JP3240027B2 - Charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic apparatus based on the so-called Carlson process, for example, a copying machine, a printer,
The present invention relates to a charging device incorporated in a facsimile or applied as a charging device incorporated in a process cartridge of these devices, and particularly as a charging device in an electrophotographic apparatus for charging a belt-shaped or drum-shaped photoconductor by particle charging. It relates to the applied invention.

[0002]

2. Description of the Related Art Conventionally, respective process means of exposure, development, transfer, cleaning (removal of residual toner), charge elimination and charging are arranged on the outer peripheral surface of a photosensitive drum, and an image is formed by a predetermined electrophotographic process. Electrophotographic apparatuses based on the so-called Carlson process are well known.

The charging means used in this type of apparatus is generally a corotron type in which a high voltage is applied to a thin tungsten wire to perform corona discharge, or a charging means in which a voltage of several hundred volts is applied to a conductive roller to contact and charge a photosensitive drum. In addition, there is a type in which a voltage is applied to a conductive brush while being brought into contact with a photosensitive drum to charge the conductive brush. However, the corotron method uses high voltage and generates ozone for safety reasons.
Many environmental problems. Further, the charging roller is unstable in charging because the contact with the photosensitive drum is a line contact. Further, in the brush charging method, the charging of the brush is likely to occur because the drum and the brush are in contact with each other to perform charging.

In order to solve such a drawback, in a state in which a charging bias is applied to a charging sleeve in which a photosensitive drum and a magnet body are inserted, magnetic particles are attached to the sleeve and a brush-like magnetic spike is formed on the photosensitive sleeve. A so-called particle charging method has been proposed, in which a charging bias is applied to a group of magnetic particles by rubbing the drum through a sleeve and charging is performed. (Japanese Patent Laid-Open No. 5
9-133569, JP-A-63-187267, etc.)

In such a charging method, when a magnetic spike is formed by a fixed magnet body, the magnetic field attenuates in proportion to the square of the distance from the magnet body. The weakest holding power. Therefore, when the photosensitive drum is rotated in this state, a centrifugal force acts on the surface of the drum, and the magnetic particles electrostatically adhering to the photosensitive drum resist the magnetic coercive force (magnetic field) from the fixed magnet assembly. Then, a force acts in a direction in which the magnetic particles separate from the charged area, and the particles adhered to the photosensitive drum adversely affect the exposure and development in the next step.

As shown in FIG. 3, in order to eliminate such a drawback, a fixed magnet body 10 covering an electrode 102 to which a charging bias power source 101 is connected without using the charging sleeve.
3 is arranged opposite to the photoconductor drum 104, and opposite to the fixed magnet body 103, and a magnet body 105 of the opposite polarity is arranged on the back side of the photoconductor drum 104, and between the magnet body 105 and the fixed magnet body 103. A technique has been disclosed in which the photoconductor is charged while the magnetic particle group 107 is held in a charged area by a magnetic field formed in the magnetic field.

[0007]

According to such technology,
Since the magnetic body for holding the magnetic particles 107 is not disposed only on one side of the charging gap 108 but on both sides, the gradient of the magnetic field (ΔH / Δt) between the charging gaps 108 is reduced. Although it can be set to a large value, the magnetizing force of the magnet and the magnetic particles depends on the particle size, and when the particle size is small, the magnetic binding force decreases geometrically exponentially. Particle leakage occurs due to particles attached to the drum surface due to the target holding force. If the electrical resistivity of the particles is reduced excessively in order to prevent the electrostatic adhesion of the particles, dielectric breakdown of the photoconductor and leakage of a photoconductor defect occur, and a pinhole or the like is formed on the photoconductor drum side by the charging bias. Is easy to occur. For this reason, in the above-mentioned apparatus, the insulating sheet 109 is hung down on the side of the fixed magnet body 103 toward the photosensitive drum side to mechanically prevent scattering of magnetic particles.

