JPH0876556A - Corona electrifying device - Google Patents

Abstract

PURPOSE: To miniaturize a corona electrifying device, to make ozone production amount small, and to perform uniform electrification by plurally providing peak parts having the same length as that of an electrode for corona discharge at a specified pitch and disposing a grid on the aperture part of a shield having a specified cross-sectional shape. CONSTITUTION: Electrode plate 111 for the corona discharge is plurally provided with the peak parts 111a being electrode parts which extend toward a photoreceptor and which have the same length as that of the electrode plate 111 at the specified pitch. This corona electrifying device 110 is constituted in a state where the saw-toothed electrode plate 111 is attached to a supporting member 112, interposed by a pressing member 114, and is dropped to the shield 113 having an aperture with width spreading toward a photoreceptor down direction and having the triangular cross-sectional shape, and a grid 115 is attached to the aperture part of the shield 113. Impressing is performed on the saw-toothed electrode plate 111, then the corona discharge is generated between the electrode and the photoreceptor, and ion produced by the discharge from the electrode part 111a mostly goes toward the direction of the grid 115. Thus, electrification ability is not lowered even though the triangular shield 113 is used without being affected by an angular aperture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge type charging device using a non-contact type sawtooth electrode used for the purpose of charging a photoconductor in an electrophotographic image forming apparatus. In particular, the present invention relates to a corona discharge type charging device of a color image forming apparatus that superimposes toners of a plurality of colors on an image forming body and collectively transfers the toners.

[0002]

2. Description of the Related Art Conventionally, corona discharge type chargers of this type are roughly classified into a wire discharge type (corotron, scorotron, dicorotron, etc.) and a pin discharge type (pin electrode type, serrated electrode type, etc.). The latter has come to be used in electrophotographic copying machines, printers, etc. in recent years because of low ozone generation. In particular, a charger having a structure using an electrode plate in which a plurality of serrated electrode parts are provided on one thin plate member is disclosed in Japanese Patent Laid-Open No. 63-1.
It is disclosed in Japanese Patent Laid-Open No. 5272 and Japanese Patent Laid-Open No. 5-45999. On the other hand, as a method of forming a multicolored color image using such a corona charging device, a monochromatic toner formed on each photoconductor is provided with the same number of photoconductors, chargers, and developers as the number of required images. A device (A) for forming a color image by superimposing an image on a transfer body or the like, or a device (B) for rotating a single photosensitive member a plurality of times to repeat charging, image exposure and development for each color to form a color image. Alternatively, there is also known a device (C) or the like that forms a color image by sequentially performing charging, image exposure, and development for each color within one rotation of one photoreceptor.

However, the above-mentioned device (A) has a drawback that the volume of the device becomes large because it requires the conveyance of a plurality of photoconductors or transfer bodies, while the device (B) has a disadvantage that the charging means, the image exposing means and the photoconductors. However, there is a restriction that the size of the formed image is limited to the surface area of the photoconductor or less, though the volume is reduced.

Further, although the apparatus (C) enables high-speed image formation, it is necessary to dispose a plurality of sets of a charging device, an image exposing means and a developing device within one circumference of the photosensitive member, and perform image exposure. The optical system may be contaminated with toner leaking from a developing device adjacent to the optical system, and the image quality may be impaired.To avoid this, it is necessary to increase the distance between the image exposure means and the developing device. There is a contradiction that the size of the device will increase.

For the purpose of avoiding the drawbacks of the above-mentioned obstacles in the apparatus (C), the substrate of the image forming body is made of a transparent material, and a plurality of image exposing means are housed therein to form an image. An apparatus has been proposed in which the photosensitive layer formed on the outer periphery of the substrate is exposed through the substrate (for example, JP-A-5-307307).

[0006]

In any case, as the color image forming apparatus becomes smaller and more complicated as described above,
As for the corona charging device (charging device), a miniaturized device with stable corona discharge has been demanded, but as shown in FIG. 6, the corona charging device 300 by the conventional wire discharge method is used.
If the size is reduced, the opening angle θ decreases, the number of ions reaching the photoconductor decreases, the distance between the shield 303 and the corona electrode 301 decreases, and the amount of ions flowing to the shield increases,
Through the grid 305, the amount of charge on the photoconductor decreases and the charge potential becomes non-uniform. In particular, in the case of a color image forming apparatus, it is necessary to make the potential uniform, and in particular, a plurality of charging means, image exposing means and developing means are arranged on the peripheral surface of the image forming body in order to downsize the apparatus. In the case of a color image forming apparatus in which toner images are formed by superimposing toner images during one rotation of the image forming body, a plurality of chargers are used together with the miniaturization of the charger, so that ozone generation is minimized. It is necessary to use a charger.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charger which solves the above-mentioned problems and which corresponds to a color image forming apparatus, has a small ozone generation amount, can be uniformly charged, and is small in size. .

