EP0715069A1 - Fuel dispersion skirt, for injector of an injected engine - Google Patents

Abstract

The injector for delivering fuel to two air inlet ducts (2,3) separated by a partition, is situated between the two ducts and has a skirt (12) which is tubular in shape and located inside the partition. The injector (11) is set at the upper end of the skirt, the lower part of which forms two fuel passages (19) which are in communication with one another inside the skirt and emerge into the two ducts through outlets. In the outlet zone the skirt wall is progressively chamfered towards its free edges (17) and has concave recesses, while the upper end of the skirt is shaped to form a seat (14) for the injector. The skirt is made in one piece with the inlet ducts, with the fuel passages and outlets (20) formed round parallel axes.

Description

The invention relates to a skirt for dispersing the fuel which it receives from a multi-jet injector, preferably a twin-jet, and which is transferred into two air intake ducts, separated from one another. by a partition, for supplying a combustion chamber of an internal combustion engine supplied with fuel by injection, and in particular an engine having at least two intake valves per combustion chamber, the injector being arranged substantially between the air ducts, and the skirt having a generally tubular shape and being disposed in the partition, downstream of the injector which it accommodates at least partially in its upstream part, having a shape of revolution preferably, while that at least its downstream part forms two fuel passages, in communication with one another towards the inside of the skirt, each opening into one of the two air ducts respectively through an outlet orifice, and demarcated between two side walls opposite of the skirt.

European patent application EP-A-0 544 978 describes a skirt of this type, produced in the form of an adapter piece which is removably mounted directly in the cylinder head of the engine, and more precisely in a housing provided partly in a partition for forming and separating the two air ducts in the cylinder head of the engine.

This skirt comprises, at its downstream end, a central partition element, which integrates with the partition for forming and separating the air ducts in the cylinder head to extend it, when the removable skirt is placed in the cylinder head, and this central partition element is pierced with a communication opening between the air ducts, at the outlet of the fuel passages of the skirt.

The assembly of the injector and the skirt directly in the cylinder head, as shown in FIGS. 2 and 3a of the aforementioned document, has the disadvantages that the skirt cannot be used as an active diffuser of the fuel coming from the injector, and that the cylinder head is of a more complex embodiment and expensive.

The object of the invention is to remedy these drawbacks, and in particular to propose a fuel dispersion skirt, usable as an active diffuser of the fuel coming from the injector, to ensure better preparation of the air-fuel mixture than that which is obtained with a skirt of the type described in EP-A-0 544 978.

Another object of the invention is to propose a fuel dispersion skirt which is better suited to the various requirements of the practice than those known, and in particular which can be mounted on a manifold or an intake manifold, moreover, of conventional structure.

To this end, the invention provides a dispersion skirt of the type presented above, which is characterized in that at least near the outlet openings of the fuel passages, each of the opposite side walls of the skirt is gradually thinned bevel thickness and / or width decreasing from upstream to downstream to its free downstream edge, thin blade, and in which is provided a concave notch with concavity turned downstream.

The concave indentations in the free edges in thin strips of the opposite walls of the skirt allow the energy contained in the air flow in the adjacent conduits to tear off films of fuel coming from the edges of the bevels, so an excellent preparation of the air-fuel mixture is ensured.

Concave openings with concavity facing downstream are certainly presented by the skirt described in EP-A-0 544 978. But the concave openings are made in the skirt only to clear access to the communication opening made in the central partition element, and to make sure that this skirt does not protrusion in the two air ducts, and does not cause a pressure drop detrimental to the flow of air in these ducts. In addition, the free edges downstream of the side walls do not have the form of thinned and indented blades, in the manner of a whistle, so that the skirt described in EP-A-0 544 978 cannot ensure the correct diffusion of the fuel in the air which is obtained thanks to the specific shape of the skirt of the invention. This good diffusion results, according to the invention, from the presence of the concave notches in the edges of thinned blades of the opposite side walls of the skirt.

