Ngk Spark Plug Company, Limited

Satoshi Nagasawa

Katsutoshi Nakayama

Hiroyuki Kameda

Katsunori Hagiwara

Akira Suzuki

Wataru Matsutani

Wataru Matutani

Tomoaki Kato

Yuichi Yamada

Toru Nakamura

Masahiro Inoue

Kazumasa Yoshida

Yohei Kozakai

A spark plug includes an insulator having an axial hole formed therethrough in the direction of an axis of the spark plug, a center electrode disposed in a front side of the axial hole and a metal shell disposed around an outer circumference of the insulator and having a collar-shaped tool engagement portion and a crimp portion located on a rear side of the tool engagement portion and reduced in diameter toward the rear, wherein the crimp portion of the metal shell is made of a carbon steel material having a grain size number equal to or greater than No. 11 as measured according to JIS G 0551.

Spark plug

A spark plug has a metal shell and a ground electrode joined at a base end portion thereof to the metal shell and includes a surface layer and a core higher in thermal conductivity than the surface layer. The core includes a first core member and a second core member. A weld region, where the ground electrode is joined to the metal shell, has an undulating shape. A distance between frontmost and rearmost ends of a part of the weld region in contact with the first core member in the axis direction is 0.15 mm or more.

Spark plug with improved ground electrode joined to metal shell

A spark plug includes a center electrode, a ground electrode, and a ground-electrode-side tip joined to the ground electrode such that at least a portion of the tip along its thickness direction is embedded in the ground electrode. The ground-electrode-side tip is joined to the ground electrode through a fusion zone formed between the ground electrode and a proximal side of the tip. On a section containing a center axis of the ground electrode and in parallel with the thickness direction of the ground-electrode-side tip, E/F&#x2267;1.1 is satisfied, where E (mm) is the longest distance along the thickness direction from an inner side of the ground electrode to a boundary between the fusion zone and the ground electrode, and F (mm) is the largest amount of embedment of the tip in the inner side surface along the thickness direction.

Spark plug having an embedded tip that is prevented from detachment due to thermal stress

A spark plug has a metal shell and a ground electrode joined at a base end portion thereof to the metal shell and includes a surface layer and a core higher in thermal conductivity than the surface layer. The surface layer has a thickness of 0.2 to 0.4 mm at a specific position that is located 1 mm from the base end portion. The spark plug satisfies the following condition: W1&#x2267;W2&#xd7;1.55&#x2212;(W3+0.25) where W1 (mm) is a width of the metal shell at a weld region of the metal shell joined with the base end portion in a specific direction that extends perpendicular to the axis direction through a center line of the ground electrode; W2 (mm) is a thickness of the ground electrode at the specific position in the specific direction; and W3 (mm) is a thickness of the surface layer at the specific position in the specific direction.

There is provided according to the present invention a manufacturing method of a spark plug that includes a cylindrical metal shell, a cylindrical ceramic insulator retained in the metal shell, a center electrode retained in the ceramic insulator and extending in an axial direction and a ground electrode having a rear end portion fixed to the metal shell and a front end portion formed with a protruding region facing a front end portion of the center electrode with a gap left therebetween and being of substantially uniform thickness except for an area where the protrusion is formed. The spark plug manufacturing method includes a press forming step for pressing the whole of a ground electrode material for constituting the ground electrode, so as to form a protruding region on a front end portion of the ground electrode material and a welding step for, after the press forming step, welding a rear end portion of the ground electrode material to the metal shell.

Spark plug manufacturing method, and spark plug

A spark plug of the present invention includes a cylindrical metal shell, a cylindrical ceramic insulator retained in the metal shell, a center electrode retained in the ceramic insulator and extending in an axial direction, and a ground electrode formed into a bent shape and having a rear end portion fixed to the metal shell and a front end portion facing a front end portion of the center electrode with a gap left therebetween. The ground electrode contains a large thickness region formed on a rear end side thereof with a large thickness, a small thickness region formed on a front end side thereof with a smaller thickness than that of the large thickness region, a protruding region formed on the small thickness region and facing the center electrode and a thickness changing region formed between the large thickness region and the small thickness region and located at a different position from a position of a minimum curvature radius region of the bent shape of the ground electrode.

Spark plug, and its manufacturing method

A center electrode includes a tapered electrode base member mount and a noble metal tip joined to the electrode base member mount via a fused portion in which the component of the noble metal tip and the component of the electrode base member mount are fused. In this state, the cross section area Sat a tip side boundary between the fused portion and the noble metal tip and the cross section area Sat a base member side boundary between the fused portion and the electrode base member mount satisfy the relational expression of S&#x3c;S. Regarding the cross section area Sat the base portion of the electrode base member mount, (S&#x2212;S)/D satisfies the relational expression of 5&#x2266;(S&#x2212;S)/D&#x2266;50. D is the shortest distance in the axis line direction from the base member side boundary to the base portion.

