Cylinder inside direct-injection gasoline-engine piston

The utility model relates to a cylinder inside direct-injection gasoline-engine piston which comprises a piston body. The cylinder inside direct-injection gasoline-engine piston is characterized in that a protrusion is installed in the middle of a top plane of the piston body; a round pit is formed in the middle of and on the lower portion of the top plane of the piston body, the diameter of the opening of the round pit is large, the diameter of the bottom surface of the round pit is small, and a part of the round pit and the protrusion are overlapped; the circle center of the opening of the round pit is located below the circle center of the top plane of the piston body, the circle center of the bottom surface of the round pit is located below the circle center of the opening, and the pit wall of the round pit is an arc-shaped transition surface; and the bottom surface of the round pit is an inclined plane. The cylinder inside direct-injection gasoline-engine piston can prevent oil mist from being partially accumulated inside a top pit of the piston, is beneficial for formation of mixed gas, and further improves combustion efficiency.