Sheet carrying device, document carrying device, image forming apparatus, and sheet carrying method

A sheet carrying device comprising:

• a paper feeding roller for sending out a sheet to a carrying path one by one from a sheet mounting tray;
• a roller driving device for rotating the paper feeding roller;
• and
• a control section for controlling the roller driving device to rotate the paper feeding roller,
• the sheet carrying device including a slip detecting device for detecting whether or not a slip of the paper feeding roller occurs in an amount equal to or more than a predetermined amount when the sheet is carried,
• the control section controlling the roller driving device so as to perform a slip-settling operation which decreases a start-up acceleration of the paper feeding roller when the slip detecting device detects that a slip of the paper feeding roller occurs in an amount equal to or more than the predetermined amount, the start-up acceleration being an acceleration from a time when the paper feeding roller starts to rotate to a time when the paper feeding roller reaches a predetermined speed,
• a sheet speed detecting device for detecting a travel speed of the sheet carried by the paper feeding roller;
• and
• a roller speed detecting device for detecting a carrying speed of the paper feeding roller in carrying the sheet,
• the control section (i) calculating a slip ratio from results of detection by the sheet speed detecting device and the roller speed detecting device, the slip ratio indicating a degree of a slip of the paper feeding roller in carrying the sheet, (ii) setting, in the slip-settling operation, a start-up acceleration of the paper feeding roller so that the start-up acceleration is lower as the slip ratio is higher, and (iii) controlling the roller driving device to rotate the paper feeding roller at the start-up acceleration thus set.

A sheet carrying method for sending out a sheet to a carrying path one by one from a sheet mounting tray by a paper feeding roller, the method comprising:

• performing a slip-settling operation for decreasing a start-up acceleration of the paper feeding roller when a slip of the paper feeding roller occurs in an amount equal to or more than a predetermined amount in carrying the document, the start-up acceleration being an acceleration from a time when the paper feeding roller starts to rotate to a time when the paper feeding roller reaches a predetermined speed, wherein the slip-settling operation comprises
• detecting a travel speed of the sheet carried by the paper feeding roller;
• detecting a carrying speed of the paper feeding roller in carrying the sheet, and
• controlling the slip-settling operation by (i) calculating a slip ratio from results of detecting the travel speed of the sheet and the carrying speed of the paper feeder roller, the slip ratio indicating a degree of a slip of the paper feeding roller in carrying the sheet, (ii) setting, in the slip-settling operation, a start-up acceleration of the paper feeding roller so that the start-up acceleration is lower as the slip ratio is higher, and (iii) rotating the paper feeding roller at the start-up acceleration thus set.