Ngk Spark Plug Company, Limited

Kazuyoshi Torii

Mamoru Musasa

Akira Suzuki

Tomoaki Kato

Naomichi Miyashita

Wataru Matsutani

Kazumasa Yoshida

Osamu Yoshimoto

Tomoo Tanaka

Hideki Teramura

Tomokatsu Kashima

Akikazu Taido

Kenji Moritani

Takashi Sekizawa

Yasuhide Shimanokami

Go Matsumura

Yuki Toumatsu

Yuya Ono

Yudai Kawaguchi

A spark plug that can reduce variation in a discharge point. The spark plug includes: a center electrode; a metal shell insulating and holding the center electrode; and a ground electrode including a base material having one end portion connected to the metal shell, and a tip connected to another end portion of the base material. The tip has a discharge surface opposed to the center electrode with a spark gap therebetween. The discharge surface has a quadrangular shape and is chamfered at four sides thereof. Only a first side which is one of the four sides is provided with a C chamfer.

Spark plug

A spark plug having a of center electrode, a ground electrode, and a noble metal tip that is laser-welded to at least one of the center electrode and the ground electrode The noble metal tip is joined to the electrode through a fused portion formed by laser welding, and the fused portion includes a first fused portion and a second fused portion.

A spark plug includes a center electrode, a ground electrode, and a noble metal tip. The noble metal tip is joined to an object member of at least one of two electrodes via a fusion zone. A projected overlap region of the noble metal tip and the fusion zone accounts for 70% or more of a projected region of the noble metal tip. The object member contains at least Si out of Al and Si such that the amount of Si is 0.4% by mass or higher and such that the total amount of Al and Si is 0.5% by mass. Multi-fusion spots exist on the surface of the fusion zone. Segments of a baseline which pass through the respective multi-fusion spots have a total length of a predetermined percentage of the length of the baseline. Joining strength to the noble metal tip can thereby be greatly improved when the member to be joined contains Si.

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

The present invention provides a spark plug which is capable of suppressing a occurrence of crack and separation by determining a structural configuration of a melting portion formed in a junction portion between a discharge portion and a pedestal portion which form an ignition portion that protrudes from a ground electrode. In a profile line shape of a cross section including a center axis P of an ignition portion, an exposure surfaceof a melting portionconnects a side surfaceof a discharge portionand a side surfaceof a pedestal portion. Further, an exterior angle &#x3b8; formed between an imaginary line Q, which passes through a boundary position X1 between the melting portionand the pedestal portionand a boundary position X2 between the melting portionand the discharge portion, and the center axis P at a node C, satisfies 135&#xb0;&#x2266;&#x3b8;&#x2266;175&#xb0;. Furthermore, a proportion T/S of a forming depth T of the melting portionto an outside diameter S of the discharge portionsatisfies T/S&#x2267;0.5.

A spark plug having a center electrode and a ground electrode including a ground electrode main body part having an end thereof facing the center electrode and a noble metal tip joined to the ground electrode main body part at a position facing a leading end of the center electrode, a spark discharge gap being formed between the leading end of the center electrode and the noble metal tip, wherein at least a portion of the ground electrode main body part, to which the noble metal tip is joined, is made of an Ni alloy containing 12 to 45 mass % of Cr, 7 mass % or less of Fe, 0.5 to 5 mass % of Al, 0.3 to 5 mass % of Si and 50 mass % or more of the balance, and wherein the joined portion and the noble metal tip are joined by laser welding or electron beam welding.

Spark plug having a ground electrode of specific alloy composition to which a noble metal tip is joined

An ignition part () of a ground electrode () includes a fused part () in which construction materials of a base portion () and a noble metal member () are fused and mixed by performing laser welding on the two. In the fused part (), an average ratio P of components originated from the noble metal member () at points K, L, and Mis equal to or greater than 80%, and an average ratio Q of components originated from the base portion at points K, L, and Mis equal to or higher than 20%, and P+Q is equal to or higher than 160%. Accordingly, it is possible to obtain joining strength in the parts in the ignition part (), thereby sufficiently preventing the generation of cracks, separation, and the like due to thermal stress.

A precious metal tip on the side of a ground electrode is indirectly joined to the front end portion of the ground electrode via a mounting part interposed therebetween. The mounting part includes a base part and a protruding part. First, in the state where the precious metal tip is in contact with the protruding part, laser welding or the like is performed thereon to form a fused part and obtain a complex, and the base part is joined to a flat surface of the ground electrode by resistance welding. The grain size of grains of the mounting part in the vicinity of the of the fused part is greater than the grain size of the grain size of the grains thereof in the vicinity of the ground electrode, and the grain size of the grains of the flange part of the mounting part is smaller than the grain size of the grains of the protruding part.

Spark plug for internal combustion engine

A spark member () is formed by joining a noble metal member () and an intermediate member () and is provided in a spark discharge gap between a center electrode and a ground electrode (). A bottom surface () of the intermediate member () is resistance-welded to an inner surface () of the ground electrode (), and a weld metal zone () is formed in the region of joint therebetween. As viewed on the section of the spark member () which contains a centerline (Q), the weld metal zone () is reliably formed within the range of the length (D) of a columnar portion () as measured along a direction orthogonal to the projecting direction of the spark member () and has a length (d) of at least 0.1 times (10% of) the length (D).

