JPH0611952A - Method and device for charging - Google Patents

Abstract

PURPOSE:To provide a method and device for uniformly charging a body to be charged, such as a photoreceptor, without causing wear of the surface. CONSTITUTION:A combination of a flexible hollow conductive roller 2 serving as a flexible conductive endless sheet and a brush 5 supporting the endless sheet 2 at the position where the sheet 2 makes contact with a body to be charged and applying pressure to the sheet 2 is used as a contact type charging member, and the endless sheet 2 is driven at a velocity at which it is substantially synchronous with the body to be charged, and a velocity difference is provided between the brush 5 and the endless sheet 2. Therefore, even if the body to be charged such as a photoreceptor is rugged or if some foreign material is attached to the surface of the photoreceptor, uniform and even charging of the photoreceptor is achieved without causing wear or damage to the photoreceptor at all, and the charging member and the photoreceptor are kept in uniform contact with each other with a relatively small force without filming the surface of the photoreceptor with toner; as a result, uniform charging and prevention of wear are made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel charging method and a charging device used therefor, and more specifically, it uniformly charges an object to be charged such as a photoconductor without causing surface wear. Method and device.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, a system is used for forming an electrostatic latent image, in which the surface of a photoconductor is uniformly charged and the photoconductor after charging is directly exposed. Conventionally, corona wires have been widely used for charging charged bodies such as photoconductors, but corona charging requires a high-voltage generator to generate corona, which increases the cost of the charging device. In addition, there is a problem that harmful components such as ozone and NO _x are generated during corona discharge to pollute the environment or deteriorate the photoreceptor. In order to solve this problem, various so-called contact charging methods have been proposed in which charging is performed by directly contacting a charging mechanism and a photoconductor, and these are roughly classified into a brush charging method, a roller charging method, and a blade charging method. .

As an example of the brush charging system, Japanese Patent Publication No. 60
JP-A-220588 discloses a brush charging device that charges a conductive brush having a conductive contact provided on a main body by contacting the photosensitive member with a specific resistance of the contact of 10 ⁰ to 10 ⁴ Ωcm.
The thickness is 3d to 6d and 50,000 to 200,000 pieces / in
A brush charging device provided in the main body at a density of ch ² is described.

Further, as an example of a roller charging device, Japanese Patent Laid-Open No. 63-149668 discloses a contact charging method in which a voltage is applied to a conductive member brought into contact with the surface of an object to be charged, and The conductive member is provided with a surface region that abuts the surface of the member to be charged, and subsequently, a surface region that gradually separates from the surface of the member to be charged as it goes downstream in the surface moving direction of the member to be charged. A pulsating voltage having a peak-to-peak voltage that is at least twice the charging start voltage is applied to form an oscillating electric field between the separated region of the member and the surface of the body to be charged, thereby performing charging. Further, JP-A-1-191161 also describes that a roller is formed of a conductive lower layer and a high resistance upper layer.

Further, as an example of a blade charging system, in Japanese Patent Laid-Open No. 3-203754, the tip portion is in contact with the member to be charged while facing the moving direction of the member to be charged, and between the member and the member to be charged. It has a charging blade arranged to form a wedge-shaped void, and the blade has a resistor as a discharge electrode to which a voltage is applied, in a portion facing the member to be charged. Charging device is described.

[0006]

[Problems that the Invention is to Solve] The contact charging method has a low applied voltage as compared with the corona charging method, therefore has the advantage that there is no generation of ozone and NO _x compounds, corona charging method However, there is a drawback that the charging becomes non-uniform. That is, in the case of brush charging, since the contact between the charging member (brush) and the member to be charged is point contact or line contact, there is a drawback that non-charged portions are generated microscopically and the charging becomes uneven. . Further, since the brush directly contacts the surface of the photoconductor, the photoconductor is likely to be worn, and the wear tendency becomes remarkable especially when the brush is rotated at a high speed for the purpose of more uniform charging. Further, the brush itself may be settled, bristles may be lost, or other performance may be deteriorated, so that its life is also short.

