Method for operating a drive unit for a motor vehicle and corresponding drive unit

Abstract

Method for operating a drive unit (1) for a motor vehicle, which has an exhaust gas generating drive unit (2) and an exhaust gas aftertreatment device (3) in the form of a three-way catalytic converter for aftertreatment of the exhaust gas, wherein, during operation of the motor vehicle, a quantity of a pollutant component of the exhaust gas is accumulated since the start of operation and an operating parameter of the motor vehicle is adjusted on the basis of the quantity of pollutant component related to a distance traveled by the motor vehicle since the start of operation, wherein, during operation, a further quantity of a pollutant component of the exhaust gas is accumulated since the start of operation.wherein the operating parameter of the motor vehicle is adjusted on the basis of the additional pollutant component quantity related to the distance traveled by the motor vehicle since the start of driving operation, wherein hydrocarbon is used as a pollutant component and nitrogen oxide as a further pollutant component, wherein the operating parameter is adjusted in a first direction when a threshold value is exceeded by the pollutant component quantity related to the distance traveled and in a second direction different from the first direction when a further threshold value is exceeded by the further pollutant component quantity related to the distance traveled, wherein a lambda setpoint for a lambda control (7) is used as the operating parameter, characterized in thatthat the lambda setpoint is adjusted depending on the aging state of the exhaust aftertreatment system and is subsequently used to operate the drive system (1) during further driving after the motor vehicle has been switched off.

Description

- MAIN PROPOSAL -

[0001] The invention relates to a method for operating a drive unit for a motor vehicle, which has an exhaust gas-generating drive unit and an exhaust gas aftertreatment device in the form of a three-way catalytic converter for aftertreating the exhaust gas, whereby, during operation of the motor vehicle, a quantity of a pollutant component of the exhaust gas is accumulated since the start of operation, and an operating parameter of the motor vehicle is adjusted based on the quantity of pollutant component related to a distance traveled by the motor vehicle since the start of operation, wherein, during operation, a further quantity of a pollutant component of the exhaust gas is accumulated since the start of operation.wherein the operating parameter of the motor vehicle is adjusted based on the amount of additional pollutants related to the distance traveled by the motor vehicle since the start of operation, wherein hydrocarbons are used as a pollutant component and nitrogen oxides as a further pollutant component, wherein the operating parameter is adjusted in a first direction when the threshold value is exceeded by the amount of pollutants related to the distance traveled, and in a second direction different from the first when a further threshold value is exceeded by the amount of additional pollutants related to the distance traveled, wherein a lambda setpoint for lambda control is used as the operating parameter. The invention further relates to a drive unit for a motor vehicle.

[0002] For example, prior art is known from US document 2017 / 0 138 285 A1. This document describes a system comprising: an exhaust aftertreatment system configured to treat emissions from an internal combustion engine via a catalyst; and a controller configured to determine an operating parameter indicating catalyst performance, determine a deterioration factor describing the deterioration of the catalyst at least partially based on the operating parameter, determine an adjustment term configured to modify an air-fuel ratio command for the internal combustion engine to account for the catalyst deterioration factor, and generate a signal indicating the adjustment term.

[0003] The publication DE 10 2020 212 725 A1 relates to a method for operating an internal combustion engine comprising providing and burning an air-fuel mixture with a first composition, determining a current composition of a combustion exhaust gas produced during combustion, determining an emission collective which, for at least one component of the combustion exhaust gas, comprises a total quantity emitted over a predetermined interval, from several successively determined current compositions of the combustion exhaust gas, and adjusting a second composition of the air-fuel mixture depending on the determined emission collective.

[0004] Furthermore, document US 2017 / 0 328 294 A1 discloses a method and a system for monitoring the condition of a vehicle catalyst.

[0005] The following documents are also known from the prior art: DE 10 2016 208 834 A1, DE 43 19 282 C1, DE 10 2018 213 076 A1, US 2021 / 0 332 769 A1, DE 10 2018 124 869 A1, DE 10 2016 224 135 A1, DE 10 2019 116 774 A1, US 2022 / 0 316 416 A1 and DE 10 2017 218 327 A1.

[0006] The object of the invention is to propose a method for operating a drive unit for a motor vehicle which has advantages over the prior art, in particular reliably monitoring pollutant emissions from the drive unit in order to ensure compliance with limit values.

