JPS6183557A - Multi-color image forming device - Google Patents

Abstract

PURPOSE:To prevent the deviation of plural colors of developed images on a transfer means by determining the peripheral length of the transfer means at the integer times of a photosensitive body thereby taking the correspondence between one point on the photosensitive body and the plural points at the peripheral length of the transfer means. CONSTITUTION:A drum 1 is electrostatically charged by a primary electrostatic charger and is subjected to slit exposing of the image irradiated by an illuminating lamp 6 in an exposing part 13. The electrostatic latent image on the drum 1 is developed by a rotary developing device 15. Transfer paper 181 is gripped by a gripper and is conveyed while the paper is wound on a transfer drum 22 by means of an electrostatic charger 25 for attraction and a press roller 26. The toner image on the photosensitive body 1 is trnsferred on said paper while the paper passes through the space between a corona charger 27 for transfer and the photosensitive body 1. The peripheral length of the transfer drum 22 is made integer times the length of the drum 1. The transfer material is fed to fixing roller pair 32, 33 upon completion of the transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field] The present invention relates to a multicolor image forming apparatus that uses electrophotography to obtain multicolor images.

[Prior art]

Generally, to obtain a multicolor image (hereinafter referred to as a color image), the original to be obtained is separated into each color component (yellow, magenta, cyan, and black in the case of full color), and each image is placed on a single direct image support. Transfer it to the body (hereinafter referred to as transfer paper) and color li! ii Obtain an image. Therefore, when obtaining a color image using electrophotography, it is necessary to use a latent image forming means that separates the original into each color component and guides them to a photoreceptor to form a static image. A multicolor image developing means and transfer means are required to visualize the image on the photoreceptor, and a transfer means for holding the paper and transferring each color image on the photoreceptor.

The latent image forming means includes means for color separating the original (for example, blue, green, and red filters in the case of pull-color reproduction) attached to the optical path system, and the photosensitive characteristics of the photoreceptor used,
A desired latent image can be formed by changing the electrostatic latent image forming conditions for each color depending on the development characteristics of the developer for each color. However, since the multicolor developing means and transfer means are means unique to a color image forming apparatus, how these means are configured and controlled has a bearing on the functionality and performance of the apparatus.

Regarding multicolor developing means, conventional developing devices are compatible with latent images of each color (for example, in the case of full color reproduction, yellow for a blue latent image, magenta for a green latent image, and cyan for a red latent image). Everything around the photoreceptor was attached, and each developing device was activated in response to each latent image to visualize the latent image. However, in this method, since all the developing devices are located around the photoreceptor, it is necessary to make the circumference of the photoreceptor extremely long.
When the photoreceptor is in the form of a drum, the outer diameter of the photoreceptor must be set to a diameter that allows four or three developing devices to be placed around the photoreceptor drum (for example, a diameter of 200 mm or more), which is a factor that hinders miniaturization of the device. It had become.

In addition, since the position where the optical image separated by one color is irradiated on the photoreceptor and the position where each color is developed are different, the development start time for each color may be different, and the time decay of the latent image obtained for each color may be different. When different, there are factors that complicate the control of the entire device.

Regarding the transfer means, in order to hold the transfer paper, the length of the transfer paper holding member, such as the length of the transfer drum, is required to be longer than the maximum length of the paper that can be copied by the apparatus. A3 size (2
97rxx x 420yo)
), the diameter of the transfer drum is 1'60, taking into consideration the rigidity of the paper leading edge holding part of the transfer drum, etc.
It has no choice but to be more than starch (420/π=133.7'). If you increase the diameter of the transfer drum (for example, about 200m) to allow for paper wrapping, the time required for one rotation of the transfer drum will increase compared to the speed at which latent image formation, development, and transfer can be performed stably. As a result, the time required for full-color image formation (the time for four or three rotations of the (transfer) drum) becomes longer, resulting in a reduction in copy speed. Due to the conditions, there are two drums (light drum and transfer drum) with a diameter of around 200 mm inside the color image forming apparatus, and four drums around one side.
Therefore, it becomes necessary to configure 1 or 3 developing units.

