EP2836697A1

EP2836697A1 - Fuel injection rail for an internal combustion engine

Info

Publication number: EP2836697A1
Application number: EP13719991.5A
Authority: EP
Inventors: Pascal Guerry; Adrien EUSTACHE; Patrick Barbe
Original assignee: Renault SAS; MGI Coutier SA
Current assignee: Renault SAS; Akwel SA
Priority date: 2012-04-10
Filing date: 2013-04-10
Publication date: 2015-02-18
Also published as: FR2989122A1; JP2015513042A; IN2014DN08311A; WO2013153324A1; BR112014024950A8; CN104246202A; BR112014024950A2; FR2989122B1

Abstract

This injection rail (1) is suitable for dampening pressure variations. To this end, it is produced with a plug (8) of variable thickness (e) constituting a deformation zone, at at least one of the ends (4) of same, and/or with an oblong section, or indeed with a section divided into two volumes by a longitudinal inner rib. Application in the motor vehicle industry.

Description

FUEL INJECTION RAMP FOR

INTERNAL COMBUSTION ENGINE

The present invention relates to fuel injection ramps for internal combustion engines, especially gasoline motor vehicles.

An injection ramp makes it possible to supply the various cylinders of an internal combustion engine with fuel by means of injectors associated with the various cylinders, the injectors being alternately open and closed as a function of time, according to the cycle of the engine.

Each injector thus periodically communicates a zone full of gasoline under pressure, typically at a pressure of about 7 bar, with the interior of the corresponding cylinder which is an air-filled zone at a pressure of between 1 and 2. bar. This communication creates, in essence, a pressure wave that propagates in the injection manifold.

In a global manner, the multiple reflections of such pressure waves in the injectors and in the ducts create pressure variations in the injectors, which modifies the quantity of gasoline injected into the opening phases of the injectors.

In the steady state of the motor, it is possible to adapt the opening times of inj ecteu rs to compensate for the previously mentioned disturbing phenomena. This solution makes it possible to compensate the differences in fuel dosage, but it prevents identical settings for each cylinder. Above all, such a solution is not appropriate for transient engine settings, that is, when switching from one mode to another.

At high frequencies, there is interference between the waves generated by the different injectors. Solutions are known to use these interferences to reduce pressure variations. However, such solutions are not applicable effectively at low frequencies, the distances between the injectors being too small. Other solutions must therefore be sought to limit pressure variations at low frequencies, typically between 0 and 100 Hz.

A first type of solution uses an active control, by implementing a pressure generator creating a wave in opposition of phase with the wave to be damped. These active control solutions, an example of which is provided by US Pat. No. 6,705,278, are very effective but they still still require complex and expensive equipment, including a calculator for the real-time calculation of the phase shift, a pressure generator with rapid response times, and means for the power supply of the pressure generator.

A second type of known solutions, aiming at limiting the variations of low frequency pressions, so as to be able to take advantage of the "deformation" of a fluid, in this case the fuel itself, or more usually the deformation of components of the injection system in contact with the fluid such as ramp, pipes or injectors, under the effect of pressure. These solutions which utilize the deformation, in particular by increasing the volumic flexibility of the assembly formed by the fluid and the surrounding structure, are simpler and more economical, in particular because they are "passive" and thus do not require no external energy supply, especially electrical.

These latter solutions may consist of increasing the flexibility of existing components of the structure, at least in certain areas of these components that are in contact with the fluid. In particular, it is possible to increase the flexibility of the injection manifold itself, as taught in JP 2009-257282.

In this case, it is necessary to find a good compromise between the flexibility on the one hand and the mechanical resistance on the other hand. The search for flexibility leads to a reduction in thickness and the choice of plastics rather than metals or metal alloys. However, to obtain sufficient mechanical strength, it would be necessary instead to increase the thicknesses, which is difficult to envisage with plastics, given the usual manufacturing processes, in particular injection molding.

A variant of these solutions consists in using the deformation of a flexible additional part or part, in contact with the fluid. Thus, these solutions may consist in the addition of foam parts inside the injection rail, in contact with the wall thereof, as shown in patent DE 10 2004 037 133. It is also possible to place soft damping elements in the very heart of the injection rail, as shown in patent EP 2 206 913. Another type of known solution consists in associating an increase in flexibility with a restriction in the flow of the fluid. The restriction can be created by a simple constriction (see US Pat. No. 7,146,965, FIG. 2A) or by a valve (see patent JP 2008-057447).

