Power converter for an electric axle drive of a motor vehicle, electric axle drive for a motor vehicle, motor vehicle and method for manufacturing a power converter

Abstract

A power converter (130) for an electric axle drive (120) of a motor vehicle is presented. The power converter (130) comprises a DC link (233), a busbar assembly (239), and a bridge circuit (235) with electrically parallel-connected switching devices (S1, S2, S3, S4, S5, S6). The busbar assembly (239) is configured to electrically connect the DC link (233) and the bridge circuit (235) and to provide electrical contact for the switching devices (S1, S2, S3, S4, S5, S6) within the bridge circuit (235). The power terminals of the switching devices (S1, S2, S3, S4, S5, S6) are connected to the busbar assembly (239) by a welded or brazed connection.

Description

[0001] The present invention relates to a power converter for an electric axle drive of a motor vehicle, to an electric axle drive for a motor vehicle, to a motor vehicle and to a method for manufacturing a power converter.

[0002] In a power converter for a motor vehicle, conventional methods for the electrical connection of semiconductor switches to other components of the power converter include, for example, surface mounting or through-hole mounting.

[0003] JP 2011-120 358 A shows a power converter.

[0004] DE 10 2020 206 199 A1 discloses a power converter.

[0005] Against this background, the present invention provides an improved power converter for an electric axle drive of a motor vehicle, an improved electric axle drive for a motor vehicle, an improved motor vehicle, and an improved method for manufacturing a power converter according to the main claims. Advantageous embodiments are described in the dependent claims and the following description.

[0006] The advantages achievable with the presented approach lie particularly in the fact that a low-inductance electrical connection can be provided between individual semiconductor elements or semiconductors within a switch and between switches within a bridge circuit, for example, a half-bridge. This reduces losses and, additionally or alternatively, improves parallelization or parallelizability. Furthermore, simple and straightforward scalability of the power converter can be achieved application-specifically across the thickness of at least one busbar of the busbar unit. Moreover, compared to a conventional, less robust soft solder connection, a robust mechanical connection, which is also electrically conductive, can be established between the individual semiconductor elements.Semiconductors can be connected by a robust, metallurgical bond, especially by welding or brazing, which can increase the service life of such a connection and thus of the power converter.

[0007] The invention relates to a power converter for an electric axle drive of a motor vehicle, wherein the power converter has an intermediate circuit, a busbar unit and a bridge circuit with electrically parallel connected switching devices, wherein the busbar unit is shaped to electrically connect the intermediate circuit and the bridge circuit to each other, wherein the busbar unit is shaped to effect electrical contacting of the switching devices within the bridge circuit, wherein power connections of the switching devices are connected to the busbar unit by a welded connection or a brazed connection.

[0008] The motor vehicle can be, for example, a land vehicle, in particular a passenger car, a motorcycle, a commercial vehicle, or the like. The power converter can be designed as an inverter. The power converter can also be referred to as a traction converter. The power converter can be configured to convert direct current (DC) from an electrical energy storage device of the motor vehicle into alternating current (AC) for an electric motor of the motor vehicle's electric axle drive.The power converter can have DC connections for direct current from a vehicle's electrical energy storage device, an intermediate circuit with at least one intermediate circuit capacitor electrically connected to the DC connections, AC connections for supplying alternating current to an electric motor of the electric axle drive, and a bridge circuit with a plurality of switching devices, the switching devices being designed to convert the direct current into alternating current. The busbar unit can have at least one busbar. The welded connection can be made by resistance welding, laser welding, or another metallurgical bond.A mechanical and electrically conductive connection between the power terminals and the busbar unit can be created through welding or brazing.

[0009] According to the invention, the busbar unit is designed to electrically connect all external connections of the power converter. The external connections can include DC connections for a direct current from an electrical energy storage device of the vehicle and AC connections for supplying an alternating current to an electric motor of the electric axle drive. Thus, a robust, low-inductance electrical connection can be provided within the power converter, which also allows for straightforward scalability.