Further, in the charging method using a conductive roller, even if a linear pressure is applied to the roller, if the photoconductor has irregularities, it becomes difficult to make the depressions and the rollers evenly contact each other. It becomes difficult to perform charging uniformly. Further, dust, paper powder, toner, etc. are usually attached to the surface of the photoconductor, and if these foreign substances are present between the roller and the photoconductor, a defective charging portion occurs in the width direction. When a high pressure is applied to the roller in order to solve these problems, there is a problem in that the photoconductor is significantly worn. It is considered effective to give a soft cushioning property to the roller surface, but with the conductive rubber, the flexibility that can be obtained is limited, and the softening agent (plasticizer) in the rubber migrates to the surface and There is also the inconvenience of being contaminated.

Further, in the blade charging method, not only the problem of non-uniform charging is caused as in the case of roller charging, but also the tendency thereof is caused by blade reversal (turning) and chattering phenomenon due to friction with the surface of the photosensitive member. In addition to becoming more remarkable, the abrasion and damage of the photoconductor become remarkable.

Therefore, an object of the present invention is to provide a charging method and apparatus capable of uniformly and uniformly charging an object to be charged such as a photoconductor without damaging it. Another object of the present invention is to provide a charging method capable of performing uniform and uniform charging even when an object to be charged such as a photoconductor has irregularities, or when foreign matter is attached to the surface of the photoconductor. To provide the equipment. Still another object of the present invention is to maintain a uniform contact state between the charging member and the photoconductor even with a relatively small force,
As a result, it is an object of the present invention to provide a charging method and apparatus capable of uniformly charging and preventing wear.

[0010]

According to the present invention, in a method of charging a charged member by physically contacting the charged member to which a voltage is applied with the charged member, the charging member is flexible. A conductive endless sheet and a brush that supports the endless sheet at the contact position between the endless sheet and the body to be charged and applies a pressing force to the endless sheet, and the endless sheet is covered with a charging voltage applied thereto. There is provided a charging method characterized in that the brush and the endless sheet are driven or driven at a speed substantially synchronized with the charging body and the brush and the endless sheet are maintained at different speeds.

Further, according to the present invention, in a device for charging a charged member by physically contacting the charged member to which a voltage is applied and the charged member, the charging member is a flexible hollow conductive roller. A brush roller coaxially and rotatably provided in the hollow conductive roller, a power feeding mechanism for applying a charging voltage to the hollow conductive roller, and a speed at which the hollow conductive roller is synchronized with the body to be charged. There is provided a charging device characterized by comprising a driving mechanism for driving the brush roller at a speed different from that of the hollow conductive roller.

Further, according to the present invention, in a device for charging a charged member by physically contacting the charged member to which a voltage is applied with the charged member, the charging member is a flexible conductive endless member. A belt, a rotatable brush roller that faces the charged body via the endless belt and presses the endless belt against the charged body, a power feeding mechanism that applies a charging voltage to the endless belt, and the endless belt as the charged body. There is provided a charging device comprising a drive mechanism that drives at a synchronized speed and a drive mechanism that drives a brush roller at a speed different from that of an endless belt.

[0013]

According to the present invention, a flexible conductive endless sheet is supported as a charging member that is contacted with a member to be charged when a voltage is applied, and the endless sheet is supported at a contact position between the endless sheet and the member to be charged. And in combination with a brush which applies a pressing part to it. In this combination, it is the flexible conductive sheet that contacts the charged member,
It is the brush that biases the member to be charged so as to come into contact with the member to be charged, and the feature of the present invention is that the charging member is functionally separated as described above.

First, since the conductive sheet is flexible, it can be deformed, and even if there are any irregularities on the surface of the member to be charged, it is possible to make uniform contact with the entire surface. Even if foreign matter such as dust, paper powder, and residual toner adheres to the surface of the body to be charged, it is possible to make uniform contact with the surface other than the adhered portion. In addition, each brush of the brush acts as a pressing spring, and also acts as a biasing spring having the finest and finest action, and enables uniform and smooth contact between the conductive sheet and the body to be charged. That is, it has already been pointed out that the contact between the brush and the body to be charged is point contact or line contact in brush charging, but in the present invention, a flexible conductive sheet is provided between the brush and the body to be charged. By interposing it, the small pressure applied by the brush makes uniform contact with the body to be charged, and uniform charging is possible. In the present invention, it is also important to drive or follow the conductive sheet at a speed substantially in synchronization with the body to be charged and to maintain the brush and the endless sheet at relatively different speeds.

