DE102021102203A1 - Method for operating a motor vehicle, vehicle system and motor vehicle - Google Patents

Abstract

The invention relates to a method for operating a motor vehicle (10), with an electric machine (18), which is power-connected to at least one wheel (26) of the motor vehicle (10) via at least one shaft (24, 34) and has a rotor (20 ) has, with a traction battery (28), and with a control device (16), the method having the following steps:
- Detecting a rotor speed and / or a torque of the electric machine (18);
- Comparing the rotor speed and/or the torque with a torque-speed map (40);
- Disconnecting the at least one wheel (26) as a function of the adjustment;
- Switching to generator operation of the electrical machine (18) due to the decoupling; and
- Recuperation of a rotational energy of the rotor (20) during generator operation in the traction battery (26) by dynamic adjustment of a generator torque depending on the detected rotor speed. The invention also includes a vehicle system and a motor vehicle.

Description

The invention relates to a method for operating a motor vehicle, which has an electric machine, a traction battery, power electronics and a control device, according to patent claim 1. The invention also relates to a vehicle system, which includes a separating clutch and a control device, according to patent claim 7 Finally, the invention relates to a motor vehicle according to patent claim 10.

Motor vehicles, in particular passenger cars, are increasingly being driven by at least one electric machine that can be used as a motor. It is also possible to use several electric machines, there are motor vehicles which have, for example, an electric machine for driving the wheels of a front axle and an additional electric machine for driving the wheels of a rear axle.

This is how it shows DE 10 2016 014 732 A1 an electrically powered motor vehicle with at least one electric front wheel drive and at least one electric rear wheel drive.

Even if the performance of traction batteries and thus the range of electrically powered motor vehicles are constantly improving, a particularly high level of efficiency of the individual vehicle components is still desirable. Energy recovery, especially by means of recuperation, also plays an important role in electromobility.

The object of the present invention is therefore to provide a method, a vehicle system and a motor vehicle by means of which an electric machine of a motor vehicle can be used particularly advantageously for generating energy for a charging process and thus chemically storing the energy in a traction battery.

According to the invention, this object is achieved by the subject matter of the independent patent claims. Advantageous developments of the invention are specified in the dependent claims.

A first aspect of the invention relates to a method for operating a motor vehicle. The motor vehicle, which is designed in particular as a passenger car, has an electric machine which is power-connected to at least one wheel of the motor vehicle via at least one shaft. The electrical machine, or E-machine for short, includes a rotor and can also have a stator. The motor vehicle also has a traction battery, which is connected to the electric machine via power electronics. In motor operation, the electric machine serves as a motor for driving the motor vehicle. In addition, the motor vehicle has a control device.

• Als Schritt 1 des Verfahrens erfolgt ein Erfassen einer Rotordrehzahl der elektrischen Maschine durch einen Drehzahlsensor und/oder es erfolgt ein Erfassen eines Drehmoments der elektrischen Maschine. Dabei kann das Erfassen des Drehmoments, welches insbesondere ein Ist-Drehmoment ist, beispielsweise ebenfalls über den Drehzahlsensor und/oder über einen weiteren Sensor, wie beispielsweise einen Drehmomentsensor, erfolgen. Bei der Rotordrehzahl handelt es sich im Wesentlichen um die Ist-Maschinendrehzahl der elektrischen Maschine, also entspricht die Rotordrehzahl einer Drehzahl der elektrischen Maschine.
• In einem Schritt 2 des Verfahrens erfolgt ein Abgleich der erfassten Rotordrehzahl und/oder des erfassten Drehmoments mit einem hinterlegten Drehmoment-Drehzahl-Kennfeld durch die Steuervorrichtung. Das Drehmoment-Drehzahl-Kennfeld hält insbesondere einen Wirkungsgrad vor, welcher bei einer bestimmten Kombination aus Drehmoment und Drehzahl, insbesondere der Rotordrehzahl, beispielsweise durch die elektrische Maschine erreicht werden kann. Dabei kann das Drehmoment-Drehzahl-Kennfeld insbesondere aber auch einen Wirkungsgrad, welcher für ein Laden der Traktionsbatterie und/oder für die Leistungselektronik charakteristisch ist, umfassen. So kann das Drehmoment-Drehzahl-Kennfeld kurz als M-n-Feld oder auch als Wirkungsgradkennfeld bezeichnet werden, da es den Wirkungsgrad in Abhängigkeit von dem Drehmoment und der Drehzahl beschreibt. Das Drehmoment-Drehzahl-Kennfeld kann durch das Multiplizieren einzelner Kennfelder erstellt werden. Das einzelne Kennfeld entspricht einem weiteren Drehmoment-Drehzahl-Kennfeld beispielsweise dem der Leistungselektronik oder dem der Traktionsbatterie. Multipliziert man die einzelnen Kennfelder der in Reihe geschalteten Komponenten, wie E-Maschine, Leistungselektronik und Traktionsbatterie, beziehungsweise Batterieladung, miteinander erhält man vorteilhafterweise das hinterlegte Drehmoment-Drehzahl-Kennfeld. So ist durch das Drehmoment-Drehzahl-Kennfeld beispielsweise bestimmbar beziehungsweise bekannt, insbesondere zumindest in erster Näherung, welcher Wirkungsgrad beispielsweise bei einem Bremsen des rotierenden Rotors aus der Rotationsenergie als chemische Energie, insbesondere mittels Rekuperation, in der Traktionsbatterie zurückgewonnen werden kann.
• In einem Schritt 3 des Verfahrens erfolgt ein Abkoppeln des wenigstens einen Rades von der elektrischen Maschine durch eine Trennkupplung in Abhängigkeit von dem Abgleich. Das Abkoppeln entspricht einem Trennen, bei welchem durch die Trennkupplung beispielsweise die wenigstens eine Welle unterbrochen und/oder von wenigstens einer weiteren Welle getrennt werden kann. Nach dem Abkoppeln ist keine Leistungsverbindung also keine Verbindung, bei welcher ein Drehmoment zwischen Rad und elektrischer Maschine übertragen wird, vorhanden. Dabei erfolgt das Abkoppeln aufgrund des Abgleichs, insbesondere dergestalt, dass die in dem Rotor gespeicherte Rotationsenergie mit einem besonders großen Wirkungsgrad in chemische Energie, welche in der Traktionsbatterie speicherbar ist, umgewandelt werden kann. Bei dem Abgleich wird also eine Drehzahl und/oder ein Drehmoment bestimmt, bei welchem der Wirkungsgrad beim Abkoppeln besonders groß ist.

