JPH07227998A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To form a beautiful dot even when there is irregularity in the electrostatic structure of a support, in an image forming apparatus constituted of a charged particle carrier, an electric field control means of charged particles and an opposed electrode, by providing an auxiliary electrode means between the electric field control means and the support. CONSTITUTION:Positive voltage is applied to a control electrode 4 corresponding to an image part from a control voltage applying circuit 8 corresponding to an image signal and the line of electric force going toward a toner carrying roller 14 is formed in the vicinity of the apertures corresponding to the image part and negatively charged toner 16 is drawn out toward the control electrode 4 and further flies toward a support 20 by the electric field formed between the support 20 and an aperture electrode element 1 by the voltage of a back electrode roller 22 to be accumulated on the support 20 to form a pixel. At this time, an auxiliary electrode 30 is arranged at the time of the formation of an image and, by applying voltage slightly lower than that of the back electrode roller 22 to the electrode 30, even if the support 20 has a fibrous structure, a uniform flying electric field is formed at a dot forming position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which can be used in copying machines, printers, plotters, facsimiles and the like.

[0002]

2. Description of the Related Art Conventionally, as one of image forming apparatuses, an electrode having a plurality of openings (hereinafter referred to as apertures) is used, and a voltage is applied to the electrode based on image data. U.S. Pat. No. 3,689,935 discloses controlling toner particles so that they can pass through the aperture and forming an image on a support by the toner particles that have passed.

This image forming apparatus comprises a flat plate made of an insulating material, a continuous reference electrode formed on one surface of the flat plate, and a plurality of control electrodes insulated from each other formed on the other surface. , An aperture electrode body having at least one row of apertures formed through each of the control electrodes, and a means for selectively applying a potential between the reference electrode and the control electrode. A means for supplying charged toner particles so that the flow of toner particles passing through the aperture is modulated by an electric potential, and a means for positioning the support in the particle flow path so that the support and the aperture electrode body can move relative to each other. It consists of and.

Also, for example, US Pat. No. 4,743,926.
Nos. 4,755,837, 4,780,733, and 4,847,796 disclose an image forming apparatus in which an aperture electrode body is arranged with a control electrode on the support side and a reference electrode on the toner supply side. There is.

In contrast, US Pat. No. 4,912,489
In the specification of the above U.S. Pat. It is described that it can be suppressed to about 1/4 as compared with the image forming apparatus.

Here, the "off" means a time when the toner particles are not attached to the support, that is, a time when a blank portion of an image is formed, and conversely, "on" means that the support is on the support. It means a time point when a toner image is formed on.

[0007]

However, in the conventional image forming apparatus as described above, the dots formed are
It may vary depending on the type and location of the support. As a countermeasure against this, we tried to improve it by changing the voltage of the back electrode, but it is difficult to fundamentally deal with the dispersion of the electric field due to the fiber structure due to uneven paper making of the support in the process, and It was a problem.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus capable of forming beautiful dots even if the electrostatic structure of the support is uneven. I am trying.

[0009]

In order to achieve this object, an image forming apparatus of the present invention is provided with a carrier for supporting and supplying charged particles, the carrier and the charged particles, and the direct control by an electric field. And an auxiliary electrode means provided between the electric field control means and the support. Is characterized by.

[0010]

In the image forming apparatus of the present invention having the above-mentioned structure, the flying electric field for flying the charged particles on the support is focused by the auxiliary electrode means, and therefore, regardless of variations in the electrostatic characteristics of the support. , Good dots can be printed.

[0011]

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

FIG. 1 is a diagram showing an outline of an image forming apparatus according to the present invention. As an upper surface of an aperture electrode body 1 as an electric field control means, there is a gap of 1 mm, and a cylindrical back electrode is provided. The rear electrode roller 22 is rotatably arranged on a chassis (not shown), and is configured to be able to convey the support 20 inserted into the gap. Further, an auxiliary electrode 30 as an auxiliary electrode means is arranged upstream of the support body 20 in the transport direction. Further, a toner supply device 10 is arranged below the aperture electrode body 1 along the longitudinal direction of the aperture electrode body 1, and further, a support body conveyed by the back electrode roller 22. A fixing device 26 is disposed at the destination of the movement of 20.

