Internal combustion engine and method for operating an internal combustion engine

Abstract

Internal combustion engine (10) with a plurality of combustion chambers (12, 14, 16, 18), which is connected by its outlet (26) to an exhaust system (30), wherein a turbine (36) of an exhaust gas turbocharger (34) is arranged in the exhaust system (30) and a main catalyst (44) is arranged downstream of the turbine (36), characterized in that a starting catalyst (38) is arranged upstream of the turbine (36) in the exhaust system (30), and wherein the internal combustion engine (10) has a shutdown mechanism (50) for cylinder shutdown, with which at least one combustion chamber (12, 18) can be switched off during operation of the internal combustion engine (10).

Description

[0001] The invention relates to an internal combustion engine and a method for operating an internal combustion engine according to the preamble of the independent patent claims.

[0002] Current emissions legislation, and increasingly stringent regulations in the future, places high demands on the raw emissions and exhaust aftertreatment of internal combustion engines. It is particularly important to minimize cold-start emissions from the internal combustion engine, as efficient conversion of pollutants in the exhaust stream of the internal combustion engine is not possible during the cold-start phase until the exhaust aftertreatment components have reached the minimum temperature required to convert the pollutants.

[0003] Exhaust aftertreatment systems with a starting catalyst are known from the prior art. This catalyst is arranged as the first exhaust aftertreatment component in the flow direction of an exhaust gas from the internal combustion engine through the exhaust system. The starting catalyst can be designed with a small volume in order to heat up as quickly as possible and thus reach its light-off temperature promptly after a cold start of the internal combustion engine. Furthermore, exhaust aftertreatment systems are known in which a catalyst is heated by means of an exhaust gas burner or an electric heating element in order to reach its light-off temperature as quickly as possible after a cold start of the internal combustion engine. Furthermore, internal engine measures such as adjusting the ignition angle towards "retard" are known to raise the exhaust gas temperature of the internal combustion engine. However, this leads to a deterioration in thermal efficiency and thus to increased fuel consumption.

[0004] Furthermore, it is known to throttle the power of the combustion engine during the warm-up phase and to prevent emission-critical operating conditions in order to minimize raw emissions during this warm-up phase.

[0005] DE 10 2012 011 603 A1 discloses an internal combustion engine with multiple combustion chambers, which is turbocharged by means of an exhaust gas turbocharger. A starting catalyst is arranged in the exhaust passage of the internal combustion engine downstream of the turbine, and another catalyst is arranged downstream of the starting catalyst to convert the pollutants in the exhaust stream of the internal combustion engine.

[0006] DE 10 2012 204 779 A1 discloses an internal combustion engine in whose exhaust system an electrically heated three-way catalyst and another three-way catalyst are arranged downstream of the electrically heated three-way catalyst. The electrically heated catalyst is heated during a cold start of the internal combustion engine in order to reach its light-off temperature as quickly as possible.

[0007] DE 10 2014 214 588 A1 discloses an internal combustion engine whose exhaust is connected to an exhaust aftertreatment system. The exhaust duct has a switchable bypass in a section between the exhaust and a turbine of an exhaust gas turbocharger, in which a catalyst is arranged. Further exhaust aftertreatment components are arranged downstream of the turbine.

[0008] DE 41 39 291 A1 describes an internal combustion engine with an exhaust gas turbocharger, with a combustion chamber arranged upstream of the turbine of the exhaust gas turbocharger. An electrically heated catalyst is arranged parallel to the exhaust line upstream of the exhaust gas turbine. To achieve improved exhaust gas decontamination and rapid start-up of the exhaust gas turbine, the exhaust gas is catalytically ignited upstream of the turbine, and the exhaust gas turbine is at least temporarily subjected to an increased exhaust gas mass flow by additional fuel and / or combustion air supply.

[0009] DE 10 2014 222 525 A1 describes an internal combustion engine with an exhaust gas turbocharger. A combustion chamber is located downstream of the turbocharger's turbine.

[0010] DE 10 2017 109 387 A1 discloses an internal combustion engine with an exhaust gas turbocharger, wherein an exhaust gas aftertreatment component is arranged downstream of the turbine of the exhaust gas turbocharger.

[0011] A disadvantage of the prior art solutions, however, is that electric heating elements or exhaust burners represent additional components that must be integrated into the exhaust system. This increases the cost of the exhaust system, and space constraints can make it difficult to accommodate an additional exhaust burner, especially in tightly packed engine compartments.

