WO2023001984A1

WO2023001984A1 - Method for operating a motor vehicle, and motor vehicle

Info

Publication number: WO2023001984A1
Application number: PCT/EP2022/070543
Authority: WO
Inventors: Alexander Von Gaisberg-Helfenberg; Jochen Martin Schmid
Original assignee: Mercedes-Benz Group AG
Priority date: 2021-07-22
Filing date: 2022-07-21
Publication date: 2023-01-26
Also published as: DE102021003758A1

Abstract

The invention relates to a method for operating a motor vehicle, the motor vehicle comprising an internal combustion engine (12) which includes an output shaft and by means of which the motor vehicle can be driven via the output shaft, and at least one catalytic converter (38) through which exhaust gas from the internal combustion engine (12) can flow and by means of which the exhaust gas is aftertreated. A temperature of the catalytic converter (38) is ascertained. A power supplied by the internal combustion engine (12) via the output shaft is limited to a limit value as a function of the ascertained temperature of the catalytic converter (38), said limit value being lower than the value of the maximum power that the internal combustion engine (12) can supply via the output shaft.

Description

Method for operating a motor vehicle and motor vehicle

The invention relates to a method for operating a motor vehicle, in particular a motor vehicle, according to the preamble of patent claim 1. The invention also relates to a motor vehicle.

DE 601 31 508 T2 discloses a known method for reducing the emissions of an electric hybrid electric vehicle of the type that has a drive train, an electric machine that delivers torque in a targeted manner to the drive train, a motor that delivers torque in a targeted manner to the powertrain, and having a catalytic converter which receives exhaust gas from the engine.

The object of the present invention is to create a method and a motor vehicle so that the motor vehicle can be operated with particularly low emissions.

This object is achieved by a method having the features of patent claim 1 and by a motor vehicle having the features of patent claim 10 . Advantageous configurations with expedient developments of the invention are specified in the remaining claims.

A first aspect of the invention relates to a method for operating a motor vehicle which is preferably designed as a motor vehicle, in particular as a passenger car. In the method, the motor vehicle has an internal combustion engine which has an output shaft. The internal combustion engine is also referred to as an internal combustion engine or internal combustion engine. The internal combustion engine is preferably a reciprocating engine, so that the output shaft is a crankshaft. The motor vehicle can be driven via the output shaft by means of the internal combustion engine. This means in particular that the Internal combustion engine can provide torque via the output shaft, by means of which the motor vehicle can be driven.

The motor vehicle also has at least one catalytic converter which can flow through the exhaust gas of the internal combustion engine and by means of which the exhaust gas is post-treated and thereby cleaned. In particular, it is provided that, in the method, the internal combustion engine is operated in its fired mode and is therefore fired. This means in particular that combustion processes take place in the internal combustion engine during fired operation of the internal combustion engine. For this purpose, the internal combustion engine has at least one combustion chamber in which combustion processes take place during fired operation. In the respective combustion process, a fuel-air mixture, also referred to simply as a mixture, is burned. The mixture comprises at least air and a particularly liquid or gaseous fuel. For example, within a respective working cycle of the internal combustion engine, the mixture is ignited at an ignition point, also referred to as the ignition angle, and is thereby burned. The respective working cycle of the internal combustion engine includes, for example, two complete revolutions of the crankshaft and thus, for example, 720 crank angles.

In order to be able to operate the motor vehicle with particularly low emissions, it is provided according to the invention that a temperature of the catalytic converter is determined, in particular by means of an electronic computing device. The electronic computing device is preferably part of the motor vehicle.

Furthermore, it is provided according to the invention that a power, in particular mechanical power, which is provided by the internal combustion engine via its output shaft, in particular in order to drive the motor vehicle, is specifically limited to a limit value by means of the electronic computing device depending on the determined temperature of the catalytic converter, which is lower than the value of the maximum, in particular mechanical, power that can be provided by the internal combustion engine via its output shaft. This is to be understood in particular as follows: During the method, the internal combustion engine is operated, for example, fired, as a result of which the internal combustion engine provides the exhaust gas. The combustion of the mixture results in the exhaust gas of the internal combustion engine. The exhaust gas can flow out of the combustion chamber or out of the internal combustion engine and consequently the catalytic converter flow through. In particular, the motor vehicle is driven by the internal combustion engine in the method and is therefore driven at a speed, in particular along a roadway.

