JPH04152153A - Image forming device - Google Patents

Abstract

PURPOSE:To improve controllability of toner flow modulation to enhance a pixel forming speed, a pixel density, and gradation properties by a method wherein a counter electrode having the same electric potential as a reference electrode is so disposed as to be proximate and opposed to an aperture of the reference electrode. CONSTITUTION:A toner positively electrified by friction with the rotation of a brush roller 20 and a supply roller 23 is fed by the brush roller 20. The toner filliped by a blade 24 is guided by a guide plate 25 and supplied between a reference electrode 3 and a reference counter electrode 5. By applying a negative voltage to a control electrode 4 on an image signal, an electric field having electric lines of force directing from the reference electrode 3 and the reference counter electrode 5 to the control electrode 4 is formed inside and below an aperture 6. The toner is attracted outside from the rear surface of an aperture electrode 1 by this electric field and held on a support body 10 by a fly electric field formed by a back electrode 11 to form a toner image part thereon. Since a maximum value of the electric field below the aperture and thereabouts can be enhanced, a toner flow controllability is improved, and a pixel forming speed, a pixel density, and gradation properties are enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus that can be used in copying machines, printers, plotter facsimiles, and the like.

[Prior Art] Conventionally, an aperture electrode body having an aperture, which is a small hole, controls the passage of toner particles through the aperture by applying an image signal, and image recording is performed in which an image is formed on a support by the passing toner particles. The device is U.S. Patent No. 3,689
, No. 935. In this proposal, the aperture electrode body includes a reference electrode made of a continuous conductor layer on one side with an insulator layer in between, and a plurality of control electrodes made of conductive layers insulated from each other in the longitudinal direction on the other side. Each control electrode has a small number of apertures (each has one row) extending through the three layers.This image recording device further applies a potential between the control electrode and the reference electrode. Means 2 for providing, for example, a control electrode drive IC, means for projecting charged toner particles such that an applied potential drives the flow of toner particles through the aperture, and a support on which a toner image is formed and an aperture electrode body are relative to each other. In this device, the magnitude of the electric field for driving the flow of toner particles is determined between the reference electrode and the control electrode. It is determined by the suppressing electric field between the electrodes, which is the applied voltage (■) divided by the distance t between these two electrodes.

[Problems to be Solved by the Invention] However, in the above configuration, the applied voltage is limited by the withstand voltage of the control electrode drive IC, etc., and a strong electric field cannot be generated. For this reason, toner controllability was poor, limiting pixel formation speed, pixel density, and gradation.

The present invention has been made to solve the above-mentioned problems, and its purpose is to improve the maximum value of the electric field that drives the flow of toner even if the applied voltage is limited. An object of the present invention is to provide an image forming apparatus that improves the controllability of toner flow modulation and improves pixel formation speed, pixel density, and gradation.

[Means for Solving the Problems] In order to achieve this object, the image forming apparatus of the present invention has the following features:
It is characterized by having a counter electrode that is provided close to a position facing the aperture of the reference electrode and has the same potential as the reference electrode.

[Function] According to the present invention having the above configuration, many of the electric lines of force connecting the control electrode and the reference electrode extend to the opposing reference electrode, and even if the voltage applied to the control electrode is the same, The electric field strength between the opposing reference electrodes, and therefore the electric field strength near the bottom of the aperture of the reference electrode, becomes strong.Therefore, the charged toner supplied near the bottom of the aperture can be sufficiently driven.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an embodiment embodying the present invention.

As shown in detail in FIG. 2, the aperture electrode body 1 has a reference electrode 3 on the toner supply source, ie, the back side, of the insulating layer 2, and a control electrode 4 on the support 10 side, ie, the front side. The control electrodes 4 are arranged in a plurality of stages in the longitudinal direction and are insulated. Further, an aperture 6 passing through the reference electrode 3, the insulating layer 2, and each control electrode 4 is provided. This aperture 6 is
Since they are provided for each control electrode 4, there are a large number of them. In this embodiment, a large number of them are formed in a line corresponding to the width of the support IO. A counter reference electrode 5 is arranged on the reference electrode 3 side of the aperture 6 and facing the aperture 6. In addition, on the control electrode 4 side of the aperture electrode body 1,
A back electrode 11 is provided which is conveyed while contacting the support 10. Each control electrode 4 is connected to a control voltage drive circuit 8 that generates a voltage based on an image signal. The back electrode 11 is connected to a high voltage power source 12. The counter reference electrode 5 and the reference electrode 3 are grounded and have the same potential.

