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.

A transfer device includes: a transfer drum that has a groove-like recess extending in an axial direction in an outer circumferential portion thereof, rotates about an axis thereof, and comes into contact with a medium being transported at a portion thereof on an upstream side of the recess in a rotation direction; a nip member, the nip member and the transfer drum forming therebetween a nip part where the medium is nipped; an application member that applies a voltage to the nip part where the medium is nipped, so that an image is transferred to the medium; and a contact mechanism that causes the nip member to come into contact only with a portion on the upstream side of the recess in the transfer drum in the rotation direction at a transfer-start time when the transfer of the image to the medium starts.

An image forming apparatus comprising includes an image carrying member including a movable surface to include a toner image; a transfer roller to form a transfer nip between the transfer roller and the movable surface of the image carrying member, to move position in a direction in correspondence to a thickness of a print medium to intersect a direction of introduction of the print medium into the transfer nip, and to receive a transfer bias voltage to transfer the toner image from the movable surface of the image carrying member to the print medium; and a movement guide structure to guide the print medium toward the transfer nip, and to move in synchronization with the movement of the position of the transfer roller to change a gap between an end of the movement guide structure facing the image carrying member and the image carrying member.

A moisture sensor detects moisture in an object. A first light-emitting element emits light. A first reflecting member reflects light reflected from the object toward the object. A light-receiving element receives light that is multiple reflected between the object and the first reflecting member. A controller determines an amount of moisture in the object based on a light reception result from the light-receiving element.

An image forming apparatus includes a first image forming portion, a second image forming portion, a belt, a charging voltage applying portion, and a transfer voltage applying portion. With respect to a movement direction of a recording material, the first image forming portion is provided upstream of the second image forming portion. In an image forming operation, a potential difference between a first transfer voltage and a potential at a first transfer portion, which is formed on a first image bearing member and does not form the image, is greater than a potential difference between a second transfer voltage and a potential at a second transfer portion, which is formed on a second image bearing member and does not form an image.

An image forming apparatus includes a first image forming portion, a second image forming portion, a belt, a charging voltage applying portion, and a transfer voltage applying portion. With respect to a movement direction of a recording material, the first image forming portion is provided upstream of the second image forming portion. In an image forming operation, a potential difference between a first transfer voltage and a potential at a first transfer portion, which is formed on a first image bearing member and does not form the image, is greater than a potential difference between a second transfer voltage and a potential at a second transfer portion, which is formed on a second image bearing member and does not form an image.

An image forming apparatus includes an image forming portion, an image input portion, a transfer unit, a transfer voltage power supply, and a control portion. The transfer unit includes a transfer roller having a metal shaft and an elastic layer laid around an outer circumferential face of the metal shaft to form a transfer nip by keeping the elastic layer in pressed contact with an image carrying member, and transfers a toner image formed on the image carrying member to a recording medium as it passes through the transfer nip. The transfer unit includes, as the transfer roller, a first roller, and a second roller having a larger axial-size elastic layer compared to the first roller. The control portion arranges the first or second roller opposite the image carrying member according to width-direction sizes of the recording medium and image data fed to the image input portion.

A transfer device includes a transfer roller, a power source and a switch device. The transfer roller may transfer an image formed on an image carrier to a transfer medium in an imaging apparatus. The transfer roller includes a rotation shaft including a conductive material, and a ion conductive member disposed around the rotation shaft. The power source may generate a transfer voltage. The switch device may selectively connect, during rotation of the transfer roller, a power-feed path from the power source to the transfer roller, among a plurality of power-feed paths based on whether the image is being transferred or not being transferred, to thereby reverse the direction of an electric field applied by the transfer voltage to the ion conductive member.

An image forming apparatus includes image bearing members, an intermediary transfer member having ion conductivity, primary transfer members, a first voltage applying portion, a secondary transfer member, a second voltage applying portion, and a controller. On the basis of image information, the controller controls a transfer voltage applied to the secondary transfer member so as to be different between a first voltage when a first region, in which a coverage indicating a ratio occupied by an image region per predetermined area is a first coverage passes through the secondary transfer portion and a second voltage when a second region, in which the coverage is a second coverage larger than the first coverage, passes through the secondary transfer portion. The controller controls a change amount of the first voltage with respect to the second voltage so as to be different between a first mode and a second mode.

An image forming apparatus includes: an image forming unit that includes a first drum supporting a recording medium and a first rotating body disposed at an axial end of the first drum, and that is configured to form an image on the recording medium; a fixing unit that includes a second drum supporting the recording medium and a second rotating body disposed at an axial end of the second drum, and that is configured to fix the image to the recording medium by heating or drying the recording medium; and a transport unit that includes a rotating member stretched between the first rotating body and the second rotating body and rotating with rotation of the first rotating body and the second rotating body and a holding unit attached to the rotating member and holding the recording medium, and that is configured to transport the recording medium from the image forming unit to the fixing unit by the rotation of the rotating member.