JPH09197765A - Image forming device - Google Patents

Abstract

(57) [Summary] [Problem] Speed variation pattern that occurs when writing each color and when transferring each color due to eccentricity of each photoconductor, eccentricity of a belt driving roller, and eccentricity of each drive system gear. Position to prevent misalignment. A relative ratio of an outer diameter of a first electrostatic latent image carrier 9a, an outer diameter of a second electrostatic latent image carrier 9b, and an outer diameter of a drive roller 21-1 of an intermediate transfer member 19, The outer diameter of the driving member 9A for driving the first electrostatic latent image carrier, the outer diameter of the driving member 9B for driving the second electrostatic latent image carrier, and the driving member 21-for driving the driving roller of the transfer body. The relative ratio of the outer diameter of 1A is the same, and the peripheral length of the first electrostatic latent image carrier and the peripheral length of the second electrostatic latent image carrier are respectively the drive roller peripheral length of the intermediate transfer member. It was an integer multiple of.

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 using an electrophotographic system such as a copying machine, a printer, and a FAX, and more specifically, it carries a supported object such as a toner and a transfer paper until the next step. The present invention relates to an image forming apparatus having a carrier that conveys a supported object.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a main part of a hybrid color printing apparatus disclosed in Japanese Patent Laid-Open No. 4-296878. This printing apparatus includes a pair of photosensitive drums 100, 1.
01, four developing devices 102a to 102d for developing the electrostatic latent image on the photoconductor with toners of different colors, and both photoconductor drums for transporting the transfer paper for transferring the developed toner image. A transfer roller 103 located between them and writing devices 104a, 104 for forming an electrostatic latent image on the photosensitive drum.
b. In the image forming operation by this apparatus, a four-color superimposed image is formed by two driving cycles (two rotations of the photosensitive drum). In the first operation cycle, the uniformly charged photosensitive drum 100 is written by the writing device ROS 104a to form an electrostatic latent image, and the cyan developing device 102a.
Is developed. The cyan toner image on the photosensitive drum 100 is conveyed to a transfer point 105 in contact with the transfer roller 103.
The transfer paper 106 is conveyed at the timing when the front end of the transfer paper and the front end of the toner image on the photosensitive drum 100 coincide with each other at the transfer point 105. After the toner image on the photoconductor 100 is transferred onto the transfer paper 106 at the transfer point 105, the transfer paper 10 is transferred.
6 is conveyed to the transfer point 107 to receive the transfer of the next different color toner images. The other uniformly charged photoconductor drum 101 is aligned with the cyan toner image on the transfer paper 106 at the same timing as the writing device ROS1.
04b receives writing. That is, ROS 104a
The position is adjusted by delaying the write timing of the ROS 104b by a predetermined time with respect to the write timing of. Then, the electrostatic latent image formed on the photosensitive drum 101 is developed by the yellow-developing device 102c. The yellow toner on the photoconductor drum 101 thus obtained
The image is conveyed to a transfer point 107 with which the transfer roller 103 is in contact. At the transfer point 107, the yellow toner image is transferred while the yellow toner image on the photosensitive drum 101 and the cyan toner image on the transfer paper 106 conveyed by the transfer roller 103 are aligned. Transferred onto the paper 106, a two-color image of the four-color superimposed image is formed. Then, the remaining two color images are transferred onto the transfer paper in the same manner as described above.

[0003]

However, in the above-mentioned conventional apparatus, the photosensitive drum 10 by the ROS 104a is used.
0, the distance from the writing position to the transfer point 105,
Since the distance from the writing position on the photosensitive drum 101 by the ROS 104b to the transfer point 107 is equal, the writing timing of the photosensitive drum 101 is delayed with respect to the writing timing of the photosensitive drum 100 in order to match the image positions of both drums. I try to write it. Therefore, the image memory that is delayed is required, and the cost increases as the memory is added. Also,
When outputting a plurality of images of only black color, the photosensitive drum 100 on the side where the black developing device 102d does not exist is also cleaned by the cleaner 108, and the transfer roller 1
03, the photoconductor drum 100 is unnecessarily consumed. Further, in the case of outputting a black monochromatic image, one of the photoconductor drums 100 does not perform the image forming operation, so that the efficiency is low.

