Device and method for operating an electromotive axle drive unit and motor vehicle

Abstract

Device (2) for operating an electromotive axle drive unit (4), having an inverter (6) for supplying high-voltage power to an electric motor (8) of the electromotive axle drive unit (4), wherein the inverter (6) has a first pole (10) and a second pole (12) and wherein the inverter (6) can be supplied with low-voltage power via the first pole (10) and / or via the second pole (12) in order to control a high-voltage power supply of the electric motor (8) of the electromotive axle drive unit (4), having a control unit (14) for controlling the inverter (6), having a shut-off device (16) for shutting off the high-voltage power supply, having a first low-voltage power supply (18) which is connected to the first pole (10) of the inverter (6), and having a second low-voltage power supply (20) which is connected to the second pole (12) of the inverter (6), wherein the shut-off device (16) has a first switching element (22) which is configured to simultaneously shut off both the first low-voltage power supply (18) and the second low-voltage power supply (20).

Description

[0001] Title: Device and method for operating an electric motor axle drive unit and motor vehicle

[0002] Description

[0003] The present invention relates to a device for operating an electric motor axle drive unit, with an inverter for high-voltage power supply of an electric motor of the electric motor drive unit, wherein the inverter has a first pole and a second pole and wherein the inverter can be supplied with a low-voltage voltage via the first pole and / or via the second pole in order to control a high-voltage power supply of the electric motor of the electric motor axle drive unit, with a control device for controlling the inverter, with a switch-off device for switching off the high-voltage power supply, with a first low-voltage voltage supply which is connected to the first pole of the inverter and with a second low-voltage voltage supply which is connected to the second pole of the inverter.The invention further relates to a method for operating an electromotive axle drive unit by means of such a device and to a motor vehicle.

[0004] A particular challenge in electromobility is to ensure the safe operation of an electric motor drive train in a motor vehicle. For example, it should be ensured at all times that an electric motor used to drive the electric motor vehicle is operated with the correct torque and speed, as well as in the intended direction of rotation, or that the torque can be reliably released. These requirements may initially appear trivial, since the structural design of the drive train in vehicles powered by combustion engines already ensures safe straight-ahead or cornering, as well as reliable decoupling of the combustion engine from the driven wheels.

[0005] However, an axle drive unit driven by an electric motor can, for example, have two independently operable electric motors, each of which is assigned to a driven wheel and which can be controlled independently of one another with a freely selectable direction of rotation and speed, or with a freely selectable torque direction and torque level. This means that in such an arrangement it is not structurally predetermined that both driven wheels rotate in the same direction of rotation and that the necessary drive torques and speeds are reliably provided for stable straight-ahead travel or cornering. Likewise, an electric motor is not usually mechanically decoupled from a driven wheel unless the driven wheel is to be driven.

[0006] Therefore, for example, it is particularly challenging to transfer an electric motor axle drive unit to a safe, torque-free state and to ensure, through control technology, that this torque-free state is actually achieved and maintained. This can be particularly problematic if an inverter assigned to the electric motor has multiple poles that are redundantly suitable for the inverter's low-voltage power supply.

[0007] Particularly for semi-autonomous or fully autonomous electric-motor ferry operation, the requirements described above must meet internally or normatively specified safety or integrity levels in order to ensure the safe operation of an electric-motor-driven vehicle at all times. Against this background, the present invention is based on the technical problem of specifying a device and a method for operating an electric-motor axle drive unit that enable a safe and reliable transfer of an electric-motor axle drive unit to a torque-free state. Furthermore, a motor vehicle is to be specified.

[0008] The technical problem described above is solved by the independent claims. Further embodiments of the invention emerge from the dependent claims and the following description.

[0009] According to a first aspect, the invention relates to a device for operating an electric motor axle drive unit, with an inverter for high-voltage power supply of an electric motor of the electric motor axle drive unit, wherein the inverter has a first pole and a second pole and wherein the inverter can be supplied with a low-voltage voltage via the first pole and / or via the second pole in order to control a high-voltage power supply of the electric motor of the electric motor axle drive unit, with a control device for controlling the inverter, with a switch-off device for switching off the high-voltage power supply, with a first low-voltage voltage supply which is connected to the first pole of the inverter, with a second low-voltage voltage supply which is connected to the second pole of the inverter, wherein the switch-off device has a first switching element,which is designed to switch off both the first low-voltage power supply and the second low-voltage power supply simultaneously.

