2015 Volume 2 Issue 3 Pages 14-00542
Hydraulic pumps are positive displacement machines and the primary components of fluid power systems that transform energy from mechanical sources to pressurized oils. The reliability and efficiency of pump components are highly dependent on the tribological characteristics of the sliding parts, which perform bearing and sealing functions. Higher pressurization and increased compactness result in higher contact pressure and oil temperature, which can cause catastrophic damage to the components and severe deterioration of the oils. Three representative hydraulic pumps—including a swash plate axial piston pump, a pressure-balance vane pump, and an external gear pump—were tested under real operating conditions to determine their thermal effects. Discharge pressures up to 21 MPa and rotational speeds up to 50 s-1 were tested. Hydraulic oils with viscosity grades of 22, 32, and 46 were used at 30°C-50°C. The thermocouples were embedded in the cylinder block, swash plate, and valve plate of the piston pump, cam ring and side plate of the vane pump, and the side plate of the gear pump. Platinum resistance thermometers were placed in the conduits close to the suction and discharge ports of the pumps. The temperatures of the sliding parts and working oils were measured simultaneously. Results indicated that for all pump tests, temperatures increased almost monotonically as the discharge pressure increased. The temperatures of the sliding parts were always higher than those of the discharge oils. With the piston pump, the temperatures at the locations corresponding to the discharge port of the swash plate and valve plate were higher. In contrast, with the vane pump, the temperature at the location on the cam ring closest to the suction port was highest.
