GB2571284A

GB2571284A - Pressure limiting valve

Info

Publication number: GB2571284A
Application number: GB1802865.4A
Authority: GB
Inventors: Akin Levent; Altinol Cuneyt
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-02-22
Filing date: 2018-02-22
Publication date: 2019-08-28
Also published as: GB201802865D0

Abstract

A pressure limiting valve 14 (PLV), a common rail 12 assembly and methods of tuning a common rail assembly are disclosed. The pressure limiting valve 14 comprises a body 28 provided with a bore (46, figure 4) with a seat member 41 at an end, surround a spill orifice 50. An adjustable valve assembly 29 comprising a valve member 30, a spring 34 and a plug 36 is arranged in the cavity (46, figure 4). The position of the retainer 36 can be adjusted and may compress the spring against the valve member. The seat 41 may be integral with the body 28 or a separate part. The disclosed fuel reservoir 12 assembly is tuned by pre-assembling the pressure relieving valve 14, fixing it in the common rail and then tuning the PLV to a target safety pressure threshold. The valve may be tuned by tightening or loosening the plug. The PLV and common rail arrangement overcomes weakness issues encountered by valves that are crimped or use shims.

Description

The present invention relates fuel injection equipment and more specifically to a common rail assembly comprising a common rail and a pressure limiting valve, said valve being provided with means to adjust the safety pressure in the common rail.

BACKGROUND OF THE INVENTION

In a diesel injection equipment, pressurized fuel stored in a high pressure reservoir, well known as a common rail, is delivered to fuel injectors which spray said fuel in the cylinders of an internal combustion engine. A pressure limiting valve, hereafter PLV, sets the maximum inner pressure of the common rail and opens a return port when said rail pressure exceeds said safety level.

Current “Pressure Limiting Valve” standard 1 PLV and Limphome 2 PLV shown in figures 1 and 2 are used as pressure limiter in a diesel common rail fuel injection system. The PLV is set to a “pressure value” in order to prevent components from excessive pressures. The PLV comprises the spring, a piston, a ball and a seat. While the spring provides appropriate force, the piston transfers said force to the ball which seals a spill orifice. The PLV opens as the ball lifts off the seat that surrounds the spill orifice when the pressure in the rail generates on the ball an opening force exceeding the spring force and then, fuel is enabled to exit the rail thus preventing excessive pressure.

Currently, the seat is assembled onto the PLV body by crimping operation and, the seat providing a sealing interface with rail it is heat treated as high grade steel. The PLV body provides rail assembly interface (thread connection) and low pressure sealing (o-ring), the body material being a regular steel which does not require heat treatment operation.

The opening pressure limit of the PLV is adjusted by arranging metal shim at the bottom face of the spring. For instance, by increasing the thickness of the shim, or by using more shims, the set pressure limit can be increased due to increased spring force. From operational point of view, this can be maintained by separating shims with respect to thickness values. According to the set pressure value, total shim thickness need to be assembled into the PLV is defined. This operation results in design complexity and opening pressure variation.

The crimping assembly of the seat to the body is becoming a weak assembly because of increased set pressures of PLV due to increasing system pressure requirements from the market. This leads crimped material to be subjected to more loads/stresses.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a pressure limiting valve, hereafter PLV, adapted to be arranged on a high pressure reservoir of a fuel injection system, said PLV comprising a body provided with a bore at an inner end of which a seat member defines a seating face surrounding the opening of a spill orifice, an adjustable valve assembly comprising at least a valve member, a spring and an adjusting plug being arranged in said bore, the position of the plug within the bore being adjustable.

The spring may be compressed between the valve member and the adjusting plug, the adjusting plug being screwed and tightened in the bore.

The PLV may further comprise an annular seal arranged around the plug for sealing between the plug and the bore.

The seat member may be integral to the body.

In another arrangement, the seat member may be a separate component arranged at an inner end of the body.