However, in the configuration in which the insulating sheet is brought into contact with the drum as described above, not only is it not possible to withstand long-term use due to abrasion or the like, but if the magnetic particles are not made of a material having good conductivity, the insulating sheet and the particles cannot be used. Undesirably, particles are fixed due to the triboelectric charging.

In view of the drawbacks of the prior art, the present invention is applied to a charging device capable of ensuring stable and uniform charging ability without causing the leakage of the charged particles and the deterioration of the charging agent even after long-term use. It is an object of the invention to provide the invention. Another object of the present invention is to provide an invention applied as a charging device capable of ensuring good circulation of magnetic particles without causing dielectric breakdown. Another object of the present invention is to provide an invention capable of obtaining a highly practical charging device that can sufficiently consider the environment, from the viewpoint of manufacturing and from the side of the user, and furthermore. I do.

[0010]

According to the present invention, as shown in FIG. 1A, a first magnet body (hereinafter referred to as a main pole A ) fixedly disposed on a charged area of a photoconductor toward the photoconductor. the non-magnetic charging sleeve enclosing a) of _1, and the back side of the photosensitive member located on the charged area, the main pole a ₁ and opposite polarities second magnet body (hereinafter referred opposing electrode B ₁₎ It arranged, while rotating the charging sleeve, in the chargeable configured the charging device of the photoreceptor through a supported magnetic particles by both the magnet body, disposed adjacent to the opposite pole B ₁ the pair Kokyoku B
_A third magnet that forms a horizontal magnetic field by making the polarity opposite to _1.
Arranging the body (hereinafter referred adjacent poles B ₂₎ to the photosensitive member back side, front
Fourth magnet body for conveying the reverse polarity of the magnetic particles Kinushikyoku A ₁
(Referred to hereinafter conveying pole _{A 3),} downstream from 該搬Okukyoku _{A 3}
Than the main poles A ₁ of disposed the magnetic particles, the magnetic particles located in the photosensitive member rotation direction upstream said conveyor pole A
Separated and dropped from the charging sleeve after being transported by ₃
Fifth magnetic body having a magnetic force of 50 Gauss or less
Arranged) that lower separating pole A ₄ in the charging sleeve and the charging sleeve is rotated in Against direction to the moving direction of the photosensitive member, the photosensitive member of the sleeve closest point P of the main pole A ₁ Contact <br/> Keru flux density in charging gap 5 position of the above, and configured as Ru greater-than the magnetic flux density at the opposite pole B ₁ of the last on contact P, preferably the
The average particle diameter of the magnetic particle group is set to approximately 10 to 40 μm , and the saturation magnetization of the magnetic particle group at a magnetic field of 1 kOe is set to 5 μm.
0 emu / g to 200 emu / g and a relative dielectric constant εr of 40
It is characterized by the following settings. The present invention is preferably the magnetic particles have a volume resistivity of the entire a mixed particles having a volume resistivity of 10 ⁶ or less electrically conductive magnetic particles and a volume resistivity of 10 ⁶ or more high-resistance magnetic particles 10
^3-10 is in the range of ⁸ Omega · cm, average particle diameter than the large west average particle diameter conductive magnetic particles of the high-resistance magnetic particles and 20μm following particle distribution in this case the high-resistance magnetic particles of 5% It is better to configure as follows. The volume resistivity is determined by placing 1.5 g of the particles in a Teflon cylindrical body having an inner diameter of 20 mm and having an electrode at the bottom, and having an outer diameter of 2 g from the top.
This is a value measured by applying a load of 1 kg to the upper surface of the electrode after inserting an electrode of 0 mmφ.

In this case, the charging sleeve is rotated in the opposite direction to the rotation direction of the photosensitive drum, and the magnetic flux density on the closest point P of the main pole A _{1 is changed to} the closest point of the opposite pole B _1. It is preferable that the magnetic flux density be larger than the magnetic flux density on P. Moreover, the maximum magnetic flux density position Q ₁ is recently photosensitive drum rotation direction upstream side of + 5 ° ~-30 ° across the contacts P, the maximum magnetic flux density position Q ₂ is -10 ° ~ +5 recently across the contacts P It is good to arrange in the range of °. More charging the sleeve in the photosensitive member movement direction downstream side The magnetic shield becomes easier by placing and the counter electrode B ₁ second magnet body having the same polarity (hereinafter referred shield electrode A _2).

