The Heart of the Drive: Why the A4VG is More Than Just a Pump

The Heart of the Drive: Why the A4VG is More Than Just a Pump

When you look at a powerful piece of mobile machinery—a combine harvester working a field, a wheel loader moving earth, or a crane lifting a heavy load—you’re seeing hydrostatic power in action. At the very heart of that powerful, precise movement is a specialized component: the closed-circuit pump. And for decades, the industry standard for this demanding job has been the Bosch Rexroth A4VG.

The A4VG Series 40 is the evolution of this legendary platform, engineered to be a complete, integrated power source for high-pressure hydrostatic drives. It isn't just a pump; it's the command center of your machine's motion.

What Makes a Closed-Circuit Pump Different?

Unlike an open-circuit pump that delivers flow to a system and returns it to a tank, a closed-circuit pump like the A4VG circulates fluid directly to and from a hydraulic motor. This creates a highly responsive hydrostatic transmission. The key is its ability to smoothly reverse the direction of flow. By moving its internal swashplate through the neutral (zero flow) position, the A4VG can seamlessly change the direction of the output motor, allowing a machine to switch from forward to reverse with incredible precision.

The Power of Integration

The A4VG Series 40 is a masterpiece of hydraulic integration. To run a closed circuit properly, you need more than just the main pump. You need a boost pump to replenish fluid, pressure relief valves for safety, and check valves to manage the loop. Traditionally, these were all separate components.

The A4VG integrates these critical functions into one compact and robust housing:

• Integrated Boost Pump: Provides a constant supply of cool, filtered oil to the main circuit.
• Integrated High-Pressure Relief Valves: Protect the entire transmission from pressure spikes and overloads.
• Integrated Boost Pressure Relief Valve: Maintains the correct pressure in the low-pressure side of the circuit.

This high level of integration means a simpler machine design, fewer potential leak points, reduced assembly time, and lower overall system cost.

Control It Your Way

Every machine is different, and the A4VG is designed to adapt. Its legendary flexibility comes from a huge range of available control options:

• Proportional Electric (EP): For modern, electronically controlled machines that require precise command over speed and direction.
• Hydraulic Pilot (HP): For systems using hydraulic joysticks or pilot signals for control.
• Direct-Operated Hydraulic (HT): A simple, robust control for direct hydraulic actuation.
• DA Speed-Related Control: An intelligent automotive-style control that adjusts displacement based on engine speed, perfect for travel drives.

The Proven Choice for High-Power Motion