Air bearing head displacement sensor and positioner

Abstract

A magnetic head slider for supporting a flying head on a magnetic disk has a plurality of rails extended longitudinally between the slider and the disk which provide the air bearing surface and define a channel parallel to the motion of the data track. A flexible beam is affixed to the leading edge of the channel providing a cantilever structure. A magnetic head is mounted on the free end of the cantilever. A pair of oppositely polarized piezoelectric crystals are mounted on the cantilever assembly. When energized by an electrical driving source, the cantilever beam is flexed upwards or downwards thereby changing the distance of the magnetic head from the disk. A capacitive proximity sensor is coupled to the magnetic head for sensing the height of the head above the data track. The output of the sensor is fed to the driving source and energizes the piezoelectric crystals in the polarity desired for the corresponding deflection of the cantilever structure. Thus, the sensor continuously monitors the height of the magnetic head from the track and provides a correction signal to maintain the transducer at a constant predetermined height above the track. In a preferred embodiment, the beam is formed from silicon nitride composition and treated by means of an ion implantation process to provide a conductive electrode for the capacitance proximity sensor. By connecting the proximity sensor, the deflectable piezoelectric transducer, and the electrical driving circuit in a closed loop, the magnetic head is maintained at a predetermined distance from the magnetic disk, notwithstanding perturbations in disk surface and changes due to dynamic instability.