JP2008102182A - Electrifying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrifying device capable of reducingthe chipping off unevenness and electrifying unevenness on the surface of a body to be electrified caused by magnetic particles when a magnetic particle carrier is rotated eccentrically to a rotation center, and to provide an image forming apparatus. <P>SOLUTION: In the electrifying device, voltage is applied to a first magnetic particle carrier 31 and a second magnetic particle carrier 32, and the surface of the body 1 to be electrified is electrified by bringing magnetic particles 35 into contact with the surface of the body 1 by the rotations of the first and second magnetic particle carriers. The electrifying device has a magnetic particle regulating member 37 that regulates a quantity of magnetic particles held on the peripheral surface of the first magnetic particle carrier. In a transfer place, the magnetic particles are transferred from the peripheral surface of the first magnetic particle carrier to the peripheral surface of the second magnetic particle carrier. When the peripheral surface of the first magnetic particle carrier is in the transfer place such that a distance from the rotation center of the first magnetic particle carrier to the peripheral face has the smallest value, the peripheral surface of the second magnetic particle carrier is in the transfer place such that a distance from the rotation center of the second magnetic particle carrier to the peripheral surface has the smallest value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging device mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, and an image forming apparatus having the charging device.

  As a charging device mounted on an image forming apparatus such as an electrophotographic copying machine or a printer, a charging roller or a magnetic brush is brought into contact with the outer peripheral surface (surface) of a photosensitive drum as an image carrier to charge the surface of the photosensitive drum. A contact charging type apparatus is known. The contact charging method is preferably a magnetic brush contact charging method from the viewpoint of charging stability. This magnetic brush type charging device constitutes a magnetic brush by carrying conductive magnetic particles on a sleeve-like magnetic particle carrier (hereinafter referred to as a charging sleeve). The surface of the photosensitive drum is charged by bringing the magnetic particles into contact with the surface of the photosensitive drum.

Patent Document 1 describes that, in a charging device having two charging sleeves, a regulating member is provided between the two charging sleeves on the side opposite to the photosensitive drum side. According to this charging device, by preventing the magnetic particles from slipping through the two charging sleeves, fluctuations in the coating amount of the magnetic particles carried on the charging sleeve can be suppressed. Therefore, it is possible to reduce shaving unevenness due to the magnetic particles on the surface of the photosensitive drum and to stabilize the contact state between the magnetic particles and the surface of the photosensitive drum and to reduce charging unevenness on the surface of the photosensitive drum.
JP 2004-361561 A

  The present invention is a further development of the above prior art.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a charging device that can reduce unevenness of the surface of a charged body and uneven charging due to magnetic particles when the magnetic particle carrier rotates eccentrically with respect to the center of rotation, and an image forming apparatus having the charging device. It is to provide.

A typical configuration of the charging device according to the present invention is as follows.
(1) magnetic particles;
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the object to be charged by bringing the magnetic particles into contact with the surface of the object to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at an equal angular velocity to each other,
The magnetic particles are transferred from the outer peripheral surface of the first magnetic particle carrier to the outer peripheral surface of the second magnetic particle carrier at the transfer position,
The distance from the rotation center to the outer peripheral surface of the second magnetic particle carrier when the outer peripheral surface position at which the distance from the rotation center to the outer peripheral surface of the first magnetic particle carrier is the minimum is at the delivery position The position of the outer peripheral surface having the minimum value is at the delivery position.

(2) magnetic particles;
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the object to be charged by bringing the magnetic particles into contact with the surface of the object to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at equal angular velocities, and the magnetic particles move from the outer peripheral surface of the first magnetic particle carrier at the delivery position to the second magnetic particle carrier. Passed to the outer peripheral surface of the magnetic particle carrier,
The distance from the rotation center to the outer peripheral surface of the second magnetic particle carrier when the outer peripheral surface position at which the distance from the rotation center to the outer peripheral surface of the first magnetic particle carrier is the maximum is at the delivery position The position of the outer peripheral surface having the maximum value is at the delivery position.

(3) magnetic particles;
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the object to be charged by bringing the magnetic particles into contact with the surface of the object to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at an equal angular velocity to each other,
The magnetic particles are transferred from the outer peripheral surface of the first magnetic particle carrier to the outer peripheral surface of the second magnetic particle carrier at the transfer position,
The distance from the rotation center of the first magnetic particle carrier at the delivery position to the outer peripheral surface is r ₁ , and the distance from the rotation center of the second magnetic particle carrier at the delivery position to the outer circumference is r ₂ , In the first magnetic particle carrier, the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center are r _{1 -max} and r _{1 -min} , respectively, When the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center in the particle carrier are respectively r _2-max and r _2-min ,
While the first magnetic particle carrier and the second magnetic particle carrier rotate once,

It is characterized by satisfying.

(4) magnetic particles;
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the charged body by bringing the magnetic particles into contact with the surface of the charged body by rotating the first magnetic particle supporting body and the second magnetic particle supporting body;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at an equal angular velocity to each other,
The magnetic particles are transferred from the outer peripheral surface of the first magnetic particle carrier to the outer peripheral surface of the second magnetic particle carrier at the transfer position,
The distance from the rotation center of the first magnetic particle carrier at the delivery position to the outer peripheral surface is r ₁ , and the distance from the rotation center of the second magnetic particle carrier at the delivery position to the outer circumference is r ₂ , In the first magnetic particle carrier, the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center are r _{1 -max} and r _{1 -min} , respectively, When the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center in the particle carrier are respectively r _2-max and r _2-min ,
While the first magnetic particle carrier and the second magnetic particle carrier rotate once,

It is characterized by satisfying.

  (5) In the charging device according to any one of the above (1) to (4), the first magnetic particle carrier and the second magnetic particle carrier among the drive members that respectively rotate and drive the first magnetic particle carrier and the second magnetic particle carrier. The drive member for rotationally driving one magnetic particle carrier is a first drive gear provided coaxially with the first magnetic particle carrier, and driving for rotationally driving the second magnetic particle carrier. The member is a second drive gear provided coaxially with the second magnetic particle carrier, and the first drive gear and the second drive gear are driven from the same drive transmission gear, respectively. It is characterized by being transmitted.

