JPS60196783A - Developing and cleaning device - Google Patents

Abstract

PURPOSE:To obtain images of good quality by constituting a developer of a developing and cleaning device, which is used as a developing device as well as a cleaning device, with two kinds of carrier different in average particle size. CONSTITUTION:A developer D which is stuck onto a developing and cleaning roll 9 and is controlled to a certain layer thickness so as to rub the surface of a photosensitive body in accordance with rotation of the roll 9. This developer D consists of a mixture of magnetic carriers 10 and 11 different in average particle size and a magnetic toner 12. With respect to magnetic carriers, a metal such as iron, nickel, or the like or their oxide or alloy is used as it is, or an insulating resin film is coated on the surface of particles of these materials.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a developing/cleaning device that serves both as a developing device and a cleaning device in an image forming apparatus or the like.

[Prior art and its problems]

A copying method in which the ζ developing device also has a cleaning function was adopted for the purpose of downsizing the image forming apparatus.
Eye 1, i:', 0, '! ! + Kaisho 4711',
This is disclosed in Publication No. +38 and the like.

For example, as shown in FIG. 1, 1 photoreceptor 1--ram 1 is surrounded by 111 electric devices 2. Exposure device 3, developing/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 fur brushes and blades that were conventionally required as a cleaning device, which not only makes the device more compact. It has various advantages, such as lower costs and the ability to recycle toner without using a toner recycling device.

In addition, Japanese Patent Application No. 58-213331 and other documents have proposed a copying system that allows the apparatus to be 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 each image forming means is arranged around the photoreceptor drum L, and in the development/cleaning/copying method, the photoreceptor drum L is Use a length shorter than the length of the maximum copy size manuscript.

In order to develop 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 of at least one rotation is performed before starting the next copying process, During this process, only static electricity removal and cleaning are performed to obtain a single copy. In the two-rotation, one-copy, one-way system, the photoreceptor drum 1.1 requires a circumference long enough to copy the maximum size of the original, and the device cannot be significantly downsized; however, with this method, the photoreceptor Since the circumference of the tram 1 is not restricted by the maximum copy size of the original, it is possible to significantly reduce the size of the apparatus.

However, in a method in which developing 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 method, a -component magnetic toner is usually used as a developer, but Jikosho has proposed a method in which a mixture of magnetic I-toner and magnetic carrier is used as a developer to amplify the 1-toner removal ability of the magnetic brush. 56-30846
It has been proposed in the Publication No. This works by creating a magnetic force between the magnetic carrier in the developer that forms the magnetic brush and the magnetic toner on the photoreceptor, increasing the magnetic brush's attraction to the magnetic toner, thereby increasing its cleaning ability. It is.

However, in systems that use a mixture of magnetic I-toner and magnetic gearia as a developer, the cleaning ability is improved compared to the case of using only magnetic toner, but it is still not sufficient and cleaning failures occur. is born.

Moreover, in this method, the following various problems occur in the resulting copied images. For example, when a developer is made by combining a high-resistance magnetic toner and a conductive magnetic carrier, the magnetic toner adheres around the magnetic carrier, and since the magnetic carrier is conductive, the resistance of the developer itself is low. In areas where the potential of the latent image is high, charges of opposite polarity to the latent image are induced in the magnetic carrier, and the magnetic carrier and the latent image stick together with the magnetic toner. This magnetic carrier is transferred in the transfer section! J: Because it is difficult to detect, it appears as a white spot on the image. This phenomenon is called carrier pull, and is noticeable in areas with a large image area, such as the center and IQ areas.

Is this due to the presence of magnetic carriers in the magnetic brush? In addition to magnetic attraction, a mechanical toner removal force is generated for the magnetic toner on the three-photon tram, and as a result, the magnetic toner adhering to the thin latent image area corresponding to the character area passes through the development area. Before it was finished, a part of it was scraped off by the magnetic brush.

As a result, a phenomenon called font thinning occurs in line image parts such as characters. Therefore, it is possible to obtain a good copy image.
2, it becomes a significant obstacle, 2 rotations 1 copy 1 type and several rotations 1 type.
This has become a major problem in the one-sided copy system.

[Purpose of the invention]

In view of the above-mentioned conventional drawbacks, the present invention uses the same magnetic brush device for both development and cleaning, and has a sufficiently high cleaning ability even though it does not have to be used for both. It is an object of the present invention to provide a developing and cleaning device capable of obtaining high-quality images without causing problems.

[Key points of the invention]

In order to achieve the above object, the present invention provides a developing/cleaning device that serves both as a developing device and a cleaning device, and is characterized in that the developer is composed of two types of carriers having different average particle diameters.

[Embodiments of the invention]

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

FIG. 3 is a block diagram of the vicinity of the developing and cleaning l call for explaining the present invention in detail. The developing/cleaning device of the present invention has a developing/cleaning roll 9 in a container (not shown), and a developer layer adhered to the developing/cleaning roll 9 and regulated to have a constant layer thickness is used for cleaning the developing base l'l- The roller 9 is configured to rub the surface of the photoreceptor as it rotates. Here, the amount of developer is as shown in FIG.

