Zero static-friction actuator pivot bearing for production disk drives

Abstract

A hydrostatic bearing assembly, with an integral rotating-shaft hydrodynamic pump, adapted for use as a stiff zero static-friction actuator pivot bearing for the head-stack assembly of a disk drive data storage apparatus. The zero static-friction pivot bearing avoids all “limit cycling” and “sticking” problems arising from static bearing friction during micro-tracking operations. The motor-driven hydrodynamic pumping element is disposed coaxially to the zero static-friction hydrostatic bearing element in a single assembly adapted for use as an actuator pivot bearing. The hydrodynamic pumping element and the hydrostatic bearing element both use a plurality of spaced-apart radial journal-bearing layers and a plurality of axial thrust-bearing layers to provide stiffness in all directions at any rotational velocity. The lubricating fluid pressure within the hydrodynamic pumping element is controlled on both sides of every bearing layer by coupling all radial journal-bearing layers and axial thrust-bearing layers to a circumferential undercut (or overcut) and by coupling these circumferential undercuts to ambient pressure through a plurality of fluid-filled passages in the several rotating and stationary elements. The fluid bearing layers are coupled to form a continuous pressure-controlled fluid film sealed at three ends by surface tension. In an actuator pivot bearing for a disk drive data storage apparatus, the hydrodynamic pump motor can be operated under the control of a dual phase-locked motor drive controller to synchronize it with a spindle motor element in a manner that cancels vibrations arising from both motors.