Two-Stage Speed Reducer Combining Harmonic and RV Mechanisms
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Solution Overview
Problem
Conventional speed reducers, such as RV and harmonic drive reducers, face issues with high volume, weight, and cost, as well as lower rigidity and shorter lifespan due to flex spline deformation and teeth difference friction.
Innovation Solution
A speed reducer design featuring a rotating wheel with a convex and concave structure, a first roller assembly, and a second roller assembly, where the convex structure contacts first rollers and the concave structure contacts second rollers, allowing for self-rotation and achieving a high reduction ratio while increasing rigidity and reducing volume and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional RV reducer is used to achieve high reduction ratio and rigidity, then the reduction ratio and rigidity are improved, but the volume, weight, and cost increase
Solution Approach 1:
The patent divides the speed reducer into two independent stages: a first stage using a harmonic drive mechanism (with wave generator, flex spline, and circular spline) and a second stage using an RV mechanism (with pinion and gear). Each stage is optimized for its specific function, allowing the overall system to achieve high reduction ratio and rigidity while minimizing weight and cost by using only the necessary components in each stage.
2Weight of stationary object
If a harmonic drive reducer is used to reduce volume and weight, then the size is reduced, but the rigidity decreases and lifespan shortens due to flex spline deformation
Solution Approach 1:
The patent segments the speed reduction function into two stages, placing the harmonic drive in the first stage where it handles the initial speed reduction with its advantage of compact size and light weight. The second stage uses the RV mechanism which provides high rigidity and load-bearing capacity. This segmentation allows each mechanism to operate in its optimal performance range.
Solution Approach 2:
The patent creates a composite mechanical system by combining two different transmission mechanisms (harmonic drive and RV mechanism) into a two-stage speed reducer. This composite structure leverages the strengths of both mechanisms: the harmonic drive's compactness and the RV mechanism's rigidity, achieving a balanced performance that neither mechanism could provide alone.
3Productivity
If a two-stage RV reducer is used to increase reduction ratio capability, then the reduction ratio is improved, but the device complexity and cost increase
Solution Approach 1:
The patent divides the speed reduction into two functional stages with distinct mechanisms optimized for their respective roles. The first stage (harmonic drive) handles the initial reduction with fewer components, while the second stage (RV mechanism) provides the final high-ratio reduction. This segmentation reduces overall complexity compared to a single-stage high-ratio RV reducer by using simpler components in the first stage.
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 provides a cost-effective, high-reduction-ratio speed reducer with increased rigidity and extended lifespan, overcoming the limitations of conventional RV and harmonic drive reducers by simplifying structure and enhancing durability.
Implementation Method 1
The elastic deformation of the flexible element can be controlled to result in a pushing action so as to transmit motion and power of mechanical transmission
Implementation Method 2
a rotating wheel (13), a first roller assembly (12) and a second roller assembly (14)... The convex structure is contacted with plural first rollers (121) of the first roller assembly (12)... The concave structure is contacted with plural second rollers (141) of the second roller assembly (14)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A speed reducer (1) includes a first transmission shaft (10), an eccentric wheel (11), a first roller assembly (12), a rotating wheel (13), a second roller assembly (14) and a second transmission shaft (15). The rotating wheel (13) includes a main body (130) and an axle hole (133). The main body (130) includes a convex structure (131) and a concave structure (132). The convex structure (131) is protruded from an outer periphery of the main body (130) and has outer teeth. The outer teeth are contacted with the corresponding first rollers (121). The concave structure (131) is concavely formed in a surface of the main body (130) and includes inner teeth. The inner teeth are contacted with plural second rollers (141) of the second roller assembly (14). Since the speed reducer (1) is designed to have four operating situations, the speed reducer (1) can have various reduction ratios.