JP3296093B2 - Charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a copying machine or a printer to which electrophotography is applied, and uniformly charges the surface of a charge receptor such as a photoreceptor or an electrostatic recording material. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device, and more particularly to a charging device in which a charging electrode is arranged so as to be in contact with a charge receptor.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, the surface of a charge receptor such as a photoreceptor is charged by a charging device, an electrostatic latent image is formed on the surface by irradiation of image light, and developed by a developer. There is known a device that visualizes an electrostatic latent image by performing the operation. As a charging device used in such an image forming apparatus, a charging device using corona discharge and a charging device using a contact charging method using a charging roll or the like are conventionally known. Charging devices that use corona discharge
A wire is stretched in the shield case so as to approach / separate from the surface of the charge receptor, and a high voltage is applied to the wire to cause corona discharge, thereby giving a predetermined charge to the surface of the charge receptor. Although such a charging device is excellent in uniform charging, it has a disadvantage that discharge products such as ozone are generated in a large amount and thus need to be treated, which tends to increase the size and cost of the device.

[0003] Therefore, recently, a charging device using a contact charging system in which a charging electrode is brought into direct contact with a charge receptor and charged is widely used. Such a charging device,
A conductive member such as an elastic roll or a brush is placed in contact with the surface of the charge receptor, and a DC voltage or a superimposed voltage of DC and AC is applied to the conductive member, and discharge is caused in a minute gap near the contact portion. The charging is performed by causing the charging. In addition, JP-A-1-93760 and JP-A-2-93.
As disclosed in Japanese Patent Publication No. -282279, an apparatus including a blade-shaped charging electrode pressed against the surface of a charge receptor is also known. In such a charging device, the amount of ozone generated is extremely small because corona discharge is not used.
Furthermore, since the conductive member is arranged so as to be in contact with the charge acceptor, it has an advantage that it is suitable for miniaturization and weight reduction of the device.

However, among the above-mentioned contact-type charging devices, those using a roll-shaped conductive member require a roll supporting device and the like, and have a drawback that the structure tends to be complicated. In addition, in order to perform uniform charging, it is necessary to improve the adhesion between the elastic roll and the charge acceptor to form stable minute voids, and to take measures such as lowering the hardness of rubber. For this reason, it is necessary to contain a large amount of process oil, and there is a disadvantage that this process oil easily transfers to a charge acceptor and adversely affects image quality. On the other hand, there is a method of increasing the outer shape accuracy of the roll in order to solve such a drawback, but it is very difficult to increase the outer shape accuracy of an elastic body such as rubber, which leads to an increase in cost such as a decrease in yield.

On the other hand, when a brush-shaped conductive member is used, although it is more effective for uniform contact than the above-mentioned roll-shaped member, it takes time and effort to manufacture the brush, and the sweep of the brush causes uneven charging. There is a drawback that it is easy to appear in the image. Further, in the method using a blade-shaped charging electrode, it is difficult to set minute gaps required for discharging, and it is difficult to perform uniform and good charging. Further, the blade-shaped charging electrode has a disadvantage that the contact pressure with the charge acceptor is large and the load on the charge acceptor increases.

Therefore, in order to avoid the above-mentioned drawbacks, a charging device disclosed in Japanese Patent Application Laid-Open No. 4-249270 has been proposed. This charging device is shown in FIGS. 12A and 12B.
As shown in FIG. 2, a flexible film-like member 102 is used as a conductive member, and the free end 10 of the film-like member is used.
2a is arranged to be in contact with the surface of the charge acceptor 101. Then, by applying a DC voltage from the power supply 104, a discharge is caused in the minute gap A in FIG. 12B, and the surface of the charge receptor is charged to a predetermined potential. The charging device shown in FIG. 12 has an advantage that stable contact can be easily obtained with a simple configuration, and the cost of the member itself is lower than other conductive members.

[0007]

However, in the charging device shown in FIG. 12, the free end 10
2a comes into contact with the charge acceptor 101, and the gap between the edge 102b of the cut surface and the charge acceptor 101 [FIG.
(A portion denoted by reference numeral B in (b)) tends to cause abnormal discharge, and when a high voltage is applied, abnormal discharge occurs and charging becomes unstable. For this reason, there is a problem that the charge acceptor cannot be charged to a high potential.

