Ngk Spark Plug Company, Limited

Sumitomo Electric Industries, Limited

Kenichi Kumagai

Yoshihiro Nakai

Masatada Numano

Kazuo Yamazaki

Kozo Amano

Teruyuki Kondo

Wataru Matsutani

Makoto Yamaguchi

Kenji Kobayashi

Hiroaki Kuki

Yoshihisa Sugiyama

Koji Mizoguchi

Tomoharu Suzuki

A spark plug comprising: a cylindrical metal shell; a cylindrical insulator provided in an inner hole of said metal shell; a center electrode provided in a leading end side inner hole of said insulator; and a ground electrode having one end bonded to a leading end side of said metal shell and having another end face forming a spark discharge gap with said center electrode, wherein said ground electrode comprises an electrode material containing from 0.5 to 1.5 wt. % of Si, from 0.5 to 1.5 wt. % of Al, from 0.02 to 1.0 wt. % of at least one of Ti, V, Zr, Nb and Hf, from 0.03 to 0.09 wt. % of C and 95.5 wt. % or more of Ni, and having a specific resistance at 20&#xb0; C. of 25 tincm or less.

Spark plug for internal combustion engine

A spark plug comprising: a cylindrical metal shell; a cylindrical insulator provided in an inner hole of said metal shell; a center electrode provided in a leading end side inner hole of said insulator; and a ground electrode having one end bonded to a leading end side of said metal shell and having another end face forming a spark discharge gap with said center electrode, wherein said ground electrode comprises an electrode material containing from 0.5 to 1.5 wt. % of Si, from 0.5 to 1.5 wt. % of Al, from 0.02 to 1.0 wt. % of at least one of Ti, V, Zr, Nb and Hf, from 0.03 to 0.09 wt. % of C and 95.5 wt. % or more of Ni, and having a specific resistance at 20&#xb0; C. of 25 &#x3bc;&#x3a9;cm or less.

To provide a spark plug in which separation of a tip can be prevented and enough wear resistance can be obtained without increasing the content of nickel in the tip portion, and a use method of the spark plug. In a spark plug () including an outside electrode () including an electrode body portion () and a tip () bonded to the electrode body portion (), and a center electrode (), and the tip () is opposed to the front end portion of the center electrode () through a spark discharge gap (G), the electrode body portion () is made of a nickel alloy containing 13 to 18% by mass of Cr, 0.03 to 0.08% by mass of C, 1 to 3.5% by mass of Mo, 0 to 0.8% by mass of Si, Al, Mn and Ti, and 68% by mass or more of Ni, and the tip () is made of a platinum alloy containing 0 to 4% by mass of Ni.

Spark plug with high durability

A spark plug including a center electrode; an insulator; a metal shell; a ground electrode; and an annular packing, all as defined herein, wherein the packing has a hardness greater than or equal to a hardness of the stepped portion of the metal shell or has a Vickers hardness of not less than 300 Hv. Preferably, a difference between the hardness of the packing and the hardness of the stepped portion of the metal shell is from 120 Hv to 160 Hv, and the packing has a Vickers hardness of not more than 500 Hv.

Spark plug

A spark plug having a tubular metallic shell ( ), an insulator ( ) fitted into the metallic shell ( ), a center electrode ( ) provided in the insulator ( ), and a ground electrode ( ), one end of the ground electrode ( ) being joined to the metallic shell ( ) by means of welding or a like process, and a spark discharge gap (g) being formed between the other end portion of the ground electrode ( ) and the center electrode ( ), the spark plug being further characterized in that: the ground electrode ( ) has an electrode base metal ( ), a Cu-based heat transfer acceleration element ( ) embedded in the electrode base metal ( ) and formed predominantly from Cu, and a noble metal chip ( ) welded to the electrode base metal ( ) at a position facing the spark discharge gap (g); and the electrode base metal ( ) is an Ni alloy containing Cr in an amount of 14%-17% by mass, Mo in an amount of 0.8%-3.5% by mass, and Ni in an amount of 68%-85.2% by mass. In a second embodiment, the ground electrode ( ) has a diffusion layer formed in a boundary between the electrode base metal ( ) and the Cu-based heat transfer acceleration element ( ), and the electrode base metal ( ) contains C in an amount not greater than 0.3% by mass.

A spark plug includes: a central electrode; an insulator surrounding the central electrode radially; a metallic shell surrounding the insulator radially; and a ground electrode having a first end connected to the metallic shell and a second end defining a side face. The ground electrode is so bent that the side face of the second end faces the central electrode. The ground electrode contains: a nickel in a range from 58% to 71% by weight, a chromium in a range from 21% to 25% by weight, an iron in a range from 7% to 20% by weight, and an aluminum in a range from 1% to 2% by weight. The ground electrode has a Vickers hardness in a range from Hv 140 to Hv 220 through a Vickers hardness test specified in Japanese Industrial Standard Z2244. A load 9.8 N is applied to the ground electrode in the hardness test.

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Nagoya, Japan

Kenichi Kumagai