FR2954963A1 - Vibration dampener for fuel injector of e.g. diesel engine of i.e. car, has liner cooperating with another liner to improve dissipation of vibrations in frequential domain and/or to dissipate vibrations in another given frequential domain - Google Patents

Abstract

The dampener has a liner (14) provided with metal elements to partly dissipate vibrations in a determined frequential domain. Another liner (15) is in contact with the former liner, and is made of an organic material to dissipate vibrations. The latter liner cooperates with the former liner to improve dissipation of the vibrations in the frequential domain and/or to dissipate vibrations in another given frequential domain. The metal elements are selected from metal wires, metal braids, metal meshes or undulated and/or folded metal sheets. The organic material is selected from polyamide and organic resin. An independent claim is also included for an internal combustion engine, comprising a fuel injector.

Description

Vibration damper and engine comprising such a shock absorber

TECHNICAL FIELD OF THE INVENTION The present invention relates to the field of vibration damping devices. The invention more particularly relates to means for reducing the noise and vibrations generated by a fuel injector for an internal combustion engine.

BACKGROUND ART One of the noise sources of today's automobile engines is the noise generated by the injectors, for diesel engines as well as for gasoline engines.

Injectors which are only one source among other sources of noise and vibration in a motor vehicle are intended to be mounted, to perform their function, on an engine cylinder head. However, one of the difficulties of making assemblies or devices allowing a good control of the vibro-acoustic excitation that they generate is the thermomechanical and chemical environment of the engine, which is particularly restrictive: the temperatures are high, and few Conventional damping materials such as rubbers can be used, moreover the clamping forces between the injector and the motor cylinder head are important, and it is furthermore necessary to have a good seal between the injector and the cylinder head.

Injectors are also vibro-acoustic sources for two reasons. First of all, the injectors are acoustic sources because of its internal moving parts which are activated for the consecutive preparation of the quantities of fuel intended to be injected into the combustion chamber or chambers according to the engine speed. These parts are generally solicited in translatory and oscillatory movement and the consecutive vibrations of the injector produce a directly perceptible acoustic radiation.

The injectors are then sources of vibration because of the dynamic forces they produce on the cylinder head, to which they are attached, and gradually on the entire engine during the preparation and injection of fuel. The same mechanisms as those already mentioned above generate vibrations. Thus, among the possible causes, each change in fuel pressure in the feed rail, and in particular each pressure discharge, generates vibrations.

All vibrations generated at the interface of the injector system and the cylinder head propagate solidly in the engine and then produce audible acoustic radiation.

Document DE102007002682 discloses a vibration damper employed in particular for damping the vibrations generated by a fuel injector for an internal combustion engine. The vibration damper comprises a lining of metal elements such as a cushion of metal son arranged according to a suitable entanglement. Part of the vibration energy is dissipated by friction between the metal elements. This vibration damper is well adapted to the high thermomechanical stresses experienced by the injector, however such a vibration damper can dissipate the vibrations generated by the injector only on a limited frequency of vibration domain. Furthermore, if it is desired to use the damper by placing it at the bottom of the injector well, it must ensure the tightness of the mounting of the injector on the cylinder head and the achievement of this important sealing function is difficult for the damper of document DE102007002682, the metal braids being too porous.

Since the mechanical effects and the operating principle of the injectors can not be changed, it is then necessary to reduce or even eliminate the transmission of vibrations to the structures in contact with the injector and in particular with the cylinder head of the engine.

The object of the invention is to propose a means which makes it possible to improve the damping of the vibrations over an extended frequency range and able to withstand high thermomechanical stresses.

The object of the present invention is achieved with a vibration damper comprising a first lining comprising a plurality of metallic elements able to partially dissipate the vibrations in a first frequency domain determined, characterized in that it comprises a second lining in contact with the first gasket, said second gasket being based on an organic material, capable of dissipating vibrations and cooperating with the first gasket to improve the dissipation of the vibrations of the first frequency domain and / or to dissipate vibrations in a second frequency domain determined .

The invention has the additional advantage of being manufactured in large series with controlled costs.