Further, since charging is performed while the film-shaped member 102 is pressed against the charge receptor 101, there is a problem that the friction coefficient at the contact portion is increased and an abnormal noise is generated due to friction. In addition, there is a problem in that the charging device vibrates due to the friction, and the gap A where the discharge is performed fluctuates, so that the charging potential is likely to be unstable.

Further, foreign matter such as a developer or an external additive or a lubricant added between the charge acceptor and the cleaning blade is clogged between the film-like member 102 and the charge acceptor 101. There is also a problem that streak-like charging failure occurs without causing discharge and image quality defects occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to prevent the generation of frictional noise at the contact portion of the charging electrode and to stabilize the surface of the charge receptor uniformly. It is an object of the present invention to provide a charging device which can be charged with good quality without image quality defects.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 comprises a flexible and semiconductive film-like member, which is in contact with a charge receptor. And a power supply for applying a charging voltage to the charging electrode, wherein the charging electrode is curved so as to form a curved surface, and the convex surface of the curved surface in contact with the charge receptor, the contact
Before and after the part, a minute gap where discharge occurs is formed in a wide range
Shape that slowly moves away from the charge receptor
The charging device is characterized in that the edge of the film-like member constituting the charging electrode is arranged so as to be separated from the surface of the charge receiving member to be charged by a distance that does not discharge.

[0012] The invention according to claim 2 is the above-mentioned claim 1.
In the charging device according to (1), the film-like member constituting the charging electrode is selected such that at least a contact portion with the charge receptor is made of an electrode material having flexibility and semi-conductivity so as to reduce a friction coefficient. It is assumed to be formed by mixing a powdery material or a granular material of the material.

[0013] The invention according to claim 3 is the above-mentioned claim 1.
In the charging device according to the above, in a portion of the charging electrode facing the charge receptor, a small piece of a material capable of reducing the friction coefficient of the surface is smaller than the surface of the film-shaped member.
It is mounted so as to protrude, and the charging electrode comes into contact with the charge receptor via the small piece.

According to a fourth aspect of the present invention, there is provided a charging electrode comprising a flexible and semiconductive film-shaped member, which is provided so as to come into contact with a charge receptor, and a charging voltage applied to the charging electrode. in applying the charging device and a power source for the charging electrode, the edges of the film-like member is covered with a small insulating material coefficient of friction, the coating portion is the Huy
The charge is formed so as to protrude from the surface of the
In contact with the receptor, the film-like member contacts the charge receptor.
And those that are arranged to face each other with a small gap
I do .

In the charging device according to the first aspect of the present invention, if the edge of the film-shaped member is separated from the charge receiving surface by a distance that does not discharge, the shape near the edge of the film-shaped member is appropriately adjusted. Can be set. Further, the film-shaped member may be formed by supporting both side edges to form a ring or the like. The film-shaped member has a volume resistivity of 10 ³ to 1.
A material of about 0 ¹⁰ Ω · cm can be used, and a material of about 10 ³ to 10 ⁵ Ω · cm is particularly desirable.

In the invention described in the second aspect, the material of the powdery or granular material mixed into the electrode material can be appropriately selected from materials capable of reducing the friction coefficient of the surface. In the charging electrode, the mixing ratio of the powdery or granular material is appropriately set so that the friction coefficient of the contact portion between the film-like member and the charge receptor can be reduced. Further, the electrode material forming the film-like member can be appropriately set in consideration of the applied voltage.

In the third aspect of the present invention, the small piece may be one which can maintain a distance between the charging electrode and the charge receptor in a gap capable of performing an appropriate discharge.
The shape, structure, and the like can be appropriately set. Further, the material for forming the small pieces can be appropriately selected from materials capable of reducing the friction coefficient of the surface.

In the invention according to the fourth aspect, the covering portion covers the edge of the film-shaped member and comes into contact with the charge acceptor, and can appropriately maintain the distance between the film-shaped member and the charge acceptor. If so, the shape, structure, and the like can be appropriately set. Further, the material of the covering portion can be appropriately set from the insulating materials.