A spark plug including: a center electrode; a substantially cylindrical insulator; a cylindrical metal shell; a ground electrode having a base end joined to a leading end portion of the metal shell and a distal end bent toward the axis line. The ground electrode includes: a thick portion provided on a base end side, a thin portion provided on a distal end side, and a stepped portion provided on an inner peripheral surface between the thick portion and the thin portion. A noble metal tip is joined to and partially embedded in the inner peripheral surface of the thin portion and disposed to form a gap between the noble metal tip and the leading end portion of the center electrode.

Spark plug for internal combustion engine and method for producing the spark plug

A spark plug including: a ground electrode including a thick portion provided on a base end side, a thin portion provided on a distal end side, and a stepped portion provided on an inner peripheral surface between the thick portion and the thin portion; a noble metal tip partially embedded in an inner peripheral surface of the thin portion; and a bulge portion provided on the inner peripheral surface of the thin portion between the stepped portion and the noble metal tip. When viewed from a side surface of the ground electrode, a relationship [a protruding height of the noble metal tip from the inner peripheral surface of the thin portion]&#x2267;[a protruding height of the bulge portion from the inner peripheral surface of the thin portion].

Spark plug for internal combustion engine having ground electrode with thick, thin and stepped portion and method for producing the spark plug

There is provided a method for controlling a plasma-jet spark plug in a four-stroke internal combustion engine, including the steps of: causing the spark plug to generate a primary discharge during either a compression stroke or an expansion stroke of the engine in such a manner as to produce a plasma by the primary discharge; and causing the spark plug to generate a secondary discharge during a time after the primary discharge and before the completion of a subsequent intake stroke of the engine.

Plasma-jet spark plug control method and device

A spark plug includes an outer electrode including an outer electrode tip of which a distal end surface is spaced from an outer peripheral surface of a leading end portion of a center electrode to define a spark discharge gap. A protruding insulator portion of a cylindrical insulator protrudes at least 1.0 mm from a leading end surface of a cylindrical metal shell. A protruding center electrode portion of the center electrode protrudes at least 3.5 mm from the leading end surface of the cylindrical metal shell. A relationship (&#x3b8;)/2&#x2267;75 degrees is satisfied where the angle &#x3b8;is defined as a central angle (degrees) of a first circular sector having a point Bas a center thereof, and the angle &#x3b8;is an average value (degrees) of the central angles of two second circular sectors having the point Bas a center thereof.

Spark plug having specific configuration of center electrode with respect to outer electrode

A plasma jet spark plug provides improved ignitability and durability by forming a part of a spark discharge gap outside the electric discharge space which generates plasma. An ignition system for the plasma jet spark plug is also disclosed. The plasma jet spark plug includes a center electrode, an insulator defining an axial bore which partially surrounds the center electrode, a cavity surrounded by an inner circumferential face of the axial bore which extends from an opening portion of a front end of the axial bore of the insulator and wherein a front end face of the center electrode is formed. A ground electrode is bent towards a front end portion of the insulator.

Plasma jet spark plug and ignition system for the same

A plasma-jet spark plug includes a metal shell, an electrical insulator retained in the metal shell, a center electrode held in an axial hole of the electrical insulator to define a cavity by a front end face of the center electrode and an inner circumferential surface of the insulator axial hole and a ground electrode fitted to a front end face of the electrical insulator and formed with an opening for communication between the cavity and the outside of the spark plug and satisfies the following dimensional relationships:d&#x2266;D&#x2266;3d;0.5 mm&#x2266;d&#x2266;1.5 mm;L1&#x2266;1.5 mm;2d&#x2266;L2&#x2266;3.5 mm; and2+{()/2}&#x2266;3.5 mmwhere D is a diameter of the ground electrode opening; L1 is a thickness of the ground electrode; d is a diameter of the cavity; and L2 is a depth of the cavity.

Plasma-jet spark plug and ignition system

A plasma-jet spark plug includes a metal shell, an electrical insulator retained in the metal shell, a center electrode held in an axial hole of the electrical insulator to define a cavity by a front end face of the center electrode and an inner circumferential surface of the insulator axial hole and a ground electrode arranged on a front end of the electrical insulator. The ground electrode has an opening defining portion defining an opening for communication between the cavity and the outside of the spark plug. The opening defining portion is located radially inside of or in contact with a first imaginary circular conical surface where the first imaginary circular conical surface has an axis coinciding with an axis of the spark plug and a vertex angle of 120&#xb0; opening toward a front end of the spark plug and passing through a front edge of the insulator axial hole.

Growing community of inventors

Nagoya, Japan

Satoshi Nagasawa