Hydrodynamic bearing, spindle motor using the same and disc drive apparatus provided with spindle motor

A spindle having a rotation axis comprising:

• a stator fixed at a bracket with which one side of a shaft and a sleeve;
• a rotor magnet secured another of said shaft and said sleeve and generating a rotating magnetic field in cooperation with said stator;
• and
• A hydrodynamic bearing comprising:
• said shaft;
• said sleeve relatively rotated with respect to said shaft;
• a bearing portion including a micro gap formed between said shaft and said sleeve, a lubricating oil retained as a working fluid in said micro gap, and a dynamic pressure generating groove formed on at least one side of an outer peripheral surface of said shaft and an inner peripheral surface of said sleeve in said micro gap, for generating a dynamic pressure so as to support a rotation of said shaft or said sleeve;
• a capillary seal portion adjoining said bearing portion, wherein the capillary seal portion comprising:
• a first capillary seal portion adjoining said bearing portion, and having a first radial gap between an outer surface of said shaft and an first inner peripheral surface of said sleeve, a dimension of said first radial gap being getting at least wider in accordance with increasing a distance from said bearing portion in said rotation axis;
• and
• a second capillary seal portion adjoining said first capillary seal portion, and having a second radial gap between an outer surface of said shaft and an second inner peripheral surface of said sleeve, a dimension of said second radial gap being getting at least wider in accordance with increasing a distance from said bearing portion in said rotation axis;
• wherein a first radial distance between the first inner peripheral surface and the rotation axis in radial direction, is getting at least shorter in accordance with increasing a distance from said bearing portion in said rotation axis, and said first inner peripheral surface forms a first angle θ1 (employing a smaller angle having the angle value in a range 0≦θ1≦90°) with respect to said rotation axis, and a second radial distance between the second inner peripheral surface and the rotation axis in radial direction, is getting at least shorter in accordance with increasing a distance from said bearing portion in said rotation axis, and said second inner peripheral surface forms a second angle θ2 (employing a smaller angle having the angle value in a range 0≦θ2≦90°) with respect to said rotation axis, and
• said first angle θ1 and said second angle θ2 have a relation θ1>θ2.

A disc drive apparatus to which a disc-shaped recording medium capable of recording information is attached, comprising:

• a housing;
• a spindle motor fixed to an inner portion of said housing and rotating said recording medium;
• and
• a means for writing or reading the information at a desired position of said recording medium,
• wherein said spindle motor comprises:
• a stator fixed at a bracket with which one side of a shaft and a sleeve;
• a rotor magnet secured another of said shaft and said sleeve and generating a rotating magnetic field in cooperation with said stator;
• and
• A hydrodynamic bearing comprising:
• said shaft;
• said sleeve relatively rotated with respect to said shaft;
• a bearing portion including a micro gap formed between said shaft and said sleeve, a lubricating oil retained as a working fluid in said micro gap, and a dynamic pressure generating groove formed on at least one side of an outer peripheral surface of said shaft and an inner peripheral surface of said sleeve in said micro gap, for generating a dynamic pressure so as to support a rotation of said shaft or said sleeve;
• a capillary seal portion adjoining said bearing portion,
• wherein the capillary seal portion comprising:
• a first capillary seal portion adjoining said bearing portion, and having a first radial gap between an outer surface of said shaft and an first inner peripheral surface of said sleeve, a dimension of said first radial gap being getting at least wider in accordance with increasing a distance from said bearing portion in said rotation axis;
• and
• a second capillary seal portion adjoining said first capillary seal portion, and having a second radial gap between an outer surface of said shaft and an second inner peripheral surface of said sleeve, a dimension of said second radial gap being getting at least wider in accordance with increasing a distance from said bearing portion in said rotation axis;
• wherein a first radial distance between the first inner peripheral surface and the rotation axis in radial direction, is getting at least shorter in accordance with increasing a distance from said bearing portion in said rotation axis, and said first inner peripheral surface forms a first angle θ1 (employing a smaller angle having the angle value in a range 0≦θ1≦90°) with respect to said rotation axis, and a second radial distance between the second inner peripheral surface and the rotation axis in radial direction, is getting at least shorter in accordance with increasing a distance from said bearing portion in said rotation axis, and said second inner peripheral surface forms a second angle θ2 (employing a smaller angle having the angle value in a range 0≦θ2≦90°) with respect to said rotation axis, and
• said first angle θ1 and said second angle θ2 have a relation θ1>θ2.