FLUID DYNAMIC PRESSURE BEARING AND SPINDLE MOTOR

摘要

PROBLEM TO BE SOLVED: To provide larger load capacity and shaft rigidity on a fluid dynamic pressure bearing at least furnished with a thurst bearing on which a thrust dynamic pressure groove made of a plural number of folded type spiral grooves is formed. SOLUTION: A pattern of a thrust dynamic pressure groove G2 is constituted by regularly arranging twelve pieces of folded type spiral grooves G20 on a circumference. Thereafter, an inside spiral groove G21 of a groove angle B extending outside to a turning point B of a radius r1 from a starting point A of an inside radius r0 is made a roughly triangular groove to draw an exponential function curve toward the outside from the starting point. Additionally, an outside spiral groove G22 of the groove angle B extending outside further to a terminal point C from the turning point B is made a roughly rectangular groove to draw an exponential function curve toward the outside from the turning point.