JP2555866B2 - Electrophotographic charging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic charging device used in a copying machine or a printer to which an electrophotographic process is applied.

[0002]

2. Description of the Related Art Conventionally, a corotron charging device as shown in FIGS. 4 and 5 is generally used in an electrophotographic apparatus such as an electrophotographic copying machine. In the charging device, insulating blocks b are provided at both ends of a shield case a having a substantially U-shaped cross section.
And a discharge wire c is stretched between the insulating blocks b so as to be located substantially in the center of the shield case a. The discharge wire c has ± 4000 to ± 80.
When a high voltage of 00V is applied, a corona discharge is generated between the photoreceptor and the charge acceptor d, and the ions generated by this corona discharge adhere to the charge acceptor d and It is designed to be charged. In addition, the shield case a surrounding the discharge wire c has a function of maintaining a constant spatial distance from the discharge wire c to strengthen and stabilize the electric field formed on the surface of the discharge wire c. There is.

However, the charging device constructed as described above requires a special device to stretch the discharge wire c having a small mechanical strength between the insulating blocks b, resulting in a high cost and a high cost. Since the discharge wire c is easily broken due to vibration during use, it is necessary to replace the discharge wire c often, and maintenance is troublesome. Another problem is that a current also flows through the shield case a in addition to the charge acceptor d during discharge, so that the discharge current increases, resulting in an increase in the size of the high-voltage power supply and an increase in the price. There is also a problem that the amount becomes large and causes pollution of the surrounding environment.

Further, in order for the charging device to operate stably, the discharge wire c, the shield case a, and the charge acceptor d.
Need enough distance to. That is, the ionization region of the corona discharge is in the range from the surface of the discharge wire c to at most 1 to several μm in the radial direction, and the space other than this region to the shield case a and the charge acceptor d is the space of the air during discharge. Ionization does not occur, and only the ions in one direction have a drift region, which has a higher spatial impedance than the ionization region. A stable corona discharge can be maintained only when the drift region has a sufficient distance. But the charging device in an attempt to more compact, or closer Kesugi the discharge wire c to the charge receptor d, discharge wire c
When the distance from the shield case a to the shield case a is reduced, the ionization region is expanded and the spatial impedance is reduced. As a result, a spark discharge is generated and the charge acceptor d is damaged. There was also a limit.

On the other hand, another charging device is disclosed in Japanese Patent Laid-Open No. 60-2.
Japanese Patent Laid-Open No. 54172 and Japanese Patent Laid-Open No. 58-76851 disclose a device using an electrode in which a conductive coating layer is formed on the surface of a conductor. However, in the case where a conductive coating layer is provided like those disclosed in these publications, since the coating layer is formed by coating a resin or the like, it is possible to make the coating layer uniform in thickness and obtain surface flatness. Have difficulty. In particular, when air bubbles are generated in the coating layer during resin application, the air bubbles impair the flatness of the surface, and the air bubbles easily discharge due to the thin film thickness of the air bubbles, resulting in uniform discharge. At the same time, the coating layer is destroyed by the abnormal discharge and the conductor is exposed, and a spark is generated between this conductor and the charge receptor to damage the charge receptor, or the abnormal discharge proceeds further from the damaged part. However, there was a problem that the life of the coating layer was shortened at an early stage. In order to improve such a problem, a solid electrode plate is formed by a plate-shaped electric resistor, a plate-shaped voltage application electrode is attached to the first surface of the solid electrode plate, and the second surface of the solid electrode plate is A charging device for electrophotography, which is opposed to a charge acceptor with a gap, has been proposed.

[0006]

However, when the solid electrode plate is installed as it is facing the charge acceptor with a gap therebetween, even if the solid electrode plate is accurately installed, the solid electrode plate is twisted or warped. If so, the gap between the solid electrode plate and the charge receptor changes, and as a result, the charge receptor cannot be uniformly charged. The present invention has been made in order to improve such a conventional problem. By regulating the twisting and warping of the solid electrode plate, it is possible to maintain a uniform distance between the solid electrode plate and the charge acceptor. It is an object of the present invention to provide a photographic charging device.

[0007]

In order to achieve the above object, the present invention provides a solid electrode plate with a plate-like electric resistor having a volume resistance of 10 ⁶ to 10 ¹³ Ωcm and a surface resistance of 10 ⁶ Ω or more. In a charging device for electrophotography, which is formed by laminating a plate-shaped voltage applying electrode on the first surface of the solid electrode plate, the end portion of the solid electrode plate is restricted from twisting or warping. It is fitted in a fitting groove provided in the insulating solid electrode support.

