REXROTH 4WRTE type electro-hydraulic proportional directional valve

REXROTH 4WRTE series pilot operated proportional directional valve: a high-performance hydraulic control solution integrating electronics and position feedback

In modern high dynamic and high-precision hydraulic control systems, proportional valves play a core role. The 4WRTE series pilot operated proportional directional valve launched by Bosch Rexroth represents the advanced level of industrial hydraulic control technology with its integrated electronic equipment (OBE), electrical position feedback, and optional spool position monitoring function. This article is based on the official technical document RE 29083, providing a comprehensive professional interpretation of the structure, principles, technical characteristics, and applications of this series of valves, aiming to provide detailed references for hydraulic system design engineers and maintenance personnel.

Product Overview and Core Advantages

The 4WRTE series valves are pilot operated, two-way proportional directional valves with electrical position feedback. Its size covers NG10 to NG35, with a maximum working pressure of up to 350 bar and a rated flow range from 25 l/min to 1000 l/min, capable of meeting a wide range of needs from medium to high flow applications. This series of valves adopts the mature 4X component series, ensuring the continuity of installation and connection dimensions.

Core design advantages:

Reliability and Safety: Adopting a validated and robust design. Its pilot valve can achieve automatic pressure compensation of the main control chamber, ensuring smooth control. The main valve core is centered by a spring (or maintained in a biased position under specific symbols), and in the event of a power failure, it can achieve equal pressure in the control chamber through a pilot valve, and ultimately be reliably reset by the spring, meeting the safety shutdown requirements of EN 60204 stop category 0.

High precision and control flexibility: extremely high response sensitivity (≤ 0.05%) and extremely low hysteresis (≤ 0.1%), combined with linear or fine tuned flow characteristics, make it very suitable for position, speed, and pressure closed-loop control.

Integration and Intelligence: The valve integrates control electronics (OBE) and inductive position sensors, achieving a compact integrated design. The optional valve core position monitoring function ("M" option, suitable for NG16 and above specifications) further enhances the safety monitoring capability of the system.

Deep analysis of structure and working principle

1. Core component composition

The 4WRTE valve essentially consists of three components integrated into a compact valve body:

Main valve stage: including valve body, main control valve core, centering spring, and optional valve core position monitoring sensor.

Integrated Electronic Equipment (OBE): includes an inductive position sensor with a main valve core, and can be optionally equipped with an electronic device protective film (code "-967") to prevent condensation.

Pilot control valve: an independent proportional valve unit that includes its own control spool/sleeve assembly, inductive position sensor, and pressure feedback channel for the centering position of the main spool.

2. Principle of closed-loop control

The operation of the valve is based on a precise electrical hydraulic position closed-loop control:

Command input: The external controller provides an analog setpoint signal of ± 10 V (interface A1/A5) or 4-20 mA (interface F1) to the integrated electronic device (OBE).

Force driven: OBE controls the proportional electromagnetic current of the pilot valve based on the feedback difference between the set value and the actual position of the main valve core, changes the electromagnetic force, and drives the movement of the pilot valve core.

Hydraulic amplification and positioning: The pilot valve outputs control oil pressure, which acts on the control chamber on the end face of the main valve core, pushing the main valve core to overcome the force of the centering spring and move. The actual displacement of the main valve core is detected in real-time by its integrated inductive position sensor and fed back to the OBE.

Closed loop regulation: OBE continuously compares the set value with the actual position feedback, adjusts the current of the pilot valve solenoid until the main valve core accurately reaches the target position proportional to the input electrical signal, achieving precise proportional control of flow rate.

3. Safety and monitoring features

Fault safety: When the power supply voltage fails or the cable is disconnected, the integrated electronic device will cut off the power of the electromagnet. The pilot valve balances the pressure in the control chamber at both ends of the main valve core, and then the centering spring pushes the main valve core back to the neutral position (for symbols E, E1-, W6-, W8-) or biases the safety position (for symbols V, V1-), achieving a safe reset.

Valve core position monitoring (option "M"): Use an independent inductive proximity switch (wired separately through a 4-pole M12x1 connector) to detect whether the main valve core deviates from the center position beyond a preset threshold (set within the valve core overlap area). This switch provides two PNP output signals, which can be used for safety monitoring functions of higher-level control systems, such as serving as a shut-off element for one of the channels in safety related dual channel applications that meet the EN 13849-1 standard (up to category 4, PL e).