Infinitely Variable Transmissions in neutral gear: Torque ratio and power re-circulation

In this paper, the power re-circulation and the torque ratio of Infinitely Variable Transmissions (IVT) are investigated. The focus is on the gear neutral condition, which is very useful in many applications but actually critical in terms of efficiency, reliability and control. An experimental investigation of the output to input torque ratio as a function of the speed ratio close to the neutral gear is shown, the results of which are compared with a theoretical model of the IVT transmission in steady-state. It is shown that the power split transmission can be utilized as a torque multiplier for vanishing output angular velocity, as requested by application to terrestrial vehicles. It is also shown that the mathematical model predicts the overall trend of the torque ratio and its value with vanishing speed ratio, a result that can be of some help for optimal control of the transmission. Furthermore, the power re-circulation in the neutral gear is discussed in detail for vanishing output torque.