GB2577080A

GB2577080A - Valve assembly

Info

Publication number: GB2577080A
Application number: GB1814848.6A
Authority: GB
Inventors: Alban George Collingborn Peter; M Gould Timothy
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-09-12
Filing date: 2018-09-12
Publication date: 2020-03-18
Anticipated expiration: 2038-09-12
Also published as: GB201814848D0; GB2577080B

Abstract

A damping valve assembly for a high pressure outlet connector in a supply pump for a common-rail diesel fuel system is disclosed. The valve assembly comprises a valve head 23 moveable between a closed position, in which it seals against a valve seat and an open position. The assembly further comprises a stem 24 connected to the valve closure 23 having a plurality of longitudinal grooves 30a, 30b, 30c, 30d to allow fluid to flow when the valve head is in either the open or closed position. A retaining ring 22 is connected to the stem and is configured to limit the magnitude of movement between the closed and open positions. The stem may also include a snubbing orifice 26 that provides a restrictive flow path when the valve is closed. The restrictive orifice 26 dampens back pressure waves in the fuel. The invention extends to a pump head and high pressure outlet connector using the valve assembly.

Description

(54) Title of the Invention: Valve assembly

Abstract Title: Damping valve assembly (57) A damping valve assembly for a high pressure outlet connector in a supply pump for a common-rail diesel fuel system is disclosed. The valve assembly comprises a valve head 23 moveable between a closed position, in which it seals against a valve seat and an open position. The assembly further comprises a stem 24 connected to the valve closure 23 having a plurality of longitudinal grooves 30a, 30b, 30c, 30d to allow fluid to flow when the valve head is in either the open or closed position. A retaining ring 22 is connected to the stem and is configured to limit the magnitude of movement between the closed and open positions. The stem may also include a snubbing orifice 26 that provides a restrictive flow path when the valve is closed.

The restrictive orifice 26 dampens back pressure waves in the fuel.

The invention extends to a pump head and high pressure outlet connector using the valve assembly.

Figure 3

Figure 1

Figure 2

3/4

Figure 3

4/4

30c 31

Figure 4

VALVE ASSEMBLY

TECHNICAL FIELD

The present disclosure relates to a valve assembly and particularly, but not exclusively, to a damping valve assembly within a high-pressure outlet connector in a supply pump for a common-rail diesel fuel system. Aspects of the invention relate to a valve assembly, to a high pressure outlet connector and to a pump head.

BACKGROUND

High pressure supply pumps for common-rail diesel fuel systems supply high pressure fuel from the pump to the common-rail via at least one high pressure outlet. Typically, the high pressure outlet can comprise a restrictive orifice to dampen excessive reflected pressure waves in the rail, which may impair the behaviour of the injector.

At high pump rotational speeds pressure within the pump may reach hundreds of bars of pumping pressure above the pressure of fuel in the rail which is dissipated by driving the high fuel flow rate through the restrictive orifice and into the common-rail. This is undesirable as it is energy inefficient and reduces the effective pumping pressure achievable by the pump.

It is therefore desirable to provide an alternative solution for damping reflected pressure waves in the rail.

SUMMARY OF THE INVENTION

According to an aspect of the invention there is provided a valve assembly for a high pressure outlet in a supply pump for a common-rail diesel fuel system, the valve assembly comprising a valve head being moveable between a closed position, in which the valve head forms a seal with a valve seat, and an open position, in which a gap is defined between the valve seat and the valve head, a stem connected to the valve head wherein the stem comprises a plurality of longitudinal grooves configured to allow fluid to flow along the longitudinal grooves when the valve head is in both the open position and the closed position and a retaining ring connected to the stem. The retaining ring is configured to limit the magnitude of movement of the valve head between the closed and open positions.

Advantageously, the valve assembly may be packaged in a relatively small package space such that it can easily be retrofitted to existing fuel pumps or high pressure outlet connectors. The high pressure outlet may be a high pressure outlet in a supply pump or a high pressure outlet connector.

Furthermore, the moveable valve member has a low mass and inertia thereby allowing it to be actuated between the open and closed positions very quickly. This advantageously minimises unwanted leakage of fuel across the valve when the valve is approaching the closed positon.

In an embodiment the stem may comprise an orifice configured to provide at least part of a restricted flow path for fluid to flow along when the valve head is in the closed position. The restrictive orifice enables fluid to flow along the longitudinal grooves and through the valve assembly when the valve is in the closed position. In one embodiment the orifice may be orientated substantially perpendicularly to a longitudinal axis of the stem. The restrictive orifice advantageously provides a restricted flow path for fuel to flow along when the valve assembly is in the closed position thereby damping reflected back pressure waves in the fuel. Furthermore, orientating the restrictive orifice perpendicularly to the longitudinal axis reduces the packaging space required for the valve assembly thus allowing it to be retrofitted to existing high pressure outlets.

