Internal combustion engine with an exhaust system

Abstract

Internal combustion engine (1) with at least two cylinders (2), each with two gas exchange exhaust valves, and with an exhaust system (3) which can be connected to conduct exhaust gas via the gas exchange exhaust valves, wherein a turbine housing with a turbine wheel (4) of an exhaust gas turbocharger (5) is arranged in the exhaust system (3) and a first exhaust gas purification system (6) is arranged downstream of the turbine housing in the flow direction of an exhaust gas, wherein a first exhaust pipe (7) branches off from the exhaust system (3) conducting exhaust gas between the internal combustion engine (1) and the turbine housing and opens back into the exhaust system (3) after the first exhaust gas purification system (6), characterized in that the exhaust gas turbocharger (5) is a twin-scroll exhaust gas turbocharger or an exhaust gas turbocharger with a segment turbine,wherein at least two cylinders (2) are combined to form a cylinder group in accordance with an ignition sequence of the internal combustion engine (1), and a first gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to a first scroll via a second exhaust pipe (8), and a second gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to a second scroll via a third exhaust pipe (9), and a second gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to the first exhaust pipe (7) via a fourth exhaust pipe (14), and a second gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to the first exhaust pipe (7) via a fifth exhaust pipe (20),

Description

[0001] The invention relates to an internal combustion engine with an exhaust system having the features of the preamble of patent claim 1.

[0002] Regarding the technical background, reference is made to German Offenlegungsschrift DE 28 51 675 A1, for example. This patent application discloses an afterburning device for the exhaust gases of internal combustion engines. It proposes a device for the afterburning of exhaust gases from internal combustion engines with a catalyst for the oxidation of CO (carbon monoxide) and HC (hydrocarbons). In this device, a portion of the exhaust gas is directed through an exhaust duct, bypassing a catalyst, in the upper load range of the internal combustion engine. A second catalyst is arranged downstream of the catalyst in the exhaust duct.

[0003] A further development of the afterburning device known from DE 28 51 675 A1 is described in the as yet unpublished German patent application with the official file number 10 2017 218 837.5. This patent application describes an internal combustion engine with an exhaust system that has an exhaust manifold connected to the exhaust manifold of the internal combustion engine. A first exhaust gas purification system is arranged in the exhaust system, and a second exhaust gas purification system is arranged downstream of it in the direction of exhaust gas flow. The first exhaust gas purification system can be bypassed via a bypass with a closure element, wherein the closure element is arranged in the exhaust manifold.

[0004] Further examples of internal combustion engines with exhaust systems can be found in the documents DE 10 2017 130 050 A1, WO 2008 / 114730 A1, US 2017 / 0321614 A1, US 2011 / 0131978 A1 and US 9 441 551 B2.

[0005] In gasoline engines, the fuel-air mixture is typically enriched (lambda < 1) at high engine speeds and high power to protect the exhaust-carrying components from thermal overload. This is especially true for turbocharged engines, where the exhaust turbine and catalytic converter could otherwise be damaged by excessively high exhaust temperatures.

[0006] The mixture enrichment leads to high CO concentrations in the exhaust gas, and the CO is disadvantageously not oxidized in the catalyst due to the lack of oxygen in the exhaust gas. In this operating range, the catalyst no longer functions as a three-way catalyst because a stoichiometric mixture (lambda = 1) is not established. This jeopardizes compliance with future vehicle approval requirements.

[0007] Today's exhaust systems, particularly those of turbocharged gasoline internal combustion engines, typically feature a turbine bypass, also known as a wastegate, with an adjustable exhaust gas mass flow through the wastegate. This wastegate adjusts the exhaust gas mass flow through the turbine, thus adjusting the turbine power and thus the desired boost pressure. A catalytic converter (also known as a close-coupled catalyst) is typically located as close as possible downstream of the turbine and downstream of the wastegate channel's feed to the main exhaust gas flow to ensure rapid warm-up after the engine starts. When the engine starts, the wastegate is also opened wide to direct as much hot exhaust gas as possible directly to the close-coupled catalyst for heating purposes.

[0008] At full load, at high engine power levels, typically high exhaust gas mass flows (approximately 30-45%) must be bypassed via the wastegate and the turbine. Since this exhaust gas is not expanded in the turbine, it is very hot. Thus, the average exhaust gas temperature after mixing the turbine outlet exhaust gas mass flow and the wastegate exhaust gas mass flow is higher than the turbine outlet temperature. This can exceed the maximum exhaust gas inlet temperature permitted for the catalytic converter. As a result, the engine's power must be throttled, which is undesirable.

