JPH07181774A - Development control system - Google Patents

Abstract

PURPOSE:To prevent the sticking of toner onto a developing roll while maintaining the life of a developer. CONSTITUTION:In this development control system by a developing device for attaining multicolor development by plural developing units 13K, 13Y, 13M and 13C fitted to a rotary body 13a, when the nonimage region of a photoreceptor 11 exists on a developing point in a developing cycle, the developing units are moved to positions where each developing roll 32 does not face the photoreceptor 11 and simultaneously the developing rolls are stopped and when the image region of the photoreceptor exists on the developing point in the developing cycle, the developing unit is moved to the position where one developing roll faces the photoreceptor and simultaneously the developing roll is rotated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus such as a copying machine, a facsimile, a printer, etc., which uses electrophotography, and more particularly to a multicolor image forming apparatus having a plurality of developing devices mounted on a rotary member. The present invention relates to a development control system of a developing device that performs development.

[0002]

2. Description of the Related Art In a multicolor image forming apparatus using electrophotography, for example, a photosensitive member is uniformly charged, and then electrostatic latent images of black, yellow, magenta, and cyan are sequentially formed on the photosensitive member. Then, each latent image is developed by a black, yellow, magenta, and cyan developing device mounted on a rotating body, and the developed toner image is transferred to a transfer paper on a rotating transfer drum in contact with the image carrier. , Rotate the transfer drum 4 times to transfer the toner images of 4 colors on the paper,
There is a system for obtaining a four-color full-color copy (for example, JP-A-63-128375).

This developing device is provided with a developing roll which closely faces the photoconductor, and the developer roll is a magnet roll for forming a plurality of magnetic patterns and is rotatable around the outer circumference of the magnet roll. And a developing sleeve supported by. The developer is attracted to the surface of the developing sleeve by the magnetic force of the magnet roll, and a magnetic brush in which magnetic carriers are connected in a spike shape is formed.By rotating the developing sleeve, the surface magnetic brush is separated from the developing sleeve and the photoconductor. Are transported to the opposite development area,
The magnetic brush is brought into close proximity or contact with the photoreceptor. At this time, a bias voltage is applied between the developing roll and the photoconductor, and a potential is set between the image portion on the photoconductor and the developing roll so as to attract the charged toner to the photoconductor. The electric potential is set between the non-image area and the developing roll so as to attract the toner to the surface of the developing roll. As a result, the charged toner is transferred only to the image portion on the photoconductor in the developing area to visualize the latent image.

By the way, in the above image forming apparatus,
If the diameter of the transfer drum and the paper size are determined, the image forming section and the non-image forming section are determined. In order to achieve a system capable of feeding in the lateral direction with the sheet size A3 by simply considering only the sheet size, the peripheral length of the transfer drum needs to be 420 mm. With this system, considering the lateral feed in the sheet size A4. , 210 mm is the image width, and the image forming section and the non-image forming section are half and half.

Conventionally, in the rotary developing device disclosed in, for example, Japanese Unexamined Patent Publication No. 4-335667, the home position is set so that each developing roll does not face the photoconductor when the machine is stopped, but the developing cycle starts once. With respect to the developing devices for the respective colors, one of the developing devices faces the photoconductor except during the switching movement, and is not returned to the home position retracted position until the development cycle is completed. Considering this in the development process,
As described above, in the unnecessary non-image section, the developing roll faces the photoconductor for a long time.

[0006]

When the developing roll is opposed to the photosensitive member in the non-image section, one of the means is as follows.
Although there is a concept of rotating the developing roll in this section, there is a problem that the charging characteristic of the developer changes due to an increase in unnecessary rotation time and the life is shortened. Although there is a concept of stopping the developing roll, the problem of wasting toner because unnecessary toner is supplied to the photoconductor, and the developing nip part because the developing roll stops and faces the photoconductor for a long time There is a problem that the surface of the developing roll is contaminated with the toner in the developer, and the image density is affected.

The present invention solves the above-mentioned problems, and in a multicolor developing apparatus for performing multicolor development by a plurality of developing devices mounted on a rotating body, the developer is transferred onto a developing roll while maintaining the life of the developer. By preventing the adhesion of the toner of
It is an object of the present invention to provide a development control system capable of obtaining a high quality image having uniform image density.

