JPH08171254A - Electrifying device - Google Patents

Abstract

PURPOSE: To improve the durability and the electrifying performance of a plate- like electrode used in a corona discharge system electrifying device. CONSTITUTION: By using the plate-like electrode 120 provided with a tooth- shaped electrode part 120A, the cross-sectional area occupied by the electrode 120 and supporting members 122 and 123 interposing the electrode 120 is made as small as possible, and air circulating ports are opened at both ends of a shielding member 121. After air sucked from one end owing to suction by a fan is discharged from the other end or air sucked from suction holes 121B at both ends and on both side surfaces is discharged from a discharge hole 121A on the upper surface so as to clean the electrode part, an ozone component is adsorbed and exhausted by a filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona charging device using a non-contact type saw-toothed electrode used for charging a photosensitive member in an electrophotographic image forming apparatus.

[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.

[0003]

However, even if the saw-toothed electrode plate is used for a long period of time to discharge, the amount of toner powder or foreign matter generated is not negligible.
As a result, uneven charging occurs. Further, since the sawtoothed electrode plate has a strong discharge directivity in the direction of the photoconductor, the generated ozone also easily flows out in the direction of the photoconductor, which promotes deterioration of the photoconductor and results in deterioration of performance and durability.

The present invention focuses on the point that a charging device using plate-shaped electrodes does not require a wire supporting member, so-called electrode block, for supporting both ends of the wire when wire-shaped electrodes are used. As a result of solving and improving the above-mentioned problems, foreign matter such as ozone and toner powder generated can be promptly and efficiently removed to the outside of the apparatus, and at the same time, the electrode section is always kept clean so that the photoreceptor to be charged can be provided. An object of the present invention is to provide a charging device that can be uniformly charged and a charging device that discharges ozone, toner powder, and the like to the outside of the device by utilizing an air flow generated by a moving image carrier. .

[0005]

The above object is to provide a corona discharge type charging device for performing corona discharge on a body to be charged by a plate electrode having a plurality of sawtooth electrode portions, wherein the charging device is the plate electrode. A charging device (first invention), comprising: a supporting member for supporting the charging device; and a shielding member for shielding the plate-shaped electrode, wherein an air flow hole is opened at an end portion of the charging device, and a plurality of charging devices. In a corona discharge type charging device that performs corona discharge to a charged body by a plate-shaped electrode having a sawtoothed electrode part, the charging device is located behind the tip of the plate-shaped electrode facing the moving charged body. This is achieved by a charging device (second invention), which is characterized by forming an air flow circulating in the end direction.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of each embodiment according to the present invention, the structure and function of an image forming apparatus to which the charging device of each invention is attached will be described with reference to FIGS. 7 and 8.

FIG. 7 shows an apparatus (A) for forming a multicolor color image by superposing toner images of respective colors on the image forming body by rotating the image forming body a plurality of times, while FIG. 1 shows an apparatus (B) for forming a multicolored color image on an image forming body by superimposing toner images of respective colors during rotation, the former being one charging device as a charging means of the image forming body. The latter is provided with a plurality of charging devices according to the number of superimposed toner images.

Members having the same function in the device (A) and the device (B) are designated by the same reference numerals.

In FIG. 7, reference numeral 10 denotes a photosensitive drum, which is an image carrier, which is applied on the OPC photosensitive drum and is grounded and driven and rotated clockwise. Reference numeral 12 is a scorotron charger of the present invention, which will be described later.
A uniform charge of _H is given by corona discharge with a grid and plate electrodes held at V _G. Prior to the charging by the scorotron charger 12, the peripheral surface of the photoconductor is neutralized by exposure by the PCL 11 using a light emitting diode or the like in order to eliminate the history of the photoconductor until the previous printing.

After uniformly charging the photosensitive member, the image exposing means 13 performs image exposure based on the image signal. Image exposure means
Reference numeral 13 is a reflection mirror 1 via a polygon mirror 131 that rotates using a laser diode (not shown) as a light emitting source, an fθ lens
The operation is performed by bending the optical path by 32, and the latent image is formed by the rotation (sub-operation) of the photoconductor drum 10.
In this embodiment, the character portion is exposed to form an inverted latent image in which the character portion has a lower transition V _L.

