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.