DE102018204358B4 - Control method for operating a motor vehicle, control unit for a motor vehicle and motor vehicle with such a control unit - Google Patents

Abstract

Control method for operating a motor vehicle (1), which has an engine (3), a transmission (4) and at least two driving modes in the form of a normal mode (6) and an economy mode (7) with different engine characteristics, a normal mode characteristic (15) of the Normal mode (6) at the same speed (12) has a higher engine power (13) than an economy mode characteristic (16) of the economy mode (7), comprising the following steps: - controlling the engine (3) according to the economy mode characteristic (15) if the Saving mode (7) is activated, - determining a minimum engine power (14) required for a current driving resistance, in particular due to a current incline (8) of a vehicle underground (2), in order to at least maintain a current speed (21) of the motor vehicle (1). - If according to the economy mode characteristic (15), the current engine power (13) is below the minimum engine power (14), determining a control strategy (10, 10', 10") of the engine (3) with which a mini mal energy consumption of the motor (3) the current speed (21) is at least maintained, and causing the execution of this control strategy (10, 10', 10"); characterized in that- if the motor vehicle (1) has a manual gearshift for selecting between at least two forward gears (18, 18'), the control strategy (10, 10', 10'') comprises one of the following two steps: • Changing the engine characteristic curve from the economy mode characteristic curve (15) to the normal mode characteristic curve (16),• displaying a downshift recommendation from the selected forward gear (18) to the lower of the at least two forward gears (18') on a display device in the vehicle interior; and/or if the motor vehicle (1) has an automatic gear shift for selecting between at least two forward gears (18, 18`), the control strategy (10, 10', 10") comprises one of the following steps: Economy mode characteristic (15) to normal mode characteristic (16), • changing the selected forward gear (18) to the lower of the at least two forward gears (18`), • reducing an accelerator pedal angle of a kickdown (11) depending on the current driving resistance, whereby as soon as the accelerator pedal angle of the Kickdown position is reached when the accelerator pedal is actuated by a user of the motor vehicle (1), the economy mode (7) is deactivated and the normal mode (6) is activated.

Description

The invention relates to a control method for operating a motor vehicle, a control unit for a motor vehicle that is designed to carry out such a control method, and a motor vehicle with such a control unit.

Several driving modes are often available in motor vehicles today, with the aid of which the motor vehicle can be operated under different predetermined driving conditions. Such a driving mode is, for example, an economy mode, which is often referred to as eco mode and which is intended to support a driver of the motor vehicle in driving as ecologically as possible. In such an economy mode, the units in the motor vehicle are operated with the highest possible efficiency, which leads, among other things, to a limitation of the acceleration and the power of the motor vehicle's engine.

The power of the engine of the motor vehicle in the economy mode is reduced in such a way that when driving uphill a current speed of the motor vehicle often cannot be maintained. Only after manual deactivation of the economy mode, for example by pressing a corresponding button in the vehicle interior, does the vehicle switch back to a normal mode and can then drive up the incline without speed reduction. The economy mode thus does not provide the most efficient solution for operating the motor vehicle when driving uphill under predetermined conditions.

the DE 10 2016 214 235 A1 shows a method for automatically adapting the acceleration of a vehicle, the vehicle comprising an active longitudinal guidance system and a set speed for the vehicle being specified. When driving up an incline is detected, a maximum adjustable acceleration for reaching the set speed is specified as a function of the incline.

the DE 10 2010 055 373 A1 describes a method for controlling the longitudinal dynamics of a motor vehicle. In this case, a target acceleration of the motor vehicle is determined as a function of a driving state variable that characterizes a driving state of the motor vehicle and an environmental variable that characterizes the surroundings of the motor vehicle, whereupon the longitudinal dynamics of the motor vehicle are controlled as a function of the target acceleration by means of an engine control unit and a brake control unit.

In the DE 10 2014 204 206 A1 describes a method for optimizing the energy consumption of a vehicle, wherein a speed profile generator for calculating an optimal speed profile takes into account an energy consumption model of the vehicle together with road gradient data corresponding to the route.

It is the object of the invention to provide a solution by means of which a motor vehicle can be operated with an optimized energy consumption even with an increased driving resistance.

This object is achieved by a control method for operating a motor vehicle and a control unit for a motor vehicle that is designed to carry out such a method for operating the motor vehicle.

The control method according to the invention for operating a motor vehicle is provided for a motor vehicle that has an engine, a transmission and at least two driving modes in the form of a normal mode and an economy mode with different engine characteristics. A normal mode characteristic of the normal mode has a higher engine output than an economy mode characteristic of the economy mode at the same speed. The control method for operating the motor vehicle comprises the following steps: First, the motor is controlled according to the economy mode characteristic when the economy mode is activated and a minimum engine power required for a current driving resistance, in particular due to a current incline of a vehicle surface, is determined in order to achieve a current speed of the motor vehicle to hold at least. If according to the economy mode characteristic the current engine power is below the minimum engine power, an activation strategy of the engine is determined, with which the current speed is at least maintained with a minimum energy consumption of the engine, and this activation strategy is initiated.

