Methods for heating exhaust gas aftertreatment components and internal combustion engines

Abstract

This invention relates to a method for heating an exhaust gas aftertreatment component in an exhaust system of an internal combustion engine. Here, the combustion chamber of the internal combustion engine is defined by a movable piston and intake and exhaust valves. A fuel injector for injecting fuel into the combustion chamber and a spark plug for igniting the combustible fuel-air mixture are arranged at the combustion chamber. The internal combustion engine has a valve lift profile conversion mechanism capable of shifting and / or changing the opening time of the exhaust valve. The method includes the following steps: - drawing fresh air into the combustion chamber; - injecting fuel into the combustion chamber; - igniting the combustible fuel-air mixture in the combustion chamber when the piston is located in the range of 10°KW to 30°KW after ignition top dead center; and - opening the exhaust valve when the piston is located in the range of 55°KW to 95°KW after ignition top dead center. The invention also relates to an internal combustion engine with an exhaust system for carrying out this method.

Description

Technical Field

[0001] The present invention relates to a method for an exhaust gas aftertreatment component, particularly a three-way catalytic converter, in an exhaust system for heating an internal combustion engine, and an internal combustion engine having an exhaust system for implementing this method. Background Technology

[0002] Given the increasingly stringent emission standards, such as the introduction of EU7, there is a particular need to significantly reduce cold-start emissions, which constitute a large portion of total emissions. During cold-start operation, immediately following engine startup, exhaust aftertreatment components are typically not sufficiently preheated to convert the original emissions generated during fuel combustion. This results in increased exhaust emissions during the cold-start phase, which can lead to non-compliance with limits even if the original emissions are fully converted after the cold-start phase. To avoid this, in internal combustion engines with exhaust aftertreatment systems known in the prior art, customer restrictions may be necessary, such as prohibiting immediate departure after engine startup or limiting power immediately following engine startup, to ensure compliance with EU7 emission limits under all required boundary conditions.

[0003] To meet the EU6 emission standards for gasoline engines, exhaust aftertreatment systems have become widespread, comprising one or more three-way catalytic converters and particulate filters. A three-way catalytic converter is a vehicle catalytic converter used for exhaust aftertreatment of internal combustion engines, in which carbon monoxide (CO), nitrogen oxides (NOx), and unburned hydrocarbons (HC) are converted into carbon dioxide (CO2), nitrogen (N2), and water vapor (H2O). The catalytic converter's name derives from the simultaneous conversion of these three harmful air pollutants. To heat the exhaust aftertreatment components of an internal combustion engine, known internal engine heating measures include adjusting the ignition angle in a "retarded" (or hysteresis) direction, for example, significantly delaying it after the piston's top dead center in the ignition cycle. In this case, the thermal efficiency of the internal combustion engine decreases and the exhaust enthalpy increases. The achievable efficiency reduction is limited by the maximum ignition retardation angle and engine running smoothness, as the delayed combustion leads to poorer ignition and combustion boundary conditions. Therefore, the known methods are unsatisfactory in this respect because the later ignition timing leads to poorer ignition conditions, making it difficult to use passive pre-combustion chamber spark plugs. Furthermore, it is known to heat the three-way catalytic converter using external heating devices, such as electric heating elements or exhaust combustors, so that the catalytic converter reaches its ignition temperature more quickly and is readily available for efficient conversion of restricted emissions after a cold start.

[0004] However, a drawback of existing exhaust aftertreatment systems is that known internal engine heating measures are not expected to meet EU7 emission standards under all operating conditions. Even with external engine heating devices, there is a short period during which the exhaust aftertreatment components have not yet reached their ignition temperature, and the original emissions are released into the environment untreated. Furthermore, external engine heating devices significantly increase the price of exhaust aftertreatment systems.

[0005] A method for exhaust gas aftertreatment of an internal combustion engine is known from patent document DE 35 06 107 A1, in which the exhaust gas of the internal combustion engine is input into an exhaust gas catalytic converter after leaving the combustion chamber of the internal combustion engine. Here, the opening of the exhaust valve of the internal combustion engine is adjusted in the direction of "advancing" in order to increase the heat input to the cooler exhaust gas catalytic converter.

[0006] Patent document DE 102 02 437A1 describes a method and apparatus for controlling an internal combustion engine, as well as a computer program. A torque model is used within the range of calculating the actual quantities and / or adjustment quantities of engine control. Here, the baseline values ​​determined under standard conditions are corrected. Furthermore, to further improve the accuracy of the model, the efficiency for converting chemical energy into mechanical energy is determined, at least based on quantities characterizing the center of gravity of combustion and quantities characterizing the opening time of the scavenging valve on the outlet side, and the optimal torque value is corrected using this efficiency.

