Reciprocating Pedal Cam Transmission for Smooth Power Transfer
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Solution Overview
Problem
Existing human-powered vehicle transmissions fail to efficiently transmit pedal power at the initiation of a stroke, leading to uncomfortable impacts and inefficient energy transfer due to varying gearing ratios that do not account for the pedal's speed and position.
Innovation Solution
A transmission system with rotating cam members and flexible tension members that vary the gearing ratio based on the pedal's position, providing a minimum gearing ratio at the intermediate position, a first value at the retracted position, and a second major value at the extended position, allowing for smooth power application and energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant gearing ratio is used in the transmission, then the structure is simple, but power transmission efficiency is poor at the initiation of pedal stroke
Solution Approach 1:
The patent applies the dynamics principle by making the gearing ratio variable rather than constant. The radial distance of the point of tangency from the cam axis varies continuously as the pedal moves from retracted to extended position, creating a dynamic transmission ratio that adapts to the pedal stroke phase. This resolves the contradiction by accepting increased structural complexity (rotating cam members with variable radius) to achieve significantly improved power transmission efficiency during pedal initiation and throughout the stroke cycle.
2Power
If the radial distance of the point of tangency is small at pedal initiation, then power transmission is improved, but the gearing ratio becomes too high causing speed mismatch
Solution Approach 1:
The patent applies parameter changes by continuously varying the radial distance parameter of the point of tangency on the cam surface. At pedal initiation (retracted position), the radial distance is small to provide high power transmission with mechanical advantage. As the pedal progresses toward extended position, the radial distance increases to reduce the gearing ratio and increase speed. This continuous parameter variation resolves the contradiction by allowing the system to optimize both power and speed at different phases of the pedal stroke.
3Productivity
If the gearing ratio varies significantly throughout the pedal stroke, then power transmission is optimized, but uncomfortable impacts occur during operation
Solution Approach 1:
The patent uses dynamics to create a smooth, continuous variation in the gearing ratio through the rotating cam members. The variable radial distance changes gradually throughout the pedal stroke rather than in abrupt steps, providing a dynamic but gentle transition between different transmission ratios. This resolves the contradiction by optimizing energy transfer efficiency through significant ratio variation while maintaining riding comfort through the smooth, progressive nature of the variation.
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 comfortable and efficient power transmission by requiring minimal initial speed to catch up with the vehicle's speed, increasing force moment as speed is gained, and naturally transitioning to the return stroke, thus enhancing the overall pedaling experience and energy efficiency.
Implementation Method 1
a flexible tension member connecting either pedal to a respective one of the rotating cam members, each flexible tension member being fastened relative to the respective rotating cam member and being wound onto the peripheral cam surface of the respective rotating cam member
Implementation Method 2
thereby providing a gearing ratio between angular movement of the rotating cam member and translational movement of the respective pedal
Data Source
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AI summary
The transmission is for transmitting a reciprocating pedal movement into a rotational movement and comprises a pair of pedals suspended for reciprocating movement, two rotating cam members (29) rotating around respective cam axes (33), each rotating cam member (29) having a peripheral cam surface (31), the rotating cam members (29) being coupled to a rotating member (35) through a respective one-way clutch. Flexible tension members (63) are connecting either peda to a respective one of the rotating cam members (29), which are eccentric to provide for a gearing ratio between angular movement of the rotating cam member (29) and translational movement of the respective pedal to vary,such that the gearing ratio has a minimum value when the pedal is in an intermediate position between its extended position and its retracted position, and major values when the pedal is in its retractedor extende dposition.