A method of reducing the windage power loss in a laser scanner motor using spiral-groove aerodynamic thrust bearings functioning as a viscous vacuum pump

We propose a spiral-groove aerodynamic thrust bearing functioning as a viscous vacuum pump in a laser scanner motor to reduce the windage power loss of a polygon mirror. The proposed bearing pumps out the air in the scanner housing using the pumping effect of the spiral-groove thrust bearing, reducing the inner pressure of the housing. The pumping performances and the static characteristics of the spiral-groove thrust bearings were investigated numerically and experimentally. Two numerical calculation methods were used to study the pumping characteristics of the spiral-groove thrust bearing. It was found that a bearing with 15 spiral grooves reduced the inner pressure of the housing to <0.01 MPa at 20,000 rpm and at bearing clearance of 2.5 μm, and this has sufficient load-carrying capacity to support the rotating shaft and the mirror.