Fine dust is a danger to human health. However, the fine dust is not only caused by exhaust emissions: each braking action releases particles. In future the new brake dust particle filter from MANN+HUMMEL will retain these emissions directly at the source.

As the level of air pollution worldwide is on the rise, the awareness of risks and consequences to human health is also increasing. Many cities plagued by contaminated air are constantly discussing the causes and possible solutions. Particles with a diameter of less than 10 micrometers (PM10) are particularly dangerous because they can penetrate pulmonary alveoli. Smaller particles than that can even directly enter the blood and cause heart disease and respiratory illnesses.

The focus of current legislation is concentrated on the exhaust emissions of the combustion engine. Other sources of fine dust such as the fine dust generated by brake abrasion have up to now been disregarded to a great extent. In Germany approximately 10,000 tons of brake dust particles are created every year. Measurements on test benches show that more than 90 percent of this consists of particles with a diameter smaller than 0.55 micrometers. The fine dust pollution is especially high at busy road junctions because at such locations many braking actions are required. But longer visits to underground railway stations can also be harmful to health. Measurements in the London underground system, for example, have registered air pollution with inhalable particles in the range of 500 to 1,120 micrograms per cubic meter. The daily limit specified by the European Union of 50 micrograms per cubic meter is therefore greatly exceeded. But it is not only vehicles with a combustion engine or trains which create the fine dust. In electric and fuel cell cars with no exhaust emissions and stationary engines braking actions also take place which result in the generation of dangerous brake dust.

New Filter

MANN+HUMMEL has developed a new solution for all of these applications in the form of the brake dust particle filter. Located close to the brake and therefore the source, the filter retains the particles which are the result of mechanical abrasion on the brake. The filter consists of a robust housing which is positioned directly in continuation to the brake caliper and captures particles created in the braking process. The new development can be fitted to any existing installation space and can be adapted to different brake sizes and concepts.

High temperature stability

For the filter media the engineers opted for a metallic based web. The fibers are resistant to corrosion and are able to withstand the high temperatures on the brake which can arise under extreme circumstances. In order to maximize the effective filter surface area and retain as much dust as possible, the filter material in the housing is arranged in pleats and bags. The experts at MANN+HUMMEL subjected the filter system to extreme conditions on the brake test bench. The result was impressive with the filter reliably retaining up to 80 percent of the particles generated in the braking process. That helps the environment, contributes towards improving the air quality and as a positive side effect prevents the soiling of wheel rims and brake systems.

The vision is for zero emissions

One of the first field tests for the brake dust particle filter was made in the ‘fine dust eater’ vehicles from MANN+HUMMEL. These vehicles have been on the road for a number of months. Their mission is to retain more fine dust than the vehicles generate themselves. To make this a success, the ‘fine dust eater’ vehicles are equipped with three different types of filter systems: a fine dust particle filter, a new type of NO2 fine dust combi filter for the cabin and a brake dust particle filter. For MANN+HUMMEL this is a further step towards implementation of the vision zero emissions. Completely new approaches are conceivable. In future, for example, vehicles which meet the EURO 5 emissions standard could offset their pollutant emissions by retaining fine dust from the ambient air and also retaining fine dust generated by the brake system. The emission balance of the complete vehicle could then be used to classify the vehicles equivalently to EURO 6 or even classify them as equal to pure electric vehicles. This would avoid driving prohibitions for such vehicles and all would stay on the road. MANN+HUMMEL is therefore making an active contribution to help residents in conurbations breath in again with relief.

2003

2004

2006

2007

2009

2010

2014

2015

2016

2018

2019

2021

First ideas of the brake dust particle filter generated

First field test with a number of vehicles in the MANN+HUMMEL fleet

Data collection on the generation of brake dust

Tests on a brake test bench with the aim of collecting more information on the particle size and temperature distribution

Development of different concepts for the brake dust particle filter

Execution of first brake tests on the road together with an OEM

Start of the ‘fine dust eater’ project - first vehicles equipped with brake dust particle filters on the front axle

Real world testing: tests under real life conditions such as snow drives, runs in wet conditions as well as mud drives

Simulation of an alpine downhill drive (Großglockner test) with a special focus on temperatures at the brake system

Tests of different filtration media to further optimize the filtration efficiency

Investigation on a light weight design for maximum weight reduction with a target of less than 500 g for passenger car applications

Investigation of the influence of design elements to the systems’ filtration efficiency