Method and device for operating a hybrid powertrain

Abstract

Method for operating a hybrid powertrain (110) of a vehicle (100), wherein the hybrid powertrain (110) comprises an internal combustion engine (120) and an electric motor (140) supplied with electrical energy by an accumulator (145), wherein an exhaust system (180) of the internal combustion engine (120) comprises an electrically heated exhaust catalyst (190) with a catalytic area (192) and a heating disc (194) configured to heat the catalytic area (192), wherein the method comprises the following steps: - Providing a first operating mode of the hybrid powertrain (110) in which there are restrictions regarding the energy consumption of the hybrid powertrain (110) and a second operating mode of the hybrid powertrain (110) in which there are no restrictions regarding the energy consumption of the hybrid powertrain (110); - Operating the hybrid powertrain (110) in the first operating mode, and propelling the vehicle (100) solely with the electric motor (140) of the hybrid powertrain (110), with the heating disc (194) of the electrically heated exhaust catalyst (190) remaining deactivated or being deactivated; or - Operating the hybrid powertrain (110) in the second operating mode and driving the vehicle (100) solely with the electric motor (140) of the hybrid powertrain (110), whereby the heating disc (194) of the electrically heated exhaust catalyst (190) remains activated or is activated, wherein, during the operation of the hybrid powertrain (110) in the first operating mode, it becomes possible to engage the internal combustion engine (120), - when a parameter of the hybrid powertrain (110) reaches a predefined threshold value or when the heating of the electrically heated exhaust catalyst (190) with the heating disc (194) is completed, and - where switching on the internal combustion engine (120) is only possible if a driving distance parameter is determined as a function of the distance traveled by the vehicle, - wherein the distance traveled is composed of a current driving cycle and / or several previous driving cycles and the distance parameter is a modeled or measured pollutant emission quantity of one or more pollutant emissions which were emitted over the distance traveled and - where the amount of pollutant emissions for the distance traveled, including emissions during the upcoming switching on of the internal combustion engine (120), is below a predefined threshold.

Description

[0001] The present disclosure relates to a method and a device for operating a hybrid powertrain of a vehicle, wherein the hybrid powertrain comprises an internal combustion engine and an electric motor supplied with electrical energy by a battery. An exhaust system of the internal combustion engine includes an electrically heated exhaust catalyst with a catalytic section and a heating element configured to supply the catalytic section of the electrically heated exhaust catalyst with thermal energy, thus heating it.

[0002] Document DE 10 2017 126 091 A1, for example, discloses a method for operating a hybrid vehicle, wherein the state of charge of an electrical energy storage device for powering the hybrid vehicle is detected and, depending on this, it is determined whether an engine start of the internal combustion engine is imminent. If an engine start of the internal combustion engine is imminent, the catalyst for the internal combustion engine is heated up.

[0003] Furthermore, DE 10 2019 208 820 A1 discloses another method for operating a hybrid drive system for a motor vehicle with an internal combustion engine and an additional drive unit. In normal operating phases, the hybrid drive system is operated using a hybrid drive strategy that specifies a load distribution between the first and second partial drive torques. During a cold start phase, the internal combustion engine is operated with minimized raw emissions, and a second partial drive torque is provided by the additional drive unit.

[0004] Finally, document DE 10 2014 220 895 A1 describes a method for engine control for a vehicle that has an internal combustion engine and an electric motor, as well as an energy storage device for the electric motor. A target value is defined, and the emission efficiency of the internal combustion engine is adjusted accordingly so that the emissions emitted by the internal combustion engine remain below a predetermined emission threshold.

[0005] Electrically heated catalytic converters are increasingly being used in hybrid vehicles, such as 48-volt hybrids or high-voltage plug-in hybrids, to reduce cold-start emissions from the combustion engine. Depending on the emissions reduction strategy, this may involve preheating the electrically heated catalytic converter before starting the engine. Otherwise, significantly higher pollutant emissions occur immediately after starting, i.e., after a cold start and during the catalytic converter's warm-up phase, compared to a warm start with a fully warmed catalytic converter.

