Stator Coil Fitting Structure With Soft Plating for Low Contact Resistance
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Solution Overview
Problem
The conduction reliability between coil segments in rotary electrical machines is limited due to insufficient contact area and plating layer functionality in existing fitting portions, particularly in the in-slot connection method where micro-level projections and depressions primarily facilitate contact.
Innovation Solution
The solution involves forming a stator coil with coil segments having protrusions and recesses, where one metal layer has a lower hardness than the other, and a metal plating layer is applied to the recess surfaces to enhance contact area and reliability, with the fitting process involving press-fitting and plastic deformation of the plating layer to fill micro-level grooves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal plating layer is formed on the fitting surface of the groove portion, then the contact area and conduction reliability between coil segments are improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The invention changes the material parameter (hardness) of the plating layer relative to the protrusion material. Specifically, the plating layer is designed to have lower hardness than the protrusion material, enabling plastic deformation during fitting. This parameter change allows the softer plating layer to flow into micro-level grooves and form intimate contact with the harder protrusion surface, significantly improving contact area and conduction reliability while maintaining manufacturability through standard plating processes.
Solution Approach 2:
The invention creates a composite structure at the fitting interface by combining two different metals: the base metal of the coil segment (e.g., copper) and the plating layer (e.g., tin, nickel, or zinc). This composite material approach leverages the advantages of both materials - the high conductivity and strength of the base metal, and the lower hardness and good conformability of the plating layer - to achieve superior electrical and mechanical contact properties.
2Reliability
If the plating layer undergoes plastic deformation to fill micro-level grooves, then the contact area increases and conduction reliability improves, but the manufacturing precision requirements increase
Solution Approach 1:
The invention applies the plating layer to the groove portion before the fitting process. This preliminary action prepares the surface in advance with a material that is specifically suited for plastic deformation and intimate contact formation. The plating layer is applied with controlled thickness and uniformity, creating a pre-conditioned surface that will reliably deform during fitting to fill micro-level grooves, thereby reducing the stringency of dimensional tolerance requirements for the underlying base metal.
Solution Approach 2:
The invention changes the physical state and mechanical properties of the plating layer through material selection and heat treatment, making it softer and more deformable than the base metal. This parameter change in hardness and ductility allows the plating layer to undergo plastic deformation at relatively low fitting pressures, filling micro-level grooves effectively without requiring extremely precise fitting dimensions, thus lowering manufacturing precision requirements while improving contact quality.
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 improves the conduction reliability and mechanical fitting force between coil segments, enhancing the overall conductivity and reducing contact resistance.
Implementation Method 1
a second metal layer having a lower hardness than the first metal is formed on at least a fitting surface of the groove portion with the projecting portion... the second metal layer having a lower hardness than the first metal
Data Source
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AI summary
The conduction reliability of a fitting connection portion between a recess and a protrusion of a stator coil of a rotary electrical machine is improved. The stator coil is formed by a first coil segment 30 including a protrusion 35 at one end and a second coil segment 40 including a recess 46 at one end. A projection side surface 35b of the protrusion 35 is a metal surface of the first coil segment 30, and a metal plating layer 50 having a lower hardness than a metal of the first coil segment 30 is formed on a metal surface of an inner wall surface 46b of the recess 46. When the coil segments 30 and 40 are joined together, the metal surface of the projection side surface 35b comes into contact with the metal plating layer 50, and therefore, gaps between both projections 38a and grooves 38b and the metal plating layer 50 are closed, and the contact resistance is reduced.