METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE OF A MOTOR VEHICLE AND MOTOR VEHICLE

Description

[0001] The invention relates to a method for operating an internal combustion engine of a motor vehicle, in which exhaust gas from the internal combustion engine is fed to at least one catalyst arranged in an exhaust system of the motor vehicle. Depending on the emission of at least one pollutant contained in the exhaust gas into the environment of the motor vehicle, the power available from the internal combustion engine is adjusted by means of a control device of the motor vehicle. Furthermore, the invention relates to a motor vehicle with an internal combustion engine.

[0002] DE 10 2019 203 798 A1 describes an emissions-based control system for an internal combustion engine. This system reduces the engine's power output to keep nitrogen oxide emissions below a threshold. The engine's power output is also reduced if the temperature of a catalyst located in the engine's exhaust system is outside a specific temperature range.

[0003] The disadvantage here is the fact that, due to the reduction in the power of the internal combustion engine, the full power of the internal combustion engine is not available to drive the motor vehicle in which the internal combustion engine is installed.

[0004] Furthermore, due to emissions legislation currently in force in Europe and under conditions that take into account the emissions occurring during actual driving (RDE, Real Driving Emissions) of a motor vehicle, the performance of a motor vehicle's internal combustion engine can be limited or reduced. This applies in particular if, after a cold start of the internal combustion engine or the vehicle's internal combustion engine, the internal combustion engine is operated at full load without a catalyst located in the motor vehicle's exhaust system being sufficiently heated during idle operation of the internal combustion engine.If, on the other hand, the internal combustion engine is operated at idle to a sufficient extent during the cold start, then the exhaust system and in particular the at least one catalyst arranged in the exhaust system of the motor vehicle can be heated up during this idle phase, in particular by increasing a torque reserve when the internal combustion engine is idling.

[0005] If, after the at least one catalytic converter has heated up, the driver subsequently requests load from the internal combustion engine, the emissions of the internal combustion engine can be converted relatively reliably by means of the at least one catalytic converter at high exhaust gas mass flows. However, if there is insufficient idling time, there is also insufficient time to heat up the at least one catalytic converter. If the catalytic converter has not yet reached its full conversion capacity, then the catalytic converter cannot fully convert the emissions of the internal combustion engine at full load and thus maximum exhaust gas mass flow. This can then lead to what is known as overrunning of the catalytic converter, i.e. a breakthrough of emissions, so that these emissions enter the environment of the vehicle in the form of unconverted pollutants.

[0006] In particular, in order to comply with emission limits during an extreme driving maneuver, such as starting the internal combustion engine and subsequently operating it at full load, it may be provided to limit the power of the internal combustion engine during full-load acceleration of the vehicle after a cold start of the internal combustion engine without sufficient idling time to heat the catalytic converter. This can be achieved by capping the torque of the internal combustion engine and the speed of the internal combustion engine. Such a strategy of limiting the power available from the internal combustion engine is based on the recognition that such extreme driving maneuvers are entirely possible within the framework of the legislation governing emissions during actual driving of the vehicle, i.e., the RDE legislation, and must therefore be taken into account.

[0007] However, such a limitation of the power of the internal combustion engine, taking into account the emission of pollutants into the environment of the motor vehicle, leads to a loss of driving comfort for a driver of the motor vehicle.

[0008] It is an object of the invention to provide an improved method of the type mentioned at the outset and to specify a motor vehicle designed to carry out such a method.

[0009] This object is achieved according to the invention by a method having the features of patent claim 1 and by a motor vehicle having the features of patent claim 10. Advantageous embodiments of the invention are the subject of the dependent patent claims and the description.