While the internal combustion engine is operated in a fired state and preferably drives the motor vehicle, the internal combustion engine provides the above-mentioned, in particular mechanical, power via its output shaft Limit value is limited, which is lower than the value of the maximum power that can be provided by the internal combustion engine. In other words, the method does not allow, ie avoids, that the internal combustion engine provides its maximum power, also referred to as nominal power, in its fired operation, but the power, so to speak, from the

Internal combustion engine can be provided via its output shaft in the operating point or is provided, limited to a power that is less than the maximum power that can be provided by the internal combustion engine, that is, than the nominal power. This can prevent the motor vehicle from emitting an excessively large amount of undesired emissions, in particular after a cold start of the internal combustion engine and during a warm-up of the internal combustion engine, in particular directly following the cold start.

Conventionally, a driver of a motor vehicle that is equipped with an internal combustion engine and can be driven by the internal combustion engine can call up the maximum engine torque that can be provided by the internal combustion engine, which is also referred to as load, immediately after the internal combustion engine has started, especially when the start is a cold start.

By retrieving the maximum engine torque, the internal combustion engine can thus provide its maximum or nominal power at correspondingly high speeds of the internal combustion engine or the output shaft. However, this is now avoided by the method according to the invention, specifically as a function of the temperature of the catalyst and thus, for example, as long as the temperature of the catalyst is lower than a predetermined or specifiable threshold value. In this way it can be avoided that an excessively large amount of undesired emissions are emitted. In order to be able to achieve particularly low-emission operation on the one hand and particularly good drivability of the motor vehicle on the other, one embodiment of the invention provides that the limiting value, which is lower than the value of the maximum power that can be provided by the internal combustion engine, to which the power of the internal combustion engine is limited , is increased with increasing temperature of the catalyst. In other words, a permissible or permitted power output of the internal combustion engine after it has been started, in particular its cold start, is only released with a delay, even for low values, depending on the temperature of the catalytic converter, also known as the catalytic converter temperature, so that the driver of the motor vehicle, for example, can only use the maximum or nominal output of the Internal combustion engine can then and only then call up, or so that then and preferably only then is allowed that the internal combustion engine provides its maximum or rated power when the temperature of the catalyst has passed or exceeded the threshold value.

In a particularly advantageous embodiment of the invention, the motor vehicle is designed as a hybrid vehicle. This means that the motor vehicle has at least one electrical machine, by means of which the motor vehicle can be driven electrically, in particular purely electrically.

In order to be able to achieve particularly low-emission operation of the motor vehicle, a further embodiment of the invention provides that the internal combustion engine is operated in such a way that a first part of the power provided by the internal combustion engine via the output shaft is used to drive the motor vehicle and a second part of the power provided by the internal combustion engine via the output shaft is used to drive the electrical machine, which is thereby operated as a generator, by means of which the second part is converted into electrical energy, which can be used in a battery, for example trained, electrical energy storage of the motor vehicle is stored. It can be seen that the second part of the power provided by the internal combustion engine via the output shaft is excess power that is not required and is not used to fulfill a current driving function or task, but the excess power is used to to operate the electrical machine as a generator and thus to convert the excess power into electrical energy by means of the generator, which is stored in the energy storage device. The electrical energy store is preferably a high-voltage component whose electrical voltage, in particular electrical operating or nominal voltage, is preferably greater than 50 volts, in particular greater than 60 volts, and is very preferably several hundred volts. For example, the energy store is designed as a high-voltage battery (HV battery). Furthermore, it is preferably provided that the electrical machine is designed as a high-voltage component whose electrical voltage, in particular electrical operating or nominal voltage, is preferably greater than 50 volts, in particular greater than 60 volts, and very preferably amounts to several hundred volts. By using the power provided by the internal combustion engine via the output shaft both to drive the motor vehicle and to drive the electric machine, the catalytic converter can be heated particularly quickly by means of the exhaust gas from the internal combustion engine, since a particularly high temperature, also referred to as the exhaust gas temperature of the exhaust gas can be realized. As a result, particularly low-emission operation of the motor vehicle can be achieved.

A further embodiment is characterized in that the power provided by the internal combustion engine via its output shaft is used to drive the motor vehicle, while the electric machine is in motor mode and is therefore operated as an electric motor, by means of which the motor vehicle is driven . This means that the motor vehicle is driven simultaneously both by means of the internal combustion engine and by means of the electric machine. Thus, both the internal combustion engine and the electric machine are used simultaneously to fulfill a current driving function or driving task. On the one hand, a particularly low-emission operation of the motor vehicle can be realized as a result. On the other hand, advantageous drivability of the motor vehicle can be ensured. This embodiment can ensure that, for example, when the limit value is so low that the power that can be provided or provided by the internal combustion engine via the output shaft is not sufficient to achieve a speed desired by the driver of the motor vehicle, for example, at which the motor vehicle is being driven to be able to realize by means of the internal combustion engine, to nevertheless realize the speed, in that the motor vehicle is driven both by means of the internal combustion engine and by means of the electric machine, in particular at the same time. Thus, for example, by the electric machine by limiting the power lack of power shortage, which means that the motor vehicle solely by driving the Internal combustion engine can not be driven at the speed desired by the driver, is compensated, so that despite the limitation of the power to the limit value, the motor vehicle can be driven at the speed desired by the driver.