[0008]

To this end, the development control system of the present invention is a development control system in which a developing device performs multicolor development by a plurality of developing devices mounted on a rotating body, and is exposed at a development point in a development cycle. When there is a non-image area on the body, each developing roll moves the developing unit to a position where it does not face the photoconductor, and the developing roll is stopped. It is characterized in that the developing device is moved to a position where the roll faces the photoconductor and the developing roll is rotated. Further, it is characterized in that a switching time is set according to the sheet size, such that each developing roll is moved to a position not facing the photoconductor and one developing roll is moved to a position facing the photoconductor.

[0009]

In the present invention, after the development of the image area is completed, the development roll of each developing device is stopped so as not to face the photoconductor, or after the development of the image area is completed, the developing roll of each developing device is rotated at a low speed. By doing so, the toner is prevented from adhering to the developing roll while maintaining the life of the developer.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 8 shows an example of a multicolor image forming apparatus to which the present invention is applied. The color electrophotographic copying machine includes an automatic document feeder 1, an image input unit 2, an image output unit 3, and a paper feeding unit 4.
Consists of. The color original document is placed on the platen glass 5 by the automatic original document feeder 1. The image input unit 2 is composed of an imaging unit 6, a wire 7 for driving the unit 6, a drive pulley 9 and the like. By using a CCD line sensor and a color filter in the imaging unit 6, in the case of four full colors, , A color original is read for each of the primary colors of light B (blue), G (green), and R (red), and after being converted into a digital image signal, this signal is the primary colors of toner K (black), Y ( Yellow), M (magenta), and C (cyan), and various data processing is performed to turn on / off the color gradation toner signal in order to improve reproducibility of color, gradation, definition, etc. It is converted into an off-state binarized signal and output to the image output unit 3.

The image output section 3 has a scanner 10 and a drum-shaped photosensitive member 11 made of an organic photosensitive member, and a charging device 12 for uniformly charging the photosensitive member 11 around the photosensitive member 11, A rotary developing device 13 for developing the electrostatic latent image into a toner image, a transfer device 14 for transferring the toner image onto a sheet, and a cleaner 15 for collecting the untransferred residual toner are arranged. Reference numeral 11 is rotationally driven by an electric motor as shown by an arrow. In the laser output unit 10a of the scanner 10, for example, a black image signal from the image input unit 2 is converted into an optical signal, and the polygon mirror 10b, the f / θ lens 10c, and the reflection mirror 10d are converted.
A latent image corresponding to the original image is formed on the photoconductor 11 via. When this black latent image is transferred to the sheet through development, the photoconductor 11 is charged by the charger 12 again after the residual toner is removed by the cleaner 15, and the laser output unit 10a outputs the yellow image signal. Output. Hereinafter, latent images of magenta and cyan image signals are sequentially formed.

The rotary developing device 13 includes a black developing device 13K, a yellow developing device 13Y, and a magenta developing device 1.
3M, cyan developing device 13C, each developing device is arranged around a rotating body 13a, and the rotating body 13a is rotatable in the direction of the arrow shown by a motor (not shown). Then, by the time the leading edge of the latent image of the first color reaches the development point, the rotating body 13a causes, for example, the black developing device 13K to reach the development point, and drives the developing roll to perform development.
The visualized image is transferred to a sheet on a transfer film at a transfer point, and the toner on the photoconductor 11 that has not been transferred is cleaned by a cleaning device to form a second color latent image. By the time the leading edge of the second color latent image reaches the development point, the rotator 13a rotates 90 degrees clockwise and reaches the yellow developing device 13Y for development. The same cycle is carried out for the third and fourth colors.

A transfer film made of a dielectric film is stretched around the outer periphery of the transfer drum 16 which constitutes the transfer device 14. The transfer drum 16 is connected to a dedicated electric motor or the photoconductor 11 by a gear, It is rotationally driven as indicated by an arrow. A transfer corotron 17, a pressing member 18, a separating corotron 19, a peeling claw 20, a charge removing corotron 21, a cleaner 22, a suction roll 23, and a suction corotron 25 are arranged inside and outside the transfer drum 16.

The paper feed trays 4a to 4a of the paper supply unit 4
The sheet conveyed and fed from 4d through the conveying roller 26, the sheet feeding guide 27 and the registration roller 28 is attracted to the transfer film by the pressing action of the suction roll 23 and the corona discharge of the suction corotron 25. Transfer drum 1
6 rotates in synchronization with the photoconductor 11, and, for example, when the toner image developed in black is transferred onto the sheet by the transfer corotron 17, the toner developed in yellow after one rotation of the transfer drum 16. The image is transferred onto the sheet by the transfer corotron 17, and subsequently the toner images developed with magenta and cyan are sequentially transferred in superposition. When the transfer drum 16 is rotated four times and the transfer of four colors is completed, the paper is neutralized by the separating corotron 19, and then the paper is peeled off.
The toner image is separated by 0, sent to the fixing device 30 via the conveying path 29, and the transferred toner image is fused and fixed, and this series of copying cycles is repeated.

