Patent ID: 6663287
Filing Date: 2003-12-16
Classification: F16C,H02K

Abstract:
A thrust dynamic pressure bearing apparatus comprising:a shaft member; a thrust plate having a bore in which the shaft member is inserted to thereby affix the shaft member to the thrust plate; a thrust bearing member disposed opposite to the thrust plate in an axial direction of the shaft member, wherein a gap is formed between opposing surfaces of the thrust plate and the thrust bearing member to thereby form a thrust dynamic bearing section in the gap; a lubrication fluid filled in the thrust dynamic bearing section; a fluid pressure generating device that generates dynamic pressure in the lubrication fluid that rotatably support the shaft member and the thrust bearing member; and insertion joint means that generates a compression stress to be applied from an internal surface of the bore of the thrust plate to an external surface of the shaft member to affix the thrust plate and the shaft member to each other, wherein the bore of the thrust plate having peripheral edge sections on both end faces of the thrust plate in the axial direction, the peripheral edge sections having chamfer sections Ca and Cb, wherein the distances from end faces of the thrust plate in the axial direction to ends of the insertion connection section having the length Lh are defined by axial lengths La and Lb, and wherein the thrust plate has an external diameter OD, an internal diameter ID and a thickness T in the axial direction, and the chamfer sections Ca and Oh have the axial lengths La and Lb in the axial direction and lengths Ra and Rb in a radial direction, respectively, which have relations as follows: ODâˆ’ID&gE;T, and La&gE;0.01T, and Lb&gE;0.01T, and Ra&gE;0.01T, and Rb&gE;0.01T, and wherein, when an equation ODâˆ’ID=4T&agr; (&agr;&lE;4) is established, the lengths La and Lb have relations with a given value of &agr; as follows: La&lE;&agr;Lb, or Lb&lE;&agr;Lb, and â€ƒwherein the axial lengths La and Lb have a relation with respect to the length Lh as La&lE;0.2Lh, or Lb&lE;0.2Lh.