Inverter device for an electric axle of a motor vehicle, and electric axle

Abstract

The invention relates to an inverter device for an electric axle (1) of a motor vehicle, comprising two separate electric machines (2, 3) to be driven via the inverter device (8), wherein the inverter device (8) comprises two separate inverters (10, 11) to which a common control device (12) and a common capacitor (13) and a common EMC filter (16) are assigned, wherein the inverters (10, 11), the control device (12), the capacitor (13) and the EMC filter (16) are accommodated in a common housing (9).

Description

[0001] Inverter device for an electric axle of a motor vehicle and electric axle

[0002] The invention relates to an inverter device for an electric axle of a motor vehicle, comprising two separate electric machines to be operated via the inverter device.

[0003] Electrically powered motor vehicles have at least one electric axle into which two separate electric motors are integrated, each driving a wheel. Each electric motor is assigned an inverter device, each of which has at least one inverter (i.e., a corresponding semiconductor power module), a control device, a capacitor, and an EMC filter. The corresponding components are arranged in a housing, with a corresponding cooling device often also provided on the housing side. This design can lead to problems integrating the inverter devices into the axle.

[0004] The invention is based on the problem of providing an inverter device which is improved compared to the above.

[0005] To solve this problem, in an inverter device of the type mentioned at the outset, it is provided according to the invention that the inverter device has two separate inverters, to which a common control device as well as a common capacitor and a common EMC filter are assigned, wherein the inverters, the control device, the capacitor and the EMC filter are accommodated in a common housing.

[0006] According to the invention, a dual inverter is proposed which has two separate inverters, i.e. two separate semiconductor power modules, each of which operates an electrical machine via a power module. However, a common control device is assigned to the two inverters, i.e. one control device controls both inverters, i.e. both power modules, accordingly. Likewise, only one common capacitor is assigned, which is connected to both inverters, for which corresponding busbars are used. Although the capacitor is somewhat larger than in the previously known design with separate inverter devices, only one common component is required here. The same applies to the EMC filter, which is also assigned to both inverters, so here too only one component is required.

[0007] All components and assemblies are housed in a common housing, which ultimately only needs to be dimensioned insignificantly larger than previously known designs with separate inverter devices. Ultimately, the housing only needs to accommodate an additional inverter as well as the slightly larger capacitor and, if necessary, the slightly larger EMC filter. However, this does not result in a significant increase in the housing size, resulting in a very compact inverter device that requires far less installation space than two separate inverter devices, each assigned to an electrical machine. On the one hand, this can save installation space and makes the integration of an electric axis possible even in correspondingly small installation space. On the other hand, assembly is also simplified since only one common inverter device needs to be integrated on the axle side.This integration takes place in the center of the axis between the two electrical machines, which are connected almost directly to the centrally arranged inverter device on both sides, viewed in the axial direction.

[0008] A useful further development provides for only one common cooling device to be provided, via which at least the two inverters are cooled together. While in the prior art, with separate inverter devices in an electrical axis, each inverter device has a separate cooling device to cool at least the inverters, i.e. the semiconductor power modules, which heat up considerably during operation, the invention provides only one common cooling device in the common housing, via which both inverters are cooled. This also results in a considerable simplification, since this cooling device is also much easier to integrate into a corresponding cooling circuit than two separate cooling devices in the prior art.

[0009] The cooling device preferably has a first plate-shaped cooling element, to which the two inverters, and optionally the control device, are thermally coupled. This plate-shaped cooling element easily enables a large-area thermally conductive coupling of the two inverters. These can, for example, be arranged directly on or attached to the plate-shaped cooling element on both sides of the element, thus resulting in a type of sandwich arrangement with the two inverters and the plate-shaped cooling element arranged between them. This allows, on the one hand, optimal thermal coupling to be achieved, and, on the other hand, both inverters can be cooled synchronously in a simple manner, resulting in a very compact arrangement.

[0010] It is also conceivable to additionally couple the cooling element to the capacitor in a thermally conductive manner. The capacitor also heats up during operation. If the capacitor is positioned closely adjacent to the first cooling device for optimized installation space and coupled to it in a thermally conductive manner, the heat generated on the capacitor side can also be absorbed and dissipated via the first cooling device.