The present invention aims to provide improved solutions, particularly simple and economical, to better control the flexibility of the volume and the mechanical strength of an injection rail, adapting it to the need for damping pressure variations, this while respecting the manufacturing process by plastic injection molding, for plastic ramps.

For this purpose, the subject of the invention is a fuel injection ramp for an internal combustion engine, the injection ramp being adapted to damp the pressure variations, this injection ramp being made at least with a plug of variable thickness constituting a deformation zone, at least at one of its ends, and / or with a section of oblong shape, over its entire length, said section being divided into two volumes by a longitudinal inner rib.

Thus, according to a first aspect of the present invention, the injection rail has a plug of adapted configuration. Since it is a plastic ramp, it is usually made of two separately molded parts, namely a cylindrical ramp body and a plug which closes the body at at least one end of the injection ramp. The stopper is usually a flat part of constant thickness, on which a pipette is grafted. From there, the inventive idea is to dissociate the pipette from the plug, by placing it in another zone of the injection manifold, and to use the plug as deformation zone adapted to damp the pressure variations. This plug is then made with a variable material thickness, for example a greater thickness at its center and lower at its periphery, which makes it possible to form an iso-constrained deformation zone. In other words, a central portion of the plug is thicker than a peripheral portion of the plug.

Such a plug of variable thickness may be provided at one end of the injection rail, or at both ends of this ramp, that is to say at each of the two ends of the injection rail. At the end or at each end of the injection ramp, this ramp may have an enlargement resulting in particular from a flared shape, so as to increase the surface of the plug provided at this end and consequently the effectiveness of said cap in its function of damping pressure variations.

In addition, from the point of view of the manufacturing process, a plastic injection in the center of the plug allows to obtain varying thicknesses between the center and the periphery, while having a uniform filling of the mold.

According to a second aspect of the invention, which may or may not be combined with the first aspect, the injection rail has an oblong cross-section along the entire length of the injection rail. Such a section, resulting in particular from two opposite parts of substantially semi-cylindrical shape joined by two other substantially flat parts, combines the strong resistance of the semi-cylindrical parts to the deformability of the flat parts. The deformability of the injection rail is thus increased, while controlling the stress. In particular, the preferred sectional shape has the advantage of being easy to control, with respect to an elliptical shape or with respect to a rectangular shape that would provide undesirable stress concentrations.

Advantageously, in the case of such an injection ramp with oblong section, the two substantially flat portions are slightly concave section, so curved profile towards the inside of the ramp. Thus, these parts are "predeformed" and, under the effect of an increase in the internal pressure, they deform first, then causing a widening of the two semi-cylindrical parts while separating these semi-cylindrical parts one of the other.

According to one embodiment of the invention, the injection ramp is made with a section divided into two volumes by a longitudinal internal rib.

The choice of a section of oblong shape, without division of this section in two volumes, makes it possible in particular to increase the flexibility of injection ramps of relatively small diameter, without reducing the wall thickness of these ramps, which is advantageous in that too small plastics thicknesses are difficult to injection mold.

Conversely, the choice of a divided section in two volumes makes it possible to increase the mechanical strength of the injection manifold without increase the thickness of the walls, which avoids an increase in manufacturing time by molding and therefore an increase in the cost of the injection ramps.

In the latter case, the injection manifold is advantageously like the union of two cylindrical parts, arranged symmetrically and connected along a flat median rib forming the longitudinal internal rib and separating the two volumes. Two parallel internal volumes are thus created, separated from each other by the flat median rib, these two volumes being able to communicate with each other at at least one end of the injection rail receiving a plug.

This last embodiment of double volume is particularly suitable when needed a very large damping capacity.

The choice of a section of oblong shape, or a division into two volumes, may or may not be combined with a plug of variable thickness constituting a deformation zone, as defined above.

