Drive arrangement for a motor vehicle

Abstract

Drive arrangement (1) for a motor vehicle, comprising an electric machine (2) having a rotor (5) and a coupling device (3) configured to selectively couple the rotor (5) with an output (4) of the drive arrangement (1) or to decouple it from the output (4), wherein the coupling device (3) is configured to decouple the rotor (5) from the output (4) in a standstill state of the rotor (5) in an actual rotor position (8), wherein the electric machine (2) is configured to move the rotor (5) in the decoupled state to a desired rotor position (9), and wherein the coupling device (3) is configured to couple the rotor (5) in the desired rotor position (9) with the output (4).

Description

[0001] The invention relates to a drive arrangement for a motor vehicle, comprising an electric machine having a rotor and a coupling device which is designed to selectively couple the rotor to an output of the drive arrangement or to decouple it from the output.

[0002] Drive assemblies for motor vehicles which have an electric machine whose rotor, for example the rotor shaft connected to the rotor, can be coupled to or decoupled from the output of the drive assembly, for example to a differential, via a coupling device, are generally known from the prior art. Typically, such a coupling device is used to decouple the electric machine from the output when the electric machine is not in use, in order to prevent drag on the drive side of the coupling assembly, for example the rotor shaft, rotor and the drive-side coupling element. This can improve the efficiency of operation of the drive assembly. If the electric machine is to be used to set torque or for recuperation, the coupling device can be closed and the rotor can be connected to the output.

[0003] In the described drive arrangements, operating states are known in which a comparatively high power or a comparatively high torque must be called upon from the electric machine. For example, if the motor vehicle or the drive arrangement is to be started from a standstill with a comparatively heavy motor vehicle or in towing or trailer operation, comparatively high torques must be provided by the electric machine. It is also known that the load on the power electronics, in particular the inverter, depends on the current rotor position, which determines the switching of the power electronics for the described operating state. In an unfavorable rotor position, it may be necessary for one of the switching elements of the inverter, ieFor example, the power semiconductor must carry a maximum current, whereas two other switching elements, for example, carry a lower current. This can result, for example, in the maximum available torque not being fully utilized due to the thermal load on the switching element in the relatively static standstill state.

[0004] The invention is based on the object of specifying a drive arrangement for a motor vehicle which is improved compared to the aforementioned, in which in particular the load distribution is improved in certain operating situations, in particular in a starting state.

[0005] The object is achieved by a drive arrangement having the features of claim 1. Advantageous embodiments are the subject of the subclaims.

[0006] As described, the invention relates to a drive arrangement for a motor vehicle. The drive arrangement has an electric machine and a coupling device. The rotor of the electric machine can be selectively coupled to an output of the drive device via the coupling device or decoupled from the output. In other words, the coupling device can establish a coupled state in which the rotor of the electric machine is coupled to the output, for example a differential or a wheel of the motor vehicle or the drive arrangement, and establish a decoupled state in which the rotor is correspondingly decoupled from the output. The coupling device can be designed, for example, as a frictional or positive coupling, for example as a claw clutch or generally as a so-called PDU (“power disconnect unit”).

[0007] The invention is based on the finding that the coupling device is designed to decouple the rotor from the output when the rotor is at a standstill in an actual rotor position, wherein the electric machine is designed to move the rotor in the decoupled state into a desired rotor position, wherein the coupling device is designed to couple the rotor to the output in the desired rotor position. In other words, the coupling device is specifically used to separate the rotor from the output, so that the rotor can be moved or rotated by the electric machine without the rotational movement being transmitted to the output.

[0008] If the rotor is in an actual rotor position that is unfavorable for an operating state to be executed when the rotor is at a standstill or, generally, when the drive arrangement is at a standstill, the rotor is decoupled from the coupling device in the standstill state. The electric machine can then move the rotor to the target rotor position, which is more advantageous for executing the operating state. Once the target rotor position has been assumed, the coupling device can reconnect or couple the rotor to the output, so that the desired operating state can then be executed, namely in the target rotor position of the rotor, which is more advantageous than the original actual rotor position.This makes it possible to provide a higher torque for the operating state starting from a standstill, for example in order to be able to carry out towing operations, trailer operation, starting operations, slope operation or the like in an improved manner.

