JPH04140777A - Dry electrophotographic printing device - Google Patents

Abstract

PURPOSE:To prevent the sticking of a flocculated substance and to prevent the occurrence of faulty printing by providing a rotation control means for rotating only a magnetic roller for a fixed time in a reverse direction to the normal rotation of a developing sleeve in a state where a developing sleeve is stopped. CONSTITUTION:When the main power source of a printing device is applied, only the magnetic roller 1 is rotated for the fixed time previously set in a direction shown by an arrow B in the state where the developing sleeve is stopped. When the roller 1 is rotated, carrier in developer is attracted and the developer near the surface of the sleeve 2 gradually flows in a direction B and the developer or the flocculated substance of the toner concentrated near a doctor blade 3 flows toward a toner hopper 5. Thus, the fear of the occurrence of the faulty printing that a void occurs in the case of printing because the flocculated substance blocks a gap between the blade 3 and the sleeve 2 when development is performed by rotating the sleeve 2 in the direction shown by the arrow A is drastically reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry electrophotographic printing apparatus, and particularly to a dry electrophotographic printing apparatus using a two-component powder development method.

[Conventional technology]

In a dry electrophotographic printing device that uses a two-component developer consisting of toner and a carrier of magnetic fine particles, a developer layer is formed on the surface of the drum as it rotates, and the toner adheres to the latent image on the photosensitive drum. A magnetic roller that rotates in the opposite direction to the developing sleeve is located inside the developing sleeve, and the developing sleeve and magnetic roller are configured to rotate simultaneously when performing development.

FIG. 1 is a longitudinal sectional view showing the general structure of this type of dry electrophotographic developing device.

A magnetic roller 1 having magnetic force is provided inside the developing sleeve 2 which is rotatably supported by the housing 4. When the developing sleeve 2 rotates in the direction of arrow A when developing, the magnetic roller 1 rotates simultaneously. Rotate in the opposite direction of arrow B. When the developing sleeve 2 and the magnetic roller 1 rotate at the same time, the magnetic fine particle carrier constituting the developer and the non-magnetic toner are agitated and the toner is charged. The charged toner adheres to the surface of the developing sleeve 2 together with the carrier, and as it rotates, the photosensitive drum (not shown)
carried in the direction of.

A doctor blade 3 is attached to the tip of the housing 4 in parallel with the developing sleeve 2, and the gap between the doctor blade 3 and the developing sleeve 2 is configured to uniformly control the thickness of the developer layer.

[Problem to be solved by the invention]

As described above, in the dry electrophotographic printing apparatus, in order to make the thickness of the developer layer on the surface of the developing sleeve 2 uniform, the doctor blade 3 is used to regulate the thickness. When the thickness of the developer layer is regulated by the doctor blade 3, the developer passes through a narrow gap with the developing sleeve 2, so extra pressure is applied to the developer in this vicinity. As a result, developer condensation may occur in this vicinity. Furthermore, the toner stored in the toner hopper 5 may condense due to its own weight to form small condensates. In the conventional dry type electrophotographic printing apparatus, only the simultaneous rotation of the developing sleeve 2 and the magnetic roller 1 necessary for development is repeatedly performed.
Following the flow of the developer near the surface of the developing sleeve 2, these condensates collect near the doctor blade 3. If these condensates block the gap between the doctor blade 3 and the developing sleeve 2, the developer will not adhere uniformly to the developing sleeve 2 in that area, resulting in a printing defect where that area becomes white when printing. There is a problem with that.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a dry photographic printing device that does not cause printing defects.

[Means to solve the problem]

The dry electrophotographic printing device of the present invention includes a developing sleeve that forms a developer layer on the surface and rotates to develop the latent image on the photoreceptor by applying toner, and a developing sleeve that is installed coaxially inside the developing sleeve. a magnetic roller that is rotatable in the opposite direction to the developing sleeve and that attracts carriers in the developer; a doctor blade that makes the thickness of the developer layer on the surface of the developing sleeve uniform; and a doctor blade that stores toner. In a dry electrophotographic printing apparatus using a two-component powder developing device having a toner hopper, only the magnetic roller is rotated for a certain period of time in a direction opposite to the normal rotation direction of the developing sleeve while the developing sleeve is stopped. The structure includes a rotation control means for controlling the rotation.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

First, the operation of an embodiment of the present invention will be described with reference to FIG. 1 mentioned above.

When the main power of the printing apparatus is turned on, only the magnetic roller 1 is rotated in the direction of arrow B for a predetermined period of time while the developing sleeve 2 remains stopped. When the magnetic roller I rotates, the carrier in the developer is attracted and receives a force in the direction of arrow B, and the developer near the surface of the developing sleeve 2 gradually flows in the direction of arrow B. This flow of developer causes the developer or toner condensate concentrated near the doctor blade 3 to flow toward the toner hopper 5 . Thereby, when the developing sleeve 2 is rotated in the direction of arrow A to perform development, the possibility that condensate will block the gap between the doctor blade 3 and the developing sleeve 2 is greatly reduced.

In addition, instead of turning on the main power of the apparatus, only the magnetic roller 1 may be rotated for a certain period of time (for example, 1 second) before the developing sleeve 2 is rotated in the developing pot, or the magnetic roller 1 may be rotated for a certain period of time (for example, 1 second). After the rotation of the developing sleeve 2 is stopped, only the magnetic roller 1 may be rotated for a certain period of time. Furthermore, the above-mentioned operation may be used in combination when the main power is turned on and when the development process starts or ends.

〔Effect of the invention〕

As described above in detail, the present invention has the effect that toner or developer condensate closes the gap between the doctor blade and the developing sleeve, thereby preventing printing defects such as white spots during printing.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing the general configuration of a two-component powder developing type developing device. ■...Magnetic roller, 2...Developing sleeve, 3...Doctor blade, 4...
Housing, 5...--toner hopper.

Claims (1)

[Scope of Claims] 1. A developing sleeve that forms a developer layer on its surface and rotates to develop the latent image on the photoreceptor by applying toner; A magnetic roller that is rotatable in a direction opposite to the sleeve and that attracts the carrier in the developer, a doctor blade that makes the thickness of the developer layer on the surface of the developing sleeve uniform, and a toner hopper that stores toner. In a dry electrophotographic printing apparatus using a two-component powder developing device, rotation control is performed to rotate only the magnetic roller for a certain period of time in a direction opposite to the normal rotation direction of the developing sleeve while the developing sleeve is stopped. A dry electrophotographic printing device characterized by comprising: means. 2. The dry electrophotographic printing apparatus according to claim 1, wherein the rotation control means is activated when the main power source of the apparatus is turned on. 3. The dry electrophotographic printing apparatus according to claim 1 or 2, wherein the rotation control means is activated when the development is completed and the rotation of the development sleeve is stopped. 4. The dry electrophotographic printing apparatus according to claim 1 or 2, wherein the rotation control means is operated before rotating the developing sleeve to perform development.