Working principle of solenoid valve

● Overall working mechanism

The solenoid valve contains a sealed chamber with holes at various positions, each connected to a different oil pipe. In the middle of this chamber is a piston, with two electromagnets on either side. When the coil of one electromagnet is energized, the valve body is attracted to that side. By controlling the movement of the valve body, different oil discharge ports can be opened or closed, while the inlet port remains open. Hydraulic fluid then flows into the respective discharge pipes and, through the pressure of the oil, pushes the piston in the hydraulic cylinder. The piston, in turn, drives the piston rod, which operates the mechanical device. Thus, by controlling the current flow to the electromagnets, the mechanical motion is controlled.

● Principles of different types of solenoid valves

Direct-acting solenoid valve: When powered, the electromagnetic coil generates a force that lifts the closing member from the valve seat, opening the valve. When power is cut off, the electromagnetic force disappears, and the spring presses the closing member back onto the valve seat, closing the valve. This type of valve can operate normally in vacuum, negative pressure, and zero-pressure conditions, but its bore diameter typically does not exceed 25mm.

The step-by-step direct-acting solenoid valve combines the principles of direct-acting and pilot-operated valves. When there is no pressure difference between the inlet and outlet, energization causes the electromagnetic force to sequentially lift the pilot valve and the main valve closure member upwards, opening the valve. When the inlet and outlet reach the required pressure difference for operation, energization causes the electromagnetic force to lift the pilot valve, increasing the pressure in the lower chamber of the main valve while decreasing the pressure in the upper chamber, thus using the pressure difference to push the main valve upwards. When de-energized, the pilot valve uses spring force or medium pressure to push the closure member downwards, closing the valve. This type of valve can operate reliably even under zero pressure difference, vacuum, or high pressure conditions, but it requires a higher power supply and must be installed horizontally.

Pilot Solenoid Valve: When powered, the electromagnetic force opens the pilot hole, causing the pressure in the upper chamber to drop rapidly. This creates a pressure differential around the closure member, with lower pressure above and higher pressure below. The fluid pressure then pushes the closure member upward, opening the valve. When power is cut off, the spring force closes the pilot hole, allowing the inlet pressure to quickly enter the upper chamber through the bypass hole. This creates a pressure differential around the closure member, with higher pressure above and lower pressure below. The fluid pressure pushes the closure member downward, closing the valve. The upper limit of its fluid pressure range is relatively high, allowing for flexible installation (custom-made), but it must meet the fluid pressure differential requirements.

Function of solenoid valve

● General use

The solenoid valve is an electromagnetic controlled industrial equipment, which is used to control the fluid automation basic element, belongs to the actuator, not limited to hydraulic and pneumatic. It can be combined with different circuits to achieve the expected control, and can ensure the accuracy and flexibility of the control.

● Functions in different scenarios

Hydraulic system: In the hydraulic system, the solenoid valve can control the flow direction, pressure and flow of hydraulic oil to achieve precise control of hydraulic actuator (such as hydraulic cylinder, hydraulic motor), such as controlling the lifting, extension and other movements of mechanical equipment.

Pneumatic system: in the control system, according to the requirements of control to adjust the various states of compressed air, cooperate with power elements (such as compressor), actuating elements (such as cylinder) and other components, so that the pneumatic system can realize a variety of functions, such as material handling, assembly and other operations on the automatic production line.

● Other application scenarios: In some water purifiers, electromagnetic valves can be used for automatic control or interconnection to achieve functions such as water flow regulation and on-off control. Additionally, there are electromagnetic valves with various functions, including water, steam, refrigeration, gas, and fire protection, which are applied in corresponding systems to control different fluids.