[0010] In a method according to the invention for operating an internal combustion engine of a motor vehicle, exhaust gas from the internal combustion engine is fed to at least one catalytic converter arranged in an exhaust system of the motor vehicle. Depending on the emission of at least one pollutant contained in the exhaust gas into an environment of the motor vehicle, a power that can be provided by the internal combustion engine is set by means of a control device of the motor vehicle. In the method, a size of a volume fraction of the at least one catalytic converter that causes the conversion of the at least one pollutant is determined. The power that can be provided by the internal combustion engine, i.e. the approved internal combustion engine power or the maximum permitted power of the internal combustion engine (2), is set depending on the respective size of the volume fraction.Accordingly, when adjusting the power that can be provided or delivered by the internal combustion engine, the volume fraction of the catalyst that has already started is taken into account, so that this volume fraction causes the conversion of at least one pollutant.

[0011] This is based on the realization that even if a small volume fraction is capable of converting at least one pollutant, the emissions released into the vehicle's environment are reduced by the exhaust gas flowing through at least one catalyst and thus also through the volume fraction that has already been activated. Because the size of this volume fraction is taken into account when adjusting the power available from the internal combustion engine, a comparatively high power output can be released from the internal combustion engine very early on.

[0012] In particular, more power can be provided early than is the case with a method in which, for example, a power limitation of the internal combustion engine is lifted after a predetermined period of time or only when a predetermined temperature of the catalyst is reached. Consequently, the method is particularly advantageous with regard to the very early release of an unrestricted or at least less severely restricted power of the internal combustion engine.

[0013] The volume fraction of the at least one catalyst that effects the conversion of the at least one pollutant can also be referred to as the active or activated volume fraction of the at least one catalyst. This is because, particularly when this volume fraction or a corresponding partial volume of a total volume of the at least one catalyst has reached a light-off temperature, a significant conversion of the at least one pollutant is achieved by means of the at least one catalyst. In other words, the activated volume fraction is sufficiently heated to achieve a specific minimum conversion rate for the at least one pollutant.

[0014] The corresponding, activated volume fraction of the at least one catalyst can be regarded or described as causing the conversion of the at least one pollutant, in particular if the conversion rate of the volume fraction is, for example, approximately 50 percent, so that at least approximately 50 percent of the at least one pollutant contained in the exhaust gas is converted by means of the catalyst.

[0015] The method is also based on the realization that a degradation or limitation of the internal combustion engine's power, which predetermines a maximum speed and maximum torque, for example, after a cold start of the internal combustion engine, is hard-coded and thus inflexible. Such a limitation therefore does not take into account the current conversion capability of the at least one catalytic converter or a corresponding exhaust gas aftertreatment device of the motor vehicle. Consequently, with such an inflexible method, the internal combustion engine's power is fixedly capped throughout the entire acceleration of the motor vehicle with the internal combustion engine operating at full load after a cold start.

[0016] With such a method, the user, especially the driver of the motor vehicle, cannot therefore access the power of the internal combustion engine in operating ranges where the conversion capability of the catalyst would actually allow the provision of higher power. These disadvantages can be eliminated by the method, which takes into account the size of the volume fraction of the catalyst that has already been activated when adjusting the power available from the internal combustion engine.

[0017] Furthermore, a fixed, inflexible specification of the power limitation of the internal combustion engine for a predetermined period of time or until a predetermined temperature of at least one catalyst is reached carries the risk that the power limitation will be too low to comply with the emission limits under all boundary conditions, which are particularly possible taking into account the emissions occurring during actual driving (RDE). This is particularly problematic in view of increasingly strict limits and higher emission requirements for internal combustion engines in motor vehicles and in view of the boundary conditions relevant to emissions-related regulations currently being discussed and potentially applicable in the future in the European Union.

[0018] The method, in which the power available from the internal combustion engine is adjusted depending on the respective size of the volume fraction, is advantageous both when the motor vehicle is designed as a motor vehicle powered exclusively by an internal combustion engine and when the motor vehicle is designed as a hybrid vehicle, in particular as a plug-in hybrid vehicle (socket hybrid vehicle). In the motor vehicle designed as a hybrid vehicle, the internal combustion engine is used to support an electric drive of the motor vehicle and / or to charge an electrical energy storage device of the motor vehicle.