(6) an image carrier;
A magnetic particle, a first magnetic particle carrier having a cylindrical shape that supports and rotates the magnetic particles on an outer peripheral surface, and a second magnetic particle carrier having a cylindrical shape having a diameter different from that of the first magnetic particle carrier. A second magnetic particle carrier that carries and rotates the magnetic particles transferred from the first magnetic particle carrier on the outer peripheral surface, and the first magnetic particle carrier and the A voltage is applied to the second magnetic particle carrier, and the magnetic particles are brought into contact with the surface of the member to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier. A charging device for charging the body surface;
In an image forming apparatus for forming an image carried on the surface of the image carrier after charging on a recording material,
The charging device is the charging device according to any one of (1) to (5).

  According to the charging device of the present invention, it is possible to reduce unevenness on the surface of a charged body and uneven charging due to magnetic particles when the magnetic particle carrier rotates eccentrically with respect to the rotation center.

  According to the image forming apparatus of the present invention, it is possible to reduce shaving unevenness and charging unevenness on the surface of the image carrier due to the magnetic particles when the magnetic particle carrier rotates eccentrically with respect to the rotation center.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 13 is a structural model diagram of an example of an image forming apparatus in which the charging device according to the present invention can be mounted. The image forming apparatus is an electrophotographic copying machine.

  In the following description, regarding the image forming apparatus and its constituent members, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material. Further, the longitudinal direction is also the axial direction of the image carrier that is a member to be charged. The short direction is a direction parallel to the recording material conveyance direction on the surface of the recording material.

  The image forming apparatus shown in the present embodiment has a drum-type electrophotographic photosensitive member 1 as an image carrier that is a member to be charged in an image forming apparatus main body A that constitutes a housing of the image forming apparatus. As the photosensitive member 1, a positively charged amorphous silicon (a-Si) type photosensitive member was used. As the positively charged a-Si photosensitive member 1, a negative charge blocking layer, a photoconductive layer, and a surface protective layer are provided on the outer peripheral surface of a cylindrical drum cylinder (conductive support) made of aluminum having an outer diameter of 84 mm. A photosensitive drum constructed by sequentially laminating is used.

  In the image forming apparatus of this embodiment, when a copy start signal (printing signal) is input, the photosensitive drum 1 rotates in the direction of the arrow, and the outer peripheral surface (front surface) of the photosensitive drum 1 is set to a predetermined potential and polarity by the charging device 2. Are uniformly charged.

  On the other hand, the document G placed on the document table 13 is scanned in the direction of the arrow while irradiating the document G with the document irradiation lamp, the short focus lens array, and the CCD sensor as an integrated unit 14. Then, the original surface reflected light of the illumination scanning light irradiated on the original G from the original irradiation lamp is imaged by the lens array and is incident on the CCD sensor. The CCD sensor has a light receiving unit, a transfer unit, an output unit, and the like. The incident reflected light (optical signal) is converted into a charge signal by the CCD light receiving unit, and sequentially transferred to the output unit in synchronization with the clock pulse by the transfer unit, and then the charge signal is converted into a voltage signal at the signal output unit, Amplified and low impedance is output to the outside as an analog signal. The analog signal thus obtained is subjected to predetermined image processing to be converted into a digital signal (image signal) and transferred to a printer unit (image forming unit). The printer unit forms an electrostatic latent image corresponding to the original image on the surface of the photosensitive drum 1 by the LED exposure unit 3 that receives the image signal from the signal output unit and emits light ON and OFF.

  The electrostatic latent image formed on the surface of the photosensitive drum 1 is developed by a developing device (developing unit) 4 using toner (developer). As a result, a toner image (development image) is obtained on the surface of the photosensitive drum 1. The toner image formed on the surface of the photosensitive drum 1 in this way is transferred onto a transfer material P (recording material) as a recording material conveyed from the feeding cassette 5 to the conveying belt 7 a by the pickup roller pair 7 via the feeding roller 6. Electrostatic transfer is performed by a transfer means 8. The transfer material P is electrostatically separated from the surface of the photosensitive drum 1 and conveyed to the fixing device 9. The fixing device 9 applies heat and pressure to the transfer material P by sandwiching and transferring the transfer material P at the fixing nip portion between the fixing roller 9a and the pressure roller 9b heated by the heat source, thereby transferring the transfer material P. A toner image is heated and fixed on P. The transfer material P on which the toner image is heated and fixed is discharged to a discharge tray 10 outside the apparatus main body A.

  The surface of the photosensitive drum 1 after the transfer of the toner image comes into contact with a cleaning member 11a provided on the cleaning unit 11, and contaminants such as transfer residual toner on the surface of the photosensitive drum 1 are removed by the cleaning member 11a. Then, the surface of the photosensitive drum 1 is exposed from the pre-exposure means 12, and the optical memory for image exposure is removed. As a result, the surface of the photosensitive drum 1 is repeatedly used for image formation.

(2) Charging Device The charging device 2 shown in the present embodiment magnetically carries conductive magnetic particles on the outer peripheral surface (surface) of a charging sleeve having a magnet inside, and the magnetic particles are placed on the surface of the photosensitive drum 1. It is a magnetic brush charging device that charges the surface of the photosensitive drum 1 by bringing it into contact.

  FIG. 1 is a longitudinal sectional view showing the relationship between the charging device 2 and the photosensitive drum 1. FIG. 2 is a plan view showing the relationship between the first charging sleeve 31, the second charging sleeve 32, and the regulating blade 37 of the charging device 2. FIG. 3 is a cross-sectional view omitting the center showing the holding structure of the first charging sleeve 31 and the second charging sleeve 32.

