JPH04334463A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To form an image of high resolving power by reducing the potential difference between a common electrode and the surface of an image carrier 1 and preventing the diffusion of an ion by changing the voltage applied to the common electrode in synchronous relation to a recording signal even when the surface potential of the image carrier is changed with the formation of a latent image. CONSTITUTION:At the time of the driving of an ion head 2, high voltage is applied to the wire 22 of an ion generating part 20 to generate corona discharge and a positive ion is generated. When the conductive support 10 of an image carrier 1 is preliminarily earthed to set the potential of said support to OV, the ion is attracted to the dielectric layer 11 on the surface of the image carrier by the potential difference between the wire 22 and the conductive support 10. Next, when a latent image is formed on the image carrier 1, the voltage applied to a common electrode 27 during a latent image forming time per one dot is changed by a voltage applying means 29 and pulse voltage is superposed on the applied voltage to a drive electrode 26 by a voltage applying means 30. By this constitution, the potential difference between both electrodes 26, 27 is made constant to prevent the change of the inflow quantity of the ion into a through-hole 25.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image forming apparatuses such as copying machines, printers, and facsimiles.

0002

2. Description of the Related Art In recent years, electrophotographic methods, which are high-speed, high-resolution recording methods, have been widely used in image forming apparatuses such as copying machines and printers. However, even faster speeds and
Higher image quality and smaller size are desired, and instead of latent image formation using charging and exposure processes in conventional electrophotographic methods, latent image formation using ion irradiation, which is suitable for faster recording and smaller equipment, has been proposed. . (For example, "Journal of Electrophotography Society"
(Vol. 25, No. 2, pp. 2-7) An example of an image forming apparatus using the above-described conventional latent image formation by ion irradiation will be described below with reference to the drawings. FIG. 6 is a block diagram of a conventional image forming apparatus, and FIGS. 7 and 8 are a block diagram and a perspective view of an ion head used therein.

In FIG. 6, 101 is an image carrier;
This is a dielectric drum in which a dielectric layer 111 is provided on a conductive support 110. 102 is an ion head, 103 is a developer holding toner, 104 is a corona transfer device, 10
5 is a heat fixing device, 106 is a static eliminator, and 107 is a cleaner. The ion head 102 will be explained in more detail using FIGS. 7 and 8. The ion head 102 includes an ion generation section 120 and an ion control section 121. The ion generating section 120 is a so-called corona discharger consisting of a wire 122 made of tungsten or the like and a substantially U-shaped shield case 123. In addition, the ion control section 12
1 includes an insulator plate 124, a through hole 125, and a drive electrode 126
, a common electrode 127. Thin insulator plate 124
is provided with a plurality of through holes 125 corresponding to the dots to be recorded, a drive electrode 126 for each through hole 125 is provided on the upper part, and a common electrode 127 common to all the through holes 125 is provided on the lower part. Each is provided. In addition,
The wire 122 has a discharge voltage applying means 128 and a common electrode 1.
27 is connected to a DC voltage applying means 129, and each drive electrode 126 is connected to a pulsed voltage applying means 130.

The operation of the image forming apparatus configured as described above will be explained below. In addition, FIG. 9
It is a graph showing the potential of each part when the ion head is driven.