[0010] According to the invention, it is therefore ensured via a single switching element, namely the first switching element, that the first pole and the second pole are switched off in that the first switching element interrupts both the first low-voltage power supply and the second low-voltage power supply. It can therefore be ensured by monitoring and controlling a single switching element that none of the poles suitable for a low-voltage power supply of the inverter is subjected to a low-voltage voltage that could lead to the electric motor being activated and torque being generated. An electric motor connected to the inverter can therefore be reliably switched off in a torque-free manner by the first switching element, since the inverter cannot provide a high-voltage power supply for the electric motor when the first switching element is open.

[0011] When it is stated here that no high-voltage power supply can be provided for the electric motor when the low-voltage power supply of the inverter is switched off, this does not mean in particular that there is no high-voltage power supply at the inverter or that the high-voltage power supply to the inverter is interrupted. Rather, the high-voltage voltage is still present at the inverter, but can no longer be provided to the electric motor in the required regulated manner due to the missing low-voltage power supply of the inverter control. In other words, the high-voltage voltage is still available at the inverter, but due to the lack of control it cannot be used to supply high-voltage power to the electric motor, so that the electric motor is torque-free.

[0012] In particular, it is provided that the first low-voltage power supply and the second low-voltage power supply are each a low-voltage power supply of an inverter control of the inverter. The inverter control can, for example, be an integral component of the inverter. The inverter control can be connected to the control device via signal lines for receiving and processing signals from the control device. The first low-voltage power supply and the second low-voltage power supply serve in particular as the supply voltage of the inverter control, which is required for the operation of the inverter control. In particular, without the supply voltage of the inverter control, no reception or processing of signals by the inverter control is possible. The terms “control” and “regulation” as well as “controlling” and “regulating” are used synonymously in this text.

[0013] It can be provided that the control device is set up to check the plausibility of a speed signal and / or a torque signal, wherein the control device is set up to switch the first switching element depending on the result of the plausibility check.

[0014] For example, as part of the plausibility check, the speed of a driven wheel and / or the speed of the electric motor can be monitored and the measured speed can be checked for plausibility in terms of magnitude and direction. If a measured speed lies outside a specified tolerance range or deviates too greatly from an expected target value, the first and second low-voltage power supplies can be interrupted by means of the first switching element in order to switch the electric motor torque-free. This also applies to the measured torque, which can also lead to the first and second low-voltage power supplies being switched off by means of the first switching element if the deviation of the measured torque from the expected target value is too great.

[0015] The control device can receive control signals or .

[0016] Torque requests can be supplied, for example, by a driver pressing an accelerator pedal. Alternatively or additionally, control signals or torque requests can be provided to the control device, at least partially automatically, by a controller of a semi-autonomous or fully autonomous ferry operation.

[0017] The inverter can be configured to provide the torque signal. Thus, a torque generated by the electric motor can be determined directly from the electrical power delivered by the inverter to the electric motor, eliminating the need for an additional sensor in the vicinity of a driven wheel or the electric motor to provide a measured actual torque value.

[0018] The inverter and / or the control device can be configured to receive a speed signal from a speed sensor. A speed sensor can be provided that measures a speed of a shaft of the electric motor. Alternatively or additionally, a speed sensor can be provided that measures a speed of the wheel driven by the electric motor. In this way, a current drive speed can be measured and fed back in a cost-effective and reliable manner.

[0019] The control device can be used to monitor a

[0020] Switching state of the first switching element a first

[0021] Have feedback. The feedback can, for example, detect whether the first switching element is switching a low-voltage voltage from a voltage source by measuring a voltage behind the first switching element. The first feedback can be routed from the shutdown device to the control device, wherein the feedback in particular provides an input signal to the control device.

[0022] The first switching element can be a first relay designed as a normally open contact, wherein the switching element is connected to a first digital output of the control device and can be switched by means of an output signal from the first digital output. In this way, reliable shutdown of the first and second low-voltage power supplies can be achieved with a cost-effective component - namely the first relay designed as a normally open contact. Thus, the first switching element is open in the non-switched state and is closed by the digital signal. This has the advantage that in the event of a fault in the control unit, the relay is opened when no digital signal is present.

