On Electro-Mechanical Brakes (EMB) spring-support can be necessary for releasing the brake without electrical energy. Advantageous brake-configurations can make use of the spring over the whole actuation range during engage and release.
Such optimized spring support is known as “energy-swing. Under loss-less conditions the spring force could be in permanent equilibrium with the force required to press the pad, i.e. the brake could be controlled without actuation energy. In reality this will not be fully achievable as actuation losses and different operational conditions need to be covered. Still, significant advantages can be gained.
The EMB of Vienna Engineering (VE) fulfills a key condition for energy-swing as it facilitates using the spring for engage- and release-support.
Car brakes must release automatically when power is off. Consequently, spring-induced engage-support must always be smaller than release-forces and release-support must ensure overcoming mechanical resistance. The VE-EMB can fulfill the requirements while maximizing the benefits by introducing a cam /rocker mechanism.
With realistic assumptions of losses, tolerances and operational influences the potential of the mechanism in terms of saving actuation energy, reducing actuator motor power and actuation timing improvement must be questioned. Besides, the related increase of complexity needs to be addressed.
This paper discusses the issues by comparing a VE-EMB without spring, the cam-rocker design and the simpler but less configurable lever-pushing method.