[0009] As described, the coupling device is fundamentally designed to selectively decouple the rotor from the output of the drive arrangement or to couple it to it. In one embodiment of the drive arrangement, the coupling device can be designed to mechanically decouple the rotor, in particular an output shaft of the electric machine connected to the rotor, for example the rotor shaft, from an output of the drive arrangement, in particular a differential. The coupling device thus establishes or releases a mechanical coupling between the rotor and the output. In the decoupled state, the rotor can be rotated in the magnetic field of the electric machine, for example by setting a corresponding magnetic field in the rotor and / or stator. The electric machine can be designed in particular as a synchronous machine.In other words, by setting a specific magnetic field in the decoupled state of the rotor, the rotor can be precisely positioned in the electric machine so that the previously described target rotor position can be assumed. Once this position has been assumed, the coupling device can reconnect the rotor to the output in the target rotor position.

[0010] According to a further embodiment, the drive arrangement can have a detection device designed to detect the actual rotor position. This enables the rotor position of the rotor to be detected during operation of the drive arrangement. For example, this position can be compared with the target rotor position. If, in the standstill state, the actual rotor position does not correspond to the target rotor position, the rotor can be rotated in the decoupled state, as described above, namely to assume the target rotor position. The detection device can, for example, comprise a rotor position sensor to determine or detect the actual rotor position. The actual rotor position can be compared with the target rotor position to determine a deviation. The deviation can be reduced or eliminated by moving the rotor.

[0011] The described drive arrangement can further be developed such that the target rotor position is determined based on a load distribution of at least one switching element of an inverter of the drive arrangement. As described above, the load distribution results from the switching state(s) of the inverter. In particular, static switching states can occur in which one switching element, i.e. a circuit breaker, carries the entire current, which is discharged via two further switching elements. This correspondingly generates a thermal load on the switch or switching element carrying the maximum current. The target rotor position can therefore be selected such that the load distribution of at least one switching element or the switching elements of the inverter is correspondingly advantageous, for example so that a more balanced load distribution can be achieved compared to a load on just one switching element.

[0012] In particular, it can be provided that the drive arrangement is designed to execute a combination state in the target rotor position, in which switching takes place between at least two switching states of the inverter. In other words, the target rotor position can describe an orientation of the rotor in the electrical machine such that a start-up state following from the target rotor position is executed by a combination state. In the combination state, there is advantageously no static switching of the inverter, but switching takes place between at least two switching states. This means that the electrical and thermal load on the switching elements of the inverter is distributed or alternated and is thus reduced for the individual switching elements compared to a static load. Accordingly, a higher torque can be set orThe individual switching elements can be subjected to lower electrical and thermal loads to achieve a given torque. Specifically, the target rotor position can be selected so that the load on the individual switching elements can be distributed evenly.

[0013] As already described, the drive arrangement can advantageously be configured to execute a starting process from a stationary state in the target rotor position. In other words, the method described above can be carried out in particular to prepare for a starting process. From the described stationary state, the rotor can thus be decoupled, transferred to the target rotor position, and recoupled to the output, so that a starting process can subsequently be carried out more effectively. This is particularly advantageous for starting processes of commercial vehicles or comparatively heavily loaded vehicles, traction operations, towing operations, hillside operations, and the like.The starting process thus relates in particular to an operating state in which a comparatively low speed, in particular from a standstill state, is to be carried out with a comparatively high torque, for example the maximum torque or in the range of the maximum torque, for example over 80% of the maximum torque.

[0014] As already described above, the coupling device can be designed as either a frictional or positive-locking coupling. In one embodiment of the drive arrangement, the coupling device can comprise a first and a second coupling element, which, for example, have teeth and gaps arranged alternately in the circumferential direction and can be brought into engagement with one another. The coupling device, in particular as a claw coupling, is designed to insert teeth of the first coupling element into gaps in the second coupling element in the desired rotor position. For example, the coupling elements can be brought into engagement with one another in the axial direction.

[0015] The target rotor position can be selected or set mechanically or by control technology in such a way that when the target rotor position is assumed, the teeth of the first coupling element can be placed in gaps in the second coupling element and vice versa. In other words, the target rotor position can be specifically set in such a way that the rotor can be directly coupled to the output by the coupling device. In particular, so-called “tooth-on-tooth positions” are prevented or avoided. This can be achieved in particular by an asymmetrical number of teeth on the coupling elements or by calculating or determining the positions in which the teeth of the first coupling element meet the gaps in the second coupling element and vice versa. For example, a control device can be provided for this purpose which determines the actual rotor position orThe target rotor position and the associated orientation of the coupling elements can be determined, recorded, or detected. In particular, it is also possible to slightly deviate from the optimal target rotor position for improved coupling, i.e., to deliberately change it to improve the coupling of the rotor to the output. It is particularly advantageous for the coupling elements to have the highest possible number of teeth, in order to be able to adjust the target rotor position as precisely as possible.

