When, in a state where a developer borne by a developer bearing member is sandwiched by an opposing portion of an image bearing member and the developer bearing member, C denotes capacitance between the image bearing member and the developer bearing member, ΔV denotes a development contrast, Q/S denotes a charge amount per unit area of the developer borne by the developer bearing member, and Δv denotes a peripheral velocity ratio which is a ratio of a peripheral velocity of the developer bearing member to a peripheral velocity of the image bearing member, a first peripheral velocity ratio is set so that |Q/S×Δv|≦|C×ΔV| is satisfied, and a second peripheral velocity ratio which is larger than the first peripheral velocity ratio is set so that |Q/S×Δv|>|C×ΔV| is satisfied.

An image forming device includes: a charging unit configured to apply charging bias voltage to a charging member and charge a surface of an image carrying body; an exposure unit configured to expose the surface of the image carrying body, and form an electrostatic latent image; a developing unit configured to apply developing bias voltage to a developer carrying body, and develop the electrostatic latent image; and a control unit configured to control timing to start applying the developing bias voltage relative to timing to start applying the charging bias voltage, wherein the control unit performs control such that the larger an absolute value of the charging bias voltage is, the shorter an interval from timing to start applying the charging bias voltage to timing to start applying the developing bias voltage becomes, and such that the smaller the absolute value is, the longer the interval becomes.

The present invention discloses a process cartridge and a power supply method therefor. The process cartridge is detachably mounted in an electrophotographic image forming apparatus, comprising a developing member rotatably mounted in the process cartridge and a voltage generating unit, the voltage generating unit is electrically connected to the conductive contact and the developing member. The process cartridge supplies power by using a data line, and the power supply method comprises: providing a conductor, and transmitting electric energy on the data line to the voltage generating unit by using the conductor. When the process cartridge is mounted in an electrophotographic image forming apparatus that outputs a DC bias voltage, because the voltage generating unit can generate an AC bias voltage, the process cartridge can work in an electrophotographic image forming apparatus that outputs a DC bias voltage and also in an apparatus that outputs an AC bias voltage.

A developing device, including: a developer containing toner and carrier; and developer bearer configured to have surface thereof bear the developer and endlessly move, and to develop latent image over surface of latent image bearer by supplying toner in developer to latent image in developing region facing the latent image bearer, wherein carrier contains fine particles, value X in volume resistivity R (=10.sup.X) (Ω.Math.cm) of carrier is 11.5-16.0, developer bearer includes: magnetic field generating unit including a plurality of magnetic poles; and developing sleeve having a cylindrical shape enclosing magnetic field generating unit, and configured to bear developer over outer circumferential surface of cylindrical shape by magnetic force of the magnetic field generating unit and perform surface moving by rotating relative to developing device body, and developing device includes developing sleeve voltage applying unit configured to apply AC component-containing voltage to developing sleeve.

An image forming apparatus includes an image bearing member and a developing device having a first developer bearing member and a second developer bearing member, disposed with a gap therebetween. A controller executes a mode in which a first difference between an amplitude of an alternating current bias of a first developing bias applied to the first developer bearing member and an amplitude of an alternating current bias of a second developing bias applied to the second developer bearing member at a time of non-image formation is set to be large compared to a second difference between an amplitude of the alternating current bias of the first developing bias applied to the first developer bearing member and an amplitude of the alternating current bias of the second developing bias applied the second developer bearing member at a time of image formation.

A developing cartridge includes a casing, a rotating member, and an electrode member. The casing may be configured to accommodate therein developer. The rotating member has a rotational shaft extending in an axial direction. The rotating member is configured to rotate about the rotational shaft and carries the developer thereon. The electrode member is configured to be electrically connected to the rotating member. The electrode member covers at least part of the rotational shaft from an orthogonal direction orthogonal to the axial direction and is arranged to confront the casing in the axial direction. The electrode member is configured to move in the orthogonal direction in accordance with a movement in the axial direction.

Provided is an image forming apparatus, including a photosensitive member, a latent image forming unit configured to form an electrostatic latent image on the photosensitive member, a developing unit configured to store developer containing toner and to develop the electrostatic latent image on the photosensitive member using the developer, a detector configured to detect an amount of the toner stored in the developing unit, and a supplying unit configured to supply toner to the developing unit.

A control unit performs control to make a direction of an electric field generated in a first area of an image carrier forming a transfer portion during image forming operation, relative to a voltage applied to a brush member in a state where the first area passes through a contact portion, different from a direction of an electric field generated in a second area of the image carrier forming the contact portion, relative to the voltage applied to the brush member during a period when operation is shifted from first operation in which the image carrier is rotated at a first speed to second operation in which the image carrier is rotated at a second speed different from the first speed, during non-image forming operation different from the image forming operation.

An image forming apparatus includes a rotatable image bearing member; a developing device including a rotatable developer carrying member, a toner content detecting portion, an electrostatic capacity detecting portion, and a switching portion configured to switch a developing condition on the basis of an output of the toner content detecting portion and an output of the electrostatic capacity detecting portion so that the developing condition is changed when the electrostatic capacity detected by the electrostatic capacity detecting portion reaches first electrostatic capacity at a first toner ratio and so that the developing condition is changed when the electrostatic capacity reaches second electrostatic capacity larger than the first electrostatic capacity at a second toner ratio smaller than the first toner ratio.

An image forming apparatus is capable of performing a second image forming operation in which a peripheral velocity ratio of a developer bearing member to an image bearing member becomes greater than that in a first image forming operation, and in which a potential difference between a developing bias applied to the developer bearing member and a supply bias applied to a supply member becomes a potential difference at which a urging force causing a developer at the contact portion between the developer bearing member and the supply member to move from the supply member to the developer bearing member becomes smaller than that in the first image forming operation, or becomes a potential difference at which a urging force causing the developer to move from the developer bearing member to the supply member is generated.