To reduce the flow-induced vibration (FIV) of the head stack assembly (HSA) in the hard disk drive (HDD), we experimentally studied the spoiler, which is put between disks. This study was carried out using a laser doppler vibrometer (LDV) to measure the amplitude of the head slider vibration. We also measured the power consumption of the spindle motor.As parameters of the spoiler shape, the thickness and the length were selected. From the experimental result, these parameters effect significantly both the head's vibration and the power consumption. This result suggests that the flow rate reduction with the spoiler causes a reduction of the HSA's FIV, and the energy loss with the spoiler causes an increase of the power consumption.We defined the spoiler's FIV-reducing efficiency as a ratio of the amplitude reduction to the power consumption increase. The length change makes the peak value. This is caused by the fact that the FIV reduction becomes almost constant when the spoiler is longer than the carriage arm length inside disk region, although the spoiler length makes power consumption monotonically large.Index Terms-Flow-induced vibration, hard disk, head stack assembly, spoiler.

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This is a report on ways to reduce flow-induced vibration of a head gimbal assembly (HGA), i.e., windage. The relation between flow-induced force and windage was investigated; as was a statistical approach to optimizing an HGA-arm configuration. The investigated HGAs were set between disks in a spin stand, and their windages were measured by using a laser Doppler vibrometer. The amplitude of sway mode was found to be almost in inverse proportion to the square of its frequency because the power spectrum of the airflow between disks is in inverse proportion to the square of its frequency. Miniaturizing HGAs is therefore an effective way to reduce windage because its natural frequencies then become higher. The windage measured for a HGA with a part length of 12, for example, is 40% less than that of one with a part length of 14.5 mm. Optimizing HGA-arm configurations by the Taguchi Method is also useful for reducing windage. The Taguchi Method is a statistical technique for designing products whose performance is not affected by outside conditions. We used an L8 orthogonal array in this investigation and found that optimizing the actuator arm thickness could reduce windage most effectively, the load-beam bend angle, and the arm shape. The windage of an optimized HGA-arm configuration was reduced to about one third that of the initial configuration. This knowledge will be useful in optimizing the parameters of an HGA and a head stack assembly to obtain hard disk drives with higher track densities.Index Terms-Flow-induced vibration, hard disk, head gimbal assembly, Taguchi method.

Xnro methods for investigating the flDw,inside an actual hard disk drive (HDD), narnely, Particle-imagevelocimetry (PIV) measureinents and fiuia simulation using tetrahedral elements hhve been developed. The HDDs used in･ the nieasurement have the same configurations as those of an actual product, but they are partly made of transparent acrylic resin, The measured velocity distribution clearly shows the flow characteristics induced by the arrn or the base configuratien. The fluid simulation considers most of an actual configuration between the two co-rotating disks. ,The simulated velocity distributions at the mid-plane between the disks agree well with those measured by the PIV The developed PIV measurement technique and fluid simulation using tetrahedral elements more effectively detemine the flow characteristics inside a HDD.

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