JPH0772705A - Electrifier - Google Patents

Abstract

PURPOSE:To execute uniform electrification, even if the surface of the contact electrifying member such as an electrifying roller has ruggendness and irregularities in a resistance value. CONSTITUTION:The elastic roller 1 whose surface resistance is 10<5>-10<11>OMEGAcm and a blade 2 (or a wire) are provided, the blade 2 is arranged so as to make its end surface parallel with the electrifying roller 1, in a space held between it and a body 3 to be electrified, on the upstream side in the movement of the body 3 to be electrified, when viewing from the elastic roller 1 and a DC voltage VB applied to the blade 2 is set so that when the electrification starting voltage of the blade 2 and the body 3 to be electrified is defined as VTH2, the absolute value of the voltage VB satisfies ¦VB¦<VTH2. Electrification unevenness occurs in a region where the electrifying roller 1 gradually approaches the photosensitive body (body to be electrified) 3. However, discharge in the region is regulated by the blade 2, to prevent the electrification unevenness caused by the ruggedness and the irregularities in the resistance value on the surface of the electrifying roller 1 and execute the uniform electrification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charger for charging a photoconductor for electrophotography.

[0002]

2. Description of the Related Art In recent years, reduction in ozone in electrophotographic devices has been demanded. Ozone is generated by discharge in air, and is mainly generated by charging and transfer in an electrophotographic apparatus. Since a large amount of ozone is generated by charging using a wire electrode, which has been widely used in the past, an apparatus that charges a roller-shaped charging member by contacting it with a photoconductor has been put into practical use as an alternative charging method.

[0003]

SUMMARY OF THE INVENTION In a device for charging a roller-shaped charging member (hereinafter also simply referred to as a charging roller) by contacting it with a photosensitive member, the simplest voltage application method is to apply a DC voltage to the charging roller. It is a method of applying. However, in the method in which a DC voltage is applied to the roller to charge the photoconductor, unevenness on the roller surface or local unevenness in resistance causes uneven charging, resulting in a reduction in image resolution or so-called fogging that causes unnecessary toner to scatter in non-image areas. Occurs, and the image quality is degraded. If the roller surface is polished to reduce irregularities, uneven charging is also reduced, but surface polishing takes time in the process and the cost increases. It is also difficult to form a surface layer having a uniform resistance value.

As a result of various experiments conducted by the inventors for investigating the cause of uneven charging, it has been found that uneven charging due to surface irregularities and uneven resistance occurs in a region where the charging roller gradually approaches the body to be charged. FIG. 2 shows the experiment at that time. In FIG. 2D, 1 is a charging roller, 3 is a photoconductor, 11 is a DC power source, and 37 is a developing device.

In FIG. 2D, the charging roller 1 is in contact with the photoconductor 3 and a DC voltage is applied from the DC power supply 11. When the surface of the photoconductor 3 is charged by the charging device 1 to a potential for obtaining a white solid image and then developed by the developing device 37, uneven charging appears as toner fog on a white background.

FIG. 2A shows a conventional charging method using a charging roller. In FIG. 2A, the charging roller 1 is driven by the photoconductor 3 to rotate. When a white solid image was developed in this state, fogging occurred all over. That is, the charging roller 1 used in the experiment was fogged by simply applying the DC voltage. Next, in FIG. 2B, the charging roller 1 was fixed so as not to rotate, and charging was performed while moving only the photoconductor 3. The white solid image at this time is
Streaky fogging occurred in the moving direction of the photoconductor 3. Therefore, in FIG. 2C, the non-conductive powder 36 is filled on the upstream side of the movement of the photoconductor as viewed from the charging roller 1 fixed so as not to rotate. This suppresses the discharge in the region where the charging roller 1 gradually approaches the photoconductor 3. At this time, a fog-free image was developed. That is, it can be seen from the experiment of FIG. 2 that uneven charging can be reduced by suppressing the discharge in the region where the charging roller 1 gradually approaches the photoconductor 3.

In view of the above problems, the present invention provides a charging device capable of uniform charging regardless of the roughness and resistance unevenness of the roller surface.

