Inverter and electric motor assembly comprising such an inverter

Abstract

The invention relates to an inverter for supplying two electric motors (27), in particular of an electric rear axle of a motor vehicle, comprising a housing (2) with a connecting flange (3) that can be secured to a securing interface (33) of a machine housing (26) and comprising a base (5) that is provided in the housing (2) and can be cooled by means of a cooling liquid, which can be supplied via at least one inlet and discharged via at least one outlet, wherein the inlet and the outlet have connection means (14, 15) for connecting to a heat exchanger (31) provided on the electric motor side; a plurality of power modules (7) are provided on a first base side (6) and a plurality of capacitors (10) are provided on an opposite second base side (9); the power modules (7) are connected to the capacitors (10) via busbars (19) that pass through one or more through-holes (20) in the base (5); connection means (34) are provided for connecting the capacitors (10) to an EMC filter (29) provided on the electric motor side; and the power modules (7) are connected, via additional busbars (21) that pass through one or more additional through-holes (22) in the base (5), to connection plugs (12), which are provided on the first base side (6) and via which the inverter (1) can be connected to connections (28) of the two electric motors (27).

Description

[0001] P241379

[0002] - 1 - Inverter and electric motor arrangement comprising such an inverter

[0003] The invention relates to an inverter for supplying two electric motors, in particular an electric rear axle of a motor vehicle.

[0004] Modern vehicles often feature an electric drive system, in which at least one of the two axles is electrically driven. A common example is a dual-motor rear axle, which has two separate electric motors. Each electric motor drives one wheel of the rear axle. An inverter is assigned to the electric motors, providing the operating voltage. The inverter is designed to power both electric motors, meaning it provides the separate operating voltages required. Typically, the inverter is installed between the two electric motors to achieve the most compact design possible for the rear axle. However, if an electric parking brake is also to be integrated into the rear axle, the integration of the necessary components eliminates the option of installing the inverter between the electric motors.

[0005] The invention is based on the problem of specifying an inverter that can be installed on the axle side despite such altered structural conditions.

[0006] To solve the problem, an inverter for supplying two electric motors, in particular an electric rear axle of a motor vehicle, is provided according to the invention, comprising a housing with a connecting flange that can be attached to a mounting interface of a machine housing and a base plate arranged in the housing, which can be cooled with a coolant that can be supplied and discharged via at least one inlet and at least one outlet, wherein the inlet and the outlet have connection means for connecting to a heat exchanger provided on the electric motor side, wherein several power modules are arranged on a first side of the plate and several capacitors are arranged on an opposite second side of the plate, wherein the power modules are connected to the capacitors via busbars extending through one or more openings in the base plate, wherein connection means for connecting the capacitors to a P241379

[0007] -2 -EMC filters are provided on the electric motor side, and the power modules are connected via the base plate by further busbars passing through one or more further openings with connector plugs provided on the first side of the plate, via which the inverter can be connected to the terminals of the two electric motors.

[0008] The invention proposes an inverter designed as a separate unit, configured as a dual inverter, comprising only the power components, namely the capacitors and the power modules. Other relevant components associated with the inverter, in the form of the EMC filter and the heat exchanger, are provided as separate elements on the machine side. They are therefore not part of the inverter or the inverter assembly, but are integrated into the rest of the overall machine system. The inverter itself has corresponding interfaces to connect its relevant components to the EMC filter on the one hand and the heat exchanger on the other.

[0009] The inverter according to the invention has a housing which features a preferably rectangular connecting flange, via which the housing, in which the corresponding power components of the inverter are housed, is connected, preferably screwed, to a machine housing of the electric motor assembly. For this purpose, a corresponding mounting interface is provided on the machine housing to which the connecting flange is attached.

[0010] Furthermore, the inverter has a base plate arranged within the housing. This base plate serves both as a support for the corresponding power components, namely the capacitors and the power modules, and simultaneously as a cooling element for these components. The base plate has cooling channels through which a coolant flows when the inverter is installed. For this purpose, at least one inlet and at least one outlet are provided on the base plate. After installation, the base plate is connected to the heat exchanger via these channels, allowing a coolant circulating within this circuit to be supplied to and discharged from the base plate. This coolant flows through the base plate and is thereby cooled by the power components.