[0011] Furthermore, according to a further development of the invention, it is conceivable for the cooling device to additionally be provided with a second plate-shaped cooling element, to which at least the capacitor, and optionally also the EMC filter, is thermally conductively coupled. This second plate-shaped cooling element enables corresponding direct cooling of the capacitor and, if necessary, also of the EMC filter. Again, a plate-shaped cooling element is used, to which the capacitor is attached in a heat-conducting manner in a flat manner, so that here too, similar to the inverters, the best possible heat transfer from the capacitor to the cooling element is possible. A coolant flows through the first plate-shaped cooling element, i.e., it is integrated into a corresponding cooling circuit. If a second plate-shaped cooling element is used for additional condenser cooling, it is expediently also flowed through by a cooling fluid.Preferably, both cooling elements are integrated into a common coolant circuit, so that the coolant first circulates through one cooling element and then through the other and dissipates the heat.

[0012] In this case, the two cooling elements are preferably arranged directly downstream of one another, meaning that a fluid-conducting connection is established between the first and second cooling elements. This is ultimately easily possible since both are accommodated in the common housing as described and, to achieve the greatest possible compactness, are arranged closely adjacent to one another.

[0013] According to an advantageous development of the invention, the first cooling element itself, to which the two inverters are coupled, is mechanically fastened in the housing and simultaneously serves as a support for the two inverters arranged on either side thereof.

[0014] The cooling element thus essentially serves a dual function: on the one hand, its original cooling function, but on the other hand, also that of a support, i.e., a holding element for the two inverters, which are attached to it with suitable fasteners. A contact interface with the largest possible surface area is preferred for optimal heat transfer.

[0015] The EMC filter itself is preferably shielded in a separate housing part, i.e. in a separate EMC chamber, and can be separated from the other components and also shielded accordingly.

[0016] In addition to the inverter device itself, the invention further relates to an electric axle for a motor vehicle, comprising two separate electric machines and an inverter device of the type described above, preferably arranged between them. The invention is explained below using exemplary embodiments with reference to the drawings. The drawings are schematic representations and show:

[0017] Figure 1 is a schematic diagram of an electric axle according to the invention comprising an inverter device according to the invention, and

[0018] Figure 2 shows a schematic diagram of an inverter device according to the invention.

[0019] Figure 1 shows an electric axle 1 according to the invention in the form of a partial view as a schematic representation. The electric axle comprises two separate electric machines 2, 3, each of which is followed by a transmission 4, 5 that operates on a corresponding output axle 6, 7, which in turn runs to corresponding driven wheels. An inverter device 8 according to the invention is arranged between the two electric machines 2, 3 and is described in more detail below with reference to Figure 2. The shared inverter device 8 serves both electric machines 2, 3, thus controlling them or supplying them with power or passing on any recuperated power.

[0020] The common inverter device 8 is shown in more detail in Figure 2 in the form of a schematic diagram. It comprises a housing 9 in which two inverters 10, 11 are accommodated. Each inverter 10, 11 is assigned to an electrical machine 2, 3.

[0021] Both inverters 10, 11 are assigned a common control device 12, via which they are controlled separately.

[0022] Furthermore, a common capacitor 13 is provided in the housing 9, which is electrically connected to both inverters 10, 11. Suitable busbars 14, 15 are provided for this purpose. These busbars can be designed, for example, one above the other, i.e., as a laminate. The electrical connection can be made, for example, by laser welding or similar means. The capacitor is dimensioned accordingly, since it is assigned to both inverters 10, 11.

[0023] Furthermore, an EMC filter 16 is provided, which is accommodated in a separate housing compartment 17 and is shielded accordingly.

[0024] During operation of the inverter device 8, heat is generated that must be dissipated. This applies in particular to the two inverters 10, 11, which are designed as semiconductor power modules and heat up accordingly depending on the load. For this purpose, a common cooling device 18 is provided, comprising a plate-shaped cooling element 19 through which a cooling fluid 20 flows, i.e., the cooling element 19 is integrated into a cooling circuit. The cooling element 19, which is fastened in the housing via suitable fastening means 21, simultaneously serves as a support for the two inverters 10, 11, which are arranged and fastened on both sides of the plate-shaped cooling element 19 in the best possible thermally conductive contact. A contact as flat as possible is preferred. Consequently, a type of sandwich arrangement is provided, consisting of the two inverters 10, 11 and the plate-shaped cooling element 19 located between them.Any heat generated passes from the inverters 10, 11 to the cooling element 19 and is dissipated via the circulating cooling fluid 20.

