EP1623107A2 - Fluid injection device - Google Patents

Abstract

The invention relates to a fluid injection device (1) comprising a protruding needle (40). One end of the aforementioned needle forms a valve (41) and can be moved between a closed position, in which the valve (41) seals the fluid-release opening (13), and a given open position, in which the valve (41) is positioned at a controlled distance from said opening (13). The invention is characterised in that the movement of the valve (41) between the closed position and the open position is produced by the controlled intrinsic extension of the protruding needle (40).

Description

 FLUID INJECTION DEVICE

The present invention relates to a fluid injection device.

The invention finds a particularly advantageous application in the automotive field, in particular as regards the injection of fuel into a combustion chamber.

A first type of injection device, known as retracting needle, is known from the state of the art. In this conventional configuration, each injector is provided in particular with a needle needle which is capable of being moved axially. This mobility is exerted between a closed position in which the distal end of the needle needle closes an opening intended for the ejection of the fluid, and an open position in which said distal end is positioned at a distance from this same opening.

It should also be noted that the opening can either be formed by a single orifice or by a plurality of holes made downstream of the seat intended to cooperate by sealed contact with the distal end of the needle needle. This latter configuration proves to be particularly suitable for injecting liquid, since the presence of a large number of orifices is such as to disturb the ejection of the liquid, and consequently to multiply the drops.

Anyway, this type of re-entrant needle injector has the disadvantage of operating almost on an all-or-nothing basis. In other words, either the needle passes a maximum quantity of fluid under pressure, or it prevents it from escaping through the opening. So the parameters of adjustment of such a system are essentially limited to the fluid pressure and the flow section of the opening.

Now in practice, and in particular in the case where the fluid is a liquid, a re-entrant needle injector almost always operates at constant pressure. Also, it is the diameter of the holes that will determine the size of the drops. But since the dimensions of the holes in question are fixed by construction, it appears particularly difficult to modify the size of the drops a little bit. Even if the re-entrant needle is opened and closed very quickly, the disturbance then created will be largely insufficient to generate a cloud of small, diffuse drops.

Thus, with an injection device with a retracting needle, it is certainly possible to control the quantity of fluid injected, but obviously it is not possible to control precisely the size and the diffusion of the drops. As is well known, this constitutes a major drawback in terms of yield.

Another important parameter to control concerns the minimum quantity that can be injected. However, in a large part of the injectors with re-entrant needles, the fluid overpressure is used to move the needle needle from its closed position to its open position. The response time of the system then depends on the importance of the pressure in question. In practice, if one wants to reduce the opening time of the re-entrant needle, it is necessary to raise the pressure of the fluid, but then the minimum quantities injected are increased. This constitutes a new disadvantage for this type of system. A second type of injection device of the state of the art, known as outgoing needles, makes it possible to remedy these difficulties. Each injector is here provided with a sort of valve consisting of a rod, one end of which forms a valve and is capable of cooperating by sealed contact with the seat defining an opening for ejecting the fluid. As in the previous case, the valve stem thus formed is mounted movable in axial displacement between a closed position in which the valve closes the opening, and an open position in which said valve is positioned at a distance from said opening.

The mobility of such a valve stem is generally achieved by using either a piezoelectric actuator or a magnetostrictive actuator. Concretely, this consists in coupling the valve stem of the injector with an additional element advantageously made of a so-called active material, that is to say capable of deforming, and in particular of elongating, when it is traversed. respectively, either by an electric current or by a magnetic field. The corresponding physical principles and the modes of implementation of such actuators being perfectly known, they will not be described further here. It will simply be recalled that the assembly is generally arranged in such a way that an excitation of the active material, respectively electrical or magnetic, generates an elongation of the additional element, and consequently a displacement of the valve stem as a whole. The distal end of the valve stem is then no longer in contact with its seat, so that the pressurized fluid can then escape through the opening.

Compared to their counterparts with retracting needles, the injectors with protruding needles has the advantage of having a variable lift at the valve. Thus, at constant pressure, it is possible to have a variable flow section over time. In the case for example of a piezoelectric actuator, as a function of the voltage applied to the additional element, there is a given elongation of the active material. The elongation then corresponding to the accessory element causes a proportional displacement of the rod ^'flap, and consequently lifting equally proportional valve.

However, outgoing needle injection devices have their own drawbacks.

With an additional element made of piezoelectric material, one can reach deformations of the order of a thousandth, that is to say about lOμm of displacement for 10mm of piezoelectric stacking. This means that the annex element must be extremely long if one wants to obtain a displacement of the valve of conventionally 50 μm. This then implies the need to control very large capacities, of the order of 3 to 3.5 μF for a stack of 30 mm for example. Consequently, considerable power is required if the switching time is to be reduced.

Furthermore, during the implementation of the outgoing needle injector, the great length of the additional element then constitutes a disadvantage in terms of weight. The assembly consisting of the valve stem, the annex element and other elastic return means then constitutes a relatively large mobile mass. The significant inertia which results will further delay the reactivity of the piezoelectric material.

Thus, essentially because of the high capacities to control and the large mass to be displaced, the injection devices with outgoing needles and with piezoelectric actuators prove to be intrinsically limited in terms of reaction time.

With an additional element in magnetostrictive material, it is essentially the problem of the inertia of the system which constitutes the main handicap. Because it should not be forgotten, the mobile mass driven in displacement is very important with the injection devices of the state of the art, since it corresponds to the combined masses of the often long rod and of the associated valve.

Also the technical problem to be solved, by the object of the present invention, is to propose a fluid injection device comprising an outgoing needle, one end of which, forming a valve, is capable of being moved in a controlled manner at any time between a closed position in which the valve closes an opening intended for the ejection of the fluid, and an open position in which said valve is positioned at a chosen distance from said opening, an injection device which would make it possible to avoid problems. of the state of the art by offering notably significantly improved reaction times, that is to say significantly reduced opening and closing times of the valve, as well as a variable opening capacity.

The solution to the technical problem posed consists, according to the present invention, in that the movement of the valve between its closed position and its position opening is generated by an intrinsic elongation of the outgoing needle.

Unlike the injection devices of the prior art, it is not a question here of displacing the outgoing needle in its entirety, but of deforming it longitudinally so as to consequently cause a displacement of its free end, that is to say that is, the one carrying the valve. The assembly is arranged so that the mobility of the valve is exerted between the closed position and the open position previously defined, the mobility being controlled at all times. The invention as defined has the advantage of allowing a considerable reduction in the mobile mass, and therefore a proportional reduction in the inertia of the system. The reaction times of this type of injection device are therefore significantly improved.

The present invention also relates to the characteristics which will emerge during the description which follows, and which should be considered in isolation or according to all their possible technical combinations.

This description given by way of nonlimiting example will make it easier to understand how the invention can be implemented, with reference to the attached drawings in which:

Figure 1 illustrates a fluid injection device according to a first embodiment of the invention.

FIG. 2 constitutes a variant of the first embodiment of FIG. 1.

FIG. 3 represents a device for injecting fluid according to a second embodiment of the invention. For reasons of clarity, the same elements have been designated by identical references. Likewise, only the essential elements for understanding the invention have been shown, and this without respecting the scale and in a schematic manner.

FIG. 1 illustrates an injection device 1 which is intended to dispense liquid fuel into a combustion chamber of a motor vehicle engine.

In this particular embodiment, chosen only by way of example, the injection device 1 mainly consists of three parts. Firstly, there is a first housing 10 in which a first housing 11 is formed axially. It is then noted that there is a second housing 20 which is itself provided with a second housing 21. These two housings 10, 20 are secured together in a sealed manner by means of a union nut 30, the implementation of which is reversible. The assembly is arranged so that the first housing 11 and the second housing 21 are communicating. The assembly of the two housings 10, 20 then forms the body of the injection device 1. Finally, note the presence of an outgoing needle 40 which takes place in the continuous space defined by the housings 11, 21.

According to this FIG. 1, the distal end of the outgoing needle 40 is shaped so as to be able to cooperate with a through hole 12 which is formed in the lower part of the first housing 10 and which defines an opening 13 intended for ejection. some cash. The distal end of the outgoing needle 40, forming a valve 41, is more precisely able to cooperate, on the one hand, by sliding contact with a guide surface 14 formed at the internal end of the through hole 12, and on the other hand, by sealed contact with a seat 15 formed in turn at the outer end of said through hole 12. Anyway, the valve 41 is able to be moved between a closed position in which it closes the opening 13, and an open position in which it is positioned at a distance from said opening 13.