[0006] In full hybrid applications of a hybrid powertrain (for example, at high voltage or, where applicable, 48 volts), purely electric driving is possible, in which the vehicle is powered by energy stored in a battery, with the internal combustion engine not running and remaining stationary. Due to the limited size of the electric motor and / or battery power limitations, the electric driving mode is typically restricted to low power demands or short driving times. If an entire journey can be completed purely electrically, it is not necessary to preheat the electrically heated exhaust catalyst, as this would only result in additional energy consumption.On the other hand, avoiding preheating the electrically heated exhaust catalyst before starting the internal combustion engine can lead to increased cold start emissions if an unexpected start of the internal combustion engine becomes necessary anyway.

[0007] The purpose of the present disclosure is therefore to provide a method and a device with which an advantageously energy-efficient and low-emission operation of a hybrid powertrain of a vehicle is made possible.

[0008] The problem is solved by the method or device comprising the features of the independent claims. Advantageous embodiments of the present disclosure are specified in the dependent claims.

[0009] According to the present disclosure, the method for operating a hybrid powertrain of a vehicle comprises the following steps. The hybrid powertrain of the vehicle includes an internal combustion engine and an electric motor as its drive system. According to different embodiments, the electric motor and the internal combustion engine can each be used individually as a drive system or in combination as the drive system for the hybrid powertrain of the vehicle. The hybrid powertrain includes an accumulator that supplies the electric motor with electrical energy. The internal combustion engine of the hybrid powertrain includes an exhaust system configured to remove and treat exhaust gas from the internal combustion engine. For the purpose of exhaust gas aftertreatment, the exhaust system includes an electrically heated exhaust catalyst.The electrically heated exhaust gas catalyst comprises a catalytic section and a heating element. Within the catalytic section of the electrically heated exhaust gas catalyst, pollutants from the exhaust gas of the internal combustion engine are converted / reduced into harmless substances. For this conversion or reduction to be possible, it is at least partially necessary that the catalytic section of the electrically heated exhaust gas catalyst has a predefined temperature, a so-called light-off temperature. This light-off temperature can be achieved by the temperature of the exhaust gas itself, through the transfer of heat energy from the exhaust gas to the catalytic section, or it is also possible for the heating element to transfer heat energy to the catalytic section, thereby enabling the catalytic section to reach the light-off temperature using the heat energy from the heating element. The process steps for operating the hybrid powertrain of the vehicle according to the present disclosure are: - Providing a first operating mode of the hybrid powertrain in which there are restrictions regarding the energy consumption of the hybrid powertrain, and a second operating mode of the hybrid powertrain in which there are no restrictions regarding the energy consumption of the hybrid powertrain; - Operating the hybrid powertrain in the first operating mode and propelling the vehicle solely with the electric motor of the hybrid powertrain, with the heating disc of the electrically heated exhaust catalyst remaining deactivated or being deactivated; or - Operating the hybrid powertrain in the second operating mode and propelling the vehicle solely with the electric motor of the hybrid powertrain, with the heating disc of the electrically heated exhaust catalyst remaining or being activated.

[0010] According to the present disclosure, a distinction is made between the first operating mode, in which a driver request is represented with the lowest possible energy consumption / fuel consumption, possibly at the expense of the maximum available torque of the hybrid powertrain, and a second operating mode, in which there are no restrictions on the maximum available torque of the vehicle's hybrid powertrain, at the expense of higher energy consumption. The first operating mode can also be referred to as the ecological operating mode (Eco mode) and the second operating mode can also be referred to as the non-ecological operating mode (Non-Eco mode). According to one embodiment, both driving modes can be further subdivided into sub-driving modes, for example, the second operating mode into "Normal" and "Sport".In the first operating mode, according to the present disclosure, when the hybrid powertrain is operated with the electric motor alone, the heating element of the electrically heated exhaust catalyst is initially kept deactivated or deactivated. This means that no additional energy is used to heat the electrically heated exhaust catalyst in the first operating mode, thus enabling the hybrid powertrain of the vehicle to operate advantageously energy-efficiently in the first operating mode. According to the present disclosure, in the second operating mode, when the hybrid powertrain is operated with the electric motor alone, the heating element of the electrically heated exhaust catalyst is activated or kept activated.This generally results in increased energy consumption in the second operating mode. However, in this mode, a low-emission start of the combustion engine can occur at any time during a sudden increase in torque demand from the driver, thus meeting the increased demand. This prevents harmful emissions from being released into the environment due to the cold, unheated exhaust catalyst. Therefore, the second operating mode allows for more dynamic driving behavior of the vehicle's hybrid powertrain, while simultaneously keeping emissions from the vehicle and the hybrid powertrain advantageously low.

