Ceramic Flat Slide Valve
Flat spool valves have the potential to reduce leakage and increase service life compared to conventional valves used in industry. Currently the first prototype of the flat spool valve, in which the control plates and the gate are made of steel, is being built and tested. Subsequently, the flat spool valve, with control plates and gate plate made of ceramic, is to be tested and proven in operation.
|Innovative valve concept||Definition of the operating conditions and preparation of a requirement profile|
|Reduction of leakage||Design of the hydraulic stage|
|Reduction of control edge wear||Development and optimization of pressure compensation|
|Increase service life & efficiency||Construction and testing of the flat slide valve|
Advantages of the Ceramic Flat Spool Valve
There are two disadvantages when using piston spool valves, which are primarily used in hydraulics for resistance control.
Between the spool and the housing, the gap between the spool and the housing causes leakage, as shown in the figure on the right. This leakage leads to a reduction in efficiency. The concept of the flat spool valve can significantly reduce the gap height and the resulting leakage. In doing so, a gap formation between the control plates and the gate is counteracted by applying a compensating force.
Due to the design of the flat spool valve it is possible to manufacture the control plates and spool plates from a ceramic material. Thereby design and material harmonize. The geometries are simple enough to be implemented cost-effectively and with sufficient accuracy from ceramic semi-finished products. Due to the high plane-parallelism and the achievable surface qualities, small gap dimensions can be achieved.
In piston spool valves, the slides are usually made of a metallic material. As shown in the figure on the left, this results in abrasive wear at the control edges. This has a negative influence on the control behaviour of the valves and leads to a limitation of the service life. The fact that the hydraulic stage of the flat spool valve will be made of a ceramic material, which in comparison to metals has a significantly higher hardness and resistance to abrasive wear, means that an increase in service life can be achieved.
The project is being carried out with experts in the field of materials engineering, the Institute for Material Applications in Mechanical Engineering (IWM) at RWTH Aachen University.
As shown in the figure, the IWM is concerned with the determination of suitable ceramics by material investigations. At ifas a prototype of the flat spool valve will be built, in which the hydraulic stage (control plates & gate plate) will initially be made of steel. With the help of the prototype, the previously developed pressure compensation is validated and optimized. The knowledge gained from the development and testing of the first prototype will be used together with the knowledge gained from the material investigation at the IWM to build a prototype in which the hydraulic stage consists of ceramic components. With these prototypes the functional verification of the ceramic flat spool valve will take place.
Development of Pressure Compensation
When designing the pressure compensation, there are two opposing design criteria. On the one hand, the force applied to the control plates must be large enough to counteract an increase in the gap between the control plates and the valve plate. On the other hand a too high compensation force causes high frictional forces, which must be overcome by an actuator. Therefore, one focus of the research project is the design of the pressure compensation.
For this purpose, a calculation program was developed in Matlab, which calculates the forces acting on the slider and thus enables rapid geometry optimisation.
Design of the Hydraulic Stage
The hydraulic stage was designed with the help of test bench trials with a 2-2-way valve, which was developed in a preliminary study at ifas. With the help of the results from the test bench trials, the flow channel geometry was predicted and subsequently optimised by CFD simulations.
A flow rate of 30 l/min with complete valve spool deflection and a pressure difference of 10 bar is planned.
The developed prototype is currently being implemented in reality at ifas and then tested.
The research project is funded by Arbeitsgemeinschaft industrieller Forschungsvereinigungen e.V. (AiF) with funds from the Bundesministeriums für Wirtschaft und Technologie (BMWi).