The transfer drum and photosensitive drum are usually connected to each other by direct or indirect iC mechanical drive transmission means (gears).

In order to prevent complication of the drive control unit, the units are connected by a chain, etc., and are driven by a single drive source, so that the moving units of the units coincide with each other.

At that time, there are problems specific to color image forming devices.
It is necessary that the images are not blurred and that there is no difference in hue when multiple copies are made. Therefore, JP 149-113635
As described in , the length of the photosensitive drum is an integral multiple of the circumference of the transfer drum, and the surface of the photosensitive drum on which the image is transferred in contact with the transfer paper is always the same surface on the photosensitive drum. The occurrence of misalignment and hue difference was suppressed. That is, since only a certain portion of the circumference of the photosensitive drum is always in contact with the transfer paper, the photosensitive drum always contacts the transfer paper at the same circumferential speed determined from the photosensitive drum surface during image transfer.

In this case, images of the same shape and different colors are transferred to the same position on the transfer paper on the transfer drum, and color misregistration does not occur.

Furthermore, the charging characteristics over the entire circumference of the photosensitive drum are not completely consistent due to the method of attaching the photosensitive member during manufacture of the photosensitive drum and the uniformity of the material of the photosensitive member. In the case of copying only one sheet, there is no problem even if the charging characteristics of the photoreceptor that forms each color image are different, but in the case of copying two or more sheets, if the charging characteristics of the photoreceptor that forms each color image are different, Colors using photoreceptors with different charging characteristics always appear emphasized or weaker than those of Ike, resulting in a difference in hue. If the photosensitive surfaces used for color image formation are always aligned, problems such as differences in hue will not occur during multiple exposures. Although the drive side legs are complicated, the drive of the photosensitive drum and photographic drum is completely separated, and the peripheral speed on each drum is controlled by using each μm effect source. If they match, it is possible to solve the color difference, but it is impossible to solve the hue difference. To give specific numerical values for the device, the outer diameter of the transfer drum was 1801, the photosensitive drum was twice as large as 360@11, and developing devices for each color were arranged around the photosensitive drum. However, in this configuration, the color image forming apparatus as a whole becomes very large because there are drums with diameters of 180 mm and 360 mm, and a group of developing units attached to the photosensitive drums.

〔the purpose〕

As described above, in a color image forming apparatus, when the photoreceptor and the transfer means are mechanically driven together, the apparatus itself has to become larger in order to take measures against color misregistration and hue difference. Therefore, it is possible to downsize the multicolor developing means and the photosensitive drum, which is a major factor in increasing the size of the device itself, and has the functions necessary for a color image forming device (no color shift and consistent hue). It is an object of the present invention to provide a device that guarantees the following.

In other words, by increasing the circumference of the transfer means by an integral number of the length of the photoreceptor, one point on the photoreceptor corresponds to multiple points on the transfer means, and the developed images of multiple colors can be printed on the transfer means without shifting. It is also designed so that no hue difference occurs.

〔Example〕

The present invention will be explained below using the figures.

:g1 Figure is a side view of a color image forming machine (hereinafter referred to as a color copying machine) using the water injection invention.

Reference numeral 1 denotes an electrophotographic photosensitive drum (hereinafter referred to as photosensitive drum) having a photosensitive layer (amorphous selenium, etc.) on its surface, which is rotatably supported by a shaft 2 and starts rotating in the direction of arrow 3 in response to a copy command.

When the drum 1 rotates to the normal position, the document 0 placed on the document table glass 4 is illuminated by an illumination lamp 6 that is integrated with the first scanning mirror 5, and the reflected light is transmitted to the second scanning mirror 7. , and are scanned by the third scanning mirror 8.

The second scanning mirror 7 integrated with the J1 scanning mirror 5
The third scanning mirror 8 moves at a speed ratio of 1:%, thereby scanning the document while keeping the optical path length between the document O and the lens 9 constant. The reflected light image passes through the lens 9, passes through the fourth mirror 10, is color-separated by a one-color separation filter 11, passes through a dustproof sealing glass 12, and is imaged onto the drum 1 by the exposure section 13.

