Patent ID: 7363914

Claim:
A fuel injector for an internal combustion engine, the injector comprising an injector body having a tip portion defining at least one spray aperture; a pintle extending within the tip portion, the pintle having a head portion engageable with a valve seat to close the spray aperture, the pintle being axially moveable between a closed position wherein the head portion abuts the valve seat and an open position wherein the head portion is spaced from the valve seat; actuating means for selectively urging the pintle towards its open position; guide means being provided within the injector body guiding the pintle for axial movement between its closed and open positions; a fuel supply chamber being defined within the injector body between the spray aperture and the guide means, characterised in that the guide means has an inner diameter D 1 and the valve seat has an inner diameter D 2 and the ratio of D 1 to D 2 is selected such that the pintle is substantially pressure balanced and thereby subjected to a predetermined resultant opening/closing force when the pintle is in its closed position and pressurised fuel is supplied to the fuel supply chamber.