JPS60254171A - Image forming device - Google Patents

Abstract

PURPOSE:To improve cleaning performance, and to prevent whiting in a solid- black part and form an image of good quality by adjusting the friction electrostatic charging characteristic between coated carriers and magnetic toner as a developer. CONSTITUTION:A photosensitive body 9 begins to make the 1st clockwise turn and is charged 10 electrostatically and exposed 11 to form an electromagnetic latent image of an original image. A magnetic brush contacts the image at a developing and cleaning part 12 to induce charges of the opposite polarity of the electrostatic latent image to a magnetic toner in the brush, and the magnetic toner is attracted to visualize the image on the photosensitive body 9. Coated carriers have almost no charge and not attracted to the latent image. The image is transferred 13 to transfer paper which is not shown in a figure. The photosensitive body is charged 10 again with the toner left and the rear half part of the original is exposed 11 to form a latent image, which is developed 12. The residual toner is cleaned completly with the magnetic brush with which the coated carriers are mixed. Consequently, the cleaning characteristic is improved and whiting in the solid-black part is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus equipped with a magnetic brush device that has both a developing function and a cleaning function.

[Prior art]

, the prior art will be explained along with the accompanying drawings.

Japanese Patent Laid-Open No. 47-1 introduced a copying system in which a developing device also had a cleaning function for the purpose of downsizing image forming apparatuses.
It is disclosed in Publication No. 1538 and the like.

For example, as shown in FIG. 1, a charging device 2. Exposure device 3. Developing and cleaning device 4. Transfer device5. Static eliminators 6 are sequentially arranged, and paper feeders 7. A fixing device 8 is provided, and these are so-called two-rotation, one-copy, one-way type, which eliminates the need for a dedicated cleaning device that was previously required, which not only reduces the size of the device but also reduces costs. Furthermore, it has various advantages such as being able to recycle the toner without using a recycling device.

Further, in Japanese Patent Application No. 58-213331, etc., a copying system has been proposed which allows the apparatus to be made more compact than the two-rotation, one-copy, one-shot system.

As shown in FIG. 2, this is similar to the conventional two-rotation, one-copy system, in which image forming means such as a charging device 2 and a developing cleaning device 4 are arranged around the photosensitive drum 1. Use a body drum I whose circumference is shorter than the length of the maximum copy size document.

In order to obtain one copy, a developing transfer process is performed over one continuous rotation, and after the transfer to the transfer paper is completed, a dedicated cleaning process is performed for at least one rotation before starting the first copying process. Inside, only static electricity removal and cleaning are performed to obtain a single copy. In the 2 rotation 1 copy one type.

The photoconductor needs to have a circumference that is large enough to copy the maximum copy size of the original, and the device cannot be significantly downsized; however, with this method, the circumference of the photoconductor is not limited to the maximum copy size of the original, It becomes possible to significantly downsize the device.

However, in a system in which both development and cleaning are performed using the same magnetic brush device, the ability to remove toner during cleaning is weaker than in the case of independent cleaning devices such as fur brush cleaning and blade cleaning.

Therefore, in the above-mentioned methods, a -component magnetic toner was usually used as a developer, but a magnetic brush made only of -component magnetic toner still had insufficient toner removal ability, and in order to improve this, 1987-308, a method of increasing the toner removal ability of a magnetic brush by using a mixture of magnetic toner and magnetic carrier as a developer was proposed.
This is proposed in Publication No. 46, etc. In this method, not only a cloning force but also a magnetic force is exerted between the magnetic brush and the magnetic toner on the photoreceptor, and the cleaning ability is strengthened by increasing the attraction force of the magnetic brush to the magnetic toner.

Also, to further improve cleaning performance.

There is a method of using a magnetic toner whose frictional charging polarity with a magnetic carrier mixed therein is the same as the polarity of the electrostatic latent image on the photoreceptor. this is.

For example, in the case of a two-rotation, one-copy system, the magnetic toner remaining on the photoreceptor after passing through the transfer section is charged to the same polarity as the photoreceptor by the transfer corona. That is, during development, the magnetic toner adheres to the electrostatic latent image due to electrostatic induction caused by the electrostatic latent image on the photoreceptor, which induces a charge with a polarity opposite to that of the electrostatic latent image. Since the toner tends to be charged to the same polarity as the photoreceptor, after passing through the transfer section, the charge of the magnetic toner on the photoreceptor has the same polarity as the electrostatic latent image on the photoreceptor. After passing through the transfer section, the photoreceptor is neutralized by an eraser lamp and enters a cleaning process.

