There are many different configurations and designs for proportional valves. A typical valve design incorporates ferrous alloy components, copper wire (coil) and a variable orifice designed to meet the necessary requirements of an application.
Maintenance of Solenoid Valves
Depending on the fluid application, material selection is critical to a solenoid valve’s life and operation. Diverse ferrous alloys are required for solenoid performance. Some of these materials can be more susceptible to corrosion than non-ferrous alloys. If a thermal management system requires fluids similar to water or antifreeze it is appropriate to use a material that has minimal degradation due to oxidization or use a plating process to protect the base material.
There is a trade-off in using plating rather than a less corrosive material. The plating process has a lower cost but is less reliable than a more expensive, less corrosive material. Plating on a component of this sort can be degraded over time and compromise the durability of the solenoid valve in corrosive environments. The decision on what material should be used is a balance between application requirements and overall cost.
Ferrous alloys are used as both static and dynamic components to complete a magnetic circuit. The magnetic flux, generated from the coil, attracts the dynamic component (armature) toward the static component (pole) creating a positional change interacting with the orifice. With highly engineered valves, intricate shapes can be used for the orifice, other than a simple circle, to create more desirable flow curves and performance. These shapes can help meet the requirements of maximum flow at the minimum supply pressure as well as achieving minimum flow at maximum supply pressure. However, with every incremental increase in performance there is another hurdle to overcome. In the case of proportional valves this hurdle is achieving zero leakage in the closed position without losing the desired proportional control.
One way TLX Technologies has achieved zero leakage is to pair a binary valve, or on-off valve, with a proportional valve into one module (Figure 2). With the binary valve able to completely restrict flow, the proportional valve will not sacrifice performance. This combination of valves can achieve fast response times with flow control accuracy up to 2%.
