Sheet transport device and image forming apparatus

A sheet transport device comprising pre-transfer sheet-transport rollers that transport a sheet to a transfer position at which an unfixed image is transferred, the pre-transfer sheet-transport rollers including a first roller in which three or more separate rollers attached to a first shaft rotate, and a second roller in which three or more separate rollers attached to a second shaft are in contact with the separate rollers of the first roller and rotate, wherein

• the hardness of an inner separate roller of the first roller is lower than the hardness of outer separate rollers of the first roller that are located outside and adjacent to the inner separate roller,
• the outside diameter of an inner separate roller of the second roller is greater than the outside diameter of outer separate rollers of the second roller that are located outside and adjacent to the inner separate roller,
• when the sheet being transported is a narrow sheet that is transported by being nipped between only the inner separate roller of the first roller and the inner separate roller of the second roller, a pressure-contact load between the inner separate roller of the first roller and the inner separate roller of the second roller is higher than a pressure-contact load between each outer separate roller of the first roller and each corresponding outer separate roller of the second roller, and
• when the sheet being transported is a wide sheet that is transported by being nipped between the inner separate roller and the outer separate rollers of the first roller and the inner separate roller and the outer separate rollers of the second roller, the pressure-contact load between the inner separate roller of the first roller and the inner separate roller of the second roller is substantially equal to the pressure-contact load between each outer separate roller of the first roller and each corresponding outer separate roller of the second roller.