JPH1184817A - Corona discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corona discharge device constituted so that a photoreceptor can be sufficiently and uniformly electrified while increasing the circumferential speed of the photoreceptor. SOLUTION: This device is provided with a metallic shield case 27c having an aperture part for discharge opened toward the photoreceptor 1, two corona wires 27a and 27b laid in the width direction of the photoreceptor 1 in the case 27c and a control grid plate 27d fitted to the aperture part of the case 27c by giving a prescribed gap between the wires 27a and 27b. Besides, a distance between the wire 27a on an upstream side in the advancing direction of the photoreceptor 1 and the side wall of the case 27c is defined as L2, a distance between the wire 27b on a downstream side and the side wall of the case 27c is defined as L3, a distance between the wire 27a and the plate 27b is defined as L4 and a distance between the wire 27b and the plate 27d is defined as L5. Then, they are arranged so as to satisfy the relation of L2=L3>L5>L4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge device generally used in an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus.

[0002]

2. Description of the Related Art In electrophotographic apparatuses, equipment using dry toner occupies the mainstream, and many copiers, laser printers,
It has been put to practical use as plain paper facsimile, etc., and has achieved remarkable development. The electrophotographic apparatus is an apparatus to which an electrophotographic process technology is applied, and visualizes an electrostatic latent image formed on a photoreceptor with toner particles.

FIG. 4 is a sectional view of a conventional corona discharge device. As shown in FIG. 4, in a conventional electrophotographic apparatus, a corona discharge device 2 is provided near a photoreceptor 1 of an image forming apparatus having a metal drum as a base material and a photosensitive receiving layer formed on an outer peripheral surface thereof. It is arranged. This corona discharge device 2
Is a metal shield case 2b having an opening formed toward the photoreceptor 1, a corona wire 2a stretched in the width direction of the photoreceptor 1 (a direction perpendicular to the paper surface) in the shield case 2b, and an opening. And a control grid plate 2c attached to the section. And the corona wire 2a
The photoreceptor 1 is uniformly charged by the corona discharge.

When an image signal is light-intensity-modulated or pulse-width-modulated by a laser driving circuit (not shown) and irradiated with an exposure light beam 4 obtained from an exposure optical system 3, the photosensitive member 1 1 is exposed, and a predetermined electrostatic latent image is formed on the outer peripheral surface of the photoconductor 1.

Here, in an image forming apparatus including an electrophotographic apparatus, recently, in order to improve work efficiency and cope with large-volume printing, it is required to improve a printing speed. To meet this demand, it is necessary to increase the peripheral speed of the photoconductor 1.

[0006]

However, in such an electrophotographic apparatus, if the peripheral speed of the photosensitive member 1 is increased, it is not possible to secure a sufficient time for the photosensitive member 1 to pass through the opening of the corona discharge device 2. . Then, problems such as lowering of charging efficiency and occurrence of discharge unevenness occur, and there is a problem that image quality is deteriorated.

Accordingly, an object of the present invention is to provide a corona discharge device capable of sufficiently and uniformly charging a photosensitive member while increasing the peripheral speed of the photosensitive member.

[0008]

According to the present invention, there is provided a corona discharge device comprising: a shield case having an opening opening toward a photoreceptor on which an electrostatic latent image is to be formed; Two corona wires stretched,
A control grid plate attached to the opening at a predetermined distance from the corona wire, wherein a distance between the corona wire of the two corona wires on the upstream side in the traveling direction of the photoconductor and the side wall of the shield case is L2. Controlling the distance between the corona wire on the downstream side in the traveling direction of the photoconductor of the two corona wires and the side wall of the shield case to L3, the corona wire on the upstream side in the traveling direction of the photoconductor among the two corona wires; Assuming that the distance from the grid plate is L4 and the distance between the corona wire of the two corona wires and the corona wire on the downstream side in the traveling direction of the photoconductor and the control grid plate is L5, the relationship of L2 = L3>L5> L4 is satisfied.

