Effect of Temperature on Braking Efficiency Stability of Magnetorheological Fluid Auxiliary Braking Devices

摘要

Fluid auxiliary braking devices can provide braking torque through hydraulic damping, fluid auxiliary braking devices can also convert vehicular inertia energy into transmission fluid heat energy during the braking, which can effectively alleviate the work pressure of the main brake. Traditional hydraulic auxiliary braking devices use transmission fluids to transmit torque, however, there is a certain lag effect during the braking. The magnetorheological fluid (MR fluid) can also be used to transmit torque because it has the advantages of controlling braking torque linearly and responding fast to the magnetic field changed. The temperature of MR fluid will increase when the vehicle is engaged in continuous braking. MR fluid temperature changes will cause a bad influence on the efficiency stability of auxiliary braking. So it is necessary to clear about the effect of temperature on MR fluid auxiliary braking torque in order to keep the braking efficiency stability through torque compensated by other factors, such as changing the magnetic field strength. In order to analyze the effect of temperature on MR fluid auxiliary braking torque, this study established the mathematical model of the MR fluid auxiliary braking device through the theory of one dimensional flow theory of hydraulic retarders, and the properties of MR fluid are described based on the Bingham model. This paper researched the change of the properties of MR fluid under the same magnetic field condition with different temperatures, and summarized how much compensated torque is needed to keep the braking efficiency stability. Research showed that when the vehicle is engaged in continuous braking, the temperature effect on the braking torque is non-linear. The braking torque increases with the increase of temperature under the same magnetic field condition, the braking torque increases fast at high rotating speed of the rotor.