Abstract: Magnetic particles for charging means disposed in contact with an electrophotographic photosensitive member for charging the electrophotographic photosensitive member based on a voltage applied thereto are provided as particles of a ferrite component represented by the following formula (1): (Fe2O3)X(A)Y(B)Z  (1), wherein A denotes at least one metal oxide component selected from the group consisting of Li2O, MnO and MgO, B denotes at least one metal oxide component different from A; X, Y and Z denote numbers representing mol ratios and satisfying the following conditions: 0.2<X<0.95, 0.01<Y<0.5, X+Y≦1, and 0≦Z<0.79. The magnetic particles show an excellent charging performance, particularly in injection charging, without causing a difficulty, such as soiling or pinhole leakage of the photosensitive member.

Abstract: An image forming apparatus including a photoreceptor having an image forming portion; a charging roller having a gap forming member on both ends thereof to form a gap between the photoreceptor and the charging roller and configured to charge the photoreceptor, wherein the gap forming members do not contact the image forming portion, and wherein the relationship t≧2g is satisfied; a light irradiator configured to form a latent image in the image forming portion; an image developer configured to form a toner image on the photoreceptor; and an image transferer configured to transfer the toner image onto a receiving material, wherein g is the gap and t represents a distance between an inside edge of one of the gap forming members and one of the two ends of the image forming portion closer to the inside edge of the gap forming member.

Abstract: An electrophotographic apparatus, includes: an electrophotographic photosensitive member and a charging device. The charging device includes a conductor particle-carrying member having an electroconductive and elastic surface, and conductor particles having a particle size of 10 nm-10 &mgr;m and carried on the carrying member so as to be disposed in contact with the photosensitive member, thereby directly injecting charges to the photosensitive member to charge the photosensitive member.

Abstract: A method for cleaning a charging brush which charges a drum including an electroconductive substrate and an insulating surface layer over the electroconductive substrate, including the steps of grounding the electroconductive substrate of the drum contacting a brush portion of the charging brush with the insulating surface of the drum while the charging brush and the drum are rotated and applying an alternating electric field to the brush portion of the charging brush to vibrate to brush portion to remove fouling adhered to the brush portion.

Abstract: An image forming apparatus includes an image bearing body. The image bearing body is charged by a charging device including a magnetic brush which is brought into contact with the image bearing body and which is formed by a magnetic particle layer. The image bearing body is exposed by a pre-exposing device after an image formed on the image bearing body is transferred to an image receiving member and before the photosensitive body is charged by the charging device. The pre-exposing device exposes the image bearing body with an exposure width smaller than a width with which the charging device charges the image bearing body in a longitudinal direction of the charging device. The exposure width is larger than an image formation width in the longitudinal direction of the charging device.

Abstract: A charging device includes a charging member for electrically charging a member to be charged which is adapted to form a nip with a member to be charged which has a surface layer having a volume resistivity of 1×109-1×1014 &OHgr;cm, said charging member having an elastic member and movable with a peripheral speed difference relative to the member to be charged; and electroconductive particles carried on said charging member to the nip, wherein a peripheral speed Vd (mm/sec) of said member to be charged, a peripheral speed Vc (mm/sec) of said charging member, a width N (mm) of the nip measured in a moving direction of said charging member, and a coverage ratio Rc of said electroconductive particles on said charging member, satisfy: N·Rc·|Vc−Vd|/Vd≧1.

Abstract: An image forming apparatus has a plurality of image forming devices for forming images in different colors. Each image forming device has an image bearing member, a charging device for charging the image bearing member, a developing device for developing an electrostatic latent image formed on the image bearing member by a developer containing toner and a carrier, and a detecting device for detecting information corresponding to the permeability of the developer in the developing device. The apparatus also has a control device for controlling the amount of the developer supplied to each developing device according to an output from the detecting device and a corresponding target value. Each charging device has magnetic particles which are brought into contact with the image bearing member. The permeability of the magnetic particles is different from the permeability of the carrier. The apparatus also has a correcting device for correcting each of the target values.

