GB2252145A

GB2252145A - Valve for fuel pumping apparatus

Info

Publication number: GB2252145A
Application number: GB9101403A
Authority: GB
Inventors: Donald Thomas Mclagan Grieve
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1991-01-22
Filing date: 1991-01-22
Publication date: 1992-07-29
Also published as: GB9101403D0

Abstract

A damping valve for a fuel pumping apparatus includes first and second body parts 10, 13 the first part defining a spigot 11 which is screwed into a recess 12 in the second body part. The end surface of the spigot is provided with an annular knife edge 19 to form a seal with the base wall of the recess. The end surface of the spigot 11 also forms a seating for a valve plate 26 which is spring biased into engagement with the seating. The valve plate has arms which are guided in slots respectively formed in an annular valve guide 24 which engages a step 23 defined in the wall of a chamber 22 in the body part 13 and locates in an annular groove 20 formed in the end surface of the spigot. <IMAGE>

Description

VALVE FOR FUEL PUMPING APPARATUS This invention relates to a damping valve unit for connection in use, between an outlet of a high pressure fuel injection pump and a pipe line which leads to the associated fuel injection nozzle of the fuel system of a compression ignition engine.

The valve unit also houses a delivery valve which is connected in series with the damping valve and being located on the upstream side of the damping valve. The duty of the delivery valve is well known its purpose being to close as quickly as possible upon cessation of the delivery of fuel by the injection pump. Many delivery valves are of the so called unloading type which permit a predetermined volume of fuel to flow back towards the injection pump before they close. The duty of the damping valve is to damp the shock waves in the column of fuel between the delivery valve and the nozzle to avoid so far as is possible, secondary injection of fuel to the engine. The damping valve usually comprises a spring loaded non-return valve which is opened during delivery of fuel to the nozzle but which closes as soon as this flow of fuel ceases.In parallel with the nonreturn valve is a restricted passage. In one construction the combined unit comprises an elongated body in which is formed a stepped axially extending bore.

The narrower end of the bore is in use connected to the pipeline and the wider end of the bore accommodates a sleeve forming the delivery valve body. Mounted within the sleeve is the delivery valve member which has a head biased into contact with a seating defined on the sleeve, by a valve spring. The valve spring at its end remote from the valve member engages an abutment. The damping valve includes a seating and a spring loaded valve member both of which are located in a reduced portion of the bore. It is known to secure the seating within the bore by deforming a portion of the wall of the bore however, the deformation of the wall is an expensive and uncertain operation which prevents removal of the damping valve in the event that it proves to be faulty. Moreover, instances have occurred where the damping valve has become displaced due to the action of the shock waves.

GB 2069623 shows a modified form of damping valve in which the body of the damping valve is held in the bore by means of a wedge action. The body of the damping valve is still located at the bottom of the bore and can prove difficult to extract in the event that the damping valve is faulty.

An alternative construction is seen US 3450120 which again shows a combined delivery valve and damping valve. The illustrated valve comprises first and second body parts, the first body part defining a bore to accommodate the spring of the delivery valve and also having a screw threaded spigot about which the second body part is engaged. A fuel flow path is defined in the spigot and the second body part and the damping valve is in the form of a seat member which is sandwiched between the end of the spigot and the second body part. The seat member is shaped to cooperate with surfaces of the spigot and the second body part to form a high pressure seal when the two parts of the body are tightened. The damping valve also includes a valve member in the form of a ball which is spring loaded into engagement with a seating formed in the seat member.The seat member is also drilled to permit restricted flow of fuel when the ball is engaged with the seating. Whilst with this construction it is possible to replace the damping valve the fact that the seat member forms the seal between the two body parts means that it can be distorted as a result of excessive tightening of the two body parts. Moreover, machining of the seat member and the surfaces of the two body parts with which the seat member cooperates, is an expensive process.

The object of the present invention is to provide a damping valve for the purpose specified in a simple and convenient form.

