Method for operating a motor vehicle and motor vehicle

Abstract

A method for operating a motor vehicle. At least one electric engine designed for driving the motor vehicle is used to recuperate electric energy. In this case, a travel of the motor vehicle during a period of time lying ahead is taken into account. During the use of at least one electric engine for recuperating the electric energy, it is taken into account whether during a thermal load of the at least one electric engine in the period lying ahead, a reduction of the power that can be output by at least one electric engine is to be expected. The at least one electric engine then recuperates an amount of electric energy during the deceleration of the motor vehicle which is smaller than the amount of electric energy that can be recuperated during the deceleration by the at least one electric engine. The invention relates in addition also to a motor vehicle.

Claims

1. A method for operating a motor vehicle, wherein during a trip of the motor vehicle in a time period lying ahead, at least one electric engine is used for recuperating electric energy, the method comprising: determining a current driving mode of the vehicle, said driving mode selected by the driver from among a plurality of selectable driving modes, each of the plurality of selectable driving modes prescribing a different optimization weighting of factors taken into account during usage of the at least one electric engine for driving and for recuperating electric energy, and power consumption and generation by components of the motor vehicle; based on a determination of the current driving mode of the vehicle and an optimization weighting associated with the current driving mode, determining an anticipated future power need of the vehicle; recuperating an amount of electric energy which is smaller than the amount of electric energy which can be recuperated during a deceleration by at least one electric engine, wherein during the usage of the at least one electric engine for recuperating electric energy, the driving mode selected by the driver of the motor vehicle and the anticipated future power need of the vehicle are taken into account and at least one of a thermal load of the at least one electric engine in the time period lying ahead and an expected reduction of the drive output that can be provided to the motor vehicle by at least one electric engine is taken into account.

2. The method according to claim 1, wherein during the use of at least one electric engine for recuperating the electric energy, a driving conduct selected by the driver of the motor vehicle is taken into account.

3. The method according to claim 1, wherein during the use of at least one electric engine for recuperating the electric energy, at least one environmental parameter is taken into account.

4. The method according to claim 1, wherein during the use of at least one electric engine for recuperating the electric energy, a current geographical position of the motor vehicle and at least one geographical position of the motor vehicle during the time period lying ahead and a characteristic of the route to be traveled on in the time period laying ahead by the motor vehicle is taken into account.

5. The method according to claim 1, wherein during the use of at least one electric engine for recuperating the electric energy, a state of an electric energy storage device of the motor vehicle is taken into account.

6. The method according to claim 1, wherein an operating brake is used for braking the motor vehicle.

7. The method according to claim 1, wherein in order to decelerate the motor vehicle, a recuperation torque is unevenly distributed to a first electric engine and to a second electric engine depending on an output of the first and second electric engines during the time period lying ahead.

8. The method according to claim 1, wherein among at least two electric engines, at least one of the at least two electric engines is chosen to receive a greater recuperation torque, wherein the at least one of the at least two electric engines has a lower efficiency with regard to recuperation of electric energy.

9. The method according to claim 1, wherein heat generated by the at least one electric engine during recuperation of the electric energy is used to heat up at least one electric storage device of the motor vehicle.

10. A motor vehicle, comprising: at least one electric engine designed to drive the motor vehicle, which can be used for recuperating electric energy, and which is provided with a control device for controlling at least one electric engine for using the same for recuperating the electric energy, wherein the control device is designed to take into account a travel of motor vehicle during a time period lying ahead, wherein the control device is designed to take into account a driving mode selected by the driver of the motor vehicle, wherein the control device is designed to take into account during the use of at least one electric engine for recuperation of electric energy at least one of a thermal load of at least one electric engine in the time period lying ahead and an expected reduction of the drive output of the one electric engine that can be obtained for the motor vehicle, and therefore to control the at least one electric engine during a deceleration of the motor vehicle so that an amount of the electric energy recuperated by at least one electric engine during a deceleration of the motor vehicle is smaller than the amount of electric energy that can be recuperated during the deceleration by the at least one electric engine, wherein the driving mode selected by the driver is one of a plurality of selectable driving modes, each of which prescribes a different optimization weighting of: factors taken into account during usage of the at least one electric engine for driving and for recuperating electric energy; and power consumption and generation by components of the motor vehicle; and wherein taking into account the driving mode selected by the driver of the motor vehicle comprises determining, based on the driving mode selected by the driver of the motor vehicle and an optimization weighting associated with the driving mode, an anticipated future power need of the motor vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the invention will be described next. For this purpose, FIG. 1 schematically illustrates a motor vehicle which is equipped with an electric engine designed to recuperate electric energy.

