Sheet mass measuring unit

A mass measuring unit for measuring a mass of a sheet of paper, comprising:

• a conveyor path configured to convey a sheet of paper;
• a rotation mechanism including a driving roller configured to rotate in contact with the sheet of paper conveyed by the conveyor path, and a motor configured to accelerate and/or decelerate the driving roller to rotate and forward the sheet of paper along the conveyor path;
• a torque detection unit configured to detect torque of the motor;
• and
• a calculation unit configured to calculate a mass of the sheet of paper, based on torque of the motor that is detected by the torque detection unit when the rotation mechanism rotates the sheet of paper, and torque of the motor that is detected by the torque detection unit when the rotation mechanism rotates no sheet of paper.

A mass measuring unit for measuring a mass of a sheet of paper, comprising:

• a conveyor path configured to convey a sheet of paper;
• a rotation mechanism including a first driving roller, a second driving roller, a first motor, and a second motor, the first driving roller rotating in contact with a surface portion of the sheet of paper conveyed by the conveyor path, the second driving roller being vertically aligned with and separate from the first driving roller, the second driving roller rotating in contact with another surface portion of the sheet of paper conveyed by the conveyor path, the first and second motors independently accelerating and/or decelerating the driving rollers such that the driving rollers rotate at different rates, thereby rotating and forwarding the sheet of paper along the conveyor path;
• a torque detection unit configured to detect torque values of the first and second motors;
• a storing unit configured to beforehand store torque values of the first and second motors detected by the torque detection unit when the rotation mechanism is idling under same conditions as when rotating the sheet of paper, with no sheet of paper conveyed by the conveyor path;
• and
• a calculation unit configured to calculate a mass of the sheet of paper, based on torque values of the first and second motors that are detected by the torque detection unit when the rotation mechanism rotates the sheet of paper during conveyance thereof, and the torque values of the first and second motors stored in the storing unit.