JPH0954479A - Charging device and image forming apparatus equipped with the charging device - Google Patents

Abstract

(57) Abstract: Corona discharge between a roller-shaped electrode rotatably provided in a non-contact state with a charged body and the charged body for uniformly charging the charged body. Cause SOLUTION: A charging device 2 for charging a photosensitive drum 1 which is a member to be charged is provided with a roller-shaped discharge roller 21 rotatably provided in a state not in contact with the photosensitive drum 1.
It is formed by a power source 23 that applies a voltage to the roller 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging an object to be charged, and more particularly to a charging device for charging an object to be charged by applying a voltage to a discharge electrode to generate corona discharge. It is about.

The present invention also provides a copying machine, a facsimile,
The present invention relates to an image forming apparatus such as a printer, and more specifically, a latent image is formed on a surface of a latent image carrier charged by the charging device by a latent image forming means, and the latent image is developed by a developing device to form an image. The present invention relates to an image forming apparatus for performing.

[0003]

2. Description of the Related Art In an image forming apparatus that forms an electrostatic latent image on the surface of a latent image carrier as a member to be charged and develops the electrostatic latent image by a developing device, the electrostatic latent image is formed. Prior to the formation of the toner, a charging process, which is a step of charging the surface of the latent image carrier with a charging device, is performed. Then, in order to improve the quality of the finally formed image, the charging process needs to uniformly charge the surface of the latent image carrier to a constant potential.

As a charging device for this charging process, a contact type charging device (hereinafter referred to as a contact type charging device) for charging a latent image carrier by bringing a conductive roller or a conductive brush to which a voltage is applied into contact with the latent image carrier. Known as a charging device) and a corona discharge type charging device (hereinafter referred to as a corona charging device) that charges a latent image bearing member by using corona discharge that is a discharge generated by dielectric breakdown of air performed in an electric field. Has been.

[0005]

However, in the above contact charging device, since the conductive brush or the like and the latent image bearing member are in contact with each other, when there is a defect such as a pinhole on the surface of the latent image bearing member, the defect may occur. There is a problem that the current is concentrated on the surface and uniform charging cannot be realized. Further, when a conductive roller is used in the contact charging device, the roller is often formed of a rubber material or a sponge material, but there is a problem that the material cost and the processing cost are high.

Among these problems, the problem that the material cost of the roller is expensive does not become a problem in the corona charging device. However, even with a corona charger,
The current may be concentrated, and the surface of the latent image carrier may not be uniformly charged at a constant potential.

The present invention has been made in view of the above problems, and the first object thereof is to provide a charging device for uniformly charging the surface of an object to be charged at a constant potential. A second object of the invention is to provide such a charging device, which charges the latent image carrier as a member to be charged uniformly at a constant potential, so that an image finally formed is of high quality. An object is to provide an image forming apparatus.

[0008]

In order to achieve at least one of the above objects, the charging device according to claim 1 is provided in a non-contact state with the body to be charged, and is rotated with respect to the body to be charged. Attached to the surface of the discharge electrode, and a roller-shaped discharge electrode that moves relative to each other, a power supply that applies a voltage to the discharge electrode to generate corona discharge in a region between the charged body and the discharge electrode. And a foreign matter removing means for removing foreign matter.

In the charging device according to claim 1, the inventors have clarified through experiments and analysis the cause that the charged state of the charged body is not always uniform even if the conventional corona charging device is used, and as a result, It was created based on. Less than,
The results of such experiments and analysis will be described. The inventors have confirmed that one of the causes of non-uniform charging is that air stays in a region between a discharge electrode that performs corona discharge and a member to be charged. If air stays in this area, ozone and nitrogen oxides that accompany the discharge will stay, preventing ionization and causing discharge in the air (corona discharge).
Are non-uniform, which results in non-uniform potential on the surface of the body to be charged.

Further, the inventors of the present invention, as one of the causes of non-uniform charging, dust in the area between the discharge electrode and the member to be charged,
It was confirmed that foreign substances such as products generated by corona discharge and dust were accumulated. When foreign matter accumulates in the area, the foreign matter adheres to the discharge electrode to make the discharge non-uniform, and the generated corona does not act uniformly on the material to be charged, resulting in an uneven charging state of the material to be charged. It becomes.

