Stepped Planetary Drive for Variable-Ratio Pedal-Electric Propulsion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing propulsion systems for vehicles operated by muscle power, such as bicycles, lack efficient mechanisms for combining human-powered and electric propulsion, and do not provide variable transmission ratios or recuperative braking capabilities.
Innovation Solution
A propulsion unit incorporating a crank device, speed modulation gear with stepped planetary gears, and an electric machine, allowing for superposition of muscle power and electric propulsion, with a control device for variable transmission ratios and optional electric assistance, and featuring a freewheel unit and recuperative operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a planetary transmission is used to reduce output rotational speed of the electrical propulsion unit, then the transmission ratio is fixed and结构简单, but the system lacks variable transmission ratios and cannot adapt to different operating conditions
Solution Approach 1:
The patent employs a stepped planetary gear set that can dynamically switch between different transmission ratios. The gear system includes multiple planetary gear stages with different reduction ratios, allowing the system to adapt to varying operating conditions by engaging different gear stages, thus resolving the contradiction between adaptability and structural simplicity.
Solution Approach 2:
The planetary transmission unit serves multiple functions: it provides both fixed and variable transmission ratios, enables speed modulation, and facilitates power combination from both crank device and electric machine. This multi-functionality allows a single gear system to address multiple operational requirements without proportionally increasing complexity.
2Productivity
If a gear unit is used to superimpose propulsive force from electric machine and crank device, then power combination is achieved, but the system lacks efficient speed modulation and variable transmission capabilities
Solution Approach 1:
The stepped planetary gear set enables dynamic speed modulation by allowing the gear system to switch between different reduction stages. This dynamic capability enhances productivity by optimizing power transmission efficiency across various operating conditions while maintaining the ability to superimpose forces from both the crank device and electric machine.
Solution Approach 2:
The planetary transmission unit acts as an intermediary mechanism that efficiently combines and modulates power from two sources (crank device and electric machine). It mediates between the different input speeds and torques, transforming them into a unified output that maximizes productivity while providing speed modulation capability.
3Adaptability or versatility
If the speed modulation gear is mounted rotatably to superimpose rotations of electric machine and crank device, then versatility is improved, but the device complexity increases
Solution Approach 1:
The patent merges the mounting structure of the speed modulation gear with the planetary gear set itself, where the planetary carrier serves as both the gear mechanism and the rotatable mounting structure. This integration allows the superposition of rotations from the electric machine and crank device while minimizing additional structural complexity.
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
Enables efficient integration of human and electric power, providing variable transmission ratios and recuperative braking, enhancing the propulsion system's efficiency and versatility.
Implementation Method 1
The speed modulation gear is in the form of a stepped planetary gear set having at least one stepped planetary gear, corresponding ring gears, and an input element
Implementation Method 2
The speed modulation gear can have a planet gear with a large diameter and, coupled thereto, a planet gear with a small diameter
Data Source
AI summary
A propulsion unit includes a crank device (3) for receiving muscle power and a speed modulation gear (1) for transmitting the muscle power onto an output gear (10) for propelling a vehicle. An electric machine (2) and a housing (6) can be mounted on the vehicle for accommodating at least some elements of the propulsion unit. The speed modulation gear (1) is in the form of a stepped planetary gear set with at least one stepped planetary gear (15), corresponding ring gears (12, 14), and an input element. The crank device (3) is couplable to one of the ring gears (12, 14), and an output element (22) of the electric machine (2) is coupled to the input element. The speed modulation gear (1) is mounted rotatably with respect to the housing (6) such that rotation of the electric machine (2) and rotation of the crank device (3) can be superimposed and transmitted onto the output gear (10).