JPH0764376A - Charging device - Google Patents

Abstract

(57) [Abstract] [Purpose] In a corona discharge type charging device, deterioration of the photoconductor is prevented by reducing the amount of ozone, nitrogen oxides, etc. generated by corona discharge, which are sprayed onto the photoconductor. To improve the service life. In a corona discharge type charging device having an electrode member in which a plurality of electrodes are formed in a sawtooth shape at a constant pitch,
A configuration in which the electrode member is arranged so as to have a predetermined angle with respect to the center line of the photoconductor on a cross-sectional view parallel to the side surface of the photoconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device of an electrophotographic apparatus for forming an image on a sheet by using an electrophotographic process such as a laser printer, a laser copying machine, a laser facsimile.

[0002]

2. Description of the Related Art FIGS. 9A and 9B are explanatory views for each charger, in which a) shows a roller charger, b) shows a brush charger, and c) shows a sawtooth charger.

In recent years, in the environment surrounding copying machines and printers, in order to reduce the amount of ozone (O ₃ ) generated by corona discharge of the photoconductor charging device, from the viewpoint of environmental safety, a charging device with a very small ozone generation amount. Copier printers that use the are being introduced to the market. Examples of the charging device that generates a small amount of ozone include roller charging using a conductive rubber material, brush charging using a conductive resin material, and sawtooth charging using a metal plate in a sawtooth shape by etching. However, the former two cases a) and b) where mechanical stress is applied to the photoconductor are directly applied to the photoconductor surface.
Since the roller and brush come into contact with each other, it may not be possible to extend the life of the photoconductor, and it is actually on the market. Used in copiers and printers. As the charging device, the sawtooth charging of c) is mainly used.

FIG. 10 is an explanatory view of a saw-toothed charger of a conventional device, and FIG. 10A shows the relative positional relationship between the saw-toothed electrode member 35 and the photoconductor 91 and the photoconductor center line 47. The member 35 is attached at an angle of 0 ° (parallel) with respect to the photoreceptor center line 47. Photoreceptor surface and the electrode member 3
The clearance of No. 5 is about 5 to 10 mm.

[0005] b) shows a part of the front view of the sawtooth electrode member, a side view and an enlarged view of the tooth tips (in a circle), and the respective dimensions are generally described in the drawing. . Here, a stainless steel plate (thickness 100 μm) is etched,
The tooth spacing is 2 mm, the tooth tip angle is 30 °, and the tooth tip R is 30 μm or less. FIG. 11a) is a side view and a corona distribution diagram of the saw-tooth charger of the conventional device. Similarly, b) is a side view and a corona distribution diagram of the wire charger. Reference numeral 39 indicates the case of the charger, and 38 indicates the surface of the photoconductor. 34
Is a wire. Further, A represents the corona distribution area of the sawtooth charger, and B represents the corona distribution area of the wire charger.

[0006]

Until now, it has been mainly used in the above-mentioned configuration. Here, the characteristics of the sawtooth charger (sawtooth charger) will be explained. Compared with the conventional wire charger, the sawtooth charger has
As shown in Fig. 11a), the distribution of the charged corona is orthogonal to the direction of the sawteeth, and the sawtooth charger has no distribution of the charged corona in the direction opposite to the photoconductor surface, so the total ozone generation amount is Although it is reduced, the distribution of corona directly hitting the photoconductor is concentrated in one part as compared with the wire charger. Further, in order to make the photoconductor charging characteristics of the wire charger and the sawtooth charger the same, it is necessary to make the wire charger corona distribution area B and the sawtooth charger corona distribution area A the same. Needs to be further increased to raise the peak of the corona distribution. (Arrow direction in FIG. 11a) However, it is generated by the sawtooth charger. Ozone (O ³ )
Has a characteristic of flowing in a direction having a high corona distribution as described above, whereby the ozone generated is concentrated on a part of the photoconductor and hastens the oxidation of the photoconductor surface. Similarly, by concentrating the corona wind at one point, the surface resistance of the photoconductor is increased (sensitivity is lowered) due to the characteristic destruction (deterioration) of the photoconductor surface. Therefore,
The oxidized layer absorbs water due to high temperature and high humidity, and there is a problem that the copied image bleeds or flows due to the water. In addition, there is a problem that the deviation of the proper copy exposure due to the decrease in the sensitivity of the photoconductor becomes large.

