JPH02105175A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To form a multicolor image without color slurring at high speed by disposing two image carriers, respectively providing two developing means in the respective image carriers and simultaneously transferring developed images of two colors on the respective image carriers on the rotor by a transfer means. CONSTITUTION:Two image carriers are disposed, where two developing means out of 5Y, 5M, 5C and 5BK are provided respectively. The developed images of two colors on the respective image carriers 1a and 1b which are developed based on latent images formed on the respective image carriers 1a and 1b are simultaneously transferred on the rotor 16 which performs revolving motion in contacting with the respective image carriers 1a and 1b by the transfer means 10a and 10b. Therefore, the revolving speed of a transfer material holding member which holds a transfer material where the image is transferred can be reduced. Thus, the speed for forming the multicolor image finally obtained can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a latent image formed on an image bearing member such as a photosensitive drum through a predetermined process is developed into each color using a plurality of developing devices, and the developed image is Regarding multicolor image forming apparatuses that transfer onto a supplied transfer material and fix this transferred image as a permanent image, in particular, a developed image that is visualized based on a latent image formed on an image carrier. The present invention relates to a multicolor image forming apparatus that obtains a color image by multiple-transferring images onto a transfer material or an intermediate transfer member that rotates synchronously in contact with an image carrier.

Beauty . Recently, multicolor image forming apparatuses using electrophotographic technology have become widespread. In order to obtain a multicolor image, especially a full color image, the original image information is color separated optically or electrically, and each color is separated to form an image corresponding to each of the separated colors. Complementary color developer, generally yellow (hereinafter abbreviated as Y) color,
Images corresponding to each color are formed using magenta (hereinafter abbreviated as M) and cyan (hereinafter abbreviated as C) color developers, and these color images are multiplexed onto a single recording material. It is necessary to do so.

Furthermore, in terms of image forming speed when the multicolor image forming apparatus is used as a normal monochrome image forming apparatus, or Y,
Considering the fact that it is difficult to reproduce black (hereinafter abbreviated as BK) even if the colors Y, M, and C are mixed due to the spectral reflectance characteristics of each developer powder having the colors M and C. 1. In a normal multicolor image forming apparatus, the above-mentioned Y, M
, C colors as well as BK color developing means are generally provided.

Until now, there have been multiple methods in which images of each color are formed through a predetermined process while holding the recording material in some kind of member, and the formed images of each color are transferred to the recording material in multiple ways to obtain a multicolor image. Color image forming apparatuses have been put into practical use, and representative examples of such conventional multicolor image forming apparatuses are shown in FIGS. 3 and 4. That is, in the system shown in FIG. 3, a plurality of image carriers 1a, lb, lc, and 1d, such as photosensitive drums, are arranged in parallel on a recording material holding member 16 that moves endlessly, and the image bearing members 1a, lb, lc, and 1d, such as photosensitive drums, are arranged in parallel on a recording material holding member 16 that moves endlessly. ,
A device that forms an image using each image carrier for each color corresponding to the original image information and transfers these images onto a single sheet of recording material to obtain a color image (hereinafter referred to as 4-drum type)
In the system shown in FIG. 4, images of each color corresponding to the JX draft image quality information are sequentially formed on one image carrier L, and the recording material is moved back and forth or endlessly accordingly to form the images of each color. This is a device (hereinafter referred to as a 1-drum type) in which a color image is obtained by sequentially transferring images onto a recording material.

Both image forming processes are already known and the details are described in electrophotography journals and the like, so further detailed explanation will be omitted.

However, the conventional multicolor image forming apparatuses described above each have the following drawbacks. That is, in the 4-drum multicolor image forming apparatus shown in FIG. 3, multicolor images can be obtained according to the movement of the recording material, so the time required for image formation is short; It is necessary to sequentially change the timing at which the image forming operation is started in each image carrier that forms the image as the recording material moves.

