Spindle motor with multiple thrust plate fluid dynamic bearing

DETAILED DESCRIPTION Thus, it is an object of the present invention to create an improved hydrodynamic bearing which is relatively insensitive to changes in load and rotational speed.
Another objective of the invention is to provide a hydrodynamic bearing having increased stiffness.
Another objective of the invention is to provide a hydrodynamic bearing useful in a spindle motor for a disc drive or the like which is stiffer than known standard spindle motors so that the stability of the system and specifically of the actuator arm and transducer relative to the rotating disc is optimized.
These and other objectives of the present invention are achieved by providing a hydrodynamic bearing useful as a bearing cartridge or as the cartridge may be incorporated into a spindle motor or the like, where the bearing includes a shaft and at least two independent bearings each comprising a thrust plate supported on the shaft and a counter plate and/or a sleeve which is capable of relative rotation around the shaft.
The use of multiple thrust plates maintains and even increases the stiffness of the overall design without any attendant increase in power consumption.
Further, the manufacturing and assembly process does not become more difficult because the gap may be maintained at a reasonable width.
More specifically, in an exemplary embodiment the bearing includes a fixed shaft and a sleeve rotating around and surrounding the shaft, and at least first and second thrust plates separated by a portion of the shaft.
In one example, the shaft includes a central reservoir or hole and one or more ports between the reservoir and a gap defined between the shaft and the sleeve to allow fluid movement through the hydrodynamic bearing.
Grooves can be found on shaft or sleeve to enhance fluid circulation through the gaps defined by the shaft and the thrust plates supported thereon and the surrounding sleeve with counter-plates, as well as to increase stiffness.
Grooves could also appear on one or more of the counterplates, or on a thrust plate surface, or a combination of both thrust plate and counterplate