Stepped Pipe Joint Structure Without Welding or Thermal Strain
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing stepped pipe members, such as those used in automobile structural components, face issues with assembly efficiency due to unstable dimensions and potential cracking, and welding processes that degrade dimensional accuracy and increase thermal strain.
Innovation Solution
A stepped pipe member design featuring radially expanded and swaged connections between large- and small-diameter pipe members, eliminating the need for welding and stabilizing the assembly process through sequential formation of specific portions and electromagnetic expansion, ensuring close contact and engagement without heat input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If drawing is performed by swaging to match inner diameter of large-diameter pipe with outer diameter of small-diameter pipe, then the pipe dimensions can be matched, but the pipe shape on inner circumferential side becomes unstable and cracking may occur
Solution Approach 1:
Instead of drawing the large-diameter pipe to reduce its inner diameter to match the small-diameter pipe (conventional approach), the invention inverts the approach by expanding the small-diameter pipe's outer diameter to match the large-diameter pipe's inner diameter. This is achieved by forming expanding portions on the small-diameter pipe that radially expand during insertion, thereby avoiding the instability and cracking issues associated with swaging the large-diameter pipe.
Solution Approach 2:
The invention changes the physical state and dimensional parameters of the small-diameter pipe by forming expanding portions with specific geometric characteristics (tapered angles, expansion ratios) that enable controlled radial expansion during insertion. This parameter change allows the small-diameter pipe to adapt its outer diameter to match the large-diameter pipe's inner diameter without compromising the structural integrity of either component.
2Strength
If holes are formed and welding is used to join the pipes, then the pipes can be securely connected, but work for forming holes and welding is increased and dimensional accuracy is degraded due to thermal strain
Solution Approach 1:
The invention replaces the welding process (thermal-chemical joining method) with a mechanical expansion and engagement system. The small-diameter pipe's expanding portions radially expand during insertion to engage with the large-diameter pipe's inner circumferential surface, creating a secure mechanical connection without requiring holes, welding operations, or associated thermal inputs that degrade dimensional accuracy.
Solution Approach 2:
The expanding portions are pre-formed on the small-diameter pipe during manufacturing with specific geometric characteristics (tapered angles, expansion ratios). This preliminary action enables the pipe to automatically expand and engage with the large-diameter pipe during the insertion process itself, eliminating the need for subsequent hole-forming and welding operations.
3Strength
If welding is performed to join the pipes, then secure connection is achieved, but dimensional accuracy is degraded due to thermal strain generated in various portions
Solution Approach 1:
The invention replaces the welding process (thermal-chemical joining method) with a mechanical expansion and engagement system. The small-diameter pipe's expanding portions radially expand during insertion to engage with the large-diameter pipe's inner circumferential surface, creating a secure mechanical connection without requiring holes, welding operations, or associated thermal inputs that degrade dimensional accuracy.
Solution Approach 2:
The invention converts the potential harm of thermal strain from welding into a benefit by using a cold-forming expansion process. The radial expansion of the small-diameter pipe's expanding portions generates beneficial compressive stresses that enhance the connection strength while avoiding the harmful thermal strains that would degrade dimensional accuracy.
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 approach enhances assembly efficiency and mounting accuracy while preventing cracking and dimensional inaccuracies, improving productivity by eliminating the need for welding and associated thermal strain.
Implementation Method 1
a coil is inserted into the small-diameter pipe member so as to radially expand the small-diameter pipe member by using electromagnetic forming
Data Source
AI summary
Formed in series along an axial-direction end portion of a large-diameter pipe member, in the following order from the pipe end, are: a large-diameter-pipe pipe-end expanding portion; a large-diameter-pipe reduced-diameter portion; a large-diameter-pipe bulging portion; and a tapered portion. Formed in series along an axial-direction end portion of a small-diameter-pipe member, in the following order from the pipe end, are: a small-diameter-pipe pipe-end expanding portion; a small-diameter-pipe enlarged-diameter portion; and a small-diameter-pipe bulging portion. The outer cylindrical surface of the small-diameter-pipe enlarged-diameter portion is in close contact with the inner circumferential surface of the large-diameter-pipe reduced-diameter portion; the inner cylindrical surface of the large-diameter-pipe bulging portion and the outer circumferential surface of the small-diameter-pipe pipe-end expanding portion are engaged; and the inner circumferential surface of the large-diameter-pipe pipe-end expanding portion and the outer cylindrical surface of the small-diameter-pipe bulging portion are engaged.