The present invention has been made in view of the above, and an object of the present invention is to provide an image forming apparatus which eliminates the above drawbacks and is inexpensive and capable of aligning toner images of respective colors. is there. It is an object of the present invention to provide an image forming apparatus capable of efficiently forming an image by using two photoconductor drums when outputting a black single color by the second black developing machine. It is an object of the third and fourth aspects to provide an efficient image forming apparatus by forming an image by dividing each photosensitive drum.

[0005]

In order to achieve the above object,
According to the invention of claim 1, first and second electrostatic latent image carriers,
A writing unit arranged on each latent image carrier for writing image information on each latent image carrier, and a plurality of developing devices for developing the electrostatic latent images on the electrostatic latent image carriers with toners of different colors. And an intermediate transfer member which is arranged so as to be contactable and separable between the two electrostatic latent image carriers in order to sequentially receive toners of different colors on the electrostatic latent image carrier and carry the toner image. A driving roller that stretches the intermediate transfer member endlessly, a plurality of belt transfer devices that transfer the toner image from the electrostatic latent image carrier to the intermediate transfer member, and a toner image from the intermediate transfer member to the transfer paper. An image forming apparatus having a paper transfer device for transferring the toner, the outer diameter of the first electrostatic latent image carrier, the outer diameter of the second electrostatic latent image carrier, and the outer diameter of the drive roller of the intermediate transfer member. The relative ratio, the outer diameter of the drive member that drives the first electrostatic latent image carrier, and the outer diameter of the drive member that drives the second electrostatic latent image carrier. And the relative ratio of the outer diameters of the driving members that drive the driving rollers of the transfer members are the same, and the circumference of the first electrostatic latent image carrier is equal to the circumference of the second electrostatic latent image carrier. , And each is set to an integral multiple of the circumference of the driving roller of the intermediate transfer member. The invention of claim 2 is characterized in that each of the plurality of electrostatic latent image bearing members is provided with at least one black developing device. According to a third aspect of the present invention, each electrostatic latent image corresponding to each image information of a plurality of originals or a plurality of image information obtained by dividing the image information of one original is provided on different electrostatic latent image carriers. It is characterized by forming an image. According to a fourth aspect of the present invention, when the image information of each of the plurality of originals read is formed on different electrostatic latent image carriers, the reading timing of each original is different. .

Since the above construction is adopted, the first aspect of the present invention is to write each color and to transfer each color by the eccentricity of each photoconductor, the eccentricity of the belt driving roller and the eccentricity of each drive system gear. Since the generated speed fluctuation patterns can always be made to coincide with each other, positional deviation can be prevented. According to the second aspect, by forming at least one black developing device on the plurality of electrostatic latent image carriers, it is possible to speed up the image formation of a single black color. According to the third aspect, the monochromatic image formation can be accelerated by dividing the monochromatic original or the monochromatic image signal into the respective electrostatic latent image carriers to form the image. According to a fourth aspect of the present invention, when the image is divided into respective electrostatic latent image carriers and the image is formed, it is possible to speed up the single-color image formation by changing the reading timing of the document and it is necessary to mount an extra memory. Disappears.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram of a color copying apparatus according to the present invention, and FIG. 2 is a configuration explanatory diagram of essential parts.
FIG. 3 is a block diagram of an example of the drive system. The configuration and operation of this device will be described below. The example of this embodiment is different from the above-mentioned conventional example in that an intermediate transfer belt is used as a transfer unit interposed between two photosensitive drums. A color image reading device (hereinafter referred to as a color scanner) 1 is
The images of the originals 3-1, 3-2 on the contact glass CG are formed on the color sensor 7 through the illumination lamp 4, the mirror groups 5-1, 5-2, 5-3 and the lens 6. , Color image information of the original document, for example, Blue, Green, Re
Each color separation light of d is read and converted into an electric image signal. And B, G, R obtained by this color scanner-1
An image processing unit (not shown) performs color conversion processing based on the color separation image signal intensity level of
Bk), Cyan (same as C), Magenta
(Same as M) and Yellow (Same as Y) color image data
Get the data. These image data are visualized as Bk, C, M, and Y by a color image recording device (hereinafter referred to as a color printer) 2 described below, and these images are superposed. A four color full color image is formed. Next, the outline of the color printer-2 will be described. The first and second writing units 8a and 8b (laser optical system or LED array, etc.) convert the color image data from the color scanner-1 into an optical signal and emit light corresponding to the original image. Writing is performed on the first and second photoconductor drums 9a and 9b, respectively, and electrostatic latent images are formed on the first and second photoconductor drums (electrostatic latent image carriers) 9a and 9b. The first and second photosensitive drums 9a and 9b respectively rotate in the directions of the arrows,
The components described below are arranged around it. First, the first and second photoconductor cleaning units 10
a and 10b are brought into contact with and separated from the photosensitive drums 9a and 9b by a contacting and separating mechanism (not shown). The first and second static elimination lamps 11a and 11b arranged adjacent to the cleaning unit are
The residual potential on the photoconductor is removed. First and second charger 12
The a and 12b uniformly charge the photosensitive drums 9a and 9b. Further, first and second potential detectors 13a and 13b for detecting the potentials of the photosensitive drums 9a and 9b, a Bk developing device 14, a C developing device 15, an M developing device 16, and Y for developing the toner of each color.
The developing devices 17 are sequentially arranged. The developable state and the non-developable state are selected according to the image forming timing and the operation mode. Further, first and second development density pattern detectors 18a and 18b for detecting the toner density on the photosensitive member, an intermediate transfer belt (intermediate transfer member) 19 and the like are also arranged.