With this configuration, it is possible to realize a corona discharge device that can sufficiently and uniformly charge the photosensitive member while increasing the peripheral speed of the photosensitive member.

[0010]

According to a first aspect of the present invention, there is provided a corona discharge device comprising: a shield case having an opening opening toward a photoconductor on which an electrostatic latent image is formed; Two corona wires stretched,
A control grid plate attached to the opening at a predetermined distance from the corona wire, wherein a distance between the corona wire of the two corona wires on the upstream side in the traveling direction of the photoconductor and the side wall of the shield case is L2. Controlling the distance between the corona wire on the downstream side in the traveling direction of the photoconductor of the two corona wires and the side wall of the shield case to L3, the corona wire on the upstream side in the traveling direction of the photoconductor among the two corona wires; Assuming that the distance from the grid plate is L4 and the distance between the corona wire of the two corona wires and the corona wire on the downstream side in the traveling direction of the photoconductor and the control grid plate is L5, the relationship of L2 = L3>L5> L4 is satisfied.

In the corona discharge device according to the present invention, if the distance between the two corona wires is L1, L1> L2 =
The relationship of L3 is satisfied.

In the corona discharge device according to the third aspect, when the distance between the control grid plate and the photosensitive member is L6, 1 mm <
The relationship of L6 <3 mm is satisfied.

According to a fourth aspect of the present invention, the diameter of the corona wire of the two corona wires on the upstream side in the traveling direction of the photoreceptor is φ1, and the diameter of the two corona wires is the downstream of the two corona wires in the traveling direction of the photoreceptor. If the diameter of the corona wire on the side is φ2, the relationship of φ1> φ2 and 40 μm <φ2 <80 μm is satisfied.

According to a fifth aspect of the present invention, the control grid plate is divided at the center of the photosensitive member in the traveling direction, and the opening of the control grid plate on the upstream side in the traveling direction of the photosensitive member among the divided control grid plates. Assuming that the ratio is R1 and the opening ratio of the downstream control grid plate is R2, 0.4 <R2 / R1 <0.
8 are satisfied.

According to these configurations, the photosensitive member can be charged sufficiently and uniformly while increasing the peripheral speed of the photosensitive member, and high image quality can be obtained even when the printing speed is increased.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic diagram of an image forming apparatus using a corona discharge device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the corona discharge device according to Embodiments 1 to 4 of the present invention. It is.

As shown in FIG. 1, the image forming apparatus according to the present embodiment is an electrophotographic apparatus for visualizing an electrostatic latent image formed on a photoreceptor 1 by electrophotographic process technology with toner particles. The photoreceptor 1 is formed by using a metal drum such as aluminum as a base material and applying a photosensitive receiving layer such as selenium (Se) or an organic photoconductor in a thin film on the outer peripheral surface.

A corona discharge device 27 is provided near the photosensitive member 1 as an electrostatic latent image carrier. As shown in detail in FIG. 2, the corona discharge device 27 includes a shield case 2 having an opening that
7c. A first corona wire 27a located on the upstream side in the rotation direction (progressing direction) of the photoconductor 1 is provided in a shield case 27c made of a metal conductive member;
The second corona wire 27b located on the downstream side is stretched in the width direction of the photoconductor 1, respectively. In the present embodiment, the first and second corona wires 27a, 27
b is made of tungsten and has a diameter of 60 μm.
It has become. However, other diameters may be used. In addition, the first and second corona wires 27a, 27
A control grid plate 27d is attached to the opening of the shield case 27c on which b is stretched.

As shown in FIG. 1, the first and second corona wires 27a and 27b are provided with a corona current supply power supply 28.
Are connected, and a grid bias voltage supply power supply 29 is connected to the control grid plate 27d. Here, the corona current supply power supply 28 outputs a current of about -1 mA,
The grid bias voltage supply power supply 29 outputs a voltage of -650 V. Thus, the first and second corona wires 27a and 27b generate corona discharge, and the photoconductor 1 is uniformly charged via the control grid plate 27d.

