Method and control device for operating a motor vehicle

Abstract

The invention relates to a method and a control device (12) for operating a motor vehicle (10). According to the invention, the driving operation of a motor vehicle (10) is blocked (52) after a failed starting attempt (50) due to insufficient starting torque of the motor vehicle (10). The performance of the motor vehicle (10) is checked for limitations (54a) and / or the previously calculated required starting torque is corrected (54b) based on information determined from the failed starting attempt. Based on a determined improvement in performance and / or a corrected required starting torque, the driving operation of the motor vehicle (10) is enabled again (56).

Description

[0001] The invention relates to a method and a control device for operating a motor vehicle.

[0002] When starting a motor vehicle from a standstill, insufficient power or torque can lead to situations where the vehicle does not start as desired or requested by the driver, or only starts with increased pressure on the accelerator pedal. Particularly on inclines, the vehicle may roll backward when the hold function is released, despite the accelerator pedal being pressed.

[0003] In order to prevent the vehicle from rolling back when starting off, it is known from the document US 2017 / 0089460 A1 that a torque that can be provided by the motor vehicle and a required starting torque for starting off are estimated and the vehicle's readiness to drive is issued depending on whether the required starting torque is exceeded by the available torque of the motor vehicle.

[0004] Furthermore, efforts are known whereby, in cases where an internal combustion engine cannot provide sufficient starting torque, an electric motor is additionally activated to provide additional starting torque to overcome the required starting torque and prevent the vehicle from rolling back. Examples of such hybrid vehicles are disclosed in documents DE 10 2018 221 398 A1 and DE 10 2013 104 515 A1.

[0005] However, it has been shown that, despite these efforts, situations still occur in which starting is not possible due to insufficient performance of the vehicle, there is a risk of rolling back and increased wear is caused by the failed attempt to start.

[0006] The invention is based on the object of developing a simple method for operating a motor vehicle which reduces the occurrence of situations in which the motor vehicle does not start despite the driving operation being authorized.

[0007] The object of the invention is achieved by a method and a control unit for operating a motor vehicle according to the independent patent claims. Preferred developments are the subject of the respective dependent claims.

[0008] A first aspect relates to a method for operating a motor vehicle. The motor vehicle preferably comprises an internal combustion engine. Particularly preferably, the motor vehicle further comprises an electric motor for additionally or alternatively providing a starting torque.

[0009] In one method step, a failed start-off attempt by the motor vehicle due to insufficient starting torque is detected. A failed start-off attempt is, for example, a failure of the motor vehicle to start moving or a rolling movement of the motor vehicle in the opposite direction of travel, for example after a hold function has been released while the motor vehicle is stationary. In this respect, a failed start-off attempt can be detected from the sensor data available in the motor vehicle's control unit, for example, data relating to the accelerator pedal position, wheel speeds, acceleration values, and the like. Furthermore, the term "failed start-off attempt" should also be interpreted to include situations in which further driving of the motor vehicle is no longer possible due to insufficient torque, for example when starting up an incline where new driving resistances exceed the power currently available from the motor vehicle.In other words, the speed of the motor vehicle becomes increasingly slower until the motor vehicle comes to a standstill, which is then recorded according to the invention as a failed attempt to start.

[0010] In a further step of the method, the driving operation of the motor vehicle is blocked in response to the detected failed start-off attempt. By blocking the driving operation, a rolling back of the motor vehicle is prevented and vehicle wear is further reduced. This step preferably takes place immediately after the failed start-off attempt has been detected. In other words, driving operation is preferably blocked first after the failed start-off attempt has been detected. Blocking driving operation is preferably carried out using the vehicle brakes and / or by activating a holding function, such as a handbrake, a gear position or a similar anti-roll device. In other words, an active intervention in the driving operation of the motor vehicle takes place to block it. In particular, this prevents a new start-off attempt by the driver, thus implementing a delay in departure.

[0011] In a further process step, a limitation of the motor vehicle's performance and / or information from the failed start-off attempt are determined to correct a previously calculated required start-off torque. For example, the motor vehicle's performance is limited by start-off restrictions imposed by its own system, such as the control unit, in order to comply with specifications. Examples of specifications include noise, consumption, or emissions controls, or settings relating to the driving mode, such as eco or economy modes. Such specifications can result in the actual start-off torque provided by the motor vehicle being insufficient to exceed the required start-off torque and enable the motor vehicle to start.By determining the information from the failed start-up attempt, the input conditions underlying the release of driving operation can be checked and their values ​​updated in order to correct, in particular increase, the previously calculated (incorrectly estimated) required starting torque and to prevent a further erroneous release of driving operation below the required (corrected) starting torque.