[0008]

In order to solve the above problems, the charger of the present invention is a conductive device having a surface gradually approaching the surface of the body to be charged and a surface gradually separating from the surface of the body to be charged. Charging member and conductive blade (or wire)
The charging member comes into contact with the surface of the moving member to be charged, and the blade is charged in the space between the charging member and the surface of the member to be charged upstream of the movement of the member to be charged as viewed from the charging member. The charging member is arranged parallel to the body surface, and a DC voltage VR (however, VR = 0V or ground is included) is applied to the charging member, and a DC voltage VB (however VB = 0V or ground is also included) is applied to the blade. The absolute value of VB is │VB-V0│ <VTH2, where VTH2 is the charging start voltage between the blade and the body to be charged and the potential on the surface of the body to be charged immediately before contact with the charging member is V0. Is satisfied.

[0009]

According to the present invention, because of the above-described structure, the discharge regulating member such as a blade regulates the discharge to the body to be charged in the region where the charging roller, which causes the uneven charging, gradually approaches the body to be charged. Uniform charging is possible.

[0010]

【Example】

(Embodiment 1) A charger according to an embodiment of the present invention will be described below.
A description will be given with reference to the drawings.

FIG. 1 is a sectional view of a charger according to the first embodiment of the present invention. In FIG. 1, 1 is a charging roller and 4
Is a conductive axis of the charging roller 1, 2 is a blade, 3 is a photoconductor, and 11 and 12 are DC power supplies.

The charging roller 1 has a multi-layer structure, the inner layer is a conductive elastic body, and the surface is covered with a resistance layer having a volume resistance of 10 ⁵ to 10 ¹¹ Ωcm. The blade 2 is electrically conductive, and is arranged on the upstream side of the movement of the photoconductor 3 as viewed from the charging roller 1 and in the space sandwiched between the charging roller 1 and the photoconductor 3. Specifically, of the end faces of the blade 2 in the longitudinal direction, the end face on the contact surface side between the charging roller 1 and the photoconductor 3 (hereinafter also referred to as the blade end face) is parallel to the photoconductor 3, and the blade end face and the photoconductor 3 Of 0.5 mm and the minimum distance between the blade 2 and the roller 1 is 0.5 mm.

Here, the charging start voltage between the charging roller 1 and the photosensitive member 3 is VTH1, the charging start voltage between the blade 2 and the photosensitive member 3 is VTH2, and the surface potential of the photosensitive member 3 immediately before contact with the charging roller 1 is V0. Assuming that the surface potential of the photoconductor 3 immediately after contact with the charging roller is V1, the applied voltage VR to the charging roller 1 is | VR | = | V1 | + VTH1. At this time, the voltage VB applied to the blade 2 is set in a range that satisfies | VB-V0 | <VTH2. Here, VB also includes ground.
Since the voltage applied to the blade 2 is equal to or lower than the charging start voltage, the blade 2 does not discharge to the photoconductor 3. With this configuration, in a region where the charging roller 1 gradually approaches the photoconductor 3 (hereinafter, also referred to as a roller proximity region), the charging roller 1
The discharge from the photoconductor to the photoconductor 3 is not regulated by the blade 2. From the experiment, it was found that when the gap between the charging roller 1 and the blade 2 is 1.5 mm or less, the discharge from the charging roller 1 to the photoconductor 3 in the roller proximity region can be regulated stably.

FIG. 3 shows a perspective view of the charger in the first embodiment. The blade 2 is arranged in parallel with the charging roller 1, and both the length of the charging roller 1 and the length of the blade 2 in the longitudinal direction are longer than the drawing width.

As described above, with the configuration described in the first embodiment,
Since the blade 2 regulates the discharge in the region where the charging roller 1 in which the charging unevenness occurs gradually approaches the photoconductor 3, the photoconductor 3 can be uniformly charged.

(Embodiment 2) A charger according to a second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a sectional view of a charger according to the second embodiment of the present invention. In FIG. 4, 1 is a charging roller, 4
Is a conductive shaft core of the charging roller 1, 22 is a conductive wire having a diameter of 100 μm, 3 is a photoconductor, and 11 and 12 are DC power supplies. The charging roller 1 is 10 ⁵ to 10 as in the first embodiment.
It is a multilayer structure covered with a resistance layer in the range of 10 ¹¹ Ω cm.