A motor vehicle can thus be operated with the control method according to the invention, which is characterized in that it comprises a driving prime mover whose force or torque is translated with the aid of a transmission. In addition, the motor vehicle is designed so that a driver has several driving modes to choose from, with at least one so-called normal mode for normal operation of the motor vehicle and a so-called economy mode, which is often also referred to as eco mode, being selectable. These two modes differ in their engine characteristics, i.e. in their dependence of engine speed on engine output. the engine The characteristic of the normal mode, ie the normal mode characteristic, has higher engine power values than a corresponding engine characteristic of the economy mode, ie the economy mode characteristic, has at the same speed.

As soon as the economy mode has been activated, the motor vehicle is operated according to the specifications of the economy mode, which means that the engine of the motor vehicle is operated according to the economy mode characteristic. In addition, other components of the motor vehicle are preferably operated in a particularly energy-efficient manner in the economy mode, such as an air conditioning system. While driving in economy mode, it is then continuously determined what power the engine of the motor vehicle must at least provide in order to be able to maintain a current speed of the motor vehicle or even to be able to accelerate the motor vehicle. This required minimum engine power is dependent on the resistances counteracting the movement of the motor vehicle, such as the gradient resistance, the air resistance or a rolling resistance. In general, the driving resistance refers to the sum of the resistances that a motor vehicle must overcome with the help of a driving force in order to travel a horizontal or inclined route at a constant or greater speed. The driving resistance is therefore calculated from the contributions of an air resistance, a rolling resistance, a gradient resistance and an acceleration resistance. If it is now determined that the determined minimum engine power is above the actual current power of the engine in economy mode, it is checked which measures can be taken to keep the current speed of the motor vehicle at least constant while still consuming as little energy as possible. The implementation of this determined so-called control strategy is then initiated.

With the control method, both a motor vehicle with an electric machine and a motor vehicle with an internal combustion engine can be operated, it being possible for the motor vehicle to have manual or automatic gear shifting. If an economy mode is now activated in this motor vehicle, on the one hand the engine characteristic curve of the engine is adjusted accordingly in order ultimately to enable the most energy-efficient driving possible by limiting the acceleration of the power. Furthermore, by activating the economy mode, interventions are made in other vehicle functions, such as an air conditioning system, which is also operated in such a way that the total energy consumption of the motor vehicle is as low as possible in this economy mode.

While driving in economy mode, the engine power required to at least maintain the speed of the motor vehicle is now determined, with a current driving resistance being taken into account to determine this minimum engine power. The driving resistance can be calculated, for example, using various engine parameters, such as speed, engine power or fuel consumption, the mass of the motor vehicle or the current speed of the motor vehicle. If the motor vehicle is driving uphill, for example, the required minimum engine power increases due to the increased gradient resistance and the situation can arise that the current engine power is below this specific minimum engine power. In this case, control strategies of the motor are determined with which the current speed can at least be maintained. The control strategy with a minimum energy consumption of the engine, which can involve, for example, a temporary change in the engine characteristic to the normal mode characteristic, is then selected and the motor vehicle is operated according to this control strategy.

With the method according to the invention it is therefore possible that even if the driving resistance is currently increased, for example due to a current incline of the vehicle's ground, the engine of the motor vehicle is controlled in such a way that fuel consumption continues to be as minimal as possible, pollutant emissions as minimal as possible and engine operation is as gentle as possible low speed is reached. The control method according to the invention is also distinguished by the fact that initially no manual user intervention is necessary in order to at least maintain the current speed even when the driving resistance is currently increased. It is therefore not necessary for the driver to deactivate the economy mode for this purpose, since the motor vehicle can automatically take measures to adapt the engine output to the current driving conditions. The economy mode continues to be displayed to the user of the motor vehicle as the selected mode since the motor vehicle continues to be operated in the most energy-efficient manner.

Maintaining the speed of the motor vehicle made possible by the method according to the invention also increases safety for the users of the motor vehicle and the users of motor vehicles driving behind the motor vehicle, since there are no unexpected reductions in the speed of the motor vehicle. In addition, no additional vehicle components are required to implement the control method, since the devices required to determine the driving resistance are standard in a motor vehicle are integrated, such as a motor control unit or a speed measuring device. In addition, it is possible with the method according to the invention to achieve a particularly comfortable driving behavior of the motor vehicle in economy mode.

In addition, it is provided that if the motor vehicle has a manual gearshift for selecting between at least two forward gears, the control strategy, with which the current speed is at least maintained with minimal energy consumption of the engine, includes one of the two following steps: a change in the engine characteristic curve from the economy mode characteristic to the normal mode characteristic or displaying a downshift recommendation from the selected forward gear to the lower of the at least two forward gears on a display device inside the vehicle.

