Internal combustion engine and method of operating it

In an internal combustion engine of the type which includes a combustion chamber, induction means including an interior wall defining an inlet passage for introducing an air/fuel charge to said combustion chamber, a throttle in said induction means, and exhaust means for exhausting a spent charge from said combustion chamber, the improvement comprising:

• means for constituting in said induction means said air/fuel charge which is leaner than stoichiometric with the possible exceptions of starting and warm-up operations, and leaner than stoichiometric, or stoichiometric, or nearly stoichiometric, at starting and warm-up operations;
• means tending to maintain the numerical value of the residual fraction at low load conditions such that the engine operates on said air/fuel charge at said low load conditions without substantial misfiring, said residual fraction being defined as follows:
• ##EQU4## vaporizing means for maintaining the said interior wall of the induction means downstream from said means for constituting an air/fuel charge substantially free from liquid fuel deposited from said charge, thereby to assist in providing a well-vaporized, uniform and homogeneous air/fuel charge in said induction means;
• and a carburetor starting circuit forming part of said mean for introducing air/fuel mixture, said starting circuit being operable under starting and warm-up conditions to introduce air/fuel mixture into the induction means under starting and warm-up conditions, said starting circuit discharging air/fuel mixture into said induction means downstream of the throttle.

In combination:

• a four stroke cycle, multiple combustion chamber internal combustion engine having a crankshaft and a piston in each combustion chamber linked to said crankshaft whereby to turn said crankshaft when the pistons reciprocate in their respective combustion chambers;
• induction means comprising an individual induction tube for each combustion chamber for introducing a charge thereto;
• exhaust means for exhausting spent charge from said combustion chambers;
• an intake valve and an exhaust valve in each combustion chamber between the respective induction tube and the exhaust means, respectively;
• means for opening and closing said intake and exhaust valves in operating sequences;
• an individual throttle valve in each of said induction tubes;
• an individual fuel injector means for each of said induction tubes for introducing fuel or a mixture of fuel and air into its respective induction tube in quantity such as to form with air passed by the throttle valves a leaner than stoichiometric charge in the respective combustion chamber;
• said multiplicity of induction tubes and throttle valves comprising means for establishing the numerical value of the residual fraction at low load conditions such that the engine operates on a lean air/fuel mixture at said low load conditions without substantial misfiring, said residual fraction being defined as follows:
• ##EQU7## a thermal reactor comprising a chamber in the exhaust means, said thermal reactor being insulated so as to maintain a temperature in said chamber sufficient to consume therein at least some of any hydrocarbon emitted from said cylinder;
• vaporizing means comprising a portion of the wall of the induction means adjacent to the entry to the combustion chamber so disposed and arranged as to be heated by heat conducted to it from the dome of the combustion chamber, whereby to provide a surface temperature sufficient to vaporize a fuel film which contacts it;
• and the fuel injector being so arranged as to discharge fuel or a mixture of fuel and air into the induction means periodically, but not during the time between about 30.degree. before top dead center and 150.degree. after top dead center of the intake stroke.