[0019] A degradation or limitation of the power that can be provided or delivered by the internal combustion engine for a fixed period of time is also disadvantageous in cases where the internal combustion engine is temporarily started in a motor vehicle designed as a hybrid vehicle. Such a start-up can occur, for example, when the electric drive of the hybrid vehicle requires assistance from the internal combustion engine. During such a start-up, it can be provided that the internal combustion engine is operated with the requested load immediately after starting in order to provide the supporting drive power. Furthermore, an increase in the load point of the internal combustion engine can be requested in the hybrid vehicle in order to charge the electrical energy storage device of the hybrid vehicle.Such operating modes of the hybrid vehicle's internal combustion engine therefore lead to a comparatively high power demand immediately after the internal combustion engine is started.

[0020] Even in such cases, it is disadvantageous if the power to be provided by the internal combustion engine is limited for a certain, fixed period of time after the internal combustion engine has been started in order to comply with emission limits. Even with such uses of the internal combustion engine, it is therefore advantageous if the power limitation is not fixed or hard-coded, but rather if the power release of the internal combustion engine is based on the actual state of the catalytic converter. This is the case with the method described here because the power that can be provided by the internal combustion engine is adjusted depending on the respective size of the volume fraction that causes the conversion of the at least one pollutant.

[0021] The method thus enables reliable control of the emissions of at least one pollutant contained in the exhaust gas, specifically for all possible combinations of a cold start of the internal combustion engine or a starting of the internal combustion engine when the motor vehicle is configured as a hybrid vehicle. This also applies to varying lengths of idle time after starting the internal combustion engine and with regard to the respective load requirements placed on the internal combustion engine by a user or driver of the motor vehicle.

[0022] This means that the internal combustion engine can provide comparatively high levels of performance at a relatively early stage and also that emission limits can be met well and reliably.

[0023] To determine the respective size of the volume fraction that causes the conversion of the at least one pollutant, a temperature of the exhaust gas flowing through the at least one catalyst is taken into account. Based on the temperature of the exhaust gas flowing through the at least one catalyst, a temperature of the catalyst and, in particular, the volume fraction of the catalyst that has already been activated can be easily deduced. Consequently, the respective size of the volume fraction of the at least one catalyst that has already been activated can be determined particularly easily.

[0024] The temperature of the at least one catalyst or of the exhaust gas flowing through the at least one catalyst can be detected by at least one temperature sensor. Additionally or alternatively, the temperature of the exhaust gas flowing through the at least one catalyst or of the catalyst can be determined based on a model of the exhaust gas temperature as a function of the respective operation of the internal combustion engine, in order to use this temperature to determine the respective size of the volume fraction.

[0025] Based on a space velocity of the exhaust gas flowing through the at least one catalyst, which is related to the respective size of the volume fraction, a current conversion capacity of the at least one catalyst for the at least one pollutant is determined. This is based on the finding that the space velocity related to the already active or activated volume fraction of the catalyst plays a role in the extent to which the at least one pollutant can be converted by the catalyst. For a specific exhaust gas throughput through the at least one catalyst, the space velocity related to the size of the already activated volume fraction of the catalyst is lower the larger the volume fraction.Therefore, the space velocity relative to the already activated or active volume of the catalyst is particularly suitable for determining the catalyst's conversion capacity for at least one pollutant. Furthermore, this space velocity is easily obtainable in the vehicle, for example, using a space velocity model.

[0026] The current conversion capability of the at least one catalyst is compared with a target conversion capability for the at least one pollutant. This makes it possible to very easily and reliably determine which power level to be provided by the internal combustion engine should be set to achieve the desired conversion of the at least one pollutant.

