EP2150695A2

EP2150695A2 - Fluid injection device

Info

Publication number: EP2150695A2
Application number: EP08805893A
Authority: EP
Inventors: André AGNERAY; Nadim Malek; Marc Pariente; Laurent Levin
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2007-05-31
Filing date: 2008-05-29
Publication date: 2010-02-10
Also published as: CN101765712B; RU2457354C2; KR20100029224A; US20110023827A1; FR2916810B1; CN101765712A; FR2916810A1; WO2008152314A2; RU2009149203A; US8746213B2; WO2008152314A3; JP2010528224A

Abstract

The invention relates to an injector comprising a nozzle that includes an opening and a seat, a needle movably mounted in the nozzle and having an end defining a valve in a contact area with the seat, a means for vibrating the valve, a first acoustic-impedance breaking area at a first distance from the valve along the nozzle, and another first acoustic-impedance breaking area at a second distance from the valve along the needle. According to the invention, each of the first and second distances is such that the respective propagation time of acoustic waves along said distance is: Ti = ni *[?/2], where r\\ is a positive integer coefficient different from zero with i = 3 for the first distance and i = 4 for the second distance, ? being a period of the vibrations.

Description

Fluid injection device

The invention relates to a device for injecting a fluid, for example a fuel, in particular for an internal combustion engine.

More specifically, the invention relates, according to a first aspect, to a fluid injection device comprising:

a nozzle having a length along an axis and having an injection orifice and a seat, the nozzle being, opposite said axis, connected to a first body,

a needle having, along said axis, a length and a first end defining a valve, in a zone of contact with the seat, the needle being, opposite this axis, connected to a second body mounted axially movable in the first body,

vibrating means for vibrating with a setpoint period τ the first end and / or the nozzle, thus ensuring between them, along said axis, a relative movement capable of alternately opening and closing the valve, the nozzle with the first body and the needle with the second body respectively forming a first and second acoustic wave propagation medium, each medium having a linear acoustic impedance I defined by the following equation: I = Σ ^* ρ ^* c , where Σ is a surface of a section of the middle perpendicular to the axis, p is a mass density of the medium, it is a speed of sound in the medium,

at least one linear acoustic impedance breaking zone, existing at a distance from the seat contact zone with the first end along the nozzle or the first body, and at least one other linear acoustic impedance breaking zone; existing at distance from the zone of contact of the first end with the seat along the needle or the second body, and

said zone and other linear acoustic impedance breaking zone being each first in order from said contact zone between the first end of the needle and the seat, in a propagation direction of the acoustic waves directed respectively towards the first and second bodies.

Such an injection device, known as an injector, makes it possible to obtain a cyclic opening with the reference period τ, at frequency, for example, ultrasound, and with controlled amplitude, of the valve of the injector, in particular, when an established regime of its operation, that is to say, during operation at a predetermined temperature outside the start and stop phases of the injector. A web formed by the fluid escaping from the nozzle at the opening of the valve, is fractionated and forms fine droplets. In an application of the injector in which it sprays fuel in a combustion chamber, the fine droplets favor a more homogeneous air / fuel mixture, which makes the engine less polluting and more economical.

According to known devices, the cyclic opening of the valve is provided by means of conventional means of vibration, for example, piezoelectric and / or magnetostrictive with corresponding excitation means. The vibrating means are arranged, for example, in an actuator converting an electrical energy, firstly, into vibrations with the setpoint period τ of the actuator, then in longitudinal reciprocating motion with the reference period τ of the needle and, therefore, its first end so excited, relative to the seat of the nozzle. To ensure a sufficient flow of the fuel when opening the valve, a resonance and substantially in phase opposition of the head of the needle and the nozzle is necessary. For this purpose, the characteristic lengths of the needle and that of the nozzle are chosen, in known manner, so that that the propagation times of acoustic waves in respective materials forming the needle and the nozzle are equal to a quarter of the vibration period τ / 4 or to odd multiples of said quarter of the period, i.e. say, at [2n + 1] * τ / 4 with an integer multiplier n, positive non-zero. A resonant structure "needle / nozzle" thus formed is generating high amplitudes of opening of the valve at low pressures, for example, equal to or less than 5 MPa, in the combustion chamber. As the fuel is injected during a compression cycle, the pressure in the combustion chamber and, therefore, back pressure at the valve increases. This back pressure can also vary depending on the operating point of the engine. With the increase of the back pressure, the intensity of the shocks of the first end of the needle on its seat, even dampened by the sheet of fuel, becomes increasingly important. The return of these shocks in the resonant structure "needle / nozzle" in quarter of a wavelength [2n + 1] * τ / 4 causes a coupling between the shock and a lifting of the first end of the needle of its seat by changing the opening width of the flap. If shocks persist, the lifting of the head becomes chaotic. The benefit of the resonances is lost. The opening of the valve becomes disordered which can make the flow of fuel difficult to control.

In this context, the present invention aims to provide a fluid injection device for at least reducing at least one of the limitations mentioned above. For this purpose, it is proposed in particular on the injection device, in accordance with the generic definition given in the preamble above, that:

the distance, called the first distance, between, on the one hand, the contact zone between the seat and the first end, and, on the other hand, the first linear acoustic impedance breaking zone along the nozzle or the first body, such as the propagation time T ₃ of the acoustic waves initiated by the means of vibrating and traversing this first distance corresponds to the following equation: T ₃ = n ₃ * [τ / 2], where n ₃ is a multiplier coefficient, nonzero positive integer, and

the distance, called the second distance, between, on the one hand, the contact zone between the first end and the seat, and, on the other hand, the first linear acoustic impedance breaking zone along the needle or of the second body, such that the propagation time T ₄ of the acoustic waves initiated by the vibrating means and traversing this second distance corresponds to the following equation: T ₄ = n ₄ * [τ / 2], where n ₄ is a multiplier coefficient, nonzero positive integer.

Thanks to this arrangement of the injector, said half-wave period, the echoes of the shocks come back with exclusively multiple times of the entire period of the needle excitation setpoint τ. The shocks produced at the nozzle seat by the backpressure waves in the combustion chamber can be likened to a condition where the stresses become very high. This situation is similar to "blocked displacement" type boundary conditions representative of the injector in half-wave period for which the displacement is zero and any stress. The shocks of the first end of the needle on the seat then propagate in the nozzle and return to phase a period later which dynamically maintains the seat of the still injector. The opening of the valve and, in particular the amplitude of this opening, will then be insensitive to the back pressure. This results in a better control of the fuel flow by the injector.

