Bicycle Drive Device Reducing Gear Downshift Wear
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bicycle drive systems with electric motors and manual transmissions face high wear during gear downshifts due to excessive actuation and transmission forces.
Innovation Solution
A drive device with a gearbox, crankshaft, electric machine, and freewheel mechanism that adjusts gear ratios and electric motor power based on sensor data from pedal crank angle, crankshaft speed, output shaft speed, and rotor shaft speed to reduce forces during gear downshifts, using sensors and a control device to manage the electric machine's current supply and decouple the rotor shaft from the output shaft when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gear downshifting is performed in conventional bicycle drive systems, then gear ratio change is achieved, but high wear occurs due to excessive actuation and transmission forces
Solution Approach 1:
The control device activates the electric machine before the gear downshifting event to pre-position the rotor shaft speed, ensuring that the speed difference between input shafts is minimized at the moment of gear engagement, thereby reducing transmission forces and wear
Solution Approach 2:
The system dynamically adjusts the rotor shaft speed parameter by controlling electric machine activation, changing the speed relationship between input shafts to optimize gear downshifting conditions and minimize harmful forces
2Ease of operation
If the electric machine is continuously powered to maintain rotor shaft speed, then smooth operation is achieved, but energy consumption increases
Solution Approach 1:
The electric machine is activated periodically and temporarily only when needed for gear downshifting events rather than continuously, providing smooth operation during critical moments while minimizing energy consumption during normal operation
Solution Approach 2:
The electric machine is activated in advance of the gear downshifting event to prepare the speed conditions, allowing for temporary energy input that achieves smooth operation without requiring continuous power supply
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 solution enables low-wear gear downshifting by reducing actuation and transmission forces, extending the lifespan of the drive system components and improving shifting efficiency.
Implementation Method 1
wherein the freewheel is arranged to decouple the output shaft from the rotor shaft when the output shaft speed is greater than the rotor shaft speed
Implementation Method 2
an electric machine with a rotor shaft for transmitting drive power from the electric machine into the gearbox
Implementation Method 3
a crankshaft with a pedal crank for transmitting drive power from a cyclist into the gearbox
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a drive device (1) for a bicycle (100), comprising: • a gearbox (2) with several gears and an output shaft (3), • a crankshaft (5) with a pedal crank (6) for transmitting drive power from a cyclist into the gearbox (2), wherein the crankshaft (5) is operatively connected to the output shaft (3), • an electric machine (7) with a rotor shaft (8) for transmitting drive power from the electric machine (7) into the gearbox (2), wherein the rotor shaft (8) is operatively connected to the output shaft (3) via a freewheel (9), • means for detecting a pedal crank angle and a crankshaft speed and generating corresponding sensor data, • means for detecting an output shaft speed and generating corresponding sensor data, • means for detecting a rotor shaft speed and generating corresponding sensor data, and • a control device (10) configured toThe invention relates to processing these sensor data and controlling a downshift from a currently engaged gear to a lower gear based on these sensor data by energizing the electric motor (7). Furthermore, the invention relates to several methods for controlling the drive device (1), a control unit (10), and a bicycle (100).