Method for operating an internal combustion engine for a motor vehicle and internal combustion engine

Abstract

Method for operating an internal combustion engine (1) for a motor vehicle, in which the internal combustion engine (1) has at least one combustion chamber (2), at least one fuel injection device (8) for introducing fuel into the combustion chamber (2), an exhaust gas tract (9) through which exhaust gas from the combustion chamber (2) of the internal combustion engine (1) flows, and at least one secondary air line (12) through which secondary air flows, which is fluidically connected to the exhaust gas tract (9) at an inlet point (14), whereby the secondary air flowing through the secondary air line (12) can be introduced into the exhaust gas tract (9) at the inlet point (14), characterized in that the internal combustion engine (1) is operated in a drying operating mode (26),in which the secondary air flowing through the secondary air line (12) is introduced into the exhaust tract (9) at the inlet point (14) and , • the internal combustion engine (1) is in overrun mode (27) in which the introduction of fuel into the combustion chamber (2) is omitted and no combustion processes take place in the combustion chamber (2), or • the internal combustion engine (1) is in a fired overrun operation (28) in which fuel is introduced into the combustion chamber (2) via the injection device (8) and the combustion processes take place in the combustion chamber (2).

Description

[0001] The invention relates to a method for operating an internal combustion engine for a motor vehicle according to the preamble of claim 1. Furthermore, the invention relates to an internal combustion engine for a motor vehicle which is configured to carry out such a method.

[0002] DE 10 2020 007 000 A1 and DE 10 2021 205 170 A1 each disclose, considered separately, an internal combustion engine for a motor vehicle, with an exhaust tract through which exhaust gas from at least one combustion chamber of the internal combustion engine flows and with a secondary air line through which secondary air flows, by means of which the secondary air flowing through the secondary air line can be introduced into the exhaust tract.

[0003] The object of the present invention is to provide a method for operating an internal combustion engine for a motor vehicle and such an internal combustion engine, in such a way that a secondary air system of the internal combustion engine can be operated particularly reliably.

[0004] This problem is solved according to the invention by a method for operating an internal combustion engine for a motor vehicle with the features of claim 1 and by an internal combustion engine for a motor vehicle with the features of claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] A first aspect of the invention relates to a method for operating an internal combustion engine for a motor vehicle, which is designed, for example, as a motor vehicle, in particular as a passenger car or as a commercial vehicle. Preferably, the motor vehicle can be driven by means of the internal combustion engine.

[0006] Preferably, the internal combustion engine has an output shaft, in particular rotatable about a shaft axis, via which the motor vehicle can be driven or is driven. The internal combustion engine preferably has at least one combustion chamber, which is, for example, designed as a cylinder. The combustion chamber is, for example, at least partially bounded by at least one housing element, which is, for example, designed as a cylinder wall, and in particular is formed, at least partially, by an engine block. For example, combustion processes take place in the combustion chamber in which a fuel-air mixture is burned, resulting in exhaust gas from the internal combustion engine.

[0007] The internal combustion engine, for example, has at least one intake manifold through which air can flow to the combustion chamber. Thus, air can be introduced into the combustion chamber via the intake manifold, particularly directly.

[0008] For example, the combustion chamber is partially delimited by a piston element, which can be referred to as a piston. The piston element is preferably, and in particular translationally, mounted to be movable relative to the housing element. For example, the internal combustion engine has a crankshaft rotatable about a crankshaft axis of rotation, which is coupled, in particular mechanically, to the piston element. Preferably, at least one connecting rod is provided by means of which a transient motion of the piston element can be converted into a rotary motion of the crankshaft. Thus, the crankshaft can be driven by the piston element via the connecting rod, and is thereby rotatable about its crankshaft axis of rotation.

[0009] The internal combustion engine has at least one fuel supply device for introducing, and in particular injecting, fuel into the combustion chamber. The fuel supply device is, for example, designed as a fuel injection device, in particular as an injector. For example, the fuel can be introduced directly into the combustion chamber via the fuel supply device, and in particular injected, or the fuel can be introduced, and in particular injected, directly into the intake manifold, and thus introduced into the combustion chamber via the intake manifold, i.e., by means of the intake manifold.

[0010] The internal combustion engine has at least one exhaust tract through which the exhaust gas from the combustion chamber of the internal combustion engine can flow. The exhaust gas from the combustion chamber can be discharged via the exhaust tract.

[0011] The internal combustion engine has at least one secondary air duct through which secondary air flows, which is, for example, part of a secondary air system of the internal combustion engine. Thus, the secondary air system can include the secondary air duct. The secondary air duct is fluidically connected or connectable to the exhaust system at at least one inlet point, in particular directly, whereby the secondary air flowing through the secondary air duct can be introduced, in particular injected, into the exhaust system at the inlet point or via the inlet point, in particular directly. The introduction of the secondary air into the exhaust system can therefore be referred to in particular as secondary air injection. The secondary air duct can in particular be referred to as a secondary air channel.

