EP1589202B1 - Exhaust manifold for internal combustion engine - Google Patents

Description

The present invention relates to an exhaust manifold for an internal combustion engine and can in particular be used with advantage in a supercharged engine.

The exhaust manifold serves to guide the exhaust from the cylinder head to the downstream equipment such as the turbocharger, the peripheral elements necessary for the post-treatment of the flue gases and the exhaust line (collectively called the exhaust face of the exhaust gas). engine). The exhaust manifold is generally equipped with several tubular conduits whose inputs are integral with a one-piece inlet flange. These ducts make it possible, from the outlet of the different exhaust pipes of the cylinder head, to direct the exhaust gases towards a single outlet integral with an outlet flange. The exhaust manifold is most often assembled to the cylinder head by means of a screw connection which joins the inlet flange with the exhaust face of the cylinder head. A metal seal is interposed between the cylinder head and the inlet flange of the exhaust manifold to provide a better seal to the exhaust gas.

In terms of manufacturing process, two large families of collectors can be distinguished.

The first family of exhaust manifolds is obtained from a gravity molding process. The collectors are usually cast iron or steel. This family of collectors has the advantage of better control of dispersions and greater latitude in obtaining compact structures.

Cast iron incorporating molybdenum and silicon have good casting and machinability properties. They therefore make it possible to obtain inexpensive collectors. On the other hand, the properties of these fonts are strongly altered at high temperatures. Current engines, characterized by very high flue gas temperatures, make their use often unsuitable.

Nickel and chromium cast irons offer better hot performance than silicon and molybdenum based fonts. By cons, their less good properties of flowability and machinability generate an additional cost on the exhaust manifold.

Finally, steels offer the best performance in terms of thermomechanical behavior. On the other hand, their poor flowability properties require specific and expensive industrial means which have a direct impact on the cost price of the finished product. In addition, the control of the manufacture of these collectors is delicate.

The second family of collectors is of the welded type. The manifold ducts can be obtained by stamping thin sheets, bending tubes or hydroforming. The materials used for the ducts are ferritic or austenitic steels.

This family of collectors offers the possibility of designing structures of small thicknesses, thus of low inertia, and of assembling materials of different mechanical and thermophysical characteristics. Moreover, the nature of the materials makes it possible to scan a range of high temperatures. However, the corresponding manufacturing processes give rise to significant geometrical dispersions.

The search for higher and higher specific powers generally leads automobile manufacturers to take advantage of the energy of the exhaust gases to drive the turbine of a turbocharger. This turbocharger, inserted between the outlet flange of the exhaust manifold and the peripheral elements necessary for the post-treatment of flue gases, is characterized by a large mass and volume.

In addition, the evolution of pollution standards towards more and more stringent requirements leads automobile manufacturers to use after-treatment devices for burnt gases that are increasingly bulky and heavier.

On the other hand, to improve the efficiency of the post-treatment of flue gases, the equipment upstream of the after-treatment device, in particular the exhaust manifold, must be characterized by a low thermal response time.

In addition, the combustion strategies adopted to improve the efficiency of the post-treatment of flue gases, especially for diesel engines, associated with specific powers up, increase the average thermal level of the exhaust gas.

Thus, with space fixed by the engine compartment, the increase in volume of the post-treatment device burnt gases and the need to improve its efficiency require more and more compact exhaust manifold designs.

On the other hand, from a dynamic point of view, the continuous increase of the masses suspended at the exhaust manifold requires an overall stiffening of the exhaust face of the engine. This benefit is generally obtained through several stiffening crutches that allow to secure the exhaust face to the powertrain itself.

Thus, the need to tend towards increasingly compact exhaust manifold structures associated on the one hand with an overall stiffening of the exhaust face of the engine, and on the other hand with an increase in the average thermal level of the exhaust gases. exhaust, contribute to a significant increase in thermomechanical stresses. This trend requires an increased effort to ensure the holding of the exhaust manifold and a good seal at each of the interfaces of the exhaust face of the cylinder head.

