Fuel injection system for a combustion engine

1. A fuel injection system for a combustion engine, comprising:

a fuel metering unit for providing a metered supply of pressurised fuel,

at least one first fuel injector,

at least one second fuel injector,

a fuel supply passage arrangement for supplying fuel from the fuel metering unit to the at least one first fuel injector and the at least one second fuel injector,

the fuel supply passage arrangement including a first valve for controlling the flow of fuel from the fuel metering unit to the at least one second fuel injector,

the first valve having a fuel inlet communicating with the fuel metering unit, a fuel supply outlet communicating with the at least one second injector, and a fuel control valve member moveable between a first position in which flow of fuel from the fuel inlet to the fuel supply outlet is prevented and a second position in which the flow of fuel from the fuel inlet to the fuel supply outlet is permitted, and

means for controlling movement of the valve member, wherein the first valve has a fuel priming outlet communicating with the at least one second fuel injector, the fuel priming outlet being positioned relative to the fuel inlet and the valve member so that (a) the flow of fuel from the fuel inlet to the priming outlet is prevented when the valve member is in its first position, and (b) the flow of fuel from the fuel inlet to the fuel priming outlet is permitted before the valve member reaches its second position.

2. A fuel injection system as claimed in claim 1 , wherein the means for controlling movement of the valve member between its first position and its second position includes means for supplying pressurised fluid to an opposite side of the valve member to the fuel from the fuel inlet.

3. A fuel injection system according to claim 2 , wherein the means for supplying pressurised fluid includes a further valve.

4. A fuel injection system according to claim 3 , wherein the further valve has at least a first port communicating with a pressurised fluid supply, and a second port communicating with the first valve.

5. A fuel injection system according to claim 4 , wherein the valve has a third port which is capable of communicating with the second port.

6. A fuel injection system according to claim 5 , wherein the third port further communicates with the at least one second injector.

7. A fuel injection system according to claim 3 , wherein the further valve is controllable so that (a), in a first condition of the further valve, the third port is closed and the first port is connected to the first valve via the second port whereby, in use, the pressurised fuel from the pressurised fuel supply urges the valve member of the first valve into its first position, and (b), in a second condition of the further valve, the first port is closed and the second and third ports are in communication so that, in use, the valve member of the first valve can move from its first position to its second position and thereby displace fuel through the second and third ports to the at least one second injector during travel of the valve member towards its second position.

8. A fuel injection system for a combustion engine, comprising:

a fuel metering unit for providing a metered supply of pressurised fuel,

at least one first fuel injector,

at least one second fuel injector,

a fuel supply passage arrangement for supplying fuel from the fuel metering unit to the at least one first fuel injector and the at least one second fuel injector,

the fuel supply passage arrangement including a first valve for controlling the flow of fuel from the fuel metering unit to the at least one second fuel injector,

the first valve having a fuel inlet communicating with the fuel metering unit, a fuel supply outlet communicating with the at least one second injector, and a fuel control valve member moveable between a first position in which flow of fuel from the fuel inlet to the fuel supply outlet is prevented and a second position in which the flow of fuel from the fuel inlet to the fuel supply outlet is permitted, and

control means for controlling movement of the valve member, wherein the control means includes a further valve having a first port communicating in use with a pressurised fuel supply, a second port communicating with the first valve, and a third port communicating with the at least one second injector,

wherein the further valve is controllable so that (a), in a first condition of the further valve, the third port is closed and the first port is connected to the first valve via the second port whereby, in use, the pressurised fuel from the pressurised fuel supply urges the valve member of the first valve into its first position, and (b), in a second condition of the further valve, the first port is closed and the second and third ports are in communication so that, in use, the valve member of the first valve can move from its first position to its second position and thereby displace fuel through the second and third ports to the at least one second injector during travel of the valve member towards its second position.

9. A fuel injection system according to claim 1 , wherein the fuel control valve member is in the form of a piston moveable within a piston chamber.

10. A fuel injection system according to claim 9 , wherein damping means is provided for damping movement of the piston from its first position to its second position.

11. A fuel injection system according to claim 3 , wherein said further valve is a ball valve.

12. A fuel injection system according to claim 4 , wherein a line connecting the second port with the first control valve member contains a flow restriction.

13. A fuel injection system according to claim 12 , wherein the flow restriction is a unidirectional flow restriction.

14. A fuel injection system according to claim 3 , wherein the fuel control system includes means for changing the condition of said further valve.