[0012]

According to the present invention, the outflow phenomenon of the magnetic particles 4 depends on the relationship between the magnetic force and the electrostatic force applied to the magnetic particles 4 at the sleeve closest point P of the photosensitive member. That is, the magnetic force Fm acting on the particles at the closest point P is: Fm = k ₁ · d ³ k ₁ : a proportional function d: the particle diameter The electrostatic force Fc acting on the particles at the closest point P is: Fc = k ₂ · (T · d) ² · ΔV ² T: function dependent on non-dielectric constant ΔV: potential difference (charging applied voltage and voltage applied to photosensitive layer) Potential difference ΔV when magnetic particles overcome magnetic force and flow out by electrostatic force is Fc ≧ Fm ΔV ≧ (T) ⁻¹ · (k ₁ · d / k ₂ ) ^1/2 1) Therefore, as is apparent from the above equation (1), if the particle diameter is too small, Fc ≧ Fm, and the particles flow out.

On the other hand, if the particle size is too large, no leakage of particles occurs, but as the particle size increases, the filling rate of the magnetic particles between the sleeve and the drum decreases, and the particles are charged even by the same charging bias. 1B, the gap 4a between adjacent magnetic particles 4 on the surface of the photoreceptor 1 increases, as shown in FIG. 1 (B). Therefore, according to the present invention, by setting the average particle size to approximately 10 μm to 40 μm, it is possible to smoothly prevent the leakage of particles from the charged region.

The magnetic coercive force of the magnetic particles depends on the saturation magnetization, and the electrostatic force induced by the charging agent increases as the relative permittivity of the magnetic particles increases. Therefore, the saturation magnetization of the magnetic particle group at a magnetic field of 1 kOe is reduced to 50 emu /
g to 200 emu / g, and a relative dielectric constant εr of 40
It is better to set below. Note the 200 emu / dielectric constant εr at least g is a magnetic particles exceeding 40, the magnetic particles 4 shown in FIG. 2 to be described later can not be separated by the separation electrode A _4, it is conveyed to the charging sleeve rotation direction downstream side The Rukoto.

The present invention has a volume resistivity of 10 ⁶ Ω · c.
m and conductive magnetic particles with a volume resistivity of 10 ⁶ Ω · c
m and a mixed particle group of high-resistance magnetic particles of at least m, and the average particle size of the high-resistance magnetic particles is larger than the average particle size of the conductive magnetic particles, specifically, the high-resistance magnetic particles. By configuring so that the particle distribution of 20 μm or less is 5% or less, it is possible to prevent leakage that is more likely to occur than in the case of a single-type charging agent. On the other hand, the average particle size of the conductive magnetic particles contributing to uniform charging is preferably small, for example, 20 μm.
The following is preferred. The mixing ratio between the high-resistance magnetic particles and the conductive magnetic particles depends on the specific volume resistivity. However, the mixing ratio of the conductive magnetic particles is preferably small, specifically, 5 to 30% by weight.

Also, as shown in FIG. 1, the magnetic particles 4 guided to the charging gap 5 of the sleeve nearest point P of the photosensitive drum 1 have a bottleneck in the gap 5, but the closest point P at the main pole A ₁ and the magnetic flux density B _A1, when the magnetic flux density of the closest point P of the counter electrode B ₁ was B _B1 "B _A1> B
_Since it is set to " _B1 ", it is sucked from the photosensitive drum 1 side to the charging sleeve 2 side. Further, in the present invention, since the charging sleeve 2 is rotated with respect to the photosensitive drum 1 in the opposite direction, that is, toward the upstream side of the charging area, the magnetic particles 4 attached to the charging sleeve 2 move from the position of the charging gap 5 to the charging gap 5. the separation electrode a ₄ flowing toward the charging area upstream, in the charged area is separated from the charging sleeve 2 enables circulation of the magnetic particles 4, it never said particles deteriorates even by long-term use.

