JPH0310954B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a toner image carrier of an electrophotographic copying device, etc., and more specifically, the present invention relates to a method for cleaning a toner image carrier of an electrophotographic copying device, etc., and more specifically, the present invention relates to a method for cleaning a toner image bearing member of an electrophotographic copying device, etc. The present invention relates to an improvement in a method for removing toner from the surface of a toner image carrier after a developing step and a transfer step using a rotating brush device.

In the above-described cleaning method, the cleaning effect is largely influenced by the scraping action by the brush of the brush device and the electrostatic attraction action by frictional charging between the brush and the toner. The latter electrostatic adsorption effect significantly reduces the cleaning effect if the triboelectric properties of the brush and toner forming materials are unstable.

Furthermore, before the toner on the toner image carrier is removed, the toner image on the toner image carrier is transferred to a transfer material such as paper in a transfer step.
At this time, corona discharge is performed for transfer. In this transfer process, for example, if the original on which the image is to be formed on the toner image carrier is larger than the transfer material or is slippery, the surface of the toner image carrier may undergo corona discharge for direct transfer without passing through the transfer material. After receiving the
The toner on the toner image carrier is charged with a charge of opposite polarity to the charge it had during image formation,
The polarity of the toner remaining after normal transfer may be different from that of the remaining toner, resulting in poor cleaning.

Furthermore, even if the above does not occur, charge is injected into the toner on the toner image carrier through the transfer material due to corona discharge in the transfer process, and the residual toner after transfer is a mixture of toner with both positive and negative charges. This can also lead to poor cleaning.

With conventional cleaning methods, it has not been possible to obtain a stable and sufficient cleaning effect due to the reasons described above. Therefore, in an electrophotographic copying apparatus in which a rotating toner image bearing member makes one copy in two revolutions using a magnetic brush device that serves both development and cleaning, corona discharge for direct transfer is particularly performed on the toner image bearing member. In order to eliminate the occurrence of cleaning failures in cases where transfer residual toner is charged with positive or negative charges,
The toner image bearing member is negatively charged to form an electrostatic latent image, developed with positively charged toner, and in the transfer process, corona discharge is performed to negatively charge the toner image, and the toner image after transfer is Japanese Patent Application Laid-Open No. 2003-1991 discloses a method in which a pre-cleaning corona discharge is carried out to give a positive charge to the residual toner after the entire surface of the carrier is exposed to light, and then cleaning is performed using a magnetic brush device to which the same positive bias voltage as used during development is applied. 52−
It is known from Publication No. 58931. However, in this method, corona discharge with a polarity opposite to the charging for image formation is performed before cleaning, so the toner image bearing member is charged with a charge opposite to the photosensitivity characteristic of the photoreceptor. This remains even after cleaning, and as a result, the charging for the next image formation becomes uneven, which not only tends to cause a decrease in image density and density unevenness, but also causes this pre-cleaning corona discharge to be repeated. This poses a problem in that the photoreceptor rapidly becomes unusable. This is because the photoreceptor has p-type and selenium photoreceptors.
There are n-type photoreceptors such as CdS and ZnO photoreceptors, and if they are p-type, they are positively charged, and if they are n-type, they are negatively charged.
An electrostatic latent image is formed by utilizing the photosensitivity characteristics of these photoreceptors, but if the p-type is negatively charged and the n-type is positively charged, the photosensitivity becomes extremely poor. Almost no charge on the body is discharged,
This is because a clear electrostatic latent image is not formed.

The present invention does not cause the above-mentioned problems, and
Moreover, even if corona discharge occurs directly on the surface of the toner image carrier during transfer, or even if the residual toner after transfer is a mixture of toner with both positive and negative charges,
The cleaning method of the present invention provides a cleaning method that can stably obtain a sufficient cleaning effect. In a method for removing toner on the surface of a toner image carrier that has undergone a transfer step and a transfer step using a rotating brush device, a corona discharge of the same polarity as in the charging step is applied to the surface of the toner image carrier before reaching the brush device after the transfer step. In addition, the brush device is characterized by using a brush that is charged with a polarity opposite to that of the charging step, and even if the brush device uses a fur brush that is charged with a polarity opposite to that of corona discharge in the charging step. Alternatively, a magnetic brush device using a magnetic carrier that is charged with a polarity opposite to that of the magnetic carrier used during development due to frictional electrification with the toner may also be applied.

Hereinafter, the present invention will be explained based on the drawings.

The figure is a schematic side view of an electrophotographic copying apparatus in which the method of the present invention is carried out when the brush device is a magnetic brush device. It is assumed that a selenium photoreceptor is used.

The toner image carrier 1 rotates clockwise, and the surface of the photoreceptor is uniformly positively charged by the charger 2. Next, the exposure device 3 projects an original image onto the charged surface, forming an electrostatic latent image. The electrostatic latent image is
Toner is applied by the magnetic brush developing device 4 and the toner is developed. This magnetic brush developing device 4 uses a developer made of a mixture of a magnetic carrier and toner, and the magnetic carrier is positively charged by friction to form a magnetic brush on the rotating developing sleeve 4a. The toner is negatively charged and carried by the magnetic brush to develop the electrostatic latent image.

