Molded Stator Busbar Structure to Prevent Resin Cracking

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Solution Overview

Problem

During the assembly of motors, the molded resin surface often cracks due to insufficient resin strength when an assembling tool applies pressure, as existing methods do not adequately support the resin surface.

Innovation Solution

The motor design incorporates a stator assembly with a molded resin that includes protrusions and claw portions, where the busbar is embedded in the resin, and the claw portions extend into the protrusions to enhance mechanical strength and prevent cracking, allowing for even stress distribution during assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If an assembling tool abuts against the molded resin surface to press the stator iron core into the casing, then the assembly process can be completed, but the molded resin surface will crack due to insufficient resin strength

Engineering Contradiction:

Improveassembly processVSAvoidmolded resin strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The molded resin is segmented into multiple protrusions distributed around the stator assembly. Each protrusion acts as an independent reinforcement element that locally supports the resin surface during assembly, preventing crack propagation while maintaining overall structural integrity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite structure by embedding the busbar assembly within the molded resin and adding protrusions. This composite design combines the electrical conductivity of the metal busbar with the mechanical support of the resin and protrusions, achieving both electrical function and enhanced mechanical strength

Inventive Principle:

Principle #40Composite materials

2Strength

If the molded resin is made stronger to prevent cracking, then the assembly process improves, but the resin may become too rigid and cause stress concentration

Engineering Contradiction:

Improvemolded resin strengthVSAvoidstress distribution

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

Instead of uniformly increasing the strength of the entire molded resin, the invention applies local reinforcement through protrusions at specific locations where stress concentration is most likely to occur during assembly. This localized approach strengthens the resin where needed while maintaining flexibility and stress distribution in other areas

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The protrusions are designed beforehand to provide cushioning support during the assembly process. They anticipate the stress that will be applied when the assembling tool presses the stator iron core into the casing, and are positioned to absorb and distribute this stress before it can cause cracking

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS20250007357A1Motor

Publication Date: 2025.01.02 NIDEC CORP(JP)

AI summary

A motor includes a casing including an opening portion on one axial side of an outer circumferential wall extending circumferentially around a central axis, and a bottom on the other axial side of the outer circumferential wall, and a molded stator assembly including a stator, a busbar assembly, and a molded resin. The busbar assembly includes a metal busbar and is supported on the stator. The molded resin covering the busbar assembly axially is located on one axial side of the stator and includes protrusions protruding towards the axial side, on a section perpendicular to the axial direction. The projection of the busbar and the projection of the protrusion overlap at least partially. The molded resin is filled between the busbar and the protrusion. Therefore, the strength of the protrusions is increased, which facilitates assembling the molded stator assembly.