A further characteristic construction of the present invention is to provide a Bk developing device 27 also on the side of the second developing device 9b so as to realize speedy black monochromatic image formation as described later. It is in the point that I made it. Intermediate transfer belt 1
At the positions corresponding to the transfer points Ta and Tb on the inner periphery of 9, the toner images on the photosensitive drums 9a and 9b are transferred to the intermediate transfer belt 19
Transfer bias to apply a bias to transfer
La (belt transfer devices) 20a and 20b are arranged, and these transfer bias rollers 20a and 20b are brought into contact with and separated from the photosensitive drums 9a and 9b by a contact and separation mechanism (not shown). The intermediate transfer belt 19 includes a transfer belt driving roller 21-1 and a driven roller 21 that rotate and drive the intermediate transfer belt 19.
-2, and a transfer belt cleaner 22 for cleaning the intermediate transfer belt 19 is provided on the outer periphery of the intermediate transfer belt 19,
The intermediate transfer belt 19 is contacted and separated by a contacting and separating mechanism (not shown). Further, at a position facing the drive roller 21-1, a paper transfer roller for moving the toner image on the intermediate transfer belt 19 onto a transfer sheet by moving the toner image on the intermediate transfer belt 19 by a contacting / separating mechanism (not shown). La (paper transfer device) 23 is arranged. Transfer paper transport rollers 26-1, 26-2, and 26-3 that transport the transfer paper are provided on the upstream side of the paper transfer position, and the transport belt 24 and the toner image on the transfer paper are fixed on the downstream side. The fixing devices 25 and so on are arranged respectively. As shown in FIG. 3, the drive gear (drive member) 9 of each of the photosensitive drums 9a and 9b
A and 9B mesh with the drive gear (drive member) 21-1A of the drive roller 21-1, and the gear ratio between the gears is set so that the photoconductor and the intermediate transfer belt rotate at a constant speed.
Each drive member may be a pulley or the like other than a gear.

Next, the order of the image forming operation (color image forming order) will be described using the examples of Bk, C, M and Y. However, the image forming order is not limited to this. When the copy operation is started by pressing down a print key (not shown) or the like, the photoconductor drums 9a and 9b and the intermediate transfer belt 19 that rotates at a constant speed with the photoconductor drums 9a and 9b start to rotate at a predetermined timing. With photoconductor cleaner 10
a, 10b, and the intermediate transfer belt cleaner 22 are brought into contact with the photoconductor drums 9a, 9b, and the intermediate transfer belt 19 by a contacting / separating mechanism (not shown), respectively.
Start training. Subsequently, after a predetermined timing, the intermediate transfer belt 19 contacts the photoconductor drums 9a and 9b by a contacting / separating mechanism (not shown). This contact operation is performed before the writing by the writing units 8a and 8b is started. The intermediate transfer belt cleaner 22 is in contact with the intermediate transfer belt 19 for cleaning during at least one revolution of the intermediate transfer belt 19 to perform cleaning, and then separated. The color scanner 1 starts reading Bk image and M image data at a predetermined timing,
Based on this image data, simultaneous optical writing and latent image formation by the writing units 8a and 8b start. Hereinafter, the electrostatic latent image formed by the Bk image data is referred to as a Bk latent image. C, M, Y
The same is true for

