Use of compliant mechanisms in gearbox applications

Abstract: The purpose of this thesis is to prove that the use of compliant mechanisms in gearbox applications is viable. Compliant mechanisms are developed for their implementation in Scania’s hybrid asynchronous gearboxes. These mechanisms are presented as a replacement for the latch assembly currently in use to hold the position of the gear-shifting elements. The objective is to implement a compliant mechanism in order to avoid wear and increase the life cycle within the given constraints, as well as to have a better understanding of this kind of mechanisms. The presented literature study shows that bistable and tristable compliant mechanisms are the most suitable ones for this application. Titanium alloys, tool steels, and bulk metallic glasses are discussed as the best material options for compliant mechanism manufacturing. A mechanism idea generation and selection process is conducted. Finite Element Analysis (FEA) is developed with the chosen bistable and tristable compliant mechanism ideas. The tristable concept results on being inappropriate for this application, as it does not fulfil the volume and positioning constraints. The bistable device is proven to be suitable, and further analysis is carried out to study its fatigue resistance and show that it fulfils all the requirements, solving the weaknesses of the latch and absorbing the impact in the shaft. Additive manufacturing methods and injection moulding are found to be incompatible with the designed mechanisms. That is why the chosen bistable mechanism is designed to be made out of different parts. Future work is presented to strengthen the weaker points of this project.