[0008]

The above object is a corona charging device of an image forming apparatus for forming a toner image on an image forming body and then transferring the toner image onto a transfer material, and extending toward the image forming body. An electrode for corona discharge having a plurality of long pointed heads at a constant pitch, a shield having a triangular or trapezoidal cross section having an opening whose width becomes wider toward the image forming body, and the opening of the shield. It is achieved by a corona charging device, characterized in that it comprises an arranged grid. In the image forming apparatus, a plurality of sets of charging means, image exposing means, and developing means are arranged around the image forming body, and the image forming body is charged by the charging means, image exposing by the image exposing means, and developing by the developing means. The corona charging device is a preferred embodiment, which is a color image forming device in which the toner image is formed on the image forming body by superposing the toner images repeatedly, and then collectively transferred to the transfer material. A corona charging device characterized in that the width of the opening is 7 to 20 mm is also a preferred embodiment, and
A corona charging device characterized in that the angle formed by the pointed portion and the opening is 10 to 60 ° is also a preferred embodiment.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming process of a color image forming apparatus having a scorotron charger, which is an embodiment of the corona charging device of the present invention, and the structure of each mechanism will be described with reference to FIG. FIG. 1 is a cross-sectional configuration diagram showing an example of a color image forming apparatus suitable for implementing the corona charging device of the present invention.

Reference numeral 10 denotes a photosensitive drum, which is a drum-shaped image forming body, and has a transparent conductive layer, an a-Si layer or an organic photosensitive layer on the outer periphery of a cylindrical substrate formed of a transparent member such as optical glass or transparent acrylic resin. A photoreceptor layer such as a layer (OPC) is formed. 110 (Y, M, C, K) is charged by a scorotron charger to the photoconductor layer of the photoconductor drum 10 by a grid held at a predetermined potential and corona discharge by a discharge wire, and the photoconductor drum 10 is charged. A uniform electric potential is applied to.

Reference numeral 12 (Y, M, C, K) is an array of light emitting elements arranged in the axial direction of the photosensitive drum 10 in an array F.
An exposure optical system composed of L, EL, PL, LED, LISA, PLZT, LCS in which elements having an optical shutter function are arranged in a line, and a self-occurring lens as an equal-magnification imaging element. The image signals of the respective colors read by the reading device are sequentially taken out from the memory and input as electrical signals to the exposure optical system 12 (Y, M, C, K).

The exposure optical systems 12 (Y, M, C, K) are all mounted on a cylindrical support member 20 and housed inside the base of the photosensitive drum 10.

Denoted at 13Y to 13K are developing devices for accommodating yellow (Y), magenta (M), cyan (C), and K (black) developers, respectively. Development sleeve that rotates in the same direction while maintaining the
130 (Y, M, C, K), developing sleeve 130 (Y, M,
C, K) supply roller 131 (Y, M,
C, K), stirring roller 132 (Y, M, C, K), 133
(Y, M, C, K).

The developing device 13 (Y, M, C, K) is charged by the above-mentioned charging device 110 (Y, M, C, K) and is exposed by the exposure optical system 12 (Y, M, C, K). The electrostatic latent image formed on the photosensitive drum 10 by image exposure is reversely developed in a non-contact state by applying a developing bias voltage.

The original image is temporarily read as an image signal for each color of Y, M, C and K from an image read by an image pickup device or an image edited by a computer in an image reading apparatus separate from this apparatus. Stored and stored in memory.

When the image recording is started, the photoconductor driving motor (not shown) is started to rotate the photoconductor drum 10 in the clockwise direction, and at the same time, a potential is applied to the photoconductor drum 10 by the charging action of the charger 110 (Y). Be started.

After the photoconductor drum 10 is applied with an electric potential,
In the exposure optical system 12 (Y), the exposure by the electric signal corresponding to the first color signal, that is, the yellow (Y) image signal is started, and the yellow (Y) of the original image is formed on the photosensitive layer on the surface by the rotational scanning of the drum. ) Form an electrostatic latent image corresponding to the image.

The latent image is reversal-developed by the developing device 13 (Y) with the developer on the developing sleeve in a non-contact state, and a yellow (Y) toner image is formed according to the rotation of the photosensitive drum 10.

Next, the photoconductor drum 10 is given a potential on the yellow (Y) toner image by the charging action of the charger 110 (M), and the second image of the exposure optical system 12 (M).
Exposure is performed by an electric signal corresponding to the color signal of No. 3, that is, the image signal of magenta (M), and the non-contact reversal development by the developing device 13 (M) causes the magenta (M) toner image on the yellow (Y) toner image. ) Toner images are sequentially superposed and formed.