  The charging device 2 of the present embodiment includes a charging container 36 as a charging frame body, two fixed magnets 33 and 34 as a magnetic field generating means, and a first charging sleeve 31 as a first magnetic particle carrier. And a second charging sleeve 32 as a second magnetic particle carrier. In addition, the charging device 2 includes conductive magnetic particles 35 and a magnetic brush layer thickness regulating member (regulating blade) 37 as a magnetic particle regulating member. These members are all elongated members extending in the same direction as the longitudinal direction of the photosensitive drum 1.

  A first charging sleeve (hereinafter referred to as a first sleeve) 31 and a second charging sleeve (hereinafter referred to as a second sleeve) 32 are each formed in a cylindrical shape from a conductive material. The first sleeve 31 and the second sleeve 32 have sleeve flanges 41 and 42 at both ends in the longitudinal direction. It is held rotatably.

  The magnet 33 is provided around the cored bar 45 inside the first sleeve 31. Both ends of the cored bar 45 are rotatably held by the flange 41 of the first sleeve 31 via bearings 47. The magnet 34 is provided around the cored bar 46 inside the second sleeve 32. Both end portions of the core metal 46 are rotatably held by the flange 42 of the second sleeve 32 via bearings 48. And the front-end | tip of the metal cores 45 and 46 is being fixed to the holding members 60c and 60d provided in the side plates 60a and 60b.

  The magnets 33 and 34 are devised as magnetic poles at positions facing each other. In general, the magnetic particles 35 tend to be separated from the surface of the first sleeve 31 and the surface of the second sleeve 32 in the vicinity of the repulsive poles where the same poles are aligned. Utilizing this, the magnetic poles at the opposing positions of the magnets 33 and 34 are arranged with the repulsive poles in the vertical direction, and the reversing poles of opposite polarity are opposed, such as the S pole on the magnet 33 side and the N pole on the magnet 34 side. I am letting.

  The magnetic particles 35 accommodated in the charging container 36 are magnetically generated by the magnetic field (magnetic force) generated by the magnets 33 and 34, and the outer peripheral surface (surface) of the first sleeve 31 and the outer peripheral surface (second surface) ( Supported on the surface). The magnetic particles 35 are transferred from the first sleeve 31 to the second sleeve 32 without passing between the first sleeve 31 and the second sleeve 32 by the rotation of the first sleeve 31 and the second sleeve 32 on the photosensitive drum 1 side. And transferred. Further, on the opposite side to the photosensitive drum 1 side, the first sleeve 31 and the second sleeve 32 rotate to be transferred from the second sleeve 32 to the first sleeve 31 without passing between the first sleeve 31 and the second sleeve 32. The That is, with the rotation of the first sleeve 31 and the second sleeve 32, the magnetic particles 35 pass from the surface of the first sleeve 31 on the photosensitive drum 1 side through the delivery position 35 c between the first sleeve 31 and the second sleeve 32. 32 to the surface. The magnetic particles 35 are transferred from the surface of the second sleeve 32 to the surface of the first sleeve 31 through the transfer position 35e between the second sleeve 32 and the first sleeve 31 on the side opposite to the photosensitive drum 1 side.

  Therefore, the delivery position 35c on the photosensitive drum 1 side is a magnetic particle carrying position for carrying the magnetic particles 35 on the surface of the first sleeve 31 until just before the transfer, and the magnetic particles 35 just after the transfer on the surface of the second sleeve 32 are taken. It is also a magnetic particle carrying position to carry. The delivery position 35e opposite to the photosensitive drum 1 is a magnetic particle carrying position for carrying the magnetic particles 35 on the surface of the second sleeve 32 until just before the transfer, and the magnetic particles just after the transfer on the surface of the first sleeve 31. It is also a magnetic particle carrying position for carrying 35.

The magnetic particles 35 preferably have an average particle diameter of 10 to 100 μm, a saturation magnetization of 20 to 250 emu / cm ³ , and a resistance of 10 ² to 10 ¹⁰ Ω · cm. In order to improve the charging ability, it is better to use the one having the lowest resistance, but considering that the photosensitive drum 1 has an insulation defect such as a pinhole, use one having a resistance of 10 ⁶ Ω · cm or more. Is preferred. In this example, the ferrite surface is oxidized and reduced to adjust the resistance, and further subjected to a coupling treatment. The average particle size is 25 μm, the saturation magnetization is 200 emu / cm ³ , and the resistance is 5 × 10 ⁶ Ω · cm. This was used as the magnetic particle 135. The resistance value is weighted with 0.65Pa (6.6kg / cm ²⁾ after the bottom area put 2g of magnetic particles for charging to metal cell 228Cm ^2, is a value measured by applying a voltage of 100V .

  The regulating blade 37 has a gap (sleeve-blade gap, hereinafter referred to as SB gap) G1 between the surface of the first sleeve 31 provided on the downstream side in the rotation direction of the photosensitive drum 1 in the first sleeve 31 and the second sleeve 32. Are facing each other. In this embodiment, the SB gap is set to 350 μm. Both ends of the regulation blade 37 are held on the side plates 60a and 60b of the charging container 36 via support members (not shown). The regulating blade 37 regulates the magnetic particles 35 carried on the surface of the first sleeve 31 in the charging container 36 and transferred by the rotation of the first sleeve 31 to a certain thickness according to the SB gap. In other words, the regulating blade 37 regulates the amount of the magnetic particles 35 taken out from the opening on the first sleeve 31 side of the charging container 36 to the surface of the photosensitive drum 1 by the first sleeve 31 and an appropriate amount on the surface of the first sleeve 31. A coating layer of the magnetic particles 35 is formed.

  The surface of the first sleeve 31 faces the surface of the photosensitive drum 1 via a gap (sleeve-drum gap, hereinafter referred to as SD gap) G2. The surface of the second sleeve 32 is opposed to the surface of the photosensitive drum 1 via a gap (SD gap) G3. The magnetic poles of the magnets 33 and 34 are arranged so that the magnetic particles 35 rise in the vicinity of the SD gaps G2 and G3 or the SD gaps G2 and G3. This stabilizes the contact of the magnetic particles 35 with the surface of the photosensitive drum 1.

