Exhaust system of an internal combustion engine

Abstract

Exhaust system of an internal combustion engine with a flow housing (12) with a flow channel (34), via which an inlet (28) of the flow housing (12) is connected to a first outlet (36) and a second outlet (44) which opens into an exhaust gas recirculation line (46), a cylinder head (10) with a first exhaust duct (30) which is directly connected to the inlet (28) of the flow housing (12), and a second exhaust gas channel (38) which is fluidically connected to an exhaust gas outlet channel (22) and into which the first outlet (36) of the flow housing (12) opens, wherein a first flap (48) is rotatably arranged in the flow channel (34), which is fluidically arranged between the inlet (28) and the first outlet (36) or between the inlet (28) and the second outlet (44) in the flow channel (34), and is movable via an actuator (70), the second exhaust duct (38) is formed in the cylinder head (10), and the flow housing (12) is flanged to the cylinder head (10), wherein the flange (40) surrounds the inlet (28) and the first outlet (36) of the flow housing (12).

Description

The invention relates to an exhaust system of an internal combustion engine, having a flow housing with a flow duct via which an inlet of the flow housing is connected to a first outlet and a second outlet which opens into an exhaust gas recirculation line, having a cylinder head with a first exhaust gas duct which is directly connected to the inlet of the flow housing, and having a second exhaust gas duct which is fluidically connected to an exhaust gas outlet duct and into which the first outlet of the flow housing opens.Exhaust systems usually consist of the exhaust gas ducts in the cylinder head and an exhaust manifold connected thereto, in which the individual exhaust gas ducts are combined. An exhaust line leads from the exhaust manifold to the turbine of an exhaust gas turbocharger, from which the exhaust line, in which some units for exhaust gas aftertreatment are still arranged, is led to the outside. In addition, an exhaust gas recirculation line branches off from the exhaust gas line upstream or downstream of the turbine, via which exhaust gas is recirculated to the cylinder for reducing pollutant. If the exhaust gas is taken upstream of the turbine, this is referred to as high-pressure exhaust gas recirculation, and if it decreases downstream of the turbine, it is referred to as low-pressure exhaust gas recirculation.EP 2 634 393 A2, EP 2 077 388 A2 and DE 10 2013 102 549 A1 disclose exhaust gas systems in which the exhaust gas recirculation in the high-pressure region is arranged directly on the cylinder head or is integrated therein.Depending on the type of engine construction, exhaust systems have also become known in which the exhaust gas recirculation in the high-pressure region is carried out only starting from one of the cylinders. However, these designs of the exhaust gas region often require too much installation space in the region of the engine compartment in the vehicle.In order to make the available installation space as optimal as possible, CN 209 053 673 U proposes a three-part exhaust manifold which is flanged to the cylinder head, each part having two connecting openings through which the exhaust gas of the 6 cylinder internal combustion engine reaches the exhaust manifold. Both lateral exhaust manifold parts open into the central part of the exhaust manifold, at which two outlets are formed, which are each assigned to a cylinder group of three cylinders and which open into an exhaust gas outlet line. The first group of cylinders is additionally connected in the central exhaust manifold part to a further outlet opening, to which an exhaust gas recirculation valve can be fastened and which leads to a high-pressure exhaust gas recirculation line.Although this configuration of the exhaust system reduces the installation space required in comparison with known embodiments, the outlay on assembly is relatively high.The object is thus to create an exhaust system which not only requires a small installation space but is also reduced with regard to the assembly effort by reducing the number of components to be mounted individually and enables reliable regulation of the exhaust gas flow. Here, an exchange of individual components, such as exhaust gas recirculation valves or exhaust flaps, should also be made possible without having to remove the entire exhaust manifold or having to fear any reaction to a turbocharger.This object is achieved by an exhaust system for an internal combustion engine having the features of the main claim 1.The exhaust system according to the invention has a flow housing with a flow channel. This flow channel begins at an inlet and opens into a first outlet and a second outlet behind a branch. The inlet is fastened directly to the cylinder head and is correspondingly connected to a first exhaust gas duct in the cylinder head, in which a second exhaust gas duct is also formed, which in turn leads to an exhaust gas outlet duct, in which a turbine of a turbocharger can also be arranged. The first outlet of the flow housing is connected to this second exhaust gas duct, while the second outlet of the flow housing is connected to an exhaust gas recirculation line. In addition, a first flap is rotatably arranged in the flow channel and is mounted in the flow housing, which flap is arranged fluidically between the inlet and the first outlet or between the inlet and the second outlet in the flow channel, and is movable via an actuator. By means of this flap, either the exhaust gas path to the turbine or to the exhaust gas recirculation duct can thus be throttled or blocked and an exhaust gas quantity distribution into these two ducts can thus take place. For such a regulation, no additional valve needs to be mounted. Instead, a division is produced in a housing