[0023] A second switching element can be connected in series downstream of the first switching element, wherein the second switching element switches the second low-voltage power supply.

[0024] By connecting the first and second switching elements in series, it can be ensured that simply opening the first switching element prevents any voltage from being passed through to the second switching element and thus to the low-voltage power supply of the second pole. This can also be referred to as cascading the first and second low-voltage power supplies.

[0025] The second switching element can, in particular, be a second relay configured as a normally open contact, wherein the second switching element can, in particular, be connected to a second digital output of the control device and can be switched by means of an output signal from the second digital output. Thus, the second switching element is open in the non-switched state and is closed by the digital signal. This has the advantage that, in the event of a control unit error, the relay is opened when no digital signal is present.

[0026] It can therefore be ensured by using two cost-effective standard components in series, namely the series-connected relays, that the electric motor is switched to a load-free or torque-free state, i.e. the inverter is transferred to a state in which no high-voltage power supply to the electric motor via the inverter is possible.

[0027] The control device can have a second feedback loop for monitoring the first switching element and the second switching element. In particular, the second feedback loop can be assigned to the first and second poles of the inverter, the second feedback loop detecting whether both the first pole and the second pole are actually de-energized and no voltage is reaching the first pole via the first low-voltage power supply and no voltage is reaching the second pole via the second low-voltage power supply. The second feedback loop can be used alternatively or in addition to the first feedback loop to detect that a high-voltage power supply to the electric motor is actually prevented.

[0028] Alternatively or additionally, the inverter can send feedback indicating whether a low-voltage power supply is present at the inverter. This can be done, for example, via a status message.

[0029] The first switching element can be connected to a voltage source. For example, this can be a voltage source that provides a voltage of 12 V or 24 V.

[0030] A fuse, in particular a melting fuse, can be connected upstream of the first switching element. In particular, the melting fuse can be arranged between the aforementioned voltage source and the first switching element.

[0031] To ensure reliable and trouble-free operation of the

[0032] In order to ensure the safety of the shutdown device, it can be provided that the shutdown device is hard-wired and, in particular, has no control logic.

[0033] The shutdown device can be a component provided separately from the control device, wherein the shutdown device is connected to the control device by means of signal lines.

[0034] The shutdown device can, for example, have a housing that is spaced apart from the control device, wherein the first switching element is accommodated, for example, in the housing of the shutdown device. In particular, the control device can have a housing separate from the shutdown device, so that components or parts of the shutdown device and components or parts of the control device are housed separately and independently of one another, and the control device and the shutdown device are separately mountable and available components.

[0035] According to alternative embodiments, it can be provided that the shutdown device is an integral part of the control device and the shutdown device is integrated into a housing of the control device, wherein in particular the first switching element can be accommodated within a housing of the control device.

[0036] According to a second aspect, the invention relates to a method comprising the method steps of: providing a device according to the invention, providing an electromotive axle drive unit and operating the electromotive axle drive unit by means of the device, wherein the first switching element, in an open state, brings about a torque-free state of the electric motor. If reference is made here to a torque-free state of the electric motor, this means that the inverter cannot or does not provide a high-voltage power supply for the electric motor. If the first switching element is open, the electric motor cannot be supplied with electrical power from a traction battery, which stores the electrical energy for the electric motor, by means of the inverter.

[0037] It can be provided that the control device switches the first switching element depending on the result of the plausibility check. In particular, it can be provided that a torque signal from the inverter and a speed signal from the electric motor and / or a speed signal from the wheel to be driven are fed as input signals to the plausibility check of the control device. If an actual value of the speed signal lies outside a predetermined tolerance range or deviates too far from a predetermined speed target value, the first switching element can be opened in order to interrupt the high-voltage power supply to the electric motor by the inverter. Alternatively or additionally, it can be provided that the high-voltage power supply to the electric motor by the inverter is interrupted by opening the first switching element if an actual value of the torque signal from the inverter lies outside a predetermined tolerance range or deviates too far from a predetermined speed target value.deviates too far from a specified target torque value.

[0038] It can be provided that the open state of the first switching element is detected by means of the first feedback. The first feedback can also be an input signal for the plausibility check and be taken into account as part of the plausibility check.