In one embodiment the retaining ring may comprise a surface configured to engage a corresponding abutment surface when the valve head is in the open position and wherein the surface and abutment surface are configured to provide a squeeze film cushioning effect when the valve head is moved to the open position, in use. In another embodiment the surface may be a chamfered surface.

The squeeze film cushioning effect advantageously reduces the forces or impact on the retaining ring and valve as the valve is moved to the open position, in use.

In another embodiment the cross-section of the stem may be a cruciform and, for example, the stem may comprise four longitudinal grooves.

In one embodiment the valve head may be moved between the open and closed positions by the pressure of fluid.

In an embodiment the retaining ring may be secured to the stem via an interference fit.

According to another aspect of the present invention there is provided a high pressure outlet connector comprising the valve assembly of the preceding aspect of the invention.

According to yet another aspect of the present invention there is provided a pump head comprising the valve assembly or high pressure outlet connector according to the preceding aspects of the invention.

Within the scope of this application it is intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any appropriate combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a cross sectional view of a fuel pump head suitable for use with embodiments of the invention;

Figure 2 shows a damping valve located within the fuel pump of Figure 1;

Figure 3 shows a front perspective view of a valve member of the damping valve of Figure 2;

Figure 4 shows a rear perspective view of a valve member of the damping valve of Figure 2;

DETAILED DESCRIPTION

In general terms, embodiments of the invention provide a valve assembly suitable for use in a high pressure outlet or a high pressure outlet connector in a supply pump for a common-rail diesel fuel system. The valve assembly comprises a valve head that is moveable between a closed position in which the valve head forms a seal with a corresponding valve seat and an open position in which a gap is defined between the valve head and the valve seat. The gap provides a flow path along which a fluid, such as diesel fuel, may flow. The valve comprises a moveable valve member comprising the valve head connected to a stem, wherein the stem carries a retaining ring. The retaining ring is configured to limit the magnitude of displacement of the valve head between the closed and open positions. Furthermore, the stem comprises an orifice orientated perpendicularly to a longitudinal axis of the moveable valve member. The restrictive orifice provides a path for fuel to flow along when the valve head is in the closed position to dampen back pressure waves in the fuel.

Advantageously, the damping valve assembly may be packaged in a relatively small package space such that it can easily be retrofitted to existing fuel pumps or high pressure outlet connectors. Furthermore, the moveable valve member has a low mass and inertia thereby allowing it to be actuated between the open and closed positions very quickly, thereby minimising unwanted leakage of fuel across the valve when the valve is approaching the closed position.

To place embodiments of the invention in a suitable context, reference will firstly be made to Figure 1 which shows a cross sectional view of a fuel pump head 10 suitable for use in a diesel fuel injection system. The pump head 10 comprises a pumping chamber 14, a fuel inlet 16 and a high pressure fuel outlet 12. Low pressure fuel flows into the pumping chamber 14 via the fuel inlet 16 prior to being pressurised within the pumping chamber 14 and pumped out via the high pressure outlet 12 to fuel injectors of the fuel injection system.

A moveable plunger 15 is located within the pumping chamber 14 and configured to pressurise the fuel received within a bore 13 in the pumping chamber 14 such that high pressure fuel may be pumped from the high pressure fuel outlet 12. Fuel located within the pumping chamber 14 is pressurised during an upward stroke (relative to the view shown in Figure 1) of the plunger 15 and forced out of the high pressure outlet 12. During the return stroke of the plunger 15 the fuel is not being compressed, and low pressure fuel is drawn into the pumping chamber

14. As such back pressure waves in the fuel may propagate back through the high pressure outlet 12.

The high pressure outlet 12 has a high pressure outlet valve or delivery valve 17. The delivery valve 17 is a non-return valve comprising a ball 19, spring loaded against an approximately conical seat by a spring 18. The delivery valve 17 is configured to prevent high pressure fuel leaking into the pump head 10 via the high pressure outlet 12. When the plunger 15 is pressurising the fuel the ball 19 is moved to an open position such that fuel may flow into the high pressure fuel outlet 12. During pumping the pressure in the pumping chamber 14 is higher than that in the rail due to fuel inertia and the restrictions in the passages. When the plunger 15 is not displacing the fuel the spring 18 actuates the ball 19 to a closed position where the ball 19 forms a seal with the conical seat. Thus the delivery valve 17 allows high pressure fuel to flow out of the high pressure outlet 12 and prevents high pressure fuel returning to the pumping chamber 14.

