JPH07209958A - Electrostatic charging device - Google Patents

Abstract

PURPOSE:To secure stable electrostatic charging capacity for a long period by specifying the magnetic force synthetic vector of two magnetic substances on a point closest to a charging sleeve on a photosensitive drum. CONSTITUTION:The charging sleeve 2 is rotated against the rotational direction of the photosensitive drum 1 and constituted so that the magnetic force synthetic vector Fn of two magnetic substances on the point P most close to the sleeve 2 on the drum 1 is positioned in an agular range thetaF around the point P (-90 deg.>thetaF>=15 deg.). In this case, the direction of the axial center O2 side of the sleeve 2 from the point P as a on a line connecting the axial center O1 of the drum 1 to the axial center O2 of the sleeve 2 is set up as O deg. and an upstream side and a downstream side in the rotataionai direction of the drum 1 are respectively set up to a minus angle and a plus angle. When a synthetic vector Fm is attracted in the inlet side direction of a charging gap 5, a grain group is moved in a direction to be retured from a leakage route to the upstream side of a charging area, so that the outflow or dispersion of grains from the charging area can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus based on the so-called Carlson process, such as a copying machine, a printer,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device incorporated in a facsimile machine or incorporated in a process cartridge of these devices, and particularly to a charging device in an electrophotographic apparatus that charges a drum-shaped photoreceptor by particle charging. Relates to the invention.

[0002]

2. Description of the Related Art Conventionally, process means for exposing, developing, transferring, cleaning (removing residual toner), discharging, and charging are arranged on the outer peripheral surface of a photosensitive drum, and an image is formed by a predetermined electrophotographic process. Electrophotographic devices based on the so-called Carlson process are well known.

The charging means used in this type of apparatus is generally a corotron system in which a high voltage is applied to a thin tungsten wire to perform corona discharge, or a conductive roller is applied with a voltage of several hundreds of volts to contact and charge a photosensitive drum. In addition, there is one in which a voltage is applied to a conductive brush so that the brush is charged while being in contact with the photosensitive drum. However, the corotron method uses a high voltage, and in terms of safety such as generating ozone,
There are many environmental problems. Further, since the charging roller is in line contact with the photosensitive drum, charging is unstable. Further, in the brush charging method, since the drum and the brush contact each other to perform charging, the charging deterioration of the brush is likely to occur.

In order to solve such a drawback, in a state where a charging bias is applied to a charging sleeve having a photosensitive drum and a magnet body inserted therein, a group of magnetic particles is attached to the sleeve to form a brush-shaped magnetic brush on the photosensitive body. A so-called particle charging method has been proposed in which a drum is rubbed and a charging bias is applied to a group of magnetic particles via a sleeve to perform charging. (JP-A-5
9-133569, JP-A-63-187267, etc.)

In such a charging method, when a magnetic brush is formed by a fixed magnet body, the magnetic field is attenuated in proportion to the square of the distance from the magnet body, so that the magnetic particles on the surface of the photosensitive drum are magnetized. The holding power is the weakest. Therefore, when the photosensitive drum is rotated in this state, a centrifugal force acts on the surface of the photosensitive drum, and the magnetic particles electrostatically attached to the photosensitive drum by the charges induced by the application of the charging voltage are fixed magnets. A force acts in the direction in which the magnetic particles separate from the charging area against the magnetic coercive force (magnetic field) from the assembly, and the particles attached to the photosensitive drum adversely affect the exposure and development in the next step.

In order to eliminate such a drawback, as shown in FIG. 6, a fixed magnet body 10 is provided which covers an electrode 102 to which a charging bias power source 101 is connected without using the charging sleeve.
3 is arranged so as to face the photosensitive drum 104, faces the fixed magnet body 103, and a magnet body 105 of opposite polarity is arranged on the back side of the photosensitive drum 104, and between the magnet body 105 and the fixed magnet body 103. There is disclosed a technique in which the photosensitive member is charged while the magnetic particle group 107 is held in the charging region by the magnetic field formed in the above.

[0007]

According to such a technique,
Since the magnet body for magnetically retaining the magnetic particle group 107 is not arranged only on one side of the charging gap 108 but on both sides thereof, the magnetic field gradient (ΔH / Δt) between the charging gaps 108 is Although it can be set to a large value, it is still impossible to completely prevent the magnetic particles from being separated from the charged area. Therefore, in the apparatus, the fixed magnet body 10 is used.
Insulating sheet 109 is hung on the side surface of No. 3 toward the photosensitive drum to prevent magnetic particles from scattering.

