Differential Device Casing with Rounded Corner for Stress Relief
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Solution Overview
Problem
Differential devices with lock-up differentials face stress concentration issues due to angular corners in the casing, which can be mitigated by increasing thickness, but this contradicts the need for downsizing.
Innovation Solution
A differential device design where the clutch member slidably fits on the side gear, maintaining concentricity without relying on the casing's internal face for guidance, allowing the casing to be freely designed to avoid stress concentration, such as using a rounded dent to relieve stress and enable downsizing while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the casing thickness is increased at the angular corner portion to reduce stress concentration, then the structural strength is improved, but the overall size of the differential device increases
Solution Approach 1:
The patent applies curvature by forming a rounded corner portion at the angular corner of the casing instead of a sharp angle. This rounded structure redistributes the stress concentration that would otherwise occur at the sharp corner, maintaining structural strength while avoiding the need to increase overall casing thickness. The rounded corner serves as a stress-relief feature that prevents crack initiation while keeping the differential device compact.
2Ease of operation
If a straight internal face is provided in the casing to guide axial movement of the clutch member, then the guidance function is improved, but stress concentration occurs at the angular corner
Solution Approach 1:
The patent replaces the straight internal face with a rounded internal face at the angular corner portion. This curved surface provides guidance for the axial movement of the clutch member while simultaneously eliminating the stress concentration that would occur at a sharp angular corner. The rounded geometry allows smooth movement guidance without creating stress concentration points.
3Volume of moving object
If the casing is downsized to meet compactness requirements, then the device size is reduced, but stress concentration and structural integrity are compromised
Solution Approach 1:
The patent incorporates a rounded corner portion in the casing design that acts as a stress-relief feature. This allows the casing to be downsized while maintaining structural integrity, as the rounded geometry prevents stress concentration that would otherwise require thicker walls. The curved corner design enables compact dimensions without compromising the strength-to-weight ratio.
Solution Approach 2:
The patent applies local quality by providing a rounded corner portion specifically at the angular corner where stress concentration would occur, while the rest of the casing maintains its standard design. This localized modification addresses the stress concentration issue only where needed, allowing the overall casing to remain thin and compact while maintaining structural integrity at the critical corner region.
Data Source
AI summary
A differential device is comprised of a casing with a first end wall and a side wall forming a corner with the first end wall; a differential gear set including an input gear and first and second side gears that are so meshed with the input gear to allow differential motion between the first and second side gears; and a clutch member being housed in and axially movable in the casing from a first position where the clutch member engages with the first side gear to limit the differential motion to a second position where the clutch member rests on the first end wall and frees the first side gear, the clutch member slidably fitting on the first side gear so as to keep the clutch member concentric with the first side gear.