Engine valves

Abstract

The present invention includes an engine valve including a stem portion and a head portion disposed at one end of the stem portion. A heat insulation layer is formed on a surface of the head portion. A heat conductive layer is formed on a surface of the stem portion.

1 . An engine valve comprising:
 a stem portion;   a head portion disposed at one end of the stem portion;   a heat insulation layer formed on a surface of the head portion; and   a heat conductive layer formed on a surface on the stem portion.   
   
   
       2 . The engine valve as in  claim 1 , wherein the heat conductive layer is made of at least one of aluminum nitride and chrome nitride. 
   
   
       3 . The engine valve as in  claim 1 , wherein the engine valve is a solid exhaust valve. 
   
   
       4 . The engine valve as in  claim 3 , wherein the heat insulation layer is formed on at least a back side surface of the head portion. 
   
   
       5 . The engine valve as in  claim 1 , wherein the heat insulation layer is formed on at least a front side surface of the head portion. 
   
   
       6 . The engine valve as in  claim 4 , wherein the heat insulation layer is formed on at least a front side surface of the head portion. 
   
   
       7 . The engine valve as in  claim 1 , wherein the heat insulation layer is made of ceramic-based material. 
   
   
       8 . The engine valve as in  claim 2 , wherein the heat insulation layer is made of ceramic-based material. 
   
   
       9 . The engine valve as in  claim 7 , wherein the heat insulation layer is made of at least one of oxide ceramic and nitride ceramic. 
   
   
       10 . An engine valve for mounting to a cylinder head of an engine, comprising:
 a body having a stem portion and a head portion disposed at one end of the stem portion;   a heat insulation layer formed on a surface of the head portion and having a heat conductivity lower than a heat conductivity of the body; and   a heat conductive layer formed on a surface on the stem portion and having a heat conductivity higher than the heat conductivity of the body.   
   
   
       11 . The engine valve as in  claim 10 , wherein:
 the heat insulation layer is formed on the surface of the head portion that is not in contact with the cylinder head.   
   
   
       12 . The engine valve as in  claim 10 , wherein the heat conductive layer is formed on at least a part of the surface of the stem portion that can contact with the cylinder head. 
   
   
       13 . The engine valve as in  claim 11 , wherein the heat conductive layer is formed on at least a part of the surface of the stem portion that can contact with the cylinder head. 
   
   
       14 . The engine valve as in  claim 10 , wherein the heat conductive layer is made of at least one of aluminum nitride and chrome nitride. 
   
   
       15 . The engine valve as in  claim 10 , wherein the heat insulation layer is made of at least one of oxide ceramic and nitride ceramic.