Außermotorische Feinstaubemissionen an Kraftfahrzeugen - Stand und Entwicklungstendenzen

Um die Verzögerung von modernen Kraftfahrzeugen gewährleisten zu können, kommen üblicherweise Reibungsbremsen zur Anwendung. Dabei kommt es aufgrund tribologischer Mechanismen zu einem Verschleiß von Scheibe und Belag, was zur Emission eines partikelförmigen Bremsstaubes führt. Die emittierten Verschleißpartikel sind den Größenordnungen des Feinstaubs zuzuordnen, gelangen nahezu ungehindert in die Umwelt und stellen ein gesundheitliches Gefährdungspotential für den Menschen dar. Für die wissenschaftliche Untersuchung sind effiziente Probenahmesysteme erforderlich, welche eine qualitativ hochwertige und reproduzierbare Probe bereitstellen. In einem ersten Teil werden Erkenntnisse zum Partikelinjektions- und ausbreiteverhalten innerhalb eines Probenahmesystems für die Erfassung partikelförmiger Bremsenemissionen vorgestellt. In einem zweiten Teil werden Primär- und Sekundärmaßnahmen zur Minimierung des Feinstaubausstoßes vorgestellt und bewertet

Testing of alternative disc brakes and friction materials regarding brake wear particle emissions and temperature behavior

In this study, different disc brakes and friction materials are evaluated with respect to particle emission output and characteristic features are derived. The measurements take place on an inertia dynamometer using a constant volume sampling system. Brake wear particle emission factors of different disc concepts in different sizes are determined and compared, using a grey cast iron disc, a tungsten carbide-coated disc and a carbon ceramic disc. The brakes were tested over a section (trip #10) novel test cycle developed from the database of the worldwide harmonized Light-Duty vehicles Test Procedure (WLTP). First, brake emission factors were determined along the bedding process using a series of trip-10 tests. The tests were performed starting from unconditioned pads, to characterize the evolution of emissions until their stabilization. In addition to number- and mass-related emission factors (PM2.5-PM10), the particle size distribution was determined. Another focus was the evaluation of temperature ranges and the associated challenges in the use of temperature readings in a potential regulation of brake wear particle emissions. The results illustrate the challenges associated with establishing a universal bedding procedure and using disc temperature measurements for the control of a representative braking procedure. Using tungsten carbide coated discs and carbon ceramic discs, emission reduction potentials of up to 70% (PM10) could be demonstrated along the WLTP brake cycle. The reduction potential is primarily the result of the high wear resistance of the disc, but is additionally influenced by the pad composition and the temperature in the friction contact area

Comparative Study on the Friction Behaviour and the Particle Formation Process between a Laser Cladded Brake Disc and a Conventional Grey Cast Iron Disc

Brake-wear particle emissions are the result of the components of a friction brake being in tribological contact, and they are classified as non-exhaust emissions. Since most of the emitted particles belong to the size classes of particulate matter (≤10 μm) and differ significantly in terms of their physico-chemical properties from automotive exhaust emissions, this source is of particular relevance to human health and, therefore, the focus of scientific studies. Previous studies have shown that coated brake discs offer significant wear and emission reduction potential. Nevertheless, no studies are available that describe the specific particle formation process, the contact conditions, the structure of the friction layer and the differences compared to conventional grey cast iron discs. The aim of this study is to describe those differences. For this purpose, the tribological behaviour, the structure of the friction layer and the associated particle dynamics within the friction contact between a laser cladding coated disc and a conventional grey cast iron disc are compared. The required investigations are carried out both ex situ (stationary) and in situ (dynamic). Parallel to the tribological investigations, the particle emission behaviour is determined on an inertia dynamometer using a constant volume sampling system (CVS) and equipment for particle number and particle size distribution measurement. The results show that, for two different brake pads, the laser cladding brake disc has lower wear and less particulate emissions than the grey cast iron brake disc. The wear behaviour of the coating varies significantly for the two brake pads. By contrast, the grey cast iron brake disc shows a significantly lower influence