Abstract: A cylinder block has a different amount of oil supply for each journal, in which a plurality of bearing saddles are arranged at intervals and main bearings, which support main journals of a crank shaft, are respectively mounted to the plurality of bearing saddles. The bearing saddles comprise oil galleries formed in the cylinder block. Oil chambers are recessed from surfaces of the plurality of bearing saddles, to which an oil is supplied through the oil galleries, and communicate with end portions of the oil galleries to store the oil supplied from the oil galleries. The main bearings have oil holes through which the oil introduced into the oil chambers flow to the main journals.

Abstract: Disclosed is a variable compression ratio device which changes a top dead center of a piston provided in an engine depending on a driving state of the engine. The variable compression ratio device may include: a lower piston reciprocally movable in a cylinder of the engine and connected with a connecting rod to rotate a crankshaft, an operation chamber, an upper piston disposed above the lower piston and partially inserted into the operation chamber, a push plate dividing the operation chamber into upper and lower spaces, a hydraulic pressure chamber which is the lower space, an elastic member provided in the upper space to push the push plate downward, a hydraulic pressure supply unit selectively supplying hydraulic pressure to the hydraulic pressure chamber, and a hydraulic pressure supply pathway connecting the hydraulic pressure supply unit and the hydraulic pressure chamber for supplying the hydraulic pressure.

Abstract: Disclosed is a variable compression ratio device which changes a top dead center of a piston provided in an engine depending on a driving state of the engine. The variable compression ratio device may include: a lower piston reciprocally movable in a cylinder of the engine and connected with a connecting rod to rotate a crankshaft, an operation chamber, an upper piston disposed above the lower piston and partially inserted into the operation chamber, a push plate dividing the operation chamber into upper and lower spaces, a hydraulic pressure chamber which is the lower space, an elastic member provided in the upper space to push the push plate downward, a hydraulic pressure supply unit selectively supplying hydraulic pressure to the hydraulic pressure chamber, and a hydraulic pressure supply pathway connecting the hydraulic pressure supply unit and the hydraulic pressure chamber for supplying the hydraulic pressure.

Abstract: A method for manufacturing a piston can prevent casting defects such as oxide inclusions or shrinkage cavities on the surface of a combustion chamber over a piston head after casting. The method includes casting a head top having a bowl by pouring a first molten metallic material into a first mold with a bonding portion of the head top to be formed at an upper portion in the first mold and a first riser on the bonding portion of the head top, casting the body by pouring a second molten metallic material into a second mold, with a bonding portion of the body to be formed at an upper portion in the second mold and a second riser on the bonding portion of the body, removing the risers from the head top and the body, and integrally bonding the head top and the body to form the piston.

Abstract: A gasoline direct injection engine that has an injector directly injecting fuel into a combustion chamber, a spark plug, an intake valve, and an exhaust valve and generates power by reciprocating a piston in a cylinder, may include a first cavity formed on a piston head of the piston to return at least some flow of the fuel injected from the injector to the spark plug, a protrusion protruding and off-set from the first cavity toward the exhaust valve, and a second cavity formed from the protrusion to the exhaust valve at a smaller height than the first cavity.

Abstract: A gasoline direct injection engine that has an injector directly injecting fuel into a combustion chamber, a spark plug, an intake valve, and an exhaust valve and generates power by reciprocating a piston in a cylinder, may include a first cavity formed on a piston head of the piston to return at least some flow of the fuel injected from the injector to the spark plug, a protrusion protruding and off-set from the first cavity toward the exhaust valve, and a second cavity formed from the protrusion to the exhaust valve at a smaller height than the first cavity.

Abstract: A balance weight system of a crankshaft includes a first balance weight in which a mass center thereof ranges from approximately +78 to approximately +82 degrees based on the horizontal line, a ninth balance weight in which a mass center thereof ranges from approximately ?82 to approximately ?78 degrees, a second balance weight in which a mass center thereof ranges from approximately +86.5 to approximately +89 degrees, a eighth balance weight in which a mass center thereof ranges from approximately ?89 to approximately ?86.5 degrees, and at least one balance weight group of which size of rotational inertia moment thereof ranges from approximately 13 to approximately 17% compared with the first or ninth balance weight, wherein rotational inertia moment size of the second and eighth balance weights ranges from approximately 15 to approximately 25% compared with the first and ninth balance weights.