According to another aspect, the invention relates to an internal combustion engine using the fluid injection device according to the invention, that is to say, such a motor where is disposed this injection device.

The injector may have the needles, the first end is extended longitudinally opposite the second body by a so-called outgoing head, and also the needles whose first end is extended longitudinally opposite the second body by a so-called incoming head.

The so-called outgoing head needle has a flared divergent shape in a direction of the axis of the injector directed from the first body to the outside of the nozzle in the combustion chamber. Preferably, the so-called outgoing head needle has a divergent frustoconical flared shape. The outgoing head closes the seat on the outside of the nozzle facing away from the first body, in the direction of the axis of the injector.

The incoming needle needle tapers in the direction of the oriented axis of the first body outwardly of the nozzle and closes the seat on the inner side of the nozzle facing the first body. The head being narrowed, its surface is less exposed to counterpressure waves. Similarly, its mass is lightened which minimizes an amplitude of the stresses on the seat at the moment of impact. The assembly of the injector is facilitated because the incoming needle can first be mounted on the second body having the actuator and then inserted into the first body. The needle to the incoming head tends to land on the seat under the effect of gravity. The injector therefore works in positive security. In the event of a defect of the return means of the second body, or even in their absence, the valve remains in closed position thus ensuring the sealing of the outgoing head injector. In addition, an accidental breakage of the needle causes its broken portion remains in the body of the injector without risk of falling into a cylinder of the engine.

Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended drawings, in which: FIG. 1 is a diagram of an injection device according to the invention arranged in a motor and equipped with an outgoing head needle connected to a second body comprising a second actuator,

FIG. 2 is a diagram of an injection device according to the invention arranged in a motor and equipped with an incoming head needle connected to the second body comprising the second actuator,

FIG. 3 is a diagram of an injection device according to the invention arranged in a motor, equipped with an outgoing head needle and a first body comprising a first actuator,

FIG. 4 is a diagram of an injection device according to the invention arranged in a motor, equipped with an incoming needle and the first body including the first actuator,

Figures 5 and 6 show diagrams illustrating an operation of the valve formed by a nozzle and an outgoing needle: closed valve (Figure 5); open flap (figure 6),

Figures 7 and 8 show diagrams illustrating an operation of the valve formed by a nozzle and an incoming needle: valve closed (Figure 7); open flap (figure 8),

Figures 9 and 10 respectively show schematically in simplified side view in partial longitudinal section: a one-piece needle in the form of a cylindrical bar (Figure 9); a compound needle comprising three segments (Figure 10),

Figures 11 and 12 respectively show schematically in simplified side view in partial longitudinal section: a cylindrical one-piece nozzle (Figure 11); a composite nozzle comprising three segments (FIG. 12),

Figures 13-16 show various assembly diagrams for the outgoing needle, Figures 17-20 show various assembly diagrams for the incoming needle,

FIGS. 21-24 show various assembly diagrams between a needle and the second actuator,

Figures 25-26 schematically show in side view variants of the outgoing needle,

Fig. 27 schematically shows a side view of a variant of the incoming needle.

An injection device, or injector, of FIGS. 1, 3 (or 2, 4) is intended to inject a fluid, for example a fuel C into a combustion chamber 15 of an internal combustion engine M or into a air intake duct, not shown.

The injector comprises two bodies, for example, cylindrical. A first body 1 representing a housing is extended, along a preferred axis AB of the injection device, for example, its axis of symmetry, by at least one nozzle 3 having a length along the axis AB and having an orifice of injection and a seat 5 (or 5 '). The linear dimensions of the first body 1, for example, its width measured perpendicular to the axis AB and / or its length measured along the axis AB, may be greater than those of the nozzle 3. The density of the first body 1 can be greater than that of the nozzle 3. The first body 1 can be connected to at least one fuel circuit 130 C via at least one opening 9. The fuel circuit 130 C comprises a treatment device 13 of the fuel C comprising, for example, a tank, a pump, a filter.

A second body 200 is mounted axially movable in the first body 1. A needle 4 has, along the axis AB, a length and a first end 6 defining a valve in a contact zone with the seat 5 (or 5 ') of the nozzle 3. The linear dimensions, of the second body 200, for example, its width measured perpendicularly to the axis AB and / or its length measured along the axis AB, may be greater than that of the needle 4. The density of the second body 200 may be greater than that of the needle 4. The needle 4 and the second body 200 are interconnected by a junction zone ZJ (Figure 3). The first end 6 is preferably extended along the axis AB by a head 7 (or T) closing the seat 5 (or 5 ') so as to ensure a better seal valve of the injector. Returning means 11 (or 11 ') of the second body 200 may be provided to hold the head 7 (or T) of the needle 4 in abutment with the seat 5 (or 5') of the nozzle 3. return means 11 (or 11 ') ensure the closure of the valve regardless of the pressure in the combustion chamber 15. The location of the point of application of the restoring forces on the second body 200 is indifferent. The return means 11 (or 11 ') may be represented by a prestressed spiral spring disposed along the axis AB downstream of the second body 200 (FIGS. 1, 3) or upstream of the second body 200 (FIGS. 2, 4). relative to the direction of flow of the fuel C towards the nozzle 3. The return means 11 (or 11 ') may also be formed by a fluidic means, for example of the hydraulic cylinder type, with the fuel C as working fluid . The clearances due to the expansions of the various elements of the first body 1 are thus advantageously caught by the return means 11 (or 11 ') so that the flow of the fuel C tends to remain insensitive to thermal variations during the various operating speeds of the engine Mr.

In addition, the injector comprises vibrating means for vibrating with a setpoint period τ the first end 6 and / or the nozzle 3, thereby ensuring relative movement along said axis (AB). suitable for alternately opening and closing the valve, as illustrated in Figures 5-6 and 7-8. The vibrations take place with a predetermined frequency v, for example, an ultrasound frequency ranging from approximately v = 20 kHz to approximately v = 60 kHz, that is to say, with the reference period τ comprising vibrations between 50 microseconds and 16 microseconds respectively. For example, a wavelength λ of vibration is about 10 ^{~ 1} m at v = 50 kHz (τ = 20 microseconds).

