Ceramic plunger for internal combustion engine high pressure fuel system

A scuff and wear-resistant, high thermal expansion, high hardness zirconia ceramic plunger for an internal combustion engine fuel system component, wherein said plunger is operably positioned entirely within an axial bore in the fuel system component to deliver a selected amount of high pressure fuel directly or indirectly to the engine combustion chamber, and said timing plunger is capable of reciprocal axial movement within the axial bore in the fuel system component under a high axial load and an additional side load on the plunger and is assembled into a bore with a diametral clearance of 76 to 128 millionths of an inch within said axial bore to maintain a desired optimum minimal diametral operating clearance while avoiding excessive fuel leakage and to maintain efficient plunger function without scuffing or sticking under the high axial, side and pressure loads and variable quality fuels encountered in the fuel system operating environment, wherein said zirconia ceramic plunger has a thermal expansion coefficient greater than 6.times.10.sup.-6 /.degree. C. and a hardness greater than 800 Kg/mm.sup.2.

A fuel system for supplying fuel under high pressure to an internal combustion engine, comprising

• a fuel system component containing a bore into which fuel is supplied periodically and from which fuel is discharged at high pressure directly or indirectly into the cylinders of the internal combustion engine, and a plunger operably positioned to reciprocate within said bore to form a variable volume fuel pressurization chamber, said plunger having a diameter slightly smaller than the diameter of said bore to form an optimum diametral clearance that is large enough to permit adequate lubrication between the external surface of said plunger and the surrounding inner surface of said bore and yet small enough to preclude excessive fuel leakage, wherein said plunger is formed of a wear-resistant high hardness, high thermal expansion ceramic material having a thermal expansion coefficient greater than 6.times.10.sup.-6 /.degree. C. and a hardness greater than 800 Kg/mm.sup.2, and said plunger being sized relative to said bore to maintain said optimum diametral clearance therewith to reciprocate freely within said bore without sticking during fuel system pump operation.