Method for operating a drive unit for a motor vehicle, corresponding drive unit and computer program product

Abstract

The invention relates to a method for operating a drive unit for a motor vehicle, which has a first drive unit generating exhaust gas, a second drive unit designed as an electric traction machine, and an exhaust aftertreatment device for aftertreating the exhaust gas, wherein a drive torque provided by the drive unit is generated jointly at least temporarily by means of the first drive unit and the second drive unit, and a first torque provided by the first drive unit as part of the drive torque is limited at least temporarily to a maximum torque.The invention provides that, for the total distance traveled by the motor vehicle since its start of travel, an exhaust component threshold value is determined using a distance-related emission limit value for at least one exhaust component, and that after the first drive unit is started, the maximum torque is determined, at least temporarily, as a function of the exhaust component threshold value. The invention further relates to a drive unit for a motor vehicle and a computer program product.

Description

[0001] The invention relates to a method for operating a drive device for a motor vehicle, which has a first drive unit generating exhaust gas, a second drive unit configured as an electric traction machine, and an exhaust gas aftertreatment device for aftertreating the exhaust gas. A drive torque provided by the drive device is generated at least temporarily jointly by the first drive unit and the second drive unit, and a first torque provided by the first drive unit as part of the drive torque is limited at least temporarily to a maximum torque. The invention further relates to a drive device for a motor vehicle and a computer program product.

[0002] US 2018 / 0156095 A1 is known from the prior art. This document describes methods and systems for controlling a vehicle engine to adapt an exhaust warm-up strategy based on vehicle network information. For example, in response to an expected temperature drop of a vehicle's catalyst below a threshold and an estimated duration thereof based on communications from outside the vehicle, it is provided to delay a catalyst heating action if it is determined that it is not capable of heating the catalyst to a temperature corresponding to the threshold. However, the catalyst heating process can be activated if it is determined that it is capable of increasing the catalyst temperature to the temperature corresponding to the threshold within a certain period of time.

[0003] Furthermore, US Pat. No. 11,560,136 B2 discloses a control device for a hybrid vehicle equipped with a route planning part that creates a route plan that sets one or more transit points on a planned route from a starting point to a destination point to divide the planned route into a plurality of travel routes and further divide the travel routes into a plurality of travel sections. The route planning part further determines which travel mode of the hybrid vehicle is to be used in each travel section, while a travel mode switching part switches the travel modes according to the route plan. The route planning part is configured to create the route plan that sets the travel modes of all travel sections in at least one route to the EV mode.

[0004] It is an object of the invention to propose a method for operating a drive device for a motor vehicle, which has advantages over known methods, in particular improving the availability of a high drive power or a high drive torque of the drive device.

[0005] This is achieved according to the invention with a method for operating a drive device for a motor vehicle having the features of claim 1. It is provided that an exhaust gas component threshold value is determined for a total distance traveled by the motor vehicle since the start of travel using a distance-related emission limit value for at least one exhaust gas component of the exhaust gas, and after starting the first drive unit, the maximum torque is determined at least temporarily as a function of the exhaust gas component threshold value.

[0006] Advantageous embodiments with useful further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments explained in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are feasible.

[0007] The drive device serves to drive the motor vehicle, i.e. to provide a drive torque directed towards driving the motor vehicle. To provide the drive torque, the drive device has the first drive unit and the second drive unit. The first drive unit is preferably in the form of an internal combustion engine, in particular a gasoline internal combustion engine or a diesel internal combustion engine. During operation of the drive device, fuel and fresh gas are supplied to the first drive unit at least temporarily, wherein the fresh gas at least temporarily contains fresh air. In addition, the fresh gas can comprise exhaust gas, provided that exhaust gas recirculation is implemented, in which the exhaust gas generated by the first drive unit is at least partially recirculated to the first drive unit, namely as a component of the fresh gas.The fuel and the fresh gas supplied to the first drive unit form a fuel-fresh gas mixture with a specific composition, which is reacted in the first drive unit.

[0008] During operation of the first drive unit, the chemical reaction between fuel and fresh gas produces exhaust gas, which is discharged to the environment outside the drive system or motor vehicle. Since the exhaust gas generated by the first drive unit contains pollutants, the exhaust gas is first fed to the exhaust aftertreatment system before being released into the environment. In the exhaust aftertreatment system, the pollutants are at least partially converted into less hazardous products. Only after passing through the exhaust aftertreatment system is the exhaust gas discharged to the environment outside.

