Electromechanical actuation of large directional control valves in flow-controlled hydraulic systems.

  Hydraulic valve Copyright: ifas

The direct electromechanical actuation of directional control valves with high nominal size is, due to high required switching forces, still a challenge. As state of the art these valves are actuated by hydraulic power which is controlled by a much smaller valve, the pilot valve. Aiming to reduce the number of components, which are necessary in a hydraulic system, the pilot valve should be removed. Therefore it is necessary to develop a new actuation system which can apply the required forces and strokes, while keeping in restrictions of the dimensions and dynamics.

 
Benefit Procedure
Evaluation of different actuator concepts as control of switching valves

Determining the requirements for new actuator concepts

Reduction of the system components by saving the piloting stage

Determination of the suitability of different actuator concepts

Increase of the system robustness by saving the piloting stage Development of test samples for valve actuation

Evaluation of the test samples

 

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Potential Actuators

For electromechanical control, various actuators such as switching solenoids, plunger coils or linear motors are used nowadays. In addition to these conventional actuators, the so-called unconventional actuators also have a great potential as possible control of valves.

Unconventional actuators include piezo crystals, which are characterized by the large achievable forces and the high achievable dynamics, as well as electro/magnetorheological fluids and thermal actuators, e.g. thermobimetals.

 

Challenges of Unconventional Actuators

Unconventional actuators are better then conventional actuators in some areas, but they also have corresponding disadvantages. Piezocrystals have advantages in terms of the force that can be applied or the dynamics that can be achieved. However, only very small movements can be realized. When using actuators, it must be ensured that they meet all requirements to a sufficient degree. If individual requirements cannot be met, the actuators can be combined with each other or with transmission components to meet all requirements to a sufficient degree. This is shown schematically in the following figure.

  Schematic representation of the actuator concept Copyright: ifas Schematic representation of the actuator concept Synthesis

The figure shows how an actuator is combined with a transmission component to form an actuator concept. On the right side the most important requirements for the synthesized concept are shown. For the valve control, the main properties are: achievable actuating force, achievable stroke and achievable dynamics of the new concept.

 

Development of a direct electromechanical control

After the development of possible actuator concepts, their suitability must be verified. For this purpose the concepts have to be realized as functional models. The manufactured functional models have then to be measured on a valve test bench available at ifas. Finally, the evaluation of the results shall show that the newly developed actuator concept is suitable as a valve actuator.

 

Acknowledgement

The project “Elektromechanische Ansteuerungen großer Schaltventile in volumenstromgeregelten Hydrauliksystemen“ is funded by the German Federation of Industrial Research Associations. The ifas would like to thank all project participants.

  Copyright: BMWi   Copyright: AIF