A transmission unit transmits driving force to be supplied from a motor to a roller pair. A switching unit acts on the transmission unit to switch a rotation direction of the roller pair by the driving force between a normal rotation and a reverse rotation. A control unit controls a rotation speed of the motor to convey the sheet at a second conveyance speed in a part of a first time period. The second conveyance speed is lower than a first conveyance speed. The first conveyance speed is a conveyance speed when the sheet is conveyed in the image forming unit. In the first time period the sheet having the image formed on the first surface is conveyed in a first direction. In a second time period the sheet is conveyed in a second direction.

In an image forming apparatus, a bias controller varies one, while keeping the other fixed, of a charging alternating-current frequency, which is the frequency of the charging alternating-current voltage, and a developing alternating-current frequency, which is the frequency of the developing alternating-current voltage. Specifically, in a case where interference fringes appear in a developed image due to interference between the charging and developing alternating-current frequencies, when the recognizable minimum pitch of the interference fringes is A.sub.1 (mm), the width of the variation region of the other frequency is B.sub.1 (Hz), the rotation speed of an image carrying member is C.sub.1 (mm/sec), and the variation speed of the other frequency in the variation region is D.sub.1 (Hz/sec), the bias controller varies the other frequency at a variation speed D.sub.1 that fulfills |D.sub.1|>B.sub.1/(A.sub.1/C.sub.1).

An image forming apparatus includes a photosensitive drum, a charging roller, a transfer roller, and a control circuit. The control circuit is configured to perform an alternating bias control. During the alternating bias control, the control circuit causes the charging roller and the transfer roller to rotate in accordance with a rotation of the photosensitive drum, and controls the charging roller to alternately turn off and on to a first bias of a predetermined polarity and the transfer roller to alternately turn off and on to a second bias of the predetermined polarity, such that at least a part of a region of the photosensitive drum biased by the first bias is not biased by the second bias, and that at least a part of a region of the photosensitive drum biased by the second bias is not biased by the first bias.

According to one embodiment, an image forming apparatus includes an image carrier, an exposing apparatus, a developing device, a transfer device, a fixing device, a history acquisition unit, an estimation unit, and an output unit. The exposing device exposes the image carrier to form an electrostatic latent image on the image carrier. The developing device includes a layer forming member to form a toner layer on a developing roller and forms a toner image by developing the electrostatic latent image. The transfer device transfers the toner image to a sheet. The fixing device fixes the toner image to the sheet. The history acquisition unit acquires a history regarding a temperature around the developing device. The estimation unit estimates a possibility that an image defect caused by the layer formation may occur on the basis of the history. The output unit outputs estimation results of the estimation.

In a first operation mode in which a first addition value for each sheet of a recording material and a first initial control temperature, when the total sum of the first addition values exceeds a predetermined threshold value, a control portion of an image heating portion, which heats an image on the recording material, of an image forming apparatus changes the first initial control temperature to a first correction control temperature. When the operation mode is changed from the first operation mode to a second operation mode in which a second addition value different from the first addition value and a second initial control temperature different from the first initial control temperature, the control portion corrects the first correction control temperature based on a difference between initial control target temperatures.

A primary transfer roller is disposed upstream or downstream from the center of rotation of a photosensitive drum in the moving direction of an intermediate transfer belt. The primary transfer roller includes a core metal and an elastic layer coating the outer circumference of the core metal and having a thickness of less than 2.0 mm. The primary transfer roller has an Asker-C hardness of 40 or higher and 85 or lower.

A method of stabilizing a marking process speed in a printing system, the printing system including a vacuum transport belt and at least one sheet onto which marking material is directly applied to print sheets, the method including printing an image on the sheet, receiving, from a sensor, data related to the image, determining, based on the data, at least one actual dimension of the image, determining if the at least one actual dimension of the image is equal to a target dimension of the image, and if the at least one actual dimension is not equal to the target dimension, adjusting one or more components of the printing system.

An image forming apparatus includes: a conveyance device; an image forming device that forms an image on a recording paper sheet conveyed by the conveyance device; and a controller that determines a conveyance speed for the recording medium in accordance with a predetermined condition and allows the conveyance device to convey the recording medium at the determined conveyance speed for the recording medium. In allowing the conveyance device to convey the recording paper sheet and subsequently allowing the conveyance device to convey a slip sheet, the controller allows the conveyance device to convey the slip sheet at the same speed as the determined conveyance speed for the recording paper sheet.

An image-forming apparatus contains a hardware processor for forming first and second reference marks on both surfaces of a first recording medium by using respective recorder. The first reference mark includes scale marks indicating coordinates in a position range relative to a first image-forming area, and the second reference mark includes an indicator indicating a position relative to a second image-forming area. The indicator is formed in a position indicating the relative position range as seen from a direction perpendicular to the surface of the recording medium. The hardware processor is also for implementing settings for adjusting the recording action of the recorder so that positional misalignment of the first and second image-forming areas diminishes based on coordinates inputted by an input section and indicated by the indicator. The hardware processor causes respective adjusted ordinary images to be formed on both surfaces of a second recording medium by the recorder.

An image forming apparatus includes: a photoreceptor that forms a toner image on a surface of the photoreceptor; a charger that charges the surface of the photoreceptor; an exposure device that exposes the surface of the photoreceptor; a developer that supplies toner to the surface of the photoreceptor; an intermediate transfer belt for transferring the toner image formed on the surface of the photoreceptor; a density sensor that detects a density of the toner image on the intermediate transfer belt; and a controller that controls the image forming apparatus.