Solenoid valves are devices designed to allow the passage of air or fluid through a chamber and govern the strength of its flow. These devices are different from normal valves in that they have fewer working parts and act upon the receipt of an electric current. Currently, they are used in most automobiles, as well as any hydraulic or gas-based closed system that relies on the regulation of gas or fluid's passage.
The proposed theoretical structure of a solenoid valve is simple. You start with a hollow T-shaped chamber. The bottom of the T is the input, through which fluid flows. At the cap of the T is an elastic diaphragm, which covers the input, preventing fluid from passing through the left arm of the T. In the right arm is housed the solenoid coil; the far end connects to an electrical source and the end which would come into contact with fluid is covered with a thin plug or piston.
The basic theory of solenoid valves and their operation is broken down into two components. The first lies in the solenoid coil, which is for all intents and purposes a metal spring. When an electrical current passes through the coil, it becomes an electromagnet and coils in on itself, pulling into a tighter space. The second part of basic solenoid valve theory is in the elastic diaphragm. It prevents fluid from passing because of the balance in fluid pressure between the input portion of the T and the output portion of the T. But when the solenoid coil contracts, it creates marginally more room and the fluid pressure in the output portion of the T decreases slightly. This causes the elastic diaphragm to pull back into the output portion, allowing fluid to pass through the two chambers freely. However, when the electrical current passing through the solenoid coil stops, the coil expands and pushes forward, equalizing the pressure between chambers and sealing them off from one another via the diaphragm. In this way, electromagnetism and fluid pressure become the basics behind the theory of solenoid valve structure and operation.
