Reaserch On The Drum Brake Dynamics Performance

Heavy duty trucks are urgently demanded for greater brake power because the vehicle gross is increased, average brake speed is raised and the power/mass ratio is enhanced. That materially embodies on how to improve drum brake torque of manufactured produce and service vehicle. Fixed pivot leading-trailing drum brakes are extensively applied on heavy duty trucks, coaches and semi-tractors, because it's brake performance is steady without reference to positive revolve or reverse revolve, the structure is simple, cost of production is low and parking system is well-suited to subjoin. This drum brake is enacted as research project in order to promote its actual output brake torque, which not only meets society demands but also improves the brake safety of heavy duty trucks of manufactured produce and service vehicles.With consideration of various friction resistances and spring coil resistances that exist physically, dynamic model is firstly built up, of which the pressure in the chamber is input and the actual brake torque is output. With this system, one brake process of vehicle is stimulated. Displacement transmission ratio and force transmission ratio are introduced into brake drum research and are considered as two reference values of brake drum. According to the brake dynamic model, two kinds of geometry models of cam actuation mechanism have been researched on their influences on the actual output braking torque, aiming to determine which mechanism should be firstly selected to enhance the brake drum output torque. Friction coefficients of various positions of brake drum model are measured by experiment, and their influences on force transmission ratio are analyzed, in order to determine the friction coefficient of which position should be restrained to improve actual brake torque. Some parameters that maximally affect brake torque undulation have been discovered by the robust design of brake model.Through the brake dynamic model, Involutes and Archimedes cam actuation mechanism have been studied in terms of their influences on brake drum torque. It...