Method and device for managing the temperature of an exhaust gas aftertreatment system of a pollutant-discharging motor vehicle

Abstract

A method for actuating a heat source for a component of an exhaust system of a drive of a motor vehicle is described. The method includes providing information items relating to a future traveling route of the motor vehicle; ascertaining a chronological sequence of a multiplicity of temperature values in the component within a predefined future time segment, where the ascertainment of the chronological sequence is based on the provided information items; determining a point in time within the time segment on the basis of the ascertained chronological sequence, where a temperature value of the multiplicity of temperature values which is assigned to the point in time is intended to satisfy a predefined criterion; and actuating the heat source before the point in time such that the temperature value satisfies the specified criterion at the point in time.

Claims

1. A method executed by a control unit for actuating a heat source for a component of an exhaust system of a drive of a motor vehicle, the method comprising: determining a current vehicle mass of the motor vehicle; providing information items relating to a future traveling route of the motor vehicle; determining a power profile of a power of the drive within a predefined future time segment, the power profile based on the vehicle mass; ascertaining a chronological sequence of a multiplicity of temperature values in the component within the time segment, wherein the ascertainment of the chronological sequence is based on the provided information items and the power profile; determining a point in time within the time segment on the basis of the ascertained chronological sequence, wherein a temperature value of the multiplicity of temperature values which is assigned to the point in time is intended to satisfy a predefined criterion; and actuating the heat source before the point in time such that the temperature value satisfies the specified criterion at the point in time, wherein actuating the heat source results in energy-efficient temperature management for the exhaust system of the drive of the motor vehicle.

2. The method as claimed in claim 1, wherein the ascertainment of the chronological sequence comprises: determining a heat quantity profile of a heat quantity which is supplied to the component within the time segment, wherein the heat quantity is generated by the drive and wherein the ascertainment of the chronological sequence is based on the heat quantity profile.

3. The method as claimed in claim 1, wherein the determination of the power profile is based on the information items relating to the future traveling route.

4. The method as claimed in claim 1, furthermore comprising: determining a speed profile of the motor vehicle within the time segment, wherein the determination of the power profile is based on the speed profile.

5. The method as claimed in claim 1, furthermore comprising: providing further information items which are indicative of the motor vehicle, wherein the further information items comprise a driving resistance curve of the motor vehicle; wherein the determination of the power profile is based on the further information items.

6. The method as claimed in claim 1, wherein the determination of the power profile includes a variation of the power profile such that an energy consumption of the drive is reduced.

7. The method as claimed in claim 1, wherein the determination of the point in time is based on the power profile.

8. The method as claimed in claim 1, wherein the drive has an internal combustion engine.

9. The method as claimed in claim 8, furthermore comprising: determining a fuel consumption of the internal combustion engine on the basis of the power profile, wherein the determination of the power profile comprises a variation of the power profile such that the fuel consumption of the internal combustion engine is reduced.

10. The method as claimed in claim 1, wherein the point in time is determined such that an emission of a pollutant from the exhaust system is reduced, the emission of the pollutant being an emission averaged over the time segment.

11. The method as claimed in claim 10, wherein the pollutant has at least one of carbon monoxide, carbon dioxide, nitrogen oxides, ammonia, hydrocarbons, particles and fine dust.

12. The method as claimed in claim 1, wherein the heat source has the drive.

13. The method as claimed in claim 12, wherein the heat source furthermore has a heating device being an electrical heating device.

14. The method as claimed in claim 13, wherein the heating device is operated at least partially by a supply of energy that is obtained by recuperation during a braking operation of the vehicle.

15. The method as claimed in claim 1, wherein the component has at least one exhaust-gas aftertreatment device including a particle filter and/or a catalytic converter.

16. The method as claimed in claim 1, wherein the predefined criterion has a condition that the temperature value lies above a predefined temperature threshold value.

17. The method as claimed in claim 1, wherein the predefined criterion has a condition that the temperature value lies below a predefined further temperature threshold value.

18. A control unit for actuating a heat source for a component of an exhaust system, the control unit configured to execute a method comprising: determining a current vehicle mass of the motor vehicle; providing information items relating to a future traveling route of a motor vehicle; determining a power profile of a power of the drive within a predefined future time segment, the power profile based on the vehicle mass; ascertaining a chronological sequence of a multiplicity of temperature values in the component within the time segment, wherein the ascertainment of the chronological sequence is based on the provided information items; determining a point in time within the time segment on the basis of the ascertained chronological sequence, wherein a temperature value of the multiplicity of temperature values which is assigned to the point in time is intended to satisfy a predefined criterion; and actuating the heat source before the point in time such that the temperature value satisfies the specified criterion at the point in time.