[0027] If the current conversion capability is lower than the target conversion capability, the power available from the internal combustion engine is set to a lower power than the maximum power of the internal combustion engine. This reliably prevents the at least one catalyst from being overrun, so that a desired minimum conversion for the at least one pollutant is achieved during operation of the internal combustion engine. In particular, this ensures that the respective limit values for emissions of the at least one pollutant into the environment of the motor vehicle are reliably adhered to.

[0028] Preferably, when adjusting the power available from the internal combustion engine, a total quantity of the at least one pollutant emitted into the environment of the motor vehicle during a journey is taken into account. This ensures that not only a limit value for the at least one pollutant, based approximately on one kilometer of travel by the motor vehicle, is adhered to, but also that a total budget of pollutants emitted during the journey is not exceeded. Consequently, requirements for compliance with emission limits can be met to a particularly high degree.

[0029] Preferably, the maximum power of the internal combustion engine is set as the power that can be provided by the internal combustion engine, even though the current conversion capacity of the at least one catalyst is lower than the target conversion capacity. This preferably occurs when the total amount of the at least one pollutant emitted into the environment while the motor vehicle is traveling is lower than a limit value of the total amount.

[0030] In this way, it is possible, in particular, to release a particularly high level of power from the internal combustion engine for a short time while observing the limit value for the total quantity. Taking into account the total quantity of at least one pollutant emitted while the motor vehicle is in motion makes it possible to permit a short-term exceedance of an emission limit value for at least one pollutant. This makes it possible to advantageously meet existing load requirements on the internal combustion engine in certain, particularly critical, situations.

[0031] To determine a target conversion capability of the at least one catalytic converter, raw emissions of the at least one pollutant caused by the internal combustion engine are preferably taken into account. These emissions occur during at least one predetermined driving maneuver of the motor vehicle while the motor vehicle is traveling. By considering the at least one driving maneuver to determine the target conversion capability, worst-case scenarios, in particular, can be used when specifying the target conversion capability or desirable minimum conversion. This advantageously makes the method highly robust and reliable.

[0032] For example, the at least one predetermined driving maneuver can be a full-throttle acceleration of the motor vehicle to a maximum permissible speed while the motor vehicle is in motion. This makes it possible to ensure compliance with emission limits for the at least one pollutant, even taking such a worst-case scenario into account.

[0033] Finally, it has been shown to be advantageous if, as the volume fraction that causes the conversion of at least one pollutant increases, an increasingly greater power output of the internal combustion engine is released than the available power. Thus, with a higher activated catalytic volume of the at least one catalyst, the released power of the internal combustion engine can be successively increased. This is particularly advantageous with regard to an appealing driving experience while driving the motor vehicle.

[0034] The motor vehicle according to the invention has an internal combustion engine and at least one catalytic converter arranged in an exhaust system of the motor vehicle, to which exhaust gas from the internal combustion engine can be fed. A control device of the motor vehicle is designed to adjust a power that can be provided by the internal combustion engine as a function of an emission of at least one pollutant contained in the exhaust gas into an environment of the motor vehicle. The control device is further designed to determine a size of a volume fraction of the at least one catalytic converter that causes the conversion of the at least one pollutant and to adjust the power that can be provided by the internal combustion engine as a function of the respective size of the volume fraction.

[0035] Consequently, the motor vehicle is designed to implement the method according to the invention. Accordingly, the motor vehicle makes it possible to release a certain power output from the internal combustion engine relatively early while still reliably complying with emission limits.

[0036] The advantages and preferred embodiments described for the method according to the invention also apply to the motor vehicle according to the invention and vice versa.

[0037] Further features of the invention emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective specified combination, but also in other combinations or on their own.

[0038] The invention will now be explained in more detail using preferred embodiments and with reference to the drawings. They show: Fig. 1 shows a schematic representation of a motor vehicle in which a control device makes the power release of an internal combustion engine of the motor vehicle dependent on an activated catalytic volume of a catalytic converter of the motor vehicle; Fig. 2 shows a curve indicating the dependence of a conversion rate for a pollutant contained in the exhaust gas of the internal combustion engine of the motor vehicle on the space velocity related to the active catalytic volume of the catalytic converter; and Fig. 3 schematically shows functional blocks in a method for emissions-based power release of the internal combustion engine of the motor vehicle.

