Method for adjusting mixture formation of internal combustion engine

Abstract

The invention relates to a method for adjusting the mixture formation of an internal combustion engine (10), in particular a hydrogen burner, having a plurality of cylinders (n), having a nitrogen oxide sensor (NOx) in the exhaust gas line, in which a nitrogen oxide sensor signal (NOx sensor) is continuously determined by a control unit (100), the mixture of each cylinder is sequentially enriched starting from one cylinder (n), and the nitrogen oxide sensor signal (NOx sensor) is continuously determined by the control unit (100). A first relative fuel quantity (rk1, n) is determined for each cylinder before the enrichment of each cylinder, a second relative fuel quantity (rk2, n) is determined for each cylinder after the enrichment has been achieved, and the achieved enrichment of each cylinder is cancelled again, in which the enrichment of each cylinder is cancelled until a predeterminable nitrogen oxide limit value (SNOx) is reached, and wherein the first relative fuel quantity (rk1, n) is determined for each cylinder before the enrichment has been achieved, and the second relative fuel quantity (rk2, n) is determined for each cylinder after the enrichment has been achieved. A difference (Dn) between the determined second relative fuel quantity and the determined first relative fuel quantity is determined for each cylinder, an average relative fuel quantity (rkm) is determined as a function of the determined difference, and a mixture formation of the internal combustion engine is adjusted for each cylinder as a function of the determined difference and the determined average relative fuel quantity.

Description

Technical Field

[0001] The invention relates to a method for regulating a mixture formation in an internal combustion engine, as well as to a computing unit and a computer program product for carrying out the method. Background Art

[0002] One possible fuel injection method for gasoline engines is intake manifold injection, which is gradually being replaced by direct fuel injection. The latter method significantly improves the fuel distribution in the combustion chamber, thus achieving better power output with lower fuel consumption.

[0003] Some gasoline engines also combine intake manifold injection and direct injection, known as a dual system. This dual system is particularly advantageous given increasingly stringent emissions requirements and limits. For example, in the mid-load range, intake manifold injection offers better emissions than direct injection. Conversely, in the full load range, direct injection reduces phenomena such as so-called knock. Summary of the Invention

[0004] The object of the present invention is to provide a method for regulating the mixture formation of an internal combustion engine, wherein the mixture formation of a fuel injection is regulated.

[0005] In a first aspect, the present invention relates to a method for regulating the mixture formation of an internal combustion engine having a plurality of cylinders, in particular a hydrogen burner, wherein the internal combustion engine has a nitrogen oxide sensor in the exhaust gas line, wherein the nitrogen oxide sensor signal is continuously determined by a control unit, wherein a target lambda value for the internal combustion engine is predetermined by a control strategy calculated on the control unit, wherein, starting from one cylinder, the mixture of the cylinders is successively enriched up to a predefinable nitrogen oxide limit value, wherein before the enrichment of the cylinders, a first relative fuel quantity is determined for each cylinder, wherein after the enrichment has been achieved, a second relative fuel quantity is determined for each cylinder, and the achieved enrichment of the cylinders is canceled again, wherein a difference between the determined second relative fuel quantity and the determined first relative fuel quantity is determined for each cylinder, wherein an average relative fuel quantity is determined as a function of the determined difference, wherein the mixture formation of the internal combustion engine is regulated for each cylinder as a function of the determined difference and the determined average relative fuel quantity. Advantageously, this method for controlling mixture formation in a multi-cylinder internal combustion engine allows for individual adjustments to the mixture for each cylinder based on measured NOx values. Compared to conventional mixture control using a lambda signal, the NOx signal is less dependent on the exhaust gas oxygen concentration and, therefore, the lambda value. A further advantage of this method is that it allows for the determination and correction of individual cylinder mixture deviations based on NOx emissions in conjunction with a lambda threshold. Because NOx emissions are exponentially related to a predeterminable NOx limit value via lambda, mixture deviations can be easily determined and are highly stable. A lambda threshold is also defined when the NOx limit value is reached. This threshold is determined during the engine's operation and subsequently stored in the control unit. This prevents cylinders from operating in a range that would result in high NOx emissions. The present invention also addresses cylinder imbalance by measuring and adjusting each cylinder's deviation from the mean clearance. This ensures that all cylinders have the same mixture state, resulting in uniform combustion and power development. The use of a NOx sensor and its reduced dependence on the oxygen concentration in the exhaust gas offer significant advantages over conventional lambda-value-based control. Overall, this approach enables precise mixture control and optimization of the mixture level in hydrogen engines, ensuring low NOx emissions and exploiting the engine's performance potential.

