Groove configuration for a fluid dynamic bearing
A groove configuration that improves angular stiffness in a fluid dynamic bearing is provided. A primary groove and a secondary groove are formed on a journal bearing or thrust bearing surface. The secondary groove apex induces a heightened pressure response at a localized area to counteract angular displacement. The primary groove extends a greater circumferential distance about the bearing surface as compared to the secondary groove. The secondary groove apex is also situated closer to an axial end of the journal bearing, or closer to an outer diameter of the thrust bearing, as compared to the primary groove apex. Bearing wear is prevented or minimized under gyroscopic loading. The improved angular stiffness may result in the heads of a storage device being accurately aligned with disc storage tracks. Discs may thus be designed with increased track densities, allowing for smaller discs and increased storage capacity of discs.
1. An apparatus comprising:
a fluid dynamic bearing defined between an inner component and an outer component, wherein the inner component and the outer component are positioned for relative rotation;
a groove configuration defined on at least one of the inner component and the outer component, wherein the groove configuration comprises:
a first primary leg connected to a second primary leg forming a primary apex therebetween; and
a first secondary leg connected to a second secondary leg forming a secondary apex therebetween, wherein
the first primary leg and the second primary leg pump fluid toward, and increase pressure at, the primary apex,
the first secondary leg and the second secondary leg pump fluid toward, and increase pressure at, the secondary apex,
the first primary leg and the second primary leg extend a greater circumferential distance about the fluid dynamic bearing surface as compared to the first secondary leg and the second secondary leg, and
the secondary apex is situated closer to an axial end of a journal bearing,
as compared to the primary apex.
2. The apparatus as in claim 1 , wherein the first primary leg and the second primary leg are connected to the first secondary leg and the second secondary leg.
3. The apparatus as in claim 1 , wherein the first secondary leg and the second secondary leg are situated a predetermined circumferential distance from an end of the first primary leg and the second primary leg.
4. The apparatus as in claim 1 , wherein the first secondary leg extends at an angle in the range of 15 degrees to 30 degrees relative to a circumferential direction about the fluid dynamic bearing.
5. The apparatus as in claim 1 , wherein the first secondary leg extends at a 90 degree angle relative to a centerline axis length of a rotating axis of one of the inner component and the outer component.
6. The apparatus as in claim 1 , wherein the first secondary leg length and the second secondary leg length are in the range of:
10 percent to 50 percent of the first primary leg length and the second primary leg length, when the groove configuration is formed on a journal bearing surface.
7. The apparatus as in claim 1 , wherein the groove configuration further comprises a first tertiary leg connected to a second tertiary leg, forming a tertiary apex therebetween, wherein the first primary leg and the second primary leg extend a greater circumferential distance about the fluid dynamic bearing as compared to the first tertiary leg and the second tertiary leg, and wherein the primary apex is situated between the secondary apex and the tertiary apex.
8. The apparatus as in claim 1 , wherein the groove configuration comprises a chevron pattern, a herringbone pattern, or a sinusoidal pattern.
9. The apparatus as in claim 1 , wherein the sum of a circumferential length of the second secondary leg and the second primary leg is set greater than the sum of the circumferential length of the first secondary leg and the first primary leg, wherein the second secondary leg is situated closer to the axial end of the journal bearing as compared with the first secondary leg, and wherein the second primary leg is situated closer to the axial end of the journal bearing as compared with the first primary leg.