CERAMIC DYNAMIC PRESSURE BEARING, MOTOR WITH BEARING, HARD DISC DEVICE, AND POLYGON SCANNER

摘要

PROBLEM TO BE SOLVED: To provide a ceramic dynamic pressure bearing in which abrasion or the like is hard to be generated at starting and stopping, and preferable rotation of the dynamic pressure bearing is realized. SOLUTION: This ceramic dynamic pressure bearing comprises: a first member 14 having a cylindrical outer peripheral surface; and a second member 15 having a cylindrical insertion hole 15a. The first member 14 is inserted into the insertion hole 15a. Radial dynamic pressure gap is formed between an inner surface of the insertion hole of the second member 15 and the outer peripheral surface of the first member 14. Both of the first member 14 and the second member 15 have percentage contents of Al component in terms of Al2 O3 of 90 to 99.5 mass %, and are constituted of alminous ceramic including sintering assistant component of oxide system of 0.5 to 10 mass % in terms of oxide. An arithmetic mean roughness Ra1 measured in an axial direction of an outer peripheral surface 15b of the second member 15 and an arithmetic mean roughness Ra2 measured in a peripheral direction of the second member 15 are adjusted to be not more than 0.2 μm.