JP2002258583A - Electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an electrifying device. SOLUTION: The electrifying device is installed opposite to the surface of a moving photoreceptor uniformly electrifies the surface of the photoreceptor, and is provided with a gate-shaped conductive case consisting of a top plate, first and second side plates erected in parallel from the top plate and to be mutually opposed, a sawtooth electrode plate for corona discharge supported in parallel with the both side plates between the both side plates inside the case and an insulation plate to cover an inner surface of the second side plate, the case is installed so that the sawtooth electrode plate is orthogonaly crossed with a moving direction of the photoreceptor, the first and second side plates are positioned on the upstream side and the downstream side of the moving direction of the photoreceptor respectively, and a grid electrode plate is provided between the case and the surface of the photoreceptor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charging device,
The present invention mainly relates to a charging device for charging or removing a photosensitive member for forming an image in electrostatic electrophotography. The present invention relates to a charging device which is used for uniformly charging the surface of a photoreceptor by corona discharge in an image forming apparatus such as a copying machine or a printer, and more particularly to a charging device provided with a sawtooth electrode plate for corona discharge.

[0002]

2. Description of the Related Art As is well known, an image forming apparatus using an electrostatic electrophotographic system is composed of process units for charging, exposing, developing, transferring, peeling, cleaning, and discharging.
That is, in the step of recording an image, first, the surface of the rotating photosensitive drum is uniformly charged by the charging device.

[0005] Next, the surface of the charged photosensitive drum is exposed to a light image of an original image via an exposure device to form an electrostatic latent image. Subsequently, toner is electrostatically attached to the electrostatic latent image on the photosensitive drum to form a toner image. Then, the toner image is transferred onto a transfer material by a transfer device, and the toner image on the transfer material is fixed by a heat fixing device. Further, the transfer residual toner remaining on the photoreceptor surface is removed by a cleaning device and collected by a predetermined collecting unit, and the photoreceptor surface after the cleaning is cleaned by a static eliminator to remove residual charges, and is prepared for the next image formation. .

[0004] The photosensitive drum is, for example, an OPC (Organic).
Photo Conductor) as a photoconductive layer on a conductive drum. As a charging device for applying a charge having a predetermined polarity to the surface of the photosensitive drum, a corona discharge device is generally used.

As a charging device utilizing corona discharge, there is known a charging device provided with a saw-tooth electrode plate having a large number of sharp projections in a row, and performing charging by corona discharge from the sharp projections (for example, Japanese Patent Application Laid-Open Publication No. H11-163873). JP-A-60-158582, JP-A-63-14176, JP-A-63-1
No. 5,272, JP-A-63-180977).

[0006]

With the recent miniaturization of the image forming apparatus, each part disposed around the photosensitive drum has been reduced in size and arranged in a narrow space. Here, an exposure unit is arranged downstream of the charging device for charging the surface of the photoconductor drum, and is formed by a discharge voltage from the charging device when the charging device and the exposure device are arranged close to each other. Exposure may be adversely affected by the electric field.

Further, the conventional charging device is for uniformly charging the surface of the photoreceptor drum in the axial direction of the drum by corona discharge, but the charging condition is slightly changed depending on various conditions. When the charging condition changes, uneven charging on the surface of the photosensitive drum occurs, which adversely affects the formed image.

As a simple improvement method for reducing the discharge unevenness, a method of increasing the current flowing through the sawtooth electrode plate is considered. However, increasing the current requires increasing the voltage applied to the sawtooth electrode plate.

When the voltage applied to the sawtooth electrode plate increases, the discharge current increases, so that the amount of ozone generated from the discharge portion increases, which also affects the surface of the photoreceptor drum, leading to a deterioration in the image quality of the original image.

When the amount of generated ozone is increased, nitrogen oxide or silicon oxide is generated by the combination of the ozone and various gases and other foreign substances in the air floating in the image forming apparatus. When this product adheres to the surface of the discharge electrode plate and the surface of the grid electrode plate, the discharge capability of the discharge electrode plate and the charge potential control capability of the grid electrode plate decrease.

Further, in order to prevent a leak discharge caused by an increase in the voltage applied to the sawtooth electrode plate, it is necessary to increase the distance from the discharge portion of the sawtooth electrode plate to the shield case. This leads to an increase in size, that is, an increase in size of the charging device itself.