Fuel in the rail is at a higher pressure than fuel in the pumping chamber 14 during a filling phase of the pumping chamber 14 as the plunger 15 moves in a downward direction (as shown in Figure 1). As the plunger 15 moves in a downward direction a vacuum is produced in the chamber 14 and fuel enters the pumping chamber 14 to fill the vacuum. The delivery valve 17 ensures that the rail is maintained at the desired pressure and that the high pressure fuel within the rail does not leak into the pumping chamber during the filling phase.

When the plunger 15 is not pressurising the fuel (during the “filling phase” as the plunger 15 moves in a downward direction) back pressure waves are reflected from the common rail (not shown) and travel from the rail to the closed delivery valve 17. When they reach the closed delivery valve 17 they are reflected back toward the rail. This can result in pressure waves being reflected between the rail and the delivery valve 17 which may inhibit the performance of the downstream fuel injectors.

To mitigate against the effect of back pressure waves propagating between the delivery valve 17and the rail, a damping valve 20 is positioned within the high pressure outlet 12. The damping valve 20 has a restrictive orifice 26 that provides a restricted flow path for fuel that is reflected from the rail to the outlet connector 12 to flow along thereby reducing the energy in the reflected waves. Back pressure waves in the fuel are undesirable as they may inhibit the performance of the downstream fuel injectors of the fuel injection system. By dissipating energy within the reflected pressure waves the damping valve 20 minimises the waves propagating between the high pressure outlet 12 and the common rail (not shown).

As best shown in Figure 2, the damping valve 20 is located within the high pressure outlet 12 of the pump head 10. The damping valve 20 has a moveable valve member 40 that comprises the valve head 23, the stem 24 and the retaining ring 22. The valve head 23 is hydraulically moveable between a closed position (as shown in Figure 2) where the valve head 23 forms a seal with the valve seat 25, and an open position (moving to the left in the illustration shown). When the valve head 23 is in the open position a gap is provided between the valve head 23 and the valve seat 25. The gap provides a flow path for fuel to flow along when leaving the high pressure outlet 12 prior to entering the common rail (not shown) within the diesel fuel system.

The valve head 23 is hydraulically operable between the closed and open positions by the pressure of the fuel being pumped out of the pumping chamber

14. When the plunger 15 pressurises the fuel in the pumping chamber 14 the valve head 23 is moved to the open position by the pressure of the fuel leaving the pumping chamber 14. When the valve head 23 is in the open position fuel flows through the gap provided between the valve head 23 and the valve seat 25 and is delivered from the high pressure outlet 12. During the return stroke of the plunger 15 no fuel is being compressed and as such the damping valve 20 is caused to move to the closed position by the back pressure waves in the fuel. Advantageously, the valve head 23 is hydraulically operable by the pressure in the fuel and as such does not require mechanical actuation between the closed and open positions.

The stem 24 is connected to the valve head 23 and serves as a guide for the valve head 23 as it is moved between the closed and open positions and/or between the open and closed positions. The stem 24 is dimensioned such that the outer diameter of the stem 24 is a sliding fit with the internal surface 29 of the outlet connector 12. This helps to ensure that the valve head 23 moves in a substantially axial direction, along the longitudinal axis 33 of the valve assembly 20, which is advantageous as it reduces the wear on the stem 24 and improves the quality of the seal between the valve head 23 and the valve seat 25.

The stem 24 also comprises a retaining ring 22 secured to the end of the stem 24 distal to the valve head 23. The retaining ring 22 is secured to the stem 24 via an interference fit although a person skilled in the art would appreciate that the retaining ring 22 may be secured to the stem 24 via any appropriate fixing means. The retaining ring 22 acts as a lift stop for the valve member 40 thereby controlling the magnitude of movement of the valve head 23 between the closed and open positions. In the embodiment shown the retaining ring 22 has a symmetrical cross-section so that it may be fitted onto the stem 24 either way round. This is advantageous as it eases the assembly task as the operator may be secured to the stem 24 in either orientation. When the moveable valve member 40 is actuated to the open position the retaining ring 22 abuts a corresponding abutment surface 21 of the high pressure outlet 12. The abutment surface 21 prevents displacement of the moveable valve member 40 and thus valve head 23 by more than a predetermined magnitude.

