MINIATURE FLUID DYNAMIC BEARING WITH IMPROVED LOAD CAPACITY

In this paper a novel design is proposed to improve the load capacity of fluid dynamic bearing (FDB) for miniature spindle motors and small-form-factor data storage applications. In contrast to conventional miniature FDB with two sets of herringbone grooves on its inner surface, the proposed miniature FDB comprises another one set of herringbone grooves on its outer surface. The proposed miniature FDB is verified numerically utilizing commercial software Advanced Rotating Machinery Dynamics (ARMD). The simulation results show that compared to the conventional miniature FDB, the proposed miniature FDB can obviously improve the load capacity of the bearing system. Overall, the results presented in this study show that the proposed miniature FDB provides another solution for miniature spindle motor applications.

Micro Pattern Forming of Spiral Grooves in a Fluid Dynamic Bearing Using Desktop Forming System

This research explores the micro-forming process of spiral groove pattern on Fluid Dynamic Bearing(FDB), which is utilized in precision driving part of the hard disk drive(HDD), using micro desktop forming system. While EDM and ECM process has been widely used to engrave the precision pattern which generates dynamic pressure on FDBs, micro forming process is newly proposed in this study to increase the productivity and to reduce the product costs. At first, desktop forming system is designed for spiral groove pattern forming. FE simulations are followed in order to evaluate the feasibility of micro-forming. The simulation results show that forming loads of 1,500Kgf is required to fabricate micro patterns with the depth of 15 μm. Finally the formability test is carried out with various forming loads. Deformed shapes and forming loads obtained from the test are compared with those from the analysis. The results fully demonstrate that micro pattern forming techniques are available to fabricate micro spiral groove patterns in FDB.

Fluid Dynamic Forces Acting on the Rotor of a Shaft-Less Miniature Pump

For a miniature pump used in many social fields, it is expected to be able to operate without any shaft and mechanical bearing. Recently, a double-suction shaft-less miniature pump has been developed at the Lab of Multiphase Flow and Biomechanics, Tsinghua University. Because the rotor of the miniature pump is rotating inside the pump casing, a fluid dynamic bearing is necessary to support the pump rotor. In this paper, a fluid dynamic bearing was designed to support the rotating impeller and motor rotor, and was manufactured combined with the miniature pump. In order to evaluate the bearing capability, the numerical simulation based on Reynolds equation was conducted for the fluid dynamic bearing. Both the performance experiment of the pump and the numerical results for the bearing indicate that the fluid dynamic bearing designed for the miniature pump in this study is usable and reliable. It is also noted that the performance including the liquid film thickness distribution, static pressure distribution, bearing capability, etc. of the bearing has been reasonably predicted using the present numerical methods. Further, the bearing capability increased remarkably with eccentric ratio between the bush and journal, and rotational speed of the pump for the fluid dynamic bearing.