Sheet finisher positioned between upstream and downstream rollers and temporarily increasing speed of the upstream rollers while maintaining speed of the downstream rollers

An image forming apparatus comprising:

• an image forming means that forms an image on a sheet;
• a first conveyance device that conveys the sheet on which the image is formed by the image forming means at a first conveyance speed;
• a second conveyance device disposed on the upstream side from the first conveyance device in the conveyance direction of the sheet, which conveys the sheet at the first conveyance speed and switches the speed into a second conveyance speed being higher than the first to convey the sheet;
• a punching device to punch the sheet, disposed between the first conveyance device and the second conveyance device;
• a sheet position detection sensor to detect a position of the sheet, which is disposed on the upstream side from the second conveyance device in the conveyance direction of the sheet;
• and
• a control unit that controls to switch the sheet conveyance speed of the second conveyance device on the basis of a detection result of the sheet-position detection sensor.

A finisher that executes a finishing of a sheet outputted from an image forming apparatus, comprising:

• a first conveyance device that conveys a sheet at a first conveyance speed;
• a second conveyance device disposed on the upstream side from the first conveyance device in the conveyance direction of the sheet, which conveys the sheet at the first conveyance speed and switches the speed into a second conveyance speed being higher than the first to convey the sheet;
• a punching device to punch the sheet, disposed between the first conveyance device and the second conveyance device;
• a sheet position detection sensor to detect a position of the sheet, which is disposed on the upstream side from the second conveyance device in the conveyance direction of the sheet;
• and
• a control unit that controls to switch the sheet conveyance speed of the second conveyance device on the basis of a detection result of the sheet position detection sensor.