When the structure and geometry of the cylinder head and / or the air intake manifold are such that the distance between the injector nose and the corresponding intake valve (s) is relatively large, the dispersion skirt of the invention is advantageously such that each side wall has, upstream of the corresponding concave notch, an area of its internal face intended to be struck by one respectively of the fuel jets coming from the injector.

The skirt thus produced, obtained by adapting its geometry, and in particular its length, to the injector, and in particular to the angle of separation or divergence between the fuel jets leaving the injector, provides an effect post-spray, using the thinned trailing edge of the blades as a post-diffuser. The post-spraying zone is thus brought closer to the intake valve or valves, and an angular refocusing of the fuel jets leaving the injector is obtained by their deflection by the side walls. This structure has the advantages of minimizing the formation of films of liquid fuel on the wall in the extension, called a chapel, of the intake duct in the cylinder head, in the vicinity of the intake valve seat or seats, and of providing more high insensitivity to a variation in the separation angle between the fuel jets leaving the injector.

Of course, when the distance between the injector nose and the corresponding intake valve (s) is not too great, the dispersion skirt may be relatively shorter than in the above variant and / or cooperate with a twin-jet injector for which the angle of separation between the jets is relatively smaller, so that the skirt can let the fuel jets pass freely in the space between its side walls, up to the outlet openings of the passages of fuel, which open into the two air ducts, limiting the post-spraying effect to cases where a liquid film of fuel is formed on the walls of the skirt.

The bevels of the opposite side walls can delimit between them a passage of constant cross section or, preferably, a diverging passage from upstream to downstream, but in no case this passage must be convergent downstream, to obtain the good diffusion of fuel sought.

Each fuel passage can be delimited between one respectively of the opposite lateral walls of the skirt and the partition separating the air ducts, but it is also possible, as known from EP-A-0 544 978, that each passage of fuel is defined between one of the side walls and a central partition element of the skirt, at its downstream end, to separate the two fuel passages from one another as well as the two ducts air.

If it is desired that the axes of the fuel passages are substantially parallel to one another, as well as possibly to the axes of the air ducts, it is advantageous that, according to a first embodiment, the bevels of the opposite side walls are formed at the downstream end portion of a central bore, preferably of revolution of the skirt.

On the other hand, if you want the axes of the fuel passages to diverge from one another downstream, it is advantageous that the bevels of the opposite side walls be formed by a divergent downstream part of a central bore of the skirt.

To this end, the divergent downstream part of the central bore can be connected to a neck, preferably of revolution, and of smaller cross section of this bore, by a substantially radial shoulder, according to a first variant, or can gradually diverge. from the neck of the bore, according to a second variant.

In the various embodiments, and as known per se from EP-A-0 544 978, it is advantageous for the central bore of the skirt to have an upstream end portion of enlarged section forming a seat for the injector.

According to a characteristic specific to the invention, the skirt is in one piece with an element of air intake pipe, comprising at least two air ducts associated with a combustion chamber, and extending between a flange for connection to a plenum of tubing and a flange for fixing to the cylinder head of the engine, flanges in which the conduits each open respectively by an inlet orifice at its upstream end and by an outlet orifice at its downstream end, the skirt being integrated into a partition for forming and separating the two conduits. Of course, a skirt being provided for each combustion chamber of the engine, all the skirts can be, in accordance with the invention, integrated in the air intake manifold to the engine, this manifold having a body made in one part provided with skirts each supporting the corresponding injector, and so that the tubing is presented as a pre-assembled and preset component, fixing directly on the cylinder head of the engine. However, the skirt according to the invention can also be removably mounted in an element of air intake pipe as defined above, in which case the skirt is attached in a housing formed in a partition for forming and separating the two conduits.

Finally, and as known from EP-A-0 544 978, the skirt according to the invention can also be removably mounted in a housing formed in a partition for forming and separating the two air ducts directly in the cylinder head of the engine.