The developed toner image is transferred onto a transfer material 5 that is conveyed from right to left in contact with the toner image carrier 1 by a conveyance device (not shown). At the transfer position, the transfer device 6 performs corona discharge on the back surface of the transfer material 5 to positively charge the transfer material 5, so that the toner leaves the electrostatic attraction of the photoreceptor and transfers to the transfer material 5.
Therefore, transcription takes place. This corona discharge injects positive charge into the toner on the toner image carrier 1 through the transfer material 5, and the toner, which originally had a negative load, is positively charged, and the toner is transferred onto the toner image carrier 1 after transfer. The remaining toner is a mixture of positively and negatively charged toner. This tendency occurs because the transfer material 5 is smaller than the original and the corona discharge is caused by the toner image carrier 1.
This becomes even more noticeable when the process occurs directly on the surface.

The pre-cleaning charger 7, which discharges a corona discharge onto the surface of the toner image bearing member after transfer, converts the residual toner in a mixed state of positive and negative charges as described above into a corona discharge of the same polarity as the corona discharge during the charging and transfer process. Therefore, it is uniformly positively charged. Here,
If the pre-cleaning charger 7 uniformly charges the residual toner negatively, the photoreceptor will also become negatively charged, which can lead to fatal problems such as deterioration of image quality due to poor photosensitivity as mentioned above. This will lead to serious consequences.

As described above, the residual toner that is uniformly positively charged and is uniformly susceptible to electrostatic force is removed from the toner image carrier by a magnetic brush cleaning device 8 using a negatively charged cleaning carrier. Removed from the first page.

In the magnetic brush cleaning device 8, an ear of a magnetic cleaning carrier is formed by a magnet disposed inside the cleaning leaf 8a that rotates in a clockwise direction, and the magnetic brush cleans the surface of the toner image carrier 1. Remove residual toner by rubbing. Since the magnetic brush is negatively charged, the uniformly positively charged residual toner is uniformly subjected to the electrostatic attraction force of the magnetic brush, and the cleaning performance of the magnetic brush cleaning device 8 is greatly improved. This will ensure stable and thorough cleaning. In order to further improve this cleaning performance,
A cleaning bias power supply 9 applies a negative bias voltage having a polarity opposite to that of the residual toner charge to the cleaning sleeve 8a. The toner adhered to and removed by the magnetic brush moves onto a toner collection drum 8b that rotates counterclockwise so as to come into contact with the magnetic brush, and is collected into a toner reservoir 8d by a scraper 8c. The toner collection drum 8b is powered by a collection bias power supply 10 so as to attract toner from the magnetic brush.
A collection bias voltage higher than the cleaning bias voltage of the cleaning sleeve 8a is applied.

When the toner image bearing member 1 from which the residual toner has been removed in the above manner is further rotated, it is charged again by the charger 2 and enters the next copying process.

The present invention has been described above with respect to the case where the photoconductor of the toner image bearing member is a p-type photoconductor, but the present invention can be implemented in the same manner with respect to an n-type photoconductor by reversing the charging polarity. It is easy to understand what is done.

Further, the present invention is applicable not only to a magnetic brush device but also to a fibrous brush device. In that case, for example, if the photoreceptor is a p-type and is to be positively charged with the pre-cleaning charger 7, the fibers of the fibrous brush should be fluorine-based fibers or acrylic fibers that are negatively charged. If the photoreceptor is an n-type and is to be negatively charged with the pre-cleaning charger 7, nylon fiber or the like that is positively charged may be used.

Further, the present invention can be applied to not only the two-component developer mentioned above but also one-component developer. That is, even if the developer consists only of toner, the problem of removing residual toner is the same as in a two-component developer, so the present invention can be applied even when a one-component developer is used. It is easy to understand that this method can be effective.

As described above, according to the method of the present invention, (1) the electrically non-uniform residual toner after the transfer process is made uniform, so its removal becomes easy, and the cleaning performance is greatly improved; (2) When electrically uniforming the residual toner, the electrophotographic properties of the photoreceptor are not impaired in any way; (3) Therefore, clear images are recorded without fogging. Remarkable effects can be obtained, such as:

[Brief explanation of drawings]

The figure is a schematic side view of an electrophotographic copying apparatus relating to implementation of the method of the present invention. 1... Toner image carrier, 2... Charger, 3...
Exposure device, 4...Magnetic brush developing device, 4a...
Developing sleeve, 5... Transfer material, 6... Transfer device, 7
...Pre-cleaning charger, 8...Magnetic brush cleaning device, 8a...Cleaning sleeve, 8b...Toner collection drum, 8c...Scraper, 8d...Toner reservoir, 9...Bias power supply for cleaning, 10... Bias power supply for recovery.

Claims (1)

[Claims] 1. In a method in which a rotating brush device removes toner from the surface of a toner image carrier that has gone through a charging step, an image exposure step, a developing step in which toner charged with a polarity opposite to that of the charging step in the charging step is attached, and a transfer step. A corona discharge having the same polarity as that in the charging step is applied to the surface of the toner image carrier before reaching the brush device through the process, and a brush device is used in which the brush is charged in the opposite polarity to the charging step. A method of cleaning a toner image carrier.