Further, in the vicinity of the photoreceptor 1, an exposure light 4 for irradiating the photoreceptor 1 with an exposure light beam 4 obtained by subjecting an image signal to light intensity modulation or pulse width modulation by a laser driving circuit (not shown). System 3 is installed. Then, the photoconductor 1 is exposed by the exposure light beam 4 to form a predetermined electrostatic latent image.

The toner 1 agitated and transported by a toner agitating member 11 rotatably supported at both ends by a developing hopper 9.
0 is supplied to the surface of the developing roller 5 which is a toner carrier, and a toner supply roller 6 is provided to scrape off the toner 10 on the developing roller 5 which has not been developed and remains. The toner supply roller 6 has a resistance value of 1 formed by forming a conductive foam around a metal shaft 6a.
The toner supply bias voltage supply power supply 26, which is a constant voltage power supply, is connected to the shaft 6a.

The developing roller 5 has a single-layer structure in which a metal shaft 5a is used as a base material and silicon rubber as a conductive elastic member is formed on an outer peripheral surface thereof, and has a resistance value of about 106Ω. The rubber hardness of the developing roller 5 is 30 to 6
The surface roughness is preferably not more than 7 μmRz, because the range of 0 ° is preferable, and the higher the surface smoothness, the more uniform the formation of the thin toner layer can be achieved. Here, the developing roller 5
Has a rubber hardness of 40 degrees and a surface roughness of 3 μmRz. A developing bias voltage supply power supply 12 which is a constant voltage power supply is connected to the shaft 5 a of the developing roller 5. Further, the toner 10 is a non-magnetic one-component toner, and is made of a polyester resin in which carbon, wax, a charge control agent and the like are uniformly dispersed.

The developing roller 5 and the toner supply roller 6 are
They are arranged so as to be in contact with each other, and have a nip width of, for example, about 2 mm. At both ends of the developing hopper 9, the developing hopper 9 is rotatably supported by shafts 5a and 6a, respectively. As shown in the figure, the developing roller 5 and the photoreceptor 1 come into contact with each other and rotate in opposite directions.
The developing roller 5 and the toner supply roller 6 come into contact with each other and rotate in the same direction. Therefore, the developing roller 5 and the toner supply roller 6 are in frictional contact.

The developing roller 5 is in contact with or close to the photosensitive member 1, and an electrostatic latent image on the photosensitive member 1 is formed by a bias voltage applied from a developing bias voltage supply power supply 12. When the toner 10 is transferred and adhered to the portion, the electrostatic latent image is visualized.

The toner stirring member 11 draws a circular locus with the rotation of the toner supply roller 6 to prevent the toner 10 accommodated in the developing hopper 9 from aggregating, and to transfer the toner 10 toward the toner supply roller 6. Transport.

A toner regulating blade 7 is provided in contact with the developing roller 5. This toner regulating blade 7
An elastic metal spring plate member 7a such as a stainless steel plate or a phosphor bronze plate and a toner regulating member 7 which comes into contact with the developing roller 5
b. The toner regulating member 7b is a metal spring plate member 7.
An elastic member such as urethane rubber or silicone rubber having a rubber hardness of 60 degrees is integrally formed at one end of the member a. Such a toner regulating blade 7 is screwed to a blade holder 8. The toner regulating blade 7a controls the developing roller 5 by, for example, a linear pressure of 80 g / c.
m, the toner 10 supplied from the toner supply roller 6 to the developing roller 5 is frictionally charged by the toner regulating blade 7, and a thin toner layer is formed on the outer peripheral surface of the developing roller 5. You. In the non-magnetic one-component contact developing system as in the present embodiment, the toner layer on the developing roller 5 preferably has a range of 0.4 to 0.6 mg / cm 2.