If the motor vehicle has a manual transmission, two options, ie two control strategies, must be considered as to how the motor vehicle can be operated. Of these two control strategies, the one that leads to lower energy consumption of the motor is selected. The two control strategies are either a change in the engine characteristic from the previously used economy mode characteristic to the normal mode characteristic of the motor vehicle or a display inside the motor vehicle that prompts the user of the motor vehicle to change the current forward gear. Because depending on the current incline, speed and rpm, it may make more sense with regard to the energy consumption of the motor vehicle engine to no longer operate the motor vehicle engine according to the economy mode, but to switch back to engine operation according to the normal mode. However, it is also conceivable that it would be more energy-efficient to continue to operate the engine in economy mode and merely reduce the current gear. In the case of a motor vehicle with a manual gear shift, however, such a downshift is only possible manually by a user of the motor vehicle, so that such a downshift recommendation can only be displayed inside the vehicle on a corresponding display device.

When selecting the control strategy for a motor vehicle with manual gearshift, a check is made as to whether, for example, driving in normal mode in fifth gear would be more efficient in terms of energy consumption than driving in economy mode in lower fourth gear at a higher speed. Depending on which of the two measures would be more energy-efficient, the implementation of the corresponding control strategy is initiated.

With the control method for operating a motor vehicle with manual gearshift, it is particularly advantageous, without manual user intervention being necessary, to either select the particularly ecological economy mode in a lower gear or switch to normal mode with regard to operating the engine. Ultimately, this achieves relatively low fuel consumption, relatively low pollutant emissions and gentle engine operation at relatively low speeds, without the need for additional vehicle hardware.

Furthermore, it is provided according to the invention that, if the motor vehicle has an automatic gearshift for selecting between at least two forward gears, the control strategy, with which the current speed is at least maintained with minimal energy consumption of the motor, comprises one of the following steps: a change in the motor characteristic from the economy mode characteristic to the normal mode characteristic, a change of the selected forward gear to the lower of the at least two forward gears or a reduction of an accelerator pedal angle of a kickdown depending on the current driving resistance, whereby as soon as the accelerator pedal angle of the kickdown position when the accelerator pedal is actuated by a user of the Motor vehicle is reached, the economy mode is disabled and the normal mode is activated.

For a motor vehicle with an automatic transmission, the most energy-efficient control strategy can therefore be selected from three possible strategies. Two possible control strategies are provided analogously to the control strategies for a motor vehicle with a manual transmission, namely changing the engine characteristic curve to the normal mode characteristic curve or changing the current forward gear according to a downshift to a lower gear.

However, motor vehicles with automatic gearshifts also often have what is known as a kickdown function. In addition to simply going full throttle, pressing the kickdown switch when the accelerator pedal stops sends a signal to the automatic transmission control. The automatic transmission usually then shifts to the gear with the best possible acceleration and revs the engine at high speeds. This application is mainly integrated into the motor vehicle for overtaking manoeuvres. When a kickdown is triggered in an economy mode, this mode is usually ended and again the normal mode of the motor vehicle is activated. Depending on the current driving resistance, ie depending on a current gradient resistance or a possibly changing air resistance or rolling resistance, the gas pedal angle at which a kickdown is triggered can be selected depending on this driving resistance. As a result, the kickdown is not triggered, as is usual, only when the gas pedal angle reaches the stop of the gas pedal, but already at a predetermined, smaller gas pedal angle.

It is therefore also checked in motor vehicles with automatic gear shifting to what extent changing the driving mode from economy mode to normal mode would enable more energy-efficient driving of the motor vehicle than downshifting the current gear and the associated driving at higher speeds while continuing to use the economy mode. However, instead of such a change in the engine characteristic curve or the forward gear, it is also possible to vary only the accelerator pedal angle of the kickdown, ie the full accelerator pedal position. It would be possible, for example, that when driving on a level road with a relatively low current driving resistance, the kickdown would be triggered when the accelerator pedal was usually pressed 90 percent, when driving on a road surface with a gradient of 10 percent, for example, i.e. with increased gradient resistance , but the kickdown is triggered when the accelerator pedal is typically pressed by 80 percent. A gradient-dependent or driving resistance-dependent accelerator pedal angle position for activating the kickdown is therefore possible. If the user of the motor vehicle now registers, for example when driving uphill, that the motor vehicle is slowing down due to the limited power of the engine in economy mode, pressing the accelerator pedal harder can end the economy mode up to the predetermined adapted kickdown position dependent on the current driving resistance, the engine according to the normal mode characteristic operated and ultimately the speed of the motor vehicle are at least maintained.

With the control method for operating a motor vehicle, either a driving mode that is still particularly ecological can be selected or it is particularly easy to switch from the economy mode back to the normal mode without manual user intervention being necessary. Ultimately, this also results in relatively low fuel consumption, relatively low pollutant emissions and gentle engine operation at relatively low speeds, without the need for additional vehicle hardware.

Alternatively, in a motor vehicle that has only one forward gear, as may be the case, for example, in a motor vehicle powered by electrical energy, the control strategy, with which the current speed is at least maintained with minimal energy consumption of the motor, includes one of the following steps: a change in the engine characteristic from the economy mode characteristic to the normal mode characteristic or a reduction in an accelerator pedal angle of a kickdown depending on the current driving resistance, with the economy mode being deactivated as soon as the accelerator pedal angle of the kickdown position is reached when the accelerator pedal is actuated by a user of the motor vehicle normal mode is activated. With the control method for operating a motor vehicle, even in a motor vehicle with a transmission with only one forward gear, without manual user intervention being necessary, it is particularly advantageous either to select a driving mode that is still particularly ecological or to switch from economy mode back to normal mode in a particularly simple manner .

