EP3425191B1 - Anti-rotation device of an injection nozzle needle - Google Patents

Description

TECHNICAL AREA

The present invention relates to a diesel fuel injector and more particularly to a device preventing rotation of the needle / valve member in the injection nozzle body.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

A diesel fuel injector includes an injector holder, a hydraulic control valve and, an injection nozzle in which a needle / valve member is slidable in a nozzle body.

The nozzle body is provided with a bore in which the needle is guided along a main axis and extends in an elongated body from a head, on which the pressure of a control chamber acts, to a tip. defining a closure face cooperating with a seat. In addition, a spring wound around the needle and compressed between a face of the needle and a face of the nozzle body continuously urges the needle to a closed position.

In operation, the needle moves according to an injection cycle passing at a high frequency from a closed position, in which the closing face is against the seat, closing a passage to fuel towards the injection holes, to an open position in which the needle is raised, the closure face being remote from the seat opening said passage and allowing fuel injection.

A known injection nozzle is described for example in the DE 10 2015 219 441 A1 .

The opening / closing movements of the needle are accompanied by the rotation of the needle and this rotation alters the characteristics of the injector by causing the injected fuel flow to vary uncontrollably.

The object of the present invention is to provide a solution which significantly alleviates or even solves the problem mentioned above.

SUMMARY OF THE INVENTION

The present invention aims to remedy the drawbacks mentioned above by proposing a simple and economical solution and in particular, an injection nozzle of a diesel fuel injector for an internal combustion engine. Said nozzle is elongated along a main axis extending between a top end and an injection tip and comprising a body provided with a bore in which a needle forming a valve member is guided. Said needle can slide axially between a closed position in which one face of the needle is in abutment against a seat defined in the body in the vicinity of the injection tip and an open position in which the needle is moved away from said seat, the nozzle further comprising a helical spring compressed between a high bearing face defined in the body and a lower bearing face defined by a flange of the needle so as to permanently urge the needle towards the closed position.

According to the invention, the helical spring is wound around the needle from a low turn integral with the needle to a high turn integral with the nozzle body so as to prevent rotation of the needle in the body.

In addition, the top coil rests on the surface against an annular face of the body, the compression of the spring preventing said top coil from rotating relative to the body.

According to a particular embodiment, the upper coil is welded to the nozzle body so as to prevent said upper coil from rotating relative to the body.

According to a particular embodiment, the injection nozzle may further comprise a support washer inserted between the upper coil of the spring and the annular face of the body.

According to another embodiment, the top turn is inserted by force into a counterbore defined between the needle and the injector body, said top turn being clipped into said counterbore. During assembly, the spring is inserted or, in other words, nested or force-fitted into the counterboring, the very last coil of the spring having to retract to pass said notch and, when said last coil exceeds the notch, it relaxes again and gets stuck at the bottom of the counterboring.

In addition, according to the invention, the portion of the needle adjacent to said collar defines a boss, around which the bottom coil of the spring is clamped.

According to a specific embodiment, said boss is conical of so as to facilitate the installation of the spring and then to wedge said lower coil.

More particularly, the bottom turn is in surface bearing against an annular face of said flange, the compression of the spring preventing said bottom turn from rotating relative to the needle.

In addition, a support washer is inserted between the lower coil of the spring and the annular face of the collar.

According to a specific embodiment, the portion of the needle adjacent to the collar and around which the spring is wound comprises an annular groove in which the bottom coil fits and is wedged between the sides of said groove.

The invention further extends to a diesel fuel injector for an internal combustion engine, said injector comprising an injection nozzle according to the preceding paragraphs.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une section longitudinale d'une buse d'injection selon l'invention et,
• la figure 2 est un détail de la figure 1 présentant un premier mode de réalisation de l'invention et,
• les figures 3 à 6 sont des détails de la figure 2 présentant d'autres modes de réalisation de l'invention et,
• la figure 7 présente des enregistrements avant/après du débit d'injection.

Other characteristics, aims and advantages of the invention will become apparent on reading the detailed description which follows, and with reference to the appended drawings given by way of non-limiting example and in which:

• the figure 1 is a longitudinal section of an injection nozzle according to the invention and,
• the figure 2 is a detail of the figure 1 presenting a first embodiment of the invention and,
• the figures 3 to 6 are details of the figure 2 presenting other embodiments of the invention and,
• the figure 7 shows before / after recordings of injection flow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A diesel fuel injector 10 comprises an injector holder assembly, a control valve and an injection nozzle 12 coaxially attached to each other and firmly held by an injector nut.

