Patent attributes
A sleeve 1 is fixed on a base. Radial dynamic-pressure generating grooves 1A and 1B are provided on an inner surface of the sleeve 1. A thrust plate 4 hermetically seals a lower opening end of the sleeve 1. A shaft 2 is inserted inside the sleeve 1, being allowed to revolve. A flange 3 is fixed at the bottom end of the shaft 2, and its lower surface is placed close to an upper surface of the thrust plate 4. Thrust dynamic-pressure generating grooves 3A and 3B are provided on the surfaces of the flange 3. Gaps A–H among the sleeve 1, the shaft 2, the flange 3, and the thrust plate 4 are filled with a lubricant 5. Hollows 1C–1F are provided on the inner surface of the sleeve 1. The gaps A and C over the thrust dynamic-pressure generating grooves 3A and 3B and their vicinities are narrower than the surrounding gaps B and D (A<B, A<D, C<B, and C<D), and the surrounding gaps B and D are narrower than the gap H in the upper opening end of the sleeve 1 and its vicinity (B<H and D<H). The gaps E and G over the radial dynamic-pressure generating grooves and their vicinities are narrower than the surrounding gaps D and F (E<D, E<F, G<D, and G<F), and the surrounding gaps D and F are narrower than the gap H in the upper opening end of the sleeve 1 and its vicinity (D<H and F<H).