However, the structure in which the insulating sheet contacts the drum as described above cannot withstand long-term use due to wear or the like. Further, in the above-mentioned configuration, unless the magnetic particles are made of a material having good conductivity, it is not preferable because the particles are fixed due to the sliding friction between the insulating sheet 109 and the particles. Pinholes are likely to occur on the photosensitive drum side.

Further, with the above construction, the magnetic coercive force of the magnetic particles is significantly increased as compared with the prior art in which the magnet body is arranged only on one side, and therefore the magnetic particle groups in the charging area cannot be replaced. However, there is a problem that the same particle group is retained and deteriorated over a long period of time.

In view of the above-mentioned drawbacks of the prior art, the present invention is a charging method capable of ensuring a stable charging ability for a long period of time without causing leakage of the charged particles and deterioration of the charging agent even after long-term use. It is an object of the present invention to provide an invention applied as a device. Another object of the present invention is to provide an invention applied as a charging device capable of ensuring good circulation of magnetic particles. Another object of the present invention is to provide an invention capable of obtaining a charging device having extremely high practicability, which can be sufficiently considered from the viewpoint of manufacturing, the user side, and the environment. To do.

[0011]

The present invention is shown in FIG.
As shown in (B), on the charging area of the photosensitive drum 1,
Non magnetic charging sleeve 2, and the main pole A ₁ and opposite polarities opposite pole on the rear side of the photosensitive drum 1 positioned on the charging area which encloses the main pole A ₁ which is fixedly disposed toward the drum In the charging device having B ₁ , the charging sleeve 2 is rotated in the against direction with respect to the rotation direction of the photosensitive drum 1, and the two magnet bodies at the charging sleeve closest contact point P on the photosensitive drum 1 are arranged. The magnetic force synthesis vector Fm of the above is centered on the closest contact point P and the following 1)
1 ') is configured so as to be located in the angular range θ _F. More preferably _{-90 °> θ F ≧ 15 °} ... 1), -35 ° ≧ θ F ≧ 0 ° ... 1 ') ( a line connecting the photosensitive drum 1 axis O ₁ and the charging sleeve 2 axis O ₂ Of these, the axis O _{2 of the} charging sleeve 2 from the closest contact point P ₂
The side direction is set to 0 °, the upstream side of the photosensitive drum rotation direction is set to a minus angle, and the downstream side is set to a plus angle. )

As a concrete means for supporting such a constitution, the maximum magnetic flux density position Q ₂ of the main pole A _{1 on} the charging sleeve 2 and the maximum magnetic flux density position of the counter pole B _{1 on} the photosensitive drum 1 are shown. as well as adapted from Q ₁ positioned on the downstream side in the rotational direction of the photosensitive drum 1, the main the recent magnetic flux density BA ₁ on the contact point P in the polar a ₁ is the recently on the contact point P in the counter electrode B ₁ It is preferable that the magnetic flux density is higher than the magnetic flux density BB _{1 of} .

In this case, the maximum magnetic flux density position Q ₁ of the opposite pole B ₁ is preferably set in the range of + 5 ° to -30 ° on the upstream side in the rotation direction of the photosensitive drum 1 with respect to the closest contact P of the charging sleeve. Preferably, the maximum magnetic flux density position Q _{2 of the} main pole A ₁ is −20 ° with the closest contact P of the charging sleeve interposed therebetween.
Within the range of + 5 °, a line connecting the charging sleeve 2 axial center O ₂ and the maximum magnetic flux density position Q ₂ of the main pole A ₁ , and the maximum magnetic flux of the photosensitive drum 1 axial center O ₂ and the opposing pole B ₁ Density position Q
_It is good to set the narrow angle of the line connecting ₁ to 0 to 50 °.

In the present invention, the volume resistivity is 10
^In the range of ³ to 10 ⁸ Ω · cm, preferably 10 ⁴ to 10 ⁸ Ω
-It is preferable to use conductive magnetic particles set to cm. In this case, this volume resistivity has an inner diameter of 2 with an electrode at the bottom.
In a 0 mm Teflon cylinder, put 1.5 g of the particles,
It is a value measured by inserting an electrode having an outer diameter of 20 mmφ from the upper part and then applying a load of 1 kg to the upper surface of the electrode.

