Understanding three types of SMC solenoid valves: principles and application analysis

SMC solenoid valve, as an automation basic component, plays a crucial role in the field of fluid control. It is not only widely used in hydraulic and pneumatic systems, but also a key member in the actuator category. In control systems, different types of solenoid valves have their own functions, among which one-way valves, safety valves, directional control valves, and speed regulating valves are more common and essential components.

The importance and classification of SMC solenoid valves

SMC solenoid valves play a significant role in automation systems, especially in hydraulic and pneumatic systems, playing an important role as actuators. The principle can be summarized into three categories: direct action, step-by-step direct action, and pilot action.

Working principle of direct acting solenoid valve

Direct acting solenoid valve is a common type of solenoid valve, and its working principle is relatively simple. When the solenoid valve is in the closed state, its internal iron core is fixed, thereby preventing the valve from opening. When the solenoid valve is powered on, the iron core will be attracted by magnetic force, overcoming the elastic force of the spring and opening the valve. This type of solenoid valve has a wide range of applications in the field of industrial automation.

In a normally closed direct acting solenoid valve, when powered on, the solenoid coil generates electromagnetic force, which overcomes the elastic force of the spring and lifts the opening member from the valve seat, allowing the valve to open. When the power is cut off, the electromagnetic force disappears, and the spring will press the open part back onto the valve seat, causing the valve to close. It should be noted that the working principle of normally open solenoid valves is the opposite. In addition, this type of solenoid valve can maintain normal operation in vacuum, negative pressure, and zero pressure environments, but its diameter usually does not exceed 25 millimeters.

Working principle of step-by-step direct acting solenoid valve

The working principle of SMC solenoid valve is different from that of normally closed direct acting solenoid valve. When the solenoid valve is powered on, its electromagnetic coil also generates electromagnetic force, but this electromagnetic force does not overcome the elastic force of the spring at once, but gradually lifts the open part through step-by-step action, thereby opening the valve. When the power is cut off, the electromagnetic force disappears, and the spring gradually presses the open part back to the valve seat, achieving the gradual closure of the valve. This design enables the step-by-step direct acting solenoid valve to perform excellently in terms of control accuracy and stability.

SMC solenoid valve combines the working principles of direct acting and pilot operated. When there is no pressure difference between the inlet and outlet, after being energized, the electromagnetic force will sequentially lift the closing parts of the pilot valve and the main valve, allowing the valves to open. When the starting pressure difference is reached between the inlet and outlet and electricity is applied, the electromagnetic force will first act on the pilot valve, causing the pressure in the lower chamber of the main valve to rise and the pressure in the upper chamber to fall, and then using this pressure difference to push the main valve upwards. After the power is cut off, the pilot valve relies on spring force or medium pressure to push the closing member downward, thereby achieving the closure of the valve.

Features: This solenoid valve can work normally in zero pressure difference, vacuum or high-pressure environments, but it should be noted that its power requirements are high and it must be installed horizontally.

Working principle and characteristics of indirect pilot solenoid valve

SMC solenoid valve, as a special type of solenoid valve, has a different working principle from the above-mentioned solenoid valves. It can also maintain a stable working state in zero pressure difference, vacuum or high-pressure environments. However, compared to the aforementioned solenoid valve, its power requirement is slightly higher, and special attention should be paid to maintaining a level during installation. Understanding its working principle and characteristics can help users better choose and use suitable types of solenoid valves.

Principle: When powered on, electromagnetic force will act on the pilot hole, causing it to open. This leads to a rapid decrease in pressure inside the upper chamber, resulting in a high pressure difference around the upper opening. This pressure difference drives the fluid pressure to push the open part upwards, thereby opening the valve. When the power is cut off, the spring force will replace the electromagnetic force, pushing the pilot hole to reopen. At this point, the pressure at the inlet will quickly enter the chamber through the bypass hole, creating a lower and higher pressure difference around the valve closing component. Similarly, this pressure difference will push the open component downwards, thereby closing the valve.

Features: This SMC solenoid valve has the characteristics of compact size, low power demand, and relatively high upper limit range of fluid pressure. In addition, it also has flexible installation methods (customized), but it should be noted that the installation must ensure that the fluid pressure difference conditions are met.

1、 Conventional solenoid valve

Conventional solenoid valves refer to electromagnetic valves that are widely used in fields such as air conditioning, electrical appliances, water treatment, and general fluid control. They can be divided into two types based on their applications: gas solenoid valves and liquid solenoid valves. Depending on their working mode, they can be divided into different structural forms such as straight through, right angle, and corner seat.

2、 Micro electromagnetic valve

Micro solenoid valve is currently one of the smallest solenoid valves, with a diameter usually below 1mm. It has the advantages of simple structure, fast response speed, and low starting voltage, and can be applied to some applications with strict space limitations, such as biomedical, petroleum mining and other fields.

3、 High pressure solenoid valve

SMC solenoid valves generally refer to solenoid valves that can withstand pressures exceeding 10MPa, mainly used in the field of high-pressure gas, liquid and other medium control. They have the characteristics of compact structure, good sealing, safety and reliability.

4、 Other types of solenoid valves

In addition to the three types of solenoid valves mentioned above, there are also different types such as direct acting solenoid valves, intermittent solenoid valves, and diaphragm solenoid valves. Among them, direct acting solenoid valves are mainly used in the field of industrial automatic control, intermittent solenoid valves are suitable for periodic working environments, and diaphragm solenoid valves have the advantages of simple structure and high flow capacity.

5、 Working principle of solenoid valve

The working principle of SMC solenoid valve is to generate a magnetic field through the current of the electromagnetic coil. The magnetic field acts on the core, causing it to move and change the position of the small iron piece, thereby controlling the flow of liquid or gas.

6、 Application areas of SMC solenoid valves

SMC solenoid valve is one of the commonly used control components in the field of industrial automation, widely used in petrochemical, light industry, metallurgy, machinery, instrumentation, environmental protection, biomedicine and other fields. Specific applications include hydraulic systems, pneumatic systems, water treatment systems, air conditioning systems, heating systems, chemical systems, power systems, etc.