JP3189421B2 - Charging method and apparatus, and electrophotographic apparatus equipped with the apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a facsimile,
The present invention relates to a printer, and more particularly, to an electrophotographic charging method and apparatus, and an electrophotographic apparatus provided with the apparatus.

[0002]

2. Description of the Related Art In recent years, electrophotographic apparatuses have been shifting from office use to personal use, and have become smaller.
There is a need for a technology for achieving maintenance-free operation. Small printers for personal use are supposed to be placed in the corner of a desk or used in ordinary homes, and may satisfy conditions such as low maintenance and low ozone exhaust. It becomes the point of spread.

An electrophotographic copying machine or printer charges a photosensitive member for image formation. A conventional charging method that uses a corona discharger is a metal wire having a diameter of about 50 to 100 μm in a grounded metal shield (the part facing the photoreceptor is open). Is stretched away from the photoreceptor to be charged by several millimeters to about 10 millimeters, and a high voltage is applied to generate corona. Since the discharge mainly occurred between the metal wire and the metal shield, much of the current flowed through the metal shield, generating a large amount of ozone. In particular, since the discharge is unstable in the case of negative discharge, a charger having a configuration in which a control electrode capable of applying a voltage is provided between the corona discharger and the photoreceptor to make the surface potential of the photoreceptor uniform is often used. In this case, in particular, the discharge current becomes large and the amount of generated ozone is also large. As a well-known example utilizing the shielding effect, Japanese Patent Publication No. S41-18311 discloses an example of stabilizing the discharge of a needle-shaped charger. A metal plate shield and a roller-shaped shield are provided as a discharge stabilizing auxiliary electrode around the needle-shaped discharge electrode, and the positional relationship between the needle, the auxiliary electrode, and the photoconductor is shown in detail. Further, the roller-shaped shield comes into contact with the photoreceptor, which is a charged body, and has a function of feeding the charged body.

On the other hand, there has been proposed a method of charging using a roller or a fur brush which is in contact with a photosensitive member. Since the contact-type charging method is a corona discharge in a minute space, the discharge current can be suppressed low, and the amount of ozone can be reduced.

FIGS. 5A and 5B are schematic views showing the structure of the charging device disclosed in Japanese Patent Publication No. 3-52058. In FIG. 5A, 20 is a photosensitive drum, 20a is a conductive substrate, and 20b is a photosensitive layer. The conductive substrate 20a is grounded. Reference numeral 21 denotes a charging roller which is in contact with the photosensitive layer 20a of the photosensitive drum 20 in an area A in FIG. Reference numeral 22 denotes a power supply for applying a voltage to the charging roller. The operation of the charging device configured as described above will be described below.

In order to apply a uniform charge to the photosensitive drum 20, a voltage waveform as shown in FIG. 6 is applied. In FIG. 6, VTH indicates a discharge starting voltage, and Vmax and Vmin indicate peak values when AC is applied in addition to DC. The AC that is actually superimposed is applied so that Vmax-Vmin becomes twice or more of VTH. As shown in FIG. 7, the discharge starting voltage refers to an applied voltage at which the surface of the photoconductor starts to be charged when the roller applied voltage (DC) is gradually increased in a dark place. In the contact area between the photosensitive drum 20 and the charging roller 21, a voltage in which DC and AC are superimposed is applied to the charging roller 21. Can be returned to the charging roller 21 by discharging in the opposite direction. The above setting is made in order to cause this charge transfer by discharge. The AC vibration is attenuated in a region where the photosensitive drum 20 and the charging roller 21 gradually separate from each other, and is focused on the applied DC voltage.

FIG. 8 is a schematic diagram showing the configuration of a charging device disclosed in Japanese Patent Application Laid-Open Nos. 64-35459 and 1-105969. In FIG. 8, reference numeral 30 denotes an example of a corona charger, which may be a fur brush, a roller, or the like. 31 volume resistivity 10 ⁰ ~10 ⁴ Ω · c
m, which is grounded via a metal core and is in contact with the photosensitive drum 20. 3
Reference numeral 2 denotes a power supply for applying a voltage to the charger 30. The operation principle of the charging device configured as described above will be described below.

