JPH0962061A - Electrostatic charging method, electrostatic charger, image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable electrostatic charging potential irrespective of environment, and to prevent an abnormal discharge by reducing the potential remaining on an electrostatic charging member after electrostatically charging a body to be electrostatically charged to such the amount that a self-discharge may not occur, before the electrostatic charging member is rotated and a voltage is impressed again. SOLUTION: The electrostatic charger is provided with a discharging brush 25 installed on a seamless endless film 20, the discharging brush 20 is prepared for discharging the potential remaining on the seamless endless film 20 after electrostatically charging the photoreceptor drum 1. An insulating film is used as the seamless endless film 20, and the film 20 is constituted so that an electrostatic charging voltage may be impressed by a planar electrode 23, and also, the film 20 comes into contact with the photoreceptor drum 1 so as to electrostatically charge by discharging in a gap formed in front of a contact nip part where the film 20 comes into contact with the photoreceptor drum 1. And after electrostatically charging the body to be electrostatically charged, the potential remaining on the electrostatic charging member is reduced to such the amount that the self-discharge may not occur before the electrostatic charging member is rotated and the voltage is impressed again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging method that can be applied to an image forming apparatus such as a copying machine or a printer to which an electrophotographic process is applied, a charging apparatus, and an image forming apparatus using the charging method.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer to which the above electrophotographic process is applied, the surface of a charge receptor such as a photosensitive drum is uniformly charged by a charging device, and then an image is exposed. By doing so, an electrostatic latent image is formed on the surface of the photoconductor drum or the like, and this electrostatic latent image is visualized by developing with a developer, and the visualized developed image is transferred and fixed on a recording paper or the like. Is configured to form an image. As a charging device used in such an image forming apparatus, a device using corona discharge and a device using a contact charging method using a charging roll are known.

Among these charging devices, the charging device utilizing corona discharge extends a discharge wire in the shield case so as to be close to the surface of the photosensitive drum, and applies a high voltage to the discharge wire to corona the corona. By causing an electric discharge, an electric charge of a predetermined polarity is given to the surface of the photosensitive drum to charge it to a predetermined potential. Such a charging device using corona discharge is excellent in uniformity of charging, but a large amount of discharge products such as ozone and nitrogen oxides are generated along with the corona discharge, so that the treatment is required. As a result, there is a problem in that the image forming apparatus tends to be large and costly.

For this reason, various charging devices of the so-called contact charging type have recently been proposed and widely used, in which charging electrodes are directly brought into contact with the photosensitive drum. Such a charging device is arranged so that a conductive member such as an elastic roll or a brush is brought into contact with the surface of the photosensitive drum, and a DC voltage or a voltage in which a DC voltage and an AC voltage are superimposed is applied to these conductive members. Charging is performed by applying and discharging in a minute gap near the contact portion between the conductive member and the photosensitive drum. In addition, as disclosed in JP-A-1-93760 and JP-A-2-282279, there is also provided an apparatus including a charging electrode that also serves as a cleaning blade pressed against the surface of the photosensitive drum. Already proposed. In such a charging device, since corona discharge is not used, the amount of ozone generated is extremely small. Further, since the conductive member may be arranged so as to be in contact with the photosensitive drum, the image forming device can be made compact and lightweight. It has the advantage of being suitable for commercialization.

However, in order to perform uniform charging in a charging device using a roll-shaped conductive member among the above-mentioned contact type charging devices, the adhesion between the elastic roll and the photosensitive drum is improved and stabilized. It is necessary to form micro voids,
It is necessary to take measures such as reducing the hardness of the rubber forming the elastic roll. Therefore, it is necessary to provide a means for impregnating the elastic roll with a large amount of process oil, and this process oil is likely to be transferred to the photosensitive drum and adversely affect image quality. On the other hand, in order to solve such a problem, there is a method of improving the outer shape accuracy of the elastic roll, but it is very difficult to improve the outer shape accuracy of an elastic body such as rubber, This leads to a new problem of lowering the yield and increasing the cost.

