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

Abstract

The invention relates to a 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 flow-through intake volume (12) and a flow-through 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 prestressed mode,where in pre-loaded operation a boost pressure (p, L ) upstream of the throttle valve (10) deviates from an intake manifold pressure (ps) downstream of the throttle valve (10), wherein in pre-tensioned operation the boost pressure (p L ) is greater than the intake manifold pressure (ps). According to the invention, the boost pressure (p L ) is adjusted to the intake manifold pressure (ps) in a first step until the intake manifold pressure (ps) is reached at a target time (tz), and then in a further step to a specified target boost pressure (p Lsoll ), which is greater than a specified target intake manifold pressure (p Ssoll ) is regulated.

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 for 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 and can also be electrically driven.

[0003] Particularly when using an internal combustion engine in a motor vehicle, rapid or frequent load changes may be necessary. This involves changing various engine parameters, one of which is boost pressure. For a harmonious buildup of traction, it is crucial that the boost pressure of the exhaust gas turbocharger is converted to a specified boost pressure as quickly and as smoothly as possible without overshoot.

[0004] To ensure that the highest possible 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 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 located between the compressor and the intake manifold in which the pressure upstream of the throttle valve, the boost pressure, is greater than the pressure downstream of the throttle valve, the intake manifold pressure.

[0005] 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.

[0006] The published patent application DE 10 2014 218 221 A1 discloses a method for detecting and describing a transient driving situation of a motor vehicle with an internal combustion engine based on a relative control deviation of a boost pressure from an intake manifold pressure.

[0007] The published patent application DE 10 2015 205 194 A1 discloses a control device for controlling and regulating an exhaust gas turbocharger using boost pressure.

[0008] From the patent specification DE 10 2006 062 213 B4 a method for adjusting an air mass flow to be provided in a charging operation of an internal combustion engine is known, wherein in the charging operation the pressure prevailing in an intake manifold is adjusted by an adjustable air mass flow and without using a throttle valve.

[0009] The published patent application DE 10 2008 042 510 A1 discloses a method for determining a boost pressure control value for setting a boost pressure of a supercharged internal combustion engine.

[0010] From the published patent application DE 10 2018 211 538 A1 a method for controlling the charging of an internal combustion engine is known.

[0011] German Patent Application DE 196 08 630 A1 discloses a method for controlling or regulating the power of a turbocharged internal combustion engine, wherein a throttle valve position and boost pressure are controlled or regulated. A charge setpoint is specified, from which a throttle valve control variable is derived. An intake manifold pressure setpoint is determined from the charge setpoint, and a boost pressure setpoint is derived by linking the intake manifold pressure setpoint with a variable that specifies a pressure drop across the throttle valve.

[0012] From the published patent application DE 10 2016 111 298 A1 a method for operating an internal combustion engine with an exhaust gas turbocharger is known, wherein a charge-based target boost pressure is determined on the basis of a charge of the internal combustion engine, an actual boost pressure is sampled, a carried actual boost pressure is determined on the basis of the actual boost pressure, an offset is determined on the basis of the charge-based target boost pressure and the target boost pressure is controlled by means of a first-order time element to the charge-based target boost pressure, provided that the carried actual boost pressure exceeds a value which is smaller by the offset than the charge-based target boost pressure.

[0013] 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 a comfortable driving operation of a motor vehicle having the internal combustion engine can be realized.

[0014] 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. An advantageous embodiment with a practical and non-trivial further development of the invention is specified in the subclaim.

[0015] 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 flow-through intake volume and a flow-through 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 pre-tensioned operation a boost pressure upstream of the throttle valve deviates from an intake manifold pressure downstream of the throttle valve, wherein in pre-tensioned operation the boost pressure is greater than the intake manifold pressure, is characterized according to the invention in that the boost pressure is regulated to the intake manifold pressure in a first step until the intake manifold pressure is reached at a target time and is maintained at the target intake manifold pressure for a period of time from the target time before it is raised to its target value with a defined gradient, which the boost pressure follows until it has also reached the target value.

[0016] Or in other words, a target boost pressure is first determined which does not cause any preload because it is either lower than or at least equal to the intake manifold pressure. Once this has been adjusted, which occurs at a specific point in time, referred to here as the target point in time, the preload is brought about with a defined gradient, or in other words, ramped in. This means that the throttle valve only has to adjust the preload under small, defined gradients, so that no or only very slight pressure overshoots in the intake manifold or subsequent vibrations that can be caused thereby arise. Or in other words, the advantage of the method according to the invention is that comfortable driving of a motor vehicle operated with the internal combustion engine according to the method according to the invention can be brought about.

[0017] 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, Fig. 2 in a pressure-time diagram, a curve of a target boost pressure, an actual boost pressure, a target intake manifold pressure and an actual intake manifold pressure set using a method according to the prior art, and Fig. 3 in a pressure-time diagram a curve of the target boost pressure, the actual boost pressure, the target intake manifold pressure and the actual intake manifold pressure set with an inventive.

[0018] In Fig. Figure 1 illustrates a schematic diagram of a drive train 1 of a motor vehicle comprising an internal combustion engine 2 with an exhaust gas turbocharger 3. 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 non-rotatably connected to an impeller (not shown in detail) of the exhaust gas turbine 5 by means of a shaft 6.

[0019] With the help of the compressor 4, air is drawn in, compressed in the compressor 4, and then, possibly cooled, fed 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.

[0020] 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 designed, 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 designed in the form of an exhaust manifold, is connected to an exhaust tract 15 of the internal combustion engine 2.

