Inner Worm Gear Differential for Compact Two-DOF Output
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Solution Overview
Problem
Existing differential mechanisms with two degrees of freedom are bulky and prone to differential errors due to the need for multiple transmission elements and a central worm gear configuration.
Innovation Solution
A compact differential mechanism is designed with an inner worm gear having spiral teeth on its cylindrical inner side and a worm wheel that meshes with the inner worm gear, allowing for two rotation outputs while minimizing the number of transmission elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a central worm gear configuration is used, then the differential mechanism can provide two degrees of freedom, but the outer diameter becomes large and the structure becomes bulky
Solution Approach 1:
The patent applies nesting by placing the worm wheel inside the worm gear, where the worm wheel revolves around the worm gear's axis. This nested configuration allows both components to occupy overlapping spatial volumes, significantly reducing the overall outer diameter compared to conventional side-by-side arrangements while maintaining the two degrees of freedom functionality.
Solution Approach 2:
The patent transitions from a conventional two-dimensional planar arrangement to a three-dimensional spatial configuration. The worm wheel is positioned to revolve around the worm gear's axis in a manner that utilizes the third dimension, allowing compact packaging of the transmission elements and reducing the mechanism's footprint in the radial direction.
2Reliability
If multiple transmission elements are used, then the differential mechanism can function properly, but the number of parts increases and differential errors increase
Solution Approach 1:
The patent merges the functions of multiple transmission elements into a single integrated worm gear-worm wheel assembly. The worm gear serves as both the central transmission element and the structural framework, while the worm wheel provides the second degree of freedom. This consolidation eliminates the need for separate planetary gears, carrier components, and other intermediate elements, thereby reducing the total number of parts and minimizing cumulative differential errors.
3Volume of moving object
If the worm gear is reduced in size, then the differential mechanism can be miniaturized, but the tooth rigidity is lowered and transmission force must be suppressed
Solution Approach 1:
The patent applies local quality by optimizing the tooth geometry and material properties specifically at the contact regions of the worm gear and worm wheel. The teeth are designed with enhanced local strength characteristics, such as increased tooth width, optimized profile shapes, and potentially different material compositions or heat treatments at critical stress zones. This allows the overall mechanism to be miniaturized while maintaining sufficient tooth rigidity and transmission force capacity through localized reinforcement rather than uniform scaling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution enables a compact differential mechanism that reduces differential errors and miniaturizes the structure, while maintaining two degrees of freedom and high affinity with conventional transmission elements.
Implementation Method 1
an inner worm gear (80) formed in a cylindrical shape, covering an outer periphery of the rotating frame (71) and rotatably provided coaxially with the rotating frame (71), and having a spiral tooth (81) formed on a cylindrical inner side; and a worm wheel (90) rotatably provided on the rotating frame (71) in a direction orthogonal to an axis of the rotating frame (71) and meshing with the inner worm gear (80)
Data Source
AI summary
A differential mechanism includes: a rotating frame rotatably provided in a main body frame; an inner worm gear formed in a cylindrical shape, covering the outer periphery of the rotating frame, and rotatably provided coaxially with the rotating frame, and having a spiral tooth formed on the cylindrical inner side; and a worm wheel rotatably provided on the rotating frame in a direction orthogonal to an axis of the rotating frame and meshing with the inner worm gear.