Engine with selective venting of unburned mixture from the piston crevice volume

Claim 1

An internal combustion engine having a cylinder with closed and open ends, a piston reciprocably disposed in the cylinder with one end opposing the cylinder closed end to define a combustion space therebetween with an annular crevice volume around said piston one end formed by clearance between the piston and cylinder, the piston being reciprocable between extreme top and bottom dead center positions, respectively, nearest to and farthest from the cylinder closed end, seal means on the piston spaced from said one end and engaging the cylinder to seal the combustion space and crevice volume from the cylinder open end and thus limit blowby leakage from the combustion space to the cylinder open end, intake means for admitting air to the combustion space for compression during a first piston stroke toward top dead center and the subsequent combustion of fuel therein, exhaust means for permitting discharge of combustion products from the combustion space following expansion on a second piston stroke toward bottom dead center, and means for collecting and recirculating to the intake means blowby gases escaping from the combustion space to the open end of the cylinder, and the improvement comprising bypass means operative to open a limited passage for gas flow from the crevice volume to the cylinder open end during each piston expansion stroke, substantially after the beginning thereof but in advance of the opening of said exhaust means on each said expansion stroke, whereby unburned fuel-air mixture is removed from the crevice volume before the exhaust step and recirculated to the intake means for readmission and burning in the cylinder, thus reducing the exhaust of unburned products from the engine.