[0021] The intake manifold 14 accommodates the compressor 4 in a flow-through manner so that the air it draws in and compresses can be supplied to the internal combustion engine 2. The exhaust 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 supplied via the exhaust tract 15 to the exhaust turbine 5 to operate the compressor 4.

[0022] Downstream of the compressor 4, a throttle valve 10 is arranged in the intake manifold 14 for regulating an air quantity to be supplied to the internal combustion engine 2 with a specific intake manifold pressure p S .

[0023] 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 Lis controllable. 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 is designed to act on the shaft 6 and thus on the operation of the compressor 4 with the aid of the boost pressure control unit 7.

[0024] The internal combustion engine 3 can be operated in a so-called pre-loaded operation, wherein in pre-loaded operation the boost pressure p L upstream of the throttle valve 10 deviates from the intake manifold pressure ps downstream of the throttle valve 10, in particular wherein in pre-tensioned operation the boost pressure p Lis greater than the intake manifold pressure ps. In other words, this means that in preloaded operation a pressure gradient is formed at the throttle valve 10.

[0025] The control of the boost pressure p L requires a set target boost pressure p LSoll , which can be provided, 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 with the aid of actuators and influence its operating state. The actuators can, in particular, comprise a fuel injector, a valve adjustment, or an ignition.

[0026] This means that the desired boost pressure p Lof the exhaust gas turbocharger 3 with the aid of the boost pressure control unit 7, which determines the target boost pressure p LSoll provides, can be regulated.

[0027] The boost pressure control unit 7 can be integrated with the control and regulation unit 8. It is proposed that the provided target boost pressure p LSoll to manipulate under certain circumstances in order to achieve an improved temporal progression of the boost pressure p L regarding the target boost pressure P LSoll In particular, the boost pressure p L quickly to the target boost pressure p LSoll approach, in particular not exceed it and have as harmonious a course as possible.

[0028] The boost pressure control unit 7 could, for example, be connected to the control and regulation unit 8 by means of an interface in order to determine the desired boost pressure p LSoll A further interface could be provided to control the boost pressure pL of the exhaust gas turbocharger 3. Such sensing and control devices are generally known, so they need not be discussed in detail here.

[0029] In Fig. 2 are in a pressure p -time t -diagram a curve of the target boost pressure P LSoll , which is marked with a bold solid line, of the boost pressure p achieved with it L , which is marked with a thin solid line, of the target intake manifold pressure p Ssoll , which is marked with a dotted line, and the achieved intake manifold pressure p S , marked with a dotted line, illustrates the pressure values ​​determined using a method according to the state of the art. Furthermore, an ambient pressure pu is shown.

[0030] The boost pressure p L is determined using the specified target boost pressure p Lsollis adjusted so directly that it has a relatively strong bend, which is clearly noticeable for the driver of a motor vehicle equipped with the internal combustion engine 2 and operated according to the method according to the prior art. In order to achieve comfortable operation of the motor vehicle in pre-tensioned operation, Fig. 3 illustrates, by way of example, a prestressed operation achieved by means of a method according to the invention. The pressure curves p Lsoll , p L , p Ssoll , p S pü are according to Fig. 2 marked.

[0031] The boost pressure p L In a first step, the intake manifold pressure ps is adjusted to the intake manifold pressure ps at a target time tz. Then, in a further step, the boost pressure p L to a specified target boost pressure p Lsoll, which is greater than a specified target intake manifold pressure p Ssoll The target time tz indicates the attainment of the intake manifold pressure ps or the target intake manifold pressure p during operation of the internal combustion engine 2 to achieve preloaded operation. Ssoll by the boost pressure p L .

[0032] The adjustment of the target boost pressure p Lsoll can be carried out via a filling control unit comprising the throttle valve 10, or it can be carried out via the boost pressure control unit 7.

[0033] In the method according to the invention, the pressure curves p Lsoll , P L , p Ssoll , ps in Fig. 3, the target boost pressure p Lsoll to the target intake manifold pressure p Ssoll regulated, and from the target time tz over a period Δt at the target intake manifold pressure p Ssoll before it reaches its target value p with a defined gradientLsollZ is raised, to which the boost pressure p L follows until it reaches the target value p LsollZ has also been reached. The period Δt advantageously ends as soon as the intake manifold pressure ps is stabilized. 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 Rounded climb p pressure ps intake manifold pressure p L boost pressure p Ssoll Target intake manifold pressure P Lsoll Target boost pressure P LsollZ Target value pu ambient pressure t time tz target time Δt time interval

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 flow-through intake volume (12) and a flow-through 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), 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), 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 prestressed mode,where in pre-loaded operation a boost pressure (p, L ) upstream of the throttle valve (10) deviates from an intake manifold pressure (ps) downstream of the throttle valve (10), wherein in pre-tensioned operation the boost pressure (p L ) is greater than the intake manifold pressure (ps), characterized by that the target boost pressure (p Lsoll ) until the target intake manifold pressure (p Ssoll ) at a target time (tz), to the target intake manifold pressure (p Ssoll ) and from the target time (tz) over a period (Δt) at the target intake manifold pressure (p Ssoll ) before it is increased to its target value (p LsollZ ) is raised, to which the boost pressure (p L ) until it reaches the target value (p LsollZ ) has also been achieved. [2] Method according to claim 1, characterized by that the period (Δt) ends as soon as the intake manifold pressure (p S ) is stably regulated.

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