Hydrostatic-mechanical power split transmission for locomotives A new CVT approach in high power applications

摘要

Continuously variable transmissions based on the principle of hydrostatic mechanical powersplit have been on the market in agricultural applications for more than a decade. In high power Diesel driven locomotives there are available two drivetrain systems; the hydrodynamic transmissions and Diesel- electric drives. There are also some applications with pure hydrostatic drives in shunting locomotives. VDS Getriebe GmbH has worked out a continuously variable transmission system for Diesel locomotives up to 1800 kW based on the principle of hydrostatic- mechanical power split. The transmission consists of a CVT module with pure hydrostatic drive at low speed and two powersplit gears shifted at synchronous rotation speeds. There are foreseen two range gears, the first for operation below 60 kph, the second range for speeds up to 130 kph. Shifting from one range to the next is done with torque interruption and electronic synchronisation by proper control of the hydrostatic power branch. Additionally a forward/reverse gearset is foreseen at transmission output for achieving same functionality in both directions. Due to the specific configuration, the required drawbar pull is achieved with reasonable hydrostatic units available for mobile applications. The big advantage in comparison to hydrodynamic transmissions is the significantly improved efficiency, especially at low speeds. The transmission is designed to achieve maximum drawbar pull of 30 tons and maximum speed above 130 kph.