First, the first writing unit 8a
A latent image of Bk is formed on the photosensitive drum 9a. In order to enable development from the front end of the Bk latent image, the Bk developing device 14 is set in the developable state before the front end of the latent image reaches the developing position of the Bk developing device 14, and the Bk latent image is transferred to the Bk toner image. To develop.
At the same time, the second writing unit 8b forms an M latent image on the second photoconductor drum 9b. In order to enable development from the front end of the M latent image, before the front end of the latent image reaches the developing position of the M developing device 16, the M developing device 16 is set in the developable state and the M latent image is transferred by the M toner. develop. After that, the Bk developing device 14
Thus, the developing operation of the Bk latent image area is continued, but when the rear end portion of the Bk latent image passes the Bk developing position, the developing operation is disabled. This is completed at least before the leading edge of the C latent image by the next C image data reaches the developing position. Similarly, the developing operation of the M latent image area is continued by the M developing device 16, but the development is disabled when the trailing end of the M latent image passes the M developing position. This is completed at least before the leading edge of the Y latent image by the next Y image data reaches the developing position.

Then, the Bk toner image formed on the first photosensitive drum 9a is transferred to the surface of the intermediate transfer belt 19 which is driven at the same speed as the first photosensitive drum 9a at the first transfer point Ta. Transport to. Hereinafter, toner image transfer from the photoconductor to the intermediate transfer belt is referred to as belt transfer. The belt transfer is performed by the first transfer bias roller 20a while the first photosensitive drum 9a and the intermediate transfer belt 19 are in contact with each other.
It is realized by applying a predetermined bias voltage to. The first photosensitive drum 9a is brought into contact with the intermediate transfer belt 19 before the writing units 8a and 8b start writing on the photosensitive drums 9a and 9b. This is to suppress load fluctuations on the photoconductor during writing as much as possible. From the photosensitive drum 9a to the intermediate transfer belt 19
The Bk toner image transferred above is conveyed to the second transfer point Tb. As shown in FIG. 2, the first writing unit 8
The distance La + Lb from the first writing position to the second transfer point Tb by a and the second by the second writing unit 8b.
The distance Lc from the writing position to the second transfer point Tb is set to be equal (La + Lb = Lc). Therefore, when writing is simultaneously started by both writing units 8a and 8b, the Bk toner image which has been transferred from the first photosensitive drum 9a onto the transfer belt 19 and has reached the second transfer point Tb, and the second photosensitive image. The tip end position of the M toner image formed on the body drum 9b matches at the second transfer point Tb, and the Bk toner image on the intermediate transfer belt 19 is applied by applying the bias from the second transfer bias roller 20b. The M toner image on the second photoconductor drum 9b can be superposed and transferred onto the upper surface in an aligned state.

Further, from the first transfer point Ta to the second transfer point Tb
Up to the distance Lb (transport distance of the Bk toner image by the transfer belt) is set to a length equal to the circumference of the intermediate transfer belt driving roller 21-1. Therefore, due to the eccentricity of the intermediate transfer belt driving roller 21-1, the first transfer point T
Even if the transfer position is slightly displaced due to the fluctuation of the roller speed during the transfer in the step a, the intermediate transfer belt drive roller 21-
Since 1 rotates once to reach the next second transfer point Tb, the speed fluctuation of the intermediate transfer belt driving roller 21-1 occurs at the second transfer point Tb as substantially the same fluctuation. As a result, the M toner image is transferred to the Bk toner
Overprinting can be performed without misalignment. This point will be described later in detail with reference to FIG.

Next, in this embodiment, when the distance between the second transfer point Tb and the first transfer point Ta (the distance in the rotational direction of the intermediate transfer belt 19) is Ld, Ld = La. Is set to. Further, as described above, Lc = La +
Lb. Therefore, when the front end of the Bk toner image on the intermediate transfer belt and the front end of the M toner image on the second photoconductor drum 9b simultaneously reach the second transfer point Tb, the first photoconductor drum 9a by the first writing unit 8a. At the same time when the writing for forming the cyan image into the
When the writing unit 8b starts writing on the second photoconductor drum 9b for forming a yellow image, the toner images of the third color (C) and the fourth color (Y) are transferred to the transfer positions Ta and Tb, respectively. Can be overlaid and transferred onto the belt in an aligned state. If this is described in detail, Bk toner image and M
At the timing when the superimposed image with the toner image reaches the first transfer position Ta after being conveyed the distance Ld by the intermediate transfer belt 19, the latent image formed by the first writing unit 8a is developed by the developing device 15 and C This coincides with the timing at which the toner image is formed and reaches the first transfer position Ta. Further, the latent image formed by the second writing unit 8b is developed by the developing device 17 and becomes a Y toner image at the second transfer position Tb at the timing when the superimposed image of the Bk toner image and the M toner image is generated. , The timing from when the C toner images are superposed at the first transfer position Ta starting from the second transfer position Tb to when the C toner images are conveyed by the intermediate transfer belt 19 and reach the second transfer position Tb. Therefore, the writing timing of the image data of the third color and the fourth color can be set earlier, and the image forming speed can be increased.

