Sheet feeding device and image forming apparatus incorporating same

A sheet feeding device comprising:

• a support configured to detachably support a roll formed of a continuous sheet wound around a spool;
• a rotation driver configured to rotate the spool supported by the support in a feeding direction and a winding direction of the continuous sheet;
• a guide including:
• a facing portion configured to face an outer circumferential surface of the roll;
• and
• a guide portion extending downstream from the facing portion in the feeding direction;
• a support shaft configured to swingably support the guide around a downstream end of the guide in the feeding direction, in a direction in which the facing portion contacts and separates from the roll;
• a biasing member configured to press the guide in a direction in which the facing portion approaches the roll;
• a leading end sensor configured to:
• retractably project from the facing portion toward the roll to contact the roll;
• and
• output a detection signal having a signal level in response to an amount of projection of the leading end sensor;
• a roller supported by the facing portion, the roller configured to contact the outer circumferential surface of the roll at a different position from the leading end sensor in a circumferential direction of the roll;
• an outer diameter sensor configured to detect an outer diameter of the roll;
• and
• circuitry configured to:
• control the rotation driver based on a signal change rate that is an amount of change in the signal level of the detection signal per unit time and a detection result of the outer diameter sensor;
• cause the rotation driver to rotate the spool in the winding direction to determine a timing at which the signal change rate of the leading end sensor exceeds a change rate threshold as a passing time at which a leading end of the continuous sheet passes through the leading end sensor;
• cause the rotation driver to rotate the spool by a rotation angle in the winding direction, from the passing time, to position the leading end at a feeding start position that is upstream from the leading end sensor and the roller in the winding direction and facing the guide portion;
• cause the rotation driver to rotate the spool in the feeding direction to feed the continuous sheet from the feeding start position along the guide portion;
• and
• change the change rate threshold based on the outer diameter of the roll detected by the outer diameter sensor.