First, the wire 122 of the ion generating section 120
Then, a voltage of 6000 V is applied by the discharge voltage applying means 128 to generate positive ions. When the conductive support 110 of the image carrier 101 is grounded and set to 0V, the generated ions are attracted to the dielectric layer 111 on the surface of the image carrier 101 due to the potential difference between the wire 122 and the conductive support 110. . The ion control section 121 controls the ion generation section 1
20 and the image carrier 101, and controls the passage of ions to control the formation of a latent image on the dielectric layer 111. In FIG. 9A, a voltage of 250 V is constantly applied to the common electrode 127 of the ion control unit 121 by the DC voltage applying means 129. When a latent image is not formed, the drive electrode 126 is set to 0V by the pulse voltage application means 130, and the potential difference (-250V) between the drive electrode 126 and the common electrode 127 is set to 0V.
Potential difference between wire 122 and image carrier 1 (6000V)
The polarity is opposite to that of the through hole 125 to prevent ions from flowing into the through hole 125. In addition, when forming a latent image, the drive electrode 1
A pulsed voltage (FIG. 9B) (-250→150V) is applied to the wire 122 and the image carrier 26 by the pulse voltage applying means 130 to create a potential difference (150V) between the drive electrode 126 and the common electrode 127. Potential difference between 1 (6000V)
The polarity is set to be the same as that of the through hole 125 to allow ions to flow into the through hole 125 and irradiate the surface of the image carrier 101. In this way, when the ions reach the dielectric layer 111, charges are accumulated on the surface of the dielectric layer 111, forming an electrostatic latent image. This electrostatic latent image has a surface potential of about 200V on the dielectric layer 111.

Next, a developing device 10 is applied to this electrostatic latent image.
3, the toner is electrostatically attached and visualized. The toner on the image carrier is transferred onto a recording medium by a corona transfer device 104, and is fixed by passing through a heat fixing device 105. The surface of the image carrier 101 is further neutralized by a static eliminator 106, and the surface potential is set to 0V. Finally, the toner remaining on the image carrier 101 is removed by a cleaner 107, and the image carrier 101 is used for the next image formation.

[0007]

However, in the above structure, when an electrostatic latent image is formed on the surface of the image carrier 101, the common electrode 127 is The potential difference between the image carrier 101 and the surface of the image carrier 101 gradually decreases. For example, when forming a latent image, the image carrier 1
The surface potential of 01 gradually increases from 0V to 200V, but since the voltage applied to the common electrode 127 is always 250V, the potential difference between the common electrode 127 and the image carrier 101 gradually decreases. ), (d). When this potential difference becomes smaller, the ions that have passed through the through hole 125 are attracted to the area around the electrostatic latent image on the image carrier 101 where the surface potential is lower, and are gradually diffused. Therefore, the potential distribution of the electrostatic latent image gradually widens, resulting in the formation of a broad latent image, which poses a problem in that high-resolution development cannot be performed.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a high-speed, compact, and high-quality image forming apparatus that forms a sharper electrostatic latent image by ion irradiation.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, an image forming apparatus of the present invention includes an image carrier having a dielectric layer provided on a conductive support, and an image carrier having a dielectric layer on the image carrier. an ion head that records an electrostatic latent image; the ion head includes an ion generating section that generates ions; a thin insulator plate provided with a plurality of through holes; a drive electrode that is provided and applies a pulsed voltage according to a recording signal; and a common electrode that is provided on the other side of the insulator plate;
A first feature includes a voltage applying means for applying a voltage to the common electrode that changes in synchronization with the recording signal, and the voltage applied to the common electrode by the voltage applying means is synchronized with the recording signal. The second feature is that it is an AC bias voltage.

0010

[Operation] With the above-described structure, when the surface of the image carrier is irradiated with ions to form an electrostatic latent image, even if the potential of the surface of the image carrier changes as the latent image is formed, the present invention always has a common potential. In order to ensure a potential difference between the electrode and the surface of the image carrier, the voltage applied to the common electrode is changed in synchronization with the recording signal, and in response, a pulsed voltage is applied to the drive electrode. Therefore, during latent image formation, the potential difference between the common electrode and the surface of the image carrier is reduced, which prevents the diffusion of ions, making it possible to form a sharper electrostatic latent image and to form a high-resolution image. It can be done. Furthermore, by setting the voltage applied to the common electrode to be an AC bias voltage synchronized with the recording signal, in addition to the above-mentioned effects, the configuration of the voltage application means can be simplified, and the entire device can be made smaller and cheaper. Can be done.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. Figures 1 and 2 are
1 is a configuration diagram of an image forming apparatus and an ion head showing an embodiment according to a first feature of the present invention; FIG.