[0039] Alternatively or additionally, the second feedback can be an input signal for the plausibility check and be taken into account as part of the plausibility check. As already mentioned, the second feedback monitors the presence or absence of a voltage from the first and second low-voltage power supplies of the first pole and the second pole.

[0040] It can therefore be provided that the plausibility check has the first feedback, the second feedback, the speed signal and the torque signal as input variables and the input variables are checked, wherein the control device switches the first switching element depending on the result of the plausibility check.

[0041] In addition, it can be provided that the control device switches the second switching element depending on the result of the plausibility check. The plausibility check can be used both to open and to close the first switching element. In this way, the plausibility check can monitor not only the switching off of the high-voltage power supply but also the switching on of the high-voltage power supply. This means that if one or more of the aforementioned input signals of the plausibility check are not within the specified range or do not correspond to the specified value, the plausibility check prevents the first switching element from being closed. This can also apply to the second switching element.

[0042] It can be provided that when the inverter is switched on, before the second switching element is closed, a switching state of the first switching element is checked by the control device, wherein the second switching element is only closed if the first switching element is also closed.

[0043] According to a third aspect, the invention relates to a motor vehicle having an electromotive axle drive unit which has an electric motor, having a device according to the invention and configured to carry out the method according to the invention.

[0044] In particular, it can be provided that the electric motor axle drive unit has two electric motors, wherein a first electric motor of the two electric motors is provided for driving a first wheel of the axle drive unit and wherein a second electric motor of the two electric motors is provided for driving a second wheel of the axle drive unit.

[0045] The motor vehicle can in particular be a goods vehicle, wherein the goods vehicle in particular has a permissible total weight of up to 7.51 (tonnes) or of more than 7.51 (tonnes), in particular a permissible total weight of up to 60 t (tonnes).

[0046] The invention is described in more detail below using an exemplary embodiment. Figure 1 schematically shows a device 2 according to the invention.

[0047] The device 2 for operating an electric motor axle drive unit 4 has an inverter 6. The inverter 6 is provided for the high-voltage power supply of an electric motor 8 of the electric motor drive unit 4. The inverter 6 converts, in a known manner, direct current provided by a traction battery (not shown) into a three-phase current required to operate the electric motor 8.

[0048] The inverter 6 has a first pole 10 and a second pole 12. The inverter 6 can be supplied with a low voltage via the first pole 10 and / or via the second pole 12 in order to provide a high-voltage power supply to the electric motor 8 of the electric motor axle drive unit.

[0049] 4. The device 2 has a control device 14 for controlling the inverter 6.

[0050] The device 2 has a shutdown device 16 for switching off the high-voltage power supply.

[0051] The device 2 has a first low-voltage power supply 18 connected to the first pole 10 of the inverter 6. The device 2 has a second low-voltage power supply 20 connected to the second pole of the inverter 6.

[0052] The shutdown device 16 has a first switching element 22 which is configured to simultaneously switch off both the first low-voltage power supply 18 and the second low-voltage power supply 20.

[0053] The control device 14 is configured to perform a plausibility check of a speed signal DI and a torque signal TI. The control device 14 is configured to switch the first switching element 22 depending on the result of the plausibility check. The plausibility check is represented in the present case by a module P of the control device 14. The module P can be a software element of the control device 14.

[0054] The inverter 6 is configured to receive the speed signal DI from a speed sensor 38. The speed sensor 38 is a resolver in the present case. The speed sensor 38 can, for example, measure a wheel speed of a wheel (not shown) to be driven by the electric motor 8 or a speed of an output shaft of the electric motor 8.

[0055] The control device 14 has a first feedback 26 for monitoring a switching state of the first switching element 22.

[0056] The first switching element 22 is in the present case a first relay 22 designed as a normally open contact, wherein the switching element 22 is connected to a first digital output 24 of the control device 14 and can be switched by means of an output signal of the first digital output 24.

[0057] A second switching element 28 is connected in series downstream of the first switching element 22, the second switching element 28 switching the second low-voltage power supply 20, the second switching element 28 being a second relay 28 designed as a normally open contact, and the second switching element being connected to a second digital output 30 of the control device 14 and being switchable by means of an output signal of the second digital output 30.

