The automatic control of electric proportional valve can be divided into intermittent control and continuous control. Intermittent control of electric proportional valve is switch control. In the pneumatic control system, the on-off directional valve with low action frequency is used to control the on-off of the gas path. Adjust the required pressure through the pressure reducing valve and the required flow through the throttle valve. This traditional pneumatic control system needs multiple pressure reducing valves, throttle valves and reversing valves if it wants to have multiple output forces and multiple moving speeds. This not only requires many parts, high cost and complicated system, but also requires manual adjustment in advance. Electro-proportional valve control belongs to continuous control, which is characterized by the change of output with the change of input (current value or voltage value), and there is a certain proportional relationship between output and input. Proportional control is divided into open-loop control and closed-loop control. Closed-loop control with signal feedback system.
The electric proportional control valve realizes the continuous proportional control of the output signal (pressure or flow) by controlling the input signal (voltage or current). The control signals of electric proportional valve are all electrical signals. Electric proportional valve is a kind of pressure reducing valve with linear proportional output with the change of input voltage or current. It belongs to linear continuous control, and its basic feature is that the output changes linearly with the change of input power. There are two kinds of proportional control: open-loop control and closed-loop control. In the closed-loop control system, when the actual value of the system output deviates from the original expected value, the system automatically corrects it to make the output change in the direction close to the original expected value, thus keeping a certain proportional relationship between the output and the input.
The traditional electric proportional valve takes electromagnet as electromechanical mode, which converts electric control signal into mechanical displacement, pushes the valve core, and realizes gas path switching or proportional control of gas pressure and flow. The electromagnet is low in price and convenient to operate and use. But it also has many disadvantages, such as high power consumption, slow response, low accuracy, loud noise, heat and electromagnetic interference. The pressure control system composed of piezoelectric proportional valve has the advantages of high precision, fast response and low cost.
Piezoelectric technology is a brand-new revolution, and the proportional valve adopting piezoelectric technology has incomparable advantages in performance compared with the traditional electric proportional valve. Piezoelectric sheet is free from mechanical friction during deformation and has the characteristics of fast response. The electric proportional valve based on piezoelectric valve plate has obvious advantages over the traditional electromagnetic proportional valve in performance. For example, the piezoelectric proportional valve adopts piezoelectric elements and semiconductor sensors. By adjusting the electrical proportional signal, the pressure and flow rate of gas can be controlled stepless with high precision, high response and no noise. The main advantages are as follows:
(1) has simple structure and fast circuit control response.
(2) Adjust the opening of the piezoelectric plate according to the voltage signal: when the voltage is high, the piezoelectric plate is deformed greatly and the output pressure is high.
(3) piezoelectric adjustment, no noise; The adjustment can reach tens of thousands of hertz.
(4) The piezoelectric adjustment is fast, the output pressure response is fast (10ms), and the pressure is stable (it can be stabilized at 0.1kpa);
Piezoelectric electric proportional pressure regulating valve can replace manual pressure regulating valve to realize real-time, accurate and continuous automatic control of force or pressure, and can be applied to various industrial automation fields, such as tension control, laser cutting or welding equipment, glass cutting or grinding equipment, glass container sealing detection, petrochemical industry and so on.
(5) The piezoelectric sheet has low power consumption, no heat generation and low power;
Because the power consumption of piezoelectric proportional valve is very low, it can meet the highest level of intrinsically safe explosion-proof requirements and can be used in various explosion-proof occasions.
(6) The piezoelectric sheet has a rubber diaphragm, which can block fine impurities and water vapor and has a long service life.
Piezoelectric proportional valve is a new technology that introduces piezoelectric technology into pneumatic valve. Compared with the traditional electric proportional valve, it has the advantages of high precision, low power consumption, fast response, no electromagnetic interference, long service life and no heat generation. It is widely used in the field of industrial and process automation control.