In FIG. 1, 1 is an image carrier, which is made of Al
Drum-shaped conductive support 1 made of (aluminum) etc.
A dielectric layer 11 that holds an electrostatic latent image is provided on top of the electrostatic latent image, and rotates in the direction of arrow A. The dielectric layer 11 may be made of any material that can form an electrostatic latent image, such as an anodic oxide film of Al, a material impregnated with a metal salt, or a material coated with Teflon, silicon, etc. , can be freely selected in consideration of abrasion resistance, and its lifespan can be extended. In addition, selenium-tellurium (Se-Te) commonly used in electrophotography and organic photoreceptors (OP
A photoreceptor such as C) may also be used.

2 is an ion head, and the ion generating section 2
0 and an ion control section 21. For ion generation, it is desirable to use aerial discharge such as corona discharge and creeping discharge. An example using corona discharge will be explained in detail using FIG. 2. The ion generating section 20 includes a wire 22 made of tungsten or the like and a substantially U-shaped shield case 23.
It is a so-called corona discharger that is stretched inside. The ion control section 21 is located between the ion generation section 20 and the image carrier 1, and controls the passage of ions to control the formation of an electrostatic latent image on the dielectric layer 11. The ion control unit 21 has a thin insulator plate 24 in which through holes 25 for ions to pass depending on the dots to be recorded are arranged in a linear or staggered manner. Drive electrodes 26 for each through hole 25 on one side, and all through holes 2 on the other side.
A common electrode 27 that is common to all the elements 5 and 5 is configured. Further, a discharge voltage application means 28 is connected to the wire 22, a first voltage application means 29 is connected to the common electrode 27, and a second voltage application means 30 is connected to each drive electrode 26 through the first voltage application means 29. It is connected. Here, the first voltage application means 2
Reference numeral 9 applies to the common electrode 27 a voltage that changes linearly in synchronization with the recording signal. Further, the second voltage applying means applies a voltage to each drive electrode 26 by superimposing a pulsed voltage on the voltage applied to the common electrode 27 by the first voltage applying means in accordance with the recording signal. It is applied. In addition, as the ion head 2,
A device using creeping discharge as disclosed in Japanese Patent No. 7-501348 may also be used.

The developing device 3 is a magnetic brush developing device using a method of developing an insulating toner by frictionally charging it and adhering it to the electrostatic latent image, and using a magnetic one-component toner as the toner. However, a developing device using non-magnetic one-component toner or magnetic two-component toner may also be used. Further, in consideration of increasing the resolution and downsizing the developing device, a developing method using conductive toner may be used.

Further, around the image carrier 1, on the downstream side in the rotational direction, there are provided a corona transfer device 4, a heat fixing device 5, a static eliminator 6,
Cleaners 7 are arranged respectively. Corona transfer device 4
is a so-called corona discharger that applies high voltage to a wire to cause an air discharge. The heat fixing device 5 is a heat roller whose surface is coated with Teflon or the like, in which a heating element such as a halogen lamp is provided, and the heat roller is pressed against a pressure roller made of an elastic material. The static eliminator 6 is a corona discharger similar to the corona transfer device 4. The cleaner 7 uses a blade made of metal or an elastic body, or a rotating roller such as a brush roller with thin fibers planted around a core metal.

The operation of the image forming apparatus configured as described above will be explained below with reference to FIGS. 1, 2, and 3. Note that FIG. 3 is a graph showing the potential of each part during driving of the ion head.

First, the wire 22 of the ion generating section 20 is
A voltage of 6000 V is applied by the discharge voltage applying means 28 to cause corona discharge and generate positive ions. When the conductive support 10 of the image carrier 1 is grounded and the potential is set to 0V, ions are electrostatically transferred to the dielectric layer 11 on the surface of the image carrier 1 due to the potential difference between the wire 22 and the conductive support 10. I am drawn to it.

