Bosch Rexroth A4VSO variable displacement hydraulic pump

The A4VSO is a variable displacement axial piston pump built on the swashplate principle and designed for open-circuit hydrostatic drives. In plain terms: it draws oil from a reservoir, pressurizes it, and delivers a flow you can adjust by changing the angle of the swashplate. Less angle means less flow. Zero angle means essentially zero flow, with the pump still spinning.

Key Technical Characteristics

Typical headline features, to be verified against the data sheet for your size and series:

• Displacement range: roughly 40 to 1,000 cm³/rev across the size range (for example 40, 71, 125, 180, 250, 355, 500, 750, 1000)
• Pressure: nominal pressure around 350 bar, with higher peak pressure allowed for short periods depending on size and series
• Mounting: standard flange and shaft options, plus a through-drive option so you can stack an auxiliary gear pump or a second axial piston pump on the same shaft
• Fluids: mineral oil (HLP per DIN 51524) is the baseline; certain biodegradable or fire-resistant fluids are possible with derating and prior approval
• Operation: designed for low noise and long service life with proper filtration and inlet conditions

Control Options: Choosing How the Pump Behaves

The control is arguably more important than the pump size. It determines how the A4VSO responds to your system. Common control families include:

Pressure control (DR / DRG)

The pump delivers whatever flow is needed up to a set pressure, then destrokes to hold that pressure with minimal flow. Ideal for presses and clamping circuits where you want pressure maintained without wasting power. DRG adds remote pressure setting.

Pressure and flow control (DFR / DFR1)

Adds a load-sensing line so the pump delivers only the flow a downstream valve demands, while a pressure cutoff still protects the system. This is the go-to choice for mobile-style load sensing in stationary machines.

Hydraulic and electro-hydraulic displacement control (HD / EO)

Here you command displacement directly, either with a hydraulic pilot signal or an electrical proportional signal with feedback. This gives precise flow control in test benches and closed-loop motion applications.

Power control

Power-limiting variants cap the product of pressure and flow so the prime mover (electric motor or diesel engine) is never overloaded. Useful when you are working near the limit of your installed motor.

Real-World Applications and Examples

Example 1: Plastic injection molding machine

An injection molder cycles between high-flow injection, high-pressure holding, and idle cooling time. A pressure-controlled A4VSO delivers peak flow during injection, then destrokes during cooling. Compared with a fixed pump and relief valve, plant engineers commonly see a meaningful drop in motor energy use and oil temperature.

Example 2: Hydraulic press

A large forming press needs heavy flow to approach the workpiece, then high pressure at low speed during pressing. A DFR-controlled A4VSO supplies the rapid approach flow and then reduces to a trickle while the press holds tonnage.

Example 3: Test stand and industrial automation

In component test rigs, an electro-hydraulic control lets the pump follow a programmed flow profile, while the controller closes the loop on pressure or speed. This is where the A4VSO's repeatability and smooth control really show.

Other typical uses

Machine tools, rolling mills and metal forming, marine and offshore deck hydraulics, waste and recycling machinery, and large power packs for industrial plants.

Troubleshooting Common Problems

Noisy pump or whining sound

Usually cavitation or aeration. Check the suction strainer, inlet hose collapse, oil level, and loose fittings that suck in air.

Low pressure or weak flow

Possible causes include internal wear, a stuck control spool, a mis-set pressure compensator, or a worn rotating group. Check the case-drain flow: a high leakage reading is a classic wear indicator.

Overheating oil

Often a system issue rather than a pump issue: a relief valve opening, an undersized cooler, or a pump running at full flow when it should be destroked.

Erratic control response

Check pilot or load-sense lines, contamination in the control valve, and the electrical signal if you use an EO control.

For more information on the A4VSO hydraulic pump, please visit https://www.baolilaihydraulic.com/product/.

Specifications

Selection Table

Q1: Can the A4VSO be repaired?

A1: Yes. Many service centers can overhaul the rotating group, bearings, and controls. Rebuilds should be tested on a test stand and ideally use original parts.

Q2: How do I choose the right control?

A2: Use DR for simple pressure holding, DFR for load-sensing efficiency, electro-hydraulic control for programmable flow, and power control when your prime mover is the limit.

Q3: What is the price and delivery time of the A4VSO hydraulic pump?

A3: We will provide the price and delivery time based on the specific model you provide.

Q4: How to purchase an A4VSO hydraulic pump?

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