[0007] Patent document DE 10 2017 208 857 A1 discloses a method for operating an internal combustion engine having at least one combustion chamber, wherein the combustion chamber is equipped with an intake valve for controlled introduction of fresh gas into the combustion chamber, an exhaust valve for controlled discharge of exhaust gas from the combustion chamber, an injector for directly introducing fuel into the combustion chamber, and an ignition device for igniting a fuel-fresh gas mixture in the combustion chamber. The intake and exhaust valves can be operated by a valve mechanism designed such that valve operation can be adjusted at least for the exhaust valve. Ignition of the fuel-fresh gas mixture is initiated by the ignition device at a defined ignition angle in each operating cycle. A first operating state and a second operating state are provided, wherein in the first operating state, on the one hand, during the exhaust stroke of the operating cycle, the exhaust valve closes relatively earlier than in the second operating state due to a relatively short opening duration, and / or during the intake stroke following the exhaust stroke, the exhaust valve opens a second time, and on the other hand, the ignition angle is set relatively later than in the second operating state.

[0008] A control device for an internal combustion engine is known from patent document DE 691 14 490T2. This control device further includes means for changing the engine power of the internal combustion engine by controlling the opening duration of the intake valve. This control device can be used to optimize emission control in carburetor engines, injection engines, and turbocharged engines. It is feasible to use a single control device for various engine applications, or to use control units with various different control devices for various applications.

[0009] Patent document DE 11 2014 000 495 T5 describes a method for heating a catalytic converter in the exhaust system of an internal combustion engine. When the catalytic converter is in an inactive state, compared to when the catalytic converter is in an active state under the same engine operating conditions, the intake air volume is increased and the ignition timing is delayed to after the top dead center of the compression stroke. The ignition timing is set such that this delay adjustment is achieved according to the load requirements of the internal combustion engine. The exhaust valve opening start time is set such that when the external load is lower than a preset reference load, before the cylinder internal pressure reaches its maximum value, the exhaust valve begins to open (or, in other words, begins to open) in the subsequent working stroke according to the combustion of the air / fuel mixture ignited at the aforementioned ignition timing, wherein the cylinder internal pressure is based on the assumption that the exhaust valve remains in the closed state.

[0010] A method for heating a catalytic converter in the exhaust system of an internal combustion engine is known from patent document US 9,810,167 B2. When the catalytic converter is in an inactive state, compared to the activated state of the catalytic converter under the same engine operating conditions, the intake air volume is increased, and the ignition timing is delayed until after top dead center of the compression stroke. The ignition timing is set such that when the external load causing rotational resistance of the internal combustion engine decreases, the delay from top dead center increases. The valve opening start time of the internal combustion engine exhaust valve is set such that when the external load is lower than a given reference load, the valve begins to open before the cylinder internal pressure reaches its peak. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to accelerate the heating of the catalytic converter in the exhaust system of an internal combustion engine, thereby ensuring more efficient exhaust gas aftertreatment, especially after the cold start of the internal combustion engine.

[0012] This technical problem is solved by a method for an exhaust aftertreatment component in an exhaust system for heating an internal combustion engine. The internal combustion engine has at least one combustion chamber, preferably three or four. Each combustion chamber is bounded by a movable piston and has at least one intake port and at least one exhaust port. The intake port is connected to the intake manifold (or intake system) of the internal combustion engine and can be closed by an intake valve. The exhaust port is connected to an exhaust system and can be closed by an exhaust valve. A fuel injector for injecting fuel into the combustion chamber and a spark plug are arranged at each combustion chamber, the spark plug being configured to ignite the combustible fuel-air mixture in the combustion chamber. The internal combustion engine includes a valve lift profile conversion mechanism capable of shifting and / or changing the exhaust valve opening time. The method includes the following steps:

[0013] - Fresh air is drawn into the combustion chamber.

[0014] - Inject fuel into the combustion chamber,

[0015] - When the piston is within the range of 10°KW (Kurbelwelle, where °KW is the crankshaft angle) to 30°KW after ignition top dead center, the combustible fuel-air mixture in the combustion chamber is ignited, and

[0016] - Open the exhaust valve when the piston is in the range of 55°KW to 95°KW, preferably in the range of 70°KW to 80°KW, after the ignition top dead center.

