Motor Case Rib Layout for Cooling and Shrink-Fit Stress
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Solution Overview
Problem
Existing motor cases experience stress concentration and non-uniform shrink-fitting stress due to protrusions, particularly around cooling water inlets and outlets, which affects rigidity and cooling performance.
Innovation Solution
A motor case design with cooling ribs and reinforcing ribs on the inner case circumferential surface, where reinforcing ribs are lower in height than cooling ribs, distributed across the upstream and downstream portions of the cooling flow path, reducing thickness differences and stress concentration while enhancing cooling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the number of protrusions (cooling ribs) is increased to improve cooling performance, then cooling performance is improved, but stress concentration in the inner case becomes stronger
Solution Approach 1:
The patent applies local quality by differentiating the height of ribs in different locations. Cooling ribs have a first height optimized for heat dissipation, while reinforcing ribs at critical stress locations (inlet/outlet portions) have a second height that is different from the first height. This local differentiation allows the structure to simultaneously achieve effective cooling and stress concentration mitigation at specific critical locations.
2Temperature
If protrusions are provided on the inner case to form cooling flow paths, then cooling performance is improved, but thickness difference occurs in the case leading to non-uniform shrink-fitting stress
Solution Approach 1:
The patent implements local quality by providing reinforcing ribs with a second height at specific locations (inlet and outlet portions of cooling water) that differ from the first height of cooling ribs. This localized structural modification compensates for thickness differences caused by cooling ribs, ensuring more uniform shrink-fitting stress distribution while preserving cooling effectiveness.
Solution Approach 2:
The patent employs asymmetry by creating ribs with two different heights rather than uniform height throughout. The cooling ribs and reinforcing ribs have asymmetric height relationships, with the reinforcing ribs being specifically designed with a different height to counteract stress concentration at critical locations, thereby achieving symmetric stress distribution despite asymmetric rib heights.
3Strength
If protrusions are not provided around inlet and outlet of cooling water, then stress concentration is reduced, but cooling performance deteriorates
Solution Approach 1:
The patent applies local quality by selectively providing reinforcing ribs with a second height at the inlet and outlet portions where cooling ribs would otherwise be absent. This localized intervention maintains stress reduction benefits while restoring cooling performance at critical heat generation zones near the inlet and outlet areas.
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 design alleviates stress concentration, maintains rigidity, and improves cooling performance by ensuring uniform flow and increased contact area with cooling water, even with increased rib density.
Implementation Method 1
a stator of a motor is shrink-fitted inside the inner case
Data Source
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AI summary
A motor case (10) includes an inner case (21) in which a stator (32) of the motor (31) is shrink-fitted, and an outer case (11) in which the inner case is accommodated. A plurality of cooling ribs (22) are provided on an outer circumferential surface of the inner case. A cooling flow path (51) is formed between the inner case and the outer case. At an upstream portion and a downstream portion of the cooling flow path, a plurality of reinforcing ribs (26) with a height lower than a height of the cooling ribs are provided on the outer circumferential surface of the inner case instead of the plurality of cooling ribs.