An image forming apparatus includes an transfer section including a transfer roller and a rotatable member and performing transfer processing in which it transfers a developer to a recording medium; a power source controller that applies a voltage to the transfer roller and measures a current value of a current that flows through the transfer roller and the rotatable member; and a main controller that calculates a first electrical resistance value between the transfer roller and the rotatable member in if the recording medium is absent between the transfer roller and the rotatable member and a second electrical resistance value between the transfer roller and the rotatable member if the recording medium is present between the transfer roller and the rotatable member on the basis of the current value measured by the power source controller, and determines a transfer voltage value for the transfer processing.

An image forming apparatus includes an image bearing member, a transfer member, a voltage source, a speed setting portion, a test mode executing portion, a renewing mode executing portion, and a setting portion for setting a voltage applied to the transfer member. In a period in which the toner image exists at the transfer portion when image formation is executed at a first speed, the setting portion sets the voltage applied to the transfer member at a first target voltage last renewed. In a period in which the toner image exists at the transfer portion when the image formation is executed at a second speed, the setting portion sets the voltage applied to the transfer member at a voltage on the basis of the first target voltage last renewed and a conversion coefficient last renewed.

An image forming apparatus includes a toner image forming unit, a nip formation member, a transfer power source, an information acquisition device, and a controller. The information acquisition device acquires specific information that specifies whether a recording sheet as a transfer target of a toner image is an uneven surface sheet having an uneven surface. The controller outputs a bias including a superimposed voltage, in which an alternating current (AC) voltage is superimposed on a direct current (DC) voltage, as a transfer bias from the transfer power source when the specific information acquired by the information acquisition device is not information corresponding to the uneven surface sheet and to output a bias including only the DC voltage as the transfer bias from the transfer power source when the specific information is the information corresponding to the uneven surface sheet.

An image forming apparatus includes a transfer unit that transfers a toner image on an image bearer onto a transfer medium. The image forming apparatus includes a control unit that controls a transfer voltage to be output to the transfer unit in accordance with a certain condition. The control unit applies currents having at least two different values while paper is not being fed. The two current values are lower than a current value during paper feeding. The control unit estimates an output voltage on a basis of a voltage detected through the application of the currents. When the estimated output voltage falls below a certain limiter voltage, the control unit controls to bring the output voltage to a value calculated through the certain condition. When the estimated output voltage exceeds the certain limiter voltage, the control unit controls to bring the output voltage to the limiter voltage.

An image forming apparatus includes: an image forming unit configured to form an image on a recording medium which is unwound from a state of being wound in a roll shape; and a control unit configured to change an image forming condition of the image forming unit such that image quality becomes uniform before and after an unwinding start position of the recording medium at the time of start of an image forming operation.

An improved image forming apparatus includes an image bearer, a nip forming member, a transfer power source, and a controller. The controller switches a transfer mode between a first mode to transfer the toner image onto a first type sheet having a surface smoothness higher than a surface smoothness of a second type sheet and a second mode to transfer the toner image onto the second type sheet. The controller controls the transfer power source to output the transfer bias having an opposite-peak duty of greater than or equal to 50% that is a duty on the side of the opposite-peak value in the first mode. The controller controls the transfer power source to output the transfer bias having an opposite-peak duty of less than 50%, which is different from the opposite-peak duty of the first mode, in the second mode.

An imaging system includes a transfer roller, a bias application device, and a controller. The transfer roller forms a transfer nip region between the transfer roller and a transfer belt, and the transfer roller transfers toner images carried on the transfer belt, onto media conveyed through the transfer nip region, during a print job. The bias application device applies a bias to the transfer roller. The controller controls the bias application device to apply a first bias to the transfer roller so that the toner image is transferred to a first medium during the printing job, apply a second bias having a polarity opposite to the first bias to the transfer roller between the first medium and a second medium following the first medium, and apply a third bias having the same polarity as the first bias to the transfer roller between the first medium and the second medium.

An image forming apparatus includes an image bearing member, an image forming portion, an endless belt, a plurality of stretching rollers including an inner roller, an outer roller, a position changing mechanism capable of changing a position of the inner roller to a first position and a second position positioned downstream of the first position with respect to a rotational direction of the endless belt, a feeding member, a feeding member driving portion, and a controller. A feeding start timing of a recording material by the feeding member depends on the position of the inner roller during transfer of a toner image onto the recording material.

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.

An image forming apparatus that forms developer images on a continuous medium includes a control part that performs a developer image forming on an intermediate transfer body with an interval; a transfer part that transfers developer images to the continuous medium; an interval detection part that detects the interval of positions to which the developer images; and an interval information memory that stores interval information of the interval. Wherein, the control part obtains the interval information from the interval information memory when starting an operation of forming the developer image, and determines a timing of forming the developer images on the intermediate transfer body based on the interval information, and when the interval is detected by the interval detection part, the control part updates the interval information in the interval information memory based on the interval that is detected.