Method for operating a motor vehicle with a hybrid drive

Abstract

Method for operating a motor vehicle (10) with a hybrid drive, wherein the motor vehicle (10) has a first drive (12) with an electric motor (14) to which an electrical energy store (16) is assigned, and a second drive as an internal combustion engine (22) with an exhaust gas aftertreatment system, in particular with at least one catalyst (24), wherein a permanent monitoring is carried out to detect a low load phase for the drive of the motor vehicle (10), wherein, depending on the detected low-load phase, a temperature for the exhaust gas aftertreatment system, in particular a temperature for the at least one catalyst (24) of the exhaust gas aftertreatment system, is monitored, where depending on a critical temperature (T krit) for the exhaust gas aftertreatment system and a modeled cooling of the exhaust gas aftertreatment system, continued operation or deactivation of the internal combustion engine (20) is carried out.

Description

[0001] The invention relates to a method for operating a motor vehicle with a hybrid drive, as well as a control unit and a computer program for carrying out the method. State of the art

[0002] Motor vehicles with hybrid drive, also known as hybrid vehicles, are vehicles that have at least two drive systems. Hybrid vehicles are typically designed as hybrid electric vehicles, powered by at least one electric vehicle and another energy converter or motor. Such a vehicle draws energy from both an electrical storage device, typically an accumulator or battery, and an additional fuel.

[0003] With the increasing popularity of assisted electric drives, it is possible to operate the vehicle purely electrically and to completely switch off the combustion engine, for example during city driving with low power requirements (low speed).

[0004] If the catalyst temperature falls below a critical threshold, suitable heating measures must be switched on again to ensure a functioning exhaust system and thus compliance with the emission targets. Disclosure of the invention

[0005] In a first aspect, the invention relates to a method for operating a motor vehicle with a hybrid drive, wherein the motor vehicle is assigned a first drive with an electric motor, and has a second drive as an internal combustion engine with an exhaust gas aftertreatment system, in particular with at least one catalyst, wherein, depending on the detected low-load phase, a temperature for the exhaust gas aftertreatment system, in particular a temperature for the at least one catalyst of the exhaust gas aftertreatment system, is monitored, Depending on a critical temperature for the exhaust gas aftertreatment system and a modeled cooling of the exhaust gas aftertreatment system, continued operation or deactivation of the combustion engine is carried out.

[0006] The process has the particular advantage that, by solely using the electric motor and deactivating the combustion engine during low-load phases where the critical temperature of the exhaust gas aftertreatment system would be undercut, cooling of the exhaust gas aftertreatment system, particularly the catalysts, due to the flow of cold exhaust gas, can be avoided. This prevents the catalysts from cooling down, thus reducing the need for fuel-intensive heating measures. This leads to an improved energy balance of the system and a reduction in emissions. Compared to the state of the art, the process thus enables more efficient use of the exhaust gas aftertreatment system and a reduction in emissions.

[0007] In a particular embodiment, the cooling behavior of the exhaust gas aftertreatment system is modeled using an exhaust gas temperature. Advantageously, the feature of the claim that the cooling behavior of the exhaust gas aftertreatment system is modeled using an exhaust gas temperature enables more precise monitoring of the exhaust gas temperature and thus more effective prevention of cooling of the catalyst during low-load phases. This allows heating measures to maintain emissions conversion to be used more effectively and specifically, leading to an improved energy balance of the system.

[0008] In an alternative embodiment, a duration of the detected low-load phase for the motor vehicle and a cooling of the exhaust gas aftertreatment system for the duration of the low-load phase are determined, wherein if the temperature of the exhaust gas aftertreatment system does not fall below the critical temperature for the determined duration of the low-load phase, the combustion engine is deactivated.

[0009] The term duration can be understood as the temporal length of a specific event or state. In the context of the present patent application, the duration refers to the length of the detected low-load phase of the motor vehicle as well as the cooling of the exhaust aftertreatment system during this phase. The duration is determined by analyzing the relevant data, such as predictive data. The duration can thus be considered a temporal variable that is crucial for implementing the described method.

[0010] In an advantageous embodiment, a duration of the detected low-load phase for the motor vehicle and the cooling of the exhaust gas aftertreatment system for the duration of the low-load phase are determined, wherein if the temperature of the exhaust gas aftertreatment system falls below the critical temperature for the determined duration of the low-load phase, suitable heating measures for the exhaust gas aftertreatment system are activated.

