JPS6356677A - Cleaning device - Google Patents

Abstract

PURPOSE:To prevent pinholes through a photosensitive layer by grounding the surface of a surface-conductive magnetic roller located upstream from the cleaning blade to be brought into contact with the surface of an image bearing body, or a photosensitive layer, or applying bias reverse in polarity to a toner. CONSTITUTION:A toner collected with the magnetic roller 4 and the cleaning blade 3 is electrically charged by frictional movement between the roller 4 and a photosensitive body 1, the scraper 7, and the like, and since the surface of the roller 4 is grounded or a means for applying a bias reverse in polarity to the toner is connected, the charge of the toner generated by triboelectrification flows to the ground and the potential of the toner lowers, thus permitting the rectification tendency of the photosensitive layer to conduct in the forward direction, or become a state near that, voltage higher than its breakdown voltage not to be applied toward the photosensitive layer, and consequently, pinholes through the photosensitive layer to be effectively prevented.

Description

Detailed Description of the Invention (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using electrostatic recording means, such as an electrostatic copying machine or a printer, and particularly to a cleaning device therefor. .

(Prior art and problems to be solved) In a well-known image forming apparatus that repeatedly transfers a transferable toner image formed on the surface of an image carrier onto a sheet-like transfer material mainly made of paper, the transfer process After each transfer, it is necessary to install a cleaning device to remove residual toner that does not contribute to the transfer and remains on the image carrier, as well as foreign substances such as paper dust, precipitates such as rosin and talc, and nitrides that are mixed with this. There is.

As this type of cleaning means, conventionally, fur brush rollers, magnetic rollers, etc. are used on the image carrier Ff! There have been proposed rollers configured to rub the toner, and rollers that actively attract toner by applying a bias to these rollers.

However, since the main purpose of these rollers is toner removal, they are usually designed to rub the image bearing member in a state in which toner does not adhere to the roller as much as possible.

For this reason, although the toner itself can be removed well, the above-mentioned foreign substances such as paper dust are not sufficiently removed and remain on the image bearing member, inevitably having an adverse effect on image quality.

In order to avoid such inconveniences, recently, an elastic roller or a magnetic roller made of sponge or the like is rubbed against the image carrier with an appropriate amount of toner applied to its surface, and then the toner is removed by a cleaning blade. A system configured to do so has been proposed.

With this configuration, various foreign substances as mentioned above can be removed along with toner, and the photosensitive layer on the surface of the image carrier can be appropriately ground to prevent deterioration of the photosensitive layer due to ozone generated within the apparatus. It is clear that

However, it has been found that this type of photosensitive layer has the disadvantage that pinholes occur in the photosensitive layer, which adversely affects the image quality over its lifetime.

This is because toner is present between the image carrier and the roller facing it, so the rollers, image carrier, and toner move against each other and become charged, and if there is no place for the charge to escape, it accumulates and becomes a high potential. As a result, when the potential exceeds the withstand voltage limit of the photosensitive layer of the image carrier, pinholes occur in the photosensitive layer, just as when a reverse voltage exceeding the withstand voltage is applied to a diode. It is considered that

On the other hand, even in the case of forward rectification, where the toner charge escapes to the photoreceptor, if too much current flows, binaholes are thought to occur in the photoreceptor layer, similar to when an overcurrent is applied to a diode. .

When the photosensitive layer on the surface of the photoreceptor is a positively charged amorphous silicon semiconductor and the toner is negatively charged.

In other words, in the case of regular development, the rectification with the photoreceptor is in the forward direction, so the charge flows into the photoreceptor, but the amount is small and there is little risk of pinhole formation, but the toner is positively charged. Sometimes, that is, in the case of reversal development, the rectification with the photosensitive layer is in the opposite direction, so pinholes are likely to occur.Similarly, when using an OPG photoreceptor, pinholes may occur when the toner is negatively charged. Holes are likely to occur, but are less likely to occur when positively charged.

Furthermore, in the case of a photosensitive layer that is bipolarly charged, such as high-resistance amorphous silicon, pinholes are likely to occur with toner of either polarity.

The present invention has been made to deal with the above-mentioned situation, and can contribute to obtaining high-quality images by maintaining the photosensitive layer on the surface of the image carrier in a stable state for a long period of time without generating pinholes. The object of the present invention is to provide a cleaning device.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides a cleaning device having a cleaning blade and a magnetic roller, in which the roller is grounded or the toner is charged. The device is characterized in that a bias applying means of opposite polarity is provided.

With this configuration, it is possible to prevent the accumulated charges from flowing toward the image carrier, thereby preventing the generation of pinholes.

(Description of Embodiments) FIG. 1 is a side view of essential parts showing an embodiment in which the present invention is applied to a copying machine equipped with a rotating cylindrical image bearing member (hereinafter referred to as a photoreceptor), and is perpendicular to the plane of the paper. photoreceptor l extending in the direction
The cleaning device 2 is disposed in parallel with and close to.

