The principle of solenoid valve and some dynamic diagrams

- Sep 23, 2019-

Solenoid valves are electromagnetically controlled industrial equipment. They are the basic components for controlling fluids. They are actuators and are not limited to hydraulic and pneumatic. Different solenoid valves function in different positions of the control system. The most common ones are check valves, safety valves, directional control valves, speed control valves, and so on.


Solenoid valves are divided into three main categories: direct-acting, step-by-step direct-acting, pilot-operated




1 direct-acting solenoid valve


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Principle: When the normally closed type is energized, the electromagnetic coil generates electromagnetic force to lift the open member from the valve seat, and the valve is opened; when the power is off, the electromagnetic force disappears, and the spring presses the open member against the valve seat, and the valve is opened. (Normally open type is opposite)


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



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2-step direct-acting solenoid valve


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Principle: It is a combination of direct motion and pilot type. When there is no pressure difference between the inlet and the outlet, after the power is applied, 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 be operated at zero pressure difference or vacuum or high pressure, but the power is large, and it must be installed horizontally.



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3 indirect pilot solenoid valve


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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 open member. The fluid pressure pushes the open member upward and the valve opens. When the power is off, the spring force leads the pilot. The hole is open, and the inlet pressure passes through the bypass hole to form a lower low and high pressure difference around the valve member, and the fluid pressure pushes the open member downward to open the valve.


Features: small size, low power, high fluid pressure range, can be installed arbitrarily (customized), but must meet the conditions of fluid pressure difference


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working principle


There are closed chambers in the solenoid valve. There are through holes in different positions. Each hole is connected with different oil pipes. The middle of the cavity is a piston. On both sides are two electromagnets. Which side of the magnet coil is energized? Side, by controlling the movement of the valve body to open or close different oil drain holes, and the oil inlet hole is normally open, the hydraulic oil will enter different oil drain pipes, and then the pressure of the oil pushes the piston of the oil cylinder, and the piston Drive the piston rod, and the piston rod drives the mechanical device. This controls the mechanical motion by controlling the current through and off of the electromagnet.


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Two-position two-way solenoid valve

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Two-position three-way solenoid valve


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Two-position four-way solenoid valve

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Three-position three-way solenoid valve


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Three-position four-way solenoid valve

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Pipeline contact solenoid valve

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Direct control solenoid valve

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