| 摘要 |
A spark plug ( 10 ) for a spark ignited internal combustion engine includes a suppressor seal pack ( 54 ) interposed between an upper terminal stud ( 46 ) and a lower center electrode ( 60 ). The suppressor seal pack ( 54 ) includes a top layer of conductive glass ( 52 ) surrounding the bottom end ( 50 ) of the terminal stud ( 46 ) and a lower glass seal layer ( 58 ) surrounding a head ( 62 ) of the center electrode ( 60 ). A resistor layer ( 56 ) fills the space between the conductive glass layers ( 52, 58 ). The resistor layer ( 56 ) has a larger first cross-sectional area ( 76 ) at its upper end and a smaller second cross-sectional area ( 78 ) at its lower end. A reducing taper ( 80 ) establishes a progressive transition between the greater and lesser cross-sectional areas ( 76, 78 ). The reducing taper ( 80 ) is located in a large shoulder region (LS) which is defined as the longitudinal dimension between the theoretical reference point ( 70 ) at the filleted transition ( 26 ) and the theoretical reference point ( 68 ) at the upper seat ( 17 ). The suppressor seal pack ( 54 ) is of the fired-in variety in which each layer ( 54, 56, 58 ) is separately filled as a granular material, tamped and then cold pressed using the terminal stud ( 46 ). The assembly is then heated in a furnace, then removed so that the terminal stud ( 46 ) can be used to hot press the suppressor seal pack ( 54 ) into a final, operative condition. The suppressor seal pack ( 54 ) has a length (SL) which is maximized by use of a positive "A" dimension (+A) defined as the longitudinal distance between the center electrode head ( 62 ) seat and the theoretical location ( 72 ) of the lower seat ( 19 ).
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