Patent ID: 7381034

Claim:
In a hydrodynamic pressure bearing type pump in which a shaft rotates to generate hydrodynamic pressure to let fluid flow, a hydrodynamic pressure bearing type pump comprising: a main body including an outer housing and an inner housing surrounded by the outer housing, the outer housing having a fluid flow inlet formed at one end portion thereof and a fluid flow outlet formed at the other end portion thereof; and a rotating portion disposed within a fluid flow passage of said fluid within said inner housing of said main body to generate hydrodynamic pressure to let said fluid flow into said fluid flow inlet and through said inner housing and to let said fluid flow from said inner housing and through said fluid flow outlet to the outside, said rotating portion comprising: a shaft extending along an axis of rotation and having a first shaft end and an opposite second shaft end, the shaft having a first shaft piece and a second shaft piece integrally connected to each other along the axis of rotation, the first shaft piece having a first shaft piece diameter and a second shaft piece having a second shaft piece diameter being larger than the first shaft piece diameter; a hydrodynamic pressure bearing connected to the first shaft end and operative for generating hydrodynamic pressure to let said fluid flow into said fluid flow inlet and through said inner housing and to let said fluid flow from said inner housing and through said fluid flow outlet to the outside when said shaft is rotated; and a rotation force generating portion disposed within said main body to generate rotation force for rotating said shaft when it is energized, the rotation force generating portion including a rotor magnet connected to the second shaft end and a coil embedded into the outer housing and surrounding the rotor magnet and a portion of the inner housing, said hydrodynamic pressure bearing including: a hydrodynamic pressure bearing body member having an inner cylindrical surface defining a shaft-receiving hole formed axially therethrough, the shaft-receiving hole sized to slidably and rotatably receive the shaft, the inner cylindrical surface having a first hydrodynamic pressure generating groove formed at the position near the side of said fluid flow inlet; and a second hydrodynamic pressure generating groove formed at the position near the side of said fluid flow outlet, wherein the first shaft piece and the second shaft piece are rotatably received in the shaft-receiving hole such that, as viewed along the axis of rotation, at least a portion of first hydrodynamic pressure generating groove surrounds the first shaft piece and the second hydrodynamic pressure generating groove in its entirety surrounds the second shaft piece.