[0010] According to one embodiment, the power connections of the switching devices can be arranged on one side only. Thus, the switching devices can be switching devices with power connections arranged on one side only. In this way, an advantageous DC+ / DC- / AC busbar for the electrical contacting of parallel-connected switching devices with power connections arranged on one side only can be implemented within a bridge circuit with correspondingly arranged voltage taps.

[0011] According to one embodiment, at least the switching devices can be implemented as discrete packages or modules. In particular, all electronic components and, additionally or alternatively, all power electronic components of the converter can be implemented as discrete packages or modules. Thus, the advantages mentioned herein can be achieved by the busbar unit regardless of the specific implementation or level of integration of the converter components.

[0012] According to one embodiment, the bridge circuit can comprise at least one half-bridge, half-bridge modules, and additionally or alternatively a B6 bridge circuit. Additionally or alternatively, the switching devices can be designed as semiconductor switching devices, in particular as bipolar transistors with an insulated gate electrode. Such an embodiment offers the advantage that efficiency can be increased by such interconnection of these switching devices in a power converter while keeping semiconductor costs low.

[0013] According to one embodiment, the power converter can have a cooling device that is thermally coupled at least to the switching devices or to all power electronic components of the power converter. Such an embodiment offers the advantage that heat dissipation from thermally active components can be optimized. This also improves short-term overload protection of components.

[0014] According to one embodiment, the power converter can have a first printed circuit board and a second printed circuit board separate from the first. At least intermediate circuit capacitors can be arranged on the first printed circuit board. At least driver circuits for the switching devices can be arranged on the second printed circuit board. The power converter can also include the driver circuits. The power converter can also have a cooling device arranged between the printed circuit boards. Such an embodiment offers the advantage that improved active heat dissipation of power electronic components can be achieved by using the cooling device on both sides.

[0015] Furthermore, the invention relates to an electric axle drive for a motor vehicle, wherein the electric axle drive comprises at least one electric machine, one transmission device and one embodiment of a power converter described herein.

[0016] The power converter can be designed as an inverter. Using the power converter, alternating current required to operate the electric machine can be provided. Using the transmission device, torque provided by the electric machine can be converted into drive torque to power at least one wheel of the vehicle. The transmission device can include a gearbox for reducing the speed of the electric machine and, optionally, a differential.

[0017] Furthermore, the invention relates to a motor vehicle with an embodiment of a power converter mentioned herein and additionally or alternatively with an embodiment of an electric axle drive mentioned herein.

[0018] Accordingly, a motor vehicle may include a power converter mentioned herein and additionally or alternatively an electric axle drive mentioned herein.

[0019] Furthermore, the invention relates to a method for manufacturing an embodiment of a power converter mentioned herein, wherein the method comprises a step of electrically connecting the intermediate circuit and the bridge circuit to each other by means of the busbar unit, wherein electrical contacting of the switching devices within the bridge circuit is effected by means of the busbar unit, wherein the power connections of the switching devices are connected to the busbar unit by welding or brazing.

[0020] By carrying out the manufacturing process, an embodiment of a power converter mentioned herein can be advantageously produced. In the joining step, a metallurgical connection can be made in the form of a welded joint by resistance welding, laser welding or the like, or in the form of a brazed joint by brazing.

[0021] The invention is explained in more detail by way of example with reference to the accompanying drawings. These show: Fig. 1 a schematic representation of an exemplary embodiment of a motor vehicle; Fig. 2 a schematic partial representation of an embodiment of an electric axle drive of a motor vehicle; Fig. 3 a flowchart of an exemplary embodiment of a method for manufacturing a power converter; Fig. 4 a partial representation of an exemplary embodiment of a power converter; Fig. 5 a partial representation of an exemplary embodiment of a power converter; Fig. 6 a partial representation of an exemplary embodiment of a power converter; Fig. 7 a partial representation of an exemplary embodiment of a power converter; and Fig. 8 a partial representation of an exemplary embodiment of a power converter.

