A4VG Series Axial Piston Variable Hydraulic Pump

Document Version: EN-2026-V1

Applicable Models: A4VG28 / A4VG40 / A4VG56 / A4VG71 / A4VG90 / A4VG125 / A4VG180 / A4VG250

A4VG Hydraulic Pump

Side View of A4VG Pump

Table of Contents

1. General Safety Instructions

2. Product Overview & Structural Features

3. Main Technical Specifications

4. Control Type Introduction

5. Transport & Storage Requirements

6. Installation Guidelines

7. Commissioning & Startup Operation

8. Daily Maintenance & Lubrication

9. Common Fault Diagnosis & Troubleshooting

10. Spare Parts & Warranty Statement

1. General Safety Instructions

1.1 Qualified Personnel OnlyOnly professional hydraulic technicians with training experience can install, commission, disassemble and repair this pump. Unauthorized operation may cause equipment damage or personal injury.1.2 Forbidden Application Scenarios

• Do not use in explosive, corrosive, underwater or aerospace equipment without ATEX certification.

• Continuous case-to-ambient pressure difference over 2 bar is prohibited; transient peak pressure ≤10 bar.

• Do not run the pump without qualified hydraulic oil and complete filtration system.1.3 Operation Safety Rules

• Cut off power and release all system pressure before disassembly or maintenance.

• Tampering with pressure adjustment caps will void the product warranty.

• Strictly follow the oil temperature, pressure and rotating speed limits in this manual.1.4 Warning Symbols Definition⚠️ Danger: Risk of severe personal injury⚠️ Warning: Risk of equipment damageℹ️ Note: Key operation reminder

2. Product Overview & Structural Features

2.1 Product Definition

A4VG series is swashplate-type variable displacement axial piston pump, specially designed for closed-circuit hydrostatic drive systems, widely matched with construction machinery: excavators, road rollers, loaders, pavers, agricultural harvesters.

2.2 Core Built-in Components

• Main pump cylinder block, piston slipper assembly, variable swashplate

• Integrated charge pump (supplies charge oil & control oil)

• Dual high-pressure relief + anti-cavitation check valve combination (port A/B)

• Standard built-in pressure cut-off valve for overload protection

• Modular control valve group (multiple control modes optional)

• Through-drive interface for tandem pump combination installation

2.3 Working Principle

1. Flow output is proportional to rotating speed and pump displacement; infinitely adjustable flow.

2. Increase swashplate angle → larger displacement & higher flow; zero swash angle → zero output flow.

3. Swing swashplate across neutral position to realize smooth reversal of oil flow and machine traveling direction.

4. Charge pump continuously replenishes low-pressure side oil to prevent cavitation; charge relief valve limits maximum charge pressure.

3. Main Technical Specifications

3.1 Pressure Parameters

表格

3.2 Rotation & Pressure Change Limit

• Max allowable pressure change rate: 9000 bar/s

• Rotation direction: Clockwise / Counterclockwise (marked on nameplate)

• Allowable speed range: 500–3000 rpm (varies by model displacement)

3.3 Hydraulic Fluid Requirements

• Recommended oil: Anti-wear hydraulic oil ISO VG32 / VG46 mineral oil

• Oil viscosity operating range: 16–40 mm²/s

• Continuous operating oil temperature: -20℃ ~ +90℃

• Short-time cold/hot limit: -40℃ / +110℃ (duration <3min)

• Required oil cleanliness: ISO 4406 Class 18/15, filter accuracy ≤10μm

3.4 Port Definition Standard

• A / B: High-pressure working ports (closed circuit main line)

• S: Charge pump suction inlet

• X1 / X2: Control pressure pilot ports

• T1 / T2: Pump case drain ports

• R: Air bleeder port

4. Control Type Introduction

Multiple modular control options for different working conditions:

1. NV: No control device (fixed displacement simple version)

2. DG: Direct hydraulic displacement control

3. HW: Mechanical servo hydraulic control

4. HD: Pilot pressure proportional hydraulic control

5. DA: Speed-sensing hydraulic control (match engine speed automatically)

6. EZ: Two-position electric on-off control with solenoid

7. EP: Proportional electric control (0–10V / 4–20mA signal, precise flow regulation)