1. Field of the Invention
The present invention relates to an improved spindle motor for driving optical media such as MDs, CDs or DVDs, and more particularly, to a spindle motor having a disc mounting portion in which a disc can be mounted on a rotor itself without an additional turntable.
2. Description of the Related Art
In general, a turntable on which an optical medium is mounted is installed on an output shaft protruding from a main body of a spindle motor for driving the optical media. The motor and the turntable are installed separately. A spindle motor including an automatic balancer installed under the turntable for automatically correcting imbalance has been suggested to prevent vibrations due to imbalance in a rotation system of a motor for high speed rotation including a medium.
Referring to in FIG. 4, which shows one of the various types of automatic balancers, a turntable T and a thin cylindrical case E installed at the bottom surface of the turntable T are installed at an output shaft of a motor portion M. A plurality of small balls B are accommodated within the cylindrical case E. Imbalance in a centrifugal force generated during rotation is corrected by using the free movement of these balls B.
However, since the conventional automatic balancer needs such a turntable or an imbalance correcting member, when a motor is to be designed to have a low profile, the features of a motor are sacrificed. Accordingly, to maintain the features of a motor, use of an expensive magnet is necessary.
Furthermore, since a stator base SB typically arranged at the lower portion of the motor is used as a support of the shaft, the height of the shaft up to the turntable greatly affects vibrations of the shaft. Thus, each member is required to have a very fine tolerance, which increases the manufacturing cost of the turntable or imbalance correcting member, and thus increases the cost of the motor.
To solve the above problems, it is an object of the present invention to provide a spindle motor having a disc mounting portion which reduces the number of parts by improving a rotor case to have a simple structure and function as a turntable
It is another object of the present invention to provide a spindle motor which has a low profile even though it has a disc mounting portion which has an automatic unbalance correcting function.
Accordingly, to achieve the above object, there is provided a spindle motor comprising a rotor case in which a shaft support portion is installed at the center of the rotor and a plurality of disc mounting guides are formed by being lifted from the upper surface around the shaft support portion at a predetermined interval, a shaft installed at the shaft support portion, a disc chuck spring having at least one disc inner hold chucking portion and arranged at the rotor case such that the chucking portion slightly protrudes radially between the disc mounting guides, a magnet arranged inside the rotor case, an armature stator facing the magnet via a gap, and a stator base where the armature stator is arranged, the stator base supporting the shaft inside the armature stator.
It is preferred in the present invention that a disc slippage prevention sheet is provided at the outer circumferential portion of the rotor case.
It is preferred in the present invention that a bulge portion is formed along the outer circumferential portion of the rotor case so that the outer circumferential portion of the rotor case bulges and a plurality of balls are arranged in the bulge portion to be used for unbalance correction.
It is preferred in the present invention that holes formed when the disc mounting guides are integrally lifted are covered by the disc chuck spring.
It is preferred in the present invention that the disc chuck spring is pressed by a magnetic body for attraction.