Nd-Fe-B Multilayer Sintered Magnet for Low Eddy Current Loss
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Solution Overview
Problem
The existing methods for producing Nd—Fe—B sintered magnets for electric vehicle and hybrid electric vehicle motors are costly due to the need for machining thick magnets into thin layers, which results in high processing costs and inefficient reduction of eddy current loss, and the use of heavy rare earth elements like Dy and Tb is resource-intensive and expensive.
Innovation Solution
A method involving the PressLess Process (PLP) or New-PressLess Process (NPLP) to produce ultra-thin Nd—Fe—B multilayer sintered magnets with a high degree of orientation, where the c-axis direction of the Nd2Fe14B tetragonal compound is oriented within the main surface of the magnet without machining, and the magnets are laminated using an adhesive or hot press compression bonding, with optional grain boundary diffusion treatment to enhance coercive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth elements (Dy, Tb) are added to increase coercive force, then coercive force is improved, but saturation magnetization and maximum energy product are lowered, and resource cost increases
Solution Approach 1:
The patent applies grain boundary diffusion to create a localized concentration of heavy rare earth elements at the grain boundaries of the Nd-Fe-B magnet. This local enrichment of Dy or Tb at the grain boundaries provides the necessary coercive force enhancement without requiring bulk addition of these expensive elements, thereby preserving the overall saturation magnetization and maximum energy product of the magnet.
Solution Approach 2:
The patent uses grain boundary phases as an intermediary medium to transport and concentrate heavy rare earth elements. By diffusing Dy or Tb through the grain boundary phase during heat treatment, the elements are selectively positioned at critical locations (grain boundaries) where they most effectively enhance coercive force, rather than being uniformly distributed throughout the magnet.
2Loss of energy
If thick Nd—Fe—B magnets are machined into thin layers, then eddy current loss is reduced, but processing cost and manufacturing complexity increase
Solution Approach 1:
The patent segments the magnet into multiple thin layers during the sintering process itself, rather than machining a thick magnet into thin layers afterward. By stacking multiple thin green compacts and sintering them together, the final product is naturally formed as a multilayer thin magnet, achieving low eddy current loss without subsequent machining operations.
Solution Approach 2:
The patent performs the lamination and thinning operations preliminarily, before the final sintering step. Multiple thin green compacts are stacked and bonded together in the desired configuration before sintering, so that the thin-layer structure is already established before the magnet reaches its final hardened state, eliminating the need for post-sintering machining.
3Loss of energy
If the thickness of unit magnet is reduced to reduce eddy current loss, then energy loss is reduced, but manufacturing difficulty and cost increase
Solution Approach 1:
The patent combines multiple manufacturing operations into a single integrated process. The stacking of thin green compacts, their bonding together, and the subsequent sintering are all performed in sequence as part of one continuous manufacturing process, rather than as separate operations. This integration simplifies the overall manufacturing complexity despite producing thin-layer magnets.
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 approach allows for the industrial production of multilayer magnets with uniform magnetic properties and reduced eddy current loss at lower costs, eliminating the need for expensive machining and minimizing the use of expensive rare earth elements, while achieving high coercive force and magnetic uniformity.
Implementation Method 1
applying a magnetic field in a direction parallel to a main surface of a cavity partitioned by the partition plates to orient the alloy powder
Implementation Method 2
performing sintering to produce a Nd—Fe—B thin plate-shaped sintered magnet
Implementation Method 3
a surface layer containing a large amount of Nd generated during the production of the unit magnet
Implementation Method 4
grain boundary diffusion treatment to enhance coercive force
Data Source
AI summary
The present invention provides: a Nd—Fe—B multilayer sintered magnet which is magnetically uniform, while having high magnetic characteristics; and a method for producing the Nd—Fe—B sintered magnet without performing a cutting step. The method of the present invention comprises the steps of: producing a Nd—Fe—B thin plate-shaped sintered magnet in which the c-axis direction of an Nd2Fe14B tetragonal compound is oriented within the main surface of the Nd—Fe—B thin plate-shaped sintered magnet, and which has a high degree of orientation of 90% or more and a thickness of 3 mm or less, without performing a cutting step, by supplying and filling an alloy powder into a mold having a structure partitioned by a plurality of partition plates arranged at a predetermined interval, applying a magnetic field in a direction parallel to a main surface of a cavity partitioned by the partition plates to orient the alloy powder, and then performing sintering, and laminating a plurality of Nd—Fe—B thin plate-shaped sintered magnets obtained by the above step.