Method for controlling an electric drive unit of a motor vehicle

Abstract

The present invention relates to a method for controlling an electric drive (100) of a vehicle by a control unit (106), wherein at least one wheel (116) of the vehicle can be driven by an electric motor (104) of the electric drive (100), the electric drive (100) having at least one energy source (108) for the electric motor (104). The method includes identifying, by the control unit (106), a request to apply a deceleration torque to the wheel (116), identifying status information (140, 142, 144) of the electric drive (100), selecting an operating mode (134, 136) of the electric motor (104) from at least two possible operating modes (134, 136) of the electric motor (104) according to the identified status information (140, 142, 144), and controlling the electric motor (104) in the selected operating mode (134, 136) to apply a deceleration torque to the wheel (116). and controlling the electric motor (104), wherein in a first operating mode (134) of the possible operating modes of the electric motor (104), the electric motor (104) is controlled to convert the rotational energy (120) of the wheels (116) into electrical energy with a first efficiency, and in a second operating mode (136) of the possible operating modes of the electric motor (104), the electric motor (104) is controlled to convert the rotational energy (120) of the wheels (116) into electrical energy with a second efficiency, the second efficiency being lower than the first efficiency.

Description

[Technical field]

[0001] The present invention relates to a method for controlling an electric drive of a motor vehicle and to a corresponding electric drive. [Background technology]

[0002] Mechanical friction brakes in automobiles have reached a satisfactory level in terms of reliability, partly due to the use of known and proven technology in a well-defined environment. However, friction brakes still have drawbacks. They contribute not inconsiderable to the total mass of the vehicle, with the majority of the mass contributed by the friction brakes being the unsprung masses. A large proportion of these unsprung masses is due to the fact that the brakes also need to be dimensioned for long braking processes in order to maintain speed during potentially very long downhill drives. An example of this is the descent from the Grossglockner at constant speed. For this reason, friction brakes also require a not inconsiderable installation space on the vehicle.

[0003] The energy absorbed by friction brakes during deceleration cannot be recovered. Rather, the energy is released to the surroundings in the form of heat. This leads to wasted energy and particulate pollution of the environment from wear products from the brake components, which are also released into the environment. For example, for a vehicle with a mass of 1600 kg on an 8% gradient, friction brakes need to absorb approximately 14 kW of mechanical power and release it as heat to maintain a speed of 40 km / h.

[0004] In addition to decelerating the vehicle by friction braking, it is also known from the prior art that the vehicle can be decelerated with the help of a drive train. Vehicle deceleration with the regeneration of the vehicle's kinetic energy should be mentioned here in particular for the electric drive train of the vehicle. Again, as in the above example, it is quite realistic that when traveling downhill like this, the required deceleration power of 14 kW can be achieved simply by properly operating the electric drive train, if a power of about 12 kW can be fed back to the battery of the drive, assuming a correspondingly efficient control of the drive.

[0005] However, deceleration of the vehicle with the drive train according to the prior art usually lacks the reliability given to friction brakes. For example, if the absorption capacity of the battery of the electric drive is insufficient, the problem arises that this possibility of decelerating the vehicle is no longer available, since energy cannot be regenerated. The same applies, for example, if the connection between the electric drive and the battery for feeding back electric energy (power) is interrupted, for example due to a defect. Overall, many components of the vehicle are involved in deceleration by regeneration, so that deceleration by regeneration is no longer possible even if one of the components fails. Summary of the Invention [Problem to be solved by the invention]

[0006] In contrast, the present invention is based on the object of specifying an electric drive and a corresponding method for controlling an electric drive that overcomes the above-mentioned drawbacks of the prior art. [Means for solving the problem]

[0007] This object is achieved by a method according to claim 1 and by an electric drive according to claim 10. Claims 2 to 9, 11 and 12 relate to advantageous refinements.

[0008] In a first aspect, the present invention relates to a method of controlling an electric drive of a motor vehicle using a controller, at least one wheel of the motor vehicle being capable of being driven by an electric motor of the electric drive, the electric drive having at least one energy source for the electric motor, the method comprising execution by the controller of the following steps: determining a requirement to apply a deceleration torque to the wheels; determining items of status information of the electric drive; selecting an operating mode of the electric motor from at least two possible operating modes of the electric motor in response to the determined items of status information; and · Operating the electric motor in a selected operating mode to apply a deceleration torque to the wheels.