The surface of the photosensitive drum 20 is charged to a potential V1 by the charger 30. Assuming that the surface potential of the leveling roller 31 is V2 (the surface potential is V2 = 0 V because the metal core is grounded), the surface potential of the photosensitive drum 20 after passing through the leveling roller 31 is determined as follows. Is done.
That is, the potential difference between V1 and V2 is equal to the discharge starting voltage V shown in FIG.
If it exceeds TH, the excess charge (difference between V1 and VTH) returns from the photosensitive drum 20 to the leveling roller 31 by discharging. When the potential difference between V1 and V2 is smaller than VTH, no discharge occurs and the potential of V1 is maintained. Accordingly, if the potential of V1 is set in advance so that V1−V2> VTH, the surface potential of the photosensitive drum 20 after passing through the leveling roller 31 becomes VTH.
Will be aligned. When a power source is connected to the leveling roller 31 and a voltage is applied, the surface potential V1 after passing through the leveling roller 31 can be controlled according to the potential of V2.

[0009]

The above charging method has the following problems. 1. A charging device using a needle or a thin wire requires a shield electrode to stabilize discharge, and the following problem occurs. (1) Discharge occurs between needles or fine wires, and a large amount of ozone is generated. (2) A large amount of current flows into the shield and a large power supply is required. (3) Needles and fine wires are generated due to the large amount of ozone generated. Dirt,
Maintenance is required. (4) Exhaust fans and other devices become complicated and large because of the large amount of ozone. Therefore, this technology is not suitable for small-sized, personal-use copiers and printers. 2. The charging method of applying a direct current and an alternating current to the roller contacting the photoconductor has the following problems. (1) Since the photoreceptor and the roller cannot be brought into close contact with each other, air vibration occurs in the contact area due to the oscillating electric field to generate an unpleasant sound. The method using the charging device and the charge eliminating roller has the following problems. (1) Since the charger requires an independently functioning charger, the mechanism becomes complicated and is not suitable for miniaturization. (2) The charging method using a needle or a thin wire causes the same problem as described in 1. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a charging method and apparatus which generate less ozone and require no maintenance, and an electrophotographic apparatus provided with the apparatus.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a charging method and apparatus having the following constitution and an electrophotographic apparatus provided with the apparatus.

The object to be charged, which rotates, and the object to be charged,
An auxiliary charging member that contacts, the object to be charged, and the charging;
A step of preparing a charging member arranged to face the auxiliary member
And applying a voltage to the charging member, discharging toward the semiconductive charging auxiliary member and the rotating member to be charged, and charging the charging auxiliary member and the member to be charged.
Than the contact area between the charging auxiliary member and the member to be charged ,
Discharging on the charging member side between the charging auxiliary member and the member to be charged.

A member to be charged which is rotatably arranged;
Serial to contact the member to be charged, a discharge electric field between the member to be charged
A semi-conductive auxiliary charging member to form, Oyo said member to be charged
And the rotation direction of the member to be charged, facing the charging auxiliary member.
Located above stream side of the auxiliary charging member in, by voltage discharges are allowed indicia <br/> pressure, the said member to be charged
And a plurality of needle-like electrodes for charging the charging auxiliary member .

A member to be charged which is rotatably arranged;
Serial to contact the member to be charged, a discharge electric field between the member to be charged
A semi-conductive auxiliary charging member to form, Oyo said member to be charged
And the rotation direction of the member to be charged, facing the charging auxiliary member.
Located above stream side of the auxiliary charging member in, by voltage discharges are allowed indicia <br/> pressure, the said member to be charged
An electrophotographic apparatus, comprising: a plurality of needle-shaped electrodes for charging a charging auxiliary member .