So that the motor vehicle can be operated particularly advantageously using the method according to the invention and a particularly large amount of energy, in particular energy that is not required to drive the motor vehicle, can be fed into the traction battery, the method has the following steps:

• As step 1 of the method, a rotor speed of the electric machine is detected by a speed sensor and/or a torque of the electric machine is detected. In this case, the torque, which is in particular an actual torque, can also be detected, for example, via the speed sensor and/or via a further sensor, such as a torque sensor. The rotor speed is essentially the actual machine speed of the electric machine, so the rotor speed corresponds to a speed of the electric machine.
• In a step 2 of the method, the detected rotor speed and/or the detected torque is compared with a stored torque/speed characteristic diagram by the control device. In particular, the torque/speed characteristic map provides an efficiency which can be achieved with a specific combination of torque and speed, in particular the rotor speed, for example by the electric machine. In this case, the torque-rotational speed characteristic diagram can also include an efficiency which is characteristic for charging the traction battery and/or for the power electronics. The torque-speed map can be referred to as the Mn field or as the efficiency map, since it describes the efficiency as a function of the torque and the speed. The torque-speed map can be created by multiplying individual maps. The individual map corresponds to another torque-speed map, for example that of the power electronics or that of the traction battery. If you multiply the individual maps of the series-connected components, such as the electric motor, power electronics and traction battery, respectively Battery charge, together you advantageously get the stored torque-speed map. For example, the torque-speed map can be used to determine or know, in particular at least in a first approximation, which efficiency can be recovered from the rotational energy as chemical energy, in particular by means of recuperation, in the traction battery when braking the rotating rotor.
• In a step 3 of the method, the at least one wheel is decoupled from the electric machine by a separating clutch as a function of the adjustment. The decoupling corresponds to a disconnection, in which, for example, the at least one shaft can be interrupted and/or separated from at least one other shaft by the disconnect clutch. After decoupling, there is no power connection, ie no connection in which a torque is transmitted between the wheel and the electric machine. In this case, the decoupling takes place on the basis of the adjustment, in particular in such a way that the rotational energy stored in the rotor can be converted with a particularly high level of efficiency into chemical energy, which can be stored in the traction battery. During the adjustment, a speed and/or a torque is thus determined at which the efficiency during decoupling is particularly high.

In order to be able to store the rotational energy of the rotor, in a step 4 of the method, the power electronics are switched or switched over to generator operation of the electrical machine due to the decoupling or for the decoupling. In generator operation, which describes the opposite state of the electric machine to motor operation, energy can be obtained for charging the traction battery. In contrast, in motor mode, the electric machine consumes electricity from the traction battery for a journey.

Finally, in step 5 of the method, the rotational energy of the rotor is recuperated, ie recovered, into the traction battery during generator operation by dynamically adapting or changing a generator torque as a function of the rotor speed detected by the speed sensor. The rotor speed now detected is a speed of the rotor independent of a speed of the wheel, since the wheel is not driven by the electric machine in generator mode because the wheel is separated from the electric machine by the separating clutch. The regenerative torque is a torque which is provided or can be provided by the power electronics, in particular in the electric machine or by the electric machine, and which is to be applied in order to direct a charging current into the traction battery. The torque is provided at least temporarily by the excess energy of the rotor, which now rotates more or less freely. Recuperation corresponds to the recovery of energy. Here, recuperation describes the storage of at least part of the rotational energy of the rotor that was applied for the rotation of the rotor.

The steps of the method can be initiated and/or carried out using the control device, or the control device can issue corresponding control commands, for example for decoupling, sending and/or receiving. Likewise, the control device can transmit, receive and/or process corresponding data, such as the rotor speed.

When the rotor is braked or when it is decelerated, ie while the rotor is coasting down, the method causes a dynamic change in the generator torque as a function of the rotor speed. In this case, the dynamic change can be provided in particular by the power electronics. When charging the traction battery, the power electronics work in particular as a rectifier, since a three-phase alternating current is provided from the electrical machine, for example, but direct current is required to charge the traction battery. The power electronics can influence the generator torque, for example by setting a current value and/or controlling a pilot control angle.

Depending on the type of electrical machine, the regenerative torque can be generated differently. In a permanently excited synchronous machine (PSM) and/or in a synchronous reluctance machine (SRM), a specific regenerative torque can be achieved by means of the power electronics by setting the current and/or the pilot control angle. With a PSM or SRM, the speed of the rotor, i.e. the rotor speed, corresponds to a speed of the magnetic field in the stator, which means that a speed difference is zero. However, in generator operation, the rotor rushes ahead and the magnetic field in the stator follows with an angular difference.

This angle difference corresponds to the pre-control angle, which can be influenced by the power electronics.

Furthermore, the power electronics can set a slip, for example, which determines an efficiency for charging the traction battery or the regenerative torque, ie a torque for charging the traction battery. If the electrical machine is designed as an asynchronous machine (ASM), the power electronics can control or regulate the current and the slip. Due to the slip, the mechanical speed of the rotor is different than a speed of the magnetic field in the stator for a specific generator torque. A differential speed occurs between the rotor speed and the speed of the magnetic field, expressed as a percentage as slip. In generator operation or in generator operation, the rotor speed is higher than the speed of the magnetic field, predetermined by the determinable slip.

