Hydraulic Orbit Motor / Gerotor Motor
They refer to the same type of low-speed high-torque hydraulic motor, adopting gerotor gear set as the core component. It consists of an inner rotor and an outer stator with one more tooth. Eccentric meshing generates volume variation, converting hydraulic energy into mechanical energy.
1. Main Structure
- Housing: Supports internal components and integrates oil ports
- Gerotor Assembly
- Stator: Fixed outer ring with internal teeth
- Rotor: Eccentric gear with fewer external teeth
- Valve Plate: Realizes flow distribution to ensure continuous rotation
- Output Shaft: Transmits torque via spline or key connection
- Auxiliary parts: Bearings, seals and end covers
2. Working Principle
1. High-pressure oil flows into expanding chambers
2. Hydraulic thrust drives the rotor to revolve and rotate eccentrically
3. Alternating chamber volume change delivers continuous torque output
4. Low-pressure oil discharges back to the oil tank
One-tooth difference and eccentric structure form sealed chambers, achieving built-in deceleration and low-speed high-torque performance.
3. Key Technical Parameters
- Displacement: 10~1000 mL/r
- Rated Pressure: 16~25 MPa, Peak Pressure: 31.5 MPa
- Rotational Speed: 10~1000 rpm
- Output Torque: 50~5000 Nm
- Volumetric Efficiency: ≥90%, Overall Efficiency: ≥80%
4. Performance Characteristics
Advantages
- Compact size with high torque and power density
- Simple structure, stable operation and low noise
- Strong impact resistance and oil contamination tolerance
- Bidirectional rotation available
- Economical cost and easy maintenance
Disadvantages
- Reduced efficiency under high rotating speed
- Slightly increased internal leakage under high pressure
5. Typical Applications
Construction machinery: Excavator slewing and travelling system, loader, forklift
Agricultural machinery: Tractor, harvester, fertilizer spreader
Industrial equipment: Conveyor, mixer, winch, robotic joint
Special vehicles: Sweeper, aerial work vehicle
6. Common Types
1. Standard Gerotor Motor: Simple structure and cost-effective
2. Geroller Motor: Equipped with rollers, lower friction, higher efficiency and longer service life, applicable for high pressure and speed
3. End-face flow distribution & radial flow distribution styles
7. Selection Guidelines
1. Select proper displacement based on actual torque and speed with safety factor of 1.2~1.5
2. Rated pressure shall be higher than system working pressure
3. Confirm installation form, shaft type and oil port position
4. Recommended hydraulic oil viscosity: 32~46 mm²/s, filtration precision ≤10 μm
Summary
Hydraulic orbit motor is also named gerotor motor. Featured with low speed and high torque, it applies eccentric meshing gerotor mechanism. It boasts compact structure, powerful torque and favorable cost performance, widely applied in construction, agricultural and industrial facilities.