The photoconductor 1 is assumed to be rotating in the direction of arrow A, and the cleaning blade 3 in the cleaning device comes into pressure contact with the photoconductor 1 to remove residual toner that does not contribute to transfer and remains on the surface of the photoconductor 1 at a transfer position (not shown). shall be scraped off.

A magnetic roller 4 is disposed upstream of the cleaning blade when viewed in the traveling direction of the photoreceptor.

The magnetic roller 4 includes a magnetic roller 4b made of a ferrite magnet, a plastic magnet, etc., and a coating made of a non-magnetic, conductive material such as aluminum or stainless steel that has a lower resistance value than the photoreceptor on its outer peripheral surface. layer 4
a, and rotate as a unit in the direction of arrow B.

A bias applying means 6 having a polarity opposite to that of the ground or the charged toner is arranged between the coating layer 4a and the ground.

It goes without saying that there are members necessary for image formation, such as a charger, a developer, and a transfer charger, located around the photoreceptor l, but these are not directly related to the present invention, so all of them will be described here. It is omitted.

During the image forming operation, residual toner remaining on the surface of the photoreceptor even after transfer passes through the roller 4 as the photoreceptor rotates, further advances to the cleaning blade 3, where it is scraped off by the roller 4. The roller reaches a position where the roller approaches the photoreceptor, and as the roller rotates, the roller moves sequentially in the clockwise direction in the drawing, and is regulated to a predetermined thickness by the scraper 7, and then roughly moves along the roller surface again.

The roller 4 and the photoreceptor 1 are brought to a position where they face each other.

As this state continues, as shown in the figure, a toner layer is formed in the area where the photoreceptor 1 and roller 4 are close to each other, and a toner pool T is formed on the cleaning blade side. The toner is mainly removed by the cleaning blade, and paper dust and other foreign substances as mentioned above are removed at the roller 4 to clean the photoreceptor, while excess toner passes through the scraper and reaches the toner storage section. , and are discharged to the outside of the cleaning device by the conveying screw 5 as necessary.

During the above-described operation, the toner collected by the row 24 and the blade 3 is charged by sliding movement between the roller 4, the photoreceptor 1, the scraper 7, etc., and the electric charge generated by this frictional charging is As mentioned above, between the roller surface and the ground, there is a bias applying means that is either grounded or has a polarity opposite to that of the toner, so that the electric charge on the toner generated by frictional charging escapes to the ground, and the potential of the toner increases. Since the rectification property of the photosensitive layer is lowered, the rectification property of the photosensitive layer is in a forward direction or a state close to this, and a voltage higher than the withstand voltage is not applied in the direction of the photosensitive layer, and the generation of pinholes can be effectively prevented.

According to experiments, good results were obtained by setting the resistance between the roller and the ground to a value of 10@Ω or less.

Figures 2A, 2B, and 2C show other configuration examples of magnetic rollers, and the one in Figure 2A has a magnetic roller 8b inside, and its outer periphery is made of low resistance material such as aluminum. It is constructed such that it is covered with a conductive sleeve 8a, and only the sleeve is rotated. The ground shall be taken from the sleeve 8a.

Fig. 2B shows conductivity made by dispersing metal powder, carbon black, etc. in urethane rubber, silicone rubber, etc., and Fig. 2C shows a structure in which the surface layer 10a is configured in the same manner as above, and the inner layer 10b is made of urethane rubber or silicone rubber. The sponge-like material is made conductive in a similar manner, so that the overall elasticity can be adjusted.

Each roller has a core bar 9a, 10 made of a conductive material.
c, and earthing shall be taken from this part.

It is easy to understand that these devices perform the same functions as those shown in FIG. 1 above.

(3) Effects of the Invention Since the present invention has the above-described configuration, it is possible to prevent the occurrence of pinholes in the photosensitive layer formed on the surface of the image carrier in an image recording device. This effectively prevents image deterioration and provides stable, high-quality images over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts showing an embodiment in which the present invention is applied to a copying machine, and FIGS. 2A, 2B, and 2C are side sectional views showing other configurations of magnetic rollers that can be used in the present invention. be. l...Photoreceptor, 2.φ.Cleaning device, 3...
Cleaning blade, 4.8.9.10...magnetic roller, 6φ/φ bias application means. Figure 1 Figure 2A

Claims (1)

[Claims] It is equipped with a cleaning blade that comes into pressure contact with the photosensitive layer on the surface of the moving image carrier, and a magnetic roller whose surface is conductive and which is located upstream of the cleaning blade as viewed in the running direction of the image carrier, and the magnetic roller and the ground are connected to each other. During this time, the cleaning device is grounded or a bias with the opposite polarity to that of the toner is applied.