Electro hydraulic proportional directional flow valve

Electro hydraulic proportional flow directional control valve: precise control solution for 10-250L/min under 25MPa high pressure

In modern hydraulic systems, directional control and flow regulation often require two independent valve components - the directional valve controls the opening and closing of the oil circuit, and the throttle valve or speed regulating valve controls the flow rate. This split type scheme not only occupies a large space and has complex pipelines, but also makes it difficult to achieve smooth acceleration/deceleration control that is deeply integrated with the electronic control system. The emergence of electro-hydraulic proportional technology has changed this situation: by changing the magnitude of the input current, the same valve core can switch the direction of oil flow and continuously adjust the flow rate, providing a structurally compact, responsive, and easy to remotely control solution for injection molding machines, presses, walking machinery, test benches, and other equipment.

The series of electro-hydraulic proportional flow directional control valves (10-250 L/min, maximum working pressure 25 MPa) introduced in this article are industrial grade products designed based on the above concept. This series includes direct acting 01 specification and pilot operated 03, 04, 06 specifications, driven by DC proportional solenoid, with built-in manual adjustment screw, supporting internal or external oil discharge, and optional pressure compensation valve kit to achieve load independent flow control. The following will provide a comprehensive technical analysis of the valve from multiple dimensions, including technical specifications, model codes, structural principles, performance curves, installation and use, and pressure compensation kits.

Product Overview and Technical Features

1.1 Core Design Philosophy

This series of valves is essentially a four-way proportional valve that can simultaneously complete direction switching and flow control. The traditional switch type electromagnetic directional valve only has two states: "on" and "off", while the proportional solenoid of the proportional valve can generate an electromagnetic force proportional to the input current, thereby pushing the valve core to overcome the spring force and move to a certain intermediate position, opening the corresponding throttle area. When the direction of input current changes, the proportional electromagnet on the other side works to switch the direction of oil flow.

The biggest advantage of this design is that it replaces the combination of "directional valve+throttle valve" with one valve, simplifying the hydraulic circuit; Realize shock free acceleration and deceleration through ramp current signals to avoid hydraulic shock; Support remote electrical control for easy integration into PLC or CNC systems.

1.2 Series division and applicable traffic

According to different diameters and rated flow rates, this series is divided into four specifications:

Specification, model, prefix, rated flow rate (L/min), maximum flow rate (L/min), structural form

01 ESD-G01 10/20 25 Direct Acting

03 ESD-G03 40/80 100 Pilot operated

04 ESD-G04 140 140 Pilot operated

06 ESD-G06 250 250 Pilot operated

The rated flow rate is measured under the condition of a pressure drop of 1.0 MPa (approximately 10 kgf/cm ²) for P → A and P → B. Users can choose the appropriate specifications based on the required speed of the actuator to avoid excessive pressure loss or decreased control accuracy.

1.3 Work pressure and environmental adaptability

The maximum working pressure for all specifications is 25 MPa (255 kgf/cm ²), which can meet the pressure rating of most industrial hydraulic systems. T-port allows for back pressure: 2.5 MPa for internal discharge type and up to 21 MPa (214 kgf/cm ²) for external discharge type, providing flexible options for pilot stage oil discharge in complex circuits.

Temperature range of hydraulic oil used: -20 to+70 ℃; Range of kinematic viscosity: 12-400 mm ²/s, recommended viscosity 15-60 mm ²/s. It is recommended to control the pollution level at NAS level 9 or higher (ISO 4406 18/15), and it is recommended to install a return oil filter with an absolute filtration accuracy of 8 μ m.

Detailed specification parameters

2.1 Electromagnetics and Dynamic Performance

Rated current: 850 mA (all specifications are consistent)

Coil resistance: 20 Ω (at 20 ℃)

Lag: ≤ 5% (when using Nachi Fujikoshi dedicated amplifier)

Response time (oil supply pressure 14 MPa, oil temperature 40 ℃, viscosity 40 mm ²/s):

ESD-G01：0.04 s

ESD-G03：0.05 s

ESD-G04：0.08 s

ESD-G06：0.10 s

Response time is defined as the time required from zero input to rated flow rate. For systems that require rapid pressure building or emergency braking, the 40 millisecond response of 01 specification is already excellent; The 100 milliseconds of the 06 specification is also reasonable for high flow valves.

2.2 Pilot pressure and flow requirements (for specifications 03/04/06)

Pilot operated valves require sufficiently high pilot pressure to ensure reliable switching and adjustment of the valve core: