Solenoid valve is the most important component of pneumatic control components, with various varieties and different structures. According to the control mode, there are two types of direct acting and pilot head type.
1. direct motion
Direct acting solenoid valve is the use of electromagnetic force directly push the valve stem (spool) commutation. According to the control mode of spool reset, there are two kinds of single electric control and double electric control. The direct acting solenoid valve has the characteristics of simple structure, compact structure and high commutation frequency. But when used for AC electromagnets, if the valve stem dies, there is a possibility of burning the coil. The stroke of the stem is affected by the stroke of the electromagnet. Therefore, it is only applicable to small valves.
In the use of direct-acting dual-electronically controlled solenoid valves, special attention should be paid to the fact that the electromagnets on both sides cannot be energized at the same time, otherwise the electromagnetic coils will be burned out. Therefore, an interlocking circuit to prevent simultaneous energization is usually installed in the electric control circuit.
2. leader type
Pilot head solenoid valve is composed of small solenoid valve and large air-controlled directional valve, also known as electronic directional valve. According to the source of the pilot-type electromagnetic-pneumatic control, it can be divided into two types: self-control (internal pilot) and other-control (external pilot). The valve which directly uses the main valve's gas source as the pneumatic control signal is called the self-control solenoid valve. The self-control solenoid valve is easy to use, but the pressure will decrease at the moment of commutation, especially when the output flow is too large, which may cause the valve to fail in commutation. In order to ensure the reversing performance of the valve or reduce the minimum working pressure of the valve, the valve with external supply pressure as the control signal of the main valve is called the other-controlled solenoid valve.
According to the composition principle of the pilot-type solenoid valve, there are single, double, two, three, two, three, four and five, cut-off and sliding column structure, so the structure and specifications of the electronic control directional valve are extremely diverse.
