AP2D28 Hydraulic Piston Pump
1. Product Overview
AP2D28 is a tandem variable displacement swashplate axial piston pump, originally developed by Uchida (Rexroth). It serves as the main hydraulic power unit widely equipped on 5–6 ton compact crawler excavators.
This integrated pump assembly combines dual variable piston pumps and built-in fixed displacement pilot gear pump. Multiple control versions are available: mechanical negative flow control and solenoid electronic proportional control. High-quality aftermarket interchange pumps are supplied as economical replacement solutions for equipment maintenance and overhaul.
Model Code Explanation
- AP2D: Uchida open-circuit tandem axial piston pump series
- 28: Theoretical displacement of each piston pump: 28 cc/rev
- Suffix letters: Define rotation direction, spline shaft specification, control valve type and oil port layout
2. Main Technical Parameters
Item Specification
Pump Type Tandem variable displacement swashplate axial piston pump (integrated pilot gear pump)
Single pump displacement 28 cc/rev
Rated Working Pressure 25.5 MPa
Maximum Peak Pressure 30 MPa
Operating Speed Range 600 ~ 2400 rpm
Volumetric Efficiency ≥91% under rated working condition
Control Mode Negative flow control / Solenoid proportional control (optional)
Shaft Configuration Multiple spline options to match various excavator brands
Applicable Fluid ISO VG46, VG68 anti-wear hydraulic oil
Operating Temperature -20℃ ~ +85℃
Standard Seals NBR; FKM high-temperature sealing kit optional
3. Working Principle
The engine drives the main shaft and cylinder block assembly to rotate. The reciprocating movement of pistons draws hydraulic oil and outputs high-pressure oil to each hydraulic circuit.
The regulator automatically adjusts the tilt angle of the swashplate according to system load, changing pump displacement to regulate output flow.
The integrated pilot gear pump provides stable control pressure oil for main pump regulators, travel motor brakes and operating pilot circuits.
4. Core Advantages
1. Compact tandem integrated structure, main pump and pilot pump combined into one assembly, perfectly adapting to the limited installation space of mini excavators.
2. Optimized load-sensing control logic, stable flow output and smooth compound movements of boom, arm and bucket.
3. Precisely manufactured internal friction pairs, low internal leakage and reliable continuous heavy-duty operation.
4. Complete structural variants to match Doosan, Hyundai, Kubota, Yuchai, Sunward and other mainstream compact excavators.
5. Easy disassembly and field maintenance; abundant spare parts available globally.
6. Cost-effective aftermarket alternative with shorter delivery lead time compared with original OEM pumps.
5. Application Range
Main hydraulic main pump for 5–6 ton compact crawler excavators.
Typical compatible machine models:
Doosan DH55, DH60, DX55, DX60;
Hyundai R55-7, R60-7;
Kubota KX161;
Yuchai YC55, YC60;
Sunward SWE55, SWE60;
Other domestic 5/6-ton mini excavators adopting AP2D28 hydraulic system.