At this time, an electrostatic repulsive force is acting between the residual potential of the photoreceptor and the magnetic toner, so that the toner can be easily sown with a magnetic brush and a good cleaning can be performed. In addition, in the case of the method shown in Figure 2, magnetic toner is used not only for transfer but also for two purposes.
By the second charging, the polarity becomes the same as that of the photoreceptor, and
The potential of the photoreceptor is also after static electricity removal with the Eret No. lamp! higher than the rank.

This generates a large electrostatic repulsive force, and the magnetic brush completely removes the toner.

When a magnetic toner having a charge polarity that is the same as that of the photoreceptor is used, in addition to improving the cleaning performance as described above, there is an advantage that there is no toner adhesion to the white background area, that is, there is no background smearing. this is.

Because the materials are selected so that the magnetic toner tends to have the same polarity as the electrostatic latent image on the photoreceptor, at low potentials, the induction of charges of opposite polarity from the electrostatic latent image to the magnetic toner is difficult. Since this does not occur, magnetic toner does not adhere to the white background area, and as a result, background smearing can be prevented.

[Problems with conventional technology]

In the image forming apparatus configured as described above, a magnetic carrier and a magnetic toner having the same frictional charging polarity as the charging polarity of the photoreceptor are used as the developer.

A problem arises in that carriers adhere to the photoreceptor.

This is due to the magnetic force of the magnetic brush acting on the magnetic carrier due to the electrostatic attraction force from the electrostatic latent image on the magnetic carrier, which has a charge of opposite polarity to the photoreceptor due to frictional charging with the magnetic toner during development. As a result, it adheres to the electrostatic latent image.

This is particularly noticeable when the potential of the electrostatic latent image is high or when the toner concentration of the magnetic toner is low and the amount of charge of the magnetic carrier is high.

Also, when magnetic carriers adhere to the electrostatic latent image.

White areas appeared on the image, which was unfavorable in terms of the quality of the copied image.

[Purpose of the invention]

In view of the above-mentioned conventional drawbacks, the present invention uses a mixture of a coated carrier and a magnetic toner as a developer, and adjusts the triboelectric charging characteristics of the coated carrier and the magnetic toner to improve cleaning properties and solid black areas. An object of the present invention is to provide an image forming apparatus equipped with a magnetic brush device that does not cause white spots.

[Summary of the Invention] According to the present invention, the above-mentioned object is achieved by using a coated carrier and a magnetic toner whose triboelectric charging characteristic with the coated carrier is the same as the polarity of the electrostatic latent image on the image bearing member or which does not generate any charge at all as a developer. This is achieved by providing an image forming apparatus characterized in that it is equipped with a magnetic brush device that performs both development and cleaning.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to one drawing.

FIG. 3 is a block diagram showing an image forming apparatus according to the present invention.

The image forming apparatus includes a photoreceptor 9, a charging device 10, an exposure device 11, and a developing/cleaning device 12 arranged around the photoreceptor 9.
, a transfer device 13, an eraser lamp 14, and the like.

The photoreceptor 9 is made of a well-known photoconductive material such as Se, ZnO, O, and PC. Further, the -charging device 1° charges the photoreceptor 9 negatively or positively by corona discharge or the like.

The exposure device 11 forms a scanned original image on the surface of the photoreceptor 3 using a combination of a lens and a mirror.

The developing/cleaning device 12 has a magnetic roll carrying a magnetic brush on its surface in an opening that rubs against the photoreceptor 9, and a developer is stored in a hopper.

The transfer device 13 transfers the toner image on the surface of the photoreceptor 9 by applying a potential of opposite polarity to the toner from the back side of the transfer paper using corona discharge. The eraser 14 optically eliminates and neutralizes the residual charge on the photoreceptor 1 after the toner image has been transferred, thereby facilitating cleaning of the residual toner.

On the other hand, the developer consists of magnetic toner and magnetic carrier.
The surface of the magnetic carrier is coated with a substance that does not generate any triboelectric charge or is only slightly charged with the magnetic toner.

In the present invention, as the core material of the coated carrier, the same material as the carrier of conventional two-component development method is used. For example, metals such as iron, nickel, cobalt manganese, etc., and oxides or alloys of these materials are used. used.

Further, the coating may be made of the same composition as the components other than the magnetic material in the toner, or any material may be used as long as it has a charging series substantially equal to that of the magnetic toner and hardly causes triboelectric charging.

Next, the operation of the image forming apparatus using the magnetic brush device of the present invention will be explained.

First, when the print switch is turned on, the photoreceptor 9 starts rotating clockwise for the first time, and a little later than that, the charging device is activated, and the circumferential surface of the photoreceptor 9 is sequentially and uniformly charged. go.

