JPH08202120A - Corona electrifier - Google Patents

Abstract

PURPOSE: To enable miniaturization and uniform electrification and to make a generated ozone quantity small by setting the values of the interval between the apexes of a comb-shaped electrode plate and the interval between the apex of the comb-shaped electrode and a control grid, in a specific range. CONSTITUTION: The value Dp of the interval between the apexes 111b of the comb-shaped electrode plate 111 is set 1mm to 4mm and the value Dg of the interval between the apex 111b of the electrode plate 111 and the control grid 115 is set two or more times the value Dp of the distance between intersections in the radiative diffusion of a corona discharge. Further, at a position where the value Dg is two or more times the value Dp, the control grid 115 is arranged. Thus, electrification unevenness due to a discharge to an adjacent comb- shaped electrode and the overlapping of the discharge from the adjacent comb- shaped electrode are eliminated to prevent the occurrence of unevenness caused by the pitch of the comb-shaped electrode. Since the unevenness of the discharge hardly occurs, the uniform electrification can be obtained and the control of the control grid 115 can be improved.

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 used for the purpose of charging a photosensitive member in an electrophotographic image forming apparatus, and more particularly to a non-contact type sawtooth electrode. The present invention relates to a corona discharge type charging device.

[0002]

2. Description of the Related Art Heretofore, as a corona discharge type charging device of this type, a wire discharge type (corotron, scorotron,
Dicorotron etc.) and pin discharge method (pin electrode type, serrated electrode type, etc.). The latter is low ozone generation,
Further, along with the downsizing of image forming apparatuses, it has come to be used in electrophotographic copying machines, printers, etc. in recent years as a downsized corona charging device. Further, it has come to be used in a color image forming apparatus as a corona charging device of low ozone generation and uniform discharge. In particular, a corona charging device 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 JP-A-63-15272 and JP-A-5-45999.
It is disclosed in Japanese Patent Publication No.

[0003]

With the downsizing and complexity of the image forming apparatus as described above, there is a demand for a small corona charging device and stable corona discharge. The corona charging device generally covers the discharge electrode with a shield member having an opening in the direction of the photoconductor, but in the case of a conventional corona charging device using a wire discharge method, when the size is reduced, the opening angle decreases, Ions that reach the photoreceptor decrease, the distance between the shield and the corona electrode gets closer,
The amount of ions flowing to the shield increases, the amount of electric charges charged to the photoconductor through the control grid decreases, and the charging potential also becomes non-uniform. Furthermore, as an improvement,
What replaces the discharge electrode with a sawtooth electrode plate has been used in recent years, but as a result of experiments conducted by the researchers of the present invention,
In the case of the sawtooth electrode, the discharge capability is higher than that of the wire discharge method, but the phenomenon that the nonuniformity of the discharge from each sawtooth electrode is promoted occurs. FIG. 11 is a diagram showing a charging unevenness measuring device, in which a corona charging device 400 provided with a sawtooth electrode plate 411 is brought into a discharging state, and an insulating layer 402 is provided on a grounded aluminum plate 401 below the corona charging device 400. , Insulating layer 402
A tungsten wire 403 having a diameter of 50 μm, which is grounded through the ammeter A, is provided on the upper part of the direction perpendicular to the longitudinal direction of the corona charging device 400, and an aluminum plate 401 provided with the tungsten wire 403 is provided in the longitudinal direction of the corona charging device 400. 5
Scanning is performed at a speed of mm / sec, the discharge state is measured by the current value flowing through the tungsten wire 403, and the charging unevenness is measured.

