GB2552384A

GB2552384A - Nozzle for a fuel injector

Info

Publication number: GB2552384A
Application number: GB1612765.6A
Authority: GB
Inventors: E Wright Keith
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2016-07-22
Filing date: 2016-07-22
Publication date: 2018-01-24
Also published as: GB201612765D0

Abstract

Nozzle body 14 of a fuel injector 10 adapted to receive a needle valve member (figure 4, 20) in a sliding fit in a bore (figure 4, 18) is surrounded by a peripheral wall (figure 4, 16) that has a wide upper cylindrical portion 36 and a narrow lower cylindrical portion 40 connected by a transverse shoulder face 38. The lower portion extends from the shoulder face to a spray extremity 42 which tapers and is adapted to spray fuel via spray holes 32 characterized in that the nozzle body further comprises a heat shield 46 arranged to protect the lower cylindrical portion. The heat shield may comprise a tubular sleeve 48 preferably fixed to the body which may have circular lower edge 56 and may also have a cup-like end cap (figure 3, 66) which may be integral with the sleeve. Space(s) (figure 4, S1, S2) may be defined between the sleeve and peripheral wall which can include a vacuum or thermally insulated material.

Description

(54) Title ofthe Invention: Nozzle for a fuel injector Abstract Title: Nozzle heat shield of a fuel injector (57) Nozzle body 14 of a fuel injector 10 adapted to receive a needle valve member (figure 4, 20) in a sliding fit in a bore (figure 4, 18) is surrounded by a peripheral wall (figure 4, 16) that has a wide upper cylindrical portion 36 and a narrow lower cylindrical portion 40 connected by a transverse shoulder face 38. The lower portion extends from the shoulder face to a spray extremity 42 which tapers and is adapted to spray fuel via spray holes 32 characterized in that the nozzle body further comprises a heat shield 46 arranged to protect the lower cylindrical portion. The heat shield may comprise a tubular sleeve 48 preferably fixed to the body which may have circular lower edge 56 and may also have a cup-like end cap (figure 3, 66) which may be integral with the sleeve. Space(s) (figure 4, S1, S2) may be defined between the sleeve and peripheral wall which can include a vacuum or thermally insulated material.

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56,58,64

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Nozzle of a fuel injector

TECHNICAL FIELD

The present invention relates to a fuel injector and more particularly to a heat shield thermally insulating the nozzle.

BACKGROUND OF THE INVENTION

The nozzle and spray holes arrangement of a diesel/fuel injector is well established and widely used on passenger cars and, medium and high duty applications alike. There are two specific concerns that continue to be the focus of many studies.

Firstly, coking deposit build up within the micro spray holes. As spray hole sizes continue to reduce to satisfy the drive for higher pressures and finer atomised sprays, so does the influence of coking deposits, as the ratio of deposit size versus spray hole size moves in an unfavorable direction.

Secondly, the increase in injection pressures leads to a need for higher strength steels to resist the increased stresses experienced at peak load. An aggravating factor in this is that operating temperature reduces the fatigue strength of chosen steels leading to costly high temperature fatigue tests being required and used of more expensive composition steels to meet the combination of these parameters.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a nozzle body of a fuel injector extending along a main axis and adapted to receive a needle valve member in a sliding fit in a bore surrounded by a peripheral wall comprising a wide upper cylindrical portion and a narrow lower cylindrical portion connected by a transverse shoulder face, said lower portion extending from said shoulder face to a distant spray extremity which tapers and is adapted to spray fuel via spray holes extending through the peripheral wall and open in the outer face of said spray extremity.

Advantageously, the nozzle body further comprises a heat shield arranged to protect said lower cylindrical portion.

Also, said heat shield comprises a tubular sleeve engaged over said lower cylindrical portion, the spray holes remaining unobstructed enabling, in use, fuel spray.

Also, the heat shield is fixed to the nozzle body in the vicinity of the shoulder face at an upper end of the sleeve and, in the vicinity of the spray holes at a lower end of the sleeve.

Also, the lower end of the sleeve forms a circular edge fixed in the neighbouring vicinity of the openings of the spray holes.

Also, the heat shield further comprises a cup-like end cap covering the spray extremity of the nozzle body.

Also, said cup-like end cap is distinct from the sleeve and has a circular edge fixed to the nozzle body in the neighbouring vicinity of the spray holes, said spray holes opening in an annular space defined between the lower end circular edge of the sleeve and the circular edge of the end cap.

Also, said cup-like end cap is integral to the sleeve, said integral heat shield being provided with holes aligned to the spray holes in order to enable fuel spray passage.

Also, said heat shield defines a space between the sleeve and the peripheral wall.

Also, said space extends between the cup-like end cap and the spray extremity of the nozzle.

Also, said sleeve and end-cap integral assembly further integrates channels extending throughout said continuous space between the openings of the spray holes and said holes provided in the heat shield.

Also, a vacuum is created in said space.

Also, said space is filled with a thermally insulating material.

Also, the sleeve is welded to the nozzle.