Here, the reason why the magnetic flux density on the closest contact point P is set to "B _A1 > B _B1 " is to achieve an effect that particles can move toward the charging sleeve 2 at the charging gap 5 position.

In particular, in order to most effectively achieve the condition of “B _A1 > B _B1 ”, the maximum magnetic flux density position Q _{1 of the} opposing pole B ₁ is close to the closest point P, although it depends on the half width of each magnet body. It is preferable to set the range of + 5 ° to −30 ° on the upstream side in the rotation direction of the photoconductor drum with the interposition therebetween, and further, the maximum magnetic flux density position Q ₂
Is preferably set in the range of −20 ° to + 5 ° across the closest contact point P. The angle between the center O ₂ of the line connecting the photosensitive drum axis O ₁ and the charging sleeve O ₂ with respect to the axis O ₂ from the closest point P
Is set to 0 °, the upstream side of the photosensitive drum is set to a minus angle, and the downstream side is set to a plus angle.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just. FIG.
The configuration of the charging device according to the embodiment of the present invention will be described based on FIG. As described above, the charging device is opposite to the photosensitive drum 1 at a charging area position via a charging gap 5 (nearest distance) of about 0.5 mm with respect to the photosensitive drum 1 rotating rightward in the drawing, That is, a non-magnetic charging sleeve 2 which is rotatable in the opposite direction (the left direction in the figure, and when viewed from the rotation axis is the same rotation direction) is disposed, and the charging sleeve 2 on the back side of the sleeve 2 is provided. The magnet assembly 3 fixedly arranged on the downstream side of the charging area is provided. still,
Reference numeral 7 denotes a bias power supply for applying a developing bias to the conductive magnetic particle group 4 via a conductive blade or a non-magnetic sleeve 2 (not shown).

Next, the arrangement of the magnetic poles of the charging sleeve 2 and the photosensitive drum 1, which is the gist of the present invention, will be described. First, the magnet assembly 3 mainly includes the magnetic particles 4 on the charging gap 5 or slightly upstream of the charging gap 5 in the rotation direction of the charging sleeve 2 and between the opposite magnetic pole B ₁ on the back side of the photosensitive drum 1. the main pole a ₁ N pole for magnetic seal for preventing leakage, further charging sleeve 2 rotating direction upstream side of the main poles a _1, the magnet body S pole for magnetic seal for performing the magnetic seal assisted by repulsive magnetic field (Hereafter, shield auxiliary pole A
Of _2), and the charging sleeve 2 rotation direction downstream side of the main poles A ₁ to form a separated electrode A ₄ is a non-magnetic band with only about 50 Gauss or less a small magnetic force on the sleeve 2, the sleeve 2 AGAIN a structure for dropping the magnetic particles 4 are transported by a magnet body a ₃ S pole which are conveyed while being carried on the sleeve 2 surface to the photosensitive drum 1 side of the charged region upstream by strike rotation.

Further, a conductive magnetic particle group 4 is interposed on a charging area sandwiched between the charging sleeve 2 and the photosensitive drum 1. Although the details of the magnetic particles 4 will be described later, the volume resistivity is arbitrarily set in a range of 10 ³ to 10 ⁸ Ω · cm, and the particle size is arbitrarily set in a range of an average particle size of 10 to 30 μm.

