Robust Optimum Design of Thrust Hydrodynamic Bearings for Hard Disk Drives

Hiromu Hashimoto, Yuta Sunami

Department of Mechanical Engineering, Tokai University, Hiratsuka, Japan.

DOI: 10.4236/am.2012.330193                

Abstract

This paper describes the robust optimum design which combines the geometrical optimization method proposed by Hashimoto and statistical method. Recently, 2.5″ hard disk drives (HDDs) are widely used for mobile devices such as laptops, video cameras and car navigation systems. In mobile applications, high durability towards external vibrations and shocks are essentials to the bearings of HDD spindle motor. In addition, the bearing characteristics are influenced by manufacturing error because of small size of the bearings of HDD. In this paper, the geometrical optimization is carried out to maximize the bearing stiffness using sequential quadratic programming to improve vibration characteristics. Additionally, the bearing stiffness is analyzed considering dimensional tolerance of the bearing using statistical method. The dimensional tolerance is assumed to distribute according to the Gaussian distribution, and then the bearing stiffness is estimated by combining the expectation and standard deviation. As a result, in the robust optimum design, new groove geometry of bearing can be obtained in which the bearing stiffness is four times higher than the stiffness of conventional spiral groove bearing. Moreover, the bearing has lower variability compared with the result of optimum design neglecting dimensional tolerance.

Keywords

Robust Optimum Design; Hard Disk Drive; Hydrodynamic Bearing; Tolerance; Statistical Method

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	K. Ono and J. Zhu, “A Comparison Study on Characteristics of Five Types of Hydrodynamic Oil Bearing for Application to Hard Disk Drive Spindles,” Transactions of the Japan Society of Mechanical Engineers, Series (C), Vol. 64, No. 622, 1998, pp. 339-345.
[2]	J. Zhu and K. Ono, “A Comparison Study on the Performance of Four Types of Oil Lubricated Hydrodynamic Thrust Bearings for Hard Disk Spindles,” Transactions of the ASME, Journal of Tribology, Vol. 121, No. 1, 1999, pp. 114-121. doi:10.1115/1.2833790
[3]	K. Matsuoka, S. Obata, H. Kita and F. Toujou, “Development of FDB Spindle Motors for HDD Use,” IEEE Transactions on Magnetics, Vol. 37, No. 2, 2001, pp. 783-788. doi:10.1109/20.917616
[4]	G. H. Jang, S. H. Lee, H. W. Kim and C. S. Kim, “Dynamic Analysis of a HDD Spindle With FDBs Due to the Bearing Width and Asymmetric Grooves of Journal Bearing,” Microsystem Technologies, Vol. 11, No. 7, 2005, pp. 499-505. doi:10.1007/s00542-005-0606-5
[5]	T. Hirayama, S. Sakai, N. Yamaguchi, N. Hishida and H. Yabe, “A Proposal of Optimum Groove Design Concepts of Spiral-Grooved Journal Bearings Applied to Spindles of Precision Equipments (1st Report, A Guide for Reduction of Amplitude of Repeatable Run-Out in Incompressible Fluid Film Bearing),” Transactions of the Japan Society of Mechanical Engineers, Series (C), Vol. 72, No. 713, 2006, pp. 241-246.
[6]	H. Yabe, T. Hirayama, S. Sakai, N. Yamaguchi and N. Hishida, “A Proposal of Optimum Groove Design Concepts of Spiral-Grooved Journal Bearings Applied to Spindles of Precision Equipments (2nd Report, A Guide for Reduction of Amplitude of Indicial Response),” Transactions of the Japan Society of Mechanical Engineers, Series (C), Vol. 72, No. 719, 2006, pp. 312-317.
[7]	S. Tohma, T. Isogai, T. Hirayama, T. Matsuoka, K. Yokozuka and S. Mori, “Frequency Analysis of Hard Disk Drive Spindle System Supported by Hydrodynamic Bearings,” Journal of Advanced Mechanical Design, Systems, and Manufacturing, Vol. 1, No. 5, 2007, pp. 717-725. doi:10.1299/jamdsm.1.717
[8]	H. Hashimoto and M. Ochiai, “Optimization of Groove Geometry for Thrust Air Bearing to Maximize Bearing Stiffness,” Transactions of the ASME, Journal of Tribology, Vol. 130, No. 3, 2008, pp. 1-11. doi:10.1115/1.2913546
[9]	M. D. Ibrahim, T. Namba, M. Ochiai and H. Hashimoto, “Optimum Design of Thrust Air Bearing for Hard Disk Drive Spindle Motor,” Journal of Advanced Mechanical Design, Systems, and Manufacturing, Vol. 4, No. 1, 2009, pp. 70-81. doi:10.1299/jamdsm.4.70
[10]	K. Y. Koak, G. H. Jang and H. W. Kim, “Whirling Tilting and Axial Motions of a HDD Spindle System Due to the Manufacturing Errors of FDBs,” Microsystem Technologies, Vol. 15, No. 10-11, 2009, pp. 1701-1709. doi:10.1007/s00542-009-0872-8
[11]	M. Fillon, W. Dmochowski and A. Dadouche, “Numerical Study of the Sensitivity Tilting-Pad Journal Bearing Performance Characteristics to Manufacturing Tolerances: Steady-State Analysis,” STLE Tribology Transactions, Vol. 50, No. 3, 2007, pp. 387-400. doi:10.1080/10402000701429246
[12]	W. Dmochowski and M. Fillon, “Numerical Study of the Sensitivity Tilting-Pad Journal Bearing Performance Characteristics to Manufacturing Tolerances: Dynamic Analysis,” STLE Tribology Transactions, Vol. 51, No. 5, 2008, pp. 573-580.
[13]	W. Xu, P. J. Ogrodnik, M. J. Goodwin and G. A. Bancroft, “The Stability Analysis of Hydrodynamic Journal Bearings Allowing for Manufacturing Tolerances. Part1: Effect Analysis of Manufacturing Tolerances by Taguchi Method,” Proceedings of Measuring Technology and Mechatronics Automation 2009, Vol. 2, Zhangjiajie, 11-12 April 2009, pp. 164-167.
[14]	P. J. Ogrodnik, M. J. Goodwin, G. A. Bancroft and W. Xu, “The Stability Analysis of Hydrodynamic Journal Bearings Allowing for Manufacturing Tolerances. Part2: Stability Analysis Model with Consideration of Tolerances,” Proceedings of Measuring Technology and Mechatronics Automation 2009, Vol. 2, Zhangjiajie, Hunan, 11-12 April 2009, pp. 168-171.
[15]	G. J. Park, T. H. Lee, H. L. Kwon and K. H. Hwang, “Robust Design: An Overview,” American Institute of Aeronautics and Astronautics, Vol. 44, No. 1, 2006, pp. 181-191.
[16]	H. Hashimoto and M. Ochiai, “Theoretical Analysis and Optimum Design of High Speed Gas Film Thrust Bearings (Static and Dynamic Characteristic Analysis with Experimental Verifications),” Journal of Advanced Mechanical Design, Systems, and Manufacturing, Vol. 1, No. 1, 2007, pp. 102-112. doi:10.1299/jamdsm.1.102
[17]	N. Kawabata, “Study on Generalization of Calculations of Lubricant Flow Using Boundary Fitted Coordinate System (Part 1, Basic Equations of DF Method and Case of Incompressible Fluids),” Transactions of the Japan Society of Mechanical Engineers, Series (C), Vol. 53, No. 494, 1987, pp. 2155-2160