[0025] Furthermore, as part of the cooling device 18, a second plate-shaped cooling element 22 is provided, on which at least the condenser 13 is arranged in heat-conducting contact. This is because heat is also generated at the condenser 13 and must be dissipated. The cooling fluid 20 also flows through the cooling element 22, wherein the two cooling elements 19, 22 are connected to one another via a connecting line 23, so that they are consequently fluidically coupled to one another and both are integrated into a common circuit. The cooling fluid therefore flows via a supply line, for example, first into the first cooling device 19 and from there via the connecting line 23 into the second cooling device 22 and from there into a discharge line back into the circuit. The supply and discharge lines are guided into the housing via corresponding housing openings and are connected to the cooling elements 19, 22 in a suitable manner. This consequently enables efficient active heat dissipation.

[0026] Figure 2 optionally shows the possibility of the second cooling element 22 also extending into the second housing compartment 17, so that cooling of the EMC filter 16 is also possible, if necessary. The EMC filter 16 would also be thermally coupled to the cooling element 22. However, this is not mandatory; the cooling element 22 can also serve exclusively for condenser cooling and be connected only to the condenser 13.

[0027] It would also be conceivable to couple the control device 16 to the first cooling element 18 in a heat-conducting manner, so that any heat generated at the control device 12 can also be dissipated.

[0028] It would also be conceivable to also make thermally conductive contact between the capacitor 13 and the first cooling element when arranged directly adjacent to the latter, so that heat generated at the capacitor 13 can be dissipated not only via the second cooling element 22, but also additionally via the first cooling element 19.

[0029] The housing itself can, for example, consist of two separate housing halves into which the corresponding components are installed, after which the two housing halves are sealed to form a sealed housing 9. Of course, the housing can also be made up of several parts, but it is always sealed when closed to prevent moisture penetration.

[0030] The inverter device 8 according to the invention is therefore a very compact component that is capable of operating both electrical machines 2, 3. Only two separate inverters 10, 11, each of which is assigned to an electrical machine 2, 3, are to be provided as duplicate components. All other components, namely the common control device 12, the common capacitor 13 and the common EMC filter 16, are to be provided only as individual components with sufficient dimensions and design; they operate both inverters 10, 11 jointly. Since the components operating both electrical machines are also accommodated in a single, common housing 9, the inverter device 8 can therefore be arranged without problems even in small installation spaces. This is because, as in the prior art, no two separate inverter devices or correspondingly dimensioned housings need to be installed on the axle side, but only one common orcentral inverter device 8, which, as shown in Figure 1, can be positioned centrally between the two electrical machines 2, 3.

[0031] List of reference symbols electric axis electric machine electric machine gear box gear box output shaft output shaft inverter device housing inverter inverter control device capacitor busbar busbar EMC filter housing compartment cooling device cooling element cooling fluid fastening means cooling element connecting cable

Claims

Patent claims 1. Inverter device for an electric axle (1) of a motor vehicle, comprising two separate electrical machines (2, 3) to be operated via the inverter device (8), characterized in that the inverter device (8) has two separate inverters (10, 11), to which a common control device (12) and a common capacitor (13) and a common EMC filter (16) are assigned, wherein the inverters (10, 11), the control device (12), the capacitor (13) and the EMC filter (16) are accommodated in a common housing (9).

2. Inverter device according to claim 1, characterized in that a common cooling device (18) is provided, via which at least the two inverters (10, 11) are cooled together.

3. Inverter device according to claim 2, characterized in that the cooling device (18) has a first plate-shaped cooling element (19) to which the two inverters (10, 11) and optionally the control device (12) are thermally coupled.

4. Inverter device according to claim 3, characterized in that the first cooling element (19) is additionally coupled to the capacitor (13) in a heat-conducting manner.

5. Inverter device according to claim 3 or 4, characterized in that the cooling device (18) has a second plate-shaped cooling element (19) to which at least the capacitor (13), optionally also the EMC filter (16), is thermally conductively coupled.

6. Inverter device according to claim 5, characterized in that the two cooling elements (19, 22) are flowed through by a cooling fluid (20) and are integrated into a common flow circuit.

7. Inverter device according to claim 6, characterized in that the two cooling elements (19, 22) are connected directly downstream of one another.

8. Inverter device according to one of claims 3 to 7, characterized in that the first cooling element (19) is mechanically fastened in the housing (9) and simultaneously serves as a support for the two inverters (10, 11) arranged on either side thereof.

9. Inverter device according to one of the preceding claims, characterized in that the EMC filter (16) is accommodated in a shielded manner in a separate housing compartment (17).

10. Electric axle for a motor vehicle, comprising two separate electric machines (2, 3) and an inverter device (6) according to one of the preceding claims.

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