Pedal Force Detection Mechanism with Axial Strain Sensing
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Solution Overview
Problem
Conventional pedal force detection mechanisms in electric-assisted bicycles fail to accurately and efficiently respond to variations in pedal force, leading to inadequate supply of auxiliary power when the force falls outside the sensitivity range of the torque sensing assembly.
Innovation Solution
A pedal force detection mechanism that includes a torque-transmitting member, a strain sensing assembly with a strain gauge, and a main drive gear, which unidirectionally transmits pedal force along the crankshaft's axial direction, utilizing a resilient ring-shaped base and supporting annular base to accurately sense torque variations, and a rotation sensor to determine appropriate auxiliary power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque sensing assembly is disposed outside the bushing of the bearing to sense pedal force variations, then the structure is simple and easy to manufacture, but the sensing range and sensitivity are insufficient, causing auxiliary power to be denied when pedal force falls outside the sensing range
Solution Approach 1:
The strain sensing assembly is nested within the shaft housing, with the resilient ring-shaped base positioned between the main thrust bearing and the supporting annular base. This nested configuration allows the sensing mechanism to be integrated into the existing crankshaft assembly, expanding the sensing range while maintaining structural compactness and avoiding excessive complexity
Solution Approach 2:
The invention introduces an axial dimension for force sensing by using the resilient ring-shaped base to detect axial strain caused by pedal force variations. This axial strain detection approach adds a new dimensional perspective to force sensing, expanding the sensing range beyond conventional radial torque sensing while integrating seamlessly into the existing bearing structure
2Measurement precision
If the strain gauge is disposed on the resilient ring-shaped base with axial-strain gap, then the detection resolution and accuracy are improved, but the device complexity increases due to multiple components
Solution Approach 1:
The resilient ring-shaped base serves multiple functions: it acts as a strain-sensing element, a structural support component, and a force transmission element. By making this single component multi-functional, the invention achieves high detection resolution through axial strain measurement while avoiding the need for separate sensing and structural elements, thereby reducing overall device complexity
Solution Approach 2:
The resilient ring-shaped base acts as an intermediary element between the main thrust bearing and the supporting annular base. It mediates the transmission of axial forces while providing strain information to the strain gauge, enabling high-resolution detection without requiring direct contact between the bearing and housing, thus simplifying the overall assembly
3Reliability
If the torque-transmitting member and internally-connected ring body rotate synchronously with axial-movement gap, then the mechanical durability is improved, but the ease of assembly is reduced
Solution Approach 1:
The invention employs dynamic clearance between the torque-transmitting member and the internally-connected ring body, allowing relative axial movement while maintaining synchronous rotation. This dynamic gap design improves mechanical durability by preventing binding and reducing stress concentrations, while the clear separation of components actually facilitates assembly by allowing independent positioning of each element
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 mechanism provides precise detection of pedal force, enabling efficient and accurate supply of auxiliary power, with a larger sensing range and higher resolution than conventional systems, and ensures mechanical durability and ease of assembly.
Implementation Method 1
a strain sensing assembly having a strain gauge, a resilient ring-shaped base and a supporting annular base
Data Source
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AI summary
A pedal force detection mechanism for an electric-assisted bicycle includes a torque-transmitting member (1), a main thrust bearing (13), a strain sensing assembly (14), and a main drive gear (21). The torque-transmitting member (1) transmits and diverts a torque along a crankshaft's axial direction. The main thrust bearing (13) abuts against the torque-transmitting member (1) to transmit the diverted torque. The strain sensing assembly (14) has a strain gauge (16), resilient ring-shaped base (15), and supporting annular base (17). The supporting annular base (17) abuts against a shaft housing (5). An axial-strain gap (6) is defined between the supporting annular base (17) and the main thrust bearing (13). The resilient ring-shaped base (15) is fitted between the main thrust bearing (13) and the supporting annular base (17). A main gear (211) and an internally-connected ring body (210) of the main drive gear (21) are integrally formed with each other. An axial-movement gap (7) is defined between the torque-transmitting member (1) and the internally-connected ring body (210).