Note also in Figure 1 that the upper part of the second housing 21 cooperates by contiguous interlocking with a closure cover 50 which is provided with a recirculation channel 51 of the pressurized liquid.

In addition, there is the presence of a supply system 60 of liquid under high pressure. This comprises a main channel 61 which is formed longitudinally in the thickness of the second housing 20 and which communicates with an intermediate channel 62 extending orthogonally to the axis of the injection device 1, at the interface of said second housing 20 and the first housing 10. The annular shape and the positioning of the intermediate channel 62 makes it possible to distribute the liquid under pressure in a plurality of secondary channels 63a, 63b which are regularly distributed in the thickness of the first housing 10 and which open into a annular cavity 64. This annular cavity 64, conventionally formed between the valve 41 and the through hole 12, has a perfectly known shape, arrangement and function which will therefore not be described further here. It will simply be specified that the assembly is shaped so as to be able to generate and regulate, in a conventional manner, a continuous circulation of liquid in direction of the internal housings 11, 21. of the injection device 1.

In accordance with the object of the present invention, the displacement of the valve 41 between its closed position and its open position is here advantageously generated by an intrinsic elongation of the outgoing needle 40.

According to a feature of the invention, the intrinsic elongation of the outgoing needle 40 takes place up to the direct vicinity of the valve 41, that is to say in particular at the level of the part of said outgoing needle 40 which is located directly near said valve 41.

It is in fact particularly advantageous for the deformation to take place as close as possible to the valve, in order to minimize as much as possible the mobile mass to be moved, which ideally should be limited to that of the valve 41. With such a configuration, the opening times and closing are consequently reduced in considerable proportions.

According to another characteristic of the invention, the outgoing needle 40 comprises a hollow rod 42 provided with a solid end 43 forming a valve 41, as well as an internal bar 44 composed of an active element 45 integral with a rear element 46, forming a mass of inertia. This internal bar 44 is also mounted to move axially inside the hollow rod 42, in the sense that it is only joined at the solid end 43, via the active element 45. Thus therefore , the active element 45 is movable in axial elongation, while the rear element is movable in axial displacement. The connection zone between the active element 45 and the rear element 46 is embodied by an interface 47. It should be noted that throughout this text, the concept of active element 45 essentially designates a piezoelectric element, or a magnetostrictive element. But any other material, the dimensions of which could be modulated under the effect of a variation of a physical quantity, could obviously be adopted.

In a particularly advantageous manner, the hollow rod 42 has a mechanical elasticity capable of allowing, in a reversible manner, its longitudinal deformation.

The mechanical elasticity involved can come from the intrinsically elastic nature of the material constituting the hollow rod 42, and / or from a particular structure, for example perforated, of said hollow rod 42. This characteristic allows the hollow rod 42 d 'offer a minimum resistance to deformation during the opening phase of the valve 41, while promoting the return to the initial state during the closing phase, as soon as the active element 45 is no longer used. The fact that the elastic energy transmitted during the deformation is returned on return, makes it possible to advantageously dispense with specific recall means, as is the case with the injection devices of the prior art.

According to another feature of the invention, the rear element 46 has a density and a rigidity substantially greater than that of the other elements making up the outgoing needle 40.

This means that the rear element 46 is made of a particularly dense and hard material so as to be able to constitute a real mass of inertia on the one hand, and not to deform under the action of the elongation of the active element 45 on the other hand.

As can also be seen in Figure 1, the injection device 1 is further provided with prestressing means 70 which are able to permanently compress the internal bar 44 against the solid end 43 of the rod hollow 42.

The goal is obviously to put the active element 45 indirectly in compression, this _. in order to optimize its capacities, in particular in terms of elongation and reactivity. Whether it is made of a piezoelectric or magnetostrictive material, it is known that such an active element 45 must imperatively be prestressed in order to be able to be used effectively. Indeed, this type of material supports more elongation than compressions, and therefore to avoid that they are in this state at any time, it is essential to provide means capable of permanently exerting a compressive force on the active element 45, even when the latter is in the elongation phase. This characteristic also makes it possible to preserve the material whose resistance to stretching is relatively low, substantially by a factor of ten compared to its resistance to compression.