[0011] - 3 - absorbs and dissipates the emitted heat. The heat exchanger itself is located on the machine side, i.e., positioned at a suitable location on or inside the machine housing.

[0012] As described, the base plate serves as a carrier for the power components. Several power modules are arranged on one side of the plate, while several capacitors are arranged on the opposite side. This means that these different power components are positioned on the two opposite sides of the plate; the base plate is located between these power components, which make contact with it as much as possible to ensure a large heat transfer surface. According to the invention, corresponding busbars are provided to connect the capacitors to the power modules. These busbars extend through one or more openings in the base plate. This means that the busbars run from the first side of the plate, where they are connected to the power modules, through the openings to the second side of the plate, where they are connected to the capacitors. This allows for the shortest possible connection distances.

[0013] As described, an EMC filter is also associated with the inverter. This filter, as described, is not part of the inverter according to the invention, which is implemented as a separate assembly, but is installed on the machine side, as is the heat exchanger. The EMC filter is to be connected to the capacitors, for which suitable connection means are provided for connecting the capacitors to the EMC filter located on the motor side. Appropriate connecting elements, such as busbars or similar, are attached to these elements so that the spatial distance between the EMC filter and the capacitor assembly can be bridged. The EMC filter has an HVDC input, whereby the current is split twice into positive and negative terminals before reaching the capacitors.

[0014] Since the inverter is designed as a self-contained, pre-configured assembly, appropriate connection options for connecting the inverter to the two electric motors it operates must naturally be provided. According to the invention, connector plugs are provided for this purpose on the first side of the plate, P241379

[0015] - 4 - The inverter can be easily connected to the machine assembly using the appropriate connection elements, i.e., the corresponding connection sockets, when it is mounted. When the inverter is placed with its connection flange onto the mounting interface on the machine housing, the connector plugs are automatically inserted into the connection sockets, thus establishing the electrical connection. The connector plugs themselves are connected to the power modules via additional busbars that connect the power modules located on the second side of the panel to the connector plugs provided on the first side of the panel.The other busbars, as well as the busbars connecting the power modules to the capacitors, are led from the second side of the base plate, where they are connected to the power modules, to the first side of the base plate, where they are connected to the connectors, via at least one or more further openings in the base plate.

[0016] The invention proposes a compact dual inverter, reduced to a separate inverter assembly comprising only the power components, which has suitable interfaces for connecting it on the one hand to the machine housing itself and on the other hand to the corresponding components of the electric motor arrangement provided on the machine housing side, namely the EMC filter and the heat exchanger as components associated with the inverter, and the corresponding connection elements of the two electric motors. This design allows the inverter to be realized as a prefabricated assembly and flanged to the side of the machine housing, whereby this lateral arrangement leaves sufficient space on the machine housing side to integrate an electrical parking lock.

[0017] In a further development of the invention, the capacitors can be arranged in a row centrally on the first side of the plate, with one or more connectors on each of two opposite longitudinal sides of the row. The capacitors are thus arranged as a compact block in a row centrally on the first side of the plate, with one or more connectors to the right and left of it. This allows for a symmetrical arrangement on this side of the plate. P241379

[0018] - 5 -

[0019] Furthermore, it is possible to arrange the power modules on the second side of the plate in two spaced-apart rows, with the busbars connecting the power modules to the capacitors being connected to the opposite sides of the power modules. The power modules are thus also arranged in blocks in two rows, but these are spaced laterally from each other, unlike the capacitors on the opposite side of the first plate. This allows the busbars to be connected in the area between the two rows of power modules, and also enables the provision of one or more openings in the base plate in this area, through which the angled busbars are routed to and connected to the capacitors. This means that a symmetrical structure is also achieved on this side.

[0020] If the arrangement of the capacitors and connectors on the first side of the plate is provided as described above, and the arrangement of the power modules on the second plate is also implemented as described above, the result is a symmetrical inverter structure. Because the capacitors protrude slightly from the first side of the plate, the inverter ultimately has a T-shaped cross-section. This T-shaped structure allows for space-saving integration and is particularly advantageous because the respective busbars—which connect the capacitor blocks to the power module blocks on the one hand, and the power modules to the connectors on the other—have the same length in both individual inverters. As described, this is a dual inverter, i.e.,The system features a first group of capacitors that supplies a first group of power modules, which in turn are connected to one or more first connectors, as well as a second group of capacitors that supplies a second group of power modules, which in turn are connected to one or more second connectors. Due to the symmetrical design, the respective arrangements of the first and second groups of capacitors and power modules, as well as the positioning of the connectors, are virtually identical or mirror images of each other, resulting in identical busbar lengths in each individual inverter. This is combined with the simultaneous cooling of all P241379 components.