Sheets 15 are stored in a sheet cassette 14 provided at the starting point of the transport path. This paper 15
Are fed one by one from the paper cassette 14 to the transport roller 17 by a half-moon shaped paper feed roller 16. Then, the fed recording sheet 15 is nipped by a pair of transport rollers 17 and transported in the direction of the photoconductor 1 as indicated by arrow A.

In order to temporarily stop the paper 15 and make the paper 15 coincide with the toner image formed on the photoreceptor 1, a driven roller 19 is provided on a transport path before reaching the photoreceptor 1. A registration roller 18 is provided in contact therewith. Further, a transfer roller 20 is provided so as to be rotatably supported in contact with the photoconductor 1. The transfer roller 20 is made of a metal such as stainless steel as a base material, and an elastic member is formed in a layer on an outer peripheral surface thereof.

When the toner image reaches the contact portion between the transfer roller 20 and the photosensitive member 1 with the rotation of the photosensitive member 1, the paper 15 is also brought into contact with the toner image by the registration roller 18 in timing. Reach the department. At this time, by applying a high voltage from the transfer bias power supply 24 to the metal shaft 20a of the transfer roller 20, the paper 1
When a charge having a polarity opposite to that of the toner 10 is applied to the back surface of the toner 5, the toner image on the photoconductor 1 is transferred onto the paper 15.

A fixing device 21 including a heat roller 22 having a heat source therein and a pressure roller 23 for nipping and conveying the sheet 15 together with the heat roller 22 is provided at a stage subsequent to the conveyance path. Therefore, the paper 15 on which the toner image has been transferred is sent to the fixing device 21, where the toner image is fixed by pressure and heat by the sandwiching rotation of the heat roller 22 and the pressure roller 23. On the other hand, the photoreceptor 1 after the toner image has been transferred onto the paper 15 has the transfer residual toner scraped off by the cleaning blade 25, and is irradiated with light by the static eliminator 13 to be neutralized, thereby preparing for the next process.

Using the electrophotographic apparatus configured as described above, the distance L4 between the first corona wire 27a and the control grid plate 27d shown in FIG. 2 is changed from 6 mm to 12 mm, and the second corona wire 27b And control grid plate 2
The printing operation was performed while changing the distance L5 from 7d to 3 mm to 15 mm, the charging efficiency was evaluated from the charging potential on the surface of the photoreceptor 1, and the charging unevenness was evaluated from the image. Evaluation is ○,
A three-level evaluation of Δ and × was made.

The distance L1 between the first corona wire 27a and the second corona wire 27b, the distance L2 between the first corona wire 27a and the side wall of the shield case 27d, the second corona wire 27b and the shield case 27d. The distance L3 to the side wall was set to 10 mm.

The process speed is 200 mm / sec.
c, the peripheral speed of the developing roller 5 was 280 mm / sec, and the peripheral speed of the toner supply roller was 192 mm / sec. The results of the evaluation are shown in Table 1.

[0034]

[Table 1]

As is clear from Table 1, when the relationship of L2 = L3>L5> L4 was satisfied in FIG. 2, the photosensitive member 1 was sufficiently and uniformly charged. In addition,
In the present embodiment, the first and second corona wires 27a, 27
Although the photoconductor 1 is negatively charged by applying a negative current to 7b, the same can be applied to the case of positive charging.

(Embodiment 2) In this embodiment, the voltages applied by the power supplies 28 and 29, the wire diameter, the developing roller 5,
Toner supply roller 6, toner regulating blade 7, toner 1
0, the characteristics of the transfer roller 20, the process speed, the peripheral speed of the developing roller 5, and the peripheral speed of the toner supply roller 6
This is the same as in the first embodiment.

Using the electrophotographic apparatus having the above configuration, L4 shown in FIG.
From 6 mm to 14 mm, L2 and L3 from 8 mm to 1
The printing operation was performed while changing the distance to 2 mm, the charging efficiency was evaluated from the charging potential on the surface of the photoconductor 1, and the charging unevenness was evaluated from the image. The evaluation was a three-level evaluation of ○, Δ, and ×. The results are shown in (Table 2).

