Method and control for controlling a charging system for an internal combustion engine

Abstract

Method for controlling a charging system (3) with a charging stage (5) for an internal combustion engine (2), wherein the charging stage (5) has a compressor (6) and a drive (8), the method comprising: Determining (31) a target boost pressure for the boost stage (5); Determining (32) a desired boost pressure build-up speed; Determining (33) a boost pressure build-up adjustment as a function of the target boost pressure build-up speed; and Controlling (34) the charging system (3) as a function of the target boost pressure and the determined boost pressure build-up adjustment.

Description

[0001] The invention relates to a method and a control system for controlling a charging system for an internal combustion engine.

[0002] In general, turbocharging systems for internal combustion engines, particularly in the automotive sector, are known for supplying cylinders of the internal combustion engine with air at overpressure for the combustion of fuel.

[0003] Turbochargers and compressors, for example, are known for providing air at positive pressure. Turbochargers have a compressor and can be equipped with their own drive for the compressor, e.g., an electric motor, or they can be powered by exhaust gas from the internal combustion engine, in which case they are also referred to as exhaust gas turbochargers.

[0004] Furthermore, turbochargers with a bypass valve, also called a wastegate, and / or with variable turbine geometry, which have adjustable, non-rotating guide vanes, are known. The gas throughput can be varied by adjusting the angle of attack of the guide vanes. Typically, the angle of attack of the guide vanes is controlled such that, at low gas throughput and high power demand, the turbocharger's power is increased by reducing the flow cross-section, and at high gas throughput and low power demand, it is increased by increasing the flow cross-section. For example, German patent application DE 10 2008 005 121 A1 discloses a method in which the variable turbine geometry is adjusted so that the turbine provides a predetermined throughput.

[0005] From the publication of European patent application EP 1 178 192 A2, it is also known to control the variable turbine geometry of an exhaust gas turbocharger depending on the operating parameters of a diesel engine, such as the speed of the diesel engine, the oil consumption of the diesel engine, the cooling water temperature, etc.

[0006] European patent application EP 1 302 644 A1 also discloses a method for controlling an exhaust gas turbocharger with variable turbine geometry in an internal combustion engine. The turbocharger comprises a turbine and a control mechanism located upstream of the turbine, which can be adjusted to vary the flow cross-section of the exhaust gas to the turbine. The control mechanism responds to a control signal generated by a control unit to adapt the control mechanism. In the event of an engine acceleration condition, a limitation is imposed on the flow range defined by the control mechanism such that this flow range cannot be smaller than a limiting flow range that depends on a parameter representative of the gas flow rate through the turbine.

[0007] German patent application DE 199 60 166 A1 also discloses a method for regulating the boost pressure in a transiently operated piston internal combustion engine with a turbocharger. In this method, the boost pressure is controlled via an engine control unit and a relief valve located upstream of the turbocharger turbine in the exhaust system. Upon initiation of an acceleration process, the engine control unit detects the pedal position and a load-proportional gradient. If a preset value for the load-proportional gradient is exceeded, the relief valve is controlled in the opening direction, resulting in a preset, controlled pressure increase.

[0008] Furthermore, the German patent application DE 10 2008 063 935 A1 shows a method for operating an internal combustion engine with an exhaust gas turbocharger having a turbine and a compressor, wherein an adjustable turbine geometry (VTG) is arranged in the turbine, wherein a boost pressure is regulated by means of the position of the VTG as a function of a difference between a predetermined target boost pressure and an actual boost pressure.

[0009] Furthermore, German patent application DE 10 2012 223 772 A1 discloses a control device for an internal combustion engine with a turbocharger including a bypass valve. The control device can control an acceleration response characteristic, operate at an optimal fuel efficiency point, and learn variation factors in an internal combustion engine.

[0010] Even though methods and controls for controlling a charging system are generally known from the prior art, it is an object of the present invention to provide an improved method for controlling a charging system and a corresponding control for controlling a charging system.

