WO2002035085A1

WO2002035085A1 - Safety valve for a system for measured fluid dispensing

Info

Publication number: WO2002035085A1
Application number: PCT/FR2001/003242
Authority: WO
Inventors: Nicolas Delmas; Philippe Masson
Original assignee: Renault
Priority date: 2000-10-27
Filing date: 2001-10-19
Publication date: 2002-05-02
Also published as: EP1336049A1; DE60123106T2; FR2816009A1; EP1336049B1; FR2816009B1; DE60123106D1

Abstract

The invention concerns a safety valve, designed to equip a system for measured fluid dispensing powered with pressurised fuel by a supply conduit and provided with a projecting rod (4) which forms a discharge valve with a first seat (7). The valve comprises at least two separate parts (9, 10), a first part forming a second seat (9), said second seat (9) being formed at the end of the fuel supply conduit and capable of co-operating with a second part, called mobile part (10), which constitutes closure means, said closure means (10) being mobile under the action of translating means (5) so as to be urged to co-operate with the second seat (9), and seal the supply conduit.

Description

SAFETY VALVE FOR DOSED DELIVERY SYSTEM OF

FLUIDS

The present invention relates to a safety valve intended to equip a fluid spraying system.

The present invention relates more particularly to a safety valve, integrated into a system used for the metered delivery of fluids, and making it possible to act, in the event of a malfunction of the shutter means of the aforementioned device, on the flow of injected fluid.

Such a system can, for example, be used in an injection device such as that described in patent application FR 99-14548, filed by the Applicant.

By this document, a particular device is known, intended for spraying fluids in the fuel injection systems of a motor vehicle, and characterized in particular in that a rod or needle deforms elastically under the stress of ultrasonic waves, so as to define at its end an annular ejection slot relative to a valve seat. More specifically, the aforementioned needle is of the outgoing or suspended type and cooperates at its other end with a mass and elastic return means housed in a cavity formed in the rear part of the housing of the injector.

The tightness of the valve formed by said needle on its seat is then ensured by the efforts of traction, exerted by the aforementioned elastic return means on the needle.

The device thus described is intended to be supplied by a pressurized fluid. In particular, the body of the injector is permanently filled with fluid and the shutter means formed by the valve on its seat seal the system at rest when no deformation is applied to the needle.

Unlike a conventional injector, an outgoing needle injector is therefore characterized by the fact that the needle is subjected to tensile stresses. In addition, in the particular case of patent application FR 99-14548, the opening is generated by deformations of the needle. Thus, in order to improve the efficiency of the device, it is necessary that said needle has a relatively small section so as to reduce the amount of energy required to open the valve.

All of the features of the device set out above, contribute to increasing the risk of the needle breaking in fatigue compared to a conventional injector. However, in the case of a rupture of the needle, the head of said needle which forms the valve shutter means is no longer kept in contact against the end of the seat and the tightness of the system at rest n is then more assured.

A drawback of the device described in patent application FR 99-14548 stems from the fact that in the event of the needle head breaking, no means of regulation is provided in order to avoid the uninterrupted injection of fuel under pressure inside the combustion chamber.

The object of the present invention is therefore to propose the production of a safety valve, making it possible to avoid the aforementioned problems, in the event of a needle rupture on an injector with outgoing needle.

According to a particular embodiment of the present invention, the stress generated by the elastic return means of the needle is used to actuate and maintain a safety valve in the high pressure supply circuit. More precisely, the initial prestressing, necessary to ensure the tightness of the valve seat, and to which the needle is subjected, is transferred, when said needle breaks, to the safety valve.

According to the same embodiment, said valve is formed, on the one hand, of a movable part whose end is at least partially spherical, and on the other hand, of a fixed seat, which may be of shape conical, shaped in the end of the channel intended to supply the injector with fuel, so that, in the event of rupture of the needle, the abovementioned spherical part, initially detached from its seat, comes to cooperate with said seat under the action of the forces generated by the elastic return means, and thus obstruct the channel through which the fuel arrives, thus preventing the said fuel from spilling inside the cylinder.

According to another characteristic of the present invention, the movable part of the valve is shaped on the end of a mass which constitutes the mechanism for break in impedance as described in patent application FR99-14548.

