With the development of hydraulic transmission and hydraulic servo systems, some hydraulic systems have emerged in production practice that require continuous control of pressure, flow, and direction, but do not require very high control precision. Since ordinary hydraulic components cannot meet the requirements for a certain level of servo capability, and using electro-hydraulic servo valves would be wasteful due to the low control precision requirements, proportional control valves, which fall between ordinary hydraulic components (on/off control) and servo valves (continuous control), have emerged in recent years.
Electro-hydraulic proportional control valves (referred to as proportional valves) are essentially inexpensive electro-hydraulic control valves with good anti-contamination performance. The development of proportional valves has followed two paths: one is the replacement of the manual adjustment input mechanism of traditional hydraulic valves with proportional electromagnets, resulting in various proportional directional, pressure, and flow valves based on traditional hydraulic valves; the other is the development by some original electro-hydraulic servo valve manufacturers who reduced the design and manufacturing precision of electro-hydraulic servo valves.
