BWI Group is entering production with a new second generation adaptive powertrain mount using its highly regarded Magneto Rheological (MR) mass control technology. By increasing the range of frequencies managed by the system, the Gen 2 technology extends the scope of application beyond high performance cars to include those where the emphasis is on refinement.
“The drive for reduced CO₂ emissions means that strategies such as engine downsizing, cylinder deactivation and stop-start are becoming common on even performance biased vehicles, but each has unfavourable effects on NVH,” said Tim Schlangen, BWI Group’s mounts engineering manager. “As a result, a new approach to powertrain isolation is required and we believe our adaptive mount is the solution. It reduces powertrain noise and vibration, improves vehicle stability and isolates the occupants from undesirable torque step events, such as quick vehicle cornering or wide open throttle.”
BWI Group’s adaptive engine mount uses MR fluid to change the damping rate in real time. The second generation can operate over a wider frequency range, partly due to the inclusion of a decoupler system, which creates a secondary path through which the MR fluid can pass, reducing mount stiffness. This enables the mount to be used on a wider selection of vehicle segments.
Gen 2 MR mounts have been improved further by the refinement of the copper coil and magnets within the units; the internal systems have been improved to give faster response and the control software has increased functionality, giving engineers greater precision and more flexibility. The combined effect is a more streamlined development process that reduces the need for test track time and access to costly development vehicles.
“This new level of tuneability enables us to further optimize the mount stiffness for more situations,” said Schlangen. “The first generation MR mounts prevented large transient powertrain events in the range 2-22 Hz from reaching the chassis; Gen 2 retains this capability while also isolating the chassis from smaller amplitude movements in the range 30-150 Hz, which is critical for refinement.”
The Gen 2 technology is proving so effective that some OEM customers are finding that vehicle suspension settings no longer have to be compromised in order to deal with particular engine vibration modes. Vehicle occupants experience a dramatic increase in the perception of quality, stability and security, as a result of reduced vehicle shake.
Developing a decoupler to work with MR fluid was particularly challenging because it is much denser than conventional passive mount glycol fluid. Much of the technology in the decoupler, such as the rubber and metal component geometry, and the rubber formulation, drew on core skills within BWI to develop solutions that remain proprietary to the company, according to Schlangen.
“We know that competitor systems work by cancelling the vibration after it has been generated, but our system is the only one which prevents it from occurring.”
BWI Group’s close relationship with vehicle manufacturers means it understands the unforeseen challenges brought on by trends such as engine downsizing. The company’s origins emerged from being a division of an OEM for over 70 years. This has created a legacy of understanding the importance of achieving optimum results at an entire vehicle level, not just at component or sub-system level.
“Maintaining a comprehensive component-to-vehicle level approach to our business is what drives our product innovation and evolutions, such as the Gen 2 MR engine mount,” said Schlangen. “It enables us to better understand the interaction of other systems on the vehicle that generate vibration and noise, significantly helping to reduce development time and cost.”
June 28, 2016