Electric drive unit for a motor vehicle and motor vehicle

Abstract

The invention relates to an electric drive unit (10), in particular for generating the driving movement of a motor vehicle, wherein the electric drive unit (10) has an electric motor (22) and a pulse-controlled inverter (28) for supplying the electric motor (22) with alternating current. The pulse-controlled inverter (28) and the electric motor (22) are arranged in a common housing (12). At least one power semiconductor (40) and / or an intermediate circuit capacitor (42) of the pulse-controlled inverter (28) is arranged at a shorter distance from the surface (36) of the housing (12) and / or a greater distance from the center (38) of the housing (12) than a control unit (44) of the pulse-controlled inverter (28) for controlling the at least one power semiconductor (40).

Description

The invention relates to an electric drive unit, in particular for generating the driving movement of a motor vehicle, and to a motor vehicle having such a drive unit for generating the driving movement.Drive units of the type in question serve in particular to bring about the travel movement of motor vehicles. The drive units must therefore have sufficient power for accelerating a motor vehicle and must also be able to be supplied with electrical energy by means of a battery system. In practice, therefore, electrical drive units have proven themselves in which the direct current typically made available by a battery system is converted into alternating current by means of a pulse inverter. The drive is operated with the alternating current. In this case, polyphase, typically three-phase alternating current is generally used.In practice, different designs have proven themselves for the pulse inverters, which are used in such motor vehicles. Thus, for example, DE 102021 209 649 A1 discloses a pulse inverter in which power semiconductors and a microcontroller for driving the power semiconductors are arranged on a single printed circuit board. The circuit board is arranged in a housing which has water cooling and can be fastened to a housing of an electric drive. EP 3 544 167 A1 discloses a similar pulse inverter in which, however, separate printed circuit boards for power semiconductors and for the electronics for controlling the power semiconductors are provided.Furthermore, electrical drive units are known from practice, which have an electric motor and a pulse inverter for supplying the electric motor with alternating current, wherein the pulse inverter and the electric motor are arranged in a common housing. The pulse inverter has at least one power semiconductor for generating the alternating current from direct current and a control unit for controlling the power semiconductors.According to the prior art, considerable effort has to be expended for cooling the power semiconductors and a frequently present intermediate circuit capacitor. In practice, therefore, liquid cooling systems for cooling the pulse inverters are frequently used. This then requires either appropriately designed separate housings for the pulse inverters or the comparatively complicated integration of liquid coolers within the housing of the electric drive unit. The advantage of the compact construction of electric drive units with a pulse inverter arranged in the housing of the electric drive unit is therefore achieved with a comparatively complicated structure, since in the drive units known from the prior art the components of the pulse inverter responsible for the heat generation are arranged far inside the drive housings.The object of the invention is therefore to show an electric drive unit and a motor vehicle with an electric drive unit, which make possible a simpler and more cost-effective construction of the drive unit.The object is achieved by an electric drive unit and a motor vehicle having the features of the independent claims. The features of the dependent claims relate to advantageous embodiments.The electric drive unit is suitable in particular for generating the driving movement of a motor vehicle. The electric drive unit has an electric motor and a pulse inverter for supplying the electric motor with alternating current.The pulse inverter and the electric motor are arranged in a common housing. The pulse inverter has a power semiconductor and a control unit for controlling the at least one power semiconductor.The object is achieved in particular in that the power semiconductor and / or an intermediate circuit capacitor of the pulse inverter is arranged at a shorter distance from the surface of the housing than the control unit. Alternatively and / or additionally, the object is achieved in particular in that the power semiconductor and / or an intermediate circuit capacitor of the pulse inverter is arranged at a greater distance from the center of the housing than the control unit.It has been found that, in the case of such a spatial arrangement of power semiconductor and / or intermediate circuit capacitor relative to the control unit, a significantly more favorable situation with regard to the heat dissipation in the electrical drive unit can be brought about. This has the result, in particular, that liquid cooling can either be completely dispensed with or the liquid cooling can be dimensioned at least to be smaller. The geometric arrangement of the liquid cooling in the electric drive unit is also simplified, since this can likewise be located closer to the surface of the electric drive unit and therefore has to be integrated less "deeply" in the system "electric drive unit".The at least one power semiconductor can be, in particular, three power semiconductors for generating