JPS61144681A - Cleaning device - Google Patents

Abstract

PURPOSE:To prevent the contamination of an electrostatic charge wire, etc. and the pinholing of an image carrying body surface by providing a flexible member which is electrostatically charged to the polarity reverse from the polarity of a toner on the down stream side of a cleaning blade when viewed in the traveling direction of the image carrying body so as to contact slidingly with the image carrying body. CONSTITUTION:The residual toner remaining on the photosensitive body without contributing to the transfer in a transfer position is brought to the position of a cleaning device 9 as a photosensitive body rotates. The toner is removed from the surface of the photosensitive body 1 by the cleaning blade 9a. The brush-shaped member 12 which consists of the fibrous flexible member and is electrostatically charged to the polarity reverse from the polarity of the toner is brought into sliding contact with the body 1 on the down stream side of the blade 9a. The toner and other pulverous particles which are not removed by the blade 9a are thereby mechanically removed; in addition, the effect of removing the same is electrostatically accelerated, by which the surface of the image carrying body entering the next image forming stage is thoroughly cleaned and the stable image quality is maintained for a long period of time without the pinholing in the photoconductive layer consisting of amorphous silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION (i) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that utilizes an electrostatic transfer process, such as an electrophotographic copying machine or a printer thereof, and particularly to a cleaning device therefor.

(Prior art and issues to be solved).

After uniformly charging the photoconductive layer on the surface of the moving image carrier,
A light image is projected onto this to form an electrostatic latent image, and powder toner is applied to this to transfer it to a transfer material as a transferable toner image. After that, it remains on the surface of the image carrier without contributing to transfer. In well-known image forming apparatuses that repeat the process of cleaning residual toner, it is extremely important to sufficiently remove residual toner and other foreign substances before starting the next image forming process in order to obtain high-quality images. It is.

Various types of cleaning means have been proposed for removing residual toner, but one is one in which the edge of a cleaning blade made of an elastic material such as rubber is pressed against the surface of the image carrier to scrape off the toner. It has been widely used in practice because it has an excellent toner removal function, is small and compact, and is advantageous in terms of cost.

However, in order to improve its development characteristics and fluidity, toner usually contains silica, vinylidene fluoride, etc., which are finer than the toner particles, and these fine particles pass through the cleaning blade. Sometimes I put it away. Further, in the case of a two-component developer, although the carrier does not originally adhere to the image carrier, a portion of the carrier may adhere to the image carrier. The fine powders and carriers mentioned above are difficult to remove sufficiently by the cleaning blade, and if they pass through the blade and reach the next charged area, they may contaminate the charger's corona discharge wire or cause leaks. This caused image unevenness, and there was a risk of producing pinhole-like defects on the photoreceptor. Also, localized wear on the edge of the cleaning blade occurs due to fine irregularities on the surface of the image carrier or adhesion of carrier.

When damage occurs, the above-mentioned defects become even more severe.

In particular, when using a photoconductive layer made of amorphous silicon as an image carrier, amorphous silicon has advantages such as high hardness, resistance to damage, and stable charging characteristics over a long period of time. This tends to damage the edge of the cleaning blade, resulting in poor cleaning.Also, the slow film formation rate during manufacturing makes it difficult to form a thick film due to cost considerations, so pinholes are difficult to form. I was unable to avoid the flaws that tend to occur.

Pinholes occur when corona discharge is applied to the toner that has adhered to the photoconductive layer due to poor cleaning, and abnormal current flows through the area in the next process, causing dielectric breakdown. Dots, black spots, etc. occur, significantly deteriorating the image quality. Of course, pinholes are likely to occur not only in amorphous silicon, but also when the photoconductive layer has a thickness of 40 μm or less.
When the thickness is less than 30μ, the occurrence becomes noticeable.

In order to avoid the drawbacks described above, it has been proposed to arrange a web cleaning device downstream of the cleaning blade, for example, when viewed in the running direction of the image carrier. The space required is large, and depending on the type of photoconductive layer on the surface of the image carrier, it may be damaged, so it cannot be said to be perfect.