Abstract: An image forming apparatus includes an image bearing body, a surface of which includes a photosensitive body having a hardness in the range of 100 to 500 (N/mm2), a charging device, which includes magnetic charging particles and is in friction contact with the image bearing body charges the image bearing body. A supporting member holds the magnetic charging particles with a magnetic force. An exposing device forms an electrostatic image by image exposing the image bearing body, which is charged by the charging means. A developing device develops the electrostatic image on the image bearing body. A transfer device transfers a developed image onto a transfer material and is in pressure contact with the image body. A pressure of the transfer material to the image bearing body is not less than 1 g/cm and not more than 100 g/cm in line pressure.

Abstract: A charging apparatus includes a charging member for being supplied with a voltage to charge a member to be charged, the charging member including an elastic member for forming a nip with the member to be charged, and said elastic member having a surface provided with a plurality of projections; wherein a speed A of a surface of said charging member (mm/sec) and a speed B of a surface of the member to be charged (mm/sec) satisfy: when B−A>0, said projections are inclined toward upstream with respect to a movement direction of the surface of the member to be charged in said nip, and when B−A<0, the projections are inclined toward downstream with respect to a movement direction of the surface of the member to be charged in said nip.

Abstract: An image-forming apparatus and an image-forming method using a cleanerless system are disclosed in which a non-contact developing assembly develops an electrostatic latent image with a magnetic one-component developer to form a magnetic-toner image and collects a magnetic toner having remained on the charging object member, a member to be charged is charged by means of a charging assembly having a charging member the surface of which is movable with a velocity differential in the opposite direction with respect to the surface of the charging object member, and conductive particles are present at least at the contact surfaces between the charging member and the charging object member.

Abstract: An image forming apparatus includes an image bearing member; a charge member, contactable to the image bearing member, for electrically charging the image bearing member, the charge member being capable of being supplied with a voltage; developing means for developing an electrostatic image formed on the image bearing member with a developer; wherein the charge member is rotatable so as to provide a first peripheral speed difference between a surface of charge member and a surface of the image bearing member when the image bearing member is charged for image formation; wherein there is provided a cleaning period for transferring the developer from the charge member to the image bearing member with a second peripheral speed difference, which is smaller than the first peripheral speed difference, between the surface charge member of and surface of the image bearing member, when a charging operation for the image formation is not effected to the image bearing member.

Abstract: A charging device, suitable for use in an electrophotographic image forming apparatus, is formed of an object to be charged, and a roller-shaped charging member disposed in contact with the object via electroconductive particles and supplied with a voltage to charge the objects. The charging member has a surface layer comprising an elastic foam and moved with a surface speed difference relative to the object. The charging member has surface cavities having an average diameter of 5 to 150 &mgr;m and occupying an areal percentage of 50 to 90%. An image forming apparatus and a process-cartridge therefor including the charging device are also provided.

Abstract: A reader controller is connected to a printer controller which controls a engine controller provided in a printer. The printer includes a controlling unit for controlling a document reader which reads documents, a receiving unit for receiving a command for the engine controller from the printer controller, and a counting unit for counting a number of documents processed by the reader controller in accordance with a control of the controlling unit, and counting a number of sheets processed by the printer controller in accordance with the command received by the receiving unit. The printer further includes a causing unit for causing a display of the reader to display the number counted by the counting unit.

Abstract: An image formation process which forms a toner image by the nonmagnetic one-component developing system by bringing an electrically conducting brush impressed with a voltage into contact with a photosensitive material to effect the uniform charging, and forming an electrostatic latent image on the photosensitive material by the exposure to the image-bearing light, wherein the toner that is used as a circularity of from 0.92 to 0.98. The nonmagnetic one-component developing system minimizes irregular electric charging that stems from the use of the electrically conducting brush. This action is obtained even in full-color developing system which effects development many times.