[0038]

[Table 2]

As is clear from Table 2, when the relationship of L1> L2 = L3 is satisfied in FIG.
Was sufficiently and uniformly charged. In the present embodiment, the photoconductor 1 is negatively charged by applying a negative current to the first and second corona wires 27a and 27b.
The same applies to the case of positive charging.

(Embodiment 3) Also in this embodiment, the voltages applied by the power supplies 28 and 29, the wire diameter, the developing roller 5, the toner supply roller 6, the toner regulating blade 7,
The characteristics and the like of the toner 10 and the transfer roller 20, the process speed, the peripheral speed of the developing roller 5, and the peripheral speed of the toner supply roller 6 are the same as those in the first embodiment.

Using the electrophotographic apparatus having the above configuration, L1, L2 and L3 shown in FIG.
Is 8 mm, L5 is 9 mm, and L6 is 0.5 mm to 4 mm.
mm, the printing operation was performed, the charging efficiency was evaluated from the charging potential on the surface of the photoreceptor 1, and the charging unevenness was evaluated from the image. The evaluation was a three-level evaluation of ○, Δ, and ×. The results are shown in (Table 3).

[0042]

[Table 3]

As is clear from Table 3, when the relationship of 1 mm <L6 <3 mm was satisfied in FIG. 2, the photosensitive member 1 was sufficiently and uniformly charged. In the present embodiment, the first and second corona wires 27
The photosensitive member 1 is negatively charged by applying a negative current to the terminals a and 27b. However, the present invention can be similarly applied to the case of positive charging.

(Embodiment 4) Also in this embodiment, the voltages applied by the power supplies 28 and 29, the wire diameter, the developing roller 5, the toner supply roller 6, the toner regulating blade 7,
The characteristics and the like of the toner 10 and the transfer roller 20, the process speed, the peripheral speed of the developing roller 5, and the peripheral speed of the toner supply roller 6 are the same as those in the first embodiment.

Using the electrophotographic apparatus having the above structure, L1, L2 and L3 shown in FIG.
8 mm and L5 9 mm, the first corona wire 2
7a diameter φ1 was changed from 40 μm to 100 μm,
The diameter φ2 of the second corona wire 27b is increased from 30 μm to 10
The printing operation was performed while changing the thickness to 0 μm, the charging efficiency was evaluated from the charging potential on the surface of the photoconductor 1, and the charging unevenness was evaluated from the image. The evaluation was a three-level evaluation of ○, Δ, and ×. The results are shown in (Table 4).

[0046]

[Table 4]

As is clear from (Table 4), φ1> φ2
When the relationship of 40 μm <φ2 <80 μm was satisfied, the photosensitive member 1 was sufficiently and uniformly charged.
In the present embodiment, the photoconductor 1 is negatively charged by applying a negative current to the first and second corona wires 27a and 27b. However, the present invention can be similarly applied to the case of positive charging.

(Embodiment 5) FIG. 3 is a sectional view of a corona discharge device according to Embodiment 5 of the present invention. Also in this embodiment, the voltages applied by the power supplies 28 and 29, the wire diameter, the characteristics of the developing roller 5, the toner supply roller 6, the toner regulating blade 7, the toner 10, the transfer roller 20, and the like, the process speed, and the peripheral speed of the developing roller 5 The peripheral speed of the toner supply roller 6 is the same as that of the first embodiment. Here, as shown in FIG. 3, the control grid plate 27d is divided at the central portion in the traveling direction of the photoconductor 1, and the aperture ratio is different between the upstream side and the downstream side in the traveling direction of the photoconductor 1. .