[0021] - 6 - The power components via the base plate designed as a cooling plate result in an extremely compact, high-performance dual inverter unit.

[0022] To connect the capacitors to the EMC filter, screw terminals can be provided on the capacitors as connection points. These terminals can be attached to the busbars that run to the EMC filter. The corresponding cable connection between the EMC filter and the capacitors or individual capacitor groups is made via these busbars, which are usually two in number and may be angled depending on where the EMC filter is installed in the machine housing.

[0023] Corresponding current sensors are regularly provided to measure the current supplied from the power modules to the connector. According to the invention, a current sensor can be provided on the first side, upstream of each connector, with a further busbar passing through each current sensor. These current sensors are also arranged on the first side, adjacent to the connectors, so that a busbar coming from the power modules can be easily routed through the respective current sensor, which, for example, operates capacitively.

[0024] In addition to the inverter itself, the invention relates to an electric motor arrangement comprising a machine frame with two electric motors housed therein, the EMC filter, and the heat exchanger, as well as an inverter of the type described above, which is attached to a mounting interface of the machine housing via its connecting flange. The inverter is connected to the machine housing via its housing through the corresponding flange connection. Simultaneously, as described, the inverter's connector plugs are inserted into the connection sockets of the electric motors during assembly. Similarly, during assembly, the EMC filter and the heat exchanger are connected to the capacitors on the one hand and the base plate on the other via the corresponding interfaces. P241379

[0025] - 7 - The mounting interface, and thus the inverter, can be arranged centrally with respect to the longitudinal axis of the machine housing, and the two electric motors can be positioned laterally and symmetrically to the inverter. This means that the entire assembly of the electric motors is symmetrical.

[0026] The inverter is arranged in the center of the longitudinal axis, with the two electric motors located to the right and left of it, and as described, the inverter is attached to the side of the machine housing.

[0027] Since only one EMC filter is provided, it can be positioned centrally with respect to the longitudinal axis of the machine housing and adjacent to, and at least partially in contact with, a housing wall that defines an oil chamber. The EMC filter is thus arranged virtually in the same mounting plane as the inverter, but with a different orientation, for example, at a 90° angle to the inverter's mounting plane. It is preferably arranged adjacent to, and at least partially in contact with, a housing wall that defines an oil chamber in which oil circulates to cool components of the electric motors. Cooling of the EMC filter can therefore be achieved via this housing wall.

[0028] The heat exchanger itself is preferably arranged adjacent to the inverter's condensers, i.e., it preferably runs parallel to the condensers and thus parallel to the base plate, so that it is positioned as close as possible to the base plate and short pipe connections are maintained between the heat exchanger and the base plate's inlet and outlet. The heat exchanger can also be arranged adjacent to a housing wall that borders an oil chamber, with the heat exchanger being fluidically connected to the oil chamber via pipe connections. This means that the fluid circulating in the oil chamber also flows through the heat exchanger via these pipe connections, as does the coolant that cools the base plate. This enables heat transfer from the coolant to the oil and the resulting heat dissipation.The housing wall has appropriate connection means to which the heat exchanger sitting on the housing wall is connected (P241379).

[0029] - 8 -can. The connections for the pipe connections to the base plate are preferably provided on opposite end faces of the heat exchanger.

[0030] The electric motor arrangement itself is preferably an electric rear axle of a motor vehicle, which therefore has two electric motors, as well as the inverter according to the invention, designed as a double inverter.

[0031] The invention is explained below with reference to exemplary embodiments and the drawings. The drawings are schematic representations and show:

[0032] Figure 1 shows a perspective view of an inverter according to the invention.

[0033] Figure 2 shows a top view of the first side of the base plate with power modules arranged on it.

[0034] Figure 3 shows a top view of the second side of the plate with capacitors, connectors and current sensors arranged on it.

