Water Hydraulic Pump Research Articles

CHARACTERISTICS OF THE BEARING/SEAL PARTS OF PISTON PUMPS AND MOTOR FOR WATER HYDRAULIC SYSTEMS

In this paper the characteristics of disk type hydrostatic thrust bearings supporting concentric loads, simulating the major bearing/seal parts of water hydraulic pumps and motors, are presented. The bearing is made up by combination of stainless steel/stainless steel and stainless steel/plastics. The characteristics are evaluated by the relationship among the load capacity, pocket pressure, film thickness, and leakage flow rate. The main results are as follows: 1) the load capacity expressed by the ratio of hydrostatic balance is not only dependent of the supply pressure (with the same restrictor) but also of the elastic modulus of materials, 2) effects of inlet pressure drop into the bearing land are much smaller than those of elastic deformation, especially in plastics, 3) the calculated results coincide well with the experimental results.

DEVELOPMENT OF HIGH PERFORMANCE COMPONENTS FOR POLLUTION FREE WATER HYDRAULIC SYSTEM

In order to construct water hydraulic systems for environmental protection, we have developed a pollution-free water hydraulic pump and a water hydraulic servo valve. With a view to secure the same efficiency as oil hydraulic systems, we used a swash plate type axial piston pump, a spool type servo valve, and all parts are lubricated with water which is the hydraulic fluid. The system is made of ceramics, plastics, and so on. The water hydraulic pump has a mechanical efficiency of 94%, a volumetric efficiency of 86%, a power-to-weight ratio 1.0kW/kgf at the pressure of 21MPa, and a rotation speed of 1800min-1 The water hydraulic servo valve has leakage of under 760cm3/min and a response of 47Hz at a pressure of 21MPa. These components have the same performance as oil hydraulic system.

Development of Water Hydraulic Servo Control System Considering Water Characteristics.

The oil hydraulic servo control system has a long history of application to various machines. However, a cleaner hydraulic fluid is necessary as we are faced with problems of fire or contamination due to oil leakage. We succeeded in improving the performance of a water hydraulic servo control syrstem over that of the oil hydraulic servo control system. Our water hydraulic servo control system is based on the analysis of the advantages of the physical properties of water for servo control. Furthermore, we can fabricate a simple water servo control system consisting of least components which can cover a wide dynamic performance range and can guarantee the same applications fields as the oil hydraulic servo control systems. Important components are the wide-dynamic-range water hydraulic pump system and the high-response, wide-dynamic-range water servo valve. The performance and durability of the system and components were tested and verified. As a result, the water hydraulic servo control systems are found to be the same as or superior to the oil hydraulic servo control system. Applying the advantages of the properties of water to a design, we can achieve better performance and lower cost with the water hydraulic servo control system than the conventional oil hydraulic servro control systems.