JPH065444B2 - Method for removing residual developer in electrophotographic apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a residual developer of an electrophotographic apparatus, and in particular, prior to a series of printing steps, the photosensitive drum is reversed from that in the printing step. The present invention relates to an electrophotographic apparatus in which a residual developer which cannot be removed only by the cleaning means provided during the printing step is removed from the surface of the photosensitive drum by using a magnetic brush by rotating the photosensitive drum surface in the direction of.

[Background of the Invention]

An electrophotographic apparatus using a two-component developer composed of a toner (for example, composed of resin and pigment) and a magnetic carrier (for example, composed of iron powder) is usually equipped with a magnet provided on a magnetic roll. The magnetic carrier is attracted to the outer circumference of the magnetic roll by the magnetic force, and the toner is attached to the surface of the magnetic carrier by the Coulomb force to form a magnetic brush on the outer circumference of the magnetic roll. By contacting at a speed, the toner adheres to the latent image portion formed on the surface of the photosensitive drum, and development is performed.

By the way, the magnetic carrier constituting such a magnetic brush has an action of removing the developer adhering to the surface of the photosensitive drum, contrary to the action of supplying the toner to the latent image portion as described above. It has been known. This is an action obtained by the impact force generated when the magnetic carrier comes into contact with the surface of the photosensitive drum. However, the electrophotographic apparatus so far has effectively adopted the removal action by the magnetic carrier described above. It was not realized.

[Object of the Invention]

It is an object of the present invention to provide an electrophotographic apparatus that effectively employs the developer removing action of the magnetic carrier.

[Outline of Invention]

In order to achieve the above object, in the residual developer removing method of the electrophotographic apparatus of the present invention, a magnetic roll in which a part of the magnetic brush is immersed in the developer accommodated in the developing machine,
A magnetic brush made of a two-component developer consisting of a toner and a magnetic carrier formed on the outer circumference of the magnetic roll so that the latent image formed on the surface of the photosensitive drum by the charging step and the exposure step is brought into contact with the surface of the photosensitive drum. Develop using
An electrophotographic apparatus having a printing step in which a developing image formed on the surface of the photosensitive drum in the developing step is transferred to a sheet, and then the developer remaining on the surface of the photosensitive drum is removed by a cleaning unit. Prior to the above, the magnetic roll is rotated in the same direction as the rotation direction in the printing step, and the photosensitive drum is rotated in the opposite direction to the rotation direction in the printing step, and the developer not removed by the cleaning unit. Is removed from the surface of the photosensitive drum by using a magnetic carrier forming the magnetic brush.

Example of Invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus according to the present invention. FIG. 2 is a time chart of the electrophotographic apparatus according to the present invention.

In FIG. 1, reference numeral 1 denotes a photosensitive drum. Photosensitive drum 1
Is a film having an optical semiconductor property formed on the surface of a metallic cylinder, and by applying light energy such as laser light 3, that part apparently changes from an insulator to a conductor. . Further, the photosensitive drum 1 rotates in the direction of arrow A during the printing step (the printing step in the present invention means charging, exposing, developing and transferring cleaning) as shown in the figure.

After the surface of the photosensitive drum 1 is uniformly charged by the charger 2, an electrostatic latent image (hereinafter referred to as a latent image) is formed through an exposure process using the laser light 3. When the latent image formed on the photosensitive drum 1 reaches the position of the developing device 4 as the photosensitive drum 1 rotates, the latent image is developed by the magnetic brush 6 around the magnetic roll 5 provided in the developing device 4.

The magnetic brush 6 is formed on the outer periphery of the magnetic roll 5 in the same manner as described in the related art, and the magnetic roll 5 is applied to the two-component developer 10 (hereinafter referred to as a developer) contained in the developing machine 4. The magnetic brush 6 is provided in the developing device 4 in such a positional relationship that a part of the magnetic brush 6 is immersed.

In FIG. 1, the photosensitive drum 1 rotates in the direction of arrow A (clockwise), while the magnetic roll 5 rotates in the counterclockwise direction. The rotation direction of the roll 5 is not limited to the above description. In short, the present invention only needs to maintain the relationship that the photosensitive drum 1 rotates clockwise and counterclockwise with respect to the magnetic roll 5 that rotates in one direction.

The developed image formed as a visible image on the surface of the photosensitive drum 1 is
Further, when the photosensitive drum 1 reaches the position of the transfer device 7 as the photosensitive drum 1 rotates, the photosensitive drum 1 is sucked toward the paper 8 and is carried to the next stage (fixing device (not shown)) by the paper transport operation of the tractor 9.