According to the embodiment shown in FIG. 3 (or 4), the first body 1 comprises an actuator, called the first actuator 20, forming part of the vibrating means, and adapted with the first body 1 and the nozzle 3 , to transmit the vibrations to the seat 5 (or

5 ') of this nozzle 3. In this embodiment, the vibrating means comprise an electroactive core 141, said first electroactive core, arranged to act on the first actuator 20 and excitation means (not shown) of the first electroactive core

141 adapted to make it vibrate with the set period τ.

According to the embodiment shown in FIG. 1 (or 2), the second body 200 comprises an actuator, called said second actuator 2, forming part of the vibrating means, and extended, along the axis AB, by the needle 4, and adapted, with the second body 200 and the needle 4, to transmit the vibrations to the first end 6 of the needle 4. In this embodiment, the vibrating means comprise an electroactive core 141, said second electroactive core, arranged to act on the second actuator 2 and excitation means (not shown) of the second electroactive core 141 adapted to vibrate with the reference period τ.

According to another non-illustrated embodiment which represents a combination of two previous modes, the injector may comprise both the first and second adapted actuators, with, respectively, on the one hand, the first body 1 and the nozzle 3, and, secondly, the second body 200 and the needle 4, to transmit the vibrations both to the seat 5 (or 5 ') of the nozzle 3 and to the first end 6 of the needle 4, respectively.

Preferably, the first and / or second electroactive cores 141 may be made using a material piezoelectric. The selective deformations of the latter, for example, the periodic deformations with the reference period τ, generating the acoustic waves in the injector ultimately result in the relative movement of the head 7 (or T) relative to the seat 5 (or 5 ') or vice versa, able to open and close alternately the valve, as mentioned above in connection with Figures 5-6 and 7-8. These selective deformations are controlled by the corresponding excitation means, for example, by means of an electric field created by a potential difference applied to electrodes integral with the piezoelectric material. Alternatively, the first and / or second electroactive cores 141 can be made using a magnetostrictive material. The selective deformations of the latter are controlled by the corresponding excitation means, for example, by means of a magnetic induction resulting from a selective magnetic field obtained using, for example, a not shown exciter. , and in particular by a coil integral with the second body 200.

It follows from the above developments that the nozzle 3 with the first body 1 and the needle 4 with the second body 200 respectively form a first and a second acoustic wave propagation medium. The acoustic properties of each of these two media along the axis AB can be represented by means of an acoustic impedance I which depends, for example, for each section of the medium perpendicular to the axis AB, of a geometry of the medium and, in particular, of a surface Σ of the middle section perpendicular to the axis AB, of a density p of the medium and of a c speed of sound in the medium: I = f (Σ , p, c). To illustrate this report, consider various simplified examples relating to the needle 4 or the nozzle 3 and illustrated respectively in FIGS. 9-10 and 11-12. For the sake of simplification, it is understood that for all these examples, the injector is provided with a single second actuator 2 coincides with the second body 200. To obtain an opening of the valve of the injector that is not very sensitive to pressure in the combustion chamber 15, the pilot injector moving the first end 6 of the needle 4, while the seat (shown in a simplified manner in FIGS. 9-12 and referenced 50) of the nozzle 3 is kept dynamically stationary or stationary, thus behaving like a vibration node.

The needle 4 and the nozzle 3 are each a body whose radial dimensions perpendicular to the axis AB are small relative to its length along the axis AB. In a solid bar 400 cited here as a simplified model of the needle 4 (Figure 9) or in a pierced bar 300 longitudinally cited here as a simplified model of the nozzle 3 (Figure 11), the propagation of acoustic waves combines the propagation a stress jump Δσ and a speed jump Δv using an equation: Δσ = Σ ^* z ^* Δv, where Σ is a surface of a section of the bar perpendicular to its preferred axis, for example, its axis of symmetry, z is an acoustic impedance defined by an equation: z = ρ ^* c where p is a density of the bar and c is a speed of sound in the bar. It is understood that the stress σ is positive for a compression and the velocity v is positive in the direction of propagation of the incident acoustic waves, that is to say, the acoustic waves initiated by the actuator 2 and oriented towards the first end 6 of the needle 4. The product I = Σ ^* z = Σ ^* ρ ^* c representative of the acoustic properties of the bar - solid or hollow - is called in the following "linear acoustic impedance" or "linear impedance".

Any variation in linear acoustic impedance I induces an echo, i.e., a weakening of the acoustic wave propagating in a direction of the bar (for example, from right to left in FIGS. 9, 11) by another acoustic wave propagating in the opposite direction of the bar (for example, from left to right in FIGS. 9, 11) from a linear impedance variation point I, for example, at a junction between the needle 4 and the actuator 2 (Figure 9) or at another junction between the nozzle 3 and the first body 1 (Figure 11). This same reasoning is applicable to any linear impedance break I, the term "break" to be understood as a linear impedance variation I exceeding a predetermined threshold representative of a difference between the linear impedance upstream and that downstream, with respect to the propagation direction of the acoustic waves, of a predetermined zone, called the rupture zone of linear impedance, located in a propagation medium of the acoustic waves and separating this medium into at least two portions with different acoustic properties ".

The injector comprises at least one linear acoustic impedance breaking zone, existing at a distance from the contact zone of the seat 50 with the first end 6 of the needle 4 along the nozzle 3 (FIG. 11) or the first body 1, and at least one other linear acoustic impedance breaking zone existing at a distance from the contact zone of the first end 6 with the seat 50 along the needle 4 (FIG. 9) or the second body 200. Said zone and other linear acoustic impedance breaking zone being each first in order from said contact zone between the first end 6 of the needle 4 and the seat 50, in a direction of acoustic wave propagation directed respectively to the first and second bodies 200.

As schematically illustrated in Figures 1 and 3 (or 2 and

4), the distance, called the first distance L ₃ , between, on the one hand, the contact zone between the seat 5 (or 5 ') and the first end 6, and, on the other hand, the first rupture zone linear acoustic impedance along the nozzle 3 or the first body 1, is such that the propagation time, called "acoustic flight time" T ₃ , acoustic waves initiated by the vibrating means 2 and running through this first distance L ₃ = f ₃ (T ₃ ) corresponds to the following equation:

T ₃ = n ₃ * [τ / 2], (E 1)

where n ₃ is a multiplier coefficient, nonzero positive integer, said first multiplier coefficient, and the distance, said second distance L ₄ , between, on the one hand, the contact zone between the first end 6 and the first seat 5 (or 5 '), and, secondly, the first linear acoustic impedance break zone along the needle 4 or the second body 200, is such that the propagation time, called acoustic flight »T ₄ , acoustic waves initiated by the vibrating means 2 and traversing this second distance L ₄ = f ₄ (T ₄ ) corresponds to the following equation:

T ₄ = n ₄ ^* [τ / 2], (E 2)

where n ₄ is another multiplier coefficient, nonzero positive integer, said second multiplier coefficient, for example, n ₄ ≠ n ₃ .