According to another characteristic of the invention, the translation of the aforementioned mass under the action of elastic return forces, in the event of a rupture of the needle, causes a translation of the movable part of the valve, so that the spherical end of said movable part comes to cooperate with the conical fixed part and thus causes the filling channel of the injector to be closed.

According to another characteristic of the invention, the fuel supply channel has a substantially smaller outlet section than the nose of the injector.

The objects, aspects and advantages of the present invention will be better understood from the description given below of two embodiments, presented without limitation, with reference to the accompanying drawings, in which: FIG. 1 represents a first embodiment of the safety valve, object of the present invention, the valve being open,

FIG. 2 represents the same view as FIG. 1, the valve being closed, FIG. 3 represents a second embodiment of the safety valve, the valve being open,

- Figure 4 shows the same view as Figure 1, the valve being closed, Figure 5 shows a sectional view of particular elements, the mass and the return means elastic of the injection system according to the second embodiment, according to different positions, so as to explain the principle of operation of the present invention. In the various figures, the common elements are represented with the same reference.

Referring to Figure 1, we have detailed a first particular embodiment of the safety valve object of the invention, in the case of integration into a metered delivery system of fluid as described in the patent application FR 99-14548, filed by the Applicant.

The injection system consists of an injector body 3 comprising an interior cavity 15 in which are arranged elastic return means 1, which exert a prestress on a rod 4, by means of a mass 5, integral with a first end, said rod 4, over a fixed length.

The other end of the rod 4 comprises a head 6 resting on a valve seat 7 disposed on the injector body 3. The system thus forms a valve which ensures at rest the seal of the injector nose.

In fact, when the injector is in operation, the internal cavity 15 of the body of the injector 3 is filled with fuel under pressure, so that the forces exerted by the fluid are distributed, at the level of the head 6 of the rod 4, on a section surface denoted SI. The utility of the prestressing exerted by the elastic return means 1 is to oppose the aforementioned forces in order to avoid detachment of the said head 6 of the rod 4 relative to the valve seat 7 under the action of pressure forces.

In practice, this preload is increased to compensate for play and to guarantee a total seal, which does not only result in a macroscopic equilibrium of the forces exerted on the head of the rod.

The internal cavity 15 of the injector housing 3 is intended to be closed by means of a closing member 12 inside which is formed a bore 8. The supply of pressurized fuel to the injector housing 3 is carried out by means of the bore 8 which opens into the internal cavity 15 of the injector housing 3 by forming an orifice, or seat 9. According to the first embodiment, the valve consists of two elements, the first consists by the seat 9, the second by a shutter means 10 which is integral with the mass 5 and extends over one end of the latter, said mass 5 cooperating in abutment with the elastic return means 1 on the opposite end, the said elastic return means 1 themselves being supported on the bottom of the internal cavity 15 of the injector housing 3.

The shutter means 10 has an upper part 11 which is at least partially conical and preferably spherical, which may, for example, be produced using a ball bearing ball, preferably of low grade (<10) so as to benefit of a good surface condition guaranteeing a good seal when being pressed on the seat 9. Said bore 8 is produced so that at least the seat 9 thus obtained is aligned with the shutter means 10, so that the upper part 11 of the shutter means 10 can come to cooperate with the seat 9 when a vertical translation along the orientation referenced A is applied to the mass 5. Said means for translating the mass 5 are provided by the elastic return means 1 when a rupture occurs in the rod. In the initial position of the device, as shown in FIG. 1, the mass 5 is in equilibrium under the joint action of the forces generated by the elastic return means 1 and the efforts to retain the rod 4 due to the action of the head 6 of the rod 4 on the valve seat 7. The upper end 11 of the shutter means 10 then defines with the seat 9, a distance e2. In the case of normal operation of the injector, the shutter means 10 therefore does not prevent the free circulation of fuel. As long as the rod 4 is not broken, the fuel flows freely through the conduit 8. It should be emphasized that it is not the pressure forces which generate the opening of the safety valve.

On the other hand, if a rupture of the rod 4 occurs as shown in FIG. 2, the mechanical equilibrium of the mass 5 is broken. Subjected then to the only force generated by the elastic return means 1, the mass 5 translates in orientation A until the shutter means 10 comes to cooperate with the seat 9 so as to cause the obstruction of the bore 8, that is to say of the fuel supply channel. In this case, the contact section between the upper part 11 of the shutter means 10 and the pressurized fluid is denoted S2. The value of the forces exerted by the pressurized fluid on the valve is therefore dependent on this value S2.