As shown in Figure 3,! 81e, when the image formation start time of the eye is set to 1=0, on the image carrier on which the image of the nth color (n=1 to 4) is formed, the image formation start time of each recording material is Shifting by the time required to move between image carriers (Jl/V), t = (nXJ1)/
It is necessary to set it to V. Here, ■ is the recording material holding member 1
The moving speed is 6, and the value is the distance between image carriers arranged equidistantly. On the other hand, the optical system that exposes the original is
Normally, the optical system is configured to move with respect to a stationary original, but in this case, the optical system scans in synchronization with the image carrier during forward movement, and then moves backward after exposure is completed. It is necessary to move and return to the starting position before the recording material comes into contact with the image carrier of the next color.

However, there is a limit to increasing the return speed of the optical system, and there is always a demand for each image carrier to have a diameter as small as practical. stores the image information once and sequentially stores the image information one by one according to the image formation start time of each image carrier.
However, the storage capacity for one image information is at least
While the recording material moves between the first color and final color image carriers, a device that can temporarily store the image information read by the scanning optical system is required, which is required for recent multicolor image forming apparatuses. Considering the dot density and gradation, it is practically difficult to implement an element with the above-mentioned storage capacity in terms of cost and processing speed unless significant image information compression is performed. .

In order to solve the above problem, it is technically possible to set the image formation start time of each color on each image carrier at the same time by sequentially increasing the diameter of each image carrier on the downstream side in the transfer material movement direction. Although this is possible, it increases the size of the multicolor image forming apparatus and is not practical in terms of serviceability and manufacturing cost.

Further, in the four-drum multicolor image forming apparatus shown in FIG. 3, an endlessly moving belt-shaped flexible insulating material is usually used as a recording material holding member.

In an image forming apparatus using electrophotography, as is well known, chargers 4a, 4b, 4C14d, charger 4a, 3b, 3c, and charger 3a, 3b, 3c are placed around the image carriers 1a, 1b, 1c, ld.
C13d, cleaning devices 12a, 2b, 2C12d for removing residual toner or developing devices 5Y, 5M, 5C55BK for visualizing latent images, and transfer charger 1
This is because it is necessary to arrange 0a, LOb, 1Oc, lod, etc., and in consideration of these, the above configuration has to be adopted in order to avoid increasing the size of the entire multicolor image forming apparatus.

However, in an image forming apparatus having the recording material holding member 16 using the belt-shaped flexible insulating material,
Due to meandering, expansion and contraction of the belt, each image carrier 1a, lb,
It is difficult to align the images of each color formed by lc and ld onto a recording material in multiple ways, and a so-called "color misregistration" image is likely to occur.

On the other hand, in the L-drum type multicolor image forming apparatus shown in FIG. 4, which is currently in practical use, the recording material is usually While holding the image carrier l through a predetermined process.
A cylindrical transfer drum 16 is used as a member for multiplexly transferring each color image formed thereon onto a recording material by a transfer charger IO. This transfer drum 16
, a flexible insulating material is arranged on the circumferential surface of a pair of annular frames, and a mechanical device such as a gear is used so that the rotational speed ratio of the image carrier 1 and this transfer drum 16 is an integer. By means of
By rotatably and synchronously interlocking these, at the contact position where the image carrier 1 and the transfer drum 16 are in contact,
The images are aligned so that the corresponding points always match to prevent "color misalignment" between the colors.

However, in such a one-drum type multicolor image forming apparatus, in order to multiplexly transfer each color image formed on the image carrier 1 onto the recording material by the transfer charger 10, the recording material The image forming speed is at most 1/4 of that of a black and white image forming apparatus which has the same image forming speed on the image carrying opening.
Also, depending on the size of the recording material, the developing units 5Y, 5M, and 5C15BK of each color installed as a rotary developing device may be used.
In order to secure time to move the developing device to be used, the transfer drum 16 may need to be rotated idly, and in that case, the image forming speed is further reduced to nearly half of that time. It has its drawbacks. Specifically, while the transfer drum 16 rotates half a rotation, the rotary developing device rotates nine times.
Let us consider the case where a full-color image is formed on a recording material whose total length is less than half the circumference of the transfer drum 16, that is, a transfer material whose total length is approximately equal to the circumference of the transfer drum 16, assuming that the transfer drum 16 moves by 0". It is clear that the former requires four rotations of the transfer drum to obtain the desired image, while the latter requires seven rotations.