The invention further extends to a nozzle assembly comprising a nozzle body defined above and a needle valve member arranged in a sliding fit in the bore provided in the nozzle body.

The invention further extends to a fuel injector comprising a nozzle assembly as defined above.

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 nozzle of a fuel injector protected with a heat shield as per a first embodiment of the invention.

Figure 2 is a magnified view of the tip of the nozzle of figure 1.

Figure 3 is a magnified view of a second embodiment of the tip of the nozzle.

Figure 4 is an axial section of a nozzle assembly protected with a third embodiment of the heat shield.

Figure 5 is a magnified view of the tip of the nozzle of figure 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A typical diesel fuel injector 10, partially represented on the figures, extends along a main axis X and comprises an actuator assembly, a control valve assembly and a nozzle assembly 12 firmly maintained together by a capnut compressing the control valve between the nozzle and the actuator.

More in detail and using the arbitrary and non-limiting orientation of the figures, the nozzle assembly 12 comprises a body 14 having a peripheral wall 16 particularly visible on figure 4, internally defining an axial X bore 18 in which is slidably adjusted a needle valve member 20. The bore 18 downwardly extends from a top end 22 open in an upper face 24 of the nozzle body 14, to a bottom tapered end 26 defining a valve seat 28 which pointy extremity opens in a small sac 30, wherefrom spray holes 32 radially depart extending through the peripheral wall 16 and opening in the outer face 34 of said wall 16.

The nozzle body 14 comprises a large upper cylindrical portion 36 connected via a shoulder face 38 to a narrow lower cylindrical portion 40 downwardly extending to spray extremity 42 that tapers down to a tip end 44 where open the spray holes 32. The tip end may be given various shapes such as the semi-spherical shape shown on the figures. In the embodiment represented on the figures, the narrow lower portion 40 comprises a short portion 40S directly in contact with the shoulder face 38 and a long portion 40L extending to the spray extremity 42.

A first embodiment of the invention is represented on figures 1 and 2 where a heat shield 46 is arranged over the short portion 40S of the narrow cylindrical portion 40. Said heat shield 46 forms a cylindrical tubular sleeve 48 extending from an open upper end 50 to a lower end 52, the upper end 50 being adjusted to the narrow portion 40 of the nozzle body and, the lower end 52 comprising an inwardly folded annular face 54 extending to a circular lower edge 56 that comes in contact with a first complementary section 58 of the spray extremity 42 of the nozzle. As can be seen on figure 2, the tip end 44 extends through the lower opening of the sleeve so that the spray holes 32 are not covered or obstructed by the sleeve, said first complementary section 58 being above the spray holes 32.

A first electron beam welding bead 60 sealingly fixes the edge 62 of the upper end 50 of the sleeve to the nozzle body and, a second electron beam welding bead 64 sealingly fixes the edge 56 of the lower end 52 to said first complementary section 58 of the spray extremity.

In a not represented embodiment, the sleeve 48 is adjusted to the section of the narrow portion 40 and it lies against the nozzle body. In the represented first embodiment the sleeve 48 is slightly larger than the narrow portion 40 and it defines an annular space SI surrounding the peripheral wall 16, said space SI being either filled with thermally insulating material such the “Microporous granular insulation” or, alternatively, a vacuum being created therein. In this later case the weld beads 60, 64 edges must perfectly seal said space SI. Use of electron beam welding operation, give rise to vacuum presence within the heat shield, by virtue of the vacuum chamber within which the assembly is placed for the welding operation, pressure can be below 0.005 Torr. This arrangement of a sleeve and space SI protects the nozzle against heat transfer from the engine block.

Conclusive tests have been performed with a metallic sleeve having a thickness comprised between 0.15mm and 0.3mm, a space S of about 0.2 mm to 0.3 mm radial distance from the sleeve to the wall.

A second embodiment of the invention is represented on figure 3 where the heat shield 46 comprises a similar sleeve 48 as in the first embodiment and, further comprises an end-cap 66 having a concave cup-like shape arranged over the tip end 44 of the nozzle. The end-cap 66 defines an opening and a surrounding edge 68 through which said tip end 44 engages in the concave space. Said surrounding edge 68 comes in contact against a second complementary section 70 of said tip end 44, said second complementary section 70 being below the opening of the spray holes 32. Similarly to the sleeve 48, the end cap 66 is fixed to the tip end 44 by a third electron welding bead 72 sealing said cap edge 68 to said second complementary section 70.

Also, although the end cap 66 can be in contact with the tip end 44, in the embodiment shown, a second space S2 is defined between the tip end 44 and the end cap 66, said second space S2 being either filled with thermally insulating material or a vacuum being made in it.

In this second embodiment, the spray holes 32 open in an annular space defined between the first 58 and second 70 complementary sections; between the sleeve 48 and the end-cap 66.

Also, as observable when comparing figures 2 and 3, the lower ends 52 of the sleeves slightly differ in that the lower edge 56 is closer to the spray holes 32 in the second embodiment, figure 3, than in the first embodiment, figure 2. Alternatively, the “short” sleeve of the first embodiment could be used on the second embodiment as well as the “long” sleeve of the second embodiment could be used on the first embodiment.

