Design considerations about the hydromechanical transmission IC2OC

Abstract

The hydromechanical transmission IC2OC operates as an Input Coupled transmission at low speeds and as an Output Coupled transmission at high speeds; a series of clutches allows the shift between two layouts. In this way the transmission speed range can be almost doubled. The design of this transmission requires the full mechanical speed value for both basic layouts. Since these values heavily influence transmission performance, their choice must be made carefully. In this paper two choice criteria for these two speeds are proposed and discussed: the first one refers to the optimal choice for each basic layout; the second sets these speeds in correspondence with the speed of the maximum energy processed in a working cycle. The effectiveness of these two criteria, applied to an off-road vehicle transmission, demonstrates that the former guarantees greater efficiency than the latter, despite its good assumptions.

Hydromechanical Transmission IC2OC: Component Sizing and Optimization

“…The transmission model used in the subsequent simulations and optimization procedure has already been presented in [25].…”

“…The full mechanical point speeds for CR2 are taken from a study [25] performed on a cycle measured by Dana Rexroth [22] on the same vehicle under examination operating in the field. The energy-weighted frequency histogram, which is obtained from the statistical study, highlights a clear bimodal trend, with two speed peaks at which the two full mechanical points can be placed:…”

“…The design procedure of this transmission is based on the knowledge of the two FMP speeds [25]. Since these are linked to the conditions of best efficiency, their choice is crucial for the overall efficiency of the transmission.…”

“…In that case, the two FMP speeds are assumed to be equal to those of IC and OC layouts, which in turn are assumed based on considerations deduced from previous works. In [25], however, two criteria for assuming the FMP speeds are presented and discussed: the first one provides the two FMP speeds equal to the optimal values for the two single layouts, derived from [15]; in the second criterion FMP speeds are assumed equal to the most frequently used speed values, which are deduced from a statistical analysis carried out on measurements involving the same vehicle under examination [22]. The second criterion, despite its good premises, leads to higher consumption than the first one.…”