[0058] The control device 14 has a second feedback 32 for monitoring a switching state of the first switching element 22 and the second switching element 28.

[0059] The first switching element 22 is connected to a voltage source 34. The voltage source 34 has a voltage of 12 V in this case. The shutdown device 16 is hard-wired and has no control logic.

[0060] The shutdown device 16 is a component provided separately from the control device, wherein the shutdown device 16 is connected to the control device 14 by means of signal lines and wherein the shutdown device 16 has a housing 36 spaced from the control device 14, wherein the first switching element 22 and the second switching element 28 are accommodated in the housing 36. A fuse 44 is connected upstream of the switching element 22.

[0061] The control device 14 has a housing 40 separate from the shutdown device 16.

[0062] The connections between the control device 14 and the inverter 6 are GAN connections or GAN bus connections.

[0063] The functioning of the device 2 is described below using the processing of a torque or power request from a vehicle driver as an example.

[0064] The control device 14 has an input module 1 which receives a power request from an accelerator pedal 42 as an input signal. The input signal is processed by the input module 1 and passed on to a processor 3. An output signal is then generated by the output module 5, which is passed on both to the plausibility check P and to the inverter 6. The inverter 6, in turn, has an input module 7, a processor 9 and an output module 11 in order to provide an output signal for the axle drive unit 4, wherein a high-voltage power supply for the electric motor 8 is controlled by means of the output signal of the output module 11.

[0065] The modules 1, 3, 5, 7, 9, 11 form a first control level which converts a request from the accelerator pedal 42 into a motor torque of the electric motor 8.

[0066] During the above-mentioned signal processing, the reliable and safe functioning of the first control level is checked by a second control level, which is described below.

[0067] The speed signal DI and the torque signal TI are provided to the inverter 6 at input modules 13, 15 and fed to the plausibility check P via an output module 17 or a processor 17. The plausibility check P also receives the output signal of the output module 5, i.e. the torque request also transmitted to the inverter 6, as an input variable. Furthermore, a signal from the first feedback 26 and the second feedback 32 is provided to the plausibility check. If the plausibility check is successful and all input signals are within predetermined tolerance limits or have the required values, the first switching element 22 and the second switching element 28 remain in the closed state, so that the electric motor 8 can be operated by means of the accelerator pedal 42.

[0068] If the plausibility check is unsuccessful, i.e., if one of the aforementioned input signals is not within the specified tolerance range or does not have the specified value, the first switching element 22 is opened via the first digital output 24. Furthermore, the second switching element 28 is opened via the second digital output 30.

[0069] By opening the first switching element 22, both the first low-voltage power supply 18 and the second low-voltage power supply 20 are interrupted, so that no voltage is present at the first pole 10 and the second pole 12. Without an input voltage at the first pole 10 and the second pole 12, the inverter 6 cannot provide a high-voltage power supply for the electric motor 8, and the electric motor 8 is torque-free.

[0070] By means of the first feedback 26 and the second feedback 32 it can be checked whether the relay 22 is actually open and whether there is actually no input voltage at the first pole 10 and the second pole 12, i.e. whether the inverter 6 is actually not in operation.

[0071] Furthermore, by means of the first feedback 26 and the second feedback 32, it can be checked whether the relay 22 is closed and whether an input voltage is present at the first pole 10 and the second pole 12, i.e. whether the inverter 6 is in operation.