Further, from the results of the above-mentioned experiments, the inventors have found that when a discharge electrode in a stopped state is used, the surface state of the electrode is non-uniform, so that Change the relative positional relationship between the discharge electrode and the body to be charged so that the part of the discharge electrode that faces the member to be charged is replaced during corona discharge even in an environment where the charge state becomes uneven. By doing so, it was confirmed that it is possible to eliminate or reduce the non-uniformity of the charged state of the charged body. This shortens the time for which the portion of the discharge electrode having a non-uniform surface condition is located at a position facing the member to be charged, and reduces the adverse effect of the non-uniformity of the discharge electrode on the member to be charged.

In the charging device according to claim 1 created from the results of the experiment and analysis, a corona discharge is generated between the roller-shaped discharge electrode in the state where the voltage is applied from the power source and the member to be charged, As a result, the body to be charged is charged.
Further, during charging, an air flow is generated in a region between the discharge electrode and the body to be charged due to rotation of the roller-shaped charging electrode, and fresh air is supplied to the region by the air flow. Further, since the roller-shaped discharge electrode rotates during charging, even if the surface state of the discharge electrode is nonuniform, the time during which this nonuniform part faces the body to be charged is shortened. Further, since the foreign matter removing device removes foreign matter such as dust adhering to the surface of the discharge electrode, the foreign matter does not accumulate in the area between the discharge electrode and the body to be charged.

A charging device according to a second aspect of the invention is the charging device according to the first aspect, characterized in that the surface of the discharge electrode is made of metal. In particular, in the charging device according to the second aspect, the surface of the roller-shaped discharge electrode is made of metal, so that the discharge electrode can have a simple structure with excellent durability.

According to a third aspect of the present invention, in the charging device, a sheet-like discharge electrode which is provided in a non-contact state with the body to be charged and which moves relative to the body to be charged, and a voltage is applied to the discharge electrode. A power source for generating a corona discharge in a region between the charged body and the discharge electrode, and a foreign matter removing unit for removing foreign matter adhering to the surface of the discharge electrode. is there. Here, in order to “relatively move” the sheet-shaped discharge electrode with respect to the body to be charged, for example, the discharge electrode is formed by an endless sheet, and the discharge electrode is formed into a rotatable roller shape. It is possible to adopt a configuration in which the electrode support member and another support member support each other.

In the image forming apparatus according to claim 3,
Corona discharge occurs between the sheet-shaped discharge electrode in the state where the voltage is applied and the member to be charged, whereby the member to be charged is charged. In addition, since the sheet-shaped discharge electrode moves relative to the member to be charged during charging, an air flow is generated in the area between the discharge electrode and the member to be charged, and fresh air is generated by the air flow. Will be supplied to the area.
Further, due to the relative movement, even if the surface state of the discharge electrode is non-uniform, the time during which the non-uniform part faces the member to be charged is shortened. Further, since the foreign matter removing device removes foreign matter such as dust adhering to the surface of the discharge electrode, the foreign matter does not accumulate in the area between the discharge electrode and the body to be charged. Further, as compared with the case of using a roller-shaped discharge electrode, the space for providing the discharge electrode can be reduced.

A charging device according to a fourth aspect is the charging device according to the third aspect, characterized in that a metal belt is used as the discharge electrode. In particular, claim 4 concerned
In the above charging device, by using a metal as the sheet-shaped discharge electrode, the discharge electrode can have excellent durability.

A charging device according to a fifth aspect of the present invention is the charging device according to the third aspect, characterized in that a resin belt subjected to a conductive treatment is used as the discharge electrode. Particularly, in the image forming apparatus according to claim 5, since the resin belt is used as the sheet-shaped discharge electrode, the sheet is to be incorporated in the apparatus with a layout having a smaller radius of curvature as compared with the case where a metal belt or the like is used. You can

According to a sixth aspect of the present invention, in a charging device, a discharge electrode provided in a non-contact state with a body to be charged and a voltage is applied to the discharge electrode, and a region between the body to be charged and the discharge electrode. Between the power source for generating corona discharge and the charged object and the discharge electrode, and the contacted state with the charged electrode, and relative movement with respect to the charged object The sheet-like interposing member and the foreign matter removing means for removing the foreign matter adhering to the surface of the intervening member on the side of the charged body are provided.

Here, in order to "move the sheet-like interposing member relative to the member to be charged", for example,
It is possible to adopt a configuration in which the interposition member is formed of a roll-shaped sheet, and the interposition member is wound while making contact with the discharge electrode.