[0012] For example, secondary air is introduced into the exhaust system via the secondary air line, particularly during heating operation of the internal combustion engine. This secondary air is introduced directly into the exhaust system to combust unburned and combustible fuel components contained in the exhaust gas, such as those originating from the combustion chamber. This allows, for example, an exhaust aftertreatment system located in the exhaust system to be heated effectively and quickly, thus ensuring particularly low-emission operation of the internal combustion engine. In other words, the exhaust aftertreatment system is supplied with secondary air, introduced into the exhaust system via the secondary air line at the inlet, particularly during heating operation, to heat the system, especially through post-oxidation.The secondary air can thus be introduced at the inlet point into at least one duct element of the exhaust system, this duct element leading, for example, to the exhaust aftertreatment system and / or to an outlet of the exhaust system, in particular referred to as an exhaust. The exhaust aftertreatment system can be understood, in particular, as a cleaning device by means of which the exhaust gas can be cleaned. The exhaust aftertreatment system is, for example, designed as a catalyst.

[0013] For example, after or during a cold start, the internal combustion engine operates in heating mode, meaning it uses secondary air injection. In heating mode, fuel is injected via the fuel injection system, and combustion takes place in the combustion chamber. This means that, for example, in heating mode, fuel is injected into the combustion chamber via the fuel injection system, and the fuel-air mixture is burned in the combustion chamber.

[0014] The introduction of secondary air, or in particular secondary air injection, refers specifically to the process of introducing or injecting secondary air into the exhaust system via the secondary air line at the inlet point, specifically bypassing or avoiding the combustion chamber. Thus, the secondary air bypasses all combustion chambers of the internal combustion engine and therefore does not originate from the combustion chamber.

[0015] To ensure particularly reliable operation of the secondary air system, i.e., to significantly increase its reliability and, in particular, to enhance its resistance to icing, the invention provides that the internal combustion engine is operated in a drying mode, distinct from the heating mode, specifically for removing condensate and / or moisture from the secondary air system, for example, from the secondary air duct. In this drying mode, the secondary air flowing through the secondary air duct is introduced into the exhaust system at the inlet point, particularly directly. In other words, the introduction, and especially the injection, of the secondary air takes place in the drying mode.This means, in particular, that the internal combustion engine is operated in drying mode with secondary air injection.

[0016] It is intended that the internal combustion engine, in its drying mode, operates in a deceleration mode, during which the injection of fuel into the combustion chamber, particularly via the fuel injection system, is discontinued. This means that during deceleration, fuel is not injected into the combustion chamber; that is, the injection of fuel is switched off. No combustion processes take place in the combustion chamber during deceleration. This means that the fuel-air mixture, or rather, no fuel-air mixture, is burned in the combustion chamber during deceleration, and consequently, no exhaust gas is produced. Deceleration can be understood, in particular, as an engine overrun phase.For example, during overrun, the air flowing through the intake manifold is directed or conveyed through the combustion chamber into the exhaust manifold. For example, during overrun, the output shaft is stationary, meaning that the vehicle is preferably not driven, particularly via the output shaft. This means that during overrun, the vehicle is preferably not driven by the internal combustion engine.

[0017] Alternatively or additionally, it is provided that the internal combustion engine operates in a fired overrun mode during the drying operation, which differs from overrun mode. In other words, the internal combustion engine operates in a fired overrun mode during the drying operation. During a fired overrun mode, fuel is introduced into the combustion chamber via the injection system. This means that during a fired overrun mode, the fuel is introduced into the combustion chamber, specifically via the injection system; the injection system is not switched off. Combustion processes take place in the combustion chamber during a fired overrun mode.This means that in the powered overrun mode, the fuel-air mixture is burned in the combustion chamber, resulting in, in particular, the exhaust gas from the internal combustion engine in the powered overrun mode. Preferably, the output shaft is stationary in the powered overrun mode, thus preferably preventing the propulsion of the vehicle, especially via the output shaft, in the powered overrun mode. In other words, in the powered overrun mode, the vehicle is preferably not propelled by the internal combustion engine.

[0018] The condensate is, for example, condensation water. The condensate and / or moisture results, for example, from the exhaust gas, especially from water contained in the exhaust gas.

[0019] For example, in overrun mode and / or in powered overrun mode, the standstill of the output shaft can be achieved or effected by decoupling the output shaft from the crankshaft, which rotates in particular around the crankshaft axis, by means of at least one coupling element.

[0020] The invention is based in particular on the following findings and considerations: In internal combustion engines with secondary air injection, for example, condensate can form in the secondary air system, such as in the secondary air duct, under certain conditions due to exhaust gas pulsations. This condensate can form primarily on the duct walls or pipe walls of air-carrying channels, such as the secondary air duct of the secondary air system. There, the condensate, also simply referred to as water, can precipitate and collect, for example, on, and especially in front of, secondary air valves or other control valves. Under very cold conditions, this condensate can cause these secondary air valves or other control valves, which can be collectively referred to as control and / or regulating elements, to freeze.

