Differential converter transmission
The differential converter gearbox is a hydromechanical, fully automatically shiftable gearbox, which is mainly used in city buses and internal combustion railcars with lower loads. It combines the advantages of the hydraulic transmission for the starting range and the mechanical transmission for the continuous driving range.
History of origin
The transmission was created through decades of experience in operation with mechanical and hydraulic transmissions. Mechanical transmissions were very efficient in power transmission, but required a separation of motor and transmission unit when starting up and shifting. The hydraulic transmission does not need this starting aid in the form of a clutch, but it is less efficient in continuous operation. This is why the differential converter transmission from Voith Heidenheim was developed for vehicles with lower drive power and preferred use of a fully automatic transmission .
The simultaneous addition of a planetary gear means that additional gear units and reversing gear units can be combined in one housing . This gear configuration ensures a steady and stable tractive effort over a wide speed range.
Structure and mode of operation
The mode of operation can be seen in the attached sketch. If the vehicle is parked and secured with the brake, the transfer case is driven by the transfer case and the pump wheel of the hydraulic converter is driven via the hollow shaft. This state is maintained when starting when the turbine wheel of the starting converter drives the output shaft via the freewheel when the converter is full. With increasing speed, the power flow looks for the path of least resistance. More and more shares are transferred directly to the output shaft via the planet gears.
The freewheel prevents these movements from being transmitted to the converter turbine wheel via the mechanical part of the gearbox and provides additional braking. After a short start-up, the operator of the vehicle can influence this process of gradual transition from hydraulic to mechanical drive by tightening the brake of the transfer case. This is recommended e.g. B. when starting on a downhill stretch under partial load . It differs from gearbox to gearbox when it automatically switches to purely mechanical operation, regardless of full load and partial load .
This process is shown in characteristic curves that indicate the relevant speeds and torques depending on the gear used in the planetary gear. For the gearboxes D 501 and D 502 they can be found in the literature. The planetary gear with the existing number of gears can be selected variably.
literature
- Voith Getriebe KG Heidenheim: hydrodynamic gears, clutches and brakes , Otto Krauskopf Verlag, Mainz 1970