In the charging device of the sixth aspect, corona discharge occurs between the discharge electrode to which the voltage is applied and the member to be charged, whereby the member to be charged is charged. Further, during charging, the sheet-shaped intervening member moves relative to the member to be charged, so that an air flow is generated in the region between the discharge electrode and the member to be charged, and fresh air is generated by the air flow. Will be supplied to the area. Further, even if the surface state of the discharge electrode is non-uniform, since there is an intervening member between the discharge electrode and the member to be charged, the influence of this non-uniformity directly affects the member to be charged. Never. Further, since the foreign matter removing device removes foreign matter such as dust adhering to the surface of the interposition member, the foreign matter does not accumulate in the area between the discharge electrode and the body to be charged.

The charging device according to claim 7 is the charging device according to claim 1,
The charging device according to claim 3 or 6, wherein the foreign matter removing means includes a scraper. Particularly, in the charging device according to the seventh aspect, the scraper scrapes off the foreign matter attached to the discharge electrode or the interposition member.

The charging device according to claim 8 is the charging device according to any one of claims 1 to 7, wherein the member to be charged is a latent image carrier on the surface of which a latent image is formed. It is what Particularly, in the charging device according to the eighth aspect, the surface of the latent image carrier which is the member to be charged is uniformly charged.

According to a ninth aspect of the present invention, in the image forming apparatus, a latent image carrier on which a latent image is formed, a charging device according to the eighth aspect, and the latent image carrier charged by the charging device. On the other hand, a latent image forming means for forming a latent image and a developing device for developing the latent image to form a visible image are provided. In the image forming apparatus according to claim 9, the surface of the latent image carrier is uniformly charged by the charging device, the latent image forming means forms a latent image on the latent image carrier, and the latent image is developed by the developing device. And the image is formed. (Hereinafter, margin)

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus and a charging device included in the copying machine will be described below. FIG. 2 is a schematic configuration diagram of the copying machine according to the present embodiment.

In FIG. 2, the photosensitive drum 1, which is the member to be charged and the latent image carrier, is rotationally driven in the direction of arrow a at a constant speed during copying. Then, the outer peripheral surface of the photosensitive drum 1 is uniformly charged by the charging device 2, and then an optical image is irradiated and formed by an exposure laser scanner 3 as a latent image forming means to form an electrostatic latent image. The charging device 2 will be described later. Next, the eraser 4 eliminates the charge on the outer surface of the photosensitive drum 1 outside the image forming area.
After that, the electrostatic latent image is developed by a developing solution in which toner is dispersed in a liquid carrier supplied from the wet type developing device 5 while passing through a region facing the wet type developing device 5 as a developing device. Becomes

The toner image is transferred by the transfer charger 7 to the recording material 6 fed from a paper feeding device (not shown). That is, the toner image is electrophoresed in the liquid carrier between the photosensitive drum 1 and the recording material 6, and moves from the photosensitive drum 1 to the recording material 6. After the recording material 6 is separated from the photosensitive drum 1, the cleaning blade 8 removes the residual toner. The cleaning blade 8 may be arranged in the trailing direction or the counter direction. Then, the surface of the photosensitive drum 1 is removed of the residual potential by the static elimination lamp 9 and is prepared for the next copying.

In the wet developing device 5, a developing roller 52 as a developing solution carrier, a squeeze roller 57 as a surplus solution removing means, and a set roller 60 as a pressing means are provided as a photosensitive drum in a developing container 51 in the order of image formation. 1 is arranged in close proximity to the first unit. The developing roller 52 rotates in the direction of the arrow b and supplies the developing solution supplied from the developing solution supply section 54 to the wedge-shaped portion 56 formed by the scraper 55 to the photosensitive drum 1. Further, a developing bias is applied to the developing roller 52, and fogging due to toner adhesion to the background portion is prevented. The squeeze roller 57 rotates in the direction of arrow c to squeeze the excess liquid carrier on the surface of the photosensitive drum 1. A squeeze roller scraper 58 is provided on the surface of the squeeze roller 5.
The developer adhering to 7 is removed. The set roller 60 is made of a conductor and is provided at a distance of 50 μm from the photosensitive drum 1. Then, a voltage having the same polarity as that of the toner is applied, and the toner particles are pressed against the photosensitive drum 1 by the electric field generated between the photosensitive drum 1 and the set roller 60.