The drum 1 is charged (for example, positively) by a primary charger, and the image irradiated by the illumination lamp 6 is slit-exposed in the exposure section 13.

The above operations are performed according to the color separation filter 11, and static aperture images of each color are obtained on the drum. Electrostatic a on drum 1
The image is visualized as a toner image by a rotating imager 15. The rotary developing device 15 has a developing position 1 on the drum 1.
At step 6, the developing devices of all colors come into contact to perform visualization. The rotary developing device 15 has yellow 151. Magenta 152. Cyan 153. and black 154, corresponding to the filters used in the color separation filter 11,
The developing device for the desired color is located at the developing position 16 on the drum 1 at the arrow 1.
It can be rotated in the 50-degree direction and approached.

The transfer material 181 in the cassette 171 is transferred to the paper feed roller 191
The second register roller 21 takes the approximate timing, and then the second register roller 21 takes the exact timing. Then, the transfer material is transferred to the grip position 39 via the conveyance guide 38.
The tip thereof is gripped by the gripper 24 of the transfer drum 22. In addition, at the grip position 39, the gripper 24
The gripper cam 23 in the transfer drum 22 opens from the transfer drum 22. Transfer paper 181
is gripped by a gripper 24 and conveyed while being wrapped around the transfer drum 22 by an adsorption charger 25 and a presser roller 26, and transferred to a transfer corona charger 27 and a photosensitive drum 1.
While passing through the photosensitive drum 1, the toner image on the photosensitive drum 1 is transferred. The transfer drum 22 grips the transfer paper 18 with a gripper 24.
While holding the tip of 1, it is rotated by the required number of rotations, and the colored image is transferred the required number of times.

The copying machine shown in the figure is equipped with two cassettes loaded with transfer paper of different sizes and types, and is configured to feed paper in a selective manner from each cassette.
71 can also be applied to the lower cassette 171, so the same dotted symbols are used for common members.

After the transfer is completed, the transfer paper 181 is moved by operating the gripper cam 28 to open the gripper 24, and moving the transfer paper 181 to the separation guide 2.
9, the transfer drum 22 is moved at the separation position 40.
The paper is separated from the paper and guided to the conveyor belt 31. Note that the charger 36 is a device for removing electric charge from the image on the separated transfer material.

The transfer material sent to the conveyor belt 31 is transferred to a pair of fixing rollers 32
．． 33 fixes and develops color by applying pressure and heating, and then discharges it to a tray 34. Further, the photosensitive drum 1 after the transfer is charged with charge remaining after the transfer by a charge removal charger 35, and its surface is cleaned by a cleaning device 37 composed of an elastic blade, and the process proceeds to the next cycle. It has become.

FIG. 2 is an external view of the rotary developing device 15, which is a multicolor developing means used in the color copying machine shown in FIG.

The rotary developing device 15 is composed of developing devices 151, 152, 153, and 154 each having a developer of four colors, and a rotating body 155 on which these developing devices are mounted. Each developing device is inserted and fixed into a rotating body 155 from the direction of the person in the figure. A rotary gear 156 is fixed to one side of the rotary body 155, and the rotary drive gear 4 is attached to the output shaft of the rotary drive motor 42.
1 and 1 are interlocked. The rotating body 155 is rotated by operating the rotary drive motor. The reason why the rotary cooperative motor is provided is that the effects of torque fluctuations and the like due to rotational drive are not transmitted to the drive of the photosensitive drum 1. Also, rotating body 1
A position 1a detection plate 157 is fixed to 55, and the position of the rotating body is detected by a group of sensors 48 fixed at various positions on the main body of the device (some of which are shown in FIG. 2). ing). A fixed plate 158 is fixed outside the rotating gear 156 in correspondence with each phenomenon, and rA 1 on the fixed plate is fixed.
The pin 43-a of the fixed arm 43 enters into the pin 58-a and fixes the rotating body 155. Note that the movement of the fixed arm 43 is controlled by a plunger 44. In FIG. 2, only a part of the fixing plate is shown.

