A kind of variable diameter appendix structure, it includes a hollow tube and a fins. It is integrally formed a sizing section and the reducer from sizing section extension on what hollow tube, is respectively provided with a plurality of different internal diameters, and the internal diameter of all big what sizing section of the internal diameter on reducer everywhere everywhere on reducer. The inner wall of fin projection what hollow tube is extended along the length direction of hollow tube. The inner space that hollow tube is supported by fin avoids hollow tube from deforming and be crushed. 一種變徑輸氣管結構，其包含一中空管體及一凸肋。於中空管體上一體構成有一定徑段以及自定徑段延伸的一變徑段，變徑段上各處分別具有複數個不同的內徑，而且變徑段上各處之內徑皆大於定徑段之內徑。凸肋凸設於中空管體的內壁面，其沿著中空管體的長度方向延伸設置。藉由凸肋以支撐中空管體的內部空間，避免中空管體變形而被壓扁。
