developing means 6a, and is detachably attached to the main body of the apparatus. There is. When the fixed developing means 6b is attached to the apparatus main body 7, as shown in FIG. 2, the developing sleeve 6b1 which is a rotatable toner carrying member and the photosensitive drum 1 have a minute gap (50 μm to 500 μm in this embodiment). ),
A developing area for supplying the toner carried on the developing sleeve 6b1 toward the photosensitive drum 1 is formed.

Further, the toner container 6b2 is provided with a feeding means 6b3 for feeding the toner to the developing sleeve 6b1 side, and a feeding roller 6b4 for feeding the toner fed by the feeding means 6b3 to the developing sleeve 6b1. Is housed. A rubber foam material such as polyurethane or silicone is preferably used for the supply roller 6b4 in order to achieve stable supply to the developing sleeve 6b1 and uniform toner application. Further, the supply roller 6
It is preferable that b4 is brought into contact with the developing sleeve 6b1 and is rotated in the direction of arrow C in FIG. 2 while providing a peripheral speed difference. A developing blade 6b5 is provided above the developing sleeve 6b1 as a regulating member for regulating the layer thickness of the toner carried on the developing sleeve 6b1, and below the developing sleeve 6b1 from below the toner container 6b2. A blowout prevention sheet 6b6 is provided to prevent the toner from being blown to the outside.

In the construction of the developing means, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2 (about -600V in this embodiment). Next, exposure scanning is performed by the exposure unit 3 that is ON / OFF-controlled according to the image data of the first color (for example, yellow), and the electrostatic latent image of the first color (about -100V in the present embodiment). ) Is formed on the photosensitive drum 1. The electrostatic latent image of the first color is developed and visualized by the yellow developing device 6Y containing the yellow toner (-polarity) of the first color. Then, the visualized first toner image is brought into pressure contact with the photosensitive drum 1 with a predetermined pressing force, and is at a speed substantially equal to the peripheral speed of the photosensitive drum 1 (in this embodiment, 100 mm /
s) is transferred to the surface of the intermediate transfer body drum 8 at the nip portion with the intermediate transfer body drum 8 which is rotationally driven in the direction of arrow D.

In this embodiment, the intermediate transfer drum is used.
8. From the NBR rubber etc. on the aluminum cylinder
The surface of the conductive elastic layer is made of carbon, fluororesin, etc.
Form a surface layer made of dispersed urethane resin with releasability
And the resistance value is about 10⁵-10 ¹⁰Ω. cm, outer diameter 1
The one with 53 mm is used.

At the time of transfer to the intermediate transfer drum 8, the drum 8 has a preset voltage (+100 in this embodiment) having a polarity opposite to the charging polarity (-) of the toner.
V) is applied. During this transfer, the intermediate transfer drum 8
The toner remaining on the photosensitive drum 1 without being transferred onto the photosensitive drum 1 is scraped off by a cleaning blade 9a, which is a cleaning unit 9 pressed against the photosensitive drum 1, and is collected in a waste toner container 9b.

Then, the above transfer process is similarly repeated for other toners (magenta, cyan, black),
In each case, toner images of different color toners contained in the respective developing devices are sequentially transferred to the intermediate transfer drum 8 and stacked to form a color image.

Further, in FIG. 1, reference numeral 10 is a cleaner for removing the toner remaining from the intermediate transfer body drum 8 without being transferred to the transfer material P from the intermediate transfer body drum 8.

The transfer material P as a recording material is fed from the feeding cassette 11 to the intermediate transfer drum 8 one by one by the feeding roller 12a and the conveying roller 12b.
A full-color toner image on the side of the intermediate transfer drum 8 is transferred and formed on the transfer material P by applying a voltage (+1000 V in this embodiment) having a polarity opposite to that of the toner from the back surface of the transfer material P to the transfer roller 13. To be done.

The transfer material P to which the full-color toner image has been transferred is separated from the intermediate transfer body drum 8 and introduced into the fixing means 14, where the toner image is heat-fixed and discharged to the discharge tray 15. Is configured.

Here, in the above-mentioned structure, when black monochromatic continuous copying is performed by the developing device 6b, black toner is scattered from the developing sleeve 6b1 in the developing device 6b, and the developing device 6b is located downstream of the developing device 6b at the home position of the rotary developing device 6c. Toner scattered on the existing 6Y and contaminates the developing sleeve 6aY, and then the developing device 6Y performs the developing operation, that is, when the developing sleeve 6aY rotates, the yellow toner and the black toner due to the scattering are mixed. However, the tint variation due to the color mixture occurred.

Therefore, in order to solve the above-mentioned problem, in the present embodiment, when 100 or more continuous copies are performed with a single black color,
The rotation developing means 6a is rotated by 120 ° from the home position every 30 sheets. After the black copying operation is completed, the rotary developing means 6a returns to the home position again.