The developing device has rollers 131-C at both ends of the developing sleeve 151-b to determine the distance from the photosensitive drum, and an input gear 151-C for driving the inside of the developing device, such as a conveying screw and rotation of the developing sleeve. A has a partially protruding shape. Note that this configuration is the same for all other developing devices.

In Figure 2, the pond developing device is omitted. On the main body side of the apparatus, there is a developing and driving force transmission means for transmitting driving force to the developing unit. One developing and driving force transmitting means is located at a position where driving force is transmitted only when the developing device approaches the photosensitive drum 1. Input gear 1
The drive gear 45Fi that meshes with the drive gear 51-a and the output from the motor 47 are transmitted through a pulley 46, and are installed on a swingable arm.

FIG. 3 shows a cross section of a conventional color copying machine. 49 is a photosensitive drum that rotates in the direction of the arrow. Reference numeral 50 indicates a multicolor developing means, and 501 to 504 are developing devices for each color. Since the imager is fixed around the photosensitive drum 49, a range B is required on the photosensitive drum 49. We believe that it is sufficient to create a photosensitive drum whose circumference is the length of the part where the developing device is installed (range B) and the part where other functional means (cleaning, charging exposure, etc.) are installed. However, as described in Japanese Patent Application Laid-open No. 49-113635, color copying machines have a unique problem of color misregistration, so the circumference of the photosensitive drum should be changed to a transfer drum with a diameter of at least 160 m+. It has no choice but to be an integral multiple of the circumference (double in Figure 3). This is a factor in increasing the size of the photosensitive drum. Increasing the size of the photosensitive drum is not only a problem in the structure of the device, but also poses the following problems. 1. Because the photosensitive drum is large, it is very difficult to manufacture the photosensitive drum pace. The photoconductor also has no choice but to be attached in sheet form to the photoconductor drum plate. For this reason, the photosensitive drum itself becomes expensive, and at the same time, the elastic blade of the cleaning device constantly scrapes the next undulation, causing the IJ to become more expensive.
It also affects the durability of the weighing device. Third, if a large drum is used, problems arise in that it is heavy and bulky during maintenance such as replacing the photosensitive drum. Second, when using a sheet-like photoreceptor, the image surface on the photoreceptor drum must be aligned with the transfer paper surface of the transfer drum. Therefore, after separating the photosensitive drum and the transfer drum with a paper jam or the like, when bringing them into contact again, it is necessary to check the condition each time, which is very inconvenient for operation. Further, since the distance from the page document image exposure position 51 to each developing device is different, the electrostatic latent image on the photosensitive drum changes from the exposure position until it is developed. Therefore, it was necessary to change the developing conditions for each developing device (applied zero pressure) and the electrostatic latent image forming conditions for each color (-substituent pressure, illumination light intensity, etc.), which was extremely disadvantageous in terms of device control. .

Returning to FIG. 1, in the present invention, since a rotary developing device is used as the multicolor developing means, the above-mentioned control problem does not occur. In addition, since the portion of the photosensitive drum related to development is limited, the photosensitive drum 49 shown in FIG.
On the periphery of the photosensitive drum, the portions without functional means indicated by C, D, and H can be omitted as long as the configuration does not cause color misregistration, making it possible to downsize the photosensitive drum. Here, we will specifically mention the miniaturization of photosensitive drums. By making photosensitive drums smaller, relatively expensive photosensitive drums can be manufactured in large quantities by means such as dipping or sputtering. A photosensitive drum without seams can be obtained, and a seamless photosensitive drum can be used.
When bringing the two drums into contact again, it is possible to bring the transfer drum into contact with the photosensitive drum at any position. In other words, when actually accessing the device, operability is improved in terms of maintenance as well.

FIG. 4 is a diagram showing the relationship between the photosensitive drum and transfer drum of the present invention and their drive system, which takes measures against color-specific problems (color misregistration, hue). Transfer drum 22
The center is cut off except for the part where the gripper 24 is arranged, and the suction sheet 21 is pasted on the surface. Inside the transfer drum 22, there are a transfer charger 279, a separate gripper cam, and a transfer drum support roller 22.