In summary, the dynamic changing of the generator torque is therefore primarily carried out by control or regulation by means of or via the power electronics.

In other words, the aim of the method according to the invention is to convert rotational energy stored in the rotor of the electric machine with a particularly high degree of efficiency shortly after the decoupling or decoupling and to store or charge it as chemical energy in the traction battery. The decoupling, ie the separation, of at least one wheel, in particular the wheels of an axle of the motor vehicle, can advantageously take place, for example, when driving on the freeway. Energy can be saved on such a highway trip due to low air resistance and/or frictional resistance.

The method for operating the motor vehicle can be carried out in particular when the motor vehicle has a further electric machine in addition to the electric machine. In this case, for example, each of the electrical machines is designed to drive the wheels of an axle of the motor vehicle. For example, the electric machine drives the wheels on the front axle and the other electric machine drives the wheels on the rear axle. It can be particularly advantageous when driving fast on the freeway, for example, to decouple the wheels or the at least one wheel on the front axle and drive the motor vehicle only through the wheels of the other axle, in this example the rear axle. In order for this to take place particularly efficiently, the rotational energy of the rotor of the electrical machine, which is separate from the wheels, is now recovered by the method according to the invention and at least partially charged into the traction battery. In order for this to take place particularly efficiently, the rotor is not braked with a constant generator torque, such as by means of a torque prescribed by a PID controller, but according to a trajectory in the torque/speed characteristic diagram. In the torque/speed map, this trajectory runs more or less along a gradient of the highest efficiency that can be achieved during recuperation, so that the energy recovered in the traction battery is particularly large.

For this purpose, the torque of the electric machine will approach zero in the method shortly before decoupling, in order to be able to open the separating clutch safely and without damage. In addition or as an alternative, other so-called introductory trajectories can also be traversed in the torque-speed characteristic diagram, in which the electric machine is guided from a zero torque to a particularly advantageous braking torque, the generator torque. This results in a family of curves of trajectories on the M-n field, which means that a particularly large amount of rotational energy can be recovered. Such a trajectory can be dependent on other parameters, such as the temperature, in addition to being dependent on the rotational speed and the torque. For example, the optimum charging current values for the traction battery differ at different temperatures.

In summary, the method according to the invention describes a particularly advantageous shutdown of the electric machine after decoupling, in order to be able to recover and store a particularly large amount of rotational energy from the rotor. The advantage resulting from the method according to the invention is that, shortly after decoupling, the rotational energy stored in the rotor can be converted with a particularly high level of efficiency into chemical energy for storage in the traction battery. This also results in the advantage that the range of the motor vehicle can be particularly advantageously increased or is particularly large. As a result, the motor vehicle can also be operated particularly cost-effectively, for example.

In an advantageous embodiment of the invention, the wheel is decoupled by the separating clutch between the wheel and a differential, which is arranged between the electrical machine and the wheel on the at least one shaft. In other words, the motor vehicle has a differential arranged on the shaft have differential gears, the purpose of which is, among other things, to drive the at least one wheel and one other wheel, which is located in particular with the at least one wheel on the same axle of the motor vehicle, in such a way that they travel at different speeds, for example when cornering, but with the same propulsive force can rotate. In addition, for example, the at least one shaft can be connected to the electric machine via a gear. If the at least one wheel is decoupled between the differential or differential gear and the wheel, only 50 percent of the torque needs to be applied during coupling, for example, than if coupling were to take place between the differential and the gear.

In other words, the disconnect clutch that can be operated by the method is arranged in such a way that it interrupts a power connection between the wheel and the differential. This results in the advantage that energy can be saved in a particularly advantageous manner for the decoupling or also during a coupling or coupling, in particular for a torque adjustment or a torque adjustment.

In a further advantageous embodiment of the invention, a wheel speed of the at least one wheel is detected by a wheel sensor, the wheel being additionally or alternatively decoupled as a function of the detected wheel speed. In other words, in addition to detecting the rotor speed and the torque, the wheel speed is detected and the decoupling and thus the recuperation that follows the decoupling is carried out as a function of the wheel speed. The wheel speed indicates the movement of the wheel and thus also a speed of the motor vehicle, for example, and correlates with the rotor speed in a state in which the clutch is closed, depending on a gear ratio, for example. By detecting the wheel speed and decoupling as a function of this, the method can be carried out particularly advantageously, since for example the moment of decoupling can be determined particularly advantageously.

In a further advantageous embodiment of the invention, the separating clutch is coupled, i.e. after decoupling, the power of the wheel is reconnected to the electric machine by synchronizing the rotor speed with the wheel speed and/or the coupling also takes place as a function of the wheel speed, the rotor speed and/or the torque of the electric machine. In other words, the separating clutch is coupled dynamically due to the synchronization or due to the dependence on the rotor speed, the wheel speed and/or the torque, so that the electric machine can be used to (further) drive the motor vehicle in a particularly advantageous manner.

In a further advantageous refinement of the invention, the dynamic adjustment of the generator torque is additionally carried out as a function of a further parameter, in particular, for example, of a temperature, for example of the electric machine and/or the traction battery. In other words, the regenerative torque when charging the traction battery is also changed as a function of the other parameter. For example, the temperature has an effect on a particularly advantageous charging current value for the traction battery. In this case, several torque/speed characteristic diagrams can be stored, one of which is selected for the adjustment as a function of the further parameter. This results in the advantage that a particularly large amount of rotational energy can be recovered by the method.