The seat member may comprise a cylindrical base and a tubular turret protruding from an inner face of the base, the spill orifice extending through the turret and the base, the turret being inserted at an end of the bore.

Said seat member may be fixed to the body.

The invention further extends to a common rail assembly comprising a common rail member defining a peripheral wall enclosing an inner space adapted to store pressurised fuel and, a PLV as described above, said PLV being arranged to open a fluid communication between said inner space and a return port provided on the common rail.

The common rail may be provided with a bore defining said inner space, said bore opening at an end and being surrounded by an annular shoulder, the PLV being tightened so that the PLV body is biased against said shoulder.

The invention further extends to a method for tuning to a targeted safety pressure threshold a common rail assembly as described above, the method comprising the following sequential major steps:

• pre-assembling the PLV thus making an untuned PLV;

• fixing said pre-assembled PLV in the common rail thus making an untuned common rail assembly;

• tuning the PLV open pressure to the targeted safety pressure threshold.

Said pre-assembling major step may comprise the following sub-steps:

• providing a body integrating a seat;

• inserting then adjustable valve assembly in the bore ;

• lightly tightening said plug so the threads are just engaged and the plug is held in the body, the closing force generated by the spring being smaller than a safety closing force corresponding to the safety pressure;

• arranging a first o-ring over the body.

The providing step may be replaced by:

• providing a body and seat assembly, the body and the seat being distinct parts.

The tightening the plug step may be replaced by:

• strongly tightening said plug so the threads are substantially fully engaged in the body, the closing force generated by the spring being superior to a safety closing force corresponding to the safety pressure.

The PLV fixing major step comprises the following sub-steps:

• engaging the pre-assembled PLV in the hollow ;

• tightening the PLV in the hollow to ensure sealing, said tightening being done by engaging a first tool T in a tool engagement feature provided on the body.

The tuning major step comprising the following sub-steps:

• arranging the assembly onto a tuning machine enabling to raise and measure the rail inner pressure;

• raising said rail pressure until the PLV switches to an open position;

• tightening the adjusting plug until the PLV switches back to a closed position;

• repeating the steps and until the rail pressure gets to the level of the targeted safety pressure threshold.

The tuning major step may comprise the following sub-steps:

• raising said rail pressure to the targeted safety pressure;

• unscrewing the adjusting plug until the PLV switches to an opening position.

An alternative method may comprise the following sequential major steps:

• pre-assembling the PLV thus making an untuned PLV;

• tuning the PLV open pressure to the targeted safety pressure threshold on a PLV tuning machine;

• fixing said tuned PLV in the common rail in order to make a common rail assembly.

The tuning major step of claim may comprise the following sub-steps:

• arranging the assembly onto a PLV tuning machine;

• raising the fluid pressure until the PLV switches to an open position;

• repeating the steps and until the fluid pressure gets to the level of the targeted safety pressure threshold.

The tuning major step may comprise the following sub-steps:

• arranging the untuned PLV onto a tuning machine wherein a HP fluid source engages the spill orifice generating an opening force on the valve member;

• raising the HP pressure to said targeted safety pressure threshold;

• unscrewing the plug until the PLV opens.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

Figures 1 and 2 are axial sections of standard and limphone PLV of the prior art.

Figures 3 and 4 are axial sections of PLV as per two embodiments of the invention.

Figure 5 is a 3D view of an end of a common rail assembly as per the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to the figures 3, 4 and 5 is described a common rail assembly 10 comprising a common rail 12 and a pressure limiting valve 14, hereafter PLV 14. The common rail 12 of a diesel fuel injection equipment is a high pressure (HP) reservoir adapted to receive pressurized fuel from a HP pump and to deliver said HP fuel to injectors arranged to spray the fuel in the cylinders of an internal combustion engine, the PLV 14 enabling HP fuel to exit the common rail when the pressure therein exceeds a safety threshold PS. In a diesel equipment, high pressure (HP) is understood to be 3000 bars and above, while low pressure (LP) to be 20 bars and below and, said safety pressure threshold PS may for instance be adjusted to 2500 bars.