The transfer charger 27 is mounted in a direction in which the portion in contact with the photosensitive drum 1 is oriented to generate corona discharge. Bunnan gripper cam 2
8th, fu is set in the vicinity of the low rank fiffi. In the separation gripper cam, cam rollers 281 of the same number as the number of grippers 24 are rotatably fixed to the gripper@285.

The gripper shaft 285 is always pushed in a fixed direction by the gripper spring 282, and the plunger 284 is actuated to move the gripper shaft 2ss, and the gripper cam roller 281 is integrated with the gripper 24. cam 24
1 to open the gripper 24.

This state is shown in FIGS. 5 and 6.

241 is a gripper cam, 242 is a rotation center axis of the gripper, and 243 is a gripper piece.

As the gripper cam 241 rides on the gripper cam roller 281 and follows the gripper cam roller 281, the gripper 24 opens around the shaft 242, and the gripper cam roller 281 rotates around the gripper shaft.

Although FIG. 4 only shows the separation gripper cam, the paper feed gripper cam 2 with the same mechanism is also shown at the paper feed position.
3 is installed.

The transfer drum support rollers 222 are paired to support the transfer drum 22.
They enter the inner groove 228 while being subjected to repulsive force against each other by the action of opposing springs 2240.

FIG. 7 shows the supported state. Although the transfer drum support rollers 222 are omitted from - in FIG. 4, they are installed on one side of the opening of the transfer drum 22 at at least three locations on the circumference of the transfer drum 22 from the photosensitive drum gear la.
A transfer gear 227 for obtaining drive, and a detection element 226 for detecting the position of the transfer drum are fixed to a separate member from the transfer drum, and a detection piece 225 is formed as a part of the transfer drum 22. has been done.

The photosensitive drum gear la is driven by a drive gear 53. The drive gear 53 connects the output of the drum drive motor 59 to the pulley 57. Drive pulley 5 by belt 58
It is driven by transmitting the signal to 6. The drive shaft 60 has a reference pulse generation plate 54, and the detection element 55 is connected to the pulse plate 5.
4, a reference pulse for controlling the transfer drum is obtained.

A drive transmission control means for controlling the reciprocating motion of the illumination system, which is described in Japanese Unexamined Patent Publication No. 49-113635, is meshed with a gear on the drive shaft 60 (not shown).

In the present invention, the circumference of the transfer drum is 2 times the length of the photosensitive drum.
In other words, it is an integer multiple. This is because an image of each color is formed on the photosensitive drum for all the photosensitive drums so that the contacting surfaces always match. The above configuration aims to suppress the occurrence of color shift and hue difference, which are problems specific to color. The reasons for solving each problem are as described below.

First, color misregistration will be explained. Normally, pitch errors always occur when manufacturing gears. Pitch error is the degree to which one tooth of a gear is longer or shorter on the pitch circumference from the standard tooth profile. If a gear with a pitch error is driven by a pond gear, the pitch error will directly appear as a change in peripheral speed on the pitch circle. In other words, the photosensitive drum gear l-a is driven by the driving gear 53, and due to the pitch error during rotation, the photosensitive drum gear l-a
The circumferential speed on the pitch circle of -a changes depending on the location. Therefore, in the portion of the transfer drum gear 227 that meshes with the photosensitive drum gear l-a, the peripheral speed changes along the curve shown in FIG. 8B. Photosensitive drum 1. Since the transfer drum 22 is integrated with each photosensitive drum gear 227, the image on the photosensitive drum is transferred to the transfer paper on the transfer drum at the peripheral speed shown in FIG. 8. The change in l′i will cause the image to expand or shrink on the image. 9th
As shown in the figure and FIG. 10, there is no problem in the above state when the transfer is performed only once, but since the transfer is performed three or four times during color image formation, the photosensitive drum 1 at each time of transfer is It is absolutely necessary to match the changes in circumferential speed.

Since the transfer drum holds the transfer paper on its circumference, the photosensitive drum always rotates an integral number of times during one rotation of the transfer drum, and one rotation of the transfer drum; It is sufficient to set the surfaces to the same K so that the circumferential speed changes are the same. FIG. 11 shows the state of the contact portion between the transfer drum and the photosensitive drum. What matters at the photosensitive drum is the rotational speed of the photosensitive drum and changes in the circumferential speed of the transfer drum contact portion. The transfer drum section shows the number of rotations of the transfer drum and the state of image transfer for each color.

