Electric Motor Switching Element Routing Through Air Gap
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Solution Overview
Problem
Existing electric motors in power tools face challenges in reducing the thread size while maintaining performance and cooling efficiency, as the geometry of the stator and rotor must be adapted for different tools, leading to increased production costs and potential disruption of air flow.
Innovation Solution
The electric motor design incorporates a switching element that extends through the air gap between the stator and rotor, with a circular curvature matching the rotor's outer circumference, allowing for a compact structure that reduces the motor housing circumference and maintains adequate cooling without adapting the stator or rotor geometry, thus minimizing thread size and flow losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a switch rod is guided inside the housing past the electric motor into the rear area, then the switching function is achieved, but the housing must surround the switch rod and air gap, increasing the thread size
Solution Approach 1:
The switching element is routed through the air gap between stator and rotor (radial dimension) rather than through the housing (axial dimension), utilizing the existing three-dimensional space within the motor assembly to achieve the switching function without increasing the external housing dimensions
Solution Approach 2:
The switching element is nested within the existing motor structure, passing through the air gap space that already exists between the stator and rotor, thereby utilizing existing internal space rather than adding external volume
2Adaptability or versatility
If the stator geometry is adapted to accommodate switching components, then the switching rod can be integrated, but production costs increase due to small quantity production
Solution Approach 1:
The switching element is designed as a universal component that can be integrated into standard motor designs without requiring custom stator geometries, allowing the same stator design to be used across multiple power tool applications while accommodating the switching function
Solution Approach 2:
The switching element is extracted as a separate, independent component rather than being integrated into the stator structure, allowing standard stators to be used while adding switching functionality through a separate element that passes through the air gap
3Area of stationary object
If the switching element extends through the air gap, then the thread size is reduced, but air flow for cooling may be disrupted
Solution Approach 1:
The switching element is given a circular cross-section that matches the curvature of the air gap between stator and rotor, allowing it to follow the natural flow paths and minimize disruption to the cooling air flow compared to straight or angular designs
Solution Approach 2:
The switching element has different geometries at different locations - a circular cross-section in the air gap region to maintain flow, and flat ends for switching contact - optimizing both cooling efficiency and switching function at different locations of the same component
4Loss of energy
If the switching element has a circular curvature matching the rotor, then flow losses are minimized, but manufacturing complexity increases
Solution Approach 1:
The switching element features a circular cross-section in the air gap region that matches the curvature of the rotor and stator, minimizing flow separation and turbulence. This curved geometry can be efficiently manufactured using standard machining or molding processes, making the increased complexity manageable
Solution Approach 2:
The switching element can be manufactured in segments or as a simple rod that is then bent or shaped, breaking down the complex curved geometry into simpler manufacturing steps that reduce overall manufacturing complexity while maintaining the beneficial circular curvature
Data Source
Figure 1~2
Figure 3~4
Figure 5A~6
AI summary
The motor (20) has a rotor rotating around a longitudinal axis (L). A stator partially encloses the rotor, and an air gap is formed between an inner circumferential surface of the stator and an outer circumferential surface of the rotor. A switch slider activates the motor and includes a switching element e.g. switching rod (30), which acts with an on-off switch e.g. push button switch (28), of the motor, and is displaceably arranged relative to the switching element. The switching element extends through the air gap between the rotor and the stator along the axis. An independent claim is also included for an electric machine tool.