New Delphi Powertrain Mounts Use Magneto Rheological Fluids to Improve Performance, Safety and Refinement; Improved Handling of Transient Torque Events

9 July 2009

Delphi’s new MR Mount is the first technology that allows precise real-time management of all the relevant frequencies created by an automotive powertrain. Click to enlarge.

Delphi Corporation has developed a new powertrain mount that uses magneto rheological (MR) fluid to change its dynamic rate in real time. MR fluid is a suspension of magnetically soft particles in a synthetic hydrocarbon fluid.

The new MR Mount prevents the build-up of resonance in a system by maintaining control of the mounted mass across all appropriate frequencies. As well as significantly reducing powertrain noise and vibration, the new mount can improve vehicle performance and stability and help isolate the occupants from torque step events such as those generated by start-stop operation.

This is the first technology that allows precise real-time management of the relevant frequencies created by an automotive powertrain, including the challenging low frequencies and higher amplitudes caused by transient torque events.

—Timothy Schlangen, Delphi’s MR Mount manager

The magneto rheological technology allows the stiffness to be tuned to control appropriate powertrain frequencies in real-time. Click to enlarge.

Powertrain mounts provide a wide range of functions. As well as suspending the mass of the engine and transmission, the mounts provide a reaction point for torque and isolate the body of the vehicle from powertrain noise and vibration. With conventional technology it is impossible to optimize the way the mounts behave for each function and each dynamic state.

Delphi was one of the first companies to address this problem of engine mount optimization, introducing glycol-filled mounts that can be tuned to control one main frequency, typically the primary engine bounce mode. The latest magneto rheological technology almost completely eliminates the need to compromise the way the mounts behave for each function and each dynamic state by allowing the stiffness to be tuned to control appropriate powertrain frequencies in real-time.

The system uses magnetically soft iron particles suspended in a base fluid, held within a cavity in the rubber body of the mount. When a magnetic field is applied by a coil, the particles become aligned, increasing the sheer stress and therefore the resistance to flow. The stronger the magnetic field, the higher the dynamic rate (effectively the stiffness) of the system.

The current is controlled by a processor that receives data already available on the vehicle data bus. This data can include throttle position, road speed, engine speed, temperature and any other information required to deliver the level of control specified by the vehicle manufacturer. Closed loop feedback is provided by direct measurement of the fluid pressure in the system, ensuring real time compensation for changing conditions as the system components age.

Benefits include improvements in powertrain isolation, vehicle stability and traction. The system also provides a solution to the refinement and stability issues associated with torque transients created by events such as engine start (useful with stop-start systems), sudden wide open throttle, braking, gear changes and moving an automatic transmission into drive. It can also improve traction, stability and occupant comfort on rough roads by managing the low frequencies created by the movement of large powertrain masses. For hybrid vehicles, it provides an affordable damping system for the wide range of frequencies generated by two different power sources.

MR Mounts also bring manufacturing and logistics benefits because the same component can be electronically tuned for a wide range of applications, allowing the parts count to be reduced. Its ability to reduce powertrain-related noise and harshness also means that other systems for sound and vibration absorption can be simplified, further reducing weight and simplifying assembly.

The first application will be for engine mounts in the new (2010) Porsche GT3. In the GT3 application, Porsche is using the technology to improve traction and stability during hard acceleration and cornering. The control unit will stiffen the mount when torque is applied, reducing power hop that can momentarily reduce the tire contact patch. Stiffening will also reduce engine roll and maintain balanced torque transfer across the vehicle.