EP1647705A1 - Injection apparatus with reduced acoustic radiations - Google Patents

Abstract

The device has units that are movable between a position for closing an orifice and a position for opening the orifice. Actuating units displace the movable units between the two positions. Damping units (30) reduce the amplitude of axial vibrations of an injection nozzle holder (10) resulting from the movements of the movable units and/or the action of the actuating units, at a predetermined frequency.

Description

The invention generally relates to a fuel injection device in a motor vehicle engine cylinder.

More specifically, the invention relates to a fuel injection device in a motor vehicle cylinder, this device comprising an injector holder of generally elongate shape in an axial direction and traversed by an axial lumen, and a rigid injection member fixed in the light, this member comprising a fuel passage orifice injected into the cylinder, a selectively movable element between a closed position of the orifice and a position of clearance of the orifice, and actuating means for moving the movable member between its shutter and release positions.

Devices of this type are known from the prior art, and emit noises due to the displacement of the movable element and / or to the action of the actuating means.

These noises are more and more marked in new motor vehicles. Indeed, automakers seek to control the amount of fuel injected, in order to reduce harmful gas emissions or reduce fuel consumption. This results in movements of the movable member of increasingly rapid and frequent, and consequently by more frequent solicitations of the actuating means.

In this context, the present invention aims to overcome the defects mentioned above and to provide a quieter injection device.

To this end, the device of the invention, moreover in conformity with the generic definition given in the preamble above, is essentially characterized in that it comprises at least first damping means for reducing the amplitude. axial vibrations of the injector holder resulting from the movements of the movable element and / or the action of the actuating means, at least a first predetermined frequency.

• Les premiers moyens d'amortissement peuvent comprendre une première masse mobile axialement et des premiers moyens élastiques liant la première masse au porte-injecteur aptes à se détendre et se comprimer axialement.
• Le porte-injecteur peut présenter au moins une portion sensiblement cylindrique, la première masse présentant la forme d'un anneau entourant ladite portion cylindrique.
• Les premiers moyens élastiques peuvent comprendre un premier organe élastique liant la première masse au porte-injecteur, cet organe étant disposé d'un premier côté axial de la première masse.
• Les premiers moyens élastiques peuvent comprendre en outre un second organe élastique liant la première masse au porte-injecteur, cet organe étant disposé d'un second côté axial de la première masse opposé au premier.
• Le premier organe élastique peut être un ressort hélicoïdal enroulé autour de la portion cylindrique, ou un ressort cylindrique enfilé autour de la portion cylindrique, ou être constitué d'une ou plusieurs rondelles élastiques, ou encore être constitué d'une pluralité de ressorts hélicoïdaux axiaux disposés à la périphérie de la portion cylindrique.
• Les premiers moyens d'amortissement peuvent comprendre un fourreau de protection cylindrique entourant la première masse et rigidement fixé sur le porte-injecteur.
• Le dispositif peut comprendre des seconds moyens d'amortissement pour réduire l'amplitude des vibrations axiales du porte-injecteur à au moins une seconde fréquence prédéterminée, les seconds moyens comprennent une seconde masse mobile axialement et des seconds moyens élastiques liant la seconde masse au porte-injecteur aptes à se détendre et se comprimer axialement.
• Le dispositif peut comprendre une bague rigidement fixée sur la portion cylindrique du porte-injecteur, les premiers moyens élastiques étant liés à cette bague et s'étendant d'un premier côté axial de celle-ci, les seconds moyens élastiques étant liés à cette bague et s'étendant d'un second côté axial de celle-ci opposé au premier côté.
• Les premiers et seconds moyens élastiques peuvent être coaxiaux à la portion cylindrique, les premiers moyens élastiques s'étendant à l'intérieur des seconds moyens élastiques.

The device of the invention may also have one or more of the following features.