[0009] The exhaust gas aftertreatment device is preferably in the form of a vehicle catalyst, in particular a three-way catalyst, oxidation catalyst, NO x Storage catalyst or as an SCR catalyst. Alternatively, the exhaust gas aftertreatment system is a particulate filter, in particular a gasoline particulate filter or a diesel particulate filter. It can also be provided that the exhaust gas aftertreatment system is a vehicle catalyst integrated into the particulate filter. For this purpose, the particulate filter is provided with a catalytic coating, for example.

[0010] In addition to the first drive unit, the drive device has a second drive unit. Unlike the first drive unit, this second drive unit is configured as an electric traction machine. The electric traction machine is preferably electrically connected to an electrical energy storage device of the motor vehicle and is operated, at least temporarily, with electrical energy extracted from this energy storage device. The drive device provides a drive torque overall, in particular at an output shaft of the drive device. For this purpose, the first drive unit and the second drive unit are each connected to the output shaft for driving purposes.

[0011] At least temporarily, the first drive unit and the second drive unit jointly generate the drive torque of the drive device, i.e., the drive torque applied to the output shaft, and are operated simultaneously to generate a respective portion of the drive torque. However, it can also be provided that the drive torque is temporarily provided solely by the first drive unit and / or temporarily solely by the second drive unit.

[0012] In any case, the portion of the drive torque provided by the first drive unit is referred to as the first torque, and the portion of the drive torque provided by the second drive unit is referred to as the second torque. The first torque and the second torque together constitute the drive torque, whereby their respective contributions to the drive torque are arbitrary. One of the torques can be zero, and the other of the torques can correspond to the drive torque.

[0013] The conversion rate and thus the conversion performance of the exhaust gas aftertreatment system, with which pollutants are converted into less hazardous products, depend in particular on the composition of the exhaust gas fed to the exhaust gas aftertreatment system and / or on the storage charge of the exhaust gas aftertreatment system, which in turn is related to the composition of the exhaust gas. Storage charge refers to the loading of the exhaust gas aftertreatment system, for example with oxygen; it describes the amount of oxygen temporarily stored in the exhaust gas aftertreatment system. The temperature of the exhaust gas aftertreatment system also influences the conversion rate. For example, the conversion rate is maximum at an operating temperature corresponding to the exhaust gas aftertreatment system and decreases at temperatures deviating from the operating temperature.

[0014] This is particularly important during a cold start of the first drive unit, where the temperature of the exhaust gas aftertreatment device essentially corresponds to its ambient temperature or is at least lower than the operating temperature. To ensure compliance with applicable emissions regulations, the first torque provided by the first drive unit is at least temporarily limited to a maximum torque. For example, the maximum torque is limited to a value that ensures that an emission limit specified for the exhaust gas component is not exceeded at a given temperature of the exhaust gas aftertreatment device.Only when the operating temperature is reached by the temperature of the exhaust gas aftertreatment device is the maximum torque adjusted towards a nominal torque of the first drive unit, in particular set to the nominal torque, or the limitation of the first torque to the maximum torque is lifted.

[0015] In particular, the first torque is limited to the maximum torque as long as the temperature of the exhaust aftertreatment system is below the operating temperature. Limiting the first torque is understood to mean an upper limit. If the first torque is less than the maximum torque, it corresponds to the first torque present before the limiting after the limiting. If, however, the first torque is greater than the maximum torque, the first torque is set equal to the maximum torque during the limiting process.

[0016] If the cold start of the first drive unit occurs at the start of travel, i.e., at the beginning of operation of the motor vehicle, a motor vehicle user typically expects such a restriction of the available drive torque. However, since the motor vehicle has the electric second drive unit and is therefore temporarily driven electrically, the cold start of the first drive unit can only occur after travel has begun, for example, due to a torque request from the user. In this case, the limitation of the first torque to the maximum torque is surprising to the user and leads to a restriction of the usability of the motor vehicle.

[0017] For this reason, the maximum torque should be determined as a function of the total distance traveled since the start of the journey. To do this, the exhaust gas component threshold value is first determined from the total distance traveled and the distance-related emission limit value. The total distance traveled is the distance traveled by the motor vehicle since the start of the journey. The start of the journey is understood, for example, to be a point in time at which the drive system is prepared for driving the motor vehicle, in particular by starting the first drive unit and / or operating the second drive unit to provide the second torque with a value other than zero.

[0018] Starting the first drive unit includes, in particular, increasing the speed of the first drive unit by towing, in particular to a minimum speed and / or an idle speed. The minimum speed is the lowest speed from which the first drive unit can automatically increase its speed further. The idle speed is a speed that is higher than the minimum speed. Alternatively, the start of travel is understood to mean the point in time at which the motor vehicle begins to move.