(3) Configuration of Rotation Drive Mechanism for First Sleeve and Second Sleeve FIG. 4 is an explanatory view showing the drive mechanism for the first sleeve 31 and the second sleeve 32.

  Reference numeral 51 denotes a first charging sleeve driving gear (hereinafter referred to as a first driving gear) as a driving member. Reference numeral 52 denotes a second charging sleeve driving gear (hereinafter referred to as a second driving gear) as a driving member. The first drive gear 51 is fixed to the flange 41 of the first sleeve 31, and the second drive gear 52 is fixed to the flange 42 of the second sleeve 32 (FIG. 2). The first drive gear 51 and the second drive gear 52 have the same number of teeth. Reference numeral 53 denotes a drive transmission gear (hereinafter referred to as a transmission gear) as a drive transmission member, which meshes with the first drive gear 51 and the second drive gear 52.

(4) Charging Processing Operation In the charging device 2, the transmission gear 53 is rotationally driven by a charging motor 90 as a driving source. Then, the first drive gear 51 receives the rotational force from the transmission gear 53 and rotates the first sleeve 31 in the same direction as the rotation direction of the photosensitive drum 1. The second drive gear 52 receives the rotational force from the transmission gear 53 and rotates the second sleeve 32 in the same direction as the rotation direction of the photosensitive drum 1. The first sleeve 31 and the second sleeve 32 rotate while carrying the magnetic particles 35 on the surfaces of the first sleeve 31 and the second sleeve 32, respectively. The magnetic particles 35 in the magnetic particle carrying region (FIG. 2) of the first sleeve 31 regulated by the regulating blade 37 are formed in a brush shape by the magnetic field generated by the magnet 33, and with the rotation of the first sleeve 31. It is conveyed to the surface of the photosensitive drum 1. The magnetic particles 35 in the magnetic particle carrying region (FIG. 2) of the second sleeve 32 are also formed in a brush shape by the magnetic field generated by the magnet 34 and are conveyed to the surface of the photosensitive drum 1 as the second sleeve 32 rotates. The

  A charging bias is applied to the first sleeve 31 and the second sleeve 32 from the corresponding charging bias power sources V1 and V2 (FIG. 1). Then, electric charges flow into the magnetic particles 35 carried in the magnetic particle carrying regions on the surfaces of the first sleeve 31 and the second sleeve 32 through the first sleeve 31 and the second sleeve 32. The magnetic particles 35 carried on the magnetic particle carrying region are charged by the flowing electric charge. The charged magnetic particles 35 come into contact with the image guarantee area (FIG. 2) on the surface of the photosensitive drum 1 to charge the image guarantee area. Here, the image guarantee area is an area where a toner image is formed in the longitudinal direction of the photosensitive drum 1, that is, an area where a latent image is formed. The image guarantee area is provided in an area inside the magnetic particle carrying area in the longitudinal direction of the photosensitive drum 1.

  Nip widths N1 and N2 (FIG. 1) formed so as to sandwich the magnetic particles 35 between the surface of the photosensitive drum 1 and the surface of the first sleeve 31 and between the surface of the photosensitive drum 1 and the surface of the second sleeve 32 are widened. By doing so, the charging performance can be improved. In order to increase the nip widths N1 and N2, it is effective to increase the diameters of the first sleeve 31 and the second sleeve 32. However, when the nip widths N1 and N2 are widened, the pressure applied to the surface of the photosensitive drum 1 is increased, and the amount of abrasion of the surface layer of the photosensitive drum 1 is increased. Further, when the diameters of the first sleeve 31 and the second sleeve 32 are increased, the charging device main body is also increased.

  For this reason, in order to keep the charging device small, maintain the charging performance, and prevent an increase in the amount of abrasion on the surface of the photosensitive drum, it is necessary to increase the diameter only for charging sleeves that require more stable charging performance. Realistic.

  In the present embodiment, the diameter of the first sleeve 31 arranged on the downstream side in the rotation direction of the photosensitive drum 1 considered to be important for equalizing the potential of the surface of the photosensitive drum 1 is φ22, and the diameter of the second sleeve 32 is Was set to φ16.

(5) Configuration for reducing unevenness on the surface of the photosensitive drum due to magnetic particles and unevenness of charging Next, the surface of the photosensitive drum 1 is scraped off by the magnetic particles 35 when the first sleeve 31 and the second sleeve 32 rotate eccentrically. A configuration for reducing unevenness and uneven charging will be described.

  In the following description, the SD gap G2 between the first sleeve 31 and the surface of the photosensitive drum 1 is referred to as a first SD gap G2. The SD gap G3 between the second sleeve 32 and the surface of the photosensitive drum 1 is referred to as a second SD gap G3.

  The first sleeve 31 and the second sleeve 32 of the charging device 2 have mechanical tolerances that can be produced when they are driven to rotate, and the transmission gear 53 of the first sleeve gear 51 and the second sleeve gear 52. Eccentric shake may occur due to meshing or the like.

  FIG. 5 is an explanatory view showing a method of measuring the eccentric runout of the first sleeve 31 and the second sleeve 32. The charging device 2 is opposed to the photosensitive drum 1, and the first sleeve 31 and the photosensitive drum 1 are installed so as to form a desired gap width. A gap measuring device 70 (manufactured by Capacitec) is fed into the first SD gap G2 formed by the first sleeve 31 and the photosensitive drum 1, the photosensitive drum 1 is stopped, and the first sleeve 31 is rotated. One SD gap G2 is measured. The eccentric deflection width of the first sleeve 31 is calculated from the fluctuation value of the first SD gap G2. Further, the eccentric deflection width of the second sleeve 32 is set so that the charging device 2 faces the photosensitive drum 1 and the second sleeve 32 and the photosensitive drum 1 form a desired gap width. The second SD gap when the gap measuring device 70 is fed into the SD gap G3 formed by the first sleeve 32 and the photosensitive drum 1, the photosensitive drum 1 is stopped, and the second sleeve 32 is rotated. G3 is measured. The eccentric deflection width of the second sleeve 32 is calculated from the fluctuation value of the second SD gap G3.

