Internal combustion engines are being developed further
Tractor development in recent years has been heavily influenced by exhaust gas legislation. Common rail injection, four-valve technology, turbochargers, intercooling and electronic engine control are the cornerstones of engine technology for diesel units that comply with the currently valid EU emission level V in order to meet the requirements for performance, consumption and emissions. In the output classes from 56 to 560 kW, the exhaust gas aftertreatment systems diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and selective catalytic reduction (SCR) are also indispensable, supplemented in some cases by exhaust gas recirculation (EGR). Many manufacturers have now approved their emission level V units for the use of HVO (Hydrotreated Vegetable Oil). However, conventional diesel engines have otherwise become somewhat quieter in the last two years.
With the CO2 problem, the spotlight has shifted to combustion engines for alternative fuels. Cummins was the first manufacturer to announce a multi-fuel engine platform (diesel/HVO, methane and hydrogen) with the 6-cylinder unit “Fuel-Agnostic X15” (14.9 l displacement) in early 2022. The basis for this is a standardised basic engine that can be combined with various cylinder head modules. FPT is following a similar path with the XC13 (6 cylinders, 12.9 l displacement), which was introduced a year ago as a “multi-fuel single base engine”. The new Cursor-X concept is also intended to showcase a modular system with cylinder head modules for diesel/HVO, methane, hydrogen and other renewable fuels.
AGCO Power has also announced a new engine platform with the CORE series. The first representative was the CORE 75 with 6 cylinders and a 7.5 l displacement, which is used in the new Fendt 700 Gen7 tractor series and can also be operated with HVO. In the future, this platform is also to be further developed to enable the use of other alternative fuels, depending on market developments. With the CORE 50 intended for the new Fendt 600 Vario series, the next engine model is already in the starting blocks. With a maximum output of 224 HP (including DynamicPower), the 200 HP mark is clearly broken for the first time in tractors by this 4-cylinder engine with a 5.0 l displacement – at a nominal speed of just 1,900 rpm.
In addition to Cummins and FPT, other non-road powertrain manufacturers working on H2 combustion engines include Deutz, JCB and Liebherr. This approach is currently also considered the most economical and feasible solution in the commercial vehicle industry for achieving CO2 reductions with carbon-free hydrogen in the short and medium term. However, the prerequisite for this is always that it comes from environmentally friendly sources. Hydrogen can be carried on the vehicles – like methane – in gaseous form in pressurised containers or in liquid form in insulated tanks. The engine technologies for these two energy sources are also similar (Otto process or High Pressure Direct Injection (HPDI)).
Gas engines breaking through into agriculture thanks to LNG?
New Holland has already benefited from the many years of experience of its sister company Iveco/FPT and in 2022 was the first manufacturer to launch a mass-produced tractor with a gas engine, the T6.180 Methane Power. The methane is carried here in gaseous form as CNG (Compressed Natural Gas) in pressurised vessels. As the energy density of CNG per litre of tank volume is only about a fifth of that of diesel, the operating times of such vehicles are generally limited. The ratio is much better with cryogenic liquid LNG, which is why it has been used in long-distance truck transport for years. In tractors, LNG has hardly been an issue so far because the usual cylindrical, vacuum-insulated tanks are difficult to integrate into the tight installation space and because larger quantities of boil-off gas can be produced due to the longer service lives involved.
With the T7.270 Methane Power LNG, New Holland now presents a gas tractor with LNG tanks that is designed to avoid these problems. Thanks to a special double-wall technology, the vacuum-insulated LNG tanks no longer need to have a cylindrical shape and can consequently be better adapted to tractor-typical space conditions – similar to diesel tanks. The T7.270 LNG can therefore carry 200 kg of methane, which is about seven times more than the approximately 30 kg of the T6.180 Methane Power (based on the integrated CNG tanks). New Holland counters the boil-off gas problem with a “cryo-cooler” that constantly keeps the methane below minus 162°C and therefore in a liquid state. The energy required for the electrically driven cooler is minimal and comes from a battery that can be charged either via an external power source or the integrated IC generator (operation with boil-off gas). This means that LNG gas engine concepts could now also become a valid propulsion option in agriculture, combined with the opportunity to use their own biogas (bio-LNG) as a vehicle fuel in CO2-neutral systems.
