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Solenoid valve principle
- Sep 17, 2018 -

Solenoid valve principle, two-position five-way, three-position five-way valve

hydraulic solenoid valve

The solenoid valves are divided into three major categories (ie: direct-acting, step-by-step direct-acting, pilot-operated), and the differences in principle and principle between the valve flap structure and materials are further divided into six. Branch subclasses (direct-acting diaphragm structure, step-and-repeat structure, pilot-membrane structure, direct-acting piston structure, step-by-step direct-acting piston structure, pilot piston structure). 

Direct acting solenoid valve:

Principle: When energized, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve is opened; when the power is off, the electromagnetic force disappears, the spring presses the closing member against the valve seat, and the valve is closed.

Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25mm.


Distributed direct-acting solenoid valve:

Principle: It is a combination of direct motion and pilot type. When there is no pressure difference between the inlet and the outlet, after energization, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upward, and the valve opens. When the inlet and outlet reach the starting pressure difference, after the energization, the electromagnetic force leads the small valve, the pressure of the lower chamber of the main valve rises, and the pressure of the upper chamber drops, so that the main valve is pushed upward by the pressure difference; when the power is off, the pilot valve uses the spring The force or medium pressure pushes the closure and moves down to close the valve. Features: It can also be operated at zero pressure difference or vacuum or high pressure, but the power is large, and it must be installed horizontally.


Pilot solenoid valve:

Principle: When energized, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a pressure difference between the upper and lower parts is formed around the closing member. The fluid pressure pushes the closing member upward and the valve opens. When the power is off, the spring force leads the pilot. The hole is closed, and the inlet pressure passes through the bypass hole. The rapid chamber forms a lower low and high pressure difference around the valve closing member, and the fluid pressure pushes the closing member downward to close the valve.

Features: The upper limit of the fluid pressure range is high, it can be installed arbitrarily (customized), but the fluid pressure difference condition must be met. The solenoid valve position means that the solenoid valve spool has two different working positions (on, off). Solenoid valve two-way, three-way solenoid valve has two or three passage ports on the valve body; for example, two-position two-way solenoid valve is one in and one out (two channels, the most common) two-position three-way solenoid valve The control liquid is one in and two out (two outs are normally open and one normally closed); the pneumatic reversing solenoid valve is one in and one out of one exhaust; the hydraulic one enters and returns one oil. The solenoid valve is used in the liquid path system to realize the on/off of the liquid path or the change of the flow direction. It generally has a valve core that can be driven by the electromagnetic force of the coil. When the valve core is in different positions, the passage of the solenoid valve It is different. There are several working positions of the valve core. The solenoid valve is called a few solenoid valves: the interface on the valve body, that is, the number of passages of the solenoid valve, there are several passage ports, and the solenoid valve is called a solenoid valve. After the solenoid valve is installed, generally all the interfaces should be connected. The so-called working position refers to the position of the spool. The valve core is in the position A when the coil is not energized, and is in the position B when the coil is energized, and the valve core is in the different positions to play or close or close the interface.

   

The two-way three-way solenoid valve is usually used with a single-acting pneumatic actuator. The two positions are controllable in two positions: on-off, and the three-way has three channels of ventilation. In general, one channel is connected to the air source, and the other two are connected. One channel is connected to the air inlet of the actuator, and one is connected to the exhaust port of the actuator. The specific working principle can refer to the working principle diagram of the single-acting pneumatic actuator. Two-position five-way solenoid valves are usually used with double-acting pneumatic actuators. Two positions are controllable: on-off, five-way is five-channel ventilation, one of which is connected to the air supply, two and two The inlet and outlet ports of the external air chamber of the cylinder are connected, and the two inlets and outlets of the internal air chamber are connected. The specific working principle can refer to the working principle of the double-acting pneumatic actuator. On the gas path (or liquid path), the two-way three-way The solenoid valve has one intake hole (connected to the intake air source), one air outlet (provided to the target equipment air source), and one exhaust hole (generally a muffler is installed. If you are not afraid of noise, you dont need to install it.). The two-position five-way solenoid valve has one air inlet hole (connected to the intake air source), one positive action air outlet hole and one reverse action air outlet hole (one positive and one reverse action air source respectively supplied to the target device), 1 One positive action vent and one reverse vent (with silencer installed). For small automatic control equipment, the gas pipe is generally 8~12mm industrial rubber pipe. Solenoid valves are generally selected from Japan SMC (high-end, but small Japanese products), Taiwan Yadeke (affordable, good quality) or other domestic brands. Electrically speaking, the two-position three-way solenoid valve is generally a single electronic control (ie, a single coil), and the two-position five-way solenoid valve is generally a dual electronic control (ie, a double coil). The coil voltage level is generally DC24V, AC220V, etc. The two-way three-way solenoid valve is divided into two types: normally closed type and normally open type. The normally closed type means that the gas path is broken when the coil is not energized, and the normally open type refers to the gas path that is open when the coil is not energized.


Normally closed two-way three-way solenoid valve operating principle: the coil is energized, the gas path is connected, and once the coil is de-energized, the gas path will be disconnected, which is equivalent to “jog”.


Normally open two-position three-way single electronically controlled solenoid valve action principle: the coil is energized, the gas path is disconnected, and once the coil is de-energized, the gas path will be connected, which is also "jog". The operation principle of the two-way five-way double electronically controlled solenoid valve: when the positive action coil is energized, the positive action air path is turned on (the positive action air outlet has gas), even if the positive action coil is powered off, the positive action air path is still connected. It will be maintained until the counter-action coil is energized. When the reverse action coil is energized, the reverse action air path is turned on (the reverse action air outlet has gas), and even if the reverse action coil is turned off, the reverse action air path is still turned on, and will continue until the positive action coil is energized. . This is equivalent to "self-locking."

   

Based on the characteristics of the two-way five-way dual electronically controlled solenoid valve, when designing the electromechanical control loop or programming the PLC program, the solenoid valve coil can be operated for 1~2 seconds, which can protect the solenoid valve coil from being easily damaged. . In addition, the two-way three-way solenoid valve can also control the double-acting cylinder (the cylinder is vertically installed, the air pressure is extended when it is extended, and the weight is pressed down when it is retracted).