Design and Development of Valve Train System for Terrain Vehicle Engine Using GT-SUITE Software

摘要

GT-VTRAIN, a multi-purpose simulation tool for the mechanical design analysis of valve train systems is used to develop the system. GT-VTRAIN is one of the six solvers of GTSUITE. There are two ways of solving models in GT-VTRAIN, either through a backward solution or a forward solution. The backward solution is an exact solution where the cam shape is calculated based on a known follower lift or valve lift. In contrast, the forward solution is an iterative solution where the follower lift and valve lift are calculated based on a known cam shape. The backward solution is used to generate the cam profile from the known lift profile (direct acting). Five valve lift profiles were generated with the aid of the software. The five designs have the same maximum lift and duration but they differ in terms of intensity or aggression. The numerical differentiation of the valve lift-degree profile will produce a velocity degree curve; the differentiation of the velocity-degree curve gives an acceleration-degree profile; and the differentiation of the acceleration-degree curve gives the jerk-degree characteristics. The design goal is to use a valve lift profile that is as aggressive as possible (higher acceleration) so as to achieve superior engine breathing characteristics, but it must be done within the mechanical limitations of the engine design. A lift-duration envelope ratio which is the area under the valve lift curve divided by that of the rectangle in which it sits is defined to judge the 'aggression', or otherwise, of a valve lift profile. The cam design feature of VT-Design is an interactive cam design tool used to generate a smooth cam or lift profile using a multiple polynomial scheme that meets the desired specifications such as the duration of the cam event, maximum lift, and maximum accelerations. High quality smoothing technique is crucial to avoid the components from being subjected to unnecessary high stress levels or unnecessary high power to drive them.