That is, FIG. 10 is a diagram showing a discharge state of a corona charging device using a sawtooth electrode plate, which is a discharge electrode of the corona charging device made using the sawtooth electrode plate.
When voltage is applied to 411 and the control grid 415, corona discharge is generated between the electrode and the photoconductor drum with discharge directivity, and most of the ions due to the discharge from the apex 411b of the sawtooth electrode 411a are generated in the control grid 415. Head in the direction. For this reason, discharge is performed without being affected by the opening angle and deteriorating the charging performance. However, the corona discharge from the sawtooth electrode has a higher discharge capability than the wire discharge method, but the phenomenon that the nonuniformity of the discharge from the individual sawtooth electrodes is promoted was observed. In particular, if the distance Dp between the apexes 411b of the sawtooth electrodes 411a is set to be equal to or less than a certain distance, the discharges interfere with each other between adjacent sawtooth electrodes and the uniformity is deteriorated. Further, if the value of Dp is increased, the discharge from the sawtooth electrodes is prevented. It was clarified that the image-forming bodies near the saw-tooth electrode are more charged, and the image-forming bodies near the saw-tooth electrode are less charged, although they do not interfere with each other and are stable, which makes uniform charging difficult. Further, in a corona charging device using a sawtooth electrode plate, corona discharge is concentrated on the apex of the sawtooth electrode, which causes uneven charging, and particularly when downsizing, spark discharge due to leakage to the shield is likely to occur. was there.

The present invention is a corona charging device which solves the above problems and uses a sawtooth electrode as an electrode, and is small in size and capable of being uniformly charged. Another object of the present invention is to provide a corona charging device that is suitable.

[0006]

The object is to have a sawtooth electrode plate for corona discharge in which a plurality of sawtooth electrodes of equal length are provided at a constant pitch, the sawtooth electrode plate for forming a latent image. In a corona charging device arranged orthogonally to the moving direction of the image forming body, in the corona charging device, a supporting member for supporting the sawtooth electrode plate, and a control grid for controlling corona discharge from the sawtooth electrode. And the distance between the vertices of the sawtooth electrodes of the sawtooth electrode plate is Dp and the distance between the vertices of the sawtooth electrodes and the control grid is Dg, the value of Dp is 1 mm or more and 4 mm or less. And D
This is achieved by a corona charging device characterized in that g is set to Dp that is twice or less (first invention).

Further, a shield member for controlling an ion flow is provided at both ends of the sawtooth electrode plate of the corona charging device in parallel with the sawtooth electrode plate. DC voltage is applied to the corona charging device, a DC voltage is applied to the control grid provided in the corona charging device, the DC voltage is applied to the control grid rather than the value of the DC voltage applied to the shield member. A corona charging device characterized in that the value of the DC voltage to be set is set low is a preferred embodiment in the first invention.

The object is to have a sawtooth electrode plate for corona discharge in which a plurality of sawtooth electrodes of equal length are provided at a constant pitch, and the sawtooth electrode plate moves in the moving direction of an image forming body for forming a latent image. In a corona charging device arranged orthogonally to, in the corona charging device, a supporting member for supporting the sawtooth electrode plate, a control grid for controlling corona discharge from the sawtooth electrode, and the sawtooth electrode plate. A conductive shield member for controlling an ion flow disposed on both sides of the sawtooth electrode plate in parallel is provided, and the shield member has an uneven side surface in a longitudinal direction facing the sawtooth electrode plate. Corona charging, which has an uneven portion having the same pitch as the pitch of the sawtooth electrodes provided on the electrode plate and is arranged so that a portion close to the apex of the sawtooth electrodes corresponds to the concave portion. It is achieved by location (second invention).

A corona charging device, an image exposure device, and a plurality of sets of developing devices are arranged around the image forming body, and the corona charging device is rotated with respect to the image forming body by rotating the image forming body a plurality of times. It is used in a color image forming apparatus in which toner images are superposed on the image forming body by repeating charging by the image exposing apparatus, image exposing by the image exposing apparatus and developing by the developing apparatus, and then collectively transferring to a transfer material. The characterizing corona charging device is a preferred embodiment in the first and second inventions.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments of the first and second inventions of the corona charging device of the present invention, an image forming apparatus having a scorotron charger, which is one embodiment of the corona charging device common to each invention, is described. The image forming process and the configuration of each mechanism will be described using the color image forming apparatus shown in FIG. FIG. 1 is a color laser printer 80 showing an example of a color image forming apparatus for implementing the corona charging device of the present invention.
FIG.