On the other hand, on the rear side of the photosensitive drum 1, the main only slightly photoconductive than the counter positions of A ₁ drum 1 rotating direction upstream side of the charging area downstream portion of the S pole magnet member (hereinafter opposite pole B
₁ ) and an N-pole magnet body (hereinafter, referred to as “horizontal magnetic field”) for forming a magnetic field (hereinafter, referred to as “horizontal magnetic field”) horizontal to the surface of the photosensitive drum 1 on the upstream side of the charging area adjacent to the opposite pole B _1. pole B ₂ hereinafter) and an adjacent arrangement, a magnetic field perpendicular to the photosensitive drum surface (hereinafter referred to as "vertical field") between the main pole a ₁ and the counter electrode B _1, also adjacent to the opposite pole B ₁ forming a horizontal magnetic field on the photosensitive drum 1 between the pole B _2.

That is, the main pole A ₁ and the counter pole B ₁ disposed opposite to each other are disposed downstream of the charging area in the rotation direction of the photosensitive drum, and a vertical magnetic field formed between the two magnet bodies A ₁ and B ₁ is provided. be magnetically holding said magnetic particles 4 due, also adjacent poles B ₂
Is disposed adjacent to the counter electrode B ₁ and upstream of the charging area,
The magnetic particle group 4 is brought into close contact with the photosensitive drum 1 by a horizontal magnetic field on the photosensitive drum 1 mainly formed between the two magnet bodies B ₂ and B ₁ .

More specifically, the arrangement of the magnetic poles will be described in detail with reference to FIG. Shield auxiliary poles A ₂ is in the charging sleeve rotation direction upstream side relative to the main poles A _1, the maximum magnetic flux density position Q ₃ on the charging sleeve of the shield auxiliary pole A ₂ is set in the range of 45 ° to 90 ° ing. The angle is the direction of a line connecting the axis O ₂ around the charging sleeve O ₂ recently to the contact point P and 0 °, 0 °
This is a value in which the deflection angle toward the downstream side in the photoconductor moving direction is set to be plus. The main poles A _1, the maximum magnetic flux density position Q ₂ in the main poles A ₁ charge on sleeve, also the photosensitive drum rotation direction downstream side of the maximum magnetic flux density positions Q ₁ in the counter electrode B ₁ of the photoreceptor drum as well as configured to be located, in particular, -20 ° ~ across Q ₂ is nearest point P +
It is preferable to set the angle in the range of 5 °, more preferably in the range of -10 ° to + 5 °. The opposite pole B ₁ represents a maximum magnetic flux density position Q ₁ is recently the recent charge on the contact point P of the main pole A ₁ in the range of the photosensitive drum rotation direction upstream side of + 5 ° ~-30 ° across the contacts P the magnetic flux density in the gap 5 position, the recent charging gap 5 position on the contact point P of the counter electrode B ₁
Arranged as becomes larger than the magnetic flux density at. In this case, the angle is the value shown in the column of action. The relationship between the main poles A ₁ and the counter electrode B ₁ represents a line connecting the maximum magnetic flux density position Q ₂ between the charging sleeve axis O ₂ the main pole A _1, the photosensitive drum axis O ₁ and the counter setting the narrow angle of a line connecting the maximum magnetic flux density positions to _{Q 1} pole _{B 1} to 0 to 50 °.

Next, the operation of the embodiment will be briefly described with reference to FIG.
Is attached in close contact with the photosensitive drum 1 and the counter electrode B ₁ on a horizontal magnetic field 4A between adjacent poles B _2, when the photosensitive drum 1 in this state is rotated clockwise, the photosensitive on a horizontal magnetic field 4A The magnetic particle group 4 moves toward the charging gap 5 while charging the body drum 1, and at the position of the charging gap 5, a repulsive magnetic field is generated between the magnetic auxiliary particles A ₁ and the counter electrode B ₁ by the shield auxiliary pole A _2, and the main pole assist a magnetic shield made of a ₁ opposite pole B _1, inclined direction of the force by the upward force according to a _1, B ₁ to the photosensitive drum upstream, moves to the sleeve 2 side of the drawing the upper left. Then the magnetic particles is not transported to the second downstream side sleeve without force on the sleeve 2 by the separation electrode A _4. In this case, setting the saturation magnetization at a magnetic field of 1KOe magnetic particles 4 to 50emu / g~200emu / g, is conveyed exceeds 200 emu / g separating electrode A ₄ pass easily charged sleeve 2 downstream the The Rukoto. On the other hand, becomes below 50 emu / g, the main pole A ₁ side magnetic particles 4 are difficult adhere to, circulation becomes difficult as a result.

