Article by Roger J. Stirnimann, Dipl.-Ing. agr., Dipl.-Ing. Wirtsch., Executive MBA, University of Agricultural, Forestry and Food Sciences, Zollikofen
(DLG). Agritechnica is regarded as the world’s most important platform for innovations in agricultural machinery, not least because of the ‘Agritechnica Innovation Award’. Once again, manufacturers have both publicized a range of new products in advance and have registered many of these world premieres for an innovation award. The following contribution provides an overview of the most important tractors trends.
Diesel engines are constantly being evolved
Tractor development continues to be extensively influenced by exhaust emission legislation. In Europe, the final grace periods for ‘transition engines’ expire at the end of 2021, after which the manufacturers are only permitted to supply tractors with exhaust emission stage Euro V engines from 2022 onwards.
Common rail fuel injection, four-valve technology, turbochargers, charge air cooling and electronic engine management remain the engine technology mainstays for being able to meet the requirements of power output, consumption and emissions. With exhaust emission stage Euro V, the diesel oxidation catalytic converter (DOC), diesel particulate filter (DPF) and selective catalytic reduction (SCR) exhaust gas aftertreatment systems are also crucial, from an engine output of 56 kW.
Conversely, the use of exhaust gas recirculation (EGR) as an internal engine technology for reducing nitrogen oxide formation remains a ‘philosophical question’. Some swear by EGR, others tend to reject it. When the engine ranges are looked at more closely, however, it is noticeable that the majority of manufacturers are pursuing a ‘mixed strategy’. Below 56 kW, the nitrogen oxide limit values can be adhered to without SCR, which is why the maximum outputs of entry-level models in the compact class often lie just below this threshold (e.g. Deutz-Fahr 5080D Keyline or McCormick X5.085).Due to the tighter limit value for the particulate mass (0.015 g/kWh) and the new upper limit for the number of particles (1×1012/kWh), there is no getting around closed-loop DPF systems in exhaust emission level V engines (19 – 560 kW output classes).
Some manufacturers are attempting to avoid the term ‘particulate filter’ in their sales literature and are instead using designations such as ‘soot catalytic converter’. However, this should not belie the fact that DPF systems are also involved here. The sole difference is the special coating of the filter honeycombs, which fosters passive regeneration at exhaust gas temperatures over 250°C. The number of active DPF regeneration processes undertaken by subsequently post-injecting diesel into the combustion chamber or through direct injection into the exhaust system can be reduced as a result.
Many tractor manufacturers are equipping their models with a boost function. So far, simple criteria such as ‘minimum vehicle speed’ and ‘minimum output at the power take-off shaft’ have usually been taken into account to release the additional output. Two years ago, Fendt introduced a power-boost concept called ‘Dynamic Performance’ in which the boost kicks in variably depending on the power needed by ancillary consumers (fan, alternator, air conditioning and air compressor). The aim of this is that the same output should always be available at the actual power take-offs (wheels, PTO shaft, hydraulic system).
John Deere is also making its ‘IPM’ (Intelligent Power Management) system ‘smarter’ in the new 6R model series, and now also takes the hydraulic output into account. However, the ‘Hydraulic IPM’ system does not operate according to the black-and-white principle, but instead measures the effective power demand of the hydraulic pump and then provides exactly this additional power. This comes into play, for instance, in seed drills with hydraulically driven blowers, because the usual release criteria are not usually fulfilled in this case.
Viscous fans enable needs-based, energy-efficient engine cooling and have already been in use for decades in tractors. However, the classic solutions with bimetal springs that bend depending on the cooling air temperature and actuate the clutch valve are increasingly being replaced by viscous electric fans. Thanks to electromagnetically actuated valves, the engine electronics can be used to control when and what quantity of silicone oil flows from the reservoir into the working chamber, thus enabling active adjustment of the fan’s rotational speed.
Fendt is now offering automatic air filter cleaning during operation for the revamped 900 and 1000 model series. A sensor measures the vacuum in the intake air system and triggers a cleaning cycle as required. The hydrostatically driven fan increases its rotational speed ten seconds before blowing out actually takes place, after which an electromagnetic pulse valve generates two short but powerful blasts of air inside the air filter elements. As a result of this, the dust is blown ‘backwards’ out of the air filter and is sucked out of the housing at the same time by the fan. The air required for this comes from a separate compressed air reservoir (10 l / 12 bar). The system functions under all operating conditions including full load. If necessary, cleaning can also be triggered manually.
Tractor engines are increasingly being equipped with automatic systems for valve clearance adjustment in order to reduce maintenance effort. The engine oil change intervals are also becoming increasingly long: the previous benchmark of 750 hours of operation has now been increased to the 1,000-hour mark. The trend towards lower rated and idling speeds is continuing.
Gas and electricity as alternatives?
The debate surrounding CO2 is also shifting alternative fuels and drive systems into focus in the agricultural sector. New Holland is benefiting from the lengthy experience of its Group sibling Iveco and is the first manufacturer to launch a series production tractor with a gas engine in the form of the T6.180 Methane. The 6-cylinder engine operates according to the spark ignition principle and can therefore be powered exclusively with gas. According to the manufacturer, the vehicle’s maximum output and torque values are identical to those of its diesel counterpart. The methane is carried along in the form of CNG (Compressed Natural Gas) in seven integrated pressure tanks (185 l / 32 kg); a so-called range extender with a further 270 l / 47 kg can be optionally mounted at the front of the tractor. Depending on application, this energy store should be sufficient for three to six hours of work. Processed biogas with a methane content of at least 83% can also be used, which should make the tractor particularly interesting for farms with their own gas production/processing facilities.
Electric drive systems continue to remain on the side lines in tractors. While studies and prototypes equipped with them have been presented time and again in the recent past, hardly any vehicles that are ready for series production have materialised so far. Battery electric vehicles are likely to make it past the line first. These are mainly suitable for light and medium-duty applications or for periodically recurring work in which sufficient time is available for intermediate charging. Often, however, conditions such as these are only met by small farmyard tractors.
