WO2019137796A1

WO2019137796A1 - Fuel common rail

Info

Publication number: WO2019137796A1
Application number: PCT/EP2018/086482
Authority: WO
Inventors: Levent AKIN; Cuneyt ALTINOL
Original assignee: Delphi Technologies Ip Limited; Delphi France Sas
Priority date: 2018-01-10
Filing date: 2018-12-21
Publication date: 2019-07-18
Also published as: GB2570114A; GB201800388D0

Abstract

A common rail (12) having an elongated body (18) extending along a longitudinal axis (L) and internally provided with a first blind bore extending along a first axis and opening in a first end and, with a second blind bore extending along a second axis and opening in a second end, said two bores being substantially parallel, the first, second and longitudinal axes being parallel and offset, the two bores being in permanent fluid communication with one another and defining together an inner volume.

Description

FUEL COMMON RAIL TECHNICAL FIELD

The present invention relates to high pressure fuel reservoir, known as a fuel common rail, of large diesel engines injection systems such as V6, V8 or engines of heavy duty trucks having six, eight or more cylinders, and also at a method of manufacturing said rail.

BACKGROUND OF THE INVENTION

Large diesel engines such as V6, V8 or engines of heavy duty truck having at least a six cylinder have at least one fuel injector per cylinder. The fuel injection system of said engines comprise a high pressure reservoir, well known as a common rail, for receiving fuel pressurised at 3000 bars or more via an inlet and, delivering said fuel to the fuel injectors via a plurality of outlets. The rail further comprises a return line and a pressure valve arranged to open or to close a backleak port connected as a function of the pressure measured by a pressure sensor.

The common rails for said large engines may be as long as lm and, a most difficult operation is to drill a 850mm long bore defining a 40 cm³ volume capacity of the common rail. Such a common rail has a mass of about 5kg.

Dividing said long rail in two shorter rails is done for V-type engines, each short rail delivering fuel to a bank of cylinders. This arrangement enables shorter drillings but does not reduce the overall mass and moreover, requires a high pressure inter-connection between said rails.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a common rail of a fuel injection equipment of an engine having at least six cylinders, said common rail being a high pressure reservoir having an inner volume defining a fuel capacity. In use, fuel pressurized in a pump is delivered and stored in said inner volume of said rail and is then is distributed to fuel injectors. The rail has an elongated body extending along a longitudinal axis between a first end and second end and internally provided with a first blind bore extending along a first axis and opening in the first end and, with a second blind bore extending along a second axis and opening in the second end. Said two bores, are substantially parallel, the first, second and longitudinal axes being parallel and offset. The two bores are in permanent fluid communication with one another defining together said inner volume. Each of the two bores, has about half the total capacity of the rail.

The cross section of the rail body may be elongated along a transverse axis perpendicularly intersecting the first axis and the second axis.

The common rail may further comprise a fuel inlet, for delivering fuel to said bores, at least six outlets for delivering fuel to said injectors and, a backleak port for connecting to a return line, all said inlet, outlets and backleak port being drilled in turrets radially extending from the rail body.

The fluid communication between the bores may be defined by the inlet or one of the outlets which drilling extends across the two bores.

Alternatively, said fluid communication between the bores may be defined by a further drilling which external opening on the outer face of the rail is sealed.

The first end of the rail body may be adapted to receive a high pressure valve, the backleak port being arranged close to said first end and, the second end of the rail body may be adapted to receive a pressure sensor.

The first bore may be in direct fluid communication with a first group of outlets and, the second bore is in direct fluid communication with a second group of the outlets.

The first and second groups of the outlets may be coplanar.

Alternatively, the first and second groups of the outlets may be perpendicular to one another.

The outlets of the first group may extend in the plan of the first and second axes.

The invention further extends to a method to manufacture a high pressure reservoir of an injection system for an internal combustion engine, the method comprising the following steps:

- manufacturing a blank of a reservoir body, said blank having the following characteristics: cl) an elongated shape extending along a longitudinal axis between a first end and an distant second end,

c2) an elongated cross section along a transverse axis perpendicular said longitudinal axis L and,

c3) a plurality of turrets - protruding from the blank and extending perpendicularly to the longitudinal axis;

- drilling from the first end a first blind bore along a first axis parallel and offset to said longitudinal axis;

- drilling from the second end a second blind bore along a second axis parallel and offset to said longitudinal axis, the second axis and the first axis being symmetrical about the longitudinal axis, the first and the second axes both perpendicularly intersecting the transverse axis.

A first group of said turrets may extends in the plan of the first and second axes and, the second group of turrets extend either in the same plan or in an second plan perpendicular to said plan.

- drilling the turrets for creating at least one inlet,, the outlets -, - said drillings extending from a top of a turret and opening in one of the bores.

