1) Description of Internal Spur Gear

From a transmission perspective, internal spur gears constitute highly efficient transmission components capable of achieving simultaneous engagement of multiple teeth and possessing robust load-bearing capacity. By enclosing the meshing region within the gear's interior, they optimise the force transmission pathway.

2) Working Principle

During meshing, the contact line of internal gear pairs is longer, whilst the number of tooth pairs engaged is typically greater than in external meshing. When force is transmitted from the pinion to the ring gear, the direction of the applied force is more conducive to reducing the radial load on the bearings, thereby minimising friction losses.

3) Characteristics of Internal Spur Gear

• Multiple-tooth meshing: Due to their curvature relationship, the overlap ratio is typically high, resulting in smoother transmission.
• Enclosed power flow: The transmission force circulates internally, providing superior structural rigidity.
• High machining precision requirements: The machining and inspection of internal gears are more challenging than external gears, necessitating broaching, hobbing, or specialised machining equipment.

4) Advantages of Internal Spur Gear

• High transmission efficiency: Thanks to low slip rates and multiple-tooth meshing, efficiency is typically superior to that of externally meshed gears of equivalent specifications.
• High load capacity: Extended contact lines and load distribution across multiple teeth enable transmission of greater torque.
• Smooth operation and low noise: High overlap reduces impact and vibration.
• Reduced radial forces: Improved bearing load conditions extend bearing service life.

5) Application

Suitable for applications demanding high transmission efficiency, smooth operation and load-bearing capacity:

• High-speed transmission systems: Such as speed-increasing units for gas turbines and centrifugal compressors.
• High-torque power-split mechanisms: Serving as core transmission components within power-split systems for heavy machinery.
• High-precision servo systems: Requiring precision gearboxes with low backlash and high rigidity.