[0021] In contrast, the method according to the invention prevents the secondary air system, and in particular the control and regulating elements, from freezing, thereby enabling particularly reliable operation of the internal combustion engine and / or the secondary air system. This significantly increases the reliability of the secondary air system, especially the secondary air injection. To achieve this, and in particular to prevent the secondary air system from freezing, the method according to the invention employs a strategy to transport, i.e., remove, the condensate and / or moisture from the secondary air system, especially from the secondary air duct.For this purpose, the drying mode can be activated during engine overrun phases, i.e., during overrun operation. This allows the secondary air system to be controlled and operated in order to purge the secondary air system, particularly its ducts and lines, with secondary air, thereby removing condensate and / or moisture from the secondary air system. This strategy can be particularly advantageous during overrun operation, also simply referred to as engine overrun, because the exhaust aftertreatment system, or multiple exhaust aftertreatment systems, can be purged with air or oxygen anyway during overrun. Additional air in the form of secondary air cannot have any, especially negative, effect on this.Furthermore, in the inventive method, the drying operation mode can be carried out during the fired overrun operation in which the internal combustion engine is operating in the drying mode. This means, in particular, that the secondary air injection can be carried out during the fired overrun operation. This is especially advantageous because the fuel is introduced into the combustion chamber and the combustion processes take place in the combustion chamber during the fired overrun operation. As a result, the condensate, which is flushed out, for example, by means of the secondary air, can evaporate particularly well with the heat released in the exhaust system, i.e., heat generated or provided by the combustion processes. The condensate can therefore evaporate more effectively than if the internal combustion engine were not operating in the fired overrun operation.Overall, it is evident that, by means of the method according to the invention, condensate and / or moisture generated, for example, during engine operation, can be removed from secondary air ducts. This prevents the freezing of the secondary air system, particularly the valves and control elements. A strategy for removing condensate and / or moisture from the secondary air system can thus be established. For example, the internal combustion engine can be operated in a normal operating mode, in which fuel is introduced into the combustion chamber via the injection device. The normal operating mode is preferably a different operating mode of the internal combustion engine from the drying mode and, in particular, from the heating mode.For example, in normal operating mode, secondary air is not introduced into the exhaust system. This means that, for instance, no secondary air is introduced or injected in drying mode. Preferably, the amount of fuel introduced into the combustion chamber via the injection device during powered overrun is less than in normal operating mode. Furthermore, the engine load of the internal combustion engine is preferably lower in powered overrun mode than in normal operating mode. The normal operating mode is preferably not an overrun mode of the internal combustion engine. This means that no overrun of the internal combustion engine takes place in normal operating mode. Preferably, in normal operating mode, the vehicle is driven via the output shaft by the internal combustion engine.For example, in the fueled overrun mode, the internal combustion engine is virtually load-free, meaning that the engine load is very low, for instance, similar to that of an idling engine. Thus, the engine load in fueled overrun mode corresponds, at least essentially, to the engine load at idle, which can be specifically referred to as the idle operating mode.

[0022] The term "fired overrun mode" can be understood to refer in particular to a transitional operation from normal operating mode and / or heating mode to idle, especially with a reduction in the engine speed. This means that the output shaft speed decreases or is reduced during fired overrun mode, particularly continuously, for example, down to an idle speed, which the output shaft exhibits at idle.

[0023] For example, the internal combustion engine has at least one electronic computing device, which can be specifically referred to as an engine control unit or may be configured as such. For example, the internal combustion engine can be selectively operated in normal operating mode, heating mode, and / or drying mode by means of the electronic computing device. This means that the internal combustion engine can be switched from normal operating mode and / or heating mode to drying mode and vice versa by means of the electronic computing device. For example, the internal combustion engine is switched from normal operating mode and / or heating mode to drying mode, particularly by means of the electronic computing device, when the internal combustion engine transitions to overrun mode and / or powered overrun mode.

[0024] In a further embodiment, it is provided that the accelerator pedal of the motor vehicle, which is movable or adjustable between at least one position actuated by the driver and a position not actuated by the driver, is in the unactuated position during powered overrun operation, particularly during powered overrun operation in drying mode. In other words, the accelerator pedal is not actuated by the driver during powered overrun operation. This means that the accelerator pedal is not actuated during powered overrun operation. The accelerator pedal can be understood, in particular, as an adjusting or controlling device by means of which a driver request regarding a torque demand from the internal combustion engine can be detected, and, in particular, an engine torque can be adjusted according to the detected driver request. The accelerator pedal can, in particular, be referred to as an accelerator pedal.

[0025] Preferably, the accelerator pedal is in the engaged position during normal operating mode and / or heating mode of the internal combustion engine. In other words, the accelerator pedal is operated by the driver during normal operating mode and / or heating mode. Preferably, when the accelerator pedal is moved from the engaged position to the disengaged position, the internal combustion engine, particularly optionally, transitions into overrun mode and / or powered overrun mode. In other words, the internal combustion engine can switch to powered overrun mode and / or overrun mode when the driver moves the accelerator pedal from the engaged position to the disengaged position, i.e., in everyday language, releases the accelerator.

[0026] Preferably, it is provided that a throttle valve, arranged in the intake tract and movable between at least two throttle valve positions, for example pivotable about at least one pivot axis, by means of which an air quantity of the air flowing through the intake tract, in particular introduced or to be introduced into the combustion chamber, can be adjusted or is adjusted, remains in the throttle valve position during the transition, in particular from the normal operating mode and / or from the heating operating mode, to the fired overrun operation, i.e. in particular to the fired overrun operation of the drying operating mode, in which the throttle valve was located in the operating mode preceding the fired overrun operation, i.e. for example in the normal operating mode and / or in the heating operating mode.In other words, during the transition or changeover, for example from normal operating mode and / or heating mode to overrun mode, the throttle valve does not move, especially pivot. Therefore, if the throttle valve is in one of its first positions during normal operating mode, it will remain in that first position even after switching from normal operating mode to overrun mode. In overrun mode, for example, the accelerator pedal is in a position where the driver is not pressing the pedal, and the throttle valve is not actuated or adjusted.