[0011] This object is achieved by the method according to the invention according to claim 1, the control according to claim 8, the internal combustion engine according to claim 9 and the motor vehicle according to claim 10.

[0012] According to a first aspect, the present invention provides a method for controlling a charging system having a charging stage for an internal combustion engine, the charging stage having a compressor and a drive, the method comprising: Determining a target boost pressure for the boost stage; Determining a target boost pressure build-up rate; Determining a boost pressure build-up adjustment depending on the target boost pressure build-up speed; and Control of the charging system depending on the target boost pressure and the determined boost pressure build-up adjustment

[0013] According to a second aspect, the present invention provides a controller for a charging system for an internal combustion engine, the controller being configured to carry out the method according to the first aspect.

[0014] According to a third aspect, the present invention provides an internal combustion engine with a charging system having a charging stage, the charging stage having a compressor and a drive, and with a controller according to the second aspect.

[0015] According to a fourth aspect, the present invention provides a motor vehicle having an internal combustion engine according to the third aspect.

[0016] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.

[0017] As mentioned at the beginning, turbocharging systems are generally known, in particular those with an exhaust gas turbocharger with variable turbine geometry and / or with a wastegate (at least one bypass valve). As also mentioned at the beginning, the guide vanes of the exhaust gas turbocharger can typically be closed sharply and quickly, meaning the flow velocity is rapidly increased when the provided boost pressure is significantly increased, for example, to meet a sudden increase in the power or torque demand of the internal combustion engine.

[0018] However, it has been shown that a strong tightening of the guide vanes typically also leads to a high exhaust back pressure and thus to gas exchange losses, which in turn counteracts the effective torque build-up of the internal combustion engine.

[0019] Surprisingly, it has been shown that a faster effective torque build-up of the internal combustion engine can be achieved if the guide vanes of the exhaust gas turbocharger are opened wider than would be the case for a maximum rapid boost pressure build-up, even if this results in a slower boost pressure build-up.

[0020] From this it can be concluded that a rapid effective torque build-up of the internal combustion engine is not necessarily guaranteed by a rapid boost pressure build-up.

[0021] Because the effective torque build-up is also possible with a lower speed of boost pressure build-up, under certain operating conditions of the internal combustion engine less fuel can be injected with a slower boost pressure build-up than with a fast boost pressure build-up, or conversely with the same amount of fuel that is injected, a certain effective torque can be generated more or faster with a slower boost pressure build-up than with a fast boost pressure build-up.

[0022] It was also recognized that there is another degree of freedom, which lies in the choice between rapid boost pressure build-up and rapid effective torque build-up.

[0023] Accordingly, a method for controlling a charging system with a charging stage for an internal combustion engine, wherein the charging stage has a compressor and a drive, comprises the steps: Determining a target boost pressure for the boost stage; Determining a target boost pressure build-up rate; Determining a boost pressure build-up adjustment depending on the target boost pressure build-up speed; and Control of the charging system depending on the target boost pressure and the determined boost pressure build-up adjustment.

[0024] The internal combustion engine may be any type of internal combustion engine, such as a gasoline engine, diesel engine or the like, and it may have any number of cylinders, such as three, four, six, eight, twelve or the like.

[0025] The turbocharging system can have one or more turbocharging stages. The turbocharging stage has a compressor and a drive, which can, for example, be variable, so that the power of the turbocharging stage can be adjusted. In some embodiments, the drive comprises an electric motor; in other embodiments, the turbocharging stage has an exhaust gas turbocharger with variable turbine geometry. As mentioned above, the variable turbine geometry typically has guide vanes that can influence the flow velocity of the exhaust gas flowing through them by changing their angle of attack. The turbocharging system can also have a wastegate.

[0026] The method determines a target boost pressure for the boost stage. This target boost pressure is derived, for example, from an operating parameter of the internal combustion engine and depends, for example, on a power or torque requirement, a (diagnostic) operating state of the internal combustion engine, or the like.