In addition, the invention may include one or more of the following features:

In a first variant, the vibration damper of the invention comprises at least one superposition of a flat layer of the first liner with a flat layer of the second liner.

In a second variant, the vibration damper of the invention comprises at least one concentric superposition of an annular layer of the first liner with an annular layer of the second liner. Preferably, the vibration damper of the invention comprises a first metal plate for maintaining the linings.

More preferably, the vibration damper of the invention comprises a second metal retainer plate taking, with the first metal plate, said sandwich linings.

Preferably, the first and / or second metal plate adheres to at least the first and / or second liner. Preferably, the metal elements of the first lining are able to dissipate the vibrations by friction between them.

Preferably, the metal elements of the first liner are selected from metal wires, metal braids, metal meshes, or corrugated and / or folded metal foils.

Preferably, the organic material of the second lining is able to dissipate the vibrations by its viscoelastic behavior.

Preferably, the organic material based on the second lining is chosen from a polyamide, an organic resin.

More preferably, the second liner comprises a so-called friction material.

Furthermore, the invention also relates to an internal combustion engine comprising a fuel injector held on a cylinder head by fixing means, characterized in that it comprises at least one vibration damper of the invention disposed at at least one of the vibration transmission interfaces generated by the injector, during its operation, to the cylinder head.

Preferably, the vibration damper has in situ, in other words once mounted on the motor, a global Young's modulus between 500 MPa and 50000 MPa. Indeed, due to the compression due to the clamping of the damper by the fastening means, the Young's modulus of the vibration damper once held by the fastening means may differ from the Young's module out of assembly.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages will appear on reading the following description of a particular embodiment, not limiting of the invention, with reference to the figures in which:

- Figure 1 is a simplified sectional representation of a fuel injector mounted in a cylinder head of an internal combustion engine. - Figure 2 is a representation in simplified sectional view of the assembly of the injector shown in Figure 1, modified by the addition of vibration damper according to the invention. - Figure 3 shows in section a first embodiment of the vibration damper according to the invention. FIG. 4 shows in half-section a second embodiment of the vibration damper according to the invention. FIG. 5 shows in half-section a third embodiment of the vibration damper according to the invention. FIG. 6 shows in half-section a fourth embodiment of the vibration damper according to the invention. FIG. 7 shows in half-section a fifth embodiment of the vibration damper according to the invention. FIG. 8 shows in half-section a sixth embodiment of the vibration damper according to the invention. FIG. 9 shows in half-section a seventh embodiment of the vibration damper according to the invention.

Detailed Description Figure 1 shows in the form of a simplified section a cylinder head 1 of an internal combustion engine. The cylinder head has an injector hole 2 and an injector well 3. A fuel injector 4 comprising at the end an injector nose 41 for injecting fuel into a combustion chamber, not shown here, is disposed at the bottom of the well 3, the nose 41 being inserted into the injector hole 2.

The injector 4 is mounted on the yoke 1 by means of a fork 5. The fork 5 is arranged so as to partially surround, by one of its two opposite ends, at a shoulder 42 of the body of the yoke. injector and to bear by the other of its ends on the cylinder head 1. The fork 5 is immobilized on the cylinder head 1 with the aid of a screw 6 engaging in a suitable tapping 7 of the cylinder head 1. washer 8 can be placed between the screw 6 and the fork 5.

By tightening the screw 6 is exerted on the fork 5 a lever, thanks to which the fork 5 presses the shoulder 42 and immobilizes the injector 4 in the cylinder head 1. It is conventionally planned to have the well 3 bottom injector, between the injector 4 and the cylinder head 1, a seal 9 of ductile metal such as a copper gasket which seals the combustion gases after immobilization of the injector 4 in the cylinder head. As an indication, the frequency range of vibrations generated by the injector 4 to be treated is between 300 Hz and 15000 Hz.

According to the arrangement shown in FIG. 2, the mounting and fixing of the injector 4 on the cylinder head 1 are modified in order to reduce or eliminate the transmission of the vibrations emitted by the injector 4 during its operation and in particular towards the cylinder head 1 To do this, preferably, it is provided to have at least one vibration damper of the invention at at least one vibration transmission interface of the injector 4 to the cylinder head 1. By transmission interface of the vibrations, a zone of contact between two parts is designated which makes it possible to bridge the passage, by solid route, of the vibrations emitted by the injector 4 towards the cylinder head 1.

