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 and also intake and exhaust channels and intake and exhaust ports. Upper end face surface of undervalve cup has guide rod, holes for valve steams 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 into extreme lower position towards piston, thus providing minimum volume of combustion chamber and maximum compression ratio, with clearance compensators being set to maximum clearance. At increase of engine load, undervalve cup shifts to side opposite to piston under action of spring, thus increasing volume of combustion chamber and decreasing compression ratio, and clearance compensators decrease value of clearance. At nominal load of engine, undervalve cup shifts into extreme upper position relative to piston, thus providing increase of combustion chamber volume to maximum value and decrease of compression ratio to minimum value, with clearance compensators being set to minimum clearance. EFFECT: increased efficiency of engine, reduced fuel consumption improved performance of engine and reliability of device. 16 cl, 4 dwg