[0039] In Fig. 1 A motor vehicle 1 is shown in a highly schematic manner, which has an internal combustion engine 2. Exhaust gas from the internal combustion engine 2 is introduced into an exhaust system 3 of the motor vehicle 1, which in Fig. 1 is shown only in a highly schematic and fragmentary manner. At least one catalytic converter 4 is arranged in the exhaust system 3.

[0040] After a cold start of the internal combustion engine 2, high raw emissions are present, and the catalytic converter 4 simultaneously has very low or no conversion capability. To prevent the emission of unconverted pollutants into an environment 5 of the motor vehicle 1 in such a case, provision can be made to limit the power of the internal combustion engine 2. This can be achieved by capping or limiting the torque delivered or provided by the internal combustion engine 2 and the speed of the internal combustion engine 2 for a predetermined period of time. However, such a method is rigid and not flexible.

[0041] In this case, the conversion capability of the catalyst 4 is therefore taken into account for the power release of the internal combustion engine 2. An exhaust gas temperature model and a space velocity model can be used for this purpose. For example, the exhaust gas temperature model can be used to determine how much of the catalytic volume of the catalyst 4 has already been activated at a specific time t. The already activated volume of the catalyst 4 causes the conversion of at least one pollutant contained in the exhaust gas of the internal combustion engine 2.

[0042] For example, in Fig. 1 illustrates a situation in which at least a small volume portion 6 of the catalytic converter 4 has already been activated. This activated or active volume portion 6 of the catalytic converter 4 thus causes the conversion of at least one pollutant. For example, the catalytic converter 4 can have a total volume of three liters, and the volume portion 6 that has already been activated or causes the conversion of the at least one pollutant can be one liter. Consequently, this volume portion 6 of the catalytic converter 4 leads to pollutants being converted to a significant extent. In contrast, the remaining volume of the catalytic converter 4, in the selected example the volume of two liters, does not yet contribute, or at least not to a significant extent, to the conversion of the at least one pollutant.

[0043] Taking the space velocity model into account, a maximum permissible or maximum allowable power of the internal combustion engine 2 can be determined for the respective activated catalytic volume or volume fraction 6. This maximum allowable power of the internal combustion engine 2 may be delivered by the internal combustion engine 2 in order to convert at least one pollutant released by the internal combustion engine 2 to a desired extent by means of the activated catalytic volume, i.e., by means of the volume fraction 6. In this way, it can be achieved, in particular, that a limitation of the torque of the internal combustion engine 2 and the speed of the internal combustion engine 2 is successively reduced, depending on the catalytic volume already activated at the respective time t, i.e., depending on the respective size of the volume fraction 6.

[0044] In particular, by taking into account the exhaust gas temperature model and the space velocity model, emissions of the internal combustion engine 2 can be reliably converted, specifically for different combinations of cold starts of the internal combustion engine 2 and / or initial starts of the internal combustion engine 2. Such initial starts of the internal combustion engine 2 can be provided if the motor vehicle 1 is designed as a hybrid vehicle in a manner not shown in detail here, which, in addition to the internal combustion engine 2, has at least one electric drive motor for moving the motor vehicle 1.

[0045] Based on Fig. 2 This is intended to illustrate an example of a space velocity model that can be used in the operation of motor vehicle 1. Fig. 2 In a coordinate system, the conversion of a pollutant is plotted in percent on an ordinate 7, and the space velocity of the exhaust gas flowing through the activated volume portion 6 of the catalyst 4 is plotted on an abscissa 8. If a corresponding exhaust gas flow is given in cubic meters per hour [m 3 < / h], and the active volume of the catalyst 4 at a particular time t and, accordingly, the volume portion 6 are also given in cubic meters [m 3 < ], the unit of space velocity is h -1 < .

