S114063 ナノテクスチャリングによる動圧気体軸受の設計指針([S11406]機素潤滑設計部門 第17回卒業研究コンテスト(6))

Abstract

Recently, the effect of textured surface facing narrow gap, where gases cannot be treated as continuum fluid even at atmospheric pressure, on the properties of air bearings is focused on. For example, Nakamori et al. reported that the friction between a dimpled surface, which is fabricated by partial polishing of diamond-coated surface, and a flat metal surface was drastically decreased to almost zero with increasing relative speed of sliding. In this work, we tried to generate such floating force between a flat surface and a textured surface fabricated by shot-peening of fine particles followed by buffing. In addition, MGL calculation was conducted to investigate the effect of textured surface shape on the floating force induced by rarefied gas flow in the narrow gap between the sliding surfaces. As a result, the ratio of metal contact and friction between the sliding surfaces was decreased to almost zero at relative sliding speeds u >2.0 m/s; MGL calculation showed that levitation pressure equal to that (1630 Pa) by the own weight of the specimen is induced by rarefied gas flow at u =2.0 m/s in the narrow gap of 0.009 pm. Furthermore, we found an optimized shape of textured surface; it was indicated by MGL calculation that the floating force induced at u=2.0 m/s and a gap height of 0.1 pm by the optimized shape is increased by 8 times from the conventional shape where a dimple fabricated by shot-peening is modeled by an isosceles triangle. Note that the air bearing (inside diameter 11 mm, length 9.6 mm) employing the optimized shape as a texturing on the sleeve was estimated to support an axle of 4 g without contact at u=2.0 m/s and floating height of 0.1 pm.