If there is a speed difference between the member to be charged and the flexible conductive sheet, the sheet will be twisted or twisted,
Not only is this undesirable in terms of smooth operation and life of the charging device, but also when such twisting or twisting occurs, uniform charging becomes difficult, which is not preferable. In the present invention, by driving or following the flexible conductive sheet at a speed substantially in synchronism with the body to be charged, there is no friction between them and it is possible to prevent wear and damage on the surface of the body to be charged. .

Further, by maintaining the flexible conductive sheet and the brush at different speeds, the brush traces over the flexible conductive sheet while the conductive sheet is in contact with the conductor. Therefore, the contact between the flexible conductive sheet and the surface of the body to be charged is performed extremely uniformly and densely.

[0017]

Preferred Embodiment of the Invention

(Charging Device) In the charging device used in the present invention, the flexible, conductive, endless sheet may be a seamless tube, that is, a flexible hollow conductive roll, or a flexible conductive endless sheet. It may be a belt.
Further, although the brush is used as a rotatable brush roller, the ears of the brush may be made of conductive organic or metal fiber or non-conductive organic or inorganic fiber. In the former case, power is supplied to the conductive sheet through a brush, and in the latter case, a power supply mechanism separate from the brush is used.

An example of the charging device of the present invention is shown in FIG.
(Cross-sectional view) and FIG. 1B (side view) will be described. The charging device 1 is roughly composed of a flexible hollow conductive roller 2 and a brush roller 3 provided in the flexible roller 2 coaxially and rotatably with respect to each other.

The brush roller 3 is composed of a drive shaft 4 and a brush 5 planted on the drive shaft 4, and in this embodiment, the brush 5 is made of conductive fibers. The hollow conductive roller 2 has rigid ends 6 at both ends, and the ends 6 have a large diameter portion 7 and a small diameter portion 8 tapered from the large diameter portion. A drive gear 9 is fixedly attached to 8. Further, a hole 10 is provided at the center of the end 6, and the drive shaft 4 of the brush roller penetrates the hole 10 to extend to the outside of the end 6.
A bearing 11 is provided between the end 6 and the brush drive shaft 4 to allow relative rotation between them. The flexible hollow roller 2 is supported on the outer circumference of the large diameter portion 7 of the end 6, and the end portion thereof is fastened by the fastening member 12 to the small diameter portion 8 of the end 6.
It is fixed to. In this specific example, the fastening member 12 is a heat-shrinkable resin ring (tube), and both ends of the flexible hollow roller 2 are fixed to the ends 6 by heat shrinkage. In addition, the inner surface of the flexible hollow roller 2 is in contact with the brush 5 housed therein and is supported by the brush 5. The large-diameter portion 7 of the end 6 serves as an abutting portion 13 that contacts a member to be charged (not shown) via a flexible roller around the end 6, and the flexible hollow roller is provided between the abutting portions 13 and 13. 2 is supported by a brush 5 and abutting portions 13, 13
The diameter is slightly larger than the outer diameter. Furthermore, in order to correctly position the flexible hollow roller 2, between the end 14 of the brush 5 and the inner end 15 of the end 6,
The push springs 16 and 16 are provided to give the flexible conductive hollow roller 2 some tension in the axial direction.

In FIG. 2 showing an example in which the charging device of FIG. 1 is applied to an electrophotographic copying machine, the charging device 1 and the image are formed around a rotary drum 21 having an electrophotographic photosensitive layer (member to be charged) 20. The exposure mechanism 22, the developing mechanism 23, the toner transfer mechanism 24, the cleaning mechanism 25, and the exposure charge eliminating mechanism 26 are sequentially arranged.

The charging device 1 as a whole is housed in a box 18 having one surface opened, and the charging device 1 is brought into contact with the photosensitive drum 21 at a constant pressure by means of a pressing spring 27 or the like. Further, the flexible hollow conductive roller 2 is driven at a speed synchronized with the photosensitive drum 21, while the brush roller 3 is driven via its drive shaft 4 at a speed different from that of the hollow conductive 2. The drive shaft 4 is electrically insulated from the machine frame and the drive system, and has a current collector (not shown), a wire 28, and a changeover switch 29.
It is connected to the DC power supply 30 and the pulsating flow charging power supply 31 via.

When the charging device 1 of the present invention is used, the photosensitive layer 20 is uniformly charged without abrasion of the photosensitive layer 20, so that an electrostatic latent image having high contrast and no disturbance is formed by image exposure. By the subsequent development and transfer, it is possible to obtain an object having high density and excellent image quality. When the brush roller is an electrically insulating brush, a current collector 17 is provided which is in pressure contact with the flexible hollow conductive roller 2 as shown in FIG.
A voltage for charging may be supplied from 7 to the roller 2.

