Importance

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Abstract

A bearing portion includes an upper dynamic pressure portion, a lower dynamic pressure portion, and an intra-bearing space defined between a lower surface of a fluid in the upper dynamic pressure portion and an upper surface of a fluid in the lower dynamic pressure portion, and not including the fluid. An airway defined in a shaft includes an inner opening arranged to be in communication with the intra-bearing space, and an outer opening arranged to be in communication with an extra-bearing space. Each of the inner and outer openings is defined in a side surface of the shaft. The extra-bearing space and the intra-bearing space are arranged to be in communication with each other through the airway. The airway is arranged to extend substantially in a straight line or lines, is angled with respect to a central axis, and has no other openings than the inner and outer openings. This contributes to preventing a gas inside of a housing from leaking out of the housing through the airway. In addition, since the airway is arranged to extend substantially in a straight line or lines to join the inner and outer openings to each other, the airway can be defined by a single process using a drill, an EDM, or the like.

First Claim