Design Optimisation of Engine Mounts for Improved Vibration Isolation in Three Wheeled Passenger Vehicles

Abstract

Powertrain mounting systems play a crucial role in the overall functioning of three-wheeled passenger vehicles equipped with a single-cylinder diesel engine. Primarily, engine mounting systems are tasked with isolating the vehicle and its occupants from the vibrations produced by the engine. A properly designed engine vibration isolation system should ensure the stable positioning of the powertrain within the vehicle, even when subjected to dynamic forces and torque loads. Furthermore, it should accommodate the general motion of the powertrain and prevent any contact between the engine, transmission, and associated components of the vehicle. The mounting system should additionally shield the engine from loads imposed by chassis torsion or twists while minimizing the shock loads transmitted to the engine caused by road undulations. Moreover, the mounting system needs to prevent the powertrain system frequency from coinciding with suspension wheel hop and tramp frequency, as well as structure-borne and human-organ resonances. Therefore, a comprehensive examination of the powertrain mount design is crucial to ensure improved vibration isolation. This paper delves into the design considerations of a powertrain mounting system for a three-wheeled passenger vehicle featuring a transversely mounted single-cylinder diesel engine at the rear. The powertrain relies on three elastomeric mounts, with two positioned at the front of the engine and one at the rear. In this paper, a design rationale and calculation methodology for determining the stiffness and location of a powertrain mounting system are presented. This approach allows for changes in mount positions within allowable practical limits, considering packaging constraints. The analysis involves studying the vibration patterns of the existing powertrain configuration by examining its rigid body mode shapes. The paper proposes an approach to modifying the stiffness and positions of the elastomeric mounts with the goal of achieving >80% modal purity. This methodology focuses on mitigating vehicle vibrations and noise associated with these mounts, with the primary aim of enhancing the performance of the mounting system, ultimately leading to improved vibration isolation performance of the powertrain mounts. Keywords: Engine Mounts, Vibration, Three Wheeled, Powertrain, diesel engine, elastomeric mounts, MATLAB, Voigt Model, DOF model, kinetic energy