Abstract: An image forming apparatus includes a main body, a sheet stack unit, an endless intermediate transfer member, a first transfer member for transferring a toner image onto the sheets conveyed from the sheet stack unit, at a nip formed between the intermediate transfer member and the first transfer member, and a second transfer member. In addition, a first voltage applying device applies a voltage to the first transfer member, a second voltage applying device applies a voltage having an opposite polarity to the second transfer member, and a controller controls the first and second voltage applying devices.

Abstract: An image forming apparatus including: a plurality of cartridges; a belt configured to abut against the photosensitive drums of the plurality of cartridges; a frame configured to axially support a plurality of rollers around which the belt is extended; and a movable member configured to be movable while supporting the plurality of cartridges, the movable member being movable between a first position in which the plurality of cartridges are in an main body of the apparatus and a second position in which the plurality of cartridges are drawn out from the main body of the apparatus, wherein the frame is provided with a plurality of positioning portions configured to allow abutment of the plurality of cartridges and determine the positions of the plurality of cartridges in the main body of the apparatus.

Abstract: The image forming apparatus includes a bearing member provided to a secondary transfer unit, the bearing member being configured to engage with a main body unit of the apparatus, a hooking-receiving member provided so as to be rotatable in the main body unit of the apparatus and opposed to the bearing member, and a rotation regulation member provided to the main body unit of the apparatus, the rotation regulation member being configured to regulate rotation of the hooking-receiving member, in which the hooking-receiving member contacts the rotation regulation member when the secondary transfer unit is closed with respect to the main body unit of the apparatus, and the hooking-receiving member rotates in a direction away from the rotation regulation member when the secondary transfer unit is opened with respect to the main body unit of the apparatus.

Abstract: In an image forming apparatus, a sheet during secondary transfer is allowed to contact with and slide on a sheet stacked on a sheet stack portion, double feeding of the sheet due to electrostatic adhesion is prevented without degrading transfer capability. When the leading edge of the sheet reaches a secondary transfer nip N2, the trailing edge of the sheet is in a state contact with the following sheet on the stack portion. A first voltage applying device applies a voltage to a secondary transfer roller. A second transfer bias voltage applying device applies a voltage to a driving roller. This application allows a toner image to be secondarily transferred from an intermediate transfer member onto the sheet at the secondary transfer nip N2.

Abstract: An image forming apparatus includes an image bearing member; a plurality of developing devices, contactable to the image bearing member, for developing a latent image on the image bearing member with toner; a rotatable member for rotatably supporting the plurality of developing devices; a detecting device for detecting a position of the image bearing member, wherein on the basis of an output of the detecting device, the rotatable member is rotated; and a control device for changeably controlling a period from timing of detection by the detecting device to timing of contact of one of the plurality of developing device, rotated by the rotatable member, to the image bearing member.

Abstract: A belt unit used for an image forming apparatus is provided. The belt unit includes a rotatable endless belt, a plurality of stretching members configured to stretch the belt, an urging member, and a contact and separation unit configured to be able to switch a position of the stretching member urged by the urging member. In moving the stretching member urged by the urging member from the separation position to the contact position, the contact and separation unit makes one end side of the stretching member urged by the urging member in a longitudinal direction coming into contact with the inner surface of the belt faster than the other end side, and temporarily decreases the movement speeds of the both ends of the stretching member in the longitudinal direction respectively before arriving at the contact position.

Abstract: A color electrophotographic image forming apparatus includes a rotatable supporting member to support a number V of developing devices. A drive transmission mechanism is provided in which each time one of the number V of engaging portions on a rotary member is disengaged from and engaged with an electric actuator, a gear portion of a rotatable supporting member gear which is rotated in synchronism with the rotary member is engaged with a driving member such that the rotatable supporting member is rotated by an angle W which satisfies (360°/V) and stopped.

Abstract: A color electrophotographic image forming apparatus includes a rotary to support and move developing devices to a development position without an independent driving motor for rotating the rotary. A number V of developing devices supported by the rotary are sequentially moved to and stopped at the development position in which the developing device faces a photosensitive drum. A drive transmission mechanism is provided in which each time one of a number M of claw portions of a trigger cam is disengaged from and engaged with a solenoid, the trigger cam makes a 1/M revolution, and once every 1/M revolution of the trigger cam, a driving force is transmitted to a rotary gear from a rotary drive gear which is rotated integrally with the trigger cam so that the rotary is stopped after being rotated by an angle W which is an aliquot part of (360°/N).

Abstract: A color electrophotographic image forming apparatus surely moves and stops each developing device supported by a rotary in a development position without an independent driving motor for rotating the rotary. By the rotation of the rotary, the V number of developing devices supported by the rotary are sequentially replaced and moved to the development position in which the developing device faces a photosensitive drum. A drive transmission mechanism is provided in which each time one of a M number claw portions of a trigger cam is disengaged from and engaged with a solenoid, the trigger cam makes a 1/M revolution, and once every 1/M revolution of the trigger cam, a driving force is transmitted to a rotary gear from a rotary drive gear which is rotated integrally with the trigger cam so that the rotary is stopped after rotated by an angle W which is an aliquot part of (360/V).

Abstract: An image forming apparatus includes an image bearing member; a plurality of developing devices, contactable to the image bearing member, for developing a latent image on the image bearing member with toner; a rotatable member for rotatably supporting the plurality of developing devices; a detecting device for detecting a position of the image bearing member, wherein on the basis of an output of the detecting device, the rotatable member is rotated; and a control device for changeably controlling a period from timing of detection by the detecting device to timing of contact of one of the plurality of developing device, rotated by the rotatable member, to the image bearing member.

Abstract: An image forming apparatus is provided which includes a plurality of optical scanners, each including a rotating polygon mirror adapted to scan and expose a surface of an image bearing medium to create an electrostatic latent image on the surface in accordance with image data. The apparatus further includes a plurality of phase detectors, each assigned to a respective one of the plurality of optical scanners for detecting rotated phases of the rotating polygon mirrors. Moreover, the apparatus includes a rotated phase controller configured to control the rotated phases of the rotating polygon mirrors. The rotated phase controller is configured to control the rotated phases of the rotating polygon mirrors in accordance with results of detection by the plurality of rotated phase detectors so that rotated phase relationships of the rotating polygon mirrors are set to a predetermined pattern.

Abstract: A color electrophotographic image forming apparatus surely moves and stops each developing device supported by a rotary in a development position without an independent driving motor for rotating the rotary. By the rotation of the rotary, the V number of developing devices supported by the rotary are sequentially replaced and moved to the development position in which the developing device faces a photosensitive drum. A drive transmission mechanism is provided in which each time one of a M number claw portions of a trigger cam is disengaged from and engaged with a solenoid, the trigger cam makes a 1/M revolution, and once every 1/M revolution of the trigger cam, a driving force is transmitted to a rotary gear from a rotary drive gear which is rotated integrally with the trigger cam so that the rotary is stopped after rotated by an angle W which is an aliquot part of (360/V).

Abstract: An image forming apparatus is provided which includes a plurality of optical scanners, each including a rotating polygon mirror adapted to scan and expose a surface of an image bearing medium to create an electrostatic latent image on the surface in accordance with image data; a plurality of phase detectors, each assigned to a respective one of the plurality of optical scanners for detecting rotated phases of the rotating polygon mirrors; and a rotated phase controller configured to control the rotated phases of the rotating polygon mirrors, wherein the rotated phase controller is configured to control the rotated phases of the rotating polygon mirrors in accordance with results of detection by the plurality of rotated phase detectors so that rotated phase relationships of the rotating polygon mirrors are set to a predetermined pattern.