Further, as shown in FIG. 4, a flexible conductive endless belt 2a can be used instead of the flexible hollow conductive roller 2, and in this case, an insulating guide roller 19a. , 19b, 19c, 19d, etc.,
The flexible conductive endless belt 2a may be supplied between the brush roller 3 and the charged body 20 at a speed synchronized with the charged body 20.

In the present invention, as the flexible conductive sheet, any material can be used as long as it satisfies the condition that it is conductive and has flexibility. For example, the sheet can be made of a conductive resin or rubber, a metal such as a foil, or a laminate of metal and a resin or rubber.

As the conductive resin or rubber, a resin or rubber mixed with various conductive agents is used.
Various thermo-flexible elastomers such as polyester elastomers, polyamide elastomers, polyurethane elastomers, soft vinyl chloride resins, styrene-butadiene, styrene / block copolymer elastomers, acrylic elastomers are preferably used, but other Nylon 6, nylon 6,6, nylon 6-nylon 6,6 copolymer, nylon 6,6-nylon 6,10 copolymer,
Polyamides such as alkoxymethylated nylon such as methoxymethylated nylon, copolyamides, or modified products thereof are also used. Of course, the resin used is not limited to those exemplified above, and for example, silicone resin, acetal resin such as polyvinyl butyral, polyvinyl acetate, ethylene vinyl acetate copolymer, ionomer and the like can be used. As the rubber, natural rubber, butadiene stereo rubber, styrene-butadiene rubber, nitrile-butadiene rubber, ethylene-propylene copolymer rubber, ethylene-
Examples thereof include propylene-non-conjugated diene copolymer rubber, chloroprene rubber, butyl rubber, silicone rubber, urethane rubber and acrylic rubber.

As the conductive agent, conductive carbon black, metal powder such as silver, gold, copper, brass, nickel, aluminum and stainless steel, and powder conductive agent such as tin oxide-based conductive agent can be used. Alternatively, a nonionic, anionic, cationic, amphoteric organic conductive agent or an organic tin conductive agent may be used.

Generally, the conductive resin or rubber has an electric resistance (specific resistance) of 10 to 10 ⁸ Ωcm,
In particular, it is preferably in the range of 10 ^{2 to} 10 ⁶ Ωcm.
The conductive agent varies depending on the kind of the conductive agent, but is mixed with 100 parts by weight of resin or rubber in an amount of 1 to 20 parts by weight, particularly 5 to 15 parts by weight so that the above resistance value can be obtained. To do. Higher conductivity can be obtained when the conductive agent particles in the conductive resin or rubber form a chain structure, but in this case, uneven charging, that is, a point-like high potential portion tends to occur. Therefore, the conductive particles are preferably uniformly and finely dispersed in the resin or rubber. For this purpose, it is important to sufficiently knead the conductive agent-containing resin or rubber, and for example, at least a part of the resin or rubber is an acid-modified resin or rubber, that is, acrylic acid,
It is also effective to use a resin or rubber obtained by copolymerizing an ethylenically unsaturated carboxylic acid such as methacrylic acid or maleic anhydride.

The conductive resin or rubber sheet used in the present invention generally varies depending on the flexibility thereof, but is generally 5
It preferably has a thickness of 0 to 400 μm, particularly 100 to 300 μm. The surface is preferably as smooth as possible, and the average roughness according to JIS B0601 is preferably 5 μm or less, and particularly preferably 1 μm or less.

The seamless tube or seamless belt can be molded by extrusion molding using a ring die, or by a method of fluid immersion of resin or rubber powder into a mandrel or cylindrical mold coated with a release agent, It can also be carried out by a dip coating method of latex, emulsion, suspension or solution.

In the present invention, a seamless metal foil can be used as the flexible conductive sheet. Examples of the metal foil include nickel, aluminum, copper, brass, tin and the like, which are obtained by an electroforming method or extrusion. The thickness of the metal foil is 20 to 80 μm, especially 30 to 5
It is preferably in the range of 0 μm.