[0007]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and a charging device according to claim 1 has a plurality of electrodes having a constant pitch in a longitudinal direction on the circumference of a photosensitive member. In a charging device of a corona discharge type having an electrode member formed in a striped shape, with respect to the arrangement of the electrode member, on a cross-sectional view parallel to the side surface of the photoconductor, the side surface that narrows the discharge part of the electrode member is The charging device has a predetermined angle with respect to the center line of the photoconductor.

The charging device according to claim 2 is the charging device according to claim 1, characterized in that an edge portion of a discharge portion of the electrode member is directed toward a center of the photoconductor.

[0009]

According to the above structure, the directional corona distribution is changed by changing the inclination of the mounting of the sawtooth electrode member, and by changing the distribution shape and the rotational direction of the photoconductor. Efficient exhaust of ozone (O ³ ) is performed to prevent deterioration of the photoconductor. Further, by arranging the tip edge portion of the sawtooth electrode member so as to be perpendicular to the surface of the photoconductor, the bright spot of corona discharge can be fixed, and the deterioration of the photoconductor can be prevented as described above.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details will be described below based on the embodiments of the present invention shown in the drawings. Needless to say, the present invention is not limited to these examples.

FIG. 1 is a side view showing the configuration of an embodiment of the image forming apparatus according to the present invention. Here, an example in which the charging device according to the present invention is applied to a copying machine is shown. As shown in the figure, the copying machine 10 of this embodiment includes a document placing table 11, a copy lamp 12, a first mirror 13, a second mirror 14,
A third mirror 15, a lens 16, a fourth mirror 17, a fifth mirror 18, a sixth mirror 19, a photoconductor drum 20 including an OPC, a charger 21, a developing tank 22, a transfer charger 23, a cleaner device 24, A blade 25, a conveyor belt 26, a fixing device 27, paper cassettes 28 and 29, and a discharge roller 30 are provided. When a document is set on the document table 11 and the copy start button is pressed, the copy lamp 12, the first mirror 13, the second mirror 14 and the third mirror 15 are parallel to each other along the document table 11. Is movable (in the direction of the bidirectional arrow shown in the figure). Light 3 emitted from the copy lamp 12
2 is reflected by the document on the document table 11 and
Mirror 13, second mirror 14, third mirror 15,
Through the lens 16, the fourth mirror 17, the fifth mirror 18, and the sixth mirror 19, the surface of the photosensitive drum 20 charged by the charger 21 is irradiated with the exposure point P. By this irradiation, an electrostatic latent image is formed on the surface of the photoconductor drum 20. This electrostatic latent image is developed into a toner image by the developing tank 22, and the toner image is transferred by the transfer charger 23 onto the paper supplied from the paper cassette 28 or 29. The sheet on which the toner image is transferred is conveyed to the fixing device 27 by the conveying belt 26, the toner image is fixed on the sheet by the fixing device 27, and then the sheet is discharged to the outside by the discharge roller 30. On the other hand, the surface of the photosensitive drum 20 after the transfer of the toner image is cleaned by the cleaner device 24 and the blade 25. This cleaning method is a blade cleaning method in which the toner is scraped off with an edge of urethane rubber.

FIG. 2a) is a perspective view of the sawtooth electrode member 35, FIG. 2b) is an enlarged view of a tooth tip portion, and FIG. 2c) is FIG. 2b).
FIG. 2d) is a layout view of the conventional electrode member, and FIG. 2e) is a layout view of the electrode member according to the present invention. In the present invention, the edge portion 36 is arranged perpendicularly to the photosensitive member surface 38, and the bright spot can be fixed. Conventionally, since the end surface portion 37 is arranged perpendicularly to the photoconductor surface 38, the bright spot is not fixed.

