Rexroth AA4VSO71 hydraulic axial piston pump

The AA4VSO71 is a variable-displacement, swashplate-design axial piston pump built by Bosch Rexroth for open-circuit hydraulic systems.

How the AA4VSO71 Works

At its core, the pump uses a rotating cylinder block containing multiple pistons arranged parallel to the drive shaft. As the shaft turns, the pistons ride against a swashplate set at an angle. That angle forces each piston to reciprocate in and out of its bore — drawing in fluid on the intake stroke and expelling it under pressure on the discharge stroke.

The Role of the Swashplate

This is the defining feature of the design. Unlike a fixed-displacement pump, the AA4VSO71's swashplate angle can be adjusted — either manually, hydraulically, or electronically, depending on the control option ordered. Tilt the plate further, and the piston stroke length increases, which increases flow output per revolution. Bring the plate toward neutral and flow drops toward zero, even while the shaft keeps spinning at full speed.

This matters enormously in real systems because it means:

The prime mover (motor or engine) can run at a constant, efficient speed

Flow output tracks actual system demand instead of running wide-open all the time

Energy that would otherwise be dumped across a relief valve simply isn't generated in the first place

Control Options

The AA4VSO71 is available with several control types, and choosing the right one is often the difference between a pump that "works" and one that's actually matched to the application:

DR (pressure control) — holds a set pressure, reducing flow automatically as the system approaches that pressure

DFR (pressure/flow control) — combines pressure limiting with flow control for more complex load profiles

EO / HS (electric proportional control) — allows flow to be commanded directly from a PLC or motion controller

LR2/LR3 (load-sensing) — matches pump output to actual downstream demand, minimizing throttling losses

Common Applications

The AA4VSO71 shows up disproportionately often in a specific band of applications — not the smallest mobile equipment, and not the largest stationary presses, but the mid-tonnage industrial equipment in between:

Plastic Injection Molding Machines

Clamping and injection circuits demand high pressure with variable flow depending on the phase of the molding cycle — fast fill, then pressure hold. Pressure-compensated control on the AA4VSO71 lets the pump deliver high flow during fill and taper down automatically during pack-and-hold, cutting heat generation and energy use.

Metal Forming and Stamping Presses

Press cycles are inherently variable-demand: rapid approach, high-force forming, then rapid return. A pump that can flex its output within a single cycle avoids the energy waste of a fixed-displacement pump running at full output through the entire stroke.

Machine Tools

CNC machining centers and grinders often use this size for clamping, tool-change, and coolant-adjacent hydraulic functions where consistent pressure with modest flow variation is needed.

Mobile and Heavy Equipment

Cranes, drilling rigs, and other mobile platforms use the AA4VSO71, where engine-driven hydraulics need to deliver variable flow without constantly changing engine RPM.

Installation and Maintenance Considerations

A few practical points that come up repeatedly in the field:

Case drain matters. Like all axial piston pumps, the AA4VSO71 needs an adequate case drain line sized to keep internal case pressure within limits — undersized or restricted case drain lines are a leading cause of shaft seal failure.

Inlet conditions are non-negotiable. Axial piston pumps are far less tolerant of suction-side restriction or aeration than gear pumps. Confirm inlet line sizing and reservoir design before blaming the pump for noise or cavitation.

Fluid cleanliness drives service life. The tight piston-to-bore and shoe-to-swashplate clearances that make these pumps efficient are the same clearances that wear quickly under contaminated fluid. ISO 4406 cleanliness codes should be verified, not assumed.

Swashplate control linkage inspection. On mechanically or hydraulically controlled units, periodically check the control linkage for wear or drift, since this directly affects how accurately the pump tracks commanded pressure or flow.

For more information on the AA4VSO71 hydraulic pump, please visit https://www.baolilaihydraulic.com/product/.

Specifications

Selection Table

Q1: What control options are available?

A1: Common options include DR (pressure control), DFR (pressure and flow control), load-sensing variants (LR2/LR3), and electric proportional controls (EO/HS/MA) for PLC-driven applications.

Q2: How do I identify the exact model I have?

A2: Check the full nameplate part number (e.g., `AA4VSO71DR/10R-PKD63N00`). Each segment after "71" encodes control type, series, rotation direction, shaft type, and seal material — Rexroth's official type-code chart is needed to decode it precisely.

Q3: What is the price and delivery time of the AA4VSO71 hydraulic pump?

A3: The specific price and delivery time will be provided based on the specific model you provide.

Q4: How to purchase an AA4VSO71 hydraulic pump?

A4: You can visit https://www.baolilaihydraulic.com/contact/ to contact us and purchase our products through various methods.