DE102019119437A1 - METHOD FOR OPERATING A MOTOR VEHICLE - Google Patents

Abstract

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

Description

The present invention relates to a method for operating a motor vehicle with an electrically assisted turbocharger having two different modes of operation and a motor vehicle.

At present there are many different approaches for operating a belt-starter-generator ( BSG - Belt Starter Generator) or integrated starter generator ( ISG - Integrated Starter Generator) in a hybrid drive train of a motor vehicle. An electrically assisted 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 Rekuperationsbetrieb.

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

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

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

According to a first aspect, this technical problem is solved by a method for operating a motor vehicle having 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 electric machine by means of the generated electrical energy and a second mode of operation in which the electrically assisted turbocharger is powered by electric energy from a battery, comprising the steps of detecting operating parameters of the internal combustion engine; and switching between the first operating mode and the second operating mode based on the determined operating parameters. The driving of the motor vehicle is carried out by the support of another electric machine. By this method, the fuel consumption of the motor vehicle can be reduced and the efficiency of the internal combustion engine can be improved.

In a technically advantageous embodiment of the method, the operating parameters of the internal combustion engine are / are an effective engine power, a mean pressure and / or an engine speed. As a result, for example, the technical advantage is achieved that particularly suitable operating parameters are used for switching between the operating modes.

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

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

In a further technically advantageous embodiment of the method, the wastegate is closed in the first operating mode. As a result, for example, the technical advantage is achieved that the selection of the mode of the electrically assisted turbocharger is implicitly integrated into the basic load control of the internal combustion engine.

In a further technically advantageous embodiment of the method, the wastegate is open in the second operating mode. As a result, for example, the technical advantage is also achieved that the selection of the mode of the electrically assisted turbocharger is implicitly integrated into the basic load control of the internal combustion engine.

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

In a further technically advantageous embodiment of the method, the first operating mode is gradually reduced during switching, while the second operating mode is gradually increased. As a result, for example, the technical advantage is achieved that a smooth operating state transition is made possible.

In a further technically advantageous embodiment of the method, the first operating mode is gradually increased when switching over, while the second operating mode is gradually reduced. As a result, for example, the likewise technical advantage is achieved that a smooth operating state transition is made possible.

According to a second aspect, this technical problem is solved by a motor vehicle which is operable in 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 electric machine by means of the generated electrical energy and in a second mode of operation, in which the electrically assisted turbocharger is powered by electric 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 switching means for switching between the first operation mode and the second operation mode based on the determined operation parameters. The motor vehicle achieves the same technical advantages as the method according to the first aspect.

Embodiments of the invention are illustrated in the drawings and will be 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 Operating modes of the electrically assisted turbocharger to improve fuel economy;
• 3 a schematic representation of a combined operating mode for improving the fuel consumption;
• 4 a power limit between the assist and recuperation modes as a function of state of charge SOC ;
• 5 an implementation of a load control strategy that allows switching between backup and recuperation;
• 6 an overview of different operating modes for charging the battery;
• 7 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 an electrical support 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 powertrain 105 in particular in a parallel hybrid design employing an internal combustion engine and an electric machine (either a belt-starter-generator BSG or an integrated starter generator ISG in a parallel arrangement in a motor vehicle 100 be used. The hybrid powertrain 105 additionally includes an electrically assisted turbocharger ( Etc - electrically Supported Turbocharger).

The turbo-charged combustion engine is equipped with an electrically assisted turbocharger Etc equipped either to provide additional compressor power to boost the boost pressure of the internal combustion engine (Boosting Support) or to recover thermal energy from the exhaust gases can be used. The electrically assisted turbocharger Etc is electrically in the electrical system of the motor vehicle 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
• - Electric boosting (Boosting) ( 101-5 . 101-6 ) from the battery 103 ,

The highest mode of operation shown above 101-1 will not be considered further below. The method relates to providing a control strategy for the hybrid powertrain 105 that the remaining five operating modes 101-1 , ..., 101-5 including a transition between the operating modes 101-1 , ..., 101-5 synchronized. The main objective of the operating strategy is to save fuel consumption in the hybrid powertrain 105 fully exploit.

The car 100 includes a switching device 125 that controlled between each operating modes 101-1 , ..., 101-6 can switch over and each of the operating modes 101-1 , ..., 101-6 enable or disable. Next includes the motor vehicle 100 a detection device 125 that different operating parameters of the motor vehicle 100 and the internal combustion engine, such as an engine speed, a mean pressure or a state of charge of a battery, with which the turbocharger is driven. The detection device 123 may suitably 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 economy. From the five lower modes of operation 1 two are particularly suitable for fuel consumption using the electrically assisted turbocharger Etc to improve.