Using the electrophotographic apparatus having the above structure, L1, L2 and L3 shown in FIG.
Is 8 mm and L5 is 9 mm, and the aperture ratio R1 of the control grid plate 27d on the upstream side in the photoconductor traveling direction is from 60% to 8
0%, the printing operation is performed by changing the aperture ratio R2 of the downstream control grid plate d from 18% to 72%, and the charging efficiency is evaluated from the charging potential on the surface of the photoconductor 1,
The charging unevenness was evaluated from the image. The evaluation was a three-level evaluation of ○, Δ, and ×. The results are shown in (Table 5).

[0050]

[Table 5]

As is clear from Table 5, the control grid plate 27d is divided at the center of the photosensitive member 1 in the traveling direction.
Assuming that the opening ratio of the upstream side of the photoconductor 1 in the traveling direction is R1 and the opening ratio of the downstream side is R2, when the relationship of 0.4 <R2 / R1 <0.8 is satisfied, the photoconductor 1 can be sufficiently and sufficiently. It was possible to charge uniformly.

In the present embodiment, the first and second
A negative current is applied to the corona wires 27a and 27b to charge the photoconductor 1 negatively. However, the same can be applied to the case of positive charging. In the above description, an example in which the corona discharge device according to the present invention is applied to an electrophotographic device has been described. However, the present invention can be widely applied to various image forming devices such as an electrostatic recording device.

[0053]

According to the corona discharge device of the present invention, the photosensitive member can be charged sufficiently and uniformly while increasing the peripheral speed of the photosensitive member. In addition, by configuring an image forming apparatus using such a corona discharge device, high image quality can be obtained even when the printing speed is increased.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus using a corona discharge device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a corona discharge device according to Embodiments 1 to 4 of the present invention.

FIG. 3 is a sectional view of a corona discharge device according to a fifth embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional corona discharge device.

[Explanation of symbols]

 Reference Signs List 1 photoreceptor 27a first corona wire 27b second corona wire 27c shield case 27d control grid plate

Claims (5)

[Claims] A shield case having an opening opening toward a photosensitive member on which an electrostatic latent image is formed; and two corona wires stretched in a width direction of the photosensitive member in the shield case. A control grid plate attached to the opening at a predetermined distance from the corona wire, wherein the corona wire of the two corona wires on the upstream side in the traveling direction of the photoconductor and the shield case are provided. The distance from the side wall to the side wall is L2, the distance between the corona wire of the two corona wires on the downstream side in the traveling direction of the photoconductor and the side wall of the shield case is L3, and the photoconductor of the two corona wires is the photoconductor. The distance between the corona wire on the upstream side in the traveling direction of the photoconductor and the control grid plate is L4, and the corona wire on the downstream side in the traveling direction of the photoconductor out of the two corona wires and the control grid plate. When the distance between the head plate and L5, L
A corona discharge device characterized by satisfying a relationship of 2 = L3>L5> L4. 2. The corona discharge device according to claim 1, wherein a relationship of L1> L2 = L3 is satisfied when a distance between the two corona wires is L1. 3. The corona discharge device according to claim 1, wherein a relationship of 1 mm <L6 <3 mm is satisfied when a distance between the control grid plate and the photoconductor is L6. 4. A corona wire having a diameter of φ1 and an upstream corona wire of the two corona wires in a traveling direction of the photoconductor.
Assuming that the diameter of the corona wire on the downstream side in the traveling direction of the photoconductor among the corona wires is φ2, φ1> φ2 and 4
2. The corona discharge device according to claim 1, wherein a relationship of 0 [mu] m <[phi] 2 <80 [mu] m is satisfied. 5. The control grid plate is divided at a central portion in the traveling direction of the photoconductor, and among the divided control grid plates, the aperture ratio of the control grid plate on the upstream side in the traveling direction of the photoconductor is defined as R1 and downstream. 2. The corona discharge device according to claim 1, wherein the relationship of 0.4 <R2 / R1 <0.8 is satisfied, where R2 is the aperture ratio of the control grid plate on the side.