[0019]

In the charging device according to the first aspect of the present invention, the charging electrode is curved so as to form a curved surface, and the convex surface of the curved surface comes into contact with the charge receptor. The charging is performed by causing a discharge in a gap before and after the contact portion. This charging electrode prevents the abnormal discharge from occurring between the cut surface of the edge of the film-shaped member and the surface of the charge-receiving member because the edge of the film-shaped member is separated from the charge-receiving surface by a distance that does not discharge. can do.
Therefore, a high voltage of + or -1000 V or more can be applied to the charging electrode, and the surface of the charge receptor can be charged to a sufficient potential of + or -500 V or more. In addition, the charging electrode comes into contact with the charge receptor on the convex side of the curved surface, and gradually separates from the surface of the charge receptor before and after that. Occurrence can be reduced.

In the charging device according to the second aspect of the present invention, the contact portion of the charging electrode with the charge receptor is formed by mixing a material having a small coefficient of friction. It is possible to reduce the coefficient of friction of the contact surface with the surface, and to reduce the generation of friction noise. Further, the toner, the external additive, the lubricating material, and the like do not stay in the contact portion, and the occurrence of charging failure due to the adhesion of foreign matter can be prevented.

In the charging device according to the third aspect of the present invention, since the charging electrode is in contact with the charge receptor via the small piece made of a material having a small coefficient of friction, the friction of the contact surface with the charge receptor is reduced. The coefficient can be reduced. Therefore, occurrence of abnormal noise due to friction is prevented. In addition, the above-mentioned small pieces do not directly contact the charge electrode and the charge receptor for discharging, and the gap between the charge electrode and the charge receptor is kept constant, so that more uniform charging is stably performed. It is possible to do.

In the charging device according to the present invention, the edge of the film-like member constituting the charging electrode is coated with an insulating material having a small coefficient of friction so that the coating contacts the charge receptor. , The cut surface of the edge of the film-shaped member does not directly contact or come close to the surface of the charge-receiving member, thereby preventing occurrence of abnormal discharge. Also,
The above-mentioned covering portion can reduce the friction coefficient of the contact surface with the charge receptor, and can prevent the occurrence of abnormal noise due to friction. Further, foreign substances are less likely to adhere between the coating portion and the charge acceptor, and the occurrence of streak-like image quality defects due to uneven charging is also prevented. In addition, since the gap between the charging electrode and the charge receptor is kept constant by the covering portion, more uniform charging can be stably performed.

[0023]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention. This charging device 10
A charging electrode 2 which is supported at a position facing the charge receptor 1, is formed by bending a semiconductive film-like member and overlapping both ends thereof to form a loop, and is connected to both ends of the charging electrode 2. And a support 4 that supports the charging electrode 2 and the metal electrode 3 and contacts the charging electrode 2 to the charge receptor 1 with an appropriate contact pressure. Further, the metal electrode 3 is connected to a power supply 5 so as to apply a voltage to the charging electrode 2. The charge receptor 1 has, for example, a configuration in which a photoconductive layer 1b is laminated on a cylindrical conductive substrate 1a.
Is grounded. Then, discharge is performed in a minute gap in the vicinity of the contact portion with the charging electrode 2 so that the charge receptor 1
Is charged.

The film-like member constituting the charging electrode 2 has a thickness of about 50 μm and a volume resistivity of 10 ³ to 10 ³ .
A semiconductive member of 10 ⁵ Ω · cm is used. The charging electrode 2 is formed by mixing conductive particles such as carbon black in a film of, for example, polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, or fluororesin. Is set appropriately, a predetermined volume resistivity can be obtained. Further, considering that the charging electrode 2 comes into direct contact with the charge receptor 1,
The tensile modulus is set to about 10 to 280 kg / mm ² . The power supply 5 can apply a DC voltage or a high voltage in which an AC is superimposed on a DC. The configuration of the power supply 5 and the applied voltage will be described later.