The common rail 12 is forged or machined, and it has an elongated tubular shape extending along a longitudinal axis L between two opposite ends. The rail 12 is provided with a longitudinal through bore 16 defining an inner space IS surrounded by a peripheral wall in which, in use, is stored said HP fuel. Moreover, a plurality of ports defining inlets for connection to said HP pump, outlets for connection to said injectors and a return port 18 for connection to a LP return line radially protrude from said peripheral wall. In one of said ends 20, shown on the figures, the rail 12 is provided with a cylindrical hollow 22 wherein is complementary inserted the PLV 14 that extends between an inner end inside the hollow 22 and an outer end protruding outside said hollow. Said hollow 22 has a cylindrical lateral face 24 and a transverse bottom face wherein opens the bore 16 limiting said bottom face to an annular sealing shoulder 26. The return port 18, drilled in a turret, extends perpendicularly to the longitudinal axis L and opens in said recess lateral face 24, between said return port and the recess opening in the very end face of the common rail, a portion of the lateral face 24 is threaded for complementary screwing and tightening of the PLV 14.

Said PLV 14 comprises a body 28 housing an adjustable valve assembly 29 comprising a ball 30, a piston member 32, a spring 34, an adjusting plug 36, a first o-ring 38 and a second o-ring 40.

In a first embodiment shown on figure 3, the body 28 integrates a seat 41 defining an integral PLV inner end. The body 28 is elongated extending between a transverse inner face 42, part to the seat 41 and pressed against the sealing shoulder 26 and, an outer face 44 ending the PLV outer end outside the hollow 22. The inner face 42 is provided with sealing means defining a “knife edge” comprising a protruding annular lip having a sharp edge rising above the face level and ensuring sealing when pressed against said shoulder face 26. To actually press said knife edge, the PLV outer end, shown in 3D in figure 5, is provided with a male hexagon 54 for complementary engagement of a tool. Other tool engagement features are of course possible depending on said tool and on the torque applied to tighten the PLV. Said knife edge is a critical part of the design ensuring sealing of the system and, the arrangement presented enables to limit the to only one knife edge while the prior art design requires two.

The inner end portion of the PLV body, defining the seat 41, has a smaller section than the hollow 22 such that, an annular void V surrounds said PLV inner end, the return port 18 opening in said void V. Beyond said end portion, the body section enlarges and is complementary' threaded and tightened in the thread of the hollow 22 and, beyond said thread portion, the body is provided with an annular groove wherein is arranged the first o-ring 38 seal.

In the body 28 is further drilled a longitudinal blind bore 46, the body being then limited to a peripheral wall surrounding said bore 46, said bore 46 extending between an outer opening in said outer face 44 and, the seat 41 where the bore bottom defines a conical seating face 48. From the center of said seating face 48, a spill orifice 50 axially extends through the seat and opens in the inner face 42. Next to the seat 41, the body is further provided with at least one through conduit 52, two being shown on the figures, radially extending through said bore peripheral wall and joining said blind bore 46 to said void V.

Inside the bore 46 is housed said adjustable valve assembly 29 arranging in said order the ball 30, the piston member 32, the spring 34, the adjusting plug 36 and the second o-ring 40.

Against the seating face 48, the ball 30 is biased by the piston member 32 in a closed position CP of the spill orifice 50, said piston 32 transmitting to the ball a closing force generated by the spring 34 that is compressed between the piston member 32 and the adjusting plug 36. Said plug 36 being complementary engaged, screwed and tightened in the outer end of the bore. The second o-ring 40 is arranged in an annular groove provided around the plug and it seals the clearance between the plug and the bore.

Alternatively to a ball, another valve member can be chosen, such as a needle tip end, a flat disc..., provided a complementary sealing match with the seating face.

