Combustion-chamber structure of engine

Abstract

A combustion-chamber structure of an engine comprises a combustion chamber which is partitioned by a cylinder block, a cylinder head, a piston, an intake valve, and an exhaust valve. The intake valve (exhaust valve) comprises an intake valve body including an umbrella part having a valve head and a valve face, a heat-insulation layer provided at the valve head and having smaller heat conductivity than the valve body, a heat-barrier layer provided to cover the valve head with the heat-insulation layer and having smaller heat conductivity than the valve body and the heat-insulation layer, and a heat-diffusion layer provided between the heat-insulation layer and the heat-barrier layer and having larger heat conductivity than the heat-insulation layer and the heat-barrier layer. The heat-diffusion layer comprises a contact portion which contacts with the cylinder head when the intake valve is closed.

What is claimed is: 
     
         1 . A combustion-chamber structure of an engine, comprising:
 a cylinder block;   a cylinder head;   a piston;   a valve; and   a combustion chamber partitioned by the cylinder block, the cylinder head, the piston, and the valve,   wherein said valve is configured to open or close a port opening to said combustion chamber and comprises an umbrella part and a stem part,   said umbrella part of the valve includes a valve body which includes a valve head facing the combustion chamber and a valve face positioned on an opposite side to the combustion chamber, a heat-insulation layer which is provided at the valve head and has smaller heat conductivity than said valve body, a heat-barrier layer which is provided to cover said valve head provided with said heat-insulation layer and has smaller heat conductivity than said valve body and said heat-insulation layer, and a heat-diffusion layer which is provided between said heat-insulation layer and said heat-barrier layer and has larger heat conductivity than said heat-insulation layer and said heat-barrier layer, and   said heat-diffusion layer comprises a contact portion which is provided to extend up a position of said umbrella part of the valve which contacts with said cylinder head when the valve is closed.   
     
     
         2 . The combustion-chamber structure of the engine of  claim 1 , wherein said cylinder head has the larger heat conductivity than said valve body. 
     
     
         3 . The combustion-chamber structure of the engine of  claim 2 , wherein said cylinder head comprises a valve seat which is provided at said port opening and with which a portion of said umbrella part of the valve body contacts, and said contact portion of the heat-diffusion layer is provided at said portion of the umbrella part which contacts with the valve seat. 
     
     
         4 . The combustion-chamber structure of the engine of  claim 3 , wherein said valve is an intake valve, and said heat-barrier layer is provided on said valve face of the umbrella part of the valve as well. 
     
     
         5 . The combustion-chamber structure of the engine of  claim 4 , wherein said heat-barrier layer is provided on said stem part of the valve as well. 
     
     
         6 . The combustion-chamber structure of the engine of  claim 3 , wherein said valve is an exhaust valve, and said heat-barrier layer is provided on said valve face of the umbrella part of the valve as well. 
     
     
         7 . The combustion-chamber structure of the engine of  claim 6 , wherein said heat-barrier layer is provided on said stem part of the valve as well. 
     
     
         8 . The combustion-chamber structure of the engine of  claim 5 , wherein said heat-diffusion layer includes a first portion which is provided between said heat-insulation layer and said heat-barrier layer at said valve head, said contact portion, and a second portion which is an underlayer of the heat-diffusion layer which is provided at said valve face and said stem part. 
     
     
         9 . The combustion-chamber structure of the engine of  claim 3 , wherein said valve is an exhaust valve, said heat-insulation layer and said heat-diffusion layer are provided to cover an entire part of said umbrella part of the valve, and said heat-barrier layer is provided to cover the entire part of the umbrella part of the valve except said contact portion of the heat-diffusion layer. 
     
     
         10 . The combustion-chamber structure of the engine of  claim 9 , wherein said heat-insulation layer, said heat-diffusion layer, and said het-barrier layer are provided to cover at least a section of said stem part of the valve which is continuous to said umbrella part of the valve. 
     
     
         11 . The combustion-chamber structure of the engine of  claim 3 , wherein said valve is an exhaust valve with cooling function in which a coolant sealing portion is formed at the valve body, said heat-insulation layer and said heat-diffusion layer are provided to cover said umbrella part of the valve, said heat-barrier layer is provided to cover the umbrella part of the valve except said contact portion of the heat-diffusion layer, and said heat-insulation layer and said heat-diffusion layer are provided to extend up to a position which overlaps with said coolant sealing portion of the valve body. 
     
     
         12 . The combustion-chamber structure of the engine of  claim 1 , wherein said cylinder head comprises a valve seat which is provided at said port opening and with which a portion of said umbrella part of the valve body contacts, and said contact portion of the heat-diffusion layer is provided at said portion of the umbrella part which contacts with the valve seat. 
     
     
         13 . The combustion-chamber structure of the engine of  claim 1 , wherein said valve is an intake valve, and said heat-barrier layer is provided on said valve face of the umbrella part of the valve as well. 
     
     
         14 . The combustion-chamber structure of the engine of  claim 1 , wherein said valve is an exhaust valve, and said heat-barrier layer is provided on said valve face of the umbrella part of the valve as well. 
     
     
         15 . The combustion-chamber structure of the engine of  claim 1 , wherein said valve is an exhaust valve, said heat-insulation layer and said heat-diffusion layer are provided to cover an entire part of said umbrella part of the valve, and said heat-barrier layer is provided to cover the entire part of the umbrella part of the valve except said contact portion of the heat-diffusion layer. 
     
     
         16 . The combustion-chamber structure of the engine of  claim 1 , wherein said valve is an exhaust valve with cooling function in which a coolant sealing portion is formed at the valve body, said heat-insulation layer and said heat-diffusion layer are provided to cover said umbrella part of the valve, said heat-barrier layer is provided to cover the umbrella part of the valve except said contact portion of the heat-diffusion layer, and said heat-insulation layer and said heat-diffusion layer are provided to extend up to a position which overlaps with said coolant sealing portion of the valve body. 
     
     
         17 . The combustion-chamber structure of the engine of  claim 12 , wherein said valve is an intake valve, and said heat-barrier layer is provided on said valve face of the umbrella part of the valve as well. 
     
     
         18 . The combustion-chamber structure of the engine of  claim 13 , wherein said heat-barrier layer is provided on said stem part of the valve as well. 
     
     
         19 . The combustion-chamber structure of the engine of  claim 14 , wherein said heat-barrier layer is provided on said stem part of the valve as well. 
     
     
         20 . The combustion-chamber structure of the engine of  claim 1 , wherein said heat-barrier layer is made of heat-resistant silicon resin which has the heat conductivity of 0.05-1.50 W/mK, and said heat-diffusion layer is made of copper-based material, Corson alloy, beryllium copper, fiber-reinforced aluminum alloy, or titanium aluminum which have the heat conductivity of 35-600 W/mK.