Compressed Powder Compact Frustum Shape
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Solution Overview
Problem
Magnetic circuit components with soft magnetic cores experience increased eddy current loss at high frequencies, and existing methods to reduce this loss, such as using coated powders and acid treatment, are hindered by productivity issues due to friction and damage of insulating coatings during compression molding, leading to prolonged treatment times and incomplete removal of bridge portions.
Innovation Solution
A compact with a trapezoidal cross-sectional shape is developed, featuring a frustum body with a larger trapezoidal surface area compared to rectangular surfaces, which reduces friction and damage during molding, allowing for shorter post-treatment times and improved productivity by minimizing bridge portion generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If coated powder is used to reduce eddy current loss, then electrical resistance increases, but insulating coating is damaged during compression molding, generating bridge portions
Solution Approach 1:
The invention changes the geometric parameters of the compact by introducing a frustum shape with specific area ratios. The large base area to small top area ratio (greater than 0.7) creates a tapered structure that reduces contact pressure and friction during molding, thereby protecting the insulating coating while maintaining the eddy current loss reduction benefit of the coated powder
2Reliability
If post-treatment is performed to remove bridge portions, then insulating coating damage is corrected, but treatment time is prolonged and productivity is reduced
Solution Approach 1:
The invention performs preliminary protection of the insulating coating during the compression molding process itself by using the frustum shape design. This preliminary action prevents bridge portion formation at the source, eliminating or minimizing the need for subsequent post-treatment steps and thereby maintaining high productivity while ensuring coating integrity
3Force
If friction between compression-molded product and die is large, then molding force is sufficient, but insulating coating is damaged and bridge portions are generated
Solution Approach 1:
The invention introduces a curved tapered surface (frustum shape) instead of flat parallel surfaces. This curved geometry reduces the contact area and distributes the molding force more evenly, decreasing friction and preventing insulating coating damage while still achieving sufficient molding force through the tapered structure
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3~4
AI summary
A compact 10 is obtained by compression-molding coated soft magnetic particles covered with insulating coatings, and is a modified frustum body having, as a main body, a frustum portion 113 sandwiched between plate-shaped portions 111 and 112 arranged in opposing relation. A vertical cross-section of the compact 10 is made up of a trapezoidal surface 113s, a long-side rectangular surface 111s joining to a long side of the trapezoidal surface 113s, and a short-side rectangular surface 112s joining to a short side of the trapezoidal surface 113s. A surface of the compact 10 in sliding contact with a forming mold is mainly constituted by an outer peripheral surface 113o of the frustum portion 113, and the outer peripheral surface 113o is inclined relative to a direction in which a compression-molded product is drawn out from the mold. Therefore, friction between the compression-molded product and the mold can be reduced, and damage of the insulating coatings can be reduced in the compact 10. Hence the compact 10 exhibits not only good productivity due to shortening of a post-treatment time, but also a low loss.