磁気ディスク装置のピボットの締結改善によるコイルねじれ振動低減の提案

抄録

We propose pivot-to-enclosure fastening improvements to reduce torsional vibration of coil in hard disk drive. The concept is decoupling the coil torsion mode from the actuator’s main resonance mode by reducing the differences in coefficient of thermal expansion between the base boss shaft and the pivot shaft, so as to suppress axial force relief in the pivot screw at 60 degrees C. Based on this concept, three approaches to pivot-to-enclosure fastening improvements were considered: 1. Long pivot screw, 2. SUS stud press fit, 3. Shaft threaded. The axial force reliefs in pivot shaft due to high temperatures were calculated for these three cases, and it was confirmed that the axial force reliefs were suppressed in all cases. The coil torsion mode gain in the frequency response functions was also reduced. Furthermore, a correlation between the coil torsion mode gains and the frequency separations from the coil torsion mode to the main resonance mode was found. Therefore, it is considered that decoupling of coil torsion mode from main resonance mode is one of key factors in coil torsion gain reduction.