DE102020003891A1 - METHOD OF OPERATING A MOTOR VEHICLE - Google Patents

Abstract

The present invention relates to a method for operating a motor vehicle with a first operating mode in which electrical energy is generated from exhaust gases of an internal combustion engine by means of an electrically assisted turbocharger and the motor vehicle is driven by an electrical machine by means of the electrical energy generated and a second operating mode in in which the electrically assisted turbocharger is driven by means of electrical energy from a battery, with the steps of detecting (S101) operating parameters of the internal combustion engine; and switching (S102) between the first operating mode and the second operating mode on the basis of the determined operating parameters.

Description

The present invention relates to a method for operating a motor vehicle with an electrically assisted turbocharger, which has two different operating modes, and a motor vehicle.

There are currently many different approaches for operating a belt starter generator (BSG - Belt Starter Generator) or an integrated starter generator (ISG - Integrated Starter Generator) in a hybrid drive train of a motor vehicle. An electrically supported turbocharger (eTC - Electrically Supported Turbocharger) is used exclusively either to improve the transient response of the internal combustion engine in a boosting mode or to improve the fuel consumption of the motor vehicle in a recuperation mode.

However, both the belt starter generator BSG or the integrated starter generator ISG are currently treated separately, despite the fact that they in principle provide the same functionality, namely electrical support (boosting) and recuperation. To make the best use of both electrical machines, a combined operating strategy is required that takes into account both the eTC electrically assisted turbocharger and the BSG / ISG starter generators. Such an operating strategy does not yet exist.

The technical object of the present invention is to provide an operating strategy for a hybrid drive train with an internal combustion engine, a starter generator BSG / ISG, an electrically assisted turbocharger and a battery.

This technical problem is solved by subjects according to the independent claims. Advantageous embodiments are the subject matter of the dependent claims, the description and the figures.

According to a first aspect, this technical object is achieved by a method for operating a motor vehicle with a first operating mode in which electrical energy is generated from exhaust gases from an internal combustion engine by means of an electrically assisted turbocharger and the motor vehicle is driven by an electrical machine by means of the electrical energy generated and a second operating mode, in which the electrically assisted turbocharger is driven by means of electrical energy from a battery, with the steps of detecting operating parameters of the internal combustion engine; and switching between the first operating mode and the second operating mode on the basis of the determined operating parameters. The motor vehicle is driven by the assistance of another electrical machine. This method can reduce the fuel consumption of the motor vehicle and improve the efficiency of the internal combustion engine.

In a technically advantageous embodiment of the method, the operating parameters of the internal combustion engine is / are an effective engine power, an average pressure and / or an engine speed. This has the technical advantage, for example, that particularly suitable operating parameters are used to switch between the operating modes.

In a further technically advantageous embodiment of the method, a state of charge of the battery is additionally detected and the switch is also carried out on the basis of the state of charge. This achieves the technical advantage, for example, that the respective operating modes are only activated when sufficient electrical energy can be provided by the battery.

In a further technically advantageous embodiment of the method, when the battery state of charge is lower, the first operating mode is activated when the engine power is lower than when the state of charge is higher. This has the technical advantage, for example, that excessive discharging of the battery is prevented.

In a further technically advantageous embodiment of the method, the charge pressure control valve is closed in the first operating mode. This has the technical advantage, for example, that the selection of the mode of the electrically assisted turbocharger is implicitly integrated into the base load control of the internal combustion engine.

In a further technically advantageous embodiment of the method, the charge pressure control valve is open in the second operating mode. This also has the technical advantage, for example, that the selection of the mode of the electrically assisted turbocharger is implicitly integrated into the base load control of the internal combustion engine.

In a further technically advantageous embodiment of the method, both operating modes are activated during the switchover between the first operating mode and the second operating mode. This has the technical advantage, for example, that an abrupt termination of an operating mode when switching can be avoided.

In a further technically advantageous embodiment of the method, when switching over, the first operating mode is gradually shut down, while the second operating mode is gradually started up. This has the technical advantage, for example, that a smooth operating state transition is made possible.

In a further technically advantageous embodiment of the method, when switching over, the first operating mode is gradually ramped up, while the second operating mode is gradually ramped down. This also has the technical advantage, for example, that a smooth operating state transition is made possible.

