Coreless Wheel Hub Motor Layout for Lower Loss and Longer Bearing Life
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Solution Overview
Problem
Conventional wheel hub motors for electric bicycles face issues such as increased weight and iron loss due to iron cores, which lead to noise and heat generation, and bearing degradation due to magnetic fields. Additionally, complex wiring is required for power and signal transmission, making installation inconvenient.
Innovation Solution
A wheel hub motor design featuring a coreless stator set and a unique bearing mounting configuration that reduces the bearing's exposure to magnetic forces, combined with a simplified power transmission system using a single power cable capable of transmitting both power and signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an iron core is used in the winding set, then the motor structure is more conventional and easier to manufacture, but the weight increases and iron loss occurs causing noise and heat generation
Solution Approach 1:
The patent removes the iron core from the winding set, transitioning from a conventional iron-core motor structure to a coreless motor structure. This extraction eliminates the source of iron loss and associated noise and heat, while also reducing the rotor weight. The coreless winding set is directly mounted on the rotor without an iron core, fundamentally changing the motor's internal structure to resolve the contradiction between manufacturing ease and weight/loss reduction.
2Shape
If bearings are disposed adjacent to rotor ends, then the motor structure is compact, but the bearings are subjected to magnetic fields causing friction and reduced service life
Solution Approach 1:
The patent repositions the bearings from the traditional axial location (at rotor ends) to a radial location (at the center of the rotor). This dimensional change in bearing placement removes the bearings from the magnetic field region between the stator and rotor, eliminating magnetic field interference and friction caused by magnetic forces. The radial positioning at the rotor center creates spatial separation between the bearings and the magnetic field, thereby extending bearing service life while maintaining motor compactness through optimized space utilization.
3Reliability
If dedicated power cables are used for each component, then power and signal transmission are reliable, but the wiring becomes complicated and installation is inconvenient
Solution Approach 1:
The patent merges multiple dedicated power and signal cables into a single integrated cable assembly. Instead of using separate cables for power transmission and signal communication between components (battery, dashboard, wheel hub motor), the invention combines all these functions into one cable, thereby reducing wiring complexity and making installation more convenient while maintaining reliable power and signal transmission through proper cable design and routing.
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 coreless stator set reduces weight and iron loss, while the optimized bearing configuration increases the service life of the bearings. The simplified power transmission system reduces wiring complexity and makes installation easier.
Implementation Method 1
The coreless stator set is disposed between the rotor sets such that, when the coreless stator set is energized, the rotor sets rotate about the central shaft
Data Source
AI summary
A wheel hub motor includes a shaft, a stator unit and a rotating unit. The stator unit includes a coreless stator set. The rotating unit includes a rotating seat set sleeved on the shaft, a bearing set, and two rotor sets fixedly mounted to the rotating seat set. The rotating seat set defines a bearing mounting space adjacent to the shaft and receiving the bearing set therein, and a rotor space radially spaced apart from the bearing mounting space and receiving the rotor sets therein. The coreless stator set is disposed between the rotor sets such that, when being energized to generate a magnetic field, the rotor sets rotate about the shaft so as to drive the rotating seat set and the bearing set to rotate.