In this manner, the Bk, C, M, and Y toner images are sequentially aligned on the same surface of the belt to form a 4-color superposed belt transfer image, and the front end of the image is a paper transfer roller. 23
Before reaching, the sheet transfer roller 23 is brought into contact with the intermediate transfer belt 19 by the contacting / separating mechanism, and the transfer sheet is conveyed all at once by the transfer sheet conveying roller 26. Then, the transferred transfer paper is conveyed to the fixing device 25 by the conveyor belt 24, and the toner is fixed on the transfer paper by the fixing device 25. At the same time, after the intermediate transfer belt 19 is separated from the photosensitive drums 9a and 9b, the belt cleaner 22 is attached to the intermediate transfer belt 19.
Are contacted with each other to clean the intermediate transfer belt, and the photoconductor drums 9a and 9b are also attached to the photoconductor cleaners 10a and 10b.
To clean for at least one lap. Then, the cleaners are separated from each other.

Next, the case of forming an image of a single black color by the apparatus of the present invention will be described. For example, when the black monochromatic image forming mode is selected, the first photoconductor drum 9a and the intermediate transfer belt 19 start rotating before writing is started,
At a predetermined timing, the photoconductor cleaner 10a and the intermediate transfer belt cleaner 22 are brought into contact with the photoconductor drum 9a and the intermediate transfer belt 19 by a contacting / separating mechanism (not shown),
Start cleaning. Furthermore, after a predetermined timing,
The contact / separation mechanism (not shown) brings the intermediate transfer belt 19 rotating at a constant speed into contact with the first photosensitive drum 9a. At this time, the intermediate transfer belt 19 is separated from the second photosensitive drum 9b. Next, the first charger 12
Writing of black image data is started by the first writing unit 8a on the first photoconductor drum 9a that has been uniformly charged by a, and a Bk latent image is formed on the first photoconductor drum 9a. At this time, the second charger 12b that uniformly charges the second photoconductor drum 9b is in the inoperative state, and the second writing unit 8b does not perform the writing operation. The second photoconductor cleaning unit 10b of the second photoconductor drum 9b is in the separated state.

In order to enable development from the tip of the Bk latent image on the first photosensitive drum 9a, the Bk developing device 14 is ready to be developed before the latent image tip reaches the developing position of the Bk developing device 14. Then, the Bk latent image is developed with a Bk toner.
After that, the developing operation of the Bk latent image area is continued,
When the trailing edge of the latent image passes the Bk developing position, the developing device is put in a non-developable state. By further rotating the first photosensitive drum 9a, the Bk toner image is conveyed to the first transfer point Ta, and this toner image is transferred to the surface of the intermediate transfer belt 19 which is in contact with the first photosensitive drum 9a. To do. This belt transfer is performed by applying a predetermined bias voltage to the second transfer bias roller 20a. Then, the Bk toner image transferred to the intermediate transfer belt 19 is transferred to the intermediate transfer belt 19.
Is conveyed to the second transfer point Tb by traveling in the direction of the arrow, the charger 12b arranged near the photoconductor drum 9b uniformly charges the photoconductor drum 9b, but the second writing unit 10b is Do not write. Moreover, M
The developing device 16 and the Y developing device are kept in an inoperative state, and no image is formed on the photosensitive drum 9b. Further, since an image is not formed on the photoconductor drum 9b, the photoconductor clear
The unifying unit 10b is separated from the photosensitive drum 9b by a contact / separation mechanism (not shown).

