Method for calculating a fresh air mass in a cylinder and control

Abstract

Method for calculating a fresh air mass in a cylinder (2) of an internal combustion engine (1), comprising: Determining (33) a heating of the fresh air (7) at a wall (2a) of the cylinder (2); and Calculating (38) the fresh air mass of the fresh air (7) in the cylinder (2) based on the determined heating of the fresh air mass.

Description

[0001] The invention relates to a method for calculating a fresh air mass in a cylinder of an internal combustion engine and a controller configured to carry out such a method.

[0002] In gasoline engines, it is generally accepted that the air volume in a cylinder's combustion chamber must be determined as accurately as possible so that the correct fuel quantity for injection can be calculated. The amount of air remaining in the combustion chamber depends on many thermodynamic variables, and it is known that filling errors can occur in the calculated air volume at different ambient temperatures.

[0003] German patent application DE 101 58 261 A1 discloses an engine management system in which a physically based model is used to determine various state variables. The state variables relate to a connecting section located between a mixing point, where recirculated exhaust gas is mixed with intake fresh air, and the intake valves of an internal combustion engine. The physical model simulates the behavior of this connecting section, so that various operating parameters of the internal combustion engine can be controlled using this model, such as the fresh air mass in the connecting section and the gas temperature. The disadvantage of this is that only the influence of the connecting section on the fresh air mass is taken into account, while other influences on the fresh air mass are ignored.

[0004] EP 1 312 783 A1 relates to a method for operating an internal combustion engine, in particular of a motor vehicle, in which air is supplied to an intake manifold via a throttle valve, in which exhaust gas is supplied to the intake manifold via an exhaust gas recirculation system and thereby has an exhaust gas temperature, in which the resulting gas mixture is supplied to a combustion chamber and thereby has a gas mixture temperature, and in which the gas mixture temperature is determined as a function of the exhaust gas temperature.

[0005] DE 10 2004 062 018 A1 relates to a method for operating an internal combustion engine, in which the air charge in a combustion chamber is determined taking into account a pressure in an intake duct. The invention further relates to a computer program, an electrical storage medium for a control and / or regulating device of an internal combustion engine, and a control and / or regulating device of an internal combustion engine.

[0006] The object of the present invention is to provide a method for calculating a fresh air mass in a cylinder of an internal combustion engine and a corresponding control for an internal combustion engine, which at least partially overcome the above-mentioned disadvantages.

[0007] This object is achieved by the inventive method according to claim 1 and the control according to claim 15.

[0008] According to a first aspect, the present invention provides a method for calculating a fresh air mass in a cylinder of an internal combustion engine, the method comprising: determining a heating of the fresh air at a wall of the cylinder; and calculating the fresh air mass of the fresh air in the cylinder based on the determined heating of the fresh air mass.

[0009] According to a second aspect, the present invention provides a controller for an internal combustion engine having at least one cylinder, an intake manifold, an intake manifold temperature sensor, an intake valve on the cylinder and an intake port upstream of the intake valve, the controller being configured to carry out the method according to the first aspect.

[0010] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.

[0011] In some embodiments, an increase in the fresh air temperature is calculated from a temperature sensor in the intake manifold to the intake valve, with the heat exchange being calculated based on the temperature difference between the component and the fresh air. Furthermore, in some embodiments, the internal combustion engine has a controlled cooling water mass flow (CFM) and thus an additional degree of freedom. It was recognized that this degree of freedom was not sufficiently taken into account in solutions or charge detection models known in the prior art.

[0012] It was also recognized that known corrections cannot take heat transfer via the cylinder wall into account, so that at very hot or very cold intake temperatures, changes in the density of the fresh air in the combustion chamber are corrected too strongly due to the effect not being taken into account. This can lead to larger errors in the fresh air calculation. In addition, it was recognized that in engines with map-controlled cooling water flows, the cooling water temperature alone is not always completely meaningful, since the heat transfer at the cylinder wall through thermal convection as a function of the water mass flow cannot be taken into account. Due to stricter emission limits in new exhaust gas test cycles and the increased requirements to achieve the lowest emission values under all ambient conditions, the heating of the fresh air by the cylinder wall is taken into account in some embodiments.

