Bicycle Hub Motor Sleeve Layout for Protected Torque Sensing

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Solution Overview

Problem

Current hub motors on bicycles face challenges in accurately sensing rider torque due to complex usage environments, leading to inconsistent performance.

Innovation Solution

A hub motor design with a torque sensor positioned on the sleeve away from the axle, protected by an outer cylinder, which prevents environmental interference and enhances sensing accuracy by using strain gauges aligned with the sleeve's circumferential direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the torque sensor is installed near the axle to sense rider torque, then the sensing function can be achieved, but water or dirt may enter the gap between the axle and sleeve and affect the sensing unit

Engineering Contradiction:

Improvetorque sensing accuracyVSAvoidenvironmental interference (water, dirt)

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The sleeve acts as an intermediary protective structure between the torque sensor and the external environment. It blocks water and dirt from entering the gap between the axle and the sensor housing, while allowing the sensing unit to remain positioned close to the axle for accurate torque measurement through the strain gauge mounted on the sleeve's outer surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The sleeve functions as a protective shell that encloses the torque sensor and sensing unit. This shell structure prevents environmental contaminants (water and dirt) from reaching the sensing components, thereby protecting the measurement system while maintaining its functionality in complex usage environments.

Inventive Principle:

Principle #30Flexible shells and thin films

2Measurement precision

If the sensing unit is positioned close to the axle for accurate torque sensing, then measurement precision improves, but the sensing unit becomes vulnerable to environmental factors

Engineering Contradiction:

Improvetorque sensing accuracyVSAvoidsensor reliability in complex environment

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The sleeve serves as a protective intermediary that shields the sensing unit from environmental damage. The strain gauge is mounted on the outer surface of the sleeve, allowing it to sense torque through the sleeve wall while remaining protected from water and dirt, thus maintaining both measurement precision and reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The design replaces direct exposure of the sensing unit to the environment with an indirect sensing mechanism. The strain gauge mounted on the sleeve outer surface detects torque through the sleeve material, substituting direct mechanical contact with protected indirect sensing, thereby improving reliability without sacrificing measurement accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If the torque sensor is protected from environmental factors, then reliability improves, but the sensing performance may be compromised

Engineering Contradiction:

Improvesensor protection from environmental factorsVSAvoidtorque sensing accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The sleeve acts as a flexible protective shell that allows strain transmission while protecting the sensing unit. The strain gauge mounted on the outer surface of this shell can detect torque-induced strains through the sleeve wall, maintaining measurement precision while providing environmental protection.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The sensing arrangement creates an asymmetric configuration where the strain gauge is positioned on the outer surface of the sleeve rather than inside. This asymmetric placement allows the gauge to sense torque through the sleeve material while remaining externally protected, resolving the contradiction between protection and sensing performance.

Inventive Principle:

Principle #4Asymmetry

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 design improves torque sensing accuracy by shielding the torque sensor from environmental factors, ensuring reliable operation and enhanced performance.

Implementation Method 1

The sensing unit is a strain gauge, and a sensing direction of the strain gauge is set along a circumferential direction of the sleeve

Methodology Applied

Scientific EffectStrain gauge measurement: Piezoresistive Effect

Data Source

PatentUS12491965B2Hub motor

Publication Date: 2025.12.09 TIEN HSIN INDS

AI summary

A hub motor includes an axle, a stator, a rotor, a casing, a sleeve, and a torque sensor. The axle is fixed to a frame of the bicycle and has a first end and a second end. The stator is fixed to the axle. The rotor is rotatably sleeved on the axle and rotates around the stator. The casing is rotatably sleeved on the axle and rotates around the rotor and the axle. The casing forms an accommodating space, a first perforation, an opening, and a side cover. The side cover closes the opening and has a second perforation. The accommodating space accommodates the stator and the rotor. The axle is arranged to pass through the casing and the side cover respectively through the first perforation and the second perforation. The sleeve is sleeved at the second end and connected to the side cover. The sleeve has an arrangement part.