According to a second aspect, this technical problem is achieved by a motor vehicle that can be operated in a first operating mode in which electrical energy is generated from exhaust gases from an internal combustion engine by means of an electrically assisted turbocharger and the motor vehicle is driven by an electrical machine by means of the electrical energy generated and in a second operating mode in which the electrically assisted turbocharger is driven by means of electrical energy from a battery, with a detection device for detecting operating parameters of the internal combustion engine and a battery for driving the electrically assisted turbocharger; and a switching device for switching between the first operating mode and the second operating mode on the basis of the determined operating parameters. The motor vehicle achieves the same technical advantages as the method according to the first aspect.

Embodiments of the invention are shown in the drawings and are described in more detail below.

• 1 eine Übersicht für die möglichen Betriebsmodi eines Riemen-Starter-Generators oder einem integrierten Starter-Generator und einem elektrisch unterstützten Turbolader;
• 2 Betriebsmodi des elektrisch unterstützten Turboladers zum Verbessern eines Kraftstoffverbrauchs;
• 3 eine schematische Darstellung eines kombinierten Betriebsmodus zum Verbessern des Kraftstoffverbrauchs;
• 4 eine Leistungsgrenze zwischen dem Unterstützungs- und Rekuperationsmodus als eine Funktion des Ladezustands SOC;
• 5 eine Implementation einer Laststeuerstrategie, die es erlaubt, zwischen einer Unterstützung und einer Rekuperation umzuschalten;
• 6 eine Übersicht über unterschiedliche Betriebsmodi zum Laden der Batterie;
• 7 eine schematische Darstellung eines kombinierten Betriebsmodus zum Laden der Batterie;
• 8 eine Übersicht über unterschiedliche Betriebsmodi zum elektrischen Unterstützen unter Verwendung der Batterie als Energiequelle;
• 9 eine schematische Darstellung eines kombinierten Betriebsmodus für eine elektrische Unterstützung unter Verwendung der Batterie als Energiequelle; und
• 10 ein Blockdiagramm eines Verfahrens zum Betreiben eines Kraftfahrzeugs.

Show it:

• 1 an overview of the possible operating modes of a belt starter generator or an integrated starter generator and an electrically assisted turbocharger;
• 2 Modes of operation of the electrically assisted turbocharger for improving fuel economy;
• 3 a schematic representation of a combined operating mode for improving fuel consumption;
• 4th a power limit between the assist and recuperation modes as a function of the state of charge SOC;
• 5 an implementation of a load control strategy that allows switching between support and recuperation;
• 6th an overview of different operating modes for charging the battery;
• 7th a schematic representation of a combined operating mode for charging the battery;
• 8th an overview of different operating modes for electrical assistance using the battery as an energy source;
• 9 a schematic representation of a combined operating mode for electrical assistance using the battery as an energy source; and
• 10 a block diagram of a method for operating a motor vehicle.

1 shows an overview of the possible operating modes 101-1 , ..., 101-6 in a hybrid drive train 105, in particular in a parallel hybrid configuration, in which an internal combustion engine and an electrical machine (either a belt starter generator BSG or an integrated starter generator ISG are used in a parallel arrangement in a motor vehicle 100. The hybrid drive train 105 comprises in addition, an electrically supported turbocharger (eTC - electrically supported turbocharger).

The turbocharged combustion engine is equipped with an electrically assisted turbocharger eTC, which can either be used to provide additional compressor power to increase the charge pressure of the combustion engine (boosting support) or to recover thermal energy from the exhaust gases. The electrically assisted turbocharger eTC is electrically connected to the vehicle's electrical system 100 integrated.

• - Rekuperation ohne Energiespeicherung (101-1, 101-2);
• - Rekuperation mit Energiespeicherung (101-3, 101-4); und
• - elektrisches Unterstützen (Boosting) (101-5, 101-6) aus der Batterie 103.

The six operating modes shown 101-1 , ..., 101-6 can be divided into three classes, namely:

• - Recuperation without energy storage ( 101-1 , 101-2 );
• - Recuperation with energy storage ( 101-3 , 101-4 ); and
• - electrical assistance (boosting) ( 101-5 , 101-6 ) from the battery 103 .

The operating mode shown furthest above 101-1 is not considered further below. The method relates to the provision of a control strategy for the hybrid drive train 105 showing the remaining five operating modes 101-1 , ..., 101-5 including a transition between the operating modes 101-1 , ..., 101-5 synchronized. The main goal of the operating strategy is to identify the potential for fuel consumption savings in the hybrid drive train 105 take full advantage of it.