[0017] Relatedly, a valve lift profile conversion mechanism is understood as a device capable of adjusting the opening time of the exhaust valve in an internal combustion engine. This can be, in particular, a shalling cam or camshaft adjuster with two different lift profiles, which adjusts the position of the camshaft relative to the crankshaft and thus adjusts the exhaust valve opening range in either an "advanced" or "delayed" direction. This method enables significantly accelerated heating of the exhaust aftertreatment components, especially the catalytic converter, after a cold start of the internal combustion engine. Therefore, emissions during the cold start phase of the internal combustion engine can be significantly reduced, allowing for reliable operation to meet particularly stringent emission standards, such as the planned EU7 standard.

[0018] Advantageous extended designs and improvements to the method for heating a catalyst according to the invention can be achieved through the features listed in the specification.

[0019] In a preferred embodiment of the invention, the exhaust camshaft of the internal combustion engine is specified to have an accessible cam profile, particularly an accessible cam, wherein a first access position of the accessible cam profile is configured to implement the described method for rapidly heating the exhaust aftertreatment components, and a second access position of the accessible cam profile is configured to achieve normal operation of the internal combustion engine with optimized fuel consumption. This enables a transition between a heating position and normal operation, in which the exhaust aftertreatment components can be heated particularly quickly, while in normal operation, the internal combustion engine can achieve particularly fuel-efficient operation.

[0020] Particularly preferred here is that the first access position results in (or causes) a longer exhaust valve opening time compared to the second access position. Relatedly, a longer opening time should be understood as the exhaust valve opening over a longer crankshaft angle range in the first access position compared to the second access position. If the engine speed is the same in both the first and second access positions, this also corresponds to a longer opening time in time. Because if the opening time is simply shifted "earlier," the exhaust valve closes before the exhaust gases are expelled into the exhaust system, and thus the post-combustion gases in the combustion chamber are recompressed, it is advantageous to extend the opening time compared to normal operation when switching to heated operation and correspondingly advancing the exhaust valve opening. Therefore, a valve lift profile conversion mechanism with two different cams is preferred over a camshaft adjuster that only changes the position of the exhaust valve opening time without changing its duration, achieving a longer opening lift in heated operation than in normal operation.

[0021] In an advantageous design of the method, the temperature of the exhaust aftertreatment component is determined, and the method is initiated when the determined temperature of the exhaust aftertreatment component is below a first threshold temperature. The first threshold temperature is preferably equal to the ignition temperature of the exhaust aftertreatment component. The temperature of the exhaust aftertreatment component can be determined, in particular, by a temperature sensor at the exhaust aftertreatment component or by a computational model in the internal combustion engine controller. By determining the temperature of the exhaust aftertreatment component, it is possible to determine in a simple manner whether additional heating of the exhaust aftertreatment component is required during the start-up of the internal combustion engine. This is advantageous because it avoids unnecessary heating stages that lead to additional fuel consumption.

[0022] In an alternative design of the method, it is specified that the exhaust gas temperature of the internal combustion engine is detected, and the method is initiated when the exhaust gas temperature is below a second threshold temperature. Since the exhaust gas temperature can generally be determined more simply and quickly than the temperature of the exhaust aftertreatment components, but since there is a correlation between the exhaust gas temperature and the temperature input to the exhaust aftertreatment components, the exhaust gas temperature can also be determined as an auxiliary quantity to determine whether additional heating of the exhaust aftertreatment components is required by the method according to the invention.

[0023] In another advantageous design of the method, the internal combustion engine is designed as an internal combustion engine turbocharged by an exhaust gas turbocharger, wherein the exhaust gas temperature upstream of the turbocharger turbine or the turbine component temperature of the turbocharger is determined, and heating measures are reduced when the exhaust gas temperature upstream of the turbine exceeds a third threshold temperature or the turbine component temperature exceeds a fourth threshold temperature. The exhaust gas temperature or turbine component temperature can be determined by temperature sensors or a computational model. By reducing the heating power, the critical limit temperature of the exhaust gas turbocharger can be prevented from being exceeded and permanent thermal damage to the exhaust gas turbocharger can be prevented.

[0024] In another preferred embodiment of the invention, when the exhaust aftertreatment component has reached a defined minimum temperature, the valve lift profile conversion mechanism shifts the opening time of the exhaust valve in a "delayed" direction. When the exhaust aftertreatment component reaches its operating temperature, shifting the opening time in a "delayed" direction reduces fuel consumption. In particular, this shift in the opening time in a "delayed" direction is combined with an adjustment of the ignition angle in an "advanced" direction to improve the thermal efficiency of the internal combustion engine.

