Ngk Spark Plug Company, Limited

Yuichi Matsunaga

Yasushi Sakakura

Yuichi Yamada

A tip that contains a noble metal is joined to a joining surface of an electrode base material of a ground electrode via a welded portion. On cross-sections of the tip and the electrode base material in a longitudinal direction of the joining surface, the welded portion has a void above the joining surface, and a continuous distance of the welded portion on the joining surface is less than or equal to 0.5 mm, whereby thermal stress due to a difference in thermal expansion between the tip and the electrode base material can be reduced. A total of continuous distances of the welded portions on the joining surface, are 0.4 times to 0.8 times a length from an end of the tip to another end thereof, whereby joining strength of the welded portion can be assured. Peeling at the tip or falling-off of the tip due to thermal stress can be less likely to occur, whereby durability of the ground electrode can be improved.

Spark plug

A spark plug () includes an insulator () having an axial hole (), a center electrode () inserted into the axial hole (), a metallic shell () provided around the insulator (), a ground electrode () whose base end portion is fixed to the metallic shell () and which has an annular portion (A) formed at a forward end portion thereof, the center electrode () being disposed radially inward of the annular portion (A), and an annular tip () which is joined to the inner circumference of the annular portion (A) and which forms a spark discharge gap () between the center electrode () and the inner circumferential surface of the annular tip (). Recesses () are provided on at least one of the inner and outer circumferences of the annular portion (A).

An ignition plug having a metallic shell with a through hole extending therethrough in an axial direction, an insulator fitted into the through hole of the metallic shell and having an axial hole extending in the axial direction, and a center electrode fitted into the axial hole of the insulator. The ignition plug further includes a cap member which covers a front end opening of the metallic shell, provided on a front end side thereof where the center electrode is disposed, to thereby form an ignition chamber at the front end portion of the metallic shell, and a ground electrode disposed within the ignition chamber and facing a circumferential surface of the center electrode directly or indirectly.

Spark plug and method of manufacturing spark plug

A technique of reducing occurrence of multiple discharge in a spark plug. The spark plug has a main ground electrode and three auxiliary ground electrodes. The position at which first auxiliary ground electrode is joined to a metallic shell is located opposite the position at which main ground electrode is joined to the metallic shell, with respect to a center electrode. The positions at which second and third auxiliary ground electrodes are joined to the metallic shell are located opposite to each other with respect to the center electrode. When the width of first auxiliary ground electrode is represented by W, the shortest distance between second auxiliary ground electrode and third auxiliary ground electrode is represented by T, and a distance which is a component of the shortest distance T in a direction orthogonal to first auxiliary ground electrode is represented by Tp, a relation W&#x2267;Tp is satisfied.

Spark plug and production method therefor

An ignition plug having enhanced seal performance, while suppressing deformation of a metallic shell thereof. The ignition plug includes a metallic shell having a crimp portion, a male screw portion, a seat portion, and a bent portion. The bent portion has a largest outer diameter (OD) portion, and first and second smallest OD portions, wherein 0.01&#x2266;(L+L&#x2212;L)/(L+L)&#x2266;0.3 is satisfied. Lis distance between a point in the first smallest OD portion farthest from center axis and a point in the second smallest OD portion farthest from center axis, Lis distance between the point in the first smallest OD portion farthest from center axis and a point in the largest OD portion farthest from center axis, and Lis distance between the point in the second smallest OD portion farthest from center axis and the point in the largest OD portion farthest from center axis.

Growing community of inventors

Nagoya, Japan

Yuichi Matsunaga