In such a charging device, when a predetermined voltage is applied from the power supply 5 to the charging electrode 2 via the metal electrode 3, the discharging is performed in a minute gap near the contact portion between the charging electrode 2 and the charge receptor 1. And ionization of the air takes place. If the negative side of the power supply 5 is connected to the metal electrode 3, negative ions or electrons flow toward the charge acceptor 1 to charge the surface to a predetermined potential, and positive ions reach the charged electrode 2 side. Neutralized. In the charging device of this embodiment, the charging electrode 2
The discharge is stable because of its large resistance, and does not lead to spark discharge (abnormal discharge). Furthermore, by using a semiconductive member for the charging electrode 2, it is possible to prevent an excessive current from flowing to any part of the gap, and to uniformly charge the charge receptor 1. Becomes

Next, the results of carrying out a charging test of the charging device using a charging test device as shown in FIG. 2 will be described. This charging test device includes a surface potential sensor 11 for detecting the potential of the surface of the charge receptor 1 and a charge removing lamp 13 for removing the surface around the charge receptor 1. Is connected to a surface voltmeter 12. Further, the charging device 10 according to the present embodiment is disposed on the upstream side of the surface potential sensor 11 in the rotation direction of the charge receptor 1, and the charging electrode 2 in the charging device 10 contacts the surface of the charge receptor 1. Is fixed to the support 4 as described above. The metal electrode 3 is connected to a power supply 15 for applying a DC voltage via a switch 17, and is connected to a DC voltage or an AC power supply 1.
6, and a voltage in which an AC component is superimposed on a DC component is applied. The power supply 15 can change the voltage arbitrarily, and the surface potential of the charge receptor 1 that changes with the voltage can be measured by the surface voltmeter 12.

FIG. 3 shows the relationship between the applied voltage when a DC voltage is applied to the metal electrode 3 and the surface potential of the charge receptor 1 in a charging test using the charging test apparatus. In this figure, when a DC voltage of 0 to -2 KV is applied from the power supply 15, the surface potential of the charge receptor 1 starts to rise from an applied voltage of about -650 V, and reaches about -1450 V at an applied voltage of -2 KV. Was confirmed. During this time, no abnormal discharge was generated by the charging device 10. On the other hand, in a charging device in which the free end of the charging electrode is in contact with the charge acceptor as disclosed in JP-A-4-249270, the surface potential of the charge acceptor reaches -450 V with an applied voltage of -1 KV. At that point, abnormal discharge occurred, and the surface potential could not be further increased. In the above-described charging device, when a voltage in which a sine wave having a peak-to-peak voltage of about 1.5 KV was superimposed as an AC component on a DC component of -500 V as shown in FIG. 4 was applied, stable charging was possible.

FIG. 5 shows the relationship between the peak-to-peak voltage and the surface potential of the charge receptor 1 when an AC component having a changed peak-to-peak voltage value is superimposed and applied to a DC component of -500 V. . In this figure, when the peak-to-peak voltage exceeds about 500 V, the surface potential of the charge acceptor 1 starts to rise,
It was confirmed that the applied voltage was close to the DC voltage value of the applied voltage at around 1100 V, and the surface potential was maintained at a constant value even when the applied voltage was further increased. Therefore, according to the charging test shown in FIG. 3 or FIG. 5, a voltage can be applied so that the surface of the charge receptor 1 is charged to an appropriate potential without causing abnormal discharge.

FIG. 6 is a schematic configuration diagram showing an image forming apparatus to which the charging device 10 is applied. The image forming apparatus includes a photoconductor (charge acceptor) 20 on which a latent image is formed by irradiating image light after uniform charging, and charges the surface of the photoconductor 20 around the photoconductor 20. In addition to the charging device 10 of the present embodiment, an exposure device 21, a developing device 22,
It has a transfer roll 25 and a cleaning device 27.
Further, a paper cassette 2 for storing the paper 24 is provided in the apparatus.
3. It has a fixing device 26 for fixing the toner image.
In such an image forming apparatus, after the photoconductor 20 is charged to a predetermined potential by the charging device 10, a laser beam corresponding to image information is exposed by the exposing device 21, and the photoconductor 2 is charged.
0, an electrostatic latent image is formed on the surface. This electrostatic latent image is developed by the developing device 22, and a visible image is formed by adhesion of toner. Further, the paper 24 is transferred from the paper cassette 23 to the photoconductor 20 and the transfer roll 2 along the paper guide 28.
5, and the toner image is transferred onto the sheet 24 by the transfer roll 25. The transferred toner image is fixed by the fixing device 26 to form one copy image. On the other hand, after the transfer process, the toner remaining on the photoconductor 20 is cleaned by the cleaning device 27, and the rotation of the photoconductor 20 starts the charging process by the charging device 10 again. Note that the voltage applied to the charging device 10 in the above process is the voltage shown in FIG.