[0027] The method determines a target boost pressure buildup rate. As explained above, whether effective torque is built up quickly or slowly depends on the boost pressure buildup rate. Depending on the requirement—whether rapid boost pressure buildup or rapid effective torque buildup is desired—either a high or low target boost pressure buildup rate is determined, or any intermediate value between rapid / slow effective torque buildup and slow / rapid boost pressure buildup can be determined. The target boost pressure buildup rate can be predefined, for example, or it can be determined by a software application or a function, e.g., depending on the operating state of the internal combustion engine.For example, with a high torque requirement, a high effective torque build-up may be primarily desired, which leads to a lower target boost pressure build-up rate than in an operating condition where a rapid boost pressure build-up is desired.

[0028] A boost pressure build-up adjustment is determined depending on the target boost pressure build-up rate. The boost pressure build-up adjustment can be a parameter or a function and can be stored, for example, as a characteristic curve or map in a control system memory, such as an engine control unit.

[0029] Finally, the turbocharging system is controlled depending on the target boost pressure and the determined boost pressure buildup adjustment. In particular, the drive for the turbocharging stage is controlled such that the boost pressure is built up according to the target boost pressure buildup rate until the target boost pressure is reached. Depending on the requirements, either a fast effective torque buildup or a fast boost pressure buildup is achieved, or any intermediate stage between fast / slow effective torque buildup and slow / fast boost pressure buildup can be selected. This allows the effective torque buildup or the boost pressure buildup to be freely scalable in some embodiments.

[0030] In some embodiments, controlling the turbocharging system as a function of the desired boost pressure and the determined boost pressure buildup adjustment includes controlling the variable turbine geometry and / or a wastegate as a function of the determined boost pressure buildup adjustment. In particular, the flow velocity is taken into account, as well as, depending on the embodiment, the angle of attack of the guide vanes of the variable turbine geometry, as already explained above, and / or an opening duration and / or an opening cross-section of a wastegate and / or a number of wastegates.

[0031] In some exemplary embodiments, the boost pressure build-up adaptation comprises a boost pressure build-up parameter, which is also referred to below as α1, α2 or α3 depending on the operating parameter it affects. The boost pressure build-up parameter can, for example, assume a value between a minimum value (e.g. zero) and a maximum value (e.g. one). The boost pressure build-up parameter can also assume the minimum or maximum value, without the present invention being restricted thereto. The free selectability of the boost pressure build-up parameter between minimum and maximum values ​​enables simple adaptation of operating parameters of the charging system or the charging stage. The boost pressure build-up parameter can be selected such that its maximum value corresponds to a maximum rapid effective torque build-up (or boost pressure build-up) and its minimum value corresponds to a maximum slow effective torque build-up (or boost pressure build-up).Accordingly, by selecting any value between the maximum and minimum values ​​of the boost pressure buildup parameter, a corresponding value for the rate of effective torque buildup (boost pressure buildup) can be selected, making the rate of effective torque buildup (boost pressure buildup) freely scalable. The minimum and maximum values ​​of the boost pressure buildup parameter can be freely selected, although for simplicity, the minimum value is assumed to be "0" and the maximum value to be "1" below. Furthermore, as mentioned, the boost pressure buildup parameter can also assume the minimum or maximum value itself.

[0032] The boost pressure build-up adjustment can include adjusting a target efficiency of the charging stage, in particular a turbine of the charging stage. For example, if the target efficiency is maximum, the fastest effective torque build-up is possible, while if the target efficiency is minimum, the fastest boost pressure build-up is possible. The target efficiency can be adjusted accordingly using the boost pressure build-up parameter α1. For example, if α1 is zero (minimum value), the target efficiency is minimum, and if α1 is one (maximum value), the target efficiency is maximum. With appropriate values ​​between zero (minimum value) and one (maximum value) of the boost pressure build-up parameter α1, any value between minimum and maximum target efficiency and thus also any value between rapid boost pressure build-up and rapid effective torque build-up can be selected.The boost pressure build-up is slower and the effective torque build-up is faster, the larger the boost pressure build-up parameter α1 is starting from zero (or the minimum value).