Σ” column-76-officeL”p=”4
1 ''Therefore, the present invention has been made in view of the above circumstances, and its purpose is to facilitate image positioning and reduce color misalignment images compared to conventional 4-drum multicolor image forming apparatuses. This is less likely to occur, and multicolor images can be formed faster than conventional one-drum multicolor image forming devices.In other words, there is no color shift compared to conventional multicolor image forming devices. An object of the present invention is to provide a multicolor image forming apparatus capable of forming fine multicolor images at high speed.

Therefore, the above object is achieved by a multicolor image forming apparatus according to the present invention. In other words, the present invention forms a multicolor image by developing a latent image formed on an image carrier through a predetermined process into each color using a plurality of developing means to form a developed image. In the multicolor image forming apparatus, two image carriers for holding the PPi image are disposed, and two developing means are disposed for each of these image carriers, A rotating body that rotates in contact with each of the image carriers by a transfer means to transfer two-color developed images of each of the image carriers that are developed based on the latent images formed on each of the image carriers. This is a multicolor image forming apparatus that is characterized by simultaneously transferring images.

1 Cliff 1 Hereinafter, the present invention will be described based on one embodiment thereof with reference to the accompanying drawings.

Referring to FIG. 1, there is shown a schematic cross-sectional view of an electrophotographic full-color (four-color) copying apparatus as an embodiment of a multicolor image forming apparatus according to the present invention. Equipped with photosensitive drums 1a and 1b as carriers,
These photosensitive drums la and 1b rotate in the directions of arrows a and b. Around each of the photosensitive drums la, 1b, there are cleaners 2a, 2b for removing surplus toner on each image carrier after development, a removal lamp 3a for neutralizing the surface of the image carrier, 3b. To make the surface of the image carrier uniformly banded? ? F electronics 4a, 4b, exposure means 17Y, L7C equipped with a laser beam emitting means and a polygon mirror for exposing the surface of the image carrier to form Wit, toner particles based on the latent image formed on the surface of the image carrier. Developing units 5Y and 5c are sequentially arranged to carry out visualization using a developer such as, chargers 4c and 4d to uniformly charge the surface of the image carrier, and a charger 4c and 4d to expose the surface of the image carrier. Exposure means 17M and 178K are provided with a laser beam emitting means and a polygon mirror to form a latent image, and the latent image formed on the surface of the image carrier is visualized using a developer such as toner particles. Developing units 5M and 5BK are sequentially arranged.

On the other hand, the recording material for recording the image formed on the image carrier, that is, the transfer material, is transferred to the paper feeder 8 (recasser) 14
The supplied transfer material passes through the registration rollers 15 and is attracted onto the transfer drum 16 by the attraction charger 9. At that time, in order to transfer the image to a predetermined position on the transfer material supplied onto the transfer drum in this way,
The registration rollers 15 control the timing at which the transfer material is attracted onto the transfer drum. In the copying apparatus shown in FIG. 1, two cassettes loaded with transfer materials of different sizes are installed, and these transfer materials are supplied in a switching manner.

In the electrophotographic full-color copying apparatus configured as described above, the original is scanned while reading the reflected light from the original illumination lamp 6 with the photoelectric converter 7 having a color separation function.
After converting the image information to be copied into an electrical signal and subjecting it to appropriate image signal processing, the exposure means 17Y, 17M, 17 each include a laser beam emitting device and a polygon mirror.
C, 178K. Thus, the laser beam emitted according to the image signal is applied to the photosensitive drum la whose surface is uniformly charged in advance by the chargers 4a and 4b and further by the chargers 4c and 4ci.

By irradiating the surface of 1b, a latent image corresponding to document image information is formed on the surface of each photosensitive drum.