[0035] Figure 4 shows a sectional view through the inverter,

[0036] Figure 5 shows an electric motor arrangement according to the invention in a side view without a mounted inverter.

[0037] Figure 6 shows the electric motor arrangement from Figure 5 in a sectional view with the inverter mounted, and

[0038] Figure 7 shows the electric motor arrangement from Figure 6 in another section plane.

[0039] Figure 1 shows a perspective view of an inverter 1 according to the invention. This comprises a pot-shaped, rectangular housing 2, on which a rectangularly circumferential connecting flange 3 is arranged, via which the inverter 1 is connected by means of a plurality of P241379

[0040] - 9 - is to be attached to a machine housing of an electric motor assembly by connecting screws 4 at a mounting interface of which will be described below. Inside the housing 2, a base plate 5 is arranged and fixed there by means of mounting screws not shown in detail here. On this base plate 5, as shown in Figure 2, several power modules 7 are arranged in two separate rows 8 on a first plate side 6. As Figure 2 shows, three power modules 7 are provided per row 8, which are laterally offset, i.e., spaced apart from each other. The power modules 7 are in direct contact with the first plate side 6 over as large an area as possible, since the base plate 5 also serves as a cooling plate. It is permeated by a cooling fluid, for example water, which will be discussed below, so that cooling of the power modules 7 is possible.

[0041] Figure 3 shows the base plate 5 with a view of the second plate side 9, which is also shown in Figure 1. In the example shown, two capacitors 10 are arranged on this side in two rows 11, with the capacitors 10 positioned almost centrally adjacent to each other. The capacitors are also arranged in direct, and as large an area as possible, contact with the second plate side 9, so that they too can be cooled by the base plate 5, which serves as a cooling plate. Furthermore, connector plugs 12 are provided on this second plate side, arranged on both sides to the right and left of the capacitors 10, with three connector plugs 12 provided on each side, corresponding to the three phases that supply the operating voltage of the two electric motors described below.

[0042] Furthermore, on the second side of the plate 9, three current sensors 13 are arranged on each side, with each current sensor 13 being assigned to a connector 12. The current supplied to the respective connector 12 is measured via these current sensors 13.

[0043] As shown in Figure 1, but also in Figures 2 and 3, an inlet 14 and an outlet 15 are provided on the base plate 5, through which a coolant supplied by a heat exchanger not shown in detail flows into the inner coolant channels P241379

[0044] The coolant can be supplied to and removed from the base plate 5, which has 10 surfaces. The coolant flows through the cooling plate 5, absorbing and transporting the heat emitted by the power modules 7 and the capacitors 10.

[0045] Figure 1 further shows three connecting cables 16 that run to a control board 17 shown in Figure 4, on which the control electronics, not shown in detail, are mounted.

[0046] Figure 4 shows a sectional view through the inverter 1, in which the individual inverter-side connections of the components are shown in more detail. The housing 2 described above and the base plate 5, which is connected to the housing 2 via mounting screws 35, are shown. Also shown are the power modules 7 on the first side of the plate and the capacitors 10 on the second side of the plate. It can be seen that the power modules 7 and the capacitors 10 are in contact with the respective plate sides over as large an area as possible, so that the coolant flowing through the base plate 5 in corresponding cooling channels 18 can absorb heat over the largest possible contact area.

[0047] To connect the power modules 7 to the capacitors 10, corresponding busbars 19 are provided. In the example shown, these busbars are angled at 90° and are connected at one end to a terminal on the respective power module 7 and at the other end to a terminal on the respective capacitor 10. Three such busbars 19 are provided for each power module 7, as shown in Figure 2. The busbars 19 pass through corresponding openings 20 in the base plate 5, i.e., they extend directly through the base plate 5 from the first plate side 6 to the second plate side 9, resulting in extremely short connection distances. Due to the staggered arrangement of the two rows 8 of the power modules 7 and the closely spaced arrangement of the capacitors 10, it is possible to route the busbars 19 in the central area.