Two types of magnetic carriers with different average particle sizes, namely a large particle size magnetic carrier 10 and a small particle size magnetic carrier 11
, and a magnetic toner 12.

The material of the magnetic carrier used is the same as that used in conventional two-component development methods, such as iron and nickel9.

metals such as cobal l□, manganese, oxides or alloys of these, and still insulating 4fl on the surface of these metals.
+It may be coated with a fat film. The developer of the present invention can be obtained by mixing two types of carriers made of such materials having different average particle diameters and a magnetic 1-ner in appropriate proportions.

Next, the operation of the apparatus configured as above will be explained.

(The electrostatic latent image formed on the photoreceptor by the exposure means is transported to the developing area as the photoreceptor rotates, and is developed by the developing and cleaning device of the present invention. That is, the electrostatic latent image is transferred onto the developing and cleaning roll 9. The deposited developer rubs the surface of the photoreceptor, and the toner in the developer adheres to the electrostatic latent image on the photoreceptor surface, resulting in a visible image.

During this development, since the magnetic carrier 10 with a large particle size and the magnetic carrier 11 with a small particle size coexist, the magnetic carrier 12 has a larger particle size than the case where only the magnetic carrier 10 with a large particle size is used. Since the conductive path () is formed, charges are more easily induced in the magnetic toner 12, and the development efficiency becomes higher.

In addition, it is better to have a magnetic carrier 11 of small particle size, which is a ferromagnetic material, in the vicinity of the magnetic carrier 1o of large particle size. The magnetic force applied to the magnetic carrier becomes stronger.

In addition, in a developer consisting of a magnetic carrier 1o with a large particle size and a magnetic toner 12, the magnetic carrier easily adheres to the latent image due to the charge induced by the latent image with a high potential, but the magnetic carrier with a smaller particle size In the developer mixed with the carrier 11, only the magnetic toner 12 of small particle size, which has a weak magnetic attraction force from the magnet in the developing/cleaning roll 9, is attached to the latent image due to the induced charge, so it does not affect the image at all. do not. Therefore, even with a developer containing a mixture of magnetic carrier 10.degree.

On the other hand, during cleaning, a magnetic brush is formed firmly by the magnetic carrier 10 with a large particle size, and the sliding force against the photoconductor surface is strong (and it acts on the magnetic particles 1 to 2 remaining on the photoconductor surface). The magnetic attraction force of the magnetic brush is also very strong. Also, since the magnetic carrier 11 with a small particle size has an extremely large specific surface area, that is, a large surface area for toner to adhere to, the magnetic brush has a high ability to capture toner. Since the magnetic carrier 11 having a small particle size rubs the surface of the photoreceptor closely, fine-grained rubbing is performed.

Therefore, while performing both development and cleaning, it has a sufficiently high cleaning ability and does not suffer from the problem of poor cleaning.

FIG. 4 shows an example of the particle size distribution of two types of carriers having different average particle diameters according to the present invention. In Figure 4, the arrow Δ
Particle 5I, shown as and B, shows a distribution with two peaks at 40μ and 5μ.

The average particle size of the large particle magnetic carrier is 40 μm, and the average particle size of the small particle i¥ magnetic carrier is 5 μm.

Therefore, a large particle carrier and a small particle carrier having these particle size distributions were mixed in a weight ratio of 10=1.
Furthermore, when close-up photography was performed using a developer in which this carrier and magnetic toner were mixed at an M amount ratio of 1:1, a high-quality image was obtained with no cleaning defects, no blank spots, and no thin characters. It was done.

(Effects of the Invention) As described above in detail, the developing and cleaning device of the present invention has a sufficiently high cleaning ability while using the same magnetic brush device for both development and cleaning. A high-quality image can be obtained without white spots or thinning of line drawings.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional 2-turn, 1-copy, and one-way type electrophotographic copying apparatus, FIG. 2 is a block diagram of a conventional several-turn, 1-copy, and one-way type electrophotographic copying apparatus, and FIG. 3 is a detailed diagram of the present invention. FIG. 4 is a structural diagram of the vicinity of the developing/cleaning roll for illustrative purposes, and FIG. 4 is a particle size distribution diagram of the carrier according to the present invention. 1... Photoreceptor 1 ram, 9... Developing and cleaning 1 call, 10... Large particle diameter magnetic carrier, 11.
...Small particle diameter magnetic carrier, 12...Magnetic toner patent Applicant: Casio Computer Co., Ltd. Same as above ID Co., Ltd. Representative Patent Attorney Yoshi Osuga 2 Fig. 1 Fig. 2 δ 65 Tadahiro Setogi B ~D

Claims (2)

[Claims] (1) A developing/cleaning device which serves both as a developing device and a cleaning device, wherein the developer is made of carriers of two types Jjl having different average grains i\. (2) The developing/cleaning device according to claim 1, wherein the two types of carriers i'+ij have two peaks in the overlap-particle size distribution curve.