Abstract
Research and/or Engineering Questions/Objective;
A driveline consisting of multiple masses and stiffness components has multiple resonance frequencies in a vehicle. Continuously excited phenomena like booming noise have been studied. Some active noise suppression measures have been applied to series production vehicle. Active controls have been proposed for unpleasant drive shafts torsional vibration, called shock & jerk, during acceleration. However, only mean value engine torque has been considered and is not sufficient for robust control design. Gear rattle is also transient phenomena during one ignition interval. There has been few publication in noise radiation of gear rattle.
Methodology;
Engine output torque profile can be generated with stroke mean torque and its amplitude modulation. Typical target torque profiles for drive shaft vibration suppression are represented including pulsation torque frequency. Then error between the target torques and realized torques, e.g. timing or distortion, are investigated. Vibration reduction with the realized torque profiles is evaluated. Appling the torque to a driveline oscillation system.A transfer function from teeth impact force to gearbox surface can be estimated with measured acceleration. The impact force contribution to gear rattle noise can be estimated with the engine torque model. Driveline oscillation models and internal combustion torque models are well established. So, numerical calculations with those models are used for the analysis.
Results;
As the resonant frequency increasing or oscillation cycle time decreasing, timing of torque raise in the two stage torque increase strategy is delayed or advanced. That causes deterioration of vibration suppression. Torque profile is deformed in steep torque change part in the pre-compensation strategy. That is also leading to deterioration. Degree of deterioration was calculated with engine speed and resonant frequency changes. Relative degree of deterioration in two stage torque increase is smaller than that of the pre-compensator.
Limitations of this study;
Target torque profiles which have been proposed in literatures are evaluated with the proposed method. However, there may be robust torque shape suitable for pulsation torque from ICEs.
What does the paper offer that is new in the field including in comparison to other work by the authors? ;
Engine torque amplitude modulation method was applied to evaluate shaped torque profiles for vibration reduction. That is quick and effective to show influence of engine speed and resonant frequency on control. Noise radiation factor was described with high pass filter to estimate gear rattle noise amplitude.
Conclusions;
A gear rattle noise estimation method to use in an early development stage was proposed as follows. First, simple and linear engine torque profile model was introduced. Second, the physical model of an idler gear rattle was introduced. The energy dissipation of the impact mesh is represented in this model. Finally, the application of the transfer function method to gear rattle noise analysis was introduced. The technique of evaluating the exciting force of gear rattle from the viewpoint of energy was examined. As a future task, the structure transfer function which contains harmonics further is required for subjective evaluation with hearing.
KEYWORDS – noise & vibration, drive line, gear rattle, transfer function, acoustic radiation power