19. A motor vehicle having a control unit for actuating a heat source for a component of an exhaust system, the control unit configured to execute a method comprising: determining a current vehicle mass of the motor vehicle; providing information items relating to a future traveling route of the motor vehicle; determining a power profile of a power of the drive within a predefined future time segment, the power profile based on the vehicle mass; ascertaining a chronological sequence of a multiplicity of temperature values in the component within the time segment, wherein the ascertainment of the chronological sequence is based on the provided information items; determining a point in time within the time segment on the basis of the ascertained chronological sequence, wherein a temperature value of the multiplicity of temperature values which is assigned to the point in time is intended to satisfy a predefined criterion; and actuating the heat source before the point in time such that the temperature value satisfies the specified criterion at the point in time.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a flow diagram of a method according to the disclosure.

(2) FIG. 2 schematically shows a detail of an internal combustion engine of a vehicle according to the disclosure.

(3) Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

(4) Before the disclosure is described in more detail with reference to the drawings, some fundamental considerations will firstly be summarized.

(5) The problem of energy-efficient actuation of heat sources for components in the exhaust system of a drive is solved through networking of various information items that are today, or will foreseeably in the future be, available in real time in the vehicle. These information items are available to the system in real time. One focus of the disclosure is on a high level of automated driving (up to and including fully autonomous driving). However, individual steps may also be used in the context of solving the problem during conventional driving operation, which is predominantly pre-selected by the driver, with limited information availability.

(6) Important steps lie in the linking of information items to predict the use of heat sources which contribute to the temperature management of the exhaust-gas aftertreatment system. For this purpose, the speed profile of the driving cycle, and the contribution of the individual drives as drive and thermal power over the course of time, are predicted. Using the predicted local temperature profile of the exhaust-gas aftertreatment system, strategies for further reducing energy demand can be optimized over time without this resulting in a departure from the required temperature window. Furthermore, particular processes for maintaining the conversion, the regeneration or other processes dependent on temperature windows can be set in terms of the point in time, such that no additional energy expenditure is required for such processes.

(7) One advantage lies in the fact that the requirements of the exhaust-gas aftertreatment system may be implemented with minimal energy by the drive strategy that is assumed to be optimal in terms of energy.

(8) Here, the disclosure allows both short-term management and long-term management, which may relate to the present driving cycle but may also operate across multiple driving cycles. The short-term management makes corrections to the most recent predicted values and thus reacts to unpredictable cross-influences. The driving-cycle-related management and also the long-term management are made more precise by way of continuous updating in accordance with the actual profile.

(9) One example is the regeneration of a particle filter. If this is not performed proceeding from ongoing driving operation (for example when driving on a freeway) because the required exhaust temperature window is not reached, this must be forced by way of additional energy expenditure. If such a point in time is approaching, the system can define the subsection in which the additional energy expenditure is minimal. Otherwise, the forced regeneration in accordance with the degree of loading of the particle filter (triggered by an exceedance of the threshold value) would possibly fall within a city driving section with low exhaust-gas temperatures and cause high additional energy consumption.

(10) Another example is the optimum point in time for the activation of a heating disk in the exhaust-gas aftertreatment system in conjunction with the prediction of when the internal combustion engine will be activated for the first time in the driving cycle.

(11) FIG. 1 shows a flow diagram of a method for actuating a heat source for a component of an exhaust system of a drive of a motor vehicle according to the disclosure.

(12) The method is for the temperature management of an exhaust-gas aftertreatment system of a pollutant-emitting motor vehicle and has the following steps:

(13) In a 1st step S101, the present vehicle mass is ascertained. The present vehicle mass may be ascertained by sensors that ascertain this quantity directly or indirectly. An indirect detection may be performed by seat occupancy sensors, interior cameras, seat belt sensors, sensors on fastening brackets or holders, by means of which the present vehicle mass is ascertained on the basis of the curb weight plus an estimated payload.

(14) In a 2nd step S102, the driving resistance curve is determined. This may be stored in the form of a vehicle-specific database or derived from previous journeys using empirical values.

