AIR INTAKE DUCT

To prevent an air intake duct from being recessed to an internal side in a simple structure.SOLUTION: A lower duct body 13b of a lower-side air intake duct 13 is formed in a flat cylindrical shape of which the length in a longitudinal direction is shorter than a length L2 in a vehicle width direction. At a lower side of a front-side opposite wall part 15, a front opening part 23 is provided for communicating a flow passage of sucked air inside of the lower duct body 13b with a flow passage of sucked air in a connection part 13c of the lower-side air intake duct 13 within the lower-side air intake duct 13. The front opening part 23 is connected to the side of an engine 3. In a rear-side opposite wall part 16, a protruding curved surface region 25 which protrudes in a spherical surface shape backwards in a substantially central part of the rear-side opposite wall part 16 is provided. The protruding curved surface region 25 is opposite to a portion of the front opening part 23 in the front-side opposite wall part 15.SELECTED DRAWING: Figure 6 【課題】簡易な構造で吸気ダクトの内部側への凹みを防止する。【解決手段】下側吸気ダクト１３の下ダクト本体１３ｂは、前後方向の長さが車幅方向の長さＬ２よりも短い扁平筒状に形成される。前側の対向壁部１５の下方には、下側吸気ダクト１３内で下ダクト本体１３ｂの内部の吸気の流路と、下側吸気ダクト１３の接続部１３ｃの吸気の流路とを連通する前方開口部２３が設けられる。前方開口部２３は、エンジン３側に接続される。後側の対向壁部１６には、後側の対向壁部１６の略中央部で後方へ球面状に突出する突出曲面領域２５が設けられる。突出曲面領域２５は、前側の対向壁部１５の前方開口部２３の一部に対向する。【選択図】図６