To improve output in the full operating range by reducing the secondary compression ratio in the low-speed operation.
In a two-cycle internal combustion engine with an exhaust control valve, having an exhaust control valve 11 for opening and closing exhaust passages 10, 10a formed on a cylinder block 3, a pressure control part 27 for reducing the secondary compression ratio in the low-speed operation of the internal combustion engine is provided in an opening and closing operation range of the exhaust control valve 11. The exhaust control valve 11 is provided in the exhaust passages 10, 10a and variably controls the exhaust timing from the lowering position in which the exhaust passage (the exhaust port 10a) is partially closed in the low-speed operation of the internal combustion engine to the rising position, in which the exhaust passage (the exhaust port 10a) is opened fully in the high-speed operation of the internal combustion engine. The pressure control part 27 is taken as a recessed groove 27 formed on the cylinder inner peripheral wall, and the recessed groove 27 is provided in the height range (H-h) of the moving width from the lowering position to the rising position of the exhaust control valve 11.
UCHIDA HIROYUKI
NAKAMURA SHIGESATO
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