It should be understood that the equations referenced E1 and E2 above must be considered as verified to a certain tolerance to take account of manufacturing constraints, for example, to a tolerance of about plus or minus 10% of the period setpoint τ, that is to say, of the order of plus or minus 20% of the half-period τ / 2. Taking into account this tolerance, the equations referenced E1 and E2 above can respectively be rewritten as follows:

T ₃ = n ₃ ^* [τ / 2] ^* (1 ± 0.2) (AND)

T ₄ = n ₄ ^* [τ / 2] ^* (1 ± 0.2) (E 2 ')

It should be noted that in practice, the first distance L ₃ = f ₃ (T ₃ ) expressed in acoustic flight time T ₃ and the second distance L ₄ = f ₄ (T ₄ ) expressed in acoustic flight time T ₄ , measured on corresponding parts manufactured on an industrial scale, may show slight variations from the reference values calculated using equations E1 and E2 above. These slight variations may be due to an effect of reported masses. The latter may correspond, for example, to the head 7 (or T) of the needle 4 and / or to a guiding boss (not shown) in a plane perpendicular to the axis AB of the end 6 of the needle 4 in the nozzle 3. Said tolerance makes it possible to take into account said mass effect reported to correct the acoustic flight time expressions of the first and second distances using equations EV and E2 'above respectively as follows:

L ₃ = f ₃ (T ₃ ) = f ₃ (n ₃ * [τ / 2] * (1 ± 0.2))

l_ ₄ = f ₄ (T ₄ ) = f ₄ (n ₄ * [τ / 2] * (1 ± 0.2))

Preferably, n ₃ = n4 for the first and second multiplying coefficients with, in particular, n ₃ = n ₄ = 1 in order to minimize the linear dimensions of the injector along the axis AB to allow maximum space for intake and / or exhaust ducts. Thus, starting from the zone of contact between the seat 5 (or 5 ') and the first end 6 of the needle 4, the nozzle 3 has constant acoustic properties on successions of length representative of the first distance L ₃ = fs (T ₃ ) substantially equal to each other in acoustic flight time and whose expression in acoustic flight time T ₃ is summarized, preferably, to a single half-period τ / 2 setpoint. Similarly, starting from the contact zone between the seat 5 (or 5 ') and the first end 6 of the needle 4, the latter has constant acoustic properties on successions of length representative of the second distance L ₄ = f ₄ (T ₄ ) substantially equal to each other in acoustic flight time and whose expression in acoustic flight time T ₄ is summarized, preferably, to a single half-period of reference τ / 2.

To facilitate its assembly, over at least 90% of the first distance L ₃ = f ₃ (T ₃ ), the injector may have a linear acoustic impedance variation of less than or equal to 5% without this variation being considered as a linear acoustic impedance break. Likewise, over at least 90% of the second distance L ₄ = f ₄ (T ₄ ), the injector may have another linear acoustic impedance variation of less than or equal to 5% without this variation being considered as a linear acoustic impedance break. During an established regime of its operation, that is to say, during operation at a predetermined temperature outside the start and stop phases of the injector, it advantageously allows alternately to open and close the valve in a way that is not very sensitive to the pressure in the combustion chamber 15. In the example illustrated in FIG. 1, representing the case with a single second actuator 2 linked to the needle 4, it is a matter of both driving the extended first end 6 of the head 7 of the needle 4 in motion and keeping the seat 5 of the nozzle 3 dynamically stationary. As mentioned above, the control in displacement of the head 7 of the needle 4 s operates by means of the selective deformations, for example, periodic with the setpoint period τ, of the second electroactive core 141 transmitted to the needle 4 via the second actuator 2. The maintenance of the dynamically immobile seat 5 is obtained thanks to maintaining its longitudinal velocity along the axis AB equal to zero, taking advantage of the periodicity of the phenomenon of the propagation of acoustic waves. Each closure of the valve during periodic landings with the set period τ of the head 7 of the needle 4 on the seat 5, produces a shock. The latter generates an acoustic wave, called incident wave, associating a jump of speed Δv and a stress jump Δσ. This wave propagates in the nozzle 3 towards the first body 1 by traversing the first distance L ₃ , then is reflected in the first linear acoustic impedance breaking zone which is merged in FIG. 1 with a recess of the nozzle 3 in the housing 1 of section, in a plane perpendicular to the axis AB, much larger than that of the nozzle 3. Once the incident wave reflected, its echo, said reflected wave, returns to the nozzle 3 to traverse the first distance L ₃ in the opposite direction, that is to say, from the first body 1 to the seat 5. The reflected wave has the same sign of the stress jump Δσ as the incident wave and the inverse sign of speed jump Δv as the incident wave. Given that the first distance is conditioned preferably by the equation: L ₃ = f ₃ (T ₃ ) = f ₃ (n ₃ * [τ / 2]), the reflected wave arrives on the seat 5 exactly at the same moment that a new incident wave is produced by the shock due to the closure of the valve, the displacement of the head 4 of the needle 4 being conditioned, too, by the second distance L ₄ preferably dependent on a multiple of the half-period of reference τ / 2: L ₄ = f ₄ (T ₄ ) = f ₄ (n ₄ ^* [τ / 2]). As a result, in the seat 5, the stresses are maintained and the speeds are canceled. The seat 5 thus has a vibration node. Under these conditions, a variation of the pressure in the combustion chamber 15 will induce an amplification of the shocks but without modifying their synchronism. The operation of the injector will therefore not be affected by this pressure variation in the combustion chamber 15.

To obtain the identity of the stress jumps Δσ when the two corresponding waves, incident and reflected, intersect, it is necessary that the reflection of the acoustic waves at the first zone of impedance breaking is the greatest possible, indeed, preferably, total. This condition of total reflection is a priori satisfied for the nozzle 3 embedded in the housing 1 linked in turn with a cylinder head 8, this configuration can be likened to an ideal case of a finished diameter rod embedded in an infinite body. Given the finite size of the actuator 2, the total reflection of the acoustic waves in the junction zone ZJ between the needle 4 and the actuator 2 (or the second body 200) is difficult to obtain. Assume that in the junction zone ZJ the second body 200 has a linear acoustic impedance U _C - _ZJ and the needle 4 has a linear acoustic impedance U- _ZJ (FIG. 3). A satisfactory compromise in terms of near-total reflection of the acoustic waves in the junction zone ZJ can be obtained if the ratio IAC-ZJ / IA-ZJ is greater than a predetermined value. Preferably, the following relationship is verified: UC-ZJ / IA-ZJ ≥ 2.5.