[0012] The invention is based on the object of reducing emissions in an internal combustion engine with an exhaust gas turbocharger, particularly during the cold start phase, and improving the heating of the exhaust gas aftertreatment components.

[0013] According to the invention, this object is achieved by an internal combustion engine with a plurality of combustion chambers, the exhaust of which is connected to an exhaust system by its outlet. A turbine of an exhaust gas turbocharger is arranged in the exhaust system, and a main catalyst is arranged downstream of the turbine. Furthermore, a starting catalyst is arranged upstream of the turbine in the exhaust system. According to the invention, the internal combustion engine comprises a cylinder deactivation mechanism, with which at least one combustion chamber can be deactivated during operation of the internal combustion engine. Cylinder deactivation allows the remaining active combustion chambers to be operated with a higher fuel quantity for the same power requirement in order to compensate for the torque loss caused by the at least one deactivated combustion chamber.This results in hotter exhaust gases for the same power output, allowing the starting catalyst to warm up faster and reach its light-off temperature sooner. This can reduce emissions immediately after a cold start and during the warm-up phase.

[0014] The features listed in the dependent claims enable advantageous improvements and non-trivial further developments of the internal combustion engine listed in the independent claim.

[0015] In a preferred embodiment of the invention, the starting catalyst has a bypass, allowing exhaust gas from the internal combustion engine to bypass the starting catalyst. A bypass can reduce flow resistance in the exhaust system when the starting catalyst is not required for exhaust gas aftertreatment during normal operation of the internal combustion engine, and exhaust gas aftertreatment is performed entirely by the main catalyst and other exhaust gas aftertreatment components downstream of the turbine of the exhaust gas turbocharger. Furthermore, the thermal load on the starting catalyst during normal operation can be reduced, thus preventing premature aging and the associated decline in conversion rates.

[0016] A further improvement to the internal combustion engine provides for the bypass to be designed as a switchable bypass, with an exhaust flow from the internal combustion engine being routed through the starting catalyst in a first operating state and through the bypass in a second operating state. A switchable bypass allows the starting catalyst to be easily coupled into or decoupled from the exhaust flow of the internal combustion engine. Thus, the starting catalyst can be activated depending on the operating situation. This ensures the conversion of pollutants even when there is a risk that the main catalyst will cool below its light-off temperature.

[0017] In a preferred embodiment of the invention, the starting catalyst is arranged in an exhaust fan of the internal combustion engine, with the exhaust gas from a first group of combustion chambers being directed through the starting catalyst, and the exhaust gas from a second group of combustion chambers being directed past the starting catalyst. This allows the exhaust backpressure of the internal combustion engine to be reduced, since the exhaust gas from the second group of combustion chambers is not blocked by the starting catalyst. This leads to an increase in power and / or a reduction in fuel consumption of the internal combustion engine.

[0018] It is particularly preferred if the second group of combustion chambers can be switched on and off by the deactivation mechanism. This means that in the first operating state, the entire exhaust gas flow of the combustion engine is directed through the starting catalyst, thereby accelerating the heating of the starting catalyst.

[0019] According to the invention, a method for operating an internal combustion engine according to the invention is proposed, wherein during a warm-up phase of the internal combustion engine, at least one combustion chamber is shut down in order to distribute the required power across fewer combustion chambers and thus raise the exhaust gas temperature. The exhaust gas flow of the internal combustion engine is directed through the starting catalyst, thereby shortening the period from the start of the internal combustion engine until the light-off temperature of the starting catalyst is reached. A method according to the invention can reduce the cold-start emissions of an internal combustion engine because the starting catalyst reaches its light-off temperature more quickly than with known solutions, enabling efficient exhaust gas aftertreatment from this point onward.Furthermore, engineers gain additional freedom in designing the combustion process, which can improve the dynamics and responsiveness of the combustion engine. In particular, chemical heating of the starting catalyst and the exhaust duct located downstream of the starting catalyst is possible once the light-off temperature is reached.

[0020] In a preferred embodiment of the method, a temperature of the internal combustion engine is detected and compared with a threshold value for the respective temperature. The method is initiated when the temperature falls below the threshold value and / or terminated when the threshold value is exceeded. In this case, with a cold internal combustion engine, at least one combustion chamber is shut down, and the exhaust gas from the remaining combustion chambers is passed through the starting catalyst. By controlling the temperature of the internal combustion engine, the switching on and off of the at least one switchable combustion chamber can be controlled particularly easily.