Battery-powered electrical systems are slowly but surely gaining ground
Battery technology is constantly being developed further and in recent years both gravimetric and volumetric energy densities (Wh/kg or Wh/l) have been continuously increased. From today’s perspective, however, batteries will probably always remain relatively large and heavy, which is why vehicles equipped with them are primarily suitable for light and moderately heavy applications or for periodically recurring work where there is enough time for interim charging. In agriculture, such conditions exist for smaller tractors, among others, which are now gradually coming onto the market.
Starting this year, Rigitrac has been building the SKE 40 Electric compact tractor (continuous/peak power traction drive 40/64 kW, battery capacity 50 kWh) in small series. The Fendt e107 V Vario narrow-track tractor (continuous/peak power 55/66 kW, battery capacity 100 kWh) and the New Holland T4 Electric Power (continuous/peak power 55/89 kW, battery capacity 110 kWh) have been announced for 2024. The charging capacities with alternating current (AC) are 22 kW for all three models, and those with direct current (DC) between 80 and 100 kW.
Fuel cell drives are still in their infancy
Fuel cell drives also count as electrical systems. Here, however, the electricity does not come from the socket, but is first generated from hydrogen on the vehicle. As fuel cells cannot react quickly to load changes and the optimum efficiency is in the medium load range, they are always combined with buffer batteries in vehicle drives. In most cases, the fuel cell is the main element and the battery is the additional element that covers peak loads and can store braking energy. However, the fuel cell can also be used to extend the range of electric battery-powered vehicles.
Current prototypes/studies are available from Fendt, among others. The HELIOS (hydrogen-electric operated tractor system) developed as part of the H2Agrar research project operates with a 100 kW fuel cell and a 25 kWh buffer battery. This means it can be assigned to the “fuel cell as main drive” concept. Five high-pressure tanks mounted above the cabin roof can carry a total of 21 kg of hydrogen (700 bar). Being able to carry enough energy for the required operating times/ranges is also a major challenge for fuel cell vehicles in general.
In the DLG competition “AgriFuture Concept Winner 2023”, Fendt also submitted a study of a mobile fuel cell that can generate electricity from green methanol to continuously recharge the battery of the Fendt e107 V Vario. The liquid methanol is carried in a 60-litre fuel tank and does not need to be pressurised or cooled. The fuel cell has an output of 15 kW and can generate around 100 kWh of electrical energy from 60 l of methanol. This enables the operating time of the e107 V Vario electric battery-powered tractor to be doubled for low/medium workloads. The fuel cell module is attached to the front or rear power lifter and the electrical connection is established using an AEF plug. This solution corresponds to the concept “fuel cell as range extender”.
Hybridisation: Solution for medium-sized and larger tractors?
CNH presents the Steyr Hybrid CVT, a modular hybrid concept for medium and large standard tractors. The prototype presented is based on a series-production model in the 6-cylinder entry-level class (output 180 HP, wheelbase < 2.8 m), but the diesel engine used here produces 260 HP. The familiar hydrostatic-mechanical stepless transmission is adopted 1:1 from the original. Completely new, on the other hand, is the front axle carrier with a spring-mounted independent suspension and two integrated electric motors. The generator is driven by the diesel engine via a transmission stage and passes on the generated electrical power (up to 75 kW) to the e-motor via the power electronics. This converts the electrical energy back into mechanical energy, which is fed via a two-stage gear unit to the ring gear of the front axle differential. However, the front axle can still be driven mechanically via a classic multi-plate clutch. In the electrical branch, there are also SuperCaps (electrostatic energy storage devices that can pick up and release a great deal of power in a short time, but can only store a small amount of energy), a braking resistor and an AEF high-voltage socket at the front and rear.