• la figure 1 est une vue schématique en élévation latérale d'un élément de tubulure à deux conduits d'admission d'air et une jupe de dispersion de carburant intégrée,
• la figure 2 est une coupe médiane selon le plan II-II de la figure 1,
• la figure 3 est une coupe transversale selon le plan III-III de la figure 2,
• les figures 4 et 5 sont des vues sensiblement analogues respectivement aux figures 3 et 2 pour une variante de réalisation de la jupe de dispersion de carburant, et
• la figure 6 est une vue analogue à la figure 3 pour une seconde variante de jupe.

Other characteristics and advantages of the invention will emerge from the description given below, without implied limitation, of exemplary embodiments described with reference to the appended drawings in which:

• FIG. 1 is a schematic side elevation view of a tube element with two air intake ducts and an integrated fuel dispersion skirt,
• FIG. 2 is a median section along the plane II-II of FIG. 1,
• FIG. 3 is a cross section along the plane III-III of FIG. 2,
• FIGS. 4 and 5 are views substantially similar respectively to FIGS. 3 and 2 for an alternative embodiment of the fuel dispersion skirt, and
• Figure 6 is a view similar to Figure 3 for a second skirt variant.

Figures 1 to 3 show an air intake manifold element 1, at least partially made of metal or preferably, molded in one piece from a synthetic material such as a thermoplastic, for the supply of air to 'A cylinder or a combustion chamber of an internal combustion engine, supplied with fuel by injection, and of the type comprising for example at least two intake valves per cylinder or combustion chamber.

The tubing element 1 comprises two air ducts 2 and 3 formed substantially side by side in its body 4, and separated from each other by a partition 5 which delimits them in their adjacent parts. Each of the two conduits 2 and 3 is bent, in this example, and extends from a flange 6 of connection to a plenum of tubing (not shown), and in which the duct 2 or 3 opens through an inlet orifice at its upstream end, to a flange 7 for attachment to the cylinder head of the engine, and in which the duct 2 or 3 opens through its outlet orifice 8 at its downstream end. The flange 7 has holes 9 for passage of members for fixing the tubing element 1 to the cylinder head of the engine so that each of the two outlet orifices 8 of the air ducts 2 and 3 is directly opposite the 'respectively one of the two intake valves of the cylinder or of the associated combustion chamber (e). Similarly, the flange 6 has holes 10 for passage of fixing members on the plenum.

When the engine is multicylinder, and for example with four cylinders in line, the tubing can comprise four tubing elements 1 mounted side by side between a common plenum, to which each of them is fixed by its flange 6, and the cylinder head of the motor, to which each is fixed by its flange 7.

The cylinder or the combustion chamber associated with each pipe element 1 is supplied with fuel by an injector, the silhouette of which is shown at 11 in FIGS. 2 and 3, and which is of the multi-jet type , and, in this example, of the twin-jet type, that is to say delivering the fuel in the form of two jets diverging from each other, and each intended to be introduced into one of the two air ducts 2 and 3.

To this end, the injector 11 is engaged and supported by its end delivering the two fuel jets in a tubular skirt 12, disposed in the partition 5 to ensure the dispersion of the fuel which it receives from the injector 11, thus mounted substantially between the two conduits 2 and 3, and the transfer of this fuel to the two air conduits 2 and 3, under conditions suitable for guaranteeing good preparation of the air-fuel mixture for entry into the cylinder head of the engine.

In this example, the skirt 12 is in one piece with the tubing element 1, because it is integrated into the partition 5, by being formed directly in the latter by a substantially cylindrical central bore 13, of substantially axis parallel to the axes of the downstream parts of conduits 2 and 3 (see Figures 2 and 3). The part 14 of the upstream end of the bore 13 has a shape of revolution preferably, of enlarged section, forming a seat for the injector 11, while downstream of the injector 11, the central and downstream parts of the bore 13 are of a substantially constant section.

In the downstream end portion of the bore 13, the skirt 12 is formed by two opposite side walls 15, each of which is progressively thinned by a bevel 16 of thickness and / or width decreasing from upstream to downstream, up to its free downstream edge 17 in thin strip, which has a concave notch 18 with concavity turned downstream and substantially symmetrical with respect to the median diametral plane of the bore 13, corresponding to the section plane III-III of the Figure 2. Between the bevels 16, which diverge downstream relative to each other and relative to the axis of the bore 13, thereby delimiting between them a divergent passage downstream, the opposite side walls 15 delimit two fuel passages 19, in communication with one another in the bore 13 inside the skirt 12, and each opening in one of the conduits 2 and 3 respectively. an outlet 20.

