Pressure regulation valve

Abstract: A pressure regulation valve is disclosed which comprises a housing (12 a , 12 b ) including first and second ports (14, 16), a support (18) for slidably supporting a tubular member (26) defining a valve seat (32) against which a valve element (24) is engageable. The tubular member (26) and valve element (24) are spring biased into engagement with one another. In use, the application of pressurized fuel to the first port (14) pushes the tubular member (26) against the stop (34), the valve element (24) being able to leave the valve seat (32) in order to permit fuel flow through the valve. If the second port (16) is at a higher pressure than the first port (14), the valve element (24) moves into engagement with the valve seat (32), the application of a high pressure resulting in the valve element (24) and tubular member (26) moving until the valve element (24) engages the support (18), further movement of the tubular member (26) permitting fuel flow through the valve from the second port (16) to the first port (14).

Description: This invention relates to a pressure regulation valve, and particularly to a valve for use in the regulation of fuel pressure in a fuel delivery line used to deliver fuel from an injection pump to an injection nozzle of a diesel internal combustion engine. The fuel systems of diesel engines commonly suffer from the problem that at the end of delivering fuel to the cylinders, the closing of the valves in the injection nozzles results in shock waves being transmitted along the fuel delivery lines towards the injection pump. Delivery valves are commonly provided in the delivery lines, and on the shock wave reaching the delivery valve, the wave is reflected and may result in the injection valve being reopened to deliver additional fuel to the engine, such additional fuel being delivered in the form of relatively large droplets leading to excessive smoke in the engine exhaust. SU-A-174903 describes a valve which permits fuel flow in one direction and prevents flow in the opposite direction, the valve including additional valve means controlling fuel flow into a chamber to absorb rather than reflect pressure waves. GB-A-728697 describes a valve which permits fuel flow in a forward direction, flow in the opposite direction being controlled by the engagement of a separate valve. It is an object of the invention to provide a pressure regulation valve in which the above described disadvantages are reduced. According to the present invention there is provided a pressure regulation valve comprising a valve element movable within a housing having first and second ports arranged to permit fuel to flow from the first port through the housing to the second port, and engageable with a valve seat forming part of a tubular member moveable within the housing in order to restrict the flow of fuel from the second port to the first port, and means for separating the valve element from the valve seat in order to selectively permit the flow of fuel from the second port to the first port, and characterized in that a clearance is defined between the member and part of the housing to permit fuel to flow therebetween, the dimensions of the clearance being chosen to damp movement of the tubular member relative to the housing. The tubular member is preferably slidable upon a support between a position in which the valve element engages with the seat, and a position in which the support lifts the valve element from the seat. The valve element is preferably movable within the housing with respect to the support. The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a pressure regulator valve in accordance with an embodiment of the invention; Figures 2, 3 and 4 are views of the valve of Figure 1 in various position, in use; and Figures 5, 6 and 7 are views similar to Figure 1 of modifications thereto. The pressure regulation valve 10 illustrated in the accompanying drawings is intended for use in the fuel system of a diesel internal combustion engine. The valve 10 comprises a two part valve housing 12 a , 12 b having an inlet port 14 arranged to be connected to a delivery port of a distributor pump, and an outlet port 16 arranged to be connected to a fuel line for carrying fuel from the distributor pump to the injector associated with a cylinder of the engine. The part 12 a of the housing provided with the inlet port 14 includes an integral tubular support 18 extending within the housing 12 b , the passage in the tubular support 18 communicating with the inlet port 14. The free end of the tubular support 18 defines a stop surface 20 which is provided with a plurality of radially extending grooves or channels. The tubular support 18 may be located by means of a projection on the housing part 12 a and which locates with the housing part 12 b . A valve element 24 is provided within the housing 12 b . The valve element 24 comprises a truncated conical element having a generally flat lower surface, the upper surface of the element being provided with a cylindrical recess within which an end of a helical spring 28 is arranged to engage, the other end of the spring 28 engaging with part of the housing 12 b adjacent the outlet port 16 to bias the valve element 24 towards the stop surface 20, movement of the valve element 24 towards the inlet port 14 being limited by engagement of the valve element 24 with the stop surface 20. The valve further comprises a tubular member 26 which takes the form of an open cylinder arranged to slide on the tubular support 18, the dimensions of the member 26 being such as to form a fluid seal between the inner surface of the member 26 and the outer surface of the tubular support 18. A helical spring 30 is arranged to engage with the end of the member 26 remote from the valve element 24, and to engage with the housing 12 a adjacent the inlet port 14 in order to bias the member 26 towards the valve element 24. The end of the member 26 adjacent the valve element 24 includes an inwardly extending flange 32 limiting movement of the member 26 with respect to the tubular support 18, the outer surface of the flange 32 being arranged to engage with part of the generally flat lower surface of the valve element 24 to form a substantially fuel tight seal, the outer surface of the flange 32 defining a valve seat. In use, starting from the position shown in Figure 1, on supplying fuel from the distributor pump to the inlet port 14, once the pressure of the fuel supplied exceeds the pressure of fuel in the delivery line by an amount sufficient to overcome the action of the spring 28, the valve element 24 will move away from the member 26. The member 26 is spring biased towards the valve element 24, but movement thereof is restricted by the engagement of the member 26 with stops 34 provided on the interior of the housing 12 b . As soon as the valve element 24 and member 26 separate, fuel flows therebetween and through channels 36 provided in the housing 12 b around the valve element 24, enabling fuel to flow from the inlet port 14 to the outlet port 16. Such a position is illustrated in Figure 2. On completion of fuel delivery to the engine, the pressure of fuel supplied to the inlet port 14 falls resulting in the valve element 24 moving towards the stop surface 20 under the influence of the spring 28, a point being reach at which the valve element 24 and member 26 contact one another cutting off communication between the inlet and outlet ports 14, 16. The valve 10 then assumes a position similar to that illustrated in Figure 1. The termination of delivery of fuel to the delivery line results in the fuel pressure therein falling, and the valve in the injection nozzle closing, terminating the delivery of fuel to the cylinder of the engine. It is common for a shock wave to occur in the delivery line upon closure of the injector, and on such a wave reaching the valve 10, the high pressure pushes the valve element 24 and member 26 towards the stop surface 20 against the action of spring 30 whereon further movement of the valve element 24 is prevented. Such movement acts to damp the shock wave by increasing the volume available to the fuel in the delivery line. This position is shown in Figure 3. Any excess pressure pushes the member 26 against the action of the spring 30, such movement separating the valve element 24 from the member 26, allowing fuel to flow therebetween and through the grooves or channels provided in the stop surface 20. Such a position is shown in Figure 4. It will be recognised that such a flow of fuel further damps the shock wave. The spring 30 associated with the member 26 is of sufficient strength to prevent fuel flowing between the valve element 24 and the member 26 when the fuel pressure in the delivery line is below approximately 140 Bar. It will therefore be recognised that damping of the shock wave does not result in the pressure of fuel in the delivery line falling below the combustion chamber pressure whilst the valve in the fuel injection nozzle is open. Once the pressure of fuel in the delivery line has stabilised, the spring 30 pushes the member 26, and hence the valve element 24 away from the stop surface 20 to a position such as that shown in Figure 1 in which the valve element 24 engages with the valve seat of the member 26, such movement forcing some of the fuel within the housing 12 a , 12 b to move into the delivery line increasing the pressure of the fuel in the delivery line. The rate at which fuel passes through the valve 10 from the outlet port 16 to the inlet port 14 as a result of excess pressure in the delivery line is dependent upon the size of the grooves or channels provided in the stop surface 20. If it is desired to increase the rate of flow, the channels or grooves may be increased in size or increased in number. Alternatively the channels or grooves may be replaced by an orifice 40 formed in the side wall of the support 18 (see Figure 5). Moreover, the clearance between the member 26 and the inner wall of the housing part 12 b can be tailored to damp the movement of the member. In the modification to the above described device illustrated in Figure 6, an aperture 42 is provided in the valve element 24 permitting a limited amount of fuel to flow therethrough regardless as to the position thereof. The provision of the aperture 42 does not significantly affect the operation of the valve 10 in damping any shock waves transmitted along the delivery line, but does not result in the final movement of the valve element 24 pressurizing the delivery line, the movement merely ensuring that the delivery line is full, excess fuel draining through the aperture 42 and out of the valve 10. In the alternative illustrated in Figure 7, the clearance 44 between the member 26 and the tubular support 18 is sufficiently large to permit fuel to flow therebetween. Such an increased clearance 44 has the same effect as the provision of the aperture 42, the fuel draining from the delivery line along a path between the member 26 and the housing 12 b and then between the member 26 and the tubular support 18.

