Fig. 1 Hydrostatic Thrust Bearing Fig. 2 Point loading of elastic half-space

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1 Characteristics of Hydrostatic Bearing/Seal Parts of Hydraulic Pumps and Motors for Water Hydraulic Systems (2nd Report, Theory) Xiongying WANG, Atsushi YAMAGUCHI In this paper, the characteristics of disk-type hydrostatic thrust bearings are discussed theoretical point of view. The bearing/seal parts are made up by combining stainless steel/stainless steel and stainless steel/plastics. The characteristics evaluated by the relationship among the load capacity, pocket pressure, film thickness and leakage flow rate are shown numerically. The main results are as follows: 1) the load capacity expressed by the ratio of hydrostatic balance is dependent not only on the supply pressure (with the same restrictor) but also on the elastic modulus of materials; 2) effects of pressure drop at the outlet land of pocket are much smaller than those of elastic deformation; and 3) the calculated results are in good agreement with the experimental results reported in a previous paper. Key words: Hydrostatic thrust bearings, Stainless steel, Industrial thermoplastics, Elastic deformation, Nozzle, Step effect, Water hydraulic pumps and motors, Theory

2 Fig. 1 Hydrostatic Thrust Bearing Fig. 2 Point loading of elastic half-space

3 Table 1 Dimensions and parameters of test apparatus Fig. 3 Schema of calculation

4 Fig. 5 Measurement of Young's modulus (a) Young's modulus in table 1 (b) Young's modulus given by Eq. (15) Fig. 4 Pocket pressure vs. balanced ratio Fig. 6 Pocket pressure vs. balanced ratio

5 (a) Supply pressure 9.0MPa (b) Supply pressure 5.0MPa Fig. 7 Pocket pressure vs. balanced ratio Fig. 8 Distribution of pressure and film thickness in the bearing/seal parts Fig. 9 Balanced ratio vs. leakage flow rate and film thickness

6 Fig. 10 Balanced ratio vs.leakage flow rate and film thickness Water Hydraulic Pumps Using Advanced Engineering Ceramics, Proc. of the 4th Scandinavian Inter. Conf. on Fluid Power, 26-29, 965/977 (1995) 4) S. Yoshimoto, Y. Anno, M. Tamura, Y. Kakiuchi, K. Kimura: Axial Load Capacity of Water -Lubricated Hydrostatic Conical Bearings with Spiral Grooves (On the Case of Rigid Surface Bearings ), Trans. ASME, J. Trib. 118, 893/899 (1996) 5) Y. Furuishi, T. Suganami, S. Yamamoto, K. Tokumitsu: Performance of Water-Lubricated Flat Spiral Grooves Bearings, Trans. ASME, J. Trib. 107, 268/273 (1985) 6) A. Yamaguchi: Formation of A Fluid Film Between A Valve Plate and A Cylinder Block of Piston Pumps and Motors (2nd Report, A Valve Plate with Hydrostatic Pads), JSME. Int. j., , 87/92 (1987) 8) T. Kazama, A. Yamaguchi: Optimum Design of Bearing and Seal Parts for Hydraulic Wear, 161, 161/171 (1993) Equipment, 9) T. Kazama, A. Yamaguchi: Experiment on Mixed Lubrication of Hydrostatic Thrust Bearings for Hydraulic Equipment, Trans. ASME, J. Trib. 117, 399/402 (1995) 10) D. Dowson, C.M. Taylor: Elastohydrostatic Lubrication of Circular Plate Thrust Bearings, Tran. ASME, J. Lub. 89, 237/244 (1967) 11) V. Castelli, G.K. Rightmire, D.D. Fuller : On the Analytical and Experimental Investigation of a Hydrostatic, Axisymmetric Compliant-Surface Threst Bearing, Tran. ASME, J. Lub. 89, 510/520 (1967) 1) H.C. Wong, N. Umehara, K. Kato: The Effect of Surface Roughness on Friction of Ceramics Sliding in Water, Wear, 218, 237/243 (1998) 3) C.A. Brookes, M.J. Fagan, R.D. James, P. Kerry, J. McConnachie: The Development of 14) Christensen, H: Elastohydrodynamic Theory of Spherical Bodies in Normal Approach, Trans. ASME, J. Lub. Tech., 92-1, 145/154 (1970)

Instability of Aerostatic Journal Bearings with Porous Floating Bush at High Speeds Masaaki MIYATAKE *4, Shigeka YOSHIMOTO, Tomoaki CHIBA and Akira CH

Instability of Aerostatic Journal Bearings with Porous Floating Bush at High Speeds Masaaki MIYATAKE *4, Shigeka YOSHIMOTO, Tomoaki CHIBA and Akira CHIBA Department of Mechanical Engineering, Tokyo University