JP2002123069A - Method for cleaning electrifying brush roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method of an electrifying brush roller whose cost is reduced because of a simple constitution and also by which an excellent image is obtained over a long term by suppressing the occurrence of an abnormal image. SOLUTION: In the cleaning method of the electrifying brush roller in which a contact electrifying means to electrify a photoreceptor by using the electrifying brush roller and a cleaning means to remove toner remaining on the photoreceptor after transfer are arranged, DC bias is applied by the electrifying brush roller at the time of outputting the image, and the DC bias is set as 0 V and AC bias is applied for more than time required for one rotation of the photoreceptor after outputting the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging brush roller cleaning method applied to an electrophotographic image forming apparatus such as a copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a photoreceptor is charged by a charging unit and then exposed to light such as a laser beam to form a latent image. The latent image is developed with charged toner in a developing device to form a toner image on a photoreceptor, the toner image is transferred to a transfer sheet, and then fixed to form a visible image on the transfer sheet. I do. Here, corona discharge is used as charging means for charging the photoreceptor. However, this corona discharger requires a high-voltage power supply, which is contrary to the tendency to downsize the image forming apparatus. In addition, the corona discharger has
Although ozone generated by applying a high voltage to a μm wire is used, this wire is easily contaminated and current efficiency is low.

For this reason, recently, a contact charging type charging means for charging the photosensitive member by contacting the photosensitive member has been widely used. As a charging means, a conductive roller-shaped elastic body is driven to contact with the photoreceptor to apply a high voltage, and a charging roller type in which a conductive plate-shaped elastic body is brought into contact with the photoreceptor. There is a charging blade method for applying a voltage, and a charging brush method for applying a high voltage similarly by bringing a conductive brush into contact with a photosensitive member. However, any of these methods has a disadvantage that the toner remaining in the cleaning device and the additive for imparting fluidity to the toner adhere to the photosensitive member because the toner is in contact with the photosensitive member.

[0004] For this purpose, for example, Japanese Patent Application Laid-Open No. 05-027 is disclosed.
Japanese Patent No. 552 discloses a contact charging device that constantly applies AC to a charging means on a flat plate. In the case of this contact charging device, since AC is applied to the photoconductor for a long time, a leak phenomenon occurs in a pinhole of the photoconductor. There is a problem that it is easy to cause such a problem that a brush made of low-resistance rayon burns. In addition, there is a problem that the photosensitive member is scraped or sensitivity is deteriorated. Further, for example, Japanese Patent Application Laid-Open No. 05-181351
In Japanese Patent Application Laid-Open Publication No. H08-209, the image forming apparatus applies a reverse bias between pages. However, there is a problem that it is not possible to remove the adhering matter that has entered the brush or the adhering matter having a small amount of charge. Also, for example, in Japanese Patent Application Laid-Open No. 05-297690, a charging device that constantly contacts a sponge with a charging member is described.
The charging brush roller has a problem in that settling occurs and an abnormal image of insufficient charging occurs. Further, when the contacting / separating mechanism is provided on the cleaning member, there is a problem that the apparatus becomes large and the cost increases.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and can reduce the cost with a simple structure, and can suppress abnormal images to improve the image quality over a long period of time. It is an object of the present invention to provide a charging brush roller cleaning method capable of obtaining a stable image.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a contact charging means for charging a photoreceptor using a charging brush roller, and a method of charging a photoreceptor remaining on a photoreceptor after transfer. In the charging brush roller cleaning method in which a cleaning unit for removing toner is disposed, the charging brush roller applies a DC bias at the time of image output, and applies a DC bias of 0 V for at least one rotation of the photoconductor after image output. A charging brush roller cleaning method in which an AC bias is applied is adopted. According to a second aspect of the present invention, there is provided the charging brush roller cleaning method according to the first aspect, wherein the electrode plate facing the charging brush roller in a non-contact manner is arranged such that the electrode plate is in contact with the charging brush roller brush near the photoconductor. And a power supply for applying AC to the opposing electrode plate is disposed. A third aspect of the present invention is the charging brush roller cleaning method according to the first or second aspect, further comprising: a conductive roller facing the charging brush roller in a non-contact manner; and a unit for cleaning the conductive roller. A power supply for applying AC or AC + DC to the conductive roller is provided as a charging brush roller cleaning method.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. (First Embodiment) In a negative-positive electrophotographic apparatus using a charging brush roller, a white spot-like abnormal image may be generated on a halftone image. In particular, when the number of sheets used in a low-temperature and low-humidity environment increased, it was found that the occurrence was remarkable. It has been clarified that this abnormal image is generated due to contamination of the charging brush. That is, as a result of observing the bristle tip of the charging brush, particles having a very small particle size were deposited at the tip of the brush with time, and when spotted with these particles, a white spot-like abnormal image occurred on the halftone image. . The above particles are considered to be easily passed through the cleaning blade because the particle size is extremely small. Next, when the particles deposited on the tip of the brush were analyzed, it was found that the particles were fine powder toner and silicon oxide (silica) added for improving the fluidity of the toner.