- extending one of the drillings to the other bore for creating a permanently open fluid communication between the first and the second bore.

- drilling the blank to create a further hole externally opening in the blank and extending through the two bores, for creating a permanently open fluid communication between the first and the second bore.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is an axial section of a common rail as per a first embodiment of the invention.

Figure 2 is an axial section of a common rail as per an alternative embodiment of the invention.

Figures 3 and 4 are two cross-sections of alternative embodiments of the common rail of figure 1 or figure 2.

Figure 5 is a 3D view of a common rail of figure 1 or figure 2. Figure 6 is a 3D view of an alternative embodiment of the common rail of figure 1 or figure 2.

Figure 7 is a method diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A common rail assembly 10 is described in reference to the figures and it comprises a common rail 12, a high pressure valve 14 and a pressure sensor 16. In figures 1 and 2 said assembly 10 is presented in axial section made in a first axial plan Pl and, in figures 3 and 4 said assembly is shown in section in a transverse plan P3 orthogonal to the first axial plan Pl . A second axial plan P2 being defined as being orthogonal to both the first axial plan Pl and the transverse plan P3.

The common rail 12 has a body 18 extending along a longitudinal axis L, that is the intersection between the two axial plans Pl, P2, said body 18 having a main member 20 elongating between a first end 22 (left of figure 1) and an opposed second end 24 (right). Said rail 12 also has a plurality of turrets radially extending from a foot joining said main member 20 to a distant top. The example shown on figure 1 has nine turrets referenced 261 to 269, when going from the first end 22 (left) to the second end 24 (right) and then from top of the figure to bottom of the figure. Said turrets 261-269 radially extend along individual axis A1-A9 that are in the first axial plan Pl perpendicular to the longitudinal axis L, said turrets defining a first group 261-264 extending on one side of the main member 20, top of figure 1, the other turrets 265-269 defining a second group, extending in the opposite direction, bottom of figure 1.

In the example shown in Figure 1 the common rail 12 is manufactured from a forged blank 12B although alternative technologies exist such as molding or machining.

Moreover, the main member 20 has a cross section elongated in a transverse direction along a first transverse axis Tl lying in the first axial plan Pl and perpendicular to the longitudinal axis L. Said elongated cross-section has two large sides 20L connected by two opposite narrow ends 20N. Figures 3 and 4 present two alternatives of common rail 12, in figure 3 all the turrets 261-269 extend from said narrow ends 20N in the first axial plan Pl in said transverse direction, a turret extending toward the top and another one extending toward the bottom, said alternative representing the arrangement shown on figures 1 or 2. In figure 4, while a turret is in the first axial plan Pl extending from the narrow end 20N toward the top, said another turret extends in the second axial plan P2 along a second transverse axis T2 perpendicular to the first transverse axis Tl said another turret extending from one of the large sides 20L of the rail body. Said second alternative is not shown in axial section.

A first blind bore 28 extending along a first axis XI parallel to the longitudinal axis L is drilled in the blank 12B from the first end 22 (open end of the first bore) toward the second end 24 (blind end of the first bore) and, a second blind bore 30 extending along a second axis X2 also parallel to the longitudinal axis L is drilled in the blank 12B from the second end 24 (open end of the second bore) toward the first end 22 (blind end of the first bore). Said to bores 28, 30 are parallel to one another, their respective axis XI, X2 lying in the first axial plan Pl and being symmetrically machined on both sides of the central longitudinal axis L, each of the bores being drilled in one of the narrow ends 20N of the elongated cross-section.

As shown on the figures 1-4, the two blind bores 28, 30 having same lengths, slightly shorter than the overall length of the rail and, same circular section with same diameter, have the same volume which together defines the volume capacity of the rail 12.

In the first end 22 is machined a first recess 32 coaxial XI to the first bore 28 and also the geometrical features (faces, threads) enabling complementary arrangement of the HP valve 14, the first bore 28 opening at the bottom of said first recess 32.

Similarly, at the second end 30 is machined a second recess coaxial X2 to the second bore 30 and, the geometrical features enabling complementary arrangement of the pressure sensor 16.

Each of the turrets 261-269 is axially A1-A9 drilled defining an inner conduit 341-349 enlarging at the top of the turret, for defining a conical seat and joining a bore 28, 30 at the opposite end.

The first, second and third turrets 261, 262, 263 define outlets adapted to be connected to HP pipes joining fuel injectors. Opposite to the conical seat, the inner conduits 341-343 define a fluid restriction prior to opening in the first bore 28.

The fourth turret 264 defines an inlet adapted to be connected to a HP pipe joining a HP pump. The associated inner conduit 344 extends without restriction and joins both the first bore 28 and the second bore 30, thus creating a permanently open fluid communication 36 between said bores 28, 30.