More specifically, it is intended to place a first vibration damper 10 instead of the metal seal 9, to dissipate the vibrations emitted by the injector 4 and transmitted to the cylinder head 1 by the bottom of the well 3. A second vibration damper 11 of the invention is disposed between the fork 5 and the shoulder 42, a third vibration damper 12 is disposed between the head of the screw 6 and the fork 5 to replace the bearing washer 8 and a fourth vibration damper 13 is placed between the fork 5 and the cylinder head 1, at the level of the support between these two parts.

Depending on the application, the vibration damper may be in different embodiments.

A first embodiment of the vibration damper of the invention is shown in section in FIG. 3. This first embodiment is more particularly adapted to the first vibration damper 10.

In this first embodiment, and in accordance with the invention, the vibration damper 10 comprises a first lining 14 comprising a plurality of metal elements capable of dissipating the vibrations of a first predetermined frequency domain, a second lining 15 contact with the first liner 14, said second liner 15 being based on an organic material, able to dissipate vibrations and cooperating with the first lining 14 to improve the dissipation of the vibrations of the first frequency domain and / or to dissipate vibrations in a second frequency domain determined.

In order to obtain a better vibro-acoustic performance while economically satisfying the various thermomechanical and sealing constraints, two complementary mechanisms for dissipating vibrations are put in cooperation here. Indeed, preferably the metal elements of the first lining 14 are able to dissipate the vibrations by friction of said metal elements together, while still preferably, the second liner 15 based on organic material is able to dissipate vibrations by its viscoelastic behavior, at scales smaller than the first liner 14. In fact, the organic material forms a continuous material at the scales where the vibrations develop, unlike the metallic elements which at these scales form a porous medium. It has a generally viscoelastic behavior and a damping factor that gives it the property of dissipating vibratory energy. The phenomena at the origin of this dissipation are complex and intervene at small scales, atomic among others, in any case smaller than the scales involved for the frictional dissipation of the first lining. The cooperation of the two dissipation mechanisms makes it possible to obtain a better damping relative to a metal lining alone and / or to allow the attenuation of vibration on a domain not covered by the first lining 14.

Preferably, the metal elements of the first lining 14 are chosen from metal wires, metal braids, metal meshes, corrugated metal sheets and / or folded. Indeed, the metal son may be for example braided, knitted or mesh for example in the form of a grid and pressed against each other by compression.

Thus, the dissipation due to friction at the level of the metal wires of the first lining 14 is on a larger dimensional scale, that of the metal wires, than the dissipation occurring in the second lining 15, which is situated at a substantially atomic.

Preferably, the vibration damper 10 comprises a first metal plate 16 for holding the linings. More preferably, the vibration damper 10 comprises a second metal holding plate 17 taking, with the first metal plate 16, said gaskets 14, 15 sandwiched.

For the first and second metal plates 16, 17, a ductile metal such as copper, or brass is preferred because it ensures for this application the seal, after clamping the injector 4 between the combustion chamber of the cylinder head 1 and the outside.

In this first embodiment, the vibration damper 10 has an overall shape of a washer with a central hole 18 for the passage of the nose 41 of the injector.

In this first embodiment, the first and second gaskets 14, 15 are preferably arranged in a concentric superposition of an annular layer of the first metal gasket 14, with a layer of the second organic gasket 15. The annular layers are substantially centered around the central hole 18. In this way, the second organic seal 15 contributes to the compressive strength of the damper 10 and seals, so that the combustion gas leaks through the damper 10 are not possible.

In a variant not shown, it is possible to have several concentric overlays of a layer of the first metal lining 14, with a layer of the second organic lining 15.