[0008] The mechanism by which a white spot-like abnormal image is generated on an image over time is caused by brush dirt. As described above, the bristle tips of the charging brush become soiled with an additive of a toner having a small particle diameter and easily slipping through the cleaning blade with time, particularly, silica or fine powder toner. These additives, particularly silica and fine powder toner, have high electrical resistance and are insulators. On the other hand, the charging brush roller is made of conductive fibers for charging the photoconductor. If the tip of the conductive charging brush becomes dirty and covered with an insulator, the resistance of the brush becomes apparently high. However, the degree of brush smearing becomes non-uniform due to the length, shape and other factors of the brush bristles. Therefore, the apparent resistance of the brush also becomes non-uniform. In a portion of the fiber whose apparent resistance has become non-uniform, the portion having a lower resistance than the surrounding brush fiber causes excessive discharge locally in the form of dots to the photosensitive member. For example, while the average charging potential on the photosensitive member is -800 V, the charging potential is about -1200 V in this portion. In this state, if exposure and development are performed in accordance with image information, an excessively discharged portion in the form of dots cannot be completely exposed, so that a white spot-like abnormal image is generated.

Further, when cleaning is performed by bringing a scraper or a cleaning member into contact with the charging brush roller, insufficient settling occurs at the abutting portion after leaving the brush bristles, resulting in uneven density abnormal images. Would. Further, since the brush fibers are soft, the ends of the brushes are damaged when they are squeezed with a scraper or the like, causing white spots due to abnormal discharge. After all, it is difficult to use a contact type cleaning means for the charging brush roller. Further, when an AC bias is superimposed on the charging brush roller, a leak phenomenon easily occurs in the photoconductor pinhole, which may cause a trouble that the brush burns.

During image output, the photoreceptor rotates counterclockwise as shown in FIG. At the same time, the charging brush roller rotates counterclockwise at a peripheral speed that is about 1.5 times that of the photoconductor. At this time, since a charging bias of -1200 V is applied to the charging brush roller, the photoconductor is charged to about -800 V.
In this state, a normal electrophotographic process is performed at the time of image output. The operation from the end of the image output until the photosensitive member is neutralized and the rotation stops is called an END processing operation. At this time, the END processing operation is started while the photoconductor remains charged at -800V. As shown in FIG. 2, the DC bias is set to 0 V and the AC bias is set to Vp-
A voltage of about p = 1 kV and 2 kHz is applied. By the application of AC, the charged brush fibers vibrate immediately before coming into contact with the photoreceptor to remove attached silica. The removed silica falls on the photoreceptor and is returned to the developing unit. At the same time, the photosensitive member is subjected to AC charge elimination to approximately 0V. Therefore, since a static elimination lamp is not required and the AC application time to the photosensitive member is very short, there is a low possibility of causing a leak. Further, damage to the photoconductor is minimized, and the life of the photoconductor is extended.

(Second Embodiment) As shown in FIG. 3, the photosensitive member rotates counterclockwise during image output. At the same time, the charging brush roller rotates counterclockwise at a peripheral speed that is about 1.5 times that of the photoconductor. At this time, -1200 is applied to the charging brush roller.
Since the charging bias of V is applied, the photosensitive member is about -8.
It is charged to 00V. In this state, a normal electrophotographic process is performed at the time of image output. The operation from the end of image output to the stop of the photoconductor is referred to as an END processing operation. At this time, the END processing operation is started while the photoconductor remains charged at -800V. As shown in FIG. 4, the DC bias voltage applied to the charging brush roller at the same time as the start was set to 0 V, and the AC bias was applied to the opposite electrode by Vp−p =
A voltage of about 1 kV and 2 kHz is applied. By the application of AC, the charged brush fibers vibrate in the vicinity of the counter electrode to remove the attached silica. The removed silica adheres to the photoconductor by the electric field between the photoconductor and the counter electrode and is returned to the developing unit. Since no AC is applied to the charging brush roller, even if a defect such as a pinhole occurs in the photoconductor, it is possible to prevent the brush from leaking and burning in the pinhole.