[0021] It is particularly preferred if the temperature of the internal combustion engine is the coolant temperature of the internal combustion engine. A possible reference variable for the control method for shutting down the second group of combustion chambers is the coolant temperature of the internal combustion engine. During a cold start, this temperature is essentially at the level of the ambient temperature and, during further operation of the internal combustion engine, remains within a temperature range that can be easily regulated via a thermostat in the radiator.

[0022] Alternatively or additionally, it is advantageously provided that the temperature of the internal combustion engine is a combustion chamber temperature of the internal combustion engine. Detecting the combustion chamber temperature can also initiate a method according to the invention. Cold combustion chambers lead to a lower exhaust gas temperature, so that at a combustion chamber temperature below the threshold value, the deactivatable combustion chambers are deactivated and the exhaust gas from the remaining combustion chambers is passed through the starting catalyst.

[0023] Furthermore, it is advantageously provided that a catalyst temperature is detected and the method is initiated when the catalyst temperature is below a threshold temperature.

[0024] Alternatively or additionally, it is provided that an exhaust gas temperature is recorded, and the process is initiated when the exhaust gas temperature is below a threshold temperature. By recording the exhaust gas temperature, it can also be estimated whether the main catalyst has already reached its light-off temperature or whether initiating the process is necessary as a heating measure to ensure the conversion of pollutants in the exhaust stream of the combustion engine.

[0025] In an advantageous embodiment of the method, the at least one deactivatable combustion chamber is operated with firing again as soon as the main catalyst has reached its light-off temperature. Once the main catalyst has reached its light-off temperature, efficient exhaust gas aftertreatment can take place through the main catalyst. Thus, the combustion chamber deactivation measure for raising the exhaust gas temperature can be terminated. Alternatively, the combustion engine can continue to be operated with combustion chamber deactivation, since combustion chamber deactivation leads to lower flow losses in the intake duct and thus to higher engine efficiency. This can save fuel.

[0026] In a preferred embodiment of the method, the exhaust gas flow of the internal combustion engine is bypassed past the starting catalyst as soon as the main catalyst has reached its light-off temperature. Switching to bypass operation for the starting catalyst can reduce exhaust backpressure. This improves the efficiency of the internal combustion engine, thereby reducing fuel consumption.

[0027] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in the individual case.

[0028] The invention is explained below in exemplary embodiments with reference to the accompanying drawings. Identical components or components with the same function are identified by the same reference numerals in the different figures. They show: Fig. 1 shows an internal combustion engine according to the invention with a cylinder deactivation system and a starting catalyst in a first operating state, in which the internal combustion engine is operated with a cylinder deactivation system in a warm-up phase; Fig. 2 shows an internal combustion engine according to the invention with a cylinder deactivation and a starting catalyst in a second operating state, in which all combustion chambers are operated in a fired operating state; and Fig. 3 an alternative embodiment of an internal combustion engine according to the invention, in which a bypass is provided with which the starting catalyst can be bypassed.

[0029] Fig. 1 shows a schematic representation of an internal combustion engine 10 according to the invention with a plurality of combustion chambers 12, 14, 16, 18. The internal combustion engine 10 is connected by its inlet to an air supply system (not shown) and by its outlet 26 to an exhaust system 30. Inlet valves 56 and exhaust valves 58 are arranged on the combustion chambers 12, 14, 16, 18, with which a fluidic connection from the air supply system to the combustion chambers 12, 14, 16, 18 or from the combustion chambers 12, 14, 16, 18 to the exhaust system 30 can be opened or closed. In the illustrated embodiment, the internal combustion engine 10 is designed as a spark-ignition four-cylinder in-line engine with direct fuel injection into the combustion chambers 12, 14, 16, 18. A fuel can be injected into the combustion chambers 12, 14, 16, 18 by means of fuel injectors 20 and ignited by means of a spark plug 62.The internal combustion engine 10 has an outlet 26 with an exhaust fan 28 in which the exhaust gases from the combustion chambers 12, 14, 16, 18 are collected and fed to a common exhaust duct 32.

[0030] A first group 22 of combustion chambers 14, 16 is designed without a shut-off mechanism, so that the intake valves 56 and the exhaust valves 58 are cyclically opened and closed upon rotation of the internal combustion engine 10, corresponding to a rotational movement of one or more camshafts 60, 64 of the internal combustion engine 10. Located in the outlet area of ​​the combustion chambers 14, 16 of the first group 22 is a starting catalyst 38, in particular an oxidation catalyst 40, through which the exhaust gas from these combustion chambers 14, 16 flows.