All materials used in this first embodiment applied to the bottom of the injector well 3 must be chemically stable for temperatures up to 350 ° C. They must be able to undergo without mechanical damage and with a controlled dimensional variation, particularly as regards the metal elements of the first lining 14 which can settle, the compression forces due to the clamping of the injector 4 against the cylinder head 1. In fact, for example, these a variation of the depression of the order of 0.1 mm from the injector nozzle 41 in the cylinder head 1 is sensitive for the control of combustion.

Preferably, the organic material at the base of the second liner 15 is selected from a polyamide, an organic resin with suitable thermomechanical properties such as, for example, an epoxy resin, a phenolic resin.

The organic material can be loaded with fibers, talc, reinforcing powders, to improve the thermal and / or mechanical properties.

More preferably, the second liner 15 comprises a so-called friction material, that is to say a composite organic matrix metal material such as that used for brake pad linings, which has the additional advantage of being little expensive and of current industrialization.

For this embodiment, the first lining 14 of metal elements is prestressed by compression during the manufacture of the vibration damper 10.

Figures 4 and 5 now show in half section respectively a second and a third embodiment of the damper 10 of the invention. Figure 4 shows the damper 10 with one of the two metal plates, here the second metal plate 17 having an edge 19 folded around the periphery of its periphery. Figure 5 shows the damper 10 with the two metal plates having an edge 19 folded around the periphery of their periphery.

In the variants shown in FIG. 4 or FIG. 5, the compression of the first lining 14 of metallic elements is carried out during manufacture by folding the edge 19 of the metal plate. This crimping is intended to compress the metal components of the first gasket 14, necessary to optimize their vibration dissipation capabilities.

FIG. 6 shows a variant in which the edge 19 is initially raised, then is folded down by the positioning and tight fitting of the injector, represented by the arrow 21. Thus, the prestressing of the metal elements is ensured by this assembly step. the injector on the cylinder head.

As shown in FIG. 7, it is possible to provide a transition zone 20 between the first gasket 14 and the second gasket 15. The transition zone 20 between the first gasket 14 and the second gasket 15 is here beveled with a profile inclined right. The transition zone 20 may also be with a curved profile, in particular to optimize the thermomechanical behavior of the second lining 15.

We now present in FIGS. 8 and 9 two other embodiments, more particularly adapted to the vibration dampers 11, 12, 13 shown in FIG.

In the embodiments illustrated in FIGS. 8 and 9, the first and second packings 14, 15 are preferably arranged in a superposition of a planar layer of the first metal packing 14, with a planar layer of the second organic packer 15, when sealing is not necessary. It is possible to have several superpositions of a flat layer of the first metal lining 14, with a flat layer of the second organic lining 15.

Furthermore, when, as shown in Figure 9, the damper comprises a layer of the first metal lining 14 symmetrical along a median plane P, it can be expected to produce two identical half sets that are secured at the level of the median plane P during the manufacture by compression thanks to the entanglement of metal elements.

Preferably, the first and / or second metal plate adheres to the organic liner with which it is in contact. In the case where the metal plate is in contact with an organic packing and according to the production method chosen, the metal plate can adhere directly to the organic material. In other cases, the metal plate may be secured to the first and / or second liner per layer of adhesive, as shown in Figure 8 with reference 22 for the case of the first liner 14. In order to improve the connection to the interfaces between the first and second packings, it is possible for the manufacture to have, as shown in FIG. 9, a mixing zone 23 between the first metal packing 14 and the second organic packing. We then move gradually from the second lining 15, in a direction normal to the median plane P of a continuous medium to a porous medium.

To best ensure the vibro-acoustic attenuation function, it is expected to respect the following main dimensioning rules: the organic materials used must have a loss factor or structural damping coefficient sufficient, at least 1% and producing an apparent damping of the whole if possible of the order of 10%; the vibration damper must create a certain dynamic and / or vibratory impedance break and provide a vibration filtering function with a lower apparent stiffness than the metals used for the injector and the cylinder head, generally steel and aluminum. Preferably, the vibration damper according to the invention has an overall elasticity in situation, in other words once mounted, quantified by a global Young's modulus of between 500 MPa and 50000 MPa.

The vibration damper of the invention may have a thickness substantially between 1 and 20 mm.

