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Method of function of hydrostatic fan drive systems

At optimum combustion temperature in the diesel engine, fuel consumption and emission levels are lowered considerably. In order to achieve this optimum combustion temperature, extremely high demands are placed on cooling circuit management. Hydrostatic fan drives are ideally suited for this purpose, as they are controllable and can, thus, provide the desired cooling power to meet every need.


Method of function

The latest generations of combustion engines require considerably more complex control systems with more than two parameters. Four elements are cooled: water, oil, charge air and the recirculated exhaust gas. Rexroth meets this requirement profile, consisting of control requirements and cooling power, with system solutions for hydrostatic fan drives in which axial piston pumps and external gear motors are combined with CAN-bus-capable control electronics that are optimized for fan drives. By means of the steplessly controllable fan speed, which is independent of the combustion engine speed, the required cooling power is provided even at low combustion engine speed.

The power is generated by an A10VO axial piston variable pump. Rexroth developed the ED control especially for fan drives. The electrohydraulic pressure controller controls the system pressure according to the valve current that the electronic control unit specifies.



Blowing the air the other way: The reversing operation

Temperatures are just one problem. The second problem is dust and dirt, which deposits itself inside the radiator, especially in the case of construction and agricultural machines. To prevent the cooling performance from deteriorating, engineers have come up with a smart solution – the reversing operation. The fan rotor direction of rotation changes at different intervals, so that air is blown in the opposite direction, carrying the dirt outside. The advantage of the reversing operation is obvious. The radiator remains unobstructed and the engine operates at ideal engine and combustion temperatures.

There are times when a fan is not needed:
The standstill option

With the optional standstill feature, the fan rotor is completely shut down during the start-up phase or when ambient temperatures are very low. Thus the internal combustion engine reaches its operating temperature faster and the exhaust gas pollutants are optimally reduced. Moreover, the consumption-optimized standstill feature permits fuel savings of up to 1 percent compared to conventional fan standstill solutions.