I. Product Categories and Core Models
Eaton and Linde (now integrated with Bosch Rexroth, though some technologies remain collaborative with Eaton) hydraulic charge pumps are primarily classified into two categories, suitable for closed-loop hydraulic systems (e.g., construction machinery, industrial vehicles):
1. Gear-Type Charge Pumps
• Representative Models:
• Eaton 7620 Series(20 cm³/rev displacement)
• Linde HPR-02 Series(technologically aligned with Eaton)
• Technical Features:
• External gear design, simple structure, and high contamination resistance.
• Integrated check valves to prevent backflow.
• Aluminum housing, lightweight (~3.2 kg), ideal for compact installations.
• Speed range: 600–3000 rpm, compatible with engine speeds.
• Typical Applications:
• Closed-loop replenishment for excavator swing motors and travel motors.
• Pressure supply for crane luffing cylinders and slewing mechanisms.
2. Vane-Type Charge Pumps
• Representative Models:
• Eaton 6423 Series(medium-pressure vane pumps)
• Linde BVP Series(variable vane pumps, some used for charge functions)
• Technical Features:
• Low noise (5–10 dB quieter than gear pumps) and minimal flow pulsation.
• Adjustable displacement (select models) for varying operational demands.
• Higher oil cleanliness requirements (NAS 6 grade).
• Typical Applications:
• Closed-loop replenishment in precision industrial vehicles (e.g., forklifts).
• Hydraulic systems for agricultural machinery (e.g., combine harvesters).
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II. Key Technical Parameter Comparison
【表格】
Parameter Eaton 7620 (Gear Pump) Linde HPR-02 (Gear Pump) Eaton 6423 (Vane Pump)
Displacement 20 cm³/rev 20 cm³/rev 10–50 cm³/rev (adjustable)
Rated Pressure 28 bar (400 psi) 30 bar (435 psi) 21 bar (300 psi)
Peak Pressure 35 bar (500 psi) 40 bar (580 psi) 28 bar (400 psi)
Speed Range 600–3000 rpm 800–3200 rpm 1000–2500 rpm
Weight 3.2 kg 3.5 kg 4.8 kg
Operating Temp. -20°C to +120°C -15°C to +110°C -10°C to +80°C
Recommended Oil ISO VG32/46 ISO VG46 ISO VG32
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III. Core Functional Analysis
1. Closed-Loop Replenishment
• Role: Compensates for oil loss due to friction and leakage in closed-loop systems, preventing cavitation.
• Implementation:
• Supplies oil to the low-pressure side via flush valves to maintain flow balance.
• The Eaton 7620’s 20 cm³/rev displacement meets replenishment needs for mid-sized excavators (20–30 tons).
2. Control Pressure Source
• Role: Provides stable low-pressure oil (typically 20–25 bar) for swashplate control mechanisms in variable pumps/motors.
• Technical Advantage:
• The Linde HPR-02’s check valve design ensures stable control pressure, reducing actuator vibration caused by fluctuations.
3. System Cooling and Lubrication
• Role: Reduces oil temperature through forced circulation, extending main pump lifespan.
• Data Support:
• The Eaton 6423’s flow pulsation coefficient ≤3% reduces system heat generation by >15%.
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IV. Typical Application Scenarios
1. Construction Machinery
• Excavators:
• Charge pumps replenish oil in swing motor closed loops, preventing cavitation during high-speed rotation.
• Example: Eaton 7620 paired with Caterpillar 320D swing systems.
• Cranes:
• The Linde HPR-02 supplies pressure for luffing cylinder control valves, ensuring smooth load lifting.
2. Industrial Vehicles
• Forklifts:
• Vane pumps (e.g., Eaton 6423) provide precise control pressure for tilt and lift cylinders, enhancing micro-movement performance.
• Wheel Loaders:
• Gear pumps compensate for leakage in working device hydraulic systems, reducing impact.
3. Agricultural Machinery
• Combine Harvesters:
• Charge pumps maintain oil balance in header lift and threshing drum drive systems.
• Tractors:
• The Linde BVP vane pump replenishes oil for rear axle closed-loop transmissions.
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V. Selection and Alternative Solutions
1. Selection Criteria
• Flow Matching: Calculate replenishment volume based on main pump displacement and speed (Formula: Q = n × V, where n = speed, V = displacement).
• Pressure Requirements: Control pressure should exceed system minimum operating pressure by 5–10 bar.
• Environmental Adaptability: Use low-pour-point oil (e.g., ISO VG22) in cold regions.
2. Recommended Alternative Models
• Higher Flow Demand:
• Eaton 7630 (30 cm³/rev) or Linde HPR-03 (32 cm³/rev).
• Lower Noise Demand:
• Eaton 6430 vane pump (noise ≤75 dB).
• Compact Space Demand:
• Linde HMR micro gear pumps (5–15 cm³/rev).