[0046] In Fig. 2 A curve 9 illustrates the conversion of at least one pollutant by means of the activated volume fraction 6 of the catalyst 4. Accordingly, the space velocity related to the active volume or the activated volume fraction 6 decreases, the larger the volume fraction 6 is. For example, in Fig. 2 A first marking 10 along curve 9 illustrates a situation in which the size of the activated volume fraction 6 is one liter. Accordingly, with a size of volume fraction 6 of one liter, a comparatively high space velocity exists relative to this active volume of the catalyst 4.

[0047] Furthermore, in Fig. 2 along curve 9, a further marking 11, which, like marking 10, is arranged on curve 9, exemplifies a situation in which the total volume of catalyst 4, for example, the entire three liters of catalyst 4, has been activated. Accordingly, the activated volume fraction 6 of catalyst 4 is equal to the total volume of catalyst 4. If the total volume of catalyst 4 is active, a correspondingly lower space velocity related to the activated or active volume results according to curve 9.

[0048] Out of Fig. 2 It is further evident that a high space velocity relative to the active volume or the size of the targeted volume fraction 6 is associated with a lower conversion rate than is the case with a larger targeted volume fraction 6. Thus, the situation indicated by the second marking 11 corresponds to a significantly higher conversion of at least one pollutant.

[0049] The corresponding relationships are here controlled by a control device 12 (see Fig. 1 ) of the motor vehicle 1, which causes a respective power release of the internal combustion engine 2. In this case, the control device 12 adjusts the power that can be provided or delivered by the internal combustion engine 2 based on emissions.

[0050] Based on Fig. 3 An exemplary implementation of a method for operating the internal combustion engine 2 of the motor vehicle 1 will be explained. Accordingly, a conversion model 13 can be stored in the control device 12, which converts the Fig. 2 explained space velocity model with the catalytic volume of the catalyst 4 activated in each case. In addition, the control device 12 takes into account a requirement for the conversion of the at least one pollutant to be performed by the catalyst 4.

[0051] For example, in Fig. 2 A horizontal line indicates a minimum conversion to be achieved by the catalyst 4. Accordingly, the Fig. 2 The horizontal line shown as an example indicates a target conversion capability 14 of the catalyst 4 for at least one pollutant under consideration. To determine the minimum conversion 15 corresponding to this target conversion capability 14 (cf. Fig. 3 ), for example, characteristic maps 16 can be used which indicate the raw emissions of the internal combustion engine 2 at a certain power output of the internal combustion engine 2.

[0052] Furthermore, taking into account the exhaust gas mass flow and the exhaust gas temperature model, a proportion of unconverted cumulative emissions can be determined. From these parameters, a requirement for the minimum conversion 15 can be derived. Fig. 3 The exhaust gas temperature model, which provides the size of the already activated volume of the catalyst 4, i.e., the size of the volume fraction 6, is illustrated by a function block 17. As a further input variable 18, the load requirement placed on the internal combustion engine 2 is preferably taken into account in this case.

[0053] If the internal combustion engine 2 is intended exclusively to drive the motor vehicle 1, this load requirement can be determined, for example, from a position of an accelerator pedal of the motor vehicle 1, which is actuated by the driver of the motor vehicle 1. If the motor vehicle 1 is designed as a hybrid vehicle, the input variable 18 can result from a load requirement for supporting the electric drive motor and / or from a load requirement for charging an electrical energy storage device (not shown) of the motor vehicle 1.

[0054] Based on the volume flow of the exhaust gas or on the mass flow of the exhaust gas depending on the input variable 18, according to Fig. 3 In a next step, the space velocity 19 related to the size of the jumped volume fraction 6 is determined. This space velocity 19 related to the size of the volume fraction 6 is in turn entered into the conversion model 13.

