Abstract: A ground electrode for a spark plug has a through hole located adjacent a firing end of the electrode, with a precious metal firing tip extending through the hole. The firing tip is compressed axially to define a bulging portion extending radially outwardly from its longitudinal axis to mechanically retain the firing tip within the through hole. The firing tip additionally has an enlarged head or otherwise expanded portion at each axial end of the tip to provide a second mechanical interlock of the tip to the g round electrode. The firing tip can then also be welded to further strengthen its connection to the ground electrode. A method of manufacturing the ground electrode and a spark plug containing the ground electrode is also disclosed.

Abstract: A spark plug includes an electrode which during assembly is inserted into a vertical bore of a ceramic insulator from beneath. The electrode has an expanded firing end protruding from the insulator bottom. Tabs at an upper end of the electrode are expanded inside the bore to engage the insulator, and this is done using a removable expanding tool inserted into the insulator. A conductive glass in granular form is poured into the bore and envelops the expanded upper end of the electrode. A sacrificial conductive push pin inserts into the upper bore over the glass granules. The sub-assembly is heated to melt the glass and the push pin is pressed down into the melted glass. Upon cooling, the glass within the insulator fuses forming a seal which further strengthens the flared engagement of the electrode to the insulator.

Abstract: A spark plug having a center electrode assembly that includes a center electrode and precious metal insert that is both mechanically interlocked and welded to the center electrode in a manner that permits trapped gases to escape from between the two components. Also disclosed is a method for manufacturing the same. During assembly, the precious metal insert is placed into a blind hole that extends axially into a lower end of the center electrode. Once in place, the center electrode is deformed around an enlarged head section of the insert to mechanically interlock the two components together. To further strengthen this attachment, the two components are welded together about their circumference. In one embodiment, the weld includes several interruptions that function as vapor vents for any gases that may be trapped. In other embodiments, a radially or an axially-extending vent hole is used in lieu of the weld interruptions.