Sheet processing apparatus, image forming apparatus, and image forming system

A sheet processing apparatus comprising:

• a sheet conveyance passage configured to receive a sheet before a following sheet at a given time interval, the sheet conveyance passage including a sheet circulation passage in which the sheet is circulated to be overlaid with the following sheet, the sheet circulation passage including at least a first passage, a second passage, and a third passage;
• a first roller disposed in the sheet circulation passage and configured to stop the sheet temporarily and convey the sheet to a downstream side in a sheet conveyance direction in which the sheet is conveyed, to correct a conveyance position of the sheet with respect to the sheet conveyance direction in the first passage;
• a second roller disposed in the sheet circulation passage and configured to receive the sheet conveyed by the first roller and convey the sheet along the second passage;
• a third roller disposed in the sheet circulation passage and configured to receive the sheet conveyed by the second roller and convey the sheet along the third passage to circulate the sheet to the first passage;
• and
• circuitry configured to control sheet conveyance speeds of the first roller, the second roller, and the third roller to convey the sheet, wherein
• the circuitry is configured to:
• circulate the sheet in the sheet circulation passage to overlay the sheet with the following sheet conveyed after the sheet in the first passage, at an upstream position of the first passage;
• and
• adjust the sheet conveyance speed of the third roller to circulate the sheet, based on a reduction amount that is obtained when a preceding amount of a leading end of the following sheet with respect to a leading end of the sheet is reduced while the following sheet is temporarily stopped due to a temporary stop of the first roller.