[0011] According to the invention, during the operation of the hybrid powertrain in the first operating mode, it becomes possible to switch on the internal combustion engine if a parameter of the hybrid powertrain reaches a predefined threshold value or if the heating of the electrically heated exhaust gas catalyst with the heating disc is completed.

[0012] According to one embodiment, the parameter of the hybrid powertrain can indicate an impending end to electric driving. In this case, even in the first operating mode, the electrically heated exhaust catalyst is preheated preventively to advantageously reduce emissions when the combustion engine starts. The parameter of the hybrid powertrain can, for example, be defined based on a driver request close to the limit of electric driving, with the electrically heated exhaust catalyst being activated when the driver request reaches the predefined threshold. According to another embodiment, the parameter of the hybrid powertrain is the battery charge level, with the electrically heated exhaust catalyst being preheated when the battery charge level reaches or falls below the predefined threshold.According to another embodiment, the parameter of the hybrid powertrain includes an anticipated acceleration event of the vehicle, such that the activation of the internal combustion engine becomes necessary due to an expected impending acceleration event. Accordingly, heating of the electrically heated exhaust catalyst is required to advantageously reduce the impending emissions of the internal combustion engine due to the upcoming acceleration process. According to a further embodiment, a combination of the aforementioned parameters is also possible.

[0013] Alternatively, during operation of the hybrid powertrain in the first operating mode, the internal combustion engine can only be engaged once the electrically heated exhaust catalyst has reached its operating temperature. In other words, starting the internal combustion engine in the vehicle's first operating mode is only possible / permitted when the electrically heated exhaust catalyst has reached the required "light-off" temperature to achieve the necessary reduction in emissions from the internal combustion engine. This ensures that the internal combustion engine can only be started when the electrically heated exhaust catalyst has reached the prescribed temperature for reducing emissions from the exhaust gas, thus advantageously achieving a reduction in emissions.

[0014] According to the invention, as an alternative to the aforementioned condition, heating the electrically heated exhaust catalyst by means of the heating disc is possible in the first operating mode as soon as a parameter of the hybrid powertrain reaches a predefined threshold value. The parameter can, for example, be one of the aforementioned parameters. Accordingly, as soon as the parameter reaches the predefined threshold value, the electrically heated exhaust catalyst is supplied with electrical energy, thereby heating the electrically heated exhaust catalyst by means of the heating disc. Thus, the electrically heated exhaust catalyst is heated first before the internal combustion engine of the hybrid powertrain is started.Accordingly, the reduction of emissions from the combustion engine of the hybrid powertrain can be carried out advantageously simply and reliably, so that overall the emissions of the hybrid powertrain are reduced and at the same time energy consumption remains reduced due to the electrically heated exhaust catalyst, since the electrically heated exhaust catalyst is only supplied with electrical energy once the parameter of the hybrid powertrain has reached the predefined threshold.

[0015] According to the invention, during operation of the hybrid powertrain in the first operating mode, the internal combustion engine can only be engaged if a driving distance parameter is determined based on the distance traveled by the vehicle and, if applicable, reaches a predefined threshold value. This driving distance parameter can, for example, be measured by sensors within the hybrid powertrain over the vehicle's distance traveled. This driving distance parameter can, for example, be integrated over the distance traveled and continuously compared with the predefined threshold value. As soon as the integrated driving distance parameter reaches the predefined threshold value, engagement of the internal combustion engine becomes possible in the first operating mode.According to one embodiment, the driving distance parameter can, for example, simply be a time period during which the hybrid powertrain operates solely on the electric motor in the first operating mode. Once this time period reaches a predefined total time, the combustion engine can be engaged. According to this embodiment, the engagement of the combustion engine is determined based on the distance traveled, thus employing a holistic view of the hybrid powertrain's operation over the entire distance traveled to decide whether the combustion engine can be engaged.