[0013] Accordingly, some embodiments relate to a method for calculating a fresh air mass in a cylinder of an internal combustion engine, the method comprising determining a heating of the fresh air at a wall of the cylinder and calculating the fresh air mass of the fresh air in the cylinder based on the determined heating of the fresh air mass.

[0014] The internal combustion engine can be a gasoline engine or diesel engine or the like and can be intended, for example, for a motor vehicle (such as a car, motorcycle, but in principle also other land, water, and / or aircraft). The number of cylinders is arbitrary and can be 1, 2, 3, 4, 5, 6, etc., depending on the embodiment.

[0015] In some embodiments, the fresh air mass is directly the mass of the fresh air in the cylinder, for example, directly after an intake process, without the invention being limited in this respect, whereas in other embodiments, the fresh air mass is represented by one or more variables, such as density, temperature, volume, etc.

[0016] The method then determines the heating of the fresh air in the cylinder at a cylinder wall. Typically, the section of the cylinder wall that is in contact with the fresh air entering the cylinder for subsequent combustion, for example, through an intake process, is taken into account, since the goal in some embodiments is to determine the correct amount of fuel to be injected based on the fresh air mass present in the cylinder. This section can be, for example, the section of the cylinder wall in the combustion chamber of the cylinder, the cylinder base (or piston surface), etc.

[0017] The method then calculates the fresh air mass of the fresh air in the cylinder based on the determined heating of the fresh air mass.

[0018] Thus, embodiments of the invention make it possible to take into account the heating of the fresh air at the cylinder wall during the intake phase, thereby increasing the accuracy of the calculated fresh air mass. As a result, in some embodiments, a higher mixture accuracy between air and fuel can be achieved at intake temperatures, coolant temperatures and coolant mass flows through the cylinder crankcase or through the cylinder head that deviate from the standard state. This temperature correction goes beyond temperature corrections in which only the heating up to the intake valve is modeled. The additional integration of the cylinder wall temperature as a thermal contact area has the advantage that, in particular, filling errors under different ambient temperatures are reduced. In some embodiments, a coolant mass flow can also be integrated into the heat transfer by means of thermal convection.

[0019] In some embodiments, the already existing temperature correction of the fresh air (mass) in the intake path up to behind the intake valve is therefore extended by the wall heat exchange between the cylinder wall and the fresh air.

[0020] In general, in some embodiments, the temperature increase of the fresh air on its way into the cylinder can be determined based on the following equation: TLuft_kor,i=αw,i⋅(Tw,l−TLuft,i−1)+TLuft,i−1

[0021] The parameter “i” represents a component that transfers heat to the fresh air on its way into the cylinder, so that “i-1” indicates the next upstream component from which the fresh air comes.

[0022] The parameter “T w,i “ represents the temperature of the wall surface “w” of the component “i” for which the heat transferred to the fresh air is to be determined.

[0023] The parameter “TLuft,i-1 “ represents the temperature (or temperature increase) of the fresh air at the next upstream component “i-1”.

[0024] The parameter “α w,i “ represents an effective heat transfer coefficient for a wall section or a contact area A i of component i, which comes into contact with the fresh air: αw,l=(Qw⋅αi⋅Ai), where “Q w “ represents the heat released at the wall “w”, “α i “ the heat transfer coefficient of the component “i” and “A i ” the contact area of component “i”:

[0025] In some embodiments, the effective heat transfer coefficient is determined empirically, e.g. on a test bench, and / or model-based.

[0026] In some embodiments, determining the heating of the fresh air comprises determining a heating of the fresh air at an inlet port to the cylinder upstream of an inlet valve of the cylinder. In some embodiments, for example, there is a temperature sensor in an intake manifold located upstream of the cylinder and through which fresh air is drawn in, such that the temperature of the fresh air in the intake manifold at the location of the temperature sensor can be determined using this temperature sensor. In some embodiments, no further temperature sensor is provided downstream of this temperature sensor, so that by including the heating of the fresh air at the inlet port to the cylinder, the heating of the fresh air on the way from the intake manifold at the location of the temperature sensor to the cylinder can be calculated more accurately.