(15) Workshop-specific information items (for example the type of tire used) and also other available information items such as tire pressure or outside temperature can increase the exactness of the driving resistance curve used hereinafter. Special cases such as the use of a trailer, roof rack, roof boxes can likewise be ascertained by sensors or indirectly and taken into consideration in the driving resistance curve. Here, present weather conditions (wind strength and direction, road condition owing to rain or snow, etc.) are incorporated generally or in certain sections. If known, the road condition can also be incorporated.

(16) In a 3rd step S103, the traveling route, at least various information items relating to the traveling route, is/are provided. This can commonly be performed on the basis of the present position of the vehicle via GPS and the destination input by the vehicle driver via a human/machine interface (HMI). This means that the entire traveling route may be known to the system. However, it can likewise be sufficient to know subsections of the traveling route or to know the likely route on the basis of repeated trips.

(17) In a 4th step S104, a speed profile is determined. On the basis of route maps with an exact altitude profile and information items from driver assistance systems, the speed profile is ascertained taking into consideration the admissible maximum speed and, on the basis of this, by way of the driving resistance curve, a power profile of the vehicle drive or drive power profile for the driving cycle that will foreseeably occur is ascertained. If the drive power profile exceeds the maximum power of the system, the speed profile is adapted accordingly. The acceleration or deceleration behavior of the vehicle can be implemented on the basis of networking-based energy management in the case of fully autonomous driving operation, or with incorporation of the identified driver/driver type. Taking into consideration present information items such as the local traffic density or known obstacles on the route (roadworks, slow-moving traffic or traffic jams, traffic light cycles, traffic movements around intersections such as roundabouts, etc.), this results in the predicted speed profile.

(18) In a 5th step S105, the power profile of the drive or the drive power profile is determined. The drive power profile may be determined on the basis of aspects of energy efficiency and the available energy during the journey. In some examples, individual subsections, which are initially to be uniquely identified, may be ascertained with regard to the drive source used or the drive sources used or the strategy used.

(19) In the case of a hybrid drive selected as an example, these may include inter alia the following subsections: subsections in which the vehicle rolls in relation to the admissible speed; subsections in which the vehicle sails in relation to the admissible speed, that is to say the electric drive is activated in order to maintain the speed; subsections in which the internal combustion engine is deactivated and purely electric driving takes place (for example temporary stop-and-go operation); subsections in which the internal combustion engine is reliably activated, for example because purely electric driving is in no case sufficient owing to an uphill gradient; subsections in which a deceleration to a standstill must take place after rolling operation. The event of a recuperation process is highly likely here. This is reliably foreseeable, for example in the case of stop signs on the route; subsections to which a drive power range can be assigned (for example in a 30 km/h zone, even under conceivable extreme conditions, it can be ruled out that the nominal power of the internal combustion engine will be demanded).

(20) In a 6th step S106, a heat quantity profile is determined for a heat quantity which is generated by a drive and which is supplied to the exhaust system or to a component of the exhaust system. In all subsections in which a drive must imperatively be used in order to achieve the predicted speed profile, the heat contribution provided by this drive for heating up the exhaust-gas aftertreatment system is ascertained. In the case of the internal combustion engine, taking into consideration the efficiency, the power output correlates with the heat flow emitted, wherein CO2-optimum operation, that is to say operation which is optimal with regard to the overall efficiency, is generally to be assumed.

(21) In a 7th step S107, further sections of the heat quantity profile are determined. To all of the subsections ascertained in the 6th step S106 that contribute to the heating of the exhaust-gas aftertreatment system, there are added the subsections in which the temperature of the exhaust-gas aftertreatment system reliably decreases owing to a lack of heat input.

(22) In an 8th step S108, the specific requirements of the exhaust-gas aftertreatment system are ascertained in model-based fashion from the predicted power profile. For example, time windows are specified in which particular temperature windows should be attained in the exhaust-gas aftertreatment system. This 8th step S108 may take place with the incorporation of untreated emissions models of the internal combustion engine. In addition, it is for example possible to define a catalytically active partial volume of a catalytic converter which is required in order to convert the pollutant mass flow, which is coupled to the power profile, in the exhaust-gas aftertreatment system to a high degree. The increase in the loading of a particle filter can likewise be predicted by way of this.

(23) In a 9th step S109, it is determined when a temperature value in the exhaust system satisfies particular predefined criteria. In some examples, all subsections of the driving profile or the traveling route in which a required temperature window is reliably attained can be ascertained on the basis of the 8th step S108. If this is the case, it can also be checked whether the further conditions for the conditioning of the exhaust-gas aftertreatment system can with high probability be implemented in the subsection. For example, a freeway section without a speed limit can with high probability be used for a particle filter regeneration owing to the certain use of the internal combustion engine in the case of current hybrid systems and the high exhaust-gas temperatures.