[0008]

[Operation] Since the insulating solid electrode support regulates the twisting and warping of the solid electrode plate by the above structure, the gap between the solid electrode plate and the charge acceptor can always be kept uniform.

[0009]

EXAMPLE FIG. 1 is a basic configuration diagram of the charging device of the present invention and its application as charging means. In this figure, 1 is a solid electrode plate of a plate-shaped high electrical resistance body having a volume resistivity of 10 ⁶ to 10 ¹³ Ωm, and 2 is a plate-shaped solid electrode plate closely attached to the first surface, for example, the back surface of the solid electrode plate 1. A voltage application electrode made of a conductor such as a metal is connected to the DC power source 4 to apply a voltage to the solid electrode 1. Reference numeral 3 denotes a charge receptor that faces the second surface of the solid electrode plate 1 with a gap of 1 mm or less. For example, a photoconductive layer on a conductive substrate is formed, and the substrate is grounded. Corona discharge is generated between and as follows.

That is, when a direct current voltage is applied to the solid electrode plate 1 through the voltage application electrode 2, ionization of air occurs in the gap between the solid electrode plate 1 and the charge acceptor 3. If the DC power source 4 is connected to the voltage applying electrode 2 on the positive polarity side,
+ Ions flow to the charge acceptor 3 side to charge them, and −
Of the ions or electrons reach the solid electrode plate 1 side and are neutralized.

Further, since the solid electrode plate 1 has a large resistance, the discharge is stable and does not lead to a spark discharge, and since the solid electrode plate 1 is made of a high electric resistance material, it is excessive in any portion of the void. It is possible to prevent a current from flowing, and it is possible to charge the charge acceptor 3 more uniformly. It is considered that this is because the gap between the solid electrode plate 1 and the charge acceptor 3 corresponds to the ionization region, and the solid electrode plate 1 itself corresponds to the high impedance drift region.

On the other hand, FIG. 2 shows an embodiment of an electronic copying machine which employs the charging device of the present invention. Next, this will be described. The charge acceptor 3 having a photoconductive layer formed on an aluminum substrate.
Has a drum shape, and its surface is uniformly charged by a charging device 21 before being irradiated with image information, and a document table on which the document 10 to be copied is placed. 11, a light source 12 that illuminates the original 10 and an optical system 9 that guides the reflected light from the original 10 to the charge acceptor 3 are installed below the original table 11.

The electrostatic latent image formed on the surface of the charge receptor 3 by the exposure step is developed into a toner image by the developing device 13 installed around the charge receptor 3, and then the transfer device 1 is formed.
4, the toner image is transferred onto the sheet 16 fed from the sheet feeding device 15. The paper 16 on which the toner image is transferred is
Is discharged by peeling charger 17 is separated from the charge receptor 3 by Rukoto sent to a fixing device 18, the fixing device 18
While the toner image on the paper 16 is fixed on the paper 16 with
After the transfer step, the untransferred toner remaining on the surface of the charge receptor 3 is neutralized by the precleaning corotron 19,
It is removed from the surface of the charge receptor 3 by the cleaning device 20.

The above is the construction and operation of the copying machine adopting the electrophotographic method. In the copying machine, the charging device 21 for uniformly charging the surface of the charge acceptor 3, the transfer device 14, and the peeling charging device. Various kinds of charging devices such as 17, and a charging device 19 for pre-cleaning are used, and the charging device of the present invention is applied to these charging devices. Next, an embodiment thereof will be described with reference to FIG.

In the charging device shown in FIG . 3, the solid electrode plate 1 is, for example , a conductive polymer made of a polymer such as a π-conjugated system, a metal chelate system, a charge transfer type complex system, or a conductive substance is a polymer. Conductive polymer kneaded into the polymer, conductive polymer kneaded with antistatic agent into polymer, conductive polymer compounded with hydrophilic rubber and polymer, added to soda lime glass or borosilicate glass It is formed from a material such as glass or ceramic to which an agent is added and whose resistance value is adjusted, and has a volume resistivity of 10 ⁶ to 10 ¹³ Ωcm and a surface resistance of 10 ⁶ Ω or more.

