Motor Frame Structure With Stress Relief Grooves for Lower Cogging Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor frames with rectangular outer shapes are difficult to attach to external members and are susceptible to non-uniformity in wall thickness, leading to increased cogging torque due to uneven stress distribution.
Innovation Solution
A motor frame with a cylindrical body featuring stress relief grooves and uniform thickness distribution, allowing easy attachment to external members and reducing cogging torque by uniformizing stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rectangular outer shape frame is used, then it is easy to manufacture with uniform thickness, but it is difficult to attach to external members and causes non-uniform stress distribution
Solution Approach 1:
The patent applies curvature by changing the frame's outer shape from rectangular to cylindrical. The cylindrical shape with rounded outer surface eliminates the stress concentration issues of rectangular corners and provides smooth stress distribution throughout the structure, while maintaining manufacturability through standard cylindrical forming processes.
2Ease of manufacture
If a rectangular outer shape frame is used, then it is easy to manufacture, but the non-uniform wall thickness causes increased cogging torque
Solution Approach 1:
The cylindrical outer shape ensures uniform wall thickness distribution around the stator core, eliminating the non-uniform stress fields that cause cogging torque. The curved geometry naturally provides equidistant thickness from the center axis, preventing magnetic circuit distortion.
Solution Approach 2:
The patent introduces local quality variations through protrusions and recesses on the cylindrical outer surface. These localized features provide attachment functionality without affecting the overall uniform thickness of the frame wall, allowing differentiation between structural integrity requirements and attachment requirements.
3Object-generated harmful factors
If stress relief grooves are added to the cylindrical frame, then cogging torque is reduced, but the device complexity increases
Solution Approach 1:
Stress relief grooves are introduced as localized features at specific positions on the cylindrical frame where stress concentration occurs. These grooves are strategically placed to relieve stress without requiring comprehensive modification of the entire frame structure, thus minimizing the increase in device complexity while effectively reducing cogging torque.
Solution Approach 2:
The frame is segmented into regions with and without stress relief grooves. The grooves are applied selectively at critical stress points rather than uniformly throughout, dividing the frame into functional zones that address stress concentration locally while maintaining overall structural simplicity.
Data Source
AI summary
The motor frame is easily attached to an external member, and the influence of non-uniformity in the circumferential direction is suppressed. Motor frame (3) includes cylindrical body (30) penetrating in a direction in which a shaft center of a rotating shaft of a motor inserted inside the cylindrical body extends. Cylindrical body (30) has four outer wall surfaces (4), inner wall surface (5), and four connecting sections (6). Inner wall surface (5) has a cylindrical inner surface shape surrounding the rotating shaft and extending along the rotating shaft. Four connecting sections (6) each are positioned at a respective one of four boundaries, each of the four boundaries being formed by a different pair of adjacent outer wall surfaces (4) among four outer wall surfaces (4). Each of four connecting sections (6) has a stress relief groove (7) recessed toward the shaft center at the respective one of four boundaries. At least one connecting section (6) has a first part and a second part along the direction in which the shaft center extends. The first part includes the stress relief groove (7). The second part includes a body section (8) not having stress relief groove (7).