The latent images are divided into the current f! for each corresponding color. @5
After the Y, 5M, 5C, and 5BK images are developed using a developer such as toner particles, the developed images are adsorbed onto the transfer drum 16 and synchronized with the respective photosensitive drums la and 1b.
The image is transferred onto the transfer material by the transfer chargers 10a and 10b, forming a transferred image on the transfer material. The transfer material to which the toner image of each color, that is, the visible image has been transferred, is neutralized by a group of static eliminators and peeled off from the transfer drum 16 by a separating claw 18, and then conveyed by a conveyor belt 12 to a fixing device 13, where it is The toner image on the transfer material, that is, the transfer image, is heated and pressurized to fix it, and then the transfer material is discharged outside the machine.

Here, the image forming sequence in the above embodiment will be further explained. Note that in the above embodiment, the photosensitive drum 1a
, 1b and the rotation speed (angular velocity) of the transfer drum 16 is 2=
1, and the toner images formed on the image carrier are in the order of Y→M-C-BK, as described above. Now, at the same time as scanning of the original is started, Y is subjected to arithmetic processing according to the image signal of the original obtained from the photoelectric converter 7.
Laser light corresponding to the image information of the component is irradiated onto the photosensitive drum la to form a latent image corresponding to the Y component, and then the latent image is processed by the developing device 5Y containing a developer such as Y color toner. is visualized to form a Y color toner image.

On the other hand, the M component is subjected to arithmetic processing in accordance with the image signal of the document obtained from the photoelectric converter 7 at the same time.

The image information of the C component and the BK component is temporarily stored in a buffer memory, etc., and the laser beam corresponding to the image information of the 1M component is delayed by the time tl shown in FIG. 2 from the start time of latent image formation of the Y component. is irradiated onto the photosensitive drum la to form a latent image corresponding to the M component, and then the latent image is visualized by the developing device 5M containing a developer such as an M color toner to form an M component.
A color toner image is formed, and a transfer charger tOa simultaneously transfers the Y and M color toner images onto a transfer material supplied in synchronization with the image forming process.

Note that the time t shown in FIG. 2 is 1. = Sentence 1/V. Here, V is the circumferential speed of the photosensitive drum or transfer drum, and the document is irradiated from Ms lightning to the point 71s2 where the photosensitive drum la is irradiated by the exposure means 17M. This is the distance on the circumference.

Next, after a delay of the time tz shown in FIG. 2 from the start time of forming a latent image of the Y component, a laser beam corresponding to the image information of the C component is irradiated onto the photosensitive drum ib to form a latent image corresponding to the C component. Then, the latent image is visualized by the developing device 5C containing a developer such as C color toner to form a 0 color toner image, and roughly from the start time of Y component latent image formation, the latent image is visualized. After a delay of time t3 shown in FIG. 2, the photosensitive drum 1b is irradiated with a laser beam corresponding to the image information of the BK component to form a WI image corresponding to the BK component, and then a developer such as BK color toner is stored. The developing device 5BK visualizes the latent image to form a BK color toner image, and the transfer charger 10b applies zero color to the transfer material supplied in time with these image forming processes. and BK color toner images are simultaneously transferred.

Note that the time t shown in FIG.
3-9.4)/v-c, and time t-3 is expressed as t3=(cross 20 cross 3-sentence 5)/v. Here, ■ is the circumferential speed of the photosensitive drum or transfer drum,
uZ is exposed to the photosensitive drum 1a-41 by the exposure means 17Y.
13 is the distance on the circumference of the photosensitive drum la from the position M S + at which the image is irradiated to the transfer position 2tU+ at which the image is transferred to the transfer drum 16 by the image carrier la;
U from the transfer position where the image is transferred to the transfer drum 16 by the image carrier 1a.

It is the distance on the circumference of the transfer drum from to the transfer positions H and U where the image is transferred to the transfer drum 16 by the image carrier ib, and the view is the position where the top of the photosensitive drum lb is irradiated by the exposure means 17C. Transfer position 'II U where the image is transferred from s3 to the transfer drum 16 by the image carrier 1b
is the distance around the photosensitive drum 1b to Z,
! 15 is a transfer position F! where the image is transferred from the position S4 where the photosensitive drum lb is irradiated by the exposure means 17BK to the transfer drum 16 by the image carrier ib! This is the distance on the circumference of the photosensitive drum to I U z.

