JPS59214872A - Cleaning method of electrostatic charge holding member of copying machine - Google Patents

Abstract

PURPOSE:To speed up operation and obtain a simple, small-sized device by allowing a blade to contact selectively an electrostatic charge holding member right before an electrostatic latent image is formed thereupon and cleaning an area corresponding to the electrostatic latent image, and operating a developing device as a cleaning device except when the electrostatic latent image is developed. CONSTITUTION:While the blade 21 contacts a photosensitive drum 1 with a copy start signal, a corona electrostatic charger 3 operates to start cleaning the latent image formation area, and an electrostatic latent image is formed. Then, the blade 21 spaces the photosensitive drum 1 with a latent image formation end signal and the corona electrostatic charger 3 stops operating. The developing device 8 operates as the developing device while the latent image formation area passes in each copying operation, and serves as the cleaning device in other periods. Residual toner on the photosensitive drum 1 is cleaned, collected in the developing device 8, and reused. Further, residual toner at the part cleaned with the blade 21 is also collected by the developing device 8 by being carried on the photosensitive drum 1 while the blade 21 spaces the drum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a charge retention member such as a photoreceptor in a copying machine.

For example, in a copying machine, an electrostatic latent image corresponding to a document image formed on a rotating electrophotographic photosensitive drum is developed with toner using a developing device using a dry developer, and this toner image is transferred to copy paper to obtain a copy. After the toner image is transferred to the copy paper, it is necessary to clean the photosensitive drum to remove the residual toner that was not transferred to the copy paper before forming the next electrostatic latent image. Conventionally, devices using a fur brush, a blade, a magnetic brush, etc. have been proposed.

However, in fur brush cleaning devices, the residual toner removed by the fur brush is generally captured by a filter using an air suction mechanism and disposed of. There is a problem that the image becomes large. On the other hand, since the blade cleaning device cleans the photosensitive drum by bringing the blade made of the elastic portion of urethane or the like into contact with the photosensitive drum, the configuration can be made simple and compact, and the cleaning can be performed well. However, in this case, since it is safe to bring the blade into contact with the photosensitive drum, there are problems such as damage to the photosensitive drum, wear of the blade, and lack of durability. Further, the magnetic brush cleaning device has the advantage that a dedicated cleaning device is not required by being used in combination with the magnetic brush developing device, and is extremely advantageous in terms of lower cost and improved maintainability of the device. However, when the developing device is also used as a cleaning device in this way, the developing device is usually placed between the latent image forming section and the toner image transferring section, so the toner image transferring section and the latent image forming section are Unlike copying machines, which have a dedicated cleaning device in between, cleaning and development cannot be performed at the same time. Therefore, when making continuous copies, it is necessary to share a few photosensitive drums to make one copy. Since it is necessary to rotate the photosensitive drum twice, it is difficult to increase the speed, and since it is necessary to make the outer circumference of the photosensitive drum longer than the maximum length of the copy paper, there is a problem that the entire apparatus becomes large.

On the other hand, in a copying machine that uses toner to develop an electrostatic latent image formed on a photosensitive drum using a developing device using a dry developer, residual toner on the photosensitive drum is developed after the toner image is transferred to copy paper. It is preferable to collect it in the device N and reuse it.

However, in the fur brush cleaning device 21, as described above, the residual toner is captured by the filter and discarded, so that it cannot be collected by the developing device. On the other hand, in a blade cleaning device, the residual toner on the photosensitive drum is collected by the blade, so that it can be collected in the developing device and used for harmful purposes. However, in conventional copying machines using this type of cleaning device, the residual toner collected by the blade is automatically collected into the developing device by a separate toner conveying means having a flexible screw or the like. Therefore, there are problems in that the apparatus becomes expensive and the structure of the toner conveying means becomes complicated. In addition, in the case where the developing device is also used as a cleaning device, the cleaned toner can be directly taken into the developing device, so it is not complicated to return the cleaned toner to the developing device as in the case where the blade is used. This method has the advantage that no special equipment is required, and is extremely advantageous in terms of lower costs and improved maintainability of the equipment. However, in this case, as mentioned above, it is difficult to increase the speed and the entire device becomes large.

