An image forming apparatus includes an image bearer; a toner image forming device; an intermediate transferor; a primary transfer power source; a secondary transfer nip forming device; and a secondary transfer power source to output a secondary transfer bias. One of two peak values of the secondary transfer bias is a transfer peak value to provide a greater transfer-directional force to move toner from the intermediate transferor toward the recording medium in the secondary transfer nip. An absolute value of the transfer peak value is greater than an absolute value of the primary transfer bias.

An image forming apparatus includes an image forming unit configured to form an image on a recording material based on first image data; a controller configured to control an image forming operation by the image forming unit; an acquisition unit configured to acquire property information related to a property of the recording material; a setting unit configured to set a control value to be used in the image forming operation; a reader configured to read an image formed on the recording material by the image forming unit and to output second image data; and a comparison unit configured to compare the first image data to the second image data, wherein the setting unit is further configured to set the control value based on a comparison result from the comparison unit and the property information.

An image forming apparatus includes a first image bearing member, a second image bearing member, an intermediate transfer belt, a first primary transfer member, a second primary transfer member, a secondary transfer outer member, a pre-secondary transfer stretch roller, a driving roller, and an execution portion. The execution portion is configured to execute a first monochromatic mode in which a bias smaller than the primary transfer bias applied to the first primary transfer member in a case where a toner image is formed on the first image bearing member is applied to the first primary transfer member, and the primary transfer bias applied to the second primary transfer member in a case where a toner image is formed on the second image bearing member is applied to the second primary transfer member.

An image forming apparatus includes an image bearing member, an intermediary transfer belt, a primary transfer roller provided so that a contact region between the roller and the belt and a contact region between the image bearing member and the belt are in a non-overlapping state with each other with respect to a movement direction of the belt, a primary transfer voltage source, a current detecting portion, an executing portion configured to acquire information on a discharge start voltage on the basis of a detection result of the detecting portion in a period other than a period of primary transfer by applying the voltage to the roller; and a setting portion configured to set, on the basis of an execution result of the executing portion, a primary transfer voltage applied to the roller by the primary transfer voltage source in the period of the primary transfer.

An imaging system includes a transfer roller having a surface to transfer a toner image onto a print medium during a printing operation of the imaging system, a conductive device to contact the surface of the transfer roller, a power source electrically connected to the conductive device, a resistance measurement device, and a controller. The transfer roller rotates according to a printing speed of the printing operation. The power source supplies a bias to the transfer roller through the conductive device during the printing operation. The resistance measurement device measures an electrical resistance of the print medium. The controller reduces the printing speed based on the electrical resistance measured by the resistance measurement device.

An image forming apparatus includes a controller and a transfer power supply portion configured to output a transfer voltage to a transfer portion so as to transfer a toner image onto a recording material. The transfer power supply portion superimposes a voltage output from a first power supply portion and a voltage output from a second power supply portion to output a superimposed voltage to the transfer portion. The first power supply portion includes a transformer including a primary coil and a secondary coil, and a rectifier circuit portion. The rectifier circuit portion includes a plurality of diodes and a plurality of capacitors. A capacitance of a predetermined capacitor to be charged by a half-wave rectified voltage of an AC voltage generated in the secondary coil is larger than a capacitance of a capacitor to be charged by a voltage higher than the half-wave rectified voltage.

An image forming apparatus comprising a transfer means for transferring, a developer image onto a recording material; a discharging unit for discharging the recording material; a first circuit that applies a first voltage of reverse polarity to the developer to the transfer unit; a second circuit that applies a second voltage of identical polarity to the developer to the transfer unit and the discharging unit; and a control unit. The control unit applies a transfer voltage which is a superposition of the first and the second voltage to the transfer unit, and applies a discharging voltage which is a partial voltage from the second voltage. When the discharging voltage is set to the first value, the control unit reduces the discharging voltage in a case where the transfer voltage is lower than a target value.

An image forming apparatus includes an image formation unit, a detection unit, a storage unit, and a control unit. When the detection unit outputs a second output value when a second recording material, which is different from a first recording material is detected, in a state where the storage unit stores a first output value output by the detection unit upon detection of the first recording material, the control unit controls an image forming condition based on at least the first output value if a differential value between the first output value and the second output value is smaller than a predetermined threshold value and controls the image forming condition based on the second output value without using the first output value if the differential value is greater than the predetermined threshold value.

An image forming apparatus includes a rotatable image bearer, a toner image forming device, a transfer device, a transfer bias power source, and a cleaner. The toner image forming device is to form a toner image on the image bearer. The transfer device contacts a surface of the image bearer to form a transfer nip between the transfer device and the image bearer. The transfer bias power source is to output a transfer bias to transfer the toner image from the image bearer onto a recording medium in the transfer nip. The cleaner is disposed downstream from the transfer nip in a direction of rotation of the image bearer, to electrostatically attract and remove toner from the surface of the image bearer to a surface of the cleaner. The transfer bias includes an alternating current component.

A characteristic measuring portion measures current-voltage characteristics of a primary transfer member before a toner image for a first surface of a sheet is primarily transferred. A characteristic information storage portion stores characteristic information that indicates the current-voltage characteristics. A first transfer voltage determining portion determines a first transfer voltage based on a first target current value and the characteristic information. A second transfer voltage determining portion determines a second transfer voltage based on a second target current value and the characteristic information that was used when the first transfer voltage was determined, the second target current value being smaller than the first target current value. A voltage control portion applies the first and second transfer voltages to the primary transfer member by a constant-voltage method when the toner images for the first and second surfaces of the sheet are primarily transferred, respectively.