Torch-ignition internal combustion engine

Claim 1

In an improved torch-ignition internal combustion engine of the type which includes a cylinder block defining therein a cylinder bore, a piston reciprocally mounted in said cylinder bore, a cylinder head mounted on the top of said cylinder block to cooperate with said cylinder bore and said piston to define a main combustion chamber, said cylinder head defining therein an intake port connected to said main combustion chamber, an intake valve for controlling the communication between said main combustion chamber and said intake port, said main combustion chamber being supplied with a fresh charge of a lean air-fuel mixture through said intake port when said intake valve is open on an intake stroke of said engine, a trap chamber confined in said cylinder head and communicated with said main combustion chamber through a torch aperture, a part of the mixture charge to said main combustion chamber being introduced through said torch aperture into said trap chamber and retained therein during a compression stroke of said engine, and a spark plug having a set of electrodes disposed within said trap chamber at a point remote from said torch aperture to ignite the mixture in said trap chamber thereby to produce a torch running through said torch aperture into said main combustion chamber for the torch-ignition of the mixture therein, said trap chamber being so shaped as to have end and peripheral walls, said torch aperture being formed in one of the end walls, said plug electrodes protruding through the other end wall into said trap chamber, wherein the improvement comprises: wall means in said trap chamber defining a generally tubular passage and cooperating with the inner periphery of said trap chamber to define therebetween a side space remote from said plug electrodes, said tubular passage being substantially axially aligned with said torch aperture, said wall means having an end spaced a distance from the other end wall of said trap chamber to define therebetween an end space connected to and continuous with both said tubular passage and said side space, said plug electrodes being disposed in said end space, the end of said side space adjacent to said one end wall of said trap chamber being communicated with the end of said tubular passage adjacent to said torch aperture, said part of the mixture charge being forced to flow from said torch aperture through said tubular passage towards said plug electrodes during the compression stroke of said engine to displace residual combustion gases away from said plug electrodes into said side space whereby said plug electrodes are exposed to and surrounded by said mixture charge part and the displaced residual combustion gases are retained in said side space until said plug electrodes ignite said mixture charge part.