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10. Internationales Fluidtechnisches

8. - 10. März | 2016
in Dresden

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09:30   ics       Großer Saal

ZF cPower - hydrostatic-mechanical powersplit Transmission

First author:
Jürgen Legner, ZF Friedrichshafen AG, Germany

Wolfgang Rebholz, ZF Friedrichshafen AG
Robert Morrison, ZF Friedrichshafen AG

Until recently, hydrostatic-mechanical power split CVT drivelines have not found a place in
construction machinery. The majority of these vehicles still use hydrodynamic powershift
transmissions, full-hydrostatic transmissions or mechanical direct-shift transmissions.
Hydrostatic drive lines are widely used in construction machinery possessing lower engine
power. The upper power range is dominated by hydrodynamic powershift transmissions.
Decisions made by vehicle manufacturers about which driveline technology to be used, have
been based mainly on reliability, durability, and cost. Fuel economy has also been a growing
trend over the past years; however the additional cost of higher technologies must be
compensated by the savings in fuel cost over a time period of 2-3 years. The transmission’s
efficiency highly contributes to the vehicle’s fuel consumption.
ZF has thoroughly studied the possible concepts of hydrostatic-mechanical power split
transmissions. The most important requirements of reliability, durability and efficiency were
taken into consideration during the concept study. An examination the most typical working
cycles showed that a construction machinery transmission needs to be fully power split in all
ranges and obtain equal performance in both driving directions. It was also observed that up
to 60% of productive time for construction and forestry equipment was spent at a speed below
12 km/h. For this speed range, achieving the highest possible efficiency is vital. The result of
this research is the ZF cPower, which is an output-coupled, fully power split transmission.