JPS60158470A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the uneven image occurring in uneven electrostatic charge with a small sized device or an image having too much solid black having no gradation by using a hollow developer as a developer. CONSTITUTION:The toner as a developer is satisfactory as far as the toner is hollow. If the size of the space occupying in each individual toner, i.e., voids are too large, the toner is brittle to the external force during agitating in a developing device 4 and therefore the toner particles are likely to be broken prior to contribution to prescribed development. The voids of the toner are therefore up to about 60-70% at the highest. The uneven image occuring in uneven charging with the small sized device or formation of an image having too much solid black having no gradation is prevented by using such toner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus that utilizes electrophotography, electrostatic recording, or the like.

C. Prior Art] For example, in a conventional electrophotographic copying apparatus, various processes such as charging, exposure, development, transfer, cleaning, and static elimination are arranged around a drum-shaped or belt-shaped photoreceptor. This method allows one copy to be obtained with one rotation of the body.

In such a copying apparatus, a cleaning device is provided independently and a cleaning process is performed to completely remove residual toner after transfer.

The disadvantage of the copying machine with the above configuration is that the cleaning device is costly and takes up a lot of space inside the machine.
It was not possible to downsize the entire copying device.

Furthermore, there was a lot of scattering in the cleaning device and its surroundings, making it necessary to clean it frequently.

Further, when the cleaned toner is collected and returned to the developing device, a dedicated toner conveying device is required, which is costly and causes malfunctions due to toner clogging.

Therefore, in order to compensate for the drawbacks of the 1-rotation, 1-copy method, a 2-revolution, 1-copy, and 1-rotation method has been proposed in which the remaining toner after transfer is collected in a 1-rotation cleaning process using a device that has both a developing function and a cleaning function. It has been put into practical use.

Since the developing and cleaning processes are performed in the same device, this method does not require an independent cleaning device, nor does it require a separate collection device, making it a low-cost, one-shot method for copying with less scattering inside the machine. It is valid as

However, in this two-rotation, one-copy system, the full-length image of the document must be developed and transferred on the photoreceptor without overlapping during the first rotation of the photoreceptor.

The circumferential length of the photoreceptor still requires approximately the same length as in the case of one-rotation copying, that is, the maximum length of the original to be copied + α.

To give a concrete example of this, when the maximum original size is 84, the length is 364 fins, so the circumference of the photoreceptor requires 364 fins + α length, and the drum diameter is about 120 φ. photoreceptor is required. For this reason, the overall size of the copying machine is almost the same as a one-rotation, one-copy, one-way system.Therefore, it is difficult to downsize the entire copying machine while keeping the maximum original size the same as the conventional method. It was difficult with the two-bokuto style.

Therefore, in order to eliminate the drawbacks of copying machines using the 5 or more methods, a developing and cleaning device is used in a 2-rotation, 1-copy method, and a photoreceptor with a circumference shorter than the length of the maximum original can be used. Therefore, the device described below has made it possible to downsize the entire copying device.

First, a photoreceptor is charged by a charging device, a latent image is formed by an exposure device, and the latent image is developed by a developing/cleaning device.

Here, the developed image is transferred to a transfer paper by a transfer device, separated from the photoreceptor, and then fixed.

After the transfer process, the photoreceptor is neutralized by an eraser lamp, and residual toner on the photoreceptor is scattered by a toner agitation fur brush roll. Even after the photoreceptor rotates once, the copying process continues, and charging, exposure, development, simultaneous cleaning, and transfer continue. Thereafter, a dedicated cleaning process of at least one rotation is performed using only static elimination and cleaning, and one copying operation is completed.

This copying method is compared to the conventional two-rotation, one-copy method.
Although it has the advantage of reducing cost by making the entire device including the photoreceptor smaller, it also has the disadvantages described below.

[Problems with conventional technology]

In order to miniaturize the device, in addition to reducing the diameter of the photosensitive drum, it is necessary to provide a shield case for the charging device with a small comb and to place the charging device and the photosensitive drum close to each other. Therefore, when attempting to charge a photosensitive drum to a desired surface potential, the charging voltage applied to the charging wire must be lower than when the photosensitive drum and charging wire are far apart or when the shield case is large. I had to.

However, when the charging voltage is lowered, corona discharge becomes non-uniform, and charging is not uniformly performed, resulting in so-called uneven charging. This phenomenon is particularly noticeable when negatively charged as a characteristic of corona discharge. Therefore, it is possible to eliminate such charging unevenness by increasing the charging voltage, but the charging potential becomes high, and if development is performed in such a state, the amount of toner that adheres will be too large. This results in a completely black image with no gradation.

Further, offset etc. at the fixing section are likely to occur.

Furthermore, there may be a large amount of toner remaining after transfer, and the developing/cleaning device may not be able to clean it completely.

Transfer may also occur during the second rotation, which is extremely undesirable in terms of image quality.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide an image forming apparatus that prevents uneven image formation due to uneven charging in a small device, or image formation with too much black and no gradation. do.

(Summary of the Invention) In order to achieve the above object, the present invention is characterized in that a hollow developer is used as the developer.

[Embodiments of the invention]

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

FIG. 1 is a block diagram of an image forming apparatus in which the present invention is implemented.

The image forming apparatus includes a photoreceptor 1 and a charging device 2 disposed around the photoreceptor. Exposure device 3. Developing and cleaning device 4. Transfer device5. Eraser lamp 6. and a fur brush roll 7 for toner agitation.