For example, document is known WO02 / 088527 a collector having the features of the preamble of claim 1.

The purpose of the invention is to propose an exhaust manifold having improved resistance to thermomechanical stresses and to allow a reduction of the vibratory levels of the exhaust face of the engine, while keeping a good seal on the exhaust face of the engine between the cylinder head. and the collector.

To this end, the invention provides an exhaust manifold as described in claim 1.

It will be noted that replacing the single-piece and / or single input flange commonly used in the prior art manifolds by a plurality of single or multiple input flanges makes it possible to eliminate practically all the geometric links likely to introduce stiffness. prejudicial to the holding of the collector and consequently to eliminate the dilated expansion caused by the membrane stiffness of the monoblock or single inlet flange.

In addition the joining of the multiple input flange (in practice a flange connected to two input ends) with the output flange allows an improvement in the rigidity of the collector structure and its dynamic behavior. In particular, in the case of a welded-type collector structure, this arrangement makes it possible to limit the thermomechanical and dynamic stresses between the outlet flange and the connection pipes.

According to a first embodiment of the exhaust manifold according to the invention for a good mechanical balance of the manifold / yoke assembly the multiple inlet flange is disposed in the central portion of the alignment and the single inlet flanges are arranged laterally. on this alignment on either side of said multiple input flange. Advantageously, the connection pipes are in a rake form whose teeth are constituted by the ducts. inlet leading to the inter-duct transom manifold connected to the outlet duct.

According to a very interesting variant of the first embodiment of the invention, the reinforcing web is integral with the conduits and / or the cross-pipe.

It will be noted that the presence of reinforcing webs (also called wedges) makes it possible on the one hand to provide sufficient rigidity at the level of the lateral inter-ducts to reduce the closure of the bent parts associated with the single inlet flange ducts (by for example, the ducts of the external stations corresponding to the cylinders 1 and 4 for a manifold with four inlet ducts) and, on the other hand, to increase the section for the passage of forces at the level of the ducts corresponding to the flange of the duct. multiple input (for example the inter-duct between the ducts of the internal stations corresponding to the cylinders 2 and 3).

According to another alternative embodiment of the collector according to the invention, the multiple input flange and said output flange are joined to each other by a L-shaped assembly block whose branches respectively carry the outlet flange and the flange. the multiple input flange.

According to yet another alternative embodiment of the collector according to the invention, the multiple input flange and said output flange are joined together by an assembly frame whose two sides are respectively carrying the output flange and the flange. multiple entry.

In summary, the combination according to the invention of a reduction of the rigidity at the level of all the inlet flanges and of a connection with high rigidity between a multiple inlet flange (breech side) and the flange of exit (exhaust side) reduces the risk of thermomechanical fatigue cracking and improves the overall dynamic behavior. The performance of a collector according to the invention is further increased with the addition of wedges at the collector inter-ducts.

Among other advantages of the invention, it will be noted that the invention is directly applicable to both types of collectors, the collectors obtained by gravity molding and the mechanically welded collectors.

• la figure 1 représente une vue schématique en perspective arrière d'un premier mode de réalisation d'un collecteur d'échappement selon l'invention;
• la figure 2 représente une vue schématique réduite en perspective avant d'une coupe longitudinale du collecteur d'échappement de la figure 1;
• la figure 3 représente une vue schématique réduite en perspective avant d'une coupe transversale du collecteur d'échappement de la figure 1;
• la figure 4 représente une vue schématique en perspective avant supérieure d'un second mode de réalisation d'un collecteur d'échappement selon l'invention;
• et la figure 5 représente une vue schématique réduite partielle en perspective avant inférieure du collecteur d'échappement de la figure 1.