On the other hand, in the case of a charging device using a brush-shaped conductive member, it is more effective for uniform contact than the above-mentioned roll-shaped member, but brush sweeps appear on the image as uneven charging. There is a problem that it is easy.

Further, in the case of a charging device using a blade-shaped charging electrode, it is difficult to set minute voids necessary for discharging, and it is difficult to perform uniform and good charging. Furthermore, in the case of a charging device that uses a blade-shaped charging electrode, and the blade-shaped charging electrode also serves as a cleaning blade, it is necessary to set a large contact pressure to the charge receptor such as the photosensitive drum.
There is another problem that the load on the photosensitive drum becomes large.

Therefore, in order to avoid the above problems, a charging device disclosed in Japanese Patent Laid-Open No. 4-249270 has already been proposed. This charging device uses a flexible film-shaped member as a conductive member, and is arranged so that the free end of the film-shaped member is in contact with the surface of the photoconductor. Then, a DC voltage is applied to this film-shaped member from a power source through a mounting substrate to cause discharge in a minute gap, and the surface of the photoconductor is charged to a predetermined potential.

Such a charging device has the advantages that it is easy to obtain stable contact with a simple structure and that the cost of the member itself is lower than that of other conductive members.

However, in a charging device using a flexible film-like member as such a conductive member, since the film-like member is arranged in a fixed state, ozone or the like generated at the time of discharge is prevented. Discharge products
There is a problem that it adheres to the surface of the film-like member and prevents normal charging, resulting in streak-shaped image defects.
This occurs because the discharge product generated in the minute gap between the film member and the photoconductor loses its place and adheres to the surface of the film member. When the film-shaped member is of a fixed type, it is difficult to clean this discharge product unless a cleaning means from the outside is provided.

In order to avoid this problem, a system in which a tubular film is rotated and used is also disclosed in JP-A-4-23.
It has already been proposed as shown in Japanese Patent No. 2977. In Japanese Patent Laid-Open No. 232977/1992, a configuration is proposed in which a roller that is driven to rotate is inserted into the film and the film is brought into contact with the photoconductor by a guide member. According to such a configuration, it is described that the slack portion of the film comes into contact with the photoconductor to carry out charging, and the slack portion of the film comes into contact with the surface of the photoconductor flexibly and widely to carry out stable charging.

[0012]

However, the above-mentioned prior art has the following problems. That is, among the above contact charging devices, in the case of using a film, a conductive material such as metal oxide or carbon is added to the film base material in order to make the electric resistance of the film a predetermined value. However, when an abnormally high voltage is applied, the electric resistance decreases and the current increases abnormally. For example, if there is a defect such as a scratch on the photoconductor that is the object to be charged, the current sharing voltage of the photoconductor is applied to the film electrode and the current increases, and the scratched part of the photoconductor is substantially discharged. Since the resistance becomes 0, the current increases abnormally,
There were serious defects such as the film and the photoconductor being burnt out and the power supply voltage drooping so that they were not charged.

Therefore, in order to prevent the applied voltage from being easily changed by resistance, an ionic conductive material such as a quaternary ammonium salt or lithium perchlorate may be used for resistance control. As a property,
Since the conductivity tends to change depending on temperature and humidity, there is a problem that the charging voltage changes.

Further, in the system in which a flexible film is rotated to apply a voltage, in the case of the charging device proposed in the above-mentioned Japanese Patent Laid-Open No. 4-232977, the shape of the portion where the roller abuts the photosensitive member is directly changed. Since it cannot be regulated, the contact state between the roller and the photosensitive member becomes unstable, and there is a problem that stable charging cannot be performed when the mechanical properties of the film change due to the environment.

Therefore, as a technique that makes it possible to obtain a stable contact state between the roller and the photosensitive member, Japanese Patent Laid-Open No.
A contact type charging device as disclosed in Japanese Patent No. 72869 has already been proposed. This Japanese Patent Laid-Open No. 5-72869 proposes a system in which a rotating roller is included in a film and the rotating roller directly contacts the film with the photosensitive member.
In this contact type charging device, the film and the photoconductor are brought into contact with each other with a stable predetermined contact pressure, the contact portion with the photoconductor is charged, and both sides of the area having the charging function are brought into contact with each other with a minute contact pressure. Since the area to be contacted is formed, it has a function of correcting the uneven charging of the photosensitive member by the area contacting with the minute contact pressure, and stable charging is performed by increasing the area of the contact portion with the photosensitive member. Is listed.