The fifth turret 265 (bottom left of figure 1) defines a backleak adapted to be connected to a return line wherein, when the HP valve 14 opens, fuel in excess in the rail is enabled to flow toward a tank. The associated inner conduit 345 extends without restriction joining the first recess 32 and none of the bores. This backleak 345 is the only inner conduit that, in use, is not in a permanently open fluid communication with the bores, the HP valve 14 controlling said fluid communication between the bores and the backleak.

The sixth 266, seventh 267 and eighth 268 turrets define outlets adapted to be connected to HP pipes joining fuel injectors. Opposite to the conical seat, the inner conduits 346-348 define a fluid restriction prior to opening in the second bore 30.

The ninth turret 349 (bottom right) is similar to the eighth turret but is used to define a second inlet joining the second bore 30 through a restriction.

To summarize, the embodiment presented on figure 1 comprises two inlets 344, 349, one 349 with restriction, one 344 without, six outlets 341, 342, 343, 346, 347, 348 and one backleak 345.

Said arrangement is only an example embodiment and, alternatives not shown, differ from said example. Indeed, the number of outlets may be more than six depending on the number of cylinders in the engine, the number of inlets can be only one, the inlets, either one or two, can be through drillings as the inlet 344 joining the two bores or, can be simple drilling such as the second inlet 349. In the latter case of simple drillings, the fluid communication 36 between the two bores 28, 30 may be provided by another unrestricted radial drilling which opening on the outer face of the body is sealed. This is shown on figure 2.

The fluid restrictions here shown arranged in the inner conduits may be arranged in the connecting pipes or elsewhere. In comparison with a long rail of the prior art that may have a lm length and a 5 kg mass, the common rail 12 of the present invention is only about 500 mm long for a total mass of 4 kg. The internal volume provided by the two bores remaining identical to 40 cm³.

In use, HP fluid enters via the inlets 344, 349 and the pressure sensor 16 delivers a signal, relevant to the actual pressure in the rail, to a command unit which computes a command signal for opening or closing the HP valve 14. As long as the rail internal pressure does not exceeds a threshold, the valve 14 is closed and, when exceeding said threshold the valve 14 opens enabling fuel to exit the rail via the backleak 345. Said pressure threshold itself may be varied by the command unit as being adjusted to the needs of the engine and, whichever it is, pressurised fuel exits the rail via the outlets 341-344, 346-348 flowing toward fuel injectors or via the backleak 345.

A further advantage of the present invention is that for fixing a lm/5kg rail onto an engine, five or more mounting pads 38 are required, while, as shown on figures 5 and 6, only two or three mounting pads 38 are required for a small rail 12 of 500 mm/ 4kg, this saving mass and time to assemble.

In relation to figure 7 is now described a method 100 of manufacturing the common rail 12, said comprising the following steps:

110) manufacturing a blank 12B of a reservoir body, said blank having the following characteristics:

cl . an elongated shape extending along a longitudinal axis L between a first end 22 and an distant second end 24,

c2. an elongated cross section along a transverse axis Tl perpendicular said longitudinal axis L and,

c3. a plurality of turrets 261-269 protruding from the blank 12B and extending perpendicularly to the longitudinal axis L.

Said manufacturing step can be done by forging or moulding or through other known manufacturing means.

120) drilling from the first end 22, a first blind bore 28 along a first axis XI parallel and offset to said longitudinal axis L;

130) drilling from the second end 24, a second blind bore 30 along a second axis X2 parallel and offset to said longitudinal axis L. The second axis X2 and the first axis XI are symmetrically arranged about the longitudinal axis L, the first and the second axes both perpendicularly intersecting the transverse axis Tl.

The blank further comprises turrets 261-269, a first group of said turrets 261-264 extending in the plan Pl of the first and second axes XI, X2 and, the second group of turrets 265-269 extending either in the same plan Pl (figure 3) or in an second plan P2 (figure 4) perpendicular to said plan Pl .

140) drilling the turrets for creating at least one inlet 344, 349, the outlets 341-343, 346-348 said drillings extending from a top of a turret and opening in one of the bores.

150) extending one of the drillings done at step 140) to the other bore for creating a permanently open fluid communication 36 between the first and the second bore.

Instead of step 150) the method may comprise the following step:

160) drilling the blank 12B to create a further hole (figure 2) externally opening in the blank 12B and extending through the two bores 28, 30 for creating a permanently open fluid communication 36 between the first and the second bore.

Said other hole may be afterward sealed by a plug or any other means.