• The first damping means may comprise a first axially movable mass and first elastic means connecting the first mass to the injector holder able to relax and compress axially.
• The injector holder may have at least one substantially cylindrical portion, the first mass having the shape of a ring surrounding said cylindrical portion.
• The first elastic means may comprise a first elastic member linking the first mass to the injector holder, this member being disposed on a first axial side of the first mass.
• The first resilient means may further comprise a second elastic member connecting the first mass to the injector holder, this member being disposed on a second axial side of the first mass opposite to the first.
• The first elastic member may be a helical spring wound around the cylindrical portion, or a cylindrical spring threaded around the cylindrical portion, or consist of one or more spring washers, or may consist of a plurality of axial helical springs. disposed at the periphery of the cylindrical portion.
• The first damping means may comprise a cylindrical protective sheath surrounding the first mass and rigidly fixed to the injector holder.
• The device may comprise second damping means for reducing the amplitude of the vibrations axial means of the injector holder to at least a second predetermined frequency, the second means comprise a second axially movable mass and second elastic means connecting the second mass to the injector holder able to relax and compress axially.
• The device may comprise a ring rigidly fixed to the cylindrical portion of the injector holder, the first elastic means being connected to this ring and extending from a first axial side thereof, the second elastic means being connected to this ring. and extending from a second axial side thereof opposite the first side.
• The first and second resilient means may be coaxial with the cylindrical portion, the first resilient means extending within the second resilient means.

• la figure 1 est une vue en perspective d'un dispositif d'injection selon l'art antérieur, avec un arraché pour laisser apparaître la structure interne du dispositif,
• la figure 2 est une vue de côté d'un dispositif d'injection selon l'invention, montrant l'implantation des moyens d'amortissement permettant de réduire l'amplitude des vibrations axiales du porte-injecteur,
• la figure 3 est une vue agrandie d'une partie de la figure 2, une moitié du fourreau de protection n'étant pas représentée pour laisser apparaître un premier mode de réalisation des moyens d'amortissement,
• la figure 4 est une vue similaire à celle de la figure 3, illustrant un second mode de réalisation des moyens d'amortissement,
• la figure 5 est une vue similaire à celle de la figure 3, illustrant une variante de réalisation dans laquelle le dispositif est dépourvu de fourreau,
• la figure 6 est une vue similaire à celle de la figure 4, illustrant une variante de réalisation dans laquelle le dispositif est dépourvu de fourreau,
• la figure 7 est une vue similaire à celle de la figure 5, illustrant un troisième mode de réalisation des moyens d'amortissement,
• la figure 8 est une vue similaire à celle de la figure 5, illustrant un quatrième mode de réalisation des moyens d'amortissement,
• la figure 9 est une vue similaire à celle de la figure 2, montrant l'implantation des moyens d'amortissement de la figure 8,
• la figure 10 est une vue agrandie d'une partie de la figure 9, montrant une variante d'implantation des moyens d'amortissement
• les figures 11A et 11B montrent différents types d'organes élastiques aptes à être utilisés dans les quatre modes de réalisation des moyens d'amortissement, et
• la figure 12 est un schéma simplifié illustrant le principe de fonctionnement des moyens d'amortissement.

Other characteristics and advantages of the invention will emerge clearly from the description which is given below, by way of indication and in no way limiting, with reference to the appended figures, among which:

• FIG. 1 is a perspective view of an injection device according to the prior art, with a snatch to reveal the internal structure of the device,
• FIG. 2 is a side view of an injection device according to the invention, showing the implantation of the damping means making it possible to reduce the amplitude of the axial vibrations of the injector holder,
• FIG. 3 is an enlarged view of a part of FIG. 2, one half of the protective sheath not being shown to show a first embodiment of the damping means,
• FIG. 4 is a view similar to that of FIG. 3, illustrating a second embodiment of the damping means,
• FIG. 5 is a view similar to that of FIG. 3, illustrating an alternative embodiment in which the device is devoid of a sleeve,
• FIG. 6 is a view similar to that of FIG. 4, illustrating an embodiment variant in which the device is devoid of a sleeve,
• FIG. 7 is a view similar to that of FIG. 5, illustrating a third embodiment of the damping means,
• FIG. 8 is a view similar to that of FIG. 5, illustrating a fourth embodiment of the damping means,
• FIG. 9 is a view similar to that of FIG. 2, showing the implantation of the damping means of FIG. 8,
• FIG. 10 is an enlarged view of a portion of FIG. 9, showing an alternative embodiment of the damping means.
• FIGS. 11A and 11B show different types of elastic members that can be used in the four embodiments of the damping means, and
• Figure 12 is a schematic diagram illustrating the principle of operation damping means.

The injection device shown in Figure 1 has the function of periodically injecting a predetermined amount of fuel into a cylinder of a motor vehicle engine.

This device comprises an injector holder 10 of general shape elongate in an axial direction X-X 'and traversed by an axial slot 11, and an injection member 20 rigidly fixed in the slot 11.

