JPS6246869B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a cleaning device for an electronic copying machine such as an electrophotographic copying machine or an electrostatic recording device. The present invention relates to a magnetic brush cleaning device that develops images and removes toner remaining on a recording medium.

(Prior art) As a cleaning method for electrophotography,
Fur brush cleaning, blade cleaning, roller cleaning, web cleaning, etc. are well known, and all of them remove residual toner by mechanically rubbing the surface of the photoreceptor with a relatively strong frictional force, so the cleaning effect is better than that of magnetic brush cleaning. better than. However, in electronic copying machines that adopt this cleaning method, the electrostatic properties may deteriorate due to abrasion of the photoreceptor surface, the life of the photoreceptor may be shortened, or the use of a photoreceptor that is resistant to wear may cause problems. I don't like it because it's limited. On the other hand, although the cleaning effect of the magnetic brush cleaning method is somewhat inferior, it is more advantageous than other cleaning methods and has a relatively simple mechanism.
However, in the conventional magnetic brush cleaning method, a method has been proposed in which a bias voltage is applied and cleaning is performed in combination with electrostatic attraction as a method of increasing the cleaning effect, but this method is not fully satisfactory.

(Objective) An object of the present invention is to allow a magnetic brush cleaning device to also serve as a developing device to perform efficient development and cleaning.

(Structure) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A recording body 17 capable of forming an electrostatic latent image on its surface, such as an inorganic or organic photoconductor or an electrostatic recording body, rotates continuously in the direction of the arrow shown in the figure, and approximately two revolutions of the recording body 17 make one rotation. In an electronic copying machine that performs a two-rotation, one-copy process that completes one copying process, the first developing-cleaning device is used as both a developing device and a cleaning device.
The figure shows the state during the first rotation of development.
FIG. 2 shows the state in which the cleaning action of the second rotation is being performed.

A first magnetic brush forming means 20 is composed of a non-magnetic sleeve 19 which has a magnetic roller 18 inside and continuously rotates counterclockwise; A second magnetic brush forming means 23 consisting of a non-magnetic sleeve 22 rotating in the direction is provided,
The second magnetic brush forming means 23 draws up the developer 25 in the developer container 24 and supplies the developer to the first magnetic brush forming means 20 .

The second magnetic brush forming means 23 includes a developer 25
A voltage of opposite polarity to the toner inside is applied,
That is, a developing bias voltage is applied to prevent toner from adhering to the non-image area of the recording medium 17.

In FIG. 1, the second magnetic brush forming means 23
A magnetic brush is formed on the non-magnetic sleeve 22 using a developer maintained at a predetermined concentration, and the electrostatic latent image on the recording medium 17 is developed. Magnet roller 18
By appropriately selecting the magnetic poles 21 and 21, the developed developer can be supplied from the second magnetic brush forming means 23 to the first magnetic brush forming means 20 by the action of the magnetic field. The magnetic brush of the first magnetic brush forming means 20 is also configured to be brought into contact with the recording medium 17 before the magnetic brush of the second magnetic brush forming means 23 comes into contact with it. In the developing action,
Compared to developing with one magnetic brush, developing with multiple magnetic brushes allows for longer development time and development area, enables high-speed development, and eliminates background stains at high density. You can get an image without.

In the magnetic brush cleaning method, the toner concentration of the magnetic brush and the cleaning performance are inversely proportional, so it is better that the toner concentration of the developer forming the magnetic brush be as thin as possible.

Therefore, by collecting and removing the toner in the developer and making the toner concentration sufficiently thin before forming the cleaning magnetic brush, a cleaning magnetic brush with a low concentration is always formed and the cleaning effect is enhanced. be able to. According to experiments, it has been confirmed that when the toner concentration of the magnetic brush reaches 5 to 6% by weight, the toner attraction force of the magnetic carrier becomes saturated and the cleaning effect decreases.

Toner for bias voltage adheres to the non-magnetic sleeve 22, and is removed by a scraping plate 26, and the scraped toner is returned to the developer container 24 to contribute again to development. Stirring blade 27
stirs the toner so that it is uniformly dispersed in the axial direction of the magnetic rollers 18 and 21. On the other hand, the developer present on the non-magnetic sleeve 19 is removed by a scraping plate 28 and returned to the developer container 24, and the developer 25 is used for circulation.