The abutment surface 21 is a conical surface on the internal surface of the high pressure outlet 12. A conical abutment surface 21 is advantageous as it maintains the outlets 12 resistance to high pressures because the conically shaped surface minimises potential areas of large stress concentrations, such as sharp corners. The retaining ring 22 has a chamfered surface 31 that corresponds to the abutment surface 21. The angle of the chamfer on the chamfered surface 31 is substantially the same as the angle of the conical surface 21. As the valve member 40 is hydraulically operated to the open position, fuel is compressed between the abutment surface 21 and the chamfered surface 31 which results in a squeeze film cushioning effect. Squeeze film cushioning is a well-known phenomenon which reduces the force of the impact between the retaining ring 22 and the high pressure outlet 20. As the retaining ring 22 and the high pressure outlet 20 approach each other the annular exit area between each boundary reduces. This causes the pressure in the film to increase which in turn causes the retaining ring 22 to slow down. In some embodiments the effect of squeeze film cushioning may only be significant over a microscopic distance prior to contact between the surfaces of the retaining ring 22 and the high pressure outlet. Furthermore, it is advantageous as it negates the requirement of a spring to dampen the impact when moving the valve member 40 between the open and closed positions.

The moveable valve member 40 is shown in further detail in Figures 3 and 4. The stem 24 is substantially cylindrical in shape. However, it is machined such that it has, for example, a cruciform cross-section. The cruciform cross-section is defined by four longitudinal grooves 30a, 30b, 30c, 30d equi-angularly spaced about the longitudinal axis 33 of the valve member 40. The longitudinal grooves 30a, 30b, 30c, 30d together define a flow path along which the fuel may flow. The retaining ring 22 is secured to the stem 24 such that the longitudinal grooves 30a, 30b, 30c, 30d and the stem 24 run through the central aperture of the retaining ring 22. The stem 24 also has an annular groove 28 positioned on the stem 24 between the valve head 23 and the longitudinal grooves 30a, 30b, 30c, 30d. The annular groove 28 advantageously assists with the manufacture and machining of the longitudinal grooves 30a, 30b, 30c, 30d.

When the plunger 16 pressurises the fuel in the pumping chamber 14 fuel is forced, firstly out through the delivery valve 17, and then into the damping valve 20 within the high pressure outlet 12. Fuel enters the damping valve 20 through the central aperture of the retaining ring 22 via the longitudinal grooves 30a, 30b,

30c, 30d. The fuel then flows along the longitudinal grooves 30a, 30b, 30c, 30d under the forward pressure of the fuel leaving the pumping chamber 14 and enters the annular groove 28. Fuel leaving the longitudinal grooves 30a, 30b, 30c, 30d fills the annular groove 28 such that fuel flows to the entire circumference of the valve head 23.

An axial drilling 35 proceeds in the axial direction 33 from the outer surface 34 of the valve head 23 and terminates in the region of the annular groove 28. The region of the annular groove 28 is defined as the region along the longitudinal axis 33 where the annular groove 28 is positioned. A restrictive orifice 26 or “snubbing orifice” is orientated substantially perpendicularly to the longitudinal axis 33 such that it connects the annular groove 28 and the axial drilling 35, as best viewed in Figure 2. The restrictive orifice 26 provides a restricted flow path along which fuel may flow when the valve head 23 is in the closed position. The restrictive orifice 26 provides a flow path for fuel that bypasses the valve seat 25 thereby enabling fuel to flow even when the valve head 23 is in the closed position and engaged with the valve seat 25. Fuel flowing through the restrictive orifice 26 when the valve member 40 is in the closed position is restricted which is advantageous when back pressure waves propagate in the fuel as the back pressure waves are dampened, thereby reducing their effect on the performance of the diesel fuel system.

The length of the restrictive orifice 26 is equivalent to the wall thickness of the stem 24 between the annular groove 28 and the axial drilling 35 which is typically very short and precise. The diameter of the restrictive orifice 26 may be varied to suit the required application of the damping valve 20. For example, the restrictive orifice 26 may have a diameter of about 0.5mm although the skilled person would appreciate that the diameter of the restrictive orifice may be varied to suit the application. For example, the diameter of the restrictive orifice may be between 0.1mm and 1mm_L Varying the diameter of the restrictive orifice 26 varies the amount of damping the restrictive orifice 26 provides on back pressure waves in the fuel and also varies the amount of “leakage” of fuel across the valve head 23 when in the closed position.

The magnitude of movement of the valve head 23 between the closed position and the open position is controlled by the retaining ring 22. The gap between the valve head 23 and the valve seat 25 is typically of the magnitude of about 0.2mm although the gap may be varied between, for example 0.1mm andlmm depending on the application,_when the valve member 40 is in the open position. The skilled person would appreciate that the pressure drop across the valve head at a given flow rate is inversely proportional to the square of the flow area. As such, a relatively small gap may significantly reduce the pressure drop across the damping valve 20 when the valve head 23 is in the open position when compared to the pressure drop associated with high pressure outlets that only have a restrictive orifice, the like of which are associated with the prior art. Furthermore, the valve must operate at high frequency and speed as the valve may operate up to 8 times per pump revolution.

