Influence of mode and design factors on the temperature condition of automobile drum brakes

Abstract

The current state of the highway pavement makes it possible to implement prompt transportation operations. These circumstances lead to the movement of vehicles at high speeds, which is impossible without a braking system capable of ensuring high braking efficiency and optimal flow of the process from the standpoint of stability and controllability. One of the main requirements for a modern automatic transmission braking system is the stability of the initial parameters, that is, parametric reliability. Therefore, it is important to have data on the brakes' operating modes and energy consumption. Only with such data is it possible to create a braking system whose output characteristic will be sufficiently stable under conditions of high energy load. Therefore, it is no coincidence that the international methodology for testing the effectiveness of vehicle brakes (UNECE Rule 13) provides for Test I, which is characterized by cyclic braking (urban conditions), and Test II, which is characterized by prolonged braking (mountain conditions). The brake mechanism is the most unstable link of the brake system; one way to increase its efficiency is to ensure sufficient energy capacity, which is limited by the temperature of the friction surface. The object of the study is the question of the equivalence of the change in the drum radius and the width of the friction belt of the brake, taking the invariance of the temperature of the friction surface under the selected test mode as the criterion of equivalence. It is shown that the role of the drum's side wall on the brake's temperature mode under different test modes can also be evaluated on grid thermal models with the involvement of the "Fourier–2 x,y,z" software complex. The effect of the heat transfer coefficient on the temperature mode of the brake due to the consideration of the gap between the drum wall and the wheel rim is shown. Derived formulas for determining the friction belt's equivalent width under the equality of heat flows, masses, and cooling surfaces.