Abstract:
A fuel injector (10) includes a plunger assembly (20) disposed within a central axial bore (18) and including a lower plunger (22), an intermediate plunger (24), and an upper plunger (26). The lower plunger (22) reciprocates to meter a variable quantity of fuel and to inject this fuel. A timing chamber (34) formed between the upper and intermediate plungers (26, 24) receives an amount of timing fluid to create a variable length hydraulic link between the plungers (26, 24). The fluid is drained from the chamber (34) through a drain passage (38) at the end of the injection cycle. In a preferred embodiment, the drain passage (38) is located along the central axis of the intermediate plunger (24), and the upper plunger (26) is provided with a projecting portion (29) which moves into position as the timing chamber (34) collapses to effectively constrict the drain passage (38), thus changing the timing fluid flow function to a function which provides greater fluid pressure in the timing chamber (34), maintaining a large downward force on the lower plunger (22) preventing additional, undesired fuel flow into the combustion chamber.
Abstract:
Un injecteur de carburant (10) comporte un ensemble piston plongeur (20), disposé dans une âme axiale centrale (18), qui comporte un plongeur inférieur (22), un plongeur intermédiaire (24) et un plongeur supérieur (26). Le plongeur inférieur (22) effectue un va-et-vient pour doser une quantité variable de carburant et l'injecter. Une chambre séquentielle (34), ménagée entre les plongeurs supérieur et intermédiaire (26, 24) reçoit une dose de fluide séquentiel destinée à créer une liaison hydraulique de longueur variable entre ces plongeurs (26, 24). Ce fluide s'écoule depuis la chambre (34) par une conduite (38) à la fin du cycle d'injection. Dans une variante préférée, la conduite (38) est située le long de l'axe central du plongeur intermédiaire (24) et le plongeur supérieur (26) est doté d'une saillie (29) qui se met en place quand la chambre séquentielle (34) se contracte pour obturer efficacement la conduite (38), ce qui modifie la fonction d'écoulement du fluide séquentiel en une fonction qui procure une pression de fluide supérieure dans la chambre séquentielle (34). Ceci permet de maintenir une force descendante importante sur le plongeur inférieur (22) afin d'éviter un écoulement de carburant supplémentaire et intempestif dans la chambre de combustion.
Abstract:
A fuel injector (10) includes a plunger assembly (20) disposed within a central axial bore (18) and including a lower plunger (22), an intermediate plunger (24), and an upper plunger (26). The lower plunger (22) reciprocates to meter a variable quantity of fuel and to inject this fuel. A timing chamber (34) formed between the upper and intermediate plungers (26, 24) receives an amount of timing fluid to create a variable length hydraulic link between the plungers (26, 24). The fluid is drained from the chamber (34) through a drain passage (38) at the end of the injection cycle. In a preferred embodiment, the drain passage (38) is located along the central axis of the intermediate plunger (24), and the upper plunger (26) is provided with a projecting portion (29) which moves into position as the timing chamber (34) collapses to effectively constrict the drain passage (38), thus changing the timing fluid flow function to a function which provides greater fluid pressure in the timing chamber (34), maintaining a large downward force on the lower plunger (22) preventing additional, undesired fuel flow into the combustion chamber.