Each outlet orifice 20 is delimited between the notch 18 of one of the bevels 16 and a central partition element 21 with parallel walls, which diametrically extends the skirt 12 at its downstream end, in order to separate one of the other the air ducts 2 and 3 and the fuel jets received by them from passages 19.

The outlet orifices 20 are preferably of parallel axes and obtained by machining, as shown in phantom in Figure 3, simultaneously forming the bevels 16 and the notches 18 in the free edges 17, or by molding, unlike FIG. 9 of EP-A-0 544 978 on which the axes of the fuel passages are inclined by an angle Θ. This solution is, for the desired precision, more economical than the skirt produced in the form of a socket which, according to the teachings of EP-A-0544978, must be machined and brought into the wall which receives it in order to avoid a significant dispersion on the surface of the passage sections due to the non-zero value of the angle Θ.

In addition, the skirt 12 is adapted, in particular in length, to the injector 11 so that each of the two diverging jets of fuel coming from the injector 11, and shown diagrammatically at 22 in FIG. 3, strikes an area 23 located upstream of the bevel 16 and the notch 18 on the internal face of one respectively of the opposite side walls 15.

Thus, each of the fuel jets 22 breaks on a side wall of the skirt 12, and the fuel of this jet is then dispersed and diffused by one respectively of the passages 19 of the skirt 12 in one respectively of the conduits d 'air 2 and 3, in which a good air-fuel mixture is formed, thanks to the whistle configuration given to each outlet orifice 20 of the skirt 12 by the cooperation of the bevel 16, of its free edge 17 in a thinned blade and its concave notch 18.

The skirt 12 thus produces a post-spraying effect by the use of the trailing edges of the thinned blades 17 of its side walls 15 as a post-diffuser, bringing the post-diffusion thus ensured closer to the outlet orifice 8 of the conduits 2 and 3, and therefore the corresponding intake valves, relative to the nose of the injector 11, from which the two fuel jets 22 come out. These jets 22 are moreover angularly refocused by their impact at 23 on the walls 15 This results in a certain compensation for too great a distance separating the nose of the injector 11 from the corresponding intake valve or valves, therefore a formation minimum of liquid fuel films on the wall of the chapelle of the intake duct in the cylinder head, and a relative insensitivity with respect to the angle of separation between the jets 22, the same spraying and preparation qualities of the air-fuel mixture being substantially obtained whether this separation angle is of the order of 18 ° or of the order of 23 °, for example.

Figures 4 and 5 show a variant which differs essentially from the embodiment of Figures 1 to 3 only by the shape of the central bore of the skirt and the structure of the opposite side walls forming the bevels. The latter are in fact formed by a divergent downstream part of the central bore of the skirt.

More specifically, in FIG. 4, the trailing edge in a thinned blade 17 ′ of each side wall 15 ′ of the skirt 12 ′ is formed at the downstream end of a diverging downstream part 13 ′ of the central bore of this skirt 12 ', this diverging part 13' extending axially over the major portion of the length of the skirt 12 'and gradually diverging from a cylindrical neck 24, of smaller cross section of the bore, directly downstream of the housing 14 of enlarged section at the upstream end of the skirt 12 '. Thus, the side walls 15 'are progressively thinned downstream due to the divergent part 13' of the bore and simultaneously the shape of the wall delimiting the air ducts 2 and 3. The central bore 13 ' and the outline of the notch 18 ′ concave in the edge of a thinned blade 17 ′ of a bevel 16 ′ of the skirt 12 ′ are shown in FIG. 5, corresponding to a partial diametral section and folded down in FIG. 4.