Other characteristics and advantages of the present invention will become apparent on reading the following description presented solely by way of nonlimiting example with reference to the accompanying drawings in which:

• the figure 1 is a schematic rear perspective view of a first embodiment of an exhaust manifold according to the invention;
• the figure 2 represents a schematic view reduced in perspective before a longitudinal section of the exhaust manifold of the figure 1 ;
• the figure 3 represents a schematic view reduced in perspective before a cross section of the exhaust manifold of the figure 1 ;
• the figure 4 represents a diagrammatic view in front perspective of a second embodiment of an exhaust manifold according to the invention;
• and the figure 5 represents a partial reduced schematic view in lower front perspective of the exhaust manifold of the figure 1 .

For the remainder of the description, reference will be made to describe the two collectors 10 and 100 according to the invention illustrated in FIGS. Figures 1 to 5 to a three-dimensional system with perpendicular planes Pxy, Pxz, and Pyz defined with respect to Figures 1 to 3 . In particular, the collector 10 is represented in figure 2 in longitudinal section cut along the plane Pyz with a rotation along the axis ZZ 'of 90 ° and represented in figure 3 in cross section cut along the plane Pxz with rotation along the axis ZZ 'of 180 ° and the collector 100 is shown in FIG. figure 4 with a rotation along the axis ZZ 'of 90 ° with respect to the figure 1 and represented at figure 5 with a rotation according to YY 'of 90 ° with respect to figure 4 .

The exhaust manifold 10 for a multicylinder internal combustion engine illustrated in FIGS. Figures 1, 2 and 3 relates to a first embodiment of the invention given solely by way of non-limiting example, in this case a manifold intended to be associated with an in-line four cylinder cylinder (not shown) or a multiple cylinder head having several groups four cylinders in line for example a motor cylinder head V8 (not shown) which will then be equipped with two collectors according to the invention. The collector 10 as illustrated is made of a mechanically welded structure but can without departing from the scope of the invention be obtained by molding cast iron or steel, the invention being advantageously applicable to both manufacturing techniques, molding and tack welding.

The collector 10 essentially comprises connection pipes made of thin steel sheets of generally rake form, the teeth of which consist of the ducts 21, inlet ducts 22, 23 and 24 of the inlet ends of the gases substantially aligned along an axis. YY ', the collector further having a general structure almost symmetrical with respect to the median plane Pxz perpendicular to the axis YY'. The ducts 21-24 have an orientation along the axis ZZ 'and lead to a crosspiece pipe 12 extending substantially parallel to the axis YY' to define three inter-ducts 12a, 12b and 12c. In practice the tubing 12 is slightly bent in its inverted V medium in the Pyz plane at the height of the inter-ducts 12b as shown in FIG. figure 2 . The manifold manifolds also have an outlet end having a gas outlet duct 14 extending substantially parallel to the axis XX 'and disposed symmetrically with respect to the median plane Pxz and opening into the central duct 12b. The outlet duct 14 carries an outlet flange 38 of the exhaust gas suitably connected by a downstream exhaust pipe to the downstream equipment (not shown) such as turbocharger, peripheral elements for aftertreatment of the flue gas and exhaust line. . The trapezoidal generally trapezoidal flange 38 formed from a plate or steel soleplate has a large central through opening 37 on which is welded the wall of the duct 14 as illustrated on FIG. figure 3 . As illustrated in detail on Figures 1 and 3 three mounting openings 32 are provided in the flange 38 at the legs 42 (small base) and 41 (wide base) to allow mounting and connection with a downstream exhaust pipe (not shown).

According to one of the features of the invention, the inlet ends constituted by the ducts 21 to 24 are distributed in free ends, in this case the external inlet ducts 21 and 24 each carrying a fastening flange 26 and 28. , and ends joined together around a multiple flange, in this case the central double flange 30 to which are associated the inner inlet ducts 22 and 23. As illustrated on the Figures 1 to 3 , the three flanges 26, 28 and 30 obtained from plates or steel soles have through openings of large diameter 16, 17, 18, 19 on which are welded the walls of the corresponding inlet ducts 21 to 24. three flanges are separated from each other and have free faces 27, 29, 31 extending in the plane Pxy. The flanges 26, 28 and 30 have through openings 32 of reduced diameter through which the rods of the wide-headed fastening bolts (not shown) screwed into threaded bores in the cylinder head of the engine receiving the In particular, the flanges 26, 28 and 30 are mounted on the exhaust face of the cylinder head with the interposition of metal sealing joints so as to separately connect each inlet duct 21 to 24 to the corresponding four corresponding exhaust openings. on the breech.