To solve this problem, for example, Japanese Patent Laid-Open No. 58-28482 discloses a method in which a cleaning blade is provided so as to be able to approach and separate from the photoreceptor, and the residual toner on the photoreceptor is removed by bringing the cleaning blade into contact with the photoreceptor. There is a method for collecting residual toner in which the accumulated toner is collected at the contact area by separating the cleaning blade from the photoreceptor for a short period of time, and conveying the accumulated toner to the developing device while remaining on the photoreceptor. Proposed.

However, in this collection method, the cleaning blade is separated from the photoreceptor only when the toner accumulated by the cleaning blade is transported to the developing device, that is, only for a short period when the accumulated toner passes through the contact part of the cleaning blade. Since the cleaning blade is always in contact with the photoconductor at other times, there are problems such as the photoconductor is easily damaged, the cleaning blade wears quickly, and it lacks durability, similar to the blade cleaning device described above. In addition, because the separation period is short, the accumulated toner adheres to the blade itself, and more particles of accumulated toner scatter, resulting in poor recovery efficiency in the developing device and dirt inside the machine. There is also the problem that maintenance becomes troublesome.

It is an object of the present invention to solve the various problems mentioned above, to increase the copying speed, to simplify and downsize the apparatus, and to enable charge retention members such as photoreceptors to be used stably for a long period of time. An object of the present invention is to provide a method for cleaning a charge retention member in a copying machine, which allows residual toner to be easily and efficiently collected in a developing device. Forming an electrostatic latent image on the charge retaining member when cleaning the charge retaining member of a copying machine in which an electrostatic latent image is formed on the charge retaining member, and this electrostatic latent image is developed with toner by a developing device and transferred to copy paper. The developing device is characterized in that the blade is selectively brought into contact immediately before cleaning an area substantially corresponding to the electrostatic latent image, and the developing device functions as a cleaning device except for developing the electrostatic latent image.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an example of a copying machine that implements the method of the present invention. The photosensitive drum 1 rotates in the direction of the arrow at the start of the copying operation, and after the residual charge is eliminated by uniform exposure by the static eliminating lamp 2, it is uniformly charged by the corona charger 8. The original to be copied is placed on the movable original platen 4 and starts moving in the direction of the arrow, and is illuminated by the illumination lamp 5 and reflecting mirror 6, and the original image is exposed to light through the fiber lens array 7. The image is projected onto the drum 1, thereby forming an electrostatic latent image corresponding to the original image on the photosensitive drum 1. This electrostatic latent image is developed with toner by a magnetic brush roller 9 of a magnetic brush developing device 8 using a dry developer, and this toner image is attached to a copy sheet fed out in advance from a cassette 10 by a pickup roller 11 and a paper feed roller 12. The images are overlapped and transferred to copy paper by the action of the transfer corona charger 18. After this copy paper is peeled off from the photosensitive drum 1 by the action of the peeling corona charger 14, it is sent to the fixing roller 15 where the toner image is fixed, and then discharged onto the copy tray 17 by the discharge roller 216.

In this embodiment, the photosensitive drum 1 is located downstream of the toner transfer section in which the transfer corona charger 13 and the stripping corona charger 14 are arranged and upstream of the static elimination lamp 2 when viewed in the rotating direction of the photosensitive drum 1. A blade 2 made of an elastic material such as urethane is arranged so as to selectively contact the
A corona charger 22 for static elimination is arranged between this blade 21 and the toner image transfer section. The blade 21 is brought into contact with the photosensitive drum 1 in response to a copy start signal indicating the start of a copying operation, and separated from the photosensitive drum 1 in response to a latent image formation end signal indicating the completion of formation of an electrostatic latent image corresponding to the copy paper. In other words, the blade 21 is activated by the copy start signal.
The position on the photosensitive drum 1 where the blade 21 comes into contact is the leading edge of the latent image forming area, and when the trailing edge of the latent image forming area corresponding to the copy paper is charged by the corona charger 8, the blade 21 is moved from this position to the photosensitive drum 1. By separating the area from the latent image, the area where the latent image is formed is cleaned immediately before forming the latent image in the copying operation. Note that the blade 21 is connected to the photosensitive drum 1.
A latent image formation completion signal for separating the copy paper from the copy paper can be obtained based on the output of the paper sensor by disposing a paper sensor on the conveyance path of the copy paper, or based on the size identification signal of the cassette 10. The polarity of the charge eliminating corona charger 22 is set to be alternating current or direct current having the opposite polarity to the potential of the latent image to be formed.

