Roll sheet conveying apparatus and sheet conveying control method

A conveying control method for a sheet conveying apparatus which conveys a sheet using:

• a roll sheet which rotates while the sheet is held in a roll;
• a sheet feeding motor for rotating the roll sheet;
• a first encoder for detecting a rotation amount of the roll sheet;
• a conveying roller for conveying the sheet fed from the roll sheet;
• a conveying motor for rotating the conveying roller;
• and
• a second encoder for detecting a rotation amount of the conveying roller,
• wherein the conveying method comprises:
• obtaining friction load torque T for rotating the roll sheet based on output current of the sheet feeding motor, output current of the conveying motor, a detected value of the first encoder, and a detected value of the second encoder;
• deriving a default mass m of the roll sheet for the friction load torque T obtained in the obtaining step by referring to a storing unit configured to store friction load information associating the friction load torque T one-to-one with a mass of the roll sheet;
• estimating moment of inertia I′ of the roll sheet for each of a plurality of conveyance operations for printing of parts of an image based on the default mass m, a first value of the first encoder detected for each of the plurality of conveyance operations and a second value of the second encoder detected for each of the plurality of conveyance operations;
• and
• controlling driving of the sheet feeding motor and the conveying motor for each of the plurality of conveyance operations based on the moment of inertia I′ to keep constant tension of the sheet.

A sheet conveying apparatus comprising:

• a supporting section for supporting a roll of a continuous sheet;
• a driving mechanism for rotating the roll supported in the supporting section;
• a detecting unit configured to detect a rotation state of the roll supported in the supporting section;
• a conveying roller for conveying the continuous sheet drawn out from the roll;
• a calculating unit configured to calculate moment of inertia of the roll for each of a plurality of conveyance operations for printing of parts of an image based on a detected value of the detecting unit detected for each of the plurality of conveyance operations;
• and
• a controlling unit configured to control at least driving of the driving mechanism for each of the plurality of conveyance operations based on the calculated moment of inertia.