Hydrodynamic bearing and spindle motor

A hydrodynamic bearing for a spindle motor, comprising:

• a shaft;
• and
• a sleeve in which said shaft is inserted;
• wherein
• an outer surface portion of said shaft that opposes an inner surface portion of said sleeve and thereby defines a bearing portion of said bearing is formed by three sequential sections, a section (a) extending a distance of L1 from a point that opposes one end of said sleeve in an axial direction thereof, a section (b) extending a distance of L2 from a point that opposes the opposite end of said sleeve in said axial direction, and a section (c) extending a distance of L3 and connecting said sections (a) and (b),
• said intermediate section (c) has a cylindrical surface portion formed therein and extending substantially parallel to an axial direction thereof,
• each of said sections (a) and (b) has a tapered surface portion formed therein in which an outer diameter thereof is decreased continuously in a direction away from said section (c), and
• an inclination of said tapered surface portion of said portions (a) and (b) is defined by “f/L3”, wherein “f” is determined as a gap between an outer surface of said section (c) of said shaft and an inner surface of said sleeve in said section (c) with respect to an axial direction of said axial direction of said sleeve, in a condition where said shaft is inclined relative to said sleeve.

A spindle motor, comprising:

• a hydrodynamic bearing, said bearing includes
• a shaft;
• and
• a sleeve in which said shaft is inserted;
• wherein said sleeve has three bearing sections, a section A extending a distance of L1 from one end thereof in an axial direction of said bearing, a section B extending a distance of L2 from the opposite end thereof in said axial direction, and a section C extending a distance of L3 between said sections A and B,
• each of said sections A and B has a tapered surface portion formed therein in which an inner diameter thereof is increased from inside to outside of said bearing,
• said section C has a cylindrical surface portion formed therein and extending substantially parallel to said axial direction, and
• an inclination of said tapered surface portion of said sections A and B is defined by “f/L3”, wherein “f” is determined as a gap between an inner surface of said section C of said sleeve and an outer surface of said shaft in said section C in a condition where said shaft is inclined relative to said sleeve.

A spindle motor, comprising:

• a hydrodynamic bearing, said bearing includes
• a shaft;
• and
• a sleeve in which said shaft is inserted;
• wherein
• an outer surface portion of said shaft that opposes an inner surface portion of said sleeve and thereby defines a bearing portion of said bearing is formed by three sequential sections, a section (a) extending a distance of L1 from a point that opposes one end of said sleeve in an axial direction thereof, a section (b) extending a distance of L2 from a point that opposes the opposite end of said sleeve in said axial direction, and a section (c) extending a distance of L3 and connecting sad sections (a) and (b),
• said intermediate section (c) has a cylindrical surface portion formed therein and extending substantially parallel to an axial direction thereof,
• each of said sections (a) and (b) has a tapered surface portion formed therein in which an outer diameter thereof is decreased continuously in a direction away from said section (c), and
• an inclination of said tapered surface portion of said portions A and B is defined by “f/L3”, wherein “f” is determined as a gap between an outer surface of said section (c) of said shaft and an inner surface of said sleeve in said section (c) with respect to an axial direction of said axial direction of said sleeve, in a condition where said shaft is inclined relative to said sleeve.