Hamm displayed a prototype of a hybrid powertrain for the HD+ 90i tandem roller at Bauma. The innovative concept has been developed to save fuel costs and maintenance effort. This new development combines the traditional internal combustion engine with a hydraulic accumulator. The internal combustion engine covers the base load while a hydraulic accumulator meets peak loads.
Hybrid solutions combine two technologies – in the automotive sector, a combination of an internal combustion engine and electric drive are common. Previous similar attempts with electric motors in rollers proved unconvincing. Hamm took a new approach. The company combined an internal combustion engine with a hydraulic system and became the first roller manufacturer to develop a technical solution suitable for series production.
9 t HD+ 90i roller with hybrid powertrain
For the first hybrid power models, Hamm chose the HD+ 90i, a popular tandem roller in the medium weight class. Up to now, this roller has operated with an 85-kW diesel engine complying with the EU level IIIB / EPA Tier 4 Interim emission standards. A detailed examination of the actual engine load during compaction showed the Hamm developers that the peak loads were only needed occasionally and even then for just a few seconds. This is the case when the roller starts up or the vibration/oscillation is activated. In the new hybrid power roller, these brief peak loads are handled by a hydraulic system, enabling the roller to be equipped with a smaller diesel engine for the same performance. The load on the diesel engine is also reduced because the radiator fans are electrically operated for optimum efficiency.
Hydraulic power storage on board
The hydraulic system works like a pumped storage power station: as soon as the power demand falls below the maximum load of the internal combustion engine, a pump fills the hydraulic accumulator. If a great deal of power is called for, such as when starting the vibration drive, the hydraulic system functions as an auxiliary drive, able to supply a maximum short-term load of up to 20 kW. Following this the cycle begins afresh with the refilling of the accumulator. The principle functions splendidly because for normal applications, the maximum load is always only called up for a matter of seconds. Afterwards there is sufficient time to replenish the accumulator.
Quieter, lower fuel consumption and less maintenance effort
This results in numerous benefits: for example, the 9 t roller can be powered by 55.4-kW engine in place of an 85-kW unit – and with the same compaction power. The smaller engine does not require an SCR catalytic converter or AdBlue. This results in advantages in terms of handling and maintenance. What’s more, the powertrain is markedly quieter. The hybrid powertrain in combination with the electric fan drives and a start-stop system enables significant savings of up to 15 percent in fuel consumption. This also substantially cuts CO2 emissions.
Available from 2017
The hybrid system is entering field trials in selected markets during 2016 and is expected to be available in the models with double vibration (VV) and oscillation (VO) as well as in the combi rollers (VT) as standard from 2017.