The piston member 32 is a cylindrical member guided in the bore 46 and it has a ball-end with a concave feature in which the ball 30 is located and, an opposite spring-end provided with a central locating protrusion surrounded by an annular spring seat.

The spring 34 is a coil spring wound between a piston-end in abutment against said piston member spring seat, the last turns being engaged around said locating protrusion and, a plug-end in abutment against a recess bottom face of the plug, the lasts turns being inserted in said recess.

The adjusting plug 36 is a substantially cylindrical member externally threaded and complementary tightened in the outer end of the bore 46. Said spring locating recess is provided on an inner side of the plug, the spring abutting at the bottom of the recess and, on an opposed outer side the plug defines a transverse face 56 provided with a central female hexagon 58 adapted to receive a tool in complementary engagement. Alternatively to a hexagon, other tool engagement features may be provided, either male or female, such as a slot or a male square.

In use, HP fuel fills the common rail bore 16 and generates on the ball 30 an opening force opposed to the closing force of the spring. As long as the rail pressure in lower than the safety pressure threshold PS said opening force is not sufficient to move the ball which remains in said closed position CP of the spill orifice 50. When the rail pressure rises above said safety pressure threshold PS, the opening force becomes predominant over the spring closing force and, the ball 30 is lifted off the seating face 48 opening a fluid communication joining the common rail bore 16 to the return port 18 via the spill orifice 50, the PLV blind bore 46, said radial conduit 52, the void V and the return port 18.

In a second embodiment presented in axial section in figure 4, the body 28 does not integrates the seat 41 and, the bore 46 extends throughout the body 28 opening at both inner end, there defining an inner transverse annular face 60, and outer end identical to the first embodiment. The seat member 41 is a distinct component comprising a cylindrical base 62 having an outer face provided with said sealing knife edge opposed to an inner face 64 wherefrom centrally protrudes a locating turret 66 inserted in the inner end of the bore 46, said base inner face 64 abutting the body inner face 60. After insertion of the turret, the inner end of the body is crimped over the turret.

The spill orifice 50 extends through the base and through the turret, the turret end defining the seating face 48.

In another alternative the turret 66 adjusted and freely inserted to the inner end of the bore, without any crimping or other fixing operation.

The following steps of a method 100 are to be followed in order to make a common rail assembly 10 comprising a common rail 12 and a PLV 14 which targeted safety pressure threshold PS is adjusted to a desired value.

A) pre-assembling the PLV 14;

B) fixing said pre-assembled PLV in the common rail 12 thus making an untuned common rail assembly;

C) tuning the PLV 14 open pressure.

The pre-assembling step A) comprises the following sub-steps:

al) providing a body 28 integrating a seat 41, as in the first embodiment or, as in the second embodiment a body 28 and seat 41 assembly;

a2) inserting in the bore 46, the ball 30, the piston 32, the spring 34 and the adjusting plug 36;

then, according to a first alternative:

a31) lightly tightening said plug 36 so the threads are just engaged and the plug is held in the body, the closing force generated by the spring being smaller than a safety closing force corresponding to the safety pressure

PS;

or according to a second alternative:

a32) strongly tightening said plug 36 so the threads are substantially fully engaged in the body, the closing force generated by the spring being superior than a safety closing force corresponding to the safety pressure PS;

a4) arranging the first o-ring over the body.

The PLV fixing step B) comprises the following sub-steps:

bl) engaging the pre-assembled PLV in the hollow 22 until the knife edge contacts the sealing shoulder 26;

b2) tightening the PLV in the hollow 22 to ensure sealing by pressing the knife edge onto said shoulder 26, said tightening being done by engaging a first tool T1 in the male hexagon 54 (or any other tool engagement feature).