[0027] Determining the heating of the fresh air at the inlet duct can be based on the following relationship: TLuft_v_EV=(TEK−TLuft_Sgr)⋅αw1+TLuft_Sgr, where T Luft_v_EV represents the temperature of the fresh air at the intake port in front of the cylinder's intake valve, T EK represents the temperature of the inlet channel, T Luft_Sgr represents the temperature of the fresh air in an intake manifold to the inlet port of the cylinder and α w1 represents an effective heat transfer coefficient of the inlet channel.

[0028] Equation (3) therefore allows the determination of the temperature increase of the fresh air at the intake port in front of the cylinder's intake valve, where the temperature T Luft_Sgr the fresh air in an intake manifold to the cylinder's inlet port is determined, for example, by a temperature sensor in the intake manifold, so that this temperature is available as a measured value. The temperature T EK of the inlet channel can be determined, for example, based on a model and / or on the basis of a cooling water temperature.

[0029] In some embodiments, the effective heat transfer coefficient α w1 A characteristic map that represents the heat transfer of the intake port as a function of engine speed and / or intake manifold pressure. This allows for a precise determination of the heating of the fresh air or the heat transfer from the intake port to the fresh air.

[0030] The effective heat transfer coefficient α w1 can be determined by measuring on a test bench, so that the heat transfer for the internal combustion engine can be determined particularly accurately.

[0031] In some embodiments, the temperature of the fresh air in the intake manifold is determined with the aid of a temperature sensor in the intake manifold, so that a measured value and, for example, no model-based value for the fresh air temperature is available as the starting point for the calculations for heating the fresh air in the intake tract, whereby the accuracy can be improved.

[0032] In some embodiments, determining the heating of the fresh air comprises determining a heating of the fresh air at an intake valve of the cylinder. In some embodiments, the intake valve is the next component in the intake path, which plays a significant role in heating the intake fresh air on its way into the cylinder after the aforementioned intake port, so that the accuracy of determining the heating can be further increased.

[0033] Determining the heating of the fresh air at the cylinder’s intake valve can be based on the relationship: TLuft_h_EV=(TEV−TLuft_v_EV)⋅αw2+TLuft_v_EV, where T Luft_h_EV represents the temperature of the fresh air at the cylinder's intake valve, T EV represents the temperature of the intake valve, T Luft_v_EV represents the temperature of the fresh air in the intake port in front of the cylinder's intake valve and α w2 represents an effective heat transfer coefficient of the intake valve.

[0034] Equation (4) therefore allows the determination of the temperature T Luft_h_EV of fresh air at the cylinder inlet valve, whereby the temperature T Luft_v_EV can be determined based on equation (3) above, so that it can be particularly accurate in some embodiments. The temperature T EVof the intake valve can, for example, be determined model-based and / or based on a cooling water temperature or oil temperature of the internal combustion engine.

[0035] In some embodiments, the effective heat transfer coefficient α w2 A characteristic map that represents the heat transfer of the intake valve as a function of engine speed and / or intake manifold pressure. This allows for a precise determination of the heating of the fresh air or the heat transfer from the intake valve to the fresh air.

[0036] The effective heat transfer coefficient α w2 can be determined by measuring on a test bench so that the heat transfer for the internal combustion engine can be determined particularly precisely or it can also be determined model-based and stored accordingly as a characteristic map.

[0037] In some embodiments, the determination of the heating of the fresh air at the wall of the cylinder is based on the relationship: TLuft_Cyl=(TZyl_Wand−TLuft_h_EV)⋅αw3+TLuft_h_EV, where T Luft-zyl represents the temperature of the fresh air at the wall of the cylinder, T Zyl_Wand the temperature of the wall of the cylinder is T Luft_h_EV is the temperature of the fresh air after the intake valve of the cylinder and α w3 represents an effective heat transfer coefficient of the cylinder wall (which is determined empirically on the test bench and / or model-based and is stored, for example, as a characteristic map).

