The process control system can be divided into two categories according to the type of actuator: continuous control system and switch control system. The actuator of the continuous control system is mainly the pneumatic control valve and the electric control valve. The actuator of the switch control system is mainly the solenoid valve. It is generally believed that solenoid valves can only be used for on-off control. For those requiring continuous control, only pneumatic or electric control valves can be used. The emergence of proportional solenoid valves has changed this view. Proportional solenoid valves were applied in the late 60s of last century, initially for hydraulic control systems. Before it appears, the main components of the hydraulic control system are servo valves, but the structure of the servo valves is complex and the price is high. So the proportional solenoid valves’ appear offers a new choice for those control systems that do not require much about the control parameters. The proportional solenoid valve has the advantages of low cost and simple structure. It improves the working stability and reliability of the hydraulic system and has been widely applied in the hydraulic control system at present.

Introduction of Proportional Solenoid

The proportional valves usually adopt proportional solenoid. It is designed according to the electromagnetic principle, and the mechanical quantity (force, torque and displacement) generated by it is proportional to the size of the input electrical signal (current). After the input electrical signal is amplified by a proportional amplifier (usually 24V DC, 800mA or larger rated current), the proportional solenoid converts it into force or displacement. During this process, the position of the valve core will be continuously controlled, so that it can continuously control the pressure, direction and flow of the hydraulic system. The solenoid for proportional valves is consisting of the hydraulic solenoid coil and solenoid tube. When the solenoid has been electrified, solenoid coil creates a magnetic field, and the magnetic force can trigger the plunger in solenoid tube to move proportionally, and the movement of solenoid plunger will actuate the hydraulic valves.

The proportional solenoid has the advantages of simple structure, low cost, large output thrust and displacement, low requirement for oil quality and convenient maintenance.

Classification of Proportional Solenoid

The proportional solenoids are mainly classified into the following categories according to their working principles. They are force control type, stroke control type and position adjustment type. In addition, there is also cartridge valve proportional solenoid, explosion-proof proportional solenoid and many other solenoids available. Some proportional solenoids are equipped with manual emergency devices at the rear. When the control circuit fails, the proportional solenoid will be cut off, and the proportional valve can be manually controlled.

Force Controlled Proportional Solenoid

The basic characteristic of the force controlled proportional solenoid is force-stroke characteristic. When the armature travel is not changed obviously, the electromagnetic force of the output can be adjusted by changing the current. As the current feedback link is set in the electronic amplifier, when the current setting value is constant and the magnetoresistance is changed, the magnetic flux will be unchanged. Then the electromagnetic remains unchanged. Due to the small stroke, the structure of the force controlled solenoid is very compact. It can be used in the pilot stage of proportional pressure valve and proportional directional valve to convert electromagnetic force into hydraulic pressure. This proportional solenoid is an adjustable DC solenoid. It is full of working fluid in the armature cavity.

Stroke Controlled Proportional Solenoid

In the stroke controlled proportional solenoid, the position of the armature is regulated by a closed loop regulating circuit. As long as the solenoid works in its permitted working area, the armature position will be unchanged. It can directly drive the valve core of the proportional directional valve, flow valve and pressure valve, and control them in any position. The solenoid stroke depends on its specifications, usually between 3~5mm.

Position Adjustable Proportional Solenoid

In the position adjustable proportional solenoid, when the position of the armature is detected by the sensor, a feedback signal will be sent out inside the valve. After that, the armature will be repositioned and adjusted. As long as the solenoid runs in the permitted working area, the armature will keep the position corresponding to the input electrical signal, which has nothing to do with the counterforce. In structure, it is basically the same as the force control and the stroke control proportional solenoid, except one end of the armature is attached to the displacement sensor.

This kind of proportional solenoid has high positioning accuracy, high load stiffness and strong anti-interference ability. Since it is a position feedback system, it should be used with a matching proportional amplifier. The position adjustable proportional solenoid is often used in proportional valves with high control accuracy. It can control the opening of the valve port when used in the proportional directional valve and the proportional flow valve and can obtain accurate output force when used in the proportional pressure valve. As for high precision valves, there are many high precision proportional valves producer, such as Bosch Rexroth in Germany, etc.

Kaidi, as a major solenoid supplier for Rexroth valves, we have mature proportion solenoids for all types of Rexroth proportional valves. We support:

Screw type hydraulic proportional solenoid. Under this type, we have GP37, GP516, and GP63, three series solenoid for proportional valves.

Bolt type hydraulic proportional solenoid. Under this type, we produce GP45, GP61, GV45, and GH263, four series of the hydraulic solenoid for proportional valves with bolt connection. These series of solenoids for proportional valves are often used in DC12V or DC 24V hydraulic proportional control systems.

Three-pin type hydraulic proportional solenoid. In this type, we have ZC32 and ZC36L solenoids for proportional valves.

GP series hydraulic proportional solenoid. This kind of solenoid is widely used in the electro-hydraulic proportional closed loop control system, equipped with the electro-hydraulic proportional amplifier. We support GP45A4, GP45B4 and GP61, four series hydraulic solenoid.

Except these, we also support the proportional solenoid for overflow valve and servo valve. All the solenoids from Kaidi have a simple structure, large force power and reasonable price. According to your requirement, we can also customize proportional solenoids for your own valves. If you are interested in our products, please feel free to contact us.

Application of Proportional Solenoid valve control system

After the proportional solenoid technology and proportional solenoid valve technology is improved, the proportional solenoid valve control system has expanded from the hydraulic industry to the household electrical appliance industry, automobile industry, water treatment, food and beverage industry, pharmaceutical industry and many other industries. It has been applied in more and more different fields of  our lives and brought us many conveniences. With the popularization and technological progress of the proportional solenoid valve control system, we believe that there will be more and more applications  in the future.

Kaidi is a solenoid manufacturer who has rich experience in providing on-off solenoid, proportional solenoid, explosion-proof solenoid and solenoid coil. We are the regular supplier of Rexroth, Yuken, Vickers, Parker solenoid. Besides, we also supply customization service based on the particular requirements of different clients. If you are interested in our products, please contact us to get a free quote!