Differential Case Ring Gear Welding to Suppress Crack Propagation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing vehicular differential devices face issues with crack development in the welded portions between the cast iron differential case and steel ring gear, leading to potential power transmission hindrances due to casting defects such as blow holes and cracks during welding.
Innovation Solution
The use of electron beam welding or laser beam welding with predetermined intervals and recessed portions between the differential case and ring gear, creating unwelded gaps to suppress crack propagation and reduce stress, while maintaining integral rotation around the rotation axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the differential case and ring gear are welded over the entire circumference to achieve weight reduction and size reduction, then the structural integrity is improved, but cracks may develop from casting defects such as blow holes and cracks in the welded portion
Solution Approach 1:
The continuous welding is segmented into multiple discrete welding portions positioned at predetermined intervals around the circumference. This segmentation interrupts the continuous weld path, preventing crack propagation from one welding portion to another, while still providing sufficient structural connection through the distributed welding portions.
Solution Approach 2:
Different regions of the differential case are treated differently: some regions have welding portions for structural connection, while other regions have non-welding portions to avoid stress concentration and crack initiation. This local differentiation optimizes both strength and reliability by applying welding only where necessary.
2Ease of manufacture
If the differential case is formed by casting to achieve complex shapes, then the manufacturing flexibility is improved, but casting defects such as blow holes and cracks are introduced that can lead to welding failures
Solution Approach 1:
The welding is divided into multiple discrete portions rather than continuous welding, which reduces the total weld length and consequently reduces the probability of defects propagating through the entire structure. This segmentation approach maintains the manufacturing flexibility of casting while mitigating the reliability issues from casting defects.
3Weight of moving object
If welding is performed to join the differential case and ring gear for integral rotation, then the weight reduction is achieved by removing bolt fastening, but the stress concentration at the welding interface may cause crack propagation
Solution Approach 1:
The welding is segmented into multiple portions around the circumference, which distributes the stress concentration across multiple discrete locations rather than one continuous high-stress zone. This segmentation prevents crack propagation while maintaining the weight reduction benefit of eliminating bolt fastening.
Solution Approach 2:
The welding portions are arranged periodically at predetermined intervals around the circumference, creating a regular pattern of stress distribution. This periodic arrangement prevents stress concentration from accumulating in one location and reduces the likelihood of crack propagation compared to continuous welding.
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 approach effectively suppresses crack development and ensures reliable power transmission by preventing crack propagation and reducing stress through the strategic placement of unwelded gaps and the use of advanced welding methods, enhancing the structural integrity of the vehicular differential device.
Implementation Method 1
the welded portion is formed by electron beam welding or laser beam welding
Implementation Method 2
the welded portion is formed by electron beam welding or laser beam welding
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A vehicular differential device (10) includes a differential case (26), a ring gear (28), and a welded portion positioned on an abutting surface (52) where the differential case and the ring gear are in contact with each other. The welded portion is configured to join the differential case (26) and the ring gear (28) for integral rotation of the differential case (26) and the ring gear (28) around a rotation axis (C1) of the vehicular differential device (10). The welded portion includes a plurality of welding surfaces (54) positioned at predetermined intervals along a circumferential direction around the rotation axis (C1).