Patent ID: 8506167
Filing Date: 2013-08-13
Classification: F16C,G11B,H02K

Abstract:
1. A dynamic bearing device comprising: a shaft member having a flange portion; a member axially opposing the flange portion; a thrust bearing surface formed on the member axially opposing the flange, the thrust bearing surface including a dynamic pressure generating groove area having a plurality of dynamic pressure generating grooves being arranged thereon; a thrust receiving surface provided on the flange portion so as to be opposed to the thrust bearing surface in an axial direction; and a thrust bearing gap formed between the thrust bearing surface and the thrust receiving surface, the thrust bearing gap for generating a pressure by a dynamic pressure effect of a fluid so as to support the shaft member in an axial direction in a non-contact manner by the pressure, wherein a reduced portion having an axial width decreasing in a radially outward direction is disposed in the thrust bearing gap, the reduced portion being formed by an inclined plane disposed at the thrust bearing surface, the dynamic pressure generating groove area is disposed on the inclined plane, a depth of each groove in the plurality of dynamic pressure generating grooves being constant relative to the inclined plane, and a pumping power of the dynamic pressure generating grooves being maximized in a radially outermost portion of the reduced portion, the thrust bearing surface has an inner dented portion and an outer dented portion each facing the thrust receiving surface, the inner dented portion is dented further than the dynamic pressure generating groove area and is disposed in an area radially inward of the dynamic pressure generating groove area, the outer dented portion is dented further than the dynamic pressure generating groove area and is formed in an area radially outward of the dynamic pressure generating groove area, and the thrust bearing gap has a uniform portion with a constant width formed on an inner diameter side of the reduced portion, and a highest pressure in the thrust bearing gap is generated in a center of the uniform portion, each dynamic pressure generating groove of the dynamic pressure generating grooves has a spiral shape, an outer-diameter end and a groove width, and for each dynamic pressure generating groove of the dynamic pressure generating grooves, the groove width increases as the dynamic pressure generating groove extends radially outwardly toward an outer periphery of the thrust bearing surface such that a largest dimension of the groove width is disposed at the outer-diameter end, and wherein the thrust bearing surface has an inner stepped portion between the inclined plane and the inner dented portion, and an outer stepped portion between the inclined plane and the outer dented portion, a radially outermost portion of the dynamic pressure generating grooves is opened into the outer stepped portion, and a radially innermost portion of the dynamic pressure generating grooves is opened into the inner stepped portion.