The present invention has been made in view of such circumstances, and stabilizes corona discharge by a sawtooth electrode plate.
In addition to enabling uniform charging without charging unevenness, it avoids the need to increase the voltage supplied to the sawtooth electrode plate, eliminates problems such as the increase in the size of the device and voltage leaks, and constantly maintains the charging characteristics. An object of the present invention is to provide a stabilizing charging device.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a charging device which is installed to face a surface of a moving photosensitive member and uniformly charges the surface of the photosensitive member. A gate-shaped conductive case composed of first and second side plates facing each other, a sawtooth electrode plate for corona discharge supported between the two side plates in the case in parallel with the two side plates, and an inner surface of the second side plate. An insulating plate, and the case is installed such that the sawtooth electrode plate is orthogonal to the moving direction of the photoconductor, and the first and second side plates are respectively located on the upstream side and the downstream side in the moving direction of the photoconductor. An object of the present invention is to provide a charging device in which a grid electrode plate is provided between the charging device and the photosensitive member surface.

Further, the present invention is a charging device which is installed opposite to the surface of a moving photosensitive member and uniformly charges the surface of the photosensitive member. A gate-shaped case composed of first and second side plates; a sawtooth electrode plate for corona discharge supported in parallel between the two side plates inside the case; the first side plate is made of a conductive material; Are each formed of an insulating material,
The case is installed so that the sawtooth electrode plate is orthogonal to the direction of movement of the photoconductor, and the first and second side plates are located on the upstream and downstream sides in the direction of movement of the photoconductor, respectively. A charging device provided with a grid electrode plate. According to this charging device, since the inner surface of the second side plate of the case is covered with the insulating plate or the second side plate itself is formed of the insulating material, the distance between the first side plate and the discharge electrode plate can be increased. It is possible to stabilize the discharge voltage even if the device is downsized.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A photosensitive member to which the present invention is applied
Including drum and belt shapes. In the present invention,
As the material of the first and second side plates and the top plate, for example, stainless steel, aluminum, or the like can be used. Also,
For example, an ABS resin, a polycarbonate resin, or the like is used as an insulating plate that covers the inner surface of the second side plate or an insulating material that forms the second side plate. As the material of the sawtooth electrode plate for corona discharge, for example, stainless steel is used, and as the material of the grid electrode plate, stainless steel, beryllium copper alloy, or the like can be used.

The case may be formed in a U-shape integrally with the same conductive material, and an insulating plate may be provided on the inner surface of the second side plate. Alternatively, the first side plate and the top plate may be integrally formed of the same conductive material and have a L shape. The second side plate may be formed of an insulating plate.

The sawtooth electrode plate for corona discharge may be installed so that the distance from the first side plate is different from the distance from the second side plate. In addition, it is preferable that the sawtooth electrode plate is installed such that the distance from the first side plate is larger than the distance from the second side plate. As a result, the distance between the first side plate and the sawtooth electrode plate can be increased, so that a structure equivalent to a structure in which the case is enlarged can be obtained, and the discharge voltage can be stabilized. Can be reduced in size.

Further, the charging device of the present invention is provided near the photosensitive drum of the image forming apparatus such that the first side plate is located upstream in the rotation direction of the photosensitive drum and the second side plate is located downstream. Preferably. As a result, the electric field generated on the downstream side in the rotation direction of the photosensitive drum can be suppressed, and the influence of the charging electric field on the exposure device can be prevented.

Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. This does not limit the present invention.
FIG. 1 is a sectional view showing an embodiment of the charging device of the present invention. In the figure, a charging device 1a includes a shield case 1
The shield case 1 is integrally formed in a U-shape from a top plate 2 and a first side plate 3 and a second side plate 4 which stand upright from the top plate 2 and face each other.

Inside the shield case 1, both side plates 3, 4
Sawtooth electrode plate 5 for corona discharge in parallel with both side plates 3 and 4
And a grid electrode plate 6 is provided outside the shield case 1 in a direction orthogonal to the discharge electrode plate 5.

The first and second side plates 3, 4 and the top plate 2 are made of a conductive material such as stainless steel.
The inner surface of the top plate 2 is covered with an insulating plate 7 made of ABS resin. The insulating plate 7 has a projection 7a, and the sawtooth electrode plate 5 is screwed to the projection 7a by a screw 8 made of resin.