The charging device 2 will be further described. FIG. 1 is a schematic configuration diagram of the charging device 2. The charging device 2 includes a discharge electrode 21 that rotates in the direction of arrow e, a power source 23 that applies a voltage to the discharge electrode 21 via a brush 22, and an ammeter 2.
4 and. The discharge electrode 21 is provided in a non-contact state with the photosensitive drum 1 at a constant distance d, and its surface is formed of a steel material, a copper material, an aluminum material, or the like. Then, in order to charge the photoconductor drum 1, a voltage according to Paschen's law is applied to the discharge electrode 21 by the power source 23, and an electric field is formed in a region between the electrode and the photoconductor drum 1 to generate the corona 25. Let The occurrence of the corona 25 can be visually confirmed as purple emission.

When a normal corona is used as the corona 25, a film corona or glow is used instead of the brush corona or streamer generated when the electric field strength between the photosensitive drum 1 and the electrode 21 is excessive. It is desirable to use. When such a corona is used, the discharge is not concentrated on a portion where the electric field is high, which occurs when a brush corona or a streamer is used, and uniform discharge is realized and the photosensitive drum 1 is uniformly charged. However, in a discharge device having a large discharge area or a long discharge length, the brush corona may coexist with the film corona or the glow to some extent. In this case, it is necessary to use a constant current power source as the power source 23 or to incorporate a high resistance in the voltage application circuit.

When a negative corona is used as the corona 25, it is desirable to use a non-pulse corona instead of the brush corona (pulse corona) generated when the electric field strength is excessive. If the pulse-free corona is used, the discharge is not concentrated, which occurs when the brush corona is used, and uniform discharge is realized and the photosensitive drum 1 is uniformly charged. However, in the case of a discharge device having a large discharge area or a long discharge length, the pulse corona may coexist with the non-pulse corona to some extent. Also in this case, it is necessary to use a constant current power source as the power source 23 or to incorporate a high resistance in the voltage application circuit.

The distance d between the photosensitive drum 1 and the discharge electrode 21 is preferably 1 mm or less, more preferably 0.5 mm or less, in order to reduce the voltage to be applied to the photosensitive drum 1 by the power source 23. Should be.

Further, in the charging device 2, the discharge electrode 2
It is desirable to provide a scraper 26 as a foreign matter removing means for removing foreign matter such as dust adhering to the surface of 1. The scraper 26 prevents foreign matter from entering between the photoconductor drum 1 and the discharge electrode 21, and is attached with one end thereof being in pressure contact with the surface of the discharge electrode 21. At the time of mounting, it is necessary to adopt a mounting method in which foreign matter is satisfactorily removed from the surface of the discharge electrode 21 and the surface is not damaged. From this point of view, in this charging device, the scraper 26 is mounted in the counter direction as shown in FIG. 1, but may be mounted in the trailing direction depending on the adjustment of the pressure contact force. The scraper 26 is made of a material such as resin, rubber, or metal that has been subjected to a surface treatment to apply the resin, and is attached to the apparatus so that other members will be in a non-conductive state.

According to the copying machine described above, as the discharge electrode 21 rotates, an air flow is generated in the area between the discharge electrode 21 and the photosensitive drum 1, and this air flow causes corona discharge in the area. Foreign matter is prevented from staying. Further, even if the surface state of the discharge electrode 21 is non-uniform, the non-uniform surface will not be located at a position facing the photoconductor drum 1 for a long time. Further, by providing the scraper 26, foreign matter is removed from the surface of the discharge electrode 21, and foreign matter is prevented from staying between the discharge electrode 21 and the photosensitive drum 1.

[Second Embodiment] A second embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus and a charging device provided in the copying machine will be described below. To do. The copying machine according to this embodiment is the same as that of the first embodiment except for the charging device. Therefore, only the charging device will be described below.

FIG. 3 is a schematic configuration diagram of the charging device 70 according to this embodiment. The charging device 70 includes the photosensitive drum 1
An endless sheet electrode 71 as a sheet-shaped discharge electrode that moves relative to the electrode 71 and a power source 73 that applies a voltage to the electrode 71 via a brush 72 are provided. The sheet electrode 71 is attached to the photosensitive drum 1 in a non-contact state by an upper support 74 having a rotatable roller shape and a lower support 75 provided near the photosensitive drum 1. The sheet-shaped electrode 73 rotates in the direction of the arrow f following the rotation of the upper support 74, and is made of a material obtained by subjecting metal or resin to a conductive treatment. The arrow a in the figure indicates the direction of rotation of the photosensitive drum 1.