The injector door 10 typically has a cylindrical portion 12 of axis X-X ', and a flange 13 formed around an intermediate portion of the cylindrical portion 12 and projecting radially outwardly. Light 11 passes through the portion cylindrical 12 over its entire length and is delimited by an inner radial face of said portion.

This inner face comprises for example on the upper side a cylindrical upper section 121 of relatively larger diameter carrying an internal thread, and on the lower side a smaller cylindrical section 122 of relatively smaller diameter, these two sections being separated by a shoulder 123.

The injector holder 10 is rigidly fixed in an orifice of the motor yoke, for example by means of an external thread (not shown) provided on a part of the axial length of the cylindrical portion 12 or by a screwed flange. in the breech and resting on the collar 13.

The injection member 20 comprises, for example, an injector body 21 provided with a lower part having a shape complementary to that of the light 11 and engaged in the latter, this part carrying an external thread cooperating with the internal threading. of the upper section 121 to rigidly fix the injection member 20 to the injector holder 10.

The injector body 21 has an axially elongated shape, and includes a pressurized fuel inlet 211 formed on an upper side, a fuel passage opening 212 formed a lower end of the body, and an internal channel 213 allowing the fuel to flow from the inlet 211 to the through hole 212.

The injection member 20 further comprises an element 22 that is selectively movable between a closed position of the orifice 212 and a position for disengaging the orifice 212, and actuating means 23 for moving the movable member 22. between its shutter and release positions.

The movable element 22 generally has the shape of an axial needle, disposed in the internal channel 213, provided with an end portion engaged in the orifice 212 and a sealing portion 221 coming from closing position of the orifice 212, resting on a seat in the internal channel 213.

The injection member 20 further comprises a return spring 24 biasing the movable member 22 axially towards the lower end of the body 21, so that the closing portion 221 is biased against the seat.

In the closed position of the movable member 22, the flow of fuel from the inlet to the port 212 is interrupted.

The actuating means 23 move the movable member 22 against the return force of the spring 24 from its closed position to its release position, the fuel arriving under pressure at the inlet 211 is then projected towards the cylinder through the orifice.

The actuating means 23 can take different forms.

In the case of a diesel engine injector, these means may be for example a piezoelectric actuator consisting of a stack of thin layers of piezoelectric crystals whose dimensions vary according to the voltage applied to the crystals. This property is used to open a valve to hydraulically move the needle.

In the case of a gasoline engine injector, these means may be constituted for example by a solenoid comprising a magnetic core integral with the needle, moved axially in the center of an electromagnetic coil.

These actuators are controlled by a suitable electronic device.

The movements of the piezoelectric actuator and / or the repeated impact of the needle on its seat, as the case may be, constitutes an excitatory phenomenon creating vibrations which propagate in the injector body 21 and the injector holder 10 .

The dynamic response of the injector holder to this excitation makes it emissive of sound waves. Moreover, because the injector holder is rigidly attached to the cylinder head, the dynamic response of the injector holder may constitute an exciter phenomenon for this cylinder head, which in turn becomes emissive.

It has been demonstrated that the noise emitted by the injector holder is mainly due to an axial deformation of the latter of the traction compression type, the injector door alternately undergoing an axial compression stress and an axial extension stress. This deformation corresponds to a natural mode of vibration of the carrier of injector of natural frequency located around for example 4000 Hertz, this clean mode being strongly solicited by the excitations coming from the actuator and / or movements of needle.

According to the invention, the device comprises at least first damping means 30 for reducing the amplitude of the axial excitation of the injector holder 10 resulting from the movements of the mobile element 22 and / or the action of the means 23, at least a first predetermined frequency F1.

This first frequency F1 is chosen equal to the natural frequency of the injector holder 10 located around 4000 Hertz.

As seen in FIG. 3, the first damping means 30 comprise a first axially movable mass 31, first elastic means 32 linking the first mass 31 to the injector holder 10, these means being able to relax and compress axially and having an overall stiffness K. The first damping means further comprise a protective sheath 33 rigidly fixed on the cylindrical portion 12.

The first mass 31 has a mass M1.

The global stiffness K and the first mass M1 are chosen so as to verify the following equation: $$\left(\sqrt{\left(\mathrm{K}/\mathrm{M}1\right)}\right)/\left(\mathrm{two}\mathrm{\pi }\right)=\mathrm{F}1$$

FIG. 2 shows that these means are implanted along the cylindrical portion 12 of the injector holder 10 between the collar 13 and a lower end of the injector holder.

