Relief valve assembly for accumulator type fuel injection nozzle

Claim 1

An accumulator type of injection nozzle comprised of an accumulator chamber adapted to be supplied with high pressure fuel, a nozzle port leading from said accumulator chamber, an injector valve moveable between a closed position and an opened position for controlling the discharge of fuel from said accumulator chamber through said nozzle port, a control chamber for receiving pressurised fuel, an actuating member supported for movement within said control chamber and associated with said injector valve for retaining said injector valve in its closed position when said control chamber is pressurised and for movement of said injector valve to its opened position when pressure is relieved in said control chamber, and relief valve means moveable between a closed position for maintaining pressure in said control chamber and an opened position for relieving said control chamber for effecting fuel discharge through said nozzle port, the improvement comprising said relief valve comprising a valve seat having a relief valve port communicating with said control chamber and surrounded by a relief valve seating area, a relief valve element moveable between the open and closed positions, said relief valve element being adapted when in its closed position to sealingly engage said relief valve port for controlling the flow therethrough, said relief valve element having a surface area facing said relief valve area of substantially greater effective area than said relief valve port, and pressure relief passages formed in at least one of said relief valve seat and said relief valve element for permitting fluid to flow away from said relief valve port as said relief valve element approaches said relief valve seat to increase sealing pressure and facilitate such movement.