4637117 Genuine Hitachi rotary gearbox for Hitachi excavator ZX870-3

Part number 4637117 is a high-pressure axial piston swing motor (integrated with reduction gearbox) specially designed for Hitachi heavy-duty excavator ZX870-3 series, compatible with ZX870-3/ZX870H-3/ZX870LC-3/ZX870LCH-3, as well as ZX850-3/ZX850-3F/EX1200-6 and other models. It is suitable for the hydraulic system of Isuzu 6WG1X engine, with a transmission ratio of 235:1, input torque of 2400N·m, output torque of 564000N·m, rated working pressure of 36MPa, maximum pressure resistance of 42MPa, rated speed of 16rpm, and weight of 208kg. Adopting axial piston structure + three-stage planetary reduction + wet multi-disc brake, it ensures stable and precise swing under heavy-duty working conditions, protects the swing bearing and structural parts, and avoids impact damage.

The plungers and cylinder block are made of 42CrMo chrome-molybdenum alloy steel with nitriding treatment, hardness HRC61-64, excellent wear resistance and anti-seizure performance. The valve plate is made of high-strength alloy, mirror-polished, with a leakage rate ≤0.5L/min. The planetary gears are made of 20CrNiMoA with carburizing and quenching treatment, tooth surface hardness HRC60-64, strong bearing capacity. The friction plates of the wet brake are made of copper-based powder metallurgy + carbon fiber composite material, with stable friction coefficient, fast braking response and thermal decay rate ≤3%. The seals are made of fluororubber (FKM), suitable for oil temperature environment from -40°C to 120°C, with excellent anti-aging and high-pressure leakage prevention performance. The housing is made of ductile iron QT800-2, after double aging treatment, the deformation is ≤0.05mm, with outstanding impact resistance and vibration resistance. It is recommended to maintain every 2000 hours under normal working conditions, replace the gear oil and seals; shorten to 1500 hours under harsh working conditions such as mines and large-scale crushing. There are no failures such as leakage, brake failure and gear wear within the maintenance cycle, which effectively extends the service life of the swing mechanism and reduces the failure rate.

Adopting an overall integrated design, special hoisting equipment (load-bearing ≥210kg) is required for disassembly and installation. Before disassembly, the pressure of the hydraulic system should be released (≤0.1MPa). During installation, the flange bolts should be tightened symmetrically and evenly according to 180-200N·m. After installation, GL-5 85W-140 heavy-duty gear oil should be added to the oil level line, and start the test run to check the swing action, braking performance and leakage. This swing motor can reduce the maintenance cost of the swing mechanism of heavy-duty excavators by more than 45%, reduce the downtime caused by brake failure and leakage, improve the operating efficiency by about 18% under working conditions such as mine stripping and ore loading, and ensure the safe, reliable and precise swing action.