FIG. 3 is a perspective view showing the sawtooth electrode plate 5 for corona discharge. The sawtooth electrode plate 5 is made of a stainless steel (SUS304) plate having a thickness of 0.1 mm, and a screw hole 5a is provided on the upper part. And a plurality of discharge projecting electrodes 5b at the lower end.
They are arranged in a sawtooth pattern at a pitch of about 5 mm. The protruding electrode 5b is formed by etching, and the pointed tip has a radius of about 30 to 40 μm.

As shown in FIG. 1, the grid electrode plate 6 provided outside the shield case 1 has a structure as shown in FIG. 7 and is made of a 0.1 mm thick stainless steel plate.
It has a mesh formed by etching and having a mesh width of 1 mm.

FIG. 2 is a sectional view showing another embodiment of the present invention. In this charging device 1b, the side plate 4 is removed from the shield case 1a shown in FIG. 1, and the insulating plate 7 is used as the second side plate 4. ing. The other structure is the charging device 1a shown in FIG.
Is equivalent to

In the embodiment shown in FIGS. 1 and 2,
Spacing L1 between first side plate 3 and sawtooth electrode plate 5 and sawtooth electrode plate 5
The sawtooth electrode plate 5 is arranged such that the relation between the distance L2 and the insulating plate 7 satisfies L1 ≧ L2.

FIG. 6 is an explanatory view of the configuration of a copying machine equipped with the charging device of the above embodiment. In FIG.
Reference numeral 1 denotes a document table 22, a copy lamp 23, a first mirror 24, a second mirror 25, a third mirror 26, a lens 27, a fourth mirror 28, a fifth mirror 29, and a sixth mirror. Mirror 30, photosensitive drum 31, charging charger 32, developing tank 33, transfer charger 34, cleaner device 35, blade 36, and transport belt 37
Fixing device 38, paper cassettes 39 and 40,
A discharge roller 41 and a display panel 42 are provided.

Copy lamp 23, first mirror 24, second
The mirror 25 and the third mirror 26 are movable in parallel (in the direction of arrow C) along the document table 22. The light 43 emitted from the copy lamp 23 is
2, the first mirror 24, the second mirror 25, the third mirror 26, the lens 27, the fourth mirror 2
8, a photosensitive drum 31 previously charged by a charging charger 32 via a fifth mirror 29 and a sixth mirror 30
To the exposure point P on the surface of. By this irradiation, an electrostatic latent image is formed on the surface of the photosensitive drum 31.

The electrostatic latent image formed on the surface of the photosensitive drum 31 is developed into a toner image by a developing tank 33, and the toner image is transferred onto a sheet supplied from a sheet cassette 39 or 40 by a transfer charger 34. Is transcribed.

The transferred sheet is conveyed to a fixing device 38 by a conveyance belt 37, and the fixing device 38
After the toner image is fixed on the sheet, the sheet is discharged to the outside by discharge rollers 41.

On the other hand, the residual toner is scraped off by the blade 36 from the surface of the photosensitive drum 31 after the transfer of the toner image, and the toner is collected by the cleaner device 35.

The charging device shown in FIGS. 1 and 2 is used as the charging charger 32 shown in FIG. In this case, as shown in FIG. 4 or FIG. 5, the first side plate 3 of the shield case 1 a or 1 b is moved upstream of the photosensitive drum 31 rotating in the direction of arrow A, The side plates 4 (or the insulating plates 7) are located on the downstream side of the rotation, and the grid electrode plates 6 are interposed between the electrode plates 5 and the photosensitive drums 31.

During image formation, a DC voltage E1 is applied to the sawtooth electrode plate 5, a DC voltage E2 is applied to the grid electrode plate 6, and a DC voltage E3 is applied to the first side plate 3. The surface potential of the photosensitive drum 31 is set to E0.

An example of the size is as follows. E1 = −6 kV to −3 kV, usually using about −5 kV. E2 = -800V to -600V E3 = -600V to -400V E0 = -800V to -600V

In each of the charging devices shown in FIGS. 1 and 2 of the present invention, an insulating side plate is disposed downstream of the photosensitive drum 31 in the rotation direction. Therefore, the electric field generated by the discharge electrode plate 5 becomes weaker on the downstream side where the insulating side plate is arranged, and becomes stronger on the upstream side where there is no insulating member. For this reason, even if the exposure device is arranged downstream of the charging device and close to the charging device, the influence of the charging electric field on the exposure process is suppressed.