As described above, in a color copying apparatus to which the invention is applied, toner images of four colors are transferred to the transfer material L- within the time period at which the transfer drum rotates once after the transfer material is attracted to the transfer drum. In particular, when the same original is continuously copied onto multiple transfer materials, the conventional 4-drum multicolor image forming method with equal latent image formation speed on the image carrier It is possible to obtain a full color image forming speed approximately equal to that of the device. Furthermore, compared to a conventional 1-drum multicolor image forming device that has the same latent image formation speed on the image carrier, the full color image forming time is significantly reduced to 1/4 to 1/7 depending on the size of the transfer material. It is possible to shorten it.

In addition, in the embodiment described in section 2, since a transfer drum, which is a rotary body that rotates in contact with the image carrier, is used as the transfer material conveyance means, each f! It is easy to synchronize with the I carrier, and unlike belt-shaped transfer material conveying means, the belt does not meander and has high rigidity, so it is more efficient than conventional 4-drum multicolor image forming devices. This is extremely advantageous in that image alignment is easy and color misalignment images are less likely to occur.

In the above embodiments, a color copying apparatus to which the present invention is particularly effective has been described, but it goes without saying that the present invention is applicable not only to copying machines but also to color printers and the like. , considering the practical size of the image carrier and the size of general transfer materials, the rotational speed ratio of the image carrier and the transfer drum is set to 2=1, but it does not necessarily have to be an integer ratio, and other than this The present invention can also be applied to the value of . Similarly, the image formation order of each color to obtain a multicolor image or the angle formed by the line segment connecting the center of each image carrier and the center of the rotating body, in other words, the distance 3 in this embodiment is also limited to the above embodiment. In addition, a rotating body such as a transfer drum is used as an intermediate transfer body that transfers the toner image formed on the image carrier, and intermediate transfer (after all color images are superimposed and transferred to the rotating body, It is also possible to form a multicolor image by transferring a visible image on a rotating body to a transfer material at once. Furthermore, in the present invention, the transfer material is not limited to so-called cut paper.

Continuously fed rolls of paper may also be used.

As explained above, according to the multicolor image forming apparatus of the present invention, the image forming speed on the image carrier is the same as that of the conventional one.
- Compared to a drum-type multicolor image forming device, the number of rotations of the transfer material holding member that holds the transfer material onto which the image is to be transferred can be significantly reduced, resulting in the formation speed of the final multicolor image. It is possible to significantly improve the image forming apparatus, and there is no need for a mobile developing device that increases the size of the image forming apparatus and causes contamination inside the apparatus. Furthermore, image positioning is easier than in the conventional four-drum multicolor image forming apparatus, and it is possible to suppress the occurrence of color misalignment images. As a result, it is possible to easily realize a multicolor image forming apparatus that can form a fine multicolor image without one color shift at high speed without increasing the size of the image forming apparatus.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an embodiment of a multicolor image forming apparatus according to the present invention. FIG. 2 is a detailed explanatory diagram of the transfer material holding member and image carrier of the multicolor image forming apparatus shown in FIG. FIG. 3 is a schematic cross-sectional view of a conventional four-drum multicolor image forming apparatus. FIG. 4 is a schematic cross-sectional view of a conventional one-drum multicolor image forming apparatus. la, lb: Image carriers 5Y, 5M, 5C, 58: Developing device 10, loa, 10b: Transfer charger 16: Transfer drum 5C5Y

Claims (1)

[Claims] 1) In a multicolor image forming apparatus that forms a multicolor image by developing a latent image formed on an image carrier through a predetermined process into each color using a plurality of developing means to form a developed image, the above-mentioned By arranging two image carriers carrying latent images and disposing two developing means for each of these image carriers, the latent image formed on each of the image carriers is The multi-color image forming apparatus is characterized in that two-color developed images of each of the image carriers are simultaneously transferred by a transfer means to a rotating body that rotates in contact with each of the image carriers. Image forming device.