[0011] In an alternative embodiment, the combustion engine is deactivated within the determined duration of the low-load phase and then reactivated.

[0012] This ensures that emissions conversion can be maintained without unnecessary energy waste. Compared to the state of the art, it enables more efficient and targeted control of the catalyst heating measures, resulting in an improved energy balance and greater effectiveness of emissions conversion.

[0013] In a further embodiment, the duration of the low-load phase is determined using predictive data.

[0014] This has the particular advantage of allowing for better prediction of when the combustion engine should be shut down to prevent the catalysts from cooling down. This leads to more efficient use of heating measures and thus an improved energy balance of the system. Compared to the state of the art, in which the duration of the off-peak phase is estimated solely based on engine load and exhaust gas temperature, the predictive data feature enables a more accurate prediction and thus better control over the system's operation.

[0015] In an advantageous embodiment, the exhaust gas aftertreatment system is heated by internal engine heating measures and / or by activating electric heaters.

[0016] It is advantageous if the exhaust aftertreatment system can be heated by internal engine heating measures and / or by activating electric heaters.

[0017] In a further embodiment, the temperature of the exhaust gas aftertreatment system is determined as a function of at least one variable selected from a group consisting of: state of the internal combustion engine, load of the internal combustion engine, speed of the internal combustion engine, ignition angle efficiency, lambda split setting, vehicle speed, ambient temperature, parameters for late injection.

[0018] In a particular embodiment, the internal combustion engine is restarted when the temperature of the exhaust gas aftertreatment system, in particular of the at least one catalyst, falls below the critical temperature.

[0019] In an advantageous embodiment, the predictive data is selected from a group consisting of: wheel power of the motor vehicle, navigation data, traffic data, state of charge of the electrical energy storage device.

[0020] By using this data, the system can more accurately characterize the low-load phases of the combustion engine and optimize the timing of engine shutdown to prevent the catalysts from cooling down. This leads to an improved energy balance of the system, as unnecessary heating measures can be avoided. Compared to the prior art, which may rely on only a few parameters to characterize the low-load phases, the feature of the claim enables more precise and efficient control of the system.

[0021] In further aspects, the invention relates to a device, in particular a control unit and a computer program, which are configured, in particular programmed, to execute one of the methods. In yet another aspect, the invention relates to a machine-readable storage medium on which the computer program is stored. Short description of the drawings Fig. 1 shows a schematic representation of a motor vehicle with an embodiment of the arrangement for carrying out the method. Fig. 2 shows a flow chart of a possible sequence of the presented procedure. Embodiments of the invention

[0022] The invention is illustrated schematically in the drawings using embodiments and is described in detail below with reference to the drawings.

[0023] Fig. Figure 1 shows a highly simplified, schematic representation of a motor vehicle, designated overall by reference numeral 10. This motor vehicle 10 includes a first drive 12 with an electric motor 14 and an associated electric storage unit 16, as well as an internal combustion engine 22, the internal combustion engine having an exhaust gas aftertreatment system. The exhaust gas aftertreatment system includes at least one catalytic converter 24.

[0024] In alternative embodiments, the exhaust aftertreatment system may also consist of several different components, such as a selective catalytic exhaust aftertreatment system (SCR) and / or one or more catalysts 24. Furthermore, the motor vehicle 10 comprises a temperature model T mod to determine the temperature of the exhaust gas aftertreatment system. The temperature model can be configured in such a way that temperatures for specific components of the exhaust gas aftertreatment system can also be determined. This temperature model can be adapted modularly to the respective system configuration and the respective components contained therein. In a preferred embodiment, a temperature sensor is arranged in the exhaust system downstream of the combustion engine. Alternatively or additionally, temperature sensors can be arranged in the components of the exhaust gas aftertreatment system.

[0025] Furthermore, the motor vehicle 10 has a fuel tank 26.

[0026] The illustration also shows a navigation system 30, into which the driver enters information about the destination address and, if applicable, route specifications, and which can calculate a route to this destination. In principle, an input from which a travel duration or distance can then be calculated can also be made in other ways, for example, by directly entering a travel distance.