[0055] Taking into account the minimum conversion 15, in a further step 20 of the Fig. 3 A schematically illustrated method is used to check whether a current conversion capability of the catalyst 4, i.e. an actual conversion achievable by means of the activated volume fraction 6 of the catalyst 4, is greater than or equal to the minimum conversion 15. If this is the case, an unrestricted power release 21 of the internal combustion engine 2 can be effected by the control device 12.

[0056] However, it may happen that the current conversion capability of the catalyst 4, i.e. the actual conversion achievable by means of the increased volume fraction 6, is less than the minimum conversion 15 and thus the actual conversion is less than the target conversion capability 14 (compare Fig. 2 ). In such a case, the method can check in a further step 22 whether an emissions budget is still available for the journey with the motor vehicle 1. Accordingly, within the framework of the Fig. 3 The method explained by way of example takes into account the total quantity of at least one pollutant emitted into the environment 5 of the motor vehicle 1 during the journey of the motor vehicle 1. If an emissions budget is still available, the control device 12 can still issue the unrestricted power release 21. According to Fig. 3Thus, despite the minimum conversion 15 not being reached, the result of the check carried out in step 22 may be that the unrestricted power release 21 is carried out.

[0057] Furthermore, the method can reach a result 23 in which the power of the internal combustion engine 2 released by the control device 12, i.e., the maximum permissible power of the internal combustion engine 2, is determined depending on the space velocity 19 and the size of the volume fraction 6. This can be the case, for example, if the check in step 22 reveals that there is no longer an emissions budget available for the journey with the motor vehicle 1.

[0058] In a variant of the method not explicitly shown here, the control device 12 can also arrive at this result 23 if the test in step 20 shows that the current conversion capacity of the catalyst 4, i.e. the conversion of the catalyst 4 that can be achieved by means of the triggered volume fraction 6, is lower than the desired minimum conversion 15. In this method, step 22 can therefore be omitted or eliminated.

[0059] The process will be illustrated again below using a numerical example. For example, the activated or active volume fraction 6 can be one liter, with the total volume of the catalyst 4 being three liters. The minimum conversion 15, i.e., the requirement for the conversion of at least one pollutant to comply with a limit value for that pollutant, can be 95 percent. From this minimum conversion 15 of, for example, 95 percent, the space velocity model determines a maximum permissible space velocity, which results in the catalyst 4 not being overrun, but instead the catalyst 4 meeting the requirements for the minimum conversion 15. For example, the maximum permissible space velocity 19 determined in this way can be 100,000 h -1<.

[0060] Since the space velocity 19 can be determined as the quotient of the exhaust gas mass flow or the exhaust gas volume flow relative to the activated catalytic volume of the catalytic converter 4, the permissible exhaust gas mass flow that may be released by the internal combustion engine 2 during operation in order to achieve the minimum conversion 15 of 95 percent can also be calculated. Accordingly, the control device 12 can calculate the power that can be provided by the internal combustion engine 2, i.e., the permissible power of the internal combustion engine 2, taking into account the emissions emitted into the environment 5 of the motor vehicle 1.

[0061] The higher the activated catalytic volume of the catalyst 4 becomes, i.e. the more the size of the volume portion 6 increases, the more the released combustion engine power, i.e. the power that can be provided by the internal combustion engine 2 of the motor vehicle 1, can be successively increased, while complying with the emission limit value for at least one pollutant.

[0062] Overall, the examples show how an improved emission-based power control of the internal combustion engine 2 can be realized.

