Abstract
Efficient distribution of heat across the surface with which the pad and the rotor of a disc brake come in contact is necessary for optimal performance of brakes. It is shown that a heat design technology achieves a steadily braking performance by means of tribology characteristics of the brake. This has several effects including improved fuel economy, important because of the demand for improved environmental performance. As a result of this design, the power unit, the vehicle package, and the vehicle base specification are greatly changed along with it, and it is necessary to lighten the vehicle. However, a certain amount of mass is required for the brake rotor as thermal capacity because the main role of the brake system is to decelerate the vehicle by converting kinetic energy into frictional thermal energy. Even with such demand, it is still important that the vehicle drives comfortably and that it is easy to brake steadily.
In this study, it is presumed that the frictional force of the corner brake is influenced by the temperature of the surface where the pad and the rotor come in contact. This paper proposes a calculation method that predicts the temperature distribution across the depth of the friction surface; an experiment has been conducted for measuring the temperature just below the friction surface to confirm the calculation method. These results agreed with the estimation from the proposed calculation method.
Temperature conditions for stabilizing the braking performance at a high temperature have been considered based on the material properties of the brake rotor measured from a normal temperature up to 1000 degrees (Celsius). The brake rotor physical properties selected for measurement are specific heat, thermal diffusivity, Young's modulus, and the Poisson ratio. The friction surface shape was taken into account so as to obtain a braking performance which was steady in consideration of the rotor material properties and the calculated temperature distribution. This distribution was derived from the friction surface shape by using the proposed calculation method. From these results, steadily braking systems can be obtained.
KEYWORDS – disc brake, heat transfer design, transient heat transfer, tribology, friction surface