[0038] Equation (5) therefore allows the determination of the temperature T Luft_Zyl of the fresh air at the wall of the cylinder, whereby the temperature T Luft_h_EV can be determined based on equation (4) above, so that it can be particularly accurate in some embodiments. The temperature T Zyl_WandThe temperature of the cylinder wall can be determined, for example, using a model. In some embodiments, the temperature T Zyl_Wand the cylinder wall is based on a simulation calculation, using a thermodynamic model of the internal combustion engine, so that the temperature can be specified as a function of, for example, a fresh air charge and a speed of the internal combustion engine and can be stored, for example, as a characteristic map. Accordingly, in some embodiments, the temperature T Zyl_Wand of the cylinder wall as a characteristic map that indicates this temperature, for example, as a function of the fresh air charge and / or the engine speed. This allows for a very precise determination of the cylinder wall temperature and thus the heating of the fresh air.

[0039] In some embodiments, the method comprises determining a reference heating of the fresh air at a wall of the cylinder based on at least one reference parameter. The reference parameter may include, for example, reference temperatures of the intake, intake port, intake valve, and / or cylinder wall temperatures. The reference temperatures can be selected arbitrarily, and those skilled in the art will appreciate that they can select the temperatures accordingly depending on the embodiment.

[0040] In some embodiments, the reference heating of the fresh air at the wall of the cylinder is basically carried out on the basis of the same calculation rules as for the heating of the fresh air at the wall of the cylinder discussed above, in particular equations (1) to (5), with the only difference that the mentioned reference temperature(s) is (are) used.

[0041] Accordingly, in some embodiments, the following relationships are used to calculate the reference heating of the fresh air at the wall of the cylinder:

[0042] Determining the reference heating of the fresh air at the inlet duct can be based on the following relationship: TLuft_h_EV_ref=(TEK_ref−TLuft_Sgr_ref)⋅αw1+TLuft_Sgr_ref, where T Luft_v_EV_ref represents the reference temperature increase of the fresh air at the intake port in front of the cylinder's intake valve, T EK_ref represents the reference temperature of the inlet channel (and corresponds, for example, to the reference cooling water temperature), T Luft_Sgr_ref represents the reference temperature of the fresh air in an intake manifold to the inlet port of the cylinder and α w1 represents an effective heat transfer coefficient of the inlet channel, as discussed above (equation (3)).

[0043] Determining the reference heating of the fresh air at the cylinder’s intake valve can be based on the relationship: TLuft_h_EV_ref=(TEV_ref−TLuft_v_EV_ref)⋅αw2+TLuft_v_EV_ref, where T Luft_h_EV_ref represents the reference temperature increase of the fresh air at the inlet valve of the cylinder, T EV_ref represents the reference temperature of the inlet valve (and corresponds, for example, to the reference cooling water temperature), T Luft_v_EV_ref represents the reference temperature of the fresh air in the intake port in front of the cylinder's intake valve (and calculated, for example, according to equation (6)) and α w2 represents an effective heat transfer coefficient of the intake valve, as discussed above (equation (4)).

[0044] In some embodiments, the determination of the reference heating of the fresh air at the wall of the cylinder is based on the relationship: TLuft_Cyl_ref=(TZyl_Wand_ref−TLuft_h_EV_ref)⋅αw3+TLuft_h_EV_ref, where T Luft_Zyl_ref represents the reference temperature increase of the fresh air at the wall of the cylinder, T Zyl_Wand_ref is the reference temperature of the cylinder wall, T Luft_h_EV_ref the - reference temperature of the fresh air after the intake valve of the cylinder (e.g. calculated according to equation (7)) and α w3 represents an effective heat transfer coefficient of the wall of the cylinder, as discussed above (equation (5)).

[0045] In some embodiments, the fresh air mass of the fresh air in the cylinder is calculated based on the determined heating of the fresh air mass and the determined reference heating, whereby the fresh air mass can be calculated particularly precisely.

[0046] In some embodiments, the above-mentioned calculations are based on the assumption that the internal combustion engine is in a stationary state and that stable temperature conditions prevail accordingly (i.e., for example, that the internal combustion engine is (stable) at an operating point).

[0047] In some embodiments, the fresh air quantity or fresh air mass in the cylinder is determined on a test bench and stored as a characteristic map, whereby, for example, the characteristic map is multidimensional and depends on one or more of the following parameters: speed, intake manifold pressure, camshaft position at the inlet and outlet, etc.