Third Embodiment As shown in FIG. 5, the photosensitive member rotates counterclockwise during image output. At the same time, the charging brush roller rotates counterclockwise at a peripheral speed that is about 1.5 times that of the photoconductor. At this time, since a charging bias of 200 V is applied to the charging brush roller, the photosensitive member is about -800.
It is charged to V. In this state, a normal electrophotographic process is performed at the time of image output. (1) In this state, DC = -1500V is applied to the conductive roller.
, An AC bias is applied with Vp-p = 1 kV and about 2 kHz superimposed. When the AC brush is applied, the charged brush fibers vibrate in the vicinity of the conductive roller and adhere to the conductive roller at the same time as the silica flies and flies by an electric field created by a DC bias. The adhered silica is peeled off from the roller surface by the roller cleaning means and collected in a tank (not shown). (2) The operation from the end of the image output to the stop of the photoconductor after the image output is referred to as an END processing operation. At the same time as the start of the END processing operation, the DC bias voltage applied to the charging brush roller was set to 0 V, and an AC bias was applied to the conductive roller by superimposing DC = −300 V with Vp−p = 1 kV, about 2 kHz. By the application of AC, the charged brush fibers vibrate in the vicinity of the conductive roller to remove attached silica. The removed silica adheres to the photoconductor by an electric field between the photoconductor and the conductive roller and is returned to the developing unit.
Since no AC is applied to the charging brush roller, even if a defect such as a pinhole occurs in the photoconductor, it is possible to prevent the brush from leaking and burning in the pinhole.

[0013]

As described above, in the charging brush roller cleaning method according to the first aspect, the brush fibers are directly vibrated, so that the attached matter of the brush can be reliably removed, and white spots on the halftone image can be removed with time. In addition to suppressing the abnormal image of the shape, the life of the photoconductor can be prolonged because the AC voltage is applied only during the photoconductor removal, and the running cost can be reduced. Since the AC application time to the photoreceptor is very short, the possibility of causing a leak can be reduced. In the charging brush roller cleaning method according to the second aspect, by applying AC to the non-contacting counter electrode, the brush attachment is caused to fly while vibrating the brush fibers, and the electric field with the photoconductor is utilized. Adhered matter can be returned to the downstream of the brush roller on the photoreceptor, and re-adhesion to the brush can be prevented. This suppresses a white spot-like abnormal image on the halftone image over time. Further, since AC is not directly applied to the brush, the photoconductor is not damaged even if there is a pinhole such as a photoconductor defect, and the brush can be prevented from leaking and burning due to the pinhole. In the charging brush roller cleaning method according to the third aspect, by applying AC to the non-contact conductive roller, the brush attachment is caused to fly while vibrating the brush fibers, and the electric field with the conductive roller is used. Thus, the deposit can be collected on the roller. This makes it possible to suppress a white spot-like abnormal image on the halftone image over time. AC is directly applied to the brush.
Is not applied, the photoconductor is not damaged even if there is a pinhole such as a photoconductor defect, and the brush can be prevented from leaking and burning in the pinhole. Further, since the charging brush roller can be cleaned even during image output, the contamination with silica can be more efficiently prevented.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a charging brush and the like in a charging brush roller cleaning method according to the first embodiment.

FIG. 2 is a diagram showing an applied bias output in the charging brush roller cleaning method according to the first embodiment.

FIG. 3 is a schematic view showing a configuration of a charging brush roller and the like in the charging brush roller cleaning method according to the second embodiment.

FIG. 4 is a diagram showing a bias output applied by opposing electrodes in the charging brush roller cleaning method according to the first embodiment.

FIG. 5 is a schematic view showing a configuration of a charging brush roller and the like in the charging brush roller cleaning method according to the third embodiment.

Claims (3)

[Claims] 1. A charging brush roller cleaning method comprising: a charging means for charging a photoconductor using a charging brush roller; and a cleaning means for removing toner remaining on the photoconductor after transfer. A charging brush roller cleaning method comprising: applying a DC bias during image output; and applying an AC bias at a DC bias of 0 V for at least one rotation of the photoconductor after image output. 2. The charging brush roller cleaning method according to claim 1, wherein the electrode plate facing the charging brush roller in a non-contact manner is located downstream of the photoconductor with respect to the brush of the charging brush roller near the photoconductor. A charging brush roller cleaning method, wherein a power source for applying AC to the opposed electrode plate is provided. 3. The charging brush roller cleaning method according to claim 1, further comprising: a conductive roller facing the charging brush roller in a non-contact manner; and a unit for cleaning the conductive roller. A charging brush roller cleaning method, wherein a power source for applying AC or AC + DC to the roller is provided.