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 undervalve cup drive mechanism. Undervalve cup at piston side provided with seats for intake and exhaust valves, and at side opposite to piston, undervalve cup is provided with insulating bushing arranged coaxially relative to intake valve seat and communicating with engine intake manifold and separating intake and exhaust manifolds of engine. Cavity for displacement of bushing is made in cylinder head in intake manifold, and sealing members are installed members are installed on outer sides of undervalve cup and bushing. Undervalve cup is furnished with guide rod from side opposite to piston. Combustion chamber is formed by piston crown, undervalve cup bottoms, intake and exhaust valves and walls of hole of undervalve cup. At minimum loads of engine and at starting, undervalve cup shifts into extreme lower position towards piston, thus providing minimum volume of combustion chamber and maximum compression ratio, 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 increasing volume of combustion chamber to maximum value and decreasing compression ration to minimum value, with clearance compensators being set to minimum clearance. EFFECT: increased efficiency of engine, reduced fuel consumption, improved engine performance and reliability of device. 13 cl, 2 dwg