which is easily accessible and replaceable without the cylinder head or the exhaust manifold having to be disassembled. This reduces the influence on the turbocharger when the valve is changed, so that otherwise necessary additional maintenance work on the turbocharger is omitted.A particularly simple construction results if the second exhaust gas duct is formed in the cylinder head, so that the exhaust gas is recirculated to the cylinder head which has previously left the latter through the first exhaust gas duct. The exhaust gas can then be guided further into a normally constructed exhaust manifold, from where it reaches the turbine housing or the exhaust gas outlet duct. For this merging, accordingly no additional channel has to be provided or mounted from the first outlet of the flow housing.This advantageously results in a particularly simple fastening in that the flow housing is flanged to the cylinder head, wherein the flange surrounds the inlet and the first outlet of the flow housing. Accordingly, the flow housing, apart from via this flange, only has to be connected to the exhaust gas recirculation line, while the connections of the inlet and the first outlet are effected by a single assembly step.Furthermore, it is advantageous if a second flap is rotatably arranged in the flow channel and is mounted in the flow housing, wherein the first flap is arranged between the inlet and the first outlet in the flow channel and the second flap is arranged between the inlet and the second outlet in the flow channel. Accordingly, in the one flow housing, both the quantity of the exhaust gas recirculated to the intake pipe and the quantity of the exhaust gas recirculated into the cylinder head or to the turbocharger can be regulated.Preferably, the actuator can be used to move the first flap and the second flap in a manner dependent on one another. Since all the exhaust gas must be discharged from the cylinder anyway, the exhaust gas flow that arises can be distributed precisely to the two outlets depending on the operating state of the internal combustion engine.In a preferred embodiment, an actuator housing is formed integrally with the flow housing, which is closed by a cover. The entire flow housing with the actuator and the flaps can be fastened to the cylinder head in a correspondingly pre-assembled manner and can be replaced accordingly. An additional fastening of an actuator housing to the flow housing is omitted, so that the assembly is simplified.Furthermore, it is advantageous if a cooling channel is formed in the actuator housing and / or in the flow housing, via which cooling channel the flaps, but above all also the actuator, can be cooled. The hot exhaust gas from the cylinder head thus does not pass with its high temperature into the flow housing and thus to the actuator.In a preferred embodiment, the cooling channel is arranged between the actuator and the flow channel, whereby the actuator is thermally separated from the flow channel and is thus protected from overheating.In an alternative embodiment, the cooling channel is formed in a flange region between the cylinder head and the flow housing, so that a significantly reduced heat flow penetrates into the flow housing. In particular, the walls of the flow housing are cooled in this way and the actuator is thus protected.Furthermore, it is advantageously possible for the first flap to be arranged directly opposite a wall of the cylinder head, that is to say to be mounted only on one side. An additional partition wall in the flow housing can thus be dispensed with.Preferably, the first exhaust gas duct leads from a cylinder of the cylinder head into the flow housing and the second exhaust gas duct leads into an exhaust manifold which is connected on the inlet side to the outlets of the cylinder head and is connected on the outlet side fluidically to an inlet of a turbine housing. Thus, the exhaust gas coming from the flow housing is first combined with the exhaust gas from the other cylinders via the second exhaust gas channel and then flows to the turbocharger. Such an exhaust system is very simple to assemble.The flow housing with the inlet, the flow channel and the two outlets is preferably formed in one piece, so that preceding assembly steps are also omitted. This results in a particularly simple construction and easy exchangeability.An exhaust system for an internal combustion engine is thus provided, with which an accurate distribution of the exhaust gas flow from a cylinder or a cylinder group to the exhaust gas outlet or into a high-pressure exhaust gas recirculation line takes place in a simple manner. The entire flow housing is easily replaceable without the need to disassemble the turbocharger or the remaining exhaust system. Thus, the costs of manufacturing and performing sevice measures can be reduced.An exemplary embodiment of an exhaust system according to the invention for an internal combustion engine is illustrated in the figure and is described below.The figure shows a perspective side view of a flow housing of an exhaust system according to the invention with cylinder head outlets shown with hatching and a partially cut-away flow housing.In the present exemplary embodiment, the exhaust system according to the invention consists of a cylinder head 10 of a four-cylinder internal combustion engine of a motor vehicle, to which a flow housing 12 and an exhaust manifold 14 are fastened. The exhaust manifold 14 has four inlets 16 which are connected to four outlets 18 of the cylinder head 10 and which, in the region of an outlet 20 of the exhaust manifold 14, merge with an exhaust gas outlet duct 22 in which a turbine housing 24 of a turbocharger 26 is arranged.The cylinder head 10 has a fifth outlet 18 connected to an inlet 28 of the flow housing 12. This outlet 18 is the end of a first exhaust passage 30 that extends from a