Injectors for the fuel injection systems of internal combustion engines

Claim 1

An injector including a fuel supply passage for a fuel injection system of an internal combustion engine which comprises: a. a nozzle body formed with a compartment and including a valve seat; b. a nozzle needle positioned within said compartment of said nozzle body and cooperating with said valve seat to form an injection valve; c. guide means for guiding said nozzle needle within said nozzle body, one end of said guide means forming a first chamber including part at least of said compartment, the other end of said guide means forming a second chamber within said injector, said first and second chambers being in fluid communication with said fuel supply passage, the cross-sectional area bounded by the other edge of contact between said nozzle needle and said valve seat being smaller than the cross-sectional area of said guide means; d. spring means for biasing said nozzle needle against said valve seat; and e. trigger valve means for opening said second chamber at a first predetermined pressure within said second chamber and for closing said second chamber at a second lower predetermined pressure within said second chamber whereby (i) an increase in fuel supply pressure causes said trigger valve means to open when the pressure in said second chamber reaches a value substantially equal to or greater than said first predetermined pressure, thereby relieving the pressure in said second chamber so that the resultant force on said nozzle needle causes the nozzle needle to lift from said valve seat for the injection of fuel and (ii) said trigger valve means recloses said second chamber when the pressure in said second chamber reduces to a value substantially equal to or lower than said second predetermined pressure, said nozzle needle being returned into contact with said valve seat under the influence of said spring means.