Bicycle Hub Transmission Power Control Mechanism
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Solution Overview
Problem
Bicycle hub transmissions require excessive manual shifting effort or strain on motorized actuators due to significant resistance when shifting gear ratios, particularly during high pedaling forces, which can lead to damage and inefficient shifting operations.
Innovation Solution
A bicycle hub transmission with a power control mechanism that includes an assist cam, pawls, and rotational power communicating elements, allowing controlled assistance to the shifting mechanism to prevent locking and reduce resistance, featuring a non-constant coefficient of rotational power output to manage excessive resistance effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a shift mechanism is used to select power transmission paths in a hub transmission, then gear ratio selection is enabled, but excessive manual shifting effort is required when significant pedaling force is applied
Solution Approach 1:
The system uses the driver's own rotational power to assist the shifting operation. When significant resistance is detected during shifting, the pawl mechanism automatically engages to transmit rotational power from the driver to the shift sleeve, making the system self-assisting without external intervention.
Solution Approach 2:
A pawl mechanism acts as an intermediary between the driver and the shift sleeve. The pawls transmit rotational power from the driver through the pawl mechanism to rotate the shift sleeve when manual shifting effort is insufficient, enabling the shift operation under high pedaling force conditions.
2Ease of operation
If a motorized actuator is used to control shifting, then manual effort is reduced, but the motor experiences unacceptable strain under high pedaling forces
Solution Approach 1:
The system eliminates the need for motorized actuators by using the driver's own rotational power to assist shifting. The pawl mechanism automatically engages when resistance is detected, allowing the driver's power to directly assist the shifting operation without placing strain on external motors.
3Ease of operation
If rotational power is transmitted from the driver to the shift mechanism to assist shifting, then shifting effort is reduced, but locking between the driver and shift mechanism may occur
Solution Approach 1:
The system dynamically engages and disengages the pawl mechanism based on shifting resistance conditions. The pawls are spring-loaded to automatically engage when resistance is detected and disengage when shifting is complete, providing conditional power transmission that prevents locking while assisting shifting when needed.
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 reduces manual shifting effort and prevents damage by providing controlled assistance to the shifting mechanism, ensuring smooth gear changes and minimizing strain on components, even under high pedaling forces.
Implementation Method 1
a pawl mechanism coupled to the shift sleeve so that pawls carried by the pawl mechanism engage a ratchet mechanism comprising a plurality of ratchet teeth formed on the inner peripheral surface of the driver
Implementation Method 2
The rotational power of the driver is thus communicated to the shift sleeve, and the shift sleeve is rotated to complete the shifting operation
Implementation Method 3
a power control mechanism that comprises at least two frictional discs controls an amount of rotational power communicated from the driver to the shift mechanism to prevent locking between the driver and the shift mechanism
Data Source
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AI summary
A hub transmission (14) for a bicycle (10) comprises a hub axle (36); a driver (70) rotatably supported to the hub axle (10); a flub shell (74) rotatably supported to the hub axle (10); a power transmitting mechanism (82) disposed between the driver (76) and the hub shell (74) for communicating rotational power from the driver (70) to the hub shell (74) through a plurality of power transmission paths; a shift mechanism for selecting the plurality of power transmission paths; a shift assist mechanism (90) for communicating rotational power from the driver (70) to the shift mechanism; and a power control mechanism (950) disposed between the driver (70) and the shift assist mechanism (90) and coupling rotational power from the driver (70) to the shift assist mechanism (90) for communicating non-constant rotational power from the driver (70) to the shift assist mechanism (90).