[0025] In an advantageous design of the method, it is specified that the method is carried out at a maximum internal combustion engine speed of 2500 rpm, preferably a maximum of 1250 rpm, especially at idle speed or increased idle speed. To heat the exhaust aftertreatment components as quickly as possible, especially at idle speed and under lower partial loads, it is necessary to introduce a corresponding amount of heat into the exhaust system.

[0026] According to the preferred design of the method, when implementing the method, the exhaust valve is closed within an angle range of 300°KW to 380°KW after the top dead center of ignition. This ensures that most of the exhaust gas is pushed into the exhaust system and that there is sufficient time for scavenging.

[0027] Another aspect of the invention relates to an internal combustion engine having at least one combustion chamber, preferably three or more. Each combustion chamber is bounded by a movable piston. At least one intake port and at least one exhaust port are provided at each combustion chamber, connecting the combustion chamber to an intake manifold or exhaust system of the internal combustion engine. Each intake port is closable by an intake valve, and each exhaust port is closable by an exhaust valve. A fuel injector for injecting fuel into the combustion chamber and a spark plug for igniting a combustible fuel-air mixture are arranged at each combustion chamber. The internal combustion engine also has a valve lift profile conversion mechanism capable of shifting and / or extending the opening time of the exhaust valve. An exhaust aftertreatment component is arranged in the exhaust system. The internal combustion engine is in effective connection with a controller configured to implement the method for heating the exhaust aftertreatment component according to the invention when machine-readable program code stored in the controller's memory unit is executed by the controller's computing unit.

[0028] Such an internal combustion engine can achieve, even without external heating measures such as exhaust gas burners or electrically heated catalytic converters, the temperature of the exhaust gas aftertreatment components can be raised to a temperature that can efficiently convert harmful substances in the exhaust gas stream of the internal combustion engine in a short time.

[0029] In a preferred embodiment of the invention, the internal combustion engine is designed as a direct-injection gasoline engine turbocharged by an exhaust gas turbocharger. The high thermal efficiency of direct-injection gasoline engines is particularly critical when it comes to rapidly heating the exhaust aftertreatment components. This challenge is amplified for direct-injection gasoline engines turbocharged by an exhaust gas turbocharger, as the turbine of the exhaust gas turbocharger must be heated before the exhaust aftertreatment components can be heated. Here, especially for direct-injection gasoline engines turbocharged by an exhaust gas turbocharger, the proposed method for heating the exhaust aftertreatment components is particularly advantageous in situations where time constraints lead to a significant deterioration in thermal efficiency and allows the corresponding heat to be introduced into the exhaust system in the shortest possible time.

[0030] According to the advantageous design of the internal combustion engine, the spark plug is designed as a hook-type spark plug. Compared with a pre-combustion chamber spark plug, the hook-type spark plug has a simpler structure and lower manufacturing cost. However, the pre-combustion chamber spark plug has advantages in defining a small ignition chamber and in the propagation of the flame front in the combustion chamber. The method according to the invention is designed to allow reliable ignition of the fuel-air mixture in the combustion chamber using a simple hook-type spark plug and to ensure the maximum possible heat input to the exhaust system for heating the exhaust aftertreatment components.

[0031] In advantageous designs, the exhaust aftertreatment component is a three-way catalytic converter or a four-way catalytic converter. In direct-injection gasoline engines, the conversion of harmful substances is typically achieved by one or more three-way catalytic converters and a particulate filter positioned after the catalytic converter. To comply with emission limits, at least one three-way catalytic converter needs to be heated to its ignition temperature as quickly as possible.

[0032] Particularly preferred is that the three-way or four-way catalytic converter is arranged in the exhaust system as a first emission reduction aftertreatment component near the engine, along the flow direction of the exhaust gas from the internal combustion engine through the exhaust system. Accordingly, "near the engine" should be understood as a location in the exhaust system having a maximum exhaust gas travel distance of 80 cm, preferably a maximum of 50 cm, from the outlet of the internal combustion engine to the inlet of the aftertreatment component.

[0033] In an advantageous embodiment of the internal combustion engine, the valve lift switching mechanism is provided with an accessible cam, by which the opening timing of the exhaust valve can be configured to open the exhaust valve earlier in a first engaged state of the valve lift switching mechanism to heat the exhaust aftertreatment components and to open the exhaust valve later in a second engaged state to achieve efficiency-optimized combustion in the combustion chamber.