[0031] A second group 24 of combustion chambers 12, 18 can be switched off by means of a switch-off mechanism 50 with an actuator 52, which is operatively connected to the camshaft 60, 64. For this purpose, cams on the camshaft 60, 64 are displaced by the actuator 52, so that the intake valves 56 and exhaust valves 58 of the switched-off combustion chamber 12, 18 no longer open. Furthermore, the fuel injection in the corresponding combustion chambers 12, 18 is switched off. Thus, in the switched-off operating state, no torque is generated by the corresponding combustion chambers 12, 18, whereby the torque generated in the combustion chambers 14, 16, which continue to be fired, must be increased by the same amount in order to keep the drive torque constant. As a result, the load in the first group 22 of combustion chambers 14, 16 increases, whereby the exhaust gas temperature T EG these combustion chambers 14, 16 is raised.

[0032] A turbine 36 of an exhaust gas turbocharger 34 and a main catalyst 44 are arranged in the common exhaust duct 32, and downstream of the turbine 36, a main catalyst 44 is preferably designed as a three-way catalyst 48 or a four-way catalyst. Further exhaust gas aftertreatment components 46, in particular further catalysts or exhaust gas filters, in particular a particulate filter, can be arranged downstream of the main catalyst 44.

[0033] The internal combustion engine 10 is connected to an engine control unit 54, via which the ignition, fuel injection and deactivation of the combustion chambers 12, 18 are controlled.

[0034] Alternatively, the internal combustion engine 10 can also have a different number of cylinders, and in particular, can be designed as a 3-cylinder, 5-cylinder, or 6-cylinder in-line engine. In this case, the deactivation mechanism 50 deactivates at least one combustion chamber 12, 14, 16, 18, preferably a group of combustion chambers, in order to increase the load for the remaining combustion chambers. Alternatively, the internal combustion engine 10 can also be designed as a V-engine or a boxer engine and have a number of cylinders between four and twelve.

[0035] In Fig. 1, the internal combustion engine 10 is shown in a first operating state, which corresponds to a cold start of the internal combustion engine 10 with a subsequent warm-up phase. During the warm-up phase, the second group 24 of combustion chambers 12, 18 is shut down by the shut-down mechanism 50, so that only the combustion chambers 14, 16 are operated in a fired state, with the load in these combustion chambers 14, 16 being increased accordingly to compensate for the torque of the deactivated combustion chambers 12, 18. The exhaust gas from the fired combustion chambers 14, 16 is passed through the starting catalyst 38, whereby it heats up and reaches its light-off temperature T as quickly as possible after the cold start of the internal combustion engine 10. LO reached. Once the light-off temperature T LOThe unburned or partially burned exhaust gas components are exothermically reacted with the residual oxygen in the exhaust gas on the catalytically active surface of the starting catalyst 38, whereby the starting catalyst 38 and the area of ​​the exhaust system 30 located downstream of the starting catalyst 38 are further heated. This also further heats the main catalyst 44.

[0036] As soon as the main catalyst 44 permanently reaches its light-off temperature T LO has been reached, the combustion chambers 12, 18 of the second group 24 are activated, and the internal combustion engine 10 is transferred to normal operation. For this purpose, the cams of the camshafts 60, 64 are shifted accordingly via the actuators 52 so that the valves 56, 58 of the activated combustion chambers 12, 18 open and close cyclically again. Furthermore, the fuel injection and ignition of these combustion chambers 12, 18 are reactivated.

[0037] In Fig. Figure 2 shows a second operating state of the internal combustion engine 10, in which all combustion chambers 12, 14, 16, 18 of the first group 22 and the second group 24 are activated and used in fired engine operation. The exhaust gas of the first group 22 of combustion chambers 14, 16 is directed through the starting catalyst 38, while the exhaust gas of the second group 24 of combustion chambers 12, 18 bypasses the starting catalyst 38 and enters the exhaust fan 28.

