FR2849470A1 - Exhaust manifold for motor vehicle turbocharged internal combustion engine has upstream and downstream flanges connected by strut plate to allow support of turbocharger - Google Patents

Abstract

The exhaust manifold (18) for a motor vehicle internal combustion engine has an upstream flange (28) for connection the engine cylinder head exhaust ports and a downstream flange (32) for connection to a turbocompressor (12). The upstream and downstream flanges are connected by a curved plate (36,42) which allows the manifold to act as a support for the turbocompressor.

Description

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  "Motor vehicle exhaust manifold with independent supporting structure" The invention relates to a motor vehicle exhaust manifold.

  The invention relates more particularly to a motor vehicle exhaust manifold which comprises: - an upstream flange for fixing the exhaust manifold to a cylinder head of an internal combustion engine; and - a downstream flange for fixing the exhaust manifold 10 to an accessory, in particular a turbocharger; and - at least one conduit which connects at least one exhaust gas outlet orifice of the cylinder head to an inlet port of the exhaust gases in the accessory.

  It is common for internal combustion engines to be supercharged by a turbocharger so as to improve their performance. The turbocharger makes it possible in particular to increase their efficiency and their power.

  According to a general structure known from the state of the art, the turbocharger comprises a turbine and a compressor which are carried by a turbocharger shaft.

  The turbine is housed in a substantially cylindrical turbine casing which generally comprises a tangential orifice for supplying the turbine.

  The turbocharger is driven in rotation by the exhaust gases which result from the combustion of the fuel in the combustion chambers of the engine and which are led to the supply port of the turbine casing. The exhaust gases are expelled from the combustion chambers via exhaust channels passing through the cylinder head of the engine, then they are collected by an exhaust manifold which guides them from the cylinder head to the turbocharger.

  The exhaust manifold mainly consists of at least one duct which is intended to channel the flow of exhaust gases to the turbocharger, and two flanges for fixing the duct. The duct has at least one inlet port which is connected to the exhaust channels of the cylinder head, and it has an outlet port which is connected to the turbocharger. The first fixing flange, called the upstream flange with reference to the direction of flow of the gases, makes it possible to fix, and to seal, the inlet opening of the duct on an external wall of the cylinder head of the engine. The second fixing flange, called the downstream flange, makes it possible to fix, and to tightly connect, the outlet outlet of the duct to the turbocharger. The collector also has the function of supporting, at least partially, the weight of the turbocharger. Thus, the weight and the forces exerted by the turbocharger are transmitted to the cylinder head successively via the downstream flange, the duct, then the upstream flange. The exhaust manifold is also designed to resist vibrations produced by the turbocharger. It is known that the exhaust manifold, that is to say the duct (s) and the two upstream and downstream fixing flanges, is made in one piece, for example in a cast iron or in a casting steel.

  However, the exhaust gases flowing in the manifold have a high temperature, and the mechanical characteristics of the exhaust manifold are changed at these temperatures. For example, the mechanical resistance of the exhaust manifold to the mechanical stresses of the turbocharger is significantly reduced. In addition, these harmful effects of temperature are favored by the very massive shapes of the upstream and downstream fixing flanges obtained in foundries. In addition, as the engines become more and more compact, the space available for the installation of the turbocharger, and more generally of the exhaust systems, is more and more limited. The physical approximation between the turbocharger and the cylinder head requires a shorter exhaust manifold. The downstream flange which makes it possible to fix the turbocharger on the exhaust manifold then becomes difficult to make in foundry because of the technical constraints linked to the compact and complex shape of the exhaust manifold. Finally, when the vehicle is equipped with an exhaust gas pollution control device of the catalyst type, it is generally necessary for the exhaust gases to cause the rapid rise in temperature of this device beyond a temperature d priming for the device to become effective.

  However, the collectors made of cast iron or steel have a very high thermal inertia, that is to say that the temperature of the duct increases slowly. As long as the manifold is not hot, the exhaust gases are cooled as they circulate in the manifold. Thus, the catalyst can only reach its initiation temperature after the collector has been heated. Such a collector is therefore detrimental to the performance of the catalyst.

  It is also known to use turbocollectors. It is a turbocharger comprising an exhaust manifold which is made integrally with the turbine casing. The exhaust gases are then collected directly at the supply inlet 25 of the turbocharger by several inlet conduits integrated into the turbocharger. There is thus only one upstream fixing flange between the turbocollector and the cylinder head. The problem of the size of the parts made in foundry is partially solved.