In the first operating mode 101 -2 operates the electrically assisted turbocharger Etc in the recuperation mode using the thermal energy from the exhaust gases. The electrical energy coming from the electrically assisted turbocharger Etc is generated directly to the belt starter generator BSG without energy in the battery 103 save. The belt starter generator BSG again works in support mode (Boosting Mode) to lower the load point of the internal combustion engine. The wastegate is closed to take advantage of the maximum recuperation potential.

In the second mode of operation 101-5 becomes the electrically assisted turbocharger Etc used for a backup operation in which the required electrical energy of the battery 103 is removed. By the electrical support of the turbocharger Etc the boost pressure of the internal combustion engine can be increased. The wastegate is fully open to minimize the charge cycle of the internal combustion engine. The boost pressure itself is not raised compared to the regular operation, but merely generated instead of the turbine via the electric machine. 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 mode of operation depends 101 - 5 from the state of charge of the battery 103 from.

• - Recuperation mode of the Etc = SOC neutral
• - Support mode of the Etc = only possible with sufficient state of charge SoC

In general, the recuperation mode of the electrically assisted turbocharger Etc only be used if sufficient exhaust enthalpy is available, ie in the range of high effective engine power. The backup operation of the electrically assisted turbocharger Etc In contrast, can be used without restriction throughout the engine map.

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

In the area 111-1 becomes the operating mode at lower engine power 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 charge exchange work .. The wastegate WG (Wastegate) is open.

In the area 111-2 becomes the operating mode at higher engine power 101-2 used in which the electrically assisted turbocharger Etc works in recuperation mode, ie generates electrical energy. The electrical energy coming from the electrically assisted turbocharger Etc is generated directly to the belt starter generator BSG to power without the energy in the battery 103 temporarily. The wastegate WG is closed.

In area 111-3 with lower engine loads none of the operating modes 101-2 or 101-5 used. The wastegate valve WG is closed.

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

4 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 itself a function of state of charge SoC the battery is.

If the state of charge falls below a lower limit SOC _{lower threshold} , the operating mode becomes 101-5 (Support) disabled and only the operating mode 101-2 (Boosting) used. If the state of charge SoC an upper limit SOC exceeds _upper threshold becomes the operating mode 101-2 disabled and only the operating mode 101-5 used. Between the lower and upper limits of the state of charge SoC can both both modes of operation 101-2 and 101-5 be activated. When the charge state SoC increases, becomes a larger part of the engine map 109 from the operating mode 101-5 covered. If, conversely, the state of charge SoC decreases, becomes a larger part of the engine map 109 from 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 a recuperation in operating mode 101-2 switch.

The implementation of the control strategy directly controls the nude authors 115 for load control. This is a simple switching between the operating mode 101 - 5 and the operating mode 101 - 2 of the electrically assisted turbocharger Etc during engine operation.

The control unit 119 controls the indicated mean effective pressure (IMEP) of the internal combustion engine 107 to a desired mean pressure by sending control commands to the three actuators 115 , Throttle, turbocharger Etc and wastegate WG (Wastegate).

As a first step, the deviation between actual and desired engine load IMEP at present is in a scalar load parameter r ₁ converted. For this purpose, a combination of a control map and a PID controller (PID controller) is used. The parameter r ₁ is then converted directly to a throttle position via a characteristic curve.

To control the turbocharger Etc becomes the parameter r ₁ converted to a desired compressor power requirement. By using power balancing, an excess or missing power can be calculated on the turbo shaft according to the requested load. The overshoot or lack of power is due to the electrically assisted turbocharger Etc compensated. However, the requested power may be the operating limits of the electrically assisted turbocharger Etc exceed.

For this reason, the output signal is limited before this to the electric machine of the electrically assisted turbocharger Etc is forwarded. If the limitation is activated, the wastegate will be added WG used to calculate the difference between the requested and the maximum power of the electrically assisted turbocharger Etc to compensate. The difference in capacity becomes a required position of the wastegate valve WG converted and superimposed on the baseline of the wastegate opening resulting from the selected operating mode of the electrically assisted turbocharger Etc is determined.

For aiding by the electrically assisted turbocharger Etc , is the wastegate WG fully open by default.

For recuperation by the electrically assisted turbocharger Etc , is the wastegate WG Fully closed by default.