In the light of the precisions above, it should be understood that, in the general case for the first and second multiplying coefficients such that n ₃ ≠ n ₄ , it is the incident waves and the reflected waves shifted by a few periods τ offset each other mutually in the seat 5 to make it dynamically fixed. This compensation may not be complete when, for example, the difference between n ₃ and n ₄ is greater than a predetermined value and / or a dissipation of the acoustic waves in the nozzle 3 (and, ultimately, its linear acoustic impedance) , exceeds a certain threshold. Therefore, the configuration of the injector with n ₃ = n ₄ and, in particular n ₃ = n ₄ = 1, appears as a priori more acoustically reliable and remains to be preferred over that where n ₃ ≠ n ₄ .

It should be understood that the first L ₃ = f (T ₃ ) and the second L ₄ = f (T ₄ ) distances respectively related to the first "nozzle 3 + first body 1" and the second "needle 4 + second body 200 »acoustic wave propagation media are defined, preferably by means of the respective acoustic flight times T ₃ = n ₃ ^* [τ / 2] and T ₄ = n ₄ ^* [τ / 2], in a context acoustic. The latter is due to the presence of the (ultra) sound vibrations of the setpoint period τ, initiated by the electroactive core 141 of the actuator 2, as mentioned above. In other words, the first L ₃ = f (T ₃ ) and the second L ₄ = f (T ₄ ) distances are between two acoustic limits. In general, a first acoustic limit for defining both the first L ₃ and the second L ₄ distances is represented by an end of a set in question ("nozzle 3 + first body 1" or "needle 4 + second body 200 "). In simplified manner, it can be considered that this first acoustic limit merges with the contact zone between the first end 6 of the needle 4 (possibly extended axially by the head 7) and the seat 5 of the nozzle 3, as illustrated in FIG. Figures 1 and 2. The second acoustic limit specific to each of the two sets is represented by the respective first linear acoustic impedance breaking zone I, as detailed above. For example, the second acoustic limit may correspond to where the diameter of the assembly in question varies in a plane perpendicular to the axis AB, for example, at the junction zone ZJ of the needle 4 with the actuator 2 or the place embedding the nozzle 3 in the casing 1 (FIG. 1, 2), it being understood that, in the junction zone ZJ, the needle 4 and the actuator 2 are produced, for example, by machining in a part one-piece material preferably having the same density and the same speed of sound, and that, in the installation location, the nozzle 3 and the housing 1 are made, for example, by machining in a monoblock piece of material preferably having the same density and the same speed of sound. Indeed, the machining in a single piece provides a simplest solution to implement during a manufacturing of said parts on an industrial scale.

However, in some cases, the acoustic limits of the bodies may not correspond to the physical limits of the bodies, as shown by two examples below. As illustrated in FIG. 12, within the first acoustic wave propagation medium, on said first distance L ₃ , there are a plurality of segments 301, 302, 303 differentiating themselves from each other by at least two criteria among the three following criteria specific to each of the segments 301, 302, 303: (a) geometry of the segment; (b) p-density of the segment; (c) velocity c of the sound in the segment, the segments 301, 302, 303 being such that their respective linear acoustic impedances - I301 = Σ3oi * p3oi * C3oi; I302 = Σ302 * p302 * C302; I303 = Σ303 * p303 * C303 - are equal to: I301 = I302 = 1303- Thus, regardless of their respective linear dimensions, no parasitic echo occurs in junction areas between two respective segments: 301/302, 302/303 , so that the first distance L ₃ remains between the seat 50 and the embedding location ST of the nozzle 3 in the first body 1 (Figure 12). Thus it is possible to make the nozzle 3 of different materials, combining them so as to provide the nozzle 3 locally and / or axially selective physical properties (other than acoustic ones), specific to each of the segments 301, 302, 303 ( for example, improving their impact resistance, reducing their mechanical wear and / or thermal expansion, etc.), provided that their acoustic properties along the AB axis represented by the respective linear acoustic impedances I301, I302, I303 remain the same: I301 = I302 = 1303- As illustrated in FIG. 10, within the second acoustic wave propagation medium, on said second distance L ₄ , there exists a plurality of segments 401, 402, 403 differing from each other by at least two of the following three criteria specific to each of the segments 401, 402, 403: (a) geometry of the segment; (b) p-density of the segment; (c) velocity c of the sound in the segment, the segments 401, 402, 403 being such that their respective linear acoustic impedances - I401 = Σ ₄ oi * p4oi * c ₄ oi; I402 = Σ _{April 02} * P402 * _c4 02; I403 = Σ403 * p403 * C403 - are equal: Uoi = I402 = Uo3- Thus, whatever their respective linear dimensions, no parasitic echo occurs in junction zones between two respective segments: 401/402, 402/403 , so that the second distance L ₄ remains between the seat 50 and the junction zone ZJ of the needle 4 in the actuator 2 (Figure 10). Thus, it is possible to make the needle 4 of different materials, combining them so as to provide the needle 4 locally and / or axially selective physical properties (other than those acoustic) specific to each of the segments 401, 402, 403 (for example, by improving their impact resistance, reducing their mechanical wear and / or thermal expansion, etc.), provided that their acoustic properties along the AB axis represented by the respective linear acoustic impedances Uoi, I402, I403, remain the same: Uoi = I402 = Uo3-

In another embodiment illustrated in Figures 1 and 3

(or 2 and 4), the junction zone ZJ between the needle 4 and the second body 200 is formed on the second body side 200 by at least one section of the second actuator 2, the section having a circular section of a predetermined diameter, said diameter D of the second actuator 2, measured in a plane perpendicular to the axis AB. The junction zone ZJ between the needle 4 and the second body 200 is formed on the needle side 4 by at least one cylindrical section of revolution of a predetermined diameter, called the diameter d of the needle 4, measured in a plane perpendicular to the axis AB. Preferably, the section of the actuator 2 and that of the needle 4 are made of material having a density p and a speed c sound identical. The diameter D of the actuator 2 and the diameter d of the needle 4 are connected by the following equation: D / d> y [Z5. Advantageously, this ratio of diameters D / d corresponds to an acceptable "acoustic embedding" of the needle 4 in the actuator 2 (FIGS. 1, 2). Thanks to this acceptable acoustic embedding, an incident wave leaving the head 7 (or T) of the needle 4 and arriving along the needle 4 in the junction zone ZJ is reflected almost completely, that is, that is, without significant losses of amplitude and / or frequency that can disturb the opening and closing of the valve with the setpoint period of τ (and, therefore, the displacement control of the head 7 (or T) of the needle 4 mentioned above).