Using such an image forming apparatus, 10,0
When a reliability test of the charging device 10 was performed by forming 00 print images, a large amount of toner adhered to the vicinity of the contact portion between the charging electrode 101 and the photoconductor in the conventional charging device shown in FIG. In contrast to the non-uniform charging, the charging device 10 of this embodiment had a small amount of toner attached to the charging electrode 2 even after printing 10,000 sheets, and the charging potential was uniform.

FIG. 7 is a schematic diagram showing a charging device according to an embodiment of the present invention. In this charging device, instead of the charging electrode 2 of the charging device shown in FIG. It has a charging electrode 32 arranged. The charging electrode 32 is arranged such that the free end 32a of the film member does not discharge from the surface of the charge receptor.

The charged electrode 32 has a volume resistivity of 10 ³ to 10 ¹⁰ Ω by dispersing conductive particles such as carbon black in a film of, for example, polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane or fluororesin. Cm, and as shown in FIG. 7B, a powder 36 of a material such as polyvinylidene fluoride or Teflon (registered trademark of DuPont), which can reduce the coefficient of friction, is used.
Almost uniformly dispersed in the film. Powder 3
The mixing amount of 6 is set to an appropriate amount so that the friction between the charging electrode 32 and the charge receptor 1 is reduced. The charging electrode 32 has a thickness of about 50 μm and a tensile modulus of elasticity of 10 to 280 K in consideration of direct contact with the charge receptor 1.
g / mm ² . The other structure of the charging device is the same as that of the charging device shown in FIG.

When a copying test was performed on 10,000 sheets using an image forming apparatus to which such a charging device was applied, it was confirmed that a good copied image could be obtained. In addition, as compared with the image quality obtained by using a charging electrode in which a material capable of reducing the friction coefficient was not mixed, the occurrence of black streak-like image quality defects due to poor charging was significantly reduced. Also,
No abnormal noise was generated due to friction.

FIG. 8 is a schematic structural view showing a charging device according to another embodiment of the present invention. This charging device has, instead of the charging electrode 32 of the charging device shown in FIG. 7, a charging electrode 42 having a shape in which a film-like member is curved and a free end 42 a is rounded in a direction opposite to the charge receptor 1. are doing. The charging electrode 42 is formed of the same material as the material forming the charging electrode 32, and is made of a powder of a material such as polyvinylidene fluoride or Teflon (registered trademark of DuPont) that can reduce the coefficient of friction. Are used. Further, the thickness and the volume resistivity are set to be the same.

The charging electrode 42 is in contact with the charge receptor 1 on the convex side near the rounded tip of the free end 42a, and discharge is performed in the minute gaps before and after the contact portion. The other structure of the charging device is the same as that of the charging device shown in FIG. Even with such a charging device, a copy test was performed using an image forming apparatus.
As in the case of the charging device shown in Fig. 7, streak-like image quality defects due to poor charging were prevented, and a good copied image was obtained. FIG.
Since the contact area is smaller than that of the charging electrode 32 shown in FIG.

FIG. 9 is a schematic structural view showing a charging device according to an embodiment of the present invention. This charging device is different from the charging electrode 2 of the charging device shown in FIG.
Further, on the convex side of the J-shaped surface of the charging electrode 52, a small piece 56 formed in a convex shape is mounted. The small piece 56 is provided over substantially the entire length of the charging electrode 52 in the width direction, and is formed so that the convex surface draws a gentle curve in the circumferential direction of the charge receptor 1. The small piece 56 is made of, for example, Teflon (registered trademark of DuPont).
The small piece 56 is in contact with the surface of the charge receptor 1 to form a minute gap between the charging electrode 52 and the charge receptor 1 and discharge is performed by the gap. It has become so. The charging electrode 52
Is formed of the same material as that of the charging electrode 2 shown in FIG. 1, and is obtained by mixing conductive powder in a proper ratio so as to have a proper volume resistivity in a film made of resin or the like. The other structure of the charging device is the same as that of the charging device shown in FIG.