[0015]

With the above-described structure of the present invention, the outflow phenomenon of the group of magnetic particles 4 as shown in FIG. 1 depends on the magnitude and direction of the magnetic force that the magnetic particles 4 receive at the closest contact point P. That is, the magnetic particles 4 most recently guided to the charging gap 5 of the contact point P while being rubbed against the photosensitive drum 1 on the charging area.
Since the gap 5 becomes a bottleneck and the outflow of the gap 5 is prevented, the magnetic flux density at the closest contact point P on the photoconductor drum is set to "BA ₁ > BB ₁ ".
From the side to the charging sleeve 2 side. At this time, if the magnetic particles 4 are attracted toward the exit of the charging gap 5 with a large deflection angle, the magnetic particles 4 fly out of the bottleneck to the outside of the charging area, and flow out or scatter.

Therefore, as shown in FIG. 1B, the closest contact P
Vector Fm of the magnetic forces of the two magnets at
Are attracted toward the entrance side of the charging gap 5 (from the left lateral side to the upper left direction in the figure), the particle group moves in the direction returning to the upstream side of the charging area from the bottleneck, whereby the particles flow out or scatter from the charging area. Can be prevented smoothly. In this case, it has been confirmed that even if the combined vector Fm is slightly on the exit side, it does not pose a big problem. Therefore, in the present invention, the vector is set within the range of the expression 1).

Since the charging sleeve 2 is an arc, the vector is within -45 ° rather than being too close to the tangential direction.
It has been confirmed by experiments that it is more preferable to set the range of the above formula 1 '). Further, according to the present invention, the charging sleeve 2 is attached to the photosensitive drum 1 in the opposite direction,
That is, since the magnetic particles 4 attached to the charging sleeve 2 flow toward the upstream side of the charging area from the position of the charging gap 5 because they are rotated toward the upstream side of the charging area, the magnetic particles 4 circulate in the charging area. It is possible to prevent deterioration of the particles even after long-term use.

The above effect can be achieved only when the particles move toward the charging sleeve 2 at the position of the charging gap 5, and the magnetic flux density on the closest contact point P is "BA ₁
> BB ₁ ”must be set. When the charging sleeve 2 is rotated against again, the main pole A ₁ should be arranged almost on the closest contact point P.

[0019] While particular depending on the half-width condition of most effectively achieving magnet body each to the "BA _1> BB _1", the maximum magnetic flux density positions to Q ₁ the opposing electrode B ₁ represents than the closest point P It is preferable to set in the range of + 5 ° to −30 ° on the upstream side in the rotation direction of the photosensitive drum 1, and further, the maximum magnetic flux density position Q ₂ is set in the range of −20 ° to + 5 ° with the nearest contact point P interposed. Further, the maximum magnetic flux density position Q between the photosensitive drum 1 axis O ₁ and the main pole A _1
The line connecting the _two , the axis O _{1 of the} photosensitive drum ₁ and the opposite pole B ₁
It is preferable to set the narrow angle of the line connecting the maximum magnetic flux density positions Q ₁ of 0 to 50 °.

The above-mentioned effect can be effectively achieved by setting the volume resistivity of the four groups of magnetic particles in the range of 10 ³ to 10 ⁸ Ω · cm. When the protrusion is 10 ³ Ω · cm or less, not only pinholes are formed on the surface of the photoconductor drum 1, but also due to an increase in electrostatic force at the start and stop of charging, on the boundary line of the magnet body on the axial end side of the photoconductor drum 1. Carrier pulling occurs, and smooth particle charging becomes impossible at 10 ⁸ Ω · cm or more.

[0021]

Embodiments of the present invention will now be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positions and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely examples, unless otherwise specified. Not too much. Figure 2
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 in the opposite direction to the photosensitive drum 1 at the charging area position via the charging gap 5 (closest spacing) of about 0.5 mm with respect to the photosensitive drum 1 rotating to the right in the figure. That is, the non-magnetic charging sleeve 2 is disposed so as to be rotatable in the against direction (the left direction in the drawing, and the same rotating direction when viewed from the rotation axis), and the rear side of the sleeve 2 is provided. A magnet assembly 3 is fixedly arranged on the downstream side of the charging area. still,
A bias power source 7 applies 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 will be described, which is the subject matter of the present invention. First the axis O ₁ of the photosensitive drum 1 Y-axis a line connecting the axis O ₂ of the charging sleeve 2, the tangent of the photosensitive drum 1 recently through the contact point P with the X-axis, each being formed by both said shaft The quadrants are clockwise in 1, 2, 3, and 4 quadrants, respectively.