In a further advantageous embodiment of the invention, a torque of another electric machine and / or a torque, which is on a further wheel, which is located on an axis of at least one wheel different axis increases when due to the decoupling by the electric Engine caused torque decreases on the at least one wheel. In other words, in particular for particularly efficient operation of the motor vehicle, for example when the electric machine drives the at least one wheel on the front axle of the motor vehicle and another electric machine drives the wheels on the rear axle of the motor vehicle, after decoupling and the corresponding acceptance of the torque on the at least one wheel, the torque of the additional electric machine or the torque acting on the at least one additional wheel is modified in such a way that the sum of the total torques generally remains constant. This allows the motor vehicle to continue driving, for example on the freeway, in a particularly advantageous manner, without the speed of the motor vehicle changing.

A second aspect of the invention relates to a vehicle system for a motor vehicle, the vehicle system comprising a separating clutch. The separating clutch can be moved between an open position and a closed position and thus serves to decouple at least one wheel of the motor vehicle from an electrical machine of the motor vehicle, which is connected to one another via at least a shaft can be power-connected or are power-connected.

The vehicle system includes the separating clutch arranged on at least one shaft of the motor vehicle, which can be moved between an open position and a closed position for reversible disconnection of a power connection between an electric machine and at least one wheel of the motor vehicle that can be communicated via the at least one shaft. Due to the separating clutch, the power connection is designed to be reversible and separable.

Furthermore, the vehicle system has a control device. The control device is designed to detect a rotor speed and/or a torque of the electric machine and to adjust the machine speed and/or the torque with a stored torque/speed characteristic diagram. Furthermore, the control device is designed to switch power electronics, it being possible for the power electronics to be switched over between motor operation and generator operation of the electrical machine.

During motor operation, the power electronics are used to use energy from a traction battery of the motor vehicle to operate the electric machine and thus to drive the at least one wheel. In generator mode, the power electronics are used to use the electric machine to charge the traction battery. The vehicle system is designed to cause rotational energy of a rotor of the electric machine to be recuperated in the traction battery of the motor vehicle in generator mode by dynamically adapting a generator torque in generator mode of the machine as a function of a rotor speed that can be detected by the control device.

In short, the vehicle system with its separating clutch and its control device is designed to carry out the method according to the invention. In this case, the generator torque describes the torque that can be generated by the power electronics in order to charge the traction battery, in particular with a particularly high level of efficiency. For this purpose, the torque-speed map has at least one efficiency or one system efficiency, which results from the interaction of the power electronics, the traction battery and the electric machine. In addition, however, other components that are connected in series with the components mentioned for charging the traction battery between the electric machine and the traction battery can also have an influence on the M-n field.

In a further advantageous embodiment of the invention, the separating clutch is designed as a claw clutch. The dog clutch is a simple way of transmitting rotary motion or torque and essentially creates a connection from one end of the first shaft to another shaft or from a first part of the at least one shaft to a further part of the at least one shaft. As a result, the separating clutch can, for example, be designed to be particularly light in a particularly advantageous manner, so that the range of the motor vehicle is particularly large.

In a further advantageous embodiment of the invention, an actuator is provided for moving the separating clutch between the open position and the closed position. In this case, the actuator is in particular an electrically driven actuator. Due to the property of the actuator to enable movement between the open position and the closed position, the actuator is used to decouple and couple the wheel from the electric machine. In this case, the actuator can open and close the separating clutch, for example by means of a pinion shaft. Additionally or alternatively, a position sensor is provided, which detects the state of the separating clutch between the open position and the closed position and can thus describe a position of the first shaft relative to the second shaft. This results in the advantage that the separating clutch can be moved particularly easily and/or particularly precisely, as a result of which the vehicle system and thus the motor vehicle can be operated particularly advantageously. After that, there is the advantage that a particularly large amount of rotational energy can be recovered.

A third aspect of the invention relates to a motor vehicle which is designed to carry out the method according to the invention and/or which has a vehicle system according to the invention.

The invention also includes the control device for the motor vehicle. The control device can have a data processing device or a processor device that is set up to carry out an embodiment of the method according to the invention. For this purpose, the processor device can have at least one microprocessor and/or at least one microcontroller and/or at least one FPGA (Field Programmable Gate Array) and/or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code that is set up to to carry out the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device.

The invention also includes developments of the motor vehicle according to the invention, which have features as have already been described in connection with the developments of the method according to the invention and the vehicle system according to the invention. Thus, advantages and advantageous configurations of the first aspect of the invention are to be regarded as advantages and advantageous configurations of the second and the third aspect of the invention and vice versa. For this reason, the corresponding developments of the method according to the invention or of the vehicle system according to the invention are not described again here.

The motor vehicle according to the invention can preferably be designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

The invention also includes the combinations of features of the described embodiments. The invention also includes implementations that each have a combination of the features of several of the described embodiments, unless the embodiments were described as mutually exclusive.

• 1 eine schematische Ansicht eines Kraftfahrzeugs mit Fahrzeugsystem, mit elektrischer Maschine, Leistungselektronik, Traktionsbatterie und wenigstens einem Rad, welches mittels einer Trennkupplung mit der elektrischen Maschine leistungsverbindbar ist;
• 2 in einem Diagramm ein Drehmoment-Drehzahl-Kennfeld, welches einen Wirkungsgrad zum Laden der Traktionsbatterie mittels der elektrischen Maschine gemäß 1 beschreibt;
• 3 in einem Diagramm eine beim Laden erzielbare Leistung in Abhängigkeit der Drehzahl;
• 4 in Diagrammen eine Zeitabhängigkeit des Drehmoments und der Drehzahl bei einem Abkoppeln der Trennkupplung;
• 5 in einem schematischen Diagramm das Zusammenwirken zwischen Steuervorrichtung, Leistungselektronik und Trennkupplung;
• 6 in einem Diagramm eine Zeitabhängigkeit einer Rotordrehzahl und einer Raddrehzahl bei einem Kuppeln der Trennkupplung;
• 7 in einem Diagramm die Zeitabhängigkeit weitere Parameter während dem Kuppeln der Trennkupplung;
• 8 in einer geschnittenen schematischen Perspektivansicht die Trennkupplung mit einem Differential und der Leistungselektronik;
• 9 in einer Schnittansicht die Trennkupplung gemäß 8;
• 10 in einer schematischen Perspektivansicht die Trennkupplung gemäß 8 und 9 mit Aktor; und
• 11 in einer schematischen Perspektivansicht der Aktor gemäß 10.