The embodiments described above are not mutually exclusive. For example, provision is made for the internal combustion engine to be operated during a first period of time in such a way that the first part of the power is used to drive the motor vehicle and the second part of the power is used to drive the electric machine. During a second period of time, the power is used to operate the motor vehicle while the electric machine is operated in motor mode. In this case, for example, the second time period precedes the first time period, or the second time period follows the first time period.

In order to be able to achieve particularly low-emission operation on the one hand and advantageous drivability of the motor vehicle on the other, a further embodiment of the invention provides that the power is limited to the limit value in such a way that the power limit to the limit value results in such a mass flow of the exhaust gas The result is that the mass flow can just about be after-treated by means of the catalyst and thereby cleaned, in particular in such a way that at least one specifiable criterion is just about met. The criterion includes, for example, that at least one component contained in the exhaust gas, in particular downstream of the catalytic converter, falls below a specifiable or specified limit.

In a further, particularly advantageous embodiment of the invention, the internal combustion engine is operated at least temporarily, for example during a third period of time, at least temporarily in an operating mode in which a throttle valve of the internal combustion engine remains in a particularly fully open position while the power generated by the internal combustion engine is whose output shaft is provided, is varied by varying the ignition angle and/or the speed of the output shaft. The feature that the throttle valve stays in the open position means that the throttle valve does not move out of the open position. A quantity of the air to be supplied to the aforementioned combustion chamber can be adjusted by means of the throttle valve. In other words, it is preferably provided that the internal combustion engine said Has operating mode in which the power output is set with the throttle valve open by varying the ignition angle and/or the speed, which is also referred to as the engine speed, that is to say is controlled or regulated. As a result, the internal combustion engine can be temporarily set to have poor efficiency during fired operation, so that more combustion energy is released into the exhaust gas of the internal combustion engine, as a result of which the at least one catalytic converter for treating the exhaust gas can be heated more quickly.

In a further, particularly advantageous embodiment of the invention, it is provided that by means of a variable valve drive and thus by means of a camshaft adjuster, an opening time at which at least one exhaust valve assigned to the combustion chamber of the internal combustion engine is opened within the respective working cycle of the internal combustion engine therefore begins to open is advanced compared to normal operation of the internal combustion engine. In particular in combination with limiting the power to the limit value, the internal combustion engine can be set to temporarily poor efficiency in fired operation, so that more combustion energy is released into the exhaust gas of the internal combustion engine, which means that the at least one catalyst for treating the exhaust gas is heated more quickly can.

In order to achieve particularly low-emission operation of the motor vehicle, it has also proven particularly advantageous if the temperature of the catalytic converter is calculated using a calculation model, in particular by means of the electronic calculation device.

A second aspect of the invention relates to a motor vehicle, preferably designed as a motor vehicle, in particular as a passenger car, which is designed to carry out a method according to the invention according to the first aspect of the invention. Advantages and advantageous configurations of the first aspect of the invention are to be regarded as advantages and advantageous configurations of the second aspect of the invention and vice versa.

Further advantages, features and details of the invention result from the following description of a preferred exemplary embodiment and from the drawing. The features and feature combinations mentioned above in the description and those mentioned below in the description of the figures and/or features and feature combinations shown alone in the figures can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the invention.

The drawing shows in:

Fig. 1 is a schematic side view of a drive train of a

motor vehicle;

Fig. 2 is a diagram illustrating a method for operating the

motor vehicle;

Fig. 3 is a diagram to further illustrate the method;

Fig. 4 is a diagram to further illustrate the method;

Fig. 5 is a diagram further illustrating the method; and

6 shows a diagram to further illustrate the method.

Elements that are the same or have the same function are provided with the same reference symbols in the figures.