Further, since the intermediate transfer belt 19 is also separated from the second photosensitive drum 9b, the Bk toner on the intermediate transfer belt 19 from the second photosensitive drum 9b side.
There is no overlapping transfer to the image, the image is formed only by the Bk toner, and the paper transfer roller 23 is attached to the intermediate transfer belt by the contact / separation mechanism before the image front end reaches the paper transfer point. The Bk toner image is transferred onto the transfer paper which is brought into contact with and transferred by the transfer paper transfer roller 26. After that, the transfer paper is conveyed to the fixing device 25 by the conveyor belt 24, and the toner is fixed on the transfer paper by the fixing device 25. After the belt transfer, the photoconductor drum 9
After separating the intermediate transfer belt 19 from a, the belt cleaner 22 is brought into contact with the intermediate transfer belt 19 to clean the intermediate transfer belt. In addition, the second photosensitive drum 9b
The second photoconductor cleaning unit is brought into contact with and the second photoconductor drum 9b is cleaned at least once. This is a cleaning for removing the toner because the toner floating in the machine adheres to the unused second photosensitive drum 9b.

FIG. 4 is a diagram showing a speed fluctuation pattern. FIG. 4 shows the outer diameter of the first photosensitive drum 9a, the outer diameter of the second photosensitive drum 9b, and the driving of the intermediate transfer belt 19. The relative ratio of the outer diameter of the roller 21-1 to the outer diameter of the drive gear (driving member) 9A that drives the first photosensitive drum 9a and the drive gear (drive) that drives the second photosensitive drum 9b. Member) 9B outer diameter dimension and intermediate transfer belt drive roller 21
The relative ratio to the outer diameter of the drive gear (driving member) 21-1A for driving -1 is set to be the same, and the circumference of the first photosensitive drum 9a and the circumference of the second photosensitive drum 9b ( When the same circumference is set to an integral multiple of the circumference of the driving roller 21-1 of the intermediate transfer belt, speed fluctuation patterns due to the respective eccentricities are shown. In this embodiment, the ratio between the outer diameter of the photoconductor (photosensitive gear) and the outer diameter of the transfer belt driving roller (driving roller gear) is set to 4: 1. Here, from the start of the first writing (Bk latent image writing and M latent image writing) of the first writing and the second writing when copying the first sheet, the second writing (C latent image writing and Y latent image writing) is performed. Writing is started as the first cycle, and the time from the start of the second writing to the start of the first writing of the second copy is the second cycle.

As is apparent from FIG. 4, after the start of the first writing on the first photosensitive drum 9a in the first cycle,
After the start of the second writing on the second photoconductor drum 9b, the speed fluctuation pattern of each photoconductor and after the start of the first writing on the first photoconductor drum 9a in the second cycle,
The speed variation patterns of the respective photoconductors after the second writing to the second photoconductor drum 9b is started are substantially the same.
In addition, the first transfer point Ta and the second transfer point T in the first cycle
The speed fluctuation patterns due to the eccentricities of the photoconductor drums 9a and 9b and the transfer belt driving roller 21 from the start of the transfer in b are the transfer in the first transfer Ta and the second transfer Tb in the second cycle. The photoconductor drum 9a from the start,
9b and the transfer belt drive roller 21 are substantially coincident with the respective speed fluctuation patterns due to eccentricity. Therefore, even if there is a speed fluctuation due to eccentricity, it is possible to prevent color misregistration (effect corresponding to claim 1).

Next, when the image forming mode for a plurality of black monochromatic originals is selected, the two originals 3-1 and 3-2 are colored.
When the copying operation is started by setting the scanner glass 1 on the contact glass 3-2 side by side, the photosensitive drums 9a, 9a
b and the intermediate transfer belt 19 start rotating before the start of writing, and the photoconductor cleaners 10a, 10
b and the intermediate transfer belt cleaner 22 by the contacting / separating mechanism (not shown), the photosensitive drums 9a and 9b and the intermediate transfer belt 1
Contact 9 respectively to start cleaning. After a lapse of a predetermined timing, the intermediate transfer belt 19 is brought into contact with the photosensitive drums 9a and 9b by a contact / separation mechanism (not shown). Next, the photosensitive drums 9a and 9b are charged by the chargers 12a and 12
It is uniformly charged by b. And the color scanner 1
Then, the reading of the original 3-1 is started at a predetermined timing, and the optical writing / latent image formation by the first writing unit 8a is started based on the image data obtained by reading the original. The first writing unit 8a forms a Bk latent image on the first photoconductor drum 9a, and the latent image tip portion reaches the developing position of the Bk developing device 14 in order to develop from the tip portion of the Bk latent image. Before that, the Bk developing device 14 is made ready for development and the Bk latent image is developed by the Bk toner. Since then
Although the developing operation of the Bk latent image area is continued, the developing device is set to the non-developable state when the rear end of the Bk latent image passes the Bk developing position.