[0012] In one method step, the driving operation of the motor vehicle is enabled based on a detected reduction in the determined limitation of the motor vehicle's performance and / or based on a correction of the previously calculated required starting torque. If the limitation of the motor vehicle's performance decreases, the motor vehicle's performance is increased, thereby increasing the probability of the motor vehicle successfully starting and reducing the occurrence of (further) failed starting attempts. By correcting the previously calculated required starting torque based on the newly determined information from the failed starting attempt, a required starting torque is determined that is more realistic.This also increases the probability of the vehicle successfully starting and reduces the occurrence of (further) failed starting attempts. This reduces inaccuracies in the input conditions and prevents the resulting incorrect authorization of driving operation. Preferably, the currently available starting torque of the vehicle is compared with the corrected required starting torque, and driving operation is only authorized when the available starting torque exceeds the corrected required starting torque. For example, intelligent authorization logic for driving operation is enabled, taking into account starting restrictions, especially temporary starting restrictions.

[0013] In a preferred embodiment, the limitation of the motor vehicle's performance includes a reduction in power and / or torque associated with a cold start of the motor vehicle in order to comply with emissions standards. Rapid heating of the catalytic converter while simultaneously keeping raw emissions as low as possible during the cold start phase is essential for meeting emissions standards, for example the Euro 7 emissions standard. Therefore, excessive power must not be released during the cold start phase, which would result in increased raw emissions. To comply with the emissions standard, it may sometimes be necessary to prevent the motor vehicle from starting for a period of time after the start request or at least to limit the power for a certain period after starting.This can ensure that not too many emissions are emitted until the conversion readiness of the (cold) catalyst is sufficient, i.e., until the temperature of the catalyst is sufficiently high. Therefore, the vehicle's performance after a cold start may be limited compared to a vehicle with a warm drive system. Thus, temporarily restricted driving performance, which could be introduced with the Euro 7 emissions standard, may result in the starting torque provided by the vehicle being insufficient after the holding function is released to ensure the vehicle starts moving, particularly on surfaces with a positive gradient. By taking such restrictions into account, further failed starting attempts can be effectively prevented.

[0014] In a further preferred embodiment, the information from the failed start-off attempt for correcting the previously calculated required start-off torque includes updated information about an environmental condition and / or a vehicle property. Based on updated information about environmental conditions and vehicle properties, the required start-off torque can be determined more precisely, thereby reducing the occurrence of (further) failed start-off attempts. Examples of vehicle properties are the weight of the motor vehicle, the weight of a coupled trailer, an engine temperature, a catalytic converter temperature and / or catalytic converter aging. Examples of environmental conditions are an ambient temperature and / or air pressure. Particularly in situations with a coupled trailer, the load condition of the trailer may initially be unknown to the motor vehicle.However, a conclusion about the loading condition of the trailer (and / or the motor vehicle itself) can be drawn from the information about the failed attempt to start.

[0015] In a further preferred embodiment, it is provided that the motor vehicle further comprises an inclination sensor. In this case, an incline of a vehicle surface (or an inclined position of the motor vehicle on the vehicle surface) is also determined using the inclination sensor, and the previously calculated required starting torque is also corrected based on the determined incline. By taking the current incline into account, a more precise calculation of the required starting torque can be carried out. Furthermore, since a rolling back of the motor vehicle is to be feared in the event of a failed starting attempt, particularly on inclines, driving operation is preferably blocked immediately after the failed starting attempt is detected. In other words, driving operation of the motor vehicle is preferably blocked in response to the detected failed starting attempt and a determined positive incline.

[0016] In a further preferred embodiment, the enabling of the driving operation of the motor vehicle is also subject to the condition that the increased performance of the motor vehicle based on the detected reduction of the determined restriction exceeds the calculated required starting torque and / or the corrected required starting torque. As a result, the departure of the motor vehicle is actively delayed until it can be assumed that the starting attempt is likely to be successful.

[0017] In a further preferred embodiment, it is provided that the driving operation of the motor vehicle is enabled after a predetermined time has elapsed if no correction of the previously calculated required starting torque is possible and / or the driving operation of the motor vehicle is enabled when the performance of the motor vehicle has increased by a predetermined amount. By enabling driving operation after a predetermined time or after an increase in performance by a predetermined amount, a new starting attempt can be made, which, if this also fails, can be used to determine new (updated) information from the failed subsequent starting attempt in order to again correct the previously calculated required starting torque.

[0018] In a further preferred embodiment, it is provided that a first driver information message regarding the blocking of the motor vehicle's driving operation is output based on the detected failed attempt to start the vehicle. This output informs the driver of the vehicle about the unwillingness to drive or the blocking of the motor vehicle's driving operation in order to avoid driver confusion.

