1. Structure and Working Principle
1.1 Core Components
• Gerotor Gear Set:
Comprises an inner ring gear (stationary) and an outer rotor (rotating). The outer rotor has one fewer tooth than the inner ring, forming a crescent-shaped working chamber.
• Cycloidal Profile: The outer rotor teeth follow a short-amplitude cycloidal curve, while the inner ring uses circular-arc teeth for gapless meshing, minimizing internal leakage.
• Face Porting Plate:
Located at both ends of the motor, it distributes high-pressure and low-pressure oil via axial sealing surfaces to drive the outer rotor.
• Porting Windows: High-pressure oil enters the working chamber through inlets, driving rotation, while low-pressure oil exits via outlets to the tank.
• Output Shaft: Connects to the outer rotor to transmit torque to the load.
1.2 Working Process
1. High-Pressure Oil Inlet: Hydraulic fluid enters the crescent chamber through the face porting plate’s inlet.
2. Volume Change: Rotation of the outer rotor alters chamber volume, creating a pressure differential for continuous rotation.
3. Low-Pressure Oil Discharge: Exhausted fluid returns to the tank via the outlet, completing the cycle.
4. Porting Switching: The face porting plate dynamically alternates high/low-pressure paths for bidirectional rotation control.
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2. Performance Characteristics
2.1 Advantages
• High Torque Density:
Large meshing area enables higher torque per unit volume than piston motors, ideal for heavy-duty applications.
• Low-Speed Stability:
Direct low-speed output (5–500 rpm) with minimal torque ripple, suitable for precision control.
• Compact Design:
Short axial length and high integration save space (e.g., in construction/agricultural machinery).
• Contamination Resistance:
Large gear clearances reduce sensitivity to oil cleanliness, lowering maintenance costs.
• Bidirectional Operation:
Reverses rotation by switching porting paths, eliminating complex valve systems.
2.2 Limitations
• Lower Efficiency:
Higher frictional losses result in volumetric efficiency (~80–85%) below axial piston motors.
• Speed Limitations:
Poor high-speed performance (typically <2000 rpm), optimized for low-speed, high-torque scenarios.
• Noise Levels:
Slightly higher gear meshing noise than piston motors, though negligible at low speeds.
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3. Typical Applications
3.1 Construction Machinery
• Crawler Cranes: Drives slewing mechanisms for low-speed, high-torque rotation.
• Excavators: Powers travel/slewing motors for precise control.
• Concrete Pump Trucks: Rotates the boom under heavy loads.
**3.2 Agricultural Equipment-Combine Harvesters: Operates header lift or conveyor chains in muddy fields.
• Tractors: Serves as rear-axle drive for high traction.
3.3 Industrial Machinery
• Injection Molding Machines: Drives mold clamping for slow, high-pressure operations.
• Die-Casting Machines: Powers clamping units under extreme pressure.
• Marine Steering Gear: Provides low-speed torque for vessel maneuvering.
3.4 Specialty Vehicles
• Fire Trucks: Elevates ladders in emergency rescue scenarios.
• Aerial Work Platforms: Rotates telescopic booms with stability.
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4. Technical Specifications (Example)
【表格】
Parameter Typical Range
Displacement 10–500 cm³/rev
Rated Pressure 16–25 MPa (up to 35 MPa)
Max Speed 500–2000 rpm
Rated Torque 50–5000 Nm (size-dependent)
Volumetric Efficiency 80–85%
Weight 5–50 kg (size-dependent)
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5. Selection and Design Considerations
• Displacement Matching: Select based on load torque requirements (higher displacement = higher torque).
• Pressure Rating: Ensure system pressure does not exceed the motor’s rated limit to prevent seal failure.
• Oil Cleanliness: Use NAS 6-grade or cleaner fluid to extend bearing/gear life.
• Thermal Management: Maintain oil temperature below 80°C to avoid seal degradation.
• Mounting Configuration: Support flange or shaft-extension installations; verify axial/radial load capacity.
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6. Maintenance and Troubleshooting
• Common Failures:
• Leakage (worn face seals)
• Torque loss (gear wear or contaminated oil)
• Abnormal noise (bearing failure or porting plate misalignment)
• Maintenance Tips:
• Replace hydraulic oil and filters every 500 hours.
• Inspect face seals every 2000 hours; replace as needed.
• Avoid prolonged overloading to prevent gear overheating.
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7. Industry Trends
• High-Pressure Designs: Optimized gear materials and porting plates for ratings >35 MPa.
• Integration with Electronics: Closed-loop speed/torque control via embedded sensors.
• Lightweighting: Aluminum housings and composite materials for electric vehicle applications.
• Noise Reduction: Advanced tooth profiling and dynamic porting compensation.