[0022] In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, without repeating these elements.

[0023] Fig. Figure 1 shows a schematic representation of an embodiment of a motor vehicle 100. The motor vehicle 100 is shown in the illustration by Fig. Figure 1 shows wheels 105 (four wheels 105 are shown by way of example), an electrical energy storage device 110 (for example, a battery), and an electric axle drive 120. The electric axle drive 120 comprises a power converter 130, an electric machine 140, and a transmission unit 150.

[0024] Electrical energy for operating the electric machine 105 is provided by a power supply unit, in this case the electric energy storage device 110. The electric energy storage device 110 is configured to provide direct current, which is converted into alternating current, for example three-phase alternating current, using a power converter 130 of the electric axle drive 120 and supplied to the electric machine 140. A shaft driven by the electric machine 140 is coupled directly or via the transmission unit 150 to at least one wheel 105 of the motor vehicle 100. Thus, the motor vehicle 100 can be propelled using the electric machine 140. According to one embodiment, the electric axle drive 120 comprises a housing in which at least the power converter 130, the electric machine 140, and the transmission unit 150 are arranged.

[0025] The power converter 130 and its components will be discussed in more detail with reference to the following figures.

[0026] Fig. Figure 2 shows a schematic partial representation of an exemplary embodiment of an electric axle drive 120 of a motor vehicle. The electric axle drive 120 corresponds to or is similar to the electric axle drive from Fig. 1. In the partial representation of Fig. 2 of the electric axle drive 120, the electric energy storage device 110, the power converter 130 and the electric machine 140 are shown.

[0027] The power converter 130 comprises an intermediate circuit 233, a busbar unit 239, and a bridge circuit 235 with electrically parallel-connected switching devices S1, S2, S3, S4, S5, S6. In the illustration of Fig. Figure 2 shows the DC connections 231 of the converter 130, the intermediate circuit 233 with at least one intermediate circuit capacitor, the bridge circuit 235 with the plurality of switching devices S1, S2, S3, S4, S5, S6, AC connections 237 and the busbar unit 239.

[0028] The busbar unit 239 is designed to electrically connect the intermediate circuit 233 and the bridge circuit 235. The busbar unit 239 is also designed to provide electrical contact for the switching devices S1, S2, S3, S4, S5, and S6 within the bridge circuit 235. The power connections of the switching devices S1, S2, S3, S4, S5, and S6 are connected to the busbar unit 239 by a welded or brazed connection.

[0029] The busbar unit 239 comprises at least one busbar, also referred to as a bus rail. In particular, the busbar unit 239 is designed and / or arranged to electrically connect all external connections of the converter 130, i.e., the DC connections 231 and the AC connections 237. According to the embodiment shown here, the power connections of the switching devices S1, S2, S3, S4, S5, S6 are arranged on one side only. The switching devices S1, S2, S3, S4, S5, S6 are arranged in two rows of three pairs of opposing switching devices S1 and S2, S3 and S4, and S5 and S6, according to the embodiment shown here. The power connections of each of the switching devices S1, S2, S3, S4, S5, S6 face the switching device arranged opposite it.

[0030] According to one embodiment, at least the switching devices S1, S2, S3, S4, S5, S6 are implemented as discrete packages. According to an alternative embodiment, at least the switching devices S1, S2, S3, S4, S5, S6 are implemented as modules. In particular, all electronic components and / or all power electronic components of the power converter 130 are implemented as discrete packages. Alternatively, all electronic components and / or all power electronic components of the power converter 130 are implemented as modules.

[0031] Depending on the embodiment, the bridge circuit 235 of the power converter 130 comprises at least one half-bridge, half-bridge modules and / or a B6 bridge circuit. The switching devices S1, S2, S3, S4, S5, S6 are, for example, designed as semiconductor switching devices, in particular as bipolar transistors with an insulated gate electrode.