Next, the respective components will be described in detail. In the toner supply device 10, the toner case 11 also serving as a housing of the entire device, and the toner 16 stored in the toner case 11 as charged particles are provided. A supply roller 12, a toner carrier roller 14 as a carrier,
The toner layer control blade 18 is provided. Here, the toner carrying roller 14 carries the toner 16 and conveys it toward the aperture electrode body 1, and the supply roller 12 supplies the toner 16 to the toner carrying roller 14.

The supply roller 12 and the toner carrying roller 14 are rotatably supported by the toner case 11 in the direction of the arrow shown in FIG. Further, the toner layer regulating blade 18
Is for adjusting the amount of the toner 16 carried on the toner carrying roller 14 to be uniform on the roller surface and for uniformly charging the toner 16, and is pressed against the toner carrying roller 14. .

As shown in FIG. 2, the aperture electrode body 1 includes a polyimide insulating sheet 2 having a thickness of 25 μm and a diameter of 1 mm.
A plurality of apertures 6 having a size of 00 μm are formed in one row, and a control electrode 4 having a thickness of 1 μm is formed on each of the apertures 6 on the upper surface. The aperture 6 and the control electrodes 4 form a control unit of the present invention. Composed. As shown in FIG. 1, the aperture electrode body 1 is pressed against the toner carrying roller 14 at the position of each aperture 6 of the insulating sheet 2 with the control electrode 4 facing the support body 20 side. ing.

Here, the positional relationship between the aperture 6 of the aperture electrode body 1 and the toner carrying roller 14 will be described in detail. As shown in FIG. 3, the center line 30 of each aperture 6 is the toner carrying roller 14. It is arranged so as to pass through the uppermost portion of the peripheral surface of and the central shaft 32 of the toner carrying roller 14. According to this, each aperture 6
Based on the uppermost part of the peripheral surface of the toner carrying roller 14,
By arranging them evenly on the left and right, the distribution of the toner 16 passing through each aperture 6 can be made uniform over the entire area of the aperture. In addition, the wall surface of the aperture 6 and the toner 16
Since the flying direction of the toner is parallel to the flying direction of the toner, it is possible to stably fly the toner.

Further, the aperture electrode body 1 itself is attached to the toner carrying roller 14 with respect to the aperture 6 as shown in FIG.
It is pressed so that it bends to the left and right about the same angle. As a result, the contact area between the aperture electrode body 1 and the toner carrying roller 14 can be increased, and the lower periphery of the aperture 6 can be pressed uniformly to the left and right, so that uneven toner concentration is minimized. Can be suppressed.

A control voltage application circuit 8 as a control voltage application means is connected between the control electrode 4 and the toner carrying roller 14. This control voltage applying circuit 8
0V to the control electrode 4 based on the image signal, or +
It is configured to apply a voltage of 50V.

Further, a first DC power source 24 as a first power source means is connected between the back electrode roller 22 and the toner carrying roller 14, and this DC power source is connected to the back electrode roller 22. A voltage of +1 kV can be applied to it.

Next, the structure of the auxiliary electrode 30 constituting the auxiliary electrode means of the present invention will be described with reference to FIG. Figure 4
FIG. 4 is a perspective view of an auxiliary electrode. The auxiliary electrode 30 has a thickness of 1
The holding member 31 is made of polyimide and has a thickness of 00 μm, a plurality of electrode portions 32, and a plurality of cutout portions 33.
The notch portion 33 has a semicircular shape corresponding to the position of the dot to be formed, that is, is formed corresponding to each aperture 6 of the aperture electrode body 1, and the electrode portion 32 is formed around it. It is provided. A second DC power supply 25 as a second power supply means is connected to the electrode portion 32 between the electrode carrier 32 and the toner carrying roller 14, and, like the back electrode roller 22, the second DC power supply. +800 by 25
A positive voltage of +900 V is applied.

