Sensor unit and image forming apparatus including sensor unit

An image forming apparatus comprising:

• an image forming unit configured to form an image on a recording material;
• a conveying unit configured to convey a recording material;
• a control unit configured to detect the recording material conveyed by the conveying unit;
• and
• a sensor unit,
• wherein the sensor unit includes:
• a light-emitting unit including a light-emitting element configured to emit light;
• a light-receiving unit including a light-receiving element configured to receive the light emitted from the light-emitting element;
• a flag configured to pass through a space between the light-emitting unit and the light-receiving unit;
• and
• a printed circuit board having a mounting surface on which the light-emitting unit and the light-receiving unit are mounted,
• wherein a cutout or a hole is formed in the printed circuit board,
• wherein the light-emitting unit and the light-receiving unit are mounted on the mounting surface of the printed circuit board so that the light-emitting element and the light-receiving element face each other, and the light emitted from the light-emitting element travels straight along the mounting surface of the printed circuit board over the cutout or the hole,
• wherein the flag is configured to move in a direction intersecting the mounting surface of the printed circuit board and enter the cutout or the hole, thereby blocking the light traveling from the light-emitting element to the light-receiving element, and
• wherein the flag moves by a leading edge of the recording material conveyed by the conveying unit coming into contact with the flag, and the light-receiving unit outputs a signal based on a light-receiving state of the light to the control unit, whereby the control unit detects the recording material.