The first mass 31 has the shape of a cylindrical ring surrounding the cylindrical portion 12.

FIG. 3 shows that the sleeve 33 comprises a cylindrical radial wall 331 coaxial with the cylindrical portion 12 and surrounding the first mass 31, and an annular bottom 332 perpendicular to the axial direction closing the sleeve 33 from a lower side.

The upper side of the sleeve 33 is open and bears on the flange 13. The cylindrical portion 12 extends over the entire length of the sleeve and passes through the bottom 332 at its center. An O-ring 333 is rigidly fixed around the cylindrical portion 12, on a lower side of the bottom 332, the sleeve 33 being embedded axially between the O-ring 333 and the collar 13.

The first mass 31 moves in the annular space between the cylindrical portion 12 and the sleeve 33.

In a first embodiment, corresponding to FIG. 3, the first elastic means 32 comprise a first elastic member 321 linking the first mass 31 to the bottom of the sleeve 33, this member being disposed on a lower axial side of the first mass 31 .

In this case, the stiffness of this first elastic member 321 corresponds to the overall stiffness K.

The first elastic member may be of several different types.

The first elastic member 321 may be a helical spring wound around the cylindrical portion, one end of which is rigidly fixed to the first mass 31 and the other to the bottom 332.

The first elastic member 321 may also be a cylindrical spring threaded around the cylindrical portion 12 fixed by its two circular free edges opposite the first mass 31 and the bottom 332.

The first elastic member 321 may also consist of one or more spring washers 323 called Belleville, serially threaded one behind the other on the cylindrical portion 12, as shown in Figure 11A.

These washers each have a frustoconical shape delimited by a small circular base and a large circular base, each washer being preferably mounted so that its large base rests against the large base of a neighboring washer, and its small base against the small base of the other adjoining washer.

The first resilient member 321 may also be comprised of a plurality of axial coil springs 324 of small diameter relative to the diameter of the cylindrical portion 12, disposed in a circle about the cylindrical portion 12, as shown in Figure 12B.

Each small spring 324 is for example fixed on one side to a ring 324 integral with the injector holder 10 and an opposite side on the mass 31.

In a second embodiment, corresponding to FIG. 4, the first elastic means 32 comprise, in addition to the first elastic member 321, a second elastic member 322 also linking the first mass 31 to the injector holder 10.

This member is disposed on an upper axial side of the first mass 31 and links the first mass 31 to the collar 13.

In this case, the respective stiffnesses K1 and K2 of the first and second elastic members 31 and 32 are chosen so that K1 + K2 = K.

K1 and K2 can be chosen freely, for example such that K1 = (n-1) K / n and K2 = K / n.

In an alternative embodiment shown in FIGS. 5 and 6, it can be seen that the first damping means 30 may not comprise sheaths 33.

They comprise in this case a ring 34 rigidly fixed on the cylindrical portion 12 of the injector holder 10, on a lower side of the first mass 31, the first elastic member 321 linking this ring 34 to the first mass 31.

The ring 34 is fixed for example by a screw cooperating with a threaded hole formed in the injector holder 10.

In a third embodiment shown in FIG. 7, the injection device comprises, in addition to the first damping means 30, second damping means 50 for reducing the amplitude of the axial excitation of the injector holder 10. at a second predetermined frequency F2.

The second means 50 comprise a second mass 51 movable axially and second elastic means 52 linking the second mass 51 to the injector holder 10, these means being able to relax and compress axially.

The first mass 31 is provided with a first upper axial side of the ring 34, the first elastic means 32 being connected to the ring 34 and extending on the upper side thereof.

The second mass 51 is provided with a second lower axial side of the ring 34, the second elastic means 52 being connected to the ring 34 and extending on the lower side thereof.

The first and second masses and the stiffnesses of the first and second elastic means are chosen so as to allow the damping of two different eigenfrequencies.

In a fourth embodiment shown in FIG. 9, the injection device comprises, as previously, first and second damping means 30 and 50, but the first and second masses 31 and 51 are arranged on the same axial side of the ring. 34.

For this purpose, the second elastic means 52 are coaxial with the first elastic means 32, and the second elastic means 52 extend inside the first elastic means 32.

The first mass 31 debates along a portion of the injector holder 10 relatively more distant from the ring 34, and the second mass 51 debates along a portion of the injector holder 10 relatively closer to the ring 34.

