NVH Refinement using Structural Optimization for Low-Powered Tractor

NVH is very important topic in development of a vehicle. Legislative requirements for driver ear level, the comparison to competitor vehicles in terms of noise and vibration as well as sound quality set very challenging targets. High noise at Driver Ear Level (DEL) and tactile vibrations of tractor is the major cause of exhaustion to the operator. With growing competition there is need for the tractor manufacturers to control noise and vibration levels. Recognizing the corrective measures to reduce the noise and vibration has a greater impact in increasing the efficiency of the product and operator comfort.

Objective of this paper is to control vehicle level noise and vibrations using vehicle level structure modifications. It includes airborne and structure borne NVH study on a tractor by measuring sound pressure and vibration levels at vehicle level. Single cylinder engine was mounted on light weight structure to meet the power and torque requirements in the tractor. Also, there is no passive vibration control system in Indian tractors. Due to this the problem of noise and vibration arises. There is need to isolate the engine and transmission vibration from the body with rubber mounts. In this way appreciable reduction in noise and vibration can be achieved. Tests were performed to distinguish the root cause of unwanted noise and vibrations produced during operation of the tractor. Abnormality in exterior noise was observed. These problems were rectified by structural alterations. Addition of acoustic side shields and oil sump cladding was beneficial for exterior noise. Vibration was found higher at all tactile locations. Addition of frame stiffeners improved vibrations significantly at all tactile locations. Attachment point stiffness also increased. Addition of masses on steering wheel, driver seat locations.