Abstract: An image forming apparatus includes an image bearing member; charger for electrically charged said image bearing member; electrostatic image forming means for forming an electrostatic image by selectively discharging a surface of said image bearing member charged by said charger; developing means for developing the electrostatic image on said image bearing member into a toner image with toner; transfer means for transferring the toner image from said image bearing member onto a transfer material; wherein said charger is capable of collecting residual toner remaining on said image bearing member after image transfer operation by said transfer means; electric field forming means for forming an electric field between said charger and said image bearing member to transfer the toner in said charger to said image bearing member; and control means for controlling a length of time for which said electric field forming means forms the electric field.

Abstract: An image forming apparatus is provided, which comprises: an image bearing member, a charging member, provided to be capable of coming into contact with the image bearing member, for charging the image bearing member with a peripheral velocity difference between the charging member and the image bearing member, and a controller for variably controlling the peripheral velocity difference at the time when charging for image formation is applied to the image bearing member by the charging member.

Abstract: Disclosed is an electrifier for electrifying a charge object member. According to the present invention, the electrifier includes: a charge rotary member, for forming a first nip with a charge object member to charge the charge object member, and for holding and carrying charge particles to the first nip; and a nip forming member for forming a second nip with the charge rotary member.

Abstract: An image forming apparatus includes an image bearing member and a charging device for electrically charging the image bearing member. The charging means includes a particle carrying member for receiving a charging bias voltage for carrying electrocondusctive magnetic particles. The particle carrying member is provided with an electrically insulated portion at an end portion within a region in which the magnetic particles are carried. An electrectrostatic image forming device forms an electrostatic image on the image bearing member charged by the charging device. A developing device develops the electrostatic image on the image bearing member. The developing device includes a developer carrying member for carrying a magnetic developer and a magnetic field generating device provided in the developer carrying member wherein the electrically insulating portion is outside a longitudinal end of the magnetic field generating device.

Abstract: A charging apparatus includes magnetic particles for rubbing with a member to be charged to electrically charge the member to be charged; a rotatable magnetic particle carrying member for carrying the magnetic particles by magnetic force; a stirring member, provided above the magnetic particle carrying member, for stirring the magnetic particles, the stirring member moving in the direction opposite from a movement direction of the magnetic particle carrying member at a position where the stirring member is opposed to the magnetic particle carrying member. The apparatus includes a magnetic brush, local anti-contamination feature.

Abstract: An image forming apparatus includes an image bearing member; electrostatic image forming means for forming an electrostatic image on said image bearing member, said electrostatic image forming means including a flexible charge member for electrically charging said image bearing member, said charge member forming a nip between said image bearing member and itself and is supplied with an oscillating voltage, wherein electroconductive particles are provided in the nip; and developing means for developing an electrostatic image formed on said image bearing member with a developer, said developing means being capable of a residual developer on said image bearing member, wherein a frequency f (cycle/sec) of the oscillating voltage and a peripheral speed v (mm/sec) of said image bearing member satisfy ¦f/v¦≧12 (cycle/mm).

Abstract: In a contact type charger including a charge roller which comes into contact with a photosensitive body and a power supply circuit which applies a direct-current fixed voltage to the charge roller, the power supply circuit further includes a resistor and applies the voltage to the charge roller through the resistor. Further, the power supply circuit includes a rectifying circuit and the resistor is disposed closer to the charge roller side than the rectifying circuit. Due to such a constitution, in response to an impedance between the photosensitive body and the charge roller, a current which flows into the charge roller is changed and an output voltage value is changed and hence, a fog on a background which is generated due to the change of the environment or change of the charge potential derived from the change of the film thickness of the photosensitive body can be prevented.