The photosensitive drum 10 as an image forming member is driven and rotated in the clockwise direction, and in order to eliminate the history of the photosensitive member until the previous printing, for example, exposure by the uniform exposure means 12a before charging using a light emitting diode is performed. Then, the peripheral surface of the photoconductor is destaticized, and the charge at the previous printing is removed.
The photoconductor drum 10 is a scorotron charger as a charging means.
After being uniformly charged to the peripheral surface by 11, the image exposing means 12
Thus, image exposure is performed based on the image signal. The image exposure means 12 is a rotating polygon mirror for the laser light emitted from the laser light source.
Rotational scanning is performed by 12b, fθ lens 12c, and reflection mirror 12
A latent image is formed on the photoconductor drum 10 through d and the like.

The peripheral portion of the photosensitive drum 10 is a developing means in which a developer composed of toner such as yellow (Y), magenta (M), cyan (C), black (K) and a carrier is filled. The developing devices 13Y, 13M, 13C, and 13K are provided, and first, development of the first color (for example, yellow) is performed by the developing sleeve 131Y. The development is performed by non-contact reversal development by applying an AC bias and a DC bias in a superimposed manner between the developing sleeve 131Y and the photosensitive drum 10.

After the development of the first color is completed, the second color (for example, magenta) image process is started, the photosensitive drum 10 is again uniformly charged by the scorotron charger 11, and a latent image based on the image data of the second color is formed. It is formed by the exposure means 12. At this time, the charge removal by the uniform exposure means 12a performed in the image forming process for the first color is not performed. The development of the second-color magenta developer is performed by the developing sleeve 131M. For development, an AC bias and a DC bias are superimposed and applied between the developing sleeve 131M and the photosensitive drum 10,
It is performed by non-contact reversal development.

For the third color (cyan) and the fourth color (black), the same image forming process as for the second color is performed, and toner images of four colors are superposed and developed on the photosensitive drum 10.

The recording paper P stored in the transfer material storage container 15
Is in synchronization with the toner image formed on the photoconductor drum 10, and the transfer belt device 14 in which the transfer belt 14a is stretched is stretched.
Is fed to the nip portion (transfer area) 14b formed between the photosensitive drum 10 and the transfer belt 14a by the transfer device 14
By c, the multicolor image on the peripheral surface of the photosensitive drum 10 is collectively transferred onto the recording paper P. The transfer belt 14a is separated from the photosensitive drum 10 during the formation of a multicolor image.

The recording paper P separated from the transfer belt device 14 by the separator 14d is conveyed to a fixing device 17 composed of two rollers having a heater inside at least one roller, and a heating fixing roller 17a. By applying heat and pressure between the pressure roller 17b and the pressure roller 17b, the toner adhered on the recording paper P is fixed and discharged to the outside of the apparatus.

After the transfer, the toner remaining on the peripheral surface of the photosensitive drum 10 is discharged to the cleaning device 19 after being discharged by the static eliminator 16, and the cleaning blade 19a made of a rubber material and abutting on the photosensitive drum 10a. The toner is scraped off into the cleaning device 19 by the screw 19b and collected by a screw 19b in a not-shown waste toner container. The photoconductor drum 10 from which the residual toner has been removed by the cleaning device 19 is exposed by the uniform exposure means 12a and then uniformly charged by the scorotron charger 11 to enter the next image forming cycle. The cleaning blade 19a is kept away from the photosensitive drum 10 during the formation of a multicolor image.

FIG. 2 shows a scorotron charger which is an embodiment of the corona charging device according to the first invention of the present invention.
It will be described with reference to FIGS. FIG. 2 is a diagram showing a sawtooth electrode plate of a scorotron charger, and FIG. 3 is a sectional configuration diagram of a scorotron charger using a sawtooth electrode plate showing an embodiment of the corona charging device of the first invention. FIG. 4 is a diagram showing a discharged state of the scorotron charger of the first invention, and FIG. 5 is a diagram showing measured values of uneven charging of the scorotron charger.

The sawtooth electrode plate 111 has a sawtooth electrode 111a in which apexes 111b, which are the tips of sawtooth electrodes 111a which are a plurality of electrode portions of equal length, are provided at a constant pitch Dp, and which is an image forming body. 2 is an electrode plate for corona discharge, which is arranged orthogonal to the moving direction of the body drum 10 indicated by the arrow. Sawtooth electrode plate 11
1 is, for example, made by etching a stainless plate having a plate thickness of 0.1 mm, and has apex 111b of the sawtooth electrode 111a.
Has a curvature of R = 40 μm or less. The control grid 115 is made by etching a stainless plate having a plate thickness of 0.1 mm, and has a mesh width of 1 mm. The side plates 113 and 114, which are shield members, are formed of, for example, a single plate made of stainless steel.