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

• 1 a schematic view of a motor vehicle with a vehicle system, with an electric machine, power electronics, a traction battery and at least one wheel, which can be power-connected to the electric machine by means of a separating clutch;
• 2 in a diagram, a torque-speed map, which according to an efficiency for charging the traction battery by means of the electric machine 1 describes;
• 3 in a diagram, a power that can be achieved during charging as a function of the speed;
• 4 in diagrams, a time dependence of the torque and the speed when the separating clutch is uncoupled;
• 5 in a schematic diagram the interaction between the control device, power electronics and separating clutch;
• 6 in a diagram a time dependency of a rotor speed and a wheel speed when the separating clutch is engaged;
• 7 in a diagram the time dependency of other parameters during the coupling of the separating clutch;
• 8th in a sectional schematic perspective view, the separating clutch with a differential and the power electronics;
• 9 in a sectional view according to the separating clutch 8th ;
• 10 in a schematic perspective view the separating clutch according to FIG 8th and 9 with actuator; and
• 11 in a schematic perspective view of the actuator according to 10 .

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 that are to be considered independently of one another and that each also develop the invention independently of one another. Therefore, the disclosure is also intended to encompass combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.

In the figures, the same reference symbols designate elements with the same function. Numerical values in the figures are examples.

1 shows a motor vehicle 10 with a vehicle system 12 in a schematic view, which has a separating clutch 14 and a control device 16 . The motor vehicle 10 also includes an electric machine 18 which has a rotor 20 and a stator 22 . The electrical machine 18 is power-connected or can be power-connected via at least one shaft 24 to at least one wheel 26 of the motor vehicle 10 . Motor vehicle 10 also includes a traction battery 28 which is connected to electric machine 18 via power electronics 30 .

The at least one shaft 24 can be connected to the at least one shaft 24 by means of a gear 32 and a further shaft 34, for example.

In the exemplary embodiment shown, motor vehicle 10 also has a differential 36 . The differential 36 is designed as a differential gear forms. This transfers a torque, mediated via the at least one shaft 24 and generated by the electric machine 18 , to the at least one wheel 26 and to a further wheel 38 . Additional shafts 34 are provided for this purpose. The two wheels, wheel 26 and wheel 38, form a front axle of motor vehicle 10, for example. Separating clutch 14 is preferably designed as a claw clutch, which easily connects one end of additional shaft 34 to the other end of additional shaft 34 can couple or separate and thus uncouple.

The right half of the 1 to the right of the dotted line, the separating clutch 14 in the closed position, in which the two shafts 34 are connected to one another for power transmission. In contrast, the illustration on the left of the separating clutch 14 shows the separating clutch in an open position in which the two shafts 34 are separated from one another and thus no power transmission from one shaft 34 to the other shaft 34 is possible.

A method for operating the motor vehicle 10 can be carried out by the motor vehicle 10 shown and the vehicle system 12 shown.

The method is used, for example when driving on the freeway, to decouple the electric machine 18 from the at least one wheel 26, with the rotational energy of the rotor 20 of the electric machine 18, which continues to rotate, being recovered by means of recuperation and being stored in the traction battery 28. As a result, the range of the electrically drivable motor vehicle 10, which is designed in particular as a passenger car, can be increased. So that the range can be increased in a particularly advantageous manner, since the excess rotational energy of the rotor 20 can be stored with a particularly high level of efficiency and in a particularly large quantity, the method comprises a number of steps.

In a first step of the method, a rotor speed of rotor 20 of electric machine 18 is detected by an in 5 speed sensor 70 shown. Additionally or alternatively, a torque of the electric machine 18 is detected in this step.

In a second step of the method, the detected rotor speed and/or the detected torque is compared with a torque/speed characteristic map 40 stored in control device 16, for example, which is shown in FIG 2 is shown. The torque/speed characteristic field 40, Mn field for short, shows an efficiency as a function of the rotor speed and the torque of the electrical machine.

In a third step of the method, the at least one wheel 26 is decoupled from the electric machine by the separating clutch 14 as a function of the adjustment. The differential 36 and the separating clutch 14 can advantageously be placed in such a way that the separating clutch 14 is arranged between the at least one wheel 26 and the differential 36, so that when the at least one wheel 26 is decoupled by the separating clutch 14, for example in comparison to a position of the separating clutch 14 between the differential 36 and the transmission 32, a relatively smaller torque acts on the shaft 34 and thus on the separating clutch 14, as a result of which, for example, the separating clutch 14 is particularly durable.

In a fourth step of the method, the power electronics 30 are switched or switched over to generator operation of the electrical machine 18 due to the decoupling. Finally, in a fifth step, the rotational energy of the rotor 20 can be recuperated during generator operation in the traction battery 28, with a dynamic adjustment of a generator torque taking place as a function of the rotor speed detected by the speed sensor.

By comparing the torque-speed map 40 and the efficiencies that can be taken from the torque-speed map 40 as a function of the torque and/or the rotor speed, the dynamic adjustment can be carried out in such a way that an efficiency for feeding in the rotational energy of the Rotors in the traction battery 28 is particularly large. The rotational energy is fed in in particular via the power electronics 30, which now function as a rectifier.