On the reference electrode 3 side of the aperture electrode body 1, a brush roller 20 and a supply roller 23 disposed parallel to the brush roller 20 are connected to a toner case 22 in which toner 22 is stored.
It is located inside. The brush of brush roller 20 and the supply roller are in contact with each other. brush roller 20
A brushing blade 24 is in contact with the aperture 6 at a position before it rotates. A guide plate 25 for guiding the toner from the scraping position of the brush scraping blade 24 to the gap between the reference electrode and the counter electrode is fixed to the counter reference electrode.

The operation of the configuration as described above will be explained in detail below.

As the brush roller 20 and supply roller 23 rotate,
The toner is positively charged by friction with the brush and is carried on the brush as a charged toner.

The toner is conveyed toward the vicinity of the brush scraping blade 24 by the rotation of the brush roller 20. Here, the toner on the brush that has been repelled by the blade 24 is thrown up by the elasticity of the brush, forms a cloud, is guided to the guide plate 25, and is supplied between the reference electrode 3 and the reference counter electrode 5.

At this time, when a negative voltage is applied to the control electrode 4 corresponding to the image area of the support 10 by the image signal, the reference electrode 4 is placed inside and under the aperture 6 of the applied control electrode 4.
An electric field having lines of electric force directed from the counter reference electrode 5 to the control electrode 4 is formed. Therefore, the positively charged toner is drawn out from the back surface of the aperture electrode 1 to the front surface by this electric field. Further, the toner particles fly onto the support 10 and are held by the flying electric field formed by the back electrode 11 to form a toner image area. By applying the same potential as the reference electrode 3 or a positive voltage to the control electrode 4 corresponding to the non-image area, the flying electric field caused by the back electrode 11 is shielded. Alternatively, an electric field having lines of electric force directed from the front surface to the back surface, that is, from the control electrode 4 to the reference electrode 3 and the counter reference electrode 5, is formed in the aperture 6 to suppress the toner from passing through the aperture. By repeating this process while transporting the support 10, a toner image is formed over the entire surface of the support 10.

In the above embodiments, the electric field strength between the opposing reference electrode 5 and the reference electrode 3 is, for example, when the aperture diameter is 0.1 m.
m, when the distance between the reference electrode 3 and the control electrode 4 is 0.1 mm, and the distance between the opposing reference electrode 5 and the reference electrode 3 is 0.1 am, and 100 V is applied to the control electrode 4, approximately 400 V/m is applied on the opposing reference electrode 5. It was cm. When there is no counter reference electrode as in the conventional case, the voltage at the same position is approximately 200 V/c+++, so this is twice that. The fact that the electric field strength is doubled at the position of the counter reference electrode 5 means that the aperture 6
The electric field strength near the bottom is also approximately doubled, and the charged toner supplied near the bottom of the aperture 6 can be driven with a sufficiently large force.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, even if the voltage applied to the control electrode is the same, the maximum value of the electric field that drives the flow of toner, especially the electric field near the bottom of the aperture, can be increased. Therefore, it is possible to provide an image forming apparatus with improved controllability of toner flow and improved pixel formation speed, pixel density, and gradation.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an image forming apparatus showing an embodiment embodying the present invention, and FIG. 2 is a perspective view showing details of the aperture electrode body of FIG. 1. 1... Aperture electrode body, 2... Insulating layer, 3...
Reference electrode, 4... Control electrode, 5... Counter reference electrode,
6... Aperture 8... Control voltage drive circuit, lO.
... Support body, 11 ... Back electrode, 12 ... High voltage power supply, 20 ... Brush roller, 22 ... Toner 23.
... Supply roller, 24 ... Brushing blade, 2
5...Guide plate.

Claims (1)

[Claims] (1) Consisting of a reference electrode consisting of a continuous conductor layer on one side with an insulator layer in between, and a plurality of control electrodes consisting of conductive layers insulated from each other in the longitudinal direction on the other side. an aperture electrode body having an aperture penetrating the three layers for each control electrode; means for selectively applying a potential between the control electrode and the reference electrode; and supplying charged toner to the vicinity of the bottom of the aperture of the reference electrode. and means for moving the support body on which the toner image is formed and the aperture electrode body relatively to position the support body in the particle flow path of the charged toner. An image forming apparatus comprising: a counter reference electrode provided close to a position facing an aperture and having the same potential as the reference electrode.