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An exhaust valve arrangement for use in a combustion chamber of a compression ignition internal combustion engine, includes a piston which is movable outwardly from the combustion chamber in response to pressure generated within the combustion chamber as a result of combustion, and an outer sleeve w

An exhaust valve arrangement for use in a combustion chamber of a compression ignition internal combustion engine, includes a piston which is movable outwardly from the combustion chamber in response to pressure generated within the combustion chamber as a result of combustion, and an outer sleeve within which the piston is movable. The outer sleeve is an exhaust valve which is actuable between open and closed positions to open and close, respectively, an exhaust passage from the combustion chamber. The exhaust valve arrangement further includes a pump chamber for receiving fluid, and a pumping plunger coupled to the piston and movable with the piston so as to pressurise fluid (e.g. fuel) within the pump chamber as the piston is urged outwardly from the combustion chamber. The pressure within the pump chamber is proportional to cylinder pressure and is sensed by a sensor which provides an output signal to an Engine Control Unit (ECU 16). An accumulator volume receives fluid that is pressurised within the pump chamber. Where the fluid is fuel, the accumulator volume is arranged to deliver fuel to one or more injectors of a common rail fuel injection system. Alternatively the accumulator volume may be arranged to deliver pressurised fluid to one or more engine systems e.g. for actuation purposes.

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The invention claimed is: 1. An exhaust valve arrangement for use in a combustion chamber of a compression ignition internal combustion engine, the exhaust valve arrangement including: a piston that is movable outwardly from a combustion chamber in response to pressure generated within the combusti