The discharge electrode plate 5 includes first and second electrodes.
By arranging the side plates 3 and 4 not at the center (L1 = L2) but near the second side plate 4 (L1> L2), the generated electric field on the downstream side in the rotation direction of the rotating drum 31 is reduced. Further suppression is possible. In addition, since a structure equivalent to a structure in which the shield case is enlarged can be obtained, the discharge voltage can be stabilized even if the shield case is downsized.

[0036]

According to the present invention, since the inner surface of the second side plate of the case is covered with the insulating plate or the second side plate itself is formed of the insulating plate, it can be used as a charging device for the photosensitive member of the image forming apparatus. When used, by disposing the first side plate on the upstream side in the rotation direction of the photosensitive drum and the second side plate on the downstream side, the discharge voltage is stabilized, and the size of the charging device can be reduced. At the same time, the electric field generated by the charging device is weakened on the downstream side, so that the influence of the electric field on the exposure step adjacent to the downstream side is suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a charging device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a charging device according to another embodiment of the present invention.

FIG. 3 is a perspective view showing a sawtooth electrode plate for corona discharge used in Examples.

4 is a layout diagram of the charging device shown in FIG. 1 with respect to a photosensitive drum.

5 is a layout diagram of the charging device shown in FIG. 2 with respect to a photosensitive drum.

FIG. 6 is a diagram illustrating the configuration of a copying machine in which the charging device of the present invention is installed.

FIG. 7 is a plan view of the grid electrode plate of the embodiment shown in FIG.

[Explanation of symbols]

 1a Shield case 2 Top plate 3 First side plate 4 Second side plate 5 Sawtooth electrode plate 6 Grid electrode plate 7 Insulation plate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Eiichi Kido, Inventor 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture F-term (reference) 2H200 FA18 HA12 HA28 HB06 HB26 HB30 HB45 HB48 MA01 MA05 NA02

Claims (8)

[Claims] 1. A charging device which is installed opposite to a surface of a moving photoconductor and uniformly charges the surface of the photoconductor, wherein a first plate and a first plate which are erected in parallel from the top plate and face each other are provided. A gate-shaped conductive case consisting of two side plates, a sawtooth electrode plate for corona discharge supported in parallel between the two side plates between the two side plates inside the case, and an insulating plate covering an inner surface of the second side plate,
The case is installed so that the sawtooth electrode plate is orthogonal to the moving direction of the photoreceptor, and the first and second side plates are respectively located on the upstream side and the downstream side in the moving direction of the photoreceptor. Charging device provided with a grid electrode plate. 2. A saw-tooth electrode plate having a distance from a first side plate of a second side plate.
The charging device according to claim 1, wherein the charging device is installed so as to have a different distance from the side plate. 3. The saw-tooth electrode plate has a distance from the first side plate of the second side plate.
The charging device according to claim 1, wherein the charging device is installed so as to be larger than a gap between the charging device and the side plate. 4. The charging device according to claim 1, wherein the case comprises a U-shaped case integrally formed of the same conductive material. 5. A charging device which is installed opposite to a surface of a moving photosensitive member and uniformly charges the surface of the photosensitive member, comprising: a top plate; A gate-shaped case composed of two side plates, and a sawtooth electrode plate for corona discharge supported between the both side plates in the case in parallel with the both side plates, wherein the first side plate is made of a conductive material and the second side plate is made of an insulating material. Each case is formed, and the case is installed so that the sawtooth electrode plate is orthogonal to the moving direction of the photoconductor, and the first and second side plates are respectively located on the upstream side and the downstream side in the moving direction of the photoconductor. A charging device provided with a grid electrode plate between the surface of the photoreceptor. 6. The charging device according to claim 1, wherein the saw-tooth electrode plate is provided such that a distance from the first side plate is different from a distance from the second side plate. 7. The sawtooth electrode plate has a distance from the first side plate of the second side plate.
The charging device according to claim 1, wherein the charging device is installed so as to be larger than an interval between the side plates. 8. The charging device according to claim 1, wherein the top plate and the first side plate are L-shaped members integrally formed of the same conductive material.