Research On Friction Characteristics Of Pneumatic Wedge Brake

The vehicle brake is considered to be the key component for vehicle safetyperformance, it has long been known as the domestic and foreign experts and scholarsconcern and search object. The quality of performance and efficiency of brake good ornot will directly affect the transport safety. These are closely related to the friction alcharacteristics of the brake. The frictional characteristics of brake are the mostimportant part of the braking performance. It directly determines the overall brakingperformance of automotive brake systems. And pneumatic wedge brake is widely usedin recent years, because it lower cost, and braking torque and efficiency are higher thannormal drum brake. So a pneumatic wedge brake was considered as the research object,and combined the finite element analysis and physical bench test to study the frictioncharacteristics of brake deeply.The mainly content of this paper are shown below:(1) In order to study geometric structure of pneumatic wedge Brake impacted onfriction properties. Described the basic structure and working principle of the brake.According to working principle, mathematical model of the finite element analysis andthe braking torque model were established. In accordance with the actual structuralparameters and working principle, the paper analyzed the stress and strain distributionstatus of the key components. Concluded requirements about braking torque, materialsand structure of the key components, in actual operating conditions.(2) In order to study pressure distribution on brake shoe impacted on frictionproperties. Through the stress analysis of pneumatic wedge brake, front and rear brakeshoe’s pressure distribution mechanical model are established. Two types ofnon-uniformity indexes of pressure distribution over brake linings are defined,evaluated the brake based on the criteria of the two indexes, and analyzed itscharacteristics with the change of friction factor. Analyzed the Von Mises stressdistribution of the friction plate, and compared with the wear tests. The result indicatesthat the brake shoe’s pressure distribution remains follow the sine law, but the unevendistribution of pressure friction plate is more prominent. Due to its structural constraints,whether it is a single brake shoe pressure distribution on the friction or brake shoepressure distribution between, the unevenness of inherent defects are difficult toimprove. (3) In order to study the heat and cooling process of pneumatic wedge Brake, andthe brake drum temperature distribution law impacted on friction properties. Establisheda thermodynamic mathematical model of the friction pair. Defined transient thermalanalysis boundary of the brake drum, thermal performance parameters of materials andcontact boundary conditions. Simulated temperature rise phenomenon of pneumaticwedge brake by using finite element transient thermal analysis method. Concludestemperature characteristics and basic law of brake drum. At last, analyzed therelationship between friction coefficient, slope, speed and the temperature rise.(4) According to QC/T239-1997Trucks, buses brake performance requirementsand QC/T479-1999test method of trucks, buses brake, done bench test with pneumaticwedge brake, got test dates about aspects of braking efficiency, Hot-recession recoverand wear. Provide accurate and reliable dates to study of brake friction characteristics.