Here, the charging start voltage between the charging roller 1 and the photosensitive member 3 is VTH1, the charging start voltage between the wire 22 and the photosensitive member 3 is VTH2, and the surface potential of the photosensitive member 3 immediately before contact with the charging roller 1 Is V0 and the surface potential of the photoconductor 3 immediately after contact with the charging roller 1 is V1, the applied voltage VR to the charging roller 1 is | VR | = | V1 | + VTH1. At this time, the voltage VB applied to the wire 22 is set in a range that satisfies | VB-V0 | <VTH2. Here, VB also includes ground.
Since the voltage applied to the wire 22 is less than the charging start voltage,
No discharge from the wire 22 to the photoconductor 3 occurs. In this structure, in the region where the charging roller 1 gradually approaches the photoconductor 3 (hereinafter also referred to as a roller proximity region), the discharge from the charging roller 1 to the photoconductor 3 is not regulated by the wire 22. Experiments have shown that when the gap between the charging roller 1 and the wire 22 is set to 1.5 mm or less, the discharge from the charging roller 1 to the photoconductor 3 in the roller proximity region can be stably regulated.

As described above, with the configuration described in the second embodiment,
Since the discharge in the region where the charging roller 1 in which the charging unevenness occurs causes the charging roller 1 to gradually approach the photoconductor 3 is regulated by the wire 22, uniform charging is possible.

(Embodiment 3) A charging device according to a third embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, the number of wires that regulate the charging from the charging roller 1 to the photoconductor 3 is one, but a plurality of wires 22 may be provided.

5 (a) and 5 (b) are sectional views of the charger in the third embodiment of the present invention. In FIG. 5 (a),
Reference numeral 1 is a charging roller, 3 is a photoconductor, 4 is a conductive shaft core of the charging roller 1, 11, 13 and 14 are DC power supplies, and 22 is a conductive wire having a diameter of 100 μm. There are two wires 22.

The charging roller 1 is 10 ⁵ to the same as in the first embodiment.
It is a multi-layer structure covered with a resistance layer in the range of 10 ¹¹ Ω cm.

Here, there are two wires 22 and the photosensitive member 3.
, VTH21, VTH22 in order from the upstream side of movement of the photoconductor 3, VTH1, the charge start voltage between the charging roller 1 and the photoconductor 3, and the surface potential of the photoconductor 3 immediately before contact with the charging roller 1. V0, the photoconductor 3 immediately after contact with the charging roller 1
If the surface potential of the charging roller 1 is V1, the voltage VR applied to the charging roller 1 is | VR | = | V1 | + VTH1. Assuming that the voltage applied to the wire 22 is VB1 and VB2 (however, including ground) from the upstream side, the absolute value of VBi is in the range that satisfies | VB1-V0 | <VTH21 | VB2-V0 | <VTH22. Set. Since the voltage applied to the wire 22 is less than the charging start voltage, the wire 22 is applied to the photoreceptor 3
No discharge occurs.

In this structure, in a region where the charging roller 1 gradually approaches the photoconductor 3 (hereinafter also referred to as a roller proximity region), discharge from the charging roller 1 to the photoconductor 3 is not regulated by the wire 22. . By various experiments,
If the gap between the charging roller 1 and the wire 22 is set to 1.5 mm or less, the charging roller 1 to the photoconductor 3 in the roller proximity area are
It was found that the discharge to the battery can be regulated in a stable manner. Furthermore, in FIG. 5 (b), one of the two wires has a resistor 16
It was also effective to add a potential difference by adding a voltage.

As described above, with the configuration described in the third embodiment,
Since the discharge in the area where the charging roller 1 in which uneven charging occurs is gradually close to the photoconductor 3 is uniformly regulated by the plurality of wires 22, uniform charging is possible.

(Embodiment 4) A charger according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 is a sectional view of a charger according to the fourth embodiment of the present invention. In FIG. 8, 1 is a charging roller and 2 is
Is a blade, 3 is a photoconductor, 4 is a conductive shaft core of the charging roller 1, and 11 and 12 are DC power supplies.

The charging roller 1 has a multi-layer structure, the inside of which is a conductive elastic body and the surface of which is covered with a resistance layer having a volume resistance of 10 ⁵ to 10 ¹¹ Ωcm. However, it is not necessary to make the resistance value the same as that of the charging roller 1. The configuration of the blade 2 is shown in FIG.

6 (a), 6 (b) and 6 (c) are sectional views of the blade 2, where 24 is a conductor and 25 is a volume resistance of 10 ⁵ to 10 ¹¹ Ω.
cm is a resistance layer, and 26 is an electrode. The resistance layer to be coated has a thickness of 30 μm. A voltage VB is applied to the conductor 24 of the blade 2 from the outside through the electrode 26.