[0048] This fresh air quantity or fresh air mass determined on the test bench is then corrected based on the determined temperature (heating) of the fresh air at the cylinder wall (according to equation (5)) and the reference temperature (heating) of the fresh air at the cylinder wall (according to equation (8)).

[0049] Accordingly, in some embodiments a correction factor is determined: FACτ_kor=TLuft_Zyl_ref / TLuft_Zyl, where the reference temperature (increase) T Luft_Zyl_ref the fresh air at the wall of the cylinder is calculated according to equation (8) and the temperature (increase) T Luft_Zyl the fresh air at the wall of the cylinder is calculated according to equation (5).

[0050] This results in a corrected fresh air quantity or fresh air mass “air mass kor “ in the cylinder as follows: Air mass cor=air mass map⋅FACτ_kor, where air mass Kennfeld the above-mentioned fresh air quantity or fresh air mass determined on the test bench and stored in the characteristic map and the correction factor FAC T_kor is calculated according to equation (9).

[0051] This makes it possible in some embodiments to carry out a very simple but precise correction of the fresh air quantity or fresh air mass stored in the characteristic map, without the need for complex and time-consuming calculations to determine the fresh air quantity or fresh air mass.

[0052] Some embodiments relate to a controller for an internal combustion engine having at least one cylinder, an intake manifold, an intake manifold temperature sensor, an intake valve on the cylinder, and an intake port upstream of the intake valve, wherein the controller is configured to execute the method described herein. The controller may, for example, be configured as an engine control unit and accordingly comprise typical elements of an engine control unit, such as one or more processors, a volatile and a non-volatile memory, an interface to a motor vehicle bus system, etc.

[0053] Some embodiments relate to a motor vehicle with such a control system and an internal combustion engine.

[0054] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 schematically illustrates an embodiment of an internal combustion engine of a motor vehicle of the present invention; Fig. 2 schematically shows an embodiment of a control of the internal combustion engine of Fig. 1 illustrates; and Fig. 3 schematically illustrates an embodiment of a method for calculating a fresh air mass according to the present invention.

[0055] An embodiment of an internal combustion engine 1 is shown in Fig. 1 schematically illustrates, wherein the internal combustion engine 1 is a gasoline engine and has four cylinders, wherein in Fig. 1 shows a sectional view of a cylinder 2 of the internal combustion engine 1.

[0056] The cylinder 2 has an inlet valve 3, an exhaust valve 4 and a combustion chamber 5, which can be compressed by a cylinder piston 6, as is basically known, and a cylinder wall 2a. The cylinder wall 2a is the inner wall of the combustion chamber 5 and in the sectional view in Fig. 1 shows a left and a right side of the cylinder wall 2a.

[0057] In combustion chamber 5, as in Fig. 1 illustrates, during the intake phase there is typically fresh air 7 and residual gas 8 that has remained in the combustion chamber 5 from a previous cycle.

[0058] The fresh air 7 is sucked in through an intake manifold 9 and passes through an inlet channel 10, which is arranged between the inlet valve 3 and the intake manifold 9, through which Fig. 1 opened inlet valve 3 into the combustion chamber 5.

[0059] After combustion, for example, the exhaust gas passes through the open exhaust valve 4 into an exhaust channel 11, as is generally known.

[0060] Cooling water 12 flows through corresponding cooling water channels, whereby in Fig. 1, a cooling water passage 13a is shown near the intake passage 10 and the intake valve 3, a cooling water passage 13b near the exhaust valve 4 and the exhaust passage 11 and a cooling water passage 13c and 13d near the left and right sides of the cylinder wall 2a, respectively.

[0061] Furthermore, a temperature sensor 14 for detecting the temperature of the fresh air 7 in the intake manifold 9 is located in the intake manifold 9 shortly before the inlet channel 10.

[0062] On its way into the cylinder 2, the fresh air 7 absorbs heat at various points and thus heats up, which leads to an increase in temperature and a change in the density of the fresh air 7.

