Σχεδίαση και βελτίωση λειτουργικών παραμέτρων πρωτότυπου συστήματος μετάδοσης κίνησης

Abstract

Most of the production vehicles developed up to date, still use internal combustion (IC) engines which are pushed for improvement in order to meet low emissions international standards. It is obvious that these standards will give way to new, stricter government regulations in the very near future, thus automobile manufacturers are already targeting zero emissions goal, by developing electric and fuel cell powered vehicles. At the same time, efficiency of every engine and power transmission components is explored, in order to achieve lower fuel consumption and higher autonomy. Nowadays, much focus has been given on new or optimized powertrain systems that can significantly improve these two targets, and are the reason Continuously Variable Transmissions (CVTs) are becoming more feasible and promising. CVT’s introduced a totally new infinite gear ratio variation, instead of the previously used manual or automatic discrete gear ratio transmissions. Their technological advantage is that they can change gear ratios at every time instant so as to achieve optimal engine efficiency. This improves the mileage, compared to traditional gear boxes, by allowing better matching of the engine operating conditions to the variable driving scenarios. The relevant literature evident that CVT use has been extensively researched and tested in IC and hybrid vehicles, resulting in reduced fuel consumption. However, to the best of our knowledge, the use of continuous variable transmission has not been researched on zero emission vehicles, such as, electric and hydrogen fuel cell vehicles. This thesis, targets to research a major part of this field, by presenting the design and development of an alternative CVT type, measure its efficiency, improve the operational parameters and provide experimental results from on road tests, using a zero emission vehicle. The scope of this thesis is the development of a new electronically controlled variable transmission system, targeting lower fuel consumption of zero emission vehicles. It includes the design, development and real driving scenarios experiments. A prototype fuel cell powered urban vehicle was used for experimentation and testing, and therefore system specifications and construction was developed accordingly. Lower energy consumption is provided by an electronically controlled change of ratio, using simple control architecture, according to driving conditions. The improved selection of operational parameters of the new system is achieved during construction, using experimental efficiency measurements and testing, that are presented and discussed. Also, at the last phase of development, on road tests are conducted in order to measure fuel consumption with and without the use of the proposed system. Results discussion provides a valuable insight of CVT use towards lower fuel consumption. Finally, the control unit operation is presented and evaluated during these tests.