The sawtooth electrode plate 111 is attached to a support member 121 made of an insulating resin, for example, ABS resin,
Similarly, the sawtooth electrode plate 111 is sandwiched between the pressing members 122 made of an insulating resin such as ABS resin. In a state where the side plates 113 and 114 are sandwiched between the saw-tooth electrode plate 111 and the pressing member 122 at both ends of the support member 121 in parallel with the longitudinal direction of the saw-tooth electrode plate 111, the support members are supported by resin screws (not shown).
121 is attached to the support member 121, and the control grid 115 is attached to the scorotron charger which is a corona charger.
100 is formed. The value of the distance between the vertex 111b of the sawtooth electrode 111a and the control grid 115 is Dg.

When the above-mentioned scorotron charger 100 is attached to the image forming apparatus so as to face the photoconductor drum 10 and an image is formed, the sawtooth electrode plate 111 receives the DC voltage E1 and the control grid. The DC voltage E2 is applied to 115, and the DC voltages E3 and E4 are applied to the side plates 113 and 114, respectively. The DC voltage applied to the side plates 113 and 114 can be taken from the same power source. By providing the support member 121 that supports the sawtooth electrode plate 111,
It is no longer necessary to use a conventional U-shaped side plate having one surface on the upper side of the sawtooth electrode, and side plates 113 and 114 are individually provided on both sides, and side plates are provided on both sides.
By providing 113, 114, the inflow of foreign matter due to the flow of wind is prevented. In addition, by separately controlling the voltages applied to both sides of the side plates 113 and 114, it is possible to control the corona discharge so that the flow of the ion wind is in a good state. It is also possible to provide it on only one side,
The side plate 113 on the upstream side in the rotation direction of the photoconductor drum 10
It is also possible to provide only this and apply a voltage only to the side plate 113 for control.

FIG. 5 shows the discharge state measured by the inventor of the present application with the scorotron charger 100 having the above-described structure in a voltage applied state by the charging unevenness measuring apparatus shown in FIG. Scan time T (sec) on the horizontal axis, that is, scorotron charger 1
00 indicates the position in the longitudinal direction, and the vertical axis indicates the current value I (μA) flowing through the tungsten wire at each position.

FIG. 5A shows the apex 111b of the sawtooth electrode 111a.
FIG. 6 is a diagram showing a discharge state when the distance Dp is set to 1 mm or less, and discharge to adjacent sawtooth electrodes occurs, and charging unevenness is remarkable. FIG. 5B shows the distance D between the apex 111b of the sawtooth electrode 111a.
It is a diagram of a discharge state when p is set to 4 mm or more. The discharges from the adjacent sawtooth electrodes do not overlap with each other and unevenness occurs according to the pitch of the sawtooth electrodes, and the discharges from the sawtooth electrodes are exposed independently. Since it reaches the body drum, uneven charging is severe. As shown in FIG. 4, the sawtooth electrode 111 that does not cause uneven discharge
If the distance Dp between the apexes 111b of a is 1 mm or more and 4 mm or less, the distance between the points where the radial spreads of the corona discharge intersect with each other is doubled, and the apex 111b of the sawtooth electrode 111a is
By disposing the control grid 115 at a position where the value Dg of the distance between the control grid 115 and the control grid 115 is 2Dp or more, the controllability of the control grid is improved, and a uniform discharge state as shown in FIG. 5C can be obtained. I can.

