Numerical and Experimental Investigation of Compressible-Brake-Fluid Flow Characteristics and Brake-Bleeding Performance in EPB Caliper

Abstract

This study investigates the compressible-brake-fluid flow characteristics within an electric parking brake (EPB) caliper during the bleeding cycles, subsequently determines the fundamental cause for reduction in brake-bleeding performance, and suggests a new design for its improvements. Three-dimensional simulation validation of the brake-fluid consumption curve is conducted through the parameter study of the air mass flow and bulk modulus. A numerical approach utilizing a three-phase (air, brake-fluid, and brake-fluid vapor) mixture model and a standard k-ω turbulence model is adopted to investigate the flow field details. Based on the unsteady simulation results and experimental verifications for the current and new models of the nut-spindle of a driving part in the EPB caliper, the primary cause for the reduction in the bleeding performance in the EPB caliper is determined to be the trapped air in the thread gap and in the space between the spindle and nut-spindle. Consequently, the head chamfer effect for the nut spindle is beneficial for removing trapped air and leads to performance improvement of 30.3 %.