In the magnet assembly 3, on the charging gap 5 or slightly in the first quadrant upstream of the charging gap 5 in the rotational direction of the charging sleeve 2, the opposing magnetic pole B on the rear side of the photosensitive drum 1 will be described later. Main pole A of the N pole that magnetically seals with ₁ to prevent leakage of magnetic particles 4.
₁ , the _{first of} the main pole A ₁ on the upstream side in the rotation direction of the charging sleeve 2
In the quadrant, an S pole magnet body (hereinafter referred to as shield auxiliary pole A ₂ ) for assisting the magnetic seal, and about 50 gauss in the fourth quadrant downstream of the main pole A _{1 in} the rotation direction of the charging sleeve 2 are provided. A non-magnetized zone A4, which is a non-magnetized region having only a small magnetic force, is formed on the sleeve 2 and is conveyed by an S-pole magnet body A ₃ which is conveyed while being carried on the surface of the sleeve 2 by the against rotation of the sleeve 2. Then, when the magnetic particles 4 come to the non-magnetic body region A4, they are dropped to the photosensitive drum 1 side on the upstream side of the charging region.

A group of conductive magnetic particles 4 is interposed on the charging area sandwiched between the charging sleeve 2 and the photosensitive drum 1. The magnetic particles 4 are conductive and have a volume resistivity of 10 ³
A range of 10 ⁸ Ω · cm is preferable. Preferably 10 ⁴ to 10
It is set at ⁸ Ω · cm. The average particle size is 10
˜30 μm, and more preferably 10 μm
It is arbitrarily set within the range of 25 μm.

On the other hand, on the rear surface side of the photosensitive drum 1, an S-pole magnet body (hereinafter referred to as opposing pole B) is provided at a downstream portion of the charging area slightly upstream of the facing position of the main pole A _{1 in} the rotation direction of the photosensitive drum 1.
₁ ) and a magnetic field horizontal to the surface of the photosensitive drum 1 adjacent to the opposite pole B ₁ and upstream of the charging area (hereinafter referred to as “horizontal magnetic field”).
N pole magnet body (hereinafter, adjacent pole B)
₂ ) are arranged adjacent to each other, and a magnetic field perpendicular to the surface of the photoconductor drum between the main pole A ₁ and the counter pole B ₁ (hereinafter referred to as “vertical magnetic field”), and the counter pole B ₁ and the adjacent pole. A horizontal magnetic field is formed on the photosensitive drum 1 with B ₂ .

That is, specifically, the main pole A ₁ and the counter pole B ₁ which are arranged to face each other are arranged on the downstream side of the charging area in the rotation direction of the photosensitive drum ₁ , and are formed between the two magnet bodies A ₁ and B _1. The magnetic particle group 4 is magnetically held by the perpendicular magnetic field and the adjacent pole B ₂ is arranged adjacent to the opposite pole B ₁ on the upstream side of the charging area to mainly form between the two magnet bodies B ₂ and B _1. The magnetic particles 4 are brought into close contact with the photosensitive drum 1 by a horizontal magnetic field on the photosensitive drum 1.

The operation of this embodiment will be briefly described below. The magnetic particle group 4 located in the charged area is the opposite pole B.
₁ and is attached in close contact with the photosensitive drum 1 on a horizontal magnetic field 4A between adjacent poles B _2, when the photosensitive drum 1 in this state is rotated clockwise, on the horizontal magnetic field 4A to the photosensitive drum 1 As the charging is performed and the charging gap 5 is approached, the charging potential is rapidly increased to move to the charging gap 5 side. At the position of the charging gap 5, the composite vector of the magnetic force formed between the main pole A ₁ and the counter pole B ₁ is set on the charging sleeve 2 side within the range of the above formula 1), so that the charging sleeve 2 side Move to and adsorb.

The magnetic particles 4B adsorbed on the charging sleeve 2 side are returned to the upstream side of the charging area as the sleeve 2 rotates, and then the non-magnetization zone by the non-magnetization zone A4 on the downstream side of the magnet body A ₃ is charged. Since the magnetic particles 4C are laid out so as to be located on the upstream side of the area, the magnetic particle group 4C conveyed to the upstream side of the charging area is magnetically released and dropped to the side of the photoconductor drum 1 to circulate the magnetic particles 4. Done.