In an advantageous embodiment of the invention, it is provided that a mass of the motor vehicle is taken into account to determine the minimum engine power and to determine the activation strategy of the engine. In addition to the economy mode characteristic, the normal mode characteristic, the current driving resistance, in particular the current incline of the vehicle's ground, and the current speed of the motor vehicle, the current mass of the motor vehicle is also taken into account as part of the control method. This makes sense since ultimately the energy consumption of the motor vehicle is dependent not only on a current driving resistance but also on the mass of the motor vehicle.

If, for example, there are several people in the motor vehicle or if the motor vehicle is heavily loaded, this also affects the energy required by the engine to operate the motor vehicle. When driving uphill, the energy consumption of the motor vehicle is therefore primarily dependent on the incline of the vehicle's underground and the mass of the motor vehicle while the current speed remains at least the same. Whether a power limitation of the engine through the economy mode makes sense in order to cope with the current incline is ultimately assessed as a function of the mass of the motor vehicle.

Taking into account the mass of the motor vehicle when determining the control strategy and the minimum engine power on which the determination of the control strategy is based ultimately means that the control method ren the control strategy can be determined particularly precisely, with which the energy consumption of the motor vehicle is minimal.

In a further advantageous embodiment of the invention, it is provided that when determining the energy consumption of the motor as part of determining the activation strategy of the motor, an engine-transmission combination of the motor vehicle, a current temperature of the motor and/or a value range of the speed is taken into account . When checking whether a change in the motor characteristic curve to the normal mode characteristic curve or possibly a change in the selected forward gear to a lower forward gear is more advantageous when considering the energy consumption of the motor, other variables are also taken into account. On the one hand, what type of engine and what type of transmission is installed in the motor vehicle is considered, since the resulting motor-transmission combination of the motor vehicle ultimately influences the energy consumption of the motor. It is also taken into account how hot the engine is at the moment and in which speed range the engine is currently working. Depending on these three variables, it can ultimately be checked whether, for example, driving in normal mode in fifth gear is more efficient than driving in economy mode in a lower gear, for example fourth gear, but at a relatively high speed. By taking these additional values into account, the activation strategy of the motor can be determined or ascertained particularly precisely and advantageously, with which minimal energy consumption, minimal pollutant emissions and gentle engine operation are made possible.

In a further advantageous embodiment of the invention, it is provided that as soon as it is determined that the current engine power according to the economy mode characteristic is above the current minimum engine power, the implementation of the activation strategy is ended after a predetermined period of time. After the execution of the control strategy, which allows a minimum energy consumption of the engine despite maintaining or increasing the current speed, is checked to what extent the current minimum engine power would still be above the current engine power if the economy mode characteristic were to continue to be used as the engine characteristic. If the current engine power according to the economy mode characteristic were above the current minimum engine power if the engine were to be operated according to the economy mode characteristic, it is no longer necessary to carry out the control strategy any further. It can thus be returned to the control of the engine according to the defaults of the economy mode with respect to the engine characteristic and, if necessary, the forward gear. However, the execution of the control strategy is only ended after a predetermined time, in order to avoid, particularly in the case of a hilly road surface, repeated switching at relatively short time intervals between operating the engine in economy mode and operating the motor vehicle according to the selected control strategy.

If the motor vehicle is in an operating state in which the engine characteristic curve of the normal mode characteristic curve is used, for example due to driving uphill, the activation strategy of the engine initially remains activated. However, as soon as the motor vehicle is back on a level roadway or a level road surface, an estimate of the current engine power according to the economy mode characteristic shows that this calculated current engine power according to the economy mode line is above the engine power required for the current trip with a specified current speed is needed. With regard to the energy consumption of the motor vehicle, it is therefore no longer sensible to operate the motor vehicle according to the control method in a modified economy mode according to one of the control strategies. After a predetermined period of time on a level road surface of two minutes, for example, the execution of the control strategy can then be ended and the motor vehicle can be operated again according to the defaults of the economy mode.

In the case of the activation strategy that has implemented a reduction in the accelerator pedal angle of the kickdown, the accelerator pedal angle of the kickdown that was selected before the implementation of the activation strategy is set again by ending the implementation of the activation strategy, for example a kickdown pedal angle of 90 percent accelerator pedal pressure. However, the economy mode would have to be activated again, since pressing the kickdown deactivated the economy mode and activated the normal mode.

If the driving resistance is increased again in the specified time window, for example by driving uphill again, a control strategy of the motor is again developed according to the control method and its implementation is initiated in order to be able to at least maintain the current speed with minimal energy consumption of the motor.

A manual user intervention is therefore not necessary either to trigger or to end the implementation of the activation strategy, which means that driving in the economy mode is particularly advantageous is also made possible when driving uphill or with other increased driving resistance.

