Differential Ring Gear Welding Layout for Thrust Load Durability
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Solution Overview
Problem
Differential devices with integral welding between the differential case and ring gear face damage due to thrust loads, leading to weld detachment and reduced strength at the welded portion.
Innovation Solution
A differential device configuration where the ring gear abuts the differential case in the axial direction, with a helical gear structure and a fitting portion welded from the outside in the radial direction, reducing thrust bending stress and securing the strength of the welded portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ring gear is welded to the differential case at a position not abutting in the axial direction, then the welding is easier to perform, but thrust bending stress occurs at the welded portion causing weld detachment
Solution Approach 1:
The ring gear is preliminarily positioned to abut the differential case in the axial direction before welding. This preliminary abutting action ensures that the welded portion is pre-aligned at the optimal position where axial thrust loads are directly transferred to the case without creating bending moments, thus preventing weld detachment while maintaining welding feasibility
2Strength
If the wall thickness of the ring gear is increased to prevent weld detachment, then the welded portion strength is improved, but the device weight and manufacturing cost increase
Solution Approach 1:
Instead of increasing strength by adding material thickness in the radial direction, the solution shifts to optimizing the axial position and orientation of the welded portion. By positioning the weld at the abutting surface in the axial direction, the design leverages the existing structural geometry to resist thrust loads, achieving high welded portion strength without increasing ring gear wall thickness or weight
3Duration of action of stationary object
If the ring gear is positioned away from the differential case to reduce stress concentration, then the welded portion durability is improved, but the structural compactness and load transmission efficiency decrease
Solution Approach 1:
The solution merges the ring gear and differential case by positioning the welded portion at the abutting surface where the ring gear directly contacts the case in the axial direction. This merging eliminates gaps and stress concentration zones, creating a unified load transmission path that simultaneously improves welded portion durability and maintains structural compactness
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 effectively suppresses damage to the welded portion, such as weld detachment, by minimizing thrust bending stress, allowing for a lighter design without increasing wall thickness and reducing welding costs.
Implementation Method 1
the ring gear and the differential case are welded at an abutting portion between the ring gear and the differential case from outside in a radial direction of the ring gear
Data Source
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AI summary
Provided is a differential device, comprising a differential case that houses a gear group, and a ring gear disposed fitted to the differential case, wherein the differential case and the ring gear are supported rotatably about a drive shaft. The ring gear comprises a helical gear having a ring-like structure, the ring gear abuts the differential case in an axial direction of the drive shaft, and the ring gear and the differential case are welded at an abutting portion between the ring gear and the differential case from outside in a radial direction of the ring gear. The ring gear has a gear portion on an outer periphery of the ring gear and a fitting portion fitted to the differential case on an inner periphery of the ring gear, and the gear portion is disposed completely outside the whole differential case in the radial direction of the drive shaft.