in each case one phase of a three-phase alternating current. The power semiconductors can be in particular components of a power semiconductor module. As a constituent of the power semiconductor module, the power semiconductors can be encapsulated with a molding compound. The power semiconductors can be, for example, metal oxide semiconductor field effect transistors (MOSFETs) and / or insulated gate bipolar transistors (IGPTs). Three-phase alternating current, in particular three-phase current, is particularly well suited for operating electric motors.The at least one power semiconductor can be, in particular, a silicon carbide metal oxide semiconductor field effect transistor (SiC MOSFET). Such power semiconductors offer the advantage that they are very energy-efficient compared to other types of power semiconductors and therefore have a comparatively low heat development in any case. The use of this type of power semiconductor is therefore particularly advantageous if a more favorable heat dissipation is to be brought about by the above-described spatial arrangement of the at least one power semiconductor, since the basic quantity of the heat to be dissipated is thus already reduced.The control unit can in particular have a printed circuit board on which in particular a processor, a microcontroller, a printed circuit, a communication interface to the vehicle and / or a communication interface for controlling the power semiconductors is arranged. The printed circuit board can be arranged in its planar extension in particular, at least substantially, parallel to the region of the housing surface which has the smallest distance from the printed circuit board. Such a spatial arrangement leads to the formation of a spatial region between this region of the surface of the housing and the printed circuit board, in which the at least one power semiconductor and / or the intermediate circuit capacitor can be advantageously classified. In other words, power semiconductors and / or intermediate circuit capacitors are arranged between the control unit of the pulse inverter, in particular the printed circuit board of the control unit of the pulse inverter, and the region of the surface of the housing which is situated closest to the control unit. In this case, power semiconductors and intermediate circuit capacitor can be arranged at the same distance from the surface of the housing; alternatively, it is also possible to arrange either the intermediate circuit capacitor or the power semiconductor at a shorter distance from the surface of the housing. An arrangement of the at least one power semiconductor between the intermediate circuit capacitor and the surface of the housing and / or an arrangement of the intermediate circuit capacitor between the power semiconductor and the surface of the housing is also possible.The intermediate circuit capacitor can have a capacitance of at least 300 μF, in particular. Intermediate circuit capacitors are required, in particular for smoothing the intermediate circuit voltage, for example in the case of recuperation. This occurs in particular when the electric drive is operated in a braking manner and electric energy is thus generated by means of the electric drive, in other words when the electric drive unit is operated in a generator mode. A sufficiently high capacitance of the intermediate circuit capacitor then makes it possible to obtain comparatively high amounts of energy in a short time by way of recuperation. The heat arising in this case in the intermediate circuit capacitor can be dissipated particularly well by its geometric arrangement described above.According to a first alternative embodiment, the drive unit may not have a liquid cooling for cooling the power unit. It has been found in connection with the present invention that such liquid cooling can ideally be completely dispensed with by the geometric arrangement. The design is considerably simplified by eliminating the liquid cooling. Furthermore, with the liquid cooling, a potential source of faults is also eliminated, in particular with regard to possible leaks. It has been shown in connection with the present invention that liquid cooling can be advantageously dispensed with, in particular in the case of drive units in a power range of 30 kW to 245 kW.According to an alternative embodiment, the drive unit can have a liquid cooling system for cooling the power unit. In particular in the case of powerful electric drives, it may be expedient nevertheless to provide liquid cooling in conjunction with the above-described geometric arrangement of power semiconductors and / or intermediate circuit capacitor. As a result, a cost advantage over the prior art can nevertheless be realized due to the more favorable arrangement of the components of the pulse inverter in the electric drive unit for heat dissipation and the integrability of the liquid cooling. It has been shown in connection with the present invention that liquid cooling can be used in an advantageous manner, in particular in the case of drive units in a power range of 245 kW to 1217 kW.The motor vehicle has an electric drive unit of the type described above. The electric drive unit serves here to generate the driving movement of the motor vehicle. The motor vehicle may further have a battery for supplying the electric drive unit with electrical energy.The motor vehicle can be designed such that the surface region of the housing of the drive unit, which has the smallest distance from the power unit, is acted upon by an air flow resulting from the travel movement of the motor vehicle when the motor vehicle is driving forward. Such a configuration of the motor