Also in such a charging device, the friction between the small piece 56 and the charge receptor 1 is reduced, so that the generation of an abnormal sound due to the friction is prevented. In addition, the charging electrode 5
2 and the charge acceptor 1 do not come into direct contact with each other, and the small piece 56 is interposed therebetween, so that the developer or lubricant that passes through the cleaning grade does not stagnate, and the generation of image defects due to foreign matter is prevented. Can be reduced. Also, the charging electrode 52 and the charge receptor 1 are formed by the small pieces 56.
, A minute gap is secured in a wide range, and stable charging becomes possible.

FIG. 10 is a schematic structural view showing a charging device according to an embodiment of the present invention. In this charging device, the covering portion 66 for covering the leading end portion of the charging electrode 62 formed of a film-like member so as to be buried is formed by the charging electrode 6.
2 is provided over substantially the entire length in the width direction. The covering portion 66 has a uniform and substantially circular cross section in the width direction of the charging electrode 62, and is formed of an insulating material having a small friction coefficient such as Teflon (registered trademark of DuPont). In this charging device, the covering portion 66 comes into contact with the surface of the charge receptor 1 so that a minute gap is maintained between the charging electrode 62 and the charge receptor 1, and the gap causes discharge. . The material of the charging electrode 62 and other configurations of the charging device are the same as those of the charging device shown in FIG.

Even in such a charging device, the charging electrode 62 does not directly contact the surface of the charge receptor 1, so that uniform charging is performed and the occurrence of image defects due to adhesion of a developer or a lubricant is reduced. . Further, the charging electrode 62 is appropriately pulled by the covering portion 66, and a constant minute gap is always maintained between the charging electrode 62 and the charge receiving member 1. Therefore, more uniform charging can be stably performed in the axial direction.

FIG. 11 is a schematic structural view showing a charging device according to another embodiment of the present invention. This charging device includes the metal electrode 63 and the support member 6 shown in FIG.
And a cleaning blade 74 for cleaning the surface of the charge receptor 1, and a charging blade supported downstream of the cleaning blade 74 in the rotation direction of the charge receptor 1. An electrode 72 and a metal electrode 73 that supports the charging electrode 72 and the cleaning blade 74 and applies a high voltage to the charging electrode 72 are provided. The charging electrode 72 has the same configuration as that of the charging electrode 62 shown in FIG. 10, and has a covering portion 76 fixed so that the tip portion is buried in the same manner as described above. The other structure of the charging device is the same as that of the charging device shown in FIG.

In such a charging device, as in the charging device shown in FIG. 10, since the minute gap is held between the charge receiving member 1 and the covering portion 66, uniform and stable charging is performed. A good copied image can be obtained. Furthermore, since the charging electrode 72 is arranged close to the cleaning blade 74, there is an advantage that space can be saved.

[0042]

In the charging device according to the first to third aspects of the present invention, the edge of the charging electrode is separated from the charge receiving surface by a distance that does not discharge, so that the occurrence of abnormal discharge is prevented, and excellent charging is achieved. Images can be obtained. In addition to this, in the charging device according to the invention described in claim 2 or 3,
It is possible to reduce the friction coefficient of the contact surface with the charge receptor, and it is possible to prevent the generation of friction noise. Further, the toner, the external additive, the lubricant and the like do not stay at the contact portion with the charge receptor, and the generation of streak-like image quality defects due to uneven charging can be prevented. Furthermore, in the charging device according to the third aspect of the present invention, the charging electrode comes into contact with the surface of the charge receptor via the small piece, and a constant gap is maintained, so that more uniform charging can be stably performed. it can.