LIST OF REFERENCES

Pl first axial plan

P2 second axial plan

P3 transverse plan

L longitudinal axis

Tl transverse axis

T2 second transverse axis

A1-A9 turret axis

10 common rail assembly

12 common rail assembly

12B blank

14 HP valve 16 pressure sensor

18 body

20 main member of the body

20N narrow end

20L large side

22 first end

24 second end

261-269 turrets

28 first bore

30 second bore

32 first recess

341 outlet

342 outlet

343 outlet

344 inlet

345 backleak

346 outlet

347 outlet

348 outlet

349 inlet

36 fluid communication

38 mounting pads

100 method

110 manufacturing

120 drilling

130 drilling

140 drilling

150 extending a drilling

160 further drilling

Claims

CLAIMS:

1. Common rail (12) of a fuel injection equipment of an engine having at least six cylinders, said common rail (12) being a high pressure reservoir having an inner volume defining a fuel capacity and wherein, in use, fuel pressurized in a pump is delivered and stored in said inner volume of said rail and is then is distributed to fuel injectors, the rail having an elongated body (18) extending along a longitudinal axis (L) between a first end (22) and second end (24) and internally provided with a first blind bore (28) extending along a first axis (XI) and opening in the first end and, with a second blind bore (30) extending along a second axis (X2) and opening in the second end, said two bores (28, 30) being substantially parallel, the first (XI), second (X2) and longitudinal (L) axes being parallel and offset, the two bores (28, 30) being in permanent fluid

communication (36) with one another and defining together said inner volume, the common rail (12) further comprising a fuel inlet (344, 349) for delivering fuel to said bores, at least six outlets (341, 342, 343, 346, 347, 348) for delivering fuel to said injectors and, a backleak port (345) for connecting to a return line, all said inlet, outlets and backleak port being drilled in turrets (261- 269) radially extending from the rail body and,

wherein the first end (22) of the rail body is adapted to receive a high pressure valve (14), the backleak port (345) being arranged close to said first end (22) and wherein, the second end (24) of the rail body is adapted to receive a pressure sensor (16).

2. Common rail (12) as claimed in the preceding claim wherein

each of the two bores (28, 30) has about half the total capacity of the rail.

3. Common rail (12) as claimed as in any one of the preceding claims wherein the cross section of the rail body (18) is elongated along a transverse axis (Tl) perpendicularly intersecting the first axis (XI) and the second axis (X2).

4. Common (12) rail as claimed in claim 1 wherein the fluid communication (36) between the bores is defined by the inlet (344) or one of the outlets which drilling extends across the two bores.

5. Common (12) rail as claimed in claim 1 wherein the fluid communication (36) between the bores is defined by a further drilling which external opening on the outer face of the rail is sealed.

6. Common rail (12) as claimed in any one of the claims 1 wherein the first bore (28) is in direct fluid communication with a first group of outlets (341, 342, 343) and, the second bore (30) is in direct fluid communication with a second group of the outlets (346, 347, 348).

7. Common rail (12) as claimed in claim 6 wherein the first and second groups of the outlets are coplanar (Pl).

8. Common rail (12) as claimed in claim 6 wherein the first and second groups of the outlets are perpendicular to one another.

9. Common rail as claimed in claim 8 wherein the outlets of the first group extend in the plan (Pl) of the first (XI) and second axes (X2).

10. Method (100) to manufacture a high pressure reservoir of an injection system for an internal combustion engine, the method comprising the following steps:

110) manufacturing a blank (12B) of a reservoir body, said blank having the following characteristics:

cl . an elongated shape extending along a longitudinal axis (L) between a first end (22) and an distant second end (24),

c2. an elongated cross section along a transverse axis (Tl)

perpendicular said longitudinal axis (L) and,

c3. a plurality of turrets (261-269) protruding from the blank (12B) and extending perpendicularly to the longitudinal axis (L); 120) drilling from the first end a first blind bore (28) along a first axis (XI) parallel and offset to said longitudinal axis (L);

130) drilling from the second end (24) a second blind bore (30) along a second axis (X2) parallel and offset to said longitudinal axis (L), the second axis (X2) and the first axis (XI) being symmetrical about the longitudinal axis (L), the first and the second axes both perpendicularly intersecting the transverse axis (Tl).

11. Method (100) as claimed in any one of the claims 10 wherein a first group of said turrets (261-264) extends in the plan (Pl) of the first and second axes (XI, X2) and, the second group of turrets (265-269) extend either in the same plan (Pl) or in an second plan (P2) perpendicular to said plan (Pl).

12. Method (100) as claimed in claim 11 further comprising the step:

140) drilling the turrets for creating at least one inlet (344, 349), the outlets

(341-343, 346-348) said drillings extending from a top of a turret and opening in one of the bores.

13. Method (100) as claimed in claim 11 further comprising the step:

150) extending one of the drillings done at step 140) to the other bore for creating a permanently open fluid communication (36) between the first and the second bore.

14. Method (100) as claimed in claim 11 further comprising the step:

160) drilling the blank (12B) to create a further hole externally opening in the blank (12B) and extending through the two bores (28, 30) for creating a permanently open fluid communication (36) between the first and the second bore.