[0009] Here, in a first one of the possible operating modes of the electric motor, the electric motor is operated such that the rotational energy of the wheels is converted into electrical energy with a first efficiency, however, in a second one of the possible operating modes of the electric motor, the electric motor is operated such that the rotational energy of the wheels is converted into electrical energy with a second efficiency, the second efficiency being lower than the first efficiency.

[0010] The invention is based on the idea that, for example in the case of insufficient capacity of the energy source, the electric motor is used to generate a deceleration torque at the wheels in a regenerative mode, so that only a very small percentage of the rotational energy of the wheels in question is converted into electrical energy. Due to the reduced efficiency of the regenerative operation in the second operating mode, a large part of the rotational energy ends up being converted into heat and stored in the electric motor and its peripherals, in particular its power electronics system, which can be dissipated by the existing cooling of the electric motor. A permanent deceleration torque can thus be provided by the electric motor without resorting to resources on the battery, this permanent deceleration torque being substantially limited by the cooling capacity of the cooling of the electric motor.

[0011] At the same time, the described method can be implemented only from the electric drive, so that no interaction with other systems of the vehicle is necessary, which is usually a source of potential failures that can jeopardize the reliability of such an approach. The reliable provision of a given deceleration torque by the electric drive allows the friction brakes of the vehicle to be designed to be smaller, since the electric motor can reliably contribute a certain percentage of the deceleration force.

[0012] Here, a "deceleration torque" should be understood very generally as a torque that is directed in the opposite direction to the rotation direction of the wheels, i.e. that would lead to a slowdown in the rotation of the wheels in the absence of other forces. However, the application of such a deceleration torque to the wheels should not be equated with a slowdown of the vehicle itself. Thus, other forces acting on the vehicle, such as for example downhill forces, do not slow down the vehicle's speed, and may even increase it, despite the deceleration torque caused by the electric motor.

[0013] In this case, the request to apply a deceleration torque to the wheels of the vehicle can be triggered, for example, by the actuation of the brake pedal by the driver of the vehicle, and also such a request can be triggered by a driving function of the vehicle, for example a cruise control system or a controlled downhill driving function (hill descent control).

[0014] Although only wheels driven by electric motors drawing energy from an energy source are described in the method, the method according to the invention can be transferred to any desired configuration of wheels, electric motors and energy sources. The method can therefore also be used in motor vehicles in which each wheel is driven by an electric motor supplied with energy from several energy sources. Here, it can be provided in particular that the electric motors assigned to the front axles of the vehicle are connected to a first energy source and the electric motors assigned to the rear axles of the vehicle are connected to a second energy source. In this case, in particular situations can arise in connection with the method in which the electric motors of the front axles operate in a different operating mode than the electric motors of the rear axles.

[0015] Here, an "electric motor" is generally understood to mean any type of electric motor suitable for generating torque at the wheels of a vehicle using electrical energy and, vice versa, for converting the torque available from the wheels into electrical energy by suitable operation. The "energy source" of an electric motor may be, for example, a battery.

[0016] An "operating mode" in the sense of the present invention, or the operation of an electric motor in such an operating mode, should be understood here as meaning a target operation of the electric motor according to the parameters specified by the selected operating mode. Using the example of a three-phase brushless DC motor, the operating mode can be used to specify, for example, when and how the voltage of the commutation block is switched. The course of the voltage in the commutation block, i.e. the specific signal form of the voltage, can also be specified by the operating mode. Here, the parameters of the operating mode are selected in such a way that the resulting efficiency of the electric motor in converting the rotational energy of the wheels into electrical energy is already different between the operating modes simply by the selected parameters. Different efficiencies of the electric motor resulting from external uncontrolled influences, such as, for example, the operating temperature of the electric motor, should not be understood as different operating modes in the sense of the present invention. On the other hand, the target setting of the operating temperature of the electric motor, which affects the efficiency, can be interpreted as an operating mode in the sense of the present invention.

[0017] According to a preferred embodiment, electrical energy is now supplied to the energy source in the first operating mode, which therefore involves the recovery of the rotational energy of the wheels, which recharges the energy source, in particular the battery.