Using the image forming apparatus described in FIG. 1, the diameter is 180 mm and the width is at least A4 size (297 mm).
The photosensitive drum 10 is rotated at a peripheral speed of 80 mm / sec, and the distance Dp between the apex 111b of the sawtooth electrode 111a is 3 mm and the apex 111 of the sawtooth electrode 111a is 111 mm.
The value Dg of the distance between b and the control grid 115 is set to 7 mm, −4.7 kV (DC) is applied to the sawtooth electrode plate 111 of R = 30 μm at the apex 111b of the sawtooth electrode 111a, and −80k is applied to the control grid 115.
0 V (DC) is applied to reduce the surface potential of the photosensitive drum 10 to -8.
In order to maintain the effective controllability of the control grid 115, the side plates 113 and 114 on both sides of the sawtooth electrode plate 111 are controlled by 00V, and are lower than the voltage applied to the control grid 115 by -600V (D
As a result of applying C) respectively, the discharge direction from the sawtooth electrode was inclined to the side plate side, and in addition to the discharge through the control grid, the discharge was also generated through the side plate, resulting in good charging uniformity. I was able to get a good image.

By using the corona charging device having the structure according to the first aspect of the present invention, the charging performance is not deteriorated and the charging is uniform, and the corona charging device is miniaturized and the device is miniaturized. The image forming apparatus, particularly the corona charging device, the image exposing device and the plurality of developing devices are arranged on the peripheral surface of the image forming body as described with reference to FIG. 1, and the toner images are superimposed by rotating the image forming body a plurality of times. After the formation, it is possible to provide a small-sized corona charging device that can be uniformly charged, generates a small amount of ozone, and is compatible with a color image forming device that performs batch transfer to a transfer material.

FIG. 6 shows a scorotron charger which is an embodiment of the corona charging device according to the second invention of the present invention.
This will be described with reference to FIG. 6 is a schematic configuration diagram of a scorotron charger using a sawtooth electrode plate showing an embodiment of the corona charging device of the second invention, and FIG. 7 is a sectional configuration diagram of the scorotron charger of FIG. FIG. 8 is a partially enlarged view of the scorotron charger seen from the upper surface of FIG.
FIG. 9 is a diagram showing the concentration distribution of corona ions in a scorotron charger using a sawtooth electrode.

The sawtooth electrode plate 211 has a sawtooth electrode 211a in which apexes 211b which are the tips of the sawtooth electrodes 211a, which are a plurality of equal-length electrode portions, are provided at a constant pitch, and a photoconductor as an image forming body. It is an electrode plate for corona discharge arranged orthogonal to the moving direction of the drum 10. The sawtooth electrode plate 211 is, for example,
It is made by etching a stainless steel plate with a plate thickness of 0.1 mm, and the curvature of the apex 211b of the sawtooth electrode 211a is R =
It is 40 μm or less. The control grid 215 has, for example, a plate thickness of 0.
It is made by etching a 1mm stainless steel plate and has a mesh width of 1mm. Side plate that is a shield member
Reference numerals 213 and 214 each have a concavo-convex shape in which a side surface in the longitudinal direction facing the sawtooth electrode plate 211 is corrugated, and has concavities and convexities at the same pitch as the pitch of the sawtooth electrodes 211a provided on the sawtooth electrode plate 211. This is a member whose surface is made conductive by metal-plating a resin molded part.

The sawtooth electrode plate 211 is dropped into the groove 223 of the support member 221 made of an insulating resin, for example, ABS resin, and fixed by, for example, an adhesive. Side plate 21
3, 214 are attached and fixed to both ends of the supporting member 221 in parallel with the longitudinal direction of the sawtooth electrode plate 211, for example, by resin screws not shown, and further control grids 215 are attached to the control grids at both ends of the supporting member 221. The scorotron charger 200, which is a corona charging device, is formed on the surfaces 224 and 225 for use by attaching and fixing them with resin screws (not shown). As shown in FIG. 8, the side plates 213, 214 provided with the saw-tooth electrodes 211a provided on the saw-tooth electrode plate 211 and having irregularities having the same pitch as the saw-tooth electrodes 211a have a concave portion at a position close to the apex 211b of the saw-tooth electrode 211a. Is located in.