Here again, the first and second masses and the stiffnesses of the first and second elastic means are chosen so as to allow the damping of two eigen modes of different frequencies.

It will be noted that in this fourth embodiment it is possible to have other masses on the lower side of the ring 34, for example third and fourth masses 61/62 linked to the ring 34 respectively by third elastic means and by means of fourth resilient means disposed within the third resilient means.

It is thus possible to dampen four eigen modes of different frequencies.

It is possible to generalize this principle and to provide on the same side of the ring 34 three or more masses distributed along the injector holder, linked to the same ring by elastic means arranged in each other.

The number of masses that can be used is however limited by implantation constraints along the tool holder (diameter and free length available) and in the environment of it.

It will further be noted that it is possible to implant the damping device or devices at all points along the injector holder. Figures 2 to 9, they have been shown on the lower part thereof, in a place where the available space is important. They can also be arranged at the top of the latter, at the level of the actuation means, as shown in FIG.

In an alternative embodiment not shown, the injection device may comprise a plurality of rings 34 distributed along the cylindrical portion 12 of the injector holder 10, one or more masses being connected by elastic means to each ring 34. It is thus multiplied the number of masses involved, and the number of eigen modes of the nozzle holder that can be amortized.

Figure 12 schematically illustrates the operating principle of the damping means.

The injector holder is likened to a mass M, mounted on a spring of stiffness k, and subjected to a periodic force F = F0 cos (ωt) representing the axial excitation resulting from the action of the actuating means 23 and / or moving the movable member 22.

This system has a mode specific to a frequency of (√ (k / M)) / (2π) = F1.

The damping means, in the case where they comprise a single mass, can be likened to a mass M1 linked to the mass M by a spring of stiffness K.

Both masses M and M1 are free to move axially.

K and M1 are chosen so as to cancel the displacement of the mass M when it is subjected to a frequency excitation ω equal to the natural frequency F1.

et $$\mathrm{u}1=\mathrm{U}1\cos \left(\mathrm{\omega }\mathrm{t}\right)$$

We denote u and u1 the respective axial displacements of the masses M and M1, these displacements expressing themselves in the form: $$\mathrm{u}=\mathrm{U}\cos \left(\mathrm{\omega }\mathrm{t}\right)$$

and $$\mathrm{u}1=\mathrm{U}1\cos \left(\mathrm{\omega }\mathrm{t}\right)$$

et $$\mathrm{U}1=\mathrm{F}0\mathrm{K}/\left(\left(\mathrm{k}+\mathrm{K}-{\mathrm{\omega }}^2\mathrm{M}\right)\left(\mathrm{K}-{\mathrm{\omega }}^2\mathrm{M}1\right)-{\mathrm{K}}^2\right)$$

Applying the fundamental principle of dynamics to masses M and M1, it comes: $$\mathrm{U}=\mathrm{F}0\left(\mathrm{K}1-{\mathrm{\omega }}^{\mathrm{two}}\mathrm{M}1\right)/\left(\left(\mathrm{k}+\mathrm{K}-{\mathrm{\omega }}^{\mathrm{two}}\mathrm{M}\right)\left(\mathrm{K}-{\mathrm{\omega }}^{\mathrm{two}}\mathrm{M}1\right)-{\mathrm{K}}^{\mathrm{two}}\right)$$

and $$\mathrm{U}1=\mathrm{F}0\mathrm{K}/\left(\left(\mathrm{k}+\mathrm{K}-{\mathrm{\omega }}^{\mathrm{two}}\mathrm{M}\right)\left(\mathrm{K}-{\mathrm{\omega }}^{\mathrm{two}}\mathrm{M}1\right)-{\mathrm{K}}^{\mathrm{two}}\right)$$

So, to cancel U, just choose K and M1 such that √ (K / M1) = ω.

The injection device described above has many advantages.

It comprises damping means for reducing the amplitude of the axial vibrations of the injector holder to at least one natural frequency responsible for the acoustic radiation of the injector holder.

Therefore, the excitation that the injector holder will impose in turn to the breech will be reduced too, which reduces the acoustic radiation of the cylinder head and surrounding parts.

The better control of the acoustic radiation of the injector holder makes it possible to increase the frequency and the speed of the movements of needles and actuators, without increasing the sound level perceived by the passengers of the vehicle, and thus gives more freedom to control the injection into the cylinders of the engine, according to objectives of reducing fuel consumption or reducing gaseous pollutant emissions.

