Product Details
                                        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.
 
Technical Specifications
| Parameter | Specification | 
|---|
| Custom Made | Available | 
| Gear Profile Type | Cylindrical Gear | 
| Manufacturing Process | Gear Milling & Gear Teeth Hobbing | 
| Teeth Grinding | Included | 
| Module (M) | 0.5-25 | 
| Number of Teeth (Z) | 58 | 
| Pressure Angle (α) | 20° | 
| Lead Angle | 0° | 
| Accuracy Grade | ISO 8-9 Grade | 
| Heat Treatment | Nitriding | 
| Surface Hardness | 650HV | 
Steel Code Grades Comparison
| CHINA/GB | ISO | ГΟСТ | ASTM | JIS | DIN | 
|---|
| 45 | C45E4 | 45 | 1045 | S45C | CK45 | 
| 40Cr | 41Cr4 | 40X | 5140 | SCr440 | 41Cr4 | 
| 20CrMo | 18CrMo4 | 20ХМ | 4118 | SCM22 | 25CrMo4 | 
| 42CrMo | 42CrMo4 | 38XM | 4140 | SCM440 | 42CrMo4 | 
| 20CrMnTi |  | 18XГT |  | SMK22 |  | 
| 20Cr2Ni4 |  | 20X2H4A |  |  |  | 
| 20CrNiMo | 20CrNiMo2 | 20XHM | 8720 | SNCM220 | 21NiCrMo2 | 
| 40CrNiMoA |  | 40XH2MA/40XHMA | 4340 | SNCM439 | 40NiCrMo6/36NiCrMo4 | 
| 20CrNi2Mo | 20NiCrMo7 | 20XH2MA | 4320 | SNCM420 |  |