NVH Development of a High Torque SUV Using a Novel Active Torque Rod System 2018-01-0685

During the last decade, fuel economy mandates (CAFE regulations) have driven engine downsizing and down-speeding trends. More recently, downsized turbos are percolating down to heavier SUVs and trucks. Larger/heavier vehicles require high torque engines to provide attractive dynamic performance. While higher torque requirements can be satisfied with new innovations like the variable compression engine, larger and more upscale vehicles also need to deliver higher quietness requirements. For this, the vibration control system for combustion induced forces with high torque engines become very important. To address both dynamic performance and quietness requirements, active engine mounts have been previously adopted, however challenges for light-weighting, downsizing, and costs have still persisted.

A new vibration isolation technology using passive and active vibration isolation system named Active Torque Rod(ATR) was studied for application to a new vehicle to realize quietness targets with a smaller, lighter, and less expensive engine mount system. The basic concept of the active torque rod is to set it’s resonance below 200 Hz so as not to degrade the acceleration noise due to down-sizing by utilizing the passive vibration-isolation region. However, the engine primary order (2^nd order) booming noise degrades due the torque rod resonance below 200 Hz. Therefore, the resonance amplitude is suppressed by utilizing an inertia mass actuator in the torque rod and inputting an out-of-phase control force corresponding to the engine 2nd order input.

Technical details of ATR has been previously presented by R. Yamauchi, et al. [4]. Therefore this paper focuses on the benefits of applying an ATR to a premium C-segment SUV under development with a new inline 4-cylinder turbocharged engine. In order to achieve the acceleration noise targets, an active upper torque rod was applied to counter the large roll reaction force input. Acceleration noise levels were reduced by about 4 dB in the 250-800 Hz range when compared to conventional (passive) torque rod system. Both acceleration noise and booming noise achieved class leading levels. The proposed mounting system is approximately 8 kg lighter than the existing active control engine mount system.