Figure 2 shows how the copying machine shown in Figure 1 prints 3 copies from one original.
Indicates the operation when continuously obtaining copies of sheets, and the symbol S
o・S, , S8 are copy start signals for each copying operation. This signal causes the blade 21 to come into contact with the photosensitive drum 1, and the corona charger 8 is activated to change the contact position with the blade 21 to the latent image forming area. At the same time, an electrostatic latent image begins to be formed on the photosensitive drum 1. In addition, codes e□, e2.
e8 is a latent image formation end signal that is generated when the blade 21 cleans the latent image forming area up to the rear end in each copying operation and is uniformly charged by the corona charger 3. This signal causes the blade 21 to close the photosensitive drum. 1 to W&, and the corona charger 3 stops operating. In this manner, in each copying operation, the frontage 0 charger 8 is operated during the period T0 between JtllJ and the time when the copy start signal force 5g6 is generated and the latent image formation end signal is generated 1-, and the frontage 0 charger 8 is activated and the blade 21 is cleaned just before. Latent image form G Kl area G small 1. A uP image is formed. In addition, the photosensitive drum l and the TIL removing corona charger 22 are activated by the copy start signal S in the first copy operation, and the generation force of the latent image formation end signal e8 in the :+bee operation after e is set to a predetermined level. It stops its operation after a certain period of time has elapsed. Here, T2 is a preparation period from the generation of the latent image formation end signal in one copy operation until the generation of the copy start signal in the next copy operation, and this period T.

varies depending on the size of copy paper used.

In addition, T8 and T8' are used for each copy operation until the copy start signal and the latent image form [i4 completion signal are generated until the leading and trailing ends of the electrostatic latent image reach the developing device 8. period, and T.

is the period from the time when development of the electrostatic latent image is completed in the final copying operation until the photosensitive drum 1 stops rotating.

In this way, the developing device 8 acts as a developing device during the period when the latent image forming area passes through the developing device 8 in each copying operation, and acts as a cleaning device at other times. The residual toner on the photosensitive drum 1 is collected in the developing device 8 and recycled. Furthermore, the remaining toner collected in the developing device 8 by this cleaning has a weak electrostatic attraction force with the photosensitive drum 1 because the photosensitive drum 1 has been neutralized by the action of the static eliminating corona charger 22 prior to cleaning. Therefore, it can be easily and effectively recovered. Also,
Since the blade 21 immediately separates from the photosensitive drum 1 after cleaning the latent image forming area on the photosensitive drum 1, residual toner in the area to be cleaned by the blade 21 is also conveyed to the developing device 8 on the photosensitive drum 1. At the same time, the residual toner collected by the blade 21 is inactive during the period when the remaining toner passes through the corona charger 3, and in this case also, the photosensitive drum 1 is in the corona charger 22 for charge removal. Since the static electricity is removed by the action, the residual toner collected by the blade 21 is also easily and effectively collected. Here, if the period T2 is set to the time during which the photosensitive drum 1 rotates more than once, all of the residual toner from the copying operation of that time is cleaned and collected by the developing device 8. In addition, if the period T2 does not correspond to one revolution of the photosensitive drum 1, that is, if the document table 4 is quickly reversed or the document is short-scanned, the circumference of the photosensitive drum 1 is far larger than the length of the copy paper. If it is large, the copy start signal for the next copy operation is generated while the developing device 8 is cleaning and collecting the residual toner from one copy operation, so at this point the residual toner directly under the blade 21 is removed. The formation of the next latent image starts while cleaning with the blade 21 from 1 to the rear end of the latent image forming area in the copying operation, and at this point, the formation of the next latent image starts from the downstream side of the blade 21 when viewed in the rotating direction of the photosensitive drum 1. The remaining toner upstream of the developing device 8 is subsequently cleaned and collected by the developing device 8.