(2) The embodiments described below are preferred embodiments of the invention. In the embodiments, the described components represent individual features of the invention, which are independent of each other and which also form the invention independently of each other and thus also individually or in other combinations than those that are indicated as components of the invention. Furthermore, the described embodiments can be also complemented by other, already described features of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) The motor vehicle 10, which is shown schematically in FIG. 1, is provided with a first electric engine 12 and with a second electric engine 14. The electric engines 12, 14 are designed for driving the motor vehicle 10. For example, the first electric engine 12 can be associated with a rear left wheel 16 of the motor vehicle and the second electric engine 14 can be associated with a rear right wheel of the motor vehicle 10.

(4) Both electric engines can be also used for recuperation of electric energy. In this case, the electric engines 12, 14 are used as generators which supply electric energy for example to an electric energy storage device 18 of the motor vehicle 10. A recuperation operation of the electric engines 12, 14 is predetermined by the control device 20. The control device 10 takes in this case into account a trip of the motor vehicle 10 during a time period lying ahead. For example, the motor vehicle 10 can travel during the time period lying ahead along the section 22 which is schematically illustrated in the FIGURE.

(5) In the present case, the control device 20 will take into account whether due to a thermal load of the electric devices 12, 14, a reduction of the power that can be output during the time period can be expected. When this is the case, at least one of the electric engines 12, 14 will recuperate during the deceleration of the motor vehicle an amount of electric energy that is less than an energy amount that can be recuperated during the deceleration by the electric engines 12, 14. In the present case, the thermal behaviors of the drive components, in particular in the form of the electric engines 12, 14 but also of the electric storage device 18, are taken into account during the recuperation.

(6) In addition, the driver of the motor vehicle can select a driving mode of the motor vehicle 10. via a user interface 24, which is shown only schematically in the present case, for example with a touch screen and/or with a touchpad and/or with a switch. This driving mode is also taken into account for the recuperation strategy, which the control apparatus 20 converts into energy during the activation of the electric engines 12, 14 for recuperation.

(7) Moreover, the control apparatus 20 takes into account the previous driving conductor of the driver of the motor vehicle 10. Furthermore, the motor vehicle 10 is equipped with a navigation system 26, by means of which the geographic position of the motor vehicle 10 can be determined. The navigation system 26 can provide further data for the control device 20, which are relevant to the route 22 to be covered in the time period lying ahead. So for example, a radius of curves 28 of the distance 22, a distance section 30 of the route 22 with a downward slope, or upward inclination or similar factors are taken into account in a predicative manner by the control apparatus 20.

(8) The calculation of the magnitude of the recuperation torque of the respective electric engine 12, 14 and of its distribution when there are several electric engines 12, 14, is carried out in the present case with a prediction for the entire use of the drive train in a prediction time period, which is to say for the time period lying ahead. In particular, this prediction time period can be the entire travel of the motor vehicle 10, from a starting location to a target location. The recuperation operation determined by the control device 20 therefore is not based only on the deceleration effect of the drive train. Instead, the entire power potential and the lifespan potential of the drive train are predicted and considered. All users or all usage functions of the drive train are in this case considered. To these usage functions belong for example the drive which is provided by the electric engines 12, 14 and the distribution of the torque to both electric engines 12, 14.

(9) In the time period lying ahead or in the prediction time period, in particular the interplay between all of the users of the drive train is optimized with the integration of a drive train mode, including for example environmental data or environmental parameters, positional data or data provided for the geographical position of the motor vehicle, and past driver data. By means of the drive train model, the control device can for example estimate whether a reduction of the of the power that can be delivered by the electric engine 12, 14 can be expected during the acceleration out of one of the curves 28 on the route 22 as a result of a thermal load of at least one of the electric engines 12, 14. This kind of derating is also influenced by the environmental parameters such as for example the ambient temperature, the radii of the curves, while the upward slopes and downward slopes of the route 22, and the topographic height will also play a role.

