The design of a braking system involves a delicate balance between the friction pair, the disc and the pad, where the pad is a complex blend of constituents to provide predictable characteristics, typically, a known and consistent friction level. In its base form the brake has to absorb the vehicle kinetic energy by converting it into heat. This heat absorption by the friction pair can result in chemical and physical interactions with the release of debris about which we know little. The paper discusses the three primary areas of concern regarding the release of brake dust aesthetic, environment and human health. The aesthetic and corrosive effects of brake dust have long been a problem and reached such levels of complaint by consumers that JD Power now rate dust contamination as a quality issue. The environmental effects were first observed as effecting salmon in San Francisco bay and the research led to the states of California and Washington to introduce legislation limiting the amount of copper in brakes. Of most concern is the rising evidence that brake dust is a human health issue with most up-to-date research clearly relating emissions and brake dust to Alzheimers disease, a terrible brain degenerative disorder. Although these issues are highlighted and discussed within the paper it is not the focus. The paper focusses more on alleviating the emissions of dust by collection at source rather than solving the problems at source. The latter continually trying to resolve the unknowns through formulation or design changes an expensive and endless demand.
The testing makes use of a collection module that totally encapsulates the brake and tests a brake on a dynamometer using and independent testing facility. The test procedure consists of a Burnish program followed by 8 different drive cycles complying with test procedure SAE J2707 METHOD B, 1 SHIFT. It will be shown that, by careful design of air circulation within a collection system, over 92% of dust generated may be removed and collected with magnets collecting the ferrous elements separately. It will also be shown that debris collection results in reduced rotor and pad wear and that the brake temperatures during the braking event are not significantly affected. It is suggested that the implementation of collecting dust at source may provide the automotive industry with a system to meet current and progressive legislative requirements.
In addition the paper will demonstrate that the module will serve as a real life mobile laboratory where the OEMs may gather data from the filters to gain a greater understanding of the characteristics of the debris being generated during braking separating ferrous from non-ferrous materials.
A semi active design is introduced to demonstrate the system may respond to driving conditions and direct cooling air accordingly. In addition it is recognised that on-vehicle vehicle is needed and that is also being addressed.
Fieldhouse John, Advisor to Industry, UK; Gelb Joe, Brake Pad Waste Collection Systems, USA.