The device may comprise several damping means, for damping the vibrations of several eigen modes of different frequencies.

It is thus possible to have two masses on the same side of a ring, linked to this ring by elastic members arranged one inside the other. This provision may be extended to three or more masses, arranged same side of the ring, linked to this ring by elastic members arranged in each other.

We can also have the masses of two opposite sides of the same ring, so as to bind two, four, six or more masses to the same ring.

It is also possible to arrange several rings along the injector holder, one or more masses being connected to each ring by elastic members.

The number of masses that it is possible to implement, and therefore the number of eigen modes that can be damped, is limited by implantation constraints along the injector holder or congestion relative to to the environment of it.

Multiple types of resilient members can be used in the damping means, depending on the desired stiffness and available space.

It is conceivable to use a mobile mass connected to the body of the injector holder by an elastic member of the elastomeric or viscoelastic type working in shear during movement of the mass.

It is also possible to modify the displaced mass and the stiffness of the elastic member, keeping a predetermined ratio between them, to adapt to the available space along an injector holder.

The means used to obtain depreciation are both simple and inexpensive.

They can be protected by a cylindrical sleeve attached to the injector holder or remain unprotected. The sleeve can also be integrated into the injector holder.

Note that the invention applies to all types of injection devices, regardless of the nature of the movable shutter member of the injection port and the nature of the actuating means.

The invention also applies regardless of the part of the engine on which the injector holder is mounted, whether the injection is direct in the combustion chamber or indirect in a pre-combustion chamber or the like.

Claims (10)

Fuel injection device in a cylinder of a motor vehicle, this device comprising an injector holder (10) of generally elongate shape in an axial direction and traversed by an axial slot (11), and an injection member (20) rigidly fixed in the lumen (11), this member comprising a hole (212) for the passage of fuel injected into the cylinder, an element (22) selectively movable between a closed position of the orifice (212) and a position of disengagement of the orifice (212), and actuating means (23) for moving the movable element (22) between its closed and disengaged positions, characterized in that it comprises at least first means of damping device (30) for reducing the amplitude of the axial vibrations of the injector holder (10) resulting from the movements of the movable member (22) and / or the action of the actuating means (23) to at least a first predetermined frequency. Injection device according to claim 1, characterized in that the first damping means (30) comprise a first axially movable mass (31) and first resilient means (32) connecting the first mass (31) to the injector holder (10) able to relax and compress axially. Injection device according to claim 2, characterized in that the injector holder (10) has at least a substantially cylindrical portion (12), the first mass (31) having the shape of a ring surrounding said cylindrical portion. Injection device according to claim 3, characterized in that the first elastic means (32) comprise a first elastic member (321) linking the first mass (31) to the injector holder (10), this organ being disposed on a first axial side of the first mass (31). Injection device according to claim 4, characterized in that the first resilient means (32) further comprises a second elastic member (322) linking the first mass (31) to the injector holder (10), this member being disposed of a second axial side of the first mass (31) opposite to the first. Injection device according to claim 4 or 5, characterized in that the first elastic member (31) is a helical spring wound around the cylindrical portion (12), or a cylindrical spring threaded around the cylindrical portion (12), or consists of one or more spring washers (33), or is formed of a plurality of axial coil springs (34) disposed at the periphery of the cylindrical portion (12). Injection device according to any one of claims 3 to 6, characterized in that the first damping means (30) comprise a cylindrical protective sheath (33) surrounding the first mass (31) and rigidly fixed to the door -injector (10). Injection device according to any one of claims 3 to 7, characterized in that it comprises second damping means (50) for reducing the amplitude of the axial vibrations of the injector holder (10) to at least one second predetermined frequency, the second means comprising a second mass (51) axially movable and second elastic means (52) connecting the second mass (51) to the injector holder (10) able to relax and compress axially. Injection device according to claim 8, characterized in that it comprises a ring (34) rigidly fixed to the cylindrical portion (12) of the injector holder (10), the first elastic means (32) being connected to said ring (34) and extending from a first axial side thereof, the second elastic means (52) being connected to said ring (34) and extending from a second axial side thereof opposite to the first side. Injection device according to claim 8, characterized in that the first and second elastic means (32, 52) are coaxial with the cylindrical portion (12), the first elastic means (32) extending inside the second resilient means (52).

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