Abstract: An object of the present invention is to provide an image forming apparatus that has an image bearing member a flexible charging member for forming a nip portion between itself and the image bearing member and charging the image bearing member, the charging member being applied with a voltage when the charging member at least charges the image bearing member for an image formation, the charging member being provided with a foamed layer on a surface thereof and the nip portion being provided with electrically conductive particles developing device for developing an electrostatic image formed on the image bearing member with a developer, the developing device executing a developing operation and, at the same time, executing a collecting operation for collecting a residual developer on the image bearing member wherein the voltage is a superposed voltage with a direct current voltage and an alternating current voltage having a peak to peak voltage which is less than the alternating current voltage applied when th

Abstract: An image forming apparatus includes a photoconductive element including a conductive support rotatably supported and a charge injection layer and a surface protection layer sequentially laminated on the conductive support. A charger includes a conductive body for injecting, when a preselected voltage is applied thereto, a charge in the charge injection layer in contact with the surface protection layer. A writing unit exposes the charged surface of the photoconductive element imagewise to thereby locally vary the potential deposited on the photoconductive element and electrostatically form a latent image. A developing unit develops the latent image to thereby produce a corresponding toner image. The toner image is transferred from the photoconductive element to a recording medium.

Abstract: An image forming apparatus includes an image bearing member; a charge member, contactable to the image bearing member, for electrically charging the image bearing member, the charge member being capable of being supplied with a voltage; developing means for developing an electrostatic image formed on the image bearing member with a developer; wherein the charge member is rotatable so as to provide a first peripheral speed difference between a surface of charge member and a surface of the image bearing member when the image bearing member is charged for image formation; wherein there is provided a cleaning period for transferring the developer from the charge member to the image bearing member with a second peripheral speed difference, which is smaller than the first peripheral speed difference, between the surface charge member of and surface of the image bearing member, when a charging operation for the image formation is not effected to the image bearing member.

Abstract: A charging apparatus includes a charging member for being supplied with a voltage to charge a member to be charged, the charging member including an elastic member for forming a nip with the member to be charged, and said elastic member having a surface provided with a plurality of projections; wherein a speed A of a surface of said charging member(mm/sec) and a speed B of a surface of the member to be charged(mm/sec) satisfy: when B−A>0, said projections are inclined toward upstream with respect to a movement direction of the surface of the member to be charged in said nip, and when B−A<0, the projections are inclined toward downstream with respect to a movement direction of the surface of the member to be charged in said nip.

Abstract: The present invention relates to an image forming apparatus which has an image bearing member for bearing a latent image, charging device for charging the image bearing member by bringing ears of electrically conductive particles into contact with the image bearing member, developing device for visualizing the latent image formed on the image bearing member as a toner image by using a developer containing toner and carrier after the image bearing member has been charged by the charging device, a permeability of the carriers being different from a permeability of the electrically conductive particles, density control device for controlling density of the developer within the developing device, the density control device detecting a permeability of the developer, comparing a detected signal value based on the detected result with a reference value, and controlling the density of the developer on the basis of the comparison result, and reference value correcting device for correcting the reference value, the ref

Abstract: An object of the present invention is to provide an image forming apparatus that has an image bearing body, charging device, wherein the charging device includes charging particle being in friction contact with the image bearing body thereby charging the image bearing body, electrostatic image forming device, developing device, and transfer device, wherein a pressure of the transfer material to the image bearing body is not less than 1 g/cm and not more than 100 g/cm in line pressure.

Abstract: A replenishing container has a first chamber for containing a toner to be replenished to a developing device, and a second chamber for containing magnetic particles to be replenished to a charging device.

Abstract: An image forming apparatus includes an image bearing member for bearing a toner image; a transfer device for transferring the toner image onto a transfer material from the image bearing member; a charger for electrically charging the image bearing member, the charger being contactable to residual toner remaining on the image bearing member after transfer of the toner image by the transfer device; a voltage applicator for applying DC and AC voltages to the charger; an image forming device for forming an electrostatic image on the image bearing member charged by the charger; a developing device for developing the electrostatic image by toner; an integrator for integrating degree of usage of the apparatus; and a controller for controlling the AC voltage applied to the charger in accordance with the integrated degree of usage provided by the integrator.

