Abstract: A tandem-type color image forming apparatus forms an image in a monochrome mode or in a full color mode. The apparatus has a controller which delays an image forming operation for a predetermined period of time when a color mode is switched from the monochrome mode to the full color mode during different images are continuously formed.

Abstract: A color image forming apparatus of the present invention comprises: an intermediate transfer member being driven to rotate by a driving roller; a plural image forming units for forming superposed toner images on the intermediate transfer member, the plural image forming units being located below the intermediate transfer belt; a transfer member for transferring the superposed toner images formed on the intermediate transfer member onto a sheet of paper in a transfer area; and a pair of rotatable conveyance rollers for conveying the paper to the transfer area in synchronization with the superposed toner images on the intermediate transfer member, wherein a first distance from a image forming position, for the image forming unit located most-downstream in the plural image forming units relative to the movement of the intermediate transfer member, to the transfer area is longer than a second distance from a nipping area formed by the pair of conveyance rollers to the transfer area.

Abstract: A tandem-type color image forming apparatus forms an image in a monochrome mode or in a full color mode. The apparatus has a controller which delays an image forming operation for a predetermined period of time when a color mode is switched from the monochrome mode to the full color mode during different images are continuously formed.

Abstract: When it is judged that a sheet S is not an ordinary paper but a thick paper or an OHP film sheet, or that the arrival of the sheet S at a pair of timing rollers 48 is delayed due to a slip for example beyond an allowable period of time, a controller 70 judges that a condition for transferring or fixing an image on the sheet S is not met. As a result, a secondary transfer roller 34 and a cleaner 38 are retreated from an intermediate transfer belt 12, and in this state, the intermediate transfer belt 12 carrying a toner image I thereon is made idle at least about one revolution without transferring the image I.

Abstract: A color image forming apparatus in accordance with the present invention including an intermediate transfer member having a movable surface. The apparatus also includes plural image forming units for forming toner images on the intermediate transfer member at each of image-forming positions, and a transfer roller for transferring the toner images formed on the intermediate transfer member onto a sheet, the transfer roller having a circumferential length equal to the distance between the adjacent image forming positions.

Abstract: An image forming apparatus comprising an intermediate transfer belt 12 having a horizontal belt part 12a, and a transfer section 34 arranged opposite the horizontal belt part 12a of the intermediate transfer belt 12 for transferring to a sheet overlaid images formed on the intermediate transfer belt 12 by a plurality of image forming sections 20Y, 20M, 20C, 20K for overlaying multiple images of respectively different color, wherein a belt unit 110 comprises a frame 112, at least three rollers 14, 16, 18 supported on frame 112, and the intermediate transfer belt 12 supported on the exterior surface of these rollers, and wherein the belt unit 110 can be installed and removed from the image forming apparatus body perpendicular to the shafts of the rollers 14, 16, 18, and parallel to the horizontal part 12a.

Abstract: A color image forming apparatus of the present invention has an intermediate transfer member having a movable surface, a plural image forming units for forming superposed toner images on the intermediate transfer member at a predetermined image forming pitch, and a transfer member for transferring the superposed toner images formed on the intermediate transfer member onto a sheet of paper, wherein the peripheral length of the intermediate transfer member is a non-integral multiple of the image forming pitch.

Abstract: A color image forming apparatus of the present invention comprises: an intermediate transfer member being driven to rotate by a driving roller; a plural image forming units for forming superposed toner images on the intermediate transfer member, the plural image forming units being located below the intermediate transfer belt; a transfer member for transferring the superposed toner images formed on the intermediate transfer member onto a sheet of paper in a transfer area; and a pair of rotatable conveyance rollers for conveying the paper to the transfer area in synchronization with the superposed toner images on the intermediate transfer member, wherein a first distance from a image forming position, for the image forming unit located most-downstream in the plural image forming units relative to the movement of the intermediate transfer member, to the transfer area is longer than a second distance from a nipping area formed by the pair of conveyance rollers to the transfer area.