FIG. 1 and FIG. 2 show an embodiment of the developing control system according to the present invention. FIG. 1 is a sectional view of a multicolor developing device,
FIG. 2 is a block diagram of the control system. In FIG. 1A, the rotary developing device 13 has a black developing device 13K, a yellow developing device 13Y, a magenta developing device 13M, and a cyan developing device 13C, and each developing device is provided around a rotating body 13a. The rotating body 13a is rotatable in the direction of the arrow in the figure by a motor (not shown). Each developing device includes a developing roller 32 and a developer transporting roller 3 in a developing housing 31.
3, 34 are provided.

Around the outer periphery of the rotating body 13a, there is one home position notch 35, which is a stop position before or after the developing cycle, and a developing position for making the developing roll 32 of each developing device face the developing position D. Notch 36
A total of eight cutouts are provided, including four K, 36Y, 36M, and 36C, and three standby cutouts 37KY, 37YM, and 37MC located in the middle of the development positioning cutouts 36K, 36Y, 36M, and 36C. ing. Rotating body 13a
Stopper 3 having an engaging roller 38 at its tip in proximity to
9 is provided, the stopper 39 is rotated by a drive source (not shown) before the rotary body 13a is rotationally moved, the engagement between the engagement roller 38 and the cutout portion is released, and the target developing device is developed. When the position D is maintained, the engagement roller 38 is fitted into the corresponding notch.

FIG. 2 is a block diagram of a control system of the multi-color developing device having the above-mentioned configuration. The control device 40 controls the development control signal 4
1. Based on the paper size signal 42 and the paper feed direction signal 43, the contents of the standby time storage unit 46 are referred to, and the stopper driving solenoid 44 and the rotating body driving motor 4 are referred to.
The output signal is output to 5. Set the presence / absence of standby and the standby time when changing colors according to the paper size and feed direction.
When it is not necessary, the developing roll is controlled so as not to face the photoconductor. In the following example, the photoconductor 1
The description will be made assuming that the diameter of No. 1 is 84 mm, the diameter of the transfer drum is 168 mm, the process speed is 160 mm / sec, and the 45 degree rotation time of the rotating body 13a is 310 msec.

First, consider a four-color mode, one-sheet copy case with paper A3 size, longitudinal feed (length 420 mm). In this case, the peripheral length of the transfer drum is 168 × π
= 527.8 mm, the difference between the peripheral length of the transfer drum and the length in the sheet feeding direction is 527.8-420 = 107.8 mm, and the process speed is 160 mm / sec for registration alignment on the transfer drum. Therefore, 107.8 ÷ 160 = 0.674 sec is the time from the end of black development of the first color to the start of yellow development of the second color. Therefore, the rotating body 1
If 3a is rotated by 90 degrees and the next developing device is positioned, the image defect does not occur (however, the rising and falling portions of the developing device driving means are excluded).

When the machine is stopped (at the end of the image forming cycle), as shown in FIG. 1 (A), the rotary member 13a serves as the home position, and the home position notch 35 is formed.
The engaging roller 38 of the stopper 39 is fitted to the stopper 39, and none of the developing devices is in a state of facing the photoconductor 11. Next, as shown in FIG. 1 (B), when the copy cycle starts, before the leading edge of the first color latent image reaches the development point D, the rotary body 13a is rotated by 45 degrees, and the development positioning notch 36K. After engaging the engaging roller 38 of the stopper 39 with the first color black developing device 13K and rotating the first color black developing device 13K from the home position to the developing position, the developing roller 32 is driven according to the image area to visualize the latent image. .

After the development of black is completed, the developing roller 32 is stopped, and then the rotating body 13a is rotated by 90 degrees to engage the engaging roller 3 of the stopper 39 with the notch 36Y for developing positioning.
8 is fitted, the yellow color developing device 13Y is made to reach the developing position, and the developing roll 32 is driven according to the image area to visualize the latent image. At this time, the time required to rotate 90 degrees is 620 msec. In order to perform registration registration on the transfer drum, it is sufficient to rotate and rotate the rotating body 13a by 90 degrees by 674 msec as described above. Does not happen. Therefore,
After the black development is completed, the developing roll 32 of the black developing device 13K is almost not in the developing position.
It is possible to prevent toner from adhering to the top. For the third color magenta development and the fourth color cyan development, the same steps as described above are performed. After the completion of the fourth color cyan development, the rotator 13
a rotates 45 degrees and returns to the home position, and none of the developing devices is in a state of facing the photoconductor 11.