[0016] According to the invention, the distance traveled is calculated from a current driving cycle and / or from several previous driving cycles, and the driving distance parameter is determined from a modeled or measured quantity of pollutant emissions from one or more pollutants emitted over the distance traveled. A driving cycle consists of the period from the start of the vehicle to its shutdown, during which the vehicle is moved from point A to point B. Several driving cycles accordingly correspond to multiple starts of the vehicle, movements from point A to point B or C, and shutdowns. Therefore, according to this embodiment, the distance traveled corresponds either to the current driving cycle, i.e., starting from the last start of the vehicle up to the present time, or the distance traveled is composed of several previous driving cycles and the current driving cycle.According to this embodiment, the driving distance parameter is a modeled or measured pollutant emission quantity. The pollutant emission quantity is the amount of pollutants emitted due to the operation of the internal combustion engine of the hybrid powertrain during the distance traveled, i.e., during the current driving cycle or during several previous driving cycles. The pollutant emission quantity can be modeled by, for example, feeding parameters of the hybrid powertrain, particularly the internal combustion engine, into the model. These parameters include operating times of the internal combustion engine, torque of the internal combustion engine, load of the internal combustion engine, or fuel consumption of the internal combustion engine. Alternatively, the pollutant emission quantity can be measured directly using sensors, for example, in the exhaust system of the internal combustion engine.Accordingly, the combustion engine can only be engaged if the amount of pollutant emissions emitted during the journey is below the predefined threshold. For example, if the hybrid powertrain was operated solely by the electric motor during the journey, no pollutant emissions were emitted. Therefore, even when the combustion engine is engaged, the overall emissions over the journey remain relatively low compared to conventional vehicles. This allows emission limits to be kept advantageously low, even when the combustion engine is engaged or engaged only briefly.

[0017] According to the invention, the internal combustion engine can be engaged if the total pollutant emissions for the distance traveled, including emissions during the impending engagement of the internal combustion engine, are below the predefined threshold. Accordingly, the emissions from the impending engagement of the internal combustion engine are also taken into account when assessing whether engagement is possible, thus providing a more comprehensive view of emissions and enabling advantageous emission reductions in specific situations. By selecting the first operating mode, the driver can consciously achieve particularly energy-efficient vehicle operation, albeit with limitations on the available drive torque.If a long distance or several driving cycles with advantageously low emissions have already been completed, a single spontaneous acceleration with increased emissions can still be permitted in individual cases without significantly increasing the overall emissions balance. In this way, a particularly advantageous compromise between energy efficiency and the responsiveness of the drive system can be achieved.

[0018] According to one embodiment, during operation of the hybrid powertrain in the second operating mode, the heating element of the electrically heated exhaust catalyst is deactivated if a driving distance parameter, determined based on the distance traveled, reaches a predefined threshold. One of the driving distance parameters can be one of the driving distance parameters mentioned above. For example, preventive preheating of the electrically heated exhaust catalyst can be omitted if the average pollutant emission quantity over the considered driving distance, including emissions during any engine start-up and subsequent heating phase of the electrically heated exhaust catalyst (possibly electrically assisted), would remain below the predefined threshold.In this way, without compromising the responsiveness of the drive system in the second operating mode, the vehicle's energy consumption can be kept low if the vehicle has already covered a sufficiently long distance with low emissions. If, in this operating mode, the driver initiates a spontaneous start of the combustion engine without a fully warmed-up electrically heated catalytic converter, preventive preheating may be reactivated, depending on the emissions balance, to ensure continued compliance with emission limits.

