Fuel pressure regulation system and an improved fuel pressure regulator for use therein
View Patent ↗A fuel pressure regulation system for a compression ignition diesel engine. The system comprises a fuel supply line connected to an inlet of a transfer pump and a transfer pressure fuel line connected between the transfer pump outlet and the high pressure fuel pump inlet. A fuel filter is positioned in the transfer pressure fuel line and a fuel spill line fluidly connects a fuel pressure regulator to the transfer pressure fuel line at a point between the transfer pump outlet and the fuel filter. A fuel return line is connected between the fuel pressure regulator and the fuel supply line and a control fuel line is connected between the fuel pressure regulator and the transfer pressure fuel line. The fuel pressure regulator comprises a bore within which is located a valve member moveable from a non-regulating position of the fuel pressure regulator to a regulating position of the fuel pressure regulator. In use, any fuel entering the bore through a control fuel line connection acts upon a valve member thrust surface which results in a force acting to open the fuel pressure regulator. Any fuel entering the bore through the fuel spill line connection enters a region between the first end and the second end of the bore. There is provided a leak passageway connected from a point between the first and second ends and a fuel return line connection. In normal operating use, a fuel flow path from the fuel spill line connection to the fuel return line connection is kept open when the fuel pressure regulator is in the non-regulating position.
1. A fuel pressure regulator comprising a bore within which is located a valve member moveable from a non-regulating position of the fuel pressure regulator wherein the valve member is moved in a direction away from a first end of the bore so as to engage fluidtightly a valve seat defined on the bore, to a regulating position of the fuel pressure regulator wherein the valve member is spaced apart from the valve seat, a control fuel line connection positioned at a second end of the bore, such that, in use, any fuel entering the bore through the control fuel line connection acts upon a thrust surface provided on the valve member resulting in a force acting on the valve member in a direction to disengage the valve member from the valve seat, an upper clearance between the valve member and the second end of the bore, a fuel spill line connection positioned in the bore such that, in use, any fuel entering the bore through the fuel spill line connection enters a region between the first end and the second end of the bore, characterised in that there is provided a lower clearance in the bore between the first end and the second end, and a leak passageway connected from a point between the lower clearance and the second end of the bore, and a fuel return line connection, such that, in normal operating use, a fuel flow path from the fuel spill line connection to the fuel return line connection is kept open when the fuel pressure regulator is in the non-regulating position.
2. A fuel pressure regulator as claimed in claim 1 , wherein the leak passageway passes through the valve member.
3. A fuel pressure regulator as claimed in claim 1 , wherein there is provided an expansion volume between the lower clearance and the upper clearance and the leak passageway is fluidly connected to that expansion volume.
4. A fuel pressure regulator as claimed in claim 3 , wherein the expansion volume extends around the periphery of the valve member.
5. A fuel pressure regulator as claimed in claim 1 , wherein, in normal operating use, the cross-sectional area of the lower clearance is large enough to enable free passage of any contaminants within the fuel entering the fuel pressure regulator through the fuel spill line connection.
6. A fuel pressure regulator as claimed in claim 1 , wherein, in normal operating use, the cross-sectional area of the upper clearance is small enough to prevent free passage of any contaminants within the fuel entering the fuel pressure regulator through the fuel spill line connection.
7. A fuel pressure regulator as claimed in claim 1 , wherein the lower clearance is located between the valve member and the bore.
8. A fuel pressure regulator as claimed in claim 1 , further comprising, in a non-regulating position of the fuel pressure regulator a lower start-up clearance and an upper start-up clearance located in the bore between the first end and the second end, the start-up clearances having a smaller cross-sectional flow area than the lower clearance.
9. A fuel pressure regulator as claimed in claim 1 , wherein the bore is provided with a widened region of increased cross-sectional area between the first end and the second end and the valve member comprises an upper region and an overlap region, wherein, in use, the upper region is located between the fuel spill line connection and the second end and the overlap region is located between the fuel spill line connection and the first end and wherein when the fuel pressure regulator is in a non-regulating position there is only a start-up clearance between a part of the upper region and the bore and wherein when the fuel pressure regulator is in the open position all of the upper region is located adjacent to the widened region such that the lower clearance is provided between the valve member and the region.
10. A fuel pressure regulator as claimed in claim 9 , wherein, in use, when the valve member moves from the non-regulating position towards the regulating position of the fuel pressure regulator is open, after a first stage of movement of the valve member the upper clearance is provided between the valve member and the widened region and the lower start-up clearance is provided between the valve member and the bore and after a second stage of movement of the valve member the upper clearance is provided between the valve member and the widened region and the lower clearance is provided between the valve member and the bore.