In order for the valve to be sealed for a fixed supply pressure P, it is necessary to comply with certain conditions for producing said valve, and in particular, an essential condition lies in the fact that the aforementioned section S2 is less than the Si section.

Indeed, if it is assumed that the initial tensile force FI exerted on the rod 4 by the elastic return means 1, which can be considered to have a stiffness K, compressed with a length Δx makes it possible to ensure the sealing of the injector nose, said nose being supplied under a pressure P. Knowing also that said pressure P exerts a force at the head 6 of the rod 4 on a cross-sectional area denoted SI, it comes:

During the rupture of the rod 4, we have noted e2 the displacement to be applied to the shutter means 10 before the latter comes to cooperate with the seat 9.

It follows that the force F2 generated by the elastic material 1 on the movable part 10 of the safety valve after the rupture of the rod 4 becomes:

If we assume that the stress to be applied to the valve to ensure its tightness must be at least equal to, or even greater than, that which ensures the tightness of the nose, it comes:

A condition for sealing the valve on its seat is then obtained by combining (1), (2) and (3):

Kx {Ax- e2) x Sl> Kx {àx) x S2

Which equals :

Δx -e2 S2

S2 <x SI and therefore - <1

Ax SI

In FIG. 3, which represents a second embodiment of the present invention, there is an architecture similar to that described in FIGS. 1 and 2, except that the shutter means 10 are no longer secured to the mass 5, and that secondary elastic return means 2 have been added between the closure member 12 of the injector housing 3 and the mass 5.

The aforementioned shutter means 10 always consists of a member of at least partially spherical shape, for example a ball bearing ball. It is placed, free in translation in direction A, inside a sheath 13 which extends between the seat 9, and the end of a pin 14 shaped on the mass 5, the sheath 13 having each of its ends an obviously annular diameter substantially smaller than that of the shutter means 10, so as to define two extreme positions between which the shutter means 10 can move.

The sleeve 13 is integrally connected at one of its two ends with the cover 12. The axis of the sleeve 13 is aligned with the seat 9, so that the shutter means 10, under the action of a translation oriented along A can cooperate with seat 9.

The second section narrowing, shaped at the other end of the sheath, defines a second annular space inside which the cylindrical pin 14 can slide, the latter being integral with the end of the mass 5.

The length of the cylindrical pin 14 is adapted so as to cause, in the event of a rupture of the rod 4, the translation of the shutter means 10 along A, until the shutter means 10 comes to cooperate with the seat 9. The means for translating the pin 14 are provided by the forces generated by the elastic material 1 on the mass 5. The valve system thus formed therefore makes it possible to block the fuel supply channel, that is to say the bore 8, generating a closure of the seat 9 by the closure means 10 during a rupture of the rod 4.

In the rest position of the system, shown in Figure 3, the shutter means 10 rests on the lower part of the sleeve 13 and the upper surface 11 of the shutter means 10 defines with the orifice 9 of the bore 8 a game e2. In the same position, the lower part of the shutter means 10 defines with the end of the cylindrical pin 14 a clearance el. In the event of the rod 4 breaking, the mass 5 moves in orientation A under the action of the elastic return means 1. This displacement fills the clearance el, then the pin 14 comes into contact with the shutter means 10 and push the latter in orientation A until the gap e2 is completely filled. The bore 8 is then closed, as shown in FIG. 4.

The sealing condition of the valve can then be expressed by taking stock of the forces exerted by the mass 5 on the shutter means 10.

FIG. 5 represents different positions of the mass 5 (shown in solid lines), and elastic return means 1 and secondary elastic return means 2 (shown in dotted lines) for a better understanding of the operating principle of the second mode of realization of the invention. Also shown on this diagram are the external forces applied to mass 5.

Denote by FI the force exerted by the elastic return means 1 of stiffness K, initially compressed by a length XI.