The invention claimed is: 1. An exhaust valve arrangement for use in a combustion chamber of a compression ignition internal combustion engine, the exhaust valve arrangement including: a piston that is movable outwardly from a combustion chamber in response to pressure generated within the combustion chamber as a result of combustion, and an outer sleeve, within which the piston is movable, wherein the outer sleeve is actuable between open and closed positions to open and close, respectively, an exhaust passage from the combustion chamber, wherein the outer sleeve has an actuator for moving the outer sleeve from the closed position into the open position, further comprising a pump chamber for receiving fluid, wherein a surface associated wit the piston defines a wall of the pump chamber so that the piston pressurises fluid within the pump chamber as the piston is urged outwardly from the combustion chamber. 2. The exhaust valve arrangement as claimed in claim 1, further comprising a biasing arrangement for urging the piston into a position in which the piston holds the outer sleeve in the closed position to close the exhaust passage. 3. The exhaust valve arrangement as claimed in claim 2, wherein the biasing arrangement includes a piston spring for urging the piston into a position in which the piston holds the outer sleeve in the closed position. 4. The exhaust valve arrangement as claimed in claim 2, wherein the biasing arrangement includes a gas or fluid pressure for urging the piston into the position in which the piston holds the outer sleeve in the closed position. 5. The exhaust valve arrangement as claimed in claim 1, wherein the piston is hollow. 6. The exhaust valve arrangement as claimed in claim 5, wherein the piston is at least partially filled with a medium for aiding heat transfer away from a surface of the piston that is exposed to gases within the combustion chamber. 7. The exhaust valve arrangement as claimed in claim 1, wherein the piston includes a main piston body in the form of a cup and a piston cap which closes the cup. 8. The exhaust valve arrangement as claimed in claim 1, wherein the piston is coupled to a pumping plunger which defines the wall of the pump chamber, the pumping plunger being movable wit the piston in response to pressure generated within the combustion chamber so as to pressurise fluid within the pump chamber. 9. An exhaust valve arrangement for use in a combustion chamber of a compression ignition internal combustion engine, the exhaust valve arrangement including: a piston which is movable outwardly from the combustion chamber in response to pressure generated within the combustion chamber as a result of combustion, an outer sleeve within which the piston is movable, wherein the outer sleeve is operable between open and closed positions to open and close, respectively, an exhaust passage from the combustion chamber, a pump chamber for receiving fluid, and a pumping plunger coupled to the piston and movable with the piston in response to pressure generated within the combustion chamber so as to pressurise fluid within the pump chamber as the piston is urged outwardly from the combustion chamber. 10. The exhaust valve arrangement as claimed in claim 9, wherein the piston is at least partially filled with a medium for aiding heat transfer away from a surface of the piston that is exposed to gases within the combustion chamber. 11. A fuel system for a compression ignition internal combustion engine, the fuel system including; an exhaust valve arrangement for the combustion chamber as timed in claim 9, and a valve assembly for controlling the supply of fluid to and from the pump chamber, whereby the valve assembly is operable to allow pressure spikes within the combustion chamber to be absorbed by movement of the plunger. 12. The fuel system as claimed in claim 11, further comprising: at least one fuel injector for delivering fuel into the combustion chamber, and an accumulator volume for receiving fluid in the form of fuel that is pressurised within the pump chamber and for storing said fuel for delivery to the or each injector. 13. The fuel system as claimed in claim 12, wherein the valve assembly comprises a rail control valve for controlling communication between the pump chamber and the accumulator volume. 14. The fuel system as claimed in claim 13, wherein the rail control valve is operable by means of an electromagnetic actuator. 15. The fuel system as claimed in claim 14, including a sensor for sensing the pressure in the pump chamber, whereby the rail control valve is actuated to open communication between the pump chamber and the accumulator volume in response to the sensed pressure. 16. The fuel system as claimed in claim 15, wherein the rail control valve is pressure balanced with respect to fuel pressure within the pump chamber that is applied to the rail control valve. 17. The fuel system as claimed in claim 13, wherein the valve assembly further comprises a non-return valve between the rail control valve and the accumulator volume. 18. The fuel system as claimed in claim 13, wherein the valve assembly further comprises a filling valve for controlling the supply of low pressure fuel to the pump chamber. 19. The fuel system as claimed in claim 18, wherein the filling valve is an actuable valve which is controllable by an engine control unit. 20. The fuel system as claimed in claim 19, wherein the filling valve is actuable by means of an electromagnetic actuator. 21. The fuel system as claimed in claim 18, wherein the filling valve is a spring-biased non-return valve. 22. The fuel system as claimed in claim 18, wherein at least a portion of the rail control valve and at least a portion of the filling valve are both movable within a common bore formed in a valve housing. 23. A fuel system for a compression ignition internal combustion engine, the fuel system including; at least one fuel injector for delivering fuel into the combustion chamber, and first and second exhaust valve arrangements, each of which includes an associated piston which is movable outwardly from the combustion chamber in response to pressure generated within the combustion chamber as a result of combustion. an outer sleeve within which the associated piston is movable, wherein the outer sleeve is operable between open and closed positions to open and close, respectively, an exhaust passage from the combustion chamber, an associated pump chamber for receiving fluid, and a pumping plunger coupled to the associated piston and movable wit the associated piston so as to pressurise fluid within the pump chamber as the associated piston is urged outwardly from the combustion chamber. 24. The fuel system as claimed in claim 23, wherein the pump chamber of the first exhaust valve arrangement is arranged to receive fuel and to deliver pressurised fuel to a first accumulator volume from where fuel is delivered to the at least one injector. 25. The fuel system as claimed in claim 23, wherein the second exhaust valve arrangement is arranged to receive a fluid other than fuel and the associated pumping plunger of the second exhaust valve arrangement is arranged to pressurise the fluid in response to movement of the associated piston and to deliver the pressurised fluid to the associated accumulator volume. 26. The fuel system as claimed in claim 25, whereby fluid within the associated accumulator volume of the second exhaust valve arrangement is delivered to an engine system. 27. The fuel system as claimed in claim 26, wherein the engine system is at least one of: an electro-hydraulic variable valve actuation system, a hydraulically assisted turbo-charger, an intensifier piston for pressurising injectable fuel. 28. The fuel system as claimed in claim 24, wherein the associated pump chamber of the second exhaust valve arrangement is arranged to receive fuel and the associated pumping plunger of the second exhaust valve arrangement is arranged to pressurise said fuel in response to movement of the associated piston of the second exhaust valve arrangement. 29. The fuel system as claimed in claim 28, wherein the associated pump chamber of the second exhaust valve arrangement is arranged to deliver the pressurised fuel to the associated accumulator volume of the second exhaust valve arrangement from where fuel is provided to the at least one injector. 30. The fuel system as claimed in claim 29, wherein the accumulator volume of the first exhaust valve arrangement is the same as the accumulator volume of the second exhaust valve arrangement so as to form a common accumulator volume for fuel to be provided to a plurality of injectors of the engine. 31. The fuel system as claimed in claim 29, wherein, in the first exhaust valve arrangement, an area ratio of the piston to the pumping plunger is greater than an area ratio of the piston to the pumping plunger in the second exhaust valve arrangement. 32. The fuel system as claimed in claim 31, wherein the associated accumulator volume of the second exhaust valve arrangement is arranged to deliver pressurised fuel for the purpose of at least one of the following: an early premixed injection, a pilot injection, a post injection, a late post injection, an after treatment regeneration injection.