Development of medium duty truck with engine mount system by Air Spring

In 2006, we presented our paper² concerning Engine Mounting Layout by Air Spring at Inter Noise 2006 in Hawaii. In 2008, the proto bench test model with light duty diesel engine was built and its actual test was conducted. As a result, a significant vibration isolation effect could be obtained and its paper¹ was presented at Inter Noise 2008 held in Shanghai, China. Then after, we organized a research project collaboration between universities, a public laboratory, vehicle engineering, and testing companies and a proto vehicle with a diesel engine mounted by four air springs was newly designed. Concurrently, the Genetic Algorism was also applied for the optimization of many parameters concerning the engine mounting layout, the calculations of stiffness matrix and inverse stiffness matrix to prevent the coupled vibration of lateral and rolling modes, and to obtain the displacement of each mounting point. Finally, the best engine mounting layout was selected to install four air springs on the torque roll axis plane. On the other hand, the original engine mount layout with cushion rubbers was completely changed to enable installation of four air springs, two lateral rods and tension rods, and four shock absorbers for the reduction of big engine movements against transient engine torque at engine start and stop, gear changes, etc. Two leveling valves were also provided on the frame for maintaining engine height against big engine torque. As a result, the engine vertical vibration level at 19.1Hz dropped below 1/5 in of the current vehicle installed with cushion rubber and the engine displacement by its big torque was within the limit. Further study such as vehicle durability test is necessary, but the air spring is very useful as a new vibration isolation material in diesel engine mounting layout.