Thread Connection Stress Reduction via Material Removal
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Solution Overview
Problem
Highly loaded thread connections in injection devices for internal combustion engines, particularly those adjacent to the bearing surface, experience excessive stress due to high preloading forces and dynamic pressure loading, with existing measures being insufficient to effectively reduce loading in these critical regions.
Innovation Solution
The thread connection design involves material removal up to a diameter exceeding the outside diameter of the internal thread, specifically reducing the rigidity of the first component at the beginning of the thread to distribute stress more uniformly, with a material removal zone having varying radii and adequate wall thickness to manage stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If material removal is performed in the region between the bearing surface and the end of the thread (conventional undercut or relief cut), then the thread cutting runout zone is created, but the stress in the first thread turns remains excessively high
Solution Approach 1:
The patent applies local quality by creating a material removal zone with specific geometric characteristics (depth and diameter exceeding the external thread diameter) localized at the beginning of the internal thread. This localized modification reduces rigidity precisely where needed (in the first thread turns) while preserving the overall structural integrity and rigidity of the component elsewhere.
Solution Approach 2:
The patent changes the geometric parameters of the material removal zone, specifically requiring that the diameter of the material removal zone exceeds the external thread diameter. This parameter change creates a more pronounced reduction in rigidity at the thread beginning compared to conventional undercuts, thereby reducing the notching effect and stress concentration in the first thread turns.
2Strength
If the thread root radius is increased to reduce the notching effect, then the load bearing capacity of the screwed joint is improved, but the thread diameter must be enlarged which increases the sealing diameter
Solution Approach 1:
The patent applies local quality by modifying only the beginning region of the internal thread with a material removal zone, while keeping the rest of the thread geometry unchanged. This localized modification reduces stress in the critical first thread turns without requiring an overall increase in thread diameter, thereby maintaining the original sealing diameter.
Solution Approach 2:
The patent segments the thread connection into different zones: the material removal zone at the beginning, the transition zone, and the remaining thread turns. This segmentation allows stress reduction to be applied specifically to the highly loaded first thread turns while preserving the load-bearing capacity and sealing characteristics of the overall thread connection.
3Stress or pressure
If material is removed to reduce rigidity at the beginning of the thread, then stress distribution is improved, but excessive material loss and reduced component rigidity occur
Solution Approach 1:
The patent defines specific parameter ranges for the material removal zone: the diameter exceeds the external thread diameter by a controlled amount, and the depth is limited to maintain adequate wall thickness. These parameter constraints ensure sufficient stress reduction while preventing excessive material loss and maintaining component rigidity.
Solution Approach 2:
The material removal zone is localized to the beginning region of the internal thread, creating a gradual transition in rigidity. This localized modification improves stress distribution in the critical first thread turns while minimizing overall material loss and preserving the global rigidity of the component.
Data Source
AI summary
A thread connection, in particular for connecting components of an injection device for internal combustion engines which conduct a high pressure medium, includes a first component and a second component. The first component has an inside thread, and the second component has an outside thread configured to be screwed into the inside thread. The second component is configured such that a face of the second component is tensioned against a contact surface of the first component upon tightening the thread connection. The first component has an axial region between the contact surface and a first convolution of the inside thread wherefrom material has been removed up to a diameter that exceeds an outside diameter of the inside thread.