In a further advantageous embodiment of the invention, it is provided that the period of time is fixed at a constant value and is dynamically adapted to a profile of the vehicle's underground, the profile of the vehicle's underground including in particular an incline and/or a curve. The specified period of time after which the execution of the control strategy is ended after it has been determined that the current engine power according to the economy mode characteristic is above the current minimum engine power can therefore be set in a fixed manner. As an alternative to this, however, a time period that adapts to the current driving situation can also be selected, ie a type of intelligent determination of the time period can be implemented. This dynamic period of time is selected depending on the current route. The course of this route can have several inclines and/or curves.

Values between a few seconds up to several minutes, for example, can be set as a constant value for the duration. An optimal constant value could, for example, be determined during corresponding test drives and then permanently set in the corresponding motor vehicles with an economy mode.

A dynamic time duration allows its value to be adjusted depending on the landscape. If the motor vehicle is, for example, on a road in a hilly landscape, it is to be expected after a first uphill drive that further uphill drives are to be expected in the near future on the current route of the motor vehicle. The duration can then be adapted to the course of the road surface. It may also be useful when driving on a road with numerous curves, in the case of an increased current driving resistance, to set a relatively long period of time after which the execution of the control strategy is only ended in order to ensure the most comfortable driving experience possible for the user of the motor vehicle make possible. This period of time, which is dynamically adapted to the course of the vehicle's ground, can be determined, for example, based on GPS map data, which can be used to estimate the course of the roadway ground in the area of the motor vehicle's current location. As a result of this dynamic period of time, a particularly advantageous driving of the motor vehicle in economy mode in driving situations with increased driving resistance is possible.

According to the invention, a control unit for a motor vehicle is also provided, the motor vehicle comprising an engine, a transmission and at least two driving modes in the form of a normal mode and an economy mode with different engine characteristics. This control unit for a motor vehicle is characterized in that the control unit is designed to carry out a method for operating the motor vehicle as described above. It is therefore possible by means of the control unit to control the engine of the motor vehicle according to the economy mode characteristic when the economy mode is activated. In addition, the control unit is designed to determine a minimum engine power required for a current driving resistance, which is necessary in order to be able to at least maintain a current speed of the motor vehicle. If, according to the economy mode characteristic, the current engine power is below the determined minimum engine power, the control unit is also designed to determine an activation strategy of the engine, with which the current speed is at least maintained with a minimum energy consumption of the engine and to cause this activation strategy to be carried out . With the help of the control unit, an economy mode of the motor vehicle and its implementation can thus be optimized taking current driving resistances into account.

In a further advantageous embodiment of the control unit for a motor vehicle, it is provided that the control unit is designed to determine the current driving resistance of the motor vehicle. The control unit thus has various control and calculation algorithms, with the aid of which the control unit can use the current speed, the current energy consumption and the current speed to determine the extent to which the current driving resistance of the motor vehicle is changing. The control unit is thus designed to determine whether the motor vehicle is, for example, driving uphill or is moving on a flat, slippery road surface.

As an alternative to a control unit that itself determines the current driving resistance of the motor vehicle, this current driving resistance can be determined using incline sensors in the motor vehicle, via an indirect measurement of the acceleration sensors, or using GPS signal processing. In this way, particularly when driving uphill, it is possible to determine an activation strategy of the motor with particular precision, since the minimum energy consumption of the motor for maintaining the current speed in the various possible scenarios can be calculated particularly advantageously. With the various possible scenarios are here This refers to the control strategies implemented, i.e. changing the engine characteristic curve to the normal mode characteristic curve, changing the selected forward gear if necessary and reducing the accelerator pedal angle of the kickdown depending on the current driving resistance.

According to the invention, a motor vehicle is also provided which includes an engine, a transmission and at least two driving modes in the form of a normal mode and an economy mode with different engine characteristics. This motor vehicle is characterized in that the motor vehicle has a control unit as described above. This motor vehicle can thus be operated particularly advantageously with the aid of the control method for operating a motor vehicle described above.

The invention also includes developments of the method according to the invention, which have features as have already been described in connection with the developments of the motor vehicle according to the invention. For this reason, the corresponding developments of the method according to the invention are not described again here.

• 1 eine schematische Darstellung eines Kraftfahrzeugs mit zwei Fahrmodi, das mit verschiedenen Ansteuerungsstrategien des Motors auf einem Fahrzeuguntergrund mit einer Steigung fährt,
• 2 eine schematische Darstellung einer Abhängigkeit einer Drehzahl von einer Motorleistung eines Kraftfahrzeugs, das in einem Normalmodus oder in einem Sparmodus betrieben wird, und
• 3 eine schematische Darstellung einer Abhängigkeit einer Geschwindigkeit eines Kraftfahrzeugs von einer Mindestmotorleistung für eine Fahrt eines Kraftfahrzeugs auf einem Fahrbahnuntergrund mit verschiedenen Steigungswinkeln.

Exemplary embodiments of the invention are described below. For this shows:

• 1 a schematic representation of a motor vehicle with two driving modes, which drives with different control strategies of the engine on a vehicle surface with an incline,
• 2 a schematic representation of a dependency of a speed on an engine output of a motor vehicle that is operated in a normal mode or in an economy mode, and
• 3 a schematic representation of a dependency of a speed of a motor vehicle on a minimum engine output for driving a motor vehicle on a road surface with different gradient angles.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention to be considered independently of one another, which also develop the invention independently of one another and are therefore also to be regarded as part of the invention individually or in a combination other than the one shown. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.

