Prechamber ignition device for an IC engine

The ignition equipment (11) is screwed (10a) into the cylinder head (10) and has electrodes (13,14) within a pre-chamber (2). The pre-chamber is separated from the principal combustion chamber (1) by a hemispherical wall (12a) which has passages (15). The passages are oriented such that flame emerging has a length of free passage greater than the distance (d) from hemispherical wall to piston (P) and does not hit the cylinder head