However, this Japanese Patent Laid-Open No. 5-72869
Since the charging device according to the publication is to charge at the contact portion between the film and the photosensitive member, in order to perform stable charging, it is necessary to provide areas contacting with a minute contact pressure on both sides of the area having a charging function. Although it needs to be formed widely, there is a problem that the charge potential becomes unstable due to the gap variation in the rotation direction accompanying the rotation of the film.

Further, as disclosed in Japanese Patent Laid-Open No. 4-268584, a charging member is composed of a conductive member to which a voltage is applied and a tubular resistance layer member which is fitted onto the conductive member and is rotatable. Also, a contact charging device configured to charge the charged body by bringing the conductive member into contact with the charged body via the resistance layer member fitted externally thereto has been proposed, In the contact charging device according to Japanese Patent Application Laid-Open No. 4-268584, since the charging is performed at the contact portion between the tubular resistance layer member and the member to be charged, there is a gap variation in the rotation direction due to the rotation of the film. Japanese Patent Laid-Open No. 7286/1993 that the charging potential becomes unstable
It has the same problem as that of Japanese Patent No.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art. The purpose of the present invention is to obtain a stable charging potential regardless of the environment and to prevent scratches on an object to be charged. It is an object of the present invention to provide a charging method, a charging device, and an image forming apparatus using the charging method, in which abnormal discharge does not occur due to the above defects.

[0019]

The charging method according to claim 1 of the present invention is a charging method in which a voltage is applied to a rotating charging member to charge the rotating charging member, and the charged object remains on the charging member after charging. The charging method is characterized in that the potential is lowered to such an amount that self-discharge does not occur before the charging member rotates and voltage is applied again.

Further, the charging device according to claim 2 of the present invention is a charging device having a rotating charging member, wherein the charging member is charged with an object to be charged and then the potential remaining on the charging member is eliminated. The charging device is provided with a means.

An image forming apparatus according to a third aspect of the present invention further comprises a rotating charging member, a voltage applying means for applying a voltage to the charging member, and a member to be charged such as a photoconductor. In the image forming apparatus, the charge removing member is provided with a charge removing unit for removing a potential remaining on the charging member.

Further, according to a fourth aspect of the present invention, in the charging device charged by a rotating flexible member, the flexible member remains on the charging member after charging the body to be charged. The charging device is characterized in that it is provided with a discharging means for discharging the generated potential.

Further, in the charging device according to claim 5 of the present invention, in the charging device for charging by the charging roll, a discharging means for discharging the potential remaining on the charging member after charging the member to be charged on the charging roll. Is a charging device.

Further, an image forming apparatus according to a sixth aspect of the present invention includes a rotating flexible member as a charging electrode,
An image forming apparatus having a voltage applying unit for applying a voltage to a flexible member and a member to be charged such as a photoconductor is provided with a discharging unit for discharging a potential remaining on the flexible member. The image forming apparatus.

Furthermore, the image forming apparatus according to claim 7 of the present invention is an image forming apparatus having a charging roll, a voltage applying means for applying a voltage to the charging roll, and a member to be charged such as a photoconductor. The image forming apparatus is characterized in that it is provided with a discharging unit for discharging the potential remaining on the charging roll.

The charging device according to claim 8 of the present invention is the charging device according to claim 4, wherein the flexible member has a volume resistivity of 10 ¹⁰ Ω · cm or less.

The image forming apparatus according to claim 9 of the present invention is the image forming apparatus according to claim 6, wherein the volume resistivity of the flexible member is 10 ¹⁰ Ω · cm or less. .

Furthermore, the charging device according to claim 10 of the present invention is the charging device according to claim 4, characterized in that the discharging means is a conductive brush.

Further, the image forming apparatus according to the eleventh aspect of the present invention is the image forming apparatus according to the sixth aspect, characterized in that the discharging means is a conductive brush.