The motor vehicle 10 , the vehicle system 12 and the method are based on the idea of using the energy that can be recovered from the rotational energy of the rotor 20 to a particularly large extent to charge the traction battery 28 . This is done by means of dynamic adaptation such that the generator torque is regulated depending on the rotor speed of the rotor 20 that is decoupled due to the open position of the separating clutch 14 when coasting or braking until the rotor 20 comes to a standstill. The rotational energy is fed into the traction battery 28 as a current flow.

In the 1 it can be seen that the electric machine 18 is connected in three phases to the power electronics 30 via its stator 22 , with a two-phase connection to the traction battery 28 from there. This is due to the fact that the electric machine 18 generally requires or provides a three-phase alternating current, whereas the traction battery 28 provides or requires direct current for charging. Due to the dynamic adjustment, the current flow for charging becomes particularly large.

Thus, a respective advantage of the motor vehicle 10, the vehicle system 12 and the method is that the range of the motor vehicle 10 can be extended.

2 shows a diagram of the torque/speed characteristic diagram 40, with the contour lines describing corresponding efficiencies. The efficiency specified in the torque/speed characteristic map 40 is referred to as the system efficiency and can result, for example, in particular by multiplying the efficiency of individual components. The system efficiency can thus be composed of the individual efficiency of the electric machine 18 with the efficiency of the power electronics 30 with the efficiency of the battery charge of the traction battery 28 . In addition, the torque/speed characteristic map 40 is generally temperature-dependent, so that at different temperatures a number of system efficiency characteristic maps can also be kept or used as a torque/speed characteristic map 40 . It has therefore proven to be useful if the dynamic adjustment of the generator torque also takes place as a function of another parameter, in particular the temperature.

In this case, in the torque/speed characteristic diagram 40, the speed is plotted along the x-axis and the torque is plotted along the y-axis, with the contour lines reflecting the efficiency.

In this case, a trajectory 42 describes particularly advantageous braking torques, that is to say regenerative torque values which characterize the regenerative torque in generator operation. If the dynamically adapted, regenerative torques of the trajectory 42 follow, the energy that can be recovered during recuperation in the traction battery 28 can be maximized or at least become particularly large.

If, on the other hand, a simple decoupling takes place, for example by means of a PID controller that is usually used, where PID stands for “proportional, integral and differential”, the trajectory is not optimal, as the two trajectories 44 and 46 show. In this case, the trajectory 44 has too low and the trajectory 46 has too high torques.

In order to be able to carry out the method advantageously, the torque of the electric machine 18 should be zero shortly before the decoupling, in order to be able to open the separating clutch 14 safely, ie without damage. For this reason, additional so-called introductory trajectories can also be present in the torque/speed characteristic map 40 . Thus, the trajectory 48 shows a decoupling at 6,000 revolutions and the trajectory 50 a decoupling at 10,000 revolutions, with which the electric machine 18 is directed from zero torque to a particularly advantageous braking torque. The method or the dynamic adjustment of the generator torque can thus be carried out on the basis of a number of trajectories, for example 42, 48 and 50, which form a set of curves. As a result, a particularly large yield of recovered rotational energy can be achieved. The advantageous trajectories 42, 48 and 50 change depending on other parameters such as temperature. Because, for example, optimum charging current values of the traction battery 28 differ from one another at different temperatures.

The dynamic adjustment of the generator torque is preferably carried out by means of the power electronics 30, for example by correctly setting a current value for the charge and/or by controlling a pilot control angle.

The efficiency shown in the torque/speed characteristic diagram 40 corresponds to a system efficiency which, as already stated, is made up of a number of system efficiencies or of a number of characteristic diagrams.

The torque/speed characteristic map 40 shows, for example, that a particularly advantageous generator torque for 4,500 revolutions per minute (rpm) is -197 newton meters (Nm), since a system efficiency of 89 percent can be achieved at this point. With higher or lower regenerative torque, the system efficiency would be less than 89 percent, which means that not so much rotational energy could flow back into the traction battery 28 or be used there for charging.

In summary, the 2 by the trajectory 42 a particularly advantageous torque for the rotor 20 depending on its Rotord speed, whereby the system efficiency is particularly high.

In contrast, the trajectory 46 shows that a shutdown or decoupling was carried out with too high a regenerative torque, and the energy that is charged in the traction battery 28 is less than would be possible. The situation is similar with the trajectory 46, in which it was switched off with too little generator torque, so that the electrical energy that can be charged in the traction battery 28 is less than possible. The trajectory 42 shown is therefore the decisive criterion when comparing the rotor speed or the torque with the stored torque-speed characteristic map 40 in order to carry out the dynamic adjustment of the generator torque (generator torque) in the method.

3 shows the three in a speed-power diagram 2 trajectories 42, 44, 46 shown and the mechanical power that can be achieved by them.

With regard to the rotational energy that can be obtained, it should be noted that the rotor 20, when uncoupled from the wheel 26, can still be connected via the shaft 24 and/or a further shaft 34, for example to uncoupled components such as gear wheels of the transmission 32, the shafts 24, 34 and the differential 36 can be connected. Therefore, for example, a transmission efficiency of the transmission 32 during energy recovery or its friction must be taken into account for the power.

Thus, the rotational energy for an example rotor is rotor 20 with an axial length of 153.9 millimeters (mm) and rotor diameter of 113 millimeters with a density of 7.87 g/cm ³ and a mass moment of inertia J of 0.0395 kg/m ² at a speed of 17,000 rpm 15.4 watt hours (Wh). The rotational energy is made up of ERotorside = ½*JRotorside*ωRotor and the other rotational energy can be described by E = ½*J*ω.