Next, consider a four-color mode, one-sheet copy case with paper A4 size, lateral feed (length 210 mm). In this case, the peripheral length of the transfer drum is 168 × π
= 527.8 mm, the difference between the peripheral length of the transfer drum and the length in the sheet feeding direction is 527.8-210 = 317.8 mm, and the process speed is 160 mm / sec for registration registration on the transfer drum. Therefore, 317.8 ÷ 160 = 1.986 sec is the time from the end of black development of the first color to the start of yellow development of the second color.

As shown in FIG. 1B, when the copy cycle starts, before the leading edge of the first color latent image reaches the development point D, the rotary member 13a is rotated by 45 degrees, and the development positioning notch 36K. After engaging the engaging roller 38 of the stopper 39 with the first color black developing device 13K and rotating the first color black developing device 13K from the home position to the developing position, the developing roller 32 is driven according to the image area to visualize the latent image. . After completing the development of black, rotate the rotating body 13a once
Then, the engagement roller 38 of the stopper 39 is fitted into the standby cutout portion 37KY, and the standby state is waited for 1366 msec. After the standby, the rotating body 13a is rotated again by 45 degrees, the engaging roller 38 of the stopper 39 is fitted into the developing positioning notch 36Y, and the second color yellow developing device 13Y reaches the developing position to reach the image area. In addition, the developing roll 32 is driven to visualize the latent image. At this time, in order to perform registration on the transfer drum, it is necessary to rotate and rotate the rotating body 13a by 90 degrees by 1986 msec as described above, but the first and second rotation times (620 msec) Standby time (1366 ms
ec) is set to 1986 msec or less, an image defect does not occur, and after the development of black is completed, the developing roller 32 of the black developing device 13K is not in the developing position. Adhesion of toner can be prevented. For the third color magenta development and the fourth color cyan development, the same steps as described above are performed. After the completion of the fourth color cyan development, the rotator 13a is rotated by 45 degrees to return to the home position, and none of the developing devices is opposed to the photoconductor 11.

FIG. 3 shows the relationship between the length of each sheet in the feed direction stored in the standby time storage unit 46 and the standby time. As described above, this waiting time is calculated from the diameter of the transfer drum, the process speed, the rotational speed of the rotating body and the paper size, and the paper feeding direction.

FIG. 4 is a sectional view of a multicolor developing device for explaining another embodiment of the present invention. The same components as those in the embodiment of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. On the outer periphery of the rotating body 13a, the home position notch 3 which is a stop position before or after the development cycle is completed.
5, and notches 36K, 36 for developing positioning for making the developing roll 32 of each developing device face the developing position D.
Four Y, 36M, and 36C, and a total of five notches are provided. A stopper 39 having an engaging roller 38 at its tip is arranged in the vicinity of the rotating body 13a.
The stopper 39 is rotated by a drive source (not shown) before the rotational movement of the roller, and the engagement between the engagement roller 38 and the notch is released, and when the target developing device is maintained at the developing position D, the engagement is performed. The rollers 38 are adapted to be fitted in the corresponding notches.

A drive device for the rotating body 13a (not shown) is composed of a stepping motor having a step angle of 1.8 degrees and a speed reducer having a speed reduction ratio of 15. Therefore, the rotating body 13
The number of pulses required to rotate a by 90 degrees is 750. Paper A3 size Longitudinal feed, rotating body 1
The pulse conditions applied to the stepping motor when rotating 3a by 90 degrees are shown in FIG. 5. In this case, the rotating body 13a can be rotated by 90 degrees in 673.62 msec, and registration on the transfer drum is performed. For this purpose, as described above, the rotator 13a may be rotated 90 degrees by 674 msec, so that an image defect does not occur. Therefore, after the development of each color is completed, the developing roll of each developing unit stops and does not face the photoconductor, so that the adhesion of the toner onto the developing roll can be prevented.

