Sheet feeding apparatus and image forming apparatus

A sheet feeding apparatus comprising:

• a sheet supporting unit configured to support a sheet bundle;
• a sheet feed unit configured to come into contact with an uppermost sheet of the sheet bundle supported by the sheet supporting unit and feed the uppermost sheet;
• an air separation unit including a fan configured to blow air, the air separation unit being configured to separate the uppermost sheet by blowing the air onto a side surface of the sheet bundle supported by the sheet supporting unit;
• a velocity detection unit configured to detect a velocity of a sheet fed by the sheet feed unit;
• a drive load detection unit configured to detect a drive load for feeding the sheet by the sheet feed unit;
• a memory unit storing information of surface properties of the sheet;
• and
• a controller configured to control the sheet feeding unit,
• wherein the controller is configured to control timing to start feeding a next sheet by the sheet feed unit based on the detected velocity of the sheet detected by the velocity detection unit and the detected drive load detected by the drive load detection unit.

An image forming apparatus comprising:

• a sheet feeding apparatus comprising:
• a sheet supporting unit configured to support a sheet bundle;
• a sheet feed unit configured to come into contact with an uppermost sheet of the sheet bundle supported by the sheet supporting unit and feed the uppermost sheet;
• an air separation unit including a fan configured to blow air, the air separation unit being configured to separate the uppermost sheet by blowing the air onto a side surface of the sheet bundle supported by the sheet supporting unit;
• a velocity detection unit configured to detect a velocity of a sheet fed by the sheet feed unit;
• a drive load detection unit configured to detect a drive load for feeding the sheet by the sheet feed unit;
• a memory unit storing information of surface properties of the sheet;
• and
• a controller configured to control the sheet feed unit and the air separation unit,
• wherein the controller is configured to:
• refer a relationship equation between a conveyance efficiency and a conveyance resistance in accordance with the information of surface properties of the sheet stored in the memory unit;
• control the sheet feed unit to feed the sheet in a set conveyance velocity;
• detect the drive load for feeding the sheet fed in the set conveyance velocity by the drive load detection unit and the conveyance velocity of the sheet fed in the set conveyance velocity by the velocity detection unit;
• calculate a theoretical conveyance efficiency based on the relationship equation and the detected drive load;
• calculate a detected conveyance efficiency based on the detected conveyance velocity by the velocity detection unit;
• and
• control an operation of the air separation unit based on the theoretical conveyance efficiency and the detected conveyance efficiency;
• and
• an image forming unit configured to form an image on the sheet fed from the sheet feeding apparatus.