JPS6150181A - Magnetic brush cleaning device - Google Patents

Abstract

PURPOSE:To obtain pictures without texture dirt by performing cleaning after reduction of the toner concentration of a magnetic brush to enhance the cleaning efficiency and forming a magnetic brush before information of the magnetic brush for cleaning to remove the toner in a developer. CONSTITUTION:The second magnetic brush forming means 23 uses the developer held at a prescribed concentration to form the magnetic brush on a nonmagnetic sleeve 22, and an electrostatic latent image on a recording body 17 is developed. Magnetic poles of magnetic rolls 18 and 21 are selected properly to supply the developer after development from the magnetic brush forming means to a brush forming means 20 by the magnetic field action. The magnetic brush formed by the forming means 20 is so constituted that this magnetic brush is brought into contact with the recording body 17 before the magnetic brush formed by the forming means 23 is brought into contact with the recording body 17. Since one magnetic brush is formed at least to remove the toner sufficiently before the magnetic brush for cleaning is formed, the toner concentration is reduced, and high-density pictures without texture dirt are obtained.

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 W copying machine or an electrostatic recording device. The present invention relates to a magnetic brush cleaning device that develops latent images and removes toner remaining on a recording medium.

(Prior Art) As cleaning methods for electrophotography, fur brush cleaning, blade cleaning, roller cleaning, web cleaning, etc. are known, and all of them mechanically rub the photoreceptor surface with a relatively strong frictional force.
The cleaning effect is better than magnetic brush cleaning because it removes residual toner. However, in electronic copying machines that adopt this leaning method, the electrostatic properties deteriorate due to abrasion of the surface of the photoreceptor, the life of the photoreceptor is shortened, or the use of a photoreceptor that is resistant to abrasion occurs. 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.
Moreover, the mechanism is relatively simple. 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, thereby allowing efficient development and cleaning.

(Structure) Examples of the present invention will be described below 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 a developing-cleaning device in which the same device serves as a developing device and a cleaning device in a type of electronic copying machine that performs a so-called 2-rotation 1-copy process that completes 1 copying process, Figure 1 shows the developing operation of the 1st rotation. Fig. 2 shows a state in which the first cleaning action is performed twice.

The first sleeve is made up of a non-magnetic sleeve 19 that has a magnetic roller 18 inside and continuously rotates counterclockwise.
A second magnetic brush forming means 23 consisting of a magnetic brush forming means 20 and a non-magnetic sleeve 22 having a magnetic roller 21 therein and rotating counterclockwise is provided. The 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 .

A voltage having a polarity opposite to that of the toner in the developer 25 is applied to the second magnetic brush forming means 23, that is.

A developing bias voltage is applied to prevent toner from adhering to non-image areas of the recording medium 17.

In FIG. 1, the second magnetic brush forming means 23 forms a magnetic brush on the non-magnetic sleeve 22 using developer maintained at a predetermined concentration, and develops the electrostatic latent image on the recording medium 17. By appropriately selecting the magnetic poles of the magnetic rollers 18 and 21, it is possible to supply a developer stream from the second magnetic brush forming means 23 to the first magnetic brush forming means 20 by the action of the magnetic field. First magnetic brush forming means 2
The magnetic brush No. 0 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 the recording medium 17.

In terms of development, developing with multiple magnetic brushes allows for longer development time and development area than with one magnetic brush, making it possible to perform high-speed development, and Images with high density and no background stains can be obtained.

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 f ratio of the developer forming the magnetic brush is 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. Something happens. According to experiments, the toner density of the magnetic brush is 5-6%
It has been confirmed that when the toner attracting force of the magnetic carrier reaches 100, the toner attraction force of the magnetic carrier becomes saturated and the cleaning effect 4 decreases.

Toner for bias voltage is adhered on the non-magnetic sleeve 22, and this is removed by a scraping plate 26, and the scraped toner is transferred to the developer container 24 in order to contribute again to development.
be returned to. The stirring blade 27 stirs the toner so that the toner is evenly distributed in the axial direction of the magnetic roller 18.21. 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 @imaged, the toner (
! (A static eliminator (not shown) that electrostatically transfers () and removes the charge remaining on the surface of the recording body after the transfer during the second rotation of the recording body 17. For example, a reverse polarity corona discharger or an AC corona discharger. etc., 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 the magnetic roller 18 about Φl++ as the center of rotation, as shown in FIG. The magnetic brush rotates several degrees as shown in FIG. The toner concentration of the magnetic brush is determined by the second magnetic brush forming means 2.
Compared to No. 3 magnetic brush, the concentration is much lower.

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 has become. For this reason, since the magnetic carriers in the toner have an electrostatic attraction ability that causes the toner to adhere, the toner remaining on the recording medium 17 can be efficiently 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 the supply of 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 having a polarity opposite to that of 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 rotationally displacing the 281st brush forming means around the magnetic roller 18, it is also possible to rotationally displace the developer container 24, that is, the entire development-cleaning device.

Furthermore, if toner adheres to the non-magnetic sleeve 19 due to application of a bias voltage, etc., the second magnetic brush forming means 2
3, a scraping plate for removing toner from the non-magnetic sleeve 19 can be provided next to the scraping plate 28.

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 one magnetic brush forming means, but the present invention is not limited to this, and two or more magnetic brush forming means may be used. Of course it's a good thing.

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.

In addition, during development, multi-stage development using a magnetic brush can be performed, so high-speed development is possible, or it is possible to produce 1q of high-density images without background stains. Furthermore, when cleaning,
Since the toner and developer collected from each non-magnetic sleeve can be collected and reused within the same device, an extremely inexpensive and compact device can be obtained.

[Brief explanation of the drawing]

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

Claims (1)

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