[0006] In one particular embodiment, mixture formation control is enabled only when the internal combustion engine is stationary or quasi-stationary. This particular embodiment has the advantage that mixture formation control is enabled only when the internal combustion engine is stationary or quasi-stationary. This means that mixture control is not activated during dynamic operating phases, such as acceleration or load changes. This ensures a stable and reliable mixture formation during these critical operating phases. This contributes to improved engine performance, efficiency, and durability.

[0007] In one advantageous embodiment, while one cylinder is being enriched, the mixture of the remaining cylinders is adjusted so that the target lambda value of the internal combustion engine remains constant. This advantageous embodiment has the advantage that while one cylinder is being enriched, the mixture of the remaining cylinders is adjusted so that the overall air-fuel mixture remains constant. This means that enriching a single cylinder does not lead to an excessive enrichment of the overall mixture. Consequently, the method is robust and the mixture level of the enriched cylinder can be determined.

[0008] In one specific embodiment, the mixture in each cylinder is leaned if the difference falls below the average relative fuel quantity. The advantage of this specific embodiment is that the mixture in the corresponding cylinder is leaned when the difference falls below the average relative fuel quantity. This allows for targeted adjustment of the mixture to ensure optimal combustion and power development. By leaning the mixture, less fuel is injected, thereby improving the air-fuel ratio. This helps reduce fuel consumption and improve engine efficiency. Optimizing combustion by leaning the mixture also reduces pollutant emissions.

[0009] In one particular embodiment, if the difference exceeds the average relative fuel quantity, the mixture for each cylinder is enriched. By enriching the mixture, the fuel quantity for the relevant cylinder is increased. This can help compensate for any imbalances between cylinders and ensure that all cylinders operate under similar conditions. This uniform combustion improves engine performance and reduces the risk of damage or wear to individual cylinders.

[0010] In one advantageous embodiment, the mixture is leaned to an average relative fuel quantity. This allows for targeted adjustment of the mixture in each cylinder to achieve optimal combustion and power development. In summary, leaning the mixture to an average relative fuel quantity allows for targeted optimization of combustion and power development. By adjusting the fuel quantity, uniform combustion is ensured in all cylinders, thereby improving engine performance, reducing emissions, and extending engine service life.

[0011] In another embodiment, the mixture is enriched to an average relative fuel amount. This allows for targeted adjustment of the mixture in each cylinder to achieve optimal combustion and power development. In summary, enriching the mixture to an average relative fuel amount allows for targeted optimization of combustion and power development. By adjusting the fuel amount, uniform combustion is ensured in all cylinders, thereby improving engine performance, reducing emissions, and extending engine life.

[0012] In one advantageous embodiment, the NOx sensor signal is continuously recorded for each cylinder during the enrichment process. If the NOx sensor signal exceeds a predeterminable NOx limit value, the method is initiated. If the NOx sensor signal falls below the activation threshold, the measurement for that cylinder is aborted and the measurement continues with the next cylinder. If the NOx sensor signal falls below the activation threshold, the measurement for that cylinder is aborted and the measurement continues with the next cylinder. This allows for efficient and rapid adjustment of the mixture for each cylinder. If a cylinder is already below the NOx limit value, no further adjustment is required because it already has optimal emissions. Therefore, the measurement for that cylinder can be skipped, saving time and resources. By continuously recording the NOx sensor signal for each cylinder and making targeted adjustments to the mixture based on NOx emissions, the method enables precise and individual enrichment of each cylinder. This further reduces NOx emissions and improves engine performance.

[0013] In a further aspect, the invention relates to a device, in particular a controller, and a computer program product, which are configured, in particular programmed, to carry out one of the methods. In another aspect, the invention also relates to a machine-readable storage medium on which the computer program product is stored. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be described in more detail below with reference to the accompanying drawings and examples, wherein:

[0015] Figure 1 This is a schematic diagram of a cylinder of an internal combustion engine.