[0009] The object of the present invention is to demonstrate a measure by which higher specific performances of the internal combustion engine can be achieved without thermal damage to the catalyst close to the engine.

[0010] This problem is solved by the features of patent claim 1.

[0011] Advantageous further developments of the invention are described in the subclaims.

[0012] Due to the inventive design of the internal combustion engine with the exhaust system, significantly higher performance of the internal combustion engine can be achieved without thermal damage to the catalyst close to the engine.

[0013] With the embodiment according to claim 2, a controlled or regulated distribution of the exhaust gas mass flow can be achieved in order to avoid overheating of the first exhaust gas purification system after the turbine of the exhaust gas turbocharger.

[0014] In order to ensure pollutant purification of the exhaust gas passed through the waste gate, a second exhaust gas purification system is preferably provided in the first exhaust pipe according to patent claim 3.

[0015] In order to achieve the best possible exhaust gas purification, according to patent claim 4, a third exhaust gas purification system is provided in the exhaust system in the flow direction of the exhaust gas behind an inlet of the first exhaust pipe.

[0016] In order to achieve the greatest possible variability in the heating behavior and with regard to exhaust gas purification, according to patent claim 5, a sixth exhaust pipe branches off from the second exhaust pipe and the third exhaust pipe in the flow direction of the exhaust gas upstream of the exhaust gas turbocharger and flows back into the exhaust system upstream of the first exhaust gas purification system.

[0017] In another particularly preferred embodiment, according to claim 6, a second shut-off element is arranged in the sixth exhaust pipe, with which the sixth exhaust pipe can be shut off. This configuration makes it possible to heat the catalyst with the bypass exhaust gas mass flow.

[0018] In a further development of the invention, according to claim 7, a gas exchange exhaust valve can be deactivated for each cylinder. If the first exhaust pipe is closed, boost pressure control and catalyst heating are carried out via the sixth exhaust pipe during partial engine load.

[0019] In a further preferred embodiment, the sixth exhaust pipe can be cooled according to claim 8, for example with a coolant of the internal combustion engine.

[0020] The invention is explained in more detail below with reference to three figures. Fig. 1 shows a first embodiment of an internal combustion engine according to the invention with an exhaust system. Fig. 2 shows a second embodiment of an internal combustion engine according to the invention with an exhaust system. Fig. 3 shows a third embodiment of an internal combustion engine according to the invention with an exhaust system.

[0021] In the following, the Fig. 1 to 3 for the same components the same reference numbers.

[0022] Fig. 1 schematically shows an internal combustion engine 1 according to the invention with an exhaust system 3. As known from the prior art, fresh air is sucked in via an intake silencer 15. The inflow of fresh air is symbolically represented by an arrow. The fresh air is then passed through an unnumbered intake line through a compressor 16 of an exhaust gas turbocharger 5 and, after the compressor 16, is further cooled in a charge air cooler 17. After the charge air cooler 17, the fresh air flows through a throttle element 18, such as a throttle valve. After the throttle element 18, the fresh air enters an air plenum 19, from which the fresh air is distributed among four cylinders 2 in the present exemplary embodiment. In these four cylinders 2, the fresh air is mixed with fuel and burned.

[0023] The exhaust gas flows from each cylinder 2 into the exhaust system 3 via two unnumbered gas exchange outlet valves, each symbolically represented by a circle. Two cylinders 2 are combined to form a cylinder group according to the cylinder sequence of the internal combustion engine 1. A typical firing order for a four-cylinder internal combustion engine is, for example, cylinder 1, cylinder 3, cylinder 4, cylinder 2. In this firing order, cylinders 1 and 4 and cylinders 2 and 3 each form a cylinder group. Another possible firing order is cylinder 1, cylinder 2, cylinder 4, cylinder 3. Here, the first cylinder (cylinder 1) is the cylinder opposite the power output side / clutch.

