Dynamic pressure gas bearing structure

A dynamic pressure gas bearing structure comprising a columnar shaft body and a hollow cylindrical bearing body being opposed to said shaft body with a clearance in the radial direction, wherein

• a substantially cylindrical gap is defined by the outer peripheral surface of said shaft body and the inner peripheral surface of said bearing body when said shaft body and said bearing body are so arranged that central axes thereof are aligned with each other,
• the thickness (h) of said gap is defined by the distance between points where a radial straight line passing through said central axes intersects with outlines corresponding to the outer peripheral surface of said shaft body and the inner peripheral surface of said bearing body respectively,
• said gap has at least one gap change portion where its thickness is changed with respect to a central angle corresponding to the circumference along the outer periphery of said shaft body,
• a gap change rate .alpha. is expressed as follows, assuming that D.sub.1 represents the diameter of said shaft body, .sub..DELTA. h represents the amount of change of the thickness of said gap, and .sub..DELTA. .theta. represents the amount of change of said central angle, and
• .alpha.=(.sub..DELTA. h/D.sub.1)/.sub..DELTA. .theta.[/.degree.]
• said gap change portion has a gap change rate in the following range:
• 1. 0.times.10.sup.-4 .ltoreq..alpha.<10.0.times.10.sup.-4.