1 shows a drive train 10 of a motor vehicle in a schematic side view. This means that the motor vehicle, which is preferably designed as a motor vehicle, in particular as a passenger car, includes the drive train 10 and can be driven by means of the drive train 10 . The drive train 10 and thus the motor vehicle include an internal combustion engine 12, also referred to as an internal combustion engine, motor or internal combustion engine, which in the exemplary embodiment shown in FIG. 1 is designed as a reciprocating piston engine. The internal combustion engine 12 has a housing element 14 embodied here as a crankcase and an output shaft, which cannot be seen in FIG. 1 , which is embodied as a crankshaft. The output shaft is rotatable about an output shaft axis of rotation 16 relative to the housing element 14 . About the output shaft Internal combustion engine 12 provide torque for driving the motor vehicle, which can thus be driven by the internal combustion engine 12. Internal combustion engine 12 has multiple combustion chambers. During fired operation of the internal combustion engine 12, combustion processes take place in the respective combustion chamber, during which a respective fuel-air mixture is burned. At least one exhaust valve and one intake valve are assigned to the respective combustion chamber. In particular, provision is made for a combustion process to take place within a respective working cycle of internal combustion engine 12 in the respective combustion chamber, while internal combustion engine 12 is being operated in its fired mode, ie fired. In the respective combustion process, the fuel-air mixture, also referred to simply as a mixture, is ignited and burned, resulting in the exhaust gas

Internal combustion engine 12 results. Within the respective work cycle, the respective mixture is ignited, in particular externally ignited, at an ignition time, also known as the ignition angle, and is thereby burned. The exhaust gas can be discharged from the respective combustion chamber via the respective outlet valve assigned to the respective combustion chamber.

In order to actuate and thus open the respective exhaust valve, internal combustion engine 12 has at least one camshaft, also referred to as exhaust camshaft, which can be rotated about a camshaft axis of rotation 18 relative to housing element 14 and in particular relative to a cylinder head 20 of the internal combustion engine. The cylinder head 20 is, for example, formed separately from the housing element 14 and is connected at least indirectly, in particular directly, to the housing element 14 . The camshaft can be driven by the output shaft via a control drive designed as a traction drive, for example, and can therefore be rotated about the camshaft axis of rotation 18 relative to the cylinder head 20 . In particular, the camshaft can be part of a valve train, which is preferably designed as a variable valve train. The variable valve drive includes, for example, a camshaft adjuster 22, also referred to as a phase adjuster, by means of which the camshaft can be rotated relative to the output shaft and its phase can therefore be adjusted, in particular while the camshaft can be driven by the output shaft via the control drive or is coupled to the output shaft. The internal combustion engine 12 has a control housing 24 in which the control drive is arranged. Furthermore, it can be seen that a refrigerant compressor 26 is held at least indirectly, in particular directly, on the internal combustion engine 12, in particular on the housing element 14 can be. The refrigerant compressor 26 can be used to compress a refrigerant of an air conditioning system of the motor vehicle, which is designed as a compression refrigerating machine, for example. The internal combustion engine 12 also has an oil pan 28 in which oil for lubricating the internal combustion engine 12 is received or can be received. The oil pan 28 is, for example, formed separately from the housing element 14 and is connected to the housing element 14 .

1 also shows an oil drain plug 30, via which the oil initially contained in the oil pan 28 can be drained out of the oil pan 28.

The motor vehicle also includes a control unit 32. The control unit 32 is an electronic computing device in the motor vehicle, or the control unit 32 is part of an electronic computing device in the motor vehicle. A method for operating the motor vehicle is carried out by means of the electronic computing device of the motor vehicle and thus by means of the control unit 32, the method being explained below with reference to the figures. The motor vehicle also has an exhaust system 34 through which the exhaust gas from the internal combustion engine 12 or from the combustion chambers can flow. The exhaust system 34 includes an exhaust manifold 36, also referred to simply as a manifold, by means of and in which the exhaust gas from the combustion chambers is combined. In other words, the combustion chambers are brought together through and in the exhaust manifold 36 . The exhaust system 34 comprises at least one catalytic converter 38 which is arranged in particular downstream of the exhaust manifold 36 and through which the exhaust gas from the combustion chambers can flow. In the method, the exhaust gas flowing through the catalytic converter 38 is post-treated and thereby cleaned by means of the catalytic converter 38 . This means in particular that at least one component contained in the exhaust gas is removed by means of the catalytic converter 38 and thus at least partially from the exhaust gas. In FIG. 1 , an arrow 40 illustrates a flow of the exhaust gas and, in particular, arrow 40 illustrates that the exhaust gas flowing through the catalytic converter 38 flows out of the catalytic converter 38 , ie exits.