In the example of FIG. 1, the prestressing means 70 comprise a compression spring 71 which acts axially on the visible section 48 of the internal bar 44.

According to another feature of the invention, the injection device 1 is provided with securing means 80 which have a dual role. The first consists in allowing immobilization of the outgoing needle 40 relative to the body of the device injection 1 when said outgoing needle 40 undergoes a force whose intensity is less than a given threshold. This first characteristic advantageously makes it possible to make ineffective the weak and / or punctual forces, such as the vibrations for example.

The second function of the securing means 80 is, however, to allow the translation of the outgoing needle 40 relative to the body of the injection device 1, as soon as the intensity of an applied force exceeds the threshold mentioned above. This second characteristic makes it possible to absorb more intense and / or continuous forces, such as those resulting for example from thermal expansions of the internal components of the injection device 1, and in particular of the outgoing needle 41.

In the particular embodiment of Figure 1, the securing means 80 firstly comprise three external grooves 82 which are formed parallel to each other on the surface of a tubular element 81, forming a shoulder. This tubular element 81 is itself rigidly secured around the outgoing needle 40, but removably, by means of a reversible assembly means constituted in the present case by a conventional cooperation between two complementary threads. Each external groove 82 also extends in a plane orthogonal to the axis of the outgoing needle 40. The securing means 80 are further provided with a helical groove 83 which is formed inside the body of the device. injection 1. The securing means 80 finally have a ball 84 for each external groove 82. The assembly is also arranged so that each ball 84 is in able to cooperate by partial interlocking, substantially half with the corresponding external groove 82 on the one hand, and substantially half with the helical groove 83 on the other hand. Concretely, the balls 84 are positioned at the points of intersection between the helical groove 83 and the external grooves 82.

In a particularly advantageous manner, the three balls 84 are distributed equidistantly, at 120 ° from one another in the present case. They can thus fully play the role of centering means for the tubular element 81, and consequently for the outgoing rod 40.

According to a characteristic of this particular embodiment, the depth of each external groove 82 is substantially greater than the radius of the corresponding ball 84, while that of the helical groove 83 corresponds substantially to the radius of each ball 84. Furthermore, each groove 82 is provided with a compression means 85 capable of pushing the ball 84 corresponding to the bottom of the helical groove 83.

Thus, each ball 84 is positioned half in the helical groove 83 on the one hand, and half in the corresponding external groove 82 on the other hand. This characteristic enables the mechanical stresses to be distributed equitably at each connection point materialized by each ball assembly 84 - external groove 82 - helical groove 83.

Anyway, when an external force of sufficient intensity is applied to the outgoing needle 40, the resulting displacement remains relatively limited. Indeed, as on the one hand the only mobility allowed is the combination of a rotation and an axial translation, and as on the other hand the pitch of the helical groove 83 is relatively small, the system can only react with small amplitudes and a very long time constant. This advantageous characteristic allows in particular the tensioning means 90, which will be described later, to fully play their role, but also to compensate for the variations in length due to thermal expansions.

As shown in FIG. 1, it should be noted that in this exemplary embodiment, the upper part of the tubular element 81 is integral with a disc 87 which advantageously constitutes a stop for the compression spring 71 of the prestressing means 70 .

According to another feature of the invention, the injection device 1 comprises tensioning means 90 which are able to keep the valve 41 of the outgoing needle 40 in abutment against its seat 15. In this exemplary embodiment , the tensioning means 90 are provided with a compression spring 91 which is arranged axially around the outgoing needle 40. Thus positioned, the compression spring 91 is able to cooperate by contact with a part 86, forming shoulder, of the tubular element 81 on the one hand, and with a part 22, forming a stop, of the body of the injection device on the other hand. FIG. 2 represents a variant of the first embodiment described above, which differs only in the nature of the prestressing means 70 employed. The latter use here pressurized liquid 72 which acts axially on the visible section 48 of the internal bar 44, as well as a regulating valve 73 which is able to limit the internal pressure of the liquid 72 to a determined value. In this particular embodiment, the regulating valve 73 is conventionally composed of a ball 74 which is supported, under the action of a compression spring 75 and via an intermediate washer 76, on a seat 77 delimiting a exhaust channel 78. Furthermore, it should be noted that there is an elastic ring at the interface between the intermediate washer 76 and the body of the regulating valve 73.