The embodiments described in FIGS. 2 to 9 are in no way limiting. According to other embodiments, embodiments based on those described in FIGS. 2 to 9, but not using a first metal plate and / or a second metal plate, are also possible embodiments of the present invention.

The use of the vibration damper of the invention to other types of attachment that an injector / breech fixing is quite possible.

The advantages of the invention are manifold: The invention has better vibro-acoustic performances, because the effects of two complementary mechanisms are combined at different mechanical scales to dissipate the vibrations: a first mode of damping by the internal behavior organic material and a second mode of damping by micro-friction at the level of the metal elements.

The fact of using these two levers also makes it possible to cover more widely the different frequency domains where it is desired to dissipate vibrations.

The vibration damper of the invention provides better resistance to the severe thermomechanical environment and can provide a sealing function, all with a relatively simple and economical architecture.

The use of an organic material allows during the production of the system the adhesion of all or part of the parts forming said system: this avoids having to resort to for example expensive solder points to ensure that the The damper as a whole is in one piece, which is useful during its assembly (or disassembly) in the engine.

The concentric layer embodiments have a better dimensional stability during compression.

The sizing of the elements composing the present invention can usefully be realized from the vibro-acoustic point of view by means of techniques such as those presented in the publication "Vibration analysis of structural modifications. Vincent's approach to circles revisited "from the journal Mécanique & Industries, Vol. 9 No. 3 (May-June 2008), p. 213.

Finally, overall, all or part of the embodiments presented here can be produced in workshops producing brake pads, thus producing inter alia friction materials, because it includes: the use of a metal plate support of other materials, -the use of glues or adhesive products where appropriate, -the use of organic materials as a binder for the production of composite linings, -the use of particles, fibers or materials of different natures that come within the composition of the gaskets, metal composites with an organic matrix, the application of a high compression and a high temperature during manufacture.

Claims (13)

Revendications1. Vibration damper comprising a first lining (14) comprising a plurality of metallic elements able to partially dissipate the vibrations in a first predetermined frequency domain, characterized in that it comprises a second lining (15) in contact with the first lining (14), said second liner (15) being based on an organic material, capable of dissipating vibrations and cooperating with the first lining (14) to improve the dissipation of the vibrations of the first frequency domain and / or to dissipate vibrations in a second frequency domain determined. 2. Vibration damper according to claim 1, characterized in that it comprises at least one superposition of a flat layer of the first gasket (14) with a flat layer of the second gasket (15). 3. Vibration damper according to claim 1, characterized in that it comprises at least one concentric superposition of an annular layer of the first liner (14) with an annular layer of the second liner (15). 4. Vibration damper according to one of the preceding claims, characterized in that it comprises a first plate (16) for holding the liners. 5. Vibration damper according to claim 4, characterized in that it comprises a second plate (17) for holding the liners taking, with the first plate (16) metal, said sandwich linings. Vibration damper according to claim 5, characterized in that the first and / or second metal plate (16, 17) adheres to at least the first and / or second lining (14, 15). 7. Vibration damper according to any one of the preceding claims, characterized in that the metal elements of the first lining (14) are able to dissipate vibrations by friction between them. 8. Vibration damper according to claim 7, characterized in that the metal elements of the first lining (14) are selected from metal son, metal braids, metal mesh or metal sheets corrugated and / or folded. 9. Vibration damper according to any one of the preceding claims, characterized in that the organic material of the second liner (15) is adapted to dissipate the vibrations by its viscoelastic behavior. 10. Vibration damper according to claim 9, characterized in that the organic material based on the second liner (15) is selected from a polyamide, an organic resin. 11. Vibration damper according to claim 9, characterized in that the second lining (15) comprises a so-called friction material. 12. Internal combustion engine comprising a fuel injector (4) held on a cylinder head (1) by fixing means, characterized in that it comprises at least one vibration damper (10, 11, 12, 13) according to any one of the preceding claims disposed at at least one of the vibration transmission interfaces generated by the injector (4), in operation, to the cylinder head (1). 13. Internal combustion engine according to claim 12, characterized in that the vibration damper has in situ a global Young's modulus between 500 MPa and 50000 MPa.