According to the invention a damping valve for use in the fuel system of an internal combustion engine, comprises first and second body parts, the first body part defining a screw threaded spigot for engagement within a screw threaded recess in the second body part, means for establishing a seal between the end surface of the spigot and the surface of the base wall of the recess, an annular seating defined on the end surface about a fuel flow passage in said spigot, an annular groove defined in the end surface of the spigot about said seating, an annular guide located in said groove, the guide extending beyond said seating and locating against a step defined in the wall of a chamber formed in the second body part, and a plate valve member spring biased into engagement with said seating, said plate valve member having outwardly extending arms which locate in axial slots formed in the guide and the plate valve member defining a restricted orifice though which fuel can pass when the valve member is in contact with the seating.

An example of a damping valve in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation through the valve, and Figure 2 is a plan view to an enlarged scale of part of the valve seen in Figure 1.

Referring to Figure 1 of the drawings the valve comprises a two part body the first part 10 of which defines a spigot 11 provided with a peripheral screw thread which in use is engaged within a complementarily threaded recess 12 formed in the second body part 13.

The first body part defines a chamber 14 in which will be housed a delivery valve assembly 9 including a delivery valve member 8 which is biased by a spring 7. Located within the spring is a volume reducer 6 held in position by the spring and also acting as a stop to limit the movement of the valve member. The first body part at its end removed from the spigot 11 being of cylindrical form and screw threaded for engagement within a recess formed in a fuel injection pump. The spigot 11 is provided with a through passage 15 and the body part 13 defined a further through passage 16 and at its end remote from the first body part is shaped to form an outlet 17 which in use, is coupled to one end of a pipeline which leads to a fuel injection nozzle of an engine with which the injection pump is associated.

The end surface of the spigot which is presented to the base wall 18 of the recess 12 is provided with an annular knife edge 19 and this engages with the surface of the base wall to establish a fuel tight seal between the two body parts. In addition, in the end surface of the spigot there is defined an annular groove 20 which extends about a seating 21 which projects forwardly of the end surface of the spigot by a small amount. The seating extends into a chamber 22 which is formed in the second body part and with which the passage 16 communicates. The wall of the chamber defines a step 23 and located between the step 23 and the base of the groove 20 is an annular valve guide 24. When the body parts are secured together the valve guide is trapped in position, the groove 20 conveniently having sloping sides.When the two parts of the body are tightened some distortion of the guide 24 takes place so that it becomes securely locked in position.

The guide as seen in Figure 2, is provided with three slots 25 which extend axially from the end surface of the guide which engages the step 23.

Also provided is a plate valve member 26 which is biased into engagement with the seating 21 by a light spring 27. The valve plate 26 is provided with in the particular example, three outwardly extending arms 28 which locate in the slots 25 to locate the valve member.

The slots 25 are sufficiently deep so that when the valve plate is in engagement with the seating, the arms are free of the base walls of the slots. Finally the valve plate is provided with a central aperture 29 to permit restricted flow of fuel from the pipeline towards the delivery valve when the valve plate is in engagement with the seating.

During delivery of fuel the valve plate will be lifted from its seating by the flow of fuel and as soon as delivery of fuel ceases, the valve plate will be urged into engagement with the seating not only by the action of the spring 27 but also by the return flow of fuel as permitted by the delivery valve. The orifice 29 is then active to damp pressure waves which may occur in the pipeline.

The construction described is such that it is possible in the event of failure of the valve, to separate the two body parts and to replace the plate valve member together with the valve guide. Moreover, the construction greatly facilitates manufacture of the damping valve since it is easy to machine the end face of the spigot in order to produce the seating and also the knife edge 19 which establishes a fuel seal between the two body parts.

Claims

1. A damping valve for use in the fuel system of an internal combustion engine comprising first and second body parts, the first body part defining a screw threaded spigot for engagement within a screw threaded recess in the second body part, means for establishing a seal between the end surface of the spigot and the surface of the base wall of the recess, an annular seating defined on the end surface about a fuel flow passage in said spigot, an annular groove defined in the end surface of the spigot about said seating, an annular guide located in said groove, the guide extending beyond said seating and locating against a step defined in the wall of a chamber formed in the second body part, and a plate valve member spring biased into engagement with said seating, said plate valve member having outwardly extending arms which locate in axial slots formed in the guide and the plate valve member defining a restricted orifice though which fuel can pass when the valve member is in contact with the seating.

2. A valve according to Claim 1, in which the means for establishing a seal comprises an annular knife edge formed on one of said surfaces.

3. A damping valve for use in the fuel system of an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.