Spark plug and method of producing the same

Abstract

A spark plug has at least two electrodes having ends facing toward one another so as to produce an electrical discharge when an electrical potential is applied to said electrodes, and a layer of an erosion-resistant material applied on each of said electrodes by electro-spark deposition so the lifetime of the spark plug comparing to existing is substantially increased.

What is claimed is:  
     
       1. A spark plug comprising 
       two electrodes having ends facing toward one another, so that when electrical potential is supplied to the electrodes, an electrical discharge is produced and a spark is generated to ignite a fuel; and  
       a layer of an erosion resistant material applied to each end of each of said electrodes by the electro-spark deposition so that a reliable diffusion bonding Is is provided between a coating and a spark plug electrode material.  
     
     
       2. A spark plug as defined in  claim 1 , wherein said layer of erosion-resistant material is composed of tungsten. 
     
     
       3. A spark plug as defined in  claim 1 , wherein said layer of erosion-resistant material is composed of platinum. 
     
     
       4. A spark plug as defined in  claim 1 , wherein said layer of erosion-resistant material is composed of a metal of 5-6th period of The Periodic Table. 
     
     
       5. A spark plug comprising 
       at least two electrodes, said electrodes having ends facing toward one another so as to produce an electric discharge when an electrical potential is applied to said electrodes and to generate a spark for igniting a fuel; and  
       a layer of an erosion-resistant material applied on each of said ends of each of said electrodes by electro-spark deposition so that a reliable diffusion bonding is provided between the a coating and the spark plug electrode substrate , and heat stresses occurring on a border between the layer and the electrode body, during the spark plug operation, are relived and a lifetime of the spark plugs plug is substantially increased.  
     
     
       6. A method of producing a spark plug, comprising the steps of forming two electrodes having ends facing toward one another so that when electrical potential is supplied to the electrodes an electrical discharge is produced and a spark is generated to ignite a fuel; and applying a layer of an erosion resistant material to each end of each of said electrodes by the electro-spark deposition so that a reliable diffusion bonding is provided between the coating and the spark plug electrode material. 
     
     
       7. A method as defined in  claim 6 , wherein said layer of erosion-resistant material is composed of tungsten. 
     
     
       8. A method as defined in  claim 6 , wherein said layer erosion-resistant material is composed of platinum. 
     
     
       9. A method as defined in  claim 6 , wherein said layer of erosion-resistant material is composed of a metal of 5-6th period of The Periodic Table. 
     
     
       10. A spark plug comprising: 
       
         at least two electrodes having respective ends; and  
       
         a layer of an erosion resistant material which is electro - spark deposited on a surface of the respective end of at least one of the electrodes.    
     
     
       11. The spark plug according to  claim 10 , wherein the surface of the respective end is capable of forming a spark.  
     
     
       12. The spark plug according to  claim 10 , wherein the layer is electro- spark deposited on the surface to establish a diffusion bonding between the surface and the layer.    
     
     
       13. The spark plug according to  claim 10 , wherein a diffusion transient zone is formed on a border between the deposited layer and the surface of the respective end, and wherein the diffusion transient zone reduces a stress as the border during an operation of the spark plug.  
     
     
       14. The spark plug according to  claim 10 , wherein the erosion resistant material includes tungsten.  
     
     
       15. The spark plug according to  claim 10 , wherein the erosion resistant material includes platinum.  
     
     
       16. The spark plug according to  claim 10 , wherein the erosion resistant material includes a metal of a  5 - 6 th period of The Periodic Table.  
     
     
       17. The spark plug according to  claim 10 , wherein the at least two of the electrodes face toward one another.  
     
     
       18. The spark plug according to  claim 10 , wherein the layer is electro- spark deposited on the surface of the respective end of each of the at least two electrodes.    
     
     
       19. A method for producing a spark plug, comprising the steps of: 
       
         providing at least two electrodes having respective ends; and  
       
         electro - spark depositing a layer of an erosion resistant material on a surface of the respective end of at least one of the electrodes.    
     
     
       20. The method according to  claim 19 , wherein the surface of the respective end is capable of forming a spark.  
     
     
       21. The method according to  claim 19 , wherein the electro- spark depositing step establishes a diffusion bonding between the surface and the layer.    
     
     
       22. The method according to  claim 19 , wherein a diffusion transient zone is formed on a border between the deposited layer and the surface of the respective end, and wherein the diffusion transient zone reduces a stress at the border during an operation of the spark plug.  
     
     
       23. The method according to  claim 19 , wherein the erosion resistant material includes tungsten.  
     
     
       24. The method according to  claim 19 , wherein the erosion resistant material includes platinum.  
     
     
       25. The method according to  claim 19 , wherein the erosion resistant material includes a metal of a  5 - 6 th period of The Periodic Table.  
     
     
       26. The method according to  claim 19 , wherein the at least two of the electrodes face toward one another.  
     
     
       27. The method according to  claim 19 , wherein the electro- spark depositing step is performed on the surface of the respective end of each of the at least two electrodes.