The present invention relates to a fuel injector for use in a fuel system of an internal combustion engine. The fuel injector has a supply passage for high pressure fuel and an injection nozzle. The injection nozzle includes a valve needle which can engage with a valve needle seating to control fuel delivery from the fuel injector. A first control valve is provided for controlling fuel pressure within a control chamber to control the valve needle. The fuel injector also includes a second control valve for controlling fuel pressure within a low pressure drain. The invention also relates to a control valve for controlling fuel pressure within a low pressure drain.
1. A fuel injector for use in a fuel system for an internal combustion engine, the fuel injector comprising:
a supply passage for high pressure fuel,
an injection nozzle including a valve needle which is engageable with a valve needle seating to control fuel delivery from the injector,
a first control valve for controlling fuel pressure within a control chamber to control the valve needle, and
a second control valve for controlling fuel pressure within a low pressure drain, the second control valve being a one-way valve;
wherein the first control valve selectively permits fuel flow from the control chamber through the second control valve and also selectively prevents fuel flow from the control chamber through the second control valve.
2. A fuel injector as claimed in claim 1 , wherein the second control valve is operable to maintain a positive pressure within the low pressure drain.
3. A fuel injector as claimed in claim 1 , wherein the second control valve comprises a second control valve member co-operable with a second control valve seat at least substantially to seal the low pressure drain.
4. A fuel injector as claimed in claim 3 , wherein the second control valve member is a resilient member and is biased towards the second control valve seat to close the second control valve.
5. A fuel injector as claimed in claim 4 , wherein the second control valve member is made of a resilient material.
6. A fuel injector as claimed in claim 3 , wherein the second control valve member comprises an O-ring or a C-clip.
7. A fuel injector as claimed in claim 6 , wherein the second control valve comprises an annular recess for locating the O-ring or the C-clip.
8. A fuel injector as claimed in claim 7 , wherein an exit port is formed in the annular recess.
9. A fuel injector as claimed in claim 3 , wherein the second control valve comprises a biasing means for biasing the second control valve member towards the second control valve seat to close the second control valve.
10. A fuel injector as claimed in claim 9 , wherein the biasing means comprises a spring or a resilient member.
11. A fuel injector as claimed in claim 3 , wherein the second control valve member consists of a ball valve member.