Spindle motor and magnetic disc device using thereof

摘要

A magnetic disc device includes a magnetic disc and a rotary shaft rotatably supporting the magnetic disc. The magnetic disk is laid in a bearing casing having one end opened, and having a bearing member at the other end. The rotary shaft is supported by a first hydrodynamic fluid bearing and a second hydrodynamic fluid bearing provided in the bearing member. The inner diameter D and the width L of the first hydrodynamic fluid bearing exhibits such a relationship as L/D>1.