KEYWORDS

Friction Mechanisms, Friction Test Methods, Automotive

THE DRAG TORQUE BEHAVIOR OF MANUAL TRANSMISSION SYNCHRONIZERS

Synchronizers generate a drag torque and hence losses, due to different speeds of the hub and the dog ring. The drag torque arises as media (lubricant and air) are being shorn between the friction surfaces. The drag torque has been investigated experimentally using special test rig and methods of measurement. Not only do operating conditions like the differential speed influence the drag torque but modifications in the degree of lubrication or construct size will also show different losses. Less lubricant between the friction surfaces reduces the drag torque. The viscosity of the lubricant exerts influence on the drag torque, too. Loss reductions in synchronizers can be achieved through modifications in operating conditions, design and via the application of tribological measures. Equations for calculating the drag torque reflect design-related, operational and tribological parameters and are an efficient tool for assessing the losses already in early phases of the development process.

AUTHORS

Maximilian Strebel, Hermann Pflaum, Karsten Stahl, Technische Universitaet Muenchen, Mechanical Engineering, Gear Research Center (FZG), Munich, Germany and Michael Wirth, BMW, Munich, Germany