[0027] In a further embodiment, the inlet point is arranged upstream of a turbine wheel located in the exhaust tract, particularly in the direction of flow of the exhaust gas and / or secondary air flowing through the exhaust tract. In other words, the secondary air introduced into the exhaust tract at the inlet point via the secondary air line can be directed to the turbine wheel. This ensures that, in drying mode, particularly during overrun and / or powered overrun, the secondary air is introduced into the exhaust tract upstream of the turbine wheel via the secondary air line at the inlet point. In other words, during drying mode, the secondary air introduced into the exhaust tract at the inlet point is directed to the turbine wheel.This allows the secondary air to be introduced into the exhaust system particularly early, i.e., particularly far upstream in relation to the flow direction, thus enabling particularly efficient heating of the exhaust system. The turbine wheel is preferably part of, in particular, a turbine of, an exhaust gas turbocharger. The exhaust gas turbocharger has, for example, at least one compressor, which in particular has a compressor wheel arranged in the intake tract for compressing the air flowing through the intake tract.

[0028] In a further embodiment, the inlet point is located within the cylinder head of the internal combustion engine. In other words, the secondary air line, and in particular the inlet point, extends at least partially within the cylinder head. This allows the secondary air to be introduced into the exhaust system via the secondary air line at the inlet point within the cylinder head, particularly directly, during the drying operating mode, especially during overrun and / or overrun. The cylinder head, or at least a section of the exhaust system extending within the cylinder head, can thus be permeated by the secondary air. This allows the exhaust system to be heated in the area of ​​the cylinder head, enabling it to be heated particularly quickly or effectively.For example, the cylinder head limits the combustion chamber at least partially, especially on a side facing away from the piston element, which can be referred to as the top side.

[0029] In a further embodiment, the internal combustion engine, and in particular the secondary air system, comprises at least one fluid energy machine by means of which the secondary air flowing through the secondary air line, particularly in the drying mode and / or the heating mode, is conveyed through the secondary air line. In other words, the fluid energy machine provides or generates at least a sufficient pressure of secondary air to introduce the secondary air into the exhaust system at the inlet point via the secondary air line. This allows a particularly large quantity of secondary air to be introduced into the exhaust system, thereby heating the exhaust system particularly effectively. Furthermore, the secondary air system, and in particular the secondary air line, can be thoroughly purged, thus removing condensate or moisture from the secondary air system particularly efficiently.The fluid energy machine is designed, for example, as a pump or a compressor. The pump can be specifically referred to as a secondary air pump. Preferably, the fluid energy machine is arranged in the secondary air line. Furthermore, the fluid energy machine is preferably permeable to the secondary air.

[0030] In a further embodiment, the internal combustion engine, and in particular the secondary air system, is provided to have at least one valve assembly, for example, arranged in the secondary air duct, by means of which the quantity of secondary air flowing through the secondary air duct, and in particular the secondary air introduced at the point of inlet to the exhaust system, can be adjusted. This allows the secondary air supply to be adjusted with particular variability, i.e., according to demand. The valve assembly can be referred to in particular as a secondary air valve and / or as a control or regulating element. For example, the quantity of secondary air introduced at the point of inlet to the exhaust system, referred to in particular as the first secondary air quantity, can be adjusted by means of the valve assembly.

[0031] In a further embodiment, the internal combustion engine, in particular the secondary air system, has at least one second valve assembly, designed separately from the valve assembly, by means of which the amount of secondary air introduced into the exhaust tract, in particular at the inlet point, can be adjusted or is adjusted. The second valve assembly is, for example, arranged in the secondary air line, or the second valve assembly is arranged in a second secondary air line, in particular different from the secondary air line, through which the secondary air can flow, and which is in particular part of the secondary air system.The second secondary air line is, for example, fluidically connected to the exhaust system via a second inlet point, which is located at a distance from the first inlet point, and in particular directly, whereby the secondary air flowing through the second secondary air line is introduced into the exhaust system at the second inlet point, and in particular directly. Thus, a second quantity of secondary air can be regulated by means of the second valve assembly, specifically the quantity of secondary air flowing through the second secondary air line and introduced into the exhaust system at the second inlet point. The second valve assembly can be referred to in particular as a secondary air valve or as a control or regulating element.

[0032] For example, it is intended that the valve assembly and / or the second valve assembly is controlled in the drying operating mode, for example during phases of towed engine operation and / or fired towed engine operation, in order to transport the condensate and / or moisture from the secondary air system, in particular from the lines or ducts of the secondary air system, by means of the secondary air. For example, the fluid power machine, in particular by means of the electronic control unit, is controlled in the drying operating mode in order to transport the moisture and / or condensate from the secondary air system, in particular from the lines or ducts, by means of the secondary air.It may therefore be provided that during phases of engine towed operation (thrust) and / or during fired engine towed operation (fired thrust) the secondary air pump and / or associated valves or control elements are activated in order to transport the moisture or condensate from the lines or channels of the secondary air system.

[0033] In a further embodiment, it is provided that the respective valve assembly is adjustable between at least one open position and one closed position. Preferably, the respective valve assembly, and thus in particular the respective secondary air line, is permeable to secondary air in the respective open position, whereas in the closed position, the flow through the respective valve assembly, and in particular the respective secondary air line, is prevented.

