Pumping characteristics of a herringbone-grooved journal bearing functioning as a viscous vacuum pump

A laser scanner motor with low power and high speed has been developed. Thi s scanner motor uses a herringbone-grooved journal bearing which functions as a viscous vacuum pump. The windage power loss of a polygon mirror is red uced since the air inside the pump housing is pumped out by hel-ringbone-gr ooved viscous vacuum action. rn this paper, the theoretical pumping charact eristic of this bearing is investigated, using the narrow-groove theory and accounting for first-order slip flow. The effects of various design parame ters on the pumping characteristics are discussed. Optimum geometric design parameters were found to obtain the minimum inner chamber pressure of the housing. The theoretical predictions considering slip flow effects are in g ood agreement with experimental measurements.