The flexible conductive sheet may be made of a single-layer material, or may be made of a laminated or multi-layer material. If the surface of the flexible conductive sheet that comes into contact with the member to be charged is formed of a high resistance layer, even if there are conductive scratches or protrusions on the surface of the photosensitive layer, leakage such as discharge can be prevented. Is effective for. The specific resistance of this high resistance layer is preferably in the range of 10 ^{8 to} 10 ¹³ Ω · cm, particularly 10 ^{9 to} 10 ¹² Ωcm, and its thickness is preferably in the range of 40 to 60 μm. The electric resistance can be easily adjusted by adjusting the blending amount of the conductive agent to be blended with the resin or rubber. As the conductive agent and the resin or rubber,
As the resin or rubber, as mentioned above, fluorine resin or rubber such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTF) can be used.
E), tetrafluoroethylene-hexafluoropropylene copolymer (PTFE.HFP) perfluoroalkoxy fluororesin, etc. are used. The use of these resins or rubbers for the high resistance layer is inactive and has a small friction coefficient, so that there is a great merit in terms of the life of the photoreceptor and the life of the flexible conductive sheet. When using a metal foil, coating or laminating of a high resistance layer is particularly recommended. The high resistance layer is formed by coating, co-lamination extrusion or the like.

As the brush, either a conductive brush or an insulating brush is used. The conductive brush is made of conductive organic or inorganic fiber and has a volume resistivity of 10 ^{2 to} 10 ⁸ Ωc.
It is preferably m, particularly in the range of 10 ^{3 to} 10 ⁶ Ωcm. Fiber thickness is 2 to 10 denier (d), especially 3
To 6d, fiber length (hair length) is 2 to 7mm, especially 3
It is good to be about 5 mm, and the flocking density is 10,000 to 20
It is preferably in the range of 10,000 / square inch, particularly in the range of 30,000 to 100,000 / square inch in order to provide a smooth and uniform pressing force. In addition, rounding the tip of the brush is suitable for suppressing abrasion of the flexible conductive sheet.

As the organic conductive fiber, synthetic or regenerated fiber in which conductive agent particles are dispersed is used. For example, polyamide fiber such as nylon 6, nylon 6,6, polyester fiber such as polyethylene terephthalate, acrylic fiber, polyvinyl. Alcohol fiber, polyvinyl chloride fiber,
Examples include rayon and acetate. To impart conductivity to the fiber, it is not limited to the method of blending a conductive agent,
A method of metallizing the fiber surface may be used. As the conductive agent, those mentioned above are used.

Carbon fibers are preferably used as the conductive inorganic fibers, but metal fibers such as stainless steel and brass are also used. As the electrically insulating brush, the above organic fiber is used except that it does not contain a conductive agent. The fineness, fiber length and flock density can be in the ranges mentioned above.

(Charging Method) In the charging method of the present invention, the flexible conductive endless sheet is driven or driven at a speed synchronized with the moving speed of the member to be charged, and the brush is different from the conductive endless sheet. Drive at the desired speed.
The brush may be driven in the same direction as the conductive endless sheet or in the opposite direction. In the case of the same direction, the moving speed of the endless sheet is preferably 1.1 to 5 times, particularly 1.5 to 3 times, and in the opposite direction, the moving speed of the endless sheet is 1.1 to 3 times. It is desirable to be in the range of double, especially 1.5 to 2, in order to make the contact between the flexible conductive sheet and the surface of the body to be charged uniformly and densely. In the present invention, the charging voltage applied to the conductive endless sheet is preferably set to 1.5 to 3.5 times, particularly 2 to 3 times, the charging start voltage value of the member to be charged.

FIG. 5 shows the relationship between the voltage applied to the conductive endless sheet and the surface potential of the charged body when the charging method of the present invention is applied when the organic photoreceptor is the charged body. (See the example below for details). From this figure, it can be seen that a good linear relationship between the applied voltage and the surface potential is maintained in the effective charging region. From this, in the charging system of the present invention, for example, a surface potential detection sensor is arranged around the photoconductor, and the applied voltage is increased or decreased based on the surface potential position detected by this sensor, It will be appreciated that the surface potential can be kept constant at the optimum value.

It is a remarkable advantage of the present invention that uniform and uniform charging can be performed only by using a DC voltage.
In order to perform charging with more uniformity, it is possible to apply a voltage in which an AC voltage is further superimposed on the DC voltage described above.
Such alternating current has a frequency of 300 to 1500.
Alternating current having a peak-to-peak voltage of 2.5 to 4 times, especially 2.8 to 3.5 times, can be used at Hz, especially 400 to 1000 Hz.