[0014]

The principle of uniform charging will be described in detail below with experimental results.

In the photoreceptor used in this embodiment, a charge generation layer in which a phthalocyanine pigment and a resin are dispersed is provided on an aluminum alloy base material, and hydrazone and a resin are mixed thereon to form a charge transport layer. A negatively charged organic photoreceptor coated to a thickness of 20 μm was used. Unless otherwise specified, the roller used in this example has a configuration in which conductive urethane rubber is provided on a core metal φ6 mm, and the outer diameter is φ1.
It is 2 mm and has a hardness of JIS A35 ° and is pressed against the photoreceptor at a predetermined pressure. The outer diameter of the photoreceptor is φ30 mm.

Hereinafter, the principle will be described sequentially. 1. Charging Roller DC Application Characteristics and Discharge Model A charging roller having a volume resistivity of 10 ⁶ to 10 ⁷ Ω · cm was brought into contact with the photoreceptor with a contact width of 1 mm, and was rotated with the photoreceptor. A direct current of 1.0 kV was applied to the charging roller, and the relationship between the roller surface roughness and the potential unevenness in the axial direction of the photosensitive member was observed. The results are shown in (Table 1). The charging unevenness depends on the surface roughness of the charging roller. The smaller the maximum surface roughness (Rmax), the smaller the unevenness.

[0017]

[Table 1]

A model of a minute discharge between the photosensitive member and the charging roller is disclosed in Japanese Patent Publication No. 3-52058 and Japanese Patent Laid-Open No. 64-354.
No. 59 discloses this. FIG. 9 is a model diagram showing a contact state between the photosensitive member and the charging roller. In FIG.
33 is a photoreceptor, 33a is an aluminum substrate, 33b is a photosensitive layer, and 34 is a charging roller. The voltage Vg applied to the gap when the voltage Vr is externally applied between the photoconductor 33 and the charging roller 34 is expressed by the following equation. Vg = (Vr−Vd) z / (z + d _OPC / κ ″) (1) Vr: Voltage applied to charging roller Vd: Photoconductor surface potential d _OPC : Thickness of photosensitive layer κ ″: Dielectric constant of photosensitive layer z: Here, the gap voltage curve and the Paschen curve of the equation (1) are plotted against the gap width as shown in FIG. Discharge occurs when the discharge Vg according to equation (1) exceeds the discharge start voltage due to Paschen. The unevenness of the photoconductor surface potential after the discharge is explained as follows. Since the charging roller 34 has irregularities on the surface, when the charging roller 34 comes close to the photosensitive member 33 having a smooth surface, there are various gap distances as shown in an enlarged view at the time of proximity shown in FIG. Assuming that the concave portion of the charging roller 34 is A and the convex portion is B, the gap voltage curve intersects the Paschen curve at two points having different gap distances in FIG. That is, the concave portion A having a large gap distance intersects the Paschen curve on the right side of the convex portion B having a small gap distance. Discharge start voltage VTH at point A
Comparing (A) with the discharge start voltage VTH (B) at point B, a discharge start voltage difference ΔVTH represented by VTH (A) = VTH (B) + ΔVTH (2) results in unevenness. The unevenness of the gap width is caused not only by the unevenness of the surface of only the charging roller 34 but also by the surface roughness of the photosensitive member 33.