By the same process, the charger 110 (C),
A cyan (C) toner image corresponding to the third color signal is further generated by the exposure optical system 12 (C) and the developing device 13 (C).
Further, the charging device 110 (K), the exposure optical system 12 (K), and the developing device 13 (K) are used to produce black (K) corresponding to the fourth color signal.
The toner images of the
A color toner image is formed on the peripheral surface within one rotation of 10.

Each of these exposure optical systems 12 (Y, M, C, K)
The exposure of the organic photosensitive layer of the photoconductor drum 10 is performed through the transparent substrate described above from the inside of the drum. Therefore, the exposure of the image corresponding to the second, third, and fourth color signals is performed without any influence of the toner image previously formed, and is equivalent to the image corresponding to the first color signal. It is possible to form an electrostatic latent image of. The photoconductor drum 10 is generated by the heat generated by the exposure optical system 12 (Y, M, C, K).
The internal temperature is stabilized and the temperature rise is prevented by the holding member.
A material with good thermal conductivity is used for 20, a heater is used when the temperature is low, and heat is radiated to the outside through a heat pipe when the temperature is high. . In addition, the developing device 13 (Y, M, C, K)
When developing with the developing sleeve 130,
A developing bias in which a direct current or an alternating current is applied to (Y, M, C, K) is applied, jumping development is performed by a one-component or two-component developer accommodated in the developing device, and the transparent conductive layer is grounded. A DC bias having the same polarity as the toner is applied to the photoconductor drum 10 to perform non-contact reversal development in which the toner is attached to the exposed portion.

The color toner image thus formed on the peripheral surface of the photosensitive drum 10 is sent out from the paper feeding cassette 15 by the sending roller 15a in the transfer device 14a, and is sent to the timing roller 16 by the carrying roller pair 15b and 15c. The photosensitive drum is conveyed and driven by the timing roller 16.
The image is transferred onto a transfer sheet P which is a transfer material that is fed in synchronization with the toner image on 10.

The transfer paper P on which the toner image has been transferred is removed from the charge on the static eliminator 14b and separated from the peripheral surface of the drum, and is then conveyed to the fixing device 17 by the conveying belt 14e. Fixing roller 17a, pressure roller 17
After being heated and pressed between b to fuse and fix the toner on the transfer paper P, the toner is discharged from the fixing device 17 by the fixing outlet roller pair 17d, and is conveyed by the paper discharging roller pair 18a and is discharged through the paper discharging roller pair 18. And is discharged onto a paper discharge tray 200 on the upper part of the apparatus.

On the other hand, the photosensitive drum 10 from which the transfer paper has been separated is cleaned by the cleaning blade 19a in the cleaning device 19.
Thus, the surface of the photosensitive drum 10 is rubbed to remove and clean the residual toner, and the toner image of the original image is continuously formed or is temporarily stopped to form a new toner image of the original image. The waste toner scraped off by the cleaning blade 19a is discharged to a waste toner container (not shown) by the toner transport screw 19b.

An embodiment of the corona charging device of the present invention will be described with reference to FIGS. 2 is a sectional view of an embodiment of the corona charging device, FIG. 3 is a view showing a sawtooth electrode plate, and FIG. 4 is an explanatory view of a corona discharge state.

Reference numeral 111 denotes an electrode plate (saw tooth electrode) for corona discharge, which has a plurality of pointed portions (saw tooth electrode portions) 111a which are electrode portions of equal length extending toward the photosensitive drum 10 which is an image forming body at a constant pitch. And a reference numeral 113 denotes a shield having a triangular cross section having an opening whose width becomes wider toward the photoconductor drum 10. The saw-tooth electrode plate 111 is sandwiched between the support member 112 and the attaching and pressing member 114 to form a shield.
The grid 115 is attached to the opening of the shield 113, and the corona charging device 110 is smaller than the conventional one.
(Y, M, C, K) is formed. Corona charging device 110 (Y, M, C, K) made in this way
FIG. 4 shows a comparison of the discharge state of the wire discharge method shown in FIG. 6 with that of the wire discharge method shown in FIG. 6, FIG. 4 (A) shows the discharge state of the wire discharge method, and FIG. It shows a discharge state by the device 110 (Y, M, C, K). Using the apparatus shown in FIG. 1, the peripheral speed of the photosensitive drum is 80 mm / sec, the applied voltage to the sawtooth electrode part is −5 KV, the shield opening width and the grid width are 15 mm, and the grid applied voltage is −70.
As a result of the experiment at 0 V, in the conventional case as shown in FIG. 4 (A), since the discharge occurs around the wire, the generated ions are oriented in the entire circumferential direction, and the charge amount of the image forming body is open. It can be seen that the angle θ is regulated. On the other hand, when a voltage is applied to the saw-tooth electrode plate 111 which is the discharge electrode of the corona charging device 110 (Y, M, C, K), the corona between the electrode and the photoconductor drum is increased. As shown in FIG. 4B, the discharge from the saw-toothed electrode portion 111a causes almost all the ions due to the discharge toward the grid. Therefore, even if the shield 113 having a triangular shape that is not affected by the opening angle is used, the charging performance is not deteriorated, and the color image forming apparatus, in particular, the circumference of the image forming body for downsizing the apparatus is achieved. A plurality of charging means, an image exposing means and a developing means are arranged on the surface, and a small amount of ozone is generated and uniform charging is possible, which corresponds to a color image forming apparatus which forms a toner image by superposing it during one rotation of an image forming body. It is possible and possible to have a small charger. The width of the shield opening was preferably 7 to 20 mm.
Even if the aperture angle is 10 to 60 °, which is narrower than before, uniform charging is possible, which is advantageous for downsizing.