• i) dans le cas où les sollicitations liées aux dilatations contrariées par la section de la bride 30 ne sont pas critiques vis à vis de la tenue de l'inter-conduits 12b, la bride multiple 30 est laissée pleine telle qu'illustrée sur les figures 1 et 3 tout en réduisant à partir de la face avant (opposée à la face portant la bride de sortie 38) sa section médiane 40 entre les deux conduits d'entrée intérieurs 22 et 23 (voir figure 3) ;
• ii) dans la négative la bride multiple 102 peut être ajourée d'une ouverture centrale 106 comme illustrée aux figures 4 et 5 et décrite ci-après en référence au collecteur 100 pour limiter la section résistante de la bride d'entrée double 102 au niveau de l'inter-conduit central 12b.

This first characteristic, applicable whatever the method of obtaining the collector (molding or mechanical welding), has the effect of making the inlet flanges 26 and 30 and the inlet flanges 30 and 28 independent at external lateral ducts 12a and 12c. This makes it possible to eliminate mechanical connections that are detrimental to the strength of the collector, in particular to eliminate the effect of the upset expansion caused by the membrane stiffness of a multiple one-piece and / or single inlet flange integral with the four ducts. With regard to the mechanical connection existing on the multiple flange 30 at the level of the inter-ducts 12b and made necessary by the severity of the mechanical stresses resulting from the joining of the multiple input flange 30 with the outlet flange 38, it is possible to envisage two types of architecture:

• i) in the case where the stresses related to the expansions annoyed by the section of the flange 30 are not critical with respect to the holding of the inter-ducts 12b, the multiple flange 30 is left full as illustrated in FIGS. Figures 1 and 3 while reducing from the front face (opposite to the face carrying the outlet flange 38) its middle section 40 between the two inner inlet ducts 22 and 23 (see figure 3 );
• ii) in the negative, the multiple flange 102 may be perforated with a central opening 106 as illustrated in FIGS. Figures 4 and 5 and hereinafter described with reference to the manifold 100 for limiting the resistant section of the dual inlet flange 102 at the central inter-duct 12b.

Optionally, the inter-ducts 12c communicate with a recirculation duct 34 carrying a flange 36 (similar to the simple flanges 26 and 28) intended to be connected to a recirculation circuit (not shown) of the exhaust gases to the intake duct of the engine cylinders (recirculation circuit also called EGR circuit and intended to reduce the emissions of gaseous pollutants, including NO and NO ₂ ).

According to another characteristic of the invention, the multiple input flange 30 is secured to the outlet flange 38 carried by the outlet duct 14 in order to improve the structural rigidity of the collector. This configuration can be achieved with a molding process on cast iron or cast steel structures. For a welded structure, the connection between the two flanges is obtained through a screwed or welded assembly, the latter method being the least expensive. This bonding makes it possible to improve the dynamic behavior of the collector, in particular with regard to the mechanical resonances of the motor assembly incorporating the collector. Moreover, in the case of mechanically welded collector, this connection makes it possible to limit the thermomechanical and dynamic stresses at the junction between the outlet flange and the inlet ducts.

This connection between multiple input flange and output flange allows to consider more or less rigid geometric solutions as needed. By way of non-limiting example, the set of inlet and outlet flanges 38 of the manifold 10 form an L-shaped assembly block as shown in FIGS. Figures 1 and 3 in which the small width tab 42 of the flange 38 is welded to the middle portion 44 of the double flange 30, which connection may or may not be stiffened by one or more brackets at the base of the junction of the two flanges 30 and 38 ( in this case there are two brackets 46, on either side of the fixing opening 39 made in the tab 42, and only one is visible on the Figures 1 and 3 ). Another more rigid frame block structure in the form of a frame and illustrated in FIGS. Figures 4 and 5 will be described hereinafter with reference to the collector 100.