In this case, although the combined vector of the magnetic force on the closest point P formed by the shield pole A ₂ and the counter pole B ₁ is not shown, by setting it toward the entrance of the charging gap 5, The pushing back direction by the magnetic field works together with the repulsive magnetic field, which is more preferable. And further wherein in the normal direction of the sleeve closest point P of the photosensitive drum, set the main pole A ₁ and the counter electrode B ₁ and to face the resultant vector of the magnetic force on the charging sleeve 2 side which is formed by the shield electrode A ₂ . As a result, the magnetic particles on the charging gap move toward the charging sleeve 2 and are attracted.

After the magnetic particles 4B adsorbed on the charging sleeve 2 are returned to the upstream side of the charging area in accordance with the rotation of the sleeve 2, the separation pole A ₄ provided downstream of the magnet body A ₃ is provided.
Are arranged so as to be located on the upstream side of the charged area, and therefore, the magnetic particle group 4 conveyed on the upstream side of the charged area.
C is magnetically released, falls to the photosensitive drum 1 side, and the circulation of the magnetic particles 4 is performed.

Next, the leakage of the magnetic particles 4 from the charging gap 5 using such an apparatus will be confirmed by experiments. First, the experimental conditions will be described. The photoconductor drum 1 is an OPC drum having a diameter of 30 mmφ and a linear velocity of 25 m /
Set to sec. The charging sleeve 2 uses an aluminum tube.
The diameter is set to 12 mmφ, and the linear velocity is set to 8 m / sec.

The magnetic flux density of each of the magnetic poles is
₁ and the adjacent pole B ₂ of each of the photosensitive drum 1 on the maximum magnetic flux density, respectively S630G of, N730G, further the maximum magnetic flux density on the main poles A ₁ and the shield auxiliary pole A ₂ of each of the charging sleeve 2 respectively N900G and S770G are set respectively.
Then, the main pole A _{1 is set} to 0 ° (the maximum magnetic flux density is set to N900).
G), when the counter electrode B _{1 is set} to −15 ° and the shield auxiliary electrode A ₂ is set to 60 °, the main electrode A ₁ , the counter electrode B _1, and the shield auxiliary electrode A ₂ on the closest point P are formed. It was confirmed by simulation that the resultant vector of the magnetic force generated was a magnetic force generated toward the gap entrance of the charging sleeve.

In this state, the charging sleeve is incorporated in an LED printer manufactured by our company, and 400 V is applied to the charging bias power supply 7 to rotate the charging sleeve in the opposite direction to the moving direction of the photosensitive drum. The state of leakage to the photosensitive drum was confirmed visually and by image formation. The magnetic particles have an average particle size of 15 μm and a volume resistivity of 10 μm.
^{5 Ω} · cm, the saturation magnetization in the magnetic field of 1KOe is 70emu /
g of ferrite carrier was used (Sample 1). As a comparative example, the magnetic particles have an average particle diameter of 30 μm, a volume resistivity of 10 ⁵ Ω · cm, and a saturation magnetization of 210 in a magnetic field of 1 KOe.
An emu / g iron powder carrier was used (Sample 2). In addition,
Each carrier had a non-dielectric constant of 40 or less. As a result of this experiment, the magnetic particles of Sample 1 were circulated well,
Good images were obtained. On the other hand, sample 2 has a separation pole A
₄ , the magnetic particles could not be separated.
Magnetic particles were surrounded, and they were not circulated smoothly, and uneven charging appeared in the image.