Following the first alternative where the step a31) “lightly tightening the plug” is executed, the PLV tuning step C) comprises the following sub-steps:

cl) arranging the untuned assembly made at step B) onto a tuning machine wherein the inlets of the rail bore are connected to a HP fluid source, the outlets are sealed and wherein the rail pressure is measured;

c2) opening said HP fluid source and filling the bore with HP fluid until the PLV 14 opens the fluid communication and, fluid exits by the return port 18;

c3) engaging a second tool T2 in the female hexagon 58, or any other tool engagement feature, and tightening the adjusting plug 36 until the PLV closes then, further raising the rail pressure and further tightening the plug until the rail pressure gets to the level of the targeted safety pressure threshold PS.

Alternatively, following the second alternative where the step a32) “strongly tightening the plug” is executed, the PLV tuning step C) comprises the following sub-steps:

c2) opening said HP fluid source and filling the bore with HP fluid raising the rail pressure to the targeted safety pressure threshold PS;

c3) engaging a second tool T2 in the female hexagon 58 (or any other tool engagement feature) and unscrewing the adjusting plug 36 until the PLV opens.

In another method 200, the PLV tuning step C) can be done before the fixing step B). Indeed, the pre-assembled PLV made at step A) can be adjusted to the targeted threshold pressure PS on a tuning machine prior to be fixed to a common rail, thus directly making a tuned assembly.

LIST OF REFERENCES

L longitudinal axis

IS inner space

PS pressure safety threshold

V void

CP

OP

TI closed position open position tool

T2 tool prior art standard PLV prior art Limphone PLV common rail assembly - CR assembly common rail pressure limiting valve - PLV bore

18	return port
20	end of the CR assembly
22	hollow
24	lateral face
26	shoulder
28	PLV body
29	adjustable valve assembly
30	ball
32	piston member
34	spring
36	adjusting plug
38	first o-ring
40	second o-ring
41	seat member
42	inner face
44	outer face
46	blind bore
48	seating face
50	spill orifice
52	conduit
54	tool engagement feature -	male hexagon
56	outer face of the plug
58	tool engagement feature -	female hexagon
60	inner face
62	base of the seat member
64	turret
100	Method
200	Method

Claims

1. Pressure limiting valve (14) (PLV) adapted to be arranged on a high pressure reservoir (12) of a fuel injection system, said PLV (14) comprising a body (28) provided with a bore (46) at an inner end of which a seat member (41) defines a seating face (48) surrounding the opening of a spill orifice (50), an adjustable valve assembly (29) comprising at least a valve member (30), a spring (34) and an adjusting plug (36) being arranged in said bore (46), the position of the plug within the bore being adjustable.

2. PLV (14) as claimed in the preceding claim wherein the spring is compressed between the valve member (30) and the adjusting plug, the adjusting plug being screwed and tightened in the bore.

3. PLV (14) as claimed in claim 2 further comprising an annular seal (40) arranged around the plug for sealing between the plug and the bore.

4. PLV (14) as claimed in any one of the preceding claims wherein the seat member is integral to the body.

5. PLV (14) as claimed in any one of the claims 1 to 3 wherein the seat member (41) is a separate component arranged at an inner end of the body.

6. PLV (14) as claimed in claim 5 wherein the seat member comprises a cylindrical base (62) and a tubular turret (64) protruding from an inner face (60) of the base, the spill orifice (50) extending through the turret and the base, the turret being inserted at an end of the bore (46).

7. PLV (14) as claimed in any one of the claims 5 or 6 wherein said seat member (41) is fixed to the body.

8. Common rail assembly (10) comprising a common rail member (12) defining a peripheral wall enclosing an inner space (IS) adapted to store pressurised fuel and, a PLV (14) as claimed in any one of the preceding claims, said PLV being arranged to open a fluid communication between said inner space and a return port (18) provided on the common rail (12).

9. Common rail assembly (10) as claimed in claim 8 wherein the common rail (12) is provided with a bore (16) defining said inner space (IS), said bore (16) opening at an end and being surrounded by an annular shoulder (26), the PLV being tightened so that the PLV body (28) is biased against said shoulder.