The effect of the surface roughness of the photoreceptor 33 and the charging roller 34 also becomes remarkable in the charging method disclosed in Japanese Patent Application Laid-Open No. 64-35459. JP-A-64-35459
In this publication, the charging roller 34 in contact with the photoconductor is diverted to a charge elimination leveling roller, and prior to the charge elimination leveling roller, the photoconductor 33 is charged using a charger to start discharging between the photoconductor and the roller. After being charged to a voltage equal to or higher than the voltage, the surface potential of the photosensitive member is made uniform by a grounded neutralizing roller (resistance: about 10 ² Ω). The inventors charged the photoconductor 33 to a surface potential of about 1000 V using a corona charger, and then brought the charging roller 34 to the ground potential to contact the photoconductor. At this time, when the surface roughness of the charging roller 34 was changed to measure the charging unevenness of the photosensitive member 33 in the longitudinal direction of the shaft, the same result as in Table 1 was obtained. That is, the uneven charging of the photosensitive member indicates that the charge holding member has surface irregularities regardless of the photosensitive member or the charging roller. 2. Uniform Charging Method Combining Ion Discharge Power Source and Semiconductive Roller FIG. 12 shows a schematic configuration diagram of a charging device implemented by the inventors. In FIG. 12, 1 is a photosensitive member, 2 is a charging roller, 3
Reference numeral denotes a discharge needle arranged on the rotation upstream side of the charging roller 2. A plurality of discharge needles 3 are arranged in the longitudinal direction of the shaft. In order to make the surface potential of the photoreceptor 1 charged even, the following features are provided in terms of configuration. (1) Arrange the discharge needles 3 so as to simultaneously charge the photoconductor 1 and the charging roller 2 (the tip of the discharge needle 3 is desirably directed to the charging roller 2 side to prevent deterioration of energization of the photoconductor 1). 2) The resistance of the charging roller 2 is the discharge needle 3 and the charging roller 2
In the meantime, the charging roller 2 has a semiconductive resistance so as to generate a stable discharge between the photoconductor 1 and the charging roller 2. It is touching and driven to rotate. The arrangement of the discharge needles 3 and the resistance of the charging roller 2 are determined based on the following concept.

Although the distance between the discharge needle 3 and the surface of the photosensitive member 1 increases as the distance from the surface of the photosensitive member 1 increases, the distance between the photosensitive member 1 and the discharge needle 3 needs to be as short as possible in order to increase the discharge efficiency and reduce the amount of ozone. . Then, conversely, discharge unevenness on the surface of the photoconductor 1 increases. This is the same as spraying water with a watering can, if you spray water from a high position, you can wet uniformly, but you can concentrate water from a low position, but it is difficult to wet a large area uniformly. It is. However, to reach a certain amount of wetting, watering from a higher position requires more water than watering from a lower position. In the present invention, in order to solve this inconsistency, the discharge needle 3
Is concentrated mainly in the direction of the charging roller 2, and the photosensitive member is charged by a partial soft discharge.

The resistance of the charging roller 2 is determined so as to stabilize the discharge of the discharge needle 3. Stabilization means that the discharge needle 3
A discharge is generated between the discharge roller 3 and the charging roller 2, and further, the discharge is prevented from reaching a spark discharge (a state in which a short circuit occurs over the entire gap between the discharge needle 3 and the charging roller 2 and the current rapidly increases). This is to avoid problems such as an increase in the load on the power supply and an increase in ozone generation. The inventors obtained a stable discharge region from experiments. Now, the discharge needle 3 and the charging roller 2
The resistance of the gap between the electrodes is Ra, the resistance of the charging roller is Rr, and the discharge starting voltage between the discharge needle 3 and the charging roller 2 is VT.
H, when the applied voltage at the time of spark discharge is VMAX and the discharge current is I, spark discharge does not occur if the relationship VTH <(Rr + Ra) × I <VMAX (3) is always satisfied at the time of discharge. The resistance of the gap at the time of discharge is 10
⁷ since sought and to 10 ⁸ Omega, the distance d2 between the charging roller 2 and the distance d1 between the discharge needles 3 and the photosensitive member 2 discharge needles 3 and approximately equal 2.5 mm, the discharge starting voltage VTH obtained from the measured -
Substituting 2.5 kV, spark discharge start VMAX-3.5 kV, and discharge current of about 35 μA, Rr becomes 7 × 10 ⁷ <Rr <1 × 10 ⁸ (4). This means the resistance of the gap that creates a state in which a space charge is stably formed in the discharge path by ions or electrons and does not cause a sudden voltage change. When a metal roller having a resistance lower than 10 ⁷ Ω is actually used as the charging roller 2, a scale-like discharge mark appears on the image. When the charging roller 2 coated with insulation was used, a black spot pattern appeared and a good image could not be obtained.

