Bicycle Drive Unit Shift Timing for Quiet Torque-Stable Gear Changes
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Solution Overview
Problem
Existing vehicles driven by muscle power, such as bicycles, face challenges in gear shifting that result in discomfort and loss of tractive force due to manual or actuator-based gear changes, often requiring motor torque adjustments that can disrupt the driving experience.
Innovation Solution
A drive unit with a transmission arrangement and control device that calculates an optimum starting condition for gear shifts based on crank position, frequency, and actuator speed, allowing gear changes to be initiated at a time of minimal muscle power torque, typically near the dead center position, thereby reducing the need for motor torque adjustments during shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If gear changes are carried out manually or by actuator during vehicle operation, then gear shifting capability is achieved, but driving comfort deteriorates due to shifting noise and loss of tractive force
Solution Approach 1:
The control device calculates an optimum starting condition for the shifting process in advance, considering current crank position, crank frequency, and actuator speed. This preliminary calculation enables the gear change to be initiated at the optimal moment when muscle power torque is minimal, thereby reducing shifting noise and maintaining tractive force during the transition.
Solution Approach 2:
The system continuously monitors real-time parameters including crank position, crank frequency, and actuator speed. This feedback mechanism allows the control device to dynamically determine the optimum starting condition for gear shifting, ensuring that changes occur at the most favorable moment to minimize disruption to the driving experience.
2Ease of operation
If motor torque is adjusted during gear shifts to accommodate manual or actuator-based changes, then gear changing is enabled, but driving comfort deteriorates due to motor torque reduction
Solution Approach 1:
The control device performs preliminary calculation of the optimum starting condition before initiating the gear shift. By determining the optimal moment in advance based on minimal muscle power torque conditions, the system can execute gear changes without requiring motor torque adjustments, thereby maintaining power output and improving driving comfort.
3Productivity
If gear shifts are executed without considering crank position and timing, then gear changing speed is improved, but reliability deteriorates due to increased shifting noise and potential failure
Solution Approach 1:
The system uses real-time feedback from crank position sensors, crank frequency measurements, and actuator speed monitoring to dynamically determine the optimum starting condition. This feedback ensures that gear shifts are executed at the most favorable moment, simultaneously achieving high shifting speed and high reliability by minimizing mechanical stress and noise during the transition.
Data Source
AI summary
A drive unit for a vehicle, such as a bicycle driven by muscle power, having a transmission arrangement for setting up a plurality of gear stages, in which a form-fitting connection of two transmission elements is set up in each case. The transmission arrangement has an input shaft, which is connectable to drive cranks, and an output shaft, which can be coupled to an output, and having a control device for carrying out gear changes. The control device may be configured to carry out the following steps: receiving a gear-shifting request to a target gear stage, calculating an optimum starting condition of the shifting process, and starting the shifting process when the optimum starting condition is met, so that the form-fitting connection of the target gear stage is set up at an optimum time.