[0016] In addition to the drive arrangement, the invention relates to an electric axle drive comprising a previously described drive arrangement. The invention further relates to a motor vehicle comprising a previously described drive arrangement and / or a previously described electric axle drive. In addition, the invention relates to a method for controlling the operation of a drive arrangement, comprising an electric machine having a rotor and a coupling device which is designed to selectively couple the rotor to an output of the drive arrangement or to decouple it from the output, wherein the rotor is decoupled from the output by means of the coupling device when the rotor is at a standstill in an actual rotor position and is moved into a desired rotor position by means of the electric machine in the decoupled state, wherein the rotor is coupled to the output in the desired rotor position by means of the coupling device.

[0017] All embodiments, details, advantages, and features described with regard to the drive arrangement are fully applicable to the electric axle drive, the motor vehicle, and the method. The method can be implemented in all its details, particularly on the drive arrangement described above.

[0018] The present invention is explained below using exemplary embodiments with reference to the figures. The figures are schematic representations and show: Fig. 1 a schematic diagram of a drive arrangement according to an embodiment; Fig. 2 a schematic diagram of an electric machine of the drive arrangement of Fig. 1 in a sectional view; and Fig. 3 a schematic representation of a flow diagram of a method for operating a drive arrangement.

[0019] Fig. 1 shows a schematic diagram of a drive assembly 1 for a motor vehicle (not shown in detail). The drive assembly 1 comprises an electric machine 2 and a coupling device 3. The coupling device 3 is designed to selectively couple the electric machine 2 to an output 4 of the drive assembly 1 or to decouple it from the output 4. For example, the output 4 can represent a differential of the drive assembly 1 or a shaft leading to a wheel of the motor vehicle that includes the drive assembly 1.

[0020] For example, in Fig. 2 in a sectional view, the electric machine 2 has a rotor 5 and a stator 6. The rotor 5 is connected, for example, by means of a rotor shaft 7 or, more generally, an output shaft to the coupling device 3, in particular to an input of the coupling device 3. When the coupling device 3 is closed, the rotor shaft 7 is connected to the output 4. When the coupling device 3 is open, the rotor shaft 7 is disconnected from the output 4.

[0021] In Fig. 2, for example, shows an exemplary actual rotor position 8, which can be detected, for example, by means of a detection device (not shown in detail), for example a rotor position sensor, of the drive assembly 1. Furthermore, a target rotor position 9 is shown purely by way of example, into which, as described below, the rotor 5 is to be set or rotated in order to be able to execute a specific operating state, in particular a starting state, more effectively.

[0022] Fig. 3 shows an exemplary sequence of a method for controlling the operation of the drive arrangement 1. The method can start in a block 10, in which the standstill state of the drive arrangement 1 can be detected. If, for example, no standstill state is assumed or no start-up state is to be executed following the standstill state, it can be provided that the method is not executed because a change in the rotor position is not necessary. If the drive arrangement 1 is switched off in a standstill state and a specific operating state, in particular a start-up state, which requires a specific torque above a torque threshold, is to be executed following the standstill state, a branch can be made from block 10 to block 11.

[0023] In Block 11, the Fig. The actual rotor position 8 shown in Figure 2 is recorded and evaluated for the operating state to be implemented. In particular, this can be compared with a target rotor position 9, which is also shown in Figure 2. Fig. 2 is shown as an example. The target rotor position 9 can be determined for the specific operating state or read from a table or a memory. Of course, the values ​​shown in Fig. The actual rotor position 8 shown in Figure 2 and the target rotor position 9 are merely examples and can be changed as desired.

