FIELD: mechanical engineering; four-stroke internal combustion engines. SUBSTANCE: proposed device contains cylinder, piston, cylinder head with intake and exhaust valves, movable cylindrical undervalve cup, camshaft with cam mechanism to operate intake and exhaust valves, and drive mechanism of undervalve cup. Undervalve cup is provided with seats for intake and exhaust valves and bushing installed inside undervalve cup coaxially with exhaust valve seat. Hole is made in cylinder head in manifold for displacement of bushing, and sealing members are installed on outer sides of undervalve cup and bushing. At least one guide rod is made on wall of undervalve cup at side opposite to piston. Combustion chamber is formed by piston crown, bottoms of undervalve cup, intake and exhaust valves and walls of hole of undervalve cup. At begging of exhaust stroke, undervalve cup, with intake valve closed, is in extreme upper position, and opened exhaust valve is in extreme lower position. At completion of exhaust stroke, as piston approaches top dead center, undervalve cup, with intake valve closed, shifts into extreme lower position, thus evacuating exhaust gases from combustion chamber and decreasing clearance (dead) volume of combustion chamber. At beginning of intake stroke, undervalve cup shifts into extreme upper position, with intake valve opened in extreme lower position. At completion of suction stroke, intake valve shifts into extreme upper position and closes. At compression stroke and during working stroke, undervalve cup, with intake and exhaust valves closed, is in extreme upper position. EFFECT: increased efficiency of engine, reduced fuel consumption, improved engine performance. 4 cl, 6 dwg
