1. Field of the Invention
The present invention relates to a spindle motor and a hard disk drive including the same.
2. Description of the Related Art
A hard disk drive (HDD), an information storage device, reads data stored on a disk or writes data to a disk using a read/write head.
A hard disk drive requires a disk driving device capable of driving the disk. As the disk driving device, a spindle motor is commonly used.
Such a spindle motor uses a hydrodynamic bearing assembly. A shaft, a rotating member of the hydrodynamic bearing assembly, and a sleeve, a fixed member thereof, have a lubricating fluid interposed therebetween, such that the shaft is supported by fluid pressure generated in the lubricating fluid.
Thus, demand for thin, high-capacity spindle motors has continuously increased. In accordance with the thinning and miniaturization of such spindle motors, bearing rigidity has been unavoidably reduced.
Bearing rigidity, an important factor determining rotational characteristics of the spindle motor, is affected by a gap between dynamic pressure grooves, that is, a bearing span length.
That is, bearing rigidity is increased with increases in bearing span length, such that rotational characteristics of the spindle motor may be improved. Therefore, even in the case that the capacity of the spindle motor is increased and the spindle motor is thinned, bearing rigidity should not be affected thereby.
In addition, the lubricating fluid injected into the hydrodynamic bearing assembly may be leaked to the outside due to an external impact or the amount thereof may be reduced due to evaporation. Due to the above-mentioned phenomena, the hydrodynamic bearing may not be able to generate sufficient fluid dynamic pressure, which may lead problems in terms of the performance and lifespan of a spindle motor.
Further, when an external impact is transferred to a spindle motor from the outside during the driving thereof, internal components in the spindle motor may be deformed, having an adverse affect on the driving of the spindle motor. Therefore, it is important to secure rigidity in the spindle motor.
Therefore, research into increasing the rigidity of the spindle motor to prevent the internal components from being deformed even when an external impact or the like is applied to the spindle motor, securing a storage space for lubricating fluid to maximize motor performance and lifespan, and preventing bearing rigidity from being reduced while realizing high-capacity and miniaturization of the spindle motor, has been urgently demanded.