Hollow blow molding electro-hydraulic proportional valves use proportional electromagnets (torque motors, force motors, servo motors, etc.) that have a driving force proportional to the input current to replace the manual given device, and are connected with the basic parts of the valve (with ordinary hydraulic control The valves are basically the same). It can be divided into electro-hydraulic proportional pressure valve, electro-hydraulic proportional flow valve, electro-hydraulic proportional directional valve, electro-hydraulic proportional composite valve and so on. The given value of the electro-hydraulic proportional valve is determined according to the input current, so it can achieve long-distance and continuous reference. The use of electro-hydraulic proportional valves can achieve open-loop control in hydraulic systems, and closed loop control can also be achieved after adding appropriate feedback detection components, but dynamic characteristics such as control accuracy will be less than the control system of electro-hydraulic servo valves. The basic part is the same as the ordinary hydraulic control valve, so it will be lower than the electro-hydraulic servo valve in terms of price and oil requirements. The electro-hydraulic proportional valve is usually supplied with a special power amplifier when it leaves the factory, so as to ensure the normal use of the proportional valve.