[0033] Boost pressure build-up adjustment can include adjusting the speed acceleration of the charging stage, in particular of an exhaust gas turbocharger. High speed acceleration leads to rapid boost pressure build-up, and low speed acceleration leads to rapid effective torque build-up. The speed acceleration can be adjusted accordingly using the boost pressure build-up parameter α2. For example, if α2 is zero (minimum value), the speed acceleration is minimal, and if α2 is one (maximum value), the speed acceleration is maximum. Using corresponding values ​​between zero (minimum value) and one (maximum value) of the boost pressure build-up parameter α2, any value between minimum and maximum speed acceleration, and thus any value between rapid effective torque build-up and rapid boost pressure build-up, can be selected.The boost pressure build-up is faster and the effective torque build-up is slower, the larger the boost pressure build-up parameter α2 is starting from zero (or from the minimum value).

[0034] Boost pressure build-up adjustment can include adjusting the power of the boosting stage, in particular adjusting the compressor's target power. A high target power leads to a rapid boost pressure build-up, and a low target power leads to a rapid effective torque build-up. The target power, in particular of the compressor of the boosting stage, can be adjusted accordingly using the boost pressure build-up parameter α3. For example, if α3 is zero (minimum value), the target power is minimal, and if α3 is one (maximum value), the target power is maximum. With corresponding values ​​between zero (minimum value) and one (maximum value) of the boost pressure build-up parameter α3, any value between minimum and maximum target power can be selected, and thus any value between rapid effective torque build-up and rapid boost pressure build-up.The boost pressure build-up is faster and the effective torque build-up is slower, the larger the boost pressure build-up parameter α3 is starting from zero (or from the minimum value).

[0035] In some embodiments, the boost pressure build-up adaptation comprises one, two or all three of the above-mentioned boost pressure build-up parameters α1, α2, α3.

[0036] Some embodiments relate to a controller for a charging system for an internal combustion engine, wherein the controller is configured to execute the method described above. The controller may comprise a processor and a memory in which the method and corresponding characteristic curves, characteristic maps, or the like mentioned above are stored. The controller may be embodied, for example, as an engine control unit.

[0037] Some embodiments relate to an internal combustion engine with a charging system and a control system as described above. Some embodiments also relate to a motor vehicle with such an internal combustion engine.

[0038] 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 a motor vehicle with a charging system and a control system; Fig. 2 illustrates the calculation of the position of the variable turbine geometry of the turbocharging system; and Fig. 3 shows a flowchart of a method for controlling the charging system.

[0039] An embodiment of a motor vehicle 1 with a gasoline engine 2 and a charging system 3, which is controlled by a controller 10, which is designed as an engine control unit, is shown in Fig. 1. The present invention is not limited to any particular engine type.

[0040] The gasoline engine 2 has four cylinders 4a, 4b, 4c and 4d, which are supplied with charged (combustion) air by the charging system 3.

[0041] The turbocharging system 3 has a turbocharging stage 5, which is designed as an exhaust gas turbocharger with variable turbine geometry. The turbocharging stage 5 is coupled to the control system 10.

[0042] The charging stage 5 has a compressor 6, which is operated via a shaft 7 with an exhaust gas turbine 8 with variable turbine geometry, wherein the exhaust gas turbine 8 is supplied with exhaust gas from the gasoline engine 2 and is operated thereby.

[0043] The controller 10 is configured to control the charging stage 5 as described below with reference to the Fig. 2 and Fig. 3 is executed.

[0044] In Fig. 2 shows a calculation scheme 20 and in Fig. 3 shows a flowchart of a method 30 for controlling the charging system 3, wherein the controller 10 is configured to carry out the method.