[0018] As already explained above, the operating mode of the electric motor is selected depending on predetermined items of status information of the electric drive. According to a preferred embodiment, the items of status information here comprise at least one state of charge of the energy source and / or the temperature of the energy source and / or the temperature of the electric motor and / or the temperature of other components of the electric drive. The other components of the electric drive can be, for example, a power electronics system of the drive, in particular an inverter, which converts the direct current voltage provided by the energy source into an alternating current voltage required for the operation of the electric motor. In particular, if the state of charge of the energy source does not correspond to a fully charged energy source, it is possible to operate the electric motor preferably in the first operating mode, so that the largest possible part of the rotational energy available from the wheels is converted into electrical energy. Here, it is preferably also taken into account whether the energy source is suitable for receiving electrical energy based on its current temperature.

[0019] The items of status information may furthermore identify fault conditions of individual components of the electric drive, for example, if it proves that the connection between the electric motor and the energy source is faulty or interrupted, i.e. that it is not possible to feed electrical energy back to the energy source, it may be possible to cause the electric motor to operate in a second operating mode.

[0020] Conversely, when selecting an operating mode, it is also taken into account whether the electric motor, for example due to its current temperature, is able to dissipate the rotational energy of the wheels as thermal energy. Likewise, the temperatures of other components of the electric drive, in particular the power electronics system of the electric motor, are preferably taken into account here as well, which likewise limit the operation of the electric motor in the second operating mode, in which the electric motor is used to dissipate thermal energy.

[0021] According to a further preferred embodiment, it is further provided that the second efficiency depends on the state of charge and / or the temperature of the energy source. For example, it can be provided that the second operating mode is used when the energy source is almost fully charged. In this case, the regeneration of the rotational energy of the wheels to the energy source is still effective, so that the second efficiency should not be too low. Here, it can also be provided that the second efficiency is continuously scaled to the current state of charge of the energy source, so that the second efficiency is continuously reduced as the charge of the energy source increases. Furthermore, it can also be provided here to set the second efficiency as low as possible, despite a slight discharge of the energy source, since the electric energy cannot be returned to the energy source due to the current temperature of the energy source.

[0022] According to a further embodiment, it is further provided that the first efficiency is the highest possible efficiency for converting the rotational energy of the wheels into electrical energy, and the second efficiency is the lowest possible efficiency for converting the rotational energy of the wheels into electrical energy using the electric motor.

[0023] According to a further embodiment, it is further provided that the motor vehicle has at least one heating circuit, to which the heat generated during operation of the electric motor in the second operating mode is supplied. The heating circuit can for example include a heater for the passenger compartment of the motor vehicle, so that the heat generated by the electric motor when the vehicle is decelerating can be used to heat the passenger compartment.

[0024] In addition to operating the electric motor in one of the two operating modes mentioned above, in which the kinetic energy of the wheels is converted into electrical energy with different efficiencies, according to a further embodiment, in a third operating mode from the above-mentioned possible operating modes of the electric motor, the electric motor is operated to apply a deceleration torque to the wheels using the electrical energy provided by the energy source. The electric motor is therefore actively energized so that it can generate a deceleration torque at the wheels. On the one hand, the active energization of the motor generates thermal energy in the electric motor, while at the same time the rotational energy extracted from the wheels is generated as heat in the electric motor. This operation can be used, for example, when a large amount of heat is required despite a small deceleration request, for example to quickly warm up the passenger compartment of the vehicle or to bring the electric drive to operating temperature. At the same time, a subsequent deceleration request can be performed in the first operating mode, since in this operating mode the energy source is at least slightly discharged.

[0025] According to a further embodiment, when selecting the operating mode of the electric motor, the absorption capacity for absorbing electrical energy of other electrical consumers of the vehicle is also taken into account. For example, operation of the electric motor in the first operating mode may be useful, even if the energy source is fully charged, if the electrical energy thus generated is drawn off by other electrical consumers of the vehicle. Here, for example, an air conditioning system or an electric heater can be mentioned as electrical consumers.

[0026] According to a preferred embodiment, the electric motor is further provided to be a brushless DC motor having a power electronics system for providing an operating voltage to the DC motor, and in order to operate the electric motor in different operating modes, only the operation of the power electronics system is adapted to the selected operating mode.

