JPH08142381A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To prevent toner from adhering to the toner control head surface or head electrode, and prevent clogging of toner in the toner passage hole and mixing of different color toners in color printing. [Structure] When the toner 1 is positively charged (or negatively charged), the relationship between the potentials of the surface of the developing roller 3, the reference electrode 11, the control electrode 12, and the back electrode 10 when the toner passage hole 7 is open and closed is shown. The setting is made as follows so that the toner 1 does not remain on the surface of the toner control head 8 or around the toner passage hole 7. VS, VC ≥ VD, VB (or VS, VC ≤ VD, VB) where VD: potential of the surface of the developing roller 3 VS: potential of the reference electrode 11 VC: potential of the control electrode 12 VB: potential of the rear electrode 10

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes a powder flying recording method in which charged toner adhering to a developing roller is directly ejected onto recording paper by electric field control to form an image without using a photoreceptor or the like. The present invention relates to an image forming apparatus such as a printer or a copying machine.

[0002]

2. Description of the Related Art In recent years, with the demand for downsizing of image forming apparatuses, a powder flying recording apparatus that electromagnetically controls the flight of toner to directly form an image on a recording paper is used for an image of a photosensitive drum or the like. Since there is no need to use a carrier and the number of printing steps is small, it is expected as a next-generation image forming apparatus.

A conventional powder flying recording apparatus will be described below.

FIG. 3 is a schematic configuration diagram of a conventional powder flying recording apparatus, which is a toner storage tank 2 for storing toner 1.
Inside the container, a developing roller 3, a sponge roller 4 for charging the toner 1, and a layer thickness regulating blade 5 for adjusting the toner layer thickness on the developing roller 3 are provided.
Is provided with an opening 6 for flying the toner 1. Below the developing roller 3 that carries the toner 1 and transports the toner 1 to the position of the opening 6, a toner control head 8 having a toner passage hole 7 that controls the flight of the toner 1 is provided. At the position facing the developing roller 3 via the toner control head 8, there is provided a back electrode 10 for electrically attracting the toner 1 having passed through the toner passage hole 7 to the recording paper 9 side, and the recording paper 9 is provided on the upper surface thereof. Is set.

FIG. 4 is a plan view showing the structure of the toner control head 8 of FIG. 3, and FIG. 5 is a sectional view of the toner control head 8 of FIG. The toner control head 8 has a structure in which reference electrodes 11 and control electrodes 12 are arranged in a matrix as shown in FIG. 4, and they are insulated by an insulator 13 as shown in FIG. Further, a plurality of toner passage holes 7 penetrating all the layers are arranged according to the required resolution.

The operation of the powder flying recording apparatus constructed as described above will be described below. Toner 1
Is a powder in which a binder resin, a pigment, and a charge control agent are kneaded and an external additive is added, and the developing roller 3 and the sponge roller 4 are
Between them is positively or negatively triboelectrically charged, and is carried on the developing roller 3 by an image force, a Van der Waals force, etc., and the toner layer thickness on the developing roller 3 is adjusted by the layer thickness regulating blade 5, and further friction is caused. It is charged and transported to the opening 6.

The flight of the toner 1 onto the recording paper 9 is
By applying a predetermined voltage to the developing roller 3, the reference electrode 11, the control electrode 12, and the back electrode 10, the electric field in the vicinity of the toner passage hole 7 is oriented so that the toner 1 can pass therethrough, or an electric field in the opposite direction is formed. It is controlled by electromagnetically opening and closing the toner passage hole 7 that prevents the toner 1 from passing through. This electromagnetic opening / closing generally involves developing roller 3 and back electrode 10.
A constant potential is applied to the reference electrode 11 and the control electrode 12
This is done by changing the potential applied to the.