(10) The potential of the power train can be utilized in an optimal manner by taking into account these parameters. In this case, the preference of the driver is taken into account so that the driving mode selected by the driver is evaluated by the control device 20. In addition, restrictions on the maximum electromotive output of the electric engines 12, 14 are taken into account in view of the lifespan of the drive train.

(11) In the present case, for example in the case of recuperation with an imminent derating, which is to say with a reduction of the output due to thermal load of one of the electric engines 12, 13, recuperation is redistributed early on to one of the electric engines 12, 14. In addition, the recuperation can be restricted when a boosting operation is desired, which is to say that when a strong acceleration of the motor vehicle 10 that is supported by the electric engines 12, 14 is desired in the shortest possible time. On the other hand, if the control device 20 should only take into account for the purposes of the recuperation strategy the fact that the electric engines 12, 14 should recover the maximum energy amount, this would lead to a derating of the electric engines 12, 14. Accordingly, no such acceleration of the motor vehicle 10 could then take place.

(12) The drive train does not need to be provided with both electric engines 12, 14 as shown in the present example. In particular, with a drive train that is provided with only one electric engine 12, the proportion of the deceleration that is not caused by the electric engine 12, is caused by an operating brake shown schematically in the present case.

(13) As users of the drive train, in particular the recuperation, the drive or the propulsion, and the transverse dynamics of the torque distribution (which is to say the so-called torque vectoring) to both electric engines 12, 14 are taken into consideration. The decision making that is used to distinguish between a greatest possible range of the motor vehicle 10 and thus also a possibly largest recuperation achievable by the electric engines 12, 14, or a greater dynamic when traveling through the route 22 is based additionally also on the parallel predictive model of the drive train, or of the drive train, and on the actual driving behavior of the driver.

(14) For example, the habits of the driver, such as acceleration after the curves 28 and similar data obtained from the previous behavior of the driver are taken into consideration. When the driver for example in certain situations frequently wants to accelerate or boost the power, the recuperation of the electric engines 12, 14 is restricted, or the recuperation torques are distributed differently to the electric engines 12, 14. In addition, the positional data or the geographical positions of the motor vehicle 10 are also fed in as data to be indicated, as well as topographic data, and the travel on the section 22 is taken into account in a predictive manner.

(15) When the at least two electric engines are available as was shown in the example above, then for example the electric engine 12, which has a poorer efficiency, can be used for recuperation when the other electric engine is then subsequently used for traction during acceleration.

(16) The optimization criteria are in particular the sum of the total requirements of the driver, the efficiency of the drive train and the predictive output capability of the drive train. In addition, the model of the drive train also plays a role, such as for example the cooling conduct of the engines 12, 14 as well as that of the energy storage device 18. The predicted thermal conduct of the driver components, including that of the electric energy storage device 18, is therefore taken into consideration. The result is that output limitations are thus avoided in this manner, which in turn leads to an optimal utilization of the drive train. Moreover, conservation of the energy of the battery or of the electric storage device 18 is also taken into consideration.

(17) The heating strategy of the drive train can also lead to an adjustment of the recuperation behavior of the motor vehicle 10, in particular after a cold start, which is to say with a cold start of the motor vehicle 10. For example, the electric engines 12, 14 may be deliberately used with a poorer efficiency for recuperation in order to heat the electric energy storage device particularly quickly.

(18) However, the driving mode that has been selected by the driver is taken into account also in this case. For example, the heating of the electric energy storage device 18 is conducted while an efficient driving mode is selected which is slower than the sport type of driving mode. This is because in the sport type of driving mode, the electric energy storage device 18 should provide a particularly large amount of electric energy for the electric engines 12 14 very quickly.

(19) The motor vehicle 10 can be in particular an electric motor vehicle or a hybrid vehicle. The motor vehicle 10 can be in addition provided with two other electric engines 34, 36. Accordingly, the electric engine 34 can be assigned to a front left wheel 38 and the electric engine 36 can be assigned to a front right wheel of the motor vehicle 10. The same principles that were mentioned in connection with the electric engines 12, 14 can be applied in an analogous manner also to the control of these electric engines 34, 36 by means of the control device 20.

(20) Overall, the example shows how the invention makes it possible to ensure that a recuperation that is appropriate for a given situation can be achieved while taking into consideration the requests of the driver and a predicted drive train potential and lifespan potential.