The formed image corresponding to the original 3-1 is formed as a Bk toner image on the first photosensitive drum 9a,
At the transfer point Ta, the image is transferred to the intermediate transfer belt 19 by the first belt transfer bias roller 20a. Then, the sheet is conveyed to the second transfer point Tb as it is, but the second intermediate transfer bias roller 20b is in the inoperative state, and the second transfer point Tb is kept as it is.
It is conveyed to the paper transfer point through b. Then, before the leading edge of the image reaches the paper transfer point, the paper transfer roller 23 is brought into contact with the intermediate transfer belt by the contact / separation mechanism, and the transfer paper transport roller 26.
The Bk toner image (formed image of the original 3-1) is transferred onto the transfer paper conveyed by. Color scanner-1 is the original 3-
When scanning 1 is completed, the originals 3 placed next to it
-2, but the image memory is not used as much as possible. Therefore, after the trailing edge of the toner image of the original 3-1 formed on the first photoconductor 9a has completely passed the second transfer point Tb, the second
The reading of the original 3-2 is started so that the front end of the toner image of the original 3-2 formed on the photosensitive drum 9b reaches the second transfer point Tb. In this way, the second writing unit 8b delays the second photosensitive drum 9 at the timing delayed by the predetermined time.
On B, a Bk latent image corresponding to the image of the original 3-2 is formed. In order to develop from the tip of this Bk latent image, the second B
Before the front end of the Bk latent image reaches the developing position of the k developing device 27, the second Bk developing device 27 is made ready for development and the Bk latent image is developed by the Bk toner. After that, B corresponding to the manuscript 3-2
The developing operation of the k latent image area is continued, but the rear end of the Bk latent image is B
k When the developing position is passed, the developing device is put in the undeveloped state.

When the trailing edge of the image of the original document 3-1 formed by the Bk toner image passes the second transfer point Tb, the second belt transfer bias roller 20b is activated and the second photosensitive drum 9b is placed on the second photosensitive drum 9b. Then, the front edge of the image of the original document 3-2 developed by the Bk toner is conveyed. Then, it is transferred onto the intermediate transfer belt 19 by the second belt transfer bias roller 20b. Thereafter, each image formed on the two transfer sheets is conveyed to the fixing device 25 by the conveying belt 24, and the toner is fixed on the transfer sheet by the fixing device 25. At the same time, the photosensitive drums 9a, 9
After the intermediate transfer belt 19 is separated from b, the belt cleaner 22 is brought into contact with the intermediate transfer belt 19 so that the intermediate transfer belt is also held and the photosensitive drums 9a and 9b are also connected to the photosensitive cleaner 10.
Clean by at least one round with a and 10b.
Then, the cleaners are separated from each other. In the above description, two black monochromatic originals have been described, but it goes without saying that an image can be similarly formed with other monochromatic colors.

As described above, in this embodiment, the electrostatic latent images corresponding to the respective image information of a plurality of originals or the plurality of image information obtained by dividing the image information of a single original are respectively different electrostatic latent images. An image is formed on the carrier. In other words, a single-color original or a single-color image signal is divided into respective electrostatic latent image carriers to form an image, whereby a single-color image can be formed quickly. Further, when the image information obtained by reading the plurality of originals is image-formed on different electrostatic latent image carriers, the reading timing of each original is made different.
That is, by changing the reading timing of the original when forming an image by dividing each electrostatic latent image carrier, it is possible to form a single color image quickly and it is not necessary to mount an extra memory.

