A generalized Reynolds equation and its perturbation equations for fluid dynamic bearings with curved surfaces

We derived a generalized Reynolds equation and its perturbation equations using meridian and angular coordinates to calculate the characteristics of fluid dynamic bearings (FDBs) with various shapes, namely journal, thrust, conical, and spherical bearings. They were transformed to the finite element equation to calculate the pressure, load, stiffness, and damping coefficients of FDBs. We verified our proposed method by comparing the measured flying height of the coupled conical and journal bearings in the spindle motor of a hard disk drive with the simulated height. Additionally, we investigated their characteristics according to flying height and conical angle.