[0024] In order for the rotor 5 to assume the target rotor position 9, the coupling device 3 is opened in block 12, so that the rotor 5 is decoupled from the output 4. In the decoupled state established in block 12, the rotor 5 is changed in block 13 from the actual rotor position 8 to the target rotor position 9, for example, by rotating it by applying a magnetic field in the electric machine 2. Once the target rotor position 9 has been assumed, the coupling device 3 is closed again in block 14, so that the rotor 5 is connected to the output 4. Coupling elements of the coupling device 3 can be provided in such a way that coupling in the target rotor position is advantageously possible. Alternatively, the target rotor position can be selected such that direct coupling is possible without the coupling elements being in tooth-to-tooth alignment.In other words, in block 14, the rotor 5 is in the desired rotor position 9, which is more advantageous for executing the operating state, in particular the start-up state, than the originally existing actual rotor position 8.

[0025] This allows the operating state to be implemented in block 15. The target rotor position 9 can be specifically selected or determined such that, in the start-up state, the electric machine 2, in particular its inverter, can be operated in a combined state. In the combined state, switching occurs between two switching states, so that the electrical and thermal load is distributed accordingly or evenly across the individual switching elements of the inverter.

[0026] Advantageously, a higher torque can be provided for a certain thermal and electrical load on the switching elements or, for a given torque, the thermal and / or electrical load on the switching elements can be reduced or evenly distributed.

[0027] The method can be executed event-based, for example, when a standstill state occurs and before the operating state is executed. In particular, the drive assembly 1 can be prepared for the execution of the start-up state using the described method.

[0028] The described method can be applied to the drive assembly 1, which is shown in Fig. 1, Fig. 2. All advantages, details and features relating to the drive arrangement 1 in Fig. 1, Fig. 2 and the procedure in relation to Fig.3 can be combined with each other as desired, are interchangeable and transferable to each other. Reference symbol 1 drive arrangement 2 electric machine 3 Coupling device 4 downforce 5 Rotor 6 Stator 7 Rotor shaft 8 Actual rotor position 9 Target rotor position 10-15 blocks

Claims

[1] Drive arrangement (1) for a motor vehicle, comprising an electric machine (2) having a rotor (5) and a coupling device (3) which is designed to selectively couple the rotor (5) to an output (4) of the drive arrangement (1) or to decouple it from the output (4), characterized by in that the coupling device (3) is designed to decouple the rotor (5) from the output (4) in a standstill state of the rotor (5) in an actual rotor position (8), wherein the electric machine (2) is designed to move the rotor (5) in the decoupled state into a desired rotor position (9), wherein the coupling device (3) is designed to couple the rotor (5) to the output (4) in the desired rotor position (9). [2] Drive arrangement (1) according to claim 1, characterized bythat the coupling device (3) is designed to mechanically decouple the rotor (5), in particular an output shaft of the electric machine (2) connected to the rotor (5), from an output (4) of the drive arrangement (1), in particular a differential. [3] Drive arrangement (1) according to claim 1 or 2, characterized by that the drive arrangement (1) has a detection device which is designed to detect the actual rotor position (8). [4] Drive arrangement (1) according to one of the preceding claims, characterized by that the desired rotor position (9) is determined based on a load distribution of at least one switching element of an inverter of the drive arrangement (1). [5] Drive arrangement (1) according to claim 4, characterized bythat the drive arrangement (1) is designed to execute a combination state in the desired rotor position (9) in which switching takes place between at least two switching states of the inverter. [6] Drive arrangement (1) according to one of the preceding claims, characterized by that the drive arrangement (1) is designed to carry out a starting process from a standstill state in the desired rotor position (9). [7] Drive arrangement (1) according to one of the preceding claims, characterized by in that the coupling device (3) has a first and a second coupling element which have alternately arranged teeth and gaps which can be brought into engagement with one another, wherein the coupling device (3), in particular as a claw coupling, is designed to introduce teeth of the first coupling element into gaps of the second coupling element in the desired rotor position (9). [8] Electric axle drive comprising a drive arrangement (1) according to one of the preceding claims. [9] Motor vehicle, comprising a drive arrangement (1) according to one of claims 1 to 7 and / or an electric axle drive according to the preceding claim. [10] Method for controlling the operation of a drive arrangement (1), comprising an electric machine (2) having a rotor (5) and a coupling device (3) which is designed to selectively couple the rotor (5) to an output (4) of the drive arrangement (1) or to decouple it from the output (4), characterized bythat the rotor (5) is decoupled from the output (4) by means of the coupling device (3) in a standstill state of the rotor (5) in an actual rotor position (8) and is moved into a desired rotor position (9) by means of the electric machine (2) in the decoupled state, wherein the rotor is coupled to the output (4) in the desired rotor position (9) by means of the coupling device (3).

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