[0034] The various embodiments of the present invention mentioned in this application can be advantageously combined with each other unless otherwise described separately. Attached Figure Description

[0035] The invention is described below with reference to the accompanying drawings in the embodiments. In the drawings:

[0036] Figure 1 A schematic diagram of an internal combustion engine with an exhaust system is shown, which is used to implement a method of heating a catalytic converter according to the invention;

[0037] Figure 2 Another schematic diagram of an internal combustion engine for implementing a method of heating a catalyst according to the invention is shown;

[0038] Figure 3 This demonstrates the ideal Otto cycle process;

[0039] Figure 4 A simplified diagram of the combustion chamber of an internal combustion engine used to implement this cyclic process is shown;

[0040] Figure 5 The diagram illustrates the trends of combustion chamber pressure and exhaust valve lift during the implementation of a preferred method for heating the exhaust gas aftertreatment component according to the invention.

[0041] Figure 6The diagram illustrates the temperature trends at different locations within the exhaust system in the method for heating an exhaust gas aftertreatment component according to the invention and in a conventional method for heating an exhaust gas aftertreatment component. Detailed Implementation

[0042] Figure 1 An internal combustion engine 10 is shown, which has at least one combustion chamber 12, preferably as shown in the figure. Figure 1 The engine shown has at least three combustion chambers 12. The internal combustion engine 10 is designed as a direct-injection gasoline engine. For this purpose, a spark plug 14, preferably a hook-type spark plug 34, for igniting the combustible fuel-air mixture, and a fuel injector 30 for injecting fuel into the corresponding combustion chamber 12 are arranged at each combustion chamber 12. Each combustion chamber 12 is connected to an intake manifold (not shown) via at least one intake port 16 and to an exhaust system 40 via at least one exhaust port 18. The fluid connection from the intake manifold to the combustion chamber 12 can be closed by an intake valve 20. The fluid connection from the combustion chamber 12 to the exhaust system 40 can be closed by an exhaust valve 22.

[0043] The exhaust system 40 includes an exhaust passage 42 in which a turbine 46 of an exhaust gas turbocharger 44 is arranged along the flow direction of the exhaust gas from the internal combustion engine 10 through the exhaust system 40, and at least one exhaust gas aftertreatment component 48 is arranged downstream of the turbine 46. Preferably, as Figure 1 As shown, a first three-way catalytic converter 50 is arranged downstream of the turbine, and at least one additional exhaust gas aftertreatment component 52, particularly a second three-way catalytic converter 54, an oxidation catalyst 58, and / or a particulate filter 56, is arranged downstream of the first three-way catalytic converter 50. The second three-way catalytic converter 54 and the particulate filter 56 can also be designed as a so-called four-way catalytic converter in a single component. Furthermore, one or more exhaust gas sensors 60 can be arranged in the exhaust system 40 to monitor the functionality of the exhaust gas aftertreatment components 48, 52. Preferably, in the exhaust system 40, a first λ sensor (or λ probe) 64 is arranged upstream of the first three-way catalytic converter 50, and a second λ sensor 66, a temperature sensor 62, and, if necessary, a hazardous substance sensor 68 are arranged downstream of the first three-way catalytic converter 50.

[0044] The internal combustion engine 10 is in active connection with the controller 80, which includes a memory unit 82 and a computing unit 84. The memory unit 82 stores one or more machine-readable program codes 86 for controlling the internal combustion engine 10, particularly for controlling the ignition timing of the spark plug 14, the injection quantity and injection timing of the fuel injector 30, and for controlling the opening time of the valves 20 and 22.

[0045] Figure 2Another schematic diagram of the internal combustion engine 10 is shown. The opening time of the intake valve 20 is controlled by the intake camshaft 24. The opening time of the exhaust valve 22 is controlled by the exhaust camshaft 26. Here, a valve lift profile conversion mechanism 38 is provided on the exhaust camshaft 26. The accessible cam profile 28 can be converted between the first opening curve and the second opening curve of the exhaust valve 22 through this valve lift profile conversion mechanism. This cam profile can be activated by the switching mechanism 36.

[0046] Figure 3 An ideal Otto cycle process is schematically illustrated, which provides the theoretical basis for the method according to the invention. Figure 4 The diagram schematically shows the combustion chamber 12 of an internal combustion engine 10 together with a piston 70, which is connected to a crankshaft 76 via a connecting rod 74 to perform this cyclic process. Here, the combustion chamber 12 is sealed by piston rings 72, which seal the gap between the piston and the cylinder wall of the combustion chamber 12 and abut against the cylinder wall. Furthermore... Figure 4 The compression volume V is shown in the figure. K and working volume V H In this idealized process, dissipation losses, mechanical friction losses, or similar losses are not considered. Furthermore, the working gas has the same properties throughout the entire cycle, and flow losses are not considered. It is also assumed that the charge mixture (Ladungsgemisch) is not completely mixed with the exhaust gas.