In the exemplary embodiment shown in the figures, the motor vehicle is designed as a hybrid vehicle. The motor vehicle includes an electric machine 42, which is operated, for example, in generator mode and can therefore be operated as a generator and in motor mode and thus as an electric motor. In the generator mode, the electric machine 42 is driven by the output shaft, that is to say via the output shaft of the internal combustion engine 12, in particular in such a way that the internal combustion engine 12 is fired Operation via the output shaft provides mechanical energy or mechanical power, the mechanical energy or the mechanical power being converted into electrical energy by means of the electrical machine 42 . The electrical energy is provided by the electrical machine 42 and can be stored, for example, in an electrical energy storage device that is not shown in detail. In motor operation, for example, the electric machine 42 drives the motor vehicle electrically. In particular, the electric machine 42 can support the internal combustion engine 12 in motor operation when driving the motor vehicle, so that, for example, the motor vehicle is driven simultaneously by means of the electric machine 42 and by means of the internal combustion engine 12 . In particular, it is conceivable here for a rotor of electric machine 42 to be non-rotatably connectable or connected to the output shaft, so that, for example, in motor operation, electric machine 42 drives the output shaft and, for example, drives the motor vehicle via the output shaft.

In the exemplary embodiment shown in FIG. 1, the internal combustion engine 12 is designed as a four-cylinder reciprocating piston engine. In this case, for example, control unit 32 is held on cylinder head 20 . In addition, for example, the exhaust system 34 is held on the cylinder head 20 . The exhaust system 34, in particular the exhaust manifold 36, can have individual exhaust gas cylinder pipes which are preferably of the same length. In the exemplary embodiment shown in FIG. 1, for example, the exhaust manifold 36 is designed as a quadruple collecting bag, by means of which the combustion chambers and thus individual strands are combined or brought together and routed into an exhaust gas aftertreatment device, which is designed here as the catalytic converter 38. The output shaft of internal combustion engine 12 can be used to drive electric machine 42, which in turn can charge the energy store, embodied, for example, as a hybrid battery, in particular by storing the electric energy provided by electric machine 42 in generator mode in the energy store.

In order to now be able to implement a particularly low-emission operation of the motor vehicle, in the method a temperature of the catalytic converter 38 is determined, in particular by means of the electronic computing device. For example, the temperature of the catalytic converter 38, also referred to as the catalytic converter temperature, is calculated using a calculation model, also referred to as a temperature model, and thereby determined, which is stored, for example, in a memory of the electronic computing device, in particular the control unit 32. Furthermore, the method provides that a mechanical power, in particular, which is provided by the internal combustion engine 12 via its output shaft, is specifically limited by means of the electronic computing device, depending on the determined catalyst temperature, to a limit value which is lower than the value of the of the internal combustion engine via its output shaft is the maximum power that can be provided. The method is preferably carried out while the motor vehicle is being driven by the internal combustion engine 12 and is being driven thereby, in particular at a speed, also referred to as driving speed, which is greater than zero. Provision is preferably made for the power provided by internal combustion engine 12 via its output shaft to be specifically limited by the electronic computing device, depending on the determined catalyst temperature, to the limit value which is lower than the value provided by internal combustion engine 12 via whose output shaft maximum power that can be provided, while the motor vehicle is driven by the internal combustion engine 12 and is therefore driven at a speed greater than 0.

The provision of the power via the output shaft by the internal combustion engine 12 is also referred to as power output. If, for example, the initially deactivated internal combustion engine 12 is started as a cold start, which is started during the start and is thus switched to its fired operation, the method determines the permissible or highest possible power output of the internal combustion engine after the start, in particular a cold start, as a function of the catalytic converter temperature is limited in such a way that the power that can be provided by the internal combustion engine 12 via the output shaft is less than the maximum power that can be provided by the internal combustion engine 12 via the output shaft. In particular, it is provided that the permissible power output after the start, in particular a cold start, of the internal combustion engine 12 is only released with a delay, even for low values, as a function of the catalytic converter temperature. In other words, it is preferably provided that the limiting value, which is lower than the maximum value of the maximum power that can be provided by the internal combustion engine and to which the power of internal combustion engine 12 is limited, is increased as the catalytic converter temperature increases. If, for example, it is determined that by limiting the power to the limit value, the power that internal combustion engine 12 provides via its output shaft is not sufficient to perform a driving task or driving function desired by the driver of the motor vehicle, such as a speed desired by the driver which the motor vehicle is to be driven, can be implemented, for example electric machine 42, which is an electric component of drive train 10, also referred to as a hybrid drive train or hybrid drive, is operated in motor mode and thus as an electric motor, so that the motor vehicle can be driven simultaneously both by means of the Internal combustion engine 12 and by means of the electric machine 42 is driven. The electric machine 42 thereby compensates for a lack of power or faulty power resulting from the limitation of the power to the limitation value, so that the motor vehicle can be driven or driven at the speed desired by the driver despite the limitation of the power to the limitation value. In particular, it is conceivable that the power required to fulfill the driving function is primarily provided by electrical components of the hybrid drive. In other words, it is conceivable that a power provided by the electric machine 42 in motor operation, in particular mechanical power, which is used to drive the motor vehicle, is greater than the power provided by the internal combustion engine 12 via the output shaft and the has limit value. It can be seen that the limitation of the power provided by the internal combustion engine 12 via its output shaft to the limiting value means that the power having the limiting value, which is provided by the internal combustion engine 12 via the output shaft, is less than the value, also referred to as the maximum value, of the maximum power that can be provided by the internal combustion engine 12 via its output shaft.