Reducing the gap or distance the valve head 23 must travel between the open and closed positions facilitates faster actuation of the valve head 23 between the open and closed positions. This minimises unwanted bypass flow or “leakage” across the valve head 23 as the valve head 23 is actuated from the open position to the closed position.

The flow area provided by the gap between the valve head 23 and the valve seat 25 is substantially equal to the flow area provided by the longitudinal grooves 30a, 30b, 30c, 30d. As the necessary flow area provided by the gap is relatively small the diameter of the stem 24 and thus the size of the longitudinal grooves 30a, 30b, 30c, 30d may also be relatively small. Typically, the diameter of the stem is between 1mm and 5mm depending on the application of the damping valve 20. Typically, the volume of fuel that must be displaced to move the valve through its full travel, in either direction, is less than 10mm³.

Minimising the diameter of the stem 24 is advantageous as it allows the damping valve 20 to be packaged in a smaller area and retrofitted to existing pump heads 10 or high pressure outlets 12. Furthermore minimising the diameter of the stem also minimises the mass and inertia of the moving valve member 40 within the damping valve 20. Reducing the mass and inertia of the moving components increases the opening and closing speeds of the damping valve 20 and also reduces the impact shock loads at the limits of travel of the moving components. The stem 24 is typically less than 0.5g.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims. For example, whilst in the embodiment described above the retaining ring 22 is secured to the stem 24 via an interference fit a person skilled in the art would appreciate that the lift stop may be a welded-on flange, a threaded nut or a collar and collets. Furthermore, whilst the above embodiments are in relation to a diesel fuel system then invention may also be used in other fuel systems, for example, petrol or bio-fuel systems.

LIST OF REFERENCES pump head high pressure outlet bore pumping chamber plunger fuel inlet delivery valve spring ball valve assembly abutment surface retaining ring valve head stem valve seat restrictive orifice annular groove internal surface

30a longitudinal groove

30b longitudinal groove

30c longitudinal groove

30d longitudinal groove chamfered surface longitudinal axis moveable valve member

Claims

CLAIMS:

1. A valve assembly (20) for a high pressure outlet connector (12) in a supply pump (10) for a common-rail diesel fuel system, the valve assembly (20) comprising:

a valve head (23) being moveable between a closed position, in which the valve head (23) forms a seal with a valve seat (25) and an open position in which a gap is defined between the valve seat (25) and the valve head (23);

a stem (24) connected to the valve head (23);

wherein the stem (24) comprises a plurality of longitudinal grooves (30a, 30b, 30c, 30d) configured to allow fluid to flow along the longitudinal grooves (30a, 30b, 30c, 30d) when the valve head (23) is in both the open position and the closed position; and a retaining ring (22) connected to the stem (24);

wherein the retaining ring (22) is configured to limit the magnitude of movement of the valve head (23) between the closed and open positions.

2. A valve assembly (20) as claimed in claim 1, wherein the stem (24) comprises an orifice (26) configured to provide at least part of a restricted flow path for fluid to flow along when the valve head (23) is in the closed position.

3. A valve assembly (20) as claimed in claim 1 or claim 2, wherein the orifice (26) is orientated substantially perpendicularly to a longitudinal axis (33) of the stem (24).

4. A valve assembly (20) as claimed in any preceding claim, wherein the retaining ring (22) comprises a surface (31) configured to engage a corresponding abutment surface (21) when the valve head (23) is in the open position and wherein the surface (31) and abutment surface (21) are configured to provide a squeeze film cushioning effect when the valve head (23) is moved to the open position, in use.

5. A valve assembly (20) as claimed in claim 4, wherein the surface (31) is a chamfered surface.

6. A valve assembly (20) as claimed in any preceding claim, wherein the cross section of the stem (24) is a cruciform and wherein the stem (24) comprises four longitudinal grooves (30a, 30b, 30c, 30d).

5

7. A valve assembly (20) as claimed in any preceding claim wherein the valve head (23) is moved between the open and closed positions by the pressure of fluid.

8. A valve assembly (20) as claimed in any preceding claim, wherein the 10 retaining ring (22) is secured to the stem (24) via an interference fit.

9. A high pressure outlet connector (12) comprising the valve assembly (20) of any preceding claim.

15

10. A pump head (10) comprising the valve assembly (20) of any of claims 1 to 8 or comprising a high pressure outlet connector (12) according to claim 9.

Intellectual

Property

Office

Application No: GB1814848.6