vehicle offers the advantage that a cooling effect of the drive unit is brought about by the air flow in the region in which heat is generated by the pulse inverter. The heat dissipation from the pulse inverter is thus improved once more.The power unit can be arranged in a region of the housing which points in the direction of travel of the motor vehicle when driving forwards. A region of the housing facing in the direction of travel of the motor vehicle when driving forwards is typically acted upon by the air flow relative to the motor vehicle generated when the motor vehicle is driving forwards, or such an inflow can be brought about particularly easily by corresponding structural measures when constructing the motor vehicle. In particular, an incident flow is possible without the air flow having to be deflected to a considerable extent.The motor vehicle can have an on-board power supply system with a mains voltage of at least 800 V for supplying the drive unit with electrical energy. Such an on-board power supply system makes it possible to save line cross sections compared to an on-board power supply system with a lower voltage. In particular, such an on-board power supply system also enables a comparatively rapid charging of a battery of such a motor vehicle. Since the pulse inverter can be used when charging the battery, for example in order to monitor a sensor system of the electrical system of the motor vehicle, better heat dissipation of the heat generated by the pulse inverter from the drive unit is advantageous even during charging processes.Further practical embodiments of the invention are described below in conjunction with the drawings. The following are shown: FIG. 1 shows a schematic exploded illustration of an exemplary electric drive unit, FIG. 2 shows an exemplary schematic illustration of the spatial arrangement of the components of the pulse inverter in the electric drive unit according to a first exemplary embodiment, FIG. 3 shows an exemplary schematic illustration of the spatial arrangement of the components of the pulse inverter in the electrical drive unit according to a second exemplary embodiment FIG. 4 shows an exemplary schematic illustration of the spatial arrangement of the components of the pulse inverter in the electrical drive unit according to a third exemplary embodiment.An exploded view of an exemplary electric drive unit 10 is shown in FIG. 1. The electric drive unit 10 has a housing 12. As in the example shown, the housing 12 can consist of a base body 14 and further housing parts 16, 18 and 20. These can be designed as a cover, as can be the housing part 16 in particular in the example shown.An electric motor 22 is arranged in the housing 12. The electric motor 22 has a rotor 24 mounted rotatably about an axis and a stator 26. Furthermore, a pulse inverter 28 is arranged in the housing 12. As in the example shown, this can be fastened to a housing part 16 designed as a cover.Furthermore, the electric drive unit 10, as illustrated by way of example, can have a sensor 30, in particular for the movement of the rotor 24, a cooling device 32, which can be formed, for example, as a unit consisting of a bearing shield and a cooling jacket, and / or a gear mechanism 34, which can in particular likewise be arranged in the housing 12.FIGS. 2 to 4 show a schematic illustration of the spatial arrangement of components of the pulse inverter 28 relative to the surface 36 and to the center 38 of the housing 12. As can be seen in FIGS. 2 to 4, at least one power semiconductor 40 and / or an intermediate circuit capacitor 42 of the pulse inverter 28 are arranged at a shorter distance from the surface 36 of the housing 12 and / or at a greater distance from the center 38 of the housing 12 than a control unit 44 of the pulse inverter 28.The control unit 44 of the pulse inverter 28 can be, in particular, an electronic circuit which comprises a printed circuit board on which, in particular, a processor, a microcontroller, a printed circuit, a communication interface to the vehicle and / or a communication interface for controlling the power semiconductors is arranged.As in the example shown in FIG. 2, the at least one power semiconductor 40 can be arranged at a shorter distance to the surface 36 of the housing 12 and / or at a greater distance to the center 38 of the housing 12 than the intermediate circuit capacitor 42.Alternatively, as in the example shown in FIG. 3, the intermediate circuit capacitor 42 may be arranged at a shorter distance to the surface 36 of the housing 12 and / or at a greater distance to the center 38 of the housing 12 than the at least one power semiconductor 40.Alternatively, as is also shown by way of example in FIG. 4, the at least one power semiconductor 40 and the intermediate circuit capacitor 42 can likewise be arranged at the same distance from the surface 36 of the housing 12 and / or from the center 38 of the housing 12.The features of the invention disclosed in the present description, in the drawings and in the claims can be essential, both individually and in any combinations, for the realisation of the invention in its various embodiments. The invention can be varied within the scope of the claims and taking into account the knowledge of the responsible person skilled in the art.List of reference characters10 Drive unit 12 Housing 14 Base body 16 Housing part 18 Housing part 20 Housing part 22 Electric motor 24 Rotor 26 Stator 28 Pulse inverter 30 Sensor 32 Cooling device 34 Transmission 36 Surface 38 Center 40 Power semiconductor 42 Intermediate circuit capacitor 44 Control unitReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 102021 209 649 A1