[0032] The DC terminals 231 are provided for a direct current from the vehicle's electrical energy storage device 110. In other words, the converter 130 can be connected to the electrical energy storage device 110 via the DC terminals 231. The intermediate circuit 233 is electrically connected to the first and second DC terminals 231. The AC terminals 237 are provided for supplying an alternating current to the electric motor 140 of the electric axle drive. In other words, the converter 130 can be connected to the electric motor 140 via the AC terminals 237. The DC terminals 231 and / or the AC terminals 237 are each designed, for example, to receive one end of a power cable and to be mechanically and electrically connected, for example, by screwing, clamping, or soldering.

[0033] The bridge circuit 235 with switching devices S1, S2, S3, S4, S5, and S6 is designed to convert direct current into alternating current. According to the embodiment shown here, the power converter 130 comprises, by way of example, six switching devices S1, S2, S3, S4, S5, and S6, namely a first switching device S1, a second switching device S2, a third switching device S3, a fourth switching device S4, a fifth switching device S5, and a sixth switching device S6. The switching devices S1, S2, S3, S4, S5, and S6 are connected in a B6 bridge circuit as a bridge circuit 235, according to the embodiment shown here. A first of the DC terminals 231 is electrically connected via the busbar unit 239 to a first power terminal of the first switching device S1, a first power terminal of the third switching device S3, and a first power terminal of the fifth switching device S5.A second of the DC terminals 231 is electrically connected via the busbar unit 239 to a first power terminal of the second switching device S2, a first power terminal of the fourth switching device S4, and a first power terminal of the sixth switching device S6. A first of the AC terminals 237 is electrically connected via the busbar unit 239 to a second power terminal of the first switching device S1 and a second power terminal of the second switching device S2. A second of the AC terminals 237 is electrically connected via the busbar unit 239 to a second power terminal of the third switching device S3 and a second power terminal of the fourth switching device S4.A third of the AC terminals 237 is electrically connected via the busbar unit 239 to a second power terminal of the fifth switching device S5 and a second power terminal of the sixth switching device S6.

[0034] According to one embodiment, the power converter 130 can be operated in reverse, so that the electric machine 140 can be used as a generator to charge the electrical energy storage device 110.

[0035] Fig. Figure 3 shows a flowchart of an embodiment of method 300 for manufacturing a power converter. Method 300 can be carried out to manufacture the power converter from one of the figures described herein or a similar power converter. The power converter is for an electric axle drive of a motor vehicle such as the motor vehicle from Fig. 1. Such a power converter comprises an intermediate circuit, a busbar unit, and a bridge circuit with electrically parallel-connected switching devices. The manufacturing method 300 comprises a connecting step 302.

[0036] In step 302 of the connection process, the intermediate circuit and the bridge circuit are electrically connected to each other using the busbar unit. In this step, the switching devices within the bridge circuit are electrically contacted using the busbar unit. Furthermore, in step 302, the power connections of the switching devices are connected to the busbar unit by welding or brazing.

[0037] In particular, step 302 of the joining process creates a metallurgical bond in the form of a welded joint by resistance welding, laser welding, or the like, or in the form of a brazed joint by brazing. This allows for the creation of a robust mechanical and electrical connection, as well as the provision of a durable power converter.

[0038] Fig. Figure 4 shows a partial representation of an embodiment of a power converter 130. The power converter 130 corresponds to or is similar to the power converter shown in one of the figures described above. In the representation of Fig. Figure 4 shows the bridge circuit 235 and the busbar unit 239 of the power converter 130. According to the in Fig. In the embodiment shown in Figure 4, the power converter 130 further comprises a first printed circuit board 432 and a second printed circuit board 434 separate from the first printed circuit board 432. At least intermediate circuit capacitors of the intermediate circuit of the power converter 130 are arranged on the first printed circuit board 432. At least driver circuits for the switching devices of the bridge circuit 235 are arranged on the second printed circuit board 434. The power converter 130 also includes the driver circuits, which are not explicitly named here for illustrative reasons. According to the embodiment shown here, the power converter 130 also includes a cooling device 436. The cooling device 436 is arranged between the printed circuit boards 432 and 434. Additionally or alternatively, the cooling device 436 is thermally coupled at least to the switching devices of the bridge circuit 235 or to all power electronic components of the power converter 130.