The charging method of the present invention is useful for charging a photoconductor using various electrophotographic methods such as a copying machine and a facsimile laser printer. Here, as the photoconductor, various photoconductors having a single-layer or laminated structure, Examples thereof include an a-Si photoconductor, a selenium photoconductor, and a single-layer or multi-layer organic photoconductor. Among these, when the power supply method of the present invention is applied to the organic photoconductor, ozone and NO _x are hardly generated. Therefore, the charge-generating pigment, charge-transporting substance, binder,
It is possible to extend the life of the dielectric material without deterioration. Of course, the charging method of the present invention is not limited to the charging in a narrow sense, and it is needless to say that the charging method can be used for static elimination by applying a bias voltage.

[0039]

The present invention will be described in more detail with reference to the following examples. Example 1 The charging device shown in FIG. 1 was mounted on a modified DC-2556 electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd. using an organic photoconductor for positive charging, and charging, exposure without applying an AC voltage, Development, transfer and fixing were performed.

The physical properties of each member of the charging device and the charging conditions are as follows. Conductive roller material: Polyurethane elastomer Inner diameter: 20mm Thickness: 0.3mm Volume resistivity: 1.4 × 10 ⁵ Ω · cm Brush roller material: Conductive rayon Outer diameter: 19.8mm Volume resistivity: 1.0 × 10 ³ Ω · cm Fiber thickness: 6 denier Fiber length: 5 mm Flock density: 100,000 / inch ² Charging condition applied DC voltage: +1500 V Brush roller rotation speed: 225 rpm (rotation direction is the same direction as the conductive roller) Conductive roller rotation speed: 150 rpm (photoconductor and driven rotation) Photoconductor peripheral speed: 157 mm / sec Surface potential: +800 V Charging start voltage: +600 V The image density of the copy obtained above is 1.44, and the fog density is The image quality was 0.002, which was a good image without black spots.

Example 2 The charging device shown in FIG. 1 was mounted on a modified DC-2556 electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd. using an organic photoreceptor for positive charging, and charging was performed without applying an AC voltage. , Exposure, development, transfer and fixing were performed.

The physical properties of each member of the charging device and the charging conditions are as follows. Conductive roller material: Polyurethane elastomer Inner diameter: 20mm Thickness: 0.3mm Volume resistivity: 1.4 × 10 ⁵ Ω · cm Brush roller material: Conductive rayon Outer diameter: 19.8mm Volume resistivity: 1.0 × 10 ³ Ω · cm Fiber thickness: 6 denier Fiber length: 5 mm Flock density: 100,000 / inch ² Charging condition applied DC voltage: +1500 V Brush roller rotation speed: 450 rpm (rotation direction is the same direction as the conductive roller) Rotation speed of conductive roller: 150 rpm (photoconductor and driven rotation) Peripheral speed of photoconductor: 157 mm / sec Surface potential: +825 V Charging start voltage: +600 V Image density of copy obtained above is 1.45, fog density is The image quality was 0.003, which was a good image without black spots.

Example 3 The charging device shown in FIG. 1 was mounted on a modified DC-2556 electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd. using an organic photoreceptor for positive charging, and charging was performed without applying an AC voltage. , Exposure, development, transfer and fixing were performed.

The physical properties of each member of the charging device and the charging conditions are as follows. Conductive roller material: Polyurethane elastomer Inner diameter: 20mm Thickness: 0.3mm Volume resistivity: 1.4 × 10 ⁵ Ω · cm Brush roller material: Conductive rayon Outer diameter: 19.8mm Volume resistivity: 1.0 × 10 ³ Ω · cm Fiber thickness: 6 denier Fiber length: 5 mm Flock density: 100,000 pieces / inch ² Charging condition applied DC voltage: +1500 V Brush roller rotation speed: 225 rpm (rotation direction is opposite to conductive roller) Conductive roller rotation speed: 150 rpm (photoconductor and driven rotation) Photoconductor peripheral speed: 157 mm / sec Surface potential: +850 V Charging start voltage: +600 V Image density of the copy obtained above is 1.46, fog density is The image quality was 0.002, which was a good image without black spots.