[0038] In Fig. 3 shows a preferred embodiment of an internal combustion engine 10 according to the invention. With essentially the same structure as Fig. 1, the starting catalyst 38 in this embodiment has a bypass 42, which can be switched via a bypass valve 66. The exhaust gas from the combustion chambers 14, 16 of the first group 22 is passed through the starting catalyst 38 during the warm-up phase and, upon reaching the light-off temperature T LOof the main catalyst and the associated switching on of the second group 24 of combustion chambers 12, 18 to a bypass operation of the starting catalyst 38, wherein the bypass valve 66 is opened and the exhaust gas of the first group 22 of combustion chambers 14, 16 is passed past the starting catalyst 38 through the bypass 42 in order to reduce the thermal load on the starting catalyst 38 and the exhaust gas back pressure during normal operation. List of reference symbols 10 Combustion engine 12 first combustion chamber 14 second combustion chamber 16 third combustion chamber 18 fourth combustion chamber 20 fuel injector 22 first group of combustion chambers 24 second group of combustion chambers 26 Outlet 28 exhaust compartments 30 Exhaust system 32 exhaust duct 34 exhaust gas turbochargers 36 turbines 38 Starting catalyst 40 Oxidation catalyst 42 Bypass 44 Main catalyst 46 exhaust aftertreatment component 48 Three-way catalyst 50 Shut-off mechanism 52 Actuator 54 Engine control unit 56 Inlet valve 58 exhaust valve 60 camshaft 62 Spark plug 64 camshaft 66 Bypass valve T Temperature T CC Combustion chamber temperature T CF Coolant temperature T EG Exhaust gas temperature T LO Light-off temperature

Claims

[1] Internal combustion engine (10) with a plurality of combustion chambers (12, 14, 16, 18), which is connected by its outlet (26) to an exhaust system (30), wherein a turbine (36) of an exhaust gas turbocharger (34) is arranged in the exhaust system (30) and a main catalyst (44) is arranged downstream of the turbine (36), characterized by in that a starting catalyst (38) is arranged in the exhaust system (30) upstream of the turbine (36), and wherein the internal combustion engine (10) has a shutdown mechanism (50) for cylinder shutdown, with which at least one combustion chamber (12, 18) can be switched off during operation of the internal combustion engine (10). [2] Internal combustion engine (10) according to claim 1, characterized by that the starting catalyst (38) has a bypass (42) with which an exhaust gas of the internal combustion engine (10) can be guided past the starting catalyst (38). [3] Internal combustion engine (10) according to claim 2, characterized bythat the bypass (42) is designed as a switchable bypass (42), wherein an exhaust gas flow of the internal combustion engine (10) is guided through the starting catalyst (38) in a first operating state of the internal combustion engine (10) and through the bypass (42) in a second operating state. [4] Internal combustion engine (10) according to one of claims 1 to 3, characterized by that the starting catalyst (38) is arranged in an exhaust gas compartment (28) of the internal combustion engine (10), wherein the exhaust gas of a first group (22) of combustion chambers (14, 16) is passed through the starting catalyst (38) and the exhaust gas of a second group (24) of combustion chambers (12, 18) is passed past the starting catalyst (38). [5] Internal combustion engine (10) according to claim 4, characterized by that the second group (24) of combustion chambers (12, 18) can be switched on and off by the switch-off mechanism (50). [6] Method for operating an internal combustion engine (10) according to one of claims 1 to 5, characterized bythat during a warm-up phase of the internal combustion engine (10) at least one combustion chamber (12, 18) is switched off in order to distribute the required power to fewer combustion chambers (14, 16) and thus to reduce the exhaust gas temperature (T EG ), wherein the exhaust gas flow of the internal combustion engine (10) is passed through the starting catalyst (38), whereby the period from the start of the internal combustion engine (10) until the light-off temperature (T LO ) of the starting catalyst (38) is shortened. [7] Method for operating an internal combustion engine (10) according to claim 6, characterized by that a temperature (T CC , T CF ) of the combustion engine (10) and compared with a threshold value for the respective temperature (T CC , T CF ), whereby the procedure is initiated when the threshold value is undershot and / or terminated when the threshold value is exceeded. [8] Method for operating an internal combustion engine (10) according to claim 7, characterized by that a coolant temperature (T CF ) or a combustion chamber temperature (T CC ) of the internal combustion engine (10). [9] Method for operating an internal combustion engine (10) according to one of claims 6 to 8, characterized by that the at least one switched off combustion chamber (12, 18) is operated in fired mode again as soon as the main catalyst (44) reaches its light-off temperature (T LO ) has been reached. [10] Method for operating an internal combustion engine (10) according to one of claims 6 to 9, characterized by that the exhaust gas flow of the internal combustion engine (10) is guided past the starting catalyst (38) through a bypass (42) as soon as the main catalyst (44) reaches its light-off temperature (T LO ) has been reached.

Images