Radial pumping oil seal for fluid dynamic bearing motor
View Patent ↗An improved rotational motor, such as a spindle motor for a disc drive, is provided. The motor first comprises a hub having a shaft portion and a horizontal body portion. The motor also comprises a sleeve surrounding the shaft portion of the hub. A fine first vertical gap is retained between the shaft and the inner diameter of the surrounding sleeve. In addition, a fine horizontal gap is provided between the upper hub portion and the top of the sleeve. A third gap is preferably provided between the hub and an outer diameter of the sleeve. The first vertical gap is filled with a lubricating liquid, such as a clean oil. A capillary seal is provided in the third gap. In one embodiment, the lubricating liquid extends into the horizontal gap. Oil pumping grooves are machined along the horizontal fluid gap. When the hub is rotated, the oil pumping grooves impel oil towards the shaft. This prevents any portion of the first vertical gap from becoming un-lubricated during rotation of the shaft.
1. A fluid dynamic bearing defined by the interface of a hub and a sleeve, the hub having a vertical shaft portion configured to rotate within the sleeve, and a horizontal body portion configured to rotate above the sleeve, the bearing comprising:
a first gap region between the shaft portion of the hub and the sleeve;
a second gap region between the horizontal body portion of the hub and the sleeve, the second gap region having a first end in fluidic communication with the first gap egion and a second end exposed to an ambient environment;
a volume of lubricating fluid within the first gap and at least proximal the first end of the second gap region; and
an oil pumping groove pattern disposed at least partially along the second gap, the oil pumping groove pattern pumping the lubricating liquid toward the first end of the second gap region during relative rotation of the hub and the sleeve.
2. The fluid dynamic bearing of claim 1 , wherein:
the first gap region comprises a substantially vertical gap; and
the second gap region comprises a substantially horizontal gap portion.
3. The fluid dynamic bearing of claim 1 , further comprising a third gap region between the hub and an outer diameter portion of the sleeve.
4. The fluid dynamic bearing of claim 3 , wherein the third gap is configured to form a capillary seal.
5. The fluid dynamic bearing of claim 1 , wherein the hub further comprises a radial shoulder for receiving a disc.
6. The fluid dynamic bearing of claim 5 , wherein the hub and sleeve are part of a spindle motor for a disc drive system.
7. The fluid dynamic bearing of claim 1 , wherein the shaft portion is adapted to rotate within the sleeve on a counterplate.
8. The fluid dynamic bearing of claim 1 , wherein the oil pumping groove pattern defines at least one groove formed in a bottom surface of the horizontal body portion of the hub.
9. The fluid dynamic bearing of claim 1 , wherein the oil pumping groove pattern defines at least one groove formed in a top surface of the sleeve.
10. The fluid dynamic bearing of claim 1 , wherein the oil pumping groove pattern defines a spiral pattern.
11. A hub and sleeve bearing, comprising:
a hub comprising a shaft portion having an outer cylindrical surface and a second portion surrounding and coupled to a first end of the cylindrical surface of the shaft portion, the second portion having an annular surface disposed substantially perpendicular to the long axis of the outer cylindrical surface of the shaft portion;
a sleeve comprising an inner cylindrical surface that is configured to face the outer cylindrical surface of the shaft portion of the hub in a substantially coaxial orientation, the inner cylindrical surface and the outer cylindrical surface defining a first gap, wherein at least a portion of at least one of the inner cylindrical surface and the outer cylindrical surface comprises a first groove pattern formed therein, the first groove pattern being configured as a fluid dynamic journal bearing and
wherein the sleeve further comprises an annular surface disposed substantially parallel to the annual surface of the second portion of the hub and defining a second gap, the second gap having a first end region in fluidic communication with the first gap and a second end region exposed to an ambient environment, wherein at least a portion of at least one of the annular surface of the sleeve and the annular surface of the second portion of the hub comprises a scond groove pattern formed therein, the second groove pattern configured to pump fluid away from the second end region and toward the fluid dynamic journal bearing.
12. The hub and sleeve bearing assembly of claim 11 , wherein the second gap is further configured to form a capillary seal by diverging distally to the axis of the outer cylindrical surface.
13. The hub and sleeve bearing assembly of claim 11 , wherein the shaft portion of the hub further comprises a radial end surface distal the first end outer cylindrical surface, the radial end surface disposed to face a radial surface of the sleeve, wherein the radial end surface of the shaft portion of the hub and the radial surface of the sleeve are further disposed to be in contact when the hub and sleeve are relatively stationary and to define a third gap when the hub rotates relative to the sleeve.