JPH0777873A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the electrification of the bottom surface of a developing unit and further, to eliminate the contamination of a transfer material and an adverse effect on a toner layer on a sleeve by making a part used as the guide of the developing unit of a nonmagnetic conductive material. CONSTITUTION:The part 11 as the lower side of the developing sleeve 10 arranged inside the container of the developing unit 4 is made of the nonmagnetic conductive material such as aluminium and a transfer material carrying path is formed by a guiding plate 12 arranged with a proper interval from the part 11. By such a constitution, even when the transfer material passing through the carrying path rubs/runs on the bottom surface 11 of the developing unit, a charge by triboelectrification is released to the earth, so that the part of the bottom surface 11 is never electrified to prevent the attracting/sticking of toner to the part. Moreover, the adverse effect on a magnetic toner layer formed on the developing sleeve 10 magnetized by a magnet inside the developing unit, caused by the part can be eliminated.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus utilizing an electrostatic transfer process such as an electrostatic copying machine and a printer, and more particularly to an image forming apparatus using magnetic toner.

[0002]

2. Description of the Related Art Generally, a known image forming apparatus as described above is provided with a cylindrical image carrier which rotates and a transfer means such as a transfer charger which is arranged to face the image carrier. It is usual that the transfer material such as paper is conveyed to the transfer site by passing between a pair of guide plates.

However, when a small machine called a personal machine has become widespread in this kind of apparatus as in recent years,
In such a device, it is becoming difficult to dispose the pair of guide plates as described above, so it is customary to convey the transfer material, but use a developing device disposed near the guide plates. Then, one in which the bottom surface of the developing device is used as one of the guide plates has been proposed.

However, in general, the container of the developing device for accommodating the toner, the developing sleeve, etc. is usually made of an insulating plastic material. Therefore, when the transfer material passes while rubbing its temporary surface, , The bottom surface is charged by friction, and affects the toner layer that is adhered and conveyed to the non-magnetic developing sleeve disposed directly above the bottom surface inside the container, and the electrostatic latent image on the image carrier from the sleeve. There is a problem that the toner applied to the toner is disturbed, which leads to deterioration of image quality, and the toner attached to the bottom surface causes contamination of the transfer material being conveyed.

The present invention has been made to cope with the above situation, and in an image forming apparatus in which the bottom surface of the container of the developing device is used as a guide when the transfer material is conveyed, An object of the present invention is to provide an image forming apparatus capable of obtaining a high quality image while avoiding the above problems by forming a portion used as the guide with a non-magnetic conductive material. .

[0006]

[Constitution of the invention]

In order to achieve the above-mentioned object, the present invention has a developing device containing a magnetic toner and having a non-magnetic developing sleeve surrounding a magnet disposed inside. In the image forming apparatus having a transfer material transport path between the bottom surface of the developing device and a guide plate arranged at a distance from the bottom surface, at least a portion of the bottom surface corresponding to the lower portion of the nonmagnetic developing sleeve is made of a nonmagnetic conductive material. And the grounding of the portion, or the bottom surface of the developing device in the above apparatus is grounded via a varistor.

With this structure, it is possible to prevent the bottom surface of the developing device, which is the conveying path, from being charged, and prevent the transfer material from being contaminated and the toner layer on the sleeve from being adversely affected.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic side view showing the configuration of an image forming apparatus to which the present invention is applied. The surface photosensitive layer of the image carrier 1 that extends in the direction perpendicular to the paper surface and rotates in the direction of the arrow shown in the figure is uniformly charged by the charging roller 2, and the image signal 3 is projected onto this charged surface to form an electrostatic latent image. Is formed.

Reference numeral 4 in the drawing denotes a developing device, and when the latent image arrives at a developing portion where the image carrier 1 and the developing device 4 face each other,
Toner is supplied to the latent image from the developing device via the developing sleeve 10 to form a toner image.

