Insulation Sheet Composition for Stator Coil Gap Filling
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Solution Overview
Problem
Conventional insulation methods for rotary electric machines face challenges in ensuring sufficient insulation varnish permeation, leading to inadequate coil fixation, reduced thermal dissipation, and compromised NVH properties due to air spaces and insufficient adhesion, which affects the long-term reliability and performance of the machines.
Innovation Solution
An insulation sheet with a thermosetting resin composition comprising a solid and liquid resin, a latent curing agent, and inorganic filler is used, which is applied to both surfaces of a base material and cured to flow and permeate narrow spaces, ensuring effective insulation and fixation between the stator coil and core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulation varnish is used to fix the coil to the stator core, then coil fixation is achieved, but the varnish does not sufficiently permeate the narrow gaps between the coil and slot inner wall, resulting in poor insulation reliability
Solution Approach 1:
The patent changes the physical state parameter of the resin from liquid (varnish) to solid (thermosetting resin composition) that can flow at heating temperature. This allows the resin to permeate narrow gaps during heating while maintaining structural integrity after curing, resolving the contradiction between permeation capability and fixation strength.
Solution Approach 2:
The patent uses a composite material consisting of solid thermosetting resin composition combined with inorganic filler particles. This composite structure provides both the flowability needed for gap permeation and the mechanical strength required for reliable fixation, addressing the limitations of conventional liquid varnish alone.
2Ease of manufacture
If low-viscosity varnish is used to improve permeability, then the varnish can permeate narrow gaps, but much of the varnish leaks out to the end surface of the core portion, resulting in insufficient adhesion inside the coil
Solution Approach 1:
The patent changes the viscosity parameter by using a solid thermosetting resin composition that exhibits flow behavior only at elevated temperatures. At room temperature, the resin maintains high viscosity to prevent leakage, while at curing temperature, it becomes fluid enough to permeate gaps effectively, thus resolving the contradiction between permeability and adhesion retention.
3Reliability
If the thickness of the insulation sheet is increased to ensure complete gap filling, then insulation performance improves, but the total thickness may exceed the gap dimension, making coil insertion difficult
Solution Approach 1:
The patent applies the dynamics principle by using a resin composition that transitions from solid to fluid state during heating. The insulation sheet is inserted in its flexible solid state, then the resin flows during heating to completely fill the gap, achieving both easy insertion and complete gap filling without increasing the initial sheet thickness.
4Strength
If thermosetting resin in semi-cured state is used to fill gaps, then fixation is achieved, but flexibility and fluidity properties are not sufficient to flow at heating temperature and permeate narrow spaces
Solution Approach 1:
The patent optimizes the curing degree parameter of the thermosetting resin composition to maintain a balance between structural integrity and flow capability. The resin is formulated to remain sufficiently fluid at heating temperature to permeate narrow spaces, while still providing adequate fixation strength, resolving the contradiction between these two properties.
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
The solution enhances insulation reliability, thermal dissipation, and vibration resistance, enabling size reduction and output increase in rotary electric machines by ensuring complete gap filling and efficient heat dissipation while maintaining mechanical strength and NVH performance.
Implementation Method 1
an insulation resin layer made of a thermosetting resin composition in an uncured or semi-cured state is formed on one or each of both surfaces of the base material
Implementation Method 2
a latent curing agent that is unreactive at 60° C. or lower
Data Source
AI summary
In the insulation sheet, an insulation resin layer made of a thermosetting resin composition in an uncured or semi-cured state is formed on one or each of both surfaces of the base material. The thermosetting resin composition contains: a thermosetting resin (A) that is in solid form at 25° C.; a thermosetting resin (B) that is in liquid form at 25° C.; a latent curing agent that is unreactive at 60° C. or lower; and an inorganic filler having a maximum particle diameter smaller than a film thickness of the insulation resin layer and having an average particle diameter smaller than 0.5 times the film thickness. The insulation resin layer of the insulation sheet is efficiently compressed into a predetermined thickness by pressure application at normal temperature and permeates a gap between a stator core and a stator coil by heating during curing treatment, whereby both members can be insulated and fixed.