[0072] List of reference symbols

[0073] 1 input module

[0074] 2 Device

[0075] 3 processors

[0076] 4 axle drive unit

[0077] 5 Output module

[0078] 6 inverters

[0079] 7 Input module

[0080] 8 Electric motor

[0081] 9 processor

[0082] 10 first pole

[0083] 11 Output module

[0084] 12 second pole

[0085] 13 Input module

[0086] 14 Control device

[0087] 15 Input module

[0088] 16 Shut-off device

[0089] 17 Output module

[0090] 18 first low-voltage power supply

[0091] 20 second low-voltage power supply

[0092] 22 first switching element

[0093] 24 first digital output

[0094] 26 first repatriation

[0095] 28 second switching element

[0096] 30 second digital output

[0097] 32 second return

[0098] 34 Voltage source

[0099] 36 Housing of the defeat device

[0100] 38 Speed ​​sensor housing accelerator pedal fuse

Claims

Claims: Device (2) for operating an electric motor axle drive unit (4) , comprising an inverter (6) for high-voltage power supply of an electric motor (8) of the electric motor axle drive unit (4) , wherein the inverter (6) has a first pole (10) and a second pole (12) and wherein the inverter (6) can be supplied with a low-voltage voltage via the first pole (10) and / or via the second pole (12) in order to control a high-voltage power supply of the electric motor (8) of the electric motor axle drive unit (4), - with a control device (14) for controlling the inverter (6) , - with a shutdown device (16) for shutting off the high-voltage power supply, - with an initial low-voltage power supply (18) , which is connected to the first pole (10) of the inverter (6), and - with a second low-voltage power supply (20) , which is connected to the second pole (12) of the inverter (6), characterized in that - the shutdown device (16) has a first switching element (22) which is configured to simultaneously switch off both the first low-voltage power supply (18) and the second low-voltage power supply (20). Device according to claim 1, characterized in that - the control unit (14) is set up to check the plausibility of a speed signal and / or a torque signal, - wherein the control device (14) is configured to switch the first switching element (22) depending on the result of the plausibility check. Device according to claim 2, characterized in that - the inverter (6) is set up to provide the torque signal and / or - the inverter (6) and / or the control unit (14) are configured to receive a speed signal from a speed sensor (38). Device according to one of the preceding claims, characterized in that The control device (14) for monitoring a switching state of the first switching element (22) has a first feedback (26). Device according to one of the preceding claims, characterized in that - the first switching element (22) is a first relay (22) designed as a normally open contact, - wherein the switching element (22) is connected to a first digital output (24) of the control device (14) and can be switched by means of an output signal of the first digital output (24). Device according to one of the preceding claims, characterized in that - a second switching element (28) is connected in series after the first switching element (22), - wherein the second switching element (28) switches the second low-voltage power supply (20), - wherein the second switching element (28) is in particular a second relay (28) designed as a normally open contact and wherein the second switching element (22) is in particular connected to a second digital output (30) of the control device (14) and can be switched by means of an output signal of the second digital output (30).

7. Device according to claim 6, characterized in that - the control device (14) for monitoring a switching state of the first switching element (22) and the second switching element (28) has a second feedback (32).

8. Device according to one of the preceding claims, characterized in that - the first switching element (22) is connected to a voltage source (34).

9. Device according to one of the preceding claims, characterized in that - the shutdown device (16) is hard-wired and in particular does not have any control logic.

10. Device according to one of the preceding claims, characterized in that - the shutdown device (16) is a component provided separately from the control device (14), wherein the shutdown device (16) is connected to the control device (14) by means of signal lines, and wherein the shutdown device (16) in particular has a housing (36) spaced apart from the control device (14), wherein in particular the first The switching element (22) is included in the housing (36). Method comprising the following steps: - Providing a device (2) according to one of the preceding claims, - Ready to steepen an electric motor axle drive unit (4) , - Operating the electromechanical Axle drive unit (4) by means of the device (2), wherein the first switching element (22) in an open state causes a torque-free state of the electric motor (8). Method according to claim 11, characterized in that - the device is designed according to claim 2 and - the control device (14) switches the first switching element (22) depending on the result of the plausibility check. Method according to claim 11, characterized in that - the device is designed according to claim 4 and - the open state of the first switching element (22) is detected by means of the feedback (26) from the control device (14). A method according to claim 11, characterized in that the device is configured according to claims 2, 3, 4, 6 and 7, the plausibility check has the first feedback (26), the second feedback (32), the speed signal and the torque signal as input variables and the input variables are subjected to a plausibility check, and the control device (14) switches the first switching element (22) depending on the result of the plausibility check. A method according to claim 11, characterized in that the device is configured according to claim 4, - when the inverter (6) is switched on, the switching state of the first switching element (22) is checked by the control unit before the second switching element (28) is closed, and the second switching element (28) is only closed if the first switching element (22) is also closed. Motor vehicle, - with an electromechanical axle drive unit (4) comprising an electric motor, - with a device (2) for operating the electromechanical axle drive unit (4) according to one of claims 1-10 and configured for carrying out a method according to one of claims 11-15.

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