Patent GB-1410611-A (GB)
Title: Internal combustion engines
IPC: F02M13/04
Filed: 1972-12-06
Abstract: 1410611 Pre-combustion chambers HONDA GIKEN KOGYO KK 6 Dec 1972 [11 Jan 1972 6 March 1972 22 Sept 1972] 56400/72 Heading F I B A four-stroke spark-ignition reciprocating piston I.C. engine has, associated with each cylinder, a main combustion chamber and a precombustion chamber, means being provided for supplying an air-fuel mixture of predetermined strength to the main combustion chamber during the induction stroke of the piston and for supplying a richer air-fuel mixture to the pre-combustion chamber during the induction stroke, and the pre-combustion chamber being provided with spark ignition means and communicating with the main combustion chamber via a flame passage whereby, upon ignition, a flame travels through the flame passage to the main combustion chamber to ignite the mixture therein, wherein the volume of the pre-combustion chamber is from 5-12% of the total combined volume of the two combustion chambers measured when the piston is at T.D.C., and the minimum crosssectional area of the flame passage is from 0.04 to 0.16 sq. cms. per cu. cm. of volume of the pre-combustion chamber, and the main combustion chamber is formed so as not to promote turbulence therein during and at the end of the compression stroke of the piston. A carburetter 15 supplies a richer-thanstoichiometric mixture to the pre-combustion chamber via the valve 10 and a passage 17 which is heated by the exhaust gas flowing through a duct 18 which has a common wall with the passage 17 over part of its length. A carburetter 14 supplies a lean mixture to the main chamber. The throttle valves of the two carburetters are mechanically linked by a cam and lever device, so that they move at different rates, the arrangement being such that the overall fuel-air mixture is richer at idling that at full throttle. The minimum cross-sectional area of the torch nozzle 3 is greater than the cross-sectional area of the Venturi of the carburetter 15. The pre-combustion chamber 5 is formed by a stainless steel cup having a wall thickness of 2 mm. the outer sur-  face of the cup being separated by an air space from the inner surface of the cavity in the cylinder head in which it is situated except at its flanged open end. There is an aperture in the wall of the cup opposite the spark plug 49 and a second aperture in alignment with the torch nozzle. The axis of the torch nozzle is out of alignment with the sparking plug aperture and is co-incident with a line which passes through, or just below the central axis through the piston when it is at T.D.C. The main combustion chamber is unsymmetrical and has its maximum height at that side of the chamber which is nearest to the auxiliary chamber. Operation. Part of the rich mixture drawn into the pre-combustion chamber enters the main chamber by passing through the torch nozzle and is dispersed in the lean mixture drawn into the main chamber. Some of this dispersed mixture flows back into the pre-combustion chamber during the compression stroke, at the end of which a small cloud of mixture having a strength intermediate between the strengths of the mixtures in the main and pre-combustion chambers, remains near the torch nozzle, and affects the rate of burning in the main chamber. The peak temperature in the main combustion chamber is reduced and thus there is a decrease in the amount of oxides of nitrogen formed, but the average combustion temperature is kept as high as possible for a long period to minimize the formation of carbon monoxide and unburnt hydrocarbons.