[0027] In a further aspect, the invention relates to an electric drive for a motor vehicle, comprising an electric motor, an energy source for the electric motor, and a controller for the electric motor, where the controller is designed to determine a request for applying a deceleration torque to wheels connected to the electric motor, to determine an item of status information of the electric drive, to determine an operating mode of the electric motor from at least two possible operating modes of the electric motor depending on the determined item of status information, and to operate the electric motor in the selected operating mode for applying a deceleration torque to the wheels, where in a first operating mode of the possible operating modes of the electric motor, the electric motor is operated such that the rotational energy of the wheels is converted into electrical energy with a first efficiency, and in a second operating mode of the possible operating modes of the electric motor, the electric motor is operated such that the rotational energy of the wheels is converted into electrical energy with a second efficiency, The second efficiency is less than the first efficiency.

[0028] According to one embodiment, it is provided here that the electric drive has at least one cooling circuit for cooling the electric motor, and the heat generated during operation of the electric motor in the second operating mode is at least partially dissipated via the cooling circuit, whereby the cooling circuit can be designed to release the heat absorbed in the electric motor to a heating circuit of the vehicle.

[0029] According to a preferred embodiment, it is further provided here that the cooling circuit comprises a control device for adjusting the cooling capacity provided by the cooling circuit, the control device being activated by the controller depending on the selected operating mode of the electric motor. For example, when the electric motor operates in the second or third operating mode, the cooling capacity of the cooling circuit can be automatically increased by appropriate activation of elements such as a circulation pump or a cooling compressor, so that the heat generated in the electric motor can be efficiently dissipated and overheating of the electric motor can be avoided.

[0030] Preferred refinements of the invention are explained in more detail below on the basis of the drawings. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 shows a schematic diagram of an electric drive according to the prior art. [Diagram 2] 2 shows a schematic diagram of different interference sources in the arrangement according to FIG. 1; [Diagram 3] 4 shows a schematic diagram of an electric motor in a second operating mode. [Figure 4] 4 shows a schematic diagram of an electric motor in a third operating mode. [Diagram 5] 1 shows a schematic diagram of an exemplary electric drive having a heating circuit. [Figure 6] 1 shows a schematic diagram of an exemplary control logic system for an electric drive device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] In the following text, similar or identical features are denoted by the same reference signs.

[0033] Fig. 1 shows a schematic diagram of an electric drive 100 according to the prior art. Here, the electric drive 100 comprises a drive unit 102 with an electric motor 104 and a controller 106 for the electric motor 104. The drive unit 102, and thus the electric motor 104, is connected to an energy source 108, for example a battery, via a DC connection 110 for supplying electric energy. In addition to the energy source 108, other electricity consumers 112 can also be connected to the drive unit 102 via the DC connection 110, which is only shown very diagrammatically in Fig. 1.

[0034] The electric motor 104 is connected to wheels 116 via a downstream transmission 114, such that the electric motor 104 can generate a torque on the wheels 116. Additionally, friction brakes 118 are disposed on the wheels 116, shown for example as disc brakes. In such an arrangement, it is known from the prior art that by appropriately activating the electric motor 104, an acceleration torque can be applied to the wheels 116 using electrical energy from the energy source 108, and that a deceleration torque is preferably applied when the rotational energy of the wheels 116 is converted into electrical energy supplied to the energy source 108.

[0035] In the prior art, the focus has typically been on making electric motors operate as efficiently as possible, so that electrical energy from the energy source 108 is converted into kinetic energy for the wheels 116, and vice versa, as efficiently as possible.

[0036] Figure 2 shows diagrammatically which fault sources in the arrangement described in Figure 1 lead to an electric drive according to the prior art generally being unable to permanently and reliably release the friction brake of the load. A first fault source or a first problematic state occurs when the energy source 108 is fully charged, i.e. when the regeneration of kinetic energy to the energy source 108 is no longer possible. A second fault source is an interruption or malfunction of the DC connection 110, as a result of which it is no longer possible to discharge electrical energy also to other electrical consumers 112. In both cases, all the kinetic energy 120 released when the wheels decelerate must be absorbed by the friction brake 118 in the form of heat 122 and released to the surrounding area.

[0037] To solve this problem and ensure reliable provision of a deceleration torque by the electric drive 100 even in the event of a malfunction of an individual component such as the energy source 108 or the DC connection 110, according to the present invention, the electric motor 104 is operated depending on the state of the individual components of the electric drive 100 to generate a deceleration torque at the wheels 116 in different operating modes.

