2015 年 81 巻 832 号 p. 15-00390
The demands for comfort vehicle are getting increased in these years. On the other hand, the demands for the weight reduction for low fuel consumption are also increasing. In order to achieve these demands, the most efficient way is to reduce the input to the vehicle body. For reducing the input from road surface to the vehicle body, the suspension plays very important roles. So far, many literatures written about reduction of the input by the suspension have been reported. However, there are less papers written about the influence of nonlinear restoring force of the suspension component such as the shock absorber and the suspension bush. Typically, time domain behavior like harshness has large displacement. Therefore, the influence of the nonlinear restoring forces is not negligible. In this paper, the influence of the nonlinear restoring force in time domain is presented. For simplicity, two dimensional model which consists of rigid links connected by the nonlinear springs and elastic beam is used. On the model, the restoring force characteristic of an actual suspension bush is taken into account to set the range of the design space for the nonlinear restoring force of springs. The instantaneous maximum beam energy is maximized and minimized in order to show the influence of the nonlinear restoring force of springs. The maximization and minimization are conducted using local optimization method by the use of the sensitivity with respect to the nonlinear restoring force coefficient. Besides, the mechanism of the change of the instantaneous maximum beam energy is discussed from the point of view of energy flow. Finally, the influence in different input characteristics is investigated by changing the speed passing over a protrusion.