  However, the production of such a device is very expensive. In addition, the device obtained is not easily adaptable to different types of motors.

  Thus, it is necessary to design and produce a type of turbocharger adapted to each type of engine, while the same turbocharger can traditionally be adapted to different types of engine by simply changing the exhaust manifold. In addition, the part of the turbocollector forming an exhaust manifold 5 is made integrally with the casing of the turbocharger which is generally made of cast iron. Such a turbocollector therefore does not solve the problem linked to the thermal inertia of the exhaust manifold.

  It is also known that the exhaust manifold mainly consists of a duct and two separate upstream and downstream flanges. The upstream and downstream flanges are fixed by welding to the pipe which is for example made of sheet metal, in particular so as to be compact.

  A sheet metal duct has a very low thermal inertia, that is to say that the temperature of the duct increases very rapidly. Thus, the exhaust gases dissipate very little heat when they circulate in such an exhaust manifold because it does not stay cold for a long time. This allows the exhaust gases to prime, quickly after starting the engine, a catalyst located downstream of the turbocharger.

  However, a turbocharger has a large mass which requires rigid and resistant holding means to withstand vibrational stresses. However, the sheet metal duct does not have a rigidity or a strength sufficient to withstand the mechanical stresses of the turbocharger. Such an exhaust manifold is therefore not capable of supporting a turbocharger without damage for a long time.

  In order to solve these problems, the invention provides an exhaust manifold of the type described above, characterized in that the downstream flange is connected to the upstream flange by at least one structural element forming a stiffener, independent of the duct, so that the collector constitutes a supporting structure of the component.

  According to other features of the invention - one of the flanges has a tab which is fixed to the other flange; - Each flange is generally in the form of a plate, and in that the upstream flange is located in a plane generally perpendicular to the plane of the downstream flange; - The tab extends in the same plane as the flange which comprises it; - The exhaust manifold comprises a bracket which mechanically connects the downstream flange to the upstream flange; - the bracket has an L-shaped section whose wings extend respectively in a plane generally perpendicular to the upstream flange and the downstream flange, so as to form a housing of generally rectangular section delimited by the bracket and the two flanges , and which surrounds the duct; - The two flanges and the structural element forming a stiffener are made integrally in one piece; - the bracket has a screen surface which extends opposite the duct and which stops the thermal radiation from the duct; - the duct is made of thin sheet metal.

  Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which one will refer to the appended figures among which: - Figure 1 schematically shows in perspective an internal combustion engine which is supercharged by a turbocharger and which is equipped with an exhaust manifold made according to the teachings of the invention; - Figure 2 shows in perspective an exhaust manifold 30 made according to the state of the art; - Figure 3 shows in perspective and on a larger scale the exhaust manifold according to the invention of Figure 1; - Figure 4 is a side view along arrow F4 of Figure 3, partially broken away; FIG. 5 is an exploded perspective view of the components of the exhaust manifold according to the invention of FIG. 3.

  In the following description, identical, analogous or similar elements will be designated by the same references. In the following description, use will be made, without limitation, of a longitudinal, vertical and transverse orientation according to the trihedron L, V, T of FIG. 1.

  FIG. 1 shows an internal combustion engine 10 of a motor vehicle supercharged by a turbocharger 12 which is supplied by the exhaust gases 15 from the engine 10 which enter there through an inlet port for the exhaust gases. The engine 10 comprises in particular a cylinder head 14 of generally transverse orientation according to FIG. 1. The cylinder head 14 comprises four channels (not shown) for discharging the exhaust gases which are intended to discharge the exhaust gases, from the combustion chambers of the engine 10 each up to an exhaust gas outlet orifice which opens into a front external wall 16 of the cylinder head 14 which is here of generally transverse and vertical orientation.

  The engine 10 includes an exhaust manifold 18 which is here produced according to the teachings of the invention. The manifold 18 is arranged between the cylinder head 14 of the engine 10 and the turbocharger 12.

  The manifold 18 is in particular intended to - channel the exhaust gases from the cylinder head 14 of the engine 10 to the turbocharger 12; - And at least partially support the weight of the turbocharger 12 so as to keep it in position.

