Injector arrangement
View Patent ↗A fuel injector includes an injector body with a bore; an injector needle located within the bore and engageable with a needle seat to control fuel injection through an injector outlet; an armature member, the armature member being engageable with an armature seat on the injector needle, the injector needle in part and the armature member in part defining a control chamber; an actuator arrangement arranged to control fuel pressure within the control chamber such that fuel pressure variations within the control chamber controls movement of the injector needle relative to the needle seat wherein the actuator arrangement is arranged to be capable of moving the armature member from a seated position in which it engages the armature seat to an unseated position in which the armature member has moved relative to the armature seat in order to bring the control chamber into fluid communication with a low pressure drain.
1. A fuel injector for use in an internal combustion engine, the fuel injector comprising:
an injector body comprising a bore;
an injector needle located within the bore and engageable with a needle seat to control fuel injection through an injector outlet, the injector needle comprising an armature seat;
an armature member which is hollow, thereby defining an internal surface of the armature member, the armature member being engageable with the armature seat on the injector needle, the injector needle in part and the internal surface of the armature member in part defining a control chamber;
an actuator arrangement arranged to control fuel pressure within the control chamber such that fuel pressure variations within the control chamber controls movement of the injector needle relative to the needle seat;
wherein the actuator arrangement is arranged to be capable of moving the armature member from a seated position in which it engages the armature seat to an unseated position in which the armature member has moved relative to the armature seat in order to bring the control chamber into fluid communication with a low pressure drain which circumferentially surrounds the control chamber.
2. A fuel injector as claimed in claim 1 , wherein the bore within the injector body comprises an annular gallery.
3. A fuel injector as claimed in claim 2 , wherein the gallery is in fluid communication with an accumulator volume via a high pressure drilling.
4. A fuel injector as claimed in claim 1 , wherein the injector needle comprises an axial drilling.
5. A fuel injector as claimed in claim 4 , wherein the axial drilling is in fluid communication with a source of high pressure fuel at a first end and in fluid communication with the control chamber at a second end.
6. A fuel injector as claimed in claim 5 , wherein the axial drilling comprises a control chamber filling orifice to control the flow of fuel from the source of high pressure fuel into the control chamber.
7. A fuel injector as claimed in claim 4 wherein the axial drilling is in fluid communication with an annular gallery within the bore of the injector body, the gallery being in fluid communication with an accumulator volume via a high pressure drilling.
8. A fuel injector as claimed in claim 1 , further comprises an armature spring member arranged to bias the armature member towards the armature seat.
9. A fuel injector as claimed in claim 1 , further comprising an injector needle spring member arranged to bias the injector needle towards the needle seat.
10. A fuel injector as claimed in claim 1 , wherein the armature seat is located at one end of the injector needle.
11. A fuel injector as claimed in claim 10 , wherein the end of the injector needle comprising the armature seat is substantially frustoconical defining an injector needle end profile, the armature seat being located on the end profile.
12. A fuel injector as claimed in claim 11 , wherein the end of the injector needle comprising the armature seat comprises more than one end profile.
13. A fuel injector as claimed in claim 10 , wherein a second end of the injector needle is arranged to engage the needle seat.
14. A fuel injector as claimed in claim 13 , wherein the actuator arrangement is arranged to move the armature member from the seated position in which it engages the armature seat to a pilot injection position and a main injection position, the rate of flow of fuel from the control chamber to the low pressure drain being greater in the main injection position than the pilot injection position.
15. A fuel injector as set in claim 1 , wherein the actuator arrangement is arranged on an extremity of the fuel injector opposite to the injector outlet.
16. A fuel injector as in claim 1 , wherein the actuator arrangement is arranged to apply a magnetic force on the armature member to move the armature member to the unseated position.
17. A fuel injector as in claim 1 , wherein engagement of the armature with the armature seat blocks fluid communication between the control chamber and the low pressure drain.