E-Bike Redirecting Gearbox With Axial Gear Decoupling
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Solution Overview
Problem
Existing electric bicycles face challenges in providing a reliable and efficient drive system with a simple structure that optimally supports the transmission of forces, particularly in scenarios where the electric motor assistance is omitted.
Innovation Solution
A drive device for electric bicycles featuring a redirecting gearbox with axially displaceable gear elements and a freewheel clutch that allows torque transmission and independent rotation of the shaft relative to the gear elements, ensuring optimal coupling and support of forces within predetermined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first gear element is rigidly fixed axially to the shaft, then the coupling between the gear element and shaft is reliable, but the shaft cannot rotate independently when the electric motor is not driving, resulting in high pedaling resistance
Solution Approach 1:
The first gear element is designed with axial mobility relative to the shaft, allowing it to dynamically adjust its axial position. When the electric motor drives the shaft, the gear element is pushed axially by forces from the second gear element to engage with the shaft. When the motor is not driving, the gear element can move axially to disengage, allowing the shaft to rotate independently without resistance. This dynamic engagement/disengagement mechanism resolves the contradiction between coupling reliability and ease of operation.
2Reliability
If complex axial positioning mechanisms are used to maintain precise gear element position, then coupling reliability is improved, but the device structure becomes more complex
Solution Approach 1:
The first gear element performs its own axial positioning through force interactions with the second gear element and the shaft. During motor-driven operation, forces from the second gear element automatically push the first gear element axially into engagement with the shaft. The system uses its operational forces to achieve positioning without requiring external complex positioning mechanisms, thereby maintaining reliability while avoiding increased complexity.
3Ease of operation
If the gear elements are allowed to move axially freely, then the shaft can rotate independently, but the coupling between gear elements fails and torque transmission is unreliable
Solution Approach 1:
The first gear element is designed with axial mobility relative to the shaft, allowing it to dynamically adjust its axial position. When the electric motor drives the shaft, the gear element is pushed axially by forces from the second gear element to engage with the shaft. When the motor is not driving, the gear element can move axially to disengage, allowing the shaft to rotate independently without resistance. This dynamic engagement/disengagement mechanism resolves the contradiction between coupling reliability and ease of operation.
Solution Approach 2:
The axial position parameter of the first gear element is allowed to change within a controlled range. The gear element can move axially to adjust its engagement state with the shaft, transitioning between engaged and disengaged positions. This parameter change enables the system to switch between torque transmission mode and independent rotation mode, resolving the contradiction between coupling reliability and independent rotation capability.
Data Source
AI summary
A drive device for an electric bicycle has a shaft and a redirecting gearbox configured for coupling with an electric motor and the shaft so that a torque is transmittable from the motor to the shaft via the gearbox. The gearbox has a first gear element rotatable about a first axis and a second gear element coupled to the first. The second gear element can rotate about a second axis running at an angle to the first axis. A torque is transmittable from the first gear element to the shaft through a coupling therebetween. The device is configured to rotate the shaft in a first rotational direction relative to the first gear element. The first gear element is axially displaceable relative to the second gear element, parallel to the first axis, within predetermined limits, the gear elements remaining coupled to one another within the predetermined limits.