1. Field of the Invention
The present invention relates generally to a disk drive unit for transferring information between a disk and a reading and/or writing head for recording and/or reproducing information. More specifically, the invention relates to a disk drive unit which is suitable for recording and/or reproducing information on a flexible disk. More particularly, the invention relates to a disk drive unit which can establish a stable of relationship between the flexible disk and the reading and/or writing head during recording and/or reproducing information on the disk.
2. Description of the Background Art
U.S. Pat. No. 4,600,955, issued on July 15, 1986 to Curtis R. Regruit and U.S. Pat. No. 4,620,250, issued on Oct. 28, 1986 to Robert G. Hill disclose so-called "contacting" type information transfer technology for recording and/or reproducing information on a flexible magnetic disk. Both of these U.S. patents propose employment of a head-to-disk stablizing unit for stably establishing head-to-disk contact. In the proposed technology, a flexible disk is rotatably housed within a disk cartridge in such a manner that the successive radial portions of the disk move over an opening formed through the disk cartridge. The opening of the disk cartridge is disposed to provide limited radial access to the disk. The head-to-disk stabilizing unit seals the opening to cause formation of a Bernoulli drawing force for forming the successive radial positions of the disk as each portion is passed over the opening. Such drawing force momentarily deflects each portion of the rotating disk toward the opening, causing a deflected portion of the disk to remain substantially in contact with a magnetic recording or reproducing head movable along the opening and thus ensuring stability of the head-to-disk contact.
In order to exert the drawing force, vacuum pressure is generated around the head. The disk is forced toward the head for establishing firm contact with the later so as to enable a steady transfer of information between the head and the disk. Such arrangement for establishing head-to-disk contact is successful to assure head-to-disk contact. However, the magnitude of vacuum pressure to be generated around the head fluctuates. Namely, fluctuation of the vacuum pressure is caused by tolerance in the surface flatness of a stabilizer block which determines the sealing ability. The sealing ability may be influenced not only by surface flatness of the stabilized block but also by waving of the flexible disk during rotation. Due to such fluctuation of magnitude of vacuum generated around the magnetic head, contacting force between the head and the disk can fluctuate to cause variation in information transfer performance.