Electric Motor Stator Bobbin Positioning to Prevent Flux Looping
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Solution Overview
Problem
The existing electric motors for electric bicycles face challenges in providing significant torque while minimizing weight and bulk, particularly due to the wide tolerance in the axial dimension of stators with separate teeth, which can lead to improper bobbin placement and motor malfunction.
Innovation Solution
A stator design with a cylindrical central part having radial teeth and openings, and bobbins with positioning pins that fit into these openings to ensure precise axial positioning, combined with a manufacturing method involving sheet-metal lamination stacking and winding, to maintain the magnetic flux and prevent magnetic flux looping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If stators with separate teeth are used to maximize winding space, then the available space for coils is improved, but the axial positioning precision of bobbins deteriorates due to wide tolerance in stacking sheet-metal laminations
Solution Approach 1:
A positioning pin is introduced as an intermediary element between the bobbin and the star. The positioning pin fits into a corresponding opening in the star, providing a mechanical reference that ensures precise axial positioning of the bobbin relative to the star, thereby compensating for the wide tolerance inherent in stacking sheet-metal laminations.
Solution Approach 2:
The invention changes the positioning parameter from direct contact between bobbin and star to indirect positioning via the positioning pin. This allows the axial position to be controlled with higher precision by the pin-opening interface rather than relying solely on the cumulative tolerance of stacked laminations.
2Ease of manufacture
If sheet-metal laminations are stacked to form the star and yoke, then the manufacturing flexibility and assembly are improved, but the axial dimension tolerance of the stator increases
Solution Approach 1:
The positioning pin acts as a mediator that decouples the tolerance accumulation from the final axial positioning. While the laminations can still be stacked with flexible tolerance for ease of manufacture, the positioning pin provides a localized reference point that ensures the bobbin is positioned with the required precision regardless of the overall stator tolerance.
3Strength
If the star wall between teeth is solid to maintain structural integrity, then the mechanical strength is improved, but magnetic flux looping occurs which reduces motor performance
Solution Approach 1:
Openings are created in the star wall between the teeth by extracting material from the solid structure. These openings interrupt the potential path for magnetic flux looping through the star wall, thereby preventing the harmful magnetic flux circulation that would reduce motor performance, while the overall structural integrity is maintained through the remaining material and the positioning pin mechanism.
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
This design ensures accurate bobbin placement, maintains magnetic flux, and enhances the performance of electric motors by reducing the risk of malfunction and improving torque delivery while minimizing weight and bulk.
Implementation Method 1
the positioning pin being configured to be positioned in an associated opening of the star so as to position the bobbin relative to the star in the axial direction
Implementation Method 2
the openings formed in the central part of the star are configured to allow and encourage circulation of the magnetic field formed by the permanent magnets of the rotor
Implementation Method 3
The openings are formed in particular so as to prevent looping of the magnetic flux originating from the permanent magnets of the rotor that is intended to be positioned at the center of the stator
Implementation Method 4
the bobbins configured firstly to receive turns of a winding wire in order to form a coil
Data Source
AI summary
A stator for an electric motor is disclosed. The stator includes a star including a cylindrical central part around which a plurality of teeth extend radially, and a plurality of bobbins configured firstly to receive turns of a winding wire in order to form a coil, and secondly to be positioned around the respective teeth of the star. The star includes a plurality of openings formed in the central part thereof between the teeth. The bobbins include a positioning pin arranged on an inner radial part of the bobbin. When the bobbin is mounted on the star, the positioning pin is configured to be positioned in an associated opening of the star so as to position the bobbin relative to the star in the axial direction.