[0019] The output is preferably optical, for example as a light signal, symbol, text or the like on a display of the motor vehicle, acoustic, for example by means of a voice output, and / or haptic, for example by means of a vibration of the steering wheel.

[0020] In a further preferred embodiment, a second driver information item is output regarding the authorization to drive the motor vehicle based on the detected reduction in the determined limitation of the motor vehicle's performance and / or based on the correction of the previously calculated required starting torque. This output informs the driver that the motor vehicle is ready to depart. The output is preferably visual, for example, as a light signal, symbol, text, or the like on a display of the motor vehicle, acoustic, for example, via a voice output, and / or haptic, for example, via a vibration of the steering wheel.

[0021] In a further preferred embodiment, the starting torque is provided by an internal combustion engine of the motor vehicle. Internal combustion engines, in particular, generate exhaust gases that cannot be adequately compensated for during cold starts due to the catalyst's insufficient conversion capability, so that emissions-related starting restrictions occur primarily in internal combustion engines. Examples of internal combustion engines include gasoline or diesel engines.

[0022] A further aspect of the invention relates to a control unit for a motor vehicle. The control unit is configured to carry out the method described above. The motor vehicle is preferably the motor vehicle described above. The advantages achieved with the method can be achieved analogously with the control unit. The disclosed feature combinations of the method can be applied analogously to the control unit. A repeated description of the features and advantages is therefore omitted.

[0023] The individual method steps of the method according to the invention are further preferably embodied as one or more processes that run on one or more processors in one or more electronic computing devices and are generated when executing one or more computer programs. The computing devices are preferably designed to cooperate with other components, in particular a control unit for operating a motor vehicle, in order to implement the functionalities described herein. Likewise, the control unit is preferably embodied as a central (single-part) or decentralized (multi-part) component.

[0024] The individual components of the control unit are further preferably embodied as one or more processes that run on one or more processors in one or more electronic computing devices and are generated when executing one or more computer programs. The computing devices are preferably configured to cooperate with other components to implement the functionalities described herein. The instructions of the computer programs are also preferably stored in a memory, such as a RAM element. However, the computer programs can also be stored in a non-volatile storage medium, such as a CD-ROM, a flash memory, or the like.

[0025] It will also be apparent to a person skilled in the art that the functionalities of several computers (data processing devices) may be combined or combined in a single device or that the functionality of a particular data processing device may be distributed among a plurality of devices in order to carry out the steps of the method according to the invention without deviating from the method according to the invention.

[0026] A further aspect of the invention relates to a computer program comprising instructions which, when the program is executed by a computer, such as a control unit for operating a motor vehicle, cause the computer to carry out the method, in particular a method for operating a motor vehicle.

[0027] Further preferred embodiments of the invention emerge from the remaining features mentioned in the subclaims.

[0028] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in the individual case.

[0029] The invention is explained below in exemplary embodiments with reference to the accompanying drawings. They show: Fig. 1 a schematic representation of a method for operating a motor vehicle according to an embodiment and Fig. 2 a schematic representation of a motor vehicle with a control unit for operating the motor vehicle according to an embodiment.

[0030] Fig. 1 shows a schematic representation of a method for operating a motor vehicle 10 according to one embodiment. The method is suitable for reducing the occurrence of situations in which the motor vehicle 10 does not start or cannot start due to insufficient starting torque despite authorization to drive has been granted. In other words, the starting torque provided by the motor vehicle 10 is not large enough in these cases to exceed the starting torque required for starting, so that the motor vehicle 10 either stops or, in the case of an incline, even rolls off in a direction opposite to the direction of travel. Such a situation is unsatisfactory for the driver of the motor vehicle 10 and can sometimes be dangerous, since the motor vehicle 10 may roll backward unintentionally due to the driver's inadvertent action.

[0031] According to a first method step 50, a failed start-off attempt of the motor vehicle 10 due to insufficient starting torque is detected. For example, the driver releases the hold function of the stationary motor vehicle and presses the accelerator pedal to attempt a start-off attempt. Due to the insufficient starting torque of the motor vehicle 10, the vehicle does not start and, due to the incline of the road surface, tends to roll away in the opposite direction to the driver's desired direction.

[0032] To effectively prevent this, a second method step 52 follows the first method step 50, after which the driving operation of the motor vehicle is disabled in response to the detected failed start attempt. For example, a brake unit of the motor vehicle 10 and a roll-off protection device are activated.