[0024] According to the invention, the exhaust gas turbocharger 5 is a twin-scroll exhaust gas turbocharger or an exhaust gas turbocharger with a segment turbine. However, it can also be designed as a mono-scroll turbine. As shown above, in the present exemplary embodiment, two cylinders 2 are combined to form a cylinder group in accordance with the firing order of the internal combustion engine 1, and a first gas exchange exhaust valve of the cylinders 2 of one cylinder group is connected to a first scroll via a second exhaust pipe 8, and a second gas exchange exhaust valve of the cylinders 2 of the other cylinder group is connected to a second scroll via a third exhaust pipe 9. Furthermore, a second gas exchange exhaust valve of the cylinders 2 of one cylinder group is connected to the first exhaust pipe 7 via a fourth exhaust pipe 14, and a second gas exchange exhaust valve of the cylinders 2 of the other cylinder group is connected to the first exhaust pipe 7 via a fifth exhaust pipe 20.

[0025] The second and third exhaust pipes 8, 9 drive the turbine 4 of the exhaust gas turbocharger 5, which is connected in a rotationally fixed manner to the compressor 16 and compresses the fresh air.

[0026] Downstream of the exhaust turbocharger 5, the exhaust gas flows through a first exhaust gas purification system 6 (a close-coupled catalyst) and, in the present exemplary embodiment, exits the exhaust system 3 into the ambient air. In reality, a downstream exhaust system with, if appropriate, further exhaust gas purification devices, such as catalysts, will be provided. An exit of the exhaust gas from the exhaust system 3 is symbolically represented by an arrow. For particularly effective pollutant conversion, a second exhaust gas purification system is provided in the first exhaust pipe 7, and a third exhaust gas purification device 12 is provided in the exhaust system 3 downstream of the first exhaust pipe 7's junction with the exhaust system 3.

[0027] Between the internal combustion engine 1 and the exhaust gas turbocharger 5, the fourth and fifth exhaust pipes 14, 20 are connected to the first exhaust pipe 7 in an exhaust-carrying manner, wherein the first exhaust pipe 7 opens back into the exhaust system 3 downstream of the first exhaust gas purification system 6 in the flow direction of the exhaust gas. At the transition from the fourth exhaust pipe 14 and the fifth exhaust pipe 20 into the first exhaust pipe 7, a first shut-off element 10, such as an exhaust flap, is provided, with which the transition of exhaust gas from the fourth exhaust pipe 14 and the fifth exhaust pipe 20 into the first exhaust pipe 7 can be prevented. The shut-off element 10 is shown in a closed position.

[0028] When the internal combustion engine 1 is at full load, the first shut-off element 10 is opened, allowing hot exhaust gas to flow past the turbine wheel 4 of the exhaust gas turbocharger 5, thus protecting the first exhaust gas purification system 6, as well as the turbine 4 itself, from thermal stress. Due to the inventive design, significantly higher full-load performances can now be achieved for the internal combustion engine 1, since the first exhaust gas purification system 6 and also the turbine 4 are thermally protected. The turbine 4 is thermally protected in that a portion of the exhaust gas mass flow is guided past the turbine 4 through the first exhaust pipe 7. - Advantage: Temperature reduction of the exhaust gas mass flow upstream of the first exhaust gas purification device 6 at rated power compared to the admixture of the wastegate exhaust gas mass flow upstream of the first exhaust gas purification system 6. - Catalytic converter heating takes longer because the wastegate exhaust gas mass flow makes no contribution. - Valves may need to be adjusted to the exhaust gas mass flow. - Disadvantage: More complex exhaust manifold, waste gate must be tight.

[0029] Fig. 2 shows a second embodiment, a further development of the internal combustion engine 1 according to the invention with the exhaust system 3. Fig. 2 differs from Fig. 1 in that the second and third exhaust pipes open into a sixth exhaust pipe 21 upstream of the turbine wheel 4, which in turn opens into the exhaust system 3 upstream of the first exhaust gas purification system 6. Furthermore, a second shut-off element 13 is arranged in the sixth exhaust pipe 21, with which the sixth exhaust pipe 21 can be shut off from the exhaust gas mass flow. Both shut-off elements 10, 13 are shown in a closed position.

[0030] In a further preferred embodiment, not shown in the figure, the sixth exhaust pipe 21 can also be designed to be cooled. This can be done, for example, with coolant from the internal combustion engine 1. - Advantage: Temperature reduction upstream of the first exhaust gas purification system 6 at rated power compared to the mixing of the wastegate exhaust gas mass flow upstream of the first exhaust gas purification system 6. - Catalytic converter heating is possible via the wastegate channel. - Valves may need to be adjusted to exhaust gas mass flow rates. - Disadvantage: More complex manifold, two waste gates, two switchable shut-off elements 10, 13.

