Pneumatic valve Solenoid valve working principle and function of detailed explanation

Pneumatic valve Solenoid valve working principle and function of detailed explanation

Pneumatic valve, as an indispensable fluid control equipment in industrial pipelines, its core components include pneumatic actuators and valves. By compressing pure air to drive valve action, pneumatic valves can quickly and precisely control the flow and blocking of pipe intermediaries, making them ideal for quick cut-off operations. In addition, pneumatic valves are equipped with a variety of accessories such as solenoid valves, air supply handling triples, limit switches, positioners, and control boxes to support the needs of field control and remote centralized control. Especially for two-position valves that only need to open and close, the solenoid valve is an indispensable part. Through the process of excitation and demagnetization, the solenoid valve achieves accurate control of the opening and closing of the pneumatic valve. In terms of the air path (or liquid path), the two-position three-way solenoid valve design has an intake hole, an outlet hole and an exhaust hole, while the two-position five-way solenoid valve adds a positive action vent and a reactionary action vent, as well as the corresponding positive action and anti-action exhaust holes. For small automatic control equipment, 8~12mm industrial rubber gas pipe is usually selected as the gas pipe material.

In terms of electrical control, the two-position three-way solenoid valve usually uses a single electronic control design, that is, a single coil, while the two-position five-way solenoid valve mostly uses a double electronic control design, that is, a double coil. The coil voltage level of these solenoid valves is usually selected DC24V, AC220V, etc. Two-position three-way solenoid valve can be divided into normally closed type and normally open type, of which normally closed type means that the gas path is disconnected in the state of no power, and normally open type is the opposite, the gas path is connected when there is no power.

Next, let's take a closer look at the operation principle of these two types of two-position three-way solenoid valves:

(1) Normally closed two-position three-way solenoid valve: when the coil is energized, the gas path is connected; Once the coil is powered off, the gas path will be disconnected, which is similar to the "point" control.

(2) Normally open two-position three-way single electronically controlled solenoid valve: its operating principle is the opposite of the normally closed type, that is, the gas path is disconnected when the coil is powered on, and the gas path is connected when the power is off, and the "point" control is also achieved.

The operation principle of the two-position five-way double-controlled solenoid valve is: when the positive acting coil is energized, the positive acting gas path will be connected (that is, the positive acting vent will have gas output). Even after the positive acting coil is powered off, the positive acting gas path will remain connected until the anti-acting coil is powered on. Similarly, when the counteracting coil is energized, the counteracting gas path is switched on (that is, there is a gas output from the reaction producing hole). After the power is turned off, the reverse acting gas path will also remain connected until the positive acting coil is energized again. This characteristic makes the two-position five-way dual-controlled solenoid valve have a "self-locking" function, similar to the memory function.

In the design of the electromechanical control loop or the preparation of the PLC program, this feature of the two-position five-way double-controlled solenoid valve can be used to only allow the solenoid valve coil to operate for 1 to 2 seconds, so as to effectively protect the solenoid valve coil and extend its service life.

Next, let's look at the principle of a single electronically controlled solenoid valve. The single solenoid valve drives the movement of the spool by controlling the current break of the solenoid coil and the action of the spring, and then controls the opening and closing of the valve.

When the right coil is energized, the left spring is compressed:

The coil on the left is powered, and the spring on the right is compressed: in a single electronically controlled solenoid valve, when the coil on one side is powered, the spring on the side will be compressed due to the action of the electromagnetic force. This is the basic working principle of a single electronically controlled solenoid valve.

In a single electronically controlled solenoid valve, when the coil on the right loses current, the spring on the left will recover due to the disappearance of the electromagnetic force, that is, extend out. This is another important operating characteristic of a single electronically controlled solenoid valve.

B Double electric control schematic

The principle of double electronically controlled solenoid valve is that the solenoid coil on both sides can control the opening and closing state of the valve by switching between power and power loss. When one coil is out of power and the other is not yet powered, the spool can remain stationary, which makes the dual-controlled solenoid valve have a memory function.

When the right electromagnetic coil loses power and the left electromagnetic coil gets power, the spool will remain stationary, which is the result of the memory function of the double electronically controlled solenoid valve.

When the left electromagnetic coil loses power and the right electromagnetic coil gets power, the spool will move to the right until it reaches the right limit position. This is due to the switching function of the double electronically controlled solenoid valve in action.

The pneumatic actuator is powered by compressed air and drives the pneumatic actuator by converting the input control signal into a pressure signal, so as to realize continuous adjustment or switch control of the valve. In addition, the pneumatic control valve can also be equipped with a variety of accessories to achieve a variety of control functions to fully meet the specific needs of the control system for the pneumatic control valve. These accessories make the function of the pneumatic control valve more perfect, reasonable and comprehensive.