[0063] First, the fresh air 7 absorbs heat into the cylinder 2 at the location of the arrow 15a in the area of the intake port 10 in front of the intake valve 3. Then the intake valve 3 releases heat to the fresh air 7 (see arrow 15b) and finally the cylinder wall 2a releases heat to the fresh air 7 (see arrows 15c and 15d).

[0064] Fig. 2 now shows a controller 20 which can execute a method 30 which will be described further below in connection with Fig. 3 is explained in more detail.

[0065] The controller 20 is designed as an engine control unit for controlling the internal combustion engine 1 and has a processor 21, a working memory 22, a read-only memory (or other non-volatile memory) 23 and an interface 24 to a bus system of the motor vehicle (e.g. CAN bus or the like), via which it is connected to the internal combustion engine 1 and the temperature sensor 14, so that it can receive data both from the internal combustion engine 1 or data relevant to it (e.g. speed, oil temperature, cooling water temperature, camshaft position, etc.) and from the temperature sensor 14.

[0066] In the read-only memory 23, for example, data such as characteristic maps, characteristic curves and the like are stored, as well as a program which contains commands so that the controller 20 is able to execute the method 30.

[0067] Fig.3 illustrates a flow chart of the method 30 for calculating a fresh air mass in the cylinder 2 of the internal combustion engine 1. The method 30 is typically carried out at an operating point of the internal combustion engine 1 and for each cylinder of the internal combustion engine 1 in the cycle of the internal combustion engine, so that the associated fresh air mass is available for the respective injection in the cylinder.

[0068] For this purpose, at 31, assuming a steady-state operating state of the internal combustion engine 1, the heating of the fresh air at the intake port 10 is first determined using equation (3) above at the corresponding current operating point of the internal combustion engine (e.g., based on the engine speed, cooling water temperature, oil temperature, camshaft position, etc.). For this purpose, the controller 20 determines the effective heat transfer coefficient for the intake port based on the characteristic map α w1, which is stored in the read-only memory 23, or determines the effective heat transfer coefficient for the current operating point of the internal combustion engine 1 based on the characteristic map. Furthermore, the controller 20 determines the current temperature T EK of the inlet channel 10 based on the temperature of the cooling water 12 and determines the temperature T Luft_Sgr the fresh air 7 in the intake manifold 9 based on corresponding temperature data which the controller 20 receives from the temperature sensor 14, so that the current temperature of the fresh air 7 in the intake manifold 9 can be determined.

[0069] This gives the control the current temperature T at 31 Luft_v_EV the fresh air 7 by means of equation (3) after it has been heated in the inlet channel 9 and before it is further heated by the inlet valve 3.

[0070] In the next step 32, the controller 20 determines a heating of the fresh air at the intake valve 3 of cylinder 2 based on equation (4). To do this, the controller (20) takes the current temperature T Luft_v_EV in front of the inlet valve 3, as determined in step 31, determines the current temperature T EV of the intake valve based on the cooling water temperature and determines the effective heat transfer coefficient for the intake valve 3 using the characteristic map α w2 , which is stored in the read-only memory 23, based on the current operating point of the internal combustion engine 1.

[0071] This gives the controller the current temperature T at 32 Luft_h_EV the fresh air 7 by means of equation (4) after it has been heated by the inlet valve 3 and with which it flows into the combustion chamber 5.

[0072] Finally, in step 33, the method 30 determines the heating of the fresh air 7 by the cylinder wall 2a based on equation (5). For this purpose, the controller 20 takes the current temperature T Luft_h_EV of the fresh air 7 after it has been heated by the intake valve 3 and as determined in step 32. In addition, the controller 20 determines the current effective heat transfer coefficient for the cylinder wall 2a (i.e., the wall section of the combustion chamber 5) with which the fresh air 7 comes into contact, based on the current operating point of the internal combustion engine 1 and on the basis of the characteristic map α w3 , which is stored in the read-only memory 23. As explained above, the temperature T Zyl_Wand the cylinder wall based on a characteristic map that is also stored in the read-only memory 23.

[0073] As a result, the control 20 receives the current temperature T at 33 Luft_zylthe fresh air 7 after it has been heated by the cylinder wall 2a.