Next, FIG. 3 shows the driving of the ion head.
Explain using. When a latent image is not formed on the image carrier 1, the first and second voltage applying means 29 and 3
The applied voltages at 0 are set to 250 V and -250 V, respectively, and the potential of the common electrode 27 is set to 250 V, and the potential of the drive electrode 26 is set to 0 V, as in the conventional case. Then, the potential difference (6000 V) between the wire 22 and the conductive support 10 and the potential difference (-250 V) between the drive electrode 26 and the common electrode 27 become opposite in polarity, and ions are prevented from flowing into the through hole 25.
No electrostatic latent image is formed.

Next, when forming a latent image on the image carrier 1, the common electrode is The voltage applied to 27 is changed by the first voltage application means 29. Further, the voltage applied to the drive electrode 26 is obtained by superimposing a pulse voltage on this voltage by the second voltage applying means 30. For example, latent image formation period (Figure 3, point A to point B)
In FIG. 3A, the voltage applied to the common electrode 27 is changed almost linearly from an initial value of 250V to 450V. Moreover, the voltage applied to the drive electrode 26 is a pulse voltage depending on the recording signal, as shown in FIG.
FIG. 3(c) assumes that the voltage (0→150V) is superimposed. At this time, as shown in FIG. 3(d), the potential difference between the drive electrode 26 and the common electrode 27 is always kept constant at 150 V, so the amount of ions flowing into the through hole 25 does not change. Also, during latent image formation, the surface potential of the image carrier 1 changes from 0V to 20V.
Even if the voltage changes to 0V as shown in FIG. 3(c), the voltage applied to the common electrode 27 is linearly changed accordingly, and the potential difference between the common electrode 27 and the surface of the image carrier 1 becomes approximately 250V as shown in FIG. 3(d). Since the electric field is kept constant, a latent image can be formed by ion irradiation in a constant electric field.

Although the voltage applied to the common electrode 27 by the first voltage applying means 29 is a voltage that changes linearly in synchronization with the recording signal, the common electrode 27 and the image carrier are connected even during the formation of a latent image. As long as a potential difference between the voltage and the voltage 1 can be constantly maintained, a voltage that changes in a sawtooth shape or a step shape may be used.

Furthermore, if the time width of the pulse voltage applied to the drive electrode 26 by the second voltage application means 30 is changed according to the recording signal, the amount of ion irradiation for each recording dot is changed, and the electrostatic latent image is Since the potential also changes, gradation recording can be easily performed.

Next, an insulating toner is electrostatically attached to this electrostatic latent image using a developing device 3 to form a visible image. The toner on the image carrier is electrostatically transferred onto a recording medium by a corona transfer device 4, and is heated and melted by a heating fixing device 5 to be fixed. The surface of the image carrier 1 is further neutralized by a static eliminator 6, and the surface potential becomes 0V. Finally, the toner remaining on the image carrier 1 is removed by a cleaner 7, and the image carrier 1 is used for the next image formation.

As described above, according to this embodiment, a voltage that changes in synchronization with the recording signal is applied to the common electrode of the ion control section of the ion head, and a voltage that changes in synchronization with the recording signal is applied to each drive electrode in accordance with the recording signal. By applying a pulsed voltage, even if the surface potential of the image carrier increases due to the formation of a latent image, the voltage applied to the common electrode is increased accordingly, so that the voltage between the common electrode and the image carrier is always increased. The potential difference is approximately constant, the electric field is stabilized, ion diffusion is reduced, a sharp electrostatic latent image can be formed, and the image forming apparatus can achieve high image quality.

An embodiment according to the second feature of the present invention will be described below with reference to the drawings. The configuration of the image forming apparatus of this embodiment is almost the same as that of the embodiment according to the first feature, so a description thereof will be omitted. Further, FIG. 4 shows a configuration diagram of the ion head used in this example. The difference from the first embodiment is that AC bias voltage application means 31 is connected to the common electrode 27, and pulse voltage application means 32 is connected to each drive electrode 26 through AC bias voltage application means 31.