It is also possible, particularly in the case of an independent, separate, further aspect, for internal combustion engine 12, in particular during its warm-up, to at least temporarily deliver greater mechanical power, i.e. make it available via the output shaft, than is required to fulfill the direct driving function, also referred to as the driving task is, so that the internal combustion engine 12 provides excess power, which is not used to drive the motor vehicle but to drive the electrical machine 42 and thus to operate the electrical machine 42 in the generator mode, so that the excess power can be stored as chemical energy in the energy store. With others In other words, it is preferably provided that the internal combustion engine 12 is operated in such a way that a first part of the power provided by the internal combustion engine 12 via the output shaft is used to drive the motor vehicle and a second part of the power provided by the internal combustion engine 12 via the Output shaft is provided, is used to drive the electric machine 42, which is thereby operated as the generator described above, by means of which the second part is converted into electrical energy, which is stored in the electrical energy storage device. The second part is the aforementioned excess power.

In order to realize a particularly efficient, effective and low-emission operation of the motor vehicle, it is also preferably provided that the internal combustion engine 12, in particular after its cold start, delivers exactly the power that leads to such a mass flow of the exhaust gas, also referred to as the exhaust gas mass flow, that the exhaust gas mass flow can just about be cleaned in the particularly partially heated catalytic converter 38 . As part of the method, it is provided in particular that the power provided by the internal combustion engine 12 via its drive shaft increases at least essentially continuously, in that the catalyst temperature rises at least essentially continuously, in particular with increasing temperature following the start Operating time of the internal combustion engine 12, which is operated fired during the operating period. If the previously mentioned power, which leads to the mentioned exhaust gas mass flow, is too great to fulfill the current driving task, excess energy generated, ie the excess power, is stored in the energy store. In other words, the excess power of the internal combustion engine 12 is used, for example, to drive the electric machine 42 and thus to operate it as a generator, by means of which the excess power is converted into electrical energy. If the power leading to the exhaust gas mass flow is too small to fulfill the current driving task, the electric machine 42 is operated in the motor mode, so that the motor vehicle can be driven or is driven simultaneously by means of the internal combustion engine 12 and by means of the electric machine 42. In order to operate the electrical machine 42 in the motor mode, the electrical machine 42 is supplied with electrical energy stored in the energy store.

The feature that the excess power of the internal combustion engine 12 is converted into electrical energy by means of the generator is Of course, it should be understood that the excess power is or is formed by mechanical energy, which is supplied to the electrical machine 42 in particular via the output shaft. As a result, the electrical machine 42 is driven and thus operated as a generator, by means of which the mechanical energy supplied to the electrical machine 42, and consequently the excess power, is converted into electrical energy.

Furthermore, it has proven to be advantageous if the internal combustion engine 12 has a combustion chamber in which the power output when the throttle valve is open is controlled or regulated by varying the ignition angle and the speed of the internal combustion engine 12 . The speed of the internal combustion engine 12 is to be understood as meaning a speed at which the output shaft rotates about the output shaft axis of rotation 16 relative to the housing element 14 , in particular during the fired operation of the internal combustion engine 12 .

Furthermore, it is conceivable that camshaft adjuster 22 can be used to set an early exhaust opening timing, thus an opening time at which the respective exhaust valve is opened within the respective working cycle is advanced compared to normal operation. The point in time mentioned, at which the respective exhaust valve is opened within the respective working cycle, is also referred to as exhaust open and coincides with a rotational position of the output shaft. As a result of the early exhaust opening, the efficiency of the internal combustion engine 12 can be reduced in comparison to normal operation, as a result of which the catalytic converter 38 can be heated particularly quickly.

