| 摘要 |
PURPOSE:To prevent tracking deviation by forming a cam means for head drive arranged coaxially to a magnetic disk by means of a plastic having nearly the same linear expansion coefficient as that of the magnetic disk. CONSTITUTION:When a floppy disk is used for a magnetic disk 2, its linear expansion coefficient is specified as (17+ or -8)X10<-6>cm/cm/ deg.C. On the other hand, as a gear cam 12, a resin known as the engineering plastic is used, its linear expansion coefficient is 8X10<-5>cm/cm/ deg.C for a polyacetal resin having self- lubrication, for example, which is nearly 4.7 times of that of the magnetic disk. A polyphenyllenesulfide resin is used for a base and carbon fibers and a tetrafluoroethylene are compounded, then the linear expansion coefficient is 17.3X10<-5>cm/cm/ deg.C, which is nearly equal to that of the magnetic disk. Thus, the tracking deviation due to the expansion/contraction of the magnetic disk due to temperature change is almost avoided.
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