Elements with the same function are each provided with the same reference symbols in the figures.

In 1 a motor vehicle 1 is shown, which initially moves on a flat vehicle surface 2 . This motor vehicle 1 comprises an engine 3, a transmission 4 with at least two forward gears 18, 18', of which the higher forward gear 18 is selected, and a control unit 5. The motor vehicle 1 can be operated in two driving modes, a normal mode 6 and an economy mode 7. These two driving modes differ in their engine characteristics in such a way that with the economy mode 7 by limiting the acceleration and the engine power 13 (see 2 ) of the motor vehicle 1 and by limiting the performance of other vehicle functions, such as an air conditioning system of the motor vehicle 1, the energy consumption of the motor vehicle 1 is reduced. In the motor vehicle 1 outlined, the economy mode 7 is activated with the aid of the control unit 5 and the normal mode 6 is not. This is illustrated by the fact that in 1 the economy mode 7 is drawn with a solid line, whereas the normal mode 6 has been drawn with a dashed line.

If the vehicle ground 2 now has a gradient 8 with a predetermined gradient angle 9, the current driving resistance of the motor vehicle 1 changes. So that the motor vehicle 1 can continue to drive at least at the same speed, a certain minimum engine power 14 (see 2 ) necessary. If this required minimum engine power 14 is above the engine power 13 that is possible according to the economy mode 7, the control unit 5 determines different control strategies 10, 10', 10" of the engine 3. These control strategies 10, 10', 10" aim to that the current speed 21 (see 3 ) can at least be maintained.

If the motor vehicle 1 is a motor vehicle 1 with an automatic gear shift for selecting between the at least two forward gears 18, 18', there are three possible control strategies 10, 10', 10" of the motor vehicle 1.

The control strategy 10 of the engine 3 of the motor vehicle 1 provides that the motor vehicle 1 remains in the economy mode 7, but the control of the engine 3 according to the engine characteristic curve of the normal mode 6, the normal mode characteristic curve 16 (see 2 ), he follows. Through this In this case, when the engine characteristic curve changes, the engine power 13 is increased to such an extent that it is above the currently required minimum engine power 14 of the motor vehicle 1 to overcome the incline 8 . The control strategy 10 thus provides that the motor vehicle 1 is in a certain way in both driving modes, with the engine power 13 being controlled according to the normal mode 6 and other components, such as the air conditioning system, according to the economy mode 7 .

A second control strategy 10' provides for the engine characteristic curve to remain in economy mode 7, but for the forward gear 18 to be changed to the lower forward gear 18' of the motor vehicle 1.

For both control strategies 10, 10' presented so far, the control unit 5 determines the probable energy consumption of the motor 3 for maintaining the current speed 21 and then selects the control strategy 10, 10' of the motor 3 with which a minimum energy consumption can be implemented. The control unit 5 therefore checks whether, for example, when driving in normal mode 6 in the fifth forward gear 18, the engine 3 would be operated more efficiently than when driving in economy mode 7 at the same speed 21 but in a lower fourth forward gear 18` and thus at increased speed 12 (see 2 ).

In order to be able to determine the control strategy 10, 10', 10" of the engine 3 and the required minimum engine power 14 as precisely as possible, the mass of the motor vehicle 1 is also taken into account. This makes sense, since it has an impact on the energy consumption of the motor vehicle 1, whether For example, there are several people inside the vehicle or the motor vehicle 1 is heavily loaded.In addition, the motor-transmission combination of the motor vehicle 1, the current temperature of the motor 3 and the current speed range of the motor 3 are taken into account when selecting the appropriate control strategy 10, 10 ', 10" considered.

The control unit 5 is also designed to determine the current driving resistance and thus the incline 8 using various parameters, such as the engine power 13 , the rotational speed 12 , the speed 21 and the energy consumption of the motor vehicle 1 . Whether the control strategy 10 or the control strategy 10' leads to a more ecological use of the motor vehicle 1 ultimately depends on the incline 8 of the vehicle underground 2 and on the mass of the motor vehicle 1. As an alternative to determining the vehicle resistance using the control unit 5, the motor vehicle 1 can also have gradient sensors, an indirect measurement can be carried out using acceleration sensors of the motor vehicle 1 in a corresponding control unit 5, or the driving resistance can be determined using GPS signal data processing.

If the motor vehicle 1 is a motor vehicle 1 with a manual gearshift, the forward gear 18, 18' cannot be changed automatically, so that with the control strategy 10` a downshift recommendation to the driver is only given to the driver on a corresponding display device inside the motor vehicle 1 of the motor vehicle 1 is issued.