FIG. 3 is a corona distribution diagram of the embodiment of the present invention. By tilting the sawtooth electrode member 35, the peak of the corona distribution on the surface 38 of the photoconductor is dispersed to avoid partial concentration of ozone. .

FIG. 4a) shows the relative positional relationship between the sawtooth electrode member 35 and the photosensitive member 91 of the present invention.
4B) is an enlarged view of the broken line portion of FIG. 4A), in which the direction of the tip of the sawtooth electrode member (sawtooth charger) 35 is tilted to the downstream side in the rotation direction of the photoconductor 91, and the directionality of the sawtooth electrode member 35 is increased. A configuration is shown in which the rotation of the photoconductor 91 is used to cause the corona wind / ozone wind to flow along the surface 38 of the photoconductor and the air is exhausted by the exhaust fan 40. FIG. 5 shows the range of inclination of the sawtooth electrode member 35 in the present invention.
FIG. 6 shows an embodiment. Due to the above-mentioned saw blade charger characteristic (directionality), when the sawtooth tilts greatly, the corona distribution, which hits the photosensitive surface, is greatly reduced.
Therefore, it can be used as a performance as a charger.
As for the inclination, as shown in FIG.
It is necessary to set the range up to the tangent line to the outer periphery of the photoconductor and excluding 30% on the photoconductor center line side. here,
The angle cannot be expressed as an angle, because the inclination greatly changes the angle of the tangent to the outer periphery of the photoconductor, depending on the diameter of the photoconductor and the distance between the saw tooth and the photoconductor. More specifically, the angle of inclination of the sawteeth is, as shown in 5, a range of centerlines A from the center of the saw blade to the center of the photoconductor and tangents B and C from the sawtooth centerline to the outer periphery of the photoconductor (A, B). Between α, A,
Between C is β), and within the range of α and β, 30% on both sides of the center line is excluded. This is because, if the inclination is larger than this, the corona distribution that hits the photoconductor is significantly reduced in the directional charger such as the saw-tooth charger.
Further, if the inclination is within 30% on both sides of the center line, the corona distribution hitting the photoconductor cannot be widely dispersed, and the effect of the present invention cannot be obtained.

Next, the construction of the sawtooth charger charger according to the present invention will be described with reference to FIG. In this embodiment, the photosensitive member has φ6.
A 0-tooth drum is used, and the saw-tooth charger is arranged at an angle of 30 ° with respect to the center line of the photoconductor in the direction of rotation of the photoconductor. Also, set the distance from the tip of the sawtooth to the photoconductor by 8
mm. The charging method was a serotron method that uses a grid electrode to stabilize the charging. (The saw blade used is one of the examples given in the prior art.) The high-voltage transformer uses a constant current type transformer.

FIG. 7 shows a method for manufacturing the sawtooth electrode member used in the present invention. Specifically, the sawtooth is formed by an etching process as described in the prior art. As shown in FIG. 7, a stainless steel substrate 51 is sandwiched with a masking material 50, an etching solution 52 is applied from the upper surface thereof, and sawtooth is formed by erosion of the solution. At this time,
Since the erosion rate of the liquid is different between the upper surface and the lower surface to which the etching liquid 52 is applied, the sawtooth shape that is formed has a directionality due to the erosion, and sharp and obtuse angles occur as shown in FIG.

FIG. 8a) shows a comparison diagram of the corona distribution between the saw-tooth charger and the wire charger (wire charger), and FIG. 8b) shows the corona distribution diagram of the saw-tooth charger with the inclination changed. . The flow of ozone and corona in the wire charger seems to flow into the photoconductor when you look at the corona distribution in Fig. 8a). However, of course, there is corona distribution on the charger case side, and when designing a charger, the distance between the wire and the case and the distance between the wire and the photoconductor surface are usually the same or the former is made smaller so that the charger case side This is because the flow of ozone is made to flow in the direction opposite to the surface of the photoconductor by strengthening the corona distribution.

