Method for operating a hybrid powertrain

Abstract

Method for operating a hybrid powertrain (20) for driving a number of wheels (23, 24) of a motor vehicle (30), wherein the hybrid powertrain (20) comprises an internal combustion engine (21) and at least one electric machine (32, 33, 34), characterized in that when at least one condition is present which characterizes a state of coasting of the motor vehicle (30), the internal combustion engine is decoupled from the number of wheels (23) by means of an electronic clutch (26) and the electric machine (32, 33, 34) is coupled to the number of wheels (23, 24), wherein the internal combustion engine (21) is switched on and off alternately for defined periods of time.

Description

[0001] The present invention relates to a method for operating a hybrid powertrain. Furthermore, the invention relates to a hybrid powertrain, a motor vehicle, a computer program product, and a computer-readable data carrier.

[0002] In the context of operating motor vehicles, minimizing fuel consumption is generally of interest. Fuel efficiency is particularly important and simultaneously presents a challenge, especially in the context of hybrid drives and autonomous driving.

[0003] In connection with automatic transmissions, as described, for example, in WO 2017 / 216 437 A1, the clutch is automatically opened or disengaged when certain operating conditions are met, so that the vehicle is temporarily in a coasting state. Further methods for operating a hybrid vehicle in coasting mode are described in DE 10 2015 223 907 A1, DE 10 2007 035 424 A1 and DE 10 2014 208 758 A1.

[0004] The object of the present invention is to make the coasting state of a motor vehicle in connection with hybrid drive systems usable for improving fuel economy.

[0005] This problem is solved by a method for operating a hybrid powertrain according to claim 1, by a hybrid powertrain according to claim 10, by a motor vehicle according to claim 14, by a computer program product according to claim 15, and by a computer-readable data carrier according to claim 16. The dependent claims contain further advantageous embodiments of the invention.

[0006] The inventive method for operating a hybrid powertrain for driving a number of wheels of a motor vehicle relates to a hybrid powertrain comprising an internal combustion engine and at least one electric machine. The electric machine can be configured as an electric motor and / or generator. Within the framework of the inventive method, when at least one condition is present that characterizes a coasting state of the motor vehicle, also known as sailing, the internal combustion engine is decoupled from the number of wheels by means of an electronic clutch, and the electric machine is coupled to the number of wheels. The electric machine can be coupled to the number of wheels already during the decoupling of the internal combustion engine, or simultaneously with the decoupling of the internal combustion engine, or subsequently after the decoupling of the internal combustion engine.

[0007] The method according to the invention has the advantage of enabling economical use of the coasting state of the vehicle. This reduces fuel consumption and increases the vehicle's efficiency. For example, the electric motor can be used to charge a battery during coasting. Furthermore, engaging the electric motor during coasting is advantageous from the perspective of vehicle safety, as the electric motor can be used for speed control.

[0008] In an advantageous embodiment, the method according to the invention is carried out in a cruise control mode. In this context, the desired vehicle speed can be efficiently maintained by means of the electric motor while coasting.

[0009] The at least one condition that characterizes a coasting state of the vehicle may include the absence of an acceleration request, in particular the failure to press or release an accelerator pedal by a user. Additionally or alternatively, a condition may include a vehicle speed above a specified minimum speed, for example, above 5 km / h or above another speed close to 0 km / h, and / or a vehicle speed below a specified maximum speed, for example, below 50 km / h. Additionally or alternatively, the at least one condition that characterizes a coasting state of the vehicle may include the presence of a braking request, for example, the application of a brake pedal by a user.The aforementioned conditions, individually or in various combinations, indicate that the motor vehicle is in a coasting state in which, by applying the inventive method, the fuel consumption of the combustion engine can be reduced and losses associated with the operation of the combustion engine, for example through friction or pumping processes, can be reduced or avoided.

[0010] Preferably, in the inventive method, the internal combustion engine is switched off or operated at idle. Alternatively, the internal combustion engine can be switched on and used to charge a battery, for example, a battery for an electric motor. In this case, the load on the internal combustion engine can be increased. This has the advantage that the coasting state of the vehicle can be used efficiently to charge a battery, thereby improving the overall efficiency of the vehicle. In both cases, the internal combustion engine is decoupled from the wheels by means of an electronic clutch, and the electric motor is coupled to the wheels.

[0011] The combustion engine is switched on and off alternately for set periods of time. This so-called on-off operation or on-off mode helps to reduce fuel consumption and improves the vehicle's efficiency.