[0031]

As described above, according to the present invention, stable charging performance can be ensured for a long period of time without causing leakage of magnetic particles during particle charging and without deterioration of the charging agent even after long-term use. . Further, according to the present invention, the present invention is applied as a charging device capable of ensuring good circulation of magnetic particles. Further, according to the present invention, the environment can be sufficiently considered from the viewpoint of manufacturing and from the side of the user, and a highly practical charging device can be obtained. And so on.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is an overall view showing a charging device according to an embodiment of the present invention.

FIG. 3 is a table showing a charging device according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoreceptor drum 2 Charging sleeve 3 Magnet assembly 4 Magnetic particle 5 Charging gap P Closest contact A ₁ Main pole B ₁ Counter pole A ₂ Shield auxiliary pole A ₄ Separation pole

Claims (6)

(57) [Claims] 1. A non-magnetic charging sleeve including a _first magnet body (hereinafter, referred to as a main pole A1 ) fixedly disposed toward the photoconductor on a charging area of the photoconductor, and on the charging area. on the back side of the position photoreceptors, the main pole a ₁ and the opposite polarity second
Disposing a magnet body (hereinafter referred to as the counter electrode B _1), while rotating the charging sleeve, in the chargeable configured the charging device of the photoreceptor through a supported magnetic particles by both magnetic bodies, wherein disposed adjacent to the opposite pole B ₁ and the pair Kokyoku B ₁ opposite polarity and
To form a third magnetic body (hereinafter referred to as an adjacent
Pole arranged B of ₂₎ the photoreceptor back side, and the main pole A ₁
A fourth magnet body for transporting magnetic particles of opposite polarity (hereinafter a transport pole)
Conveyed that A _3), 該搬 than Okukyoku A ₃ from the main pole A ₁ of disposed downstream the magnetic particles by the magnetic particles the conveying pole A ₃ a group located in the photosensitive member rotation direction upstream side
50 moths of separating or dropping from the charging sleeve after being
Fifth magnet having the following magnetic mouse (hereinafter separated electrode A ₄
The) that placed in the charging sleeve and the charging sleeve is rotated in Against direction to the moving direction of the photosensitive member, the photosensitive member sleeve recent charging gap position on the contact point P of the main pole A ₁ the magnetic flux density in the charging device, characterized in that configured as Ru greater-than the magnetic flux density at the opposite pole B ₁ of the last on contact P. To 2. A within charging sleeve in the photosensitive member movement direction downstream side, according to claim 1, characterized in that arranged the sixth magnet of the opposite poles of the same polarity (hereinafter referred shield auxiliary poles A ₂₎ Charging device. 3. The method according to claim 1, wherein the magnetic particles have an average particle diameter of about 10 to 10.
The saturation magnetization in a magnetic field of 1 kOe is set to 50 emu at 40 μm.
3. The charging device according to claim 1, wherein the relative dielectric constant εr is set to not more than 40 / g to 200 emu / g. 4. The magnetic particle group having a volume resistivity of 10
⁶ is a mixed particles of less conductive magnetic particles and a volume resistivity of 10 ⁶ or more high-resistance magnetic particles, there volume resistivity as a whole in the range of 10 ³ ~10 ⁸ Ω · cm high resistivity magnetic particles 4. The charging device according to claim 3, wherein the average particle diameter of the conductive particles is larger than the average particle diameter of the conductive magnetic particles. 5. The charging device according to claim 4, wherein a distribution of the high-resistance magnetic particles of 20 μm or less is 5% or less. 6. maximum magnetic flux density position Q ₂ on the charging sleeve of the main pole A ₁ is also the photosensitive drum rotation direction downstream side of the maximum magnetic flux density positions Q ₁ in the counter electrode B ₁ of the photoreceptor drum together configured to position the maximum magnetic flux density position Q ₁ is recently photosensitive drum rotation direction upstream side of + 5 ° ~-30 ° across the contacts P, the maximum magnetic flux density position Q ₂ is the closest point P -10 ° ~ +
2. The charging device according to claim 1, wherein the charging device is disposed within a range of 5 [deg.].