WO2019068567A1

WO2019068567A1 - Fuel injector

Info

Publication number: WO2019068567A1
Application number: PCT/EP2018/076353
Authority: WO
Inventors: George A MEEK; Aneeq QUADIR
Original assignee: Delphi Technologies Ip Limited; Delphi France Sas
Priority date: 2017-10-04
Filing date: 2018-09-27
Publication date: 2019-04-11
Also published as: GB201716191D0; GB2567171A

Abstract

A fuel injector (10) defines a HP supply conduit (56), a LP return conduit (58) extending from a control chamber (32) to a return outlet port and, a first fluid communication (F1) joining said HP conduit to the control chamber, a second fluid communication (F2) joining the control chamber to the LP conduit, and a third fluid communication (F3) joining said first fluid (F1) communication to said second fluid communication (F2), a chamber control valve (34) alternatively opening or closing said third fluid communication (F3).

Description

Fuel injector TECHNICAL FIELD

The present invention relates to a diesel fuel injector and more particularly to fluid communications arranged to control a valve member.

BACKGROUND OF THE TNVENTION

To enable or prevent diesel fuel injection, a fuel injector is provided with a needle valve member that reciprocally moves under the influence of the pressure in a control chamber wherein high pressure (HP) fuel enters via a large inlet and via a throttled inlet (INO). To enable said injection, an electrovalve opens a low pressure (LP) port (SPO) and closes said large inlet for the fuel retained in said control chamber to draining and, as the chamber pressure drops the needle valve member lifts and opens spray holes. Reciprocally, to prevent the injection the valve closes the SPO and the chamber pressure rises again, pushing the needle back closing said holes.

The INO's throttling effect enables an asymmetry in the chamber pressure rising rate necessary to control the needle movement in accordance to the engine needs but, during an injection event, although the large inlet is closed, a smaller quantity of HP fuel continues to enter the chamber via the F O and directly leaks off via the open SPO generating power losses. SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a fuel injector adapted to be arranged on an internal combustion engine, said injector having a body wherein is guided a needle valve member extending from a tip end to a head top face moving, in use, under the influence of the pressure in a control chamber between a closed position preventing fuel injection and a fully open position enabling said fuel injection via spray holes.

Said control chamber is defined by a peripheral face and a ceiling face of the body and also by said needle head top face and, the fuel injector defines a high pressure (HP) supply conduit extending from an inlet said spray holes, a return low pressure (LP) conduit extending from said control chamber to a return outlet port. The fuel injector further defines:

a first fluid communication joining said HP conduit to the control chamber,

a second fluid communication joining the control chamber to the LP conduit, and

a third fluid communication joining said first fluid communication to said second fluid communication, a chamber control valve alternatively opening or closing said third fluid communication.

Also, he first fluid communication defines a throttle INO.

Also, the first fluid communication is permanently open.

Also, the second fluid communication is selectively opened or closed by an outlet control valve, and the needle valve member partially defines said chamber control valve.

Also, the needle top face complementary cooperates with said ceiling face to define the chamber control valve controlling said third fluid communication.

Also, said chamber valve controlling the third fluid communication defines a seat line.

Also, the first fluid communication opens on the outer bound of the ceiling face seat line and, the second fluid communication opens on the inner bound of the ceiling face seat line.

Also, the first fluid communication opens on the inner bound of the ceiling face seat line and, the second fluid communication opens on the outer bound of the ceiling face seat line.

Also, a hollow is provided on the needle top face opening on the inner bound seat line, said hollow being in permanent fluid communication with the fluid communication that opens on the inner bound seat line.

Also, the fuel injector further defines a fourth fluid communication joining said HP conduit to the control chamber.

Also, said fourth fluid communication is selectively opened or closed by an inlet control valve, said fourth fluid communication being closed when the second fluid communication is open and being open when the second fluid communication is closed. Also, the inlet control valve and the outlet control valve are integrally part of a -way control valve.

