The journal radial runout of a hybrid flexure pivot-tilting pad bearing is analyzed under step load to improve the spindle rotation accuracy. The influences of the bearing structure and operating parameters on spindle rotation accuracy are investigated by analyzing the maximum overshoot and the transition time of the journal. A pressure distribution model and a torque balance equation of pads
as well as a journal movement equation
are established. Numerical simulation results of the rotor center trajectory are obtained by combining the finite difference method with the Euler method. The results show that when the rotational speed keeps the same
the maximum overshoot and the transition time reduce by either increasing the preload or reducing the radius clearance. Reducing the area or width-length ratio of the oil chamber decreases the maximum overshoot. When the width-length ratio is the same
the transition time increases at the beginning and then decreases with the increasing of rotational speed. The maximum overshoot increases with the increasing of rotational speed within the certain scope. These results indicate that the spindle rotation accuracy can be improved by either increasing the preload coefficient or reducing the radius clearance.
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references
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