[0016] The solid electrode plate 1 is formed in a generally inverted chevron cross section, a base of the voltage application electrode 2 are in close contact with the upper surface, so the DC power source 4 is applied to the voltage application electrode 2 ing. The solid electrode plate 1 has a thickness of 200
It is attached to the insulating solid electrode support 5 so as to face the charge acceptor 3 with an air source of μm present. As a mounting means, a fitting groove 5a into which both side edges of the solid electrode plate 1 can be inserted is formed obliquely in the insulating solid electrode support 5 in advance, and the insulating solid electrode support 5 is fitted in these fitting grooves 5a. The solid electrode plate 1 is fixed to the insulative solid electrode plate support 5 by inserting both side edges of the solid electrode plate 1 from the end side of the solid electrode plate. Even if 1 has a twist or a warp, the twist and the warp can be corrected by inserting it into the insulative solid electrode support 5, so that the distance between the solid electrode plate 1 and the charge acceptor 3 is kept uniform over the entire length. be able to.

Further, by forming the solid electrode support 5 with an insulating material, it is possible to prevent current from leaking from the solid electrode plate 1 to the insulative solid electrode support 5, so that the solid electrode plate 1 is deteriorated by the leak. Can also be prevented.

The charge acceptor 3 is formed by using the charging device having the above structure.
After being uniformly charged, an electrostatic latent image is formed on the surface of the charge acceptor 3 by an exposure process, the electrostatic latent image is developed into a toner image by the developing device 13, and then the electrostatic latent image is sent from the paper feeding device 15 in a transfer process. Paper 1 that has been transferred onto a separate paper 16 and has a toner image transferred thereon
No. 6 was sent to the fixing device 18 to transfer the toner image onto the paper 16. As a result, it was confirmed that a good copy image was obtained. Further, the same experiment was conducted by changing the volume specific resistance of the solid electrode 1 plate, and when the volume specific resistance was less than 10 ⁶ Ωcm, spark discharge was apt to occur in a part of the solid electrode plate 1, and 10 ¹³ Ω was set. If the voltage exceeds the limit, it is difficult to obtain a sufficient current required for charging, and it has been found that the power supply voltage must be increased considerably. Therefore, the volume resistivity of the solid electrode plate 1 is preferably in the range of 10 ⁶ Ωcm to 10 ¹³ Ωcm. As a material applicable to the solid electrode plate 1, plastic is preferable, and in order to obtain a necessary resistance value, it can be adjusted by adding an ion conductive material.

Next, regarding the surface resistance of the solid electrode plate 1, if a surface-active material or the like is applied to the surface of the solid electrode plate 1 to prevent contamination, the surface resistance may decrease. In such a case, for example, if the surface resistance of the solid electrode plate 1 is 10 ⁶ Ω or less, spark discharge may occur even if the bulk resistance is high. Therefore, at least the surface resistance of the solid electrode plate 1 must be maintained at a value higher than 10 ⁶ Ω or higher. If the gap between the solid electrode plate 1 and the charge acceptor 3 exceeds 500 μm, the discharge may be localized and black spots may occur in the obtained copy. Therefore, it is desirable that the gap be 500 μm or less.

[0020]

As described in detail above, according to the present invention, since the end portion of the plate-shaped solid electrode plate is fitted in the fitting groove formed in the insulating solid electrode support, Since the insulating solid electrode support regulates the occurrence of twisting or warpage of the solid electrode plate, the distance between the solid electrode plate and the charge acceptor can be kept uniform over the entire length. As a result, the charge receptor can be uniformly charged, and a fitting groove is formed in the insulating solid electrode support in advance, and the end portion of the solid electrode plate is fitted into this fitting groove for easy assembly. ,
It can be implemented easily and inexpensively.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a basic configuration of the present invention.

FIG. 2 is an explanatory diagram showing an application sequence of an electrophotographic copying machine using the electrophotographic charging device of the present invention.

FIG. 3 is a sectional view of an electrophotographic charging device according to an embodiment of the present invention.

FIG. 4 is an explanatory view showing a conventional charging device.

FIG. 5 is an explanatory diagram showing a conventional charging device.

[Explanation of symbols]

1 ... Solid electrode plate, 2 ... Voltage application electrode, 3 ... Charge receptor,
5 ... Insulating solid electrode support 5a ... Fitting groove.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-76851 (JP, A) JP-A-59-3885 (JP, A) JP-A-60-254172 (JP, A)

Claims (1)

(57) [Claims] 1. A solid electrode plate is formed of a plate-shaped electric resistor having a volume resistance of 10 ⁶ to 10 ¹³ Ωcm and a surface resistance of 10 ⁶ Ω or more, and the solid electrode plate has a plate-like shape on a first surface thereof. In a charging device for electrophotography, which is formed by adhering the voltage applying electrodes, the end portion of the solid electrode plate is fitted into a fitting groove provided in an insulating solid electrode support body for controlling twisting and warping of the solid electrode plate. A charging device for electrophotography, which is characterized by being combined.