  FIG. 6 is an explanatory diagram showing a result of calculating the amount of eccentricity of the first sleeve 31 from the average value of the measured values of the first SD gap G2. FIG. 7 is an explanatory diagram showing the result of calculating the eccentric amount of the second sleeve 32 from the average value of the measured values of the second SD gap G3.

  As shown in FIG. 6, the first sleeve 31 has an eccentric runout width of one rotation cycle (absolute value of the difference between the maximum value and the minimum value) of about 36.0 μm. The fluctuation is repeated. As shown in FIG. 7, the second sleeve 32 has an eccentric runout width of one rotation cycle (absolute value of the difference between the maximum value and the minimum value) of about 27.8 μm. The fluctuation is repeated.

  FIG. 8 is an explanatory diagram illustrating an example in which the first sleeve 31 and the second sleeve 32 rotate eccentrically with respect to the rotation center. The eccentric rotation trajectories of the first sleeve 31 and the second sleeve 32 are indicated by a one-dot chain line.

Rotation center _{O 1} maximum and minimum values, respectively _{r 1-max} of the distance from the rotation center _{O 1} when rotated eccentrically to the first sleeve 31 surface to the first sleeve _31, and _{r 1-min} . Rotation center _{O 2} maximum and minimum values, respectively _{r 2-max} of the distance from the rotation center _{O 2} in the case of rotating eccentrically to the first sleeve 32 surface to the second sleeve _32, and _{r 2-min} . Further, the distance from the rotation center O _{1 in} the first sleeve 31 to the transfer position 35 c on the surface of the first sleeve 31 that holds the magnetic particles 35 just before the transfer is defined as r ₁ . Further, the distance from the rotation center O ₂ to the delivery position 35c for carrying the magnetic particles 35 immediately after the transfer in the second sleeve 32 surface and r ₂ in the second sleeve 32. Among these distances, r _{1 -max} , r _{1 -min} , r _{2 -max} , and r _{2 -min} are values that do not change. r ₁ is a value that changes as the first sleeve 31 rotates. r _{2 is} also a value that changes as the second sleeve 32 rotates.

In the present embodiment, the calculation result of the eccentric deflection width of the first sleeve 31 and the second sleeve 32 shown in FIGS. 6 and 7 is used to determine the outer peripheral surface position of the minimum value r _1-min of the first sleeve 31. obtains an outer peripheral surface position of the minimum value _{r 2-min} of the second sleeve 32, the outer peripheral surface position from the outer circumferential surface position of the minimum value _{r 1-min} of the first sleeve 31 minimum _{r 2-min} of the second sleeve 32 The teeth engaged with the transmission gear 53 of the first sleeve gear 51 and the second sleeve gear 52 are adjusted so that the magnetic particles 35 can be transferred.

FIG. 9 is an explanatory diagram illustrating a state in which the magnetic particles 35 are transferred from the outer peripheral surface position of the first sleeve 31 having the minimum value r _{1-min to} the outer peripheral surface position of the second sleeve 32 having the minimum value r _2-min . .

As shown in (a), at time t = t ₀ , the magnetic particles 35 are at the position of the SB gap G1 between the regulating blade 37 and the first sleeve 31, and the outer peripheral surface of the first sleeve 31 having the minimum value r _{1 -min} . It shall be carried in position.

The magnetic particles 35 are conveyed to the position of the first SD gap G2 between the first sleeve 31 and the photosensitive drum 1 at t = t ₁ after Δt ₁ shown in (b) as the first sleeve 31 rotates. .

Further, the magnetic particles 35 are conveyed from the first SD gap G2 position to the delivery position 35c during t ₁ <t <t ₂ shown in (c). Here, the second sleeve 32 rotates at an angular velocity equal to the angular velocity of the first sleeve 31. Therefore, the outer peripheral surface position of the minimum value r _2-min of the second sleeve 32 reaches the delivery position 35c substantially simultaneously with the outer peripheral surface position of the minimum value r _1-min of the first sleeve 31. That is, at the delivery position 35c, the outer peripheral surface position of the first sleeve 31 having the minimum value r _{1-min and} the outer peripheral surface position of the second sleeve 32 having the minimum value r _2-min are opposed to each other. As a result, the magnetic particles 35 are transferred from the outer peripheral surface position of the first sleeve 31 at the minimum value r _{1 -min to} the outer peripheral surface position of the second sleeve 32 at the minimum value r _{2-min at} the delivery position 35 c.

Further the magnetic particles 35 are conveyed to the second S-D gap G3 position between the second sleeve 32 and the photosensitive drum 1 to t = t ₂ after Delta] t ₂ shown in accordance with the rotation of the second sleeve 32 (d) The

  FIG. 10 is an explanatory diagram illustrating the measurement results of the SB gap G1, the first SD gap G2, and the second SD gap G3 in FIGS. 9A to 9D.

At time t = t ₀ , the outer peripheral surface position of the minimum value r _1-min of the first sleeve 31 is at the SB gap G1 position that is closest to the regulating blade 37 (FIG. 9A).

  At time t = t1, the outer peripheral surface position moves to the first SD gap G2 position (FIG. 9B). Since the fluctuation of the SB gap G1 and the fluctuation of the first SD gap G2 at this time are both caused by the eccentricity of the first sleeve 31, the fluctuation of the first SD gap G2 is SB. This substantially coincides with the variation of the gap G1 delayed by Δt1. Therefore, since the first SD gap G2 varies so as to match the variation in the amount of magnetic particles carried on the surface of the first sleeve 31 due to the variation in the S-B gap G1, the first SD The amount of change in pressure applied to the surface of the photosensitive drum 1 in the gap G2 is small.

