Fluid dynamic bearing system

Abstract

The fluid dynamic bearing system has at least one stationary part, and at least one rotating part that is supported rotatable about a rotational axis with respect to the stationary part. A bearing gap filled with bearing fluid is formed between mutually opposing surfaces of the stationary and of the rotating part. The bearing system includes at least one fluid dynamic radial bearing and at least one fluid dynamic axial bearing that are disposed along sections of the bearing gap. In one aspect of the invention, an annular sealing gap for sealing open ends of the bearing gap has one end connected to the bearing gap and one end connected to an annular reservoir, the outside radius of the reservoir measured from the rotational axis being larger than the outside radius of the sealing gap.

Description

BACKGROUND OF THE INVENTION[0001]The invention relates to a fluid dynamic bearing system, used preferably for the rotatable support of a spindle motor. Spindle motors supported in this way are used, for example, for driving hard disk drives.DESCRIPTION OF THE PRIOR ART[0002]A fluid dynamic bearing system generally comprises at least two bearing parts that are rotatable with respect to one another and that form a bearing gap filled with a bearing fluid, such as bearing oil, between associated bearing surfaces. Bearing patterns that are associated with the bearing surfaces and that act on the bearing fluid are provided using a well-known method. In a fluid dynamic bearing, the bearing patterns taking the form of grooved patterns are formed as depressions or raised areas usually on one or on both bearing surfaces. The bearing patterns act as bearing and / or pumping patterns that generate hydrodynamic pressure within the bearing gap when the bearing parts rotate with respect to one anoth...

AI Technical Summary

Benefits of technology

[0008]It is the object of the invention to provide a fluid dynamic bearing that is constructed so as to allow bearing fluid to be easily and reliably filled into the bearing gap.

[0013]The edges of the reservoir or the adjoining surfaces of the bearing may additionally be provided with a barrier film to prevent these surfaces from being moistened with bearing fluid.

[0016]According to the invention, the bearing to be filled is thus put in position and the entire amount of bearing fluid to be filled in is fed into the reservoir. The bearing can subsequently be removed from the filling device and the bearing fluid found in the filling reservoir can then slowly travel by means of capillary action right through the sealing gap into the bearing gap. This process can take well over ten minutes. The advantage here is that the actual filling process for filling the bearing fluid into the reservoir is very fast and the bearing can then be removed from the filling device and placed at rest where the bearing fluid can fully migrate into the bearing gap. In a preferred embodiment of the invention, the surfaces that border the filling reservoir are slanting surfaces that facilitate the bearing fluid to flow into the sealing gap and from there to the bearing gap. Due to the slanting surfaces of the filling reservoir, no bearing fluid remains in the reservoir region.

[0018]The sealing gap, which is disposed between the reservoir and the bearing gap, forms a capillary seal that prevents leakage of bearing fluid from the bearing gap back into the reservoir. The sealing gap may comprise a tapered capillary seal, i.e. it may have a region that widens into a taper. In addition to the capillary seal, the sealing means may comprise a dynamic pumping seal that is marked by pumping patterns disposed on the stationary or on the rotating bearing part.

Problems solved by technology

The introduction of bearing fluid into the bearing gap is quite complex, because the bearing gap is only a few micrometers wide.

In the case of bearings open at both ends, however, it is consistently difficult to introduce the bearing fluid into the region of the open ends of the bearing using an appropriate dosing device.

In particular, the region of the lower open end of the bearing gap is mostly hidden under the hub or bearing bush and thus hard to reach.

Because the lower bearing gap opening is difficult to reach, there is the risk of contamination of the bearing with bearing fluid during filling.

Since a sealing ring that comes into contact with the bearing fluid is used, possible contamination of the surfaces of the bearing cannot be ruled out.