Spark plug and weld metal zone

A spark plug () including a center electrode () and a ground electrode (), which is formed by joining a ground electrode chip () to a ground electrode base material () via an intermediate member (). A method for producing the spark plug (100) includes providing a projecting portion () on the intermediate member (), and projection-welding the intermediate member () to the ground electrode base material () by means of the projecting portion (), to thereby join the intermediate memberto the ground electrode base material (). Further, the intermediate member () of the spark plug () includes a cylindrical columnar portion () which is joined to the ground electrode chip (), and a flange portion () which is joined to the ground electrode base material () and which flange portion () has a diameter greater than that of the cylindrical columnar portion ().

Method for producing spark plug and spark plug

A spark plugcomprised of a metal shell, an insulator, a center electrodeand a ground electrode. A rear-end face of the ground electrodeis welded to a front-end face of the metal shell, and a bent portionlocated at the intermediated position in the longitudinal direction is bent toward the center of the spark plug. The ground electrodeassumes a circular-shape with a diameter of 2 mm or less whereby an inflow of an air-fuel mixture is not disturbed even when the air-fuel mixture directly flows into a back face of the ground electrode. The ground electrodeis comprised of an outer layerA made of a nickel alloy and an inner layerB made of pure copper with an excellent thermal conductivity, in which a ratio of a cross-sectional area of the inner layerB to the entire cross-sectional area of the ground electrodeis 10% or more to 35% or less. Thus, the spark plugwhich is excellent in heat sinking ability and can prevent a spring back phenomenon due to a difference in a coefficient of thermal expansion.

Spark plug for use in an internal-combustion engine with a bilayer ground electrode

A spark plug () including a center electrode () and a ground electrode (), which is formed by joining a ground electrode chip () to a ground electrode base material () via an intermediate member (). A method for producing the spark plug () includes providing a projecting portion () on the intermediate member (), and projection-welding the intermediate member () to the ground electrode base material () by means of the projecting portion (), to thereby join the intermediate memberto the ground electrode base material (). Further, the intermediate member () of the spark plug () includes a cylindrical columnar portion () which is joined to the ground electrode chip (), and a flange portion () which is joined to the ground electrode base material () and which flange portion () has a diameter greater than that of the cylindrical columnar portion ().

Method for producing spark plug by projection welding and spark plug thereof

There is provided a spark section () of needle-like shape protruding from an inner surface () of a ground electrode () to define a spark gap between the spark section and an electrode tip on a center electrode. The spark section () has a noble metal member () and an intermediate member () joined to each other. The materials of the noble metal member () and the intermediate member () are selected in such a manner that the thermal conductivity of the intermediate member () is lower than that of the noble metal member (). This limits heat radiation through the heat radiation passage from the noble metal member () through the intermediate member () to the ground electrode () so as to maintain the noble metal member () at a higher temperature than conventional types and reduce a quenching effect of the noble metal member () on a flame core generated in the spark gap for improvement in ignition performance.

A spark plug including: a center electrode as defined herein; a substantially cylindrical insulator as defined herein; a cylindrical metal shell as defined herein; and a ground electrode as defined herein, wherein a spark discharge gap is provided between the leading end portion of the center electrode and the leading end portion of the ground electrode, and the ground electrode has a bulging curved face on a side opposite to a side in which the center electrode is provided, and a maximum of width of the ground electrode within a range of &#xb1;1 mm from a center point of the spark discharge gap in the axial direction, as viewed in a direction where the center electrode and the ground electrode overlap, is 105% or less of a width of an ordinary portion having a substantially constant width.

A spark plug comprising: a center electrode extending in a direction of an axis of said spark plug; a cylindrical insulator which has a shaft hole, and which holds said center electrode in said shaft hole in a state where a tip end of said center electrode is projected from a tip end face of said insulator; a metal shell which holds said insulator; and a ground electrode in which one end is joined to a tip end face of said metal shell, and which extends from said one end toward another end, wherein said ground electrode has an inner side face which faces said center electrode, and an outer side face which is a back face with respect to said inner side face, said outer side face is formed as an arcuately curved face when viewed from a side of said another end in an extending direction of said ground electrode, and a columnar noble metal tip is joined to said inner side face.

Spark plug including ground electrode with arcuately curved face

There is provided a method for producing a spark plug in which welding strength between a noble metal tip and an electrode joined by laser welding can be restrained from becoming weak. A noble metal tip () to be joined to a center electrode () or ground electrode of a spark plug to form a spark discharge gap is resistance-welded to each electrode containing no noble metal and then laser-welded. In the noble metal tip () exposed under a severe environment involving spark discharge, a molten portion () formed in such a manner that a portion of the noble metal tip () and a portion of the electrode are melted by laser welding and a non-molten portion () on the noble metal tip () side are apt to be peeled from each other in a boundary surface () between the molten portion () and the non-molten portion (). The noble metal content in the molten portion () however becomes higher because a flange portion is formed in a bottom portion by pressing force applied on the noble metal tip () at the time of resistance welding and then irradiated with a laser beam. Accordingly, peeling can be prevented from occurring in the boundary surface ().

Growing community of inventors

Aichi, Japan

Kazuyoshi Torii