Claims: A pressure regulation valve comprising a valve element (24) movable within a housing (12 a , 12 b ) having first and second ports (14, 16) arranged to permit fuel to flow from the first port (14) through the housing (12 a , 12 b ) to the second port (16), and engageable with a valve seat (32) forming part of a tubular member (26) moveable within the housing (12 a , 12 b ) in order to restrict the flow of fuel from the second port (16) to the first port (14), and means (18) for separating the valve element (24) from the valve seat (32) in order to selectively permit the flow of fuel from the second port (16) to the first port (14), and characterized in that a clearance is defined between the member (26) and part (12 b ) of the housing (12 a , 12 b ) to permit fuel to flow therebetween, the dimensions of the clearance being chosen to damp movement of the tubular member (26) relative to the housing (12 a , 12 b ). A valve as claimed in Claim 1, wherein the tubular member (26) slidable upon a support (18) between a position in which the valve element (24) engages with the seat (32), and a position in which the support (18) lifts the valve element (24) from the seat (32). A valve as claimed in Claim 2, wherein the valve element (24) is movable within the housing (12 a , 12 b ) with respect to the support (18). A valve as claimed in Claim 3, wherein the support (18) is provided with at least one passage arranged to permit fuel to flow therethrough when the valve element (24) is lifted from the seat (32). A valve as claimed in Claim 4, wherein the at least one passage comprises at least one groove provided in a face (20) of the support (18) arranged to engage the valve element (24). A valve as claimed in Claim 4, wherein the at least one passage comprises at least one orifice (40) provided in the wall of the support (18). A valve as claimed in any one of Claims 1 to 3, wherein the valve element (24) is provided with an opening (42) extending therethrough permitting a limited amount of fuel flow from the second port (16) to the first portion (14) when the valve element (24) is in engagement with the valve seat (32). A valve as claimed in Claim 2 or Claim 3, wherein a clearance (44) of sufficiently large width to permit fuel flow therethrough is provided between the support (18) and the tubular member (26). A valve as claimed in Claim 2 or Claim 3, wherein the valve member (24) is spring biased into engagement with the valve seat (32).

Inventors: COOKE MICHAEL PETER, COOKE, MICHAEL PETER
Applicants: LUCAS IND PLC, LUCAS INDUSTRIES PUBLIC LIMITED COMPANY
Application year: 1995
Main classification: F02M55
IPC codes: F02M55, F02M59