Compound Planetary EVT for Off-Road CVT Slippage Elimination
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Solution Overview
Problem
Off-road vehicles face challenges with belt slippage and excessive wear in continuously variable transmissions during extreme conditions, necessitating a more reliable and efficient transmission system.
Innovation Solution
An electrically variable transmission with a compound planetary gear assembly and two motor generators operating on parallel rotational axes, allowing for variable speed control and smooth power delivery without the limitations of belt-driven systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If belt-driven continuously variable transmissions are used, then variable speed control is provided, but belt slippage and excessive wear occur during extreme off-road conditions
Solution Approach 1:
The patent replaces the belt-driven mechanical system with an electrically variable transmission system that uses electric motors and a compound planetary gear assembly. This substitution eliminates the belts that cause slippage and wear, while maintaining variable speed control capability through electronic actuation of the planetary gear sets.
Solution Approach 2:
The invention removes the belt-driven components from the transmission system entirely, extracting only the essential function of variable ratio control. By eliminating the belts and pulleys, the harmful slippage and wear are removed while the core transmission function is preserved through a different mechanical architecture.
2Area of stationary object
If compound planetary gear assembly with parallel rotational axes is used, then compact footprint is achieved, but device complexity increases
Solution Approach 1:
The patent employs parallel rotational axes instead of concentric arrangements, utilizing a different spatial dimension to achieve compactness. By stacking planetary gear sets with parallel axes rather than nesting them concentrically, the design reduces the overall footprint while managing complexity through standardized modular components.
Solution Approach 2:
The invention merges two planetary gear sets into a compound assembly where the first and second planet carriers are coupled together for common rotation. This combination achieves compact footprint by integrating multiple gear functions into a unified structure, while the shared rotation simplifies control compared to independent gear sets.
3Ease of operation
If two motor generators are used for variable speed control, then smooth power delivery is achieved, but device complexity increases
Solution Approach 1:
The patent uses motor generators that can operate in multiple modes: as motors to drive the planetary gear sets for variable speed control, and as generators to provide regenerative braking. This multi-functionality achieves smooth power delivery across different operating conditions while reducing overall system complexity by using the same components for multiple purposes.
Solution Approach 2:
The electrically variable transmission system incorporates control mechanisms that monitor the operational state of the planetary gear assembly and motor generators, adjusting their operation to maintain smooth power delivery. This feedback control enables coordinated operation of the dual motor generators, achieving seamless power transmission while managing system complexity through intelligent control.
Data Source
AI summary
An electrically variable transmission for an off-road vehicle including an internal combustion engine with a crankshaft. The electrically variable transmission includes a compound planetary gear assembly having a first planetary gear set with a first ring gear, a first sun gear and a first planet carrier and a second planetary gear set with a second ring gear, a second sun gear and a second planet carrier. The planet carriers are coupled together for common rotation and are coupled to an output gear for common rotation therewith. The first ring gear is in torque transferring communication with the crankshaft. The first sun gear is in torque transferring communication with a first motor generator. The second sun gear is in torque transferring communication with a second motor generator. The rotational axes of the compound planetary gear assembly and each of the motor generators are parallel rotational axes.