Structural optimization methods and techniques to design light and efficient automatic transmission of vehicles with low radiated noise

This paper discusses design methodologies for automatic transmission of vehicles to achieve light weight and low radiated noise. Light weight design is a fundamental requirement for protecting the environment and improving fuel economy. In addition, quietness is another requirement for comfortable drive. However, in the design of automatic transmission, these two requirements are usually in trade-off relationship and engineers spend a long time to reach a desired design. This paper deals with the design approaches using structural optimization method for minimizing the radiation noise and the mass of automatic transmission. The weakly coupled analysis of elastic and acoustic problem are considered for evaluating the radiated noise problem, where the modal frequency analysis is first solved using the finite element method and the acoustic problem for computing a noise radiated from the surface of the automatic transmission is then solved using the boundary element method. Three different structural optimization methods, topometry, topography and freeform optimization, are applied for the design of outer casing of automatic transmission. The optimization results show that the optimization methods successfully found the light weight and low radiated noise design of outer case, and can be used at the early stage of the design process of automatic transmissions. The freeform optimization gives better solution compared with the result of topography optimization from the standpoint of the sound pressure reduction effect while the mass reduction effect is reduced in freeform optimization to satisfy the sound pressure constraint.