The invention will in any case be better understood, and other characteristics will be highlighted, with the aid of the description which follows, with reference to the appended schematic drawing representing, by way of example, some embodiments of FIG. this fuel injection ramp:

Figure 1 shows, very schematically, a conventional injection rail;

Figure 2 shows, similarly, an injection rail according to the present invention, with a single plug constituting a deformation zone;

Figure 3 illustrates a first variant of this injection rail;

Figure 4 illustrates a second variant, with two plugs;

Figure 5 shows, in section and on an enlarged scale, one end of the ramp with its plug of variable thickness;

Figure 6 shows, in cross section, an oblong section injection ramp, according to the present invention;

Figure 7 shows, in cross section, a variant of the oblong section injection rail;

Figure 8 illustrates the deformation of the injection ramp of the figure Figure 9 is another cross-sectional view of the injection manifold of Figures 7 and 8, in line with an injector housing;

Figure 10 is a cross-sectional view of another embodiment, in which the injection manifold is divided internally into two volumes.

Referring to FIG. 1, a conventional injection rail 1 comprises a body 2 cylindrical along the length, the two ends of which are designated 3 and 4, respectively. The first end 3 is closed off by a plug 5. 6. The body 2 laterally has a series of housings 7 open on the outside, in which are placed four injectors (not shown) in the illustrated example. .

An injection rail 1 according to the invention, as shown in FIG. 2, has a plug 8 of variable thickness (as specified below) placed at the second extremity 4 of the body 2, this extremity 4 being opposite. to that 3 receiving the pipette 6. In this embodiment, the body 2 of the injection rail 1 retains a cylindrical shape, from one end 3 to the other 4.

In a first variant, illustrated in Figure 3, the second end 4 of the body 2 of the injection rail 1 is enlarged, this end 4 having a flared shape. The surface of the plug 8 placed at this end 4 is thus increased.

In a second variant, illustrated in FIG. 4, a first plug 9 of variable thickness is provided at the first end 3 of the body 2 of the injection manifold 1, and a second plug 10 of variable thickness is provided at the second end 4 of the body 2 of the same injection rail 1. In this second variant, the pipette 6 is connected laterally to the body 2 of the injection rail 1.

FIG. 5 represents, on a larger scale, an end 4 of the body 2 of the injection rail 1, with its plug 8 of variable thickness e. The thickness e is here greater in the center of the plug 8 and lower at the periphery of this plug 8, with a gradual decrease in the radial direction, as the distance from the central axis A of the ramp .

Made of molded plastic, the plug 8 is welded to the corresponding end 4 of the body 2 of the ramp. The plug 8, or each of the two plugs 9 and 10, constitutes a zone of deformation which occurs during the operation of the injection manifold 1, so as to damp the pressure variations inside said ramp.

FIG. 6 shows another embodiment, in which the damping of pressure variations is obtained by conferring on the body 2 of the injection molding machine an oblong-shaped section, favoring its deformation. This oblong section results from two opposite parts 1 1 and 12 of semi-cylindrical shape which are joined by two parts 1 3 and 14 of flat shape, parallel to each other. Of course, the plug (not shown) placed at one end of this rpm has a corresponding oblong shape.

In a variant, shown in FIGS. 7 and 8, the body 2 of the injection rail 1 retains a section of oblong shape, but the two parts 13 and 14, which join the parts 1 1 and 12 of semi-cylindrical shape , themselves have a curved profile. More particularly, the two parts 1 3 and 14 are here of concave section and curved towards the inside of the injection manifold 1, at least in the absence of pressure inside this ramp (see FIG. and the dashed line in Figure 8). Under the effect of an internal pressure, the two parts 1 3 and 14 initially curved inward deform outwards and this deformation causes itself to widen the two parts 1 1 and 1 2 semi form -cylindrical and their spacing from each other (see the dashed line in Figure 8).

As shown in Figure 9, in such an injection ramp 1 of oblong section, one of the two parts 1 1 and 12 of substantially semicylindrical shape may comprise internally a flat surface 1 5, extending long itud inally at the level of housing 7 injectors. Such a configuration is advantageous in relation to the manufacturing process of the body 2 of the injection rail 1 by plastic molding. The inside of the body 2 is formed by a main pin which is removed at the end of the injection of the plastic material. Secondary pins are used to form the housings 7 of the injectors, these secondary pins to come into contact with the main pin to prevent plastic penetration between these pins, the outlet of the housing 7. To simplify the manufacturing process and makes it Because it is more reliable, it is preferable for the secondary pins to rest on a flat, non-curved part of the spindle. main. This flat part must itself be present over the entire length of the body 2 of the ramp, to allow demolding with removal of the main spindle, which justifies the development of the flat bearing 1 5 which extends longitudinally in passing over all the injector locations. This configuration can also contribute to the volume flexibility of the ramp, while retaining sufficient strength.