fourth cylinder 32 of the cylinder head 10 to the outlet 18. In the flow housing 12, a flow channel 34 extends from the inlet 28 to a first outlet 36 which is connected to a second exhaust gas channel 38 in the cylinder head 10 and which extends from the outlet 36 of the flow housing 12 or the entry of the cylinder head 10 corresponding thereto to one of the four outlets 18 of the cylinder head 10 which are connected to the exhaust manifold 14, while the other three outlets 18 are each directly connected to one of the other three cylinders 32. The flow housing 12 is directly attached to the cylinder head 10 via a flange 40 such that the first outlet 36 and the inlet 28 are disposed in the common flange plane.The flow channel 34 in the flow housing 12 has a branch 42, so that the flow channel 34 also extends to a connection plane offset by 90° with respect to the flange plane on the side of the flow housing 12 remote from the first outlet 36, where it opens out at a second outlet 44. This second outlet 44 is connected to an exhaust gas recirculation line 46, via which high-pressure exhaust gas recirculation to the internal combustion engine can be carried out.In the flow housing 12, between the inlet 28 and the first outlet 36, a first flap 48 is rotatably arranged, by means of which a free cross section of the flow channel 34 to the first outlet 36 can be regulated.This flap 48 consists of a shaft 50, on which a flap body 52 is fastened by means of screws, which are not visible, and which is mounted in the flow housing 12 on a side facing away from the cylinder head 10. Between the flap body 52 and the cylinder head 10 a wall 56 is formed which forms part of the bearing surface of the flange 40 and separates the inlet 28 from the first outlet 36, wherein this wall 56 could also be dispensed with, wherein the flap 48 would then be arranged directly opposite a wall 57 of the cylinder head 10.Between the inlet 28 and the second outlet 44, a second flap 58 is also rotatably arranged in the flow housing 12, by means of which flap a free cross section of the flow channel 34 to the second outlet 44 is regulated. This flap 58 also consists of a shaft 60, on which a flap body 62 is fastened by means of screws 64 and which is mounted in the flow housing 12 on a side facing away from the cylinder head 10.Between the flap body 62 and the cylinder head 10 a wall 66 is formed which also forms part of the bearing surface of the flange 40, separates the inlet 28 from the second outlet 44 and in which a first cooling channel 68 is formed which extends along the flange plane around the inlet 28 and the first outlet 36. This cooling channel 68 is formed as a groove in the flange surface which is closed by the cylinder head 10.The two shafts 50, 60 are rotatable via a common actuator 70 which consists of an electric motor 72 and a downstream transmission 74 which are arranged in an actuator housing 76 which is formed integrally with the flow housing 12 and the open side of which, from which the electric motor 72 and the transmission 74 are mounted, is closed by a cover 78. This cover 78 can also serve to accommodate a circuit board for control purposes and has a plug 80. A receptacle 82 of the actuator housing 76 for the electric motor 72 extends over the flow housing 12 in the direction of the cylinder head 10, wherein a second cooling channel 84 is formed in the flow housing 12 between the flow channel 34 and the receptacle 82 of the electric motor 72, via which second cooling channel the electric motor 72 is thermally shielded from the flow channel 34. The first cooling channel 68 is connected to the second cooling channel 84 via a cooling line 86. The first cooling duct 68 and the second cooling duct 84 thus effectively prevent overheating of the actuator 70, even though it is arranged in the hot exhaust gas region.The two flap bodies 52, 62 are coupled to one another via the actuator 70 or the gear 74 in such a way that there is a rotational angle offset of 90° with respect to one another, so that an opposite rotation is always carried out upon actuation. This means that always one flap 48 is rotated in a closing direction to the same extent as the other flap 58 is rotated in an opening direction and vice versa. Accordingly, an approximately equal total cross section is always available for the flow, so that the exhaust gas flow flowing into the inlet 28 is divided by the two flaps 48, 58 depending on the position of the two flaps 48, 58, but without an increased total resistance being opposed to it. Thus, the exhaust gas flow which reaches the high-pressure exhaust gas recirculation line and the exhaust gas flow which is supplied to the turbocharger can be very accurately regulated.In the event of failure of the actuator or clamping of a flap or the like, only the two flange connections to the cylinder head and to the exhaust gas recirculation line have to be released in order to be able to carry out an exchange. The flow housing with the flaps and the actuator can then be removed and, if appropriate, completely or individual parts can be exchanged. A reaction of such an exchange to the turbocharger is eliminated due to the connection to the cylinder head, so that both the initial assembly and the subsequent service measures are significantly simplified.It should be clear that the scope of protection of the present main claim is not limited to the described embodiment. Thus, only one of the two flaps can also be used for regulation or the two flaps can be actuated separately. The structural design of the flow housing or the mounting of the flaps can also be designed differently. The use of a non-electromotive actuator is also conceivable. Further, the first outlet may also be connected to the exhaust manifold if the second exhaust passage is formed in the exhaust manifold, as appropriate. Further variants are also conceivable.

