Improvements in brake fluid standardization to avoid noise & wear problems

<gf:p>Brake fluids offer large temperature ranges of incompressible fluidity for dynamic braking performance. Modern brake fluids combine increased boiling points in “dry” (new fluid) and “wet” (used fluid after few years in vehicle) conditions with reduced cold viscosity to achieve minimized vapor lock risks with more dynamic pressure build up performances. However, reduced lubrication performance risks have been observed within the development of first modern brake fluids. Since sealing rings in braking systems are “lubricated” by brake fluid and form tribo-systems, lubrication performance of the brake fluid is essential in vehicle application and is currently integrated into brake fluid standardization. Automated driving and increasing noise requests due to electrification will further increase tribological requests for the pressure medium. In order to avoid future wear and noise problems, it is essential to develop and validate appropriate test methods to assess and prescribe lubrication performance of brake fluids. Within the project TriNoWe – funded by the Federal Ministry for Economic Affairs and Energy (BMWi) – the impact parameters, stress conditions and their dependencies based on a deep tribo-system analysis were identified to develop appropriate test methods. A valid noise lab test method – provoking the product behavior in a lab test – was developed as DIN 51834-5 and was already introduced as pass/fail into international brake fluid standards. For wear, an appropriate test method based on identical test specimen and comparable tribometer use (but with incline setting, high temperature and longer load run time with load increasing starts and stops) – applicable after performed noise test – was developed as DIN 51834-6. It is in release phase by finished round robin tests to be also introduced into brake fluid standardization soon.</gf:p>