The method shown can be used particularly advantageously in a motor vehicle 10 which includes a further electrical machine which is different from the electrical machine 18, the further electrical machine having further wheels on a further axis which is different from the axis of the at least one wheel 26 can drive. Thus, the method can play out particular advantages, for example, in motor vehicles with an all-wheel drive, which is driven by at least two electric machines, since, for example, when driving on the motorway, the electric machines are each optimized for a different speed range, so that it can appear sensible to use particularly advantageous energy to save, switch off one of the electrical machines, in particular the electrical machine 18, at a certain speed in order to advantageously recover energy for the traction battery. The method can also be carried out if, for example, the motor vehicle 10 does not have any axles in the traditional sense, since each wheel 26 and 38 has its own electric machine.

4 shows a diagram of speeds, the rotor speed and a wheel speed of the at least one wheel 26 as a function of time. Curve 52 shows rotor speed and curve 54 shows wheel speed. The wheel speed of the at least one wheel 26 can be increased by an in 5 shown wheel sensor 78 are detected. It is advantageous that the at least one wheel 26 is uncoupled as a function of the detected wheel speed.

Furthermore, the 4 a torque acting on the at least one wheel 26 or on a front axle and a rear axle driven by a further electric machine as a function of time. Curve 56 represents the total torque and curve 58 represents the torque caused by electric machine 18 . The curve 60 shows the torque which is caused by a further electric machine, in particular at the wheels of a further axle. This shows that the total torque 56 remains constant, as a result of which the motor vehicle 10 can be driven with the same power or continue at the same speed.

The point in time t ₀ shows the point in time at which the control device 16 provides the signal for opening or separating the separating clutch 14 . The time interval 62 indicates the signal propagation time until regulation for a zero torque takes place, which takes a time according to the time interval 64 . If the torque is zero, another signal takes place, which takes a signal propagation time 66 . So that at time t ₁ the separating clutch 14 can be safely opened. From time t ₁ the rotor speed of electric machine 18 is reduced to a standstill, in particular due to the dynamically adjusted generator torque of electric machine 18, which is now in generator mode. Curve 58 shows that the torque when decoupling approaches zero. In this case, the control device 16 can prescribe the braking torque, that is to say the generator torque, for example by means of a PID controller. In this case, Δn/Δt, i.e. the change in speed over time, could be almost constant.

This is how it shows 4 Furthermore, that a torque of a further electric machine and/or a torque that is applied to a further wheel, which is located on an axle that is different from an axle of the at least one wheel 26, is increased if due to the decoupling or the initiation of the decoupling process Torque caused by the electric machine on the at least one wheel decreases.

5 shows a possible interconnection or interaction of the control device 16 with the power electronics 30 and the separating clutch 14 in a schematic view. The vehicle system 12, which includes the control device 16 and the separating clutch 14, is highlighted. Control device 16 receives the wheel speed as signal 68 from speed sensor 70. Control device 16 sends signal 72 as a command to decouple and/or couple separating clutch 14 to an actuator 74.

The actuator 74 is supplied with electrical energy, for example, from a vehicle electrical system 76 , in particular a 12-volt vehicle electrical system, of the motor vehicle 10 . The signal 68, which describes the wheel speed, can be detected by means of the wheel sensor 78, which can be assigned to a chassis 80 of the motor vehicle 10. A position sensor 82 determines a state of the separating clutch 14 between the open position and the closed position, with position data 84 being able to be returned to the control device 16 . Based on the comparison, the control device 16 also sends a setpoint torque 86 to the power electronics 30 , which in turn reports the speed of the electric machine 18 back to the control device 16 with the signal 88 .

The control device 16 can include, for example, a PID controller and/or a drive control unit.

The diagram of 6 shows the time course of the wheel speed and the rotor speed for a coupling of the separating clutch 14, the rotor speed being synchronized with the wheel speed. Additionally or alternatively, the coupling can take place as a function of the wheel speed, the rotor speed and/or the torque of the electric machine 18 . The point in time t ₀ in the diagram shown is the 6 the point in time at which the control device 16 sends the signal to close the separating clutch 14 . The time interval 90 is the duration of the signal propagation time and is required for the calculation of a target torque. Finally, in the time interval 92, the synchronization of the electrical machine 18 takes place, the two speeds, ie the wheel speeds and rotor speeds, being adjusted at the time t ₂ , and during the time interval 94 a signal propagation time again prevails. The time interval 96 then characterizes the mechanical actuator adjustment time which the actuator 74 requires to close the separating clutch 14 . Finally, at time t ₁ , the clutch is securely closed and torque flow or power transmission to the at least one wheel 26 or to the axle, which includes the at least one wheel 26 , starts.

The deviation of the recorded speeds and thus the error in the rotor speed and/or the wheel speed is plus/minus 30 revolutions per minute. The closing shown takes place in a similarly dynamic manner as the setting or adjustment of the generator torque or the braking torque. The diagram shows the 7 a dynamic closing of the separating clutch 14 at a motor vehicle speed of 135 km/h, the closing time totaling 595 milliseconds. The area 98 of the diagram of the 7 shows the synchronization of the speed. The times t ₀ and t ₁ correspond to the times of in 6 diagram shown. The speed is synchronized in a time interval of 340 milliseconds (ms) from one revolution from 0 to 900 (rpm).

Section 100 of the diagram shows the torque of electric machine 18 in newton meters. The target torque in phase 1 is 80 newton meters and in phase 2 265 newton meters, as the two different curves make clear.

Area 102 shows a desired connection, area 104 the command to close the separating clutch 14, area 106 of the diagram shows feedback that the separating clutch 14 is securely closed.

In the case of the diagrams of 6 and 7 The values shown are values that are obtained in an experimental setup with the 8th until 10 shown embodiment of a separating clutch 14 were obtained.