[0047] Preferably, the present invention relates to a method for a direct-injection four-stroke gasoline engine boosted by an exhaust gas turbocharger 44. Each stroke is constituted by one piston stroke of the piston 70 or half a revolution of the crankshaft. In a four-stroke gasoline engine, changes in state can correspond to working strokes. (Refer to the following...) Figure 3 To describe this:

[0048] The first stroke, also known as the intake stroke, includes air intake or drawing in. During the intake process, the piston 70... Figure 4 The air moves downwards and combustion chamber 12 is filled with fresh air. This corresponds to the line connecting points 0 and 1 in the diagram.

[0049] The second stroke, also known as the compression or decompression stroke, involves the compression of the combustion chamber charge, during which the piston 70... Figure 4 The center moves upwards. This corresponds in the diagram to the isentropic line between points 1 and 2, and the isochoric heat transfer q. ZU This is achieved through ignition and combustion of the gas charge, which corresponds to the line connecting points 2 and 3 (isochoric combustion).

[0050] The third stroke, or power stroke, involves isentropic expansion, during which the piston 70 moves downwards again due to exothermic combustion. This corresponds to the line connecting points 3 and 4 in the diagram.

[0051] The fourth stroke, also known as the exhaust stroke (heat dissipation), involves the piston 70 moving upwards again. Due to the opening of the exhaust valve 22, the exhaust gas expands outwards at bottom dead center but does not continue to do work (the line connecting points 4 and 1), and the remaining exhaust gas is pushed outwards through the piston stroke (the line connecting points 1 and 0). During this process, the heat q contained in the exhaust gas... Ab It is released into the environment. This ideal process does not consider the residual amount in the compression chamber before reaching the environmental state.

[0052] Figure 5 The diagram illustrates the trends of combustion chamber pressure and exhaust valve lift according to a preferred embodiment of the invention and a conventional method based on a heated catalyst.

[0053] Here, the curve with reference numeral 90 represents the direction of combustion chamber pressure, and reference numeral 92 represents the direction of valve lift of exhaust valve 22 during conventional catalytic converter heating operation as known in the prior art.

[0054] Furthermore, the curve with reference numeral 94 indicates the direction of combustion chamber pressure during catalytic converter heating operation according to the invention, while reference numeral 96 points to the curve describing the direction of valve lift of exhaust valve 22 during catalytic converter heating operation according to the invention.

[0055] In known methods for heating catalytic converters in gasoline internal combustion engines, the ignition 91 of the gas charge in one of the cylinders occurs relatively late after the top dead center of the ignition, for example, at 40° KW after the top dead center of the ignition, and the opening of the exhaust valve 22 at the outlet of the combustion chamber 12 also occurs relatively late, for example, in the range of 155° KW to 175° KW after the top dead center of the ignition.

[0056] In the method according to the invention for heating the exhaust gas aftertreatment component 48, particularly the three-way catalytic converter 50, in the exhaust device 40 of a direct-injection gasoline engine having at least one combustion chamber 12, the ignition 95 of the gas charge in the combustion chamber 12 occurs within an angular range of 10° KW to 30° KW after the ignition top dead center, while the opening of the exhaust valve 22 occurs within an angular range of 55° KW to 95° KW after the ignition top dead center.

[0057] The ability to open the exhaust valve early can be achieved through the valve lift curve conversion mechanism 38, and especially through the accessible cam profile 28.

[0058] Alternatively, the transition between heated and normal operation can be accomplished by an exhaust camshaft phase adjuster with a very wide adjustment range and a cam profile used not only in heated operation, wherein the adjustment range is assumed to be at least 120°KW.

[0059] Preferably, the exhaust camshaft 26 has an accessible cam profile 28, wherein the cam profile for heating operation has a larger opening range than the cam profile for normal operation. Preferably, the cam profile for heating operation has an exhaust valve lift curve (or exhaust valve rise curve) with a control width of 250° to 290°KW, preferably about 270°KW, relative to a valve lift of at least 1 mm.

[0060] An embodiment with an accessible cam profile 28 and a control width of 250° to 290° kW is particularly preferred because it allows for optimal design of the exhaust valve opening and closing timings for the operating point. Compared to embodiments with camshaft adjusters having a larger adjustment range, this embodiment avoids the associated disadvantages, namely, a higher residual gas ratio in the combustion chamber 12 due to the inevitably very early exhaust valve closing, which is accompanied by reduced airflow and suboptimal ignition conditions in the combustion chamber 12.