Next, after the recording body 17 is developed, the toner image is electrostatically transferred to a transfer paper, and during the second rotation of the recording body 17, a static eliminator ( (not shown), for example, with a reverse polarity corona discharger or an alternating current corona discharger, and passes through the developing and cleaning device again. After at least the image area of the recording medium 17 has been developed, the second magnetic brush forming means 23 rotates several degrees around the axis of the magnetic roller 18 as shown in FIG. Displaced to a non-contact position. That is, the recording medium 17 after transfer and charge removal comes into contact only with the magnetic brush of the first magnetic brush forming means 20. The toner concentration of the magnetic brush is much lower than that of the magnetic brush of the second magnetic brush forming means 23. This is because a large amount of toner adheres to the non-magnetic sleeve 22 of the second magnetic brush forming means 23 to which the bias voltage is applied, and when the developer is supplied to the first magnetic brush forming means 20, the density is already low. It's summery. Therefore, since the magnetic carrier in the developer has an electrostatic attraction ability that causes the toner to adhere, the toner remaining on the recording medium 17 can be effectively removed and collected by the magnetic brush. It can be done.

Since the second magnetic brush forming means 23 is displaced while substantially maintaining the positional relationship with the first magnetic brush forming means 20 during development, there is no problem in supplying the developer.

During the cleaning operation shown in FIG. 2, in order to further increase the cleaning efficiency of the first magnetic brush forming means 20, it is also possible to apply a voltage of opposite polarity to the toner to the first magnetic brush forming means 20.

In addition, it goes without saying that the same implementation can be performed even when the rotation direction of the recording medium 17 is clockwise in FIGS. 1 and 2. Furthermore, instead of rotating the second magnetic brush forming means around the magnetic roller 18, it is also possible to rotate the developer container 24, ie the entire development-cleaning device.

In addition, when toner adheres to the non-magnetic sleeve 19 due to application of a bias voltage, etc., the scraping plate 28 is used to remove toner from the non-magnetic sleeve 19, similar to the second magnetic brush forming means 23.
It can also be placed after.

The toner concentration of the developer in the developer container 24 is maintained at a predetermined development concentration by a known photoelectric, electrical, magnetic, or other toner concentration detection method.

In addition, in the above-mentioned embodiment, a case was described in which two magnetic brush forming means were used as the magnetic brush forming means, but the present invention is not limited to this, and two or more magnetic brush forming means may be used. Good things are natural.

As described above, according to the present invention, when cleaning residual toner using a magnetic brush, cleaning is performed after lowering the toner concentration of the magnetic brush, so cleaning efficiency is extremely high. Before forming the magnetic brush, at least one magnetic brush is formed to sufficiently remove the toner in the developer, so that the toner concentration can be lowered, and the cleaning effect can be reduced even if used for a long time. do not have. Further, during development, multi-stage development using a magnetic brush can be performed, so high-speed development is possible, or an image with high density and no background stain can be obtained. Furthermore, during cleaning, the toner and developer collected from each non-magnetic sleeve can be collected and reused within the same device, making it possible to obtain an extremely inexpensive and compact device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a developing operation state of a developing-cleaning device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a cleaning operation state of the developing-cleaning device shown in FIG. 17... Recording body, 20... First magnetic brush forming means, 23... Second magnetic brush forming means, 24... Developer container, 25... Developer.

Claims (1)

[Claims] 1. In a developing/cleaning device in which the same device serves as both a developing device and a cleaning device, a first magnetic brush forming means for bringing a magnetic brush into contact with the surface of a photoreceptor, and a developer being supplied from a developer container to the first magnetic brush forming means. a second magnetic brush forming means for supplying toner, a bias voltage applying means for attracting toner to the second magnetic brush forming means, and a magnetic brush formed in the second magnetic brush forming means being brought into contact with the recording medium during development. A magnetic brush cleaning device comprising a second magnetic brush forming means switching means for selectively switching between a first position and a non-contact second position separated from the recording medium during cleaning.