[0074] In step 34, the controller 20 determines a current reference heating of the fresh air at reference temperatures of intake, intake port, intake valve, and cylinder wall temperature stored in the read-only memory 23 according to equation (6), wherein the calculation is performed at the current operating point of the internal combustion engine 1. The controller 20 thus determines a reference temperature for the temperature T EK_ref of the intake duct either based on a stored temperature value or based on a reference temperature of the cooling water. The same applies to the temperature of the fresh air 7 in the intake manifold 9 T Luft_Sgr_ref , for which a stored reference temperature is taken. The corresponding effective heat transfer coefficient is determined analogously to step 31.

[0075] This gives the controller 20 a reference temperature T at 34 Luft_v_EV_refthe fresh air 7 after it has been heated by the inlet duct 10 at reference conditions.

[0076] In step 35, the controller 20 determines a current reference heating of the fresh air at the intake valve 3 of cylinder 2 according to equation (7). For this purpose, a reference temperature T EV_ref of the inlet valve, which is stored, for example, in the read-only memory 23 or corresponds to the reference cooling water temperature, and the reference temperature T determined in step 34 is Luft_v_ref The determination of the corresponding effective heat transfer coefficient for heat transfer at the intake valve is carried out analogously to step 32.

[0077] This gives the controller 20 a reference temperature T at 35 Luft_h_EV_ref the fresh air 7 after it has been heated by the inlet valve 3 at reference conditions.

[0078] In step 36, the controller 20 determines a current reference heating of the fresh air at the cylinder wall 2a of the cylinder according to equation (8). For this purpose, a reference temperature T Zyl_Wand_ref of the cylinder wall, which can either be stored or model-based (or can also be based on the cooling water temperature and can take into account a mass flow of the cooling water), and the reference temperature T determined in step 35 Luft_h_EV_ref of the fresh air 7 after it has been heated by the intake valve 2. The corresponding effective heat transfer coefficient for the transfer of heat from the cylinder wall 2a to the fresh air 7 is determined analogously to step 33.

[0079] Thus, the control 20 receives the temperature T at 36 Luft_Zyl_ref the fresh air 7 after it has been heated by the cylinder wall 2a.

[0080] At 37, the control 20 now determines the correction factor FAC T_korfor the fresh air mass of the fresh air 7 in the combustion chamber 5 according to equation (9), by determining the ratio of the current reference temperature (equation (8)) of the fresh air 7 at the current operating point of the internal combustion engine 1 and the corresponding current temperature (equation (5)) according to T Luft_Zyl_ref / T Luft_Zyl calculated.

[0081] At 38, the controller 20 now determines the current fresh air mass air mass at the current operating point of the internal combustion engine 1 kor according to equation (10), by calculating a fresh air mass from a characteristic map stored in the read-only memory 23. Kennfeld which was determined on a test bench, and this fresh air mass with the correction factor FAC T_kor , which was determined in step 37.

[0082] Thus, the control 20 receives the corrected fresh air mass air mass at step 38 kor, which (also) takes into account the heating of the intake fresh air 7 by the cylinder wall 2a. List of reference symbols 1 internal combustion engine 2 cylinders 2a Cylinder wall 3 Inlet valve 4 exhaust valve 5 Combustion chamber 6 cylinder pistons 7 Fresh air 8 Residual gas 9 Intake manifold 10 Inlet channel 11 Exhaust channel 12 Cooling water 13a-d cooling water channels 14 Temperature sensor 15a-c arrows (heat absorption) 20 Control 21 processor 22 RAM 23 Read-only memories 24 Interface 30 Methods for calculating a fresh air mass in a cylinder 31 Determining a heating of the fresh air in the intake duct to the cylinder 32 Determine heating at the intake valve 33 Determine heating on cylinder wall 34 Determine reference heating of the fresh air in the intake duct to the cylinder 35 Determine reference heating at the intake valve 36 Determine reference heating on cylinder wall 37 Determine correction factor 38 Determine corrected fresh air mass