[0016] Figure 2 Schematic diagram of a mixture formation method for an internal combustion engine with a dual fuel metering device. DETAILED DESCRIPTION

[0017] exist Figure 1 1 and 2. The cylinder 102 of an internal combustion engine 100 is schematically illustrated as an example. The cylinder 102 has a combustion chamber 103, which is expanded or contracted by moving a piston 104. The internal combustion engine herein may in particular be a gasoline engine, a diesel engine or a hydrogen burner.

[0018] Cylinder 102 has an intake valve 105 for introducing air or a fuel-air mixture into combustion chamber 103. Air is supplied via an intake manifold 106, part of the air supply system, on which fuel injectors 107 are located. The inhaled air passes through intake valve 105 and enters combustion chamber 103 of cylinder 102. A throttle valve 112 in the air supply system is used to set the desired air mass flow rate into cylinder 102. Furthermore, an air mass sensor 99 is located in intake manifold 106, specifically upstream of throttle valve 112, for measuring relative air mass. This sensor can be, in particular, a hot film air mass meter (HFM).

[0019] The internal combustion engine can be operated in an intake manifold injection process in which fuel is injected into the intake manifold 106 by means of a fuel injector 107 , thereby forming an air-fuel mixture there, which enters the combustion chamber 103 of the cylinder 102 through an intake valve 105 .

[0020] The internal combustion engine can also be operated using a direct injection process. To this end, a fuel injector 111 is positioned on the cylinder 102 to inject fuel directly into the combustion chamber 103. Through this direct injection, the air-fuel mixture required for combustion is formed directly in the combustion chamber 103 of the cylinder 102. The cylinder 102 is also equipped with an ignition device 110 for generating an ignition spark to initiate combustion in the combustion chamber 103.

[0021] After combustion, the combustion exhaust gases are discharged from the cylinder 102 via the exhaust manifold 108. Exhaust is dependent on the opening of the exhaust valve 109, which is also located on the cylinder 102. The opening and closing of the intake valve 105 and the exhaust valve 109 are used to implement the four-stroke operation of the internal combustion engine 100 in a known manner. The lambda value of the exhaust gas in the exhaust manifold 108 can be determined using a lambda sensor.

[0022] Internal combustion engine 100 can operate using direct injection, intake manifold injection, or a hybrid mode. This allows the optimal operating mode for internal combustion engine 100 to be selected based on the current operating point. For example, when operating at low speeds and low loads, internal combustion engine 100 can operate in intake manifold injection mode; when operating at high speeds and high loads, direct injection mode can be used. However, over a wide operating range, operating internal combustion engine 100 in a hybrid mode is desirable. In this mode, fuel is supplied to combustion chamber 103 in a proportional manner via intake manifold injection and direct injection.

[0023] Furthermore, a computing unit designed as a controller 115 is provided for controlling the internal combustion engine 100 . The controller 115 can operate the internal combustion engine 100 in direct injection, intake manifold injection, or mixed mode. The controller 115 can also record the value of the nitrogen oxide sensor 123 .

[0024] Controller 115 actuates the injection valves in the intake manifold and the injection valves in the cylinders, using them to predetermine the fuel quantity supplied to the internal combustion engine. The required fuel quantity is set by a lambda controller integrated in controller 115, primarily based on the engine load and the required lambda value. The basic setting is preferably performed by an adjustable pilot controller included in the lambda controller. To this end, the output signal of the pilot controller is superimposed on the output signal of the lambda controller. The pilot controller determines the fuel quantity primarily based on the engine load. The relationship between the engine load and the predetermined fuel quantity is preferably stored in a characteristic map of controller 115. Due to system drift, the relationship between the engine load and the predetermined fuel quantity may change. To compensate for this, a control cycle is provided within the scope of mixture control, in which this relationship is relearned in the pilot controller.

[0025] During mixture control, systematic errors in the fuel-air mixture are corrected using preferred control measures and the control values ​​determined thereby. Various types of errors can occur, leading to mixture deviations. Errors in determining the amount of air supplied to the internal combustion engine have a multiplicative effect on fuel metering, while errors due to blowby effects or delayed tightening of injection valves have an additive effect. Multiplicative errors are particularly pronounced in the medium load range of internal combustion engine 100, while additive errors predominate at low loads. Therefore, when adjusting fuel metering according to known methods, it is preferred to adjust the multiplicative error in the medium load range and the additive error in the low load range. Since multiplicative errors also have an effect in the low load range, and additive errors also have an effect in the medium load range, adjustments are performed alternately between the two load ranges until the pilot controller achieves sufficiently stable control.

