JPS61144680A - 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 and to obtain a cleaning effect stable for a long period of time by providing brush-shaped members consisting of flexible wires on the down stream side of a cleaning blade in sliding contact with the image carrying body. CONSTITUTION:The members 12, 13 which are bundled with the flexible wires and are formed into a brush shape are pressed to the surface of a photosensitive body 1 on the down stream side of the cleaning blade 9a when viewed in the traveling direction of the photosensitive body to remove the toner and other materials from the surface up to the arrival of the surface of the image carrying body at the electrostatic charge position. The surface of the image carrying body is thus made thoroughly cleaned of photoconductivity prior to the entry to the next image forming stage and therefore the deterioration of the image quality owing to defective cleaning is prevented and the image having the stable and good quality for a long period of time is thus obtd.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrophotographic copying machine or a printer, and particularly to a cleaning device therefor. .

(Prior art and problems to be solved) After uniformly charging the photoconductive layer on the surface of a moving image carrier,
A light image is projected onto this to form an electrostatic latent image, powder toner is applied to this, and this is transferred to a transfer material as a transferable toner image, after which 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. , which has an excellent toner removal function, is small and compact, and is advantageous in terms of cost, has been widely used in practice.

However, in order to improve its development characteristics and fluidity, toner usually contains silica, strontium titanate, vinylidene fluoride, etc., which are finer than the toner particles, and these fine particles are removed by the cleaning blade. may pass through. 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 be removed 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 may cause image unevenness, and abnormal discharge is likely to occur through these, which may result in pinhole-like defects on the photoreceptor. Further, if local wear or damage occurs on the edge of the cleaning blade due to fine irregularities on the surface of the image carrier or adhesion of carrier, the above-mentioned defects become even more serious.

In particular, when a photoconductive layer made of amorphous silicon is used as an image carrier, amorphous silicon has advantages such as its hardness, which is hard to scratch, and its charging characteristics are stable over a long period of time. This tends to damage the edge of the cleaning blade, resulting in poor cleaning, and pinholes occur because the film formation speed during manufacturing is slow, making it difficult to form a thick film due to cost considerations. I couldn't avoid this easy flaw.

Pinholes occur as a result of dielectric breakdown caused by abnormal current flowing through the residue of toner and other substances that adhere to the photoconductive layer due to poor cleaning when corona discharge is applied in the next process. White dots, black dots, etc. appear on the screen, significantly degrading the image quality. The occurrence of pinholes is of course limited to amorphous silicon, and tends to occur when the thickness of the photoconductive layer is less than 40 .mu.m, and becomes more noticeable when the thickness is less than 30 .mu.m.

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, it has been proposed to provide multiple stages of cleaning blades, but 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, which increases wear and damage on the blade edge 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 have also been proposed.

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

The present invention was developed in view of the disadvantages of paper, and a hair-like flexible member is disposed between the cleaning means, which is the final step of one image forming step, and the charging region, which is the first step of the next step. This removes the aforementioned fine additives, prevents contamination of charging wires, etc., prevents the generation of pinholes on the surface of the image carrier, stabilizes the image carrier over a long period of time, and provides IJ-ning effect. The purpose of this invention is to provide a leaning device that can

(2) Structure of the invention (technical means for solving problems and their effects) The present invention has been made to deal with the situation described above, and is intended to remove residual toner on the surface of a moving image carrier. After that,
During the charging site, which is the initial stage of the next imaging process,
A large number of flexible hair-like members are formed into a brush shape and are brought into contact with the surface of the image carrier.

With this configuration, fine particles such as the aforementioned silica and strontium titanate that are still attached to the surface of the image carrier can be collected on the upstream side of the charged area without being scraped off by the cleaning blade. death,
It is possible to bring the surface of the image carrier that reaches the charged portion into a state in which toner and other foreign matter are sufficiently removed.

(Description of Examples) Examples in which the present invention is applied to a rotating cylindrical image carrier (photoreceptor) will be described below.

The attached drawing is a schematic side view of the main parts of a copying machine showing only the vicinity of the photoreceptor, in which the surface photoconductive layer of the photoreceptor 1, which is formed into a rotating cylindrical shape and rotates in the direction indicated by the arrow, is charged by a charger 2. It shall be charged uniformly. Amorphous silicon is used as the photoconductive layer.

