SHEET FOLDING DEVICE

PROBLEM TO BE SOLVED: To control occurrence of a problem about a misalignment in folding and scrape of a toner which are generated at a folding roller pair on the upstream side when a tip of a sheet enters a folding roller pair on the downstream side, with easy means, in a sheet folding device wherein each one of a folding roller among a plurality of folding roller pairs is commonized. SOLUTION: The sheet folding device performs a folding process for inserting a deflection of the sheet to be conveyed in a nip of the folding roller to be pressure-contacted. In the sheet folding device, a first folding roller 21 and a second folding roller 22 as well as the folding roller 22 and a third folding roller 23 are arranged so that each of them pressure-weld, thereby forming a first nip 71 and a second nip 72. The commonized second folding roller is applied pressure by a tensioner 73 so that a nip pressure F1 of a first nip 71 on the upstream side is larger than that of a nip pressure F2 of a second nip 72 on the downstream side, in respect to a sheet convey direction. COPYRIGHT: (C)2011,JPO&INPIT