[0007] According to the invention, this is achieved by a method for operating a drive unit for a motor vehicle with the features of claim 1.

[0008] Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments described in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are possible.

[0009] The drive system serves to propel the motor vehicle, thus providing the drive torque directed towards propelling the motor vehicle. To provide this drive torque, the drive system comprises the drive unit, which is preferably designed as an internal combustion engine. During operation, the drive unit is supplied with fuel and fresh gas at least intermittently, the fresh gas containing fresh air at least intermittently. Additionally, the fresh gas may contain exhaust gas if exhaust gas recirculation is implemented, in which the exhaust gas generated by the drive unit is at least partially returned to the drive unit as a component of the fresh gas. The fuel and fresh gas supplied to the drive unit form a fuel-fresh gas mixture with a specific composition, which is then reacted within the drive unit.

[0010] During operation of the engine, exhaust gas is produced due to the chemical reaction of fuel and fresh air. This exhaust gas is discharged towards the outside environment of the engine or vehicle. Since the exhaust gas produced by the engine contains pollutants, it is first routed to an exhaust aftertreatment system before being released into the environment. In the exhaust aftertreatment system, the pollutants are at least partially converted into less harmful products. Only after passing through the exhaust aftertreatment system is the exhaust gas discharged into the environment. The exhaust aftertreatment system is typically a vehicle catalytic converter, specifically a three-way catalytic converter. However, it can also be designed as a particulate filter, particularly a gasoline particulate filter, with an integrated vehicle catalytic converter, for example, with a catalytic coating.

[0011] To prevent the emission of an impermissibly high quantity of pollutants, it is planned to accumulate the quantity of pollutants emitted since the start of driving. Driving is defined as the period between the start and end of driving. Driving begins at the start point and ends at the end point. Driving begins as soon as the drive system or drive unit is engaged or prepared for movement. This means that driving begins, in particular, when the driver activates the drive system or drive unit, for example, by turning on the ignition.

[0012] Driving mode ends when the driver switches off the drive system or drive unit, for example, by deactivating the ignition. Driving mode begins when the drive system or drive unit is switched on, and driving mode ends when it is switched off. When not in use, the vehicle is stationary, particularly with the parking brake engaged.

[0013] Throughout the entire driving process, from the start to the end, the quantity of pollutants is determined cumulatively or integrally. This means, in particular, that the pollutant throughput is determined and accumulated or integrated over time to obtain the total quantity. The quantity of pollutants is then expressed, for example, in a unit of weight, especially in milligrams.

[0014] The pollutant component throughput is calculated, for example, by multiplying the pollutant component concentration in the exhaust gas by the exhaust gas flow rate, i.e., the amount of exhaust gas flowing from the engine to the outside environment per unit of time. The pollutant component quantity can be determined in any way. For example, it can be determined based on a sensor reading and / or using a pollutant model. The sensor could be, for example, a lambda sensor or a NO sensor. x -Sensor, an oxygen sensor, or similar. The pollutant component is, for example, hydrocarbon or nitrogen oxide.

[0015] The amount of pollutants is calculated based on the distance traveled by the vehicle since the start of operation. The distance traveled is therefore reset at the start of the journey, for example to zero or a value just slightly greater than zero, to avoid errors when dividing the amount of pollutants by the distance traveled. The amount of pollutants calculated based on distance traveled is expressed in a unit that describes the mass of the pollutants relative to the distance traveled, for example, grams per kilometer.

[0016] The value derived from relating the amount of pollutants to the distance traveled, i.e., from dividing the amount of pollutants by the distance traveled, is used to adjust the operating parameters of the vehicle, particularly the drive system or drive unit. The operating parameter, or at least a change in the operating parameter, is thus a function of this value. The described procedure ensures that a distance-related limit value for the pollutant is reliably met.

[0017] A further development of the invention provides that, if the distance traveled since the start of operation falls below a minimum distance, the minimum distance is used as the distance traveled; otherwise, the actual distance traveled is used. The actual distance traveled is thus recorded, for example, by means of a suitable sensor, a navigation device, or the like. If the actual distance traveled is less than the minimum distance, the minimum distance is used to determine the aforementioned value, which results from dividing the amount of pollutants by the distance traveled. Accordingly, in this case, the minimum distance is used as the distance traveled since the start of operation.

