Ngk Spark Plug Company, Limited

Atsushi Ozeki

Keisuke Kure

Takashi Tamada

A method of manufacturing a metal shell assembly for a spark plug including a cylindrical metal shell that extends in a direction of a central axis and which has a screw portion formed in an outer peripheral surface thereof, and a bar-shaped ground electrode that extends from a front end portion of the metal shell, the method including: disposing an intermediate assembly, having the ground electrode provided in a metal shell intermediate body, between a plurality of rolling dies having process surfaces facing each other; forming the screw portion by performing a rolling process on the intermediate assembly by the plurality of rolling dies while the intermediate assembly is interposed between the plurality of rolling dies; and positioning the ground electrode in a circumferential direction about a central axis of the intermediate assembly between the disposing and forming steps.

Method of manufacturing metal shell assembly for spark plug, method of manufacturing spark plug, and apparatus for manufacturing metal shell assembly for spark plug

A method for measuring a deviation from a joint target position of a member to which a measuring object is joined, in particular, measuring the deviation of an electrode position of a spark plug. The deviation of a ground electrode from an optimal igniting position Ois measured while a metallic shell is engaged with a female thread jig. A distance '&#x3b5;' between an axis A of the ground electrode and a reference straight line LS is calculated. The distance '&#x3b5;' is a vertical length from the axis A to the reference straight line LS. An angle &#x201c;&#x3b1;&#x201d; between a first straight line Land the reference straight line LS is calculated using the distance &#x201c;&#x3b5;&#x201d; and a predetermined distance &#x201c;&#x3b2;&#x201d; between the axis A of the ground electrode and an axis O of the metallic shell.

Method for measuring deviation of joint position of member and method for producing spark plug

In a method for measuring deviation of a ground electrode from an optimal igniting position, a metallic shell is engaged with a female thread jig. Then the axis O of the metallic shell, a predetermined first measuring point Pand a predetermined second measuring point Pon a front end face of the ground electrode are detected. Then, a circumferential angle &#x3b2;formed between a reference straight line 'LS' connecting O to the optimal igniting position O, and a first straight line Lwhich connects O to Pis measured, followed by a measurement of a circumferential angle &#x3b2;formed between LS and a second straight line Lconnecting O to PThereafter, the deviation of the ground electrode from Ois measured as a circumferential angle '&#x3b1;' between &#x201c;LS&#x201d; and a third straight line Lconnecting the axis O to the center C of the front end face.

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Seto, Japan

Atsushi Ozeki