Denote by F2 the force exerted by the elastic material 2 of stiffness K is initially compressed by a length X2. When the rod 4 breaks, the balance of forces on the mass 5 is then written:

FI = K. (X1 - el - e2) F2 = K. (X2 + el + e2) The shutter means 10 is therefore subjected to a force F3, obtained by difference between FI and F2:

F3 = K. [(Xl-X2) -2 (el + e2)]

This force is opposed to the pressure forces which apply at the level of the orifice 9 of the bore 8, on a section S2.

To guarantee the seal between the seat 9 and the shutter means 10, it is considered that the same stress must be applied as that calculated to ensure the seal between the head of the rod 4 and the valve seat 7, it therefore comes :

F l, e.te _ F ob _k turateur F <e _t t _f e = Kx ⁽ X, 1-X ₇ 2) /

° the shutter ° head I

F _obιrateUr = Kx [{X _x -X _l ) -2x {e, Ae ₁ )}

° shutter 2

Therefore we must have

S, <(l- ^{2 (gl + g2)} ) xS,

- N, -N ₂

In accordance with the previous case, the functionality of the system is dependent on the ratio of sections SI and S2.

With this second embodiment of the valve, an essential advantage is obtained in that the hydrodynamic forces generated on the shutter means by the flow of the fluid through the orifice do not risk generating forces on the mass and thus modify the preload applied to the rod.

Another advantage of this embodiment comes from the fact that the guiding in translation of the part mobile shutter means is no longer provided by the mass but by the sleeve, which reduces the guiding constraints in translation of the mass.

At the same time, the presence of a clearance el makes it possible to absorb possible variations in height of the mass, caused for example by phenomena of thermal expansion, without this modifying the flow rate of the valve in the open position.

Another advantage of this second embodiment is to allow decoupling in the production of the movable part of the shutter means of the safety valve and that of the mass. Thus, the use of a calibrated ball bearing ball as a shutter means no longer requires, for example, taking into account the means for fixing said ball to the solid.

Finally, the possible variation in thickness between the upper part of the mass can be easily taken into account by modifying the height of the pin, shaped at the end of the mass.

For all these reasons, this second embodiment of the safety valve is particularly suitable in the case of integration into a fluid spraying device, as described in patent application FR99-14548, filed by the Applicant.

Of course, the invention is in no way limited to the embodiments described and illustrated which have been given only by way of example. On the contrary, the invention includes all the technical equivalents of the means described as well as their combinations if these are carried out according to the spirit.

Claims

CLAIMS:

[1] Safety valve, intended to equip a metered fluid delivery system supplied with fuel under pressure via a supply conduit and equipped with an outgoing rod (4) which forms an ejection valve with a first seat ( 7), characterized in that it comprises at least two distinct parts (9,10), a first part forming a second seat (9), said second seat (9) being shaped at the end of the supply conduit in fuel and able to cooperate with a second part, called the mobile part (10), which constitutes the shutter means, said shutter means (10) being able to move under the action of translation means (5) in order to cooperate with the second seat (9), and close the supply conduit.

[2] Safety valve according to claim 1, characterized in that the shutter means (10) are actuated in the event of breakage of the rod (4).

[3] Safety valve according to claim 3, characterized in that said translation means (5) comprise a mass (5) connected to the rod (4) and which, under the action of elastic return means ( 1), exert a force on the rod (4) which, in the absence of breakage of the rod (4), tends to maintain at least part of the rod (4) against the first seat (7).

[4] Safety valve according to any one of claims 1 to 3, characterized in that the second seat (9) and the shutter means (10) are shaped so that the contact surface between said second seat (9) and said shutter means (10) are of the cone-on-sphere type.

[5] Safety valve according to any one of claims 1 to 4, characterized in that the shutter means (10) are produced using a calibrated rolling ball.

[6] Safety valve according to any one of claims 1 to 5, characterized in that the shutter means (10) are integrally linked to the translation means (5).

[7] Safety valve according to any one of claims 1 to 6, characterized in that the shutter means (10) are free in translation inside a guide sheath (13), and can cooperate with translation means (5).

[8] Safety valve according to claim 7, characterized in that in the absence of breakage of the rod (4), the shutter means (10) and the translation means (5) are separated by a distance not zero.

[9] Safety valve claim 8, characterized in that the separation of the shutter means

(10) and translation means (5) is obtained by secondary elastic return means (2) adapted to exert a force on the translation means (5) substantially in the same direction as that exerted by the means elastic return (1) and opposite direction.