Bone Conduction Transducer Flux Segmentation
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Solution Overview
Problem
Conventional bone conduction headphones require high excitation power for the coil due to the high magnetic resistance of ring magnets, leading to short battery life and significant distortion in signal transmission.
Innovation Solution
The electromagnetic signal converter design includes a soft-magnetic yoke, electric coil, elastically suspended armature, and a permanent magnet where the magnetic flux is divided into at least two paths, one outside the permanent magnet, reducing the overall magnetic resistance and allowing for lower excitation power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a ring magnet is used in the conventional signal converter design, then the magnetic bias is generated, but the magnetic resistance is high requiring high excitation power
Solution Approach 1:
The magnetic flux path is segmented into two separate paths: one through the permanent magnet and another through the air gap and soft magnetic housing. This segmentation allows the coil flux to bypass the high magnetic resistance of the permanent magnet, reducing the required excitation power and extending battery life.
Solution Approach 2:
The soft magnetic housing acts as an intermediary that provides an alternative low-resistance path for the magnetic flux. By introducing this intermediate magnetic circuit element, the system reduces the overall magnetic resistance without compromising the magnetic bias generation.
2Device complexity
If the coil and permanent magnet overlap in the longitudinal direction, then the structure is compact, but the magnetic flux paths coincide causing high magnetic resistance
Solution Approach 1:
The design transitions from a longitudinal overlap arrangement to a radial arrangement where the permanent magnet is positioned at the periphery and the coil is positioned axially. This dimensional reorganization separates the magnetic flux paths while maintaining structural compactness.
3Reliability
If the coil flux must overcome the high magnetic resistance of the ring magnet, then the magnetic bias is maintained, but significant distortion occurs due to frequency doubling and suppression of weak signals
Solution Approach 1:
By segmenting the magnetic flux paths, the coil flux is divided into components that can bypass the permanent magnet's high resistance path. This reduces the nonlinear effects and signal distortion while maintaining the necessary magnetic bias for reliable operation.
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 minimizes the total magnetic resistance, extending battery life and reducing distortion by allowing for the same mechanical deflection with lower excitation power, while also using a space-saving, plate-shaped permanent magnet for improved efficiency.
Implementation Method 1
a permanent magnet which is magnetized in the direction of the longitudinal axis of the yoke in order to generate a magnetic bias of the yoke and the armature
Implementation Method 2
the electrical signals are fed to the coil, which sets the armature into vibration
Implementation Method 3
the permanent magnet and the coil do not overlap each other in the direction of the longitudinal axis of the yoke... a current-proportional force to be generated by the coil on the armature
Implementation Method 4
an elastically suspended soft magnetic armature which... is movable along the longitudinal axis of the yoke
Implementation Method 5
means are provided to divide the magnetic flux generable by the coil into at least two flux paths, one of which lies outside the permanent magnet
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to an electromagnetic signal transducer for a bone conduction hearing aid, comprising: - a soft magnetic yoke (1), - an electrical coil (2) arranged concentrically to the longitudinal axis of the yoke (1), - an elastically suspended soft magnetic armature (4) which, viewed in the direction of the longitudinal axis (5) of the yoke (1), is separated from the yoke (1) by a working air gap (8) and is movable along the longitudinal axis (5) of the yoke (1), and - a permanent magnet (9) which is magnetized in the direction of the longitudinal axis (5) of the yoke (1) in order to generate a magnetic bias of the yoke (1) and the armature (4).To reduce the excitation power for the coil, it is provided that the permanent magnet (9) and the coil (2) do not overlap each other in the direction of the longitudinal axis of the yoke (1) and means are provided to divide the magnetic flux that can be generated by the coil (2) into at least two flux paths, one of which is outside the permanent magnet (9), thereby minimizing the total magnetic resistance of the magnetic circuit as seen by the coil (2).