JPH0566592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus in which a magnetic brush device is used both as a developing device and a cleaning device.

[Prior art and its problems]

2. Description of the Related Art In recent years, there has been a desire for image forming apparatuses such as copying machines to be smaller and lower in price, and in response to this demand, image forming apparatuses of a so-called two-rotation, one-copy system have been developed, which serve both as a developing device and a cleaning device.

FIG. 1 is a block diagram of such an image forming apparatus.

A charging device 2, a toner disturbing member 3, an exposure device 4, a developing/cleaning device 5, a transfer device 6, and a static eliminator 7 are provided around the photoreceptor 1, and further includes a paper feeding device 8 and a fixing device 9. The first rotation of the photoconductor 1 performs charging, exposure, development, and transfer, and the second rotation performs charge removal, disturbance of residual toner images, and cleaning, and the second rotation of the photoconductor 1 produces one copy. is obtained.

Further, FIG. 2 shows another conventional example, in which the photoreceptor 1
7, a charging device 9 and a toner-disturbing bristle brush 1 are placed around the charging device 9.
0, exposure device 11, developing and cleaning device 1
2, a transfer device 13 and an eraser lamp 14 are arranged, and further includes a paper feed device 15 and a fixing device 16.

This is because in a copying system that uses both a developing device and a cleaning device, the circumference of the photoreceptor 17 is
A document shorter than the length of the maximum copy size is used, the development and transfer process is performed using an area exceeding one rotation of the photoreceptor 17 to form one copy, and after the transfer process is completed, the next copy process is started. The image forming apparatus uses a process in which the photoreceptor 17 performs at least one rotation dedicated cleaning process before entering the image forming apparatus, and one copy can be obtained while the photoreceptor 17 rotates several times. In the two-rotation, one-copy method, it is necessary to use a photoreceptor with a circumference long enough to copy the maximum size original, and the machine cannot be significantly downsized; however, according to this method, the circumference of the photoreceptor is Since there is no restriction on the maximum copy size of the original, the device can be significantly downsized.

However, in order to save space and reduce costs in these image forming apparatuses, if a single high voltage generating unit is used for both the charging device and the transfer device, an unnecessary charged area will be generated on the photoreceptor. It's coming. This means that when the high pressure generating unit is turned off, the timing must be after the visible image on the photoreceptor has been completely transferred onto the transfer paper. On the other hand, the charging device only needs to place an amount of charge on the photoreceptor corresponding to the length of the document, but if charging continues until the end of transfer, charging will occur beyond the trailing edge of the latent image corresponding to the document. Its length on the surface of the photoreceptor corresponds to the distance from the charging position to the transfer position.

When such unnecessary charging occurs, the charging potential is extremely high, so when the toner passes through the development position, it becomes a solid black image and adheres to the photoreceptor, and it is difficult to develop this amount of toner. It is extremely difficult to remove with a cleaning device. Therefore, at the start of the next copy, toner remains on the photoreceptor, resulting in a defective copy image.

[Purpose of the invention]

The present invention has been developed in view of the above-mentioned drawbacks of the conventional technology, and while the charging process and the transfer process are performed by the same high-voltage generating unit, unnecessary charging areas are excluded from the photoconductor, thereby reducing the unnecessary charge on the photoconductor. An object of the present invention is to provide an image forming apparatus that does not cause toner adhesion.

[Key points of the invention]

In order to achieve the above object, the present invention provides an image-bearing device installed downstream of a charging device and upstream of a developing/cleaning device in an image forming apparatus that performs image forming processing by using both a developing device and a cleaning device. When a conductive toner-disturbing member that rubs against the body surface and the surface of the image carrier that the toner-disturbing member rubs are charged with charges that contribute to image formation, the toner-disturbing member will absorb the charge on the surface of the image carrier. Applying a potential that does not disturb the charges, and when unnecessary charges that do not contribute to image formation are charged on the surface of the image carrier that the disturbance member rubs, apply a potential to the toner disturbance member that removes the unnecessary charges. It is characterized by having a bias voltage application means.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a block diagram of an image forming apparatus showing an embodiment of the present invention. In FIG. 3, a charging device 23, a toner-disturbing bristle brush 24, a developing/cleaning device 2
5, a transfer device 26 and an eraser lamp 27 are arranged in this order, and furthermore, an exposure device 28, a fixing device 29, etc. are provided, respectively. Toner agitation bristle brush 2
4 is a conductive bristle brush with a resistance of about 10 ⁴ to ^{10 10} Ω·cm, and as shown in FIG.
8, the voltage is the same as the surface potential of the photoreceptor, or
A ground potential is applied. The timing chart in FIG. 5 shows the timing of this switching.