[0030]

The charging device according to the present invention is a charging device having a rotating charging member, wherein the charging member is provided with a discharging means for discharging the potential remaining on the charging member after charging the member to be charged. ing. As the above-mentioned charging member, for example, a member for charging a flexible insulating film having a volume resistivity of 10 ¹² Ω · cm or more with an object to be charged is used. Is applied so that the film is contacted so as to be charged by discharging in the gap before and after the contact nip in which the film contacts the charged body, and the charged body is contacted at the contact portion between the film and the charged body. It is desirable to adopt a structure in which the electrodes are in contact with the back side of the film when viewed from the side. With such a configuration, the charged body can be discharged only once in either the rotation entrance side (pre-nip) gap or the rotation exit side (post-nip) gap. In the discharge, positive ions and negative ions or electrons are generated in the same amount, and the film is charged with a charge having a polarity opposite to that of the material to be charged. Therefore, the electric field in the gap becomes 0, and the discharge is stopped. Therefore, the charged body is charged to a predetermined potential, and at the same time, the current does not flow any more. Therefore, even if there is a defect such as a hole in the charged body, there is no abnormal current, and there is no problem such as burnout or charging. The problem of defects does not occur.

Further, when an insulating film is used as the charging member, for example, the volume resistivity is 10 ¹² Ω.
When the thickness is about cm or more, the film acts as a capacitance necessary for discharging, and therefore the charging potential does not change even if the environment changes.

In the charging device according to the eighth and ninth aspects of the present invention, the volume resistivity of the flexible member is 10 ¹⁰ Ω · cm.
Since it is below, the static elimination means becomes unnecessary.

Further, in the charging device and the like according to the tenth and eleventh aspects of the present invention, since the discharging means is a conductive brush,
It is possible to sufficiently eliminate static electricity without damaging the flexible member.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 2 shows an embodiment of an image forming apparatus to which the charging device according to the present invention is applied.

In FIG. 2, reference numeral 1 denotes a photosensitive drum as a cylindrical electrostatic latent image carrier, and a primary charger as a charging device according to the present invention is provided around the photosensitive drum 1. 2, a developing device 3, a transfer roll 4, and a cleaning device 5 are arranged. Of these image forming members, the members other than the transfer roll 4 are integrally formed as an image forming unit 6. This image forming unit 6
Is detachable from the image forming apparatus main body 7, and when the toner contained therein is consumed, the unit 6 is replaced.

The photosensitive drum 1 is uniformly charged to a predetermined potential by the primary charger 2, and then the laser beam 10 from the laser beam generator 9 having the semiconductor laser (not shown) and the polygon rotary mirror 8 therein. An electrostatic latent image corresponding to an image is formed at a predetermined position on the surface of the photosensitive drum 1. The electrostatic latent image formed on the surface of the photosensitive drum 1 is developed by the developing device 3 and becomes a toner image. At that time, the laser beam 10 is adapted to write the image portion, and the toner having the same polarity as the surface potential of the photoconductor drum 1 charged by the primary charger 2 is charged with the toner. Is developed on the laser light irradiation part.

The developing device 3 has at least the developing roll 3
The developing device 3 is provided with the magnetic toner 3c. The magnetic toner filled in the developing device 3 is adsorbed on the surface of the developing roll 3a by the magnetic force of the developing roll 3a, and then regulated to a predetermined layer pressure by the layer forming member 3b, and a necessary charge is generated. Be charged. Then, the toner adsorbed on the surface of the developing roll 3a and frictionally charged to have a predetermined layer pressure and a predetermined polarity moves to a developing position close to the surface of the photosensitive drum 1 as the developing roll 3a rotates. Then, the electrostatic latent image formed on the surface of the photosensitive drum 1 is developed by the toner layer.

The toner image formed on the photosensitive drum 1 is transferred onto the transfer paper 13 which is conveyed from the paper feed cassette 11 by the registration roll 12 at a predetermined timing by the contact charging of the transfer roll 4. After the transfer ends
The transfer sheet 13 on which the toner image is transferred is conveyed to the fixing device 15 by the conveying belt 14 and subjected to a fixing process.
It is discharged to the outside of the device. The fixing device 15 is inserted between the fixing roll 15a and the pressure roll 15b and is fixed by heat and pressure.

