The definition, classification and principle of solenoid valve

Definition
Solenoid valve is a basic component of automation used to control fluids and is an actuator;it is not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. Factory mechanical devices are generally controlled by hydraulic steel, so solenoid valves are used.
Working principle: There is a closed cavity in the solenoid valve, with through holes at different positions. Each hole leads to a different oil pipe. There is a valve in the middle of the cavity, and two electromagnets on both sides. Which side is the magnet coil? When the valve body is energized, it will be attracted to which side, and the movement of the valve body is controlled to block or leak out different oil drain holes. The oil inlet hole is normally open, and the hydraulic oil will enter different oil drain pipes and then pass through The pressure of the oil pushes the oil-rigged piston, the piston drives the piston rod, and the piston rod drives the mechanical device. In this way, the mechanical movement is controlled by controlling the current of the electromagnet.

Classification and Principle
Solenoid valves at home and abroad are divided into three major categories in principle (namely: direct-acting, step-by-step direct-acting, pilot-operated), and Based on the differences in disc structure and materials and the differences in principle, it is divided into six subcategories (direct-acting diaphragm structure, step-by-step heavy disc structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, pilot piston structure).
①Direct-acting solenoid valve
Principle: When the power is on, the solenoid coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens;when the power is off, the electromagnetic force disappears, and the spring presses the closing member against the valve seat. on, the valve is closed.
Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.
②Distributed direct-acting solenoid valve
Principle: It is a principle that combines direct-acting and pilot-operated. When there is no pressure difference between the inlet and outlet, after power is turned on, the electromagnetic force directly connects the pilot small valve and the main valve. The valve closing parts are lifted upward in turn, and the valve opens. When the inlet and outlet reach the starting pressure difference, after power is turned on, the electromagnetic force pilots the small valve. The pressure in the lower chamber of the main valve increases and the pressure in the upper chamber decreases, thereby using the pressure difference to push the main valve upward;when the power is turned off, the pilot valve uses the spring Force or medium pressure pushes the closing member to move downward to close the valve.
Features: It can also operate safely under zero pressure difference or vacuum or high pressure, but the power is large and it must be installed horizontally.
③Pilot solenoid valve
Principle: When energized, the electromagnetic force opens the pilot hole, and the pressure in the upper chamber drops rapidly, forming an upper, lower, and higher pressure difference around the closing member. The fluid pressure pushes the closing member to move upward. The valve opens;when the power is off, the spring force closes the pilot hole, and the inlet pressure quickly passes through the bypass hole and forms a pressure difference between the lower and upper parts around the valve closing part. The fluid pressure pushes the closing part downward to close the valve.
Features: The upper limit of the fluid pressure range is relatively high, and it can be installed arbitrarily (customization is required) but the fluid pressure difference condition must be met.
When using it, you should consider some of its characteristics, such as media characteristics, ambient temperature, operating frequency, power supply and other factors.