Claims

1. Method for operating an internal combustion engine (2) of a motor vehicle (1), in which exhaust gas from the internal combustion engine (2) is fed to at least one catalytic converter (4) which is arranged in an exhaust system (3) of the motor vehicle (1), and in which a power which can be supplied by the internal combustion engine (2) is set by means of a control device (12) of the motor vehicle (1) as a function of an emission of at least one pollutant contained in the exhaust gas into the surroundings (5) of the motor vehicle (1), characterized in that a size of a partial volume (6), effecting the conversion of the at least one pollutant, of the at least one catalytic converter (4) is calculated, wherein the partial volume (6) is sufficiently heated in order to achieve a specific minimum conversion rate for the at least one pollutant, and the power which can be supplied by the internal combustion engine (2), that is the maximum allowed power of the internal combustion engine (2), is set as a function of the respective size of the partial volume (6), wherein a temperature of the exhaust gas flowing through the at least one catalytic converter (4) is taken into account in order to calculate the respective size of the partial volume (6) which effects the conversion of the at least one pollutant, a current conversion capacity of the at least one catalytic converter (4) for the at least one pollutant is calculated based on a space velocity (19), relative to the respective size of the partial volume (6), of the exhaust gas flowing through the at least one catalytic converter (4), the current conversion capacity of the at least one catalytic converter (4) is compared with a target conversion capacity (14) for the at least one pollutant, and a lower power than the maximum power of the internal combustion engine (2) is set as the power which can be supplied by the internal combustion engine (2) when the current conversion capacity is less than the target conversion capacity (14).

2. Method according to Claim 1, characterized in that a total quantity of the at least one pollutant emitted into the surroundings (5) of the motor vehicle (1) when the motor vehicle (1) is being driven is taken into account for setting the power which can be supplied by the internal combustion engine (2).

3. Method according to Claim 2, characterized in that the maximum power of the internal combustion engine (2) is set as the power which can be supplied by the internal combustion engine (2) despite the fact that the current conversion capacity of the at least one catalytic converter (4) is less than the target conversion capacity (14) when the total quantity of the at least one pollutant emitted into the surroundings (5) when the motor vehicle (1) is being driven is less than a threshold value of the total quantity.

4. Method according to one of the preceding claims, characterized in that engine-out emissions of the at least one pollutant, caused by the internal combustion engine (2), which occur in the case of at least one predetermined driving manoeuvre of the motor vehicle (1) when the motor vehicle (1) is being driven are taken into account in order to calculate the target conversion capacity (14) of the at least one catalytic converter (4).

5. Method according to one of the preceding claims, characterized in that, in the case of an increase in the size of the partial volume (6) which effects the conversion of the at least one pollutant, a higher and higher power of the internal combustion engine (2) is released as the power which can be supplied, that is the released power of the internal combustion engine (2) is increased gradually with a higher activated catalytic volume of the at least one catalytic converter (4).

6. Motor vehicle (1) with an internal combustion engine (2) and with at least one catalytic converter (4) which is arranged in an exhaust system (3) of the motor vehicle (1) and to which exhaust gas from the internal combustion engine (2) can be fed, and with a control device (12) which is designed to set a power which can be supplied by the internal combustion engine (2) as a function of an emission of at least one pollutant contained in the exhaust gas into the surroundings (5) of the motor vehicle (1), characterized in that the control device (12) is designed to calculate a size of a partial volume (6), effecting the conversion of the at least one pollutant, of the at least one catalytic converter (4), wherein the partial volume (6) is sufficiently heated in order to achieve a specific minimum conversion rate for the at least one pollutant, and to set the power which can be supplied by the internal combustion engine (2), that is the maximum allowed power of the internal combustion engine (2), as a function of the respective size of the partial volume (6), wherein a temperature of the exhaust gas flowing through the at least one catalytic converter (4) is taken into account in order to calculate the respective size of the partial volume (6) which effects the conversion of the at least one pollutant, and wherein the control device (12) is designed to calculate a current conversion capacity of the at least one catalytic converter (4) for the at least one pollutant based on a space velocity (19), relative to the respective size of the partial volume (6), of the exhaust gas flowing through the at least one catalytic converter (4), to compare the current conversion capacity of the at least one catalytic converter (4) with a target conversion capacity (14) for the at least one pollutant, and to set a lower power than the maximum power of the internal combustion engine (2) as the power which can be supplied by the internal combustion engine (2) when the current conversion capacity is less than the target conversion capacity (14).