2014 Volume 45 Issue 4 Pages 58-65
This article describes the friction characteristics at a vane tip, which causes primary loss of torque in a balanced vane pump, through the measurement of the coefficient of friction at the vane tip using cylindrical test rings having various values of inner surface roughness. Especially, the influence of operating conditions such as operating pressures, rotational speeds and oil temperature on the friction characteristics is experimentally investigated. Under the situation that the coefficient of friction becomes lower by lessening the surface roughness in the region of less than 0.7 µmRz, the coefficient of friction increases with an increase in the pressure acting on the vane in this region. However, both a rise in oil temperature and a decrease in the rotational speed (the vane sliding speed) make the coefficient of friction higher independently of the surface roughness. In addition, a mathematical model for the friction characteristics at the vane tip under a fixed pressure condition is proposed by using the sliding speed of the vane and the oil temperature instead of the viscosity of oil as parameters. It can well simulate the relationship between the coefficient of friction and the operating conditions for each ring with a different value of the surface roughness.