Finally, FIG. 10 shows a last embodiment in which the injection manifold 1 or at least its body 2 is divided into two voids 1 6 and 1 7, by separating the second one from the one on the other. Especially, the body 2 of the ramp is here as the meeting of two cylindrical portions 1 8 and 1 9 symmetrical to each other, connected in a longitudinal central rib 20 oriented longitudinally.

From the axis A of one or other of the two cylindrical portions 18 and 19, the planar midrib 20 is advantageously seen at an angle α of about 68 °. The choice of such an angle optimizes the realization, in the sense of obtaining an identical stress throughout the body section 2 of the injection rail (for a rib 20 of the same thickness as the two parts cylindrical 18 and 19).

In a manner not shown, the two vol umes 1 6 and 1 7 separated by the rib 20 can communicate with each other, especially at the end of the ramp receiving the plug. This plug may itself be of varying thickness, as described above.

It goes without saying that the invention is not limited to the embodiments of this fuel injection rail which have been described above, by way of examples; it embraces, on the contrary, all variants of implementation and application respecting the same principle. It is thus, in particular, that one would not depart from the scope of the invention by modifying the forms of detail of the ramp and its various parts, or by adapting this ramp for example to a number of injectors different.

Claims

1. Fuel injection rail for an internal combustion engine, the injection rail (1) being adapted to damp the pressure variations, characterized in that it is produced with at least one plug (8, 9, 10) of variable thickness (e) constituting a zone of deformation at least at one of its ends (3, 4), and / or with an oblong cross-section along its entire length, said section being able to be divided into two volumes (16, 17) by a longitudinal internal rib (20).

2. Injection rail according to claim 1, characterized in that the or each plug (8, 9, 1 0) is made with a thickness (e) greater in its center and lower at its periphery.

3. Injection rail according to claim 1 or 2, characterized in that the plug (8) of variable thickness (e) is provided at one end (4) of the injection rail (1), this end (4) being opposed to that (3) receiving a pipette (6). 4. Injection rail according to claim 1 or 2, characterized in that a plug (9, 1 0) of variable thickness (e) is provided at each of the two ends (3,

4) of the injection rail (1), a pipette (6) being connected laterally to a body (2) of the injection rail (1).

Injection rail according to any one of claims 1 to

4, characterized in that it has, at one extremity (4) or at each end (3, 4), an enlargement resulting in particular from a flared shape, so as to increase the surface of the plug (8, 9, 10) provided at this end.

6. Injection rail according to any one of claims 1 to

5, characterized in that it has a section of oblong shape resulting from two opposite parts (1 1, 1 2) of substantially semi-cylindrical shape joined by two other parts (13, 14) of substantially flat shape.

7. Injection rail according to claim 6, characterized in that the two parts (1 3, 14) substantially flat are slightly concave section, so curved inward profile of the ramp (1).

8. Injection rail according to claim 6 or 7, characterized in that one of the two parts (1 1, 12) of substantially semi-cylindrical shape internally comprises a plane bearing (15) extending longitudinally at the level of housings (7) of injectors.

9. Injection rail according to claim 10, characterized in that it is carried out with a section divided into two volumes (16, 17) by a longitudinal internal rib (20), the injection rail being presented as the meeting two cylindrical parts (1 8, 19), arranged symmetrically and connected in a plane central rib forming the longitudinal internal rib (20) and separating the two volumes (16, 17).

Injection rail according to claim 9, characterized in that the planar median rib (20) is viewed from the axis (A) of one or the other of the two cylindrical parts (18, 19), at an angle of about 68 °.

1 1. Injection rail according to claim 9 or 10, characterized in that the two volumes (16, 17), separated from each other by the plane central rib (20), communicate with each other at the less at one end of the injection rail (1) receiving a plug (8).