Claims

Exhaust system of an internal combustion engine, having a flow housing (12) with a flow duct (34), via which an inlet (28) of the flow housing (12) is connected to a first outlet (36) and a second outlet (44), which opens into an exhaust gas recirculation line (46), a cylinder head (10) with a first exhaust gas duct (30), which is directly connected to the inlet (28) of the flow housing (12), and a second exhaust gas duct (38), which is fluidically connected to an exhaust gas outlet duct (22) and into which the first outlet (36) of the flow housing (12) opens, wherein a first flap (48), which is arranged fluidically between the inlet (28) and the first outlet (36) or between the inlet (28) and the second outlet (44) in the flow duct (34), is rotatably arranged in the flow duct (34), and is movable via an actuator (70), the second exhaust passage (38) is formed in the cylinder head (10), and the flow housing (12) is flanged to the cylinder head (10), wherein the flange (40) surrounds the inlet (28) and the first outlet (36) of the flow housing (12).Exhaust system of an internal combustion engine according to claim 1, characterized in that a second flap (58) is rotatably arranged in the flow channel (34), wherein the first flap (48) is arranged between the inlet (28) and the first outlet (36) in the flow channel (34) and the second flap (58) is arranged between the inlet (28) and the second outlet (44) in the flow channel (34).Exhaust system of an internal combustion engine according to Claim 2, characterized in that the first flap (48) and the second flap (58) can be moved in a manner dependent on one another by means of the actuator (70).Exhaust system of an internal combustion engine according to one of the preceding claims, characterized in that an actuator housing (76) which is formed integrally with the flow housing (12) is closed by a cover (78).Exhaust system of an internal combustion engine according to one of the preceding claims, characterized in that a cooling duct (68, 84) is formed in the actuator housing (76) and / or in the flow housing (12).Exhaust system of an internal combustion engine according to Claim 5, characterized in that the cooling duct (84) is arranged between the actuator (70) and the flow duct (34).Exhaust system of an internal combustion engine according to Claim 5 or 6, characterized in that the cooling duct (68) is formed in a region of the flange (40) between the cylinder head (10) and the flow housing (12).Exhaust system of an internal combustion engine according to one of the preceding claims, characterized in that the first flap (48) is arranged directly opposite a wall (57) of the cylinder head (10).Exhaust system of an internal combustion engine according to one of the preceding claims, characterized in that the first exhaust gas duct (30) opens into the flow housing (12) from a cylinder (32) of the cylinder head (10), and the second exhaust gas duct (38) opens into an exhaust manifold (14) which is connected on the inlet side to the outlets (18) of the cylinder head (10) and is connected on the outlet side fluidically to an inlet of a turbine housing (24).Exhaust system of an internal combustion engine according to one of the preceding claims, characterized in that the flow housing (12) is formed integrally with the inlet (28), the flow duct (34) and the two outlets (36, 44).

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