JPH0341828B2 - - Google Patents

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.

Relating to an imaging device.

[Technical Background of the Invention] Recently, as this type of developing device, a grid consisting 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 a DC and/or AC bias voltage to the grid and the developing roller, the single-component toner transported by the developing roller is made to fly, and the toner is formed into a kind of powder cloud between the developing roller and the grid. A device that develops an electrostatic latent image on a photoreceptor drum is being developed.

[Problems with background technology]

However, this type of developing device has the following problems. In other words, in order to obtain stable image quality, it is necessary to form a sufficiently charged toner layer on the developing roller as a toner holding member, but in conventional devices, the toner layer provided close to the developing roller Since the toner is only tribo-electrified with the regulating blade, sufficient tribo-electrification of the toner cannot be obtained. As a result, phenomena such as flying toner with a small amount of charge adhering to the non-latent image area of the photoreceptor drum occur, resulting in fogging of the copied image, or blurring or thickening of the lines of the copied image. There was a problem that occurred.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a developing device that can uniformly apply a sufficient charge to toner and that can always provide stable and clear image quality without fogging. Our goal is to provide the following.

[Summary of the invention]

The present invention provides a toner supply section with a conductive mesh body that the toner contacts or passes through, and applies a predetermined potential to the mesh body according to the polarity of the toner to charge the toner passing through the mesh body. It is designed to be applied sufficiently and uniformly.

[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 carrier, such as a photosensitive drum, in an electronic copying machine, on the surface of which an electrostatic latent image corresponding to an image of a document is formed by an exposure 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. This developing device 2 will be explained as follows.
3 is a toner supply unit that supplies one-component toner 4;
A conductive mesh member 5 is stretched in a substantially horizontal state below the interior thereof, and the toner 4 passes through this mesh member 5 and falls downward. Reference numeral 6 denotes a toner holder, such as a conductive developing roller, which conveys the toner 4 supplied from the toner supply section 3. Its surface is sandblasted so that it can convey the toner, and it rotates in the direction of arrow b in the figure. Reference numeral 7 denotes a regulating blade that uniformly levels the thickness of the toner conveyed by the developing roller 6. A grid 8 is disposed between the photosensitive drum 1 and the developing roller 6. This grid 8 includes, for example, a plurality of conductive wires 9 as shown in FIG.
are arranged parallel to each other, and both ends of each of these wires 9 are supported by wire support plates 10, 10, respectively. Each of the wires 9... is connected to the photoreceptor drum 1 as shown in FIG.
They are arranged in an arc shape so that the distances from the surface of the photosensitive drum 1 are the same, that is, they are concentric with the photosensitive drum 1. Here, each wire 9... has an insulating thin film formed on its surface and has a diameter of 120μ.
m, and are arranged at 1 mm intervals. The insulating thin film on the surface is necessary to prevent discharge from occurring between the developing roller 6, the photoreceptor, and the drum 1.

On the other hand, 11 is a DC current for applying a predetermined potential to the mesh body 5, 12 and 13 are bias power supplies for the developing roller 6, 12 is a DC power supply, and 13 is an AC power supply. Further, 14 and 15 are bias power supplies to the grid 8, 14 is a DC power supply,
15 is an AC power source. Then, the above DC power supply 1
1, 12, and 14 are switches 1 for changing the polarity (positive or negative) of the output voltage according to the polarity of the toner used;
6, 17, and 18.

In such a configuration, first, for example, a non-magnetic negatively charged toner (average particle size 10.98 microns) with a specific resistance of 2.1×10 ¹³ Ωcm is used as the toner 4, and the output voltage of the DC power supply 11 is set to −600 μm. The negative voltage was applied to the mesh body 5 in the form of a volt. As the mesh body 5, a fine grain standard sieve (JIS Z-8801) with 100 mesh (sieve mesh opening 0.149 mm) was used. For such toner charging conditions, the output voltage of the DC power supply 12 is -200 volts, and the output voltage of the AC power supply 13 is set to -200 volts.
output voltage of 2000 volts (frequency is 1KHz), output voltage of DC power supply 14 is +200 volts, AC power supply 1
An experiment was conducted with the output voltage of AC power supply 13 and 15 set to 1000 volts (frequency is 1KHz) and the output voltage of AC power supplies 13 and 15 in the same phase. There were no sharp lines, and stable and clear copied images were always obtained. That is, frictional charging of the toner by the regulating blade 7 and the developing roller 6 alone does not provide a sufficient amount of toner charge necessary for development, and the flying toner with a small amount of charge is deposited on the non-latent image area of the photoreceptor drum 1. However, by installing a conductive mesh body 5 in the toner supply unit 3 and applying a DC voltage of several hundred volts to it, the toner 4 can be removed from the mesh. When the toner 4 contacts and passes through the body 5, an electric charge is injected into the toner 4, and the electric charge can be applied sufficiently and uniformly to the toner 4 without producing a reversely charged toner, so that a stable and clear copy image is always obtained. That's what you get. Furthermore, by changing the voltage applied to the mesh body 5, the amount of charge on the toner 4 can be arbitrarily controlled, thereby making it possible to adjust the image density.

Next, for example, as toner 4, the specific resistance is 4.3×
10 ¹⁰ Ω・cm magnetic negatively charged toner (average particle size
11.2 microns), a voltage of -400 volts was applied to the mesh body 5, and the other conditions were the same as in the previous case. As in the previous case, there was no fog and the line was sharp. As a result, stable and clear copied images were always obtained.

In the above-mentioned embodiments, a case has been described in which the present invention is implemented in a developing device of an electronic copying machine, but the invention is not limited thereto, and can be similarly implemented in a developing device such as an electronic printer or a facsimile machine.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a developing device that can uniformly apply a sufficient charge to toner and can always provide stable and clear image quality without fogging. .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a detailed configuration diagram of the grid in the same embodiment. 1... Photosensitive drum (image carrier), 2... Developing device, 3... Toner supply section, 4... Toner, 5...
...Mesh body, 6...Developing roller (toner holding body),
8... Grid, 9... Wire, 11, 12, 1
4...DC power supply, 13,15...AC power supply.

Claims (1)

[Scope of Claims] 1. A toner supply section, and a toner holder disposed in close proximity to the toner supply section and an image carrier on which an electrostatic latent image is formed, and for conveying the toner supplied from the toner supply section. and a developing device that develops the electrostatic latent image by applying a bias voltage to the toner holder to cause the toner conveyed by the toner holder to fly, the developing device comprising: a developing device provided in the toner supply section; a conductive mesh body through which the toner contacts or passes; a first power source that outputs a positive DC voltage; a second power source that outputs a negative DC voltage; and outputs of the first and second power sources. A developing device comprising a selection means for selecting a voltage according to the polarity of the toner and applying the selected output voltage to the mesh body.