What is the classification and principle of proportional valves?

What is the principle and classification of proportional valves?

【 Answer 】 Proportional control valves are mainly used for open loop control; The output of the proportional control valve is proportional to the input signal, and the magnetic force generated by the electromagnetic coil in the proportional control valve is proportional to the current.

In traditional hydraulic control valves, hydraulic pressure can only be controlled at a fixed value. For example, the pressure valve operates at a certain set pressure, the flow valve maintains the set flow rate, and the directional valve switches on/off in the direction of the liquid flow. Therefore, the system functions composed of these control valves are subject to some limitations. With the advancement of technology, many hydraulic systems require flow and pressure to continuously or proportionally change with the input signal of the control valve. Although hydraulic servo systems can meet their requirements and have high accuracy, for most industries, they do not require the system to have such high quality. Instead, they hope to ensure certain control performance, while being cheap, reliable, and easy to maintain. Therefore, proportional control valves have developed in this context.

Proportional control valves can be divided into three categories: pressure control valves, flow control valves, and directional control valves.

Pressure control valve: The manual adjustment device that replaces the guided proportional relief valve with a proportional solenoid valve becomes the guided proportional relief valve, and its output hydraulic pressure is continuously or proportionally controlled by the input signal.

Flow control valve: A proportional solenoid valve is used to replace the manual adjustment device of a throttle valve or speed control valve, and the throttle opening of the throttle valve or speed control valve is controlled by an input signal. Its output flow can be continuously or proportionally controlled. Therefore, the opening of the throttle can be determined by the voltage of the input signal.

Directional control valve: The proportional solenoid valve replaces the general solenoid valve of the directional valve to form a direct acting proportional directional valve. Its sliding shaft can not only rotate, but also the displacement stroke can be continuously or proportionally changed. Therefore, the oil flow area between the connecting oil ports can also be continuously or proportionally changed. Therefore, the proportional directional control valve can not only control the direction of motion of the actuator, but also control its speed.

The above content is compiled based on the problems encountered by students in their actual work, for reference. If there are any problems, please communicate and correct them in a timely manner.