As is clear from the diagram, each color (Y, -'v■,
, C9B K ), the peripheral speeds of the three optical drums are completely consistent during image transfer. Note that the figure shows an example in which the circumferential length of the transfer drum is twice the circumferential length of the photosensitive drum.

FIG. 12 shows an example in which the transfer drum circumference is seven times the photosensitive drum circumference. The manner in which the circumferential speed of the photosensitive drum that comes into contact during image transfer for each color changes is completely different for each color, and the purpose of preventing color misregistration cannot be achieved.

Next, the hue difference will be explained. , it is possible to completely match the charging characteristics of the photoreceptor on the photosensitive drum over the entire circumference.
This is extremely difficult in terms of manufacturing the photosensitive drum. Even if a product with matching charging characteristics is created, the temperature around the photosensitive drum will depend on the environment in which the device is used (low temperature, high humidity, continuous copying).

Due to humidity changes, it is impossible for the band characteristics etc. around the entire circumference of the photosensitive drum to change in the same way. In other words, it is unrealistic to expect to obtain the same charging characteristics on the photosensitive drum.

Now, let us assume that the charging characteristics of two arbitrary particles on the photosensitive drum are shown by curves A and B in FIG. Can you get a high potential and get the developer? Suppose it's sweet. In the case of normal one-time transfer, even if a plurality of copies are made using a photoconductor having a charging characteristic of λ or B, the difference in ΔV does not seem so strange. However, there are 11 colors! ii When forming an image, each color (Y, M
, C, BK) All image formation is performed in areas having the characteristics of A, and each color surface image is formed on the second sheet using the characteristics of B for Y and the area having the characteristics of A.', then 2 Although the first image is the same as the first, it has a strong yellow tinge, and there is a difference in hue between the first and second images, giving it a great sense of discomfort and color. In other words, it is desirable that the charging characteristics of the photoreceptors used for each color image be the same, or in other words, that the same portions of the circumference of the photoreceptor drum be used. FIG. 12 shows the rotation speeds and the portions used for image formation when the transfer drum circumference is twice the photosensitive drum circumference. Figure A13 shows each rotation speed and image forming surface when the transfer drum circumference is made seven times the +V light drum circumference. The ones in Figure 12 are Y and M.

Since the same surface on the photosensitive drum is always used for both C and BK, no difference in hue occurs between the first and second sheets. However, in FIG. 14, the image forming surfaces of sYtM, C, and BK are different for each sheet, and a hue difference occurs between the first sheet and the second sheet.

In the case of Fig. 13, method 1 is used to prevent the occurrence of hue difference.
After forming the image on the first sheet, there is a method of rotating the photosensitive drum and the transfer drum and waiting until the image can be formed in the same state as the first sheet. In the case of Figure 14, the diameter ratio is 15-8, so
The second image is formed at the 121st rotation of the photosensitive drum (=15X
8+1,120 is the greatest common divisor of 15:8). However, this is not practical because the time from the 7th rotation to the 120th rotation of the photosensitive drum is wasted and the copying speed of the apparatus is reduced.

In view of the above, by making the circumferential length of the transfer drum an integral multiple of the length of the photosensitive drum, color misregistration and hue difference, which are specific to color, can be solved. Next, the control of the rotational effector when the transfer drum diameter and the photosensitive drum diameter are set in the above-mentioned relationship will be described.

Assuming that the maximum scanning distance of the scanning optical system (first mirror 5, illumination lamp 6, second mirror 7, and third mirror 8) in FIG. It is slightly shorter than the circumference (referred to as l!). This is because the maximum scanning distance is equal to the maximum length of paper that can be wrapped around the transfer drum, and there is a portion of the gripper etc. on the circumference of the transfer drum. For this reason, when the length of the wire wrapped around the transfer drum is different, in other words, the size with a longer optical scanning distance (
For example, when the size is short (for example, A4),
The number of rotations of the transfer drum until the transfer is performed three times or four times is different.