Fuel injection is indirectly controlled by a solenoid valve which opens or closes a discharge channel allowing the hydraulic pressure to be lowered or increased in a control chamber 14 under the influence of which a valve member 16 moves between an open position PO, or injection, and a closed position PF, or no-injection.

More particularly with reference to the figure 1 , the nozzle 12 shown in axial section has a body 18 elongated along a main axis X and comprises a main member 20 and a top guide member 22, these two members 20, 22 together defining a bore 24 in which the valve member 16 , needle-shaped, is axially guided between a top guide 26 defined in the top guide member 22 and a bottom guide 28 defined towards the bottom of the main member 20.

For the sake of clarity and simplification, the top-bottom orientation of the figure is used in the description, without any limiting intention.

Said needle 16 is also permanently urged by a spring 30 compressed between a lower bearing face 32 integral with the needle and a high bearing face 34 integral with the upper guide member 22.

The needle 16 has an elongated cylindrical body extending from a head 36 guided in the top guide 26 and partly defining said control chamber 14 to a point 38 defining a closure face 40 adapted to cooperate with a face of seat 42 defined in the body 18. Between the head 36 and the point 38, but closer to the head, the needle comprises an annular flange 44 surrounding the body of the needle and extending radially therefrom so as to define the lower bearing face 32 against which the spring 30 bears, said lower bearing face 32 facing the upper guide member 22. In the closed position PF, the needle is in the lower position the shutter face 40 in sealed contact against the seat face 42 thus closing the fuel passage to the injection holes provided in the nozzle body and, in the open position PO the needle is raised, the closure face 40 being remote from the face of the seat 42 thus opening said passage.

The upper guide member 22 is a cylindrical body complementarily arranged against the main member 20 and is provided with a turret forming an axial tubular extension 46 X extending from a lower face of said cylindrical body to a distal end forming said upper bearing face 34 of the spring. As shown, said turret 46 extends into an enlarged portion of bore 24 formed within the top of main member 20 of the nozzle body itself. The bore 24 continues axially in said turret 46 defining the face of the top guide 26 against which the head of the needle slides.

In operation, the needle 16 moves at a high frequency and, to prevent rotation of the needle around the main axis X, the latter is maintained in its original angular orientation by means of the spring 30 whose ends are kept integral with the upper bearing face 32 for the upper end 48 of the spring and, with the lower bearing face 34 for the lower end 50 of the spring.

Said spring 30 is a helical spring wound from a high turn forming the upper end 48 to a lower turn forming the lower end 50, the upper coil 48 and the lower coil 50 being erected so as to define at each of said ends a transverse face.

According to a first embodiment presented in figure 2 , a first washer 52, or upper washer, is inserted between the upright face of the upper coil 48 and the upper bearing face 32 of the turret and, a second bearing washer 54, or lower washer, is inserted between the upright face of the lower coil 50 and the lower bearing face 32 of the collar. The compression of the spring associated with the annular surface of the washer makes it possible to increase the coefficient of friction and ensures the two ends of the spring are secured with on the one hand the upper guide member and on the other hand with the needle.

According to a second embodiment presented in figure 3 the upper end 48 of the spring, comprising the last upper coil, but which may also include the next neighboring coil, is inserted and wedged in a countersink 56 defined in the turret 46 and forming an annular groove around the periphery of the opening of the needle head guide bore. The top or turns 48 of the spring are inserted into said countersink 56 and wedge by friction against the outer face of the countersink while being supported against the upper bearing face 34 which is the transverse annular face forming the bottom of the countersink 56.

In a fastening alternative presented in figure 3 , the or the upper turns 48 of the spring are inserted and clipped into said counterbore 56, said outer face of the counterbore being provided with an annular bulge forming a notch reducing the section of said counterbore. During assembly, the spring is forcefully inserted into the countersink 56, the very last coil of the spring is forced to retract to pass said notch and, when said last coil exceeds the notch, it relaxes again and gets stuck at the notch. counterbore bottom.

A similar solution by wedging the lower end 50 is now presented in figures 4, 5 and 6 according to several alternatives.

The alternative of figure 4 proposes to form a slight boss 60 slightly increasing the diameter of the body of the needle at the level of the collar 44 and to wedge said lower end 50 of the spring by inserting the lower turns 50 around this slight boss 60.

The alternative of figure 5 proposes to machine the body of the needle at the level of the collar, so as to form an annular groove 58 surrounding the body of the needle, the groove of which the sides are, on the one hand, a boss slightly widening the body of the needle. the needle and, on the other hand, the collar 44 itself. In said groove 58, the lower coil 50 of the spring gets stuck around the bottom of the groove and between these opposite sides. In the alternative shown, said boss is itself machined so as to form a conical face 62 which widens as it approaches the collar and facilitates the engagement of the lower turns 50 of the spring during assembly.