Next, the leakage of the magnetic particles 4 from the charging gap 5 using such a device is confirmed by an experiment. First, the experimental conditions will be described with reference to FIGS. The photoconductor drum 1 is an OPC drum, and its diameter is set to 30 mmφ and its linear velocity is set to 25 m / sec. The charging sleeve 2 is made of an aluminum tube and has a diameter of 12 mmφ and a linear velocity of 8 mm.
Set to m / sec. Magnetic particles 4 have an average particle size of 1
Ferrite core particles having a size of 8.0 μm and a volume resistivity of 5 × 10 ⁶ Ω · cm are used, and the maximum magnetization in a magnetic field of 1 kOe is set to 60 emu / g. Then, 400V is applied to the charging bias power source 7 to set the surface potential of the photoconductor to 350V.

The magnetic flux density of each magnetic pole is the opposite pole B.
₁ and the maximum magnetic flux density, respectively S630G on the photoconductive drum 1 of each of the adjacent poles B _2, N730G, further main poles A ₁ and the maximum magnetic flux density, respectively N900G of on the shield electrode A ₂ of each of the charging sleeve 2 (1100 only for sample No. 10
G), S770G (940 for sample No. 10 only)
Set each in G). Then, as shown in FIG.
When the arrangement angles of the magnetic poles of the main pole A ₁ , the counter pole B _1, and the shield pole A ₂ are set to θ ₁ , θ ₂ , and θ ₄ , the magnetic forces of the two magnet bodies at the closest contact P are combined. Vector F
The angle θ of m and the photosensitive drum 1 on the closest contact point P
The magnetic force Fm of the surface was measured.

Under the respective conditions described above, the photosensitive drum 1
When the leakage state of the magnetic particles 4 was investigated by rotating the charging drum and the charging drum at the linear velocity, the experiment No. in the range of θ _F of −35 ° to 0 °.
3 to 7 have no leakage at all, and θ _F is +1
In Experiment Nos. 2 and 5 up to 5 °, particles were slightly ejected from the charging gap 5, but there was no leakage to the downstream side of the drum.
There was a leak about. This confirmed the effect of the present invention.

Next, the magnetic pole arrangement angle θ between the main pole A ₁ and the counter pole B _1
1, in order to examine the theta _2, it was measured similar by changing the deflection angle of the maximum magnetic flux density position of the main poles A ₁ and the counter electrode B _1, the opposed poles B ₁ as shown in FIG. 4 Photoconductor
The maximum magnetic flux density position on the ram 1 Q ₁ is may be set to a range of the photosensitive drum 1 rotating direction upstream side of + 5 ° ~-20 ° more recent contacts P. Also, since θ ₁ is -20 ° and θ ₂ can be set in a wide range, it produces a good result, so -30
It is presumed that there will be no problem even with ° depending on the set value of θ ₂ .

The change in the magnetic field strength H on the closest contact point P when the main pole A ₁ is set at the position of 0 ° and the opposite pole B ₁ is swung upstream in the rotation direction of the photosensitive drum 1 is shown in FIG. Shown in. In this case, the curve H ₁ shows the change in the magnetic field strength on the point P of the main pole A ₁ , the curve Hma is the combined curve of the magnetic field strengths Ha and H ₁ of the opposite pole B ₁ , and the curve Hmb is the opposite pole B. shows _one of the composite curve of the magnetic field strength Hb and H _1. As can be understood from this figure, the curves Hm of various magnetic field strengths have a maximum value and can be used at this value, but when the deflection angle of θ ₁ is -30 ° or more, the magnetic velocity density converges and the It is not preferable because it is the same as the case where there is no counter electrode B _{1 in} . Further, as shown in FIG. 4, the maximum magnetic flux density position Q ₂ has an angle θ ₂ of −20 ° to + with the closest contact point P interposed.
5 °, preferably -10 ° to + 5 °, and a line connecting the charging sleeve 2 axial center O ₂ and the maximum magnetic flux density position Q ₂ of the main pole A ₁ and the photosensitive drum 1 axial center. The narrow angle of the line connecting O ₁ and the maximum magnetic flux density position Q ₁ of the opposite pole B ₁ is 0 to 5
It is also understood that it is better to set it to 0 °.

[0034]

As described above, according to the present invention, stable charging ability can be secured 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, it is applied as a charging device capable of ensuring good circulation of magnetic particles. Further, according to the present invention, it is possible to obtain a charging device having extremely high practicality, because it is possible to sufficiently consider the environment from the viewpoint of manufacturing, the user side, and the like. It has various remarkable effects.

