Friction Stir Joining Rotary Tool for Liquid-Cooled Jacket Groove Reduction
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Solution Overview
Problem
Existing methods for manufacturing liquid-cooled jackets using friction stir joining result in increased concave groove size and surface roughness, along with bulging portions due to inadequate material pressing and fluidization control.
Innovation Solution
A method involving a rotary tool with a base-end-side pin and a tip-end-side pin, where the taper angle of the base-end-side pin is greater than that of the tip-end-side pin, and a stairs-like pin step portion on the outer surface of the base-end-side pin, allowing controlled friction stirring to reduce groove size and surface roughness, and a provisional joining step to stabilize the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction stir joining is performed with only the stir pin contacting the metal members (as in Patent Document 1), then defects are prevented and load is reduced, but the concave groove widens and joined surface roughness increases
Solution Approach 1:
The rotary tool is divided into two functional parts: a stir pin for friction stirring and material mixing, and a shoulder portion for pressing and controlling material flow. This segmentation allows each part to perform its specific function optimally, preventing defects while maintaining surface quality.
Solution Approach 2:
The stir pin and shoulder portion are combined into a single integrated rotary tool assembly, allowing simultaneous material fluidization and pressing action. This merging enables the plastically fluidized material to be properly contained and pressed, reducing concave groove width and surface roughness while preventing defects.
2Object-generated harmful factors
If the shoulder portion presses the plastically fluidized material (as in conventional friction stir joining), then burr generation is prevented, but concave groove size increases when joining height changes
Solution Approach 1:
The shoulder portion is designed with specific local geometric features including a pressing surface and a groove. The pressing surface applies localized pressure to control material flow and prevent burrs, while the groove accommodates excess material. This local quality design allows effective burr prevention while maintaining consistent concave groove dimensions despite joining height variations.
3Stability of the object's composition
If tapered surfaces are provided on the shoulder portion and stir pin (as in Patent Document 2), then stable joining is achieved, but the groove does not function properly and surface roughness increases
Solution Approach 1:
The rotary tool features asymmetric design elements: the shoulder portion has a pressing surface on one side and a groove on the other, and the stir pin has an asymmetric profile with different radii of curvature. This asymmetry allows the pressing surface to provide stable joining while the groove effectively manages material flow, preventing the groove dysfunction and surface roughness problems seen in symmetric tapered designs.
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
The method effectively reduces the size of concave grooves and surface roughness, enhances joining quality, and reduces deformation due to thermal contraction by controlled material flow and pressure distribution during friction stir joining.
Implementation Method 1
friction stir joining in which a lower end surface of the shoulder portion is pushed onto a metal member
Implementation Method 2
By pressing the shoulder portion onto the metal member, the plastically fluidized material can be pressed
Data Source
AI summary
Provided is a method for manufacturing a liquid-cooled jacket, to reduce the size of a recessed groove on a surface of a metal member and also to reduce roughness of a jointed surface. The method includes: a placing step of placing a sealing body on a jacket body, a first main joining step of performing friction stirring by moving a main joining rotary tool around to a first overlapped portion, and a second main joining step of performing friction stirring to a second overlapped portion. The main joining rotary tool has a base-end-side pin and a tip-end-side pin. A taper angle of the base-end-side pin is greater than a taper angle of the tip-end-side pin and a stairs-like pin step portion is formed on an outer circumferential surface of the base-end-side pin.