[0012] In a preferred variant, cruise control mode is activated. The system then checks whether a first set of predefined conditions for decoupling the combustion engine from the wheels is met. It further checks whether a second set of predefined conditions for operating the combustion engine in an on-off mode is met. Fuel consumption during on-off operation is estimated, thus determining a hypothetical consumption. The actual fuel consumption is then determined. If the actual fuel consumption is higher than the estimated fuel consumption during on-off operation, and both the first and second sets of conditions are met, the powertrain operates in on-off mode. In this mode, propulsion is provided by the electric motor when the combustion engine is switched off.The first set of defined conditions could, for example, include the condition that there is no braking or acceleration request, for example, from a user. The second set of defined conditions could, for example, include the condition that the battery charge level is above a defined threshold.

[0013] The powertrain can include a battery connected to the electric motor. If the battery charge level is above a defined minimum, an electronic clutch located between the combustion engine and the electric motor can be opened or disengaged. The combustion engine can then be switched off, and propulsion can be provided by the electric motor. In another variant, if the battery charge level falls below a defined minimum, the electronic clutch between the combustion engine and the electric motor can be closed or engaged. The load on the combustion engine can be increased, and the battery can be charged by the electric motor.

[0014] In a further variant, the powertrain can be operated in a cruise control mode designed for speed and / or engine speed control, in particular adaptive speed and / or engine speed control, and / or distance control, and / or for executing an autonomous driving mode. This makes it possible to apply the inventive method in an efficiency-enhancing manner in the context of various driver assistance functions. In particular, a requested target speed can be set, and if the distance of the vehicle to a vehicle ahead is less than a target distance, a lower target speed can be set.

[0015] The hybrid powertrain according to the invention comprises an internal combustion engine and at least one electric motor. The hybrid powertrain is designed to execute a previously described method according to the invention. The hybrid powertrain according to the invention has the same features, properties, and advantages as the previously described method according to the invention.

[0016] In an advantageous embodiment, the hybrid powertrain includes a transmission. The hybrid powertrain can be configured as a parallel hybrid powertrain. The electric motor can be located at position P2, P3, or P4. The designations P2, P3, and P4 indicate the position of the electric motor within the powertrain. P stands for parallel, and the number indicates the installation location of the electric motor in the powertrain. In a P2 configuration, the electric motor is located between the combustion engine and the transmission, with a coupling between the combustion engine and the electric motor. In a P3 configuration, the electric motor is located at the transmission output. In a P4 configuration, the electric motor and the combustion engine act on different axes.

[0017] In the case of a P2 arrangement, two electronic couplings can be provided, wherein a first electronic coupling is arranged between the internal combustion engine and the electric machine and a second electronic coupling is arranged between the electric machine and the transmission.

[0018] In another variant, the hybrid powertrain can be designed as a full hybrid powertrain. Furthermore, the hybrid powertrain can include a planetary gear set. The embodiments and configurations mentioned here in connection with the hybrid powertrain according to the invention are also applicable in connection with the method according to the invention described above.

[0019] The motor vehicle according to the invention comprises a hybrid powertrain according to the invention as described above. It has the same features and advantages as the method according to the invention described above and the hybrid powertrain according to the invention as described above. The motor vehicle can be a passenger car, a truck, or a motorcycle.

[0020] The computer program product according to the invention comprises instructions which, when the program is executed by a computer, cause the computer to execute a method according to the invention as described above. The computer program product according to the invention is stored on the computer-readable data carrier according to the invention. The computer program product according to the invention and the computer-readable data carrier have the advantages already mentioned above.

[0021] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying figures. Although the invention is illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived by a person skilled in the art without departing from the scope of protection of the invention. Fig. Figure 1 schematically shows an embodiment of the method according to the invention in the form of a flowchart. Fig. 2 schematically shows a the Fig. 1. Supplementary embodiment of the method according to the invention in the form of a flowchart. Fig. Figure 3 shows a schematic diagram to illustrate an on-off mode. Fig. Figure 4 schematically shows a hybrid powertrain according to the invention. Fig. Figure 5 schematically shows a motor vehicle according to the invention.

[0022] The Fig. 1 and Fig. Figure 2 shows embodiments of the method according to the invention in the form of flowcharts. In step 1, a cruise control mode is activated. In step 2, it is checked whether specified conditions for decoupling the combustion engine from the wheels are met and whether specified conditions for operating the combustion engine in an on-off mode are met.

