A controller is able to, in a case where the controller receives a correction instruction for image density, execute a phase detection mode for detecting a phase of an image bearing member and detecting a phase of a developer bearing member and change an image forming condition for an image forming unit during an image formation mode based on respective phases of the image bearing member and the developer bearing member detected in the phase detection mode and an image density of a toner pattern, and a ratio of a circumferential velocity of the developer bearing member to a circumferential velocity of the image bearing member during the phase detection mode is different from a ratio of a circumferential velocity of the developer bearing member to a circumferential velocity of the image bearing member during the image formation mode.

An image forming apparatus includes a photoreceptor, an exposure unit, a developing unit, and a control unit. The control unit sets the toner-layer-forming electric potential difference lower than an electric potential when forming the image on the print medium, forms a combined patch for calibration by the set toner-layer-forming electric potential difference for calibration, so as to adjust the developing-bias potential by measuring a print density of the formed combined patch. The combined patch includes a first patch and a plurality of second patches. The plurality of second patches have a width within a range of 0.2 mm to the predetermined value in the peripheral-velocity direction of the photoreceptor, extend with a length equal to or more than the predetermined value in the rotation-shaft direction of the photoreceptor, and are arranged at a predetermined interval in the peripheral-velocity direction of the photoreceptor.

An image forming apparatus includes a developer bearing member, a supply member, first and second voltage application units, and a control unit. Assuming that a difference between a voltage to be applied to the developer bearing member by the first voltage application unit and a voltage to be applied to the supply member by the second voltage application unit in the image forming operation is defined as a first supply contrast, and a difference between the voltage to be applied to the developer bearing member by the first voltage application unit and the voltage to be applied to the supply member by the second voltage application unit in the preliminary rotation operation is defined as a second supply contrast, the control unit controls the second supply contrast to be less than the first supply contrast or to have polarity reversed from polarity of the first supply contrast.

An image-forming apparatus includes a rotatable developer-bearing member to bear a developer composed of a toner particle and a transfer promoting particle attached to the toner particle. When F denotes pressing force for pressing the developer-bearing member against an image-bearing member, and N denotes a total number of the transfer promoting particles interposed between the toner particle and the image-bearing member, adhesion strength Ft between the transfer promoting particle and the toner particle measured by pressing the transfer promoting particle against the toner particle at a pressing force per unit transfer promoting particle F/N and adhesion strength Fdr between the transfer promoting particle and the image-bearing member measured by pressing the transfer promoting particle against the image-bearing member at the pressing force per unit transfer promoting particle F/N, satisfy Ft<Fdr. Electrical discharge is generated upstream of a transfer portion in a movement direction of an intermediate transfer belt.

An image forming apparatus includes a photoconductive drum, a developing roller, a humidity sensor configured to detect a humidity, and a controller configured to execute a single-side printing, a first-double-side printing and a second double-side printing. The controller is configured to execute the first double-side printing in which images are printed at a first developing-bias voltage on both the first surface and the second surface of the sheet when the humidity detected by the humidity sensor is greater than a threshold value. The controller is configured to execute the second double-side printing in which an image is printed at a second developing-bias voltage, which is less than the first developing-bias voltage, on the second surface of the sheet when the humidity detected by the humidity sensor is equal to or less than the threshold value.

An image forming apparatus that is capable of executing image forming operation includes an image bearing member; a developer carrying member that faces the image bearing member in a state of keeping a predetermined gap therefrom, and develops a latent image on the image bearing member using developer; a frame that supports the developer carrying member; applying units that applies developing voltage, in which DC voltage and AC voltage are superimposed, to the developer carrying member; a conductive member that is disposed in the frame; a detecting unit that detects AC current induced in the conductive member by applying the developing voltage to the developer carrying member; and a control portion that controls the applying units. The control portion controls the developing voltage in the image forming operation, based on the AC current which the detecting unit detects in a case where the voltage is applied by the applying units.

An image forming apparatus includes a photosensitive member, a charging member, an electrostatic image forming portion, a developing member, a transfer member, a transfer voltage source, a brush member, a brush voltage source, and a controller capable of executing a cleaning operation. The controller carries out control so that the cleaning operation includes a first operation in which a potential difference is formed between the transfer member and the photosensitive member so that toner charged to a normal charge polarity is moved from the transfer member toward the photosensitive member, and a second operation in which a potential difference is formed between the brush member and the photosensitive member so that the toner charged to the normal charge polarity is moved from the photosensitive member toward the brush member.

An image forming apparatus includes image forming units. A controller includes an execution section, a measurement section, and a prediction section. The execution section controls execution of a developer refresh operation in which toner is ejected from a developer bearing member to an image bearing member so that a specific image forming unit replenishes a development device with the toner from the developer bearing member. The measurement section measures respective surface potentials of the image bearing members included in other image forming units while the specific image forming unit is executing the developer refresh operation. The prediction section uses measurement results of the respective surface potentials of the image bearing members included in the other image forming units for a prediction on the surface potential of the image bearing member included in the specific image forming unit.

An image forming apparatus comprising an image bearing member, a developer bearing member, a drive unit for driving the image bearing member and the developer bearing member in varied peripheral speeds, a control unit, a developing voltage application unit, a supply member for supplying a developer to the developer bearing member, and, a supply member voltage application unit, wherein the control unit executes a first image forming mode in which a rotational peripheral speed ratio between surface movement speeds of the developer bearing member and the image bearing member is not more than 1 and a second image forming mode in which the rotational peripheral speed ratio is larger than 1, and, the control unit controls the drive unit so that a difference between developing voltage and supply voltage becomes larger in the second image forming mode than in the first image forming mode.

In a cartridge, a housing has a developer accommodating portion and includes a first side wall and a second side wall. A coupling member is disposed at a position opposite to the developer accommodating portion with respect to the first side wall. A detection body is disposed at a position opposite to the developer accommodating portion with respect to the second side wall. A first driving force transmission member is positioned at the same side with the coupling member with respect to the first side wall, and transmits driving force from the coupling member to a rotating member. A second driving force transmission member is positioned at the same side with the detection body with respect to the second side wall, and transmits driving force from the rotating member to the detection body.