Spark Plug Housing Thread Forming for Electrode Position Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The thickness tolerance and captive attachment method of the sealing washer in existing spark plug manufacturing processes negatively affect the angular position accuracy of the ground electrode in internal combustion engines, particularly in modern direct injection systems.
Innovation Solution
The sealing element is mounted onto the spark plug housing before thread formation, allowing the thread to be formed by reshaping, with an inner diameter smaller than the nominal thread diameter for captive assembly without pressing or caulking, ensuring the thickness of the sealing element does not influence the ground electrode's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sealing washer is mounted after thread formation using conventional captive attachment methods, then the sealing element can be securely fixed, but the thickness tolerance of the sealing washer negatively affects the angular position accuracy of the ground electrode
Solution Approach 1:
The sealing element is mounted onto the spark plug housing before the thread is formed, rather than after. This preliminary mounting allows the thread formation process to simultaneously create both the threaded connection and the captive fastening of the sealing element, eliminating the influence of sealing element thickness variations on the angular position of the ground electrode.
Solution Approach 2:
The invention changes the sequence of manufacturing operations, specifically altering when the sealing element is mounted relative to thread formation. By mounting the sealing element before thread formation, the process parameters change such that the thread rolling simultaneously secures the sealing element and creates the threaded connection, decoupling the sealing element thickness from the ground electrode angular position.
2Manufacturing precision
If the sealing element is mounted before thread formation, then the positional accuracy of the ground electrode is improved, but additional manufacturing steps may be required for captive fastening
Solution Approach 1:
The invention merges two functions into a single operation: the thread formation process simultaneously creates the threaded connection and the captive fastening of the sealing element. By forming the thread on the housing section after the sealing element is pre-mounted, the thread rolling process deforms the housing material to mechanically interlock with the sealing element, achieving captive attachment without separate pressing or caulking steps.
Solution Approach 2:
The thread formation process serves dual purposes: creating the external thread for screwing the spark plug into the engine and simultaneously securing the sealing element in a captive manner. The housing material deforms during thread rolling to mechanically lock the sealing element, making the sealing element self-securing through the thread formation process itself without requiring additional fastening operations.
3Ease of manufacture
If a forming process is used for thread production, then the nominal diameter of the thread is larger than the original outer diameter, enabling captive assembly, but the process requires precise control of diameter relationships
Solution Approach 1:
The invention applies local quality by creating a diameter relationship specifically at the sealing element mounting location. The housing section is designed with specific dimensional characteristics that allow the sealing element to be pre-mounted, and the thread formation process locally deforms the material to create the captive fastening. The nominal diameter of the formed thread is intentionally made larger than the original outer diameter to provide the interference fit for captive assembly.
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 positional accuracy of the ground electrode and achieves captive fastening without additional manufacturing steps, ensuring precise angular orientation and secure sealing without material connections or diameter changes.
Implementation Method 1
If a thread is produced by a forming process and not, for example, by thread cutting, the nominal diameter of the thread that is ultimately obtained is larger than the original outer diameter of the section on which the thread is applied
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method for producing a spark plug (1), comprising the following steps in the given order: - providing a spark plug housing (2) that has a cylindrical section (7), - attaching a sealing element (11) onto said section (7) and - forming a screw thread (8) on the section (7) by means of a forming process, - an inner diameter (12) of the sealing element (11) being smaller than a nominal diameter (13) of said screw thread (8).