In line with the maxim "Vision Zero", ZF’s objective is to reduce not only accidents and downtimes due to failures, but also emissions to zero. Above all in the agricultural field, this target is always linked to a sustainable increase in productivity.
The integrated generator solution: ZF-TERRA+
ZF-TERRA+ offers a solution for high voltage and low voltage generator systems used in continuously variable tractor transmissions of the TERRAMATIC series. The generator module is integrated in the housing of the transaxles. Mechanical power supplied by the engine is converted into electric power and can be used directly on the implement or on the tractor.
Through the generation and use of electric power a higher power can be allowed on the diesel engine as it is not transferred to the mechanical transmission drivetrain but directly converted into electric power.
A relatively large engine, for example, can thus be combined with a smaller transmission (transmission downsizing). By using the available electric power it is also possible for a lighter tractor to operate larger implements in combination with an electric traction drive.
The ZF Terra+ generator platform is built on synergies with other ZF divisions (passenger car and truck).
ZF TERRA+ is available in two different versions.
High voltage version:
The high-voltage generator and inverters serve as a tractor power source, delivering up to 80 kW of continuous electric power. Furthermore an extension to a hybrid system is possible. (Fig. 1)
Low voltage version:
For applications with a continuous electric power requirement of up to 15 kW, we use low voltage 48 V electric motors and inverters such as those found in hybrid transmission passenger cars. (Fig. 2)
Electric single-wheel drive ZF eTRAC
The high-performance high voltage generator module ZF TERRA+ in combination with the electrical single-wheel drive ZF eTRAC (Fig. 3) ensure optimum progress of the trailer or attachment in terrain (Traction Management) (Fig. 4). With this concept ZF demonstrates how intelligent mechanical systems can also be applied in off-highway applications.
The scope of deployment for this novel driveline design is wide ranging. Electric driven axle systems for trailers and slurry tankers as well as electric driven stabilizer wheels for various implements are just some examples of this. Due to the sharing of the drive power between the tractor and trailer or attachment there are substantial advantages in difficult driving situations. The highly dynamically controlled traction support from the electrical drive facilitates working under difficult conditions. Consequently, cultivation of the fields during adverse weather conditions with softened ground is possible. The time frames available to the farmer for field work are therefore significantly lengthened.
The electric traction drive is reducing tractive effort coming from the tractor. Therefore either more powerful implements can be operated, or a smaller tractor can be used. This increases productivity and reduces fuel consumption and soil compaction.
The electric drive is realized with a fluid-cooled three-phase asynchronous motor with a high power density and a 2-stage transmission. The rated voltage is 400 V AC. The electric power available matches many requirements in diverse agricultural application.
Electric drive systems for Zero Emission Tractors
All-electric tractors with energy accumulators - whether batteries or fuel cells - have a whole raft of advantages compared with diesel-powered vehicles, especially when it comes to agricultural engineering and municipal applications. Driving with zero-emission and a considerably reduced noise level rank among the major advantages.
One of the key drivers is full zero-emission operation. This is part of ZF’s “Vision Zero” strategy for pollution-free vehicle systems.
ZF uses the following drive topologies to provide synergies between these electric drive systems and other applications:
ZF eTRAC GPE 25 low voltage solutions (Fig. 5) allow synergies with established electric drive solutions from the material handling sector, and the eVD high voltage solutions (Fig. 6) with electric passenger car and commercial vehicle solutions under development. This approach improves availability while enabling industrialization by boosting volumes.
Continuously variable front axle drive ZF eFAD
The continuously variable front axle drive ZF eFAD (Electric Front Axle Drive) helps optimizing traction, driving comfort and efficiency in the entire driveline. The advantages of this electric front axle solution compared to a rigid all-wheel connection are:
The ZF eFAD concept can be implemented with or without power split. The central drive without power split (Fig. 7), requires a high-voltage system on the tractor. For the power split version (Fig. 8) a low-voltage system is sufficient. Both designs are equivalent in performance und cover at least the performance capability of a conventional rigid front axle drive.
Contrary to the classic all-wheel driveline for tractors consisting of a rigid coupling between the front and rear axle as well as an all-wheel clutch, the ZF eFAD concept eliminates this rigid coupling. As a result, the disadvantages of a rigid coupling (twisting, unstable handling, tire wear) are eliminated. In addition to compensating the above mentioned disadvantages, the ZF eFAD concept provides also the advantages of a continuously variable control of the front axle drive. This means that the lead of the front axle is continuously adjustable to the requirements of the driving situation. For narrow cornering the lead can be increased, thus allowing a reduced turning radius. For fast road travel the lead is set to zero, however, the permanent all-wheel drive remains active.
This improves the driving safety as well as the driving stability. In field service the lead is continuously variable at the optimum level as needed. This results in fuel saving depending on the application conditions.