Oil dynamic bearing, motor supported on oil dynamic bearing and disk drive carrying the motor

A motor comprising:

• an oil dynamic bearing having a bearing center;
• a fixed unit;
• a rotary unit;
• a magnet arranged integrally with the rotary unit;
• and
• a stator arranged integrally with the fixed unit in opposed relation to the magnet;
• wherein the oil dynamic bearing includes:
• two bearing portions for rotatably supporting the rotary unit about a rotational axis, in which at least one of the opposed surfaces of the fixed unit and the rotary unit is formed with a plurality of dynamic pressure generating grooves, and an oil is held in the minuscule gap between the fixed unit and the rotary unit including a part or the whole of the dynamic pressure generating grooves;
• wherein the two bearing portions include:
• first and second taper seal portions, each of the taper seal portions having an outer pressure-side seal end portion communicating with an atmosphere and an inner pressure-side seal end portion connected respectively to an each bearing far end of the two bearing portions, the bearing far end portion defined at a far end farther from selected one of the rotational axis and the bearing center of the oil dynamic bearing;
• and
• a third taper seal portion having an outer pressure-side seal end portion communicating with the atmosphere and an inner pressure-side seal end portion connected in common to an each bearing near end of the two bearing portions, the bearing near end locating nearer to selected one of the rotational axis and the bearing center of the oil dynamic bearing;
• and
• wherein the two bearing portions have different directions from the bearing near end to the bearing far end and each taper seal portion has a gradually wider distance between the opposed surfaces of the fixed unit and the rotary unit at a observing point in proportion to the observing point moving from the inner pressure-side seal end portion to the outer pressure-side seal end portion;
• and
• wherein the third taper seal portion is arranged in a virtual truncated cone space having an upper circle and a lower circle, the upper circle is formed by the bearing far end portion of the upper bearing portion and the lower circle is formed by the bearing far end portion of the lower bearing portion;
• and
• wherein each oil interface with an air is formed in each of the taper seal portions connected to the bearing far ends of the two bearing portions;
• and
• wherein the dynamic pressure generating grooves of the two bearing portions have the shape of an unbalanced herring bone to induce an oil dynamic pressure pushing the oil toward the bearing far end of each bearing portion;
• and
• wherein a third oil interface with an air is formed in the third taper seal portion while the rotary unit is not rotating, and the third oil interface is divided into and formed at two divided oil interfaces at a vicinity of each of the bearing near ends of the bearing portions while the rotary unit is rotating;
• and
• wherein at least selected one of the divided oil interfaces is formed in an area having the dynamic pressure generating grooves.