PURPOSE: To make an opening/closing of door smooth by providing plural leaf springs on a gear and integrally forming these leaf springs so as to cause a deflection in the shaft direction of the gear to be exerted.

CONSTITUTION: To open/close the door, an operating button is pressed, thereby the door lock is disengaged and a rotary gear is started to rotate around a supporting shaft 22 as the center. Along with this procedure, the rotation is conveyed to teeth 23a of the gear 23 which is engaged with the rotary gear. Since pressing parts 24b of the plural leaf springs 24 are being pushed onto a wall 21a of supporting holder 21 at this time, the deflection in the shaft direction is generated on a spring part 24a of the gear 23 by the springs 24, then the rotation of gear 23 is restricted. The rotation of rotary gear is thereby made smooth, and the door can be smoothly opened. Also when the door is closed, the rotation of a gear system becomes smooth by the restriction of springs 24 on the gear 23, then the door can be closed with the smooth rotation.