A third control strategy 10" provides that the motor vehicle 1 continues to drive in economy mode 7. However, an accelerator pedal angle for triggering a kickdown 11 is reduced depending on the current driving resistance set, i.e. depending on the incline 8. In general, a kickdown 11 , i.e. by fully pressing the gas pedal, ending the economy mode 7 and changing back to the normal mode 6. However, if the motor vehicle 1 is on a vehicle surface 2 with a slope 8 with a slope angle 9 greater than zero, this accelerator pedal angle of the kickdown position can be reduced, so that, for example, the economy mode 7 is already exited at an accelerator pedal angle that corresponds to an accelerator pedal pressure of around 80 percent 10" thus becomes the economy mode 7 ends, so that the motor vehicle 1 would no longer drive in the economy mode 7 even after the end of the control strategy 10".

If one of the activation strategies 10 or 10′ is selected, this activation strategy 10 or 10′ is maintained for a predetermined period of time even after driving uphill when driving on a level vehicle surface 2 . This predetermined period of time either has a constant value or is selected to be dynamically adapted to a course of the vehicle's underground 2 . After the predetermined period of time, the activation strategy 10 or 10' is ended, that is, the engine characteristic curve returns to the engine characteristic curve of the economy mode 7, ie to the economy mode characteristic curve 15 (see 2 ), changed or the forward gear 18' increased again to the forward gear 18.

This period of time is particularly advantageous if the course of the road surface 2 turns out to be an incline or a curve, as is usual, for example, in a hilly landscape or in a mountainous landscape.

By dynamically controlling the set time period, adapted to this course of the road surface 2, it can be ensured that there is no constant switching between the standard economy mode 7 and the economy mode 7 during one of the control strategies 10 or 10', which results in less comfortable driving of the motor vehicle 1 would become. Such a dynamic period of time can be determined based on corresponding GPS signal data, for example, and last a few seconds up to several minutes. For example, after driving uphill with a gradient angle 9 greater than zero, as soon as a road surface 2 with a gradient angle 9 less than or equal to zero is reached, the limitation of the power according to the economy mode 7 is reactivated only after the predetermined period of time. Previously, while driving on the vehicle surface 2 with an incline angle 9 greater than zero, in which the power range of the economy mode 7 would not have been sufficient, the power limitation of the engine 3 according to the economy mode characteristic curve 15 was lifted with the help of a corresponding evaluation in the control unit 5, so that, for example, the maximum available engine power 13, as is possible in normal mode 6, was available. However, the actual driving mode of the motor vehicle 1 is not changed for this, because the motor vehicle 1 remains in the economy mode 7 and only the engine characteristic changes to the normal mode characteristic 16, if this is the more energy-efficient control strategy 10 compared to a downshift of the forward gear 18 of the motor vehicle 1.

In 2 the dependency of the speed 12 on the engine power 13 is outlined. A specific minimum engine power 14 is required to at least maintain a current speed 21 of a motor vehicle 1 , this minimum engine power 14 being dependent on a current driving resistance, for example an incline 8 of the vehicle ground 2 with a predetermined incline angle 9 . Furthermore, the minimum engine power 14 depends on the mass of the motor vehicle 1 .

In 2 the economy mode characteristic 15 and the normal mode characteristic 16 are also shown. The speeds 12 of various forward gears 18 of the transmission 4 of the motor vehicle 1 are also sketched as points on these two characteristic curves, the economy mode characteristic curve 15 and the normal mode characteristic curve 16 . These forward gears 18 are the forward gears 18 six to two of the transmission 4, with the number of gears decreasing as the speed 12 increases.

In 2 it becomes clear that the engine output 13 is reduced at the same speed 12 by the selection of the economy mode 7 . If the motor vehicle 1 is in a driving situation in which the instantaneous engine speed 19 marked with a cross is observed, an instantaneous engine power 20 is below the required minimum engine power 14. At this instantaneous engine speed 19, the transmission 4 has the third forward gear 18". In order to at least maintain the current speed 21 of the motor vehicle 1 in order to at least maintain the energy consumption of the motor 3, the motor characteristic curve will now change to the normal mode characteristic curve 16, so that the instantaneous engine power 20' is reached. The instantaneous engine power 20' is clearly above the minimum engine power 14, so that this change Motor characteristic for normal mode characteristic 16, the speed 21 of the motor vehicle 1 can be kept at least constant at the current driving resistance.

In 3 the required total power requirement 24 of the motor vehicle 1 is shown as a function of the speed 21 and the gradient angle 9 . The motor vehicle 1 has a normal mode maximum power 22 and an economy mode maximum power 23 . If the motor vehicle 1 now drives on a vehicle surface 2 with different incline angles 9 of 12 degrees, 10 degrees, 8 degrees and 0 degrees, the four outlined total power requirements 24, 24', 24" and 24'" result. This makes it clear that from a certain speed on a predetermined incline 8, the total power requirement 24, 24', 24'' and 24''' is above the economy mode maximum power 23, so that the speed 21 of the motor vehicle 1 in economy mode 7 does not increase on these inclines 8 can be held.

In this power-speed range, the engine power 13 can be increased so much with the described control method for operating a motor vehicle 1 using the control strategy 10 that an instantaneous engine power 20 is above a current minimum engine power 14 and between the normal mode maximum power 22 and the economy mode maximum power 23. Maintaining the current speed 21 without initiating a control strategy 10, 10', 10" is only possible in the power-speed range below the economy mode maximum power 23. In the power-speed range above the normal mode maximum power 22, the corresponding gradients 8 can Current speeds 21 are not maintained because the engine power 13 is not sufficient.