The bevels 16 'of this skirt 12' are thus formed by the opposite internal lateral faces of the downstream part of this divergent bore 13 ', and these bevels 16' can arise at the level of the nozzle of the injector 11. In cooperation with a central partition element 21 ', of triangular section widening to the downstream end of the pipe element, these bevels 16 'delimit two fuel passages 19', which are no longer substantially parallel axes, as in the previous example of Figures 1 to 3, but inclined one on the other so that they diverge relative to each other downstream, the fuel diffused by each passage 19 ', after the percussion of the corresponding jet from the injector 11 on the zone 23' of the internal face of the corresponding side wall 15 'followed by its post-spraying on the thinned blade 17' of this wall 15 ', as in the previous example, being substantially guided by the corresponding bevel 16' and the side face facing the central wall element 21 ', which is substantially parallel to this bevel 16'.

In the variant of FIG. 6, the bevels 16 "of the opposite side walls 15" thinned downstream are also delimited on the internal face of a divergent downstream part 13 "of the central bore of the skirt 12", and can also arise at the level of the nose of the injector 11. But this divergent portion of bore 13 "is connected to the cylindrical neck 24 'of the bore by a substantially radial shoulder 25, and, moreover, the end upstream, in the form of a thin strip, of the central wall element 21 "is engaged axially upstream beyond the free edges 17" of the bevels 16 "and between the latter, whereas in the variant of FIGS. 4 and 5, the upstream end of the central wall element 21 'is axially spaced downstream of the free edges 17' of the bevels 16 '.

In the variant of FIG. 6, the divergent fuel passages 19 "are thus better delimited and separated from one another, each between two substantially parallel faces, one of which is a bevel 16" and the other a lateral face of the upstream part of the central wall element 21 ".

A more significant difference compared to the skirt 12 ′ in FIGS. 4 and 5 is that the skirt 12 "in FIG. 6 is sufficiently short, taking into account the angle of separation jets of the injector 11, so that these jets pass freely, as shown in FIG. 6, in the space between the side walls 15 "and in the passages 19" opening into the air ducts 2 and 3. The 12 "skirt therefore produces a post-spraying effect only when a film of liquid fuel is formed on the walls of the 12" skirt.

In the variants of FIGS. 4 to 6, the fuel passages 19 'or 19 ", as well as the bore portions 13' or 13", bevels 16 'or 16 "and free edges 17' or 17" which limit them, and the central partition element 21 'or 21 "can be produced in a simple manner by making cylindrical bores oriented along the inclined axes of the passages 19' or 19", in the partition dividing the air ducts, from the face of the tubing element which is turned towards the cylinder head of the engine, and up to the neck 24 or the shoulder 25, the neck 24 or 24 'and the enlarged upstream end portion 14 being machined from the other side of the tubing element. These cylindrical holes simultaneously produce the notches such as 18 ′, with a concavity facing downstream, in the free edges 17 ′ or 17 ″ of the opposite walls 15 ′ or 15 ″.

As a variant, the fuel passages in the skirts can also be formed by parallel holes in short skirts or even by holes which are inclined relative to one another in long skirts.

In the three examples described above, the skirt 12, 12 ′ or 12 "is directly formed in the partition 5 separating the two air ducts 2 and 3. But, in other variants not shown, the skirt can be produced as described above but in the form of a removable part, which is attached to a tubing element which can have a structure practically identical to that of FIG. 1, with the difference that the skirt is fitted in a tubular housing formed in this partition 5. In another variant, also not shown, such a skirt removable can be attached directly to the cylinder head of the engine, by mounting in a tubular housing formed in a partition which partially delimits and separates two air ducts or channels formed directly in the cylinder head.

