Sensor unit and image forming apparatus therewith

A sensor unit comprising:

• a sheet conveying passage through which a sheet is conveyed;
• a first housing which extends in a width direction perpendicular to a conveying direction of the sheet and which constitutes a first conveying face of the sheet conveying passage;
• a second housing which extends in the width direction and which constitutes a second conveying face of the sheet conveying passage arranged opposite the first conveying face with a predetermined gap;
• an edge detection sensor which is arranged in one of the first and second housings and which detects a side edge, along the conveying direction, of the sheet passing through the sheet conveying passage;
• and
• a gap adjuster which supports the first housing movably from a first position where a size of the gap equals a reference value in a direction in which the size of the gap increases from the reference value,
• wherein
• when, with the first housing arranged at the first position, a sheet with a thickness greater than the reference value passes through the sheet conveying passage, the first housing moves in the direction in which the size of the gap increases as the sheet enters the sheet conveying passage, to allow passage of the sheet.