In FIG. 8b), if the inclination is equal to or greater than the tangent line of the outer periphery of the photoconductor, the corona distribution on the photoconductor is greatly reduced (in the direction of the arrow), and even if the output is increased, the same waveform area as that of the wire charger cannot be obtained, and 30 on both sides of the center line
If it is within%, the same waveform area as that of the wire charger is obtained, but the waveform distribution is almost the same as that of the conventional saw-tooth charger, and it is understood that the effect of the present invention cannot be obtained.

Others The present invention is not limited to the embodiments described above and shown in the drawings, and it is needless to say that the present invention can be appropriately modified and implemented without departing from the scope of the invention.

[0020]

According to the present invention, with the above configuration, the directional corona distribution is changed by changing the inclination of the attachment of the sawtooth electrode member, and the direction and the rotational direction of the photoconductor are changed. By satisfying the above conditions, ozone (O ₃ ) is efficiently exhausted, and deterioration of the photoconductor is prevented. Further, by arranging the tip edge portion of the sawtooth electrode member so as to be perpendicular to the surface of the photoconductor, the bright spot of corona discharge can be fixed, and the deterioration of the photoconductor can be prevented as described above.

[Brief description of drawings]

FIG. 1 is a side view showing the configuration of an embodiment of an image forming apparatus according to the present invention.

2 (a) to (e) are explanatory views of an embodiment of the device of the present invention.

FIG. 3 is a corona distribution diagram of an example of the present invention.

4 (a) and 4 (b) are explanatory views of an embodiment of the present invention.

FIG. 5 is an explanatory diagram of an example of the present invention.

FIG. 6 is an explanatory diagram of an example of the present invention.

FIG. 7 is a diagram showing a method for manufacturing an electrode member used in the present invention.

8 (a) and 8 (b) are corona distribution diagrams of an example of the present invention.

9A is an explanatory diagram of a roller charger. FIG. b) It is explanatory drawing of a brush charger. c) An illustration of a sawtooth charger.

10A and 10B are explanatory views of a sawtooth charger of a conventional device.

FIG. 11 a) Corona distribution chart of the saw-tooth charger of the conventional device. b) Corona distribution map of the wire charger.

[Explanation of symbols]

 11 Document Placement Table 12 Copy Lamp 13 First Mirror 14 Second Mirror 15 Third Mirror 16 Lens 17 Fourth Mirror 18 Fifth Mirror 19 Sixth Mirror 20 Photoreceptor Drum 21 Charger 22 Developing Tank 23 Transfer charger 24 Cleaner device 25 Blade 26 Conveyor belt 27 Fixing device 28 Paper cassette 29 Paper cassette 30 Ejection roller 34 Wire 35 Serrated electrode member 36 Edge part 37 End face part 38 Photoconductor surface 40 Exhaust fan 41 Grid 45 Photoconductor outer peripheral tangent line 46 Peripheral tangent line of photoconductor 47 Photoconductor centerline 50 Masking material 51 Stainless steel base material 52 Essent liquid 91 Photoconductor 92 Roller 93 Brush 94 Sawtooth electrode member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eisaku Hatanaka 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Takashi Sakai 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Osaka Within the corporation

Claims (2)

[Claims] 1. A corona discharge type charging device having an electrode member in which a plurality of electrodes are formed in a sawtooth shape at a constant pitch in the longitudinal direction on the circumference of the photosensitive member, and in regard to the arrangement of the electrode member, A charging device characterized in that, on a cross-sectional view parallel to the side surface, a side surface of the electrode member that narrows a discharge portion has a predetermined angle with respect to a center line of the photoconductor. 2. The charging device according to claim 1, wherein an edge portion of the discharge portion of the electrode member is directed toward the center of the photoconductor.