  In order to facilitate understanding of the invention, we will first describe an exhaust manifold 18 produced according to the state of the art and represented in FIG. 2.

  The collector 18 mainly consists of a bent conduit 5 of complex shape also called "plenum", which is here made of thin sheet metal and which has a large upstream oblong orifice 24 through which the exhaust gases enter, and an orifice downstream circular upper 26 centered by which the exhaust gases exit. Such a conduit 22 is shown in Figure 5 within the scope of the invention.

  The upstream orifice 24 of the exhaust gases is wide enough to collect the exhaust gases from the four exhaust channels of the cylinder head 14 in the case of a four-cylinder cylinder head.

  As shown in FIG. 2, an upstream fixing flange 28 in the form of a thick plate of generally vertical transverse orientation is fitted around the upstream orifice 24 of the duct 22. The upstream flange 28 has holes 30 on its periphery longitudinal axis which are intended to position the exhaust manifold 18 on the front external wall 16 of the cylinder head 14, and to fix it for example by means of screws.

  As can be seen in FIG. 5, the flange 28 has four holes 29 for the passage of exhaust gases which are in accordance with the four exhaust channels of the cylinder head 25 when the flange 28 is fixed on the cylinder head 14 .

  A downstream fixing flange 32 in the form of a thick plate of horizontal and longitudinal orientation is fitted around the downstream orifice 26. The periphery of the downstream flange 32 here has two holes 34 of vertical axis which are intended to allow the 30 positioning and fixing of the turbocharger 12 on the exhaust manifold 18.

  The two flanges 28 and 32 thus extend in generally orthogonal planes.

  According to this embodiment of the prior art, when the manifold 18 is fixed to the cylinder head 14 and the turbocharger 12 is mounted on the flange 32 of the exhaust manifold 18, the duct 22 of the exhaust manifold 18 5 supports the weight of the turbocharger 12. The bend in the duct 22 must in particular withstand a high concentration of mechanical and thermal stresses.

  In order to solve the problems inherent in such a design, the invention proposes an improved exhaust manifold 18 10 such as that shown in FIGS. 3 to 5.

  This collector 18 comprises main elements similar to those described above. Thus, this manifold 18 comprises a conduit 22 for the exhaust gases, and upstream 28 and downstream 32 fixing flanges. These elements are illustrated in detail in Figure 5.

  To stiffen the structure of the turbocharger 18, the downstream fixing flange 32 is here extended backwards by a horizontal tab 36 so that the rear free end 38 of the tab 36 is received in a notch 39 formed in the upper edge 20 40 of the upstream flange 28. The two upstream flanges 28 and downstream 32 can thus be rigidly fixed to each other, for example by welding or by embedding, independently of the duct 22. Thus the forces created by the turbocharger 12 , such as the weight and the vibrations, are taken up directly by the flange 28 and therefore by the cylinder head 14, that is to say without "passing" through the conduit 22.

  In addition, as shown in FIGS. 3 to 5, in this embodiment, the exhaust manifold 18 also includes a reinforcement bracket 42 which is intended to constitute a reinforcement in order to stiffen the reinforcement formed by the flanges 28 and 32.

  As illustrated in FIG. 4, the bracket 42 is here a thick bent and bent sheet metal plate which has two wings 48 and 52 generally perpendicular, and which has an L-shaped section. The first vertical upper wing 48 of the bracket 42 extends substantially upwards to the front end 50 of the lower face of the downstream fixing flange 32. The second lower horizontal wing 52 of the bracket 42 extends substantially 5 towards the rear until the lower end 54 of the front face of the upstream fixing flange 28.

  The curve of the bracket 42 envelops the conduit 22 substantially and at a distance. The angle 47 of the bracket 42 is substantially adjacent to the projecting part of the elbow of the conduit 10 22. The bracket 42, the upstream flange 28 and the downstream flange 32 form a housing which surrounds the duct 22.

  The bracket 42 is thus fixed by its two ends, for example by welding, to the two upstream flanges 28 and downstream 32 for fixing. Thanks to such a manifold 18, the thin sheet metal duct 22 has the sole function of channeling the exhaust gases to the turbocharger 12, while the support and maintenance functions of the turbocharger 12 are provided by the two flanges 28, 32 and the bracket 42. Thus, unlike the collector 20 produced according to the state of the art in FIG. 2, the duct 22 is generally not subjected to the mechanical stresses resulting from the presence of the turbocharger 12.

