Soft Magnetic Yoke Drawing Process for Moving-Iron Microphones
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Solution Overview
Problem
Conventional magnetic yokes for moving-iron microphones/transducers have complex and costly manufacturing processes, leading to structural defects such as heat damage and air gaps that reduce magnetic permeability, limiting their performance and competitive advantage.
Innovation Solution
A frame-shaped soft magnetic yoke is manufactured using a drawing and cutting process for metal tubes, ensuring a single-piece configuration with uniform edges and chamfered bends, connected via resistance, laser, or ultrasonic welding, and made from high-permeability materials like soft iron or Permalloy, optimizing the magnetic circuit and mechanical assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lamination method with resistance welding is used to manufacture magnetic yoke, then manufacturing process can be completed, but heat from resistance welding damages internal magnetic structure and reduces magnetic permeability
Solution Approach 1:
The patent removes the harmful resistance welding step from the manufacturing process. Instead of laminating sheets and welding them, the invention uses a single-piece soft magnetic material that is directly formed into the yoke shape, extracting the source of heat damage and magnetic structure degradation.
Solution Approach 2:
The patent combines multiple manufacturing steps (forming sheets, laminating, welding) into a single forming operation. The soft magnetic material is directly formed into the complete yoke structure with integrated magnetic circuit, eliminating the need for assembly and welding operations.
2Ease of manufacture
If casting method with powder metallurgy is used to manufacture magnetic yoke, then manufacturing process can be completed, but dense air gaps are formed and damage internal magnetic structure reducing magnetic permeability
Solution Approach 1:
The patent replaces the complex casting mold system with a simpler forming process using soft magnetic material that can be directly shaped. This eliminates the need for expensive and complex casting molds while achieving better magnetic properties.
Solution Approach 2:
The patent changes the material state from powdered metal (casting) to soft magnetic material (forming). This parameter change from powder metallurgy to material forming eliminates air gap formation and produces a dense, continuous magnetic structure with superior permeability.
3Ease of manufacture
If conventional lamination or casting methods are used, then magnetic yokes can be manufactured, but manufacturing cost is high and process variation is large
Solution Approach 1:
The patent segments the manufacturing process into a single forming operation rather than multiple steps (laminating + welding or molding + casting). This simplification reduces process variation and improves consistency while lowering manufacturing costs.
Solution Approach 2:
The patent replaces the mechanical lamination and welding system or the powder metallurgy casting system with a direct forming process. This substitution eliminates complex mechanical assembly steps and reduces process complexity, leading to lower costs and better consistency.
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 method simplifies the manufacturing process, reduces costs, protects the internal magnetic structure, and enhances the performance of microphones/transducers by ensuring material integrity and magnetic permeability, allowing for various configurations and edge thicknesses as thin as 0.02 mm.
Implementation Method 1
the soft magnet having two end surfaces, whereby the inner through hole extends from one of the end surfaces to the other end surface and an outer peripheral surface between the two end surfaces
Implementation Method 2
said soft magnet with the inner through hole was formed as a single piece by drawing a soft magnetic material adapted for manufacture of the magnetic yoke
Implementation Method 3
the inner through hole of the soft magnet is connected with the magnetic piece of the moving-iron microphone/transducer by laser welding
Implementation Method 4
the outer peripheral surface of the soft magnet is connected with the armature of the moving-iron microphone/transducer by resistance welding, laser welding, or ultrasonic welding
Data Source
Figure 1~3
Figure 4~6
AI summary
The invention provides a magnetic yoke used for a moving-iron microphone/transducer comprising soft magnet in shape of a frame having an inner through hole. The soft magnet has two end surfaces from one of which to the other extends the inner through hole and an outer peripheral surface which extends around the inner through hole. The soft magnet is one-piece configured. The invention also provides a method for manufacturing the above magnetic yoke comprising drawing a soft magnetic material adapted for manufacture of the magnetic yoke to form a soft magnetic tube with an inner through hole by adopting drawing process for metal tube; and cutting the soft magnetic tube along a direction perpendicular to a length direction of the inner through hole in terms of a desired size of the magnetic yoke, to obtain the soft magnet of the magnetic yoke. As compared with the conventional magnetic yokes, the magnetic yoke of the invention has simpler structure and lower manufacturing cost. The magnetic circuit is greatly improved due to a novel manufacturing process. Additionally, the magnetic yoke can be made in various shapes and thus can be used in many occasions. Thus the invention has good application prospect.