Similarly, at time t = t ₁ , the magnetic particles 35 held at the outer peripheral surface position of the minimum value r _1-min of the first sleeve 31 at the position of the first SD gap G2 are not changed until Δt ₂ . The two sleeves 32 are transferred to the outer peripheral surface position of the minimum value r _1-min (FIG. 9C). Then, the magnetic particles 35 supported on the outer peripheral surface position of the minimum value r _1-min of the second sleeve 32 move to the second SD gap G3 at time t = t ₂ .

A first sleeve 31 the second sleeve 32 for rotational angular velocity is equal to the variation of the second S-D gap G3 is substantially synchronized with that of the variation of the first S-D gap G2 delayed Delta] t _2. Therefore, since the second SD gap G3 fluctuates so as to match the amount of magnetic particles carried on the surface of the first sleeve 31, the pressure applied to the surface of the photosensitive drum 1 by the second SD gap G3. It is possible to reduce the fluctuations of.

  By calculating the difference between the eccentric deflection width of the surface of the first sleeve 31 at the delivery position 35c and the eccentric deflection width of the surface of the second sleeve 32 at the delivery position 35c, the influence of the eccentric deflection of the sleeves 31 and 32 can be calculated. The size can be indicated. The difference between the eccentric deflection widths of the first sleeve 31 and the second sleeve 32 is calculated from the following mathematical formula (1).

  Further, the eccentric deflection width of the surface of the first sleeve 31 is calculated from the following mathematical formula (2). The eccentric runout width on the surface of the second sleeve 32 is calculated from the following mathematical formula (3).

  FIG. 11 is an explanatory diagram showing a calculation result inside the absolute value symbol of Expression (1).

  As shown in the figure, the difference between the maximum value and the minimum value of the eccentric deflection width in one rotation cycle of the first sleeve 31 and the second sleeve 32 is 20.0 μm. This difference value 20.0 μm is smaller than the eccentric deflection width of the first sleeve 31 and the second sleeve 32 shown in FIGS. 6 and 7.

  In the second SD gap G3, fluctuations in the contact state of the magnetic particles 35 with the surface of the photosensitive drum 1 due to the eccentric shake of the second sleeve 32 can be reduced.

  In the charging device 2 of the present embodiment, the SB gap G1 value varies due to the eccentric rotation of the first sleeve 31. When the SB gap G1 value varies, the amount of magnetic particles carried on the surface of the first sleeve 31 varies. When the SB gap G1 value becomes larger than the set value, the amount of magnetic particles carried on the surface of the first sleeve 31 increases. Conversely, when the SB gap G1 value becomes smaller than the set value, the amount of magnetic particles carried on the surface of the first sleeve 31 decreases.

  When the amount of magnetic particles carried on the surface of the first sleeve 31 is less than the set amount, the contact width between the magnetic particles 35 and the surface of the photosensitive drum 1 becomes narrow. Therefore, the pressure applied between the magnetic particles 35 and the surface of the photosensitive drum 1 is reduced, and the amount of abrasion of the surface layer of the photosensitive drum 1 is reduced. However, since the contact width between the magnetic particles 35 and the surface of the photosensitive drum 1 is narrowed, the charging performance is deteriorated.

  On the other hand, if the amount of the magnetic particles carried on the surface of the first sleeve 31 is larger than the set amount, the contact width between the magnetic particles 35 and the surface of the photosensitive drum 1 becomes wide and charging performance is improved. As a result, the amount of abrasion of the surface layer of the photosensitive drum 1 increases. Therefore, when the amount of magnetic particles carried on the surface of the first sleeve 31 is larger than the set amount, it is important to keep the contact state between the magnetic particles 35 and the surface of the photosensitive drum 1 more uniform.

  However, the SB gap G <b> 1 varies due to the eccentric rotation of the first sleeve 31, and it is difficult to stop the variation in the amount of magnetic particles carried on the first sleeve 31. In such a case, in order to keep the contact state between the magnetic particles 35 and the surface of the photosensitive drum 1 more uniform, the first SD gap is adjusted in accordance with the fluctuation of the amount of magnetic particles carried by the first sleeve 31. What is necessary is just to make it change G2 and 2nd SD gap G3.

  Both the SB gap G <b> 1 and the first SD gap G <b> 2 vary due to the eccentricity of the first sleeve 31. As a result, the first SD gap G2 value varies in accordance with the variation in the amount of magnetic particles carried on the first sleeve 31 caused by the variation in the S-B gap G1. ing. Therefore, the fluctuation range of the pressure generated between the magnetic particle 35 and the surface of the photosensitive drum 1 in the first SD gap G2 is small.

  However, due to the eccentric rotation of the first sleeve 31, the amount of magnetic particles carried on the first sleeve 31 varies with one rotation period of the first sleeve 31. When the fluctuation cycle of the first sleeve 31 differs from the fluctuation cycle of the second SD gap G3 due to the eccentric rotation of the second sleeve 32, the magnetic particles 35 transferred to the second sleeve 32 and the photosensitive drum 1 The fluctuation range of the pressure applied to the surface becomes large.

  In this embodiment, since the first sleeve 31 and the second sleeve 32 rotate at the same angular velocity, the magnetic particles 35 are transferred from the surface of the first sleeve 31 to the surface of the second sleeve 32. This is performed at the same position for each rotation of the sleeve 32. As a result, fluctuations in the contact state between the magnetic particles 35 and the surface of the photosensitive drum 1 are periodically generated in one rotation cycle of the first sleeve 31 and the second sleeve 32. Therefore, the fluctuations in the contact state are made constant. be able to.

  Further, when the first sleeve 31 and the second sleeve 32 are rotated once, the absolute value of the difference between the eccentric deflections of the first sleeve 31 and the second sleeve 32 at the delivery position 35c of the magnetic particles 35 is always the first value. It is smaller than the maximum value of the eccentric deflection width of the sleeve 31 and the second sleeve 32. For this reason, it is possible to greatly reduce fluctuations in the contact state between the magnetic particles 35 affected by the eccentric shake of the first sleeve 31 and the second sleeve 32 and the surface of the photosensitive drum 1, and reduce uneven charging on the surface of the photosensitive drum 1. can do.