Further, FIG. 6 shows the pulse conditions applied to the stipping motor when the rotary band 13a is rotated 90 degrees in the paper A4 size longitudinal feed. In this case, the rotary body 13a is 1985.34 msec. It can be rotated and moved by 90 degrees. For registration registration on the transfer drum, 1986 msec as described above.
Since the rotator 13a may be rotated 90 degrees by this time, no image defect occurs. Therefore, after developing the image area,
Since the developing roll of each developing unit is separated from the developing position in a stopped state, it is possible to prevent toner from adhering to the developing roll. As described above, by setting the time for 750 pulses according to each case, it is possible to reduce the unnecessary facing time and the unnecessary developing roll rotation time.

The present invention is not limited to the above embodiments, and various modifications can be made by those having ordinary knowledge in the technical field to which the present invention belongs. For example, in the above-described embodiment, the paper size and the feeding direction are described, but the case where the development order is different in the color mode, the edit mode, etc. is dealt with by the same idea, and the rise and fall of the drive device of the developing roll is performed. By taking the time into consideration, the developing roll is opposed to the photoconductor for the minimum time that is possible in the system, so that it is possible to reduce the unnecessary facing time and also the unnecessary developing roll rotation time.

Further, by adopting a drive transmission system capable of rotating the developing roll before reaching the developing position, and stopping the developing roll after moving from the developing position after the completion of the developing process, the stopped developing roll is made to be a photosensitive member. It is also possible not to face.

FIG. 7 is a block diagram of a control system showing another embodiment of the present invention. In each of the above embodiments, after the development of the image area is completed, the developing roll of each developing device is stopped so as not to face the photoconductor. However, in this embodiment, the configuration is similar to that of the embodiment of FIG. After the development of the image area is completed using the rotary developing device, in the non-image area, the development roll is rotated at low speed with the development device stopped at that position, and the development device is moved in time with the next development. I am trying to let you. Therefore, the control device is configured to output a normal drive rotation signal and a low speed rotation signal to the developing roll drive motor based on the exposure system ON / OFF signal. Therefore, in the non-image area, rotate the developing roll all the time,
By not creating a state in which one point on the developing roll always faces the photoconductor, toner does not adhere to the developing roll, and further, by lowering the rotation speed of the developing roll below the normal rotation speed, The load on the developer can be reduced as compared with the normal rotation state, and the life of the developer can be extended.

[0030]

As is apparent from the above description, according to the present invention, in a multicolor developing device for performing multicolor development by a plurality of developing devices mounted on a rotating body, after completion of development of an image area, each development is performed. The developing roll of the developing unit is stopped so as not to face the photoconductor, or after the development of the image area is completed, the developing roll of each developing unit is rotated at a low speed, so that the life of the developer is maintained and the developing roll on the developing roll is maintained. Prevents adhesion of toner,
It is possible to obtain a high-quality image with uniform image density.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multi-color developing device showing an embodiment of a development control system according to the present invention. FIG. 1 (A) is a home position, FIG. 1 (B) is a developing position, and FIG. 1 (C). FIG. 6 is a diagram showing a standby position.

FIG. 2 is a configuration diagram of a control system in FIG.

FIG. 3 is a diagram showing a relationship between a feed direction length of each sheet and a standby time stored in a standby time storage unit.

FIG. 4 is a sectional view of a multicolor developing device for explaining another embodiment of the present invention.

5 is a diagram showing an example of frequency and pulse number data of the stepping motor of the embodiment of FIG.

6 is a diagram showing an example of data of frequency and pulse number of the stepping motor of the embodiment of FIG.

FIG. 7 is a configuration diagram of a control system showing another embodiment of the present invention.

FIG. 8 is a configuration diagram showing an example of a multicolor image forming apparatus to which the present invention is applied.

[Explanation of symbols]

11 ... Photosensitive member, 13a ... Rotating member, 13K, 13Y, 13
M, 13C ... Developing device 32 ... Developing roll, 36K, 36Y, 36M, 36C ...
Notch for development positioning 37KY, 37YM, 37MC ... Notch for standby, 39 ...
stopper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Tomizawa 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. In a development control system using a developing device for performing multicolor development by a plurality of developing devices mounted on a rotating body, each developing roll is exposed to light when a non-image area of the photosensitive member is present at a developing point in a developing cycle. When the developing unit is moved to a position not facing the body and the developing roll is stopped, and when the image area of the photoconductor is at the developing point in the developing cycle, one developing roll is moved to the position facing the photoconductor. A development control system characterized by rotating the developing roll together. 2. A switching time is set according to the paper size, wherein each developing roll is moved to a position not facing the photoconductor and one developing roll is moved to a position facing the photoconductor. The development control system according to claim 1.