In some cases, to assemble the injector, it is essential to introduce the needle 4 separately from the second actuator 2 (and / or the needle 4 separately from the head 7 (or T) of the needle 4) in the first body 1. The manufacture in one piece or monobloc of the second actuator 2 with the needle 4 and / or the needle 4 with its head 7 (or T) is then unsuitable. To assemble the injector in this case, the second actuator 2 and the needle 4, on the one hand, and / or the needle 4 and the head 7 (or T) of the needle 4, on the other hand, can be secured together with a connection type "male / female" for assembling said two parts. This connection can be obtained, for example, on the one hand, by a dowel, preferably central, that is to say, aligned on the axis AB, and forming a screw, preferably a threaded screw, and, on the other hand, by a bore, preferably, central, that is to say, aligned on the axis AB and tapped (Figures 13-24). The stud may be secured to the needle 4 (see stud 41, said first stud 41, in Figures 13, 17, 23-24 or stud 61 in Figure 16), or the second actuator 2, or the head 7 (or T): see stud 71, said second stud 71, in FIGS. 15, 19. The term "integral studs" - of the needle 4, of the second actuator 2, of the head 7 (or T) - as illustrated by the references 41, 61, 71 in FIGS. 13, 17, 23-24, 16, 15, 19, must be understood in the broad sense, that is to say, also describe a "male" portion of said "male / female" connection, including the "male" portion being an end, preferably threaded, obtained, for example by machining needle 4 or the second actuator 2, or the head 7 (or T), and used to assemble the needle 4 with the second actuator 2 or the needle 4 with its head 7 (or T). The stud may also be an independent piece (see pin 42 independent of the needle 4 and the second actuator 2 in Figures 14, 18, 21-22). The assembly of the actuator 2 with the needle 4 and / or the needle 4 with its head 7 (or T) requires a good acoustic coupling between them. This means a homogeneous distribution of the stresses on the contact surface between the second actuator 2 and the needle 4 and / or the needle 4 and its head 7 (or T). For this, bearing surfaces facing respectively the second actuator 2 against the needle 4 (see the bearing surfaces 201 and 202 in Figures 21, 22, 24) and / or the needle 4 against his head 7 (or T) may have predetermined flatness and / or roughness, for example less than 1 μm. The facing bearing surfaces are preferably perpendicular to the axis AB (FIGS. 21-24). Preferably, the threaded stud comprises at least one non-threaded portion. In an example relating to the second actuator 2 and the needle 4 (FIG. 23) with the stud 41 secured to the needle 4, the unthreaded portion 180 is disposed downstream of the thread 18 with respect to the direction of the axis AB . The unthreaded portion 180 allows a possibility of a slight rotation of the needle 4 about the axis AB so as to position the needle 4 on the second actuator 2 by controlling, during their assembly, a force of tightening between their respective abutment surfaces opposite 201, 202. In addition, the presence of the unthreaded portion 180 facilitates a clearance of a machining tool during the manufacture of the needle 4 to facilitate the realization of the bearing surface 202 with the predetermined flatness and / or roughness. In another example not illustrated in the figures and relating to the stud in independent piece, its unthreaded portion can be arranged at a distance predetermined ends of the stud, for example, in the middle of the stud. The needle 4 of diameter d may have at least one reinforced portion 43, for example cylindrical of revolution, with a diameter D1 such that D1> d. The reinforced portion 43 could be immediately adjacent to the second actuator 2 of diameter D with, preferably, D1 <D (FIGS. 20-22). Preferably, the reinforced portion 43 is such that a linear acoustic impedance variation I between this reinforced portion 43 and a remaining portion of the needle 4 is less than or equal to 5% without this variation being considered as a break linear acoustic impedance. With this reinforced portion 43, the risk of breakage of the needle 4 in an immediate vicinity of the "male" portion (threaded screw 41, 18) induced by the connection to the stud 41 as illustrated in Figures 23-24 or the "female" portion (nut 17, 16) induced by the connection to the stud 42 as illustrated in Figs. 21-22, are minimized. Preferably, the dowel and / or the corresponding bore is at least locally covered with a lubricating means 181 (Figure 24), for example, at the thread 18 (see exploded view in Figure 23). The respective facing surfaces of the second actuator 2 against the needle 4 and / or the needle 4 against its head can in turn be fertilized covered by the lubricating means. At first sight, the effect of presence of the lubricant means would contribute to a separation of the second actuator 2 of the needle 4 and / or the head of the needle 4. However, the presence of the lubricant means ensures, in fact here, a better structural continuity of the second actuator 2 to the needle 4 and / or the head to the needle 4 by filling any intermediate space (for example, between two thread grooves) which improves a transmission of acoustic waves. Thanks to the lubricant means, the intimacy between the respective facing surfaces of the second actuator 2 against the needle 4 and / or the needle 4 against its head is increased. This makes it possible to avoid local variations in stresses due to the passage of acoustic waves. In addition to its filling function, the lubricant means can also play a role of a bonding means which further solidifies the second actuator 2 with the needle 4 and / or the head with the needle 4. This transformation of the lubricant means into "glue" is due, for example, to a physico-chemical change of the lubricant means under the effect of the temperature in the combustion chamber 15.

In another embodiment, the first stud 41, the bearing surface 201 of the second actuator 2 against the needle 4 and the respective bearing surface 202 of the needle 4 against the second actuator 2, are covered with glue . Preferably, the second stud 71, a bearing surface of the first end 6 against the head 7 of the needle 4 and a respective bearing surface of the head 7 of the needle 4 against the first end 6, are covered with glue.

In another embodiment, the actuator 2 and the needle 4, on the one hand, and / or the needle 4 and its head 7, on the other hand, are acoustically joined together by gluing, preferably without stud, no drilling.