After the transfer process is completed, the residual toner on the photosensitive drum 1 is removed by the blade 5 of the cleaning device 5.
It is cleaned by a and prepared for the next image forming step. Then, in the case of continuously forming images, the charging process by the primary charger 2 is continuously performed, and all the processes described above are repeated to output a plurality of continuous prints.

By the way, the charging device according to this embodiment is
In a charging device having a rotating charging member, the charging member is provided with a charge removing means for removing charge to a potential remaining on the charging member after charging the member to be charged.

Next, the structure of one embodiment of the charging device according to the present invention will be described. The charging device according to this embodiment is used as the primary charger 2.

That is, the charging device 2 according to this embodiment.
1 is arranged so as to face the photoconductor drum 1 as the member to be charged, and this photoconductor drum 1 has an electrode 1a grounded below the OPC photoconductor layer. are doing. The charging device 2 includes, for example, an insulating seamless endless film 20 having a thickness of about 50 μm and a volume resistivity of 10 ¹² Ω · cm as a charging member. The insulating seamless endless film 20 is formed. As the material to be used, for example, synthetic resin such as polyamide, polyimide, urethane, polyethylene, polyester is used. The seamless endless film 20 is driven by two rollers 21 and 22 to rotate in synchronization with the photosensitive drum 1. Further, on the back side of the seamless endless film 20, a conductive plate electrode 23 is arranged,
The flat electrode 23 applies a voltage while contacting the seamless endless film 20, and at the same time, the gap between the surface of the film 20 in contact with the surface of the photosensitive drum 1 and the photosensitive drum 1 is on the pre-nip side (the moving direction of the film). It is arranged such that the upstream side) has a thickness of 50 μm or less.
A predetermined DC voltage is applied to the plate electrode 23 by a DC power supply 24. Further, on the surface side of the seamless endless film 20, after charging the photosensitive drum 1 on the surface opposite to the flat plate electrode 23,
A destaticizing brush 25 as a destaticizing unit for destaticizing the potential remaining on the film 20 is arranged, and the destaticizing brush 25 is grounded. The charge on the seamless endless film 20 is set to a low level in advance by the static elimination brush 25, and when the film 20 and the photoconductor drum 1 come close to each other, the voltage between the gaps has a discharge start voltage determined by the size of the gap. When it exceeds, discharge starts.

With the above arrangement, the charging device according to this embodiment can obtain a stable charging potential regardless of the environment and prevent abnormal discharge due to defects such as scratches on the charged object as follows. A device can be provided.

That is, in this embodiment, as shown in FIG.
1250 V is applied by the DC power supply 24. And
When the photosensitive drum 1 is rotating, the seamless endless film 20 is also rotated by the two rollers 21 and 22 at a speed equal to the peripheral speed of the photosensitive drum 1. The charge on the seamless endless film 20 is set to a low level in advance by the static elimination brush 25, and when the film 20 and the photosensitive drum 1 come close to each other, when the voltage between the gaps exceeds the discharge start voltage determined by the size of the gap. , Discharge starts. The plate electrode 23 of the charging device 3
When a negative DC voltage is applied to, the electrons and negative ions adhere to the surface of the photoconductor drum 1 to charge the surface of the photoconductor drum 1, and the seamless endless film 20 itself is charged with positive ions. Since the electric field between the seamless endless film 20 and the surface of the photosensitive drum 1 becomes 0, the discharge is stopped.

In the region of the seamless endless film 20 which is once discharged in this manner, the discharge is stopped because the volume resistivity of the film 20 is high and the electric charge is not continuously supplied when the film 20 is separated from the plate electrode 23. However, since the seamless endless film 20 rotates at the same speed as the surface of the photosensitive drum 1, the new seamless endless film 20 continuously moves to the vicinity of the discharge position where it contacts the flat electrode 23, Film 2 as above
When 0 and the photoconductor drum 1 are close to each other, when the voltage between the gaps exceeds the discharge start voltage determined by the size of the gap, the discharge starts. Therefore, the charging of the surface of the photoconductor drum 1 by the seamless endless film 20 is repeated continuously, and as a result, the surface of the photoconductor drum 1 is uniformly charged to a predetermined potential.