[0038] An electric motor 104 is shown in Fig. 3 as an example of this. As shown on the left side of the figure, in the situation shown it is not possible to feed back electric energy from the drive unit 102 to the energy source 108 via the DC connection 110. This may be the case for example of a fully charged energy source 108 or a failure of the DC connection 110. In this case, according to the invention, it is provided that the electric motor 104 is operated by suitable activation of the power electronics system 107 and continues to convert the rotational energy 120 of the wheels 116 into electric energy in order to generate a deceleration torque on the wheels 116, but with the lowest possible efficiency.

[0039] As a result, only a small portion of the rotational energy 120 of the wheels 116 is converted into electrical energy, and the current 124 thus generated is preferably completely converted into heat by the electric motor 104 and the power electronics 107, or by an inverter 126 connected upstream of the electric motor 104. In contrast, the majority of the rotational energy 120 is converted into heat 122, which is generated in the electric motor 104, and can be dissipated by cooling the electric motor 104.

[0040] However, as long as electrical energy can be fed back to the energy source 108 via the DC connection 110, the electric motor is operated in a first operating mode for decelerating the wheels 116 by appropriate operation of the power electronics system 107, whereby the rotational energy 120 of the wheels 116 is converted with as high an efficiency as possible into electrical energy which is then supplied to the energy source 108. Here, the operating parameters of the electric motor 104 in this operating mode are designed such that the electric motor 104 generates as little heat as possible.

[0041] A third operating mode of the electric motor 104 is shown diagrammatically in Fig. 4 and can be used, for example, when the energy source is fully charged, the DC connection 110 is intact, and the electric motor 104 is still relatively cool. In this case, the electric motor is actively energized by suitable actuation of the power electronics system 107 by the controller 106 in a targeted manner such that a deceleration torque is applied to the wheels 116 using the electric energy to generate a deceleration torque. As a result, both the used electric energy and the rotational energy 120 of the wheels 116 are generated as thermal energy 122 in the electric motor 104, which can be dissipated by suitable cooling.

[0042] FIG. 5 shows a schematic diagram of an exemplary electric drive 100, which is connected to a heating circuit 130 of a vehicle. Here, the controller 106 of the drive unit 102 has a control logic system 132 that switches between different operating modes of the electric motor 104 to generate a deceleration torque depending on the situation. Here, a first operating mode 134 is designed by appropriately adjusting the operating parameters of the electric motor 104, in particular using a suitable control logic system of the associated power electronics system, so that the electric motor 104 converts with the highest possible efficiency the kinetic energy 120 of the wheels 116 into electrical energy to generate a deceleration torque, which is then fed to the energy source via the DC connection 110. This first operating mode 134 is used, for example, when the energy source is not fully charged and the DC connection 110 is fully functional.

[0043] On the other hand, in a second operating mode 136, the operating parameters of the electric motor 104 are appropriately adjusted so that the electric motor 104 converts the kinetic energy of the wheels 116 into electrical energy to generate a deceleration torque with the lowest possible efficiency. The heat generated in this process is dissipated in the heating circuit 130 and can be used, for example, by a corresponding radiator 138, to heat the passenger compartment of the vehicle.

[0044] 6 shows a schematic diagram of the control logic system 132 for the electric drive 100, as mentioned above, where the control logic system 132 is first designed to determine items 140, 142 and 144 of status information of the electric drive, such as status information 140 relating to the functioning of the DC connection 110, status information 142 relating to the readiness of the energy source 108 to receive electric energy, which readiness is influenced for example by the state of charge and temperature of the energy source 108 or by the readiness of other electricity consumers 112 to receive electric energy.