[0034] For example, it is designed that in drying mode the valves are open simultaneously or alternately. In other words, in drying mode, particularly during the transition to drying mode, both valves are opened simultaneously or alternately. This allows the secondary air system to be cleared of condensate or moisture as needed.

[0035] A second aspect of the invention relates to an internal combustion engine for a motor vehicle, which is configured to carry out a method according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention, and vice versa.

[0036] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0037] This shows: Fig. 1 A schematic representation of an internal combustion engine according to the invention, which can be operated by means of a method according to the invention; and Fig. 2 a schematic process diagram of a process according to the invention.

[0038] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0039] Fig. Figure 1 shows a schematic representation of an internal combustion engine 1 for a motor vehicle. The motor vehicle can be driven by means of the internal combustion engine 1. In the exemplary embodiment, the internal combustion engine 1 is designed as a reciprocating engine, in particular as a reciprocating piston engine.

[0040] The internal combustion engine 1 has at least one combustion chamber 2, wherein in the exemplary embodiment the internal combustion engine 1 has several combustion chambers 2, 3, 4, 5, for example, which are designed separately from one another. The internal combustion engine 1 is thus, for example, designed as a four-cylinder engine. Combustion processes can take place in each of the respective combustion chambers 2 to 5, in which a fuel-air mixture is burned, and exhaust gas from the internal combustion engine 1 can be generated during these combustion processes.

[0041] In the exemplary embodiment, the internal combustion engine 1 has at least one intake manifold 6 through which air can flow and through which air can be supplied to the respective combustion chambers 2 to 5. Furthermore, in the exemplary embodiment, the internal combustion engine 1 has a throttle valve 7 arranged in the intake manifold 6 and movable between at least two throttle valve positions, by means of which the amount of air flowing through the intake manifold 6 can be adjusted. For example, a first position is an open position in which air flows through the intake manifold 6, thereby introducing air into the respective combustion chambers 2 to 5 via the intake manifold 6. For example, a second throttle valve position is a closed position in which air does not flow through the intake manifold 6.

[0042] The internal combustion engine 1 has at least one fuel injection device 8 for introducing fuel into the combustion chamber 4 to 5, in particular the respective combustion chamber. In the exemplary embodiment, several fuel injection devices 8 are provided, with each combustion chamber 2 to 5 being assigned, for example, one of the respective fuel injection devices 8, by means of which fuel can be introduced into or is introduced into the respective combustion chamber 2 to 5. The respective fuel injection device 8 is designed, for example, as a respective injector, in particular for injecting the fuel into the respective combustion chamber 2 to 5.

[0043] Furthermore, the internal combustion engine 1 has at least one exhaust gas tract 9 through which the exhaust gas from the respective combustion chamber 2 to 5 can flow, and through which the exhaust gas from the respective combustion chamber 2 to 5 can be discharged.

[0044] In the exemplary embodiment, at least one exhaust aftertreatment device 10, which is designed, for example, as a catalyst, is arranged in the exhaust tract 9. Furthermore, in the exemplary embodiment, a turbine wheel 11 is arranged, which is preferably located upstream of the exhaust aftertreatment device 10 in the direction of flow of the exhaust gas flowing through the exhaust tract 9. In particular, it is provided that the turbine wheel 11 can be driven, or is driven, by the exhaust gas flowing through the exhaust tract 9, preferably to drive a compressor wheel arranged in the intake tract 6 for the compression of the air flowing through the intake tract 6.

[0045] In the present embodiment, the exhaust system 9, which can be referred to as the exhaust system, or a turbine comprising the turbine wheel 11, is designed as a multi-flow, in particular a double-flow, system. Thus, the exhaust system 9 has, for example, a first conduit 9a through which the exhaust gas can flow, and through which the exhaust gas can be discharged from a first and a fourth of the combustion chambers 2, 5, and the exhaust system 9 has at least a second conduit 9b through which the exhaust gas can be discharged from a second and a third of the combustion chambers 3, 4. The first conduit 9a is, for example, fluidically connected to the turbine at a first connection point, in particular directly, and the second conduit 9b is, for example, fluidically connected to the turbine at a second connection point, in particular a second connection point, which is different from the first connection point, and in particular directly.