[0023] If the specified conditions are not met, the process reverts to the previous step. If the specified prerequisites are met in step 2, meaning all checked conditions are fulfilled, then in step 3 the fuel consumption during on-off operation is estimated, i.e., a hypothetical fuel consumption is determined. The actual fuel consumption is then determined and compared with the estimated fuel consumption. If the actual fuel consumption is higher than the estimated fuel consumption during on-off operation, the process proceeds to step 4. If the actual fuel consumption is not higher than the estimated fuel consumption in step 3, the process reverts to step 2. Steps 2 and 3 can also be performed in a different order or concurrently.

[0024] In step 4, a request for an alternative transition to an on-off mode is issued. In on-off mode, propulsion is provided by the electric motor when the combustion engine is switched off.

[0025] In the Fig. In step 5, an on / off mode is triggered. In step 6, it is checked whether the battery's state of charge is above a defined minimum state of charge (SOC > SOC). minIf this is the case, then in step 7 an electronic clutch located between the combustion engine and the electric motor is opened or disengaged, the combustion engine is switched off, and propulsion is provided by the electric motor. If, in step 6, the battery charge level is not above a defined minimum charge level, or in particular, if it is below a defined minimum charge level, then in step 8 an electronic clutch located between the combustion engine and the electric motor is closed or engaged, the load on the combustion engine is increased, and the battery is charged by the electric motor. Following steps 7 and 8, the process continues from step 6.

[0026] The Fig. Figure 3 illustrates an on / off mode. Fig. Figure 3 shows a diagram where the x-axis represents time t and the y-axis represents the fuel consumption a of the combustion engine. The diagram refers to a state in cruise control mode at a set speed target. The horizontal line 10 represents the torque requirement and the corresponding fuel consumption when operating solely on the combustion engine. The sections 11 represent sections or intervals in which the combustion engine is switched off and the vehicle is driven by the electric motor. The sections 12 represent sections or intervals in which the combustion engine is switched on and the electric motor is regenerating, i.e., being used as a generator to charge a battery. As in the Fig. As shown in Figure 3, the combustion engine is switched on and off alternately for defined periods or time intervals. This reduces fuel consumption while simultaneously meeting the torque requirement and operating the vehicle at the specified target speed.

[0027] The Fig. Figure 4 shows a hybrid drive train according to the invention in various embodiments. The hybrid drive train 20 comprises an internal combustion engine 21, a transmission 22, and a number of wheels 23, 24. It also comprises at least one electric motor 32, 33, 34 and a battery 25. The electric motor 32, 33, 34 can be arranged in different positions. In the Fig. Figure 4 shows variants P2, P3 and P4, whereby only one of the variants shown can be present in each case.

[0028] In a P2 configuration, the electric motor 32 is arranged between the internal combustion engine 21 and the transmission 22. A first electronic clutch 26 is arranged between the electric motor 32 and the internal combustion engine, and a second electronic clutch 27 is arranged between the electric motor 32 and the transmission 22. In the P3 configuration, the electric motor 33 is arranged at the output of the transmission 22. In this variant, the electronic clutches 26 and 27, as well as the electric motor 32, can be omitted.

[0029] In the P4 configuration, an additional axle with 24 wheels is provided. In this variant, the electric motor 34 acts on this axle, i.e., on an axle different from the axle on which the internal combustion engine 21 acts. In this variant, the clutches 26 and 27, as well as the electric motors 32 and 33, can be omitted. The electric motors 32, 33, and 34 are connected to a battery 25. The electric motors can be supplied with power by the battery 25, and they can also charge the battery 25. In principle, the hybrid drive train 20 according to the invention includes at least one of the electric motors 32, 33, or 34 shown.

[0030] The Fig. Figure 5 schematically shows a motor vehicle 30 according to the invention. The motor vehicle according to the invention comprises a hybrid powertrain 20 according to the invention. Reference symbol list 1 Cruise control mode switched on 2. Are the specified conditions for decoupling the internal combustion engine from the wheels met, and are the specified conditions for operating the internal combustion engine in an on-off mode met? 3. Fuel consumption during on-off operation: none as current fuel consumption? 4. Requirements for a transition to an on-off mode 5 On-Off mode triggered 6. Battery charge level above a defined minimum charge level (SOC > SOC) min )? 7. Switching off the combustion engine and driving by means of an electric motor 8. Increasing the load on the combustion engine and charging the battery using the electric machine 10 Fuel consumption for requested torque 11. Combustion engine off, drive by electric motor 12. Combustion engine on, regeneration of the electric machine 20 Hybrid powertrain 21 Internal combustion engine 22 gearboxes 23 wheels 24 wheels 25 battery 26 Clutch 27 Clutch 30 motor vehicles 32 Electric machine 33 Electric machine 34 Electric machine a fuel consumption t time