The operation of such a system being perfectly known, it will not be described here further. It will simply be specified that the purpose of the regulating valve 73 is to control the overpressure of the liquid present inside the injection device 1, and more precisely to fix said pressure at a defined value corresponding to the level of prestressing which is wish to apply to the active material 45.

It will also be specified that the presence of pressurized liquid 72 inside the injection device 1 here results directly from the recirculation phenomenon established to cool the internal components. But of course, an independent high pressure liquid system could very well be adopted as an alternative.

In the first embodiment of Figures 1 and 2, the outgoing needle 40 contains an active piezoelectric element 45 whose length is likely to be increased under the effect of an electric field. Furthermore, the elongation of the active piezoelectric element 45 is able to deform longitudinally the external part of the outgoing needle 40, which surrounds said active piezoelectric element 43. However, and in accordance with the second embodiment shown in FIG. 3, an injection device 100 can be provided with an outgoing needle 140 containing an active magnetostrictive element 145 whose length is able to be increased under the effect this time from a magnetic field. Here again, the assembly is arranged so that the elongation of the active magnetostrictive element 145 is such as to deform longitudinally the external part of the outgoing needle 140, which surrounds said active magnetostrictive element 145.

In practice, and as can be seen in FIG. 3, it is then conventionally to provide for the presence of a solenoid 200 and a tube made of magnetic material 201 arranged axially inside the injection device. Concretely, the magnetic tube 201 is positioned concentrically around the solenoid 200, which is itself positioned concentrically around the magnetostrictive element 145.

According to a feature of this second embodiment, when the active element 145 is magnetostrictive, the rear element 146 can be, advantageously chosen non-magnetic. The outgoing needle 140 then further comprises two intermediate elements 147, 148 which are positioned respectively, between the rear element 146 and the active element 145 on the one hand, and between said active element 145 and the solid end 143 of the hollow rod 142 on the other hand. Each intermediate element 147, 148 is moreover made of a magnetic material capable of looping the lines of the magnetic field used to excite the active element 145. It should be noted that, like these intermediate elements 147, 148, the function of the magnetic tube 201 is also to loop the magnetic field lines generated to control the elongation of the active element 145.

The prestressing means 170 of this second embodiment are identical to those, described in the context of FIG. 1, of the first embodiment. However, the variant of the first embodiment, that is to say the one using pressurized fluid, could obviously be easily adapted to the injection device 100 of this second embodiment.

Of course, the invention also relates to any motor vehicle provided with at least one injection device as previously described.