These components and the serial-parallel hybrid structure enable numerous functions that are new to tractors. These include the variable, actively controlled forward travel of the front axle (E-steering), the electric boost function for rapid acceleration during transport (E-boost), the compensation of peak loads (E-torque filling), purely diesel-electric driving during light work and rapid changes of direction at low engine speeds in each case (E-CVT mode/E-shuttle), along with the brake retarder with 20 kW continuous power (E-braking). Other functions include variable torque distribution between the axles (E-torque vectoring) and the delivery of electric power of up to 75 kW to implements (E-implement).
Evolutionary further development for gearboxes
CNH’s hybrid concept fits into the trend towards holistic drive concepts that go beyond previous diesel engine gearbox systems to enable new functions. Previous examples include Fendt’s VarioDrive gearbox/all-wheel drive concept and John Deere’s eAutoPowr gearbox with electro-mechanical power split and the option of current output to implements. Fendt introduced VarioDrive for the first time in 2015 for the 1000 series and since then has been successively moving this concept downwards into lower performance classes. Following the 900 and 700 series, the tension-free all-wheel drive, which is permanently engaged up to 25 km/h, has now also been introduced in the new 4-cylinder 600 Vario series. John Deere has been installing the eAutoPowr in the 8R410 top model, for which there was previously no continuously variable transmission option, since 2022.
New stepped and continuously variable gearboxes have not been announced in the past two years, but there have been interesting further developments. Claas also uses the Eccom 5.5 continuously variable gearbox from ZF, which was introduced together with a new pump transfer case for the previous XERION series (4200/4500/5000) for the 2023 model year, on the new XERION models in the 12 series (maximum output up to 653 HP). However, due to the high torques of the 15.6-litre unit with six cylinders and a turbo compound from Mercedes-Benz, a “high-drive stage” is integrated into the pump gearbox. This allows the gearbox input torques to be reduced and the engine outputs to be transmitted at higher speeds. At Agritechnica, Claas will also introduce a new front loader mode for the Arion 500 and 600 tractor models with their own continuously variable gearboxes (EQ200/EQ220). This enables torque/thrust control via the accelerator pedal when driving into bulk material or manure piles, as is the case with wheel loaders or telescopic loaders with hydrodynamic torque converters. This should make filling the front loader implements easier and more convenient.
Chassis technology is being adapted
Chassis technology is becoming more important as the power and weight of large tractors increase. Claas therefore developed new triangle track drives for the 12-series XERION series, which are built in-house. This design was necessary because the new flagships are also equipped with Ackermann steering and not the usual articulated steering in this performance class. The large drive wheel of the track drives, together with the two deflection rollers, is mounted on a main frame that can oscillate +/- 10°. The boogie suspension of the two intermediate rollers is integrated in a separate swing arm, which is damped using rubber elements. In Europe, the 12-series models are offered exclusively with the track drives, which are also called TERRATRAC. For markets with less strict width requirements, the tractors are also available with wheeled undercarriages. Twin tyres with the dimension 800/70R42 and consequently an outer diameter of 2.15 m can be mounted here, which is not yet offered by the “articulated competitors”.
Case IH, the pioneer in 4-track undercarriages and triangle tracks on large tractors, has also stepped up its efforts. To apply the 778 HP maximum power of the new flagship Quadtrac 715 (6-cylinder engine with 15.9 l displacement and 2-stage turbocharging) to the ground, the track drives were lengthened by 10 cm and the diameter of the drive wheel was increased to over 100 cm. These can now also be ordered with the PowerFlex undercarriage suspension, which not only provides more comfort, but also better ground tracking. Spring-mounted triangle track drives were previously only available for large combine harvesters, but not for heavy tractors.
Tyre pressure adjustment systems (Central Tire Inflation System – CTIS) are increasingly being offered from the factory by tractor manufacturers. These include both integrated solutions and those with externally routed lines. Due to the increasing importance of stub axles worldwide (among other things, as a result of mechanical weed control), Fendt has adapted the “VarioFlex Duals” system with a 3 m stub axle and a duo-wheel hub, which has proven itself overseas, to an approvable external width < 2.55 m for Europe. The use of wheel weights and the integrated VarioGrip tyre pressure adjustment system continues to be possible.
