Hybrid Induction Welding for Flash-Free Piston Assembly
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Solution Overview
Problem
Existing methods for joining piston parts in internal combustion engines, such as friction welding, resistance welding, and laser welding, result in significant flash or scrap material, residual stress, and cracking along the weld.
Innovation Solution
The hybrid induction welding method, which involves heating the upper and lower piston parts' joining surfaces by induction, bringing them into contact, and then rotating one part while applying pressure to form a strong weld with minimal flash and residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If friction welding is used to join piston parts, then the piston parts are joined together, but significant flash or scrap material is created in the cooling chamber
Solution Approach 1:
The patent changes the physical state and parameters of the joining surfaces by heating them to elevated temperatures before joining. This thermal parameter change allows the surfaces to bond without creating flash material, as the heated surfaces flow and merge cleanly rather than creating excess material that must be removed.
Solution Approach 2:
The patent replaces the mechanical friction-based joining system with a thermal-induction-based joining system. Instead of relying on mechanical friction to generate heat and join surfaces (which creates flash), the patent uses induction heating to thermally prepare the surfaces for clean joining, eliminating the harmful flash byproduct.
2Strength
If resistance welding or laser welding is used to join piston parts, then the piston parts are joined together, but residual stress and cracking occur along the weld
Solution Approach 1:
The patent carefully controls and changes the thermal parameters during the joining process by using induction heating to raise the joining surfaces to optimal bonding temperatures. This controlled thermal parameter change ensures uniform heating and cooling, minimizing thermal gradients that would otherwise cause residual stress and cracking, thereby improving weld reliability.
3Temperature
If conventional induction welding is used to join piston parts, then the joining surfaces are heated by induction, but flash and scrap material are still produced
Solution Approach 1:
The patent applies preliminary action by heating the joining surfaces to elevated temperatures through induction heating before the actual joining occurs. This pre-heating prepares the surfaces by raising their temperature to optimal bonding conditions, allowing them to flow and merge cleanly without generating flash material during the joining process.
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 produces a strong, homogenous metallurgical bond across the weld with minimal or no flash, reducing residual stress and the likelihood of cracking, thereby enhancing the durability and service life of the piston.
Implementation Method 1
heating the upper piston part and the lower piston part in the region of the joining surfaces brought in direct contact by induction
Implementation Method 2
rotating a least one of the piston parts while the heated joining surfaces contact one another
Data Source
Figure 1~1A
Figure 2~3
Figure 4~5B
AI summary
A hybrid induction welded piston including an upper piston part welded to a lower piston part is provided. The piston is produced by induction heating the upper piston part and the lower piston part, and bringing the parts together to a part growth compensated position. The method then includes rotating the upper piston part 17 to 34 degrees clockwise and then 17 to 34 degrees counterclockwise. In addition to controlling the axial position and degree of rotation, the force applied to the piston parts is controlled so that preferably no flash is formed in a narrow cooling chamber of the piston. During the rotating steps, the pressure gradually increases to a maximum level which occurs while the upper piston part is rotating in the second direction. The piston includes a homogeneous metallurgical bond across the weld and no indentation on the outer surface at the weld prior to machining.