MAGNETO-RHEOLOGICAL POWERTRAIN MOUNTS

Description

BWI Group’s Magneto-Rheological (MR) Powertrain Mounts are used in the automotive powertrain environment and are designed to isolate vibrations from the vehicle’s body while also providing exceptional powertrain motion control.

Unlike conventional hydraulic mounts which provide peak damping at a single frequency and amplitude, the Magneto-Rheological (MR) Powertrain Mounts can provide high damping over a broad frequency and amplitude range.

Using magneto-rheological (MR) fluid to change the damping rate in real time, these powertrain mounts may be “firmed up” with high levels of lateral acceleration for more direct cornering, or “softened” for maximum comfort during straight-ahead driving.

Furthermore, the combination of effective control of powertrain motion with good attenuation of noise and vibration simultaneously improves vehicle stability and interior refinement.

The original Magneto-Rheological (MR) Powertrain Mounts were engineered for performance and configured for premium sports car applications. They prevented large transient powertrain movements (in the frequency range of 2-22 hz) from reaching the chassis.

The second generation design retains this capability while also providing isolation from smaller amplitude movements in the critical comfort range of 30-150 hz, enabling the technology to be applied to touring vehicles where superior levels of refinement are required.

Technology

Magneto-Rheological Powertrain Mounts exploit the novel characteristics of MR fluid. In the presence of a magnetic field, the MR fluid will “stiffen up.” In the absence of a magnetic field, it will flow like a normal liquid. This property can be used to control stiffness and viscous damping within the mounts.

The mount contains an electromagnetic coil that can generate a variable magnetic flux across the fluid passages. When the coil current is turned off, the MR fluid is not magnetized, the iron particles are randomly dispersed within the fluid, and the fluid behaves like conventional hydraulic oil.

When the coil is energized, the magnetic field causes the particles to align into fibrous structures in the direction of the magnetic flux. The strength of the bond between the particles in the structures is proportional to the strength of the applied magnetic field, so changing the current provides real-time variable damping with a very large range of force variation.

Applications

Unwanted powertrain movement can hamper vehicle handling by intermittently reducing tire contact loads at the road surface, especially during large torque transients or on bumpy roads. To counter this, conventional engine mounting strategies designed to increase stiffness can lead to noise, vibration, and harshness (NVH) issues, as vibrations are transmitted more directly into the vehicle’s passenger compartment.

However, when using BWI Group’s Magneto-Rheological (MR) Powertrain Mounts, stiffness and damping can be adapted to multiple vehicle conditions, yielding greater refinement, dynamics, and drivability characteristics.

Magneto-Rheological (MR) fluid technology also allows for the dynamic rate to be instantly changed between the base dynamic rate of the rubber-molded assembly and the molded assembly’s bulge rate. Most applications can benefit from using a softer base rate molded assembly as the required stiffness increase under large amplitude events can be achieved by altering the force required to push the fluid through the orifice.

The Magneto-Rheological (MR) Powertrain Mounts controller adjusts the mount damping and dynamic stiffness in response to specific driving conditions, resulting in the optimal mount setting for any given vehicle state.

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 the evolution of product innovation.