Ngk Spark Plug Company, Limited

Takuya Shimamura

Jiro Kyuno

Tomoaki Kato

Naomichi Miyashita

Disclosed is a production method of a spark plug in which a ground electrode has an electrode base and a tip welded to a surface of the electrode base via a weld metal. The production method includes an image capture step, an image analysis step and an inspection step. The image capture step is to capture image data about the surface of the electrode base to which the tip has been welded. The image analysis step is to perform analysis of the image data, thereby detecting an edge of the electrode base and an edge of the weld metal, determining a center point of a contour of the weld metal and then detecting an edge of the tip in a specific area of the image data. The inspection step is to inspect a welding position of the tip based on the detected edges of the electrode base and the tip.

Production method of spark plug

A spark plug has an electrode including a base portion and a tip joined to a specific surface that is a specific outer surface of the base portion, the tip forming a spark discharge surface. Respective relative positions of a plurality of points on an outer surface of a target portion of the electrode including the base portion and the tip joined to the base portion, which is a portion including at least a portion of the specific surface of the base portion and the tip, are identified to generate three-dimensional coordinate data representing the three-dimensional shape of the target portion. The coordinate data is analyzed to determine whether the target portion of the electrode includes a predetermined unintentional portion that is an unintended portion. An electrode including the unintentional portion is excluded from objects to be manufactured, and an electrode not including the unintentional portion is used to assemble the spark plug.

Method of manufacturing spark plug

A spark plug includes a metal shell formed with a mounting male thread portion and a radially outwardly protruding seat portion and a solid annular gasket disposed between the male thread portion and the seat portion. The gasket has a recessed portion formed with a depth in the direction of an axis such that the recessed portion has an opening at a front end surface of the gasket () located opposite to the seat portion. The front end surface of the gasket includes an inner peripheral front end surface region decreasing in thickness toward an inner periphery of the gasket and an outer peripheral front end surface region formed radially outside the inner peripheral front end surface region. The opening of the recessed portion is located radially inside an innermost periphery of the outer peripheral front end surface region.

Spark plug

A spark plug includes an insulating insulator and a metal shell. The metal shell includes a caulking portion, a seat portion with a tapering surface, a thread portion with a thread size equal to or less than M12, and a protrusion. The insulating insulator includes a lock portion locked to the protrusion, and is secured to the metal shell in a state held between the caulking portion and the protrusion.

A spark plug comprises an insulator and a metal shell. The insulator includes a nose length portion at the forward end, and a tapered portion, extending from the rear end of the nose length portion toward the rear end of the insulator, increased in diameter toward the rear end. The metal shell includes a shoulder portion, protruding inward and having a retaining surface by which the tapered portion is retained, and a male thread portion on the outer peripheral side of the shoulder portion, and the thread diameter of the male thread portion is set to Mor less. When the insulator's cross-sectional area, perpendicular to an axis, passing through the boundary between the nose length section and tapered portion is B (mm), and the metal shell's cross-sectional area, perpendicular to the axis, passing through the tip of the retaining surface is C (mm), 2.80&#x2266;C/B&#x2266;3.50 is satisfied.

Disclosed is a spark plug having an insulator with good breakage resistance. A spark plugcontains a ceramic insulator, a plate packingand a metal shell. The ceramic insulatorhas, on an outer circumferential surface thereof, a step portion, a leg portionand a curved surface portionbetween the step portionand the leg portion. The metal shellhas, on an inner circumferential surface thereof, a taper portion. The ceramic insulatoris fixed in the metal shellwith the step portionretained on the taper portionvia the plate packing. Herein, 50% or more of an inner circumferential edge portion IP of the plate packingis in contact with a part of the ceramic insulatorlocated front of a middle region CP of the curved surface portion

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Iwakura, Japan

Takuya Shimamura