[0048] Also shown are the connectors 12 arranged to the right and left of the capacitors 10, as well as the adjacent current sensors 13. To connect the connectors 12 to the power modules 7, further busbars 21 are provided, which connect at one end to corresponding terminals of the P241379

[0049] - 11 - Power modules 7 are connected, with each power module 7 being connected to a further busbar 21. The other end of each is connected to a connector 12, as shown in Figure 3. Each busbar 21 is guided through a current sensor 13, as shown in both Figure 4 and Figure 3, so that the supplied current can be capacitively detected. The other busbars 21 are also guided directly through the base plate 5 in corresponding further openings 22, as shown in Figure 4. This also makes it possible to keep the connecting struts as short as possible.

[0050] As described, Figure 1 also shows the control board 17 and the connecting lines 16 running to it. Also shown are two power boards 23 on which the power modules 7 are arranged, the power boards 23 being attached in a suitable manner in the housing 2, just like the control board 17.

[0051] The inverter 1 has a symmetrical design, mirroring the central plane 24 indicated in Figure 4. The lengths of the busbars 19 and 21 on either side are equal, as shown in Figure 4, resulting in virtually identical connection lengths in both inverter blocks. This also leads to an extremely compact, T-shaped design, allowing for space-saving integration of the inverter. Furthermore, all power components that heat up during operation—namely, the power modules 7 and the capacitors 10—are intrinsically cooled by the integrated cooling system on the base plate 5.

[0052] Figure 5 shows an electric motor arrangement 25 according to the invention, comprising a machine housing 26 in which two electric motors (not shown in detail) are arranged. One such electric motor 27 is shown by way of example in Figure 7; as described, two such electric motors are provided, which are received in the two lateral housing sections shown in Figure 5.

[0053] Figure 5 shows a mounting interface 33 to which the connecting flange 3 of the inverter 1 is screwed. Corresponding connection sockets 28 are also shown in Figure 5, the number of which corresponds to the respective number of P241379

[0054] - 12 - Connection plugs 12 per side corresponds to three connection sockets 28 per side, into which the connection plugs 12 are inserted during assembly. Furthermore, the figure shows an EMC filter 29, which, as also shown in Figure 6, is located inside the machine housing 26. Like the inverter 1, which is shown in Figure 6, it is located centrally with respect to the longitudinal axis of the electric motor assembly 25; it runs at an angle of approximately 90° to the mounting plane of the inverter 1. The EMC filter 29 is connected to the capacitors 10 via two busbars 30, for which corresponding screw terminals 34 are provided on the capacitors 10 and their respective contact rails, as shown in Figure 1.

[0055] Figures 5 and 6 further show a heat exchanger 31 connected to the connection means 14, 15, forming a closed circuit via the heat exchanger 31, the connection means 14, 15, and the base plate 5, in which a coolant, conveyed by a conveying device (not shown in detail), circulates. The heat exchanger 31 itself is arranged on a housing wall 32, which defines an oil chamber containing oil that cools the electric motors 27. The heat exchanger 31 is fluidically connected to this oil chamber via pipe connections passing through this housing wall 32, allowing the oil to circulate through the heat exchanger 31 and enabling heat transfer from the coolant to the oil.

[0056] Figure 7 shows a sectional view similar to Figure 6, but in a different plane. While Figure 6 shows a sectional view in the longitudinal center of the electric motor assembly 25, i.e., centered in Figure 5, Figure 7 shows a sectional view in the plane of the connector plugs 12 and sockets 28. The sockets are connected to corresponding inputs of the associated electric motor 27 to energize its stator.

[0057] Figures 6 and 7 in particular show the extremely compact design of the electric motor assembly 25, which could, for example, be an electric rear axle of a motor vehicle. Although the inverter 1 is no longer arranged axially between the electric motors as is often the case, since in a P241379

[0058] - 13 - Electric motor arrangement 25 as shown. Since this is not possible due to the integration of an electrical parking lock between the electric motors, the design of the inverter 1 according to the invention as a separate, compactly configured unit, which only has the power components in the form of the power modules 7 and capacitors 10, nevertheless allows a compact arrangement on the machine housing in the area of ​​the electric motors 27. This is possible because the EMC filter 29 and the heat exchanger 31 are arranged as separate components, independent of the inverter 1, in the machine housing, as shown in Figures 5 and 6, and are thus integrated there in a space-saving and compact manner. It is only necessary to connect the corresponding fluidic and electrical interfaces during assembly, insofar as this does not occur automatically during joining, as in the case of the connector plugs 12 and sockets 28. P241379

