Design considerations about the hydromechanical transmission IC2OC

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 each layout. 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.