Ngk Spark Plug Company, Limited

Hiroaki Kuki

Yuichi Yamada

Yoshihiro Matsubara

Naomichi Miyashita

Akira Suzuki

Wataru Matsutani

Hiroyuki Kameda

Mamoru Musasa

Makoto Yamaguchi

Jiro Kyuno

Kenji Nunome

Kazumasa Yoshida

Kenji Ishida

Kenichi Kumagai

Reimon Fukuzawa

Kazuhiko Mori

Masayuki Segawa

Shoichiro Ito

Ryuma Kawachi

Tomoaki Ueda

Takashi Sano

Yuji Hirano

A spark plug includes an insulator and a center electrode. The insulator includes: a first cylindrical portion; a truncated cone-shaped portion whose outer diameter reduces toward a front end side; and a second cylindrical portion formed at a front end side of the truncated cone-shaped portion. A diameter C of the center electrode is not larger than 2.2 mm. A total I of a volume of the truncated cone-shaped portion and a volume of the second cylindrical portion, a volume E of the center electrode from a position at a rear end of the truncated cone-shaped portion to a position at a front end of the second cylindrical portion, and the diameter C satisfy I/E&#x2267;4.2333C&#x2212;19.79C+24.869.

Spark plug for voltage resistance and suppression of side sparking and oxidation

A spark plug includes an insulator and a metal shell arranged around the insulator and having a thread portion formed with a thread diameter of M12. The insulator has an engagement portion held on a step portion of the metal shell via a plate packing and a leg portion located to leave a clearance between the leg portion and an inner circumferential surface of the metal shell. Assuming that: L (mm) is a distance from a front end of the plate packing toward the front; and A (mm) is a size of the clearance, a site of the clearance where the size A becomes 0.5 mm or smaller is located at or rear of a position of 2.0 mm from the front end toward the front; and a relationship of A&#x2267;L&#xd7;0.2+0.2 (mm) is satisfied within a range of 3.0&#x2266;L&#x2266;4.0.

Spark plug reducing metal shell to improve fouling resistance

A spark plug for an internal combustion engine capable of ensuring sufficient gastightness of a combustion chamber and meeting demand for a reduction in diameter.

Spark plug for internal combustion engine

A spark plug having an insulator with improved breakage resistance. The spark plug has a cross-section that satisfies the following relationship: 0.6 mm&#x3c;=L, where 'A' represents a connection point between a support portion of the insulator and an insulator trunk portion formed at a front end side with respect to the support portion, where 'B' represents a position closer to the outer circumference side among the positions of (a) an innermost position of a contact portion where the support portion and a packing are in contact with each other and (b) an intersection of the support portion and a virtual straight line that is parallel to an axial line of the spark plug and extends from an innermost circumferential end of a stepped portion of a metal shell, and where &#x201c;L&#x201d; represents a length of a path from point &#x201c;A&#x201d; to point &#x201c;B&#x201d; along a surface of the insulator.

Spark plug

A spark plug includes an insulator having an axial hole extending in the direction of an axis, and a terminal electrode disposed at a rear end portion of the axial hole. An identifier bearing externally visible identification information is joined to the rear end surface of the terminal electrode. The identifier has a thickness of 0.03 mm or greater along the direction of the axis.

Spark plug with an identifier

A spark plugincludes an insulator, a metal shell, a center electrodeand a ground electrode. A spark discharge gapis formed between a front end portionof the center electrodeand the ground electrode. The metal shellhas a through holetherein and a metal convex portioninwardly radially projecting in the through hole. The metal convex portionincludes a convex rearward face, a convex inner circumferential faceand a convex forward face. The through holehas an inner diameter A (mm) at a front end side inner circumferential face, which is located at the front end side with respect to the convex forward face. The insulatoris inserted in the through holeand has a first insulator taper portion, a second insulator taper portionand a basebetween the taper portions. The present invention satisfies the following representations: G&#x2266;(A&#x2212;B)/2; A&#x2267;7.3; and 2&#x2266;XX&#x2266;4, where 'B' (mm) is an outer diameter of a border K between an insulator front end portion 38 and the second insulator taper portion, where 'G' (mm) is a distance of a spark discharge gap, and where &#x201c;XX&#x201d; (mm) is a length from a very-end portion FF of the convex inner circumferential faceto the border K in the axial Cdirection.

A spark plug including a center electrode and a ground electrode. A center electrode noble metal tip is joined to a leading end portion of a center electrode, and a ground electrode noble metal tip is joined to a center-electrode-side side surface of the ground electrode. A distal end portion of the ground electrode noble metal tip protrudes from a distal-end surface of the ground electrode by 0.1 mm to 1.5 mm. A center-electrode-side side surface of the ground electrode noble metal tip projects from a center-electrode-side side surface by 0.15 mm to 0.6 mm. The ground electrode includes chamfered portions. Thickness lengths and widthwise lengths of the respective chamfered portions achieved within a cross section perpendicular to a center axis of the ground electrode are set to 0.2 mm or more.

Spark plug for internal combustion engine and method for manufacturing spark plug

There is provided a spark plug wherein an insulator and a metallic shell, when observed in a section made by a plane including an axis of a spark plug, have therebetween a gap of less than 0.45 mm at a more front end side than an engagement position of a packing and a first insulator stepped portion, and the gap is provided axially from a most front end side engagement position of the packing and a first insulator stepped portion as a starting point to a finishing point that is apart from the starting point by 1.2 mm or more toward the front end side while being apart from a front end surface of the metallic shell by 7.9 mm or more toward a rear end side.

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 having a center electrode formed from an electrode base material , which is made of an Ni alloy containing an alloy component (e.g., Cr) capable of forming an oxide semiconductor having a resistivity of negative temperature coefficient. Thus, a corrosion suppression layer originating from the components of the electrode base material is formed on the surface of a tip end portion of the insulator so that corrosion (channeling) of the surface of the tip end portion of the insulator due to creeping spark discharge can be effectively suppressed. In addition, when the constituent metal of the electrode base material has a coefficient of thermal conductivity of 17 to 30 W/m&middot;K, the heat transfer performance of the electrode is enhanced, so that durability against electrode consumption can be greatly improved.

Spark plug with nickel alloy electrode base material

In a creeping discharge type spark plug, the firing surface forming portions of a center electrode and a ground electrode are made of a metallic material containing a corrosion impeding component consisting of one or more of Fe, Cr and Cu. The spark plug is attached to an internal combustion engine. When it is operated under conditions of a predetermined high speed and high load, a corrosion impeding layer containing a corrosion impeding component is formed on the surface of the top end of an insulating member, with progression of spark discharge in spark discharge gaps. The corrosion impeding layer thus formed protects the center electrode from the attack by the creeping discharge spark. Therefore, the channeling is considerably effectively prevented or restricted.

Growing community of inventors

Nagoya, Japan

Hiroaki Kuki