[0033] According to a first alternative of a third method step 54a, a limitation of the performance of the motor vehicle 10 is determined. For this purpose, a reduction in power and / or torque associated with a cold start of the motor vehicle 10 to comply with emissions specifications is taken into account by the control unit 12 of the motor vehicle 10. Since too much power, which would result in increased raw emissions, must not be released during a cold start phase, the control unit 12 limits the performance of the motor vehicle 10 for a certain period of time to comply with an emissions standard. Since the catalytic converter, which has an improved conversion capacity with increasing temperature, heats up at the same time, this downhill limitation is fundamentally a temporary downhill limitation that essentially correlates with the heating time of the catalytic converter.

[0034] According to a second alternative of a third method step 54b, additional or alternative information from the failed start-off attempt is determined to correct the previously calculated required start-off torque. The previously calculated required start-off torque may have been calculated based on incorrect or inaccurate values ​​of the input conditions for enabling the failed start-off attempt. Due to the failed start-off attempt, control unit 12 may have new sensor values ​​available, which may allow a conclusion to be drawn about a required start-off torque that was calculated to be too low. In other words, new or updated information about the ambient conditions and properties of motor vehicle 10 is obtained from the failed start-off attempt in order to calculate the (actually) required start-off torque more precisely.

[0035] In a fourth method step 56, the driving operation of the motor vehicle 10 is released based on a detected reduction in the determined limitation of the performance of the motor vehicle 10 and / or based on a correction of the previously calculated required starting torque.

[0036] Fig. Figure 2 shows a schematic representation of the motor vehicle 10 with a control unit 12 for operating the motor vehicle 10 according to one embodiment. In addition to the control unit 12, the motor vehicle 10 comprises a memory 14, a plurality of sensors 16, and a drive system 18, with the individual components each being connected to the control unit 12. The control unit 12 is designed to carry out the Fig. 1 and accordingly accesses the memory 14, the sensors 16 and the drive system 18. List of reference symbols 10 motor vehicle 12 Control unit 14 storage 16 sensors 18 Drive system 50 first process step - recording failed start-up attempts 52 Second procedural step - Blocking driving operations 54a, 54b third procedural step - determining a restriction and information 56 fourth procedural step - release of driving operation 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 2017 / 0089460 A1

[0003] DE 10 2018 221 398 A1

[0004] DE 10 2013 104 515 A1

[0004]

Claims

[1] Method for operating a motor vehicle (10), comprising the steps of: - detecting (50) a failed attempt to start the motor vehicle (10) due to insufficient starting torque, - blocking (52) the driving operation of the motor vehicle (10) in response to the detected failed start-up attempt, - determining (54a) a limitation of the performance of the motor vehicle (10) and / or determining (54b) information from the failed start-up attempt in order to correct a previously calculated required start-up torque and - Enabling (56) the driving operation of the motor vehicle (10) based on a detected reduction in the determined limitation of the performance of the motor vehicle (10) and / or based on a correction of the previously calculated required starting torque. [2] Method according to claim 1, wherein the limitation of the performance of the motor vehicle (10) comprises a reduction in power and / or torque associated with a cold start of the motor vehicle (10) in order to comply with emission specifications. [3] Method according to one of the preceding claims, wherein the information from the failed start attempt for correcting the previously calculated required start-up torque comprises updated information about an environmental condition and / or a vehicle characteristic. [4] Method according to one of the preceding claims, wherein the motor vehicle (10) further comprises an inclination sensor and the method further comprises the step: - Determining a gradient of a vehicle surface using the inclination sensor, wherein the correction of the previously calculated required starting torque is further carried out based on the determined gradient. [5] Method according to one of the preceding claims, wherein the enabling (56) of the driving operation of the motor vehicle (10) further occurs under the condition that the increased performance of the motor vehicle (10) based on the detected reduction of the determined restriction exceeds the calculated required starting torque and / or the corrected required starting torque. [6] Method according to one of the preceding claims, wherein the enabling (56) of the driving operation of the motor vehicle (10) takes place after a predetermined time has elapsed if no correction of the previously calculated required starting torque is possible, and / or the enabling (56) of the driving operation of the motor vehicle (10) takes place when the performance of the motor vehicle (10) has increased by a predetermined amount. [7] A method according to any one of the preceding claims, further comprising the step of: - Outputting a first driver information about the blocking of the driving operation of the motor vehicle (10) based on the detected failed start-off attempt. [8] A method according to any one of the preceding claims, further comprising the step of: - Outputting a second driver information item about the release of the driving operation of the motor vehicle (10) based on the detected reduction of the determined limitation of the performance of the motor vehicle (10) and / or based on the correction of the previously calculated required starting torque. [9] Method according to one of the preceding claims, wherein the starting torque is provided by an internal combustion engine of the motor vehicle (10). [10] Control device (12) for operating a motor vehicle (10), which is designed to carry out the method according to one of the preceding claims.

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