[0039] Fig. Figure 5 shows a partial representation of an embodiment of a power converter 130. The power converter 130 corresponds to or is similar to the power converter shown in one of the figures described above. In the representation of Fig. Figure 5 shows only six switching devices S1, S2, S3, S4, S5, S6 of the bridge circuit and the busbar unit 239 as examples of the power converter 130.

[0040] Fig. Figure 6 shows a partial representation of an embodiment of a power converter 130. The power converter 130 corresponds to or is similar to the power converter shown in one of the figures described above. In the representation of Fig. Figure 6 shows, by way of example, six switching devices S1, S2, S3, S4, S5, S6 of the bridge circuit and the busbar unit 239 of the power converter 130.

[0041] Fig. Figure 7 shows a partial representation of an embodiment of a power converter 130. The power converter 130 corresponds to or is similar to the power converter shown in one of the figures described above. In the representation of Fig. Figure 7 shows, by way of partial sectional view, only four switching devices S1, S2, S3, S4 of the bridge circuit, the busbar unit 239 and part of the cooling device 436 of the power converter 130.

[0042] Fig. Figure 8 shows a partial representation of an embodiment of a power converter 130. The power converter 130 corresponds to or is similar to the power converter shown in one of the figures described above. In the representation of Fig.8 are shown by way of example of the power converter 130, based on a partial section view, two switching devices S1, S2 of the bridge circuit, their two power connections 838, the busbar unit 239 and a part of the cooling device 436.

[0043] With reference to the figures described above, exemplary embodiments and advantages of exemplary embodiments are briefly explained again in other words and summarized below.

[0044] According to one embodiment, a busbar connection or its arrangement in the form of the busbar unit 239 is provided, wherein all potentials of the power terminals of the inverter or power converter 120, i.e., DC+, DC-, and phase output, are or are contacted in a common arrangement or assembly. This can be implemented with discrete semiconductor packages or modules. In other words, according to one embodiment, for example, a busbar configuration of an inverter or power converter 120 is provided for the electrical contacting of parallel-connected, discrete semiconductor packages or switching devices S1, S2, S3, S4, S5, S6 with power terminals 838 arranged on one side within a bridge circuit 235, in particular a half-bridge, by means of the busbar unit 239.In other words, according to one embodiment, a DC+ / DC- / AC busbar is provided for the electrical contacting of parallel-connected, discrete semiconductor packages or switching devices S1, S2, S3, S4, S5, S6 with power terminals 838 arranged on one side within a half-bridge or half-bridge modules with correspondingly arranged voltage taps, using the busbar unit 239. According to one embodiment, the cooler or cooling device 406 and 30 can be used on both sides, thus enabling active heat dissipation for all power electronics components. Furthermore, the mutual dependency of requirements for the electrical and / or thermal and mechanical design or construction is advantageously resolved or balanced out, thereby creating / enabling a degree of design freedom.This allows for heat dissipation and current-carrying components to be located on the underside of the package, while simultaneously providing access for control and logic on the top side. This creates a prerequisite for an optimized overall inverter design, particularly with regard to thermal performance, electrical performance, and cost / power density, etc. The thermal connection (especially transient) of the discrete package can thus be optimized, particularly with improved short-term overload capacity. Furthermore, HV-LV coupling and design freedom can be improved if all pins (power and control) are integrated into the same substrate (PCB). This is achieved, in particular, by implementing the busbar unit 239 as an electrical connection from the DC link 233 to the half-bridge or bridge circuit 235, by welding or brazing the pins, and / or by separating the control and power sections.