[0026] In particular, internal combustion engine 100 can be configured as an internal combustion engine with one or more engine banks. Specifically, a separate intake manifold injection valve can be provided in the air supply section of each cylinder. Similarly, each air supply section of each engine bank can have a separate throttle valve for regulating the incoming air. Furthermore, internal combustion engine 100 can include multiple exhaust manifolds, each of which is equipped with a lambda sensor for measuring the air-fuel ratio.

[0027] Internal combustion engine 100 is preferably an internal combustion engine having 2, 3, 4, 6 or 8 cylinders.

[0028] The term "mixture formation" refers to the process of preparing the air-fuel mixture for an internal combustion engine. This process plays a decisive role in the engine's performance and efficiency. The mixture is created with a specific ratio of air and fuel to ensure optimal combustion. This mixture is typically formed using an injection system that injects fuel into the air stream. The air-fuel ratio is controlled by various parameters, such as throttle position, injection timing, and injection quantity. Adjusting the method of mixture formation allows the mixture to be tailored to the specific requirements of each cylinder for optimal performance and efficiency.

[0029] Figure 2 A functional diagram illustrating the method is shown. In a first step 500, the method's start conditions are checked. If it is determined that internal combustion engine 100 is in a stationary or quasi-stationary operating mode or point, the control method is allowed to start. For example, if the speed change and / or the air mass flow change and / or the engine torque change and / or the accelerator pedal position change remain essentially unchanged within a predetermined time interval, then internal combustion engine 100 is in a stationary or quasi-stationary operating mode or point. Advantageously, the described method checks whether the relative air mass (ratMAir) changes slightly within a predetermined time interval. If the change in relative air mass (ratMAir) does not exceed a predeterminable threshold value within this time interval, it can be assumed that internal combustion engine 100 is in a stationary or quasi-stationary operating point, and the method is allowed to start. Another essential criterion for the method is that the split factor facSplt is between 1 and 0. The split factor predetermines the distribution of the fuel quantities injected by the intake manifold injection valves and the direct injection valves. Compared to known methods in the prior art, this method has the advantage of being able to diagnose both the manifold injection path and the direct injection path while both valves are operating simultaneously. This diagnosis does not require shutting down either path (intrusive testing). Therefore, if a stationary or quasi-stationary operating state is detected, the method is initiated and continued in step 510.

[0030] Next, in step 500 , the method starts from the beginning.

[0031] In step 510, the controller 115 continuously determines and stores the nitrogen oxide sensor signal NOx sens The method for a 4-cylinder internal combustion engine is described below. The method can also be used without restriction for internal combustion engines with more than two cylinders. The internal combustion engine can preferably be designed as a gasoline, diesel or even hydrogen burner. An air-fuel model is stored in the controller 115, which determines the target air-fuel mixture λ Soll , and is predefined for four cylinders. In this case, the air-fuel model determines the relative fuel quantity for each cylinder n and predefines this fuel quantity for each cylinder.

[0032] Starting from the first cylinder n1 of the internal combustion engine, the mixture of the first cylinder n1 is enriched. Before enrichment, the controller determines and stores a first relative fuel quantity rk of the first cylinder n1. 1，1 During the enrichment of the mixture of the first cylinder n1, the air-fuel regulation model regulates the mixture of the remaining cylinders so that the target air-fuel mixture λ of all cylinders n is Soll The enrichment of the first cylinder n1 continues until the NOx sensor signal NOx sens Exceeding or reaching a predefinable nitrogen oxide limit value S NOx Predeterminable nitrogen oxide limit value S NOx It is determined during the engine application phase and is subsequently stored in the controller 115 .

[0033] Since the NOx emission is exponentially related to the predeterminable NOx limit value via lambda, mixture deviations can be easily determined and are very stable. When the NOx limit value is reached, a lambda threshold is also defined. This threshold is determined during the engine application phase and is subsequently stored in the controller. If the NOx sensor signal NOx sens Exceeding the predefinable nitrogen oxide limit value S NOx , the second relative fuel quantity rk of the first cylinder n1 is determined and stored 2，1 .

[0034] In another embodiment, if the nitrogen oxide sensor signal NOx sens The predeterminable nitrogen oxide limit value S is not exceeded NOx , the measurement of the corresponding cylinder can be cancelled. For example, the NOX sensor signal sens A predeterminable nitrogen oxide limit value S must be achieved NOx The time or degree of thickening is predetermined.

