To
improve overall performance, present-day tractors bank on continuously
variable drives based on hydrostatic technology. Some tractor manufacturers
have developed special transmissions to reach this goal, in which a
mechanical part interconnects with a hydrostatic part. Both transmission
types are usually combined in a single housing and contribute to performance
to a constantly varying degree.During the process, the two transmission
types are constantly engaged and in service; neither of the parts is
shut off.
The commonly used term for this special
transmission model is Continuously Variable Transmission (CVT). The
term is used to express that this transmission model truly is a stepless
transmission. With this CVT drive, the power generated by the diesel
engine is split at transmission input into a mechanical and hydrostatic
power branch. In the hydrostatic power branch that is supplied by Linde
Hydraulics rotational speed is generated by changing the swash plate
angle of the variable pump; compared with the diesel engine speed this
rotational speed is very variable, in both rotational directions. Both
power branches are combined in the planetary transmission, where the
rotational speed that is supplied directly from the engine is superimposed
by the hydrostatic speed.
The result is a continuously variable
output speed, which corresponds to a continuously variable driving speed-from
vehicle standstill to maximum speed. These different operating statuses
are achieved using the hydrostatic compact transmission model K-02 from
Linde Hydraulics. It consists of an electrically controlled HPV-02 variable
pump that supplies oil to a back-to-back mounted HMF-02 hydraulic fixed
displacement motor, directly and without any detours. Both engines are
integrated in a single cast housing and can be installed as a compact
assembly; the cast housing itself is installed in the main transmission
housing.
The optimum interplay between the mechanical
and hydrostatic systems is made possible through ingenious control electronics
that provide the driver with entirely new options.
Simple operation relieves the burden
on the driver and thus increases driving safety. A control lever for
driving forward/reversing as well as the accelerator, or even just a
single lever, are the controls the driver has to operate. Selecting
gears and disengaging the clutch are no longer required. The vehicle
accelerates continuously in line with the accelerator pedal from 0 to
maximum speed.When the driver takes his foot off the accelerator pedal,
the vehicle automatically brakes smoothly until the vehicle comes to
a complete stop. The standstill can even be actively regulated, for
example on a slope. A requirement for this kind of active standstill
control is the sensitive and hysteresis-free conversion of the electronic
driving signals by the K-02 unit. Thanks to this characteristic, it
is also possible to easily implement a cruise control function.
About Linde Hydraulics
Linde Hydraulics is a division of Linde material handling. Cast
parts, cylinders and steel construction supplement the product range
of drive technology which currently encompasses hydraulic pumps and
motors in addition to electronic controls, peripheral equipment, directional
control valves, swing drives and hydraulic axles.
Their customers are manufacturers of
industrial applications and mobile machines such as construction machines,
agricultural and forestry machines and municipal vehicles. As an expert
in mobile hydraulics, Linde Hydraulics develop and manufacture highly
demanding applications in-house. Linde Hydraulics also supplies the
three forklift brands of the Kion Group: Linde, Still and OM.
....CONTD
