Patent ID: 8808073

Claim:
An air passage open/close device comprising: a casing having an air passage; and a sliding door having a board member slidably located in the casing, the board member opening or closing the air passage of the casing, wherein the casing has a guide groove for guiding a movement of the board member, the guide groove having an upstream wall extending in a direction of the movement of the board member and being located at an upstream side of the board member in an air flow direction, and a downstream wall opposing to the upstream wall and being located at a downstream side of the board member in the air flow direction, wherein the board member is configured to be elastically deformed when the board member is arranged in the casing, the board member in an unrestrained state has a curvature radius set larger than a curvature radius of the upstream wall and a curvature radius of the downstream wall, the board member has opposing ends in the direction of the movement of the board member, the opposing ends being in contact with the downstream wall when the board member is arranged in the casing, the board member has a middle part between the opposing ends in the direction of the movement of the board member, the middle part being in contact with the upstream wall when the board member is arranged in the casing; the entire board member has no opening part passing through the board member in a thickness direction of the board member, the sliding door has a gear attached to and driving the board member, the gear has a rack having a plurality of gear teeth arranged on the board member, and the rack extends in the direction of the movement of the board member, and the board member has a peripheral part located on an outer side from the rack in a width direction of the board member, and the peripheral part is inserted between the upstream wall and the downstream wall.