Method for operating an internal combustion engine with an exhaust gas turbocharger

Abstract

The invention describes a method for an internal combustion engine with an exhaust gas turbocharger, which includes the intake and exhaust volumes, as well as the compressor and turbine. A throttle valve and boost pressure control unit are integrated into the intake manifold. In "preloaded operation," the boost pressure upstream of the throttle valve is higher than the intake manifold pressure downstream. This method uses a torque model that specifically considers the charge exchange losses caused by the preload to precisely determine the current torque.

Description

[0001] The invention relates to a method for operating an internal combustion engine with an exhaust gas turbocharger according to the preamble of patent claim 1.

[0002] It is well known that an exhaust gas turbocharger is installed on an internal combustion engine to ensure efficient operation. The exhaust gas turbocharger can increase boost pressure in the cylinders of the internal combustion engine to increase power. The exhaust gas turbocharger is powered by the exhaust gas from the internal combustion engine; it can also be electrically driven.

[0003] Particularly when an internal combustion engine is used in a motor vehicle, rapid or frequent load changes in the internal combustion engine may be necessary. This involves changing various parameters of the internal combustion engine, one of which is the boost pressure. For a harmonious build-up of tractive power, it is crucial that the boost pressure of the exhaust gas turbocharger is converted into a predetermined boost pressure as quickly and without overshoot. In order to ensure that a potentially high boost pressure for the highest possible torque of the internal combustion engine can be accessed quickly and with as little delay as possible, it is possible to operate the internal combustion engine in what is known as preloaded mode. Preloaded mode refers to operation of the internal combustion engine in which the boost pressure actually generated by the exhaust gas turbocharger is greater than the pressure in the intake manifold of the internal combustion engine.This means that a pressure ratio is present at a throttle valve arranged between the compressor and the intake manifold, in which the pressure in front of the throttle valve, the boost pressure, is greater than the pressure after the throttle valve, the intake manifold pressure.

[0004] If the boost pressure is now built up for an operating point in pre-loaded operation, this can lead to abnormal driving behavior. The reasons for this are that very steep boost pressure gradients occur, particularly at high engine speeds and pressure levels. The throttle valve is therefore sometimes unable to regulate the intake manifold pressure to the desired value at these steep boost pressure gradients. Furthermore, if the throttle valve closes quickly when boost pressure is building up, build-up effects occur which can manifest themselves in further deviations or pressure fluctuations, since the control units involved in the corresponding control process, a so-called charge control unit for positioning the throttle valve and a boost pressure control unit for regulating the boost pressure, can oscillate against each other.

[0005] The wastegate of the exhaust gas turbocharger can be operated in two modes. Typically, the goal in the first mode is to generate sufficient boost pressure to achieve a specific cylinder charge with the throttle valve open. In the second mode, the boost pressure is higher than desired, and the throttle valve is adjusted to preloaded operation. However, this preloaded operation leads to altered gas exchange losses, which must be taken into account when determining the current torque of the internal combustion engine so that typical operating parameters of the internal combustion engine can be correctly determined.

[0006] From the published patent application DE 196 08 630 A1 a method is known in which a pressure drop at a throttle valve is specified and a boost pressure setpoint is derived from this pressure drop and an intake manifold pressure setpoint.

[0007] The published patent application DE 199 57 200 A1 describes a method in which a correction of an injection quantity is determined with the aid of an inverse model in relation to exhaust gas heating measures.

[0008] The publication "Model-Based Control of Brake Mean Effective Pressure in a Euro 6 1.6l Diesel Engine Featuring Mult-After-Injection Patterns", Finesso, R., Marell, o., Spessa, E., Alfierei, V., et. al., SAE Int. J. Engines 14 (5): 713-732, 2021, DOI:10.4271 / 03-14-05-0043, https: / / iris.polito.it / handle / 11583 / 2915696?mode=simple, presents a model in which the influence on the generated torque is determined using a pump mean effective pressure. The influence of preloaded operation can be seen via an exhaust pressure, whereby the exhaust pressure can be adjusted using a wastegate or a variable turbine geometry of an exhaust gas turbocharger.

[0009] The object of the present invention is to provide a method for operating an internal combustion engine with an exhaust gas turbocharger, in particular in a preloaded operation, with the aid of which an optimized driving operation of a motor vehicle having the internal combustion engine can be realized.

[0010] The object is achieved according to the invention by a method for operating an internal combustion engine with an exhaust gas turbocharger having the features of patent claim 1. Advantageous embodiments with expedient and non-trivial further developments of the invention are specified in the respective subclaims.