[0027] The illustration also shows an arrangement designated overall by reference numeral 40. This arrangement 40, which is embodied, for example, as a control unit of motor vehicle 10, acquires predictive data that makes it possible to determine a remaining energy requirement to reach the specified destination and a remaining energy availability, taking into account the charge state of energy storage device 16. Based on this, the combustion engine 20 is adjusted, i.e., switched off, for example. The control unit 40 can also evaluate the topology and traffic information of the selected route for internal calculations.

[0028] The term off-peak phase can be understood as a phase in which the vehicle has only a low load and the combustion engine produces little power. During this phase, the exhaust gas aftertreatment system is not heated up sufficiently to operate effectively. Cooling of the exhaust gas aftertreatment system during the off-peak phase can lead to a deterioration in emissions. It is therefore important to determine the duration of the off-peak phase and to specifically heat the exhaust gas aftertreatment system during this time to ensure optimal performance. The duration of the off-peak phase can be determined using predictive data that can come from various sources such as the vehicle's wheel power, navigation data, traffic data, and the state of charge of the electrical energy storage system.Advantageously, the feature of the claim enables the duration of the detected low-load phase for the motor vehicle and the cooling of the exhaust gas aftertreatment system to be determined for the duration of the low-load phase. This allows the combustion engine to be switched off during longer low-load phases to prevent the exhaust gas aftertreatment system from cooling down, thus reducing or eliminating the need for heating measures.

[0029] The term navigation data can be understood as information used to determine the optimal route for a motor vehicle. This data may include, for example, the vehicle's geographical position, the position of the destination, road conditions, traffic information, and other relevant information. Navigation data can come from various sources, such as a GPS system, a mobile phone, or a navigation system in the vehicle itself. It is used to recommend the best possible route to the driver and can also contribute to optimizing driving behavior and reducing emissions by enabling the vehicle to adjust the route and speed accordingly.

[0030] The term traffic data can be understood as information about traffic on the road that can be collected from various sources. This data can include, for example, information about traffic density, vehicle speed, the number of vehicles on the road, and the direction of traffic flow. Traffic data can be collected from various sources, such as traffic monitoring cameras, GPS systems in vehicles, or cell phone towers that track the movements of mobile phones. This data can then be used to analyze traffic patterns and identify traffic problems in order to avoid or reduce traffic congestion. With regard to the described patent, traffic data can be used to generate predictive data that can be incorporated into the process for reducing emissions from motor vehicles.

[0031] Fig.2 shows a flowchart of a possible sequence of the presented procedure.

[0032] In a first step 100, the journey begins, with the driver initially entering a destination into a navigation device.

[0033] The method then continues in step 105.

[0034] In a step 105, the control unit 40 continuously detects low-load phases. For this purpose, the control unit 40 advantageously monitors several input variables of the motor vehicle 10, such as an engine load, a speed n eng , the accelerator pedal position or similar variables that allow a conclusion to be drawn about a low-load phase.

[0035] If a low load phase is detected, the process continues in step 110.

[0036] In step 110, a duration for the off-peak phase is determined using a model stored on control unit 40 and the predictive data. The duration indicates the modeled time for how long the motor vehicle 10 will be traveling during the off-peak phase. The method then continues in step 115.

[0037] In a step 115, the cooling of the exhaust gas aftertreatment system is modeled based on the current temperature for the exhaust gas aftertreatment system for the determined duration of the low load phase.

[0038] It can be assumed that in continuous low-load phases, a sufficiently high heat energy input is not introduced into the exhaust gas system, and that a continuous exhaust gas mass flow (ṁ exh ) accelerated cooling of the exhaust aftertreatment system occurs.

[0039] For this purpose, a modeled temperature T kat,modwhich corresponds to the temperature of the exhaust gas aftertreatment system towards the end of the low-load phase.

[0040] The method then continues in step 120.

[0041] In a step 120, the control unit 40 checks whether the modeled temperature T kat,mod of the exhaust aftertreatment system below a critical temperature T krit for the exhaust aftertreatment system.

[0042] The critical temperature T krit preferably describes a light-off temperature for the at least one catalyst 24 of the exhaust gas aftertreatment system. The critical temperature T krit for the exhaust gas aftertreatment system can preferably be specified in an application phase for the motor vehicle 10.

