JPS58132765A - Developing device - Google Patents

Abstract

PURPOSE:To improve flying of toner, to enhance image density, and to stabilize image quality, by arranging each wire of grid so as to uniformize the distance extending to an image bearing drum and the electric field between the grid and an image bearing drum. CONSTITUTION:A grid 7 consists of plural conductive wires arrnged in parallel to each other, each wire 8 is supported with wire holding plates 9, 9 at both ends, and each wire is arcuately arranged concentrically with a photosensitive drum 1 to equalize the distance between each wire and the drum surface. An insulating thin film is formed on the surface of each wire, and it is disposed at 1mm. intervals, and it has 120mum diameter. Said thin film is necessary to prevent discharge toward the drum 1 and toward a developing roll 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a developing device for developing an electrostatic latent image formed on a photosensitive drum of, for example, an electronic copying machine.

[Technical background of the invention]

Recently, as a type of developing device, a grid made of a plurality of parallel wires is provided between a photosensitive drum as an image bearing member and a developing roller as a toner holding member. By applying even-odd voltages of DC and/or AC to the toner, the toner conveyed by the dust roller is caused to fly, and the toner is transferred between the developing roller and the grid and dots into a kind of cloud state. The electrostatic latent image on the photoreceptor drum is 3J! e is being developed.

[Attractions of background technology]

However, this type of developing device often suffers from the following problems. That is, in the case where the image carrier has a circular outer circumferential surface such as a photosensitive drum, if the grid and dot wires are simply arranged in a plane, the distance from the image carrier varies greatly depending on the arrangement position. Therefore, the electric field between the grid and the image carrier becomes non-uniform, which affects the flight of toner, and as a result, the quality of the copied image is significantly affected.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to make the electric field between the grid and the image carrier uniform, and to create a good condition for toner flight, resulting in an improved image density. It is an object of the present invention to provide a developing device which is expensive and can always provide stable image quality.

[Summary of the invention]

The present invention is designed to equalize the electric field between the grid and the image carrier by arranging the grid and do wires at the same distance from the image carrier. .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an image bearing member 9 of an electronic copying machine, such as a photosensitive drum, on the surface of which an electrostatic latent image corresponding to the image of a document is formed by a non-lighting means (not shown). Rotate in the direction of arrow a. Note that this photosensitive drum 1 is electrically grounded. A developing device 2 is disposed close to a portion facing the photosensitive drum 1. To explain this developing device 2, numeral 3 is a toner supply section that supplies one-component toner 4, and 5 is a toner holder, such as a metal developing roller, that conveys the toner 4 from this toner supply section 3, and its surface is covered with toner. It is sandblasted so that it can be transported, and rotates in the direction indicated by the arrow in the figure. A blade 6 uniformly levels the thickness of the toner conveyed by the developing roller 5. 1 is gri, do,
It is arranged between the photosensitive drum 1 and the developing roller 5. This grid consists of, for example, a plurality of conductive wires 8, as shown in FIG. 9, respectively.

Each of the wires 8 is arranged so that the distance from the surface of the photoreceptor drum 1 is the same as shown in FIG.
That is, they are arranged in an arc shape so as to be concentric with the photoreceptor drum 1. Each of the wires 8 has an insulating thin film formed on its surface, has a diameter of 120 μm, and is arranged at one interval. The thin insulating layer on the surface is necessary to prevent discharge from occurring between the developing roller 5 and the photosensitive drum 1. On the other hand, 10 and 11 are bias power supplies for the developing roller 5, 10 is a DC power supply, and 11 is an AC power supply. 9, 12 and 131d are bias power supplies for the door, 12 is a DC power supply, and 13 is an AC power supply.

Note that the above DC power supply 10. , J2 are configured so that the polarity (positive or negative) of the output voltage can be switched by a changeover switch 14, 15 according to the polarity of the toner used.

In such a configuration, for example, a negatively charged toner is used as the toner 4, and the output voltage of the DC power supply 10 is set to 12
00 & Ruto, the output voltage of AC power supply 11 is 2000 delts (frequency is 1kHz), and the output voltage of DC power supply 12 is +5
00 melt, the output voltage of AC power supply 13 was set to 1000 melt (frequency is 1 kHz), and the output voltage of AC power supply 11. Comparing the image quality with the standard developing device, the image density was also higher and stable copied images were always obtained. That is, each wire 8 of the grid 7 is arranged in an arc shape so as to be concentric with the photoreceptor drum 1.
By making the distance between each wire 8 and the surface of the photoreceptor drum 10 the same, the electric field between the door and the photoreceptor drum 1 is uniform, and a good condition is created for toner flight. Since the image density can be increased, the image density can also be increased, and copies of stable image quality can always be obtained.

Furthermore, since an insulating thin film is formed on the surface of each wire 8 for the grille and door, it is possible to prevent electrical discharge from occurring between the wires 8 and the developing roller 5 or between the photoreceptor drum 1. can.

〔Effect of the invention〕

As described in detail above, according to the present invention, the electric field between the grid and the image carrier becomes uniform, and a good condition for toner flight can be created, so that the image #Ii can be printed with high density and always stable. It is possible to provide a developing device that can provide good image quality and can also prevent discharge from occurring between the edges and the image carrier or toner holder.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, and FIG. 2 is a configuration diagram showing details of grids and dots in the same embodiment. DESCRIPTION OF SYMBOLS 1... Photosensitive drum (image carrier), 2... Developing device, 3... Toner supply section, 4... Toner, 5... Developing roller (toner holding body), 7... Grid, 8...
・Wire, 10.12...DC power supply, 11.13...
·AC source. Applicant's agent Patent attorney Hikosai Suzue 1 Prisoner 2

Claims (2)

[Claims] (1) A toner holder that is disposed close to and facing an image carrier on which an electrostatic latent image is formed and that conveys toner from a toner supply section, and a space between this toner holder and the image carrier. and a grid consisting of a plurality of wires arranged parallel to each other, and by applying a biased voltage of DC, AC, or DC to the toner holder and the grid, the toner is transported by the toner holder. In a developing device that develops the electrostatic latent image by causing the toner to fly and forming the toner into a kind of 79 cloud between the toner holder and the grid and do, each wire of the grid is used as an image carrier. A developing device that recognizes the fact that the body parts are arranged at the same distance. (2) The developing device according to claim 1, wherein each wire of the grid has an insulating film formed on its surface.