The exhaust gas of the internal combustion engine 12 flowing through the exhaust system 34, also referred to as the exhaust tract, contains energy, in particular thermal energy, which is introduced into the exhaust tract or to the exhaust tract by the exhaust gas flowing out of the combustion chambers and subsequently flowing into the exhaust tract and flowing through the exhaust tract is delivered. As a result, the exhaust tract and thus the catalytic converter 38 are heated. Two forms of energy in particular are at work here: a first of the forms of energy is thermal energy, which is contained in particular in the exhaust gas mass flow or in its temperature or absolute temperature. The second form of energy is chemical energy, which consists in particular or is formed in that exothermic chemical reactions of exhaust gas components are implemented in the operating temperature range of the catalyst, such as For example, one based on the oxidation of carbon monoxide with the residual oxygen contained in the exhaust gas (2CO+O2 -> 2CO2).

The respective mixture includes air and, in particular, liquid fuel, which is introduced, for example, into the respective combustion chamber, in particular injected directly. In particular, the fuel is introduced into the respective combustion chamber within the respective working cycle, in particular injected directly, so that a predefinable or predetermined quantity of the fuel is introduced into the respective combustion chamber within the respective working cycle. The exhaust gas mass flow depends on the quantity of fuel injected into the respective combustion chamber per working cycle, also referred to as fuel quantity, in particular multiplied by the number of working cycles, the number of working cycles in turn depending on the speed of the output shaft, also referred to as engine speed. A temperature of the exhaust gas, also referred to as the exhaust gas temperature, depends on a thermal energy released during the respective combustion of the respective mixture and on a mechanically delivered work. The temperature of the exhaust gas is increased compared to conventional solutions by operating the internal combustion engine 12 with retarded ignition angles which are poor for efficiency, with a wide open throttle valve and increased speed. To compensate for the reduced efficiency, more fuel is burned, which leads to an increase in temperature. The output, also referred to as engine output, and thus the efficiency of the conversion are adjusted by varying the ignition angle.

FIG. 2 shows a diagram with the time plotted on the abscissa 44 . The power P, the speed n and the load T of the internal combustion engine 12 are plotted on the ordinate 46 of the diagram. The load T, which is provided by the internal combustion engine 12 via its output shaft, is the respective, aforementioned torque for driving the motor vehicle and/or the electric machine 42.

If, for example, a conventional internal combustion engine is started at a point in time to, and the internal combustion engine basically does not deliver any mechanical power or is idling, the temperature of the catalytic converter 38 only reaches its steady-state temperature or light-off temperature and thus its full effectiveness in the point in time U with regard to the after-treatment of the exhaust gas. A time course shown in FIG 48 illustrates the temperature of the catalytic converter 38, and a curve 50 illustrates the speed of the internal combustion engine 12, the speed of which is the idle speed in the present case. A curve 52 illustrates the power, also referred to as engine power, which the internal combustion engine 12 provides via the output shaft.

If, for example--as is shown in FIG. 3--the conventional internal combustion engine delivers power from the moment the engine is started, the exhaust system heats up more quickly because, in comparison to FIG. 2, the thermal power additionally heats the catalytic converter due to the increased exhaust gas mass flow or exhaust gas volume flow. It reaches its full effectiveness somewhat earlier, in this case at a point in time t2. If the maximum engine power is delivered before time t2, for example from a time ti, exhaust gas that is not optimally cleaned may be emitted between times ti and t2. If the engine power is increased too quickly from 0 to the maximum value, exhaust gas that is not optimally cleaned is also emitted between times to and ti if no appropriate countermeasures have been taken. The problems mentioned above can now be avoided by the method which can be seen in particular from FIG. 4 . In the method, the internal combustion engine 12 is limited by the electronic computing device, in particular by means of the control unit 32, for example at least essentially continuously as a function of the catalyst temperature from the start of the engine to a maximum power output that is lower than the maximum power that can be provided by the internal combustion engine 12. As a result, the catalytic converter 38 only achieves its full effectiveness, compared to FIG is expelled. The engine power that can be released is released at least essentially continuously as a function of the catalytic converter 38, which, for example, heats up at least essentially continuously. Thus, for example, as the temperature of the catalyst 38 increases, the limit value is progressively increased.

In particular, it is provided that the internal combustion engine 12 emits an increased mechanical power, for example with a given time profile of the power required to fulfill the driving task, which can be seen in particular from FIG. 5 . A curve 54 in FIG. 5 illustrates the power required to fulfill the current driving task. From the curves 52 and 54 it can be seen that the power illustrated by curve 52, which is actually made available by internal combustion engine 12 via the output shaft, is greater than the power actually required to fulfill the driving task (curve 54). In comparison to curve 54 and thus in the curve to the power required to fulfill the current driving task, internal combustion engine 12 thus provides excess power 56 via its output shaft. The excess power is stored in the energy store. In other words, the excess power is used to operate the electrical machine 42 in generator mode and thus as a generator, which uses the excess power to generate or provide electrical energy that is stored in the energy store. As a result, the catalytic converter 38 is quickly heated. If exactly the power is delivered that leads to an exhaust gas mass flow that can just about be cleaned in the partially effective catalytic converter 38, then the internal combustion engine 12 or the motor vehicle reaches its or its full capacity at a particularly early point in time ti, without an excessively large amount to emit unwanted pollutants.

