Friction insert for oriented valve

Friction insert for oriented valve for a valve-controlled ignition prechamber arranged in an internal combustion engine cylinder head which caps a combustion chamber, the prechamber comprising a lamination cavity, in which ignition means and a lamination injector open, the cavity being connected to the combustion duct by a lamination duct which opens into the chamber in the form of a non-magnetic prechamber tip, in which a lamination valve is accommodated, which can close off the conduit and which is oriented by an orientation pin which can slide into an axial guide orifice arranged in the tip, the valve and the pin, together forming a valve having a guide pin, while the non-magnetic prechamber tip forms with the valve and when this does not close off the lamination duct, a torch ignition prechamber which connects the lamination cavity to the combustion chamber by way of at least one gas ejection orifice comprising:

• at least one external valve body guide cylindrical bearing surface arranged at the periphery of the valve having a guide pin;
• at least one first valve body guide means which is resistant to abrasive wear and which is fixedly mounted in the non-magnetic prechamber tip, the first means having, at least locally, an inner diameter that is both smaller than that of the tip, and that is also substantially larger than the outer diameter of the external valve body guide cylindrical bearing surface, the axial thickness of the first means and the axial position in the non-magnetic prechamber tip of the first means being formed such that the external valve body guide cylindrical bearing surface can slide with a small clearance into the first means, and this in order to guide radially the valve having a guide pin over all or part of its stroke in the non-magnetic prechamber tip;
• at least one external pin guide cylindrical bearing surface arranged at the periphery of the orientation pin;
• at least one second orientation pin guide means which is resistant to abrasive wear and which is fixedly mounted in the axial guide orifice, the second means having, at least locally, an inner diameter that is both smaller than that of the orifice, and that is also substantially larger than the outer diameter of the external pin guide cylindrical bearing surface, the axial thickness and the axial position of the means being formed such that the external pin guide cylindrical bearing surface can slide with a small clearance into the second means, and can maintain the longitudinal axis of the valve having a guide pin almost parallel to that of the non-magnetic prechamber tip over all or part of the stroke of the valve.