Thereafter, the seamless endless film 20 charged with positive ions as described above is neutralized by the static elimination brush 25, and the charge on the seamless endless film 20 is set to a low level in advance by the static elimination brush 25.

Thus, the charging device 2 according to the above embodiment
In a charging device 2 having a rotating seamless endless film 20, the seamless endless film 20 is provided with an antistatic brush 25 for neutralizing the potential remaining on the seamless endless film 20 after charging the photosensitive drum 1. ing. As the seamless endless film 20, for example, a flexible insulating film having a volume resistivity of 10 ¹² Ω · cm is used, and a charging voltage can be applied to the film 20 by a flat electrode 23. Is composed of
The film 20 is in contact with the photosensitive drum 1 so as to be charged by discharging in a gap before the contact nip in which the film 20 abuts. With such a configuration, the photosensitive drum 1 can be discharged only once in the rotational approach side (pre-nip) gap. In the discharge, positive ions and negative ions or electrons are generated in the same amount, and the film 20 is charged with positive ions having a polarity opposite to that of the photoconductor drum 1. Therefore, the electric field in the gap becomes 0, and the discharge is stopped. Therefore, since the photosensitive drum 1 is charged to a predetermined potential and no more current flows, even if the photosensitive drum 1 has a defect such as a hole, there is no abnormal current and there is a problem such as burning. There is no problem of charging failure.

Further, when the insulating film 20 is used as the charging member, for example, the volume resistivity is 10
^When the film thickness is about ¹² Ω · cm, the film 20 acts as a capacitance necessary for discharging, so that the charging potential does not change even if the environment changes.

Experimental Example 1 The charging test of the present invention was carried out in the configuration of FIG. The seamless endless film 20 has a volume resistivity of 10
It is a PVdF film having a thickness of ¹³ Ω · cm and a thickness of 50 μm. The member to be charged is an O having a thickness of 18 μm and a relative dielectric constant of about 3.
PC (organic photoconductor) 1. The film 20 and the photosensitive drum 1 are pressed against this film so that the end of the voltage applying electrode on the pre-nip side and the gap between the film 20 and the photosensitive drum 1 are close to each other at 50 μm and the peripheral speed is 100 mm.
When -1250V was applied while rotating at / s, the surface potential of the OPC photosensitive drum 1 became -400V. When the voltage was further increased, the charging potential increased by the increased voltage. The fluctuation of the electric potential was about 10 V, and when the photosensitive drum 1 was developed and transferred by a usual electrophotographic method, a uniform image was obtained. Rotation speed is 100 mm / s
It was found that the same result was obtained below, and that the potential was decreased as the speed was increased, but almost the same potential was obtained up to 300 mm / s. Further, even under the condition that the photoconductor drum 1 has a scratch, abnormal discharge does not occur, and a problem such as a decrease in potential around the scratch does not occur.

Experimental Example 2 Similar to Experimental Example 1, the voltage applying electrode 23 was arranged at a position where the seamless endless film 20 and the photosensitive drum 1 were separated from each other in the opposite direction to FIG. 1, and the gap of the post nip was set to 50 μm or less. As a result of experiments, similar results were obtained and it was confirmed that uniform charging was possible.

The material of the film used here is PVd.
It is not limited to F, but as described above, if the resistance value of polyamide, polyimide, urethane, polyethylene, polyester, etc. is basically 10 ¹² Ω · cm or more, the function of the present invention can be realized. It has been confirmed.

Further, the electrode used for the charge removal is not limited to the brush, and may be a conductive plate electrode, a conductive roller, or the like.