[0061] The method according to the invention results in a significant increase in exhaust enthalpy. In order to ensure reliable ignition of the fuel-air mixture in the combustion chamber 12 even at such a late ignition time, a hook-type spark plug 34 is preferred over a pre-combustion chamber spark plug, since a pre-combustion chamber spark plug may not be able to ensure ignition of the fuel-air mixture at the described opening and ignition times.

[0062] exist Figure 6 The diagram illustrates the temperature trends in the exhaust system in the method of heating the exhaust gas aftertreatment component according to the present invention and in a conventional method of heating the exhaust gas aftertreatment component. Here, curve 100 shows the temperature of the exhaust gas from the internal combustion engine 10 before the turbine 46 of the exhaust gas turbocharger 44 in the method of heating the exhaust gas aftertreatment component 48 according to the present invention. Curve 102 shows the temperature trend over time near the inlet of the three-way catalytic converter 50 of the engine. Curve 104 shows the temperature trend over time near the center of the three-way catalytic converter 50 of the engine, and curve 106 shows the temperature trend over time near the outlet of the three-way catalytic converter 50 of the engine. Curve 108 shows the temperature trend over time before the turbine 46 of the exhaust gas turbocharger 44 in a conventional engine internal heating method known in the prior art for heating exhaust gas aftertreatment components. Curve 110 shows the temperature trend over time near the center of the three-way catalytic converter 50 of the engine in a conventional engine internal heating method. A comparison of curves 104 and 110 shows that, compared to conventional engine internal heating methods, the center of the three-way catalytic converter 50 reaches the first threshold temperature T significantly faster in the method according to the present invention. S1 .

[0063] List of reference numerals

[0064] 10 internal combustion engines

[0065] 12 Combustion Chambers

[0066] 14 Spark Plugs

[0067] 16 air intakes

[0068] 18 exhaust ports

[0069] 20 intake valves

[0070] 22 exhaust valves

[0071] 24 intake camshaft

[0072] 26 Exhaust Camshaft

[0073] 28 connectable cams

[0074] 30 fuel injectors

[0075] 32 Camshaft Adjuster

[0076] 34 hook-type spark plug

[0077] 36 Switching mechanism for accessible cams

[0078] 38 Valve Lift Curve Conversion Mechanism

[0079] 40 Exhaust device

[0080] 42 Exhaust passage

[0081] 44 Exhaust Gas Turbocharger

[0082] 46 Turbines

[0083] 48 Exhaust gas aftertreatment components

[0084] 50 Three-way catalytic converter

[0085] 52. Other exhaust gas aftertreatment components

[0086] 54 Second- and three-way catalytic converters

[0087] 56 Particulate Filter

[0088] 58 Oxidation Catalyst

[0089] 60 Exhaust Gas Sensor

[0090] 62 Temperature Sensor

[0091] 64 First λ sensor

[0092] 66 Second λ sensor

[0093] 68 Hazardous Substance Sensors

[0094] 70 Piston

[0095] 72 Piston Rings

[0096] 74-link

[0097] 76 Crankshaft

[0098] 80 controller

[0099] 82 memory units

[0100] 84 computing units

[0101] 86 Machine-readable program code

[0102] 90 Combustion chamber pressure (standard)

[0103] 91 Ignition via conventional catalytic converter heating

[0104] 92. Exhaust valve lift (standard)

[0105] 94 Combustion Chamber Pressure (New)

[0106] 95 Ignition (New)

[0107] 96 Valve Lift (New)

[0108] Temperature before the turbine (new)

[0109] 102. Temperature at the inlet of the three-way catalytic converter (new)

[0110] 104 Temperature at the center of the three-way catalytic converter (new)

[0111] 106. Temperature at the outlet of the three-way catalytic converter (new)

[0112] Temperature before the turbine (normal) 108

[0113] 110 Temperature at the center of the three-way catalytic converter (normal)

Claims

1. A method for heating an exhaust aftertreatment component (48) in an exhaust system (40) of an internal combustion engine (10), said internal combustion engine having at least one combustion chamber (12), wherein, The combustion chamber (12) is bounded by a movable piston (70) and has an intake port (16) and an exhaust port (18). The intake port is connected to an intake manifold of the internal combustion engine (10) and can be closed by an intake valve (20). The exhaust port is connected to an exhaust device (40) and can be closed by an exhaust valve (22). A fuel injector (30) for injecting fuel into the combustion chamber (12) is arranged at the combustion chamber (12). The internal combustion engine has a spark plug (14) configured to ignite the combustible fuel-air mixture in the combustion chamber (12). The internal combustion engine has a valve lift profile conversion mechanism (38) capable of shifting and / or changing the opening time of the exhaust valve (22). The method includes the following steps: - Fresh air is drawn into the combustion chamber (12); - Inject fuel into the combustion chamber (12); - When the piston (70) is in the range of 10°KW to 30°KW after the top dead center of ignition, the combustible fuel-air mixture in the combustion chamber (12) is ignited; and - When the piston (70) is in the range of 55°KW to 95°KW after the top dead center of ignition, open the exhaust valve (22), where, The exhaust camshaft (26) has an accessible cam profile, wherein a first access position of the accessible cam profile is configured for implementing the method, and a second access position of the accessible cam profile is configured for achieving energy-optimized normal operation of the internal combustion engine (10), wherein... Compared to the second access position, the first access position results in a longer opening time for the exhaust valve (22).