Yellow (Y) is formed on the periphery of the photosensitive drum 10.
Developers each containing a developer composed of toner such as magenta (M), cyan (C), black (K), and a carrier.
14 is provided, and first, the development of the first color is performed by the developing sleeve 141 which contains a magnet and holds the developer and rotates. The developer is a carrier in which a ferrite core is coated with an insulating resin around it, a polyester as a main material, a pigment according to the color, and a charge control agent,
The toner is composed of toner to which silica, titanium oxide, etc. are added.
The layer is regulated to a layer thickness (developer) of 600 μm and transported to the development area.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is 0.2 mm, which is larger than the layer thickness (developer).
As 1.0 mm, DC bias of AC bias and V _DC of V _AC is applied to overlap therebetween. Since V _DC and V _H and the toner are charged with the same polarity, the toner that is given the opportunity to be separated from the carrier by V _AC does not adhere to the V _H portion, which has a higher potential than V _{DC, and} has a potential higher than V _DC. attached to a lower V _L portion of visualized (reversal development) is carried out.

After the visualization of the first color is completed, the process proceeds to the image forming step for the second color, the uniform charging is performed again by the scorotron charger 12, and a latent image based on the image data for the second color is formed by the image exposing means 13. To be done. At this time, the charge elimination by the PCL 11 performed in the image forming process for the first color is not performed because the toner adhered to the image portion for the first color scatters due to the sudden decrease in the potential around the image.

Again, V is applied over the entire surface of the photosensitive drum 10.
A latent image similar to that of the first color is formed on the portion of the photoconductor having the _H potential and the image of the first color is not developed, but development is performed again on the portion having the image of the first color. In the portion to be performed, the latent image of V _M ′ is formed by the toner attached to the first color due to the light blocking and the charge of the toner itself, and the development is performed according to the potential difference between V _DC and V _M ′. When the first color image is formed by forming a VL latent image in the overlapping portion of the first color image and the second color image, the balance between the first color and the second color is lost, so that the exposure amount of the first color is reduced and V _H > It may be set to an intermediate potential such that V _M > V _L.

An image forming process similar to that for the second color is performed for the third and fourth colors, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

On the other hand, the recording paper P carried out from the paper feeding cassette 15 via the half-moon roller 16 is temporarily stopped and is fed to the transfer area by the rotation operation of the timing roller 17 when the transfer timing is adjusted.

In the transfer area, the transfer roller 18 is pressed against the peripheral surface of the photoconductor drum 10 in synchronization with the transfer timing, and the recording paper P that has been fed is sandwiched and a multicolor image is transferred at once. .

Then, the recording paper P is discharged by the pointed electrodes 19 provided in the vicinity of the photoconductor drum 10 to remove the charge.
Separated from the peripheral surface of the sheet and conveyed to the fixing device 20, where the heat roller 20
The toner is melted by heating and pressurizing the pressure roller 1 and the pressure-bonding roller 202, and then the toner is discharged to the outside of the apparatus through the paper discharge roller 21. The transfer roller 18 is a photosensitive drum after the recording paper P has passed.
Prepared for the next toner image formation by retracting from the peripheral surface of 10.

On the other hand, the photosensitive drum 10 in which the recording paper P is separated
Removes and cleans the residual toner by pressing the blade 221 of the cleaning device 22, and again receives the charge removal by the PCL 11 and the charge by the charger 12 to start the next image forming process. The blade 221 moves immediately after cleaning the surface of the photoconductor and retracts from the peripheral surface of the photoconductor drum 10.

On the other hand, the photosensitive drum 10 in FIG. 8 is formed by coating an organic photosensitive layer (OPC) composed of a transparent conductive layer on the outer periphery of a base formed of a transparent member such as optical glass or clear acrylic resin, and grounded. It is rotated clockwise in this state.

