Closed loop micro dosing for oil lubrication of precision bearings in high speed machine spindles using capacitive flow metering

A micro dosing system is presented, that inhibits a novel method of micro fluidic flow metering. Developed for micro lubrication of low viscous oil in high speed bearings of machine spindles it was shown to precisely deliver flow rates from 21 nl/s up to 50 nl/s with medium size sensor and 2 nl/s to 20 nl/s with small size sensor. The flow metering is based on speed measurement of moving phase boundaries of a two-phase slug flow in a fluidic micro channel, generated by two silicon micro pumps, using capacitive measurement with an array of segmented electrodes.