Abstract: In an intake structure of an internal combustion engine, on an intake upstream side from a valve seat of an intake port, a convex portion is provided which protrudes to an inside of the intake port in a place near an outer circumferential portion of a cylinder chamber when viewed from an upper side of the cylinder chamber. The convex portion includes an upstream guide surface extending from an apex of the convex portion to the intake upstream side, and a downstream guide surface extending from the apex to an intake downstream side and including a curved surface recessed inside the convex portion at a middle portion thereof.

Abstract: In an intake structure of an internal combustion engine, on an intake upstream side from a valve seat of an intake port, a convex portion is provided which protrudes to an inside of the intake port in a place near an outer circumferential portion of a cylinder chamber when viewed from an upper side of the cylinder chamber. The convex portion includes an upstream guide surface extending from an apex of the convex portion to the intake upstream side, and a downstream guide surface extending from the apex to an intake downstream side and including a curved surface recessed inside the convex portion at a middle portion thereof.

Abstract: A counterbalancing shaft accommodating structure includes: a pair of counterbalancing shafts, provided in an oil pan attached to a lower end portion of an engine; and a housing, adapted to accommodate the counterbalancing shafts in the oil pan. An upper end portion of the housing is provided further upwards than the lower end portion of the engine. An opening is formed continuously to expand over both rotational axes of the pair of counterbalancing shafts in an upper surface of the housing.

Abstract: A counterbalancing shaft accommodating structure includes: a pair of counterbalancing shafts, provided in an oil pan attached to a lower end portion of an engine; and a housing, adapted to accommodate the counterbalancing shafts in the oil pan. An upper end portion of the housing is provided further upwards than the lower end portion of the engine. An opening is formed continuously to expand over both rotational axes of the pair of counterbalancing shafts in an upper surface of the housing.

Abstract: A structure of a chamber in a combustion engine includes a ring-groove portion formed on the piston, a squish-area making portion formed on a top surface of the piston for a squish-area, an outer edge portion formed around the top surface excepting the squish-area making portion, and a land portion formed around a side surface between the ring-groove portion and the top surface. The land portion includes, a squish-land portion formed between the ring-groove portion and the squish-area making portion, an outer-edge-land portion formed between the ring-groove portion and said outer edge portion, the outer-land portion being smaller than the squish-land portion in height.

Abstract: To improve both fuel consumption and quality of exhaust gas quality the present invention as a structure of a chamber in a combustion engine includes a ring-groove portion formed on the piston, a squish-area making portion formed on a top surface of the piston for a squish-area, an outer edge portion formed around the top surface excepting the squish-area making portion, and a land portion formed around a side surface between the ring-groove portion and the top surface. The land portion includes, a squish-land portion formed between the ring-groove portion and the squish-area making portion, an outer-edge-land portion formed between the ring-groove portion and said outer edge portion, the outer-land portion being smaller than the squish-land portion in height.