Spark plug with alloy chip

Abstract

Spark plug has a central electrode, an insulator provided exterior to the central electrode, main metallic shell provided exterior to the insulator in such a way that the central electrode protrudes from one end, and a ground electrode coupled at one end to the main metallic shell and which has the other end disposed to face the central electrode 3 , with a chip being secured to either the central electrode or the ground electrode or both to form spark discharge gap g. The chip is made of a metal based on Ir which contains Rh in an amount ranging from 3 to 50 wt (50 wt % being not inclusive).

1. A spark plug comprising:
 a central electrode; 
 an insulator provided exterior to the central electrode; 
 a main metallic shell provided exterior to the insulator; 
 a ground electrode coupled to one end of the main metallic shell and having one end coupled to the main metallic shell and another end facing the central electrode; and 
 an igniting portion secured to at least one of the central electrode and the ground electrode, and forming a spark discharge gap; 
 wherein a taper portion is formed at a tip end side of the central electrode, and the chip is bonded to the tip end face of the taper portion so as to form the igniting portion; 
 wherein the igniting portion includes an Ir-based alloy including Rh in an amount ranging from over 10% to less than 30% wt %. 
 
     
     
       2. A The spark plug according to  claim 1 , wherein the Ir-based alloy includes Rh in an amount ranging from 15 to 25 wt %. 
     
     
       3. A The spark plug according to  claim 1 , wherein the Ir-based alloy includes Rh in an amount ranging from 18 to 22 wt %. 
     
     
       4. A method for producing a spark plug including a central electrode; an insulator provided exterior to the central electrode; a main metallic shell provided exterior to the insulator; a ground electrode having one end coupled to the main metallic shell and another end facing the central electrode; and an igniting portion secured to at least one of the central electrode and the ground electrode and forming a spark plug gap; the method comprising:
 placing a chip including an Ir-based alloy including Rh in an amount ranging from over 10 wt % to less than 25 wt % on a tip end face of the central electrode comprising Ni alloy; and   forming an annular welding portion laid across the chip and the central electrode, so as to form the igniting portion including an Ir-based alloy including Rh in an amount ranging from over 10 wt % to less than 25 wt %.   
     
     
       5. The spark plug according to the method of claim 4, wherein the welding portion is exposed to an outer periphery of the chip, and is not exposed to the tip end face of the chip. 
     
     
       6. The spark plug according to the method of claim 4, wherein the central electrode is arranged such that the whole of the taper portion protrudes from an outside of an opening edge of a through hole of the insulator, the central electrode being inserted into the through hole. 
     
     
       7. The spark plug according to the method of claim 4, wherein the chip is produced by working a molten alloy including an Ir-based alloy including Rh in an amount ranging from over 10 wt % to less than 30 wt % at 700° C. or more by hot rolling or hot forging to a wire or rod shape, and thereafter, cutting the worked alloy to a specified length in a longitudinal direction. 
     
     
       8. The spark plug according to the method of claim 4, wherein the chip is produced by working a molten alloy including an Ir-based alloy including Rh in an amount ranging from over 10 wt % to less than 30 wt % at 700° C. or more by hot rolling to a sheet, hot blanking the sheet to a chip of a specified shape, and welding and bonding the chip. 
     
     
       9. The spark plug according to the method of claim 4, wherein the igniting portion includes an Ir-based alloy including Rh in an amount ranging from 15 wt % to less than 25 wt %. 
     
     
       10. The spark plug according to the method of claim 4, wherein the igniting portion includes an Ir-based alloy including Rh in an amount ranging from 18 wt % to less than 22 wt %. 
     
     
       11. A spark plug comprising:
 a central electrode;   an insulator provided exterior to the central electrode;   a main metallic shell provided exterior to the insulator;   a ground electrode coupled to one end of the main metallic shell and having another end facing the central electrode; and   an igniting portion secured to at least one of the central electrode and the ground electrode, and forming a spark discharge gap;   wherein a taper portion is formed at a tip end side of the central electrode, and the chip is bonded to the tip end face of the taper portion so as to form the igniting portion;   wherein the igniting portion includes an Ir-based alloy including Rh in an amount ranging from over 10% to less than 30% wt %.   
     
     
       12. A spark plug according to claim 11, wherein the Ir-based alloy includes Rh in an amount ranging from 15 to 25 wt %. 
     
     
       13. A spark plug according to claim 11, wherein the Ir-based alloy includes Rh in a amount ranging from 18 to 22 wt %.