The charging roller 2 is configured so that the distance from the photosensitive member 1 gradually decreases. This is for the purpose of stabilizing the discharge between the photoreceptor 1 and the charging roller 2 by a discharge with a short discharge path (Townsend discharge, in comparison, a discharge between the discharge needle 3 and the charging roller 2 is a streamer discharge with a long discharge path). What is done. Therefore, contact with a member having a sharp portion (sharp corner or the like) is not desirable. In this case, since the discharge is also performed, there is an appropriate value for the resistance of the gap between the photoconductor 1 and the charging roller 2 so that the discharge is stably performed. The discharge starting voltage between the charging roller 2 and the photoconductor 1 is VTH,
Maximum voltage VMAX at which no abnormal discharge marks appear, charging roller 2
Is Rr, and the resistance of the gap between the charging roller 2 and the photosensitive member 1 is Ra, and VTH <(Rr + Ra) .times.I <VMAX (5) as in (1). Ra is 10 as in the case of (3).
⁷ as the ~10 ⁸ Ω, VTH = 580V obtained from the measured
(The film thickness of the photoconductor 1 is 20 μm), and VMAX = 700 V is substituted, and the following formula can be obtained: 1 × 10 ⁷ <Rr <1 × 10 ⁸ (6) Therefore, the length and pitch of the needles of the discharge needles 3 and the distance from the photoconductors must be adjusted so that the charge of the photoconductor 1 by the discharge of the discharge needles 3 can be charged to about VMAX. For this purpose, a pulsating flow such as an alternating current or a pulse may be applied to the discharge needle 3.

The method of equalizing the potential of the surface of the photoconductor 1 by the charging roller 1 after the photoconductor 1 is charged by the discharge needles 3 is more uniform than when charging is performed by directly applying a voltage to the charging roller. This is done for the following reasons.

FIG. 13 is an enlarged view of the surface of the photoconductor 1.
As described above, the surface of the photoconductor 1 has irregularities due to the blade, the toner, and the like. In the figure, (a) is a film thickness d, (b) is a film thickness d ', and d>d'. The area in this proximity is discharged by the discharge needle 3 and the surface thereof has an equivalent charge Q.
Is charged. The charging is performed at a discharge starting voltage VTH or higher so that a discharge occurs between the photosensitive member 1 and the charging roller 2. At this time, the charging voltage of each area is expressed as follows: (a) Vd = Q / (κε / d) (5) (b) Vd ′ = Q / (κε / d ′) (6) , Vd> Vd '. Therefore, when facing the grounded charging roller 2, the voltage applied to the gap between the charging roller 2 and the photoconductor 1 is larger in the region (a). For this reason, the amount of electric charge returning to the charging roller 2 by the discharge is larger in the region (a), and finally the potential of the surface of the photoconductor 1 becomes almost equal to VTH. On the other hand, when the voltage is directly applied to the charging roller 2, the potential difference between the photoconductor 1 and the charging roller 2 is always the same regardless of the regions having different film thicknesses, and the unevenness as described in the equation (2) occurs. . Actually, even if a scratch of about 10 μm was intentionally made on the surface of the photoreceptor 1 with sandpaper, no scar was observed on the image by the charging method of the present invention.
When applied directly to the surface, scars appeared clearly on a white background.

As described above, the discharge needle 3 is mainly discharged toward the charging roller 2 and the photosensitive member 1 is simultaneously charged by a soft discharge of a part thereof. By adjusting the photoconductive member 1 to be semiconductive for stabilization and charging the photoreceptor 1 and then bringing the photoreceptor 1 into contact with the charging roller 2, uniform charging not affected by unevenness of the surface of the photoreceptor 1 can be obtained.

[0026]

FIG. 1 is a schematic structural view of an image forming apparatus (electrophotographic apparatus) according to an embodiment of the present invention.

Reference numeral 1 is the same as the above-described photosensitive member (charged member) . The thickness of the photosensitive layer is 20 μm as described above.
The relative dielectric constant (κ ″) is 3. The charging roller 2 (charging compensation)
Auxiliary member) and 3 discharge needles (charging member) are the same as described above.
The volume resistivity of the charging roller 2 brought into contact with the photoreceptor 1 at a predetermined pressure is determined as follows.

Hereinafter, specific figures will be shown with reference to the drawings.
The image forming apparatus of the present invention will be described.

FIG. 2 is a front view showing the shape of the discharge needle.
The length (L) of the needle and the pitch (P) of the needle can be arbitrarily selected depending on the charging speed, the size of the discharge region, and the like. In this embodiment, L = 3 mm, P = 2 mm, and the thickness is 0, respectively. A 1 mm stainless steel plate was used. W is determined according to the copy width. As shown in FIG. 3, the discharge needles 3 are arranged at a distance d1 from the charging roller 2 and at a distance d2 from the photoconductor 1 (arbitrarily selectable depending on the charging speed, the size of the discharge area, and the applied voltage). Then, d1 = 2.5 mm, d2 =
2.5 mm. The tip of the discharge needle 3 is almost the charging roller 2
Install so that it faces. The charging roller 2 is made of an ion conductive urethane elastomer containing a metal salt, and has a hardness of about 35 degrees according to JISA. The charging roller 2 and the photoreceptor 1 abut at a predetermined pressure, specifically 10 to 150 g / cm, and are driven to rotate with the photoreceptor. Contact width (nip) at this time
Was about 1 mm, and the resistance between the metal core and the roller surface was about 3 × 10 ⁷ Ω when 500 V was applied. The charging roller 2 may be provided with a thin (about 10 μm) insulating layer on a conductive rubber layer to adjust the resistance to about 10 ⁷ Ω.

[0030]

[Table 2]

Table 2 shows that the photosensitive roller 1 passed through the charging roller 2 when a voltage of -2 kV was applied to the discharge needle 3 with respect to the grounded charging roller 2 using the above-described resistance roller as the charging roller 2. The surface potential and the potential unevenness are shown. The discharge current of the discharge needle 3 is 50 μA, and 35 μA flows into the inner charging roller 2. Table 2 compares the unevenness when using the charging rollers 2 having different surface roughness. The results are independent of the maximum surface roughness.

The resistance of the charging roller 2 is determined so as to stabilize the discharge by the discharge needle 3 and the discharge between the charging roller 2 and the photosensitive member 1 as described in the operation. May be adjusted according to the contact distance and the moving speed. Depending on the conditions, a voltage may be externally applied to the charging roller 2 to control the discharging conditions, or a resistor may be inserted between the charging roller 2 and the ground to control the discharging conditions.

(Comparative Example) The charging roller 2 has a resistance of 1
0 ⁷ Omega using lower 10 ² to 10 ³ Omega conductive roller of the discharge trace scales pattern appears on the entire image. The surface potential unevenness of the photoconductor 1 was as large as 50 to 100 V. Further, as shown in FIG. 4, a volume resistivity of 10 ² to
A charging roller 2 having a conductive rubber layer 6 of 10 ³ Ω · cm, insulated coating on the conductive rubber layer 6 and having a resistance of 10 ¹¹ Ω.
When black was used, a black spot pattern appeared on a white background portion of the image, and the surface potential unevenness of the photoreceptor 1 was as large as about 200 V, and a good image was not obtained.

[0034]

As described above , according to the present invention, uniform charging can be performed on the member to be charged.