[0059] - 14 - List of reference symbols

[0060] 1 Inverter

[0061] 2 cases

[0062] 3 Connecting flange

[0063] 4 connecting screws

[0064] 5 Base plate

[0065] 6 plate side

[0066] 7 Power module

[0067] 8th row

[0068] 9 plate side

[0069] 10 Capacitor

[0070] 11th row

[0071] 12 connector plugs

[0072] 13 Current sensor

[0073] 14 Inflow

[0074] 15 Procedure

[0075] 16 connecting cables

[0076] 17 Control board

[0077] 18 cooling channels

[0078] 19 Busbar

[0079] 20 Breakthrough

[0080] 21 Busbar

[0081] 22 Breakthrough

[0082] 23 Powerboard

[0083] 24 Middle level

[0084] 25 Electric motor arrangement

[0085] 26 machine housings

[0086] 27 Electric motor

[0087] 28 connection sockets

[0088] 29 EMC filters

[0089] 30 busbar

[0090] 31 Heat exchanger P241379

[0091] - 15 - 32 Housing wall

[0092] 33 Mounting interface

[0093] 34 screw terminals

[0094] 35 fastening screws

Claims

P241379 - 16 - Patent claims 1. Inverter for supplying two electric motors (27), in particular an electric rear axle of a motor vehicle, comprising a housing (2) with a connecting flange (3) attachable to a mounting interface (33) of a machine housing (26) and a base plate (5) arranged in the housing (2), which can be cooled with a coolant that can be supplied and discharged via at least one inlet and at least one outlet, wherein the inlet and the outlet have connection means (14, 15) for connecting to a heat exchanger (31) provided on the side of the electric motor, wherein several power modules (7) are arranged on a first side (6) of the plate and several capacitors (10) are arranged on an opposite second side (9) of the plate, wherein the power modules (7) are connected to the capacitors (10) via the base plate (5) in busbars (19) extending through one or more openings (20),wherein connection means (34) are provided for connecting the capacitors (10) to an EMC filter (29) provided on the electric motor side, and wherein the power modules (7) are connected via further busbars (21) passing through the base plate (5) in one or more further openings (22) to connector plugs (12) provided on the first side (6) of the plate, via which the inverter (1) can be connected to terminals (28) of the two electric motors (27).

2. Inverter according to claim 1, characterized in that the capacitors (10) are arranged in a row (11) centrally on the first plate side (6) and one or more connector plugs (12) are provided on each of two opposite longitudinal sides of the row (11).

3. Inverter according to claim 1 or 2, characterized in that the power modules (7) are arranged in two spaced-apart rows (8), wherein the busbars (19) connecting the power modules (7) to the capacitors (10) are connected to the mutually facing sides of the power modules (7). P241379 - 17 - 4. Inverter according to one of the preceding claims, characterized in that screw terminals (31) can be attached to the capacitors (10) as connection means via the busbars (30) which run to the EMC filter (29).

5. Inverter according to one of the preceding claims, characterized in that a current sensor (13) is provided on the first plate side (6) upstream of each connector (12), wherein a further busbar (21) is guided through each current sensor (13).

6. Electric motor arrangement comprising a machine housing with two electric motors (27) housed therein, an EMC filter (29) and a heat exchanger (31), and an inverter (1) according to one of the preceding claims, which is attached with its connecting flange (3) to a fastening interface (33) of the machine housing (26).

7. Electric motor arrangement according to claim 6, characterized in that the mounting interface (33) and thus the inverter (1) is arranged centrally with respect to the longitudinal axis of the machine housing (26) and the two electric motors (27) are positioned laterally and symmetrically to the inverter.

8. Electric motor arrangement according to claim 6 or 7, characterized in that the EMC filter (29) is arranged centrally with respect to the longitudinal axis of the machine housing (26) and adjacent and at least partially in contact with a housing wall that defines an oil space.

9. Electric motor arrangement according to one of claims 6 to 8, characterized in that the heat exchanger (31) is arranged adjacent to the capacitors (10) of the inverter (1) and adjacent to a housing wall (32) which defines an oil space and is fluidically connected to the oil space via line connections.

10. Electric motor arrangement according to one of claims 6 to 9, characterized in that it is an electric rear axle of a motor vehicle.

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