Overall, the examples show how using the control method to operate a motor vehicle vehicle 1 when driving the motor 3 according to the economy mode characteristic curve 15 when the economy mode 7 is activated, in the case of an increased current driving resistance, for example due to an incline 8 of the vehicle underground 2, using various available control strategies 10, 10', 10" a current speed 21 of the motor vehicle 1 can at least be maintained. For this purpose, it is not necessary for the driving mode of the motor vehicle 1 to be changed from economy mode 7 back to normal mode 6, but it is possible without a manual driving mode change by a user of the motor vehicle 1 To increase engine power 13 of the engine 3 such that the slope 8 can be overcome without speed reduction.

Reference List

1

motor vehicle

2

vehicle underground

3

engine

4

transmission

5

control unit

6

normal mode

7

saving mode

8th

pitch

9

pitch angle

10, 10', 10"

control strategy

11

kickdown

12

number of revolutions

13

engine power

14

minimum engine power

15

economy mode characteristic

16

normal mode characteristic

17

maximum speed

18, 18', 18"

forward gear

19

instantaneous engine speed

20, 20'

instantaneous engine power

21

speed

22

Normal mode maximum performance

23

Economy mode maximum performance

24, 24', 24'', 24'''

total power requirement

Claims (8)

Control method for operating a motor vehicle (1), which has an engine (3), a transmission (4) and at least two driving modes in the form of a normal mode (6) and an economy mode (7) with different engine characteristics, a normal mode characteristic (15) of the Normal mode (6) has a higher engine power (13) at the same speed (12) than an economy mode characteristic (16) of the economy mode (7), comprising the following steps: - Controlling the engine (3) according to the economy mode characteristic (15) if the Economy mode (7) is activated, - determining a minimum engine power (14) required for a current driving resistance, in particular due to a current incline (8) of a vehicle surface (2), in order to at least maintain a current speed (21) of the motor vehicle (1). - If, according to the economy mode characteristic (15), the current engine power (13) is below the minimum engine power (14), determining a control strategy (10, 10', 10") of the engine (3) with which, at a m minimum energy consumption of the motor (3), the current speed (21) is at least maintained, and causing this activation strategy (10, 10', 10") to be carried out; characterized in that - if the motor vehicle (1) has a manual gearshift for selecting between at least two forward gears (18, 18'), the control strategy (10, 10', 10'') comprises one of the following two steps: • Changing the Engine characteristic curve from the economy mode characteristic curve (15) to the normal mode characteristic curve (16), • displaying a downshift recommendation from the selected forward gear (18) to the lower of the at least two forward gears (18') on a display device in the vehicle interior; and/or - if the motor vehicle (1) has an automatic gear shift for selecting between at least two forward gears (18, 18`), the control strategy (10, 10', 10") comprises one of the following steps: • Changing the engine characteristic curve from the Economy mode characteristic (15) to normal mode characteristic (16), • Changing the selected forward gear (18) to the lower of the at least two forward gears (18`), • Reducing an accelerator pedal angle of a kickdown (11) depending on the current driving resistance, whereby as soon as the accelerator pedal angle of the Kickdown position when the accelerator pedal is actuated by a user of the motor vehicle (1) is reached, the economy mode (7) is deactivated and the normal mode (6) is activated. Control method according to the preceding claim, characterized in that a mass of the motor vehicle (1) is taken into account to determine the minimum engine power (14) and to determine the activation strategy (10, 10', 10") of the engine (3). Control method according to one of the preceding claims, characterized in that when the energy consumption of the engine (3) is determined as part of the determination of the control strategy (10, 10', 10") of the engine (3), an engine-gearbox combination of the motor vehicle ( 1), a current temperature of the engine (3) and/or a value range of the speed (12) is taken into account Control method according to one of the preceding claims, characterized in that as soon as it is determined that the current engine power (13) according to the economy mode characteristic (15) is above the current minimum engine power (14), the implementation of the activation strategy (10, 10') is stopped after a predetermined period of time. , 10") is terminated. tax procedure claim 4 , characterized in that the period of time is set to a constant value or is dynamically adapted to a course of the vehicle ground (2), the course of the roadway ground (2) comprising a gradient and/or a curve. Control unit (5) for a motor vehicle (1), comprising an engine (3), a transmission (4) and at least two driving modes in the form of a normal mode (6) and an economy mode (7) with different engine characteristics , characterized in that the control unit (5) is designed to carry out a method for operating the motor vehicle (1) according to one of the preceding claims. Control unit (5) after claim 6 , characterized in that the control unit (5) is designed to determine the current driving resistance of the motor vehicle (1). Motor vehicle (1) comprising an engine (3), a transmission (4) and at least two driving modes in the form of a normal mode (6) and an economy mode (7) with different engine characteristics , characterized in that the motor vehicle (1) has a control unit (5 ) after one of the Claims 6 or 7 having.

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