The car 100 comprises a switching device 125 that controlled between the individual operating modes 101-1 , ..., 101-6 can switch and any of the operating modes 101-1 , ..., 101-6 can activate or deactivate. The motor vehicle also includes 100 a detection device 125 , the different operating parameters of the motor vehicle 100 and the internal combustion engine can detect, such as an engine speed, an average pressure or a state of charge of a battery with which the turbocharger is driven. The detection device 123 can include suitable sensors for this purpose.

2 shows the operating modes 101-2 and 101-5 of the electrically assisted turbocharger eTC to improve fuel consumption. From the five lower operating modes 1 two are particularly suitable for improving fuel economy using the eTC electrically assisted turbocharger.

In the first mode of operation 101-2 the electrically assisted eTC turbocharger works in recuperation mode using the thermal energy from the exhaust gases. The electrical energy generated by the eTC electrically assisted turbocharger is used directly to power the belt starter generator BSG to drive with no energy in the battery 103 save. The belt starter generator BSG in turn works in support mode (boosting mode) in order to lower the load point of the internal combustion engine. The boost pressure control valve is closed in order to use the maximum recuperation potential.

In the second operating mode 101-5 the electrically assisted turbocharger eTC is used for an assist operation in which the required electrical energy from the battery 103 is removed. The boost pressure of the combustion engine can be increased through the electrical support of the eTC turbocharger. The charge pressure control valve is fully open in order to minimize the gas exchange work of the internal combustion engine. The boost pressure itself is not increased compared to normal operation, but only generated by the electric machine instead of the turbine. This improves the efficiency of the internal combustion engine.

• - Rekuperationsmodus des eTC = SOC neutral
• - Unterstützungsmodus des eTC = nur möglich bei ausreichendem Ladezustand SoC

During the first operating mode 101-2 represents a closed system that is autonomous and independent of the state of charge ( SoC - State of Charge) of the battery 103 can be operated, the availability of the second operating mode depends 101-5 on the state of charge of the battery 103 from.

• - Recuperation mode of the eTC = SOC neutral
• - eTC support mode = only possible if the SoC is sufficiently charged

In general, the recuperation mode of the electrically assisted turbocharger Etc can only be used if sufficient exhaust gas enthalpy is available, ie in the range of high effective engine power. The support operation of the electrically assisted turbocharger Etc can, on the other hand, be used in the entire engine map without restriction.

3 shows a schematic representation of a combined operating mode for improving fuel consumption. The engine map 109 is spanned by the axes of motor speed (X-axis) and motor load. The engine map 109 will operate on three different modes 101-2 , 101-5 and 101-7 pictured. These are characterized by different engine outputs and engine loads.

In the area 111-1 becomes the operating mode at lower engine powers 101-5 used in which the electrically assisted turbocharger Etc electrically through the battery 103 is driven and thus provides the required boost pressure for the internal combustion engine with reduced gas exchange work .. The boost pressure control valve WG (wastegate) is open.

In the area 111-2 becomes the operating mode at higher engine outputs 101-2 used in which the electrically assisted turbocharger Etc works in recuperation mode, ie generates electrical energy. The electrical energy produced by the electrically assisted turbocharger Etc generated is used directly to power the belt starter generator BSG to drive without the energy in the battery 103 buffer. The boost pressure control valve Flat share is closed.

In area 111-3 with lower engine loads, none of the operating modes will 101-2 or 101-5 used. The boost pressure control valve Flat share is closed.

The areas 111-1 , 111-2 and 111-3 in the engine map 109 are not static in their size and expansion, but depend in turn on a state of charge SoC the battery 103 from. That means that the performance limit 113 between areas 111-1 and 111-2 is not static, but depends on the state of charge SoC shifts.

4th shows a performance limit 113 between the operating mode 101-2 and 101-5 as a function of the state of charge SOC. Switching between the operating mode 101-2 and 101-5 becomes through a performance limit 113 P _{act, recup} defines which itself is a function of the state of charge SoC the battery is.

If the state of charge falls below a lower limit SOC _{lower threshold} , the operating mode is 101-5 (Support) deactivated and only the operating mode 101-2 (Boosting) used. If the state of charge SoC exceeds an upper limit SOC _{upper threshold} , the operating mode 101-2 deactivated and only the operating mode 101-5 used. Between the lower and the upper limit of the state of charge SoC can use both operating modes 101-2 and 101-5 be activated. When the charge level SoC increases, a larger part of the engine map becomes 109 of the operating mode 101-5 covered. If vice versa the state of charge SoC drops, a larger part of the engine map becomes 109 of the operating mode 101-2 covered. The operating _strategy can be optimized by simply changing the parameters SOC _{lower threshold} and SOC _{upper threshold} .

