No.1011E 2014Compact/Lightweight - Related Technologies Special Edition Mathematical Analysis of Efficiencies in Hydraulic Pumps for Automatic Transmissions

Hydraulic System Engineering Dept., Automotive Systems Business Headquarters
Hydraulic System Engineering Dept., Automotive Systems Business Headquarters, Doctor of Engineering
Abstract This paper deals with a mathematical analysis of pump effi ciencies in an internal gear and a balanced vane pumps. They are commonly used in current automatic transmissions including a continuously variable transmission. For these pumps, the infl uence of oil temperature as well as pump-operating pressures and pump speeds is clarified by using mathematical models taking oil temperature into consideration, which are constructed on the basis of actual measured fl ow and torque data under various pump-operating conditions. For fuel economy in a vehicle, because the pump should be operated under conditions to obtain higher pump effi ciencies, it is very important to understand the relationship between the pump effi ciencies and the pump-operating conditions. This paper reveals that the mathematical models representing the leakage fl ow and friction torque characteristics accurately is helpful to investigate the pump efficiencies as well as the flow and torque performance under various pump-operating conditions. As a result, the overall effi ciency decreases at extremely low and high oil temperatures. In the internal gear and the balanced vane pumps tested in this work, the region with a higher overall effi ciency lies around an oil temperature of 80℃ .
Keyword fluid power system, hydraulic pump, leakage flow, friction torque, pump efficiency, mathematical model
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