Denso Corporation

Toshikazu Shimizu

Kozo Takamura

Satoru Kadowaki

Yasushi Kawashima

Hiroya Ishiguro

Kouji Yamanaka

A spark plug includes a center electrode having an end portion, and an earth electrode having an opposing portion opposed to the end portion via a gap. The end portion has an end-projecting portion. The opposing portion has an opposing-projecting portion opposed to the end-projecting portion. The end-projecting portion and the opposing-projecting portion have non-projection direction opposing surfaces which are parallel to and opposed to each other with a minimum distance and in a direction other than a projection direction. A first opposing area of a portion which includes the non-projection direction opposing surfaces and where the end-projecting portion and the opposing-projecting portion are opposed to each other with the minimum distance is larger than a second opposing area obtained when a plane of the end-projecting portion and a plane of the opposing-projecting portion, which are orthogonal to the projection direction, are opposed to each other in the projection direction.

Spark plug for an internal combustion engine

A spark plug has a cylindrical housing case, a cylindrical glass insulator, a center electrode, and an earth electrode fixed to the cylindrical housing case. The earth electrode has a projected part which is projected toward the center electrode. The projected part has a facing surface which faces the center electrode and is most close to the center electrode in a spark discharge gap. This gap is formed between the center electrode and the earth electrode. The facing surface is covered with a plating layer. A base material, with which the earth electrode is made, is exposed on a side surface of the projected part around the facing surface of the projected part. The base material of the earth electrode is made of Ni alloy containing not less than 90 wt % Ni, and preferably, Ni within a range of 90 wt % to 98 wt %.

Spark plug of internal combustion engine having an earth electrode having an exposed side surface on a projecting part

In producing a spark plug including a central electrode having a first chip including noble metal and an earth electrode having a second chip including the noble metal, a spark gap being disposed between the first and second chips, a chip including the noble metal. The chip is welded to an end of the central electrode and to an end of the earth electrode. The welded chip is cut to form the first and second chips and the spark gap.

Method of producing a spark plug

A spark plug has an insulator having a through hole extending in an axial direction thereof and an insulator leg portion at an end thereof, a resistor disposed in the through hole, a central electrode disposed in the through hole to face a central electrode side end face of the resistor and protruding from an insulator end face of the insulator leg portion, and a housing holding the insulator. A length between the insulator end face and the central electrode side end face of the resistor is equal to or larger than 1.5 times as large as a length of the insulator leg portion in the axial direction. Accordingly, temperature at a contact portion between the resistor and the central electrode is prevented from being increased, resulting in long life of the spark plug.

Growing community of inventors

Okazaki, Japan

Toshikazu Shimizu