The blade 2 is arranged on the upstream side of the movement of the photosensitive member 3 as viewed from the charging roller 1 and in the space sandwiched between the charging roller 1 and the photosensitive member 3. Specifically, when the surface of the blade 2 that directly faces the photoconductor 3 is referred to as a blade end face, the blade end face is parallel to the photoconductor 3, the blade end face is in contact with the photoconductor 3, and the blade end face and the roller 1 It is arranged so that the distance to is 0.5 mm.

By bringing the end surface of the blade 2 into contact with the photosensitive member as described above, a minute gap between the blade 2 and the charging roller 1 is stably secured, and the charging roller 1 is gradually charged to approach the photosensitive member. The regulation effect can be enhanced and uneven charging can be prevented.

The purpose of coating the surface of the blade 2 with the resistance layer is to prevent pinholes in the photoconductor. That is, there is a case where a photoconductive layer on the surface of the photoconductor is peeled off and a conductive substrate appears, that is, a so-called pinhole, occurs after long-term use. In this case, there is a risk of abnormal discharge from the conductive blade 2 to the pinhole. So blade 2
If a high resistance layer in the range of 10 ⁵ to 10 ¹¹ Ωcm is provided on the surface of, the leak current to the pinhole can be prevented.

Here, the charging start voltage between the charging roller 1 and the photosensitive member 3 is VTH1, the charging start voltage between the blade 2 and the photosensitive member 3 is VTH2, and the surface potential of the photosensitive member 3 immediately before the contact with the charging roller 1 is expressed. V0, the photoconductor 3 immediately after contact with the charging roller 1
If the surface potential of the charging roller 1 is V1, the voltage VR applied to the charging roller 1 is | VR | = | V1 | + VTH1. At this time, the voltage VB applied to the blade 2 is set in a range that satisfies | VB-V0 | <VTH2. Here, VB also includes ground.
Since the voltage applied to the blade 2 is equal to or lower than the charging start voltage, discharge from the blade 2 to the photoconductor 3 does not occur. With this configuration, in a region where the charging roller 1 gradually approaches the photoconductor 3 (hereinafter, also referred to as a roller proximity region), the charging roller 1
The discharge from the photoconductor to the photoconductor 3 is not regulated by the blade 2. From the experiment, it was found that when the gap between the charging roller 1 and the blade 2 is 1.5 mm or less, the discharge from the charging roller 1 to the photoconductor 3 in the roller proximity region can be regulated stably. As a matter of course, both the length of the charging roller 1 in the longitudinal direction and the length of the blade 2 are longer than the drawing width on the surface of the photoconductor 1.

That is, with the configuration described in the fourth embodiment, the discharge in the area where the charging roller 1 in which the charging unevenness occurs is gradually close to the photoconductor 3 is regulated by the blade 2, so that uniform charging is possible. Become.

(Embodiment 5) Hereinafter, a charger according to a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 9 is a sectional view of a charger according to the fifth embodiment of the present invention. In FIG. 9, 1 is a charging roller and 3 is
Is a photoconductor, 4 is a conductive shaft core of the charging roller 1, 11 and 12 are DC power supplies, 32 is a conductive wire having a diameter of 300 μm and coated with a resistance layer having a volume resistance of 10 ⁵ to 10 ¹¹ Ωcm, Is. The charging roller 1 is 1 as in the first embodiment.
It is a multilayer structure covered with a resistance layer in the range of 0 ⁵ to 10 ¹¹ Ωcm. The structure of the wire 32 is shown in FIG.

In FIG. 7, 1 is a charging roller, 3 is a photoconductor, 27 and 28 are cross sections of wires 32, 27 is a conductive shaft, 28 is a volume resistance covering the conductive shaft 27.
It is a resistance layer of ⁵ to 10 ¹¹ Ω cm. Wire diameter is 30
The thickness of the resistance layer to be coated is 0 μm and 30 μm.

By bringing the wire 32 into contact with the photosensitive member as described above, a minute gap between the wire 32 and the charging roller 1 is secured, and the charging regulation effect in the region where the charging roller 1 gradually approaches the photosensitive member. And uneven charging can be prevented.

The purpose of coating these resistive layers was as in Example 4.
It is a countermeasure for the photoconductor pinhole as well. That is, there is a case where the photoconductive layer on the surface of the photoconductor is peeled off and a so-called pinhole appears where the conductive substrate appears due to long-term use. In this case, there is a risk of abnormal discharge from the conductive wire 32 to the pinhole. Therefore, if a high resistance layer in the range of 10 ⁵ to 10 ¹¹ Ωcm is provided on the surface of the wire 32, the leak current to the pinhole can be prevented.

Here, the charging start voltage between the charging roller 1 and the photosensitive member 3 is VTH1, the charging start voltage between the wire 32 and the photosensitive member 3 is VTH2, and the surface potential of the photosensitive member 3 immediately before contact with the charging roller 1 is obtained. Is V0 and the surface potential of the photoconductor 3 immediately after contact with the charging roller 1 is V1, the applied voltage VR to the charging roller 1 is | VR | = | V1 | + VTH1. Here, the voltage VB applied to the wire 32 is set in a range that satisfies | VB−V0 | <VTH2. Here, VB also includes ground.
Since the voltage applied to the wire 32 is less than the charging start voltage,
No electric discharge from the wire 32 to the photoconductor 3 occurs. In this configuration, in the area where the charging roller 1 gradually approaches the photoconductor 3 (hereinafter also referred to as the roller proximity area), the discharge from the charging roller 1 to the photoconductor 3 is not restricted by the wire 32. From various experiments, it has been found that when the gap between the charging roller 1 and the wire 32 is set to 1.5 mm or less, the discharge from the charging roller 1 to the photoconductor 3 in the area near the band roller can be stably regulated.

According to the structure described in the fourth embodiment, the wire 32 regulates the discharge in the region where the charging roller 1 in which the charging unevenness occurs gradually comes close to the photosensitive member 3.
Uniform charging is now possible.

(Embodiment 6) In Embodiment 5, only one wire is used to regulate the charging from the charging roller 1 to the photosensitive member 3, but as shown in Embodiment 6, a plurality of wires 22 may be provided. .

A sixth embodiment of the charger according to the present invention will be described below with reference to the drawings. FIG. 10 is a sectional view of a charger according to the sixth embodiment of the present invention. In FIG. 10, 1 is a charging roller, 3 is a photoconductor, 13 and 14 are DC power supplies, 4 is a conductive axis of the charging roller 1, 22 is a conductive wire having a diameter of 100 μm, and 32 is a conductive layer coated with a resistance layer. It is a sex wire. There are three wires 22 and one wire 32. Wire 32 which was coated with a thickness of 30μm resistance layer diameter 300μm volume resistivity in conductive wires 10 ⁵ ~10 ^{1 1} Ω cm, in contact with the surface of the photoreceptor 3. The charging roller 1 is the same as that of the first embodiment.
It is a multilayer structure covered with a resistance layer in the range of ⁵ to 10 ¹¹ Ωcm.

Here, the three wires 22 and the photoconductor 3 are provided.
The charging start voltage between VTH21, VTH22, VTH23, the wire 23 and the photoconductor 3 is set in order from the rotation upstream side of the charging roller 1.
Is VTH24, the charging start voltage between the charging roller 1 and the photoconductor 3 is VTH1, the surface potential of the photoconductor 3 before passing the charging roller 1 is V0, and the photoconductor 3 after passing the charging roller 1 is VTH24. Assuming that the surface potential is V1, the voltage VR applied to the charging roller 1 is | VR | = | V1 | + VTH1. Assuming that the voltage applied to the wire 22 is VB1, VB2, VB3 (including ground) in this order from the upstream side,
The absolute value of VBi (i = 1,2,3) is | VB1-V0 | <VTH21 | VB2-V0 | <VTH22 | VB3-V0 | <VTH23 In addition, the voltage applied to the wire 23 is VB4 Including), the absolute value of VB4 is set in a range that satisfies | VB4-V0 | <VTH24. Since the voltages applied to the wires 22 and 23 are both equal to or lower than the charging start voltage, discharge from the wires 22 and 23 to the photoconductor 3 does not occur.

In this structure, in the region where the charging roller 1 gradually approaches the photoconductor 3, the discharge from the charging roller 1 to the photoconductor 3 is not restricted by the wires 22 and 23. From various experiments, it was found that the discharge from the charging roller 1 to the photoconductor 3 can be stably regulated by setting the gap between the charging roller 1 and the wires 22 and 23 to be 1.5 mm or less.