FIG. 14 shows the relationship between the entire circumference of the transfer drum and the traveling distance. ea is the scanning distance when the size is long, /b
is the scanning distance when the size is short. Note that la', lb
′ is, in each case, from the transfer drum total length l, ea, l
! Indicates the remaining distance excluding b. When the scanning optical system scans la, the scanning optical system scans ea at a speed of V and returns at a predetermined return speed V'. If the return speed is set to Ja V's -T or higher, the scanning optical system will return to its original position during one rotation of the transfer drum, and the entire document can be scanned anew from the next rotation of the transfer drum. It is. However, the total length of the transfer drum is large enough to wrap around the maximum length and form part of the gripper, so % la/l
a becomes 5 or 6 or more. When V' is set to 5 times or more of V, when the scanning optical system returns very much, (in numerical terms l!a=420 (A3 length)/a'=160
Xπ-420#80) The shock of stopping becomes very large and is transmitted to the entire device, affecting the durability of the device 1 such as image blurring during image transfer. Therefore, even if a problem occurs in V, it does not affect anything else (V'=
By setting 3XV)K and making the transfer drum return until it rotates twice, images of each color can be transferred without affecting the durability of the device, such as one-stroke distortion.

Next, when the scanning optical system scans /b, lb/lb' is between 1 and 2, so v' is changed to l! Even if the speed is the same as in case a, the original position is 11t during one rotation of the transfer drum.
It is possible to return to That is, when scanning a distance of lb, the image on the photosensitive drum can be transferred to the transfer paper every time the transfer drum is rotated once.

As described above, in order for the transfer drum to transfer onto a long size paper, the transfer drum must rotate six or eight times, and for a short size, the transfer drum must rotate three or four times. Therefore, depending on the paper size used, the transfer drum may rotate once or twice.
By rotating the rotary developing device for a predetermined time for each rotation, the electrostatic latent images of each color formed on the photosensitive drum by the scanning optical system can be developed. For this purpose, means for detecting the rotation of the transfer drum and means for measuring time in synchronization with the rotations of the photosensitive drum and the transfer drum are required.

In the present invention, the section 225 and the detection element 226 in FIG. 4 serve as transfer drum rotation detection means, and the reference pulse generation plate 54 and detection element 55 serve as time measurement means.

To explain how the rotary developing device is operated, in FIG. 4, the drive motor 59 is operated and the detection element 55.226 is also operated at the same time.

After a certain period of time has elapsed since the transfer drum section 225 is detected by the detection element 226, in other words, by counting a certain number of pulses generated from the detection element 55, the plunger 44 is actuated, and the motor 41 receives the signal from the detection element 48. The rotary developing device is rotated by performing constant rotation while detecting it. After rotating the plunger 44. The motor 41 is stopped. continue,
The transfer drum continues to rotate, and the detection cable 226 is moved again.
When the section 225 is detected, the rotary developing device is rotated twice again after the same time has elapsed.

Repeat this operation twice. In the example just described, a short size paper is wound around the transfer drum that operates the rotary developing device every time the transfer drum is rotated, but in the case of a long size paper,
The detection element 226 detects the section 225 once during the first rotary developer operation and once during the second rotary developer operation. In other words, the rotary developing device is operated every 4 times when the copying drum is used. Note that the time (the number of pulses counted) from when the detection element 226 detects the section 225 to when the rotary developing device is rotated is the same for both long and short paper sizes. This is because the position of the tip of the 7 blades on the transfer drum is constant in both cases.After the rotary developing device is rotated, the developing motor 47 rotates the sleeve in the developing device for the size of the paper being used. This can be realized by operating for a time that is preset in the control circuit or by counting the pulses generated from the detection element 55.

Figures 15 and 16 show the control method described above. FIG. 15 shows the long size, and FIG. 16 shows the short size. Note that the operation of each rotary developing device is also shown. The mark at the transfer drum in the figure is the detection element 22.
6 is the time to detect the section 225. When configuring the actual device, by changing the position of the detection element 226,
Needless to say, the time required for operation of the rotary developing device changes.

