Air passage opening and closing device

An air passage opening and closing device comprising:

• a case configured to define an opening portion of an air passage;
• a sliding door slidably disposed in the case to open and close the opening portion, the sliding door including a resinous door body having a plate-like shape;
• and
• a gear mechanism configured to drive the sliding door and to move the sliding door in a door movement direction,
• wherein the door body has first and second plate surfaces opposite to each other,
• wherein the case has a case-side seal surface at two edges of the opening portion in a width direction of the door body, the case-side seal surface being adapted to abut against the first plate surface of the door body,
• wherein the gear mechanism includes a driven side gear that is integrally molded with the door body using resin, and a driving side gear that is located to be engaged with the driven side gear,
• wherein the driven side gear protrudes from the second plate surface of the door body and extends in a direction parallel with the door movement direction, at two edge portions of the second plate surface of the door body in the width direction, and
• wherein the driven side gear has a hollow space opened toward a direction parallel to the width direction.