In the charging device according to the fourth aspect of the present invention, the edge of the charging electrode is covered with the coating portion so that the charging electrode does not come into contact with the surface of the charge receptor, so that occurrence of abnormal discharge can be prevented. . Further, since a fixed gap is maintained between the charging electrode and the charge acceptor, more uniform charging can be stably performed. Further, the coefficient of friction of the contact surface with the charge acceptor is reduced, and occurrence of abnormal noise can be prevented. Further, foreign matters are less likely to adhere between the coating portion and the charge receptor, and the occurrence of streak-like image quality defects due to uneven charging can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram showing a charging test device for performing a charging test of the charging device shown in FIG. 1;

FIG. 3 is a diagram illustrating a relationship between a DC voltage applied to a charging device and a surface potential of a charged charge receptor in the charging test device.

FIG. 4 is a diagram showing an example of a voltage applied to the charging device shown in FIG. 1;

FIG. 5 is a diagram showing a relationship between a peak-to-peak voltage of an AC component of a voltage applied to a charging device and a surface potential of a charged charge receptor in the charging test device.

FIG. 6 is a schematic configuration diagram showing an image forming apparatus using the charging device shown in FIG. 1;

FIG. 7 is a schematic configuration diagram showing a charging device according to an embodiment of the invention described in claim 2;

FIG. 8 is a schematic configuration diagram showing a charging device according to another embodiment of the invention described in claim 2;

FIG. 9 is a schematic configuration diagram showing a charging device according to an embodiment of the invention described in claim 3;

FIG. 10 is a schematic configuration diagram showing a charging device according to an embodiment of the present invention.

FIG. 11 is a schematic configuration diagram showing a charging device according to another embodiment of the invention described in claim 4.

FIG. 12 is a schematic configuration diagram showing a conventional charging device.

[Explanation of symbols]

 1 Charge acceptor 2, 32, 42, 52, 62, 72 Charging electrode 3, 33, 43, 53, 63, 73 Metal electrode 4, 34, 44, 54, 64 Support 5, 35, 45, 55, 65 , 75 Power supply 10 Charging device 11 Surface potential sensor 12 Surface potential meter 13 Static elimination lamp 15 DC power supply 16 AC power supply 17 Switch 20 Photoconductor 21 Exposure device 22 Developing device 23 Paper cassette 24 Paper 25 Transfer roll 26 Fixing device 27 Cleaning device 28 Par guide 56 Small piece 66, 76 Coating part 74 Cleaning blade

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yuka Nakayama 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. (56) References JP-A-6-138749 (JP, A) JP-A-4-107478 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/02

Claims (4)

(57) [Claims] 1. A charging device comprising a flexible and semiconductive film-shaped member, which is provided so as to be in contact with a charge acceptor, and a power source for applying a charging voltage to the charging electrode. In the device, the charging electrode is curved so as to form a curved surface, contacts the charge receptor on a convex side of the curved surface, and forms a contact portion.
Before and after, a minute gap where discharge occurs is formed in a wide range
As shown in the figure, the shape gradually moves away from the charge receptor.
The charging device is characterized in that the edge of the film-like member constituting the charging electrode is spaced apart from the surface of the charge receiving member to be charged by a distance that does not discharge. 2. The charging device according to claim 1, wherein the film-like member constituting the charging electrode has a flexible and semiconductive electrode material at least at a contact portion with a charge receptor. A charging device characterized by being formed by mixing a powdery or granular material of a material selected to reduce the coefficient of friction. 3. The charging device according to claim 1, wherein a small piece of a material capable of reducing a surface friction coefficient is provided on a portion of the charging electrode facing the charge receptor.
Attached so as to protrude from the surface of the film-like member.
The charging device is characterized in that the charging electrode comes into contact with the charge receptor via the small piece. 4. A charging device comprising a flexible and semiconductive film-shaped member and provided with a charging electrode provided in contact with a charge acceptor, and a power supply for applying a charging voltage to the charging electrode. In the apparatus, the charging electrode may be formed such that an edge of the film-shaped member is coated with an insulating material having a small coefficient of friction, and the coating portion protrudes from a surface of the film-shaped member.
A film-shaped member formed and in contact with the charge acceptor
Are arranged so as to face the charge acceptor with a small gap.
A charging device characterized by being placed .