12 (Y), 12 (M), 12 (C) and 12
(K) is a scorotron charger, which is a charging means of the present invention described later, and is charged by a grid held at a predetermined potential with respect to the above-mentioned organic photoreceptor layer of the photoreceptor drum 10 and corona discharge by a plate electrode. Do the photoconductor drum 10
A uniform electric potential is applied to.

Reference numeral 13 denotes an exposure optical system which is an image exposure means, and includes LEDs, FL, EL, P arranged in the axial direction of the photosensitive drum 10.
It is composed of a light emitting element such as L and a SELFOC lens. The image signals of the respective colors read by the separate image reading device are sequentially taken out from the memory and input to the exposure optical systems 13 as electric signals. The emission wavelength of the light emitting device used in this example is in the range of 600 to 900 nm.

Each of the exposure optical systems 13 is mounted on a columnar support member 130 and is housed inside the base of the photosensitive drum 10. The exposure optical system 13 may be composed of a combination of an optical shutter member such as LCD, LISA, PLZT and the like, and an image forming lens such as a Selfoc lens in addition to the above-mentioned light emitting element.

Numeral 14 is a developing device which is a developing means for accommodating each of yellow (Y), magenta (M), cyan (C) and black (K) developers, and each has a predetermined size with respect to the peripheral surface of the photosensitive drum 10. Developing sleeve 14 that rotates in the same direction while maintaining the gap
Equipped with 1.

Each of the developing devices 14 does not contact the electrostatic latent image on the photosensitive drum 10 formed by the charging by the charging device 12 and the image exposure by the exposure optical system 13 by applying a developing bias voltage. Reverse development in the state.

Next, the process of the color image forming apparatus in this apparatus will be described.

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

When the image recording is started, the photoconductor drive motor is rotated to rotate the photoconductor drum 10 in the clockwise direction, and at the same time, the charging action of the charger 12 (Y) starts to apply the potential to the photoconductor drum 10. To be done.

After the photoconductor drum 10 is applied with an electric potential,
In the exposure optical system 13 (Y), image exposure is started by an electric signal corresponding to the first color signal, that is, the image signal of yellow (Y), and the yellow (of the original image of the original image is formed on the photosensitive layer on the surface by rotational scanning of the drum). An electrostatic latent image corresponding to the image of Y) is formed.

The latent image is reversely developed by the developing device 14 (Y) with the developer on the developing sleeve in a non-contact state, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 is further given a potential on the yellow (Y) toner image by the charging action of the charger 12 (M), and the second color signal of the exposure optical system 13 (M), that is, Image exposure is performed by an electric signal corresponding to a magenta (M) image signal, and non-contact reversal development by the developing device 14 (M) causes magenta (M) toner on the yellow (Y) toner image. The images are sequentially superimposed and formed.

By the same process, the cyan (C) toner image corresponding to the third color signal is finally generated by the charger 12 (C), the exposure optical system 13 (C) and the developing device 14 (C), and finally. Black (K) corresponding to the fourth color signal by the charger 12 (K), the exposure optical system 13 (K) and the developing device 14 (K)
Toner images are sequentially superposed and formed on the photosensitive drum.
A color toner image is formed on the peripheral surface within one rotation of 10.

The color toner image thus formed on the peripheral surface of the photosensitive drum 10 is a transfer material which is a transfer material which is conveyed from the paper feed cassette 15 by the transfer roller 18 and is synchronously fed by the driving of the timing roller 17. Transferred to paper.

The transfer paper on which the toner image has been transferred is separated from the peripheral surface of the drum by removing the charge at the pointed electrode 19, and the toner is welded at the fixing device 20 and then the paper is discharged through the paper discharge roller 21. It is discharged onto the upper tray.

On the other hand, the photoconductor drum 10 from which the transfer paper has been separated removes and cleans the residual toner in the cleaning device 22 to continue the formation of the toner image of the original image, or temporarily stops the toner of the new original image. Wait for image formation.