In Figure 15, the rotating developing device was rotated once every two times the transfer drum. However, if the scanning optical system for forming an electrostatic latent image is a fixed scanning system using a laser or the like, the return time of the scanning optical system Since this restriction is eliminated, it goes without saying that image formation may be performed by rotating the rotary developing device for each rotation of the transfer drum.

〔effect〕

As described above, according to the present invention, color copying machines can be made more compact and easier than ever while using a small diameter seamless photosensitive drum that is difficult to use in conventional color copying machines using a rotating developer. Make it sexual,
Problems peculiar to color copying machines: 0 color misregistration, 'j: i number of hue differences during copying.

In the description of the present invention, a rotary developing device has been described as an example of a multicolor developing means, but any means capable of developing each color at a certain level on the photosensitive drum can be applied to the present invention. Moreover, regarding the color reason, it is also possible to use three colors. on the other hand,
In addition to photosensitive drums, the present invention is also effective for devices that use an ion flow control method or a method that forms a latent image on an insulating drum using needle-like electricity.

[Brief explanation of the drawing]

Fig. 1 is a side view of a color image forming apparatus to which the present invention is applied;
The figure is a side view of a conventional color image forming apparatus, FIG. 4 is a perspective view of the drive system of the photosensitive drum and transfer drum of the present invention, and FIG.
6 and 6 are side views showing the gripper rotating operation, FIG. 7 is a sectional view showing the support roller of the transfer drum, FIG. 8A is an explanatory view showing the relationship between the photosensitive drum, the transfer drum, and the drive gear, 8
Figure B is a graph showing changes in the circumferential speed of the photosensitive drum and the transfer drum, and Figures 9 and 10 are graphs showing changes in the circumferential speed of the photosensitive drum when the circumferential lengths of the photosensitive drum and transfer drum are changed. An explanatory diagram showing the relationship between the colors transferred to the transfer drum side. Figure 11 is a graph diagram showing the state of the contact area between the transfer drum and the photosensitive drum. Figure 12 is a graph showing the relationship between the colors transferred to the transfer drum side. 4
Explanatory diagram showing the occurrence of color shift in the case of /3 times, 1st
Figure 3 - Hanashi ↓ Heat is an explanatory diagram showing an example of solving a problem, Part 1
FIG. 4 is an explanatory diagram showing the relationship between the entire circumference of the transfer drum and the scanning distance, and FIGS. 15 and 16 are timing charts according to the control method of the present invention. In the figure, 1 is a photosensitive drum, 15 is a developing device, and 22 is a developing device.

Claims (2)

[Claims] (1) Repeating the process of forming a latent image corresponding to each color component on an image carrier, developing this latent image with a developer of each color corresponding to the color component, and transferring this developed image onto a transfer member. An apparatus for obtaining a multicolor image includes: a seamless image carrier that moves endlessly at a predetermined circumferential speed; a means for forming a latent image according to each color component on the endlessly moving image carrier; A multicolor developing means that can select to develop the electrostatic latent image of each color with a developer of each color at a predetermined position on the movable image carrier, and is integrated with the endless movable image carrier. A transfer material is supported in order to transfer each color developed image on the endless movable image carrier to a transfer body while being driven by an operating drive transmission member, and has a circumference that is an integral multiple of the circumference of the endless movable image carrier. 1. A multicolor image forming apparatus comprising: a transfer material supporting member or an image supporting member having a long length and moving endlessly at the same speed as the endlessly moving image bearing member. (2) In the multicolor image forming apparatus according to claim 1, the endlessly movable image carrier is moved within a drive means that provides drive to a drive transmission member integrated with the endlessly movable image carrier. means for obtaining a reference pulse synchronized with; and means for obtaining a signal for each endless movement of the transfer material support member or the image support;
The multicolor developing means includes means for selectively executing development of a desired color at a predetermined position of the endlessly movable image carrier, and each time the endlessly moving signal is obtained a predetermined number of times, A multicolor image forming apparatus characterized in that a selection executing means of the multicolor developing means is controlled by a reference pulse obtained from a reference pulse generating means.