Finally, a further possibility of the method is described with reference to FIG. With the same power output curve over time (curve 52) as shown in FIG. 3, the internal combustion engine 12 outputs the power at higher speeds than in the operationally warm state or than in conventional solutions. As a result, there are more work cycles per unit of time and therefore more combustion than when the engine is at operating temperature or in conventional solutions. Therefore, the maximum amount of fuel can be injected and burned more frequently in a unit time. Despite the same mechanical output power, more thermal power is converted. Internal combustion engine 12 is operated with reduced efficiency so that internal combustion engine 12 does not emit more mechanical power despite greater thermal output. This happens due to an unfavorably retarded ignition point. The excess thermal power is essentially released into the exhaust gas and heats up the catalytic converter 38 very quickly, so that it already reaches its steady-state temperature at time ti. The exhaust gas is optimally cleaned. To reduce the efficiency, the internal combustion engine 12 can be operated with unfavorably late ignition angles and/or unfavorably early exhaust control times, ie times at which the respective exhaust valve opens. Reference List

10 power train

12 internal combustion engine

14 housing element

16 output shaft axis of rotation

18 camshaft axis of rotation

20 cylinder head

22 camshaft adjusters

24 control housing

26 refrigerant compressor

28 oil pan

30 oil drain plug

32 control unit

34 exhaust system

36 exhaust manifold

38 catalyst

40 arrow

42 electric machine

44 abscissa

46 ordinates

48 History, Catalyst temperature

50 course, engine speed

52 history, engine performance

54 history, required engine power

56 excess power n speed

P performance

T last t time to, 1 ,2,3,4 points in time

Claims

patent claims

1. A method for operating a motor vehicle, in which the motor vehicle has an internal combustion engine (12) having an output shaft, by means of which the motor vehicle can be driven via the output shaft, and at least one catalytic converter (38) through which exhaust gas from the internal combustion engine (12) can flow, by means of which the Exhaust gas is after-treated, characterized in that:

- A temperature of the catalyst (38) is determined;

- A power provided by the internal combustion engine (12) via its output shaft, depending on the determined temperature of the catalytic converter (38) is limited to a limiting value which is lower than the value of the internal combustion engine (12) via its output shaft maximum deliverable power;

- the limiting value, which is lower than the value of the maximum power that can be provided by the internal combustion engine (12), and to which the power of the internal combustion engine (12) is limited, is increased as the temperature of the catalytic converter (38) increases; and

- the power is limited to the limit value in such a way that limiting the power to the limit value results in such a mass flow of the exhaust gas that the mass flow can just about be after-treated by the catalytic converter (38) and thereby cleaned.

2. The method according to claim 1, characterized in that the motor vehicle has an electric machine (42) by means of which the motor vehicle can be driven.

3. The method according to claim 1 or 2, characterized in that the internal combustion engine (12) is operated in such a way that a first part of the power provided by the internal combustion engine (12) via the output shaft is used to drive the motor vehicle and a second part the power provided by the internal combustion engine (12) via the output shaft is used to drive the electric machine (42), which is thereby operated as a generator, by means of which the second part is converted into electric energy, which is used in an electric Energy storage of the motor vehicle is stored.

4. The method according to any one of the preceding claims, characterized in that the power provided by the internal combustion engine (12) via its output shaft is used to drive the motor vehicle while the electric machine (42) in a motor mode and thereby as a Electric motor is operated, by means of which the motor vehicle is driven.

5. The method according to any one of the preceding claims, characterized in that the internal combustion engine (12) is operated at least temporarily in an operating mode in which a throttle valve of the internal combustion engine (12) remains in an open position while the power generated by the internal combustion engine ( 12) is provided via its output shaft by varying the firing angle and/or a speed of the output shaft.

6. The method according to any one of the preceding claims, characterized in that by means of a variable valve train of the internal combustion engine (12), an opening time at which at least one exhaust valve assigned to a combustion chamber of the internal combustion engine (12) is opened within a respective working cycle of the internal combustion engine (12), in the Compared to normal operation of the internal combustion engine (12) is advanced.

7. The method according to any one of the preceding claims, characterized in that the temperature of the catalyst (38) is calculated using a calculation model.

8. Motor vehicle which is designed to carry out a method according to any one of the preceding claims.