FIG. 3 shows a black monochromatic continuous copy (A4 paper size, image duty 7% horizontal band in the main scanning direction).
During the operation, the difference in tint variation of the color monochromatic image (magenta, yellow, cyan) between when the above-mentioned operation of the rotary developing means is not performed and when the above-mentioned operation of the above-mentioned rotary developing means is performed, That is, a color difference was shown. Each initial color monochromatic image (A4 paper size, horizontal band in the main scanning direction with image duty of 7%) is used as the initial, and 30 continuous black monochromatic images are formed while forming the same image as the initials. Intermittently), and the color difference ΔE between the initial image and the image after passing every 30 sheets is X-Rit.
It was measured using eSP68. The horizontal axes of FIGS. 3 and 5 represent the number of copies in black monochromatic continuous copying, and the vertical axes represent the color difference between the initial color of each color. Although it is generally said that the allowable color difference ΔE is 6.5 or less, FIG.
In FIG. 5, when the above operation is not performed, the continuous black single color copy is 300 sheets, and the color difference ΔE of the yellow single color at that time is 6.5. On the other hand, when the above operation is performed, the single black continuous color is 1000. Even in the case of one sheet, the color difference ΔE could be maintained below the allowable color difference (ΔE = 6.5) for all colors.

As described above, it is possible to reduce the color mixture due to the scattered toner accumulated on the developing sleeve, and it is possible to form a high-quality color image with no tint variation.

Incidentally, in the above embodiment, the operation is carried out by taking various experimental numerical values as an example, but it goes without saying that these numerical values are not limited respectively. In addition, the operation is performed during continuous copying of single color,
The present invention is not limited to this, and is effective in performing the operation other than continuous copying.

(Second Embodiment) Next, a second embodiment will be described below. Note that the image forming process in this embodiment is almost the same as that in the above-described first embodiment, and thus a duplicate description will be omitted.

In the first embodiment, it has been shown that when continuous black monochromatic copying is performed, the rotational variation of the color developing device can be reduced by the rotational developing means performing the rotational operation during the black monochromatic developing operation. However, when continuous black monochromatic copying is performed for a longer period of time, even when the rotary developing unit performs the operation in the first embodiment, the permissible color difference (ΔE = ΔE = The value exceeds 6.5), and variation in tint occurs.

Therefore, in the present embodiment, when continuous black monochromatic copying is performed for a long period of time, the developer carrying members 6aM, 6aM, 6
The black toner deposited on the aC and 6aY was discharged onto the image carrier.

In the present embodiment, when continuous copying of 500 or more black single colors is performed, the rotary developing means 6a is moved from the home position to the position of 12 every 30 sheets in the first embodiment.
The operation of rotating by 0 ° is performed, and the scattered toner discharging operation described below is performed every 500 sheets.

At the end of continuous copying of 500 black monochrome sheets, in FIG. 6, the developing device 6M is moved to a developing position close to the surface of the photosensitive drum 1 by the rotary developing means 6a, and the primary charger 2 moves the horizontal belt in the main scanning direction ( In the present embodiment, the electrostatic latent image 100 uniformly charged to −100 V is formed in the sub-scanning direction (10 mm), and in FIG. 7, as the photosensitive drum 1 rotates, a bias of −300 V is applied to the developing sleeve 6aM. Is applied to generate a potential difference between the photosensitive drum 1 and the developing sleeve 6aM (200 in this embodiment).
V), the scattered toner on the surface of the developing sleeve 6aM is developed on the electrostatic latent image 100 on the photosensitive drum 1. Needless to say, the developing sleeve 6aM does not rotate during this period. In FIG. 8, the toner developed on the photosensitive drum 1 is collected by the cleaning device 9 without being transferred on the intermediate transfer drum 8 (transfer current in this operation is 0 μA in this embodiment). The same operation is sequentially performed for 6C and 6Y.

FIG. 10 shows a black single color continuous copy (A4
Paper size, horizontal band in the main scanning direction with an image duty of 7%)) During the operation, the rotation operation of the rotation developing means is not performed,
Further, when the scattered toner discharging operation is not performed, the rotating operation of the rotary developing unit is performed in FIG. 11, and when the scattered toner discharging operation is not performed, and in FIG. 12, the rotating operation of the rotary developing unit is performed. And the difference in tint variation of the monochromatic color image (magenta, yellow, cyan), that is, the color difference, when the above-mentioned scattered toner discharge operation was performed. Each initial color monochromatic image image (A4 paper size, horizontal band in the main scanning direction with an image duty of 7%) is used as an initial while forming an image similar to the initial for every 30 continuous black monochromatic copies.
After passing 000 sheets (30 sheets intermittently), the initial image and 30
X-Rite SP68 is used to determine the color difference ΔE from the image after passing each sheet.
Was measured using. The horizontal axis of each of FIGS. 10, 11, and 12 represents the number of copies when black monochromatic continuous copying is performed, and the vertical axis represents the color difference of each monochromatic color from the initial stage. It is generally said that the allowable color difference ΔE is 6.5 or less.
0, FIG. 11, and FIG. 12, in the case of FIG. 10, continuous black monochromatic copying is 300 sheets, and the color difference ΔE of the monochromatic yellow is 6.5, and the color difference ΔE for cyan and yellow is 10000.
The color difference at the end of printing is less than the permissible color difference (ΔE = 6.5), but it is becoming remarkable. In the case of FIG. 11, the color difference ΔE in the case of 10,000 continuous black monochromatic colors exceeded the permissible color difference (ΔE = 6.5) in the vicinity of about 8000 to 9000 sheets for all colors. On the other hand, FIG.
In the case of 2, the color difference ΔE could be maintained below the permissible color difference (ΔE = 6.5) for all colors in the case of 10000 black continuous black sheets, and ΔE could be maintained at a low numerical value.