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

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

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

Whenever a recuperation by the electrically assisted turbocharger Etc is possible, this is preferably used, since it compared to the belt-starter-generator BSG more efficient is electrical energy through the electrically assisted turbocharger Etc to create. The belt starter generator BSG is used only for charging in that part of the engine map in which no recuperation by the electric supported turbocharger Etc is possible or if the requested charging power is the maximum recuperation potential of the turbocharger Etc exceeds.

7 shows an engine map 117 a combined mode of operation for charging the battery 103 , The engine map 117 is spanned by the axes 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 different operating modes 101 - 5 and 101 - 6 for electrical assistance using the battery 103 as an energy source.

An electrical support can be used to discharge the battery 103 , ie reducing the state of charge SoC , or to support the internal combustion engine 107 be used in transient driving situations. For a discharge, the electrical energy is free. When deciding which device to support, only a specific fuel consumption of the internal combustion engine (BSFC - Brake Specific Fuel Consumption) is relevant.

For a transient support, the electrical energy can not be considered as free. The effectiveness depends on the engine efficiency during the assist phase and the costs associated with generating the electrical energy consumed during backing up.

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 motor speed (X-axis) and motor load.

Transient support is realized as follows. Below the full load of the internal combustion engine (solid black line) in the area 123-1 is only the electrically assisted turbocharger Etc used for supporting, as this more efficient compared to a support by the belt starter generator BSG is (an electrical power input is amplified by the air path to the mechanical power output on the crankshaft).

It can be assumed that it is not possible to operate the internal combustion engine efficiently or safely beyond this line. Therefore, in the field 123 - 2 if the requested load exceeds the full load of the internal combustion engine (eg at full acceleration of the motor vehicle 100 ), the belt starter generator BSG 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 become 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 will be in step S102 between the first operating mode 101-2 and the second mode of operation 101-5 switched. In this case, the one operating mode 101-2 activated while the other operating mode 101-5 is deactivated or vice versa.

The method can be used to design new hybrid powertrains 105 and for calibration of hybrid powertrain functionalities 105 be used.

The operational strategy follows a heuristic approach based on specific rules and parameters that define under what conditions the electric machines are used for boosting or recuperation. This operating strategy may be for specific driving cycles, such as WLTC or RDE , be optimized to specifically optimize CO2 emissions or other parameters in this driving cycle. In addition, the operational strategy allows to optimize the design of the system and its components in early development phases by means of simulations.

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

All method steps may be implemented by means suitable for carrying out the respective method step. All functions performed by objective features may be a method step of a method.

The scope of the present invention is given by the claims and is not limited by the features illustrated in the specification or shown in the figures.

LIST OF REFERENCE NUMBERS

100

motor vehicle

101

operation mode

103

battery

105

Hybrid powertrain

107

internal combustion engine

109

Engine map

111

Area

113

power limit

115

actuators

117

Engine map

119

Area

121

Engine map

123

detector

125

switchover

ISG

integrated starter generator

BSG

Belt starter generator

Etc

Electrically assisted turbocharger

SoC

SOC

WG

Wastegate

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 means of an electric machine (BSG) the generated electric power 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), comprising the steps: Detecting (S101) operating parameters of the internal combustion engine (107); and Switching (S102) between the first operation mode (101-2) and the second operation mode (101-5) based on the determined operation parameters. Method according to Claim 1 wherein the operating parameter of the internal combustion engine (107) is an effective engine power, a mean pressure (BMEP) and / or an engine speed. Method according to one of the preceding claims, wherein additionally a state of charge (SoC) of the battery (103) is detected and the switching (S102) is additionally performed on the basis of the state of charge (SoC). Method 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 wastegate (WG) is closed. Method according to one of the preceding claims, wherein in the second operating mode (101-5), the wastegate (WG) is open. Method according to one of the preceding claims, wherein during the switching between the first operating mode (101-2) and the second operating mode (101-5) both operating modes (101-2, 101-5) are activated. Method according to Claim 7 wherein, in the switching, the first operation mode (101-2) is gradually shut down while the second operation mode (101-5) is gradually increased. Method according to one of the preceding claims, wherein when switching the first operating mode (101-2) is gradually increased, while the second operating mode (101-5) is gradually reduced. A motor vehicle (100) which is operable in 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 means of an electric machine (BSG) the electric energy generated 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 means (125) for switching between the first operating mode (101-2) and the second operating mode (101-5) based on the determined operating parameters.

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