The photoreceptor 22 is formed into a drum shape that is rotatable in the direction of the arrow as shown in FIG. 3, and its surface is made of a photoconductive material such as Se, ZnO, or an organic photoconductive material. In addition, the circumferential length of the photoreceptor 22 is shorter than the size of the transfer paper on which the image is formed, and if the size of the transfer paper is A4, for example, a photoreceptor 22 with a diameter of about 50 mm is used. Ru. This circumference is approximately half the circumference of a photoreceptor used in a normal two-rotation, one-copy type copying machine. The developing/cleaning device 25 is configured to perform both development and cleaning, and the developer is attached to the surface of the sleeve and rubbed against the photoreceptor and the surface. As the developer, for example, a mixture of high resistance magnetic toner and magnetic carrier is used, but other types of developer may also be used.

The exposure device 28 includes a light source, a lens, and a plurality of mirrors, and projects an exposed image of the document onto the photoreceptor 22.

When a print button (not shown) is turned on, each device starts operating and the photoreceptor 22 starts rotating in the direction of the arrow. As the photoreceptor 22 rotates, the surface of the photoreceptor 22 is first charged by the charging device 23.
Uniformly charged to the required potential.

The surface of the photoreceptor 22 is coated with a toner-disturbing bristle brush 24.
At this time, the same voltage as the charge is applied to the bristle brush, so the photoreceptor 22
The upper charge is not affected in any way. Next, a latent image is formed on the surface of the photoreceptor 22 by an exposure device 28, and development is performed by a developing/cleaning device 25. On the other hand, the transfer paper is sent to the transfer section by the paper feeding device 15 in synchronization with the visible image on the photoreceptor 22, and the toner on the photoreceptor 22 is transferred to the transfer paper by the transfer corona of the transfer device 26. .

Thereafter, the separation device 19 separates the transfer paper from the photoreceptor 2.
After the image is separated from the paper sheet 2, sent by the feed roller 20, and fixed by the fixing device 29, the image is transferred to the paper ejection roller 21.
is ejected from the aircraft. In this image forming apparatus, the circumference of the photoconductor 22 is shorter than the maximum size of transfer paper that can be used, so for example, when forming an image on a transfer paper longer than the circumference of the photoconductor 22, the image is Even after the transfer process is completed, the image forming process is continuously performed on the surface of the photoreceptor used in the process. That is, after the transfer process is completed, the surface of the photoconductor in the portion corresponding to the leading edge of the document enters the static elimination process, and the photoconductor 22 is erased by the eraser lamp 27.
Charges remaining on the surface are erased.

Thereafter, the surface of the photoreceptor 22 is charged again by the charging device 23 to continue image formation. At this time, the photoreceptor is charged, and at the same time, residual toner remaining on the photoreceptor after the transfer process is charged to the same polarity as the photoreceptor. On the other hand, since the toner-disturbing bristle brush 24 used in the next step is applied with the same voltage with the same polarity as the charged photoconductor, the photoconductor and the residual toner, and the residual toner and the bristle brush, tend to repel each other, resulting in a disturbance effect. As a result, the residual toner after transfer is uniformly disturbed on the photoreceptor 22. Furthermore, the toner is further removed by the bias voltage applied to the toner-disturbing bristle brush 24.
The toner-disturbing bristle brush 24 is constantly kept clean.

Subsequently, the exposure device 28 continues the exposure process for forming the first continuous image.
A new electrostatic latent image is formed on the photoreceptor 22. At this time, the residual toner is uniformly and thinly dispersed on the photoreceptor 22, so that it does not interfere with the formation of the electrostatic latent image.

The new latent image formed in the area over one rotation of the photoreceptor 22 is made visible by being cleaned at the same time as development in the next developing/cleaning device 25, and transferred onto transfer paper in the subsequent transfer process. be done.

In this way, in the image forming process that involves more than one revolution of the photoreceptor 22, after one sheet of image formation is completed, that is, the trailing edge of the image formed on the photoreceptor is completely transferred onto the transfer paper. After that, the high voltage generation unit is turned off and the charged corona stops discharging along with the transfer.