(Embodiment 1) The structure of the charging device 12 according to the first invention will be described with reference to FIGS.

Reference numeral 120 is a plate-like electrode for corona discharge having a saw-toothed electrode portion 120A formed at its tip at equal intervals, and has a thickness of 0.1 m.
It is made by etching a thin m plate such as a stainless plate.

Reference numeral 121 denotes a stainless steel shield member having a U-shaped cross-section with both ends and one side surface open, and also serves as a casing member of the charging device 12.

Reference numerals 122 and 123 denote support members formed of an electrically insulating synthetic resin material, and are the plate-like electrodes 12 described above.
It is attached and fixed to the inside of the upper surface of the shield member 121 via a resin screw or the like while sandwiching 0.

Since the supporting members 122 and 123 have a very small cross-sectional area in the shield member 121 as shown in each AA sectional view of FIG. 2, both ends of the charging device 12 are used as air circulation holes. It is possible to adopt a structure in which foreign substances such as ozone and toner in the shield member 121 generated by corona discharge are forcibly excluded.

FIG. 2A shows a cross-sectional shape of the charging device 12 in which only both ends are opened as air passage holes. As shown in FIG. 3A, an ozone filter is provided at one end of the passage hole. A duct D containing f and a fan F is connected.

The outside air sucked through the flow hole at the other end by the operation of the fan F passes through the inside of the shield member 121 and is sucked into the duct D, and the ozone filter f adsorbs and purifies ozone components. It is then exhausted to the outside of the device by the fan F.

In addition, FIG. 2B shows that the above-mentioned both ends are opened and the discharge hole 121A is formed at the center of the upper surface of the shield member 121.
The cross-sectional shape of the charging device 12 that opens the
As shown in (b), the duct D containing the ozone filter f and the fan F is connected to the discharge hole 121A provided near the central portion of the shield member 121.

The air sucked from the flow holes at both ends by the operation of the fan F diffuses ozone, which tends to stay at the ends of the shield member 121, to the central portion and is sucked into the duct D, and the ozone filter The ozone component is adsorbed and purified by f and exhausted to the outside of the device by the fan F.

Further, the suction holes 1 are provided on both sides of the shield member 121.
By opening 21B and sucking air on the peripheral surface of the photosensitive drum 10, ozone leaking from the gap between the shield member 121 and the peripheral surface of the drum can be collected and eliminated.

(Embodiment 2) The structure of the charging device 12 according to the second invention will be described with reference to FIGS.

Reference numeral 120 is a plate-like electrode for corona discharge having a saw-toothed electrode portion 120A formed at its tip portion at equal intervals, and has a thickness of 0.1 m.
It is made by etching a thin m plate such as a stainless plate. Reference numeral 121 denotes a stainless steel shield member having a U-shaped cross-section with both ends and one side surface open, and also serves as a casing member of the charging device 12.

Reference numerals 122 and 123 denote support members made of an electrically insulating synthetic resin material, and are the above-mentioned plate-like electrodes 12
It is attached and fixed to the inside of the upper surface of the shield member 121 via a resin screw or the like while holding 0.

Since the supporting members 122 and 123 have a very small cross-sectional area in the shield member 121 as shown in each AA sectional view of FIG. 5, both end portions of the charging device 12 are used as air circulation holes, and the corona is used. The ozone in the shield member 121 generated by the discharge can be forcibly removed.

FIG. 5A shows the charging device 12 in which the discharge holes 121A are further opened on the upper surface of the shield member 121 together with the above-mentioned circulation holes at both ends. As shown in FIG. 6A, the shield member 121 is shown. An ozone filter f and a duct D containing a fan F are connected to the discharge hole 121A on the upper surface of the fan.

The air sucked through the flow holes at both ends by the operation of the fan F diffuses ozone, which tends to stay at the ends of the shield member 121, to the central portion of the photosensitive drum.
The air near the peripheral surface of 10 becomes an air flow with the rotation, and the air sucked from the rotation upstream side of the drum surface of the charging device 12 is
After forming a vertical air flow from the front end direction to the rear end direction of the electrode portion 120A of the plate-shaped electrode 120, the ozone component is adsorbed and purified by the ozone filter f through the discharge hole 121A, and the fan F outside the device. Exhausted to.