The developer 10 left on the surface of the photosensitive drum 1 without being transferred from the surface of the photosensitive drum 1 to the sheet 8 side is thereafter sucked and removed by a fur brush 11 provided as a cleaning unit.

In this way, according to the present invention, the photosensitive drum 1 is rotated in the direction of arrow B before the first printing is performed and then the second printing is started, and the photosensitive drum not removed by the fur brush 11 is used. It was decided to include a step of removing the residual developer on the surface 1 using a magnetic carrier forming a magnetic brush.

FIG. 2 is a time chart showing an operation example of the electrophotographic apparatus according to the present invention. As shown here, during the printing process, the photosensitive drum 1 is rotated in the direction of arrow A as described above. Outside the printing process period, the photosensitive drum 1 is rotated in the direction of arrow B as described above. The time during which the photosensitive drum 1 rotates in the direction of the arrow B may be constantly rotated outside the printing process period, or may be rotated only for a predetermined time set in advance. Further, the rotation operation of the photosensitive drum 1 in the direction of the arrow B may be performed for each printing process as shown in FIG. 2, or may be performed for each preset number of times of printing.

In FIG. 1, reference numeral 12 is a sub-charging device that operates when the photosensitive drum 1 is rotated in the direction of arrow B, and is necessary as a means for charging the surface of the photosensitive drum 1 to the same polarity as the charging polarity of the toner. Used accordingly.

[Advantage of the Invention] According to the present invention, a latent roller formed on the surface of a photosensitive drum by a charging step and an exposure step is provided, which has a magnetic roll in which a part of a magnetic brush is immersed in a developer accommodated in a developing machine. The image is developed using a magnetic brush of a two-component developer composed of toner and a magnetic carrier formed on the outer circumference of the magnetic roll so as to contact the surface of the photosensitive drum, and is formed on the surface of the photosensitive drum by the developing step. In an electrophotographic apparatus having a printing step in which a developer is left on the surface of the photosensitive drum by a cleaning unit after the developed image is transferred to a sheet, the magnetic roll is rotated during the printing step before the printing step. And the photosensitive drum is rotated in the opposite direction to the rotation direction during the printing process, and is not removed by the cleaning unit. Since the developer is removed from the surface of the photosensitive drum by using the magnetic carrier forming the magnetic brush, the magnetic roll can be configured to rotate in one direction, and as a result, the configuration of the developing machine can be simplified. can do.

Further, since the magnetic roll is driven only in one direction, the developer contained in the developing machine, that is, the residual developer can be removed by the magnetic carrier while always maintaining a stable mixed state of the toner and the magnetic carrier, Each time the residual developer is removed, the mixed state of the toner and the magnetic carrier is not disturbed each time. Therefore, after the residual developer is removed, the next printing step can be started immediately, and it is possible to provide an unprecedented electrophotographic apparatus that effectively employs the developer removing action of the magnetic carrier.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus according to the present invention, and FIG.
The figure is a time chart of the electrophotographic apparatus according to the present invention. In the figure, 1 is a photosensitive drum, 2 is a charger, 3 is a laser beam, 4 is a developing device, 5 is a magnetic roll, 6 is a magnetic brush, and 7
Is a transfer device, 8 is a paper, 9 is a tractor, 10 is a developer, 11 is a fur brush, and 12 is a sub charger.

Claims (1)

[Claims] 1. A photosensitive drum having a magnetic roll in which a part of a magnetic brush is immersed in a developer accommodated in a developing machine, and a latent image formed on a surface of the photosensitive drum by a charging step and an exposing step is formed on the photosensitive drum. Develop with a magnetic brush of two-component developer consisting of toner and magnetic carrier formed on the outer circumference of the magnetic roll so as to contact the surface, and transfer the developed image formed on the surface of the photosensitive drum to the paper by the developing step. After that, in an electrophotographic apparatus having a printing step in which the developer remaining on the surface of the photosensitive drum is removed by a cleaning unit, the magnetic roll is rotated in the same direction as the rotation direction during the printing step before the printing step. And the photosensitive drum is rotated in a direction opposite to the rotating direction during the printing process, and the developer not removed by the cleaning unit is removed by the magnetic Residual developer removing method of an electrophotographic apparatus characterized by having a step of removing from said photosensitive drum surface of a magnetic carrier to form a brush.