Next, the exposure device 11 exposes the original image onto the photoreceptor 9 to form an electrostatic latent image. In a magnetic brush contact brush, this electrostatic latent image induces a charge of opposite polarity to the electrostatic latent image on the magnetic toner in the magnetic brush.

For this magnetic toner, the electrostatic attraction force between the electrostatic latent image and the electrostatic latent image overcomes the magnetic force of the magnetic brush.
Development is performed by adhering magnetic toner to the electrostatic latent image.

On the other hand, the coated carrier has almost zero charge due to frictional charging with the magnetic toner, and compared to the case of conventional carriers that have charges of opposite polarity to the electrostatic latent image, there is less charge from the electrostatic latent image. Electrostatic attraction is extremely weak.

On the other hand, 1. Ordinary magnetic toner contains only about 70% by weight of fine magnetic powder.

The magnetic force becomes stronger in proportion to the volume, and since the carrier has a volume several tens of times larger than that of the magnetic toner, the magnetic force of the magnet roll acting on the carrier is far greater than the magnetic force acting on the magnetic toner. Strong against As a result, the electrostatic attractive force between the electrostatic latent image and the electrostatic latent image does not overcome the magnetic force of the magnetic brush.

Carrier adhesion to the photoreceptor does not occur.

On the other hand, the manually fed transfer paper 9 is fed to the registration roll 17 by the paper feed roller 16, and further sent to the transfer area by the registration roll 17 in synchronization with the toner image on the surface of the photoreceptor 9, and in this transfer area. The image is transferred by the transfer device 13.

The transfer paper is immediately fixed by a separating device 18 and by a device 15 consisting of a photoreceptor 9.

After the transfer, residual toner that has not been transferred remains on the photoreceptor 9. Eraser light is emitted from the eraser lamp 14 to erase the residual charge on the photoreceptor 9 from above the residual toner.

Further, since the circumference of the photoreceptor 9 is shorter than the length of the original, the photoreceptor 9 continues the copying process even after making one rotation.

The photoreceptor 9 is charged again by the charging device 10 while the residual toner remains on the photoreceptor 9 . The residual toner becomes the same polarity as the electrostatic latent image on the photoreceptor by the transfer device 13 and the charging device 10. After being exposed by the exposure device 11, residual toner is removed by the developing/cleaning device I2.

At this time, the residual toner is not completely cleaned due to the strong sliding force of the magnetic brush mixed with the coated carrier and the magnetic attraction force, as well as the strong electrostatic repulsion between the photoreceptor and the magnetic toner. It will be done.

At the same time, the latent image is visualized by the magnetic toner in the magnetic brush. Then, when the portion corresponding to the rear edge of the document is transferred onto the paper and the partial area corresponding to the rear wheel of the document on the photoreceptor 9 passes the eraser lamp 14, the first copying process is completed at that point, and the cleaning process is completed. The first copying operation is completed through a dedicated process.

As explained in detail above, the developing and clearing device of the present invention has a sufficiently high cleaning ability even though the same magnetic brush device is used for developing and cleaning purposes, and in addition, white areas such as solid black areas are not developed. You can obtain high-quality images without any problems.

〔Effect of the invention〕

According to the image forming apparatus of the present invention configured as described above, although the same magnetic brush device is used for both development and cleaning, it has sufficiently high cleaning performance, and white areas such as solid black areas are produced with good quality without causing any phenomenon. You can get a good image.

Further, the cleaning process may be kept to a minimum.

Furthermore, the toner has a wide allowable density range and is free from scumming.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a conventional image forming apparatus, and FIG.
This figure is a block diagram of another conventional image forming apparatus, and FIG. 3 is a block diagram showing an embodiment of the present invention. 9... Photoreceptor, 10... Charging device. 11... Exposure device, 12... Developing and cleaning device, 13... Transfer device. 14... Eraser lamp, 15... Fixing device,
16... Paper feed roller, 17... Registration roll, 18... Separation device. Patent Applicant: Casio Computer Co., Ltd. Yoshiyuki Osuga, Patent Attorney, ID Co., Ltd.

Claims (2)

[Claims] (1) A magnetic brush device that performs both development and cleaning using a coated carrier and a magnetic toner whose triboelectric charging characteristic with the coated carrier is the same as the polarity of the electrostatic latent image on the image carrier, or which does not generate any charge at all, as a developer. An image forming apparatus comprising: (2) A developer comprising a magnetic toner and a coated carrier using, as a coating material, a material having approximately the same rank in the triboelectrification series as the remaining components of the magnetic toner except for the magnetic component. An image forming apparatus according to claim 1.