After a period T8' after the generation of the latent image formation end signal e in the copying operation for the final sheet, the development in the copying operation ends, and the developing device 8 starts cleaning the photosensitive drum l. Here, the period T is the period until the rotation of the photosensitive drum 1 is stopped after the completion of development.

is optional, at least as long as the time required for the developed toner image to be completely transferred to the copy paper during the copying operation is at least as long as possible.
For example, if this period T is set to the time during which the photosensitive drum 1 makes one rotation or more, the entire circumference of the photosensitive drum 1 can be cleaned by the developing device 8.

As described above, in this embodiment, the toner collected by cleaning with the blade 21 is conveyed to the developing device 8 and collected as the photosensitive drum 1 rotates due to the separation of the blade 21. In order to effectively convey and collect the collected toner to the developing device 8 without scattering it, the photosensitive drum l and the blade 21 in FIG.
The angle θ formed by the line connecting the contact point with the center of the photosensitive drum 1 and the perpendicular line passing through the center of the photosensitive drum 1 is O≦θ≦30.
Alternatively, it is preferable to arrange the blade 21 at a position upstream of the developing device 8 so that the rotation of the photosensitive drum 1 is directed downward.

Note that the present invention is not limited to the above-mentioned examples, and can be modified or modified in many ways.

For example, the charge eliminating corona charger 22 may be used as a co-developing device 8.
It may be configured to operate only during the period when the area to be cleaned passes through. In addition, this static elimination corona charger 22
is arranged near the upstream side of the developing device 8, and is turned OFF while passing through the latent image forming area to be developed.

Other than that, the photosensitive drum 1 may be neutralized by being turned on. In this way, the corona charger 8 for uniform charging can be kept ON all the time during the copying operation. Further, the corona charger 8 is provided with a static elimination function, and is turned off after the latent image is formed, and a voltage for static elimination is applied while passing through the area to be cleaned by the small co-developing device 8. The static eliminating corona charger 22 can also be omitted.

Furthermore, the developing device 8 may have a different developing bias between developing and cleaning. As described above, according to the present invention, the blade comes into contact with the charge retaining member almost only during the period of latent image formation. Because of this, damage to the charge retention member and friction between the two can be effectively prevented, so that it can be used stably for a long period of time.

In addition, the amount of toner collected by cleaning with the blade is small, and most of the residual toner is collected by cleaning with the developing device, so it is not necessary to collect the toner collected with the blade into the developing device, and its collection efficiency can be improved. At worst, the overall residual toner recovery efficiency is extremely good. Furthermore, since cleaning by the blade and cleaning by the developing device are used in combination, there are advantages in that the apparatus can be made smaller and the copying speed can be increased.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an example of a copying machine that implements the method of the present invention, and FIG. 2 is a timing chart for explaining its operation. 1... Photosensitive drum 2... Static elimination lamp 3...
・Corona charger 4...Movement stand 5...Illumination lamp 6...Reflector 7...Fiber lens array 8...Developing device 9...Magnetic brush roller 10...Cassette 11...Pickup roller] 2...Paper feed roller 13...Four transfer charger 14...Peeling corona charger 15...Fixing roller 16...Ejection roller]
7...Copy tray 21...Blade 22.
・・Kamegawa corona charger

Claims (1)

[Scope of Claims] L. A copying machine that forms an electrostatic latent image on an endless charge holding member that rotates along a predetermined path, develops this electrostatic latent image with toner using a developing device, and transfers it to copy paper. In cleaning the charge particles, a blade is selectively brought into contact with the blade immediately before the electrostatic latent image is formed on the charge retaining member to clean an area substantially corresponding to the electrostatic latent image, and the electrostatic latent image is developed. 1. A method for cleaning a charge retaining member in a copying machine, characterized in that the developing device functions as a cleaning device except for the following steps. 2. The method of cleaning a charge holding member in a copying machine according to claim 1, wherein the charge holding member is neutralized by corona discharge before being cleaned by the developing device. & The residual toner collected at the contact area between the blade and the charge retention member by cleaning with the blade is removed by 1 (
2. The method of cleaning a charge holding member in a copying machine according to claim 1, wherein the L charge holding member is placed on the charge holding member and transported to the developing device for recovery.