The uniformly charged photoconductive layer forms an electrostatic latent image by focusing a reflected light image 3 from an original to be copied (not shown) thereon;
Further, as the photoreceptor rotates, toner is supplied to the developing device 4 to form a transferable toner image.

This transferable toner image approaches a transfer material 6, which is separately supplied toward the photoreceptor from a conveyance path 5, at the position of the transfer charger 6, and at this position, the toner image is transferred to the transfer material.

The transfer material carrying the toner image is then separated from the photoreceptor by the action of the separation electrodes 7, separation rollers 8, etc., and is carried on the conveyance means 10 to a fixing position (not shown).Meanwhile, at the transfer site, the transfer material Toner remaining on the surface of the photoreceptor without being transferred reaches the cleaning device 4 as the photoreceptor rotates, or is scraped off from the surface of the photoreceptor by the cleaning blade 9a.

After the toner is removed, the surface of the photoreceptor is further exposed to a static eliminating light source 1.
1, the residual charge is removed and the image is transferred to the charger 2 for the next image forming operation.

In such copying machines, as mentioned earlier, a small amount of toner may pass through the cleaning blade alone, and silica is mixed in to improve development characteristics.

It is extremely difficult to completely block particulates such as strontium titanate.

For this reason, in the illustrated embodiment, a brush-like strip made of aramid fiber, acrylic fiber, nylon fiber, polyester fiber, etc. and having an appropriate diameter is provided on the downstream side of the cleaning blade when viewed in the traveling direction of the photoreceptor. The members 12 and 13 formed as shown in FIG.

The effect can be obtained by disposing at least one such brush-like member on the downstream side of the cleaning blade, but the foreign matter removal function is further improved by disposing a plurality of such brush-like members.

In this case, a coarsely flocked member 12 is arranged on the upstream side of the photoreceptor traveling direction, and a densely flocked member 12 is arranged on the downstream side, and large particles such as toner are placed in the coarsely flocked member 12, and fine particles such as silica are placed in the densely planted member 12. It is best to remove it.

Furthermore, the two or more brush-like members may be placed anywhere between the cleaning blade and the charger 2, but it has been confirmed that the removal function will deteriorate if the adjacent members are brought too close together, so the distance between them is It is preferable to leave a gap of I N111 or more.

Next, in order to confirm the effect of the present invention, a comparison was made with a known copying machine.

The copying machine basically has the same configuration as the one in the attached drawings, and uses a 22μ thick photoreceptor made of amorphous silicon, producing 50 copies per minute (photoreceptor circumferential speed: 350 H1/sec). A paper passing test was conducted on the paper without the brush-like members 12 and 13 shown in the figure at a speed of .

Toner: 100 parts of polyester resin, 6 parts of magnetic material
A one-component insulating toner consisting of 0 parts and 3 parts of a charge control agent contains 0.4% by weight of silica to improve charging characteristics and fluidity.
, 3% by weight of strontium titanate added, average particle size 1
A 2 μm one was used.

As a result of paper passing tests using this method, damage began to occur at the edge of the cleaning blade after around 10,000 sheets, and toner began to pass through the blade.

If paper continued to be fed, when the part corresponding to the defective cleaning part passed through the charger, an abnormal current flowed towards that part, creating a pinhole in the photoreceptor, and a white spot appeared in the solid black part of the copy.

Furthermore, by this time, silica, strontium titanate, etc. have adhered to the entire surface of the wire of the charger 2, and toner has also adhered to the back position when viewed from the front of the charger, causing uneven discharge. was occurring.

Furthermore, it has been confirmed that the above-mentioned silica, strontium titanate, etc. can pass through the cleaning blade and cause contamination of the charger even when the cleaning blade is functioning normally. This is what I used to do.

Next, a paper passing test was conducted using the above-mentioned known method to which a brush 13 was attached. In this case, charger 2. It is assumed that the photoreceptor 1 has been replaced with a new one, and that the entire inside of the apparatus has been cleaned.

As a brush member, 2000 ÷52 acrylic monofilaments/square inch were planted, and the width was 61 m, and the filaments were brought into contact with the photoconductor while the photoconductor was being eaten, so that the filaments rubbed the surface of the photoconductor. I made it.