When the toner image reaches the transfer portion where the transfer roller 5 is arranged as the image carrier 1 rotates, the transfer material P is transferred to the developing device bottom surface 11 and the guide plate in synchronization with the toner image. The toner image on the side of the image carrier is transferred to the transfer member through the transfer path 12 and is transferred to the transfer portion.

After the transfer is completed, the transfer material P is separated from the image carrier 1 by the action of the charge elimination needle 6, and the toner image is fixed and fixed in the fixing device 9 through the conveying path 9 ', and then discharged to the outside of the apparatus.
At the time of transfer, the residual toner remaining on the image carrier 1 without contributing to the transfer is removed by the cleaning device 7, and the residual charge is removed by the pre-exposure 8 so that the image carrier can enter the next image forming step. It becomes a state.

In such an apparatus, as shown in the drawing, a portion 11 corresponding to the lower part of the developing sleeve 10 disposed inside the container bottom of the developing device and corresponding to the lower portion in the drawing is made of a non-magnetic conductive material such as aluminum. And a guide plate 12 arranged at an appropriate interval to form a transfer material conveying path.

FIG. 2 is an enlarged view showing only the developing unit 4 of the above apparatus, in which a magnet 13 is arranged and a developing sleeve 10 made of a non-magnetic material is arranged. . Also, in the developing device container, particularly the sleeve 10
The portion 11 corresponding to the lower part of the is made of a non-magnetic conductive material and is grounded.

With this structure, even if the transfer material passing through the conveying path slides on the bottom surface 11 of the developing device, the electric charge due to frictional charging escapes to the ground, so that the portion concerned is not charged. It is possible to prevent the toner from adsorbing and adhering to the portion. This part is the magnet 1 inside the developing unit.
It is also possible to effectively prevent the magnetic toner layer formed on the developing sleeve 10 from being magnetized by the magnetic field 3 having an adverse effect.

FIG. 3 shows another embodiment, in which only the structure of the developing device is shown, and the parts corresponding to those in FIG. 2 are designated by the same reference numerals. , And the description thereof will be omitted.

In this structure, the non-magnetic conductive portion 11 on the bottom surface of the developing device is grounded via a varistor 14 of about 500V. With such a configuration, the charge of the transfer material escapes through the portion 11 even in a high humidity environment, so that the transfer omission can be prevented and the electrostatic attraction force to the toner does not become a problem. The size can be reduced, and the transfer material can be prevented from being contaminated by the toner adhering to this portion.

Further, although not shown in the drawings, the required portion of the bottom surface of the developing device container is made of a plastic in which carbon is dispersed to adjust the volume resistivity to give an appropriate conductivity, thereby reducing the weight. The same effects as those of the apparatus of the above embodiment can be obtained while reducing the cost.

[0018]

As described above, according to the present invention,
In an image forming apparatus in which at least a part of the bottom surface of the developing device is used as a transfer material conveying path, the transfer material passing therethrough is effectively contaminated, and the deterioration of image quality is effectively prevented, and an image in the utilization chamber is obtained. There is a great deal of contribution to this.

[Brief description of drawings]

FIG. 1 is a schematic side view of an image forming apparatus to which the present invention is applied.

FIG. 2 is an enlarged side sectional view showing a developing device portion of the above.

FIG. 3 is a side sectional view of a developing device according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charging roller 3 Image signal 4 Developing device 5 Transfer roller 6 Static eliminator 7 Cleaning device 9 Fixing device 10 Developing sleeve 11 Non-magnetic conductive part 14 Varistor

Claims (2)

[Claims] 1. A developing device having a non-magnetic developing sleeve for accommodating a magnetic toner and surrounding a magnet disposed therein, wherein a developing device bottom surface and a guide plate spaced apart from the developing device are provided. In an image forming apparatus serving as a transfer material transport path, at least a portion of the bottom surface corresponding to a lower portion of the nonmagnetic developing sleeve is formed of a nonmagnetic conductive material,
An image forming apparatus in which the portion is grounded. 2. An image forming apparatus according to claim 1, wherein the bottom surface of the developing device is grounded via a varistor.