The rapid advent of personal computer brings lots of improvement to the external peripheral devices. A hard disk, a disk drive, an optical recording and reproducing instrument (DVD player), an image scanner, and a printing machine are some common external peripheral devices and are generally used in offices. Among them, the disk drive is prevalent for data storage. The DVD (digital versatile disc) of the latest development has 17 GB storage capacity, possesses high transmission characteristics, and causes wide utility of the DVD player by the consumers.
FIG. 1 shows a partly perspective view of a conventional disk drive 100 to include a driving motor 120 for rotating an optical disk 200 disposed thereabove, and a reading mechanism 140. The reading mechanism 140 includes a guide rail 142 and a pick-up head 144 retained slidably in the guide rail 142 below the optical disk 200 for reading the same. During the reading operation, the laser beam in the pick-up head 144 will focus continuously along the track in the optical disk 200 so as to read the data while traveling reciprocally along the guide rail 142.
The driving motor 120 needs to rotate at high speed in order to increase the reading capacity of the pick-up head 144. Presently, in some of the disk drives, the driving motor is arranged in such a manner to rotate the most at 10000 rpm. However, when the driving motor is thus arranged, the following drawbacks result:
(i) chucking noise results due to high rotation speed of the optical disk 200;
(ii) vibration of the optical disk 200 caused due to high rotation speed along a horizontal plane may cause indefinite focusing and tracking of the laser beam in the pick-up head 144;
(iii) vibration of the optical disk 200 is aggravated in case the latter itself is formed with scratches, labels, or deformed track, and eventually may lead to a sudden rupture of the optical disk under high rotation.