When the toner passage hole 7 is electromagnetically closed, the toner 1 does not fly to the recording paper 9, and only when the toner passage hole 7 is opened, the toner 1 passes through the toner passage hole 7 and the developing roller 3 is opened.
The recording paper 9 along the lines of electric force formed between the back electrode 10 and the back electrode 10.
Adheres to The reference electrode 11 and the control electrode 12 are connected to a control circuit (not shown) that generates a signal according to image information and a drive circuit (not shown) that applies a voltage based on the signal, and each dot On the other hand, an image is formed on the recording paper 9 by performing such electromagnetic opening / closing control of the toner passage hole 7. In the case of color printing, such an operation may be sequentially performed for yellow, magenta, cyan and black.

After that, the recording paper 9 is transported to the fixing unit 14. The fixing unit 14 is provided with a heating roller 16 having a high-intensity lamp 15 therein and a pressure roller 17 having elastic surface. Here, the toner 1 on the recording paper 9 is melted and pushed into the fibers of the paper, and the printing is completed.

[0010]

Such a powder flying recording apparatus has a small number of parts as compared with a laser printer using an electrophotographic technique because it does not require a photosensitive drum, an optical system or a transfer process. Therefore, it is advantageous in terms of downsizing and cost reduction of the device.

However, when the toner 1 is positively charged (in the case where the toner has a negative potential, it is shown in parentheses),
Surface of developing roller 3, reference electrode 11, control electrode 12, back electrode
The relationship between the respective potentials of 10 is VS, VC <VD, VB (or VS, VC> VD, VB), where VD: the potential of the surface of the developing roller 3 VS: the potential of the reference electrode 11 VC: the potential of the control electrode 12 VB When the toner 1 in this case has a positive potential, the lines of electric force 18 in the developing space are as shown in FIG. 6, and the upper surface of the toner control head 8, the reference electrode 11, and the control electrode 12 are shown. It can be seen that there is the toner 1 that flies toward the recording paper 9 and does not reach the recording paper 9. However, FIG. 6 shows only the electric force lines 18 coming in and out of the developing roller 3, and the arrows show the directions of the electric force lines 18.

When the toner 1 is negatively charged, the lines of electric force 18 in the developing space are as shown in FIG. Where 240d
Taking pi as an example, toner 1 with an average particle size of about 10 μm
Will pass through the toner passage hole 7 of about 100 μm,
When the residual toner 19 attached to the toner passage hole 7 is accumulated,
Toner clogging occurs.

When the toner clogging occurs, not only the image is not stable, but in color printing, due to the presence of the residual toner 19 around the toner passage hole 7, color mixing between different color toners occurs, resulting in deterioration of image quality. I had a problem. Such a problem becomes more serious as the diameter of the toner passage hole 7 is reduced to achieve higher resolution.

The present invention solves the above-mentioned conventional problems, in which the toner 1 is the upper surface of the toner control head 8 or the reference electrode 1.
1. By forming an electric field that does not fly toward the control electrode 12, toner adhesion around the toner control head 8 and the toner passage hole 7 is prevented, and toner clogging and color mixing between different color toners do not occur. The purpose is to provide a device.

[0015]

SUMMARY OF THE INVENTION In order to solve these problems and achieve the object, the present invention provides a toner control head capable of electromagnetically opening and closing a toner passage hole with a head electrode, and the toner control head. In an image forming apparatus having a toner carrier that holds the toner on the surface sandwiching it and supplies it to the position of the opening, and a back electrode, and configured to transfer the toner that has passed through the toner passage hole to a recording material, When the toner is positively charged (or negatively charged), the relationship between the potentials of the developing roller surface, the reference electrode, the control electrode, and the back electrode when the toner passage hole is open and closed is VS, VC ≥ VD, VB (or VS, VC ≤ VD, VB).

However, VD: potential of developing roller surface VS: potential of reference electrode VC: potential of control electrode VB: potential of rear electrode

[0017]

According to the present invention, by setting the potential of each electrode as described above, the toner does not adhere to the reference electrode and the control electrode of the toner control head, and therefore, the toner control head surface and the periphery of the toner passage hole are prevented. Since the toner does not remain, it is possible to obtain a stable and high-quality image in which toner clogging does not occur and color mixing does not occur between toners of different colors.

