DESIGN OPTIMIZATION OF SPIRALLY GROOVED THRUST AIR BEARINGS FOR POLYGON MIRROR LASER SCANNERS

Polygon mirror laser scanners have been widely used in computer peripheral equipment and office automation systems, and improvement in scanning quality has been desired. In light of this, the use of self-acting air bearings has been recommended in spindle design to realize superior performance in terms of rotational speed and rotational errors. This study concerns the analysis of characteristics of spirally grooved thrust air bearings. Namely, it reports the rigidity, load capacity, power loss and critical damping factors. Employed in this study are the finite element method (FEM) and the computer simulation method in order to obtain a numerical solution to the Reynolds equation. Based on calculation results, the load characteristics and the effects of various design parameters of the bearing are discussed, and optimization principles for designing the bearing are proposed. The proposal may be summarized as follows. ( 1 ) The bearing rigidity and load capacity are closely related to the spiral groove width, depth, length in the radial direction and spiral groove pump-in angle, and the number of grooves should be as large as possible. ( 2) Decrease in the bearing clearance and increase in the bearing outer radius together achieve the best damping characteristics.