5 shows an implementation of a load control strategy that allows between support in the operating mode 101-5 and recuperation in operating mode 101-2 to switch.

The actors are responsible for the implementation of the control strategy 115 for load control directly. A simple switchover between the operating mode is thereby achieved 101-5 and the operating mode 101-2 of the electrically assisted turbocharger Etc enabled during engine operation.

The control unit 119 controls the indicated actual mean effective pressure (IMEP) of the combustion engine 107 to a target medium pressure by sending control commands to the three actuators 115 , Throttle valve, eTC turbocharger and WG (wastegate) charge pressure control valve.

As a first step, the deviation between the actual and target engine load IMEP at the current point in time is converted into a scalar load parameter r ₁ . A combination of a control map and a PID control unit (PID controller) is used for this. The parameter r ₁ is then converted directly into a position of the throttle valve via a characteristic curve.

To control the turbocharger eTC, the parameter r _{1 is converted} into a target compressor output request. By using power balancing, excess or lack of power on the turbo shaft can be calculated according to the requested load. The excess or lack of power is compensated by the electrically assisted turbocharger eTC. However, the requested power can exceed the operating limits of the electrically assisted turbocharger eTC.

For this reason, the output signal is limited before it is passed on to the electric machine of the electrically assisted turbocharger eTC. If the limitation is activated, the charge pressure control valve WG is also used to compensate for the difference between the requested and the maximum output of the electrically assisted turbocharger eTC. The power difference is converted into a required position of the boost pressure control valve WG and superimposed on the baseline of the boost pressure control valve opening, which is determined by the selected operating mode of the electrically assisted turbocharger eTC.

For assistance from the electrically assisted turbocharger eTC, the charge pressure control valve WG is fully opened by default.
For recuperation by the electrically assisted eTC turbocharger, the charge pressure control valve WG is completely closed by default.

This results in the technical advantage that the selection of the mode of the electrically assisted turbocharger eTC is implicitly integrated into the base load control of the internal combustion engine, so that a smooth operating state transition is made possible.

6th shows an overview of the different operating modes 101-3 and 101-4 to charge the battery 103 . In the case of an exceptionally low state of charge SoC (which is even below the SOC _{lower threshold} ), a charge request is requested by the control system.

The electrical energy can either be generated and supplied again by the belt starter generator BSG or the electrically assisted turbocharger eTC. Which of the two electrical machines is used for recuperation is defined in a further engine map based on the actual operating point of the internal combustion engine.

Whenever recuperation by the electrically assisted turbocharger eTC is possible, this is preferably used, since it is more efficient in comparison to the belt starter generator BSG to generate electrical energy by the electrically assisted turbocharger eTC. The belt starter generator BSG is only used for charging in that part of the engine map in which recuperation by the electrically assisted turbocharger eTC is not possible or if so the requested charging power exceeds the maximum recuperation potential of the turbocharger eTC.

7th shows an engine map 117 a combined operating mode for charging the battery 103 . The engine map 117 is spanned by the axes of motor speed (X-axis) and motor load. In the area 119-1 the battery is powered by the electrically assisted turbocharger Etc loaded. In the area 119-2 becomes the battery 103 using the belt starter generator BSG loaded.

8th shows an overview of the different operating modes 101-5 and 101-6 for electrical support using the battery 103 as an energy source.

Electrical assistance can help discharge the battery 103 , ie lowering the charge level SoC , or to support the internal combustion engine 107 be used in transient driving situations. The electrical energy is free of charge for a discharge. When deciding which device is to be supported, only a specific fuel consumption of the internal combustion engine (BSFC - Brake Specific Fuel Consumption) is relevant.

For a transient support, the electrical energy cannot be regarded as free of charge. The effectiveness depends on the motor efficiency during the support phase and the costs associated with generating the electrical energy that is consumed during the support phase.

9 shows an engine map 121 a combined mode of operation for electrical assistance using the battery as an energy source. The engine map 121 is spanned by the axes of motor speed (X-axis) and motor load.

Transient support is implemented as follows. Below the full load of the internal combustion engine (continuous black line) in the area 123-1 only the electrically assisted turbocharger eTC is used for assisting, as it is more efficient compared to assisting by the belt starter generator BSG (an electrical power input is amplified through the air path up to the mechanical power output at the crankshaft).