[0018]

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

(Embodiment 1) Since the configuration of the powder flying recording apparatus for carrying out this embodiment is the same as that of the conventional example, it will be described with reference to FIG. The toner storage tank 2 provided with an opening 6 for flying the toner 1 has a developing roller 3, a sponge roller 4, and a layer thickness regulating blade 5. In addition, the developing roller 3
A toner control head 8 that electromagnetically opens and closes the toner passage hole 7 to control the flight of the toner 1 is provided underneath the toner passage. The toner 1 that has passed through the toner passage hole 7 reaches the recording paper 9 on the back electrode 10. To do.

The structure of the toner control head 8 is the same as that of the conventional one. As shown in FIGS. 4 and 5, the reference electrode 11, the control electrode 12,
It is composed of an insulator 13. The material and thickness of each electrode of the toner control head 8 and the insulator 13 have appropriate flexibility,
Also choose to have the appropriate tensile strength.

For example, when the material of each electrode is copper and the material of the insulator 13 is polyimide, the thickness of the reference electrode 11 is 18 μm, the control electrode 12 is 18 μm, and the distance between the lower surface of the reference electrode 11 and the upper surface of the control electrode 12 is 25 μm. , The upper surface of the reference electrode 11 and the lower surface of the control electrode 12 are covered with the insulator 13 up to a distance of 20 μm. It is assumed that the toner passage holes 7 have a diameter of 150 μm and are arranged in a grid pattern at intervals of 500 μm. The arrangement of the toner passage holes 7 is arbitrary and may be a staggered arrangement or the like. The distances between the developing roller 3 and the toner control head 8 and between the toner control head 8 and the back electrode 10 are set to 100 μm and 400 μm, respectively.

The operation of the powder flying recording apparatus constructed as above will be described. Toner 1 is obtained by kneading a styrene acrylic or polyester binder resin, a pigment carbon black, and a charge control agent CCA, and adding silica as an external additive.

The toner 1 stored in the toner storage tank 2 is
The developing roller 3 and the sponge roller 4 are positively charged by friction. The surface of the developing roller 3 is made of a conductive material, and the frictionally charged toner 1 is attached to the surface of the developing roller 3 by the image force, the Van der Waals force or the like with respect to the developing roller 3 and reaches the opening 6. Be transported. A predetermined potential is applied to the developing roller 3 and the back electrode 10 to fly the toner 1, and the reference electrode 11 and the control electrode 12 of the toner control head 8 are ejected.
The flying of the toner 1 is controlled by changing the potential applied to the toner according to the image signal. At that time, when the toner 1 is positively charged, the potentials of the surface of the developing roller 3, the reference electrode 11, the control electrode 12, and the back electrode 10 in the open and closed states of the toner passage hole 7 are VS, VC ≥ VD, VB. However, each potential is set so that VD: potential on the surface of the developing roller 3, VS: potential on the reference electrode 11, VC: potential on the control electrode 12, VB: potential on the back electrode 10. For example, the potential VD on the surface of the developing roller 3 is -200V, and the potential VB on the back electrode 10 is -1200V. When opening the toner passage hole 7 electromagnetically, the potential VS of the reference electrode 11 is -190V, the potential VC of the control electrode 12 is -190V, and when closing the potential VS of the reference electrode 11.
Is set to 0V, and the potential VC of the control electrode 12 is set to 0V.

The states of the lines of electric force 18 in the developing space when the toner passage hole 7 is opened and closed are shown in FIGS. 1 (a) and 1 (b), respectively. However, only the lines of electric force 18 coming in and out of the developing roller 3 are shown, and the arrows in the figure show the directions of the lines of electric force 18. Even when the toner passage hole 7 is in the open state (a), the toner 1 on the developing roller 3 reaches the recording paper 9 without adhering to the upper surface of the toner control head 8, the reference electrode 11 and the control electrode 12.