As described above, the photosensitive member and the discharge auxiliary member having a semiconductive resistance are simultaneously charged by the discharge needle, and the resistance of the discharge auxiliary member is adjusted to the semiconductive region, whereby the charging roller and the discharge needle are charged. Alternatively, a stable discharge is caused between the photoconductors, thereby enabling a charging system with low ozone generation with a simple configuration. In addition, this method can follow variations in the surface irregularities of the member to be charged, and enables stable uniform discharge.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a front view showing the shape of a discharge needle according to an embodiment of the present invention.

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

FIG. 4 is a sectional view showing the configuration of a charging roller used in a comparative example with respect to the embodiment of the present invention

FIG. 5 is a schematic diagram for explaining the operation of a conventional charging device and a schematic diagram showing a state in which a charging member is in contact with an image carrier.

FIG. 6 is a diagram showing a waveform of a voltage applied to a conventional charging member.

FIG. 7 is a diagram illustrating a relationship between a voltage applied to a charging roller and a surface potential of a charged band, and illustrating a discharge starting voltage.

FIG. 8 is a schematic configuration diagram for explaining another conventional charging device.

FIG. 9 is a model diagram showing a contact state between a photosensitive member and a charging roller.

FIG. 10 is an enlarged view showing a contact state between a photosensitive member and a charging roller.

FIG. 11 is a diagram in which a gap voltage between a photosensitive member and a charging roller and a Paschen curve are plotted with respect to a gap width.

FIG. 12 is a schematic structural view of the charging device of the present invention for explaining the operation.

FIG. 13 is an enlarged view of the surface of the photosensitive member for explaining that the charging method according to the method of the present invention can perform uniform charging regardless of unevenness of the photosensitive member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Discharge needle

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-268574 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/02 G03G 15/02

Claims (9)

(57) [Claims] An object to be charged which rotates and an object to be charged
A charging auxiliary member that abuts on the member to be charged and the belt;
Preparing a charging member arranged to face the charging auxiliary member
Applying a voltage to the charging member to discharge the semi-conductive charging auxiliary member and the rotating member to be charged, thereby charging the charging auxiliary member and the member to be charged; and Than the contact area between the auxiliary member and the member to be charged ,
Discharging on the charging member side between the charging auxiliary member and the member to be charged. 2. The charging method according to claim 1, wherein the discharging by the charging member is mainly performed toward the discharge auxiliary member, and a part of the discharging is performed toward the member to be charged. 3. The charging method according to claim 1, wherein the discharging step is performed in a region where the distance between the discharge auxiliary member and the member to be charged gradually decreases. 4. A member to be charged is rotated movably disposed, the contact the member to be charged, discharge electric field between the member to be charged
Forming a semi-conductive charging auxiliary member, and opposing the object to be charged and the auxiliary charging member;
Wherein in the rotation direction of the charging member located above stream side of the auxiliary charging member, by the voltage discharges are allowed applied, before
A charging device comprising: a plurality of needle-like electrodes for charging the member to be charged and the charging auxiliary member . 5. The charging device according to claim 4, wherein the charging auxiliary member has a region where the distance from the member to be charged gradually decreases. 6. The charging device according to claim 4, wherein said charging auxiliary member has a roller shape. 7. A member to be charged is rotated movably disposed, the contact the member to be charged, discharge electric field between the member to be charged
Forming a semi-conductive charging auxiliary member, and opposing the object to be charged and the auxiliary charging member;
Wherein in the rotation direction of the charging member located above stream side of the auxiliary charging member, more that voltage discharges are allowed applied, before
An electrophotographic apparatus comprising: a plurality of needle-like electrodes for charging the member to be charged and the charging auxiliary member . 8. The electrophotographic apparatus according to claim 7, wherein the charging auxiliary member has a region where the distance from the member to be charged gradually decreases. 9. The electrophotographic apparatus according to claim 7, wherein said charging auxiliary member has a roller shape.