Rexroth Hydraulic Piston Pump A4VSO71 Series 280 Bar Pressure Rating

The A4VSO series is a swashplate-type axial piston pump designed for open-circuit systems. Its flow output is proportional to the input drive speed and its displacement volume. The displacement is infinitely variable by adjusting the angle of the swashplate. It's known for its excellent suction characteristics, low noise, long service life, and high power-to-weight ratio. Multiple control options are available to meet various system requirements.

The A4VSO series offers a wide range of variable control methods. The most commonly used include: • DR/DRG: Pressure Control (Constant Pressure) • LR: Constant Power Control (Hyperbolic) • EO/EO2: Electroproportional Control Other available controls include FR (Flow Control), MA (Manual Control), EM (Electric Motor Control), HW/HM/HS/HD (Various Hydraulic Controls), and DS (Secondary Control for speed sensing).

The DR control maintains a constant system pressure by changing the swashplate angle. When the system pressure reaches the spring-set value on the DR valve, the control mechanism acts to reduce the pump's displacement, delivering only the flow required to maintain the set pressure. This functionality is sometimes referred to as "Pressure Cut-Off" in some pump literature. It's important to note that a system safety valve is still essential because the DR control's response is relatively slow compared to sudden pressure shocks; the safety valve handles transient pressure spikes.

Both DRG and DP are forms of constant pressure control, but they are designed for different applications: • DRG (Remote Pressure Control): Allows the pressure setpoint for the pump to be adjusted remotely via an external pressure control valve. • DP (Multi-Pump Parallel Pressure Control): Specifically designed for systems where multiple pumps work in parallel. It contains an additional element (a variable orifice, valve 5) that mechanically links to the swangle. This design automatically compensates for differences between pumps, ensuring they share the load equally and operate at the same swashplate angle when working together at the set pressure. The DP control has a larger control deviation (~6.5 bar) compared to DRG (~3 bar).

When multiple pumps with standard DR controls are set to the same pressure and run in parallel, slight inherent differences in their response characteristics and pressure settings can cause them to not reduce displacement (cut off) at exactly the same time and rate. This lack of synchronization can lead to interactions between the pumps, resulting in pressure fluctuations and potentially causing severe pipeline vibration.