[0003] EP 3 544 167 A1

[0003]

Claims

Electric drive unit (10), in particular for generating the travel movement of a motor vehicle, wherein the electric drive unit (10) has an electric motor (22) and a pulse inverter (28) for supplying the electric motor (22) with alternating current, wherein the pulse inverter (28) and the electric motor (22) are arranged in a common housing (12), characterized in that at least one power semiconductor (40) and / or an intermediate circuit capacitor (42) of the pulse inverter (28) is arranged at a shorter distance from the surface of the housing (12) and / or a longer distance from the center (38) of the housing (12) than a control unit (44) of the pulse inverter (28) for controlling the at least one power semiconductor (40).Drive unit (10) according to Claim 1, characterized in that the at least one power semiconductor (40) is three power semiconductors (40) for generating in each case one phase of a 3-phase alternating current.Drive unit (10) according to Claim 1 or 2, characterized in that the at least one power semiconductor (40) is a silicon carbide metal oxide semiconductor field effect transistor (SiC-MOSFET).Drive unit (10) according to one of the preceding claims, characterized in that the control unit has a printed circuit board on which in particular a processor, a microcontroller, a printed circuit, a communication interface to the vehicle and / or a communication interface for controlling the power semiconductors is arranged.Drive unit (10) according to one of the preceding claims, characterized in that the drive unit (10) has no liquid cooling for cooling the pulse inverter (28).Drive unit (10) according to one of Claims 1 to 4, characterized in that the drive unit (10) has a liquid cooling system for cooling the power unit.Motor vehicle having an electric drive unit (10) according to one of the preceding claims for generating the driving movement of the motor vehicle.Motor vehicle according to Claim 7, characterized in that the motor vehicle is designed in such a way that the surface region of the housing (12) of the drive unit (10), which has the smallest distance from the power unit, is acted upon by an air flow resulting from the driving movement of the motor vehicle during forward travel of the motor vehicle.Motor vehicle according to either of Claims 7 and 8, characterized in that the power unit is arranged in a region of the housing (12) which points in the direction of travel of the motor vehicle when driving forwards.Motor vehicle according to one of the preceding claims 7 to 9, characterized in that the motor vehicle has an on-board power supply system with a mains voltage of at least 800 V for supplying the drive unit (10) with electrical energy.

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