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 part of a fuel injector as per a first embodiment of the invention.

Figure 2 is an axial section of part of a fuel injector as per a second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A diesel fuel injector 10, partially represented on the figures, comprises an injection nozzle assembly 12 over which is firmly fixed a control valve assemblyl4.

The nozzle assembly 12 comprises a body identified as a nozzle barrel 16 in which is arranged a needle valve member 18 guided along a longitudinal axis X between a lower guiding means, not shown, and a upper guiding means.

Said upper guiding means comprises an upper guide member 20 fixed atop said nozzle barrel 16 and provided with an axial X through bore 22, or upper guiding bore 22, in which is slidably guided a head end 24 of the needle.

Also, a valve plate 28 is positioned sandwiched between the upper face of the upper guide member 20 and the lower face of a control valve body 26. Said plate 28 closes said guiding bore 22 defining the ceiling face 30 of a control chamber 32 defined as the upper part of the guiding bore 22 comprised between the head 24 of the needle and said ceiling face 30.

Also, the head 24 of the needle cooperates with said ceiling face 30 defining a control chamber valve 34 that is closed along a circular seat line 36 when the needle 18 is in fully open position as shown on the figures and that opens when the needle 18 moves away from said position. The head 24 of the needle is further provided with a small hollow 38 opening in the top transverse face of said head 24, said hollow opening being surrounded by said circular seat line 36. The volume of the hollow 38 is part of the control chamber 32 and, the hollow can take any other shape than the represented conical profile.

The valve plate 28 is also provided with a through valve hole 40 offset to the longitudinal axis X and concentric with a hydraulic bore 42 drilled through the control valve body 26. Said hydraulic bore 42 opens at one end in the lower face of the control valve body 26 in said complementary valve hole 40 and, at the other end, in the bottom of a recess 44, defining an armature chamber 44, dug in the upper face of the control valve body 26. An armature-stem assembly 46 comprises a hydraulic stem 48 crimped in a disc-like magnetic armature 50, the stem 48 being longitudinally guided in said hydraulic bore 42 and the armature 50 being in said armature chamber 44. The stem 48 downwardly extends to a lower end protruding out of the hydraulic bore 42 into said valve hole 40 and therein defining a 3-way valve 51 comprising an inlet valve 52 and an outlet valve 54. The armature 50 cooperates with a solenoid, not shown, that when energised generates a magnetic field upwardly attracting the armature-stem assembly 46 then closing the inlet valve 52 and opening the outlet valve 54 and, when the solenoid is not energised a spring, not shown, pushes back the armature-stem assembly 46 away from the solenoid opening the inlet valve 52 and closing the outlet valve 54.

Alternatively to said arrangement two 2-way valves can be arranged instead of the 3-way valve.

The inlet valve 52 is defined by a shoulder face of the stem cooperating with an inlet seat face surrounding the opening of the hydraulic bore in the lower face of the control valve body and, the outlet valve 54 is defined by the very end of the stem cooperating with an outlet seat face defined in the upper face of the upper guide member 20.

The fuel injector 10 is further provided with a high pressure (HP) conduit 56 extending from an injector inlet to spray holes, not shown, and with a low pressure (LP) conduit 58 extending from the control chamber 32 to an outlet port not shown.

A first fluid communication Fl is defined between the HP conduit 56 and the control chamber 32, and it comprises a first groove 60 dug in the upper face valve plate 28 and closed by the under face of the control valve body, thus forming a closed conduit and, a throttle orifice 62, known as an INO (Inlet Nozzle Orifice) drilled through the valve plate from said first groove 60 to the ceiling face 30 of the control chamber. This first fluid communication Fl is permanently open but restricted by the throttle of the INO 62, enabling a limited quantity of HP fuel to enter the control chamber.