Furthermore, although it has been proposed to provide multiple stages of cleaning blades, since the cleaning blades have an excellent toner removal function, the amount of toner that reaches the blades in the second stage and below is extremely small, resulting in the blade and image being damaged by toner. This is not preferable because the lubricating function between the carriers is reduced and the frictional force becomes excessive, resulting in increased wear and damage to the blade edges and the surface of the image carrier. Further, since the cleaning blade basically does not have a sufficient function of removing fine powder such as silica as described above, no significant effect can be expected with this method.

Furthermore, the additives in toner, such as fine powder such as silica and carrier, are often charged with the opposite polarity to that of the toner, so it is recommended to use a fur brush that rotates at high speed and has bristles of forward and reverse polarity. Toners with forward and reverse polarity are also provided.

Additives and the like are often present in the same location, which is undesirable as it causes striped patterns and poor leaning.

In order to cope with such a situation, the present invention has been developed to remove toner to be removed between a cleaning area which is the final stage of one image forming process of an image forming apparatus and a primary charging area which is the first process of the next image forming operation. By arranging a flexible member of the same polarity or opposite polarity, toner and other fine particles that have passed through the cleaning blade can be reliably removed, preventing contamination of the charging wire and the image carrier. It is an object of the present invention to provide a cleaning device that has stable functions and does not generate pinholes on the surface.

(2) Structure of the invention (Technical means 2 to solve the problem) In order to achieve the purpose of constriction, the present invention provides an image forming apparatus that runs endlessly using an electrostatic transfer process.
At a position between the cleaning area, which is the final stage of one image forming process, and the primary charging area, which is the first stage of the next image forming process, the image is formed by the charging characteristics of the toner, etc. that respond to the charging characteristics of the surface of the image carrier. A flexible member consisting of a thin strip that is charged to the same polarity or the opposite polarity when rubbed against the image carrier is configured to rub against the image carrier, singly or in combination.

With this configuration, toner and other fine particles that could not be removed by a cleaning blade etc. are not only mechanically removed, but also electrostatically promoted, allowing the next image forming process to proceed. The surface of the image carrier can be sufficiently cleaned and a stable cleaning effect can be obtained.

(Description of Embodiments) The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a side view schematically showing the structure of a well-known copying machine in the vicinity of an image carrier. A charger 2 that uniformly charges the layer, an exposure section 3 that projects a light image of the original onto this charging surface to form an electrostatic latent image, a developer 4 that converts the latent image into a transferable toner image, and is separately transported. transfer material (not shown)
a transfer site where the image is brought close to the photoreceptor near the transfer charger 6;
A static eliminator charger, a separation roller 8, a conveyance means 10, and the like are arranged to separate the transfer material carrying a toner image from the photoconductor and feed it to a fixing site (not shown).

Further, residual toner remaining on the photoconductor at the transfer site without contributing to the transfer reaches the cleaning device 9 as the photoconductor rotates, and is removed from the surface of the photoconductor by the cleaning blade 9a. Then, after residual charges are removed from the surface of the photoreceptor by a neutralizing light source, the next image forming process is started.

In a copying machine having such a well-known configuration, the photoconductive layer is made of amorphous silicon, and the toner is a one-component toner consisting of 100 parts of styrene acrylic polymer resin, 60 parts of magnetic material, and 3 parts of a charge control agent, and 0.00% silica. Adding 4% by weight externally,
The particles used had an average particle size of 12μ and a particle size distribution of 5 to 22μ.

As a result of the paper feeding test, the edge of the cleaning blade was damaged and toner began to pass through the blade after about 10,000 sheets.

Furthermore, at that point, the wire of the charger 2 was completely covered with silica, and toner was also observed on the front and back sides of the charger, and the image quality was degraded due to uneven discharge.

Next, a paper passing test was conducted using a brush-like member made of a fibrous flexible material arranged downstream of the cleaning blade as described above.

Since the amorphous silicon photoreceptor is positively charged, toner of negative polarity is used in the case of positive development, but for this reason, the toner remaining after transfer is often of weak positive polarity.