According to a very interesting feature of the first embodiment of the invention, the ducts of at least two adjacent inlet ends are interconnected by a reinforcing web. Advantageously, the reinforcing web is integral with the conduits and the inter-ducts of the cross-pipe. By way of non-limiting example, the collector 10 has reinforcing webs 48, 49, 50 on each of the inter-ducts 12a, 12b, 12c. As can be seen on the figure 3 showing the section of a sail (in this case the sail 49), the webs consist of two contiguous sheets integrally formed with the adjacent inter-ducts (12b) and welded together and to the inlet ducts (22). and 23). In particular for the collector 10 of welded half-shell type the webs are obtained directly by stamping. With regard to mechanically welded collectors with curved structures the reinforcement sails are obtained by welding flat products. Finally, in the case of collectors obtained by molding, the reinforcing webs are made of material with the cross-pipe and the corresponding inlet ducts and obtained directly at casting.

This characteristic of reinforcement veils (also called wedges) makes it possible to increase the bending rigidity and the membrane rigidity of the inter-ducts. In fact, the increase of the resistance section with respect to the forces at the level of the inter-ducts 12a and 12c makes it possible to reduce the stresses associated with compressive membrane stresses. In addition, the increase of the bending stiffness makes it possible, on the one hand, to reduce the closure of the bent parts associated with the single inlet flange ducts 21 and 24 in the outer position (bending caused by the friction forces at the collecting interface and breech and by the expansion at the inter-duct 12b) and secondly to improve the sealing of the collector interface / breech at the separate flanges 26, 28. Finally at the inter -conduit 12b, the solicitations are predominantly of membrane type and essentially related to the expansions thwarted by the multiple input flange 30. Although the reinforcing web 49 increases the bending stiffness of the inter-duct 12b, l addition of this decoupled web of the multiple flange 30, for the most part, reduces the compressive thermomechanical membrane stresses.

The Figures 4 and 5 are perspective views of a second embodiment of an exhaust manifold according to the invention 100. The collector 100 is very close to the collector 10 which it represents, in fact, an interesting variant in terms of the robustness of the connection between the multiple input flange and the output flange. In particular, the collector 100 comprises, with two exceptions (the replacement of the double flange 30 by the double flange 102, and the addition of the spacer 104), the same elements as those of the collector 10 and mounted in a quasi-identical configuration. identical to that of the collector 10. Consequently the identical or quasi-identical elements for the two collectors will keep the same reference numerals and will not be described again, the description of the collector 10 given with reference to the Figures 1 to 3 being for the most part directly applicable to collector 100 with reference to Figures 4 and 5 , the changes made in the collector 100 being further specified below.

In particular, the exhaust manifold 100 differs from the manifold 10 by a structural modification, namely the strengthening of the connection between the central multiple inlet flange 102 and the outlet flange 38 by the addition of an L-shaped spacer 104 welded between the middle portion of the multiple flange 102 and the wide tab 41 of the outlet flange 38. Thus the assembly block solarizing the multiple input flange 102 and the output flange 38 is presented in the form of an assembly frame of rectangular structure of which two sides are respectively carrying the output flange 38 and the multiple input flange 102 and the other two sides are constituted by the L-shaped spacer 104.

Furthermore, the multiple inlet flange 102 is in the form of an elongated sole provided with two openings 17 and 18 associated with the two inner inlet ducts 22 and 23 disposed on either side of a central through opening. 106 disposed to the right of the outlet flange 38 to limit the resistant section of the double inlet flange 102 at the central inter-duct 12b.

The invention is not limited to the exhaust manifolds described but also covers various variants in which in particular the position of the multiple inlet flange can be modified with respect to the central position described above with reference to the collectors 10 and 100 and / or the orientation of the outlet flange with respect to the multiple inlet flange (described at about 90 ° for the collectors 10 and 100) can be modified for example to 180 ° with in particular the use of a U-shaped piece spanning the inter-duct 12b and welded to the flange 102.