Continuous development of comfort functions
Many manufacturers have introduced new and in some cases larger cabs with digital operating and display systems for their tractor series in recent years (examples: FendtONE operating concept or Massey Ferguson 8S cab). In the recent past, however, the development of cabins and operating systems has tended to take place in the “evolutionary” area.
Case IH introduces “Adaptive 360° Work Lighting”, a lighting system that provides homogeneous illumination around the tractor without increasing the number of headlights. An important element are the fold-out holders at the front halfway up the cabin. The settings of the headlights mounted on these, together with those on the rear wings, can be carried out from the cabin and then saved. The stored implements/working widths can be called up via the “automatic implement” mode in the lighting menu of the tractor control panel. For ISOBUS implements, this is carried out automatically when hitching up. Consequently, there is no longer any need to choose between constantly readjusting the work lights and a one-off compromise setting for various units.
Previous cruise control systems are mostly controlled according to the wheel speeds and therefore to the theoretical driving speed. The slip (positive or negative) caused by traction resistance or uphill/downhill gradients is usually not taken into account. Fendt now bases the “Real Speed Cruise Control” function on the effective driving speeds recorded via GPS or radar sensors, thereby improving compliance with the SET speed. This is advantageous, among other things, when applying fertiliser and crop protection agents.
With ErgoSteer, Fendt is also introducing joystick steering in the left armrest – in addition to the steering wheel. This can also be used to change the direction of travel and activate lane guidance. Self-centring makes it possible to drive straight ahead precisely at all times, and the steering sensitivity can be set individually on the tractor control panel. An interesting aspect here is: ErgoSteer can be retrofitted to all tractors with FendtONE.
In today’s tractors, the tractive force is usually controlled via the lower links. Raising or lowering the 3-point linkage often results in the position of tillage implements no longer being parallel to the ground, which can have a negative effect on the quality of work. In order to optimise this, Claas now also includes the hydraulic top link in the multidimensional 3-point control. To determine the position, height measuring sensors are mounted on the implement at the front and rear, which then transmit the signals to the tractor’s control electronics. These signals are converted into a control setting for the top link length via an additional hydraulic control unit, resulting in automatic adjustment of the implement’s longitudinal tilt.
Autonomy presents new challenges
Automatic steering systems and programming options for recurring operating sequences, e.g. at the headland, have been available on tractors for years. The next step is now to try to “autonomise” the tractor-implement units. Depending on the autonomy level, the driver should only need to monitor the work processes; in extreme cases, he/she should no longer be needed at all. Several manufacturers are therefore presenting systems for the yard-field transfer of fully autonomous vehicles or for monitoring the quality of work. An example of this is the Krone/Lemken Vehicle Transportation System (VTS) for the autonomous Process Engineering Unit (VTE). A drawbar allows the vehicle and its implements to be moved to the field by a “normal” tractor. The steering strategy is adapted to the speed so that it is stable at high speeds and follows closely in curves/entrances. The service brake of the autonomous towing vehicle, which is considered a towed vehicle on the road when using the new VTS system, is applied using a standard 2-conductor air brake system.
New Holland is taking a slightly different approach with the T4 Electric Power battery-powered tractor, introducing interesting autonomy and safety features for it that could already be beneficial for practical use in the near future. The camera systems mounted on the cab roof and at the front of the bonnet enable, for example, a 360° all-round tractor view that can be transmitted to the cab control panel, recognition of rear-mounted implements for simplified hitching, and automatic PTO disconnection if people get too close to the PTO shaft. In addition, there are the functions “Route Mode” (tractor follows a set driving sequence, for example in orchards), “Invisible Bucket” (improved overview during front loader work by “editing out” the implements on the cab control panel) and “Follow Me”. The “Follow Me” mode should be particularly interesting for work in which the driver must constantly climb up and down in order to move the vehicle forward a few metres, as is the case, for example, when harvesting vegetables manually or erecting fences. To do this, the driver must activate the mode on the tractor control panel and then go to the front detection area of the tractor for “identification”. The tractor then only follows this person. In addition, there is a gesture control system which enables the tractor to receive driving instructions by means of hand signals