For the photoreceptor 1, conventionally known photoconductive materials such as Se, ZnO, OPC, etc. can be used, but ZnO is most suitable in consideration of manufacturing cost, cleanability, and safety. The toner used as a developer is good if it is hollow, but if the space occupied by each toner, that is, the porosity is too large, it will become brittle against external forces during stirring in the developing device. .

Each particle is easily damaged and damaged before it contributes to the desired development (and no improvement in image quality can be expected. Therefore, the porosity of the toner is at most about 60 to 70%.

On the other hand, if the porosity is as low as 5% or 10%, there will be no difference from conventional toners, and the effects of the present invention cannot be obtained.

Next, the operation of the image forming apparatus in which the present invention is implemented will be described. First, when the print switch is turned on, the photoreceptor 1 starts rotating clockwise for the first time, and the charging device 2 is activated. The circular surface of the photoreceptor 1 is sequentially and uniformly charged. At this time, the voltage applied to the charging wire of the charging device 2 is as follows.

The surface potential of the photoreceptor 1 is at a fairly high level because the size is set to such an extent that uniform corona discharge occurs.

The exposure device 3 exposes the original image onto the photoreceptor 1 to form a latent image. This latent image is developed by the hollow-component magnetic toner of the present invention deposited on a magnetic brush in a developing/cleaning device 4.

Because each toner particle is hollow inside.

By developing the photoreceptor 1 that carries a latent image with a fairly high potential, even if a large amount of toner adheres to the latent image, the net amount of toner that contributes to the actual image density is not excessive; An image with good gradation can be obtained.

On the other hand, the transfer paper is fed from a cassette by a paper feed roller 8, and sent to a transfer area by a registration roll 9 in synchronization with the toner image on the surface of the photoreceptor 1, where the image is transferred by the transfer device 5. Ru. The transfer paper is immediately fixed by a device 11 comprising a photoreceptor 1 from a separating device 10 .

According to the toner of the present invention, even if the toner adheres to an apparent amount,
Since the amount that substantially contributes to the image density after fixing is not large, malfunctions such as offsets and jams do not occur during fixing.

After the transfer, residual toner that has not been transferred remains on the photoreceptor 1. Eraser light is emitted from the eraser lamp 6 to erase the residual charge on the photoreceptor from above the residual toner. This irradiation with the eraser lamp 6 causes the residual charge to disappear, and the electrostatic adhesion of the toner to the photoreceptor 1 is extremely weak.The residual toner is easily removed from the photoreceptor 1 by the toner agitation fur brush roll 7 that rotates once. Disturbed.

Further, since the circumferential length of the photoreceptor 1 is shorter than the length of the original, the photoreceptor 1 continues the copying process even after making one revolution. That is, the photoreceptor 1 is charged again by the charging device 2 with the residual toner scattered almost uniformly on the photoreceptor 1, and exposed by the exposure device 3.

At this time, the residual toner is uniformly dispersed on the photoreceptor 1, so it does not become a hindrance during the formation of the latent image (the latent image is removed by the developing and cleaning device 4).

Be visualized.

At the same time, the remaining toner is removed from the developing/cleaning device 4.
Most of the cleaning is done by the magnetic brush.

Since the small amount of toner that remains without being cleaned in the untransferred area is substantially very small, the quality of the image will not deteriorate even if it is transferred during the next transfer.

A portion corresponding to the rear edge of the original is transferred, and a partial area corresponding to the rear edge of the original on the photoreceptor l is erased by the eraser lamp 6.
Once the copying process has passed, the copying process ends and a cleaning-only process begins.

FIG. 2 shows a configuration diagram of another image forming apparatus in which the present invention is implemented. A photoreceptor 1, a charging device 2, an exposure device 3, a developing/cleaning device 4, a transfer device 5, an eraser lamp 6, and a fur brush roll 7 for toner agitation arranged around the photoconductor 1.
It is composed of.

However, the only difference from FIG. 1 is the toner agitation fur brush roll 7 and the exposure path of the exposure device, but the basic operation and principle are exactly the same.

In addition, although the hollow one-component magnetic toner has been described in 9 and above, the same effect can be obtained even if a two-component developer having a hollow toner is used.

〔Effect of the invention〕

According to the hollow toner of the present invention configured as above,
Even if development is performed on a photoconductor that carries a latent image with a fairly high surface potential, the actual amount of toner will not be large enough to produce a good one-tone copy, and it will be difficult to produce a high-quality image. Obtainable.

In other words, even if the device is made smaller, the photoreceptor used and the charging device are placed close together, and the shield case is made smaller, the
An image with excellent gradation can be obtained without causing image unevenness.

Furthermore, no offset occurs during fixing, and no afterimages due to insufficient cleaning appear on the copy paper.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a copying machine in which the present invention is implemented. FIG. 2 is a block diagram of another copying machine in which the present invention is implemented. ■...Photoreceptor 2...Charging device 4...Developing/cleaning device 6...Eraser 7...Fur brush roll for toner agitation 11...Fuser patent applicant Casio Computer Co., Ltd. Same as above I.D. Co., Ltd. Representative Patent Attorney Yoshiyuki Osuga

Claims (1)

[Claims] An image forming apparatus characterized in that a hollow developer is used as a developer.