[0045] In a first step 31, the controller 10 determines a target boost pressure for charging stage 5. The target boost pressure results, for example, from a torque request to the gasoline engine 2 or the like. For this purpose, the controller 10 has, for example, stored a characteristic curve in its memory in which a corresponding target boost pressure is stored for each torque or other operating parameter of the gasoline engine 2. Furthermore, the controller 10 can have different characteristic curves stored for different operating modes of the gasoline engine 2.

[0046] In a next step 32, the controller 10 determines a target boost pressure buildup rate. As explained above, whether an effective torque is built up quickly or the boost pressure is built up quickly depends on the boost pressure buildup rate. The boost pressure buildup rate can, for example, also be stored in a characteristic curve or a characteristic map in the controller 10 and determined depending on a torque demand on the gasoline engine 2 or an operating state of the gasoline engine 2.

[0047] In a next step 33, the controller 10 determines a boost pressure build-up adjustment depending on the target boost pressure build-up speed.

[0048] For this purpose, the controller 10 in the present example determines a boost pressure build-up parameter α1, α2 and / or α3, wherein the boost pressure build-up parameter is stored, for example, in a characteristic curve or a characteristic map, e.g., as a function of the boost pressure build-up speed, which in turn is indicative of how quickly the boost pressure or the effective torque is built up.

[0049] In step 34, the controller controls the charging system 3 depending on the target boost pressure and the determined boost pressure build-up adjustment.

[0050] In the present embodiment, the controller 10 controls the exhaust gas turbine 8 or its variable turbine geometry and thus, for example, the angle of attack of guide vanes of the variable turbine geometry and the flow velocity achieved thereby.

[0051] As explained above, the boost pressure build-up parameter can be entered at various points in the control of the exhaust gas turbine 8, as well as in Fig. 2 is shown.

[0052] Fig. 2 illustrates the calculation 20 of the target power and the target position 29 of the exhaust gas turbine 8. The calculation is shown in blocks 21 - 25 for illustrative purposes, without the present invention being limited in this respect.

[0053] When calculating 20 the target power and the target position 29 of the variable turbine geometry, e.g., when calculating the angle of attack of the guide vanes, various variables are included in the calculation 25 of the target power of the exhaust turbine 8 and the associated target position of the variable turbine geometry, which are ultimately taken into account in an overall calculation block 25. In embodiments in which a wastegate is present, the opening duration and / or the opening cross-section of the wastegate are calculated accordingly.

[0054] In a block 21, the target efficiency of the exhaust gas turbine 8 is determined and passed to the overall calculation block 25.

[0055] As explained above, a boost pressure buildup parameter α1 can intervene at this point and "trim" the target efficiency, so that, for example, with a value of zero (minimum value) for the boost pressure buildup parameter α1, a minimum target efficiency is calculated in block 21, and with a value of one (maximum value) for the boost pressure buildup parameter α1, a maximum target efficiency is calculated. As already explained above, with a minimum target efficiency, the boost pressure buildup is rapid, and with a maximum target efficiency, the effective torque buildup is rapid.

[0056] In addition, the calculation unit 20 receives a target pressure ratio 26 based on the determined target boost pressure. The target pressure ratio 26 is calculated in a block 22 to calculate a compressor power of the compressor 6, with the determined compressor power being passed to a block 23, in which a turbine power is calculated from the compressor power.

[0057] In block 23, in which the turbine power is calculated, a boost pressure buildup parameter α3, as described above, can intervene to adjust the compressor power. A high target power for the compressor, as described above, leads to a rapid boost pressure buildup, and a low target power leads to a rapid effective torque buildup. The boost pressure buildup parameter α3 can be used to adjust the target power of the compressor of the charging stage accordingly. A value of zero (minimum value) for α3 results in a minimum target power, and a value of one (maximum value) for α3 results in a maximum target power of the compressor.

[0058] The turbine power determined in block 23 from the adjusted compressor power is forwarded to a block 24 in which a speed or speed acceleration for the exhaust gas turbine 8 is determined from the turbine power.

