FIELD: mechanical engineering; four-stroke internal combustion engines. SUBSTANCE: proposed device contains cylinder, piston, cylinder head with intake and exhaust valves, movable 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, intake and exhaust channels and intake mad exhaust ports. Upper end face surface of undervalve cup has guide rod, holes for valve stems and hole connecting intake channels of undervalve cup with space between upper end face surface of undervalve cup and bottom of hole of undervalve cup. Combustion chamber is formed by piston crown, bottoms of undervalve cup, intake and exhaust valves and walls of hole of undervalve cup. At minimum engine loads and at starting, undervalve cup shifts towards piston, providing minimum volume of combustion chamber and maximum compression ratio. At increase of engine load, undervalve cup shifts in direction opposite to piston under action of spring, thus increasing volume of combustion chamber and decreasing compression ratio. At nominal engine load, undervalve cup shifts into extreme upper position relative to piston, thus increasing volume of combustion chamber and decreasing compression ratio to minimum value. EFFECT: increased efficiency of engine, reduced fuel consumption, improved engine performance and reliability of device. 20 cl, 4 dwg
