Platinum-based alloy for spark plug electrodes incorporating palladium and iridium
A spark plug comprising: an insulator shell; a center electrode inside the insulator shell such that one end of the center electrode protrudes from the insulator shell; a metal shell exterior to the insulator shell; a side ground electrode having one end coupled to the metal shell and the other end facing the protruding end of the center electrode to form a spark discharge gap between the center electrode and the side ground electrode; and a metal tip on at least one of the side ground electrode or the center electrode, located at the spark discharge gap, that is a platinum-based alloy including 23-35 weight percent palladium, greater than 0 to 10 weight percent iridium and the balance being platinum.
1. A spark plug comprising:
an insulator shell;
a center electrode inside the insulator shell such that one end of the center electrode protrudes from the insulator shell;
a metal shell exterior to the insulator shell;
a side ground electrode having one end coupled to the metal shell and the other end facing the protruding end of the center electrode to form a spark discharge gap between the center electrode and the side ground electrode; and
an electrode tip secured to at least one of the side ground electrode or the center electrode, located at the spark discharge gap, the electrode tip comprising a platinum-based alloy comprises 20 to 35% by weight of palladium, from 5 to 15% by weight of iridium, and the balance of the alloy being platinum, all % by weight being based on the total weight of the alloy.
2. A spark plug according to claim 1 , wherein the electrode tip is secured to both the center electrode and the side ground electrode and the electrode tips have a coefficient of thermal expansion (CIE) that is similar to that of the center electrode and the side ground electrode.
3. A spark plug according to claim 1 , wherein the center electrode and the side ground electrode comprise nickel based alloys.
4. A spark plug according to claim 2 , wherein the electrode tips are configured as a pad or rivet or a wire.
5. A spark plug according to claim 1 wherein the electrode tip is joined to the center electrode or the side ground electrode by resistance welding.
6. A spark plug comprising:
an insulator shell;
a center electrode inside the insulator shell such that one end of the center electrode protrudes from the insulator shell;
a metal shell exterior to the insulator shell;
a side ground electrode having one end coupled to the metal shell and the other end facing the protruding end of the center electrode to form a spark discharge gap between the center electrode and the side ground electrode; and
an electrode tip secured to at least one of the side ground electrode or the center electrode, located at the spark discharge gap, the electrode tip comprising a platinum-based alloy, wherein the platinum based alloy comprises 23 to 35% by weight of palladium, from 5 to 10% by weight of iridium, and the balance of the alloy being platinum, all % by weight based on the total weight of the alloy.
7. An electrode tip for a spark plug, the electrode tip being formed from a platinum alloy comprising 23-35 weight percent palladium, greater than 0-10 weight percent iridium and the balance being platinum.
8. The electrode tip as in claim 7 , wherein the platinum alloy comprises 35 weight percent palladium, 10 weight percent iridium and 55 weight percent platinum.
9. The electrode tip as in claim 7 , wherein the platinum alloy comprises 25 weight percent palladium, 10 weight percent iridium and 65 weight percent platinum.
10. The electrode tip as in claim 7 , wherein the platinum alloy comprises 23 weight percent palladium, 10 weight percent iridium and 67 weight percent platinum.