Example 4 The charging device of FIG. 1 was mounted on a modified DC-2556 electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd. using an organic photoreceptor for positive charging, and charging was performed without applying an AC voltage. , Exposure, development, transfer and fixing were performed. The physical properties and charging conditions of each member of the charging device are as follows.

Conductive roller material: Polyurethane elastomer Inner diameter: 20 mm Thickness: 0.3 mm Volume resistivity: 1.4 × 10 ⁵ Ω · cm Brush roller material: Conductive rayon Outer diameter: 19.8 mm Volume resistivity: 1.0 × 10 ³ Ω · cm Fiber thickness: 6 denier Fiber length: 5 mm Flock density: 100,000 pieces / inch ² Charging condition applied DC voltage: +1500 V Brush roller rotation speed: 300 rpm (rotation direction is conductive roller) Opposite direction) Rotational speed of conductive roller: 150 rpm (photoconductor and driven rotation) Peripheral speed of photoconductor: 157 mm / sec Surface potential: +850 V Charging start voltage: +600 V Image density of the copy obtained above is 1.46, The fog density was 0.003, and the image was a good image without black spots.

Example 5 The charging device of FIG. 1 was mounted on a modified DC-2556 electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd. using an organic photoreceptor for positive charging, and charging was performed without applying an AC voltage. , Exposure, development, transfer and fixing were performed. The physical properties and charging conditions of each member of the charging device are as follows.

Conductive roller material: Polyvinyl chloride elastomer Inner diameter: 20 mm Thickness: 0.2 mm Volume specific resistance: 1.0 × 10 ³ Ω · cm Brush roller material: Conductive rayon Outer diameter: 19.8 mm Volume specific Resistance: 1.0 × 10 ³ Ω · cm Fiber thickness: 6 denier Fiber length: 3 mm Flock density: 100,000 / inch ² Charging condition applied DC voltage: +1500 V Brush roller rotation speed: 225 rpm (rotational direction is conductive) The same direction as the roller) Rotation speed of conductive roller: 150 rpm (rotating with the photoconductor) Peripheral speed of the photoconductor: 157 mm / sec Surface potential: +800 V Charging start voltage: +600 V The image density of the copy obtained is 1.42 The fog density was 0.003, and the image was good without black spots.

Example 6 An electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd. in which the charging device shown in FIG. 1 was modified so as to use a negative charging type organic photoconductor.
It was mounted on a modified DC-2556 machine and charged, exposed, developed, transferred and fixed without applying an AC voltage.

The physical properties of each member of the charging device and the charging conditions are as follows. Conductive roller material: Polyurethane elastomer Inner diameter: 20mm Thickness: 0.1mm Volume resistivity: 8.0 × 10 ⁵ Ω · cm Brush roller material: Conductive rayon Outer diameter: 19.8mm Volume resistivity: 1.0 × 10 ³ Ω · cm Fiber thickness: 6 denier Fiber length: 5 mm Flock density: 100,000 / inch ² Charging condition applied DC voltage: -1700 V Brush roller rotation speed: 225 rpm (rotation direction is the same direction as the conductive roller) ) Conductive roller rotation speed: 150 rpm (photoconductor and driven rotation) Photoconductor peripheral speed: 157 mm / sec Surface potential: -880 V Charging start voltage: -800 V The image density of the copy obtained above is 1.45, The fog density was 0.002, which was a good image without black spots.

Example 7 The charging device shown in FIG. 1 was mounted on a modified DC-2556 electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd., which uses an organic photoreceptor for positive charging, and charging is performed while superimposing and applying an alternating voltage. Exposure, development,
Transfer and fixing were performed.

The physical properties and charging conditions of each member of the charging device are as follows. Conductive roller material: Polyurethane elastomer Inner diameter: 20mm Thickness: 0.3mm Volume resistivity: 1.4 × 10 ⁵ Ω · cm Brush roller material: Conductive rayon Outer diameter: 19.8mm Volume resistivity: 1.0 × 10 ³ Ω · cm Fiber thickness: 6 denier Fiber length: 5 mm Flock density: 100,000 pieces / inch ² Charging condition Applied DC voltage: +1100 V Applied AC voltage: 1800 V _PP (waveform is sine wave) AC frequency: 500 Hz brush Roller rotation speed: 225 rpm (rotation direction is the same direction as the conductive roller) Conductive roller rotation speed: 150 rpm (photosensitive member driven rotation) Peripheral speed of photosensitive member: 157 mm / sec Surface potential: +800 V Charging start voltage: +600 V or more The resulting copy had an image density of 1.40 and a fog density of 0.002, and was a good image without black spots.

