Rexroth A4VSO125 Variable Piston Pump 280 Bar Horizontal Diesel

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.