CVJ Outer Joint Melt-Welding Under Vacuum
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Solution Overview
Problem
The existing welding methods for outer joint members of constant velocity universal joints face challenges such as burr generation, increased manufacturing costs, and unstable welding quality due to friction press-contact and gas pressure issues during laser or electron beam welding, which affect the accuracy and inspection of the joining process.
Innovation Solution
A melt-welding method is employed where the cup and shaft members are brought into abutment under atmospheric pressure or lower, preventing surface thickening and allowing for reliable inspection and reduced manufacturing costs by eliminating the need for additional processes like lathing and ventilation holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If friction press-contact is used to join cup member and shaft member, then the joining process is simple, but burrs are generated on the joining portions requiring additional lathing process
Solution Approach 1:
The harmful burrs generated during joining are extracted and removed through a controlled lathing process. The patent specifically targets and removes only the necessary burrs from the outer diameter surface while preserving the integrity of the joining portions, thereby resolving the contradiction between simple joining and surface accuracy.
Solution Approach 2:
The lathing process is applied locally only to the outer diameter surfaces of the joining portions where burrs are generated, rather than processing the entire component. This localized approach maintains manufacturing simplicity while achieving the required surface accuracy at critical areas.
2Manufacturing precision
If lathing process is applied to remove burrs from high hardness and distorted shape, then burr removal is achieved, but lathe tip is significantly abraded and cracked increasing cycle time
Solution Approach 1:
The cup member and shaft member are pre-heated to 300-650°C before the lathing process. This preliminary heating action reduces the hardness of the burrs and the base material, making them more susceptible to cutting. As a result, the lathing process can be performed with lower cutting forces, reducing lathe tip wear and allowing higher cutting speeds, thereby decreasing cycle time while maintaining burr removal quality.
Solution Approach 2:
The temperature parameter of the workpiece is changed from room temperature to 300-650°C before lathing. This parameter change significantly alters the material properties, reducing hardness and improving machinability. The heated state allows for more efficient material removal with less tool wear, resolving the contradiction between burr removal quality and productivity.
3Manufacturing precision
If laser welding or electron beam welding is used to prevent surface thickening, then surface accuracy is improved, but gas pressure variation in hollow cavity causes blowing of molten material and deformation
Solution Approach 1:
The cup member and shaft member are pre-heated to 300-650°C before welding. This preliminary heating action equalizes the temperature distribution and reduces thermal gradients during welding. By pre-heating, the material becomes more ductile and less susceptible to rapid cooling and cracking. The pre-heating also reduces the temperature differential between the molten pool and surrounding material, minimizing gas pressure variations and preventing blowing of molten material and deformation, thereby improving welding quality stability while maintaining surface accuracy.
Solution Approach 2:
The temperature parameter of the workpiece is changed from room temperature to 300-650°C before welding. This parameter change fundamentally alters the welding behavior by reducing thermal shocks and gas pressure variations. The elevated temperature state allows for stable melt-pool formation and controlled solidification, preventing defects such as blowing and deformation while maintaining the surface accuracy benefits of laser or electron beam welding.
4Reliability
If ventilation hole is provided in hollow cavity portion to prevent blowing and deformation, then welding quality is improved, but additional process step is added increasing manufacturing cost
Solution Approach 1:
The cup member and shaft member are pre-heated to 300-650°C before welding, which eliminates the need for ventilation holes. This preliminary heating action prevents gas pressure variations that would otherwise require ventilation pathways. By pre-heating, the material expands uniformly and gas pockets are eliminated or stabilized, preventing blowing and deformation without requiring additional structural modifications or process steps, thereby improving welding quality while avoiding increased device complexity.
Solution Approach 2:
The temperature parameter is changed to 300-650°C before welding, which fundamentally changes the physical state of the material and eliminates the need for ventilation holes. This parameter change prevents the formation of gas pockets and pressure variations that would require additional process steps. The elevated temperature ensures uniform expansion and stable welding without requiring ventilation features, resolving the contradiction between welding quality and device complexity.
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 method enhances the quality of welding portions, reduces manufacturing costs, and ensures stable welding quality through reliable inspection, making it suitable for long stem type constant velocity universal joints.
Implementation Method 1
melt-welding end portions of a cup member and a shaft member
Implementation Method 2
the melt-welding the end portions being performed in a state in which the sealed hollow cavity portion is under atmospheric pressure or lower
Data Source
AI summary
A welding method for an outer joint member of a constant velocity universal joint includes constructing a cup section having track grooves, which engage with torque transmitting elements, formed along an inner periphery thereof and a shaft section that is formed on a bottom portion of the cup section by two or more separate members, joining a cup member forming the cup section and a shaft member forming the shaft section, and melt-welding end portions of the cup member and the shaft member. The cup member and the shaft member are shaped so that a sealed hollow cavity portion is formed when the end portions of the cup member and the shaft member are brought into abutment against each other, the melt-welding of the end portions being performed when the sealed hollow cavity portion is under atmospheric pressure or lower.