2. The method according to claim 1, characterized in that, The accessible cam shape is an accessible cam (28).

3. The method according to claim 1, characterized in that, The temperature of the exhaust gas aftertreatment unit (48) is determined, and the method is initiated when the temperature of the exhaust gas aftertreatment unit (48) is lower than a first threshold temperature.

4. The method according to claim 1, characterized in that, The internal combustion engine (10) is designed as an internal combustion engine (10) supercharged by an exhaust gas turbocharger (44), wherein the exhaust gas temperature (T) upstream of the turbine (46) of the exhaust gas turbocharger (44) is determined. EG The component temperature (T) of the turbine (46) of the exhaust gas turbocharger (44) or the exhaust gas turbocharger (44) T ), and when the exhaust gas temperature upstream of the turbine (46) (T EG Temperatures exceeding the third threshold temperature or the component temperature of the turbine (46) (T) T When the temperature is above the fourth threshold temperature, reduce heating.

5. The method according to claim 1, characterized in that, When the exhaust aftertreatment component (48) has reached the defined minimum temperature, the opening time of the exhaust valve (22) is shifted toward the "delayed" direction by the valve lift curve conversion mechanism (38).

6. The method according to claim 1, characterized in that, The method is implemented when the internal combustion engine (10) rotates at a maximum speed of 2500 rpm.

7. The method according to claim 1, characterized in that, When implementing the method, the exhaust valve (22) is closed in an angle range of 300°KW after the top dead center of ignition to 380°KW after the top dead center of ignition.

8. The method according to claim 1, characterized in that, In the first access position, the accessible cam profile has an exhaust valve lift curve with a control width of 250°KW to 290°KW, and the exhaust valve (22) is lifted at least 1 mm from the valve seat of the exhaust valve within this control width.

9. An internal combustion engine (10), having -At least one combustion chamber (12), wherein, The combustion chamber (12) is bounded by a movable piston (70) and has an intake port (16) and an exhaust port (18). The intake port is connected to the intake passage of the internal combustion engine (10) and can be closed by an intake valve (20). The exhaust port is connected to an exhaust device (40) and can be closed by an exhaust valve (22). A fuel injector (30) for injecting fuel into the combustion chamber (12) is arranged at the combustion chamber (12). - Spark plug (14), which is configured to ignite the combustible fuel-air mixture in the combustion chamber (12), and - A valve lift profile conversion mechanism (38) capable of shifting and / or changing the opening time of the exhaust valve (22), - The exhaust gas aftertreatment component (48) arranged in the exhaust device (40), and - A controller (80) configured to implement the method according to any one of claims 1 to 8 when machine-readable program code (86) stored in a memory unit (82) of the controller (80) is executed by a computing unit (84) of the controller (80).

10. The internal combustion engine (10) according to claim 9, characterized in that, The internal combustion engine (10) is a direct-injection gasoline engine that is turbocharged by an exhaust gas turbocharger (44).

11. The internal combustion engine (10) according to claim 9, characterized in that, The spark plug (14) is a hook-shaped spark plug (34).

12. The internal combustion engine (10) according to claim 9, characterized in that, The exhaust gas aftertreatment component (48) is a three-way catalytic converter (50).

13. The internal combustion engine (10) according to claim 12, characterized in that, The three-way catalytic converter (50) is arranged close to the internal combustion engine as the first emission reduction exhaust gas aftertreatment component (48) in the exhaust device (40) along the flow direction of the exhaust gas flow of the internal combustion engine (10).

14. The internal combustion engine (10) according to claim 9, characterized in that, The valve lift curve conversion mechanism (38) has an accessible cam (28) by which the opening time of the exhaust valve (22) can be adjusted to open earlier in the first access state of the valve lift curve conversion mechanism (38) to heat the exhaust aftertreatment component (48) and later in the second access state to achieve efficiency-optimized combustion in the combustion chamber (12).

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