[0046] The internal combustion engine 1 has at least one secondary air duct 12 through which secondary air can flow or is flowing, which is, for example, part of a secondary air system 13 of the internal combustion engine 1. The secondary air duct 12 can, for example, be understood to be a secondary air duct section. The secondary air duct 12 or the secondary air system 13 is fluidically, and in particular directly, connected to the exhaust tract 9 at at least one inlet point 14, whereby the secondary air flowing through the secondary air duct 12 can be, and in particular is, introduced into the exhaust tract 9 at the inlet point 14, and is introduced via the secondary air duct 12 or by means of the secondary air system 13. In the Fig. In the embodiment shown in Figure 1, several, for example four, such inlet points 14, 15, 16, 17 are provided. For example, a first and a fourth of the inlet points 14, 17 are fluidically, and in particular directly, connected to the first duct section 9a of the exhaust system 9. For example, a second and a third of the inlet points 15, 16 are fluidically, and in particular directly, connected to the second duct section 9b of the exhaust system 9. The secondary air system 13, in particular the secondary air duct 12, has, for example, several duct elements 18, 19, 20 through which the secondary air can flow. For example, the secondary air flowing through a first of the power elements 18 can be divided between a second and a third duct element 19, 20. Thus, the second and the third duct element 19, 20 are, for example, connected or switchable in parallel to each other, in particular fluid-mechanically, i.e., flowable through each other in parallel.In the direction of flow of the secondary air through the duct elements 18, 19, 20, at least one branch point is arranged between the first duct element 18 and the second and third duct elements 19, 20, wherein the secondary air flowing through the first duct element 18 can be introduced into the second and third duct elements 19, 20 via the branch point. For example, the second duct element 19 is connected, in particular directly, fluidically to the first and fourth inlet points 14, 17. For example, the third duct element 20 is connected, in particular directly, fluidically to the second and third inlet points 15, 16. Thus, the secondary air flowing through the second duct element 18 can be introduced, in particular directly, into the exhaust tract 9, in particular into the first duct section 9a, at the first and fourth inlet points 14, 17.Furthermore, the secondary air flowing through the second conduit element 20 can be introduced at the second and third inlet points 15, 16, in particular directly, into the exhaust gas tract 9, in particular into the second conduit section 13.

[0047] In the Fig. In the embodiment shown in Figure 1, the internal combustion engine 1, in particular the secondary air system 13, comprises at least one fluid energy machine 21, which is designed, for example, as a pump or a compressor. The pump can be referred to as a secondary air pump. It is provided that the secondary air flowing through the secondary air line 12 or the secondary air system 13 can be conveyed or is conveyed through the secondary air line 12 or the secondary air system 13 by means of the fluid energy machine 21. In the embodiment shown, the fluid energy machine 21 is arranged in the secondary air line 12, in particular in the first line element 18.

[0048] The secondary air system 13 is, for example, designed as a secondary air circuit. For example, the secondary air system 13, in particular the secondary air line 12, is fluidically connected, especially directly, to the intake tract 6, preferably bypassing or avoiding the respective combustion chambers 2 to 5. This allows, for example, the air flowing through the intake tract 6 to be introduced, as secondary air, via the secondary air line 12, especially bypassing the respective combustion chambers 2 to 5, into the exhaust tract 9 at the respective inlet points 14 to 17, especially directly. It can be provided, for example, that the fluid energy machine 21 is the compressor arranged in the intake tract 6.

[0049] For example, the secondary air system 13 has at least one control and / or regulating device 22. The control and / or regulating device 22 allows the quantity of secondary air flowing through the secondary air system 13, in particular the secondary air duct 12, to be adjusted. In the Fig. In the embodiment shown in Figure 1, the control and / or regulating device 22 has at least one first valve assembly 23, which is arranged, for example, in the second conduit element 19. It is preferably provided that the secondary air volume flowing through the secondary air line 12, and in particular the secondary air volume flowing through the second conduit element 18, can be adjusted or set by means of the first valve assembly 23. Furthermore, the control and / or regulating device 22 has at least one second valve assembly 24, which is separate from the valve assembly 23 and is arranged, for example, in the third conduit element 20. It is preferably provided that the secondary air flowing through the secondary air line 12, and in particular the third conduit element 20, can be adjusted or set by means of the second valve assembly 23.In other words, it is preferably provided that the amount of secondary air introduced into the exhaust gas tract 9, particularly at the respective inlet points 14 to 17, can be adjusted by means of the valve assembly 23, which can in particular be referred to as the first valve assembly 23, and / or by means of the second valve assembly 24. The control and / or regulating device 22, in particular the first and / or the second valve assembly 24, is preferably arranged downstream of the fluid power machine 21, in particular in the direction of flow of the secondary air system 13 or the secondary air line 12. The respective valve assembly 23, 24 can in particular be referred to as the respective control and / or regulating valve for the secondary air.In the secondary air circuit, secondary air valves in the form of valve devices 23, 24 are arranged, which release or block the secondary air, for example coming from the pump or the compressor, to the cylinder head and / or to the exhaust aftertreatment device 10, in particular selectively.

[0050] For example, the secondary air system 13 has at least one check valve 25, which is arranged, for example, in the secondary air line 12, in particular in the first line element 18. For example, the at least one check valve 25 is arranged, in particular in the flow direction of the secondary air described in the secondary air line, upstream of the control and / or regulating device 22 and / or downstream of the fluid energy machine 21.

[0051] The secondary air introduced into the exhaust tract 9 by means of the secondary air system 13, particularly at the respective inlet points 14 to 17, can heat the exhaust tract 9, especially the exhaust aftertreatment device 10, for example by post-oxidation. For this purpose, the secondary air introduced into the exhaust tract can be directed at least in the vicinity of the exhaust aftertreatment device 10. Post-oxidation can be understood, for example, as the combustion of unburned fuel entering the exhaust tract 9 from the respective combustion chambers 2 to 5. In particular, it is evident that the secondary air introduced into the exhaust tract 9 by means of the secondary air system 13 bypasses the combustion chambers 2 to 5 of the internal combustion engine 1 and thus does not flow through the combustion chambers 2 to 5 or through any combustion chamber 2 to 5 of the internal combustion engine 1.

[0052] Fig.Figure 2 shows a schematic process diagram to illustrate a method for operating the internal combustion engine 1. The internal combustion engine 1 is thus designed to carry out the method.

