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: In an image forming apparatus in which multiple photoconductors for corresponding developers of different colors are disposed along a transfer belt or paper conveyance belt, the photoconductors are disposed at intervals that are each an integer multiple of the outer circumference length of the driving roller that drives the transfer belt or paper conveyance belt, and the distance between at least one pair of photoconductors is made different from the distances between the other pairs of photoconductors. As a result, in comparison with when all of the photoconductors are disposed at equal intervals, the degree of freedom in arranging the multiple image forming units that each include an photoconductor can be increased, while color shift among the developed images of the difference colors on the transfer belt or the like is prevented.

Abstract: In an image forming apparatus in which multiple photoconductors for corresponding developers of different colors are disposed along a transfer belt or paper conveyance belt, the photoconductors are disposed at intervals that are each an integer multiple of the outer circumference length of the driving roller that drives the transfer belt or paper conveyance belt, and the distance between at least one pair of photoconductors is made different from the distances between the other pairs of photoconductors. As a result, in comparison with when all of the photoconductors are disposed at equal intervals, the degree of freedom in arranging the multiple image forming units that each include an photoconductor can be increased, while color shift among the developed images of the difference colors on the transfer belt or the like is prevented.

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.