As a result of the paper passing test, after about 10,000 sheets, toner came out from the cleaning blade, but the image was normal, and around 25,000 sheets, silica was observed to adhere to the charging wire. At this time, when observing the inside of the machine, toner is deposited on the front surface (blade side) of the brush-like member 13.
Some of it was also attached to the filament forming the brush-like member.

It was also found that silica and strontium titanate were attached to each filament so that when the brush-like member was taken out and strongly dabbed, the silica etc. was dispersed in a mist-like form and a considerable amount of silica etc. was adsorbed. did.

In addition, the tip of the filament of the brush-like member near the part that contacts the photoconductor is saturated with toner, silica, strontium titanate, pieces of paper, etc., and if copying continues, the charging wire will become contaminated. hand,
Obvious image unevenness appeared after 30,000 to 35,000 sheets were passed.

Next, the inside of the machine is cleaned, and the charging wire, cleaning blade, and brush-like member 13 are all replaced with new ones, and the brush-like member 12, which is coarser (flocked) than the brush-like member, is installed on the upstream side of the brush-like member 13. I arrived and did a paper test.

The brush-like member 12 was made of ≠50 acrylic seven filaments, 350 filaments/square inch, and a width of 6 inches, and was pressed against and rubbed against the photoreceptor.

As a result, the toner passed through the blade on about 10,000 copies, but normal images were obtained.

Approximately 45 times, silica etc. were found on the charger wire.
,000 sheets or more.

When we observed the interior of the machine, we found that not only was toner deposited on the upstream side of the brush-like member 12 where it contacts the photoconductor, but also on the side near the base of the filament (the surface of the photoconductor). A considerable amount of toner was also seen in the area (away from the plane), and it is assumed that this is also effective in collecting toner that has been scattered inside the aircraft for some reason.

Further, there is almost no toner attached to the densely planted brush-like member 13, which is silica (particle size 10 to 20 mμ).

It was observed that strontium titanate (particle size slightly less than 1μ) was attached to each filament.

Image unevenness occurred when 50,000 to 55,000 sheets were passed. With the above configuration, when the brush-like members 12 and 13 were replaced every 30,000 sheets and paper feeding was continued, 1
Even after passing 00,000 sheets, good images were obtained.

The above exchange may be performed manually or automatically.

As explained above, by disposing a brush-like member made of fibers of an appropriate material on the downstream side of the cleaning blade of the cleaning device (as seen in the running direction of the image carrier), the surface of the image carrier is heated until it reaches the charged area. It was confirmed that toner and other substances on the surface were removed extremely well, and even better results could be obtained by disposing a plurality of brush-like members with different densities.

Note that when two or more brush-like members are arranged, it is preferable to arrange them in order from the coarse-bristled brush-like member to the side closest to the cleaning blade.

Although the present invention is applied to a copying machine in which two brush-like members are arranged, the present invention is not limited to copying machines, and the number of brush-like members and the filament material are also as described above. It is easy to understand that not only this but also various kinds of materials can be used.

Further, in the illustrated embodiment, the cleaning device and the brush-like member are formed separately, but the entire structure may be integrally constructed without changing the relative arrangement of each part.

(3) Effects of the invention Since the present invention has the configuration described above,
In image forming apparatuses that use the electrostatic transfer process, the photoconductivity is reliably and thoroughly cleaned before starting the next image forming process, effectively preventing deterioration of image quality due to poor cleaning and ensuring long-term maintenance. It is possible to obtain stable, high-quality images over a period of time.

[Brief explanation of the drawing]

The accompanying drawing is a schematic side view of the main parts showing the case where the present invention is applied to a copying machine. 1... Photoreceptor, 2... Charger, 4... Developer, 6
. . . Transfer charger, 9 . . Cleaning device, 12.
13...Brush-like member.

Claims (3)

[Claims] (1) A cleaning device in which a cleaning blade is brought into pressure contact with a moving image carrier, and a brush-like member made of a flexible wire is rubbed on the image carrier downstream of the cleaning blade. (2) A cleaning device according to claim 1, comprising a plurality of brush-like members arranged in the image carrier traveling direction. (3) The cleaning device according to claim 2, wherein the flexible wires of the plurality of brush-like members are formed more roughly toward the member closer to the cleaning blade.