Kaoru Matsuoka

Thin-film piezoelectric DSA for HDD

A new dual-stage actuator (DSA) for positioning a magnetic head for high-density hard disk drives was proposed and developed. This DSA device is characterized by applying sputter-deposited thin-film lead-zirconate-titanate material (PZT), instead of the previously proposed bulk type actuator. The device performance was found to be outstanding with peak-to-peak head displacement of 1.2 /spl mu/m at an applied voltage of /spl plusmn/5 V, and suspension resonance frequency higher than 15 kHz, yielding a servo bandwidth of more than several kHz.

Development of FDB spindle motors for HDD use

The areal recording density of an HDD has increased noticeably at a rate of 60% to 100% a year, and further increases are expected in the future. In line with this trend, increasingly exacting tolerances are required regarding off-track errors of heads. Ball bearings have been conventionally used in spindle motors. However, off-track errors caused by non-repeatable run outs (NRRO) are approaching the control limit. Expectations for the implementation of spindle motors incorporating fluid dynamic bearings (FDBs) are rising. In this paper, we discuss FDB spindle motors, which are thought of as the future mainstream of HDD.

Manufacturing process of piezoelectric thin-film dual-stage actuator and its reliability for HDD

A new dual-stage actuator for positioning a magnetic head for high-density hard disk drives was proposed and developed. This dual-stage actuator device is characterized by the sputter-deposited thin-film PZT, featuring large displacement of 1.2 /spl mu/m and high-resonance frequency over 15 kHz. In this paper, reliability against temperature, humidity, and mechanical shock was investigated to ensure the practical application to the drive products.

Automatic design method of brushless DC motors for VCRs

An automatic design method for all types of brushless DC motors for VCRs was developed. Quick and easy motor design with no trial manufacture was realized, enabling a motor of minimum size to achieve maximum efficiency. In carrying out this work, the authors systematized the parameters governing the motor characteristics of a brushless DC motor and theoretically analyzed and clarified the correlations between parameters and characteristics. Various experiments were conducted to increase the reliability of the theoretical analysis of the magnetic circuit. Some motor rules vital in motor design were identified and used to devise an algorithm for automatic motor design, and interactive software was developed on the basis of this algorithm. The resulting design method is a highly practicable one and permits an optimum motor design that satisfies all the conditions imposed by the equipment in which the motor is to be used. >

In-Situ Wear Monitoring of Slider and Disk Using Acoustic Emission

The methodology has been developed for both the evaluation and analysis of slider/disk interface phenomena. We have been studying the direct relationships between the acoustic emission (AE) signal and wear of materials. The power in the AE signal is directly related to the power required for material removal in the wear process. This technique has been successfully applied to monitoring the wear of the tri-pad contact slider and the disk. The AE transducers were directly mounted onto both the arm with the slider and the disk in order to measure the slider/disk contact behavior. The AE transducer output from the disk was transmitted by the slip ring and the brush. The predicted wear of the slider and the disk based on the AE signals were computed from the relationship mentioned above. The measured wear of the slider and the disk were obtained by atomic force microscopy (AFM) and an optical surface analyzer (OSA) respectively. According to the experimental results, the predicted wear of both the slider and the disk using AE signals agreed with the wear which was measured. Therefore, wear can be estimated and monitored indirectly in-situ using the AE signals without direct measurements of the wear volume.

Evaluation Technique of Head/Tape Contact Using Acoustic Emission

A new on-line methodology has been developed for both evaluation and analysis of head/tape interface phenomena. It uses the direct relationships between the power in the acoustic emission (AE) signal and wear, and between the power in the AE signal and the normal force acting on the magnetic head. The AE transducer is directly mounted onto the head assembly of a VCR mechanism in order to measure the head/tape contact behavior. This technique has been used to : (a) monitor the effect of relative humidity on head wear; (b) investigate the wear characteristics of Mn-Zn ferrite as a function of crystallographic orientation without direct measurement of the wear volume; and (c) evaluate tape abrasiveness. Explicit correlations were also obtained for the normal force acting on the magnetic head, the tape wrap angle around the head, and the reproduced signal flatness in terms of the tape transverse stress distribution. Moreover, the normal force as a function of the tape stress distribution is closely related to the longitudinal tape vibration at the head exit region.

Piezoelectric thin film reliability for HDD dual-stage actuator

Summary form only given. A new dual-stage actuator for positioning a magnetic head for high-density hard disk drives (HDDs) was proposed and developed. This dual-stage actuator device is characterized by the sputter-deposited thin film PZT, featuring large displacement of 1.2 microns and high resonance frequency over 15 kHz. In this work, reliability against temperature, humidity, heat cycle, and mechanical shock was investigated to ensure the practical application to the drive products.