Rexroth A4VG125 axial piston variable hydraulic pump

The A4VG125 is a swashplate-type axial piston pump, a design chosen for its excellent power-to-weight ratio and ability to smoothly vary flow output. As a variable displacement unit, it allows the hydraulic system to draw only the power required for the task, significantly improving fuel efficiency and reducing heat generation compared to fixed-displacement alternatives. Its designation as a "closed circuit" pump means it is ideally suited for hydrostatic transmissions, where fluid circulates directly from the pump to the motor and back, enabling precise speed and direction control of actuators like wheel motors and winch drives.

Critical Design Features for Enhanced Performance

The A4VG125's performance is not merely a result of its size, but rather a product of several key design features that enhance its functionality, safety, and system integration capabilities.

Integrated Boost Pump and Circuit Protection

A defining feature of the A4VG125 series is the integrated boost pump. This component is not an add-on; it is essential for the health of the closed-loop system. The boost pump serves two primary functions: it supplies low-pressure, cool oil to the main circuit to replace leakage and enhance cooling, and it provides essential pilot oil for the pump's control system. The system is further protected by high-pressure relief valves with an integrated boost function, which prevent pressure spikes from damaging components. A standard adjustable pressure cutoff feature provides an additional layer of control, allowing the system to automatically limit pressure, thereby protecting against overload conditions.

Versatile Control and Expansion Capabilities

The A4VG125 is engineered for application-specific control. It supports various control mechanisms, including:

EP Electric Proportional Control: Provides precise, infinitely variable pump displacement proportional to an input current signal, ideal for electronic system integration.

HD Hydraulic Control: Displacement is controlled proportionally to a pilot pressure, offering robust and reliable manual or remote operation.

Another significant feature is the through-drive capability. This design allows for the mounting of additional pumps—up to the same nominal size—directly onto the rear of the A4VG125. This facilitates the construction of compact, efficient multi-pump power units without requiring complex and space-consuming drivetrain components.

Application and Integration Considerations

When selecting an A4VG125, engineers must consider the specific configuration requirements. The pump is available in both SAE (inch) and metric versions to comply with regional standards. The model code itself provides detailed information on control type, direction of rotation, and other specific features, such as the "NSF52F071" designation seen in many specifications, which often denotes specific porting, shaft, or mounting flange configurations.

A notable consideration is the pump's integration into the overall system architecture. The performance and longevity of the A4VG125 are dependent on the cleanliness and quality of the hydraulic fluid. Its high operating pressures necessitate meticulous filtration and system flushing during installation to prevent premature wear.

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Specifications

Selection Table