When the above-mentioned scorotron charger 200 is mounted facing the photoconductor drum 10 to form an image, a DC voltage E1 is applied to the sawtooth electrode plate 211 and a DC voltage E2 is applied to the control grid 215. However, the DC voltage E3 is applied to the side plates 213 and 214, respectively. Sawtooth electrode 21
FIG. 9 shows the concentration distribution of corona ions generated by the corona discharge from the apex 211b, which is the apex of 1a, and the concavo-convex portion having the same pitch as the pitch of the sawtooth electrodes 211a provided on the sawtooth electrode plate 211. Side plates 213, 214 having
However, since the portion of the sawtooth electrode 211a that is close to the apex 211b is a concave portion, the generated corona ions have the side plates 213, 21 centered on the apex 211b.
It spreads evenly on the uneven parts of 4, and uneven charging hardly occurs and uniform charging is performed. Further, the phenomenon that the electric field becomes strong at the apex portion is alleviated, and the generation of spark discharge due to the leak to the side plate is prevented. Using the image forming apparatus described with reference to FIG. 1, the diameter is 180 mm, the width is at least capable of supporting up to A4 size (297 mm), and the peripheral speed is 80 m.
Using the photoconductor drum 10 rotated at m / sec, sawtooth electrode
The pitch of the apex 211b of the 211a is 5 mm, and R of the apex 211b is 4
-5 kV (DC) is applied to the 0 mm sawtooth electrode plate 211, and -600 V (DC) is applied to the control grid 215 to control the surface potential of the photoconductor drum 10 at -600 V.
As a result of an experiment in which −500 V (DC) was applied to 3,214, respectively, uniformity of charging was obtained and a good image could be obtained.

By using the corona charging device having the structure according to the second aspect of the invention, uniform charging can be obtained without deteriorating the charging performance, and the corona charging device can be downsized and the device can be downsized. The image forming apparatus, particularly, the corona charging device, the image exposing device, and the plurality of developing devices are arranged on the peripheral surface of the image forming body as described in FIG. 1, and the toner images are superimposed by rotating the image forming body a plurality of times. Thus, it is possible to provide a small-sized corona charging device that is capable of uniform charging, produces a small amount of ozone, and is compatible with a color image forming apparatus that performs batch transfer onto a transfer material after being formed.

[0031]

According to the first aspect of the present invention, the distance Dp between the vertices of the sawtooth electrode is set to 1 mm or more and 4 mm or less, and the value Dg of the distance between the vertices of the sawtooth electrode and the control grid is set so as to correspond to each other of the radial spread of the corona discharge. By arranging the control grid at a position where the distance is Dp which is twice the distance of the intersecting points or more and Dg is twice the Dp or more, uneven charging due to discharge to adjacent sawtooth electrodes and adjacent sawtooth electrodes Of a corona charging device that prevents the occurrence of unevenness in accordance with the pitch of the saw-toothed electrodes, prevents uneven discharge, uniform charging, and improved controllability of the control grid Became possible.

According to the second aspect, by providing the side plates individually on both sides, the inflow of foreign matter due to the flow of wind is prevented. Further, by separately controlling the voltages applied to the side plates, it becomes possible to control the corona discharge so that the flow of the ion wind is in a good state.

According to the third or fourth aspect, the discharge direction from the sawtooth electrode is inclined to the side plate side, and in addition to the discharge through the control grid, the discharge is also generated through the side plate to obtain the uniform charging. A good image could be obtained.

According to the fifth aspect, the side plate having the uneven portion having the same pitch as the pitch of the sawtooth electrodes provided on the sawtooth electrode plate is provided, and the side plate is arranged so that the portion close to the apex of the sawtooth electrode becomes the concave portion. As a result, the corona ions generated by the corona discharge spread evenly on the uneven portion of the side plate centering on the apex of the sawtooth electrode, and uniform charging is less likely to occur. Further, the phenomenon that the electric field becomes strong at the apex portion is alleviated, and the leak to the side plate is prevented.

According to the sixth aspect of the present invention, the charging performance is not deteriorated and the charging uniformity is obtained. The color image forming apparatus, especially the image forming apparatus, which is downsized together with the downsizing of the corona charging apparatus is provided. A color image in which a corona charging device, an image exposure device, and a plurality of developing devices are arranged on the peripheral surface of the formed body to form toner images by superposing a plurality of rotations of the image formed body, and then collectively transferred to a transfer material. It has become possible to provide a compact corona charging device capable of performing uniform charging, generating a small amount of ozone, and corresponding to a forming device.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a color laser printer showing an example of a color image forming apparatus that implements a corona charging device of the present invention.

