Browse Publications Technical Papers 2004-40-0005

Non-Traction Pericyclic CVTs 2004-40-0005

A non-traction pericyclic continuously variable transmission system technology is described. Pericyclic motion involves oscillation, nutation and stepless circular pitch indexing. A kinetic prototype has been designed, fabricated and experimentally tested confirming stepless/smooth variable speed ratio capability under electro-mechanical control. This paper presents experimental results and compares key features of state-of-the-art traction (i.e., friction) based and gear/traction combination systems with proposed conceptual architectures for pericyclic continuously variable transmission systems (P-CVTs). Preferred non-traction pericyclic CVT conceptual designs are (i) high power density gearless roller/cam systems or (ii) advanced bevel type face gear systems. P-CVTs have a control system and three main components: a reaction control rotor; a pericyclic motion converter; an output rotor. Pericyclic CVTs predictably have very high operating efficiencies (i.e., 98% or more) at fixed speed ratios, provide direct ratio reductions of at least 50:1 in a single stage, and can accommodate the engine torque of the prime movers of high powered vehicles. P-CVT systems have inherent design features providing the capability of producing reverse rotation and neutral positions without use of additional hardware and control equipment. The P-CVTs are not power limited due to their architectural design features and pericyclic kinematics that permit operating contact ratios that can be orders of magnitude greater than traction CVTs. Although calculations show P-CVTs have recirculating power losses associated with the operation of the reaction control rotor, they predictably have low mesh losses in operational efficiency (i.e., up to 20% of that experienced in traction CVTs). The absence of sliding (in the roller/cam embodiments) and their extensive simultaneous overlapping of the pericyclic CVTs concentrated large area load-bearing contacts during torque transfer account for the lower mesh losses. Conceptual electro-mechanical pericyclic CVT (EM P-CVT) systems, with embodied motor/generator elements convert mechanical energy (prime mover's input torque/speed) directly into electric energy for various applications (i.e., operation of reaction control rotor, hybrid vehicles, output drive, etc.). Separate EM P-CVT or P-CVT units could be developed for mounting in vehicle wheel hubs for direct wheel drive. Pending experimental verification of projected system efficiencies and the management of recirculating power, P-CVTs could provide significant near-term improvements in fuel economy with accompanying reduction in vehicular emissions without sacrifice in vehicle performance. Further experimental work, including design, fabrication and testing of a scale or subscale power model, is required to verify expected improved automotive operational performance characteristics, overall efficiencies and cost of manufacture.


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