A third embodiment is now described in reference to the figures 4 and 5. In said third embodiment, an integral heat shield 46 comprising a sleeve 74 closed at its lower end with an integral end cap portion 76 is arranged over the narrow portion 40 of the nozzle. To accommodate fuel spray, tubular channels 78, aligned to the spray holes 32, extends through the continuous space comprising both SI, S2, between the sleeve 74 and the peripheral wall 16. In addition to the first welding bead 60 similar to the bead described in the first embodiment, the integral sleeve 74 is fixed thanks to a plurality of fourth electron welded beads 80 welding the inner edge of each channel 78 to the surrounding of the corresponding spray hole 32.

LIST OF REFERENCES

X main axis annular space tip end space fuel injector nozzle assembly body of the nozzle peripheral wall bore needle open top end of the bore upper face of the body 26 bottom tapered end of the bore 28 valve seat sac spray hole outer face of the peripheral wall upper cylindrical portion of the nozzle body shoulder face lower cylindrical portion of the nozzle body

40S short portion

40L long portion spray extremity tip end of the spray extremity heat shield sleeve upper end of the sleeve lower end of the sleeve folded face lower edge of the sleeve first complementary section first welding bead upper edge of the sleeve second welding bead end cap edge of the end cap second complementary section third electron welding bead integral sleeve end cap portion channels fourth electron welded bead

Claims

1. Nozzle body (14) of a fuel injector (10) extending along a main axis (X) and adapted to receive a needle valve member (20) in a sliding fit in a bore (18) surrounded by a peripheral wall (16) comprising a wide upper cylindrical portion (36) and a narrow lower cylindrical portion (40) connected by a transverse shoulder face (38), said lower portion (40) extending from said shoulder face (38) to a distant spray extremity (42) which tapers and is adapted to spray fuel via spray holes (32) extending through the peripheral wall (16) and open in the outer face of said spray extremity, characterized in that the nozzle body (14) further comprises a heat shield (46) arranged to protect said lower cylindrical portion (40).

2. Nozzle body (14) as claimed in the preceding claim wherein said heat shield (46) comprises a tubular sleeve (48) engaged over said lower cylindrical portion (40), the spray holes (32) remaining unobstructed enabling, in use, fuel spray.

3. Nozzle body (14) as claimed in claim 2 wherein the heat shield (46) is fixed to the nozzle body in the vicinity of the shoulder face (38) at an upper end (50) of the sleeve and, in the vicinity of the spray holes (32) at a lower end (52) of the sleeve.

4. Nozzle body (14) as claimed in claim 3 wherein the lower end (52) of the sleeve forms a circular edge (56) fixed in the neighbouring vicinity of the openings of the spray holes.

5. Nozzle body (14) as claimed in any one of the claims 3 or 4 wherein the heat shield (46) further comprises a cup-like end cap (66) covering the spray extremity (42) of the nozzle body.

6. Nozzle body (14) as claimed in the combination of claims 5 and 4 wherein said cup-like end cap (66) is distinct from the sleeve (48) and has a circular edge (68) fixed to the nozzle body in the neighbouring vicinity of the spray holes (32), said spray holes (32) opening in an annular space defined between the lower end circular edge (56) of the sleeve and the circular edge (68) of the end cap.

7. Nozzle body (14) as claimed in the combination of claims 5 and 3 wherein said cup-like end cap (66) is integral to the sleeve (74), said integral heat shield being provided with holes aligned to the spray holes (32) in order to enable fuel spray passage.

8. Nozzle body (14) as claimed in any one of the claims 2 to 7 wherein said heat shield defines a space (SI, S2) between the sleeve (48, 74) and the peripheral wall (16).

9. Nozzle body (14) as claimed in the combination of claims 8 with any one of the claims 5 to 7 wherein said space (S2) extends between the cup-like end cap (66) and the spray extremity (42) of the nozzle.

10. Nozzle body (14) as claimed in any one of the claims 8 or 9 when taken in combination with claim 7 wherein said sleeve (74) and end-cap integral assembly further integrates channels (78) extending throughout said continuous space (SI, S2) between the openings of the spray holes and said holes provided in the heat shield.

11. Nozzle body (14) as claimed in any one of the claims 8 to 10 wherein vacuum is created in said space (SI, S2).

12. Nozzle body (14) as claimed in any one of the claims 8 to 10 wherein said space (SI, S2) is filled with a thermally insulating material.

13. Nozzle body (14) as claimed in any one of the claims 8 to 12 wherein the sleeve (48, 74) is welded to the nozzle.

14.

Intellectual

Property

Office

Application No: GB1612765.6

14. Nozzle assembly (12) comprising a nozzle body (14) as claimed in any

5 one of the preceding claims and a needle valve member (20) arranged in a sliding fit in the bore (18) provided in the nozzle body (14).

15. Fuel injector (10) comprising a nozzle assembly (12) as claimed in claim