Patent ID: 7311593

Claim:
An air passage switching device comprising: a casing for defining an air passage having an opening portion; a film member for opening and closing the opening portion, the film member having a first end portion fixed to a peripheral portion of the opening portion and a second end portion opposite to the first end portion; a winding shaft to which the second end portion of the film member is fixed, wherein the winding shaft is capable of moving in a first direction separated from the first end portion of the film member and in a second direction approaching the first end portion of the film member while rotating, and the second end portion is wound on or unwound from the winding shaft such that a length of the film member from the first end portion is changed when the winding shaft is moved while rotating; an actuator for operating the winding shaft, the actuator disposed in an interior of the winding shaft; a fixing member which fixes the actuator; a guide unit which guides the fixing member to be moved in the first direction or the second direction together with the winding shaft, a deceleration unit disposed in the interior of the winding shaft for reducing a rotation of the actuator; and an output shaft connected to the actuator to be rotatable; wherein the deceleration unit transmits the rotation of the actuator to the winding shaft; the deceleration unit includes a male screw member coupled to the output shaft to be rotatable by the rotation of the output shaft, a female screw member threadingly engaging the male screw member, the female member being restricted from rotating by the fixing member and a screw recess extending in a screw shape in an axial direction of the winding shaft is formed on an inner peripheral surface of the winding shaft; the female screw member has a pin which is slidably fitted in the screw recess; the male screw member has a substantially cylindrical shape extending parallel to the axial direction of the winding shaft; and the winding shaft is disposed rotatably relative to the fixing member.