Hitachi Construction Machinery has introduced an upgraded "Triple-Pump" hydraulic system for its Zaxis-7 series medium excavators. In a standard hydraulic excavator, the machine typically uses a "Dual-Pump" system. One pump drives the left travel and boom, the other drives the right travel and arm. The pilot system (controlling the joystick) and the swing motor are usually powered by a gear pump connected to the main pumps, drawing power from the same engine.
The problem arises during "Combined Operations"-for example, when the operator is swinging to the left while simultaneously lifting the boom and tracking backwards. The engine load spikes because all functions draw from the same power source, causing the engine to "lug" (drop RPM) and the operation to slow down.
The new Hitachi "Triple-Pump" system adds a dedicated "Third Pump" specifically for the swing circuit and pilot system. This third pump is directly driven by the engine but has its own flow regulator. When the operator swings, the load is handled by the third pump, leaving the two main pumps to focus entirely on the boom and arm. The engineering benefit is a smoother power curve. The system also features "Swing Priority Logic." When the operator swings, the system detects the load on the third pump and slightly reduces the flow to the main pumps to keep the engine RPM stable. This ensures the machine never stalls, even during the most complex trenching cycles. Field tests show a 12% reduction in fuel consumption during high-intensity slope finishing work because the engine operates at a more constant, efficient RPM range.
