Customized Precision Parts Machining Internal Spur Gear for Power Transmission

1) Description of Internal Spur Gear

Internal spur gears are specialised gearing designed to achieve specific motion conversion and functional integration. They serve not only as transmission components but also, in certain applications, as structural supports or motion trajectory controllers.

2) Working Principle

Beyond conventional rotational motion transmission, internal spur gears can achieve substantial speed reduction ratios within specific mechanisms, such as planetary gear trains with a small number of teeth. Their operating principle relies on the difference in tooth count between the planetary gear and the internal ring gear, enabling a significant reduction ratio through a minute tooth difference.

3) Characteristics of Internal Spur Gear

• Functional integration: Often designed to serve concurrently as a bearing housing, casing, or part of a drum, achieving functional unification.
• Tooth difference design: In harmonic drives and cycloidal drives, the internal gear profile may not be an involute curve but a specialised tooth form.
• Variable mounting methods: Internal gears may be fixed (such as stationary ring gears in planetary mechanisms) or movable.

4) Advantages of Internal Spur Gear

• Capable of achieving exceptionally high transmission ratios: In under-cut gearing, a single stage can achieve reduction ratios exceeding one hundred, resulting in an extremely compact structure.
• High functional integration: Reduces the number of components, simplifying the overall structure.
• Versatile motion configurations: By fixing either the internal or external gear, a wide variety of distinct motion output configurations can be derived.

5) Application

Primarily employed to achieve specialised motion functions and exceptionally high gear ratios:

• Cycloid pinwheel reducer: The internal gear functions as the ‘pinwheel’, meshing with the cycloid wheel to deliver high reduction ratios and exceptional rigidity.
• Harmonic reducers: The meshing of the flexible gear with the rigid gear (internal gear) is central to achieving precision motion.
• Indexing mechanisms for specialised machine tools: Serving as the core transmission and support components for large rotary tables.
• Flow meters: Utilised in specialised metering equipment such as oval gear flow meters.