Patent ID: 7237955
Filing Date: 2007-07-03
Classification: F16C,G11B

Abstract:
1. A hydrodynamic bearing comprising: a sleeve having a bearing hole at the nearly central portion thereof, a shaft rotatably inserted into said bearing hole of said sleeve, and a nearly disc-shaped flange secured to one end of said shaft, one face of said flange opposing to the end face of said sleeve and the other face thereof opposing to a thrust plate provided to hermetically seal a region including said end face of said sleeve, wherein herringbone-shaped first and second dynamic pressure generation grooves are provided on at least one of the inner circumferential face of said sleeve and the outer circumferential face of said shaft so as to be arranged in the direction along said shaft, herringbone-shaped third dynamic pressure generation grooves are provided on at least one of the opposed faces of said flange and said thrust plate, said first, second and third dynamic pressure generation grooves are filled with oil having a kinematic viscosity of 4 cSt or more at 40° C. of temperature, one of said sleeve and said shaft is secured to a base and the other is secured to a rotatable hub rotor, and where an outside diameter of the herringbone pattern of said third dynamic pressure generation groove is designated as d wherein A is a value of 0.05 or more to less than 1.0.