As described above, with the configuration described in the sixth embodiment,
Since the discharge in the region where the charging roller 1 in which uneven charging occurs is gradually close to the photoconductor 3 is uniformly regulated by the plurality of wires 22 and 23, uniform charging is possible.

In the first to sixth embodiments, the charging member is a roller, but the shape is not limited to a roller, and any charging member having a surface gradually approaching the charged body and a surface gradually separated from the charged body can be used. Similarly, it has the effect of preventing uneven charging.

Further, in Examples 1 to 6, the charging roller 1 is used.
Has a multi-layer structure, the charging roller 1 having a single-layer structure has the same effect. The volume resistance of the charging roller 1 having a single layer structure is 1
The range of 0 ⁵ to 10 ⁹ Ω cm is preferable.

Further, in the third embodiment, the plurality of wires 22 are shown in FIG.
Although the configuration is such that a voltage is supplied to each from an external power source as shown in (a), one power source may be divided into resistors and used as shown in FIG. 5 (b).

In addition, in the third embodiment, the charge regulating wire 22 is used.
Although the number of wires 22 is two, three or more wires 22 may be arranged.

In the fourth embodiment, the blade coating is the conductor 24.
6B is covered with the resistance layer 25, the coating may cover only the surface of the conductor 24 facing the photoconductor 3 as shown in FIG. 6B.
As shown in (c), the resistance layer 2 is provided only at a portion contacting the photoconductor 3.
You may coat with 5.

Further, the charging roller 1 can be used not only for charging but also for discharging electricity. For example, when the applied voltage to the charging roller 1 is set to 0v (that is, ground), the charged dielectric material or the photosensitive material is discharged. Also has the effect of uniform static elimination.

[0053]

As described above, the present invention provides a conductive charging member and a conductive blade (or wire) having a surface gradually approaching the surface of the body to be charged and a surface gradually separating from the body to be charged. The charging member is in contact with the surface of the moving member to be charged, and the blade is in the space between the charging member and the surface of the member to be charged upstream of the movement of the member to be charged when viewed from the charging member. DC voltage VR (however, VR = 0V or ground is included) is applied to the charging member, and DC voltage VB (however VB is applied to the blade.
= 0V or ground is included), and the charging start voltage between the blade and the body to be charged in the above positional relationship is VTH2,
When the potential of the surface of the body to be charged immediately before contact with the charging member is V0, the absolute value of VB satisfies | VB-V0 | <VTH2, so that the charging roller, which is the cause of uneven charging, is gradually applied to the body to be charged. Since discharge to the body to be charged in a region approaching is controlled by the blade, uniform charging is possible.

[Brief description of drawings]

FIG. 1 is a sectional view of a charger according to a first embodiment of the present invention.

FIG. 2 (a) is an experimental diagram for investigating the cause of uneven charging, (b) is an experimental diagram for investigating the cause of uneven charging, and (c) is an experimental diagram for investigating the cause of uneven charging. d) Experimental diagram for investigating the cause of uneven charging

FIG. 3 is a perspective view of a charger according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a charger according to a second embodiment of the present invention.

5A is a sectional view of a charger according to a third embodiment of the present invention. FIG. 5B is a sectional view of a charger according to a third embodiment of the present invention.

6A is a sectional view of a blade in a fourth embodiment of the present invention, FIG. 6B is a sectional view of a blade in a fourth embodiment of the present invention, and FIG. 6C is a fourth embodiment of the present invention. Sectional view of the blade in

FIG. 7 is a sectional view of a wire according to a fifth embodiment of the present invention.

FIG. 8 is a perspective view of a charger according to a fourth embodiment of the present invention.

FIG. 9 is a sectional view of a charger according to a fifth embodiment of the present invention.

FIG. 10 is a sectional view of a charger according to a sixth embodiment of the present invention.