[0045] The items of status information thus determined are fed to a decision logic system 146 which, by examining the determined items of status information 140, 142, 144 together, determines whether an incoming request for the electric drive 102 to apply a deceleration torque to the wheels 116 should be implemented in a first operating mode of the electric motor 104 or in a second operating mode of the electric motor 104 as described above. Depending on the output of this decision logic system 146, the operating parameters of the electric motor 104 according to the first or second operating mode are then used by the controller when operating the corresponding power electronics system 106, so that the electric motor 104 converts the rotational energy of the wheels 116 into electrical energy either with the highest possible efficiency or with the lowest possible efficiency. This application relates to the invention described in the claims, but also includes the following as other aspects. 1. A method of controlling an electric drive (100) of a vehicle using a controller (106), wherein at least one wheel (116) of the vehicle can be driven by an electric motor (104) of the electric drive (100), the electric drive (100) having at least one energy source (108) for the electric motor (104), the method comprising: determining a requirement to apply a deceleration torque to said wheels (116); determining items (140, 142, 144) of status information of said electric drive (100); selecting an operating mode (134, 136) of said electric motor (104) from at least two possible operating modes (134, 136) of said electric motor (104) in response to said determined items of status information (140, 142, 144); operating the electric motor (104) in the selected operating mode (134, 136) to apply the decelerating torque to the wheels (116); Including the execution of In a first one of the possible operating modes of the electric motor, the electric motor is operated such that rotational energy of the wheels is converted into electrical energy with a first efficiency; In a second one of the possible operating modes of the electric motor, the electric motor is operated such that the rotational energy of the wheels is converted to electrical energy with a second efficiency; the second efficiency is lower than the first efficiency; method. 2. 2. The method of claim 1, wherein the electrical energy is supplied to the energy source (108) in the first operating mode (134). 3. 3. The method according to claim 1 or 2, characterized in that the items of status information (140, 142, 144) comprise at least one state of charge of the energy source (108), and / or the temperature of the energy source (108), and / or the temperature of the electric motor (104), and / or the temperature of other components (107) of the electric drive (100). 4. 4. The method of claim 3, wherein the second efficiency depends on the state of charge and / or the temperature of the energy source (108). 5. 5. The method according to any one of claims 1 to 4, characterized in that the first efficiency is the highest possible efficiency for converting the rotational energy (120) of the wheels (116) into electrical energy, and the second efficiency is the lowest possible efficiency for converting the rotational energy (120) of the wheels (116) into electrical energy using the electric motor (104). 6. The method according to any one of claims 1 to 5, characterized in that the motor vehicle has at least one heating circuit (130), and heat generated during operation of the electric motor (104) in the second operating mode (136) is supplied to the heating circuit (130). 7. 7. The method according to any one of claims 1 to 6, characterized in that in a third operating mode of the electric motor (104), the electric motor (104) is operated such that it applies the deceleration torque to the wheels (116) using electrical energy supplied by the energy source (108). 8. 8. The method according to any one of claims 1 to 7, characterized in that when selecting the operating mode (134, 136) of the electric motor (104), the absorption capacity of other electrical consumers (112) of the vehicle to absorb electrical energy is taken into account. 9. 9. The method according to any one of claims 1 to 8, characterized in that the electric motor (104) is a brushless DC motor having a power electronics system (107) for supplying an operating voltage to the DC motor, and in order to operate the electric motor (104) in the different operating modes, only the operation of the power electronics system (107) is adapted to the selected operating mode (134, 136). 10. 1. An electric drive system (100) for a motor vehicle having an electric motor (104), an energy source (108) for the electric motor (104), and a controller (106) for the electric motor (104), the controller (106) comprising: determining a demand for applying a deceleration torque to a wheel (116) connected to said electric motor (104); determining items (140, 142, 144) of status information of the electric drive (100); determining an operating mode (134, 136) of the electric motor (104) from at least two possible operating modes (134, 136) of the electric motor (104) in response to the determined items of status information (140, 142, 144); operating the electric motor (104) in the selected operating mode (134, 136) to apply the decelerating torque to the wheels (116); Designed to In a first one of the possible operating modes of the electric motor, the electric motor is operated such that rotational energy of the wheels is converted into electrical energy with a first efficiency; In a second one of the possible operating modes of the electric motor, the electric motor is operated such that the rotational energy of the wheels is converted to electrical energy with a second efficiency; the second efficiency is lower than the first efficiency; An electric drive unit (100). 11. The electric drive (100) of claim 10, characterized in that the electric drive (100) has at least one cooling circuit for cooling the electric motor (104), and heat generated during operation of the electric motor (104) in the second operating mode (136) is at least partially dissipated via the cooling circuit. 12. 12. The electric drive (100) of claim 11, characterized in that the cooling circuit has a control device for regulating the cooling capacity provided by the cooling circuit, the control device being operated by the controller (106) in response to the selected operating mode (134, 136) of the electric motor (104).