Therefore, we investigated all types of brush-like aramid fibers and nylon fibers that are positively charged by rubbing against the photoreceptor. Actually, the Nomex (made by DuPont)
420 (product name) (more than 2 strands) i1550 bristle/square inch brush-like member was formed to a width of 6111K and was rubbed against the photoconductor to pass the paper, and the toner was removed after about 10,000 sheets. There was some flashing, but it did not affect the image quality.
．． Silica was observed on the charger wire after 50,000 to 30,000 sheets were passed. Observations inside the machine showed that toner was deposited on the front side of the brush-like member, and silica was also clinging to the fibers of the brush. It was found that silica was attached.

Next, we used a brush-like member made of Teflon fiber that charges negatively when it rubs against the photoreceptor. The toner adhered to the Teflon fiber, but silica did not, and the charger wire stopped after 10,000 sheets were passed. Contaminated with silica.

Note that the negative silica used at this time was Taranox (trade name) Silica T-500 manufactured by Nippon Aerogel. The particle size of this toner is 10 to 20 microns, and it has been discovered that this toner cannot be removed sufficiently with a cleaning blade, and the user must carry out maintenance.
This was dealt with by cleaning contaminated charging wires, etc.).

From the above results, when using negative toner for development,
To remove fine particles such as silica that are charged to the same polarity as the toner, a brush-like member made of aramid fiber, nylon fiber, etc., which is easily charged to the opposite polarity to the toner, is used on the downstream side of the cleaning device. It was found to be suitable for

Furthermore, since some residual toner has a weak polarity that is opposite to the polarity of the toner, Teflon, which is easily charged to the same polarity as the toner, is placed upstream of the brush-like member and downstream of the cleaning device. If a brush-like member made of fiber or the like is provided, residual toner of opposite polarity can be removed in advance, so that after the toner is charged with reverse polarity, the brush-like member can more effectively remove fine particles such as silica. .

Figure 1 shows the cleaning blade 9 when viewed from the photoreceptor traveling direction.
The brush member 12 is formed by arranging the above-mentioned reverse polarity charging type brush member 12a and positive polarity charging type brush member 12b on the downstream side of a, and both brushes 12a and 12b. There is a gap of 1uL or more between 12
It is preferable to produce c.

In cases where toner or additives are forcibly given either polarity due to the static neutralization effect before cleaning,
Of course, it is possible to use a brush member made of fibers with charging characteristics corresponding to this.

It has been confirmed that when brush members of both forward and reverse polarities are arranged side by side as shown in Figure 1, it is possible to withstand the passage of 30,000 to 35,000 sheets. Still both brush members 12a.

When the spacing between the sheets 12b was set to 5u, the sweeping action was performed by both members, and the paper could withstand passing of 45,000 sheets.

Furthermore, as shown in FIG. 2, two sets of brush-like members 13.1
4, it was possible to pass 70,000 sheets.

The present invention has been described above with respect to a copying machine that uses an amorphous silicon photoreceptor, but it is easy to find a material that can be charged positively or negatively even in a copying machine that uses other materials as a photoconductive layer. It is easy to understand that this effect can be obtained. It is also readily understood that the fiber materials used are not limited to those mentioned above.

Additionally, throughout the above experiments, it appears that the contamination of the charger wire was also responsible for the destruction of the 7'' contacting layer with the substrate in the amorphous silicon photoreceptor, and no pinholes were generated at all.

(3) Effects of the Invention Since the present invention has the above configuration, toner, additives, etc. that have not been captured by the cleaning means can be reliably removed before starting the next image forming process. The dog prevents contamination of the charger wire and helps to maintain stable image quality over a long period of time without the occurrence of pinholes, especially in the amorphous silicon layer, caused by this.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an embodiment in which the present invention is applied to a copying machine, and FIG. 2 is an enlarged view of main parts showing another embodiment of the present invention. 1... Photoreceptor, 2... Charger, 4... Developer, 6
...Transfer charger, 9...Cleaning device, 12,
13゜14...Brush-like member. Figure 1

Claims (2)

[Claims] (1) A cleaning device in which a flexible member that is charged to the opposite polarity to the toner is placed on the downstream side of the cleaning blade when viewed in the running direction of the image carrier so as to rub against the image carrier. (2) A flexible member that is charged to the opposite polarity to the toner and a flexible member that is charged to the same polarity are arranged side by side in the running direction of the image carrier on the downstream side of the cleaning blade when viewed in the running direction of the image carrier. A cleaning device arranged to rub.