[0018] However, if the actual distance traveled is greater than or equal to the minimum distance traveled, the actual distance traveled is used as the distance traveled since the start of driving and used accordingly to determine the value. For example, a minimum distance of at least 5 km, at least 7.5 km, at least 10 km, at least 12.5 km, or at least 15 km is used as the minimum distance traveled. Preferably, the minimum distance is at least 8 km, at least 10 km, or at least 12 km. This approach achieves a realistic assessment of the pollutant emissions from the drive system, as it avoids unrealistically high values ​​for the value due to short distances traveled and prevents excessive influence of high pollutant component throughput at the start of driving on the vehicle's operating parameters.

[0019] A further development of the invention provides that the operating parameter is adjusted only if the amount of pollutants relative to the distance traveled exceeds a threshold value. Exceeding this threshold value is equivalent to excessive pollutant emissions. If this condition is met, pollutant emissions must be reduced to ensure compliance with the relevant limit value. For this reason, the operating parameter is adjusted only when the threshold is exceeded. This approach ensures reliable compliance with the limit value.

[0020] A further development of the invention provides that the operating parameter is adjusted in such a way as to reduce the amount of pollutants emitted per unit of distance traveled. For example, the adjustment is made depending on the pollutant component, with the direction in which the operating parameter must be adjusted for different pollutants to achieve the reduction in the amount of pollutants being stored. The described procedure enables reliable compliance with the limit value even with age-related changes in the drive system, in particular the exhaust aftertreatment system.

[0021] The invention provides that, during driving, the quantity of a further pollutant component in the exhaust gas is accumulated since the start of driving, and the vehicle's operating parameter is adjusted based on this additional pollutant component quantity relative to the distance traveled by the vehicle since the start of driving. The procedure for the additional pollutant component is identical to that for the other pollutant component; that is, the additional pollutant component quantity is determined and related to the distance traveled by the vehicle since the start of driving. The operating parameter, or its adjustment, is derived from this determined value.

[0022] The described procedure can be applied to any number of additional pollutant components, for example, to just one additional pollutant component or to several additional pollutant components. Accordingly, there could be, for instance, a first additional pollutant component, a second additional pollutant component, and so on. The explanations for the first pollutant component are analogous for each subsequent pollutant component or for each of the multiple additional pollutant components. The described procedure ensures reliable compliance with multiple limit values ​​for different pollutant components in the exhaust gas.

[0023] The invention provides that the operating parameter is adjusted in a first direction when the threshold value is exceeded by the amount of pollutant component related to the distance traveled, and in a second direction different from the first when a further threshold value is exceeded by the amount of additional pollutant component related to the distance traveled. The first and second pollutant components are thus pollutant components that require opposing adjustments of the operating parameter in order to reduce the respective amount of pollutant component.

[0024] If both operating parameters exceed their respective thresholds, the operating parameter for reducing the amount of pollutants is adjusted, for example, for the pollutant component for which the threshold value is exceeded further than the amount of pollutants related to the distance traveled. Alternatively or additionally, a fault signal may be generated. When the fault signal occurs, the driver is preferably notified, for example, visually and / or audibly. It may also be possible to deactivate the drive system or at least the drive unit, or reduce its rated power, to ensure compliance with the limit value or multiple limit values. In each case, this ensures that the drive system operates within the limit value.

[0025] A further development of the invention provides that at least one of the following parameters is used as an operating parameter: a control parameter of the lambda control, in particular relating to a modulation of a target combustion air ratio and / or an adjustment of the combustion air ratio following a deceleration operation of the drive device, a heating duration for the exhaust aftertreatment device, an operating parameter of a camshaft adjustment and an operating parameter of a gear shift transmission of the drive device.

[0026] The lambda setpoint describes the value to which the actual lambda value is adjusted using lambda control. Typically, the lambda setpoint is equal to one or at least nearly equal to one. However, depending on the age of the engine components, particularly the exhaust aftertreatment system, it may be necessary to adjust the lambda setpoint to ensure compliance with the limit value(s), so that the amount of pollutants emitted per unit of distance traveled is less than the threshold value.

