Electrohydraulic fan drives in control: This illustration shows the major components of Sauer Danfoss’ electrohydraulic fan drive used in Scania’s buses. The electronic fan controller communicates with the vehicle’s main control to regulate fan speed via electrohydraulic pressure control.First in Europe
Scania is the first company in Europe to use this type of system on buses, and the benefits are clear. Compared to a conventional fixed-displacement control or belt-driven system, efficiency is increased substantially, with low pressure loss and reduced pump noise. Using an electronic valve instead of a load-sensing or bypass valve further rules out the need for a thermostatic hydraulic valve, which is often adversely affected by extremes of hot or cold. The end result is a more energy-efficient control over a far wider temperature range. Moreover, eliminating the thermostatic valve and associated hoses contributes to making the system more compact and easier to assemble.
Customized version
For one of Scania’s larger bus models, where the fan drive pump is driven through a power take-off (PTO), Sauer-Danfoss has developed a customized version of the axial-piston pump with its own PTO. This allows the pump to be mounted in the position normally occupied by the fuel pump. With all the engine PTO outlets in use for other bus functions, the fuel pump can be connected to the PTO on the axial piston pump instead — allowing Scania to continue using a standard engine.
Scania’s road tests routinely challenge buses with the cold climates of northern Sweden to the high temperatures and steep gradients of Spain. Operational performance and passenger comfort have proven exceptional under any condition. In that, the small but effective Sauer-Danfoss fan drive plays a part that defies its size.
Sauer-Danfoss’ gear pumps, gear motors, and hydraulic fan drives are available through its Turolla Open Circuit Gear division. Visit www.turollaocg.com for full details, including local sources. For information on piston pumps and motors and other products, visit www.sauer-danfoss.com.