[0019] The distance-related emission limit relates to at least one exhaust component of the exhaust gas and specifies the quantity of the exhaust component permitted to be released into the outside environment per unit distance. For example, the distance-related emission limit is specified in grams per kilometer (g / km). The total distance traveled and the emission limit therefore determine the quantity of the exhaust component that the drive system is permitted to emit since the start of the journey. The exhaust component threshold is specified, for example, in grams (g).

[0020] Since the cold start of the first drive unit often occurs after the motor vehicle has already covered at least part of the total distance traveled electrically, i.e. solely using the electric traction motor, a comparatively large emissions budget is already available, which is described by the exhaust gas component threshold value. Accordingly, according to the invention, the maximum torque is determined at least temporarily as a function of the exhaust gas component threshold value. Thus, in particular after a section of the total distance traveled by means of the electric traction motor, after the first drive unit has been started, a higher first torque can be provided by the latter than with a maximum torque determined by the temperature of the exhaust gas aftertreatment device. This significantly improves the availability of the drive power of the drive device.

[0021] A further development of the invention provides that a cumulative exhaust component quantity is determined for the entire distance traveled by the motor vehicle, and the maximum torque is determined from a difference between the exhaust component threshold value and the exhaust component quantity. The cumulative exhaust component quantity describes the quantity of at least one exhaust component that the drive device has already emitted since the start of the journey, i.e., while traveling the entire distance. The emissions budget still available for the first drive unit results from the difference between the exhaust component threshold value and the exhaust component quantity; it therefore describes the quantity that the drive device could still have emitted while traveling the entire distance.

[0022] This amount is now immediately available for operating the primary drive unit, so that even when the primary drive unit is operated regardless of temperature, the distance-related emission limit is not exceeded and applicable regulations are reliably complied with. For example, the maximum torque is determined from the total difference. However, it can also be specified that only a portion of the difference, for example, a maximum of 80%, a maximum of 60%, or a maximum of 40% of the difference, is used to determine the maximum torque. This ensures reliable compliance with the emission limit.

[0023] A further development of the invention provides that the maximum torque is selected such that only a portion of the difference is used to operate the first drive unit. This has already been pointed out. Operating the first drive unit after it has been started should not consume the entire emissions budget, so that the power of the first drive unit remains available long-term after starting. For this reason, only that portion of the difference is used to determine the maximum torque, for example, a maximum of 80%, a maximum of 60%, or a maximum of 40% of the difference. Consequently, the advantages already mentioned are achieved.

[0024] A further development of the invention provides that the exhaust gas component threshold value is determined taking into account a minimum distance traveled from the total distance traveled. Therefore, if the total distance traveled is less than the minimum distance traveled, the exhaust gas component threshold value is determined from the minimum distance traveled, or the total distance traveled prior to determining the exhaust gas component threshold value is set equal to the minimum distance traveled. If the total distance traveled is greater than the minimum distance traveled, the total distance traveled is used directly to determine the exhaust gas component threshold value. In other words, a constant first distance traveled value is used for a first part of the total distance traveled, and a variable distance traveled value describing the distance traveled is used for a second part of the distance traveled. The minimum distance traveled is, for example, 10 km.Thus, the emission of a certain amount of the exhaust component is permitted from the start of the journey over the minimum distance. This amount only increases further once the minimum distance is reached and the total distance traveled is reached. The procedure described above achieves the advantages already explained.

[0025] A further development of the invention provides that the limiting is carried out, in particular only until the temperature of the exhaust gas aftertreatment device has reached a target temperature. Limiting is therefore carried out as long as the temperature of the exhaust gas aftertreatment device is lower than the target temperature. Once the target temperature is reached, the limiting is terminated, thus releasing the first torque without limitation. The target temperature is understood, in particular, to be the aforementioned operating temperature of the exhaust gas aftertreatment device. The described procedure ensures sufficient power of the drive device.

[0026] A further development of the invention provides that a first torque is determined from the exhaust gas component threshold value and a second torque from the temperature of the exhaust gas aftertreatment device, and the maximum torque is determined from the first torque and the second torque. The temperature of the exhaust gas aftertreatment device therefore influences the maximum torque in addition to the exhaust gas component threshold value. The first torque is determined from the exhaust gas component threshold value, in particular from the difference between the exhaust gas component threshold value and the exhaust gas component quantity, and the second torque is determined from the temperature. The second torque is selected, for example, such that an absolute emission limit value for the at least one exhaust gas component is maintained at the current temperature of the exhaust gas aftertreatment device.

[0027] The maximum torque is then determined proportionally from the first torque and the second torque. For example, the first torque contributes a first portion to the maximum torque and the second torque contributes a second portion. The first portion is, for example, at least 60%, at least 75% or at least 90% and the second portion is at most 10%, at most 25% or at most 40%. In the manner described, not only the distance-related emission limit but also the absolute emission limit is reliably complied with. The absolute emission limit is understood to be a limit value that describes, for example, the permissible proportion of at least one exhaust gas component in the exhaust gas released into the outside environment.

[0028] A further development of the invention provides that the starting is performed as part of an initial start or a restart. The initial start is understood to be the first start of the first drive unit since the start of the journey. In the case of a restart, the first drive unit has already been started for the first time during the start of the journey, after which it was stopped again. In either case, the first drive unit is started as a cold start, meaning the temperature of the exhaust gas aftertreatment system is lower than the operating temperature. This again serves to achieve the advantages already mentioned.

[0029] A further development of the invention provides that the starting takes place at a time interval from the start of the journey, in particular when the total distance traveled is different from zero. The first drive unit is therefore not started at the start of the journey, but only later. For example, the motor vehicle is initially driven solely with the aid of the second drive unit, which alone provides the drive torque for this purpose. Preferably, the motor vehicle, using the second drive unit, already covers a total distance traveled that is different from zero before the first drive unit is started. In this case, an emissions budget is already available which is greater than the emissions budget available at the start of the journey. This applies in particular if the first drive unit is started when the total distance traveled is greater than the minimum distance traveled.This ensures that the drive system delivers high performance in a particularly reliable manner.

[0030] The invention further relates to a drive device for a motor vehicle, in particular for carrying out the method according to the statements in the context of this description, which has a first drive unit generating exhaust gas, a second drive unit designed as an electric traction machine and an exhaust gas aftertreatment device for aftertreating the exhaust gas, wherein the drive device is provided and designed to generate a drive torque provided by the drive device at least temporarily by means of the first drive unit and the second drive unit jointly and to limit a first torque provided by the first drive unit as part of the drive torque to a maximum torque at least temporarily.

[0031] The drive device is further provided and designed to determine an exhaust gas component threshold value for a total distance traveled by the motor vehicle since the start of its journey using a distance-related emission limit value for at least one exhaust gas component of the exhaust gas and, after starting the first drive unit, to determine the maximum torque at least temporarily as a function of the exhaust gas component threshold value.

[0032] The advantages of such a design of the drive device or such a procedure have already been pointed out. Both the drive device and the method for its operation can be further developed according to the explanations in this description, so reference is made to these in this regard.

[0033] Furthermore, the invention relates to a computer program product comprising instructions that cause the drive device to execute the explained method steps according to the embodiments of this description. Regarding the advantages and possible advantageous developments, reference is made to the entire description.

[0034] The features and feature combinations described in the description, in particular the features and feature combinations described in the following description of the figures and / or shown in the figures, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also considered to be encompassed by the invention that are not explicitly shown or explained in the description and / or the figures, but which follow from or can be derived from the explained embodiments.

[0035] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. Fig. 1 a diagram in which an emission budget and a maximum torque for a first drive unit of a drive device are plotted over time.

[0036] The Fig.1 shows a diagram explaining a method for operating a drive device for a motor vehicle. The drive device has a first drive unit, in particular an internal combustion engine, which generates exhaust gas, and a second drive unit designed as an electric traction machine. The two drive units jointly generate, at least temporarily, a drive torque provided by the drive device. The first drive unit serves to provide a first torque and the second drive unit provides a second torque, wherein the drive torque results from the sum of the first torque and the second torque. The exhaust gas generated by the first drive unit is fed to an exhaust gas aftertreatment device for aftertreatment. After passing through the exhaust gas aftertreatment device, the exhaust gas is discharged into an environment external to the drive device.In order to prevent an inadmissibly high amount of at least one exhaust gas component of the exhaust gas from entering the outside environment, the first torque provided by the first drive unit is at least temporarily limited to a maximum torque.

[0037] The maximum quantity of exhaust gas component that may be released into the outside environment by the drive system is described by an emissions limit value which depends on the distance traveled by the motor vehicle. In order to be able to provide the highest possible drive power of the drive system or the highest possible drive torque at all times, an exhaust gas component threshold value is determined from the distance-related emissions limit value and the total distance traveled by the motor vehicle since the start of the journey. The maximum torque is then determined from the exhaust gas component threshold value and the first torque is limited to the maximum torque, at least temporarily. The limitation preferably occurs until, and in particular only until, a temperature of the exhaust gas aftertreatment system has reached or exceeded an operating temperature of the exhaust gas aftertreatment system.

