SPARK PLUG AND MANUFACTURING METHOD FOR SAME

Title:

SPARK PLUG AND MANUFACTURING METHOD FOR SAME

Document Type and Number:

WIPO Patent Application WO/2012/042758

Kind Code:

A1

Abstract:

This spark plug includes a resistor in which a connecting portion for electrically connecting a center electrode and a terminal fitting within the axial bore of an insulator has a porosity of 5.0% or less. According to another aspect, this spark plug has a shrinkage ratio ((D - C/D) × 100 of 35% or greater, where fill length D denotes the length from the back end of the center electrode to the back end of a connecting member constituting the connecting portion, and connecting portion length C denotes the length from the back end of the center electrode to the tip of the terminal fitting. This manufacturing method for a spark plug comprises a step in which the terminal fitting is disposed within the axial bore so as to be in contact with a powder for forming the connecting portion, wherein an exposed length H and a powder portion diameter B' satisfy formulae (1) H ≥ -3.1B' + 18, (2) H ≥ -0.85B' + 11, and (3) B ≤ 5, where exposed length H (mm) denotes the length in the axial direction from the back end of the insulator to the tip of a first constituent portion of the terminal fitting exposed from the axial bore, and powder portion diameter B' (mm) denotes the inside diameter in a region of the axial bore where the powder for forming the connecting portion is disposed.

Inventors:

YOSHIDA HARUKI (JP)
HONDA TOSHITAKA (JP)
FUKUSHIMA HOUJU (JP)

Application Number:

PCT/JP2011/005023

Publication Date:

April 05, 2012

Filing Date:

September 07, 2011

Export Citation:

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Assignee:

NGK SPARK PLUG CO (JP)
YOSHIDA HARUKI (JP)
HONDA TOSHITAKA (JP)
FUKUSHIMA HOUJU (JP)

International Classes:

H01T13/20; H01T21/02

Foreign References:

JP2010123626A	2010-06-03
JP2005327743A	2005-11-24
JP2009245716A	2009-10-22

Other References: