Electro hydraulic proportional directional flow valve

5.2 T-port piping

For pilot operated valves (G03/G04/G06), the T port (T port of the pilot valve) must be filled with oil and no air chamber is allowed. When piping, ensure that the return oil pipeline is submerged below the oil tank level and avoid sharing with the high-pressure return oil pipeline, which may cause back pressure impact.

5.3 Valve installation direction

In order to prevent the movement of the valve core from being affected by gravity, the valve should be installed horizontally (spool axis line horizontal). If vertical installation is necessary, the manufacturer should be consulted to see if it is allowed and if it is necessary to adjust the spring preload force.

5.4 Combination use with pressure compensation valve

When the actuator load changes significantly, the output flow rate of a conventional proportional valve will vary with the load pressure (similar to the characteristics of a throttle valve). In order to achieve load independent flow control, it is necessary to cooperate with a pressure compensation valve. This series provides a dedicated pressure compensation valve kit (JHF series) that can be installed between the valve and the base plate or integrated into the pipeline to maintain a constant pressure difference at the valve port, thereby allowing the flow rate to be proportional only to the input current.

The specific parameters and installation methods of the pressure compensation valve will be described separately in the following text.

5.5 Additional measures under special working conditions

High brake pressure system: For example, when a hydraulic motor brakes quickly, a high-pressure impact will be generated on the return oil side. At this time, counter balance valves should be installed on both sides of the motor.

Vertical oil cylinder: When using a single rod cylinder and the piston rod extends too quickly during downward movement, a balance valve should be installed on the return side to prevent overspeed and falling.

High pilot pressure: If the pilot pressure exceeds 9 MPa, a P-port pressure reducing valve (such as OG-G01-P1-21) must be installed and set to 2 MPa.

5.6 Installation bolts and tightening torque

The specifications and tightening torque of the installation bolts attached to the valve are as follows:

Model, bolt specification, quantity, tightening torque N · m (kgf · cm)

ESD-G01 M5×45 4 5～7 (51～71)

ESD-G03 M6×35 4 10～13 (102～133)

ESD-G04 M6×45 2 10～13 (102～133)

ESD-G06 M12 × 60 6 45-55 (460-560) or 60-70 (610-715)

Attention: G06 provides two sets of torque values, which may correspond to different materials or sealing methods. The actual markings should prevail.

Performance curve analysis

6.1 Input current flow characteristics

The document provides the input current flow characteristic curve measured under the conditions of pressure drop Δ P=1.0 MPa and oil viscosity of 32 mm ²/s. Curve display:

As the current increases from 0 mA to the rated current of 850 mA, the flow rate gradually increases from zero to the rated value.

The curve exhibits a certain degree of nonlinearity, especially in the low current region (dead zone). Usually, amplifiers provide a "dead zone compensation" function to improve the accuracy of small signal control.

The lag is less than 5%, which means that under the same current, there is little difference in flow rate when approaching from two different directions. This is sufficient for open-loop proportional control systems, but for closed-loop precise control, it is recommended to use proportional valves with displacement feedback.

From the curves of ESD-G04 and G06, it can be seen that the flow regulation range is wide and has good linearity in the middle section. Users can set acceleration/deceleration times through a ramp generator (usually integrated into an amplifier) to achieve smooth speed changes.

6.2 Pressure flow characteristics

The pressure flow characteristic curve shows the maximum flow rate that the valve can pass through under different valve port pressure differentials. When the pressure difference increases, the flow rate also increases, but it is limited by the maximum opening area of the valve port and eventually tends to saturation. These data are crucial for system designers to calculate pressure loss and determine the set pressure of the pump.

For example, when 250 L/min is required, if ESD-G06 is used, the corresponding valve port pressure difference is about 1.0-1.2 MPa. If the system allows for higher pressure loss, the valve diameter can be reduced to save costs, but the heat generation must be accounted for.

Pressure compensation valve kit (JHF series)

7.1 Why is pressure compensation necessary

The ordinary proportional directional valve is essentially an adjustable flow port, and its flow formula is Q=K ⋅ A ⋅ Δ P

Q=K⋅A⋅ ΔP， Where Δ P is the pressure difference before and after the valve port. When the load changes, Δ P changes accordingly, and even if the valve core opening area A remains unchanged, the flow rate will fluctuate. In hydraulic systems, this can cause the actuator speed to vary with changes in load, affecting machining accuracy or motion stability.