[0038] In the diagram, curve 1 describes the exhaust component threshold value over time. It can be seen that this value remains constant up to a point in time t1. This is because it is calculated taking into account a minimum distance, for example, 10 km, which the vehicle has traveled up to time t1. Subsequently, the exhaust component threshold value continues to rise with increasing total distance traveled.

[0039] Curves 2, 3, and 4 describe the quantity of the exhaust component over time. In the case of curve 2, the first drive unit is started immediately at the start of travel. To always maintain the exhaust component threshold, the first torque is severely limited. For curve 3, the first drive unit is started later, namely shortly before time t1 is reached. Since the vehicle has completely covered the entire distance traveled so far, the quantity of exhaust component is zero. Accordingly, a significantly larger first torque can be permitted without reaching the exhaust component threshold.

[0040] For curve 4, the first drive unit is started even later, namely well after time t1. This means that an even larger emissions budget is available, so that the first torque can be selected to be even higher. This fact is clearly illustrated by curve 5, which shows the maximum torque for the three cases mentioned. For curve 2, a maximum torque of 30 Newton meters is available, for curve 3 a maximum torque of 100 Newton meters, and for curve 4 a maximum torque of 200 Newton meters; these values ​​are purely exemplary. In any case, it is clear that the described procedure ensures satisfactory driving performance of the vehicle even with a cold start of the first drive unit. LIST OF REFERENCE SYMBOLS: 1 History 2 History 3 History 4 History 5 History QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2018 / 0156095 A1

[0002] US 11,560,136 B2

[0003]

Claims

[1] Method for operating a drive device for a motor vehicle, which has a first drive unit generating exhaust gas, a second drive unit designed as an electric traction machine and an exhaust gas aftertreatment device for aftertreating the exhaust gas, wherein a drive torque provided by the drive device is generated at least temporarily by means of the first drive unit and the second drive unit together and a first torque provided by the first drive unit as part of the drive torque is limited at least temporarily to a maximum torque, characterized bythat an exhaust gas component threshold value is determined for a total distance traveled by the motor vehicle since the start of the journey using a distance-related emission limit value for at least one exhaust gas component of the exhaust gas and, after starting the first drive unit, the maximum torque is determined at least temporarily as a function of the exhaust gas component threshold value. [2] Method according to claim 1, characterized by that a cumulative exhaust component quantity is determined for the total distance travelled by the motor vehicle and the maximum torque is determined from a difference between the exhaust component threshold value and the exhaust component quantity. [3] Method according to one of the preceding claims, characterized by that the maximum torque is selected in such a way that only part of the difference is used to operate the first drive unit. [4] Method according to one of the preceding claims, characterized by that the exhaust gas component threshold value is determined taking into account a minimum driving distance from the total driving distance. [5] Method according to one of the preceding claims, characterized by that the limitation is carried out until a temperature of the exhaust aftertreatment device has reached a target temperature. [6] Method according to one of the preceding claims, characterized by that a first torque is determined from the exhaust gas component threshold value and a second torque is determined from the temperature of the exhaust gas aftertreatment device and the maximum torque is determined from the first torque and the second torque. [7] Method according to one of the preceding claims, characterized by that the start is carried out as part of a first start or a restart. [8] Method according to one of the preceding claims, characterized bythat the start is carried out at a different time than the start of the journey. [9] Drive device for a motor vehicle, in particular for carrying out the method according to one or more of the preceding claims, which has a first drive unit generating exhaust gas, a second drive unit designed as an electric traction machine and an exhaust gas aftertreatment device for aftertreating the exhaust gas, wherein the drive device is provided and designed to generate a drive torque provided by the drive device at least temporarily by means of the first drive unit and the second drive unit jointly and to limit a first torque provided by the first drive unit as part of the drive torque at least temporarily to a maximum torque, characterized bythat the drive device is further provided and designed to determine an exhaust gas component threshold value for a total distance traveled by the motor vehicle since the start of its journey, using a distance-related emission limit value for at least one exhaust gas component of the exhaust gas, and to determine the maximum torque at least temporarily as a function of the exhaust gas component threshold value after starting the first drive unit. [10] Computer program product comprising instructions which cause the drive device according to claim 9 to carry out the method steps according to one or more of claims 1 to 8.

Images