[0035] Subsequently, the enrichment of the first cylinder n1 is canceled, and the mixture change of the remaining cylinders is also canceled, so that the target air-fuel mixture (λ Soll ). Step 510 is now repeated for each additional cylinder n until the first relative fuel quantity rk is determined for all cylinders n. 1，n and the second relative fuel quantity rk 2，n .

[0036] The method then continues in step 520 .

[0037] In step 520, a second relative fuel quantity rk is determined for each cylinder n. 2，n and the first relative fuel quantity rk 1，nThe difference D n Then, according to the determined difference D of the relative fuel quantities of the n cylinders, n , determine the average relative fuel quantity rk m This is preferably achieved by averaging:

[0038] n is the number of cylinders.

[0039] The method then continues in step 530 .

[0040] In step 530, for each cylinder n, the difference D is determined. n Whether it exceeds or falls below the average relative fuel quantity rk m .

[0041] If the determined difference D n Exceeding the average relative fuel quantity rk m , then the mixture of each cylinder n is enriched. This is preferably performed by an air-fuel control model.

[0042] If the determined difference D n Lower than average relative fuel quantity rk m , then the mixture of each cylinder n is made leaner. This is preferably performed by an air-fuel control model.

[0043] In a particular embodiment, the average relative fuel quantity rk m The value of makes each cylinder richer or leaner.

[0044] In another embodiment, the relative fuel amounts may also be converted into air-fuel ratios and the method may be performed based on these air-fuel ratios.

[0045] The method can then start over or end in step 500 .

Claims

1. Method for regulating the mixture formation of an internal combustion engine (10) having a plurality of cylinders (n), in particular a hydrogen burner, in, The internal combustion engine (10) has a nitrogen oxide sensor (NOx) in the exhaust gas line, The controller (100) continuously determines the nitrogen oxide sensor signal (NOx sens ), In this case, starting from one cylinder (n), the mixture of each cylinder (n) is enriched successively until a predefined nitrogen oxide limit value (S NOx ), Before each cylinder (n) becomes rich, a first relative fuel quantity (rk) is determined for each cylinder (n). 1，n ), In this case, after the enrichment has been achieved, a second relative fuel quantity (rk 2，n ) and cancel the enrichment already achieved for each cylinder (n) again, Wherein, the second relative fuel quantity (rk) determined for each cylinder (n) is determined 2,n ) and the determined first relative fuel quantity (rk 1,n ) between the difference (D n ), According to the determined difference (D n ) Determine the average relative fuel quantity (rk m ), Where, for each cylinder (n), the difference (D n ) and the determined average relative fuel quantity (rk m ), the mixture formation of the internal combustion engine (10) is adjusted.

2. The method according to claim 1, characterized in that If the internal combustion engine (10) is in a stationary or quasi-stationary operating state, it is possible to start adjusting the mixture formation.

3. The method according to claim 1, characterized in that During the enrichment of one of the cylinders, the mixture of the remaining cylinders is adjusted so that the target lambda value (λ Soll ) remains constant.

4. The method according to claim 1, wherein If the difference (D n ) is lower than the average relative fuel quantity (rk m ), the mixture of each cylinder (n) becomes leaner.

5. The method according to claim 1, characterized in that If the difference (D n ) exceeds the average relative fuel quantity (rk m ), the mixture of each cylinder (n) becomes richer.

6. The method according to claim 3, characterized in that Lean the mixture to the average relative fuel amount (rk m ) value.

7. The method according to claim 4, characterized in that The mixture is enriched to the average relative fuel amount (rk m ) value.

8. The method according to claim 1, characterized in that During the enrichment process, the nitrogen oxide sensor signal (NOx sens，n ), if the nitrogen oxide sensor signal (NOx sens，n ) exceeds a predeterminable nitrogen oxide threshold value (S NOx ), it is allowed to start the method, if the nitrogen oxide sensor signal (NOx sens，n ) is lower than the start threshold (S NOx ), the measurement of the cylinder (n) is abandoned and the measurement of the next cylinder is continued.

9. A computing unit (115) configured to carry out the method according to any one of the preceding claims.

10. A computer program product which, when executed on a computer unit (115), causes the computer unit (115) to carry out the method according to any one of claims 1 to 9.

11. A machine-readable storage medium having stored thereon the computer program product according to claim 10.

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