FIG. 5 shows another embodiment of the corona charging device, in which the sawtooth electrode plate 111 is sandwiched between the supporting members 142 and the holding members 144 so that the width becomes wider toward the photosensitive drum 10. Drop into a trapezoidal cross-section shield 143 with an opening, and grid in the opening of the shield 143.
145 is attached to form a corona charging device 140 which is smaller than before. Also in this case, as a result of conducting an experiment using the apparatus of FIG. 1 as in the above-mentioned embodiment, it was possible to provide a small-sized charger which produces a small amount of ozone, can be uniformly charged. The width of the shield opening was still preferably 7 to 20 mm.

[0028]

EFFECT OF THE INVENTION A corona discharge electrode having a plurality of equal-length pointed heads extending toward the image forming body at a constant pitch and a triangular or trapezoidal shape having an opening whose width becomes wider toward the image forming body. A corona charging device consisting of a shield with a cross-sectional shape and a grid arranged in the opening of the shield, which corresponds to a color image forming device, produces a small amount of ozone, is capable of uniform charging, and is compact in size. It was possible to provide a vessel. In particular, a color image in which a plurality of charging means, image exposing means, and developing means are arranged on the peripheral surface of the image forming body to superimpose toner images during one rotation of the image forming body in order to downsize the apparatus. In case of forming device,
Along with the miniaturization of the charger, it has become possible to provide a charger that generates as little ozone as possible as a moisture resistance measure for the transparent photoconductor.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing an example of a color image forming apparatus suitable for implementing a corona charging device of the present invention.

FIG. 2 is a sectional view of an embodiment of a corona charging device.

FIG. 3 is a diagram showing a sawtooth electrode plate.

FIG. 4 is an explanatory diagram of a corona discharge state.

FIG. 5 is a sectional view showing another embodiment of the corona charging device.

FIG. 6 is a sectional view showing a conventional corona charging device.

[Explanation of symbols]

 10 Photoconductor drum 12 Exposure optical system 13 Developing device 14a Transfer device 14b Static eliminator 15 Paper cassette 16 Timing roller 17 Fixing device 18 Paper ejection roller pair 19 Cleaning device 110 Scorotron charger 140 Corona charging device 111 Sawtooth electrode plate 111a Sawtooth electrode Part 112,142 Support member 113,143 Shield 114,144 Holding member 115,145 Grid P Transfer paper

Claims (4)

[Claims] 1. A corona charging device of an image forming apparatus for forming a toner image on an image forming body and then transferring the toner image onto a transfer material,
A corona discharge electrode having a plurality of equal-length pointed heads extending toward the image forming body at a constant pitch, and a triangular or trapezoidal cross-sectional shape having an opening whose width increases toward the image forming body A corona charging device comprising a shield and a grid arranged in the opening of the shield. 2. The image forming apparatus, wherein a plurality of sets of charging means, image exposing means and developing means are arranged around the image forming body, and the image forming body is charged by the charging means, image exposing and developing by the image exposing means. 2. The corona charging device according to claim 1, wherein the color image forming device performs a batch transfer onto a transfer material after forming a toner image on the image forming body by superposing the toner image on the image forming body by repeating development by means. 3. The width of the opening of the shield is 7 to 20.
The corona charging device according to claim 1 or 2, wherein the corona charging device is mm. 4. The angle formed by the pointed portion and the opening is 10
The corona charging device according to claim 1 or 3, wherein the corona charging device has an angle of -60 °.