Finally, the invention is not limited to exhaust manifolds having 4 inlet ducts but also covers, for example, manifolds with 3, 5 and 6 ducts in which two ducts are secured to a double inlet flange which is itself secured. at the outlet flange, the other ducts being associated with separate flanges.

Claims (10)

1. Exhaust manifold (10, 100) for a multi-cylinder internal combustion engine comprising connecting pipes linked to one another, one of which pipes being a cross-pipe (12), into which discharge

   - a plurality of inlet branch pipes (21, 22, 23, 24) essentially in alignment and intended to be attached to exhaust ports in the cylinder head of the engine, and

   - an exhaust branch pipe (14) intended to be attached to an exhaust pipe,

   in which the inlet branch pipes (21, 22, 23, 24) are arranged as branch pipes having free extremities (21, 24), each carrying a single inlet flange (26, 28), and as branch pipes having extremities (22, 23) joined together by means of a multiple inlet flange (30, 102) carried by the said branch pipes having extremities joined together, the said single and/or multiple inlet flanges (26, 28, 30, 102) being intended to be connected to the said exhaust ports and being separated one from the other,
   in which at least one multiple inlet flange (30, 102) is joined to an exhaust flange (38) carried by the exhaust branch pipe (14) of the manifold, and
   in which at least two adjacent inlet branch pipes (21-22, 22-23, 23-24) are linked together by means of a reinforcing rib (48, 49, 50),
   characterized in that the said reinforcing rib (48, 49, 50) also links the said two adjacent branch pipes (21-22, 22-23, 23-24) to the said cross-pipe (12).
2. Exhaust manifold according to Claim 1, characterized in that the said reinforcing rib (48, 49, 50) is made of the same material as the said inlet branch pipes (21-22, 22-23, 23-24) and/or the cross-pipe (12).
3. Exhaust manifold according to one of Claims 1 and 2, characterized in that the said connecting pipes exhibit the form of a rake, of which the teeth are formed by inlet branch pipes (21, 22, 23, 24) discharging into the cross-pipe between the branch pipes (12a, 12b, 12c) connected to the exhaust extremity.
4. Exhaust manifold according to one of the preceding claims, characterized in that the multiple inlet flange (30) and the exhaust flange (38) are joined together by an L-shaped mounting piece, of which the legs support the exhaust flange (38) and the multiple inlet flange (30) respectively.
5. Exhaust manifold according to one of Claims 1 to 3, characterized in that the multiple inlet flange (102) and the exhaust flange (38) are joined together by a mounting frame, two sides of which support the exhaust flange (38) and the multiple inlet flange (102) respectively.
6. Exhaust manifold according to one of the preceding claims, characterized in that the multiple inlet flange (30, 102) joins together two inlet extremities (22, 23), and in that the said exhaust flange (38) is arranged in relation to the multiple inlet flange (30, 102) between the said inlet extremities (22, 23).
7. Exhaust manifold according to Claim 6, characterized in that the multiple inlet flange (102) exhibits the form of an extended sole plate provided with two openings (17, 18) associated with the two inlet extremities (22, 23) and arranged to either side of a central opening (106) arranged in line with the exhaust flange (38).
8. Exhaust manifold according to one of Claims 6 and 7, characterized in that the said exhaust flange (38) is arranged essentially perpendicular to the said multiple inlet flange (30, 102).
9. Exhaust manifold according to one of the preceding claims, characterized in that the multiple inlet flange (30, 102) is arranged in the central part of the said alignment, and in that the single inlet flanges (26, 28) are arranged laterally on the said alignment to either side of the said multiple inlet flange (30, 102).
10. Exhaust manifold according to one of the preceding claims, characterized in that it comprises four inlet branch pipes (21, 22, 23, 24) arranged as two branch pipes having extremities (22, 23) joined together by means of a multiple inlet flange (30, 102) arranged between two branch pipes having free extremities (21, 24).

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