[Brief description of drawings]

FIG. 1A is a basic configuration diagram of the present invention. (B) shows the relationship of the combined vector of the main pole and the opposite pole.

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

FIG. 3 is a table showing a relationship between a combined vector of magnetic forces of both magnet bodies and particle leakage by changing positions of a main pole and an opposite pole in the embodiment of FIG.

FIG. 4 is a table showing a relationship between a magnetic pole arrangement angle of a main pole and a counter pole and particle leakage.

FIG. 5 is a graph showing the magnetic velocity density when the main pole is 0 ° and the counter pole is swung upstream in the rotation direction of the photosensitive drum.

FIG. 6 is a table showing a charging device according to a conventional technique.

[Explanation of symbols]

1 Photoreceptor Drum 2 Charging Sleeve 3 The Magnet Assembly 4 Magnetic Particles 5 Charging Gap P Closest Contact A ₁ Main Pole B ₁ Opposing Magnetic Pole

Claims (7)

[Claims] 1. A first magnet body (hereinafter referred to as a main pole) fixedly arranged on a charging area of a photosensitive drum toward the drum.
A non-magnetic charging sleeve containing a magnet, and a second magnet body having a polarity opposite to that of the main pole (hereinafter referred to as a counter pole) on the back side of the photosensitive drum located on the charging area. In a charging device configured to charge a photosensitive drum via a group of magnetic particles carried by a body, a magnetic force synthesis vector Fm of the two magnet bodies at a charging sleeve closest contact point P on the photosensitive drum is: Charging device characterized by being configured so as to be located within the angle θ _F range of the following formula 1) with the closest point P as the center −90 °> θ _F ≧ + 15 ° ... 1) (photosensitive drum shaft center O ₁ of the line connecting the charging sleeve axis O _2, recently direction from the contact point P charging sleeve axis O ₂ side and 0 °, set the rotational direction of the photoreceptor drum upstream minus angle, the downstream side to the positive angle. ) 2. A charging sleeve closest contact point P on a photosensitive drum.
Magnetic force synthesis vector Fm of the two magnets in
The charging device according to claim 1, wherein the charging device is located within an angle range of the following formula 1 ') about the nearest contact point P as a center. -35 ° ≥ θ _F ≥ 0 ° ... 1'). 3. The charging device according to claim 1, wherein the charging sleeve is configured to rotate in an against direction with respect to a rotating direction of the photosensitive drum. 4. The volume resistivity of the magnetic particle group is from 10 ³ to
The charging device according to claim 1, wherein the charging device is set in a range of 10 ⁸ Ω · cm. 5. A non-magnetic charging sleeve that encloses the main pole is provided on the charging area of the photosensitive drum, and the opposite pole is provided on the back side of the photosensitive drum located on the charging area. In a charging device configured to charge a photoconductor through a group of magnetic particles carried by both magnet bodies, a maximum magnetic flux density position Q on the charging sleeve of the main pole
₂ is located downstream of the maximum magnetic flux density position Q ₁ on the photoconductor drum of the opposite pole in the photoconductor drum rotation direction, and the magnetic flux density on the closest contact P of the main pole is 2. The charging device according to claim 1, wherein the charging device is configured so as to have a magnetic flux density higher than that of the closest contact P at the opposite pole. 6. The angle theta ₁ of the maximum magnetic flux density position photoconductor from the nearest points P Q ₁ drum rotation direction upstream side + 5 ° ~ -
6. The charging device according to claim 5, wherein the charging device has a shaft center O ₁ and a charging sleeve shaft O _2.
Of the line connecting the charging sleeve axis O ₂ from the closest contact point P
The side direction is set to 0 °, the upstream side of the photosensitive drum rotation direction is set to a minus angle, and the downstream side is set to a plus angle. ) 7. The maximum magnetic flux density position Q ₂ is in the range of −20 ° to + 5 ° across the nearest contact point P, and the charging sleeve axial center O ₂ and the maximum magnetic flux density position Q ₂ of the main pole are set. lines and the photoconductor drum axis O ₁ and charging device opposite poles of the maximum magnetic flux density position Q ₁ line narrow angle claim 5 set at 0 to 50 ° of connecting (photosensitive drum axis O connecting Of the line connecting ₁ and the charging sleeve axis O ₂ , the direction from the closest point P to the charging sleeve axis O ₂ side is set to 0 °, the upstream side in the rotation direction of the photosensitive drum is set to a negative angle, and the downstream side is set to a plus angle. Yes.)