Abstract: The present invention provides an image forming apparatus comprising a shiftable image bearing member, and an electrifying device adapted to electrify the image bearing member and having magnetic particles contacted with the image bearing member and a magnetic particle carrying device for magnetically holding and carrying the magnetic particles, and wherein a peak position of magnetic flux density of the magnetic particle carrying device near the image bearing member is located at a downstream side of a most approaching position between the magnetic particle carrying device and the image bearing member in a shifting direction of the image bearing member.

Abstract: An image forming apparatus comprising an image bearing member and electrostatic image forming means including electrification means which is disposed in contact with the above described image bearing member at an electrification location for injection electrification of the image bearing member, and configured to set a peripheral speed different between the above described electrification means and the above described image bearing member which is smaller when an area of the image bearing member to be an image forming area is at the above described electrification location than that when at least a portion of an area of the image bearing member to be a no-image forming area is at the electrification location.

Abstract: An image forming apparatus includes a movable image bearing member; charging means including a charge member for electrically charging the image bearing member with electroconductive particles between the charge member and the image bearing member; developing means for developing a latent image with toner mixed with electroconductive particles; wherein the latent image is formed on the image bearing member having been charged by the charging means, and a toner image provided by development of the latent image by the developing means is transferred onto a recording material; wherein the electroconductive particles mixed in the toner is carried by the image bearing member and is fed to between the charge member and the image bearing member; and a width A, measured in a direction perpendicular to a moving direction of the image bearing member, in which the electroconductive particle are present between the charge member and the image bearing member, a width B in which the developing means is capable of effecting

Abstract: A charging apparatus includes a first charging member of being supplied with a voltage to charge a member to be charged. A first charging member has magnetic particles in the form of a magnetic brush contactable to the member to be charged. A second charging member charges a region of the member to be charged corresponding to an end portion, in a longitudinal direction of the charging member, of the magnetic particles, wherein by the second charging member, the region has a potential of the same charge polarity of the voltage when the region reaches a charging position of this first charging member.

Abstract: A charging apparatus includes a member to be charged having a charge retaining layer for retaining a charge and an electroconductive base. A charging member capable of being supplied with a voltage is provided to charge the member to be charged. The charging member includes magnetic particles in the form of a magnetic brush contactable to the member to be charged, wherein the member to be charged has an electroconductive member electrically insulated from the electroconductive base in a region corresponding to an end portion, in a longitudinal direction of the charging member.

Abstract: An image forming apparatus capable of preventing contamination of a brush-roller charger with toner depositions includes a photoconductor, a brush-roller charger, an image development mechanism, an image transfer mechanism, a cleaning mechanism, a power supply mechanism, and a controller. The photoconductor carries an electrostatic latent image thereon. The brush-roller charger rotates in contact with the photoconductor and initializes a surface of the photoconductor by applying a charge thereto. The image development mechanism contacts the surface of the photoconductor and supplies toner to develop a toner image according to the electrostatic latent image on the surface of the photoconductor. The image transfer mechanism transfers the toner image from the photoconductor to a recording sheet. The cleaning mechanism cleans the surface of the photoconductor. The power supply mechanism supplies power to the brush-roller charger.