A second fluid communication F2 is defined between the control chamber 32 and the LP conduit 58 and it comprises, a through hole 64, known as a SPO (Spill Path Orifice) restricted but less-restricted than the INO, drilled through the valve plate from the ceiling face 30 of the control chamber to a second groove 66 dug in the upper face of the valve plate 28 and closed by the under face of the control valve body, thus forming a closed conduit, to an annular void 68 surrounding the stem lower end in the valve hole 40. Said void 68 joins the LP conduit 58 that is drilled in the upper guide member 20 and that opens right below the valve hole 40, said opening defining said outlet seat face of the outlet valve 54.

Controlled by the 3 -way valve 51, said second fluid communication F2 is open when the outlet valve 54 is open, the inlet valve 52 being closed, enabling HP fuel to exit the control chamber and, it is closed when the outlet valve 54 is closed preventing such exit.

A third fluid communication F3 is defined in the control chamber 32 that is split by said seat line 36 on either side of which the INO and the SPO are opened.

Figure 1 shows a first embodiment of the invention where the INO 62 opens inside the seat line 36 and the SPO opens outside said seat line 36 and, figure 2 shows a second embodiment of the invention where the INO opens outside the seat line 36 and the SPO opens inside said seat line 36.

Controlled by the displacements of the needle 18, said third fluid communication F3 is only closed when the needle is in fully open position, the needle head face being urged in contact against the ceiling face of the control chamber along said seat line 36.

A fourth fluid communication F4 is defined between the HP conduit 56 and the control chamber 32 and it comprises a channel 70 drilled in the control valve body 26 between said HP conduit 56 and the hydraulic bore where it opens in a second annular void 72 surrounding the stem 48, said second void 72 extending to the inlet valve 52 where it joins the second groove 66 and the SPO 64. Controlled by the 3 -way valve 51 , said fourth fluid communication F4 is open when the inlet valve 52 is open, the outlet valve 54 being closed, and it is closed when the inlet valve 52 is closed.

Key operational phases of the fuel injector 10 are now described.

In a first phase the solenoid is not energised. A spring, not shown, downwardly pushes the armature-stem assembly 46 away from the solenoid. The inlet valve 52 is open, the outlet valve 54 is closed. HP fuel fills the control chamber entering via the open fourth fluid communication F4. The pressure in the control chamber rises and the needle valve 18 is urged toward a closed position preventing fuel injection. The four fluid communication states are:

Fl is open. A restricted flow of HP fuel enters the control chamber; F2 is closed. HP fuel is retained in the control chamber.

F3 is open.

F4 is open for HP fuel to fill the control chamber wherein pressure rises.

In a second phase the solenoid is energised generating a magnetic field that upwardly attracts the armature-stem assembly 46 toward the solenoid. The inlet valve 52 closes, the outlet valve 54 opens. HP fuel in the control chamber drains via the second fluid communication F2 that is open. The pressure in the control chamber drops and the needle valve 18 lifts. Fuel injection occurs.

During the needle travel between said closed position and the fully open position, the second fluid communication F2 is already open while the third fluid communication F3 is still open therefore, only during this ballistic phase, a minor fuel quantity leaks from the INO to the SPO and to drain. At the end of said opening ballistic phase, when the needle is in fully open position the third fluid communication F3 closes stopping said minor leak. The four fluid

communications states are:

Fl is open. A restricted flow of HP fuel enters the control chamber; F2 is open. Fuel drains the control chamber.

F3 is closed.

F4 is closed. HP fuel does not enter the control chamber via F4. The injectors of the first embodiment, figure 1, and of the second embodiment, figure 2, operate similarly and only differ by the INO and the SPO arrangement in the valve plate 28.

In the first embodiment (figure 1) the INO opens centrally in the ceiling face 30 while the SPO opens on the other side of the seat line 36 on the periphery of the ceiling face and, when the 3 -way valve 51 commutes HP fuel enters the control chamber on the peripheral area.

In the second embodiment (figure 2) the INO opens on the periphery of the ceiling face 30 while the SPO opens centrally on the other side of the seat line 36 and, when the 3 -way valve 51 commutes HP fuel enters the control chamber on the central area and fills the hollow 38.