[0019] According to one embodiment of the above-described design, during operation of the hybrid powertrain in the second operating mode, the distance traveled is compiled from a current driving cycle and / or from several previous driving cycles, and the distance parameter includes a modeled or measured quantity of pollutant emissions from one or more pollutants emitted over the distance traveled. According to this embodiment, in the second operating mode, the heating element of the electrically heated exhaust catalyst is deactivated when the distance traveled parameter reaches the predefined threshold, wherein the distance traveled is compiled from a current driving cycle and / or previous driving cycles, and the distance traveled parameter includes a modeled or measured quantity of pollutant emissions from one or more pollutants.Pollutant emissions can be measured, for example, using a sensor within the exhaust system of the internal combustion engine; it is also conceivable that pollutant emissions can be modeled using a model that takes parameters of the internal combustion engine as input variables, such as operating times, torque, load or injection quantity, from which the pollutant emissions can then be modeled / determined.

[0020] According to one embodiment, the driver of the vehicle performs the switch between the first and second operating modes, or the driving mode is changed automatically. According to another embodiment, the switch between the first and second operating modes can only be performed when the vehicle is stationary.

[0021] According to a further aspect of the present disclosure, a device for operating a hybrid powertrain of a vehicle comprises a control unit configured to perform one of the methods mentioned above, wherein the hybrid powertrain comprises an internal combustion engine, an accumulator, and an electric motor, wherein an exhaust system of the internal combustion engine comprises an electrically heated exhaust catalyst with a catalytic section and a heating element, and wherein the hybrid powertrain is configured to propel the vehicle. The device may, for example, be a control unit for controlling and regulating the hybrid powertrain or a part thereof. It is also conceivable that the device is part of the control unit or is installed as an additional control unit, for example, in the vehicle with the hybrid powertrain.

[0022] Exemplary embodiments and further developments of the method and the device according to the present disclosure are shown in the figures and are explained in more detail below.

[0023] It shows: Fig. 1: a schematic representation of a vehicle with a hybrid powertrain according to a first embodiment, Fig. 2: a schematic representation of an electrically heated exhaust gas catalyst according to a first embodiment.

[0024] Fig. Figure 1 schematically shows a vehicle 100 with a hybrid powertrain 110. The hybrid powertrain 110 comprises an internal combustion engine 120 and an electric motor 140. According to this embodiment, the internal combustion engine 120 and the electric motor 140 are connected in series and can drive the hybrid powertrain 110 either individually or in combination. Other arrangements are also conceivable. The hybrid powertrain 110 further comprises a clutch 130, which is arranged between the internal combustion engine 120 and the electric motor 140. The clutch 130 is open when the hybrid powertrain is driven only by the electric motor 140. The clutch 130 is closed when the hybrid powertrain 110 is driven by the internal combustion engine 120.The hybrid powertrain 110 further comprises a transmission 150, which, according to this embodiment, is arranged downstream of the electric motor 140 and serves to shift between different available gears. The hybrid powertrain 110 further comprises a differential 160, which, according to this embodiment, is arranged on the rear axle of the vehicle 100 and is configured to distribute the torque coming from the hybrid powertrain 110 to the two different rear tires 170. The hybrid powertrain 110 further comprises an accumulator 145, which is configured to provide the electrical energy for the electric motor 140. The internal combustion engine 120 further comprises an exhaust system 180, which is configured to treat the exhaust gas of the internal combustion engine 120 in such a way as to meet the legal emission requirements. The exhaust system 180 therefore comprises an electrically heated exhaust catalyst 190.According to this embodiment, the electrically heated exhaust catalyst 190 is supplied with electrical energy from the accumulator 145.

[0025] Fig. Figure 1 further shows a control unit 200, which is arranged inside the vehicle 100. The control unit 200 uses input data 210 and generates output data 220, the output data 220 being used to operate the hybrid powertrain 110 of the vehicle 100. The input data 210 is at least one parameter of the hybrid powertrain 110.

[0026] Fig. Figure 2 shows a schematic detail view of the exhaust system 180 of the internal combustion engine 120 and, in particular, of the electrically heated exhaust catalyst 190 of the exhaust system 180. The electrically heated exhaust catalyst 190 comprises a catalyst section 192 and a heating disc 194. The heating disc 194 is supplied with electrical energy from the accumulator 145. Heating is necessary to heat the catalyst section 192 of the electrically heated catalyst 190 so that the catalyst section 192 reaches the light-off temperature, enabling exhaust gas treatment to be carried out quickly and achieving the desired exhaust gas treatment and emission reduction.

