The invention discloses an overhead-valve
combustion chamber of a two-
stroke gasoline direction injection engine. The overhead-valve
combustion chamber is a cavity encircled by a cylinder cover, an intake valve, an
exhaust valve, a
piston, a cylinder sleeve, a
gasoline injector and a
spark plug. The inclined surface of a ceiling at the intake side of the cylinder cover is composed of two connected inclined surfaces having different included angles with the axis of the
piston, and a spherical
gasoline avoiding pit is sunken in the inclined surface; the position of an intake door seat is higher than the ceiling at the intake side in a vertical direction, and the intake door seat and the ceiling form a step; the gasoline
injector is a piezoelectric
crystal outwards-opening gasoline
injector and arranged at the centre of the cylinder with the
spark plug; and the centre of the
piston is bulged, the top surface of the bulge is inclined, and a spherical pit is sunken in the top surface. According to the overhead-valve
combustion chamber disclosed by the invention, reverse tumble
scavenging is realized through the step on the ceiling, and intake short-circuit is reduced; wall
wetting due to
fuel oil is reduced through the gasoline avoiding pit, the top surface of the bulge of the piston and the pit of the piston; and a layered
mixed gas is organized through the outwards-opening gasoline injector arranged at the centre. The overhead-valve
combustion chamber disclosed by the invention is capable of realizing efficient
scavenging for the two-
stroke gasoline engine, optimizing the layering of the
fuel oil and reducing the wall
wetting due to the
fuel oil, and beneficial to realizing the
miniaturization of the gasoline engine.