Stator Resin Voids: Communication Grooves and Retention Parts
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Solution Overview
Problem
In three-phase rotary electric machines, voids form due to residual air trapped during resin injection, especially in the upper portion of the stator core, and resin can flow out through communication grooves intended for air discharge, leading to foreign substances and reduced structural integrity.
Innovation Solution
A three-phase rotary electric machine design featuring a three-phase terminal fixing member with communication grooves that allow air discharge while incorporating a hindrance structure, such as retention parts or protrusions, to prevent resin from flowing out, thereby suppressing void formation and resin leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If communication grooves are formed to discharge residual air to the outside, then void formation is suppressed, but resin flows to the outside forming foreign substances
Solution Approach 1:
The communication groove is designed with varying cross-sectional areas along its length. The first communication groove has a larger cross-sectional area at the air discharge end than at the resin injection end, creating a flow resistance that allows air to escape while preventing resin from flowing outward. This local variation in groove geometry resolves the contradiction by providing different flow characteristics for air and resin at different positions.
Solution Approach 2:
The communication groove geometry is pre-designed to create a flow resistance barrier before resin can potentially leak outward. By configuring the groove with a larger cross-section at the discharge end, the structure proactively prevents resin leakage while maintaining air discharge capability, rather than attempting to address leakage after it occurs.
2Stability of the object's composition
If through-holes are provided for rivet pins to integrate the stator core, then residual air can be discharged, but the through-holes are closed when the upper portion is filled with resin, making it difficult to discharge air
Solution Approach 1:
The communication groove is divided into multiple sections with different cross-sectional areas. The groove is segmented along its length such that the first section (near air discharge) has a larger area while the second section (near resin injection) has a smaller area. This segmentation allows the groove to perform multiple functions: maintaining structural integrity like a through-hole while providing adequate air discharge path.
Solution Approach 2:
Different sections of the communication groove have different geometric properties tailored to specific functions. The larger cross-sectional area at the air discharge end facilitates air escape, while the smaller cross-sectional area near the resin injection end provides structural support and prevents resin leakage. This local differentiation resolves the contradiction between structural integration and air discharge.
3Manufacturing precision
If resin is injected from the lower portion side to reduce void formation, then residual air can be discharged via through-holes, but the through-holes close when the upper portion is filled, preventing air discharge
Solution Approach 1:
The communication groove design creates a dynamic flow resistance that adapts to the injection process. During resin injection, the pressure differential naturally causes air to rise and escape through the groove, while the groove's geometry (larger area at discharge end) ensures that once resin reaches the groove, its flow is restricted. This dynamic behavior resolves the contradiction between enabling air discharge during injection and preventing resin leakage.
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
Effectively discharges residual air to prevent voids and retains resin within the structure, enhancing the machine's integrity and reducing foreign substances, thus improving the manufacturing process.
Implementation Method 1
at least one communication groove for communicating an inner circumferential side with an outer circumferential side of the stator core is formed at the fixing member contact part... residual air can be discharged to the outside when the resin is injected
Implementation Method 2
a hindrance structure for hindering the resin from flowing to the outside is formed in the communication groove
Implementation Method 3
the hindrance structure may also be formed as a retention part that retains the resin by widening a portion of the communication groove. Resin tends to expand when its pressure is released, hence when the resin arrives at the retention part, its pressure is released to a certain extent so that it expands and is retained
Data Source
AI summary
Communication grooves for communicating an outer circumferential side with an inner circumferential side of a stator core are formed at a contact face, that contacts the stator core, of a three-phase terminal fixing member. Furthermore, a retention part deeper than the communication grooves is formed. When resin is injected, air between the stator core and a stationary mold and between the stator core and a movable mold is discharged to the outside through the communication grooves, and thus it is possible to suppress formation of voids between the stator core and the stationary mold and between the stator core and the movable mold. In addition, the resin expands by releasing its pressure at the retention part, and thus it is possible to suppress the resin from flowing to the outside through the communication grooves.