10. Method (100) for tuning to a targeted safety pressure threshold (PS) a common rail assembly (10) as claimed in any one of the claims 8 or 9, the method comprising the following sequential major steps:

A) pre-assembling the PLV (14) thus making an untuned PLV;

B) fixing said pre-assembled PLV in the common rail (12) thus making an untuned common rail assembly;

C) tuning the PLV (14) open pressure to the targeted safety pressure threshold (PS).

11. Method (100, 200) as claimed in claim 10 wherein the pre-assembling major step A) comprises the following sub-steps:

al 1) providing a body (28) integrating a seat (41);

a2) inserting then adjustable valve assembly (29) in the bore (46);

a31) lightly tightening said plug (36) so the threads are just engaged and the plug is held in the body, the closing force generated by the spring being smaller than a safety closing force corresponding to the safety pressure PS;

a4) arranging a first o-ring (38) over the body.

12. Method (100, 200) as claimed claim 11 wherein the providing step al 1) is replaced by:

al2) providing a body 28 and seat 41 assembly, the body and the seat being distinct parts.

13. Method (100, 200) as claimed in any one of the claims 11 or 12 wherein tightening the plug (36) step a31) is replaced by:

a32) strongly tightening said plug (36) so the threads are substantially fully engaged in the body, the closing force generated by the spring being superior to a safety closing force corresponding to the safety pressure PS.

14. Method (100, 200) as claimed in any one of the claims 10 to 13 wherein the PLV fixing major step B) comprises the following sub-steps:

bl) engaging the pre-assembled PLV in the hollow (22);

b2) tightening the PLV in the hollow (22) to ensure sealing, said tightening being done by engaging a first tool (Tl) in a tool engagement feature (54) provided on the body (46).

15. Method (100, 200) as claimed in claim 14 taken in combination with claim

11, the tuning major step C) comprising the following sub-steps:

cl) arranging the assembly (10) onto a tuning machine enabling to raise and measure the rail inner pressure;

c2) raising said rail pressure until the PLV 14 switches to an open position;

c3) tightening the adjusting plug (36) until the PLV switches back to a closed position;

c4) repeating the steps c2) and c3) until the rail pressure gets to the level of the targeted safety pressure threshold PS.

16. Method (100, 200) as claimed in claim 14 taken in combination with claim

13, the tuning major step C) comprising the following sub-steps:

c2) raising said rail pressure to the targeted safety pressure (PS);

c3) unscrewing the adjusting plug (36) until the PLV switches to an opening position (OP).

17. Method (200) for tuning to a targeted safety pressure threshold (PS) a common rail assembly (10) as claimed in any one of the claims 8 or 9, the method comprising the following sequential major steps:

A) pre-assembling the PLV (14) as per any one of the claims 11 to 13 thus making an untuned PLV;

C) tuning the PLV (14) open pressure to the targeted safety pressure threshold (PS) on a PLV tuning machine;

B) fixing, as per claim 14, said tuned PLV in the common rail (12) in order to make a common rail assembly (10).

18. Method (200) as claimed in claim 17 taken in combination with claim 11 wherein the tuning major step C) of claim 17 comprises the following sub-steps:

cl) arranging the assembly (10) onto a PLV tuning machine;

c2) raising the fluid pressure until the PLV (14) switches to an open position;

c4) repeating the steps c2) and c3) until the fluid pressure gets to the level of the targeted safety pressure threshold PS.

19. Method (200) as claimed in claim 17 taken in combination with claim 13 wherein the tuning major step C) of claim 17 comprises the following sub-steps:

cl) arranging the untuned PLV onto a tuning machine wherein a HP fluid source engages the spill orifice (50) generating an opening force on the valve member;

c2) raising the HP pressure to said targeted safety pressure threshold PS;

c3) unscrewing the plug (36) until the PLV opens.