In a preferred embodiment of the injection device, the so-called outgoing head 7 of the needle 4 is flared in the direction of the axis AB oriented towards the outside of the nozzle 3 in a plane perpendicular to the axis AB (FIGS. 1 and 3) and closes the seat 5 on the outside of the nozzle 3 facing away from the second actuator 2. The head 7 may be of divergent shape towards the outside of the nozzle 3 in the direction of the axis AB . By way of illustration, FIGS. 1, 3, 5-6, 13-16 show the diverging head 7 of frustoconical shape. Other divergent shapes of the head 7 may be envisaged, for example, a shape of the head not shown in the figures whose diameter perpendicular to the axis AB increases exponentially along the axis AB to the seat 5. From preferably, at least one side wall 74 (frustoconical in the example in FIG. 13) of the head 7 forms with the axis AB a predetermined angle α such that α> 90 °. In the case of the diverging head 7, for example, frustoconical, the seat 5 of the nozzle 3 is preferably of respective shape diverging towards the outside of the nozzle 3 in the direction of the axis AB (FIG. 3, 5-6), for example, frustoconical, to ensure a better seal of the injector with the closed valve (figure 5). In this case, it should be understood that the first acoustic limit used to determine the first distance L ₄ in relation to the second medium "needle 4 + second body 200" of propagation of the acoustic waves, is taken at the mid-height of the diverging frustoconical head 7 (FIG. 1, 3). It is the same for the second distance L3 in relation to the first medium "nozzle 3 + first body 1" propagation of acoustic waves (Figures 1, 3). In a less preferred solution, the diverging frustoconical head 7 may be replaced by a flared head 76, for example, cylindrical in the form of a disc of diameter D2 greater than that of the needle 4 and perpendicular to the preferred axis AB (Figure 25). Between the end 6 of the needle 4 and the cylindrical head 76 could be introduced a cylindrical portion, or divergent 77, for example frustoconical, of maximum diameter D3 as that of the outgoing head 7 described above, such that d < D3 <D2 (Figure 26).

It is recalled that the second actuator 2 is mounted axially movable relative to the housing 1 via the return means 11 (Figures 1 and 3). These are likely to deform, for example, elastically, exerting a predetermined force for a very small elongation, for example, less than 100 microns, so as to pull the head 7 of the needle 4 against the seat 5 of the nozzle 3 along the axis AB to ensure the closing of the valve regardless of the pressure in the combustion chamber 15.

In another preferred embodiment (FIGS. 2, 4, 7-8, 17-20), the so-called incoming T-head of the needle 4 narrows in the direction of the privileged axis AB oriented towards the outside of the nozzle 3 and closes the seat 5 'of the inner side of the nozzle 3 facing the second actuator 2 (or the second body 200). The head T may be of convergent shape towards the outside of the nozzle 3 in the direction of the axis AB (FIGS. 2, 4, 7-8, 17-20). By way of illustration, Figures 2, 4, 7-8, 17-20 show the convergent head T of frustoconical shape. Other convergent shapes of the head T can be envisaged, for example, a shape of the head not shown in the figures whose diameter perpendicular to the axis AB decreases exponentially along the axis AB to the seat 5 '. Preferably, at least one lateral wall 75 (frustoconical in the example in FIG. 17) of the head T forms with the axis AB a predetermined angle β such that: 0 ° <β <90 °. In the case of the convergent head, for example, frustoconical, the seat 5 'of the nozzle 3 is preferably of respective shape converging towards the outside of the nozzle 3 in the direction of the axis AB (FIG. , 4, 7-8), for example, frustoconical, to ensure a better seal of the injector with the closed valve (Figure 7). In this case, it should be understood that the first acoustic limit used to determine the first distance L ₄ in relation to the second medium "needle 4 + second body 200" of propagation of the acoustic waves, is taken at the mid-height of the Convergent frustoconical head T (Figures 2, 4). It is the same for the second distance L ₃ in relation to the first medium "nozzle 3 + first body 1" propagation of acoustic waves (Figures 2, 4). In a less preferred solution, the needle 4 comprises a composite head 79 made of at least two parts. The first portion 76 is, for example, cylindrical in the form of a disk of diameter D2 greater than that of the needle 4 and perpendicular to the preferred axis AB (Figure 27). The second part 78 disposed downstream of the first part 76 in the direction of the axis AB (oriented, as before, towards the outside of the nozzle 3) is cylindrical with a diameter D3 such that: D3 <D2 with, preferably, D2 <d. Thus, the two-part composite head 79 narrows in the direction of the AB axis. The second portion 78 could have a convergent shape, for example, convergent frustoconical like that of the incoming head T described above.

It is recalled that the second actuator 2 is mounted axially movable relative to the housing 1 via the return means 11 '(Figures 2 and 4). These are likely to deform, for example, elastically, exerting a predetermined force for a very low elongation, for example, less than 100 μm, so as to push the head T of the needle 4 against the seat 5 'of the nozzle 3 along the axis AB to ensure the closure of the valve regardless of the pressure in the combustion chamber 15.

In another embodiment, at least one of the housing 1, the needle 4, the nozzle 3, the head 7 (or T) comprises at least one portion made, for example, of at least one of (a) treated steel; (b) titanium; (c) titanium alloy. These materials cited here by way of non-limiting illustration have satisfactory acoustic characteristics, expand at high temperatures in a limited way and are little exposed to mechanical wear. Preferably, the nozzle 3 and, in particular, its seat 5 (or 5 '), are made of treated steel whose mechanical strength is greater than that of titanium or its alloy. It is the same for the head 7 (or T) of the needle 4. As for the needle 4, it is preferably made of titanium or a titanium alloy, lighter than the treated steel. However, the simplicity of making a "head 7 (or T) + needle 4" assembly in one piece, for example, by simply machining the "head 7 (or T) I needle 4" assembly in a single piece, may prefer a needle 4 steel, for example, treated steel.

