Sheet conveying apparatus, image forming apparatus, sheet conveying distance calculation apparatus and sheet length calculation apparatus

A sheet conveying distance calculation apparatus, comprising:

• a conveying amount measuring unit that measures a conveying amount of the sheet conveyed by a sheet conveying unit, the sheet conveying unit including
• a drive roller which is driven to be rotated by a driving unit,
• a driven roller which is rotated in accordance with the drive roller while the sheet is interposed between the drive roller and the driven roller, and
• a rotary encoder provided on a rotational axle of one of the drive roller and the driven roller;
• a first detection unit positioned downstream of the sheet conveying unit and detecting passing of a front end portion of the sheet downstream of the sheet conveying unit in a conveying direction of the sheet;
• a second detection unit positioned upstream of the sheet conveying unit and detecting passing of a rear end portion of the sheet upstream of the sheet conveying unit in the conveying direction of the sheet;
• and
• a conveying distance calculation unit that calculates a conveying distance of the sheet based on the measured result by the conveying amount measuring unit and the detected results detected by the first detection unit and the second detection unit,
• wherein the conveying amount measuring unit measures the number of pulses generated by the rotary encoder as a rotation amount, and
• wherein the first detection unit is positioned apart from the drive roller and the driven roller not to overlap with the drive roller and the driven roller in the conveying direction.

A sheet length calculation apparatus, comprising:

• a conveying amount measuring unit that measures a conveying amount of the sheet conveyed by a sheet conveying unit, the sheet conveying unit including
• a drive roller which is driven to be rotated by a driving unit,
• a driven roller which is rotated in accordance with the drive roller while the sheet is interposed between the drive roller and the driven roller, and
• a rotary encoder provided on a rotational axle of one of the drive roller and the driven roller;
• a first detection unit positioned downstream of the sheet conveying unit and detecting passing of a front end portion of the sheet downstream of the sheet conveying unit in a conveying direction of the sheet;
• a second detection unit positioned upstream of the sheet conveying unit and detecting passing of a rear end portion of the sheet upstream of the sheet conveying unit in the conveying direction of the sheet;
• and
• a sheet length calculation unit that calculates a conveying distance of the sheet based on the measured result by the conveying amount measuring unit and the detected results detected by the first detection unit and the second detection unit,
• wherein the conveying amount measuring unit measures the number of pulses generated by the rotary encoder as a rotation amount, and
• wherein the first detection unit is positioned apart from the drive roller and the driven roller not to overlap with the drive roller and the driven roller in the conveying direction.