  In the present embodiment, while the first sleeve 31 and the second sleeve 32 make one rotation, the absolute value of the difference in eccentric deflection between the first sleeve 31 and the second sleeve 32 is always the first sleeve 31 and the second sleeve 32. You may make it become smaller than any one eccentric deflection width. That is, the same effect can be obtained if the following expressions (4) and (5) are satisfied.

  In addition, while the first sleeve 31 and the second sleeve 32 make one rotation, the absolute value of the difference in eccentric deflection between the first sleeve 31 and the second sleeve 32 is always the eccentricity of both the first sleeve 31 and the second sleeve 32. It may be made smaller than the swing width. That is, the same effect can be obtained if the relationship of the following mathematical formula (6) is satisfied.

Further, while the first sleeve 31 and the second sleeve 32 make one rotation, the maximum value r _2-max of the second sleeve 32 from the outer peripheral surface position of the maximum value r _1-max of the first sleeve 31 at the transfer position 35c. You may make it convey the magnetic particle 35 to an outer peripheral surface position. Even if such a configuration is adopted, the same effect can be obtained. In this case as well, it is only necessary to adjust to shift the meshing positions of the first drive gear 51 and the second drive gear 52 with respect to the transmission gear 53.

  In the present embodiment, the first drive gear 51 and the second drive gear 52 that rotationally drive the first sleeve 31 and the second sleeve 32 respectively receive drive force from the same transmission gear 53. Further, the first drive gear 51 and the second drive gear 52 have the same number of teeth. Therefore, the rotational angular velocities of the first sleeve 31 and the second sleeve 32 can be accurately kept equal with a simple configuration. Further, when adjusting the position of the delivery position 35 c for transferring the magnetic particles 35 between the first sleeve 31 and the second sleeve 32, the teeth of the first drive gear 51 and the second drive gear 52 that mesh with the transmission gear 53 are used. It only needs to be shifted, and there is no need to readjust after the position is adjusted.

  In this embodiment, since the rotational angular velocities of the first sleeve 31 and the second sleeve 32 are equal, the magnetic particles 35 are transferred from the first sleeve 31 to the second sleeve 32. The positional relationship between the circumferential positions is always kept appropriate. As a result, the charging conditions on the surface of the photosensitive drum 1 are stabilized, and potential unevenness on the surface of the photosensitive drum 1 can be reduced over a long period of time.

  Further, in this embodiment, since it is possible to reduce the variation in the contact state between the magnetic particles 35 and the surface of the photosensitive drum 1 in the second SD gap G3, the second SD gap G3 is made larger than the conventional one. Even if it is wide, sufficient charging performance is maintained. As a result, the pressure that is constantly applied to the surface of the photosensitive drum 1 can be reduced, and the amount of abrasion of the surface layer of the photosensitive drum 1 can be reduced.

  In this embodiment, the diameter of the first sleeve 31 is made larger than the diameter of the second sleeve 32. However, even if the diameter of the first sleeve 31 is made smaller than the diameter of the second sleeve 32, the charging condition is stabilized. Actions / effects occur.

  Another example of the charging device according to the present invention will be described.

  In the present embodiment, members / portions common to the charging device 2 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The charging device 2 shown in the present embodiment has the same configuration as the charging device of the first embodiment except that the first sleeve 31 and the second sleeve 32 are individually rotated.

  FIG. 12 is an explanatory diagram showing a driving mechanism for the first sleeve 31 and the second sleeve 32 of the charging device 2 of the present embodiment.

  Reference numeral 54 denotes a first drive transmission gear (hereinafter referred to as a first transmission gear) as a drive transmission member, which meshes with the first drive gear 51. The first transmission gear 54 is rotationally driven by a first charging motor 91 as a drive source. When the first transmission gear 54 is rotationally driven by the charging motor 91, the first drive gear 51 receives a rotational force from the first transmission gear 54, and the first sleeve 31 moves in the same direction as the rotational direction of the photosensitive drum 1. Rotate to Reference numeral 55 denotes a second drive transmission gear (hereinafter referred to as a second transmission gear) as a drive transmission member, which meshes with the second drive gear 52. The second transmission gear 55 is rotationally driven by a second charging motor 92 as a drive source. When the second transmission gear 55 is rotationally driven by the charging motor 92, the second drive gear 52 receives a rotational force from the second transmission gear 55 and causes the second sleeve 32 to rotate in the same direction as the rotational direction of the photosensitive drum 1. Rotate to The rotation speeds of the charging motor 91 and the charging motor 92 are set so that the first sleeve 31 and the second sleeve 32 are rotated at equal angular speeds.

Also in the charging device 2 of the present embodiment, since the first sleeve 31 and the second sleeve 32 rotate at the same angular velocity, the magnetic particles 35 are transferred from the surface of the first sleeve 31 to the surface of the second sleeve 32. 31 and the second sleeve 32 are performed at the same position every rotation.
Therefore, the same effect as the charging device 2 of the first embodiment can be obtained.

FIG. 3 is a longitudinal sectional view showing the relationship between the charging device and the photosensitive drum according to the first embodiment. FIG. 3 is a plan view showing the relationship between the first charging sleeve, the second charging sleeve, and the regulating blade of the charging device according to the first embodiment. Central omitted cross-sectional view showing a holding structure of a first charging sleeve and a second charging sleeve of the charging device according to the first embodiment. Explanatory drawing showing the drive mechanism of the 1st sleeve of the charging device which concerns on Example 1, and a 2nd sleeve. Explanatory drawing showing the method of measuring SD gap in a present Example. Explanatory drawing showing the measured value of the 1st SD gap G2 of the charging device which concerns on Example 1. FIG. Explanatory drawing showing the measured value of the 2nd SD gap G3 of the charging device which concerns on Example 1. FIG. Explanatory drawing showing an example in which the 1st sleeve and 2nd sleeve of the charging device which concern on Example 1 rotate eccentrically with respect to a rotation center. Explanatory drawing showing a mode that a magnetic particle is transferred from the outer peripheral surface position of the minimum value of the 1st sleeve of the charging device which concerns on Example 1 to the outer peripheral surface position of the minimum value of a 2nd sleeve. Explanatory drawing showing the measurement result of SB gap of the charging device which concerns on Example 1, 1st SD gap, and 2nd SD gap. Explanatory drawing showing the calculation result of the difference of the eccentric deflection width of the 1st sleeve of the charging device which concerns on Example 1, and a 2nd sleeve Explanatory drawing showing the drive mechanism of the 1st sleeve of the charging device which concerns on Example 2, and a 2nd sleeve. Configuration model diagram of an example of an image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... photosensitive drum, 2 ... charging device, 31 ... 1st charging sleeve, 32 ... 2nd charging sleeve, 35 ... magnetic particle, 37 ... regulation blade, 51 ...・ First charging sleeve driving gear, 52... Second charging sleeve driving gear, 53.

