What is the electro-hydraulic digital control valve in the Type A hydraulic press

The use of computers to control the electro-hydraulic system of small hydraulic presses is an inevitable trend in the development of hydraulic technology in the future. Since the signal that the electro-hydraulic proportional valve or servo valve can accept is a continuously changing current or voltage, and the computer command is digital information of "on" or "off", "digital to analog" conversion must be carried out to use the computer for control, and a series of electronic hydraulic "interface" equipment is required. As a result, the equipment is complex, cost is increased, reliability is reduced, and daily use and maintenance is quite difficult. Under this technical requirement, in order to solve the above problems, digital valves emerged in the early 1980s, which have the advantages of easy interface with computers, high reliability, good repeatability, and low price.
There are various methods for small hydraulic presses to accept computer digital control, and the most mature technology nowadays is the incremental digital valve, which is a hydraulic valve driven by a stepper motor. At present, there are a series of products such as digital flow valves, pressure valves, and directional valves. The stepper motor can accept pulse signals amplified by the driving power supply sent by the computer, and rotates a certain angle for each pulse signal received. The rotation of the stepper motor is converted into linear displacement through mechanisms such as cams or screws, thereby pushing the valve core (for directional valves and flow valves) or compressing the spring (for pressure valves), achieving hydraulic valve control over direction, flow, or pressure.
The small hydraulic press adopts an incremental digital flow valve. After the computer sends a signal, the stepper motor 1 rotates and converts it into axial displacement through the ball screw 2, driving the throttle valve core 3 to move. The valve has two throttle ports. When the valve core moves, the non full circumference throttle port on the right is first opened, resulting in a smaller flow rate; Continuing to move, open the second full cycle throttle on the left, with a large flow rate of up to 3600L/min. The flow rate of the valve is compensated for by the relative thermal expansion of the valve core 3, valve sleeve 4, and connecting rod 5, thereby maintaining stable flow rate.