Claims

A fluid injection device comprising:

a nozzle (3) having a length along an axis (AB) and having an injection orifice and a seat (5), the nozzle (3) being, opposite said axis (AB), linked to a first body,

a needle (4) having, along said axis (AB), a length and a first end (6) defining a valve, in a zone of contact with the seat (5), the needle (4) being, at opposite this axis (AB), connected to a second body (200) mounted axially movable in the first body (1),

vibrating means (2) for vibrating with a setpoint period τ the first end (6) and / or the nozzle (3), thus ensuring between them, along said axis (AB), a movement relative to open and close alternately the valve, the nozzle (3) with the first body (1) and the needle (4) with the second body (200) respectively forming a first and a second wave propagation media acoustic, each medium having a linear acoustic impedance (I) defined by the following equation: I = Σ ^* ρ ^* c, where Σ is a surface of a section of the middle perpendicular to the axis (AB), p is a density of the medium, it is a speed of sound in the middle,

at least one linear acoustic impedance breaking zone, existing at a distance from the contact zone of the seat (5) with the first end (6) along the nozzle (3) or the first body (1), and at least one other linear acoustic impedance breaking zone existing at a distance from the contact zone of the first end (6) with the seat (5) along the needle (4) or the second body (200), and said zone and other linear acoustic impedance breaking zone being each first in order from said contact zone between the first end (6) of the needle (4) and the seat

(5), in a propagation direction of the acoustic waves oriented respectively to the first (1) and second (200) bodies,

characterized in that the distance, said first distance (L ₃ ), between, on the one hand, the contact zone between the seat (5) and the first end (6), and, on the other hand, the first zone linear acoustic impedance breaking along the nozzle (3) or the first body (1), is such that the propagation time (T ₃ ) of the acoustic waves initiated by the vibrating means (2) and traversing this first distance (L ₃ ) corresponds to the following equation: T ₃ = n ₃ * [τ / 2], where n ₃ is a multiplier coefficient, nonzero positive integer, and

in that the distance, called the second distance (L ₄ ), between, on the one hand, the contact zone between the first end (6) and the seat (5), and, on the other hand, the first zone of linear acoustic impedance breaking along the needle (4) or the second body (200), is such that the propagation time (T ₄ ) of the acoustic waves initiated by the vibrating means (2) and traversing this second distance (L ₄ ) corresponds to the following equation: T ₄ = n ₄ * [τ / 2], where n ₄ is a non-zero positive integer multiplier.

2. Device for injecting fluid according to claim 1, characterized in that within the first acoustic wave propagation medium, on said first distance (L ₃ ), there are a plurality of segments (301), ( 302), (303) differing from one another by at least two of the following three criteria specific to each of the segments (301), (302), (303): (a) geometry of the segment; (b) p-density of the segment; (c) velocity c of the sound in the segment, the segments (301), (302), (303) being such that their respective linear acoustic impedances (l ₃ oi), (I302), (I303) are equal: I301 =

I302 = I 303-

3. Device for injecting fluid according to claim 1 or 2, characterized in that within the second acoustic wave propagation medium, on said second distance (L ₄ ), there is a plurality of segments (401). , (402), (403) differing from each other by at least two of the following three criteria specific to each of the segments (401), (402), (403): (a) geometry of the segment; (b) p-density of the segment; (c) velocity c of the sound in the segment, the segments (401), (402), (403) being such that their respective linear acoustic impedances (Uoi), (I402), (I403) are equal: I401 = I402 = Uo3-

4. fluid injection device according to one of claims 1 to 3, characterized in that the needle (4) and the second body (200) are interconnected by a junction zone (ZJ) which transmits the acoustic waves, in that in the junction zone (ZJ) the second body (200) has a linear acoustic impedance U _C - _ZJ and the needle (4) has a linear acoustic impedance U- _ZJ , and in that the following relationship is verified:

5. Device for injecting fluid according to one of claims 1 to 4, characterized in that the first body (1) comprises an actuator, said first actuator (20) forming a part of the vibrating means, and adapted, with the first body (1) and the nozzle (3), to transmit said vibrations to the seat (5) of this nozzle (3).

6. Device for injecting fluid according to claim 5, characterized in that the vibrating means comprise an electroactive core (141) arranged to act on the first actuator (20) and means for exciting the electroactive core ( 141) adapted to make it vibrate with the set period τ.

7. Device for injecting fluid according to any one of claims 1 to 6, characterized in that the second body (200) comprises an actuator, said second actuator (2), forming part of the vibrating means, and extended, along the axis (AB), by the needle (4), and adapted, with the second body (200) and the needle (4), to transmit said vibrations to the first end (6) of this needle (4).

8. Device for injecting fluid according to claim 7, characterized in that the vibrating means comprise an electroactive core (141) arranged to act on the second actuator (2) and excitation means of the electroactive core ( 141) adapted to make it vibrate with the set period τ.

9. Injection device according to claim 7 or 8, characterized in that the junction zone (ZJ) between the needle (4) and the second body (200) is formed on the second body side (200) by the at least one section of the second actuator (2), the section having a circular section of a predetermined diameter, called the diameter (D) of the second actuator (2), measured in a plane perpendicular to the axis (AB), in the junction zone (ZJ) between the needle (4) and the second body (200) is formed on the needle side (4) by at least one cylindrical section of revolution of a predetermined diameter, called the diameter ( d) of the needle (4), measured in a plane perpendicular to the axis (AB), and in that the diameter (D) of the actuator (2) and the diameter (d) of the needle ( 4) are related by the following inequality:

10. Injection device according to one of claims 1 to 9, characterized in that the first end (6) of the needle (4) is extended along the axis AB by a head (7 ') which goes into narrowing along the axis AB towards the outside of the nozzle (3), and in that the head (7 ') closes the seat (5') on the inside of the nozzle (3) facing the second body (200) ).

11. Device for injecting fluid according to one of claims 1 to 9, characterized in that the first end (6) the needle (4) is extended along said axis AB by a head (7) which is flared along the axis AB oriented towards the outside of the nozzle (3), and in that the head (7) closes the seat (5) on the outside of the nozzle (3).

12. Device for injecting fluid according to any one of claims 7 to 11, characterized in that the second actuator (2) and the needle (4) are secured with a first stud (41). threaded.

13. Device for injecting fluid according to any one of claims 10 to 12, characterized in that the first end (6) and the head (7) of the needle (4) are secured with the aid of a second bolt (71) threaded.

14. fluid injection device according to claim 12, characterized in that the first pin (41), a bearing surface (201) of the second actuator (2) against the needle (4) and a respective surface of support (202) of the needle (4) against the second actuator (2) are covered with glue.

15. Device for injecting fluid according to claim 13, characterized in that the second stud (71), a bearing surface of the first end (6) against the head (7) of the needle (4) and a respective bearing surface of the head (7) of the needle (4) against the first end (6), are covered with adhesive.

16. Internal combustion engine (M) using the fluid injection device according to any one of claims 1 to 15.