SCREW ROTOR AND FLUID MACHINE

To provide a screw rotor and a fluid machine capable of improving cooling efficiency by an axial distribution of cooling force of a cooling liquid circulating in a through-hole of the screw rotor.SOLUTION: A male rotor 1A of an air compressor is composed of a tooth part 3A formed with a tooth groove, a suction side shaft portion 4A extending outward from a suction side end surface of the tooth part 3A, and a discharge side shaft portion 5A extending outward from a discharge side end surface of the tooth part 3A. A cooling liquid circulates in a through-hole 14A of the tooth part 3A, a through-hole 15A of the suction side shaft portion 4A, and a through-hole 16A of the discharge side shaft portion 5A. In the through-hole 16A of the discharge side shaft portion 5A, the peripheral length of a diametrical cross-section in a part A1 in an axial direction including a range corresponding to a discharge side air seal 12A and a range from the discharge side air seal 12A to a discharge side end surface of the tooth part 3A, is larger than the peripheral length of a diametrical cross-section in the rest A2 in the axial direction including a range corresponding to a discharge side bearing 7A.SELECTED DRAWING: Figure 4 【課題】スクリューロータの貫通穴に流通する冷却液の冷却力の軸方向分布により、冷却効率の向上を図ることができるスクリューロータ及び流体機械を提供する。【解決手段】空気圧縮機の雄ロータ１Ａは、歯溝が形成された歯部３Ａと、歯部３Ａの吸入側端面より外側に延在する吸入側軸部４Ａと、歯部３Ａの吐出側端面より外側に延在する吐出側軸部５Ａとで構成されており、歯部３Ａの貫通穴１４Ａ、吸入側軸部４Ａの貫通穴１５Ａ、及び吐出側軸部５Ａの貫通穴１６Ａに冷却液が流通する。吐出側軸部５Ａの貫通穴１６Ａは、吐出側エアシール１２Ａに対応する範囲及び吐出側エアシール１２Ａから歯部３Ａの吐出側端面までの範囲を含む軸方向の一部分Ａ１における径方向断面の周長が、吐出側軸受７Ａに対応する範囲を含む軸方向の残りの部分Ａ２における径方向断面の周長より大きい。【選択図】図４