Spindle motor with hydrodynamic bearing structure having capillary seal and disk drive apparatus including same

A spindle motor comprising:

• a stationary portion including a shaft arranged to extend along a central axis extending in a vertical direction;
• and
• a rotating portion supported to be rotatable about the central axis around the shaft;
• wherein
• the stationary portion includes:
• the shaft;
• a circular plate portion arranged to extend radially outward from the shaft;
• a cylindrical or substantially cylindrical wall portion arranged to extend upward from an outer edge of the circular plate portion;
• and
• a plate portion having a circular or substantially circular ring shape and arranged to surround the shaft above the circular plate portion;
• the rotating portion includes a sleeve including an annular portion having a circular or substantially circular ring shape, a cylindrical portion arranged to extend upward from an outer edge of the annular portion, and a communicating hole arranged to pass through the annular portion in an axial direction;
• an outer circumferential surface of the plate portion is arranged opposite to an inner circumferential surface of the cylindrical portion with an upper capillary seal portion defined therebetween, the upper capillary seal portion being arranged to gradually decrease in radial width with decreasing height;
• an outer circumferential surface of the sleeve is arranged opposite to an inner circumferential surface of the wall portion with a lower capillary seal portion defined therebetween, the lower capillary seal portion being arranged to gradually decrease in radial width with decreasing height;
• between the stationary and rotating portions, a lubricating oil is arranged in a space including:
• the upper capillary seal portion;
• a first gap defined between a lower surface of the plate portion and an upper surface of the sleeve;
• a second gap defined between an outer circumferential surface of the shaft and an inner circumferential surface of the sleeve;
• a third gap defined between a lower surface of the sleeve and an upper surface of the circular plate portion;
• the communicating hole arranged to bring the first and third gaps into axial communication with each other;
• and
• the lower capillary seal portion;
• an upper surface of the lubricating oil is located in the upper capillary seal portion when the spindle motor is in a stationary state;
• a lower surface of the lubricating oil is located in the lower capillary seal portion when the spindle motor is in the stationary state;
• a first angle defined between the outer circumferential surface of the plate portion and the inner circumferential surface of the cylindrical portion at the upper capillary seal portion in a section taken along a plane including the central axis is in a range of about 1 degree to about 8 degrees;
• a second angle defined between the outer circumferential surface of the sleeve and the inner circumferential surface of the wall portion at the lower capillary seal portion in a section taken along the plane including the central axis is in a range of about 1 degree to about 10 degrees;
• the upper capillary seal portion is arranged to have a maximum radial width smaller than that of the lower capillary seal portion;
• and
• the upper capillary seal portion is arranged to have an axial length smaller than that of the lower capillary seal portion.