Claims

[1] Method for operating a hybrid drive train (20) for driving a number of wheels (23, 24) of a motor vehicle (30), wherein the hybrid drive train (20) comprises an internal combustion engine (21) and at least one electric machine (32, 33, 34), characterized by that when at least one condition exists which characterizes a state of coasting of the motor vehicle (30), the internal combustion engine is decoupled from the number of wheels (23) by means of an electronic clutch (26) and the electric machine (32, 33, 34) is coupled to the number of wheels (23, 24), wherein the internal combustion engine (21) is alternately switched on and off for predetermined periods of time. [2] Method according to claim 1, characterized by that the procedure is carried out in cruise control mode. [3] Method according to claim 1 or claim 2, characterized bythat the at least one condition which characterizes a state of coasting of the motor vehicle (30) comprises the absence of an acceleration request and / or a speed of the motor vehicle above a specified minimum speed and / or a speed of the motor vehicle below a specified maximum speed and / or the presence of a braking request. [4] Method according to one of claims 1 to 3, characterized by that the combustion engine (21) is switched off or is operated at idle or the combustion engine (21) is switched on and is used to charge a battery (25). [5] Method according to one of claims 1 to 4, characterized by , that - a cruise control mode is switched on (1), - checking whether a first number of specified conditions for decoupling the internal combustion engine (21) from the wheels (23) are met (2), - checking whether a second number of specified conditions for operating the internal combustion engine (21) in an ON-OFF mode are met (2), - the fuel consumption during ON-OFF operation is estimated (3), - the current fuel consumption is determined (3), - if the current fuel consumption is higher than the estimated fuel consumption during an ON-OFF operation and the first and second number of conditions are met, the drive train (20) is operated in the ON-OFF mode, wherein when the internal combustion engine (21) is switched off, a drive is carried out by means of the electric machine (32, 33, 34) (4). [6] Method according to one of claims 1 to 5, characterized bythat the drive train (20) comprises a battery (25) connected to the electric machine (32, 33, 34) and if the battery charge level is above a specified minimum charge level, an electronic clutch (26) between the internal combustion engine (21) and the electric machine (32, 33, 34) is opened, the internal combustion engine (21) is switched off and the drive is carried out by means of the electric machine (32, 33, 34) (6, 7). [7] Method according to one of claims 1 to 6, characterized by that the drive train (20) comprises a battery (25) connected to the electric machine (32, 33, 34) and if the battery charge level is below a predetermined minimum charge level, an electronic clutch (26) between the internal combustion engine (21) and the electric machine (32, 33, 34) is closed, the load of the internal combustion engine (21) is increased and the battery (25) is charged by means of the electric machine (32, 33, 34) (6, 8). [8] Method according to one of claims 1 to 7, characterized by that the drive train (20) is operated in a cruise control mode which is designed for speed and / or engine speed control and / or for adaptive speed and / or engine speed control and / or for distance control and / or for executing an autonomous driving mode. [9] Method according to claim 8, characterized by that if a requested speed target value is set and the distance of the motor vehicle to a vehicle in front is less than a target distance, a speed target value is set which is less than the requested speed target value. [10] Hybrid drive train (20) comprising an internal combustion engine (21) and at least one electric machine (32, 33, 34), characterized by that the hybrid drive train (20) carries out a method according to one of claims 1 to 9. [11] Hybrid drive train (20) according to claim 10, characterized by in that the hybrid drive train (20) comprises a transmission (22) and is designed as a parallel hybrid drive train, wherein the electric machine is arranged at position P2 (32), P3 (33) or P4 (34). [12] Hybrid drive train (20) according to claim 10 or 11, characterized by that the hybrid drive train (20) is designed as a full hybrid drive train. [13] Hybrid drive train (20) according to one of claims 10 to 12, characterized by that the hybrid drive train (20) comprises a planetary gear. [14] Motor vehicle (30) comprising a hybrid drive train (20) according to one of claims 10 to 13. [15] A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 9 or 11 to 13. [16] A computer-readable data carrier on which the computer program product according to claim 15 is stored.

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