In the charging device 70, in order to charge the photosensitive drum 1, a voltage is applied to the sheet electrode 71,
An electric field is formed in a region between the electrode and the photosensitive drum 1 to generate the corona 76. Here, in order to favorably generate the corona 76, it is necessary to prevent the conductive substance from being disposed at a position closer to the sheet electrode 71 than the photosensitive drum 1. Therefore, in order to achieve this goal,
It is desirable to provide an insulating cover (not shown) around the sheet electrode 71.

Further, a scraper 77 for removing foreign matters adhering to the surface of the sheet electrode 71 is provided so as to be in a non-conductive state with other members in a state where one end of the scraper 77 is pressed against the sheet electrode 71. Is desirable.

According to this copying machine, when the sheet electrode 71 rotates, an air flow is generated in the area between the sheet electrode 71 and the photosensitive drum 1, so that the foreign matter generated by corona discharge in the area is caused by this air flow. Are prevented from staying. Further, even if the surface condition of the sheet electrode 71 is non-uniform, the non-uniform surface will not be located at a position facing the photoconductor drum 1 for a long time. Further, by providing the scraper 26, foreign matter is removed from the surface of the sheet electrode 71, and foreign matter is prevented from staying between the sheet electrode 71 and the photosensitive drum 1.

[Third Embodiment] Hereinafter, a third embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus and a charging device provided in the copying machine will be described. To do. The configuration of the copying machine according to this embodiment is the same as that of the first embodiment except for the charging device. Therefore,
Hereinafter, only the charging device will be described.

FIG. 4 is a schematic configuration diagram of the charging device 80 according to this embodiment. The charging device 80 includes the photosensitive drum 1
The discharge electrode 81 provided in a non-contact state, a power source 82 for applying a voltage to the electrode 81, and the discharge electrode 81 between the discharge electrode 81 and the photoconductor 1 so as to be in contact with the photoconductor drum 1. And an intervening member 83 interposed in contact with each other. The interposition member 81 is made of a roll-shaped resistor sheet, and the roll is rotatably supported by a shaft 84 and one end thereof is wound by a winding shaft 85, and the surface thereof is indicated by an arrow g. It moves in the direction and moves relative to the photosensitive drum 1. As the interposition member 83, a material having a resistance value of about 10 ⁶ to 10 ¹² Ωcm is used, and more specifically, a non-woven fabric or a fiber processed for adjusting the resistance value is used. Here, the resistance value of the interposition member 83 is defined as a value at which the discharge between the photoconductor drum 1 and the discharge electrode 81 is prevented and the discharge between the members is favorably performed.

The discharge electrode 81 may be rotated along with the movement of the interposition member 83 during the charging operation, or may be fixed and not rotated. The arrow a in the figure indicates the rotation direction of the photosensitive drum 1. Further, it is desirable to provide a scraper 87 for removing foreign matter adhering to the surface of the interposition member 83 so that one end of the scraper 87 is in pressure contact with the sheet electrode 71 and is in a non-conductive state with other members. In order to charge the photosensitive drum 1 in the charging device 80 having the above-described configuration, a voltage is applied to the discharge electrode 81, an electric field is formed in the region between the electrode and the photosensitive drum 1, and the corona 86 is removed. generate.

According to this copying machine, when the intervening member 83 rotates, an air flow is generated in the area between the interposing member 83 and the photoconductor drum 1. Therefore, foreign matter or the like caused by corona discharge due to this air flow is applied to the photoconductor. Adhesion to the drum 1 is prevented. Further, the provision of the interposition member 83 prevents the leak between the photosensitive drum 1 and the discharge electrode 81. Further, if the scraper 87 is provided, foreign matter is removed from the surface of the interposition member 83, and it is better prevented that the foreign matter stays between the interposition member 83 and the photosensitive drum 1.

In the above description, the interposition member 8
Although the roll-shaped sheet wound by the winding shaft 85 is used as 3, the endless belt supported by a plurality of support shafts and rotating may be used instead. However, in view of the fact that the interposition member 83 deteriorates with use, it is preferable to use a roll-shaped sheet that is successively used with a new surface and has excellent operability for replacement.