Claims (7)

Magnetic particles,
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the object to be charged by bringing the magnetic particles into contact with the surface of the object to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at an equal angular velocity to each other,
The magnetic particles are transferred from the outer peripheral surface of the first magnetic particle carrier to the outer peripheral surface of the second magnetic particle carrier at the transfer position,
The distance from the rotation center to the outer peripheral surface of the second magnetic particle carrier when the outer peripheral surface position at which the distance from the rotation center to the outer peripheral surface of the first magnetic particle carrier is the minimum is at the delivery position The charging device is characterized in that the position of the outer peripheral surface having the minimum value is at the delivery position. Magnetic particles,
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the object to be charged by bringing the magnetic particles into contact with the surface of the object to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at equal angular velocities, and the magnetic particles move from the outer peripheral surface of the first magnetic particle carrier at the delivery position to the second magnetic particle carrier. Passed to the outer peripheral surface of the magnetic particle carrier,
The distance from the rotation center to the outer peripheral surface of the second magnetic particle carrier when the outer peripheral surface position at which the distance from the rotation center to the outer peripheral surface of the first magnetic particle carrier is the maximum is at the delivery position The charging device is characterized in that the position of the outer peripheral surface having the maximum value is at the delivery position. Magnetic particles,
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the object to be charged by bringing the magnetic particles into contact with the surface of the object to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at an equal angular velocity to each other,
The magnetic particles are transferred from the outer peripheral surface of the first magnetic particle carrier to the outer peripheral surface of the second magnetic particle carrier at the transfer position,
The distance from the rotation center of the first magnetic particle carrier at the delivery position to the outer peripheral surface is r ₁ , and the distance from the rotation center of the second magnetic particle carrier at the delivery position to the outer circumference is r ₂ , In the first magnetic particle carrier, the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center are r _{1 -max} and r _{1 -min} , respectively, When the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center in the particle carrier are respectively r _2-max and r _2-min ,
While the first magnetic particle carrier and the second magnetic particle carrier rotate once,

A charging device characterized by satisfying Magnetic particles,
A first magnetic particle carrier having a cylindrical shape that carries and rotates the magnetic particles on an outer peripheral surface;
A second magnetic particle carrier having a cylindrical shape with a diameter different from that of the first magnetic particle carrier,
A second magnetic particle carrier that carries and rotates magnetic particles transported from the first magnetic particle carrier on the outer peripheral surface;
Have
While applying a voltage to the first magnetic particle carrier and the second magnetic particle carrier,
A charging device for charging the surface of the charged body by bringing the magnetic particles into contact with the surface of the charged body by rotating the first magnetic particle supporting body and the second magnetic particle supporting body;
A magnetic particle regulating member for regulating the amount of magnetic particles carried on the outer peripheral surface of the first magnetic particle carrier;
Have
The first magnetic particle carrier and the second magnetic particle carrier rotate at an equal angular velocity to each other,
The magnetic particles are transferred from the outer peripheral surface of the first magnetic particle carrier to the outer peripheral surface of the second magnetic particle carrier at the transfer position,
The distance from the rotation center of the first magnetic particle carrier at the delivery position to the outer peripheral surface is r ₁ , and the distance from the rotation center of the second magnetic particle carrier at the delivery position to the outer circumference is r ₂ , In the first magnetic particle carrier, the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center are r _{1 -max} and r _{1 -min} , respectively, When the maximum value and the minimum value of the distance from the rotation center to the outer peripheral surface when rotating eccentrically with respect to the rotation center in the particle carrier are respectively r _2-max and r _2-min ,
While the first magnetic particle carrier and the second magnetic particle carrier rotate once,

A charging device characterized by satisfying   Of the drive members that respectively drive the first magnetic particle carrier and the second magnetic particle carrier, the drive member that drives the first magnetic particle carrier is the first magnetic particle carrier. A first drive gear provided coaxially with the body, and a drive member for rotationally driving the second magnetic particle carrier is a second drive gear provided coaxially with the second magnetic particle carrier. 5. The driving gear according to claim 1, wherein the first driving gear and the second driving gear are each transmitted with a driving force from the same driving transmission gear. 6. Charging device. An image carrier;
A magnetic particle, a first magnetic particle carrier having a cylindrical shape that supports and rotates the magnetic particles on an outer peripheral surface, and a second magnetic particle carrier having a cylindrical shape having a diameter different from that of the first magnetic particle carrier. A second magnetic particle carrier that carries and rotates the magnetic particles transferred from the first magnetic particle carrier on the outer peripheral surface, and the first magnetic particle carrier and the A voltage is applied to the second magnetic particle carrier, and the magnetic particles are brought into contact with the surface of the member to be charged by rotation of the first magnetic particle carrier and the second magnetic particle carrier. A charging device for charging the body surface;
In an image forming apparatus for forming an image carried on the surface of the image carrier after charging on a recording material,
6. The image forming apparatus according to claim 1, wherein the charging device is a charging device according to any one of claims 1 to 5.   The image forming apparatus according to claim 6, wherein the image bearing member is an electrophotographic photosensitive member, and the electrophotographic photosensitive member is an amorphous silicon photosensitive member.