Differential Gear Crown Wheel Welding via Axial Beam
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Solution Overview
Problem
The existing methods for welding a crown wheel to a differential casing in motor vehicle gear assemblies face challenges such as difficult weld quality control, high costs, and complex press-quenching processes, especially when dealing with multiple final drive ratios and case-hardened materials.
Innovation Solution
A design featuring a circular flange with an axially protruding lip and a radially extending recess on the crown wheel, allowing for a flat axial face during press-quenching and minimizing hard machining, along with a high-energy beam welding approach that bisects the angle between the circular faces, supports the crown wheel for effective welding while reducing the need for multiple mounting fixtures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the crown wheel is case hardened after final machining to provide a hard surface, then wear resistance is improved, but the welding process becomes more difficult and expensive
Solution Approach 1:
The crown wheel is case hardened before welding to the differential casing, rather than after. This preliminary hardening allows the soft core material to be exposed at the welding interface, making welding easier and more cost-effective while still providing the hard wear-resistant surface on the outer portions that contact gears
Solution Approach 2:
The crown wheel has different material properties in different regions: the outer portions have case hardening for wear resistance, while the welding interface exposes the softer core material for easier welding. This local differentiation of material properties resolves the contradiction between wear resistance and weldability
2Ease of manufacture
If the crown wheel is machined with an outward stepped form before hardening to ease removal of the hard case, then welding accessibility is improved, but the press-quenching process becomes more complex and time-consuming
Solution Approach 1:
The case hardening is performed before welding, not after. This eliminates the need to machine away the hard case later to access the welding interface, as the soft core material is already exposed or accessible before hardening occurs. The sequential reordering of operations simplifies the overall manufacturing process
3Manufacturing precision
If multiple mounting fixtures are provided for press-quenching different crown wheels with different final drive ratios, then welding precision is improved, but device complexity and cost increase
Solution Approach 1:
A single mounting fixture design is used for press-quenching all crown wheels regardless of their different final drive ratios. The fixture is designed to accommodate various crown wheel configurations without requiring multiple specialized fixtures, reducing complexity while maintaining welding precision through proper positioning and support
4Ease of manufacture
If the crown wheel is welded to the differential casing with a radially applied weld to access the welding interface, then welding is enabled, but the crown wheel back face must be cut away and is not flat
Solution Approach 1:
Instead of accessing the welding interface from the radial direction (which requires cutting away the back face), the welding is performed from the axial direction. The axial face of the crown wheel is kept flat to provide a proper welding surface, and the welding tool approaches from the axial direction to join the crown wheel to the differential casing flange
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 solution simplifies the welding process, reduces costs, and ensures reliable assembly by maintaining a flat axial face during press-quenching, minimizing hard machining, and providing a robust weld that resists gear thrust, thus addressing the difficulties in existing methods.
Implementation Method 1
welding is performed by a high energy beam bisecting an angle between the circular faces
Implementation Method 2
the crown wheel must be press-quenched during the hardening process to prevent warping thereof
Implementation Method 3
the crown wheel is case hardened after final machining
Data Source
AI summary
An assembly of a crown wheel and a differential casing of a differential gear assembly is adapted to welding. The differential casing has a circular flange with an axially extending lip engaged in a circular groove of the crown wheel, which is further relieved at a radially outer side to give clearance for a high energy welding beam. An interface between the crown wheel and the circular flange is in one example a frusto-conical surface, which presents an oblique angle to the welding beam.