HITACHI ZX450-3 9199338 K5V200DPH-XMXR-OE02 Excavator Main Pump Assembly

HITACHI ZX450-3 9199338 K5V200DPH-XMXR-OE02 excavator main pump assembly

The axial piston pump with a tilting swashplate is the undisputed workhorse for primary hydraulic circuits in modern excavators. Its core principle involves multiple pistons arranged axially (parallel to the drive shaft) within a rotating cylinder block. Each piston features a slipper pad riding on a non-rotating swashplate angled relative to the drive shaft's axis. As the cylinder block rotates, the pistons reciprocate within their bores: moving outward during the half-rotation where the swashplate distance increases (suction stroke, drawing fluid from the inlet port), and being forced inward during the opposite half-rotation where the distance decreases (discharge stroke, pressurizing fluid to the outlet port). The critical structural element for variable displacement is the adjustable swashplate angle. By changing this angle (typically via a hydraulic servo piston controlled by the operator or machine electronics), the stroke length of the pistons is altered. A larger angle increases piston stroke and thus pump displacement (flow rate), while a zero angle results in zero displacement. Key structural components include the drive shaft, rotating cylinder block with precision piston bores, pistons with slippers, swashplate with tilt mechanism, valve plate (stationary, with kidney-shaped ports for inlet/outlet), and a robust housing. In excavators, this design offers exceptional efficiency across a wide operating range, precise flow control essential for coordinated multi-function operation, and high-pressure capabilities needed for digging forces.