As described above, it is possible to reduce the color mixture due to the scattered toner accumulated on the developing sleeve, and it is possible to form a high-quality color image with no tint variation.

Incidentally, regarding the above-mentioned embodiment, the operation is carried out by taking various experimental numerical values as an example, but it goes without saying that these numerical values are not limited respectively. Further, the toner discharging operation is performed after the completion of the single-color continuous copy, but the present invention is not limited to this, and the operation is performed in the non-image portion (paper interval) during the single-color continuous copy, or in the case other than the continuous copy. It is also effective in performing actions

[0039]

According to the present invention, an image carrier, a charging device for charging the image carrier by applying a charging bias, and an image for forming an electrostatic latent image on the charged surface of the image carrier. An image forming apparatus equipped with an information writing device, a fixed developing device for developing the electrostatic latent image with a developer, and a developing device for developing with a rotary developing device that rotatably supports at least two developing devices. In the above, while the fixed developing unit is performing the developing operation, the rotational developing unit is rotated without performing the developing operation, thereby reducing the variation in tint due to the color mixture of the developers and forming a high quality color image. can do.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment.

FIG. 2 is a diagram for explaining the first embodiment.

FIG. 3 shows the number of black monochromatic copies in the first embodiment,
FIG. 3 is a diagram showing the relationship of color differences between yellow, magenta, and cyan single-color images.

FIG. 4 is a diagram for explaining a conventional example.

FIG. 5 shows the number of black monochromatic copies in the first embodiment,
FIG. 3 is a diagram showing the relationship of color differences between yellow, magenta, and cyan single-color images.

FIG. 6 is a diagram for explaining the second embodiment.

FIG. 7 is a diagram for explaining the second embodiment.

FIG. 8 is a diagram for explaining the second embodiment.

FIG. 9 is a diagram for explaining the first embodiment.

FIG. 10 is a diagram showing the relationship between the number of black monochrome copies and the color difference between each of the yellow, magenta, and cyan monochrome images in the second embodiment.

FIG. 11 is a diagram showing the relationship between the number of black monochrome copies and the color difference between each of the yellow, magenta, and cyan monochrome images in the second embodiment.

FIG. 12 is a diagram showing the relationship between the number of black monochromatic copies and the color difference between yellow, magenta, and cyan monochromatic images in the second embodiment.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsuneji Masuda             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation F-term (reference) 2H300 EA06 EA08 EA10 EB02 EB09                       EB12 EB18 EB24 EC02 EC04                       EF03 EF08 EG01 EH11 EJ02                       EJ09 EJ15 EJ40 EJ45 EJ47                       EJ50 EJ52 FF05 GG02 GG29

Claims (7)

[Claims] 1. An image carrier, a charging device for charging the image carrier by applying a charging bias, and an image information writing device for forming an electrostatic latent image on a charged surface of the image carrier. In the image forming apparatus, a fixed developing unit for developing the electrostatic latent image with a developer and a developing unit for developing the electrostatic latent image with a rotary developing unit that rotatably supports at least two developing units are provided. An image forming apparatus having a mechanism in which the rotary developing means rotates without performing a developing operation while the developing means is performing a developing operation. 2. The image forming apparatus according to claim 1, wherein the rotary developing unit rotates so that the developing unit moves to an arbitrary position. 3. The image forming apparatus according to claim 1, wherein the fixed developing device is arranged upstream of the rotary developing device in the rotation direction of the image carrier. 4. The rotating developing means has a mechanism that rotates while the developing processing is being performed by the fixed developing means, without performing the developing operation, at a preset number of times of the developing operation of the fixed developing means. Claim 1 characterized by the above.
3 to 3. 5. The fixed developing device contains a black developer, black is a magnetic one-component developer, and the other is a two-component developer obtained by mixing a non-magnetic toner and magnetic particles. It is encapsulated and characterized.
The image forming apparatus described. 6. The rotary developing means, after completion of the developing operation of the fixed developing means, does not rotate the developer carrying member of the rotary developing means, so that the toner is applied to a non-image portion on the image carrying body. The image forming apparatus according to any one of claims 1 to 4, wherein the image forming apparatus has a mechanism for performing a discharging operation. 7. The image forming apparatus according to claim 1, wherein the image bearing member is composed of a photosensitive member including a surface layer containing amorphous silicon.