[0031] Fig. 3 shows a third embodiment, a further development of the internal combustion engine 1 according to the invention with the exhaust system 3 from Fig. 2. The internal combustion engine 1 in Fig. 3 differs from the internal combustion engine in Fig.2 in that a gas exchange exhaust valve can be deactivated for each cylinder 2. Thus, the power control of the internal combustion engine 1 can also be achieved via the valve train, especially at partial load. The two shut-off elements 10, 13 are again shown in a closed position. - Advantage: Temperature reduction upstream of the first exhaust gas purification system 6 at nominal power compared to the admixture of the wastegate exhaust gas mass flow upstream of the first exhaust gas purification system 6 via the switchable gas exchange outlet valves, the bypass can be reliably sealed. - Catalytic converter heating is possible via the wastegate channel. - Valves may need to be adjusted to the exhaust gas mass flow rate. - Disadvantage: More complex manifold, two wastegates, switchable shut-off elements 10, 13.

[0032] Of course, the design according to the invention can also be used for V8 internal combustion engines or inline six-cylinder or V12 internal combustion engines. LIST OF REFERENCE SYMBOLS 1 internal combustion engine 2 cylinders 3 Exhaust system 4 Turbine wheel 5 exhaust gas turbochargers 6 first exhaust gas purification system 7 first exhaust pipe 8 second exhaust pipe 9 third exhaust pipe 10 first shut-off element 11 second exhaust gas purification system 12 third exhaust gas purification system 13 second shut-off element 14 fourth exhaust pipe 15 intake silencer 16 compressors 17 intercooler 18 Throttle element 19 air collectors 20 fifth exhaust pipe 21 sixth exhaust pipe

Claims

[1] Internal combustion engine (1) with at least two cylinders (2), each with two gas exchange exhaust valves and with an exhaust system (3) which can be connected to conduct exhaust gas via the gas exchange exhaust valves, wherein a turbine housing with a turbine wheel (4) of an exhaust gas turbocharger (5) is arranged in the exhaust system (3) and a first exhaust gas purification system (6) is arranged behind the turbine housing in the flow direction of an exhaust gas, wherein between the internal combustion engine (1) and the turbine housing a first exhaust pipe (7) branches off from the exhaust system (3) conducting exhaust gas and opens back into the exhaust system (3) after the first exhaust gas purification system (6), characterized byin that the exhaust gas turbocharger (5) is a twin-scroll exhaust gas turbocharger or an exhaust gas turbocharger with a segment turbine, wherein at least two cylinders (2) are combined to form a cylinder group in accordance with an ignition sequence of the internal combustion engine (1), and a first gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to a first scroll via a second exhaust pipe (8) and a second gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to a second scroll via a third exhaust pipe (9) in such a way that exhaust gas is carried out, and wherein a second gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to the first exhaust pipe (7) via a fourth exhaust pipe (14) and a second gas exchange outlet valve of each cylinder (2) of a cylinder group is connected to the first exhaust pipe (7) via a fifth exhaust pipe (20) in such a way that exhaust gas is carried out. [2] Internal combustion engine according to claim 1, characterized bythat a first shut-off element (10) is arranged in the first exhaust pipe (7), with which the first exhaust pipe (7) can be shut off. [3] Internal combustion engine according to claim 1 or 2, characterized by that a second exhaust gas purification system (11) is arranged in the first exhaust pipe (7). [4] Internal combustion engine according to claim 3, characterized by that a third exhaust gas purification system (12) is arranged in the exhaust system (3) in the flow direction of the exhaust gas behind an inlet of the first exhaust pipe (7). [5] Internal combustion engine according to one of claims 1 to 4, characterized by that a sixth exhaust pipe (21) branches off from the second exhaust pipe (8) and the third exhaust pipe (9) in the flow direction of the exhaust gas upstream of the exhaust gas turbocharger (5) and opens back into the exhaust system (3) upstream of the first exhaust gas purification system (6). [6] Internal combustion engine according to claim 5, characterized bythat a second shut-off element (13) is arranged in the sixth exhaust pipe (21), with which the sixth exhaust pipe (21) can be shut off. [7] Internal combustion engine according to one of claims 1 to 6, characterized by that a gas exchange exhaust valve can be deactivated for each cylinder (2). [8] Internal combustion engine according to claim 6 or 7 in its reference to claim 5 or 6, characterized by that the sixth exhaust pipe (21) is coolable.

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