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Development of a New Continuous Variable Tractor Transmission With Hydrostatic Mechanical Powersplit
Technical Paper
974193
Sector:
Language:
English
Abstract
It is well known that lots of experts have tried to realize a
CVT for tractors for a long time. First developments go back to the
year 1907 (car manufacturer Renault).
Scientific investigations concerning continuously variable
tractor drives, however, became known rather late after the Second
World War (Meyer in 1959).
There was no breakthrough on a wide basis, although some
remarkable developments were presented the last time. You will
probably know some of them. In opposite to that, pure hydrostatic
vehicle drives for garden tractors were produced in large numbers
in U.S. and Japan. In the last time, CVT transmissions from CLAAS
(HM8), FENDT (Vario), STEYR (S-matic), and ZF (Eccom 1,5) were
introduced.
In principle there are two basic directions concerning the
development of powersplit CVT: 1. Such, with small hydrostatic
units and additional gears (4 or 8), and 2. such, with bigger
hydrostatic units without additional gears, but with two
ranges.
I would like to concentrate on the second point.
We decided to choose the second development direction to avoid
the problems of the additional gears and electronic shift system.
Therefore, we needed special hydrostatic units which were not
available on the market.
The requests for the hydrostatic units were: extremely high
efficiency; large swivel ranges; low noise operation; low
production costs; manufacturing possible without machine
investment; possibility of an integrated fitting.
In the first step, these hydrostatic units were develoepd at
FENDT until we found a suitable partner for the further
development, who was able to produce these high quality units. The
partner we found was SAUER-SUNDSTRAND and we had very good
cooperation during the developemtn of such an important basic
component.