Research On Key Mechanism And Heat Fading Of Air Disc Brake For Commercial Vehicles

Under the new technology environment and policy requirements,high efficiency and stability of air disc brake is of great significance to the braking safety for commercial vehicles.It will play a very positive role in improving the performance and stability and brand competitiveness of air disc brake products to grasp the period of strategic opportunity for research and development of air disc brake and complete the reserve work on theoretical research of the key mechanism and heat fading for air disc brake.In view of the fact that the independent intellectual property rights of the key mechanism and the theoretical research on heat fading of air disc brake are insufficient at present,this paper studies the characteristics of the force amplifier and the working principle of the clearance self-adjusting mechanism in the key mechanism,and carries out theoretical modeling,numerical calculation and experimental research on the thermal fading problem of the contact between friction pairs.The main study of this paper are as follows:Firstly,the policy support and market demand of air disc brake for commercial vehicles in China are introduced.The research status of key mechanisms of air disc brake at home and abroad and heat fading are introduced and compared.The shortcomings of domestic air disc brake products compared with foreign ones and the problems that need to be solved further are analyzed and summarized.Secondly,the components of air disc brake are separated and its functional model is established.The total functions of air disc brake are divided into six sub-functions,and the effects of key mechanisms and heat fading on sub-functions are summarized.Then,based on the characteristics of the elementary force amplifier,the pressure arm is simplified to a combination of variable angle wedge mechanism andlever mechanism,and its force-increasing characteristics are described mathematically.The design process of the key parameters of the pressure arm is proposed and its static analysis is carried out.Then the working process of clearance self-adjusting mechanism is described,and the working principle of typical clearance self-adjusting mechanism of several well-known foreign manufacturers is studied.Each part of the system is segmented and abstracted as a functional carrier.Finally,a functional model of the system is re-established,which broadens the thinking for the design and development of clearance self-adjusting mechanism.Secondly,the classification and mechanism of thermal degradation are studied.Based on the contact mechanics model of rough surface of friction pairs and the theory of adhesion friction,the formula of friction coefficient is derived.The thermal physical properties of lining materials are summarized.The relationship between friction coefficient and temperature is divided into three stages: growth,stability and decline.A mathematical model of temperature characteristics of friction coefficient is constructed.Finally,the numerical calculation model of transient thermal analysis of friction pairs is established,and the working condition parameters needed in the simulation analysis are determined.The transient temperature field simulation and thermal characteristics analysis of friction pairs are carried out.The simulation results and heat fading model are verified by bench test.This paper makes a useful attempt on the theoretical research on the key mechanism and heat fading of air disc brake for commercial vehicles.It has some reference value for the further innovation and development of products,and has some theoretical significance for the further study of heat fading.