Hydrostatic bearings are important elements that directly affect machining accuracy in machine tools. Although hydrostatic bearings using water can reduce environmental influence compared with those using oil, they have low rigidity and damping properties. By investigating the properties of water used for working fluid of hydrostatic bearings, there is a possibility that the characteristics of hydrostatic bearings using water can be improved. Therefore, in this study, the relationship between the properties of water used as a working fluid of hydrostatic bearings and the characteristics of bearings was investigated. For this purpose, a hydrostatic bearing characteristics evaluation system using water was constructed. The characteristics of hydrostatic bearings were examined by varying the components and temperature of water. The experimental results show that the composition and temperature of working water affect the performance of water hydrostatic bearing.

1. [1] T. A. Osman, Z. S. Safar, and M. O. A. Mokhtar, “Design of annular recess hydrostatic thrust bearing under dynamic loading,” Tribology Int., Vol.24, No.3, pp. 137-141, 1991.
2. [2] S. C. Sharma, S. C. Jain, and D. K. Bharuka, “Influence of recess shape on the performance of a capillary compensated circular thrust pad hydrostatic bearing,” Tribology Int., Vol.35, No.6, pp. 347-356, 2002.
3. [3] S. C. Sharma, V. M. Phalle, and S. C. Jain, “Performance analysis of a multirecess capillary compensated conical hydrostatic journal bearing,” Tribology Int., Vol.44, No.5, pp. 617-626, 2011.
4. [4] J. E. Mayer and M. C. Shaw, “Characteristics of an externally pressurized bearing having variable external flow restrictors,” J. of Basic Engineering, Vol.85, No.2, pp. 291-296, 1963.
5. [5] W. B. Rowe and J. P. O’Donoghue, “Diaphragm valves for controlling opposed pad hydrostatic bearings,” Proc. of the Institution of Mechanical Engineers, Vol.184, No.12, pp. 1-9, 1969.
6. [6] C. K. Singh and D. V. Singh, “Stiffness optimization of a variable restrictor-compensated hydrostatic thrust bearing system,” Wear, Vol.44, No.2, pp. 223-230, 1977.
7. [7] X. Zuo, J. Wang, Z. Yin, and S. Li, “Comparative performance analysis of conical hydrostatic bearings compensated by variable slot and fixed slot,” Tribology Int., Vol.66, pp. 83-92, 2013.
8. [8] H. Sawano, Y. Nakamura, H. Yoshioka, and H. Shinno, “High performance hydrostatic bearing using a variable inherent restrictor with a thin metal plate,” Precision Engineering, Vol.41, pp. 78-85, 2015.
9. [9] D.-C. Chen, M.-F. Chen, C.-H. Pan, and J.-Y. Pan, “Study of membrane restrictors in hydrostatic bearing,” Advances in Mechanical Engineering, Vol.10, No.9, pp. 1-8, 2018.
10. [10] T.-H. Lai, T.-Y. Chang, Y.-L. Yang, and S.-C. Lin, “Parameters design of a membrane-type restrictor with single-pad hydrostatic bearing to achieve high static stiffness,” Tribology Int., Vol.107, pp. 206-212, 2017.
11. [11] J. Wang, G. Gong, and H. Yang, “Control of bulk modulus of oil in hydraulic systems,” Proc. of the 2008 IEEE/ASME Int. Conf. on Advanced Intelligent Mechatronics, pp. 1390-1395, Xian, China, July 2-5, 2008.
12. [12] T. Tsubouchi and J. Shinoda, “Characterization of oily high bulk modulus fluid,” Tribology Online, Vol.5, No.5, pp. 230-234, 2010.
13. [13] K. Kuze, H. Sawano, H. Yoshioka, and H. Shinno, “Hydrostatic bearing with high bulk modulus fluid,” Key Engineering Materials, Vols.523-524, pp. 532-537, 2012.
14. [14] Y. Nakao, K. Suzuki, K. Yamada, and K. Nagasaka, “Feasibility study on design of spindle supported by high-stiffness water hydrostatic thrust bearing,” Int. J. Automation Technol., Vol.8, No.4, pp. 530-538, 2014.
15. [15] Y. Nishitani, S. Yoshimoto, and K. Somaya, “Numerical investigation of static and dynamic characteristics of water hydrostatic porous thrust bearings,” Int. J. Automation Technol., Vol.5, No.6, pp. 773-779, 2011.
16. [16] Y. Nakao, M. Mimura, and F. Kobayashi, “Water energy drive spindle supported by water hydrostatic bearing for ultra-precision machine tool,” Proc. of ASPE 2013 Annual Meeting, Vol.18, 2003.
17. [17] X. Wang and A. Yamaguchi, “Characteristics of hydrostatic bearing/seal parts for water hydraulic pumps and motors. Part 1: Experiment and theory,” Tribology Int., Vol.35, No.7, pp. 425-433, 2002.
18. [18] X. Wang and A. Yamaguchi, “Characteristics of hydrostatic bearing/seal parts for water hydraulic pumps and motors. Part 2: On eccentric loading and power losses,” Tribology Int., Vol.35, No.7, pp. 435-442, 2002.
19. [19] X. Deng, H. Gates, R. Fittro, and H. Wood, “Methodology of turbulence parameter correction in water-lubricated thrust bearings,” J. of Fluids Engineering, Vol.141, No.7, 071104, 2019.
20. [20] A. H. Slocum, P. A. Scagnetti, N. R. Kane, and C. Brunner, “Design of self-compensated, water-hydrostatic bearings,” Precision Engineering, Vol.17, No.3, pp. 173-185, 1995.
21. [21] H. Sawano, T. Iwasa, Y. Nishibeppu, T. Miyoshi, and S. Katono, “Investigation of the influence of fluid properties on bearing characteristics in hydrostatic bearing using water,” Proc. of the 17th Int. Conf. on Precision Engineering, C-1-4, Kamakura, Japan, November 12-16, 2018.
22. [22] “Periodic water quality test results of Kawasaki City, May, 2019,” 2019 (in Japanese). http://www.city.kawasaki.jp/800/cmsfiles/contents/0000083/83113/201905shinai.pdf [Accessed September 5, 2019]
23. [23] JIS-Z8803:2011, “Methods for viscosity measurement of liquid,” 2011.
24. [24] National Astronomical Observatory of Japan, “Chronological scientific tables 2019,” Maruzen, p. 528, 2018 (in Japanese).