Simulation and test of a very efficient friction brake actuator with a statically balanced spring mechanism

Abstract

Current automotive brake systems (pneumatic/hydraulic) are based on a split design: a central unit providing pressure and brake calipers transforming this pressure into clamping forces. Existing electromechanical brake calipers work without a central unit; but despite their simplicity they are not yet used. One major reason is the need of high forces and high electrical power for loading brake pads and calipers during braking. A possible solution is the application of a statically balanced spring mechanism; it stores elastic energy in a preloaded reversible spring mechanism integrated in the caliper. Using a nonlinear linkage mechanism, the stored energy transfers back and forth to and from the elastic parts of the brake caliper. Consequently, the additional power needed for applying and releasing the brake reduces significantly. The article analyzes the basic feasibility of such an actuator based on a double slider crank mechanism, which is determined for an application in a typical automotive disk brake caliper with high clamping forces of 20 kN. Experimental results from a demonstrator under real friction and stiffness conditions are presented and analyzed based on a theoretical model. The results prove the benefits of reducing driving power and also reveal critical points of the design.