FIG. 2 is a diagram showing a sawtooth electrode plate of a scorotron charger.

FIG. 3 is a cross-sectional configuration diagram of a scorotron charger using a sawtooth electrode plate showing an embodiment of the corona charging device of the first invention.

FIG. 4 is a diagram showing a discharge state of the scorotron charger of the first invention.

FIG. 5 is a diagram showing measured values of uneven charging of a scorotron charger.

FIG. 6 is a schematic configuration diagram of a scorotron charger using a sawtooth electrode plate showing an embodiment of a corona charging device of the second invention.

7 is a cross-sectional configuration diagram of the scorotron charger of FIG.

FIG. 8 is a partially enlarged view of the scorotron charger seen from the upper surface of FIG.

FIG. 9 is a diagram showing a concentration distribution of corona ions in a scorotron charger using a sawtooth electrode.

FIG. 10 is a diagram showing a discharging state of a corona charging device using a sawtooth electrode plate.

FIG. 11 is a diagram showing a charging unevenness measuring device.

[Explanation of symbols]

 10 Photoconductor drum 11, 100, 200 Scorotron charger 12 Image exposure means 13Y, 13M, 13C, 13K Developing device 17 Fixing device 19 Cleaning device 80 Color laser printer 111, 211 Sawtooth electrode plate 111a, 211a Sawtooth electrode 111b, 211b Vertex 113,114,213,214 Side plate 115,215 Control grid 121,221 Support member 223 Groove E1, E2, E3, E4 DC voltage

Claims (6)

[Claims] 1. A saw-tooth electrode plate for corona discharge in which a plurality of equal-length saw-tooth electrodes are provided at a constant pitch, said saw-tooth electrode plate with respect to a moving direction of an image forming body for forming a latent image. In the corona charging device arranged orthogonally to each other, in the corona charging device, a support member for supporting the sawtooth electrode plate,
A control grid for controlling corona discharge from the sawtooth electrode is provided, a value of a distance between vertices of the sawtooth electrode of the sawtooth electrode plate is Dp, and a value of a distance between the vertices of the sawtooth electrode and the control grid is Dg. And the value of Dp is 1 mm or more,
A corona charging device characterized by having a Dg of 4 mm or less and a Dg of twice the Dp or less. 2. The corona charging device according to claim 1, wherein shield members for controlling ion flow are provided at both ends of the sawtooth electrode plate of the corona charging device in parallel with the sawtooth electrode plate. apparatus. 3. The corona charging device according to claim 2, wherein a DC voltage is applied to the shield member. 4. A DC voltage is applied to the control grid provided in the corona charging device, and the value of the DC voltage applied to the control grid is set lower than the value of the DC voltage applied to the shield member. The corona charging device according to claim 3, wherein: 5. A saw-tooth electrode plate for corona discharge in which a plurality of saw-tooth electrodes of equal length are provided at a constant pitch, the saw-tooth electrode plate being relative to a moving direction of an image forming body for forming a latent image. In the corona charging device arranged orthogonally to each other, in the corona charging device, a support member for supporting the sawtooth electrode plate,
A control grid for controlling the corona discharge from the sawtooth electrode, and a conductive shield member for controlling the ion flow arranged on both sides of the sawtooth electrode plate in parallel with the sawtooth electrode plate are provided, and the shield member is, The side surface in the longitudinal direction facing the sawtooth electrode plate has an uneven shape, has an uneven portion having the same pitch as the pitch of the sawtooth electrodes provided on the sawtooth electrode plate, and has a concave shape at a portion close to the apex of the sawtooth electrode. A corona charging device characterized in that it is arranged so as to correspond to a part. 6. A corona charging device, an image exposure device, and a plurality of sets of developing devices are arranged around the image forming body, and the corona charging device is rotated with respect to the image forming body by rotating the image forming body a plurality of times. It is used in a color image forming apparatus in which toner images are superposed on the image forming body by repeating charging by the image exposing apparatus, image exposing by the image exposing apparatus and developing by the developing apparatus, and then collectively transferring to a transfer material. The corona charging device according to claim 1, wherein the corona charging device is a corona charging device.