[0044]

EXAMPLES Hereinafter, examples in which the copying machine according to the embodiment is more concretely described will be described. The copying machine of this example is the same as the copying machine according to the first embodiment, except that an aluminum roller having a diameter of 20 mm or a hard alumite roller obtained by performing an electrochemical treatment on the aluminum roller is used as the discharge electrode 21, and the distance d is 0. It was set to 0.1 mm. The ratio of the peripheral speed of the photosensitive drum 1 to the peripheral speed of the discharge electrode 21 was set to 3.

FIG. 5 shows the photosensitive drum 1 in this embodiment.
Potential difference between the discharge electrode 21 and the discharge electrode 21 (hereinafter, simply referred to as potential difference)
Is a graph showing the relationship between the discharge current and the discharge current. White circles indicate the case where an aluminum roller is used as the discharge electrode, and black circles indicate the case where the hard alumite roller is used. As can be seen from FIG. 5, even when the aluminum roller is used, the discharge starts when the potential difference is about 850 to 880V. Then, in the vicinity of the voltage at which the discharge is started, there is no difference in the discharge current regardless of which roller is used. However, in the region where the discharge current exceeds 70 μA, the discharge current value when using the aluminum roller is higher than the discharge current value when using the hard alumite roller at the same potential difference.

In order to charge the photosensitive drum 1,
It is not desirable to use a voltage in the vicinity of the voltage at which the discharge has started. This is because the discharge state is unstable here and it is difficult to uniformly charge the photosensitive drum 1. On the other hand, if the voltage is too high, the photosensitive drum 1
Sparks between the charging electrode and the
As mentioned above, brush corona and pulse corona are easily mixed in the corona. Therefore, it is desirable to use a voltage that prevents both of these adverse effects. Further, the occurrence of spark discharge and the mixture of brush corona and the like need to be eliminated by using a constant current power source as the power source 23 or incorporating a high resistance in the voltage application circuit as described above.

[0047]

According to the first aspect of the present invention, since the roller-shaped rotating body rotates during discharging, non-uniform charging due to air staying between the discharge electrode and the body to be charged. Is prevented and uniform charging is realized. Further, according to the present invention, since the roller-shaped rotating body rotates when discharging, even if the surface state of the discharge electrode is uneven, this uneven portion faces the member to be charged. The time is shortened, the adverse effect of nonuniformity of the discharge electrode on the member to be charged is reduced, and uniform charging is realized. Further, according to the present invention, since the foreign matter removing device removes the foreign matter adhered to the discharge electrode, the foreign matter does not accumulate in the area between the discharge electrode and the body to be charged, and the unevenness of charging due to the accumulation of the foreign matter occurs. Is eliminated and uniform charging is realized.

In particular, according to the second aspect of the present invention, the surface of the roller-shaped discharge electrode is made of metal, so that the discharge electrode can be made simple and excellent in durability.

According to the third aspect of the invention, since the sheet-shaped discharge electrode moves relative to the member to be charged during charging, air stays between the discharge electrode and the member to be charged. It is possible to prevent non-uniform charging due to, and to realize uniform charging. Further, according to the present invention, even if the surface state of the discharge electrode is non-uniform due to the relative movement, the time for which the non-uniform portion faces the member to be charged is shortened, and the non-uniformity of the discharge electrode is reduced. The adverse effect of uniformity on the body to be charged is reduced, and uniform charging is realized. Further, according to the present invention, since the foreign matter removing device removes the foreign matter attached to the discharge electrode, the foreign matter does not accumulate in the area between the discharge electrode and the body to be charged, and uneven charging due to the foreign matter accumulates. Is eliminated and uniform charging is realized. Furthermore, it is not necessary to use a roller-shaped discharge electrode that has to be upsized to some extent, and the space for providing the discharge electrode can be reduced, so that the degree of freedom in design can be increased.

In particular, according to the invention of claim 4, by using a metal as the sheet-shaped discharge electrode, the discharge electrode can be made excellent in durability.

In particular, according to the invention of claim 5, since a resin belt having excellent flexibility is used as the sheet-shaped discharge electrode, a layout with a smaller radius of curvature as compared with the case where a metal belt or the like is used. Can be built into the device, and the degree of freedom in design is increased.