[0011] A method according to the invention for operating an internal combustion engine with an exhaust gas turbocharger, wherein the internal combustion engine has an engine block with a through-flow intake volume and a through-flow exhaust gas volume, wherein the intake volume is connected to an intake manifold of the internal combustion engine in a flow-through manner, and the exhaust gas volume is connected to an exhaust tract of the internal combustion engine in a flow-through manner, and wherein a compressor of the exhaust gas turbocharger is accommodated in the intake manifold in a flow-through manner, and an exhaust gas turbine of the exhaust gas turbocharger is accommodated in the exhaust tract in a flow-through manner, and wherein a throttle valve is arranged downstream of the compressor in the intake manifold, and wherein the exhaust gas turbocharger has a boost pressure control unit, and wherein the internal combustion engine is operable in a preloaded mode,wherein, in preloaded operation, a boost pressure upstream of the throttle valve deviates from an intake manifold pressure downstream of the throttle valve, wherein, in preloaded operation, the boost pressure is greater than the intake manifold pressure, uses a torque model to determine the current torque of the internal combustion engine. According to the invention, an influence of the preload on gas exchange losses of the internal combustion engine is taken into account in the torque model, whereby a torque error is determined, which is compared and weighted with a torque determined without taking into account the influence of the gas exchange losses. This means that a comparison and weighting relative to the torque determined without taking into account the influence of the gas exchange losses are carried out to assess the torque error.

[0012] The advantage of the method according to the invention is that by taking into account the influence of the preload on the gas exchange losses of the internal combustion engine, a current, correct torque of the internal combustion engine can be determined for its improved functioning.

[0013] Advantageously, the torque model is based on the current speed of the combustion engine.

[0014] To determine the torque error, the intake manifold pressure, boost pressure, ambient pressure, current engine speed, and cylinder charge are preferably used. These are operating parameters of the internal combustion engine that can be easily measured and thus determined very accurately, allowing the actual torque present during preloaded operation to be determined.

[0015] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. They show: Fig. 1 shows a schematic diagram of a drive train with an internal combustion engine of a motor vehicle, and Fig. 2 shows a block diagram of a function block for determining a torque error of a torque model.

[0016] In Fig.1 illustrates a drive train 1 of a motor vehicle comprising an internal combustion engine 2 with an exhaust gas turbocharger 3 in a schematic diagram. The exhaust gas turbocharger 3 has a compressor 4 and an exhaust gas turbine 5, wherein an impeller (not shown in detail) of the compressor 4 is connected in a rotationally fixed manner to an impeller (not shown in detail) of the exhaust gas turbine 5 by means of a shaft 6.

[0017] With the help of the compressor 4, air is sucked in, compressed in the compressor 4, and then fed, possibly cooled, to the internal combustion engine 2. Fuel is also supplied to the internal combustion engine 2, which is combusted with the air in the internal combustion engine 2. The resulting exhaust gas is fed to the exhaust turbine 5, whereby the impeller of the exhaust turbine 5 is set in rotation and, via the shaft 6, the impeller of the compressor 4 is also set in rotation, thus driving the compressor.

[0018] The internal combustion engine 2 has an engine block 11 with a flow-through intake volume 12 and a flow-through exhaust volume 13. The intake volume 12, which may be configured, for example, in the form of an air plenum, is connected to an intake manifold 14 of the internal combustion engine 2. The exhaust volume 13, which is typically configured in the form of an exhaust manifold, is connected to an exhaust tract 15 of the internal combustion engine 2.

[0019] The compressor 4 is accommodated in the intake tract 14 in a flow-through manner so that the air sucked in and compressed by it can be fed to the internal combustion engine 2. The exhaust gas turbine 5 is accommodated in the exhaust tract 15 in a flow-through manner so that the exhaust gas expelled from the internal combustion engine 2 can be fed via the exhaust tract 15 to the exhaust gas turbine 5 to operate the compressor 4.

[0020] Downstream of the compressor 4, a throttle valve 10 is arranged in the intake line 14 for regulating an air quantity to be supplied to the internal combustion engine 2 with a specific intake manifold pressure p nD . The intake manifold pressure p nD is thus the pressure downstream of the throttle valve 10. A certain cylinder charge m depends on this air quantity z , the amount of air actually remaining in a cylinder 16 of the internal combustion engine 1 during a power stroke. Since the amount of fuel is usually negligible relative to the amount of air, this can be neglected.

[0021] Furthermore, the exhaust gas turbocharger 3 has a boost pressure control unit 7, with the aid of which the operation of the exhaust gas turbocharger 3 and thus a boost pressure p provided by the compressor 4 vD is adjustable. The boost pressure p vD is the pressure upstream of the throttle valve 10.

[0022] The boost pressure control unit 7, which has conventional control elements and sensors operatively connected to the control elements, is operatively connected to a control device of the exhaust gas turbocharger 3 (not shown in detail). The control device can be an adjustable guide vane arranged in the exhaust gas turbocharger 3 or a wastegate valve, which influences the amount of exhaust gas acting on the impeller of the exhaust gas turbine 5. Likewise, the exhaust gas turbocharger 3 could also have an electric drive, which, with the aid of the boost pressure control unit 7, is designed to act on the shaft 6 and thus on the operation of the compressor 4.