The alternative of figure 6 offers, similarly to the alternative of the figure 4 , to wedge said lower end 50 and the inside of the turns 50 against a slight boss 64 formed in contact with the collar. In this alternative, said boss 64 is conical slightly and gently increasing the diameter of the needle at the level of the collar 44 so as to facilitate the installation of the spring.

Other blocking alternatives, not shown, can also be implemented, in particular, for example, a simple weld point can secure the last turn of the spring with the upper guide member or with the needle.

Furthermore, the blocking solutions presented here can be mixed in this way, any of the solutions proposed for blocking the upper end, bearing washer, counterbore, welding, can be used with any of the solutions used to clamp the 'low end, boss, annular groove ...

The figure 7 shows two records of the flow of fuel injected as a function of time. The above recording corresponds to that of an injector 10 in which the needle 16 is free to rotate. The recording below is from the same injector after the needle is prevented from rotating.

It can be seen that the locking in rotation of the needle 16 clearly stabilizes the injected flow rate, the top curve being very rough, while the bottom one is relatively flat.

REFERENCES USED

X

main axis

PO

open position

PF

closed position

10

fuel injector

12

nozzle

14

Control Chamber

16

valve member - needle

18

nozzle body

20

main body member

22

top guide member

24

bore

26

top guide

28

bottom guide

30

competence

32

lower support face of the spring

34

upper support face of the spring

36

needle head

38

needle point

40

shutter face

42

front of the seat

44

collar

46

tubular extension - turret

48

high end of the spring - high coil

50

lower end of the spring - lower coil

52

high support washer

54

low support washer
56 counterboring
58 throat
60 boss
62 tapered engagement face

64

conical jamming boss

Claims (10)

1. Injection nozzle (12) of a diesel fuel injector (10) for an internal combustion engine, said nozzle (12) being elongate along a main axis (X) between an upper end and an injection tip and comprising a body (18) provided with a bore (24) in which a needle (16), forming a valve member, is guided, said needle (16) being able to slide axially between a closed position (PF) in which one face of the needle (40) is in abutment against a seat (42) defined in the body (18) close to the injection tip, and an open position (PO) in which the needle (16) is at a distance from said seat, the nozzle (12) further comprising a coil spring (30) that is compressed between an upper bearing face (34) defined in the body and a lower bearing face (32) defined by a collar (44) of the needle so as to always urge the needle (16) towards the closed position (PF),
   characterized in that
   the coil spring (30) is wound around the needle (16) from a bottom turn (50) that is secured to the needle to a top turn (48) that is secured to the nozzle body (18), so as to prevent the needle from rotating in the body, and in which the portion of the needle that is adjacent to said collar (44) defines a boss (60, 64) around which the bottom turn (50) of the spring is tightly wrapped.
2. Injection nozzle (12) according to the preceding claim, in which the top turn (48) bears areally against an annular face (34) of the body, the compression of the spring preventing said top turn from rotating relative to the body.
3. Injection nozzle (12) according to either of the preceding claims, in which the top turn (48) is welded to the nozzle body, so as to prevent said top turn from rotating relative to the body.
4. Injection nozzle (12) according to Claim 2, further comprising a bearing washer (52) inserted between the top turn (48) of the spring and the annular face (34) of the body.
5. Injection nozzle (12) according to Claim 1, in which the top turn (48) is forced-fitted into a recess (56) defined between the needle and the injector body, said top turn being snap-fitted into said recess.
6. Injection nozzle (12) according to Claim 1, in which said boss (64) is conical so as to facilitate the installation of the spring and then to wedge said bottom turn (50).
7. Injection nozzle (12) according to any one of Claims 1 to 5, in which the bottom turn (50) bears areally against an annular face (32) of said collar, the compression of the spring preventing said bottom turn from rotating relative to the needle.
8. Injection nozzle (12) according to Claim 7, further comprising a bearing washer (54) inserted between the bottom turn of the spring and the annular face of the collar.
9. Injection nozzle (12) according to Claim 7, in which the portion of the needle which is adjacent to the collar (44) and around which the spring is wound comprises an annular channel (58) into which the bottom turn (50) is inserted and is wedged between the flanks of said channel.
10. Diesel fuel injector (10) for an internal combustion engine, said injector comprising an injection nozzle (12) according to one of the preceding claims.

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