Differential Device Joining Structure Strain Reduction
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Solution Overview
Problem
Conventional differential devices face issues with assembling precision due to thermal and mechanical strains caused by press-fitting and welding, leading to potential durability problems and increased width in the axial direction, which complicates integration into transmission systems.
Innovation Solution
The differential device incorporates a design with a welded portion, a press-fitted portion, and a connecting surface that allows deformation during press-fitting, dispersing stress and preventing strain concentration, while maintaining strength and torque transmission capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If press-fitting means and welding means are used to join the input part and differential case, then the connection strength is improved, but thermal strain and mechanical strain occur causing decreased assembling precision
Solution Approach 1:
The joining structure is divided into multiple segments: a press-fitted portion for initial mechanical connection, a welded portion for thermal bonding, and a connecting surface with space allowing deformation. This segmentation allows each portion to serve its specific function while collectively reducing strain concentration and improving assembling precision.
Solution Approach 2:
Different portions of the joining structure have different properties: the press-fitted portion provides mechanical interference fit, the welded portion provides thermal bonding strength, and the connecting surface provides deformation space. This local differentiation optimizes both connection strength and assembling precision by placing appropriate joining characteristics in appropriate locations.
2Power
If the input part is designed in certain layout or form (e.g., helical gear), then the torque transmission capability is improved, but thrust load causes stress concentration on welded portions decreasing durability
Solution Approach 1:
The connecting surface is designed with extended end portions that locally increase the welded area and provide stress distribution zones. This local quality enhancement allows the input part to maintain its torque transmission capability while the extended welding portions distribute thrust load stresses, preventing stress concentration and improving durability.
3Power
If the differential device is designed with conventional structure, then the torque transmission is maintained, but the width in axial direction increases complicating integration into transmission systems
Solution Approach 1:
The joining structure utilizes the radial dimension by extending the connecting surface end portions outward in the radial direction. This dimensional approach allows stress distribution and enhanced welding area without increasing the axial width, enabling compact differential device design that maintains torque transmission capability while facilitating integration into transmission systems.
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 design effectively reduces mechanical strain, enhances durability, and allows for a more compact form factor, facilitating easier integration into transmission systems with improved assembly precision and reduced size.
Implementation Method 1
the cover portion is fitted to a welded portion of the input member in an axial direction of the input member and joined by welding
Implementation Method 2
the cover portion is press-fitted to a press-fitted portion located inward of the welded portion
Implementation Method 3
a connecting surface connecting the welded portion and the press-fitted portion and forming a space between the connecting surface and the cover portion, the space allowing deformation of the press-fitted portion during the press-fitting
Implementation Method 4
the connecting surface includes one end portion continuous to the welded portion, the one end portion extending outward from the welded portion in the radial direction
Data Source
AI summary
In a differential device distributing rotational force acting on a differential case to a pair of output shafts, the differential case including an input member and a cover portion, assembling precision of the differential device is enhanced by suppressing strain due to welding and press-fitting. The input member includes: a welded portion fitting the cover portion in axial direction and joined by welding; a press-fitted portion located inward of the welded portion in radial direction and axial direction and press-fitted to the cover portion; and a connecting surface connecting the welded portion and the press-fitted portion and forming a space between the connecting surface and the cover portion, the space allowing deformation of the press-fitted portion during press-fitting. The connecting surface includes one end portion continuous to the welded portion and extending outward from the welded portion in radial direction.