Electric Bicycle Gear Shifting at Standstill
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Solution Overview
Problem
Conventional electric bicycles with stationary gear shifts face starting problems due to high engaged gears when stationary, as they cannot shift gears without pedaling, leading to inefficient starting.
Innovation Solution
An electric drive system with a control unit, torque sensor, and electric actuator allows gear shifting without pedaling by moving the chain into a lower gear when no torque is detected, enabling easier restarts and optimizing gear engagement based on vehicle speed and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional gear shift system is used, then the structure is simple, but gear shifting cannot be performed when stationary
Solution Approach 1:
The patent combines the electric drive system with the gear shift actuation system. The electric drive motor is used to rotate the crank mechanism, which drives the chain to move to a different sprocket, thereby achieving gear shifting. This merging of functions allows gear shifting without requiring a separate manual shifting mechanism.
Solution Approach 2:
The patent replaces the traditional mechanical gear shifting mechanism (which requires manual pedal input) with an electrically-driven system. The electric drive motor substitutes for the mechanical pedaling action, enabling the chain to be moved without the driver applying force to the pedals.
2Productivity
If the bicycle remains in high gear when stationary, then the gear shift system is simple, but starting problems occur
Solution Approach 1:
The control unit automatically shifts the gear to a lower gear before the driver attempts to start pedaling. This preliminary gear change prepares the transmission system for the upcoming motion, ensuring that the chain is positioned on a sprocket that provides sufficient mechanical advantage for easy starting.
Solution Approach 2:
The control unit monitors the stationary state of the bicycle and uses this feedback information to automatically adjust the gear position. When the system detects that the bicycle has been stationary for a period, it triggers an automatic gear downshift to optimize starting conditions.
3Ease of operation
If the chain is moved by electric drive when stationary, then gear shifting is enabled, but energy consumption increases
Solution Approach 1:
The electric drive motor performs only the minimum necessary action to move the chain to the appropriate sprocket position. The motor provides just enough torque to overcome the static friction and move the chain, rather than continuously driving the bicycle. This partial action minimizes energy consumption while achieving the gear shifting objective.
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 gear shifting at a standstill, reducing starting difficulties and enhancing driving comfort by automatically engaging a lower gear when stationary, thus improving efficiency and reducing wear on components.
Implementation Method 1
an electric actuator for actuating the gear shift
Implementation Method 2
at least one torque sensor, which is set up to detect a torque applied by a driver to the crank mechanism
Data Source
Figure 1
AI summary
The present invention relates to a pedal-driven vehicle, in particular an electric bicycle, comprising an electric drive (2), a power supply (6), a chain (7), a gear shift mechanism (4), an electric actuator (3) for actuating said gear shift mechanism (4), and a control unit (5) for controlling said electric drive (2) and said electric actuator (3), said control unit (5) being designed to actuate, when there is a gear change command, the electric drive (2) in order to move the chain (7) so that a gear can be changed by means of the electric actuator (3). The invention also relates to a method for operating a pedal-driven vehicle.