[0024]

As described above, according to the first aspect of the invention, the outer diameter of the first electrostatic latent image carrier, the outer diameter of the second electrostatic latent image carrier, and the outer diameter of the drive roller of the intermediate transfer member are set. Relative ratio, the outer diameter of the drive member that drives the first electrostatic latent image carrier, the outer diameter of the drive member that drives the second electrostatic latent image carrier, and the drive that drives the drive roller of the transfer member. The relative ratio of the outer diameters of the members is the same, and the peripheral length of the first electrostatic latent image carrier and the peripheral length of the second electrostatic latent image carrier are respectively set to the drive roller peripheral length of the intermediate transfer member. Since it is an integral multiple of, the speed fluctuation patterns that occur when writing each color and when transferring each color due to the eccentricity of each photoconductor, the eccentricity of the belt drive roller, and the eccentricity of each drive system gear Since they can be matched at all times, positional deviation can be prevented. According to the second aspect of the present invention, since each of the plurality of electrostatic latent image bearing members is provided with at least one black developing device, a black monochromatic image can be formed quickly. According to a third aspect of the present invention, each electrostatic latent image corresponding to each image information of a plurality of originals or a plurality of image information obtained by dividing the image information of one original is provided on different electrostatic latent image carriers. Form an image. In other words, a single-color original or a single-color image signal is divided into respective electrostatic latent image carriers to form an image, whereby a single-color image can be formed quickly. According to the fourth aspect of the invention, when the image information of each of the plurality of originals read is image-formed on different electrostatic latent image carriers, the reading timing of each original is different. That is, when the image is formed by dividing the electrostatic latent image carrier into each, the single-color image formation can be speeded up by changing the reading timing of the document, and it is not necessary to mount an extra memory.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram of writing and transfer position relationship of the color image forming apparatus of FIG.

FIG. 3 is an explanatory diagram of a drive system of the color image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a speed fluctuation pattern of the color image forming apparatus of the present invention.
FIG.

FIG. 5 is an explanatory view of a conventional example.

[Explanation of symbols]

1 color image reading device (color scanner), 2
Color image recording device (color printer), 3 originals, 4 illumination lamps, 5 mirror groups, 6 lenses, 7
Photoelectric conversion element (eg CCD), 8a first writing optical unit, 8b second writing optical unit, 9a
1st photoconductor, 9b 2nd photoconductor, 10a 1st photoconductor cleaning unit, 10b 2nd photoconductor cleaning unit, 11a 1st static elimination lamp, 11b 2nd
Charge eliminating lamp, 12a first charger, 12b second charger, 13a first potential sensor-, 13b second potential sensor-, 14 Black (Bk) developing device, 15C
yan (C) developing device, 16 Magenta (M) developing device, 17 Yellow (Y) developing device, 18a first development density pattern detector, 18b second development density pattern detector, 19 intermediate transfer belt, 20a First belt transfer bias roller, 20b Second belt transfer bias roller, 21-1 Belt drive roller, 21-2 Belt driven roller, 22a Belt cleaning unit, 22b Belt cleaning unit , 23 paper transfer bias roller, 24 transfer transport belt, 25
Fixing device, 26 transport roller, 27 second Blac
k developing device

Claims (4)

[Claims] 1. A first and second electrostatic latent image carrier, a writing unit arranged on each latent image carrier for writing image information on each latent image carrier, and each electrostatic latent image carrier. A plurality of developing devices for developing the above electrostatic latent images with toners of different colors, and a pair of static toners for successively receiving toners of different colors on the electrostatic latent image carrier to carry toner images. An intermediate transfer member disposed in contact with and separated from the electrostatic latent image carrier, a drive roller for stretching the intermediate transfer member endlessly, and a toner image from the electrostatic latent image carrier to the intermediate transfer member. In an image forming apparatus having a plurality of belt transfer devices for transferring, and a paper transfer device for transferring a toner image from an intermediate transfer member to a transfer paper, an outer diameter of a first electrostatic latent image carrier and a second electrostatic latent image carrier. The relative ratio between the outer diameter of the latent image carrier and the outer diameter of the drive roller of the intermediate transfer member, and the drive member for driving the first electrostatic latent image carrier. Diameter and the relative ratio of the outer diameter of the drive member that drives the second electrostatic latent image carrier and the outer diameter of the drive member that drives the drive roller of the transfer member are the same, and the first electrostatic latent image An image forming apparatus characterized in that the circumference of the carrier and the circumference of the second electrostatic latent image carrier are each an integral multiple of the circumference of the driving roller of the intermediate transfer member. 2. The image forming apparatus according to claim 1, wherein each of the plurality of electrostatic latent image bearing members is provided with at least one black developing device. 3. An electrostatic latent image corresponding to a plurality of image information of a plurality of originals or a plurality of image information obtained by dividing the image information of one original is formed on different electrostatic latent image carriers. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: 4. When the image information of each of the plurality of originals read is image-formed on different electrostatic latent image carriers, the reading timing of each original is different. 3. The image forming apparatus according to item 3.