Claims

[1] Method for calculating a fresh air mass in a cylinder (2) of an internal combustion engine (1), comprising: Determining (33) a heating of the fresh air (7) at a wall (2a) of the cylinder (2); and Calculating (38) the fresh air mass of the fresh air (7) in the cylinder (2) based on the determined heating of the fresh air mass. [2] Method according to claim 1, wherein determining the heating of the fresh air (7) comprises determining (31) a heating of the fresh air at an inlet channel (10) to the cylinder (2) upstream of an inlet valve (3) of the cylinder (2). [3] Method according to claim 2, wherein the determination of the heating of the fresh air (7) at the inlet duct (10) is based on the following relationship: TLuft_v_EV=(TEK−TLuft_Sgr)⋅αw1+TLuft_Sgr, where T Luft_v_EV represents the temperature of the fresh air at the intake port (10) in front of the intake valve (3) of the cylinder (2), T EKrepresents the temperature of the inlet channel (10), T Luft_Sgr represents the temperature of the fresh air (7) in an intake manifold (9) to the inlet port (10) of the cylinder (2) and α w1 represents an effective heat transfer coefficient of the inlet channel (10). [4] A method according to claim 3, wherein the effective heat transfer coefficient α w1 comprises a characteristic map which represents the heat transfer of the inlet channel (10) as a function of a rotational speed and / or an intake manifold pressure. [5] Method according to claim 4, wherein α w1 determined by measurement on a test bench. [6] Method according to one of claims 3 or 4, wherein the temperature of the fresh air (7) in the intake manifold (9) is determined by means of a temperature sensor (14) in the intake manifold (9). [7] Method according to one of the preceding claims, wherein determining the heating of the fresh air (7) comprises determining (32) a heating of the fresh air (7) at an inlet valve (3) of the cylinder (2). [8] Method according to claim 7, wherein the determination of the heating of the fresh air (7) at the inlet valve (3) of the cylinder (2) is based on the relationship: TLuft_v_EV=(TEV−TAer_v_EV)⋅αw2+TLuft_v_EV, where T Luft_h_EV represents the temperature of the fresh air (7) at the inlet valve (3) of the cylinder (2), T EV represents the temperature of the inlet valve (3), T Luft_v_EV represents the temperature of the fresh air (7) in the intake duct (10) in front of the intake valve (3) of the cylinder (2) and α w2 represents an effective heat transfer coefficient of the inlet valve (3). [9] Method according to claim 8, wherein the temperature T Luft_v_EVthe fresh air (7) in the intake duct (10) upstream of the intake valve (3) of the cylinder (2) is determined according to one of claims 2 to 6. [10] Method according to one of the preceding claims, wherein the determination (33) of the heating of the fresh air (7) at the wall (2a) of the cylinder (2) is based on the relationship: TLuft_Cyl=(TZyl_Wand−TLuft_h_EV)⋅αw3+TLuft_h_EV, where T Luft_zyl represents the temperature of the fresh air (7) at the wall (2a) of the cylinder (2), T Zyl_Wand the temperature of the wall (2a) of the cylinder (2), T Luft_h_EV is the temperature of the fresh air after the inlet valve (3) of the cylinder (2) and α W3 represents an effective heat transfer coefficient of the wall (2a) of the cylinder (2). [11] Method according to claim 10, wherein the temperature T Zyl_Wand the wall (2a) of the cylinder (2) is represented by a characteristic map which depends on the speed of the internal combustion engine (1). [12] Method according to claim 10 or 11, wherein the temperature T Luft_h_EV the fresh air (7) after the inlet valve (3) of the cylinder (2) is determined according to one of claims 7 to 9. [13] Method according to one of the preceding claims, further comprising determining (36) a reference heating of the fresh air (7) at the wall (2a) of the cylinder (2) based on at least one reference parameter. [14] Method according to claim 13, wherein the fresh air mass of the fresh air (7) in the cylinder (2) is calculated based on the determined heating of the fresh air mass and the determined reference heating. [15] Control for an internal combustion engine (1) having at least one cylinder (2), an intake manifold (9), an intake manifold temperature sensor (14), an intake valve (3) on the cylinder (2) and an intake port (10) upstream of the intake valve (3), wherein the control (20) is configured to carry out the method according to one of the preceding claims.

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