[0027] The in Fig.The control unit 200 shown, for example, is used to execute the method for operating the hybrid powertrain 110 of the vehicle 100, wherein the method comprises the following steps, distinguishing between a first operating mode and a second operating mode. When the hybrid powertrain 110 is operated in the first operating mode, wherein, if the hybrid powertrain 110 is operated with the electric motor 140 alone, the heating disc 194 of the electrically heated exhaust catalyst 190 is initially deactivated or remains deactivated. Alternatively, when the hybrid powertrain 110 is operated in the second operating mode, wherein, if the hybrid powertrain 110 is operated with the electric motor 140 alone, the heating disc 194 of the electrically heated exhaust catalyst 190 is activated or remains activated.Depending on the operating mode of the hybrid powertrain 110, a different operating strategy is proposed for the electrically heated exhaust gas catalyst 190. In the first operating mode, heating is completely omitted to reduce energy consumption, while in the second operating mode, heating is continuous to advantageously reduce emissions from the combustion engine 120 during a potential cold start. Accordingly, low-emission and energy-efficient operation of the hybrid powertrain 110 is possible.

Claims

[1] Method for operating a hybrid powertrain (110) of a vehicle (100), wherein the hybrid powertrain (110) comprises an internal combustion engine (120) and an electric motor (140) supplied with electrical energy by an accumulator (145), wherein an exhaust system (180) of the internal combustion engine (120) comprises an electrically heated exhaust catalyst (190) with a catalytic area (192) and a heating disc (194) configured to heat the catalytic area (192), wherein the method comprises the following steps: - Providing a first operating mode of the hybrid powertrain (110) in which there are restrictions regarding the energy consumption of the hybrid powertrain (110) and a second operating mode of the hybrid powertrain (110) in which there are no restrictions regarding the energy consumption of the hybrid powertrain (110); - Operating the hybrid powertrain (110) in the first operating mode, and propelling the vehicle (100) solely with the electric motor (140) of the hybrid powertrain (110), with the heating disc (194) of the electrically heated exhaust catalyst (190) remaining deactivated or being deactivated; or - Operating the hybrid powertrain (110) in the second operating mode and driving the vehicle (100) solely with the electric motor (140) of the hybrid powertrain (110), whereby the heating disc (194) of the electrically heated exhaust catalyst (190) remains activated or is activated, wherein, during the operation of the hybrid powertrain (110) in the first operating mode, it becomes possible to engage the internal combustion engine (120), - when a parameter of the hybrid powertrain (110) reaches a predefined threshold value or when the heating of the electrically heated exhaust catalyst (190) with the heating disc (194) is completed, and - where switching on the internal combustion engine (120) is only possible if a driving distance parameter is determined as a function of the distance traveled by the vehicle, - wherein the distance traveled is composed of a current driving cycle and / or several previous driving cycles and the distance parameter is a modeled or measured pollutant emission quantity of one or more pollutant emissions which were emitted over the distance traveled and - where the amount of pollutant emissions for the distance traveled, including emissions during the upcoming switching on of the internal combustion engine (120), is below a predefined threshold. [2] Method according to claim 1, wherein during the operation of the hybrid powertrain (110) in the second operating mode the heating disc (194) of the electrically heated exhaust catalyst (190) is deactivated when the driving distance parameter, which is determined as a function of the distance traveled, reaches the predefined threshold value. [3] Method according to one of the preceding claims, wherein a change between the first operating mode and the second operating mode is carried out by the driver of the vehicle or an automated change of driving mode is carried out. [4] Device for operating a hybrid powertrain (110) of a vehicle (100), wherein the hybrid powertrain (110) comprises an internal combustion engine (120), an accumulator (145) and an electric motor (140), wherein an exhaust system (180) of the internal combustion engine (120) comprises an electrically heated exhaust catalyst (190) with a catalytic section (192) and a heating disc (194), wherein the device comprises a control unit (200) configured to perform a method according to one of the preceding claims.

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