Abstract: An image forming method includes (i) a charging step of using a charging device including conductive magnetic particles, a rotatable conductive-magnetic-particle carrying member for carrying and conveying the conductive magnetic particles, and a plurality of magnetic-field generation means provided within the conductive-magnetic-particle carrying member, and charging a surface of an image bearing member by applying a voltage to the conductive-magnetic-particle carrying member and causing the conductive magnetic particles to contact the image bearing member, (ii) a latent-image forming step of forming an electrostatic latent image on the charged surface of the image bearing member, and (iii) a developing step of using a developing device facing the image bearing member and including a two-component developer including a toner and magnetic carrier particles, a developer carrying member for carrying the two-component developer, and a plurality of magnetic-field generation means provided within the developer carr

Abstract: An image forming apparatus includes an image bearing member for bearing an electrostatic image, and a charging device for charging the image bearing member mixed into the magnetic brush. The charging device includes a magnetic brush sliding in contact with the image bearing member and has magnetic particles. The image forming device forms the electrostatic image on the image bearing member charged by the charging device. A developing device develops the electrostatic image on the image bearing member with the toner. A replenishing device replenishes the electrostatic image on the image bearing member with a toner. A replenishing device replenishes the charging device with the magnetic particles in accordance with a consumption amount of the toner.

Abstract: An electrophotographic apparatus includes an electrophotographic photosensitive member, and (i) a charger, (ii) an imagewise exposure device, (iii) a developing device and (iv) a transfer device, disposed in this order opposite to the photosensitive member. The charger includes a charging member including magnetic particles disposed in contact with the photosensitive member so as to charge the photosensitive member based on a voltage received thereby. The magnetic particles are surface-coated with a coupling agent having a linear alkyl group having a least 6 carbon atoms. The developing device also functions to recover residual toner remaining on the photosensitive member processing by the transfer device and the charger. Because of the coating with such a specific coupling agent, the charging magnetic particles can exhibit good triboelectric changeability for the transfer residual toner for a long period.

Abstract: An image forming apparatus where the resistivity value of magnetic carrier in a developer of a two-component developing device is higher than that of magnetic particles for charging in a magnetic brush contact charger, the charging performance of the magnetic brush charging is prevented from being lowered even when the magnetic carrier is mixed into the magnetic brush contact charger, and thus, a satisfactory image without fog, unevenness in the image, and the like can be obtained for a long time even when it is applied to a cleanerless system according to the cleaning method simultaneous with developing.

Abstract: A charging device for electrophotography includes a charging brush, having many fibers extending in radial around a rotation shaft and contacted with a surface of a photosensitive drum, for rotating to electrically charge the surface of the photosensitive drum with the fibers, and a charging control member located on a downstream side of a contact between the charging brush and the photosensitive drum in a rotation direction of the charging brush for temporarily retarding a movement of the fibers of the charging brush to increase an effective density of the fibers to be contacted with the surface of the photosensitive drum. Particularly, an end of the charging control member is at a distance of at least 1 mm from the contact between the charging brush and the photosensitive drum.

Abstract: An image-forming apparatus includes a photosensitive member having a gamma for latent image of 3 or more, electrification facilities, light exposure facilities, image development facilities, image transfer facilities, cleaning facilities, and a charge erasing light source which applies an alternating current electric field at a frequency of 50 Hz to 1 kHz to a portion of the photosensitive member which is excited through light exposure by the charge erasing light source. Images with high quality and high resolution can be stably formed without residual images, even when continuous image formation is performed by utilizing a high gamma electrophotographic photosensitive member.

Abstract: An image forming apparatus has an auxiliary charging device provided near a transfer device side of the charging device for charging an image forming apparatus including an image bearing member bearing an electrostatic image thereon. The charging device charges the image bearing member. The charging device constitutes electrically conductive magnetic particles in contact with the image bearing member to thereby effect charging. The image forming device forms an electrostatic image on the image bearing device charged by the charging device. A developing device develops the electrostatic image on the image bearing member using a toner. A transfer device transfers the toner image on the image bearing member to a transfer material. An auxiliary charging device provided near the transfer means side of the charging device charges the residual toner after transfer to a polarity opposite to a charging polarity of the charging device, wherein the magnetic particles temporarily collect the residual toner.

