In-cylinder fuel-injection type internal combustion engine, piston for in-cylinder fuel-injection type internal combustion engine and process for manufacturing piston for in-cylinder fuel-injection type internal combustion engine

Abstract

A piston for in-cylinder fuel-injection type internal combustion engine includes a piston body, a low thermal conductor, and a piston head. The low thermal conductor is disposed on the top of the piston body. The low thermal conductor includes a low thermally-conductive substrate, and a coating layer. The low thermally-conductive substrate has opposite surfaces. The coating layer includes alumina fine particles (Al 2 O 3 ). The coating layer is adhered on at least a part one of the opposite surfaces of the low thermally-conductive substrate that makes a cast-buried or enveloped surface to be cast buried or enveloped in the piston head.

1 - 10 . (canceled) 
     
     
         11 . A process for manufacturing piston for in-cylinder fuel-injection type internal combustion engine,
 the piston comprising: a piston body having a top, and being disposed reciprocably within a cylinder in a cylinder block of the internal combustion engine; a low thermal conductor for forming a low thermally-conductive zone whose thermal conductivity is lower than that of the surroundings, and the low thermal conductor making at least a part of a fuel collision zone with which liquid fuel is collidable, the liquid fuel being injected from a fuel injection valve into the cylinder, the fuel injection valve being disposed in a cylinder head that is disposed on the cylinder block; and a piston head in which the low thermal conductor being disposed on the top of the piston body is cast buried;   the manufacturing process comprising the steps of:   adhering a coating material comprising alumina fine particles onto at least a part of one of opposite surfaces of a low thermally-conductive substrate, thereby forming a coating layer on one of the opposite surfaces; and   casting the piston head while contacting the one of the opposite surfaces of the low thermally-conductive substrate that is provided with the coating layer with a molten metal of aluminum alloy, thereby making an aluminum-alloy piston head in which the low thermal conductor is cast buried.   
     
     
         12 . The manufacturing process according to  claim 11 , wherein the adhering step comprises a step of immersing at least a part of one of the opposite surfaces of the low thermally-conductive substrate into a dispersion liquid in which the coating material is dispersed in a dispersant. 
     
     
         13 . The manufacturing process according to  claim 11 , wherein the adhering step comprises a step of applying a dispersion liquid in which the coating material is dispersed in a dispersant onto at least a part of one of the opposite surfaces of the low thermally-conductive substrate. 
     
     
         14 . The manufacturing process according to  claim 12 , wherein the adhering step further comprises a step of drying the low thermally-conductive substrate which has been immersed into the dispersion liquid. 
     
     
         15 . The manufacturing process according to  claim 13 , wherein the adhering step further comprises a step of drying the low thermally-conductive substrate on which the dispersion liquid has been applied. 
     
     
         16 . The manufacturing process according to  claim 12 , wherein the dispersant comprises water or alcohol. 
     
     
         17 . The manufacturing process according to  claim 13 , wherein the dispersant comprises water or alcohol. 
     
     
         18 . The manufacturing process according to  claim 12 , wherein dispersion liquid comprises the coating material in a mixing proportion of from 1 to 2 by mass with respect to a mass of the dispersant. 
     
     
         19 . The manufacturing process according to  claim 13 , wherein dispersion liquid comprises the coating material in a mixing proportion of from 1 to 2 by mass with respect to a mass of the dispersant. 
     
     
         20 . The manufacturing process according to  claim 11 , wherein the coating material comprises at least one member that is selected from the group consisting of alumina powders and alumina-containing clays. 
     
     
         21 . The manufacturing process according to  claim 20 , wherein the coating material comprises a mixture of an alumina powder and an alumina-containing clay. 
     
     
         22 . The manufacturing process according to  claim 20 , wherein the alumina-containing clay is mixed with the alumina powder in a mixing proportion of from 0 to 80 by mass with respect to a mass of the alumina powder. 
     
     
         23 . The manufacturing process according to  claim 20 , wherein the alumina-containing clays comprise an alumina-silica hydrate. 
     
     
         24 . The manufacturing process according to  claim 14 , wherein the low thermally-conductive substrate is dried at a temperature of 50° C. or more in the drying step. 
     
     
         25 . The manufacturing process according to  claim 15 , wherein the low thermally-conductive substrate is dried at a temperature of 50° C. or more in the drying step.