[0023] The internal combustion engine 2 can be operated in a so-called pre-loaded operation, wherein in pre-loaded operation the boost pressure p vD upstream of the throttle valve 10 from the intake manifold pressure p nD downstream of the throttle valve 10, in particular, wherein in pre-tensioned operation the boost pressure p vDis greater than the intake manifold pressure p nD In other words, this means that in preloaded operation a pressure gradient is formed at the throttle valve 10.

[0024] The control of the boost pressure p vD can be adjusted, for example, with the aid of a control and regulation unit 8 of the internal combustion engine 2. The control and regulation unit 8 can additionally be configured to record parameters of the internal combustion engine 2, such as an intake air mass or a lambda value downstream of the internal combustion engine 2, and to control the internal combustion engine 2 and influence its operating state with the aid of actuators. The actuators can, in particular, comprise a fuel injector, a valve adjustment, or an ignition.

[0025] In this control and regulation unit 8, characteristic maps and / or functions for operating the internal combustion engine 2 are stored so that the internal combustion engine 2 can be operated in a preferentially optimized manner, for example with regard to fuel consumption and operating temperatures.

[0026] A method according to the invention uses a so-called torque model 17 stored in the control unit 8, which is relevant for operating the internal combustion engine 2. With the help of this torque model 17, based on the current cylinder charge mz and the current speed n ist of the internal combustion engine 2, a current torque is determined. However, if the internal combustion engine 2 is running in preloaded operation, the usual gas exchange losses that occur in non-preloaded operation may change, in particular increase.

[0027] In order to determine correct torques via torque model 17 even in preloaded operation, it is necessary to introduce correction factors into torque model 17. These gas exchange losses can be corrected using calibratable maps based on an engine speed.

[0028] Thus, the torque model 17 has a function module 18 for determining a faulty torque M F , which is determined using the correction factors.

[0029] In the calculation and / or determination of the faulty torque M F go the boost pressure p vD , the intake manifold pressure p nD , an ambient pressure p u , the cylinder charge mz and a current speed n ist The resulting torque error M F is compared with the original torque, which was determined without the correction factors, and weighted.

[0030] The calculation and / or determination of the correction factors can be based on empirically or simulatively determined characteristic maps and / or functions. List of reference symbols 1 drivetrain 2 internal combustion engine 3 exhaust gas turbochargers 4 compressors 5 exhaust turbine 6 Wave 7 Boost pressure control unit 8 Control and regulation unit 9 Communication line 10 Throttle valve 11 Engine block 12 intake volume 13 Exhaust gas volume 14 Intake manifold 15 Exhaust system 16 cylinders 17 Torque model 18 Function module M F Missing torque m Z Cylinder filling n ist Current speed p pressure p nD Intake manifold pressure p vD boost pressure p u Ambient pressure

Claims

[1] Method for operating an internal combustion engine (2) with an exhaust gas turbocharger (3), wherein the internal combustion engine (2) has an engine block (11) with a through-flow intake volume (12) and a through-flow exhaust gas volume (13), wherein the intake volume (12) is connected to an intake line (14) of the internal combustion engine (2) in a flow-through manner, and the exhaust gas volume (13) is connected to an exhaust tract (15) of the internal combustion engine (2) in a flow-through manner, and wherein a compressor (4) of the exhaust gas turbocharger (3) is accommodated in the intake line (14) in a flow-through manner, and an exhaust gas turbine (5) of the exhaust gas turbocharger (3) is accommodated in the exhaust tract (15) in a flow-through manner, and wherein a throttle valve (10) is arranged downstream of the compressor (4) in the intake line (14), and wherein the exhaust gas turbocharger (3) has a boost pressure control unit (7), and wherein the Internal combustion engine (3) can be operated in a preloaded mode,where in preloaded operation a boost pressure (p, vD ) upstream of the throttle valve (10) from an intake manifold pressure (p nD ) downstream of the throttle valve (10), whereby in pre-tensioned operation the boost pressure (p vD ) is greater than the intake manifold pressure (p nD ), and wherein the method uses a torque model (17) to determine a current torque of the internal combustion engine (2), characterized by that an influence on gas exchange losses of the internal combustion engine (2) caused by the preload is taken into account in the torque model (17), wherein a faulty torque (M F ), which is compared and weighted with a torque determined without taking into account the influence of the gas exchange losses. [2] Method according to claim 1, characterized by that the torque model (17) is based on a current speed (n ist ) of the internal combustion engine (2). [3] Method according to claim 1 or 2, characterized by that to determine the faulty torque (M F ) the intake manifold pressure (p nD ), the boost pressure (p vD ), an ambient pressure (p u ), the current speed (n ist ) and a cylinder filling (m Z ) can be used.

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