Claims (14)

Fuel dispersion skirt received from a multi-jet injector, preferably twin-jet (1), and transferred into two air intake ducts (2, 3) separated by a partition (5), for the supply to a combustion chamber of an internal combustion engine supplied with fuel by injection, and in particular to at least two intake valves per combustion chamber, the injector (11) being disposed substantially between the conduits air (2, 3), and the skirt (12, 12 ', 12 ") having a generally tubular shape and being arranged in the partition (5), downstream of the injector (11) which it accommodates at least partially in its upstream part (14), preferably having a shape of revolution, while at least its downstream part forming two fuel passages (19, 19 ', 19 "), in communication with one another towards the 'interior of the skirt (12, 12', 12 "), each opening into one respectively of the two air ducts (2, 3) by an outlet orifice (20), and delimited between re two opposite side walls (15, 15 ', 15 ") of the skirt (12, 12', 12"),
characterized in that at least near the outlet orifices (20), each of the opposite side walls (15, 15 ', 15 ") is progressively thinned at a bevel (16, 16', 16") in thickness and / or decreasing width from upstream to downstream to its free downstream edge (17, 17 ', 17 "), in thin strip, and in which is formed a notch (18, 18')) concave with turned concavity downstream. Skirt according to claim 1, characterized in that each side wall (15, 15 ') has, upstream of the corresponding concave notch (18, 18'), an area (23, 23 ') of its internal face intended to be struck by at least one jet (22) of fuel from the injector (11). Skirt according to either of Claims 1 and 2, characterized in that the bevels (16, 16 ', 16 ") of the side walls (15, 15', 15") define a passage between them diverge from upstream to downstream. Skirt according to one of claims 1 to 3, characterized in that the outlet orifice (20) of each fuel passage (19, 19 ', 19 ") is delimited between one respectively of the opposite side walls (15 , 15 ', 15 ") and a central partition element (21, 21', 21"), at the downstream end of the skirt (12, 12 ', 12 "), to separate the fuel passages (19, 19 ', 19 ") and air ducts (2, 3). Skirt according to one of claims 1 to 4, characterized in that the bevels (16) of the opposite side walls (15) are formed at the downstream end part of a central bore (13), preferably of revolution, of the skirt (12). Skirt according to one of Claims 1 to 4, characterized in that the bevels (16 ', 16 ") of the opposite side walls (15', 15") are formed by a divergent downstream part (13 ', 13 ") d 'a central bore of the skirt (12', 12 "). Skirt according to claim 6, characterized in that the divergent downstream part (13 ") is connected to a neck (24 '), preferably of revolution, and of smaller cross section of the central bore of the skirt (12" ) by a substantially radial shoulder (25). Skirt according to claim 6, characterized in that the diverging downstream part (13 ') of the central bore diverges progressively from a neck (24), preferably of revolution, and of smaller cross section of this central bore. Skirt according to any one of Claims 6 to 8, characterized in that the bevels (16 ', 16 ") of the opposite side walls (15', 15") arise at the level of the injector nose (11). Skirt according to any one of Claims 5 to 9, characterized in that its central bore has an upstream end portion of enlarged section forming a seat (14) for the injector (11). Skirt according to any one of Claims 1 to 10, characterized in that it is in one piece with an air intake tube element (1), comprising at least two air ducts (2, 3) associated with a combustion chamber, and extending between a flange (6) for connection to a plenum of pipe and a flange (7) for fixing to the cylinder head of the engine, flanges (6, 7) in which the conduits (2, 3) each open out respectively through an inlet orifice at its upstream end and through an outlet orifice (8) at its downstream end, the skirt (12, 12 ', 12 ") being integrated into a partition (5 ) forming and separating the two conduits (2, 3). Skirt according to any one of Claims 1 to 11, characterized in that the fuel passages (19) and their outlet orifices (20) are formed around axes substantially parallel to one another. Skirt according to any one of claims 1 to 10, characterized in that it is removably mounted in an air intake tubing element (1), comprising at least two associated air ducts (2, 3) to a combustion chamber, and extending between a flange (6) for connection to a plenum of pipe and a flange (7) for fixing to the cylinder head of the engine, flanges (6, 7) in which the conduits (2, 3) each open respectively by an inlet orifice at its upstream end and by an outlet orifice (8) at its downstream end, the skirt being added in a housing formed in a partition (5) for forming and separating the two conduits (2, 3). Skirt according to any one of claims 1 to 10, characterized in that it is removably mounted in a housing formed in a partition for forming and separating the two air ducts directly in the cylinder head of the engine.

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