It has been shown, for example, that a further potential saving of approximately 50 milliseconds in the closing switching time could be achieved by shortening the actuator closing time if, for example, an optimized power supply to the actuator 74 can be ensured. In this case, the current controller settings of a PID controller, which is held up to the control device 16, were set from P: 0.09, I: 0.01, D: 0.4 with a test time of the synchronous speed of 30 milliseconds and an n _dif = 30 Revolutions per minute.

8th shows both the power electronics 30 and the differential 36 as well as the separating clutch 14 designed as a claw clutch in a sectional perspective view.

The separating clutch 14 shown comprises a pinion shaft 108, an oil filler screw 110, a thin section bearing 112, roller bearing 114, radial shaft sealing rings 116, an oil drain screw 118, a needle bearing 120, a locking claw 122 mounted on a spline and a shifting claw 124 with splines for shifting. Furthermore, the separating clutch 14 comprises a rotationally decoupled sleeve 132 with teeth and a compression spring 134.

The sectional view of 9 shows a detailed view of the area in the dotted box 8th .

The separating clutch 14 can, as in 10 shown, include a separate housing 128, which can also be attached in test operations, for example, because of a post-integration for carrying out a concept phase. The housing 128 has a plexiglass pane 126 provided for test purposes, which is used, for example, to measure times for a high-speed camera to look through and to check assembly. When operated in a motor vehicle 10, in contrast to operation on a test bench, the plexiglass pane 126 is dispensed with.

The actuator 74 whose housing enclosure in 11 is shown, in a simple configuration comprises an electric motor with a worm stage and a spur gear stage, the pinion shaft 108 being able to be driven via the connection 130, as a result of which the separating clutch 14 can be moved between its open position and its closed position.

Further embodiments of the separating clutch are available as an alternative and/or in addition to the embodiment according to FIG 9 conceivable. For example, a modular approach can be followed or a simple screw-on solution. The vehicle system 12 shown, the motor vehicle 10 shown and the method shown make it possible to switch off the electric machine 18 in a particularly advantageous manner after it has been decoupled by means of the separating clutch 14 of the at least one wheel 26, whereby a quasi-maximization of the recovered energy which is stored in the traction battery 28 can be stored. In this way, it is advantageously possible for the excess rotational energy to be converted into chemical energy, which can be charged in the transaction battery 28, with the greatest possible efficiency (in view of the torque/speed characteristic map 40).

Overall, the examples show how an optimal shutdown after decoupling an electric machine 18 can be provided.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102016014732 A1 [0003]

Claims (10)

Method for operating a motor vehicle (10), with an electric machine (18), which is power-connected via at least one shaft (24, 34) to at least one wheel (26) of the motor vehicle (10) and has a rotor (20). a traction battery (28), which is connected to the electric machine (18) via power electronics (30), and to a control device (16), the method having the following steps: - Detecting a rotor speed of the electric machine (18) by a speed sensor (70) and / or detecting a torque of the electric machine (18); - the rotor speed and/or the torque are compared with a stored torque/speed characteristic diagram (40) by the control device (16); - Decoupling the at least one wheel (26) from the electric machine (18) by a separating clutch (14) as a function of the adjustment; - Switching the power electronics (30) in a generator operation of the electrical machine (18) due to the decoupling; and - Recuperation of a rotational energy of the rotor (20) during generator operation in the traction battery (26) by dynamic adjustment of a generator torque depending on the detected rotor speed. procedure after claim 1 , characterized in that the decoupling of the at least one wheel (26) by the separating clutch (14) between the wheel (26) and a differential (36) which is between the electric machine (18) and the wheel (26) at the at least a shaft (24, 34) is arranged, takes place. procedure after claim 1 or 2 , characterized in that a wheel speed of the at least one wheel (26) is detected by a wheel sensor (78) and/or the at least one wheel (26) is decoupled as a function of the detected wheel speed. Method according to one of the preceding claims, characterized in that for coupling the separating clutch (14) the rotor speed is synchronized with the wheel speed and/or the coupling is carried out as a function of the wheel speed, the rotor speed and/or the torque of the electric machine (18 ) he follows. Method according to one of the preceding claims, characterized in that the dynamic adjustment of the generator torque is additionally carried out as a function of at least one further parameter, in particular a temperature. Method according to one of the preceding claims, characterized in that a torque of a further electrical machine and/or a torque which is applied to a further wheel which is located on an axle which is different from an axle of the at least one wheel (26) is increased, if due to the decoupling, a torque caused by the electric machine (18) on the at least one wheel (26) decreases. Vehicle system (12) of a motor vehicle (10) comprising a separating clutch (14) which is arranged on at least one shaft (24, 34) of the motor vehicle (10) and can be moved between an open position and a closed position in order to release a clutch via the at least one shaft (24 ) communicable power connection between an electric machine (18) and at least one wheel (26) of the motor vehicle (10) form reversibly separable, and further comprising a control device (16), which - for detecting a rotor speed and/or a torque of the electrical machine (18), for adjusting the machine speed and/or the torque with a stored torque-speed characteristic diagram, and - is designed for switching power electronics between motor operation and generator operation of the electric machine, - wherein the vehicle system (12) is designed to recuperate rotational energy of a rotor (20) of the electric machine (18) in a traction battery (28) of the motor vehicle (10) in generator mode by dynamically adapting a generator torque in generator mode of the electric machine (18) as a function of the rotor speed which can be detected by the control device (16). Vehicle system (12) according to claim 7 , characterized in that the separating clutch (14) is designed as a claw clutch. Vehicle system (12) according to claim 7 or 8th , characterized in that an actuator (74), in particular an electrically driven one, is provided for moving the separating clutch (14) between the open position and the closed position and/or a position sensor (82) is provided which monitors the state of the separating clutch (14) between the open position and the closed position detected. Motor vehicle (10), which for performing a method according to one of Claims 1 until 6 is formed and / or which is a vehicle system tem (12) after one of the Claims 7 until 9 having.

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