Single-Stage Planetary Reducer With Dual Annular Gears
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Solution Overview
Problem
Conventional gear reducers, such as planetary gear trains and harmonic drives, face limitations in achieving high speed-reduction ratios while maintaining structural simplicity, durability, and cost-effectiveness, particularly for industrial robots requiring high torque and large force/torque density.
Innovation Solution
A high-ratio planetary gear reducer design featuring a carrier, planetary gears, a fixed annular gear, and a rotating annular gear, where the number of teeth for the rotating annular gear is set by the equation Zo = Zf ± Np, allowing for a high speed-reduction ratio in a single stage configuration without a sun gear, and optimizing module and pressure angle settings to enhance durability and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a planetary gear train is used to achieve high speed-reduction ratio, then the reduction ratio can be increased, but the structure complexity increases due to multiple stages and misalignment of input and output shafts
Solution Approach 1:
The patent merges the functions of multiple planetary gear stages into a single-stage configuration by using two annular gears with different tooth counts that simultaneously mesh with the planetary gears. This integration achieves high speed-reduction ratio (several tens to several hundred:1) while maintaining a simplified single-stage structure with input and output shafts on the same line.
Solution Approach 2:
The patent introduces a new dimensional parameter by using two annular gears with different tooth counts (Zf and Zo) instead of the conventional single annular gear. This additional degree of freedom in gear configuration enables high reduction ratios without requiring multiple stages, thereby simplifying the overall structure.
2Speed
If a harmonic drive is used to achieve high speed-reduction ratio, then the reduction ratio can be increased, but the manufacturing cost increases due to expensive wave generator
Solution Approach 1:
The patent replaces the expensive wave generator in harmonic drives with a simpler rotating annular gear that has the same number of teeth as the number of planetary gears. This substitution significantly reduces manufacturing cost while achieving the same high speed-reduction ratio, making the system more economically viable for industrial robots.
Solution Approach 2:
The patent creates a simplified copy of the harmonic drive mechanism by using a rotating annular gear with tooth count Zo = Np (number of planetary gears) instead of the complex wave generator. This copied structure replicates the high reduction ratio function at a fraction of the cost.
3Speed
If a planetary gear train is used to achieve high speed-reduction ratio, then the reduction ratio can be increased, but the weight and volume increase due to multiple stages
Solution Approach 1:
The patent combines multiple gear stages into a single-stage configuration using two annular gears with different tooth counts. This merging eliminates the need for multiple separate stages, thereby reducing the overall weight and volume of the gear reducer while maintaining high speed-reduction ratio.
4Device complexity
If the number of teeth of rotating annular gear is not optimized, then the structure is simpler, but the durability decreases due to fatigue fracture
Solution Approach 1:
The patent optimizes the number of teeth of the rotating annular gear by setting it equal to the number of planetary gears (Zo = Np). This specific parameter configuration ensures proper meshing and load distribution, preventing fatigue fracture and improving durability while maintaining the simplicity of the single-stage structure.
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 design achieves a high speed-reduction ratio of several tens to several hundred:1 with a simplified structure, improves durability by avoiding fatigue fractures, and reduces manufacturing costs associated with expensive wave generators.
Implementation Method 1
one or more planetary gears, a fixed annular gear and a rotating annular gear. The at least one planetary gear is rotatably supported by the carrier at an eccentric position relative to a rotational axis of the carrier. The fixed annular gear meshes with one or more the planetary gears
Implementation Method 2
one or more planetary gear which is rotatably supported by the carrier in an eccentric position relative to a rotational axis of the carrier
Data Source
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AI summary
A high-ratio differential reducer is provided. A carrier is connected to an input shaft. At least one planetary gear is supported to be rotatably supported by the carrier in an eccentric state from the carrier. A fixed annular gear meshes with the planetary gear in a state of being coaxially arranged with the carrier. A rotating annular gear meshes with the planetary gear in a state of being coaxially arranged with the fixed annular gear and has the number of teeth set by Equation below: Zo=Zf±Np where Zo is the number of teeth of the rotating annular gear, Zf is the number of teeth of the fixed annular gear, and Np is the number of planetary gears.