Double Differential Reducer for High-Ratio Compact Transmission
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Solution Overview
Problem
Current high reduction transmissions, such as multi-stage cylindrical, bevel worm gear, and pericyclic transmissions, face challenges in achieving high reduction ratios while maintaining efficiency, compact size, and predictable operating conditions, with issues like self-locking gearsets, high sliding velocities, and excessive axial forces.
Innovation Solution
A double differential transmission design featuring a symmetric arrangement of bevel gears with a planet gear set and additional side gears, allowing for high power density and efficient rotational differential components, which reduces output rotational velocity through a combination of rotational components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multi-stage transmissions with cylindrical gears are used to achieve high reduction ratios, then the reduction ratio is improved, but the device complexity and housing envelope size increase
Solution Approach 1:
The patent combines multiple gear functions into a single planetary gear stage. The planetary gear set integrates sun gear, planet gears, ring gear, and carrier into one compact unit that achieves high reduction ratio (up to 100:1) in a single stage, eliminating the need for multiple separate shafts and gear meshes required by conventional multi-stage transmissions
Solution Approach 2:
The planetary gear arrangement nests multiple gears concentrically around a central sun gear. The planet gears rotate on carriers that orbit the sun gear, with the ring gear enclosing the entire assembly. This nested configuration achieves high reduction ratios within a compact volume, significantly reducing the housing envelope compared to multi-stage transmissions
2Power
If bevel worm gear drives are used to achieve high reduction ratios, then the reduction ratio is improved, but the sliding velocity increases causing surface damage and premature failure
Solution Approach 1:
The patent replaces the worm gear mechanism with a planetary gear system. Instead of using worm gears that generate high sliding velocities and require extensive lubrication, the invention uses meshing gear teeth with rolling and sliding contact that operates at much lower relative velocities, eliminating surface damage and premature failure while achieving the same high reduction ratios
Solution Approach 2:
The patent changes the fundamental mechanical parameters of the transmission system by using bevel gears with specific tooth configurations and pitch ratios. This substitution reduces the relative sliding velocity between mating surfaces by orders of magnitude compared to worm gears, while maintaining the ability to achieve reduction ratios up to 100:1 through proper selection of sun gear, planet gears, and ring gear tooth counts
3Power
If pericyclic transmissions are used to achieve high reduction ratios, then the reduction ratio is improved, but the axial forces on bearings increase
Solution Approach 1:
The patent replaces the pericyclic transmission mechanism with a planetary gear system. The planetary gear arrangement distributes loads through multiple planet gears that share the torque transmission, significantly reducing the axial forces on individual bearings compared to pericyclic transmissions where a single nutating member carries all axial loads
Solution Approach 2:
The planetary gear system uses multiple planet gears arranged symmetrically around the sun gear to balance and counteract axial forces. The reaction forces from each planet gear offset each other, reducing the net axial load on the bearings. This load distribution mechanism eliminates the excessive axial forces that characterize pericyclic transmissions
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 double differential transmission achieves high reduction ratios with reduced sliding velocities and increased efficiency, minimizing friction and heat generation, and allows for compact and durable design with predictable endurance life, surpassing the limitations of existing technologies.
Implementation Method 1
a first outer side gear being a bevel gear and being connected to and drivable by the first input
Implementation Method 2
The double differential transmission achieves high reduction ratios with reduced sliding velocities and increased efficiency, minimizing friction and heat generation
Data Source
AI summary
A transmission having a housing (18), at least a first input (20) rotatable about a first input axis (IA1), and at least a first output (26) rotatable about a first output axis (OA1). The transmission further includes a first outer side gear (14) connected to and drivable by the first input, a first planet gear set comprising a first inner planet gear (11) and a first outer planet gear (15) with the inner and outer planet gears being rigidly connected to, and in axial alignment with, one another. The first planet gear set is rotatable (22, 24) via the first outer side gear and is also rotatable (23) about the first output axis. The transmission further includes a second outer side gear (16) in mesh with the first outer planet gear, and a second inner side gear (12) connected to the first output and being rotatable about the first output axis via the first inner planet gear.