Armature Cross-Section Design for Electromechanical Transducer Driving Force
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Solution Overview
Problem
Conventional electromechanical transducers face challenges in achieving a large driving force relative to input power while maintaining excellent magnetic characteristics and reliability, due to the difficulty in setting the stiffness of the armature to match the negative stiffness near the balanced position, where magnetic forces change non-linearly with displacement.
Innovation Solution
The design incorporates an armature with a shape where the cross-sectional area is smaller at a predetermined position between magnetic flux regions, allowing magnetic flux saturation within the range of displacement, and utilizes first and second elastic units to provide restoring forces, ensuring the armature is displaced by magnetic forces and returned by spring forces, thus increasing driving force efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stiffness of the armature is increased to prevent attraction to magnets, then reliability is improved, but driving force relative to input power decreases
Solution Approach 1:
The armature is designed with non-uniform cross-sectional area, featuring a narrower portion at the center and wider portions at the ends. This local variation in geometry allows different regions to serve different functions: the narrower central region provides magnetic flux saturation to limit magnetic force changes, while the wider end regions maintain sufficient structural stiffness. This resolves the contradiction by allowing the armature to be stiff enough for reliability while limiting magnetic force variations to improve driving force efficiency.
2Force
If the cross-sectional area of the armature is increased to increase magnetic force, then driving force is improved, but magnetic flux saturation cannot be achieved within displacement range
Solution Approach 1:
The armature employs localized cross-sectional area variation with a narrower central portion and wider end portions. The narrower central region creates magnetic flux saturation within the operational displacement range, which limits the change in magnetic force to approximately 5% or less. This ensures that the magnetic force remains relatively constant, improving the ratio of driving force to input power while still providing sufficient total magnetic force through the wider end regions.
3Ease of manufacture
If the armature is designed with uniform cross-section for ease of manufacture, then ease of manufacture is improved, but magnetic characteristics and driving force efficiency deteriorate
Solution Approach 1:
The armature features a specific non-uniform cross-sectional profile with a narrower central portion and wider end portions. While this requires more complex manufacturing than a uniform cross-section, the invention provides clear geometric specifications that enable practical fabrication. The manufacturing complexity is justified by the significant improvement in driving force efficiency achieved through magnetic flux saturation in the narrower region, which limits magnetic force variations and improves power conversion efficiency.
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 configuration enables a significant increase in driving force relative to input power while maintaining reliable magnetic characteristics, allowing for a larger driving force with improved shock resistance and ease of processing.
Implementation Method 1
an electromechanical transducer that comprises a driving unit including an armature, a yoke, a coil, magnets and any other member... configured to drive the armature in response to an electric signal supplied to the coil so that relative vibration between the armature and other members is transduced into mechanical vibration or sound
Implementation Method 2
The restoring force is given by elastic force of the armature itself in the case of the Patent Reference 1 while it is given by elastic force of the spring members in the case of the Patent Reference 2
Implementation Method 3
the armature has a shape in which a cross-sectional area at a predetermined position between the two regions is smaller than a cross-sectional area at the two regions, and magnetic flux flowing in the first direction in the armature is saturated within a range of displacement of the armature
Data Source
AI summary
An electromechanical transducer of the invention comprises a structural unit, an armature, and the first and second elastic units. The structural unit includes magnets, a yoke and a coil. The armature includes an inner portion disposed to pass through inside the structural unit and two outer portions protruding from the inner portion in a first direction, and the armature constitutes a magnetic circuit with the structural unit via two regions through which components of the magnetic flux flow in reverse directions in the inner region. The elastic units give restoring forces to the outer portions in response to displacement of the armature due to magnetic forces of the magnetic circuit. In the armature, a cross-sectional area at a predetermined position between the two regions is smaller than that at the two regions, and magnetic flux flowing in the first direction within a range of displacement of the armature.