Electric Compressor Stator Shrink-Fit Failure Prevention
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Solution Overview
Problem
Shrink-fitting failures occur in electric compressors due to uneven boundary between the shrink-fitting surface and mill-scale surface on the motor case, causing asymmetric contact and rotation moments that prevent proper insertion of the stator.
Innovation Solution
The introduction of enlarged-diameter portions on the inner circumference of the motor case, ensuring equal distance from the insertion surface to the opening around the circumference, reduces variations in insertion length and contact area, thereby preventing rotation moments and insertion failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the side wall thickness is increased inward to accommodate mounting portions and accommodation chambers, then the structural strength and functionality are improved, but the inner peripheral surface becomes uneven causing shrink-fitting failures
Solution Approach 1:
The invention applies local quality by creating an enlarged-diameter portion at a specific location on the inner peripheral surface of the motor case. This localized geometric modification ensures that the shrink-fitting surface maintains uniform dimensional characteristics in the axial direction, while other portions of the motor case can have varying thicknesses to accommodate mounting portions and accommodation chambers. The enlarged-diameter portion acts as a localized compensation feature that ensures reliable shrink-fitting without requiring uniform increase in overall side wall thickness.
2Productivity
If the motor case is produced by casting followed by selective machining, then productivity is improved and production costs are reduced, but the inner peripheral surface geometry becomes complex making it difficult to ensure uniform shrink-fitting dimensions
Solution Approach 1:
The invention applies preliminary action by incorporating the enlarged-diameter portion directly into the casting mold design. This allows the geometric compensation feature to be formed during the initial casting process, before any subsequent machining operations. By pre-establishing the correct dimensional relationship in the mold, the need for complex post-casting machining to achieve uniform shrink-fitting dimensions is eliminated, thereby maintaining high productivity while ensuring manufacturing precision.
3Ease of manufacture
If the inner peripheral surface is shaped with an inclination to facilitate mold removal, then ease of manufacture is improved, but the distance from the mill-scale surface to the central axis varies causing asymmetric contact during shrink-fitting
Solution Approach 1:
The invention applies local quality by creating a localized enlarged-diameter portion on the inclined inner peripheral surface. This localized modification compensates for the dimensional variations caused by the overall inclined geometry, ensuring that the shrink-fitting surface has uniform characteristics in the axial direction. The enlarged-diameter portion acts as a localized correction that maintains contact symmetry during shrink-fitting, while preserving the beneficial inclined geometry for ease of manufacture and mold removal.
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 allows for successful shrink-fitting of the stator by ensuring equal distances and reducing frictional forces, preventing insertion failures and ensuring proper positioning of the stator within the motor case.
Implementation Method 1
heating the motor case to thermally expand it and fixing the stator in the motor case more firmly due to shrinkage of the motor case when its temperature decreases
Data Source
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AI summary
To provide an electric compressor in which the occurrence of shrink-fitting failures can be prevented when a stator is shrink-fitted in a motor case. Provided are a casing (67) in which the inner circumferential surface of the cylinder is provided with a first inner circumference (101) and a second inner circumference (103) whose radius is larger than the first inner circumference (101), the inner circumference (101) having an inclination that becomes more distant from a central axis (C) from a bottom face (79) toward an opening (85); a compressing unit that compresses fluid; and a rotor and a stator that rotationally drive the compressing unit, wherein the first inner circumference (101) and the second inner circumference (103) are provided with a substantially cylindrical insertion surface (105) whose radius is larger than the second inner circumference (103) and in which the stator is inserted; and at least the first inner circumference (101) is provided with an enlarged diameter portion (109) whose radius is larger than the insertion surface (105) and which makes the distance from the end at the opening (85) side of the insertion surface (105) to the opening (85) substantially equal.