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.

A control portion has a conversion portion that converts image data to be used for forming a recorded image by using either a first conversion condition which has been set such as to obtain a first gradation characteristic in the image to be formed on the recording material when a first image forming operation is executed or a second conversion condition which has been set such as to obtain a second gradation characteristic, which is different from the first gradation characteristic, in the image when a second image forming operation is executed, a peripheral velocity ratio between an image bearing member and a developer bearing member being larger during the second image forming operation than during the first image forming operation, and enables the first image forming operation or the second image forming operation to be performed on the basis of converted image data.

An electrophotographic image forming apparatus which sequentially performs charging, exposure, development, transfer and cleaning on each surface portion of a photoreceptor during rotation includes: a cleaning blade configured to scrape off toner from the surface of the photoreceptor; a detecting unit configured to detect a rotation angle of the photoreceptor; and a control unit configured to control each of a start process and an end process of rotation of the photoreceptor and charging, development and transfer of the photoreceptor, wherein, in the end process, the control unit estimates a position of a surface portion of the photoreceptor, at which a charged state caused by a peeling discharge remains even after the stop of the photoreceptor, from the rotation angle from the time of start of deceleration of the photoreceptor to the time of stop of the photoreceptor, and adjusts parameters necessary for the next start process or end process.

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 apparatus includes a controller capable of executing a normal mode in which an electrostatic image formed on an image bearing member is developed by setting a peripheral velocity ratio of a developer bearing member relative to the image bearing member to a prescribed peripheral velocity ratio, and a color gamut enlargement mode in which a color gamut of an image to be formed on a recording medium is enlarged as compared to the normal mode by setting the peripheral velocity ratio of the developer bearing member relative to the image bearing member to a larger peripheral velocity ratio than the peripheral velocity ratio in the normal mode, wherein the controller identifies image color gamut information included in image data and forms an image by selecting the normal mode or the color gamut enlargement mode in accordance with the image color gamut information.

Changing of a peripheral speed ratio, resulting in change of the developer amount per unit area, enables the detection unit to detect the developer amount with sufficient accuracy.

An image forming apparatus includes a rotatable image bearing member and a rotatable developing member to carry developer made up of toner particles and carrier particles adhered to surfaces of the toner particles. Where a pressing force pressing the developing member against the image bearing member is F1, a total number of the carrier particles interposed between the toner particles and the image bearing member is N1, and an adhesion Ft between a carrier particle and a toner particle, measured when the carrier particle is pressed against the toner particle with F1/N1 that is a pressing force per unit carrier particle, and an adhesion Fdr1 between the carrier particle and the image bearing member, measured when the carrier particle is pressed against the image bearing member with F1/N1, satisfy Ft≤Fdr1.

A motor control apparatus includes: a current supply unit configured to supply coil current to a plurality of coils of a motor by controlling, based on a first command value of excitation current and a second command value of torque current, voltage to be applied to the plurality of coils; a first setting unit configured to set the first command value; a second setting unit configured to set the second command value; and a control unit configured to use first control in starting of rotation of a rotor of the motor, and switch control to second control after rotation speed of the rotor becomes greater than predetermined speed. The first setting unit is further configured to set a value greater than 0 as the first command value before the control unit switches control from the first control to the second control.

According to one embodiment, an image forming apparatus includes a printer and a controller. The printer performs image formation on a sheet at a first speed relating to a speed of image formation or at a second speed slower than the first speed. The controller acquires information on deterioration of developer contained in an own apparatus, and controls the printer to perform image formation at the first speed when the information does not satisfy a predetermined condition indicating that the developer is deteriorated and to perform image formation at the second speed when the information satisfies the predetermined condition.

A controller is configured to execute a larger gamut technology mode in which the controller performs image formation by controlling a ratio of a rotation speed of a development roller to a rotation speed of a photosensitive drum such that the ratio becomes a second speed ratio higher than a first speed ratio in a normal mode. The controller is configured to, when the controller executes the larger gamut technology mode, control transfer voltage based on a humidity around an image forming apparatus.