[0053] In order to operate the internal combustion engine 1, in particular the secondary air system, with exceptional reliability, and especially to significantly increase protection against freezing of components of the internal combustion engine 1, it is provided that the internal combustion engine 1 is operated, or can be operated, in a drying mode 26, in particular for the removal of condensate and / or moisture from the secondary air system 13 or the secondary air line 12. In the drying mode 26, the secondary air flowing through the secondary air system 13, i.e., via the secondary air line 12, is introduced into the exhaust gas tract 9 at the respective inlet points 14 to 17, in particular directly.This means that the introduction, in particular the injection, of secondary air via the secondary air system takes place, i.e., is carried out, in the drying operating mode 26. Furthermore, in the drying operating mode 26, the internal combustion engine 1 is in overrun mode 27, in which the introduction of fuel, in particular via the respective fuel injection device 8, into the respective combustion chambers 2 to 5 is omitted and no combustion processes take place in the respective combustion chambers 2 to 5. The overrun mode 27 can therefore be referred to in particular as unfired overrun mode 27.Alternatively, in the drying operating mode 26, the internal combustion engine 1 is in a fired overrun mode 28, which differs in particular from the unfired overrun mode 27, in which fuel is introduced, in particular injected, into the respective combustion chambers 2 to 5 via the respective fuel injection device 8, and the combustion processes take place in the respective combustion chambers 2 to 5. This allows the condensate or moisture, which can form or has formed in the secondary air system 13 during regular engine operation due to exhaust gas pulsations, to be transported away from the secondary air system 13, i.e., removed, in order to prevent, for example, the freezing of at least a partial area or component of the secondary air system 13.The secondary air system 13, in particular the secondary air duct 12, can therefore be purged by the secondary air in the drying operating mode 26, in particular to remove condensate and / or moisture from the secondary air system 13. This purging of the secondary air system 13 can be carried out particularly well in the unfired thrust operation 27 and / or in the fired thrust operation 28, since there is, for example, no exhaust gas or only a very small amount of exhaust gas in the exhaust tract 9. In particular, this prevents exhaust gas from re-entering the secondary air system 13 due to exhaust gas pulsations.

[0054] Regular engine operation can be understood to mean, in particular, a normal operating mode 29 of the internal combustion engine 1. Specifically, it is intended that the engine load of the internal combustion engine 1, also simply referred to as the load, is smaller, in particular significantly smaller, in the fired overrun mode 28 than in the normal operating mode 29. For example, the engine load in the fired overrun mode 28 is less than 10%, in particular less than 5%, 3%, or 1% of the engine load in the normal operating mode 29. The internal combustion engine 1 is thus operated almost without load in the fired overrun mode 28. For example, the engine load in the unfired overrun mode 27 is zero.

[0055] For example, it is provided that the internal combustion engine 1 transitions from normal operating mode 29, in which the internal combustion engine 1 is neither in fired thrust operation 28 nor in unfired thrust operation 27, to drying operating mode 26 as soon as the internal combustion engine 1 enters thrust operation, that is, in particular, transitions from normal operating mode 29 to unfired thrust operation 27 or to fired thrust operation 28. To transition to drying operating mode 26, an electronic computing device, which is designed, for example, as an engine control unit, can control the fluid energy machine 21 and / or the control and regulating device 22, that is, at least one of the valve assemblies 23, 24, for example, for a certain period of time, in particular to introduce secondary air into the exhaust tract 9 via the secondary air system.For example, the drying operating mode 26 can be switched off, particularly by means of the electronic computing device, for instance, as soon as the driver or the engine control unit requests a load. This means that the internal combustion engine 1 can switch from the drying operating mode 26, particularly again, to the normal operating mode 29. For this purpose, the fluid energy machine 21 and / or the control and regulating device 22 can be controlled, particularly by means of the electronic computing device, and in particular switched off again, for example, as soon as the driver and / or the engine control unit requests a load. In particular, it is provided that the internal combustion engine 1, for example, in the drying operating mode 26, can be operated, or is operated, optionally in the unfired overrun mode 27 or in the fired overrun mode 28.

[0056] Thus, for example, it is provided that in the unfired overrun mode 27 and / or in the fired overrun mode 28, an accelerator pedal 32 of the motor vehicle, movable between at least one position 30 actuated by the driver and an unactuated position 31, is in the unactuated position 31, and in particular in the normal operating mode 29 is in the actuated position 30.

[0057] For example, it is provided that the accelerator pedal 32 is in the activated position 30 in the normal operating mode 29 of the internal combustion engine 1, and that when the accelerator pedal 32 is moved from the activated position 30 to the unactivated position 31, the internal combustion engine 1 transitions into either the powered overrun mode 28 or the unpowered overrun mode 27. Preferably, it is provided that the throttle valve 7 remains in the same position during the transition from the normal operating mode 29 to the powered overrun mode 28 as it was in the preceding normal operating mode 29. This means that, particularly when the internal combustion engine 1 transitions into the powered overrun mode 28, the throttle valve position in the drying operating mode 26 is not changed compared to the preceding normal operating mode 29, i.e., it remains constant.In particular, the throttle valve 7 is not in a closed position during the fired overrun operation 28. This means that air can enter the respective combustion chambers 2 to 5 via the throttle valve 7.

