Cooling structure of piston in engine

Abstract

A cooling structure of a piston in an engine, in which oil is injected toward a top portion of the piston reciprocating within a cylinder of the engine to cool the top portion of the engine. The cooling structure may include an oil guide surface including at least a thick wall portion of a peripheral wall of the piston which is provided with a ring groove and extends continuously from an inner surface of the peripheral wall of the piston to a reverse surface of the top portion of the piston.

What is claimed is: 
     
         1 . A cooling structure of a piston in an engine, in which oil is injected toward a top portion of the piston reciprocating within a cylinder of the engine to cool the top portion of the engine, comprising:
 an oil guide surface including at least a thick wall portion of a peripheral wall of the piston, which is provided with a ring groove and extends continuously from an inner surface of the peripheral wall of the piston to a reverse surface of the top portion of the piston.   
     
     
         2 . The cooling structure of the piston in the engine, according to  claim 1 ,
 wherein protruding portions are provided to sandwich the oil guide surface from both sides in a circumferential direction of the piston.   
     
     
         3 . The cooling structure of the piston in the engine, according to  claim 1 ,
 wherein the thick wall portion of the peripheral wall of the piston has a recess at an inner side thereof, and a bottom surface of the recess forms at least a portion of the oil guide surface.   
     
     
         4 . The cooling structure of the piston in the engine, according to  claim 1 ,
 wherein a swelling portion is formed continuously with the thick wall portion of the peripheral wall of the piston, and the oil guide surface is formed to extend from the swelling portion to the thick wall portion.   
     
     
         5 . The cooling structure of the piston in the engine, according to  claim 1 ,
 wherein the oil guide surface is formed at an exhaust side of the piston.   
     
     
         6 . The cooling structure of the piston in the engine, according to  claim 1 , comprising:
 an injection nozzle for injecting the oil to the piston, the injection nozzle being directly coupled to a main gallery of the oil inside of a crankcase.   
     
     
         7 . The cooling structure of the piston in the engine, according to  claim 1 ,
 wherein an injection nozzle is positioned to inject the oil to the piston from a timing corresponding to a location below a center of a stroke from a bottom dead center to a top dead center, when the piston is moving upward from the bottom dead center toward the top dead center.   
     
     
         8 . The cooling structure of the piston in the engine, according to  claim 1 ,
 wherein the oil guide surface is recessed relative to a portion of the peripheral wall of the piston which portion is adjacent to the oil guide surface in a circumferential direction of the piston.   
     
     
         9 . A cooling structure of a piston in an engine, in which oil is injected toward a top portion of the piston reciprocating within a cylinder of the engine to cool the top portion of the engine, comprising:
 an oil guide surface extending continuously from an inner surface of a peripheral wall of the piston to a reverse surface of the top portion of the piston,   the oil guide surface being recessed relative to a portion of the peripheral wall of the piston which portion is adjacent to the oil guide surface in a circumferential direction of the piston.   
     
     
         10 . The cooling structure of the piston in the engine, according to  claim 9 ,
 wherein an injection direction of the oil is substantially parallel to an axis of the piston, and the oil is injected from an opposite side of the piston with respect to a crankshaft of the engine.   
     
     
         11 . The cooling structure of the piston in the engine, according to  claim 10 ,
 wherein in a state in which the piston is at top dead center, the oil guide surface is positioned so as not to overlap with a connecting rod of the engine when viewed from a direction of the axis of the piston.   
     
     
         12 . The cooling structure of the piston in the engine, according to  claim 10 ,
 wherein the oil guide surface is positioned so as not to overlap with the crankshaft of the engine when viewed from a direction of the axis of the piston.   
     
     
         13 . The cooling structure of the piston in the engine, according to  claim 12 ,
 wherein an injection position of the oil is set so as not to overlap with the crankshaft of the engine when viewed from the direction of the axis of the piston.