(24) In a 10th step S110, it is determined when a temperature value in the exhaust system does not satisfy particular predefined criteria. In a reversal of the 9th step S109, it is now possible to ascertain those subsections of the driving profile that may possibly lead to a departure from a required temperature window. It is possible to ascertain subsections in which entry into the temperature window will become imperatively necessary in order that no excessive pollutant emissions, an inadmissible reduction in efficiency of parts of the exhaust-gas aftertreatment system or even (partial) damage to the system occurs (so-called temperature-critical subsections).

(25) In an 11th step S111, it is checked whether the subsections ascertained in the 10th step S110 can be shortened or avoided in an energy-neutral manner by way of a change in the power profile, such as in the drive strategy, and thus in the higher-level thermal management. If this is possible, the power profile, such as the planned drive strategy, is corrected accordingly.

(26) In a 12th step S112, heat sources are actuated such that temperature values in the exhaust system satisfy predefined criteria at a predefined point in time. Such a heat source may for example be the internal combustion engine of the vehicle or an electrical heating device, for example a heating disk, in the exhaust system. For the remaining temperature-critical subsections, the strategy as to how the exhaust-gas aftertreatment system or parts thereof may be brought into the temperature window is ascertained by analyzing the likely status of the heat sources/sinks available at the point in time. Here, the variant that allows the least expenditure of energy for the raising or lowering of the temperature level is preferentially chosen.

(27) In preparation for travel, steps 1 to 12 may be used to predict drive, energy and thermal management for the entire journey, taking into consideration any information items available in the system or provided by networking.

(28) In a 13th step S113 and a 14th step S114, deviations from the predicted profile are taken into consideration. Such deviations may result from all of the influencing factors that were not included in the prediction. These are primarily those that have a short-term and rather random influence on the course of travel (for example a required vehicle deceleration owing to unpredictable events and obstacles occurring on the road or along the route). Therefore, the predicted setpoint profile of the relevant variables, for example the traveling route, the chronological sequence of the temperature value, the speed profile and/or the power profile, must be continuously compared with the real driving profile.

(29) Here, in the 13th step S113, a continuous short-term adaptation of the strategies is performed in order that the required operation of the exhaust-gas aftertreatment system can take place in a precisely accurate manner.

(30) In the 14th step S114, the adaptations made in step 13 are taken into consideration in the predicted profile. In parallel with the respectively presently occurring driving operation, steps 1 to 12 are carried out continuously in order to update and refine the forecast. Furthermore, the information items learned during one driving cycle may be incorporated into the precalculation of the next driving cycle by the system.

(31) FIG. 2 schematically shows a detail of an internal combustion engine 100 of a vehicle according to the disclosure.

(32) A fresh-air path of the internal combustion engine 100 begins at the gas inlet 110 of the internal combustion engine, at which an air filter 111 is arranged. The supply of fresh air to the engine can be adjusted, and thus the cylinder charging can be influenced, by various active or passive adjusting elements in the fresh-air path. Such adjusting elements are for example throttle flaps 112, 115, air recirculation flaps 113, air cycle valves 116, swirl or tumble flaps 117 or a compressor 114 of an exhaust-gas turbocharger.

(33) The gas supply into the exhaust system of an internal combustion engine can be adjusted by a fully or partially variable valve drive 120. In some examples, the gas flow (exhaust-gas mass flow) through various components in the exhaust system, for example through a catalytic converter 130, can be controlled in closed-loop fashion and fluidically influenced by various active or passive adjusting elements in the gas path of the exhaust system. Such adjusting elements are for example exhaust-gas flaps 123, a wastegate 122 or a variable turbine geometry (VTG) actuator 121 in the turbine of an exhaust-gas turbocharger.

(34) An exhaust-gas recirculation (EGR) arrangement can produce a connection between the exhaust system and the fresh-air path. The connection may branch off upstream of the catalytic converter (high pressure EGR) or downstream of the catalytic converter (low pressure EGR). The exhaust-gas recirculation arrangement may be controlled in closed-loop fashion for example by EGR valves or EGR flaps 125.

(35) The catalytic converter 130 includes a heating device 140 with heating elements, for example heating disks. An electronic control unit 150 controls the fuel supply to the internal combustion engine 100, the heating device 140 and the active and passive adjusting elements in the gas path between gas inlet 110 and gas outlet 124.

(36) A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.