Rear-Suspension Compensating Device for Chain Pull and Pedal Kickback
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Solution Overview
Problem
Pedal-assisted bicycles with rear suspension experience chain pull and pedal kickback during suspension travel, destabilizing the rider and overstressing the chain, which is not effectively addressed by existing compensating devices due to interference with electric motor control systems.
Innovation Solution
A compensating system with a freewheel device and compensating device interposed between the drive and muscle shafts, allowing angular forward compensation strokes opposite to the freewheel device's free stroke, ensuring the drive shaft remains stable and the electric motor control is not deceived.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a compensating device is applied to the crankset to compensate for suspension travel, then chain pull and pedal kickback are reduced, but the electric motor control system is deceived and false torque readings occur
Solution Approach 1:
The compensating device is segmented into a mechanical compensation mechanism (freewheel device) and a control isolation mechanism (torque sensor positioning). The freewheel device handles the mechanical compensation while the torque sensor is positioned to read only the muscle shaft torque, separating the compensation function from the measurement function to avoid deception of the control system.
Solution Approach 2:
The torque sensor acts as an intermediary element positioned between the muscle shaft and the drive shaft. It selectively measures the torque applied by the rider on the muscle shaft while being insulated from the compensating device's mechanical movements, thus providing accurate torque readings to the control system without being affected by suspension travel compensation.
2Power
If the drive shaft is directly coupled to the gear wheel, then power transmission is efficient, but the drive shaft experiences violent rotation during suspension compression
Solution Approach 1:
The compensating device serves as an intermediary between the drive shaft and the gear wheel. It absorbs the violent rotation movements during suspension compression through its mechanical design (freewheel device with controlled free stroke), allowing the drive shaft to remain stable while still transmitting power efficiently to the gear wheel through the chain.
Solution Approach 2:
The harmful violent rotation component is extracted and isolated into the compensating device's free stroke mechanism. The freewheel device allows controlled movement in the compensation direction while blocking reverse movement, effectively separating the unstable suspension-induced motions from the stable power transmission path of the drive shaft.
3Object-affected harmful factors
If the freewheel device allows unlimited free stroke, then the muscle shaft is fully isolated from stress, but the compensating stroke cannot be limited to prevent over-compensation
Solution Approach 1:
The compensating device provides partial compensation by limiting the free stroke to a predetermined angle that corresponds to the maximum expected suspension travel. This partial action is sufficient to handle normal riding conditions while preventing over-compensation that would cause instability, balancing isolation effectiveness with controlled precision.
Solution Approach 2:
The predetermined angle limit is set in advance based on the suspension system's characteristics. This preliminary configuration ensures that the compensating stroke will never exceed the actual suspension travel under normal conditions, preventing over-compensation while maintaining adequate stress isolation for the muscle shaft.
Data Source
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AI summary
The present invention relates to a pedal-assisted bicycle comprising a suspension system (12) of the rear wheel in relation to the frame which allows a predetermined relative displacement (H1) between them, characterised in that the crankset (20) comprises : - a freewheel device (36) operatively interposed between the drive and muscle shafts (44 and 45); - a compensating device (40) operatively interposed between the drive shaft (45) and the gear wheel (26), configured to generate between the two an angular forward compensation stroke (A1) between a rest position, and a compensation position, wherein said forward compensation stroke is limited to a predetermined angle (A1) and is opposite to the free stroke of the freewheel device (36).