Experimental Example 3 As the resistance of the seamless endless film 20, 10 ¹⁰
When the same experiment as in Experimental Example 1 was performed using a Ω · cm, the same result as in Experimental Example 1 was obtained at a rotation speed of 50 mm / s or less without using a static elimination electrode. This is because the relaxation time constant of the charge, which is determined by the resistance and the capacitance of the film 20, is shorter than the time required for the film to make one rotation, so that self-discharge can be performed. If the speed is slow, there is no need for static elimination means, and the cost can be reduced.
Here, when the relaxation time constant of the film 20 is τ, the relative dielectric constant of the film 20 is ε, and the volume resistance value is ρ, the relaxation time constant τ is represented by τ = ε × ρ.

Second Embodiment FIG. 3 shows a second embodiment of the present invention. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals. In this second embodiment, charging is performed by a charging roll. In the charging device described above, the charging roll is provided with a discharging means for discharging the potential remaining on the charging member after charging the body to be charged.

That is, in the second embodiment, the charging device 2
The charging member is not composed of a seamless endless film, but is composed of a charging roll 30 formed in a roll shape. The charging roll 30 is formed by coating the outer circumference of a metal shaft 31 with an insulating synthetic resin 32 such as PVdF, polyamide, polyimide, urethane, polyethylene, polyester to a predetermined thickness. After the charging roll 30 is in contact with the photoconductor drum 1, the surface of the charging roll 3 is charged, but the charge is neutralized by the charge removal brush 25 to lower the potential and the next charging becomes possible. There is.

The other structure and operation are the same as those of the above-mentioned embodiment, and the description thereof will be omitted.

[0058]

As described above, according to the present invention,
It is possible to provide a charging method, a charging device, and an image forming apparatus using the same, in which a stable charging potential can be obtained regardless of the environment and abnormal discharge does not occur due to a defect such as a scratch on an object to be charged.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing one embodiment of a charging device according to the present invention.

FIG. 2 is a block diagram showing an embodiment of an image forming apparatus to which the charging device according to the present invention is applied.

FIG. 3 is a configuration diagram showing a second embodiment of a charging device according to the present invention.

[Explanation of symbols]

1 photoconductor drum, 20 seamless endless film, 21, 22 roller, 23 flat plate electrode, 24 DC power supply, 25 static elimination brush.

Claims (11)

[Claims] 1. A charging method in which a voltage is applied to a rotating charging member to charge the charged member, and the potential remaining on the charging member is charged until the charging member rotates and a voltage is applied again. A charging method characterized by being reduced to an amount that does not cause self-discharge. 2. A charging device having a rotating charging member, characterized in that said charging member is provided with a discharging means for discharging the charged body to a potential remaining on the charging member after charging the charged body. 3. An image forming apparatus having a rotating charging member, a voltage applying unit for applying a voltage to the charging member, and a member to be charged such as a photoconductor, and a discharging unit for discharging a potential remaining on the charging member. An image forming apparatus characterized by being provided. 4. A charging device for charging by a rotating flexible member, wherein the flexible member is charged with an object to be charged,
A charging device comprising: a discharging unit for discharging a potential remaining on a charging member. 5. A charging device for charging with a charging roll, characterized in that said charging roll is provided with a discharging means for discharging the potential remaining on the charging member after charging the body to be charged. 6. An image forming apparatus having a rotating flexible member as a charging electrode, a voltage applying unit for applying a voltage to the flexible member, and a member to be charged such as a photoconductor, which is a flexible member. An image forming apparatus, comprising: a discharging unit for discharging a residual electric potential. 7. An image forming apparatus having a charging roll, a voltage applying unit for applying a voltage to the charging roll, and a member to be charged such as a photosensitive member is provided with a discharging unit for discharging a potential remaining on the charging roll. An image forming apparatus characterized by the above. 8. The volume resistivity of the flexible member is 10 ¹⁰ Ω · c.
The charging device according to claim 4, wherein the charging device has a thickness of m or less. 9. The volume resistivity of the flexible member is 10 ¹⁰ Ω · c.
The image forming apparatus according to claim 6, wherein the image forming apparatus has a thickness of m or less. 10. The charging device according to claim 4, wherein the charge removing unit is a conductive brush. 11. The image forming apparatus according to claim 6, wherein the charge removing unit is a conductive brush.