Abstract: A color image forming apparatus of the present invention comprises an intermediate transfer member having a movable surface, a plural image forming units for forming superposed toner images on the intermediate transfer member at a predetermined image forming pitch, and a transfer member for transferring the superposed toner images formed on the intermediate transfer member onto a sheet of paper, wherein the peripheral length of the intermediate transfer member is a non-integral multiple of the image forming pitch.

Abstract: A color image forming apparatus in accordance with the present invention comprises: an intermediate transfer member having a movable surface; a plural image forming units for forming toner images on the intermediate transfer member at each of image-forming positions; and a transfer roller for transferring the toner images formed on the intermediate transfer member onto a sheet, the transfer roller having a circumferential length equal to the distance between adjacent image forming positions.

Abstract: When it is judged that a sheet S is not an ordinary paper but a thick paper or an OHP film sheet, or that the arrival of the sheet S at a pair of timing rollers 48 is delayed due to a slip for example beyond an allowable period of time, a controller 70 judges that a condition for transferring or fixing an image on the sheet S is not met. As a result, a secondary transfer roller 34 and a cleaner 38 are retreated from an intermediate transfer belt 12, and in this state, the intermediate transfer belt 12 carrying a toner image I thereon is made idle at least about one revolution without transferring the image I.

Abstract: An image forming apparatus comprising an intermediate transfer belt 12 having a horizontal belt part 12a, and a transfer section 34 arranged opposite the horizontal belt part 12a of the intermediate transfer belt 12 for transferring to a sheet overlaid images formed on the intermediate transfer belt 12 by a plurality of image forming sections 20Y, 20M, 20C, 20K for overlaying multiple images of respectively different color, wherein a belt unit 110 comprises a frame 112, at least three rollers 14, 16, 18 supported on frame 112, and the intermediate transfer belt 12 supported on the exterior surface of these rollers, and wherein the belt unit 110 can be installed and removed from the image forming apparatus body perpendicular to the shafts of the rollers 14, 16, 18, and parallel to the horizontal belt part 12a.

Abstract: The recording sheet supporting surface of the transport belt comes in contact with the photosensitive drums for cyan, magenta, yellow, and black in the color copy mode, and is separated from the photosensitive drums aside from the photosensitive drum used for forming a black image in the monochrome copy mode with the image forming units for cyan, magenta, and yellow not being activated. With this separating operation, the distance on the transportation path of the recording sheet measured from the synchronizing roller to the transfer position of the photosensitive drum used for forming a black image in the monochrome copy mode is longer than in the color copy mode. Thus, the start time of scanning the surface of the photosensitive drum used for forming the black image is delayed in the monochrome mode according to the difference in distances between the color and monochrome modes.

Abstract: An inverting document feeder feeds a document from the document tray to the position where the image reader reads the document, turns the document over, and then reads the second side. Document size determination sensors detects the document passing through, and determines the size of the document from detections signals of the width of the document and the time elapsed between the detection of the top end of the document and the detection of the bottom end of the document. When the top end of the document reaches the document reading position, image reading is started by a scanner, regardless of whether the document size has been determined or not. The image data thus obtained are written into and read out of a memory unit in a specified order.

Abstract: An image forming apparatus operates in a color mode using a plurality of image holding components and in a monochrome mode using one of the plurality of image holding components to perform the image formation. The mode is switched between the color mode and the monochrome mode in accordance with information, such as the number of monochrome images having been successively formed, the number of monochrome images to be successively formed, a time period having been taken for the monochrome image formation, productivity or life priority specified the user, and a standby state of the image forming apparatus in the color mode or the monochrome mode, with a distance between the recording sheets to be transported being controlled according to predetermined conditions.

Abstract: An image forming apparatus equipped with a monochrome mode and color mode, in which the transfer drum is made to rotate without any paper wrapped around it to clean the transfer drum each time a series of copy operations is completed. By controlling the cleaning period through increasing or decreasing the number of non-paper rotations in response to the last copy operation mode, the transfer drum may be adequately cleaned at all times, and the amount of wear on the transfer drum and cleaning device caused by the cleaning operation is reduced.