[0027] Additionally, the control parameter of the lambda control can be used as an operating parameter. This describes, for example, the modulation of the air-fuel ratio, i.e., lambda modulation. For instance, a control parameter, such as the gain of a control element of the lambda control, is used as an operating parameter.

[0028] Additionally, the target air-fuel ratio and / or its change following overrun operation of the engine can be used. Overrun operation refers to the operation of the engine while it is driven by an external torque, particularly caused by the vehicle's movement. During overrun operation, the engine essentially draws fresh air or gas through the exhaust aftertreatment system, thus filling it with oxygen. Immediately following overrun operation, the lambda setpoint must be adjusted to reduce this saturation, allowing the temporarily stored oxygen to be discharged from the exhaust aftertreatment system.

[0029] Additionally, the heating duration for the exhaust aftertreatment system can be used as an operating parameter. The exhaust aftertreatment system includes a heating element that operates throughout the heating period to heat the system. The heating period preferably begins immediately upon commencement of driving and ends—depending on the duration of driving—before the end of driving. With increasing heating duration, the amount of pollutants is typically reduced, particularly at the beginning of driving. The camshaft adjustment can also be used as an operating parameter. The amount of pollutants can be influenced by adjusting the camshaft relative to the crankshaft in one direction or the other.

[0030] Furthermore, an operating parameter of the transmission can also be used. The transmission is part of the drive system and is located between the drive unit and at least one driven wheel axle of the vehicle. The transmission allows selection of one of several gears, corresponding to different gear ratios. The operating parameter of the transmission describes, in particular, the transmission shift points, for example, engine speeds, at which an upshift or downshift occurs.

[0031] It may be possible to use exactly one of the aforementioned parameters as an additional operating parameter. However, using multiple parameters, especially all parameters, is particularly preferred. The described approach ensures particularly reliable compliance with the limit values.

[0032] A further development of the invention provides that the operating parameter is subsequently used to operate the drive system during driving. According to the invention, the operating parameter is used to operate the drive system in subsequent driving operations following the initial driving phase after the vehicle has been switched off. In the former case, the change in the operating parameter has a direct influence on the currently ongoing driving operation. In the latter case, it has no effect or only a minor effect on the current driving operation, but is applied from the beginning of the subsequent driving operation. The procedure depends on the specific choice of the operating parameter. The advantages already mentioned can be achieved using the described procedure.

[0033] The invention provides that hydrocarbons are used as the pollutant component and nitrogen oxides, in particular nitrogen monoxide and / or nitrogen dioxide, as a further pollutant component. The pollutant component is thus hydrocarbons and the further pollutant component is nitrogen oxides, the latter containing nitrogen monoxide, nitrogen dioxide, or both. The aforementioned pollutant components are considered particularly critical. However, compliance with the respective limit values ​​can be ensured with the described procedure.

[0034] The invention naturally also relates to a method for operating a motor vehicle, wherein a drive unit of the motor vehicle is operated according to the descriptions in this document.

[0035] The invention further relates to a drive device for a motor vehicle with the features of claim 6, in particular for carrying out the method according to the explanations in this description.

[0036] The advantages of such a drive system design and such a procedure have already been mentioned. Both the drive system and the method for operating it can be further developed as described in this document, and reference is made to these details.

[0037] The features and combinations of features described in the description, in particular those described in the following figure description and / or shown in the figures, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown or explained in the description and / or the figures, but which emerge from or can be derived from the explained embodiments, are also to be considered as encompassed by the invention.

[0038] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without limiting the invention. The drawing shows: Fig. 1 a schematic representation of a drive unit for a motor vehicle, Fig. 2 several diagrams in which the curves for a driving operation of the motor vehicle with a first value of an operating parameter are plotted, as well as Fig. 3 several diagrams in which the curves for the driving operation of the motor vehicle are plotted for a second value of the operating parameter.

[0039] The Fig. Figure 1 shows a schematic representation of a drive unit 1 for a motor vehicle. The drive unit 1 includes a drive assembly 2, which in the embodiment shown here is designed as an internal combustion engine. Additionally, the drive unit 1 has an exhaust aftertreatment system 3, which is preferably a vehicle catalyst. During operation of the drive unit 1, fresh gas and fuel are supplied to the drive assembly 2 at least intermittently, where they react. The resulting exhaust gas is discharged via the exhaust aftertreatment system 3 towards the external environment of the drive unit 1. The direction of exhaust gas flow is indicated by arrow 4.