At this time, the air flow removes ozone and removes and cleans foreign substances such as toner powder, paper powder, and dust adhering to the electrode portion 120A.

If the air sucked from the upstream side of the rotation of the drum surface is discharged to the downstream side of the rotation or is also sucked from the downstream side of the rotation, a vortex of air is generated inside the shield member 121. Since the air flow may be generated and disturb the above-mentioned air flow, the shield member 121 makes the gap with the upstream drum surface larger than the gap with the downstream drum surface, and the value of Δ shown in the drawing is as much as possible. It should be small and close to the drum surface.

Further, FIG. 5B shows that the plate electrode 120 is installed so as to be inclined with respect to the peripheral surface of the photosensitive drum 10 so that the tip of the electrode portion 120A faces a slightly upstream side of rotation of the drum. 1 shows an example of a charging device 12 in which an air flow in a shield member 121 is easily formed along a plate electrode 120.

The above-mentioned shield member 121 has a discharge hole 1 on the upper surface.
21A and a side surface of the drum on the downstream side of the rotation are also provided with an exhaust hole 121A so that the air sucked from the end of the shield member 121 and the upstream side of the rotation of the drum surface 120A of the plate-shaped electrode 120 can be provided. After forming the air flow from the front end direction to the rear end direction, the air flow is divided into the two discharge holes 121A and discharged to the outside of the apparatus.

[0056]

According to the present invention, both the first invention and the second invention form an air flow in the casing member of the charging device to quickly and efficiently remove ozone generated by corona discharge to the outside. The electrode part of the plate-shaped electrode can be cleaned so that the charging device itself has a long life and does not deteriorate the performance of the photoconductor, and can always apply a uniform potential to the photoconductor surface. The device will be provided.

[Brief description of drawings]

FIG. 1 is a vertical configuration diagram of a charging device according to a first invention.

FIG. 2 is a cross-sectional view of the charging device according to the first invention.

FIG. 3 is a perspective view of the charging device according to the first invention.

FIG. 4 is a vertical sectional view of a charging device according to a second invention.

FIG. 5 is a cross-sectional view of the charging device according to the second invention.

FIG. 6 is a perspective view of a charging device according to a second invention.

FIG. 7 is a cross-sectional configuration diagram of the image forming apparatus (A).

FIG. 8 is a cross-sectional configuration diagram of the image forming apparatus (B).

[Explanation of symbols]

 10 Photosensitive drum 12 Charging device (apparatus) 13 Image exposure means (exposure optical system) 14 Developing device 15 Paper feed cassette 17 Timing roller 18 Transfer roller 19 Pointed electrode 20 Fixing device 22 Cleaning device 120 Plate electrode 120A Electrode part 121 Shield member 121A Discharge hole 121B Suction hole 122,123 Support member 124 Grid

Claims (5)

[Claims] 1. A corona discharge type charging device for performing a corona discharge on an object to be charged by a plate electrode having a plurality of sawtooth electrode parts, wherein the charging device includes a support member for supporting the plate electrode and the plate. 2. A charging device comprising a shield member that shields the electrode, and an air flow hole is opened at an end of the charging device. 2. The charging device is configured so that air is taken in through the flow hole opened at one end and exhausted through the flow hole opened at the other end.
The charging device described. 3. The charging device intakes air through the flow holes that are open at both ends and exhausts air through a discharge hole that is open at the center of the casing member.
The charging device described. 4. A corona discharge type charging device for corona-discharging an object to be charged by a plate-shaped electrode having a plurality of sawtooth electrode parts, wherein the charging device faces the moving object to be charged. A charging device, characterized in that an air flow is formed which circulates in the rear end direction from the front end direction of the electrode. 5. The charging device according to claim 4, wherein a tip portion of the plate electrode is inclined along an air flow.