It can be assumed that it is not possible to operate the internal combustion engine efficiently or safely beyond this line. Hence, in the area 123-2 if the requested load exceeds the full load of the internal combustion engine (e.g. when the motor vehicle is fully accelerated 100 ), the belt starter generator BSG is activated to provide additional torque to the crankshaft.

10 shows a block diagram of the method for operating the motor vehicle 100 . In a first step S101 are the operating parameters of the internal combustion engine 107 and the battery 103 for driving the electrically assisted turbocharger eTC determined by appropriate sensors.

Depending on the specific operating parameters, step S102 between the first operating mode 101-2 and the second operating mode 101-5 switched. One operating mode is thereby 101-2 activated while the other operating mode 101-5 deactivated or vice versa.

The process can be used to design new hybrid powertrains 105 and for calibrating the functionality of hybrid powertrains 105 be used.

The operating strategy follows a heuristic approach based on specific rules and parameters that define the conditions under which the electrical machines are used for support (boosting) or recuperation. This operating strategy can be optimized for specific driving cycles, such as WLTC or RDE, in order to optimize CO2 emissions or other parameters in this driving cycle. In addition, the operating strategy allows the design of the system and its components to be optimized in the early development phases using simulations.

All the features explained and shown in connection with individual embodiments of the invention can be provided in different combinations in the subject matter of the invention in order to simultaneously realize their advantageous effects.

All method steps can be implemented by devices that are suitable for carrying out the respective method step. All functions that are carried out by objective features can be a process step of a process.

The scope of protection of the present invention is given by the claims and is not restricted by the features explained in the description or shown in the figures.

List of reference symbols

100

Motor vehicle

101

operation mode

103

battery

105

Hybrid powertrain

107

Internal combustion engine

109

Engine map

111

Area

113

Performance limit

115

Actuators

117

Engine map

119

Area

121

Engine map

123

Detection device

125

Switching device

ISG

integrated starter generator

BSG

Belt starter generator

Etc

electrically assisted turbocharger

SoC

State of charge

Flat share

Boost pressure control valve

Claims (10)

Method for operating a motor vehicle (100) with a first operating mode (101-2), in which electrical energy is generated from exhaust gases of an internal combustion engine by means of an electrically assisted turbocharger (eTC) and the motor vehicle (100) by an electrical machine (BSG) by means of the generated electrical energy is driven and a second operating mode (101-5), in which the electrically assisted turbocharger (eTC) is driven by means of electrical energy from a battery (103), with the steps: Detecting (S101) operating parameters of the internal combustion engine (107); and Switching (S102) between the first operating mode (101-2) and the second operating mode (101-5) on the basis of the determined operating parameters. Procedure according to Claim 1 , wherein the operating parameter of the internal combustion engine (107) is an effective engine power, a mean effective pressure (BMEP) and / or an engine speed. Method according to one of the preceding claims, wherein a state of charge (SoC) of the battery (103) is additionally detected and the switchover (S102) is additionally carried out on the basis of the state of charge (SoC). Procedure according to Claim 3 wherein at a lower state of charge (SoC) of the battery (103), the first operating mode (101-2) is activated at a lower engine power than at a higher state of charge (SoC). Method according to one of the preceding claims, wherein in the first operating mode (101-2) the charge pressure control valve (WG) is closed. Method according to one of the preceding claims, wherein in the second operating mode (101-5) the charge pressure control valve (WG) is open. Method according to one of the preceding claims, wherein both operating modes (101-2, 101-5) are activated during the switchover between the first operating mode (101-2) and the second operating mode (101-5). Procedure according to Claim 7 wherein, when switching, the first operating mode (101-2) is gradually shut down, while the second operating mode (101-5) is gradually started up. Method according to one of the preceding claims, wherein when switching over, the first operating mode (101-2) is gradually ramped up, while the second operating mode (101-5) is gradually ramped down. Motor vehicle (100) which can be operated in a first operating mode (101-2) in which electrical energy is generated from exhaust gases from an internal combustion engine by means of an electrically assisted turbocharger (eTC) and the motor vehicle (100) by means of an electrical machine (BSG) the generated electrical energy is driven and in a second operating mode (101-5), in which the electrically assisted turbocharger (eTC) is driven by means of electrical energy from a battery (103), with: a detection device (123) for detecting operating parameters of the internal combustion engine (107); and a switching device (125) for switching between the first operating mode (101-2) and the second operating mode (101-5) on the basis of the determined operating parameters.

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