According to the sixth aspect of the invention, since the sheet-shaped intervening member moves relative to the member to be charged during charging, air stays between the discharge electrode and the member to be charged. It is possible to prevent non-uniform charging due to, and to realize uniform charging. Further, according to the present invention, since there is an intervening member between the discharge electrode and the body to be charged, even if the surface state of the discharge electrode is non-uniform, the effect of this non-uniformity is Uniform charging is achieved without directly reaching the body. Further, according to the present invention, since the foreign matter removing device removes the foreign matter adhering to the intervening member, the foreign matter does not accumulate in the area between the discharge electrode and the body to be charged, and uneven charging due to the foreign matter accumulates. Is eliminated and uniform charging is realized.

In particular, according to the invention of claim 7, since the foreign matter removing means is provided with a scraper, the structure can be simplified as compared with the case where a brush is used as the means.

In particular, according to the invention of claim 8, the surface of the latent image carrier, which is the member to be charged, is charged by using each of the inventions described above, so that uniform charging is realized.

According to the ninth aspect of the invention, a latent image is formed on the latent image carrier uniformly charged by the charging device,
Since the latent image is developed to form an image, good image formation can be realized without causing an image defect that occurs when a latent image is formed on a latent image carrier in which charging is uneven. It

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a transfer device included in an electrophotographic copying machine according to a first embodiment.

FIG. 2 is a schematic configuration diagram of an electrophotographic copying machine according to the first embodiment.

FIG. 3 is a schematic configuration diagram of a transfer device included in the electrophotographic copying machine according to the second embodiment.

FIG. 4 is a schematic configuration diagram of a transfer device included in an electrophotographic copying machine according to a third embodiment.

FIG. 5 is a graph showing the relationship between the discharge current and the potential difference between the photosensitive drum 1 and the discharge electrode 21 in the copying machine according to the example.

[Explanation of symbols]

 1 Photosensitive Drum 2 Charging Device 3 Exposure Laser Scanner 4 Eraser 5 Wet Development Device 6 Recording Paper 7 Transfer Charger 8 Cleaning Blade 9 Electrification Lamp 21 Discharge Electrode 22 Brush 23 Power Supply 24 Ammeter 25 Corona 26 Scraper 51 Development Container 52 Development Roller 54 Developer Supply Part 55 Scraper 56 Wedge 57 Squeeze Roller 58 Squeeze Roller Scraper 60 Set Roller 70 Charging Device 71 Sheet Electrode 72 Brush 73 Power Supply 74 Upper Support 75 Lower Support 76 Corona 77 Scraper 80 Charging Device 81 Discharge Electrode 82 Power Supply 83 Intervening member 84 Shaft 85 Winding shaft 86 Corona 87 Scraper

Claims (9)

[Claims] 1. A roller-shaped discharge electrode, which is provided in a non-contact state with a member to be charged and which moves relative to the member to be charged when it is rotated, and a voltage is applied to the discharge electrode. A charging device comprising: a power source for generating a corona discharge in a region between the discharge electrode and the discharge electrode; and a foreign matter removing unit for removing foreign matter adhering to the surface of the discharge electrode. 2. The charging device according to claim 1, wherein the surface of the discharge electrode is made of metal. 3. A sheet-shaped discharge electrode, which is provided in a non-contact state with a member to be charged and which moves relative to the member to be charged,
A power source for applying a voltage to the discharge electrode to generate corona discharge in a region between the charged body and the discharge electrode; and a foreign matter removing unit for removing foreign matter adhering to the surface of the discharge electrode. Charging device characterized in that 4. The charging device according to claim 3, wherein a metal belt is used as the discharge electrode. 5. The charging device according to claim 3, wherein a resin belt subjected to a conductive treatment is used as the discharge electrode. 6. A discharge electrode provided in contact with a body to be charged, and a power supply for applying a voltage to the discharge electrode to generate corona discharge in a region between the body to be charged and the discharge electrode. A sheet-like interposing member that is in contact with the discharge electrode between the charged body and the discharge electrode and is in contact with the charged body, and that moves relative to the charged body, And a foreign matter removing unit that removes foreign matter attached to the surface of the sheet-shaped intervening member on the charged body side. 7. The charging device according to claim 1, claim 3, or claim 6, wherein the foreign matter removing means includes a scraper. 8. The charging device according to claim 1, wherein the member to be charged is a latent image carrier on the surface of which a latent image is formed. 9. A latent image carrier on which a latent image is formed, a charging device according to claim 8, and a latent image forming device for forming a latent image on the latent image carrier charged by the charging device. An image forming apparatus comprising: an image forming unit; and a developing device that develops the latent image to form a visible image.