Hub Variable Ratio Transmission One-Way Clutch
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Solution Overview
Problem
Existing bicycle wheel hubs with variable ratio transmission systems face issues such as complexity, cost, and inefficiency in combining mechanical and electrical power inputs, leading to 'pedal dropping' phenomena and inadequate 'get home' capability, especially when battery power is depleted.
Innovation Solution
A hub with a single epicyclic gearset and a one-way clutch that connects the hub to the carrier upon torque application, eliminating pedal dropping and allowing seamless power transmission from both mechanical and electrical sources, featuring a one-way clutch mechanism with jamming balls and springs for rotational locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single epicyclic gearset is used instead of two compounded gearsets, then device complexity is reduced and manufacturing cost decreases, but transmission ratio variability is limited
Solution Approach 1:
The transmission system is segmented into two independent power paths: a mechanical path through the epicyclic gearset and an electrical path through the motor/generator. This segmentation allows each path to be optimized independently, reducing overall complexity while maintaining versatility through the controller's ability to blend power sources.
Solution Approach 2:
The motor/generator serves multiple functions: it can operate as a motor to provide electrical power input, as a generator to recover braking energy, and as a controller to manage power distribution. This multi-functionality compensates for the limited gear ratios of the single epicyclic gearset, maintaining adaptability while reducing complexity.
2Reliability
If a one-way clutch is added to connect hub to carrier, then pedal dropping is eliminated and power transmission consistency improves, but device complexity increases
Solution Approach 1:
The one-way clutch acts as an intermediary element between the carrier and hub, allowing free rotation in one direction while preventing reverse rotation. This mediator component eliminates pedal dropping by ensuring unidirectional power flow without requiring complex control systems or additional actuators.
3Adaptability or versatility
If two motor/generators are used in the epicyclic gearset, then power combination capability improves and get home capability is enhanced, but assembly complexity and wiring complexity increase
Solution Approach 1:
The stators of both motor/generators are merged into a single common stator structure, eliminating the need for separate windings and reducing wiring complexity. The controller manages both motors through this unified stator, simplifying assembly while maintaining the ability to combine mechanical and electrical power inputs.
4Loss of energy
If the common carrier is connected to rotate with the hub member, then power transmission efficiency improves, but the ability to handle high torque inputs is reduced
Solution Approach 1:
The connection between the common carrier and hub member is made dynamic through the one-way clutch, which engages to transmit torque efficiently when power is being delivered to the hub, but disengages to allow the carrier to rotate independently when handling high torque inputs or during regenerative braking, thus adapting to different operational conditions.
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 results in a smaller, lighter, and cheaper hub that ensures consistent power transmission, eliminates pedal dropping, and enables efficient operation with either mechanical or electrical input, including regenerative braking and battery recharging.
Implementation Method 1
a one-way clutch, which includes a drive member, which is constituted by the common carrier, and a driven member, which is connected to rotate with the hub member, the one-way clutch being arranged to connect the hub member to rotate with the carrier as soon as the carrier rotates faster than the hub member
Data Source
AI summary
A hub comprises a cylindrical, hollow hub member which is mounted to rotate about its axis and accommodated in whose interior is a continuously variable ratio transmission system having an input, which is mounted to rotate about the axis, and an output mounted to rotate with the hub member. The transmission system comprises a single epicyclic gearset including a sun gear in mesh with a plurality of planet gears mounted to rotate about respective planet shafts carried by a common carrier, which is mounted to rotate with the input about the axis. The planet gears are in mesh with an annulus gear, which is connected to rotate with the rotors of first and second electric motor/generators, respectively. The electrical connections of the stators of the two motor/generators are connected by a controller arranged to control the transmission of power from one motor/generator to the other. The hub further includes a one-way clutch, which includes a drive member, which is constituted by the common carrier and a driven member, which is connected to rotate with the hub member. The one-way clutch is arranged to connect the hub member to rotate with the carrier as soon as the carrier rotates faster than the hub member.