[0043] If the modeled temperature T kat,mod the critical temperature T kritThe still-activated combustion engine 20 can be switched off, and the motor vehicle can be operated purely electrically by the first drive 12. By switching off the combustion engine 22, fuel can be saved on the one hand, and emissions can be reduced on the other.

[0044] If the modeled temperature T kat,mod the critical temperature T krit Various heating measures can be carried out for the exhaust gas aftertreatment system.

[0045] For example, internal engine heating measures such as post-injection of fuel can be implemented to generate waste heat in the exhaust system to heat the exhaust aftertreatment system. Alternatively, if a catalytic converter with electric heating discs (eKat) is installed, the temperature in the exhaust aftertreatment system can be increased by activating the electric heating discs.

[0046] In an alternative embodiment, the combustion engine 20 can be deactivated, and from the moment the critical temperature T krit by the modeled temperature T kat,mod of the catalyst 24, a heating measure can be activated and cooling of the exhaust gas aftertreatment system is prevented.

[0047] Furthermore, by switching off the combustion engine 22, the exhaust gas mass flow ṁ exh significantly reduced, so that the exhaust aftertreatment system cools down less.

[0048] The method can then be terminated or continued in step 105.

Claims

[1] Method for operating a motor vehicle (10) with a hybrid drive, wherein the motor vehicle (10) has a first drive (12) with an electric motor (14) to which an electrical energy storage device (16) is assigned, and a second drive as an internal combustion engine (22) with an exhaust gas aftertreatment system, in particular with at least one catalyst (24), wherein a permanent monitoring is carried out to detect a low load phase for the drive of the motor vehicle (10), wherein, depending on the detected low-load phase, a temperature for the exhaust gas aftertreatment system, in particular a temperature for the at least one catalyst (24) of the exhaust gas aftertreatment system, is monitored, where depending on a critical temperature (T krit) for the exhaust gas aftertreatment system and a modeled cooling of the exhaust gas aftertreatment system, continued operation or deactivation of the internal combustion engine (20) is carried out. [2] Method according to claim 1, characterized by that a cooling behavior of the exhaust gas aftertreatment system by means of an exhaust gas temperature (T exh ) is modeled. [3] Method according to claim 1, characterized by that a duration of the detected low-load phase for the motor vehicle (10) and a cooling of the exhaust gas aftertreatment system for the duration of the low-load phase are determined, wherein when the temperature of the exhaust gas aftertreatment system reaches the critical temperature (T krit ) for the determined duration of the low load phase, the combustion engine (22) is deactivated. [4] Method according to claim 1, characterized bythat a duration of the detected low-load phase for the motor vehicle (10) and the cooling of the exhaust gas aftertreatment system is determined for the duration of the low-load phase, wherein if the temperature of the exhaust gas aftertreatment system falls below the critical temperature (T krit ) for the determined duration of the low load phase, suitable heating measures for the exhaust gas aftertreatment system are activated. [5] Method according to claim 4, characterized by that the combustion engine (22) is deactivated within the determined duration of the low load phase and then reactivated. [6] Method according to claims 2 to 5, characterized by that the duration of the off-peak phase is determined using predictive data. [7] Method according to claim 4 or 5, characterized by that the exhaust aftertreatment system is heated up by internal engine heating measures and / or by activating electric heaters. [8] Method according to one of the preceding claims, characterized by that the temperature of the exhaust gas aftertreatment system is determined as a function of at least one variable selected from a group consisting of: state of the internal combustion engine (22), load of the internal combustion engine (22), speed of the internal combustion engine (22), ignition angle efficiency, lambda split setting, vehicle speed, ambient temperature, parameters for late injection. [9] Method according to claim 4, characterized by that the internal combustion engine (22) is restarted when the temperature of the exhaust gas aftertreatment system, in particular of the at least one catalyst (24), falls below the critical temperature (T krit ) falls. [10] Method according to one of the preceding claims, characterized by that the predictive data is selected from a group consisting of: Wheel power of the motor vehicle, navigation data, traffic data, state of charge of the electrical energy storage device (16). [11] Computer program which is designed to carry out a method according to one of claims 1 to 10. [12] An electronic storage medium comprising a computer program according to claim 11. [13] Device, in particular control device (40), which is designed to carry out a method according to one of claims 1 to 10.

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