[0059] In block 24, where the speed acceleration is calculated, the boost pressure buildup parameter α2 can intervene, as described above, which adjusts the speed acceleration. As explained above, a high speed acceleration leads to a rapid boost pressure buildup, and a low speed acceleration leads to a rapid effective torque buildup. The speed acceleration can be adjusted accordingly using the boost pressure buildup parameter α2. If α2 is zero (minimum value), the speed acceleration is minimal, and if α2 is one (maximum value), the speed acceleration is maximum.

[0060] The adjusted speed acceleration is transferred to the overall calculation block 25. Additional data, such as the turbine mass flow 27 and the exhaust gas temperature 28 upstream of the exhaust turbine, are also included in the overall calculation block 25.

[0061] From all received data, the overall calculation block 25 calculates the target position 29 of the variable turbine geometry, i.e. the target position of the guide vanes.

[0062] Even though all three boost pressure build-up parameters α1, α2 and α3 are used in the present embodiment, the present invention is not limited thereto, but only one or any combination of two boost pressure build-up parameters may be used. List of reference symbols 1 motor vehicle 2 Otto engine (internal combustion engine) 3 Charging system 4a-d cylinders of 2 5 charging stage (exhaust gas turbocharger) 6 compressors of the charging stage 7 Wave of 5 8 turbines out of 5 10 Control 20 Calculation of target performance and target position of 5 21 Calculation block target efficiency 22 Compressor power calculation block 23 Turbine power calculation block 24 Calculation block speed acceleration 25 Total calculation block 26 Target pressure ratio 27 Turbine mass flow 28 Exhaust gas temperature before the turbine 29 Target position for guide vanes 30 methods for controlling 5 31 Determine target boost pressure 32 Determine target boost pressure build-up speed 33 Determine boost pressure build-up adjustment 34 Controlling the charging system α1 boost pressure build-up parameter for target efficiency α2 boost pressure build-up parameters for speed acceleration adjustment α3 Boost pressure build-up parameters for compressor power adjustment

Claims

[1] Method for controlling a charging system (3) with a charging stage (5) for an internal combustion engine (2), wherein the charging stage (5) has a compressor (6) and a drive (8), the method comprising: Determining (31) a target boost pressure for the boost stage (5); Determining (32) a desired boost pressure build-up speed; Determining (33) a boost pressure build-up adjustment as a function of the target boost pressure build-up speed; and Controlling (34) the charging system (3) as a function of the target boost pressure and the determined boost pressure build-up adjustment. [2] Method according to claim 1, wherein the charging stage (5) comprises an exhaust gas turbocharger with variable turbine geometry and / or a wastegate. [3] Method according to claim 2, wherein the controlling (34) of the charging system (3) as a function of the desired boost pressure and the determined boost pressure build-up adjustment comprises controlling the variable turbine geometry and / or the wastegate as a function of the determined boost pressure build-up adjustment. [4] Method according to one of the preceding claims, wherein the boost pressure build-up adaptation comprises a boost pressure build-up parameter (α1, α2, α3) which can assume a value between a minimum value and a maximum value in order to adapt the boost pressure build-up. [5] Method according to one of the preceding claims, wherein the boost pressure build-up adjustment comprises the adjustment of a target efficiency of the charging stage (5). [6] Method according to one of the preceding claims, wherein the boost pressure build-up adjustment comprises the adjustment of a speed acceleration of the charging stage. [7] Method according to one of the preceding claims, wherein the boost pressure build-up adjustment comprises the adjustment of a power of the charging stage (5). [8] Control for a charging system for an internal combustion engine, wherein the control (10) is designed to carry out the method according to one of the preceding claims. [9] Internal combustion engine with a charging system (3) with a charging stage (5), wherein the charging stage (5) has a compressor (6) and a drive (8), and with a control according to claim 8. [10] Motor vehicle with an internal combustion engine according to claim 9.

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