Internal combustion engine

Claim 1

An internal combustion engine comprising: (a) a plurality of cylinders split into first and second groups; (b) an air intake passage provided therein with a throttle valve and divided downstream of said throttle valve into first and second branches for supplying air to said first and second groups of cylinders, respectively, said second intake passage branch provided near its inlet with a stop valve normally open to allow the flow of air into said second group of cylinders; (c) an exhaust passage through which exhaust gases are discharged from said cylinders to the atmosphere; (d) an EGR passage having its one end opening into said exhaust passage and the other end opening into said second intake passage branch, said EGR passage having therein an EGR valve adapted to normally close so as to interrupt exhaust gas recirculation into said second intake passage branch and to open so as to allow exhaust gas recirculation thereinto when the engine load is below a predetermined value; (e) split engine control means responsive to engine load conditions for cutting off the supply of fuel to said second group of cylinders and closing said stop valve to cut off the flow of air to said second group of cylinders, thereby rendering said second group of cylinders inactive when the engine load is below the predetermined engine load value; and (f) attenuation means for attenuating pressure waves resulting from exhaust pulsations and propagated through said EGR passage toward said second intake passage branch sufficient to substantially prevent exhaust gases recirculated in said second intake passage branch from escaping through said stop valve into said first intake passage branch when said second group of cylinders is inactive.