[0058] In the exemplary embodiment, the respective inlet points 14 to 17 are arranged within a cylinder head 33 of the internal combustion engine 1, whereby, particularly in the drying operating mode 26, the secondary air is introduced into the exhaust tract 9 at the respective inlet points 14 to 17 within the cylinder head 33 by means of the secondary air system 13 or via the secondary air line 12. Furthermore, in the exemplary embodiment, the secondary air is introduced into the exhaust tract 9 upstream of the turbine wheel 11 at the respective inlet points 14 to 17, particularly in the drying operating mode 26.

[0059] Preferably, the respective valve assembly 23, 24 is adjustable between an open position and a closed position. For example, in the drying operating mode 26, the valve assemblies 23, 24 are open simultaneously or alternately. The valve assemblies 23, 24 can therefore be opened simultaneously, particularly synchronously, or alternately.

[0060] Numerals, such as "first," "second," "third," etc., are intended solely for differentiation and do not, in particular, indicate a sequence. This means that the corresponding numerals can be interchanged at will. Reference symbol list 1 Internal combustion engine 2 first combustion chamber 3 second combustion chamber 4 third combustion chamber 5 fourth combustion chamber 6 Intake tract 7 Throttle valve 8 Fuel injection device 9 Exhaust system 9a first line section 9b second line section 10 Exhaust aftertreatment system 11 Turbine wheel 12 Secondary air line 13 Secondary air system 14 first induction point 15 second induction point 16 third induction point 17 fourth induction point 18 first conductor element 19 second conductor element 20 third conductor element 21 Fluid energy machine 22 Control and / or regulating device 23 first valve assembly 24 second valve assembly 25 Check valve 26 Drying operating mode 27 unfired pusher operation 28 fired pusher operation 29 Normal operating mode 30 activated positions 31 unactivated position 32 Accelerator pedal 33 Cylinder head

Claims

[1] Method for operating an internal combustion engine (1) for a motor vehicle, in which the internal combustion engine (1) has at least one combustion chamber (2), at least one fuel injection device (8) for introducing fuel into the combustion chamber (2), an exhaust tract (9) through which exhaust gas from the combustion chamber (2) of the internal combustion engine (1) flows, and at least one secondary air duct (12) through which secondary air flows, which is fluidically connected to the exhaust tract (9) at an inlet point (14), whereby the secondary air flowing through the secondary air duct (12) can be introduced into the exhaust tract (9) at the inlet point (14) via the secondary air duct (12), characterized by , that the internal combustion engine (1) is operated in a drying operating mode (26) in which the secondary air flowing through the secondary air line (12) is introduced into the exhaust tract (9) at the inlet point (14) via the secondary air line (12) and • the internal combustion engine (1) is in overrun mode (27) in which the introduction of fuel into the combustion chamber (2) is omitted and no combustion processes take place in the combustion chamber (2), or • the internal combustion engine (1) is in a fired overrun operation (28) in which fuel is introduced into the combustion chamber (2) via the injection device (8) and the combustion processes take place in the combustion chamber (2). [2] Method according to claim 1, characterized by , that a motor vehicle accelerator pedal (32) which can be moved between at least one position (30) operated by a driver and an unoperated position (31) is in the unoperated position (31) in the powered overrun operation (28). [3] Method according to claim 2, characterized by, that the accelerator pedal (32) is in the actuated position (30) in a normal operating mode (29) of the internal combustion engine (1) and the internal combustion engine (1) transitions into the fired overrun mode (28) when the accelerator pedal (32) is moved from the actuated position (30) to the unactuated position (31), wherein a throttle valve (7) arranged in an air-flowing intake tract (6) of the internal combustion engine (1) and movable between at least two throttle valve positions, by means of which an air quantity of the air flowing through the intake tract (6) can be adjusted, remains in the throttle valve position in which the throttle valve (7) was located in the normal operating mode (29) when transitioning from the normal operating mode (29) to the fired overrun mode (28). [4] Method according to any one of the preceding claims, characterized by, that the inlet point (14) is arranged upstream of a turbine wheel (11) arranged in the exhaust tract (9), whereby in the drying operating mode (26) the secondary air is introduced into the exhaust tract (9) via the secondary air line (12) at the inlet point (14) upstream of the turbine wheel (11). [5] Method according to any one of the preceding claims, characterized by , that the inlet point (14) is arranged within a cylinder head (33) of the internal combustion engine (1), whereby in the drying operating mode (26) the secondary air is introduced into the exhaust tract (9) via the secondary air line (12) at the inlet point (14) within the cylinder head (33). [6] Method according to any one of the preceding claims, characterized by a fluid energy machine (21) by means of which the secondary air flowing through the secondary air line (12) is conveyed through the secondary air line (12). [7] Method according to any one of the preceding claims, characterized by at least one first valve device (23) by means of which a secondary air quantity of the secondary air flowing through the secondary air line (12) can be adjusted. [8] Method according to claim 7, characterized by at least one second valve assembly (24) designed separately from the first valve assembly (23), by means of which the amount of secondary air introduced into the exhaust tract (9) can be adjusted. [9] Method according to claim 8, characterized by that the respective valve device (23, 24) are adjustable between at least one respective open position and one respective closed position, wherein in the drying operating mode (26) the valve devices (23, 24) are open simultaneously or alternately. [10] Internal combustion engine (1) for a motor vehicle, which is designed to carry out a method according to one of the preceding claims.

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