Patent ID: 8488215

Claim:
A driving unit, comprising: a shaft; a first helical gear coaxially connected to the shaft; a second helical gear perpendicular to and engaged with the first helical gear; a holding member for rotatably supporting the shaft and rotatably holding the first and second helical gears; and a driver for driving and rotating the shaft in both a first rotational direction and a second rotational direction opposite to the first rotational direction, wherein the holding member includes: an accommodating portion which includes an opening used to insert the first helical gear and into which at least the first helical gear is inserted through the opening; a shaft insertion hole which communicates with the accommodating portion and through which the shaft is inserted; a first receiving portion for receiving a force, which is received from the second helical gear by the first helical gear and acting in a direction to push the first helical gear to the back of the accommodating portion, by coming into contact with the first helical gear or a part of the shaft when the shaft and the first helical gear are rotated in the first rotational direction; and a second receiving portion provided on the inner peripheral surface of the shaft insertion hole or inside the shaft insertion hole for receiving a force, which is received from the second helical gear by the first helical gear and acting in a direction to push the first helical gear from the interior of the accommodating portion to the opening, by coming into contact with the first helical gear or a part of the shaft when the shaft and the first helical gear are rotated in the second rotational direction.