Hydrodynamic bearing device
View Patent ↗A hydrodynamic bearing device in which an incline between the center line of a shaft and the center line of a sleeve can be eliminated, rotational precision improved, and NRRO reduced, characterized in that different bearing lengths (L 1 and L 2 ) are selected for radial bearing portions and that at least any one parameter selected from among groove depths of pressure generating grooves, groove angles formed between the grooves and the radial direction of an shaft, and groove width ratios [a/(a+b)] of groove width (a) in relation to the sum (a+b) of the groove width (a) and ridge width (b) is caused to vary among the plurality of radial bearing portions.
1. A hydrodynamic bearing device, comprising:
a sleeve and a shaft rotatably located around a common axis, said axis defining an axial direction;
fluid interposed between said sleeve and shaft;
a plurality of bearing portions extending along the axial direction of at least one of an external peripheral surface of the shaft or an internal peripheral surface of the sleeve, each bearing portion having a different bearing length in the axial direction; and
said plurality of bearing portions having pressure generating grooves, each groove having a depth, each bearing portion having a different groove depth.
2. The hydrodynamic bearing device according to claim 1 , wherein said plurality of radial bearing portions comprises a first bearing portion having a first length and a first groove depth and a second bearing portion having a second length and a second groove depth, said first length being greater than said second length and the first groove depth being greater than the second groove depth.
3. The hydrodynamic bearing device according to claim 1 , wherein the fluid comprises a gas.
4. The hydrodynamic bearing device according to claim 1 , wherein the pressure generating grooves comprise a herringbone shape.
5. A hydrodynamic bearing device, comprising:
a sleeve and a shaft rotatably located around a common axis, said axis defining an axial direction;
fluid interposed between said sleeve and shaft;
a plurality of bearing portions extending along the axial direction of at least one of an external peripheral surface of the shaft or an internal peripheral surface of the sleeve, each bearing portion having a different bearing length in the axial direction; and
said plurality of bearing portions having pressure generating grooves in at least one of said surfaces, each groove having a width A, and being separated from an adjacent groove by a ridge having a width B, each portion having a different groove width ratio A/(A+B).
6. The hydrodynamic bearing device according to claim 5 , wherein the fluid comprises a gas.
7. The hydrodynamic bearing device according to claim 5 , wherein said plurality of radial bearing portions comprises a first bearing portion having a first length and a first groove width ratio and a second bearing portion having a second length and a second groove width ratio, said first length being greater than said second length and said first groove width ratio being greater than said second groove width ratio.
8. The hydrodynamic bearing device according to claim 5 , wherein the pressure generating grooves comprise a herringbone pattern.
9. A hydrodynamic bearing device, comprising:
a sleeve and a shaft rotatably located around a common axis, said axis defining an axial direction;
fluid interposed between said sleeve and shaft;
a plurality of bearing portions extending along the axial direction of at least one of an external peripheral surface of the shaft or an internal peripheral surface of the sleeve;
said plurality of bearing portions having pressure generating grooves in at least one of said surfaces, each groove having a groove angle between the groove and a radial plane intersecting the shaft; and
said plurality of bearing portions comprising a first bearing portion having a first length and a first groove angle and a second bearing portion having a second length and a second groove angle, said first length being greater than said second length and said first groove angle being smaller than said second groove angle.
10. The hydrodynamic bearing device according to claim 9 , wherein the fluid comprises a gas.
11. The hydrodynamic bearing device according to claim 9 , wherein the pressure generating grooves comprise a herringbone pattern.