Abstract: An image forming apparatus comprises a charging member, an image bearing member and a developer bearing member. The charging member comprises a first magnetic field generating device, wherein a first magnetic field with a first magnetic pole closest to the image bearing member has a half-value width &agr;°. Measuring from a center of the charging member, an angle between a closest point of the image bearing member and a maximum magnetic flux density of the first magnetic pole is &thgr;c°. The developer bearing member comprises a second magnetic field generating device, wherein a second magnetic field with a second magnetic pole closest to the image bearing member has a half-value width &bgr;°. Measuring from a center of the developer bearing member, an angle between a closest point of the image bearing member and a maximum magnetic flux density of the second magnetic pole is &thgr;d°.

Abstract: An electrophotographic recording apparatus includes a photosensitive drum on which an electrostatic latent image can be written, a developing device for developing the latent image of a charged visible image with a one-component developer, and a transferring device for electrostatically transferring the charged visible image from the drum to a sheet or paper. The developing device has a conductive foam rubber roller for entraining the developer to form a developer layer therearound and for bringing the layer to the drum for the development of the latent image, a conductive blade resiliently engaged with the foam rubber roller for uniformly regulating a thickness of the developer, and an electric source for applying electric energy to the blade to electrically charge the developer layer by a charge-injection effect.

Abstract: An image forming apparatus having a roller-shaped charging brush includes a first member for raising the brush pile and cleaning it while rotating in contact with the roller-shaped charging brush and a second member located at a position following the first member in the rotation direction of the roller-shaped charging brush, for shaping the brush pile raised by the first member while contacting with the roller-shaped charging brush. A combination of the first and second members can provide a satisfactory charging function at all times.

Abstract: A charging apparatus includes a magnetic brush charging member for being supplied with a voltage to electrically charge a member to be charged, said charging member including a magnetic particle layer contactable to the member to be charged and a carrying member for carrying the magnetic particle layers, wherein said magnetic particle layer is moved along a peripheral surface of said carrying member; and stirring means, contactable to said magnetic particle layer carried by said carrying member, for stirring said magnetic particle layer in a longitudinal direction of said carrying member.

Abstract: A magnetic particle for charging is disclosed. The magnetic particle includes magnetic particles having particle diameters of 5 .mu.m or more. The magnetic particles having particle diameters of 5 .mu.m or more have a standard deviation of short-axis length/long-axis length of 0.08 or more, and a volume resistance value in the range of 10.sup.4 to 10.sup.9 .OMEGA.cm. Also, provided are a charging member, a charging device, a process cartridge and an electrophotographic apparatus, using the magnetic particle.

Abstract: A charging device for charging a member to be charged includes a charging member to which a voltage is applicable to charge the member to be charged, the charging member having a magnetic brush of magnetic particles contactable to the member to be charged, and a supporting member for supporting the magnetic particles; wherein the the magnetic particles have a resistance value of 1.times.10.sup.4 -1.times.10.sup.7 (Ohm) when 1-1000(V) is applied thereto.

Abstract: An image forming apparatus has an image forming unit for forming a toner image on a recording material, the image forming unit including an image bearing member for bearing a toner image, and a charging device provided with a magnetic particle layer contactable to the image bearing member to charge the image bearing member; and a determining device for determining an image forming condition of the image forming unit in accordance with a physical quantity relating to a toner amount introduced in the magnetic particle layer or deciding prohibition of the image forming operation of the image forming unit.

Abstract: An image forming apparatus includes an image bearing member, a charging device for charging the image bearing member, the charging device including a charging member for being supplied with a voltage and for forming a nip with the image bearing member and including electroconductive particles in the nip, a developer develops, with one-component developer, an electrostatic latent image formed on the image bearing member using the charging device; the developer including a developer carrying member for carrying the developer, wherein the developer carried on the developer carrying member during a developing operation is contacted to the image bearing member at a contact position where peripheral movement directions of the image bearing member and the developer carrying member are the same, and wherein a surface speed of the image bearing member Vd and a surface speed of the developer carrying member Vs satisfy:1.2<Vs/Vd<2.5.