[Explanation of symbols]

 1 Charging Roller 2 Blade 3 Photoreceptor 11, 12 DC Power Supply 22, 23 Conductive Wire

Front page continuation (72) Inventor Junichi Nauma, 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toshiki Yamamura, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] 1. A conductive charging member having a surface gradually approaching the surface of the charged body and a surface gradually separating from the surface of the charged body, and a conductive blade, wherein the charging member moves. In contact with the surface, the blade is arranged parallel to the surface of the body to be charged in the space sandwiched between the surface of the body to be charged and the surface of the body to be charged upstream of the movement of the body to be charged viewed from the charging member. A DC voltage VR is applied or grounded to the charging member, a DC voltage VB is applied or grounded to the blade, the charging start voltage between the blade and the body to be charged in the above positional relationship is VTH2, immediately before contact with the charging member. When the electric potential of the surface of the body to be charged is V0, the absolute value of VB satisfies | VB-V0 | <VTH2. 2. A conductive elastic roller and a conductive blade are provided, said roller being in contact with the surface of a moving body to be charged, said blade being in contact with said roller on the upstream side of the movement of the body to be charged as seen from said roller. The roller is arranged in parallel with the surface of the body to be charged in the space sandwiched by the surface of the charged body, and the DC voltage VR is applied to or grounded on the roller, and the DC voltage VB is applied to or grounded on the blade at the position described above. When the charging start voltage between the blade and the body to be charged and the potential of the surface of the body to be charged immediately before the roller contact are V0 and V0, respectively, the absolute value of VB must satisfy | VB-V0 | <VTH2. Characteristic charger. Preferably, when the surface of the blade surface facing the charged body is directly referred to as a blade end surface, the gap width between the blade end surface and the roller is 1.5 mm or less, and the gap between the blade end surface and the charged body. The charging device according to claim 1 or 2, wherein the width is 1.5 mm or less. 4. The surface of the blade has a volume resistance of 10 ⁵ -1.
The charging device according to claim 1, wherein the charging device is coated with a resistance layer of 0 ¹¹ Ωcm. 5. The charger according to claim 4, wherein the blade is in contact with the body to be charged. 6. The charging device according to claim 1, wherein at least the blade surface in contact with the body to be charged is covered with a resistance layer having a volume resistance of 10 ⁵ Ωcm or more. . 7. A surface of the blade which is in contact with the member to be charged and a surface which faces the member to be charged via a gap are covered with a resistance layer having a volume resistance of 10 ⁵ Ω cm or more. The charging device according to claim 1, 2, or 3. 8. A conductive elastic roller and a conductive wire, wherein the roller contacts a surface of a moving body to be charged, and the wire is located on the upstream side of the movement of the body to be charged as seen from the roller. The roller is arranged in parallel with the surface of the photosensitive member in the space between the charged members, and the DC voltage VR is applied to the roller.
Is applied or grounded, and a DC voltage VB is applied to the wire.
Is applied or grounded, the charging start voltage between the wire and the charged body in the above positional relationship is VTH2, and the surface potential of the charged body immediately before contact with the roller is V0, the absolute value of VB is | VB- A charging device characterized by satisfying V0 | <VTH2. 9. Desirably, the gap width between the wire and the roller is
9. The charger according to claim 8, wherein the gap width between the wire and the body to be charged is 1.5 mm or less and 1.5 mm or less. 10. The surface of the wire has a volume resistance of 10 ⁵ to 10.
10. The charger according to claim 8 or 9, which is coated with a resistance layer of 10 ¹¹ Ωcm. 11. The charger according to claim 10, wherein the wire is in contact with the body to be charged. 12. A conductive elastic roller and a plurality of conductive wires or a wire covered with a conductive layer having a volume resistance of 10 ⁵ to 10 ¹¹ Ω cm, wherein the roller is provided on the surface of a moving body to be charged. All of the wires come into contact with each other and are arranged in a space between the roller and the charged body on the upstream side of the movement of the charged body as viewed from the roller, and among the plurality of wires, the roller and the charged body When the wire closest to the contact surface is called a first wire, at least the first wire is arranged in parallel with the surface of the body to be charged, a DC voltage VR is applied or grounded to the roller, and there are i wires. DC voltages VB1, VB2, ..., VBi are applied or grounded in order, and the charging start voltage between the wire and the body to be charged in the above-mentioned positional relationship is VTH21, VTH22 ,.
H2i, where V0 is the surface potential of the body to be charged immediately before the contact with the roller, the absolute value of VBi is A charger characterized in that 13. Preferably, when the wire closest to the contact surface between the roller and the body to be charged among the plurality of wires is called the first wire, the gap width between the first wire and the roller is 1.
13. The charger according to claim 12, wherein the gap width between the first wire and the body to be charged is 5 mm or less and 1.5 mm or less. 14. When the wire closest to the contact surface between the roller and the body to be charged among the plurality of wires is called a first wire, at least the first wire is in contact with the body to be charged. Item 12. The charger according to Item 12 or 13.