In the auxiliary electrode 30, the notch 33 faces the aperture 6 of the aperture electrode body 1 and the electrode portion 32.
Is arranged between the aperture electrode body 1 and the back electrode roller 22 so as to be positioned on the upstream side in the transport direction of the support body 20, and the support body 20 moves between the auxiliary electrode 30 and the back electrode roller 22. It is possible.

Next, the operation of the image forming apparatus configured as described above will be described.

First, by rotating the toner carrying roller 14 and the supply roller 12 in the direction of the arrow shown in FIG. 1, the toner 16 sent from the supply roller 12 is rubbed against the toner carrying roller 14 to be negatively charged. The toner is carried on the toner carrying roller 14. Toner 1 carried
The layer 6 is thinned by the layer regulation blade 18 and charged, and then is conveyed toward the aperture electrode body 1 by the rotation of the toner carrying roller 14. Then, the toner on the toner carrying roller 14 is supplied under the aperture 6 while being rubbed by the insulating sheet 2 of the aperture electrode body 1.

Here, in accordance with the image signal, the control voltage applying circuit 8 adds + to the control electrode 4 corresponding to the image portion.
A voltage of 50V is applied. As a result, an electric force line from the control electrode 4 toward the toner carrying roller 14 is formed in the vicinity of the aperture 6 corresponding to the image portion due to the potential difference between the control electrode 4 and the toner carrying roller 14. As a result, the negatively charged toner receives an electrostatic force in the direction of higher electric potential, passes through the aperture 6 from the toner carrying roller 14, and is drawn out to the control electrode 4 side. The extracted toner 16 further flies toward the support 20 due to the electric field formed between the support 20 and the aperture electrode body 1 by the voltage applied to the back electrode 22, and the toner 16 on the support 20 rises. To form pixels.

A voltage of 0V is applied from the control voltage applying circuit 8 to the control electrode 4 corresponding to the non-image portion.
As a result, since no electric field is formed between the toner carrying roller 14 and the control electrode 4, the toner carrying roller 1
The toner 16 on 4 does not pass through the aperture 6 because it is not subjected to electrostatic force.

At this time, at the time of image formation, the auxiliary electrode 30 is arranged and a voltage slightly lower than that of the back electrode roller 22 is applied to the electrode portion 32 thereof, so that a uniform flying electric field is formed on the support. It That is, since the auxiliary electrode 30 is provided on the paper, a uniform flying electric field is formed at the dot formation position even if the support 20 has a fiber structure. The reason for this is currently being analyzed, but the following reasons can be considered. The combined electric field configuration of the back electrode roller 22 and the auxiliary electrode 30 increases the electric field strength in a very small area on the support, and causes the lines of electric force to tend to concentrate in the basin. Since the toner flies in the flight area along the electric lines of force, naturally, if there is an extremely strong area on the support, it will fly toward that area. Therefore, unlike the conventional case where the flying electric field is formed only by the back electrode arranged on the back surface of the paper, good dots are formed regardless of the property of the support.

Further, the support 20 is fed by one pixel in the direction perpendicular to the aperture row while the toner 16 forms one row of pixels on the surface thereof. Then, the toner image is formed on the entire surface of the support 20 by repeating the above process. Then, the formed toner image is fixed on the support 20 by the fixing device 26.

If an insulating toner is used in the image forming apparatus constructed as described above, the toner carrying roller 14 is used.
The insulation between the control electrode 4 and the control electrode 4 is maintained, and the aperture 6 does not cause dielectric breakdown.

In the above process, the control electric field generated by the control electrode 4 is formed between the control electrode 4 and the inside of the aperture 6, and between the aperture 6 and the toner carrying surface of the toner carrying roller 14 which faces the aperture 6. Toner 1
Since the control electric field can be directly applied to 6, the control efficiency is good.

Further, even if a part of the supplied toner 16 receives a mechanical force or the like by sliding with the aperture electrode body 1 and enters the aperture 6 corresponding to the non-image portion, inside the aperture 6 Since it can be controlled so as not to pass through the aperture 6 by the electric field, the toner controllability is good.

Further, since the toner carrying roller 14 and the aperture electrode body 1 are opposed to each other with the toner layer in between, the control voltage can be lowered and the inexpensive drive element can be provided because they can be arranged at a relatively short distance. Can be used.

