Patent ID: 7215508

Claim:
A ceramic dynamic-pressure bearing comprising: a first member formed of ceramic and having a cylindrical outer surface, a second member formed of ceramic and having a cylindrical reception hole formed therein, the first member being inserted into the reception hole of the second member in such a manner as to be rotatable, relative to the second member, about an axis, and a thrust plate formed of ceramic facing at least one end face of the second member as viewed along the axis of rotation, the end face of the second member and a face of the thrust plate in opposition to the end face serving as thrust dynamic-pressure gap definition surfaces so as to define a thrust dynamic-pressure gap therebetween; and the ceramic dynamic-pressure bearing satisfies at least one of the conditions (iv) and (v): (iv) the thrust dynamic-pressure gap definition surface of the second member which faces the thrust plate is crowned such that an inner circumferential portion thereof projects by an amount greater than 0 μm and not greater than 2.5 μm with respect to an outermost circumferential portion thereof; and (v) the thrust dynamic-pressure gap definition surface of the thrust plate which faces the second member is crowned such that an inner circumferential portion thereof projects by an amount greater than 0 μm and not greater than 2.5 μm with respect to an outermost circumferential portion thereof.