The choice of an embodiment or the other may be driven by development or manufacturing parameters. Thanks to said fluid communications the fuel leaks are almost stopped and energy is saved.

LIST OF REFERENCES

X longitudinal axis

Fl fluid communication

F2 fluid communication

F3 fluid communication

F4 fluid communication

10 injector

12 nozzle assembly

14 control valve assembly

16 nozzle barrel

18 needle valve member

20 upper guide member

22 upper guiding bore

24 head of the needle

26 control valve body

28 valve plate

30 ceiling face

32 control chamber

34 control chamber valve

36 seat line

38 hollow

40 valve hole hydraulic bore

recess - armature chamber armature-stem assembly stem

magnetic armature

3 -way valve

inlet valve

outlet valve

high pressure (HP) conduit low pressure (LP) conduit first groove

INO

SPO

second groove

annular void

channel

second annular void

Claims

CLAIMS:

1. Fuel injector (10) adapted to be arranged on an internal combustion engine, said injector having a nozzle barrel (16) wherein is guided a needle valve member (18) extending from a tip end to a head top face (24) moving, in use, under the influence of the pressure in a control chamber (32) between a closed position preventing fuel injection and a fully open position enabling said fuel injection via spray holes, said control chamber (32) being defined by a peripheral face and a ceiling face (30) of the body and also by said needle head top face (24), the fuel injector (10) defining a high pressure (HP) supply conduit (56) extending from an inlet said spray holes, a return low pressure (LP) conduit (58) extending from said control chamber (32) to a return outlet port and, the fuel injector (10) further defining

a first fluid communication (Fl) joining said HP conduit to the control chamber,

a second fluid communication (F2) joining the control chamber to the LP conduit, and

a third fluid communication (F3) joining said first fluid (Fl)

communication to said second fluid communication (F2), a chamber control valve (34) alternatively opening or closing said third fluid communication (F3) and, wherein, the needle top face (24) complementary cooperates with said ceiling face (30) to define the chamber control valve (34) controlling said third fluid communication (F3) and,

wherein said chamber valve (34) controlling the third fluid communication (F3) defines a seat line (36) and,

wherein the first fluid communication (Fl) opens on the ceiling face on the outer bound of the ceiling face seat line (36) and, the second fluid communication (F2) opens on the inner bound of the ceiling face seat line (36).

2. Fuel injector (10) as claimed in the preceding claim wherein the first fluid communication (Fl) defines a throttle (INO 62).

3. Fuel injector (10) as claimed in any one of the preceding claims wherein, the first fluid communication (Fl) is permanently open,

the second fluid communication (F2) is selectively opened or closed by an outlet control valve (54), and

the needle valve member (18) partially defines said chamber control valve (34).

4. Fuel injector (10) as claimed in claim 1 wherein the first fluid

communication (Fl) opens on the inner bound of the ceiling face seat line (36) and, the second fluid communication (F2) opens on the outer bound of the ceiling face seat line (36).

5. Fuel injector (10) as claimed in any one of the preceding claims wherein a hollow (38) is provided on the needle top face (24) opening on the inner bound seat line (36), said hollow (38) being in permanent fluid communication with the fluid communication (Fl, F2) that opens on the inner bound seat line (36).

6. Fuel injector (10) as claimed in any one of the preceding claims further defining a fourth fluid communication (F4) joining said HP conduit (56) to the control chamber (32).

7. Fuel injector (10) as claimed in claim 6 wherein said fourth fluid communication (F4) is selectively opened or closed by an inlet control valve (52), said fourth fluid communication (F4) being closed when the second fluid communication (F2) is open and being open when the second fluid

communication (F2) is closed.

8. Fuel injector (10) as claimed in claim 7 wherein the inlet control valve (52) and the outlet control valve (54) are integrally part of a 3-way control valve (51).