1993-11-01

Engineering Method for Rating Shift Quality 932996

It is common for difficult shifting to occur in synchronized transmissions. High shift effort is recognized as a basic performance malfunction that takes place during synchronization. This paper examines shift quality in vehicles with synchronized transmissions. The present study is working on three categories: a mathematical model and computer simulation of transmission shifts, an experimental verification of the model and program, and an engineering method for rating shift quality.
The mathematical model in this study is a refinement of a model from an earlier paper [1]. With experience, this model has seen revisions that allow the results to be more accurate than the previous ones. The model takes into considerations many elements that affect the synchronizing process such as: synchronizing torque, inertia of both clutch disc(s) and transmission components, clutch drag, viscous drag in the transmission, shifting RPM's, etc. Furthermore, the model includes parameters of the shift linkage that effect the synchronizing torque such as: handball load, mechanical advantage and efficiency of the linkage, resilient forces of some linkage components, material and geometry of synchronizers, etc. The computer simulation program has been written based on the above mathematical model. Simulation experiments give results in terms of synchronizing time for the maximum, but acceptable, handball load.
The model and the program were correlated through extensive in-truck experimentation. The important parameters affecting shift quality, and especially shift effort, were recorded for various actual shifts performed in many different ways by various operators. The actual data was reflected to the certain unified conditions to develop a numerical correlation with theoretical results.
This correlated simulation program allowed an in depth study into all of the parameters of shift quality. With this data, conclusions and recommendations were made as to the important concerning shift quality. Moreover, the simulation program was used to develop an engineering method for rating shift quality. Examples of the rating system are illustrated by a shift quality matrix.
The present study will be helpful towards making further advancement in the area of shift quality and future developments in the design of synchronizers and efficient linkages.

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