Nozzle assembly a fuel injector and an internal combustion engine comprising such an injector

1. A nozzle assembly for injecting fuel into a combustion chamber of an engine, the assembly comprising

a first needle and a second needle controlling respectively fuel flow towards a first series of outlets and a second series of outlets,

a source of fuel under pressure, and

a passive control valve, separate from the first needle and the second needle, adapted to select, based on fuel feeding pressure from the source, either one of the first needle and the second needle to be activated for fuel delivery to the combustion chamber.

2. A nozzle assembly according to claim 1 , wherein the passive control valve controls a flow of fuel coming from two back-pressure chambers acting on the needles.

3. A nozzle assembly according to claim 2 , wherein the passive control valve is adapted to selectively connect, depending on the pressure level of the driving fuel coming from the source, either of the back-pressure chambers with a discharge line.

4. A nozzle assembly according to claim 1 , wherein it includes a solenoid valve adapted to pilot one of the needle, depending on the selection made by the passive control valve.

5. A nozzle assembly according to claim 4 , wherein the solenoid valve controls the connection between the discharge line and a low pressure circuit.

6. A nozzle assembly according to claim 1 , wherein two fuel paths are defined between a source of fuel under pressure and the passive control valve, each path including a back-pressure chamber acting on one of the needles.

7. A nozzle assembly according to claim 6 , wherein each fluid path includes at least two throttles located respectively upstream and downstream of the corresponding back-pressure chamber.

8. A nozzle assembly according to claim 6 , wherein the throttles are made in at least a part mounted on a body of the assembly which surrounds the needles.

9. A nozzle assembly according to claim 7 , wherein one throttle is located between the source of fuel under pressure and each back-pressure chamber.

10. A nozzle assembly according to claim 9 , wherein a dedicated throttle is located on the entry line of each backpressure chamber.

11. A nozzle assembly according to claim 9 , wherein a throttle is located on a feeding line common to both back-pressure chambers.

12. A nozzle assembly according to claim 7 , wherein one throttle is located between each back-pressure chamber and the passive control valve.

13. A nozzle assembly according to claim 7 , wherein one throttle is located downstream of the passive control valve.

14. A nozzle assembly according to claim 1 , wherein the outlets series include a first series of outlets distributed around a central axis with a frustroconical configuration having a first angle and a second series of outlets coaxial with the first series, with a frustroconical configuration having a second angle whose value is superior to the value of the first angle.

15. A nozzle assembly according to claim 1 , wherein it comprises two back-pressure chambers, each back-pressure chamber acting on one needle.

16. A nozzle assembly according to claim 15 , wherein the back-pressure chambers and the needles are coaxial.

17. A nozzle assembly according to claim 1 , wherein the passive control valve comprises a valve core movable in translation within a valve body and subject, on one side, to the action of the fuel feeding pressure and, on the other hand to the action of elastic return means.

18. A fuel injector comprising a nozzle assembly according to claim 1 .

19. An internal combustion engine comprising at least a cylinder provided with a fuel injector comprising a nozzle assembly according to claim 1 .