The present invention relates to a control valve for a fuel injector. The control valve has a control valve body which defines a supply passage for high pressure fuel. A control chamber and a pressure compensating chamber are provided in the control valve. The control chamber and the pressure compensating chamber are both in fluid communication with the supply passage. A control valve member is provided for controlling fuel pressure in the control chamber. The pressure compensating chamber is spaced radially outwardly from the control chamber. The invention also relates to a control valve member having a pressure compensating cavity.
1. A control valve for a fuel injector, the control valve comprising:
a control valve body;
a supply passage for high pressure fuel; a control chamber and a pressure compensating chamber, the control chamber and the pressure compensating chamber both being in fluid communication with the supply passage such that the supply passage communicates high pressure fuel to the control chamber and to the pressure compensating chamber;
a low pressure fuel return line;
and a control valve member mounted in the control chamber which selectively prevents fluid communication between the control chamber and the fuel return line and between the pressure compensating chamber and the low pressure fuel return line and which selectively permits fluid communication between the control chamber and the fuel return line and between the pressure compensating chamber and the low pressure fuel return line for controlling fuel pressure in the control chamber;
wherein the pressure compensating chamber is spaced radially outwardly from the control chamber.
2. A control valve as claimed in claim 1 , wherein the pressure compensating chamber comprises an annular chamber.
3. A control valve as claimed in claim 1 , wherein the control chamber and the pressure compensating chamber are arranged concentrically.
4. A control valve as claimed in claim 1 , wherein the control chamber is in fluid communication with the supply passage via the pressure compensating chamber.
5. A control valve as claimed in claim 1 further comprising a sleeve located in the control valve body, the pressure compensating chamber being formed between an outer surface of the sleeve and the control valve body.
6. A control valve as claimed in claim 5 , wherein the sleeve is a restriction fit in the control valve body; and/or at least one high pressure seal is formed between the sleeve and the control valve body.
7. A control valve as claimed in claim 5 , wherein an inner surface of the sleeve forms a seal with the control valve member.
8. A fuel injector comprising a control valve as claimed in claim 1 .
9. A control valve as claimed in claim 1 , wherein the control chamber and the pressure compensating chamber are both in fluid communication with the supply passage when the control valve member is closed.
10. A control valve as claimed in claim 1 , wherein the control chamber and the pressure compensating chamber are both in fluid communication with the supply passage regardless of the position of the control valve member.