[0045] In other words, a power converter 120 is presented with welded pins or power connections 838 on a busbar or bus unit 239. This improves, in particular, electrical and thermal contact and consequently performance, achieves more robust contact, leading to an increased lifetime of the power converter 120, mitigates a previous weakness in the form of the pin cross-section because the bus unit 239 is brought close to the package, thus enabling preparation for SiC, and allows scalability with regard to the number of parallel semiconductors or switching devices, whereby a number of semiconductors or switching devices can be selected depending on package performance and robustness. Reference sign 100 motor vehicles 105 wheels 110 electrical energy storage 120 electric axle drive 130 power converters 140 electric machine 150 gearbox unit 231 DC connections 233 Intermediate circle 235 Bridge circuit 237 AC power outlets 239 busbar unit S1 first switching device S2 second switching device S3 third switching device S4 fourth switching device S5 fifth switching device S6 sixth switching device 300 manufacturing processes Step 302 of connecting 432 first circuit board 434 second circuit board 436 Cooling device 838 Power connection

Claims

[1] Power converter (130) for an electric axle drive (120) of a motor vehicle (100), wherein the power converter (130) has an intermediate circuit (233), a busbar unit (239) and a bridge circuit (235) with electrically parallel-connected switching devices (S1, S2, S3, S4, S5, S6), wherein the busbar unit (239) is shaped to electrically connect the intermediate circuit (233) and the bridge circuit (235) to one another, wherein the busbar unit (239) is shaped to effect electrical contacting of the switching devices (S1, S2, S3, S4, S5, S6) within the bridge circuit (235), wherein power connections (838) of the switching devices (S1, S2, S3, S4, S5, S6) are connected to the busbar unit (239) by a welded connection or a brazed connection, wherein the Busbar unit (239) is formed to electrically connect all external terminals (231, 237) of the power converter (130) to one another. [2] Power converter (130) according to the preceding claim, wherein the power terminals (838) of the switching devices (S1, S2, S3, S4, S5, S6) are arranged on one side. [3] Power converter (130) according to one of the preceding claims, wherein at least the switching devices (S1, S2, S3, S4, S5, S6) are designed as discrete packages or as modules. [4] Power converter (130) according to one of the preceding claims, wherein the bridge circuit (235) comprises at least one half-bridge, half-bridge modules and / or a B6 bridge circuit, and / or wherein the switching devices (S1, S2, S3, S4, S5, S6) are designed as semiconductor switching devices, in particular as bipolar transistors with an insulated gate electrode. [5] Power converter (130) according to one of the preceding claims, with a cooling device (436) which is thermally coupled at least to the switching devices (S1, S2, S3, S4, S5, S6) or to all power electronics components of the power converter (130). [6] Power converter (130) according to one of the preceding claims, with a first circuit board (432) and a second circuit board (434) separate from the first circuit board (432), wherein at least intermediate circuit capacitors of the intermediate circuit (235) are arranged on the first circuit board (432), wherein at least driver circuits for the switching devices (S1, S2, S3, S4, S5, S6) are arranged on the second circuit board (434), and with a cooling device (436) which is arranged between the circuit boards (432, 434). [7] Electric axle drive (120) for a motor vehicle (100), wherein the electric axle drive (120) comprises at least one electric machine (140), a transmission device (150) and a power converter (130) according to one of the preceding claims. [8] Motor vehicle (100) comprising a power converter (130) according to one of claims 1 to 6 and / or an electric axle drive (120) according to claim 7. [9] Method (300) for producing a power converter (130) according to one of claims 1 to 6, wherein the method (300) comprises a step (302) of electrically connecting the intermediate circuit (233) and the bridge circuit (235) to one another by means of the busbar unit (239), wherein an electrical contacting of the switching devices (S1, S2, S3, S4, S5, S6) within the bridge circuit (235) is effected by means of the busbar unit (239), wherein the power terminals (838) of the switching devices (S1, S2, S3, S4, S5, S6) are connected to the busbar unit (239) by welding or brazing.

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