  The two flanges 28, 32 and the bracket 42 therefore form a carcass or frame 56, that is to say a rigid and advantageously compact structure intended to support the turbocharger 12.

  In this embodiment, the cylinder head 14 of the combustion engine 10 includes a water cooling device.

  The upstream fixing flange 28 which is fixed to the external wall 30 before 16 of the cylinder head 14, benefits, by thermal conduction, from the thermal regulation effects of the cooling device. Its temperature is thus kept low compared to the temperature of the exhaust gases.

  The surfaces in contact with the downstream flange 32 on the upstream flange 28, and the bracket 42 on the upstream flange 28 are large enough, so that the downstream flange 32 and the bracket 42 are also cooled by thermal conduction with the flange upstream 28.

  Thus, the structure 56 generally benefits from the thermal regulation effects of the cylinder head cooling device 14. The support structure 56 is therefore kept at a temperature low enough that its mechanical properties are not impaired.

  On the other hand, the contact surface between the duct 22 made of thin sheet metal and the two flanges 28, 32 made of thick sheet metal is sufficiently small so that the effects of cooling by thermal conduction are negligible.

  In addition, the duct 22, thanks to its low thermal inertia, rapidly rises in temperature as soon as the passage of the exhaust gases begins.

  In addition, the shape of the envelope of the bracket 42 advantageously makes it possible to stop the thermal radiation coming from the conduit 22. Thus, the bracket 42 can for example be interposed between the catalyst and the conduit 22. The radiation emitted by the conduit 22 does not reach, and therefore does not heat, the catalyst whose operation would be liable to be degraded by uncontrolled heating.

  According to an alternative embodiment, not shown, the exhaust manifold 18 has several inlet ports for the exhaust gases which are individually connected to each exhaust gas discharge channel.

  According to another variant not shown, the upstream flanges 30 28 and downstream 32 are made integrally in one piece.

  According to yet another variant, not shown, the upstream flanges 28 and downstream 32 are made integrally with the bracket 42.

Claims (9)

  1. Exhaust manifold (18) of a motor vehicle of the type which comprises: - an upstream flange (28) for fixing the exhaust manifold (18) to a cylinder head (14) of an internal combustion engine (10 ); and - a downstream flange (32) for fixing the exhaust manifold (18) to a component of the exhaust line, in particular a turbocharger (12); and - at least one conduit (22) which connects at least one exhaust gas outlet port of the cylinder head (14) to an exhaust gas inlet port in the component (12), characterized in that the downstream flange (32) is connected to the upstream flange (28) by at least one structural element (36, 42) forming a stiffener, independent of the conduit (22), so that the manifold (18) constitutes a support structure for the component (12). 2. Exhaust manifold (18) according to the preceding claim, characterized in that one of the flanges (32) has a lug (36) which is fixed to the other flange (28).   3. exhaust manifold (18) according to one of the preceding claims, characterized in that each flange is generally in the form of a plate, and in that the upstream flange (28) is located in a plane generally perpendicular to the plane 25 downstream flange (32).   4. Exhaust manifold (18) according to the preceding claim taken in combination with claim 2, characterized in that the tab (36) extends in the same plane as the flange (32) which comprises it.   5. Exhaust manifold (18) according to any one of the preceding claims, characterized in that it includes a bracket (42) which mechanically connects the downstream flange (32) to the upstream flange (28).   6. exhaust manifold (18) according to claim 5 taken in combination with claim 4, characterized in that the bracket (42) has an L-shaped section whose wings (48, 52) extend respectively in a plane generally 5 perpendicular to the upstream flange (28) and to the downstream flange (32), so as to form a housing of generally rectangular section delimited by the bracket (42) and the two flanges (28, 32), and which surrounds the duct (22).   7. Exhaust manifold (18) according to one of the 10 preceding claims, characterized in that the two flanges (28, 32) and the structural element forming a stiffener (36, 42) are made integrally in one room.   8. Exhaust manifold (18) according to one of claims 5 or 6 possibly taken in combination with claim 7, characterized in that the bracket (42) has a screen surface which extends opposite the conduit and which stops the thermal radiation from the conduit (22).   9. exhaust manifold (18) according to any one of the preceding claims, characterized in that the duct 20 (22) is made of thin sheet metal.