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Optimum performance counts
K-02 units for continuously variable tractor drives
To improve overall performance, present-day tractors bank on continuously variable drives based on Linde 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 "CVT" (Continuously Variable Transmission). 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 future of the tractor is stepless. K-02 units for continuously variable transmissions also guarantee, in addition to precise control of the driving speed without interruption of tractive power, optimum utilization of the diesel power in all operating statuses.
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, e.g. 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. Visible and noticeable benefits of this innovative drive system are:
– Sensitive start-up
– Smooth gear change
– No interruption of tractive power
– Observing precise crawling speed
– High efficiency
– Low fuel consumption over entire operating range
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