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 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 image forming device that forms image by transferring toner image formed by developing electrostatic latent image formed on a photoreceptor from the photoreceptor to an intermediate transfer body by applying a transfer bias to a transfer member and putting the transfer member in contact with the intermediate transfer body. The device includes: a current supplier selectively supplying a first constant current and a second constant current to the transfer member; a first voltage acquirer acquiring a first voltage occurring between the transfer member and the intermediate transfer body while the transfer member is supplied with the first constant current; a second voltage acquirer acquiring a second voltage occurring between the transfer member and the photoreceptor while the transfer member is supplied with the second constant current; and a thickness acquirer acquiring a value indicating photoreceptor layer thickness of the photoreceptor by using the first and second voltages.

An image forming apparatus includes an image carrier that carries a toner image; a transfer part that is disposed so as to be in contact with the image carrier and transfers the toner image carried by the image carrier to a recording medium; and a charge applying part that is disposed on an upstream side of the transfer part in a recording-medium transport direction and charges the recording medium such that an amount of charge in the recording medium varies according to the position therein in a direction intersecting a recording-medium transport direction when the recording medium has reached the transfer part.

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.

An image formation apparatus includes: a process device that forms a developer image; a transfer device that transfers the developer image formed by the process device onto a recording medium; a voltage applier that applies a voltage to the transfer device; and a voltage controller that acquires information on a width of the recording medium in a direction orthogonal to a medium conveyance direction, and controls the voltage applied by the voltage applier to the transfer device based on the width of the recording medium.

A transfer device includes a transfer member to which a bias voltage is applied and that transfers a toner image, which is carried on an image carrier, onto a sheet while nipping the sheet between the transfer member and the image carrier when the sheet is transported to the transfer member; and a pressing member that includes a spring member and a first rubber damper, which are arranged in series with each other, and that presses the transfer member against the image carrier.

A transfer apparatus includes a transfer unit, a first detector, a supplying unit, a second detector, and a controller. The transfer unit transfers a toner image onto an object. The first detector detects humidity. The supplying unit supplies, to the transfer unit, a transfer voltage, a setting voltage in a first case, and a setting current in a second case. The second detector detects a current flowing through the transfer unit upon supply of the setting voltage and a voltage across the transfer unit upon supply of the setting current. The controller controls the supplying unit such that, when transfer is performed in the first case, a transfer voltage derived using the setting voltage and the detected current is supplied, and when transfer is performed in the second case, a transfer voltage derived using the setting current and the detected voltage is supplied to the transfer unit.

An image forming apparatus includes an image bearer including a first image portion to bear a first toner image, a second image portion to bear a second toner image, and a non-image portion to bear an adjustment pattern. A transferor forms a transfer nip with the image bearer. A controller controls the power source to output an image bias as a transfer bias to transfer the first toner image and the second toner image onto a first recording medium and a second recording medium, respectively, in the transfer nip when the first image portion and the second image portion pass through the transfer nip and output a non-image bias as the transfer bias when the non-image portion passes through the transfer nip. The controller performs a constant current control on the image bias and performs a constant voltage control when the image bias switches to the non-image bias.

A voltage maintenance element is connected to a contact member that contacts a primary transfer surface area of an intermediate transfer belt to which toner images are transferred from a plurality of image carriers between stretch members, in such a way as to prevent the electric potential of the intermediate transfer belt from varying between respective image forming stations.