Spring-Loaded Gear Shift for Low-Torque-Loss E-Bike Transmissions
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Solution Overview
Problem
Pedally propelled vehicles face challenges in efficient gear shifting due to the combination of rider torque and motor torque, leading to torque loss and complexity in shifting mechanisms, especially for less experienced riders.
Innovation Solution
A gear shift system that includes a movable shift element, an energy source, and an energy storage element, such as a pre-loaded coil spring, which is configured to move the shift element quickly and reliably, reducing torque loss and dependency on rider behavior, and can be integrated with existing multi-speed gear systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional gear shift mechanism is used in pedally propelled vehicles with motor support, then the system can provide multi-speed capability, but the combination of rider torque and motor torque causes torque loss and reduces shifting reliability
Solution Approach 1:
The control system initiates energy delivery to the energy storage element before the actual gear shift occurs. This preliminary charging of the spring with potential energy ensures that when the shift is commanded, the stored energy is immediately available to move the shift element, overcoming the combined torque from rider and motor without loss.
Solution Approach 2:
The system uses timed, periodic energy delivery to the energy storage element based on detected riding conditions and cadence. By delivering energy in controlled periods rather than continuously, the system maintains readiness for shifting while minimizing energy consumption and avoiding torque loss during normal operation.
2Ease of operation
If gear shifting relies on rider technique and timing, then experienced riders can achieve efficient shifts, but less experienced riders struggle and shifting becomes cumbersome
Solution Approach 1:
The control system automatically detects riding conditions, cadence, and shift requirements, then autonomously controls energy delivery to the energy storage element and actuates the gear shift. This eliminates the need for rider skill or manual intervention, making shifting equally easy for all riders while reducing the time required.
Solution Approach 2:
The system continuously monitors riding conditions and cadence, using this feedback to determine when and how to deliver energy to the energy storage element. This closed-loop control ensures shifts occur at optimal moments without requiring rider judgment, improving both ease of operation and timing precision.
3Reliability
If the gear shift mechanism must handle large torque from rider and motor, then the transmission can be controlled, but the lifetime of the shift mechanism and transmission is reduced
Solution Approach 1:
The energy storage element (spring) acts as an intermediary between the control system and the shift element. It stores potential energy and releases it during shifting, mediating the force requirements and allowing the mechanism to operate with reduced direct torque exposure, thereby extending component lifetime.
Solution Approach 2:
The control system delivers energy to the energy storage element in advance of the shift event, cushioning the torque demand during the actual shift. This pre-loading of the spring ensures the shift occurs smoothly without subjecting the transmission components to excessive peak torques.
4Speed
If the energy source continuously provides power to overcome torque during shifting, then shifting can be forceful, but energy consumption increases and shifting speed decreases
Solution Approach 1:
The energy source delivers power in periodic, controlled pulses to charge the energy storage element rather than continuously. This allows the spring to accumulate potential energy over time, which is then released rapidly during the shift event, achieving high shifting speed while minimizing overall energy consumption.
Solution Approach 2:
The energy storage element is charged in advance before the shift is needed. This preliminary energy accumulation allows the actual shift to occur rapidly using stored energy, rather than requiring continuous high-power delivery during the shift, thus improving speed while reducing energy use.
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 system enables more instantaneous and reliable gear shifting with reduced torque loss, improving shifting precision and longevity of the shifting mechanism, and can be used in various vehicle configurations with or without motor support.
Implementation Method 1
an energy storage element, such as a pre-loaded coil spring, which is configured to move the shift element quickly and reliably
Data Source
AI summary
A vehicle and a vehicle gear shift system includes a movable shift element configured to shift gears in a multispeed gear system of the vehicle; an energy source; and an energy storage element, wherein the energy source is configured to load or charge the energy storage element with potential energy, and the energy storage element is configured to move the shift element.