1. Definition & Function
TheHydraulic Pumpis the core power source of the hydraulic system in Hitachi 330/350 series excavators (e.g., EX330, EX350), responsible for converting mechanical energy from the engine into hydraulic energy to provide high-pressure oil for the machine's movements, including travel, swing, boom, arm, and bucket operations.
• Key Roles:
• Supplies stable hydraulic flow and pressure to drive hydraulic cylinders and motors.
• Works in conjunction with theMain Control Valveto distribute oil to various actuators, enabling compound actions (e.g., simultaneous boom lifting and swing).
• Type:
• Variable Displacement Axial Piston Pump: Adjusts displacement via swashplate angle changes to meet varying load demands.
• Dual-Pump Configuration: Some models use a main pump + auxiliary pump design to enhance system efficiency.
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2. Structural Components
The Hitachi 330/350 hydraulic pump primarily consists of the following parts:
1. Pump Housing
• Material: High-strength cast iron or aluminum alloy to withstand high pressure (typically 30–35 MPa) and vibration.
• Function: Houses core components such as pistons and the swashplate, ensuring sealing integrity.
2. Piston Assembly
• Axial Pistons: Adjust displacement through swashplate angle variations (usually 7–9 pistons).
• Slippers: Reduce friction between pistons and the swashplate, extending service life.
3. Swashplate
• Angle Adjustment: Driven by the displacement control mechanism to vary pump output (0–maximum displacement).
• Material: High-hardness alloy steel with heat treatment for wear resistance.
4. Valve Plate
• Function: Distributes high-pressure and low-pressure oil to ensure sealing in piston chambers, preventing internal leakage.
5. Displacement Control Mechanism
• Types:
• Pressure Compensation Control: Automatically adjusts displacement based on load pressure.
• Load-Sensing Control (LS Control): Precisely supplies oil according to operational demands, reducing energy consumption.
• Components: Control valves, springs, servo pistons, etc.
6. Bearings & Seals
• Roller Bearings: Support rotating parts to minimize friction and heat generation.
• Seals: Prevent hydraulic oil leakage (e.g., O-rings, V-seals).
7. Charge Pump
• Auxiliary Pump: Provides low-pressure oil (≈1.5–3 MPa) for closed-loop circuits to compensate for leakage and cool the system.
• Flow Rate: Typically 5%–10% of the main pump’s total flow.
8. Cooling System
• Radiator: Reduces oil temperature via fans or hydraulic oil coolers to prevent overheating.
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3. Technical Specifications (Example: EX330-6/EX350-6)
【表格】
Parameter Range/Description
Applicable Models Hitachi EX330-6, EX350-6 Excavators
System Pressure Max. 34.3 MPa (350 kgf/cm²)
Main Pump Displacement Variable: 0–145 cc/rev (EX330)0–160 cc/rev (EX350)
Speed Range Stable output at engine speeds of 1,800–2,200 rpm
Total Flow Rate Max. ≈300–350 L/min (dual-pump combined)
Charge Pump Flow ≈25–35 L/min
Weight ≈150–180 kg (including charge pump)
Lubrication Self-lubricated by hydraulic oil (requires periodic replacement)
Recommended Oil ISO VG46 or Hitachi-approved anti-wear hydraulic fluid