[0040] Viewed in the direction of exhaust gas flow, a first probe 5 is located upstream of the exhaust gas aftertreatment device 3 and a second probe 6 is located downstream. The two probes 5 and 6 serve to measure a property of the exhaust gas upstream and downstream of the exhaust gas aftertreatment device 3. In the illustrated embodiment, the probes 5 and 6 are lambda probes. The first probe 5 is preferably configured as a wideband lambda probe and the second probe 6 preferably as a narrowband lambda probe.

[0041] The composition of the fuel-air mixture reacted in the drive unit 2 is adjusted by means of a lambda control unit 7. This unit receives as input variables both a first air-fuel ratio determined from a measurement taken by the first sensor 5 and a second air-fuel ratio determined from a measurement taken by the second sensor 6. The lambda control unit 7 consists of the actual lambda controller 8 and a trim controller 9. The output variables of the controllers 8 and 9 are compared with a lambda setpoint value supplied via an input 10, namely by a corresponding computing unit 11. The lambda setpoint value represents an operating parameter of the motor vehicle or the drive unit 1.

[0042] It is intended that, during vehicle operation, the quantity of a pollutant component is determined cumulatively or integrally since the start of operation. This quantity is then related to the distance traveled since the start of operation. The resulting value, or the corresponding quantity of pollutants, is subsequently used to adjust the operating parameter, for example, to adjust the lambda setpoint.

[0043] The Fig. Figure 2 shows several diagrams. The first diagram (top left) shows curve 12, the second diagram (top right) shows curve 13, the third diagram (bottom left) shows curves 14 and 15, and the fourth diagram (bottom right) shows curves 16 and 17. Curve 12 describes the vehicle's speed over a distance traveled, expressed in kilometers per hour. Curve 13 shows the composition of the fuel-air mixture supplied to the drive unit 2 as the air-fuel ratio, also over the distance traveled. Curves 14 and 15 show the quantity of pollutants resulting from the vehicle's speed (curve 12) and the lambda value (curve 13) since the start of operation, based on the distance traveled by the vehicle since the start of operation, specifically for a first pollutant component of the exhaust gas.The first pollutant component is, for example, hydrocarbons.

[0044] Curves 16 and 17 show the same results for a second pollutant component of the exhaust gas, for example, nitrogen oxide. Curves 14 and 16 show the amount of pollutant components related to the distance traveled for a first variant of the exhaust aftertreatment system 3, while curves 15 and 17 show the amount for a second variant. The two variants differ, for example, only in their age. Curves 14 and 16, as shown, describe a newer variant of the exhaust aftertreatment system 3, while curves 15 and 17 describe an older variant.

[0045] Curves 13 to 17 describe the operation of the drive unit 2 with operating parameters optimized for the first variant of the exhaust aftertreatment system 3. It is clearly evident that, according to curves 14 and 16, the amount of pollutant components emitted is low for the first variant of the exhaust aftertreatment system 3. This also applies to the second variant of the exhaust aftertreatment system 3 for the first pollutant component, but not for the second pollutant component, as curves 15 and 17 show. In particular, a threshold value of 50 mg / km is exceeded for the second pollutant component.

[0046] The Fig.Figure 3 also shows the four diagrams already described, with curves 12 to 17. However, curves 13 to 17 show the operation of the drive unit 2 with a second value of the operating parameter, in this case the lambda setpoint, which is optimized for the second variant of the exhaust aftertreatment system 3. It can be seen that, according to curve 15, although the amount of pollutant component measured for the first pollutant component is now higher, it is still less than a limit of 55 mg / km. Furthermore, according to curve 17, the limit for the second pollutant component is now also met.

[0047] The described procedure ensures compliance with limit values ​​for the pollutant component, particularly regardless of the aging state of the exhaust aftertreatment system 3. REFERENCE MARK LIST: 1 Drive unit 2 Drive unit 3 Exhaust aftertreatment system 4 Arrow 5 1. Probe 6 2nd probe 7 Lambda control 8 Lambda controllers 9 trim controls 10 Entrance 11 Computing equipment 12 Course 13 Course 14 Course 15 Course 16 Course 17 Course

Images