By the way, charging is unnecessary on the photoconductor because it continues even after the area necessary to form a latent image corresponding to the original on the photoconductor has passed through the charging section until the trailing edge of the image is completely transferred to the transfer paper. A charged area is created. In the present invention, the toner-disturbing bristle brush 24 is controlled to be in the ground state as soon as the charged area necessary for latent image formation finishes passing through the toner-disturbing bristle brush 24. The very high unwanted charge is then discharged by contact with the grounded conductive bristle brush, and the potential of the unwanted charged area is reduced to a very low level. Conventionally,
A large amount of toner adheres to this area by the developing/cleaning device 25, but according to the present invention,
Since the charging potential is extremely low, only a very small amount of toner adheres to the toner, and the developing/cleaning device 25 can sufficiently clean the toner.

In addition, the toner-disturbing bristle brush 24 disturbs the residual toner while removing the charge on the surface of the photoreceptor, but the photoreceptor and the residual toner have the same polarity and repel each other, so the toner-disturbing bristle brush 24 disturbs the residual toner approximately in the same way as in the area necessary for forming a latent image. Effectively, the toner is evenly distributed on the photoreceptor.
Although some toner adheres to the bristle brush, the amount is so small that it does not pose a problem.

Further, the toner adhering to the bristle brush moves to the photoreceptor side when a bias charge of the same polarity is applied to the bristle brush during the next copying, and no toner accumulates on the bristle brush.

In this way, in an image forming process that involves more than one rotation of the photoreceptor 22, after the formation of one sheet of image is completed, the photoreceptor 22 is A post-processing process dedicated to cleaning is performed for one or more rotations. That is, in this dedicated cleaning process, the charging device 2
3. With the exposure device 28 and transfer device 26 inactive, the residual toner and residual charge on the photoreceptor 22 are completely erased by the eraser lamp 27, toner-disturbing bristle brush 24, and developing/cleaning device 25. At this time, the toner-disturbing bristle brush 24 is at ground potential and rubs the surface of the photoreceptor 22.
Since the residual charge is removed and the residual toner is disturbed, a high disturbance effect is produced, which contributes to improving the cleaning ability of the next developing/cleaning device 25.

When this cleaning-only post-processing step is completed, a new image forming step is started, and the above-described steps are repeated again.

As described above in detail, the image forming apparatus of the present invention has the toner-disturbing bristle brush 24 conductive,
By setting this to the ground state, unnecessary charged areas can be neutralized, making it possible to obtain stable, high-quality images.

In the above-described embodiment, the toner-disturbing bristle brush was grounded when dealing with an unnecessary charged area, but in order to further enhance the static elimination effect, a voltage of opposite polarity to the charge on the photoreceptor 22 was applied to the toner-disturbing bristle brush. You may.

〔Effect of the invention〕

As described above in detail, according to the image forming apparatus of the present invention, charging and transfer can be performed by one high voltage generation unit.

Further, a blank exposure device is not required.

Therefore, it is possible to reduce the size and cost of the image forming apparatus.

Furthermore, cleaning failures due to large amounts of toner adhesion do not occur.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional image forming apparatus, FIG. 2 is a block diagram showing another conventional example, FIG. 3 is a block diagram of the image forming apparatus of this description, and FIG. 4 is a main part of the present invention. The enlarged configuration diagram, FIG. 5, is a timing chart of the present invention. 1, 22... Photoreceptor, 2, 9, 23... Charging device, 4, 11, 28... Exposure device, 5, 12, 2
5... Development and cleaning device, 6, 26... Transfer device, 9, 16, 29... Fixing device, 18...
Bias device, 10, 24... Toner agitation bristle brush, 14, 27... Eraser lamp.

Claims (1)

[Scope of Claims] 1. In an image forming apparatus that performs image forming processing by using both a developing device and a cleaning device, an image forming apparatus that is provided downstream of a charging device and upstream of a developing and cleaning device and that slides the surface of an image carrier. a conductive toner-disturbing member that rubs; and when the surface of the image carrier that the disturbance member rubs is charged with charges that contribute to image formation, the toner-disturbing member does not disturb the electrical charge on the surface of the image carrier; When a potential is applied and the surface of the image carrier that is rubbed by the disturbance member is charged with unnecessary charges that do not contribute to image formation,
An image forming apparatus comprising: bias voltage applying means for applying a potential to the toner disturbing member to remove the unnecessary charge.