The recording paper 9 on which the toner image is formed is fixed to the fixing unit.
It is transported to 14 and fixed, and printing is completed.

(Embodiment 2) When the toner 1 is negatively charged, each potential is set so that VS, VC≤VD, VB. For example, the developing roller 3
The surface potential VD is 200V, and the back electrode 10 potential VB is 1200V.
In this case, when opening the toner passage hole 7 electromagnetically,
The potential VS of the reference electrode 11 is 190 V and the potential VC of the control electrode 12 is 1
90V, when closed, the potential VS of the reference electrode 11 is 0V,
The potential VC of the control electrode 12 may be set to 0V. At this time, the lines of electric force 18 in the developing space when the toner passage hole 7 is open and closed are as shown in FIGS. 2 (a) and 2 (b), respectively. In this case, the flying direction of the toner 1 is opposite to the direction of the electric force lines 18.

[0027]

As described above, the image forming apparatus of the present invention forms an electric field that does not fly toward the toner control head surface, the reference electrode and the control electrode, so that the toner control head surface and the periphery of the toner passage hole are formed. The toner adhesion can be prevented, and toner clogging and color mixing between different color toners do not occur in color printing.

[Brief description of drawings]

FIG. 1 is a diagram showing a state of lines of electric force in a developing space in an opened state (a) and a closed state (b) of a toner passage hole according to the first embodiment of the present invention.

FIG. 2 is a diagram showing a state of lines of electric force in a developing space in an opened state (a) and a closed state (b) of a toner passage hole according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a powder flying recording apparatus according to the related art and the present invention.

FIG. 4 is a plan view showing the configuration of the toner control head of FIG.

5 is a cross-sectional view taken along the line AA showing the configuration of the toner control head of FIG.

FIG. 6 is a diagram showing a state of lines of electric force in a developing space when a potential is set in the case of a conventional positive potential toner.

FIG. 7 is a diagram showing a state of lines of electric force in a developing space when a potential is set in the case of a conventional negative potential toner.

[Explanation of symbols]

1 ... toner, 2 ... toner storage tank, 3 ... developing roller,
4 ... Sponge roller, 5 ... Layer thickness regulating blade, 6 ...
Opening part, 7 ... Toner passage hole, 8 ... Toner control head, 9 ... Recording paper, 10 ... Back electrode, 11 ... Reference electrode,
12 ... Control electrode, 13 ... Insulator, 14 ... Fixing part, 15 ... High-intensity lamp, 16 ... Heating roller, 17 ... Pressure roller,
18 ... Electric force lines, 19 ... Residual toner.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G03G 15/08 502 E

Claims (3)

[Claims] 1. A toner control head capable of electromagnetically opening and closing a toner passage hole with a head electrode, and a toner carrier for supporting toner on the surface of the toner control head and supplying the toner to the position of the toner control head. In an image forming apparatus having a back electrode and configured to transfer the toner having passed through the toner passage hole to a recording material, an electric field for preventing the toner from adhering to the electrode provided in the toner control head is formed. Image forming apparatus. 2. The toner is positively charged, and the potentials of the developing roller surface, the reference electrode, the control electrode, and the back electrode when the toner passage hole is open and closed are VS, VC ≧ VD, VB, where VD 2. The image forming apparatus according to claim 1, wherein the following relationships are satisfied: potential of developing roller surface VS: potential of reference electrode VC: potential of control electrode VB: potential of back electrode. 3. The toner is negatively charged, and the potentials of the developing roller surface, the reference electrode, the control electrode, and the back electrode when the toner passage hole is open and closed are VS, VC ≤ VD, VB, where VD 2. The image forming apparatus according to claim 1, wherein the following relationships are satisfied: potential of developing roller surface VS: potential of reference electrode VC: potential of control electrode VB: potential of back electrode.