Claims

1. Fluid injection device (1, 100) comprising an outgoing needle (40, 140) one end of which, forming a valve (41, 141), is capable of being moved between a closed position in which the valve (41 , 141) closes an opening (13, 113) intended for the ejection of the fluid, and a given opening position in which said valve (41, 141) is positioned at a controlled distance from said opening (13, 113), characterized in that the movement of the valve (41, 141) between its closed position and its open position is generated by an intrinsic elongation controlled at all times by the outgoing needle (40, 140). 2. Injection device (1, 100) according to claim 1, characterized in that the intrinsic elongation of the outgoing needle (40, 140) takes place up to the direct vicinity of the valve (41, 141). 3. Injection device (1) according to one of claims 1 or 2, characterized in that the outgoing needle (40) comprises an active piezoelectric element (45) whose length is capable of being increased under the effect of an electric field, and in that the elongation of the active piezoelectric element (45) is able to deform longitudinally the outgoing needle (40) comprising said active piezoelectric element (45). 4. Injection device (100) according to one of claims 1 or 2, characterized in that the outgoing needle (140) comprises an active element magnetostrictive (145) the length of which is capable of being increased under the effect of a magnetic field, and in that the elongation of the active magnetostrictive element (145) is capable of deforming the outgoing needle (140) longitudinally comprising said magnetostrictive active element (145). 5. Injection device (1, 100) according to any one of claims 1 to 4, characterized in that the outgoing needle (40, 140) comprises a hollow rod (42, 142) provided. a solid end (43, 143) forming a valve (41, 141), as well as an internal bar (44, 144) composed of an active element (45, 145) integral with a rear element (46, 146) forming a mass of inertia, and in that the internal bar (44, 144) is, on the one hand, mounted axially movable inside the hollow rod (42, 142), and on the other hand, secured to the solid end (43, 143) of the hollow rod (42, 142) via the active element (45, 145). 6. Injection device (1, 100) according to claim 5, characterized in that the rod (42, 142) has a mechanical elasticity capable of allowing its longitudinal deformation in a reversible manner. 7. Injection device (1, 100) according to one of claims 5 or 6, characterized in that the rear element (46, 146) has a density and a rigidity substantially greater than those of the other components of the outgoing needle (40, 140). 8. Injection device (100) according to any one of claims 1 to 7, characterized in that the active element (145) is magnetostrictive, in that that the rear element (146) is non-magnetic, and that the outgoing needle (140) further comprises two intermediate elements (147, 148) positioned respectively between the rear element (146) and the active element (145 ) on the one hand, and between said active element (145) and the solid end (143) of the rod (142) on the other hand, each intermediate element (147, 148) being made of a magnetic material capable of looping back the lines of the magnetic field used to excite the active element (145). 9. Injection device (1, 100) according to any one of claims 1 to 8, characterized in that it comprises prestressing means (70, 170) capable of permanently compressing the internal bar (44, 144) against the solid end (43, 143) of the hollow rod (42, 142). 10. Injection device (1, 100) according to claim 9, characterized in that the prestressing means (70, 170) comprise a compression spring (71, 171) acting axially on the visible section (48, 148) of the internal bar (44, 144). 11. Injection device (1) according to claim 9, characterized in that the prestressing means (70) comprise, on the one hand, pressurized fluid (72) acting axially on the visible section (48) of the internal bar (44), and on the other hand, a regulating valve (73) capable of limiting the internal pressure of said fluid to a determined value. 12. Injection device (1, 100) according to any one of claims 1 to 11, characterized in that it comprises securing means (80, 180) capable of allowing, on the one hand, immobilization of the outgoing needle (40, 140) relative to the body of the injection device (1, 100) when said outgoing needle (40, 140) undergoes a force whose intensity is less than a given threshold, and on the other hand, the translation of the outgoing needle (40, 140) relative to the body of the injection device (1, 100) when the intensity of the applied force exceeds said threshold. 13. Injection device (1, 100) according to claim 12, characterized in that the securing means (80, 180) comprise: - at least three external grooves (82, 182) formed parallel to one another on the surface of a tubular element (81, 181), forming a shoulder, itself rigidly fixed but removably around the outgoing needle ( 40, 140), each external groove (82, 182) extending in a plane orthogonal to the axis of said outgoing needle (40, 140), - a helical groove (83, 183) formed inside the body of the injection device (1, 100), - And a ball (84, 184) for each external groove (82, 182), each ball (84, 184) being able to cooperate by partial interlocking substantially for half with the corresponding external groove (82, 182) on the one hand , and substantially half with the helical groove (83, 183) on the other hand. 14. Injection device (1, 100) according to claim 13, characterized in that the depth of each external groove (82, 182) is substantially greater than the radius of the corresponding ball (84, 184), in that the depth of the helical groove (83, 183) corresponds substantially to the radius of each ball (84, 184) , and in that each external groove (82, 182) comprises a compression means (85, 185) capable of pushing the ball (84, 184) corresponding to the bottom of the helical groove (83, 183). 15. Injection device (1, 100) according to any one of claims 1 to 14, characterized in that it comprises tensioning means (90, 190) capable of holding the valve (41, 141) of the outgoing needle (40, 140) bearing against its seat (15, 115). 16. Injection device (1, 100) according to claim 15, characterized in that the tensioning means (90, 190) comprise a compression spring (91, 191) which is arranged axially around the needle outgoing (40, 140) and which cooperates by contact, on the one hand, with a part (86, 186) forming a shoulder of the tubular element (81, 181), and on the other hand, with a part (22, 122) forming a stop for the body of the injection device (1, 100). 17. Motor vehicle, characterized in that it comprises at least one injection device (1, 100) according to any one of the preceding claims.