JPS5994771A - Developing device of electrophotography - Google Patents

Abstract

PURPOSE:To suppress a rise of the potential of a toner layer and to prevent unstable picture density and a photographic fog by floating electrically a trimmer member which faces a magnet roll or grounding through a high resistance. CONSTITUTION:The trimmer 4 arranged facing the magnet roll 2 is floated electrically or grounded through a resistance 5 with a high resistance value, e.g. 150MOMEGA. Therefore, when charges generated by frictional electrostatic charge flows from the trimmer 4 to the toner layer side, the potential of the trimmer 4 becomes negative by the floating resistance or grounding resistance of the trimmer 4 to charge the toner layer negatively, suppressing the rise in the toner layer potential. Consequently, unstable picture density and a photographic fog are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic developing device, and more particularly to a developing device capable of suppressing an increase in the frictional potential of toner on a developing sleeve.

In the conventional developing machine, as shown in FIG. 1, the trimmer a, which is a developer layer thickness regulating member, ranks first in the same class as the developing sleeve b.

For this reason, a friction band vil was generated between the trimmer a and the toner, and in some cases, the voltage 11i1 increased to about +300V in the developing area. This toner single layer potential has the same effect as the developing bias, and has the disadvantage of causing unstable image density and fogging in the background area. As shown in FIG. 2, the toner layer potential increases as the number of copies increases.

The present invention has been made to eliminate and improve the above-mentioned drawbacks of the prior art, and by electrically floating the trimmer member or grounding it via a high resistance, it is possible to further suppress the increase in potential of the toner. The present invention aims to provide a developing device.

Embodiments of the present invention will be described below with reference to FIGS. 3 and 4.

In the figure, 1 is a photoconductor, and 2 is a magnet roll constituting a developing device.The electrostatic latent image formed on the surface of the photoconductor 1 is transferred to magnetic toner 3, which is a developer, by facing the magnet roll 2. It is designed to be developed. Magnetic toner 3 attached to the surface of the magnet roll 2 at this time
The layer thickness is regulated by a trimmer 4 provided opposite to the magnet roll 2. The magnet roll 2 is grounded. The trimmer 4 is then electrically floated (Fig. 3) or grounded via a resistor 5 with a high resistance value, for example 150 MΩ (Fig. 4).
.

Therefore, when the electric charge flows from the trimmer 4 to the toner layer side due to the electrification, the potential of the trimmer 4 becomes negative Tli due to the floating resistance of the trimmer 4 (in the case shown in Fig. 3) or the ground resistance (in the case shown in Fig. 4). ;Move to position and trimmer 4
A negative charge is applied to the toner layer from the toner layer, and an increase in the potential of the toner layer is suppressed.

Figure 5 shows the change in the toner layer potential with respect to the number of copies, similar to Figure 2. In the figure, C is the case where the trimmer 4 is directly grounded (conventional example), and d is the case where the trimmer 4 is directly grounded (conventional example), and d is the case where the trimmer 4 is directly grounded (conventional example). In the case of grounding, as is clear from this figure, the increase in toner potential relative to the number of copies could be suppressed compared to the conventional example.

FIG. 6 shows the change in the potential of the trimmer 4 according to the number of copies made in the invention. As the number of copies increases, the potential is maintained at about -200V.

Since the present invention is as described above, it is possible to suppress an increase in the potential of the toner due to frictional charging, and to prevent instability of image density and fogging in the background area due to an increase in the potential of the toner.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration explanatory diagram showing a conventional example, FIG. 2 is a diagram showing changes in toner single layer potential with respect to the number of copies, and FIG.
FIG. 4 is a schematic configuration explanatory diagram showing an embodiment of the present invention, FIG. FIG. 6 is a diagram showing the change in trimmer potential with respect to the number of copies in the present invention. 1 is a photoreceptor, 2 is a magnet roll, 3 is a magnetic toner,
4 is a trimmer. Figure 1 Kojiichichichi (Figure 4 Poupiichichi (Miyako)

Claims (1)

[Claims] In an electrophotographic developing device in which an electrostatic latent image on the surface of a photoreceptor 10 is developed with magnetic toner 3 using a magnet roll 2, a developer layer thickness regulating member such as a trimmer 4 provided opposite to the magnet roll 2 is used. An electrophotographic developing device characterized by being electrically floated or grounded with high resistance.