Electric Power Steering Cylindrical Portion Thickness Reduction
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Solution Overview
Problem
Conventional electric power steering apparatuses face challenges in reducing the thickness of the cylindrical portion where the torque detection sleeve is fitted, due to requirements for maintaining torsion rigidity and component weight, especially when components are made smaller and lighter.
Innovation Solution
The solution involves a radial engagement mechanism between the female and male stopper portions, where the engagement height decreases from the distal end to the base end, with an auxiliary circumferential groove on the cylindrical portion overlapping the stopper engagement region, allowing the cylindrical portion to be thinner by improving torsion rigidity and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the cylindrical portion thickness is reduced to make components smaller and lighter, then weight and size are improved, but torsion rigidity deteriorates
Solution Approach 1:
The patent applies local quality by creating a stopper engagement region with enhanced structural properties at a specific location on the cylindrical portion. This region has different mechanical characteristics (higher rigidity) compared to other areas, allowing the cylindrical portion to maintain thin overall thickness while having localized reinforcement where torque transmission occurs. The stopper engagement region's specialized structure provides the necessary torsion rigidity without increasing the overall thickness of the cylindrical portion.
Solution Approach 2:
The patent segments the engagement structure into distinct female stopper portions and male stopper portions that fit together. This segmentation allows for optimized stress distribution and localized reinforcement at the engagement interface. The divided structure enables the cylindrical portion to be thinner overall while maintaining sufficient torsion rigidity through the specialized engagement region design.
2Ease of manufacture
If the cylindrical portion thickness is reduced, then manufacturing cost is improved, but stress concentration worsens
Solution Approach 1:
The patent addresses stress concentration by creating a localized stopper engagement region with optimized geometric properties. This region features carefully designed female and male stopper portions that distribute stresses evenly at the engagement interface. The local quality enhancement ensures that even though the overall cylindrical portion is thin and uses less material, the critical engagement area has sufficient structural integrity to handle torque transmission without excessive stress concentration.
Solution Approach 2:
The patent incorporates preliminary design features in the stopper engagement region that pre-distribute potential stress concentrations before torque is applied. The geometric configuration of the engaged stopper portions is designed in advance to guide stress flow and prevent concentration at critical points, allowing the use of thinner cylindrical portions with reduced material cost while maintaining durability.
Data Source
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AI summary
An electric power steering apparatus includes an input shaft to which steering force from a steering wheel is applied, an output shaft to which assisting force generated by an electric motor is applied, and a torque detection sleeve. One of the input shaft and the output shaft includes a cylindrical portion having a female stopper portion and a circumferential groove. The other of the input shaft and the output shaft has a male stopper portion being in concave-convex engagement with the female stopper portion and relatively rotatable in a given angular range. An edge of a base end portion of the torque detection sleeve is clinched to the circumferential groove. The circumferential groove is provided on a portion of an outer peripheral surface of the cylindrical portion radially overlapping a stopper engagement region in which the female stopper portion and the male stopper portion are engaged with each other.