Claims

1. A method of controlling an electric drive (100) of a motor vehicle using a controller (106), wherein at least one wheel (116) of the motor vehicle can be driven by an electric motor (104) of the electric drive (100), the electric drive (100) having at least one energy source (108) for the electric motor (104), the method comprising: - determining a requirement to apply a deceleration torque to said wheels (116); - determining items (140, 142, 144) of status information of said electric drive (100); selecting an operating mode (134, 136) of the electric motor (104) from at least two possible operating modes (134, 136) of the electric motor (104) in response to the determined items of status information (140, 142, 144); - operating said electric motor (104) in said selected operating mode (134, 136) to apply said decelerating torque to said wheels (116); Including the execution of In a first one of the possible operating modes of the electric motor, the electric motor is operated such that rotational energy of the wheels is converted into electrical energy with a first efficiency; In a second one of the possible operating modes of the electric motor, the electric motor is operated such that rotational energy of the wheels is converted into electrical energy with a second efficiency; the second efficiency is less than the first efficiency; when selecting the operating mode (134, 136) of the electric motor (104), the absorption capacity (112) of other electric consumers (112) of the vehicle to absorb electric energy is taken into account. method.

2. The method of claim 1, characterized in that the electrical energy is supplied to the energy source (108) in the first operating mode (134).

3. 3. The method according to claim 1 or 2, characterized in that the items of status information (140, 142, 144) comprise at least one state of charge of the energy source (108), and / or the temperature of the energy source (108), and / or the temperature of the electric motor (104), and / or the temperature of other components (107) of the electric drive (100).

4. The method of claim 3, wherein the second efficiency depends on the state of charge and / or the temperature of the energy source (108).

5. 5. The method according to claim 1, wherein the first efficiency is the highest possible efficiency for converting the rotational energy (120) of the wheels (116) into electrical energy, and the second efficiency is the lowest possible efficiency for converting the rotational energy (120) of the wheels (116) into electrical energy using the electric motor (104).

6. The method according to any one of claims 1 to 5, characterized in that the motor vehicle has at least one heating circuit (130), and heat generated during operation of the electric motor (104) in the second operating mode (136) is supplied to the heating circuit (130).

7. The method according to any one of claims 1 to 6, characterized in that in a third of the possible operating modes of the electric motor (104), the electric motor (104) is operated such that it applies the deceleration torque to the wheels (116) using electrical energy supplied by the energy source (108).

8. The method according to any one of claims 1 to 7, characterized in that the electric motor (104) is a brushless DC motor having a power electronics system (107) for supplying an operating voltage to the DC motor, and in order to operate the electric motor (104) in the different operating modes, only the operation of the power electronics system (107) is adapted to the selected operating mode (134, 136).

9. An electric drive (100) for a motor vehicle having an electric motor (104), an energy source (108) for the electric motor (104), and a controller (106) for the electric motor (104), the controller (106) comprising: determining a demand for applying a deceleration torque to a wheel (116) connected to said electric motor (104); determining items (140, 142, 144) of status information of the electric drive (100); determining an operating mode (134, 136) of the electric motor (104) from at least two possible operating modes (134, 136) of the electric motor (104) in response to the determined items of status information (140, 142, 144); operating said electric motor (104) in said selected operating mode (134, 136) to apply said decelerating torque to said wheels (116); Designed to In a first one of the possible operating modes of the electric motor, the electric motor is operated such that rotational energy of the wheels is converted into electrical energy with a first efficiency; In a second one of the possible operating modes of the electric motor, the electric motor is operated such that rotational energy of the wheels is converted into electrical energy with a second efficiency; the second efficiency is less than the first efficiency; when selecting the operating mode (134, 136) of the electric motor (104), the absorption capacity (112) of other electric consumers (112) of the vehicle to absorb electric energy is taken into account. An electric drive unit (100).

10. 10. The electric drive (100) of claim 9, characterized in that the electric drive (100) has at least one cooling circuit for cooling the electric motor (104), and heat generated during operation of the electric motor (104) in the second operating mode (136) is at least partially dissipated via the cooling circuit.

11. 11. The electric drive (100) of claim 10, wherein the cooling circuit has a control device for regulating the cooling capacity provided by the cooling circuit, the control device being actuated by the controller (106) in response to the selected operating mode (134, 136) of the electric motor (104).

12. The method according to any one of claims 1 to 8, characterized in that the electric drive (100) has at least one cooling circuit for cooling the electric motor (104), and heat generated during operation of the electric motor (104) in the second operating mode (136) is at least partially dissipated via the cooling circuit.

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