In addition, the insulating sheet 2 of the aperture electrode body 1
Is directed toward the toner carrying roller 14 side, so that the toner
Even if 6 is not present, the control electrode 4 and the toner carrying roller 14 do not come into contact with each other and electrically short-circuit, and the drive element is not destroyed.

Further, since the aperture electrode body 1 and the toner 16 on the toner carrying roller 14 are in contact with each other at the entrance portion of the aperture 6, the toner 16 accumulated at the entrance portion of the aperture 6 is not supported. Since the toner 16 is pushed away by the toner sequentially supplied, the toner 16 does not accumulate and bridge to block the aperture 6.

The present invention is not limited to the embodiments described in detail above, and various modifications can be made without departing from the spirit of the invention.

For example, in the above embodiment, the control voltage of the aperture corresponding to the non-image portion is set to 0V, but this may be a negative voltage. In this case, an image with less fogging can be obtained. Further, in the above embodiment, the aperture electrode body is used as the toner flow control means, but it is also possible to use, for example, a knitted electrode body as described in the specification of US Pat. No. 5,036,341.

Further, in the above-described embodiment, the voltage is uniformly applied to each electrode portion 32 of the auxiliary electrode 30, but the control in which the voltage of + 50V is applied from the control voltage applying circuit 8 according to the image signal is controlled. A positive voltage of +800 to + 900V may be applied to the electrode portion 32 corresponding to the electrode 4 by the second DC power supply 25.

Further, in the above-mentioned embodiment, the notch 33 which is open in the carrying direction of the support is used so that the dots formed on the support do not come into contact with the holding member 31 of the auxiliary electrode 30. However, as long as the formed dots are configured not to contact the auxiliary electrode 30 by a spacer or the like, the configuration shown in FIG. 5 may be used. Figure 5
It is a perspective view of the auxiliary electrode of the 2nd Example of this invention. The parts having the same functions as those in the first embodiment will be described with the same drawing numbers. In this embodiment, the opening portion 35 is circular and the electrode portion 32 is formed around it. Even with such a configuration, good printing can be expected.

[0038]

As is apparent from the above description, in the image forming apparatus of the present invention, the auxiliary electrode forms the flying electric field for flying the charged particles toward the support in a focused form. Therefore, good dots can be printed regardless of variations in the electrostatic characteristics of the support.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment embodying the configuration of an image forming apparatus of the present invention.

FIG. 2 is a perspective view showing a configuration of an aperture electrode body used in the image forming apparatus of the present invention.

FIG. 3 is a diagram schematically showing a configuration of an aperture electrode body and a toner carrying roller used in the image forming apparatus of the present invention.

FIG. 4 is a perspective view of an auxiliary electrode used in the image forming apparatus of the present invention.

FIG. 5 is a perspective view showing another embodiment of the auxiliary electrode.

[Explanation of symbols]

 1 Aperture Electrode 2 Insulating Sheet 4 Control Electrode 6 Aperture 8 Control Voltage Applying Circuit 14 Toner Carrying Roller 22 Back Electrode Roller 24 DC Power Supply 30 Auxiliary Electrode 31 Holding Member 32 Electrode 33 Cutout 34 Opening

Claims (4)

[Claims] 1. A carrier for supporting and supplying charged particles, an electric field control unit arranged between the carrier and the charged particles for directly controlling the flow of the charged particles by an electric field, and the electric field control unit are supports. An image forming apparatus comprising an opposed electrode arranged with the electrode sandwiched therebetween, characterized in that auxiliary electrode means is provided between the electric field control means and the support. 2. The image forming apparatus according to claim 1, wherein a voltage having the same polarity as that of the counter electrode is applied to the auxiliary electrode means. 3. The electric field control means includes a large number of control portions for controlling the passage of charged particles, and the auxiliary electrode means has a notch or an opening having an electrode portion at a position facing the control portion. The image forming apparatus according to claim 1, wherein a hole is formed. 4. The image forming apparatus according to claim 2, wherein a voltage is selectively applied to an electrode unit facing a control unit controlled to allow the charged particles to pass therethrough.