The operation of the image forming apparatus configured as described above will be explained with reference to FIG. Figure 5 shows the second
3 is a graph showing the potential of each part during driving of the ion head in the example of FIG. . The voltage applied to the common electrode 27 by the AC bias voltage applying means 31 is, for example, as shown in FIG.
As shown in the figure, DC voltage (350V) and AC voltage (20V) are
The AC frequency is set to 1/T (recording time of 1/1 dot) so as to give one amplitude during the latent image forming period T of 1 dot. Further, the phase is set so that the voltage takes a peak value immediately before the end of latent image formation. Then, compared to the conventional case where a constant DC voltage is applied to the common electrode 27, a sufficient potential difference between the common electrode 27 and the surface of the image carrier 1 is secured even just before the end of latent image formation, so that the ion flow is increased. Diffusion is reduced, a sharp electrostatic latent image can be formed, and high image quality of the image forming apparatus can be achieved. Further, as the AC bias voltage applying means 31, a general AC power source used for applying a bias voltage to a developing device can be used, and the configuration of the apparatus can be simplified.

As described above, when forming an electrostatic latent image, by applying an AC bias voltage synchronized with the recording signal to the common electrode 27 by the AC bias voltage applying means 31,
In addition to the effects of the first embodiment, the configuration of the voltage application means corresponding to the first voltage application means 29 in the first embodiment can be simplified, and the entire device can be made smaller and cheaper. .

[0027]

As described above, according to the present invention, when an electrostatic latent image is formed by irradiating the surface of an image carrier with ions, the potential of the surface of the image carrier changes as the latent image is formed. Also, in order to always maintain a potential difference between the common electrode and the surface of the image carrier, the voltage applied to the common electrode is changed in synchronization with the recording signal, and in response, a pulsed voltage is applied to the drive electrode. do. Therefore, the diffusion of the ion current generated due to the reduction in the potential difference between the common electrode and the surface of the image carrier as the latent image is formed is prevented, and a sharper electrostatic latent image can be formed, resulting in high-resolution image formation. can be done. Furthermore, by setting the voltage applied to the common electrode to be an AC bias voltage synchronized with the recording signal, in addition to the above-mentioned effects, the configuration of the voltage application means can be simplified, and the entire device can be made smaller and cheaper. Can be done.

[Brief explanation of drawings]

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

FIG. 2 is a configuration diagram of an ion head used in the same embodiment.

FIG. 3 is a graph showing the potential of each part during driving of the ion head in the same example.

FIG. 4 is a configuration diagram of an ion head used in a second embodiment of the present invention.

FIG. 5 is a graph showing the potential of each part during driving of the ion head in the same example.

FIG. 6 is a configuration diagram of a conventional image forming apparatus.

FIG. 7 is a configuration diagram of an ion head used in a conventional image forming apparatus.

FIG. 8 is a perspective view of an ion head used in a conventional image forming apparatus.

FIG. 9 is a graph showing potentials at various parts during driving of an ion head used in a conventional image forming apparatus.

[Explanation of symbols]

1 Image carrier 2 Ion head 20 Ion generation part 21 Ion control section 24 Insulator plate 25 Through hole 26 Drive electrode 27 Common electrode 29 First voltage application means 30 Second voltage application means 31 AC bias voltage application means

Claims (2)

[Claims] 1. An image carrier comprising a dielectric layer provided on a conductive support, and an ion head for recording an electrostatic latent image on the image carrier, the ion head generating ions. a thin insulator plate provided with a plurality of through holes; a drive electrode provided on one side of the insulator plate for applying a pulsed voltage in accordance with a recording signal; An image forming apparatus comprising: a common electrode provided on the other side of a body plate; and voltage applying means for applying a voltage that changes in synchronization with the recording signal to the common electrode. 2. The image forming apparatus according to claim 1, wherein the voltage applied to the common electrode by the voltage applying means is an AC bias voltage synchronized with the recording signal.