[0053]

According to the present invention, a flexible conductive endless sheet is used as a contact type charging member, and the endless sheet is supported at a contact position between the sheet and a member to be charged and a pressing force is applied to the endless sheet. The endless sheet is driven or driven at a speed substantially in synchronism with the charged body by using a combination with a brush, and a speed difference is given between the brush and the endless sheet. It is possible to make a uniform and solid surface contact between the two without giving a charge, and it is possible to carry out a uniform and uniform charging. In particular, even if there is unevenness on the surface of the body to be charged and foreign matter adheres to the surface of the photoconductor, uniform and uniform charging is possible without the influence, and toner filming is not formed on the surface of the photoconductor. There are also advantages.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a charging device of the present invention,
(A) is sectional drawing, (b) is a side view.

FIG. 2 is a schematic diagram showing an example in which a charging device is applied to a copying machine.

FIG. 3 is a schematic diagram showing an example in which a current collector is used as a voltage applying unit to a charging device.

FIG. 4 is a schematic view showing a charging device using a belt.

FIG. 5 is a graph showing the relationship between the applied voltage and the surface potential of the body to be charged when the charging device of the present invention is used.

[Explanation of symbols]

 2 flexible roller 3 brush roller 4 drive shaft 5 brush 2a endless belt

Front page continuation (72) Inventor Akinori Nishida 1-22-28 Tamazo, Chuo-ku, Osaka Mita Engineering Co., Ltd. (72) Teruaki Higashiguchi 1-2-2 Tamazo, Chuo-ku, Osaka Mita Engineering Incorporated (72) Inventor Isao Iwakawa 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (12)

[Claims] 1. A method for charging a charged body by physically contacting a charged member to which a voltage is applied and the charged body, wherein the charging member is a flexible conductive endless sheet, and the endless sheet. A brush that supports the endless sheet at a contact position with the charged body and applies a pressing force to the endless sheet, and drives the endless sheet at a speed substantially synchronized with the charged body while applying a charging voltage to the endless sheet. Or a charging method characterized in that the brush and the endless sheet are driven at different speeds. 2. The charging method according to claim 1, wherein the flexible conductive endless sheet is a seamless tube. 3. The charging method according to claim 1, wherein the flexible conductive endless sheet is a seamless endless belt. 4. The charging method according to claim 1, wherein the brush is a rotatable brush roller. 5. The charging method according to claim 1, wherein the brush is a brush made of a conductive organic or inorganic fiber. 6. The charging method according to claim 1, wherein the brush is a brush made of non-conductive organic or inorganic fiber. 7. The charging method according to claim 1, wherein the brush is driven in the same direction as the moving direction of the endless sheet and at a speed 1.1 to 5 times the moving speed of the endless sheet. 8. The charging method according to claim 1, wherein the brush is driven in a direction opposite to the moving direction of the endless sheet and at a speed 1.1 to 3 times the moving speed of the endless sheet. 9. The charging method according to claim 1, wherein the charging voltage applied to the endless sheet is a DC voltage which is 1.5 to 3.5 times the charging start voltage value of the member to be charged. 10. The charging method according to claim 1, wherein the charging voltage applied to the endless sheet is a DC voltage 1.5 to 2 times the charging disclosed voltage value of the member to be charged, and an AC voltage further superimposed thereon. 11. An apparatus for charging a charged body by physically contacting a charged member to which a voltage is applied and the charged body, wherein the charging member is a flexible hollow conductive roller.
A brush roller coaxially and rotatably provided in the hollow conductive roller, a power feeding mechanism for applying a charging voltage to the hollow conductive roller, and the hollow conductive roller driven at a speed synchronized with the body to be charged. And a drive mechanism for driving the brush roller at a speed different from that of the hollow conductive roller. 12. An apparatus for charging a charged member by physically contacting a charged member to which a voltage is applied with the charged member, wherein the charging member is a flexible conductive endless belt, and an endless belt. A rotatable brush roller that faces the member to be charged via the endless belt and presses the endless belt against the member to be charged, a power feeding mechanism that applies a charging voltage to the endless belt, and the endless belt is driven at a speed synchronized with the member to be charged. And a driving mechanism that drives the brush roller at a speed different from that of the endless belt.