THE TORQUE ON THE INPUT SHAFT OF AN AXIAL-PISTON SWASH-PLATE TYPE HYDROSTATIC PUMP

Traditionally, the theoretical torque on the input shaft of a hydrosta tic pump has been determined using a macroscopic ''power-in, power-out '' approach that neglects the time-varying aspects of this quantity an d the compressibility of the hydraulic fluid within the circuit. In co ntrast to the traditional approach, this research analyzes and sums th e basic forces within the machine to compute the instantaneous torque exerted on the shaft. It is shown that the instantaneous torque repeat edly varies by 1.5 percent of its maximum value and that resonant freq uencies of the pump occur at even multiples of the ''piston-pass'' fre quency. Furthermore, an integral average of the instantaneous torque i s performed and shown to deviate by a maximum of 3 percent from the tr aditional method of computing this quantity.