Eddy Current Reducer Spoke Geometry for Fatigue-Resistant Braking
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Solution Overview
Problem
Conventional eddy current deceleration devices do not adequately consider the bending loads in the circumferential and axial directions applied to the spokes, leading to fatigue damage and reduced durability.
Innovation Solution
The eddy current deceleration device is designed with spokes that have specific neutral axes positions when bent in both circumferential and axial directions, reducing the maximum tensile stress and thereby preventing or reducing fatigue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spoke design is used, then the structure is simple, but fatigue damage occurs due to repeated bending loads in circumferential and axial directions
Solution Approach 1:
The spoke is designed with an asymmetric transverse sectional shape where the distance from the neutral axis to the front surface in the rotating direction is made shorter than the distance to the rear surface. This asymmetric configuration reduces the maximum tensile stress that occurs at the front surface during braking, thereby preventing fatigue damage while maintaining structural simplicity
Solution Approach 2:
The neutral axis is intentionally positioned closer to the front surface in the rotating direction, creating non-uniform stress distribution that favors fatigue resistance. This local optimization of the neutral axis position addresses the specific loading conditions without requiring complex overall structural changes
2Force
If braking force is increased, then deceleration performance is improved, but bending load on spokes increases causing fatigue damage
Solution Approach 1:
By making the transverse sectional shape asymmetric with the neutral axis closer to the front surface, the design allows higher braking forces to be applied without increasing the maximum tensile stress at the critical front surface, thus enabling improved deceleration performance while maintaining spoke durability
Solution Approach 2:
The geometric parameters of the spoke cross-section are optimized to change the stress distribution characteristics, allowing the spoke to withstand higher braking forces without fatigue damage
3Object-affected harmful factors
If spoke length in axial direction is reduced, then air resistance is decreased, but bending resistance in axial direction is reduced
Solution Approach 1:
The asymmetric transverse sectional shape with optimized neutral axis position compensates for the reduced axial length by creating a more efficient stress distribution, allowing the spoke to maintain sufficient bending resistance while minimizing air resistance
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 effectively reduces fatigue damage to the spokes, improving the durability of the eddy current deceleration device while allowing for a reduction in size and weight, enabling higher braking forces and improved fuel efficiency.
Implementation Method 1
a rotor body, which is an electric conductor, rotates within magnetic fields produced by a row of magnets and thereby eddy currents are generated on the rotor body
Implementation Method 2
The eddy currents and the magnetic fields interact with each other to generate a braking force
Implementation Method 3
Joule's heat is produced in the rotor body on which eddy currents flow, and a temperature of the rotor body rises
Implementation Method 4
This causes thermal expansion of the rotor body to increase its diameter
Data Source
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AI summary
An eddy current deceleration device (100) includes a rotor (10) and a stator (20). The rotor (10) includes a hub (12), a rotor body (11), and a spoke (13). The spoke (13) has neutral axes (N1, N2). The neutral axis (N1) is a neutral axis when the spoke (13) is bent in a circumferential direction of the rotor body (11). The neutral axis (N1) is positioned forward in a rotating direction (R) of the rotor (10) with respect to a center line (C1) of the spoke (13) in the circumferential direction. The neutral axis (N2) is a neutral axis when the spoke (13) is bent in an axial direction of the rotor body (11). The neutral axis (N2) is positioned on a rotor body (11) side with respect to a center line (C2) of the spoke (13) in the axial direction.